Analysis of reactor configurations for combined anaerobic-aerobic biotreatment of perchloroethylene

Chlorinated ethenes are ubiquitous environmental pollutants of public concern due to their potential toxicity and carcinogenicity. Under appropriate conditions anaerobic bacteria mediate the dechlorination of perchloroethylene (a common dry cleaning solvent) to lesser chlorinated byproducts. In turn, these lesser chlorinated compounds are amenable to further degradation to harmless products via the action of aerobic bacteria.; Research documenting the acclimation and eventual stoichiometric degradation of PCE to lesser chlorinated products by anaerobic sludge granules is presented. A novel data analysis technique capturing the complexities of a sequential reductive dechlorination pathway is outlined. The application of this technique to data in the literature points to important competitive effects in the system studied. In addition, salient aspects of anaerobic and aerobic degradation mechanisms are incorporated into a reactor level model. Through application of this model, a number of current and innovative biotreatment strategies are considered. Results indicate that the performance of combined anaerobic-aerobic systems may benefit from the addition of a recycle stream. This strategy is particularly effective in systems employing reductive dechlorination which exhibit competitive kinetics.