Microbial community dynamics in diesel waste biodegradation using sequencing batch bioreactor operation mode (SBR)

Abstract

The dynamic of molecular microbial community during diesel waste biodegradation was investigated. The waste was treated in bioreactors operated in sequencing batch operation mode (SBR) in four cycles of 72 h, using optimized setpoints (pH, initial waste load, C:N ratio, aeration). Optimal conditions allowed the system to reach biodegradation of 53.3, 96.0, 76.2 and 75.0% at the end of cycles one, two three and four, respectively. Oxygen uptake rate (OUR) indicated increases in microbial activity from cycle one to cycle two (124.9 to 252.9 mgO2/L/h) and decreases in cycles three and four (120.4 to 108.8 mgO2/L/h, respectively). Investigations of microbial diversity showed changes in the microbial community members at the end of the cycle one. Significant reductions in the relative ecotoxicity were observed beginning with cycle two, and the reductions extended until the end of process. The SBR operation mode proved to be an efficient method for treating the diesel waste, and the process allowed for relevant reductions in the hydrocarbon content of the waste along with an increase in its environmental quality. Changes in the microbial members are evidence of the synergistic action of the microbiota in the process.

Key words: Microbial diversity, denaturing gradient gel electrophoresis, sequencing batch, biodegradation.