Investigation of multi-stage desalination using a passive solar-driven membrane (PSDM) system: a critical analysis for Unserved and underserved areas (UUA) in the Philippines

The utilization of alternative and sustainable desalination methods geared towards geographically isolated and disadvantaged areas is gaining attention. The Passive Solar Driven Membrane (PSDM) desalination system, which relies on thermal and membrane processes, possesses key advantages to delivering safe water in rural and remote areas of an archipelagic location. This study explores the PSDM system using 1, 2, 4, 7, and 10 stages to determine the productivity, yield and salinity using simulated seawater, providing valuable insights regarding the system’s performance under Philippine atmospheric conditions. Desalination of 3.5% salt solution was conducted on a rooftop setting with PSDM multi-stages. Results show the average productivity of the 1, 2, 4, 7, and 10 stages are 93.84, 328.57, 401.47, 203.701, and 258.15 g/kWh respectively. The number of stages shows no correlation to the final salinity, showing a 94% - 96% reduction in the salinity of the distilled water at all stages. Such quality water can be used for irrigation for crops, livestock, household use, and potable water. Furthermore, membrane characterizations using SEM and WCA showed how the morphology and hydrophobicity of membranes influence the desalination process. The decreasing salt deposits and increasing distance from the heat source correlate with the effectiveness of the membrane design.