21 st Annual Conference

1. 21st Annual Conference

2. Chemical-enhanced Soil Washing for Land Decontamination Dr. Dan Tsang Lecturer Department of Civil and Natural Resources Engineering University of Canterbury

3. Contaminated Site Remediation • Land contamination • human health risks • impact on ecosystem • Risk-based land management • reduce potential risk to an acceptable level • site-specific risk-based treatment objectives • Managerial actions • Remedial actions X Source Pathway Receptor

4. Key drivers • Excavation and landfill disposal (‘dig and dump’) • ease of use, quick, applicable for complex contamination • landfill space? • transportation? fuel? greenhouse gas? • backfill materials? • United States Hazardous Waste Laws • Section 121 (b) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, or Superfund) prescribes remedial actions that “permanently and significantly reduces the volume, toxicity, or mobility of the hazardous substances, pollutants, and contaminants” • “Superfund Amendments and Reauthorization Act of 1986 (SARA) expressed a preference for permanent remedies (that is, treatment) over containment or removal and disposal in remediation of Superfund sites.” (USEPA, 2007) U.S. EPA (2007) Treatment Technologies for Site Cleanup: Annual Status Report (Twelfth Edition).

5. Key drivers • European Union (EU) Landfill Directive and Landfill Tax • implementation in summer 2004 reduced the available landfill space for all forms of waste disposal and banned co-disposal of soils from contaminated land and non-hazardous wastes • tightened further in 2005 in that no wastes can be sent to hazardous waste landfills in excess of 6% organic matter and the new Waste Acceptance Criteria require that all wastes sent to hazardous waste landfills have to be pre-treated • prices for disposal to hazardous landfill have risen dramatically, e.g., in the UK, to above £100/m3, and frequently in the region of £150/m3 • Excavation and landfill disposal – less economically attractive • Remediation industry looking for alternative methods Council of the European Union (1999) Council Directive 1999/31/EC of 26th April 1999 on the Landfill of Waste

6. Technology Overview • Soil washing • ex-situ on-site soil remediation • physical–chemical approach • majority of contamination associated with fine soil particles • physical separation of large, clean soil particles • mineral-processing equipment • significant volume reduction • Soil washing project at Elgin in the UK • reuse more than 80% (2,770 m3) of excavated soil • otherwise require haulage off-site to landfill and equivalent amount of clean quarried stone imported • minimise truck movements • avoid more than 275 return lorry trips, 70,000 vehicle miles, associated emissions, noise, congestion and health and safety issues (USEPA, 2001)

7. Technology Overview • Applicability • SVOCs (e.g., PAHs and PCBs), fuels, heavy metals, radionuclides, and pesticides • contaminants sorbed on fine particles, or as surface coatings and discrete precipitates • sufficient space for on-site treatment

8. Hydrocarbons (Olympic Park, London, UK) TPH; 50,000 tons (Lezo, Spain) Hydrocarbons; 500,000 tons (East London, UK) Creosote (Edmonton, Canada) As; 410,000 tons (Vineland Chemical, NJ, USA) Cr, Cu, Ni; 19,200 tons (King of Prussia, NJ, USA) Crude oil (Alberta, Canada)

9. Technology Overview • Soil washing • physical separation • Chemical-enhanced soil washing • chemical extraction • physical separation and chemical extraction clean soil fractions Physical Separation contaminated soil contaminated soil fractions processed, clean soil Chemical Extraction contaminated soil contaminated washing solution clean soil fractions Physical Separation contaminated soil processed, clean soil fractions Chemical Extraction contaminated soil fractions contaminated washing solution

10. Chemical-enhanced soil washing • Produce a cleaner sand fraction that otherwise fails to meet the specified cleanup goals • Or treat the entire soil matrix, including the fines fraction Rotating Drum Rotating Screwpump

11. (chemical additives) (>2 mm) (<2 mm) Chemical-enhanced soil washing U.S. EPA mobile soil washing system (mineral-processing equipment)

12. Chemical-enhanced soil washing SDS (anionic) • Chemical agents • surfactants, cosolvents, chelating agents, acids • Surfactants • reduce surface and interfacial tension, mobilizing residual organics • solubilisation of hydrophobic organics by surfactant micelles • Cosolvents • water-miscible organic solvents • increase effective aqueous solubility of hydrophobic organics • e.g., methanol, ethanol, propanols CTAB (cationic) C12E4 (nonionic) Surfactant-Enhanced Soil Washing for crude oil contamination (Alberta, Canada)

13. Chemical-enhanced soil washing • Chemical agents • surfactants, cosolvents, chelating agents, acids • Chelating agents (chelants) • enhance metal extraction by forming soluble complexes • non-biodegradable – EDTA, DTPA • biodegradable – NTA (carcinogenic), S,S-EDDS EDDS metal-EDDS complex EDTA metal-EDTA complex

14. Case Study Site Overview Free-Phase Product Plant Feed Cleaned Soil Soil Washing Plant • former hydrocarbon storage facility in Spain • 50,000 tons of soils contaminated with total petroleum hydrocarbon • surfactant-enhanced soil washing • higher throughput rate and lower cost compared to thermal treatment • 30 to 50 ton-per-hour feed capacity mobile treatment plant

15. Case Study • from 1950 to 1994 Vineland Chemical Co. manufactured arsenic-based herbicides in New Jersey • contamination of soil, sediment, and groundwater of the plant site (54 acres), a low-lying nearby marsh, the Blackwater Branch, the Maurice River and Union Lake • National Priority List (Superfund site) • USEPA tenured to USACE (US Army Corps of Engineers) and ART to plan, design, and execute the selected remediation • bench-scale treatability and process optimization studies in late 2001 • construction activities included • plant building, soil treatment plant, plant support systems, chemical storage area and outside contaminated and clean soil storage pads • plant construction was completed in the fall of 2003 Plant Fabrication Equipment Assembly

16. Case Study • initial remedial design – 180,000 tons of contaminated soil located at the Plant Site (source control) and Blackwater Branch (river areas), with the potential for future treatment of additional volumes)   • sandy soils; arsenic concentrations ranged from < 20 to > 10,000 ppm • excavation, staging and blending plan – desired feed concentration of arsenic (60-90 ppm) • commissioning and prove-out phase – full-scale operations at original design rate of 56 tons per hour • comprehensive plant optimization in July 2004 – capacity increased from 56 to >70 tons per hour, resulting in savings of US$ 3M Soil Treatment Plant

17. Case Study • unit operations: • wet screening, hydrocyclones • chemical extraction • arsenic precipitation, leachate regeneration, water clarification • sand dewatering, fines thickening and filter press dewatering • trommel and vibrating wet screens to remove oversize materials (> 2 mm) from the feed soil • hydrocyclones to separate the fines (< 100 mm) Soil Screening Soil Feeding

18. Case Study • sand slurry – mixed with chemical agents at 130 oF in four in-series leaching tanks • rotating ball mill – remove arsenic coatings from higher-concentration feed materials • clean sand (< 20-ppm cleanup level) • only 1.3 percent of treated soils required retreatment • contaminated water – pH adjustment for arsenic precipitation and flocculation • sludge generated and fines – consolidated and disposed off-site Leaching Tanks Soil Extraction Arsenic Precipitation Clean Soil

19. Case Study • operations completed in 2007 • a total of 410,000 tons processed – largest of its kind in the US • 94 percent of treated soils returned to the site as clean backfill • 6 percent disposed • classified by USACE and USEPA as a “great success” • “Its success offers great promise for use on other site operable units or for similar efforts within the Superfund program.”

20. Summary • Chemical-enhanced soil washing • Ex-situ, on-site, physical-chemical process • Heavy metals, fuels, SVOCs, pesticides, etc • Mineral-processing equipment • Volume reduction, contaminant extraction, soil reuse as cleanfill or construction materials Thanks for your time – Questions are most welcome (daniel.tsang@canterbury.ac.nz) Kinetic interactions in soil washing/flushing: Tsang, D.C.W.; Yip, T.C.M.; Lo, I.M.C. (2009). Environ. Sci. Technol., 43, 837-842. Yip, T.C.M.; Tsang, D.C.W.; Ng, K.T.W.; Lo, I.M.C. (2009). Environ. Sci. Technol., 43, 831-836. Zhang, W.; Tsang, D.C.W.; Lo, I.M.C. (2008). J. Hazard. Mater., 155, 433-439. Tsang, D.C.W.; Zhang, W.; Lo, I.M.C. (2007). Chemosphere, 68, 234-243. Zhang, W.; Tsang, D.C.W.; Lo, I.M.C. (2007). Chemosphere, 66, 2025-2034. Modeling extraction: Yip, T.C.M.; Tsang, D.C.W.; Ng, K.T.W.; Lo, I.M.C. (2009). Chemosphere, 74, 301-307. Modeling transport: Tsang, D.C.W.; Lo, I.M.C.; Chan, K.L. (2007). Environ. Sci. Technol., 41,3660-3667.

21. 21st Annual Conference