Membrane Distillation

Membrane distillation (MD) is a relatively new process that is being investigated worldwide as a low-cost, energy-saving alternative to conventional separation processes such as distillation and reverse osmosis (RO). There are four different configurations for MD processes, depending on the way in which the partial pressure gradient in the vapour phase is established: direct-contact membrane distillation (DCMD), air gap membrane distillation (AGMD), sweeping gas membrane distillation (SGMD), and vacuum membrane distillation (VMD). Industrial applications of MD may be classified into four main groups pure water production; waste water treatment; food industry; and concentration of organic and biological solutions. The basic separation process principle of membrane distillation is a combined, simultaneous heat and mass transfer mechanisms. A MD module design for a particular separation process is a trade-off of between a number of factors, such as cost, membrane performance-including thermal stability, selectivity, and thermal conductivity.