The natural organic matter(NOM) rejection using microfiltration necessitates pretreatments for better removal efficiency. Adsorption and coagulation are used as typical pretreatments to microfiltration. The MF-PAC system consists of an adsorber reactor into which the water including NOM and PAC slurry are added. But in this case, it is impossible that a gel layer, which results in flux decline and irreversible fouling, is formed on membrane surface. This study proposed a modified MF-PAC process using a pre-deposited PAC cake layer(PAC dynamic membrane). This external PAC cake layer can adsorbs and entraps NOM before it reaches the primary membrane surface. Therefore, it was expected that a PAC dynamic membrane can decrease the formation of a gel layer.
So this study investigated NOM rejection, flux decline and characteristics in the microfiltration process which has a different pretreatment. To facilitate comparison, we evaluated resistances using a resistances in-series model and conducted a molecular weight distribution experiment. The feed concentration was about 5 mg/L as total organic carbon(TOC).
Three processes in which experiments were conducted were as follows:
① the existing MF-PAC process
② PAC dynamic membrane process
③ MF-coagulation process in condition of the charge neutralization
As a result, the PAC dynamic membrane process was inefficient because the PAC cake layer could not form stably in crossflow condition and was too short of the contact time. The MF-coagulation was the most efficient. It was found that the small and large fraction of humic acid could be removed in the MF-PAC processes and the medium in MF-coagulation well.
