Consecutive chemical cleanings of hollow fiber ultrafiltration membranes from a pilot-scale surface water treatment plant

The effects of the order of chemical cleaning protocols on the removal of hollow fiber ultrafiltration (HUF) membrane foulants, and restoration of membrane surface properties, were identified through autopsies of fouled HUF membrane modules from a pilot-scale surface water treatment system (Hongcheon-gun, Kangwon province, Republic of Korea). Quantitative and qualitative differences in the extracted HUF membrane foulants were found to depend on the types of chemical cleaning protocols applied, the consecutive cleaning protocol II (CP II; 0.1 N NaOH -> 0.1 N HCl; the sum of DOC = 215.19 mgC m⁻2; the sum of TN = 17.82 mg N m⁻2; the sum of metals = 25.14 mg m⁻2) extracted both organic and inorganic foulants from HUF membrane surfaces more effectively than consecutive cleaning protocol I (CP I: 0.1 N HCl -> 0.1 N NaOH; the sum of DOC = 189.89 mg C m⁻2; the sum of TN = 13.66 mg N m⁻2; the sum of metals = 9.95 mg m⁻2). Furthermore, the surface morphological characteristics of the cleaned HUF membrane using CP II were relatively similar to the virgin membrane surface compared to those of the cleaned HUF membrane using CP I. These findings demonstrated that the sequential coupling of two different chemical cleaning protocols played critical roles in removing organic and inorganic foulants from the fouled HUF membrane surfaces and restoration of membrane surface elementary composition potentially related to HUF membrane performances.