Abstract: The disclosure relates to the technical field of energy saving and consumption reduction, and in particular, to a gas-liquid recycling device. A gas-liquid recycling device and a method of using same provided by the disclosure includes a gas-collection hood, a gas delivery pipe and a liquid delivery pipe. A gas inlet port of the gas delivery pipe is connected to the gas collection hood, a gas outlet port of the gas delivery pipe is inserted into a liquid outlet port of the liquid delivery pipe, and a liquid inlet port is located at an end of the liquid delivery pipe opposite to the liquid outlet port.

Abstract: The present invention relates to a mainstream deammonification process for removing ammonium from wastewater that suppresses NOB growth and produces a sludge having good settling characteristics, the process comprising: clarifying the wastewater stream in a primary clarifier (12) and producing a primary effluent; directing a first portion of the primary effluent to a biological treatment reactor (14) and removing carbon to produce treated wastewater; directing treated wastewater into an integrated fixed film activated sludge (IFAS) deammonification reactor (16) integrating nitritation and anammox processes and that is provided with intermittent aeration; directing a second portion of the primary effluent to the IFAS deammonification reactor (16) by-passing the biological treatment reactor (14), and injecting this second portion only during periods of air off and refraining from injecting during periods of air on, directing the IFAS deammonification reactor (16) effluent to a secondary clarifier (18) and produ

Abstract: Methods and compositions are provided for performing an in vivo proximity-ligation in combination with DNA capture technology to cross-link physically adjacent DNA sequences within a mixed population of cells and isolate cross-linked DNA junctions where at least one DNA sequence of interest is present.

Abstract: In one embodiment, a system includes first anoxic moving bed biofilm reactor (MBBR) configured to receive a fluid containing selenium and to process the fluid via a first biofilm disposed on a first media to produce a first MBBR fluid by removing nitrogen from the fluid. The system further includes a second anoxic MBBR fluidly coupled to the first MBBR to receive the first MBBR fluid and to process the first MBBR fluid via a second biofilm disposed on a second media to produce a selenium enriched fluid, followed by a solid-liquid separation system to remove selenium in solid form as sludge and produce a treated effluent containing equal to or less than 5 micrograms of selenium per liter. The system includes a plurality of first sensors and first actuators disposed on the first MBBR, and a plurality of second sensors and second actuators disposed on the second MBBR.

Abstract: Embodiments of the present disclosure involve methods, devices, and systems for hydrating polymers using multiple mixing chambers. Adjacent mixing chambers may be coupled using an under-over baffle, and each mixing chamber may be generally rectangular with rounded corners.

Abstract: A reactor closed to the atmosphere and method using same for nitrate removal are disclosed.

Abstract: Disclosed is a process for treating wastewaters including at least one step of aerobic biological treatment of the wastewaters in a biological reactor (3), as well as a step of ozonation during which ozone is injected into one or more circuits (1, 6) arranged to transport a respective fluid into the biological reactor (3). Also disclosed is a device relating thereto.

Abstract: A process is disclosed for treating a Bayer process waste comprising a slurry containing bauxite residue and dissolved aluminum. The process comprises supplying the waste to a settling area to cause the bauxite residue to settle out of the slurry, thereby producing a supernatant liquor. The process further comprises neutralizing the supernatant liquor with a solution containing magnesium and calcium to produce a neutralized slurry containing precipitated hydrotalcites and thickening the neutralized slurry to produce a clarified effluent and a compacted slurry containing the precipitated hydrotalcites, part of said compacted slurry being recirculated to the supernatant liquor to be neutralized and/or directly to the neutralizing step. The clarified effluent and the compacted slurry are disposed of separately. Also disclosed is a plant for treating a Bayer process waste.

Abstract: A method for controlling gas circulation in a mineral flotation process in a system including one or more flotation cell unit(s) with an apparatus including a gas recirculation loop, a flushing system including an expulsion line for connecting pressure side of the gas recirculation loop to atmosphere and a suction line including a water lock, or means, other than a water lock, for restricting the gas flow and preventing back flow of unpurified gas to the atmosphere, for connecting suction side of the gas recirculation loop to the atmosphere.

Abstract: A process for producing a biomass for use in the treatment of Fischer-Tropsch (FT) reaction water includes introducing a nutrient component comprising Carbon (C), Nitrogen (N) and Phosphorus (P), and water into an aerobic reaction zone containing a sewage sludge, and maintaining, in the aerobic reaction zone and under aerobic conditions, a F/M ratio of 0.25-2 kg COD/kg MLSS, where F/M=Food to Microorganism Ratio; COD=Chemical Oxygen Demand, expressed as mg oxygen/B of liquid in the aerobic reaction zone; and MLSS=Mixed Liquor Suspended Solids, expressed as mg solids in the aerobic reaction zone/B of liquid in the aerobic reaction zone. The F/M ratio is maintained for a period of time, to produce a biomass suitable for use in the treatment of FT reaction water.

Abstract: A method for removing sludge from a crude oil storage tank comprising a bottom and a moveable roof configured to float on the top of a quantity of crude oil disposed in said storage tank, where the method includes reducing a volume of crude oil in the storage tank to about a level of a sludge sediment in the storage tank, measuring a topology of the sludge disposed on said bottom, reliquefying asphaltene deposits, pumping the reliquefying asphaltene deposits out of the storage tank, wherein the method is performed without the entry of one or more persons into said storage tank.

Abstract: The disclosed lagoon biological treatment system helps existing wastewater treatment facilities meet stricter discharge permits mandated by the EPA utilizing a facility's existing wastewater treatment infrastructure. Influent is pumped into and processed in an aerated or non-aerated lagoon system, thus initially treating the wastewater to remove BOD5 (Biochemical Oxygen Demand) and TSS (Total Suspended Solids) down to approximately 20-30 mg/L. Then the wastewater is transferred to and processed in a nitrification reactor that is designed to maintain a minimum water temperature needed to further treat the wastewater to stricter EPA standards. Wastewater may also be further processed in a denitrifying reactor if necessary to meet local requirement. Finally, effluent water is sent to a settling lagoon for final clarification prior to discharge.

Abstract: A method and installation for treating wastewater containing ammonia includes feeding activated sludge from an aeration tank into a hydrocyclone. The sludge is separated into a specifically heavy fraction containing mostly anaerobic ammonia-oxidizing bacteria (anammox) and a specifically light fraction containing mostly aerobic oxidizing bacteria (AOB), which are returned to the aeration tank. The hydrocyclone includes a roughened inner wall surface for at least partially removing an organic or inorganic cover layer disposed on the anaerobic ammonium-oxidizing bacteria (anammox).

Abstract: The wastewater treatment method is to obtain demanganized wastewater, through a step wherein an acid or an alkali is added to sulfuric acid acidified wastewater to adjust pH to not less than 4.0 and not more than 6.0, whereby the sulfuric acid acidified wastewater is separated into a dealuminized solution and an aluminum precipitate; a step wherein a slurrying solution is added to the aluminum precipitate to form a slurry, then an alkali is added to adjust pH to not less than 9.0 and not more than 9.5, whereby an pH-adjusted aluminum precipitate slurry is formed; a step wherein an alkali is added to the dealuminized solution to adjust pH to not less than 8.0 and not more than 9.0; and others.

Abstract: The invention is a method of two-phase anaerobic digestion where monitoring and adjusting the nitrogen status (carbon to nitrogen molar ratio, i.e. C/N molar ratio or total or ammoniacal nitrogen content) enables maintaining optimum conditions during the process. The method improves the use of a variety of feedstock materials or facilitates monodigestion of one feedstock. Especially the introduction of nitrogen rich feedstock materials in the process is amended. A community of hydrolyzing and acidogenic microorganisms in the first phase digester performs ammonification i.e. release of organic nitrogen as ammonia. Nitrogen and phosphorus are removed and recovered from the digestate which then undergoes biogasification in the second phase of the process. Reject water from biogasification can be recycled within the process.

Abstract: An aeration system (10) which feeds air to multiple water basins (12) and method. A plurality of local processor based control modules (208) is provided. Each module controls the operation of a compressor unit (11) to effect functions including changes in compressor power level, thermal control and blow-off during compressor start-up. The compressor units (11) are assembled in systems and each system is allocated to a different basin so that no two compressors (22) provide air to the same basin (12). A plurality of control operations are performed with a central processor (300) wherein the central processor directly controls aeration valves 324 in each basin 12 based on monitored oxygen levels.

Abstract: The object is to provide an activated sludge treatment method whereby production of excess sludge is brought substantially to zero; and a method for upgrading existing waste water treatment equipment, employing this method.

Abstract: Methods and systems are provided for drying wet biosolids to produce a class A biosolids. Generally described, the method of treating biosolids includes drying a wet biosolids in an indirect dryer to produce a partially dried biosolids and drying the partially dried biosolids in a direct dryer in series with and downstream of the indirect dryer to produce a class A biosolids. The indirect dryer and direct dryer may be operated at an average temperature of greater than about 100° C. and may have a total combined residence time of less than about 60 minutes. Also provided are systems for drying wet biosolids including an indirect biosolids dryer and a direct biosolids dryer in series. The methods and systems are particularly effective at reducing the moisture content of the biosolids from greater than 85% to less than 10% by weight.

Abstract: A method is provided for removing BOD and ammonium from wastewater in a mainstream process that includes deammonification. Wastewater including BOD and ammonium is directed to a first sequence batch reactor (SBBR). The wastewater is treated in the first SBBR and in the process nitrite is accumulated such that the wastewater includes a nitrite-to-ammonium stoichiometric ratio that enables anammox bacteria to effectively remove ammonium and nitrite from the wastewater. Thereafter the wastewater is directed the wastewater from the first SBBR to a second SBBR. The second SBBR is operated under anoxic conditions and employs anammox bacteria to remove ammonium and nitrite from the wastewater. In certain embodiments, a pre-denitrification step or process is employed in the first SBBR to remove BOD.

Abstract: A biomass drying system includes a rotary biomass dryer that includes a helically threaded auger shaft rotatably driven by a prime mover, such as an electric motor. No external source of heat is required to dry a wet biomass material that is supplied to an input of the biomass dryer. Instead, the helical threads on the shaft have a variable width, designed to gradually increase the compression applied as the biomass material is advanced through a generally cylindrical bore in the biomass dryer. A variable compression nozzle is disposed at a distal end of the bore and can be adjusted to achieve a desired level of a parameter such as the moisture content of the dried biomass material produced by the system. The variable compression nozzle, which can be automatically controlled, includes longitudinally extending segments that are forced radially inwardly to increase the compression force applied to the biomass material.

Abstract: A system and method includes an aeration subsystem that excites enzymes in the liquid waste passing through the septic system. The aeration subsystem includes a compressor section that compresses the liquid waste and an injector section that injects oxygen into the compressed liquid waste. The system further includes a driver subsystem for driving the compressor section and a control subsystem for activating and deactivating the driver subsystem.

Abstract: A process and an apparatus for low-emission storage of biodegradable materials by means of aeration, without aerobic conditions materializing in the material, permits a more consistent feed of the downstream stages in the process. Aeration inhibits methanogenesis and the risk potential of an explosive gas mixture forming in the storage vessel or in the components of the system exhausting waste gas. Closed loop control of the aeration adapts the rate of aeration to the biological activity in the stored material and minimizes air input so as to minimize the loss of methanogenesis potential by aerobic conversion of the matter whilst minimizing the energy required for aeration. The process is characterized in that controlling the aeration in the storage vessel inhibits relevant methanogenesis.

Abstract: By acidifying manure, emissions of methane gas and ammonia gas are prevented significantly. The method for the acidification of manure is provided by an acidic flow of an anaerobic digestion device and/or the flow of sulphuric and/or sulphurous acid from a device that removes hydrogen sulphide gas from biogas from an anaerobic digestion device by chemical and/or biological oxidation to sulphuric acid. When manure is digested, acidification has the advantage that more methane is formed in the digestion process by the prevention of the formation of methane by acidification in the storage process, the advantage that the part of ammonia that would be emitted as a gas is now stored as a nitrogen mineral in the digested manure for use as fertilizer, and the advantage is that the manure has a pH value that is more preferable for digestion processes in the case the manure will be digested.

Abstract: A system and method for ozone vent gas reuse is provided. The disclosed system and method involve controlling or conditioning the ozone vent gas stream or degassing unit vent gas stream and directing the stream to a mechanically agitating contactor in an aerobic section of the wastewater treatment system. The oxygen content of the vent gas stream is controlled so as to ensure sufficient oxygenation to the aerobic section of the wastewater treatment system. Control may be effected by adjusting the oxygen content of the vent gas stream in response to sensor or measurement inputs characterizing the gas contents of the vent gas stream or the dissolved oxygen levels. The volumetric flow of the vent gas stream to the aerobic section may also be controlled by adjusting the rotational speed of the mechanically agitating contactor in an aerobic section of the wastewater treatment system.

Abstract: The invention relates to a method of treating wastewater, and includes capturing carbon dioxide and oxygen produced during treatment of the wastewater by a wastewater treatment system, and using the captured carbon dioxide and oxygen to promote the growth of algae contained within the wastewater treatment system.

Abstract: In a wastewater treatment plant using methane gas, a by-product of anaerobic sludge digestion, to generate energy in a combustor to run the plant, a system for collecting the gas stream from the plant biological process and feeding the gas stream, containing nitrous oxide emissions, into the combustor. The nitrous oxide is thermally reduced down to nitrogen (N2) and oxygen (O2).

Abstract: A method and system for treating domestic sewage and organic garbage are provided. The method comprises the steps of: multi-phase separation, retting, generating sewage gas, and optional biological denitrification and dephosphorization, which can convert the domestic sewage and organic garbage into clear water, sewage gas, organic manure and sludge. The system comprises a multi-phase separation device, a retting device, a sewage gas generating device and a biological denitrification and dephosphorization device, which can treat the domestic sewage and organic garbage effectively and environmental friendly to achieve a reduction in pollution emission.

Abstract: The invention concerns a method for purifying wastewater loaded with organic matter, said method including: a step of contacting wastewater with a biological culture containing a purifying biomass and a step of separating performed by filtration through organic or inorganic membranes. The invention is characterized in that at least part of the biological culture is subjected to an oxidative stress step enabling a liquor to be obtained by the action of at least one oxidizing agent used in small amount so as to preserve the biological activity of the purifying biomass while modifying the microbial floc to make it denser.

Abstract: A method and apparatus for reducing the footprint of chemical/mechanical/biological wastewater treatment facilities employing sulfur dioxide disinfection and chemical dewatering of solids in conjunction with an environmental biological systems for treating the separated treated wastewater.

Abstract: This invention is a new and useful method for controlling the temperature and biodegradation rate of an anaerobic or aerobic landfill or other enclosed or partially enclosed waste mass. The heat generated by a waste mass is carried away by air and moisture within the air resulting from evaporation of liquid within the waste mass as air passes through the waste mass. With the invention, the resulting exhaust gases are passed through a system acting as a heat exchanger and an exhaust gas director.

Abstract: The present invention relates to a method for cleaning waste water, particularly for the continuous cleaning of waste water in the paper industry, wherein oxygen or an oxygen-containing gas and waste water to be cleaned are delivered to an aerobic reactor, the waste water is brought into contact with aerobic microorganisms in an aerobic reactor in order to degrade impurities contained in the waste water, and the cleaned waste water is delivered out of the aerobic reactor. At least a part of the waste water undergoes a pressure release flotation step before being fed into or after being delivered out of the aerobic reactor for the purpose of at least partial softening. In addition, the present invention relates to a device suitable for carrying out the method according to the invention.

Abstract: Provided herein are methods and system for the production of biogas, U.S. Environmental Protection Agency classified Class A Biosolids, and pathogen reduced organic liquid fertilizer. Through the digestion of waste materials using sequential phases in an efficient digestion process, enhanced biomass conversion efficiency and improved output of products (in quantity and/or quality) are obtained with a significant reduction in dwell time in each phase.

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

Abstract: Methods and apparatus for continuing, automated control of wastewater treatment processes. In certain preferred embodiments, method and apparatus for control of aeration in suspended growth biological treatment processes, especially in activated sludge processes.

Abstract: An inclined plate coupled membrane bioreactor for treating feed water having excessive level of nutrients in particular chemical oxygen demand and total nitrogen and suspended solids has an aerobic bioreactor for nitrification and aerobic biodegradation in which membranes are submerged for permeate extraction, and an anoxic bioreactor for denitrification within which the inclined plates are outfitted to confine as much anoxic sludge as possible. An air oxygenating and an air scouring are continuously provided to the aerobic bioreactor to maintain a desired aerobic environment and to mitigate membrane fouling while an intermittent air blowing is provided to the anoxic bioreactor to blow out gaseous content generated through denitrification and to rectify the uniformed flow along the inclined plates. The aerobic sludge is recycled to the lower compartment of anoxic bioreactor and the supernatant of anoxic bioreactor is collected as weir effluent and delivered to the downstream aerobic bioreactor.

Abstract: A system and method for the treatment and reduction of sludge via ozonation in a wastewater treatment process is disclosed. The sludge treatment system comprises: a sludge ozonation reactor coupled to an activated sludge treatment basin and adapted to receive a liquid stream of sludge containing biosolids from the activated sludge treatment basin. The sludge treatment system also includes an ozone-enriched gas injection system operatively coupled to the reactor and adapted to inject ozone-enriched gas into the liquid stream at or upstream of the sludge ozonation reactor. The sludge ozonation reactor is configured to allow effective gas-liquid contacting between the ozone-enriched gas and the liquid stream so as to oxidize the biosolids in the liquid stream and initiate bacterial cell lysis thereby reducing the biosolids. Upon reduction of the biosolids, the liquid stream is returned via a return line to the activated sludge basin or other discharge point.

Abstract: The present invention has an object to provide a biomembrane filtration apparatus which can treat a nitrate nitrogen and nitrite nitrogen in an anaerobic state to stably remove them together with SS with efficiency and, simultaneously, can biologically remove the residual hydrogen donor as well remaining in the water to be treated in one and the same biomembrane filtration apparatus by a fixed bed biomembrane filtration method and a method therefore. As the means to achieve such an object, one embodiment of the present invention provides a biomembrane filtration apparatus having a packed layer packed with a particulate packing material to which microorganisms are to attach; an inlet for a liquid to be treated arranged above the packed layer to feed the liquid to be treated; and a gas feed opening arranged under the packed layer to feed a substantially oxygen-free gas or a gas containing trace amounts of oxygen.

Abstract: Removal of oxidized contaminants from water. Perchlorate and other oxidized contaminants are reduced and removed from water with a method using a primary electron acceptor.

Abstract: A wastewater treatment plant includes (i) an aeration vessel having a bottom portion, a top portion and a side portion disposed therebetween to hold a quantity of wastewater, the top portion and the bottom portion being disposed at least 20 feet apart from one and the other to define a depth, the depth being capable of being substantially filled with wastewater; (ii) a coarse bubble diffuser disposed proximal to the bottom portion, the diffuser having a plurality of orifices orientated horizontally toward the side portion; the orifices having a diameter of at least 0.125 inches; and (iii) a source of enriched oxygen gas in fluid communication with the diffuser; wherein the enriched oxygen gas exiting the orifices prevents settling of solid components of the wastewater without the use of a mechanical mixer. Further, the depth of the aeration vessel may be at least about 20 feet or deeper, for instance at least about 30 feet or deeper.

Abstract: The present invention relates to a lagoon partitioned for hog waste treatment, and the method of waste treatment in said lagoon. More particularly, the present invention relates to a lagoon for hog waste, which is partitioned into zones separated by walls, comprising a first zone for storing and settling hog waste, a second zone for carrying out sequence batch reaction onto the supernatant from the first zone, a third zone for storing processed liquid materials from the second zone, and a fourth zone for fermenting the solid materials from the first and second zones, wherein a passageway with a pump is installed between the respective two zones for transference of solid and liquid waste materials.

Abstract: An improved method for the aerobic thermophilic treatment of organic material of the type in which air is passed through organic matter contained in a reactor, in which at least a portion of the air that has passed through the organic matter in the reactor being captured and again passed through the organic matter.

Abstract: Devices, systems and methods for filling and processing microfluidic devices are disclosed. A device of the system comprising a priming block is disclosed, that functions to drive fluid into a plurality of separation networks in a microfluidic device, using air pressure or electromotive force. The priming block may be incorporated into a microfluidic device preparation system additionally comprising a platform for positionally holding the microfluidic device and a sample array and fluid dispensing modules that are movable in any direction relative to the platform of the microfluidic device. The preparation system may be further incorporated into a greater system that performs processing functions either preceding or following the preparation system, including sample array preparation, and processing and analysis of the samples contained in the prepared microfluidic devices. Methods for operation of the various components of the disclosed systems are also provided.

Abstract: An anaerobic process in accordance with the present invention includes the step of digesting an organic substrate in a first anaerobic reactor to provide reactor contents comprising solids and liquid products of digestion. The process also includes a step of removing a portion of the reactor contents, and a step of pasteurizing all or part of the removed reactor contents by direct contact with a hot or inhibitory fluid to cause pathogen destruction. The fluid may be in a gaseous or liquid phase and the fluid may have inhibitory effects which causes the organisms to undergo lysis.

Abstract: An improved method for the aerobic thermophilic treatment of organic material of the type in which air is passed through organic matter contained in a reactor, in which at least a portion of the air that has passed through the organic matter in the reactor being captured and again passed through the organic matter.

Abstract: A system and method for treating farm animal waste, such as hog and poultry waste, to remove volatile organic compounds (VOCs) from wastewater treatment pits and thus control smell is disclosed. The farm animals are housed in structures equipped with grated flooring to permit animal waste to fall into pits or reservoirs below. The pits contain water inoculated with a special assemblage of natural microbes to which oxygen is supplied through piping arranged in the pits. These special microbes have an affinity for ammonia and convert much of the animal waste into carbon dioxide, fatty acids, and water. The system also includes a second piping network situated beneath the grated flooring which serves to create a negative air situation by which escaping foul-smelling air is pulled back into the wastewater to permit further action on the VOCs by the microbes in the water.

Abstract: Process for recovering and reusing effluent gas from an ozonization reactor in a plant for treating effluent, especially sewage, which includes a biological reactor, a clarifier and an ozonization reactor. The effluent gas from the ozonization reactor is brought, as a cocurrent, into contact with a stream of water containing compounds that can be oxidized by the ozone, so that the residual ozone is removed and efficiently consumed. The effluent gas thus stripped of the residual ozone is then, optionally, pressurized using a fluid taken from the plant so as to produce a gas/liquid mixture. The gas liquid mixture is converted into an emulsion of fine bubbles, and the emulsion is introduced into the biological reactor, preferably near the bottom of the latter.

Abstract: A process is described for the aerobic treatment of effluent in a reactor of the UASB type, into the bottom of which the effluent to be treated is fed and, at the same time, oxygen is fed in an amount such that the growth of a facultative and an aerobic biomass is promoted. An apparatus for the aerobic treatment of effluent is also described, which apparatus consists of a UASB rector, distributors for supplying liquid and aeration means being located at the bottom of the reactor and means for integrated settling of biomass and gas collection being located at the top of the reactor. The apparatus can also be an integrated anaerobic/aerobic reactor.

Abstract: A nutrient concentrate for stimulation of growth for the accelerated cultivation and growth of hydrocarbon-consuming microorganisms as well as a process for their use in bioremediation is disclosed. The concentrate is an admixture of water-soluble and/or oil-soluble compounds of phosphorus (P) and nitrogen (N) and other components. The concentrate is in the form of a liquid water-based preparation and contains an ester of phosphoric acid as both an emulsifier and a P source. Further, from 10 to 40% by weight urea is contained in the concentrate as a N source. The invention also relates to the treatment of polluted soils, waters, and articles using a diluted aqueous solution of the concentrated admixture.

Abstract: A starting mixture of liquid and solid organic wastes that is susceptible to at least partial microbiological degradation, with formation of biogas, is treated by the following process. The mixture is mechanically separated into a first sludge phase with enriched dry substance and a first liquid phase containing dilute solids. The first liquid phase is subjected to anaerobic treatment leading to formation of biogas and to the development of a second sludge phase and a second liquid phase. The first sludge phase is subjected to aerobic treatment resulting in the formation of compost, fertilizer, or feed. At least part of the second sludge phase is recirculated into the starting mixture, thereby causing the formation of biogas in the starting mixture and facilitating decomposition of higher compounds contained in the starting mixture.

Abstract: A system for thermophilic aerobic destruction of pathogenic organisms and organic matter within waste water treatment sludge includes a tank for maintaining the sludge and an air transfer apparatus for injecting air into the sludge near the bottom thereof so as to bubble up through the sludge and react exothermically with the thermophilic microorganisms therein so as to kill or destroy the mesophilic micro- organisms within the sludge. The thermophilic reaction is preferably controlled within a desired temperature range by control of the flow of fresh air versus recycled air being injected into the sludge. The fresh air to recycle air ratio can be controlled by several different mechanisms so as to produce the desired temperature range. The air is also utilized to mix the sludge within the tank. A pumping apparatus is also provided for transferring sludge into and out of the tank and for recirculating the sludge for purposes of auxiliary mixing.