Development and pilot testing of full-scale membrane distillation modules for deployment of waste heat

Membrane distillation is an attractive technology for extracting fresh water from seawater. Newly developed modules have been used in pilot tests and bench scale tests to demonstrate the potential of producing excellent product water quality in a single step, little need for water pretreatment and a thermal energy requirement of approximately 520 MJ/m3 water. Evaluations for large scale applications in the future, using low cost waste heat and assuming an energy requirement of 140–230 MJ/m3, are indicating operational costs competitive to conventional desalination techniques, such as reversed osmosis and multi-effect distillation.

► Salt separation factors above 10,000 have been obtained in large pilot tests.
► Thicker membranes reduce internal heat losses and improve energy efficiencies.
► Degassing the influent improves the permeance, but was sometimes not found.
► Modeling of the permeance showed unused module areas at low channel velocities.
► The potential of low cost desalination has been shown in various cost evaluations.