Structure and on-site formation of biofilms in paper machine water flow

Paper machine biofilms formed in situ on stainless steel surfaces were studied. A robust flow cell was fitted to side stream (1.8 m s(-1)) of the spray water circuit of a paper machine. This on-site tool allowed for assessing the efficacy of antifoulants and the adequacy of steel polishing under mill conditions. A rapid fluorescence-based assay was developed to quantify the biomass of shallow biofilms on machine steel. The fluorescence matched the ATP content measured for the same biofilms. Electrolytic polishing reduced the tendency of biofouling of 500 grit surface steel. Biofilm grew under machine conditions as clusters on the steels, showing uniformly coccoid, filaments or short rods; only one cell type in each cluster. The biofilm clusters excluded latex beads of 0.02 microm with hydrophilic or with hydrophobic surfaces from penetrating more than three to four layers of cells. Under the high hydraulic flow at the machine (1.8 m s(-1)), the biofilm grew in 7 days 6-10 microm thick. The high flow rate guided the shape of the biofilm clusters emerging after the primary attachment of cells. Adhered individual bacteria were the platform on steel to which solids such as paper machine fines then accumulated.