This research work was carried out to determine natural organic matter (NOM) removal in floating media filter coupled with microfiltration membrane applied to the treatment of river water in Bangkok, Thailand. polyaluminum chloride was found to be the most effective coagulant providing enhanced coagulation effect for NOM removal. Optimum filtration rate of floating media filter was 11 m(3)/m(2) h at which highest NOM removal efficiencies of 82.2% was achieved. Subsequent treatment in microfiltration membrane unit operated at a filtration rate of 0.45 m(3)/m(2) d provided total NOM removal of 85.7-86.6%. Periodical cleanings of floating media filter and microfiltration membrane were accomplished by using air scouring coupled with water flushing at every 8 and 24 h interval. As a result of NOM removal, the sum of trihalomethane (THM) ratio was reduced from 0.5-1.1 in raw water to 0.2-0.6 in treated water. Membrane fouling Study revealed that both turbidity and NOM affected transmembrane pressure (TMP) built Up but particulate fouling provided greater impact on TMP as compared to organic adsorption on the membrane surface.