Abstract:

Based on a laboratoryscale anaerobicanoxicoxic (A/A/O) process acclimated with municipal wastewater as carbon source, the effect of internal return ratio on denitrifying phosphorus removal in the system was investigated at internal return ratio of 100%, 200% and 300%, and anaerobic/anoxic batch experiments were performed to study sludge characteristicsThe results indicated that the contribution of anoxic P removal to total P removal became larger, denitrifying phosphorusaccumulating organisms’ (DNPAOs) anoxic P uptake and denitrification capacity per polyhydroxyalkanoates (PHAs) utilized increased firstly, and then decreased, while anaerobic P release capacity per PHAs accumulated and aerobic P uptake capacity per PHAs utilized were rarely influenced by increasing internal return ratioWhen internal return ratio was set at 200%, denitrifying phosphorus removal and biological nutrient removal efficiency were the highestThe results in the batch experiments also showed that higher or lower nitrate concentrations at the beginning of anoxic stage could influence DNPAOs’ anoxic P uptake and PHAs utilization rates, but their intrinsic characteristics were almost never affected.