Benzene Removal in Laboratory Scale Model Wetland under Different Electron Acceptor Conditions Treating Sulfate-Rich Wastewater
Constructed wetlands (CWs) are shown to be suitable for the treatment of water contaminated with benzene. However, due to the high sulfate concentration (around 850 mg/L) in influent, sulfate reduction will be stimulated in CWs. Subsequently, the toxicity of sulfide will be a catastrophe to the plants, and the treatment performance of CWs will be impaired. In this study, nitrite and nitrate were used as competitor with sulfate for electron acceptor to prevent the sulfate reduction. With the inflow benzene concentration ranged from 21.6-103 μg, and the accumulation of sulfide reached up to 39%, the removal efficiency of benzene decreased from 86% to 27%. However, with the addition of nitrite and nitrate, the sulfide accumulation was inhibited successfully, and the benzene removal efficiency recovered to 85%. In conclusion, both nitrite and nitrate can be an option for preventing sulfate reduction and sulfide toxicity in CWs treating sulfate-rich wastewater.