Reverse osmosis membranes act as very effective filters. Therefore any suspended solids, colloids or heavy metals entrained within the water run the risk of fouling the membrane surface. An effective pre-treament system to remove these impurities before the water gets to the membranes is essential. The pre-treatment system will be designed to take into account the feed water and water quality needs.
Multi-media filtration (MMF)
This level of filtration removes course particles in the 20-25 micron range. It is suitable for a variety of intake waters. These filters use multi-layers of different media including various coarseness of sands, pumice, anthrice or garnet as filters.
Microfiltration is designed to remove particles in the 0.1 - 1 micron range. The microfiltration process removes contaminants through a microporous membrane. These membranes affectively remove pathogens and large bacteria.
Ultrafiltration is another membrane filtration process not fundamentally different from microfiltration except in terms of the size of molecules it retains. The pores of ultrafiltration membranes can remove particles of 0.001 - 0.01microns from fluids. This removes most viruses, bacteria, colloids and silts (SDI) from the intake water.