Preliminary investigation of quorum quenching effects on sludge quantity and quality of activated sludge process

The Quorum Sensing (QS) system has attracted the interest of researchers as a cell-cell communication system. In activated sludge processes, the production of extracellular polymeric substances (EPS), bio-films and floc formation are regulated by the QS system. Hence, disruption of the QS system, called Quorum Quenching (QQ), could have a significant effect on the quality and quantity of excess sludge. In the present research, the quorum quenching bacteria, Rhodococcus sp. BH4 was used as a quorum quencher and was entrapped in an alginate structure (QQ beads). Three separate sequential batch reactors (SBR) were constructed and operated as a control reactor, a Low-QQ reactor (containing 150 QQ beads), and a High-QQ reactor (containing 600 QQ beads). Results indicated that the presence of QQ beads in the aeration reactor leads to a decrease in EPS content and mean floc particle size in the both Low-QQ and High-QQ reactors. The eukaryotic community was changed significantly so that the QS disruption caused an enhancement in microbial predation. The presence of QQ beads also led to a 16 and a 26% decrease in the Y-obs coefficient within the Low-QQ and High-QQ reactors, respectively. Findings of this research revealed a new application of the QQ system in the activated sludge process, but additional studies are needed. (C) 2018 Elsevier Ltd. All rights reserved.