Abstract: A biosolids treatment system comprising a storage tank for containing a quantity of biosolids sludge, a system of disinfection piping within the storage tank comprised of a segment of inner biosolids piping having a plurality of holes spirally arranged at a desired spacing around its perimeter concentrically arranged with a segment of outer steam piping, delivery pumps for delivering a quantity of biosolids to the storage tank, biosolids pumps for delivering a flow of biosolids from the storage tank to the inner biosolids piping; and steam pumps for delivering a flow of steam to the outer steam piping and thereby injecting a flow of steam from the outer steam piping into the inner biosolids piping for thermally disinfecting the flow of biosolids in the inner biosolids piping. The system includes computerized controls for continuously and simultaneously monitoring and operating the biosolids and steam pump means.

Abstract: A method of cleaning a filter clogged with flocculating materials is provided. The method comprises determining the flocculated materials clogged on the filter and adding a dispersing agent to break up said flocculated materials to form dispersed precipitates. Then the dispersed precipitates are removed from the filter in a regular cleaning such as backflushing.

Abstract: A process for the preparation of concentrated solutions or suspensions of anionic organic compounds is described, which process comprises a) acidifying an aqueous solution or dispersion of an anionic organic compound that comprises salts and/or impurities to a pH of 4.5 or less, if the pH is above that value, so that the anionic organic compound becomes insoluble in water and precipitates out in the form of the free acid, b) bringing the suspension obtained from the previous step to a salt content below 2% by weight, based on the total weight of retentate, by means of ultra-filtration with a ceramic membrane or an acid-resistant organic membrane having a pore size of from 1 to 20 nm, and c) optionally washing out of the salts with water at a pH of less than 4.

Abstract: The precipitation and removal of suspended fat and protein components and other suspended solids from a given solution can be accomplished by the addition of an aluminate to complex with the fat and protein components and the addition of a flocculating agent to flocculate the aluminate/fat and protein component complexes into insoluble particles capable of removal by conventional technology, which insoluble particles can be rendered to produce tallow.

Abstract: A process for dewatering and reducing pathogens in liquid waste sludge having a liquid component and a sludge solids component. Alkaline material is added to the liquid waste sludge. Flocculent may then be mixed with the liquid waste sludge. The liquid waste sludge is then fed into a screw press having a screw. The screw simultaneously heats and dewaters the liquid waste sludge for a sufficient period of time and at a predetermined temperature for the sludge solids component from the screw press to be pasteurized. An apparatus is also provided for carrying out the process for dewatering and reducing pathogens in liquid waste sludge.

Abstract: A system and method for dewatering a continuous stream of slurry at high flow rates demonstrates enhanced efficiency, economy and ease of operation. A stream of slurry is subject to continuous or continual measurement of flow rate and pulp density and the measurements are used to control the rate of addition of a flocculating agent to the slurry. The flocculated slurry is delivered to a dewatering unit where it is passed through a diffuser and evenly delivered to a tracking screen for filtering solids from a liquid filtrate. The pulp density of the filtrate may also be measured and used to control addition of a flocculating agent. The tracking screen is adjusted to achieve an angle of repose suited to the particular composition of the filter cake. The diffuser has a base having a horizontal section aspect ratio of from about 1:1 to about 4:1 and continuously changing vertically into an upper portion having a horizontal section with an aspect ratio of from about 40:1 to about 100:1.

Abstract: Chloride is selectively isolated as NaCl from N-phosphonomethyliminodiacetic acid process wastes by evaporative crystallization of the caustic neutralized brine.

Abstract: Disclosed is a method of removing heavy metals contained in exhaust gas which has been generated by burning a waste liquid containing the heavy metals discharged in a process of producing organic compounds. The method includes the steps in the order of: (a) a combustion step of burning the waste liquid to produce exhaust gas; (b) a gas-liquid contact step of rendering a liquid containing an alkali compound in contact with the exhaust gas to collect the heavy metals in bottoms of the liquid; and (c) a coagulating step of adding a coagulant to the bottoms to coagulate the heavy metals in the bottoms for removal of the heavy metals. According to this method, the heavy metals contained in the exhaust gas can be efficiently separated and removed.

Abstract: Novel methods and apparatuses are disclosed for the treatment of wastewater to reduce often associated offensive odors by promoting aerobic conditions through decreasing the amount of oxygen required to maintain aerobic cultures and/or aerobic biological activity in the wastewater.

Abstract: A method of recovering elementary phosphorus from an aqueous sludge containing about 1 to about 15 wt % dispersed particles of phosphorus is disclosed. To the sludge is added about 1 to about 20 wt %, based on the weight of the phosphorus present in said sludge, of a phosphate salt that has the general formula: where R is an alkali metal or ammonium and n is 0 to 30. The phosphorus in the sludge is melted and the solids in the sludge are separated from liquid phosphorus and water. Liquid phosphorus is then separated from the water.

Abstract: A floating mobile self-contained membrane filtration treatment vessel that is suitable for use in the treatment of contaminated marine waters and shipboard wastes including, but not limited to, ballast water, graywater, and blackwater and excess dredge waters. The mobile treatment vessel preferably includes a micro or ultrafiltration membrane treatment system for micron and submicron sized particulate removal.

Abstract: Apparatus for the treatment of a wiping solution, which includes ink flocculation apparatus for flocculating ink contained in a used wiping solution by the addition of a flocculant to the used wiping solution; solid-liquid separation apparatus for separating, into sludge and a filtrate, the used wiping solution containing the ink which is flocculated by the ink flocculation apparatus through filtration of the used wiping solution; distilled water production apparatus for producing distilled water and a concentrated solution through heating of the filtrate which is separated by the solid-liquid separation apparatus; water recycling apparatus for recycling the distilled water which is produced by the distilled water production apparatus as a raw material of a wiping solution; and post treatment apparatus for separating the concentrated solution into steam and a solid residue through heating of the concentrated solution which is produced by the distilled water production apparatus.

Abstract: A method of dewatering a mixture of coal tailings, water and contaminants comprising the steps of (a) providing a tank having a base surface and introducing said mixture of coal, tailings, water, and contaminants to said tank and allowing said coal tailings to settle on said base surface, (b) removing the coal tailings from said base surface of said tank along with water and contaminants and then separating said water and at least some of said contaminants from said coal tailings wherein said separated contaminants are suspended in said separated water, (c) adding an agent selected from one or more of the group consisting of a coagulant and a flocculent to said water and suspended contaminants separated from the coal tailings in step (b), (d) allowing the agent added in step (c) to coagulate or flocculate with the suspended contaminants to form a coagulated or flocculated mass and a quantity of supernatant water, and (e) separating the coagulated or flocculated mass formed in step (d) from the quantity of sup

Abstract: A method of treating an industrial waste liquor containing 1-cyclopropyl-7-(3-methyl-1-piperazinyl)-6-fluoro-8-methoxy-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid (gatifloxacin), comprising adding aqueous sulfuric acid to said liquor to form a sulfate of said gatifloxacin, and/or a hydrate of said sulfate; and the sulfate, and/or hydrate of said sulfate, made by said method.

Abstract: The present invention describes a procedure for the removal of sodium sulphate from a phosphate solution that has been used for absorption of SO2 from flue gases, whereby a precipitate forms when the absorption solution is regenerated by evaporation. In this procedure a part of the precipitate is separated from its solution and treated with water and SO2 for transformation of disodium-hydrogen phosphate into monosodium dihydrogen phosphate in the aqueous solution, whereby the sodium sulphate remains undissolved and is removed by filtration, whereafter the filtrate is added back to the main process.

Abstract: A process for forming small micron-sized (1-10 &mgr;m) protein particles is provided wherein a protein, a solvent system for the protein and an antisolvent for the protein solvent system are contacted under conditions to at least partially dissolve the protein solvent system in the antisolvent, thereby causing precipitation of the protein. The solvent system is made up of at least in part of a halogenated organic alcohol, most preferably 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). Preferably, a solution of the protein in the solvent system is sprayed through a nozzle into a precipitation zone containing the antisolvent (preferably CO2) under near- or supercritical conditions.

Abstract: A process is disclosed for obtaining colloid-forming metal particles from an aqueous mine waste solution containing that metal in ionic form. In accordance with this process, an aqueous mine waste solution containing that metal in ionic form is provided having a pH value of about 4.0 to about 6.5. The solution is electrified with direct current a about 1.2 to about 2.0 volts to reduce the desired metal ions to colloidal metal particles. A slurry of cellulose particles is agitatingly added to the colloid composition followed by a flocculant to form a solid phase cellulosic floc containing the colloid. The solid and liquid phases are separated, and the solid phase is dried, fluxed and heated to a temperature sufficient to melt the flux and colloid and form larger metal particles that can then be recovered. The colloid-forming metal is preferably gold.

Abstract: A method for the treatment of a wiping solution, characterized by including: adding a flocculant to a used wiping solution for flocculation of ink contained in said used wiping solution; filtering said used wiping solution for separation of said used wiping solution into sludge and a filtrate; heating said filtrate to produce distilled water and a concentrated solution; returning said distilled water for recycling to serve as a raw material of a wiping solution; and heating said concentrated solution for separation of said concentrated solution into steam and a solid residue. An apparatus for performing the method of the present invention is also disclosed.

Abstract: A method of dewatering a mixture of coal tailings, water and contaminants comprising the steps of (a) providing a tank having a base surface and introducing said mixture of coal, tailings, water, and contaminants to said tank and allowing said coal tailings to settle on said base surface, (b) removing the coal tailings from said base surface of said tank along with water and contaminants and then separating said water and at least some of said contaminants from said coal tailings wherein said separated contaminants are suspended in said separated water, (c) adding an agent selected from one or more of the group consisting of a coagulant and a flocculent to said water and suspended contaminants separated from the coal tailings in step (b), (d) allowing the agent added in step (c) to coagulate or flocculate with the suspended contaminants to form a coagulated or flocculated mass and a quantity of supernatant water, and (e) separating the coagulated or flocculated mass formed in step (d) from the quantity of sup

Abstract: Fatty oil and acids, glycerol, glycols, lactic acid, urea, fertilizer, carbohydrates, ethanol are recovered or produced from sewer sludge by the process of concentrating and filtering out the solid sewer sludge, hydrolysis of the cellulose in the sewer sludge by an alkali or acid catalyst to carbohydrates, fermentation of the carbohydrates to produce ethanol, then recover the ethanol by distillation or membrane technology. The glycerol, glycols and lactic acids are recovered by membrane technology. The polysacchride carbohydrates are hydrolyzed to monosacchrides then fermented to alcohol. The unsoluble sewer sludge and the salts such as ammonium sulfate, nitrogen containing compounds and urea from the aqueous solution left after the ethanol is distilled off are mixed, dried and utilized as fertilizer.

Abstract: Wastewater can be treated using a combination of a settleable solids separator, such as a vortex separator, and a gas floatation separation system.

Abstract: Paint detackifiers and/or sedimentation agents are provided which contain amorphous alumina and/or alumina in pseudoboehmite or boehmite form having an average crystallite size of from 0.1 to 15 nm and/or the hydrates and hydroxyalkylpolysaccharides thereof.

Abstract: Disclosed is a method of recovering elemental phosphorus from a sludge that contains water, dirt, and elemental phosphorus. In the first step, the sludge is melted. A mixture is formed of the melted sludge and about 0.5 to about 5 wt % of an oxidizing agent, based on the weight of elemental phosphorus in the sludge, and about 75 to about 580 wt % water, based on the weight of the sludge. The mixture is stirred until a continuous elemental phosphorus phase forms. The purified phosphorus phase is separated from the mixture.

Abstract: The present invention relates to a sludge treatment plant in which sludge is flocculated and then dewatered to form a cake and a reject liquor is modified by recycling 3 to 40% of the reject liquor into the sludge immediately before the dewatering process.

Abstract: The present invention relates to a high speed coagulant-flocculant and sedimentation method for treating waste water, which permits a speedy treatment of waste water including stormwater runoff and also permits a valuable reuse of the sludge produced in the course of treatment.

Abstract: The precipitation and removal of suspended fat and protein components and other suspended solids from a given solution can be accomplished by the addition of an aluminate to complex with the fat and protein components and the addition of a flocculating agent to flocculate the aluminate/fat and protein component complexes into insoluble particles capable of removal by conventional technology, which insoluble particles can be rendered to produce tallow.

Abstract: An apparatus and method for separating microalgae from water without rupturing cells. The method comprises the steps of flocculation, flotation and dehydration. Microalgae suspension from a reservoir is passed to a mixer unit where flocculation is carried out, using modified starch or other flocculating agents. The suspension is then directed to a flotation column. Dissolved gas in water is transferred to the flotation column through a disperser. A layer of foam containing microalgae is formed on the liquid layer in the column, which can be skimmed off through an overflow outlet. The flotation column is a telescopic column of adjustable height, which enables the position of the overflow outlet to be aligned with the level of the foam layer for efficient foam removal. Foam containing microalgae is then passed to a filtration unit for cloth filtration, followed by drying in a drying chamber.

Abstract: A process for treating sludge comprising the addition of sulphuric acid and anhydrous ammonium to the sludge inside a granulator in order to produce an exothermic reaction which generates sufficient heat to evaporate the water contained in the sludge, thus eliminating all the pathogen and non pathogen microorganism, and producing a dry product having a low pH, free of polluting agents and a high commercial value.

Abstract: A remediation agent and process produces a treated water that meets discharge standards required by local regulations and generates stabilized waste which does not require further treatment prior to disposal. The composition of the treatment chemical is applicable to the treatment of industrial wastewaters and more specifically those from automobile production, metal finishing, metal processing, oil refineries, textiles, wood treatment, tannery, circuit board manufacturing, and other miscellaneous industrial waste streams from operations such as paints, coatings, adhesives, soap and detergents, chemicals, and food processing.

Abstract: An apparatus performs a process for treating development waste liquor containing photosensitive resin and surface active agent. The process subjects the waste liquor to treatment for diminishing the efficacy of the surface active agent to result in separation of the resin from the waste liquor. The waste liquor is then irradiated with ultraviolet light at 300-400 nm. The apparatus contains a tank, a stirrer, an ultraviolet source and a filter.

Abstract: The precipitation and removal of suspended fat and protein components and other suspended solids from a given solution can be accomplished by the addition of an aluminate to complex with the fat and protein components and the addition of a flocculating agent to flocculate the aluminate/fat and protein component complexes into insoluble particles capable of removal by conventional technology, which insoluble particles can be rendered to produce tallow.

Abstract: A cleaning apparatus for a radiation source assembly in a fluid treatment system is described. The cleaning system comprises: a cleaning sleeve comprising a cleaning ring for engagement with a portion of the exterior of the radiation source assembly; a slidable member magnetically coupled to the cleaning sleeve, the slidable member being disposed on and slidable with respect to a rodless cylinder; and motive means to translate the slidable member along the rodless cylinder whereby the cleaning sleeve is translated over the exterior of the radiation source assembly. A radiation source module comprising the cleaning apparatus is also disclosed. The radiation source module is particularly useful for ultraviolet radiation of wastewater while having the advantages of in situ cleaning of the radiation source as when it becomes fouled.

Abstract: A process is disclosed for obtaining colloid-forming metal particles from an aqueous mine waste solution containing that metal in ionic form. In accordance with this process, an aqueous mine waste solution containing that metal in ionic form is provided having a pH value of about 4.0 to about 6.5. The solution is electrified with direct current a about 1.2 to about 2.0 volts to reduce the desired metal ions to colloidal metal particles. A slurry of cellulose particles is agitatingly added to the colloid composition followed by a flocculant to form a solid phase cellulosic floc containing the colloid. The solid and liquid phases are separated, and the solid phase is dried, fluxed and heated to a temperature sufficient to melt the flux and colloid and form larger metal particles that can then be recovered. The colloid-forming metal is preferably gold.

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 from 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 like 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 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 from 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 like 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 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: Disclosed is a method of recovering elemental phosphorus from a sludge that contains water, dirt, and elemental phosphorus. In the first step, the sludge is melted. A mixture is formed of the melted sludge and about 0.5 to about 3 wt % of an oxidizing agent, based on the weight of said elemental phosphorus in the sludge, and about 75 to about 400 wt % water, based on the weight of the sludge. The mixture is stirred until a continuous elemental phosphorus phase forms. The purified phosphorus phase is separated from the mixture.

Abstract: A wastewater treatment apparatus for use in an offshore marine environment includes a vertically elongated vessel having upper and lower end portions, wherein at least half of the vessel is submerged during use. The vessel provides an interior for containing fluid during use and is attachable to an offshore marine structure such as a fixed platform or floating marine rig. An influent flow line adds produce wastewater to the interior of the vessel. An effluent is provided for discharging treated fluid from the vessel interior. The upper end portion of the vessel interior defines a free oil separation section, the lower end portion of the vessel interior defines a disposal caisson section. The middle section of the vessel interior defines an induced gas flotation section. A plurality of spargers are provided at the gas flotation section for emitting bubbles at multiple elevational positions within the middle section of the vessel interior.

Abstract: Modification of phosphoric acid manufacturing provides improved process waters: decontaminated water pH-adjusted to be only slightly acidic, scrubber process water, gypsum stack water, and a composite of the latter two waters. The composite water undergoes two-stage neutralization with clarification, eliminating precipitatable contaminants, in forming the pH-adjusted water, which in turn is useful in forming scrubber process water or gypsum stack water, as needed, Resulting gypsum stacks and rainfall surge ponds, having been made relatively fluoride-free through such processing modification, and preferably also having been lined, supersede previous gypsum stacks and acid gypsum ponds—whether lined or not.

Abstract: A method for separating benzene from a hydrocarbon mixture containing benzene and at least one other organic material is carried out by treating the hydrocarbon mixture with at least one cyclodextrin to form complexes of the cyclodextrin with at least a portion of the benzene present in the hydrocarbon mixture. The cyclodextrin-benzene complexes then are separated from the hydrocarbon mixture.

Abstract: Wastewater streams containing tacky or sticky components and heavy metals, such as photoresist-containing streams from printed-circuit board manufacture and water streams from paint spraying processes, can be detackified and the metals simultaneously removed by addition of a metal salt, such as an iron salt, and a sulfide material. The combination of metal salts and sulfide reacting products produces a detackified metal sulfide sludge that improves the filterability of the wastewater while also removing dissolved metal ions from the wastewater.

Abstract: A method for the treatment of radioactive evaporator concentrates from the evaporation system of nuclear plants comprises the steps of (a) freeing the evaporator concentrates from undissolved components, (b) crystallizing the sodium sulfate contained in the evaporator concentrates as Glauber's salt (Na2SO4.10 H2O) on an immersion cooler, (c) recrystallizing the Glauber's salt deposited on the immersion cooler, (d) optionally, repeating the recrystallization step (c) once or several times, (e) separating essentially inactive sodium sulfate from the process, and (f) recycling the depleted evaporator concentrates of step (a) to the evaporation system.

Abstract: A process for the treatment of a solid waste slurry formed from solid waste particles mixed with a liquid includes delivering a solid waste slurry to a first solid-liquid separation means for separating a first amount of the solid waste particles from the slurry, followed by delivering the solid waste slurry from the first solid-liquid separation means to a tank where the solid waste slurry is stirred to maintain the solid waste particles in suspension. The solid waste slurry is then discharged from the tank with a portion of the solid waste slurry being recirculated back to the tank while a second portion of the solid waste slurry is delivered to a second solid-liquid separation means for separating a second amount of the particles from the slurry.

Abstract: A method in a paper machine for arrangement of water circulation therefor and arrangement of a water circulation system in a paper machine. In view of full or partial closing of the water circulations in a paper machine, the wash water flows from the fabrics and from other devices in the paper machine as well as the water drained from the paper web to be produced are recovered selectively based on the place of origin thereof in the paper machine. At least a part of the recovered different water flows are cleaned, and the cleaned water flows are recirculated to applications of reuse suitable in view of their washing potential in the papermaking process.

Abstract: A simple, rapid, efficient and inexpensive process for on-site recycling of wastewater with minimal odor wherein the solid wastes generated by the water treatment process are dewatering on-site by solar energy to water content levels below those required for disposal. All operations, including solar dewatering, are accomplished in a compact unit which may be mobile. The solar dewatering unit includes a drying pan over which a solar collector window arrangement is disposed. In the process, wastewater, a water purifying composition and an oxidizing agent are additively mixed together in a first reactor settling tank and the resulting composition is neutralized to a pH of between 7.5-9.4. The added water purifying composition is then allowed to precipitate wherein it binds to and precipitates heavy metals as well as other impurities. The precipitated purifying composition forms a non-hazardous sludge at the bottom of the tank.

Abstract: A process for treating a development waste liquor containing a photosensitive resin and a surface active agent, which includes subjecting the waste liquor to a treatment for diminishing the efficacy of the surface active agent, thereby separating the resin component from the development waste liquor, thereafter irradiating the development waste liquor with an ultraviolet ray having a wavelength of 300 to 400 nanometers to cure the resin component in the development waste liquor, and then removing the resulting solids.

Abstract: A method of treatment of an arsenic sludge obtained from a solid-liquid separation step on arsenic waste water by adjusting the value of pH to 12 or higher by adding a calcium compound is disclosed. The method is characterized by addition of hydrated lime and calcining the sludge.

Abstract: In the method for the humid treatment of effluents containing a compound selected from the group consisting of H.sub.2 SO.sub.4, free SO.sub.2, SO.sub.3.sup.-, or SO.sub.4.sup.= and having a pH lower than 5, the effluents are reacted with a basic compound. Particles selected from the group consisting of CaCO.sub.3.MgCO.sub.3, MgCO.sub.3 and a mixture of these, are used for treating the said effluents, the said particles having a particle size such that at least 95% of the particles selected from the group consisting of CaCO.sub.3.MgCO.sub.3 and MgCO.sub.3 have a particle size smaller than 75 .mu.m. After treatment magnesium sulfate in the form of a solution or brine is recovered.

Abstract: A solids separation system may be used to separate solids, such as cuttings from drilling fluids used in well drilling operations. The system includes a settling tank having transverse baffles defining a fluid receiving chamber, a fluid output chamber and one or more intermediate chambers. Fluid introduced into the fluid receiving chamber can flow in a sinuous path through apertures in the baffles to the fluid output chamber. Solids settle to the bottom of the settling tank. A material conveyor, preferably an auger, extends along a bottom surface of the settling tank to an outlet port in the fluid receiving chamber. A centrifuge is connected to the output port to receive fluid in which solids have been concentrated. Fluid output from the centrifuge is reintroduced into the settling tank. The apparatus and method of the invention permit a single centrifuge to be used to handle a higher volume of fluid than is possible with conventional methods and apparatus. This provides significant cost savings.

Abstract: An efficient and economical process for the waste treatment of spent metal plating solutions, primarily spent electroless nickel solutions, to significantly reduce the metal content therein, so as to permit direct discharge to municipal water systems without violation of the law. The waste treatment process is a sequential two-step chemical precipitation process, whereby the dissolved metal content is precipitated first by sodium borohydride reduction, followed by sodium dimethyldithiocarbamate precipitation, with an intermediate filtration step and pH adjustment step interposed there between. The amount of metal-bearing sludge produced is minimal. Furthermore, the bulk of the metals in the sludge may be recovered and reused, resulting in significant reduction in hazardous waste disposal costs.