Comparison of Biofoulants in BNR-MBR and Conventional MBR (C-MBR) Systems

Two continuous MBRs treating municipal wastewater were compared in terms of fouling propensity: a biological nutrient removal (BNR-MBR) and a conventional (C-MBR). The soluble microbial products (SMP) and the extracellular polymeric substances (EPS) as well as their hydrophobic fractions were measured as protein and carbohydrate. The fouling rates were compared in both MBRs. The fouling rate was higher in the C-MBR system compared to the BNR-MBR due to higher concentrations and hydrophobicity of SMP which increased pore blocking resistance. The lower EPS concentrations per gVSS and hydrophobicity in the C-MBR resulted in floc size deterioration, which combined with a higher concentration per unit membrane area increased cake layer resistance. The findings of this study refute the notion that anoxic/anaerobic processes integral to biological nutrient removal (BNR) systems are conducive to membrane fouling. Additionally, this study concluded that membrane fouling is predominantly governed by the mixed liquor solids concentrations which affect SMP productions and characteristics.