Chlorine-based compounds have been used as a disinfectant in drinking water treatment plants for decades because of their excellent sterilisation efficiency and low cost. However, the formation of disinfection by-products during chlorination is a cause for concern. Peracetic acid (PAA) is a strong oxidant with a redox potential higher than that of chlorine and does not form harmful disinfection by-products. It is thus a potential alternative for chlorine-based disinfectants. However, PAA decomposes rapidly in water at a rate that is highly affected by many factors, such as organic compounds and pH. The aim of this study is to investigate the stability of PAA during drinking water disinfection. To accomplish this, we studied methods for rapid detection of residual PAA and PAA decay in drinking water. Residual PAA was detected in water by the spectrophotometry-total chlorine reagent (SPTCR) method with a PAA concentration range of 0.090-10 mg/L (R2 = 0.9943). Decay tests of PAA in drinking water and other sources of water showed that the decay process conformed to the first-order kinetic model with fast and slow reactions. Among four factors, pH was the key factor in the decay process because an alkaline environment significantly promotes the decomposition of PAA. In addition, total organic carbon (TOC), conductivity, and initial PAA concentration also affected PAA decay. Experimental and statistical analyses suggested that these factors affected PAA decay in the following descending order of influence: TOC, initial PAA concentration, and conductivity. In real water matrices, the PAA decay rate increased with increasing initial PAA concentration.
Keywords: Decay kinetics; Detection method comparison; Influencing factor; Peracetic acid; Real water matrix.