Effects of Humic and Particulate Matter on Membrane Fouling in the Coagulation- Membrane Filtration System

Humic substances and turbid particles in water sources intended for drinking water can contribute to membrane fouling during membrane filtration processes. This study investigates the effects of filtration characteristics in a coagulation-membrane system on water treatment, particularly using synthetic water containing kaolin (< 60 mg/L) as a colloid and humic acid (< 5 mg/L) as organic matter. Coagulation was performed using a jar test with alum (< 10 gm/L) as a coagulant, followed by a membrane filtration process using a stirred dead-cell filter. The experiments involved increasing the driving pressure and stirring strength at an alum dose of 5 mg/L. The results demonstrated a significant reduction in kaolin levels with increased driving pressure and stirring strength, whereas humic acid remained unaffected. The remaining permeate flux (J/Jo) in the membrane process decreased with increasing driving pressure and decreasing stirring strength. Specifically, at a driving pressure of 30 kPa, J/Jo was 10% lower than that at 50 kPa, whereas at a stirring strength of 100 rpm, J/Jo was 10% higher than that at 50 rpm. Notably, water containing only kaolin exhibited a relatively lower remaining permeate flux than water containing both humic acid and alum with kaolin. The results indicate that both humic acid and alum contribute to particle aggregation in water, but residual alum increases membrane fouling. Therefore, optimal permeate flux can be achieved using lower driving pressure and higher stirring strength at an appropriate coagulant dosage.