SolidificationStabilization

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Solidification/Stabilization

• Sanjay K. Mohanty
• Civil Environmental Engineering Department
• University of Hawaii at Manoa

December 29th, 2004
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Outline

• Heavy metal Remediation technology
• Solidification and Stabilization
• Contaminants For Treatment
• Site Avtex Fibres Superfund Site, Virginia
• Remediation Design / Plan
• Cost Analysis

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Heavy metal Remediation Technology

• Chemical Oxidation
• Electrokinetic Separation
• Soil Washing
• Permeable treatment walls
• Phytoremediation
• Capping
• Vitrification
• Solidification/Stabilization

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Solidification Stabilization

• Definition
• Process that encapsulate a waste to form a solid
  material and to restrict contaminant migration by
  decreasing the surface area exposed to leaching
  and/or by coating the waste with low-permeability
  materials.. (EPA)
• Objective
• Stabilization of material prior to land disposal
• Stabilization of contaminants to be left in place
  as part of site cleanup
• Strategy
• Reduce the permeability/mobility.
• Reduce level of Toxicity
• Limit the solubility (fixation)
• Application
• Land Disposal
• Site remediation
• Solidification of industrial waste

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Solidification and Stabilization Cont.
Contaminants

• Inorganic wastes
• Heavy Metal
• Fluorides, Iodine, Borosilicate
• Organic wastes
• Oil, Grease
• Pesticides
• Chlorinated Hydrocarbons
• Solvents
• Organics

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Solidification and Stabilization Cont.
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Solidification and Stabilization Cont.
Principle

• Mechanism
• Macro-encapsulation
• Micro-encapsulation
• Adsorption
• Detoxification

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Solidification and Stabilization Cont.
Factor affecting the solidification/stabilization

• Particle size
• Particle size distribution
• Soil Homogeneity and isotropy
• Unconfined Compressive strength
• Atterberg limits
• Permeability
• Bulk Density

• Contaminant property
• Surface area of the waste
• pH
• Redox potential
• Oil and grease
• Ion-exchange capacity

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Solidification and Stabilization Cont.
Schematic of CFS Process
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Solidification and Stabilization Cont.
Typical Auger/Caisson and Reagent/Injector Head
Systems
In situ/ Ex situ heavy- metal stabilization
process
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Solidification and Stabilization Cont.

• Advantages
• Permanent treatment option
• Efficient at lower depth (8 10 ft)
• Handle larger volume of wastes (in situ)
• Cost effective by avoiding mobilization of soil
  (in situ)
• Avoid possible air contamination while
  transportation (in situ)

• Limitation
• Depth of contaminants
• Incompatibility of wastes with variations of this
  process
• Weathering of the materials used for fixation
  (reliability)
• Uniformity
• Increase in volume during solidification
• Solidified material may hinder future site use
• Processing of contamination below the water table
  may require dewatering
• Cost associated with mixing and installing
  horizontal subsurface barrier

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Project Site

• Avtex Fibres Superfund Site, Front Royal,
  Virginia
• Site History
• Rayon and other synthetic production (1940
  1989)
• Wastes and by-products were disposed in site
• PCB contamination found in Shenandoah River
  (1989)
• Shutdown of the plant in 1989.
• Added to NPL site in June 10, 1986.
• Contaminant of concern

• Groundwater
• Carbon bisulfide
• Ammonia
• Arsenic
• Antimony
• Phenol
• High pH

• Soil
• Lead
• Arsenic
• PCBs

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Site picture
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overview
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(No Transcript)
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landfill
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Remediation Design / Plan

• Mixture design and Development
• Portland cement mix technology
• Evaluate different factor associated with this
  technique
• Evaluate the Site risk
• Cost Analysis
• Remedial Alternative

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Cost Analysis

• Material
• Mixing
• Landfill disposal and maintenance
• Protect public health

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References

• Conner, J. R. 1990. Chemical Fixation and
  Solidification of Hazardous Wastes. Van Nostrand
  Reinhold. New York
• LaGrega, M. D., Buckingham, P. L.,Evans J. C.
  1994. Hazardous Waste Management. McGraw-Hill
  Series in water resources and Environmental
  Engineering.
• http//www.epa.gov/reg3hwmd/super/sites/VAD0703586
  84/index.htm
• Yong, R. N. 2000. Geoenvironmental Engineering
  Contaminated Soils, Pollutant Fate and
  Mitigation, 307 pp. CRC Press, Boca Raton, FL.
• http//clu-in.org/asr/

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Comments!
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Acknowledgement
Special Thanks to William
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Thank You