Performance and membrane fouling in an integrated membrane coagulation reactor (IMCR) treating textile wastewater

• The IMCR had good performances in color removal when it was used to treat textile wastewater.
• Membrane fouling experienced three phases and a higher PACl dose aggravated the membrane fouling.
• The fractal dimension of floc formed with PACl 1 mmol/L was 1.88 while it reached 2.22 with PACl 1.4 mmol/L.
• Independent of the membrane MWCO, lower molecular weight (MW) fractions resulted in the irreversible membrane fouling.

An integrated membrane coagulation reactor (IMCR) was employed to treat textile wastewater. Color could be removed almost completely and chemical oxygen demand (COD) removal efficiency could reach 88% with polyaluminum chloride (PACl) dose 1.2 mmol/L, influent pH 5.5 and hydraulic retention time (HRT) 3 h. Membrane fouling experienced three phases and a higher PACl dose aggravated the membrane fouling. The contact angle of new membrane was 52.5 degrees while the fouled ones’ were around 81 degrees. The fractal dimension of floc formed with PACl 1 mmol/L was 1.88 while it reached 2.22 with PACl 1.4 mmol/L. A more permeable filter cake was formed with PACl 1 mmol/L and could alleviate the membrane fouling effectively. Both the trans-membrane pressure (TMP) and TMP increment were greater when the IMCR was equipped with larger molecular weight cutoff (MWCO) membrane. The physically reversible and irreversible filtration resistances (Rf) of the IMCR with membrane MWCO 50, 100 and 150 kDa were 3.2, 9.1 and 31.4 times of there intrinsic membrane filtration resistances, respectively. Membrane was fouled more seriously when the higher MWCO membrane was used during the IMCR process. Independent of the membrane MWCO, lower molecular weight (MW) fractions resulted in the irreversible membrane fouling.