This study investigates how a chemical used in water treatment, hexamethylenediaminetetra(methylenephosphonic acid) (HDTMP), can be broken down using ultraviolet (UV) light, manganese (Mn²⁺), and hydrogen peroxide (H₂O₂). The research finds that adding hydrogen peroxide significantly speeds up the breakdown of HDTMP, while manganese also helps but to a lesser extent. The study provides insights into how these methods can be used to treat wastewater containing persistent chemicals like HDTMP.