Thermodynamically enhancing propionic acid degradation by using sulfate as an external electron acceptor in a thermophilic anaerobic membrane reactor

Wei Qiao, Kazuyuki Takayanagi, Qian Li, Mohammad Shofie, Fang Gao, Renjie Dong, Yu You Li

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

In this study, sulfate was employed as an external electron acceptor for enhancing the degradation of propionate in a thermophilic anaerobic membrane reactor (AnMBR). The organic loading rate (OLR) was increased gradually from the initial 3.9 kg-COD/m3d to the inhibiting OLR of 14.6 kg-COD/m3d. Feeding was stopped for 98 days but the process did not recover until 500 mg/L of sulfate was added into the AnMBR. After that, the enhanced propionate degradation was achieved up to an OLR of 15 kg-COD/m3d with a reduced sulfate addition of 300 mg/L. However, the thermodynamic calculation indicated that the syntrophic propionic acid degradation, coupled with methanogenesis, was unfavorable with a △G of +3 kJ/mol under the enhanced conditions. Conversely, the utilization of propionic acid by sulfate reduction bacterial (SRB) would be more favourable by having a much lower △G of −180 kJ/mol. The hydrogen conversion was presumed to go through the methanogenesis pathway according to the thermodynamic results. The mechanism of the propionic and hydrogen metabolism was supported as well by comparing the microbial communities with and without sulfate addition. As a result, the role of the sulfate enhancing propionic degradation can be concluded by combining the process performance, thermodynamic, and microbiology results.

Original languageEnglish
Pages (from-to)320-329
Number of pages10
JournalWater Research
Volume106
DOIs
Publication statusPublished - 2016 Dec 1

Keywords

  • 16S rRNA
  • Anaerobic membrane reactor
  • Hydrogen
  • Propionic acid
  • Thermodynamic

ASJC Scopus subject areas

  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

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