United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/625/R-98/004
December 1998
vxEPA Handbook
Advanced Photochemical
Oxidation Processes
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EPA/625/R-98/004
December 1998
HANDBOOK ON ADVANCED PHOTOCHEMICAL
OXIDATION PROCESSES
Center for Environmental Research Information
National Risk Management Research Laboratory
Office of Research and Development.
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Printed on Recycled Paper
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Notice
This document's preparation has been funded by the U.S. Environmental Protection Agency (U.S. EPA) under
Purchase Order No. 7C-R442-NTLX issued to Tetra Tech EM Inc. The document has been subjected to U.S.
EPA peer and administrative reviews and has been approved for publication as a U.S. EPA document.
Mention of trade names or commercial products does not constitute an endorsement or recommendation for
use.
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Foreword
The U.S. Environmental Protection Agency (U.S. EPA) is charged by Congress with protecting the Nation's
land, air, and water resources, Under a mandate of national environmental laws, the Agency strives to
formulate and implement actions leading to a compatible balance between human activities and the ability of
natural systems to support and nurture life. To meet this mandate, EPA's research program is providing data
and technical support for solving environmental problems today and building a science knowledge base
necessary to manage our ecological resources wisely, understand how pollutants affect our health, and
prevent or reduce environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for investigation of
technological and management approaches for reducing risks from threats to human health and the
environment. The focus of the Laboratory's research program is on methods for the prevention and control
of pollution to air, land, water, and subsurface resources; protection of water quality in public water systems;
remediation of contaminated sites and groundwater; and prevention and control of indoor air pollution. The
goal of this research effort is to catalyze development and implementation of innovative, cost-effective
environmental technologies and to develop scientific and engineering information needed by U.S. EPA to
support regulatory and policy implementation of environmental regulations and strategies.
A key aspect of the Laboratory's success is an effective program for technical information dissemination and
technology transfer. The Center for Environmental Research Information (CERI) is the focal point for these
types of outreach activities in NRMRL.
This summary document, Handbook on Advanced Photochemical Oxidation Processes, produced by CERI,
is a technical resource guidance document for environmental engineering practitioners.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
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Abstract
This handbook summarizes commercial-scale system performance and cost data for advanced photochemical
oxidation (APO) treatment of contaminated water, air, and solids. Similar information from pilot- and bench-
scale evaluations of APO processes is also included to supplement the commercial-scale data. Performance
and cost data is summarized for various APO processes, including vacuum ultraviolet (VUV) photolysis,
ultraviolet (UV)/oxidation, photo-Fenton, and dye- or semiconductor-sensitized APO processes. This
handbook is intended to assist engineering practitioners in evaluating the applicability of APO processes and
in selecting one or more such processes for site-specific evaluation.
APO has been shown to be effective in treating contaminated water and air. Regarding contaminated water
treatment, UV/oxidation has been evaluated for the most contaminants, while VUV photolysis has been
evaluated for the fewest. Regarding contaminated air treatment, the sensitized APO processes have been
evaluated for the most contaminants, while VUV photolysis has been evaluated for the fewest.
APO processes for treating contaminated solids generally involve treatment of contaminated slurry or leachate
generated using an extraction process such as soil washing. APO has been shown to be effective in treating
contaminated solids, primarily at the bench-scale level.
IV
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Contents
Section
Notice
Foreword '"
Abstract IV
Tables y
Figures viii
Acronyms, Abbreviations, and Symbols 'x
Glossary , X'
Acknowledgments xv
Executive Summary ES-1
1 Introduction • • 1-1
1.1 Purpose and Scope • • 1-1
1.2 Organization 1-3
1.3 References .. 1-4
2 Background -2- 1
2.1 APO Technologies -2- 1
2.1.1 VUV Photolysis 2-1
2.1.2 UV/Oxidation Processes 2-2
2.1.3 Photo-Fenton Process 2-2
2.1.4 Sensitized APO Processes 2-4
2.2 Commercial-Scale APO Systems 2-6
2.2.1 Calgon perox-pure" and Rayox® UV/H2O2 Systems 2-7
2.2.2 Magnum CAV-OX®UV/H2O2 System 2-8
2.2.3 WEDECOUV/O3 Systems 2-8
2.2.4 U.S. Filter UV/O3/H2O2 System 2-9
2.2.5 Matrix UV/Ti02 System 2-11
2.2.6 PTI UV/03 System. 2-12
2.-2.7 ZentoxUV/TiO2System 2-12
2.2.8 KSE AIR UV/Catalyst System 2-13
2.3 APO System Design and Cost Considerations 2-13
2.4 References ..2-14
3 Contaminated Water Treatment 3-1
3.1 Contaminated Groundwater Treatment 3-1
3.1.1 VOC-Contaminated Groundwater 3-I
3.1.2 SVOC-Contaminated Groundwater 3-8
3.1.3 PCB-Contaminated Groundwater 3-10
3.1.4 Pesticide- and Herbicide-Contaminated Groundwater 3-10
3.1.5 Dioxin- and Furan-Contaminated Groundwater 3-12
3.1.6 Explosive- and Degradation Product-Contaminated Groundwater 3-12
3.1.7 Humic Substance-Contaminated Groundwater 3-14
3.1.8 Inorganic-Contaminated Groundwater 3-14
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Contents (Continued)
Section Page
3.2 Industrial Wastewater Treatment , 3-21
3.2.1 VOC-Contaminated Industrial Wastewater 3-21
3.2.2 SVOC-Contaminated Industrial Wastewater 3-22
3.2.3 Dye-Contaminated Industrial Wastewater 3-23
3.2.4 Inorganic-Contaminated Industrial Wastewater 3-25
3.2.5 Microbe-Contaminated Industrial Wastewater 3-25
3.3 Municipal Wastewater Treatment 3-28
3.4 Drinking Water Treatment 3-28
3.5 Landfill Leachate Treatment 3-29
3.5.1 High-COD Landfill Leachate 3-29
3.5.2 SVOC-Contaminated Landfill Leachate 3-29
3.6 Contaminated Surface Water Treatment., , , 3-31
3.6.1 SVOC-Contaminated Surface Water. , 3-31
3.6.2 PCB-Contaminated Surface Water 3-31
3.6.3 Pesticide- and Herbicide-Contaminated Surface Water 3-31
3.7 References 3-32
4 Contaminated Air Treatment 4-1
4.1 SVE Off-Gas Treatment 4-I
4.2 Air Stripper Off-Gas Treatment 4-8
4.3 Industrial Emissions Treatment 4-10
4.3.1 VOC-Containing Industrial Emissions 4-10
4.3.2 SVOC-Containing Industrial Emissions 4-11
4.3.3 Explosive- and Degradation Product-Containing Industrial Emissions 4-11
4.4 Automobile Emission Treatment 4-14
4.5 References 4--|4
5 Contaminated Solids Treatment , , , , , . . . . 5-I
5.1 Contaminated Soil Treatment , , ., 5-1
5.1.1 SVOC-Contaminated'Soil 5-1
5.1.2 PCB-Contaminated-SaiL 5-2
5.1.3 Pesticide- and Herbicide-Contaminated Soil 5-2
5.1.4 Dioxin- and Furan-Contaminated Soil , ,,.., 5-2
5.2 Contaminated Sediment Treatment , , 5-5
5.3 Contaminated Ash Treatment ..,..,....,.,. , -c~5
5.4 References 5-5
Appendix
Technology Vendor Contact Information
vi
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Tables
lahla Eaflfi
ES-1 Contaminated Water Treatment ES-5
ES-2 Contaminated Air Treatment ES-8
i-1 Oxidation Potential of Several Oxidants in Water 1-1
1-2 Rate Constants for 0, and *OH Reactions with Organic Compounds in Water 1-2
3-1 Contaminated Groundwater Treatment 3-15
3-2 Industrial Wastewater Treatment 3-26
3-3 Landfill Leachate Treatment • 3-30
4-1 SVE Off-Gas Treatment : - 4-7
4-2 Air Stripper Off-Gas Treatment 4~9
4-3 Industrial Emissions Treatment 4-13
5-1 Contaminated Soil Treatment 5-4
VII
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Figures
Figure
/-/ Performance and cost data organization 1-3
2-I Scheme of chemical reactions in the photo-Fenton reaction 2-3
2-2 Absorption spectra of H2O2 and potassium ferrioxalate in aqueous solution 2-4
2-3 Simplified Ti02 photocatalytic mechanism 2-6
2-4 Flow configuration in a Calgon UV/H2O2 system 2-7
2-5 Flow configuration in a Magnum CAV-OX® UV/H202 system 2-8
2-6 Flow configuration in a WEDECO UV/03 system for water contaminated with chlorinated
VOCs 2- 9
2-7 Flow configuration in a WEDECO UV/O3 system for biologically treated landfill leachate 2-10
2-8 Flow configuration in a US Filter UV/O3/H2O2 system 2-10
2-9 Flow configuration in a Matrix wafer 2-11
2-I 0 Flow configuration in the Matrix UWTiO2 system 2-12
2-11 Flow configuration in the PTI UV/O3 system 2-13
VIII
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/4J/cm2-min
Ag
AIR
AOX
APO
BOD
BTEX
Calgon
CB
CFC-113
cfu/mL
CHQ
cm
CO
COD
CP
cu
2,4-D
DBCP
DCA
DCAC
DCB
DCE
DCP
DNG
eCB
EE/O
eV
Fe(ll)
Fe(lll)
Fe(lll)(OH)2+
Fe203
g
GAC
hv
h VB
H2O
H202
HCI
HHQ
H M P A
H-
Acronyms, Abbreviations, and Symbols
Greater than
Less than
Microgram per square centimeter-minute
Microgram per liter
Micromole per liter
Silver
Adsorption-integrated-reaction
Adsorbable organic halide
Advanced photochemical oxidation
Biochemical oxygen demand
Benzene, toluene, ethylbenzene, and xylene
Calgon Carbon Corporation
Chlorobenzene
Trichlorofluoroethane
Colony forming unit per milliliter
Chlorohydroquinone
Centimeter
Carbon monoxide
Chemical oxygen demand
Chlorophenol
Concentration unit
2,4-Dichlorophenoxyacetic acid
1,2-Dibromo-3-chloropropane
Dichloroethane
Dichloroacetylchloride
Dichlorobenzene
Dichloroethene
Di chlorophenol
Dinitroglycerin
Electron in the conduction band
Electrical energy consumption per order-of-magnitude contaminant removal
Electron volt
Ferrous iron
Ferric iron
Ferrihydroxalate
Ferric oxide
Gram
Granular activated carbon
Light energy
Hole in the valence band
Water molecule
Hydrogen peroxide
Hydrochloric acid
Hydroxyhydroquinone
Hexamethylphosphoramide
Hydrogen radical
IX
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Acronyms, Abbreviations, and Symbols (Continued)
IEA
kg
KSE
kW
kWh/m3
L
Umin
m
M-W
M'V1
m3
m3/h
Magnum
Matrix
MCL
mg/L
min
MNG
MTBE
mW/L
mW/cm2-sec
4-NA
N2O
NDMA
NG
nm
NO
NO2
NOX
4-NP
NQ
NREL
0(1D)
O&M
O,
*OH
PAH
PCB
PCDD
PCDF
PCE
PCP
Irreversible electron acceptor
Kilogram
KSE, Inc.
Kilowatt
Kilowatt-hour per cubic meter
Liter
Liter per minute
Meter
Liter per mole-centimeter
Liter per mole-second
Cubic meter
Cubic meter per hour
Magnum Water Technology, Inc.
Matrix Photocatalytic, Inc.
Maximum contaminant level
Milligram per liter
Minute
Mononitroglycerin
Methyl-ferf-butyl ether
Milliwatt per liter
Milliwatt per square centimeter-second
4-Nitroaniline
Nitrous oxide
N-nitrosodimethylamine
Nitroglycerin
Nanometer
Nitric oxide
Nitrogen dioxide
Nitrogen oxides
4-Nitrophenol
Nitroguanidine
National Renewable Energy Laboratory
Singlet oxygen
Operation and maintenance
Oxygen
Superoxide ion
Ozone
Hydroxide ion
Hydroxyl radical
Polynuclear aromatic hydrocarbon
Polychlorinated biphenyl
Polychlorinated dibenzo-p-dioxin
Polychlorinated dibenzofuran
Tetrachloroethene
Pentachlorophenol
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Acronyms, Abbreviations, and Symbols (Continued)
PDU
pfu/mL
ppbv
ppmv
psia
PTI
RDX
scmm
SITE
SnO2
SVE
S V 0 C
2,4,5-T
TCA
TCE
2,3,5-TCP
Ti02
1,3,5-TNB
TNT
TOC
TOX
TPH
UDMH
U.S. Filter
U.S. EPA
uv
vc
voc
vuv
w
WEDECO
Zentox
ZnO
Photolytic Destruction Unit
Plaque-forming unit per milliliter
Part per billion by volume
Part per million by volume
Pound per square inch absolute
Process Technologies, Inc.
Cyclonite
Standard cubic meter per minute
Superfund Innovative Technology Evaluation
Tin oxide
Soil vapor extraction
Semivolatile organic compound
2,4,5-Trichlorophenoxyaceticacid
Trichloroethane
Trichloroethene
2,3,5-Trichlorophenol
Titanium dioxide
1,3,5-Trinitrobenzene
2,4,6-Trinitrotoluene
Total organic carbon
Total organic halides
Total petroleum hydrocarbons
Unsymmetrical dimethylhydrazine
U.S. Filter/Zimpro, Inc.
U.S. Environmental Protection Agency
Ultraviolet
Vinyl chloride
Volatile organic compound
Vacuum ultraviolet
Watt
WEDECO UV-Verfahrenstechnik
Zentox Corporation
Zinc oxide
XI
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Glossary
Anatase. The brown, dark-blue, or black, tetragonal crystalline form of titanium dioxide
Band gap. The energy difference between two electron energy bands in a metal
Batch reactor. A container in which a reaction is performed without any inflow or outflow of material during
the reaction
Bioassay test. A test for quantitatively determining the concentration of a substance that has a specific effect
on a suitable animal, plant, or microorganism under controlled conditions
Biochemical oxygen demand (BOD). The amount of dissolved oxygen consumed by microorganisms during
biochemical decomposition of oxidizable organic matter under aerobic conditions. The BOD test is widely
used to measure the pollution associated with biodegradable organic matter present in wastewaters.
Black light. Ultraviolet (UV) radiation having a relatively long wavelength (in the approximate range of 315
to 400 nanometers). It is also called UV-A, near-UV, or long-wave radiation.
Brookite. A brown, reddish, or black, orthorhombic crystalline form of titanium dioxide
Catalyst. A substance that alters the rate of a chemical reaction and that may be recovered essentially
unaltered in form and amount at the end of the reaction
Chemical oxygen demand (COD). A measure of the oxygen equivalent of organic matter that is susceptible
to oxidation by a strong chemical oxidant under acidic conditions. The COD test is widely used to measure
the pollution associated with both biodegradable and nonbiodegradable organic matter present in
wastewaters.
Complex. A compound formed by the union of a metal ion with a nonmetallic ion or molecule called a ligand
or complexing agent
Conduction band. An energy band in a metal in which electrons can move freely, producing a net transport
of charge
Congener. A chemical substance that is related to another substance, such as a derivative of a compound
or an element belonging to the same family as another element in the periodic table. For example, the 209
polychlorinated biphenyls are congeners of one another.
Doping. Introduction of a trace impurity into ultrapure crystals to obtain desired physical properties.
Transistors and other semiconductor devices are created by carefully controlled doping.
Electrical conductivity. A measure of the ability of a solution to carry an electrical current. It varies with both
the number and type of ions present in a solution.
Electromagnetic radiation. A form of energy that appears to be both waves and particles (called photons).
It includes visible light, UV radiation, radio waves, X-rays, and other forms differentiated by their wavelengths
and equivalent energies.
Excimer laser. A laser containing a noble gas such as argon or krypton and another gas such as fluorine.
It functions based on the creation of a metastable bond between the two gas atoms that readily return to the
ground state and is a useful source of UV radiation.
First-order reaction. A chemical reaction in which the decrease in concentration of component "A" with time
is proportional to the residual concentration of "A'
XII
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Glossary (Continued)
Half-life. The time required for a given material to decrease to one-half of its initial amount during a chemical
reaction
Hydraulic retention time. The time spent by a unit volume of water in a reactor expressed as the ratio of
the reactor volume to the influent flow rate
Implicit price deflator. The ratio of gross national product (GNP) measured at current prices to GNP
measured at prices in some base year
Long-wave radiation. UV radiation having a relatively long wavelength (in the approximate range of 315 to
400 nanometers). It is also called UV-A radiation, near-UV radiation, or black light.
Maximum contaminant level (MCL). A value set by the US. Environmental Protection Agency (U.S. EPA)
representing the maximum permissible level of a contaminant in water that is delivered to any user of a public
water system. MCLs are derived from health risks that are modified based on practical considerations.
Molar absorption coefficient. The reduction in light intensity while light passes through a solution of unit
concentration and unit path length
Near-ultraviolet radiation. UV radiation having a relatively long wavelength (in the approximate range of 315
to 400 nanometers). It is also called UV-A radiation, long-wave radiation, or black light.
Oxidant. A chemical that decreases the electron content of other chemicals
Oxidation potential. The difference in electrical potential between an atom or ion and the state in which an
electron has been removed to an infinite distance from this atom or ion
Photochemical oxidation. A chemical reaction influenced or initiated by light that removes electrons from
a compound or part of a compound
Photochemical reaction. A chemical reaction induced or catalyzed by light or other electromagnetic
radiation
Photoconductivity. The increase in electrical conductivity displayed by many nonmetallic solids when they
absorb electromagnetic radiation
Photodecarboxylation. Removal of a carboxyl radical through a photochemical reaction
Photo-Fenton process. Generation of hydroxyl radicals through decomposition of hydrogen peroxide using
ferrous or ferric iron under near-UV radiation or visible light
Photolysis. Use of radiant energy (electromagnetic radiation) to produce a chemical change
Pseudo-first-order reaction. A chemical reaction that appears to follow first-order reaction kinetics for a
specific reactant when all other reactants are present at levels in excess of stoichiometry
Quantum yield. For a photochemical reaction, the number of moles of a reactant consumed or the number
of moles of a product formed per Einstein of light (per mole of photons) absorbed at a given wavelength
Radical. An uncharged species containing one or more unpaired electrons
Rutile. A reddish-brown, tetragonal crystalline form of titanium dioxide
XIII
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Glossary (Continued)
Saturated organic compound. An organic compound in which all the available valence bonds along the
carbon chain are attached to other atoms
Semiconductor. A solid crystalline material whose electrical conductivity lies between the conductivities of
a conductor and an insulator. A semiconductor's conductivity can be significantly changed by exposure to
light (photoconductivity), addition of small amounts of certain impurities (doping), or both.
Sensitizer. A chemical that lowers the activation energy of a reaction, thereby increasing the reaction rate
Singlet oxygen. Oxygen with no unpaired electrons. It is more reactive than triplet oxygen (oxygen with two
unpaired electrons-the ground state).
Solar radiation. Electromagnetic radiation emitted by the sun
Steady state. The condition of a system during which system characteristics remain relatively constant with
time after initial transients or fluctuations have disappeared
Superfund. A program established in 1980 by U.S. EPA to identify abandoned or inactive sites where
hazardous substances have been or might be released to the environment in order to ensure that the sites
are cleaned up by responsible parties or the government, evaluate damages to natural resources, and create
a claim procedure for parties that have cleaned up sites or spent money to restore natural resources
Superfund Innovative Technology Evaluation Program. A program established by U.S. EPA to encourage
development and implementation of innovative technologies for hazardous waste site remediation, monitoring,
and measurement
Ultraviolet radiation. Electromagnetic radiation in the wavelength range of 4 to 400 nanometers
Unsaturated organic compound. An organic compound in which not all the available valence bonds along
the carbon chain are attached to other atoms
XIV
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Acknowledgments
This handbook was prepared under the direction and coordination of Mr. Douglas Grosse and Ms. Norma
Lewis of the U.S. Environmental Protection Agency (U.S. EPA) National Risk Management Research
Laboratory (NRMRL) in Cincinnati, Ohio. Mr. Grosse served as the project officer and Ms. Lewis served as
the technical coordinator for the project. Contributors to and reviewers of this handbook were Mr. Grosse and
Ms. Lewis; Dr. William Cooper of the University of North Carolina at Wilmington; Mr. Timothy Chapman of
BDM Federal; and Dr. Fred Kawahara, Dr. E. Sahle-Demessie, and Mr. Vincents Gallardo of U.S. EPA
NRMRL. The handbook cover was designed by Mr. John McCready of U.S. EPA NRMRL.
This handbook was prepared for U.S. EPA NRMRL by Dr. Kirankumar Topudurti, Ms. Suzette Tay, and
Mr. Eric Monschein of Tetra Tech EM Inc. (Tetra Tech). Special acknowledgment is given to Mr. Nikhil Laul,
Mr. Jon Mann, Ms. Jeanne Kowalski, Mr. Stanley Labunski, Dr. Harry Ellis, Mr. Michael Keefe, and Mr. Gary
Sampson of Tetra Tech for their assistance during the preparation of this handbook.
xv
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Executive Summary
Over the past two decades, environmental regulatory
requirements have become more stringent because
of increased awareness of the human health and
ecological risks associated with environmental
contaminants. Therefore, various treatment
technologies have been developed over the last 10
to 15 years in order to cost-effectively meet these
requirements. One such group of technologies is
commonly referred to as advanced oxidation
processes. These processes generally involve
generation and use of powerful but relatively
nonselective transient oxidizing species, primarily
the hydroxyl radical (-OH) and in some cases the
singlet oxygen. The «OH can be generated by both
photochemical and nonphotochemical means to
oxidize environmental contaminants. This handbook
discusses the applicability of advanced
photochemical oxidation (APO) technologies for
treatment of contaminated water, air, and solids (soil,
sediment, and ash).
The primary purpose of this handbook is to
summarize commercial-scale APO system
performance and cost data for treatment of
contaminated water, air, and solids. In addition, it
presents similar information drawn from pilot- and
bench-scale evaluations of APO technologies as a
supplement to the commercial-scale data. The
handbook is intended to serve as an APO reference
document for remedial project managers, on-scene
coordinators, state and local regulators, consultants,
industry representatives, and other parties involved
in management of contaminated water, air, and
solids. Specifically, it should assist these intended
users in evaluating the applicability of APO
technologies and in selecting one or more APO
technologies for site-specific evaluation.
This handbook is not intended to summarize all the
APO performance and cost data available in the
literature. Rather, it is intended to present
information on state-of-the-art APO technologies for
treating contaminated environmental media.
Commercial-scale APO system performance and
cost data is presented in greater detail than pilot-
scale results because the handbook is intended for
practitioners, Similarly, pilot-scale results are
presented in greater detail than bench-scale results.
In addition, pilot- and bench-scale results are
presented only where they supplement commercial-
scale APO system evaluation results or where they
fill information gaps, such as those associated with
by-product formation.
This handbook presents an introduction (Section 1);
provides background information on various APO
technologies, typical commercial-scale APO
systems, andsystem design and cost considerations
(Section 2); and summarizes APO system
performance and cost data for treating contaminated
water, air, and solids (Sections 3, 4, and 5,
respectively). References cited in each section are
listed at the end of the section. APO technology
vendor contact information is presented in the
appendix.
This executive summary briefly describes the APO
technologies and summarizes the commercial-scale
system performance and cost data for treatment of
contaminated water, air, and solids. Tables ES-1
and ES-2 at the end of the executive summary
present commercial-scale performance and cost
data for contaminated water and contaminated air
treatment using various APO processes.
APO Technologies
APO technologies can be broadly divided into the
following groups: (1) vacuum ultraviolet (VUV)
photolysis, (2) ultraviolet (UV)/oxidation processes,
(3) the photo-Fenton process, and (4) sensitized
APO processes. These APO technologies and their
variations are briefly described below.
VUV Photolysis
Photolysis of water using UV radiation of a
wavelength shorter than 190 nanometers yields
•OH and hydrogen radicals (H*). Contaminant
degradation in water and in a relatively high-humidity
air stream can be accomplished through oxidation by
*OH or reduction by H« because VUV photolysis of
water produces powerful oxidizing species (*OH) and
reducing species (H«). Commercial-scale VUV
photolysis systems are not currently available.
However, bench-scale study results indicate that
VUV photolysis is effective in treating contaminated
water and humid air streams.
UV/Oxida tion Processes
UV/oxidation processes generally involve generation
of *OH through UV photolysis of conventional
oxidants, including hydrogen peroxide (H202) and
ozone (0,). Both UV/H2O2 and UV/03 processes
are commercially available. Some APO technology
vendors also offer variations of these processes (for
ES-1
-------
example, UV/O3/H2O2 and UV/h^O^proprietary cata-
lyst). The commercial-scale UV/oxidation systems
available for contaminated water treatment include
the (1) Calgon Carbon Corporation (Calgon) perox-
pure™ and Rayox® UV/H2O2 systems; (2) Magnum
Water Technology, Inc. (Magnum), CAV-OX®
UV/H202 systems; (3) WEDECO UV-
Verfahrenstechnik (WEDECO) UV/H2O2 and UV/03
systems; and (4) U.S. Filter/Zimpro, Inc. (U.S. Filter),
UV/03/H202 system. The only commercial-scale
UV/oxidation system available for contaminated air
treatment is the Process Technologies, Inc. (PTI),
UV/O3 system. UV/oxidation treatment systems for
contaminated solids generally treat contaminated
slurry or leachate generated using an extraction
process such as soil washing.
Photo-Fenton Process
Decomposition of H2O2 using ferrous iron (Fe(ll)) or
ferric iron (Fe(lll)) under acidic conditions yields *OH.
The rate of removal of organic pollutants and the
extent of mineralization using the Fe(ll)/H2O2
and Fe(lll)/H2O2 reagents are improved considerably
by irradiation with near-UV radiation and visible light.
This process is called the photo-Fenton reaction,
The only commercial-scale photo-Fenton system
available is the Calgon Rayox® ENOX water
treatment system.
Sensitized APO Processes
Sensitized APO processes can be broadly
categorized as dye-sensitized and semiconductor-
sensitized processes. These categories are
described below.
In a dye-sensitized APO process, visible light is
absorbed by a sensitizing dye, which excites the dye
molecules to a higher energy state. The excited dye
then transfers some of its excess energy to other
molecules present in the waste stream, producing
a chemical reaction. When dissolved oxygen
accepts energy from the excited dye molecule (for
example, methylene blue or rose bengal'), the
dissolved oxygen is converted to singlet oxygen, a
powerful oxidant. This APO process has not yet
become commercially viable.
In a semiconductor-sensitized APO process, metal
semiconductors are used to destroy environmental
contaminants by means of light-induced redox
reactions. These reactions, involve generation of
conduction band electrons and valence band holes
by UV irradiation of semiconductor materials such as
titanium dioxide (Ti02). In this process, the
formation and availability of *OH are maximized by
addition of oxidants such as H2O2 and 0,.
The Matrix UV/TiO2 system is a commercial-scale
sensitized APO system for contaminated water
treatment. The 'commercial-scale sensitized APO
systems for contaminated air treatment include the
(1) Zentox Corporation (Zentox) UV/TiO2 system;
(2) Matrix Photocatalytic, Inc. (Matrix), UV/TiO2
system; and (3) KSE, Inc. (KSE), Adsorption-
Integrated-Reaction (AIR) UV/catalyst system.
Contaminated Water Treatment
APO has been shown to-be an effective technology
for treatment of contaminated water. Matrices to
which APO has been applied include the following:
(1) contaminated groundwater, (2) industrial
wastewater, (3) municipal wastewater, (4) drinking
water, (5) landfill leachate, and (6) contaminated
surface water. As shown below, a number of APO
processes have been evaluated in terms of their
effectiveness in treating various waterborne
contaminants. Of these processes, UV/oxidation
has been evaluated for the most contaminant
groups, while VUV photolysis has been evaluated for
the fewest.
Table ES-I at the end of this executive summary
presents commercial-scale performance and cost
data for contaminated water treatment using various
APO processes. This table shows that UV/oxidation
processes have been found to be effective in treating
various contaminants. Other APO processes,
including the photo-Fenton and sensitized APO
processes, have also been found to be effective, but
for only a limited number of contaminant groups.
The treatment costs vary widely depending on the
type and concentration of contaminants treated and
the APO system used for treatment. The information
sources cited in this handbook should be carefully
reviewed before a cost comparison is made because
the cost estimates presented in the literature were
not made using a consistent set of assumptions.
ES-2
-------
Contaminant Group
Volatile Organic Compounds
(VOC)
Semivolatile Organic
Compounds (SVOC)
fokgtilorinated Biphenyls
Pesticides and Herbicides
Dioxins and Furans
Explosives and Their
Degradation Products
Humic Substances
Inorganics
Dyes
Microbes
APO Process Status for Contaminated Water Treatment
VUV Photolysi
Q
Q
Q
0
Q
Q
Q
Q
Cl
Q
> UV/Oxidation
*
*
Q
•
Q
*
Q
Q
•
*
Photo-Fenton
*
*
cl
0
0
a
a
a
Q
a
Sensitized
*
0
0
0
cl
0
0
0
0
0
lotes: * = Commercial-scale, • = Pilot-scale, 0 = Bench-scale, Q = Developmental
Contaminated Air Treatment
APO has been shown to be an effective technology
for treatment of contaminated air. Matrices to which
APO has been applied include the following: (1) soil
vapor extraction (SVE) off-gas, (2) air stripper off-
gas, (3) industrial emissions, and (4) automobile
emissions. As shown below, a number of APO
processes have been evaluated in terms of their
effectiveness in treating various airborne
contaminants. Of these processes, the sensitized
APO processes have been evaluated for the most
contaminant groups, while the VUV photolysis
process has been evaluated for the fewest.
Table ES-2 at the end of this executive summary
presents commercial-scale performance and cost
data for contaminated air treatment using various
APO .processes. This table shows that sensitized
APO processes have been found to be effective in
treating various contaminants. One UV/oxidation
process, the UV/03 process, has also been found to
be effective, but only for VOCs. The table also
shows that the available treatment cost information
is limited.
Contaminant Group
VOCs
svocs
Explosives and Their
Degradation Products
| Inorganics
APO Process Status for Contaminated Air Treatment
VUV Photolysis I UV/Oxidation
O
cl
Q
Q
*
•
. Q
Q
Sensitized
*
Q
*
0
Notes: * = Commercial-scale, • = Pilot-scale, 0 = Bench-scale, Q = Developmental
Contaminated Solids Treatment
APO has been shown to be an effective technology
for treatment of contaminated solids, primarily at the
bench-scale level. Most evaluations involved
generating a leachate or slurry by washing the
contaminated solids with water, surfactant solution,
or an organic solvent and then applying an APO
process to treat the contaminated leachate or slurry
in a manner similar to contaminated water treatment.
Use of an APO process to treat contaminated slurry
may require frequent APO system maintenance
because solids in the slurry will coat the light source
and inhibit transmission of light.
ES-3
-------
Solid matrices to which APO has been applied
include the following: (1) contaminated soil,
(2) contaminated sediment, and (3) contami-
nated ash. As shown below, a number of APO
processes 'have been evaluated in terms of their
effectiveness in treating various contaminated solids.
Of these processes, the UV/oxidation, photo-Fenton,
and sensitized APO processes have been evaluated
to some extent, but little data is available on the
effectiveness of VUV photolysis.
The commercial-scale performance data for
contaminated solids treatment is limited to one
UV/oxidation process, the UV/H202 process. A
Calgon perox-pure™ system was used to treat soil
contaminated with pesticides. The influent to the
perox-pure™ system, which was generated by an
on-site soil washing system, primarily contained
0.49,1.1, and 3.9 mg/L of disulfoton, thiometon, and
oxadixyl, respectively. A sand filter was used to
remove suspended solids from the influent to the
perox-pure™ system. The system achieved
removals of up to 99.5 percent. No cost information
is available. Based on the limited performance
results, APO processes appear to show promise for
treating contaminated solids.
Contaminant Group
svocs
PCBs
Pesticides and Herbicides
Dioxins and Furans
APO Process Status for Contaminated Solids Treatment
VUV Photolysi
Q
Q
Q
Q
> UV/Oxidation
Q
Q
*
• Q
Photo-Fenton
Q
0
Q
Q
Sensitized
0
Q
0
0
Votes: "A" = Commercial-scale, 0 = Bench-scale, Q = Developmental
ES-4
-------
Table ES-I. Contaminated Water Treatment
CONTAMINATED
MATRIX
CONTAMINANT
GROUP PROCESS
SYSTEM
PERFORMANCE DATA
Contaminant
Concentration Percent Removal
APPROXIMATE COST
(4998 U.S. Dollars)
IW/Oxidation Processes
Contaminated
Sroundwater
/OCs
JV/H202
iranular
ictivated
Carbon
'ollowed by
IV/H2O2
IV/H2O
bllowea by Air
itripper
IV/H2O2
Saigon
>erox-pure™
Jalgon Rayox®
Saigon Rayox®
lalgon Rayox®
rtagnum
:AV-OX® i
Benzene
Chlorobenzene
Chloroform
I.l-Dichloroethane
(DCA)
1,2-DCA
1 ,4-Dichlorobenzene
1 ,2-Dichloroethene
(DCE)
Methylene chloride
Tetrachloroethene
(PCE)
1 ,1,1-Trichloroelhane
(TCA)
Trichloroethene (ICE)
Vinyl chloride (VC)
1,2-DCE 8
52 micrograms per liter
(/;g/L)
3,100A) 96
>99.9
93.6 to >97
>95.8 to >99.5
>92
>99.5
>99 to >99.9
>86
>98.7 to >99.9
92.9
>93 to >99.9
>95.8 to >97
91.4
TCE 14,700 ^g/L 99.9
Methylene chloride
Methylene chloride
IPCE
1.1.1-TCA
I Benzene
ds-1,2-DCE
ltrans-1.2-DCE
PCE
"TCE
Total petroleum
hydrocarbons
6.9 ng/L
60 nQ/L
6,000 nQ/L
100M9/L
250 to 500 Aig/L
250 ng/L
200 uQlL
Wugli.
1 ,500 to 2,000 A98.3
>99.9
>99
99.9
>99.9
>99.9
>98
99.9
99.9
VC I53 WQ/L >99.7
$0.08 [operation and
maintenance (O&M)!. to
$1.50/cubic meter (m3)
(capital and O&M)
$0.09/m3 (O&M)
$0.3 1/m3 (O&M)
Not available
$0.32 (O&M) to $1 .50/m3
(capital and O&M)
m
to
en
-------
Table ES-I. Contaminated Water Treatment (Continued)
CONTAMINATED
MATRIX
CONTAMINANT
GROUP
PROCESS
SYSTEM
PERFORMANCE DATA
Contaminant Concentration Percent Removal
APPROXIMATE COST
(1998 U.S. Dollars)
IV/Oxidation Processes (Continued)
Contaminated
5roundwater
Continued)
VOCs
(Continued)
svo cs
Explosives and
Their
Degradation
Products
UV/H2O2
UV/O3
UV/Oa/H2O2
UV/H202
UV/H2O2
Magnuiru
CAV-OX® II
WEDECO
WEDECO
U.S. Filter
Calgon
perox-pure™
Calgon Rayox
Calgon
perox-pure™
Calgon Rayox®
Benzene
TCE
Benzene
1,2-DCA
C1S-1.2-DCE
Ethylbenzene
v c
PCE
TCE
1,1 -DCA
1.1,1-TCA
TCE
Pentachlorophenol
(PGP)
N-
nitrosodimethylamine
(NDMA)
Polynuclear aromatic
hydrocarbons
Phenol
Benzathiazole
1,4-Dithiane
1 ,4-Oxathiane
Cyclonite
Thiodiglycol
1 ,3,5-Trinitrobenzene 1
Nitroglycerin (NG)
Nitroguanidine
250 to 500 ^g/L
1 ,500 to 2.000 /jg/L
31 0 //g/L
54 M9/L
46 /jg/L
41 M9/L
34 ^g/L
160^g/L
330 ng/L
9.5 to 13/Lig/L
2 to 4.5 ng/L
50 to 520 ngfL
15 mg/L
20/jg/L
1 to 2 mg/L
2mg/L
20 ng/L
200 Aig/L
82 /^g/L
28 mg/L
480 A87
92
86
96.6
99
65
87
99 to >99
99.3
>99.9
>99.9
>99.9
>82
>98
>97
>82
>97
96
>99.9
>99.9
$1.50/m3 (capital and
O&M)
$0.39/m3 (O&M)
$0.1 9/m3 (O&M)
$0.08 to $5.60/m3 (O&M)
$1.20/m3(0&M)
$0.1 0/m3 (O&M)
$0.02/m3 (O&M)
$13 to $34/m3 (capital and
O&M)
m
CO
CD
-------
Table ES-I. Contaminated Water Treatment (Continued)
CONTAMINATED
MATRIX
CONTAMINANT
GROUP
PROCESS
SYSTEM
PERFORMANCE DATA
Contaminant
Concentration I Percent Removal
i
APPROXIMATE COST
11998 U.S. Dollars)
UV/Oxidation Processes (Continued)
ndustrial
Vastewater
andfill Leachate
VOCs
svocs
UV/H2O2
UV/H2O2
Microbes UV/H2O2
COD UV/O3
Calgon
perox-pure"
Calgon Rayox
Magnum.
CAV-OX® II
Magnum
CAV-OX® II
WEDECO
Acetone
Isopropyl alcohol
Chemical oxygen
demand (COD)
NDMA
Unsymmetrical
dimethylhydrazine
Phenol
Salmonella
COD
20 mg/L
20mg/L
1 ,000 mg/L
30 M9/L to 1,400 mg/L
6. 000 mg/L
20ng/L
1 million colony forming
units per milliliter
900 mg/L
>97.5
>97.5
Not available
>98.3 to >99.9
Not available
>99.9
>99.9
>90
$1.10/m3(O&M)
$0.83 to$150/m3 (capital
and O&M)
Not available
Not available
$6.80/m3 (capital and
O&M)
Photo-Fenton Process
Contaminated
Groundwater
Industrial
Wastewater
svocs
VOCs
Photo-Fenton
Photo-Fenton
Calgon Rayox F
ENOX
Calgon Rayox® C
ENOX
C P
0 D
1 ,000 vg/L
3, 000 mg/L
Flow stream to be
reinjected: 90
Flow stream to be
discharged: 99
>98.4
$0.36/m3 (O&M)
$44/m3 (O&M)
Sensitized APO Process
Contaminated
Groundwater
'DCs
JWTiO2
Matrix
Benzene 400 to1,100Aig/L
1,1 -DCA
1,1-DCE
ds-1,2-DCE
PCE
1,1.1-TCA
TCE
Toluene
Total xylenes
660 to8492
98
m
-ij
-------
Table ES-2. Contaminated Air Treatment
CONTAMINATED
MATRIX
CONTAMINANT
GROUP
PROCESS
SYSTEM
PERFORMANCE DATA
Contaminant Concentration Percent Removal
APPROXIMATE COST
(1998 U.S. Dollars)
JV/Oxidation Process
5VE Off-Gas
VOCs
UV/O3
iensitized APO Processes
iVE Off-Gas
ir Stripper Off-
ias
idustrial
missions
VOCs
VOCs
VOCs
Explosives and
Their
Degradation
Products
UV/Catalyst 1
UV/TiO2
UV/Catalyst \
UV/Catalyst \
UV/Ti(yO3 Z
PTI
:SE AIR IV
Matrix
SE AIR
SE AIR
entox
cis-l ,2-DCE
PCE
TCE
Toluene
Total VOCs
22 parts per million by volume
(ppmv)
31 ppmv
28 ppmv
1 4 ppmv
1,000 to 1,100 ppmv as carbon
74.0
89.7
80.8
93.1
95.9
ethane
PCE
PCE
1,1,1-TCA
TCE
1.2-DCA
Total VOCs
Pentane
NG
2,000 to 4,000 ppmv
1 to 150 ppmv
1 ,200 ppmv
Not available
1 60 ppmv
0.9 to 3 ppmv
2,000 ppmv
2,100 ppmv
1 .7 ppmv
Minimal
>99
95.2
Not removed
98.1
About 99
>99
>99.9
99.2
(c
$3.80/pound of VOCs
removed (capital and O&M)
Not available
Not available
Not available
For a 1.8-stan<1ard cubic
meter per minute (scmm)
System
$53.320 (capital)
$376 (monthly energy)
$1,672 (annual maintenance)
For a 4.4-scmm Systern
$183.000 (capital)"
$7,800 (annual operating)
For an 18-scmm System
$175,00010 $260,000
s pita 1)
m
CO
CO
-------
Section 1
Introduction
Improper waste disposal practices have resulted in
contamination of various environmental media. Over
the past two decades, environmental regulatory
requirements have become more stringent because
of increased awareness of the human health and
ecological risks associated with environmental
contaminants. In many cases, conventional
treatment technologies, such as air stripping, carbon
adsorption, biological treatment, and chemical
oxidation using ozone (0,) or hydrogen peroxide
(H2O2), have limitations. For example, stripping and
adsorption merely transfer contaminants from one
medium to another, whereas biological treatment
and conventional chemical oxidation have low
removal rates for many environmental contaminants,
including chlorinated organics. Therefore, various
alternative treatment technologies have been
developed over the last 10 to 15 years in order to
cost-effectively meet environmental regulatory
requirements. One such group of technologies is
commonly referred to as advanced oxidation
processes,
Advanced oxidation processes generally involve
generation and use of powerful but relatively
nonselective transient oxidizing species, primarily
the hydroxyl radical (*OH); in some vapor-phase
advanced oxidation processes, singlet oxygen or
O(1D) has also been identified as the dominant
oxidizing species (Loraine and Glaze 1992).
Table 1-1 shows that *OH has the highest
thermodynamic oxidation potential, which is perhaps
why *OH-based oxidation processes have gained the
attention of many advanced oxidation technology
developers. In addition, as shown in Table 1-2, most
environmental contaminants react 1 million to
1 billion times faster with »OH than with O3, a
conventional oxidant. *OH can be generated by both
photochemical processes (for example, ultraviolet
[UV] radiation in combination with O3, H2O2, or a
photosensitizer) and nonphotochemical processes
(for example, electron beam irradiation, 0, in
combination with H2O2, or Fenton's reagent). This
handbook discusses the applicability of advanced
photochemical oxidation (APO) technologies for
treatment of contaminated water, air, and solids (soil,
sediment, and ash).
This section discusses the purpose and scope
(Section 1 .1) and organization (Section 1.2) of this
handbook.
Table 1-1. Oxidation Potential of Several Oxidants in Water
Oxidant Oxidation
*OH
0(1D)
03
H202
Perhydroxy radical
Permanganate ion
Chlorine dioxide
Chlorine
02
Note:
a Source: CRC Handbook 1985
Potential (eVf
2.80
2.42
2.07
1.77
1.70
1.67
1.50
1.36
123
1.1 Purpose and Scope
The primary purpose of this handbook is to
summarize commercial-scale APO system
performance and cost data for treatment of
contaminated water, air, and solids, In addition, it
presents similar information drawn from pilot- and
bench-scale evaluations of APO technologies as a
supplement to the commercial-scale performance
and cost data. The handbook is intended to serve
as an APO reference document for remedial project
managers, on-scene coordinators, state and local
regulators, consultants, industry representatives, and
other parties involved in management of
contaminated water, air, and solids. Specifically, it
should assist these intended users in evaluating the
applicability of APO technologies and in selecting
one or more APO technologies for site-specific
evaluation.
For the purposes of this handbook, commercial-,
pilot-, and bench-scale systems are defined as
follows:
. A commercial-scale system is a System
manufactured by an APO technology vendor
and available for purchase or leasing from
the vendor.
1-1
-------
Table 1-2. Rate Constants for 0, and *OH Reactions with Organic Compounds in Water
Rate Constant (M^V1)"
Compound Type
Acetylenes
Alcohols
Aldehydes
Alkanes
Aromatics
Carboxylic acids
Chlorinated alkenes
Ketones
Nitrogen-containing organics
Olefins
Phenols
Sulfur-containing organics
03
50
icr2toi
10
10'2
1 to 10Z
10-3to10-2
10'1 to 103
1
10to102
1to450x103
103
10to1.6x103
*OH
108to109
108 to 1C9
109
106to109
108to101Q
107to109
109to1011
109to1010
108to1010
109to1011
109 to 1010
109to1010
Note:
Sources: Cater and Others 1990; Dussert 1997
A pilot-scale system is a system designed
and fabricated by an engineering firm to
(1) estimate the performance and cost of a
particular APO technology, (2) identify field
operational problems of the technology and
their resolutions, and (3) evaluate scale-up
requirements for implementing the
technology. A commercial-scale system is
selected after the pilot-scale system proves
to be successful.
A bench-scale system is a system that
(1) is of much smaller scale than
commercial- and pilot-scale systems, (2) is
used to evaluate the feasibility of a
particular APO process, (3) is used to gain
more insight into the process kinetics and
mechanisms, and (4) .may be used to
generate a preliminary cost estimate for
comparison with the costs of alternative
technologies. A pilot-scale evaluation of a
system may follow successful performance
by a particular APO process at the bench-
scale level.
This handbook is not intended to summarize all the
APO performance and 'cost data available in the
literature. Rather, it is intended to present
information on state-of-the-art APO technologies for
treating contaminated environmental media.
Commercial-scale APO system performance and
cost data is presented in greater detail than pilot-
scale results because the handbook is intended for
practitioners. Similarly, pilot-scale results are
presented in greater detail than bench-scale results.
In addition, pilot- and bench-scale results are
presented only where they supplement commercial-
scale APO system evaluation results or where they
fill information gaps, such as those associated with
by-product formation.
This handbook does not address nonenvironmental
APO technology applications. For example, it does
not discuss APO technology applications in
(1) industrial processes (for example, use of a UV/O3
process for surface cleaning to improve adhesive
bonding) and (2) the manufacture of various
products used in residential and commercial
buildings and tunnels (for example, titanium dioxide
[TiO2]-coated ceramic tiles and glass). Poulis and
others (1993) and Fujishima (1996) summarize such
APO applications.
Finally, the information included in this handbook is
derived from an extensive literature review, and thus
the level of detail presented varies depending on the
information sources available. Specifically, the
treatment costs included should be considered only
order-of-magnitude estimates because most of the
references used do not state the assumptions made
in estimating treatment costs. To facilitate quick
APO technology comparisons, cost estimates from
the literature were adjusted for inflation using implicit
price deflators for gross national product and are
1-2
-------
presented in 1998 U.S. dollars herein. This
approach has been proposed by the U.S.
Department of Commerce and is used to estimate
financial assurance requirements under Resource
Conservation and Recovery Act Subtitle C as
documented in 40 Code of Federal Regula-
tions 264.142(b). Cost estimates reported in
currencies other than U.S. dollars were converted to
U.S. dollars using the exchange rates for the
appropriate years before adjusting them for inflation.
1.2 Organization
This handbook is divided into six sections and
one appendix. Section 1 presents an introduction to
the APO handbook. Section 2 provides background
information on various APO technologies, typical
commercial-scale APO systems, and system design
and cost considerations. Sections 3, 4, and 5
summarize APO system performance and cost data
for treating contaminated water, air, and solids,
respectively. References cited in each section are
listed at the end of the section. The appendix
contains APO technology vendor contact
information.
To facilitate user access to information, the
handbook presents performance and cost data for
each environmental medium by matrix, contaminant
group, scale of evaluation, technology evaluated,
and technology vendor or proprietary system (see
Figure l-l). For example, where performance and
cost data for water (the medium) is summarized,
groundwater (matrix 1) is discussed before other
matrices. For the groundwater matrix, volatile
organic compounds (VOC) or contaminant group 1
is discussed before other contaminant groups.
For the VOC contaminant group, commercial-scale
applications are summarized before pilot- and
bench-scale evaluations. Similarly, the commercial-
scale applications are organized by APO technology
and by vendor or proprietary process. If bench-scale
results for a particular contaminant were derived
using a synthetic matrix (for example, distilled water
spiked with target contaminants), the results are
included under the matrix that is described first. For
example, in general, bench-scale results derived
using synthetic wastewater are presented under the
groundwater matrix because the groundwater matrix
is the first matrix discussed in Contaminated Water
Treatment (Section 3). However, bench-scale
results for dye removal in synthetic wastewater are
not presented under the groundwater matrix
because no commercial- or pilot-scale results are
available for dye removal in groundwater. Therefore,
bench-scale results for dye removal in synthetic
wastewater are appropriately presented under the
industrial wastewater matrix.
Environmental
Medium
(Water)
/
/
\
N
Matrix 1
(Groundwater)
Matrix 2
(Industrial
Wastewater)
Matrix 3
(Municipal
Wastewater)
I7
• >
\
\
/
Contaminant
Group 1
(VOCs)
Contaminant
Group 2
(Pesticides
and
Herbicides)
Contaminant
Group 3
(Explosives)
/
\
\
Commercial
Scale
Pilot
Scale
Bench
Scale
/
\
\
APO
Technology 1
(UV/H202)
APO
Technology 2
(UV/03)
APO
Technology 3
(UWTiOj)
Vendor/Proprietary Process 1
(Calgon/perox-pure™)
Vendor/Proprietary Process 2
(Calgon/Rayox8)
Note: The information in parentheses represents a typical example.
Figure l-l. Performance and cost data organization.
1-3
-------
1.3 References
Cater, S.R., K.G. Bircher, and R.D.S. Stevens.
1990. "Ray ox? A Second Generation
Enhanced Oxidation Process for Groundwater
Remediation." Proceedings of a Symposium on
Advanced Oxidation Processes for the
Treatment of Confaminafed Water and Air.
Toronto, Canada. June.
CRC Handbook of Chemistry and Physics (CRC
Handbook). 1985. Edited by R.C. Weast, M.J.
Astle, and W.H. Beyer. CRC Press, inc. Boca
Raton, Florida.
Dussert, B.W. 1997. "Advanced Oxidation."
Industrial Wastewater. November/December,
Pages 29 through 34.
Fujishima, Akira. 1996. "Recent Progresses in TiO,
Photocatalysis." Abstracts, -The Second
International Conference on TiO2 Phofocatalyfic
Purification and Treatment of Water and Air.
Cincinnati, Ohio. October 26 through 29, 1996.
Page 67.
Loraine, G.A., and W.H. Glaze. 1992. "Destruction
of Vapor Phase Halogenated Methanes by
Means of Ultraviolet Photolysis." 47th Purdue
Industrial Waste Conference Proceedings.
Lewis Publishers, Inc. Chelsea, Michigan.
Poulis, J.A., J.C. Cool, and E.M.P. Logtenberg.
1993. "UV/Ozone Cleaning, a Convenient
Alternative for High Quality Bonding
Preparation." International Journal of Adhesion
and Adhesives. Volume 13, Number 2.
Pages 89 through 96.
1-4
-------
Section 2
Background
This section provides background information on
APO technologies (Section 2.1), commercial-scale
APO systems (Section 2.2), and APO system design
and cost considerations (Section 2.3). The level of
detail included in this section should be adequate to
allow the user to comprehend the performance and
cost data included in Sections 3, 4, and 5 of this
handbook. For additional information, the references
cited in Section 2 should be consulted.
2.1 APO Technologies
As described in Section 1, APO technologies use
•OH generated by photochemical means to oxidize
environmental contaminants. As implied by the term
APO, light energy is one of the essential components
of an APO technology. Depending on the type of
APO technology employed, UV radiation (of
wavelengths from 100 to 400 nanometers [nm]) or
visible radiation (400 to 700 nm) is used to produce
*OH.
The wavelength required to carry out an APO
process is generally determined by the principle
involved in production of «OH by the particular APO
technology. For example, for a UV/TiO2 technology,
light of a wavelength shorter than 387.5 nm is
required because Ti02 (anatase form) has an energy
band gap of 3.2 electron volts (eV) and can be
activated by UV radiation of a wavelength shorter
than 387.5 nm. Similarly, visible radiation can be
used in a dye-sensitized APO technology because
the wavelength at which dyes absorb significant
radiation is in the visible radiation wavelength range
(for example, 666 nm for methylene blue), In some
cases, solar radiation may be used because it starts
at a wavelength of about 300 nm at ground level.
However, solar radiation may not be the best choice
for a UV7TiO2 technology because only a small
portion of the total solar spectrum is in the 300 to
387.5 nm range.
APO technologies can be broadly divided into the
following groups: (1) vacuum UV (VUV) photolysis,
(2) UV/oxidation processes, (3) the photo-Fenton
process, and (4) sensitized APO processes. These
APO technologies and their variations are briefly
described below.
2.1.1 VUV Photolysis
The UV spectrum is arbitrarily divided into three
bands: UV-A (315 to 400 nm), UV-B (280 to
315 nm), and UV-C (100 to 280 nm) (Philips Lighting
1985). Of these' bands, UV-A and UV-C are
generally used in environmental applications. UV-A
radiation is also referred to as long-wave radiation,
near-UV radiation, or black light. Most UV-A lamps
have their peak emission at 365 nm, and some have
their peak emission at 350 nm. UV-C radiation,
which is also referred to as short-wave radiation, is
used for disinfection of water and wastewater. The
spectral output of the low-pressure mercury vapor
lamps used for disinfection purposes -is mostly at
254 nm, with only 5 to IO percent of the output at
185 nm. Often the 185-nm emission that leads to
the in situ formation of 0, from oxygen (0,) in the
surrounding atmosphere is cut off from the
germicidal lamps; doped silica or a sodium barium
glass sleeve is used to cut off radiation below
200 nm. However, in some photochemical
applications, a high-quality quartz sleeve such as
Suprasil that transmits the 185-nm radiation is used
to take advantage of the high energy associated with
the shorter wavelength (one mole of photons at
254 nm equals 471 kilojoules, whereas one mole of
photons at 185 nm equals 647 kilojoules). According
to Unkroth and others (1997), in general, the
quantum yield of mercury vapor lamps is too low for
most photochemical reactions to occur. Therefore,
for some applications, more, efficient radiation
sources such as excimer lasers (high-intensity
pulsed radiation) and excimer lamps are evaluated
as alternatives to conventional UV radiation sources.
The high energy associated with UV radiation of a
wavelength shorter than 190 nm can photoiyze water
to yield *OH and hydrogen radicals (H«), a process
referred to as VUV photolysis (Gonzalez and others
1994). Contaminant degradation in water and in a
relatively high-humidity air stream can be
accomplished through oxidation by *OH or reduction
by H» because VUV photolysis of water produces
powerful oxidizing species (*OH) and reducing
species (H-)- This process is particularly useful in
treating waste streams contaminated with
compounds that are difficult to oxidize. For example,
2-I
-------
the -OH reaction rate constant for chloroform is
5 x io6 liters per mole-second (M'V), whereas the
H* reaction rate constant for chloroform is
1 .1 x 107 M'V1 (Buxton and others 1988).
Commercial-scale VUV photolysis systems are not
currently available. However, bench-scale studies
conducted using xenon-xenon excimer lamps with a
peak emission of 172 nm indicate that VUV
photolysis of water has significant potential for
cleaning up contaminated water (Jacob and others
1993; Gonzalez and others 1994). In addition, VUV
photolysis has been shown to be effective at the
bench-scale level in treating humid air streams
contaminated with halogenated methanes (Loraine
and Glaze 1992).
2.1.2 U V/Oxida tion Processes
Most commercial UV/oxidation processes involve
generation of *OH through UV photolysis of
conventional oxidants, including H2O2 and O3.
However, generation of *OH by photolysis of chlorine
using UV-A and UV-C radiation, which has been
observed by Nowell and Hoigne (1992), has yet to be
commercialized. A summary of the chemistry of
UV/H2O2 and UV/O3 processes is presented below.
More information is provided by Glaze and others
(1987).
UV Photolysis of H2O2
Generation of *OH by UV photolysis of H202 is
described by the following equation:
H2O2 + light energy (hv)
2-OH
(2-1)
Low-pressure mercury vapor UV lamps with a
254-nm peak emission are typically used to produce
UV radiation, but these lamps may not be the best
choice for a UV/H202 process because the
maximum absorbance of UV radiation by H2O2
occurs at about 220 nm and because the molar
absorption coefficient of H2O2 at 254 nm is low, only
19.6 liters per mole-centimeter (M~1cm~1). If low-
pressure mercury vapor lamps are used, a high
concentration of H2O2 is needed in the medium to
generate sufficient -OH because of the low molar
absorption coefficient. However, high concentrations
of H2O2 may scavenge the *OH, making the
UV/H2O2 process less effective. To overcome this
limitation, some APO technology vendors use high-
intensity, medium-pressure, broad band UV lamps;
others use high-intensity, xenon flash lamps whose
spectral output can be adjusted to match the
absorption characteristics of H2O2 or another
photolytic target.
UV Photolysis of 0,
UV photolysis of 0, in water yields H2O2, which in
turn reacts with UV radiation or 0, to form *OH as
shown below.
O3 + hv + H2O -» H2O2 + O2
H2O2 + hv - 2-OH
20, + H2O2 -* 2'OH + 30,
(2-2)
(2-3)
(2-4)
Photolysis of O3 in wet air produces -OH as shown
below.
0,
0,
H2O
2'OH
(2-5)
(2-6)
Because the molar absorption coefficient of 0, is
3,300 M'1cm'1 at 254 nm, UV photolysis of 0, is not
expected to have the same limitation as that of H2O2
when low-pressure mercury vapor UV lamps are
used. In addition, if the 185-nm emission is not cut
off from the low-pressure mercury vapor lamps, the
0, formed in situ is photolyzed to yield -OH
(Bhowmick and Semmens 1994).
Both UV/H202 and UV/03 processes are
commercially available. Some APO technology
vendors also offer variations of these processes (for
example, UV/03/H2O2 and UV/H2O2/proprietary
catalyst).
2.1.3 Photo-Fenton Process
The dark reaction of ferrous iron (Fe(ll)) with H202
known as Fenton's reaction (Fenton 1894), which is
shown in Equation 2-7, has been known for over a
century.
Fe(ll)
H202
ferric iron (Fe(lll))
+ hydroxide ion (OK)
+ *OH
(2-7)
The *OH thus formed either can react with Fe(ll) to
produce Fe(lll) as shown below,
(2-8)
2-2
-------
or can react with and initiate oxidation of organic
pollutants present in a waste stream. This process
is effective at pH levels less than or equal to 3.0.
Decomposition of H2O2 is also catalyzed by Fe(lll)
(Walling 1975). In this process, H2O2 is
decomposed to the water molecule (H2O) and 02,
and a steady-state concentration of Fe(ll) is
maintained during the decomposition, as shown
below.
Fe(lll) + H202 * [Fe(lll). . . O2H]2+ + H*
** Fe(ll) + HO2- + H+ (2-9)
HO2- + Fe(lll) -* Fe(ll) + H+ + 0,
(2-I 0)
The Fe(ll) ions react with H2O2 to generate *OH (see
Equation 2-7), which then react with organic
pollutants. However, the initial rate of removal of
organic pollutants by the Fe(lll)/H2O2 reagent is
much slower than that for the Fe(ll)/H2O2 reagent,
perhaps because of the lower reactivity of Fe(lll)
toward H202. This process is only effective at an
acidic pH level of about 2.8 (Pignatello 1992).
The rate of removal of organic pollutants and the
extent of mineralization with the Fe(ll)/H2O2 and
Fe(III)/H2O2 reagents are improved considerably by
irradiation with near-UV radiation and visible light
(Ruppert and others 1993). This process is called
the photo-Fenton reaction (see Figure 2-I).
Photoenhancement of reaction rates is likely
because of (1) photoreduction of Fe(lll) to Fe(ll);
(2) photodecarboxylation of ferric carboxylate
complexes; and (3) photolysis of H2O2, all of which
are briefly described below.
1. Photoreduction of Fe(M) to Fe(ll): Irradiation of
the hydroxylated Fe(lll) ion or ferrihydroxalate
(Fe(lll)(OH)"*)virraqueous solution produces the
Fe(ll) ion and -OH (Faust and Hoigne 1990) as
-shown below.
Fe(III)(OHr + hv - Fe(ll) + *OH
(2-11)
This is a wavelength-dependent reaction, and the
quantum yields of *OH and Fe(ll) ion formation
decrease with increasing wavelength. For example,
the quantum yield of -OH is 0.14 at 313 nm and
0.017 at 360 nm (Faust and Hoigne 1990). In
addition to the -OH produced by the reaction shown
in Equation 2-I 1, the photogenerated Fe(ll) can
participate in the Fenton reaction (see Equation 2-7),
generating additional «OH and thus accelerating the
rate of removal of organic contaminants.
CFe
W
. Photolysis of
Fe (III) Complex
avelengt
1
Fer
Rea
Fe(ll)
i > 300 nm
00)
t
ton
:tion
+ HA
W
Photolysis of
HA
avelengt
1
Direct
Photolysis
A + hv
i < 300 nm 1
A*
Uo2
"oxidized
*OH
Radical
Radical
Reaction 4—
•OH+A
1
A-
Uo2
^oxidized
Note: "A" is the target contaminant. "A"' and "A«" are reaction intermediates.
Figure 2-1. Scheme of chemical reactions in the photo-Fenton reaction (Source: Kim and Others 1997).
2-3
-------
2. Photodecarboxylafion of ferric carboxylate com-
plexes: Fe(lll) ions form stable complexes and
associated ion pairs with carboxylates and
polycarboxylates (for example, anion of oxalic acid).
These complexes are photochemically active and
generate Fe(II) ions when irradiated, according to
Balzani and Carassiti (1970), as shown below.
Fe(lll)(RCO2)2+
Fe(ll) + CO,
+ R-
(2-12)
The radical R- can react with dissolved 0, and
degrade further. The Fe(ll) ions can in turn
participate in the Fenton reaction and generate
additional «OH. Carboxylates are formed during
photocatalyzed oxidation of organic pollutants; thus
photodecarboxylation, as shown in Equation 2-12, is
expected to play an important role in treatment and
mineralization of organic contaminants.
3. Photolysis of H2O2: Some direct photolysis of
H2O2 occurs (see Equation 2-I); however, in the
presence of strongly absorbing iron complexes, this
reaction contributes only in a minor way to
photodegradation of organic contaminants.
Many wastewaters exhibit high absorbance at
wavelengths below 300 nm. Competition for UV light
from the wastewater and poor absorption of UV light
at 254 nm by H2O2 make UV/H2O2 treatment less
useful in some situations. In these cases, the UV-
visible/ferrioxalate/H2O2 process (Equation 2-12)
provides advantages, as ferrioxalate has a high
molar absorption coefficient at wavelengths above
200 nm (see Figure 2-2), absorbs light strongly at
longer wavelengths (up to 450 nm) and generates
*OH with a high quantum yield. Zepp and others
(1992) have shown that photolysis of ferrioxalate in
the presence of H202 generates -OH that can react
with and oxidize organic pollutants in solution,
Safarzadeh-Amiri (1993) has shown that irradiation
of a ferrioxalate/H202 mixture with UV-visible light is
a very effective process for removal of various
organic pollutants in water.
The Calgon Carbon Corporation (Calgon) Rayox®
enhanced oxidation (ENOX 910) process takes
advantage of the ferrioxalate photo-Fenton chemistry
and supplements the UV/H2O2 process with a
proprietary catalyst in some applications.
18
15
T 12
9
6
3
Potassium
Fenrioxalate
200 250 300 "350 400
Wavelength (nm)
450
500
Figure2-2. Absorption spectra of H2O2 and potassium
ferrioxalate in aqueous solution (Source:
Safarzadeh-Amiri and Others 1997).
2.1.4 Sensitized APO Processes
Sensitized APO processes can be broadly
categorized as dye-sensitized and semiconductor-
sensitized processes. These categories are
described below.
Dye-Sensitized APO Processes
In a dye-sensitized APO process, visible light is
absorbed by a sensitizing dye, which excites the dye
molecule to a higher energy state. The excited dye
then transfers some of its excess energy to other
molecules present in the waste stream, producing a
chemical reaction. When dissolved 0, accepts
energy from a sensitizer (for example, methylene
blue or rose bengal), the dissolved 0, is converted
to O(1D), an effective oxidant. This APO process
has yet to become commercially viable, perhaps
because of the difficulty associated with removing
the dye from the treated waste stream (Li and others
1992).
Semiconductor-Sensitized APO Processes
Semiconductors are solids that have electrical
conductivities between those of conductors and
those of insulators. Semiconductors are
characterized by two separate energy bands: a low-
energy valence band and a high-energy conduction
2-4
-------
band. Each band consists of a spectrum of energy
levels in which electrons can reside. The separation
between energy levels within each energy band is
small, and they essentially form a continuous
spectrum. The energy separation between the
valence and conduction bands is called the band gap
and consists of energy levels in which electrons
cannot reside.
Light, a source of energy, can be used to excite an
electron from the valence band into the conduction
band. When an electron in the valence band
absorbs a photon,' the absorption of the photon
increases the energy of the electron and enables the
electron to move into one of the unoccupied energy
levels of the conduction band. However, because
the energy levels of the valence band are lower than
those of the conduction band, electrons in the
conduction band eventually move back into the
valence band, leaving the conduction band empty.
As this occurs, energy corresponding to the
difference in energy between the bands is released
as photons or heat. Semiconductors are said to
exhibit photoconductivity because photons can be
used to excite a semiconductor's electrons and allow
easy conduction.
Semiconductors that have been used in
environmental applications include TiO2, strontium
titanium trioxide, and zinc oxide (ZnO). TiO2 is
generally preferred for use in commercial APO
applications because of its high level of
photoconductivity, ready availability, low toxicity, and
low cost. TiO2 has three crystalline forms: rutile,
anatase, and brookite. Studies indicate that the
anatase form provides the highest *OH formation
rates (Tanaka and others 1993).
TiO2 exhibits photoconductivity when illuminated by
photons having an energy level that exceeds the
TiO2 band gap energy level of 3.2 eV. For TiO2, the
photon energy required to overcome the band gap
energy and excite an electron from the valence band
to the conduction band can be provided by light of a
wavelength shorter than 387.5 nm. When an
electron in the valence band is excited into the
conduction band, a vacancy or hole is left in the
valence band. Such holes have the effect of a
positive charge. The combination of the electron in
the conduction band (e"CB) and the hole in the
valence band (h+VB) is referred to as an electron-hole
pair. The electron-hole pair within a semiconductor
band tends to revert to a stage where the electron-
hole pair no longer exists because the electron is in
an unstable, excited state; however, the band gap
inhibits this reversal long enough to allow excited
electrons and holes near the surface of the,
semiconductor to participate in reactions at the
surface of the semiconductor.
A simplified TiO2 photocatalytic mechanism is
summarized in Figure 2-3. This mechanism is still
being investigated, but the primary photocatalytic
mechanism is believed to proceed as follows (Al-
Ekabi and others 1993):
TiO + hv
VB
(2-13)
At the Ti02 surface, the holes react with either H2O
or OH' from water dissociation to form -OH as
follows:
h+VB + H2O -» *OH + H+
h+VB + OH- -»*OH
(2-14)
(2-15)
An additional reaction may occur if the electron in the
conduction band reacts with 0, to form superoxide
ions (O2«') as follows:
e'CB t 0,
(2-16)
The O2-~ can then react with H20 to provide
additional «OH, OH-, and 0, as follows:
2O2«- + 2H2O -* H2O2 + 2OH" + 0, (2-17)
H2O2 + e-CB -* OH' + 'OH (2-18)
The OH- can then react with the hole in the valence
band as shown in Equation 2-15 to form additional
•OH. One practical problem with semiconductor
photoconductivity is the electron-hole reversal
process. The overall result of this reversal is
generation of photons or heat instead of «OH. The
reversal process significantly decreases the
photocatalytic activity of a semiconductor. One
possible method of increasing the photocatalytic
activity of a semiconductor is to add irreversible
electron acceptors (IEA) or oxidants to the matrix to
be treated. Once lEAs accept an electron in the
conduction band or react with O2'', the lEAs
dissociate and provide additional routes for *OH
generation. H202 is an IEA and illustrates the role
that lEAs may play in APO processes. When the
IEA H2O2 accepts an electron in the conduction
band, it dissociates as shown in Equation 2-18.
Therefore, H2O2 not only inhibits the electron-hole
reversal process and prolongs the lifetime of the
photogenerated hole, but it also generates additional
•OH.
2-5
-------
Photon
TiO2 Particle in Water
Figure 2-3. Simplified TiO2 photocatalytic mechanism.
0, is also used as an IEA and may undergo the
following reaction:
20, + 2e-CB - 0, + 20,'
(2-1 9)
The 0, and O2-~ can generate additional -OH in
accordance with Equations 2-1 6 through 2-1 8.
Several commercial-scale semiconductor-sensitized
APO systems are available for treating both
contaminated water and air.
2.2 Com'mercial-Scale APO Systems
This section describes typical commercial-scale APO
systems for water and air. No commercial-scale
APO systems for solids are available. However, an
APO system for water can be used to treat the
contaminated leachate generated by leaching
contaminants from soil using a soil washing process
that is commercially available. The information
included in this section was obtained from APO
vendors or from published documents. The level of
detail provided varies depending on the source of
information used.
The commercial-scale APO systems for water
described in this section include the (1) Calgon
perox-pure™ and Rayox® UV/H202 systems;
(2) Magnum Water Technology, Inc. (Magnum),
CAV-OX® UV/H2O2 system; (3) WEDECO- UV-
Verfahrenstechnik (WEDECO) UV/O3 systems;
(4) U.S. Filter/Zimpro, Inc. (U.S. Filter), UV/O3/H2O2
system; and (5) Matrix Photocatalytic, Inc. (Matrix),
UV/TiO2 system. The commercial-scale APO
systems for air described in this section include the
(1) Process Technologies, Inc. (PTI), UV/O3 system;
(2) Zentox Corporation (Zentox) UV/TiO2 system;
and (3) KSE, Inc. (KSE), Adsorption-lntegrated-
Reaction (AIR) UV/catalyst system.
Other commercially available systems, including
(I) the Calgon Rayox® ENOX 510, 710, and 910
systems, photo-Fenton systems for water treatment,
and (2) the Matrix UVfno2 system for air treatment,
are not described in this section because the
vendors stated that these systems are very similar to
their other APO systems and did not provide
additional information. In addition, the WEDECO
UV/H2O2 commercial-scale water treatment system
is not described in this section because the vendor
did not provide a system description. However,
according to a case study narrative provided by
WEDECO (1998), the UV/H202 system consists of
(1) two UV reactors in series with one low-pressure
mercury vapor lamp in each reactor and (2) an H2O2
dosing station. The narrative also states that the
system is operated as a "once-through" system (no
recirculation).
2-6
-------
2.2.7 Calgon perox-pure™ and
Rayox® U V/H2O2 Sys terns
The Calgon perox-pure™ and Rayox® UV/H202
treatment systems are designed to remove organic
contaminants dissolved in water. These systems
use UV radiation and H2O2 to oxidize organic
compounds present in water at milligram per liter
(mg/L) levels or less. These systems produce no air
emissions and generate no sludge or spent media
that require further processing, handling, or disposal.
The systems use medium-pressure mercury vapor
lamps to generate UV radiation. The principal
oxidants in the systems, *OH, are produced by direct
photolysis of H2O2 at UV wavelengths.
A typical Calgon UV/H2O2 system is assembled from
the following portable, skid-mounted components: an
oxidation unit, an H2O2 feed module, an acid feed
module, and a base feed module. A schematic flow
diagram of a typical Calgon UV/H2O2 system is
shown in Figure 2-4. The oxidation unit shown in
Figure 2-4 has six reactors in series with one
15-kilowatt (kW) UV lamp in each reactor and a total
volume of 55 liters (L). Each UV lamp is mounted
inside a UV-transmissive quartz tube in the center of
each reactor such that wafer flows around the quartz
tube.
In a typical application of the Calgon system,
contaminated water is dosed with H2O2 before the
water enters, the first reactor; however, a splitter can
be used to add H2O2 at the inlet to any reactor in the
oxidation unit. In some applications, acid is added to
lower the influent pH and shift the carbonic acid-
bicarbonate-carbonate equilibrium to carbonic acid.
This equilibrium is important because carbonate and
bicarbonate ions scavenge «OH. After chemical
injections, the contaminated water flows through a
static mixer and enters the oxidation unit. Water
then flows through the six UV reactors. In some
applications, base is added to the treated water to
adjust the pH in order to meet discharge
requirements, if necessary.
Solids may accumulate in this system as a result of
oxidation of metals (such as iron and manganese),
water hardness, or solids precipitation. Accumulated
solids could eventually coat the quartz tubes, thus
reducing treatment efficiency. Therefore, the quartz
tubes encasing the UV lamps are equipped with
wipers that periodically clean the tubes and reduce
the impact of accumulated solids.
Contaminated
Water
Treated
Water
UV Lamp (typical)
Reactor
Static
Mixer
Oxidation Unit
Figure 24. Flow configuration in a Calgon UV/H2O2 system.
2-7
-------
2.2.2 Magnum C/\V-OX® UV/H202
System
The CAV-OX® process was developed by Magnum
to remove organic contaminants dissolved in water.
The process uses hydrodynamic cavitation, UV
. radiation, and H2O2 to oxidize organic compounds
present in water at mg/L levels or less. In the
CAV-OX process, organic contaminants in water are
oxidized by *OH and hydroperoxyl radicals produced
by hydrodynamic cavitation, UV radiation, and H2O2.
A typical CAV-OX® UV/H2O2 system consists of a
portable, truck- or skid-mounted module with the
following components: a cavitation chamber, an
H202 feed tank, and UV reactors (see Figure 2-5).
Depending on the application, Magnum uses the
CAV-OX® I (low-energy) or the CAV-OX® II (high-
energy) process for treating contaminated water.
The CAV-OX® I process uses one UV reactor with
six 60-Watt (W), low-pressure UV lamps; the reactor
is operated at 360 W. The CAV-OX® II process uses
two UV reactors, each with one high-pressure UV
lamp operated at 2.5 or 5 kW. The CAV-OX®
process generates UV radiation using mercury vapor
lamps. Each UV lamp is housed in a
UV-transmissive quartz tube mounted entirely within
the UV reactor. The low-energy reactor has a
volume of about 40 L, and each high-energy reactor
has a volume of about 25 L.
In a typical application of a CAV-OX® system,
contaminated water is pumped to the cavitation
chamber. Here the water undergoes extreme
pressure variations, resulting in hydrodynamic
cavitation. H2O2 is usually added to the
contaminated water in-line between the cavitation
chamber and the UV reactor. However, H2O2 may
also be added to the contaminated water in-line
before the cavitation chamber. Inside the UV
reactor, H2O2 photolysis by UV radiation results in
additional formation of *OH that rapidly react with the
organic contaminants. Treated water exits the UV
reactor for appropriate disposal.
2.2.3 WEDECO UV/O3 Systems
WEDECO commercial-scale UV/O3 system designs
vary depending on the application. Figure 2-6 shows
a system designed to remove chlorinated VOCs in
water. This system consists of a UV reactor, an 0,
generator, an 0, absorption tank, and a catalytic 0,
decomposer. In a typical application, contaminated
water first enters a UV reactor containing several
UV-C lamps. The UV-irradiated water is recycled
through the system for in-line 0, gas addition and
then for 0, absorption in the 0, absorption tank.
The ozonated water is then returned to the UV
reactor after it is mixed with additional contaminated
water. The chlorinated solvents present in the
combined waste stream are removed by the «OH
generated in the UV reactor. Until the system
reaches steady state, 100 percent of the UV-
irradiated water is recycled. Once the system
reaches steady state, only a small portion of the UV-
irradiated water is recycled, and the remaining water
(treated water) is disposed of appropriately.
Undissolved 0, present in the off-gas from the 0,
absorption tank is decomposed to 0, in the catalytic
0, decomposer before the off-gas is emitted to the
atmosphere.
Contaminated
Water
2.5- or 5-kW
UV Reactor
2.5- or 5-kW
UV Reactor
Treated
' Water
CAV-OX® I
Treated
Water
CAV-OX® I
Figure 2-5. Flow configuration in a Magnum CAV-OX* UV/H20, system.
2-8
-------
Treated Off-Gas
Catalytic O3
Decomposer
Contaminated Water
Treated Water
Figure 2-6. Flow configuration in a WEDECO UV/O3 system for water contaminated with chlorinated VOCs.
Figure 2-7 shows a WEDECO system designed for
chemical oxygen demand (COD) and adsorbable
organic halide (AOX) removal from biologically
treated landfill leachate. This system is similar to the
system described above except that this system has
two 0, absorption tanks and the contaminated water
flows through the absorption tanks before it flows
through the UV reactor.
2.2.4 U.S. 'Filter UV/O./H2O2 System
The U.S. Filter UV/oxidation treatment system uses
UV radiation, O3, and H2O2 to oxidize organics in
water. This system was formerly known as the
Ultrox system. The major components -of this
system are the UV/oxidation reactor, 0, generator,
H2O2 feed tank, and catalytic 0, decomposition out of the reactor for appropriate disposal.
spargers uniformly diffuse 0, gas from the base of
the reactor into the contaminated wafer. H2O2 is
introduced in the influent line to the reactor from a
feed tank. An in-line static mixer is used to disperse
the H2O2 into the contaminated water in the influenf
feed.
In a typical operation, contaminated water first
comes in contact with H2O2 as it flows through the
influent line to the reactor. The water then comes in
contact with UV radiation and 0, as it flows through
the reactor at a rate selected to achieve the desired
hydraulic retention time. As the 0, in the reactor is
transferred to the contaminated water, -OH are
produced. The *OH formation from 0, is catalyzed
by UV radiation and H2O2. The treated water flows
(Decompzon) unit.
The UV/oxidation reactor shown in Figure 2-8 has a
volume of 600 L and is 1 meter (m) long by 0.5 m
wide by 2 m high. The reactor is divided by five
vertical baffles into six chambers and contains
24 low-pressure mercury vapor lamps (65 W each)
in quartz sleeves. The UV lamps are installed
vertically and are evenly distributed throughout the
reactor (four lamps per chamber).
Each chamber also has one stainless-steel sparger
that extends along the width of the reactor. The
0, that is not transferred to the contaminated water
will be present in the reactor off-gas. This off-gas 0,
is subsequently removed by the Decompzon unit
before the off-gas is vented to the atmosphere. The
Decompzon unit uses a nickel-based proprietary
catalyst to decompose reactor off-gas 0, to 0,.
The Decompzon unit can accommodate flows of up
to 900 standard cubic meter (m3) per minute (scmm)
and can reduce 0, concentrations in the range of 1
to 20,000 parts per million by volume (ppmv) to less
than (<) 0.1 ppmv.
2-s
-------
Treated Off-Gas
Biologically Treated
Landfill Leachate
Catalytic 0,
Decomposer
Treated Water
Figure 2-7. Flow configuration in a WEDECO UV/O3 system for biologically treated landfill leachate.
UV Lamp
(typical) "
UV/Oxidation
Reactor —
O3Gas
CZD*-1
fe ^
*
^
Treated
Off-Gas
Decompzon
Unit
O3 Sparger
Static Mixer
Contaminated
Water
H2O2 Feed Tank
Figure 2-8. Flow configuration in a U.S. Filter UV/03/H2O2 system.
Treated
" Water
2-10
-------
2.2.5 Matrix UV/TiO2 System
The Matrix UV/Ti02 system is designed to treat liquid
wastes containing organic contaminants. The Matrix
system uses UV light with its predominant emission
at a wavelength of 254 nm, the anatase form of the
TiO2 semiconductor, and oxidants to generate -OH.
A typical Matrix treatment system contains many
photocatalytic reactor cells; the exact number of cells
varies depending on the application. Each cell is
1.75 m long and has a 4.5-centimeter (cm) outside
diameter. A 75-W 254-nm UV light source is located
coaxially within a 1.6-m-long quartz sleeve. The
quartz sleeve is surrounded by eight layers of
fiberglass mesh bonded with the anatase form of
TiO2 and is enclosed in a stainless-steel jacket.
Each cell is rated for a maximum flow rate of about
0.8 liter per minute (L/min).
A typical Matrix treatment system consists of two
units positioned side by side in a mobile trailer. Each
unit consists of 12 wafers, and each wafer consists
of six photocatalytic reactor cells joined by
manifolds. A block placed in each wafer channels
contaminated water into three reactor cells at a time.
The flow configuration in a wafer is shown in
Figure 2-9. The overall maximum flow rate for this
configuration is 2.4 Umin. Each set of three cells
along the path where the contaminated water flows
is defined as a path length. Therefore, each wafer
has two path lengths. Each unit has 24 path lengths,
resulting in a total of 48 path lengths for the two
units. The Matrix system can be operated with fewer
path lengths than those available in a given system.
H2O2 and 0, are injected at multiple path lengths
throughout the Matrix system. The exact number of
injection points varies depending on the application.
Figure 2-10 shows the flow configuration in the
Matrix UV/TiO2 treatment system. Beginning with
the first wafer, contaminated water enters path
length 1 (the first set of three reactor cells in Unit 1)
and then path length 2 (the second set of three
reactor cells in Unit 1). After treatment is completed
in the first wafer, contaminated water flows to the
second wafer and enters path length 3 (the first set
of three reactor cells in Unit 2) and then path
length 4 (the second set of three reactor cells in
Unit 2). This process continues 'until the
contaminated water has passed through all 24
wafers (48 path lengths). The treated water exiting
path length 48 is disposed of appropriately.
Treated Water
Block
Contaminated
Water
Photocatalytid Cell (typical)
Figure 2-9. Flow configuration In a Matrix wafer.
2-11
-------
Wafer /
(typical) \
(
(
C
48©0© ©0®47
41®®® ©©©42
^Q © © 0®039
330©0 ©Q©34
32©©© 0®®31
25® 00 © © ©26
240©© ©0®23
17®®® ©®©18
ia©0© ®®®15
9000 ©©©10
8©©© 0007
1 (3tl (%) fib (7} (7) (T)2
LJ
-------
Treated Air
Regenerated Spent
Adsorbent Adsorbent
Ambient Air
Closed-Loop
Steam and '
Condensate
Desorber
Condenser
r\
1
,1
4-~
1
i
i
n '
i
i
-j
VOC Vapor
Low-Pressure
"* Sweep Steam
Boiler
System
j
r
b-J
Chiller Water
System
o ; 'o r.
1
Photolytic
0 | | 0 | i
o ' •' o ; I
i
0 ' 'O
Reactors |
o ' ' O
o " " o
*n
Acidic Gas
Scrubber
1
1
*
Water
em
Organic/Aqueous
Condensate Storage
Treated Recycled Air
Figure 2-11. Flow configuration in the PTI UV/03 system.
modular design allows multiple modules to be
connected, in series or in parallel in order to achieve
the desired level of performance. Within a module,
UV lamps are mounted inside quartz glass sleeves
to isolate the lamps from the process gas and to
allow cooling air flow over the lamps. Replaceable
catalyst media are placed in the reactor through a
removable side door. The catalyst consists of
Degussa P25 TiO2 applied to a proprietary support
material that is designed to be chemically stable
under Zentox system operating conditions and to
provide low-pressure drop through the reactor. The
system uses 0, as an IEA and UV lamps with their
predominant emission at a wavelength of 254 or
350 nm. The 350-nm UV lamps are considered to
be a good alternative for treating certain air streams
that form a polymeric coating on 254-nm UV lamps.
The Zentox system is designed for ambient
temperature operation but is capable of running at
temperatures up to 85 °C.
2.2.8 KSE AIR W/Catalyst System
The KSE AIR system combines two unit operations,
adsorption and chemical oxidation, and uses UV
light, a proprietary catalyst, and 0, present in the
contaminated air to treat air streams containing
VOCs, including chlorinated and nonchlorinated
compounds, In a typical system application, the
contaminated air stream containing VOCs flows into
the photocatalytic reactor. The VOCs are trapped on
the surface of a proprietary catalytic adsorbent. This
adsorbent is continuously illuminated with UV light,
removing the concentrated VOCs trapped on the
surface by enhanced photocatalytic oxidation. Thus,
the system at the same time removes VOCs and
continuously regenerates the catalytic adsorbent.
The system operates at ambient temperature, as the
catalyst is activated by UV light. Treated air is
discharged to ambient air or to a polishing unit if
further treatment is required.
2.3 APO System Design and Cost
Considerations
Bolton and others (1996) present a simple, practical
scale-up approach for designing APO systems. This
approach requires that information on key process
variables, such as UV dose and concentrations of
oxidants and catalysts, be generated by performing
treatability studies. The approach assumes that
contaminant removal follows first-order kinetics. The
approach should therefore be appropriately modified
when contaminant removal deviates from first-order
kinetics.
As stated above, the UV dose (the amount of UV
power to be radiated per unit volume of
contaminated water treated) and the concentrations
of oxidants and catalysts to be used are the primary
design variables to be optimized when sizing an
APO system. Treatability studies should be
performed to measure the UV dose required to
achieve a desired effluent contaminant
concentration. The UV dose for a particular stream
is determined in an iterative manner by examining
the effects of selected process variables-such as
pH, oxidant concentration, and choice of
catalyst-on the treatment process.
2-13
-------
Before determining the UV dose to achieve a specific
percent contaminant removal, electrical energy
required to achieve one order-of-magnitude
contaminant removal per unit volume of waste
treated (EE/0) should be determined from treatability
studies, EE/O combines light intensity, hydraulic
retention time, and contaminant percent removal into
'a single measure and is expressed in the units of
kilowatt hour per cubic meter (kWh/m3). The
economics of APO are driven primarily by electrical
power, flow rate, and percent removal, and EE/0
provides a simple, fairly accurate tool for (1) sizing
the full-scale system and (2) estimating capital and
operating costs.
After the EE/O is determined through treatability
studies, the UV dose required in a specific case is
calculated using the following equation:
UV dose = EE/O x log (C/Cf)
where
(2-20)
C, is the initial concentration (expressed in any
units), and
Cf is the anticipated or required discharge
standard (expressed in the same units as Cj).
Once the required UV dose is known, the electrical
operating cost associated with supplying UV energy
can be calculated as follows:
Electrical cost ($/m3) = UV dose (kWh/m3)
x power cost
($/kilowatt-hour) (2-21)
Lamp replacement costs typically range between 30
and 50 percent of the electrical cost (for preliminary
costing purposes, a conservative value of 45 percent
is used here). The next key parameter is the
chemical reagent doses to be used. The chemical
reagent dose (including the oxidant and any added
catalyst) requirement depends on the compound to
be treated and is based on treatability test results.
Therefore, the total APO system operating cost can
be calculated as follows.
Total APO system operating cost ($/m3) =
(1.45 x electrical cost) +
chemical reagent cost (2-22)
Capital cost is a function of system size, which in
turn is a function of the UV power required to remove
selected contaminants. The following equation can
be used to determine the total UV power required:
UV power (kW) = EE/O x flow (cubic
meter per hour [m3/h])
x log (C/Cf)
= UV dose
xflow(m3/h) (2-23)
Once the required UV power is known, the
associated capital cost can be estimated by
obtaining price quotations from the APO system
vendors.
2.4 References
AI-Ekabi, H., B. Butters, D. Delany, W. Holden, T.
Powell, and J. Story. 1993. "The Photocatalytic
Destruction of Gaseous Trichloroethylene and
Tetrachloroethylene Over immobilized Titanium
Dioxide." Photocatalytic Purification and
Treatment of Water and Air. Edited by D.F. Ollis
and H. AI-Ekabi. Elsevier Science Publishers
B.V. Amsterdam. Pages 719 through 725.
Balzani, V., and V. Carassiti. 1970. Photochemistry
of Coordination Compounds. Academic Press.
London. Pages 145 through 192.
Bhowmick, M., and M.J. Semmens. 1994.
"Ultraviolet Photooxidation for the Destruction of
VOCs in Air." Water Research. Volume 28,
Number 11. Pages 2407 through 2415.
Bolton, J.R., K.G. Bircher, W. Tumas, and C.A.
Tolman. 1996. "Figures of Merit for Advanced
Oxidation Technologies." Journal of Advanced
Oxidation Technologies. Volume 1. Pages 13
through 17.
Buxton, G.V., C.L. Greenstock, W.P. Helman, and
A.B. Ross. 1988. "Critical Review of Rate
Constants for Reactions of Hydrated Electrons,
Hydrogen Atoms, and Hydroxyl Radicals
(•OH/'O") in Aqueous Solution." Journal of
Physical and Chemical Reference Data. Volume
17. Pages 513 through 886.
Faust, B.C., and J. Hoigne. 1990. "Photolysis of
Fe(lll)-Hydroxy Complexes as Sources of «OH
Radicals in Clouds, Fog, and Rain."
Atmospheric Environment. Volume 24A.
Pages 79 through 89.
Fenton, H.J.H. 1894. "Oxidation of Tattaric Acid in
Presence of Iron." Journal of the Chemical
Society. Volume 65. Page 899.
2-14
-------
Glaze, W.H., J.W. Kang, and D.H. Chapin. 1987.
"The Chemistry of Water Treatment Processes
Involving Ozone, Hydrogen Peroxide, and
Ultraviolet Radiation." Ozone Science &
Engineering. Volume 9. Pages 335
through 352.
Gonzalez, M.C., A.M. Braun, A.B. Prevot, and E.
Pelizzetti. 1994. 'Vacuum-Ultraviolet (VUV)
Photolysis of Water: Mineralization of Atrazine."
Chemosphere. Volume 28, Number 12.
Pages 2121 through 2127.
Jacob, L, T.M. Hashem, M.M. Kantor, and A.M.
Braun. 1993. Vacuum-Ultraviolet (VUV)
Photolysis of Water: Oxidative Degradation of 4-
Chlorophenol." Journal of Photochemistry and
Photobiology, A: Chemistry. Volume 75.
Pages 97 through 103.
Kim, S-M., S-U. Geissen, and A. Vogelpohl. 1997.
"Landfill Leachate Treatment by a Photoassisted
Fenton Reaction." Water Science &
Technology. Volume 35, Number 4. Pages 239
through 248.
Li, X., P. Fitzgerald, and L. Bowen. 1992.
"Sensitized Photo-Degradation of Chlorophenols
in a Continuous Flow Reactor System." Water
Science & Technology. Volume 26, Numbers 1
and 2. Pages 367 through 376.
Loraine, G.A., and W.H. Glaze. 1992. "Destruction
of Vapor Phase Halogenated Methanes by
Means of. Ultraviolet Photolysis." 47th Purdue
Industrial Waste Conference Proceedings.
Lewis Publishers, Inc. Chelsea, Michigan.
Nowell, L.H., and J. Hoigne. 1992. "Photolysis of
Aqueous Chlorine at Sunlight and Ultraviolet
Wavelengths-ll. Hydroxyl Radical Production."
Water Research. Volume 26, Number 5.
Pages 599 through 605.
Philips Lighting. 1985. Germicidal Lamps and
Applications. Philips Lighting Division.
Netherlands. November.
Pignatello, J.J. 1992. "Dark and Photoassisted
Fe3+- Catalyzed Degradation of Chlorophenoxy
Herbicides by Hydrogen Peroxide."
Environmental Science & Technology.
Volume 26. Pages 944 through 951.
Ruppert, G., R. Bauer, and G.J. Heisler. 1993. "The
Photo-Fenton Reaction-An Effective
Photochemical Wastewater Treatment Process."
Journal of Photochemistry and Photobiology A:
Chemistry. Volume 73. Pages 75 through 78.
Safarzadeh-Amiri, A. 1993. "Photocatalytic Method
for Treatment of Contaminated Water."
US. Patent No. 5,266,214.
Safarzadeh-Amiri, A., J.R. Bolton, and S.R. Carter.
1997. "Ferrioxalate-Mediated Photodegradation
of Organic Pollutants in Contaminated Water."
Water Research. Volume 31, Number- 4.
Pages 787 through 798.
Tanaka, K., T. Hisanaga, and A. Rivera. 1993.
"Effect of Crystal Form of TiO2 on the
Photocatalytic Degradation of Pollutants."
Photocataiytic Treatment of Water and Air.
Edited by D.F. Ollis and H. AI-Ekabi. Elsevier
Science Publishers B.V. Amsterdam.
Pages 169 through 178.
Unkcoth, A., V. Wagner, and R. Sauerbrey. 1997.
"Laser-Assisted Photochemical Wastewater
Treatment." Water Science & Technology.
Volume 35, Number 4. Pages 181 through 188.
Walling., C. 1975. "Fenton's Reagent Revisited."
Accounts of Chemical Research. Volume 8.
Pages 125 through 131.
WEDECO UV-Verfahrenstechnik (WEDECO). 1998.
Letter Regarding Case Studies on WEDECO UV
Oxidation Process. From Horst Sprengel. To
Kumar Topudurti, Environmental Engineer, Tetra
Tech EM Inc. April 21.
Zepp, R.G., B.C. Faust, and J. Hoigne. 1992. "The
Hydroxyl Radical Formation in Aqueous
Reactions (pH 3-8) of Iron(ll) with Hydrogen
Peroxide: The Photo-Fenton Reaction."
Environmental Science & Technology.
Volume 26. Pages 313 through 319.
2-15
-------
-------
Section 3
Contaminated Water Treatment
APO has been demonstrated to be an effective
technology for treatment of contaminated water.
Matrices to which APO has been applied include the
following: (1) contaminated groundwater,
(2) industrial wastewater, (3) municipal wastewater,
(4) drinking water, (5) landfill leachate, and
(6) contaminated surface water. Collectively, APO
has been applied to the following types of
waterborne contaminants: VOCs, semivolatile
organic compounds (SVOC), polychlorinated
biphenyls (PCB), pesticides and herbicides, dioxins
and furans, explosives and their degradation
products, humic substances, inorganics, dyes, and
microbes.
To assist an environmental practitioner in the
selection of an APO technology to treat
contaminated water, this section includes
(1) commercial-scale system evaluation results for
UV/H2O2,. UV/O3, UV/O3/H2O2, photo-Fenton, and
UV/TiO2 processes and (2) pilot-scale system
evaluation results for UV/H2O2, photo-Fenton,
solar/TiO2, and solar/TiO2/H2O2 processes. This
section also summarizes supplemental information
available from bench-scale studies of APO
processes.
As described in Section 1.2, this handbook
organizes performance and cost data for each matrix
by contaminant group, scale of evaluation
(commercial, pilot, or bench), and APO system or
process, In general, commercial- and pilot-scale
applications are discussed in detail. Such
discussions include, as available, a system
description, operating conditions, performance data,
and system costs'presented in 1998 dollars. Bench-
scale studies of APO processes are described in
less detail and only if they provide information that
supplements commercial- and pilot-scale evaluation
results. At the end of each matrix section, a table is
provided that summarizes operating conditions and
performance results for each commercial- and pilot-
scale study discussed in the text.
3.1 Contaminated Groundwater
Treatment
The effectiveness of APO technologies in treating
contaminated groundwater has been evaluated for
various contaminant groups, including VOCs,
SVOCs, PCBs, pesticides and herbicides, dioxins
and furans, explosives and their degradation
products, humic substances, and inorganics. This
section discusses APO technology effectiveness
with regard'to each of these contaminant groups.
3. /. 1 VOC-Contaminated Groundwater
This section discusses treatment of VOCs in
groundwater using the UV/H,O,, UV/O
3'
UV/O3/H202, and UV/Ti02 processes on a
commercial scale. Additional information on VOC
removal using the UV/H2O2> solar/TiO2, and
solar/TiO2/H2O2 processes at the pilot scale and
(2) UV/H2O2 and UV/TiO2 processes at the bench
scale is also included.
Commercial-Scale Applications
This section summarizes the effectiveness of
the Calgon perox-pure" UV/H2O2, Calgon Rayox®
UV/H202, Magnum CAV-OX® UV/H2O2, WEDECO
UV/H202, WEDECO UV/O3, U.S. Filter UV/O3/H2O2,
and Matrix UVn"iO2 treatment systems in removing
the following VOCs from contaminated groundwater.
APO Process'
UV/H2O2
UV/03
UV/03/H202
UV/TiO,
VOCs Removed
Benzene; CB;
chloroform; I ,1 -DCA;
1,2-DCA; 1,4-DCB;
1,2-DCE; ethylbenzene;
methylene chloride;
PCE;1,1,1-TCA;TCE;
TPH;'VC
T C E , P C E
TCE
Benzene; 1 ,1-DCA;
1,1-DCE;cis-1,2-DCE;
PCE;1 ,1,1-TCA;TCE;
toluene; xylenes
Calgon perox-pure™ UV/H2O2 Systems
A Calgon perox-pure" UV/H2O2 system' was
demonstrated in September 1992 under the
U.S. Environmental Protection Agency (U.S. EPA)
Super-fund Innovative Technology Evaluation (SITE)
program. This demonstration involved removing
VOCs from groundwater at Lawrence Livermore
National Laboratory, Site 300, in Tracy,. California
(Topudurti and others 1994).
3-1
-------
Trichloroethene (TCE) and tetrachloroethene (PCE)
were the primary groundwater contaminants at
Site 300, with concentrations ranging from 890 to
1,300 micrograms per liter (//g/L) and 71 to 150 /^g/L,
respectively. In addition, 1 ,1 ,l-trichloro-ethane
(1,1,1-TCA); 1,1-dichloroethane (1,1-DCA); and
chloroform were present in groundwater in trace
amounts. Two sets of system test runs were
conducted: Runs 1 through 8 used raw groundwater,
while Runs 9 through 14 used groundwater spiked
with about 150 /zg/L of 1,1,1-TCA; 1,1-DCA; and
chloroform each. Average influent total organic
halide (TOX) and AOX concentrations were
measured at 800 and 730 /^g/L, respectively. A flow
rate of 38 L/min was maintained in all runs except
Runs 7 and 8, which had a flow rate of 150 Umin.
The H2O2 dose ranged from 30 to 240 mg/L. The
influent pH levels for Runs 1 and 2 were 8.0 and 6.5,
respectively, while Runs 3 through 14 had an influent
pH level of 5.0.
The system treated about 150 m3 of VOC-
contaminated groundwater at Site 300. For the
spiked groundwater, optimum operating conditions
were determined to be a flow rate of 38 L/min, an
influent H2O2 concentration of 40 mg/L, an H2O2
dose of 25 mg/L in the influent to Reactors 2 through
6, and an influent pH of 5.0 (see Figure 2-4 for a
system layout). TCE; PCE; and 1 ,1-DCA removals
in groundwater exceeded 99.9, 98.7, and
95.8 percent, respectively. Also, 1 ,1,1-TCA and
chloroform were removed by a maximum of 92.9 and
93.6 percent, respectively. TOX removal ranged
from 93 to 99 percent, and AOX removal ranged
from 95 to 99 percent.
The treated effluent met California drinking water
action levels and federal drinking water maximum
contaminant levels (MCL) for the abovementioned
compounds at the 95 percent confidence level.
Bioassay tests showed that, while the influent was
not toxic, the effluent was acutely toxic to freshwater
test organisms (the water flea [Ceriodaphnia dubia]
and fathead minnow [Pimephales promelas]). The
toxicity was attributed primarily to the H202 residual
in the effluent.
Groundwater remediation costs were estimated for
two scenarios. In Case 1 (raw groundwater), the
groundwater was assumed to have only two
contaminants that are relatively easy to oxidize (TCE
and PCE). Groundwater remediation costs were
$2.1 0/m3 of water treated for a 190-L/min system, of
which the Calgon perox-pure™ direct treatment cost
totaled $0.89/m3. In Case 2 (spiked groundwater),
the groundwater was assumed to have five
contaminants, two of which are relatively easy to
oxidize (TCE and PCE), and three of which are
difficult to oxidize (1,1,1-TCA; 1,1-DCA; and
chloroform). Groundwater remediation costs were
$3.30/m3 of water treated for a 190-L/min system, of
which the Calgon perox-pure™ direct treatment cost
totaled $1.50/m3.
In another field study, a Calgon perox-pure™ system
was tested at the Old O-Field site at Aberdeen
Proving Ground in Maryland in April and May 1991
(Topudurti and others 1993). The primary VOCs in
the groundwater at the site included 1,2-
dichloroethene (1,2-DCE); benzene; and chloroform,
which were present at concentrations of 200,52, and
41 /j.g!L, respectively. In addition, 1,2-DCA; TCE;
and methylene chloride were present in the
groundwater at concentrations of 22,21, and 8 ng/L,
respectively. Iron (120 mg/L) and manganese
(2.5 mg/L) were also present in the groundwater at
the site. Contaminated groundwater (a total of
140 m3) was pumped from three wells to two holding
tanks, where it was pretreated by a metals
precipitation system. During the metals precipitation
pretreatment process, iron and manganese were
removed by 99.8 and 99.2 percent to levels of 0.2
and 0.02 mg/L, respectively. After pretreatment, the
groundwater pH was adjusted to 7. Then the influent
entered the UV/oxidation system. Four tests were
conducted at a flow rate of 60 Umin; the hydraulic
retention time was about 5 minutes. In Tests 1, 2,
and 3, the H2O2 doses were 45, 90, and 180 mg/L,
respectively; the doses were equally divided into
three parts and added by a splitter at (1) the influent
line to the first reactor, (2) the effluent line from the
first reactor, and (3) the effluent line from the second
reactor. In Test 4, a total H2O2 dose of 45 mg/L was
added to the influent line to the first reactor; the
splitter was not used.
The treated effluent met federal MCLs -for all
compounds. Removals of 1,2-DCE; benzene;
chloroform; 1,2-DCA; TCE; and methylene chloride
were >99, >96, >97, >92, >93, and >86 percent,
respectively. The influent to and effluent from the
system passed the bioassay tests; the water was not
acutely toxic to freshwater test organisms (the
fathead minnow, Daphnia magna, sheepshead
minnow, and mysid shrimp). Although specific
process by-products were not identified, the effluent
pH was observed to decrease by about one unit,
indicating that some of the by-products were acidic.
The study did not include a treatment cost estimate.
In another field test, a Calgon perox-pure™ UV/H2O2
system was used to evaluate the feasibility of
applying APO to remediate VOC-contaminated
groundwater at Kelly Air Force Base in San Antonio,
3-2
-------
Texas. Groundwater from two highly contaminated
sites at Kelly Air Force Base, designated as
Sites E-l and E-3 of Zone 2, was used in the test
(Klink and others 1992).
The primary VOCs at Site E-l were 1,2-DCE; PCE;
TCE; and vinyl chloride (VC), which were present at
concentrations of 11,000; 2,500; 1,700; and
1,200 ^g/L, respectively. Site E-3 groundwater was
contaminated with chlorobenzene (CB); VC; 1,2-
DCE; l,4-dichlorobenzene(1,4-DCB);and 1,1-DCA,
which were present at concentrations of 3,100;
1,700; 430; 420; and 400 /zg/L, respectively.
Groundwater samples from both sites were
pretreated using pre-oxidation with H2O2 followed by
filtration through a 3-micron filter to remove dissolved
contaminants such as iron and manganese and
suspended solids, which can reduce transmission
of UV light. The system was operated at flow
rates of 490 (Site E-l) and 940 (Site E-3) Umin.
For Site E-l, an H2O2 concentration of 50 mg/L, a pH
of 5.5, and a retention time of 2 minutes were
selected as the preferred operating conditions. For
Site E-3, an H2O2 concentration of 100 mg/L, a pH of
5.1, and a retention time of 4 minutes were selected
as the preferred operating conditions. Removals at
Site E-l were >99.9 percent for 1,2-DCE; PCE; and
TCE and 95.8 percent for VC. At Site E-3, the
removals of CB; VC; 1,2-DCE; 1,4-DCB; and
1 ,1 -DCA were >99.9, >97, >99.1, >99.5, and
>99.5 percent, respectively.
The estimated capital cost of groundwater treatment
to meet drinking water standards was $115,000 for
Site E-l and $241,000 for Site E-3. These estimates
assume a flow rate of 75 and 130 Umin for the
systems at Sites E-l and E-3; respectively.
Operation and maintenance (O&M) costs were
projected to be $2,800 and $13,000 per month for
Sites E-l and E-3, respectively. These O&M costs
covered all required chemicals but not the
pretreatment and groundwater extraction systems.
In 1989, a Calgon perox-pure" UV/H202 system
was used to remove TCE from groundwater that
served as a municipal drinking water source in
Arizona. The drinking water well contained 50 to
400 t^g/L of TCE. The Calgon perox-pure" Model
SSB-30R system treated the groundwater at a flow
rate of 510 Umin using 15 kW of power. TCE
concentrations were reduced to <0.5 /ug/L, which
corresponds to >99.7 percent removal. In addition to
meeting the target effluent level requirement, the
system met the local community requirement for a
low-visibility, quiet treatment system that could be
operated in the middle of a large residential area.
The total O&M cost estimated by the vendor was
about $0.08/m3 of water treated, including electricity,
H2O2, and general maintenance costs (U.S. EPA
1993).
Calgon Rayox® UV/H202 System
The Calgon Rayoxe UV/H2O2 system was used to
treat groundwater contaminated with halogenated
VOCs at the Groveland Wells Superfund site in
Groveland, Massachusetts (Weir and others 1996).
The primary VOCs of concern at the site were TCE
and 1,2-DCE, which were present in the
groundwater at concentrations of 4,700 and
810 //g/L, respectively. The optimal treatment
conditions, based on the lowest system operating
cost, were an H2O2 dose of 25 mg/L, a flow rate of
1.5 m3/min, and use of a 60-kW system consisting of
four 15-kW UV lamps, Under theseconditions, the
technology effectively removed TCE and 1,2-DCE
from groundwater at the site and met surface water
discharge limits, achieving removals of 99.9 and
91.4 percent, respectively. -The estimated capital
cost for the system was $110,000, and the O&M cost
was $0.09/nr.
The Calgon Rayoxe UV/H2O2 technology has been
combined with more conventional water treatment
systems, such as air stripping and granular activated
carbon (GAC), in field studies to treat VOC-
contaminated groundwater. Performance data for
these hybrid systems is discussed below.
In a field test, a Calgon Rayox® UV/H2O2 system
was combined with air stripping to remediate VOC-
contaminated groundwater at the Millville Municipal
Airport in New Jersey in, March 1994. The hybrid
system consisted of two 90-kW Calgon Rayoxe units
and a Low Profile Shallow Tray@ air stripper. The
hybrid system was designed to treat up to 760 Umin
of contaminated groundwater (Bircher and others
1996).
PCE was the primary VOC present in the
groundwater, with concentrations of about
6,000 @g/L; also 1,1,1 -TCA and methylene chloride
were present at concentrations of 100 and 60 /zg/L,
respectively. Adequate treatment was achieved
using one 90-kW unit and a flow rate of 450 L/min.
H2O2 was added to the influent at a concentration of
25 mg/L.
The combined Calgon Rayox®/air stripping system
was able to almost completely degrade the VOCs in
the groundwater. Specifically, while the Calgon
Rayoxe UV/H202 system reduced the initial
concentrations of PCE; 1 ,1,1 -TCA; and methylene
3-3
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chloride by 99.8,20, and 16.7 percent, respectively,
the final concentrations of these compounds in the
air stripper effluent were all <1 /zg/L, indicating
>99.9, 99, and 98.3 percent removal, respectively.
These results show that for an unsaturated
compound such as PCE, most of the removal
occurred in the Calgon Rayoxe system, while for the
saturated compounds (1 ,1 ,1 -TCA and methylene
chloride), most of the removal occurred in the air
stripper. No cost information was available.
In another field test, a Calgon Rayox® UV/H2O2
system was used to treat VOC-contaminated
groundwater after treatment with GAC at the Fort
Ord Remedial Action Site in Monterey, California
(Bircher and others 1996). The Fort Ord site
groundwater was contaminated with methylene
chloride at concentrations up to 6.9 ^glL and other
organics. The treatment system consisted of two
9,100-kilogram (kg) carbon adsorption units in series
and four 90-kW Calgon Rayoxnjntts in parallel.
Groundwater was fed through the carbon adsorption
units at flow rates of up to 2,700 L/min. The pH of
the effluent from the carbon adsorption units was
adjusted to 5.0 using sulfuric acid. The pH-adjusted
water was then treated by the Calgon Rayoxe
UV/H2O2 system.
Organics other than methylene chloride were
removed primarily by the GAC, while methylene
chloride was primarily removed by the Calgon
Rayoxe UV/H2O2 system. The system reduced the
concentration of methylene chloride to 0.5 //g/L, a
removal of 92.6 percent, using the four 90-kW units.
A total of eight 90-kW units would have been needed
to achieve this percent removal if the Calgon Rayoxe
UV/H2O2 system had been used alone. The capital
cost of the combined GAC/Calgon Rayox® system
was $730,000, compared to $1 million if the Calgon
Rayoxe technology had been used alone. Operating
costs were estimated to be $0.31/m3 of water treated
for the GAC/Calgon Rayoxe hybrid system, whereas
the Calgon Rayoxe UV/H2O2 system alone would
have cost $0.58/m3 of water treated to operate.
Magnum CAV-Otf*
System
The Magnum CAV-OX® UV/H2O2 system was
demonstrated at Edwards Air Force Base in
California under U.S. EPA's SITE program in I993 to
remove VOCs from groundwater (U.S. EPA 1994).
The primary groundwater contaminants at the site
were TCE and benzene. During the demonstration,
influent concentrations of TCE and benzene ranged
from 1,500 to 2,090 //g/L and 250 to 500 (j.g/1,
respectively. Three configurations of the CAV-OX®
UV/H2O2 system were demonstrated: (1) the
CAV-OX® I low-energy system, which contained six
60-W UV lamps (broad band with a peak at 254 nm)
and operated at a flow rate of 1.9 to 5.7 L/min;
(2) the CAV-OX® II high-energy system operating at
5 kW and 3.8 to 15 L/min; and (3) the CAV-OX® II
high-energy system operating at 10 kW and 3.8 to
15 L/min.
About 32 m3 of contaminated groundwater was
treated during the demonstration. The optimum
operating conditions, percent removals, and
estimated costs associated with the CAV-OX® I and
II systems are as follows:
CAV-OX® I: influent H2O2 concentration =
23 mg/L; flow rate = 2.3 Umin; average
removal of TCE and benzene =
99.9 percent; groundwater remediation cost
for 95-L/min system = $3.80/m3 of water
treated (of which CAV-OX® I direct cost =
$1.50/m3)
. CAV-OX® II: influent H2O2 concentration =
48 mg/L; flow rate = 5.3 Umin; average
removal of TCE and benzene =
99.8 percent; groundwater remediation cost
for 95-L/min system = $4.07/m3 of water
treated (of which CAV-OX® II direct cost =
$1.50/m3)
In 1990, the CAV-OX® I low-energy system was
used at a former Chevron service station in Long
Beach, California, to remediate groundwater
contaminated by leaking underground storage tanks
(U.S. EPA 1994). The system used at the site
consisted of a cavitation chamber, a centrifugal
pump, an H2O2 injection process, and 12 60-W UV
lamps housed in two stainless-steel reaction
chambers. The primary contaminant of concern in
site groundwater was total petroleum hydrocarbons
(TPH), which was present at 190 mg/L. Pretreated
influent was pumped into the CAV-OX® system at a
flow rate of 38 Umin. The H2O2 dose was
maintained at 20 mg/L. About 2 years was required
to remediate the site; during this period, the
CAV-OX® I low-energy process was operational
99.9 percent of the time. After 2 years of operation,
99.9 percent of the TPH in the groundwater had
been removed. The overall cost was $0.47/m3 of
water treated; however, it is unclear what is included
in this cost.
In 1997, the CAV-OX® I UV/H2O2 system was used
to treat VOC-contaminated groundwater at a military
site; the name and location of the 'site are
unavailable. The primary contaminant of concern
was TCE, which was present in groundwater at an
3-4
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average concentration of 1,800 i*g/L. Cis-1,2-DCE;
trans-1,2-DCE; VC; and PCE were also present at
concentrations of 250, 200, 53, and 11 ^g/L,
respectively. The system achieved the following
removals for VOCs: 99.9 percent for TCE;
>99.9 percent for cis-1,2-DCE; >99.9 percent for
trans-1,2-DCE; >99.7 percent for VC; and
>98 percent for PCE. The estimated total direct
operating cost was $0.32/m3 of water treated, which
includes $0.06/m3 for 30 mg/L of 35 percent H202 (at
$1.17/kg), $0.1 5/m3 for electricity (at $0.08/kilowatt-
hour), $0.06/m3 for maintenance, and $0.05/m3 for
replacement of 12 lamps once per year (Magnum
1998).
WEDECO UV/H2O2 System
A commercial WEDECO UV/H2O2 system was used
to treat VOC-contaminated groundwater. The
primary contaminants in the groundwater were 1,2-
DCA; cis-1,2-DCE; benzene; ethylbenzene; and VC,
which were present at concentrations of 54,46,310,
41, and 34 ^g/L, respectively. The 1,2-DCA
concentration was reduced by only 9 percent.
However, removals for cis-1,2-DCE; benzene;
ethylbenzene; and VC were >87, 93, 92, and
86 percent, respectively. The total cost estimate for
the WEDECO groundwater treatment system was
$0.39/m3 of water treated, which includes $0.15/m3
for electricity, $0.1 6/m3 for system operation and UV
lamp replacement, and $0.08/m3 for H2O2
(WEDECO 1998).
WEDECO UV/O3 System
A commercial-scale WEDECO UV/03 system was
used to treat groundwater contaminated with TCE
and PCE at concentrations of 330 and 160 /^g/L,
respectively. The system was operated at a flow
rate of 10 m3/h, an 0, dose of 5 mg/L, and a UV-C
light intensity of 30 milliwatt per liter (mW/L). Under
these conditions, the system achieved 99.0 and
96.6 percent removals for TCE and PCE,
respectively. The estimated treatment cost was
$0.19/m3 of water treated; of this cost, $0.08/m3 was
for electricity, $0.04/m3 was for O&M, and $0.07/m3
was for capital equipment (Leitzke and Whitby 1990).
U.S. Filter UV/O^H2O2 System
The U.S. Filter UV/O^H2O2 system, formerly known
as the Ultrox system, was demonstrated at the
Lorentz Barrel and Drum site in San Jose, California,
under the U.S. EPA SITE program in February and
March 1989 (Topudurti and others 1993). Primary
contaminants in the groundwater at the site were
TCE; 1 ,1 -DCA; and 1,1,1 -TCA, which were present
at concentrations of 50 to 88 ^g/L, 9.5 to 13 /J.Q/L,
and 2 to 4.5 ^g/L, respectively. Eleven test runs
were performed to evaluate the U.S. Filter
UV/O3/H2O2 system under various operating
conditions. The flow rate was maintained at
0.14 rrvVmin. Optimum conditions for treatment were
an influent pH of 7.2, a retention time of 40 minutes,
an 0, dose of 110 mg/L, an H2O2 dose of 13 mg/L,
and use of 24 65-W UV lamps.
Under these conditions, the system achieved
removals as high as 99 percent for TCE; 65 percent
for 1 ,1-DCA; and 87 percent for 1,1,1-TCA. While
most VOCs were removed by chemical oxidation,
1 ,1-DCA and 1 ,1 ,1 -TCA were removed by 0,
stripping in addition to oxidation. Specifically,
stripping accounted for 12 to 75 percent of the total
1,1,1 -TCA removal and 5 to 44 percent of the total
1 ,1 -DCA removal. The off-gas treatment unit
(Decompzon unit) reduced reactor off-gas 0, by
more than 99.9 percent to levels <0.1 ppm. Capital
costs for the UV/oxidation unit and 0, generator in
the system were estimated to range between
$88,000 and $320,000. O&M costs for the system
can be as low as $0.08/m3 of treated water if only
oxidant and electrical costs are considered or can
exceed. $5.6/m3 of treated water if extensive
pretreatment is required.
The U.S. Filter UV/O3/H2O2 system was field-tested
by the U.S. Department of Energy at the Kansas City
Plant in Missouri in 1988. TCE was present in the
groundwater at a concentration 520 //g/L. During the
field test, the flow rate through the system ranged
from 20 to 38 Umin. The TCE removal achieved by
the system was >99 percent. Capital and O&M
costs were estimated to be $380,000 and $5/m3 of
water treated, respectively (U.S. EPA 1990).
Matrix UV/TiO2 System
Under U.S. EPA's SITE program, the Matrix UV/TiO2
system was demonstrated to destroy VOCs in
groundwater at the U.S. Department of Energy's
K-25 Site on the Oak Ridge Reservation in Oak
Ridge, Tennessee, in August and September 1995
(Topudurti and others 1998).
The primarygroundwater contaminants at the K-25
Site included 1 ,1-DCA; 1 ,1,1-TCA; xylenes; toluene;
cis-1,2-DCE; and 1 ,1-DCE, which were present in
concentrations ranging from 660 to 840 ^g/L, 680 to
980 ^g/U 55 to 200 /ug/L, 44 to 85 ^g/L, 78 to
98 //g/L, and 120 to 160 ^g/L, respectively.
Groundwater was also spiked with TCE, PCE, and
benzene—contaminants not present at high
concentrations in groundwater at the Oak Ridge
3-5
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Reservation but present at many Superfund
sites-to produce system influent concentrations
ranging from 230 to 610 //g/L; 120 to 200 t*g/L; and
400 to 1 ,1 00 ^g/L, respectively. H202 and 0, were
added to the Matrix system influent at concentrations
of 70 and 0.4 mg/L, respectively, in order to enhance
treatment performance in certain runs. Influent flow
rates varied from 3.8 to 9.1 Umin. Groundwater
alkalinity ranged from 270 to 300 mg/L calcium
carbonate, and the pH ranged from 6.5 to 7.2. The
Matrix system did not require pH adjustment of
groundwater prior to treatment. The groundwater
also contained high concentrations of iron and
manganese (about 16 and 9.9 mg/L, respectively).
To prevent fouling of the photocatalytic reactor cells
during the demonstration, an ion-exchange
pretreatment system was used to remove Iron and
manganese in the groundwater.
During the demonstration, the Matrix system (see
Figure 2-I 0) treated about 11,000 L of contaminated
groundwater. In general, at path length 48, removals
of up to 99 percent were observed for benzene;
toluene; xylenes; TCE; PCE; cis-1,2-DCE; and
1,1-DCE. However, low removals were observed for
1 ,1 -DCA and 1,1,1-TCA, which were reduced by no
more than 21 and 40 percent, respectively. The
demonstration showed that the percent removals at
path length 24 (halfway through the system) can be
increased to match the removals at path length 48
by adding H2O2 at a dose of 70 mg/L. This finding
indicates that the equipment cost and electrical
energy cost could be reduced by 50 percent by
adding H2O2 at a relatively low cost. The system
effluent met the Safe Drinking Water Act MCLs for
benzene; cis-1,2-DCE; and 1 ,1-DCE. However, the
effluent did not meet the MCLs for PCE; TCE;
1,1-DCA; and 1,1,1-TCA. VOC removal was
generally reproducible for most VOCs when the
Matrix system'was operated on different occasions
under identical conditions. Treatment by the Matrix
system did not reduce groundwater toxicity to
freshwater test organisms (the water flea
[Ceriodaphnia dubia] and fathead minnow
[Pimephalespromelas]). The estimated groundwater
remediation cost for the Matrix system is about
$18/m3 of water treated. Of this cost, the Matrix
system direct treatment cost was about $7.60/m3 of
water treated.
Pilot-Scale Applications
VOCs in groundwater have been removed using
APO processes on a pilot scale. This section
presents pilot-scale evaluation results for the
UV/H2O2, so!ar/TiO2, and solar/TiO2/H202 processes
in removing the following VOCs.
| APO Process. | VOCs Removed |
. UV/H2O2
• Solar/TiO2
. Solar/TiO,/H,O,
Benzene
. TCE
. BTEX
UV/H202
A UV/H2O2 system was pilot-tested by the Gateway
Center Water Treatment Plant in Los Angeles,
California, to treat groundwater contaminated with
benzene prior to the groundwater's discharge to the
Los Angeles River. The system consisted of an
H2O2 injection unit; a 360-kW UV reactor; and two
vessels containing 9,100 kg of activated carbon
each. The average concentration of benzene in the
untreated groundwater was 35 ^g/L. The influent pH
averaged 6.8, and the flow rate was maintained at
about 3.2 m3/min. Under these conditions, the
UV/H2O2 system achieved 98 percent removal of
benzene. The treated groundwater's pH was
adjusted using sodium hydroxide to meet the
discharge limit. No cost information was reported
(Oldencrantz and others 1997).
So/ar/77O2
A pilot-scale solar/TiO2 system designed by
researchers at the National Renewable Energy
Laboratory and Sandia National Laboratory was
field-tested at a Super-fund site at Lawrence
Livermore National Laboratory in Tracy, California, to
treat TCE-contaminated groundwater (Mehos and
Turchi 1993). The system used at -Lawrence
Livermore National Laboratory consisted of a
concentrating solar collector and a mobile equipment
skid.. The reactor for the study consisted of a
0.051 -cm-diameter borosilicate glass pipe that ran
along the length of the solar collector at the focal line
of the parabolic troughs. The influent TCE
concentration was about 110 f^g/L, and the raw
groundwater's pH averaged 7.2. Powdered TiO2
catalyst was added to the influent as a concentrated
slurry at a dose of 800 to 900 mg/L. The flow rate
was maintained at 15 Umin, corresponding to a
retention time of 10 minutes.
The study results showed that lowering the pH of the
influent groundwater significantly increased
the percent removal of TCE by reducing the
concentration of bicarbonate ion, a known scavenger
of «OH. Lowering the pH from 7.2 to 5.6 increased
TCE removals from 91 to 99 percent. The projected
treatment cost for a full-scale, 380-m3/day treatment
system at the Lawrence Livermore National
Laboratory site was $0.83/m3 of water treated.
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So/ar/7/O/H2O2
In a pilot-scale field test at Tyndall Air Force Base in
Florida, a solar/Ti02/H2O2 batch system was used to
treat jet fuel contaminants-specifically, 2 mg/L of
total benzene, toluene, ethylbenzene, and xylene
(BTEX)—in groundwater. The treatment unit
consisted of a photoreactor area made up of 15
nonconcentrating solar panels. TiO2 doses of 0.5 to
1 mg/L and an H2O2 dose of 100 mg/L were used.
Removal rates for BTEX and total organic carbon
(TOC) were slightly higher at pH levels of 4 and 5,
suggesting that an acidic medium is beneficial. From
about 50 to 75 percent of the BTEX was removed
during the 3-hour studies. The TOC concentration,
which ranged from 70 to 90 mg/L initially, remained
relatively unchanged, suggesting that while parent
compounds were destroyed, complete mineralization
did not occur. The estimated treatment cost,
including capital and O&M costs and based on a flow
rate of 38 m3/day, was $20 to $29/m3 of water
treated (Turchi and others 1993).
Bench-Scale Studies
This section summarizes the results of bench-scale
studies of the effectiveness of APO processes for
VOC removal from groundwater. The bench-scale
results are summarized only for studies that provided
information beyond the commercial- and pilot-scale
applications summarized above. The level of detail
provided varies depending on the source of
information used. For example, VOC percent
removals and test conditions are not specified for
some of the bench-scale studies because such
information is unavailable in the sources. Bench-
scale study results on VOC removals and treatment
by-products in groundwater and synthetic
wastewater matrices for the following VOCs by
UV/H2O2 and TiO2 are discussed,
| APO Process | VOCs Removed
I
• UV/H2O2
• UWTi02
. Acetone, naphthalene,
TCE, PCE
. Chloroform, ethylbenzene,
nitrobenzene, MTBE
UV/H2O2
Hirvonen and others (1996) report on UV/H202
treatment of well water contaminated with TCE and
PCE in a batch UV reactor. TCE and PCE
concentrations were initially 100 and 200 ^g/L,
respectively. The UV dose was 1.2 W/L, the H202
dose was 140 mg/L, and the influent pH was 6.8.
Treatment resulted in 98 and 93 percent removals of
TCE and PCE, respectively, in 5 minutes.
Chlorinated by-products formed included trichloro-
acetic acid and dichloroacetic acid.
A Calgon Rayox® UV/H2O2 bench-scale reactor was
used to study degradation of acetone in synthetic
wastewater. Acetone was present at concentrations
of 30 to 300 mg/L. The H2O2 dose was varied from
100 to 544 mg/L. The initial concentrations of
acetone and H2O2' significantly affected the initial
rate of acetone degradation. At a high pH,
by-products of acetone degradation-specifically,
acetic acid, formic acid, and oxalic
acid-accumulated, competed for *OH, and slowed
down acetone removal (Stefan and others 1996).
By-product formation during naphthalene
degradation by UV/H2O2 treatment was studied
using synthetic wastewater. By-products of the
reaction included naphthol; naphthoquinone;
bicyclo[4,2,9]octa-1,3,5-triene; 2,3-dihydroxy-benzo-
furan; 1 (3h)isobenzofuranone; benzaldehyde;
phthalic acid; benzoic acid; phenol; hydroxy-
benzaldehyde; hydroxyacetophenone; and dimethyl-
pentadiene (Tuhkanen and Beltran 1995).
UV/TiO2
UVrriO2 degradation of chloroform in distilled water
was studied using pure silver (Ag)-loaded TiO2. At
an initial chloroform concentration of 200 mg/L,
44 percent of the chloroform was removed when Ag-
loaded TiO2 was used, and 35 percent was removed
when pure (unloaded) TiO2 was used. The addition
of Ag as a sensitizer improved the performance of
the UV/TiO2 process (Kondo and Jardim 1991).
UV/TiO2 degradation of ethylbenzene was studied.
The initial concentrations of ethylbenzene and TiO2
were 0.32 to 5.4 mg/L and 1,000 mg/L, respectively.
The reaction by-products identified include
4-ethyIphenol, acetophenone, 2-methylbenzyl
alcohol, 2-ethylphenol, and 3-ethylphenol. At an
initial pH of 4.5, about 65 minutes was required for
complete mineralization (Vidal and others 1994).
Minero and others (1994) studied photocatalytic
degradation of nitrobenzene using the UV/TiO2
process. Within 1 hour, >90 percent mineralization
was achieved using 200 mg/L of TiO2. The reaction
by-products identified include 2-, 3-, and
4-nitrophenol and dihydroxybenzenes.
Photodegradation of methyl-terf-butyl ether (MTBE)
in synthetic wastewater using the UV/TiO2 process
was studied. The optimum amount of catalyst was
100 mg/L, above which increased turbidity reduced
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360 minutes of irradiation at a pH of 7.0 (Jardim and
others 1997).
UV/ZnO
Richard and Boule (1994) studied photochemical
oxidation of salicylic acid using the UV/ZnO process.
At a ZnO dose of 2,000 mg/L and under
O2-saturated conditions, 2,5-dihydroxybenzoic acid;
2,3-dihydroxybenzoic acid; and pyrocatechol were
identified as by-products.
3.1.3 PCB-Contaminated Groundwater
No commercial- or pilot-scale information was
available on the effectiveness of APO in treating
groundwater contaminated with PCBs. Two bench-
scale studies for the following PCBs are summarized
below.
APO Process
. Solar/diethylamine .
. Solar/TiO2
PCBs Removed
PCB congeners:
66, 101, 110, 118,
138 (Aroclor 1254)
• Aroclor 1248
Lin and others (1995) studied photodegradation of
five PCB congeners—66,101,110,118,138—under
simulated sunlight in the presence of the sensitizer
diethylamine. These congeners represent
45.5 percent of all Aroclor 1254 congeners. PCBs
were present in synthetic wastewater at a
concentration of 1 .0 mg/L. With a diethylamine dose
of 1 /j.g/L and a reaction time of 24 hours, congeners
66, 101, 110, 118, and 138 were degraded by 89,
99,84, 98, and 78 percent, respectively. Congener
138 generated five congeners during photochemical
oxidation; specifically, congeners 85, 87,97,99, and
118 were generated during 1 hour of treatment.
PCB removal from synthetic wastewater has also
been studied using the solar/Ti02 process in a
bench-scale study by Zhang and others (1993).
Aroclor 1248 was present in synthetic wastewater at
a concentration of 320 mg/L. At a Ti02 dose of
50,000 mg/L, 83 percent removal of Aroclor 1248
was observed in 4 hours.
3.7.4 Pesticide- and Herbicide-
Contaminated Groundwa ter
No evaluations of commercial-scale APO processes
for removing pesticides and herbicides from
groundwater were available. However, one APO
process (UV/03) has been evaluated at the pilot
scale, and several such APO processes have been
evaluated at the bench scale. The results of these
evaluations are summarized below.
Pilot-Scale Application
Kearney and others (1987) conducted a UV/O3 pilot-
scale study involving treatment of pesticide in
synthetic wastewater. The concentration of each
contaminant (alachlor; atrazine; Bentazon; butylate;
cyanazine; 2,4-dichlorophenoxyacetic acid [2,4-D];
metolachlor; metribuzin; trifluraline; carbofuran; and
malathion) was varied at three levels: 1 0, 100, and
1,000 mg/L. The treatment unit used consisted of
66 low-pressure mercury vapor lamps with a total UV
output of 455 W at 254 nm. The flow rate through
the system was varied from 8 to 40 Umin. For
pesticides at initial concentrations of 10 to 100 mg/L,
>99.9 percent removal was observed. For the
1 ,000-mg/L initial concentrations, the removals
ranged from 75 to 85 percent. The time required for
90 percent removal depended on the initial pesticide
concentration and increased as the initial
concentration increased (about 20 minutes for a
10-mg/L initial concentration and 60 minutes for a
1 00-mg/L initial concentration).
Bench-Scale Studies-
Pesticides and herbicides in water have been
removed using the VUV, UV/H2O2, UV/O3, photo-
Fenton, and UVfi"iO2 processes at the bench-scale
level. This section summarizes bench-scale results
for APO treatment of the following pesticides and
herbicides; information on by-products and
contaminant percent removals is provided where
available.
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APO Process
UV/H2O2
UV/03
Photo-Fenton
UV/TiO,
Pesticides and
Herbicides Removed
Atrazine
2,4-D
Simazine
Methyl parathion,
metolachlor
Alachlor; atrazine;
Basagran; Bentazon;
carbofuran; 2,4-D;
1,2-dibromo-
3-chloropropane;
dichlorvos; Diquat;
Diuron;
monocrotophos;
Monuron;
pendimethalin;
propazine; propoxur;
simazine
vuv
The VUV process was evaluated in terms of
mineralization of atrazine (22 mg/L) in synthetic
wastewater. By-products identified include
ammelide, ammeline, and cyanuric acid. The yield
of the by-products of atrazine degradation (for
example, cyanuric acid) from VUV photolysis was
found to be about half the yield obtained in UV/TiO2
reactions (Gonzalez and others 1994).
UV/H202
Pichat and others (1993) studied UV/H202 treatment
of 2,4-D in synthetic wastewater. The initial
concentration of 2,4-D was 80 mg/L. At an H202
dose of 99 mg/L, mineralization of the compound
was nearly complete (>99 percent) within 3 hours.
UV/03
The UV/Og process was evaluated in oxidation of
simazine in synthetic wastewater. The initial
concentration of simazine was 4 mg/L. The retention
time in the reactor was 15 minutes. Complete
oxidation of the compound was observed when
34 milligrams per minute of 0, was applied at a pH
of 7.2. By-products of the reaction included chloro-
diamino s-triazine, aminochloro ethylamino
s-triazine, diaminohydroxy s-triazine, amino-
dihydroxy s-triazine, and cyanuric acid (Lai and
others 199.5).
Photo-Fen ton
The photo-Fenton reaction was used to treat
metolachlor(2-chloro-N-[2-methyl-6-ethylphenyl]-N-
[2-methoxy-1 -methylethyl]acetamide) and methyl
parathion in synthetic wastewater. The initial
concentrations of metolachlor and methyl parathion
ranged from 28 to 57 mg/L and 26 to 53 mg/L,
respectively. The doses of H2O2 and Fe(lll) used
were 340 and 350 mg/L, respectively. Under a black
light, metolachlor was completely mineralized to
carbon dioxide in 6 hours; details on methyl
parathion degradation were not available. Organic
by-products of the metolachlor reaction included
chloroacetate, oxate, formate, and serine.
By-products of methyl parathion degradation
included oxalic acid; 4-nitrophenol; dimethyl
phosphoric acid; and traces of O,O-dimethyl-
4-nitrophenyl phosphoric acid (Pignatello and Sun
1995).
UV/TlOg
The UV/TiO2 process was evaluated for treating
synthetic wastewater containing 2,4-D and propoxur
at 50 mg/L each. At a pH of 4 and with a TiO2 dose
of 180 mg/L, 2,4-D and propoxur concentrations
were reduced by 97 and 73 percent, respectively.
The primary by-products of 2,4-D degradation were
formaldehyde; 2,4-DCP; and 2,4-DCP formate.
According to the Microtox test, which measures
toxicity based on the quantity of light emitted by
the luminescent bacterium Photobacterium phos-
phoreum before and after exposure to an aqueous
sample, 2,4-D by-products are more toxic than the
parent compounds after partial degradation. These
results indicate the importance of completely
destroying the by-products during treatment (Lu and
Chen 1997).
UV/Ti02 was applied to treatment of synthetic
wastewater containing dichlorvos at an initial
concentration of 50 mg/L. The UV/TiO2 process was
tested at pH levels of 4 and 8 for 3 hours. Greater
removal was observed at a pH of 4. However, the
toxicity of the solution increased 2.5 times that of the
parent compound during the irradiation period. At a
pH of 8, although the percent removal was lower
than it was -at a pH of 4, toxicity decreased during
the illumination period (Lu and others 1993).
The UV/TiO2 process was tested in terms of
oxidation of atrazine (22 mg/L), simazine (20 mg/L),
and propazine (23 mg/L) in synthetic wastewater.
The by-products of UV/TiO2 photodegradation of all
3-11
-------
three compounds were ammeline; ammelide; and
1,3,5-triazine-2,4-diamine-6-chloro. Cyanuric acid
was the final product of the reactions (Pelizzetti and
others 1992).
The California Department of Health Services,
Sanitation and Radiation Laboratory tested the
UV/TiO2 process in destruction of 1,2-dibromo-3-
chloropropane (DBCP) in contaminated groundwater
taken from a polluted well in the vicinity of Fresno,
California. The initial DBCP concentration of
2.9 /j.g/L was decreased to 0.4 ^g/L (an 86 percent
removal) using 0.25 percent Ti02 catalyst on silica
gel and UV light (a 1-kW xenon lamp) in about
6 hours (Halmann and others 1992).
Degradation of carbofuran (220 mg/L) in synthetic
wastewater was studied using a UV7TiO2 process.
Under a 400-W medium-pressure mercury lamp and
TiO2-coate_d glass plates (with a surface coverage of
2.5 x 10~5 g/cm2), complete mineralization was
achieved after 15 hours of irradiation at a pH of 6. A
fluorescent compound appeared as an intermediate
during photooxidation. The degradation rate was
relatively low at high pH values (Tennakone and
others 1997).
Hua and others (1995) photodegraded
monocrotophos using the UV7TiO2 process. At a
flow rate of 0.030 liter per minute (L/min) and an
initial monocrotophos concentration of 11,000 mg/L,
51 percent of the compound degraded after 1 hour.
Addition of H2O2 to the UV/Ti02 system significantly
enhanced degradation, For example, when 62 mg/L
of H2O2 was added to a solution containing
10,000 mg/L of monocrotophos, 10 percent more
degradation was observed after 1 hour than was the
case with UWTiO2 alone.
Kinkennon and others (1995) studied UV/TiO2
degradation of the herbicides Basagran, Diquat, and
Diuron in synthetic wastewater at a concentration of
10 mg/L each. Under a 1 -kW high-pressure xenon
lamp, Basagran, Diquat, and Diuron concentrations
were reduced by 95 percent in 1 hour, 90 percent in
90 minutes, and 90 percent in 1 hour, respectively.
Pramauro and others (1993) applied the UWTi02
process to degrade Monuron, or 3-(4-chlorophenyl)-
l-l -dimethylurea, in synthetic wastewater. Light was
provided by a 1,500-W xenon lamp. With an initial
Monuron concentration of 20 mg/L, 100 mg/L of Ti02
catalyst, and a pH of 5.5, >99.9 percent removal of
the contaminant took place in 30 to 40 minutes. The
compound 4-chlorophenyl isocyanate was identified
as an intermediate that was decomposed after about
35 minutes of irradiation.
UV/TiO2 treatment of pendimethalin and alachlor at
initial concentrations of 100 and 51 mg/L,
respectively, was evaluated. Using a 120-W, high-
pressure mercury lamp and a TiO2 dose of
250 mg/L, 60 percent removal was achieved for
pendimethalin in 3 hours compared to only
10 percent degradation in the absence of Ti02.
Alachlor was degraded much more quickly under the
same conditions (95 percent removal in 20 minutes).
The by-products of pendimethalin degradation were
2,6-dinitro 3,4-dimethylaniIine and 6-nitro
3,4-dimethylaniline. The byproducts of alachlor
degradation were hydroxyalachlor and ketolachlor
(Moza and others 1992).
Pelizzetti and others (1989) studied degradation of
the herbicide Bentazon, or 3-isopropyl-2,1 ,3-
benzothiadiazin-4-one-2,2-dioxide, using the
UV/TiO2 process in a batch system. Using a
1,500-W xenon lamp and 50 mg/L of TiO2, the initial
Bentazon concentration of 20 ^g/L was reduced to
<0.1 /^g/L (>99.5 percent removal) after 10 minutes
of irradiation.
3.1.5 Dioxin- and Furan-Contaminated
Groundwa ter
Dioxins and furans have been removed-from
synthetic wastewater using the photo-Fenton
process at the bench-scale level. Pignatello and
Huang (1993) studied the fate of polychlorinated
dibenzo-p-dioxin (PCDD) and polychlorinated
dibenzofuran (PCDF) contaminants in the herbicide
2,4,5-trichlorphenoxyacetic acid (2,4,5-T) during
photo-Fenton treatment. PCDD and PCDF were
initially present at concentrations of 2.3 and
0.0016 uglL, respectively. The highest removals
were observed in aerated solutions at a pH of 2.8
and with an H202 dose of 1,700 mg/L. Under these
conditions, 89 to >99.9 percent removal of the PCDD
and PCDF was achieved in 1 hour except for
octachloro-dibenzofuran, which was degraded by
66 percent.
3.7.6 Explosive- and Degradation
Product-Contaminated
Groundwa ter
Explosives and their degradation products in
groundwater have been treated using the UV/H2O2
process at the commercial scale. Removal of
explosives and their degradation products from
groundwater using the UV/TiO2 process has been
evaluated at the bench scale. The results of the
commercial- and bench-scale evaluations are
discussed below.
3-12
-------
Commercial-Scale Applications
This section presents performance data from field
studies using the Calgon perox-pure™ and Calgon
Rayox® UV/H202 treatment systems to remove the
following explosives and their degradation products
from groundwater.
APO Process .
• UV/H202
Explosives and Their
Degradation Products
Rbmoved
Benzathiazole;
1,4-dithiane;NG;NQ;
1 ,4-oxathiane; RDX;
thiodiglycol;1,3,5-TNB
Calgon perox-pure™ UV/H2O2 System
A Calgon perox-pureiM UV/H2O2 system was used
to treat contaminated groundwater at the Old 0-Field
Site of Aberdeen Proving Ground in Maryland. The
groundwater contaminants at the Old 0-Field site
included thiodiglycol; 1 ,4-dithiane; and 1,4-oxathiane
at concentrations of 480, 200, and 82 //g/L,
respectively. Benzathiazole and 1,3,5-
trinitrobenzene (TNB) were also present in the
groundwater at concentrations of 20 and 15 ^g/L,
respectively. Four tests were conducted at a flow
rate of 60 L/min; the hydraulic retention time was
about 5 minutes. In Tests 1, 2, and 3, the H2O2
doses used were 45, 90, and 180 mg/L, respectively;
the doses in these tests were equally divided into
three parts and added by the splitter at (1) the
influent line to the first chamber, (2) the effluent line
from the first chamber, and (3) the effluent line from
the second chamber. In Test 4, a total H2O2 dose of
45 mg/L was added to the influent line to the first
reactor; the splitter was not used. The treated
effluent met federal MCLs for all compounds.
Removals of thiodiglycol; 1,4-dithiane; 1,4-oxathiane;
benzathiazole; and 1,3,5-TNB were >97, 98, 97, 82,
and 96 percent, respectively. No cost information
was provided for the system (Topudurti and others
1993).
Also, a Calgon perox-pure™ UV/H2O2 system was
used to treat groundwater at the former Nebraska
Ordnance Plant in Mead, Nebraska. site
groundwater contained 28 ^g/L of cyclonite (RDX),
the primary ordnance compound used at the site.
The 30-kW system used at the site consisted of six
5-kW lamps, each mounted horizontally above one
another in separate 6-inch reactor chambers. The
groundwater flowed in series in a serpentine pattern
to each reactor chamber. The field study was
performed at a (1) flow rate of 310 L/min, (2) pH of
7.0, (3) HA, dose of 10 mg/L, and (4) UV dose of
0.53 kWh/m The RDX concentration was reduced
by more than 82 percent. The total operating cost
for a system with a flow rate of 29,000 Umin was
estimated to be $0.02/m3 of water treated, which
includes the costs of power, lamp replacement, and
H2O2 (Calgon 1998).
Calgon ftayox® UV/H2O2 System
'A Calgon Rayox® UV/H202 system was installed at
the Indian Head Division, Naval Surface Warfare
Center, in Indian Head, Maryland, to treat
nitroglycerin (NG) production wastewater and
nitroguanidine (NO) wastewater. The system
reduced NQ levels from 2,700 . to 1 mg/L
(>99.9 percent removal) and NG levels from 1,000 to
1 mg/L (>99.9 percent removal) using a UV dose of
450 kWh/m3. By-products of NG degradation
included 1,2-dinitroglycerin (DNG); 1,3-DNG;
mononitroglycerin (MNG); nitrogen; nitrate; nitrite;
and ammonia. By-products of NQ degradation
included nitrate, nitrite, and ammonia. The treatment
cost for NG production wastewater was estimated to
be $13/m3 of water treated, and the cost for treating
NQ wastewater was estimated to be $34/m3 of water
treated (Hempfling 1997).
Bench-Scale Studies
Schmelling and Gray (1995) examined UV/TiO2
photodegradation of 2,4,6-trinitrotoluene (TNT) in a
slurry reactor. When a 50-mg/L solution of TNT was
treated using UV/TiO2 in the presence of O2, about
90 percent of the TNT was oxidized to carbon
dioxide in 2 hours. Oxidative by-products included
trinitrobenzoic acid, trinitrobenzene, and
trinitrophenol. In a subsequent study, the same
reaction was tested under conditions typically
observed in field applications. Schmelling and
others (1997) compared TNT degradation rates in
the UV/TiO2 process at pH levels of 5.0 and 8.5.
The degradation rate was higher at a pH of 5.0,
where >90 percent removal was observed in 1 hour;
3 hours was needed to achieve the same removal at
a pH of 8.5. When varying concentrations of humic
acids (1,10, and 20 mg/L representative of low,
medium, and high values observed in natural waters)
were added to TNT solutions, degradation rates
increased with increasing concentrations of humic
acid.
3-13
-------
3.1.7 Humic Substance-Contaminated
Groundwa ter
A UV/TiO2 process was used to remove a brown
discoloration in synthetic wastewater introduced by
humic acid, which was present at a concentration of
0.1 mg/L. The batch reaction took place under a
250-W, medium-pressure mercury lamp. During the
reaction, the discoloration decreased by half in about
12 minutes. However, it took 1 hour to mineralize
only 50 percent of the humic substances to carbon
dioxide and H2O. Some of the reaction by-products
were highly fluorescent (Eggins and others 1997).
3.1.8 Inorganic-Contaminated
Groundwa ter
Bench-scale treatment of cyanide (2.6 mg/L) in
synthetic wastewater (2.6 mg/L) was conducted
using a UV/ZnO process. At a pH of 11, and using
a ZnO dose of 8,000 mg/L, more than 95 percent of
cyanide was destroyed in 9 minutes. Reaction
by-products include cyanogen and the cyanate ion
(Domenech and Peral 1988).
3-14
-------
Table 3-1. Contaminated Groundwater Treatment
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST CONDITIONS
RESULTS
Percent Removal
Additional
Information
COST
(1998 U.S. Dollars)
REFERENCE
rOCs (Commercial Scale)
)V/H2O2
Calgon
lerox-pure™)
IV/H2O2
Calgon
erox-pure™)
V/H2O2
Saigon
erox-pure™)
V/H2O2
'algon
jrox-pure™)
Raw Groundwater
TCE: 890 to 1 ,300 ,ug/L
PCE: 71 to150yug/L
Spiked Groundwater
TCE: 690 to 1 ,000 uglL
PCE: 63 to 92 //g/L
1.1-DCA:120to 170^9/L
1,1,1-TCA: 110to130/jg/L
Chloroform: 140 to 240 Aig/L
1,2-DCE: 200 Mg/L
Benzene: 52 yug/L
Chloroform: 41 yug/L
1 ,2-DCA: 22 ^g/L
TCE: 21 M9/L
Methylene chloride: 8^g/L
Site_E£L
1 ,2-DCE: 11,000,ug/L
PCE: 2,500 ^g/L
TCE: 1 ,700 ^g/L
vc: 1,200 ^g/L
Site
CB: 3,100 /jg/L
vc: 1. 700 /ug/L
1 ,2-DCE: 430 ,ug/L
1.6DCB: 420 yug/L
1,1-DCA:400,ug/L
TCE: 50 to 400 mg/L
Flow rate: 38 to 150 L/min
Reactor volume: 57 L (total)
Light source: six 5-kW mercury lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 30 to 240 mg/L
Influent pH: 8.0. 6.5. 5.0
Flow rate: 60 L/min
Reactor volume: 300 L
Light source: four 15-kW mercury
lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 doses: 45, 90. 180 mg/L
Retention time: 5 min
Siie_E=i
Flow rate: 490 L/min
Light source: 90-kW system
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 50 mg/L
Influent pH: 5.5
Retention time: 2 min
Siie_E=a
Flow rate: 940 L/min
Light source: 270-kW system
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 100 mg/L
Influent pH: 5.1
Retention time: 4 min
Flow rate: 510 L/min
Reactor volume: not available
tight source: one 15-kW UV lamp
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: not available
TCE: >99.9
PCE: >98.7
1 ,I-DCA:>95.8
1,1,1-TCA: 92.9
Chloroform: 93.6
1.2-DCE:>99
Benzene: >96
Chloroform: >97
1,2-DCA:>92
TCE: >93
Methylene chloride:
>86
Site
1,2-DCE:>99.9
PCE: >99.9
TCE: >99.9
VC: >95.8
Site
CB: >99.9
vc: >97
1,2-DCE:>99.1
1,4-DCB:>99.5
I,1-DCA:>99.5
>99.7
Effluent acutely toxic to
freshwater test
organisms
Effluent not toxic to
freshwater test
organism
None
None
i
None
Case 1 : Raw
Groundwater
Remediation cost:
$2.10/m3
Calgon perox-pure"
cost: $0.89/m3
Case 2: Spiked
Groundwater
Remediation cost:
$3.30/m3
Calgon perox-pure™
cost: $1 .50/m3
Not available
Sltfi-Ezl:
For a 75-L/min System
Equipment cost:
$115,000
O&M cost:
$2.800/month
Kite 3 '
Fora 130-L/min
System
Equipment cost:
$241 ,000
O&M cost:
$13.000/month
O&M cost: $0.08/m3
Topudurti and
others 1994
Topudurti and
others 1993
Kllnk and
ithers 1992
U.S. EPA 1993
CO
I
en
-------
Table 3-1. Contaminated Groundwater Treatment (Continued)
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST CONDITIONS
RESULTS
Percent Removal
Additional
Information
COST
(1998 U.S. Dollars)
REFERENCE
VOCs (Commercial Scale) (Continued) •
UV/H2O2
(Calgon
Rayox )
UV/H2O2
Followed by Air
Stripper
(Calgon
Rayox®)
GAC Followed
by UV/H2O2
fCalgon
Rayox®)
JV/H2O2
[Magnum
DAV-OX®)
JV/H202
Magnum
JAV-OX®)
TCE: 4,700 ng!L
1 ,2-DCE:810;ug/L
PCE: 6.000 M9/L
1,1,1-TCA: 100 f^g/L
Methylene chloride: 60 nQlL
Methylene chloride: 6.9 /^g/L
TCE: 1 ,500 to 2,000 //g/L
Benzene: 250 to 500 ^glL
TPH: 190 mg/L
Flow rate: 1 .5 m3/min
Light source: four 15-kW UV lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 25 mg/L
Flow rate: 450 L/min
Light source: one 90-kW UV lamp
Wavelength: broad band with a peak
at 254 nm
H2OZ dose: 25 mg/L
Flow rate: 2,700 Umin (total)
Light source: four 90-kW UV lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: not available
Influent pH: 5.0
CAV-OX I System
Flow rate: 2.3 L/min
Light source: six 60-W UV lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 23 mg/L
CAV-OX II system
Flow rate: 5.3 Umin
Light source: 5-kW and 10-kW
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 48 mg/L
Flow rate: 38 Umin
Light source: 12 60-W UV lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 20 mg/L
TCE: 99.9
1 ,2-DCE: 91 .4
Before Air Stripper
PCE: 99.8
1.1,1-TCA: 20
Methylene chloride:
16.7
92.6
r.AY-DY 1 System,
TCE: 99.9
Benzene: 99.9
CAV-OX II System
TCE: 99.8
Benzene: 99.8
99.9
None
Percent Not a
Air Stripper
PCE: >99.9
1,1,1-TCA: >99
Methylene chloride:
>98.3
None
None
None
i
None
Equipment cost:
$110,000
O&M cost: $0.09/m3
v a i I a b I e
For a 2,700 L/m!n
Rayox®/GAC Systsm n
Equipment cost:
$730,000
O&M cost: $0.31/m3
CAV-OX-I System
Remediation cost:
$3.80/m3
Magnum cost:
$1.50/m3
CAV-OX II System
Remediation cost:
$4.07/m3
Magnum cost:
$1 .50/m3
CAV-OX 1 System
$0.47/m3
Weir and other:
1996
Bircher and
others 1996
Bircher and
hers 1996
U.S. EPA 1994
U.S. EPA 1994
U.S. EPA 1994
CO
I
O)
-------
Table 3-1. Contaminated Groundwater Treatment (Continued)
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST CONDITIONS
RESULTS
Percent Removal
Additional
Information
COST
(1998 U.S. Dollars)
REFERENCE
VOCs (Commercial Scale) (Continued) • •
UV/H2O2
(Magnum
CAV-K®)
UV/H2O2
(WEDECO)
LJV/O3
[WEDECO)
L)V/O3/H2O2
[U.S. Filter)
JV/O3/H2O2
US. Filter)
TCE: 1 .800 ^g/L
cis-1 ,2-DCE: 250 uglL
trans-1 ,2-DCE: 200 j/g/L
vc: 53 f/g/L
PCE: 11 ^g/L
1,2-DCA:54^g/L
ds-1 ,2-DCE: 46 f^g/L
Benzene: 310 ^g/L
Ethyl Benzene: 41 yug/L
vc: 34 uglL
TCE: 330 ^glL
PCE: 160 ng/L
TCE: 50 to 88 ^g/L
1,1-DCA:9.5to 13/jg/L
1,1,1-TCA:2to4.5A/g/L
TCE: 520 ^g/L
Flow rate and retention time: not
available
Reactor volume: not available
Light source: six 60-W UV lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 30 mg/L of 35 percent
H202
Flow rate: 3.8 to 15 L/min
Reactor volume: not available
Light source: two low-pressure
mercury lamps
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: not available
Flow rate: 10 m3/h
Light source: UV-C 30-mW/L
H2O2 dose: 5 mg/L
Flow rate: 0.14 mg3/min
Light source: 24 65-W UV lamps
Wavelength: broad band with a peak
at 254 nm
0, dose: 1 10 mg/L
H2O2 dose: 13 mg/L
Influent pH: 7.2
Retention time: 40 min
Flow rate: 20 to 38 L/min
Reactor volume: 2,700 L
Light source: 72 65-W lamps
Wavelength: broad band with a peak
at 254 nm
Oxidant doses: not available
TCE: 99.9
cis-1 ,2-DCE: >99.9
trans-1 ,2-DCE:>99.9
vc: >99.7
PCE: >98
1,2-DCA: 9
cis-1 ,2-DCE: >87
Benzene: 93
Ethylbenzene: 92
vc: 86
TCE: 99
PCE: 96.6
TCE: 99
1,1-DCA:.65
1,1,1-TCA: 87
>99
None
None
None
1,1-DCAand
1 .1 ,1-TCA removal due
to stripping by 0, and
oxidation
None
CAV-OX I System
$0.32/m3
(includes H2O2,
electricity,
maintenance, and lamp
replacement costs)
$0.39/m3
(includes electricity,
O&M, lamp
replacement, and H2O2
costs)
$0.1 9/m3
(includes electricity,
O&M, and equipment
costs)
Equipment cost:
$88,000 to
$320,000
O&M cost: $0.08 to
$5.60/m3
(depending on
pretreatment
requirements)
Equipment cost:
$380,000
O&M cost: $5/m3
Magnum 1998
WEDECO 1998
Leitzke and
Whltby 1990
Topudurti and
others 1993
U.S. EPA 1990
CO
-------
Table 3-1. Contaminated Groundwater Treatment (Continued)
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST CONDITIONS
RESULTS
Percent Removal
Additional
Information
COST
(1998 U.S. Dollars)
REFERENCE
(OCs (Commercial Scale) (Continued)
JV/TiO2
Matrix)
1 ,1-DCA:660to840A92
cis-1 ,2-DCE: 96
1 ,1-DCE: 97
TCE: 93
PCE: a2
Benzene: 99
Aldehydes and
haloacetlc acids
No acute toxicity
reduction for fathead
minnows and water
fleas
50 percent reduction in
equipment and
electrical energy costs
realized through H2O2
addition
Treatment cost:
$18/m3
Matrix direct cost:
$7.60/m3
Topudurti and
others 1998
VOCs (Pilot Scale)
UV/H2O2
Solar/TiO2
Solar/TiO.2/H2O2
Benzene: 35 ^g/L
TCE: 100mg/L
fotal BTEX: 2 mg/L
Flow rate: 3.2 m3/min
Light source: 360-kW reactor
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: not available
Influent pH: 6.8
Flow rate: 15 Umin
Light source: solar (>300 nm)
TiO2 dose: 800 to 900 mg/L
Influent pH: 5.6 and 7.2
Retention time: 10 minutes
Flow rate: 38 m3/day
Reactor volume: 530 L
Light source: not available
Wavelength: 380 nm
TiO2 dose: 0.5 to 1 .0 mg/L
H2O2 dose: 100 mg/L
Influent pH: 4-5
Retention time: 3 hours
98
TCE: 99 at pH 5.6;
91 at pH 7.2
50 to 75
Effluent pH adjusted
with sodium hydroxide
None
None
Not available
For 380-m3/day System
$0.83/m3
$20 to $29/m3
(including capital and
O&M costs)
Oldencrantz
and others
1997
Mehosand
Turchi 1993
Turchl and
others 1993
-------
Table 3-1. Contaminated Groundwater Treatment (Continued)
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST CONDITIONS
RESULTS
Percent Removal
Additional
Information
COST
(1998 U.S. Dollars)
REFERENCE
SVOCs (Commercial Scale)
UV/H2O2
(Calgon
perox-pure™)
UV/H2O2
(Calgon
Rayox®)
JV/H2O2
'Calgon
k 99.9
Phenol: 799.9
799.9
Flow stream to be
reinjected: 90
Flow stream to be
discharged: 99
None
None
None
None
5
For a 260-L/min
System
O&M cost: $1 .20/m3
(including electricity,
chemical, and general
maintenance costs)
Not available
For a 2,300-L/min
System
Operating cost:
$0.10/rrr
Operating cost:
0.36/m3
U.S. EPA 1993
Cater and
others 1990
Calgon 1996
Calgon 1996
'esticides and Herbicides (Pilot Scale)
JV/O3
Pesticides:
10; 100; 1,000 mg/L
(alachlor; atrazine; Bentazon;
butylate; Cyanazine; 2,4-D;
metolachlor; metribuzin;
trifluraline; carbofuran;
malathion)
Flow rate: 8-40 Umin
Light source: 66
UV lamps: 450 W
Wavelength: 254 nm
0, dose: not available
Influent pH: not available
Retention time: 20 to 60 min
Pesticides with initial
concentrations of 10
to 100 mg/L: >99.9
Pesticides with initial
concentrations of
1 ,000 mg/L: 75 to 85
None
Not available
Kearney and
others 1987
Explosives and Their Degradation Products (Commercial Scale)
JV/H2O2
Calgon
ierox-pure™)
Thiodiglycol: 480 ^g/L
1,4-Dithiane: 200jug/L
1,4-Oxathiane: 82 ^g/L
Benzathiazole: 20 ^g/L
1,3,5-TNB:15,ug/L
Flow rate: 60 Umin
Reactor volume: 300 L
Light source: four 15-kW mercury
lamps
Wavelength: not available
H2O2 doses: 45, 90, and 1 80 mg/L
Retention time: 5.3 min
Thiodiglycol: >97
1,4-Dithiane: ^98
1 ,4-Oxathiane: >97
tenzathiazole: >82
1 ,3.5-TNB: 96
Vendor: Calgon
perox-pure ™
Site: Old O-Field Site
Aberdeen Proving
Ground, Maryland
Not available
Topudurti and
others 1993
-------
Table 3-1. Contaminated Groundwater Treatment (Continued)
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST CONDITIONS
RESULTS
Percent Removal
Additional
Information
COST
(1998 U.S. Dollars)
REFERENCE
Explosives and Their Degradation Products (Commercial Scale) (Continued) : ••-. . ... v •• .
UV/H2O2
(Calgon
perox-pure™)
UV/H2O2
(Calgon
Rayox®)
RDX: 28 /^g/L
NG: 1 ,000 mg/L
NQ: 2,700 mg/L
Flow rate: 310 Umin
Reactoivolume: not available
Light source: six 5-kW lamps
UV dose: 0.53 kWh/m3
Wavelength: not available
H2O2 dose: 10 mg/L
pH = 7.0
Flow rate: not available (batch)
Reactor volume: not available
UV dose: 450 kWh/m3
Wavelength: not available
H2O2 dose: not available
>82
799.9
Former Nebraska
Ordnance Plant. NE
By-products
NG: 1,2-DNG; 1,3-
DNG; MNG;
nitrogen; nitrate;
nitrite; ammonia
NQ: nitrate, nitrite, and
ammonia
For a 29.000 L/min
System
$0.02/m3 (induding
power, lamp
replacement, H2O2,
and general
maintenance)
NG: $13/m3
NQ: $34/m3
Calgon 1998
Hempfling 1997
co
r^
o
-------
3.2 Industrial Wastewater Treatment
The effectiveness of APO technologies in treating
industrial wastewater has been evaluated for various
contaminant groups, including VOCs, SVOCs, dyes,
inorganics, and microbes. This section discusses
the APO technology effectiveness with regard to
each of these contaminant groups.
3.2.1 VOC-Contaminated Industrial
Wastewater
This section discusses treatment of VOCs in
industrial wastewater using the UV/H2O2 and photo-
Fenton processes on a commercial scale.
Information on VOC-contaminated industrial
wastewater treatment using the UV/H2O2 and
semiconductor-sensitized processes at the bench-
scale level is also included.
Commercial-Scale Applications
This section summarizes the effectiveness of the
Calgon perox-pure™ UV/H2O2 and Calgon Rayox®
photo-Fenton (ENOX) treatment systems in
removing the following VOCs from industrial
wastewater.
APO Process
• UV/H202
Photo-Fenton
VOCs Removed
. Acetone, isopropyl
alcohol
. Various solvents
(individual VOCs not
measured)
Calgon perox-pure™ UV/H2O2 System
In 1992, a Calgon perox-pure™ UV/H2O2 system
was installed at the Kennedy Space Center in Florida
to treat industrial wastewater. The primary
contaminants in the wastewater included acetone
(20 mg/L) and isopropyl alcohol (20 mg/L). A10-kW
Calgon perox-pure™ system initially treated 19,000-
to 23,000-L batches of contaminated water at the
site. The system was subsequently converted to a
flow-through mode and was operated at a flow rate
of 19 L/min and with an H2O2 dose of 100 mg/L. The
system achieved >97.5 percent removal for acetone
and isopropyl alcohol, meeting the treatment facility
discharge requirement. The total estimated O&M
cost reported by the vendor was at $1 .10/m3 of water
treated, which includes the costs of electricity
($0.61/m3), H2O2 ($0.18/m3), and general
maintenance (SO.StThf)1 {US? EPA 1993).
Calgon Kayox® Photo-Fenton (ENOX)
System
The Calgon Rayox® photo-Fenton (ENOX) system
was used to treat wastewater from a liquid crystal
display equipment manufacturing plant in Puerto
Rico. The wastewater contained various solvents
used to clean electronic components; no information
on the specific chemicals and their concentrations
was available. The wastewater COD level was
3,000 mg/L; its pH level was 11.1; and its alkalinity
level was 1,100 mg/L as calcium carbonate. A _
30-kW Rayox® photo-Fenton system was used to
treat the wastewater. At a UV dose of 160 kWh/m3,
the COD level was reduced to <50 mg/L, a
>98.4 percent removal. The total operating cost of
the treatment system was $44/m3 of water treated,
which includes the costs of electricity, lamp
replacement, H2O2, ENOX catalyst, and pH
adjustment (Calgon 1998).
Bench-Scale Studies
This section summarizes the results of bench-scale
studies of the effectiveness of UV/H2O2 and
semiconductor-sensitized processes in removing the
following VOCs from industrial wastewater.
APO Process
*
UV/H2O2
Solar/TiO2;
Solar/ZnO
VOCs Removed ---
. Various chlorinated
VOCs (individual
VOCs not measured)
. Chloroform,
dimethylamine,
methanol
UV/H2O2
Smeds and others (1994) evaluated the
effectiveness 'of the UV/H2O2 process in treating
spent chlorination wastewater from a kraft pulp mill.
The wastewater contained various chlorinated
organics and was characterized by measuring AOX
(1,300 g per ton of pulp processed). The highest
AOX removal (86 percent) was achieved at a
temperature of 100 °C over a pH range of 2 to 12;
pH had no significant effect on AOX removal;
Semiconductor-Sensitized Processes
Peyton and DeBerry (1981) evaluated the
effectiveness of semiconductor-sensitized processes
(solar/Ti02 and soiar/ZnO) in treating wastewater
contaminated with dimethylamine, methanol, and
chloroform. At the end of a 6-hour reaction period,
3-21
-------
multiple combinations of semiconductors and
reaction pH levels yielded various percent removals
for the three VOCs: (1) Ti02 at a pH of 10 reduced
the dimethylamine concentration by 55 percent,
(2) TiO2 at a pH of 7 reduced the methanol concen-
tration by 51 percent, and (3) ZnO at a pH of 7
reduced the chloroform concentration by 50 percent.
3.2.2 SVOC-Contaminated Industrial
Wastewater
This section discusses treatment of SVOCs in
industrial wastewater using the UV/H2O2 process on
a commercial scale. Information on SVOC removal
(1) at the pilot-scale level using the photo-Fenton
process and (2) at the bench-scale level using the
UV/03, photo-Fenton, and semiconductor-sensitized
processes is also included.
Commercial-Scale Applications
This section summarizes the effectiveness of the
Calgon Rayox® and Magnum CAV-OX® UV/H2O2
systems in removing the following SVOCs from
industrial wastewater.
APO Process
• UV/H2O2
SVOCs Removed
• NDMA, phenol, UDMH
Calgon Rayox® UV/H2O2 System
A Calgon Rayox® UV/H2O2 system was used to treat
NDMA-contaminated wastewater from a rubber
manufacturing company. The initial NDMA
concentration in the wastewater was 30 //g/L. The
Calgon Rayox® system, which was operated at a
flow rate of 45 L/min, reduced the NDMA
concentration in the wastewater by more than
98.3 percent. The treatment cost was estimated to
be $0.83/m3 of water treated, but details of this
estimate were unavailable (Calgon 1996).
In another Calgon Rayox® UV/H2O2 system
application, NDMA-contaminated process
wastewater from a specialty chemicals
manufacturing company was treated using a
380-L/min system. The wastewater contained
600 i^gll of NDMA and 1,000 mg/L of COD. The
system achieved >99.9 percent removal of NDMA;
no information was available on COD removal. The
treatment cost was estimated to be $1 .10/m3 of
water treated, but details of this estimate were
unavailable (Calgon 1996).
Aerospace industry wastewater contaminated with
NDMA and unsymmetrical dimethylhydrazine
(UDMH) at 1,400 and 6,000 mg/L,.respectively, was
treated using a Calgon Rayox® UV/H2O2 system.
The system treated about 1,500 Uday of wastewater
(in batch mode) and removed more than
99.9 percent of the NDMA from the wastewater. The
treatment cost was estimated to be $1 50/m3 of water
treated, but details of this estimate were unavailable
(Calgon 1996).
Magnum CAV-OX® UV/H2O2 System
The Magnum CAV-OX® II high-energy UV/H2O2
system was field-tested to treat effluent from a
pharmaceutical plant. The wastewater contained
phenol at 20 /j.g/L. Three tests were conducted at
flow rates of 7.6, 15, and 23 L/min. H2O2 was used
at a dose of 60 mg/L. At flow rates of 7.6, 15, and
23 L/min, the percent removal of phenol was >99.9,
99, and 96 percent, respectively. No treatment cost
information was available (U.S. EPA 1994).
Pilot-Scale Application
This section summarizes removal of 3,4-xylidine
from industrial wastewater at the pilot-scale level
using the photo-Fenton process. Wastewater
containing 3,4-xylidine at an initial concentration of
2,700 mg/L was treated using the photo-Fenton
process in a recirculating batch reactor. A total of
500 L of wastewater was treated in each batch. With
a UV dose of 20 W/L, an H202 dose of 4,200 mg/L,
a ferrous sulfate dose of 3,000 mg/L, and a pH of 3,
more than 99.9 percent of the 3,4-xylidine had been
removed after 30 minutes of treatment. The H2O2
concentration had less effect than the ferrous sulfate
concentration on 3,4-xylidine removal (Oliveros and
others 1997).
Bench-Scale Studies
This section summarizes the results of bench-scale
studies of the effectiveness of UV/O3, photo-Fenton,
and semiconductor-sensitized processes in
removing the following SVOCs from industrial
wastewater.
3-22
-------
APO Process £
. UV/03
Photo-Fenton
. Solar/ZnO
VOCs Removed
. 4-CP, phenol, several
reactive azo dyes,
several unspecified
svocs
. 4-CP, several reactive
azo dyes
. Phenol
UV/03
Beltran and others (1997a, 1997b) evaluated the
UV/O3 process's effectiveness in treating distillery
and tomato processing plant wastewaters containing
phenols and other chemicals. The UV/O3 process
achieved 90 percent COD removal from tomato
processing plant wastewater compared to 30 to
50 percent using ozonation alone. The UV/O3
process also achieved the highest COD removal for
distillery wastewater; the percent removal was not
reported. For both wastewaters, the UV/O3 process
was found to be significantly more effective than UV
photolysis and UV/H2O2 processes.
Photo-Fenton
Industrial dye wastewater containing 4-CP and a
mixture of reactive azo dyes was used to compare
the effectiveness of UV/O3, UV/H2O2, UV/TiO2, and
photo-Fenton processes. Under laboratory
conditions, 4-CP had been degraded by 75 percent
after 90 minutes of wastewater treatment in the
photo-Fenton process; this process was also found
to be the most effective mineralizing 4-CP (Ruppert
and others 1994).
Chen and others (1997) evaluated various APO
processes, including the UV/H2O2 and photo-Fenton
processes, for phenol and COD removal from
industrial wastewaters. They concluded that the
photo-Fenton process achieved the highest phenol
and COD removal rates of the processes evaluated.
Phenol at an initial concentration of 25 mg/L was
reduced by more than 99.9 percent in 10 minutes
under the following test conditions: a UV-A light
intensity of 4 kilowatts per liter; H2O2 dose of
70 mg/L; and ferric chloride dose of 8.1 mg/L. No
details on COD removal were available.
Semiconductor-Sensitized Processes
Peyton and DeBerry (1981) evaluated the
effectiveness of semiconductor-sensitized processes
(solar/TiO2 and solar/ZnO) in treating wastewater
contaminated with phenol. At the end of a 6-hour.
reaction period, the highest phenol removal
(53 percent) was achieved using ZnO at a pH of 7.
3.2.3 Dye-Contaminated Industrial
Wastewater
Dyes have been removed from industrial wastewater
using UV/H2O2, UV/O3, and semiconductor-
sensitized processes. This section describes the
use of these processes in pilot-scale applications
and bench-scale studies.
Pilot-Scale Applications
This section summarizes the removal of the following
dyes from industrial wastewater at the pilot-scale
level using the UV/H2O2 process.
APO Process
• UV/H202
Dyes Removed
Reactive Blue 21,
Reactive Red 195,
unspecified
A pilot-scale UV/H202 system was installed at a pulp
and paper mill in South Carolina to remove colored
organics from industrial wastewater. The
wastewater also contained chlorinated organics; the
specific chemicals and their concentrations are
unknown. A UV dose of 80 milliwatts per square
centimeter-second (mW/cm2-sec) was maintained.
An 80 percent color removal was achieved at an
H2O2 dose of 840 mg/L and a flow rate of 190 L/min.
In general, increasing H2O2 concentration resulted in
an increase in color removal. Color reduction was
not influenced by pH, indicating that the bleaching
operation wastewater did not have to be pretreated
for pH adjustment. Specific treatment cost estimates
were not available (Smith and Frailey 1990).
Also on the pilot scale, the UV/H2O2 process was
applied to spent reactive dyebath wastewater
containing Reactive Blue 21 and Reactive Red 195
at initial concentrations of 300 and 20 mg/L,
respectively. The highest removals were achieved
at H2O2 doses of 3,000 and 1,000 mg/L for Reactive
Blue 21 and Reactive Red 195, respectively. The
UV/H202 process was 'most effective with a neutral
pH. Specific percent removals were not available
(Namboodri and Walsh 1996).
Bench-Scale Studies
This section summarizes information on removal of
the following dyes from actual and simulated
industrial wastewaters at the bench-scale level using
3-23
-------
UV/H2O2? UV/O3, and semiconductor-sensitized
processes.
APO Process D
yes Removed
UV/H202
UV/03
UV/TiO,
UV/Ti02/SnO2
Acid Black 1,
Reactive Black 5,
Reactive Orange 16,
Vat Blue 6,
Vat Red 10
. Several unspecified
dyes
. Acid Blue 40, Basic
Yellow 15, Direct
Blue 87, Direct Blue
160, Reaction
Red 120, several
unspecified dyes
Acid Orange 7
UV/H202
Shu and others (1994) evaluated the effect of pH on
UV/H2O2 process effectiveness in treating synthetic
wastewater containing azo dyes; they used Acid
Black 1 as the model compound. Optimum
degradation was observed in the pH range of 3.0 to
5.2. Other information, such as percent removal
data, was unavailable.
Unkroth and others (1997) used an excimer laser as
an alternative to mercury lamps in treating
commercial coloring agents for linen. The laser was
used to irradiate four dyes-Reactive Orange 16,
Reactive Black 5, Vat Red 10, and Vat Blue 6-at
UV wavelengths of 193 nm (argon-fluorine) and
248 nm (krypton-fluorine). Greater decolorization
was achieved at the shorter wavelength. When laser
irradiation at 193 nm was coupled with use of H2O2,
almost complete oxidation of the dyes was achieved
with 2 to 7 times less energy. Vat dyes, which need
about 10 times higher energy doses for removal than
do reactive dyes, were reduced from 25 mg/L to
about 2 mg/L, a 92 percent removal. Irradiation with
mercury lamps heated the wastewater to 60 °C,
while laser irradiation did not alter the wastewater's
temperature.
UV/03
Biologically pretreated paper mill wastewater
containing 70 to 600 mg/L of COD as a result of dye
processes was treated using the UV/03 process.
Reaction by-products formed include sulfuric acid
and oxalic acid. High temperatures (40 °C) and high
pH values (9 and above) resulted in high 03
consumption. A temperature increase from 25 to
40 °C and variations in pH levels did not significantly
affect the process's effectiveness. The estimated
UV/03 treatment cost, based on biologically
pretreated effluent with 400 mg/L of COD and
80 percent COD removal, was $2.38/m3 of water
treated, which includes electricity, capital, and
maintenance costs (Oeller and others 1997).
Semiconductor-Sensitized Processes
Li and Zhang (1996) evaluated the effectiveness of
the UV/TiO2 process in treating synthetic wastewater
containing eight dyes at an initial concentration of
100 mg/L each. Under a black light in a batch
reactor and with a TiO2 dose of 1,000 mg/L, color
removal was >95 percent after 4 to 6 hours of
treatment. COD and TOC removals from the
wastewater ranged from 30 to 70 percent, depending
on the dyes present. Biochemical oxygen demand
(BOD) increased as COD and TOC decreased,
suggesting that UV/TiO2 photooxidation may
enhance the biodegradability of the wastewater and
may require postbiological treatment.
Tang and An (1995a, 1995b) studied UWTiO2
treatment of synthetic wastewater containing five
commercial dyes: Acid Blue 40, Basic Yellow 15,
Direct Blue 87, Direct Blue 160, and Reaction
Red 120. The initial concentration of each dye was
about 100 mg/L. More than 5 hours was required to
completely mineralize the dyes. At higher dye
concentrations, reaction rates and percent removals
were lower. The oxidation rate decreased as the
number of azo linkages in a dye molecule increased.
A UV/TiO2 process was used in batch studies to
remove COD in and decolorize the wastewater from
5-fluorouracil manufacturing. Complete decolori-
zation and significant COD removal were achieved
in 20 hours of reaction time. Addition of H2O2 to the
UV/TiO2 system significantly increased the
decolorization and COD removal rates. Diluting the
wastewater also increased the COD removal rate.
Direct photolysis resulted in no COD reduction but
did achieve color reduction (Anheden and others
1996).
Textile dye effluent containing Acid Orange 7 was
treated using UV/TiO^tin oxide (SnO2) process. At
an initial concentration of 42 mg/L, the dye was
degraded by 95 percent after irradiation for.
30 minutes. The optimum mass ratio of the two
semiconductors for fastest degradation of Acid
Orange 7 was 2:1, Sn02 to TiO2 (Vinodgopal and
Kamat 1995).
3-24
-------
3.2.4 Inorganic-Contaminated
Industrial Wastewater
This section presents information on the following
inorganics removal from industrial wastewater at the
bench-scale level using semiconductor-sensitized
processes. No commercial- or pilot-scale
information is available.
APO Process
Solar/TiO2
• UV/TiO2
Inorganics Removed
Free and complexed
cyanide, hexacyanate
Ferricyanide
Rader and others (1993) achieved >99.9 percent
cyanide removal in 11 days while using a solar/TiO2
process to treat hexacyanate solution. In a later
study, Rader and others (1995) were able to achieve
>99.9 percent free and complex cyanide removal
from precious metal mill effluent containing cyanide
at 48 mg/L in 3 days. In both cases, nitrate
formation was observed, indicating complete
oxidation of cyanide.
Aqueous ferricyanide solution (26 mg/L as cyanide)
was treated using TiO2 and a 4-W UV lamp or solar
radiation in a bench-scale study. The highest
removal rate was observed at a pH of 10.
Photodegradation of ferricyanide using a 4-W UV
lamp resulted in 93 percent degradation after
9 hours, while with solar radiation, more than
99.9 percent of the ferricyanide was removed in
1.5 hours (Bhakta and others 1992).
3.2.5 Microbe-Contaminated industrial
Wastewater
This section discusses removal of microbes
(Salmonella) from industrial wastewater at the
commercial-scale level using a Magnum CAV-OX®
UV/H2O2 system. No' pilot- or bench-scale
information was available.
The Magnum CAV-OX® UV/H2O2 system was
evaluated during treatment of pathogens in
wastewater associated with chicken farming. The
primary contaminant of concern in the wastewater
was the bacterium Salmonella. The concentration of
this bacterium in the influent was about 1 million
colony-forming units per milliliter (cfu/mL). Tests
were conducted at Perdue Farms in Bridgewater,
Virginia, using a CAV-OX® I low-energy unit and a
CAV-OX® II high-energy unit. The wastewater was
processed through the CAV-OX® units at a flow rate
of 3.8 L/min. The CAV-OX® I unit was operated with
six 60-W UV lamps, and the CAV-OX® I! unit was
operated with two UV lamps of 2.5 to 5-kW intensity.
The H2O2 dose was 80 mg/L. Under these
conditions, the CAV-OX® II unit performed much
better than the CAV-OX® I unit. The final
concentration of Salmonella exiting the CAV-OX® II
unit was 0.01 cfu/mL (>99.9 percent removal). No
cost information was provided (U.S. EPA 1994).
3-25
-------
Table 3-2. Industrial Wastewater Treatment
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST CONDITIONS
RESULTS
Percent Removal
Additional information
COST
(1998 U.S. Dollars)
VOCs (Commercial Scale)
UV/H2O2
(Calgon
perox-pure™)
Photo-Fenton
(Calgon Rayox
ENOX)
Acetone: 20 mg/L
Isopropyl alcohol:
20 mg/L
COD: 3,000 mg/L
Individual VOC
concentrations unknown
Flow rate: 19 Umin
Light source: 10-kW
Wavelength broad1 band1 wflft a peak
at 254 nm
H2O2 dose: 100 mg/L
Flow rate: batch/recycle
Reactor volume: not available
UVdose:160kWh/m3
Wavelength: not available
H2O2 dose: not available
nfluent pH: 11.1
Alkalinity: 1 ,1 00 mg/L as calcium
carbonate
Acetone: >97.5
sopropyl alcohol: >97.5
>98.4
Treatment of Kennedy
Space Center wastewater
Treatment of electronics
industry wastewater
Met COD regulatory limit
'$1 .10/m3 (including
electricity, H2O2, and
maintenance costs)
$44/m3 (including
electricity, lamp
replacement, H2O2,
ENOX catalyst, and pH
adjustment costs)
REFERENCE
I.S. EPA 1993
lalgon 1998
SVOCs (Commercial Scale) j
UV/H202
(Calgon Rayox )
UV/H2O2
(Calgon Rayox )
UV/H2O2
(Calgon Rayox )
UV/H202
(Magnum
CAV-orii)
NDMA: 30 /jg/L
NDMA: 600 /jg/L
COD: 1,000 mg/L
NDMA: 1,400 mg/L
UDMH: 6,000 mg/L
Phenol: 20 ^g/L
Flow rate: 45 Umin
Reactor volume: not available
Light source: proprietary UV lamps
Wavelenath: not available
H2O2 dose: not available
Flow rate: 380 Umin
Reactor volume: not available
Light source: proprietary UV lamps
Wavelength: not available
H-,Oo dose: not available
Flow rate: not applicable (batch)
Reactor volume: not available
Light source: proprietary UV lamps
Wavelength: not available
H,O, dose: not available
Flow rate: 7.6 L/min
Reactor volume: not available
Light source: 2 UV lamps of 2.5 to
5-kW intensity
Wavelength: broad band with a peak
at 254 nm
H2O2 dose: 60 mg/L
>98.3
NDMA: >99.9
COD: not available
MDMA: >99.9
JDMH: not available
>99.9
Treatment of rubber
manufacturing industry
wastewater
Treatment of specialty
chemical industry
wastewater
Treatment of aerospace
industry wastewater
Treatment of
pharmaceutical industry
wastewater
$0.83/m3
$1 .10/m3
$150/m3
Not available
Calgon 1996
Calgon 1996
Dalgon 1996
J.S. EPA 1994
CO
M
CD
-------
Table 3-2. Industrial Wastewater Treatment (Continued)
PROCESS CONTAMINANT
(SYSTEM) CONCENTRATION TEST CONDITIONS
RESULTS
Percent Removal
Additional Information
COST
(1998 U.S. Dollars)
REFERENCE
SVOCs (Pilot Scale)
Photo-Fenton
3,4-Xylidine: 2,700 mg/L
Flow rate: not applicable
(recirculating batch)
Reactor volume: 500 L
Reaction time: 30 minutes
Wavelength: not available
UV dose: 20 W/L
H2O2 dose: 4,200 mg/L
Ferrous sulfate dose: 3,000 mg/L
Influent pH: 3
>99.9
Not available
Not available
Dyes (Pilot Scab
UV/H2O2
Microbes (Comn
UV/H2OZ
(Magnum
cAv-oni)
Colored and chlorinated
organics: not available
Flow rate: 190 Umin
Reactor volume: not available
Light source: two Teflon-based UV
lamps
Wavelength: 254 nm
UV dose: 80 mW/cm2-sec
H2O2 dose: 840 mg/L
Influent pH: 10-11
Colon 80
Chlorinated organics:
not available
None
Not available
Oliveros and
Ars 1997
1
1
l_
Smith and
Frailey 1990
srcial Scale) : : : ^ : \A • •''.'••
Salmonella:
1 million cfu/mL
Flow rate: 3.8 L/min
Reactor volume: not available
Light source: 2 UV lamps of 2.5- to
5-kW intensity
Wavelength: broad band with a peak
at 254 nm
H,O, dose: 80 mg/L
>99.9
Treatment of poultry
industry wastewater
Not available
U.S. EPA 1994
GO
N>
-------
3.7 References
Alberici, R.M., and W.F. Jardim. 1994.
"Photocatalytic Degradation of Phenol and
Chlorinated Phenols Using Ag-TiO2 in a Slurry
Reactor." Water Research. Volume 28,
Number 8. Pages 1845 through 1849.
Anheden, M., D.Y. Goswami, and G. Svedberg.
1996. "Photocatalytic Treatment of Wastewater
from 5-Fluorouracil Manufacturing." Journal of
Solar Energy Engineering. Volume 118.
Pages 2 through 8.
Armon, R., N. Laot, N. Narkis, and I. Neeman. 1996.
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Section 4
Contaminated Air Treatment
APO has been demonstrated to be an effective
technology for treatment of contaminated air.
Matrices to which APO has been applied include the
following: (1) soil vapor extraction (SVE) off-gas,
(2) air stripper off-gas, (3) industrial emissions, and
(4) automobile emissions. Collectively, APO has
been applied to the following types of airborne
contaminants: VOCs, SVOCs, explosives and their
degradation products, and nitrogen oxides (NO,).
To assist an environmental practitioner in the
selection of an APO technology to treat
contaminated air, this section includes
(1) commercial-scale system evaluation results for
the UV/03, UV/catalyst, and UV/TiO2 processes and
(2) pilot-scale system evaluation results for the
UV/TiO2, solar/TiO2, and UV/O3 processes. This
section also presents supplemental information from
bench-scale studies of APO processes.
As described in Section 1.2, this handbook
organizes the performance and cost data for each
matrix by contaminant group, scale of application
(commercial, pilot, or bench), and APO system or
process used. In general, commercial- and
pilot-scale applications are discussed in detail. Such
discussions include, as available, a system
description, operating conditions, performance data,
and system costs. Bench-scale studies of APO
processes are described in less detail and only if
they provide information that supplements
commercial- and pilot-scale evaluation results. At
the end of each matrix section, a table is provided
that summarizes operating conditions and
performance results for each commercial- and
pilot-scale study discussed'in the text.
4.1 SVE Off-Gas Treatment
APO has been shown to be an effective treatment
technology for VOC-contaminated off-gas from SVE
systems. Treatment systems based on UV/O3,
UV/catalyst, and UV/TiO2 processes have been
developed at the commercial scale. A treatment
system based on the UV/Ti02 process has been
demonstrated at the pilot-scale level. Bench-scale
studies of the VUV, UV/O3, and UV/TiO2 processes
also have been performed. Commercial- and
pilot-scale VOC treatment system performance and
cost data, where available, are provided below.
Summaries of the bench-scale studies follow the
commercial- and pilot-scale system discussions.
Commercial-Scale Applications
Treatment of VOC-contaminated SVE off-gas using
APO has been demonstrated at the commercial
scale at a wide range of concentrations (1 to
4,000 ppmv). This section discusses the
effectiveness of the PTI UV/O3, KSE AIR
UV/catalyst, and Matrix UV/Ti02 treatment systems
in removing the following VOCs from SVE off-gas.
APO Process
UV/O3
•UV/Catalyst
• UV/TiO2
VOCs Removed
. cis-1,2-DCE;PCE;
TCE; toluene;
total VOCs
Carbon tetrachloride,
methane, PCE, TCE,
toluene,
trimethylbenzene,
xylene
. PCE;1,1,1-TCA;TCE
In application of these systems, removals exceeding
90 percent for TCE; PCE; 1,1,1-TCA; and toluene
have been achieved. Removals of cis-1,2-DCE and
methane have not met with the same success. As
discussed below, VOC removal is a function of the
system used as well as the contaminant type and
concentration. Of the three systems that have been
demonstrated, cost data was available only for PTI's
UV/03 system.
PTI UV/O3 System
A PTI UV/O3 system was field-tested using
VOC-contaminated off-gas drawn from an SVE
system at Site 9 of Naval Air Station North Island in
San Diego County, California (PTI 1998). Feed gas
for the PTI system was supplied by a slipstream of
off-gas from the SVE system. Before entering the
PTI system, the SVE off-gas passed through an
air-water separator to remove any free moisture.
Make-up air was also used to vary the flow and
concentration of contaminants.
The primary contaminants in the SVE off-gas at
Site 9 included PCE; TCE; cis-1,2-DCE; and toluene.
Total VOCs entering the PTI system ranged in
concentration from 1,000 to 1,100 ppmv as carbon.
The primary VOCs in the feed gas were as follows:
PCE (31 ppmv); TCE (28 ppmv); cis-1,2-DCE
(22 ppmv); and toluene (14 ppmv). For the test, the
4-I
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PTI system operated at steady state for about
18 days, during which time the system achieved
89 percent on-line availability. The maximum flow
rate treated was 12 scmm.
During the field test, the average removal for total
VOCs was 95.9 percent. Average removals for
primary VOCs were as follows: 89.7 percent for
PCE; 80.8 percent for TCE; 74.0 percent for
cis-1,2-DCE; and 93.1 percent for toluene. Reaction
by-products analyzed for during the test included
hydrochloric acid (HCI), chlorine, phosgene, and
carbon monoxide (CO). HCI, chlorine, and
phosgene were measured at the PTI system outlet
at 0.18, 0.04, and 11 parts per billion by volume
(ppbv), respectively. The amount of CO produced in
the PTI system was determined to be between 31
and 56 ppmv.
Although PTI did not report treatment costs for the
system demonstrated, it used results from the test to
scale up costs for an 85-scmm system; 85 scmm
was the flow capacity of the SVE system at Site 9.
PTI's estimated equipment and operating cost at the
site was $3.80/pound of VOC treated, assuming
(1) use of an 85-scmm system; (2) treatment of
95,000 pounds of VOCs per year for 3 years; and
(3) 95 percent removal of the VOCs treated.
KSE AIR UV/Catalyst System
The KSE AIR UV/catalyst system was demonstrated
using VOC-contaminated off-gas from an SVE
system at Loring Air Force Base in Aroostook
County, Maine (Kittrell and others 1996a). This
demonstration was conducted in coordination with
the U.S. EPA SITE Emerging Technology Program.
KSE's AIR system contains KSE's proprietary
catalyst and 60 UV lamps. Information on the
composition of the catalyst and the wavelength of the
UV lamps was not available.
The primary contaminants in .the SVE off-gas
included PCE and methane. Over a 30-day period
of system evaluation, PCE concentrations in the SVE
off-gas varied significantly, diminishing from
150 ppmv during the first few days to <1 ppmv at the
end of the demonstration. Methane concentrations
ranged from 2,000 to 4,000 ppmv throughout the
demonstration. Additional VOCs identified at low
levels <1 ppmv in the off-gas included toluene,
xylene, TCE, trimethylbenzene, and carbon
tetrachloride. The flow rates treated ranged from 1.4
to 2.0 scmm.
For most of the demonstration, the KSE system
achieved >99 percent removal of PCE, while
methane removal was minimal. KSE attributed the
minimal methane removal to the catalyst
composition, which had been selected for PCE
removal.
Matrix UV/Ti02 System
The Matrix UV/TiO2 system was field-tested using
VOC-contaminated off-gas drawn from an SVE
system located at the U.S. Department of Energy
Savannah River Superfund site in Aiken, South
Carolina (Anonymous 1995). The Matrix system
consisted of a fluorescent lamp (with UV output of
300 to 400 nm) encased by a fiberglass mesh sleeve
coated with Ti02 catalyst. Before entering the
system, SVE off-gas passed through a cyclone
separator . and filter to remove moisture and
particulates, respectively.
The primary contaminants in the SVE off-gas at the
site included TCE; PCE; and 1 ,1 J-TCA. TCE and
PCE concentrations in the SVE off-gas ranged from
110 to 190 ppmv and 700 to 1,200 ppmv,
respectively. The feed stream concentration of
1 ,1,1-TCA was not reported. The flow rates treated
for the test ranged from 0.0028 to 2.8 scmm;
however, performance data is available for only
three flow rates: 0.71, 1.4, and 2.1 scmm.
VOC removals varied widely during the test period.
For instance, TCE removal varied from 49.5 to
98.1 percent. The highest TCE removal
(98.1 percent) was achieved when, the feed stream
TCE concentration was 160 ppmv and the flow rate
was 0.71 scmm. Similarly, PCE removals varied
widely,, ranging from 52.7 to 95.2 percent. The
highest PCE removal (95.2 percent) was achieved
when the feed stream PCE concentration was
1,200 ppmv and the flow rate was 0.71 scmm. The
Matrix system did not remove 1,1,1 -TCA.
Small quantities of carbon tetrachloride, chloroform,
dichloroacetyl chloride (DCAC), hexachloroethane,
methylchloroformate, pentachloroethane, and
trichloroacetyl chloride were identified as reaction
by-products. The chemical-specific concentrations
were not available.
Pilot-Scale Application
A pilot-scale UV/TiO2 system developed by
researchers at the University of Wisconsin in
Madison was field-tested using VOC-contaminated
off-gas drawn from an SVE extraction well in the
M area of the Savannah River site in Aiken, South
Carolina (Read and others 1996). The UV/TiO2
system consisted of two photoreactor flow cells
4-2
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(each 9.2 x 10"4 m3) packed with TiO2 catalyst.
Positioned in the middle of each flow cell was a
long-wave, 40-W fluorescent UV black light lamp.
The UV output was not reported.
The primary contaminants in the SVE off-gas
included TCE (56 to 290 ppmv) and PCE (2,300 to
3,860 ppmv). Additional VOCs present at lower
levels were 1,1,1-TCA (up to 38 ppmv) and 1 ,1-DCE
(up to 150 ppmv). System performance was also
evaluated using diluted VOC concentrations.
Dilution of the SVE off-gas was achieved by adding
ambient air to the feed stream upstream from the
UV/TiO2 system. Dilution resulted in the following
chemical-specific feed stream concentrations:
<80 ppmv for TCE; <800 ppmv for PCE; below
detection limit (1 ppmv) for 1,1,1 -TCA and 1,1 -DCE.
During 8 days of system operation, system
temperature ranged from 75 to 110 °C, and the flow
rate ranged from 5.0 x 10"4 to 6.0 x 10~3 scmm. 0,
was added to the system at 5.0 x 10"4 scmm near
the end of the field test to evaluate its effect on
system performance.
Under both undiluted and diluted feed stream
conditions, removals exceeding 97 percent were
observed for TCE; PCE; 1,1,1-TCA; and 1 ,1-DCE.
Treatment of the undiluted off-gas, however, yielded
significantly more reaction by-products. The reaction
by-products identified included phosgene,
chloroform, carbon tetrachloride, pentachloroethane,
and hexachloroethane. After the feed stream was
diluted with ambient air to reduce the total VOC
concentration to below 1,000 ppmv, reaction
by-products identified under undiluted conditions,
except for hexachloroethane, were reduced to below
1 ppmv; hexachloroethane was detected at
concentrations of <10 ppmv. The highest VOC
removals occurred when supplemental 0, was
added to the system. Specifically, TCE and PCE
removals exceeded 99.9 percent when their
concentrations in the feed stream were 66 and
502 ppmv, respectively. The concentrations of all
reaction by-products previously identified, including
hexachloroethane, were reduced 'to <1 ppmv.
However, according to Read and others (1996),
addition of 0, would not be cost effective for a
full-scale system.
Bench-Scale Studies
The treatment of VOCs using VUV, UV/03, and
UV/Ti02 processes has been evaluated at the
bench-scale level using synthetic matrices. Many
bench-scale studies have been conducted to
evaluate the effect of several key UV/Ti02 process
variables. In contrast, the VUV and UV/O,
processes have received much less attention despite
bench-scale results indicating that these processes
provide effective treatment of certain types of
contaminants. This section provides information that
supplements commercial- and pilot-scale evaluation
results for removing the following VOCs from
contaminated air matrices including SVE off-gas,.
A P O P r o c
ess VOCs Removed
UV/O,
Carbon tetrachloride,
chloroform,
trichlorofluoroethane
Carbon tetrachloride;
chloroform; PCE;
1,1,1-TCA; TCE
Acetic acid, acetyl
aldehyde; acetone;
benzene; 1 -butanol;
butylraldehyde; ethanol;
formaldehyde; formic acid;
methyl mercaptan; PCE;
2-propanol; 1,1,1 -TCA;
TCE; toluene; xylenes
VUV Photolysis
Treatment of three halogenated methanes (carbon
tetrachloride, chloroform, and trichlorofluoroethane
[CFC-113]) was studied by Loraine and Glaze (1992)
using a VUV system. For this study, VUV conditions
were established using a xenon-xenon excimer lamp
with a maximum UV output at 172 nm. The study
showed that carbon tetrachloride and chloroform
were removed by a pseudo-first-order process, while
CFC-113 was removed by a zero-order process.
Removals of 95 percent were achieved for all three
VOCs using the following run times: 25 minutes for
carbon tetrachloride, 16 minutes for chloroform, and
238 minutes for CFC-113. The initial VOC
concentrations and reaction by-products were not
reported.
UV/03
The removal kinetics of three saturated VOCs
(carbon tetrachloride; 1 ,1,1-TCA; and chloroform)
and two unsaturated VOCs (TCE and PCE) using
the UV/O3 process were studied by Bhowmick and
Semmens (1994). For this study, two UV lamps
were used: one UV lamp with its predominant output
at 254 nm and with a small output at 185 nm (about
5 percent), and one UV lamp with output only at
254 nm. For the saturated VOCs, the study showed
that removal rates were higher for the lamp with
output at 254 and 185 nm and that the rates were
4-3
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unaffected by addition of 0,. The removal rates
were also higher for unsaturated VOCs using the
lamp with output at 245 and 185 nm; however,
addition of 0, improved the removal rates for TCE
and PCE up to 30 and 12 percent, respectively. 0,
was most effective for removing the unsaturated
compounds at concentrations between 2 and
3 mg/L. Removals of both the unsaturated and
saturated VOCs followed first-order kinetics, and the
rate constants were an order of magnitude higher for
the unsaturated VOCs than for the saturated VOCs.
In addition, moisture was found to favor the
chloroform; 1 ,1,1 -TCA; and TCE removal kinetics but
had no impact on the PCE and carbon tetrachloride
removal kinetics. Phosgene was identified as a
reaction by-product.
UV/Ti02
Treatment of VOCs using the UV/Ti02 process at the
bench-scale level has received significant attention.
Bench-scale studies of interest have focused on
evaluating the effects of the following key process
variables: supplemental oxidants (0,, O3, and H2O2),
water vapor, co-catalysts, reaction pressure, and
co-contaminants. Additional bench-scale UV/TiO2
studies have evaluated removal of high-level VOC
concentrations and formation of reaction
by-products. Summaries of these bench-scale
UV/TiO2 studies are provided below. Some of the
studies evaluated more than one process variable;
such studies are described with emphasis on the
process variable for which supplemental information
is called for herein.
Effect of Supplemental Qxidants
Several bench-scale studies have demonstrated that
oxidants such as O2, O3, and H p 2 can enhance
VOC removals by the UV/Ti02 processes. For
instance, Wang and Marinas (1993) evaluated the
effect of adding 0, on removal of TCE by the
UV/TiO2 process. This study was conducted with
reactor inlet TCE and 0, concentrations ranging
from 5 to 7 ppmv and 24 to 2,700 ppmv,
respectively, and in the absence of humidity. The
study showed that TCE removals increased from 30
to 88 percent with increasing 0, concentrations up
to 500 ppmv. At higher 0, concentrations, TCE
removal remained relatively constant, ranging from
86 to 91 percent.
Similarly, supplemental 0, and H2O2 were shown to
enhance removal of VOCs (2-propanol, benzene,
toluene, xylene, and ethanol) by the UV/Ti02
process (Nimlos and others 1995). In this study,
removal of 2-propanol increased from 39 percent
without 0, to >99.7 percent with supplemental 0,.
When subjected to a mixture of benzene,.toluene,
and xylene, the TiO2 catalyst was deactivated:
however, once 0, was added, removals of 79, 95,
and >99.7 percent were achieved for benzene,
toluene, and xylene, respectively. The individual
effects of supplemental 0, and H2O2 on removal of
ethanol by the UV/TiO2 process were also evaluated.
The study showed that ethanol removal increased by
more than an order of magnitude (to >90 percent
removal) after individual additions of 0, and H2O2.
Information on the initial VOC concentrations and on
the concentrations of 0, and H2O2 additions was not
clearly provided.
Effect of Water Vapor
Based on studies conducted at the bench-scale
level, water vapor appears to have differing effects
on removal of VOCs by the UV/TIO2 processes. In
general, the effects appear to depend on the water
vapor concentration as well as the type and
concentration of the target VOC. For instance,
Anderson and others (1993) observed that the
presence of water vapor in the reactant gas stream
decreased the initial reaction rates of TCE (specific ••
values were not reported) below the rates observed ~
under water-free conditions; however, water vapor
was required to maintain photocatalytic activity for
extended periods. For the water-free reactant
stream, the TCE reaction rate decreased by
50 percent after 2 hours of irradiation. The decrease
in photocatalytic activity was attributed to fewer OH-
in a water-free environment to adsorb on the surface
of the TiO2 catalyst, as OH0 is the primary oxidant for
photochemical oxidation of TCE. The reaction rate
of TCE was independent of water vapor over the
water vapor/TCE mole ratio of 4.2 x ifl"4 to 0.027.
Raupp and others (1994) also observed that the
presence of water vapor in reactant gas streams
decreased the initial reaction rates of TCA, benzene,
and acetone below the rates observed under
water-free conditions; however, water was required
to maintain photocatalytic activity for extended
periods.
The effect of water vapor on removal of TCE at
various concentrations by a UWTiO2 process was
evaluated by Berman and Dong (1994). The study
showed that when the initial TCE concentration was
800 ppmv, TCE removal exceeded 99.9 percent as
water vapor concentrations increased up to
50,000 ppmv; however, when the initial TCE
concentration was 4,500 ppmv, TCE removal
decreased from about 98 to 87 percent as water
vapor concentrations increased over the same
range. The negative effect of water vapor on TCE
4-4
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removal was attributed to competition between TCE
and water vapor for sites on the TiO2 catalyst.
Peral and Ollis (1992) observed that the effect of
water vapor on removal of VOCs (acetone,
1 -butanol, butyraldehyde; and m-xylene) using the
UV/TiO2 process also depends on the type of
chemical being treated. For acetone at an initial
concentration of about 84 ppmv, the study showed
that water vapor inhibits acetone removal.
Specifically, the removal rate for acetone decreased
from about 1 to 0.16 ^g/cn^-min as the water vapor
concentration was increased from about 40 to
14,000 ppmv. In contrast, the removal rate for
m-xylene was found to increase from about 0.12 to
0.20 Aig/cm2-min as the water vapor concentration
increased from 0 to about 1 ,400 ppmv. At higher
water vapor concentrations (7,500 ppmv) the
removal rate decreased, reaching about
0.07 Mg/cm2-min. Variations in water vapor concen-
tration were shown to have no significant effect on
the removal rates of l-butanol and butyraldehyde.
The initial concentrations for m-xylene, 1-butanol,
and butyraldehyde were not clearly reported.
Effect of Co-Cat&.&
The effect of co-catalysts and various fluorescent
light sources on VOC removal by the UV/TiO2
process was investigated by Watanabe and others
(1993). For this study, the individual effects of
various metals, including copper (II), Fe(ll),
platinum (II), strontium (II), cobalt (II), nickel (II), and
palladium (II), coated on a TiO2 catalyst at 0.1 to
1 molar percent were evaluated with regard to
methyl mercaptan removal under various fluorescent
light sources. Under black light conditions, addition
of platinum (II), strontium (II), cobalt (II), nickel (II), or
palladium (II) as a co-catalyst was demonstrated to
diminish removal of methyl mercaptan, while addition
of copper (II) and Fe(ll) enhanced removal. The
highest methyl mercaptan removal was achieved
after addition of copper (II). The study also showed
that the percent removal of methyl mercaptan in the
absence of light, under pink light, and under regular
fluorescent light was an order of magnitude lower
than under black light. Under black light conditions,
removal of methyl mercaptan was shown to increase
from about 1 5 percent without a co-catalyst to about
90 percent with addition of copper (II) as a
co-catalyst at 1 .0 molar percent.
Fffert nf Reaction
The effect of reducing reaction pressure on TCE
removal in a UV/TiO2 system was evaluated by
Annapragada and others (1997). The initial
concentrations of TCE and water vapor were
adjusted for reaction pressure changes such that
their initial concentrations under standard conditions
were the same in all experiments. For example,
7.2 micromoles per liter (/zmol/L) of TCE and
1,400 //moj/L of water vapor at 21.5 pounds per
square inch absolute pressure (psia) are equivalent
to 1.6 ^mol/L of TCE and 320 ^mol/L of water vapor
at 4.9 psia; both conditions would correspond to
4.9 //mol/L of TCE and 980 ^mol/L of water vapor
under standard conditions. The study showed that
as reaction pressure was reduced from 21.5 to
4.9 psia, TCE removal increased from 59 to
85 percent. The increase in TCE removal was
attributed to reduced competition between TCE and
water vapor for adsorption sites on the TiO2 catalyst.
At reduced pressure, the amount of water vapor that
condenses is less, resulting in relatively more
adsorption sites for TCE.
Competitive Effect of Co-Contaminants
The single-contaminant and multiple-contaminant
kinetics of TCE and toluene were studied using the
UV/TiO2 process by Luo and Ollis (1996). In a gas
stream containing TCE at concentrations up to
140 ppmv, >99.9 percent TCE removal was
achieved. In a gas stream containing toluene, 20 to
8 percent removals were achieved for concentrations
ranging from about 20 to 140 ppmv, respectively.
Study of TCE and toluene mixtures revealed a
strong promotion-inhibition behavior in which TCE
enhances toluene removal and toluene reduces TCE
removal. When the TCE concentration was
140 ppmv and the toluene concentration was below
26 ppmv, almost complete removal was achieved for
both toluene and TCE. When the toluene
concentration was increased to levels above
42 ppmv, TCE was hardly removed, and toluene
removal exhibited only a slight increase. When the
TCE concentration was decreased to 42 ppmv,
toluene and TCE removals both dropped significantly
(to >60 percent).
Removal of Hiah-l evel VOC Concentrations
Several bench-scale studies indicate that the ability
to remove VOCs using the UV/TiO2 process
depends strongly on the type and concentration of
the compound being treated. For example, AI-Ekabi
and others (1993) observed chemical- and
concentration-dependent effects on photochemical
oxidation of high-level TCE and PCE concentrations.
The study showed >99 percent removal of TCE for
initial TCE concentrations ranging from 7,400 to
11,000 ppmv. TCE removal decreased and varied
from 92 to 94 percent for initial TCE concentrations
4-5
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ranging from 17,000 to 23,000 ppmv. Similarly,
>99 percent removal of PCE was observed for an
initial PCE concentration of 3,100 ppmv, but for initial
PCE concentrations ranging from 4,600 to
9,200 ppmv, PCE removal was reduced and varied
from 93 to 96 percent. In addition, Holden and
others (1993) observed that benzene removal
increased from 10 to 73 percent in a UWTiO2 system
after the initial concentration of benzene was
reduced from 140,000 to 2,200 ppmv.
Reaction By-Product Formation
A quantitative and qualitative evaluation of TCE
reaction by-products in a UV/TiO2 system as a
function of flow rate (retention time) was conducted
by Holden and others (1993). For this study, the
reaction by-products from complete removal of TCE,
which was present at an initial concentration of
24,500 ppmv, were evaluated after the flow rates
through the reactor were set at 1 * 10"4, 5 * 10~5,
2.5 x 1 O'5, and 1 .O * 10"5 scmm. For each of the
flow rates evaluated, the following by-products were
identified in varying distributions: DCAC, phosgene,
carbon dioxide, chlorine, CO, HCI, and oxides of
chlorine. The study showed that as the flow rates
decreased (1 .0 x 10" to 2.5 x irj5 scmm}, phosgene
concentrations increased and DCAC concentrations
decreased, indicating that DCAC was being
converted to phosgene. When the flow rate
was further decreased from 2.5 x IQ-S to
1 .0 x 1 O"5 scmm, DCAC was completely removed,
and the phosgene concentration was relatively
lower. Collectively, this change in distribution
suggests that DCAC is the primary reaction
by-product of TCE photochemical oxidation. This
change also suggests that at sufficiently low flow
rates, both DCAC and phosgene may not be present
as final by-products of TCE photochemical oxidation.
Reaction by-products formed during ethanol removal
were studied by Nimlos and others (1996) using the
UV/TiO2 process. The study revealed that removals
exceeding 99 percent could be achieved for ethanol
concentrations ranging from 40 to 200 ppmv. Acetyl
aldehyde, formaldehyde, and carbon dioxide were
identified as the primary reaction by-products; acetic
acid, formic acid, ethyl acetate, methyl formate, ethyl
formate, and methyl acetate were identified at lower
concentrations. To better examine the kinetics of
ethanol, the study also evaluated (in individual tests)
by-product formation from UV/TiO2 photolysis of
acetyl aldehyde, formaldehyde, acetic acid, and
formic acid. For acetyl. aldehyde concentrations
ranging from 50 to 200 ppmv, >99 percent removal
was achieved; identified by-products included
formaldehyde, acetic acid, and methyl formate.
Removal of formaldehyde concentrations ranging
from 80 to 400 ppmv exceeded 80 percent; formic
acid, methyl formate, and methanol were identified
as reaction by-products. Acetic acid removal
exceeded 99 percent for concentrations ranging from
80 to 180 ppmv; reaction by-products included
primarily formaldehyde. Carbon dioxide was
identified as the reaction by-product of formic acid.
4-6
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Table 4-1. SVE Off-Gas Treatment
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST
CONDITIONS
RESULTS
Percent Removal Additional Information
VOCs (Commercial Scale)
UV/O3
(PTI)
UV/Catalyst
(KSE AIR)
UV/TiO2
[Matrix)
Total VOCs: 1,000 to 1.100 ppmv
as carbon
PCE: 31 ppmv
TCE: 28 ppmv
cis-1,2-DCE: 22 ppmv
Toluene: 14 ppmv
PCE: 150 to 1 ppmv
Methane: 2,000 to 4,000 ppmv
PCE: 1,200 ppmv
TCE: 160 ppmv
1 ,1,1-TCA: not available
Flow rate: 12 scmm
Reactor volume: not
available
Light source: low-pressure
UV lamps with output at
185 to 254 nm
Flow rate: 1 .4 to 2.0 scmm
Reactor volume: not
available
Light source: 60 UV lights;
intensity and
wavelength not
available
Flow rate: 0.71 scmm
Reactor volume: not
available
Light source: one fluorescent
lamp with UV output at
300 to 400 nm
Total VOCs: 95.9
PCE: 89.7
TCE: 80.8
Cis-1 ,2-DCE: 74.0
Toluene: 93.1
PCE: >99
Methane: minimal
PCE: 95.2
TCE: 98.1
1,1.1-TCA: not
removed
Reaction By-products
HCI: 0.18 ppbv
Chlorine: 0.04 ppbv
Phosgene: 1 1 ppbv
CO: 31 to 56 ppmv
Not available
Reaction By-products
Carbon tetrachioride
Chloroform
DCAC
Hexachioroethane
Methylchloroformate
Pentachloroethane
Trichioroacetyl chloride
COST
(1998 U.S. Dollars)
For an 85-scmm System
$3.80/pound of VOCs
treated
Not available
Not available
REFERENCE
PTI 1998
Kittrell and
others 1996a
Anonymous
1995
VOCs (Pilot Scale)
jvmo2
TCE: 66 ppmv
PCE: 502 ppmv
1,1-DCE: below detection limit
1.1 ,1-TCA: below detection limit
Flow rate: 5.0 x 10"4 scmm
Reactor volume: two
9 2 x ICrtn3 flow cells
Light source: two 40-W
fluorescent UV black
light lamps
Temperature: 100 °C
O2 addition: 5.0 x 10~* scmm
TCE: >99.9
PCE: >99.9
1 ,1-DCE: not available
1.1,1-TCA: not
available
He
Reaction By-products
Phosgene: <1 ppmv
Chloroform: <1 ppmv
Carbon tetrachlortde:
<1 ppmv
Pentachioroethane:
<1 ppmv
xachloroethane:
<1 ppmv
None
I
Read and others
1996
-------
4.2 Air Stripper Off-Gas Treatment
APO has been shown to be an effective treatment
technology for air stripper off-gas contaminated with
low-level VOC concentrations. At the commercial
scale, KSE's AIR UV/catalyst system has achieved
nearly 99 percent removal of low-level 1,2-DCA
concentrations. At the pilot-scale level, a UV/TiO2
system achieved 93 percent removal of low-level
ethanol concentrations. Cost information was not
available for either of these two systems.
Bench-scale studies of VOC removal using the
UV/Ti02 process are described in Section 4.1. The
commercial- and pilot-scale systems that have been
used to treat VOCs in air stripper off-gas are
described below.
Commercial-Scale Application
This section discusses the effectiveness of the KSE
AIR UV/catalyst commercial-scale treatment system
in removing VOCs from air stripper off-gas. The
KSE system was demonstrated using air stripper
off-gas contaminated -with low-level 1,2-DCA
concentrations at Dover Air Force Base in Delaware
(Kittrell and Quinlan 1995a). KSE's system
consisted of a single vessel containing a proprietary
catalyst and varying numbers of black light UV lamps
(the system had a 60-lamp capacity). The
composition of the catalyst and the wavelength and
intensity output of the UV bulbs were not reported.
The system received contaminated air via a
slipstream directly from the combined effluent of two
air stripping towers without further treatment.
During the 1 0-week period of system operation, the
inlet air stream was saturated with water vapor and
contained 1,2-DCA concentrations ranging from 0.9
to 3 ppmv. The flow rate through the reactor ranged
from 1.4 to 1.7 scmm and averaged 1.2 scmm.
During the initial stages of the demonstration when
30 of the 60 black light UV lamps were illuminated,
1,2-DCA removal averaged 96 percent. By
illuminating additional lamps in the later stages of the
demonstration, KSE was able to increase 1,2-DCA
removal; specifically, when seven and later eight
more lamps were illuminated, 1,2-DCA removal
averaged >96 percent and about 99 percent,
respectively. Reaction by-products were not
analyzed for during the demonstration.
Pilot-Scale Application
This section discusses the effectiveness of a
pilot-scale UV/TiO2 system in removing VOCs from
air stripper off-gas. A pilot-scale UV/TiO2 system
was field-tested by National Renewable Energy
Laboratory (NREL) researchers using ethanol-
contaminated off-gas from an air stripper at the
Coors Brewery in Golden, Colorado (Nimlos and
others 1995). The waste treatment areas at the
facility contained several holding pits that held
beer-laden wastewater prior to biological treatment.
The UV/TiO2 system was tested using a sidestream
of off-gas from a blower assembly that had been
installed to strip ethanol from one of the pits. The
system, a recirculating batch reactor, consisted of a
series of three 8,-inch Pyrex tubes coated on the
inside with TiO2 and illuminated with four banks of
black lights with their UV output at 360 nm (the
intensity was not reported),
For this study, which was conducted over 2 days, the
inlet off-gas was saturated with water vapor (to
achieve 100 percent relative humidity) and contained
initial concentrations of ethanol ranging from 6.4 to
40 ppmv. Ethanol removal over this concentration
range varied from about 78 to 93 percent. The
highest ethanol removal (93 percent) was observed
at an initial concentration of 15 ppmv and with a
retention time of 0.4 second.
4-8
-------
Table 4-2. Air Stripper Off-Gas Treatment
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST
CONDITIONS
RESULTS
Percent Removal Additional Information
VOCs (Commercial Scale)
UV/Catalyst
(KSE AIR)
1 ,2-DCA: 0.9 to 3 ppmv
Flow rate: 1 .4 to 1 .7 scmm
Reactor volume: not available
Light source: about 45 UV black
light lamps; intensity not
available
Water vapor: 100 percent relative
humidity
VOCs (Pilot Scale)
UWTiO2
Ethanol: 15 ppmv
Flow rate: not available
(recirculating batch)
Reactor volume: three 8-inch Pyrex
tubes
Light source: four banks of UV
lamps with UV output at
360 nm; intensity not available
Water vapor: 100 percent relative
humidity
Retention time: 0.4 second
About 99
Not available
COST
(1998 U.S. Dollars)
Not available
REFERENCE
Kittrell and Quinlan 1995a
About 93
tot available
Not available
Nimlos and others 1995
CO
-------
4.3 Industrial Emissions Treatment
Although only a limited number of applications have
been developed, APO has been shown to be an
effective treatment technology for VOCs, SVOCs,
and explosives in industrial emissions. At the
commercial-scale level, APO systems based on
UV/catalyst and UV/TiO2 processes have been
developed for treatment of VOCs and explosives and
their degradation products, respectively. Pilot-scale
systems for treatment of VOCs using the solar/Ti02
process and SVOCs using the UV/03 process have
been demonstrated. Bench-scale studies of VOC
removal using UV/TiO2 and UV/O3 processes are
described in Section 4.1. In addition to performance
data, system cost information is available for
commercial-scale systems designed to treat VOCs
and explosives. The commercial- and pilot-scale
systems available to treat industrial emissions are
described below.
4.3. 1 VOC-Confaining Industrial
Emissions
This section discusses removal of VOCs in industrial
emissions using the UV/catalyst process at the
commercial scale. Additional information on VOC
removal using the solar/Ti02 process at the
pilot-scale level is also included.
Commercial-Scale Applications
This section discusses the effectiveness of the KSE
AIR UV/catalyst treatment system in removing the
following VOCs from industrial emissions.
APO Process
• UV/Catalyst
VOCs Removed
Aliphatic hydrocarbon,
pentane
KSE's AIR system was demonstrated using
high-level voc (aliphatic hydrocarbon)
concentrations in emissions from the Chering-Plough
Corporation contact lens manufacturing facility in
Cidro, Puerto Rico (Kittrell and others 1996b). The
source of the VOCs was an aliphatic hydrocarbon
(Shell Sol B HT) solvent used in the lens vats within
the facility. KSE's AIR system contains a proprietary
catalyst and UV lamps. The number of lamps and
their wavelength and intensity were not reported.
The system received contaminated air from exhaust
hoods that drew solvent vapor emissions from the
surface of the vats.
Over the 2-week demonstration period, the system
achieved high removals (>99 percent) for feed
stream total VOC concentrations ranging from 1,900
to 2,000 ppmv. The flow rate through the system
ranged from 0.3 to 0.8 scmm and corresponded to
retention times <1 second. The highest VOC
removal was achieved with an initial feed stream
total VOC concentration of 2,000 ppmv and a flow
rate of 0.3 scmm. Using gas chromatography, KSE
observed that no reaction by-products were formed
during the demonstration. Compound-specific
detectors were used to monitor for CO,
formaldehyde, and acetaldehyde, and none of the
compounds was detected.
KSE's estimated capital cost for a 1.8-scmm system
with a percent removal >99 percent was $53,320.
Monthly energy and annual maintenance costs for
the system at the Chering-Plough Corporation facility
were estimated at <$376 and $1,672, respectively.
KSE's AIR UV/catalyst system was also
demonstrated using pentane emissions from an
expandable polystyrene plant (Kittrell and others
1996b). During this demonstration, high pentane
removals (99.2 to 99.9 percent) were achieved for
feed stream pentane concentrations ranging from
340 to 3,600 ppmv at 20 percent relative humidity.
The rate of flow through the system ranged from 0.3
to 0.9 scmm and corresponded to retention times
<1 second. The demonstration showed that relative
humidity, which varied from 20 to 100 percent, had
no impact on system performance. Specifically,
when KSE increased the relative humidity to
100 percent, pentane removal " exceeded
99.9 percent with an initial pentane concentration of
2,100 ppmv and a system flow rate of 0.8 scmm.
Using gas chromatography, KSE observed that no
reaction by-products were formed during the
demonstration. Compound-specific detectors were
used to monitor for CO, formaldehyde, and
acetaldehyde, and none of the compounds was
detected.
Based on the demonstration, KSE's estimated
capital cost for a 4.4-scmm system with pentane
removal >99 percent was $183,000. Annual
operating costs were estimated at $7,800.
Pilot-Scale Application
This section discusses the effectiveness of a
pilot-scale solar/Ti02 system in treating
VOC-contaminated industrial emissions. A
pilot-scale system was field-tested by NREL
researchers using VOC-laden paint booth emissions
4-10
-------
at E/M Corporation's North Hollywood painting plant
(Nimlos and others 1995). VOCs identified-in the
emissions included ethanol, toluene, and methyl
ethyl ketone. The system used for the study was a
modified version of the recirculating batch reactor
used by NREL for treating air stripper off-gas
contaminated with ethanol (see Section 4.2, Pilot-
Scale Application). Specifically, the system was
modified to use sunlight as the UV light source, and
supplemental 0, was added to the feed gas at
concentrations ranging from 500 to 2,600 ppmv.
The study showed that 99 percent removal of total
VOCs ranging in concentration from 250 to
350 ppmv was achieved in 3 to 4 seconds when the
concentration of 0, exceeded 1,000 ppmv.
4.3.2 SVOC-Containing Industrial
Emissions
This section discusses the effectiveness of a
pilot-scale UV/O3 system in treating SVOC-
contaminated industrial emissions. A pilot-scale
UV/O3 system was field-tested using chlorophenol
emissions from a plant making selective weed killers
(Barker and Jones 1988). The system (a gas
scrubber) consisted of a 150-L spray section and a
15-L sump section. Located in the sump were I I
I S-W low-pressure mercury lamps supplying 1 I W/L.
The UV output of the low-pressure mercury lamps
was not reported. 0, was supplied to the sump
section by an 0, generator. The sump liquor was
maintained at a pH of 5 to 6 and a temperature of 40
to 50 "C. The feed gas was supplied to the interface
of the sump and spray sections at a flow rate of
either 1.2 or 2.0 scmm.
The demonstration showed that UV light had very
little effect on removal of chlorophenol. In the
presence of UV light and O,, whose concentra-
tion varied from 10 to 30 g/m , removals exceeding
99 percent were achieved for chlorophenol
concentrations ranging from I to 130 ppmv. The
highest chlorophenol removal (>99.9 percent) was
achieved when the inlet chlorophenol and
0, concentrations were 34 ppmv and 30 g/m3,
respectively. Chlorophenol removals in the absence
of UV light still exceeded 99 percent for inlet
concentrations ranging from 3 to 5 ppmv and with 0,
concentrations ranging from 10 to 30 g/m3. Based
on TOC analyses, however, the study revealed that
the combination of UV light and 0, was important for
removing compounds other than chlorophenol in the
feed stream.
4.3.3 Explosive- and Degrada tidn
Product-Containing Industrial
Emissions
This section discusses the effectiveness of the
Zentox UV/Tf02 commercial-scale treatment system
in removing NG from industrial emissions. Zentox's
system was demonstrated using NG-containing
emissions from a propellant annealing oven at the
U.S. Naval Surface Warfare Center, Indian Head
Division Extrusion Plant (Turchi and Miller 1998).
Stack gas from the heating process was drawn from
the oven stack to the Zentox system.
Days I and 2 of the 4-day demonstration were used
to (I) determine whether addition of supplemental 0,
improves NG removal and (2) evaluate the relative
advantages of germicidal lamps (50 W with UV
output at 254 nm) and black light lamps (64 W with
UV output at 350 nm). Results indicated that 0,
addition at 45 to 120 ppmv in combination with either
germicidal or black light lamps was required to
achieve rapid oxidation of NG to NO,. Black lights,
however, were found to perform better in converting
NG to nitrogen dioxide. Use of the germicidal lamps
resulted in formation of an organic film on the lamps
because of direct photolysis of higher molecular
weight compounds present in the feed gas. Based
primarily on these results, black lights and
supplemental 0, were selected for subsequent tests
under steady-state conditions during days 3 and 4.
Results from days 3 and 4 demonstrate that the
Zentox system is capable of achieving high
(>97 percent) NG removals. On day 3, the system
was operated with 28 lamps, four catalyst banks,
and a flow rate of 1.4 scmm. 0, concentrations in
the feed gas were maintained at 140 ppmv, and inlet
NG concentrations ranged from 1.6 to 2.1 ppmv.
Under these conditions, NG removal exceeded
97 percent. The highest removal (99.2 percent) was
observed when the initial NG concentration was
I .7 ppmv. The target removals for the
demonstration were 80 to 85 percent, so Zentox
increased the loading rate on day 4 by increasing the
flow through the reactor to 2.1 scmm, reducing the
number of catalyst banks by half, and reducing the
number of UV lamps to 17. 0, concentrations in the
feed gas were maintained at 45 ppmv, and inlet NG
concentrations ranged from 1.7 to 3.3 ppmv. Under
these conditions, NG removal exceeded 80 percent.
On both days 3 and 4, NO, was observed as a
reaction by-product at concentrations <25 ppmv.
4-11
-------
Zentox's estimated capital costs for a 650-scmm $100,000 to $150,000. Operating costs were not
full-scale system with an NG percent removal reported. According to Zentox, the capital costs are
>97 percent range from $175,000 to $260,000. expected to be lower once more field tests have
Estimated capital costs for the same size system been conducted to identify the optimum 0, feed
with an NG percent removal >80 percent range from concentration and catalyst formation.
4-12
-------
Table 4-3. Industrial Emissions Treatment
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
TEST
CONDITIONS
RESULTS
Percent Removal Additional Information
COST
(1998 U.S. Dollars)
REFERENCE
'DCs (Commercial Scale)
JV/Catalyst
KSEAIR)
Total VOCs: 2,000 ppmv
Pentane: 2,100 ppmv
Flow rate: 0.3 scmm
Reactor volume: not available
Light source: UV lamps
(wavelength and intensity
not available)
Retention time: <1 second
Flow rate: 0.8 scmm
Reactor volume: not available
Light source: UV lamps
(wavelength and intensity
not available)
Retention time: <1 second
Relative humidity: 100 percent
>99
>99.9
Treatment of emissions
from a contact lens
manufacturing plant
Reaction by-products not
detected
Treatment of emissions
from an expandable
polystyrene plant
Reaction by-products not
detected
For a 1.8-scmm System with
>99 Percent Removal
Capital cost: $53.320
Energy cost: $376/month
Maintenance cost: $1,672/year
For a 4.4-v
>99 Percent Removal
Capital: $183,000
Annual operating: $7,800
Kittrell and others
1996b
Kittrell and others
1996b
'OCs (Pilot Scale)
iolar/TiO2
VOCs (Pilot
IV/03
Total VOCs (ethanol,
toluene, and methyl
ethyl ketone): 250 to
350 ppmv
Scale)
Chlorophenol: 34 ppmv
Flow rate: not available
(recirculating batch)
Reactor volume: three 8-inch
Pyrex tubes
Light source: sunlight
0, addition: >1 ,000 ppmv
Retention time: 3 to 4 seconds
Flow rate: 1 .2 or 2.0 scmm
Reactor volume: not available
Spray section: 150 L
Sump section: 15 L
Light source: 11 15-W
low-pressure mercury
lamps
0, addition: 30 g/m3
pH: 5 to 6
Temperature: 40 to 50 °C
99
>99.9
Treatment of paint booth
emissions
Treatment of emissions
from a chemical weed
killer manufacturer
i
Not available
Not available
Nimlos and other:
1995
Barker and Jones
1988
xplosives and Their Degradation Products (Commercial Scale)
V/Ti(y03
.entox)
NG: 1.70 ppmv
Flow rate: 1 .4 scmm
Reactor volume: not available
Light source: 28 64-W black
lights with output at
350 nm
Temperature: ambient
0, addition: 140 ppmv
99.2
Treatment of NG
emissions from an
annealing oven
Reaction Ry-product
NO,: <25 ppmv
Capital Cost for a 650-scmm
System with >97 Percent
Removal
$175,000 to $260,000
Turchi and Miller
1998
GO
-------
Water and Air. Cincinnati, Ohio. October 26
through 29, 1996.
Turchi, C., and R. Miller. 1998. "Photocatalytic
Oxidation of Energetic Compounds from a
Propellant Annealing Oven." Eighth
International Symposium on Chemical Oxidation
Technologies for the Nineties. Nashville,
Tennessee. April 1 through 3, 1998.
Wang, K., and B.J. Marinas. 1993. "Control of VOC
Emissions from Air-stripping Towers:
Development of Gas-phase Photocatalytic
Process." Photocatalytic Purification and
Treatment of Wafer and Air. Edited by D.F. Ollis
and H. AI-Ekabi. Elsevier Science Publishers
B.V. Amsterdam. Pages 733 through 739.
Watanabe, T., A. Kitamura, E. Kojima, C.
Nakayama, K. Hashimoto, and A. Fujishima.
1993. "Photocatalytic Activity of TiO2 Thin Film
under Room Light." Photocatalytic Purification
and Treatment of Wafer and Air, Edited by D.F.
Ollis and H. AI-Ekabi. Elsevier Science
Publishers B.V. Amsterdam. Pages 747
through 751.
4-16
-------
Section 5
Contaminated Solids Treatment
APO has been demonstrated to be an effective
technology for treating contaminated solids, primarily
at the bench-scale level. Most evaluations involved
generation of a leachate or slurry by washing the
contaminated solids with water, surfactant solution,
or an organic solvent and then applying an APO
process to treat the contaminated leachate or slurry
in a manner similar to contaminated water treatment.
Use of an APO process to treat contaminated slurry
may require frequent APO system maintenance
because solids in the slurry will coat the light source
and inhibit transmission of light.
Solid matrices to which APO has been applied
include the following: (1) contaminated soil,
(2) contaminated sediment, and (3) contaminated
ash. Collectively, APO has been applied to the
following types of contaminants: (1) svocs,
(2) PCBs, (3) pesticides and herbicides, and
(4) dioxins and furans. One commercial-scale
application of an APO process (Calgon perox-pure™
UV/H2O2) for treating contaminated solids is reported
in the literature. This section describes the
commercial-scale application of this process and
several bench-scale evaluations of APO processes
for treating contaminated solids. A table
summarizing operating conditions and performance
results for the commercial-scale Calgon perox-
pure™ UV/H2O2 system is included this section.
5.1 Contaminated Soil Treatment
The effectiveness of APO technologies in treating
contaminated soil has been evaluated for various
contaminant groups, including SVOCs, PCBs,
pesticides and herbicides, and dioxins and furans.
This section discusses APO treatment technology
effectiveness with regard to each of these
contaminant groups.
5.7.7 S VOC-Contamina ted Soil
SVOCs in soil have been treated using sensitized
photochemical processes at the bench-scale level.
The effectiveness of these processes in removing
the following SVOCs from contaminated soil is
described below.
APO Process
Photo
sensitization
UV/TiO,
SVOCs Removed
Anthracene, biphenyl,
9H-carbazole, m-cresol,
fluorene, PCP,
phenanthrene, pyrene,
quinoline
Acenaphthene,
acenaphthylene,
anthracene,
benzo(a)anthracene,
benzo(a)pyrene,
benzo(b)fluoranthene,
benzo(g,h,i)perylene,
benzo(k)fluoranthene,
chrysene, 2-CP,
dibenzo(a,h)anthracene,
fluoranthene, fluorene,
indeno(1,2,3-cd)pyrene,
naphthalene,
phenanthrene, pyrene
Dupont and others (1990) evaluated the
effectiveness of various sensitizers (methylene blue,
riboflavin, peat moss, diethylamine, and anthracene)
under UV or visible light in removing SVOCs from
contaminated slurries at the bench-scale level. The
study also evaluated the effectiveness of the
UV/H2O2 process in decontaminating the slurries.
Three types of soil (silty clay, sandy loam, and silty
loam) were spiked with several SVOCs, including
anthracene, biphenyl, 9H-carbazole, m-cresol,
fluorene, PCP, phenanthrene, pyrene, and quinoline,
at 500 milligrams per gram each. Soil slurries were
generated by mixing the contaminated soils with
methylene chloride and water. Anthracene was
found to be the most effective sensitizer; other APO
processes did not show a statistically significant
improvement over direct photolysis. On the contrary,
diethylamine inhibited photodegradation of other
SVOCs. The study concluded that soil type is a
significant factor in photodegradation of compounds,
indicating the need for site-specific assessments of
soil-phase photodegradation.
5-1
-------
In another bench-scale study, Ireland and others
(1995) evaluated the effectiveness of the UV/TiO2
process in decontaminating soil slurries containing
16 PAHs, including fluoranthene, pyrene, benzo(a)-
anthracene, chrysene, benzo(b)fluoranthene,
benzo(k)fluoranthene, and benzo(a)pyrene. Soil
contaminated with motor oil (1) was spiked with the
PAHs at concentrations ranging from 1.6 to
6.4 milligrams per kilogram, (2) extracted using
triethylamine, and (3) slurried using water. The
concentrations of PAHs in the slurry varied from 580
to 660 mg/L. Two 15-W bulbs providing light with
wavelengths from 300 to 400 nm were placed 1 cm
from a 40-milliliter slurry aliquot. Within 24 hours of
irradiation, all PAHs except chrysene and pyrene
were degraded by more than 85 percent; chrysene
and pyrene were degraded by 33 and 66 percent,
respectively.
(1992) evaluated the
2 process in treating soil
Pelizzetti and others
effectiveness of UV/TiO
slurries contaminated with 2-CP at 20 mg/L. At a
colloidal TiO2 dose of 500 mg/L and after 60 minutes
of UV irradiation, about 95 percent of the 2-CP was
removed.
5.1.2 PCB-Contaminated Soil
PCBs in contaminated soil have been treated using
the photo-Fenton process at the bench-scale level.
McLaughlin and others (1993) investigated the effect
of temperature on removal of PCBs in diatomaceous
earth slurries using the photo-Fenton process. PCB
congener (2,2',5-trichlorobiphenyl and 2,2',4,5,51-
pentachlorobiphenyl) removals were studied at two
temperatures (27 and 60 "C). At an H2O2 dose of
0.8 mg/L, an Fe(ll) dose of 2 mg/L, and a pH of 3,
and in 5 hours of reaction time, the investigators
observed (1) 2,2',5-trichiorobiphenyI removals of 84
and 96 percent at 27 and 60 °C, respectively; and
(2) 2,2',4,5,5'-pentachlorobiphenyl removals of 80
and 85 percent at 27 and 60 °C, respectively. They
concluded that the rate of the PCB removal is a
function of PCB concentration in solution and the
number of chlorine atoms in the PCB (the removal
rate decreases with an increasing number of chlorine
atoms).
5.7.3 Pesticide- and Herbicide-
Contaminated Soil
This section discusses treatment of the following
pesticides and herbicides in soil using (1) the
UV/H2O2 process on a commercial-scale level and
(2) the UV/Ti02 process at the bench-scale level,
APO Process
. UV/H2O2
• UWTi02
Pesticides and Herbicides
Removed
. Disulfoton, oxadixyl,
parathion, propetamphos,
thiometon
. Atrazine
A 180-kW Calgon perox-pure™ UV/H2O2 system
was used to treat soil contaminated with disulfoton,
thiometon, parathion, propetamphos, and oxadixyl.
The influent to the perox-pure™ system, which was
generated by an on-site soil washing system,
primarily contained 0.49, 1.1, and 3.9 mg/L of
disulfoton, thiometon, and oxadixyl, respectively.
Parathion and propetamphos were present in the
influent at relatively low levels (0.8 mg/L or less).
The perox-pure™ system was operated at flow rates
ranging from 6 to 20 m3/h (corresponding to retention
times of 12 to 3 minutes), an H2O2 dose of 50 mg/L,
and a pH of 7. A sand filter was used to remove
suspended solids from the influent to the perox-
pure™. system. The system achieved removals of
up to 99.5 percent. However, suspended solids that
were not captured by the filter caused frequent
scaling of UV lamps, which resulted in frequent
shutdown of the system (Egli and others 1994).
At the bench-scale level, atrazine was found to be
effectively removed in soil slurries (about 2 percent
solids) using the UV/TiO2 process. In soil slurries
containing 20 mg/L of atrazine, at a colloidal TiO2
dose of 500 mg/L, and after 60 minutes of UV
irradiation, atrazine removal of about 95 percent was
achieved (Pelizzetti and others 1992).
5.1.4 Dioxin- and Furan-Contamina ted
Soil
Dioxins and furans in soil have been treated using
UV7TiO2 and UV/anthracene processes at the
bench-scale level. The effectiveness of these
processes in removing the following dioxins and
furans from contaminated soil is described below.
APO Process
• UV/Ti02
. UV/
Anthracene
Dioxins and Furans '
Removed
2,7-
Dichlorodibenzodioxin
• Dibenzofuran
5-2
-------
Pelizzetti and others (1992) evaluated the In another bench-scale study, Dupont and others
effectiveness of the UV7TiO2 process in degrading (1990) found that dibenzofuran could be removed
2,7-dichlorodibenzodioxin in soil slurries (about 2 from soil slurries using UV irradiation and
percent solids) at the bench-scale level. At an initial anthracene, a sensitizer. In this process, the half-life
concentration of 10 mg/L and a TiO2 dose of of dibenzofuran was estimated to be about 80 days.
500 mg/L, about 90 percent of the 2,7-dichloro- More information on use of sensitizers is included in
dibenzodioxin was removed in about 15 hours of UV Section 5.1 .1.
irradiation.
5-3
-------
Table 5-1. Contaminated Soil Treatment
PROCESS
(SYSTEM)
CONTAMINANT
CONCENTRATION
Pesticides and
UV/H202
(Calgon
perox-pure™)
TEST
CONDITIONS
RESULTS
Percent Removal Additional Information
COST
(1998 U.S. Dollars)
REFERENCE
Herbicides (Commercial Scale) : •
Disulfoton: 0.49 mg/L
Thiometon: 1.1 mg/L
Oxadixyl: 3.9 mg/L
Reactor volume: 1 m3
Flow rate: 6 to 20 rrvVn
Light source: high-pressure mercury
vapor lamps (1 80 kW)
Wavelength: not available
H2O2 dose: 50 mg/L
Reaction time: 3 to 12 min
pH: 7
Disulfoton: 97.9
Thiometon: 99.1
Oxadixyl: 99.5
Suspended solids in
influent coated the UV
lamps, causing frequent
system shutdown
Not available
Egli and others 1994
en
-------
5.2 Contaminated Sediment
Treatment
Limited information is available on the effectiveness
of APO in treating contaminated sediment. No
commercial- or pilot-scale results were available.
This section describes the effectiveness of a
UV/TiO2 process in treating PCB-contaminated
sediment at the bench-scale level.
Chiarenzelli and others (1995) evaluated the
effectiveness of the UV/TiO2 process in
decontaminating sediment collected from a shallow
embayment of the St. Lawrence River near
Massena, New York. The sediment was
contaminated with PCBs at concentrations of 27 to
38 milligrams per kilogram. The UV/TiO2 process
achieved about 88 percent PCB removal when the
contaminated sediment slurry was irradiated for
about 48 hours using UV-A light in the presence of
Ti02.
5.3 Contaminated Ash Treatment
Limited information is available on the effectiveness
of APO in treating contaminated ash. No
commercial- or pilot-scale results were available.
This section describes the effectiveness of a
UV/Ti02 process in treating PCB-contaminated ash
at the bench-scale level.
Chiarenzelli and others (1995) evaluated the
effectiveness of the UV/TiO2 process in
decontaminating a slurry consisting of furnace ash,
core sands, and slag from an aluminum foundry.
The initial concentration of PCBs in the slurry was
about 220 mg/L. Only 45 percent PCB removal was
observed when the slurry was irradiated for about
24 hours using UV-A light in the presence of TiO2.
However, 88 percent removal was achieved when
UV-C light was used instead of UV-A light. The
inability of UV-A irradiation to achieve high removals
suggests that the solar/TiO2 process may not be an
effective alternative to the UV/TiO2 process for
treating some wastes, particularly ash to which
PCBs are strongly bound.
5.4 References
Chiarenzelli, J., R. Scrudato, M. Wunderlich, D.
Rafferty, K. Jensen, G. Oenga, R. Robers, and
J. Pagano. 1995. "Photodecomposition of
PCBs Absorbed on Sediment and Industrial
Waste: Implications for Photocatalytic Treatment
of Contaminated Solids." Chemosphere.
Volume 31. Number 5. Pages 3259
through 3272.
Dupont, R.R., J.E. McLean, R.H. Hoff, and W.M.
Moore. 1990. "Evaluation of the Use of Solar
Irradiation for the Decomposition of Soils
Containing Wood Treating Wastes." Journal of
Air Waste Management Association.
Volume 40. Pages 1247 through 1265.
Egli, S., S. Lomanto, R. Galli, R. Fitzi, and C. Munz.
1994. "Oxidative Treatment of Process Water in
a Soil Decontamination Plant: II. Pilot Plant and
Large Scale Experiences." Chemical Oxidation
Technologies for the Nineties. Volume 2.
Edited by W.W. Eckenfelder, A.R. Bowers, and
J.A. Roth. Technomic Publishing Company, Inc.
Lancaster, Pennsylvania. Pages 264
through 277.
Ireland, J.C., B. Davila, H. Moreno, S.K. Fink, and S.
Tassos. 1995. "Heterogeneous Photocatalytic
Decomposition of Polyaromatic Hydrocarbons
over Titanium Dioxide." Chemosphere.
Volume 30. Number 5. Pages 965 through 984.
McLaughlin, D.B., D.E. Armstrong, and A.W. Andren.
1993. "Oxidation of Polychlorinated Biphenyl
Congeners Sorbed to Particles." 48th Purdue
Industrial Waste Conference Proceedings.
Lewis Publishers, Chelsea, Michigan.
Pages 349 through 353.
Pelizzetti, E., C. Minero, V. Carlin, and E. Borgarello.
1992. "Photocatalytic Soil Decontamination."
Chemosphere. Volume 25. Number 3.
Pages 343 through 351.
5-5
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APPENDIX
TECHNOLOGY VENDOR CONTACT INFORMATION
Vendor'
Dalgon Carbon Oxidation
Technologies
KSE, Inc.
Magnum Water Technology
Matrix Photocatalytic, Inc.
Process Technologies, Inc.
U.S. Filter/Zimpro, Inc.
iWEDECO
Zentox Corporation
Contact Person
Robert Abernethy
J. R. Kittrell
Dale Cox or
Jack Simser
Bob Henderson
John Ferrell or
Michael Swan
Rick Woodling
H. Sprengel
Rich Miller
Address
130 Royal Crest Court
Markham, ON L3R OA1
Canada
P.O. Box 368
Amherst, MA 01004
600 Lairport Street
El Segundo, CA 90254
22 Pegler Street
London, Ontario N5Z 2B5
Canada
1160 Exchange Street
Boise, ID 83716-5762
2805 Mission College Blvd.
Santa Clara, CA 95054
Diamlerstra(3e 5
D-4900 Herford
Germany
2140 NE 36th Ave.
Suite 100
Ocala, FL 34470
Phone No.
(905) 477-9242
(413)549-5506
(310) 322-4143 or
(310) 640-7000
(519) 660-8669
(208) 385-0900
(408) 727-7740
(05221) 391 1
(353) 867-7482
A-1
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