EFFECT OF HEAVY METALS ON FOULING BEHAVIOR IN MEMBRANE BIOREACTORS

Presence of heavy metals is considered to be a major challenge in wastewater treatment. In this research the effect of heavy metals such as nickel (Ni), chromium (Cr), and manganese (Mn) on fouling in membrane bioreactors was investigated. Fouling tendency of a cellulose acetate membrane was evaluated in MBRs with different concentrations of the mentioned elements. The concentrations of extractable extracellular polymeric substances in the mixed liquor at the steady-state condition and different concentrations of heavy metals were compared. Also the effects of concentration of heavy metals on mean floc diameter, hydrophobicity, and hence the fouling propensity of membrane was investigated. The Analysis of variance (ANOVA) method has been used to illustrate the important factors for the prediction of the fouling behavior. Results showed that different salts of the same heavy metal ion and various concentrations of heavy metals in wastewater had different effects on sludge properties and hence induced different fouling tendency of sludge.