Investigation of Energy-Related Wastewater Impacts on Disinfection By-Product Formation in Drinking Water

Elevated bromide and iodide in drinking water sources contribute to the formation of toxic brominated and iodinated disinfection by-products (DBPs) during drinking water treatment. Energy extraction and utilization processes, including hydraulic fracturing (HF) and coal-fired power plants (CFPPs), produce wastewaters with bromide/iodide levels on the order of tens to thousands of mg/L. These wastes have the potential to impact drinking water sources through both intentional (e.g., direct discharge) and accidental (e.g., basin overflow, spill) release pathways. This research focuses on a combination of quantitative and non-targeted approaches to assess DBP formation impacts from HF and CFPP wastewaters, with complementary toxicity studies contributed by collaborators. The HF studies reported here are the first non-targeted investigations of the formation of DBPs from both geogenic (phenolics) and anthropogenic (surfactant) organic DBP-precursors. In both cases, high-resolution mass spectrometry (MS) was crucial to the identification of never-before-reported DBPs. Fifty-six iodo-phenolics were identified, comprising three homologous series of iodinated phenolics, including two new classes of DBPs: iodocresols and iodoxylenols. Many of these newly-identified DBPs were cytotoxic in mammalian cell assays. In addition, over 300 new sulfur-containing DBPs were identified in gas-extraction wastewaters. These originated from a mixture of isomers of olefin sulfonate (dodecene sulfonate) surfactant, a common fracking fluid additive. Brominated, iodinated, and chlorinated sulfonate-based DBPs were identified, as well as halogenated di-S-species, derived from surfactant impurities. Chlorine and chloramine disinfection of these gas wastewaters increased cytotoxicity by several orders of magnitude, with chloraminated water being the most toxic. We also conducted the first experimental investigation of the impacts of CFPP wastewater on resulting DBP formation from chlorination and chloramination. It is the most comprehensive quantification of DBPs from CFPP impact, as well as the first to assess CFPP impact on iodide and iodo-DBP formation. The presence of CFPP waste significantly enhanced the formation of brominated and iodinated DBPs, as well as calculated cyto- and geno-toxicity, under both disinfection conditions. While chloramination resulted in lower overall DBP formation, higher levels of iodo-DBPs, including highly toxic iodinated haloacetamides, formed with CFPP impact. Speciation and toxicity associated with formation of these CFPP and HF waste-derived DBPs is important for energy waste-impacted drinking water treatment plants that may consider switching from chlorination to chloramination, which will effectively control regulated DBPs, but could result in higher-toxicity drinking water