Novel photo-activated method for removal of mercury from industrial wastewater

Mercury-laden wastewaters need new treatment options to meet current and pending regulations. Some facilities employ a sulfide precipitation process to lower the concentrations of Hg in their discharge through chelation and filtration. However, this process still results in mercury concentrations higher than the imposed limits for discharge by upcoming U.S. EPA regulations. This paper focuses on a simple approach, Ultraviolet Activated Chelation (UVAC), which has resulted in mercury concentrations as low as 10 ppt when applied to wastewaters from three industrial facilities. An investigation into the effect(s) of certain variables on the treatment process, such as pH and residence time, was carried out through batch experiments using plant wastewater. A discussion on UVAC effectiveness is based on results from the completion of a pilot-scale UVAC system that was designed, fabricated, and operated based on bench-scale experimental data. Concentrations as low as 12 ppt were obtained for the majority of the four-month pilot study.