Monitoring reductions in arsenic concentrations during groundwater recharge and recovery operations

The Truckee Meadows Water Authority (TMWA) owns and operates twenty nine wells that provide drinking water to the metropolitan areas of Reno and Sparks in Nevada. In order to ensure compliance with the new maximum contaminant level for arsenic of 10 μg/L in drinking water, TMWA has been testing the effectiveness of artificial groundwater recharge using treated surface water to reduce the concentration of natural occurring arsenic in the groundwater. The recharge of nine TMWA wells and two Washoe County wells with treated surface water proved to be an effective way of improving the quality of the groundwater.; The amount of water that was recharged at each well varied depending on the aquifer characteristics, groundwater level, and the configuration of the recharge system. During the recovery period, the concentration of arsenic in each of the wells studied was lower than the historical background concentration. It is believed that this is a result of repeated, subsequent recharge and recovery operations which have been conducted. As water demands continue to increase in the TMWA and Washoe County service area over time due to population growth, using artificial groundwater recharge to store treated surface water during the winter months until it is needed in the summer months could prove to be a very critical component of the region's water supply system in the future.