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: Apparatus for jet aeration of wastewater which may be readily retrieved for cleaning or other servicing and replaced in service. Methods of placing the aeration apparatus in service are also provided.

Abstract: A method and apparatus for biological aerobic treatment of wastewater wherein oxygen is induced into a mixed liquor flow path and a method and apparatus for separating the liquid withdrawn from the mixed liquor flow path into a clear liquid stream and a flock laden stream. A streaming specific gravity separator of unique construction and operation separates the mixed liquor into a clear liquid stream and a flock laden stream, withdrawing the clear liquid stream from the system and directing the flock laden stream back into the mixed liquor flow path. The separator functions within the system to be self-controlling for load increases or decreases.In accordance with preferred embodiments of the system, the separator may be positioned inside or outside of an oxidation ditch. The separator may also be utilized in combination with an aeration basin.

Abstract: This invention pertains to a submerged fixed-film biological distribution system. It includes a plurality of vertical chambers adjacent each other having corrugated packings therein. Air or oxygenating gas is introduced at the bottom of select alternating chambers so that an upflowing liquor is generated in those chambers and a downflowing liquor generated in the adjacent chambers. Contaminated waste is biologically digested by microorganism retained on the corrugated packings, such digesting occurring in all chambers.

Abstract: Methods and apparatus for decanting clarified waste water in a sequencing batch reactor or the like.

Abstract: Methods and apparatus for subcyclonic grit separation under aeration conditions utilizing elevated wastewater hydraulic jet recirculation systems.

Abstract: A plurality of aerators are arranged in a preselected pattern on the floor of a basin or lagoon containing waste water. Compressed air is supplied to the aerators by aeration pipes anchored by hanger brackets to the floor of the basin. Each aerator has a porous diffuser plate through which the air is passed and released into the waste water in the form of ultra fine air bubbles less than 60 microns in diameter. The air bubbles are generated in an intense manner with a high rate of air flow to increase the mixing action and liquid circulation pattern, and to create turbulent boils at the surface which provide surface aeration from atmospheric air and re-entrainment of air from eddy current circulation.

Abstract: In a process for the biological purification of waste water by mixing a sludge-water mixture and air in an activation chamber charged continuously with waste water, activated sludge and air and from which an equivalent quantity of sludge-water mixture is discharged, the sludge-water mixture is guided along with the air in the activation chamber so as to define at least one loop shape motion. In a further embodiment of the process that part of the sludge-water mixture that does not continue its loop shape course is submitted to a biological after-reaction, preferably occurring in the activation chamber, while avoiding backmixing with the mixture in loop shape motion.

Abstract: An integral clarifier is provided that operates without a pump by deriving the clarifier feed stream and its accompanying pump head from the flow being pumped through the draft tube of a draft tube circulator/aerator assembly in a complete mix system or in a basin oxidation ditch. The clarifier feed stream is delivered to the clarifier with this pump head substantially intact to create a differential hydraulic head between the surface of the clarified liquor within the clarifier and the surface of the mixed liquor within the complete mix tank or within the endless channel of the barrier oxidation ditch. The clarifier may be located in any suitable place but is preferably alongside the complete mix tank or alongside the discharge channel of the barrier oxidation ditch, within the discharge channel so that its upstream side forms the barrier, or surrounded by the endless channel, particularly if the clarifier and the ditch are circular in shape.

Abstract: According to an embodiment thereof, the method comprises using a pair of reaction vessels, sequentially, to treat the sludge. Both vessels are pressurized, and the first thereof has an aerator for aerating the sludge, and receives sulfuric acid and chlorine thereinto through a port. A dewatering device is provided upstream of the first vessel, and the outlet of the first vessel is coupled to an inlet of the second vessel through another dewatering device. The second vessel defines a final-treatment chamber in which the sludge is exposed to ozone, air and lime. The treatment method, then, comprises the steps namely: introducing the sludge into the first vessel and oxidizing and depressing the pH of the sludge so introduced, and recycling the sludge in the first vessel over a given period of time. Thereafter the sludge is dewatered and conducted to the second vessel wherein it is exposed to air, ozone and lime, as aforesaid, and discharged after a like period of time.

Abstract: A low pressure valveless floating aeration system for providing oxygen and circulation to a water impoundment, utilizing one or more floating elongate members supporting a substantially uniform assemblage of air diffusers spaced above the bottom of the impoundment. Air at a comparatively low pressure is supplied to said elongate members and thence to said air diffusers, such that a large number of tiny bubbles will rise up from the air diffusers through the water of the impoundment, bringing about a desirable amount of circulation in the water. Because the air diffusers are suspended from members floating on the water surface, the depth at which the diffusers are located can be made uniform, or the diffusers can be suspended at gradually decreasing depths at locations remote from the air supply.

Abstract: An effluent treatment system using a tank having a length between 3.5 and 6 times its width with an inlet at one end, a surface decanter at the other end, and submerged diffused aeration nozzles. Effluent input is continuous and cyclic operation involves air diffusion, rest period and then decanting. Transverse baffles may be used in the tank to cope with shock organic loads obviating the need for hydraulic or organic pre-balancing.

Abstract: This flow-control apparatus for an oxidation ditch comprises a barrier which divides a channel of an oxidation ditch into an intake channel and a discharge channel, at least one submerged turbine which pumps mixed liquor from the intake channel, and at least one discharge duct which connects each turbine to the discharge channel and passes beneath the barrier. Compressed air is supplied to each turbine and/or to each discharge duct. Activated sludge is fed to the anoxic portion of the ditch and/or to each turbine which provides complete mix and propels the mixed liquor in plug-type flow through the channels of the oxidation ditch. By selectively and independently controlling turbine speed and amount and/or feed location of compressed air, the timed aerobic/anoxic ratio for the ditch can be controlled in accordance with independent parameters, such as seasonal temperatures.

Abstract: A waste water stream is clarified by phase separation of a part of the stream in a clarifier positioned in an oxidation ditch, through the establishment of a head differential between the level of liquid in the clarifier and the level of liquid in the oxidation ditch.

Abstract: A barriered circulator/aerator in the endless channel of a barrier oxidation ditch provides a directly pumped flow of mixed liquor into a central liquor inlet zone and an energy-release induced flow of mixed liquor into a surrounding liquor inlet zone at the inlet of a deep oxygen contact duct which passes beneath the barrier to the discharge channel on the downstream side thereof. It further provides mixing of diffused air with the directly pumped flow and/or the induced flow and then moving the combined air-liquor flows into the deepest portion of the contact duct where point-source pressurized aeration of both flows occurs. Eddy jet diffusers are preferably used for aerating the induced flow. Oxygen transfer efficiencies are obtained that are 1.6-2.2 times as great per brake horsepower per hour as that attainable by 100% pumping of the mixed liquor in a total barrier oxidation ditch, as disclosed in U.S. Pat. No. 4,260,278.

Abstract: In a process for mixing a gas and a liquid in an apparatus having an axial flow down-pumping impeller located in a draft tube and preceded by a first baffle wherein a vortex and turbulence are created and gas is drawn into the vortex, the improvement comprising providing liquid velocity of at least one foot per second, increasing the turbulence, providing a second baffle below the impeller, and a high shear zone between impeller and the second baffle.

Abstract: The invention provides a process for the performance and control of chemical or biochemical process cycles in two or a plurality of series-connected reaction stages or basins, with which gassing of a fluid is controllable. The process provides for a recirculation of the fluid between reaction stages or basins in that the basins are preferably arranged concentrically to one another, can be charged selectively, and have at least one connection between one another through which the fluid passes so that the contents of the basins are caused to assume a horizontal rotational flow. Recirculation of the fluid is provided by overflow dams, wall openings, or other devices.

Abstract: In a ring channel aeration system, circulation is provided by one or more hydraulic jumps while the major portion of the energy consumed in aeration is allocated to the release of oxidative process gas through horizontally non-propulsive bubble release means having an oxygen transfer efficiency of at least about 6. The hydraulic jump(s) may be powered by discharge of gas (e.g. the same gas used for aeration) through gas discharge means, in which case the system of gas discharge means and bubble release means may have an overall oxygen transfer efficiency of at least about 6. The invention has advantages of flexibility and resultant energy savings as compared to single device circulation/aeration systems, in that excessive energy need not be consumed in aeration to obtain the requisite circulation and vice versa.

Abstract: Methods are provided for converting both plug flow and complete mix basins of the prior art into barrier oxidation ditches. Circulator/aerators are described that can be prefabricated and dropped onto the floor of an existing basin so that, in combination with at least one partition, if needed, an endless channel is created with minimum disruption of the activated sludge process.

Abstract: A method and an apparatus for dissolving gas in a body of sewage comprising providing a skirt member having a lower open end extending upwardly from said body of sewage to define a volume of said sewage separate from an adjacent body of clarified liquid in said tank, removing a flow of sewage from said body of sewage and pressuring said flow, introducing oxygen into said pressurized flow to form a mixture of oxygen and sewage, introducing said mixture as a jet downwardly into the inlet of a chamber disposed in said volume defined by said skirt member to induce sewage in said chamber and thereby oxygenate said sewage, discharging said oxygenated sewage downwardly through an outlet of said chamber at a reduced velocity, and reducing the momentum of said discharged oxygenated sewage by directing the same onto baffles spaced from the outlet of said chamber.

Abstract: A pressurized aeration tank is provided which comprises an inner barrel arranged on the tank axis and an axial-flow impeller of optimum characteristics mounted therein, the inner barrel and the outer barrel or body portion of the tank being particularly proportioned and arranged relative to each other to define in the tank a circuitous flow passage of minimal total resistance loss. With this tank structure, a highly improved plant efficiency of BOD removal is readily obtainable with the use of concentrated activated sludge and aerobic microorganisms, mainly of the Opercularia group, in a specified range of tank pressure.

Abstract: A waste water treating apparatus includes a circulation type aeration tank having a downward flow chamber and an upward flow chamber extending in the depth direction and communicating with each other at the upper and lower ends thereof. An oxygen containing gas is supplied to the downward flow chamber and waste water and return sludge are supplied to a given position or elevation of the upward flow chamber to be mixed with a mixed liquor flowing through the upward flow chamber, whereby a reduction zone with a low concentration of dissolved oxygen is formed at the upper portion of the upward flow chamber. Denitrification takes place in the above described reduction zone.

Abstract: An apparatus and a method for biological treatment of waste waters achieving biological oxidation of organic matter, biological nitrification and denitrification of nitrogenous compounds and biological removal of phosphorus and clarification of the treated waste water in a single reaction tank in a single suspended growth sludge system without the use of traditional compressors, mixers, recirculation pumps, piping and valving and without the use of the traditional clarifier.

Abstract: A method of aerating liquids, particularly for aerobic growing of microorganisms, has the steps of forming a circumferential stream of liquid, forming a longitudinal stream of liquid, and superimposing these streams so as to form a combined closed spiral-shaped stream. An arrangement is provided in which the circumferential stream is formed by an upright conduit tube and an impeller, the longitudinal stream is formed by a distributing element with a plurality of nozzles, and the superimposing of the streams is attained by fixedly mounting the distributing element relative to the impeller.

Abstract: A method for the secondary treatment of sewage (and apparatus therefor) having a step in which sewage is circulated in a system having a riser and a downcomer communicating with each other at their upper and lower ends and in which an oxygen-containing gas is supplied to the sewage as it passes through the downcomer. The method is intended for use in the aeration and/or digestion steps of the secondary treatment of sewage. The riser and downcomer are preferably located in a shaft extending into the ground for at least 40 meters below a basin containing the sewage.

Abstract: An aerator for aerating a body of water such as a catfish pond, or the like, operates by stirring the water in the body of water. A paddlewheel having movable paddles stirs the water near the surface to mix oxygen-rich surface water with oxygen-deficient deep water.

Abstract: An improvement is provided in the operation of a long vertical shaft bioreactor in the treatment of waste which comprises circulating waste liquor and oxygenating gas through the bioreactor in which the uppermost portion of the shaft (the surface basin) is under supra-atmospheric pressure. The use of a pressurized surface basin subjects the waste to improved oxidizing conditions in a critical zone of the bioreactor and results in more effective biodegradation of the waste. By precise control of surface basin pressure, adequate levels of oxygen in the waste are maintained for biodegradation purposes while unwanted gas, such as carbon dioxide and nitrogen, are disengaged. The pressure on the surface of the waste in the basin is controlled so as to ensure that the concentration of oxygen in the waste is subsaturated and retained while the unwanted gas concentration is super saturated and becomes disengaged.

Abstract: Methods are provided for converting both plug flow and complete mix basins of the prior art into barrier oxidation ditches. Circulator/aerators are described that can be prefabricated and dropped onto the floor of an existing basin so that, in combination with at least one partition, if needed, an endless channel is created with minimum disruption of the activated sludge process.

Abstract: A process for the biological purification of effluent which is contaminated with nitrogen in the form of ammonium, nitrite or nitrate ions or in the form of organic compounds, by oxidizing the nitrogen under aerobic conditions and reducing the nitrogen under anaerobic conditions, wherein the sewage to be treated, mixed with activated sludge, is subjected, in an aeration basin, to oxygen-containing gas bubbles introduced from below and is thereby simultaneously enriched with dissolved oxygen, to oxidize carbon compounds and nitrogen compounds, and transported upward, by the buoyancy of the gas bubbles, releases gas at the surface of the liquid and, due to the higher average density of the mixture of lower gas content, in part automatically again flows downward in the aeration basin, to undergo further aeration, while in part it overflows into a denitrification basin which communicates with the aeration basin through an opening at the liquid surface, and an opening at the bottom of the partition, is mixed, in t

Abstract: A process for the secondary treatment of wastewater by a modified air activated sludge system comprising aerating wastewater containing bacteria until the BOD level of the wastewater is reduced by at least 90%, the food to microorganism ratio of the wastewater being greater than one, introducing the aerated wastewater under pressure to a flotation cell to separate suspended solids including bacteria from the pressurized wastewater by dissolved air flotation clarification, recycling said suspended soilds and bacteria to said aeration step in an amount sufficient to maintain said food to microorganism ratio and removing and disposing of the remaining reduced BOD level wastewater.

Abstract: An improved method and apparatus is provided for the treatment of sewage waste in a long vertical shaft bioreactor wherein waste sewage is caused to circulate under air injected oxidizing conditions around a loop comprising adjacent riser and downcomer chambers connected at their upper and lower ends. The improved method comprises the steps of introducing influent waste at depth into the riser chamber at a point higher in the riser than the point of air injection and withdrawing treated effluent from the riser at a point lower in the riser than the point of air injection. A separation chamber may also be operatively connected to the riser chamber to recover sludge for return to the bioreactor. The method provides an improvement in oxygen uptake rate and reduces the anoxic zone in the reactor thus providing additional capacity for BOD.sub.5 removal.

Abstract: A waste water treatment plant providing biological oxidation, biological nitrification and denitrification and biological removal of phosphorus and clarification of the treated waste water in a single reaction tank in a single suspended growth sludge system without the use of the traditional compressors, surface aerators, mixers, recirculation pumps, sludge scrapers, sludge return pumps, piping and valving.

Abstract: A method for the secondary treatment of sewage (and apparatus therefor) having a step in which sewage is circulated around a system having a riser and a downcomer communicating with each other at their upper and lower ends and in which an oxygen-containing gas is supplied to the sewage as it passes through the downcomer. The method is intended for use in the aeration and/or digestion steps in the secondary treatment of sewage. The riser and downcomer are preferably located in a shaft extending into the ground for at least 40 meters below a basin containing the sewage.

Abstract: This invention provides a method for treating wastewater by circulating wastewater around a system comprising a downcomer and a riser which communicate directly at their lower ends, the level of the wastewater in the downcomer being maintained above the level of the wastewater in the riser to provide a hydrostatic pressure head which causes circulation of the wastewater around the system, supplying a gas containing oxygen to the wastewater as it passes through the downcomer, pumping the wastewater from the top of the riser back into the top of the downcomer and removing treated wastewater from the riser at the same rate as wastewater is introduced into the system characterized in that the height of the hydrostatic pressure head is controlled by adjusting the height at which treated wastewater is removed from the riser and the level of the wastewater in the riser. The invention also provides an apparatus for putting the method into practice.

Abstract: A method and apparatus for the treatment of wastewater in which the wastewater is circulated around a system comprising a downcomer and a riser communicating with each other at their lower ends, the level of the wasterwater in the downcomer being maintained above the level of the wastewater in the riser and providing a hydrostatic pressure head which causes circulation of the wastewater around the system at a pre-selected rate, a gas containing free oxygen is supplied to the wastewater as it passes through the downcomer, and the wastewater is pumped from, or form near, the top of the riser back into the downcomer (or vessel communicating therewith) at a position(s) above the highest level to which the wastewater in the downcomer can fluctuate during normal operation of the system when operating at maximum load.

Abstract: An improved method and apparatus is provided for maintaining a constant gas-to-solids ratio in the effluent from a long vertical shaft waste treatment bioreactor. In a vertical bioreactor wherein waste is circulated under air-injected oxidation conditions around a loop comprising adjacent downcomer and riser chambers connected at their terminals and operatively connected to a separation apparatus, the improvement comprises withdrawing treated effluent from the riser chamber into a cylindrical vessel from whence the effluent is directed either to the separation chamber or into the influent stream depending on the total level of fluid in the bioreactor. Removal of large air bubbles from the effluent is also effected in the cylindrical vessel. The method provides improved gas-to-solids ratio in the effluent and improves sludge flotation in the separation apparatus.

Abstract: A process for treating wastewater with oxygen in which oxygen of a higher concentration than atmospheric oxygen is contacted at least intermittently with the water surface and introduced into the wastewater through agitation of the water surface. At least a part of the total volume of the wastewater is treated by carrying out alternately at least two of the following three modes of operation: (a) surface aeration of the wastewater using atmospheric air; (b) oxygenation while maintaining atmospheric pressure above the wastewater; and (c) oxygenation while maintaining positive pressure above the wastewater with the operating modes alternating with each other in response to variations in the volume and/or character of the wastewater being treated. The wastewater is circulated on a horizontal course and is exposed to the introduction of oxygen or oxygen-enriched air in one or several sections of its course whereas it is exposed to the atmosphere on the remainder of its course.

Abstract: In the activated sludge process for treating wastewater loss of biologically active microorganisms from the aeration-mixing tank to the clarifier is reduced and the biological process whereby wastewater is treated is made more efficient by the addition of inert solid particulate matter to the liquid while in the aeration tank to provide mobile sites upon which the organisms will attach and grow.

Abstract: A method for treating water is disclosed. The method is applicable for the treatment of waste water within lagoons and ponds wherein the treatment of the waste water is accomplished mainly through aeration.

Abstract: In a long vertical shaft activated sludge bioreactor for the treatment of waste water and the flotation/separation of solids therefrom, an improvement is provided whereby fluctuations in flow through the bioreactor are maintained level without the use of complex control mechanisms and whereby separation from the effluent of dispersed air bubbles occurs directly in the flotation/separation vessel rather than in the shaft or an auxiliary vessel. The improvement provides for the installation of a holding reservoir between the shaft and the flotation/separation vessel. Influent passes through the reservoir on its way to the bioreactor and some make-up effluent from the flotation/separation vessel is directed into the holding reservoir as the level of liquid in the reservoir falls. In addition, means are provided in the separation/flotation vessel to split off large dispersed gas bubbles which would otherwise disrupt sludge flotation.

Abstract: Process and apparatus for treating waste water by circulating it, together with oxygen-containing gas, through communicating downflow and upflow pipes enclosed in a treatment chamber, the pipes being open at their bottom ends, and controlling the flow of waste water/gas mixture from the downflow pipe to cause gas bubbles to escape downwardly, or part downwardly and part upwardly, in the treatment chamber.

Abstract: Dual baffle aerators substantially prevent back-mixing of freshly aerated liquor into aerator intakes and provide directional propulsion. By connecting two or more such devices to form a barrier across the channel of an oxidation ditch, homogeneous aeration is provided to the mixed liquor.Barriered pump/aerator assemblies utilizing directional mix jet aerators (eddy jet) can also be combined with dual-baffle aerators.An adjustably apertured barriered pump assembly is opened sufficiently to conserve momentum in the translationally flowing liquor while preventing back-mixing of aerated liquor.Processes for providing point-source or multi-source aeration, by using two or more barriered pump assemblies, can be provided at one barrier and the advantages of point-source homogeneous aeration can be provided at another barrier, at least one barrier being adjustably apertured.

Abstract: Organic wastes, such as animal manure, are fed into an elongated digester tank at one end thereof in slurry form. The slurry slowly moves to the other end of the tank for subsequent disposal. During the residence time in the tank decomposition of the waste occurs yielding methane gas and carbon dioxide. A cover over the digester collects the gas generated. A heat exchange arrangement causes transverse stirring of the slurry as it passes through the tank enhancing the decomposition process. Scum suppressors on the surface of the slurry prevent interference with the formation and release of the methane gas. The settling of solids is controlled by the use of gas jets disposed along the bottom of the tank.

Abstract: A method and apparatus is provided whereby a pressurized long vertical shaft bioreactor is protected against extreme surges of influent waste liquid. The method provides for the transfer of excess waste from the top of the bioreactor head tank to an adjacent collection vessel where, in response to the pressure created in the bioreactor, the collected waste is caused to overflow and is returned to the influent waste stream. The method permits the return of waste from the reactor to the influent stream while bypassing the normal circulation route through the reactor. Simplification of control is provided and float or level control valves may be eliminated thereby reducing construction, operating and maintenance costs.

Abstract: An activated sludge treatment method of waste water which comprises (a) the step of micronizing as far as possible the sludge in the waste water containing the BOD component to a degree not to have the cells of the microorganisms therein broken or destroyed and adsorbing the BOD component to the micronized sludge, and (b) the step of oxidizing the BOD component adsorbed to the sludge by blowing in an oxygen-containing gas and flocculating the sludge. By this method, the treatment of waste water is accomplished with a shortened residence time of the waste water in an installation for the treatment and with the production of excess sludge in a considerably reduced amount.

Abstract: A method of and an apparatus for aerating and circulating a liquid in a vessel comprising utilizing a surface aerator and a bottom mixing rotor mounted on a hollow common shaft. The rotor entrains liquid and air into the hollow center of the common shaft from the liquid surface region and affects a downward two-phase flow in the hollow center. The gas-liquid mixture is subsequently injected into the liquid body through the channels of the rotor which communicate with the hollow center of the shaft. The discharged jet streams disperse the entrained gas bubbles throughout the liquid body and provide turbulent mixing in the bottom section of the vessel. The present invention not only provides sufficient bottom mixing but also enhances the mass transfer efficiency of the surface aeration by enriching the gas content in the surface layer of the liquid.

Abstract: The present invention relates to a process and an apparatus for dispersing a gas in a liquid flowing within a vertical cycle through two reaction zones arranged in parallel within a reactor, the liquid/gas mixture flowing upwards in the first reaction zone due to the air-lift pump effect and being degassified at the transition from the first reaction zone to the second reaction zone and the completely or partly degassified liquid flowing down and the liquid being remixed with gas (preferably air) at the transition from the second to the first reaction zone below the two reaction zones.

Abstract: The disclosed invention is a continuous bioconverter or dry closet and method capable of aerobically and bacteriologically converting human and other organic wastes to principally carbon dioxide and water vapor. The closet comprises a collecting vessel containing a medium suitable for supporting aerobic decomposition. In accordance with the invention, the decomposition is a substantially total conversion of organic wastes to gases. In a preferred embodiment in the closet are two parallel shafts, each supporting a rotationally mounted pair of opposing auger-type blades (see FIGS. 1, 2 and 3) which provide a most efficient stirring action, resulting in a complete and continuous aeration (oxidation) of the aerobic bacteria in the chemically reactive organic mixture.

Abstract: A waste treatment apparatus provides a cylindrical vessel adapted to receive a waste water flow therethrough to be treated. The vessel provides an aeration chamber at the outer peripheral portion thereof, with a desirable generally helical flow being generated by aeration bubbles striking angularly deposed baffle plates. A clarifier is provided at the central portion of the cylindrical vessel for clarifying a liquid which enters the clarifier from the aeration chamber. The clarifier comprises a first settling chamber and a second decant chamber through which clear water is collected and transmitted to a chlorination chamber for subsequent discharge. The angularly deposed baffle plates are mounted in the upper portion of the aeration chamber and aid in spinning waste water in a circular or curved path. Likewise, a pair of aeration diffusers mounted in the lower portion of the aeration chamber near the center of the cylindrical vessel move waste water to be treated upwardly and outwardly in a circular path.

Abstract: An apparatus and method for treating aqueous waste material having a biochemical oxygen demand comprises a method utilizing a vessel in which a volume of waste material establishes itself into an upper zone of clarified waste material and a lower zone of liquid containing bacterial sludge. Liquid from the lower zone is mixed with incoming sewage and the resulting mixture is fed first to an oxygenation chamber and then to a stilling chamber located in the upper zone of the vessel. Baffle means is located within the vessel for deflecting and reducing the momentum of the aqueous waste material as it leaves the stilling box and falls to the lower zone.