Anoxic Biological Phosphorus Uptake∕Release with High∕Low Intracellular Polymers

This study investigates the denitrification∕phosphate uptake and denitrification∕phosphate release characteristics among denitrifying phosphate accumulating organisms (DNPAO), denitrifier, and nondenitrifying phosphate accumulating organisms (non-DNPAO) in a biological nutrient removal process named TNCU-I, using a series of anoxic batch experiments with and without added acetate under high∕low intracellular polymer conditions. The results showed 47% phosphate uptake in the anoxic tank of the TNCU-I process. Additionally, due to the combined attribution of denitrifier and DNPAO, the experiments with both added acetate and phosphate produced higher denitrification rates than experiments with only acetate added. Furthermore, DNPAO contributed 42% of the denitrification reaction. The sludge exhibited simultaneous phosphate uptake and release under anoxic conditions when acetate was added. When no acetate was added, the specific phosphate uptake rate for the high intracellular polymer level was higher than that found at the low intracellular polymer level. Moreover, the phosphate uptake rate of non-DNPAO was observed to be 2.46 times greater than that of the DNPAO. The phosphate uptake per unit polyhydroxyalkanoates (PHA) consumption (γPO4/PHA) for the non-DNPAO was 1.08 times greater than that of DNPAO. Thus, this study demonstrates that the utilization efficiency of PHA by non-DNPAO is not significantly different with the utilization efficiency of PHA by DNPAO.