PASSIVE PERMEATE-SIDE-HEATED SOLAR MEMBRANE DISTILLATION: TUBULAR AND MULTISTAGE PLANAR SYSTEMS WITH HYDROPHOBIC AND HYDROPHILIC MEMBRANES

In this research, a multistage (i.e., three stages) planar, and a tubular passive permeateside-heated interfacial solar membrane distillation (ISMD) has been developed. The three-stage system had an system energy efficiency of 62% in producing distilled water at an average daytime irradiance of 422 W/m2 with average distillate flux of 5 kg/(m2·day), which is higher than that of the single-stage planar systems. Production rate of distilled water in each stage of the three-stage planar system per unit area of footprint was 3.3 kg/(m2·day), while the production rate per unit area of footprint of single-stage system was 1.6 kg/(m2·day). Also, a hydrophilic nanoporous (PES NF) membrane was used in our study, which has not been found in the research of conventional MD systems. No penetration of hydrophilic nanoporous membrane was found during the operation of single-stage planar systems under simulated sunlight. The membrane was able to produce distilled water for 114 days under simulated sunlight using municipal wastewater as feed water. On the other hand, hydrophobic (0.20 and 0.45 μm) PVDF membranes were penetrated by feed water (i.e., wastewater) after approximately 50 days.