Abstract: An activated sludge sewage treatment process wherein sewage is received into a sewage treating basin in first zone into which activated sludge is mixed and retained for a period sufficient to form a non-bulking sludge and absorb biodegradable dissolved compounds into the activated sludge, and aerated and subjected to a quiescent condition to permit settling of the sludge in a zone characterized in that it has less than approximately twenty percent of the biochemical oxygen demand of the original sewage and where in the sludge is non-bulking, decanting treated sewage from the upper portion of the basin after allowing the sludge to settle, and cyclically repeating the process, anaerobically fermenting the influent sewage, and recycling anaerobically fermented partially treated sewage to the input of the influent sewage is disclosed.

Abstract: A skimmer for decanting treated liquid from sewage treatment basins comprising a weir, barrier, sealing means and mounting means so constructed and disposed as to define a solids-free decantation zone of increasing size during lowering of the weir during decantation is described.

Abstract: An improved weir for removal of liquid from wastewater systems which is positively driven and which decants wastewater only over a leading edge of an elongated weir and removes the water through downcomers is disclosed.

Abstract: A wastewater treatment reaction vessel is operated with repeated sequences of aeration and non-aeration, using a single vessel or multiple vessels alternately, activated sludge which is acclimated for BOD reduction, nitrification or biological denitrification and phosphorus removal is absorptively reacted with influent wastewater, and the combined flow is passed into subsequent absorptive reactor volumes, reducing the BOD such that the effluent BOD is less than twenty percent that of the influent.