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Item 4DCITY OF SOUTH LADE MEMORANDUM (June 7, 2011) To: Shana Yelverton, City Manager From: Robert H. Price, P.E., Director of Public Works Subject: Approve an annual agreement for providing odor control treatment at lift stations with Premier Chemicals, LLC in the amount of $87,600.00 Action Requested: Approve an annual agreement for providing odor control treatment at lift stations with Premier Chemicals, LLC in the amount of $87,600.00 Background Information: Since the construction of the Shady Lane and Lonesome Dove Sanitary Sewer Lift Stations in 2000, the city has spent approximately $85,000 per year to prevent hydrogen sulfide production in the sewer system from affecting the residents of the Kirkwood Hollow neighborhood. Premier Chemicals has been providing this service for Southlake and TRA since 2006 because previous attempts to control the hydrogen sulfide with other products were not successful. The cost per gallon for this service has remained constant since June 2008. The projected increases are due to increased waste water flows at the two lift stations where the product is used. Premier Chemical is a sole source provider and patent holder of this technology. An additional benefit to this technology is the prevention of grease buildup in the lifts stations eliminating the need for City crews to remove and dispose of excess grease. Staff is recommending that Council accept the proposal offered by Premier Chemical, LLC to guarantee a rate $2.40 per gallon for their services for a 12 -month period with an estimated annual cost of approximately $87,600.00. Financial Considerations: Funding for this program is available in the current operating budget of the Waste Water Division. Strategic Link: The annual purchase agreement for the chemical treatment of wastewater links to the city's strategy map relative to the strategic focus area of Performance Management and Service Delivery. The specific corporate objectives that are met by this agreement include: Providing high quality customer service by eliminating odors released in the collection system and optimizing the use of technology with state of the art treatment of wastewater. Citizen Input/ Board Review: N/A Legal Review: None Alternatives: The City Council may approve or deny the agreement to provide odor control treatment at lift stations. Supporting Documents: Annual Contract Pricing Renewal Letter Patent Documentation Staff Recommendation: Approve an annual agreement for providing odor control treatment at lift stations with Premier Chemicals, LLC in the amount of $87,600.00 Staff Contact. Robert H. Price, P.E., Public Works Director Chuck Kendrick, Deputy Director of Public Works - Operations MJ aate++■■ � , J' J_iff■■ j _.J --I CHjEMICALS= LLC May 11, 2011 Chuck Kendrick Public Works Operations Manager City of Southlake Phone (817) 748 -8080 Fax (817) 748 -8103 ckendrick(u�ci. southlake.tx.us Re: Annual Contract Pricing Renewal Chuck: Pursuant to your request for a renewal of the annual contract for Thioguard, I am submitting this letter to update you on the terms of the agreement. You may submit Purchase Orders either on a per load basis, or a Blanket PO may be issued for the duration of the price in effect. Pricing after the term noted may change due to production costs, freight, etc. In addition, please note that the annual usage may go up as a result of increased flows through the treated Southlake system, since we currently feed proportionally to flow. Flows were estimated at 0.7 mgd during the initial contract, but current flows are estimated to be 0.93 mgd. The costs below reflect changes to the current wastewater treatment flows. Expected Thioguard Costs Dosing: Product dosages may range from 40 -95 gallons of Thioguard per million gallons of wastewater treated. An initial dosage rate is calculated by taking the total dissolved sulfide measurement and multiplying by 1.7. In this case, a range of 10 -25 mg/L dissolved sulfides measured at the Lonesome Dove and Shady Lane FM discharge times 1.7 would equate to an initial dosage of 17 - 42.5 gallons of Thioguard per MGD of wastewater to be treated. Additional Thioguard is added to account for certain wastewater factors such as initial pH, FOG, CO , ,, retention time and desired HS gas odor /corrosion results. On a daily basis, we are estimating 53 -93 gallons of Thioguard consumed per day for the 0.93 mgd treatment lines associated with the Lonesome Dove and Shady Lane LS. THIOGUARD: 52.40 /gallon delivered to Southlake Truckload of material (— 4,000 gallons of Thioguard) Valid: 8/1/2011— 6/30/2012 Estimated Annual Cost (at max dosage) of 100 GPD of Thioguard and assuming 0.93 MGD Flow: $87,600.00 On an annual basis, at a maximum dosage rate of 100 gallons of Thioguard per mgd of wastewater treated, total cost is estimated at 100 gpd x $2.40 x 365 = $87,600.00, although the maximum dosage rate may not be necessary to obtain the desired results. NOTE. The figures contained herein are based on approximate dosing schedules. The price per gallon is based on the following assumptions: • Two feed locations (Lonesome Dove LS, Shady Lane LS) • Feed unit configuration allowing full - truckload deliveries 20108 C.R. 186, Flint, Texas 75762 O: 903 -245 -6316 I F: 903 - 894 -7552 htto: NN - NN.uremierchemicals.com mevansr6loremierchemicals.com �RF�1�FR M M Mr s W M��M i CHEMICALS, LLC Acceptance: Signature Title Print Name Date Please do not hesitate to call if you have any questions or require additional information. I look forward to working with you and the City of Southlake on this project. Sincerely, Mary P. Evans South Central Regional Account Manager Premier Chemicals, LLC Thioguard TST Phone: 903.245.6316 20108 CR 186 Flint, Texas 75762 Email: mevansnnremierchemicals.com 20108 C.R. 186, Flint, Texas 75762 O: 903 -245 -6316 I F: 903 - 894 -7552 htto: NN - NN.uremierchemicals.com mevansr6loremierchemicals.com .mil �!�'11111Fl� CHEM /GALS, LLC May 11, 2011 300 West Barr Harbor Suite 250 West Conshohocken, PA 19406 Tel: (610) 828 -6929 Mr. Chuck Kendrick Fax: (610) Operations Manager Department of Public Works — City of Southlake 1905 E. Continental Blvd. Southlake, TX 76092 Re: Premier Chemicals, LLC's THIOGUARD® Magnesium Hydroxide Slurry Proposal to City of Southlake Dear Mr. Kendrick, I have been asked to provide you a brief description of the claim coverage for U.S. Patent No. 5,833,864, entitled METHOD FOR THE REDUCTION AND CONTROL OF THE RELEASE OF GAS AND ODORS FROM SEWAGE AND WASTE WATER, (the "'864 Patent "). The patent relates to using magnesium oxide or hydroxide to control odor in municipal sewerage or wastewater. The '864 Patent includes 26 claims directed towards controlling odor in sewers by adding magnesium hydroxide or magnesium oxide. For example, claim 1 broadly claims controlling odor in municipal sewerage or wastewater that includes at least one compound which can be reduced to form hydrogen sulfide. Odor is controlled by simply adding an effective amount of magnesium hydroxide or magnesium oxide to the municipal sewerage or wastewater. I have included a copy of the patent with this letter. Premier has spent a great deal of effort, research, time, trial and error, as well as significant funds, in order to obtain the patent rights described above and to develop a product of the quality that our customers require. We believe the efforts expended to obtain such patent is indicative of the effort our Company will put forward to insure the City of Southlake will receive a competitive, efficient and high quality product that will produce superior results. I hope that this helps in your understanding of Premier's patent position, however, if you wish to discuss the enclosed or have any questions please do not hesitate to contact me. Very truly yours, Stephen A. Becker Vice President, General Counsel and Secretary cc: P. AN M. Madolora T. Miller THIOGUARD PATENT LTR. u11uuisiA111111111iwunu'i11111isiiiiueimonu United States Patent [19] Miller et al. [11] Patent Number: 5,$33 [45] Date of Patent: *Nov. 10, 1998 [54] METHOD FOR THE REDUCTION AND CONTROL OF THE RELEASE OF GAS AND ODORS FROM SEWAGE AND WASTE WATER [75] Inventors: Thomas M. Miller, Walnut. Calif.; Mark A. Shand, Findlay, Ohio [73] Assignee: PSC Technologies, Inc.. King of Prussia, Pa [ * ] Notice: This patent issued on a continued pros- ecution application filed under 37 CFR 1.53(d), and is subject to the twenty year patent term provisions of 35 U.S.C. 154(a)(2). [213 Appl. No.: 680,502 [22] Filed: Jul. 8, 19% Related U.S. Application Data [63] Continuation of Ser. No. 386,735, Feb. 10, 1995, abandoned. [51] Int. C1. . ............................... CO2F 1/66; CO2F 11/00 [52] U.S. Cl ........................... 210/724; 210/749; 210/916; 210/903 [58] Field of search ...... ............................... 2101724. 749, 210/916.903 [56] References Cited U.S. PATENT DOCUMENTS 2,852,584 9/1958 Kornac ... ............................... 2101916 3,080,253 3/1963 Dietz et al. . 11/1988 Kayser et 21. . 3,377,271 411968 Cann .......... ............................... 210/45 3,697,322 1011972 Lee at al. . 611995 Angell ...... ............................... 210/751 3,705,098 1211972 Shepherd at al .......................... 210/63 3,862,851 1/1975 Speits at al.. 3,974,783 8/1976 Flynn ......................... I................ 11018 4,118,319 10/1978 Miyanohata at al . ...............1 —, 210/51 4,125,466 11/1978 Miyanohara at al . ................1— 210/67 4,169,906 1011979 Hallstrom at al. . 4,456,635 6/1984 Albanese at al. . 4,615,918 10/1986 Reichert at al. . 4,668,541 511987 Fageduud . 4,670,315 611987 Hillerneier at al. . 4,675,114 6/1987 Zagyvai at al .......................... 2101666 4,710,404 1211987 Reichert at al. . 4,786,525 11/1988 Kayser et 21. . 5,228,995 7/1993 Stover ...... ............................... 210/917 5,246,641 9/1993 Perkins at al. . 5,422,015 611995 Angell ...... ............................... 210/751 FOREIGN PATENT DOCUMENTS 1326682 411963 France . 424919 3/1935 United Kingdom. 2123516 2/1984 United Kingdom . OTHER PUBLICATIONS Excerpts from AS CE Manuals and Reports on Engineering Practice No. 69 titled "Sulfide in Wastewater Collection and Treatment Systems ". Davis Process Division of Davis Water & Waste Industries, Inc.; Process Division Technical Bulletin No. B-401. Biox- ide ... the natural solution, A Proprietary Product Designed to Promote Naturally Occurring Process Within Wastewater Collection and Treatment Systems Which Eliminate Order Producing Compounds. Sewer Corrosion Control and Rehabilitation, County Sani- tation Districts of Los Angeles County, 5 rages. Caustic Spray For Sewer Crown Corrosion. Control, by Jamie Baida, 11 Pages. Microbial Energy Generation/Oxidation of Inorganic Sub- strates, pp. 158 -159. Preparing Collection Systems for Water Conservation, pp. 52 -57, Water Environment & Technology, Aug. 1993. (List continued on next page.) Primary Examiner- -Neil McCarthy Anomey, Agen4 orFinn— Ostrolent Faber, Garb & Soffen, LLP [57] ABSTRACT A method for reducing and controlling the formation and release of acid gases and odors associated therewith, par- ticularly from hydrogen sulfide, in sewerage or waste water, wherein magnesium hydroxide and/or magnesium oxide are added to the sewerage or waste water. 26 Claims, 3 Drawing Sheets 7 NlBfOWI` / 2 4\ STORAGE TANK DR DRUM �� f pH = 6,8, H2S =0.3 ppm pH =9.9, H2S = 0.07ppm DtRECTION OF FLOW 5,833,864 OTHER PUBLICATIONS Metals Meet Their Match, pp. 69-73, Water Environment & Technology, Sep. 1993. Product Report/Surfactants for household detergents —pet rochernical raw materials and uses, pp. 40-41 & 46, C&EN, Jan. 24, 1994. Generation and Control Sulfide in Filled Pipes, by Dr. Richard D. Pomeroy, Pomeroy and Associates, Pasadena, Calif., From Sewage and Industrial Wastes, vol. 31, No. 9. 1959. Process Design Manual for Sulfide Control in Sanitary Sewerage Systems, U.S. Environmental Protection Agency Technology Transfer, Oct. 1974, 9 Pages. 700 80 60 PERCENT 40 20 S H S' FIG. 1 H N 6 7 8 9 10 11 pH EFFECT" OF pH ON HYDROGEN SULPHIDE EQUILIBRIUM vo 0 e a �o 0 w 04 W ao �P AQUEOUS 20 19 18 17 =M 15 14 13 12 11 10 9 8 SULPHIDE (ppm) FIG. 2 WASTEWATER pH 10 9.5 9 8.5 8 7,5 7 i0 0 :. c Q MI CD FIG. 3 z o Mg(OH)2 2 4 ;.. 0 STORAGE TANK OR DRUM to ao 5 3 PH = 6.8, H2S = 0.3 ppm pH =9.1, H2S = 0.07ppm w w DIRECTION OF FLOW Ul 4 W W W V 5,833:864 X METHOD FOR THE REDUCTION AND CONTROL OF THE RELEASE OF GAS AND ODORS FROM SEWAGE AND WASTE WATER CROSS - REFERENCE TO RELATED APPLICATIONS This application is a continuing application of U.S. Ser. No. 081386.735 filed Feb. 10. 1995 now abandoned BACKGROUND OF THE INVENTION t 1. Field of the Invention The present invention relates to the control of gaseous release and of odors associated with sewerage and waste water and more particularly, to the reduction and control of the release of acid gases, such as hydrogen sulfide, from 15 sewerage or waste water. 2. Description of the Related Art Sewerage and waste water generally contain sulfates and other contaminants which. upon reduction, become (directly or indirectly) gaseous compounds which are released gen- 20 erating unpleasant odors. For example, sulfates are reduced to sulfides associated with the release of hydrogen sulfide gas. The reduction of sulfates can proceed by the action of sulfate- reducing bacteria including Desulfouibro sulfricans. Hydrogen sulfide and other acid gases which are released 25 include potentially dangerous contaminants and lead to unpleasant odors. Several methods have been proposed and used to control the release of hydrogen sulfide. These include methods which reduce the growth of the anaerobic bacteria or which 30 chemically bind sulfides. However, these methods have drawbacks, such as high costs, implementation difficulties and safety concerns. In particular• ferrous and ferric chloride (iron) and liquid caustic soda (sodium hydroxide. pH 13 --14) are currently 35 added to sewers to control sulfide generation and corrosion. The iron is added continuously to bind the sulfide as a nonsoluble iron sulfide precipitate. Caustic 'soda is generally added semi- weekly to provide a thirty minute, high pH, shock dose to the anaerobic bacteria. 40 The addition of caustic soda acts by neutralizing the sulfuric acid which has already been formed by the bacteria, inac- tivating and destroying the bacteria, and limiting the forma- tion of new colonies of bacteria. The use of caustic soda has been found to have several 45 drawbacks. First, caustic soda only has a temporary effect on the bacteria. Second, caustic soda is hazardous and is highly toxic to humans. Even a small amount of caustic soda can cause permanent blindness. It is expected that in the future the generation of hydrogen 50 sulfide (H will increase, particularly as more municipali- ties adopt water conservation programs that include the installation of low -flow plumbing devices. As a result of the reduced flows in such systems, water may be retained longer in the pipes, wet wells and force mains of the collection 55 system; damming caused by settled solids and grease may increase; and less dissolved oxygen (DO) may be present due to increased biochemical oxygen demand (BOD). Absent the teachings of the present invention. all of these changes might otherwise exacerbate the problems addressed 60 by the invention. V SUMMARY OF THE IN ENTTON It is therefore an object of the present invention to provide methods which are safe and effective for controlling the 65 formation and release of acid gases, particularly hydrogen sulfide. 2 It is also an object of the present invention to provide a method of maintaining a level of hydrogen sulfide which is below an acceptable level. It is a further object of the invention to provide methods of reducing or eliminating odor associated with waste water or sewerage. It is also an object of the present invention to provide a method to minimi the formation and release of both hydrogen sulfide and ammonia in waste water or sewerage. It has been found that the formation and release of acid gases, particularly hydrogen sulfide, which are associated with the unpleasant odor of sewerage and waste water can be controlled or eliminated by introducing magnesium hydrox- ide and/or magnesium oxide into the contaminated water. Moreover. it has surprisingly been shown that magnesium hydroxide is able to maintain a pH level which minimi the levels of both hydrogen sulfide and ammonia. Further, the levels of hydrogen sulfide and the pH of the contami- nated water can be maintained at an acceptable level for a significant period of titre. Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS For the purpose of illustrating the invention, there is shown in the drawings an embodiment which is presently preferred; it being understood, however, that the invention is not limited by the precise arrangements and instrumentali- ties shown. FIG. 1 is graph of the relative concentrations of hydrogen sulfide and ionized hydrogen sulfide at various pH levels; FIG. 2 is a graph of the pH level and aqueous sulfide level after the addition of magnesium hydroxide; and FIG. 3 is a diagram of a representative configuration for the addition of magnesium hydroxide and/or oxide to waste water or sewerage. DETAILED DESCRIPTION OF THE INVENTION It has been found that the addition of an agent including magnesium hydroxide (Mg(OH) and/or magnesium oxide (MgO) to sewerage or waste water which is contaminated with compounds which can be reduced to acid gases, reduces or eliminates the release of these gases and the odor associated therewith. The addition such an agent to sewerage or waste water is able to alter the pH of the solution into a preferred range of approximately 7.5 to 9.5, and to maintain pH in that pre- ferred range for extended periods. The amount of the agent needed to achieve the preferred pH varies with the amount of water to be treated. Monitoring pH of the treated water during addition of the agent is recommended so that the operator may increase or decrease the amount of agent as necessary. In general. the fraction of hydrogen sulfide relative to ionized hydrogen sulfide which is present in solution is dependent on the pH of the solution. It is desirable to reduce the level of hydrogen sulfide which is not ionized so as to reduce the unpleasant and harmful odors associated there- with. As discussed in more detail. below, applicants have discovered that a pH of 7.5 -9.5 (especially 8.0 -9.0) is particularly preferred both for reducing release of acid gas and also for maintaining better levels of other compounds as well. 5.833,864 3 4 As shown in FIG. 1, which compares the ratio of hydro- tolerance of common acid producing bacteria. It is noted that gen sulfide to ionized hydrogen sulfide, at a constant small amounts of lime (calcium hydroxide). can be added to temperature, the percentage of ionized hydrogen sulfide magnesium hydroxide and/or magnesium oxide slurry to increases with an increase in pH. The largest effect is seen increase the pH and enhance the slurry's ability to kill in the pH range of 6.0 to 8.0. In particular, at a pH of 6.0, 5 bacteria. It is anticipated that other biocides or hardening 90.1% is hydrogen sulfide, while at a pH of 8A, only 8.3 agents such as sodium silicate, sodium bi- sulfate, magne- is hydrogen sulfide. Further, at a pH of 8.5, 3 % is hydrogen sium sulfate, magnesium chloride. phosphates, or other sulfide and at a pH of 9.0, the hydrogen sulfide level drops materials intended to impart mechanical strength, may be to less than 1%. added to further enhance its performance. Therefore, due to the relative insolubility of the agent of 10 Secondly, as the bacteria is re- established, the alkalinity the invention, conditions can be maintained over time in provided by the magnesium hydroxide and/or magnesium which the amount of hydrogen sulfide which is present or oxide neutralizes the acids produced by the bacteria and released is reduced and therefore, the odors associated with prevents the rapid re- establishment of bacteria. the release or presence of hydrogen sulfide are minimiz or A magnesium hydroxide and/or magnesium oxide slurry eliminated. In some embodiments, hydrogen sulfide levels 15 can be prepared by adding, caustic calcined magnesium are desirably reduced to six parts per million or less. oxide (MgO), preferably in a dry powder form, to water. The Further, it has surprisingly been found that, at the pre- magnesia can be obtained from any of the /mown suppliers ferred pH's of the invention, the undesirable release of including Premier Services Corporation, King of Prussia, ammonia is also minimized. In contrast to hydrogen sulfide Pa. Premier Services sells magnesia in dry powder form levels, which decrease as the pH increases, the release of 20 under the trademark MAGOX ®. ammonia gas increases with an increase in pH. Therefore, a when magnesium oxide is added to water it undergoes balance is preferred in which the pH level is both (1) high hydration and is converted to magnesium hydroxide. The enough to reduce the formation and release of hydrogen rate of this reaction can be varied depending upon the sulfide and (2) low enough to prevent the formation and surface area of the MgO, starting water temperature, vessel release of ammonia. It has been found that the optimal 25 configuration, and agitation. Either a slowly hydrating MgO. balance can be achieved by maintaining a pH in the range of or a fully hydrated Mg(OH) slurry may be added to the approximately 7.5 to 9.5. especially 8.0 to 94, and most contaminated water. preferably, by maintaining a pH of approximately 8.3. A magnesium hydroxide slurry can also be purchased Moreover, a pH level substantially above 9.0 can be from any of the known suppliers. including Premier Services harmful to bacteria which are beneficial to treatment of 30 which sells a magnesium hydroxide slurry under the trade - waste water and sewerage. In comparison to other pH mark AQUAMAG®, increasing compounds, magnesium hydroxide has been In a preferred embodiment of the invention, a specially found to slowly reach and maintain a pH in the desired range hydrated and formulated slurry, marketed by Premier Ser- without substantially overshooting the maxim level. As 35 vices Corporation under the trademarkTHIOGUARDIM. is such; there is less osmotic shock and the helpful organisms added to sewerage or waste water. Without intending to be are not destroyed. broad by theory, it is believed that this slurry offers a safe, Therefore, magnesium hydroxide and/or oxide have been economic alternative reagent for acid neutralization and found to be particularly suitable for the prevention of odor water treatment and has been found to be particularly release in sewerage and waste water since the alkalinity and 40 effective in controlling odors inter alia by achieving the pH properties of magnesium hydroxide are such that it is easy and other effects discussed herein. It is believed to neutralize for the operator to keep pH levels within the preferred-range harmful sulfuric acid. It is an off-white slurry composed discussed above, without inadvertently raising pH so far predominately of agglomerated magnesium hydroxide par - above the preferred range that the undesirable effects dis- ticles and is made from hydrated calcined natural magnesite cussed above become problematic. 45 or precipitated from sea water, bitterns, or brines. Table I, Moreover, it has been found that the low solubility of the below, sets forth a representative chemical analysis of it on magnesium leads to a time released alkalinity so that the pH a loss free basis. level is more stable and is maintained upstream for a longer period of time. As shown in FIG. 2, magnesium hydroxide TABLE"I was able to maintain a pH of above 7.5 and a level of 50 Viscosity, aeutipo= 8004M, typically 3000 aqueous sulfides at or below 5 ppm for thirty days. % Solids 55-65 In addition to the benefits of magnesium hydroxide and/or specific Surface Area Typically 10 m Chemical Analysis (Dry Basis), wt % oxide discussed above, the use of magnesium hydroxide and/or oxide is preferable for a number of reasons. First, it M90 90.99 is noted that magnesiumhydroxide requires no placarding or 55 Cal] 0.3 -4.0 special handling and presents "no chemical hazard to the s o 0.3 -4.0 R 03 0,1 -2.0 environment, users, or the public. Second, magnesium hydroxide has a higher neutralizing capacity per mole than caustic soda due to its two OH ions. Third, the by- products The component 8 refers to natural impurities such as produced by the reaction of magnesium with hydrogen 6o A1 and Fe 103 which are indigenous to ore bodies. Other sulfide tend not to be hazardous as with some by- products of insolubles besides (or in addition to) SiO,, e.g. MgCO hydrogen sulfide reactions. Finally, the magnesium require- and/or CaCO may "be included. The product THIO- ments are less dependent on sulfide concentration. GUARD'm is made from natural ore and there are some It is believed that two mechanisms are responsible for the natural variations in the percentages of various ingredients effectiveness of magnesium hydroxide and/or magnesium 65 as shown inter alia in Table L oxide. First, magnesium hydroxide has a pH of approxi- In a preferred embodiment, as shown in FIG. 3, the mately 10 -5, which, while safe to humans, is above the magnesium hydroxide or magnesium oxide in the form of a 5,833.864 5 slurry is topically applied to a stream of sewerage or waste water. in particular, a storage_ tank or drum 1 which holds magnesium hydroxide and/or magnesium oxide pumps the magnesium through a maintenance hole 2 to a sewerage flow 3. Odors from downstream maintenance holes 4 and corro- sion on crowns and maintenance holes 5 are reduced or eliminated. Addition of sufficient THIOGUA,RDTM to the sewerage to raise the pH to 9.0 -9.5, which takes somewhere between 8.5 -100 mg/l, dependent upon type of sewerage is sufficient to reduce odor and corrosion problems in sanitary sewers. This occurs because at this pH dissolved hydrogen sulphide gas is at a minimum and does not tend to escape into gaseous phase and contribute to odor and corrosion. For instance addition of THIOGUAI2DTM to sewerage at approximately 100 mg/1 results in an almost instantaneous drop of aqueous sulphides from an initial 16 ppm to less than 1.0 ppm for a period of 4 days and a subsequent rise to between 6-6.5 for a period of 50 days. Apart from its ability to alter sewerage pH to reduce dissolved hydrogen sulphide gas, there is a surface reaction between THIOGUARDT'm and dissolved hydrogen sulphide, which results in adsorption of the gas onto the solids phase. Mg(OH)2 +H28„ L-- Mg(OH)2CH2S), -Mg(HS h +20 rMgSO Further reaction results in the formation of magnesium hydrosulphide, which can be oxidized by dissolved oxygen to form soluble magnesium sulphate which does not sub- stantially contribute to odor or corrosion. Due to its limited solubility in water, it is very slow to release hydroxyl ion (OH in normal pH range of sewerage compared to other alkalis such as lime and caustic soda. M9(OH) +2011 35 Consequently, THIOGUARDTM is able to continue to raise the pH downstream o, the original point of addition without resulting in excessively high local pH's. For instance. add- ing it at a rate of 100 mg(l to sewerage is capable of sustaining a pH greater than 8.5 for 24 hours. 40 Its use to control odor /corrosion problems in sewerage is not limited to just hydrogen sulphide but could encompass other acidic gases /vapors such as sulphur dioxide and sul- phur compounds which contain an ionizable hydrogen ion, such as mercaptans containing the --SH group. 45 It should be realized by those skilled in the art that the magnesium hydroxide and/or magnesium oxide can be added to any other water or liquid solution that is contami- nated by compounds which can be reduced to acid gases, particularly sulfates and mercaptans. 50 The characteristics of the magnesium hydroxide and/or magnesium oxide slurry can be varied to provide the opti- mum, pumping characteristics and to treat different levels of contamination. The properties of the slurry can be varied by any of the 55 known methods including changes in the solids to water ratio, or by the use of polymers to enhance or alter these properties as desired for differing field conditions or equip- ment configurations, e.g., increasing or decreasing the water content or by adding in more magnesia powder. 60 It is recommended that the slurry should include at least 30 %. preferably at least 50 %a, by weight magnesium com- pound in the form of magnesium oxide, magnesium hydrox- ide or a mixture thereof. Magnesium oxide can also be mixed with sodium silicate 65 to produce a slurry which. when dried, yields a hard alkaline material composite of unhydrated magnesium oxide encap- 6 sulated in sodium silicate. In some embodiments, this dry form may constitute the agent added to sewerage or waste water in accordance with the invention. The acid produced by surface bacteria is neutralized by the sodium silicate. In 5 addition, as the sodium silicate dissolves, the magnesium oxide is exposed, thereby dehydrating the bacteria and neutralizing the hydrogen sulfide. Although the present invention has been described in relation to particular embodiments thereof, many other 10 variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims. We claim: 1. A method for reducing the formation and release of 15 hydrogen sulfide in municipal sewerage or waste water, comprising the step of. adding an effective amount of an agent that includes a compound selected from the group consisting of mag- nesium hydroxide and magnesium oxide to said 20 municipal sewerage or waste water, wherein said municipal sewerage or waste water includes at lease one compound which can be reduced to form hydrogen sulfide. 2. The method as recited in claim 1, wherein said agent 25 is a slurry further including sodium silicate. 3. The method, as recited in claim 1, wherein said agent is a hard alkaline material composite of unhydrated magne- sium oxide encapsulated in sodium silicate. 4. The method, as recited in claim. 1, wherein the com- 30 position is a slurry including: Chemical Analysis (lass tree basis) wt % M9 about 924s%n Cao. about 5-3.5% 8 2 0 3 abort 5 -1.5% insolubles about .5 -3.0% viscosity, cps about 500 - 10,000 density, lb/gal about 11.2 -11.8 % solids by wt % about 45-55 S. The method, as recited in claim 1, wherein said agent is substantially continuously added to said sewerage or waste water. 6. A method of controlling hydrogen sulfide odor assod- ated with municipal sewerage or waste water, comprising the step of: adding an effective amount of an agent that includes a compound selected from the group consisting of mag- nesium hydroxide and magnesium oxide to said municipal sewerage or waste water, wherein said municipal sewerage or wastewater includes at least one compound which can be reduced to form hydrogen sulfide. 7. A method of obtaining a minimal level of hydrogen sulfide and of ammonia in municipal waste water or sewerage, comprising the step of: adding an effective amount of an agent that includes a compound selected from the group consisting of mag- nesium hydroxide and magnesium oxide to said municipal sewerage or waste water, wherein said municipal sewerage or waste water includes ai least one compound which can be reduced to form hydrogen sulfide. 8. The method of claim 1, wherein said agent is added in an amount effective to reduce hydrogen sulfide levels to no more than 6 parts per million. 5,833,864 7 8 9. The method of claim 6, wherein said agent -is added in an amount effective to reduce hydrogen sulfide levels to no more than 6 parts per million. 10. The method of claim 7. wherein said agent is added in an amount effective to reduce hydrogen sulfide levels to no more than 6 parts per million. 11. The method of claim 1, wherein said agent is added in an amount effective to maintain pH of said sewerage or waste water between 7.5 and 9.5. 12. The method of claim 6, wherein said agent is added in an amount effective to maintain pH of said sewerage or waste water between about 7.5 and 9.5. 13. The method of claim 7, wherein said agent is added in an amount effective to maintain pH of said sewerage or waste water between about 7.5 and 9.5. 14. The method of claim 1, wherein said agent is added in 18. The method of claim 6, wherein said agent is added in an amount effective to maintain pH of about 8.3. 19, The method of claim 7, wherein said agent is added in an amount effective to maintain pH of about 8.3. . 5 20. The method of claim 1, wherein lime is also added. 21. The method of claim 6, wherein lime is also added. 22. The method of claim 7, wherein lime is also added. 23. The method of claim 1, wherein said agent is a slurry comprising 30-50% by weight of said magnesium 24. The method of claim 6, wherein said agent is a slurry 10 comprising 30-50% by weight of said magnesium. 25. The method of claim 7, wherein said agent is a slurry comprising 30-50% by weight of said magnesium. 26, The .method, as recited in claim 1, wherein the composition is a slurry including: Physical and Chemical is Properties of THIOGUARDTm Chemical Analysis (Dry Basis), wt % an amount effective to maintain pH of said sewerage or waste water between about 8.0 and 9.0. 15. The method of claim 6, wherein said agent is added in an amount effective to maintain pH of said sewerage or 20 waste water between about 8.0 and 9.0. 16. The method of claim 7. wherein said agent is added in an amount effective to maintain pH of said sewerage or waste water between about 8.0 and 9.0. 17. The method of claim 1. wherein said agent is added in 25 an amount effective to maintain pH of about 8.3. MHO about 90-39 cao about 0,3 -4.0 S'0 about 0.3 -4.0 8 3 0 3 about 0.1 -2.0 Viscosity 800 -0000 cendpoue: % Solids about 55-65.