Effects of feed water C/P ratio on performance of anaerobic-anoxic-oxic process

With the deterioration of eutrophication in China, nitrogen and phosphorus removal from wastewater have caught more and more attention; while influent C/P ratio is one of the most important influence factors. To investigate the effects of feed water C/P ratio on the performance of anaerobic-anoxic-oxic process, four different feed water C/P ratios were designed, that is 55, 45, 34, 23, so as to study the variations of COD, TN, PO43--P and sludge characteristics with the C/P ratio. The results showed that when the C/P ratio was lower than 32, P removal efficiency increased as C/P ratio increased linearly, while the C/P ratio was higher than 32, the P removal efficiency maintained at 90%-98%, and effluent P concentration was lower than 0.5 mg &middot L-1. In contrast, regardless of the C/P ratio, excellent COD (90%) and good total nitrogen removal (75%-84%) were maintained throughout the experiments. However, P percentage in the wasted activated sludge (WAS) increased as the C/P ratio decreased. It was also found that denitrifying P removal existed under different C/P ratios by controlling the operation, and nitrogen and phosphorus removal efficiency could be improved.