Toxicity of Wastewater with Elevated Bromide and Iodide after Chlorination, Chloramination, or Ozonation Disinfection

Abstract

Water reuse is receiving unprecedented attention as many areas around the globe attempt to better-manage their fresh water resources. Wastewaters in coastal regions may contain elevated levels of bromide (Br) and iodide (I) from seawater intrusion or high mineral content in the source waters. Disinfection of such wastewater is essential to prevent the spread of pathogens; however, little is known about the toxicity of the treated wastewater. In this study, we evaluated the genotoxicity to Chinese hamster ovary (CHO) cells induced by municipal secondary wastewater effluent amended with elevated Br and I after disinfection by chlorine, chloramines, or ozone. We calibrated and applied an N-acetylcysteine (NAC) thiol reactivity assay as a surrogate for thiol reactivity with biological proteins (glutathione) of wastewater samples. Chlorination of wastewaters produced CHO cell genotoxicity comparable to chloramination, 3.9 times more genotoxic than the nondisinfected controls. Ozonated wastewater was at least 3 times less genotoxic than the samples treated with chlorine-based disinfectants and was not significantly different compared with the nondisinfected controls. Positive and significant correlations were observed among genotoxicity, cytotoxicity, and NAC thiol reactivity for all disinfected samples. These results indicate that the ozonation of wastewater with high Br and I levels may yield organics with lower genotoxicity to CHO cells than chlorine-based disinfection. NAC thiol reactivity, although excluding the possible effect of bromate from ozonation in this work, could be used as a rapid in chemico screen for potential genotoxicity and cytotoxicity in mammalian cells exposed to disinfected wastewaters.

Disinfection Byproduct Recovery during Extraction and Concentration in Preparation for Chemical Analyses or Toxicity Assays

“…Many previous studies on the toxicological effects of whole disinfected water involved extracting ≥10 L of water samples followed by bioassays. ,, To test whether our findings for the 1-L extractions would apply to extractions involving larger volumes of water, we scaled up the different methods to perform duplicate 10-L extractions of the DBPs formed after chlorinating four creek waters (see Table S5 for basic water quality parameters). We compared XAD resin extraction and SPE (eluted with EtOAc) for Creeks A and B.…”

“…While THMs and HAAs have been used to measure DBP exposure for epidemiology studies, there is growing interest in measuring unregulated (semi-)­volatile classes (e.g., haloacetonitriles) based on studies indicating that they could contribute more to the cytotoxicity of disinfected waters and that their concentrations do not correlate with THM concentrations . Recoveries of unregulated, (semi-)­volatile DBPs were lowest for XAD resin extraction (<30%), one of the most frequently employed techniques, ,− , including the U.S. EPA studies. , While recoveries were generally higher with SPE and LLE, they were below 70% for most of the (semi-)­volatile DBPs examined. Even these mediocre recoveries required solvent exchange, risking the potential for toxicity associated with incomplete removal of MtBE or EtOAc from the DMSO during N 2 blowdown.…”

“…Even these mediocre recoveries required solvent exchange, risking the potential for toxicity associated with incomplete removal of MtBE or EtOAc from the DMSO during N 2 blowdown. Recoveries of most unregulated, (semi-)­volatile DBP classes would be negligible for XAD resin extraction coupled with EtOAc elution when the EtOAc is evaporated nearly to complete dryness before resuspension in DMSO. ,− , …”

“…As most DBPs occur at relatively low concentrations (ng/L to μg/L levels) in disinfected water, extraction and concentration are needed to identify novel DBPs and facilitate the detection of biological effects in toxicity assays. Solid-phase extraction (SPE) using XAD resins has been used extensively to extract and concentrate DBPs in disinfected waters for bioassays, ,− including a standard operating procedure for studies by the U.S. EPA . XAD resin extraction typically involves passing ≥10 L of disinfected water through a mix of XAD-2 and XAD-8 resins, eluting the sorbed compounds with ethyl acetate, and concentrating the extract to ≤1 mL using rotoevaporation and nitrogen (N 2 ) blowdown .…”

Global Transcriptional Analysis of Nontransformed Human Intestinal Epithelial Cells (FHs 74 Int) after Exposure to Selected Drinking Water Disinfection By-Products

“…Future research is now needed to investigate the potential augmented risk associated with the presence of DBPs as complex mixtures (Teuschler and Simmons 2003; Massalha et al 2018; Dong et al. 2017; Plewa et al.…”