Ascorbic acid, also known as vitamin C, is used in water and wastewater treatment industries as a reducing agent and an antioxidant. It helps in the removal of chlorine and chloramine disinfectants from water. It also helps in neutralizing free radicals that may be present in the water, improving its quality and taste. Ascorbic acid is typically added to the water during the disinfection process or as a post-treatment step.