Long-term competition between sulfate reducing and methanogenic bacteria in UASB reactors treating volatile fatty acids
- Agricultural Univ. of Wageningen (Netherlands). Dept. of Environmental Technology
The competition between acetate utilizing methane-producing bacteria (MB) and sulfate-reducing bacteria (SRB) was studied in mesophilic (30 C) upflow anaerobic sludge bed (UASB) reactors treating volatile fatty acids and sulfate. The UASB reactors treated a VFA mixture (with an acetate:propionate:butyrate ratio of 5:3:2 on COD basis) or acetate as the sole substrate at different COD:sulfate ratios. The outcome of the competition was evaluated in terms of conversion rates and specific methanogenic and sulfidogenic activities. The COD:sulfate ratio was a key factor in the partitioning of acetate utilization between MB and SRB. In excess of sulfate, SRB became predominant over MB after prolonged reactor operation: 250 and 400 days were required to increase the amount of acetate used by SRB from 50 to 90% in the reactor treating, respectively, the VFA mixture or acetate as the sole substrate. The competition for acetate was further studied by dynamic simulations using a mathematical model based on the Monod kinetic parameters of acetate utilizing SRB and MB. The simulations confirmed the long term nature of the competition between these acetotrophs. A high reactor pH ({+-}8), a short solid retention time (<150 days), and the presence of a substantial SRB population in the inoculum may considerably reduce the time required for acetate-utilizing SRB to outcompete MB.
- OSTI ID:
- 619418
- Journal Information:
- Biotechnology and Bioengineering, Journal Name: Biotechnology and Bioengineering Journal Issue: 6 Vol. 57; ISSN BIBIAU; ISSN 0006-3592
- Country of Publication:
- United States
- Language:
- English
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