Water Science & Technology: Water Supply Vol 1 No 4 pp 25–33 © IWA Publishing 2001
Direct coagulation pretreatment in nanofiltration of waters rich in organic matter and calcium
A. I. Schäfer*, A.G. Fane** and T.D. Waite***
*UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering and Industrial Chemistry, University of New South Wales, Sydney 2052, Australia
**UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering and Industrial Chemistry, University of New South Wales, Sydney 2052, Australia
***Centre for Water and Waste Technology, School of Civil and Environmental Engineering, University of New South Wales, Sydney 2052, Australia
ABSTRACT
Nanofiltration (NF) can remove natural organic matter (NOM) and multivalent ions from surface waters. Large hydrophobic organics and calcium ions are responsible for irreversible fouling of nanofiltration membranes and thus a decrease of process efficiency and increase in cleaning requirements. Fouling due to the precipitation of organic-calcium complexes and the impact of colloids and coagulant (FeCl3) on the precipitation of these species was investigated. Coagulation in solution (as opposed to in the boundary layer) did not cause significant flux decline and was able to prevent irreversible fouling under conditions which were previously determined as detrimental. The rejection was varied if a strongly charged solid was deposited on the membrane.
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