STUDY ON SOLUBILIZATION OF EXCESS SLUDGE BY SUBCRITICAL WATER PROCESS WITH ALKALI ADDITION

Abstract

The amount of sewage sludge produced in municipal wastewater treatment plants in Japan is increasing every year correlating with the increasing of urban population. Therefore, the solubilization process, one method to reduce and recover the resource from the sludge, was considered as a promising solution. Especially, subcritical water process was applied to dissolve various of matters in the sludge. Moreover, it was possible to recover the resources from the dissolved sludge with some kinds of treatment. In the study, alkali was applied to be added in subcritical water process for the sludge solubilization in different temperatures. As the results, solubility of sludge was improved by 15%. Besides, the optimum addition amount of alkali that affected the resources (sugar, protein, phosphate and ammonia nitrogen) leaching from the sludge was evaluated.