ABSTRACT
The phenolic compounds are a major contaminant class often found in industrial wastewaters and the biological treatment is an alternative tool commonly employed for their removal. In this sense, monitoring microbial community dynamics is crucial for a successful wastewater treatment. This work aimed to monitor the structure and activity of the bacterial community during the operation of a laboratory-scale continuous submerged membrane bioreactor (SMBR), using PCR and RT-PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA libraries. Multivariate analyses carried out using DGGE profiles showed significant changes in the total and metabolically active dominant community members during the 4-week treatment period, explained mainly by phenol and ammonium input. Gene libraries were assembled using 16S rDNA and 16S rRNA PCR products from the fourth week of treatment. Sequencing and phylogenetic analyses of clones from 16S rDNA library revealed a high diversity of taxa for the total bacterial community, with predominance of Thauera genus (ca. 50%). On the other hand, a lower diversity was found for metabolically active bacteria, which were mostly represented by members of Betaproteobacteria (Thauera and Comamonas), suggesting that these groups have a relevant role in the phenol degradation during the final phase of the SMBR operation.
Subject(s)
Bacteria/isolation & purification , Biodiversity , Bioreactors/microbiology , Industrial Waste/analysis , Petroleum , Phenols/metabolism , Bacteria/classification , Bacteria/genetics , Bacteria/metabolism , DNA, Bacterial/genetics , DNA, Ribosomal/genetics , Molecular Sequence Data , Petroleum/analysis , Phylogeny , RNA, Ribosomal, 16S/genetics , Thauera/classification , Thauera/genetics , Thauera/isolation & purification , Thauera/metabolismABSTRACT
The effect of hydraulic retention time (HRT) on membrane bioreactors (MBR) operation is discussed. A brief literature review on this topic indicates that biased conclusions can be drawn if data is obtained under non steady-state conditions. Another relevant aspect regarding steady-state operation includes activated sludge adaptation to bioreactor running conditions. In addition, wastewater components also have influence on steady-state achievement and MBR performance.
