OVERVIEW OF FORWARD OSMOSIS
WHAT IS FORWARD OSMOSIS?
Forward Osmosis (FO) is a natural membrane process found in nature capable of extracting pure water from impure sources. Unlike Reverse Osmosis (RO), which uses hydraulic pressure to drive water across a semi-permeable membrane, FO uses a “draw” solution to draw water across it. Water is spontaneously drawn across a membrane whenever one solution is higher in salt concentration (draw solution) than another (feed solution). The difference in salt concentration is known as the osmotic gradient (Δπ) and is the free and natural energy used in powering this water extraction process.
As water is drawn from the feed solution into the draw solution, two things occur; the feed becomes concentrated, and the draw solution becomes diluted. The result of this is a reduction in the osmotic gradient and in turn a reduction in the flow rate across the membrane known as flux rate. For forward osmosis to operate continuously, the drawn water within the draw solution must be removed continuously so that a maximum draw concentration can be maintained.
REVOLUTIONARY THREE STEP PROCESS
Forward Water Technologies has developed a unique and patented industrial FO technology, utilizing their revolutionary three Step process, achieving high-rate water extraction within a low energy continuous process.
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1
Water Extraction Process
Water is drawn across an FO membrane into a salt draw solution. The combination of a patented draw solution and a unique FO membrane, effectively “locks” the draw solution on one side of the membrane, making it the first true closed loop process
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2
Water/Salt Separation
The process of water/salt separation is accomplished using a patented “Switchable Water Salt” (SWS) as the draw solution and low-grade heat (60-85°C). When low-grade heat is applied to the SWS, it phases from a liquid to a gas. As gas leaves solution, clean water is left behind. The thermal energy needed to drive this process can be from waste heat, solar thermal, geothermal or other sources.
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3
Salt Draw Reconcentration
As gas leaves solution it is captured within the closed loop system and passively cooled between 10-15°C causing it to phase back into liquid as a SWS concentrate. The SWS is collected and recycled back to the FO membranes in Step 1, establishing a continuous process. Passive cooling needed to drive this process can be from cooling towers, geothermal, heat exchangers or other sources.
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ADVANCED WATER RECOVERY IN A THREE STEP PROCESS
The three step process developed by Forward Water Technologies, enables industrial forward osmosis systems to extract the greatest amount of water from the most challenging process streams, using minimum energy for continuous operations. The fusing together of advancements in chemistry, material science and best operating practices has resulted in the world most advanced and efficient industrial forward osmosis system, surpassing conventional technologies in the delivery of greater value with reduced CAPEX/OPEX.