A new polyether sulfone membrane which was recently developed, has now been used for the purification of colored groundwater. This new nanofiltration membrane was developed to selectively remove organic material with molecular weight greater than 1,000 daltons, while passing most salts. This characteristic is ideal for applications which have low salinity, but high color or other organic compounds. This membrane differs from traditional polyamide RO membranes as it is chlorine tolerant and has a large negative surface charge. This makes it ideal for waters containing high organic levels. This membrane has been extensively pilot tested with other traditional nanofiltration membranes. The membrane had the best combination of high flux, high color removal and minimal hardness removal. As a result of these features the membrane was selected for a 27.8 ML (7.35 mgd) water treatment plant at the Irvine Ranch Water District. The full-scale plant contains about 1,300 pieces of 33.9 square metres (365 sq feet) spiral wound elements. The full-scale plant has been completed and start-up of the first train has been completed. The feed color units (CU) were in excess of 200 CU, while the permeate was less than 5 CU, which meets the requirement of the plant. This is one of the largest membrane plants designed to only remove color from the water.

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