There are two types of reverse osmosis filtering membranes. Thin film composite membranes (PA) are made from polymide, polysulfone and a fabric support sheet.
An asymmetric membrane (CA) is composed of cellulose acetate in a single dense layer supported by a secondary spongy layer.
The table below compares the two.
| Parameters | PA Membrane | CA Membrane |
| Operating pH range | 2~12 | 4~6 |
| Operating Pressure (Kg/cm2 ) | 15 | 30 |
| Salt Rejection (%) TDS | 99+ | 98 |
| Silica (SiO2) | 99+ | <95 |
| Salt Rejection Change after 3years | 99%→98.7% | 98%→96% |
| Chlorine Tolerance | <0.1 ppm | 1 ppm |
| Membrane Fouling | High | Low |
