SBIR-STTR Award

The applicability of using dual co-substrates, alternately fed, to effectively produce a microbial community with two different populations of organisms able to co-metabolize TCE will be tested. The underlying concept is to avoid problems of substrate competition by alternately "changing" the different groups ot TCE co-metabolizers by alternating substrate feed. While one group is being fed substrate (and the oxidase enzyme activity recharged), the other group will be actively degrading TCE in the absence of their primary substrate (enzyme activity and reducing power "stored" during the prior growth cycle is used or "discharged"). The dual co-substrates that will be tested for co-metabolic TCE degradation are: methane, propane, toluene and phenol. Methane, propane, phenol/toluene support growth of three distinct microbial populations which produce specific oxygenases for co-metabolic TCE degradation. Although the ultimate objective is to advance this concept for in-situ treatment, this phase one effort will be conducted using a system that is easier to manipulate and allows more straightforward data interpretation. For these proposed tests, a laboratory scale fluidized bed reactor (FBR). The reactor will be started-up with methane, propane and toluene as co-substrates. TCE will be fed to the reactor continuously; the primary substrates will be alternatively fed into the reactors. Four dual substrate combinations and three different feed cycle times will be tested. The TCE removal performance will be evaluated based on volumetric TCE removal rates, and co-substrate/TCE conversion ratios. The reactor system and test procedures used will allow a rigorous mass balance for TCE, dissolved oxygen, and primary substrates used to be performed.

Keywords:
AEROBIC BIODEGRADATION PHENOL PROPANE CO-METABOLISM TOLUENE METHANE TRICHLOROETHYLENE

The use of dual co-substrates, to grow two separate microbial communities that can cometabolize TCE, has been shown in the Phase I effort to enhance the degradation rate of TCE by well over 200% in a reactor system compared to only one substrate at the same level of substrate COD. Based on these results, this technology will be tested at two sites in a fluidized bed reactor (FBR) system to determine the effectiveness, ease and robustness of operation and cost effectiveness. Results will also be extended to in-situ applications. During Year 1 laboratory tests will be conducted to develop an understanding of how to apply the results learned in reactor systems to in-situ treatment. Year 2 work will then leverage off experiences gained during Year 1 field reactor tests and in-situ laboratory testing for an in-situ field test. The use of dual co-substrates can be enabling technology that is readily adapted for use with other biological approaches for TCE oxidation including cometabolic bioventing, vapor phase reactors and soil treatment. This should result in increased rates and, therefore, reduced capital and operational costs