Investigating the impacts of pre-treatment and alternative disinfection on pollutant elimination and byproduct formation in an emergency water supply system

Abstract

Extreme weather events have significantly increased the risk of microbial contamination in water sources, necessitating the evaluation of alternative disinfectants whose reactivity and byproduct formation in real water matrices remain insufficiently explored. This study investigates an integrated treatment system combining carbon adsorption and ion exchange pretreatment with ultra-low pressure reverse osmosis (ULRO) for purifying both synthetic and real contaminated source waters. Three disinfectants—peracetic acid (PAA), performic acid (PFA), and sodium hypochlorite—were evaluated for their impact on water purification performance and disinfection byproduct (DBP) formation. The integrated system demonstrated high efficiency in meeting national drinking water standards, achieving 60–90% removal of total organic carbon and 65–80% of total nitrogen. Furthermore, UV<inf>254</inf> absorbing organic matter (1560–3800 Da) was reduced by 50–90%, and all coliform bacteria were eliminated. Regarding DBPs, bromoform was the dominant trihalomethane, while monochloroacetic and trichloroacetic acids were the primary haloacetic acids. PFA treatment resulted in the highest bromoform concentrations, and increased haloacetic acid formation compared to chlorine, correlating with an increase in humic-like organics within the hydrophilic fraction. Biological dissolved organic carbon (BDOC) assays revealed that while RO achieved peak biological stability under chlorination, applying PAA compromises water biostability. Crucially, a low-dose chlorination–PAA mixture significantly enhanced the biological stability of feed water, compared to chlorination alone. Strategic optimization of disinfectant mixtures is essential to balance biological stability and control the BDOC formation across diverse water treatment units.