Improved hydrogen production in the single-chamber microbial electrolysis cell with inhibition of methanogenesis under alkaline conditions

Abstract

The aim of this study was to investigate hydrogen production enhanced by methanogenesis inhibition in the single-chamber microbial electrolysis cell (MEC) under alkaline conditions. With 50 mM bicarbonate buffer and 1 g L -1 acetate, the MEC was tested at pH = 8.5, 9.5, 10.5, and 11.2, respectively, within 124 d operation. Effective methanogenesis inhibition in the MEC increased with pH from 8.5 to 11.2. At pH 11.2, Methanobacteriaceae reached the lowest absolute quantity ( i.e. , biomass and mcrA gene copy number of methanogens) within the microbial community in the cathodic biofilm among the pH values. Under the alkaline conditions, a hydrogen percentage of 85-90% and a methane percentage < 15% were achieved within 25 cycles (50 d) of operation. The maximum current density in the MEC reached 83.7 ± 1.5 A m -3 with the average electrical recovery of 171 ± 18% and overall energy recovery of 72 ± 3%. The excellent performance of the MEC at pH = 11.2 was attributed to the low abundance of methanogens within the cathodic biofilm (2.23 ± 0.46 copy per cm 2 ), low cathodic biomass (0.12 ± 0.01 mg protein per g), and low anode potential (-0.228 mV vs. saturated calomel electrode). Results from this study should be valuable to expand applications of the MEC with methanogenesis inhibition in alkaline wastewater treatment.

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Identifiers

DOI

10.1039/c9ra05483a

PubMed

35530221

Journal

RSC Advances

Year

2019