The pressure required depends on the type and level of contaminants in the water. For example, producing purified water from sea water requires more than 10 times the applied pressure than regular tap water requires. Supplying more pressure than required provides better separation and a higher production rate. Figure 1 shows how reverse osmosis works. How the reverse Osmosis process works.
RO treatment reduces the levels of most dissolved compounds and suspended matter present in water.
However, the process does not efficiently remove all compounds. The efficiency of the membrane to reject the contaminant molecules depends on the pollutant concentration and chemical properties of the pollutant. Membrane type and operating conditions also affect the degree of pollutant removal. Table 1 lists some potential water contaminants and their typical ranges of rejection with an RO system. Rejection percentage is the percent of a particular contaminant not crossing the membrane, i.e., rejected by the membrane.