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SIMULATION OF IN SITU BIODEGRADATION OF 1,4-DIOXANE UNDER METABOLIC AND COMETABOLIC CONDITIONS
Barajas-Rodriguez, F.J., L.C. Murdoch, R.W. Falta, and D.L. Freedman.
Journal of Contaminant Hydrology 223:103464(2019)

The study compared bioremediation options using microbes that co-metabolize 1,4-dioxane following growth on a primary substrate with microbes using 1,4-dioxane as a sole substrate. The comparison used a transport model that incorporated advection, dispersion and biodegradation reactions. The model was coupled to an approximate steady-state air sparging simulation calibrated with field data for 1,4-dioxane and propane concentrations from a previous pilot study. The two approaches were evaluated under different conditions including initial 1,4-dioxane concentration and oxygen, propane, and biomass loading rates. Remediation success was based on the time to reach an average 1,4-dioxane concentration of 1?µg/L and the percent of 1,4-dioxane biodegraded after 10?years of simulation. The initial concentration of 1,4-dioxane strongly influenced effectiveness. When initial concentrations were <10?mg/L, propane-driven cometabolism led to faster remediation, whereas metabolic biodegradation was faster when initial concentrations were ?10?mg/L. Below 0.25?mg/L, the viability of metabolic biodegradation improved, but cometabolism by propanotrophs still required less time to reach 1?µg/L. Biomass injection rates had a strong effect on the rate of metabolism but not cometabolism. The performance of both cultures was negatively affected by a decrease in oxygen injection rate. The endogenous decay coefficient and the dispersion rate for biomass had a significant impact on cometabolic and metabolic biodegradation of 1,4-dioxane. The maximum specific rate for cometabolism of 1,4-dioxane, the dispersion rate for 1,4-dioxane, and effective porosity also had significant effects on the time to achieve remediation with propanotrophs.



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