Air Products and Chemicals, Inc.

Sun-Nan Hong

Marshall L Spector

Charles S Block

Michael S Chen

Olaf J Noichl

Robert P Seebohm

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.

Method for minimizing diurnal swing in phosphorus content of effluent

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. The mixed liquor thus freed of macrobubbles is then passed through a hydraulic pressure zone enroute to the clarifier in which pressure zone the nuclei microbubbles are caused to dissolve.

Avoidance of rising sludge in biological wastewater treatment clarifiers

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.

Process for the removal of ammoniacal nitrogen in the BOD sorption zone

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.

Removal of phosphates and BOD from wastewaters

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.

Treatment of wastewater containing phosphorus compounds

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.

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Emmaus, PA, United States of America

Sun-Nan Hong