BIOLOGISK KVÄVE- OCH FOSFORAVSKILJNING UNDER TVÅ ÅRS DRIFT I FULL SKALA VID SÄRDALS AVLOPPSRENINGSVERK / Biological Nitrogen and Phosphorus Removal during Two Years of Full Scale Operation at Särdals Wastewater Treatment Plant

In the wastewater plant at Särdal a biological treatment of phosphorus and nitrogen has been working successfully since 1990. At optimal conditions in spring and autumn of 1991 and 1992 the discharges were 0.3 mg/l of phosphorus and 6 mg/l of nitrogen. The removal of phosphorus was 93 % and of nitrogen 78 %. Summer and winter discharges of nitrogen and phosphorus were higher than spring and autumn. During 18 of 24 months the average concentrations of phosphorus and nitrogen in the discharge are 1.0 mg/l of phosphorus and 6.9 mg/l of nitrogen. The high discharges during the wintertime were dependent on the escape of the sludge as a result of high flows through the plant. At summertime the high discharges were dependent on changes in the biological process. In order to optimalize the biological process the operation of the wastewater plant was changed in the summer of 1991 and 1992. The operation of the plant will be changed again in the summer of 1993 based upon previous results. “Complete abstract not presented.”