Sequential effects of cleaning protocols on desorption of reverse osmosis membrane foulants: Autopsy results from a full-scale desalination plant

The sequential effects of the cleaning protocols on the desorption of the reverse osmosis (RO) membrane foulants related to the recovery of the membrane surface characteristics were examined through the autopsies of the fouled RO membrane module from the full-scale seawater desalination plant in the Gijang province (Pusan, Republic of Korea). Although the types of cleaning agents were found to be a key factor affecting the desorption of the RO membrane foulants, the sequential cleaning protocol I (SCP I; 0.1 N NaOH → 0.1 N HCl → deionized (DI) water) more effectively desorbed both the organic and inorganic foulants from the RO membrane surfaces compared to the sequential cleaning protocol II (SCP II: 0.1 N HCl → 0.1 N NaOH → DI water). Moreover, the contact angle and the negative surface zeta potential of the cleaned RO membrane with SCP I were higher than those of the cleaned RO membrane with SCP II. These results demonstrated that the strategic pairing of three different cleaning agents governed the desorption efficiencies of the organic and inorganic foulants and the restoration of the membrane surface features in association with the performances of the RO membranes (i.e., permeate flux and salt rejection).