Removal efficiency of organic matters was investigated using a hybrid membrane systems combined with a nano filtration system and an activated carbon process. The surface water of Chitose river which contains relatively high concentratoin of organic matters (i.e. humic substances) was treated. The results of this study indicated that pre-coagulation process did not improve the removal efficiency of organic matters. The removal efficiency of dissolved organic matters by the activated carbon process gradually decreased to only 30% and reached an equiliburium condition, while that of the NF system was always over 90%. Although manganese could not be sufficiently removed by even the NF process and/or any combinations of these processs, applying chlorination before the MF process promoted the complete removal.
