Statistical analysis and optimization of simultaneous biological nutrients removal process in an intermittently aerated SBR

Abstract

Simultaneous removal of carbon and nutrients from a synthetic wastewater in aerobic/anoxic sequence batch reactor (SBR) was investigated. The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). Two significant independent variables, cycle time and aeration time, were studied to analyze the process. Five dependent parameters--total COD (TCOD) removal, total nitrogen re- moval, total phosphorus removal, total Kjeldahl nitrogen removal and effluent nitrate concentration--were monitored as the process responses. The region of exploration for the process was taken as the area enclosed by cycle times (2, 4.25 and 6.5 h) and aeration times (30, 40 and 50 min/h) boundaries. The maximum COD (87.18%) and TKN (78.94%) removal efficiencies were obtained at the cycle time and aeration time of 6.5 h and 50 min/h, respectively. While the maximum TN (71.15%) and phosphorus (68.91%) removal efficiencies were obtained at cycle time of 6.5 h and aeration time of 40 min/h. As a result, high cycle time (6.5 h) and moderate aeration time (40 min/h) were found to be the optimal region for maximum carbon and nitrogen removal efficiencies.