Anaerobic treatment of volatile and semivolatile organic compounds in municipal wastewater

The potential of the expanded bed Granular Activated Carbon (GAC) anaerobic reactor in treating a municipal wastewater containing Resource Conservation and Recovery Act (RCRA) volatile (VOC) and semivolatile organic compounds was studied. The GAC anaerobic reactor was followed by an aerobic nitrification tank. The GAC anaerobic reactor was operated at an empty bed residence time of 3.35 hours, whereas the nitrification tank was operated as a chemostat at a hydraulic residence time of 10 hours. A total of six VOCs (methylene chloride, chlorobenzene, carbon tetrachloride, chloroform, toluene, and tetrachloroethylene) and six semivolatiles (o-chlorophenol, naphthalene, nitrobenzene, p-nitrophenol, di-n-butyl phthalate, and lindane) were fed to the GAC anaerobic reactor each at a concentration of 1 mg/L. The VOCs and semivolatiles were fed to the reactor as a mixture along with primary effluent from a local sewage treatment plant. The GAC anaerobic reactor was found to achieve greater than 94% removal of all VOCs except chloroform, which was removed to an extent of 75%. The semivolatiles were removed in excess of 95%. The combined GAC anaerobic reactor-aerobic nitrification system was able to achieve removal efficiencies for chemical oxygen demand and ammonia-nitrogen in excess of 97%.