Anaerobic degradation of phenol and related aromatics

• Phenol and other simple aromatic compounds have been found in water leached from landfills, showing that these types of compounds could be either present in disposed waste, or released from it via transformation and degradation processes. Hence, the fate anddegradation potential of such compounds under landfilling conditions is of great concern. Therefore, using micro-organisms from landfills, I have investigated the anaerobic biodegradation of phenol, dimethyl phthalate, 3-chlorobenzoate, 2,4,6-trichlorophenol, tetrabromophthalic acid and aniline. The compounds were chosen to represent substrates of potentially important reactions in the transformation and degradation of aromatic compounds. 24 waste samples from landfills and a time series of samples taken over five years from fourlandfill simulation reactors (in all 20 waste samples) were used as sources of microorganisms. The capacity of these waste samples to degrade the halogenated aromatics was poor or completely absent, indicating that halogenated compounds could be more persistent inlandfills than in other previously investigated anaerobic environments. Phenol and dimethyl phthalate were more readily transformed by most landfill samples, but the degradation capacity was poorer in the landfill simulation experiments. Here the unique sampling series showed an increase in degradation capacity with time, indicating that one to two years is needed to allow a micro-flora capable of degrading aromatic compounds to develop. However, the landfill samples showed higher degradation potentials than the simulation reactor samples, even from the later stages.A more extensive study designed to elucidate the phenol degradation pathway under anaerobic, fermenting conditions is also presented. Here, phenol was for the first time shown to be degraded to non-aromatic products in a non-methanogenic fermenting culture. The endproductsformed were benzoate, acetate and butyrate. The conversion of phenol to benzoate was proved to be an electron sink reaction, used during processes such as degradation of glucose and is a new example of the diversity of compounds that can used as electronsinks/ acceptors in anaerobic environments. The degradation pathway in the studied cultureproceeds via fom1ation of 4-hydroxybenzoate, 4-hydroxybenzoyl-CoA and benzoyl-CoA, and the activity of a CoA-transferase which activates 4-hydroxybenzoate was measured.

Ämnesord

SAMHÄLLSVETENSKAP  -- Annan samhällsvetenskap -- Tvärvetenskapliga studier inom samhällsvetenskap (hsv//swe)

SOCIAL SCIENCES  -- Other Social Sciences -- Social Sciences Interdisciplinary (hsv//eng)

Nyckelord

Aromatic compunds

anaerobic degradation

Fysik

Kemi

INTERDISCIPLINARY RESEARCH AREAS

TVÄRVETENSKAPLIGA FORSKNINGSOMRÅDEN

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