Effect of cod/n ratio and ph on nitrification in a laboratory-scale constructed wetlands treating septic tank wastewater
Department of Environmental Science and Technology, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing, PR China 100029
Abstract
The constructed wetlands (CWs) were operated to investigate the effect of influent COD/N ratio and the pH value on nitrification. With an influent concentration of 100 mg L-1 NH4+-N, four COD/N ratios (i.e., 2, 4, 6 and 10) and six pH (i.e.: 7.5, 8.0 8.5 9.0 9.5 and 10) were tested. The results showed that the removal rate of ammonium-N decreased from 35.78% to 0.39% as COD/N ratio increased from 2 to 10. The removal rate of ammonium-N increased from 16.5% to 35.2% as the pH value increased from 7.5 to 9.5, while it dropped to 18.17% as the pH value reached 10.0. The optimal COD/N ratio of 2 and pH value of 8.5-9.0 were obtained for the removal of organic matter and ammonium-N in CWs.
Keywords
COD/N ratio; constructed wetlands; nitrification; pH; septic tank; wastewater