APPLICATION AND IMPLICATION OF ZERO-VALENT IRON FOR TRANSFORMATION OF DISINFECTION BY-PRODUCTS: A COMPARISON STUDY BETWEEN NANOSCALE PALLADIZED IRON AND MICROSCALE IRON

摘要

The objectives of this study were aimed at (1) investigating the feasibility of using nanoscale Pd/Fe particles as an effective reagent for the degradation of disinfection by-products (DBPs), and (2) preliminarily evaluating the potential impact on public health risks when interaction between DBPs and cast iron pipe walls occurs in the water distribution systems. Transformation of trihalomethanes (THMs) including chloroform, bromoform, dichlorobromomethane and dibromochloromethane by nanoscale and microscale iron particles was examined. Transformation of dibromomethane was also studied. Complete dehalogenation of THMs by nanoscale Pd/Fe particles was achieved in less than one hour. Methane, accounting for 60-90% of the THMs lost, was the major product. The fast reaction rate offers a great potential for the use of nanoscale Pd/Fe particles in the treatment of DBPs. A repetitive experiment to study the long-term performance of nanoscale Pd/Fe particles indicated they lasted over 700 hours without exhausting their ability to dehalogenate THMs in a closed batch system. Because THMs readily react with iron, a significant change of levels and identity of THMs may occur in the water distribution systems comprised of cast iron pipes. Nevertheless, the preservation of drinking water with high dissolved oxygen concentrations is a practical method to stabilize the water quality during the transportation.