Treatment of Organic Matter and Tetracycline in Water by Using Constructed Wetlands and Photocatalysis

In this study, the ability of a bench-scale simulated constructed wetland (CW) to remove organic matter (OM) and tetracycline (TC) from water was examined. The performance of CW was evaluated by varying the initial concentrations of the target compounds and the hydraulic retention times (HRTs). Findings showed that OM removal efficiencies were 55.2-80.8%, 28.1-71.9% and 72.1-79.7% for ultraviolet absorbance at 254 nm (UV-254), dissolved organic carbon (DOC) and soluble chemical oxygen demand (sCOD) respectively, under 1 day-HRT, whereas higher initial DOC concentration achieved better removal efficiencies. Changing from 1 day-HRT to 2 day-HRT, the removal efficiency of OMs remained practically unchanged, while that of NH3-N increased considerably, from 61.7% to 73.0%, implying that the removal of ammonia in CW needs a longer time for complete treatment. CW also showed an excellent performance in removing TC, especially in the first two hours of operation through the absorption process. In addition, the findings from this research revealed an improvement in effluent water quality when photocatalysis (TiO2/alpha-Al2O3, with ultraviolet A (UVA) irradiation) was used as the post-treatment following CW, presented by the increase in removal efficiency of OMs of the combined system compared to that of CW alone. This study points to the possible and promising application of the low-cost water treatment system for dealing with OMs and TC in water.