Determining the influence of active cells and conditioning layer on early stage biofilm formation using cellulose acetate ultrafiltration membranes

Membrane biofouling is a complicated process and can include both abiotic and biotic fouling. The objective of this research was to determine the contribution of conditioning layer in the presence of active cells to early stage membrane biofouling. Membranes were operated for 4, 11, and 24 h using buffered synthetic water composed of a conditioning layer (130.14 ppm sodium acetate trihydrate) and either inactive (fixed) or active cells (103 cells/mL). This study was performed using cross flow filtration through cellulose acetate (CA) ultrafiltration (UF) membranes. Flux decline, biofilm activity, biofilm surface area coverage, and biofilm morphology (surface roughness and skewness) were monitored over time. While biofilm surface area coverage could not effectively distinguish membranes being filtered with active and inactive cells, permeate flux data indicated that the presence of active cells resulted in significantly more flux decline. Feature height analyses (TM-AFM) combined with biofilm metabolic activity assessment allowed the consideration of abiotic and biotic fouling. The membrane resistance increased in the presence of active bacterial cells, regardless of the level of abiotic fouling. However, abiotic fouling and bacterial cell activity are not independent since abiotic fouling serves as a food source that helps activate cells.

► Active cells in feed water resulted in more flux decline than fixed cells.
► AFM analyses and activity assessment were used effectively to characterize biofilm.
► Abiotic fouling was less important than cell activity for creating flux decline.