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Emerging Contaminant Sources Fate in Recharged Treated Wasterwater, Lake Havasu City, Arizona
Citation:
Wilson, D. C. AND T. L. JONES-LEPP. Emerging Contaminant Sources Fate in Recharged Treated Wasterwater, Lake Havasu City, Arizona. Environmental and Engineering Geoscience. Association of Engineering Geologists, Denver, CO, 19(3):231-251, (2013).
Impact/Purpose:
Due to drought in the southwestern United States (US), sources of clean water resources have become ever scarcer. This has lead a growing number of water management entities to utilize wastewater effluent to stretch their water consumptive needs. Effluent has been utilized directly from wastewater treatment plants primarily for nonresidential irrigation and to recharge depleted groundwater resources via percolation ponds or injection wells. Several water providers in the Phoenix Active Management Area of central Arizona recharge their wastewater effluent into groundwater reservoirs. This is done intentionally for water return credit from the Central Arizona Groundwater Replenishment District in order to pump future groundwater as authorized by Title 48 of the Arizona Revised Statutes http://www.cagrd.com/Operations/WaterSupplies.aspx). Other water providers recover the wastewater effluent for irrigation use (Wilson, 2007; http://www.scottsdaleaz.gov/Water/Water_Supply_Planning/Sustainable_Supply/Ground water___Sustainability).
Description:
In 2008 the City of Lake Havasu, Arizona, began a subsurface, effluent injection program to store treated wastewater effluent, which will eventually be seasonally recovered to balance the demand for irrigation during the summer months. As a proactive measure, the City decided to include monitoring a suite of pharmaceuticals and other emerging contaminants (PECs) along with required regulatory constituents, e.g., nitrate. Potential contributing sources of PECs throughout the water system were identified; resulting in only six constituents detected in the source and treated municipal water, all at concentrations less than 50 ng/L. Thirty-one PECs were identified in the City’s wastewater effluent streams, with concentrations ranging from just above the non-detect level to 9000 ng/L (pseudoephedrine), clearly showing the dominating local urban use of these compounds. As the effluent was injected into alluvial sediments via vadose zone wells, water was periodically sampled from nearby monitoring wells. Preliminary results indicated that at least half of the PEC concentrations fell below detection limits (< 10 ng/L) within 100 meters (330 feet) of the injection wells. However, a few PEC (e.g., sulfamethoxazole, benzophenone, phenytoin, etc.) concentrations remained above their respective detection limit 300 meters (~1000 feet) away from the injection wells.