Typical Rejection Characteristics of Thin Film Composite (TFC) Reverse Osmosis Membranes

Below are the typical rejection (removal) percentages of a standard thin film (TFC) reverse osmosis membrane. These are averages based on experience and are generally accepted within the industry. They are not a guarantee of performance. Actual rejection can vary according to the chemistry of the water, temperature, pressure, pH and other factors.

We should point out that the listing below is of items that are treated by the RO membrane alone. Home RO units, which consist of carbon filters as well as a membrane, can remove innumerable chemical contaminants that are not listed on this chart. Here’s an article that explains what carbon filtration adds to the total removal capability of home RO units.

Estimated Reverse Osmosis Rejection Percentages

The reverse osmosis process uses a semi-permeable membrane to reject a wide variety of impurities. Here is a partial list.

Aluminum 97-98% Nickel 97-99%
Ammonium 85-95% Nitrate 93-96%
Arsenic 94-96% Phosphate 99+%
Bacteria 99+% Polyphosphate 98-99%
Bicarbonate 95-96% Potassium 92%
Boron 50-70% Pyrogen 99+%
Bromide 93-96% Radioactivity 95-98%
Cadmium 96-98% Radium 97%
Calcium 96-98% Selenium 97%
Chloride 94-95% Silica 85-90%
Chromate 90-98% Silicate 95-97%
Chromium 96-98% Silver 95-97%
Copper 97-99% Sodium 92-98%
Cyanide 90-95% Sulphate 99+%
Ferrocyanide 98-99% Sulphite 96-98%
Fluoride 94-96% Zinc 98-99%
Iron 98-99%
Lead 96-98% Insecticides 97%
Magnesium 96-98% Detergents 97%
Manganese 96-98% Herbicides 97%
Mercury 96-98% Virus 99+%
TDS (Total Dissolved Solids) 95-99% Hardness 93-97%

Figures given above are not actual test figures but are manufacturers’ estimates of normal TFC membrane performance