Sustainable Recovery of Potable Water from Saline Waters

摘要

A new low-temperature phase change desalination process capable of being driven by low-grade or waste heat sources was developed and demonstrated at prototype scale. The proposed process is based on simple but sound scientific principles, and has the potential to produce potable-quality water in a sustainable manner, without any reliance on grid power. In this project, theoretical experimental studies were conducted to characterize and demonstrate the feasibility of the process. Based on theoretical simulations, a typical absorption refrigeration system driven by a 25 m2 solar collector and rated at a cooling rate of 3.25 kW (0.975 tons of refrigeration for typical domestic application) can produce 4.5 kg/h (108 L/d) of desalinated water. The net grid energy required for this case was 208 kJ/kg of desalinated water. The feasibility of an alternate configuration that could be driven solely by solar energy incorporating solar photovoltaic panel and a battery bank was demonstrated at prototype scale. Results of this study showed that a freshwater production rate of 0.25 kg/h (6 L/d) can be sustained at evaporation temperatures as low as 40oC using a solar PV panel of area 6 m2. The study also demonstrated that the system was able to produce EPA-recommended potable-quality water from the effluent of a municipal wastewater treatment plant, with the following removal efficiencies of key contaminants: > 93% total dissolved solids; >95% nitrates; > 97% ammonia; and > 99.9% coliform bacteria. Since this process can be driven entirely by renewable or waste energy, unlike the traditional desalination processes, it does not contribute to any greenhouse gas emissions.