99/00377 Thermodynamics of oxidative conversion of complex hydrocarbon-containing chemical systems and its modelling on a computer

Abstract

Phenol and seven alkylphenols (o-, m- and p-cresol, 2.5-, 2.6-, 3.4- and 3,5-dimethylphenol) were added at various concentrations to aliquots of domestic anaerobic sludge in Hungate serum bottles and these were incubated at 37°C. The concentration of methane in the headspace gas was monitored to determine if the phenolics were fermented to methane or if they inhibited the anaerobic process. Only phenol and p-cresol were fermented to methane. At 500 mg l−1 (but not at 300 mg l−1) 2,5-, 3,4- and 3,5-dimethylphenol reduced the rate and the amount of methane produced. The cresols were inhibitory at 1000 mg l−1 but not at 400 mg l−1.In cultures supplemented with acetate and propionate (VOA), and in unsupplemented cultures, phenol at concentrations up to 500 mg l−1 was fermented to methane. Between 800 and 1200 mg l−1 phenol, methane production was neither enhanced nor inhibited relative to control cultures containing no phenol. Inhibition of methane production was evident when phenol was present at ⩾ 2000 mg l−1. Thus the methanogens are less susceptible to phenol inhibition than are the phenol-degrading acid formers. In similar experiments with p-cresol: enhanced methane production was observed at concentrations of ⩽ 400 mg l−1; no enhancement or inhibition was observed at 600 mg l−1; and inhibition was noted when p-cresol was present at ⩾ 1000 mg l−1.