Chlorination of Emerging Contaminants for Application in Potable Wastewater Reuse: Disinfection Byproduct Formation, Estrogen Activity, and Cytotoxicity. Kristin H. Cochran, Danielle C. Westerman, Cassiana C. Montagner, Scott Coffin, Lorivic Diaz, Benjamin Fryer, Gary Harraka, Elvis Genbo Xu, Ying Huang, Daniel Schlenk, Dionysios D. Dionysiou, and Susan D. Richardson*
Susan Richardson’s research aims to improve the safety of drinking water, including potable reuse water (wastewater turned into drinking water)
With increasing water scarcity, many utilities are considering potable reuse of wastewater as a source of drinking water. However, not all chemicals are removed in conventional wastewater treatment, and disinfection byproducts (DBPs) can form from these contaminants when disinfectants are applied during or after reuse treatment, especially if applied upstream of advanced treatment processes to control biofouling. Richardson’s group investigated the chlorination of seven priority emerging contaminants (17β-estradiol, estrone, 17α-ethinylestradiol, bisphenol A (BPA), diclofenac, p-nonylphenol, and triclosan) in ultrapure water, along with the impact of chlorination on real samples from different treatment stages of an advanced reuse plant to evaluate the role of chlorination on the associated cytotoxicity and estrogenicity.
She reports the formation of 28 novel DBPs not previously known when the seven priority
ECs were chlorinated (with and without bromide). However, the cytotoxicity of chlorinated ECs varied—sometimes increasing toxicity (e.g., β-estradiol, estrone), sometimes decreasing toxicity (e.g., p-nonyl phenol), and sometimes not changing cytotoxicity much (e.g., diclofenac) relative to the parent compounds. Also, the estrogenicity varied, with large reductions for chlorinated hormones (β-estradiol, estrone, ethinylestradiol) but increases for diclofenac and p-nonylphenol.
Thus, these effects are contaminant-specific. At the same time, chlorinated samples from a real advanced reuse water treatment utility demonstrated reduced estrogen activity following microfiltration, RO filtration, and advanced oxidation with UV-H2O2, except for microfiltration with bromide present. Because final advance oxidation-treated waters that were chlorinated (+ bromide) still showed ∼50% estrogen activity compared to nonchlorinated advanced oxidation-treated waters and compared to the nonchlorinated wastewater-impacted river waters, the compounds responsible for this estrogenicity should be determined in the future. Future studies should also analyze the cytotoxicity and estrogen activity of indirect potable reuse wastewater injected into groundwater, post-aquifer filtration, and before and after drinking water treatment. It is possible that many contaminants will be removed or reduced in concentration during aquifer filtration and storage and may not contribute to the formation of contaminant DBPs. Finally, future studies should investigate the formation of DBPs from these emerging contaminants at concentrations expected to occur in these potable reuse treatments.
