In the U.S. and the European Union, scrubbers are installed on all new coal-fired power plants because their technology is considered the best available for removing SO2. A zero-liquid-discharge system is the best technology for treating wet scrubber wastewater. With the future promising stricter limits on power plants' water use, ZLD systems that concentrate scrubber purge streams are sure to become as common as ZLD cooling tower blowdown systems.