The temperature-dependent kinetics and bacteria regrowth by performic acid and sodium hypochlorite disinfection

Sodium hypochlorite (NaOCl) has been widely used as a disinfectant in water and wastewater treatment, because of its high efficiency and low cost, whereas the bio-toxicity of its disinfection byproducts (DBPs) raised great concern. Performic acid (PFA) produces less DBPs and shows strong oxidation abilities. In this study, the effect of temperature on NaOCl and PFA disinfection as well as bacteria regrowth were evaluated. Firstly, the inactivation of Escherichia coli, Staphylococcus aureus, and Bacillus subtilis by NaOCl and PFA at 4 and 20 degrees C, detected by cell cultured-based plate counting were fitted to kinetic models, and the predicted CTs were calculated. The results showed that NaOCl was more effective than PFA for E. coli and S. aureus inactivation, and the temperature was positively correlated to disinfection. Secondly, bacteria regrowth was evaluated at different temperatures (4 and 20 degrees C) of disinfection and storage. The results showed that the bacteria inactivated by NaOCl regrew prominently, especially for those inactivated at 4 and stored at 4 degrees C, probably through the mechanism of reactivation of viable but non-culturable (VBNC) bacteria. PFA was superior in suppressing bacteria regrowth, and it may be used as an alternate disinfectant in water treatment in cold environment.