Browsing by Subject "Brackish groundwater"
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Item Feasibility of brackish water desalination as an alternative water supply in the Barton Springs/ Edwards Aquifer conservation district(2015-05) Barraza, Alan; King, Carey Wayne, 1974-; Kreitler, Charles W.Growing demands for water across the State of Texas has prompted many entities to take into consideration alternative means of obtaining water. The Edwards Aquifer within the Barton Springs/Edwards Aquifer Conservation District (BSEACD) has long been an invaluable and reliable resource in providing high quality water at a low cost. The continued population growth within the BSEACD along with continued drought conditions have strained the resource to the point of having restrictions being placed on production. These restrictions are in response to the potential impact of over-pumping water wells, water quality, springflow, and endangered species. At current permitted pumping, even with all curtailments allowed by statutory authority and current rules, the BSEACD cannot meet Desired Future Conditions during an ongoing drought of record. Within the boundaries of the BSEACD, there exist opportunities for groundwater production in the brackish portion of the Edwards and Trinity aquifers. This paper presents the economic feasibility of undertaking a brackish groundwater desalination project in the saline portion of the Edwards aquifer and also considers technical and regulatory obstacles. It is based upon a model that incorporates prevailing market and hydrogeologic conditions within Central Texas and the BSEACD, such as total dissolved solids content, brackish well depth, concentrate well depth, capital and operational costs of desalination facilities, electricity demands and costs, and water costs into its calculation. Results from this study indicate a reverse osmosis desalination project between the modeled range of 1.25 MGD to 12.5 MGD would be economically feasible. At 2.76 MGD the water would cost $748 per acre foot ($2.30 per 1,000 gal) to produce and gradually decreases in cost as the size of the facility increases due to economics of scale. At approximately 10 MGD of desired daily product generation the optimal price of $648 per acre-foot ($1.99 per 1,000 gal) is reached. While a desalination project within the BSEACD may be economically feasible, there are technical and regulatory obstacles that must be overcome before such project can take commence.Item Improving recovery in reverse osmosis desalination of inland brackish groundwaters via electrodialysis(2010-08) Walker, William Shane, 1981-; Lawler, Desmond F.; Freeman, Benny D.; Katz, Lynn E.; Kinney, Kerry A.; Liljestrand, Howard M.As freshwater resources are limited and stressed, and as the cost of conventional drinking water treatment continues to increase, interest in the development of non-traditional water resources such as desalination and water reuse increases. Reverse osmosis (RO) is the predominant technology employed in inland brackish groundwater desalination in the United States, but the potential for membrane fouling and scaling generally limits the system recovery. The general hypothesis of this research is that electrodialysis (ED) technology can be employed to minimize the volume of concentrate waste from RO treatment of brackish water (BW) and thereby improve the environmental and economic feasibility of inland brackish water desalination. The objective of this research was to investigate the performance sensitivity and limitations of ED for treating BWRO concentrate waste through careful experimental and mathematical analysis of selected electrical, hydraulic, and chemical ED variables. Experimental evaluation was performed using a laboratory-scale batch-recycle ED system in which the effects of electrical, hydraulic, and chemical variations were observed. The ED stack voltage showed the greatest control over the rate of ionic separation, and the specific energy invested in the separation was approximately proportional to the applied voltage and equivalent concentration separated. An increase in the superficial velocity showed marginal improvements in the rate of separation by decreasing the thickness of the membrane diffusion boundary layers. A small decrease in the nominal recovery was observed because of water transport by osmosis and electroosmosis. Successive concentration of the concentrate by multiple ED stages demonstrated that the recovery of BWRO concentrate could significantly improve the overall recovery of inland BWRO systems. A mathematical model for the steady-state performance of an ED stack was developed to simulate the treatment of BWRO concentrates by accounting for variation of supersaturated multicomponent solution properties. A time-dependent model was developed that incorporated the steady-state ED model to simulate the batch-recycle experimentation. Comparison of the electrical losses revealed that the electrical resistance of the ion exchange membranes becomes more significant with increasing solution salinity. Also, a simple economic model demonstrated that ED could feasibly be employed, especially for zero-liquid discharge.