Water quality assessment of solar-assisted adsorption desalination cycle

This study focuses on the water quality assessment (feed, product and brine) of the pilot adsorption desalination (AD) plant. Seawater from the Red Sea is used as feed to the AD plant. Water quality tests are evaluated by complying the Environmental Protection Agency (EPA) standards with major primary and secondary inorganic drinking water pollutants and other commonly tested water quality parameters. Chemical testing of desalinated water at the post desalination stage confirms the high quality of produced fresh water. Test results have shown that the adsorption desalination process is very effective in eliminating all forms of salts, as evidenced by the significant reduction of the TDS levels from approximately 40,000 ppm in feed seawater to less than 10 ppm. Test results exhibit extremely low levels of parameters which are generally abundant in feed seawater. The compositions of seawater and process related parameters such as chloride, sodium, bromide, sulfate, calcium, magnesium, and silicate in desalinated water exhibit values of less than 0.1 ppm. Reported conductivity measurements of desalinated water are comparable to distilled water conductivity levels and ranged between 2 and 6 μS/cm while TOC and TIC levels are also extremely low and its value is less than 0.5 ppm. © 2014 Elsevier B.V. All rights reserved.

AD technology provides a breakthrough solution for the continuing global thirst for new fresh water resources that uses only lowtemperature waste heat which is deemed non-payable. Furthermore, AD process can produce cooling power and fresh water simultaneously using waste heat or renewable energy sources such as solar or geothermal energy. AD technique is relatively inexpensive and has a low operational cost when compared to conventional desalination technologies such as multi-stage flash or reverse osmosis. The chemical assessment of distillate has proven that the water quality of AD process is independent of high feed salinity (up to TDS N 220 ppt or 22% by weight) inside the evaporator even at high recovery ratio. The residual brine can be fed directly to other concentrator or crystallizer for salt recovery purposes. In addition, the chemical quality of produced fresh water has been experimentally demonstrated to be comparable to deionized water quality. The product water of AD process can undergo further treatment for pH adjustment and disinfection and be introduced as a cost effective, environment friendly and low maintenance source of potable drinking water technology in desert regions and water-scarce countries. Acknowledgment The authors gratefully acknowledge the help of Dr. Tahir Yapici, Mr. Mohammed Khalid and Mr. Bashir Warsama from KAUST Analytical Core Lab, who assisted in performing the analytical testing.