the biochemical oxidation of two wastewater feeds , one containing at least ten times more ammonia nitrogen , and the other at least ten times more chlorinated hydrocarbons , than present in a conventional municipal wastewater stream were treated in an aerated packed bed bioreactor inoculated with microorganisms especially cultured and acclimated to the task . arbitrarily shaped pieces of numerous microporous synthetic resinous materials are discovered to provide not only an excellent packing for the bioreactor , but also a peculiar catalytic function not normally associated with a bio - support . microporous polytetrafluoroethylene appears to be too inert to generate a high level of microbial activity for either feed which was tested , while microporous polyethylene appears to be exactly what the cells ordered . such activity cannot reasonably be correlated to the overall size of the micropores alone , because a calcined dolomite having substantially the same range of average pore sizes , exhibits a removal rate , measured as mg / min / m 2 of surface , which is generally about ten times lower than the rate obtained with the plastic biosupport , all other process conditions being the same . the comparison was made by simultaneously feeding several columnar glass reactors , each having a packed bed of different porous plastic packing , and one with commercially available microporous celite ®. as one might expect , the removal rate per unit volume of packing appeared not to correlate with the removal rate per unit of surface area , since the distribution of cells over the surface , and the rate at which the substrate is fed to the cells are the determining factors for removal rate . shape of the micropores in the packing appear to influence activity .