Disinfection of Wastewater with Peracetic Acid (PAA) and UV Combined Treatment: A Pilot Study

UV irradiation is one of the most commonly used wastewater disinfection methods. Significant advantages of using the UV-based disinfection are that it leaves no residual and does not form any disinfection by products (DBPs) in the treated wastewater. However, the high-energy cost is the major downside of the UV-based disinfection. For the past three years, Metropolitan Sewer District of Greater Cincinnati (MSD) has been investigating the use of peracetic acid (PAA) alone and in combination with UV to increase the disinfection efficiency and reduce the cost of disinfection treatment. Here we are reporting the results from a full-scale plant-level pilot study we conducted at MSD’Muddy Creek Treatment Plant (MCTP) to investigate the impact of PAA pre-treatment on UV disinfection and the rate of microbial inactivation. It was observed that pre-treating secondary effluent with low doses of PAA results in an increased UV efficiency, which can significantly increase the rate of microbial inactivation when compared with individual treatments with PAA or UV separately. In our studies, the combined PAA-UV treatment achieved significantly greater log reduction in fecal coliform, and E. coli counts. The results from this plant-level pilot study validates our previously conducted lab and side-stream pilot studies that a PAA-UV sequential treatment is more effective than the UV or PAA treatments separately. The disinfection efficiency was directly proportional to the dose of PAA during the pre-treatment of secondary effluent.