Many bioprocesses depend on the effective formation of a biofilm on a solid support. In the present study, three different surface treatments (sandblasting, pure-O-2 plasma, and He-O-2 plasma treatments) were conducted on polypropylene (PP) Pall rings used as a support in biotrickling filters for air pollution control. The intent was to modify the ring surface and/or electrochemical properties in order to possibly improve cell adhesion, wetting properties, and possibly reduce the start-up time and increase the performance of the biotrickling filters.. The surface treatments were found to generally increase the hydrophilicity and the zeta potential of the surfaces. However, the startup and performance of lab-scale biotrickling filters packed with treated Pall rings were not significantly different than the control with untreated rings. Cell and colloid, deposition experiments conducted in, flow cells showed that the treated surfaces and the. hydrodynamic conditions were not. favorable for cell deposition indicating that there could be significant opportunities for improving packings used in environmental bioprocess applications. Biotechnol. Bioeng..2009;103: 1060-1067. (C) 2009 Wiley Periodicals, Inc.