Abstract: A process is disclosed for the detoxification of effluents containing cyanide by treating with a mixture of hydrogen peroxide and phosphoric acid.

Abstract: A process for controlling the concentration of aluminum in the brine of a membrane chlor-alkali cell is disclosed wherein the brine has its calcium carbonate settler solids digested in the calcium chloride flow stream by the addition of an inorganic mineral acid to bring the pH to about 2.0 to about 3.0 to solubilize the aluminum in the brine. The brine has the pH adjusted upwardly to reprecipitate the aluminum onto carrier particles and then removes the reprecipitated aluminum and carrier particles from the brine by filtration or centrifugation.

Abstract: The present invention concerns a floatation clarifying/flocculating procedure for purifying liquid, in which particles of impurities present in a liquid to be purified or impurities dissolved in the liquid which have been converted into particle form with the aid of flocculating chemicals, are separated from the liquid to be purified and carried to the surface of the liquid, to form thereon a sludge bed. The sludge bed is conducted out through a sludge trough to a sewer or equivalent, and flocculating chemicals are then added to the remaining liquid thus already at least partially purified, so that the chemicals form dirt particles with the impurities still present in a dissolved state but which have not yet been removed from the remaining liquid.

Abstract: In the method for concentrating/dehydrating sewage sludge including activated sludge with the aid of organic polyelectrolytes and/or inorganic flocculators the activated sludge portion is produced in an aerated biologic clearing step in presence of--based on the amount of liquid flowing into the clearing step--5 to 0.01 parts by weight per million parts by weight of at least one compound selected from the group consisting of folic acid, dihydrofolic acid and at least an ammonium alkali metal salt, alkaline earth metal salt and alkanolammonium salt thereof.

Abstract: A process for obtaining available elements from seawater is described, which process includes two separation steps. The first separation step involved adjusting the pH of seawater to a low pH by adding a strong acid having sulphate ion, adding a strongly alkaline agent thereto in amount sufficient to provide a high pH and separating the precipitate formed thereby from the filtrate. The second separation step involves concentrating the filtrate, cooling the concentrated filtrate and separating a precipitate thereby formed. Each precipitate and each filtrate obtained in these steps has characteristic components and can be utilized for many purposes, for example, for food additives, as a solvent for paint, as combustion aids, or as alkaline agents for neutralization etc.

Abstract: A method and system for removing toxic substances such as selenium and molybdenum from agricultural irrigation water achieves nearly 100% removal of the toxic substance economically, by a chemical reduction process. The process is particulary efficacious for removing naturally occurring selenium and molybdenum from irrigation water which has seeped through the ground and taken compounds of these metals into solution. Preferably, the drain tile water solution is first concentrated, to about 30% dissolved solids. This may be economically accomplished by on site evaporation in an open pond which is impermeable to seepage. Next the concentrated brine solution is heated, preferably to about 150.degree. F., and a reducing agent such as finely powdered iron is added to bring, for example, the selenium down from a +6 valence to +4 and lower valences. Wettable sulfur is added to the slurry to greatly improve the effectiveness of the iron in reducing the solution. The slurry is constantly agitated.

Abstract: A method of removing macromolecular organic dissolved and colloidal compounds from the effluents of a paper and cellulose mill by using waste sludge containing fibers and chemicals. The sludge is acidified to a pH of approx. 2 by a mineral acid prior to adding into the effluent. Organic material is precipitated with fibers in a sedimentation vessel at a pH of 4.5-6.

Abstract: A process for the removal of cyanide and other impurities from an aqueous solution is disclosed. The process comprises adding copper ion and ferrous ion as reagents to the solution at a pH of about 4 to 8 with a ratio of copper to cyanide in the range of 3:1 to 10:1 by weight and with a ratio of iron to copper of at least 0.3:1 by weight.

Abstract: This disclosure concerns a composition and process for separating solids from an oil and water mixture. The composition comprises lime and calcined perlite of a size distribution such than 0-5% is retained on 30 mesh, 45-65% is retained on 50 mesh, 80-90% is retained on 100 mesh and 90-100% is retained on 200 mesh screens. The process is particularly applicable to separating solids from an oily sludge to produce a recoverable oil product and a non-leaching filter cake which is environmentally acceptable.

Abstract: A process is disclosed for removing heavy metals, dissolved aluminum, sulfides and organic compounds from a caustic etch solution, thereby regenerating the etching power of the solution or facilitating its disposal into the environment. The process consists of forming a first filtrate from which heavy metals present in the solution have been removed, and a second filtrate obtained by precipitating and oxidizing residual chemicals remaining in the first filtrate. The latter is done over a selected pH and temperature range. The second filtrate is then either reclaimed back to the etching tank, or subjected to ozonization prior to disposing of it into the environment.

Abstract: A method of removing lignin from bleach plant effluents by using cellulose fibres. The method comprises an acidous phase during which sludge containing cellulose fibres is added to the acidous effluent, and an alkaline phase during which alkaline waste water is added to the effluent-sludge solution. A portion of the produced fraction containing fibres is recirculated to the acidous phase for reuse of the fibres.

Abstract: A process for deasphalting a heavy hydrocarbon feedstock, comprising two stages of precipitation from the feedstock of an asphaltene fraction alone or, alternatively, of a resin fraction along with the asphaltene fraction, by means of a heavy solvent and a light solvent, respectively, is disclosed.In accordance with the process, the heavy solvent and the light solvent both contain, in different proportions, at least one hydrocarbon having 3 carbon atoms and at least one hydrocarbon having at least 5 carbon atoms, the proportion of the hydrocarbon having 3 carbon atoms being higher in the light solvent than in the heavy solvent.

Abstract: The invention relates to a process for improving the sedimentation and filtering properties of waste waters and/or slurries and muds containing clay minerals. The waste waters and/or slurries obtained in the various technologies and containing clay minerals and optionally also other solid components are treated with compounds containing ions having a hydrated ionic diameter of from 0.12 to 0.15 nm and a co-ordination number of 12.

Abstract: A process for removing nickel and phosphorus species from a spent electroless nickel plating solution is described. This process involves an initial precipitation of phosphite values from the plating solution, followed by oxidation of hypophosphite and remaining phosphite to phosphate values, and the final removal of phosphate and nickel by lime precipitation. The treated plating solution is then separated from the precipitants, such as by filtration, and preferbly contain less than 1 milligrams/liter of nickel and/or total phosphorus species. This process is a cost effective method for treating spent electroless nickel plating solutions which is readily adaptable for on-site use.

Abstract: A process for treating an aqueous alkaline spent mixture produced during preparation of circuit boards and comprising a photopolymer resin. According to the method, first, an acid, a polyvalent cation and a coagulation aid are mixed with the spent mixture to produce a heterogeneous treated mixture comprising coagulated, precipitated photopolymer resin and an aqueous phase. Then, the coagulated, precipitated photopolymer resin is separated from the aqueous phase to produce a non-tacky, non-gumlike photopolymer resin sludge.

Abstract: A method for recovering useful animal feed supplements and a purefied brine from saline waters, such as oil and gas field brine wastes, involving the steps of adding an oxidizing agent to the brine to convert the divalent ferrous ions in the brine to ferric ions, then adding phosphoric acid in an amount approaching the stoicheometric equivalent of the divalent calcium ion the brine, then raising the pH of the brine to between 9 and 10 utilizing a material selected from the group consisting of sodium hydroxide or a mixture of sodium hydroxide and sodium carbonate followed by filtration to extract the feed supplement and thereafter adding a sufficient amount of hydrochloric acid to bring the pH to 7 and then crystallizing the sodium chloride from the resultant purefied brine solution.

Abstract: A chemical treatment for the removal for manganese or manganese and fluoride from an aqueous waste effluent obtained from the acid-fluoride washing or alkali (non-fluoride) washing in a step in the manufacture of aluminum cans. The treatment consists of adding in an acid medium sufficient phosphate ion to react with the manganese and/or fluoride and thereafter adding in an alkali medium sufficient calcium ion to react with the manganese, phosphate and/or fluoride. The ratio of phosphate to calcium ion added is 3:1 to 1:2.5.

Abstract: The present invention involves a treatment technique for drastically reducing the volume of hazardous sludge generated by the chemical reduction of chromium contaminants and the precipitation of heavy metal contaminants from contaminated electroplating wastewater. The wastewater is first adjusted to a pH of from about 8 to 10 and then treated with sodium sulfide to provide sulfide ions to effect precipitation of heavy metal contaminants followed by treatment with ferrous sulfate or ferrous chloride to provide ferrous ions to chemically reduce the hexavalent chromium to its trivalent state. This method produces approximately one-fourth the sludge generated by the previously known acidic reaction treatment using only ferrous sulfide.

Abstract: A method is provided for treating contaminated wastewater of pH ranging from about 1.5 to 3 containing phosphate ions and fluoride ions. The method comprises treating the said wastewater with an amount of alkaline agent selected from the group consisting of limestone (CaCO.sub.3) and lime [CaO or Ca(OH).sub.2 ] sufficient to raise and maintain the pH at a level of about 3.5 to 6.5 following uniform mixing thereof in a first stage precipitation step to effect substantial precipitation of the contaminants. The treated wastewater is passed to a first stage settler to effect solid/liquid separation and provide a sludge of the precipitated contaminants which is removed and separated to provide an effluent substantially impoverished in the aforementioned contaminants, following which the contaminant-impoverished effluent is treated in a second stage precipitation step with lime in an amount sufficient to raise and maintain the pH of the effluent at a level of at least about 10.

Abstract: Redissolution and/or reoxidation of metals precipitated by chemical reduction from aqueous solutions can be prevented by adding a bicyclic, aromatic, organonitrogen compound to the solution in a amount insufficient to cause precipitation of said metal but sufficient to prevent the redissolution and reoxidation of the precipitate. The compounds added can be selected from benzotriazoles, benzothiazols and benzimidazoles.

Abstract: A method is disclosed for the elimination of hazardous metal wastewater and sludges by recovering the non-ferrous metals zinc, nickel, copper (II), cadmium or chromium (III) present in an aqueous sludge comprising mixed metal hydroxides by selectively precipitating the ferrous metal ions present while maintaining the non-ferrous metal ions in solution, isolating the precipitate and then precipitating the non-ferrous metal ions from solution.

Abstract: A method is provided for the treatment of wastewater of pH ranging from about 1.5 to 3 containing at least about 100 ppm phosphorus as phosphate ions, at least about 50 ppm fluorine as fluoride ions and ammonia in excess of about 15 ppm NH.sub.3 (N)--T, the method comprising removing the phosphate and fluoride ions from the wastewater in a two-stage precipitation step; the first stage precipitation being conducted at a pH ranging from about 3.5 to 6.5 using an alkaline material selected from the group consisting of limestone (CaCO.sub.3) and lime [CaO or Ca(OH).sub.2 ] sufficient to form a precipitate which is removed to provide a filtrate of the wastewater which is treated in a second stage precipitation at a pH of at least about 10.5 using lime as the alkaline material sufficient to form a precipitate which is removed to provide substantially a clear effluent containing ammonia.

Abstract: A process of treating industrial waste water contaminated with environmentally unacceptable amounts of sulfuric acid and heavy metals such as lead, copper or zinc is disclosed which permits lowering of the concentration of the contaminants to a level permitting discharge to the sewer. Waste water resulting from floor wash and spray washing of lead acid batteries prior to shipment from the manufacturing facility contains sufficient sulfuric acid to cause the pH to normally be at a level of about 2 along with heavy metal contaminants present in concentrations which require treatment for removal before the discharge water will meet EPA standards. The water to be treated is directed to a first reaction and settling vessel where calcium carbonate is added along with an oxidation medium such as air which also functions to stir the stored waste water.

Abstract: A process for the removal of essentially chromium-free sulfate from a chromate and sulfate-containing chlorate liquor which includes mixing the chlorate liquor having a pH of between about 2.0 and 6.0 with a calcium-containing material at a temperature and for a time sufficient to form a sulfate-containing precipitate predominantly of glauberite, Na.sub.2 Ca(SO.sub.4).sub.2, and separating the substantially chromium-free glauberite from the chlorate liquor.

Abstract: A process is provided for the recovery of one or more useful products including fertilizer, animal feed supplements, iron oxide, magnesia, salt, purified brine, and purified water from brines. The source of the brines can be oil and gas field wastes, seawater or effluent from a seawater desalination plant, or other inland brine sources. Iron and magnesium are initially precipitated from the brine. Then phosphoric acid is added to the brine followed by an alkaline agent to produce precipitates useful as fertilizer and animal feed supplements. The remaining salt in the brine may then be removed and recovered along with purified water.

Abstract: A waste water control method and means comprising three basic units, a first unit including a flush booth wherein a radiator, or the like, may be exteriorly sprayed and/or interiorly flushed in the usual manner, and a multi-compartmented sump arranged for receiving the fluid draining from the spraying and/or flushing operation; a second unit including a first settling compartment wherein the fluid from the sump is received for a separation of heavy particles or components of the fluid from lighter components thereof, the lighter components of the fluid being directed to a first holding compartment for a chemical bath treatment thereof to substantially eliminate undesirable organic matter from the fluid; and a third unit including a second settling compartment for receiving the fluid from the first holding compartment to provide a final separation of heavier components of the fluid from the lighter components thereof, and a second holding compartment in communication with the second settling compartment for re

Abstract: A method for removing heavy metals from wastewater streams removes such heavy metal by treating heavy metal-containing wastewater with a water soluble tri-thio carbonate, particularly an alkali metal tri-thio carbonate, such as sodium tri-thio carbonate (Na.sub.2 CS.sub.3) to precipitate heavy metals therefrom.

Abstract: A method of removing complexed zinc-cyanide from wastewater involving a multiple stage process including, in a first step, control of ferrous ions to a critical minimum concentration of 250 to 400 ppm, together with pH control in the first and also a second step, together with recycling of a portion of sludge precipitated in the process. Improved sludge stability is achieved by aeration to oxidize precipitated ferrous hydroxide to ferric hydroxide, immediately before settling the sludge in a thickener.

Abstract: A noxious metal(s) containing waste material is treated with an acid solution of a metal of group VIIa or VIII of the Periodical System, preferably iron or manganese. Subsequently, the metal of group VIIa or VIII dissolved in the acid is precipitated as a metal hydroxide and simultaneously the noxious metal(s) dissolved from said waste by said acid solution are incorporated in said precipitating metal hydroxide.The waste material together with precipitated metal hydroxide is subjected to an immobilization treatment.Manganese hydroxide is particularly suitable for removing cadmium.An acid solution of iron and preferably simultaneously manganese to be used for treating the waste is obtained by dissolving oxysludge caught during iron or steel manufacture.The method is particularly for treating dredged harbor sludge.

Abstract: This invention relates to a process for removing nitrocresols and picric acid contaminants from a wastewater stream generated in the production of nitroaromatics, particularly dinitrotoluene, by the mixed acid technique. The process involves contacting the crude dinitrotoluene generated by the mixed acid technique with an alkaline medium to generate an alkaline wash water containing water soluble nitrocresols and picric acid therein. This wastewater is separated from the organic component and recycled for contact with further quantities of crude dinitrotoluene product from the reactor. When the concentration of the water soluble salts of nitrocresols and picric acid is of sufficient concentration the wash water is treated with aqueous acid in sufficient proportion to convert the water soluble salts to water insoluble organics. After treatment with acid, the organic material is separated from the wastewater and the organics incinerated.

Abstract: The invention relates to a method for purifying aqueous solutions containing at least one impurity element from the group consisting of arsenic, phosphorus, mercury and other heavy metals and solid matter by precipitation in at least two stages with the aid of precipitation reagents possessing ions capable of forming not-readily dissolved hydroxide precipitate. In accordance with the invention the main part of the precipitation reagent is introduced to the stage or stages following the first stage. The impurity element-containing precipitate formed in the aqueous solution subsequent to adding the reagent is separated therefrom substantially completely, and is returned so as to be present in the first precipitation stage, while that part of the solution which has been freed from precipitate in a later stage is withdrawn from the system. Substantially all the impurity element amount present in the ingoing aqueous solution are separated therefrom in the form of a sludge prior to the second precipitation stage.

Abstract: A method for dewatering phosphate slimes and recovering a liquid solution involves adding a calcium sulfate hemihydrate to the slimes, mixing the resulting admixture to effect formation of calcium sulfate dihydrate crystals in the admixture, and recovering a liquid solution from the resulting crystal-containing admixture.The calcium sulfate hemihydrate addition may be followed by addition of calcium sulfate dihydrate. The calcium sulfate hemihydrate addition may be preceded by acidification of the slimes to pH 1-3 with sulfuric acid, which addition may be followed by the addition of other calcium salts to the slimes.A sufficient amount of calcium oxide or calcium carbonate or both may be added to the recovered liquid solution to raise the pH of the liquid solution to a value above about 6.0. Mixing permits calcium phosphate salts to precipitate, allowing for separately recovering the calcium phosphate salts and a dephosphated liquid portion.

Abstract: A method of removing complexed zinc-cyanide from wastewater involving a multiple stage process including, in a first step, control of ferrous ions to a critical minimum concentration of 250 to 400 ppm, together with pH control in the first and also a second step, together with recycling of a portion of sludge precipitated in the process.

Abstract: The invention provides an improvement in the disposal of a waste water coining iron-cyanide complexes including ferricyanides by the reduction of the ferricyanide ions into ferrocyanide in the presence of a zinc salt to precipitate the ferrocyanide ions in the form of zinc ferrocyanide. The improvement comprises the use of a sulfite, e.g. sodium sulfite, and a thiosulfate, e.g. sodium thiosulfate, in combination as the reducing agent whereby the reduction of the ferricyanide ions is complete within a relatively short time without being affected by the atmospheric oxygen or other factors.

Abstract: A process for purifying an acid aqueous solution containing heavy metals by adding sulfide ions to said acid aqueous solution at a first pH lower than 3.4, precipitating a first heavy metal, adding sulfide ions again to said first precipitate containing acid aqueous solution, after adjusting to a pH of higher than 4, to precipitate a second heavy metal, and then removing the resultant first and second precipitates from the acid aqueous solution.

Abstract: The disclosure relates to a process for after-treating extraction residues, termed raffinates, originating from the extractive decontamination of crude phosphoric acid. To this end, the disclosure provides for the raffinates to be converted to two separate solid matter fractions of differant chemical composition by admixing the raffinates with a calcium compound so as to establish a pH-value of 1.2 up to 2.5. Next, the resulting precipitate consisting essentially of gypsum is filtered off as a first solid matter fraction, and washed with water. The resulting filtrate and the wash water are made into a mixture and predetermined proportions of calcium compound are added so as to obtain, after complete reaction, a fully reacted filter cake with a pH-value of 9 up to 12, the resulting suspension being filtered off at a pH-value of 6 to 8. The filter cake consisting essentially of calcium phosphate is separated as the second solid matter fraction, and allowed to react completely.

Abstract: The separability of latex floc dispersed in water is improved by adding a small proportion of portland cement thereto.

Abstract: A method of purifying waste water from oil well rigs in order that the water may be made suitable for reuse on the rig or disposed of conventionally is disclosed. The method incorporates a series of aerators and corresponding collection tanks to first aerate, then collect, the waste water a number of times. In each collection tank, sediment precipitates to the bottom of the tank, permitting the clearer water to overflow, or to be skimmed, from the collection tank. A soluble aluminum salt is added to the waste water at an initial stage of aeration in order to coagulate waste particles within the water and form solid precipitates which then settle to the tank bottom, permitting the clearer water to pass on to subsequent aerators and sedimentation tanks, until ultimately, the water may be disposed of without polluting or contaminating the environment.

Abstract: A method for removing low concentrations of soluble copper in the form of cupric cation and cuprocyanide and cupricyanide anions comprises first adding ferric cation, or ferrous cation and a soluble oxidizing agent, in an amount in excess of the stoichiometric amount required to form the ferric salts of the cuprocyanide and cupricyanide anions, and after a predetermined time adding an environmentally acceptable soluble precipitant to precipitate substantially all of the remaining excess ferric cation. By this procedure, very small concentrations of soluble cupric cation and the ferric salts of the cuprocyanide and cupricyanide anions, which are typically present in such low concentrations that they remain essentially permanently suspended in colloidal solution, are removed by the insoluble ferric compound which is present in much higher concentrations.

Abstract: A method for the removal of heavy metal ions from an aqueous solution which comprises the steps of admixing an aqueous slurry of FeS.sub.2 with a heavy metal ion bearing aqueous solution at a pH above 7, preferably 8-12, the slurry providing at least the stoichiometric amount of FeS.sub.2, preferably 2 to 6 times the stoichiometric amount of FeS.sub.2, for precipitating the heavy metal ions from the solution as sulfides and separating the precipitated sulfides from the aqueous solution. Desirably, a portion of the heavy metal ions are precipitated from the solution as heavy metal hydroxides and the precipitated hydroxides are separated from the solution prior to admixing the solution with the FeS.sub.2 slurry.

Abstract: Soluble sulfide residue, and small amounts of cyanide and oil, can be removed from scrubber water waste, particularly such waste produced by the process of manufacturing polyolefins from natural gas, by adding to the scrubber water waste a pickle acid waste, typically from steel operations, in an amount containing sufficient dissolved ionic iron to essentially completely react with all sulfide present and to precipitate it as iron sulfide. The cyanide ion can react to form iron ferrocyanide, which is substantially coprecipitated with the iron sulfide. Small amounts of oil present can also be coprecipitated.

Abstract: A pumpable water-purifying dispersion containing iron(II)sulphate, the iron(II)sulphate being dispersed in an aqueous phase with a dispersing agent containing an alkaline earth metal and a basic anion. The best dispersion properties are obtained when the dispersing agent is calcium carbonate or calcium hydroxide, whereby the resultant composition having a content of up to about 70% solid iron(II) sulphate, calculated as heptahydrate on the total weight of the composition, can be obtained and handled without difficulty. The aqueous phase can, to advantage, comprise metal ions active in water-purification, such as Fe.sup.2+, Fe.sup.3+ and Al.sup.3+.The invention also provides a method for producing the composition.

Abstract: Disclosed is a process for removing boron compounds from aqueous effluents. The effluents are contacted, under stirring, with a divalent metal sulphate Me.sub.I SO.sub.4 and a divalent metal hydroxyde Me.sub.II (OH).sub.2, the sulphate-hydroxyde couple being selected from the group consisting of BeSO.sub.4 --Ba(OH).sub.2 ; BeSO.sub.4 --Sr(OH).sub.2 ; BeSO.sub.4 --Ca(OH).sub.2 ; MgSO.sub.4 --Ba(OH).sub.2 ; MgSO.sub.4 --Sr(OH).sub.2 ; MgSO.sub.4 --Ca(OH).sub.2 ; CaSO.sub.4 --Ba(OH).sub.2 ; CaSO.sub.4 --Sr(OH).sub.2 ; SrSO.sub.4 --Ba(OH).sub.2 ; ZnSO.sub.4 --Ba(OH).sub.2 ; ZnSO.sub.4 --Sr(OH).sub.2 ; ZnSO.sub.4 --Ca(OH).sub.2 ; CdSO.sub.4 --Ba(OH).sub.2 ; CdSO.sub.4 --Sr(OH).sub.2 and CdSO.sub.4 --Ca(OH).sub.2. The sulfate Me.sub.I SO.sub.4 and the hydroxide Me.sub.II (OH).sub.2, by reaction with each other, cause the sulphate Me.sub.II SO.sub.4 and the hydroxide Me.sub.I (OH).sub.2 to precipitate.The amount of Me.sub.II (OH).sub.2 is at least stoichiometric in respect of the amount of Me.sub.I SO.sub.

Abstract: A method of treating scrubber sludge removed from a gas scrubbing apparatus of the type adapted to reduce SO.sub.x content in the treated gas, is provided. The method comprises collecting the spent residue from a fluidized combustion bed of the type wherein lime or calcium carbonate particles are suspended in a fluidized medium and wherein a carbonaceous fuel is ignited proximate said fluidized medium to absorb therein substantial amounts of SO.sub.x which is generated upon ignition of said carbonaceous fuel. The fluidized bed combustion residue is then subjected to a separating treatment wherein a slurry of residue is mechanically agitated. The supernatant liquor from the slurry is separated therefrom, leaving a precipitate material which latter material is mixed with sludge. The novel composition comprises a combination of scrubber sludge and fluidized bed combustion residue precipitate, as above mentioned.

Abstract: The invention provides an apparatus for the conditioning of sludges comprising two vertically arranged cylindrical vessels. An overflow pipe connecting the two cylindrical vessels is installed tangentially to the upper portions of the cylindrical vessels and may be provided with a detachable coupling. A sludge feed pipe is connected to the first cylindrical vessel and is installed in a direction tangentially opposite the overflow pipe above the bottom of the first vessel. A feed tube is installed tangentially into the sludge feed pipe. Two additional feed tubes are installed tangentially into the overflow pipe. A discharge pipe is installed in a direction tangentially opposite the overflow pipe above the bottom of the second vessel.

Abstract: A process for achieving the partial dewatering of an organic sludge by isolating a batch of the sludge, acid adjusting its pH into a range from 3 to 5, and adding an oxidizing reagent in the presence of the acid in sufficient quantity so that within one-half hour the cellular structure of the sludge has been partially broken down and enough occluded water released therefrom to increase the pH by at least one, while at the same time changing the color of the sludge to a light tan and deodorizing it and killing the pathogens therein, the sludge and other solids settling down below the supernatant liquid with a clear line of demarcation therebetween.

Abstract: A process for obtaining calcium fluoride from the pond water of phosphoric acid plants and recycling the high phosphate defluorinated water to the pond is disclosed. Sufficient calcium carbonate is added to a solution having a pH of about 0.8, containing about 1% fluoride, 1% phosphate and less than 0.4% sulfate, to raise the pH thereof to 2-3, whereby calcium fluoride is precipitated as a major component, calcium phosphates and calcium sulfates are precipitated as minor components. The calcium fluoride precipitate obtained is washed with raw pond water to reduce the phosphate content and with ammonium carbonate solution to reduce the sulfate content. In this manner an industrially useful fluorspar is obtained. The low fluoride supernatant liquid is then mixed with sufficient raw pond water to bring the pH into the range 1.5-2.0 and the resulting suspension is then held in a lagoon for 5-21 days to permit separation of silica.

Abstract: An apparatus and a process are provided which are particularly suited for treatment of sludge eminating from a metal finishing solution regeneration process, especially aluminum finishing solution. The sludge is washed on a horizontal belt vacuum filter from which a majority of the washing fluid is returned to the regeneration process. A portion of the washing water is wasted. After washing, the sludge is reslurried. Thereafter, the reslurried sludge is pumped to a reaction vessel in the presence of carbon dioxide under pressure. Sufficient carbon dioxide is provided to react with excess lime in the sludge to produce calcium carbonate and a substantially neutral pH. The sludge after carbonation is dewatered in a rotary drum vacuum filter and thereafter is suitable for placement in a landfill.

Abstract: A process for removing dissolved radioactive materials from aqueous solution by adjusting pH of the solution to greater than 9.0 and incorporating approximately 80 to 100 mg/l of alum, lowering the pH of the solution to a range of between 5.5 and 7.0.

Abstract: Phosphoric acid is purified by a process which comprises treating the crude acid solution with a body feed agent, powdered carbon and a flocculating agent to cause a major portion of the soluble and insoluble impurities to be removed in a single operation. In the preferred process, hot wet process phosphoric acid from the plant filter is first cooled to a temperature of from about 100.degree. F. to about 130.degree. F. and then treated in the above-described manner.