OPERATIONAL FACTORS AFFECTING ENHANCED BIOLOGICAL PHOSPHORUS REMOVAL AT THE WASTE-WATER TREATMENT-PLANT IN HELSINGBORG, SWEDEN

Enhanced biological phosphorus removal (EBPR) has since 1992 been run as a full-scale UCT-process in a part of the waste water treatment pla nt in Helsingborg. Between June 1993 and July 1991 an extended operati onal and microbiological investigation was conducted. It was shown tha t the major phosphorus removal mechanism was biological and that at th e most 10% of the soluble phosphorus entering the biological reactor, was removed due to chemical reactions. The VFA-potential in pre-treate d waste water has been found to be a key factor. At the waste water tr eatment plant in Helsingborg I mg phosphorus is removed for each 14 mg VFA-potential added. COD, soluble COD and BODI are correlated to the VFA-potential, which means that these measurements can be used as oper ational parameters. If enough VFA-potential is present, the concentrat ion of soluble phosphorus will be lower than 0.3 mg/l in the effluent even at temperatures below 10 degrees C. The mean concentration of sol uble phosphorus in the effluent has been 0.29 mg/l during the period O ctober 1993-July 1994. Effluent nitrogen concentration was during the evaluation period between 8-10 mg/l and it was found that PHA was one of the major carbon sources for denitrification. Compared with a pre-d enitrification process in combination with simultaneous precipitation, both the filament index and the DSVI were lower in the EBPR process. Other operational factors that affect the process are oxygen and nitra te concentrations in flows to the anaerobic reactor and the degree of internal recirculation from the aerobic to the anoxic reactor. Copyrig ht (C) 1996 IAWQ.