Agenda 05/22/2012 Item #16C 25/22/2012 Item 16.; .%.
EXECUTIVE SUMMARY
Recommendation to waive competition and authorize the purchase of VX456, chemical solution for
use at both the South and North County Water Reclamation Facilities, in the estimated annual
amount of $120,000.
OBJECTIVE: To obtain approval of the purchase of VX456 from Siemens Water Technology for use
at both wastewater treatment facilities.
CONSIDERATIONS: VX -456 is a chemical provided by Siemens under U.S. Patent 5,984,993. This
proprietary product is applied during the sludge ( biosolids) press process. It mitigates odors that may be
produced during the pressing, storage and disposal of sludge (biosolids).
Prior to the addition of VX -456, sodium chlorite was used in the press process. The sodium chlorite was
inefficient in the reduction of odors, resulting in customer complaints and possible regulatory compliance
violations. The Wastewater Department consulted with an odor control vendor, Siemens, for assistance in
finding a product that will eliminate odors through the pressing, storage and disposal of sludge
( biosolids).
A pilot test was performed using VX456 at the North County Water Reclamation Facility. The pilot study
was successful at controlling odors through the process. It has proven to be a technology that efficiently
and effectively controls odors, while minimizing impact to the surrounding neighborhoods. It is
imperative that this chemical continues to be utilized at the Water Reclamation Facilities to ensure
regulatory compliance and commitment to the Public Utilities Department good neighbor policy.
FISCAL IMPACT: The fiscal impact is an estimated $120,000 annually. Funds are available in the
Water /Sewer Fund (408) Cost Center 233312.
LEGAL CONSIDERATIONS: This item is legally sufficient and requires a majority vote for Board
approval. - JBW
GROWTH MANAGEMENT IMPACT: There is no impact on the growth management plan
associated with this action.
RECOMMENDATION: That the Board of County Commissioners, as Ex- officio Governing Board of
the Collier County Water -Sewer District, waive competition and approve the purchase of VX456 from
Siemens Water Technology for a period of five years.
CERTIFICATION BY THE PURCHASING DIRECTOR: By approval of this Executive Summary,
the Purchasing Director certifies that
1. It is in the best interest of the County to continue with this product, and
2. The recommended vendor holds a patent and, therefore, is the sole provider of this
product.
Prepared By: Dale R. Waller, M.P.A — Wastewater Plant Manager, Public Utilities
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Attachments: Siemens- VX456 pdf
VX456 Patent pdf
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5/22/2012 Item
5/22/2012 Item 16.C.2-
COLLIER COUNTY
Board of County Commissioners
Item Number: 16.C.2.
Item Summary: Recommendation to waive competition and authorize the purchase of
VX456, chemical solution for use at both the South and North County Water Reclamation
Facilities, in the estimated annual amount of $120,000.
Meeting Date: 5/22/2012
Prepared By
Name: Jon Flomerfelt
Title: Chemist
4/26/2012 3:48:45 PM
Submitted by
Title: Plant Manager,Wastewater
Name: WallerDale
4/26/2012 3:48:46 PM
Approved By
Name: HapkeMargie
Title: Operations Analyst, Public Utilities
Date: 4/27/2012 8:38:11 AM
Name: Steve Messner
Title: Plant Manager,Water
Date: 4/27/2012 8:58:03 AM
Name: WallerDale
Title: Plant Manager,Wastewater
Date: 5/3/2012 1:53:38 PM
Name: ParkerNicole
Title: Contracts Specialist,Purchasing & General Services
Date: 5/3/2012 2:59:41 PM
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Name: JohnsonScott
Title: Purchasing Agent,Purchasing & General Services
Date: 5/4/2012 12:15:07 AM
Name: MarkiewiczJoanne
Title: Manager - Purchasing Acquisition,Purchasing & Gene
Date: 5/4/2012 12:32:07 PM
Name: MarkiewiczJoanne
Title: Manager - Purchasing Acquisition,Purchasing & Gene
Date: 5/4/2012 12:32:25 PM
Name: WhiteJennifer
Title: Assistant County Attorney,County Attorney
Date: 5/9/2012 1:43:46 PM
Name: YilmazGeorge
Title: Director - Wastewater,Wastewater
Date: 5/10/2012 1:34:20 PM
Name: WhiteJennifer
Title: Assistant County Attorney,County Attorney
Date: 5/14/2012 11:44:51 AM
Name: KlatzkowJeff
Title: County Attorney
Date: 5/14/2012 1:11:19 PM
Name: GreenwaldRandy
Title: Management/Budget Analyst,Office of Management & B
Date: 5/14/2012 1:36:44 PM
Name: OchsLeo
Title: County Manager
Date: 5/14/2012 4:02:30 PM
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5/22/2012 Item 16.C.-2.
SIEMENS Industry
Mr. Jon Pratt
Collier County, NCWRF
10500 Goodlette Rd.
Naples, FL 34109
E -mail: jonpratt @colliergov.net
RE: VX- 456® FOR BELT PRESS ODOR CONTROL
Dear Jon:
5/22/2012 Item 16.0..2.
September 7, 2011
We at Siemens are pleased that VX -4560 has been a successful part of your odor control program at the
North Water Reclamation Facility. We are pleased to be able to renew your pricing for VX -4560 for the
coming year. The price for full -load quantities (min. 40,000 lb.) is $0.94 per pound. The price for less
than full load quantities is $1.29 per pound. This price will remain in effect until September 30, 2012.
Siemens Industry, Inc. is the sole provider of VX -456' solution for odor control for the wastewater
industry. -
Thanks again for the opportunity to be of service to Collier County, Jon. Please give me a call at 941-
928 -0453 of you have any questions on this information or if I can be of assistance in any way.
Sincerely,
Siemens Industry, Inc.
V au f4uu v h a.rshma.w, P. E.
Vaughan Harshman, P.E.
Technical Sales Representative
Cc: Rich Lalama, Siemens
Craig Bliss, Siemens
Johnny Arteaga, Collier County, ivanarteaaa(a'�colliergov.net
Siemens Industry, Inc. 2650 Tallevast Road Tel: +1 941 -355 -2971
Sarasota, FL 34243 Fax: +1 941 359 -7985
USA www.siemens.com /water
Page 1 of 1
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Cv er County
Purchasing - Sole Source
Waiver Request
5/22/2012 Item 15.._.
'Print forte i,
To Be Submitted To Acquisitions Agent Fo. mole Soures..P#rchases• Aj4 pyE ice:
tPRl�1R TO Ei1TIl�G A iQUtS1QN)
Purchases above $30Q0 require three quotes ar<tormat corrtpetlioh The depaeim lent must
request ccinsidemfici : to waive the, qom etJ1fwr6 purcizasm tiftr stn t° - Purattes#r!g o
P 9rgcess ael,i?dtiase ffroc(t 8 sk °trendt5r$,asole`icirce"
purchase. Waive of .sole source over - 50,Q00 will rirquire epprova! b the 6'oard of G3urtty trgi�rtrfissirirters. To gtial#fli> +8
waiver and a sole source purchase, one flf the ategaires listed'beiow moist a p*,
Sole Source must meet two (2) tests. Produ Nt"rvicehechnology-4s #te only one thatcan property_.i rer#amt:the intended fitnCtic rx;
AND vendor is only one ready, willing and able to meet County's requiren'ebts.
Date Department]
,
Vendor Name' /'1C�
Item or Service
Select the category and provide rationale which supports time justification to consider waiving
the competitive process for this purchase (attach all supporting documentation)
(' Emergency: There is a public health or safety issue that requires immediate product or service (i.e. disasters).
Provide explanation
One -of-a -kind: There is no competitive product (one- of- a-kind, and /or is available from only one vendor).
Provide explanation
of research
(~ Compatibility/Proprietary: There is only one product or service capable of meeting existing conditions and the service can be
obtained from only one vendor. (OEM)
Provide Explanation
r No Substitute: A component or replacement part has no substitute and can be obtained from only one vendor.
Provide Explanation
(^ Authorized Distributor: Provide a letter from the manufacturer stating single source authorized distributor(s).
What similar types of products (other companies) have you researched to find like features and operability to determine this is a
sole source purchase? Attach documentation.
It is a felony to knowingly circumvent a competitive process for commodities orservices by fraudulently '
specifying sole source. Florida Statute 838.22(2).
Requested b :
4 Y Date
1
Department Director., . Date—
Acquisitions Agent•. Date
Packet Page -1449-
id
United States Patent: 5984993
5/22/2012 Item 16.C.2.
USPTO FIAT mT FuLL-TI XT' AND II4'IA as DATAaASE
Hoev�e
E�ui k t ds ar,ce Pat N—t —i filet
View Cart Add to Cart
IMa92
United States Patent
Mainz , et al.
Method and composition for odor control
Abstract
(IOfI)
5,984,993
November 16,1999
A method and composition are provided for controlling odor from waste products. The composition
comprises a combination of chlorite salt and nitrate salt. The method includes the step of contacting the
waste products or their surrounding airspace with the composition.
Inventors: Mainz; Eric L. (Colwich, KS), Griffith; David B. (Wichita, KS)
Assignee: Vulcan Materials Company (Wichita, KS)
Appl. No.: 09/044,876
Filed: March 20, 1998
Current U.S. Class:
Current International Class:
Field of Search:
2711363
3966450
3967039
3997462
71/12 ; 210/758; 210/916; 252/187.23; 422/28; 422/5;
424/76.5; 424/76.6; 424/76.7; 71/15
C05F 7/00 (200601.01); C05C 5100 (20060101); C05C
5/02 (20060101); CO2F 1150 (20060101); A61 L
11/00 (20060101); A61 L 9/01 (20060101); CO2F
1/76 (20060101); C05F 003/00 (); CO2F 001/72 0; A61L
011 /00 (); A61 L 009/00 ()
210/916,758 422/28,5 71/11,12,15
424/76.1,76.21,76.5,76.6,76.7 252/187.23
References Cited lReferenced Bvl
U.S. Patent Documents
June 1955
June 1976
June 1976
December 1976
Waibel
O'Neill et al.
Ninane et al.
Denaeyer et aI.
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United States Patent: 5984993
4007262
4108771
4681687
4911843
4995987
5114587
5336431
5820822
1175851
February 1977
August 1978
July 1987
March 1990
February 1991
May 1992
August 1994
October 1998
Foreign Patent Documents
Jul., 1989
Other References
5,122/2012 Item 16.0.2,
Bowers
Weiss
Mouche
Hunniford et al.
Whitekettie et al.
Hagerstedt
Richards et al.
Kross
JP
A Jobbagy, et al., "Sewer System Odour Control In The Lake Balaton Area ", Wat. Sci.
Tech., vol. 30, No. 1, pp. 195 -204, 1994..
CA 122:196088, "Deordorization of Sludge for dewatering by controlled adding chlorite ",
Hina. Seiya (Kurita Water Ind Ltd., Japan) Jpn. Kokai Tokkyo Koho JP 06320195 A2
941122 Heisei, 12 pp. (Japanese)..
R.E. Paine and K.C. Thompson, "Polyelectrolyte Conditioning of Sheffield Sewage Sludge ",
Wat. Sci. Tech., vol. 16, Vienna, pp. 473-486..
CA 104:10062b, "Control of odors from sewage sludge ", Bosshard, Stephan; Ost Karl
(Degussa [Schweiz] A. -G., 8040 Zurich Switz.), Gas Wasser, Abwasser 1985, 65(7), 410 -13
(Ger). .
CA 85:82749t, "Slime and oder elimination in process water of the paper industry ", Schwab,
Heinrich; Kaschke, Wenner (DEGUSSA Wolfgang, Wolfgang/Nanau, Ger.)., Paper
(Darmstadt) 1975 29(10A, Spec. Issue), 43 -51, (Ger). .
Martin Lang, "Chemical Control of Water Quality in a Tidal Basin ", Journal- -Water
Pollution Control Federation, pp. 1410 -1419, Sep. 1966. .
Dague, Journal- -Water Pollution Control Federation, p. 586. .
Plant Operations, p. 301, Mar. 1981. .
Fundamental Principles of Bacteriology, pp. 328 -330. .
H.A. Painter, A Review of Literature on Inorganic Nitrogen Metabolism in Microorganisms
pp. 399 -400. .
Design Manual, "Odor and Corrosion Control in Sanitary Sewerage Systems and Treatment
Plants ", Center for Environmental Research Information, U.S. Environmental Protection
Agency, Office of Research and Development, Oct. 1.985, pp. 8-9..
Results of Literature Search.,
Primary Examiner: Straub; Gary P.
Assistant Examiner: Wong; Melanie C.
Attorney. Agent or Firm: Burns, Doane, Sweeker & Mathis, L.L.P.
Claims
What is claimed is:
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United States Patent: 598499' 1 5/22/2012 Item 16.0.2.
1. A method for controlling odor from waste products, the method comprising the step of:
contacting the waste products or their surrounding airspace with a composition comprising a
combination of chlorite salt and nitrate salt in a weight ratio of about 2.25:1 chlorite salt to nitrate salt.
2. The method according to claim 1, wherein the chlorite salt is an alkali or alkaline earth metal chlorite.
3. The method according to claim 2, wherein the chlorite salt is selected from the group consisting of
sodium chlorite, calcium chlorite, and potassium chlorite.
4. The method according to claim 1, wherein the nitrate salt is selected from the group consisting of
sodium nitrate, calcium nitrate, and potassium nitrate.
5. The method according to claim. 1, wherein the composition comprises from 0.5 to 99.5% by weight of
the chlorite salt.
6. The method according to claim 1, wherein the composition is in the form of an aqueous solution.
7. The method according to claim 6, wherein the composition comprises from about 0.5 to about 50% by
weight of the chlorite salt, and from about 1 to about 99% by weight of water.
8. The method according to claim 7, wherein the chlorite salt is sodium chlorite and the nitrate salt is
sodium nitrate.
9. The method according to claim 8, wherein the composition comprises about 22.5% by weight of
sodium chlorite, about 10% by weight of sodium nitrate, and about 67.5% by weight of water.
10. The method according to claim 1, wherein the composition further comprises an acid, hypochlorite,
aldehyde, or ketone.
Description
FIELD OF THE INVENTION
The present invention relates to a method and composition for controlling odor from waste products
such as organic waste produced by metabolic processes, including human and animal waste, as well as
industrial wastes, effluents, sewage, and the like.
BACKGROUND OF THE INVENTION
The occurrence of volatile odorous substances is one of the problems associated with the collection and
treatment of various waste materials. Domestic sewage is the largest volume source of odorous waste for
which sulfides and thiols are very common odor causing constituents. Sulfides are most prominent, with
hydrogen sulfide being the most objectionable odor - bearing compound in such wastes. Because of the
magnitude of domestic sewage that is collected and treated and the prominence of odorous sullidic
compounds associated with this waste, the present invention is particularly directed, but not limited to
the control of hydrogen sulfide and other sulfide odors in sewage. As used herein, the term "hydrogen
sulfide" (H.sub.2 S) also includes other sulfides of divalent sulfur.
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United States Patent: 5984993 5/22/2012 Item i 5.C.2
Biological activity, especially anaerobic decomposition of compounds containing sulfur, is responsible
for the formation of most odorous sulfur compounds, especially H.sub.2 S. Sulfate ion (SO.sub.4.sup. -2)
is the most common starting material for the generation of H.sub.2 S. In the absence of oxygen, sulfate -..
reducing bacteria (for example, desulfovibrio desulfuricans) will metabolize sulfate ion. together with
organic matter present to form H.sub.2 S, as represented by the following equation:
The odor.associated with H.sub.2 S is similar to rotten egg odor. H.sub.2 S is toxic in low
concentrations. Hydrogen sulfide is also corrosive towards steel and concrete. The presence of H.sub.2 S
and other odor causing compounds in waste materials is a major concern for waste handling systems.
One aspect of the occurrence of malodorous compounds that is often the driving force behind efforts to
control odor is complaints received from citizens living in the area. Such odors are generally regarded as
a public nuisance and a. health hazard.
Hypochlorite (sodium or calcium), potassium permanganate, sodium nitrate, ferrous and ferric chloride,
ferrous sulfate, hydrogen peroxide, chlorine, chlorine dioxide, and sodium chlorite have been widely
used for the control of odor in wastes, and sewage waste in particular. For example, articles have been
published and patents have been granted for the use of sodium chlorite and sodium. nitrate individually
to control odorous compounds. The following references mention the use of sodium chlorite by itself for
odor control:
"Control of Odors from Sewage Sludge," Gas, Wasser, Abwasser, Vol. 65, pp. 410 -413 (1985) in
Chemical Abstracts 104:10062 (German);
"Polyelectrolyte Conditioning of Sheffield Sewage Sludge," Water Science Technology, Vol. 16, pp.
47' )-486 (1984) in Chemical Abstracts 102:100249;
"Slime and Odor Elimination in Process Water of the Paper Industry," Papier, Vol. 29, pp. 43 -51 (1975)
in Chemical Abstracts 85:82749 (German); and
"Deodorization of Sludge for Dewatering by Controlled Adding Chlorite," Japanese Patent Publ. No.
06320195 (1994).
The following patents mention the use of nitrate by itself for odor control:
"Method of Sewage Treatment," U.S. Pat. No. 5,114,587 (May 9,1992);
"Process for Removal of Dissolved Hydrogen Sulfide and Reduction of Sewage BOD in Sewer or Other
Waste Systems," U.S. Pat. No. 4,911,843 (Mar. 27, 1990); and
"Use of Alkali Metal Nitrites to Inhibit H.sub.2 S Formation in Flue Gas Desulfurization System
Sludges," U.S. Pat. No. 4,681,687 (Jul. 21, 1987).
In addition, patents have been issued for the use of oxidants in combination with nitrates. For example,
U.S. Pat. No. 4,108,771 contains claims directed to the use of sodium chlorate and ammonium nitrate for
odor control of waste materials. U.S. Pat. No. 3,966,450 contains claims directed to the use of hydrogen
peroxide and the addition of nitric acid to generate nitrate salts. U.S. Pat. No. 5,200,092 contains claims
directed to the use of potassium permanganate with nitrate salts for odor control.
Some of the treatments mentioned above have advantages in certain applications. However, they also
suffer from various drawbacks. Some of the disadvantages of the above - mentioned treatment chemicals
are listed below.
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United States Patent: 5984993
5/22/2012 Item 16.C.2.
Hypochlorite /chlorine Loses strength during storage.
Reacts with ammonia for additional consumption. Forms chlorinated VOCs. Generates chlorine odor
with over - doses. Has no long -term effect. Potassium Permanganate Is labor intensive. Causes
discoloration with over - doses. Results in precipitation of manganese. Nitrates Have no immediate or
short term effect. Produce nitrogen by- products which can present treatment problems. Iron Salts Are
ineffective for non - sulfide odors. Cause build -up of solids. Impure products can contain heavy metals.
Can be toxic to microorganisms. Deplete dissolved oxygen and alkalinity. Hydrogen. Peroxide Requires
catalysis for non - sulfide odors. Causes foaming. Is not long lasting. Chlorine Dioxide Requires a
generator. Generates chlorine -type odor with over- doses. Is not long lasting. Sodium Chlorite Can be
costly in high doses.
In view of the disadvantages mentioned above, there is a need in the art for a method and composition
for abating odor in waste materials that is cost effective and that not only works well on all malodorous
compounds, but that does not produce undesirable by- products. Accordingly, it is an object of the
present invention to address this need in the art. This and other objects of the present invention will
become more apparent in light of the following surnmary and detailed description of the invention and
the appended claims.
SUMMARY OF THE INVENTION
Briefly, the present invention relates to a method and composition for controlling odor from waste
products. The composition comprises a combination of chlorite salt and nitrate salt. Preferably, the
composition comprises a combination of sodium chlorite and sodium nitrate. The method according to
the present invention comprises the step of contacting the waste products or their surrounding airspace
with the composition.
Malodorous compounds can be destroyed easily, rapidly, at a reasonable cost and continue to be
controlled with the composition according to the present invention. Sodium chlorite has been found to
be extremely effective in control of sulfide and other malodorous compounds found in sewage. This
reaction is extremely rapid, requiring only seconds.
An additional benefit with the use of sodium chlorite is that it does not react with ammonia, so that
dosing concentrations are not elevated due to ammonia demand. Sodium chlorite is generally sold in
solution form (up to 50% strength), which can be easily dosed by pump action. The solution does not
lose strength over time.
Sodium nitrate is added to promote residual control of sulfide formation. The sodium nitrate alters the
environment, i.e., the waste, such that the sulfate- reducing bacteria stop producing H.sub.2 S. The
concentration of nitrate salt in the solution may vary according to the residual odor control desired. The
greater the amount of nitrate, the more the residual control of sulfide.
It was surprisingly and unexpectedly found that the combination of sodium chlorite and sodium nitrate
provided synergism for odor control. The combination of these compounds can provide more odor
control than the sum of their individual effects.
DETAILED DESCRIPTION OF THE INVENTION
The composition for controlling odor from waste products according to the present invention comprises
a combination of chlorite salt and nitrate salt. As used herein, the term "controlling odor" means
reducing and /or eliminating odor that is offensive to humans. Such odors are usually caused by volatile
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United States Patent: 5994993
sulfides and other volatile odorous substances.
5/22/2012 Item
The waste products treatable with the present invention include, but are not limited to organic waste
produced by metabolic processes, including human and animal waste, as well as industrial wastes,
effluents, sewage, and the like. The chlorite salt employed in the composition is preferably an alkali or
alkaline earth metal chlorite and is more preferably selected from the group consisting of sodium
chlorite, calcium chlorite, and potassium chlorite. Likewise, the nitrate salt is preferably selected from
the group consisting of sodium nitrate, calcium nitrate, and potassium nitrate.
The composition can be employed as a solid mixture. Preferably; the composition comprises from 0.5 to
99.5% by weight of the chlorite salt and from 0.5 to 99.5% by weight of the nitrate salt. In a preferred
embodiment, however, the composition is employed in the form of an aqueous solution. Preferably, the
solution comprises from about 0.5 to about 50% by weight of the chlorite salt, from about 0.5 to about
50% by weight of the nitrate salt, and from about 1 to about 99% by weight of water. In a particularly
preferred formulation, the composition comprises about 22.5% by weight of sodium chlorite, about 10%
by weight of sodium nitrate, and about 67.5% by weight of water.
A solution of sodium chlorite and sodium nitrate according to the invention can be used easily to destroy
the malodorous characteristics of odor causing compounds such as sulfides found in sewage and other
waste products. The solution can be pumped into the material to be treated (liquid, sludge, or solid) or
sprayed onto the surface or into the airspace surrounding the material.
The sodium chlorite provides rapid control of malodorous compounds such as sulfides. The treatment
concentration is directly dependent upon the amount of odor causing compounds with chlorite demand
that are present in the waste.
The sodium nitrate alters the environment, i.e., the waste, so that the sulfate reducing bacteria stop
producing H.sub.2 S. The stoppage of H.sub.2 S production using nitrate is not immediate, can take
from 10 -24 hours, and will remain until no nitrate is present. The concentration of nitrate salt present in
the treatment solution may vary depending upon the amount of residual control of malodorous
compounds that is required. Nitrate is less costly than chlorite and thus lowers the cost per pound of the
treatment solution. Using a combination of nitrate plus chlorite treatment of sulfide odors also has an
unexpected beneficial effect. It has been surprisingly found that the treatment combination is capable of
controlling sulfide odors much more effectively than the sum of the control when using either nitrate or
chlorite alone.
The waste material to be treated may vary in temperature within normal operating conditions above the
freezing and below the boiling point of the waste. The reaction rate may vary depending upon the
temperature, which increases with increasing temperature. High temperatures in malodorous waste are
generally undesirable due to an increase in volatilization of the odor causing compounds. The pH of the
waste material may vary from I to 14.
Sodium chlorite, when added to acidic materials, will generate chlorine dioxide, which is also effective
in destroying malodorous compounds. The reaction rate of sodium chlorite to chlorine dioxide increases
as pH becomes lower. It is preferred, however, to avoid the use of chlorine dioxide for creating sewage.
Laboratory tests have demonstrated that chlorine dioxide can cause the formation of a strong, bile -like,
odor in sewage. Sodium chlorite does not form such a bile -like odor in the same application.
Nonetheless, chlorine dioxide may be desired for use when sterilization is important, since it is actually
a stronger oxidant than sodium chlorite. Certain other compounds when present, can cause sodium
chlorite to react to form chlorine dioxide, such as acid, hypochlorite, aldehydes, and ketones.
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United States Patent: 5984993 5/22/2012 Item 16.C.2.
W."- .. 91a11�•�
The invention will now be described with reference to the following examples. The examples, however,
are provided to illustrate the invention and are not deemed to limit any aspect thereof.
Example 1
Effect of Sodium Nitrate Addition to Odor Control of Sewage Treated with Sodium Chlorite
A series of tests were conducted in the laboratory to determine the effect of adding a nitrate salt to
sodium chlorite to impart residual control of malodorous compounds in sewage. Samples of sewage
sludge from a municipal treatment plant in the Midwest were treated with varying concentrations of
sodium chlorite with and without sodium nitrate, also of varying concentrations. The treatment
chemicals were added to approximately 50 grams each of sewage sample in small plastic bottles. The
bottles were capped, shaken, and stored at room temperature. After 15 minutes, the samples were
physically smelled to determine the degree of odor destruction as compared to a control sample of
untreated sewage. The sample bottles were then re- capped, allowed to remain at room temperature for
twenty -four hours, and then re- tested for odor destruction. The results of the testing are contained in
Tables 1 -4 below.
In the Tables, the odor of the untreated sample was arbitrarily given a value of 100. Values of less than
100 were given to the treated samples according to the amount of decrease in odor, as a subjective
observation. The odor at a value of 100 was typical of raw sewage and was extremely unpleasant. The
odor at a value of I could be described. as humus, not an unpleasant odor and typical of normal soil.
TABLE I Apparent Odor for Treatment with
NaClO.sub.2 and No NaNO.sub.3 PPM NaCIO.sub.2
274 547 1090 2693 PPM NaNO.sub.3 0 0 0 0 Odor After 10 5 3 1 15 Mins. Odor After 80 40 20 8 24
Hrs,
TABLE 2 Apparent Odor for Treatment with 25:1
NaCIO.sub.2 to NaNO.sub.3 PPM NaCIO.sub.2 248 495
990 2475 PPM NaNO.sub.3 10 20 40 100 Odor After 10 5 3 1 15 Mins. Odor After 40 20 10 4 24 Hrs.
TABLE 3 Apparent Odor for Treatment with 4.75:1
NaCIO.sub.2 to NaNO.sub.3 PPM NaCIO.sub.2 238 475
950 2375 PPM NaNO.sub.3 50 100 200 500 Odor After 10 5 3 1. 15 Mins. Odor After 20 10 5 2 24 Hrs.
TABLE 4
NaCIO.sub.2 to NaNO.sub.3
900 2250 PPM NaNO.sub.3
Hrs.
Apparent Odor for Treatment with 2.25:1
PPM NaCIO.sub.2 225 450
100 200 400 1000 Odor After 10 5 3 1 15 Mins. Odor After 24 10 5 3 1
As can be seen from Table 1, sodium chlorite renders the sewage nearly odorless after a dose of 2693
ppm. Also as seen from Table 1, after 24 hours the odor starts to return as bacteria generate additional
malodorous compounds. However, the samples that contain sodium nitrate, as in Tables 2 -4, retard the
formation of new odor causing compounds. The degree of residual odor control is dependent on the
concentration of nitrate.
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Example 2
Oxidative Effect of Sodium Nitrate on Sulfide
A series of tests were conducted in the laboratory to measure the ability of sodium nitrate to oxidize
sulfide.
A sulfide water sample was prepared by dissolving 20 grams of sodium sulfide (Na.sub.2 S) in 1000
mLs of de- ionized water. The sample was adjusted to a pH of 7 with acetic acid and a phosphate buffer.
A 10% sodium nitrate (NaNO:sub.3) solution was also prepared. Sample bottles were spiked with 1:0
mL of the sulfide stock, varying amounts of the nitrate stock, and filled to a total volume of 100 mLs.
This procedure allowed for a constant concentration of sulfide while varying the nitrate concentration.
The samples were analyzed for sulfide using Standard Method 4500- S.sup.2 -- F (from Standard
Methods for the Examination of Water and Wastewater, 19.sup.th ed., 1995, pp. 4 -127), which is an
iodometric back - titration method. This method involves adding excess iodine to the sample, which is
reduced according to the concentration of sulfide present. The excess iodine is then titrated with sodium
thiosulfate to determine, by difference, the amount of iodine consumed by the sulfide.
The samples were analyzed at 1, 24, 48, and 72 hours from the time of initial dosing with NaNO.sub.3.
The samples were stored in sealed glass bottles, in the dark, at room temperature. The normality of the
iodine solution used was 0.0162 N, and the normality of the sodium thiosulfate was 0.20 N. Each
titration consisted of 5 mLs of iodine solution, 5 mLs of sample, about 100 mLs of de- ionized water,
potassium iodide (KI), and starch. A Hach digital titrator was used for the titrations. The results of all
the tests are shown in Table 5 below.
TABLE 5
Sulfide Control by Oxidation with Sodium Nitrate Sample A B C D E F G H I NaNO.sub.3 Wt. % 0
0.01 0.05 0.1 0.2 0.5 12 4
158 165 163 165 164 163 162 161 162 Sulfide % 0 0 0 0 0 0 0 0 0 Control 24 Hrs PPM 150
157 163 164 155 154 Sulfide % 0 0 0 0 0 0 0 0 0 Control 48 Hrs PPM 149 152 162 150 154
1 Hr PPM
152 152 156
161 158 154
157 Sulfide % 0 0 0 0 0 0 0 0 0 Control 72 Hrs PPM 141 154 156 141 157 157 150 15' ) 146 Sulfide % 0
00000000 Control
There was no observed oxidative effect of sodium nitrate on the concentration of sulfide present in any
of the test samples. As seen from the results shown in Table 5, sulfide concentrations varied somewhat
from the beginning of the test to the end, but in no case was there less sulfide in any of the nitrate- treated
samples than in the untreated control. Therefore, it would be reasonable to conclude that any decrease in
sulfide observed. in tests using media other than water, such as sewage sludge, would be the result of
factors other than chemical oxidation by nitrate.
Example 3
Effect of Sodium Nitrate Addition to Odor Control of Sewage Treated. with Sodium Chlorite
A series of laboratory tests were conducted using sewage sludge collected from a Midwestern sewage
plant. The sewage sludge samples were spiked with sodium sulfide (Na.sub.2 S) to increase the
concentration of treatable sulfide. A 3000 mL batch of sewage sludge was spiked with a liquid solution
of sodium sulfide, and the batch was adjusted with sulfuric acid to a pH of 5.5 to 6.0. Plastic bottles
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United States Patent: 5984993
5/22/2012 Item 16.0.2.
were filled with 200 mLs of sludge each. The samples were then dosed with sodium nitrate, sodium
chlorite, and the combination of the two. The samples were then capped, shaken, and centrifuged. A
portion of the centrificate was titrated iodimetrically using Standard Method 4500- S.sup.2- F (from
Standard Methods for the Examination of Water and Wastewater, 19.sup.th ed., 1995, pp. 4 -127). The
samples were then re- shaken and set aside at room temperature. This analysis was repeated at 24, 48,
and 72 hours.
Samples of the sulfide fortified master sludge sample were treated with sodium nitrate at concentrations
of 100, 200, and 300 parts per million. A second set of master sludge samples was treated with 225, 450,
and 675 parts per million sodium chlorite. A third set of master sludge samples was treated with a
combination of sodium nitrate plus sodium chlorite using 100/225, 200/450, and 300/675 respective
ppm sodium nitrate /ppm sodium chlorite ratios.
The results for samples treated with sodium nitrate are shown in Table 6 below. Sulfide concentrations
were determined at 1, 24, 48, and 72 hours. As seen below, in general it was recorded that nitrate gave
only modest control of the sulfide after one hour and also at 48 hours.
TABLE 6 Control of Sulfide Odor Versus Time with
Sodium Nitrate B C D Sample A 100 PPM 200 PPM 300 PPM PPM Sulfide Control NaNO.sub.3
NaNO.sub.3 NaNO.sub.3 1 Hour 276 ppm S.sup.-2 201
196 216 % Control 0.0 27.2 29.0 21.7 24 Hours 164 ppm S.sup.-2 179 172 172 % Control 0.0 0.0 0.0
0.0 48 Hours 169 ppm S.sup.-2 139 152 1.59 % Control 0.0 17.8 10.1 5.9 72 Hours 144 ppm S.sup. -2
137 144 137 % Control 0.0 4.9 0.0 4.9 % Control =
[(Initial Sulfide Conc. - Sulfide Conc. of Treated Solution) .times. 100] / Initial Sulfide Conc.
The results for samples treated with sodium chlorite are shown in Table 7 below. Due to the high level
of sulfide in the samples, significant reduction of sulfide was not seen until the chlorite dose of 675 ppm.
At this treatment level, the percent control was 66 percent after 1 hour. The percent control decreased
with time, being only about 5 percent after. 72 hours. Overall, chlorite was much more effective at
reducing sulfide as compared to nitrate.
TABLE 7 Control of Sulfide Odor Versus Time with
Sodium Chlorite F G H Sample A 225 PPM 450 PPM 675 PPM PPM Sulfide Control NaC1O.sub.2
NaCIO.sub.2 NaClO.sub.2 1 Hour 276 ppm S.sup.-2
188 199 94 % Control 0.0 31.9 27.9 65.9 24 Hours 164 ppm S.sup. -2 222 179 107 % Control 0.0 0.0 0.0
34.8 48 Hours 169 ppm S.sup. -2 179 164 137 % Control 0.0 0.0 0.0 18.9 72 Hours 144 ppm S.sup. -2
164 157 137 % Control 0.0 0.0 0.0 4.9 % Control =
[(Initial Sulfide Conc. - Sulfide Conc. of Treated Solution) .times. 100] / Initial Sulfide Conc.
The results for samples treated with a formulation containing a combination of sodium nitrate and
sodium chlorite are listed in Table 8 below. It was unexpectedly found that this combination of nitrate
and chlorite was much more effective at reducing and controlling sulfide as compared to the control
achieved by summing the sulfide reductions from separate nitrate and chlorite treatments. This improved
control can best be described as a synergistic effect.
TABLE 8 Sulfide Control Versus Time for a
Combination of Sodium Nitrate Phis Sodium Chlorite Combination Combination Combination Sample
A of of of PPM Sulfide Control B+ F C+ G D+ H I
Hour 276 ppm S.sup. -2 94 72 61 % Control 0.0 65.9 73.9 77.9 24 Hours 164 ppm S.sup. -2 97 79 22 %
Control 0.0 40.9 51.8 86.6 48 Hours 169 ppm S.sup. -2 89.0 64.0 29.0 % Control 0.0 47.3 62.1 82.8 72
Hours 144 ppm S.sup. -2 92 72 42 % Control 0.0 36.1 50.0 70.8
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United States Patent: 5984993
5/22/2012 Item
% Control = [(Initial Sulfide Cone. - Sulfide Cone. of
Treated Solution) .times. 100] / Initial Sulfide Cone.
The percent synergy determined for the combination of nitrate plus chlorite treatment is shown in Table
9 below. It can be surprisingly seen that beginning at the 24 hour time period and continuing through 72
hours, the majority of the control of sulfide was due to the synergy.
TABLE 9 Percent Control of Sulfide Odor Measured as
Synergistic Effect of Sodium Nitrate Plus Sodium Chlorite Formulation % Synergistic Combination
Combination Combination Control of of of Hours B + F C + G D + H
1 10.3% 23.1% 0.0% 24 100.0 100.0 59.8 48 62.4 78.9
70.0 72 86.4 100.0 86.2 Percent Synergist Effect =
{[Sulfide after Combination Treatment - (Sulfide after Nitrate Treatment + Sulfide after Chlorite
Treatment)] .times. 1001 / Sulfide after Combination Treatment
A convenient method for quantifying the synergistic effect was calculated as follows:
where
a= Percent Control of Sulfide after Nitrate Treatment:
b= Percent Control of Sulfide after Chlorite Treatment; and
c= Percent Control of Sulfide after Combination Treatment.
As an example of the synergistic effect, the advantage of the combined formulation is demonstrated
more fully in Table 10 below. This Table shows the data for the experiment using the highest chemical
doses of the combination formulation tested., i.e., 300 ppm sodium nitrate plus 675 ppm sodium chlorite.
TABLE 10
Percent Control of Sulfide Versus Time and Comparison of Additive and Combination Effects of
Treatment of Sulfide with Nitrate and Chlorite a b (a + b) c Percent Additive Effect Combination Effect
Combination Effect Control NaNO.sub.3 NaCIO.sub.2 300 ppm NaNO.sub.3 300 ppm NaNO.sub.3
Percent Synergistic Hours 300 ppm 675 ppm 675 ppm NaCIO.sub.2 675 ppm NaCIO.sub.2 Control
1 21.7%
65.9% 87.6% 77.9% 0.0% 24 0.0 34.8 34.8 86.6 59.8 48 5.9 18.9 24.8 82.8 70.0 72 4.9 4.9 9.8 70.8 86.2
As seen in Table 10 above, exceptional control of sulfide was achieved with the combination of nitrate
plus chlorite as compared to the additive effects of nitrate and chlorite. The combination is especially
effective beginning at some period after one hour through 72 hours and beyond. At 72 hours, only 10
percent control of sulfide was achieved with the additive effects of separate nitrate and chlorite
treatment as compared to the 70.8 percent control with the combination of nitrate plus chlorite treatment.
Therefore, the synergistic effect accounted for 86 percent of the control, i.e., {[70.8 -
(4.9 +4. 9)1.times.1001/70.8=86.2%.
While the invention has been described with reference to particular preferred embodiments and
examples, it is to be understood that variations and modifications may be resorted to as will be apparent
to those skilled in the art. Such variations and modifications are to be considered within the purview and
the scope of the claims appended hereto.
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