The effect of acetate was examined during the p-removal and denitrification of wastewater. The plant was operated based on the sequenc ng-batch-biofilm-reactor (SBBR) process. As microbial media. ca. 9 mm Bio-Flow granules made from polyethylene and polypropylene were used. Three preparations were made to compare the level of biological p-removal and denitrification. In comparison to the batch test, 42 mg/L (AC 30) and 84 mg/L (AC 60) of NaCH3COO were mixed with the 500 mL of raw wastewater and the effect of the acetate concentration on the level of p-removal was monitored. All samples were immediately filtered with 0.45 mu m membrane filter, and PO4-P, NO3-N, NO2-N and acetate were analyzed using Ion Chromatography. whereas P-total and chemical oxygen demand (COD) were measured by a spectrophotometer. The p-removals for the WW, WW + AC 30 and WW + AC 60 preparations were found to be 9.4, 9.1 and 13.1 mg/L, respectively. The WW + AC 30 preparation did not show any significant effect on the p-removal, while p-removal in WW + AC 60 preparation was higher than that in the other two preparations. A comparison of the data revealed the COD: NO3-N:AC:P ratio of the WW. WW + AC 30 and WW + AC 60 preparations to be 18.07:2.90:6.8 7: 1, 21.28:2.45:5.98:1 and 15.95:2.75:6.18:1, respectively. The experimental results showed that approximately 7 mg/L of acetate was consumed per 1 mg/L of p-removal. (C) 2008 Elsevier B.V. All rights reserved.