Process Modeling of Trihalomethanes During Aquifer Storage and Recovery
AdvisorCooper, Clay A.
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Aquifer storage and recovery has been used to meet consumer demand, particularly in the southwestern United States, by injecting treated water underground during wet periods and recovering water during dry periods. Trihalomethanes are the most common disinfection by-products found in chlorinated water, a result of chlorine reacting with dissolved organic matter, and are linked to adverse human health effects. The study objective is to examine processes associated with the attenuation of trihalomethanes surrounding a dual-use well using a numerical model with data and physical and chemical processes pertinent to the Las Vegas Springs aquifer. Thirty-one well data sets provided by the Southern Nevada Water Authority, a chloride mass balance to adjust for dilution, calculated parameters such as liquid diffusion coefficient, and estimated parameters such as longitudinal dispersivity were used to build a single layer, confined, homogeneous, and isotropic model to simulate trihalomethane attenuation. Trihalomethane concentrations at the well during recovery were moderately sensitive to flow rates and porosity, and highly sensitive to a high reaction rate and a low longitudinal dispersivity. The chemical reaction between trihalomethanes and aquifer material was slow with a reaction rate of -0.0032 1/day. A numerical model of trihalomethane attenuation during aquifer storage and recovery may provide water utilities with a tool to monitor trihalomethane transport as it concerns public drinking water.