Peracetic Acid: Deciphering the Risks and the Opportunities
- Thomas Worley-Morse, Melanie Mann, Saya Qualls, and Rob Sharp
Peracetic acid (PAA), an equilibrium product of hydrogen peroxide and acetic acid, is an emerging disinfectant that is attracting attention as a green, effective alternative to chlorine that does not produce chlorinated disinfection byproducts. Additional benefits include a low effluent toxicity, the fact that residual quenching may not be required, and its potential use for wet weather disinfection. Although the number of utilities in the United States using PAA as a primary disinfectant is increasing and many more utilities have piloted PAA, it is still difficult to determine where PAA is most applicable due to concerns associated with PAA such as its current higher cost relative to chlorine, its effectiveness towards coliphages and viruses, the emerging regulatory issues, and the potential for microbial regrowth.
Based on our recent work, PAA is neither a solution to all disinfection issues, nor is PAA to be avoided. PAA is an alternative disinfectant that can meet treatment needs under certain drivers and conditions. Our presentation highlights our experience which includes, but is not limited to, the following: 1) Jar testing for wet weather disinfection for an Ohio utility showed that similar contact times for sodium hypochlorite and PAA were needed to meet the required inactivation; however, sodium hypochlorite was ultimately recommended for disinfection; 2) PAA decay studies that demonstrated that the PAA residual can remain stable for over 30 minutes, with dose requirements dependent upon water type; 3) A PAA pilot for a Tennessee utility conducted to gain regulatory approval that included whole effluent toxicity tests and a laboratory bioassay that demonstrated no effluent toxicity and provided a laboratory-derived measurement of chronic toxicity; and 4) a study on effluent from a utility in New England that found that the inactivation rates of fecal bacteria versus enterococci depended on the wastewater characteristics.
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