For unknown reasons I started to notice that after sometimes (0.5-1.0 hr) of operating crossflow filtration system, the flux increases steadily with corresponding decrease of rejection of the monitored ions (SO4 and Cl-). several types of membranes were tested with the same problem including NF270, BW30, NF, NFS, etc.

initially we thought something wrong with the cell so we changed it and used brand new Sterlitech cell. We also thought that some needle like pracipitates may have formed, we cleaned the whole system using 4 % cetric acid by circulation for 30 min then thoughly circulating UPW.

The cell we are using is Sepa CF Med/High Foulant System, 316 SS, 75 Mil with an active area of 140 cm2.

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