Presentation on theme: "CE 510 Hazardous Waste Engineering"— Presentation transcript:
1 CE 510 Hazardous Waste Engineering Department of Civil EngineeringSouthern Illinois University CarbondaleInstructor: Jemil YesufDr. L.R. ChevalierLecture Series 11:Overview of Hazardous Waste Remediation, Treatment and Disposal
2 Course GoalsReview the history and impact of environmental laws in the United StatesUnderstand the terminology, nomenclature, and significance of properties of hazardous wastes and hazardous materialsDevelop strategies to find information of nomenclature, transport and behavior, and toxicity for hazardous compoundsElucidate procedures for describing, assessing, and sampling hazardous wastes at industrial facilities and contaminated sitesPredict the behavior of hazardous chemicals in surface impoundments, soils, groundwater and treatment systemsAssess the toxicity and risk associated with exposure to hazardous chemicalsApply scientific principles and process designs of hazardous wastes management, remediation and treatment
3 Major ConceptsTop priority is waste minimization and pollution preventionReductionRecyclingSecond tier of waste management is treatmentEmphasis on the destruction of the hazardous chemicalsSelection of treatment processes based onProperties of chemical(s)ConcentrationsComplexity of the matrix
4 Major Concepts Final option is long-term containment with no treatment Landfill disposalHowever, landfill disposal represents a long-term threat of potential environmental releasesHence low priority as a management alternative
5 Priorities in hazardous waste management, minimization and prevention Waste GenerationTreatmentpH neutralizationMetals removalOrganic removalThermal treatmentSource and VolumeReductionsMaterials substitutionSegregationReuseProcess modificationDisposalLandfillsRecyclingSolventsProcess waterAcids
6 Hierarchy of Source Removal and Remediation Methods First PriorityDrumsTanksSludgesOther containers of source materials (e.g. bags, bins, etc.)Second PriorityContaminated surface soilsContaminated subsurface solidsLNAPLDNAPLThird PriorityContaminated groundwaterContaminated surface waters
9 Hazardous Waste Treatment Ex-situ processes - RemovalRemoval – treatment - disposalGroundwaterVadose zone subsurface soilSurface soilMore expensive than in-situEasier to control than in-situtreatmentInjection wellRecovery wellgroundwater flowcontaminated regionPump-and-treat
10 Hazardous Waste Treatment In-situ“in place”No excavationGroundwater is not pumped out and treatedLess labor intensive (cost savings)Minimal site disturbance
11 Hazardous Waste Treatment: Effects of Sorption Contaminant Saturation conc.Contaminant conc. In aqueous phaseCoefficient for contaminant desorption
12 Hazardous Waste Treatment: Effects of Sorption Effects of sorption on groundwater remediation through 1) asymptotic approach to reaching clean-up levels and 2) the release of contaminants to the aqueous phase after the pump-and-treat process has stoppedBecause of the dependence of pump-and-treat groundwater remediation on sorption/desorption, its use has been in decline.
13 Hazardous Waste Treatment: Reactor Analysis Most designs and analyses of engineering processes are based on mass balance and reactor analysisThree modelsBatch ReactorsCFSTRsPlug- flow reactors
14 Hazardous Waste Treatment: Reactor Analysis Batch ReactorsNo influent or effluentWastes treated by adding reagentsFirst order reaction is expressed as
15 Hazardous Waste Treatment: Reactor Analysis Continuous flow stirred tank reactors (CFSTR)Effluent concentration is the same as the concentration in the reactorFirst order reaction is expressed as
16 Hazardous Waste Treatment: Reactor Analysis Plug-flow reactors (PFR)Characterized by no mixing or dispersionWater moves in a “plug” through the reactorFirst order reaction is expressed as
17 Textbook Problem 12.18A groundwater containing 560 µg/L of tolune is to be treated to 5 µg/L in a plug-flow UV/H2O2 reactor. If the steady-state hydroxyl radical concentration is 2x10-10 M, determine the required detention time in the reactor. kOH- for tolune is 4x109.
18 Hazardous Waste Treatment: Reactor Analysis Almost all hazardous waste treatment systems are designed using reactor fundamentalsSee figures 12.9 through 12.11
19 Classification of Remediation and treatment Processes Environmental engineering treatment systems classification:PhysiochemicalBiologicalHazardous waste treatment systems are complex due to:Thousands of contaminantsWidely varying concentration and characteristicsTreatment required for different media
20 Classification of Remediation and treatment Processes Classification of remedial and treatment technologies based on pathways and functionSorptionVolatilizationAbioticBioticNeutralizationStabilizationThermal processes
21 Sorption ProcessesGAC, Ion Exchange , Stabilization (a.k.a. Solidification or fixation), soil washing and thermal desorptionGACHigh surface area: m2/gHydrophobic surface characteristicsGAC made from many sources:WoodBituminous coal materialsCoconut shells and NutshellsLignite
22 GAC Treatment Dynamics of gravity flow GAC treatment Influent Exhausted carbonAdsorption zone (MTZ)Unused carbonEffluent
23 StabilizationStabilization: Addition of stabilizing material to hazardous waste so as to alter the chemistry of the waste and render it less toxic, less mobile and less solubleSolidification: the modification of a liquid or slurry waste to a solid material by adding solids or other reagentsWastes treated by stabilizationLiquid and slurry organic and inorganic hazardous wastes generated under RCRAHazardous wastes at contaminated sitesResiduals from other treatment processes
25 Volatilization Processes Air stripping, Soil Vapor Extraction (SVE)Air stripping has been used for decades for the removal of ammonia, sulfur dioxide, and hydrogen sulfide from waterWhen hazardous waste is stripped from aqueous phase into gaseous phase, contaminants may become hazardous air pollutantsHence, GAC scrubbers and other secondary process modifications are implemented to lower concentration below regulation levels
26 SVESVE is a cleanup technology commonly used to remove VOCs and semi-VOCs from the vadose zone or from piles of excavated soilsMost important variables for SVE process selection include Porosity, and Contaminant volatilitySVE is one of the most accepted remediation technology since 1970sSVE has been used in 25% of the 170 superfund sitesPhysical components of SVE include: A vapor extraction well, a vacuum blower, air water separator, and vapor treatment system (GAC or biofilters)
27 Abiotic Transformation processes Chemical oxidation/reduction: converts HWs to non-hazardous or less toxic compounds that more stable, less mobile, and/or inert states.Involves the transfer of electrons from one compound to another, i.e., one reactant is oxidized (loses electrons) and one is reduced (gains electrons)Most common design application is the Advanced oxidation processes (AOPs) with oxidizing agents such as:Ozone, UV/ozone, H2O2/ozone, UV/H2O2Fentons’s Reagent (H2O2/catalysts)
28 Class exampleIf (a) O3 is present at 10-5 mM or (b) OH· at 10-5 mM, what is the time required to oxidize 10 mg/L TCE to 1 µg/L TCE? The rate constant for the reaction of ozone with TCE is 17 M-1sec-1. Assume oxidant concentrations are constant.
29 Biotic Transformation processes Application of biological processesBioremediation techniques are destruction techniques directed toward stimulating microorganisms to grow and use the contaminants as a food and energy sourceThe main process variables in the design and operation of bioremediation include:Oxygen supplypHBioavailabilityNutrientsToxicityTemperature
30 Biotic Transformation processes Terminal electron acceptorElectron donor sourceNutrientsRecovery wellInjection wellPlume of sorbed contaminantsGW flowAn in situ groundwater bioremediation system
31 Other Treatment processes BioventingLandfarmingThermal processes-IncinerationAir spargingPhytoremediationBiopilesCompostingSlurry phase biological treatmentMore reference on remediation technologies can be accessed at
32 Ultimate Disposal- HW Landfills Primary goals of HW management are:Minimization and pollution preventionTreatment (emphasis on destruction)Some HWs cannot be minimized or treatedE.g. some PCBs and metal bearing soils, residues from other treatment processesHence, need for Landfill disposalsLandfills are designed to contain waste, while minimizing releases to environmentSee figs and 12.23
33 Summary of Important Points and Concepts The priorities of managing HWs, in decreasing order of importance, are minimization/prevention, treatment/remediation, and disposal.HW minimization efforts hold the potential of decreasing the mass, volume and toxicity of wastes at the sourceHW remediation and treatment processes may be considered applications of hazardous waste pathways. Therefore, treatment processes may be grouped into sorption, volatilization, abiotic transformation, and biotic transformation processes. Another class-Thermal processes
34 Summary of Important Points and Concepts HW remediation and treatment processes may also be classified by schemes such as in situ and ex situ processes OR as RCRA wastes or CERCLA-type HW sites.Treatment process selection and design requires consideration of the contaminant characteristics and the matrix of the waste (i.e., liquid, soil, sludge, etc.)Almost every HW management system may be conceptualized as a reactor as a basis for analysis and design.