Abstract: This invention relates to a method and materials for inhibiting the growth of algae in swimming pools by introducing silver chloride onto a filter in a re-circulating system, whereby the silver chloride will dissolve and, thus, introduce silver ion into the body of water in the pool.

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: A method is disclosed for attaining concurrent biological nitrification and dentrification in an aerobic zone of an activated sludge treatment plant. The method comprises aerating a mixed liquor in an aerobic stage of a secondary treatment zone to attain nitrification of ammonia values to NO.sub.x, transferring the mixed liquor to a settling zone where activated sludge is allowed to settle from the mixed liquor, transferring at least a portion of the sludge to an anaerobic sludge holding zone where it is held for a prolonged period, and returning the aged sludge from the sludge holding zone to the secondary treatment zone for mixing with influent wastewater. By holding the sludge in the sludge holding zone for a prolonged period, a culture of organisms is developed which exhibits an oxygen respiration block in the presence of NO.sub.x. When returned to the aerobic zone where nitrification is achieved, these organisms utilize the NO.sub.

Abstract: A modified activated sludge system is provided wherein wastewater containing BOD.sub.5 and phosphate values is admixed in an initial zone with biomass-containing recycled sludge to form a mixed liquor under conditions effecting sorption of BOD.sub.5 in the biomass. Subsequently, said mixed liquor is subjected to aeration in an oxidation zone under conditions for effecting oxidation of BOD.sub.5, such that oxidizing agent is incorporated into the oxidation zone at a rate not substantially exceeding the rate of oxidation. By such operation, considerable savings in power requirements for oxygen transfer to the mixed liquid are had, while developing and maintaining a dense non-bulking biomass having the properties of good removal of phosphate from the wastewater influent.

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: An improved method of operating an activated biomass process wherein influent and activated biomass are initially contacted under anaerobic conditions to form a mixed liquor, the mixed liquor is subsequently oxygenated, thereafter activated biomass is separated from the mixed liquor and at least a portion of the separated biomass is introduced into the initial contacting step. The improved method comprises maintaining both the F/M ratio and the BOD/P ratio within particular ranges, preferably relative to each other.

Abstract: An organic product material having a high nitrogen and phosphorous content is produced as the product of a biological system for the treatment of a BOD-containing influent which also contains phosphorous and fixed nitrogen. The biological treatment system comprises the reaction of a mixed liquor composed of an activated biomass and a BOD-containing influent initially under anaerobic conditions and thereafter treating such mixed liquor under oxic conditions. The treated material is then separated into a supernatant liquid in which the BOD is depleted and a dense, activated biomass. A portion of this biomass is employed in forming the mixed liquor for the initial anaerobic treatment, while the remaining portion of the biomass is recovered as product. The living biomass product can be used in the fermentation industries. Alternatively, the product can be used as such or further processed, e.g. dried, for employment as a fertilizer or a nutrient in animal feeds.

Abstract: A modified activated sludge system is provided wherein BOD-containing wastewater and recycled sludge are initially admixed under anaerobic conditions in the substantial absence of oxygen or oxidizing agents and subsequently subjected to aeration and clarification. By the disclosed operation the selective production of non-bulking biomass is favored while effective removal of phosphates is obtained. By a further alternative modification, nitrates and nitrites are also removed by interposing an anoxic treating zone between the anaerobic zone and the aerating zone.

Abstract: A multistage treatment is disclosed for the removal of carbonaceous BOD and nitrogenous pollutants from wastewaters, wherein the influent wastewater undergoes successive nitrification-denitrification in the presence of recycled activated sludge containing a mixed culture biomass comprising heterotrophic and autotrophic organisms. The initial mixing of the wastewater with recycled sludge is effected in the presence of sufficient oxygen to maintain oxic conditions. The mixed liquor from the initial oxic treatment, without intermediate separation of solids, is passed to an anoxic stage wherein nitrites and nitrates (NO.sub.x .sup.-, x = 2,3) formed by oxidation of ammonium compounds are reduced to nitrogen gas. Any number of oxic treating stages each followed by an anoxic stage may be employed. The final treating stage prior to solids separation from the mixed liquor may be either oxic or anoxic. The separated solids constitute the activated sludge recycled to at least the initial mixing stage.

Abstract: A modified activated sludge system is provided wherein BOD-containing wastewater and recycled sludge are initially admixed under anaerobic conditions in the substantial absence of oxygen or oxidizing agents and subsequently subjected to aeration and clarification. By the disclosed operation the selective production of non-bulking biomass is favored while effective removal of phosphates is obtained. By a further alternative modification, nitrates and nitrites are also removed by interposing an anoxic treating zone between the anaerobic zone and the aerating zone.