Model for Treatment of Trichloroethylene by Methanotrophic Biofilms

Abstract

A biofilm model for the cometabolic degradation of trichloroethylene (TCE) by methane oxidizing (methanotrophic) bacteria is derived. Methane utilization and TCE transformation were modeled using diffusive mass transport, Monod kinetics, competitive inhibition, TCE transformation product toxicity, and growth, decay and inactivation of the methanotrophic bacteria. Reported low rates of TCE degradation by biofilms were found to be compatible with the high rates found in dispersed growth studies. The slower rates result from phenomena inherent in biofilms, and not necessarily from a difference in performance characteristics of the organisms. The possibility that biofilms may not be copper-limited is also considered. Other model predictions include an optimum methane concentration that maximizes TCE flux. Also, survival of a biofilm should only occur when the methane concentration is above a certain minimum value (S\dm\di\dn), which is linearly related to TCE concentration. The model is general and can be applied to other primary substrates and chlorinated aliphatic hydrocarbons (CAHs).