Performance of horizontal subsurface flow constructed wetland in the removal of tannins Available to Purchase

A horizontal subsurface flow constructed wetland (HSSFCW) was employed to remove tannins from the effluent of a tannins extracting company. Two HSSFCW cells with hydraulic retention time (HRT) of 9 d and packed with limestone were used. One cell without macrophytes was used as a control, while the second cell was planted with Phragmites mauritianus. Results indicated that HSSFCW was capable of treating tannin wastewater that has been seeded with primary facultative pond sludge. Tannins and chemical oxygen demand (COD) removal efficiency of 95·9% and 90·6% with outlet concentration of 27  mg/L and 86  mg/L, respectively, were obtained in the planted cell; while the tannins and COD removal efficiency of 91·1% and 89·5% with outlet concentration of 57  mg/L and 96  mg/L, respectively, were obtained in the control cell.