Influence of hydrogen on the reductive dechlorination of tetrachloroethene (PCE) to ethene in a methanogenic biofilm reactor: role of mass transport phenomena
✍ Scribed by Federico Aulenta; Claudio Di Tomassi; Cinzia Cupo; Marco Petrangeli Papini; Mauro Majone
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2006
- Tongue
- English
- Weight
- 502 KB
- Volume
- 81
- Category
- Article
- ISSN
- 0268-2575
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
This study investigated the influence of H~2~ bulk liquid concentration in the range 2–120 µmol L^−1^ on the kinetics of vinyl chloride (VC) formation from tetrachloroethene (PCE) and VC dechlorination to ethene in a methanogenic biofilm reactor containing Dehalococcoides spp. as the putative dechlorinating micro‐organism. Both VC formation and dechlorination showed a definite increase in rate with increasing H~2~ bulk liquid concentration, following a pattern typical of Michaelis–Menten kinetics. The estimated maximum VC formation rate (81.7 ± 9.4 µmol L^−1^ h^−1^; mean value ± 90% confidence interval) was about ten times higher than the estimated maximum VC dechlorination rate (8.2 ± 1.0 µmol L^−1^ h^−1^), while the estimated apparent half‐velocity coefficient for H~2~ for VC formation (1.5 ± 1.4 µmol H~2~ L^−1^) was more than six times lower than that for VC dechlorination (9.1 ± 5.1 µmol H~2~ L^−1^), confirming that the last step of PCE dechlorination (i.e. conversion of VC to ethene) was much more H~2~‐sensitive than the previous ones. The estimated maximum methane formation rate was 462.1 ± 213.5 µmol L^−1^ h^−1^ and the estimated apparent half‐velocity coefficient was 104.7 ± 89.4 µmol H~2~ L^−1^. Experiments at different temperatures indicated the presence of severe internal (diffusional) mass transfer limitations and, in turn, of steep H~2~ concentration gradients through the biofilm, which strongly influenced the estimated apparent half‐velocity coefficients for H~2~ use. The results of this study emphasise the importance of considering mass transfer phenomena when predicting the rate of PCE dechlorination and the outcome of competition for H~2~ in natural or engineered bioremediation systems. Copyright © 2006 Society of Chemical Industry