In-situ Flushing of Petroleum Contaminated Soil K. Volchek, W.P. Wong, D. Velicogna (SAIC Canada) C.E. Brown (Environment Canada) Remediation Technologies Symposium Banff, Alberta October 15-17, 2003
Acknowledgements This work was supported by The Program on Energy Research and Development (PERD) Environment Canada The City of Calgary
Scope of the presentation Principle of in-situ flushing Lignin derivatives as prospective flushing agents Work objectives Experimental setup Results and discussions Petroleum hydrocarbons Heavy metals Conclusions and recommendations
Principle of the process Source: P.Benchimol, M.Pandit Remediation of Contaminated Soils Civil Eng. Dept., Virginia Tech, 1998
Main features of in-situ flushing Lower costs associated with in-situ treatment (no soil excavation/ building demolition required) Minimal interruption of commercial/industrial activities at the site Treatment rates are generally slower than for ex-situ treatment Open treatment system
Lignosulfonates as prospective flushing agents By-product of pulp and paper industry (~3,000,000 t/year worldwide). Uses: vanillin, industrial surfactants, polymer fillers, etc. Chemical properties: phenolic, carboxylic, aldehyde groups. Act as mild surfactants Bind metal ions.
Work objectives Bench-scale study To evaluate commercially available lignosulfonates as flushing agents in in-situ treatment of petroleum contaminated soils In case of a successful treatment Provide recommendations for for a pilot-scale study
Experimental setup Phase I aqueous solubility tests Oil added to 100 ml of water or LS solution Parameters under evaluation: type and concentration of LS, ph, and contact time PHC water or LS solution
Experimental setup Phase II slurry leaching 100-200 g samples of contaminated soil (spiked and actual) Parameters under evaluation: type and concentration of LS, ph, and contact time
Experimental setup Phase III column leaching 1,000-1,500 g samples of contaminated soil Parameters under evaluation: volume and concentration of flushing solution, pressure, and contact time
Experimental setup Phase IV leachate treatment Membrane filtration used to concentrate contaminates and reduce the leachate volume
Test results: The effect of lignosulfonate concentration on the solubility of petroleum hydrocarbons 100 90 80 70 TPH (ppm) 60 50 40 30 20 10 0 500 1000 2000 3000 5000 Ammonium Lignosulfonate (ppm)
Results of slurry leaching: Diesel fuel 6000 Diesel fuel in the leachate (area counts) 5000 4000 3000 2000 1000 Lignin Water 0 Spiked soil samples
Results of slurry leaching: Heavy oils 2500 Heavy oils (area counts) in the leachate 2000 1500 1000 500 Lignin Water 0 Spiked soil samples
Results of column leaching: Total petroleum hydrocarbons 45000 40000 Concentration of TPH (ppm) in the soil 35000 30000 25000 20000 15000 10000 5000 0 Soil Samples Initial soil Soil Cell 1 Soil Cell 2
Test results: Leachate treatment Desal 5 G50 G20 Permeates generated using semi-permeable membranes Desal-5, G50 and G20 (all of GE Osmonics) Concentrate is biodegradable
Removal of heavy metals Contaminants* Percentage removal conventional process with lignin derivatives Hg 0% 15% U 0% 42% Cd 26% 70% Cr (III) 0% 24% Pb 29% 75% * Initial concentrations: 500 mg/l
Stabilization of hexavalent chromium 35 Total chromium in the leachate (ppm) 30 25 20 15 10 5 0 0 20 60 100 ph 4 ph 7 ph 10 Lignosulfonate/chromium mass ratio
Conclusions and recommendations Lignosulfonates enhance the removal of petroleum hydrocarbons from soil in in in-situ flushing Ammonium lignosulfonate is the most effective agent Leachate can be concentrated using membrane filtration Heavy metal removal observed. Possibility for the treatment of mixed contaminated soil Stabilization of hexavalent chromium in the soil observed Pilot-scale trial is recommended
Flow chart of the proposed pilot test system
Cross section of the treatment zone