Performance of Tropical Vertical Subsurface Flow Constructed Wetlands at Different Hydraulic Loading Rates

The hydraulic loading rate (HLR) plays a vital role in pollutant removal in constructed wetlands. This study evaluated the effects of HLR variation on pollutant removal in continuously fed vertical subsurface flow (VSSF) constructed wetlands in tropical conditions. Three VSSF wetland beds (Length: 1.4 m, Width: 0.5 m and Depth: 0.6 m), filled with 10–20 mm gravel media, were set up in a tropical region. Two beds were planted with a locally available emergent macrophyte narrow-leaf cattail (Typha angustifolia), and the remaining bed was used as a control without plants. The performance of these wetland mesocosms was tested at different HLRs of 2.5, 5, 7.5, 10, 12.5, 15, 20, 25, and 30 cm day−1 changing at 2 week intervals in two phases over a period of 6 months. The results revealed that both VSSF wetland systems are capable of substantial reduction of pollutants with a good buffering capacity up to 25 cm day−1 HLR.