Abstract: Disclosed herein is a safety outlet. The safety outlet includes a casing having at least one hole into which a pin of a plug is inserted; and at least one drain pipe forming a drain channel for independently communicating the at least one hole and the outside of the casing; wherein the drain channel provided in the at least one drain pipe each serves as drain passage separated from each other, and the drain pipe is partitioned so as to maintain sealing between inside of the casing and the drain channel, wherein a contact portion connected to a power terminal arranged outside of the at least one drain pipe is provided in the at least one drain pipe.

Abstract: Powder blends are described comprising blends of particulate water soluble high molecular weight polymer flocculants. The polymer flocculants can include polyethylene oxide, polyacrylamide, copolymers thereof and combinations thereof. The powder blends allows the use of fine powders while reducing potential air quality and safety issues. The powder blends can be used for waste water purification, fiber dewatering, and the like. The powder blends can be diluted by a water dilution flow prior to entering a waste water stream.

Abstract: A method for removing an unwanted chemical from a working fluid of a system includes: 1) pumping into a tank a working fluid that includes an unwanted, first chemical; 2) injecting into the tank a second chemical in an amount that provides or substantially provides a stoichiometric ratio relative to the amount of the unwanted, first chemical in the working fluid; 3) mixing the second chemical with the working fluid in a first portion of the tank to generate a molecule that precipitates out of the working fluid and that includes the unwanted, first chemical; 4) holding the working fluid in a second portion of the tank to separate the molecule from the working fluid; and 5) ejecting the working fluid from the second portion. The flow rate of the working fluid and the size of the first and second portions of the separation tank are coordinated to make the working fluid take at least 4 minutes to flow through the tank.

Abstract: A process for recovering polyhydroxyalkanoates (PHAs) from cellular biomass of bacteria, said biomass being obtained by fermentation and in the form of a cellular biomass slurry in aqueous suspension, comprising the steps of: submitting the slurry to operations of injection of PHA solvent, agitation and heating, in order to form a suspension comprising PHA solvent with the dissolved PHA, water and insoluble residues; recuperating the solvent enriched with PHA; rapidly cooling the solution of PHA solvent to precipitate the dissolved PHA; micro-filtrating the suspension of PHA precipitated in the solvent, in order to separate a paste concentrated with precipitated PHA; washing with water, heating and agitating the concentrated PHA paste, to promote evaporation of the solvent and to obtain a suspension containing PHA granules; agitating and shearing the PHA granules and depleting the residual solvent; and separating the purified PHA particles from the suspension.

Abstract: In a device and a process for purifying water which is contaminated with sulphate ions and heavy metal ions, the water is collected in a water reservoir and a substance having basic activity in water is fed to the water reservoir in such a manner that a precipitant having heavy metal ions is precipitated from the water, wherein at least a subquantity of water is taken off from the water reservoir and is separated into pure water which is substantially freed from sulphate ions and heavy metal ions and dirty water which is enriched with sulphate ions and heavy metal ions. The dirty water is at least in part recirculated to the water reservoir, as a result of which a concentration of sulphate ions in the water reservoir is achieved such that a precipitant having sulphate ions is precipitated from the water.

Abstract: A method for treating low barium frac water includes contacting a frac water stream with a radium selective complexing resin to produce a low radium stream, passing the low radium stream through a thermal brine concentrator to produce a concentrated brine; and passing the concentrated brine through a thermal crystallizer to yield road salt.

Abstract: A radial rotary dryer improves drying efficiency for sludge and other substances, prevents clogging phenomenon, and is realized in a simple structure. The radial rotary dryer includes spaces formed by inner and outer drums and partitioned by a plurality of radial plates. The substances, which have been introduced through a drum inlet together with hot blowing air, sequentially move throughout all spaces and are dried during drum rotation. The substances are discharged through an opposite side of the inner drum. A lift plate is attached at one surface of each radial plate to improve the drying efficiency. Hammers are attached to an opposite surface of the radial plate to free-fall according to the rotation of the drum, thereby crushing the substances. The radial rotary dryer is useful to dry sewage sludge, food waste, or other industrial substances with the best drying efficiency, the minimum installation space, and a crushing function.

Abstract: Provided is a standalone integrated water treatment system for a distributed water supply including a filter input a coagulation system in operative connection with the filter input, wherein the water is subjected to a coagulation process to create pin floc from suspensions in the water. A maturation buffer tank in operative connection with the coagulation system aggregates floc in size within the water. A spiral separator separates the water into two water streams, a first stream of water having most of the floc removed, and a second stream of water which includes a concentrated amount of the floc. An optional filtration system is configured to receive the first stream of water and perform a filtration operation thereon. A sterilization system is configured to perform a sterilization operation on the first stream of water. The water is then output from the sterilization system as potable water.

Abstract: Methods of treating water, methods of removing radium from water, methods for controlling the amount of at least one target element removed from water and the amount of at least one target element in a pellet, a pellet and treated water. The method may generally include providing water including a principal ion and a target element, contacting the water with a fluidized bed, the fluidized bed including seed material, and controlling at least one of a type and a size of the seed material to remove principal ion and target element from the water. The target element may include radium. The principal ion may include calcium, magnesium, etc.

Abstract: A coagulation treatment method for water to be treated that is capable of reducing the degree of inflow of micro flocs reaching a sand filtration layer while realizing a higher density and miniaturization of micro flocs and flocs in a state where the use of an inorganic coagulant is limited by dramatic improvement in residual percentage in a contact-media accumulation tank, based on obtaining a residual percentage (filtration rate) not less than 80% of flocs with particle diameters not less than 7.0 ?m in a contact-media accumulation tank from a stage that the water to be treated starts to pass through by interposing the contact-media accumulation tank in a micro flocculation step and a sand filtration step, and filling flocs with particle diameters not less than 7.0 ?m in advance at an inlet of the contact-media accumulation tank and/or the vicinity of the inlet.

Abstract: The invention aims at enabling, in a catalytic decarbonation apparatus, inert particles coated with calcium carbonate to be constantly and systematically extracted from the reactor, with no risk of clogging the discharge pipes. Therefor, said pipes (7?a, 7?b) have an inside diameter ranging between 40 and 60 mm and they have a downward incline up to their connection to an outside discharge conduit (8?), except, possibly, a horizontal portion starting from the orifice through which they emerge into the reactor (1?).

Abstract: The invention relates to a method for decontamination of a liquid effluent including one or more radioactive chemical elements to be eliminated including the following steps: a step of bringing into contact in a stirred fluidised bed, in a first zone of a reactor, of the said liquid effluent with solid particles able, by coprecipitation and/or adsorption and/or ion exchange, to capture and retain the said radioactive chemical element or elements, as a result of which a suspension of solid particles is obtained containing the said radioactive chemical element or elements; a step of settling, of the said suspension, in a second zone of the same reactor, where this second zone is separate from the first abovementioned zone, as a result of which a solid phase is obtained including the solid particles containing the said radioactive chemical element or elements to be eliminated, and a liquid phase with a reduced or zero content of the said radioactive chemical element or elements to be eliminated; and a step of

Abstract: Improved fluidized bed precipitators (20, 46, 62, 74, 108, 112, 134, 168) especially useful for the treatment of waste waters containing soluble phosphorus are provided, having upright, primary fluidized bed sections (22, 48, 64, 76, 110, 114, 136) and obliquely oriented solids settling sections (28, 54, 68, 120, 144) which enhance the settling of small particles (166) and return thereof to the fluidized bed sections (22, 48, 64, 76, 110, 114, 136). The precipitators (20, 46, 62, 74, 108, 112, 134, 168) may also be equipped with a solids detection/withdrawal assembly (178) made up of one or more pressure transducers (180, 182) operable to determine the pressures within the fluidized bed sections 22, 48, 64, 76, 110, 114, 136) as a measure of bed densities, along with a selectively operable valve (172) which may be opened to periodically remove solids without clogging.

Abstract: A coagulation sedimentation process for water to be treated in which an inorganic coagulant used in a purified water treatment system is limited, and remaining micro flocks and flocks are made greater in density and finer in particle size, thus obtaining clear water better in quality and reducing the amount of sludge production, including a micro flocculation step for micro-flocculating in advance fine suspended particles in water to be treated, a flocculation step for the micro flocks, and a sedimentation separation step for the flocks, in which as a final stage of the flocculation step, a flock-forming inclined plate whose pitch width is from 5 mm or more to 50 mm or less is provided, and an inorganic coagulant is limited so that the turbidity of the water to be treated after passage of the inclined plate at a ratio to that before passage is 4/5 or less.

Abstract: A system and method for the treatment of water for human consumption using a naturally occurring inorganic catalyst working within a pH range between 3 and 13, combining the inorganic catalyst at 3 parts per million to an oxidant, primarily hydrogen peroxide and a metal salt used as a coagulant and a primary catalyst, resulting in an efficient and economical phasic water purification and filtration system and process. The inorganic catalyst is a zeolite a synthetic zeolite or preferably chabazite.

Abstract: A system and method that uses mature floc as seed particles to promote aggregation in a water treatment process is provided. The seed particles do not need to be recovered as they separate out with the waste steam after a spiral separation. One implementation is to prepare the mature floc off-line and inject periodically into the buffer tank, as needed. Another implementation is to tap into the more mature floc downstream and feedback, as needed, to the buffer tank.

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: Process involving repeatedly applying some of the liquid composition to the granular filter media to remove water from the liquid composition by passing through the granular filter media with the particulate solids collecting on top surface of granular filter media. Water is first allowed to fill from below to just above the top layer of the filter media. A non-porous liner is located on the inner, bottom surface of the container. A drain pipe, having small openings, is located on top of the liner in the valley. A porous layer of large filter media, with the drain pipe therein, is located in the bottom of the container. A grid having open passageways, with fine filter media therein, is located on top thereof. A layer of fine filtrate sand is located on top of the grid.

Abstract: Arrangement for separating suspension, in particular for treatment of wastewater. A flocculating suspension is separated from the liquid by filtration in a fluidized layer in a sludge blanket, wherein the flocks are created from the separated suspension and fluidization is maintained by the rising stream of liquid while liquid with suspension enters the fluidized layer from the bottom and the liquid freed from suspension is discharged above the surface of the sludge blanket represented by the interface between the fluidized layer and the liquid without suspension. Thickened separated suspension in the form of flocks from a sludge blanket is withdrawn from a zone of the fluidized layer the velocity of upward flow in the fluidized layer decreasing in the upward direction.

Abstract: The present invention has an object to provide a compact aggregation precipitation method and an apparatus therefor which prevent the outflow of flocs and do not deteriorate the turbidity elimination performance even in start-up early stages. As the means to accomplish such an object, the present invention provides a method of adding an inorganic flocculant and, optionally, an organic polymer flocculent to the water to be treated and agitating the resulting mixture to effect aggregation precipitation treatment which comprises introducing the agitated solution into a first chamber of a separation tank where flocs are allowed to grow to effect solid-liquid separation and, simultaneously, the separated water is discharged out of the separation tank.

Abstract: A method of separating suspension, in particular for treatment of waste water, wherein the flocculating suspension is separated from the liquid by filtration in a fluidized layer in a sludge blanket wherein the flocks are created from the separated suspension and the fluidization is maintained by the rising stream of liquid, while the liquid with suspension enters the fluidized layer from the bottom and the liquid freed from suspension is discharged above the surface of the sludge blanket represented by the interface between the fluidized layer and the liquid without suspension. The thickened separated suspension in form of flocks from a sludge blanket is withdrawn from the zone of the fluidized layer, the velocity of upward flow in the fluidized layer essentially decreasing in the upward direction.

Abstract: A method of removing arsenic from water by using a reactor that is provided with a fluidized bed of carriers is disclosed. An arsenic-containing influent is mixed in the reactor with a sulfide aqueous solution or metallic salt aqueous solution at a predetermined pH, thereby resulting in formation of crystals of arsenic sulfides or arsenic acid metal salts. The arsenic contained in the influent is thus removed by crystallization. An effluent with a reduced arsenic content is discharged from the reactor. The carriers, on which the crystals are formed, are periodically removed from the reactor which is replenished with fresh carriers immediately after.

Abstract: An apparatus and method for removing phosphorus from a wastewater effluent stream from a hog waste lagoon. The wastewater effluent is introduced to the bottom of an inverted cone-shaped continuous crystallizer including a fluidized bed of struvite therein. An effective amount of ammonia is introduced to the wastewater effluent at the bottom of the crystallizer to elevate the pH of wastewater effluent a predetermined amount. An effective amount of magnesium is also introduced to the wastewater effluent at the bottom of the crystallizer. The composition adjusted wastewater effluent is then continuously passed upwardly through the fluidized bed of struvite to reduce the total phosphorus content of the wastewater effluent a predetermined amount of up to about 80% or more. The treated wastewater effluent stream is removed from the top of the crystallizer, and struvite crystals that grow large enough to sink from the bottom of the crystallizer are periodically removed from a collection chamber therebeneath.

Abstract: A method is provided for thickening sludge produced through a ballasted flocculation process. The sludge and granular material from the ballasted flocculation process are directed to a sludge separator where the sludge is separated from the granular material. Thereafter the separated sludge is sent to a degassing area and the sludge is degassed. A flocculating agent is mixed or injected into the sludge. The sludge is directed to a sludge thickener with a load at a sill calculated on the surface of the thickener greater than 200 kgMIS/m2/day. This process produces a thickened sludge having a concentration greater than 10 gm/I.

Abstract: The enhanced deliquifying of the compacted bed of deep bed thickener/clarifier is disclosed. Such an apparatus comprises a vessel receiving a slurry of liquid and solid particles suspended in the liquid. The vessel defines a free settling zone, a hindered settling zone intermediate, an upper clarification zone and a lower compaction zone. A deliquifying member is provided in the vessel extending up between at least two zones for facilitating the upward flow of free liquid from one of the lower zones and the settling of particulates. A rotating rake shaft with pickets are so designed to release the interstitial liquid trapped in a lower zone. The pickets provide pathways for liquid to release generally vertically. The release liquid travels upward to the deliquifying member and on into the clarification zone. The lower zone, freed of the interstitial water, further collapses becoming more concentrated or dense.

Abstract: A method of removing phosphoric acid contained in wastewater which comprises comprehensively immobilizing calcium or a compound thereof with a solid polymer optionally together with magnetite and contacting the calcium-containing polymer with the wastewater to react the phosphoric acid contained in the wastewater with the calcium and thereby yield calcium apatite.

Abstract: Disclosed is a process for reducing the amount of silicon in brine. More specifically the silicon content of the brine is reduced to 1 ppm or less by using low caustic excess. The disclosed process can also be characterized as lowering sodium hydroxide excess (caustic excess) while maintaining the sodium carbonate level thereby obtaining a brine with a low level of silicon. A further purification step employs a sludge blanket.

Abstract: A treating method and apparatus for treating a manganese containing water by crystalizing and removing a soluble manganese in a water to be treated containing carbonic acid ions by passing the water to be treated as an upward flow through a fluidized bed reaction tower having no support bed and containing manganese sand as a fluidized bed material and by adjusting a pH value of the water to be treated in said fluidized bed. A suspended manganese is also removed together with said soluble manganese in the water to be treated by forming a suspended solid in the water to be treated into a layer on said manganese sand fluidized bed by removing said layer of suspended solid. Further, a desired quantity of the treated water is introduced into the water to be treated for circulatory use.

Abstract: Small amorphous silica particles are used to provide a relatively large surface area upon which silica will preferentially adsorb, thereby preventing or substantially reducing scaling caused by deposition of silica on evaporative cooling tower components, especially heat exchange surfaces. The silica spheres are contacted by the cooling tower water in a sidestream reactor, then separated using gravity separation, microfiltration, vacuum filtration, or other suitable separation technology. Cooling tower modifications for implementing the invention process have been designed.

Abstract: Process for the treatment of polluted metal-mechanic industrial waste water and urban water, comprising: treating the polluted water with an acid liquor including ferrous chloride and hydrochloric acid, in order to promote the denaturalization of protein present in metal-mechanic industrial water or urban water and generate a clarifying and purifying flocculus from said polluted water.

Abstract: A process for the removal of dissolved metals and/or metalloids from an aqueous medium having a high content of salt wherein the aqueous medium in the presence of manganese (II) ions and an oxidation agent is passed through a particulate carrier material having a specified density, initial average grain size and flow rate, so as to fluidize carrier material particles in the aqueous medium, and whereby the coated material particles thereby formed are separated from the aqueous medium.

Abstract: A process to purify wastewater by chemical oxidation is disclosed. The purification is carried out in a fluidized bed of a suitable particulate carrier upon which the iron(III) compound produced by Fenton's reaction crystallizes or coats, thereby reducing the sludge content of effluent over 50%. In addition, the fluidized bed improves the COD removal by way of thoroughly mixing the wastewater with adding agents.

Abstract: Disclosed is a method for treating highly concentrated wastewater by electrolysis and oxidization, said method being characterized in that the electrolysis and oxidization are carried out in a fluidized bed of a suitable particulate carrier. The electrolytic reduction efficiency of ferric ions is improved by the fluidized particulate carrier, and thus a high proportion of iron(III) to iron(II) can be sustained in the system. This invention allows extensive purification of wastewater with improved efficiency.

Abstract: Arsenic and TOC are removed from drinking water or wastewaters by use of finely-divided metallic iron in the presence of powdered elemental sulfur or other sulfur compounds such as manganese sulfide, followed by an oxidation step. A premix may be produced for this process, by adding the iron, sulfur and oxidizing agent to water in a predetermined pH range. The iron and sulfur are mixed for a period of time dependent upon the temperature and pH of the water and the presence of complexing or sequestering minerals and organic acids in the water. An oxidizing agent is added to the mixture and agitating is continued. In a preferred embodiment the oxidizing agent is hydrogen peroxide. Water is decanted from the mixture after a sufficient reaction time, to produce a concentrated premix. This premix can be added to water intended for drinking or to industrial effluents containing toxic materials.

Abstract: Metal ions and/or complexes of metal ions are removed from a solution by formation of an insoluble chelated complex of the metal ions and a polymeric precipitating agent. A two-step process of mixing the influent with the precipitating agent is used to induce rapid precipitation and obtain large, self-agglomerated precipitate without addition of flocculating agent and/or pH adjustment. In addition, parallel loops are employed to simultaneously discharge treated metal-free solution and effectively collect/remove the precipitate-containing sludge without interfering with each other. The metal capturing capacity of the polymeric precipitant is maximized by forcing the influent solution through layers of the collected precipitate and by recycling unsaturated metal-precipitant complexes in the processing loop.

Abstract: Method for recovering etchant from etching waste liquid 11 containing iron chloride is disclosed, wherein iron powder is mixed with iron chloride waste solution containing metal ions having a lesser ionization tendency than iron ion in an mixing vessel so as to cause a reaction between the iron powder and the metal ions and remove the precipitated metal from the iron chloride waste solution.

Abstract: A wastewater treatment method involving mixing of the wastewater with an activated sludge and water that has been supersaturated with air under high pressure is described. After the pressure is reduced two processes are carried out which are biological oxidation of pollutants by activated sludge and flotation of suspended solids. A portion of the treated water is saturated with air and returned to the beginning of the process. The waste activated sludge is removed along with some floated and biologically non-oxidated pollutant particles.

Abstract: A method for treating cyanide contaminated water is disclosed. This method generally involves passing the contaminated water through a bed containing elemental iron, to form a precipitate by a reaction between the iron and any of various cyanide species which exist in the water. The method can be applied either above ground or in situ in the subsurface environment.

Abstract: Spent solutions from photographic processors are fed into a conduit (18) to which subsequently are added precipitating agents from a first source (22) and flocculating agents from a second source (28); so that, well grown or ripened clumps of flocculated solids are formed along the conduit before being emptied into a gravity collecting vessel and shipping container (38) from which clarified liquids are displaced by a mass (50) of accumulated flocculated solids, typically through a filter (58, 142, 150, 158, 162, 166, 220)for removal of any unsettled fines. Many of the clumps of flocculated solids become enlarged enough to individually extend across and substantially fill a cross-sectional area of the conduit. As a result, the enlarged clumps substantially block passage of and strain from the solution remaining fine particles which then adhere to the clumps.

Abstract: An apparatus for waste water treatment, wherein fluorine contained in waste water is treated into a fluoride through a chemical reaction and sludge containing the fluoride is thickened and dehydrated into a sludge cake, has first and second tanks each packed with calcium carbonate mineral. In the first tank, waster water containing fluorine is agitated by air discharged from an air diffuser and caused to react with the calcium carbonate mineral. Through this reaction of the waste water with the calcium carbonate mineral and action of microorganisms on the surface of the calcium carbonate mineral, a pH value and a fluorine concentration of the waste water is adjusted till the pH value and the fluorine concentration fall within their respective predetermined ranges.

Abstract: Arsenic and TOC are removed from drinking water or wastewaters by use of finely-divided metallic iron in the presence of powdered elemental sulfur or other sulfur compounds such as manganese sulfide, followed by an oxidation step. A premix may be produced for this process, by adding the iron, sulfur and oxidizing agent to water in a predetermined pH range. The iron and sulfur are mixed for a period of time dependent upon the temperature and pH of the water and the presence of complexing or sequestering minerals and organic acids in the water. An oxidizing agent is added to the mixture and agitating is continued. In a preferred embodiment the oxidizing agent is hydrogen peroxide. Water is decanted from the mixture after a sufficient reaction time, to produce a concentrated premix. This premix can be added to water intended for drinking or to industrial effluents containing toxic materials.

Abstract: A water quality improvement process is provided for acid water containing sulphate and/or sulphite ions. The water is continuously fed into a fluidized bed containing calcium carbonate particles. The water consumes calcium carbonate and has its pH increased while calcium sulphate CaSO.sub.4 and/or CaSO.sub.3 are produced.

Abstract: Improved methods for removal of disinfection by-products, halomethanes, precursors thereof and other organic contaminants from water being processed for use as potable or industrial water involve adding to the water being treated in a zone separate from the conventional clarification, softening and filtration steps, and downstream of at least the clarification step, between about 1 to 1000 ppm of powdered activated carbon (PAC), between about 1 to 1000 ppm of bentonite and between about 0.1 to 100 ppm of flocculant polymer, based upon one million parts of the water. The relative proportions of PAC, bentonite and polymer within the stated ranges are selected to give a sludge having a sludge cohesion factor "k" between about 0.5 and 5, especially between 0.6 and 1.5.

Abstract: There is disclosed a pulsating sludge bed clarifier especially for the treatment of low turbidity waters, which uses incline plates in the sludge bed and some recirculated sludge. The clarification is greatly enhanced by recirculating a relatively small part of the sludge concentrate to a reactor chamber used for the premixing of water to be treated and the coagulant. The small amount of recirculated sludge cuts down significantly on the polymer flocculant, which is the most expensive chemical in the process that is required to be used, and can also serve to improve the adsorption of colors and similar materials, increase the density of the sludge blanket, and improve the rate of throughput of the system.

Abstract: This invention relates to a process for removing copper ions from highly acidic waste water generated during the manufacture of dyes or pigments or intermediates thereof. The waste water is exposed at a pH less than about 1 to a bed of suspended iron particles, preferably a fluidized bed of iron particles, having a particle size of from about 200 to about 950 micrometers.

Abstract: New systems for the purification of liquids containing suspended solids and/or dissolved solid materials basically include a conical flocculator unit and a conjoined conical clarifier unit. The flocculator has a cylindrical lower portion, frustum middle portion and large diameter cylindrical top portion while the clarifier is essentially a large diameter cylindrical top portion over a lower frustum portion. Water or other liquid to be purified enters the flocculator lower portion via opposed, unequally sized nozzles to assume a helical flow upward past a series of deflector plates positioned at the top of the lower flocculator portion while a sludge blanket forms therein. A double flume plus slot arrangement located at the junction of the flocculator with the clarifier separates solids from liquid as fluid flow from the flocculator passes into the clarifier where it is subjected to further separation of sludge from clarified liquid with part of the sludge being recycled to the flocculator.

Abstract: The liquid from which impurities are to be removed is introduced by being distributed throughout the entire top or bottom surface of the filtering medium. The filtering medium includes at least a bed of wood ash through which the liquid is allowed to flow for removing at least part of its impurities to give a purified liquid. The liquid can flow through the filtering medium either by gravity, under pressure or can be forced upwardly through the filtering medium. This type of filtering medium has proved to be cheaper to build and used and is more efficient than those presently known.

Abstract: The invention relates to a process for the removal of fluoride from waste water in the form of a slightly soluble salt by mixing the waste water with a reagent. According to the invention the fluoride containing waste water is thoroughly mixed with the water soluble reagent at a suitable pH in a reactor of the fluidized bed type, which is provided with an appropriate seed material, on which the fluoride salt crystallizes out, whereby the thus obtained pellets comprising the seed material with the crystalline fluoride salt, is removed from and new seed material is added to the reactor from time to time. According to the present process as reagent CaCl.sub.2 is used, whereas the pH is adjusted to an appropriate value.

Abstract: A process for treating industrial waste water containing hexavalent chromium (Cr.sup.+6) and other heavy metals is disclosed which comprises reduction of Cr.sup.+6 to trivalent chromium (Cr.sup.+3) and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream at a pH of about 7 to 9 under conditions such that sludge production by the process of the invention is substantially less than that characteristic of prior art processes. Polymers are added to the solution to assist flocculation and clarification of the waste stream. More specifically, the invention comprises adding sulfide ion in a sulfide to hexavalent chromium ratio of about 0.7-2.5:1 and adding ferrous ion in a ferrous to hexavalent chromium ratio of about 0.5-5.0:1. The waste stream pH is preferably maintained in the range of about 7.2 to 7.5.