Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/133796
TECHNOLOGY plants from 2012 data in the study area. A conservative estimate of US$ 2/ft2 (US$ 21.50/m2) of liner, installed, was developed based on the use of a highquality, 2-ply synthetic liner. The results (Figure 2) reveal that, based on a simple cost comparison, the installed liner cost will exceed the land cost and is the financial limiting factor. Liner alternatives that are less expensive, with equal performance, are a reasonable option; however that and the ability to reduce the concentrate disposal volume is not enough to improve the cost-effectiveness of implementing evaporation ponds for concentrate management alone. Additional reduction of the land, and subsequent liner area, must be developed in addition to the optimization of the desalination process efficiency. in a vertical orientation over or beside the evaporation ponds and saturating the material with the concentrate. This effectively increases the surface area for evaporation vertically, in exchange for horizontal area. The energy component of this technique is only involved in transferring the concentrate from the pond to the material. Initial findings reveal that a low head, low horsepower suction pump can provide the required energy needed to meet the saturation requirement, operating on an intermittent basis. This technique of enhanced evaporation was piloted on a bench-scale model, where different materials and orientations were used over various time of the year. Those results were used to develop the enhanced ImpLEmENTING ENHaNCEd EvapOraTION Evaporation over an open body of water, such as an concentrate pond is the result of the influence of five components: 1. Wind velocity (a function of height above the water surface) 2. Air temperature (also a function of height above the water surface) 3. Specific humidity (also a function of height above the water surface) 4. Surface area 5. Net solar radiation. CapEX & OpEX COsT Mechanical methods are available that increase the radiation, the humidity, wind velocity, or air temperature components of the evaporation equation to enhance the evaporation. However, these are found to have large energy requirements, large footprints, or large capital and operating costs. The experimental portion of our ongoing research involves implementing materials areas located within regions where the average evaporation exceeds the average precipitation, and are deemed suitable for evaporative methods to manage concentrate from membrane processes. A comparison of the costs revealed that with the implementation of enhanced evaporation, the cost could be reduced by 65% and the required land area could be reduced by 50%. The cost comparison was then plotted over a projected 50-year operating life cycle as depicted in Figure 4. CONCLusIONs Pressure on water resource managers and policy-makers to meet growing community water demands with limited, diminishing, or over allocated fresh water supplies provides the opportunity to increase the LEGEND ARID SEMIARID HIGHLAND STUDY LOCATION Figure 3. Experimental study area rate, based on vertical area provided and local climate information including temperature, humidity, elevation and noting that the only evaporation occurring during daylight would be recognized, even though evaporation may still happen after sunset and before sunrise. Next the capital and operation and maintenance costs were developed for the enhanced evaporation technique. The costs for implementing traditional and enhanced evaporation ponds for municipal scale desalination concentrate management were then developed over the study area shown in Figure 3. YEars FrOm INITIaL INsTaLLaTION Figure 4. Lifecycle Cost Comparison | 34 | Desalination & Water Reuse | May-June 2013 Monthly evaporation and precipitation measurements were developed for each of the 21 study reliance on brackish water supplies. As engineers it is our responsibility to identify the effectiveness, value and costs associated with the options in concentrate management associated with adding brackish water supplies and reuse to a community's water resources portfolio and to provide sustainable solutions to meet community's needs. In our recent concentrate management and membrane treatment projects, we have found that the construction of such facilities is becoming increasingly common in urban areas and isolated areas, where affordable ample level terrain is not available. The results of this cost-based analysis demonstrate that evaporation can be an effective and cost-competitive solution when compared with inland disposal of concentrate to surface waters, to municipal sewers, or by deep-well injection. The improvement in membrane process efficiencies and the implementation of enhanced evaporation are the mechanisms that help provide cost-effective solutions to manage concentrate streams.l