Water cost analysis of different membrane distillation process configurations for brackish water desalination

Membrane distillation (MD) is a process used for water desalination. However, its commercialization is still hindered by its increased specific cost of production. In this work, several process configurations comprising Direct Contact and Permeate Gap distillation membrane units (PGMD/DCMD) were investigated to maximize the production rate and consequently reduce the specific water cost. The analysis was based on a cost model and an experimentally validated MD model. It was revealed that the best achievable water cost was approximately 5.1 $/m3 with a production rate of 8000 m3/y. This cost can be further decreased to approximately 2 $/m3 only if the heating and cooling energies are free of cost. Therefore, it is necessary to decrease the MD capital investment to produce pure water at economical prices.