Abstract
The amount of excess sludge produced in municipal wastewater treatment plants in Japan is increasing every year as the urban population increases. Phosphorus in excess sludge could be a potential phosphorus resource since at present, phosphate rock is being exhausted all over the world. Every year, Japan imports large quantities of phosphorus from abroad but much are discharged as excess sludge. Therefore, solubilization process, one method of recovering phosphorus from sludge, could be a promising solution. In this study, subcritical water process, a new technology that solubilizes sludge under subcritical condition, was applied before the phosphorus in sludge was recovered with magnesium ammonium phosphate (MAP) process. As a result, the solubilization rate of excess sludge achieved approximately 80% and about 94-97% of the phosphorus could be recovered.
