EPA 600/D-82-345
Ronald Hill page 1 of 34
HAZARDOUS WASTE DISPOSAL ALTERNATIVES: FOUR OPTIONS
FOR HAZARDOUS WASTE DISPOSAL PAPER FOR PUBLICATION
IN CIVIL ENGINEERING MAGAZINE SPETEMBER 1981 ISSUE
Summary
Approximately 41,235 thousand wet metric tons of hazardous waste
were produced in 1980. Nearly 83 percent of this waste was treated and
disposed of on-site by the producer. The remaining 17 percent was
handled by off-site commercial facilities. The methods used include
secure landfills, land treatment, deep well injection, incineration,
resource recovery, and chemical, biological, and physical treatment.
This article focuses on four options: secure landfills with the option
of fixation before landfilling, land treatment, mine storage, and deep
well injection. Engineering design and construction information is
presented for each option.
by
Ronald Hill, Director
Norbert Schomaker, (Member, ASCE), Chief, Disposal Branch
Robert Landreth, Sanitary Engineer
Carlton Wiles, Chemical Engineer
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Introduction
It has been estimated that the production of hazardous waste in the
United States was 41,235 thousand wet metric tons in 1980. Figure 1
illustrates the industries that are the major contributors. The single
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largest source is the chemicals and allied products industry, accounting
for 62 percent of the total. Approximately 83 percent of the hazardous
waste produced is treated or disposed of on-site by the industry. The
remaining waste is handled by commercial off-site facilities. Figure 2
presents the waste management options utilized. As noted, landfill ing
and treatment are the options utilized. As noted, landfill ing and
treatment are the options used for approximately 66 percent of the
waste. The remaining waste is either incinerated, land treated, deep
well injected, or recovered. This article will focus on four options:
secure landfills with the option of fixation before landfill ing, land
treatment, mine storage, and deep well injection.
Secure Landfills
A secure hazardous waste landfill means a facility which has received
a permit from the U.S. Environmental Protection Agency (USEPA) or from a
state authorized by the USEPA to issue permits to dispose of hazardous
waste by the landfill method.
The secure landfill concept encompasses much more than just the
simple burial of hazardous material. Hazardous waste landfills must be
carefully engineered to provide long-term protection of groundwater,
surface water, air, and human health. Figure 3 shows a' secure landfill.
Although the state-of-the-art is still developing, a number of techniques
are now available for effectively reducing the adverse health and environ-
mental effects from landfills.
The environmental problems associated with hazardous waste landfills
can be divided into two broad classes. The first class includes fires,
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explosions, toxic fume production, and other problems caused by incompatible
materials being mixed. The second class includes contamination of
surface and groundwaters. The first class of problems can be adequately
handled by proper management through use of controlled mixing of incompatible
wastes; segregation of materials in separate landfill cells; and pretreatment
of wastes. The problems associated with the second class are more
difficult, but can be handled by proper siting, appropriate design and
operation of cover, waste cells and subcells, leachate management system,
and provisions for long-term management of the facility through closure,
post closure, and monitoring activities.
The following describes these considerations and elements of landfill
design which are important as they relate to permanent status and to interim
status standards of the USEPA. Since the currently proposed regulations
reflect increased flexibility in permitting for hazardous waste landfills,
no one set of design criteria is proposed or advocated.
In siting landfills four general areas need to be considered:
groundwater quality, surface water quality, air quality, and potential
for subsurface migration of leachates and gases. In addition, specific
requirements have been established, such as location with 200 feet (61
m) of a fault and/or in a 100-year flood plain. Groundwater and surface
water quality cannot be adversely affected. The following eight factors
need to be considered:
o Volume and physical and chemical characteristics of the waste;
o Hydrogeological characteristics of the facility and the surrounding
land;
o Quantity, quality, and direction of groundwater flow;
o Proximity and withdrawal rates of groundwater uses;
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o Establishment of existing groundwater quality including other
sources of contamination;"
o Potential for human health risks;
o Damage to wildlife, crops, vegetation, and physical structures
caused by exposure to waste constituents;
o Persistence and permanence of the potential adverse effects.
All surface water discharges must be in compliance with the National
Pollutant Discharge Elimination System (NPDES) requirements. Rainfall
patterns in the area need to be considered to determine the appropriate
controls for diversion of runoff from adjacent lands and control of
runoff from the facility. Runoff which has contacted the waste is
assumed to be contaminated and must be specifically tested to determine
appropriate discharge conditions.
Air quality needs to be considered in order to prevent adverse
effects to the air caused by volatilization, gas generation, gas migration,
and wind dispersal of landfilled hazardous wastes. Subsurface migration
of leachate is considered to be a distinct form of environmental degradation
apart from contamination of groundwater, which is subsequently drawn for
use. Subsurface migration is of primary concern in relation to contami-
nation of nearby subsurface structures and vegetative kill. Both the
saturated and unsaturated zone must be considered in evaluating the
potential for subsurface migration. Knowledge of waste' characteristics
and the geology of surrounding area is needed, as well as land use
patterns in the immediate vicinity.
A design consideration for landfills is a liner to contain the
waste and intercept the leachate. Although the regulations do not
require the construction of a liner for all landfills, it is recognized
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that many landfills will be constructed using liners in order to. contain
the hazardous waste. Liners can either be of earthen material or synthetic
membranes. Generally, the liner requirement will involve the placement
of materials onto the floor and sides of the disposal area. Under
appropriate conditions, it might be possible to use the natural in-place
material which underlies the facility as part of the liner. The amount
of leachate that will be generated in the landfill is a critical factor
in assessing the liner design. This assessment must involve a consideration
of the waste type (e.g., liquid content, biodegradability, solubility,
migratory potential), the volume of waste, and climatic conditions in
the area (e.g. rainfall). In assessing the performance of the liner,
the characteristics of the liner material must be examined. The perme-
ability of the liner material is a central concern. Thickness, suscepti-
bility to cracking or tearing, and resistance to adverse weather conditions
are important liner considerations. For earthen liners, the compacted
density and moisture content of the material is also significant. For
synthetic membrane liners, longevity based on degradability (chemical
resistance) and resistance to wear (structural integrity) are significant.
Any emplaced liner must be installed in a manner that will protect the
function and physical integrity of the liner. For example, the operator
must assure that the installation process does not cause rips or tears
in the liner material and that any seams in the liner are properly
joined.
All landfills must have some kind of leachate and runoff control
system for management of these liquids. The design and operation of the
facility significantly affects the amount of contaminated liquid which
must be managed. If the facility intends to discharge collected leachate
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or runoff to surface waters, compliance with the USEPA and the state
water quality standards and discharge requirements must be met. Any
leachate or runoff which qualifies as a hazardous waste must be managed
in accordance with hazardous waste regulations.
The concept of landfill cells has been incorporated into the regula-
tions. A landfill cell is "a discrete volume of hazardous waste landfill
which uses a liner to provide isolation of wastes from adjacent cells or
wastes." Cells may be physically separate areas of landfills or trenches,
and as such can be used to separate incompatible wastes. The use of the
cell concept will permit different cells to have different closure
requirements and financial arrangements. A leachate monitoring system
is required for new landfills and landfill cells.
All landfills must have some type of cover when it is closed. The
function and design of the cover will depend on the operator's strategy.
The cover may be used as a means to prevent wind dispersal and to avoid
public contact with the waste in the landfill. Under other circumstances
it may be used as a barrier designed to keep liquids out of the facility
and to minimize the production of leachate. Whatever approach is taken,
the development of the cover specifications should be coordinated with
the design of the liner in order to avoid the "bathtub" effect. This
.occurs when a relatively permeable cover is placed over a facility that
has a relatively impermeable liner. Such a facility may simply fill up
with water and overflow, carrying waste constituents with it. A minimum
set of technical factors needs to be considered in cover design. These
factors include cover materials, final surface contours, porosity and
permeability, thickness, length and steepness of slope, and type of
vegetation. Allowances should be made for deep-rooted vegetation and to
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prevent water from pooling. The design will depend on the availability
and characteristics of on-site or nearby soils, and a number of other
site specific factors. The final cover design could simply be the
placement, compaction, grading, sloping, and vegetation of on-site
soils, or it could be a complex design utilizing a combination of compacted
clay or membrane placed over a graded and sloped base and covered by
topsoil and vegetation.
A detailed plan describing the manner in which the landfill will be
closed and maintained during the post-closure period is required. The
subjects to be addressed in the closure plan are: (1) control of pollutant
migration from the facility via groundwater, surface water, and air; (2)
control of surface water infiltration including prevention of pooling;
and (3) prevention of erosion. The factors that must be considered in
properly closing a landfill are: waste characteristics (type, amount,
mobility, rate of migration)', cover characteristics (material, surface
contours, porosity, and permeability, slope, length of run of slope,
type of vegetation on the cover); and characteristics of the local
environment (climate,'location, topography, surrounding land use, geological
and soil profiles, surface and subsurface hydrology).
The overall objectives of the closure and post-closure are to
minimize the need for further maintenance of the facility and to restrict
the escape of hazardous materials. The relevant factors are essentially
the same as those considered for closure. An additional factor that is
important during the post-closure period is the maintenance of any
groundwater monitoring system or leachate and runoff control system at
the facility. These measures are often necessary because leachate can
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continue to be produced and to migrate long after the waste is placed
in the landfill.
To assist in the design of hazardous waste secure landfills, there
has been a compilation of all research efforts to date in documentary
form, i.e. Technical Resource Documents (TRD's). These documents are a
compilation of research efforts and state-of-the-art techniques to date
and were developed primarily for use by the permit writers for evaluating
facility designs and potential performance of new waste disposal facilities.
These documents can also be used as (a) guidance by owners/operators of
interim status facilities especially for closure and post-closure cover
consideration and (b) assistance to the owner/operator and permit official
in identifying and evaluating the technologies which can be used to
control potential adverse effects of human health and the environment
and in complying with the regulations. Eight TRD's have been completed
to date. Six documents have been prepared that relate to secure landfills.
They are: .
TRD 1, Evaluating Cover Systems for Solid and Hazardous Waste (SW-
867):* This document presents a procedure for evaluating closure covers
on solid and hazardous waste to assess a complete evaluation.
TRD 2, Hydrologic Simulation on Solid Waste Dipsosal Sites (SW-
868); This document provides a computer package to aid planners and
designers by simulating hydrologic characteristics of landfill" operation
to eliminate percolation through the waste and control the formation of
leachate.
*TRD's are available from Solid Waste Publications, U.S. Environmental Pro-
tection Agency, Cincinnati, Ohio 45268. Use SW numbers when ordering.
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TRO 3, Landfill and Surface Impoundment Performance Evaluation (SW-
869): This document describes how to evaluate the capability of various
landfill designs to control the leachate release.
TRO 4, Lining of Waste Impoundment and Disposal Facilities (SW-
870): This document provides information and guidance on the performance,
selection, and installation of specific liners for various disposal
situations based on the current state-of-the-art of liner and other
pertinent technology.
TRD 5, Management of Hazardous Waste Leachate (SW-871): This
document presents management options that a permit writer or hazardous
waste landfill operator may consider in controlling and treating leachate.
TRO 6, Guide to the Disposal of Chemically Stabilized and Solidified
Wastes (SW-872): This document provides basic information on stabili-
zation/solidification of industrial waste to ensure safe burial of waste
containing harmful materials.
Stabilization/ Sol idification
Waste stabilization/solidification is a pretreatment process that
has been proposed to insure the safe disposal of wastes containing
harmful constituents. Terminology has been developed and borrowed from
other fields to describe the technology. "Solidification" is the
pretreatment process that will improve the handling and physical charac-
teristics of the waste. This could be as simple as adding soil, saw
dust, cement, lime, fly ash, etc., to change a sludge from a semi-
solid/liquid to a solid material, either a monolithic block, soil -like
material, or pellets. Generally, the solidification process does not
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chemically change the waste. "Stabilization" is the pretreatment process
that induces a chemical change to the waste constituents. This chemical
change produces an insoluble form of the waste constituent or places the
waste in a matrix that is insoluble. Physical enhancement of the waste
usually accompanies the stabilization process.
The types of waste streams usually treated by this technology are
the inorganic sludges. Although organic sludges have been treated, the
treatment has not been as successful as with inorganic wastes, especially
when compared to the durability of the product and its capacity to prevent
leaching of the wastes. However, research activities by industry are
developing treatment processes which will stabilize/solidify organic
wastes.
Treatment processes currently available include cement based processes,
pozzolanic processes (not containing cement), thermoplastic techniques
(including bitumen, paraffin, and polyethylene), organic polymer processes,
self cementing processes, and glassification and production of synthetic
minerals or ceramics. These processes are described in detail elsewhere,*
Depending on the waste streams and the degree of hazard to be treated, the
options are quite varied. Needless to say, all options will not work
with all wastes. Each treatment has to be tailored to the individual
waste. In situations where a variety of wastes is received at a central
treatment facility, blending of several wastes may resuH in a waste
material that is suitable for treatment.
Due to the relative newness of the technology, physical properties
of the end product are usually described by soil or concrete terminology.
*Guide to the Disposal of Chemically Stabilized and Solidified Waste. USEPA
Report SW 872, Washington, D.C., 1981.
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These are useful in making comparisons with other materials that are
well described in the literature. There are limitations on the use of
the physical property-data. Properties that are important to the contain-
ment success of the different types of treatment processes vary greatly
with the treatment type. For example, the unconfined compressive strength
of a treated waste is meaningful only for those processes that limit
containment loss by producing a solid monolith. Processes that produce
soil-like or plastic, spongy masses or encapsulates require completely
different testing regimes.
Unconfined comprehensive strength and permeability are most commonly
reported for the treatment processes that produce monolithic products
for which high strength values'and low permeabilities are said to be
indicative of good containment. Compressive strengths of 10s to 106
N/m2 and permeabilities of 1CT5 to 1C"7 cm/sec are not unusual for
concrete based systems. Organic admixtured systems are usually plastic
(low strength) and vary from highly permeable to impermeable depending
on the kinds and amounts of additive used. Treatments that produce clay
or soil-like products cannot be tested using the physical property
testing procedures designed for concrete-like products. These products
usually have relatively high permeability and depend on containing the
pollutants by binding them inside a molecular matrix.
Results of leaching tests are commonly reported by vendors of waste
treatment systems. The leaching test protocol becomes very important.
Unfortunately, there is no universally accepted procedure. Results
are reported for quick 1-hour distilled water tests to long-term field
tests. Presently, there is no required chemical leach test available to
predict the ultimate containment of treated toxic waste, but test protocols
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developed for the nuclear waste industry can be employed to model waste
containment. The problem of radionuclear waste escape from solids
formed using matrices of cement, asphalt, ceramic, or glass media can be
modeled using expressions that take into account diffusion and concentration-
dependent dissolution.
In many stabilized/solidified wastes the containment properties
depend on limiting the surface area across which transfer of potential
pollutants can occur. Physical testing systems are required to judge
the durability of the solidified waste.
Physical testing of waste materials becomes very important when the
conditions for shallow land burial are not ideal. For example, durability
testing is important where cover will not be sufficient to prevent
cyclic wetting and drying, or freezing and thawing. If the cover is
permeable, all of the containment for the waste may depend on the production
of an impermeable monolith. However, for treated materials that can be
ground to a powder and still not lose materials to leaching, the durability
tests would be important only for structural integrity and would have
little meaning for containment characteristics.
In general the stronger, more impermeable, and durable a treated
waste, the more effective will be its containment. If the material does
not fragment to create dust or increase the surface area for exchange,
losses will be minimized. Cement-based treated wastes can be prepared
with properties that approach commercial concrete. Tests have shown
compressive strengths up to 2,500 Ibs/sq in., with excellent durability,
permeabilities of 7.9 x 10"4 cm/sec and less that 20 percent weight loss
after 12 freeze-thaw cycles. Small column leach testing (IAEA method)
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has shown that in cement-based systems the strongest material has the
minimum contaminant loss.
Where the maximum possible concentration tests show potentially
hazardous levels of toxicants, durability would have to be very high to
demonstrate that physical characteristics of the material will prevent
this "worst case" situation from occurring.
When solidified wastes are buried, the major factor limiting the
loss of material from the monolithic mass is diffusion of the chemical
constituents to the surface of the solid. The rate of solution of
material at the surface is large compared to the diffusion rate.
Diffusion in a solid can be assessed using tests such as the Uniform
Leaching Procedure (ULP). The results of the ULP are given as effective
diffusivities (measured in cm2/sec).
Effective diffusivities or Teachability constants can be used in
comparing the containment afforded by different solidification systems
and for predicting the long-term losses from masses of wastes. Very
little information is available on effective diffusivities of solidified
industrial wastes. Most data on Teachabilities of solidified waste come
from nuclear waste treatment. Usually the elements and the types of
material treated differ greatly from typical industrial wastes. In ~
general, glass-fused wastes have had lower loss rates than plastic
(bitumen) encapsulated materials, and plastic (bitumen) "materials have
lower Toss rates than cement-based materials. Determining effective
diffusivities appears to be the best documented system for comparing
the retention of different constituents of waste using the same solidifica-
tion system as for comparing the containment produced by different
solidification systems on one waste.
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Treated waste material may vary greatly from batch to batch due to
variation in wastes incorporated or the conditions of treatment. In
cement or pozzolan-based systems, small amounts of interfering materials
can drastically reduce strength, durability, and chemical containment.
In some solidificiation operations in which the material is poured out
to solidify as a monolithic mass, solidification may not occur, and if
an additional layer is poured over the unsuccessfully solidified wastes,
a highly Teachable zone in the waste mass is created. Such poor operating
practices should be avoided.
Any treatment process should include a system for determining the
character of the treated waste and a provision for reprocessing the
material before final deposition if the treatment process was unsuccessful.
The exact sampling pattern for determing treatment quality would depend
on the variability of the feedstock for the treatment system and the
quantity of waste treated. In batch operations, each separate batch
should be leach tested and tested to determine selected physical properties,
In a cement- or pozzolan-based system, any large changes in set-time or
texture of the treated waste should be cause for a more complete testing
sequence.
Periodically, samples should be cored from aged solidified wastes
to determine if breakdown and loss of contaminants have occurred. If
the physical properties, strength, and durability have not decreased and
the permeability of core materials has remained low, the assumption of a
low-permeability monolith of waste is justified. Leach testing of core
material can be used to ascertain any decrease in containment properties
with age. If a landfill operation can demonstrate that the treated
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waste is not breaking down, longer periods can be permitted between
resampling of treated waste.
Most waste materials that are currently being considered for disposal
have no present value, and thus all solidification/stabilization costs
represent additional expenses to be added to the ultimate cost of the
product or service sold. A complete economic analysis must consider
costs of waste transportation, materials, and equipment required for
stabilization/solidification, skill levels of treatment plant operators,
fees or royalties for use of patented processes, and cost of transporting
and landfill ing treated wastes. This type of analysis often must be
undertaken on a case-by-case basis. However, to obtain an initial
impression of the usefulness of different waste treatment systems now
and in the future, it is possible to restrict economic considerations to
present and projected costs for materials, equipment, and energy. In
most treatment systems, the cost of materials required is the major item
regulating present and projected costs. Table 1 outlines the present
and future economic considerations for major waste stabilization/solidifi-
cation systems.
Land Treatment
Properly designed and managed land treatment systems are an accept-
able technology for treating and disposing of selected industrial hazardous
waste. Such systems are not the answer to all waste problems but, when
properly applied, they can provide an efficient and cost effective
treatment and disposal alternative.
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Land treatment of hazardous wastes Involves the planned and systematic
use of the soil's top layer for biological, chemical, and physical
treatment. The process is a dynamic one involving the interaction of
waste, site, soil, climate, and biological activity (usually aerobic) to
degrade, immobilize, or deactivate the waste constituents. The objective
is to eliminate or reduce contaminants to acceptable limits, usually
through biological degradation. Land treatment systems can be designed
to treat almost any waste, but they should be used primarily for wastes
that can be degraded or chemically altered to eliminate or reduce the
hazardous components to acceptable levels.
The design and operation of a successful system depends on careful
study and consideration of its key components: waste, site, soil, and
climate. Essentially the design process involves determining the amount
of an acceptable waste that can be applied to an acceptable site.
Projected long-term use of the site is also an important design factor.
If, for example, the intention is to use the completed site for grazing
animals, the design and operation must prevent interactions of wastes,
soils, and plants that could result in ingestion of contaminated materials.
Land treatment is an open process which can cause impacts on- and
off-site to groundwater, surface water, air, and plants, and other environ-
mental concerns. Thus, the design approach must consider the total
system, including waste characterization, site selection and preparation,
proper operation and management, monitoring, closure, and post-closure.
Specific criteria may not be available to determine clearly many of the
factors; however, information is generally available to provide reasonable
ranges for design parameters. Values that fall outside of these ranges
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may indicate that additional data are required and/or that conditions
are not acceptable for successful land treatment.
Most available data are for individual waste constituents and their
reactions with soils. Design problems thus occur when the constituents
are present in complex waste mixtures that have the potential for syner-
gistic or antagonistic reactions. When wastes are complex and when
values fall outside reasonable ranges, laboratory and pilot tests may be
required before proper design can be completed. Data from waste-soil
interaction studies must be interpreted to determine feasibility, accept-
able waste loading rates, management needs, and monitoring requirements.
The interpretation should consider each important waste constituent
independently unless adequate information is available to do otherwise.
Application rates and feasibility are closely related. Almost any
waste can be treated by land disposal, but allowable loading rates may
require an impractically large area. Economics then becomes the limiting
factor. Acceptable loading rates are calculated for each waste con-
stituent based on its interaction with the soil, climate, and other site
conditions. The component that most restricts the waste application is
selected.
Several categories of limiting waste constituents must be considered
when determining application rates:
o The constituent that limits the amount of waste that can be
applied annually is called the rate limiting constituent
(RLC). Once this factor is determined, the land area required
to treat the waste can be estimated by simply dividing annual
waste receipts (kg/yr) by acceptable loading rates (kg/ha-yr).
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o The constituent that limits the amount of waste that may be
applied in a single dose but that is rapidly decomposed or
immobilized is the application limiting constituent (ALC).
This factor does not necessarily control the annual loading
rate, but it establishes the number of applications that can
be made during that period. An example may be a constituent
that becomes toxic to the active microorganisms in large
quantities but that is acceptable in the same or larger quantities
to the remaining system components. If the waste contains
such a constituent, maximum annual waste applications are
determined by dividing the RLC loading rate by the ALC loading
rate. In many cases the rates will be the same.
o The constituent that limits the total quantity, of waste that
can be applied to a site is referred to as the capacity.
limiting constituent (CLCj. This constituent is usually some
accumulating species such as a heavy metal. The CLC may also
be the RLC when a waste contains a large concentration of a
specific rate-limiting metal. Since many industrial toxic
wastes have low metal contents, some organic compound, water,
or another constituent may control the RLC, and the metal may
be the CLC. The CLC controls and establishes the maximum
useful life of a facility unless other design features determine
otherwise.
Individual constituents of concern in the design process include
organics, water, metals, nitrogen, and selected nonhazardous constituents.
The hazards posed by waste organics may generally include acute
toxicity to soil biota, phytotoxicity to plants, acute or chronic toxicity
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to animals, and danger of fire or explosion. These may occur during
land treatment as a result of volatilization, leaching, runoff, and
degradation. All of thess possibilities must be considered in calculating
the application rates. Degradation, which is the major objective of
land treatment, can be determined by respirometer studies and by green-
house and pilot studies in the field. These rates, can be observed over
a range of waste loading rates and soil conditions. Determinations can
be made of waste levels above-which essential biological activity is
slowed or stopped. Plant toxicity assays can determine concentrations
harmful to plants. When the waste half-life and its microbial toxicity
and phytotoxicity are determined, the recommended safe loading rates can
be determined.
A high water content in the waste may limit application rates be-
cause of climatic conditions. Site precipitation, evapotranspiration,
and soil permeability data can be used to develop a water balance, which
can then be used to determine the season for waste application and to
develop an acceptable water management plan.
One important factor to be considered in facility design is that
untreated wastewater must not leave the premises. Excess water can also
create-major management problems. Two options available are to design
the facility for zero water discharge (in situations where annual water
inputs are less than outputs) or to treat the wastewater.
Management of metals involves sorbtion of the applied elements in
the soil so that no toxic hazard results. Environmental damage can
occur through leaching of selected anions (e.g., selenium and molybdenum)
or metals that are solubilized because of low soil pH. Most metals,
however, are relatively immobile in soils with neutral to basic conditions.
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Thus allowable metal applications often depend on site closure plans.
For example, if the latter calls for removing the contaminated soil,
total metals applied may be greater than in a closure plan calling for
few restrictions to final land use.
Metal constituents will normally control the total amount of waste
applied to a site even if another constituent controls the application
rates. Allowable amounts for selected metals that show little movement
in soils are shown in Table 2.
Nitrogen is of concern when it is present in high concentrations.
Excesses can cause environmental and health problems. Nitrogen inputs
should equal nitrogen removals in order to maintain acceptable levels of
nitrates in runoff and groundwaters. Nitrogen is often the RLC in land
treatment systems.
Although not hazardous, other constituents must be considered in
designing the system. Excessive amounts of phosphorus, inorganic acids,
bases, salts, and halide may cause problems in the land treatment processes
or may cause some loss of environmental quality through contamination of
groundwater or surface water. Each such constituent should be evaluated
and considered when determining acceptable waste loading rates.
The basic design objective is to develop a system where the soil,
waste, and site conditions interact to yield the desired degradation
and/or deactivation of the hazardous waste constituents. Allowable
application rates are calculated by determining key waste constituents
that are limiting because of their interaction with the soil, climate,
and other site conditions. After each potentially problem-causing
constituent is considered, a comparison is made to select the one that
is most limiting. When the limiting constituents and the allowable
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loading rates have been determined, the required land area, applications
per season, and facility life can be determined.
A monitoring program is an essential component of facility design and
management. This essential program should include provisions to assure
that the waste input does not change significantly, that degradation and
treatment is taking place, that unacceptable levels of toxic constituents
and contaminants are not leaving the facility or building up in the
system to levels that restrict proper treatment, and that soil conditions
(pH, moisture, etc.) are satisfactory.
Closure'of the facility is also an important consideration in
design and operation. This process begins when the last load of waste
has been accepted. The. type of final closure chosen will greatly influence
the level of degradation required. Three closure procedures are available:
o To stabilize the site with vegetation and use soil conservation
methods that will prevent any problems to human health or the
environment.
o To remove the contaminated material to a hazardous waste
treatment or disposal facility.
o To cap the treatment area as required for a landfill to control
infiltration and erosion.
If the hazardous waste land treatment facility has been properly
designed, successful operation hinges on a single factor: management.
Improper management is probably the most frequent cause of problems at
land treatment facilities. Proper management involves assuring that (1)
applications rates are not exceeded, (2) berms, ponds, waterways, etc.
are properly maintained, (3) required cultivation, liming, and fertilization
are practiced, (4) proper monitoring is conducted, and (5) other activities
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Ronald Hill page-22~o.f 34
required for proper operation are carried out.
Land treatment is an old concept that offers an acceptable alternative
for managing hazardous wastes. Properly designed and managed systems
can treat selected hazardous wastes efficiently and economically. The
technique has suffered from an image that includes surface dumping and a
misunderstanding of its potential when properly applied. Land treatment
deserves adequate consideration as a hazardous waste treatment alternative.
Mine Storage
One option for the disposal of hazardous waste is storage within
underground mines. The hazardous waste, which has been solidified, is
packed in drums and transported down the mine shaft and placed in pre-
pared rooms. The disposal area is divided into several sections, each
receiving specific wastes that are compatible with each other. As a
room within the mine is filled, it is sealed off. If the mine is properly
selected,, the atmosphere is very dry and the drums have an indefinite life
unless they are corroded from the inside. One advantage of this method
is that the waste can be received at a later date if necessary. Figure
4 illustrates a conceptual waste handling system.
Salt, potash, and gypsum deposits have been identified as having
the highest potential for waste storage. Worked out portions of exist-
ing or inactive-mines would be most appropriate since the cost of devel-
oping the site would be minimized. Salt deposits have many advantages.
First of all, as shown in figure 5, they are widely distributed through-
out the United States. Many are located in close proximity to major
industrial areas where the majority of hazardous wastes are produced.
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Ronald Hill page 23 of 34
Thus, the transportation of hazardous wastes over long distances and the
risk associated with it are minimized. - These deposits often have large
volumes of underground openings available. Salt has good structural
properties including high compressive strength (comparable to concrete)
and plasticity. It is typically well isolated from aquifers by adjacent
deposits that are both thick and impervious as; is the salt itself. Most
salt deposits occur in areas of low seismic risk and large geologic
stability. Chemically, salt is compatible with nearly all hazardous ,
compounds.
Although mine depositories for low level radioactive wastes have
been used in the United States, underground mines have not been used for
hazardous waste. An exemplary situation does exist in Herfa-Newrode,
Germany. Kali & Salz A.G. has developed a worked-out section of a
potassium salt mine for the depository of more than 700 compounds. In 7
years over 240,000 tonnes of solid waste have been deposited in the
mine. Currently, 35-40,000 tonnes are deposited annually.
The disposal area has a cover of impervious rock salt approximately
170m thick that segregates it from an upper aquifer and a 100m thick
layer below that serves as a barrier to the lower strata. In order to
prepare the mine for waste depositing, the rooms are cleaned of waste
rock, made higher, and the roof bolted.
A negotiation between Kali & Salz and the waste producers takes
place before any waste is accepted at the mine. Free flowing waste, any
waste that produces a gas that when mixed with air will ignite, radio-
active waste, waste that will self-combust, or waste that produces
dangerous gases are not accepted. The German mining and environmental
authorities must approve the storage. No processing of the waste takes
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Ronald Hill page 24 of 34
place at the mine. The producer must process the waste so that it is
not free flowing. The waste arrives at the mine in one of three basic
types of containers, i.e. SB-gallon steel drums, fiber drums, and plastic-
lined paper bags. The mine has been separated into 19 different storage
categories. Compatible wastes are stored together. The waste is moved
from the unloading area and down the shaft on pallets. Pallets are
carried by truck to the disposal site, then unloaded and stacked with a
fork lift. They are normally stacked 2-3 drums high. After an area has
been filled with drums, a brick wall is constructed across the face of
the room. The main purpose of this wall is to assist the ventilation
system.
The disposal practice is controlled in several ways. A manifest
system is used to assure.the producers and the environmental authorities
that the waste has arrived at the mine. Each waste is coded according
to its producer and location in the mine. An air monitoring system is
used to assure safety of the mines. In 1980, the cost of disposal, not
including transportation to the mine, was 148 DM/tonne (approximately
$80/ton). The major expense is the preparation of the rooms. The dis-
posal program employs a total of 25 people for one shift per day.
Deep' Well Disposal
Deep well waste disposal involves the injection of liquid waste into
subsurface geologic formations by means of wells. The technique is based
on the concept that liquid wastes can be injected into and contained by
geologic strata not having other actual or potential uses of a more beneficial
nature. Thus, long-term isolation of the waste material from man's usable
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Ronald Hill page 25 of 34
environment is accomplished. This practice has been used extensively by
the petroleum industry to dispose of brine produced during oil recovery.
Since the 1950's there has been a steady increase in the use of wells for
the disposal of other types of industrial waste. Over 250 wells injecting
approximately 130 different chemical compounds are now in operation. Deep
*eel disposal is not without controversy. Proponents argue that it is a
safe economical method to dispose of a diverse variety of wastes, while
opponents are concerned with groundwater pollution, and further utiliza-
tion of the aquifer. Some states have limitations on the types of wastes
/vhich can be injected, for example, chlorinated hydrocarbons.
The geologic formation is the key factor in deep well injection.
Figure 6 presents a generalized map of these areas in the United States
tfith potentially suitable geologic conditions. Specific factors that must
De considered for an underground reservoir are: (1) uniformity, (2)
large areal extent, (3) substantial thickness, (4) high porosity and
Dermeability, (5) low pressure, (6) a salaquifer (an aquifer containing
Drackish water, salt water or brine), (7) separation from fresh water
norizons, (8) adequate overlying and underlying aquicludes, (9) no poorly
slugged wells into the reservoir, and (1) compatibility between the
nineralogy and fluids of the reservoir and the injected waste. Those
injection wells that have created environmental problems have been located
in unsuitable geologic settings, or have been poorly engineered and in-
stalled for the geologic conditions present.
Good engineering and construction of an injection well are critical
to its success. The first concern in planning, construction, and operation
is the protection of potable waters and minerals of economic value. The
second concern is the possibility of corrosion of the tubular goods and
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Ronald Hill page-26-of. 34
cementary materials used in well construction. If a casing string or
the cement sheath behind the casing fs materially damaged, then uncon-
trolled movement of the injection fluid into zones that contain potable
water or minerals will occur.
Once the geologic conditions are understood, the design of the tubing
string, which serves to conduct the injected material to the injection
face, is made. The tubing string should be constructed of a material
which has the mechanical properties for the depth of the well, has adequate
flow characteristics, and is compatible with the injection fluid. The
tubing string is placed within the casing. The casing is cemented into
place. The cement system should be planned to be compatible with the
injected fluid. External casing packers and string packers at the injection
zone to protect the casing and cement are additional safety features.
»
The completion technique often used is equipping the tubing with a
packer set in the casing above the disposal zone. (See figure 7.) The
packer provides a seal to isolate the annulus space above the packer from
the waste fluids. The annulus space is filled with an inert liquid and
placed under pressure. Thus, if there is a failure of the tubing, packer,
or casing, the annulus pressure will change and serve as an alarm.
Often the injection liquid must be treated before injection to remove
solids that might plug the system. In some cases the liquid must receive
chemical treatment to make the liquid compatible with the aquifer.
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Ronald Hill
Figure 1
rcent^ce of 1930 Kazardcjs Haste Gene
Standard Industrial Classification \S
T-taL = 41,235
tnousanc
WMT
SJC 23
CHEMICALS AND
ALLIED PRODUCTS
SIC 33
PRIMARY METALS
INDUSTRIES
10%
SIC 37
TSAVSPQSTATia.'J
EQ'JIPYEflT
SIC 36
ELECTHIC A.'.'O
ELECTnor.'IC EQUIPMENT
3iC 29
,-:7"GlEl!.M A.'.'O
COAL PrOD'JCTS
SIC 34
FA8HICATEQ
METAL PRODUCTS
Source: Hazardous Waste Generation and Commercial Hazardous Waste Management
Capacity - An Assessment. U.S. Environmental Protection Agency
Publication SW-894, Washington, D.C. 1980.
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Ronald Hill
Figure 2
c Hazardous Waste Volumes Trssted/Disposed by Ccrrr.e
ff-.Tice Facilities by '.'lasts Management Cpticr.s
1930
(Millions of Wet Metric Tons)
-.- ' 3 1
INCINERATOR1
0.40
RESOURCE1
RECOVERY
0.42
.DEE? WEIL
INJECTION
0.79
iA,'fO TREATV^JTI
OLAR EVAPORATION
0.54
CHEMIMl. BIOLOGICAL
AMD PHYSICAL TREATMENT
2.2: TOTAL TREATED
2.12 NET TREATED
SECURE LAf.'CfL
CHEMICAL TREA,
WASTES lO'.'SR
0.23
TOTAL
SECURE
LA,'JDF!LL
2.70
TOTAL V/ASTE VOLUME = 7.19
(INCLUDES LANDFILL/CHEMICAL
TREATMENT OVERLAP)
Source:
Hazardous Waste Generation and Commercial Hazardous Waste Management
Capacity - An Assessment. U.S. Environmental Protection Agency
Publication SW-894, Washington, D.C. 1980.
-------
MINE HOIST
3A.PRETREATMENT OR
VOLUME REDUCTION
1. COMPOUNDS ARRIVE BY
RAIL OR TRUCK FROM
WASTE GENERATORS
2. RECEIVING. CLASSIFICATION,
ANALYSIS, INVENTORY i
TEMPORARY STORAGE
HEAD FRAME
PACKAGING OR
REPACKAGING
3C. TRANSPORT TO SHAFT DIRECT
FROM 2 OR FROM 3B
4. LOWER INTO
MINE COMPLEX
TRANSPORT TO
STORAGE CELL
6. INVENTORY & RECORD AMOUNT
AND LOCATION IN THE MINE
^*Mg^WWtYfl
>TV7i!tRtfi&yWWXrKV?X^^
Figure 4. Waste Handling Flow Chart for Disposal of Hazardous Waste 1n a Mine.
Source: Evaluation of Hazardous Waste Emplacement in Mined Openings. USEPA publication EPA 600/2-75-040,
Cincinnati, Ohio, 1975.
-------
/
SEVIER BASIN
PARADOX BASIN
LEGEND
SALT DOME BASIN
BEDDED ROCK SALT
SALT MINES
PERMIAN BASIN.
(NORTH)
APPALACHIAN
BASIN
PERMIAN BASIN
(SOUTH)
\ fr W. ^
Aj'aVIRGIN .P
\ VALLEYS
SUPAI ,
BASIN '
500
Figure 5. Major United States Salt Deposits and Mines,
Source: Evaluation of Hazardous Waste Emplacement in Mined Openings. USEPA publication EPA 600/2-75-040,
Cincinnati, Ohio, 1975.
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Ronald Hill
page 31 of 34
LtGENO
Unfavorable under
all conditions
Generally unfavorable bul may hove - ' ''-. *'
limited use under restricted conditions
favorable under
controlled conditions
Disposal Wells
Abandoned or pkujycd Disposal Wells
Fi
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Ronald Hi
GAUGt
A CASING STRING SMALL 3£ CEMENTED,
7HAT CEMENT SHALL 3E IT LEAST SO FT.
INTO THE XEXT LA/^OiS ST^IiNG.
Figure 1. Completion of Haste Injection Well
Source: Review and Assessment of Deep-Well Injection of Hazardous Waste.
USEPA publication EPA 600/2-77-029a, Cincinnati, Ohio, 1977.
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Itu.ul.l III I)
page 33 of 34
lAliLt 1.
PULSINI ANO t'UOJLClLU LCOtiUtflC COKSIOUUUIOHS FOR MASK STABILI Ml 10H/
SOLIDIFICATION SYSUMS
Type o( tiuutment
sys tern
Lenient-based
I'u/ /O 1 till 1 L
lliL't iikiplas tic
(bi tumon- based)
Oi ganic polymer
(polyester system)
jfl 1 -cL'iwnl ing
Class I 1 nation/
niiiic-ial synthesis
llajor
materials required
Portland Cement
Lime Flyasli
Bi lumen
Drums
I'olymur
Catalyst
Or uius
(jypsuui (from waste)
Feldspar
Amount of ma- Cost of ma-
Unit terial required terial required
cost of to treat 100 Ibs to treat 100 Ibs Iquipiiient Ineigy
material of raw waste of raw waste Trends in price costs use
$0.03/lb
i0.03/lb
$0.05/lb
$27/drum
il.ll/lb
$17/tlrum
* A
$O.OJ/lb
100 Ib i 3.00
100 Ib V 3.00
1JO Ib $IB.60
O.U drum
43 Ib of J27.XO
polyester-
catalyst mix
10 Ib **
Varies
Stable Low Low
Stable Low Low
Bitumen prices Very High High
are rising
rapidly because
of oil prices
Price could rise Very High High
rapidly due to
oil shortage
Stable llodeiate Moderate
Stable High Very Iligii
« 11,1:,i-d on the full cost ol fc'JI/ton.
** tk'ijl igible but energy cost lor calcining aru appreciable.
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Ronald Hill
page 34 of 34
TABLE 2. CURRENTLY ACCEPTED CUMULATIVE SOIL
LOADING LIMITS FOR SELECTED METALS
METAL
Arsenic
Cobalt
Chromium
Nickel
Lead
Zinc
ppm
500
500
1000
100
1000
500
LOADING LIMIT IN SOIL
kg/ha- 15 cm
1120
1120
2240
220
2240
1120
lb/acre-6 in.
1000
1000
2000
200
2000
1000
SOURCE: U.S. EPA 1980, Hazardous Waste Land Treatment, SW-874.
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