Natural attenuation of chlorobenzene in a deep confined aquifer during artificial recharge process

This paper discusses natural attenuation of chlorobenzene (CB) elimination in a deep confined aquifer in a certain test site in China during a groundwater artificial recharge process. Pilot-scale experiments were conducted in laboratory, including adsorption and biodegradation experiments. The results from the adsorption experiments indicated that the adsorption rate increased within the temperature range 0–20 °C. Processes were fitted to the pseudo-first-order and pseudo-second-order kinetic equations, Freundlich and Langmuir models. Maximal amounts of adsorption were 20.747, 21.505 and 23.364 µg/g at 0, 10 and 20 °C, respectively. The adsorption of CB was an endothermic process. The results from the biodegradation experiments indicated that the processes were well fitted by the Monod and first-order decay kinetics equations at different temperatures. It showed that the Monod µ_max changed from 0.0314 to 0.0387 h^-1, and the half-life (t_1/2) decreased from 3.02 to 1.46 d with an increase in temperature from 0 to 20 °C. The influence of temperature on the biodegradation rate was expressed by the Arrhenius equation. This study provides information on the mechanisms of natural attenuation of CB in the subsurface environment, whilst also providing the necessary technical information for the security of artificial recharge implementation.

Keywords
Artificial recharge; Groundwater; Chlorobenzene; Adsorption; Biodegradation