Activated sludge process and plant to purify waste water - employs high rate of sludge recycling to reduce size of installation

摘要

Process is of the type in which actuated sludge settling out from purified water in a clarification zone is recycled to an aeration zone. Ratio of the flow rate or recycling sludge to the vol. of the clarification zone is maintained between 3 and 12 hrs.-1. In cross section, the clarification pref. has downwardly convergent, symmetrical sidewalls and is screened into two, superimposed, communicating zones by an upwardly convergent ridged baffle. Purified water is drawn off at the top of both clarification zones. The sidewalls are pref. inclined to the horizontal at 45-55 degrees and the baffle ridge angle is pref. 70-90 degrees. Used in biological purificn. of waste water partic. polluted effluent from industrial premises mfg. food prods., paper, textiles, chemicals, plastics, etc.