Soil WashingNeed for the TechnologyDOEDOE Waste ManagementSlide 5Examples of Contaminated Waste Sites with ‘Mixed Wastes’Possible Site Management StrategiesPump and Treat LimitationsSlide 9Soil Washing - Process DescriptionPowerPoint PresentationEPA Mobile Soil-Washing SystemWash Water AdditivesSoil Washing: Pros and ConsSynthetic Contaminated Soil (Zinc and Methylene Blue)Remediation StrategiesExpectationsAnalytical MethodsSoil Washing: Potential Experiment ObjectivesMonroe L. Weber-Shirk School of Civil and Environmental EngineeringSoil WashingSoil Washing“There is a need for increased use of new separation technologies (such as soil washing) that reduce the quantity of waste requiring solidification/stabilization, or allow the recycling of valuable metals.”“There is a need for increased use of new separation technologies (such as soil washing) that reduce the quantity of waste requiring solidification/stabilization, or allow the recycling of valuable metals.”--EPA 1993Need for the TechnologyEPA estimates that over 20 million cubic yards of soil at current NPL sites (national priority list) are contaminated with metalsDOE (Department of Energy) estimates 10s of millions of cubic yardsLeaking Underground Storage Tanks (UST) contribute 56 million cubic yardsDOD (Department of Defense) ?Volume reduction technologies!!DOEDOEThe nuclear arms race and its aftermath have created the largest and most complex problem of environmental remediation and waste management in U.S. historyThe problem is so complicated and costly that there is a tendency in the nuclear establishment to simply bury the problem, literally and figuratively, creating what have been called national sacrifice zonesThe current Department of Energy (DOE) best estimate for partial environmental restoration and waste management and disposal is $227 billion over a 75-year period$90 to $400 per cubic yard operating costThe nuclear arms race and its aftermath have created the largest and most complex problem of environmental remediation and waste management in U.S. historyThe problem is so complicated and costly that there is a tendency in the nuclear establishment to simply bury the problem, literally and figuratively, creating what have been called national sacrifice zonesThe current Department of Energy (DOE) best estimate for partial environmental restoration and waste management and disposal is $227 billion over a 75-year period$90 to $400 per cubic yard operating costContaining the Cold War Mess:Restructuring the Environmental Management of the U.S. Nuclear Weapons ComplexMarc FioravantiArjun Makhijani, Ph.D.October 1997DOE Waste ManagementDOE Waste ManagementLLW = Low-Level WasteMLLW = Mixed Low-Level WasteTRU = TransuranicHLW = High-Level WasteSNF = Spent Nuclear FuelGCD =Greater Confinement DisposalNTS = Nevada Test SiteLANL = Los Alamos National LaboratoryORNL = Oak Ridge National LaboratorySoil WashingA technology for volume reduction of contaminated soilPotentially removes ‘mixed wastes’ from contaminated soil so the soil can be returned to the original siteReferencesGriffiths, R. A. 1995. “Soil-washing technology and practice” Journal of Hazardous Materials 40(2): 175-189.Semer, R. and K. R. Reddy. 1996. “Evaluation of soil washing process to remove mixed contaminants from a sandy loam” Journal of Hazardous Materials 45(1): 45-57.Examples of Contaminated Waste Sites with ‘Mixed Wastes’DOE/DOD sites with radioactive metals plus organic scintillation cocktails.Cornell chemical dump near airport: organic solvents, metal salts, ... all dumped in close proximity to each other.Coal gas plants pyrolysis was used to get coal gas (for street lamps)also produced coal tars containing polycyclic aromatic hydrocarbons (PAHs) and coal ash that has high metal concentration.Printers ink contained both organic dyes and leadDumpsPossible Site Management StrategiesSeal off site (clay barriers, concrete cover, fences to keep people and animals out...)Remove contaminated soil - huge volumes!Remove contaminants using an in-situ separation process pump and treatin situ bioremediationelectro-chemical remediationRemove contaminants from excavated soilsoil washing, bioremediation, thermal desorptionPump and Treat LimitationsPollutants absorb (within), adsorb (on surface), sorb (don’t know precise mechanism), or attach to the soil. High retardation factors. Immobile.Soil propertiesnegatively charged at neutral pHSiO2 has a PZC of pH 2-3 (at this pH enough hydrogen ions have reacted with the surface to make it neutral). At lower pH the surface would be positively charged.Therefore cations (metals) easily bind to the negatively charged soil.Point of zero chargePoint of zero chargeSoil WashingSeparation of fine soil particles from larger soil particlescontaminants adhere to particle surfacessmall particles have more surface area/unit massremoval of fines from a contaminated soil also removes most of the contaminantsSeparation of contaminants from the finessolubilize contaminants in the wash watersurfactants, acids, bases, chelating agents, alcohols,...Soil Washing - Process DescriptionExcavate contaminated soilRemediate the contaminated soilRemove large debris or particles larger than 2 in.Separate all contaminants from the soilremove sand after initial water washsilt/clay fraction requires further treatmentTreat or dispose of residuesReturn soilEPA Mobile Soil-Washing SystemFeed SoilFeed SoilWash WaterWash WaterCoarse FractionCoarse FractionChemical AdditivesChemical AdditivesClean WaterClean ProductHydrocyclonesHydrocyclonesDrum WasherTrommelFine FractionFine FractionStirredTankStirredTankStirredTankStirredTankStirredTankStirredTankStirredTankStirredTankContaminant + waterContaminant + watersolubilize metalssolubilize metalsorganic acidsorganic acidsWash Water AdditivesGenerally undesirablecomplicate recycling or disposal of wash wateradditional unit processes needed to remove additivesAdditives are contaminant specificacids and chelating agents: ________ _______bases: improve extraction of _______ _____surfactants and organic-solvents: improve extraction of ____ _________ organicslow solubilitylow solubilitySoil Washing: Pros and Consclosed system: controlled conditionssignificant volume reduction of contaminated