The effect of redox potential changes on reductive dechlorination of pentachlorophenol and the degradation of acetate by a mixed, methanogenic culture

The effect of changes in redox potential on methanogenesis from acetate, and on the reductive dechlorination of pentachlorophenol (PCP), was evaluated using a computer‐monitored and feedback‐controlled bioreactor. PCP was transformed via 2,3,4,5‐tetrachlorophenol (2,3,4,5‐TeCP) to 3,4,5‐trichlorophe...

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Bibliographic Details
Published in:Biotechnology and bioengineering 1999-04, Vol.63 (1), p.69-78
Main Authors: Stuart, S. L., Woods, S. L., Lemmon, T. L., Ingle Jr, J. D.
Format: Article
Language:English
Subjects:
Bioconversion
Biodegradation of pollutants
Biological and medical sciences
Bioreactors
Biotechnology
Cell culture
Composition effects
Dehalogenation
Environment and pollution
Feedback control
Fundamental and applied biological sciences. Psychology
Industrial applications and implications. Economical aspects
kinetics
Methanogens
pentachlorophenol
pH effects
redox potential
Redox reactions
reductive dechlorination
Thermal effects
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Summary:The effect of changes in redox potential on methanogenesis from acetate, and on the reductive dechlorination of pentachlorophenol (PCP), was evaluated using a computer‐monitored and feedback‐controlled bioreactor. PCP was transformed via 2,3,4,5‐tetrachlorophenol (2,3,4,5‐TeCP) to 3,4,5‐trichlorophenol (3,4,5‐TCP). In 6‐ to 12‐d experiments, pH, acetate concentration, and temperature were held constant; the redox potential, defined here as the potential measured at a platinum electrode (EPt), was maintained at different set points, while transformation of multiple PCP additions was monitored. Without redox potential control, the value of EPt for the culture was approximately −0.26 V (vs. SHE). The value of EPt was elevated from −0.26 V for periods up to 10 h by computer‐controlled addition of H2O2 or K3Fe(CN)6. Methanogenesis continued during a relatively mild shift of EPt to −0.2 V with H2O2, but was halted when EPt was raised to −0.1 V with either H2O2 or K3Fe(CN)6. Methanogenesis resumed when EPt returned to −0.26 V. During periods in which EPt was elevated significantly and methanogenesis stopped, transformation of PCP and 2,3,4,5‐TeCP continued at progressively slower rates, but the rate of 2,3,4,5‐TeCP transformation was diminished to a greater extent. When a small volume of pure H2 was added to the reactor headspace, while EPt was maintained at −0.1 V, reductive dechlorination rates increased dramatically. Lower H2 concentrations during periods of oxidant addition, perhaps due to the effect of the oxidant on H2‐producing bacteria, may contribute to decreased reductive dechlorination rates. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 69–78, 1999.
ISSN:0006-3592
1097-0290
DOI:10.1002/(SICI)1097-0290(19990405)63:1<69::AID-BIT7>3.0.CO;2-2