Removal of sediment and other suspended particles is critical to the efficient, cost effective operation of any treatment system. Performed using depth filtration media, the RO prefilter (A) assures efficient RO membrane performance. Keeping the particle level low also can reduce the frequency of RO membrane cleaning.
To assure that the water in the distribution loop remains pure, Filters C and D are used to remove contaminants that might enter the system or particles that are shed by system components. These filters may be used for bioburden reduction, for sterilizing filtration or for ultrafine particle removal. Membrane filters with pore sizes of 0.10 μm are used as Filter C. Either a tangential flow ultrafilter or 0.03 μm rated dead-end filter are used for filter D. A filter using membrane with a positive charge may be chosen because of its ability to remove organic molecules, including pyrogens that are smaller than the pore size of the membrane.
Water temperature has an effect on the choice of filter configurations used in POU applications for ultrafine particle removal. As with the filters in the distribution loop, filters with pore sizes of 0.22 μm, 0.10 μm, or 0.03 μm are usually used.
Polyethersulfone and nylon 6,6 membrane materials are not adversely affected even at temperatures at the boiling point of water. However, when choosing a filter for high temperature operation (greater than 80ºC), remember that the polypropylene cage and core need to be reinforced. Critical Process Filtration has enhanced hardware that will remain integral at higher temperatures.