Use of Peracetic Acid as a Wastewater Disinfectant to Eliminate the Formation of Chlorinated Disinfection By-products and Inhibit the Activity of Endocrine Disrupting Compounds

While the chlorination process is the most commonly used disinfection technology for municipal wastewater in the US, formation of harmful chlorinated DBPs has become a concern, and is one of the major drivers for wastewater utilities to consider alternative disinfection technologies. Studies in 1970s found that trihalomethanes (THMs), which include chloroform, dichlorobromomethane, dibromochloromethane and bromoform, can be formed from chlorinated disinfection processes1. Since that, numerous and even more toxic DBPs have been identified as the result of the wastewater chlorination process. These include, for example nitrosamines2 and cyanide3-4. Some of these DBPs have been identified as human carcinogens or probable human carcinogens. They could also be toxic to aquatic organisms. Once these DBPs are formed, adding a de-chlorination process will not remove them. Depending on site specific conditions, utilities may have discharge limits on DBPs in their National Pollutant Discharge Elimination System (NPDES) permits. For comparison purpose, the corresponding maximum contaminant levels (MCLs) in accordance to the primary drinking water standard in US are also included in the table. Similar to other water quality parameters, the limit values of DBPs in NPDES permits vary from plant to plant, depending primarily on the dilution factor of the wastewater effluent discharging into the receiving stream, the target sensitive aquatic organisms to be protected, and the use designation of the receiving stream.In addition to disinfection by-products, endocrine disrupting compounds (EDCs) and pharmacological and personal care products (PPCPs) may have a profound impact on human health and sensitive receiving bodies, such as wetlands, through discharge via wastewaters into the environment. EDCs may enter the environment through wastewater discharge as a result of incomplete metabolism of medicinal compounds, such as synthetic estrogen, or through leaching from waste materials, such as the plasticizer bis-phenol A. Disruption of normal endocrine cycles may cause abnormal growth, reproduction and development in wildlife and potentially cause hormonal dysfunction and cancer in humans.Recently, peracetic acid (PAA) has gained momentum as an alternative disinfection technology to chlorine5-7. Peracetic acid is delivered as an equilibrium solution of peracetic acid, hydrogen peroxide, acetic acid (vinegar) and water, and has been used in a variety of industries as a disinfectant and sterilant. While its use as a wastewater disinfectant has been relatively recent, over the past four years, its effectiveness on controlling bacterial microorganisms is well-known8. Upon reaction with bacteria and viruses, natural organic matter, reduced metals and suspended solids, PAA decomposes to oxygen, water and acetic acid. As a result, no chlorinated by-products are formed. In addition, PAA does not survive long under environmental conditions, so its overall impact on the environment is small, as compared to chlorine.This study investigates the impact of peracetic acid disinfection of wastewater on the formation of chlorinated disinfection by-products and on the inactivation of endocrine disruptor compounds.