Application Of New Evaluation Item In Microbial Electrolysis Cell And Methane Production Analysis In Scale-up Bioreactor

Microbial electrolysis cell (MEC) is a promising wastewater treatment technologywith simultaneous hydrogen or methane recovery. MEC has a sustainable future, butfaces many challenges, such as cathodic materials, evaluation system and poorperformance of scale-up reactors. This paper investigated the hydrogen productionperformance of MECs with activated carbon catalyst (AC) and stainless steel mesh (SS)cathode and evaluated the hydrogen performance using new evaluation system. Thispaper also investigated the performance of baffled microbial electrolysis cell(ABR-MEC) and analyzed the source of methane production and the succession ofanodic bacterial community under different hydraulic retention times (HRTs).MECs with AC and SS (AC/SS-MEC) were investigated in terms of hydrogenproduction performance under different applied voltages. Based on conventionalevaluation system, the maximum volumetric current density and the maximumhydrogen production rate reached the peak at1.4V. The energy efficiency reached thepeak at1.0V and1.2V. The hydrogen production efficiency was enhanced with theenhanced applied voltage. Based on new evaluation system, AC/SS-MEC obtained themaximum average current density and average hydrogen production rate at1.2V. Thereason that hydrogen production enhanced with the increased applied voltage wasdiscovered. The treatability efficiency was introduced to represent energy efficiency.The performance of ABR-MEC was investigated under different HRTs. WhenHRT was reduced from2days to1day, the daily hydrogen production decreased, andthe daily methane production increased. When HRT was reduced from1day to0.5day,the daily hydrogen production decreased, and the daily methane production alsodecreased. The source of methane production was analyzed from the calculation ofelectron equilibrium. When HRT was2days, the main source of methane productionwas hydrogenotrophic methanogen. When HRT was1day, the main source of methaneproduction was acetoclastic methanogen. The succession of anodic bacterial communityunder different HRTs was analyzed using pyrosequencing. Exoelectrogenic biofilm wasinhibited when HRT was reduced from2days to1day, thereby decreasing thehydrogen production and methane production of ABR-MEC. The performance of methane production was investigated in continuousABR-MEC under different applied voltages and substrate concentration. Compared tosubstrate concentration, increasing applied voltages could enhance methane productionrate quickly, but lowered the energy efficiency.