Abstract: Method and system for processing of a liquid (“contaminant liquid”) containing water and containing urine and/or other contaminants in a two step process. Urine, or a contaminated liquid similar to and/or containing urine and thus having a relatively high salt and urea content is passed through an activated carbon filter to provide a resulting liquid, to remove most of the organic molecules. The resulting liquid is passed through a semipermeable membrane from a membrane first side to a membrane second side, where a fortified drink having a lower water concentration (higher osmotic potential) than the resulting liquid is positioned. Osmotic pressure differential causes the water, but not most of the remaining inorganic (salts) contaminant(s) to pass through the membrane to the fortified drink. Optionally, the resulting liquid is allowed to precipitate additional organic molecules before passage through the membrane.

Abstract: Solid and liquid concrete waste is collected from a construction site and safely off-loaded at a treatment site. Solid waste is separated and sent to a crusher to be made into road bed aggregate. Liquid waste is put in a first tank to settle the solids, then moved to a second tank to settle remaining fine solids, and moved to a third tank coupled to a circulation pump with CO2 gas injection to lower the pH. The liquid in the third tank is then filtered before discharging for recycle, irrigation or dust control. A precipitate agent is preferable added to the liquid in the third tank to remove heavy metals and the precipitate is periodically backwashed from the filter into the first tank. The sludge created in the settling and filtering process is periodically dewatered in the first tank and mixed with the solid concrete waste sent to the crusher.

Abstract: A fluidized bed reactor (14) for removing phosphorus and nitrogen from wastewater has a column comprising a number of sections. (15A, 15B, 15C, 15D) The diameter of the column changes stepwise between the sections. A flow velocity in excess of 100 cm/min is maintained in a lowermost one of the sections and lower flow velocities are maintained in subsequent sections. A struvite supersaturation ratio is controlled in part by recycling wastewater from an outlet of the column. Struvite pellets are removed periodically from the bottom of the column.

Abstract: The present invention relates to a procedure for elimination of boron from sea-water by reverse osmosis membranes characterized in that it comprises: adding to sea-water a composition consisting of at least one metal together with at least one antiscaling-dispersant agent, and a second phase in which an alkalinizing agent is added until a pH of between 8-9.5 is achieved, which can furthermore consist of a third phase in which the fluoride content of the sea-water is increased following the second phase, or a third phase in which a high molecular weight alcohol is added to the water.

Abstract: A method for reducing barium concentration in waste streams. Hydrous manganese oxide (HMO) is formed in solution/slurry and mixed with water containing barium such that the hydrous manganese oxide exhibits a negative charge at a desired pH. Barium from the water is adsorbed onto the negatively charged HMO surface. The HMO with adsorbed barium is separated from the water, producing treated effluent having a reduced barium concentration.

Abstract: Systems and methods for treating aqueous fluids and their associated methods of use are disclosed. In one embodiment, a method comprises providing an untreated aqueous fluid with a first concentration of a contaminant. The method further comprises chemically treating the aqueous fluid to precipitate at least a portion of the contaminant. The method further comprises mechanically treating the aqueous fluid to remove at least some of the precipitated contaminant from the aqueous fluid, and to produce a treated water with a second concentration of the contaminant, wherein mechanically treating the aqueous fluid comprises flowing the aqueous fluid through a centrifuge. The method further comprises placing the treated water in a first well bore of the well treatment operation.

Abstract: A process and an apparatus are described for treating seven types of saline waters each having a concentration of total dissolved solids exceeding 1 g/L, wherein the concentration of total dissolved solids, the ratio of the chloride ion concentration to the bicarbonate ion concentration and the ratio of the chloride ion concentration to the sulphate ion concentration of each of the water types are as indicated in Table 1. The process includes the steps of contacting the water with a first reagent comprising a source of calcium ions selected from calcium oxide and calcium hydroxide to form a first solid product which is recovered. The process includes a further step of subjecting at least a portion of the partially processed water to at least partial evaporation so as to promote the formation of a precipitate and a mother liquor. The precipitate is recovered as a second product.

Abstract: Hydrocarbon stimulation fluids are often used to increase the permeability and productivity of oil and gas reservoirs. The fluid itself is made up of a mixture of hydrocarbons and various chemicals designed to induce gel formation and gel breaking. The successful removal of these chemicals from the fluid has been achieved, through a process of acid-washing and filtration. This will allow the fluid to be re-used many times for further fracturing processes.

Abstract: A composition and method for cleaning, sanitizing and maintaining contained bodies of water such as swimming pools, wading pools, fountains, ornamental ponds, etc. The composition includes pre-determined percentages of copper sulfate, zinc sulfate, and aluminum sulfate by weight. The composition and method reduce amounts of chlorine and an amount of labor associated with the cleaning, sanitization and maintenance of contained bodies of water.

Abstract: A method for generating new water with attached water rights comprising identifying a source of production water and treating the water in appropriate ways to provide water appropriate for beneficial use such as agriculture, irrigation, industrial or municipal or potable applications. Appropriate permits are obtained to create the new water with attached water rights.

Abstract: Hydrocarbon stimulation fluids are often used to increase the permeability and productivity of oil and gas reservoirs. The fluid itself is made up of a mixture of hydrocarbons and various chemicals designed to induce gel formation and gel breaking. The successful removal of these chemicals from the fluid has been achieved, through a process of acid-washing, mixing with a settling agent, centrifugation and filtration. This will allow the fluid to be re-used many times for further fracturing processes.

Abstract: Processes, methods and systems are provided herein for lowering the concentration of phosphorus in wastewater. The process includes adding a suitable amount of an aluminum-based coagulant/flocculent, for example, an aluminum-silicate coagulant/flocculent product to the wastewater while maintaining the pH of the wastewater at between about 4.5 and about 6.65. This step provides an eventual effluent stream of precipitated aluminum-based, phosphorus-containing flocs dispersed in the wastewater. The next step involves physically removing, as by filtering, the precipitated aluminum-based, phosphorus-containing flocs which is dispersed in the wastewater. These steps are able to provide a wastewater effluent containing less than about 0.03 mg total phosphorus per liter of wastewater. The disclosure also teaches novel methods and systems for carrying out the novel process.

Abstract: A method and system for removing contaminating iron from an acid pickle bath. The method comprises the steps of removing at least a portion of the acid pickle solution containing an amount of contaminating iron therein from a primary acid pickle bath, raising the pH of the at least the portion of the acidified acid copper solution with a pH adjuster to a level which is conducive to the precipitation of iron, precipitating the contaminating iron from the acidified acid copper solution, and acidifying the acid copper solution back to operating conditions for the system. Once the portion of the acid pickle solution has been treated, it is returned to the primary acid pickle bath.

Abstract: Pollutants, such as heavy metals, phosphorus, and pathogenic organisms, are removed from water by adding a chemical coagulant to water within an enclosure. With mixing, coagulation and flocculation occur, and a floc containing the pollutant settles to the enclosure bottom; so the treated water above the floc is free from at least some of the pollutant. Some of the treated water is removed from the enclosure, and new water is added. The new water and the settled floc are mixed to resuspend floc components. The process is repeated until the floc no longer exhibits contaminant-removal capability. In an alternate system, a matrix element is deployed within the enclosure, which captures a portion of the floc that settles within the water column. Pollutants in new water added to the enclosure encounter these suspended floc particles and are subsequently removed from the water.

Abstract: The invention is directed to a process for the conversion of cellulosic biomass, in particular lignocellulose-containing biomass into fermentable sugars. The invention is further directed to apparatus suitable for carrying out such processes. According to the invention biomass is converted into fermentable sugars by contacting in a reactor said biomass with an acid, while passing an inert gas stream capable of taking up water through said reactor, by which the pH in said reactor can be controlled.

Abstract: A system is provided that includes: (a) a mobile platform; (b) an input pump operatively connected to be capable of pumping a treatment stream through the system; (c) a centrifugal separator operatively connected downstream of the input pump to centrifugally treat the treatment stream; (d) a borate filter operatively connected downstream of the centrifugal separator to filter the treatment stream capable of removing at least some of a borate when the treatment stream is at a pH of 8 or above; and (e) a chemical-additive subsystem operatively connected to be capable of: (i) selectively adding one or more chemical agents to the treatment stream upstream of the centrifugal separator, wherein the chemical agents can be selected to be capable of precipitating dissolved ions selected from the group consisting of: sulfate, calcium, strontium, or barium, magnesium, iron; and (ii) selectively adding a chemical agent to the treatment stream upstream of the borate filter to increase the pH of the treatment stream to 8 o

Abstract: A cleaning and purifying composition including at least one solvent, an alkaline agent, a deflocculant, at least one surfactant selected from the group comprising an alcohol ethoxylate surfactant, an alkylamino-polyethoxy-sulfate surfactant, a polyether-phosphate ester surfactant, a surfactant that is a phosphate ester of an ethoxylated alcohol, and a surfactant that is a polyethyleneglycol monoaklyl ether, and a bonding agent.

Abstract: A process for the treatment of industrial waste water. The process includes the steps of admixing partially-treated waste water containing precipitated impurities with a flocculating agent in a flocculation basin, directing the admixed waste water to an elongated sedimentation basin, allowing flocculated solids in the waste water to settle to the bottom of the sedimentation basin, removing the settled solids from the bottom of the sedimentation basin and directing the treated water from the sedimentation basin. The process can further include the step of adjusting the pH of the waste water to precipitate impurities in the waste water prior to the addition of the flocculation agent. The elongated sedimentation basin can include a pair of sloped sides to consolidate the settled solids at the bottom of the basin. The settled solids can then be removed by suction. The basins can be formed from the excavation or impoundment of earth in an area adjacent to a waste water-generating facility.

Abstract: A method and apparatus is provided for the purification of water, in particular to the removal of surfactants and optionally organic, inorganic and/or biological contaminants from water using adsorption filtration techniques.

Abstract: This invention relates to the field of phosphate removal from a body of water, especially in pools and spas. It is an improved method of removal of phosphate from pools and spas by the topical addition with a hand held, hose end sprayer of a phosphate scavenging agent or composition, such as aluminum chlorohydrate and a suitable chemical for pH adjustment, allowing the scavenging agent or composition and phosphate to interact and for the resultant product to settle to the floor of the pool or spa. After twenty-four hours the sediment on the floor is removed by vacuuming. After a second twenty-four hour period any additional sediment that has settled to the floor is removed by repeating the vacuuming procedure.

Abstract: The invention relates to a method for separating suspended solid materials from aqueous systems, in which the latter is mixed with a flocculant made of polymer colloidal particles with cationic surface charge and subsequently the flocculated material is separated from the aqueous system.

Abstract: A wastewater treatment process for treating wastewater comprising a water-based dispersion containing a surfactant, a colorant and silica, as well as other solid matter, wherein the wastewater is treated using a polysilicato-iron coagulant.

Abstract: A waste stream is treated in a pre-filter having media, preferably sand, connected below a zero-valent metal column reactor incorporating a metal with reducing potential, preferably elemental iron (Fe0); the combination preferably configured as a single unit. The waste stream is pumped through the pre-filter to trap solids and deoxygenate it, then enters the reactor and is subjected to a reducing process. Most of the Fe0 is transformed to the ferrous ion (Fe+2), mixed with the reduced product, and fed to a continuous stirred tank reactor (CSTR) in which Fenton oxidation occurs. The output is then sent to a sedimentation tank and pH-neutralized using a strong base such as sodium hydroxide (NaOH). The aqueous portion is drawn off and the sludge pumped from the sedimentation tank. The system is monitored and controlled to optimize required additives, while monitoring of pressure drop across the pre-filter and column reactor establishes replacement requirements.

Abstract: A method of removing arsenic and heavy metals from water using metal salt hydroxidegels is provided. The arsenic present in water is adsorbed onto the hydroxide-gels which can effectively be filtered through a diatomaceous earth (DE) filtration bed. The combination of DE mixed hydroxide-gels is also effective in removing arsenic from water and heavy metals from water.

Abstract: Methods of treating a high salinity liquid, such as seawater, containing boron are provided, including adjusting the pH of the liquid to about 8 to about 9.5, optionally adding a scale inhibitor to the liquid, passing the liquid through a reverse osmosis device, and recovering a permeate having a boron concentration less than about 2 ppm. One embodiment includes removing colloidal matter from the liquid using a membrane filtration system, such as ultrafiltration or microfiltration, prior to passing the liquid through the reverse osmosis device, and preferably prior to adjusting the pH of the liquid.

Abstract: A hybrid chemical/mechanical dewatering sewage treatment plant and method employing rapid sludge chemical dewatering technology in conjunction with slower conventional mechanical dewatering solids agglomeration and disposal methods to meet operating constraints and environmental permitting restrictions and siting limitations for disposal of sewage and wastewater.

Abstract: The present invention relates to a process for treating wastewater containing suspended solids comprising adding to the wastewater a treating substance in an amount sufficient to enhance at least one of (a) the settling rate of the solids, (b) the bulk density of the solids and (c) the filterability of the solids, said treating substance being selected from the group consisting of (i) bauxite refinery residue known as red mud, and (ii) red mud that has been at least partially reacted with calcium and/or magnesium ions so as to have a reaction pH, when mixed with five times its weight of water, of less than 10.5. In addition, the invention relates to processes for reducing the concentration of dissolved phosphorus-containing species in wastewater, for decreasing the odour of a material having an odour due to the presence of one or more sulphur-containing substances and for decreasing the propensity to develop odours and a composting process.

Abstract: A method is provided for removing uranium from water. The method includes the mixing of a boron reagent with water contaminated with uranyl dication ions, leading to removal of the uranium from that water.

Abstract: A chemical/biological wastewater treatment plant method and apparatus employing rapid sludge chemical dewatering technology in conjunction with an environmental biological system for treating the separated treated wastewater by land applying it for plant consumption, and/or passing it through aqueous plant or microbial reduction of the dissolved solids and ammonia for BOD compliance to produce water of sufficient quality to meet open stream and ocean effluent discharge requirements; and disposing of the high BTU low moisture solids.

Abstract: The present invention relates to methods for the separation of materials from heterogeneous fluids and provides a means of effecting stimulant-sensitive flocculation and consolidation of solid suspensions within a liquid medium. Specifically, the present invention provides a method of controlling the state of a suspension of solid particles in a liquid, including applying to the suspension a stimulus adapted to control inter-particle forces between the solid particles. The stimulus is reversibly operable to control attraction and/or repulsion. Means of consolidating a sediment bed and of separating the resultant liquids-rich and solids-rich phases are also within the ambit of the invention.

Abstract: The invention relates to a method and installation for treating water for human consumption, for an industrial process, for agricultural purposes or for other purposes. The method used to remineralize raw water comprises a stage in which carbon dioxide and at least one inorganic base are injected. According to the invention, the method comprises the following stages: the flow Q of raw water is separated into a flow Q1 and a flow Q2; only flow Q1 is remineralized by injecting carbon dioxide and at least one inorganic base, said remineralization being carried out in at least one remineralization basin; remineralized flow Q1 is mixed with untreated flow Q2.

Abstract: A method of decolorizing a colored effluent comprising (i) a colored substance; and (ii) a polyvalent carboxylic acid or a polyvalent aminocarboxylic acid, the method including the steps of: (a) controlling a hydrogen ion exponent (pH) of the colored effluent to be in a range in which two or more carboxylic acid groups in the polyvalent carboxylic acid or the polyvalent aminocarboxylic acid does not dissociate; (b) adding an inorganic metal salt to the colored effluent so as to allow the inorganic metal salt to react with the colored substance to form a precipitation in the colored effluent, and (c) eliminating the precipitation from the colored effluent.

Abstract: Contaminated waste streams or soil or sludge is subjected to a first treatment stage with an acid liquor at a pH below 2 and at a solids content from 5 to 30%; then the liquid and solid phases from the first treatment stage are separated; the solids from the first treatment stage are mixed with a fresh acid liquor at a pH below 2 and a solids content from 5 to 30%; the liquid and solid phases from the second treatment stage are separated; the liquor separated from the first treatment stage is reacted with a base to precipitate the metals; the precipitated metals are separated and the liquor is recycled for reuse in the process; the solids separated from the second treatment stage are neutralized to adjust the pH to a level acceptable for a soil conditioner or fertilizer or other customized products; and the liquor from the second stage is used as the acidic liquor in the first treatment stage.

Abstract: The present invention generally relates to a copper metal recovery system, able to integrate with a waste treatment system of a circuit board manufacture plant, includes a stirring unit, a crystallization unit and a pressure filtering unit. More than 2 parts of weight of acidic copper-containing etching process effluent, less than 1 parts of weight of copper-containing slurry, and less than 1 part of weight of waste mixture of an acidic copper-containing photolithography effluent and an acidic frame etching effluent are charged into the stirring unit to conduct decomposition. Alkaline hydroxide reacts with decomposition products in the crystallization unit. The temperature of the crystallization unit is at least 80° C. The pressure filtering unit outputs a copper hydroxide solution or a copper oxide solution.

Abstract: A process for removing solids from a water-based flush solution, The process includes: providing dirty flush solution; directing the dirty flush solution to a treatment vessel; adding one or more chemicals to the treatment vessel to form a treated flush solution; separating aggregated paint compounds from the treated flush solution to form a filtered flush solution; and directing the filtered flush solution to spray application equipment. The flush system of the invention includes a treatment vessel, wherein the dirty flush solution is mixed with one or more chemicals to form a treated flush solution; a primary separation unit to remove particles including aggregated paint compounds from the treated flush solution to form a filtered flush solution; and transfer lines to direct the filtered flush solution to spray application equipment. The filtered flush solution contains: 1% to 5% by weight of a water soluble organic solvent; 0.

Abstract: A method is described for clarifying man-made static water bodies in which polyaluminum silicate sulfate is added to the water of the water body. Superior flocculation is achieved through the use of polyaluminum silicate sulfate which results in cleaner and more aesthetically pleasing water at a lower cost and with less waste material. Polyaluminum silicate sulfate is also available in a dry form which makes transport and storage easier and less costly. The effect of adding polyaluminum silicate sulfate is a cleaner, clearer, sparkling water body.

Abstract: A method for removing fluorine from wastewater includes the steps of: adding a fluorine-reactive agent, that comprises a water-soluble sodium compound and a water-soluble aluminum compound, into the wastewater so as to form sodium ions and aluminum ions in the wastewater and so as to precipitate sodium aluminum fluoride by reaction of the sodium ions and the aluminum ions with fluorine ions in the wastewater; and removing the precipitate of sodium aluminum fluoride from the wastewater.

Abstract: A portable waste disposal system for cementuous slurry comprises a collapsible wire cage, a waterproof containment bag inside the wire cage and a filtration bag inside the waterproof containment bag. The system enables the cementuous slurry generated during the plastering of a swimming pool and pumped from inside a swimming pool to a location adjacent the pool be disposed of quickly and safely. The liquid generated during the process may be neutralized and left on site, thereby avoiding transport of such liquid.

Abstract: Acidic metal-bearing wastewaters are treated to produce a finished water of sufficient purity to meet discharge standards while recovering metals removed in forms which are commercially valuable. The metals are selectively precipitated, either in a batch or in a continuous system, for removal of individual metal products in a specific sequence of steps from the wastewater. In each step, the pH is adjusted to the specific pH range and sulfide ion is introduced to precipitate the metals, excepting the removal of ferric iron and aluminum which is achieved using hydroxide precipitation. Bioconversion process using unique equipment converts sulfate in the wastewater to the hydrogen sulfide gas required for the precipitation process. This bioconversion process reduces the sulfate in the wastewater so that the water can be directly discharged or used for agricultural applications.

Abstract: Method for removal of heavy metal ions from aqueous wastes, which are produced during electroplating and other industrial processes. The method comprises a precipitation process that is conducted in a magnetic field.

Abstract: A method for removing metals from metal-containing acidic mine wastewater uses a basic sludge produced by the method for treating the wastewater. The wastewater is mixed with a lime slurry and with the basic sludge. This mixture is allowed to separate into an aqueous effluent and an acidic sludge. The effluent is mixed with the lime slurry and with a composition containing an iron compound, to produce a mixture. This mixture is allowed to separate into an aqueous effluent and the basic sludge. Lignin derivatives, such as calcium lignosulfonate, may be included in the treatment mixture.

Abstract: The present invention relates to a method for producing drinking water having a reduced cluster width and being capable of emitting FIR (Far Infrared Rays) energy by using a solution derived by chemical treatment of a charge generating material.

Abstract: A method and apparatus for treating heavy-metal-containing wastewater using a sulfidizing agent. Sulfidizing treatment is carried out by adding a sulfidizing agent to heavy-metal-containing wastewater, while detecting hydrogen sulfide gas generated from the wastewater, such as to maintain a state in which hydrogen sulfide gas is just starting to be generated from the wastewater. When separately recovering each of a plurality of metals from wastewater in which are mixed ions of the plurality of metals, there is repeated for each of the metals a process in which the acidity of the wastewater is adjusted to within a range suitable for the metal to be separated out and recovered, a sulfidizing reaction is carried out on that metal, and the metal sulfide produced is precipitated and filtered off.

Abstract: A method and system for decreasing the concentration of at least one metal in an aqueous solution. The metal may be molybdenum, tungsten, or both. An aqueous solution is introduced into at least one reaction zone, and at least one source of hydroxide ions is provided into the at least one reaction zone in an amount sufficient to precipitate at least some of the mass of the at least one metal. The aqueous solution includes a mass of the at least one metal and a mass of at least one reducing agent. The at least one reducing agent includes at least ferrous iron from at least one source of the at least one reducing agent. A composition of tungsten ferrite or molybdenum tungsten ferrite may be formed. The method may be used for purifying water, for the refining of metals, or to facilitate a chemical analytical determination.

Abstract: The invention relates to a method for the removal of metals from their aqueous solution with lime precipitation, in conditions where a precipitate of metal hydroxide and gypsum is formed, which settles well and is easy to filter. The metals are precipitated from their aqueous solutions at a high pH value and the slurry is recirculated several times in the precipitation space, whereby the gypsum is precipitated as separate crystals instead of a solid layer. The method is particularly suitable for neutralization of the aqueous solution from the pickling of refined steel. Using this method enables the removal of metals and fluoride from the water in question.

Abstract: Processes, methods and systems are provided herein for lowering the concentration of phosphorus in wastewater. The process includes adding a suitable amount of an aluminium-based coagulant/flocculent, for example, an aluminium-silicate coagulant/flocculent product to the wastewater while maintaining the pH of the wastewater at between about 4.5 and about 6.65. This step provides an eventual effluent stream of precipitated aluminium-based, phosphorus-containing flocs dispersed in the wastewater. The next step involves physically removing, as by filtering, the precipitated aluminium-based, phosphorus-containing flocs which is dispersed in the wastewater. These steps are able to provide a wastewater effluent containing less than about 0.03 mg total phosphorus per liter of wastewater. The disclosure also teaches novel methods and systems for carrying out the novel process.

Abstract: A solid formulation for use with sodium chloride and a chlorine generator to provide safe, clean chlorinated recreational water. The formulation comprises a chlorine stabilizing agent and a phosphate remover agent. An enhanced salt comprising a chlorine stabilizing agent, a phosphate remover agent and sodium chloride is also described. The formulation and enhanced salt can also contain a metal chelating agent and a pH balancing agent. A cleaning agent may also be included. A fast dissolving sodium cyanurate compound is used for the chlorine stabilizing agent. A method, kit, and system for providing safe, clean chlorinated recreational water are also disclosed.

Abstract: This invention offers an integrated technology in sequential treatment of wastewater. Low biodegradable organics and heavy metal ions are both contained in wastewater from surface finishing processes. The aim of the invention is to find the solution for treatment of organics and heavy metal ions in complicated wastewater that contains organics and heavy metal ions sequentially. Low biodegradable organics are oxidized by a fenton process with pH ranging from 2 to 5 and temperature ranging from 20° C. to 100° C. Heavy metal ions are then treated by a ferrite process with pH ranging from 8 to 12 and temperature ranging from 20° C. to 100° C. The integrated technology of the fenton process and the ferrite process (2FP) is advantageous to treat the wastewater from surface finishing processes, decrease the production of iron sludge caused in the fenton process and increase the quality of ferrite products.

Abstract: The present invention refers to a method of separating casein from animal milk, especially, after defatting the animal milk as the pretreatment, the processing of the defatted milk aforesaid through a ceramic filtration membrane to remove the casein in the milk. The pretreatment process of separating the casein from the milk is then complemented by other processes of purification, so as to obtain the target protein of higher purity.

Abstract: A method of treating, in wastewater purification, sludge containing organic matter, divalent iron and phosphorus, in which the sludge that is treated is made to contain dissolved iron and phosphorus at a molar ratio Fe:P of above 1:1, the sludge is treated at 0–100° C. with an acid at a pH of 1–5 for dissolution of divalent iron and phosphorus from the sludge, the sludge is supplied with an oxidizer selected from hydrogen peroxide and percompounds, wherein divalent iron is oxidized by Fenton's reaction to trivalent iron, and (i) trivalent iron is precipitated as trivalent iron phosphate (ii) free radicals with a deodorization and sanitation effect are formed by Fenton's reaction, the sludge is then dewatered at a pH of at most 7, and the aqueous solution obtained in dewatering is recirculated to the wastewater purification.