Experimental study of multi-effect membrane distillation (MEMD) for treatment of water containing inorganic salts

A novel multi-effect membrane distillation (MEMD) process has been implemented to treat water containing four different inorganic solutes. The 4-stage MEMD module was developed based on the air-gap configuration. The influence of operating parameters like concentration, feed temperature, flow rate and operating time on permeate fluxes of zinc sulfate, sodium fluoride, magnesium chloride and sodium carbonate solutions was observed. Concentration had negligible effect on the MEMD's permeate flux, while its performance increased with increasing feed temperature and flow rate. Its separation efficiency was stable at more than99.91% throughout the experiment. In addition, its specific energy consumption after the recovery of the latent heat of vaporization and sensible heat of brine was measured at different component concentrations and found to be independent of the type of component.