Formation, speciation, and temporal variability of DBPs in drinking water distribution systems in the context of ASR operations and extended storage periods.

As climate change induces changes in water quality and available water quantity of drinking water supply sources, the final product water quality changes in terms of trace organics including disinfection byproducts (DBPs) formed during water treatment. In this study, the seasonal variability and speciation of DBPs across nine sample sites within a drinking water distribution system serving ∼400k people over a one-year period was investigated considering the governing parameters of water quality and treatment/transport/storage of finished water. The system considered treats surface water from a river and practices aquifer storage and recovery to address seasons water availability changes. Eighty-eight (88) sample sets were collected and held for 6-months in the laboratory to simulate extended storage scenarios associated with ASR operations, and each was analyzed at 9 different timesteps for concentration and speciation of chlorinated DBPs. Samples from groundwater influenced sites exhibited significantly lower total organic carbon (TOC) compared to other sites from the river source, and also were observed to have the lowest DBP formation. Three sites exceeded the Maximum Contaminant Level (MCL) for four total trihalomethanes (THM4) within 30-60 days of storage. Chloroform was the predominant THM4 species, even in groundwater-influenced locations, whereas di- and tri-chloroacetic acid (DCA and TCA) were the most prevalent haloacetic acids (HAA5). Extended water age at one site, coupled with low initial chlorine concentrations exhibited higher initial THM4 concentrations and flat DBP formation curves. The study results provide new insights into DBP occurrence and fate in drinking water distribution systems which consider water storage such as in ASR.