Biofilm formation on surfaces of glass and Teflon exposed to treated water

Biofilm formation on glass and Teflon cylinders, situated on top of each other in vertical glass columns exposed to different types of treated water at a flow rate of 0.2 m/s, was determined using ATP analysis and heterotrophic plate counts. Biofilm formation rates (BFR) of these water types, as calculated from the linear relationship between exposure time and biomass accumulated on the cylinder (glass) surface, were 11.1 ± 0.7 pg ATP/cm2 • d (r = 0.96) for treated ground water (TGW), 38.2 ± 4.7 pg ATP/cm2 • d (r = 0.90) for treated river water (TRW) and 382 ± 30 pg ATP/cm2 • d (r = 0.94) for TGW supplemented with 100 μg of acetate-C/1, respectively. Maximum levels of accumulated biomass were 1300 pg ATP/cm2 after 114 d of exposure for TGW, 3200 pg ATP/cm2 after 78 d of exposure for TRW and 26,000 pg ATP/cm2 after 65 d of exposure for TGW with acetate, respectively. Material and position of the cylinder in the columns either had no significant or a small effect on biofilm formation, depending on the water type. The effect of acetate addition on the BFR of TGW clearly demonstrated that biofilm formation was energy-source limited in this water type. These observations show that the experimental setup is suited for assessing BFRs of treated water.