Figure F7. Illustration of forward- and reverse-osmosis systems where water is driven across a semipermeable membrane. Forward osmosis uses the osmotic gradient (Δπ) to counteract hydrostatic pressure (ΔP). Reverse osmosis uses a hydraulic piston to create a hydrostatic pressure in excess of the osmotic gradient and “filter” the salt. Typical downhole OsmoSamplers include at least one pump and multiple sample coils. Alzet membranes are white.
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