Efficiency of a constructed wetland in controlling organic pollutants, nitrogen, and heavy metals from sewage

Introduction: constructed wetlands are efficient systems in controlling sewage pollutants. These systems have a low cost of maintenance and operation and their discharges can be further re-used for irrigation and agricultural purposes. The present study aimed at evaluating the efficiency of such a system in removing various types of pollutants, including organic and mineral compounds, nitrogen, and heavy metals. Material and method: the system investigated in the present study was composed of two stabilization units, each of them contained two anaerobic ponds and twelve beds. The performance of the system was evaluated by taking 24-hour samples from the system discharges. Data were analyzed using SPSS software package version 12. Findings: the efficiency of the ponds of the first unit in removing COD and BOD were 29.49±21.8 and 42.63±15 percent, and for the ponds of the second unit were 29.85±18.44 and 66.42±21.81 percent. Moreover, the beds were capable to separate 51.25 percent of all received cadmium. The nitrogen removal efficiency of the system was not acceptable. Conclusion: although the wetland investigated in the present did not have the desired efficiency, a desirable level of efficiency would be achievable by optimizing the operational and maintenance condition of the system