Nitrogen removal from nitrate-laden wastewater by integrated vertical-flow constructed wetland systems

Nitrogen removals from nitrate-laden wastewater using two replicated, pilot-scale integrated vertical-flow constructed wetland systems (IVCWs) were investigated. Seasonal variation of the treatment performance and the critical environmental influencing factors was analyzed. Over a study period of 14 months, the system was able to achieve moderate nitrogen removals with mean removal efficiencies of 56.2% and 55.1%, mass removal rates of 762.1 mg m−2 d−1 and 819.7 mg m−2 d−1 for nitrate and TN, respectively, under a relatively low influent COD:N ratio of 1.67. Water temperature and DO concentration were the primary factors affecting nitrogen removal. The seasonal order of nitrogen removal efficiency was: summer > autumn > spring > winter. Predictive models with statistical confidence were developed for nitrogen removals employing on-line parameters as indicators.