Impact of anti-scalant on fouling of reverse osmosis membranes in reclamation of secondary effluent

摘要

The objective of the study was to evaluate the impact of anti-scalant on fouling of reversenosmosis (RO) membranes in reclamation of secondary effluent which was produced by anconventional activated sludge process at Kranji Water Reclamation Plant with the capacity ofn151,000m3/d. The study was carried out using a RO pilot plant with the capacity of 2.4m3/h.nThe RO plant was in 2:1 configuration and was operated at 75% recovery and at membrane fluxnof 17 lm22 h21. Pilot trials were conducted with and without anti-scalant. Compositions of feednand concentrate streams were analyzed and the pilot data were normalized. The results of thenstudy showed that the plant operation was stable during the first few days after stopping dosagenof anti-scalant but after 3–6 days of operation the membranes were fouled. The time lag effect ofnanti-scalant without dosage was not reported previously and could be potentially beneficial tonsave chemicals. The membrane fouling was more serious at the second stage due to thenformation of calcium phosphate scale when the pilot plant was operated without anti-scalant.nThe flux of fouled membranes could be completely recovered after clean-in-place (CIP) with citricnacid, indicating that scaling dominated the fouling of the RO membranes. These findings in thenstudy could be applied to select an appropriate anti-scalant for prevention from formation ofncalcium phosphate scale in the RO operation.