Domestic Wastewater Treatment Through Constructed Wetlands: Comparative Analysis of Horizontal, Vertical, and Hybrid Flow Systems

This study evaluates the performance of three constructed wetland (CW) configurations: horizontal flow (HFCW), vertical flow (VFCW), and hybrid vertical-horizontal flow (HVHCW)-for the treatment of domestic wastewater in a decentralized context in India. A pilot-scale system was operated under real wastewater loading for 8 weeks, with weekly sampling (n = 8 per system) and triplicate analysis per sample. Key water quality parameters assessed included biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonia nitrogen (NH₃-N), nitrate nitrogen (NO₃-N), and total phosphorus (TP). Analytical protocols followed APHA (2017) standard methods. The HVHCW configuration achieved the highest removal efficiencies, with mean values of 94.4% for BOD and 96.8% for TSS, outperforming both single-stage systems. One-way ANOVA revealed statistically significant differences (p < 0.05) across systems for most parameters, and Tukey's HSD post hoc test confirmed HVHCW's superiority. Nitrate removal, while observed, was not statistically significant (p > 0.05), indicating the need for design enhancements to support denitrification. These results underscore the potential of hybrid CWs as low-cost, eco-sustainable solutions for decentralized wastewater management in developing regions.