Sustainable solar powered vaccum membrane distillation for water treatment

Abstract

Water recycling in a sustainable manner is increasingly being practiced around the world as a supplementary water resource. Water extraction, treatment, transport and distribution all requires energy and very few studies consider the aspects of water-energy nexus. This research compared three innovative solar-based treatment systems and assessed their effectiveness through a multi-criteria decision analysis method based on three sustainability pillars. The solar powered vacuum membrane distillation (SVMD) system became the most sustainable technology option. Vacuum membrane distillation (VMD) is an emerging technology for water treatment which comprises of evaporation and condensation processes that mimic the natural water cycle A lab scale VMD treatment system was set up to demonstrate the response of the permeate flux rate to the various operating parameters. The permeate flux rate achieved were between 0.27 to 6.44 L/m2.h. Also, variation of these parameters was investigated in terms of energy consumption to determine an efficient combination of operating parameters. Optimum operating parameters were 7 kPa pressure, 65 C temperature and 1 L/min flow rate. The water quality tests performed for four brackish water samples showed that VMD process remove 99.9 % TDS. An innovative SVMD unit was designed, assembled and tested over a two month period. It was found that the SVMD system performance is remarkably influenced by the amount of energy transported to the feed water. Daily variation of the permeate flux was the result of changes in feed-water temperature that was affected by solar irradiance, ambient temperature and wind speed.