EXAMINATION OF THE ACTIVATED-SLUDGE MODEL NO-2 WITH AN ALTERNATING PROCESS

Three series of data obtained in a pilot-scale alternating-type activa ted sludge nutrient removal process are examined in light of the recen tly introduced Activated Sludge Model No.2 (ASM2). The first data seri es was collected while adding acetate to the inlet to improve phosphat e removal. ASM2 can explain why phosphate levels first rise before an improvement occurs based on a slow build-up of internally stored polyh ydroxyalkanoates (PHA). The second and third data series represent bat ch experiments performed in the pilot plant, and show the effect of ni trate on phosphate release. ASM2 could describe the second data series well after including one additional reaction to account for denitrifi cation by phosphate accumulating organisms. The third data series exam ines the effect of the rate of acetate addition, and shows that this a ffects the rate of anoxic phosphate release more strongly than it does the denitrification rate.