Abstract: A membrane bioreactor system includes one or more biological reactors and one or more membrane tanks with each membrane tank having one or more membrane filters. To control membrane fouling, various process control variables are employed. First, the membrane filters are cleaned by an air scouring process where bubbles are moved upwardly adjacent the membrane filters and clean the same in the process. To control membrane fouling, a process is utilized that dynamically varies the air scouring flow rate (V) as a function of transmembrane pressure (TMP). In addition, the process entails allowing permeation to start and stop which results in a series of cycles where each cycle includes a permeation phase and a relaxation phase.

Abstract: A membrane bioreactor system includes one or more biological reactors and one or more membrane tanks with each membrane tank having one or more membrane filters. To control membrane fouling, various process control variables are employed. First, the membrane filters are cleaned by an air scouring process where bubbles are moved upwardly adjacent the membrane filters and clean the same in the process. To control membrane fouling, a process is utilized that dynamically varies the air scouring flow rate (V) as a function of transmembrane pressure (TMP). In addition, the process entails allowing permeation to start and stop which results in a series of cycles where each cycle includes a permeation phase and a relaxation phase.

Abstract: A wastewater treatment system is provided that includes first and second reactors, each operative to nitrify or denitrify wastewater contained therein. Downstream from the first and second reactors is a membrane reactor that operates under aerobic conditions and includes one or more submersed membranes for separating solids. Extending between the membrane reactor and each of the first and second reactors is a return activated sludge line with appropriate controls for permitting return activated sludge to be directed to one of the reactors at a time. To nitrify and denitrify wastewater, a wastewater influent stream is alternatively directed to the anoxic reactors which are alternatively operated under aerobic and anoxic conditions so as to nitrify or denitrify the wastewater contained therein.

Abstract: A multi-phase process for removing phosphorus from wastewater in a triple ditch or triple basin system where wastewater influent is sequentially directed to each of the three basins or ditches, sometimes referred to as first and second outer basins and an intermediate basin. During each phase of the process, the mixed liquor in at least one of the basins is subject to settling. In one or more phases of the process, the mixed liquor, in certain basins, is subjected to anaerobic and aerobic treatment. Anaerobic treatment results in the growth or proliferation of phosphorus storing microorganisms. These phosphorus-storing microorganisms take up phosphorus when the mixed liquor is subjected to aerobic conditions. One of the basins, the intermediate basin, can be designed to have a volume greater than either of the first or second outer basins. Further, the triple basin or triple ditch system is designed to transfer mixed liquor suspended solids or biomass from one basin to another.

Abstract: A multi-phase process for removing phosphorus from wastewater in a triple ditch or triple basin system where wastewater influent is sequentially directed to each of the three basins or ditches, sometimes referred to as first and second outer basins and an intermediate basin. During each phase of the process, the mixed liquor in at least one of the basins is subject to settling. In one or more phases of the process, the mixed liquor, in certain basins, is subjected to anaerobic and aerobic treatment. Anaerobic treatment results in the growth or proliferation of phosphorus storing microorganisms. These phosphorus-storing microorganisms take up phosphorus when the mixed liquor is subjected to aerobic conditions. One of the basins, the intermediate basin, can be designed to have a volume greater than either of the first or second outer basins. Further, the triple basin or triple ditch system is designed to transfer mixed liquor suspended solids or biomass from one basin to another.

Abstract: A Method of treating sludge prior to dewatering by mixing with the sludge a cationic metal in the form of an iron or aluminum slat along with a cationic polymer. The addition of the iron or aluminum salt substantially reduces the amount of polymer required for acceptable dewatering, thusly significantly reducing the cost of the dewatering process. The method is enhanced by subjecting the prior digested sludge to mesophilic aeration prior to the cationic metal salt and polymer being added.

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: Abnormally lowered reduction in the rate of phosphorus removal from influent wastewater in an activated sludge system, occurring particularly following periods of increase in flow rate of wastewater entering the system, is avoided by controlling the maximum F/M in that portion of the system in which oxidation is occurring so as not to exceed 0.9 and maintaining a defined relation between the maximum and minimum F/M during any 24 hour operating period.

Abstract: The problem of rising sludge in biological wastewater treatment secondary clarifiers is overcome by minimizing entrainment of nitrogen gas with mixed liquor entering the transfer pipe to the clarifier such that the level of dissolved nitrogen in the biomass settling in the clarifier remains less than that in equilibrium with nitrogen gas at the pressure prevailing in the biomass. This invention is most efficacious in cases where soluble oxides of nitrogen are present and are reduced by the biomass to elemental nitrogen. In accordance with one described embodiment the excess nitrogen is removed by degassing of the mixed liquor in the effluent pit of the system by deepening and widening the usual pit in such manner that the rate of descent of mixed liquor therein to a discharge outlet is less than 0.4 feet per second and the depth is greater than 4 feet, thus permitting the gas-containing macrobubbles to rise to the surface of the pit where these are degassed.

Abstract: The present invention provides for an improved method of operating an activated sludge system whereby a significant amount of ammoniacal nitrogen is removed in the BOD sorption zone, which does not later appear in the system as protein or NOX. The improved method for achieving said ammoniacal nitrogen removal comprises decreasing the ammoniacal nitrogen concentration of the mixed liquor in the oxidation zone to a point where the mixed liquor leaving the oxidation zone has an ammoniacal nitrogen concentration less than about 0.3 ppm. Additionally, an overall F/M.sub.o ratio equal to or greater than about 0.05 is maintained.

Abstract: The treatment of wastewater with activated biomass to remove BOD and phosphorus values in a system in which the wastewater influent is initially mixed with recycled active biomass in an anaerobic zone and then subjected to aeration in an oxic zone, wherein the residence time of the mixed liquor in the oxic zone is reduced. At least part of the biomass-containing sludge separated from the mixed liquor subjected to further oxidation in a separate zone before admixture with the wastewater influent.

Abstract: Wastewater containing phosphorus values and BOD is initially admixed with recycled sludge containing activated biomass under anaerobic conditions, then contacted with oxygen-containing gas, followed by separation of a dense sludge layer from the mixed liquor. A portion of the sludge layer, containing the activated biomass, is held under non-aeration conditions for sufficient time to reduce any nitrates and/or nitrites contained therein, before admixture of the recycled sludge with the wastewater influent.

Abstract: A wastewater treatment system of the activated sludge type is disclosed having an aeration basin provided with staggered partitions and of a particular geometrical design and mode of operation whereby more efficient purification of the wastewater may be achieved in a system of a given size.

Abstract: A wastewater treatment system of the activated sludge type is disclosed having an aeration basin provided with staggered partitions and of a particular geometrical design and mode of operation whereby more efficient purification of the wastewater may be achieved in a system of a given size.