ENCYCLOPEDIA OF ENVIRONMENTAL SCIENCE AND ENGINEERING - HAZARDOUS WASTE MANAGEMENTHISTORICAL OVERVIEW ppt

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HAZARDOUS WASTE MANAGEMENT
HISTORICAL OVERVIEW
The development of the Resource Conservation and Recovery
Act of 1976 dates to the passage of the Solid Waste Disposal
Act of 1965, which first addressed the issues of waste dis-
posal on a nationwide basis. Prior to the 1960s land disposal
practices frequently included open burning of wastes to
reduce volume, and were controlled only by the general need
to avoid creating a public health impact and nuisance, such
as a bad smell or visual blight—problems that one could see,
smell, taste or touch. At that time, what few landfill con-
trols existed were generally focused only on the basics of
sanitation, such as rodent control, and the prevention of fires.
The early concept of the “sanitary” landfill was to cover the
waste with soil to reduce pests and vermin, create separate
chambers of earth to reduce the spread of fire, and control
odor and unsightly appearance—the key environmental con-
cerns of the time.
Throughout the ’60s and into the ’70s, the use of indus-
trial pits, ponds or lagoons on the land were viewed as legit-
imate treatment systems intended to separate solids from
liquids and to dissipate much of the liquids. They were not
only intended to store waste, but also to treat it. That is,
solids would sink when settling occurred and the liquid
could be drained, evaporated, or allowed to percolate into
the ground. The accumulated solids ultimately would be
landfilled.
Similarly for protection of receiving waters, pollu-
tion control laws prior to the mid-1960s were generally

concerned with water-borne diseases and nuisances. The
concept of water pollution was far more closely linked to
the bacterial transmission of disease and physical obstruc-
tion or offense than it was to the impact of trace levels of
chemicals. Waterways were viewed as natural systems that
could handle waste if properly diluted and if the concentra-
tions were within the assimilative capacity of the rivers and
streams. The environmental concerns were primarily odor,
appearance, oxygen content, and bacterial levels. Individual
chemical constituents and compounds, at this time, were not
typically regulated in a waterway.
The science of testing for and measuring individual con-
taminants was unrefined and typically not chemical specific
until the 1970s. Water and wastewater analyses were gen-
erally limited to indicator parameters, such as Biochemical
Oxygen Demand, turbidity, suspended solids, coliform bac-
teria, dissolved oxygen, nutrients, color, odor and specific
heavy metals. Trace levels of individual chemical com-
pounds and hazardous substances as we know them today
were not among the parameters regularly analyzed.
“Hazardous waste” became a household word in the late
1970s with the publicity surrounding the Love Canal inci-
dent. How much waste has been disposed of is still ques-
tionable. Unfortunately, significant amounts were “thrown
away” over the past decades and have endured in the envi-
ronment in drum disposal sites such as “The Valley of the
Drums” and in land disposal facilities where they have not
degraded.
Throughout the ’70s and ’80s significant changes were
made in the laws governing environmental protection. New

laws adopted in the ’70s include the Clean Air Act, the
Federal Water Pollution Control Act, Safe Drinking Water
Act, Resource Conservation and Recovery Act (RCRA),
Toxic Substance Control Act, Marine Protection Research
and Sanctuaries Act, and in 1980 the “Superfund” (CERCLA)
statute. Of all the laws passed in the ’70s, RCRA has had the
greatest impact on the definition of wastes and the manner
in which these wastes were to be managed, treated and
handled. RCRA
1
required the US Environmental Protection
Agency to establish management procedures for the proper
disposal of hazardous wastes. These procedures are part of
the Code of Federal Regulations dealing with environmental
protection. They cover a “cradle-to-grave” procedure which
regulates generators, transporters, storers and disposers of
hazardous materials. Regulations for generators and trans-
porters of hazardous wastes may also be found in the Code
of Federal Regulations.
2,3
Subsequent revisions to RCRA in 1984 included the pro-
visions dealing with underground tanks, the restriction of
land disposal of a variety of wastes, corrective action require-
ments for all releases, and the inclusion of a requirement of
© 2006 by Taylor & Francis Group, LLC
HAZARDOUS WASTE MANAGEMENT 451
the EPA to inspect government and privately owned facilities
which handle hazardous waste.
Today the law is again being considered for revision, and
among the issues that are always under discussion include

“how clean is clean” when remediating industrial and landfill
sites. The cleanup standards are not consistent among state and
federal programs, frequently causing significant discussion
among responsible parties and regulators. At this time, risk
assessments are used more often in an effort to design remedial
programs that are appropriate for the media, and the resources
being protected. A risk assessment might provide, for example,
the necessary information to set differing groundwater cleanup
goals in a sole source aquifer, than in an industrialized area sit-
uated above a brackish water-bearing zone where the ground-
water will not again be used for potable purposes.
With the preceding paragraphs as general background,
the brief discussion which follows on hazardous wastes
emphasizes some of the technologies that have been suc-
cessfully used for the treatment and disposal of hazardous
wastes, and remediation of contaminated properties.
HAZARDOUS WASTE DEFINED
Hazardous wastes encompass a wide variety of materials. In
1987, the US EPA estimated that approximately 238 million
tons could be classified as hazardous. This number is probably
generous but suffice it to say that a great deal of material of a
hazardous and dangerous nature is generated and disposed of
every year.
The Resource Conservation and Recovery Act defines a
hazardous waste as a solid waste that may cause or signifi-
cantly contribute to serious health or death, or that poses a
substantial threat to human health or the environment when
improperly managed. Solid waste, under the present guide-
lines, includes sludges, liquids, and gases in bottles that are
disposed of on the land.

From this working definition, a number of wastes have
been defined as hazardous. These include materials that are
ignitable, corrosive, reactive or explosive or toxic. These char-
acteristic identifiers are further delineated in the regulations.
4
In addition, using these general characteristics and specific
tests, the US Environmental Protection Agency has listed
materials from processes, such as electroplating, or specific
classes of materials, such as chlorinated solvents, or speci-
fic materials, such as lead acetate, or classes of compound, such
as selenium and its compounds, which must be managed as
“hazardous wastes” when they are disposed. This list changes
periodically. In many cases disposers have treated materials
not on the list as hazardous if they believe them to be so.
Some general classes of materials such as sewage,
mining and processing of ore wastes are excluded by law at
the present time.
Managing Wastes
Advancements in science and technology have given us
opportunities to address environmental contamination issues
in ways that are technologically more advanced, and more
cost and time efficient than ever before. Technologies that
were unknown, unproven and unacceptable to regulatory
agencies just a few years ago, now exist and are being imple-
mented at full scale. Regulations have changed, as have gov-
ernment policies governing cleanup and enforcement.
On a technical level, many ideas for hazardous waste
treatment and remediation were rejected a few years ago
by the engineering, business and regulatory community as
being unproven or unreliable. Entrepreneurial scientists and

engineers have adapted their knowledge of manufacturing
process chemistry and engineering to the sciences of geol-
ogy and hydrogeology and have refined the necessary equip-
ment and techniques for waste treatment and remediation.
Technologies have been tested at bench and pilot scale, and
many have proven effective on a large scale. Pressure by the
industrial community for engineers and regulators to reach a
common ground has driven the process.
Contaminated soil and groundwater remedial techniques
have tended toward the “active” end of the spectrum, with
the installation of pumps, wells and above ground treatment
systems of the capital and labor intensive variety. Progress
has been made at the opposite end of the spectrum, rang-
ing from intrinsic bioremediation, which involves no active
treatment, to incremental levels of treatment that are far less
costly than ex-situ pump and treat methods.
Programs like the EPA SITE (Superfund Innovative
Technology Evaluation) Program and other Federal test and
evaluation facilities, University research organizations and
privately sponsored technology incubator and test evaluation
facilities have been very successful in testing and establishing
new hazardous waste treatment and disposal technologies.
Currently, there are several dozen organizations nationally
that specifically focus on the development of emerging haz-
ardous waste treatment technologies. The results have been
very positive, and many of today’s front-edge technologies
are the offspring of programs such as these.
On a regulatory/compliance level, the extensive time
frame for receipt of approvals led many companies down
the path of the traditional treatment and disposal methods,

since they were “proven,” as well as being approvable by the
regulatory agencies. Environmental agencies have become
more sophisticated, and cleanup levels are more often based
on risk rather than standards set at an earlier data in tech-
nical and regulatory development. More than ever, agency
personnel are now trained as specialists in the various seg-
ments of the environmental industry, including risk assess-
ment, hydrogeology, remediation engineering and personal
protection. As a result, the agencies are often more willing
to engage in discussions regarding site specific conditions
and remedial goals. Further, modifications to state permit-
ting programs have allowed variations on typical operating
permits for new and emerging technologies that appear to
have promise.
An analysis of Superfund remediation activities indi-
cates that significant progress has been made in the use of
innovative technologies for site remediation. The predomi-
nant new technologies used at Superfund sites include soil
© 2006 by Taylor & Francis Group, LLC
452 HAZARDOUS WASTE MANAGEMENT
vapor extraction (SVE) and thermal desorption. It is impor-
tant to note that there are many derivative technologies that
will now stand a greater chance of receiving government and
industry support as a result.
Remediation technologies that are derived from soil
vapor extraction include dual phase extraction and sparing.
The two phases are typically a) removal of free product or
contaminated groundwater and b) vapor. The in-situ addition
of certain compounds by sparging into the soil and ground-
water has made bioremediation attractive. The addition of

the additional components to an earlier technology that was
moderately successful has made the modified treatment train
much more effective. The new treatment train is therefore
more approvable.
On a financial level, methods have been developed for
the evaluation of large projects to provide a greater degree
of financial assurance. The concept of the “unknown” cost
of remediation due to the inability of scientists to accurately
see and measure subsurface contamination is diminishing.
Probabilistic cost analyses are frequently completed on
assignments so that final remediation costs can be predicted
within a much narrower range.
Management practices have changed dramatically over
the past 20 years at most industries. They have been driven
by the improvements in technologies, as well as the laws and
regulations. The real estate boom of the 1980s also impacted
operating practices, as many properties were bought and sold
during this time. The desire of buyers to be assured that they
were purchasing “clean” properties, as well as some state
environmental property transfer requirements, was the gen-
esis of facility environmental audits as we now know them.
For purposes of discussion, hazardous wastes fall primar-
ily into two categories, organic and inorganic. Some manage-
ment technologies will apply to both, but in general organic
material can be destroyed to relatively innocuous end prod-
ucts while inorganic material can only be immobilized. The
key technologies for hazardous waste management include:
• Pollution Prevention
• Recycling and Reuse
• Waste Minimization

• Chemical Treatment and Detoxification
• Destruction
• Stabilization
• Land disposal
Of these, land disposal is the least attractive alternative from
the standpoint of long-term liability exposure and environ-
mental impact.
Waste Concentration—A Key Where a waste must be ulti-
mately disposed of, concentration or volume reduction is
beneficial. The simplest approach to this is to separate wastes
at the source; that is, at the place of origin. This will increase
handling costs and effort, but will more than pay dividends in
minimizing analytical and disposal costs. First, it will mean
that analysis must be done less frequently. Second, waste can
be disposed of at the lowest degree of care consistent with the
most hazardous contaminant, thus minimizing the volume of
waste that must get a greater degree of care because of slight
cross-contamination by a more toxic material. This is true
whether the material is in the liquid or solid state.
Another method of reducing volume is concentration.
For liquids, this generally means distillation or evapora-
tion. Evaporation to date has been acceptable, however, with
increased emphasis on the presence of volatile hazardous
materials in the atmosphere, evaporation ponds, will, in all
probability, no longer meet the necessary standards for waste
control and management. In addition, ponds must be per-
mitted under RCRA, which imposes additional financial and
operating requirements on the waste concentrator. Double
and triple effect evaporators and distillation units will be
acceptable but are very energy-expensive. Innovative tech-

niques will be required because of the high energy of the
traditional liquid separation systems.
Where a material is dissolved in water or an organic sol-
vent, precipitation may be advisable. The solid can then be
separated out from the majority of the liquid by filtration
or other liquid/solid separation technology. Typical of this
would be the precipitation of lead by the use of a sulfide salt,
resulting in lead sulfide which has extremely low solubility.
The solid may be suitable for reclamation at present or be
stored in a secure landfill in a “non- or less-hazardous form”
for eventual reuse.
Pollution Prevention The passage of Pollution Prevention
Laws has driven many industries toward better utilization of
their resources. Many companies now actively participate
in the preparation and update of a pollution prevention pro-
gram, designed to guide personnel toward goals established
to improve waste generation and disposal practices.
Traditional environmental quality and pollution control
programs typically focus on an end-of-pipe approach. The
pollution prevention plan approach typically begins earlier
in the “equation” by reviewing an operation and making
modifications that will positively impact a facility. Some
examples include reducing harmful chemical purchases,
increasing operation efficiencies, and ultimately generating
a smaller quantity of waste.
The pollution plan approach will include involvement
by a wider range of facility personnel than the traditional
environmental management approach. Purchasing, account-
ing, production and engineering all participate. Proponents
suggest that a program is easy to implement, although corpo-

rate personnel involved in the effort know that it is an effort
which requires broad-based management support, is time
consuming, and not necessarily inexpensive to implement.
The benefits are potentially significant, as reduced emissions
make it easier to comply with discharge standards, and will
reduce long-term liabilities.
Recycling and Reuse In many cases, in addition to eco-
nomically attractive alternatives, a very attractive alternative
will be recycling or reuse of hazardous wastes. The eco-
nomic realities of the regulations, where disposal of a barrel
of waste can demand a 5–$10 per gallon, and up to $1,200 per
© 2006 by Taylor & Francis Group, LLC
HAZARDOUS WASTE MANAGEMENT 453
ton or greater fee, may make processing for recycling and/or
reuse the best practice. In the present context, we are defining
recycling as internal to the plant, and reuse as external to the
plant. This is not a legal definition which defines recycling as
essentially both internal and external, but it is helpful in this
discussion.
Internal recycling will require, in general, high efficiency
separation and potential additional processing. Thus, if a sol-
vent is being recycled, impurities such as water, by-products,
and other contaminants must be removed. Depending on the
volumes involved, this may be done internally to the process
or externally on a batch basis.
Reuse involves “selling” the waste to a recycle and
reclaimer. The reclaimer then treats the waste streams and
recovers value from them. The cleaned-up streams are then
his products for sale.
From a regulatory, liability perspective, there are advan-

tages to reuse as the liability for the waste ends when it is
successfully delivered to the reclaimer. Because he pro-
cesses the material, he then assumes responsibility for the
products and wastes that are generated. If the material is
internally recycled, then the recycler, that is the plant, main-
tains responsibility for any wastes that are generated as a
result of the recycling operation.
In some cases, it may be desirable to dispose of wastes
directly to the user. This is particularly true when there are
large quantities involved and a beneficial arrangement can be
worked out directly. Waste exchanges have been organized
to promote this type of industrial activity. Detailed discus-
sions of their mode of operation can be obtained directly
from the exchanges.
Waste Minimization The alternative scenario develop-
ment will be not only site, but substance specific. Two basic
approaches to hazardous waste management are:
1) In-process modifications
2) End-of-pipe modifications
Each will have advantages and disadvantages that are pro-
cesses, substance, and site specific.
In-process alternatives include changing process con-
ditions, changing feedstocks, modifying the process form
in some cases, or if necessary eliminating that process and
product line.
In-process modification is generally expensive and must
be considered on a case-by-case basis. There are some poten-
tial process modifications that should be considered to mini-
mize the production of toxic materials as by-products. These
include minimization of recycling so side-reaction products

do not build up and become significant contributors to the
pollution load of a bleed stream. For example, waste must
be purged regularly in the chlorination of phenols to avoid
the build-up of dioxin. It may also be desirable to optimize
the pressure of by-products. For example, phenol is produced
and found in condensate water when steam-cracking naphtha
to produce ethylene unless pressures and temperatures are
kept relatively low.
It may be desirable to change feedstocks in order to elim-
inate the production of hazardous by-products. For example,
cracking ethane instead of naphtha will yield a relatively
pure product stream.
Hydrazine, a high energy fuel, was originally produced
in a process where dimethylnitrosamine was an intermediate.
A very small portion of that nitrosamine ended up in a waste
stream from an aqueous/hydrocarbon separation. This waste
stream proved to be difficult, if not impossible, to dispose of.
A new direct process not involving the intermediate has been
substituted with the results that there are no noxious wastes
or by-products.
In the ultimate situation, production of a product may
be abandoned because either the product or a resulting
by-product poses an economic hazard which the corpo-
ration is not willing to underwrite. These include cases
where extensive testing to meet TSCA (Toxic Substances
Control Act) was required. They include the withdrawal of
pre-manufacturing notice applications for some phthalate
ester processes. However, production of certain herbicides
and pesticides was discontinued because a by-product or
contaminant was dioxin.

Treatment/Destruction Technology
Chemical Treatment/Detoxification Where hazardous mate-
rials can be detoxified by chemical reaction, there the mol-
ecule will be altered from one that is hazardous to one or
more that are non-hazardous, or at least significantly less
hazardous. For example, chlorinated hydrocarbons can be
hydro-dechlorinated. The resulting products are either HCl
or chlorine gas and nonchlorinated hydrocarbons. A number
of these processes are being developed for the detoxification
of PCB (polychlorinated biphenols) and are being demon-
strated as low concentrations of PCB’s in mineral oil. The
end products, if concentrated enough, can be useful as feed-
stocks or the hydrocarbons may be used as fuel.
Cyanide can be detoxified using any number of chemi-
cal reactions. These include a reaction with chlorine gas to
produce carbonate and chlorine salt. Cyanide can also be
converted to cyanate using chlorine gas. In addition, ozone
can be utilized to break up the carbon-nitrogen bond and
produce CO
2
and nitrogen.
Hexavalent chromium is a toxic material. It can be
reduced to trivalent chromium which is considerably less
hazardous and can be precipitated in a stable form for reuse
or disposal as a non-hazardous material. Chromium reduc-
tion can be carried out in the presence of sulfur dioxide to
produce chromium sulfate and water. Similar chemistry is
utilized to remove mercury from caustic chlorine electroly-
sis cell effluent, utilizing sodium borohydride.
Lead, in its soluble form, is also a particularly difficult

material. Lead can be stabilized to a high insoluble form
using sulfur compounds or sulfate compounds, thus remov-
ing the hazardous material from the waste stream.
Acids and bases can most readily be converted to non-
hazardous materials by neutralizing them with appropriate
© 2006 by Taylor & Francis Group, LLC
454 HAZARDOUS WASTE MANAGEMENT
base or acid. This is probably the simplest chemical treat-
ment of those discussed and is widely applicable; care must
be taken, however, to insure that no hazardous precipitates or
dissolved solids forms.
Incineration Incineration has been practiced on solid
waste for many years. It has not, however, been as widely
accepted in the United States as in Europe where incin-
eration with heat recovery has been practiced for at least
three decades. Incineration of industrial materials has been
practiced only to a limited extent; first, because it was more
expensive than land disposal, and second, because of a lack
of regulatory guidelines. This has changed because land-
fills are not acceptable or available, costs for landfilling are
becoming extremely high, and regulatory guidance is avail-
able. Equipment for incineration of industrial products has
been, and is available, however, it must be properly designed
and applied.
Incineration is the oxidation of molecules at high tem-
peratures in the presence of oxygen (usually in the form
of air) to form carbon dioxide and water, as well as other
oxygenated products. In addition, products such as hydro-
gen chloride are formed during the oxidation process. The
oxidation, or breakdown, takes place in the gaseous state,

thus requiring vaporization of the material prior to any reac-
tion. The molecules then breakdown into simpler molecules,
with the least stable bonds breaking first. This occurs at rela-
tively lower temperatures and shorter times. It is followed by
the breakdown of the more stable, and then the most stable
bonds to form simple molecules of carbon dioxide, water,
hydrogen chloride, nitrogen oxides, and sulfur oxides, as
may be appropriate.
Thus, the primary considerations for successful oxi-
dation or destruction are adequate time and temperature.
Good air/waste contact is also important. Regulatory guide-
lines require a destruction and removal efficiency (DRE)
of 99.99% thus, time and temperature become all the more
important. For the most refractory compounds, such as
PCB’s, residence times in excess of three seconds and tem-
peratures in excess of 1000°C are required. These tempera-
tures may be reduced in light of special patented processes
utilizing oxidation promoters and/or catalysts. As a result of
the high required DRE, a test burn is required to demonstrate
adequate design.
In addition to time and temperature considerations,
there are other important factors which must be consid-
ered when designing or choosing equipment to incinerate
industrial waste. Most important is adequate emission gas
controls. Where materials which contain metals, chlorides,
or sulfides are to be incinerated, special provisions must be
made to minimize emission of HCl, SO
2
, and metal oxides.
Usually a scrubber is required, followed by a system to

clean up the scrubber-purge water. This system includes
neutralization and precipitation of the sulfur and metal
oxides. In addition, where high temperature incineration
is practiced, control of nitrogen oxides to meet air quality
emissions standards must be considered. These substances
do not present insurmountable technological challenges, as
they have been handled satisfactorily in coal-fired power
plant installations, but they do present added economic and
operating challenges.
Several types of incineration facilities should be con-
sidered. Unfortunately, the standard commercial incinera-
tor utilized or municipal waste will generally not prove
adequate for handling industrial waste loads because the
temperatures and residence times are inadequate. Municipal
incinerators are designed to handle wastes with an energy
content below 8000 Btu/pound, while industrial wastes can
have heating values as high as 24000 Btu/pound. Municipal
incinerators are generally not designed to accept industrial
wastes.
A number of incinerator facilities have been built for
industrial wastes. Small, compact units, utilizing a single
chamber with after-burner, or two-stage, multi-chamber
combustion are available. In general, a single-state unit will
not suffice unless adequate residence time can be assured.
Rotary kiln incinerators are of particular interest for
the disposal of industrial materials. Generally, they are
only applicable for large-scale operations, and can handle
a large variety of feedstocks, including drums, solids and
liquids. Rotary cement kilns have been permitted to accept
certain types of organic hazardous materials as a fuel

supplement.
Of increasing interest for industrial incineration is the
fluid bed incinerator. This has the additional advantage of
being able to handle inorganic residues, such as sodium
sulfate and sodium chloride. These units provide the addi-
tional advantage of long residence time, which may be desir-
able when the waste is complex (e.g., plastics) or has large
organic molecules. On the other hand, gas residence times
are short, and an after-burner or off-gas incinerator is often
required in order to achieve the necessary DRE.
Incineration has been used successfully for the disposal
of heptachlor, DDT, and almost all other commercial chlori-
nated pesticides. Organo-phosphorous insecticides have also
been destroyed, but require a scrubbing system, followed by
a mist eliminator, to recover the phosphorous pentoxide that
is generated.
Some special incineration applications have been imple-
mented. These include:
• An ammonia plant effluent containing organics
and steam is oxidized over a catalyst to form CO
2
,
water and nitrogen;
• Hydrazine is destroyed in mobile US Air Force
trailers which can handle 6 gpm of 100% hydra-
zine to 100% water solutions, and maintain an
emission has which contains less than 0.03 pound/
minute of NO x ;
• Chlorate-phosphorous mixtures from fireworks
ammunition are destroyed in a special incinerator

which has post-combustion scrubbing to collect
NO x , P
4
O
10
, HCl, SO
2
and metal oxides;
• Fluid bed incinerators which handle up to 316 tons
per day of refinery sludge and 56 tons of caustic
are being utilized.
© 2006 by Taylor & Francis Group, LLC
HAZARDOUS WASTE MANAGEMENT 455
Wet Air Oxidation Although not strictly incineration, wet
air oxidation is a related oxidation process. Usually air, and
sometimes oxygen, is introduced into a reactor where haz-
ardous material, or industrial waste, is slurried in water at
250° to 750°F.
Operating pressures are as high as 300 psig. Plants have
been built to treat wastes from the manufacture of polysulfite
rubber and other potentially hazardous materials. Emissions
are similar to those obtained in incineration, with the excep-
tion that there is liquid and gaseous separation. Careful eval-
uation of operating conditions and materials of destruction
are required.
Pyrolysis Pyrolysis transforms hazardous organic materi-
als by thermal degradation or cracking, in the absence of an
oxidant, into gaseous components, liquid, and a solid resi-
due. It typically occurs under pressure and a temperature
above 800°F.

To date, the process has found limited commercial applica-
tion but continues to be one that will eventually be economically
attractive, the prime reason being the potential for recovery of
valuable starting materials. A great deal of experimentation has
been carried out both on municipal and industrial wastes. For
example, polyvinyl chloride can be thermally degraded to pro-
duce HCl and a variety of hydrocarbon monomers, including
ethylene, butylene, and propylene. This is a two-stage degrada-
tion process with the HCl coming off at relatively low tempera-
tures (400°C) and the hydrocarbon polymer chain breakdown
can be obtained with Polystyrene, with styrene as the main
product, and most other polymers. Experimental work carried
out in the early 1970s by the US Bureau of Mines, indicates
that steel-belted radial tires can be pyrolyzed to reclaim the
monomers, as well as gas and fuel oil.
Other target contaminant groups include SVOCs and
pesticides. The process is applicable for the treatment of
refinery, coal tar, and wood treating wastes and some soils
containing hydrocarbons.
Disposal Technology
Land Storage and Disposal Disposal of hazardous mate-
rials to the land remains the most common practice. It
is highly regulated and a practice which has been limited
because of public pressure and federal rules which require
the demonstration of alternate means of disposal. The design
of secure landfills for the acceptance of hazardous materials
must be such that ground waters, as well as local populations
are protected. The US Environmental Protection Agency has
implemented strict landfills. In practice all landfills accept-
ing hazardous wastes must insure that the wastes stored in

close proximity are compatible so that no violent reactions
occur should one or more waste leak.
Federal and State regulations prohibit the disposal of
liquids in landfills. Of equal importance to the disposal of
hazardous wastes, whether solid or semi-solid, is the assur-
ance that material will not leach away from the landfill or
impoundment. This assurance is provided by the use of
“double-liners” with a leak detection system between the
liners, a leachate collection system for each cell, and a leach-
ate treatment system designed and operated for the facility.
In dilute form liquid wastes can be “landfarmed” where
microbial action will decompose the compounds over time.
This methodology has been utilized over many years for
hydrocarbons and has worked well. For highly toxic com-
pounds, such as chlorinated organics, it is less attractive even
though decomposition does occur. Land treatment of PCB
contaminated soils has been tested with some success.
Stabilization The stabilization of hazardous materials prior
to land disposal is frequently practiced. Generally, the stabi-
lization is in the form of fixing the hazardous material with
a pozzolanic material, such as fly ash and lime, to produce a
solid, non-leachable product which is then placed in land dis-
posal facilities. Typically, this methodology is applicable to
inorganic materials. Most of the commercial processes claim
that they can handle materials with some organic matter.
Polymer and micro-encapsulation has also been uti-
lized but to a significantly lesser extent than the commer-
cially available process which utilize pozzolanic reactions.
Polymers which have been utilized include polyethylene,
polyvinylchloride and polyesters.

Grube
9
describes a study of effectiveness of a waste
solidification/stabilization process used in a field-scale
demonstration which includes collecting samples of treated
waste materials and performing laboratory tests. Data from
all extraction and leaching tests showed negligible release
of contaminants. Physical stability of the solidified material
was excellent.
Remediation Technologies
Natural Attenuation and Bioaugmentation The concept of
natural attenuation, or intrinsic bioremediation, has gained
a greater acceptance by the regulatory community as data
presented by the scientific community have demonstrated
the results of natural attenuation, and the costs and time
frames associated with traditional remedial methods.
1
This
approach is most appropriate for the dissolved phase ground-
water contamination plume. It is still necessary to remove or
remediate the source zone of an affected aquifer, after which
natural attenuation may be a reasonable approach to the dis-
solved phases.
Natural attenuation should not be considered “No
Action.” It requires a solid understanding of the contami-
nant, geologic and aquifer characteristics, and a defined plan
of action. The action involves demonstrating that the con-
taminants will breakdown, will not migrate beyond a speci-
fied perimeter, and will not impact potential receptors. It
may involve the stimulation of microorganisms with nutrients

or other chemicals that will enable or enhance their ability to
1
Example of traditional remediation methods are ex-situ treatment of soil
and groundwater, such as soil excavation/disposal, groundwater pump-
and-treat using air stripping and granulated carbon polishing.
© 2006 by Taylor & Francis Group, LLC
456 HAZARDOUS WASTE MANAGEMENT
degrade contaminants. Some limitations may include inappro-
priate site hydrogeologic characteristics (including the inability
of the geostrata to transport adapted microorganisms) and con-
taminant toxicity. Monitoring and reporting is required, and a
health-based risk assessment may be required by regulators.
Natural attenuation is frequently enhanced by several
components, such as the creation of a barrier or the addition
of a chemical or biologic additive to assist in the degradation
of contaminants.
The overall economics of this approach can be sig-
nificantly more favorable than the typical pump-and-treat
approach. One must be careful to consider, however, that the
costs of assessment will equal or exceed that necessary for
other methods, and the costs associated with sentinel moni-
toring will be borne for a longer period of time.
Barriers This has been used in instances where the over-
all costs of the remedial action is very high, and the geo-
logic features are favorable. It involves the installation of
a physical cut-off wall below grade to divert groundwater.
The barriers can be placed either upgradient of the plume
to limit the movement of clean groundwater through the
contaminated media, or downgradient of the plume with
openings or “gates” to channel the contaminated groundwa-

ter toward a remedial system. This technology has proven
to be more efficient and less costly than traditional pump
and treat methods, but also requires favorable hydrogeologic
conditions. It allows for the return of treated groundwater to
the upgradient end of the plume with a continuous “circu-
lar” flushing of the soil, rather than allowing the dilution by
groundwater moving from the upgradient end of the plume.
The result is greater efficiency, and a shorter treatment time
period. While the cost of the cutoff wall is significant, it is
important to conduct a proper analysis of long-term pump-
and-treat costs, including the operation and maintenance of
a system that would otherwise be designed to accept a much
larger quantity of groundwater.
The creation of a hydraulic barrier to divert upgradient
groundwater from entering the contaminant plume allows
the pumping of groundwater directly from the affected area
and often allows the reinjection of the treated water back
into the soils immediately upgradient of the plume. This
allows for the efficient treatment of the impacted area, with-
out unnecessary dilution of the contaminated groundwater
plume. It does, however, require an accurate assessment of
the groundwater regime during the assessment stage. This
promising concept is not radical, but its use in connection
with natural remediation is growing rapidly.
Passive Treatment Walls Passive treatment walls can be
constructed across the flow path of a contaminant plume to
allow the groundwater to move through a placed media, such
as limestone, iron filings, hydrogen peroxide or microbes.
The limestone acts to increase the pH, which can immobi-
lize dissolved metals in the saturated zone. Iron filings can

dechlorinate chlorinated compounds. The contaminants will
be either degraded or retained in concentrated form by the
barrier material.
Physical Chemical Soil Washing Soil is composed of a
multitude of substances, with a large variance in size. These
substances range from the very fine silts and clays, to the
larger sand, gravel and rocks. Contaminants tend to adsorb
onto the smallest soil particles, as a result of the larger sur-
face per unit of volume. Although these smaller particles
may represent a small portion of the soil volume, they may
contain as much as 90% of the contamination.
Soil washing involves the physical separation, or clas-
sification, of the soil in order to reduce the volume requiring
treatment or off-side disposal. It is based on the particle size
separation technology used in the mining industry for many
decades. The steps vary, but typically begin with crushing
and screening. It is a water-based process, which involves
the scrubbing of soil in order to cause it to break up into the
smallest particles, and its subsequent screening into various
piles. The fraction of the soil with the highest concentra-
tion of contamination can be treated using technologies fre-
quently used by industry. The goal is to reduce the quantity
of material that must be disposed. The clean soil fractions
can often be returned to the site for use as fill material where
appropriate.
The use of soil washing technology has some limitations,
including a high initial cost for pilot testing and equipment
setup. It will be most useful on large projects (requiring reme-
diation of greater than 10,000 cubic yards of soil). Sites with
a high degree of soil variability, and a significant percentage

of larger particles will show the greatest economic benefit.
Soil Vapor Extraction Soil Vapor Extraction (SVE) is an
effective method for the in-situ remediation of soils contain-
ing volatile compounds. Under the appropriate conditions
volatile organic compounds will change from the liquid
phase to the vapor phase, and can be drawn from the subsur-
face using a vacuum pump. There are several factors neces-
sary for the successful use of this technology, including 1)
the appropriate properties of the chemicals of concern (they
must be adequately volatile to move into a vapor phase),
and 2) an appropriate vapor flow rate must be established
through the soils.
Air is drawn into the soils via perimeter wells, and
through the soils to the vapor extraction well. It is drawn to
the surface by a vacuum pump and subsequently through a
series of manifolds to a treatment system such as activated
carbon or catalytic oxidation.
A concentration gradient is formed, whereby in an effort
to reach equilibrium, the liquid phase volatile contaminants
change into the vapor phase and are subsequently transported
through the soils to the treatment system.
This technology is particularly effective for defined spill
areas, with acceptable soils. It is most effective in remediating
the soils in the vadose zone, the area that is in contact with
the fluctuating groundwater table. Groundwater contaminated
with these compounds and similar soil conditions can be reme-
diated using air sparging, a variation of soil vapor extraction.
A variation of this technology is thermal enhanced SVE,
using steam/hot air injection or radio frequency heating to
increase the mobility of certain compounds.

© 2006 by Taylor & Francis Group, LLC
HAZARDOUS WASTE MANAGEMENT 457
Air Sparging Air sparging is the further development of
soil vapor extraction, wherein that process is extended so that
soils and groundwater in the capillary fringe can be effec-
tively treated. Air sparging involves injecting air or oxygen
into the aquifer to strip or flush volatile contaminants from
the groundwater and saturated soils. As the air channels up
through the groundwater, it is captured through separate vapor
extraction wells and a vapor extraction system. The entire
system essentially acts as an in-situ air stripper. Stripped,
volatile contaminants usually will be extracted through soil
vapor extraction wells and usually require further treatment,
such as vapor phase activated carbon or a catalytic oxida-
tion treatment unit. This technology is effective when large
quantities of groundwater must be treated, and can provide
an efficient and cost-effective means of saturated zone soil
and groundwater remediation.
The biological degradation of organic contamination
in groundwater and soil is frequently limited by a lack of
oxygen. The speed at which these contaminants are degraded
can be increased significantly by the addition of oxygen in
either solid or liquid form. Air sparging is often combined
with in-situ groundwater bioremediation, in which nutrients
or an oxygen source (such as air or peroxide) are pumped
into the aquifer through wells to enhance biodegradation of
contaminants in the groundwater.
Oxygen Enhancement/Oxidation In this in-situ process,
hydrogen peroxide is used as a way of adding oxygen to
low or anoxic groundwater, or other oxidative chemicals are

added as an oxidant to react with organic material present,
yielding primarily carbon dioxide and water. The application
of this technology is typically through the subsurface injec-
tion of a peroxide compound. It has been injected as a liquid,
above the plume, and allowed to migrate downward through
the contaminated plume. Alternately, it has been placed as a
solid in wells located at the downgradient edge of the plume;
in this fashion it can act as a contamination “barrier,” limiting
the potential for contaminated groundwater to move offsite.
As the organic contaminated groundwater moves through the
high oxygen zone, the contaminant bonds are either broken,
or the increased oxygen aid in the natural biodegradation of
the compounds.
The process is exothermic, causing a temperature
increase in the soils during the process. This acts to increase
the vapor pressure of the volatile organic compounds in the
soil, and subsequently increases volatilization of the con-
taminants. This process can be utilized in connection with
a soil vapor extraction and/or sparging system to improve
remediation time frames.
It does not act, however, on the soil groundwater vadose
zone. This may not be a critical flaw, however, since the strate-
gic placement of the wells may positively impact the contami-
nant concentrations adequately to meet cleanup standards.
Dual Phase Extraction Dual phase extraction is an effec-
tive method of remediating both soils and groundwater in
the vadose and saturated zones where groundwater and
soil are both contaminated with volatile or nonvolatile
compounds. It is frequently used for contaminant plumes
with free floating product, combined with known contami-

nation of the vadose zone. This technique allows for the
extraction of contaminants simultaneously from both the
saturated and unsaturated soils in-situ. While there are
several variations of this technique, simply put, a vacuum
is applied to the well, soil vapor is extracted and ground-
water is entrained by the extracted vapors. The extracted
vapors are subsequently treated using conventional treat-
ment methods while the vapor stream is typically treated
using activated carbon or a catalytic oxidizer.
The process is frequently combined with other technolo-
gies, such as air sparging or groundwater pump-and-treat to
minimize treatment time and maximize recovery rate.
Chemical Oxidation and Reduction Reduction/oxidation
reactions chemically convert hazardous contaminants to
nonhazardous or less toxic compounds that are more stable,
less mobile and/or inert. The oxidizing agents typically
used for treatment of hazardous contaminants are ozone,
hydrogen peroxide, hypochlorites, chlorine and chlorine
dioxide. These reactions have been used for the disinfec-
tion of water, and are being used more frequently for the
treatment of contaminated soils.
The target contaminant group for chemical reduction/oxi-
dation reactions is typically inorganics, however hydrogen
peroxide has been used successfully in the in-situ treatment
of groundwater contaminated with light hydrocarbons.
Other Technologies Many other technologies are being
applied with increasing frequency. The following is only a
very brief description of several that have promise.
• Surfactant enhanced recovery Surfactant flushing
of non-aqueous phase liquids (NAPL) increases

the solubility and mobility of the contaminants in
water, so that the NAPL can be biodegraded more
easily in the aquifer or recovered for treatment
aboveground via pump-and-treat methods.
• Solvent extraction Solvent extraction has been
successfully used as a means of separating haz-
ardous contaminants from soils, sludges and
sediments, and therefore reducing the volume
of hazardous materials that must be treated. An
organic chemical is typically used as a solvent,
and can be combined with other technologies,
such as soil washing, which is frequently used
to separate, or classify, various soil particles into
size categories. The treatment of the concentrated
waste fraction is then treated according to its spe-
cific characteristics. Frequently, the larger volume
of treated material can be returned to the site.
• Bioremediation using methane injection The method
earlier described for the injection of hydrogen per-
oxide into wells has also been successfully utilized
using methane. It is claimed that this bioremedia-
tion process uses microbes which co-metabolize
methane with TCE and other chlorinated solvents,
© 2006 by Taylor & Francis Group, LLC
458 HAZARDOUS WASTE MANAGEMENT
potentially cutting treatment costs and time frames
by 30 to 50%.
• Thermal technologies The EPA has conducted
tests of thermally-based technologies in an evalu-
ation of methods to treat organic contaminants

in soil and groundwater. Low temperature ther-
mal desorption is a physical separation process
designed to volatilize water and organic contami-
nants. Typical desorption designs are the rotary
dryer and the thermal screw. In each case, mate-
rial is transported through the heated chamber via
either conveyors or augers. The volatilized com-
pounds, and gas entrained particulates are subse-
quently transported to another treatment system
for removal or destruction.
Mobile incineration processes have been developed
for use at remedial sites. While permitting is frequently a
problem, the economics of transporting large quantities of
soil can drive this alternative. One method is a circulating
fluidized bed, which uses high-velocity air to circulate and
suspend the waste particles in a combustion loop. Another
unit uses electrical resistance heating elements or indirect-
fired radiant U-tubes to heat the material passing through
the chamber. Each requires subsequent treatment of the off
gases. Also certain wastes will result in the formation of a
bottom ash, requiring treatment and disposal.
In summary, the current business and regulatory climate
is positive for the consideration of alternate treatment tech-
nologies. The re-evaluation of ongoing projects in light of
regulatory and policy changes, as well as new technological
developments may allow cost and time savings. The arse-
nal of techniques and technologies has developed substan-
tially over the years, as has our knowledge of the physical
and chemical processes associated with the management of
wastes. Effluents and contaminated media are now easier to

target with more efficient and cost-effective methods.
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RICHARD T. DEWLING
GREGORY A. PIKUL
Dewling Associates, Inc.
© 2006 by Taylor & Francis Group, LLC