Effects of electro-coagulation on fouling mitigation and sludge characteristics in a coagulation-assisted membrane bioreactor

Although much research effort has focused on methods to mitigate fouling of membrane bioreactors (MBRs), fouling is still inevitable. This paper aims to corroborate the roles of electro-coagulation approach within a coagulation-assisted MBR, termed electro-MBR. The effects of electro-coagulation on sludge characteristics and fouling behavior were investigated. A batch-scale experiment was carried out to identify an optimum electric current condition for electro-MBR study, in which the electro-MBR and a traditional MBR were identically set for numerous comparisons. The average fouling rate was substantially reduced 7.8 fold resulting in no chemical cleaning requirements during the entire operation of the electro-MBR. Enhanced sludge compressibility and controlled growth of filamentous bacteria positively affected by electro-coagulation were also obtained in the electro-MBR. This paper suggests that fouling mitigation in electro-MBR can be attributed to two mechanisms: (i) charge neutralization and adsorption for soluble foulants; (ii) electro-chemical oxidation for bound foulants. Furthermore, we conclude that electro-coagulation can simultaneously alter morphology and microbial structure of sludge flocs to become more compressible with lower fouling tendency, which would be beneficial for the mitigation of membrane fouling in electro-MBR.