Methanogenic biodegradation of creosote-derived contaminants in natural and simulated ground water ecosystems
Wastes from an abandoned wood preserving plant in Pensacola, Florida have contaminated the near surface sand-and-gravel aquifer with creosote-derived compounds and pentachlorophenol. The contaminated ground water is enriched in organic fatty acids, benzoic acid, phenol, 2-, 3-, 4-methylphenol, indole, oxindole, quinoline, isoquinoline, 1(2H)-quinolinone, 2(1H)-isoquinolinone, benzothiophene, benzofuran, naphthalene, and indene. Evidence is presented that the methanogenic degradation of the compounds listed above and concomitant microbial growth in batch microcosms derived from contaminated aquifer material can be described using Monod kinetics. The K{sub s} values obtained for the biodegradation of the phenolic compounds in this study are much lower than published values, indicating that the aquifer microorganisms may have developed enzyme systems and transport mechanisms that are adapted to low nutrient conditions. The values for k{sub d} are much less than {mu}{sub max}, and can be neglected in the microcosm studies. The low Y values, approximately an order of magnitude lower than theoretical values, and the low numbers of microorganisms in the aquifer derived microcosms suggest that these organisms may use some unique strategies to survive in the subsurface environment. Studies of the degradation pathways of the homocyclic and heterocyclic aromatic compounds on the basis of intermediate compounds have revealed that the process consists of both a major and a minor pathway. The first transformation step of the major pathway consists of oxidation and cleavage of the heterocyclic ring. After cleavage of this ring, the substituent side chains and the remaining homocyclic ring are subjected to various reactions including oxidation, decarboxylation, desulfurylation or ammonification, and O-methylation. These reactions are followed by the reduction of the homocyclic ring, cleavage of this ring, {beta}-oxidation, and mineralization.
- Research Organization:
- Stanford Univ., CA (United States)
- OSTI ID:
- 39329
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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