Using intermittent ozonation to remove fouling of ultrafiltration membrane in effluent recovery during TFT-LCD manufacturing

An ultrafiltration membrane process was used to treat the secondary effluent from the manufacturing of thin film transistor-liquid crystal display (TFT-LCD). A bench-scale system was performed to evaluate the efficiency of fouling removal by dosing tap water with ozone intermittently. It was observed that about 90% of the initial permeate flux was maintained after 120 min ozone washing, when the residual ozone concentration in the tap water flow was maintained at about 0.885 mg/L for 5 min ultrafiltration and 2.5 min ozone washing in every operation cycle. Ozone not only destroyed the fouling on the membrane, but also oxidized some solutes that had been adsorbed onto the inner pore fiber, especially with organic matter, thereby decreasing the fouling and increasing the permeate flux further. So, using intermittent ozonation can remove the fouling on ultrafiltration membranes and save the ozone consumption effectively.