While the chlorination process is the most commonly used disinfection technology for municipal wastewater in the U.S., formation of harmful chlorinated DBPs has become a concern and is one of the major drivers for wastewater utilities to consider alternative disinfection technologies. Studies in 1970s found that trihalomethanes (THMs)—which include chloroform, dichlorobromomethane, dibromochloromethane and bromoform—can be formed from chlorinated disinfection processes. Since that, numerous and even more toxic DBPs have been identified as the result of the wastewater chlorination process. These include, for example nitrosamines and cyanide. Some of these DBPs have been identified as human carcinogens or probable human carcinogens. They could also be toxic to aquatic organisms. Once these DBPs are formed, adding a dechlorination process will not remove them. Depending on site-specific conditions, utilities may have discharge limits on DBPs in their National Pollutant Discharge Elimination System (NPDES) permits. For comparison purpose, the corresponding maximum contaminant levels (MCLs) in accordance to the primary drinking water standard in U.S. are also included in the table. Similar to other water quality parameters, the limit values of DBPs in NPDES permits vary from plant to plant, depending primarily on the dilution factor of the wastewater effluent discharging into the receiving stream, the target sensitive aquatic organisms to be protected and the use designation of the receiving stream.