Abstract: A waste water treatment process wherein an iron contactor or iron contact are immersed in a treatment tank, into which waste water flows. In the treatment tank sulfate reducing bacteria are made to coexist with activated sludge or biofilters, wherein a velocity of flow of agitating stream on the outer surfaces of said iron contactor or contactors is set at 10 to 20 cm/sec, under an aerobic treatment. Iron ions are made to elute from said iron contactor or contactors by utilizing electrochemical iron corrosion through the agency of oxygen concentration cells on the outer surfaces of said iron contactor or contactors on conditions that dissolved oxygen concentration in the treatment tank is 1 to 3.2 mg/l and the oxidation-reduction potential is -200 to -400 millivolts (mV). Under an anaerobic treatment, iron ions are made to elute by utilziing microorganism-corrosion on the outer surfaces of said iron contactor or contactors on condition that dissolved oxygen concentration in the treatment tank is 0 mg/l.

Abstract: A method for biologically removing approximately seventy-five percent of the phosphate contaminants from wastewater comprises controlling the aerator to a single activated sludge tank according to the turbidity of the water and the effluent requirements. Oxic, anoxic, and anaerobic reactions occur sequentially over the entire volume of the single reactor. Greater phosphate removal requires a simultaneous chemical precipitation.

Abstract: Wastewater containing impurities refractory to secondary treatment is first introducted into an aerobic biological treatment stage operating with an oxygen-enriched stream and subsequently into a precipitation stage where the biologically treated wastewater is combined with Ca(OH).sub.2 to precipitate Ca(OH).sub.2 CaCO.sub.3 sludge which adsorbs or occludes impurities. The clear liquid, separated from the resultant sludge, is passed to a second precipitation stage where it reacts with a CO.sub.2 and oxygen-containing waste gas at least in part from the aerobic biological treatment stage, thereby forming additional CaCO.sub.3. Waste gas withdrawn from the second precipitation stage, being enriched in oxygen is recycled to the aerobic biological treatment stage.

Abstract: The invention relates to a method for processing manure, comprising the steps of:i) adding an organic carrier liquid to the manure;ii) concentrating the mixture of manure and carrier liquid;iii) condensing the formed vapor;vi) anaerobic treating of the condensate; andv) aerobic treating of the effluent from the anaerobic treatment.Preferably the effluent deriving from the anaerobic treatment is denitrified in a denitrification unit and nitrified in a nitrification unit, and wherein a portion of the sludge-influent mixture from the nitrification unit is recirculated to the denitrification unit.The treating yield is greater than 90%, preferably greater than 95%, such as 97-99% BOD.

Abstract: A method of treating lake water to remove suspended solids and to precipitate and inactivate phosphorus comprises adding aluminum hydroxide sulfate to the water in a concentration such that the pH of the water is maintained at a level of greater than 6.0 and precipitation of suspended solids and precipitation and inactivation of phosphorus occurs. This invention is advantageous in that it provides a method of removing suspended solids as well as precipitating and inactivating phosphorus in water while simultaneously preventing the solublizing of toxic amounts of aluminum into the water with subsequent detrimental effects to aquatic life.

Abstract: The present invention entails a process for treating wastewater utilizing a return activated sludge process. Primary sludge is separated from the wastewater stream and conveyed into a fermentation tank and held a sufficient time to permit hydrolysis of suspended solids so as to produce soluble substrates. Part of the soluble substrates are mixed with nutrified return activated sludge and held for a selected time period to form conditioned return activated sludge. Thereafter, the conditioned return activated sludge is mixed in an initial aerobic treatment zone with pretreated wastewater. Thereafter, the mixed conditioned return activated sludge and pretreatd wastewater is conveyed through a series of treatment zones, which includes at least one anoxic treatment zone, to which part of the soluble substrates are added, where nitrogen and other pollutants are removed from the wastewater.

Abstract: An amorphous substance obtained by mixing volcanic ash with or without added clay and water and, if necessary, a surfactant, kneading the mixture, and shaping and firing. Additives such as camphor or naphthalene may be included prior to firing for plasticity and to form pores. The resultant mixture possesses an ability to adsorb phosphorus selectively. When this substance is placed in contact with a phosphorus-containing liquid, it removes phosphorus from the liquid.

Abstract: The present invention entails a process for treating wastewater utilizing a return activated sludge process. Primary sludge is separated from the wastewater stream and conveyed into a fermentation tank and held a sufficient time to permit hydrolysis of suspended solids so as to produce soluble substrates. The soluble substrates are mixed with the return activated sludge and held for a selected time period in an anoxic zone, to form conditioned, denitrified return activated sludge, followed by anaerobic treatment, to produce microorganisms that are capable of biologically removing phosphorus. Thereafter, the conditioned return activated sludge is mixed in an initial aerobic treatment zone with pretreated wastewater. Thereafter, the mixed conditioned return activated sludge and pretreated wastewater may be conveyed through a series of treatment zones, which may include at least one anoxic treatment zone.

Abstract: The present invention discloses a phosphate adsorbent comprising an MgO-TiO.sub.2 complex as an active ingredient and a phosphate adsorbent having said complex deposited on active carbons. In the preferred embodiments of the present invention, the MgO/TiO.sub.2 molar ratio in the complex is in the range of 99.99/0.01 to 80/20, the specific surface area of the adsorbent as measured by BET method is in the range of 50 to 700 m.sup.2 /g. and the absorbent shows a crystal diffraction pattern of MgO in powder X-ray diffractometry. The phosphate adsorbent according to the present invention is useful as an antihyperphosphoremial agent, an adsorbent for hemoperfusion and a therapeutical agent for renal diseases.

Abstract: Cationic organic impurities such as ternary sulfonium ions and quaternary ammonium and phosphonium compounds are effectively removed from polar liquids such as water or water/alcohol mixtures by contacting the polar liquid with an absorbent comprising a trinitroarenol such as a picric acid. This method is particularly effective for removing such cationic impurities from polar liquids containing organic zwitterions.

Abstract: Wastewater and recycled activated sludge are homogeneously mixed in a first aeration zone by injecting an oxygen-containing gas such as air into the lower portion of the zone under conditions which produce a complete mix reaction and sufficient oxygen is supplied to meet the biological oxygen demands of the mixed liquor. The gas is introduced, preferably by a plurality of fine bubble membrane diffusers, in the form of fine bubbles having a diameter less than about 4 mm. The bubbles provide both the mixing to keep solids in suspension and the oxygen required to maintain the overall dissolved oxygen content in the first aeration zone as close to 0 as possible. The mixed liquor is sequentially contacted with an oxygen-containing gas in second and third aeration zones under conditions which produce a complete mix reaction, preferably by fine bubble membrane diffusers, clarified and a portion of the settled sludge is recycled to the first aeration zone.

Abstract: There is disclosed an activated sludge wastewater treatment process which comprises aerating a mixed liquor comprising phosphate-containing influent wastewater and activated sludge in an aeration or high-purity oxygen zone to reduce the BOD/COD content of the wastewater and to cause the microorganisms present to take up phosphate. A phosphate-enriched sludge in which the phosphorus is present primarily in the sludge solids is separated from the mixed liquor to provide a substantially phosphate-free effluent. At least a portion of said phosphate-enriched sludge is passed to a phosphate pre-stripping zone, either in a separate tank or within the phosphate stripper tank itself, where BOD/COD-containing water, or feedwater, containing at least 50 mg/L of BOD, is added to poise the sludge organisms to begin enhanced rapid release of dissolved phosphate by pre-stripping it from the sludge or poising the sludge for rapid, enhanced release of phosphate. Then, the sludge is passed to a phosphate stripping zone.

Abstract: A process for treating wastewater to biologically remove phosphorous as well as lowering ammonia, TSS and BOD levels is provided. The process employs a plurality of basins which may be individually controlled to achieve anaerobic, anoxic or aerobic conditions. The basins are reconfigurable in that the flow of influent to a basin, transfer of mixed liquor between basins and effluent discharge from a basin can be varied to create a treatment cycle which has features of both continuous and batch processes while minimizing recycle rates and hydraulic level changes.

Abstract: A method is disclosed for reducing the amount of a first contaminant and second contaminant in a solution to environmentally safe levels, said solution having a substantially greater amount of the first contaminant than the second contaminant. The method comprises: contacting the solution with an activated or calcined product of a compound having the formula A.sub.6 B.sub.2 (OH).sub.16 C.4H.sub.2 O, wherein A is a divalent metal cation, B is a trivalent metal cation and C is a mono- to tetravalent anion. The method further comprises separating the solution from the contacted product. The method is particularly useful for removing both selenium and sulfate, arsenic and sulfate, or arsenic and phosphate from a waste water stream. An unpredicted preference for selenium and arsenic, in the presence of other contaminants including sulfate and phosphate, was also shown herein.

Abstract: A method of treating raw water containing phosphorous and nitrogen compounds and organic matter in which the raw water is passed through an aerobic zone containing a porous material. Anaerobic treatment is carried out in the presence of a hydrogen donor. The porous material is tobermorite and/or xonotlite with a porosity of 50% to 90% and is produced by foaming and hardening a silica-based material, a lime-based material and water, and subjecting the porous material to hydrothermal synthesis. The order of the aerobic and anaerobic treatments may be varied.

Abstract: For improvement of the phosphate redissolution taking place under anaerobic conditions, the treatment is conducted under anaerobic conditions, preferably in a settling tank, into which unsettled raw sewage and a return sludge from the secondary settling tank are introduced. The sludge retention time of the return sludge is generally over 5 hours, preferably 10-24 hours. In any case, the sludge detection time exceeds the hydraulic detection time.The new process can be performed by using most existing plants with relative small investment expenditures and provides a phosphorus elimination on the order of magnitude of 90%.

Abstract: A high-rate biological waste water treatment process for removing organic tter, phosphorus and nitrogen nutrients from municipal waste water comprising the steps of mixing the influent waste water in an initial anaerobic reactor zone to maintain the biological solvents in suspension with a denitrified mixed liquor from a downstream anoxic reactor zone, typically at a flow rate of 0.5 to two times the waste water flow rate. The reactor zone serves to select microorganisms capable of accumulating quantities of phosphorus in excess of that required for simple cell growth and reproduction. The phosphorus removal occurs due to the removal of excess sludge (waste activated sludge) produced in the process wherein such sludge can be removed from the clarifier underflow or as a mixed liquor directly from the biological reactor.

Abstract: A method of removing organic phosphorus-based poisonous substances from water contaminated therewith and of subsequently destroying the toxicity of the substance is disclosed. Initially, a water-immiscible organic is immobilized on a supported liquid membrane. Thereafter, the contaminated water is contacted with one side of the supported liquid membrane to selectively dissolve the phosphorus-based substance in the organic extractant. At the same time, the other side of the supported liquid membrane is contacted with a hydroxy-affording strong base to react the phosphorus-based substance dissolved by the organic extractant with a hydroxy ion. This forms a non-toxic reaction product in the base. The organic extractant can be a water-insoluble trialkyl amine, such as trilauryl amine. The phosphorus-based substance can be phosphoryl or a thiophosphoryl.

Abstract: A method of treating sewage is disclosed that is particularly suitable for one or a small group of residential dwellings in environmentally sensitive areas. The raw sewage is flowed first into an aerobic first cell where it is aerated and forced into a highly aerobic condition where aerobic bacteria grow and consume phosphorus in a vigorous life cycle and then die. Substantial primary unloading of B.O.D., T.S.S., coliform, and phosphorous is accomplished in this first cell. The fluid from the first cell overflows into a second cell where additional sedimentary clarification occurs and it goes anaerobic. A third cell has an upwelling flow through a porous medium substrate where anaerobic bacteria converts nitrogen in nitrates and nitrites to nitrogen gas, and the fluid then flows into a fourth holding cell. The effluent in the holding cell can then be flowed intermittently through a sand filter that has a bed of dolemite for final removal of residual phosphorus before it flows into a drain field.

Abstract: Waste water purification employing the activated sludge process with batch-wise waste water feed to the aeration tank. There is continuous aeration and water discharge from the tank. The process has a fixed dosing cycle based on historical values for the curve of the bacterial activity with the batch-wise waste water feed or a function of indicator values for this activity, specifically as a function of the oxygen concentration in the tank through an appropriate control, which briefly opens the waste water feed when, for example, an oxygen electrode indicates that an adjustable limit value has been exceeded. By means of such an oxygen electrode, an alarm signal can simultaneously be tripped if the high oxygen consumption expected after the admission of the waste water does not occur. The process is specifically useful for the treatment of waste waters which tend to form too much bulking sludge.

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 the purification of effluent, in which the effluent to be purified is first introduced into a high-loaded activation stage operated as an adsorption stage, then is passed through an intermediate clarifier with sludge offtake and subsequently introduced into a low-loaded stage to which a final clarification stage with sludge offtake is connected. Microorganisms work in the adsorption stage. The sludge is maintained in the initiation phase by means of the sludge takeoff from the intermediate clarification stage. Nitrification and subsequently denitrification can be carried out in the low-loaded stage. Sludge from the intermediate clarification stage can be reintroduced as recycled sludge into the adsorption stage, and sludge from the final clarification stage can be re-introduced as recycled sludge into the low-loaded stage. Also excess sludge is drawn off and thickened.

Abstract: A modified activated sludge system is provided wherein wastewater containing BOD.sub.5 and phosphate values is admixed in an initial zone with biomass-containing recycled sludge to form a mixed liquor under conditions effecting sorption of BOD.sub.5 in the biomass. Subsequently, said mixed liquor is subjected to aeration in an oxidation zone under conditions for effecting oxidation of BOD.sub.5, such that oxidizing agent is incorporated into the oxidation zone at a rate not substantially exceeding the rate of oxidation. By such operation, considerable savings in power requirements for oxygen transfer to the mixed liquid are had, while developing and maintaining a dense non-bulking biomass having the properties of good removal of phosphate from the wastewater influent.

Abstract: A process is disclosed for the biological treatment of sewage, which envisages the use of raw cellulosic materials brought into contact with the fouled water in the presence of cellulose-devouring micro-organisms, and is centered particularly on separation of the sewage's nitrogen and phosphorus content.

Abstract: A process is described for recovering phosphorus from pond sludge found in ponds located near phosphorus plants. An aqueous solution of the sludge, which has a phosphorus concentration in the range of 5% to 70% by weight, is heated at a temperature in the range of 165.degree. F. to 212.degree. F., preferably for about 1/2 hour to about 6 hours, washed with water at an elevated temperature, and then reheated. A phosphorus layer having an enhanced concentration of recoverable elemental phosphorus is formed as a result of this process.

Abstract: Water or sewage which contains sludges containing organic waste materials or waste materials which can be chemically precipitated are mixed with a flocculant consisting of a metal salt solution and are subsequently degasified. Thereafter, the pure water and organic sludge containing admixed metal hydroxide are separated from each other. The pH value of the sludge mixture is decreased until the metal hydroxides are dissolved as metal salts so that the organic sludge can be separated from the resulting metal salt solution. The metal salt solution is recirculated for re-use as a flocculant. Because the separated sludge still contains metal salts, it is treated with wash water and may possibly be further acidified. After the separation, the pH value of the wash water is increased to precipitate a metal hydroxide sludge, which is separated from the wash water and recycled to the degasified sewage.

Abstract: The specification discloses a novel calcium silicate water-treating agent exhibiting a superior ability to remove various kinds of phosphorus compounds or other environmental pollutants contained in wastewater, the calcium silicate water treating agent comprising a burned product which is prepared by burning a mixture containing as main constituents calcium compound, thermally decomposable to calcium oxide (CaO), and SiO.sub.2 -containing compound at a temperature of 1300.degree. to 1600.degree. C., the molar ratio of CaO/SiO.sub.2 of the resultant burned product being in the range of 1.5 to 5.0, preferably 2.0 to 4.0. In this water treating agent, SiO.sub.2 component may be partially replaced by Al.sub.2 O.sub.3 and/or Fe.sub.2 O.sub.3. A further water treating agent is prepared by heating the hydrate of the burned product prepared above at a temperature of 50.degree. to 700.degree. C.

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: Hazardous waste containing inorganic compounds which contain heavy metals or particular hazardous anionic groups or which are hazardous halides or non-metal oxides or sulfides is contacted with molten aluminum to provide reduction to lower less hazardous oxidation state.

Abstract: A method of improving the phosphorus elimination capacity of a lake (11). Flexible wall (16) is extended from the bottom (21) of the lake a substantial distance toward the surface (23) of the lake at the beginning of the vegetation period of the lake to separate the lower parts of a minor portion of the lake from the lower parts of the rest of the lake. Sheets (18) are positioned between an inlet channel (12) and the flexible wall (16) as growth areas for algae. The flexible wall (16) is lowered around the end of the vegetation period to allow the flushing away of sedimented algae from the bottom of the minor portion of the lake.

Abstract: An improved process is described for removing phosphorus from industrial waste water by contacting the waste water with ozone to convert reduced or organic phosphates into ortho-phosphates, and precipitating the soluble ortho-phosphates by treatment with lime. The precipitated material can be filtered, and the filtrate treated with activated carbon to produce an effluent stream having low levels of phosphorus.The process of this invention is particularly effective at low treatment temperatures, enabling efficient treatment of the waste water during periods of cold weather.

Abstract: A process of recovering elemental phosphorus from sludge is disclosed wherein the sludge is flash evaporated utilizing a heat transfer means and then separated from the solid impurities contained therein.

Abstract: Cholinesterase inhibiting agents such as nerve gas agents and pesticide agents are destroyed by reaction with molten aluminum and the gaseous products are analyzed and recycled if they are not essentially free of such agents.

Abstract: A wastewater treatment reaction vessel is operated with repeated sequences of aeration and non-aeration, using a single vessel or multiple vessels alternately, activated sludge which is acclimated for BOD reduction, nitrification or biological denitrification and phosphorus removal is absorptively reacted with influent wastewater, and the combined flow is passed into subsequent absorptive reactor volumes, reducing the BOD such that the effluent BOD is less than twenty percent that of the influent.

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 method of removing nitrogen and phosphorus from waste water by using an activated sludge including aerobic bacteria is disclosed. The waste water is fed continuously and gradually into a treatment basin in which the sludge is contained so that a mixed liquor consisting of the waste water and the sludge is formed therein. A cycle consisting of an agitating step and an aerating step is repeated at least two times and each cycle is finished within two hours, with the ratio of the agitating time to the aerating time being between one to one and to one. In the agitating step, the mixed liquor presents an anoxic condition and a succeeding anaerobic condition. Denitrification occurs in the anoxic condition and the aerobic bacteria release phosphorus in the anaerobic condition. During the aerating step, nitrification is caused while the bacteria excessively ingest phosphorus from the mixed liquor.

Abstract: Abnormally lowered reduction in the rate of phosphorus removal from influent wastewater in an activated sludge system, occurring particularly following periods of increase in flow rate of wastewater entering the system, is avoided by controlling the maximum F/M in that portion of the system in which oxidation is occurring so as not to exceed 0.9 and maintaining a defined relation between the maximum and minimum F/M during any 24 hour operating period.

Abstract: A method is disclosed for removing certain contaminant phospholene and phospholane oxides or sulfides from organic fluid or fluid mixtures wherein the fluid or fluid mixture is contacted with a cation exchange resin insoluble in the mixture at a temperature of from about 20.degree. C. to about 100.degree. C.

Abstract: An improved process for treating aqueous effluents and purge streams to selectively remove polluting elements such as iron, copper, lead and mercury therefrom is described. The procedure comprises contacting the effluent with a poly(dithiocarbamate) chelating agent whereby the polluting elements are absorbed. The resin is extracted with an acidic aqueous solution having a pH of from about 4 to about 6; and removing the resin. When this is done, the residual content of these polluting elements in the effluent is reduced to a level below EPA required levels so that the effluent can safely be discharged into the surrounding ecosystem. The poly(dithiocarbamate) resin containing the polluting elements can be disposed of, for example, by being deposited in an unsecured landfill.

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: Waste-containing (contaminated) waters are treated for reuse and disposal with acceptable environmental improvements by adding a sulfate salt of aluminum and/or iron alkalized to form a waste-cohering hydroxide floc in one or more treatment plants, recovering the flocs and wastes by contacting with sulfur oxides to redissolve the aluminum and/or iron for reuse, in which case low cost sulfur containing fuels are utilized to provide heat and sulfur for recovering over one-half of the sulfur dioxide for reuse and reducing the lime required to neutralize the acidity.

Abstract: A system is provided for restoring and maintaining a eutrophied natural body of water such as a lake. The system includes an initial treatment or takedown phase to precipitate phosphates, if necessary. A second or final phase includes the utilization of a series of dispensers in the lake water and in the watershed area to continually add measured, slightly less than stoichiometric amounts of secondary phosphate precipitating cations, such as soluble complexes of trivalent cations, to continually inactivate phosphates, with hydroxo complexes, fluoro complexes and complexes of weak organic acids, including amino acids, being preferred.

Abstract: A process and apparatus are provided for the biological purification of phosphate-containing wastewater, wherein the wastewater is treated, in the presence of activated sludge at least a portion of which is fixed on a carrier material. The process is conducted in at least one aerobic, an anaerobic, and optionally an anoxic zone, to thereby discharge a substantially phosphate-free wastewater stream. In order to attain a high purifying effect with low cost expenditure, the activated sludge is carried on a movable carrier. The carrier material is conveyed from the anaerobic zone, optionally through the anoxic zone, to the aerobic zone, and simultaneously a like amount of carrier material is returned from the aerobic zone, optionally through the anoxic zone, to the anaerobic zone. In this process, the activated sludge is enriched with phosphates, and a portion of the phosphate-enriched activated sludge is separated from the discharged effluent.

Abstract: Wastewater containing phosphorus values and BOD is initially admixed with recycled sludge containing activated biomass under anaerobic conditions, then contacted with oxygen-containing gas, followed by separation of a dense sludge layer from the mixed liquor. A portion of the sludge layer, containing the activated biomass, is held under non-aeration conditions for sufficient time to reduce any nitrates and/or nitrites contained therein, before admixture of the recycled sludge with the wastewater influent.

Abstract: The treatment of wastewater with activated biomass to remove BOD and phosphorus values in a system in which the wastewater influent is initially mixed with recycled active biomass in an anaerobic zone and then subjected to aeration in an oxic zone, wherein the residence time of the mixed liquor in the oxic zone is reduced. At least part of the biomass-containing sludge separated from the mixed liquor subjected to further oxidation in a separate zone before admixture with the wastewater influent.

Abstract: The invention is directed to a process for recovering elemental phosphorus values from phosphorus-containing waste materials. The process comprises reducing the size of the solid particulate materials of the sludge and forming a uniform homogenous sludge which is filtered through a high-pressure thin-cake filter resulting in a filtrate high in phosphorus values.The invention also discloses a pump retrieval means for retrieving the sludge from contaminated disposal areas and a preconditioning dewatering means for thickening and clarifying the sludge prior to comminuting the solids contained therein and filtrating to recover the phosphorus values contained therein.

Abstract: A method for removing and recovering ammonium and/or potassium and/or phosphate ions from wastewater is presented which comprises:permitting said wastewater to pass through at least one bed of ion-exchange resins capable of removing selectively those nutrient ionsregenerating those ion-exchange resins with a Na Cl solution or other suitable regenerant solutions so that said nutrient ions may be obtained in a much more concentrated formadding to said regeneration eluates (or, eventually, directly to wastewater) at least one Mg salt, in proper pH conditions so as to precipitate hydrous MgNH.sub.4 PO.sub.4 and/or MgKPO.sub.4, slightly soluble salts of great agronomic value.

Abstract: This invention relates to a process for the biological purification of phosphate-containing wastewater wherein the wastewater is gas-treated, i.e. aerated, in an oxygenation tank in the presence of activated sludge for degrading organic hydrocarbon compounds and absorption of phosphate by microorganisms present in the activated sludge. The wastewater-activated sludge mixture is then withdrawn from the oxygenated tank and divided, in a post clarification stage, into purified, essentially phosphate-free water and phosphate-containing sludge. The phosphate-containing sludge is recycled, at least in part, into the oxygenation tank. A partial stream of wastewater-activated sludge mixture is branched off from the oxygenation tank, and/or recycle sludge is branched off as a partial stream from the post clarification stage, and the mixture is subjected to flotation treatment for thickening. A thus-obtained, low-phosphate flotage, i.e. subnatant liquor, is discharged from the flotation unit.

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: A modified activated sludge system is provided wherein BOD-containing wastewater and recycled sludge are initially admixed under anaerobic conditions in the substantial absence of oxygen or oxidizing agents and subsequently subjected to aeration and clarification. By the disclosed operation the selective production of non-bulking biomass is favored while effective removal of phosphates is obtained. By a further alternative modification, nitrates and nitrites are also removed by interposing an anoxic treating zone between the anaerobic zone and the aerating zone.