A laboratory column experiment is set up to test the transport of oil spilled in a sandy aquifer. The test column, 5 cm in diameter and 0.75 m in length, is packed with sand having a median grain dia...
A laboratory column experiment is set up to test the transport of oil spilled in a sandy aquifer. The test column, 5 cm in diameter and 0.75 m in length, is packed with sand having a median grain diameter of approximately 0.5 mm and porosity of 0.27. The sand was taken from a natural river bed; therefore, microbes-related biological process is expected to present. A mixture of feed solution containing conservative Cl and a surrogate biodegradable hydrocarbon is continuously pumped at a constant flow of 5 L/day. The mixture has an initial Cl concentration of 200 mg/L and hydrocarbon concentration of 100 mg/L. Since Cl is conservative, biodegradation is unlikely. The test hydrocarbon, however, has a first-order biodegradation rate constant of 0.12 hr1. As a control, the column was first tested using the mixture of Cl and hydrocarbon solution spiked with 500 mg/L sodium azide (NaN3) to inhibit the biodegradation. A duplicate column with the exact same packing materials and porosity was tested with the mixture of CI and hydrocarbons without biocide NaN3. a. Estimate specific discharge and water flow velocity in m/d. b. Estimate longitudinal dispersion coefficient in m2/d c. Estimate the effluent concentration of Cl at 2 hr. d. Estimate the effluent concentration of hydrocarbon at 2 hr with the addition of NaN3. e. Estimate the effluent concentration of hydrocarbon at 2 hr without the addition of NaN3. a. Comment your results by comparing the results from (d) and (e).
A laboratory column experiment is set up to test the transport of oil spilled in a sandy aquifer. The test column, 5 cm in diameter and 0.75 m in length, is packed with sand having a median grain diameter of approximately 0.5 mm and porosity of 0.27. The sand was taken from a natural river bed; therefore, microbes-related biological process is expected to present. A mixture of feed solution containing conservative Cl and a surrogate biodegradable hydrocarbon is continuously pumped at a constant flow of 5 L/day. The mixture has an initial Cl concentration of 200 mg/L and hydrocarbon concentration of 100 mg/L. Since Cl is conservative, biodegradation is unlikely. The test hydrocarbon, however, has a first-order biodegradation rate constant of 0.12 hr1. As a control, the column was first tested using the mixture of Cl and hydrocarbon solution spiked with 500 mg/L sodium azide (NaN3) to inhibit the biodegradation. A duplicate column with the exact same packing materials and porosity was tested with the mixture of CI and hydrocarbons without biocide NaN3. a. Estimate specific discharge and water flow velocity in m/d. b. Estimate longitudinal dispersion coefficient in m2/d c. Estimate the effluent concentration of Cl at 2 hr. d. Estimate the effluent concentration of hydrocarbon at 2 hr with the addition of NaN3. e. Estimate the effluent concentration of hydrocarbon at 2 hr without the addition of NaN3. a. Comment your results by comparing the results from (d) and (e).