Effect of Adsorption/Coagulation-Membrane Filtration System for Reducing Turbid and Humic Substance from River Water

Natural organic matter (NOM) and colloid in river water used for drinking can foul membrane filtration. This study explores the effects of both NOM and colloid removal and filtration characteristics for adsorption/coagulation-membrane system on water treatment, specifically with synthetic water containing kaolin (< 50 mg/L) as a colloid and humic acid (< 3.5 mg/L) as NOM. The experiments involved adsorption using powdered activated carbon (PAC), coagulation using a jar test with alum (<5 mg/L) as a coagulant and a membrane filtration (MF) process using a stirred dead-cell filter. As a result, both coagulation and MF reduced significantly kaolin but did not affect humic acid, whereas PAC adsorption in reducing humic acid was higher 30% than that of coagulation and MF. A remaining permeate flux (J/Jo) of membrane process was reduced with increasing filtration time. J/Jo at PAC and alum dosage were lower 10% than that of no addition, while J/Jo at humic acid without kaolin was higher 40-60% than that of PAC and alum dosage. In particular, the water containing only kaolin resulted in a relative lower remaining permeate flux than that containing humic acid, PAC and alum with kaolin. The results indicate that both humic acid, PAC and alum play a important role in aggregating a particle in the water. However, a residual PAC and alum play a crucial role in increasing membrane fouling. Thus, it should be lower driven pressure and higher stirring strength to increase permeate flux at an appropriate PAC and coagulant dosage.