AWWA MTC64638

In the current study, direct contact membrane distillation (DCMD) and forward osmosis (FO) are being investigated as alternative processes to enhance water recovery from brackish water, or more specifically, from brines generated during brackish water desalination. DCMD is a non-pressure-driven separation process involving the transport of mass and heat through a hydrophobic, microporous membrane. The driving force for mass transfer is the vapor pressure difference across the membrane. In VEDCMD, warmer feed water is in contact with the feed side of the membrane and a cooler water stream, under vacuum, is in direct contact with the opposite side of the membrane. The temperature difference between the streams and the vacuum applied on the permeate side of the membrane induce the vapor pressure gradient for mass transfer. The vacuum configuration of DCMD has been shown to increase flux by up to 85% over the traditional configuration. FO is a non-pressure-driven separation process involving the diffusion of water through a semipermeable membrane. Water diffuses from a stream of low solute concentration to a draw solution (DS) stream of high osmotic pressure. The driving force for mass transport is the difference in osmotic pressure between the DS and feed solution. FO is shown to effectively concentrate a variety of feed streams, including municipal wastewater, landfill leachate, grey water, fruit juices, and beverages. Studies have shown that both DCMD and FO can efficiently treat and highly concentrate a wide range of feed solutions. Includes 11 references, tables, figures.