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The Energy Water Nexus : UT School of Law Slide 2 Slide 3 Brackish vs Seawater Slide 4 Brackish : 1 or 3? 10 ppt Seawater > 10 ppt Slide 5 Positive impacts of Brackish Groundwater Desalination? Reduce development pressure on other sources May allow other sources to be used for environment Costs make water conservation more attractive Slide 6 Unit Cost ($/ac-ft) Texas Water Supply Options Source : TWDB 2012 State Water Plan Slide 7 Environmental Considerations for Brackish Groundwater Desalination Ecological effects of brine disposal Increased energy needs Aquifer depletion or contamination Slide 8 Environmental Considerations for Brackish Groundwater Desalination Ecological effects of brine disposal Increased energy needs Aquifer depletion or contamination Slide 9 What is Brine? Slide 10 Slide 11 Brine Disposal Considerations Contamination from chemicals used for pretreatment, membrane cleaning and preservation Contamination for concentrated source water constituents (arsenic & radionuclides) Changes in salinity regime caused by brine itself Contamination or impairment of fish resources and habitats Slide Design stolen from Dr. George Ward Slide 12 Environmental Considerations for Brackish Groundwater Desalination Ecological effects of brine disposal Increased energy needs Aquifer depletion or contamination Slide 13 -variable thickness? -little data/modeling Slide 14 Environmental Considerations for Brackish Groundwater Desalination Ecological effects of brine disposal Increased energy and water needs Aquifer contamination Slide 15 Additional energy to produce brackish desalinated water? ~6.8 Kwh to produce 1,000 gal desalinated water 170 gpd is per capita use or 62,000 gal/year 421 kWh to produce enough desalinated water for year this is 3% of the amount used on individual annual basis iStockphoto/Larry Lawhead Data Source: Stillwell, King, Webber Slide 16 Additional carbon to produce brackish desalinated water? ~6.8 Kwh to produce 1,000 gallons desalinated water 6,800 Kwh to produce 1 Mgd or 137 Mwh for 20Mgd CO2 emissions: Coal = 142kg/d Gas = 71 kg/d this is 5 times the amount of emissions from a conventional surface water source iStockphoto/Larry Lawhead Data Source: Stillwell, King, Webber Slide 17 Additional water needs for 20 Mgd Brackish Desal facility? 6.8 mW for 1 million gal brackish water 15 40k gallons for 1 mW assume 66% recovery 3 8 Mgd additional water needs for power to process 30 Mgd iStockphoto/Larry Lawhead Slide 18 Additional water needs for 20 Mgd Desal facility? Australian desalination plants producing 36-120 Mgd use wind, solar, wave A Drought-Proof Source of Water? 3 8 Mgd? Slide 19 Positive impacts of Brackish Groundwater Desalination? Reduce development pressure on other sources May allow other sources to be used for environment Costs make water conservation more attractive Works well with water conservation programs Works well with renewable energy Slide 20 Slide 21 From Clayton, Stillwell, Webber Slide 22 Wind Suitability in Texas Slide 23 From Clayton, Stillwell, Webber Brackish Wells in Texas Lubbock Midland Abilene Slide 24 Unit Cost ($/ac-ft) Texas Water Supply Options Source : TWDB 2012 State Water Plan Slide 25 Meanwhile back in Australia Slide 26 The Sierra Clubs Perspective Photo: Jennifer Ellis, National Wildlife Federation Tyson Broad Lone Star Chapter Sierra Club With proper planning, siting, attention to all energy and environmental factorsDesal plants could be a significant part of a comprehensive water supply program that includes advanced water conservation and drought management measures.