Methanotrophic activity and microbial community dynamics in a UASB sludge

Abstract

This study determined the methanotrophic activity in anaerobic sludge from a pilot-scale UASB reactor. Four batch experiments, with three replicates, were performed in 110 mL antibiotic flasks. The results showed that the maximum rate was 115 µmolCH4.d-1 and the methanotrophic activity was 2.3 mmolCH4.gTVS1 .d-1, indicating that the methanotrophic microorganisms play a key role within the UASB reactor since they are part of the sludge microbiota and may consume some of the methane produced inside the reactor. Therefore, these microorganisms may reduce possible methane losses, either atmospheric and/or dissolved in the treated effluent. The microbial community was investigated by molecular tools (PCR-DGGE) and two DNA sequences related to methanotrophic bacteria, Methylocystis sp. (similarity of 93%) and Methylocaldum sp. (similarity of 98%) to 16S rRNA gene sequences, were detected. The methanotrophic activity and the identification of the community of main microorganisms involved allow the reduction of methane into the atmosphere and contribute to the system’s mass balance between production and consumption.