CE 510 Hazardous Waste Engineering

Report
CE 510
Hazardous Waste Engineering
Department of Civil Engineering
Southern Illinois University Carbondale
Instructor: Jemil Yesuf
Dr. L.R. Chevalier
Lecture Series 11:
Overview of Hazardous Waste Remediation, Treatment and Disposal
Course Goals
 Review the history and impact of environmental laws in the
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United States
Understand the terminology, nomenclature, and
significance of properties of hazardous wastes and
hazardous materials
Develop strategies to find information of nomenclature,
transport and behavior, and toxicity for hazardous
compounds
Elucidate procedures for describing, assessing, and
sampling hazardous wastes at industrial facilities and
contaminated sites
Predict the behavior of hazardous chemicals in surface
impoundments, soils, groundwater and treatment systems
Assess the toxicity and risk associated with exposure to
hazardous chemicals
Apply scientific principles and process designs of hazardous
wastes management, remediation and treatment
Major Concepts
 Top priority is waste minimization and
pollution prevention
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Reduction
Recycling
 Second tier of waste management is
treatment
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Emphasis on the destruction of the hazardous
chemicals
Selection of treatment processes based on
 Properties of chemical(s)
 Concentrations
 Complexity of the matrix
Major Concepts
 Final option is long-term containment with
no treatment
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Landfill disposal
However, landfill disposal represents a long-term
threat of potential environmental releases
Hence low priority as a management alternative
Priorities in hazardous waste management,
minimization and prevention
Waste Generation
Source and Volume
Reductions
•Materials substitution
•Segregation
•Reuse
•Process modification
Recycling
•Solvents
•Process water
•Acids
Treatment
•pH neutralization
•Metals removal
•Organic removal
•Thermal treatment
Disposal
•Landfills
Hierarchy of Source Removal and
Remediation Methods
 First Priority
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Drums
Tanks
Sludges
Other containers of source materials (e.g. bags, bins, etc.)
 Second Priority
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Contaminated surface soils
Contaminated subsurface solids
LNAPL
DNAPL
 Third Priority
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Contaminated groundwater
Contaminated surface waters
Second Priority: LNAPL
Second Priority: DNAPL
Hazardous Waste Treatment
 Ex-situ processes - Removal
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Removal – treatment - disposal
 Groundwater
 Vadose zone subsurface soil
 Surface soil
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More expensive than in-situ
Easier to control than in-situ
http://www.frtr.gov/matrix2/section1/list-of-fig.html#2
treatment
Injection well
Recovery well
groundwater flow
contaminated region
Pump-and-treat
Hazardous Waste Treatment
 In-situ
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“in place”
No excavation
Groundwater is not pumped out and
treated
Less labor intensive (cost savings)
Minimal site disturbance
Hazardous Waste Treatment:
Effects of Sorption
Contaminant Saturation conc.

dC
dt
 k C s  C 
Coefficient for contaminant
desorption
Contaminant conc. In aqueous
phase
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 stopped
Because of the dependence of pump-and-treat groundwater
remediation on sorption/desorption, its use has been in decline.
Hazardous Waste Treatment:
Reactor Analysis
 Most designs and analyses of engineering
processes are based on mass balance and
reactor analysis
 Three models
 Batch Reactors
 CFSTRs
 Plug- flow reactors
Hazardous Waste Treatment:
Reactor Analysis
 Batch Reactors
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No influent or effluent
Wastes treated by adding
reagents
First order reaction is
expressed as
C
Co
e
 kt
Hazardous Waste Treatment:
Reactor Analysis
 Continuous flow stirred tank reactors
(CFSTR)
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Effluent concentration is the same as the
concentration in the reactor
First order reaction is expressed as
C
Co

1
1  k
Hazardous Waste Treatment:
Reactor Analysis
 Plug-flow reactors (PFR)
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Characterized by no mixing or dispersion
Water moves in a “plug” through the reactor
First order reaction is expressed as
C
Co
e
 k
Textbook Problem 12.18
A groundwater containing 560 µg/L of
tolune is to be treated to 5 µg/L in a
plug-flow UV/H2O2 reactor. If the steadystate hydroxyl radical concentration is
2x10-10 M, determine the required
detention time in the reactor. kOH- for
tolune is 4x109.
Hazardous Waste Treatment:
Reactor Analysis
 Almost all hazardous waste treatment
systems are designed using reactor
fundamentals
 See figures 12.9 through 12.11
Classification of Remediation
and treatment Processes
 Environmental engineering treatment
systems classification:
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Physiochemical
Biological
 Hazardous waste treatment systems are
complex due to:
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Thousands of contaminants
Widely varying concentration and characteristics
Treatment required for different media
Classification of Remediation
and treatment Processes
 Classification of remedial and treatment
technologies based on pathways and function
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Sorption
Volatilization
Abiotic
Biotic
Neutralization
Stabilization
Thermal
processes
http://www.frtr.gov/matrix2/section1/list-of-fig.html#2
Sorption Processes
 GAC, Ion Exchange , Stabilization (a.k.a.
Solidification or fixation), soil washing and
thermal desorption
 GAC
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High surface area: 1000-1400 m2/g
Hydrophobic surface characteristics
 GAC made from many sources:
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Wood
Bituminous coal materials
Coconut shells and Nutshells
Lignite
GAC Treatment
 Dynamics of gravity flow GAC treatment
Influent
Exhausted carbon
Adsorption zone
(MTZ)
Unused carbon
Effluent
Stabilization
 Stabilization: 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
soluble
 Solidification: the modification of a liquid or slurry
waste to a solid material by adding solids or other
reagents
 Wastes treated by stabilization
 Liquid and slurry organic and inorganic hazardous
wastes generated under RCRA
 Hazardous wastes at contaminated sites
 Residuals from other treatment processes
Stabilization Agents
 Organic agents:
Organically modified lime
 Organic polymers (polyethylene)
 Bitumen
 Asphalt
 Inorganic agents: Cement, Lime
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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
water
 When hazardous waste is stripped from aqueous phase
into gaseous phase, contaminants may become
hazardous air pollutants
 Hence, GAC scrubbers and other secondary process
modifications are implemented to lower concentration
below regulation levels
SVE
 SVE is a cleanup technology commonly used to remove
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VOCs and semi-VOCs from the vadose zone or from piles
of excavated soils
Most important variables for SVE process selection
include Porosity, and Contaminant volatility
SVE is one of the most accepted remediation technology
since 1970s
SVE has been used in 25% of the 170 superfund sites
Physical components of SVE include: A vapor extraction
well, a vacuum blower, air water separator, and vapor
treatment system (GAC or biofilters)
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:
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Ozone, UV/ozone, H2O2/ozone, UV/H2O2
Fentons’s Reagent (H2O2/catalysts)
Class example
If (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.
Biotic Transformation processes
 Application of biological processes
 Bioremediation techniques are destruction techniques
directed toward stimulating microorganisms to grow
and use the contaminants as a food and energy source
 The main process variables in the design and operation
of bioremediation include:
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Oxygen supply
pH
Bioavailability
Nutrients
Toxicity
Temperature
Biotic Transformation processes
Electron
donor
source
Recovery well
Terminal
electron
acceptor
Nutrients
Injection well
Plume of sorbed contaminants
GW flow
An in situ groundwater bioremediation system
Other Treatment processes
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Bioventing
Landfarming
Thermal processes-Incineration
Air sparging
Phytoremediation
Biopiles
Composting
Slurry phase biological treatment
More reference on remediation technologies can be
accessed at
http://www.frtr.gov/matrix2/top_page.html
Ultimate Disposal- HW Landfills
 Primary goals of HW management are:
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Minimization and pollution prevention
Treatment (emphasis on destruction)
 Some HWs cannot be minimized or treated
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E.g. some PCBs and metal bearing soils, residues
from other treatment processes
 Hence, need for Landfill disposals
 Landfills are designed to contain waste, while
minimizing releases to environment
 See figs. 12.22 and 12.23
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 source
 HW 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
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 CERCLAtype 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.

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