Energy duty in direct contact membrane distillation of hypersaline brines operating at the water-energy nexus

In the context of global climate crisis and growing world population there is the urgent need for viable technical solutions to harvest energy from alternative, renewable and continuous sources and to recover pure water at affordable costs. Herein, we capitalize on the study of direct contact membrane distillation technology treating hypersaline solutions simulating reverse electrodialysis outgoing mixed streams, in the logic of valorising the otherwise environmentally threating brine, in an integrated system operating at the water-energy nexus.Experimental results in terms of transmembrane water flux and dissolved salts rejection, indicate that DCMD is a feasible option to treat feed solutions with concentrations as high as 228 g L-1 total dissolved solids, while recovering pure water from brines which are practically impossible to be dewatered through reverse osmosis. Specific thermal energy consumptions and gain to output ratios, calculated under different feed compositions and flow rates for polypropylene and polyvinilidenefluoride membranes, indicated the possibility to tailor the thermal energy requirements of the MD stage by controlling the ratio between the streams at different salinity that are partially mixed in the RED unit and to potentially adapt it to the available amount of heat.