Biological phosphorus removal from wastewater in a single reactor combining anaerobic and aerobic conditions

Abstract

In this investigation, phosphorus removal experiment was conducted in a single reactor combining anaerobic and aerobic conditions. Attempts have been made to delineate phosphorus and organic removal mechanisms and to evaluate the removal efficiencies with different internal recyle ratios, N/P ratios and varying SRT conditions. The removal efficiencies of TOC, BOD and COD were observed to be higher than 95%, 90% and 90% in all runs, respectively. It is further estimated that the optimal operational conditions for phosphorus removal are observed when the aerobic internal recycle rate is 100% with the inlet height 0.2H. The percent removal efficiencies were 92% for T-P and 90% for PO4-P. While, large differences in the removal of phosphorus with N/P ratios were observed; at influent TKN/T-P of 2.5, 3.6 and 5.1 removal efficiencies for T-P were 89%, 68% and 56%, respectively. Those removal efficiencies decreased as the N/P ratios increase in wastewater. In case of SRT, high removal efficiencies are observed with the solids retention time of 10 days rather than with SRT's of 5 or 20 days. These results indicate this new process, KNCR (Kist Nutrient Removal Compact Reactor), to be an excellent means of reducing phosphorus emissions into the environment.