Hydrodynamics Analysis for an Upflow Integrated Anaerobic Digestion Reactor with Microbial Electrolysis under Different Hydraulic Retention Times: Effect of Bioelectrode Spatial Distribution on Functional Communities Involved in Methane Production and Organic Removal

Abstract

The electrode plays a significant role in an integrated anaerobic digestion reactor with microbial electrolysis that can increase energy production. Optimizing electrode positions by means of hydrodynamic analysis was proven feasible. In this work, different spatial distributions of bioelectrodes in upflow integrated anaerobic digestion reactors were researched to obtain a highly effective configuration. The hydrodynamic characters of each reactor were evaluated by a residence time distribution (RTD) test and computational fluid dynamics (CFD) simulation. The optimal structural design in this work was in that electrodes were placed at the bottom of the reactor with the cathode placed above the anode. It had an obvious hydrodynamics advantage and generated maximum methane production of 304.5 mL CH4/L reactor/day and a maximum chemical oxygen demand (COD) removal of 92.1% at a hydraulic retention time (HRT) of 36 h. The better flow pattern was in favor of mass transfer and further improved the reactor performance. The hydrodynamics character also affected the distribution of functional communities attached to the electrode surface. Results implied that Enterobacteriaceae and Desulfovibrio were sensitive to hydrodynamic shear. Methanogens on electrodes had the highest diversity under higher hydrodynamic shear when electrodes were placed on the bottom of the reactors with the best flow regime among that of other positions.

Marketability Prospects of Microbial Fuel Cells for Sustainable Energy Generation

“…The hydrodynamic behavior of the reactor can also be tested by computational fluid dynamics and residence time distribution simulation. Geo et al reported that, if the electrode is kept at the bottom of the reactor with the anode placed below the cathode, the maximum methane generation of 304.5 mL occurs in CH 4 L –1 of reactor day –1 , with a maximum COD removal of 92.1%. Kim et al fabricated 12 MFCs with different internal structures.…”

Review and perspectives of enhanced volatile fatty acids production from acidogenic fermentation of lignocellulosic biomass wastes

“…The use of horizontally oriented electrodes in upflow anaerobic bioreactors with built-in electrochemical system had also been investigated. It has been found that the optimal design in such a case occurred when the working electrode was placed at the bottom (Gao et al 2020 ). However, most of current researchers only focused on lab-scale reactors (e.g., volume less than 500 mL) (Jiang et al 2019 ) and only wastewater, glucose or food waste have been utilized as substrates to perform electrochemical fermentation (Jiang et al 2020 ; Liu et al 2019b ; Zhou et al 2019 ).…”

Enhancing the anode performance of microbial fuel cells in the treatment of oil-based drill sludge by adjusting the stirring rate and supplementing oil-based drill cuttings

“…To overcome the harmful effects of low interaction e ciency between bacteria and anode material, studies have shown that high shear rates (below the tensile strength level) lead to stronger microbial aggregation and more compact bacterial colony structures (Jones &Buie 2019, Pham et al 2008, Pinck et al 2020. High shear can be realized by prolonging hydraulic retention times (Gao et al 2019), rotating anode electrodes (Pan et al 2019) and applying agitation to the cathode chamber (Islam et al 2019). For instance, it has been reported that the power and current densities of polydimethylsiloxane (PDMS)-based microscale MFCs increase with increasing ow rate and that maximum power densities and current densities were 0.71 mW/m 2 and 1.8 mA/m 2 , respectively, which higher than that were realized by previous PDMS-based micro MFCs (Yoon et al 2018).…”