Direct contact membrane distillation for the treatment of wastewater for a cooling tower in the power industry

Water abstraction for cooling requirements in energy production accounts for more than 40% of the total gross abstraction in the European Union, thus driving the interest in using alternative water resources. The current study presents the application of direct contact membrane distillation for the treatment of wastewater from a flue gas desulphurization (FGD) plant for potential applications in cooling towers. Membrane distillation (MD) performance of two commercial lab-scale membrane modules (in capillary and flat configuration) was compared in terms of flux, specific energy consumption (SEC), and rejection towards non-volatiles present in wastewater samples, pretreated according to various protocols. For the flat module, two commercial membranes were tested. In all cases, a good quality permeate was produced, with stable flux over experimental time. SEC of MD for wastewater treatment, calculated experimentally, varied from 946 to 2,830 kWh/m3 for the various applied membranes operating under different conditions. MD allows extracting more than 80% freshwater from FGD wastewater stream while maintaining high (.99.60%) rejection towards electrical conductivity.