INDIRECT POTABLE WATER REUSE: AN ALTERNATIVE FOR WATER QUALITY MANAGEMENT IN THE LAS VEGAS VALLEY

The ever increasing population in Las Vegas Valley has spurred the development of new water management policies for providing water and wastewater infrastructure to address the consequent high demand for water and high amounts of wastewater generation. Current plans to address water demand include importation of water from Muddy and Virgin Rivers and northern counties, desalination of seawater with trade-payoff in California, water banking in Arizona and California, and more intense water conservation efforts in Las Vegas Valley. In Las Vegas Valley, water and wastewater are intrinsically related because treated wastewater effluent is returned back to Lake Mead, the drinking water source for the Valley's residents. Furthermore, return credit is given to Nevada when wastewater is returned to Lake Mead, thereby augmenting Nevada's water allocation from the Colorado River. While the return of treated wastewater augments the water supply, it is a major contributor of nutrient, TDS, and and other contaminants to Lake Mead.A plan consisting of a pipeline/tunnel/submarine diffuser (SCOP) is currently being implemented that will convey tertiary wastewater effluent to another location in Lake Mead as an effort to minimize the effects of phosphorus on the lake productivity. This plan does not address the removal of other contaminants that are present in the effluent. In this paper, we have performed a complete water balance for the Las Vegas Valley and have investigated an alternative to SCOP–Indirect Potable Water Reuse (IPWR). IPWR would involve the use of reverse osmosis membrane to treat tertiary wastewater effluent for use in the potable water system. It was found that an IPWR system would have several advantages over SCOP in terms of water quality of Lake Mead and downstream Colorado River, economic benefit to all major stakeholders, and a potential for trading water allocation for TDS removal from the Colorado River.