Abstract: A ground water contamination remediation process includes the steps of identifying a source and location of land-based ground water contamination and excavating the soil above and within the location of the contamination to create a void. The width and depth of the void is increased to a predetermined size until the contaminated ground water is exposed creating a man-made treatment lake by allowing the contaminated ground water to partially fill the void. In one embodiment, the water in the treatment lake is aerated to reduce the amounts of hydrogen sulfide, methane, and biodegradable compounds in the contaminated water. In another embodiment, an adsorbent material is added to the treatment lake so to isolate per- and poly-fluoroalkyl substances (PFAS). The adsorbent material is applied to or mixed into PFAS contaminated water, PFAS is adsorbed, and the solid adsorbent materials settle to the bottom of the lake for subsequent management or removal.

Abstract: The present invention describes a process involving a new method of use for methyl isothiocyanate (MITC)-generating compounds in the treatment of organic waste material to reduce vector attraction. The present invention results in waste that is more suitable for use as a fertilizer and meets the standard for vector attraction reduction (VAR) as established by the U.S. Environmental Protection Agency. The method includes the application of MITC generating compounds, such as metam sodium, to organic waste material, resulting in the generation of MITC. The MITC generated by the process of the present invention results in a loss of attraction for organic waste material normally experienced by disease-transmitting pests such as flies and rodents.

Abstract: The present invention relates to a method for purifying highly alkaline waste water from a stainless steel slag treatment process. This waste water contains between 0.5 and 5 mg/l of trivalent chromium (Cr(III)) and between 0.5 and 1.0 mg/l of molybdenum. To reduce the chromium and molybdenum content a trivalent iron is added to the waste water in the form of a water soluble ferric salt and the trivalent iron is allowed to co-precipitate with said chromium and molybdenum by lowering the pH of the waste water. It was found that by performing the co-precipitation at a pH of 3.5 to 5.7, both the chromium and the molybdenum content could be effectively reduced to a level of less than 0.5 mg/l, and this without having to provide large amounts of trivalent iron in the waste water, without having to repeat the purification process for several times, without having to add sulphide to the waste water, and without having to lower and raise the pH of the waste water for more than one time.

Abstract: Described are chemical formulations that remove heavy metals from waste solutions containing a chelating agent. Also disclosed are methods for removing heavy metals from waste solutions utilizing such chemical formulations.

Abstract: A hybrid chemical/mechanical water treatment plant and method employing rapid sulfur dioxide chemical disinfection and dewatering technology in conjunction with lime and oxidization/reduction agents to removal pharmaceuticals and personal care products from waters to meet operating constraints and environmental permitting restrictions and siting limitations for water treatment.

Abstract: A hybrid chemical/mechanical water treatment plant and method employing rapid sulfur dioxide chemical disinfection and dewatering technology in conjunction with lime and oxidization/reduction agents to removal pharmaceuticals and personal care products from waters to meet operating constraints and environmental permitting restrictions and siting limitations for water treatment.

Abstract: Systems and associated methods for treating contaminant-containing wastewater are provided. The systems generally include a reducing zone for reducing the oxidation-reduction potential of the water and a clean-up zone comprising zero valent iron for removing at least a portion of the contaminant from the contaminant-containing water. The systems are operable to remove one or more contaminants from the contaminant-containing water and are operable for extended durations without clogging due to the formation of iron hydroxides.

Abstract: Methods to reduce hexavalent chromium (Cr(VI)) in chromite processing wastes include one or more of the following steps: contacting the chromite processing wastes with an oxygen scavenger or chemical reducer; permitting the chromite processing wastes to react with the oxygen scavenger or chemical reducer; contacting the chromite processing wastes with ferrous ion; contacting the chromite processing wastes with sulfide ion; and, contacting the chromite processing wastes with ferrous sulfide.

Abstract: Disclosed is a method of removing nitric acid from an aqueous liquid containing various components such as vegetable extract, and nitrate ion is removed selectively without spoiling the taste or other components, by subjecting the aqueous liquid to chromatographic treatment with an amphoteric ion exchanger to separate nitrate ion from other components contained in the aqueous liquid. A nitric acid-reduced drink is produced by preparing a raw drink material comprising an extract or juice of plant tissue; removing nitric acid from the raw drink material with use of the method of removing nitric acid from an aqueous liquid as described above; and preparing a drink using the raw drink material after the removing of nitric acid.

Abstract: A water filtration device (3) and method which removes heavy metals and organic compounds from raw water is provided.

Abstract: A method is taught for converting metal contaminants in the soil to less toxic forms as well as permitting their removal from groundwater. A first reactive solution comprising ferrous sulfate and an acid selected from the group consisting of sulfuric acid and phosphoric acid is injected to decomplex contaminants and precipitate them as insoluble compounds. A second reactive solution comprising hydrogen peroxide, and an acid selected from the group consisting of sulfuric acid and phosphoric acid is then injected to destroy organic liquids and enhance decomplexation. The pH of the first solution may range from 3 to 5, and the pH of the second solution range from 3 to 7, preferably 5 to 7. The process is particularly effective where chromium compounds such as hexavalent chromium are the contaminants.

Abstract: A method is disclosed for treating a flushing solution from an ion exchanger used in electroplating operations by co-precipitating or selectively precipitating out metal hydroxides derived from metal ions from the structures being plated in the electroplating bath, metal ions from the electrodes use in the electroplating bath and metal ions from the plating metal used in the electroplating bath, and a pH raising agent having a cation with a valence of at least 2. After the metals are precipitated out of the flushing solution, the flushing solution is aerated with carbon dioxide to precipitate out the cation from the pH raising agent as a carbonate. The carbonate precipitate is removed from the flushing solution and the resulting solution consists essentially of water that may be recycled for use in the electroplating plant or safely discharged into the environment.

Abstract: A test for determining the presence of multi-valent metal contaminants, such as arsenic, mercury and chromium, when present in certain valence states and a system for removal of these contaminants from water. Multi-valent metal salts, for example, Cr+6, which are highly toxic, can be detected and potentially removed from water through a redox reaction by reaction with iron or cobalt salts to obtain a reductive elimination of the Cr+6 by conversion to Cr+3. The determination may be in the form of a test, such that a tableted composition can be introduced into water for reduction of a metal salt, such as Cr+6 to Cr+3 in order to provide a visual indication thereof. The system for the conversion of Cr+6 or other reducible metal salts to other lower valence states having less toxicity would rely upon introduction of a metal salt in the form of a reducing agent which would be introduced into the water allowing for a reduction/oxidation action to take place.

Abstract: The aim of this invention is to resolve problems in sludge treatment methods, and to render sludge containing harmful substances produced in large amounts in chromium plating works harmless with reproducibility by effective use of certain substances. The invention resolves these problems by separating metal ions such as iron, copper, zinc and chromium contained in chromium plating effluent or a mixed solution of chromium plating solution, chromium plating effluent and chromic acid wash water in an impurity recovery electrolysis tank A in the form of a sludge, extracting the sludge, washing the sludge with water, separating the wash water containing chromic acid, drying the sludge which sedimented in the water washing step by natural or assisted drying, adding a natural organic substance to the sludge and reduction calcinating the sludge.

Abstract: The invention relates to a process for treating a chromate waste liquid containing an organic acid component. This process includes (a) adding a chromium precipitation accelerating agent containing at least one of a calcium component and a magnesium component, to the chromate waste liquid; and (b) adjusting the chromate waste liquid to having a first pH of 9 or higher, thereby precipitating a chromium component from the chromate waste liquid and thereby reducing a concentration of a dissolved chromium component of the chromate waste liquid.

Abstract: A method is taught for converting metal contaminants in the soil to less toxic forms as well as permitting their removal from groundwater. A first reactive solution comprising ferrous sulfate and an acid selected from the group consisting of sulfuric acid and phosphoric acid is injected to decomplex contaminants and precipitate them as insoluble compounds. A second reactive solution comprising hydrogen peroxide and an acid selected from the group consisting of sulfuric acid and phosphoric acid is then injected to destroy organic liquids and enhance decomplexation. The pH of the first solution may range from 3 to 5, and the pH of the second solution range from 3 to 7, preferably 5 to 7. The process is particularly effective where chromium compounds such as hexavalent chromium are the contaminants.

Abstract: A method is disclosed for recovering and separating precious and non-precious metals from waste streams, which removes, separates, and recovers such metals in a cost effective manner with more than 95% removal form waste streams and with minimal amounts of unprocessed solids and sludge remaining in the environment. Metals such as chromium, manganese, cobalt, nickel, copper, zinc, silver, gold, platinum, vanadium, sodium, potassium, beryllium, magnesium, calcium, barium, lead, aluminum, tin; and the lie are removed and recovered from the waste streams with at least 95% removal and other metals and compounds, such as antimony, sulfur, and selenium are removed and recovered from waste streams with at least 50% removal. The method employs a unique complexing agent comprising a carbamate compound and an alkali metal hydroxide which facilitates the formation of the metals into ionic metal particles enabling them to be readily separated, removed and recovered.

Abstract: A composition for the detackification and clarification of acid and alkaline paint and lacquer waste waters and paint spray booth wastes, comprising:an inorganic-organic and/or organic adduct alloy polymer composition having the formula:A.multidot.B.sup.+ .multidot.D.sup.+wherein: A=[(SiO.sub.2 /Me.sup.I.sub.2 O).sub.u Me.sup.II.sub.m Me.sub.m.sup.III(OH).sbsp.p.sup.(SO.sbsp.4.sup.).sbsp.y.sup.(Aci) (2m+3n)-p-2y].sub.rwhere r=1 to 98% bw; u=0 to 10% bw; ##STR1## where: x=0 to 98% bw; Z is a divalent substituted or unsubstituted aliphatic, cycloaliphatic, heterocyclic or aromatic radicalD.sup.+ =(PQAM).sub.wwherew=2 to 98% b.w. of polyquaternized polymer (PQAM)Me.sub.m.sup.II is selected from the divalent cationic group comprising: Mg, Zn, Ca, and Fe.sup.2+m=0 to 5Me.sub.n.sup.III is a tri-or more valent metal selected from the group comprising: Fe, Al, and Al--Zn complexes;n=1 to 20Aci is selected from the monovalent anionic group comprising Cl.sup.-, Br.sup.-, I.sup.-, NO.sub.3 --, H.sub.2 PO.sub.4 --, CH.

Abstract: The present invention relates to a process for treating contaminated water to precipitate metals without increasing the total dissolved solids content. In particular, the invention relates to the use of phosphoric acid and calcium hydroxide or calcium oxide to adjust the pH of chromium contaminated groundwater during the treatment process without increasing the total dissolved solids (TDS).

Abstract: Method and apparatus for handling water used in plating processes to eliminate discharge of pollutants including a plating tank for chrome plating selected materials, at least one rinse tank which holds rinse water where parts from the plating tank are rinsed to remove chrome compounds used in the plating tank and transfer means to transfer water from the rinse tank to a purification tank where hydrazine is added to the rinse water in quantities sufficient to maintain selected pH in the water returned to one of the rinse tanks for precipitation of the chromic compounds to chromic hydroxide which can be easily filtered for disposal as a dry material. High quality water such as deionized water is added to the rinse tank to makeup lost water and a catalyst such as cobalt salt can be added to the purification tank to assist in reduction of the chromic compounds.

Abstract: The invention relates to a method of removing iron compounds and chromium compounds from an aqueous electrolytic solution. Said method is characterized by the following succession of steps:a) adding hydrogen peroxide to the solution and, if necessary, adapting the acidity of the solution so that the pH value of the solution is .gtoreq.7;b) separating the iron hydroxide formed;c) adapting the acidity of the solution so that the pH value of the solution is <4;d) adapting the acidity of the solution so that the pH value of the solution is .gtoreq.7;e) separating the chromium hydroxide formed.The above-described method provides a simple manner of selectively removing chromium compounds and iron compounds from an aqueous electrolytic solution which preferably contains sodium nitrate. The necessary redox reactions take place via oxidation and reduction of C ions by means of hydrogen peroxide.

Abstract: A method for the removal of metal from a metal-containing aqueous medium wherein the aqueous medium is passed through a particulate carrier material in the presence or ferrous iron and an oxidant and at such velocity and in such direction that the carrier material particles are fluidised in the aqueous medium and wherein metal-containing coatings are formed on the surfaces of the carrier material particles and wherein the particles thus coated are separated from the aqueous medium. A method for the production of iron oxyhydroxide-containing adsorbent wherein the carrier material particles are fluidised in an aqueous medium in the presence ferrous iron and an oxidant so as to form iron oxyhydroxide coatings on the particles and wherein the particles thus formed are separated from the aqueous medium.

Abstract: A system for treating groundwater contaminated with acidity or other contaminants is disclosed. The system involves excavating a trench into the aquifer in the path of the contaminant plume, and placing a body of active material in the trench. The active material depends on the particular contaminant: organic carbon may be used when the contaminant is ferrous sulphate, or hexavalent uranium oxide, or dissolved nitrate; pyrite or elemental iron may be used when the contaminant is eg chromium oxide. The active material causes the contaminant, by chemical reaction, to change its oxidation-reduction state, and to precipitate harmlessly in the body of material.

Abstract: A process for removing dissolved oils and greases from an aqueous solution which also may contain dissolved heavy metals is provided wherein the aqueous solution is mixed with a source of ferrous ion and dithionite ion in a first step at acidic pH to reduce and permit removal of solid heavy metal, is present and to separate oils and greases from the aqueous solution. Solution from the first step if reacted in a second step with hydroxide slurries obtained from third and fourth steps. A second step solution from the second step is reacted in a third step with an alkali composition and a third solution. Optionally, the third solution is reacted with a chelating agent for iron and an oxidizer in a fourth step. A solution of chelated iron from the fourth step, when practical is disposed of. Oils and greases are recovered from the first step such as by skimming.

Abstract: A method for reducing reducible metals comprising combining one or more reducible metals with an elemental metal, and then with a reducing agent to form a reduced metal. The mixture may then be stabilized and recovered.

Abstract: Hexavalent chromium is removed from aqueous sodium nitrate solutions by reacting hexavalent chromium with an aqueous slurry consisting essentially of ferrous hydroxide and barium sulfate whereby the chromium is reduced to trivalent chromium and precipitated as chromic hydroxide. Adulterating compounds and unwanted ions are not introduced to the electrolytic solution.

Abstract: A highly flexible multi-step treatment technology for chemical fixation and stabilization of leachable chromium, particularly hexavalent chrome, in contaminated soils, solid wastes, concrete, sludge, sand and gravel and waste waters is disclosed. The process comprises reducing hexavalent chromium to chromous (Cr.sup.2+) and chromic (Cr.sup.3+) forms in the presence of water under alkaline conditions and fixing the reduced chromium forms with phosphate.The process reduces Toxicity Characteristic Leaching Procedure chromium levels below the regulatory threshold of 5 mg/l as required by the USEPA.

Abstract: Heavy metal ions react with ferrous dithionite in acidic aqueous solution. They are reduced to metallic particles that are suitable for recycling and reuse when recovered from the acidic water. Chelating agents that are present are deactivated by bonding to the ferrous ions. Ferrous dithionite, (FeS.sub.2 O.sub.4) is either generated in-situ or ferrous ions and dithionite ions can be provided by other methods. An alkali metal hydroxide is utilized to precipitate remaining heavy metal ions including ferrous and ferric ions.

Abstract: Metallic iron particles are added to an aqueous solution containing hexavalent chromium and mechanically agitated. Enough of the surface of the iron particles remains precipitate-free to reduce substantially all the hexavalent chromium to trivalent chromium. Adjustment of pH allows the formation of insoluble precipitates which may be separated from solution using conventional techniques. The properties of the aqueous electrolyte solution are retained, and the solution may be reused.

Abstract: A system for treating groundwater contaminated with acidity or other contaminants is disclosed. The system involves excavating a trench into the aquifer in the path of the contaminant plume, and placing a body of active material in the trench. The active material depends on the particular contaminant: organic carbon may be used when the contaminant is ferrous sulphate, or hexavalent uranium oxide, or dissolved nitrate; pyrite or elemental iron may be used when the contaminant is e.g. chromium oxide. The active material causes the contaminant to transform or break down by chemical reaction into harmless precipitates and substances.

Abstract: A method has been devised for removing chromium ions from a chromium ion containing liquid and recovering chromium oxide in a usable form by (a) adjusting the temperature of the liquid to an optimal temperature to maximize reduction and simultaneous precipitation of the chromium oxide; (b) adding a reducing agent to the liquid to form a mixture, where the reducing agent is at least one inorganic sulfur compound selected from the group of sulfur compounds where sulfur is in the 4.sup.+ oxidation state; and (c) adjusting the pH of the mixture to a pH between 5 and 7; (d) optionally further adjusting the pH of the mixture to a pH between above 7 to 12; and (e) separating the chromium from the mixture.

Abstract: Solutions such as for example groundwater, drinking water, extracting solutions and effluents contaminated with metals, radioactive species and organics, singly or in combination, are treated by first removing undesirable oxidizing agents from the contaminated solution. Then the contaminated solution is separately treated with aqueous solutions of ferrous sulfate and hydroxide, which precipitate substantially all of the contaminants. Next, the precipitate is treated with a flocculant and/or a coagulant to form an easily dewaterable and separable solid. The solid contaminants are readily removed from the cleansed solution. The process utilizes a novel combination of steps which maximizes contaminant removal, minimizes waste volume, and produces a recyclable solution and a manageable waste stream. The preferred hydroxide solutions are sodium hydroxide, calcium hydroxide, and ammonium hydroxide.

Abstract: There is disclosed a method of treating a solution, e.g., an alkaline or acidic solution, containing heavy metals ions therein. With respect to alkaline solutions, the method includes providing a body of the solution; contacting the body with a material such as carbon dioxide to change the pH, e.g., to lower the pH to a pH in the range of 9 to 10.5; then treating the solution to further change the pH and cause precipitation of hydroxides, including chromium hydroxide; and separating the hydroxide precipitates from the solution to provide a substantially neutral solution having a reduced amount of chromium ions, for example, contained therein.

Abstract: A process for removing dissolved heavy metal from an aqueous solution is provided where the aqueous solution is mixed with a source of ferrous ion and dithionite ion in a first step at acidic pH to reduce and permit removal of the heavy metal. Solution from the first step is reacted in a second step with hydroxide slurrys obtained from third and fourth steps. A second solution from the second step is reacted in a third step with an alkali composition and a third solution. The third solution is reacted with a chelating agent for iron and an oxidizer in a fourth step. A solution of chelated iron from the fourth step is disposed of.

Abstract: A composition for the detackification and clarification of acid and alkaline paint and lacquer waste waters and paint spray booth wastes, comprising:an inorganic-organic and/or organic adduct alloy polymer composition having the formula:A.multidot.B.sup.+ .multidot.D.sup.+wherein:A=[(SiO.sub.2 /Me.sup.I.sub.2 O).sub.u Me.sup.II.sub.m Me.sub.m.sup.III(OH) p.sup.(SO 4.sup.) y.sup.(Aci) (2m+3n)-p-2y].sub.4wherer=1 to 98% bw;u=0 to 10% bw; ##STR1## where: x=0 to 98% bw; Z is a divalent substituted or unsubstituted aliphatic, cycloaliphatic, heterocyclic or aromatic radicalD.sup.+ (PQAM).sub.wwherew=2 to 98% b.w. of polyquaternized polymer (PQAM)Me.sub.m.sup.II is selected from the divalent cationic group comprising: Mg, Zn, Ca, and Fe.sup.2+m=0 to 5Me.sub.n.sup.III is a tri-or more valent metal selected from the group comprising: Fe, Al, and Al-Zn complexes;n=1 to 20Aci is selected from the monovalent anionic group comprising Cl.sup.-, Br.sup.-, I.sup.-, NO.sub.3 --, H.sub.2 PO.sub.4 --, CH.sub.3 COO.sup.-, OH.

Abstract: A process and equipment is disclosed for minimizing sludge formation in removal of chromium and heavy metals from chromium contaminated groundwater by using sodium sulfite for oxygen removal thereby minimizing the amount of ferrous salt necessary for reduction of chromium VI to chromium III in an alkaline solution and also minimizing the amount of excess iron salt to coprecipitate as an hydroxide to effect essentially complete removal of other heavy metals.

Abstract: The present invention provides a composition and process for the treatment of waste water containing chromium compound, for example water from a plating operation which includes significant concentration of a toxic chromium compound such as chromic acid. The chromium bearing solution is mixed with sufficient amount of hydrazine which can include selected minor concentrations of a cobalt salt to react with the chromium compound and render it insoluble. The chromium bearing water is introduced to a vessel which can have a baffle so that water introduced on one side of the baffle flows along a side of, then under the baffle and overflows on the other side. The hydrazine, which can include cobalt salt, is introduced to the incoming water at a rate to control the pH of the effluent from the vessel at a selected value of pH sufficient to remove all chromium from the effluent.

Abstract: A method has been devised for removing chromium ion from a chromium ion containing liquid and recovering chromium oxide in an usable form by (a) adjusting the temperature of the liquid to an optimal temperature to maximize reduction and simultaneous precipitation of the chromium oxide; (b) adding a reducing agent to the liquid to form a mixture, where the reducing agent is at least one inorganic sulfur compound selected from the group of sulfur compounds where sulfur is in the 4.sup.+ oxidation state and (c) adjusting the pH of the mixture to a pH between 5 and 7.

Abstract: A method and composition for treating wastewater streams is provided. The composition includes a zirconium salt and preferably a zirconium carbonate. In addition to the zirconium salt; a ferrate, a reducing agent, a weighting agent and an anionic coagulating agent can also be employed. The method includes the steps of adjusting the pH of a wastewater stream to between about pH 6.5 and about pH 14, adding the composition, precipitating contaminants from the wastewater stream and separating a solution having a reduced contaminants content therefrom.

Abstract: A process for precipitating and removing chromium compounds in which chromium is in the hexavalent state from aqueous liquids, particularly, alkaline earth metal or alkali metal chlorate-rich solutions containing chloride, chlorate, and bichromate ions produced by the electrolysis of brine. In the process, hydroxylamine, hydroxylamine sulfate, hydroxylamine formate or hydroxylamine hydrochloride is used as a reducing agent to react and co-precipitate at a neutral or acid pH with hexavalent chromium ions present in the aqueous liquid, the reaction and precipitation taking place, generally, at a pH of about 4.0 to about 6.5 and, a temperature of about 50.degree. C. to about 100.degree. C. Precipitated oxides and hydroxides of divalent and trivalent chromium can be removed, for instance, by filtration.

Abstract: A method of removing Cr.sup.+6 from a solution is provided. In removing the Cr.sup.+6, an effective amount of an alkali metal dithionite is added to the solution to reduce substantially all of the Cr.sup.+6 to Cr.sup.+3. A soluble material is provided in the solution which will form a precipitate. Further, the soluble material is selected such that it will coprecipitate and tie up any dissolved or colloidal Cr.sup.+3 formed as a result of the reduction of the Cr.sup.+6. In one embodiment, the solution is alkaline and preferably, the pH of the solution is reduced sufficiently such that the soluble material will quickly precipitate and form the coprecipitate material with the Cr.sup.+3. Thereafter, the solution is filtered to remove the coprecipitated material from the solution and thereby form a supernatant solution suitable for waste discharge which has substantially lowered chromium values. The precipitate has the Cr.sup.+3 tied up in an insoluble non-leachable form.

Abstract: A method for processing residual fixing-baths, whereby a residual fixing-bath after demetalization by means of sulfide or by means of electrolysis, is acidified with a mixture of nitric acid and sulphuric acid, and the precipitated sulphur is removed. A liquid suitable as a gas washing liquid for flue gases and/or liquid fertilizer component is also prepared by an integrated processing of two or three waste materials.

Abstract: A process for removing at least a portion of any iron, copper, nickel and chromium ions that are chelated by a alkylenepolyamine polyacetic acid or salt in an aqueous liquid waste. The process comprises the steps of (a) adjusting the pH of the liquid to above about 10; (b) adding sufficient sodium sulfide to react with at least a portion of the copper ions; (c) separating precipitated iron and copper compounds; (d) adding nitric acid to adjust the pH to the range of about 6 to 8; (e) adding sufficient sodium nitrite to the liquid to react with at least a portion of the nickel and chromium present; (f) heating the liquid to above about 575.degree. F. for at least about 15 minutes to facilitate precipitation of nickel and chromium; and (g) separating precipitated solids to leave a non-hazardous filtrate.

Abstract: A method of removing undesired ions, such as chlorine, hypochlorite, chromium, cyanide and heavy metal ions, from an aqueous preparation containing one or more of said ions consists of adding to the aqueous preparation an effective amount of magnesium bisulfite to inactivate the undesired ions and then adjusting the pH of the mixture to an appropriate pH. Compositions containing magnesium bisulfite and divalent and trivalent ions are disclosed.

Abstract: A composition for treating toxic metals in solid waste, sludge or slurry is provided. The composition includes a reducing agent such as ferrous sulfate or sodium sulfite and a fixative containing solid calcium oxide or solid magnesium oxide. The composition may also include an acid such as sulfuric acid.

Abstract: An integrated process for heavy metal and cyanide removal in aqueous waste stream from plating processes wherein cyanide is oxidized by hypochlorite at approximately pH of 11.5 and hexavalent chromium is reduced to trivalent chromium at ambient temperature with ferrous sulfate at pH of 9.5; excess hypochlorite from cyanide destruction reacts with ferrous sulfate and additional ferrous sulfate is added to reduce hexavalent chromium to trivalent chromium to allow hydroxide co-precipitation with hydroxides of the ferric iron and hydroxides of copper, chromium, zinc, cadmium, manganese, etc., which are then separated by settling and filtration.

Abstract: A method of reducing soluble Cr(VI) levels in aqueous wastes from 200 ppm or more to less than 1 ppm, particularly to less than 0.05 ppm, preferably to less than 0.01 ppm, uses fermentative sulfate-reudcing anaerobic bacteria to reduce Cr(VI) to Cr(III) and immobilize the latter as the extememly insoluble hydroxide. The process is readily adapted to operate continuously using a bioreactor containing sludge with sulfate-reducing anaerobic bacteria and operated as a chemostat.

Abstract: A system and method for removing heavy metals, such as hexavalent chromium from water. The system comprises at least two reactor containers for independently mixing chemicals with water. The system further comprises a flocculator and a clarifier whereby each container can separately treat water therein and separately transfer the treated water to the flocculator such that water treated in batches at the containers can be treated in a relatively independent manner with relatively constant results. The method of chemically treating the water in the containers includes decreasing the pH value, adding a reducing agent and then increasing the pH value in preparation for precipitating the heavy metals in the clarifier.

Abstract: A process for treating industrial waste water containing hexavalent chromium (Cr.sup.+6) and other heavy metals is disclosed which comprises reduction of Cr.sup.+6 to trivalent chromium (Cr.sup.+3) and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream at a pH of about 7 to 9 under conditions such that sludge production by the process of the invention is substantially less than that characteristic of prior art processes. Polymers are added to the solution to assist flocculation and clarification of the waste stream. More specifically, the invention comprises adding sulfide ion in a sulfide to hexavalent chromium ratio of about 0.7-2.5:1 and adding ferrous ion in a ferrous to hexavalent chromium ratio of about 0.5-5.0:1. The waste stream pH is preferably maintained in the range of about 7.2 to 7.5.