Protein (BSA) fouling of reverse osmosis membranes: Implications for wastewater reclamation

Effluent organic matter (EfOM) has been known to contribute significantly to organic fouling of reverse osmosis (RO) membranes in advanced wastewater reclamation. In this study, the effects of feed solution chemistry (calcium concentration, ionic strength, and solution pH) and feed foulant composition on fouling of RO membranes by bovine serum albumin (BSA) – selected to represent proteins in EfOM – are investigated. Crossflow fouling experiments show that RO membrane fouling by BSA is enhanced at higher calcium concentration and at a solution pH at the BSA isoelectric point (pH 4.7). It is further demonstrated that BSA fouling of RO membranes is significantly enhanced in the presence of alginate (a model polysaccharide) as co-foulant. There appears to be an initial synergistic fouling effect when RO membranes are fouled by both BSA and alginate, as compared to fouling by BSA or alginate alone. Foulant–foulant adhesion forces, determined by AFM force measurements under solution chemistries identical to those of the crossflow fouling experiments, further confirm the trends of the fouling profiles. It is consistently shown that solution chemistries and foulant compositions that induce higher fouling rates are associated with greater foulant–foulant adhesion forces.