Abstract
Biofouling is one of the main drawbacks of membrane bioreactors (MBRs). Among the different methods, the quorum-quenching (QQ) technique is a novel method as it delays biofilm formation on the membrane surface through disruption of bacterial cell-to-cell communication and thus effectively mitigates membrane biofouling. QQ bacteria require a certain concentration of dissolved oxygen to show their best activities. Despite the importance of the amount of aeration, there have not been enough studies on aeration condition utilizing the separate determination of pure QQ effect and physical cleaning effect. This research aimed to find the optimum aeration intensity by separation of the two effects from QQ and physical cleaning. Three bead type conditions (no bead, vacant bead, and QQ beads) at three aeration intensities (1.5, 2.5, and 3.5 L/min representing low, medium, and high aeration intensity) were applied. From the results, no QQ effect and small QQ effect were observed at low and high aeration, while the greatest QQ effect (48.2% of 737 h improvement) was observed at medium aeration. The best performance was observed at high aeration with QQ beads having a 1536 h operational duration (303% improvement compared to the no bead condition); however, this excellent performance was attributed more to the physical cleaning effect than to the QQ effect.
Highlights
Biofouling is one of the main constraints associated with membrane bioreactors (MBRs) as it increases the operational costs and energy usage [1]
The quorum sensing (QS), bacterial cell-to-cell communication process is responsible for the formation of cake layers on membranes resulting in biofouling [2]
The result of the current study suggests that a decision should be made among the choices whether physical cleaning should be maximized by increasing aeration with a greater energy cost or the QQ effect should be maximized by adding the effort of making
Summary
Biofouling is one of the main constraints associated with membrane bioreactors (MBRs) as it increases the operational costs and energy usage [1]. The quorum sensing (QS), bacterial cell-to-cell communication process is responsible for the formation of cake layers (biofilms) on membranes resulting in biofouling [2]. It is a complex process which involves the development of biofilm layers on the surfaces of membranes by producing autoinducers known as acyl homoserine lactones (AHLs) [3]. The concentration of AHLs increases in the MBRs and results in the deposition of cake layers on the membranes [4] It causes a rise of transmembrane pressure (TMP) until it reaches a point where the filtration slows down or even stops in some cases [5]. This stage is called membrane biofouling [6]. The membrane modules are fouled and need to be cleaned by stronger methods or replaced with new ones
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