Abstract
Integrated microbial fuel cell (MFC) and membrane bioreactor (MBR) systems are a promising cost-effective and energy-saving technology for wastewater treatment. Membrane fouling is still an important issue of such integrated systems in which aeration (oxygen) is replaced with anode electrodes (anodic respiration). Here, we investigated the effect of culture conditions on the membrane fouling potential of fouling-causing bacteria (FCB). In the present study, Klebsiella quasipneumoniae strain S05, which is an exoelectrogenic FCB isolated from a MBR treating municipal wastewater, was cultured with different external electron acceptors (oxygen, nitrate, and solid-state anode electrode). As results, the fouling potential of S05 was lowest when cultured with anode electrode and highest without any external electron acceptor (p < 0.05, respectively). The composition of soluble microbial products (SMP) and extracellular polymeric substances (EPS) was also dependent on the type of electron acceptor. Protein and biopolymer contents in SMP were highly correlated with the fouling potential (R2 = 0.73 and 0.81, respectively). Both the fouling potential and yield of protein and biopolymer production were significantly mitigated by supplying electron acceptors sufficiently regardless of its types. Taken together, the aeration of MBR could be replaced with solid-state anode electrodes without enhancement of membrane fouling, and the anode electrodes must be placed sufficiently to prevent the dead spaces in the integrated reactor.
Highlights
It is important to reduce or omit energy intensive aeration in order to facilitate wider applications of membrane bioreactors (MBRs) (Ren et al, 2014; Yuan and He, 2015; Li et al, 2016)
More than 98% of S05 grew as planktonic cells in the mixed liquor (ML) rather than biofilms attached on the anode electrode regardless of the type of external electron acceptor (Supplementary Figure S2)
The fouling potential was high with following order; no external electron acceptor, nitrate, oxygen and anode electrode
Summary
It is important to reduce or omit energy intensive aeration in order to facilitate wider applications of membrane bioreactors (MBRs) (Ren et al, 2014; Yuan and He, 2015; Li et al, 2016). In this regards, integration of microbial fuel cell (MFC) and MBR is an interesting approach, because the integrated system has several advantages, including better effluent water quality, no or less requirement of aeration, and reduction of sludge (Wang et al, 2011; Yuan and He, 2015; Katuri et al, 2018). A pure culture of Geobacter sulfurreducens strain principle compartment analysis (PCA), an exoelectrogenic bacterium, produced less biopolymer and exhibited lower membrane fouling under anodic respiration condition than under fumarate (anaerobic) respiration condition (Ishizaki et al, 2016b)
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