Abstract: This invention relates to a method for improving the utilization of water-soluble, high molecular weight (molecular weight above about 1,000,000) polyelectrolytes in the dewatering of aqueous suspensions. By aging a mixture of the polyelectrolyte and water for a period of at least 6 hours to form an aged solution the amount of polyelectrolyte required to effectively dewater an aqueous suspension may be reduced to as little as 50% of the amount required when an unaged solution is used.

Abstract: A method of treating wastewater containing a contaminant selected from the group consisting of heavy metal cations, tars, oils and phenols or mixtures thereof, comprising mixing said wastewater with an effective amount of desulfurization slag, the composition of said slag including calcium oxide, calcium sulfide and iron oxides, causing deposition of said contaminant from the mixture, and separating the deposit from the supernatant liquid.

Abstract: The flocculation performance, for instance on low pressure or other pressure filtration (such as a belt press), of a solution of a high molecular weight organic polymeric flocculant having IV above 4 is improved by subjecting the solution to degradation, preferably by mechanical shear such as through a Silverson mixer or by a fast rotating blade.

Abstract: An apparatus and process for liquid removal from a mixture with solid particulate materials utilizing a screw conveyor within a housing for transport of solids, the screw conveyor upcoming side being in proximity to the housing means and the screw conveyor downcoming side being spaced from at least a portion of the housing means to form a liquid collection volume from which the liquid is removed.

Abstract: An in-line system is provided for treating acid mine drainage which basically comprises the combination of a jet pump (or pumps) and a static mixer. The jet pump entrains air into the acid waste water using a Venturi effect so as to provide aeration of the waste water while further aeration is provided by the helical vanes of the static mixer. A neutralizing agent is injected into the suction chamber of the jet pump and the static mixer is formed by plural sections offset by 90 degrees.

Abstract: Coal liquors are clarified by contacting them with high molecular weight copolymers of from about 70 to about 99 mole percent of a nonionic water-soluble monomer such as acrylamide and from 1 to 30 mole percent of a cationic monomer such as methacryloylethyl trimethyl ammonium chloride or methacrylamidopropyl trimethyl ammonium chloride.

Abstract: Solids suspensions are dewatered by filter plate pressing by adding a flocculant downstream of the filter press pump(s), the pump(s) being of the positive displacement type whereby the amount of flocculant required can be determined from the speed of the pump(s). Apparatus is provided which includes a filter plate press, one or more filter press pumps of the positive displacement type, and means for sensing the speed of the pump(s) and for controlling the dose of flocculant in dependence thereon. A mixer is constructed as a cylindrical chamber with radial inlets and axial outlets, and includes plate-like impellers.

Abstract: A method and apparatus for distributing a water purifying chemical, particularly a flocculating-agent concentrate, throughout a stream of water to be purified. In accordance with the method, the concentrate is introduced into the stream of water transversally to its direction of flow under the action of rotational motion, to achieve a distribution time of at most one second.

Abstract: A hollow body, a rotor, with holes in the bottom and the side wall, is immersed down into a liquid and rotated with the help of a shaft suspended over the liquid.The liquid, which enters the rotor through the hole in the bottom, will, on account of the centripetal force, acquire a surface in the shape of a paraboloid of revolution. The centripetal force will throw the liquid out through the holes in the side wall, while new liquid will continuously enter through the bottom of the rotor.The shaft for the rotor can be hollow, and through this gas, solid or liquid materials can be added to the liquid.The invention makes possible the treatment in various ways of different types of liquid, from aqueous suspensions to molten metal.

Abstract: An effluent precipitation and neutralization chamber is useful for treating x-ray photographic chemicals prior to discharging them into a drain. Desilvered photographic fixer is mixed with spent developer within the chamber. The resulting iron precipitates settle to the bottom of the chamber or adhere to ribbon-like flow restrictors within the chamber. Relatively clear fluid of approximately neutral pH concentration is discharged to the drain. The chamber is openable for removing and properly disposing of the iron precipitates.

Abstract: Apparatus and method for removing hardening calcium-containing and similar minerals from water, in which raw water is passed through a passage, having a reduced cross-sectional area, in an elongated core of a suitable alloy. The passage is provided with closely-spaced parallel walls which have been polished to an image reflective smoothness and etched to create a multiplicity of randomly-positioned microscopic channels and a multiplicity of complementary mesas having smooth, flat tops. The reduced cross-sectional area causes a pressure drop in accordance with Bernoulli's Principle, which causes carbon dioxide to come out of solution, the presence of which inhibits precipitation of calcium carbonate and forms carbonic acid to attack existing scale. The small size and shape of the mesas allow calcite crystals to begin to grow but permit them to break off after a certain size has been attained. The freed calcite crystals then provide nuclei for crystals to grow from the supersaturated solution.

Abstract: A solid-liquid slurry, particularly sugar juice, is flocculated and clarified in an arrangement including a clarifier tank containing therein a mud bed of concentrated removed solids. A preflocculating vessel extends into the top of the clarifier tank and includes upper and lower chambers. The slurry is introduced into the upper chamber to flow turbulently therein, thereby deaerating the slurry. The slurry is transferred from the upper chamber to the lower chamber while the turbulent flow of the slurry is changed to a laminar flow. A flocculating agent, for example a suitable polymer, is introduced into the slurry, such that solids of the slurry coagulate as flocs in the lower chamber. The thus preflocculated slurry is introduced directly into the clarifier tank at a level beneath the surface of the mud bed therein. The liquid of the slurry percolates upwardly through the mud bed and is filtered, thus forming clarified liquid, and the flocs of solids settle downwardly into and form the mud bed.

Abstract: A polymer admixture comprising a first cationic polymer having a molecular weight between about 2,500-1,000,000 in admixture with a second cationic polymer having a molecular weight between about 1,000,000-50,000,000 wherein said admixture contains a weight ratio of first polymer to second polymer between about 50:1 to 1:50, has greatly improved properties for treating and clarifying waste waters contaminated with oily waste and dispersed solids. The first cationic polymer is preferably a homopolymer, and the second cationic polymer is preferably a copolymer of acrylamide containing the same cationic monomer used to synthesize the first cationic polymer.

Abstract: An oil-containing slurry waste containing a soap component in the oil component thereof is foamed by stirring so that the oil component adheres to the froth produced by the foaming and rises to the surface of the slurry waste by virtue of buoyancy. Consequently, the oil component in the slurry waste is separated from the slurry waste in a highly concentrated form as entrained by the froth. The oil thus separated is suitable for reuse. The slurry waste having a low oil content can be easily treated for disposal.

Abstract: High rate filtration system includes an upflow filter vessel containing a bed of buoyant media followed by a downflow filter vessel containing a bed of nonbuoyant media. The upflow filter vessel is unobstructed by cross-sectional, media-confining screens. A horizontal trough structure collects filter effluent and makes it possible to clean the bed by diffusing air into the liquid below the bed so that average fluid density in the bed is reduced. The reduction in fluid density results in expansion of the bed as media particles descend by gravity.

Abstract: An injection and mixing device for the introduction of flocculant into aqueous material, such as sewage or sludge, prior to dewatering is disclosed. The device includes an angled housing and injection means for introducing the flocculant into the housing countercurrent to the incoming flow of aqueous material. The combination of the turbulence caused by the angled housing and the countercurrent injection evenly and rapidly disperses the flocculant within the aqueous material regardless of the material's solids content. A downstream sparger ring is also disclosed for use with high solids content material.

Abstract: Waste paper is defiberized within a container or receptacle in a thick stock range at a low water level. Thereafter, by further infeeding water, the obtained slurry or the like is diluted to a consistency of less than 7% while continuing the defiberizing operation. Finally, the obtained stock suspension is withdrawn through a sieve or screen located at the floor of a defiberizing container. The defiberizing container or receptacle used for performing the method possesses a lower region having a smaller diameter, above which there is located an upper region having a larger diameter.

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: An apparatus and method for treating for disposal organic waste material carried within a sludge, by adding to the sludge an alkali metal silicate and a setting agent, is disclosed. The apparatus includes several mixers, each having a trough with an input end and a discharge end, at least one rotatable shaft mounted longitudinally along the trough, a plurality of blades mounted to the shaft, and a drive for rotating the shaft. The sludge is deposited within a first mixer, and then directed from the mixer into a tank. A series of chopper pumps recirculate the sludge into the tank, and alternatively, the sludge may be passed through an additional mixer. Leaving the tank, the sludge is directed into a second mixer at its input end. Water is introduced at the input end, and a setting agent is added along the trough at a point adjacent the input end. Further along the trough, an alkali metal silicate is introduced. The mixture is recovered from the second mixer, and carried to a remote location for setting.

Abstract: The invention relates to the chemical removal of phosphorus compounds from waste water, this waste water being treated with one or more metal compounds, without any problems presenting themselves as regards the separation of the metal phosphate compounds. To achieve this, the waste water is treated with the metal compound in a fluidized bed of metal phosphate particles.The invention also relates to a process for the purification of waste water in which the effluent from a biological purification is subjected to the above-mentioned method for the removal of phosphorus.

Abstract: Coal particles are agglomerated in pulp water of coal particles by agitating the pulp water in the presence of a binder, which comprises conducting agglomeration in a plurality of zones, the zones being communicated one after another, and transferring the pulp water from one zone to another while agitating the pulp water in each zone and increasing a pulp concentration of the pulp water from one zone to another. Agitating power for the agglomeration is reduced with the successively increasing pulp concentration.

Abstract: This invention relates to flocculation apparatus for the purification of liquids, particularly water, wherein provision is made for initial vigorous mixing of the coagulants in the liquid followed by a gradually diminishing agitation of the liquid and flocculent to provide proper flocculation; the apparatus comprising a circular flat bottomed chamber, a central circular well having openings through its wall spaced apart circumferentially and vertically, a plurality of radially extending rotatable arms supported above the chamber, each arm carrying downwardly depending blades spaced apart along the length of the arms and positioned to intersperse with a plurality of series of vertical fixed blades extending radially from the well, and upwardly from the floor of the chamber, the blades extending substantially the full depth of the chamber, at least one feed chamber in communication with the chamber through an opening in the wall thereof, means for rotating the arms and an outlet from the bottom of the well lead

Abstract: Process for clarifying water to coagulate and flocculate particles suspended therein, by introducing into the water an aqueous solution of ferric polychloride having a temperature of at least 85.degree. C.

Abstract: A process for dewatering aqueous sludges of organic nature by adding to the sludge a cationic organic flocculant to effect a first stage agitation of vigorous intensity, and then adding thereto an anionic organic flocculant to perform a second stage agitation of mild intensity and subjecting the thus formed flocs to a dewatering operation, which process comprises the use of a cationic organic flocculant composed of any combination of A- and B-components, wherein the A-component consists of one or more polymers selected from the group consisting of A.sub.1 - and A.sub.2 -components, in which the A.sub.1 -component consists of polymers having a structural unit of vinylimidazoline or partially hydrolyzed products thereof and the A.sub.

Abstract: In the separation of solids out of a flushing liquid such as used in flushing out boreholes and the like drilled or cut in rock, concrete, masonry and similar materials, a flocculant is added to the flushing liquid before it enters a settling tank so that the removal of the solids is accelerated. As a result, a supply of flushing liquid, free from solids, is always available from the settling tank. The flushing liquid flow is directed through the feed line into the settling tank. Before the liquid enters the settling tank it is passed in contact with a flocculant so that the liquid picks up a dosed quantity of the flocculant. To assure the optimum effect, after contacting the flocculant, the liquid is mixed and then passed into the settling tank.

Abstract: Bitumen recovery from a tar sands emulsion or other bituminous oil-in-water emulsion is increased by milling the emulsion for a time sufficient to cause a bitumen-rich liquid fraction to rise to the surface, and separating such fraction. Addition of water to the starting emulsion or during milling further enhances the recovery of bitumen.

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: This specification discloses a greatly simplified method and system for recovering coal from a particulate coal bearing slurry (1) in which an appropriate hydrophobic liquid or emulsion of hydrophobic liquid in water (2) is introduced into the inlet of a centrifugal turbulent flow slurry pump (3) simultaneously with the introduction of said coal bearing slurry to said pump inlet, said hydrophobic liquid being introduced in a quantity sufficient to achieve substantially intimate contact between said hydrophobic liquid and coal particles in said slurry whereby the coal may be separated from the slurry by discharging the slurry from the pump directly over a simple static screen or other suitable separating device (4) whereupon the separated coal matter (5) may be collected for subsequent use.

Abstract: A method for removing the excess sodium and byproducts of reaction which occur during the destruction of PCBs from oil. A predetermined quantity of water is mixed with the decontaminated oil and the byproducts, which include sodium chloride and polyphenyl polymer, to form sodium chloride and sodium hydroxide. Centrifuging removes most of the oil from the remaining aqueous mixture which then is agitated and treated with carbon dioxide gas to form less hazardous sodium carbonate and sodium bicarbonate. Any excess carbon dioxide gas is vented to the atmosphere and the sodium carbonate and sodium bicarbonate is collected into containers for disposal. Small amounts of oil remaining in the aqueous waste mixture that is discharged from the centrifuge is decanted from the remaining material in a waste separator due to its lighter specific gravity. A pump intermittently injects waste from the waste separator into a converter where it reacts with the carbon dioxide gas.

Abstract: A process for dewatering sewage sludges, the dewatering characteristics of which have been improved by adding an organic flocculant, on a chamber filter press, wherein the greater part of the water in the flocculated sludges is removed by gravity filtration in a process step upstream of the chamber filter press, without application of a pressure difference, and the actual pressure filtration, on the chamber filter press, is only then carried out.In principle, commercial products can be used as the organic flocculant. These are water-soluble, macromolecular compounds which have been obtained by polymerization or copolymerization of acrylamide, acrylic cid and/or their salts, or of esters of acrylic acid or methacrylic acid with specifically modified alcohol components.

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: A method comprising operating steps required for safely operating wet oxidation reactors in which combustible substances are oxidized at elevated temperatures and pressures using pure oxygen. The steps satisfy the criteria that a potential of oxidation is established prior to introducing oxygen and maintained until after oxygen flow is stopped; that an inert gas, either from an external source or generated in situ, is present in the reactor from before oxygen flow is introduced until after oxygen flow is stopped; and that the oxygen introducing means is clean for oxygen use from prior to the introduction of oxygen flow until after the oxygen flow is stopped.

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 method is disclosed for the recovery of bitumen from a sludge. The sludge is diluted with water and subjected to high-shear agitation and aeration and the sludge settled to obtain an upper bitumen-containing froth layer and a lower sludge layer of reduced bitumen content. The recovery of bitumen is increased over that obtained with aeration and mixing with mild agitation or with aeration alone or with agitation alone.

Abstract: A process and apparatus for the chemical-mechanical treatment and purification of ground and surface waters and effluents of various types employs adding materials for coagulation, flocculation, precipitation, sedimentation and altering the pH value. The process comprises separate process stages carried out successively as follows: (1) a first initial process stage wherein certain additives are admixed to the raw water by stirring; (2) a second initial process stage wherein contact sludge is admixed by stirring; (3) a third initial process stage wherein a flocculent aid and possibly also at least some of the other materials added in the first stage are admixed by stirring with high energy input; and alternatively (4) a fourth initial process stage for the formation of course flocs and completion of reaction of the previously added materials and formation of settleable particles and conglomerations of particles together with adsorbed and attached and occluded raw water components with moderate movement.

Abstract: A process for dewatering sludges, which comprises performing a first stage agitation of the sludge to be dewatered during addition of a first high molecular weight flocculant developing in an aqueous solution an electric charge in polarity opposite to that of the sludge to effect neutralization of the electric charge of the sludge, conducting subsequently a second stage agitation of the sludge during a further addition of a second high molecular weight flocculant developing in an aqueous solution an electric charge in polarity opposite to that of said first flocculant to cause flocculation of the sludge and subjecting the so flocculated sludge to a dewatering operation, wherein a flocculant composed of a natural high molecular organic compound or a derivative thereof is used for at least one of said first and second flocculants with simultaneous employment of high power agitation for said first stage agitation, which process obtain a dewatered cake having low moisture content with efficient dewatering of the

Abstract: A method for regulating the granulometric characteristics of the components in metallurgical slags comprising the step of imparting a vibration to the slag, after the separation of the slag from the metallurgical furnace while the slag is being cooled. The imparted vibration frequency and amplitude is adjustable and ranges respectively from 12 to 100 Hz and 0.2 to 5 mm and when circular vibration is imparted from 0.4 to 12 mm.

Abstract: A method for removing suspended solids and dissolved salts from water comprising setting up a whirlpool in the water, injecting a concentrated solution of flocculating agent into the whirlpool, withdrawing spent flocculating agent combined with contaminant from the bottom of the whirlpool, and withdrawing purified water flowing over the top of the whirlpool. Apparatus for water purification according to this method is also disclosed.

Abstract: A process and apparatus for the purification of industrial waste water containing solid particles. The apparatus contains at least two treatment sections. The first treatment section is a settling tank containing an agitation means, preferably an inclined deflector plate against which the waste water is directed to form a rolling wave and causing solid particles to coagulate and settle. The partially cleaned waste water overflow from the first stage is conveyed to the lower portions of the second stage into spaces between inclined plates which form an inclined plate pack clarifier. The solid particles are taken off from the bottom of the second treatment section, and clarified water is taken off from the top.

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: A method of and apparatus for continuously removing dispersed particles which can be flocculated from a liquid containing said particles, such as wastewaters, wherein flocculation of said particles is caused to take place in a turbulent pipe flow by the injection and rapid mixing of a coagulant and/or coagulant aid in said turbulent pipe flow which simultaneously flocculates said particles and transports the mixture of flocculated particles and liquid into a settling tank for clarification. A controlled quantity of dispersed floc from said settling tank is continuously recirculated into said pipe flow at a station where mixing of the coagulant and/or coagulant aid is achieved, so as to reduce the length of said pipe to a desired size and the flow rate of said injected coagulant and/or coagulant aid.

Abstract: A method for the lime stabilization of wastewater sludge, includes the steps of dewatering sludge so as to produce a sludge cake containing from about 10 to 60% by weight of dry solids and rapidly and intimately mixing and reacting the sludge cake with calcium oxide so as to produce stabilized sludge pellets. An apparatus for performing the process is also provided.

Abstract: Efficient dewatering of slimes is achieved by admixing the slimes with a flocculating agent, followed by mechanical manipulation to effect rapid removal of water and consolidation of solids. The required mechanical manipulation may be accomplished, e.g., by tumbling the mixture through a rotating cylindrical screen or by passing it across a vibrating screen.

Abstract: Purifying waste waters contaminated with tensides, from nuclear power plants and other plants in which radioactive substances are processed wherein before return of the water to the plant, the water is passed through an evaporator and a mixed-bed filter. Contaminant content of the water is materially reduced by first acidifying the waste water to a pH of 2.5-3, then treating with activated carbon, KMnO.sub.4, MnSO.sub.4 and CaCO.sub.3, and thereafter raising the pH to 8.5-9. The mixture is permitted to form a lower sludge layer and a supernatant water layer. The sludge layer is sent to waste disposal and the supernatant layer is directed to the evaporator.

Abstract: A process is provided for treating spent geothermal brine to remove silica. The process includes introducing the brine into the reaction zone of a reactor-clarifier and allowing the brine to flow therefrom into the clarification zone of the reactor-clarifier. In the clarification zone, particles settle from the brine and are urged to the center of the tank beneath the reaction zone, and the settled particles are drawn upwardly into the reaction zone by an impeller. The particles mix with the brine in the reaction zone to form a substantially uniform distribution therein to provide nuclei for silica precipitation from the brine. A stream of sludge is removed from the bottom of the reactor-clarifier and disposed of.

Abstract: A process and apparatus for the treatment of untreated water. The untreated water mixed with a flocculating agent is introduced tangentially into the circumferential area of a tank through a feed connection directed at the tank wall. The tank includes a perforated partition circumferentially spaced from the wall of the tank and a conduit in the center of the tank which passes axially through the tank bottom and whose upper end carries a circular overflow disc located below the water level of the tank. Alternately, the partition comprises upper and lower rings, between which there are disposed guide plates which form openings distributed over the circumference of the partition. The circumferential speed of the water flowing through the partition is reduced by braking such that the occurrence of upwardly directed, secondary flows is prevented and clean water is led downward through the center of the tank.

Abstract: An assembly for separating particulate matter from an influent carrier comprises a perforated plate for separating an inner compartment from an outer compartment, and for transferring the influent between the inner and outer compartment with a minimum amount of a convective momentum that is associated with disturbing the settling matter. In practicing the process, suspensions are introduced into the assembly at the inner compartment. An agitator subassembly, within the inner compartment, sequentially fast mixes and slow mixes the influent to respectively insure mixing of the influent with additives and to promote agglomeration of the suspensions. Flow paths in the perforated plate function to cancel all velocity components of the momentum, except for vertical downward acting velocity components, thereby maximizing the rate of settlementation.

Abstract: Liquid to be treated flows into a combined sedimentation and thickening tank. The upper part of this tank is a sedimentation zone in which the liquid passes through parallel flow paths between downwardly inclined separator plates below which the solids fall to the bottom of the tank into the thickening zone whereat the solids are stirred and removed by a suitable stirring and scraping device. The liquids flowing with the solids through the parallel paths are removed at the end of said paths and delivered directly to the top of the sedimentation zone thus leaving the thickening zone essentially flow-free. Flocculants may be added to the water to be treated in a separate flocculation compartment arranged upstream from the sedimentation compartment. A separate destabilization compartment may be provided upstream from the flocculation compartment. A square sedimentation zone may merge smoothly into a circular thickening zone. The thickening zone may extend beneath the flocculation compartment for compactness.

Abstract: In a process for pretreating hazardous waste prior to solidification the waste is received in containers (10). The containers are deposited in a large vessel containing a chemical pretreatment media (9) and subjected to an agitating process in the vessel whereby the containers are ruptured and their contents deposited in the media. Neutralization, precipitation and chemical modification processes are envisaged in the container. After pretreatment the liquid is removed for ultimate solidification.

Abstract: Process waste waters at a pH of about 7 contaminated with radioactive isotopes are decontaminated by (a) adjusting the pH to about 5.8, (b) adding CaO or Ca(OH).sub.2 to raise the pH to about 8.5, (c) agitating the mixture for at least 5 minutes to effect intimate contact and produce a suspension of solids containing radioactive contaminants, and (d) separating the suspension of solids from the water by centrifuging. Removal of radioactive uranium isotopes with an alpha emission is effected at a pH of about 10. The process provides a method for concentrating radioactive contaminants in water for subsequent ultimate storage and also purifies the contaminated water so it may be safe to discharge it into the sewer. The treatment may be carried out in a plurality of stages in series.