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Denitrifying Rate

FIGURE 4.5 Simulation oftoluene mineralization under sequential aerobic, denitrifying, and iron-reducing conditions in a closed batch system. TIC, total inorganic carbon.

FIGURE 4.5 Simulation oftoluene mineralization under sequential aerobic, denitrifying, and iron-reducing conditions in a closed batch system. TIC, total inorganic carbon.

out any lag period immediately after the start of the simulation. The degradation rate is highest at the beginning while oxygen is still present but decreases constandy over time. Once nitrate is depleted (after 8 days), the simulated Fe(OH)3 concentration also starts to decrease. The simulation results in Fig. 4.5 show also that the total inorganic carbon concentration increases during the phase at which oxygen and nitrate act as electron acceptors. However, once iron reduction has started, the total inorganic carbon con centration starts to decrease again as the solution becomes (or, more precisely, would become) oversaturated with respect to siderite (FeC03), which therefore precipitates. Figure 4.5 also depicts pH changes during the three phases of the numerical experiment. The changes would even be more pronounced if calcite (CaC03) did not buffer the pH changes. The simulation results indicate therefore that even the (dissolved) calcium concentrations are ultimately affected by toluene oxidation.

Copyright © 2005 American Society for Microbiology (ASM) Retrieved from www.knovel.com

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