ZDD - ACHIEVING MAXIMUM WATER RECOVERY

摘要

Increasing population, decreasing water supply (volume and quality), and droughts are leading to increased competition between users (municipal, irrigation, power, etc.) of freshwater. The Zero Discharge Desalination (ZDD) process maximizes the volume of product water from a brackish source while minimizing impacts to the environment caused by waste disposal. ZDD has been evaluated at a pilot scale at several locations including New Mexico, Texas, California and Florida. ZDD technology utilizes a combination of processes and usually employs a combination of Electrodialysis Metathesis (EDM), a variant of electrodialysis, and reverse osmosis (RO) or nanofiltration (NF), as well as various forms of pre-treatment techniques. One mode of operation, called Basic Mode, utilizes EDM to treat RO concentrate and produce a highly concentrated stream of sodium salts of all the anions in the feed and another concentrated stream of chloride salts of all the cations. The salt-depleted diluate stream from the EDM can either be blended with the RO feed or a portion can be directly blended with the RO permeate depending on project goals and source water quality. The two concentrated streams are mixed to precipitate insoluble salts such as calcium sulfate (gypsum), and there is a potential to recover NaCl and magnesium salts from the remaining liquid. Previous pilot studies have demonstrated overall water efficiencies of 95-99% on a brackish ground water with sparingly soluble calcium sulfate and moderate silica levels (Alamogordo, NM). The University of Texas at El Paso's Center for Inland Desalination Systems (CIDS) was awarded funding from the US Bureau of Reclamation's Desalination and Water Purification Research program. This effort is a collaborative project between CIDS and Veolia Water Solutions and Technologies. ZDD will be demonstrated at a larger scale at the Brackish Groundwater National Desalination Research Facility (BGNDRF) in Alamogordo, NM. The tasks during the first year will be to evaluate a system capable of producing 20 gallons per minute of treated water and to design, build, and purchase a system capable of 30-40 gpm of treated water. In Years 2 and 3 the team will operate the larger system, evaluate waste stream optimization, and evaluate the potential for incorporation of renewable energy.