Sustainable low temperature desalination: A case for renewable energy

In this paper, different configurations for running a low temperature desalination process at a production capacity of 100 litersday are presented. Renewable energy sources such as solar and geothermal energy sources are evaluated as renewable, reliable, and suitable energy sources for driving the low temperature desalination process round the clock. A case study is presented to evaluate the feasibility of sustainable recovery of potable water from the effluent streams of wastewater treatment plant. Results obtained from theoretical and experimental studies demonstrate that the low temperature desalination unit has the potential for large scale applications using renewable energy sources to produce freshwater in a sustainable manner. The following renewable energywaste heat recovery configurations may produce around 100 litersday of desalinated water: (1) solar collector area of 18 m² with a thermal energy storage (TES) volume of 3 m³; (2) photovoltaic thermal collector area of 30 m² to provide 14-18 kW electricity and 120 litersday freshwater with an optimum mass flow rate of the circulating fluid around 40-50 kgh m²; (3) A geothermal source at 60 C with a flow rate of 320 kgh; and (4) waste heat rejected from the condenser of an absorption refrigeration system rated at 3.25 kW (0.95 tons refrigeration), supported by 25 m² solar collector area and 10 m³ TES volume. Additionally, the secondary effluent of local wastewater treatment plant was processed to recover potable quality water. Experimental results showed that 95 of all the water contaminants such as biological oxygen demand (BOD), total dissolved solids (TDS), total suspended solids (TSS), ammonia, chlorides, nitrates, and coliform bacteria can be removed to provide clean water for many beneficial uses.