Experimental and economic investigation of sweeping gas membrane distillation/pervaporation modules using novel pilot scale device

With the increasing demand for freshwater, the disposal of the highly saline water resulting from industrial processes and seawater desalination plants has become a critical environmental problem. Reverse osmosis (RO) cannot endure high salinity feed streams higher than 75 g/L. Membrane distillation (MD) and pervaporation (PV) techniques have been proving their capability to desalinate high-salinity brines. The sweeping gas MD/PV (SGMD/SGPV) technique has a lower heat loss to the permeate side as air is used to carry the water vapour, but it is rarely evaluated at larger scales. A pilot-scale desalination device was designed and constructed for an MD/PV surface area of 1.17 m2 to analyse the performance of SGMD/SGPV. The resultant fluxes reached 13.2 L m−2h−1 and 9.2 L m−2h−1 at feed salinities of 35 g/L and 125 g/L, respectively, with 99.6 % salt rejection (% SR) at 70 °C. Furthermore, an economic analysis of the overall system shows that it requires minimal maintenance costs to be competitive in water production. Overall, it provides an appealing alternative to small-scale, stand-alone desalination systems capable of generating high-quality drinking water from very salty water.