응집제주입농도가 응집-분리막여과시스템의 여과성능과 막오염에 미치는 영향

초록

Recently, membrane filtration (MF) has been adopted by water treatment plants to enhance the quality of finished water. However, MF fouling poses a significant challenge in water treatment processes. Coagulation as a pretreatment has been effective in reducing membrane fouling. This study examines how natural organic matter (NOM) and turbid particles in drinking water sources can cause membrane fouling during MF processes. This study explores the impact of filtration characteristics in a coagulation membrane system on water treatment using synthetic water with kaolin (< 60 mg/L) as the colloid and humic acid (< 3 mg/L) as the NOM. The coagulation process involved a jar test with alum (< 0.2 mmol/L) as the coagulant, followed by membrane filtration using a stirred dead-cell filter. The study found that at a low alum dosage of 0.05 mmol Al/L, no visible flocs formed, but the remaining permeate flux (J/Jo) of the synthetic water decreased due to humic acid and aluminum complexation. As the alum dosage increased, the remaining permeate flux improved due to flocs formation. This suggests that the coagulant dosage is crucial in determining the effectiveness of MF, as coagulation can both alleviate and exacerbate membrane fouling. The remaining permeate flux (J/Jo) in the membrane process declined with increasing driving pressure and decreasing stirring strength. Specifically, a driving pressure of 30 kPa resulted in J/Jo 10% lower than that at 50 kPa, whereas a stirring strength of 100 rpm achieved J/Jo 10% higher than that at 50 rpm. These findings indicate that an optimal permeate flux can be achieved with lower driving pressure and higher stirring strength given an appropriate coagulant dosage.

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