Mitigation of reverse osmosis membrane fouling by electrochemical-microfiltration- activated carbon pretreatment

Abstract

In this study, a hybrid electrochemical-microfiltration-granular activated carbon adsorption (e-MF-GAC) pretreatment process was developed and demonstrated for controlling reverse osmosis (RO) fouling. Compared to ultrafiltration (UF), e-MF-GAC pretreatment resulted in 30% higher permeate flux. Results in this study show the complementarity among individual treatment processes of e-MF-GAC for removing inorganic/organic foulants and small organic molecules, leading to superior performance over conventional UF pretreatment. This hypothesis is validated by systematic feed water and foulant composition analysis as well as fluorescence excitation-emission matrix and X-ray diffraction spectroscopic characterization of the organic and inorganic foulants on the membrane surface, respectively. Organic foulants on the membrane were mostly protein-like compounds and their disposition onto the membrane surface was much lower after pretreatment using e-MF-GAC compared to UF. Similarly, after e-MF-GAC-RO pretreatment, organic content in the RO concentrate was lower than that after UF pretreatment. Results in this study provide the basis for further research at pilot scale to assess the economic viability of the proposed e-MF-GAC process as an alternative to conventional UF pretreatment for mitigating RO membrane fouling.