RECOVERY OF VALUABLE ELEMENTS FROM SURPLUS ACTIVATED SLUDGE USING EXISTING SLUDGE TREATMENT FACILITIES

Abstract

 Loading of Mg and P into anaerobic digester from surplus activated sludge was 3 and 4 times greater than that from raw sludge, which indicates that surplus activated sludge would be a target in reducing Mg loading into anaerobic digester. Anaerobic release of Mg, P and K from the surplus activated sludge was accelerated by the addition of thickened raw sludge and these elements in the centrifugal separate liquid was concentrated using a prototype of electrodialyzer. Furthermore, anaerobic cultivation of surplus activated sludge with thickened raw sludge in the existing storage tank during 6 hours decreased the contents of Mg, P and K in the thickened surplus activated sludge by 40 - 50%. These findings suggest that accelerated anaerobic release of the elements from surplus activated sludge could provide an opportunity to recover Mg, K and P from the separate liquid discharged from the subsequent mechanical thickener and decrease the Mg loading into the digester for inhibiting a blockage of sludge transport pipes due to struvite.