Management of Wastes from Wood Preserving Facilities · 2018. 6. 13. · P. AARNE VESILIND Graduate...
Transcript of Management of Wastes from Wood Preserving Facilities · 2018. 6. 13. · P. AARNE VESILIND Graduate...
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MANAGEMENT OF WASTES FROM WOOD PRESERVING FACILITIES
CHARLES ARTHUR GOVE
P. AARNE VESILIND
Graduate Student and Professor
Department of Civil and Environmental Engineering
Duke University
Durham, North Carolina
INTRODUCTION
Wood preserving is a significant, diverse and well established
industry with five hundred forty-seven known operating plants in
the United States. (1) The principal product of these plants is
chemically treated wood for use as railroad ties, utility poles,
and construction materials. In 1984, the industry treated about
500 million cubic feet of wood products. (2)
Wood is chemically treated to reduce or prevent decay by
microorganisms, attack by insects and to increase its resistance
to fire. Adequate preservation requires the use of large
quantities of toxic chemicals which could cause environmental
damage and may even result in adverse health effects.
Wastewaters from these plants contain not only the normal
sanitary wastes, but unusable and contaminated preservatives
which no longer can be used for the processes. Two other sources
of wastewater are stormwater surface runoff and excess process
water. Solid residues include sludges from wastewater treatment,
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insoluble organic materials from waterborne salts, and
contaminated soils from spills or from drippage.
In older plants, the discharge of wastewaters requires
treatment, which has proven to be costly and technically
difficult. As a result, many small plants have chosen to close
their doors instead of invest the money in treatment processes.
This has been because the capital simply has not been available
to them due to their small size and independent operation. These
abandoned plants probably represent serious future clean-up
problems for the regulatory agencies.
The newer facilities, constructed in the past ten years, have
incorporated within their design various pollution prevention
technologies that satisfy environmental regulations and
provide greater efficiency in operation. In reviewing the records
of this industry, it is clear that early recognition of the "zero
discharge" or "total containment" allowed the industry to
modernize and flourish in North Carolina.
The objective of this paper is to review the status of this
industry in North Carolina, to describe the evolution and use of
pollution prevention strategies for wood preservation plants, and
finally to suggest strategies for existing plants for attaining
self containment and zero discharge which will ultimately result
in economic benefit to the plants.
HISTORICAL DEVELOPMENT
The need to protect wood from various forms of decay and
physical weathering has been recognized since ancient times.
Noah was commanded to use pitch while constructing the ark, and
accounts of the use of similar agents are found in other passages
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of ancient history. In modern times, different chemicals and
treatments have been tried for wood preservation. Early attempts
include the 1754 patent of John Lewis for the preservation of
wood with bituminous substances (creosote) and 1837 patent of
Margary for treatment in a solution of acetate or sulfate of
copper. (3) Despite these attempts, the actual widespread use of
chemically preserved wood did not begin until the latter part of
the nineteenth century.
The first wood preserving plant in the United States was
placed in operation in 1875 with the construction of a pressure
creosote treating plant in Gautier, Mississippi. (4) The
industry developed rapidly due to the expansion of railroad
systems throughout the country, (1875-1925), and the need for
durable railroad ties. (5) This demand resulted in large-scale
use of creosote treated hardwood products. Further growth was
stimulated after 1925 by the need for treated poles by the
rapidly developing utility companies.
The need for a building material that could survive in marine
environments presented-another use for creosote treated wood.
However the marine borer, Limnoria Tripunctata was able to- -
successfully attack creosote treated marine pilings, and this
prompted further research in the use of other potential chemical
preservatives, resulting in the development of pentachlorophenol
(1930), copper chromium arsenate (1933) and amonical copper
arsenate (1939). (6) With treated wood products successfully
demonstrated, potential uses for treated wood expanded to include
such products as poles, pilings, fence posts, guardrails, bridge
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structures, boardwalks, and other lumber products. New demands
for treated wood created a need for more versatile products and a
much greater output.
Presently, the wood treating industry uses the following three
chemicals:
. creosote
. pentachlorophenol
. waterborne inorganic arsenicals
While research directed toward developing chemicals and
treating processes is continuing, no new preservatives have been
found to be realistic options for the near term mainly due to
long periods of required testing. Therefore, the industry is
dependent on the preservatives presently in use.
PRESERVATIVE USED FOR TREATING WOOD
Creosote, pentachlorophenol and waterborne inorganic
arsenicals are the major pesticide chemicals used for wood
preservation. Treated wood production in 1984 by preservatives
was: 138 million cubic feet by creosote solutions, 54 million
cubic feet by pentachlorophenol and 301 million cubic feet by
waterborne arsenical preservatives. The major products treated,
which account for 89% of the total production, were lumber and
timber (268 million cubic feet), crossties, switch and bridge
ties (97 million cubic feet) and poles (78 million cubic feet).
(7)
Creosote is produced as a distillate of coal tar and is a
mixture of many compounds, mainly aromatic hydrocarbons. It is
primarily used to improve the weathering characteristics of wood,
provide protection from insects and fungi, and promote
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insolubility in water. Disadvantages of creosote treated
products are color, oily unpaintable surfaces and tendency to
bleed. The railroad industry uses creosote almost exclusively to
treat cross and switch ties; 99.5% of creosote treated wood
total. (8)
Pentachlorophenol is a crystalline compound dissolved in a
light petroleum oil. Pentachlorophenol treated products are
resistant to insects and fungi and are more paintable than
creosote. 55.5% of all utility poles and greater than 90% of all
utility pole crossarms are treated with pentachlorophenol. (9)
Waterborne preservatives are compounds of arsenic, chromium,
copper zinc, and fluoride. The principal preservative is copper
chromium arsenate (CCA) which differs from creosote and
pentachlorophenol in that it is a water soluble inorganic as
opposed to an oily organic substance. Waterborne preservatives
produce clean, ordorless, paintable products. Disadvantages of
waterborne preservatives are that the wood must be dried before
it is treated rather than using a simultaneous processing step.
(10)
Until the mid-twentieth century, the total volume of wood
preserved corresponded directly to the volume of creosote used.
Since the early 1950's there has been a general decrease in the
consumption of creosote treated products and a corresponding
increase in the use of waterborne and pentachlorophenol
preservatives. Following 1965 there has been an increase in
total wood preserved but a further decrease in creosote
consumption. During the last fifteen years, use of waterborne
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treated wood for construction has increased approximately
eightfold, while the use of creosote and pentachlorophenol has
decreased about ten percent. (11)
THE WOOD PRESERVATION PROCESSES
Wood preserving is a specialized operation as the specie of
the wood treated, preservative used and type of product influence
ways in which the wood is treated. In addition, environmental
regulations have forced process changes such that there appear to
be no standardization in operations, the process can therefore be
described only in very general terms. Figures 1 and 2 present
block flow diagrams of the wood preserving process for pressure
treatment using oil-based and waterborne preservatives.
Wood preserving is a two stage process; first the wood is
preconditioned to reduce its moisture content, second the wood is
treated with preservatives. The methods used to pretreat or
condition wood depend on the type of wood being treated. In the
United States, most of the wood is preconditioned by ambient air
seasoning, kiln drying, or steaming. Southern pine must be
steamed before it is to be treated with either creosote or
pentachlorophenol. Mixed hardwoods including oak, and woods to
be treated with waterborne preservatives are generally kiln or
air dried and seldom steamed.
Following preconditioning, the wood is impregnated with
preservative by either pressure or non-pressure methods.
Pressure treatments involve the application of pneumatic or
hydrostatic pressure to wood in the presence of chemical
preservatives. Pressure treating accounts for greater than 95%
of all wood treated. Non-pressure processes include thermal,
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brush, dip, spray, diffusion, vacuum, and soaking methods.
Pressure methods produce deeper penetration of the
preservative. The two pressure techniques used to achieve
greater impregnation are the empty cell and full cell processes.
For woods requiring less penetration of oil-based preservative,
the empty cell process is used. Following conditioning of the
wood, the retort is pressurized causing contraction of air within
the cell walls of the wood. Preservative is then introduced into
the vessel and forced into the voids created in the cell walls.
The full cell process maximizes impregnation of the wood and is
normally employed with waterborne preservatives. In this
process, the pretreated wood in placed in the retort and a vacuum
is imposed causing evacuation of the air trapped within the wood,
next the preservative is entered and pressure is administered to
force the solution into the wood. Generally the vessel is heated
which allows the waterborne preservative to react with the acids
formed from the wood sugars and become "fixed" in the wood. In
both procedures a portion of the preservative solution may drip
from the wood during its removal from the retort. (12)
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ENVIRONMENTAL IMPACT OF WOOD PRESERVATION
Concern over the deteriorating quality of the environment has
focused attention on pollution in its various forms and on the
wood preserving industry's contribution to the problem. Since
the chemicals used to treat wood are toxic and wastes from the
treating plants are potentially damaging to the environment,
various agencies have conducted studies on chemical pesticides
used in wood preservation.
Creosote is a broad spectrum wood preservative that has been
used for this purpose for over one hundred years in the United
States. The very fact that creosote has been widely used
commercially as a preservative with little or no evidence of
adverse health effects, suggests that its effects on human health
and the environment might be minimal. However, there are
instances of fish kills associated with contamination of streams
and lakes by creosote and process wastewater from creosoting
operations. (13) Perhaps more important, the Environmental
Protection Agency has identified creosote as a known carcinogen.
(14)
Pentachlorophenol and its salts are widely used biocides in
the United States. The principal use of pentachlorophenol is for
wood preservation, in excess of 80% being used for this purpose
and other activities associated with the forest products
industry. (15) Pentachlorophenol is lethal to a wide variety of
living organisms, both plant and animal. The major issues of
concern are the environmental effects of impurities present in
commercial grade pentachlorophenol and of breakdown products,
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which are generally classified as chlorinated dioxins and are the
subject of study because of their extreme toxicity. (16)
Copper chromium arsenate is an inorganic arsenical compound
that is a major pesticide chemical now in use for wood
preservation. Although the toxic properties of arsenic have been
known for centuries, the mutagenicity and carcinogenicity of
arsenical toxicity have only received intense investigation in
the past few decades. Studies are underway to determine the
effects of interaction with other toxic metals and physiological
states on the nature of arsenic toxicity. (17)
All preserved wood contains chemicals known to be toxic.
Analyses of solid wastes have been shown to include hazardous
components such as the wood preservatives pentachlorophenol,
creosote and the heavy metal salts. (18) Considerable evidence
also exists which associates direct human contact with these
chemicals to adverse health effects. (19)
THE WOOD PRESERVING INDUSTRY
Wood preserving plants are distributed throughout the united
States, with the majority located in forested regions. Due to
the expense of transportation, wood preservers tend to be located
close to timber cutting operations. In 1984, sixty percent of
all active facilities were located in the South, from east Texas
to Maryland, and greater than thirty-five percent of all new
plants were built in Georgia, North Carolina and Virginia. (20)
The total size and economic characteristics of the wood
preserving industry has been a matter of considerable
uncertainty. In 1977 the Census of Manufacturers identified 457
facilities, however the actual number of plants operating then is
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estimated at 631 facilities. ( 2 1 ) A recent study, Wood----
Preservation Statistics 1983-84, conducted by the International
Statistics Council has identified 547 active plants in the United
States with 326 operating in the South and thirty located in the
state of North Carolina. ( 2 2 ) A survey of the wood treating
activities in the state of North Carolina conducted as part of
the present study has identified forty facilities in operation
during 1984. Table 1 is a summary of the locations of these
plants in North Carolina.
Although there is disagreement as to the exact size of the
industry, it is acknowledged that the wood preserving industry is
composed principally of a large number of small privately owned
plants and a few large integrated corporations. Most firms in
the industry operate only one plant and specialize in one type of
preservative treatment process. Smaller firms tend to further
specialize on particular preserved wood products. Therefore no
single facility or process can be considered "typical", and such
diversity creates considerable difficulty in pollution control.
Preserved wood is largely a commodity market modified by
transportation costs providing regional advantages. Demand
elasticity in the industry varies among products but the major
factors governing demand are competition within the industry,
economic climate and the cost effectiveness of alternative
products. Since the early 1970's the industry has experienced
significant cost increases for raw materials, especially
chemicals and wood, but has been able to establish higher retail
prices, although with reduced margins. (23)
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TABLE 1
Location:
Mountain
Piedmont
Coastal
Process
Pressure
Non-pressure
Number of Plants-
10
12
18
35
5
Preservative(l)
Creosote
Pentachlorophenol
Waterborne Inorganic (CCA)
Other
3
9
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1
[(1) note: Two of the treating facilities employ twotypes of preservatives]
POLLUTION CONTROL IN WOOD PRESERVING PLANTS
The wood preserving industry is currently confronted with the
problem of pollution control to satisfy environmental
regulations. The primary wastes associated with wood
preservation are high volume water streams with various levels of
preservatives. Water pollution is therefore the most serious
problem affecting the industry owing to the extreme toxicity of
the chemical preservatives and the special treatment and disposal
methods required. Recent legislation has discouraged the use of
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lagoons and evaporation ponds, and thus has resulted in the
development of source control technologies to comply with water
quality standards.
An evaluation of the industry has shown that source control
technologies for pollution abatement can greatly reduce the
expense associated with wastewater treatment. Some of the
methods used by various plants include:
. reduction of the amount of excess toxic chemicals
entering a waste stream
. reductionof the water volume contact with
preservative
. segregation of waste streams
. maximizing separation and recycle of chemicals to the
treating process.
These techniques are applied throughout the wood preserving
process, including chemical handling, wood preconditioning,
environmental contact and operational practices.
The use of toxic chemicals for wood preserving requires
special handling procedures. Currently, the majority of
creosote, pentachlorophenol, and waterborne CCA are sold,
transported and stored in bulk. Bulk shipments are unloaded by
closed systems that pnuematically force the preservative into
storage facilities. However, a small segment of the industry
purchases small quantities which generate container waste. The
use of dedicated recyclable drums with rinseable plastic liners
and unloading with a closed system has been identified as a
source control method that would eliminate container waste and
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reduce human contact with these substances.
Preconditioning of wood is necessary to reduce its moisture
content and improve its treatability. This is accomplished by
open air drying, kiln drying, or pressure steaming in a retort.
Steaming the wood produces a wastestream composed of water with
preservative, wood fiber, silt, wood sugars, wood acids and oil.
Reduction of steaming by use of air and kiln drying eliminates a
major wastewater stream. In instances where steam conditioning
is necessary or preferred, waste reduction can be accomplished by
decreasing the water volume contact with preservative. Steaming
is necessary for the treatment of southern pine with creosote and
pentachlorophenol, since the wood must be treated while hot to
prevent the formation of sludge on the wood's surface. Converting
from open to closed steaming substantially reduces the volume of
cylinder effluent that must be treated by recycling the steam
condensate separately from the preservative. (24)
In order to increase production and reduce yard inventory when
treating hardwood products, steaming is preferred due to its
greater efficiency over air drying and problem with cracking and
warpage from kiln drying. The use of separate retorts for steam
conditioning and treating physically separates the conditioning
operation from the treatment process. This eliminates the
contamination of the steam condensate waste stream with
preservative.
The most significant pollution problem associated with the
wood treating process is area contamination from storm runoff and
area washdowns. This occurs when excess preservative drips from
the freshly treated charge before it becomes "fixed" in the wood
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structure and consequential spills that accompany opening the
pressure cylinder door are transported by rainwater runoff and
water used to clean-up drips and spills. Areas under and in the
vicinity of the treating cylinder are the sources of this
contamination. Containment of the excess preservative from a
"freshly pulled" charge is essential to eliminate the unwanted
discharge of chemicals into the environment. Covering the
cylinder entrance and charge preparation area reduces both the
amount of foreign matter and volume of rainwater that would have
to be collected and treated. The installation of spill basins,
drip pads with collection troughs, and sumps beneath the retort
and preparation area allows recycling of the chemical
preservative for further use. At plants using water-borne
chemicals, the recycled preservative is used as makeup water in
preparing new solutions. For facilities using oil-based
preservatives, the wastestream is recycled to an oil/water
separator for recovery of preservative. Collection systems as a
source control technology not only act as pollution control but
soon pay for themselves in recovered preservative. (25)
There are a number of operational practices which are
relatively low cost source control measures that can
significantly reduce and simplify the wastestreams to be
collected and treated. These practices include pretreatment
procedures, p rocess methods, handling of freshly treated wood,
and preventative maintenance.
Prior to the treatment process, the wood should be examined to
assure that it is clean and properly seasoned in order to avoid
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unnecessary contamination of the preservative solution with wood
acids, sugars, fibers, and other foreign matter. Additionally,
the treating solution should be thoroughly mixed and free from
contamination. Careful stacking of the wood in the retort
assures that after pressure impregnation the excess preservative
can freely drain away from the charge by pumping from the
cylinder. Maximizing the duration and vacuum applied, further
improves the collection of unabsorbed preservative. Freshly
treated charges normally drip preservative for several hours
before chemical fixation occurs in the wood, therefore in order
to contain this "kick back" (drippage) and eliminate area
contamination, it is essential to maximize the amount of time
that the wood is allowed to remain in the evacuated cylinder and
on the drip pad. Before the wood is moved either for storage or
shipment, it should be inspected to insure that the product is
clean and dry.
Leaks in pipes and pumps are another common source of
contamination and represent a loss of usable preservative. The
early detection of leaks through periodic and systematic checking
of plumbing at a treating facility provides pollution control
that reduces operating costs by recovering preservative that
would otherwise be lost. Changes in operational procedures are
practices that should be considered before investing in treatment
systems, since they are significantly less expensive and provide
a better return on investment by recovering valuable raw
materials (preservative).
The storage of spent or contaminated chemicals, or of
contaminated stormwater runoff has traditionally been in unlined
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lagoons. Such storage is no longer legal, and a question of
lining lagoons with clays to prevent groundwater contamination
has been asked. In order to answer this question, a series of
tests using hydrostatic permeameters with various compacted
clays, simulating clay liners, were conducted. The wood
preserving waste was placed under pressure on these clays and
their permeability measured.
The results show slight increases in permeability, but no
breakthroughs in the tests which lasted for eighteen weeks.
However, a longer test with a waste similar to wood preserving
waste lasted for more than a year and resulted in a catastrophic
breakthrough. The implications are that clay liners could be
considered at best a temporary solution for the storage of wood
preserving wastes.
ENVIRONMENTAL REGULATION
The Environmental Protection Agency under the Resource
Conservation and Recovery Act of 1976 issued a series of
hazardous waste regulations on the wood preserving industry. The
segment of the industry treating with creosote and/or
pentachlorophenol was extensively studied by the agency prior to
the enactment of the legislation. These regulations relating
liability insurance, closure of hazardous waste facilities,
retro-fitting of plants and monitoring of certain hazardous waste
facilities represent major problems to many owners of wood
preserving plants, especially those treating with oil-based
preservatives (creosote, pentachlorophenol).
The wood preserving industry is composed of a large number of
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small privately owned plants and a few large integrated
corporations. About two-thirds of all plants treating wood are
believed to be "small generators" of hazardous waste and are thus
exempt from most hazardous waste regulations. However, many of
these plants will be subject to costly regulations for management
of hazardous wastes. (26)
In general, the small privately owned treating facilities are
single-plant companies. The projected cost of compliance to
proposed environmental regulations falls disproportionately on
these smaller firms. Proposed liability insurance requirements
apply to each owner rather than each plant, so insurance costs
per volume of output are much greater for the single-plant
company than for the large multi-plant corporation. Obtaining
capital investment funds to renovate existing facilities to
satisfy environmental regulations represent major problem to the
majority of owners of wood preserving plants. (27)
Although the industry is composed of many small firms, the
eight largest companies control about half of the market. (28)
Therefore, a highly competitive market exists among the smaller
producers and the extent to which increased costs stemming from
environmental regulation can be passed on to consumers is greatly
limited by the relatively strong competition among wood treaters.
The proposed liability insurance requirements and providing
financial assurance for future plant closure impose substantial
costs for many wood preserving plants. Furthermore, the rapidly
escalating rates and difficulty in obtaining pollution insurance
places a severe financial hardship on smaller firms.
The segment of the wood preserving industry treating with
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waterborne inorganic salts does not seem likely to be seriously
affected by the hazardous waste regulations since inorganic
plants are required to be at "zero discharge". Consequently,
recent expansion in the industry has occurred with the
construction of new waterborne inorganic treating facilities and
modification and expansion of existing treating operations to
handle waterborne preservatives.
Although it would appear that converting the segment of the
industry treating with oil-based organic chemicals to inorganic
waterborne preservatives would eliminate waste generation
associated with the wood preserving industry, problems with the
disposal of solid residues still exist. Each of the treatment
processes result in the formation of solid residues including
sludge from the work tank system and wastewater treatment sludge.
Inorganic processes produce less hazardous waste per charge of
wood than oil-based treatments, however the amount of wastewater
treatment sludge by each process is approximately equal. Wastes
generated from oil-based organic preservatives tend to be
biodegradable, whereas wastes from inorganic arsenicals are not.
Presently these solid residues are disposed of at hazardous waste
landfills. Additionally, the markets for oil-based organic and
water-borne inorganic preservatives are sufficiently different
that substitution of chemicals is unlikely.
ECONOMIC IMPACT
Treated wood is primarily used for crossarms, lumber, pilings,
poles, railroad ties, and timber. In most situations, treating
wood increases its life expectancy to five or more times that of
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untreated wood. (29) Substitute materials such as concrete,
steel or untreated wood, while producing less hazardous waste
than the wood treating process, represent more expensive
alternatives for treated wood products. Therefore, the
elimination of the wood preserving industry would have a major
economic impact in the United States.
Declining supplies and higher prices for naturally resistant
woods, such as cedar and redwood, have resulted in increased
demand for treated softwoods, such as yellow pine. Wood treated
with inorganic arsenicals has provided a suitable substitute for
domestic construction, such as decking. In 1984, 268 million
cubic feet (4,257 million board feet) of treated lumber and
timbers were produced, with 94% treated with waterborne
preservatives. (30) Due to the wide variety of uses for treated
lumber, it is not possible to quantify the economic impact of
non-wood substitute materials, however the likely substitutes of
plastic, steel and concrete all have costs greater than wood.
Qualitatively, the restriction of waterborne inorganic arsenicals
as a chemical preservative would have an adverse economic effect
on the construction business. (31)
Traditionally, the American railroad industry has relied
exclusively on creosote treated wood products for crossties,
switch and bridge ties, and pilings. Concrete is a technically
feasible substitute as railroad ties, however its use is
incompatible with wood ties, requiring the complete replacement
of all wood ties in a given section of track with concrete ties.
This substitution of concrete ties for wood ties represents an
annualized increase in cost of 3.4 billion 1978 dollars for the
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first year and 2.4 billion 1978 dollars thereafter, a cost that
will most likely be absorbed by the American taxpayer. (32) wood
treated with waterborne inorganic arsenicals are unacceptable
substitutes for creosote treated products due to changes in the
mechanical properties of the material, notably a hardening of the
wood. In 1984, 78 million cubic feet of pressure treated wood
poles were produced. Oil based preservatives provided 85% of
this production, 43 million cubic feet treated with
pentachlorophenol and 23 million cubic feet treated with creosote
solutions. (33) In this application, creosote and
pentachlorophenol are potential substitutes for each other. The
Environmental Protection Agency has projected that the increased
cost for replacement of treated poles with non-wood substitutes
would range from 1.3 billion dollars to 2.1 billion dollars
annually. (34)
Approximately 12 million cubic feet of treated wood pilings
were produced in 1984. Creosote and waterborne preservatives
accounted for greater than 97% of the production, 58% by creosote
and 40% by inorganic arsenicals. (35) In this particular
application, creosote and inorganic arsenicals are not potential
substitutes, owing to the ineffectiveness of creosote treated
pilings in the marine environment and untreatability of certain
wood species with waterborne preservatives. The use of non-wood
substitutes for treated wood pilings, projects an annualized cost
increase by 33% for concrete and 67% for steel. (36)
Economic evaluation of alternative materials for treated wood
products favors the continued use of preserved wood. Although
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concrete and steel produce less hazardous waste than the wood
treating process, there are increased energy and environmental
costs relating to mining, processing and manufacturing of
substitute materials. Additionally, wood is a renewable domestic
resource whereas the estimated annual need for 29 million tons of
cement, sand, gravel, and crushed stone along with the 1.7
million tons of steel for substitute products holds implications
of a greater dependence on the importation of non-wood raw
materials. (37)
The substitution of oil-based organics with waterborne
inorganic preservatives is a complex issue and in particular
applications they are mutually exclusive. For many uses,
creosote and pentachlorophenol are potential substitutes,
cancellation of either would result in the use of alternatives
rather than in the use of non-wood substitutes. Elimination of
the organic arsenicals would have an adverse economic effect on
the construction industry. Restriction of the use of waterborne
inorganic chemicals and either of the oil-based preservatives
would result in a shift to untreated wood and non-wood
substitutes.
Based on information developed from the 1977 Census of
Manufacturers, an estimated 30,700 people were employed in
treating wood and related timber activities in 1978. During this
period the wood preserving industry employed 13,300 directly in
treating operations, paid 140 million dollars in wages and
consumed 796 million dollars of wood raw materials. An
additional 17,400 jobs in producing, harvesting and processing of
timber were dependent on the wood preserving industry. (38)
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These benefits accrue to many thousands of citizens directly
and indirectly dependent on the industry in more than 500
communities, most of which are small rural towns in which the
production, processing, and preservation of wood products are
major sources of employment and income. This is especially true
in the state of North Carolina where 95% of the plants are
located in small rural communities. Finding new jobs for workers
displaced by cessation of wood treating operations could entail
substantial transfer costs to many families. Many workers might
not find new jobs because of the lack of opportunities in these
rural areas resulting in at least temporary dependence on
unemployment insurance and welfare.
In 1984 the wood preserving industry provided a market for
more than 500 million cubic feet of standing timber and logs,
much of which came from relatively low-quality trees not suitable
for higher value use, or species for which only a limited market
would exist unless treated. (39) The industry thus promotes sound
forestry management and improved forest environments by utilizing
materials that would otherwise not be marketed and reducing the
demand for higher quality products.
CONCLUSIONS
Wood preserving is a substantial industry in the United States
with extreme significance in the southeastern states that range
from Texas to Maryland. It is composed primarily of small
privately owned facilities that treat wood with toxic chemicals
to produce railroad ties, utility poles, lumber and timber.
Although the wastestreams resulting from the treating processes
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are damaging to the environment, the industry has achieved a
large reduction in the amount of hazardous waste it produces
through source control technologies. 'In fact most new facilities
have incorporated many of these methods in the design and
construction of new plants.
Although it is possible to construct "zero discharge" plants,
some of the older facilities still produce hazardous waste which
could be a health hazard or pose a threat to the environment,
such as the contamination of groundwater systems with chemicals
that are known carcinogens and suspected mutagens and teratogens.
For older plants, the following specific measures can be
implemented which will result in decreased waste production,
increased retention and use of chemicals and potential savings in
treatment cost:
[l] Installation of drip pads for collecting preservative
during extraction from the treatment cell.
[2] Installation of a roof over the treated lumber, thus
preventing the production of contaminated stormwater
runoff.
[3] Careful inspection of piping and pump seals and
elimination of leaks.
[4] Installation of overflow tanks which would accept
inadvertant overflows from chemical storage tanks.
[5] Installation of recycle systems which would filter out
grit, dirt, and wood fibers from recoverable
preservative.
[6] Installation of oil/water separators at oil-based
organic facilities which would recover reusable excess
25
-
preservative.
Since many of the source control measures developed by much of
the industry improve operating efficiency in addition to
providing pollution control, implementation will be achieved
through an increase in awareness with more facilities adopting
better operating procedures and replacing older equipment as the
recognition that pollution prevention pays is not merely a
slogan.
Unfortunately, this fragmented industry of small companies in
a highly competitive market has great difficulty in funding
research in source control technologies and obtaining the capital
investment necessary to renovate existing facilities to satisfy
environmental regulations. Therefore in order to assist the
industry and protect the environment it is suggested the
following measures be considered.
[ l ] A program of challenge grants be initiated where the
state governments provide either matching funds or low
interest loans for the construction or purchase of
source control systems.
[2] The funding of additional research into source control
technologies with an emphasis on examining the
methods employed by the petrochemical, metal-plating,
and coal byproducts industries and their potential
application to the wood preserving industry.
[3] Consideration of a state sponsored programthat would
provide liability insurance for facilities that
implement and observe state-of-the-art source control
26
-
technologies by licensing such plants through a
state agency.
27
-
[ l ]
[2]
[3]
[4]
[5]
[ 6 ]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
References
Micklewright, James T. Wood Preservation Statistics, 1983 & 1984A Report to the Wood Preserving Industry in the United StatesJanuary 1986 page 2
ibid. page 2
Burt, Henry Potter "On the Nature and Properties of Timberwith Descriptive Particulars of Several Methods, Now in Use,for its Preservation from Decay" January 11, 1853 881 inNo. 881 Institute of Civil Engineers Volume XII Session 1852-3Published by the Institution 1853 London page 215
The Biologic and Economic Assessment Of Pentachlorophenol,Inorqanic Arsenicals, Creosote I: Wood PreservativesEnvironmental Protection Agency technical-bulletin 1658-l
November 1980 Washington, D.C. page 36
Wood Preserving Industry Multimedia Emission InventoryEPA-600/2-81-066 Environmental Protection AgencyApril 1981 Washington, D.C. page 10
ibid. page 10
Micklewright, James T. Wood Preservation Statistics,- -pas- 4
1983 & 1984- -
Wood Preserving Industry Multimedia Emission InventoryEPA-600/2-81-066 page 13
ibid. page 13
ibid. page 13
ibid. page 14
Gurfinkel, German Wood Engineering Southern Forest- -Products Association 1973 New Orleans, Louisiana page 124
The Biological and Economic Assessment Of Pentachlorophenol,Inorganic Arsenicals, Creosote Volume I: Wood Preservatives
Technical Bulletin 1658-1- -
page x x v 1 1
Wood Preserving Industry Multimedia Emission InventoryProject Summary EPA-600/S2-81-066 Environmental ProtectionAgency September 1981 Washington, D.C. page 3
Rao, K. Rango Pentachlorophenol; Chemistry, Pharmacologyand Environmental Toxicology Plenum Press 1978 New York page 3
ibid. page 13
-
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
Fowler, Bruce A. Biological and Environmental Effects ofArsenic Elsevier 1983 New York page 277
Wood Preserving Industry Multimedia Emission Inventor- -EPA-600/2-81-066 Environmental Protection Agency- April 198
Washington, D.C. page 18
Wood Preserving Industry Multimedia Emission Inventory- - - - - - - - - - - - -Project Summary EPA-600/S2-81-066 page 3
Micklewright, James T. Wood Preservation Statistics, 1983 & 1984- - -Appendix II
Josephson, H. R. Economic Impacts of Hazardous Waste Regulationson the Wood Preserving Industry Prepared for the American- -Wood Preservers Institute October 1981 page 7
Micklewright, James T. Wood Preservation Statistics 1983 & 1984- -table 2
Economic Impact Analysis of Alternative Pollution ControlTechnologies Wood Preserving Subcategory of the Timber ProductsIndustry EPA-440/2-79-018 U.S. Environmental Protection Agency,Office of Water Planning and Standards September 1979
Washington, D.C. page 29
Thompson, Warren S. "Pollution Control" in Wood Deteriorationand Its Prevention by Preservative Treatments; Volume II.Preservatives and Preservative Systems Darrel D. ----Nicholas editorSyracuse University Press 1973 Syracuse, New York page 366
ibid. page 370
Josephson, H.R. Economic Impacts of Hazardous Waste Regulationson the Wood Preserving Industry page 7- - -
Economic Impact Analysis of Alternative Pollution ControlTechnologies EPA -44-/2-79-018 page 11
ibid. page 21
Micklewright, James T. Wood Preservation Statistics,page 2
1983 & 1984- - -
ibid. page 2
Wood Preservative Pesticides: Creosote, Pentachlorophenoland the Inorganic Arsenicals Position Document 2/3EPA-540/9-82-004 Environmental Protection Agency March 1982
Washington, D.C. page 30
ibid. page 28
-
[33] Micklewright, James T. Wood Preservative Statistics, 1983 & 1984- _ -page 2
[34] Wood Preservative Pesticides: Creosote, Pentachlorophenoland the Inorganic Arsenicals EPA-540/9-82-004 page 32- -
[35] Micklewright, James T. Woodtable 1
Preservative Statistics, 1983 & 1984- _ -
[36] Wood Preservative Pesticides: Creosote, Pentachlorophenoland the Inorganic Arsenicals. Position Document 4EPA/540/9-84/003 Environmental Protection Agency July 1984
Washington, D.C. page 36
[37] The Biologic and Economic Assessment OfInorganic Arsenicals, Creosote Volumetechnical bulletin 1658-1 page xxvii
[38] ibid. page xxii
PentachlorophenolI: Wood Preservatives- -
[39] Micklewright, James T. Wood Preservation Statistics, 1983 & 1984- - - - - - - -page 2
-
APPENDIX:
Hydraulic Conductivity of Clay Soils
Exposed to Wood Preserving Wastes
The wood preserving industry utilizes hazardous chemicals in
the treatment of wood. The treating process therefore generates
hazardous waste, represented by the preservative that is not
impregnated into the wood. This excess preservative is collected
for recycling and stored in steel tanks, concrete lined pits or
clay lined lagoons.
Abandoned lagoons containing wood preservative wastes have
recently been targeted for "Superfund" cleanup operations.
Therefore, the importance of investigating the effects of wood
wastes on clay soils has just recently been recognized. Hence, a
series of experiments were conducted to determine the hydraulic
conductivity of clay soils permeated with wood preserving wastes.
The state of North Carolina has 40 wood preserving plants,
of which 29 use waterborne preservatives. This significant use
of inorganic chemicals and the possible incompatibility of the
test equipment with organic substances, such as the oil-based
preservatives, led to the selection of a waterborne preservative
as the test specimen. The particular material tested is a
chromated copper arsenate, type C (CCA-C), obtained from a
confidential location in eastern North Carolina.
The wood preserving waste tested contains ions of CU, Zn,
Cr, and As in various concentrations with an extremely low pH of
approximately 2. Research has shown that clays flocculate if
-
they are percolated with bi- or multivalent rich solutions,
resulting in a slight increase in hydraulic conductivity. Also,
the effect of an extremely low pH on the clay could lead to a
gradual breakdown of the clay lattice resulting in a dilute
amorphous silica gel. The solubility of such a gel is fairly
high, so the hydraulic conductivity could be expected to increase
with time.
The effect of inorganic waste on clay liners was tested
using hydrostatic fixed-wall permeameter cells. (Figure A-1)
These different clays were tested and the waste was placed on top
of the compacted clays at a pressure of 14 psi for eighteen
weeks. (Details of the test procedure are found elsewhere. [A-l])
Results from these tests showed a gradual increase in
hydraulic conductivity after the application of the waterborne
inorganic waste. The increase in hydraulic conductivity for the
different clays were approximately:
. 0.4E-7 cm/s - White Stone Clay
. 0.5E-7 cm/s - Faceville Clay
. 0.1E-7 cm/s - Hoytville Clay
These results agreed with the previous results for other types of
wastes. [A-2]
Because of a lack of time and equipment, the wood preserving
waste cells were run for only eighteen weeks. One experiment,
using a high ionic strength and low pH waste which could be
expected to react in a similiar way to wood preserving waste, was
continued for over a year until it broke through the clay. The
breakthrough, and the obvious change in the physical character of
-
the clay, suggests that clay liners in lagoons holding wood
preserving wastes are at best temporary storage solutions.
Although it is not possible to draw any definite conclusions
from the tests performed within the scope of this research, a
gradual increase in hydraulic conductivity could be expected
during prolonged testing of a flexible-wall cell with clay
permeated with inorganic wood preservation waste, and the
breakthrough with a similiar waste indicates potential clay liner
destruction with prolonged exposure. The implications of this
conclusion suggest that clay lined lagoons are at best short term
solutions for the storage of hazardous wastes generated by wood
treating facilities.
References: Appendix
[A-1] J. Jeffrey Peirce Hydraulic Conductivity of Clay- -Soils Exposed to Inorganic Waste Liquids Generated bySeveral Industries U.S. Environmental ProtectionAgency, Contract No. 68-03-3149, 24-4 pgs. 76-88
[A-2] ibid. pg. 94
-
Bibliography
Biologic and Economic Assesment of Pentachlorophenol,Inorganic Arsenicals, Creosote Volume I: Wood PreservativesEnvironmental Protection Agency technical bulletin 1658-1November 1980 Washington, D.C.
Burt, Henry Potter "On the Nature and Properties ofTimber, with descriptive particulars of several methods, nowin for its Preservation from Decay" January 11, 1853in Institution of Civil Engineers, Volume XII,Session 1852-53 1853 London
'Economic Impact Analysis of Alternate Pollution ControlTechnologies Wood Preserving Subcategories of the TimberProducts Industry EPA-440/2-79-018 U.S. EnvironmentalProtection Agency, Office of Water Planning and StandardsSeptember 1979 Washington, D.C.
Fowler, Bruce A. Biological and Environmental Effects ofArsenic Elsevier 1983 N e w Y o r k - - -
Goldstein, Irving S. editor, Wood Technology: Chemical- -Aspects ACS Symposium Series 43 American Chemical SocietyWashington, D.C. 1977
Gurfinkel, German Wood Engineering Southern ForestProducts Association 1973 New Orleans, Louisiana
Josephson, H.R. Economic Impacts of Hazardous Waste- - - -Regulations on the Wood Preserving Industry
- -Prepared for- -
the American Wood Preservers Institute October 1981
Micklewright, James T. Wood Preservation Statistics, 1983-84A Report to the Wood Preserving Industry In the UnitedStates January 1986
Nemerow, Nelson L. Industrial Water PollutionAddison-Wesley Publishing Company 1978Reading, Massachusetts
-
Nicholas, Darrel D. editor, Wood Deterioration and Its- - Prevention by Preservative Treatments; Volume I: Degradationand Protection of Wood, Volume II: Preservatives andPreservative Systems Syracuse University Press 1973-----Syracuse, New York
Overcash, Michael R. editor Decomposition of Toxic and NontoxicOrganic Compounds in Soils Ann Arbor Science Publishers- -1981 Ann Arbor, Michigan
Rao, K. Ranga Pentachlorophenol; Chemistry, Pharmacology,and Environmental Toxicology Plenum Press 1978 New York
Wood Preserving Industry Multimedia Emission InventoryEPA-600/2-81-066 Environmental Protection AgencyApril 1981 Washington, D.C.
Wood Preserving Industry Multimedia Emmission InventoryProject Summary EPA-600/S2-81-066 Environmental ProtectionAgency September 1981 Washington, D.C.
Wood Preservative Pesticides: Creosote, Pentachlorophenol- -and the Inorganic Arsenicals Position Document 2/3- -EPA-540/9-82-004 Environmental Protection AgencyMarch 1982 Washington, D.C.
Wood Preservative Pesticides: Creosote, Pentachlorophenoland the Inorganic Arsenicals Position Document 4EPA/540/9-84 Environmental Protection AgencyJuly 1984 Washingon, D.C.