Long-term competition between sulfate reducing and methanogenic bacteria in UASB reactors treating volatile fatty acids

• Published in: Biotechnology and bioengineering 1998-03, Vol.57 (6), p.676-685
• Main Authors: Omil, F., Lens, P., Visser, A., Hulshoff Pol, L. W., Lettinga, G.
• Format: Article
• Language: English
• Subjects: acetate; Acetates - metabolism; Anaerobiosis; Bacteria; Biochemical oxygen demand; Bioconversion; Biodegradation, Environmental; Biological and medical sciences; Biological sewage treatment; Biological treatment of waters; Bioreactors; Biotechnology; competition; Computer Simulation; Environment and pollution; Environmental Technology; Fatty acids; Fatty Acids, Volatile - metabolism; Fundamental and applied biological sciences. Psychology; granular sludge; Industrial applications and implications. Economical aspects; Mathematics; methanogenesis; Methanomicrobiaceae - metabolism; Milieutechnologie; Models, Biological; pH effects; Sectie Milieutechnologie; Sewage sludge; simulation; Sub-department of Environmental Technology; sulfate reduction; Sulfates - metabolism; Sulfur compounds; Sulfur-Reducing Bacteria - metabolism; Volatile organic compounds; WIMEK
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/(SICI)1097-0290(19980320)57:6<676::AID-BIT5>3.0.CO;2-I

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 (upward velocity 1 m h−1; pH 8) 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 (COD:sulfate ratio lower than 0.67), 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 (