Air/water cleaning for the control of particulate fouling

Fouling of feed spacers in spiral wound membrane elements due to particulate fouling and biofouling is one of the main operational problems of nanofiltration or reverse osmosis membrane plants. Removal of particulate fouling from spiral wound membrane elements is investigated using frequent air/water cleaning (AWC). In a pilot setup two spiral wound elements were operated in parallel and were fed by tap water containing suspended solids. The reference membrane (REF) was fed with tap water pre-filtered with a 1.0-μm cartridge filter and fouled within 50 days indicated by a 55% increase in the pressure drop. The second membrane element (AWC) was fed with unfiltered tap water (with an average turbidity of 0.3 NTU) resulting in a 73% increase in the pressure drop within a few days of operation. By using air/water cleaning, the pressure drop decreased to initial pressure drop values, indicating complete removal of particulate fouling. It was concluded that periodical air/water cleaning proved to be effective in controlling membrane spacer channel fouling as a result of particles in the feed water.