The effect of redox potential changes on reductive dechlorination of pentachlorophenol and the degradation of acetate by a mixed, methanogenic culture
✍ Scribed by S. L. Stuart; S. L. Woods; T. L. Lemmon; J. D. Ingle Jr.
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 186 KB
- Volume
- 63
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
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, 3,4,5tetrachlorophenol (2,3,4,4,4,. 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 (E Pt ), was maintained at different set points, while transformation of multiple PCP additions was monitored. Without redox potential control, the value of E Pt for the culture was approximately -0.26 V (vs. SHE). The value of E Pt was elevated from -0.26 V for periods up to 10 h by computer-controlled addition of H 2 O 2 or K 3 Fe(CN) 6 . Methanogenesis continued during a relatively mild shift of E Pt to -0.2 V with H 2 O 2 , but was halted when E Pt was raised to -0.1 V with either H 2 O 2 or K 3 Fe(CN) 6 . Methanogenesis resumed when E Pt returned to -0.26 V. During periods in which E Pt 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 H 2 was added to the reactor headspace, while E Pt was maintained at -0.1 V, reductive dechlorination rates increased dramatically. Lower H 2 concentrations during periods of oxidant addition, perhaps due to the effect of the oxidant on H 2 -producing bacteria, may contribute to decreased reductive dechlorination rates.