SEKUNDÄR FOSFATUTLÖSNING I SYSTEM FÖR BIOLOGISK FOSFORAVSKILJNING / Secondary Release in Biological Phosphorus Removal Systems
During the autumn of 1991 laboratory tests and pilot plant studies were carried out at LTH and Sjölunda sewage treatment plant in Malmö. The aim was to investigate the influence of secondary release of phosphate in biological phosphorus removal systems. Secondary release of phosphate was observed under aerobic conditions both in the laboratory tests and in the pilot plant studies. However this secondary release was found to be of less importance. A small release of phosphate was observed in the second anoxic reactor, when the concentration of nitrate was negligible, but it is impossible to decide if it is secondary or primary release. The release had no adverse effect on the phosphate uptake in the following aerobic reactors; the concentration of phosphate in the effluent was still near zero.