High nitrogen and phosphorous content biomass produced by treatment of a BOD-containing material

An improved high nitrogen-, and phosphorus- content biomass characterized by a phosphorous content of at least about 3.96% and produced by the operation of an activated sludge process which inhibits proliferation of filamentous biomass, said process consisting essentially of:

• (a) first forming a mixed liquor by mixing activated biomass with nitrogen-, phosphorus-, and BOD-containting influent and initially treating the mixed liquor under anaerobic conditions such as to be substantially free of NO.sub.x.sup.- and to have a dissolved oxygen content of less than 0.7 ppm;
• thereby effecting selective production of nonfilamentous microorganisms capable of sorbing BOD under anaerobic conditions, whereby said mocroorganisms effect a decrease in BOD content of said mixed liquor;
• (b) oxidizing BOD in the mixed liquor to cause removal of BOD by contact with oxygen containing gas under conditions selected to maintain a dissolved oxygen content of at least 1 ppm;
• (c) settling the oxidized mixed liquor so as to separate a supernatant liquid from a more dense biomass;
• (d) employing a portion of the separated biomass as the activated biomass in an initial mixing with BOD-containing influent;
• and
• (e) recovering another portion of the settled and separated biomass as product.