Verification of Sludge Reduction by Ozonation with Phosphorus Recovery Process at a Demonstration Plant

Abstract

Since excess sludge is generated by the process of the biological treatment of waste water, the effect of ozonation on sludge reduction by ozonation is being noted. The mechanism of sludge reduction by ozonation is the process of applying the liquefaction of microbial cells by ozonation as described here. Sludge reduction by ozonation liquefies microbial cells in the sludge and consequently the organic matter, phosphorus and nitrogen, which consist of the cells dissolved into the liquid. When the dissolved matters are run through the biological treatment process, the organic matter and nitrogen are removed again by the activated sludge through the addition of oxygen. We took note of the fact that the major part of the exhaust gas from the ozone reactor is oxygen, and made the best use of this exhaust gas as an oxygen supply resource to develop a biological treatment process (Anaerobic – Anoxic – Oxic) by excess sludge reduction. We set up this plant and made evaluations of the process capability at the site of EXPO 2005 Aichi, Japan. In this paper we demonstrate the construction of the plant and the results of the operation. The main results are: (1) The gas issued from the ozone reactor contained sufficient oxygen for the reaction in the oxic tank; and, (2) The sludge generation of the ozonation process was reduced to 24% of the conventional process. The removal of COD and T-N also worked well.