Effect of protein, polysaccharide, and oxygen concentration profiles on biofilm cohesiveness


F. Ahimou,1 M. J. Semmens,1 G. Haugstad2, P. J. Novak1

1Department of Civil Engineering, University of Minnesota, 500 Pillsbury Dr. SE, and 2Characterization Facility, Institute of Technology, University of Minnesota, 100 Union Street SE, Minneapolis, Minnesota 55455

Abstract

The formation of biofilm on surfaces has great environmental and economic implications. For beneficial applications of biofilms, it is important to control biofilm cohesiveness to optimize process performance. In this study a membrane–aerated biofilm (MAB) reactor inoculated with activated sludge was used to grow mixed culture biofilms of different ages and thicknesses. The cohesion, or cohesive energy per unit volume of biofilm, based on a reproducible method using atomic force microscopy, was determined at different locations within the depth of the biofilms. In addition, protein and polysaccharide concentrations within the biofilm depth were measured, as well as the dissolved oxygen (DO) concentration profile within the biofilm. It was found that the biofilm cohesion increased with depth but not with age. Biofilm cohesive energy per unit volume was strongly correlated with the biofilm polysaccharide concentration, which increased with depth in the MAB. In a 12–day old biofilm, DO also increased with depth and may therefore be linked to polysaccharide production. In contrast, the protein concentration was relatively constant within the biofilm and did not appear to influence cohesion.