Step-feed sequence batch reactor filled with surface-modified carriers can enhance nitrogen removal from low C/N ratio wastewater

It is difficult to achieve efficient nitrogen removal from low C/N ratio wastewater if there is no extra carbon source addition. In this study, integrated floating-film activated sludge (IFFAS) process filled with surfacemodified carriers (rough, hydrophilic and positive-charged surface) was employed to enhance nitrogen removal performance. By applying step-feed sequence batch reactor strategy, high total nitrogen (TN) removal loading of 0.062 +/- 0.010 kg/(m(3)circle d) could be achieved under the inflow flow ratio of 2:1:1 without external carbon source when treating low C/N ratio wastewater (C/N ratio: 3.5). In comparison, TN removal loading was only 0.031 +/- 0.010 kg/(m(3 circle)d) in activated sludge, and 0.057 +/- 0.014 kg/(m(3)circle d) in IFFAS filled with conventional carrier system. The step-feed sequence batch reactor strategy resulted in complete utilization of influent carbon source for denitrification. The low C/N ratio also promoted microbial by-products production that enhanced nitrogen removal. Meanwhile, surface-modified carriers induced the mixed distribution of nitrifiers and denitrifiers. This study proposed a low-cost and efficient approach for nitrogen removal from low C/N ratio wastewater, showing potential in actual application.