Removal of nitrogenous compounds from polluted river water by floating constructed wetlands using rice straw and ceramsite as substrates under low temperature conditions

To reduce the loading of nitrogenous compounds under low temperature conditions (4.3-9.2 °C), we used two floating constructed wetlands (FCWs), assembled from either rice straw (FCW-RS) or light ceramsite (FCW-LC) as a substrate for microorganisms and macrophytes. Under batch conditions, the concentrations of total nitrogen (TN), ammonium nitrogen (NH4+N), nitrate nitrogen (NO3−N) and nitrite nitrogen (NO2−N) in raw water were 1.32-2.97, 0.50-1.32, 0.41-1.10, and 0.18-1.24 mg/L. The average removal rates of TN, NO3−N and NH4+N after 7 d using FCW-RS and FCW-LC were 78.2%, 62.1%, 81.2% and 65.5%, 42,2%, 71.6%, respectively. Both the FCW-RS and FCW-LC systems proved to be proficient in nitrogenous compounds removal, and FCW-RS showed less NO2−N accumulation.