Characteristics of flat-sheet ceramic ultrafiltration membranes for lake water treatment: A pilot study

Abstract

In order to explore the characteristics of ceramic membranes in the treatment of surface water with high turbidity and high content of organic matters, a pilot-scale test was carried out on the water treatment process composed of pre-zonation, coagulation, sedimentation, and ultrafiltration using flat-sheet ceramic membranes. The water purification effect of the combined process and the influences of different operating parameters on membrane fouling were comprehensively investigated. The results showed that the effluent turbidity of the combined process could be controlled below 0.1 NTU, and the removal rates of CODMn, DOC and UV254 in the raw water were 58%, 49%, and 45%, respectively. The membrane fouling rate largely depended on the permeate flux; when the constant permeate fluxes were set at 80, 100, 120 and 150 L m−2h−1, the rising rates of the transmembrane pressure (TMP) in the early stage were 0.18, 0.42, 1.20 and 2.04 kPa/h, respectively. The permeate production period had a relatively small effect on the membrane fouling rate, and the “high-intensity short-time” mode was demonstrated more efficient than the “low-intensity long-time” mode during backwashing. Under the optimized conditions, no chemical cleaning was required by the ceramic membranes during 12 days of continuous operation, with the TMP increasing by only 20 kPa. A series of characterizations suggested that the irreversible membrane fouling was mainly caused by proteins, humic substances and silicates. The chemical cleaning strategy with the combined use of NaClO and acid cleaning agents was recommended for the recovery of membrane performance.