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Agenda 2/14/2023 Item #16C 2 (Authorize expenditures under sole-source waivers for pruchase of specialized proprietary equipment and sevices from Hydro inermational and huber technology inc)16.C.2 02/ 14/2023 EXECUTIVE SUMMARY Recommendation to authorize expenditures under sole -source waivers for purchase of specialized proprietary equipment and services from Hydro International and Huber Technology, Inc., needed to establish, repair, and maintain operations at wastewater treatment facilities to meet demand and maintain compliance. OBJECTIVE: To continue consistency with the equipment utilized at the wastewater plants and provide continuous and proactive operation and maintenance of these facilities, as required, to meet the needs of the public and ensure that the Public Utilities Department ("PUD") remains in regulatory compliance with Florida Administrative Code Chapter 62-600 (Domestic Wastewater Facilities) and Chapter 62-610 (Reuse of Reclaimed Water and Land Application); as well as other local, State, and federal rules and regulations. CONSIDERATIONS: On July 10, 2018, (Agenda Item 16.C.9), the Board authorized two single -source waivers and 26 sole -source waivers for the purchase of equipment, including service parts, kits, interface components, software, service and support for existing and replacement applications for a period of five years. On December 10, 2019, (Agenda Item 16.C.4), the Board authorized eight additional sole -source waivers. With the continued expansion of the County and in support of maintenance, repair and replacement, operational, and capital improvements projects, PUD recommends allowing future purchases under two sole -source Waivers for the following two highly specialized proprietary product categories needed to construct, repair, and maintain wastewater treatment facilities to maintain compliance and meet customer demand: (1) HUBER Technology, Inc. ("HUBER") screening systems, and (2) Hydro International ("Hydro") grit removal systems. This equipment requires regular maintenance to sustain 24/7 operations, meet customer demand, and stay in compliance with all regulatory agency requirements. These specific items are required because they are proprietary in nature and cannot be directly replaced with an alternate product, and require the Board's approval to purchase them under a sole source waiver. Further, processes and structures are tailored to a product's physical configuration, treatment capacity, and efficiency, which prevents alternate products from being installed without significant rework. Attachment 1 is the Waiver request forms for those systems, which includes the purpose, explanation, market research, manufacturing, and inventory of available parts. On July 12, 2022, (Agenda Item 1 LN) the Board certified the existence of a valid public emergency necessitated by the need to expedite the completion of the North County Water Reclamation Facility's new Pretreatment Facility ("Headworks" project #20-7722). During the course of the design of the Headworks project the HUBER screening systems and Hydro grit systems were recommended as the most suitable based on the superior performance and record of operations and maintenance. In addition to the Headworks project, the Golden Gate Water Reclamation Facility and the Northeast Utilities Water Reclamation Facility projects are also under design, and three independent engineering design firms (AECOM, Inc., Carollo Engineers, Inc., and Tetra Tech, Inc.) have all recommended the use of the same systems supplied by HUBER and Hydro. Staff is recommending that the Board approve the attached sole -source waiver exemptions to provide a consistency of utilizing HUBER screening systems and Hydro grit systems on all three County facility projects. The above recommended proactive approach is necessary to ensure the County meets the needs of the public and regulatory compliance with local, state and federal laws. Similar Huber screens have been implemented in Sanibel, Bonita Springs, Babcock Ranch, and Marco Island utility operations. Likewise, similar Hydro grit removal systems have been implemented in the Golden Gate Wastewater Treatment Plant, South County Water Reclamation Facility, Venice, Cape Coral, Three Oaks, and Fort Myers utility operations. Engineering consultant AECOM, Inc. performed a third party assessment on the equipment and services offered by HUBER and Hydro and its findings and recommendations are included in Attachment 2 "NCWRF Pretreatment Facility - Sole Source Waiver Request for Certain Wastewater Process Equipment and Services." Engineering consultant Carollo Engineers, Inc. has extensive experience with these manufacturers and also conducted an evaluation of the current level service requirements. Carollo's findings and recommendations are included in Packet Pg. 828 16.C.2 02/ 14/2023 Attachment 3 supporting staffs sole source requests. Engineering consultant Tetra Tech, Inc. has extensive experience with these manufacturers and also conducted an evaluation of the current level service requirements. Tetra Tech's recommendation is included in Attachment 4 supporting these sole source requests. Affidavits from each of the three firms is attached confirming no conflict of interest with their recommendation to utilize the respective grit and screening systems equipment. In order to identify this equipment in the future solicitation specifications for these projects, the sole -source designation is required. All these projects will be bid for construction within the next six months to two years and subsequent contracts will be presented to the Board for approval. Should staff see a need in the future for service they will bring back to the Board maintenance or service agreements required for the these products. In accordance with Section Eleven, sub -paragraph 10 of the Collier County Procurement Ordinance, as amended, staff requests that the Board find that it is in the best interest of the County to waive competition and allow procurement of the requested products and services required to meet the PUD's operational needs. Staff intends to repeat this product assessment process within the next three to five years to ensure that best -value continues to be provided through changes in the market and technology with the intent of future standardization. FISCAL IMPACT: Annual expenditures will be controlled by the Board -approved budget. As and when needed, funds are available in the Collier County Water -Sewer District Operating Fund (408), and the Wastewater User Fee Fund (414). As the utility system ages, the quantity of materials purchased will vary depending on the actual repair/replacement needs. LEGAL CONSIDERATIONS: This item is approved as to form and legality, and requires majority vote for Board approval.-SRT GROWTH MANAGEMENT IMPACT: This project meets current Growth Management Plan standards to ensure the adequacy and availability of viable public facilities. RECOMMENDATION: That the Board of County Commissioners, Ex-officio the Governing Board of the Collier County Water -Sewer District, authorizes expenditures under sole -source waivers for specialized proprietary equipment and services from Hydro International and Huber Technology, Inc. needed to establish, repair, and maintain operations at wastewater treatment facilities to meet demand and maintain compliance. Prepared by: Matt McLean, P.E., Director, Engineering and Project Management Division ATTACHMENT(S) 1. Attachment 1 - Waiver Requests(PDF) 2. Attachment 2 - AECOM - Sole Source Analysis to County (PDF) 3. Attachment 3 - Carollo - NEWRF_Headworks Manf Standardization _Ltr 11-18-2022 (PDF) 4. Attachment 4 - Tetra Tech Golden Gate MBR Screens and Grit Memo 01-11-2023 (PDF) 5. [Linked] Attachment 1.1 - NCWRF Pretreatment Sole Source Waiver - Engineer's Evaluation & Market Research (PDF) Packet Pg. 829 16.C.2 02/14/2023 COLLIER COUNTY Board of County Commissioners Item Number: 16.C.2 Doe ID: 24014 Item Summary: Recommendation to authorize expenditures under sole -source waivers for purchase of specialized proprietary equipment and services from Hydro International and Huber Technology, Inc., needed to establish, repair, and maintain operations at wastewater treatment facilities in order to meet demand and maintain compliance. Meeting Date: 02/14/2023 Prepared by: Title: Project Manager, Senior —Public Utilities Planning and Project Management Name: Wayne Karlovich 12/12/2022 12:51 PM Submitted by: Title: Director — Public Utilities Planning and Project Management Name: Matthew McLean 12/12/2022 12:51 PM Approved By: Review: Procurement Services Ana Reynoso Level 1 Purchasing Gatekeeper Procurement Services Sandra Herrera Additional Reviewer Procurement Services Sara Schneeberger Additional Reviewer Public Utilities Planning and Project Management Craig Pajer Public Utilities Planning and Project Management Matthew McLean Procurement Services Sue Zimmerman Additional Reviewer Wastewater Robert Von Holle Additional Reviewer Corporate Compliance and Continuous Improvement Megan Gaillard Public Utilities Department Public Utilities Department County Attorney's Office Office of Management and Budget County Attorney's Office Office of Management and Budget County Manager's Office Board of County Commissioners Drew Cody Level 1 Division Reviewer George Yilmaz Level 2 Division Administrator Review Scott Teach Level 2 Attorney Review Debra Windsor Level 3 OMB Gatekeeper Review Jeffrey A. Klatzkow Level 3 County Attorney's Office Review Susan Usher Additional Reviewer Dan Rodriguez Level 4 County Manager Review Geoffrey Willig Meeting Pending Completed 01/25/2023 4:43 PM Completed 01/26/2023 11:44 AM Completed 01/26/2023 2:07 PM Additional Reviewer Completed 01/26/2023 4:58 PM Additional Reviewer Completed 01/27/2023 8:27 AM Completed 01/30/2023 9:06 AM Completed 01/30/2023 9:18 AM Additional Reviewer Completed 01/30/2023 12:51 PM Completed 01/30/2023 1:18 PM Completed 01/30/2023 1:57 PM Completed 01/31/2023 3:25 PM Completed 01/31/2023 3:28 PM Completed 02/01/2023 9:02 AM Completed 02/02/2023 1:27 PM Completed 02/07/2023 8:17 AM 02/14/2023 9:00 AM Packet Pg. 830 16.C.2.a Attachment 1 Waiver Request Forms: 1. Huber Technology, Inc. 2. Hydro International C c0 G Q Y I_ M V a r r Q Packet Pg. 831 16.C.2.a Co ey County Waiver Request Form Instructions Completed waiver requests accompanied by any associated backup documentation (sole source letter, business case, etc.) must b� submitted to the division's Procurement Strategist for any procurement, without competition, in excess of $3,000. Waiver request. greater than $50,000 will require approval by the Board of County Commissioners. Sole source refers to a procurement where the selection of one particular supplier to the exclusion of all others may be based on havin( only one supplier in the marketplace, proprietary technology, copyright, patent, or a supplier's unique capability. Single source refers to a procurement directed to one source because of standardization, warranty, geographic territory, or other factors even though other competitive sources may be available. Requester Name: Wayne Karlovlch, PE Division: EPMD Item/Service:SCreening Systems Vendor Name:HUBER Technology Historical Not to Exceed Is there an agreement associated with this Countywide $0 Requested 12/1 /22-9/30/27 Amount per BCC Approved fiscal Budget waiver to be reviewed by Contracts? Spend: date range: Fiscal Year: ❑ Yes ❑✓ No ❑✓ Sole Source ❑ Single Source ❑ One Time Purchase ❑✓ Multiple Purchases Description of Purchase: Enter a description of the item(s) that will be purchased under this waiver. Influent multi -rake bar coarse screens, coarse screening washpresses, 2-mm drum screens (fine screens), rotamat fine screenings washpresses, and other screening equipment and screening handling systems, services, and appurtenances necessary for the screening systems. Purpose: Describe in detail, the public purpose of the requested item(s) and why it is essential to County operations. To ensure that Collier County Water and Wastewater Division complies with all applicable local, State, and federal codes, laws, regulations, standards, policies and operating permits. To provide suitable wastewater screening systems to ensure treatment performance meets the requirements of the downstream process, and to minimize operation and maintenance costs resulting from screenings and other debris accumulation in downstream systems and treatment processes. Information Technology: Select Yes if the products/services are related to Information Technology. If yes, please provide the Purchasinc Compliance Code (PCC) number or email approval documentation. ElYes ✓❑ No If yes, provide the PCC number: Revised 06/17/2021 Packet Pg. 832 16.C.2.a Co�r County Waiver Request Form Justification: Identify the criteria that qualifies this purchase as a sole or single source. Select from the list below. Check all that apply (if box is checked, please make sure to provide an explanation below): ❑✓ Sole Source ❑✓ Only Authorized Vendor or Distributor: Is this vendor the only vendor authorized to sell this product/service? If yes, explain below and provide documentation from the manufacturer confirming claims made by the distributors. ❑✓ No Comparable Product or Service: Is there another vendor who can provide a similar producf/service, regardless of cost, convenience, timeliness, etc.? ❑✓ Product Compatibility: Does this product/service provide compatibility with existing equipment that prohibits switching to another comparable brand/vendor? If yes, provide the detailed explanation below, including what would occur if the other brand/vendor were used. ❑ Proprietary: Is this product/service proprietary? If yes, provide a detailed explanation below on how its use is restricted by patent, copyright or other applicable laws and provide documentation validating that claim. ❑ Single Source ❑ Standardization: Is this product/service part of a purchase that the County has already standardized on? If yes, please provide the detailed information below. Date of BCC Standardization: BCC Agenda Item number: ❑ warranty: Is this the only vendor able to complete factory -authorized warranty services on County owned equipment? If yes, provide the documentation verifying the warranty. ❑ Geographic Territory: Is this vendor the only vendor authorized to sell this product/service in our region? If yes, provide documentation from the manufacturer confirming those claims. ❑ Other Factors: Any other reason not listed above, explain below. Explain: How does this purchase meet the identified sole or single source criteria listed above? Huber Technology is the sole supplier of equipment and service technicians for Huber SE products Our research concluded no other vendor manufactures and distributes a complete integrated package of screening and screening handling equipment able to fulfill capacity, removal efficiency, and performance requirements. No other vendor manufactures a similar product to the Drum Screen Liquid (DSL), the critical piece of equipment that protects a Membrane Bioreactor (MBR). The submerged horizontal drum design is specifically intended to provide an ultra -fine screening option for high flow rates with zero bypass of screenings or unscreened wastewater. The screenings handling system is specifically designed to process the high volume of wash water containing very fine solids. The County will benefit if one company has single source responsibility for the selection of and interface between the screens, the screening transfer systems and the washing and compaction equipment. This includes integration of all the control panels and instrumentation included in the scope of supply. Sole source avoids conflicts and interface between multiple equipment suppliers. Q Revised 06/17/2021 Packet Pg. 833 16.C.2.a Co�r County Waiver Request Form How was the decision made to use this vendor? Describe in detail if a formal standardization process was performed via Procurement or if there is a historical precedence established for the use of the product, please explain purchase, and use history and the current level of County investment in the product. Our research concluded no other vendor provides comparable products for the drum screen fine screens. The fine screens are a critical pretreatment requirement for MBR and Ludzak-Ettinger (MLE) activated sludge processes. The Huber screens have been used locally at Sanibel Island, Bonita Springs, Babcock Ranch, and Marco Island for MBR pretreatment. The equipment and manufacturer was also selected for two other Collier County wastewater treatment facilities by different engineering consultants and contractors, emphasizing its suitability. The item/service require replacement, service parts, kits, interface components, service and support to be procured in order to maintain 24/7 operations, meet demand and stay in compliance as stated in the Purpose Explain why it is in the County's best interest to use this product/service rather than issuing a competitive solicitation: What are the benefits from the continued use? Are there costs that would be incurred if a different vendor/product were used? What would occur if another brand/vendor were used? The equipment is required in specific applications and serve to optimize performance, process train reliability and maintenance requirements. The drum screen liquid fine screens are completely submerged with a totally enclosed screenings discharge pipe both of which minimize release of odors. In addition, the equipment listed has a high hydraulic capacity, therefore capable of handling flows with less units than would be required with other fine screen equipment. The cost of utilizing more smaller units is estimated to be $34 million at the NCWRF on the estimated $50 million pretreatment project. Explain how this pricing compares to other vendors/products and is it considered to be fair and reasonable: Provide information on historical use and whether pricing has increased/decreased. If sole source and no other product is available, provide the cost for addressing the needs via an alternate approach. As the equipment listed is the most suitable and cost-effective for our individual application, a side -by -side competitive bid is not practical as additional units and larger expanded structures would be required. Additional costs to prepare multiple designs would be required. The additional capital cost of utilizing more smaller units is estimated to be $3-4 million at the NCWRF on the estimated $50 million pretreatment project. Operational costs increase in proportion with the number of units installed. The additional maintenance costs for utilizing screens that allow screenings and unscreened wastewater to bypass is not possible to estimate. The equipment listed is easy to maintain and has low operation and life -cycle costs. Will this purchase obligate us to future ancillary products or services? Either in terms of maintenance or standardization. ❑✓ Yes ❑ No If yes, explain what types: Purchase of Huber Technology equipment will obligate us to future purchases for replacement parts, equipment, maintenance items and services. U) a� a� L 0 Cn 2 0 0 N N N N 7 N L > c m E a a� E U a a Revised 06/17/2021 Packet Pg. 834 16.C.2.a Co�r County Waiver Request Form Market research and market alternatives: When was the last time a market evaluation was performed to determine if either the technology or vendor offerings have changed? Based on the life expectancy of the product, when do you anticipate evaluating the market again? Please attach a detailed market evaluation report should the complexity, duration, and dollar amount of the purchase be a high risl to the County. Market research was completed over the past three months and included a variety of sources. HUBER Technology has over 150 years of industrial applications experience with over 50,000 installations worldwide. HUBER has provided over 3,500 pieces of equipment in the USA and HUBER's Multi -Rake Bar Screer RakeMax® has over 3,000 installations. HUBER is recognized as the market leader for screening and screening handling equipment and has an extraordinary level of expertise and continued product development as compared with other vendors. In 2019 HUBER Technology Inc. opened a 66,000 sq. ft. manufacturing facility in Denver, NC and at a recent groundbreaking ceremony, the company announced an expansion to 206,000 sq. ft. due to be completed in 2023 It is planned that all HUBER products for North America will be wholly manufactured in the USA, ensuring compliance with the Build America, Buy America (BABA) Act. All Aftermarket services are already provided in the USA. On average the facility holds a $4,000,000 inventory of spare parts. The company employs 14 site technicians, expanding to 24 in 2023. There are presently 2 site technicians that live in Florida. Additional market research will be carried out in the next five years. It is a felony to knowingly circumvent a competitive process for commodities or services by fraudulently specifying sole source. Florida Statute 838.22(2). Requested by %� PE Wayne a r ovI V Digitally signed by Signature: KarlovichWa ne Ka'te:20 Wayne y 05e0:02022.,,.2817:2s:27 Date: , Division Director: Matthew McLean, PE MeaU=oee�opoM Signature: McLeanMatthewo8 o°ps°°oeed;o-o„°9wam°° Date: Department Head: George Yilmaz, Ph.D, PE Digitally signed by vilmazGeorge Signature: YllmaZGeOrge Date: Required If over $50,000 OSoo?022.11.2911:39:22 Procurement Strategist: g Sara S ch n e e b e rg e r gnedby Schneeber erSa Digitally sierSara Signature g Date:2 22.11.291 g Date: 2022.11.29 12 1 s 47 Date: ra -os,00, Procurement Director: Sue Zimmerman Digitally signed by Signature: ZlmmermanSue Date.2 22.11 2 Date: 2022.11.29 12:22:17 Date: Or designee -os'oo' For Procurement Use Only: ❑✓ Approved ❑ Requesting Additional Information ❑ Requires RFI/Intent to Sole Source ❑ Rejected Procurement Comments: ❑ Current FY _ Approval ❑✓ Multi -Year Approval Start Date: 11/29/2022 End Date: 09/30/2027 Q Revised 06/17/2021 Packet Pg. 835 16.C.2.a Hue WASTE WATER Solutions October 14, 2022 Collier County Subject — Sole Source Letter To whom it may concern: This letter serves as a sole source document for servicing and supplying OEM parts and equipment for a� products manufactured by Huber SE, HydroPress Huber AB and Huber Picatech AG. L 0 Huber Technology Inc. is a subsidiary of the original manufacturer, Huber SE and the only source for authorizec service technicians in the United States and Canada. Moss Kelley, Inc./MKI Services, Inc. represents Hubei N Technology Inc. in the state of Florida and has the authority to distribute OEM parts and equipment. 0 Please let me know should you need further details. N N Sincerely,CD 0 a CD L CD > E 0 Henk-Jan van Ettekoven a President c m E U a r 9735 NorthCross Center Court I Suite A I Huntersville I NC 1 28078 1 USA Office (704) 949-1010 1 Fax (704) 949-1020 1 www.huber-technology.com r Q Packet Pg. 836 16.C.2.a Co�r County Waiver Request Form Instructions Completed waiver requests accompanied by any associated backup documentation (sole source letter, business case, etc.) must b� submitted to the division's Procurement Strategist for any procurement, without competition, in excess of $3,000. Waiver request. greater than $50,000 will require approval by the Board of County Commissioners. Sole source refers to a procurement where the selection of one particular supplier to the exclusion of all others may be based on havin( only one supplier in the marketplace, proprietary technology, copyright, patent, or a supplier's unique capability. Single source refers to a procurement directed to one source because of standardization, warranty, geographic territory, or other factors even though other competitive sources may be available. Requester Name: Wayne Karlovlch, PE Division: EPMD Item/Service: Grit Removal System Vendor"ame:Hydro International Historical Not to Exceed Is there an agreement associated with this Countywide 1 000 000* Spend: $ Requested 12/l /22-9/30/27 date range: Amount per BCC Approved Fiscal Budget Fiscal Year: waiver to be reviewed by Contracts? Yes ❑✓ No ❑✓ Sole Source ❑ Single Source ❑ One Time Purchase ❑✓ Multiple Purchases Description of Purchase: Enter a description of the item(s) that will be purchased under this waiver. Grit King®, HeadCell®, GritCleanseTM, and other grit equipment, including all other ancillary equipment, services, and appurtenances necessary for a complete grit removal system. Purpose: Describe in detail, the public purpose of the requested item(s) and why it is essential to County operations. To ensure that Collier County Water and Wastewater Division complies with all applicable local, State, and federal codes, laws, regulations, standards, policies, and operating permits. To provide efficient grit removal systems to ensure treatment performance meets the requirements of the downstream process, and to minimize operation and maintenance costs resulting from grit and other debris accumulation in downstream systems and treatment processes. Information Technology: Select Yes if the products/services are related to Information Technology. If yes, please provide the Purchasinc Compliance Code (PCC) number or email approval documentation. ElYes ✓❑ No If yes, provide the PCC number: U) L Revised 06/17/2021 Packet Pg. 837 16.C.2.a Co�r County Waiver Request Form Justification: Identify the criteria that qualifies this purchase as a sole or single source. Select from the list below. Check all that apply (if box is checked, please make sure to provide an explanation below): ❑✓ Sole Source ❑✓ Only Authorized Vendor or Distributor: Is this vendor the only vendor authorized to sell this product/service? If yes, explain below and provide documentation from the manufacturer confirming claims made by the distributors. ❑✓ No Comparable Product or Service: Is there another vendor who can provide a similar producf/service, regardless of cost, convenience, timeliness, etc.? ❑✓ Product Compatibility: Does this product/service provide compatibility with existing equipment that prohibits switching to another comparable brand/vendor? If yes, provide the detailed explanation below, including what would occur if the other brand/vendor were used. ❑✓ Proprietary: Is this product/service proprietary? If yes, provide a detailed explanation below on how its use is restricted by patent, copyright or other applicable laws and provide documentation validating that claim. ❑ Single Source ❑ Standardization: Is this product/service part of a purchase that the County has already standardized on? If yes, please provide the detailed information below. Date of BCC Standardization: BCC Agenda Item number: ❑ warranty: Is this the only vendor able to complete factory -authorized warranty services on County owned equipment? If yes, provide the documentation verifying the warranty. ❑ Geographic Territory: Is this vendor the only vendor authorized to sell this product/service in our region? If yes, provide documentation from the manufacturer confirming those claims. ❑ Other Factors: Any other reason not listed above, explain below. Explain: How does this purchase meet the identified sole or single source criteria listed above? Hydro International is the sole source manufacturer of this equipment. The grit removal systems are required in specific installations because they are proprietary in nature and fit in their individual applications. Use of an alternate vendor is not compatible with the existing treatment equipment and treatment plant processes and would require complete redesign of the treatment systems. Hydro International equipment products contain patented and proprietary design features unique to Hydro International. Moss Kelley, Inc./MKI Services, Inc. is the sole source local representative for replacement parts and components for the Hydro International line of products. Our research concluded no other vendor manufactures and distributes a complete integrated package of grit removal and handling equipment able to fulfill capacity, removal efficiency, and performance requirements. No other vendor manufactures a similar product to the Headcell grit removal equipment. The stacked tray design is specifically designed to capture fine grit particles (sugar sand) found in our wastewater. The County will benefit if one company has single source responsibility for the selection of and interface between the grit systems, the grit washing and dewatering equipment. This includes integration of all the control panels and instrumentation included in the scope of supply. Sole source avoids conflicts and interface between multiple equipment suppliers. Revised 06/17/2021 Packet Pg. 838 16.C.2.a Co�r County Waiver Request Form How was the decision made to use this vendor? Describe in detail if a formal standardization process was performed via Procurement or if there is a historical precedence established for the use of the product, please explain purchase, and use history and the current level of County investment in the product. The HeadCell® technology is proprietary, patented, and has no equivalent product. The equipment listed exists in specific installations that require replacement, service parts, kits, interface components, software, service and support to be procured in order to maintain 24/7 operations, meet demand and stay in compliance as stated in the Purpose. Our research concluded no other vendor provides comparable products and this equipment to be most suitable for the application. Similarly, the equipment and manufacturer was also selected for two Collier County wastewater treatment facilities by different engineering consultants, emphasizing its suitability. * The County currently has an estimated $1,000,000 of investment in equipment provided by Hydro International. The equipment is installed at the South County Water Reclamation Facility and the Golden Gate WWTP. Explain why it is in the County's best interest to use this product/service rather than issuing a competitive solicitation: What are the benefits from the continued use? Are there costs that would be incurred if a different vendor/product were used? What would occur if another brand/vendor were used? The manufacturer and equipment have a proven track record of successful installations backed by many case studies. The HeadCell and Grit King units each have 1,000 installations in the US. The Grit King is currently installed at the County's SCWRF and Golden Gate facilities. The equipment is effective in capturing and removing fine grit, which can impact downstream processes and reduce effectiveness of treatment facilities. The design of the equipment is completely different from any proven competitive technology, therefore a side -by -side competitive bid is not practical or cost effective. Each individual application of the equipment is tailored to the products physical and operation configuration such that the use of alternate products would require rework to the design and physical components of the structures, supports, connecting piping, and electrical systems. Explain how this pricing compares to other vendors/products and is it considered to be fair and reasonable: Provide information on historical use and whether pricing has increased/decreased. If sole source and no other product is available, provide the cost for addressing the needs via an alternate approach. The equipment listed is the most suitable and cost-effective for our individual applications. Superior grit removal efficiency results in reduced deposition in downstream processes, which maintains hydraulic capacity, plant process efficiency, effluent quality and minimizes process interruptions. In addition, the equipment itself and the installation have lower construction costs, requires little maintenance, has no moving parts, takes up a small footprint and frees up process space, therefore reducing capital and operational & maintenance costs. Use of an alternate technology results in poor removal efficiency of grit and deposition downstream which increases annual operating costs for the County by an estimated $700,000 per year. Will this purchase obligate us to future ancillary products or services? Either in terms of maintenance or standardization. ❑✓ Yes ❑ No If yes, explain what types: Purchase of Hydro International equipment will obligate us to future purchases for replacement parts, equipment, maintenance items and services. U) as a� L 0 Cn 2 0 r O N N N N a a� c m E a a� E M U a a Revised 06/17/2021 Packet Pg. 839 16.C.2.a Co�r County Waiver Request Form Market research and market alternatives: When was the last time a market evaluation was performed to determine if either the technology or vendor offerings have changed? Based on the life expectancy of the product, when do you anticipate evaluating the market again? Please attach a detailed market evaluation report should the complexity, duration, and dollar amount of the purchase be a high risl to the County. Market research was completed over the past three months and included a variety of sources. Hydro International has been in business for 50+ years and serves customers in more than 40 countries. The HeadCell separator is listed in the Water Environment Federation (WEF) Manual of Practice #8 and in the manual Design of Municipal Wastewater Treatment Plants by Metcalf & Eddy as a Multiple -Tray Vorte) System. The HeadCell utilizes multiple stacked trays to provide increased surface area when compared to conventional grit removal technologies. By stacking multiple trays vertically, a single HeadCell unit provides grit removal performance equivalent to multiple conventional grit removal systems in a significantly reduced cost and smaller footprint. There are over 125 HeadCell units installed in Florida. In addition, a headworks project in Atlanta that utilized HeadCell equipment won the 2018 National Excellence Award from the Design Build Institute of America. Additional market research will be carried out in the next five years. It is a felony to knowingly circumvent a competitive process for commodities or services by fraudulently specifying sole source. Florida Statute 838.22(2). Requested by Wayne ar ovic Digitally signed by Signature: KarlovichWa KavichWayne y ne rb Date: 05'00?022.11.28173746 Division Director: Matthew McLean, PE MeaU=oee�opoM Signature: McLeanMatthewo8 o°ps°°oeed;o-o„°9wam°° Date: Department Head: George Yilmaz, Ph.D, PE Digitally signed by vilmazGeorge Signature: YllmaZGeorge Date:?022.11.2911:40:50 Date: Required If over $50,000 Procurement Strategist g Sara S ch n e e b e rg e r Schneeber erSa Digitally signed by Signature: g SchneebergerSara g Date: 2022.11.29 12:17:26 Date: ra -05'00' Procurement Director: Sue Zimmerman Digitally signed by Signature: ZlmmermanSue ZimmermanSue Date: 2022.11.29 12:22:49 Date: Or designee -05'00' For Procurement Use Only: ❑✓ Approved ❑ Requesting Additional Information ❑ Requires RFI/Intent to Sole Source ❑ Rejected Procurement Comments: ❑ Current FY _ Approval ❑✓ Multi -Year Approval Start Date: 11/29/2022 End Date: 09/30/2027 L a� L 0 2 0 0 N N N CD CD Lm c E L V M Q c d E t U M r Q Revised 06/17/2021 Packet Pg. 840 16.C.2.a Water & Wastewater Solutions October 14,2022 Collier County Re: Sole Source Hydro International Hydro International equipment is product that contains patented and proprietary design features unique to Hydro International. Moss Kelley, Inc./MKI Services, Inc. is the sole source local representative for replacement parts and components for the Hydro International line of products. Replacement parts can be obtained directly from: MKI Services Inc., 7284 W. Palmetto Park Road, Suite 304 Boca Raton, FL 33433 Ph (954)755-2092 Ben McDorman wbm@mosskelley.com Pat Herrick National Sales Manager Packet Pg. 841 16.C.2.b AXOM November 17, 2022 Mr. Matthew McLean, P.E. Division Director Collier County Public Utilities Department Engineering and Project Management Division 3339 Tamiami Trail East, Suite 303 Naples, FL 34112 AECOM 239-278-7996 tel 4415 Metro Parkway Ste. 404 239-278-0913 fax Fort Myers, FL 33916 www.aecom.com Re: NCWRF Pretreatment Facility - Sole Source Waiver Request for Certain Wastewater Process Equipment and Services Dear Matt: The Collier County Public Utilities Department (PUD) operates and maintains the following wastewater treatment facilities: North County Water Reclamation Facility (NCWRF), South County Water Reclamation Facility (SCWRF), Orange Tree Wastewater Treatment Facility (OTWWTF), and Golden Gate Wastewater Treatment Plant (GGWWTP). AECOM Technical Services, Inc. (AECOM) is currently providing professional services for the design and construction of the NCWRF Headworks (Pretreatment) Facility under Contract #20-7722. Continuous and pro -active operation and maintenance of these facilities is required to meet the needs of the public and ensure that the PUD remains in regulatory compliance with Florida Administrative Code Chapter 62-600 (Domestic Wastewater Facilities) and Chapter 62-610 (Reuse of Reclaimed Water and Land Application); as well as other local, state, and federal rules and regulations. To meet these important objectives, the PUD requires that certain items/services be procured in an efficient and cost-effective manner. Accordingly, Attachment 1 includes two wastewater process equipment/service vendors that have been identified as appropriate to require sole source waivers for the proposed NCWRF Pretreatment Facility Specific "Collier County Waiver Request Forms" have been completed for each of these items and reviewed by the County Procurement Department for applicability and sufficiency. Key points of justification for the two specific wastewater process equipment/services included in Attachment 1 are as follows: Each is either currently or proposed to be used in existing PUD wastewater facilities and will provide consistency across multiple installations and/or applications. Each was evaluated as compared to other manufacturers and determined to be the most suitable for the NCWRF Pretreatment Facility application based on superior performance and record of operations and maintenance. Packet Pg. 842 A=COM 16.C.2.b • Each represents an item/service that utilizes high quality materials/capabilities that are consistent with the PUD's use/application and with the municipal wastewater and reclaimed water industry. • Each periodically requires replacement, service parts, kits, interface components, software, service, and support to be procured in a timely manner to maintain and/or quickly restore operations, meet intended service, and remain in regulatory compliance. • Each is unique and/or proprietary in nature and should not be replaced with an alternate product. To use replacement parts form unauthorized sources would void the product warranty and jeopardize the integrity of the primary piece of equipment. • Each individual application of the equipment is tailored to the products physical and operational configuration such that the use of alternate products would require rework to the associated structure, supports, connecting piping and/or electrical systems. • Each has only one local/regional supplier and/or utilizes a supplier's unique capability. In addition, the County has ongoing and trusted relationships with each of these identified suppliers. AECOM agrees that it is critical for the PUD to provide continuous and dependable service to its customers and to remain in regulatory compliance. A key element to providing this level of service is the ability to procure certain items/services dependently, efficiently, and cost effectively. A specific sole source procurement for the two identified wastewater items in Attachment 1 is prudent and responsible; and recommended by AECOM to be in the County's best interest. Sincerely, AECOM Technical Services, Inc. Ulm ` Ronald R. Cavalieri, P.E., BCEE Associate Vice President Packet Pg. 843 16.C.2.b ATTACHMENT 1- SOLE SOURCE WAIVER REQUEST FORM SUMMARY Collier County Public Utilities Department Category Item/Service Vendor Name Sole Source Supplier WASTEWATER PROCESS Screening System Huber Moss Kelley/MKI EQUIPMENT Services, Inc. WASTEWATER PROCESS Grit Removal System Hydro International Moss Kelley/MKI EQUIPMENT Services, Inc. Page 1 of 1 Packet Pg. 844 16.C.2. b �i Co ter CO.14"ty Procurement Services Division Conflict of Interest Affidavit The Vendor certifies that, to the best of its knowledge and belief, the recommendations rendered in support of IiUBER Technology and Hydro International does not pose an organizational, financial conflict or ownership (collectively a "conflict') which calls into question the Consultant's ability to render impartial advice to the government. By the signature below, the firm (employees, officers and/or agents) certifies, and hereby discloses, that, to the best of their knowledge and belief, all relevant facts concerning past, present, or currently planned interest or activity (financial, contractual, organizational, or otherwise) which relates to the recommendations above has been fully disclosed and does not pose a conflict. AECOM Technical Services, Inc. Company Name (gs% , GtA/Mi Signature Ronald R. CavalierL P.E., BCEE — Assoc. Vice President Print Name and Title State of Florida County of Lee The foregoing instrument was acknowledged before me by means of hysical presence or © online notarization, this jaj� day of (month),'? (year), by (name of person acknowledging). Personally Known OR Produced Identification Type of Identification Produced (Signature of Notary Public) (Print, Type, or Stamp Commissioned Name of Notary Public) CHERIE C. wOLTER (490 NotaryPublic- Statt of Florida CommlSsion M NH 061153 My Comm. Expires Nar 16. 2024 Bonded through National Notary a,ssn. Packet Pg. 845 16.C.2.c Car'',9A1'% Engineers... Working Wonders With Water® November 18, 2022 Mr. Wayne Karlovich, P.E. Supervisor- Project Manager Collier County Public Utilities Department 3339 Tamiami Trail E, Suite 303 Naples, FL 34112 2728 North University Drive, Building 2700, Coral Springs, Florida 33065 P.954.837.0030 F.954.837.0035 Subject: Northeast Water Reclamation Facility- Headworks Screening and Grit Removal Design Dear Mr. Karlovich: As part of Amendment 8 to Agreement No.04-3673 Design of the Northeast Water Reclamation Facility (NEWRF) and Water Treatment Plant (NEWTP) project, Carollo is updating the design of the Northeast Water Reclamation Facility completed in 2010 to reflect changes that have occurred since 2010 that require an update to the design. Several workshops were conducted with County staff to discuss the current level of service requirements, original design concepts, new technologies, industry trends, and technology/operational preferences and standardization at existing County treatment facilities. The headworks facility forthe NEWRF will provide preliminary treatment consisting of coarse screening, grit removal, flow equalization, and fine screening. Coarse screens will remove large submerged and floating debris and solids from the incoming raw sewage to prevent damage to downstream equipment and inference with the treatment processes. Grit operations will remove grit and fine sands to reduce wear on downstream equipment and minimize grit/sand accumulating in treatment basins that could reduce treatment capacity. Flow equalization will attenuate flows to equalize hydraulic, organic, and nutrient loading to downstream processes to improve process control and minimize upsets. Fine screens will remove remaining small particles from the flow stream to protect the downstream membranes. As a result of the workshops with County staff and operational requirements for the plant, the following equipment technologies were selected for the design of the plant: • Coarse screens - 6mm multi -rake screens • Fine screens - 2mm rotary drum screens • Grit removal - Stacked tray vortex -type The County is in the process of upgrading the headworks facilities at its existing North County and Central County (Golden Gate) WRFs. The upgrades are designed based on screening equipment manufactured by Huber and grit removal equipment manufactured by Hydro International. To provide for consistency of equipment across the County's facilities, the NEWRF headwork equipment will also be designed with Huber screening equipment and Hydro International grit removal equipment as the basis of design. Carollo has extensive experience with these manufacturers and knowledge of their products in similar installations. 2006441 NEWRF_Headworks_Manf_Ltr.docx WAT E R OUR FOCUS OUR BU OUR P Packet Pg. 846 16.C.2.c Mr. Wayne Karlovich, P.E. Collier County Public Utilities Department November 18, 2022 Page 2 Based upon our experience and professional judgement, the equipment will meet the project performance requirements and provide reliable service. If you have any questions or require any additional information, please contact me at 305-815-4724. Sincerely, CAROLLO ENGINEERS, INC. Brian LaMay, P.E. Preliminary Desig 7ReportTask Lead CC: Craig Pajer, Collier County Bob Cushing, Carollo Dean Milton, Carollo c Packet Pg. 847 16.C.2.c Conflict of Interest Affidavit The Vendor certifies that, to the best of its knowledge and belief, the recommendations rendered in support of HUBER Technology and Hydro International does not pose an organizational, financial conflict or ownership (collectively a "conflict") which calls into question the Consultant's ability to render impartial advice to the government. By the signature below, the firm (employees, officers and/or agents) certifies, and hereby discloses, that, to the best of their knowledge and belief, all relevant facts concerning past, present, or currently planned interest or activity (financial, contractual, organizational, or otherwise) which relates to the recommendations above has been fully disclosed and does not pose a conflict. Carollo Engineers, Inc. Com Name ignature an LaMay, P.E. Print Name and Title State of Florida County of Broward The foregoing instrument was acknowledged before me by means of M physical presence or El online notarization, this // day of Z (month), —1D 23 (year), by 0'r l s-, A A7 (name of person acknowledging). r sOIL! pu LUZ MARINA GONZALEZ Notary Public - State of Florida '•, Q Commission # HH 286786 (St ature otary Pu lic) ovn`' My Comm. Expires Jul 12, 2026 Bonded through National Notary Assn. zaz Personally Known OR Produced Identification Type of Identification Produced , Type, or Stamp Commissioned Name of Notary Public) Packet Pg. 848 16.C.2.d TETRA TECH MEMORANDUM To: Wayne Karlovich, P.E. Supervisor - Project Management of Subregional Utilities From: Tyler Wainright, P.E. Tetra Tech Inc. Date: January 11th, 2023 Subject: Golden Gate MBR Expansion — Screening and Grit Removal Design Background Tetra Tech recently completed the design of a 4 million gallon per day (MGD) expansion of the Golden Gate Wastewater Treatment Plant (WWTP) which includes the conversion of the existing plant to a membrane bioreactor (MBR) treatment facility. The use of MBR's at this facility requires a higher level of screening and grit removal than currently exists at the Golden Gate WWTP. Screens The proposed screening system which has been designed at the Golden Gate WWTP consists of a two -stage screening design. Located at the top of the headworks structure are two (2) mechanically cleaned composite angle bar screens - RakeMax Model 4160x775/6 from Huber Technology, Inc. Further down the process train located immediately prior to the biological treatment tanks are two (2) tank mounted rotating perforated plate screens - Rotamat Perforated Plate Screen RPPS STAR/1800/2 from Huber Technology, Inc. The purpose of these screening systems is to remove large (6mm) and fine (2mm) solids from the influent wastewater prior to treatment. Screening is of particular importance for an MBR system in order to prevent frequent fouling of the proposed membranes. Grit Removal The proposed grit removal system which has been designed at the Golden Gate WWTP consists of two (2) stacked tray grit, sand, and solids separators — the Headcell Grit Removal System by Hydro International. Due to near - coastal location of the Golden Gate WWTP and the type of influent waste streams received at the plant, grit removal will be required for this facility. Similar to screening, grit removal is an important pre-treatment process for MBR facilities. When selecting the proposed screening and grit removal systems at the Golden Gate WWTP, Tetra Tech reviewed a variety of systems and met with multiple suppliers, engineers, and utility operators to review the various manufacturers and systems which are currently available. Based on our review and our prior experience with these units at adjacent local utilities, it is our professional opinion that the selected screens and grit removal systems will provide the County with a high-level of operational performance and are well suited for the proposed application. Resilient Sustainable Infrastructure 10600 Chevrolet Way, Suite 102 Estero FL, 33928 Tel 239.390.1467 tetratech.com Packet Pg. 849 16.C.2.d Should you have any question, please contact us directly at 239-390-1467. Sincerely, Digitally signed by Tyler C Wainright Date:2023.01.11 21:02:11-05'00' Tyler Wainright, P.E. Tetra Tech Inc. Cc: Craig Pajer, P.E., Collier County Corinne Trtan, Collier County TETRA TECH IEW Packet Pg. 850 16.C.2.d Co ter C014"ty Procurement Services Division Conflict of Interest Affidavit The Vendor certifies that, to the best of its knowledge and belief, the recommendations rendered in support of HUBER Technology and Hydro International does not pose an organizational, financial conflict or ownership (collectively a "conflict") which calls into question the Consultant's ability to render impartial advice to the government. By the signature below, the firm (employees, officers and/or agents) certifies, and hereby discloses, that, to the best of their knowledge and belief, all relevant facts concerning past, present, or currently planned interest or activity (financial, contractual, organizational, or otherwise) which relates to the recommendations above has been fully disclosed and does not pose a conflict. Company Name `iQStigeD�e�g. JASEDHINDERSd Notary Public Signature CommissioM Comm. Ex�''Y ! Print Name a(d Title p Pr State of 1t County of The forego ng instru t was ac owledged before me by means of 0 physical presence or, 0 o ine notarization, this - t = day of: month), 20 2-(year), by '-T'Yt 6-IL M IE (name of person acknowledging). Personally Known OR Produced Identification ,F(, ot, W 5 Z 1 -� �) r 36n Type of Identification Produced (Sig�iature of Notary Public) (Print, Type or Stamp Commissioned Name of Notary Public) Packet Pg. 8 1771 AECOM 4415 Metro Parkway Ste. 404 Fort Myers, FL 33916 www.aecom.com 239-278-7996 tel 239-278-0913 fax January 13, 2023 Matt McLean, P.E. Division Director Collier County Public Utilities Department Engineering & Project Management Division 3339 Tamiami Trail East, Site 303 Naples, FL 34112 Re: NCWRF Pretreatment Facility - Sole Source Waiver Request for Certain Wastewater Process Equipment and Services – Engineer’s Evaluation Dear Matt: AECOM technical Services, Inc. (AECOM) previously provided a Letter to Collier County dated November 17, 2022 recommending a sole source procurement for two wastewater process equipment items, which included Huber DSL Fine Screens and Headcell grit removal system furnished by Hydro International. As noted in the Letter, each was evaluated as compared to other manufacturers and determined to be the most suitable for the NCWRF Pretreatment Facility application based on superior performance and record of operations and maintenance. While a formal technical memorandum or presentation were not prepared, AECOM completed an informal evaluation of the recommended equipment. A summary of AECOM’s evaluation and technical justification for sole source procurement of the equipment is provided below: Huber DSL Fine Screens High throughput capacity while maximizing separation efficiency Provides for in-channel installation, maximizing odor containment via covers and does not require additional wastewater pumping Quality construction with high quality materials to maximize equipment life and minimize O&M costs Suitable for future conversion of downstream process to MBR Ability for future conversion from 2mm screening to 1mm screening as required to accommodate future downstream process needs Only rotary drum screen in the 1mm category with capacity to pass design flow with proposed (3 plus 1) layout. Equipment design minimizes headloss through unit resulting in more efficient overall headworks configuration Headcell Grit Removal Only unit identified that was capable of meeting all performance criteria as dictated in the County design criteria package (DCP) Compact unit to minimize space requirements was necessary to fit within available space Equipment design accommodates high turndown ratio expected at the NCWRF Headloss through this equipment is minimized resulting in more efficient overall headworks configuration Quality construction with high quality materials and no moving parts within vessel to maximize equipment life and minimize O&M costs Independently proven grit removal performance in the industry and used in other AECOM projects across the country Please contact me if you have any questions or if you require any additional information. Sincerely, AECOM Technical Services, Inc. Ronald R. Cavalieri, P.E., BCEE Associate Vice President WEFTEC 2014 Relative Performance of Grit Removal Systems B. McNamaral, M. Sherony*2, and P. HerricP rHampton Roads Sanitation District,40l Lagoon Road, Norfolk, VA 12505, USA 2Hydro International,2925 NW Aloclek Drive #140, Hillsboro, OR 97l24,IJSA msherony(@h)rdro - i nt. c om ABSTRACT Grit is a nuisance material that causes abrasive wear to mechanical equipment increasing maintenance and operational costs while reducing equipment performance and useful life. Grit that is not captured in the headworks accumulates in processes throughout the plant, reducing capacity and detention time, and adversely influencing flow and circulation patterns2. Deposited grit must be manually removed, handled, hauled and disposed. Abrasive wear, process inefficiencies and basin cleaning operations increase treatment plant operating expenses. Choosing a grit removal technology has often been based on equipment price with little regard for device efficacy and consequent grit removal efficiency. The industry has lacked an unbiased side-by-side comparison of the currently available technologies. As a result, owners and engineers are forced to navigate a field of, what can be conflicting, performance claims made by various equipment manufacturers. This situation is perpetuated by the fact that there is no accepted, peer reviewed test standard for grit sampling and analysis. The purpose of this paper is to encapsulate various grit removal system performance data generated by a consistent and repeatable sampling and analysis methodology for the purpose of comparing virtually all grit removal technologies in terms of their effectiveness. Results determined with this sampling method corroborates with the operating history and performance at the tested plants with respect to grit removal, suggesting the accuracy of the test method6 The data provides an unbiased side-by-side comparison of the actual performance of grit technologies based on a repeatable sampling and analysis methodology that owners and engineers can utilize to protect plants from deposition, abrasive wear and associated costs from this nuisance material. Keywords: Grit, removal efficiency, aerated grit basin, mechanically induced vortex unit, stacked tray system, structured flow unit, detritus tank, test methodology, grit sampling, surface loading rate INTRODUCTION Biological processes continue to evolve toward better effluent quality in a smaller footprint. The current trend of housing these processes and systems in smaller and smaller footprints imply an inherent inability to store grit and debris. Treatment plants now operate with reduced numbers of maintenance and operations staff, which in turn is resulting in significant reductions in the available resources and time to tackle and address the negative impacts of grit and debris. Copyright @201 4 Water Environment Federation 4919 WEFTEC 2OI4 Headworks screening and grit removal are the primary protection for all treatment processes and equipment in a wastewater treatment plant, yet it has been the most neglected part of the plant. To improve solids removal, screen openings on influent screens have trended progressively smaller over the past I 0- I 5 years. Years ago, screen openings were frequently 25 mm ( I ") and larger. Today, screens are commonly supplied with 6 mm(/o") openings. It is logical that advancing grit removal processes, to effectively remove incoming grit, are becoming a higher priority in plant designs. Selecting grit removal technologies can be a challenge due to the lack of comparative performance data available within the wastewater industry. Owners and engineers are forced to navigate a field of, what can be conflicting, performance claims made by various equipment manufacturers. This situation is perpetuated by the fact that there is no accepted, peer reviewed test standard for grit sampling and analysis. As there are no Standard Methods for the comprehensive measurement and analysis of sampled grit, most parties utilize conventional ASTM D-422 to obtain the physical particle size distribution of grit collected by various means. Standard Method 2540 for solids testing is used for determining Total, Fixed, and Volatile Solids. A method that Engineers and Owners have found effective, splits the sample with half being tested via ASTM D-422 and the other half being wet sieved and characteized based on settling velocity3. tn addition to physical size distribution, settling velocity is often the most important and useful criterion in grit system design. Settling velocity is central to grit system design as technologies used to collect influent grit are predominantly sedimentation processes2. Sedimentation basins and aerated grit basins (AGB) are recognized as gravity processes. Vortex processes utilizing a forced vortex type flow regime also rely predominantly on gravity for separation. When the force balance on a particle is evaluated within a forced vortex type flow regime in a basin, gravity is shown to be the predominant force, well in excess of the centrifugal forces generated by slow rotational velocity. While settling velocity is an important criterion in grit system design, the removal efficiency data presented in this paper is based on particle size distribution alone and does not consider settling velocity. Settling velocity is discussed elsewherea. As most performance guarantees are based on2.65 specific gravity (SG) it is worth noting that measured performance can vary widely from performance claims. While some of the variance is certainly attributed to the SG of grit being less than 2.65 and other factorsa, wide variations from performance claims are likely influenced by other factors such as short circuiting and/or inaccurate sizing. METHODOLOGY Effective test methodology must provide accurate, consistent, repeatable and reproducible results. One of several grit sampling methods used by owners and engineers is the vertical slot sampler (VSS) The VSS is designed to draw off a known vertical slice of the influent water column to provide an accurate sample of incoming solids. Although not detailed in ASTM manuals or Standard Methods, sampling using the VSS has been found to produce results that are repeatable, effective and allow efficiency comparisons at different treatment plantss. Further, Copyright 02014 Water Environment Federation 4920 WEFTEC 20I4 results determined with the VSS corroborates with the operating history and performance at those plants with respect to grit removal, suggesting the accuracy of the test method6. This same test methodology can be used for comparison of grit removal efficiency of various technologies. The VSS methodology used in the referenced studies provides a repeatable sampling and analysis methodology that allows for the relative comparison of removal efficiency for different devices. The test methodology typically includes a margin of error of +l- 5%o and is described eslewhere3's. Data collected and presented herein has been made available in various industry publications and reports as cited. Hampton Roads Sanitation District (HRSD) performed comprehensive testing at five of their wastewater treatment plants in2007 and 2008 utilizing the VSS sampling method. The equipment tested included three different mechanically induced vortex systems (MIV), a Detritus tank system and an aerated grit system (AGB)5. During the same period, HRSD conducted a side-by-side pilot test comparing the stacked tray Eutek HeadCell@ unit and the structured flow Grit King@ unit. Both systems were tested for removal efficiency using the VSS sampling methodT. Data collected on the HRSD AGB has been excluded from this paper. During the above referenced testing, which was performed on dry weather flows, it was determined that the grit was settling in the force main as there was not sufficient energy in the collection system to transport grit to the plant. At peak diurnal flows the velocity in the force main was 0.5 m/s (1.7 fps), when 0.9 - 1.5 m/s (3.5-5.0 fps) is needed to re-suspend settled solids and grit6. Therefore, data from testing on the AGB was inconclusive. However, the same collection and analysis methodology was used in Columbus GA on an AGB, that data is included in this paper. This paper provides removal efficiency, utilizing identical and consistent sampling and analysis methodology, of virtually every type of grit removal technology, thus allowing comparison of removal efficiency of these technologies. The processes represented include AGB, vortex grit removal systems, and detrifus tanks. The vortex units include mechanically induced vortex (MIV) units, stacked tray units and structured flow vortex units. RESULTS Mechanically Induced Vortex (MIV) Units HRSD Chesapeake-Elizabeth Treatment Plant The Chesapeake Elizabeth Treatment Plant (CETP) is a 9l ML/d (24 MGD) capacity plant operating with an average flow of approximately 72MLld (19 MGD). Grit removal equipment consists of two (2) 7.3 m (24') diameter MIV units, one unit was in operation during the study. Design removal parameter for each unit is 95%o removal of 150 pm particles,2.65 SG, at I 14 ML/d (30 MGD), and95o/o removal of 270 pmparticles,2.65 SG, at 265MLld (70 MGD). Average flow during testing was 71.1 ML/d (18.79 MGD), which is well below the rated capacity of the grit unit. The measured removal efficiency was 48-52%o of all grit I 50 pm and larger and 45-50% of all grit 106 micron and larger. Removal efficiency of particles > 297 microns, a slightly larger particle than the performance claim, was 72-78o/o or roughly 20% less than the claimed removal. Copyright 02014 Water Environment Federation 4921 WEFTEC 20I4 Table #l Removal of MIV HRSD Virsinia Initiative Plant The Virginia Initiative Plant (VIP) is a l5l ML/d (40 MGD) capacity plant with an average flow of approximately I l0 ML/d (29 MGD). The plant employs three 6.1 m (20 ft) diameter MIV units, one unit was in operation during the study. The vortex manufacturer states that each unit will remove 65% of 150 pm git,2.0 SG, at l0l ML/d (26.7 MGD). Average flow during three days of testing was 99.2I|lf'Lld (26.23 MGD), very near the rated capacity of the grit units. The measured removal efficiency was 43-45o/o of all grit I 50 pm and larger, 20% below the claimed efficiency, and 43-44o/o of all grit 106 micron and larger. Table #2 Removal of MIV Detritus Tank HRSD James River Treatment Plant The testing at HRSD included testing at the James River Treatment Plant (JRTP) which operates detritus tanks for grit removal. The JRTP is aT6MLld (20 MGD) capacity plant with an average flow of approximately 49l|l{Lld (13 MGD). The JRTP employs four detritus tanks. Each detritus tank is 8.5m (28') diameter with a design capacity of 24.6 ML/d (6.5 MGD). Each unit is designed to remove grit particles 150 pm and larger, with 2.65 SG. Average flow to the plant during three days of testing was 48.75 ML/d (12.88 MGD) with one of the detritus tank units out of service; therefore each unit was processing approximately 16.27 }dLld (4.3 MGD) or %o Removal Efficiency CETP #50 Mesh (>297 microns) #70 Mesh (<297 microns >2ll microns) #100 Mesh (<2tt microns >150 microns) Total o/o Removal 150 pm and up Total %6 Removal 106 pm and up Thu. May 17,2007 72.6 l9.t 7.0 48. I 45.8 Fri. May 18,2007 77.8 28.9 14.7 52.1 50.9 o/o Removal Efficiency VIP #50 Mesh (>297 microns) #70 Mesh (<297 microns >2ll microns) #100 Mesh (<2tt microns >150 microns) Total o/o Removal 150 pm and up Total o/o Removal 106 pm and up Sun. May 20,2007 57.7 29.8 22.7 4s.3 44.3 Mon. May 21, 2007 60.5 26.8 23.2 45.1 43.7 Tue. May 22,2007 59.3 33.2 27.9 43.3 43.3 Copyright @2014 Water Environment Federation 4922 WEFTEC 2OI4 roughly 33% below their rated capacity. The measured removal efficiency was 66-730/o of all grit I 50 pm and larger and 57 -680/o of all grit 106 micron and larger. Table #3 Removal of Detritus Tank Aerated Grit Basin Columbus GA South Water Reclamation Facilitv The City of Columbus, GA South Water Reclamation Facility (SWRC) operates four AGB units that receive a combined average daily flow of approximately 106 ML/d (28.0 MGD). A rain event occurred on January 28'h,2008 resulting in an increase in the flow to 143.84 ML/d (38 MGD) with a maximum hourly flow of 185.5 ML/d (49 MGD). As can be seen from the results below, when the flow to the grit chamber increased the removal efficiency decreased, as would be expected. The plant has two AGB that are 5.l8m x I 1.89m (17' x 39') and two basins 3.96m x 10.97m ( l3' x 36'). While no design removal efficiency data exists, total surface area available for grit settling is 210 m2 12,262 ft2). Based on the average flow of 106 ML/d (28.0 MGD), the AGB system has a surface loading rate (SLR) of 0.35 m3/min./m2 (8.6 gprr/ft2) and would be expected to remove a significant percentage of fine particles, 106 micron and below. The plant notices a decrease in removal efficiency at flows in excess of 132.5 ML/d (35 MGD). Once the flow reaches 132.5 MLld (35 MGD) the SLR increases to 0.435 m3lmin.lr* (10.7 gpn/ft2). Based on SLR alone the basin would still be expected to retain a percentage of fine particles at 132.5 ML/d (35 MGD) with particle size retained increasing, and overall capture efficiency decreasing, as flow continues to rise. The measured removal efficiency was 35-70o/o of all grit I 50 pm and larger and 32-670/o of all grit 106 micron and larger when the wet weather data is included. Removal efficiency improves to 58-70o/o of all grit 150 pm and larger and 53-67% of all grit 106 micron and larger during average flow of 106 ML/d (28.0 MGD). While excluding the performance during the wet weather event indicates improved performance, removal efficiency is well below what would be expected based solely on SLR. Copyright @2014 Water Environment Federation 4923 o/o Removal Efficiency #70 Mesh (<297 microns >2ll microns) #100 Mesh (<2tt microns >150 microns) Totalo/o Removal 150 pm and up Total o/o Removal 106 pm and up JRTP #50 Mesh (>297 microns) 72.6 4t.7 66.2 57.3Sun. Jun 17,2007 8l.8 73.2 67.7Mon. Jun 18,2007 76.9 77.2 66.6 71.2 64.2Tue. Jun 19,2007 82.6 74.7 55.3 WEFTEC 2OI4 Table #4 Removal of Aerated Grit Basin Stacked Tray System HRSD Army Base Treatment Plant While considering a new grit system for their Army Base Treatment Plant (ABTP), HRSD tested two grit removal technologies side-by-side in December of 2007. The stacked tray Eutek HeadCell@ unit was tested side-by-side a Grit Kiog* structured flow unit using the same sampling and testing methodology. During the pilot test the stacked tray HeadCell unit was fed at 38.6-38.8 m3ftr 1t 70-17l gpm). At that flow rate the Stacked Tray unit was designed to remove 95o/o of all grit75 micron and larger, with2.65 SG, however performance was not tested for 7 5 micron particles. The measured removal efficiency was 92-93o/o of all grit I 50 pm and larger and89-90%o of all grit 106 micron and larger. Table #5 Removal of Stacked Structured Flow System HRSD Army Base Treatment Plant During the side-by-side testing at the ABTP the 1.2 m (4') diameter structured flow Grit King pilot unit was fed at a rate of 38.8 m3/tr (170 gpm) on December 17ft and25.4 m3ltr 1t l2 gpm) on December 19m. Design removal parameter at the higher flow is95%o of all grit 106 micron and larger, 2.65 SG. At the lower flow of 25.4 m3lhr 1t l2 gpm) the removal would be expected tobe 95Yo of all grit 75 micron and larger, 2.65 SG, however removal efficiency for 75 micron particles was not reported. As would be expected, the removal efficiency improves at the lower flow rate as loading rate to the unit is reduced. The measured removal efficiency was 90-95% of all grit 150 pm and larger and87-93oh of all grit 106 micron and larger. o/o Removal Efficiency Columbus #50 Mesh (>297 microns) #70 Mesh (<297 microns >211 microns) #100 Mesh (<2tt microns >150 microns) Totalo/o Removal 150 pm and up Total o/o Removal 106 pm and up Jan27,2008 81.8 49.8 42.2 70.5 67.2 21.7 32.5Jan 28, 2008 53.0 13.s 3s.6 Jan29,2009 66.3 60.0 44.4 58.7 53. r o% Removal Efficiency Stacked Tray #50 Mesh (>297 microns) #70 Mesh (<297 microns >2ll microns) #100 Mesh (<2ll microns >150 microns) Total%o Removal 150 pm and up Total%o Removal 106 pm and up Dec 17,2001 95.8 90.4 8l.s 91.9 88.8 Dec 19,2001 95.7 93.0 85.6 92.5 89.3 Copyright @2014 Water Environment Federation 4924 WEFTEC 2OI4 Table #6 Removal of Structured Flow Vortex Unit DISCUSSION As can be seen from the above data, testing results for the mechanically induced vortex technology were considerably below the manufacturers' claimed removal efficiency even when running the unit well below design flows. The testing results indicate this technology had its highest measured removal efficiencies for large grit particles, approximately 600/o+ removal of particles larger than297 micron, and very low performance removing smaller particles, with less than30o/o removal of particles 210 micron and smaller. At CETP the MIV was designed to remove95o/o of grit 150 micron and larger, with 2.65 SG at a flow of I l4 ML/d (30 MGD). When operating at63%o of the design flow (71.1 ML/d (18.79 MGD), the measured removal efficiency of grit particles 150 microns and larger was 48-52%o, which is more than 40o/o less than the stated claim. The 7.3 m (24') diameter MIV unit has a surface area of 47.83 m2 (452 ft\, which results in an estimated SLR of 1.18 m3lmin.lnf (28.97 gprn/ft, at 7 | .l ML/d ( I 8.79 MGD). Based on the SLR the MIV technology would, in theory, be expected to retain a large percentage of particles approximately 165 micron and larger. The measured removal efficiency for much larger particles, 297 microns and larger, was only 72- 78%. The low removal efficiency suggests the importance of considering the likely effects of grit settling velocity and other criteria. Based on operational data from VIP it was found that placing more vortex units into service improved grit removal. During 2007 the plant averaged99 ML/d (26.2MGD) and used one vortex unit 83% of the year. For 2008, two vortex units were in service for 75%o of the year and grit production increased 50% over 2007 performance. HRSD determined that operating a vortex close to the maximum rated hydraulic efficiency may not be advisable for some treatment plants. Further they concluded that with this technology placing additional grit removal units in service during high hydraulic events can minimizethe impacts of grit slug loads on downstream unit processes. While test data indicates the Detritus tank achieves higher removal efficiency than the MIV technology, the Detritus tank also fell short of design removal efficiency while operating at 660/o of design flow. Test data shows relatively high removal efficiencies of large grit particles,TToh+ removal of particles larger than297 micron and, as would be expected, reduced capability of removing smaller particles, 640/0+ removal of particles 210 micron and smaller. Although an Copyright @2014 Water Environment Federation 4925 o/o Removal Efficiency Structured Flow #50 Mesh (>297 microns) #70 Mesh (<297 microns >2ll microns) #100 Mesh (<2tt microns >150 microns) Total%o Removal 150 pm and up Total%o Removal 106 pm and up Dec 17, 2007 93.6 89.4 78.7 90.3 87.s Dec 19, 2007 - rtz gpm 97.4 94.3 89.0 95.0 92.7 WEFTEC 20I4 older style technology, sampling and analysis for the detritus tank displayed some of the higher removal efficiencies of the technologies tested. Removal efficiency would be expected to decline at peak design flow. The AGB results were comparable to those for the Detritus tank during the plant average flow, 58-670/o of all grit 106 microns and larger was removed. During wet weather when the system received the design flow rate, removal efficiency was reduced to 32.5yo. Even considering the small increase in flow during the rain event, which was in the region of 135-175% of average, the quantity of grit increased substantially from 3.36 glm3 (28.1 lbs./MG) to 8.89 glm3 (14.2 lbs./MG). The fraction of grit smaller than297-microns also increased significantly. The increased grit quantity and elevated fraction of small grit resulted in the measured poor removal efficiencies. A reduction in removal efficiency at higher flows is expected, however, during the elevated flow, influent grit concentration also increased by a factor of more than 2.5 times the prior day dry weather influent levels. A removal efficiency of 32-35o/o of the heavier grit load will obviously not be adequate to protect the plant from deposition and abrasive wear. The stacked tray system and structured flow unit test results exhibited very high removal rates. While the performance results for these two technologies were performed as a pilot study they are consistent with full scale performance tests, using the identical test method, at other facilities8,e. Measured removal efficiency for both technologies was slightly below manufacturers claimed removal efficiencies, within +l- 8%. This small deviation is very near the margin of error in testing. Comparatively, these two technologies provide very high removal efficiencies of large grit particles, g3o/o+ removal of particles larger than 300 micron. The measured removal efficiency of particles 150 - 210 micron was only slightly less and ranged from 78-90%+. Both of these technologies displayed the highest removal efficiency of the technologies tested, in all cases >87 .5o/o of all influent grit 1 06 micron and larger was captured. CONCLUSIONS Grit sampling using the VSS method produces results that are repeatable, accurate and effective. The results corroborate with grit system performance and plant operating history therefore this data provides insight into what most operators' experience. Using this common testing method allows comparison of performance of various grit removal technologies and can assist in improving grit system design and justifuing advanced processes. Table #7 Relative Performance of Grit Removal Devices Copyright 02014 Water Environment Federation 4926 Technology % of Design Flow Design Removal Efficiency at l00o/o Flow Measured Total % Removal 150 um and up Measured Total % Removal 106 lrm and up MIV 27-90 95oZ removal of 270 pm,2.65 SG 650lo removal of 150 pm,2.0 SG 43-s2 43-50 Detritus Tank 66 150 pm and larger, 2.65 SG 66-71 57 -68 AGB 66 -100 Unknown 35-70 32-67 Stacked Tray 100 95olo removal of 75 um,2.65 SG 9t-92.5 89-90 Stmcrured Flow Vortex 66- I 00 95o/o removal of 106 um,2.65 SG 90-95 87 -93 WEFTEC 2014 Based on the reported and referenced testing, the technologies that displayed the lowest removal efficiencies were the AGB and the MIV technology. The measured removal efficiency for both technologies was well below claimed removal at peak flows. The AGB displayed a relative removal of only 32Yo of all grit 106 micron and larger when operated at peak design flow. Results for the AGB improve to 53-670lo when influent flow to the unit is reduced to 660/o of design. The MIV technology removed 43-51% of incoming grit 106 micron and larger when operated at 27-90% of design flows. As is true of all SLR based technologies, the MIV technology shows higher removal efficiencies at lower flows. When operating near design flow rate, removal efficiency was in the 43-45o/o range for all grit 106 micron and larger. As flows decrease, to 63oh of average flow and l2o/o of peak flow, the efficiency increases, but only marginally, to 45-50o/o removal of grit 106 micron and larger. The detritus tank displayed a higher removal rate, removing 57 -690/o of all grit 106 micron and larger when operating at average flows, in the region of 66%o of peak design flow. The AGB displayed similar results when operated at 66oh of peak flow. When flows increased to peak, the AGB removal efficiency dropped to 32o/o and the detritus tanks would be expected to have similar results as flows increase. The structured flow vortex and stacked tray vortex units had very high removal rates, none lower than87.5o/o of incoming grit 106 micron and larger. These results are significantly (20%to 55%o) higher than any of the other technologies tested. Over the life of the facility, the difference in captured grit is substantial. Also of note, is the fact that high removal results were achieved with the equipment running at peak design flow. None of the technologies tested met their performance claim exactly, although the technologies that targeted the finest particles displayed the best results and came closest to achieving their performance claim. Systems designed for high removal efficiency of small particles, 106 micron and finer, should remove 85% or more of grit entering the plant. The measured decrease in performance with increased flows provides strong evidence that the tested technologies are strongly influenced by loading rate and gravity to capture and retain grit. A better understanding of in situ grit settling velocity will allow for more efficient design which would afford the plant increased protection from abrasive wear and deposition. Wet weather is an important consideration in grit system design. The impact of wet weather flows was documented during testing of the ABG in Columbus, GA. Considering the small increase in flow during the rain event, 135-160% of average, the quantity of grit increased much more dramatically, to more than}.S times the volume entering the plant during the prior day average flow. One would expect the greatest increase would be of coarse grit particles but the o,r..ull gradation was finer. Grit quantities increased across all size ranges but the grit fraction Copyright 02014 Water Environment Federation 4927 WEFTEC 20I4 larger than297 micron decreased, from 61 .7%o to 39.0o/o, while particles in the 105-210 micron range increased from 20.6% to 39.7%o of the total. Overall, a 60%o increase in flow resulted in a 48Yo decrease in performance. Significant increase in grit volumes during wet weather events is a common phenomenonlO and indicates the need to design the grit system for effective removal at peak hydraulic loadings. The AGB and MIV performed poorly at peak design flow and based on the data the detritus tank would be expected to perform similarly to the AGB. Measured removal efficiencies were less than what would be expected based on SLR alone indicating process inefficiencies or grit settling velocity implications. Designing the grit removal system for high removal efliciency at peak hydraulic loading will protect the plant from the negative impacts of grit. Advanced, compact, high-efficiency grit removal processes are therefore the more appropriate proven choice to protect plants from deposition, abrasive wear and associated costs from this nuisance material. ACKNOWLEDGEMENTS The authors would like to thank Mr. Cliff Arnett, Senior Vice President, Columbus Water Works and Mr. Mike Taylor, Superintendent, Columbus Water Works, South Columbus Water Resources Facility for permission to use data from their testing and providing the additional information needed to compile the comparisons. REFERENCES l. Cote, Brink and Adnan (2006) Pretreatment Requirements for Membrane Bioreactors. WEFTEC 2. Sherony, Herrick, (2011) A Fresh Look at an Old Problem. Design Criteria for Effective Grit Removal. New England Water Environment Association Journal, Spring 201I 3. https : //blackdoqanal).tical. corn/Methods. html (July 20 I 2) 4. Osei, Gwinn & Andoh. (2012) Development of a Column to Measure Settling Velocity of Grit. World Environmental & Water Resources Congress 2012 Conference Proceeding Paper 5. McNamara, Griffiths & Book. (2009) True Grit. A Grit Removal Efficiency Investigation at Five Wastewater Treatment Plants. WEFTEC Conference Proceedings 6. McNamara. (2010) True Grit. The Conduit, Virginia Water Environment Association Winter 2010 7. McNamara, Kochaba, Griffiths & Book (2009) Grit vs. Grit. A Pilot Evaluation Comparing Two Grit Removal Technologies. WEFTEC Copyright O2014 Water Environment Federation 4928 WEFTEC 2OI4 8. Horton. (201l) Yellow fuver Grit Selection - Gwinnett County. Georgia Water Professionals 201I Annual Conference and Expo, Conference Session 9. McKimm & Creed. (2007) Pump Station 4259 Grrt Removal System Replacement Project WR444159 at the Marine Corps Air Station, Cherry Point, NC Performance Testing Report 10. New York State Department of Environmental Conservation, Technology Transfer Document, Wet Weather Operating Practices for POTWs with Combined Sewers Copyright O20l 4 Water Environment Federation Performance Evaluation HRSD Army Base WWTP Norfolk, VA Prepared for: Hydro International 2925 NW Aloclek Drive Suite 140 Hillsboro, OR 97124 Prepared by: Black Dog Analytical, LLC 2401 E. 2659th Road Marseilles, IL 61341 May 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 ii TABLE OF CONTENTS 1.0 INTRODUCTION AND OBJECTIVES ............................................................... 1-1 2.0 METHODS AND MATERIALS .......................................................................... 2-2 2.1 Obtaining Representative Grit Fixed Solids (FS) Sample ............................. 2-2 2.2 Determination of Grit Particle Distribution .................................................... 2-6 2.3 Determination of Sand Equivalent Size (SES) Distribution .…………...….. 2-6 2.4 Sand Equivalent Size Description...………………………………………...…...2-7 2.5 Solids Analysis ................................................................................................. 2-9 3.0 DISCUSSION OF RESULTS: TRIAL NO. 1 ................................................... 3-10 3.1 Distributional Data ......................................................................................... 3-11 3.2 Settling Velocity Data ..................................................................................... 3-13 3.3 Performance Evaluation ................................................................................ 3-15 4.0 DISCUSSION OF RESULTS: TRIA NO. 2 ..................................................... 4-16 4.1 Distributional Data ......................................................................................... 4-16 4.2 Settling Velocity Data ..................................................................................... 4-18 4.3 Performance Evaluation ................................................................................ 4-20 5.0 CONCLUSIONS .............................................................................................. 5-21 6.0 BIBLIOGRAPHY ............................................................................................. 6-22 LIST OF APPENDICES Appendix A Raw Data A-1 Concentration Calculation Spreadsheet A-2 Solids Analysis Bench Sheets A-3 Grit Concentration Calculation Bench Sheet A-4 SES Data Analysis A-5 SES Charts A-6 Median SES versus Median Physical Size Appendix B Calculations GRIT STUDY – ARMY BASE WWTP MAY 2016 iii LIST OF FIGURES Figure 2.1 Headcell Influent Sampling Site ............................................................................ 2-2 Figure 2.2 Headcell Effluent Sampling Site/Sampler …………….…………………………………………2-2 Figure 2.3 PVC Splitter and Valve ………………………………..……………………………….…………..… 2-2 Figure 2.4 Grit Settler ……………………………………………..…..……………………………….……..……. 2-5 Figure 2.5 Seed Sand Addition ………………………………..…..……………………………….……..……. 2-5 Figure 2.6 Modified Imhoff Cone for SES Measurements …..……………………..………………... 2-7 Figure 2.7 Physical Size versus Sand Equivalent Size: Cumulative Distributions ................. 2-8 Figure 3.1 Army Base WWTP Flow Data ……………………………………………………………..…….. 3-10 Figure 3.2 Fractional Distribution of Grit at the Army Base WWTP: Trial No. 1 North Unit – April 18, 2016 ………………………………………….……………………………………..……... Error! Bookmark not defined.11 Figure 3.3 Cumulative Distribution of Grit at the Army Base WWTP: Trial No. 1 North Unit – April 18, 2016 ………………………………………………………………………….………….…. 3-12 Figure 3.4 Concentrations of Grit at the Army Base WWTP: Trial No. 1 North Unit – April 18, 2016 ……………………………………………………………………………………..…. 3-12 Figure 3.5 Comparision of the Army Base WWTP North Headcell Influent Grit Physical Size and Sand Equivalent Size: April 18, 2016 ....................................................... 3-13 Figure 3.6 Comparision of the Army Base WWTP North Headcell Effluent Grit Physical Size and Sand Equivalent Size: April 18, 2016 ....................................................... 3-14 Figure 3.7 Median Size Distribution of Grit at the Army Base WWTP vs. a Clean Sand Distribution: April 18, 2016 .............................................................................. 3-14 Figure 4.1 Fractional Distribution of Grit at the Army Base WWTP: Trial No. 2 North Unit – April 19, 2016 ………………………………………….……………………………………..……... 4-16 Figure 4.2 Cumulative Distribution of Grit at the Army Base WWTP: Trial No. 2 North Unit – April 19, 2016 ………………………………………………………………………….………….…. 4-17 Figure 4.3 Concentrations of Grit at the Army Base WWTP: Trial No. 2 North Unit – April 19, 2016 ……………………………………………………………………………………..…. 4-17 Figure 4.4 Comparision of the Army Base WWTP North Headcell Influent Grit Physical Size and Sand Equivalent Size: April 19, 2016 ....................................................... 4-18 Figure 4.5 Comparision of the Army Base WWTP North Headcell Effluent Grit Physical Size and Sand Equivalent Size: April 19, 2016 ....................................................... 4-19 Figure 4.6 Median Size Distribution of Grit at the Army Base WWTP vs. a Clean Sand Distribution: April 19, 2016 .............................................................................. 4-19 LIST OF TABLES Table 2.1 Sieve Size Equivalents ............................................................................................... 2-6 Table 3.1 Headcell Performance Evaluation Sampling Period: April 18, 2016 ................. 3-10 Table 3.2 Predicted Removal Efficiencies (%) of a System Designed to Remove Grit of a Specific SES at the Army Base WWTP: April 18, 2016 ....................................... 3-13 Table 3.3 Fractional Removal Efficiencies of the Army Base North Headcell: April 18, 2016 - Trial No. 1 ……………………………………………………………………………………………….… 3-10 Table 4.1 Headcell Performance Evaluation Sampling Period: April 19, 2016 ................. 4-16 Table 4.2 Predicted Removal Efficiencies (%) of a System Designed to Remove Grit of a Specific SES at the Army Base WWTP: April 19, 2016 ....................................... 4-18 GRIT STUDY – ARMY BASE WWTP MAY 2016 iv Table 4.3 Fractional Removal Efficiencies of the Army Base North Headcell: April 19, 2016 - Trial No. 2 ……………………………………………………………………………………………….… 4-20 Definitions and Abbreviations Acronym Definition gpm Gallon(s) per minute Grit A settleable inorganic kernel with attached organics larger than 50 microns and characterized by physical size and settling velocity Grit Concentration The amount of grit present in the waste stream based on the fixed solids measurements Grit Fixed Solids (FS) Also expressed as “fixed solids” - the inorganic portion of sample remaining after organics are removed by ashing in a muffle furnace at 550oC lbs/MG Pounds per million gallons MG Million gallons MGD Million gallons per day NR1 The Reynolds number for the trial SES NR2 The Revised Reynolds number SAA Surface Active Agents - – material affixed to the grit particle, such as organics, fats, oils, and greases that may affect the settling velocity of municipal grit Sample All material accumulated in the bottom of the grit settler which includes settleable organics Sand Equivalent Size (SES) The sand particle size, measured in microns, having the same settling velocity as the selected grit particle Sed h, cm The height of water in the Imhoff cone through which the sediment passed to reach the surface of accumulated material during SES determination Sed Time, sec The time required for sediment to reach the recorded volume during SES determination Sed. Vol., cc Sedimentation Volume (cc or ml) – The amount of material that settles in the Imhoff Cone during SES determinations SES, dl, u Trial Sand Equivalent Size, in microns VIS Vertically Integrated Sampler Vol Frac, % The cumulative sedimentation percentage occurring during SES determination WWTP Wastewater Treatment Plant GRIT STUDY – ARMY BASE WWTP MAY 2016 1-1 1.0 INTRODUCTION AND OBJECTIVES The Hampton Roads Sanitary District of Virginia is assessing the performance of a Headcell grit collector at their Army Base Wastewater Treatment Plant (WWTP). Results will determine if the unit meets guaranteed performance specifications. In conventional grit removal system design, grit has commonly been treated as clean sand with a specific gravity of 2.65. Metcalf and Eddy’s Wastewater Engineering: Treatment and Reuse (standard textbook) says “Grit consists of sand, gravel, cinders, or other heavy materials that have specific gravities or settling velocities considerably greater than those of organic particles”. These inorganic solids are often associated with Surface Active Agents (SAA) that include fats, oils, greases, and other organic materials can lower their effective specific gravity to 1.3 (Tchobanoglous 2003). The shape and composition of grit and inert solids also greatly affects settling velocities. Material with similar effective specific gravities may have very different settling velocities due to the shape of the particle. When determining quantities of grit during this study, grit will be defined as settleable inorganic material larger than 50 microns. Settling velocities, attached organics and SAA have been considered during the on-site laboratory analyses. The settling velocity is expressed as the Sand Equivalent Size (SES), which is the sand particle size having the same settling velocity as the more buoyant grit particle. Materials less than 50 microns in size have been considered silt or clay and thus excluded from the data. Objectives The purpose of this study was to assess the removal efficiency of the newly installed grit removal system under normal flow conditions. GRIT STUDY – ARMY BASE WWTP MAY 2016 2-2 2.0 METHODS AND MATERIALS 2.1 Obtaining Representative Grit Fixed Solids (FS) Sample Sampling segments were defined as two (2) two-hour trials conducted on consecutive days. Trials were initiated when flows stabilized after the peak morning climb. Influent samples were collected by securing Vertically Integrated Sampler in the channel close to the Headcell inlet chute. (Figure 2.1). A VIS is designed to collect a homogenous sample of grit from the entire height of the water column. The sampler was plumbed to a two-inch gas powered trash pump and sample was drawn continuously by the pump throughout each study period. Flow exiting the trash pump was returned to the South Headell that was not in service. Headcell effluent samples were collected with a weir sampler, providing sampling ports at four locations across the length of the Headcell effluent weir (Figure 2.2) Figure 2.1 Headcell Influent Sampling Site GRIT STUDY – ARMY BASE WWTP MAY 2016 2-3 Figure 2.2 Headcell Effluent Sampling Site/Sampler GRIT STUDY – ARMY BASE WWTP MAY 2016 2-4 A portion of the sample collected by the trash pump was diverted to a grit settler. A PVC wye was used to split the flow (Figure 2.3), and a valve following the wye was used to increase flow to the settler if necessary. A one-inch hose supplied the grit settler, while a single two-inch hose returned the majority of flow back to the waste stream. Figure 2.3 PVC Splitter and Valve Grit settlers (Figure 2.4) are constructed from 55-gallon plastic drums with an influent port and a discharge weir. Flow enters the tank and is diverted to the side with a 90o elbow to reduce the velocity and turbulence. Grit settles to the bottom of the tank, and wastewater exits through the discharge fitting at the top of the tank and is returned to the waste stream. 50-micron grit with a Specific Gravity of 2.65 settles at a rate of 5.02 in/min. ((g(sgp – 1)d2p/18v)*196.850 = inches/minute). In order to settle this grit, the overflow rate must be less than 3 gpm/ft2 of surface area. The settler has a diameter of 24-inches, or a surface area of 3.14 ft2 (ܣൌߨݎଶ ). At 10 gpm, the overflow rate (Q/A) is 3.18 gpm/ft2, satisfying the design requirements for the settler (10gpm/3.14ft2 = 3.18 gpm/ft2). The actual settler feed rate is adjusted to between 7.5 and 8.0 gpm to insure settling of fine grit, and this is checked by timing the overflow rate of the settler with a 5-gallon bucket and stopwatch. Feed rates are checked periodically and adjusted when necessary. GRIT STUDY – ARMY BASE WWTP MAY 2016 2-5 Figure 2.4 Grit Settler Seed sand was used to supplement native grit concentrations (Figure 2.5). Six hundred pounds of Granusil 5010 per trial was added gradually to a bucket of water and siphoned into the Headcell influent chute. A concentration increase of at least 500 lbs/MG was targeted. The size distribution of seed sand is listed below in Table 2.1 Figure 2.5 Seed Sand Addition GRIT STUDY – ARMY BASE WWTP MAY 2016 2-6 2.2 Determination of Grit Particle Distribution A maximum 200-gram portion of the sample collected by the Grit Settler is immediately classified through a series of sieves. Wet sieving for size fractions and the SES settling tests are conducted on fresh grit from the sewer waste stream samples as the Surface Active Agents (SAA) attached to the grit kernel may substantially reduce its effective specific gravity and consequently it’s settling velocity. If the total sample size exceeds 200-grams, the sample is split and the fraction is recorded on the field bench sheet. Sieve sizes used are listed below in Table 2.1. Table 2.1 Sieve Size Equivalents Opening Granusil 5010 U.S. Sieve Size Tyler Equivalent Microns Inches % Retained 1/4 3.25 mesh 6300 0.2500 1/8 6.5 mesh 3180 0.1250 #12 10 mesh 1680 0.0661 #20 20 mesh 841 0.0331 #50 48 mesh 297 0.0117 12.6 #70 65 mesh 210 0.0083 30.9 #100 100 mesh 149 0.0059 32.8 #140 150 mesh 106 0.0041 17.7 #200 200 mesh 74 0.0029 5.3 #270 270 mesh 53 0.0021 0.7 Pan 2.3 Determination of Sand Equivalent Size (SES) Distribution Settling tests were conducted immediately on solids passing the U.S. #20 sieve and sequentially retained on the #50, #70, #100, #150, #200, and #270 sieves. Large organics often interfere with the settling of grit on screens larger than #50. A portion of the retained material is placed into a modified Imhoff cone and filled with water (see Figure 2.6). The column is inverted, and as the grit settles in the cone corresponding time and volume measurements are recorded. The objective of these measurements is to determine the size of a sand sphere having the same settling velocity as the collected grit fraction. GRIT STUDY – ARMY BASE WWTP MAY 2016 2-7 Figure 2.6 Modified Imhoff Cone for SES Measurements 2.4 Sand Equivalent Size Description The settling velocity of a grit particle depends on several factors that may include surface active agents affixed to the grit particle, the composition, and the shape of the grit particle. Particles with slow settling velocities are said to be “light” and may have low specific gravity or be angular in shape. Conversely, fast settling particles are said to be “heavy” and may have high specific gravities and a rounder shape. Clean, round silica sand is known to have a Specific Gravity of 2.65. However, because grit is seldom clean or round, and may not be made of silica, settling velocities are often much slower. Like Specific Gravity, Sand Equivalent Size is a way of describing the settling characteristics of municipal grit. By definition, Sand Equivalent Size (SES) is “the clean sand particle size, measured in microns, having the same settling velocity of the collected grit particle”. For example, a 300-micron silica sand particle with a specific gravity of 2.65 will settle at a known velocity. A 300-micron grit particle composed of a different material (i.e., limestone), or a silica sand particle (2.65 SG) with a shape that is not round, will settle slower, perhaps with a settling velocity similar to that of a 150-micron sand particle. Therefore, we say that the 300-micron grit particle has a Sand Equivalent Size of 150-microns. Additionally, sieve analyses are a “two-dimensional” test, and ignore the thickness of the grit particle. Therefore, a visually “coarse” distribution may in fact behave like a much finer one. By comparing the physical size and the SES of the grit, the effects of shape and composition can be demonstrated. The following is an example of a “companion plot” that charts physical size and SES of municipal grit. GRIT STUDY – ARMY BASE WWTP MAY 2016 2-8 Figure 2.7 Physical Size versus Sand Equivalent Size: Cumulative Distributions The preceding chart compares cumulative physical and SES distributions. For example, from Figure 2.7, 49% of the charted grit has a physical size of 300-microns and larger, while only 25% of the grit has a Sand Equivalent Size of 300-microns and larger. This difference is a result of particle composition and shape previously discussed, and this grit is characterized as “light”. As particles become smaller, they attain a more rounded, uniform shape resulting from larger, flat particles breaking up into smaller pieces. Grit chamber design must consider the settling velocity of the grit, as specific gravity and physical size distributions alone fail to provide enough information to predict grit settling behavior. Removal efficiencies can be estimated based on the information contained in the preceding companion chart. Using Sand Equivalent Size, the following chart gives some examples of performance expected from a grit chamber designed around specific particle sizes plotted in the preceding companion chart. Predicted Removal Efficiencies (%) of a System Designed to Remove Grit of a Specific SES Sample Site 300-micron SES Design 150-micron SES Design 100-micron SES Design 75-micron SES Design Influent 25.0 72.0 92.0 96.0 GRIT STUDY – ARMY BASE WWTP MAY 2016 2-9 2.5 Solids Analysis The weight measurements of the grit particles retained on each of the ten sieves were determined according to methods SM2540B and SM2540E as outlined in Standard Methods for the Examination of Water and Wastewater, 1998 APHA, AWWA, WEF, 20th edition. Fixed solids fractions were arranged into fractional and cumulative distributions. From this data a cumulative curve factoring physical size and weight of fixed solids is generated. All solids data are listed in Appendix A-2 “Solids Analysis Benchsheet.” Data from the settling tests are entered into a spreadsheet for each size fraction that converts the settling velocities and volumes into Sand Equivalent Size. The SES value generated is plotted against the corresponding volume fraction to generate a series of SES charts. Each chart is divided into 25-micron SES intervals and the percentages of grit falling within each interval are entered into a spreadsheet for analysis. From this data, a cumulative curve factoring SES and weight of fixed solids per size fraction is generated. By comparing the “SES” curve with the “Physical Size” curve, we can determine the amount of grit that can bypass a grit removal system designed around a known sand particle size. The SES charts are also used to compare the average SES within a sieve fraction with the average physical size of clean, round silica sand for that same sieve fraction. To calculate the concentration of grit present in the sewer during normal flow conditions, the volume of wastewater sampled each day is compared to the measured volume of wastewater passing through the sewer during the sampling periods. The total amount of grit collected during each sampling period is applied to the total volume of wastewater to determine the lbs/MG of grit present in the collection system. GRIT STUDY – ARMY BASE WWTP MAY 2016 3-10 3.0 DISCUSSION OF RESULTS: TRIAL 1 Samples were collected on April 18, 2016 from the North Headcell. Sampling conditions are listed below in Table 3.1. Flows averaged 9.7 MGD for the duration of the trial. Flows for both trials are plotted below in Figure 3.1 Figure 3.1 Army Base WWTP Flow Data Table 3.1 Headcell Performance Evaluation Sampling Period: April 18, 2016 Site Start Time Finish Time Hours Settler Feed Rates (gpm) Gallons Sampled Grit Chamber Influent 13:15 15:30 2.25 8.52 1,151 Grit Chamber Effluent 13:15 15:30 2.25 8.60 1,160 GRIT STUDY – ARMY BASE WWTP MAY 2016 3-11 3.1 Distributional Data Figures 3.2 and 3.3 plot the fractional and cumulative distributions, and Figure 3.4 plots the fractional concentrations of grit collected from the grit chamber influent and effluent sites. The distribution of influent grit was fine, with 31.5% of material larger than 297- microns and 68.5% smaller than 297-mirons. For effluent grit, 4.7% of material was larger than 297-microns and 95.3% smaller than 297-mirons. Concentrations of influent grit were below average, with 39.44 lbs/MG entering the North Headcell. Targeted concentrations of seed sand were based on 12-MGD. Actual average flow was 9.7 MGD resulting in a seed sand concentration of 659.74 lbs/MG, and a total influent concentration of 699.24 lbs/MG (Figure 3.4). Figure 3.2 Fractional Distribution of Grit at the Army Base WWTP: Trial No. 1 North Unit – April 18, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 3-12 Figure 3.3 Cumulative Distribution of Grit at the Army Base WWTP: Trial No. 1 North Unit – April 18, 2016 Figure 3.4 Concentrations of Grit at the Army Base WWTP: Trial No. 1 North Unit – April 18, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 3-13 3.2 Settling Velocity Data Sand Equivalent Size (SES) vs. Physical Size companion plots can be used to determine grit removal system design parameters. Table 3.2 lists theoretical removal efficiencies for a system designed to remove grit based on the SES data collected from the influent sampling site. Predicted efficiencies listed in Table 3.2 are shown graphically in Figure 3.5. Table 3.2 Predicted Removal Efficiencies (%) of a System Designed to Remove Grit of a Specific SES at the Army Base WWTP: April 18, 2016 Sample site 300-micron SES Design 150-micron SES Design 100-micron SES Design 75-micron SES Design North HC Influent 9.3 57.8 88.4 99.7 Figures 3.5 and 3.6 compare the physical and Sand Equivalent Size (SES) distributions of the influent and Headcell effluent samples, and Figure 3.7 compares the physical size distributions with a clean sand distribution. Values found in Figure 3.7 are determined from the median SES of material on each sieve, and fractional data is not applied as is the previous companion charts. Figure 3.5 Comparison of the Army Base WWTP North Headcell Influent Grit Physical Size and Sand Equivalent Size: April 18, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 3-14 Figure 3.6 Comparison of the Army Base WWTP North Headcell Effluent Grit Physical Size and Sand Equivalent Size: April 18, 2016 Figure 3.7 Median Size Distribution of Grit at the Army Base WWTP vs. a Clean Sand Distribution on April 18, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 3-15 Settling velocities for Headcell influent and effluent material were slow flow fractions larger than 250-microns physical size, likely due to particle shape (Figure 3.7). 3.3 Discussion of Results: Performance Evaluation Efficiencies were determined by comparing fractional concentrations of post-screen influent and grit chamber effluent grit, plotted above in Figure 3.4. Table 3.3 lists the fractional efficiency of the North Headcell based on the physical size of the material. Performance was good, achieving 98.3% removal efficiency for material larger than 105- microns, and a total efficiency of 97.5%. The North unit met the specified 95% removal efficiency. Table 3.3 Fractional Removal Efficiencies of the Army Base WWTP North Headcell: April 18, 2016 – Trial No. 1 Size Fraction Concentration of Influent Grit FS (lbs/MG) Concentration of Effluent Grit FS (lbs/MG) Removal Efficiency (%) >297-microns 95.57 0.82 99.1 <297-microns >210-microns 208.43 0.65 99.7 <210-microns >149-microns 223.37 2.16 99.0 <149-microns >105-microns 127.96 7.36 94.2 <105-microns >74-microns 39.07 6.17 84.2 <74-microns >53-microns 4.84 0.44 90.8 Total 699.24 17.60 97.5 Total >105-microns 655.33 10.99 98.3 GRIT STUDY – ARMY BASE WWTP MAY 2016 4-16 4.0 DISCUSSION OF RESULTS: TRIAL 2 Samples were collected on April 19, 2016 from the North Headcell. Sampling conditions are listed below in Table 4.1. Flows averaged 10.55 MGD during the trial. Flows for both trials are plotted above in Figure 3.1 Table 4.1 Headcell Performance Evaluation Sampling Period: April 19, 2016 Site Start Time Finish Time Hours Settler Feed Rates (gpm) Gallons Sampled Grit Chamber Influent 10:45 13:00 2.25 8.31 1,121 Grit Chamber Effluent 10:45 13:00 2.25 8.39 1,133 4.1 Distributional Data Figures 4.1 and 4.2 plot the fractional and cumulative distributions, and Figure 4.3 plots the fractional concentrations of grit collected from the grit chamber influent and effluent sites. The distribution of influent grit was fine, with 21.0% of material larger than 297- microns and 79.0% smaller than 297-mirons. For the Headcell effluent grit, 11.5% of material was larger than 297-microns and 88.5% smaller than 297-mirons. Concentrations of influent grit were extremely high, with 343.47 lbs/MG entering the North Headcell. Adding influent concentrations to the seed sand resulted in a total influent concentration of 950.11 lbs/MG (Figure 4.3). While sampling was initiated at the conclusion of the peak flow ramp up, there may have been a lag in the peak grit concentration resulting in an abundance of material being present during the trial. Figure 4.1 Fractional Distribution of Grit at the Army Base WWTP: Trial No. 2 North Unit – April 19, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 4-17 Figure 4.2 Cumulative Distribution of Grit at the Army Base WWTP: Trial No. 2 North Unit – April 19, 2016 Figure 4.3 Concentrations of Grit at the Army Base WWTP: Trial No. 2 North Unit – April 19, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 4-18 4.2 Settling Velocity Data Sand Equivalent Size (SES) vs. Physical Size companion plots can be used to determine grit removal system design parameters. Table 4.2 lists theoretical removal efficiencies for a system designed to remove grit based on the SES data collected from the influent sampling site. Predicted efficiencies listed in Table 4.2 are shown graphically in Figure 4.4. Table 4.2 Predicted Removal Efficiencies (%) of a System Designed to Remove Grit of a Specific SES at the Army Base WWTP: April 19, 2016 Sample site 300-micron SES Design 150-micron SES Design 100-micron SES Design 75-micron SES Design North HC Influent 16.6 61.9 86.5 99.5 Figures 4.4 and 4.5 compare the physical and Sand Equivalent Size (SES) distributions of the influent and Headcell effluent samples, and Figure 4.6 compares the physical size distributions with a clean sand distribution. Values found in Figure 4.6 are determined from the median SES of material on each sieve, and fractional data is not applied as is the previous companion charts. Figure 4.4 Comparison of the Army Base WWTP North Headcell Influent Grit Physical Size and Sand Equivalent Size: April 19, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 4-19 Figure 4.5 Comparison of the Army Base WWTP North Headcell Effluent Grit Physical Size and Sand Equivalent Size: April 19, 2016 Figure 4.6 Median Size Distribution of Grit at the Army Base WWTP vs. a Clean Sand Distribution on April 19, 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 4-20 Similar to Trial No. 1, settling velocities for Headcell influent and effluent material were slow flow fractions larger than 250-microns physical size (Figure 4.6). 4.3 Discussion of Results: Performance Evaluation Efficiencies were determined by comparing fractional concentrations of post-screen influent and grit chamber effluent grit, plotted above in Figure 4.3. Table 4.3 lists the fractional efficiency of the North Headcell based on the physical size of the material. The unit removed 95.4% of material larger than 105-microns, and a total efficiency of 94.1%. The unit met the specified 95% removal targeted by the agreement. Table 4.3 Fractional Removal Efficiencies of the Army Base WWTP North Headcell April 19, 2016 – Trial No. 2 Size Fraction Concentration of Influent Grit FS (lbs/MG) Concentration of Effluent Grit FS (lbs/MG) Removal Efficiency (%) >297-microns 148.58 6.41 95.7 <297-microns >210-microns 259.90 3.47 98.7 <210-microns >149-microns 290.68 8.40 97.1 <149-microns >105-microns 182.18 22.25 87.8 <105-microns >74-microns 60.78 13.32 78.1 <74-microns >53-microns 7.98 2.03 74.5 Total 950.11 55.88 94.1 Total >105-microns 881.35 40.53 95.4 GRIT STUDY – ARMY BASE WWTP MAY 2016 5-21 5.0 CONCLUSIONS The following conclusions were drawn from the results of this grit evaluation: Trial No. 1 1. At the Army Base WWTP, 31.5% of grit was larger than 297-microns and 68.5% was smaller than 297-mirons. (Figures 3.2 and 3.3). 2. Concentrations of native influent grit were 39.44 lbs/MG. Seed sand concentrations were 659.74 lbs/MG (See Figure 3.4) 3. The North Headcell removed 98.3% of material larger than 105-microns, and a total efficiency of 97.5%. Specifications required 95% removal of material 110- microns and larger (Table 3.3). Trial No. 2 1. For Trial No. 2, 21.0% of material was larger than 297-microns and 79.0% was smaller than 297-mirons. (Figures 4.1 and 4.2). 2. Concentrations of native influent grit were 343.47 lbs/MG. Seed sand concentration were 606.64 lbs/MG. (See Figure 4.3) 3. The North Headcell removed 95.4% of material larger than 105-microns, and a total efficiency of 94.1%. Specifications required 95% removal of material 110- microns and larger (Table 4.3). GRIT STUDY – ARMY BASE WWTP MAY 2016 6-22 6.0 BIBLIOGRAPHY Clesceri, L., Greenberg, A. and Eaton, A., “Standard Methods for the Examination of Water and Wastewater”, 20th Edition, 1998, American Public Health Association, Washington, DC Tchobanoglous, G., Burton, F.L. and Stensel, H.D., “Wastewater Engineering: Treatment and Reuse”, 4th Edition, 2003. TATA McGraw-Hill GRIT STUDY – ARMY BASE WWTP MAY 2016 APPENDIX A RAW DATA A-1 Concentration Calculation Spreadsheet A-2 Solids Analysis Bench Sheets A-3 Grit Concentration Calculation Bench Sheet A-4 SES Data Analysis A-5 SES Charts A-6 SES Chart Analysis A-7 Median SES versus Median Physical Size GRIT STUDY – ARMY BASE WWTP MAY 2016 A-1 Concentration Calculation Spreadsheet GRIT STUDY – ARMY BASE WWTP MAY 2016 A-2 Solids Analysis Bench Sheets GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 A-3 Grit Concentration Calculation Bench Sheet GRIT STUDY – ARMY BASE WWTP MAY 2016 A-4 SES Data Analysis GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 A-5 SES Charts GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 A-6 SES Chart Analysis GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 GRIT STUDY – ARMY BASE WWTP MAY 2016 A-7 Median SES versus Median Physical Size GRIT STUDY – ARMY BASE WWTP MAY 2016 APPENDIX B CALCULATIONS GRIT STUDY – ARMY BASE WWTP MAY 2016 Drag Coefficient (Cd) 24/NR + 3/sqrt NR + 0.34 Reynolds number (NR) (settling velocity of particle)(diameter of particle)/kinematic viscosity Stoke’s Law Settling velocity (m/s) = g(sgp – 1)d2p/18v Where g = acceleration due to gravity (9.81 m/s2) sgp = specific gravity of particle dp = diameter of particle v = kinematic viscosity (m2/s) % Total Solids (grams dry weight/grams wet weight)*100 % Total Volatile Solids [(grams dry weight - grams ash weight)/ grams dry weight]*100 Computational Fluid Dynamics Analysis of a Vortex Grit Removal System Mark H. Chien1, Alexander Borys1, and Joseph L. Wong1* 1 East Bay Municipal Utility District, 375 11th Street, Oakland, California 94607 *To whom correspondence should be addressed. Email: jwong@ebmud.com ABSTRACT A vortex grit removal system (two tanks rated at 70 MGD each) was installed at East Bay Municipal Utility District (EBMUD) in its Main Wastewater Treatment Plant in 2006 to improve grit removal from influent wastewater. Although use of the system has made some reductions in energy use and odors at the plant, independent performance testing concluded that the specific grit removal efficiencies were not being met. EBMUD retained AECOM to develop a computational fluid dynamics (CFD) model to analyze the vortex grit system, and to evaluate design modifications that would potentially improve grit removal. The CFD model included a particle tracking component to assess grit travel through the system. Numerous design and operational modifications were tested and evaluated based on in-tank velocity and turbulence, relative grit removal, and short-circuiting potential. Based on model results, AECOM recommended removal of several vortex grit tank components, including an internal influent baffle, the cover of the grit hopper and an in-tank propeller. AECOM also recommended that both vortex grit units be operated during dry weather, resulting in average flow rates of approximately 35 MGD per unit. After the modifications were implemented, a repeat performance test was completed. Preliminary test results indicate that removal efficiency has increased for 50-mesh, 70-mesh and 100-mesh grit. KEYWORDS: grit, vortex grit tank, computation fluid dynamics, CFD, Flow-3D INTRODUCTION Grit in the influent stream of municipal wastewater treatment plants, if not removed at the headworks, causes numerous impacts downstream that can significantly affect overall plant operation and maintenance costs. These impacts include (but are not limited to) accelerated wear on downstream equipment (e.g., dewatering centrifuges, pumps, heat exchangers), increased downtime and cleaning costs for digesters and other facilities, and reduced capacity of digesters. EBMUD contracted for the construction of a vortex grit removal system (two tanks rated at 70 MGD each) in its Main Wastewater Treatment Plant in 2006 to improve grit removal. Additional benefits from the project were to decrease energy use and odors compared to the existing aerated grit removal system. Although use of the vortex grit system has made some reductions to energy use and odors, an independent grit removal performance test (Black & Veatch, 2009) concluded that the specified removal efficiencies were not being met. Test results indicated that the removal efficiencies for 50-mesh, 70-mesh and 100-mesh grit were 77%, 65% and 60%, respectively, compared to performance specifications of 95%, 85% and WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6020 65%. As a result, EBMUD retained AECOM to develop a computational fluid dynamics (CFD) model to analyze the vortex grit system and evaluate design modifications that would potentially improve grit removal by the vortex grit system. METHODOLOGY AECOM developed a model of one of the vortex grit tanks in Flow-3D, a CFD modeling software package. Base Hydraulic Model AECOM’s base hydraulic model representing existing conditions included definition of the system geometry, modeling of the fluid volume as a system of discrete cells, application of boundary conditions (flow and water surface elevation), dynamic simulation of fluid flows, and field verification. The modeled system geometry included the influent and effluent channels, the vortex grit tank, the internal influent and effluent baffles, the grit collection hopper at the bottom of the tank, the hopper cover plate, and the rotating propeller above the hopper (Figure 1). An orthogonal mesh of cells was applied to the entire fluid volume. The fluid cell sizes varied depending on the complexity of the geometry and ranged from 1 in. x 1 in. x 1 in. cells near the propeller to 4 in. x 4 in. x 4 in. cells in the influent and effluent channels. The resulting mesh included approximately 800,000 active (fluid) cells. The downstream (effluent channel) boundary condition was specified as a known water surface elevation, which is controlled by the downstream primary sedimentation tanks. The upstream boundary condition was specified as a flow rate. The upstream water surface elevation was calculated during the dynamic simulation of the base hydraulic model. WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6021 Figure 1. Vortex Grit System Components AECOM ran the base hydraulic model at flow rates of 35 and 70 MGD to achieve steady-state hydraulic conditions. The model was validated with field hydraulic measurements of water surface elevations and channel velocities. Model results indicated an overall total head loss through the entire system (from the influent channel to the effluent channel) of 19.5 inches at 70 MGD. The location of a hydraulic jump in the effluent channel was also correctly predicted by the model (Figure 2). WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6022 10 ft/s 0 ft/s 10 ft/s 0 ft/s Figure 2. Base Model Velocity Magnitude - Isometric View Propeller Analysis AECOM used the impeller sub-model feature available within Flow-3D to dynamically simulate the effect of the rotating propeller above the hopper cover plate. This sub-model defines a cylindrical object representing the area swept by the propeller blades, and describes the effect of the rotating blades as a steady-state net momentum change imparted to the fluid by the object. The effect of the blades is set using calibration constants which describe the magnitude of momentum transfer and the ratio of axial to radial forces. The calibration constants were developed using the General Moving Object (GMO) sub-model, another feature used to model moving objects in Flow-3D. Unlike the impeller sub-model, AECOM used the GMO sub-model to define the actual geometry of the individual propeller blades and, based on the known rotational velocity, calculated the momentum effect of the propeller on the surrounding fluid. Since detailed propeller analysis using the GMO sub-model was too computationally-intensive in conjunction with the dynamic simulation of the base model (a 24 ft. diameter tank, and influent and effluent flows), the propeller shaft and blade were analyzed in a small, closed “laboratory vessel” of 6 ft. x 6 ft. x 5 ft. in order to determine its effects on the fluid. Calibration constants derived from the GMO sub-model were then applied to the impeller sub-model described above and used as part of the dynamic simulation of the entire system model for each of the applicable model runs. This approach allowed for detailed analysis of the propeller in isolation, without unnecessarily expending computational resources on repeatedly simulating the constant-speed propeller motion once the effects on the fluid were determined. Grit Particle Model Grit behavior was modeled using a particle tracking module. Two particle sizes were chosen as representative of coarse and medium grit (Table 1). Based on previous laboratory test results, AECOM used a specific gravity of 1.4 for “wet” grit particles (e.g., including grease and other surface active agents, moisture, etc.). For each model run, these particles were introduced into the influent channel after hydraulic steady-state was reached. Because the model had limited WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6023 ability to describe grit travel along the tank bottom and into the hopper, the grit removal efficiency was determined for each model run based on grit retention in the vortex grit tank. In other words, it was assumed that the grit would eventually enter the hopper after being retained in the tank. Development of a fully-calibrated grit model proved to be challenging and would have required extensive additional resources. Instead, AECOM interpreted the grit removal results as a relative indicator of grit removal efficiency, rather than as a prediction of actual removal efficiency in the field. Relative grit removal efficiency results were compared among the various model runs, and significant differences in the results between two runs were considered to be a good indicator of potential changes in actual grit removal efficiency. Simulation of Design Modification Potential design modifications were tested by AECOM both individually and in combination, including removal of the propeller blades, removal of the hopper cover plate, removal of the internal influent and effluent baffles (Figure 1), installation of an effluent channel baffle of varying heights (Figure 3), removal of the internal effluent baffle guide vane, and adjusting the height of the internal effluent baffle guide vane (Figure 1). Numerous other modifications were considered but were not evaluated. The potential design modifications were evaluated by AECOM based on reduction of velocity and turbulence inside the tank, relative grit removal efficiency using the grit particle model, and short-circuiting potential based on minimum fluid travel time through the system. Changes in tank velocity and turbulence were evaluated by comparing isometric, plan, and elevation view color plots of velocity magnitude and turbulent kinetic energy for different model runs. Figure 3. Effluent Channel Baffle Location WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6024 RESULTS Base System Hydraulic Model Evaluation of the base model at the design flow rate of 70 MGD confirmed the primary vortex flow pattern in the tank. The maximum fluid velocity within the tank was determined to be 6 feet per second (Figure 4). The propeller-assisted secondary (toroidal, or donut-shaped) flow pattern described by the manufacturer was not observed by AECOM in the model of the tank. The flow within the tank is described with plan and vertical section view velocity magnitude plots as shown in Figure 4, 5 and 6. Bottom Cut (2.5 ft. Above Tank Floor) Top Cut (8 ft. Above Tank Floor) ft/s 8 6 4 2 0 B B A A Bottom Cut (2.5 ft. Above Tank Floor) Top Cut (8 ft. Above Tank Floor) ft/s 8 6 4 2 0 B B B B A A Figure 4. Base Model Velocity Magnitude - Plan View WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6025 Figure 5. Base Model Velocity Magnitude - Vertical Section A-A Figure 6. Base Model Velocity Magnitude - Vertical Section B-B Isolated Propeller Analysis Based on analysis in the isolated laboratory vessel, AECOM found that the propeller had a significant radial component and that fluid was propelled radially-outward at the tank bottom. Also, AECOM found that the close proximity of the propeller off the floor (three inches) hindered the development of an upward axial motion in the center of the tank (i.e., fluid could not easily re-circulate back to the center of the vessel under the propeller). The result is that the SECTION A-A SECTION B-B Influent Effluent Channel Effluent Channel WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6026 actual flow pattern that was developed in the isolated laboratory vessel is outward at the bottom, up along the vessel walls, and back down in the center toward the propeller (Figure 7). Note that this pattern was not observed in the base model (full-size tank, Figure 8) because, as discussed below, the overall effect of the propeller was not significant compared to flows into, out of, and around the tank. Figure 7. Propeller-Induced Flow in Isolated Laboratory Vessel Simulation of Design Modification A summary of the design modification simulations performed by AECOM and the modeling results is presented as model runs A through N in Table 1. WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6027 Table 1. Summary of Model Runs and Results Model Run Propeller (1)Hopper CoverInt. Influent BaffleInt. Effluent BaffleEffluentGuide VaneEffluent ChannelBaffleRelative Coarse(2) Grit Removal Relative Medium(3) Grit Removal Min. Fluid Travel Time (4) Max. Tank Velocity Max. TKE %(5,6) %(5,6) sec ft/s ft2/s2 70 MGD (Design Flow Rate) A. Base Model √√√√Std None 74% 2% 56 6 1.5 B. Remove Propeller X √√√Std None 76% 2% -- 6 1.5 C. Remove Hopper Cover √X √√Std None 77% 2% -- 6 1.5 D. Remove Internal Influent Baffle √√X √Std None 90% 2% 53 5 1.3 E. Remove Internal Influent Baffle and Effluent Guide Vane √√X √None None 82% <1% 50 GR GR F. Remove Internal Effluent Baffle (incl. Effluent Guide Vane) √√√X None None 83% 2% 44 6 0.9 G. Remove All Internal Baffles √√X X None None 62% 2% 45 4 0.7 H.Add 6" Effluent Channel Baffle √√√√Std 6 in. 83% 1% -- 6 1.5 I.Add 12" Effluent Channel Baffle √√√√Std 12 in. 83% 2% -- 6 1.5 J. Combination (FINAL)XXX √Std None 88% 12% --GR GR K. Combination X X X √Std 19.5 in. 89% 7% -- 5 0.9 L. Combination X X X √Raised None 87% 9% 67 GR GR 35 MGD M. Base Model √√√√Std None -- -- -- 2 0.6 N. Combination X X X √Std 19.5 in. 100% 72% -- 2 0.2 NOTES: √Component present. X Component removed. -- Not evaluated. GR AECOM reported results velocity and turbulence results graphically. Maximum values were not specifically determined. TKE Turbulent Kinetic Energy Std Standard guide vane provided by manufacturer. 1. Propeller removed means removal of the blades, but retention of the drive shaft and fluidizer impeller inside the grit hopper. 2. 3. 4. Used as an indicator of short-circuiting potential. 5. 6. Modeled grit removal efficiencies are not intended to predict actual grit removal efficiencies in the field. Grit particles size and specific gravity were chosen as representative values that would exhibit observable differences in removal efficiency. The significance of the modeled removal efficiencies is the relative differences in values between simulation runs. Removal efficiencies calculated based on capture of particles within the tank, as opposed to capture within the grit hopper. Coarse grit particle (including attached organic matter) defined as a diameter of 649 µm and a specific gravity of 1.4, nominally representating a particle size range between 18 and 50 mesh size. Medium grit particle (including attached organic matter) defined as a diameter of 254 µm and a specific gravity of 1.4, nominally representating a particle size range between 50 and 70 mesh size. DISCUSSION A narrative discussion of the key model runs and findings is provided below. WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6028 Propeller Removal (Model Run B) AECOM determined that the propeller was a weak momentum source relative to the fluid flows into, around, and out of the tank. The propeller has a diameter of 3 feet in a 24 foot diameter tank, with a rotational velocity of approximately 21 rpm. The propeller only affected fluid flow in the very near-field portion of the tank, with no observable effect on the larger flow patterns throughout the tank (Figure 8). The propeller-assisted secondary flow pattern was not observed. Because the imparted momentum is radially-outward adjacent to the propeller, AECOM concluded that the propeller may actually be preventing grit from reaching the center of the tank and the entrance to the grit hopper. Based on this analysis, AECOM recommended removal of the propeller. Figure 8. Propeller Effect in Base Model Tank – Propeller Blades Not Shown Hopper Cover Removal (Model Run C) AECOM’s model results did not show any conclusive differences when the grit hopper cover plate was removed. The grit particle model was not able to accurately model grit travel along the tank bottom; therefore, the removal of the hopper cover could not be fully evaluated by the model. However, AECOM obtained additional information from two other wastewater treatment plants in Boston and Milwaukee suggesting that removal of the hopper cover plate appeared to increase grit removal. Internal Influent Baffle Removal (Model Run D) AECOM found that removal of the internal influent baffle reduced velocity and turbulence inside the tank and increased relative grit removal, albeit with a small increase in short-circuiting potential (Figure 9). Based on these model results, AECOM recommended removal of the internal influent baffle. Run A Run B WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6029 Figure 9. Velocity Magnitude Near Tank Bottom - Model Runs A and D Internal Effluent Baffle Removal and Related Modifications (Model Run E, F, L) Removal of the internal effluent baffle and associated guide vane decreased tank turbulence and increased relative grit removal, but also caused an increase in short-circuiting potential (model run F, compared to model run A). Removal of only the guide vane was also evaluated, while the effluent baffle itself was retained (model run E, compared to model run D), but AECOM found that this increased short-circuiting potential and decreased relative grit removal. Finally, raising the effluent baffle guide vane (i.e., raising the outlet point) was evaluated (model run L, compared to model run J), but results suggested a performance decrease. AECOM concluded that removal or modification of the effluent baffle and guide vane was not advisable. Effluent Channel Baffle Addition (Various Model Runs) Baffle heights from 6 inches to 19.5 inches were added at the tank outlet as a possible means of reducing flow velocities. Each baffle had a 6 inch gap at the bottom to allow grit passage. Preliminary results indicated that an effluent channel baffle improved relative grit removal (model runs H, I, compared to run A). However, the results were inconclusive when an effluent channel baffle was evaluated in combination with other design modifications (model run K, compared to run J). Because the performance benefit was not conclusive, and the addition of an effluent channel would have required additional operational effort for cleaning and possibly for baffle height control, AECOM did not recommend addition of this baffle. Flow Rate Reduction (Model Runs M, N) Evaluation of the model at a reduced flow rate of 35 MGD showed a significant reduction in maximum tank velocity from 6 ft/sec at 70 MGD to 2 ft/sec at 35 MGD (model run M, compared to model run A, Figure 10) as well as a significant increase in relative grit removal (model run N, compared to model run K). Reductions in tank velocity and relative grit removal were significantly greater under reduced flow conditions than for any of the modifications tested at the design flow rate. While reducing flow rate is a viable solution to increase grit removal efficiency, it is less desirable because it limits process capacity and may cause unintended settling in the influent channel. Run A – Base Model Run D- No Influent Baffleft/s 8 6 4 2 0 Influent Baffle WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6030 Figure 10. Velocity Magnitude Near Tank Bottom - Model Runs A and M Combination Run (Model Run J) Three potentially beneficial design modifications (internal influent baffle removal, propeller removal, and hopper cover removal) were evaluated simultaneously. The results were similar to removal of the internal influent baffle alone and confirmed that the modifications could be applied in combination. CONCLUSIONS Based on the model results, AECOM recommended the following design modifications: Removal of the internal influent baffle; Removal of the propeller blades (while retaining the drive shaft and a grit fluidizer in the grit hopper); and Removal of the grit hopper cover plate. AECOM also recommended that both vortex grit tanks be operated during dry weather, resulting in reduced flow rates in each vortex grit tank. The three design modification recommendations (removal of the internal influent baffle, the propeller blades and the grit hopper cover) were implemented in April 2010, and a repeat of the grit removal performance test was performed by Black & Veatch in July 2010. Preliminary test results indicate that removal efficiency has increased (Table 2). Run A – 70 MGD Run M – 35 MGDft/s 8 6 4 2 0 WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6031 Table 2. Grit Removal Performance Test Results Average Grit Removal Efficiency Grit Mesh Size Plant Flow 50-mesh 70-mesh 100-mesh Particle size range (1)MGD > 300 µm 212 to 300 µm 150 to 212 µm Before Modifications (2)58 77% 65% 60% After AECOM-Recommended Modifications (Preliminary Data) 61 90% 75% 61% Performance Specification --95% 85% 65% NOTES: 1. Size based on sieve analysis after drying and volatilization of organic matter. 2. Grit Removal Performance Test - VGT2 EBMUD Main Plant, Black & Veatch, February 2009. ACKNOWLEDGEMENTS The authors would like to express their appreciation to the AECOM project team (Ryan Edison, David Wood, Megha Bansal and James Kern) and the Black & Veatch project team (Jim Clark, Sanjay Reddy, and Gary Hunter) for their dedicated efforts throughout this project. REFERENCES AECOM. 2009. Computational Fluid Dynamics Analysis for Vortex Grit Removal System – Technical Memorandum. AECOM. 2010. Computational Fluid Dynamics Analysis for Vortex Grit Removal System – Report Addendum. Black & Veatch, Inc. 2009. Grit Removal Performance Test – Vortex Grit Tank No. 2 EBMUD Main Plant. WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 6032 WEFTEC 20I4 Relative Performance of Grit Removal Systems B. McNamaral, M. Sherony*2, and P. Herrick2 lHampton Roads Sanitation District,40l Lagoon Road, Norfolk, VA 12505, USA 2Hydro International,2925 NW Aloclek Drive #140, Hillsboro, OR 97L24,IJSA msheronlr(D hydro-int. com ABSTRACT Grit is a nuisance material that causes abrasive wear to mechanical equipment increasing maintenance and operational costs while reducing equipment performance and useful life. Grit that is not captured in the headworks accumulates in processes throughout the plant, reducing capacity and detention time, and adversely influencing flow and circulation pattems2. Deposited grit must be manually removed, handled, hauled and disposed. Abrasive wear, process inefficiencies and basin cleaning operations increase treatment plant operating expenses. Choosing a grit removal technology has often been based on equipment price with little regard for device effrcacy and consequent grit removal efficiency. The industry has lacked an unbiased side-by-side comparison of the currently available technologies. As a result, owners and engineers are forced to navigate a field of, what can be conflicting, performance claims made by various equipment manufacturers. This situation is perpetuated by the fact that there is no accepted, peer reviewed test standard for grit sampling and analysis. The purpose of this paper is to encapsulate various grit removal system performance data generated by a consistent and repeatable sampling and analysis methodology for the purpose of comparing virtually all grit removal technologies in terms of their effectiveness. Results determined with this sampling method corroborates with the operating history and performance at the tested plants with respect to grit removal, suggesting the accuracy of the test method6' The data provides an unbiased side-by-side comparison of the actual performance of grit technologies based on a repeatable sampling and analysis methodology that owners and engineers can utilize to protect plants from deposition, abrasive wear and associated costs from this nuisance material. Keywords: Grit, removal efficiency, aerated grit basin, mechanically induced vortex unit, stacked tray system, structured flow unit, detritus tank, test methodology, grit sampling, surface loading rate INTRODUCTION Biological processes continue to evolve toward better effluent quality in a smaller footprint. The current trend of housing these processes and systems in smaller and smaller footprints imply an inherent inability to store grit and debris. Treatment plants now operate with reduced numbers of maintenance and operations staff, which in turn is resulting in significant reductions in the available resources and time to tackle and address the negative impacts of grit and debris. Copyright 02014 Water Environment Federation 4919 WEFTEC 20I4 Headworks screening and grit removal are the primary protection for all treatment processes and equipment in a wastewater treatment plant, yet it has been the most neglected part of the plant. To improve solids removal, screen openings on influent screens have trended progressively smaller over the past 1 0- I 5 years. Years ago, screen openings were frequently 25 mm ( I ") and larger. Today, screens are commonly supplied with 6 mm (Yo") openings. It is logical that advancing grit removal processes, to effectively remove incoming grit, are becoming a higher priority in plant designs. Selecting grit removal technologies can be a challenge due to the lack of comparative performance data available within the wastewater industry. Owners and engineers are forced to navigate a field of, what can be conflicting, performance claims made by various equipment manufacturers. This situation is perpetuated by the fact that there is no accepted, peer reviewed test standard for grit sampling and analysis. As there are no Standard Methods for the comprehensive measurement and analysis of sampled grit, most parties utilize conventional ASTM D-422 to obtain the physical particle size distribution of grit collected by various means. Standard Method 2540 for solids testing is used for determining Total, Fixed, and Volatile Solids. A method that Engineers and Owners have found effective, splits the sample with half being tested via ASTM D-422 and the other half being wet sieved and characteized based on settling velocity3. In addition to physical size distribution, settling velocity is often the most important and useful criterion in grit system design. Settling velocity is central to grit system design as technologies used to collect influent grit are predominantly sedimentation processes2. Sedimentation basins and aerated grit basins (AGB) are recognized as gravity processes. Vortex processes utilizing a forced vortex type flow regime also rely predominantly on gravity for separation. When the force balance on a particle is evaluated within a forced vortex type flow regime in a basin, gravity is shown to be the predominant force, well in excess of the centrifugal forces generated by slow rotational velocity. While settling velocity is an important criterion in grit system design, the removal efficiency data presented in this paper is based on particle size distribution alone and does not consider settling velocity. Settling velocity is discussed elsewherea. As most performance guarantees are based on2.65 specific gravity (SG) it is worth noting that measured performance can vary widely from performance claims. While some of the variance is certainly attributed to the SG of grit being less than 2.65 and other factorsa, wide variations from performance claims are likely influenced by other factors such as short circuiting and/or inaccurate sizing. METHODOLOGY Effective test methodology must provide accurate, consistent, repeatable and reproducible results. One of several grit sampling methods used by owners and engineers is the vertical slot sampler (VSS) The VSS is designed to draw off a known vertical slice of the influent water column to provide an accurate sample of incoming solids. Although not detailed in ASTM manuals or Standard Methods, sampling using the VSS has been found to produce results that are repeatable, effective and allow efficiency comparisons at different treatment plantss. Further, Copyright 02014 Water Environment Federation 4920 WEFTEC 2OI4 results determined with the VSS corroborates with the operating history and performance at those plants with respect to grit removal, suggesting the accuracy of the test method6. This same test methodology can be used for comparison of grit removal efficiency of various technologies. The VSS methodology used in the referenced studies provides a repeatable sampling and analysis methodology that allows for the relative comparison of removal efficiency for different devices. The test methodology typically includes a margin of error of +l- 5o/o and is described eslewhere3's. Data collected and presented herein has been made available in various industry publications and reports as cited. Hampton Roads Sanitation District (HRSD) performed comprehensive testing at five of their wastewater treatment plants in2007 and 2008 utilizing the VSS sampling method. The equipment tested included three different mechanically induced vortex systems (MIV), a Detritus tank system and an aerated grit system (AGB)s. During the same period, HRSD conducted a side-by-side pilot test comparing the stacked tray Eutek HeadCell@ unit and the structured flow Grit King@ unit. Both systems were tested for removal efficiency using the VSS sampling methodT. Data collected on the HRSD AGB has been excluded from this paper. During the above referenced testing, which was performed on dry weather flows, it was determined that the grit was settling in the force main as there was not sufficient energy in the collection system to transport grit to the plant. At peak diurnal flows the velocity in the force main was 0.5 m/s (1.7 fps), when 0.9 - 1.5 m/s (3.5-5.0 fps) is needed to re-suspend settled solids and grit6. Therefore, data from testing on the AGB was inconclusive. However, the same collection and analysis methodology was used in Columbus GA on an AGB, that data is included in this paper. This paper provides removal efficiency, utilizing identical and consistent sampling and analysis methodology, of virtually every type of grit removal technology, thus allowing comparison of removal efficiency of these technologies. The processes represented include AGB, vortex grit removal systems, and detritus tanks. The vortex units include mechanically induced vortex (MIV) units, stacked tray units and structured flow vortex units. RESULTS Mechanically Induced Vortex (MIV) Units HRSD Chesapeake-Elizabeth Treatment Plant The Chesapeake Elizabeth Treatment Plant (CETP) is a 9l ML/d (24 MGD) capacity plant operating with an average flow of approximately 72}ifdLld(19 MGD). Grit remova[equipment consists of trvo (2) 7.3 m (24') diameter MIV units, one unit was in operation during the stuOy. fe-sfqnremoval parameter for each unit is95% removal of 150 pm particles,2.65 Sb, at I l4ML/d (3 0 MGD), and 95%o removal of 27 O pm particle s, 2.65 SG, ai 265 }71Lld (70 MGD). Average flow during testing was 7l.l ML/d (18.79 MGD), which is well below ihe rated capacity of the grit unit. The measured removal efficiency was 48-52%o of all grit 150 pm andlarger and 45-50Yo of all grit 106 micron and larger. Rembval efficiency of p#icles > 2g7microns, a slightly larger particle than the performance claim, was 72-i8%or roughly 20% lessthan the claimed removal. Copyright O2014 Water Environment Federation 4921 WEFTEC 2OI4 Table #l Removal of MIV HRSD Vireinia Initiative Plant The Virginia Initiative Plant (VIP) is a 151 ML/d (40 MGD) capacity plant with an average flow of approximately I l0 ML/d (29 MGD). The plant employs three 6.1 m (20 ft) diameter MIV units, one unit was in operation during the study. The vortex manufacturer states that each unit will remove 650/o of 150 pm git,2.0 SG, at 101 ML/d (26.7 MGD). Average flow during three days of testing was 99.2.}l{.Lld (26.23 MGD), very near the rated capacity of the grit units. The measured removal efficiency was 43-45Yo of all grit 150 pm and larger, 20% below the claimed efficiency, and 43-44%o of all grit 106 micron and larger. Table #2 Removal of MIV Detritus Tank HRSD James River Treatment Plant The testing at HRSD included testing at the James River Treatment Plant (JRTP) which operates detritus tanks for grit removal. The JRTP is aT6MLld (20 MGD) capacity plant with an average flow of approximately 49 MLld(l3 MGD). The JRTP employs four detritus tanks. Each detritus tank is 8.5m (28') diameter with a design capacity of 24.6 ML/d (6.5 MGD). Each unit is designed to remove grit particles 150 pm and larger, with 2.65 SG. Average flow to the plant duriig three days of-testing was 48.75 ML/d (12.88 MGD) with one of the detritus tank units out oiservice; iherefore eich unit was processing approximately 16.27 ML/d (4.3 MGD) or oZ Removal Efficiency CETP #50 Mesh (>297 microns) #70 Mesh (<297 microns >2tl microns) #100 Mesh (<211 microns >150 microns) Total %o Removal 150 pm and up Totalio Removal 106 pm and up 7.0 48. l 45.8Thu. May 17,2007 72.6 I 9 I Fri. May 18,2007 77.8 28.9 14.7 52.1 50.9 o/o Removal Efficiency Total %o Removal 150 pm and up VIP #50 Mesh (>297 microns) #70 Mesh (<297 microns >2ll microns) #100 Mesh (<211 microns >150 microns) Total%o Removal 106 pm and up 45.3 44.3Sun. May 20,2007 57.7 29.8 22.7 23.2 45.1 43.7 Mon. May 21, 2007 60.5 26.8 27.9 43.3 43.3Tue. May 22,2007 59.3 33.2 Copyright O20 I 4 Water Environment Federation WEFTEC 20I4 roughly 33% below their rated capacity. The measured removal efficiency was 66-730/o of all grit I 50 pm and larger and 57 -68%o of all grit 106 micron and larger. Table #3 Removal of Detritus Tank Aerated Grit Basin Columbus GA South Water Reclamation Facilitv The City of Columbus, GA South Water Reclamation Facility (SWRC) operates four AGB units that receive a combined average daily flow of approximately 106 ML/d (28.0 MGD). A rain event occurred on January 28'h,2008 resulting in an increase in the flow to 143.84 ML/d (38 MGD) with a maximum hourly flow of 185.5 ML/d (49 MGD). As can be seen from the results below, when the flow to the grit chamber increased the removal efficiency decreased, as would be expected. The plant has two AGB that are 5.18m x I1.89m (17' x 39') and two basins 3.96m x 10.97m (13' x 36'). While no design removal efficiency data exists, total surface area available for grit settling is 210 mz 12,262 ft2). Based on the average flow of 106 ML/d (28.0 MGD), the AGB system has a surface loading rate (SLR) of 0.35 m3lmin.h] (8.6 gpm/ft2) and would be expected to remove a significant percentage of fine particles, 106 micron and below. The plant notices a decrease in removal efficiency at flows in excess of 132.5 ML/d (35 MGD). Once the flow reaches 132.5 lr/rLld (35 MGD) the SLR increases to 0.435 m3/min./m2 (10.7 gprr/ft2). Based on SLR alone the basin would still be expected to retain a percentage of fine particles at 132.5 ML/d (35 MGD) with particle size retained increasing, and overall capture efficiency decreasing, as flow continues to rise. The measured removal efficiency was35-70oh of all grit 150 pm and larger and32-670/o of all grit 106 micron and larger when the wet weather data is included. Removal efficiency improves to 58-70oh of all grit 150 pm and larger and 53-670/o of all grit 106 micron and larger during average flow of 106 ML/d (28.0 MGD). While excluding the performance during the wet weather event indicates improved performance, removal efficiency is well below what would be expected based solely on SLR. Copyright O2014 Water Environment Federation 4923 oZ Removal Efficiency JRTP #50 Mesh (>297 microns) #70 Mesh (<297 microns >2ll microns) #100 Mesh (<2tt microns >150 microns) Totalo/o Removal 150 pm and up Total o/o Removal 106 pm and up Sun. Jun 17,2007 81.8 72.6 41.7 66.2 57.3 77.2 66.6 73.2 67.7Mon. Jun 18,2007 76.9 71.2 64.2Tue. Jun 19,2007 82.6 74.7 55.3 WEFTEC 20I4 Table #4 Removal of Aerated Grit Basin Stacked Tray System HRSD Army Base Treatment Plant While considering a new grit system for their Army Base Treatment Plant (ABTP), HRSD tested two grit removal technologies side-by-side in December of 2007. The stacked tray Eutek HeadCell@ unit was tested side-by-side a Grit Kirrg'structured flow unit using the same sampling and testing methodology. During the pilot test the stacked tray HeadCell unit was fed at 38.6-38.8 m3/hr 1t70-l7l gpm). At that flow rate the Stacked Tray unit was designed to remove 95%o of all grit 75 micron and larger, with 2.65 SG, however performance was not tested for 75 micron particles. The measured removal efficiency was 92-93%o of all grit 150 pm and larger and 89-90o/o of all grit 106 micron and larger. Table #5 Removal of Stacked Structured Flow System HRSD Army Base Treatment Plant During the side-by-side testing at the ABTP the 1.2 m (4') diameter structured flow Grit King pilot unit was fed at a rate of 38.8 m3/hr (170 gpm) on December 17tr and25.4 m3/hr 1112 gpm) on December 19ft. Design removal parameter at the higher flow is95% of all grit 106 micron and larger, 2.65 SG. At the lower flow of 25.4 m3/hr (l l2 gpm) the removal would be expected to be 95o/o of all grit 75 micron and larger, 2.65 SG, however removal efficiency for 75 micron particles was not reported. As would be expected, the removal efficiency improves at the lower flow rate as loading rate to the unit is reduced. The measured removal efficiency was 90-95% of all grit 150 pm and larger and 87 -93%o of all grit 106 micron and larger. o/o Removal Efficiency Columbus #50 Mesh (>297 microns) #70 Mesh (<297 microns >2ll microns) #100 Mesh (<2tt microns >150 microns) Total o/o Removal 150 pm and up Total o/o Removal 106 pm and up Jan27,2008 81.8 49.8 42.2 70.s 67.2 Jan 28, 2008 53.0 13.5 21.7 35.6 32.5 Jan29,2009 66.3 60.0 44.4 58.7 53. I o/o Removal Efficiency Stacked Tray #50 Mesh (>297 microns) #70 Mesh (<297 microns >211 microns) #100 Mesh (<211 microns >150 microns) Total/o Removal 150 pm and up Total oh Removal 106 pm and up Dec 17,2001 95.8 90.4 81.5 91.9 88.8 Dec 19,2001 95.7 93.0 8s.6 92.5 89.3 Copyright O2014 Water Environment Federation 4924 WEFTEC 2014 Table #6 Removal of Structured Flow Vortex Unit DISCUSSION As can be seen from the above data, testing results for the mechanically induced vortex technology were considerably below the manufacturers' claimed removal efficiency even when running the unit well below design flows. The testing results indicate this technology had its highest measured removal efficiencies for large grit particles, approximately 60%o+ removal of particles larger than297 micron, and very low performance removing smaller particles, with less than30Yo removal of particles 210 micron and smaller. At CETP the MIV was designed to remove95%o of grit 150 micron and larger, with 2.65 SG at a flow of ll4}l{Lld (30 MGD). When operating at 630/o of the design flow (71.1 ML/d (18.79 MGD), the measured removal efficiency of grit particles 150 microns and larger was 48-52o/o, which is more than 40%o less than the stated claim. The 7.3 m (24') diameter MIV unit has a surface area of 41.83 m2 (452 ft\, which results in an estimated SLR of 1.18 m3lmin.krt Q8.97 Wrn/ft\ at7l.l ML/d (18.79 MGD). Based on the SLR the MIV technology would, in theory, be expected to retain a large percentage of particles approximately 165 micron and larger. The measured removal efficiency for much larger particles, 297 microns and larger, was only 72- 78%. The low removal efficiency suggests the importance of considering the likely effects of grit settling velocity and other criteria. Based on operational data from VIP it was found that placing more vortex units into service improved grit removal. During 2007 the plant averaged 99 ML/d (26.2 .}ldGD) and used one vortex unit 83% of the year. For 2008, two vortex units were in service for 75%o of the year and grit production increased 50o/o over 2007 performance. HRSD determined that operating a vortex close to the maximum rated hydraulic efficiency may not be advisable for some treatment plants. Further they concluded that with this technology placing additional grit removal units in service during high hydraulic events can minimizethe impacts of grit slug loads on downstream unit processes. While test data indicates the Detritus tank achieves higher removal efficiency than the MIV technology, the Detritus tank also fell short of design removal efficiency while operating at 66% of design flow. Test data shows relatively high removal efficiencies of large grit particles,TTo/o* removal of particles larger than297 micron and, as would be expected, reduced capability of removing smaller particles, 640/0+ removal of particles 210 micron and smaller. Although an Copyright @2014 Water Environment Federation 4925 %o Removal Efficiency Structured Flow #50 Mesh (>297 microns) #70 Mesh (<297 microns >211 microns) #100 Mesh (<2tt microns >150 microns) Total o/o Removal 150 pm and up Total%o Removal 106 prm and up Dec 17, 2007 93.6 89.4 78.7 90.3 87.5 Dec 19, 2007 - ttz gpm 97.4 94.3 89.0 9s.0 92.7 WEFTEC 2OI4 older style technology, sampling and analysis for the detritus tank displayed some of the higher removal efficiencies of the technologies tested. Removal efficiency would be expected to decline at peak design flow. The AGB results were comparable to those for the Detritus tank during the plant average flow, 58-670/o of all grit 106 microns and larger was removed. During wet weather when the system received the design flow rate, removal efficiency was reducedto 32.5%. Even considering the small increase in flow during the rain event, which was in the region of 135-175% of average, the quantity of grit increased substantially from 3.36 glm3 (28.1 lbs./MG) to 8.89 glm3 (74.2 lbs./MG). The fraction of grit smaller than297-microns also increased significantly. The increased grit quantity and elevated fraction of small grit resulted in the measured poor removal efficiencies. A reduction in removal efficiency at higher flows is expected, however, during the elevated flow, influent grit concentration also increased by a factor of more than 2.5 times the prior day dry weather influent levels. A removal efficiency of 32-35% of the heavier grit load will obviously not be adequate to protect the plant from deposition and abrasive wear. The stacked tray system and structured flow unit test results exhibited very high removal rates. While the performance results for these two technologies were performed as a pilot study they are consistent with full scale performance tests, using the identical test method, at other facilities8'e. Measured removal efficiency for both technologies was slightly below manufacturers claimed removal efficiencies, within +l- 8%. This small deviation is very near the margin of error in testing. Comparatively, these two technologies provide very high removal efficiencies of large grit particles, 93o/o+ removal of particles larger than 300 micron. The measured removal efficiency of particles 150 - 210 micron was only slightly less and ranged from 78-90%+. Both of these technologies displayed the highest removal efficiency of the technologies tested, in all cases >87 .5o of all influent grit 106 micron and larger was captured. CONCLUSIONS Grit sampling using the VSS method produces results that are repeatable, accurate and effective. The results corroborate with grit system performance and plant operating history therefore this data provides insight into what most operators' experience. Using this common testing method allows comparison of performance of various grit removal technologies and can assist in improving grit system design and justifuing advanced processes. Table #7 Relative Performance of Grit Removal Devices Technology % of Design Flow Design Removal Efficiency at l00Yo Flow Measured Total % Removal 150 pm and up Measured Total % Removal 106 pm and up MIV 27-90 95o/o removal of 270 pm,2.65 SG 65%o removal of 150 um,2.0 SG 43-52 43-50 Detritus Tank 66 1 50 pm and larger, 2.65 SG 66-71 57 -68 AGB 66 -100 Unknown 3s-70 32-67 Copyright O2014 Waterhvironment Federation Stacked Tray 100 95Yo removal of 75 pm,2.65 SG 9t-92.s 89-90 Structured Flow Vortex 66-100 95Yo removal of 106 pm,2.65 SG 90-95 87 -93 WEFTEC 20I4 Based on the reported and referenced testing, the technologies that displayed the lowest removal efficiencies were the AGB and the MIV technology. The measured removal efficiency for both technologies was well below claimed removal at peak flows. The AGB displayed a relative removal of only 32%o of all grit 106 micron and larger when operated at peak design flow. Results for the AGB improve to 53-670lo when influent flow to the unit is reduced to 660/o of design. The MIV technology removed 43-51% of incoming grit 106 micron and larger when operated at 27-90o/o of design flows. As is true of all SLR based technologies, the MIV technology shows higher removal efficiencies at lower flows. When operating near design flow rate, removal efficiency was in the 43-45o/o range for all grit 106 micron and larger. As flows decrease, to 630/o of average flow and l2o/o of peak flow, the efficiency increases, but only marginally, to 45-50Yo removal of grit 106 micron and larger. The detritus tank displayed a higher removal rate, removing 57 -69% of all grit 106 micron and larger when operating at average flows, in the region of 66% of peak design flow. The AGB displayed similar results when operated at 66%o of peak flow. When flows increased to peak, the AGB removal efficiency dropped to 32%o and the detritus tanks would be expected to have similar results as flows increase. The structured flow vortex and stacked tray vortex units had very high removal rates, none lower than 87 .5%o of incoming grit I 06 micron and larger. These results are signific antly (20o/o to 55%) higher than any of the other technologies tested. Over the life of the facility, the difference in captured grit is substantial. Also of note, is the fact that high removal results were achieved with the equipment running at peak design flow. None of the technologies tested met their performance claim exactly, although the technologies that targeted the finest particles displayed the best results and came closest to achieving their performance claim. Systems designed for high removal efficiency of small particles, 106 micron and finer, should remove 85o/o or more of grit entering the plant. The measured decrease in performance with increased flows provides strong evidence that the tested technologies are strongly influenced by loading rate and gravity to capture and retain grit. A better understanding of in situ grit settling velocity will allow for more efficient design which would afford the plant increased protection from abrasive wear and deposition. Wet weather is an important consideration in grit system design. The impact of wet weather flows was documented during testing of the ABG in Columbus, GA. Considering the small increase in flow during the rain event, 135-160% of average, the quantity of grit increased much more dramatically, to more than 2.5 times the volume entering the plant during the prior day average flow. One would expect the greatest increase would be of coarse grit particles but the overall gradation was finer. Grit quantities increased across all size ranges but the grit fraction Copyright @2014 Water Environment Federation 4927 WEFTEC 2OI4 larger than297 micron decreased, from 61 .7o/o to 39.Uyo, while particles in the 105-210 micron range increased from 20.6% to 39 .7o/o of the total. Overall, a 600/o increase in flow resulted in a 48o/o decrease in performance. Significant increase in grit volumes during wet weather events is a common phenomenonlo and indicates the need to design the grit system for effective removal at peak hydraulic loadings. The AGB and MIV performed poorly at peak design flow and based on the data the detritus tank would be expected to perform similarly to the AGB. Measured removal efficiencies were less than what would be expected based on SLR alone indicating process inefficiencies or grit settling velocity implications. Designing the grit removal system for high removal efficiency at peak hydraulic loading will protect the plant from the negative impacts of grit. Advanced, compact, high-efficiency grit removal processes are therefore the more appropriate proven choice to protect plants from deposition, abrasive wear and associated costs from this nuisance material. ACKNOWLEDGEMENTS The authors would like to thank Mr. Cliff Arnett, Senior Vice President, Columbus Water Works and Mr. Mike Taylor, Superintendent, Columbus Water Works, South Columbus Water Resources Facility for permission to use data from their testing and providing the additional information needed to compile the comparisons. REFERENCES l. Cote, Brink and Adnan (2006) Pretreatment Requirements for Membrane Bioreactors. WEFTEC 2. Sherony, Herrick, (2011) A Fresh Look at an Old Problem. Design Criteria for Effective Grit Removal. New England Water Environment Association Journal, Spring 201I 3 . http s : //b lackdo ganalytical. corn/M ethods. html (July 20 I 2) 4. Osei, Gwinn & Andoh. (2012) Development of a Column to Measure Settling Velocity of Grit. World Environmental & Water Resources Congress 2012 Conference Proceeding Paper 5. McNamara, Griffiths & Book. (2009) True Grit. A Grit Removal Efficiency Investigation at Five Wastewater Treatment Plants. WEFTEC Conference Proceedings 6. McNamara. (2010) True Grit. The Conduit, Virginia Water Environment Association Winter 2010 7. McNamara, Kochaba, Griffiths & Book (2009) Grit vs. Grit. A Pilot Evaluation Comparing Two Grit Removal Technologies. WEFTEC Copyright @2014 Water Environment Federation 4928 WEFTEC 2OI4 8. Horton. (201 1) Yellow River Grit Selection - Gwinnett County. Georgia Water Professionals 20l l Annual Conference and Expo, Conference Session 9. McKimm & Creed. (2007) Pump Station 4259 Grit Removal System Replacement Project WR444159 at the Marine Corps Air Station, Cherry Point, NC Performance Testing Report 10. New York State Department of Environmental Conservation, Technology Transfer Document, Wet Weather Operating Practices for POTWs with Combined Sewers Copyright O2014 Water Environment Federation 4929