Horizontal subsurface wetland with Phragmites australis to reduce BOD5, COD, and Total Coliforms

Abstract

This study evaluated the efficiency of a horizontal subsurface flow constructed wetland in removing BOD5, COD, and total coliforms, considering hydraulic retention time (HRT) and the presence of Phragmites australis. Results showed that HRT had a significant impact on the removal of evaluated parameters, with removal percentages increasing as retention time lengthened. In the control system (without plants), BOD5 removal reached 65.51%, COD 77.81%, and total coliforms 84.16% after 8 days. In the system with Phragmites australis, these values increased to 89.16%, 89.96%, and 94.54%, respectively, indicating that the presence of plants significantly improves system efficiency. Statistical analyses confirmed that both HRT and plant presence have significant effects (p < 0.05) on parameter removal, although no significant interaction was found between them (p > 0.05). This suggests that the effects of both factors are independent, but their combination offers optimal results. In conclusion, this study highlights the importance of implementing constructed wetlands with long retention times and incorporating Phragmites australis as an effective strategy to maximize the removal of organic matter and microorganisms in wastewater treatment.