Reliability and economic feasibility of online monitoring of constructed wetlands performance

This study aimed at determining the reliability and feasibility of constructed wetlands (CWs) performance evaluation by online monitoring. Redox potential (E-H), turbidity and ammonium (NH4) were continuously monitored for one year by means of online sensors in a pilot plant based on horizontal sub-surface flow constructed wetlands (HSSF CWs). Results were compared with conventional laboratory analyses. Online measures and laboratory analyses showed good agreement for NH4 (r = 0.84, p < 0.01). A significant correlation was also found for: online turbidity vs. Total suspended solids (TSS) (r = 0.85, p < 0.01); online turbidity vs. Biochemical oxygen demand (BOD) (r = 0.88; p < 0.01) and E-H vs. BOD (r = -0.62; p < 0.01). Results suggested that in full-scale CWs, continuous monitoring of turbidity, E-H and NH4 would help to both daily monitoring and improvement of CWs performance. A general overview about economic aspects suggested that, continuous monitoring of wastewater quality could be technically feasible and cheaper than traditional chemical-based monitoring.