Water. desalination + reuse

November/December 2012

Water. Desalination + reuse

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PROJECTS PROJECTS Hybrid solar energy for Navajo Nation MD project _________ Mitch Haws, Program Manager, Bureau of Reclamation, USA ___ Editor���s Note: The University of Arizona and the US government���s Bureau of Reclamation are developing a project combining advanced water treatment in the form of membrane distillation with hybrid solar energy to provide water supplies for the Native-American area, Navajo Nation, in the south-west USA. Installation is currently under way and the system will be tested for a year from March 2013. MANY NATIVE Americans living on reservations in the southwest lack access to running water, sanitary facilities and lineconnected electricity. The Navajo Nation, a semi-autonomous Native-American region covering parts of Arizona, New Mexico and Utah, has been faced with these water and energy challenges for generations. The water available to its rural population is often impaired or from non-regulated sources because no other water is economically accessible. Many tribal members are forced to haul water from distant wells. UnivERSiTy Of ARizOnA PROJECT In January 2012, the University of Arizona (UA) completed the Navajo Nation Solar Desalination Research Pilot Demonstration Project report for the Bureau of Reclamation. The report indicates that rural Navajo water users pay a larger share of their income to get their water compared with other water-users in the region. Researchers at UA, in partnership with the Navajo Nation and the Bureau of Reclamation, have developed an applied research site to test off-grid, advanced water-treatment technologies using renewable energy. This concept is being developed and funded in partnership with UA and Reclamation���s Science & Technologies Research Program. SOlAR/MD SySTEM UA researchers focused on sustainability factors in designing a solar energy and brackish-water desalination system to supply water, initially, for livestock. With the knowledge gained from this Figure 1. CoGenra SunPac 12 non-potable application, a subsequent objective is to develop a renewable energy/ advanced water treatment package to supply the rural/remote dispersed population with potable water. The applied design and research project combines a Concentrating Photovoltaic Thermal Hybrid (CPVTH) system as the heat and electrical energy source, with Membrane Distillation (MD) technology for the advanced water treatment system. One objective of the project is to develop a system using ���off-the-shelf ��� products that are simply designed to minimize the operation, maintenance and replacement costs. The researchers envision a stand-alone system producing distilled water to be blended with the lesser quality water. This will serve as livestock water and is a prerequisite step in developing a potable water system for human consumption. PROJECT iMPlEMEnTATiOn Researchers sampled five wells within the southwestern chapters of the Navajo Nation known to have brackish water and chronic imbalances of supply and demand. Water quality, depth to static water level, well | 20 | Desalination & Water Reuse | November-December 2012 condition and location of supply in relation to demand were surveyed. As the criteria for selection were developed, well site No 5T-529, about 15 miles (24 km) from Leupp, Arizona, was determined to be the candidate well for the research (Figure 2). Originally, this well was developed using a traditional livestock windmill with a pumping rate capacity of 3-5 gallons of water per minute (0.2-0.3 L/s) when the wind blows. Although wind velocities are considered consistent in the fall, winter and spring months, peak water-demand occurs in summer when wind resources are insufficient or highly variable. Since solar-energy-based pumping systems are used throughout the world, researchers determined that pumping rates could be doubled and the seasonal variability mitigated by retrofitting the existing well site. The anticipated increase in water production will produce an immediate benefit to local water users and livestock producers. The Navajo Department of Water Resources installed nearly 50,000 gallons (190,000 L) of storage capacity and 7 miles (11 km) of conveyance pipeline to serve livestock water users with limited access to water. With anticipated advancements in water treatment technology, this conveyance system now used by livestock producers could be converted to deliver water for potable use. Navajo well 5T-529 provided an excellent opportunity to improve water service to livestock producers and test the efficacy of a solar energy-based advanced water treatment system. The well���s water quality analysis provided water chemistry data necessary for the researchers to conceptualize the design of the treatment system. The well���s total dissolved solids were determined to be approximately 1,400 parts per million with no other remarkable water chemistry constituents of concern identified. The local livestock drink this water but demand continues to exceed supply in a region where 10 years of drought have limited the availability of surface storage supplies. Since well 5T-529 is on a mesa higher in elevation than much of the area, it could be a main distribution point for water without requiring energy for distribution. A research facility is currently under construction at the well site. A solar water-pumping system was installed by the Navajo Nation and is temporarily being operated by a gas-powered generator until construction of the CPVTHS is complete. NExT PhaSE The next phase, scheduled for November 2012, will furnish and install the CPVTHS system using a SunPac 12 unit supplied by CoGenra of Mountain View California (see Figure 1). In March 2013, the MD system will be designed and installed by students from the School of Engineering and Environmental Science at UA. The system will be tested for a year. Students will focus on system optimization Figure 2. The Navajo Well 5T-529 test facility and a control system. A summary report of findings containing the research thesis, objectives, assumptions, investigations, parameters, designs, modifications, operations and costs will be reported in a peer-reviewed publication at the conclusion of the testing/monitoring cycle in early 2014. l ViSiT ONliNE desalination.biz 2013 Membrane Technology CONFERENCE & EXPOSITION The AMTA/AWWA 2013 Membrane Technology Conference will be the premier event for membrane applications in North America. Register by January 24, 2013 for the best rates! February 25���28, 2013 Presented by Henry B. Gonzalez Convention Center San Antonio, TX America���s Authority in Membrane Treatment Improving America���s Waters Through Membrane Treatment and Desalting The Authoritative Resource on Safe Water �� www.awwa.org/amta November-December 2012 | Desalination & Water Reuse | 21 |

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