Abstract: A sewage treatment apparatus including a treatment tank with a floor, walls and having an upper aperture. A hopper having a clarifier chamber is centrally disposed in the treatment tank, maintained at a predetermined height above the treatment tank floor by hopper supports. A deflector cone is centrally disposed on the floor of the treatment tank, its vertex being received in the lower aperture of the hopper. The exterior of the hopper, the deflector cone and the inner walls of the treatment tank define an annular aerator chamber, subdivided into a plurality of aerator zones. Diffusers disposed in each aerator zone introduce oxygenation of and induce flow of sewage in the treatment tank. A cover mounted over the treatment tank aperture maintains a pressurized pocket of air above the sewage for increased oxygenation of the sewage. Treated sewage passes from the aerator zones into the clarifier chamber, then into the environment.

Abstract: A wastewater treatment system has at least one treatment chamber and at least one settling chamber. An influent conduit connects the treatment chamber to a source of wastewater. A pump is provided for transferring treated wastewater, the treated wastewater being a water/biomass mixture, from the treatment chamber to the settling chamber by way of a transfer conduit. An effluent conduit removes treated wastewater from the settling chamber. A treatment system is provided for treating water in the treatment chamber. A biomass conditioner in the transfer conduit conditions the biomass by removing energy from the water/biomass mixture.

Abstract: An activated sludge process for reducing the amount of N.sub.2 O released to the atmosphere during biological oxidation of NH.sub.3, includes the following steps: mixing wastewater influent containing NH.sub.3 and BOD with activated sludge to provide a mixed liquor in a first enclosed aerobic treatment zone wherein an oxygen containing gas is introduced, the first enclosed aerobic treatment zone having two or more stages in which gas and liquor phases are staged and oxygen is transferred to the liquid phase and BOD is metabolized and NH.sub.3 is oxidized to NOx and N.sub.2 O, wherein the pN.sub.2 O is maintained at a level greater than 2 mm Hg; transferring the mixed liquor and gas to a second enclosed treatment zone having two or more stages, in which gas and liquid phases are staged, and wherein NOx and N.sub.2 O are reduced to N.sub.

Abstract: In the embodiments of the invention described in the specification, an arrangement for biological treatment of wastewater includes a basin with an aeration region and a clarification region separated by a movable wall having a passage between the bottom of the wall and the bottom of the basin. The aeration region includes a plurality of diffuser arrangements for aerating the wastewater and the clarification region includes a sludge removal duct and at least one turbulence generator for periodically stirring up sludge particles which have been deposited on surfaces of the clarification region remote from the sludge removal duct and recirculating sludge through the wall passage to the aeration region and permitting sludge to resettle on surfaces closer to the sludge removal duct. The movable wall may be positioned to include one or more diffuser arrangements from the aeration region within the clarification region.

Abstract: A process for the treatment of aqueous effluent with a view to its purification, the process including at least one stage consisting of causing the water to pass into the interior of at least one battery of several biological filters with fixed cultures or other devices with fixed cultures operating in parallel, characterized in that it comprises supplying the filters at constant flow and to cause the number of filters supplied and the number of filters not supplied in the battery, to be varied, in accordance with the total flow of aqueous effluent to be treated. Such a process allows the performance of biofilters and other devices with fixed cultures to be improved.

Abstract: This invention refers to an original solution for the purification of contaminated water streams with the activated sludge method, involving: a) a two-stage aeration system operating at high rate and low rate conditions respectively, where the first stage operates in anoxic conditions promoting denitration, whereas the second stage operates under oxidant conditions so that nitrates are removed to an extent of 70%; b) a system for moving the biological sludge, where the sludge produced in the first aeration tank is totally rejected, and that produced in the second aeration tank is recycled to the first.

Abstract: An integral activated sludge wastewater treatment system has a vessel having at least one internal baffle dividing the vessel into at least one treatment chamber and at least one settling chamber. The settling chamber is at least partially defined by a first wall of the baffle. The treatment chamber is at least partially defined by a second wall of the baffle. A recycle pump is provided for recycling aerated wastewater from the treatment chamber back into the settling chamber and inducing a downward sludge velocity in excess of the velocity that would be caused by gravity alone.

Abstract: A process for removing nitrocresols in a crude aqueous alkaline dinitrotoluene wash stream derived by nitration of toluene using a mixed acid technique followed by treatment with aqueous alkaline material in which the crude aqueous alkaline dinitrotoluene wash stream is mixed with a dilute oxidizing acid such as nitric acid, heated to 130.degree. to 180.degree. C. for a period of time required to reduce the nitrocresols to a level at which it does not precipitate from the mixed acidic wash stream at temperatures above about 60.degree. C., and removing the remaining nitrocresols by conventional methods such as adsorption or activated sludge biotreatment.

Abstract: The invention concerns a process for increasing the purification yield in the activation tank of a station for the purification of waste waters employing the so-called "activated sludge" process. According to the invention, talc, pyrophyllite, kaolin or mica, possibly cationized, are added to the biomass, these having a particle size less than 100 .mu.m in quantities of up to 2.0 g per liter of waste waters. A great improvement in solid/liquid separation is observed at the outlet from the activation tank as well as an increase in the purification yield for carbonaceous pollution, nitrogenous pollution and phosphate-containing pollution even when the station operates at medium or high load.

Abstract: A system for treating wastewater wherein the need for the addition of an external carbon source during the denitrification step is reduced or eliminated. In accordance with the system, the centrate is removed from the centrifuge at the end of the treatment process and is fed back into the denitrification zone, where it serves as a carbon source during the denitrification reaction. By eliminating the need for an external carbon source, the operating costs of the system are dramatically reduced. Furthermore, since the centrate is not fed into the wastewater stream entering the plant and is therefore not subjected to unnecessary processing, the process is more efficient than existing methods.

Abstract: A wastewater treating apparatus has first, second and third bioreactors. Each bioreactor has, in an upper position, a reaction/sprinkling portion for exhaust gas treatment. The first bioreactor has, in a lower position, a submerged portion including an aerobic upper portion and an anaerobic lower portion. The aerobic upper portion includes a membrane filter. A membrane concentrated liquid produced by the membrane filter is introduced into a mixing tank. A mixture of an alcohol, fine powdered material and membrane concentrated liquid from the mixing tank is introduced, together with a developer-containing wastewater, into the anaerobic lower portion, so that a granular sludge is formed therein. The granular sludge contains anaerobic microorganisms in a high concentration level and is therefore capable of treating the wastewater without necessity of wastewater dilution or use of chemicals.

Abstract: A system for purifying a liquid including a reactor and a clarifier with the clarifier arranged at an elevated position relative to the reactor so that residue from the clarifier can be returned to the reactor hydrostatically. Liquid in the reactor is aerated using an agitating means with the agitating means also used to transfer liquid from the reactor to the clarifier. The liquid is fed to the clarifier at a constant, controlled rate.

Abstract: The present invention relates to modified glass fiber membranes which exhibit sufficient hydrophilicity and sufficient electropositivity to bind DNA from a suspension containing DNA and permit elution of the DNA from the membrane. Generally, the hydrophilic and electropositive characteristics are expressed at the surface of the modified glass fiber membrane. Preferred modified glass fiber membranes of the present invention include glass fiber membranes that have been modified by treatment with trifluoroacetic acid (TFA), BCl.sub.3, SiCl.sub.4, NaOH, F.sup.-, AlCl.sub.3 alone or in combination, with or without water. The modified glass fiber membranes of the present invention are particularly useful in processes for purification of DNA from other cellular components.

Abstract: A process for biologically removing nitrogen and other nutrients from wastewater using recycled activated sludge. A mixed liquor is formed from influent wastewater and recycled activated sludge and then treated in two successive nitrogen removal stages, each stage having an anoxic denitrification zone and an aerobic nitrification zone. The first nitrogen removal stage entails circulating the mixed liquor back and forth between the anoxic zone and the aerobic zone. The mixed liquor is then transferred to a final clarifier where activated sludge is separated from purified supernatant. To increase the NO.sub.x.sup.- reducing enzymatic activity of denitrification microorganisms, the activated sludge is retained in the final clarifier for a time period sufficient to permit adaptation of these microorganisms to a nitrate/nitrite-respiring metabolic pathway.

Abstract: An automated wastewater treatment miniplant intended for installation and use with individual residences. Wastewater such as raw sewage is received in a settling tank to remove suspended solids, and then flows to an intermediate tank where the sewage is aerated and churned to promote aerobic treatment of organic materials in the sewage. When the wastewater in the intermediate tank reaches a predetermined level, a batch of that wastewater is transferred to an aerator-clarifier tank where further aerobic treatment of the batch wastewater occurs under controlled conditions, without dilution with incoming wastewater. Further aerobic decomposition of the wastewater takes place in the aerator-clarifier tank. Sludge is allowed to settle in that tank, and supernatant liquid within that tank is periodically withdrawn for dispersal in a drain field. Sludge is periodically returned to the intermediate tank to augment the biomass in that tank. Some sludge is periodically wasted from the system.

Abstract: An improved apparatus for treating waste mixed liquor comprising a long vertical downcomer chamber; an adjacent long vertical riser chamber; a surface basin; said downcomer chamber and said riser chamber operatively communicating directly with each other at their lower ends and through said basin at their upper ends to form a circulatory loop; means for injecting an oxygen-containing gas in said downcomer and riser chambers at depth; a flotation-sedimentation vessel adjacent said surface basin; a first waste liquor influent conduit opening into said riser chamber at depth and operatively communicating with said vessel to provide a first waste liquor influent from said vessel to said riser chamber; a treated liquor effluent first conduit opening into said riser chamber and operatively in communication with said vessel to provide a treated waste liquor first effluent to said vessel from said riser chamber; the improvement comprising a treated waste liquor effluent second conduit having an inlet opening into sai

Abstract: In the aeration reactor described in the specification, an aeration basin has two aeration cells separated by a dividing curtain and connected in series so as to normally receive wastewater in the first aeration cell and then pass the wastewater to the second aeration cell which is followed by a clarifier to separate sludge from the treated wastewater. A liquid level detector in the reactor responds to surges in the rate of flow of the wastewater through the reactor to redirect incoming wastewater and return sludge from the first aeration cell into the second aeration cell and isolate the first aeration cell to preserve active sludge in that cell.

Abstract: A process for purifying waste water containing sulphide, comprises oxidizing the sulphide to elemental sulphur in a reactor with sulphide-oxidizing bacteria in the presence of oxygen, and separating from the waste water at least a part of the sulphur formed during the oxidation, while recycling a part of the elemental sulphur separated from the reactor effluent into the reactor in such a way that a concentration of elemental sulphur of at least 1 g/l is maintained in the reactor. The sulphur, in the form of aggregates, is used as a carrier material for the sulphide-oxidizing bacteria.

Abstract: Methods and apparatus for treating waste streams utilize controlled introduction of microscopic gaseous bubbles to create, in a single vessel, as many as three separate biological environments in discrete, stratified zones. In preferred embodiments, bubbles of air are introduced at the bottom of the vessel, creating an aerobic zone in this vicinity. Depletion of oxygen by microorganisms resident in this layer creates an anoxic zone that drifts upward, establishing itself above the aerobic layer. The two layers remain segregated due to the intolerance of aerobic microorganisms for the overlying anoxic environment, the sharpness of the interface depending on the degree of intolerance.

Abstract: In a process for dehydration and concentration of sewage sludge containing activated sludge with the aid of organic and/or inorganic flocculators, the activated sludge content is produced in an aerated biological purification stage in presence of a composition containinga) folic acid and/or dihydrofolic acid or at least one ammonium, alkali metal, alkaline earth metal and/or alkanolammonium salt thereof andb) a water-soluble molybdenum compound,whereby an improved sludge dehydration of the activated sludge content is achieved.

Abstract: A nocardia foaming controlling method of waste water treatment includes a step of injecting cationic polymer to a retention activation sludge line within the final clarifiers of the traditional waste water treatment process. When polymer is returned along with retention activation sludge to the aeration basins, the polymer's hydrophilic nature reduces the surface tension created between air bubbles and nocardia enriched floc. This allows nocardia to pass through the aeration basins, to eventually escape the treatment system.

Abstract: This invention is directed to an activated sludge treatment process for removing phosphorus and nitrogen from wastewater. The process includes providing wastewater influent and activated sludge in a stressed contact zone to form a mixed liquor. In a luxury contact zone, the mixed liquor is mixed and aerated and the organisms in the activated sludge take up at least portion of the phosphorus. The method further includes separating the activated sludge from the mixed liquor, and returning at least a portion of the activated sludge to the stressed contact zone. The inventive process accomplishes wastewater treatment without having to pass the wastewater through an anaerobic zone.

Abstract: Waste water is treated by an activated sludge process, the equipment for which is provided with an aeration tank unit comprised of three tanks of a first tank, a second tank and a third tank, said waste water and microorganisms being fed into the first tank while the ratio of aeration in the first tank ranges from 0.5 to 0.8 by volume/minute relative to the amount of liquid in the first tank, the ratio of aeration in the second tank ranges from 0. 1 to 0.4 by volume/minute relative to the amount of liquid in the said second tank and the ratio of aeration in the third tank ranges from 0.1 to 0.3 by volume/minute relative to the amount of liquid in the third tank, the improvement which comprises carrying out said treatment by passing air containing ozone in an amount of from 0.01 to 0.16 wt. % relative to the amount of oxygen during the aeration into the first tank.

Abstract: A method is disclosed for using the simple, environmentally-friendly organic compounds gamma-butyrolactone and benzyl alcohol to develop and to strip free radical-initiated, addition polymerizable resists, cationically cured resists and solder masks and Vacrel photoresists. In all cases the developers and strippers include gamma butyrolactone or benzyl alcohol. The developers and strippers optionally also include a minor amount of methanol, ethanol, isopropyl alcohol, propylene glycol monomethylacetate, ethylene glycol monomethyl ether, formamide, nitromethane, propylene oxide, or methyl ethyl ketone, acetone and water. During development of the photopatterned resist or solder mask, the unpolymerized regions are dissolved in the disclosed developers. During stripping of the resist or solder mask, the polymerized regions are debonded from a circuit board in the disclosed strippers.

Abstract: A wastewater feed containing an ultimate BOD/COD ratio >0.6 is well-suited for especially acclimated thermophilic and/or caldo-active living micro-organisms ("hot cells") which thrive in an autothermal aerobic (ATA) reaction zone having an ATA bioreactor ("ATAB") operating at substantially ambient atmospheric pressure in combination with a MF or UF membrane filtration device from which a solids-free permeate may be withdrawn. This combination, of ATAB and membrane device is a "membrane bioreactor" (ATA MBR), which operates autothermally with a feed containing biodegradable organic materials having a BOD of at least 5,000 mg/L, preferably at least 10,000 mg/L (10 g/L) with a minor portion of "municipal" wastewater or domestic sewage. Operation of the ATAB, preferably in the thermophilic range from 45.degree. C.-75.degree. C., with constant HRT from 1 to 12 days, is contingent upon maintaining a stable population of live hot cells.

Abstract: The present invention provides apparatus and method for increasing the wastewater treatment capacity of an existing pond treatment facility wherein the facility includes at least one treatment pond and means for bringing influent wastewater to the pond. Apparatus according to the present invention includes a porous baffle placed into the pond so as to separate the pond into two separate and distinct, but fluidly connected portions. The baffle thus divides the pond into a first portion for treatment of biological solids in the wastewater with the use of concentrated bacteriological growth and a second portion which provides a reservoir to accommodate high rates of wastewater flows and organic loads such as will occur with storm water flow.

Abstract: A biochemical process system and apparatus for removal of toxic volatile organic compounds (VOCs), volatile inorganic compounds (VICs), heavy metals, and surfactants from contaminated soil, liquid and gas streams, by means of combined washing, pH adjustment, biochemical reaction, gas stripping, scrubbing, adsorption and regeneration is described. This process system involves soil washing with surfactant, soil-water separation, liquid pumping; liquid treatment using an enclosed gas stripping bioreactor and dissolved air flotation technology; gas purification using a foam collector, a wet scrubber and a self-regenerative gas-phase granular activated carbon (GAC) contactor; and recycling of GAC-purified gas for further liquid treatment by gas stripping and biochemical reactions. The process system is extremely cost-effective for removal of both volatile and nonvolatile pollutants from a contaminated site and eliminates the problem of secondary gas contamination caused by conventional air stripping towers.

Abstract: A cyclical process for degrading waste organic matter to gaseous products and substantially zero volume of solid matter by subjecting the waste alternately and cyclically to stages of mesophilic and thermophilic digestion in which the organisms from one stage are inactivated and become a substrate for the organisms in the next stage, this inactivation resulting from a temperature shift. At the end of the cycle, solids are collected and returned to the first microbial digestion stage for recycling together with a fresh input of waste.

Abstract: A method for preventing activated sludge from losing its settling ability, which sometimes happens in solid/liquid separation in an activated sludge treatment of an aqueous organic waste and causes the so-called bulking and scumming of the sludge. This method involves adding either (a) a nonionic and/or an anionic surfactant, (b) a combination of a nonionic surfactant with a cationic surfactant of a form of quaternary ammonium salt or (c) a combination of a nonionic surfactant and a cationic surfactant of a form of a quaternary ammonium salt with a cationic organic flocculant, to the activated sludge treatment system.

Abstract: The present invention entails a nitrification-denitrification wastewater treatment process where nitrification and denitrification is carried out in three separate treatment basins. First, wastewater influent is directed from a supply line into a first basin where the wastewater is subject to denitrification. Wastewater held in a second basin is subjected to nitrification while the influent wastewater is directed into the first basin. Effluent from the first basin that is being filled is directed directly to a third basin which performs both denitrification and nitrification at various times during the total process. Purified wastewater from the third basin is directed to a clarifier which separates activated sludge from the purified wastewater and the activated sludge is returned and mixed with the influent wastewater. After a selected time period the influent wastewater being directed to the first treatment basin is switched to where the wastewater influent is now directed into the second treatment basin.

Abstract: A method for controlling and/or optimising a process in which a biological system comprising mixed cultures of microorganisms, biodegradable material, one or more biogenic fluorophores and optionally other soluble and/or insoluble and/or suspended substances in an aqueous environment is subjected to one or several separation processes and/or to chemical reactions and/or to biological treatment so as to obtain as a final product purified water which has a substantially lower content of biodegradable matter than the biological system, which method comprises monitoring the microbiological activity of the biological system and/or fluctuations thereof by on-line measurement of fluorescent emission and/or variations therein for at least one of the fluorophores in the system when irradiated with light and controlling one or several parameters of the process by using results from the measurement as measured variable(s) in an on-line automatisation system.

Abstract: The specification discloses a process and apparatus for the purification of wastewater in several successive stages wherein the wastewater is aerated in a first region and is then subjected to intermediate clarification in a second region and including a post-clarification aeration in a third region and post-clarification sedimentation in a fourth region.In order to provide a simple, space-saving, low-cost yet reliable wastewater treatment arrangement, the apparatus is arranged to include all four regions in one basin by providing separating walls in the basin. These regions can be preceded by other processing stage regions and followed by filtering or storage regions.In order to allow adjustment for varying loads and for changing relationships between hydraulic and biochemical loads, the separating walls between the regions are arranged to be movable to permit changes in the relative volumes of the regions.

Abstract: Disclosed is an improved method for oxygenation of liquid waste. The method comprises drawing a low pressure stream of liquid waste from a liquid waste tank and introducing an oxygen-containing gas thereto to provide a mixture of liquid waste and gas. Thereafter, the mixture is pumped into a high pressure stream wherein the pressure is maintained in the range of 50 to 1000 psig to obtain an oxygen enriched dispersion. The oxygen enriched dispersion is then discharged into the holding tank.

Abstract: A physical-biochemical process system and apparatus for removal of toxic volatile organic compounds (VOCs) and other organics from contaminated groundwater or wastewater is described. This process system involves influent pumping groundwater or wastewater treatment by air stripping, biological oxidation and powdered activated carbon (PAC) adsorption in an enclosed gas stripping bioreactor, air purification by granular activated carbon contactor, and recycling of GAC-purified air for further groundwater or wastewater treatment. The bioreactor effluent is processed processed by a clarifier, a filter and a disinfection unit. The clarifier sludge is partially recycled to the bioreactor and partially wasted. The process system is cost-effective and eliminates the problem of secondary air contamination caused by conventional gas stripping tower and coventional biological treatment processes.

Abstract: A process is provided for the treatment of water containing sulphide wherein the sulphide is oxidized in an aerobic reactor having a minimum sulphide sludge load. The minimum sulphide load is at least 10 mg of sulphide per mg of the nitrogen present in the sludge per hour, the sludge load being calculated on the basis of the sulphide oxidizing part of the biomass. The minimum sulphide load may also be defined as 25 mg of sulphide per liter of reactor material per hour. The sulphide can be largely oxidized to elemental sulphur which is then separated and reused. Waste water also containing organic matter in addition to varying levels of sulphide is purified without interference of filamentous bacteria using a two-step aerobic process. The process for sulphide removal can be used for the treatment of waste water having high levels of sulphur compounds such as sulphate, sulphite and thiosulphate by first reducing these sulphur compounds in an aerobic step.

Abstract: In a two-stage activation plant, part of the activated sludge (sludge circuit (1)) from the first stage (11) is transferred to the second stage (12) and part of the activated sludge (sludge circuit (2)) from the second stage (12) is transferred to the first stage (11), so that mixed biocenoses are formed in both stages (11 and 12). The biomass to be denitrified from the first stage is transferred to the second stage by the sludge circuit (1) and the biomass to be nitrified from the second stage is transferred to the first stage by the sludge circuit (2), so that not only carbon compounds are decomposed but nitrogen compounds may be removed by nitrification and denitrification in both stages (11 and 12).

Abstract: A process for inactivating the biological activity of DNA, especially recombinant DNA, is disclosed. The process includes the step of heating the DNA at 60.degree. to 100.degree. C. in the presence of an acid other than percarboxylic acid at a concentration of at least 0.2 mM and a pH value of maximum 4, preferably 3.

Abstract: Waste water containing biodegradable matter is fed to a rotating biological contactor (RBC) (15) from an inlet tank (10) and is discharged from the RBC-containing chamber into a humus tank (21). The RBC is divided into separated upstream (15A) and downstream (15B) sections, the chamber (17) containing the downstream section being fed with water to be processed at a controlled rate from the chamber (16) containing the upstream section. A balancing chamber, for isolating the downstream section of the RBC from variations in flow of waste water to the inlet tank (10), includes the upstream section (15A, 16) of the RBC which can act sacrificially in respect of toxic incursions in the waste water.

Abstract: The present invention relates to an air emission control system for removing volatile organic compounds (VOCs) and other objectionable contaminants from an emitted gas stream which is generated from a water treatment means. Specifically the improved air emission control system of this invention relates to collecting, dehumidifying, bypassing, diluting, monitoring, purifying recycling and reusing the emitted gas stream, and also relates to feeding an inert gas, upon demand, for reducing oxygen content of said emitted gas stream, in turn, for preventing a gas purification contactor from being ignited and/or exploded due to oxidation of carbonaceous substances inside said gas purification contactor. A complete water treatment and gas emission control system is developed by applying the air emission control system to either single stage water treatment or multiple stage water treatment.

Abstract: A process is provided for the treatment of water containing sulphide wherein the sulphide is oxidized in an aerobic reactor having a minimum sulphide sludge load. The minimum sulphide load is at least 10 mg of sulphide per mg of the nitrogen present in the sludge per hour, the sludge load being calculated on the basis of the sulphide oxidizing part of the biomass. The minimum sulphide load may also be defined as 25 mg of sulphide per liter of reactor material per hour. The sulphide can be largely oxidized to elemental sulphur which is then separated and reused. Waste water also containing organic matter in addition to varying levels of sulphide is purified without interference of filamentous bacteria using a two step aerobic process. The process for sulphide removal can be used for the treatment of waste water having high levels of sulphur compounds such as sulphate, sulphite and thiosulphate by first reducing these sulphur compounds in an aerobic step.

Abstract: A wastewater treatment system is provided which includes (a) two chambers in which microbiological cultures grow aerobically, a first chamber which receives wastewater to be treated and a second chamber which produces activated sludge; (b) a float sludge separator for removing from the system float sludge made with the aerobic culture from the first chamber; and (c) an activated sludge separator for separating activated sludge, which is settleable, and treated wastewater from the aerobic culture in the second chamber. In the system, one portion of the activated sludge from the activated sludge separator is fed to the first chamber, to seed culture growth there, and another portion of the activated sludge is recycled to the second chamber, to seed culture growth there.

Abstract: A process and apparatus is disclosed for treating waste water. After treatment, essentially no sludge remains for disposal. The treatment includes mixing the waste water with activated sludge solids in an aeration tank (15). The mixed liquor from the tank is then moved to a clarifier settling tank (17). About 5-25% of the activated sludge separated in the settling tank is returned to an aerobic digester (23) and treated for about 16-24 hours. The aerobic digester can be a batch unit or a continuous process unit. After treatment in the aerobic digester, the activated sludge solids are returned to the aeration tank (15).

Abstract: The present invention is directed to a method for increasing the capacity of a sewage treatment plant. In the method, oxygen is injected into the recycle sludge stream from the settling tank prior to introducing the recycle sludge stream into the secondary waste water treatment tank.

Abstract: A wastewater treatment system and method is disclosed, including a circular aeration basin and a contiguous annular clarifier channel. Rotational flow of an aerated mixture of untreated wastewater and return sludge is induced in the aeration basin at its periphery with relatively less turbulent flow at the center.A clarifier inlet is fluidly connected to the aeration basin through openings provided in the aeration basin wall, the clarifier inlet including means to dissipate turbulence.A sludge removal manifold extends within the clarifier having valve-controlled suction arms. The spaced suction arms provide for precise control of sludge blanket depth and sludge age independent of rate of sludge return to the basin.Process sludge withdrawn from the clarifier is mixed with raw wastewater and returned to the aeration basin.The relatively less-turbulent flow in the central area of the basin allows process sludge to accumulate in said central area.

Abstract: A process is disclosed for treating wastewater from a polymerization process. The wastewater contains volatile residual monomer, for example acrylonitrile monomer. The method includes the steps of pretreating the wastewater with an amount of oxygenated waste activated sludge to reduce the levels of residual monomer in the wastewater stream in order to reduce the volatilization of the volatile residual monomer into the atmosphere during further treatment of the wastewater stream. Preferably the process involves steps of neutralization, primary clarification, cooling, aeration and secondary clarification to provide a wastewater treatment process that has a minimum of air emissions of residual volatile hydrocarbon monomer and which provides a final treated water effluent that has the desired pH level, temperature, biological oxygen demand and a suspended solids level for emission of the treated water into the environment.

Abstract: A wastewater treatment plant comprising a pretreatment chamber, aeration chamber and a settling chamber designed to minimize or eliminate sludge buildup at the bottom of the aeration chamber. Two support walls are provided. The combined function of one support wall and an angular portion at the bottom of the common wall between the aeration and settling chamber is to regulate the flow pattern in the aeration chamber and return settled biodegradable matter from the bottom of the settling chamber to the aeration chamber for further treatment. The fluid flow created by the wall structure enhances the action of the settling chamber and elinates dead zones in the aeration chamber thus minimizing sludge buildup.

Abstract: In a biological wastewater treatment process including secondary clarification, the improvement comprising monitoring the salinity of the wastewater flowing to secondary clarification and adjusting the salinity of the wastewater flowing to secondary clarification by adding water or by adding salt.

Abstract: In an intermittent aeration activated sludge process in which aeration and agitation is repeated alternately, a first aeration tank and a second aeration tank are connected to each other and an ORP meter is applied to each tank. In the first aeration tank, the sum of an aeration period and a denitrification period of an agitation step is controlled to a predetermined period T.sub.gs based on a time when a bending point appeared on an ORP curve in a previous cycle. In the second aeration tank, the sum of an aeration period and an agitation period is controlled to a predetermined period T.sub.ds longer than T.sub.gs based on a time when an ORP measured value reached a predetermined value in a previous cycle. Operations of the first and second aeration tanks are simultaneously transferred from the agitation to the aeration based on detection of the predetermined ORP value. As a result, a necessary anaerobic condition period is secured in the first aeration tank.

Abstract: The invention is a process for purifying wastewater containing organic and color-causing pollutants. The three unit processes include a first stage aerobic or anaerobic biophysical treatment, a second stage oxidizer treatment, and a third stage adsorbent contact treatment. The biophysical treatment removes the majority of the pollutants while the oxidizer treatment destroys residual organics and color-causing pollutants. The adsorbent contact treatment destroys any residual oxidizer in the wastewater and/or adsorbs any residual oxidation products. The preferred adsorbent is powdered activated carbon and the preferred oxidizer is some form of chlorine, e.g. sodium hypochlorite. The process may be operated in either a continuous flow mode or a batch flow mode.

Abstract: A method of treating photographic processing wastes is disclosed. The method comprises (1) mixing a silver-recovery system waste and a development system waste from photographic processing to produce a waste mixture, (2) adding to said waste mixture phosphorus as a nutritive substrate in an amount corresponding to at least 2% based on the COD value of the waste mixture, and (3) subjecting the resulting waste mixture to a bio-oxidation treatment using microflora containing sulfur-oxidizing bacteria. The method enables a continuously treatment of high concentration photographic processing wastes with high efficiency over a long period of time.