he John J. Carroll Treatment Plant provides state-of-the-art drinking water treatment for 41 communities in Eastern Massachusetts served by the MWRA. Completed in 2005, the plant uses ozonation - and later, ultraviolet disinfection - corrosion control and chloramination to treat up to 405 million gallons of water daily. This treatment provides improved drinking water quality and strengthens the region’s ability to comply with the Federal Safe Drinking Water Act. The MWRA has reduced the amount of chlorine used in the water treatment process, thereby reducing disinfection by-products and improving taste.