Ethene ETH is often associated with vinyl chloride (VC) in contaminated groundwater, as it is formed along with vinyl chloride during reductive dechlorination of higher chloroethenes (e.g., perchloroethylene and trichloroethylene). In the present study the interaction between VC and ETH during their aerobic biodegradation by enrichment cultures was investigated. The cultures were able touse both compounds as growth substrates. In mixture experiments, the degradation rate of one substrate was affected by the presence of the other. A biokinetic model based on competitive inhibition described well the observed substrate interactions over a range of initial VC (0-144 umol L-1) and ETH (0-37.5 umol L-1) concentrations, using parameters estimated from single-substrate experiments. Notably,half-velocity coefficients could be used as competitive inhibition coefficients. This finding shows the importance of obtaining accurate measurements of half-velocity coefficients in order model competitive inhibition processes. Simulation results showed that when the initial ETH concentration was raised from 0 to 30 umol L-1, the apparent half-velocity coefficient for VC (KVC APP) increased by nearly threetimes, from 12.9 to 35.4 umol L-1. This finding has strong environmental implications because a low half-velocity coefficient for VC is regarded as the major prerequisite for achieving efficient and complete VC degradation. Moreover, the effect of ETH on the efficiency of VC removal is strongly dependent on the KVC/KETH ratio, consequently determination of KETH for VC-degrading microbes is importan twhen biodegradation or bioaugmentation is considered for clean up of VC-contaminated sites. Additional model simulations, using the ratio of KVC to KETH for previously characterized VC- and ETH-utilizing microorganisms values ranged from 0.06 to 1.2 showed that their ability to degrade VC in the presence of ETH may differ significantly.
MODELING SUBSTRATE INTERACTIONS DURING AEROBIC BIODEGRADATION OF MIXTURES OF VINYL CHLORIDE AND ETHENE
AULENTA F;LEVANTESI C;TANDOI V
2006
Abstract
Ethene ETH is often associated with vinyl chloride (VC) in contaminated groundwater, as it is formed along with vinyl chloride during reductive dechlorination of higher chloroethenes (e.g., perchloroethylene and trichloroethylene). In the present study the interaction between VC and ETH during their aerobic biodegradation by enrichment cultures was investigated. The cultures were able touse both compounds as growth substrates. In mixture experiments, the degradation rate of one substrate was affected by the presence of the other. A biokinetic model based on competitive inhibition described well the observed substrate interactions over a range of initial VC (0-144 umol L-1) and ETH (0-37.5 umol L-1) concentrations, using parameters estimated from single-substrate experiments. Notably,half-velocity coefficients could be used as competitive inhibition coefficients. This finding shows the importance of obtaining accurate measurements of half-velocity coefficients in order model competitive inhibition processes. Simulation results showed that when the initial ETH concentration was raised from 0 to 30 umol L-1, the apparent half-velocity coefficient for VC (KVC APP) increased by nearly threetimes, from 12.9 to 35.4 umol L-1. This finding has strong environmental implications because a low half-velocity coefficient for VC is regarded as the major prerequisite for achieving efficient and complete VC degradation. Moreover, the effect of ETH on the efficiency of VC removal is strongly dependent on the KVC/KETH ratio, consequently determination of KETH for VC-degrading microbes is importan twhen biodegradation or bioaugmentation is considered for clean up of VC-contaminated sites. Additional model simulations, using the ratio of KVC to KETH for previously characterized VC- and ETH-utilizing microorganisms values ranged from 0.06 to 1.2 showed that their ability to degrade VC in the presence of ETH may differ significantly.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
