Toxicity of three F-substituent aromatics in anaerobic systems

BACKGROUND: The commercial use of organofluorine compounds has dramatically increased over the past few years. However, little information has been reported on the potential toxicity of organofluorine compounds to anaerobic digestion processes. In this work, the effects of 4-fluorophenol (p-FP), 4-fluorobenzoic acid (p-FB) and 4-fluoroaniline (p-FA) on methanogenesis and biodegradability were evaluated using sucrose-fed systems. RESULTS: The anaerobic biodegradation of three test compounds was not observed in the study. Adsorption of p-FP, p-FB and p-FA to the sludge fitted the linear model well (r2 > 0.94). The partition coefficient Kd was 25 L kg-1 for p-FP, 16 L kg-1 for p-FB and 26 L kg-1 for p-FA. Both methanogensis and hydrolysis acidification were inhibited in the presence of three test compounds. The half maximal inhibitory concentrations (IC50s) of methanogenic activity were 339, 1390 and 1907 mg L-1 for p-FP, p-FB and p-FA, respectively. A significant linear correlation (R2 = 0.99, P < 0.05) was obtained between the half maximal inhibitory concentrations and the most negative atomic charges of molecules (q-) of the three F-substituent aromatics. CONCLUSIONS: Three F-substituent aromatics had specific effects on methanogensis, hydrolysis acidification and syntrophic cooperation in anaerobic systems. Copyright (c) 2012 Society of Chemical Industry