Drinking Water Quality and Risk Challenges from Increasing Source Water Bromide: Effects of Climate and Energy Changes

2018-10-22T21:00:53Z (GMT) by Chelsea Kolb
Disinfection is a critical step in drinking water treatment, killing pathogenic organisms and ensuring the water is safe for consumption. However, disinfection byproducts (DBPs) form during treatment when disinfectants react with naturally occurring organic matter, bromide, iodide or other contaminants present in source waters. DBPs are of concern in drinking water because they are carcinogenic and teratogenic, and some DBPs are regulated. Source water bromide can shift DBP speciation toward higher risk brominated species and may shift some<br>DBPs toward unregulated forms. While naturally occurring bromide concentrations are typically quite low, elevated levels can be found in coastal groundwater and estuary sources and where surface waters are impacted<br>by anthropogenic activities such as energy extraction and utilization activities. Elevated bromide concentrations in source waters may lead to higher risk to consumers, even while water continues to meet regulatory compliance requirements. TTHM does not adequately capture risk of the regulated species when source water bromide concentrations are elevated, and thus would also likely be an inadequate surrogate for many unregulated brominated<br>species. Alternative surrogate measures, including THM3 and the bromodichloromethane concentration, are more robust surrogates for species-specific THM risk at varying source water bromide concentrations.<br>Recently, climate change has been associated with increasing bromide concentrations incoastal groundwater and estuaries sources resulting from saltwater intrusion and in inland surface water sources as a result of anthropogenic factors. This work evaluated elevated bromide concentrations resulting from saltwater intrusion in coastal groundwater systems and from anthropogenic discharges from coal fired power plants operating wet FGD units.<br>Coastal utilities treating a↵ected groundwater sources will likely meet regulatory levels for THMs, but even small changes in saltwater intrusion can have significant e↵ects on finished water concentrations and may exceed desired health risk threshold levels due to the extent<br>of bromination in the THM. As a result of climate change, drinking water utilities using coastal groundwater or estuaries should consider the implications of treating high bromide source waters. In surface waters in the Monongahela River Basin, coal-fired power plants with wet FGD account for most of the total observed bromide concentrations at a drinking water intake<br>downstream. For the modeled bromide load, coal power plant discharges contribute an additional 24 mg/L TTHM half of the time during the period evaluated, exceeding the 10−5<br>risk threshold. As source water bromide concentrations increase, TTHM may be inadequate as a surrogate measure for DBP risk. Alternative regulatory strategies may better protect human health.<br>