PULP AND PAPER:
THE REDUCTION OF TOXIC EFFLUENTS
Science and Technology Division
PULP AND PAPER INDUSTRY AS A POLLUTION SOURCE
The Structure of Woody Materials
Dioxins and Furans
OF COMPOUNDS HAZARDOUS TO HUMAN HEALTH
ABATEMENT BY THE PULP AND PAPER INDUSTRY
In-Plant Process Changes
End-of-Pipe Biological Treatment Processes
Pollution Abatement A Case Study
PULP AND PAPER:
THE REDUCTION OF TOXIC EFFLUENTS
The manufacture of pulp
and paper is a resource-intensive industry that consumes large amounts
of energy, water, and trees. It is a mature industry that is innovative
and adapts rapidly to technological change in order to remain competitive
in the international market. The emergence of this technology as a major
industry in Northern Europe and North America took place during the latter
half of the nineteenth century, a time when there was little thought given
to the possible detrimental effects of industrial pollution on the environment
or human health. In the United States, pulp and paper mills are now considered
the nations third largest polluter.(1)
In Canada, it has been estimated that this industry is responsible for
50% of all the waste dumped into the nations waters(2)
and also accounts for approximately 5.6% of the common air contaminants
from known industrial sources.(3)
Pollution from the pulp
and paper industry is both a tradition in Canada, and a consequence of
international economic reality. The technologies exist for substantially
reducing emissions, particularly those that are a risk to human health.
However, pulp and paper mills represent capital expenditures in the high
hundreds of millions of dollars, and retrofitting a mill with new process
technologies for pollution abatement regularly costs additional hundreds
of millions of dollars. Such huge expenditures put pulp and paper companies
at a disadvantage with competitors in countries without stringent effluent
controls The implementation of environmental protection will have to proceed
in a manner that sustains the economic health of the pulp and paper industry,
yet ensures human health and environmental quality.
To tackle this problem in
a cost-effective manner it is necessary to understand the nature of the
problem, and identify the specific compounds that endanger human health
and environmental quality. It is then possible to choose and install new
process technologies to prevent the production of toxic effluents. Alternatively,
depending upon economic circumstances and the age of the mill, it may
be more cost-effective to add an end-of-pipe waste water treatment system.
There is a large degree of variation in the pulping and bleach plant technologies
used in mills. Accordingly, the solution for one mill cannot be applied
to the environmental problems of the whole industry.
Egyptian papyrus and Chinese
silk cloths were the first writing materials. The first true paper, prepared
from fibrous cellulose-containing plant material, was manufactured in
China in the year 105 A.D. At that time, Chinese clothing was made largely
from China grass (Boehmeria nivea), a common fibrous plant. Worn-out
clothing was collected by rag merchants and sold to paper makers, who
recycled the cellulose content into paper.(4)
The technology of paper-making
slowly crossed the Arab world, and by the year 1150 made its way to Europe
through Moorish Spain. From 1150 to the middle of the 19th century the
feedstock for paper-making remained recycled cellulosic materials, such
as rags, rope, fish nets, and burlap. European clothes were made primarily
of either linen or wool. Flax, from which lien is made, was therefore
the dominant source of European paper for centuries.(5)
The flax plant Linum
usitatissimum) grows to 1.2 metres in height, and produces woody fibres,
which are much longer than real wood fibres and unlike them are easily
separated, very strong, and supple-soft. These qualities are valued for
the production of specialty papers that are soft, yet very strong. Today,
most of the worlds bank notes are printed upon a high-value flax
paper produced in Canada.
The first paper mill in
Lower Canada was established in 1803, in the village of St. Andrews, near
present-day Lachute, P.Q. By 1820, a number of mills had begun operation
across Upper and Lower Canada. Until Confederation, these mills were generally
small, and depended upon linen and cotton rags and recycled rope, jute
cloth, flax wastes and straw, for their raw feedstock. In Georgetown,
Ontario, the Barber paper mill installed straw boilers in 1861, and made
paper from straw from local farms. At this time, all the cellulosic substrates
used in paper-making were either already well processed or raw materials
from which cellulose fibres could be extracted easily. Wood was not used
as a substrate, as the technology and equipment had not been developed
to chisel and grind wood down inexpensively into a size that could be
used in the established paper-making process.
In about 1850, John Taylor
of the Don Valley Paper Mill, Toronto, was the first to develop and later
patent a Canadian process for making wood pulp. The use of wood as a cellulosic
feedstock was the first major technological break-through in paper-making
in 1,700 years. This advancement dramatically transformed the industry.
Today in Canada, 144 large pulp and paper mills consumer vast quantities
of wood, and produce both raw pulp and finished papers for the world market.
PULP AND PAPER INDUSTRY AS A POLLUTION SOURCE
the sources of pollutants from this industry it is necessary to review
the composition of the primary substrate, wood, and the chemical and mechanical
processing that it undergoes to produce the quality pulps needed for paper-making.
The Structure of Woody Materials(6)
The three main component
groups of wood are cellulose, hemicellulose, and lignin. Although the
concentration of these three components can vary from species to species,
the proportions are roughly 50% cellulose, 25% hemicellulose and 25% lignin.
Cellulose is a very long linear molecule composed of repeating glucose
units. Bundles of cellulose molecules from microfibrils, which build up
to fibrils, and finally to cellulose fibres. Hydrogen bonding takes place
between linear molecules to result in a strong microcrystalline structure.
Cellulose, being nothing more than glucose in a tightly bound molecular
structure, is quite susceptible to degradation by microorganisms. In spite
of this, cellulose is generally not easily attacked by bacteria and moulds,
because of the protective hemicellulose and lignin covering that enwraps
the cellulose fibres.
Hemicellulose is composed
of a random arrangement of five-carbon sugars. These long-branching molecules
surround the cellulose fibres, and intrude into pores in the cellulose.
Hemicellulose forms chemical bonds with the next layer, lignin, and essentially
acts as a chemical bonding agent between cellulose and lignin.
Lignin is a complex phenylpropanoid
polymer that surrounds and gives strength to the cellulose-hemicellulose
framework. Lignin is composed of three phenol-based building blocks that
polymerize in a completely random fashion. This random structure is very
difficult to degrade. When slow degradation does take place, phenolic
compounds, which are generally toxic, are released. As a result on a limited
number of microorganisms derive benefit from the biological breakdown
of lignin. The aromatic content of lignin, expressed as monomeric phenol,
is approximately 51%. It is the phenolic compounds released from lignin
during the chlorine bleaching of pulp that are responsible for a large
percentage of the toxic compounds released in pulp mill effluents.
In addition, wood contains
1.5 5% extractives, a general designation for wood components that
may be extracted by organic solvents. These include resin acids, fats,
waxes, terpenoid compounds, tannins, flavonoids, stilbenes, and troppolines.
While extractives are generally present in mill wastes at much lower concentrations
than phenolic materials, some of these compounds are relatively toxic,
and can significantly reduce water quality and marine habitat in the lakes
and rivers that receive mill effluents.
The purpose of pulping is
to free the cellulose fibres from the other wood components in as pure
and undamaged a condition as possible. There are many pulping procedures;
these evolve and change as economic and market circumstances dictate.
The first widely used pulping method was the stone-groundwood process;
this had the advantages of high yield and little waste, but resulted in
damaged fibres that lacked strength. This process decreased in popularity
when chemical pulping, which produced longer, stronger fibres, was developed.(7)
During the early half of
the twentieth century, sulphite pulping predominated in Canada, until
it was replaced by Kraft pulping. Today Kraft mills account for a very
large share of total pulp production. For example, in 1984 46.5% of all
Canadian pulp was produced by the Kraft process.(8)
Besides the production of high quality fibre, the other major advantage
is the spent-liquor system, which recovers tall oil (fatty and resin acids),
turpentine, bioenergy, and recycles inorganic chemicals.(9)
The Kraft process is now
being challenged by chemithermo-mechanical pulping (CTMP). In the CTMP
process, chemistry, temperature, and mechanical parameters can be varied
to optimize the release of cellulose from specific wood species. The economic
advantages of CTMP are many: strength, brightness and versatility of the
pulp produced; lower energy requirements; less need for processing; reduced
water usage; the wide range of wood species that can be used; and, most
important, the extremely high yield of pulp (90-92% of available cellulose
fibre versus 4042% for Kraft pulping).
Unfortunately, the new developments
that make the pulp and paper industry more competitive are not necessarily
designed to reduce pollution. The basic CTMP process, unlike Kraft pulping,
does not incorporate a recycling-recovery step. With CTMP, the reduced
water flow, combined with higher fibre recovery that releases large amounts
of lignin and extractives, greatly increases the potential for release
of concentrated toxic effluents.(10)
This problem is exacerbated if the organic waste stream receives chlorine-bleaching
effluents. CTMP plants could have been devastating to the Canadian environment
had they been built 20 years ago. Stringent pollution regulations are
now in force, however, and, as new CTMP mills are built, they incorporate
the necessary pollution control devices to ensure that mill effluents
pass toxicity monitoring. In fact, the new goal of the pulp and paper
industry is the development of "zero-emission" or "closed-loop"
CTMP mills, where all wastes are recovered and process water is recycled.
There are very few sulphite
pulp mills still operating in Canada, and the newly built CTMP mills generally
meet pollution effluent standards. This leaves Kraft pulping as the primary
source of toxic pulp mill effluents. Figure 1 and the following brief
overview of the operation of a conventional Kraft pulp mill and bleach
plant describe pollution sources.
Figure 1. General Flow
Diagram for a Kraft Pulp Mill and Bleach Plant
and Lindstrom (1984).
Logs and debarked and then
put through a chipper. The pulping process beings by treating wood chips
at 160 180oC in a "white liquor" solution of sodium sulphide
and sodium hydroxide. This treatment cleaves lignin ether bonds; and dissolves
90 to 95% of the lignin, essentially all hemicellulose, and wood extractives,
and a small amount of cellulose-derived polysaccharides. Approximately
55% of the original wood is dissolved in what is now termed the "black
liquor." By-products are recovered, and the liquor evaporated to
high concentration and then burned for recovery of energy and inorganic
The evaporated phase, which
may contain inorganic sulphur in the form of sulphate, sulphite, or dithionite,
is trapped in a condenser producing a concentrated sulphur waste water
stream termed evaporator condensate. Highly volatile fugitive emissions
from the condenser, and volatile compounds and gases from the burnt concentrated
black liquor are released to the atmosphere. Air contaminants released
from pulping include particulate matter, sulphur dioxide, and total reduced
sulphur (TRS) compounds. The TRS compounds consist primarily of hydrogen
sulphide, methyl mercaptan, dimethyl sulphide, and dimethyl disulphide.
It is these compounds that contribute to the characteristic foul odors
associated with pulp mills. The very low odour threshold of these pollutants
means that disagreeable odours can be discerned by smell at concentrations
that are seldom hazardous to human health. Accordingly, the main effect
of pulp mill airborne emissions is the reduction of aesthetic air quality,
although, the blackening by hydrogen sulphide of homes and buildings in
proximity to pulp mills is not uncommon.(12)
The pulping process is terminated
when the pulp still contains 5 10% lignin, as further delignification
would harm fibre quality. In the bleach plant the pulp is made into a
3% slurry and treated with a chlorine charge of 60 70 kg/t, at
pH 1.5 2.0. This is followed by filtration and then an alkali treatment
(35 40 kg/t), pH 11, at 55 70oC. Subsequent bleaching
treatments may vary, but usually proceed through a series of hypochlorite,
chlorine dioxide, alkali, and chlorine dioxide processing steps. After
each treatment stage the pulp is filtered and the process liquids combined
as bleachery effluent.(13)
During bleach plant treatment,
approximately 1 kg of extractives, 19 kg of polysaccharides, and 50 kg
of lignin are dissolved from 1 tonne of softwood pulp. Chlorine can react
with all of these organic wastes to produce structurally diverse organochlorine
compounds. However, most reactions take place with the lignin fraction
producing simple but toxic monoaromatic compounds such as chlorinated
phenols, guaiacols, and catechols, as well as high molecular weight chlorolignins.
The latter compounds are thought to be nontoxic, as their large size precludes
their penetration or transport across cell membranes. In spite of this,
they are not environmentally benign, as they carry chromophoric structures
that discolour receiving waters. Also, there is the potential for the
release of toxic compounds as the chlorolignins slowly degrade.(14)(15)(16)
Dioxins and Furans
(PCDDs) and polychlorinated dibenzo-p-furans (PCDFs) have been identified
in emissions from the pulp industry. Their concentration in stack gases
from the burning of condensed black liquor is very low. In Sweden it has
been estimated that the annual production of 4 million tonnes of pulp
results in approximately 2 grams of PCDD and PCDF congeners emitted
into the air.(17)
PCDDs and PCDFs also are
produced during pulp bleaching, where they are formed from chlorinated
phenols, and particularly from chlorinated 2-phenoxyphenols. Bleachery
effluents account for the release of 5 15 grams total PCDD and
PCDF congeners per year in Sweden. Accordingly, the Swedish pulp industry
is responsible for only a very small amount (1.7%) of the approximately
1 kg of PCDDs and PCDFs released from all sources in that country. This
has been verified by comparison of isomer patterns. The pulp industry
produces primarily 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin and 2, 3, 7,
8-tetrachloro-dibenzo-p-furan, while the isomer profiles from incinerator
operations are distinctly different.(18)
Similarly, in the United States, it was estimated that in 1990 the pulp
and paper industry would be contributing only 1.5% of the approximately
40 kg of total PCDDs and PCDFs released to the environment annually.(19)
Although total environmental
contribution is quite low, the pulp and paper industry has spent large
sums of money on research and development to eliminate or at least greatly
reduce these compounds in effluents and paper products. The industry is
threatened by publicity and public fear of dioxins, which peaked with
the discovery of dioxin in milk cartons. It has been possible to reduce
the dioxin level in milk carton cardboard to 2 parts per trillion, a level
indistinguishable from typical background levels in milk.(20)
OF COMPOUNDS HAZARDOUS TO HUMAN HEALTH
During the past century
many chlorinated organic pesticides, solvents, refrigerants, etc., that
have been chemically synthesized, have been found to be highly toxic,
and/or extremely difficult to degrade and remove from the environment.
These man-made chemicals are called xenobiotics. They are not natural
chemicals, in that they have never been produced in nature by animal or
plant metabolism. As such, they have no natural enemies; that is, microorganisms
have not been in contact with these chemicals long enough to evolve the
enzyme systems necessary for their rapid degradation. Similarly, many
of the chlorinated organic compounds randomly synthesized during pulp
bleaching are toxic xenobiotics that will persist for long periods in
The situation can often
be made worse if pulp mill effluents are released to oxygen-limited or
depleted (anaerobic) waters. Certain species of anaerobic bacteria can
methylate chlorinated organic compounds, thereby making the compounds
less toxic to the bacteria. Unfortunately, this mechanism generally increases
both the toxicity and lipophilicity of the compound to higher animals.
Lipophilic compounds are preferentially soluble in fats. When a methylated-chlorinated
compound is consumed by fish or fowl, rather than being completely eliminated
in the urine it may become sequestered in body fat in a phenomenon termed
"bioaccumulation." The toxic compound becomes more and more
concentrated as it is carried up the food chain.(21)
Wood is approximately 50%
cellulose. this means, even after taking into consideration by-product
recovery, the volume and variety of organic and chlorinated organic wastes
generated by the pulp and paper industry is immense. The magnitude of
this waste problem necessitates the identification of those chemicals
that pose a significant threat to human health. the identification of
toxic, mutagenic, and potentially carcinogenic compounds and the waste
streams that produce them is essential in order to mitigate them at source
and to develop technologies for their safe degradation.
Although a large variety
of chlorinated compounds are present in pulp mill effluents, they are
seldom at concentrations that would cause acute toxicity. For example,
the minimum lethal oral doses (for human beings) of the common bleach
effluent compounds trichloromethane and pentachlorophenol are 14.8 grams
and 1.2 grams respectively for a 70 kg adult.(22)(23)
Accordingly, the danger to human health from organochlorines emanating
from pulp and paper mills is primarily through long-term exposure via
drinking water, and bioaccumulation through the consumption of contaminated
The toxic compounds most
often identified in aquatic life below pulp and paper mill effluent discharge
points are tri-, and tetrachloroguaiacols, tetrachlorocatechols and di-,
tri-, tetra-, and pentachlorophenols.(24)(25)
Also of concern is the lignin breakdown product acetovanillone, which
has been found to undergo chemical degradation and chlorination to produce
toxic chlorinated acetones. The most toxic of these is 1, 1, 3-trichloroacetone
which has been found in bleachery effluents at concentrations up to 2.4
Considerable attention has
also been directed toward identification of the mutagenic (and thereby
potentially carcinogenic) compounds in pulp mill effluents. Strategies
for the evaluation of pulp-mill effluents for mutageni potential have
generally followed three approaches: assessment of whole effluent streams,
of fractionated effluent streams, and of pure compounds known to be effluent
components. In the first approach, authentic waste solutions are tested,
in which chemical and physical interactions and possible synergistic effects
are maintained. The many studies performed on whole pulp mill waste streams
are all in agreement that the first-chlorination-stage effluent shows
high mutagenic activity, while other effluents and process streams show
no or reduced mutagenicity.(27)
Examination of fractionated
effluent streams, and the individual testing of approximately 300 known
constituent chemicals of pulp mill effluents, showed that 39 compounds
exhibited weak to very strong mutagenic activity. Two resin acids (neoabietic
and 7-oxodehydroabietic acid), two chlorinated spirodiones, tri-, tetra-,
penta-, and hexachloroacetone, and a number of chlorinated alipathic hydrocarbons
were identified as mutagenic agents.(28)(29)
demonstrating substantial mutagenicity, do not pose a serious human health
risk as these compounds are quite unstable and tend to degrade rapidly
in receiving waters.(30)
On the other hand, chlorinated aliphatic hydrocarbons, such as trichloro-
and tetrachloroethylene, and their breakdown products are known mammalian
carcinogens.(31) The observation
that two resin acids exhibited mutagenic activity is of concern, as these
acids degrade very slowly in anaerobic environments. Resin acids have
also been found to bioaccumulate in fish at sublethal concentrations.
The combination of persistence, bioaccumulation, and mutagenic activity
makes these compounds a potential health risk.(32)
The most potent bacterial
mutagen in pulp mill effluents was identified as 3-chloro-4-(dichloromethyl)-
5-hydroxy-2(5H)-furanone (MX). This compound was found to be responsible
for 30 to 50% of the mutagenicity of chlorination-stage effluents. In
the Ames test, MX demonstrated a mutagenic potential nearly two-fold greater
than the extremely potent mould metabolite aflatoxin B1.(33)
This is therefore a compound of concern. Research has shown that MX stability
decreases with increasing pH in the range of pH 2 6. Most waste
water treatment facilities operate at a pH of 6 7. Accordingly,
MX should be deactivated and destroyed at pulp mills where the bleach
plant effluent goes directly for conventional waste water treatment. However
MX could pose a serious risk if mill effluents were discharged directly
to receiving waters. This is particularly so in Canada and Northern Europe
where lake and river waters may be slightly acidic due to poor buffering
capacity, high humic acid content, and acid rain.
Dioxins are routinely described
in the news media as extremely dangerous, toxic, cancer-causing agents.
In spite of the extreme public fear of dioxins, it has not been established
that the polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-p-furans
pose a serious threat to human health. There is some indication, however,
that dioxins increase the risk of soft-tissue sarcomas in heavily exposed
industrial workers; and, acute dioxin exposure is known to have caused
nausea and a relatively long-lasting (2-3 years) skin condition called
There have been no human deaths from acute toxicity of dioxins, even though
over 200 people in Nitro, West Virginia, in 1949, and 37,000 people in
Seveso, Italy, in 1976, were possibly exposed to dioxin-laden dust. In
these incidents many contaminated animals died; however, human suffering
was limited to nausea and cases of severe chloracne. Follow-up studies
have not shown an increased incidence of cancer or birth defects. Although
dioxin and furan cogeners do not appear to be highly toxic to human beings,
they are extremely toxic to certain species of animals. For example, in
the guinea pig the LD50 dosage for dioxin is 0.6 micrograms/kg; while
the LD50 concentration for hamsters is about 5000 times greater.(36)
Many countries are now legislating
discharge limits for pulp and paper mill effluents. For 1991 the Swedish
permissible discharge limit was set at 1.2 to 1.3 kg total organic chlorine
per tonne of pulp.(37) This
means that for each tonne of pulp produced, only 1.3 kg of organic material
that is chemically reacted (combined) with chlorine can be discharged
to the aqueous environment. Three Canadian provinces have initiated discharge
regulations using the more stringent generic classification of Absorbable
Organic Halogen (AOX).(38)
This is more stringent, because it includes all halogen compounds (chlorine,
fluorine, bromine, etc.) that might be chemically bonded or absorbed to
organic matter issuing from a pulp mill. The Ontario discharge limit was
set at 2.5 kg AOX/tonne pulp, with a further reduction to 1.5 kg AOX/tonne
pulp by 1993. A similar preliminary limit was set in British Columbia,
with mandatory secondary treatment in 1991, and reduction to 1.5 kg AOX/tonne
pulp by the end of 1994. In Quebec AOX levels of 1.5 kg/tonne pulp and
zero detectable levels for dioxins and furans are to be met by 31 December
For comparison, the average AOX discharge in untreated effluent from a
Kraft mill is 8.0 kg per tonne of softwood pulp.(41)
In December 1991, the Canadian
government announced new federal regulations to control pulp mill pollution.
As of 1 January 1994, any measurable level of dioxins or furans in pulp
mill effluent will constitute a violation of the regulations. In addition,
wood chips that might be contaminated with preservatives and certain defoaming
agents can no longer be used in the pulping process as they might contribute
to the release of toxic pollutants.(42)
While these regulations are national in scope, each province has the right
to impose even more stringent regulations within its own jurisdiction.
Of the many pollutants in
pulp and paper mill effluents, only dioxins and furans have been evaluated
by Health and Welfare Canada as "priority substances." Dioxins
and furans were declared to be toxic and to pose a possible risk to human
health. For this reason, the federal government legislated specifically
on dioxins and furans and did not include other known pollutants. This
was not a "half-hearted" attempt at regulation, as some environmental
groups have claimed; rather, it is expected that the process changes and
the product substitution necessary to prevent the formation of dioxins
and furans will have the effect of reducing the overall release of chlorinated
organic compounds to less than 2 kg AOX/t.
Meeting these discharge
limits will not be easy. In some cases it will mean the earlier closure
of out-dated plants as the pulp and paper industry phases out old sulphite
and Kraft mills and replaces them with new, more competitive, chemithermomechanical
pulping plants. Compliance ill definitely mean the adoption of alternative
methods to reduce chlorine bleaching and the establishment of high-efficiency
treatment facilities. Attainment of pollution abatement goals will also
be very expensive. For example, Canadian Pacific Forest Products Ltd.
spent $60-million on state-of-the-art treatment facilities for a pulp
mill in Dryden, Ontario. This mill now meets Ontario AOX discharge regulations.(43)
ABATEMENT BY THE PULP AND PAPER INDUSTRY
Research and the development
of new processes and techniques to curtail the release of toxic effluents
from pulp and paper mills are following two approaches. The first strategy
is the development of new pulping processes with emphasis on improved
delignification, and the replacement or partial replacement of chlorine
for bleaching. The second approach is the development of new biological
treatment processes, particularly hybrid or dual systems that capitalize
on the advantages afforded by both anaerobic and aerobic digestion.
In-Plant Process Changes
A new process called oxygen
delignification has been found to be quite effective in removing the lignin
and hemicellulose fraction from cellulose, and leaving the fibres relatively
undamaged. The major environmental advantage is greater lignin removal,
so that less lignin enters the bleach plant.
No toxic chlorinated organic
compounds would be released in mill effluents if chlorine could be completely
eliminated from the pulp-bleaching process. Partial replacement of chlorine
by chlorine dioxide has been found to reduce greatly the emission of organochlorines,
while complete substitution with hydrogen peroxide eliminates these toxic
compounds. The use of hydrogen peroxide gives the additional benefit of
assisting in the breakdown of other organic contaminants in the effluent
through chemical oxidation reactions. Pulp bleached by hydrogen peroxide
is not, however, as white as chlorine-bleached pulp.
End-of-Pipe Biological Treatment Processes
At present, most pulp and
paper mills use aerated lagoons to treat their wastes prior to discharging
them into receiving waters. This is done to ensure that the effluents
meet Biological Oxygen Demand (BOD) discharge limits and pass fish toxicity
tests. More sophisticated and expensive forms of waste water treatment
will be required, however, if the pulp and paper industry is to meet the
new, more stringent, discharge limits set for absorbable organic halogens.
It is essential that these new treatment technologies be designed to degrade
those chemicals that pose the greatest threat to human health. the chemicals
of concern are those that are toxic and/or mutagenic, have a tendency
to bioaccumulate, and are difficult to degrade. Using these criteria,
the degradation of all mutagenic compounds, resin acids, and chlorinated
phenols, guaiacols, catechols, and chlorinated aliphatic hydrocarbons
should be the focus of new treatment processes.
As previously stated, highly
chlorinated compounds are quite stable and difficult to degrade. It is
possible, however, for bacteria in the anaerobic environment (no oxygen)
to conduct a transformation reaction whereby chlorine ions are replaced
by hydrogen ions. The more chlorine ions that are removed, the more reactive
the compound becomes, and the more susceptible to aerobic (oxygen present)
microbial degradation in a conventional activated sewage sludge digester.(44)(45)
Accordingly, the establishment of sequential anaerobic-aerobic waste-water
treatment facilities at Kraft pulp and paper mills will greatly help these
plants to reduce their toxic emissions.
treatment also effectively degrades mutagenic compounds and chlorinated
aliphatic compounds, which are known mammalian carcinogens. However, resin
acids cannot be degraded in an anaerobic environment. In fact, resin acids
are highly toxic to anaerobic bacteria, and can cause an anaerobic waste-water
system to fail.(46) Therefore,
the sequential system is not recommended for CTMP wastes that often contain
high concentrations of resin acids. However, these acids can be degraded
by aerobic digestion. In Sweden a three-stage process of aerobic-anaerobic-aerobic
has been investigated and found to degrade both resin acids and organochlorines
Pollution Abatement A Case Study
Over a 15-year period, alterations
in pulp processing and waste treatment at the E.B. Eddy Forest Products
Ltd. Kraft mill in Espanola, Ontario, have enabled this mill not only
to meet but to exceed the Ontario 1993 discharge limit of 1.5 kg AOX/t
pulp. In 1970, this mill discharged effluent directly into the Spanish
River, polluting the river for 32 km, and upsetting the benthic population
to the mouth of the river, a distance of 52 km.
In 1977, North Americas
first oxygen delignification process was started as an extension of the
pulp-cooking process. This resulted in 50% lower lignin in put to the
bleach plant, increased pulp brightness and strength, and a 23% reduction
in bleaching cost. Biological treatment was implemented in 1983. This
consisted of a 12-hour settling basin (primary treatment), a 6-day aerated
lagoon (secondary treatment), and a 12-hour quiescent zone to settle biosolids.
Strict controls were put
in place. Evaporator condensate was steam-stripped and burnt. Black liquor
soap scum was skimmed and processed into tall oil. As well, in-plant spill
collection and a sewer monitoring system were established. These controls
all served to protect the microbial population of the lagoon from shock
loads of effluent. Finally, in 1988 chlorine dioxide substitution for
chlorine bleaching was instituted. At 52% substitution, dioxins and furans
could not be detected in pulp or in bleachery effluents, and AOX effluent
emissions were reduced to below 1 kg/t pulp. The environmental improvements
at this mill have been so pronounced that the Spanish River is no longer
polluted and supports pickerel fishing. In addition, the quiescent zone
and outfall pond support cattails, ducks and beavers.(48)
Many pulp and paper mills
use chlorine as a bleaching agent to produce high-quality white pulp.
The high organic content of mill waste, coupled with the presence of chlorine,
results in the production of many highly toxic chlorinated organic compounds.
Of prime concern are chlorinated phenols, guaiacols, catechols, furans,
dioxins, aliphatic hydrocarbons and the highly mutagenic agent MX. In
addition, two natural wood resin acids, neoabietic and 7-oxodehydroabietic
acids, exhibit mutagenic activity. These compounds pose a human health
risk through long-term exposure via drinking water, and through bioaccumulation
along the food chain.
The pulp and paper industry
is starting to implement new technologies that greatly lower the concentration
of toxic substances in mill effluents. In-plant reduction of toxic emissions
is being effected through the installation of new oxygen delignification
processes, and replacement or partial replacement of chlorine by hydrogen
peroxide or chlorine dioxide for pulp bleaching. End-of-pipe clean-up
of mill effluents can be accomplished by new biological treatment processes,
such as sequential anaerobic-aerobic digestion. Stringent regulation f
of pulp and paper mill discharge by provincial and federal authorities
will necessitate large capital expenditures by the industry. This may
mean the early closure of old mills, and economic hardship for many communities.
At the same time, however, these regulations will ensure improved environmental
quality and a reduction of the risk to human health that is posed by this
Axegard, P. "Improvement
of Bleach Plant Effluent by Cutting Back on C12." Pulp and Paper
Canada, Vol. 90, 1989, p. 78-81.
Basta, J. et al.
"Low AOX, Possibilities and Consequences." 1989 Pulping Conference,
Tappi Press, Atlanta, 1989, p. 427-436.
Carruthers, George. Paper
in the Making. Garden City Press Coop., Toronto, 1947, 712 p.
Cheremisinoff, P.N. "High
Hazard Pollutants: Asbestos, PCBs, Dioxins, Biomedical Wastes." Pollution
Engineering, Vol. 21, 1989, p. 58-65.
Crittenden, G. "Operation
Zero." Hazardous Materials Management, Vol. 2, 1990, p. 8-11.
Douglas, G.R. et al.
"Mutagenic Activity in Pulp Mill Effluents." Water Chlorination:
Environmental Impact and Health Effects. R.L. Jolley et al.
(eds.). Vol. 3, Ann Arbor Science, Ann Arbor, 1980, p. 865-880.
Douglas, G.R. et al.
"Mutagenicity of Pulp and Paper Mill Effluent: a Comprehensive Study
of Complex Mixtures." Short-Term Bioassays in the Analysis of
Complex Environmental Mixtures III. M.D. Waters, et al.
(eds.). Plenum Press, New York, 1983, p. 431-459.
Dreisbach, R.H. Handbook
of Poisonings: Prevention, Diagnosis, and Treatment. 10th ed. Lange
Medical Publ., Los Altos, California, 1980, 364 p.
Dubelstein, P. and N.C.C.
Gray, "The Effects of Secondary Treatment on AOX Levels in Kraft
Mill Effluents." 76th Annual Symposium of the Canadian Pulp and
Paper Association, Montreal, 1990, p. 317-324.
Environment Canada. Emissions
and Trends of Common Air Contaminants in Canada: 1970-1986. Report
EPS 7/AP/17. Environment Canada, Ottawa, 1986, 104 p.
Environment Canada. New
Federal Regulations to Control Pulp Mill Pollution. News Release PR-HQ-091-45.
Environment Canada, Ottawa, 1991.
Haggblom, M. "Mechanisms
of Bacterial Degradation and Transformation of Chlorinated Monoaromatic
Compounds." Journal of Basic Microbiology, Vol. 30, 1990,
Hall, Eric R. et al.,
"Organochlorine Discharges in Wastewaters from Kraft Mill Bleach
Plants." Environmental Conference of the Canadian Pulp and Paper
Association, Vancouver, 1988, p. 53-62.
Kierkegaard, A. and L. Renberg.
"Chemical Characterization of Organochlorine Compounds, Originating
from Pulp Mill Effluents in Fish." Water Science and Technology,
Vol. 20, 1988, p. 165-170.
Kringstad, K.P. and K. Lindstrom.
"Spent Liquors from Pulp Bleaching." Environmental Science
and Technology, Vol. 18, 1984, p. 236A-247A.
McConnell, E.E. et al.
"The Comparative Toxicity of Chlorinated Duibenzo-p-dioxin Isomers
to Mice and Guinea Pigs." Toxicology and Applied Pharmacology,
Vol. 37, 1976, p. 146-153.
McKague, A.B. et al.
"Chloroacetones in Pulp Mill Chlorination Stage Effluents."
Environmental Toxicology and Chemistry, Vol. 9, 1990, p. 1301-1303.
McKague, A.B. et al.
"Chloroacetones: Mutagenic Constituents of Bleached Kraft Chlorination
Effluent." Mutation Research, Vol. 91, 1981, p. 301-306.
Meier, J.R. et al.
"Studies on the Potent Bacterial Mutagen, 3-chloro-4-(dichloromethyl)-5-hydroxy-
2(5H)-furanone: Aqueous Stability, XAD Recovery and Analytical
Determination in Drinking Water and in Chlorinated Humic Acid Solutions."
Mutation Research, Vol. 189, 1987. p. 363-373.
Mikesell, M.D. and S.A.
Boyd. "Complete Reductive Dechlorination and Mineralization of Pentachlorophenol
by Anaerobic Microorganisms." Applied and Environmental Microbiology,
Vol. 52, 1986, p. 861-865.
Miller, R.E. and F.P. Guengerich.
"Metabolism of Trichloroethylene in Isolated Hepatocytes, Microsomes,
and Reconstituted Enzyme Systems Containing Cytochrome P450." Cancer
Research, Vol. 43, 1983, p. 1145-1152.
Munro, F.C. "Environmentally
Influenced Evolution of E.B. Eddy Espanolas Bleaching Sequences."
Bleach Plant Operations, Tappi Press, Atlanta, 1990, p. 13-24.
Nazar, M.A. and W.H. Rapson.
"pH Stability of Some Mutagens Produced by Aqueous Chlorination of
Organic Compounds." Environmental Mutagenesis, Vol. 4, 1982,
Neilson, A.H. et al.
"The Environmental Fate of Chlorophenolic Constituents of Bleachery
Effluents." Tappi Journal, Vol. 73, 1990, p. 239-247.
Nestmann, E.R. et al.
"Mutagenicity of Resin Acids Identified in pulp and Paper Mill Effluents
Using the Salmonella/Mammalian Microsome Assay." Environmental
Mutagenesis, Vol. 1, 1979, p. 361-369.
Paasivirta, J. et al.
"Transportation and Enrichment of Chlorinated Phenolic Compounds
in Different Aquatic Food Chains." Chemosphere, Vol. 9, 1980,
Paasivirta, J. et al.
"Polychlorinated Phenols, Guaiacols, and Catechols in Environment."
Chemosphere, Vol. 14, 1985, p. 469-491.
Schroeder, H.G. "Acute
and Delayed Chloroform Poising: A Case Study." British Journal
of Anaesthesia, Vol. 37, 1965, p. 972-975.
Sierra-Alvarez, R. and G.
Lettinga. "The Methanogenic Toxicity of Wood Resin Constituents."
Biological Wastes, Vol. 33, 1990, p. 211-226.
Sinclair, William F. Controlling
Pollution from Canadian pulp and Paper Manufacturers: A Federal Perspective.
Environment Canada, Ottawa, 1990, 360 p.
Springer, A.M. Industrial
Environmental Control: Pulp and Paper Industry. John Wiley and Sons,
N.Y., 1986, p. 3.
Stillman, R. "Dioxin."
Hazardous Materials Management, Vol. 2, 1990, p. 38-42.
Swanson, S.E. et al.
"Emissions of PCDDs and PCDFs from the Pulp Industry." Chemosphere,
Vol. 17, 1988, p. 681-691.
Tana, J.J. "Sublethal
Effects of Chlorinated Phenols and Resin Acids on Rainbow Trout Dslmo
gairdneri)." Water Science Technology, Vol. 20, 1988,
Welander, T. "An Anaerobic
Process for Treatment of CTMP Effluent." Water Science Technology,
Vol. 20, 1988, p. 143-147.
A.M. Springer, Industrial Environmental Control: Pulp and Paper Industry,
John Wiley and Sons, N.Y., 1986, p. 3.
William F. Sinclair, Controlling Pollution from Canadian Pulp and Paper
Manufacturers: A Federal Perspective, Environment Canada, Ottawa,
1990, 360 p.
Environment Canada, Emissions and Trends of Common Air Contaminants
in Canada: 1970-1980, Report EPS 7/AP/17, Environment Canada, Ottawa,
1986, 104 p.
George Carruthers, Paper in the Making, Garden City Press Coop.,
Toronto, 1947, 712 p.
K.P. Kringstad and K. Lindstrom, "Spent Liquors from Pulp Bleaching,"
Environmental Science and Technology, Vol. 18, 1984, p. 236A-247A.
Kringstad and Lindstrom (1984), p. 236A-247A.
Kringstad and Lindstrom (1984), p. 236A-247A.
Kringstad and Lindstrom (1984), p. 236A-247A.
A.H. Neilson et al., "The Environmental Fate of Chlorophenolic
Constituents of Bleachery Effluents," Tappi Journal, Vol.
73, 1990, p. 239-247.
J. Paasivirta et al., "Polychlorinated Phenols, Guaiacols,
and Catechols in Environment," Chemosphere, Vol. 14, 1985,
S.E. Swanson et al., "Emissions of PCCDs and PCDFs from the
Pulp Industry," Chemosphere, Vol. 17, 1988, p. 681-691.
R. Stillman, "Dioxin," Hazardous Materials Management,
Vol. 2, 1990, p. 38-42.
A. Kierkegaard and L. Renberg, "Chemical Characterization of Organochlorine
Compounds, Originating from Pulp Mill Effluents in Fish," Water
Science and Technology, Vol. 20, 1988, p. 165-170.
H.G. Schroeder, "Acute and Delayed Chloroform Poisoning: A Case Study,"
British Journal of Anaesthesia, Vol. 37, 1965, p. 972-975.
R.H. Dreisbach, Handbook of Poisonings: Prevention, Diagnosis, and
treatment, 10th ed., Lange Medical Publ., Los Altos, California, 1980,
J. Paasivirta et al., "Transportation and Enrichment of Chlorinated
Phenolic Compounds in Different Aquatic Food Chains," Chemosphere,
Vol. 9, 1980, p. 441-456.
J.J. Tana, "Sublethal Effects of Chlorinated Phenols and Resin Acids
on Rainbow Trout (Salmo gairdneri)," Water Science Technology,
Vol. 20, 1988, p. 77-85.
A.B. McKague et al., "Chloroacetones in Pulp Mill Chlorination-stage
Effluents," Environmental Toxicology and Chemistry, Vol. 9,
1990, p. 1301-1303.
G.R. Douglas et al., "Mutagenic Activity in Pulp Mill Effluents,"
Water Chlorination: Environmental Impact and Health Effects, R.L.
Jolley et al. (eds.), Vol. 3, Ann Arbor Science, Ann Arbor, 1980,
G.R. Douglas et al., "Mutagenicity of Pulp and Paper Mill
Effluent: a Comprehensive Study of Complex Mixtures," Short-Term
Bioassays in the Analysis of Complex Environmental Mixtures III, M.D.
Waters et al. (eds.), Plenum Press, New York, 1983, p. 431-459.
A.B. McKague et al., "Chloroacetones: Mutagenic Constituents
of Bleached Kraft Chlorination Effluent," Mutation Research,
Vol. 91, 1981, p. 301-306.
M.A. Nazar and W.H. Rapson, "pH Stability of Some Mutagens Produced
by Aqueous Chlorination of Organic Compounds," Environmental
Mutagenesis, Vol. 4, 1982, p. 435-444.
R.E. Miller and F.P. Guengerich, "Metabolism of Trichloroethylene
in Isolated Hepatocytes, Microsomes, and Reconstituted Enzyme Systems
Containing Cytochrome P450," Cancer Research, Vol. 43,
1983, p. 1145-1152.
E.R. Nestmann et al., "Mutagenicity of Resin Acids Identified
in Pulp and Paper Mill Effluents Using the Salmonella/Mammalian-Microsome
Assay," Environmental Mutagenesis, Vol. 1, 1979, p. 361-369.
J.R. Meier et al., "Studies on the Potent Bacterial Mutagen,
3-chloro-4-(dichloromethyl)-5-hydroxy- 2(5H)-furanone: Aqueous
Stability, XAD Recovery and Analytical Determination in Drinking Water
and in Chlorinated Humic Acid Solution," Mutation Research,
Vol. 189, 1987, p. 363-373.
R. Stillman (1990), p. 38-42.
P.N. Cheremisinoff, "High Hazard Pollutants: Asbestos, PCBs, Dioxins,
Biomedical Wastes," Pollution Engineering, Vol. 21, 1989,
E.E. McConnell et al., "The Comparative Toxicity of Chlorinated
Dibenzo-p-dioxin Isomers to Mice and Guinea Pigs," Toxicology
and Applied Pharmacology, Vol. 37, 1976, p. 146-153.
J. Basta et al., "Low AOX, Possibilities and Consequences,"
1989 Pulping Conference, Tappi Press, Atlanti, 1989, p. 427-436.
P. Axegard, "Improvement of Bleach Plant Effluent by Cutting Back
on C12," Pulp and Paper Canada, Vol. 90, 1989, p. 78-81.
P. Dubelsten and N.C.C. Gray, "The Effects of Secondary Treatment
on AOX Levels in Kraft Mill Effluents," 76th Annual Symposium
of the Canadian Pulp and Paper Association, Montreal, 1990, p. 317-324.
G. Crittenden, "Operation Zero," Hazardous Materials Management,
Vol. 2, 1990, p. 8-11.
Eric R. Hall et al., "Organochlorine Discharges in Wastewaters
from Kraft Mill Bleach Plants," Environmental Conference of the
Canadian Pulp and Paper Association, Vancouver, 1988, p. 53-62.
Environment Canada, New Federal Regulations to Control Pulp Mill Pollution,
News Release Pr-HQ-091-45, Ottawa, Environment Canada, 1991.
Crittenden (1990), p. 8-11.
M.D. Mikesell, and S.A. Boyd, "Complete Reductive Dechlorination
and Mineralization of Pentachlorophenol by Anaerobic Microorganism,"
Applied and Environmental Microbiology, Vol. 52, 1986, p.
M. Haggblom, "Mechanisms of Bacterial Degradation and Transformation
of Chlorinated Monoaromatic Compounds," Journal of Basic Microbiology,
Vol. 30, 1990, p. 115-141.
R. Sierra-Alvarez and G. Lettinga, "The Methanogenic Toxicity of
Wood Resin Constituents," Biological Wastes, Vol. 33, 1990,
T. Welander, "An Anaerobic Process for Treatment of CTMP Effluent,"
Water Science Technology, Vol. 20, 1988, p. 143-147.
F.C. Munro, "Environmentally Influenced Evolution of E.B. Eddy Espanolas
Bleaching Sequences," Bleach Plant Operations, Tappi Press,
Atlanta, 1990, p. 13-24.