Ecotoxicity evaluation of pure peracetic acid (PAA) after eliminating hydrogen peroxide from commercial PAA

In recent years, disinfection of inflowing Combined sewer overflows (CSO) water in the CSO discharge structures has been studied using Peracetic acid (PAA) to minimize the impact from the discharge of untreated CSO to the surface waters. Degradation of hydrogen peroxide was slower than PAA when it was used to disinfect CSO. All previous toxicity studies was based on commercial PAA mixture and variance on toxicity value was observed due to different PAA: hydrogen peroxide ratio. In this study, hydrogen peroxide was eliminated from the PAA mixture using potassium permanganate to avoid the strict environmental risk assessments of hydrogen peroxide to obtain the permit from the authorities. Ecotoxicity data of PAA without hydrogen peroxide was obtained by conducting the battery of ecotoxicity test: the bioassays using Vibrio fischeri, Daphnia magna and Pseudokirchneriella subcapitata. Effect concentration (EC50) of PAA without hydrogen peroxide was 0.84 mg/L for Vibrio fischeri and 2.46 mg/L for Pseudokirchneriella subcapitata, respectively whereas lethal concentration (LC50) was 0.74 mg/L for Daphnia magna. The toxicity results showed that pure PAA was less toxic to the most commonly used aquatic species for toxicity tests compared to the commercial PAA.