Characterization of sulfate-reducing bacteria anaerobic granular sludge and granulometric analysis with grey relation

Abstract

We constructed a bench-scale up-flow anaerobic sludge reactor to systematically investigate the physicochemical characteristics of sulfate-reducing bacteria (SRB) anaerobic granular sludge and evaluate the granular size by a grey relational analysis. Results indicated that the granulation proportion was improved from 17.9% to 68.7% with the sulfate reduction efficiency larger than 90% under gradually shortened hydraulic retention time (HRT) and increased organic loading. Larger SRB granule sludge showed a higher specific gravity and settling velocity. The seed sludge was negatively charged, and the surface charge decreased with the incremental granular diameter. The maximal hydrophobicity and granulation proportion were 69.9% and 42.4%, respectively, for the granular diameter ranging from 1.5 to 2.5 mm. Extracellular polymeric substance (EPS) of the sludge exhibited the highest ratio of protein to polysaccharide (PN/PS) for the granular diameter in the range of 0.5 to 1.5mm. Based on the grey relational analysis of the SRB anaerobic sludge granulation, the correlation degree of the inherent influencing factors was PN/PS>surface charge> hydrophobicity. The theoretical evaluation would be conducive to granulation control during the potential application.