A Full-scale Verification of an Excess-sludgeless Operation using Ozone and Activated Sludge Treatment

Abstract

A new activated sludge process which produces no excess sludge has been developed and operated successfully in a full-scale plant. The process is composed of ozonation stage and biological treatment stage. Ozone treatment enhances biological degradation of activated sludge, which is decomposed in a subsequent biological treatment. Sludge is mineralized by the recirculation between the stages. The process has been eliminating excess sludge completely for more than one and half years. The MLVSS concentration was kept about 4, 000mg/L consistently without withdrawing excess sludge. The accumulation of inert materials in the activated sludge was not observed for both inactive organics and inorganic substances, such as Fe, Al and SiO2. The inorganic substances contained in the influent water was thought to be solubilized through the treatment. The ratio of MLVSS to MLSS decreased slightly at initial phase of operation, and was kept constant afterward. The acceleration test was carried out to clarify whether inactive organics were built up in a long term operation. It was verified that the inactive organics will not be accumulated in the activated sludge for more than 7 years.