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The effect of redox potential changes on reductive dechlorination of pentachlorophenol and the degradation of acetate by a mixed, methanogenic culture
Author(s) -
Stuart S. L.,
Woods S. L.,
Lemmon T. L.,
Ingle J. D.
Publication year - 1999
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19990405)63:1<69::aid-bit7>3.0.co;2-2
Subject(s) - pentachlorophenol , reductive dechlorination , redox , degradation (telecommunications) , chemistry , biodegradation , environmental chemistry , oxidation reduction , organic chemistry , biochemistry , engineering , telecommunications
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 (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. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 69–78, 1999.