Disinfection byproducts and cellular toxicity from UV/chlorine advanced oxidation for potable reuse and drinking water treatment compared to chlorination and UV/hydrogen peroxide

This work explored treatment byproducts and cellular toxicity resulting from UV/chlorine advanced oxidation for potable water reuse and drinking water treatment, in comparison to chlorine and UV/hydrogen peroxide as treatments widely considered acceptable to use. Waters from six full or large demonstration-scale potable water reuse or drinking water treatment plants were treated with lab and pilot-scale UV/chlorine, chlorine alone, and UV/hydrogen peroxide and analyzed for 43 known disinfection byproducts and four types of cellular toxicity. The byproducts and toxicity were almost always near or below detection limits for waters treated with reverse osmosis. For the other waters, UV/chlorine generally led to small (< 10 μg/L or < 40 %) increases in the byproduct concentrations over chlorine alone, though cellular toxicity following the two treatments was similar. While UV/chlorine formed more byproducts than UV/hydrogen peroxide within the UV reactor, there was little difference in the byproducts and cellular toxicity between the waters treated by either AOP plus secondary chlorination. One UV/chlorine byproduct of potential concern observed in this work was chlorate, as up to 15 % of the chlorine photolyzed during UV/chlorine converted to chlorate.