Analysis of microbial communities associated with anaerobic solvent degradation in sequencing batch reactors by traditional and molecular tools

Abstract

In recent years, discharges of the organic solvents have been subjected to stringent environmental regulations because of their undesirable effect on living organisms in aquatic environments and human health. Organic solvents such as methanol, isopropanol and toluene are found in wastewaters of several industries such as refineries, paint and pharmaceutical manufacturers. Treatment of solvent-containing wastewaters using anaerobic reactors has gained much attention in recent years as a cost-effective option compared to other treatment methods. However, there are still some concerns in the application of anaerobic treatment processes for this kind of wastewaters due to possible detrimental effect of the compounds present in the waste streams on both activity and microbial community playing crucial role in anaerobic digestion. Defining the effects of solvents on both microbial community structure and activity changes in anaerobic reactors may lead to improvements in the understanding of interactions in the bioreactors, thereby obtaining better reactor performance. Within the scope of the thesis, effects of methanol, propanol and toluene on microbial diversity and activity have been examined for acclimated and unacclimated sludge in anaerobic sequencing batch reactors (ASBR) using particularly Fluorescent in situ Hybridization (FISH), Denaturant Gradient Gel Electrophoresis (DGGE) techniques and Specific Methanogenic Activity (SMA) tests, respectively. In the ASBRs fed with solvents, microbial diversity changed significantly throughout the course of the operation where different wastewater compositions were fed to the anaerobic reactors. In ASBRs fed with solvent-containing synthetic wastewater, percentage of active population in the reactor decreased over the period of operation of the reactors.|Keywords: Bioreactors, Anaerobic treatment, Sequencing batch reactors, Microbial Ecology, Organic Solvents