On September 30, 2015, the United States Environmental Protection Agency (“EPA”) finalized a proposed rule to regulate wastewater discharges from power plants.  The new rule sets limits on dissolved pollutants permitted in these discharges, and focus on mercury, selenium, and arsenic—toxic metals previously unregulated in this context.

Since the 1980s, air pollution controls on power plants have improved greatly.  Scrubbers installed to comply with Clean Air Act requirements have significantly reduced air emissions, but divert the metals and other pollutants captured at the smokestacks to wastewater streams.  Regulation of this wastewater has not been updated accordingly.  Since the last revision, in 1982, wastewater has only been controlled for suspended solids, not dissolved pollutants.  A 2009 EPA study revealed these shortcomings and prompted the Agency to develop new regulations.

The finalized rule applies to all steam electric power plants, except for those smaller than 50 megawatts in production capacity, and oil-fired plants.  Coal-fired plants are expected to be the most heavily affected, and new coal and petroleum coke plants are subject to additional, more stringent controls.  Out of approximately 1,080 steam electric power plants in the U.S., 134 are expected to require new investments in order to comply with the regulations.

Along with effluent limits on toxic metals and dissolved solids, the rule establishes zero discharge limits on pollutants in ash transport water and flue gas mercury control wastewater.  Plants will have to utilize chemical or biological treatment to achieve even stricter limits on pollutants in flue gas desulfurization wastewater.  The regulations will take effect in 2018, and compliance will be phased in through 2023.