The objective of this study is to investigate how the molecular weight distribution of the organic substances affects their treatment efficiencies and the reduction of disinfection by-products (DBPs) in the various unit operations of a full-scale water treatment plant. The results indicate that the membrane with a smaller molecular weight cut-off is more effective for removing the organic substances and its associated water quality parameters from the raw water. For example, using the membrane with a molecular weight cut-off of 0.5 K (500 daltons), the removal efficiency of DOC from the raw water sample can be as high as 88%. Removal efficiencies of other water quality parameters such as UV254 absorbance, THMFP and AOXFP are generally between 65–69%. When undergoing the various unit operations in the conventional water treatment plant, most organic substances are removed in the coagulation process followed by sedimentation.

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