Standardised RO Testing

The performances of high pressure membranes can be assessed with standard testing methods, recommended by the suppliers and available on their websites or product descriptions. Those methods generally involve a feed solution of 32,000 ppm NaCl and pressure of 55 bar for SWRO, and 2,000 ppm at 15.5 bar for BWRO. SWRO membranes have performances ranging between 99.6 - 99.9% NaCl rejection and a permeability of 0.45 – 0.94 L.m⁻².h⁻¹.bar⁻¹. While BWRO membranes have a performance that ranges from 98.5 – 99.8% NaCl rejection and a permeability of 1.3 – 7.4 L.m⁻².h⁻¹.bar⁻¹. Overall, there is a trade-off between salt rejection and permeability, with an increase in productivity resulting in a decrease in product quality. Additionally, RO membranes can be modified for a variety of requirements, including high productivity, high rejections, low energy, low fouling and high boron rejection. For comparison, NF membranes by the same manufactures have a NaCl rejection between 55 – 90% with a permeability of between 6.3 and 8.6 L.m⁻².h⁻¹.bar⁻¹.