Simultaneous removal of nitrogen and phosphorus from swine wastewater in a sequencing batch biofilm reactor

In this study, the performance of a sequencing batch biofilm reactor (SBBR) for removal of nitrogen and phosphorus from swine wastewater was evaluated. The replacement rate of wastewater was set at 12.5% throughout the experiment. The anaerobic and aerobic times were 3 h and 7 h, respectively, and the dissolved oxygen concentration of the aerobic phase was about 3.95 mg·L^-1. The SBBR process demonstrated good performance in treating swine wastewater. The percentage removal of total chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) was 98.2%, 95.7%, 95.6%, and 96.2% at effluent concentrations of COD 85.6mg·L^-1,NH₄⁺-N 35.22mg·L^-1, TN44.64 mg·L^-1, and TP 1.13mg·L^-1, respectively. Simultaneous nitrification and denitrification phenomenon was observed. Further improvement in removal efficiency of NH₄⁺-N and TN occurred at COD/TN ratio of 11:1, with effluent concentrations at NH₄⁺-N 18.5 mg·L^-1 and TN 34 mg·L^-1, while no such improvement in COD and TP removal was found. Microbial electron microscopy analysis showed that the filler surfacewas coveredwith a thick biofilm, forming an anaerobic-aerobicmicroenvironment and facilitating the removal of nitrogen, phosphorus and organicmatters. A long-termexperiment (15 weeks) showed that stable removal efficiency for N and P could be achieved in the SBBR system.