Treatment of anaerobic granules with heat and two chemical treatments, contacting with 2-bromoethanesulfonate (BES) and with BES+Chloroform, were applied to suppress hydrogen-consuming microorganisms. Three mesophilic expanded granular sludge bed (EGSB) reactors - RHeat, RBES and RBES+Chlo - were inoculated with the treated sludges and fed with synthetic sugar-based wastewater (5 gCODL−1, HRT 20-12h). Morphological integrity of granules and bacterial communities were assessed by quantitative image analysis and 16S rRNA gene based techniques, respectively. Hydrogen production in RHeat was under 300 mLH2L−1d−1, with a transient peak of 1000 mLH2L−1d−1 after decreasing HRT. In RBES+Chlo hydrogen production rate did not exceed 300 mLH2L−1d−1 and there was granule fragmentation, release of free filaments from aggregates, and decrease of granule density. In RBES, there was an initial period with unstable hydrogen production, but a pulse of BES triggered its production rate to 700 ± 200 mLH2L−1d−1. This strategy did not affect significantly granules structure. Bacteria branching within Clostridiaceae and Ruminococcaceae were present in this sludge.
This work demonstrates that methods applied to suppress hydrogen-consuming microorganisms can cause changes in the macro- and microstructure of granular sludge, which can be incompatible with the operation of high-rate reactors. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc.
Publication Type: Papers