Bench-Scale Evaluation of Peracetic Acid and Twin Oxide as Disinfectants in Drinking Water

Chlorine is widely used as an inexpensive and potent disinfectant in the United States for drinking water. However, chlorine has the potential for forming carcinogenic and mutagenic disinfection by-products (DBPs). In this study, bench scale experiments were conducted at the U.S. Environmental Protection Agency's (EPA's) Test and Evaluation (T&E) Facility in Cincinnati, Ohio on peracetic acid (PAA), an alternative disinfectant for drinking water which is purported to reduce DBP formation. PAA has been extensively studied as a disinfectant in wastewater and to a lesser extent in drinking water. The tests were carried out in a nanopure water matrix. The total organic carbon (TOC) level in the test water was increased to target levels of 0.5 to 1.5 mg/L by the addition of humic acid. E. Coli was added as the target microbial organism at initial concentrations of 10⁶ Colony Forming Units (CFU)/100 ml. PAA doses were varied from target levels of 0.5 to 2.5 mg/L for contact times of 10 minutes. E. Coli log removal rates above 4.5 were achieved for disinfectant concentrations above 1 mg/L and were insensitive to TOC levels. DBP analyses did not detect any total trihalomethane production (TTHMs) arising from the disinfection process. No conclusions could be drawn concerning bacterial regrowth in the disinfected samples. Future work will compare disinfection efficiency and DBP production of PAA with Twin Oxide ^TM, a chlorine dioxide based powder disinfectant.