Monday, 7 November 2005
8

Developing Strategies to Extract Salts and Water from Concentrate for Beneficial Use.

Wesley, Augustus Brown and Naomi Assadian. Texas Agricultural Experiment Station, 1380 A&M Circle, El Paso, TX 79927

The availability of adequate water in terms of quality and quantity is the number one issue affecting agriculture and communities of far West Texas. Non-potable supplies (NPS) are being targeted for irrigation. NPSs differ from fresh water supplies not only in nutrient composition, but also in varying salinity constituents and concentrations. A potential source of concentrate water (CW) is from desalination plants. Total dissolved solids may exceed 33,000 mg/L. We hypothesize that brine has the potential to be a valuable irrigation product with appropriate management. Safe and beneficial application of CW and others NPS for irrigation will promote regional water conservation, decrease the cost of water treatment and disposal to rural and urban communities, and reduce the cost of production inputs at the field or managed landscape. Treatments of bench-scale experiments include Inland Brine Concentrate (IBC) and seawater brine concentrate (SBC) at salt concentrations ranging from 0 – 14,000 mg/L. A comparison of concentrates provides insight to the kinetics and precipitation products of multi-salt solutions at increasing ionic strengths. The hypothetical salt composition of IBC is based on Hydronautics software estimates using nanofiltration to desalinate groundwater in Dell City, Texas. Results show that IBC concentrations of calcium and sulfate exceed typical elemental ranges of concentrate produced from desalting seawater. Increases in calcium and sulfate ions increased the rate and quantity of precipitation in IBC in comparison to SBC. Ongoing experiments also show that the introduction of bicarbonates, increased temperature, and metal coagulants show an acceleration of the rate and total salt precipitation (in some cases by as much as 30% in calcium, 40% in sodium and 70% in sulfates). Our continuing challenge is to find low cost strategies to precipitate salts pure enough for commercial purposes and to produce water to meet irrigation standards.

Handout (.pdf format, 20291.0 kb)

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