CIRCULATION OF PHOSPHORUS IN A SYSTEM WITH BIOLOGICAL P-REMOVAL AND ANAEROBIC SLUDGE DIGESTION / Fosforcirkulation i ett system med biologisk fosforavskiljning och anaerob slamstabilisering
If a high loaded activated sludge process is to be part of a process scheme for nutrient removal anaerobic digestion of the biological sludge has to be considered. However, even when plants are upgraded with a low loaded activated sludge process for nutrient removal anaerobic digestion may be of interest if the energy perspective is considered. When an EBPR (Enhanced Biological Phosphorus Removal) sludge is subjected to anaerobic digestion phosphate release can be expected. However the release has also been reported to be substantially smaller than expected due to precipitation with metal salts present in the sludge. In order to address questions related to the digestion of an EBPR sludge a laboratory study was performed where EBPR sludges from one high loaded process and one low loaded process, were digested. In this paper these results are presented and discussed.