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

Abstract

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 3h and 7h, respectively, and the dissolved oxygen concentration of the aerobic phase was about 3.95mg·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, TN 44.64mg·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 18.5mg·L−1 and TN 34mg·L−1, while no such improvement in COD and TP removal was found. Microbial electron microscopy analysis showed that the filler surface was covered with a thick biofilm, forming an anaerobic–aerobic microenvironment and facilitating the removal of nitrogen, phosphorus and organic matters. A long-term experiment (15weeks) showed that stable removal efficiency for N and P could be achieved in the SBBR system.