Subsurface transport of microorganism and its application to bioremediation of groundwater contaminated by halogenated organic compound

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Laboratory column tests confirmed that the transport characteristics of microorganism, Clostridium bifermentans DPH-1 activating tetrachloroethylene (PCE) dechlorination, was well described by a mobile-immobile two-region model (TRM), which has been used in physical transport model of aqueous pollutants through soils. Determined TRM parameters implied that bacterial injection into ground at large amount of concentration is difficult in a rehabilitation manner for widely dispersed contaminated groundwater. Calibrated parameters were carefully evaluated in conjunction with test conditions and features of the soils tested in column. Practical estimation were proposed in transport parameters to simulate bacteria transport and degradation of PCE in bio-augmentation. Biological reaction was identified as first-order kinetics from batch tests where the bacterium strain was mixed with halogenated aliphatic compounds of PCE or TCE (trichloroethylene) as initial pollutant. PCE dechlorination to cis-dichloroethylene (cDCE) via TCE was mathematically described by Monod type function based on Michaelis-Menten equation while the microbial growth rate was not well represented by Monod function. Thus, a relationship between the microbial growth rate and the concentration of PCE and TCE was newly proposed and its appropriateness was verified through a numerical simulation of PCE dechlorination in a fixed-bed reactor column.