Assessing the validity of solar membrane distillation for disinfection of contaminated water

Together with desalination, reuse of wastewater is considered as a solution to mitigate thewater deficit in many areas. Membrane distillation (MD) is a technology increasingly proposedfor desalination and water treatment. The process is supposed to produce pure distillate,and this is what this paper evaluates. Biologically contaminated water was used in acommercial prototype of spiral-wound liquid-gap MD coupled with solar thermal energy toassess the suitability of the process for removing pathogens. Tests were done during severalhours for different operating conditions. The produced distillate, the rejected concentratedsolution and the feed water were monitored through time and samples were taken formicrobiological analysis. Results proved the efficiency of solar MD to produce a contaminantfreedistillate when Escherichia coli, Fusarium solani and Clostridium sp spores were present inthe feed water. Furthermore, in the first two cases the population of biological contaminantsin the concentrated decreased below the detection limit during the experiments. However, inthe case of Clostridium sp spores, these were not totally inactivated in the concentrated solution.Therefore, it was necessary to apply a post treatment before reclaiming the concentratedsolution. The technology used was a photo-Fenton process carried out in a compoundparabolic collector reactor. The combination of MD and photo-Fenton achieved completeabatement of Clostridium sp. spores, which was not accomplished in previous experimentswhen photocatalysis alone was applied to wastewater.