Abstract. Ultrafiltration (UF) membrane was prepared by blending polyvinyl chloride (PVC) with ZnO nanoparticle (ZnO-Np) and acetone as additives, and then used to treat peat water. The influence of PVC and ZnO-Np concentration on membrane morphology and humic substance rejection were studied. The experimental results showed that the increase of PVC and ZnO-Np concentration in the membrane solution enlarged the pore size of the UF membrane. Agglomeration of particles was found when 2 wt.% of ZnO-Np was added into the membrane solution. The addition of 10 wt.% of PVC concentration and 1 wt.% of ZnO-Np resulted in peat water flux above 100 Lm-2h -1 and average humic substance removal of 61%. When the concentration of PVC and ZnO-Np was increased to 12 and 2 %wt, the humic substance rejection was decreased to 40%. More irreversible fouling occurred in the UF-PVC
membrane that prepared by low PVC and high ZnO-NP concentration, which is indicated by the low value of the FRR.