Ultra filtration (UF) is a separation process by using membranes with pore sizes in the range of 0.1 to 0.001 micron. Typically, ultra filtration will remove high molecular-weight substances, colloidal materials, and organic and inorganic polymeric molecules. Low molecular-weight organics and ions such as sodium, calcium, magnesium chloride, and sulfate are not removed. Because only high-molecular weight species are removed, the osmotic pressure differential across the membrane surface is negligible. Low applied pressures are therefore sufficient to achieve high flux rates from an ultra filtration membrane.