Anaerobic biodegradability of alkylphenols and fuel oxygenates in the presence of alternative electron acceptors

Alkylphenols and fuel oxygenates are important environmental pollutants pro duced by the petrochemical industry. A batch biodegradability test was cond ucted with selected ortho-substituted alkylphenols (2-cresol, 2,6-dimethylp henol and 2-ethylphenol), fuel oxygenates (methyl tert-butyl ether, ethyl t ert-butyl ether and tert-amylmethyl ether) and tert-butyl alcohol (TBA) as model compounds. The ortho-substituted alkylphenols were not biodegraded af ter 100 days of incubation under methanogenic, sulfate-, or nitrate-reducin g conditions. However, biodegradation of 2-cresol and 2-ethylphenol (150 mg l(-1)) was observed in the presence of Mn (IV) as electron acceptor. The b iodegradation of these two compounds took place in less than 15 days and mo re than 90% removal was observed for both compounds. Mineralization was ind icated since no UV-absorbing metabolites accumulated after 23 days of incub ation. These alkylphenols were also slowly chemically oxidized by Mn (IV). No biodegradation of fuel oxygenates or TEA (150 mg l(-1)) was observed aft er SO or more days of incubation under methanogenic, Fe (III)-, or Mn (IV)- reducing conditions, suggesting that these compounds are recalcitrant under anaerobic conditions. The fuel oxygenates caused no toxicity towards aceto clastic methanogens activity in anaerobic granular sludge.