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

Abstract

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.