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

Abstract

Together with desalination, reuse of wastewater is considered as a solution to mitigate the water deficit in many areas. Membrane distillation (MD) is a technology increasingly proposed for 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 a commercial prototype of spiral-wound liquid-gap MD coupled with solar thermal energy to assess the suitability of the process for removing pathogens. Tests were done during several hours for different operating conditions. The produced distillate, the rejected concentrated solution and the feed water were monitored through time and samples were taken for microbiological analysis. Results proved the efficiency of solar MD to produce a contaminant-free distillate when Escherichia coli, Fusarium solani and Clostridium sp spores were present in the feed water. Furthermore, in the first two cases the population of biological contaminants in the concentrated decreased below the detection limit during the experiments. However, in the 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 concentrated solution. The technology used was a photo-Fenton process carried out in a compound parabolic collector reactor. The combination of MD and photo-Fenton achieved complete abatement of Clostridium sp. spores, which was not accomplished in previous experiments when photocatalysis alone was applied to wastewater.