Stability in Denitrifying Bioreactors

In one area of our research, denitrifying bioreactors serve as the model systems for studying the relationship between functional stability and microbial community dynamics. The stability of denitrifying communities is of particular interest to our group, because denitrification is an important step in the treatment of contaminated groundwater at the Oak Ridge Field Research Center (FRC). Denitrification is also of general interest due to its role in wastewater treatment, remediation of sites contaminated with mixed wastes, and the global nitrogen cycle.

For denitrifying bioreactors for treatment and remediation, we define stable denitrification as the complete reduction of nitrate to nitrogen gas without the accumulation of the intermediates of the denitrification pathway (nitrite, nitric oxide, nitrous oxide).  The bacteria that reduce nitrate are diverse in their tendencies to accumulate intermediates of the pathway and the endproduct generated from nitrate reduction.  The functional diversity of nitrate reducing bacteria suggests that the stability of denitrification in a bioreactor depends upon which bacteria are present (community composition) and how they are changing over time (community dynamics).

To examine these relationships, we are studying the function and community dynamics in model dispersed growth bioreactors. The reactors were inoculated with the same community used to inoculate our denitrifying reactor at the NABIR Field Research Center.  Results to date have shown that instability events correlate with fluctuations in specific populations within the community. Current work focuses on determining metrics for stability of function and community dynamics in replicated bioreactors, the use of bioaugmentation to increase stability, and the effect of diversity on stability.

This page was written by Margy Gentile.


Model dispersed growth denitrifying bioreactor