The researcher will investigate: 1) whether substrate enhancement occurs with other xenobiotic compounds, particularly other substituted phenols (chloro- and methyl-) which are among the more mobile hazardous contaminants; 2) the effect of a single supplemental substrate on degradation of a mixture of two or more xenobiotic compounds by bacterial consortia in cell recycle systems; 3) if large populations of degrading bacteria can be maintained in a biofilm growing on inert particles without added supplemental feed; 4) whether the activated sludge floc or biofilm morphology protects individual bacteria from toxicity effects of xenobiotic compounds. After the laboratory experiment, the nominee will carry out simulations at pilot- or demonstration-scale. These will allow the P.I. to investigate the effects of mixing, aeration and biomass separation, variables that are best studies in large scale, and to verify the predictive models on large biodegradation systems. One benefit of this research is that phenomena identified in pure bacterial cultures can be researched in mixed populations. Usually this application is made by engineers without research on the mechanism in mixed communities of microorganisms which develop in nonsterile field processes. A second benefit is the investigation of non-specific enhancement mechanisms, like the growth of floc particles to retain bacteria, so that a single biodegradation process can be used in many contaminant removal systems. Finally, some conditions which greatly affect biodegradation cannot be studied in bench-scale simulations. Doing research at a larger scale will help to avoid process failures which occur when scale-up effects are not understood.
