The North Texas Municipal Water District moves an average of 266 million gallons of water through its Wylie treatment plant each day.

In response to a circulating Facebook post from California-based environmental activist Erin Brockovich questioning the district’s methods of chlorine maintenance, the North Texas Municipal Water District said in a news release Thursday that the district’s water is safe and complies with regulations from state and national environmental agencies.The NTMWD provides water to about 1.7 million people in 10 counties, including Plano, Frisco and McKinney in Collin County.Brockovich posted Wednesday from her official Facebook account criticizing the district’s practice of using two disinfecting chemicals, chlorine and chloramine, which is a combination of chlorine and ammonia. In the past, she has raised questions about the same methods in water districts supplying other Texas cities, including Austin and Houston.The water district is nearing the end of its annual chlorine maintenance phase, which was expected to take place Feb. 26 through March 26. In advance of the monthlong process, district officials said tap water remains safe to drink, although some customers may notice a chlorine smell or taste.In its news release, the district said the most commonly used disinfectants for water treatment are chlorine, chloramine and ozone.“NTMWD, like many water providers, uses all three [disinfectants],” the news release states. “Ozone is the most powerful disinfection process and chlorine is used to ensure the water remains safe as it moves through the pipes throughout the regional and local system.”Brockovich claims the practice of using chlorine causes byproducts, including trihalomethanes, to form that are toxic but are “just not yet regulated.”Mike Rickman, deputy director of operations and maintenance at NTMWD, said that water quality and safety is a top priority and that the district works closely with officials on a local, state and federal level.“This is a safe and scientifically proven method to ensure that treated water remains safe as it moves through the distribution system,” Rickman said.The district said routine monitoring of bacteria, disinfectant and other “parameters,” including trihalomethanes, occurs during the chlorine maintenance period. The samples are collected by water operators licensed by the Texas Commission on Environmental Quality and analyzed in accredited laboratories.A previous version of this story misstated the name of a water district official. His name is Mike Rickman, not Mick Rickman.