Development of a continuous flow model system for studies of biofilm formation on polymers and its application on PVC-C and PVC-P: Article prepared for submission

Migration of bioavailable compounds from polymeric pipe materials in drinking water distribution systems may cause bacterial aftergrowth. Present methods for microbial testing of polymeric materials are based on batch or semi-batch tests, but a continuous flow model system may provide a better test system. In this study, a continuous flow model system was developed, for investigating biofilm formation on polymers, simulating conditions in the distribution system. Commercially available pipes were used for exchangeable test pieces, which allowed for testing over prolonged time periods. Test pieces could be harvested from three different combinations of flow velocity and residence time. Biofilm formation was followed by ATP analysis on test material (chlorinated polyvinylchloride, PVC-C), negative control (stainless steel) and positive control (plasticized polyvinylchloride, PVC-P) incubated in separate flow model systems. Results show a good agreement between biofilm densities on test pieces from
the developed flow model system and batch-incubated test pieces during 16 weeks of incubation; average values during 8 to 16 weeks of operation were 40 pg ATP/cm2 for steel, 60 pg ATP/cm2 for PVC-C, while most of the very deviating values for PVC-P were between 2-13,000 pg ATP/cm2. During 43 weeks of operation of the continuous flow model systems the biofilm formation increased on all three materials, with biofilm formation on PVC-C at the
same level as on the negative steel control (values of 75-200 pg ATP/cm2), but at a level one hundred times higher on the positive PVC-P control. With the materials tested no specific effects of varying flow velocities and residence times in the flow model systems were observed.