VOLATILE FATTY ACIDS AS ELECTRON DONORS FOR THE REDUCTIVE DECHLORINATION OF CHLOROETHENES

ABSTRACT

Uses of a mixture of six volatile fatty acids (VFAs) including acetic, propionic, butyric, isobutyric, valeric and isovaleric acids as electron donors for the reductive dechlorination of chloroethenes have been investigated by both microcosm and column studies. The fates of tetrachloroethene (PCE), cis-dichloroethene (cis-DCE) and vinyl chloride (VC) in the presence of VFAs and in the absence of VFAs were respectively documented. The results showed that VFAs stimulated complete reductive dechlorination of chloroethenes, either as direct substrates for the dechlorinating bacteria or via H₂ formed during VFAs-degradation. There were sequential utilizations of different VFAs by fermenting bacteria. In the microcosm, propionic acid was the first to be used, followed by acetic, butyric, isobutyric, valeric, and isovaleric acids, and their mean first-order degradation rates obtained were 0.128, 0.048, 0.016, 0.027, 0.025 and 0.003 day⁻¹, respectively. In the column, propionic acid was the first to be used, followed by butyric and valeric acids, and their calculated first-order degradation rates were 0.833, 0.403 and 0.260 day⁻¹, respectively.

Keywords:

• Volatile fatty acids
• Chloroethenes
• Hydrogen
• Reductive dechlorination
• Electron donors
• Degradation rate
• Bacteria

ACKNOWLEDGMENTS

This project was financially supported by the Royal Netherlands Academy of Arts and Science, Chinese Major State Basic Research Development Program: Study on the Environmental Pollution Mechanisms and Control Theory (G1999045711), Chinese postdoctoral science foundation (2000), and the Scientific Foundation for Returned Overseas Chinese Scholars, Ministry of Education (2001).