EPA-600/2-76-232
October 1976
Environmental Protection Technology Series
WATER REUSE IN A
PAPER REPROCESSING PLANT
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-232
October 1976
WATER REUSE IN A
PAPER REPROCESSING PLANT
by
Leale E. Streebin, George W. Reid, Paul Law
School of Civil Engineering § Environmental Science
University of Oklahoma
Norman, Oklahoma 73069
and
Charles Hogan
Big Chief Roofing Company
Ardmore, Oklahoma 73401
Grant S-801206
Project Officer
John Ruppersberger
Food and Wood Products Branch
Industrial Environmental Research Laboratory - Cincinnati
Corvallis, Oregon 97330
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory - Cincinnati, U.S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
ii
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FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on our
health often require that new and increasingly more efficient pollution con-
trol methods be used. The Industrial Environmental Research Laboratory -
Cincinnati (lERL-Cl) assists in developing and demonstrating new and improved
methodologies that will meet these needs both efficiently and economically.
"Water Reuse in a Paper Reprocessing Plant" is a product of the above
efforts. It discusses the feasibility of water reuse in a paper reprocess-
ing plant. The zero discharge technology reduces the overall production
costs with no degradation of product quality. The application of such
technology is of mutual benefit to both the environment and to industry. For
further information please contact the Food and Wood Products Branch of the
Industrial Environmental Research Laboratory, Cincinnati.
David G. Stephan
Director
Industrial Environmental Research Laboratory - Cincinnati
iii
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ABSTRACT
This project was undertaken to determine the feasibility of water reuse
in a paper reprocessing plant with the goal being to "close the loop" or
to demonstrate zero discharge technology. Before the project began,
Big Chief Roofing Company at Ardmore, Oklahoma, was discharging
7.89 I/sec (125 gpm). Normal operation is now zero discharge with
approximately 0.76 I/sec (12 gpm) fresh water make-up replacing evapora-
tive losses. However, weekly clean-ups still result in an effluent of
approximately 15.14 M^ (4000 gallons) a week. Additional clear water
storage capacity could eliminate this weekly discharge. Project scope
included identifying and solving problems resulting from increased recycle
of process water, and determining costs, benefits, and effect on product
quality.
The favorable cost/benefit ratio experienced at the plant demonstrated
an economic advantage of in-plant control over end-of-pipe treatment.
Attaining zero discharge operation has the further benefit of eliminating
the problems, cost and liabilities associated with operation under a
discharge permit. Economic benefits observed during zero discharge
operation included reduced water supply costs, reduced wastewater treat-
ment costs, improved yield, improved drainage and greater dryer section
capacity due to increased operating temperatures, and resultant increased
production. The benefits we're partially offset by shorter felt lives,
increased corrosion control cost, and process modification cost. No
degradation of product quality was observed.
This report was submitted in fulfillment of Grant Number S-801206 by
Big Chief Roofing Company under the (partial) sponsorship of the
Environmental Protection Agency. Work was completed as of December 1974.
iv
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TABLE OF CONTENTS
Page
Foreword ill
Abstract iv
List of Tables vi
Acknowledgments vii
Sections
1. Conclusions 1
II. Recommendations 3
III. Introduction 4
IV. Literature Survey 7
V. Manufacturing Process and Reuse Facilties 33
VI. Experimental Analyses and Procedures 40
VII. Results and Discussions 45
VIII. References 67
IX. Appendices 72
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TABLES
No. Page
1 Comparison of Roofing Felt Quality 47
2 Summary of Wastewater Characteristics 50
3 Summary of Corrosion Rates, Rmdd 51
4 Summary of Felt Life 53
5 Effect of Various Slimicides on Bacteria 56
6 Total Bacteria Present/ML 57
7 Optimum Conditions for QAC Effectiveness 57
8 Operational Cost Comparison 65
9 Cost Comparison 65
vi
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ACKNOWLEDGEMENTS
The help and participation of Mr. John Schilling, felt mill superinten-
dent, and other plant personnel at Big Chief Roofing Company are acknowl-
edged with sincere thanks. The work of Mr. William White, formerly pro-
ject coordinator of Big Chief, is gratefully acknowledged.
The support of the project by the U.S. Environmental Protection Agency
and the help of Mr. John Ruppersberger is greatly appreciated.
The assistance of Margaret Johanning in the preparation and editing of
the final manuscript is acknowledged with sincere appreciation.
vii
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SECTION I
CONCLUSIONS
Based on the findings from this plant scale investigation, the following
conclusions were drawn:
1. One hundred percent water reuse is technically and economically
feasible in an organic felt mill. To assure 100 percent
reuse consistently at Big Chief Roofing, additional clear water
storage is required.
2. Product quality has not been adversely affected by water reuse.
3. The operational costs for processing increased slightly. Based
on felt life, water use, and pH, slime and foam control, the
daily operational costs increased from $73 to $99.
4. The power costs for waste treatment decreased from $34 per day
for no water reuse to zero dollars per day for 100 percent
water reuse or zero discharge.
5. The total operational costs were essentially the same for all
alternatives, i.e., the savings in power costs for waste treat-
ment plus the purchase of water were offset by additional
operational costs.
6. Foam and slime control were not significantly affected by water
reuse.
7. Scale was not a major problem at Big Chief. The only significant
operating problem resulting from scale and other deposits was
blinding of the Zurn micromatic screen which reduced its
throughput.
8. Maintenance problems have not increased significantly during
the period of water reuse.
9. When water reuse is practiced, the process water chemical
concentration increases from 2 to 6 times the concentrations
under conventional operating conditions.
10. Corrosion of plant equipment resulting from water reuse can be
adequately controlled by maintaining the pH above 6.0.
11. The pickup felt life decreased with an increase in water reuse.
Average felt life was 75 days during no water reuse and 50 days
during 100 percent water reuse.
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12. Tentative results indicate slime deposits and the resulting
slime holes in the product can be effectively controlled by
the addition of 3 mg/1 of a mixture of quaternary ammonium
compounds to the system.
13. Kerosene satisfactorily and economically controls the foam.
14. The hydrasieve satisfactorily removes the coarse suspended solids
from the system but does not prevent plugging of the showers for
cleaning the pickup felt.
15. The micromatic screen has not functioned satisfactorily since
its installation. The removal efficiencies were much lower
than expected and numerous mechanical failures prevented its
use during a significant portion of the study. When it was
operating satisfactorily, however, it did prevent plugging of
the shower for cleaning the pickup felt.
16. Should the clays and other fillers from the waste paper concen-
trate and reduce the porosity in the product, the ratio of
wood flour to waste paper could be changed to maintain the required
porosity.
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SECTION II
RECOMMENDATIONS
Based on the results from this study, the following changes and/or
additions are recommended:
1. Develop methods for disposing of the sludge from the bottom
of the filtered water storage tanks. Possible methods include:
1) maintaining the sludge in suspension, thereby allowing it
to be deposited on the felt mat, 2) pumping the sludge from
the bottom of the tanks through an atomized spray nozzel onto
the felt mat, 3) concentrate the sludge and place in a land-
fill or spread on land.
2. Develop methods for removing the dissolved solids and a higher
percentage of suspended solids which would allow 100 percent
water reuse in a paper reprocessing plant manufacturing higher
quality papers.
3. Install automatic pH controls and continuous chemical feed
systems.
4. Develop a monitoring and information system for production
personnel which would include liquid level alarms, conductivity,
and pH sensors which would indicate deterioration of water
quality.
5. Insure adequate surge and storage capacities for filtered
white water. At Big Chief Roofing, this required a minimum
of 113.56 M3 (30,000 gallons) during the period when the
hydrapulper was used and 227.12 M3 (60,000 gallons) when the
paper beater was used.
6. Select a microscreen for removing solids from the white water
to insure uninterrupted operation of the showers.
7. Select a microscreen with a capacity, at expected solids
loading, equal to the peak flow into the white water pit. At
Big Chief the peak flow is three times the average flow to
the filtered water storage tank.
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SECTION III
INTRODUCTION
PROJECT OBJECTIVES
The objectives of this project were to decrease or possibly eliminate
liquid waste from paper reprocessing industries. In the past, since
the cost of fiber from used paper was inexpensive, high waste treatment
efficiencies were not required or enforced, and in'many cases water was
plentiful and relatively inexpensive. For .these reasons, the recovery
of fiber and the conservation or reuse of water was not considered
justifiable. With the advent of PL 92-500 (1) , state and federal reg-
ulatory agencies require higher effluent qualities resulting in higher
treatment efficiencies. Therefore, industries are investigating least
cost methods of pollution control. These methods include water reuse,
and product and by-product recovery.
The specific objectives of this study were to:
1. Determine the feasibility of total water reuse, thereby elim-
inating any waste discharge and the attendant waste disposal
problems.
2. Determine effects of water reuse on product quality.
3. Predict the increase in operational costs due to increased
corrosion rates, scale formation, slime growths and solids
deposits.
4. Determine savings from decreased waste treatment costs, fiber
losses, and water use.
5. Conduct a cost-effectiveness analysis of alternative combina-
tions of water reuse and by-product recovery versus waste
treatment.
NEED FOR PROJECT
This study was directed toward control of water pollution from paper
reprocessing industries. The potential for these industries is prac-
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tically unlimited since paper is the largest individual component of
municipal solid wastes. It constitutes more than 45 percent of the
total waste volume generated each year. If segregated and satisfac-
torily processed for reuse, the waste paper would provide approximately
25 percent of the raw material for the paper industry (2).
At the end of World War II, approximately 35 percent of the wood fiber
products were recycled in the United States but since that time the
percentage of paper stock utilized as secondary fibers has continued to
decrease. The reason for this decrease is that certain mills can pro-
duce virgin pulp ready for a paper machine at costs less than that for
recycled fiber (2). Although the virgin material may presently be
cheaper, if the cost of solid wasfe disposal, and the social costs of
resource reductions and solid wastes are considered, it can be antici-
pated that paper recycling will be favored in the future. It is,
therefore, necessary to determine the least cost method of pollution
control for the industries. This method may be total reuse or zero
discharge.
There is a need to determine the feasibility of water reuse in a paper
reprocessing plant with the goal being to "close the loop" reducing
wastewater discharged and water requirements. As mentioned in the
report, "Cost of Clean Water", (3) data are not available to compare
the expenditures for in-plant modifications with the cost savings in
wastewater treatment, a cost-effectiveness analysis. This study defines
the problems resulting from recycling of the process waters, determines
the magnitude of these problems, and develops methods of control thereby
increasing the reuse factor with the ultimate goal being complete reuse,
i.e., zero liquid waste discharge.
There are a great number of paper mills nationwide that use reprocessed
fiber for making wall board, container board, boxboard, building paper,
building board, composition shingles, etc. In Oklahoma, there are four
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mills using reprocessed fiber. One produces paper for dry wall, two
produce felt for composition shingles and also further process the felt
into shingles and one produces both felt for shingles and paper for dry
wall. This study was conducted on a felt mill. There are more than 60
of these plants nationwide. Three of these are within 322 km (200 miles)
of Ardmore, Oklahoma, the home of Big Chief Roofing where the study was
conducted. Two of these felt mills plus both of the Oklahoma plants
that produce paper for dry wall are experiencing problems with their
waste treatment systems and will have to expand them or convert their
plants and practice more water reuse. The other plant producing
composition shingles essentially has a "closed loop" but is experiencing
high operational and maintenance costs.
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SECTION IV
LITERATURE SURVEY
INTRODUCTION
The pulp and paper industry, like most industries, is currently faced
with the dual problem of diminishing sources of water and more stringent
water quality standards for its effluent. The pulp and paper industry
is particularly vulnerable to increasingly stringent water controls
because of high water usage. The paper industry is the third largest
user of water. Liquid wastes resulting from pulp and paper mills have a
potential for polluting surface waterways on the basis of their high
volume, BOD and suspended solids. Regulatory agencies have set pound
per ton production limits on BOD and suspended solids which may be met
by reducing the effluent concentration, reducing the effluent volume
or a combination of both.
The Federal Water Pollution Control Act Amendments of 1972 (PL 92-500)
declared as a national goal that the discharge of pollutants into
navigable waters should be eliminated by 1985. This is commonly referred
to as "zero pollutant discharge". In attaining this goal, an attempt
has been made to spread the economic impact over two five-year interim
goals. No later than July 1, 1977, most industrial sources must achieve
effluent limitations which require application of "the best practicable
control technology currently available". No later than July 1, 1983,
effluent limitation must be achieved by most industrial sources which
require application of "the best available technology economically
achievable".
In the pulp and paper industry, personnel who have broad technical know-
ledge in the industry generally concur that.an existing mill cannot
economically achieve zero discharge of wastewater unless some peculiar
set of circumstances exists. They also feel that new mill complexes
may be able to achieve zero discharge if certain processes in the
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developmental stages are proven in practice in combination with other
systems and if an appropriate mix of industries or systems can be
arranged at a single location (4).
To approach the 1985 goal will require a combination of reductions in
wastewater generation, maximization of wastewater reuse, and the devel-
opment and application of unique new treatment techniques. Major fac-
tors which determine the feasibility of water reuse are the effect of
reuse on product quality, the frequency of accidental discharges of
wastewaters, and the ability to dispose of liquid wastes adequately
without polluting ground water or the air. Wastewater streams have
been reused in the pulp industry for many years in order to reduce
fiber, heat, and chemical losses as well as to reduce raw water demands.
Haynes (5) -reported that in the Southern Kraft Industry, the reuse of
process waters was, on the average, 240 percent of the intake.
The technology required to achieve the 1985 goal at some mills is avail-
able as demonstrated by a system developed for the Charmin Paper Company
by C.A. Barton, et al (6), and Celotex Company by A.H. Phillip (7). Speci-
fic processes which have been utilized by some paper industries to
treat their wastewaters include microstraining for more efficient fiber
and solids removal (8), reverse osmosis (9 & 10), and the use of spe-
cial strains of microorganisms, e.g., soil microorganisms for micro-
biological breakdown of fibers, cellulose nnd lignin (11).
A discussion of the status and needs for the paper industry's water
protection technology is given by Gellman and Blosser (12). It covers
the processes used for effluent clarification, sludge dewatering and
disposal, removal of oxygen-demanding, non-settleable materials and
improving aesthetic effects of effluent waters, i.e., odor, foam,
color and turbidity.
Water reuse or recirculation is becoming more attractive in many areas
of the country because of the effective manner in which it deals not
only with water pollution, but with the limited water supply. Numerous
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industries, e.g., steel, pulp and paper, sugar beets, are already prac-
ticing water reuse or recycling in their plants.
J. Eller, et al (13), distinguishes reuse as the utilization of water
that has been used previously for another purpose and recycling as the
use of the same water one or more times for the same purpose. An exam-
ple of water reuse is the direct use of municipal wastewaters as cool-
ing waters by steel plants. Successive use of waters, however, needs
to meet certain water quality standards and oftentimes these waters
have to be subjected to some form of treatment. A broad spectrum of
quality criteria exists for industrial water supplies because of the
highly variable nature of industrial water use. Some of these criteria
are given in a paper by K. D. Lindstedt, et al (14).
In the case of recycling, relatively large volumes of water are made
available for reuse while the raw water inflow is relatively small.
Intake is limited by the amount lost by evaporation, consumption or
blowdown. If blowdown is not desirable, dissolved solids build up may
be controlled by the inclusion of a treatment step into the recycle
system (6). Several methods of removal of excessive organic or inor-
ganic materials in the recirculating water are available.
J. E. Eller, et al (13), offers an economic comparison of once-through
and recycle systems along with the following observations:
1. The feasibility of recycling with respect to cost depends
upon the savings appreciated by handling a smaller volume
of water as compared to the cost of treating the effluent
for recycle.
2. Recycling systems are best when contaminant additions are
either low or easily removed and quality requirements are
not stringent; e.g., cooling operations.
3. Recycle systems often allow for product recovery not pos-
sible in once—through system.
4. Recycle systems offer more attractions as final effluent
requirements become more stringent.
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WATER RECYCLING AND RENOVATION
The sheet formation and drying operations have received the greatest
attention in water reuse programs since a large volume of high quality
water is utilized in these processes. In these operations, recycling
of white water is mandatory because of low fiber consistency of the
furnish which flows to the headbox of the paper machine. The web of
pulp which is formed on a Fourdrinier, cylinder, or other drainage wire
must drain sufficiently before it is lifted from the wire and trans-
ferred to a pressing and drying section. Since a large volume of water
drains through this wire, a high flow rate is necessary. This flow
rate is maintained if the fiber and fragments which are deposited in
the forming device are removed. This is accomplished by washing with
high pressure showers that use filtered white water.
Albert Thomas (15) demonstrated a "closed loop" white water system for
manufacture of tissue and paper towels. In his system, there were two
main sources of water for reuse: 1) filtered water from three save-alls,
and 2) the remaining clean white water. The higher quality water was
used in the wire showers (except breast roll shower) on all machines.
It was also used for sealing water in the Nash vacuum pumps. The poorer
quality water was used for stock dilution at the save-all, machine
repulper, and machine chest consistency regulator. By closing up the
white water system, the effluent from the mill was reduced by about
4921 M3/day (1.3
than 1.0 percent.
o
4921 M /day (1.3 mgd) and the fiber loss reduced from 2.3 percent to less
Lyman Aldrich and Raymond Janes (16) studied a system producing high
opacity offset paper. On three continuous 3-5 day runs using a 76.2 cm
(30 in.) wide Fourdrinier paper machine, no operational problems were
encountered when 97 percent water reuse was practiced. Closing the water
system, from 72 percent to 97 percent resulted in the following benefits:
1) savings of 18 percent of fiber while maintaining opacity and ash con-
tent, 2) savings of 50 percent alum and 20 percent resin while maintaining
sizing, and 3) a 50 percent reduction in total BOD in the effluent.
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Negligible differences (less than 10 percent decrease) were found in
paper strength properties, suspended solids, felt filling or pressing
efficiency, dirt in paper, and printability.
Water from the press section is usually the last source for which recy-
cling is attempted, but some mills are straining this water to remove
felt hair and are recycling it along with other white water. Usually
felt hair contamination varied with the running time of the felts. Less
than 20 percent of the felt hairs were of a size considered to be trouble-
some in printing grades. Tests with several types of screens indicated
good felt hair removals and filler recovery. With a 325 mesh stainless
medium, 80 percent removal of the felt hair was achieved. Removal of
wool felt hair was 97 percent, removal of the smaller, smoother synthe-
tics was 55 percent. Filler recovery was 90 percent (17).
The vacuum pump systems, if operated with the proper amount of seal
water, conserve both water and power. An excess amount of seal water
causes excessive water use, requires more power, and reduces pump capac-
ity. This problem can be eliminated at each pump by using pressure
reducing valves and properly sized orifices. This combination provides
just the correct amount of sealing water necessary for good operation.
A seal water shutoff valve should be interlocked with the pump's prime
mover to prevent flow on shutdown (18). Reuse of vacuum pump seal water
is accomplished either by treating the pump water system as one link in
a series with one or more other water systems, or as a separate closed
cycle (19). The former involves one of the following methods:
1. Feeding the pumps with fresh water and discharging to
another system.
2. Feeding the pumps with reused water and sewering the
discharge.
3. Feeding the pumps with reused water and discharging
to another system.
The first and second methods reduce both fresh water demand and effluent
discharge by a volume equivalent to the vacuum pump seal water flow. The
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third method reduces fresh water demand and effluent by as much as twice
the vacuum pump flow.
A closed system of seal water for vacuum pumps can result in an increase
in temperature with a corresponding decrease in vacuum. The temperature
and vacuum can be controlled by installing cooling towers or by adding
fresh water.
The Venta Nip Presses, which have become so popular for water removal in
press sections, require shower water. Therefore, the consumption of
fresh water on the paper machine increases when these presses are used.
This problem can be solved by recycling the vacuum seal water or by
using white water as the shower water. This white water was passed
through a 40 mesh screen to prevent plugging of the showers. Showers
which have been the most successful in white water service are the self-
cleaning types such as the Bird-Aquapurge or the Broughton (5).
A lime-magnesium precipitation system is used to recondition the white
water as make up for a tissue operation of Kimberly-Clark at Fullerton,
California (20). This has resulted in lowering make up water require-
3 3
ments to 23.32 M /metric ton (6500 gal/ton) compared with 85.88 M /metric
ton (25,000 gal/ton) at another modern installation where water reuse is
not practiced. Pressure filtration methods have also been used to
improve the quality of the white water. A system was developed for
recycling white water by W.S. Davis and others at Weyerhaeuser Company,
Miquon, Pennsylvania (17). Process effluent was collected from individual
paper machines and then pumped to a surge tank. From here it flowed to
the primary clarifier. After chemical treatment and coagulation, the
white water was filtered through a special sand and gravel filter to re-
move the last traces of turbidity. Problems encountered at the beginning
of the program included plugging of the sand filter, slime build up in
the holding tank and filtered water lines, and the residual color remain-
ing in the filtrate. Apparent color and slime problems were solved by
adding enzymes to the clarifier at a level of six parts per million.
The enzymes suppressed the dispersing power of the starch and degraded
12
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the starch molecules enhancing settling of the clay and titanium dioxide
particles (as well as the fiber fines and the color bodies attached to
them). Particles that were not removed by the clarifier were easily
removed by the filters. Removal of apparent color and suspended solids
from white water has permitted the use of make up water consisting of
15 percent reconditioned white water.
According to a survey by the Water Division of TAPPI (5), most of the
water recycling program emphasis is within the paper processing area.
One of the reasons is that a number of the nonintegrated paper mills
are quite old and were constructed when there was little thought given
to the water required in the process. The significant factors promot-
ing recycling of water were water supply problems and the need for fiber
recovery systems. The recycling schemes reported were all quite simple.
Most of the installed hardware was for the purpose of recovering fiber,
whereas the recovery of water for recycling was incidental.
A study reported by Leo J. Eimmerman (19) has outlined the steps of a
water recycling program. The first phase of the program consisted of
preparing a detailed flow diagram of all operations. The second step
was to measure the water flow quantities and to verify them by a water
balance. Once the flow diagram and balance were complete, a detailed
study on each system and subsystem determined if they could be modified
or operated in a manner to reduce water consumption or to reuse water.
Some potential water conservation and recycle methods were cited in
the report. In the paper machine area, many potential savings were
possible. Fresh water showers should be kept to an absolute minimum,
but where used, flows should be as low as practical. If possible, the
showers on existing machines should be converted to use clarified white
water. Older showers should be periodically rechecked and nozzles
changed if found to be worn. Main sheet knock off showers should be
controlled to operate on break only. Pump pressures should be moni-
tored and controlled to prevent high flows.
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Well designed save-all systems with proper controls along with adequately
trained personnel will increase water savings considerably. If they
are not operated properly, the resulting poorly clarified white water
will cause shower plugging, a loss of production, and shortening of felt
life. A save-all should be operated on a steady flow basis for the best
clarity and all excess cloudy water recirculated with only the clearest
water released from the system (19).
A promising approach to water reuse has been proposed for a bleached
Kraft operation (21). This approach proposes to alter processing to
facilitate water recycling. This was to be accomplished by:
1. Washing the pulp in a completely countercurrent fashion,
from the final bleach stage to the brown stock washers.
2. Using cleaned, evaporated condensate to wash the bleached
pulp.
3. Using a mixture of chlorine and chlorine dioxide in the
chlorination (first) stage of bleaching.
4. Recovering the spent bleaching chemicals, namely sodium
chloride by evaporating white liquor.
5. Using part of the pure crystalline sodium chloride to
make sodium chlorate; using additional sodium chloride
along with sodium chlorate and sulfuric acid to make
all the chlorine dioxide and chlorine required for bleach-
ing, and to make all the sodium sulfate required for make-
up of pulping chemicals.
The effluent-free Kraft mill can be achieved with existing technology
and process equipment not radically different from that now used in
Kraft mills. However, removal of heat from the mill may be a problem
and may even require an evaporative air cooler. It would be advan-
tageous to generate as much electrical power from the excess heat as
possible (22).
There are several tertiary treatment schemes proposed to upgrade the
mill discharge and make it suitable for water reuse. A process to pro-
duce a clear, colorless effluent from a bleached Kraft mill was devel-
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oped by Fuller and reported by Haynes (5). According to Haynes, "The
combination of an activated sludge process and chemical precipitation
with alum reduced biochemical oxygen demand (BOD) to less than one part
per million and the color to five chloroplatinate units". This, Haynes
stated, was a remarkable achievement considering the high color and BOD
from a Kraft mill discharge. The problem encountered in this process
was the high dissolved solids content which was approximately 520 mg/1.
This process could be utilized to augment mill supply but complete
recycling would result in a higher dissolved solids content than could
be tolerated.
Reverse osmosis has been applied to a water reuse program (23). Reverse
osmosis is a unit operation in which clarified water is separated from
the remaining wastes for process reuse, and the organics are concentrated
for processing by more conventional techniques. Significant problems
have resulted from use of this system. It has been impossible to obtain
a high concentration of dissolved solids in the concentrate from the
reverse osmosis system. The process is capable of concentrating a stream
containing one percent to ten percent dissolved solids and recovering
90 percent of the process water for reuse. This leaves too much residual
volume for disposition without further concentration by evaporation.
Other problems encountered include an extremely high pressure drop across
2
the membrane, over 42.18 kg/cm (600 psig), and low flux rates, 81.5- to
2 2
407.5 I/day/M (2-10 gal/day/ft ). Although the reverse osmosis process
does not represent a complete solution for water recycling in the pulp
and paper mill, it does have a place. This process has the potential of
removing not only color and BOD but also dissolved solids, both organic
and inorganic. At Green Bay Packaging, Inc., Green Bay, Wisconsin, a
method of recycling weak waste has been developed and incorporated that
results in volume reduction and pollutant concentration in the waste stream.
Rapson and Reeve (22) forecast "substantial savings" in both capital and
operating costs for nn effluent-free bleached Kraft pulp mill. The net
capital savings (compared with complex water treatment facilities) is
$6 million for a 907.2 metric ton/day (1000 ton/day) mill. Net operating
cost savings is $9.65/metric ton ($8.75/ton) of bleached pulp.
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The significant capital and operating savings are supplemental to the
main advantages of elimination of aqueous effluents from the bleach
Kraft pulp mill, namely: 1) prevention of aqueous effluent with a
resulting increase in pulp yield, 2) elimination of the sodium chloride
now being introduced into the receiving streams, 3) elimination of the
problem of color in effluents which is usually not removed and is often
enhanced by secondary treatment, 4) elimination of the toxicity of pulp
mill effluents, much of which remains after secondary treatment, and
5) elimination of dissolved organic matter which consumes oxygen in the
receiving streams. Another problem avoided is that of introduction of
nutrients (nitrogen and phosphorus compounds) used in secondary water
treatment. These nutrients are subsequently introduced into the receiv-
ing stream and their elimination will help prevent the growth of unwanted
algae and other microorganisms (22).
Up to this point the methods and benefits of water recycling have been
discussed. There are also problems that arise as a result of water
reuse.
PROBLEMS IN WATER RECYCLING
Problems resulting from water recycling can be categorized as: 1) cor-
rosion, 2) scale, 3) biological slimes, 4) foam and 5) decreased pro-
duct quality and production rates. As the percentage of water reuse
increases, the related problems will become more complex and inter-
related. Naturally, the problems mentioned may not all be present in
the mill at any one time, nor may they manifest themselves to a point
where they significantly affect operations. Nevertheless, they should
be considered as endemic to systems that have a high water reuse rate.
These problems are interrelated and thus, will occur in combinations.
Corrosion
Corrosion is one of the major problems accompanying a tight water reuse
recycle system resulting in reduced equipment life. The amount of
or
16
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corrosion that may be tolerated in an industrial plant depends on the
equipment involved. In a thick-walled pipe carrying water, a large
amount of attack can proceed before holes develop. On the other hand,
on high speed equipment such as pumps or a paper refiner, a small amount
of corrosion in a localized area may result in complete failure.
Corrosion due to water recycling can assume many different forms and
can be present in most areas of the mill: 1) the steam generating
facility, 2) stock preparation areas, 3) the paper forming area, 4) the
dryers and 5) in the water treatment system. The different forms of
corrosion associated with water recycling include electrolytic corro-
sion, corrosion associated with protective films, and bacterial corro-
sion.
The reaction of metals with aqueous environments is called electrolytic
corrosion. The reactions involved in electrolytic corrosion are electro-
chemical in nature and are given by T. P. Hoar (24), C. F. Cheng (25),
M. Pourbaix (26), and others (27 & 28) to explain the corrosion process.
In electolytic corrosion, metal leaves the metallic state by anodic
dissolution to aqueous cations in solution or by anodic conversion to a
solid compound. These reactions are accompanied by an equivalent cath-
odic reduction of some constituent in the aqueous electrolyte. The
anodic and cathodic reactions depend on the type of metal involved and
the nature of its aqueous environment. Iron and alloys based on iron
can be corroded in both aerated solutions and deaerated acid solution.
In aerated natural waters, oxygen reduction is the predominant reaction
at the cathode. The products formed are hydrated ferric oxides and
magnetite. None of these products of attack provide any marked restrict-
ing influence on the electrochemical process. Their adhesion to the sur-
face and their protective action are much weaker than that provided by
calcium carbonate; thus, the corrosion of iron in soft waters does not
decrease appreciably with time (25).
17
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In a solution with a pH value of about four where the- concentrations of
dissolved oxygen and hydrogen ions are comparable, the hydrogen evolu-
tion type of attack becomes increasingly important. This evolution of
hydrogen occasionally gives rise to some concern in the corrosion of
iron and steel in closed systems where the presence of a flammable gas
may be demonstrated. This is due to the ability of iron to liberate
hydrogen from water. In closed systems the small amount of oxygen pres-
ent initially in the water is soon consumed and subsequently a slow
cathodic evolution of hydrogen takes place. Simultaneously, a film of
magnetite is formed on the metal surface which eventually stifles fur-
ther reaction (25). Even in the absence of air, corrosion of iron can
take place in waters if sulfate reducing bacteria are active. These
bacteria are present in most waters and in systems where the sulfate
concentration is adequate. They will proliferate in regions where the
oxygen concentration is sufficiently low. The bacteria are able to use
the cathodic hydrogen which would otherwise slow down or stop the cor-
rosion process (25 & 29).
In any given circumstance more than one of the above reactions may par-
ticipate in the overall cathodic process and the predominant reaction
may vary with time. In acid solutions reduction of heavy metal ions
and hydrogen ions can occur, while in only slightly acidic or alkaline
solutions a certain amount of hydrogen is evolved even when oxygen is
present. In a closed vessel or in one where oxygen is limiting, corro-
sion can proceed by oxygen reduction until all the oxygen has been re-
moved; then sulfate reducing bacteria can take over (30).
Corrosion can be affected by the corrosion product itself due primarily
to electrochemical polarization during the formation and breakdown of
these protective films (25). The nature and properties of the protec-
tive films that form on some metals or alloys are very important from
the standpoint of resistance to corrosion (31). The ability of these
films to protect the metal depends on the speed with which they form
when originally exposed to the environment, their resistance to wear,
and the rate of re-formation when destroyed or damaged.
18
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Stainless steels depend heavily on a protective film for their resistance
to corrosion. Variations in the amount of attack on steel by water with
varying pH but constant velocity are apparently duo to the nature and
composition of the surface scales formed. Cnrhon steel exposed to dis-
tilled water at 50°C (122°F) showed little attack at pH values of 6 and 10,
and high rates at a pH of about 7 to 9 and below 6. The scale on the
species exhibiting high rates of deterioration were granular in nature
and consisted of magnetite. Below a pH of 5, the corrosion product film
was increasingly more soluble as the pH was reduced. In regions of low
attack, the corrosion products were ferrous and ferric hydroxides which
are more protective probably because they hinder the transfer of oxygen
and ions (31).
Tests on copper and brass in sodium chloride solutions with or without
oxygen showed that copper was attacked more often than brass in the
oxygen saturated solution. The copper was covered with a black and yel-
low-brown film of cupric chloride, while the brass was covered with a
more protective, dark gray cupric oxide film (31).
Investigations dealing with corrosion mechanisms often deal with prop-
erties of the corrosion products formed (32). Several forms of corro-
sion can be the result of reactions between metal surfaces and the cor-
rosion medium. Some of these are listed below.
Tuberculation—Tuberculation corrosion is formed by iron con-
suming or iron depositing bacteria such as Crenothrix and sul-
fate reducing bacteria such as Sporovibrio desulfuricans.
Uniform attack—This is the most common form of corrosion.
It is normally characterized by a chemical or electrochemi-
cal reaction which proceeds uniformly over the entire exposed
surface. The metal becomes thinner and eventually fails.
Galvanic o£ two-metal corrosion—This condition occurs when
two dissimilar metals are in contact with each other (or
19
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otherwise electrically connected) and exposed to a con-
ductive solution. A potential is set up and a current
flows. Corrosion on the less corrosion resistant metal
is increased and attack on the more resistant material
decreased as compared to their behavior when not in con-
tact. The most familiar example is galvanized steel pipe
which is pipe coated by dipping in or electroplating with
zinc.
Concentration cell corrosion—This can also form because
of differences in the environment. The two most common
are metal ion cells and oxygen cells.
1. Metal ion cells—a metal tends to corrode at a
slower rate as the concentration of its ions in
solution increases. Metal in contact with a
more dilute solution will become anodic and metal
in contact with a more concentrated solution will
be cathodic.
2. Oxygen cells—oxygen concentration cells develop
where there are areas low in oxygen and others high
in oxygen content. Concentration cells may be caused
by differences in velocity of the solution. They
are associated with essentially stagnant conditions
which may be caused by holes, gasket surfaces, lap
joints, surface deposits and crevices.
Graphitization—Gray cast iron sometimes shows the effects of
selective leaching particularly in relatively mild corrosive
environments. The cast iron appears to become graphitized in
that the surface layer has the appearance of graphite. What
happens in graphitization is a selective leaching of the iron
or steel matrix and an interlocking graphite network is left
behind. The carbon is cathodic to iron and an excellent gal-
vanic cell exists. White cast iron has essentially no free
carbon, hence it is not subject to graphitization.
Erosion-corrosion—The acceleration of the rate of deterio-
ration of a metal because of movement between a corrosive
20
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fluid and the metal surface is called erosion-corrosion.
Generally this movement is quite rapid, and mechanical or
abrasion effects are often involved. Metal is removed from
the surface as ions or it forms corrosion products which are
swept from its surface. This type of corrosion is, there-
fore, enhanced by an increase in velocity.
I n order to make any evaluation of the probable corrosive action of a
water in a paper reprocessing plant, it is essential to have adequate
knowledge of the physical and chemical properties of water. Factors
that must be considered are: temperature, pH, flow velocity, dissolved
constituents in the water, how these vary during processing, and pos-
sible ways in which the water quality can be economically improved in
order to reduce corrosion. Therefore, the possible direct or second-
ary influence of increased concentrations of pollutants and the pre-
sence of various microorganisms due to reuse must be considered.
Dissolved oxygen (DO)—For a water of a given pH, an increase
in the dissolved oxygen level results in a near linear in-
crease in the corrosion rate up to a maximum (30). For dis-
t LI.led water, the critical level is approximately 8 mg/1 at
25°C (77°F). This is increased as the temperature is raised or
increased by the presence of dissolved salts. It is de-
creased by an increase in water velocity and pH being only
4 mg/1 at pH 10. The ultimate decrease in corrosion rate
at higher oxygen levels results from the formation of pas-
sive films on the metal surface. The effects of dissolved
oxygen is related to the rate of formation, nature and sta-
bility of the protective film.
Dissolved ions—Substances which give rise to hydrogen ions
in solution are reported to increase the corrosiveness of
the medium. These are organic acids which originate from
wood and wood pulp (33 & 34).
21
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Some anions like chromate, phosphates, silicates, and berates decrease
corrosion rates and are known as inhibitors, while others like chlorides
and sulfates are known to enhance corrosion and are classified as aggres-
sive ions. These anions have been shown to increase the corrosivity of
iron, aluminum, chromium and iron-chromium alloys, while not affecting
tantalum, titanium, zirconium, molybdenum or tungsten. Butler and
Stroud (35) found that the rate of corrosion of mild steel varied directly
with chloride concentration. Other investigators (36 & 37) evaluated the
effect of chloride and other ions on steel and reported that chloride and
sulfate are the ions most detrimental to steel although the presence of
other salts, e.g., of bicarbonate also exert an accelerating effect on
corrosion rate.
Velocity—The effect of velocity on aqueous corrosion is
complex. An increase in water velocity usually results in
enhanced corrosion rates through depolarization of the cath-
odic reaction by ensuring a more plentiful supply of oxygen.
It may also sweep away partially protective corrosion prod-
ucts. It is possible, however, for increased flow rates to
prevent corrosion by reducing the number of stagnant areas
and so prevent differential aeration cells from becoming
established. At very high flow rates, corrosion varies with
pH and the high corrosion rates are associated with the for-
mation of a less protective magnetite film (25). Critical
velocities vary for different metals.
Temperature—The effect of temperature varies with the nature
of the system. The corrosion rate approximately doubles for
every 30°C (86°F) rise in temperature until all the oxygen is
consumed, then the rate falls. In an open system, the corro-
sion rate increases with temperature rise until the decrease
in solubility of oxygen outweighs the accelerating effect of
temperature.
22
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With use the composition of water often changes either by evaporation,
the extraction of steam in steam generating equipment, or in the addi-
tion of pollutants during use as process waters. This will result in
an increase in dissolved solids, and unless water is regularly bled off,
the concentration may become very large. Furthermore, the content of
aggressive salts such as chlorides and sulfates increases continuously
owing to their high solubility while, at the same time, scale forming
salts, having a low solubility, are precipitated. This results in an
increase in aggressive ion concentration and a decrease in the concen-
tration of potentially restricting ions. The amount of water reuse in
certain circumstances may be dictated by the magnitude of the increase
in corrosion and the difficulty in corrosion control.
Several methods to control corrosion rates are available. These methods
include: selection of corrosion resistant materials; cathodic protec-
tion; insulation between bimetallic surfaces; protective coatings; water
treatment which includes ion removal, pH control and, the addition of
inhibitors and restrainers. Inhibitors or restrainers include: calcium
bicarbonate, chromates and dichromates, nitrites, polyphosphates, sili-
cates, sodium benzoate and organic inhibitors.
Material selection—The basic problem in the prevention
of corrosion is the correct selection of a material at
the design stage. The success of this aspect of corro-
sion control will depend upon: knowing in advance the
reuse engineering and corrosive conditions to which an
item will be exposed; using a special material must be
cost equivalent to making an item of the cheapest mater-
ial and replacing it on a regularly planned basis; and
availability of all the material involved in specifica-
tions (38, 39 & 40).
Cathodic protection—This consists of making a metallic
structure in its entirety the cathode of a purposely
23
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designed electrochemical cell which protects it from
corrosion (31). Sacrificial anodes like magnesium (41)
and zinc (27) have been initially used in the protection
of steel. Recent reviews of the present state of devel-
opment of cathodic protection techniques both in the
area of sacrificial anodes and impressed current pro-
tection systems are offered by J. H. Morgan (42) and
J. B. Cotton and others (43, 44, 45 & 46).
Coatings—The materials used for protective coatings may
be organic or inorganic. M. Clarke (47) and others (39
& 48) review the more common metal coatings and their
methods of application. An extensive evaluation of the
properties and resistances of zinc filled inorganic coat-
ings is made by NACE, Technical Unit Committee, headed
by M. W. Belue, Jr. (49).
Water treatment—Corrosion cells need electrolytes, the
most common being water. Thus, it has been necessary to
treat waters involved to reduce their ability to trigger
and support corrosion cells. Water treatment methods may
be divided into mechanical and chemical. The most popular
mechanical technique is the use of deaerators to remove
dissolved oxygen. This is usually done under an inert
atmosphere. Chemical treatment usually involves the con-
trolled addition of a chemical to alter the corrosive
quality of the water which may include:
1. Base exchange or ion exchange—ion exchange
resins are used to remove some undesirable
ions in the water.
2. pH control—the addition of chemicals to adjust
pH can serve more than one purpose. They may
bring the pH to acceptable levels, precipitate
metallic salts from solution or keep certain
salts in solution, whichever condition is re-
quired.
24
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3. Inhibitors—an inhibitor is a chemical niklod
to the water to inhibit specific corrosion
reactions. Kennedy (50) reported on organic
inhibitors for aqueous solution. These inhib-
itors were relatively non-toxic, film-forming
amines which can be absorbed readily on to the
metal surface. The resulting organic film then
acts as a barrier. These inhibitors were par-
ticularly effective in reducing the corrosion
brought about by hydrogen sulfide, hydrogen
chloride and carbon dioxide. The inhibitors
used for iron and steel are organic and inor-
ganic substances whose actions have also been
studied by such investigators as Cartledge (51),
Hackerman (52 & 53) and others (54, 55, 56 & 57).
Besides preventing local attack or general corrosion, inhibi-
tors and restrainers serve a number of other desirable func-
tions such as avoiding the blockage of pipes and screens by
corrosion products, keeping the waters "clean" for biological
or aesthetic reasons and maintaining optimum conditions for
heat transfer. In a paper reprocessing plant, the prevention
of blockages may be more important than the reduction in cor-
rosion since most of the process water eventually passes through
the screen on the cylinder of the paper machine.
Scale
The reuse of process water is frequently limited by the formation of
scale or similar encrustations in various parts of the recirculating
water system. These deposits can plug filters, screens, wires and
forming fabrics. They can block or restrict the flow of stock or water
through pumps and pipelines and can build up on the paper machine to
the point of causing damage to machine clothing and parts as well as
reducing the quality of the paper produced.
Scale is a deposit that results from the crystallization, precipitation
or coagulation of nonresinous substances. The most common chemical
constituent of such deposits are calcium carbonate and calcium sulfate,
25
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although other cations, like iron and manganese could also be deposited
as their oxides.
Some of the operational difficulties caused by scale deposits are:
1) obstruction of fluid flow, 2) impedance of heat transfer, 3) wear of
metal parts and, 4) localization of corrosion attack (58). Corrosion
and scaling often occur hand in hand. When fouling or failure develops,
the cause is often traced to a combination of scale and corrosion prod-
uct deposits. This was found to be the case in a stainless steel di-
gester by Scott (39). Scale deposits cause contact and crevice corro-
sion and thereby start surface deterioration. Localized attack may
occur from an oxygen concentration cell under the scale. Scale also
has been found to increase pitting and stress corrosion cracking. This
indicates that prevention of scale would eliminate a good deal of cor-
rosion.
The problem of evaluating and solving corrosion and fouling of water
systems can be complicated by a continually changing environment, like
fluctuations in pH, temperature, velocity, hardness, chloride ion con-
centration, dissolved oxygen, oxidizable organic material and others.
This was found by McAllister et al (59), in their study of scaling and
corrosion of condenser tubes exposed to river water. Other important
considerations in this study were the addition, at regular intervals,
of chlorine for control of biological growth and also addition of
caustic for corrosion control. Some of the findings of interest in
circulating and recirculating waters are the following:
1. The rate of fouling is not a function of velocity but
of chloride ion concentration and hardness.
2. The addition of enough caustic to change the pH from
6.8 - 7.1 to 9 - 10, did not dissolve scale nor cause
any more scale to deposit but the severity of pitting
increased.
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Slime
Slime in domestic water supplies can cause plugging of transmission
lines and objectionable tastes and odors. In industrial water systems,
slime results in a loss of operating efficiency, reduction of heat trans-
fer, corrosion, foul odors and deterioration of product quality (60).
Slime deposits in paper mill systems are microbiological or chemical (61).
Biological deposits consist of large numbers of bacteria, fungi and/or
yeasts together with fines and crystalline material. Bacterial slimes
may be gray-white, yellow, orange-brown or even black in color. Fungi
usually contribute to slimes only in conjunction with bacteria. Algal
slimes are blue-green to green in appearance and will only grow in the
presence of sunlight (60).
Chemical or inorganic slime deposits are usually found to contain pitch,
alumina, clays, hydrated silica resins, iron sulfides and fine fibers.
Most paper mill slimes are combinations of microbiological and chemical
material.
The required nucleus for the agglomeration of slime deposits is consid-
ered to be the bacterial cell. Studies by Opperman (61) show that fim-
briated bacteria may be responsible for the growth of slime deposits
because of the extremely fine protein fibrils or fimbrial which extend
beyond their capsules and could, therefore, be in a better position for
attachment to fibers and other organisms. In support of this theory,
slimes from 51 mills were examined with the result that 83 percent con-
tained fimbriated bacteria.
The advent of the closed system in paper mills brought with it a great
increase in microbiological problems as a direct result of the concen-
tration of nutrients, formation of stagnant areas and close contact for
extended periods with different genera of organisms. Among the organ-
isms that reportedly achieved major importance in paper mills because
of the use of closed systems are (62):
27
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1. The nonsporeformers such as Flavobacterium, Pseudomonas
and Enterobacter.
2. Aerobic sporeformers such as the Bacillus species.
3. Anaerobic nonsporeformers such as the sulfate reducers.
4. Yeasts and molds such as Penicillium and Aspergillus.
In addition to these, Clostridium organisms have been in 51 percent of
300 samples examined in counts ranging from 100 to several thousand per
milliliter or gram of sample. Clostridium species are anaerobic, hetero-
trophic, sporeforming bacteria which produce large amounts of gas and
putrefactive odors such as hydrogen sulfide which is also corrosive.
Some species are cellulose decomposers and can form slime under anaero-
bic conditions. In paper mill systems, the anaerobic conditions required
by Clostridium species can be found under slime layers formed by other
bacteria, under scale or corrosion products and at the bottom of slur-
ries of such materials as clays, starches and proteins.
Slime deposits may consist not only of bacterial colonies but also may
contain fungal hyphae matted together with fibers and debris. C. Wang
(63) reported on the species and frequency of the fungi found in repre-
sentative pulp and paper mills in New York State. Among the most abun-
dant in species and number were the Fungi Imperfecti, especially Asper-
gillus niger and Aspergillus fumigatus.
The solution of problems created by slime growths involves either the
use of mechanical or chemical methods or both. Often, mechanical clean-
ing can prove to be satisfactory, especially when chemical treatment is
expensive and without permanent effect (64). In either case, the best
answer to a slime problem must be low in cost, safe, noncorrosive and
effective against a wide range of organisms throughout the entire sys-
tem while avoiding substantial labor costs (60).
The common name for chemical agents used to control slime growth is
slimicide. In the pulp and paper industries, a large number of slimi-
28
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cides are in constant use and several of these are fairly effective in
meeting the requirements for slime control previously discussed. Among
these are the quaternary ammonium compounds, chlorinated phenols, some
amines, organo-sulfur compounds, and silver compounds.
Slime growths in pipelines carrying fresh water are due to outgrowths of
fresh water organisms which can be treated effectively with chlorine at
doses of 9-12 ppm or with copper sulfate at 9-18 ppm. Although copper
sulfate seems to be more effective than chlorine, the differences in cost
of $71.65/metric ton ($65/ton) for chlorine and $170.86/metric ton
($155/ton) for copper sulfate is favorable to chlorine. In long conduits
or in systems which are not very accessible, chemical treatment is often
resorted to as cheaper and more practical than mechanical cleaning.
Before a chemical treatment is chosen, however, a thorough study of the
organisms causing the difficulty should be made and the most effective
treatment used. Other conditions must also be ascertained. For example,
if the alkalinity of the water is high, copper sulfate may be relatively
ineffective. In open ditches or conduits, sunlight may render chlorine
useless. Other chemicals such as the chlorinated hydrocarbons should
be used with caution not only because of tastes and odors, but because
of possible toxicity (65). The corrosiveness and other damaging effects
of oxidizing chemicals such as calcium hypochlorite in the case of metal
pipes and screens may also preclude their use in certain systems.
Product Quality and Production Rates
Water reuse in paper mills tends to decrease product quality and decreases
the drainability of the sheet during formation as a result of the in-
creased concentration of finely dispersed particles such as clay. These
problems can be partially overcome by using drainage aids. The term
drainage aid is widely used in industry but not well defined. A drain-
age aid is a high molecular weight polyelectrolyte which improves water
removal. This improvement may take place at various points during the
papermaking process not always only on the forming section (66). Improved
water removal can be directed toward various objectives including:
29
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1) increasing production, 2) lower steam consumption, 3) improved
formation, 4) improved ply-bonding in multi-ply sheets and 5) extended
use of less expensive raw materials.
The theoretical background and mechanism of drainage aid has been dis-
cussed in a recent paper by Edward Strazdins (67) . He discussed the
work by LaMer and his co-workers which led to the conclusion that the
bridging of particles by high molecular weight polymers is the princi-
pal mechanism in producing flocculation. In this type of polymer-solid
interaction, only segments of the polymer attach first by forming
physical or electrostatic bonds. The remaining free end of the polymer
then adsorbs onto another particle that has a free adsorption site.
Formation of the polymer bridges can occur even against appreciable
electrostatic charge barriers. This type of mechanism is predominant
in effecting flocculation and retention with anionic polyacrylamides.
The theory of the bridging mechanism only applies to finely dispersed
particles such as clay. However, for grossly different systems, such
as fiber suspensions, it is not immediately clear to what extent these
concepts can be applied to explain the retention and fiber flocculation
mechanisms. In a fiber system, the surface charge of the treated fiber
played a major role. If the charge of the system is low, the estab-
lished bonds between the adsorbent and adsorbate have a better chance to
survive the disruptive action of hydrodynamic shear. Under conditions
where the final charge of fiber remains high (either on the negative or
positive side), retention of emulsions becomes increasingly difficult.
The established networks are easily disrupted, the desorbed particles
bear the same charge as fibers and electrostatic repulsion prevents
readsorption. Best retention of a cationic size emulsion is effected
when the system is near the isoelectric point. To maintain this con-
dition, additional cationic polymer must be added. To effect maximum
retention in the mill, the cationic emulsion-type sizing agents must be
introduced beyond the point of severe agitation. The best points of
addition are usually near the machine headbox (67).
30
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Water removal is, perhaps, the most serious factor limiting machine
speed today. Among the important factors in this problem arc the
viscosity of water and the need for fibrillating and swelling cellu-
lose fibers in order to develop fiber bonding and paper strength. It
is difficult to imagine a method whereby the viscosity of water can be
significantly reduced. The effect of increased temperature, presently
employed in some parts of the industry, is limited and higher tempera-
tures reduce swelling of the fiber, reduce papermakers' hydration, and
cause substantially lower strength. Significantly greater machine
speeds and faster drainage will be attained in the future mainly by
reduction in beating, refining and fibrillation, and by increasing use
of synthetic fibers. The simultaneous requirements for stronger and
lighter weight paper will demand that more and better additives of
several types be used in such paper (68).
Derivatives of polyacrylamide and polyethylenimines are rapidly gaining
in importance as retention aids. Both form complexes with cellulose.
The polyethylenimines appear to form salts with the carboxyl group of
cellulose fiber in a neutral or slightly alkaline stock suspension while
the polyacrylamides appear to be bound to the fiber by "aluminum mor-
danting action" under acid conditions (69). While both types of addi-
tives cause retention, the polyethylenimines have the added advantage
of causing improved flocculation, increased drainage and wet strength.
Chemical manufacturers are spending considerable effort on programs
directed toward their improvement on introduction to the industry.
According to the report of John W. Swanson (68), the addition on the
order of 250 g/metric ton (0.5 Ib/ton) of certain cationic polymers
such as polyamines and anionic high molecular weight polyacrylamides
to beater pulp will significantly increase drainage rate and freeness
of fiber slurry and removal of water at the presses.
According to the current survey by A. W. Dyck (70), the use of retention
and drainage aids shows rapid growth in the papermaking industry. The
31
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use of retention aids results in substantial chemical savings that amount
to as much as 15 percent of the wet end additives and reduces stream
pollution by retaining fines and filler in the sheet that would ordinar-
ily be'lost in the mill effluent. In addition to providing these bene-
fits, drainage aids contribute markedly to an increase in productivity
by increasing the rate of water removal on the Fourdrinier and permit a
significant reduction in the energy required in the drying operation.
The latter is particularly important in today's insufficient papermak-
ing capacity and the present energy crisis.
The growth in the use of retention and drainage aids has been triggered
by ecological pressure (71). Mills which previously did not use reten-
tion aids suddenly felt themselves forced to do so in response to pres-
sures to reduce stream pollution. The use of retention aids is addi-
tionally stimulated by a growing interest in recycling and the need to
operate the recycling process under conditions leading to a goal of
zero discharge of effluent. In this connection, many mills also use
retention and drainage aids in save-alls, machine headbox and clarifiers
where these chemicals act as flocculants to reduce pollution loads from
paper mill effluents.
The use of retention aids was also justified on the basis of economics.
As a retention aid, polyacrylaraide performs its nominal task of increas-
ing dry strength and also results in greater retention of fines and
faster drainage of water on the wire (70). One must balance these
advantages and the rather high cost of the polymer against the lower
cost of many other available dry strength additives, and against other
methods of increasing dry strength (more beating, stronger pulp, etc.).
However, in the final analysis a polyacrylamide resin may be the most
economic alternative because: 1) a smaller percentage of polyacrylamide
may impart the same degree of dry strength as larger amounts of starches
and gum, and 2) polyacrylamide can result in higher levels of dry
strength properties than other additives regardless of the amount used.
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SECTION V
MANUFACTURING PROCESS AND REUSE FACILITIES
MANUFACTURING PROCESS
Big Chief Roofing Company manufactures organic felt, a thick, absorbent
paper mat which is suitable for saturation with asphalt to form shingles
and other roofing products. Waste paper and wood flour are the basic
raw materials used in felt manufacturing. Two grades of waste paper are
used in equal portions at Big Chief. These are mixed paper and corru-
gated. The mixed paper is a standard grade of waste paper, which as its
name implies, includes any paper product ranging from milk cartons to
carbon paper. Corrugated paper is also a standard grade of waste paper
which includes any type of cardboard ranging from that found in heavy
corrugated boxes to that found in cereal boxes. The wood flour is saw-
dust that has been ground fine enough to pass through a twenty mesh
screen.
The felt is composed of approximately 75 percent waste paper and 25 per-
cent wood flour. The fibers from the waste paper bond together to give
the felt the tensile strength necessary for further processing and the
wood flour provides bulk and porosity necessary for asphalt penetration.
The process is diagramed in Figure 1.
Approximately 30 tons/day of waste paper are transported in bales from
the storage area to a paper beater (hydrapulper) where the paper is
blended with water from the white water pit to produce a pulp of approxi-
mately 3 percent consistency. Live steam is injected in the beater to
aid in pulping. For the initial stages of the project, a Shartle Dilts
breaker beater equipped with a bed plate fitted with 2.38 cm (15/16 in.)
holes to allow continuous operation was used to produce the pulp from
the waste paper. Pulp, which is beaten sufficiently to pass through the
holes in the bed plate, flows from the beater to the stock chest. In
33
-------
PAPER
STORAGE
YARD
__ FOKKtIFT
PAPER
RECEIVED 9V
TRUCK OR RAIL
LEGEND:
PRODUCT FLOW
FLOW PRIOR TO WATER REUSE
FLOW AFTER WATER REUSE
FILTERED WATER
NOTES:
PRIOR TO WATER REUSE
1 BAUER '%
' HYDRASIEVE "»K
r
L ri F*a ttfArca pnuf I ZURN i p& j I
t.ihS'saS'lK!!—LuifC._^| MICHOMATIC I— -HRECEIVER TANK |~
I I SCREEN j 1 I
• ^«»«B^»_ «I L^MH^MMiil
IFILTCRED WATER!
i.
CLEAR WATER
PUMP FIL TERED WA TER
.J
STORAGE
r-
I
a
\
FIGURE 1. PROCESS FLOW DIAGRAM
-------
the latter stages of the project, the paper beater was replaced with a
hydrapulper. The hydrapulper is driven by a 149.2 kw (200 Hp) electric
motor and has a capacity of 68 metric tons/day (75 tons/day). Metals,
rocks, plastics, and wire are removed automatically. The pulp from the
beater (hydrapulper) flows to two paper stock chests with dimensions
of 3.05 x 3.05 x 9.14 meters (10 x 10 x 30 feet) which are continuously
agitated. The pulp is pumped from the chests to a headbox which utilized
a sliding weir to control the flow of pulp to the Jordan refiner. (Big
Chief uses a Miami, Number 2, Jordan Refiner to refine and thoroughly
mix the pulp and wood flour). At the inlet of the refiner, approximately
9.07 metric tons (10 tons) of wood flour per day are added to the pulp.
The wood flour is transported to the mill, in bulk form, by rail. A
pneumatic pipe conveyor empties the box cars into the wood flour storage
tank. A screw conveyor, with a Reeves variable speed drive, delivers
the proper amount of wood flour to the inlet of the Jordan refiner. The
mixture (stock) leaves the refiner and flows into the machine stock
chest. The stock is pumped from the machine chest to a Brammer differ-
ential pressure consistency regulator which brings the stock to a con-
sistency of 2.5 percent. An adjustable weir on the consistency regu-
lator allows the proper amount of stock to flow by gravity to a headbox
where water from the fan pump dilutes it to 0.6 percent. The diluted
stock (furnish) flows from the headbox to a 14 plate Impco flat screen
fitted with 0.13 cm (0.05 in.) slots. The particles which do not pass
through the screen are returned to the machine stock chest for further
refining. The furnish flows from the screen to the headbox of the cylinder
vat. The headbox utilizes a series of baffles to distribute the furnish
evenly across its width. The furnish then enters a direct flow, single
overflow, cylinder vat manufactured by Black Clawson.
The forming cylinder is 1.52 M (60 in.) in diameter, 2.29 M (90 in.) long,
and is covered with a 14 x 20 mesh stainless steel wire. As the forming
cylinder rotates, water from the furnish flows to the inside of the
cylinder depositing a fiber mat on its periphery. The mat is removed
35
-------
from the cylinder by the couch roll and is transported by a woven fabric
(pickup felt) over a suction box, a suction roll and finally through the
press section. In sheet couching and transfer, the pickup felt is the
medium which removes the sheet from the forming cylinder and conveys it
from one water removal device to the next.
Water removal from the stock suspension is accomplished in great quanti-
ties as the sheet is formed and pressed. The stock suspension is approx-
imately 0.6 percent oven dry in the cylinder vat, 13 percent oven dry
after couching and 43 percent oven dry leaving the press section. To
permit this rapid dewatering, the pickup felt must be porous enough to
allow water to be drawn from the sheet, through it and into the suction
box or suction roll. The felt also cushions the sheet during couching
and pressing. Failure to provide adequate cushioning can cause the sheet
to crush or rupture.
The pickup felt does not have constant characteristics throughout its
life. It is repeatedly compacted and allowed to expand by passage
through the water removal devices and is gradually filled with paper
fibers, pigment, dirt, grit and slime. Throughout its life, the felt
tends to become less porous and looses its compressibility. Ultimate
failure of the felt usually occurs when holes develop or it becomes so
plugged and firm that the paper sheet crushes. To obtain a long and
uniform felt life, Big Chief employs a number of felt conditioning devices
such as a felt whipper, felt showers, worm roll and a suction box. These
all help keep the felt as clean and fully conditioned as possible. The
adjustable felt whipper roll and the tail roll are 17.78 cm (7 in.)
diameter, fully wormed rolls. These rolls serve to maintain the original
felt width, prevent wrinkles, condition the felt and loosen foreign
materials for easier removal. After the worm roll, a water shower
saturates the felt from the side which contacts the wet sheet, called the
sheet side. Another shower, after the whipper, washes the felt from the
opposite side removing the particles loosened by the whipper.
36
-------
The felt whipper employed at Big Chief is 35.56 cm (14 in.) in diameter
with four, 5.08 cm (2 in.) diameter brass hnts. Tt rotates nt 290 rpm,
striking the sheet side of the felt. The force of the blows is controlled
by adjusting the wet felt whipper roll. The intensity of the blows will
determine the wear it induces on the felt. Very intense blows will cause
excessive wear. The felt whipper conditions the water saturated felt by
mechanically beating it to loosen contaminating foreign material.
Striking the felt with rapid blows separates entrained foreign particles
from the felt and suspends these particles in the saturating water.
After a final felt shower, the felt passes over a suction box. The suc-
2
tion box has a 1.91 cm (3/4 in.) slot and pulls a vacuum of 0.07-0.17 kg/cm
(2-5 in. of mercury) depending on the porosity of the felt. The suction
2
box creates a 0.21-0.28 kg/cm (3-4 psi) vacuum on the sheet side of the
felt drawing water and the foreign material entrained in the water into
the suction box.
The sheet is further dewatered by a 40.64 cm (16 in.) diameter, 1134 kg
2
(2500 Ib) press roll that applies 7.87 kg/cm (112 psi) pressure to the
sheet. Under the press roll there is a vacuum roll which is subjected
2 2
to a 0.70 kg/cm (10 psi) to 1.05 kg/cm (15 psi) vacuum. After pressing,
the sheet is dry enough to support itself and enters the dryers without
aid of a supporting fabric.
The dryer section is composed of 67 steam heated dryers and a hot air
system all housed in an open hood. The dryers are 0.914 M (3 ft) in
diameter and are mounted in two tiers. They are heated to approximately
138°C (280°F) by steam at 3.52 kg/cm (50 psig). The hot air is
transported by a duct which runs the length of the dryer section. A
series of headers take the air from this duct and distribute the air
evenly across the width of the machine. The headers are located in
every dryer pocket and are fitted with 1.91 cm (3/4 in.) holes on
12.70 cm (5 in.) centers. The sheet enters the dryers at 57 percent
moisture and leaves at 3 percent moisture. After drying, a finish is
37
-------
pressed on the sheet with the calender stack. The calender stack con-
sists of two 25.40 cm (10 in.) diameter steel rolls which exert a
2
1.76 kg/cm (25 psi) nip pressure on the sheet. The felt is then trimmed,
rewound, and stored for further processing into saturated and coated
products.
REUSE FACILITIES
Total water use in the process prior to this study averaged 7.89 I/sec
(125 gpm) or 17,170 M3 (4,536,000 gal) per month of which 3,270 M3
o
(864,000 gal) are lost by evaporation in the process, and 13,900 M
(3,672,000 gal) are discharged to the treatment system. The fresh water
purchased from the city enters the system through the shower nozzles,
pump seals, periodically from water added to fill the cylinder vat
during start-ups (approximate!;
wash the equipment and floors.
3
during start-ups (approximately 15 M (4000 gal)), and through hoses to
The dilution water in the furnish is drawn into the paper machine cylinder.
This water is reused as dilution water at the consistency regulator and
the flat screen. Excess cylinder water and water extracted from the
organic felt mat by the suction roll and press section, and water used
for cleanup flows to the white water pit. From the white water pit,
water is pumped to the beater. (Prior to water reuse, excess white water
was discharged to the treatment system).
In order to control pollution from the paper making process, and to con-
serve water, Big Chief Roofing Company installed water reuse facilities.
The water reuse facilities were designed to screen white water to remove
the suspended solids so that it could be used in place of fresh water.
The facilities include a Bauer hydrasieve, a Zurn micromatic screen, a
filtered water storage tank, and the required pumps, pipes and other
appurtenances. These screens can be used individually or in series depending
on the required water quality.
38
-------
The hydrasieve is an inclined, stainless steel screen over which the
wastewater cascades. It was designed to remove the gross solids, pro-
tect the micromatic screen, and possibly provide water of sufficient
quality for reuse. The design of the hydrasieve allows removal of solids
with a particle size of approximately 170 microns which is one-half as
large as the wire spacing. The hydrasieve has a flow capacity of
9.46 I/sec (150 gpin). The screening surface has the rugged durability
necessary to handle the gross particles which may be swept into the
white water pit and hence, be pumped into the process potentially damaging
the micromatic screen.
The Zurn micromatic screen is a horizontal rotating drum type strainer.
The periphery of the drum is covered with an extremely fine, 35 micron,
stainless steel woven fabric. The white water enters the center of the
partially submerged 1.22 M (4 ft) drum through an open end and flows
outward through the straining media. The debris remains on the interior
surface of the drum and is transported upward over a stationary waste
collector located inside the drum above the water level. A row of water
jets positioned directly above and outside the drum uses a small percent-
age of product water to flush the fibers and other solids from the
interior surface of the drum into the waste collector and then into the
white water pit.
The effluent from the micromatic screen and/or hydrasieve is pumped to
3
a 113.6 M (30,000 gal) filtered water storage tank. This water is
subsequently reused in the showers and for cleanup. The suspended solids
with a particle size greater than 170 microns removed by the hydrasieve
are returned to the machine chest.
39
-------
SECTION VI
EXPERIMENTAL ANALYSES AND PROCEDURES
All analyses, with the exception of solids, bacterial, corrosion, and
product quality were performed according to the 13th edition of Stand-
ard Methods for the Examination £f_ Water and Wastewater (70). Solids
were determined gravimetrically after separation from the waste by cen-
trifugation and drying. Corrosion tests were performed following pro-
cedures as outlined in the American Standards for Testing Materials (71).
To determine the effects of water reuse on product quality, samples of
the product were sent to the Chicago Paper Testing Laboratory. All tests
on product quality were performed according to the Technical Association
of Pulp and Paper Industries Standards. The routine water analyses were
performed in the Sanitary Engineering Research Laboratory in the Depart-
ment of Civil Engineering and Environmental Science at the University of
Oklahoma. A limited number of solids and product quality tests needed
for operational control, were performed in the quality control labora-
tory at Big Chief Roofing Company. Analyses and measurements performed
as routine tests included: alkalinity, chemical oxygen demand (COD),
chloride, conductivity recorded as TDS, pH, and solids determination.
Periodic tests included bacterial control and temperature.
BACTERIAL CONTROL
In order to control bacterial slimes and to determine the effects of
various slimicides and chemicals on bacteria in the water being reused,
a modified sensitivity disc technique was employed. Absorbent discs,
7 mm in diameter, were cut from millipore filter pads and saturated with
solutions containing known concentrations of the slimicidal agents to be
tested. Excess liquid on the outer surface of the discs was removed by
placing them for one minute on an absorbent paper mat. The discs were
then placed on agar plates which had previously been seeded with enough
bacterial inoculum from the reused water to produce a smooth lawn. The
40
-------
seed consisted of 0.5 ml of a 0.01 dilution of water from the paper
reprocessing system. The agar plates used were glucose nutrient agar
buffered to pH 7. The plates were incubated at 37°C (98°F). Controls
were run by placing absorbent paper discs saturated with distilled water
on the agar plates.
A second technique was employed in which 100 ml batch samples of reuse
water and known concentrations of slimicide were placed in 250 ml shaker
flasks and maintained at 48°C (118°F) for 48 hours. These conditions
simulated existing plant conditions while operating at 85 percent water
reuse. Plate counts were made to determine the effectiveness of the
slimicide.
CHLORIDE
The mercuric nitrate method was used in the determination of chloride.
CORROSION
In order to determine the magnitude of the increase in corrosion, both
laboratory and full scale studies were performed. All tests for corro-
sion followed the American Standards for Testing Materials.
The test coupons were composed of materials used in construction of the
plant such as mild steel, stainless steel, bronze and cast iron. The
coupons were finished to approximately a 120 grit surface by mechanical
grinding. The average size of a coupon was 1.9 x 1.9 x 0.15 cm. The
cast iron and mild steel coupons were cleaned to bare metal using rea-
gent grade concentrated hydrochloric acid inhibited with five percent
stannous chloride and two percent antimonious oxide by weight. After
immersing in the above solution, with vigorous stirring for 25 minutes,
the coupons were washed and rinsed with distilled water, placed in an
acetone bath, air dried and weighed to the nearest 0.0001 gram. The
test coupons were placed in water at the plant that was either quiescent,
moderately turbulent or highly turbulent. A nylon line was used to sus-
pend the coupons in water. The tests were run for a period of 15 to 30
days. Then the coupons were removed from the system, dried, weighed and
cleaned as before and reweighed.
41
-------
Corrosion tests were also performed using a laboratory model. The stud-
ies were performed using 250 Erlentneyer flasks containing 150 ml of waste
which was agitated in a water bath shaker that held nine flasks. The shaker,
operated at an amplitude of 3.81 cm (1.5 in.)' and a frequency of 110 cycles
per minute, was used to simulate the turbulence in the plant. The tempera-
ture of the flasks were maintained between 46 and 48°C (115-118°F) which
was the average temperature of the water in the plant. The clean and
prewelghed coupons were suspended above the bottom of the flasks with a
piece of nylon string. The flasks were emptied and filled with new waste
every four days. During the four day period, distilled water was added
to replenish the water lost from evaporation. The pH of the wastes was
measured. The tests were run for a period of 15 to 30 days after which
the coupons were removed from the flasks, cleaned as before, then weighed.
The weight loss was determined and converted to corrosion rate expressed
in milligrams/square meter/day using the following formula:
Rmdd = 100,000
Where: Rmdd = corrosion rate
Wo = original weight in grams
Wf = final weight in grams, after cleaning
A = exposed area of the coupons in square centimeters
T = duration in days
PAPER TESTING
In order to determine the effect of water reuse on paper quality at Big
Chief, a series of product samples was submitted to the Chicago Paper
Testing Laboratory for evaluation. The samples were selected according
to the Technical Association of Pulp and Paper Industries (TAPPI) stand-
ard T-4000. At this laboratory, the samples were conditioned in accor-
dance with TAPPI standard T-402 os-70, defining the standard condition-
ing and testing atmosphere for paper, board, pulp handsheets and related
products. The following tests were performed according to TAPPI standards:
42
-------
1. Weight per unit area (basis weight or substance) of
paper and paper board, T-410 os-68.
2. Thickness (caliper). of paper and paper board, T-411
os-68.
3. Air resistance of paper (porosity), T-460 os-68.
4. Bursting strength of paper, T-403 ts-63.
5. Tensile breaking strength of paper and paper board,
T-404 ts-66.
6. Stretch of paper and paper board, T-457 m-46.
7. Internal tearing resistance of paper, T-414 ts-65.
Tests were performed in the quality control laboratory at Big Chief
Roofing Company for tensile strength, kerosene absorption, basis weight
and moisture content. With the aid of these tests, the speed of the
machine and the flow of waste paper and wood flour to the cylinder vat
were regulated since these factors controlled the porosity, strength,
basis weight and moisture content of the sheet.
SODIUM
The flame photometric method was used in the determination of sodium
content. A model DH Beckman quartz spectrophotometer was used in the
analysis.
SOLIDS
The centrifuge technique was used to separate the filterable and nonfil-
terable solids since the nonfilterable solids include a high percentage
of clays, fillers and fines. These can only be removed by centrifuga-
tion or filtration through a millipore filter. Filters with openings of
only a few microns plugged rapidly. Sample sizes that could consistently
be filtered through the millipore filters were too small to give repro-
ducible results. Therefore the following procedure was used for solids
determinations:
43
-------
Filterable Solids
1. Thoroughly mix the sample and transfer a 40 ml aliquot into
a 50 ml centrifuge tube.
2. Centrifuge at 10,000 rpm for 10 minutes in a Sorval super-
speed centrifuge.
3. Transfer 20 ml of the supernatant to a predried, tared,
evaporating dish.
4. Evaporate to dryness at 103°C (217°F).
5. Cool in a desiccator and weigh.
6. The total filterable solids are reported in mg/1 as the
increase in weight due to the residue after evaporation.
7. The residue was ignited at 600°C (1112°F) in a muffle furnace
for two hours. The loss of weight after ignition was reported
as mg/1 filterable volatile solids. The residue was reported
as mg/1 filterable fixed solids.
Nonfilterable Solids
1. Mix the sample thoroughly and transfer a 40 ml aliquot into
a tared evaporating dish.
2. Evaporate to dryness in a drying oven at 103 C (217 F).
3. Cool in a desiccator and weigh.
4. The increase in weight due to the residue after evapora-
tion was reported in mg/1 as total solids.
a) Ignite the total solids residue at 600°C (1112°F) in a
muffle furnace for two hours.
b) The residue remaining after ignition was reported as
mg/1 total fixed solids. The loss of weight after
ignition was recorded as mg/1 total volatile solids.
5. The nonfilterable volatile solids were obtained by subtract-
ing the filterable volatile solids from the total volatile
solids. The nonfilterable fixed solids were obtained in a
similar manner.
44
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SECTION VII
RESULTS AND DISCUSSION
This study was divided into three phases—no water reuse (conventional),
85 percent water reuse and 100 percent water reuse. In this section,
the data from the three phases are presented and the results are com-
pared. This comparison sets forth:
1. The effects of water reuse on product quality.
2. The effects of water reuse on process water quality.
3. The problems resulting from water reuse.
4. A cost effective analysis.
EFFECTS OF WATER REUSE ON PRODUCT QUALITY
When the role of water in the organic felt making process is examined,
it is reasonable to expect that water reuse will have little or no
effect on product quality. Water acts as a mechanical transport and
dispersion medium which allows pumping of the pulp slurry and forming
of the sheet. Water is also used as a cleaning agent in conditioning
the pickup felt and to carry away fine solids.
It is reasonable to expect a layer of fines and clay type fillers to
concentrate when water is reused. This tends to decrease the porosity
of the organic felt which in turn decreases the absorption of asphalt,
thereby adversely affecting its use as a roofing product. Wood flour,
which has greater size and more absorption, can replace the fines so
that a bulky, porous sheet can be formed. Control of the flow of wood
flour into the product then helps compensate for the increased concen-
tration of fines.
The most noticeable effect of water reuse on paper quality is a slight
increase in the number of imperfections in the sheet. These imperfec-
45
-------
tions are in the form of crushing and slime spots or holes. Crushing is
an imperfection in the formation of the sheet. It occurs when pressure
is applied to the sheet to remove free water and the water is unable to
move vertically. In this case, hydraulic pressure forces the water to
move horizontally disrupting sheet formation. Crushing is normally
caused by a pickup felt which is not porous enough to allow the water to
be squeezed from the sheet, or by too high a nip pressure or uneven nip
pressure at the couch roll or press section. At Big Chief, crushing
normally occurs at the couch roll and is usually caused by localized
plugging of the pickup felt.
Localized plugging of the felt often occurs when nozzles of the felt
conditioning showers plug. This reduces the effectiveness of felt
conditioning in that area. Plugging of felt showers is more prevalent
when filtered white water is used in the showers than when fresh water
is used. Increased sheet crushing is, therefore, an indirect result of
water reuse. Its extent can be minimized by regular cleaning and check-
ing of the felt conditioning showers.
In order to determine the effects of water reuse on paper quality,
40 product samples were submitted to the Chicago Paper Testing Laboratory
for evaluation. Twenty samples were submitted during the period of no
water reuse and twenty during 85 percent water reuse. The results of
the statistical analyses of the data from these tests, recorded in
Appendix A, are listed in Table 1. Based on these analyses, there were
no significant differences between the various product quality parameters
at the one percent level of significance. Since there was no significant
degradation in product quality at 85 percent water reuse and the product
quality control tests performed at Big Chief during zero discharge
indicated no significant change, tests were not performed at the Chicago
Paper Testing Laboratory during 100 percent water reuse.
46
-------
TABLE 1. COMPARISON OF ROOFING FELT QUALITY
(85% WATER REUSE AND NO WATER REUSE)
Mean
Parameter
2
Basis weight, g/M
Caliper, mil
Mullen, pt
Tensile strength MD,
g/cm
Tensile strength CMD,
g/cm
Elongation MD,
percent
Elongation CMD,
percent
Tear Elmendorf MD,
grams
Tear Elmendorf CMD,
grams
Porosity Gurley,
/ •% t\ f\ _ _
85 percent
water reuse
504
68.6
38.1
7232
4278
6.5
7.5
305
359
4.7
No
water reuse
•494
68
38.2
7500
4178
6.5
7.5
319
376
4.7
Standard
85 percent
water reuse
17.6
2.1
2.4
678
262
0.1
0.4
32
44
0.5
Deviation
No
water reuse
16.2
2.5
2.9
750
393
0.3
0.6
27.7
47.2
0.6
t
1.85
.81
.12
1.17
0.94
0.0
0.0
1.46
1.16
0.0
-------
EFFECT OF WATER REUSE ON PROCESS WATER QUALITY
Prior to this study the water demand at Big Chief Roofing was approxi-
mately 7.86 I/sec (125 gpm) resulting in a waste discharge of 6.31 I/sec
(100 gpm) and evaporative and other losses of 1.55 I/sec (25 gpm).
During the initial stage of this study, the effluent from the mill was
reduced to approximately 0.95 I/sec (15 gpm) which represents an 85 per-
cent reduction. During the latter stages of the study, more extensive
water reuse was practiced resulting in a further reduction of waste
discharge to approximately 15.14 M (4000 gal) per week which was dis-
charged at the time of clean-up. This approaches 100 percent water reuse
or zero discharge. When the system is operating at zero discharge,
0.76-0.88 I/sec (12-14 gpm) is required to replenish the water lost by
evaporation from the dryers. The decrease in consumptive losses (25 gpm
to 12-14 gpm) from the initial to the final phase of the study was due
to in-plant changes.
The water quality in the system fluctuates considerably since a small
change in flow can result in a significant dilution or concentration of
the chemicals in a system where water use is low. Gross additions of
fresh water, such as during start up, drastically dilute the chemicals
in the system. The chemical quality of the water in the system is also
affected by the composition of the waste paper. The waste paper used
at Big Chief Roofing is composed of a wide range of paper products.
Each bale of waste paper has different ratios of various products
depending on the paper available from the distributors. The composi-
tion of the various paper products varies considerably in fiber charac-
teristics, fillers, coatings, ink, glue, etc., which in turn affects
the water quality in the system. For example, certain high quality
paper is composed of 30-35 percent by weight clay with particle sizes
less than 10 microns. These particles are dispersed throughout the sys-
tem and cannot be removed by screening or other physical processes.
Therefore, they concentrate in a closed system resulting in a high nonfil-
terable fixed solids concentration. Binders, fillers, and other sizing
chemicals can also affect the dissolved solids content of the system.
48
-------
Other grades of paper such as newsprint, have no binder or fillers added,
thus their use will result in lower dissolved and suspended solids concen-
trations in the reprocessing system, but if too much newsprint is used
a weak sheet is produced. The cleanliness of the bales also affects the
composition of the system. The waste paper bales contain dirt, grit,
plastic, metal, styrofoam, etc. These foreign materials obviously affect
the chemical composition of the system.
A summary of the major characteristics of wastewater during the period
of no water reuse, 85 percent water reuse, and 100 percent water reuse,
is given in Table 2. The data from which this summary was prepared are
included in Appendices B-D. When water reuse is practiced, chemical
concentrations increased considerably reaching equilibrium after 6 to
10 days.
At equilibrium the concentration of filterable fixed solids increased
from approximately 320 mg/1 at no water reuse to 1150 mg/1 at 85 per-
cent reuse to 1960 mg/1 at 100 percent reuse. The dissolved solids
increased from 1530 to 5100 to 8210 mg/1 at 0-, 85-, and 100 percent
reuse, respectively. The COD increased from 1590 to 5560 to 8780 mg/1
during the same periods. The concentration factors ranged from 1.1 to
3.5 for 85 percent reuse and from 1.9 to 6.2 for 100 percent reuse.
These increases enhance the available food supply for bacterial growth
and the decrease in water use increases the retention time in the sys-
tem, thereby giving the bacterial slimes time to form. The concentra-
tion of the aggressive ions, such as chlorides and other ions which are
measured by an increase in conductivity (TDS), contribute to the accel-
eration of corrosion rates.
PROBLEMS RESULTING FROM WATER REUSE
Potential problems that are consequences of the decreased water quality
are: corrosion, decreased felt life, sheet crushing, slime deposits,
foam, scale, sludge deposits, plugging of screens and showers in the
paper forming area and the water cleaning system.
49
-------
TABLE 2. SUMMARY OF WASTEWATER CHARACTERISTICS
Parameter
COD
mg/1 0_
Chloride
mg/1
IDS
mg/1
Filterable
fixed solid,
mg/1
Filterable
volatile solid
mg/1
Nonfilterable
fixed solid
mg/1
Nonfilterable
volatile solid
mg/1
PH
Alkalinity
mg/1 CaC03
No
Water Reuse
.. Standard
Mean
deviation
1587
52
394
319
1214
197
243
6
279
311
.6 16.0
105
160
360
69
54
.8 0.2
64
85% Water Reuse
M Standard Concentra-
deviation tion factor
5564 458 3.50
91.2 9.6 1.73
1262 221 3.20
1150 145 3.60
3947 420 3.25
211 61 1.07
393 156 1.62
6.1 0.3
568 67 2.04
100% Water
w Standard
Mean , . . .
deviation
8781 203
183.2 6.1
1960 51
1960 9.6
6250 231
370 41
830 180
6.4 0.1
1081 10
Reuse
Concentra-
tion factor
5.53
3.45
4.97
6.14
5.15
1.88
3.42
3.87
-------
Corrosion
With the increased concentration of dissolved solids due to water reuse,
the corrosion rates were expected to increase. In order to determine
the magnitude of the increase, coupons were placed at strategic points
in the system and in a laboratory model. The results of the corrosion
tests are given in Table 3. (Data given in Appendix E.)
TABLE 3. SUMMARY OF CORROSION RATES, Rmdd
(mg/M2/day)
Coupon Material
Brass
Stainless steel
Mild steel
Cast iron
No
water reuse
1.87
0.02
32.75
30.10
85%
water reuse
5.10
0.04
74.44
50.95
100 %
water reuse
16.83
0.07
88.75
85.40
As expected the results shown an increase in corrosion rates when water
reuse is practiced for all materials tested. The practical significance
of the increase has not been determined since there has not been any
significant increase in the cost or frequency of replacement of parts
and equipment at Big Chief to date.
Corrosion is a significant problem in systems where the pH is not con-
trolled. In a paper reprocessing plant which practices water reuse,
the pH tends to drop as a result of organic acids which are generated
from waste paper and wood flour. In a solution with a low pH, hydro-
gen evolution type of attack is the dominant form of corrosion. There-
fore, the control of pH plays an important role in solving the corrosion
problem in many systems. This is verified by experience in the Dainger-
field Manufacturing Plant in Daingerfield, Texas which also uses waste
51
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paper and wood fiber for the production of organic felt. Water reuse in
this plant was imperative due to the unavailability of space for an ade-
quate treatment system. During the initial stages of start up in this
plant when complete water reuse was practiced, corrosion problems were
almost prohibitory. Large pump casings would be destroyed within a few
weeks and pipes and flat metal sheets would last only a few days. With-
out pH control, the pH would drop below five as a result of the acidic
nature of the paper and the decomposition of organic materials into
organic acid. By increasing and maintaining the pH at approximately 7.0,
the corrosion problem was essentially eliminated. At Big Chief, the pH
was maintained at 6.1 + 0.4 during water reuse. This required 68 kg
(150 Ib) of anhydrous caustic soda each day during 85 percent water
reuse and 108 kg (240 Ib) during 100 percent water reuse. It is, there-
fore, necessary to monitor and control the pH in the system to avoid
corrosion associated with acidic conditions and scale problems associated
with basic conditions.
Temperature also plays a role in corrosion. The hydrogen ion activity
is greater in high temperature water than in low temperature water.
Since the average temperature of the system is about 20-25 C (63-77 F)
higher when reuse is practiced than when no reuse is practiced, the
corrosion rates were also expected to increase. The temperature effects
were not isolated in this study but are reflected in the corrosion data
since the coupons were placed in the operating system.
The flow velocity and turbulence are also important factors that affect
the corrosion rate. Generally the corrosion rate increases with increas-
ing velocities to a maximum value of 60 M/min (200 ft/min). Any further
increase in flow rate results in a decrease in the rate of corrosion.
The coupons which were placed in a moderately turbulent or highly turbu-
lent area in the system gave higher corrosion rates than those placed in
quiescent areas. Any build up of slime, fiber or other protective films
on the surfaces of the coupons was inhibited by the turbulence. The
coupons that were placed in a quiescent area gave a lower corrosion rate
because in a quiescent media, the protective film prevents further corrosion.
52
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Felt Life
When water reuse is practiced, it is expected to have a detrimental
effect on the life of the pickup felt. The filtered white water has a
high suspended solids concentration which cannot be removed by the hydra-
sieve or the microscreen. These particles of foreign material are trap-
ped by the felt, and if the felt cleaning systems are inefficient they
may cause plugging. Any increase in bacteriological content of the
white water may also lead to plugging problems.
Table 4 represents the life of the pickup felt obtained at Big Chief
over the past five years.
TABLE 4. SUMMARY OF FELT LIFE
Condition Wear, days
No water reuse 75
85 percent water reuse 64
100 percent water reuse 50
To develop this data the felts were grouped according to the conditions
which prevailed during the life of the felt, i.e., was filtered white
water or city water used for felt conditioning. Felts which were re-
moved because of manufacturing defects, excessive stretching, mechani-
cal failure, etc., were not included in the report. Felts that over-
lapped the periods of no water reuse and water reuse were also excluded
from the report. When no water reuse is practiced, the average felt
life is about 75 days. The average felt life is reduced to 64 days when
85 percent water reuse is practiced and to 50 days when the system is
closed, i.e., zero discharge. This prevails in spite of the fact that
the white water enters the felt conditioning showers at approximately twice
the temperature and pressure of the city water. The filtered white water
enters the showers at 7.03 kg/cm2 (100 psi) and 38-54°C (100-130°F) while
f\
.city water enters the showers at 3.51 kg/cm (50 psi) and 10-21°C (50-70°F).
53
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The felt conditioning showers serve to saturate the pickup felt and
loosen the particles of embedded foreign material. The water then
serves as a medium to trap and transport the particles which the show-
ers, whipper and worm roll loosen so that they can be removed from the
felt by the vacuum box. The manufacturers of modern fabrics recommend
2
shower pressure of 5.27 kg/cm (75 psi) or higher and water temperatures
of up to 40°C (140°F) to obtain the best cleaning action of the felt.
Although the recommended temperature and pressure were maintained during
the period of water reuse, the felt life was shorter than during the
period of no water reuse. This was because of the high suspended solids
concentration in the filtered white water or plugging of the felt condi-
tioning showers. When a shower nozzle plugs, the area of the felt serviced
by the nozzle is left unsaturated which leads to localized felt plugging
and hence localized crushing of the mat.
At Big Chief, the nozzles of the felt conditioning showers were cleaned
periodically. At the beginning of the study, an average of three nozzles
would completely plug and others partially plug each eight hour shift.
This problem was primarily due to the unreliability of the Zurn micro-
matic screen. During the first several months, failure of the trunion
bearings and the gear box, and blinding of the screen prevented its use.
When the microscreen was not in use, plugging problems were particularly
acute. When plugging occurred, as evidenced by crushing of the mat,
detergents were used in an attempt to open the felt. If these were
unsuccessful, the felt was replaced. When the microscreen was in opera-
tion, plugging of the shower nozzles was minimal. This indicates the
necessity for matching the shower nozzle opening with the white water
screen. The shower nozzle must be considerably larger than the screen
opening. Larger nozzles result in high water use for felt conditioning,
which, in turn, results in higher pumping costs.
Studies were performed to determine the flow rate required for felt con-
ditioning. The felt conditioning showers were originally equipped with
0.241 cm (0.095 in.) orifice spray nozzles and were later replaced with
54
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0.157 cm (0.062 in.) nozzles. The water used decreased from 4.42 I/sec
(70 gpm) to 2.21 I/sec (35 gpm) as a result of the change. The felt life
was approximately the same for both conditions indicating that the felt
life is independent of the quantity of water used if the quantity required
for saturation of the felt is met or exceeded.
Slime
Increased quantities of slime deposits were found in the system at Big
Chief during periods of water reuse. As noted in the literature survey,
these deposits can produce deleterious effects on product quality and
also result in damage to metal components of the system.
Many types of chemical agents, or slimicides, are employed to control
slime growths. Quaternary ammonium compounds (QAC) were selected for
use at Big Chief because they are effective in low concentrations and
are less likely to damage metal components. Since chemicals may exhibit
synergism, a series of tests were performed using the following mixtures
of quaternary ammonium compounds:
1. Tetradecyl dimethyl benzyl ammonium chloride—25%
2. Dodecyl dimethyl benzyl ammonium chloride—20%
3. Hexadecyl dimethyl'benzyl ammonium chloride—5%
4. Inert ingredients—50%
The effective concentration of this mixture, required for control of the
slime bacteria present in the Big Chief system, was determined using the
sensitivity disc technique. In addition, effective slimicidal concen-
trations of a commercial slimicide (RX-12), and sodium were also deter-
mined. The commercial slimicide contained the following ingredients:
1. Sodium penta chlorophenate^-33.8%
2. Sodium 2,4,5-trichlorophenate—8.5%
3. Sodium salts of other chlorophenates—5.9%
4. Sodium dimethyl dithiocarbonate—2%
5. Inert ingredients including solubilizing and dispersing
agents—49.8%
55
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The effectiveness of sodium for controlling slime growth was determined
since it is added to the system as sodium hydroxide for pH control.
The results of the relative effectiveness of the three types of chemi-
cals are presented in Table 5. From these results, it is apparent that
the QAC mixture was the best slimicide with respect to control of the
bacteria present in the system at Big Chief. The QAC mixture was approx-
imately 100 times as effective as the commercial slimicide and 1000 times
as effective as sodium. The concentration of sodium in the system dur-
ing 100 percent water reuse was 1120 mg/1 which is much lower than that
required to inhibit slime growth. In order to verify the effective-
ness of the QAC mixture, it was tested under conditions similar to
those in the process at Big Chief.
TABLE 5. EFFECT OF VARIOUS SLIMICIDES ON BACTERIA
Slimicide Concentration Effect
(ppm)
Quaternary ammonium
compound (QAC) mixture 3 Good zone of clearing
Commercial slimicide (RX-12) 400 Good zone of clearing
Sodium (as sodium hydroxide) 8000 Good zone of clearing
Note: Good zone of clearing defined as no growth to approximately
3-4 mm beyond the edge of the sensitivity disc
Shaker flasks containing 100 percent reuse water were incubated at 48 C
(118°F) with 3 ppm of the QAC mixture for one week. The results of this
experiment are given in Table 6. The QAC mixture was effective in con-
trolling slime bacteria when used at a concentration of 3 ppm. Concen-
trations of the compound greater than 6 ppm may lead to foaming problems.
Other parameters such as hardness, pH and temperature of the 100 percent
reuse water, were at acceptable levels for effective microbial action
by the QAC mixture. A summary of these conditions is shown in Table 7.
The comparison shows the conditions were suitable for the use of
quaternary ammonium compounds. Prior to the termination of the study,
56
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3 mg/1 of the QAC mixture was Introduced into the system for a short
period of time. Tentative results of slimicidal activity measured by
total plate count indicated a decrease in bacterial concentrations at
less than 50 percent of the cost of the commercial slimicide. The QAC
mixture is a relatively inexpensive, noncorrosive chemical which
performed well at Big Chief. When compared with other slime control
chemicals, it appears to be the best alternative.
TABLE 6. TOTAL BACTERIA PRESENT/ML
Time
(days)
0
1
2
3
4
5a
6
7
QAC mixture
(3 ppm)
2 x 106
3
1 x 10
—
2
1 x 10
8 x 102
__
50
50
Control
(no QAC)
2 x 106
6
1 x 10
—
5
3 x 10
6 x 105
—
2 x 105
1.5 x 105
On day 5, an additional 3 ppm of the mixture was added.
TABLE 7. OPTIMUM CONDITIONS FOR QAC EFFECTIVENESS (74)
Parameter
Hardness
PH
Temperature
Desirable
500 ppm or less
6.0 or higher
24°C or higher
Actual
346 ppm
6.5
48°C
57
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Foam
Foam Is another problem which can be accentuated when water reuse is
practiced. Foam occurs when air is dispersed in a solution that con-
tains surface active agents. The surface active agents concentrate in
the film surrounding each bubble increasing its stability. If the rate
of bubbles rising to the surface exceeds the rate at which they break,
a surface foam or froth appears.
Fibers and other suspended solids often adhere to the film surrounding
the bubble as it rises to the surface. This "froth flotation" affects
the concentration of fibers, filler particles, dirt and slime at or
near the free water surfaces in the system. Froth flotation is most
evident in the white water pit. Water cascading into the pit from sue-.
tion boxes and rolls, or other sources, entrains air. This entrained
air causes froth flotation which forms a mat of fibers, filler parti-
cles, dirt and slime on the surface of the pit. Pieces of this mat
can break off and be pumped to the hydrasieve or heater. Pieces going
to the hydrasieve will be screened into the machine chest, removed by
the flat screen and eventually dispersed by the Jordan. Those entering
the hydrapulper will be dispersed by the hydrapulper and the Jordan.
In either case, the mat will be dispersed before it can cause problems
in the cylinder vat. However, froth can form or reform in the headbox
or the cylinder vat. This froth can seriously impair product quality
by forming holes or spots in the paper.
Air dispersed in paper making stock can cause many problems in addition
to the formation of surface foam. Some of these associated problems
are: 1) reduction of pump efficiencies and air locking of pumps,
2) interference with drainage of stock on the cylinder molds adversely
affecting formation, 3) reduction in the strength of both the wet web
and the finished sheet, and 4) promotion of growth of many slime form-
ing microorganisms.
58
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Foam can be controlled by chemical agents or mechanically by sprays.
Sprays are commonly used in paper mills to inhibit foam prior to form-
ing of the paper on the paper machine.
There are many commercially available foam control agents that satis-
factorily control foam in paper mills. Kerosene is most widely used
for foam control since it effectively reduces air entrainment in the
system. However, kerosene has a deleterious effect on the felt, the
rubber covered rolls, the BOD level and the slime potential. It also
presents a fire hazard. In spite of these shortcomings, at Big Chief
kerosene has proven to be the most available and economical foam con-
trol agent.
Scale
The reuse of process water is frequently limited by the formation of
scale or similar encrustations in various parts of the recirculating
water system. These deposits can plug filters, screens, wires and
forming fabrics. They can block or restrict the flow of stock or
water through pumps and pipelines and can build up on the paper machine
to the point of causing damage to machine clothing and parts as well as
reducing the quality of the paper produced.
Process water from a felt mill utilizing secondary fiber and wood flour
contains high concentrations of fine suspended solids, wood, chemicals
leached from the recycled fiber, wet-end additives, and broke. All of
these can introduce into the recirculating water system materials with
scaling potentials. If the water supply has a high calcium hardness,
then there is a possibility of calcium carbonate scale. The calcium
hardness in fresh water is frequently present in solutions as the
bicarbonate. In the water reuse system, the salts are concentrated by
evaporation and the carbon dioxide is removed by heat and aeration,
thereby resulting in the precipitation and deposition of calcium car-
bonate. The magnitude of this problem is a function of pH since cal-
cium carbonate is soluble in acids.
59
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Other dissolved salts that may be present in the water supply causing
potential scale problems include soluble ferrous and manganous compounds,
These compounds can be oxidized and deposited as their insoluble oxides.
Water containing these salts supports the growth of iron or. manganese
utilizing bacteria that contribute additional deposition problems.
Many of the usual paper machine wet-end additives (alum, fillers and
pigments used in making the paper from which the recycled fiber is
obtained) can contribute to scale problems. Excessive concentrations
of alum can lead to the precipitation of aluminum hydroxide which may
form a chemical slime, plug wet felts, or form a scale on surfaces
exposed to the reused water and concentrated salts. The mineral fil-
lers and pigments used in paper making can build up to rather high
concentrations in water reuse systems if retention on the paper machine
is relatively low. As the concentration of suspended, nonfibrous
solids in the water increases, due to reuse, there is a greater ten-
dency for these solids to form scale deposits.
To prevent deposition of scale in water recycling systems, it is nec-
essary to limit the concentration of scale-forming materials in the
recycled process water or to prevent those materials that are present
from forming encrustations on exposed surfaces. Limiting the quantity
of water recycled by increasing the amount bled off from the system
would obviously reduce the concentration of scale-forming constituents,
but such an approach is contrary to the goal of more efficient water
reuse. Methods that are compatible with the goal would include:
velocity control, improved clarification, treatment to remove dis-
solved solids and use of chemical additives.
The traditional methods of scale control used in treating recirculating
cooling water systems have been used in pulp and paper mill white water
systems with varying degrees of success. For example, polyphosphates,
which have had wide application in industrial water processes, have
been used to control scale in white water systems. Polyphosphates are
60
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sequestering agents which help keep metal ions in solution. They are
also used as dispersants for solids which may help in controlling
solids deposits in water .reuse systems. Organic chelating agents such
as EDTA can be used to control scale. They form chelates or complexes
with polyvalent metal ions and under certain circumstances can prevent
precipitates from forming. Dispersing agents of various types such as
synthetic organic surfactants, tannins and lignosulfonates can be used
if needed to prevent the deposition of suspended solids, including fil-
lers and pigments, as well as materials that might be precipitated from
solution. Synthetic organic polyelectrolytes can also be used to con-
trol scale in white water systems.
Scale was not a major problem at Big Chief. The pH was maintained
slightly above 6.0 which controlled calcium carbonate deposits. Other
dissolved salts did not cause significant scale problems. The only
significant operating problem resulting from a combination of scale and
other deposits was blinding of the Zurn micromatic screen which signifi-
cantly reduced its throughput. Many cleaning agents such as detergents,
caustic soda, phosphoric acid based cleaners, and steam were used to
clean the screen. The most successful combination of cleaners was a
solution of phosphoric acid followed by caustic soda.
Water Balance
In the design of a water reuse system, it is imperative that water fil-
tering, storage and surge capacities be sufficient to filter and store
the excess process water during periods when the flow from the process
(supply) exceeds the demand and to supply water to the process when the
demand exceeds the supply. Inadequate storage and surge capacities
result in wasting water during periods of low water use and the require-
ment for make-up water during periods of high water use.
As the system at Big Chief was originally designed, it was not possible
to obtain zero discharge. The problem with the original system centered
around the inherent unsteady operation of the paper beater. Due to the
61
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quality of the waste paper, the beaters operation was constantly inter-
rupted by plugging, cleaning and ragging of the beater. When the sys-
tem was operating properly, steady state, 15.78 I/sec (250 gpm) of white
water was pumped to the beater and 6.31 I/sec (100 gpm) through the
hydrasieve and micromatic screen to the clear water storage tank. When
the beater was shutdown for cleaning and ragging, the white water pit
filled rapidly and overflowed into the effluent receiving pit unless the
excess white water could be screened and stored in the filtered water
storage tank. Since the hydrasieve and micromatic screens were only
designed for 9.46 I/sec (150 gpm), the excess 12.62 I/sec (200 gpm) was
wasted. To achieve zero discharge it was necessary to increase the capac-
ity of the screens and to provide additional storage capacity for the
white water or to reduce the surges resulting from the unreliable paper
beater. At Big Chief, the problem was solved by replacing the paper
beater with a hydrapulper. This change decreased the surges resulting
in a smoother operation allowing the operators to achieve zero discharge.
To assist the operators in maintaining a steady state operation, a stock
chest level controller and consistency regulator were also installed.
With these equipment changes, the operators can maintain the paper stock
chest at a relatively constant level i 15 cm (6 in.). This differential
can easily be compensated for in the existing white water pit and storage
tank.
As mentioned above, zero discharge could have also been obtained by
increasing the capacities of the screens and the white water storage
tanks. At Big Chief this would have required increasing the capacity of
the screens to 22.1 I/sec (350 gpm) and doubling the filtered white water
storage capacity.
Sludge Deposits
A problem of minor significance was the disposal of the clays, fillers
and fines which settled out in the filtered water storage tanks. At
Big Chief these solids were disposed of in existing lagoons for waste
treatment. In other systems these solids would have to be retained in
the system, removed by placing on the product or transported to an
ultimate disposal facility such as a sanitary landfill.
62
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Preliminary studies were performed to determine the feasibility of add-
ing retention aids to the system for the purpose of retaining the clays,
fillers, etc., on the felt mat. These studies, although not conclusive,
indicated that up to 50 percent of the fine suspended solids could be
retained which also resulted in a higher white water quality for reuse.
An additional advantage is that more water could be extracted from the
felt mat while it is on the paper machine, thereby increasing the effi-
ciency and/or capacity of the dryers. Another possible method of
disposing of the fines is to pump them from the bottom of the filtered
water storage tank through atomized spray nozzles onto the felt mat.
This was not explored and, therefore, the effects on product quality and
the mechanical problems involved would have to be explored.
ECONOMIC ANALYSIS OF WATER REUSE
One of the specific objectives of this study was to conduct a cost-
effectiveness analysis of alternative combinations of water reuse and
by-product recovery versus waste treatment. Since the cost of fiber
from waste paper is very inexpensive, the savings due to fiber recov-
ery does not significantly affect the potential for water reuse. The
fibers do, however, exert an oxygen demand and therefore affect the
cost of waste treatment if they are not removed from the waste stream.
The economic feasibility of water reuse in a paper reprocessing plant is
a function of the change in maintenance costs as a result of reuse. To
determine the change in maintenance costs, the maintenance records before
and after were compared and plant maintenance personnel were interviewed.
This comparison was made by concentrating on the life of the Jordan plug
and shell, the face wire on the paper forming cylinder, the pickup felt,
pumps, and pipes in the system. These components were selected because
they are subjected to high velocities and velocity gradients and, there-
fore, were expected to undergo the highest corrosion rates.
The life of the Jordan plug and shell has averaged 3% months over a four
year period prior to water reuse and there has been no noticeable change
during the periods of 85 percent reuse.
63
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Based on studies to date, which are admittedly of short duration, there
has been no decrease in the life of the face wire on the paper forming
cylinder as a result of water reuse. No dramatic changes have been
noted in the life of the pumps and pipes in the system. A nominal num-
ber of pipes has been replaced since water reuse was initiated but
none of these has failed since replacement. The assistant felt mill
superintendent, who has been with the company for several years, has
noticed a slight increase in the pipe failures during water reuse. He
indicated this increase was 10-15 percent.
Overall, it is difficult to weigh the increase in maintenance costs
incurred as a direct result of water reuse over a period of short dura-
tion unless drastic changes occur. Based on limited data, it is pos-
sible to state that there is no significant increase in maintenance of
the equipment due to water reuse.
The itemized daily operational costs of the various alternatives are given
in Table 8, and the yearly operational costs based on operating the plant
320 days a year are given in Table 9. The operational costs are essen-
tially the same for all alternatives.
The capital costs of a waste treatment system required to meet the 1977
standards as set forth in PL 92-500, assuming no water reuse, is approx-
imately $150,000. This system would not meet the 1985 standards. The
capital costs of the waste treatment system required for 85 percent water
reuse is $80,000 and the cost of the 100 percent water reuse system is
$45,000. This is a complete retention system and, therefore, would meet
the 1985 standards. The capital costs of a zero water reuse system required
to meet the 1985 standards was not estimated because: 1) the operational
cost of the zero water reuse alternative was slightly higher than the
85 percent water reuse system and 2) the capital cost of the zero water
reuse system required to meet the 1977 standards was significantly higher
than for 85 percent water reuse. The capital cost of the 100 percent
o
water reuse system, including an additional 114 M (30,000 gallon) fil-
64
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TABLE 8. DAILY OPERATIONAL COST COMPARISON
Parameter
Felt
Water
pH control
Slime control3
Foam control
Power (waste treatment)
TOTAL
aAssuming quaternary
used the cost would
No 85%
Water Reuse Water Reuse
$ 12
33
0
8
20
34
$107
ammonium compound
exceed $18.
$ 14
21
23
8
20
14
$100
is used, if
100%
Water Reuse
$ 17
18
36
8
20
0
$ 99
RX-12 is
TABLE 9. COST COMPARISON
Parameter
Operations, annual
(320 days)
Capital
Capitalized Cost
No
Water Reuse
$ 34,240
150,000
639,100
85%
Water Reuse
$ 32,000
80,000
537,100
100%
Water Reuse
$ 31,680
45,000
497,600
65
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tered water storage tank which is required to insure 100 percent water
reuse, is $45,000. The capital costs of the various alternatives are
given in Table 9. This table also- includes the capitalized cost. The
capitalized cost is the sum of the construction cost plus operating and
maintenance costs (0 & M) capitalized by converting O&M to a sum of
money at 7 percent interest which would yield the operating and main-
tenance costs. This does not include a sum for replacement.
The costs, of necessity, are subject to some small errors. The basic
goal of this project is to meet the regulatory requirements and to do
so by the least cost alternative. A benefit/cost, or cost effective-
ness analysis requires an assessment of benefits as well as costs.
There has been no attempt to appraise the benefits of pollution abate-
ment, instead it is used as a constraint in assessing the costs of the
three alternatives.
From Tables 8 and 9, it can be seen that though major savings in cap-
ital costs are possible, the capital costs are a. relatively small
amount of the capitalized costs.
If a plant had attempted to treat its wastes first, and then was forced
to reuse, the cost of the 85 percent alternative would be slightly less
than the 100 percent reuse alternative, that is assuming waste disposal
lagoons are already in existence. It is interesting to note that the
operational cost for pH control increases from 0 to $36, and the power
decreased from $34 to 0 with reuse; or a trade-off between chemicals
and power.
Since the operational costs are approximately the same for all alterna-
tives, the most feasible system is one with the lowest first cost that
can meet the 1985 standards. In this case, that is 100 percent water
reuse or zero discharge.
66
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SECTION VIII
REFERENCES
1. U.S. Congress. Senate. PL 92-500. S. Doc. 2770, 92nd Congress (1972).
2. Darnay, A. and W. Franklin. The Role of Packaging in Solid Waste
Management 1966 to 1976, U.S. Dept. of Health, Education, and Welfare.
Superintendent of Documents, U.S Govt. Printing Office, Washington, D.C.
20402, (1969).
3. Cost of Clean Water, Vol. Ill, U.S. Dept. of Interior, Superintendent
of Documents, U.S. Govt. Printing Office, Washington, D.C. 20402
(November 1967).
4. Hendrickson, E.R. and H.S. Oglesby. "Process Design and Operation
for Zero Effluent Discharge", TAPPI. 57(4):71(April 1974).
5. Haynes, D.C. "Water Recycling in the Pulp and Paper Industry",
TAPPI, 57(4):45(April 1974).
6. Barton, C.A., J.F. Byrd, R.C. Peterson, J.H. Walter, and P.H. Woodruff.
"A Total Systems Approach to Pollution Control at a Pulp and Paper
Mill", J_. Water Poll. Control Fed., 8:1471(1968).
7. Philipps, A.H. "Disposal of Insulation Board Mill Effluent by Land
Irrigation", J_. Water Poll. Control Fed., 43:1749(August 1971).
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9. Henden, E., Paul Bennett, and Shyamala Narayanan. "Organic Compound
Removed by Reverse Osmosis", Water & Sew. Works, 116:466(December 1969),
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Reverse Osmosis to Processing of Spent Liquor from Pulp and Paper
Industries", TAPPI, 50:455(September 1967).
11. "Continuous Microbiological Purification of Wastewater from Paper
and Wasteboard Industries", Abstract, Eng. Index, 70(Part I):2005
(1970).
12. Gellman, I. and R.O. Blosser. "Paper'Industry Water Quality Pro-
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43:1547(July 1971).
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13. Eller, J., D. Ford and E. Gloyna. "Water Reuse and Recycling in
Industry", _J. Amer. Water Works Assoc.. 62:149(March 1970).
14. Linstedt, K., E. Bennett, S. Woric. "Quality Consideration in
Successive Water Use", J. Water Poll. Control Fed.. 43:1681(August 1971)
15. Thomas, Albert. "No. 3 Mill White Water Process and Re-Use System",
Amer. Paper Ind.. 54:38(November 1972).
16. Aldrich, L. and R. Janes. "White Water Reuse on a Fine Paper
Machine", TAPPI, 56(3):92(March 1973).
17. Davis, W., R. Kraiman, J. Parker, and C. Thurburg. "Recycling Fine
Paper Mill Effluent by Means of Pressure Filtration", TAPPI,
56:89(January 1973).
18. Reeves, J. and L. Ritter. "Conserving Water on Paper Machines",
TAPPI, 51(11):67A(November 1968).
19. Eimmerman, L. "Saving Energy Through Recycling Paper Mill Process
Water", Amer. Paper Ind.. (April 1974).
20. Le Compte, A. "Advanced Practical Water Recycle in Tissue Manu-
facture", TAPPI, 56(7):51(July 1973).
21. Rapson, W. and D. Reeve. "The Effluent-free Bleached Kraft Pulp
Mill", TAPPI, 56:112(September 1973).
22. Rapson, W. and D. Reeve. "Avoid Pollution by Total Water Recycle",
Can. Chem. Processing, 56(4):25(April 1972).
23. Nelson, W., and G. Walvaven. "Recycle of Paper Mill Waste Waters
and Application of Reverse Osmosis:, TAPPI, 56:54(July 1973).
24. Hoar, T. P. "Electrochemical Principles of the Corrosion and Pro-
tection of Mefals", J_. of Appl. Chem., ll:121(April 1961).
25. Cheng, C.F. "Corrosion Aspects of Iron Austenitic Stainless Steel
and Iconel in High Temperature Water", Corrosion, 20:34It(Novem-
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26. Pourbaix, M. "A Comparative Review of Electrochemical Methods of
Assessing Corrosion and the Behavior in Practice of Corrodible
Material", Corros. Sci., 5:677(1965).
27. Fisher, A.O. "New Methods for, Simulating Corrosion Plant Condition
in the Laboratory", Corrosion, 17:93(May 1961).
28. Von Fraunhofer, J.A. "Corrosion in Hot Water Central Heating",
Brit. Corros. J., 6:23(January 1971).
68
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29. Sardesco, J. B. and R. E. Pitts. "Corrosion of Iron in an H_0-
C°2~H2° Svstem Composition and Protectiveness of the Sulfide Film
as a Function of pH", Corrosion, 21: 250 (November 1965).
30. Uhlig, H. H. ."Effect of Metal Composition and Structure on Corro-
sion and Oxidation", Corrosion, 19: 231t (July 1963).
31. Bosich, J. R. Corrosion Prevention for Practicing Engineers. New
York: Barnes and Noble, 1970.
32. Strauss, M. S. and M. C. Bloom. "Corrosion Mechanism in Reaction
of Steel with Water and Oxygenater Solution", J^ Electrochem. Soc.,
107: 75 (1960).
33. Donovan, P. D. and J. Stringer. "Corrosion of Metals and Their
Protection in Atmosphere Containing Acid Vapors", Brit. Corros.
J^, 6: 132 (1971).
34. Knotkova-Cermakova, D. and J. Ulckova. "Corrosion Effect of Plas-
tics, Rubber and Wood on Metals in Confined Space", Brit. Corros.
J^, 6: 17 (January 1971).
35. Butler, G. and E. G. Stroud. "The Influence of Movement and Temper-
ature on the Corrosion of Mild Steel: High Purity Water", J. of
Appl. Chem.. 15: 325 (July 1965).
36. Rowe, L. C. and M. S. Walker. "Effect of Mineral Impurities in
Water on the Corrosion of Alluminum and Steel", Corrosion, 17: 105
(July 1961).
37. Pourbaix, A. "Characteristics of Localized Corrosion of Steel in
Chloride Solutions", Corrosion, 27: 449 (1971).
38. Cams, C. L. "Corrosion Resistance of Stainless Steel Overlays in
Kraft Digesters", Corrosion, 17: 21 (June 1961).
39. Scott, W. H. "Pulp Digester Corrosion Control", Corrosion, 17: 14
(June 1961).
40. Smith L. L. "Some Problem in Performance of Rubber Coverings on
Paper Machine Rolls", TAPPI, 47: 118 A (August 1964).
41. Seo, Masao. "Performance of Zinc Alloy Anodes", Corros. Eng., 10:
145 (April 1961).
42. Morgan, J. H. "Cathodic Protection Review", Brit. Corros. Jr., 5:
237 (November 1970).
43. Cotton, J., P- Hayfield, J. Morgan. "Corrosion, a Literature Review",
Brit. Corros. J., 1:123(November 1965).
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44. Alman-Naess, A. "Corrosion Protection of Drying Cylinders in
Papermaklng Machines by Cathodic Polarization", Corros. Sci.,
6:205 (1966).
45. Ba'rdal, Einan. "pH and Potential Measurement on Mild Steel and Cast
Iron During Periodic Cathodic Polarization at 20°C and 90°C", Corros,
Sci., 11:371 (June 1971).
46. Hammer, N.E. "Applying Cathodic Protection to a Papermaking Cylin-
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47. Clarke, M. "Protective Metal Coatings—A Review", Brit. Corros. J_.,
6:197 (September 1971).
48. Wasson, L.C. "Cathodic Protection Proposed for Vapor Area in Pulp
Digesters", Corrosion, 17:27 (June 1961).
49. Belue, M.W. "Zinc Filled Inorganic Coatings", Corrosion, 17:107
(August 1961).
50. Kennedy, J.G. "Inhibitors for Aqueous Solution", Anti-Corros.,
Methods and Materials. 14:8 (April 1967).
51. Cartledge, G. H. "Recent Studies of the Action of Inorganic Inhi-
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52. Hackerman, N. "Recent Advances in the Understanding of Organic
Inhibitors", Corrosion 18:332t (September 1962).
53. Hackerman, N., R. Hurd and R. Annand. "Some Structure Effects of
Organic N-Con-taining Compounds on Common Inhibition", Corrosion,
18:37t (January 1962).
54. Akiyama, A. and K. Nobe. "Corrosion Inhibition of Zone-refined
Iron by Ring-Substituted Benzoic Acids", Corrosion, 26:439
(October 1970).
55. Hatch, G.B. "Influence of Inhibition on the Differential Aeration
Attack of Steel", Corrosion, 21:179 (June 1965).
56. Bloom, M., M. Krulfeld, and W. Fraser. "Some Effects of Alkalis on
Corrosion of Mild Steel in Stream Generating System", Corrosion,
19:327t (September 1963).
57. Desai, N., and B. Punzani. "60/40 Brass Corrosion: Inhibition of
Corrosion in NaOH Solutions", Anti-Corros., Methods & Materials,
5:7 (September 1971).
58. Jones, L.W. "Development of a Mineral Scale Inhibitor", Corrosion,
7:110 (July 1961).
70
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Scaling and Corrosion in Condenser Tubes Exposed to River Water",
Corrosion, 17:95 (December 1961).
60. Wrangler, G. "A Chemical for Controlling Water Slime", Metals and
Materials, 192:414 (September 29, 1961).
61. Opperman, R. and L. Wolfson. "Mechanism of Slime Formation:
Frimbriae", TAPP1, 44:905 (December 1961).
62. Wolfson, L. and R. Michalski. "The Incidence and Effects of the
Anaerobic Bacteria: Clostridium in Paper Mill Systems", TAPPI,
47:4 (April 1964).
63. Wang, C. "Roberts on Fungus Flora of Pulp and Paper in New York",
TAPPI, 44:785 (November 1961).
64. Wrangler, G. "Silacide Excellent Slimicide", Paper Ind. 43:776
(March 1962).
65. Dych, A. "New Developments for Slime Control", Paper Ind. 44:273
(August 1962).
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67. Strazdins, Edward. "Factors Affecting Retention of Wet-End Addi-
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68. Swanson, J. "Chemical Additives: New Dimensions for Papermaking",
Amer. Paper Ind., :39 (March 1970).
69. Dyck, A. "PIMA", Amer. Paper Ind., 12:12 (April 1973).
70. Dyck, A. "Papermaking Chemicals", Amer. Paper Ind., 30:42 (April 1973).
71. Dyck, A. "Papermaking Chemicals", Amer. Paper Chem. 33: (November 1971)
72. American Public Health Association. Standard Methods for the Exami-
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73. American Society for Testing and Materials. "Preparing, Cleaning,
and Evaluating Corrosion Test Specimens", Annual Book of_ ASTM Stand-
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74. Ehlers, V. and E. Steel. Municipal and Rural Sanitation, McGraw-Hill:
New York (1965).
71
-------
SECTION IX
APPENDICES
Page
A. (1) Test Results on Individual Samples of Roofing Felt 73
Paper (No water reuse)
(2) Test Results on Individual Samples of Roofing Felt 74
Paper (85% Water reuse)
B. Wastewater Characteristics (No water reuse) 75
C. Wastewater Characteristics (85% water reuse) 77
D. Wastewater Characteristics (100% water reuse) 79
E. Corrosion Rates 82
72
-------
APPENDIX A-l. TEST RESULTS ON INDIVIDUAL SAMPLES OF ROOFING FELT PAPER
(NO WATER REUSE)
oo
Tensile strength
Sample
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
(g/cm)
MD
6411
7625
7982
6661
7965
7197
7661
7482
9018
7197
6304
7322
6589
7804
7625
8179
8715
6893
8411
7107
CMD
4625
4625
4214
4000
3875
3571
4446
4107
4447
4929
3393
3661
3714
4322
4322
4322
4268
3929
4536
4286
Elongation
MD CMD
7.0
7.0
6.2
6.8
6.8
6.2
6.2
6.2
6.6
6.2
6.2
6.6
6.4
6.4
6.4
6.6
6.4
6.4
6.6
6.4
6.8
6.8
7.0
7.0
7.0
6.8
7.2
7.0
7.6
6.8
7.2
7.2
8.2
8.2
7.8
8.8
8.2
8.4
7.8
7.6
Tear,
MD
264
320
328
352
304
344
296
320
304
304
304
304
296
328
368
320
352
296
304
376
Elmendorf
(g)
CMD
312
328
360
528
352
424
368
376
393
320
416
383
320
384
368
392
368
392
384
352
Porosity,
Gurley
(sec/lOOcc)
5.5
4.4
4.0
5.3
4.6
5.7
5.3
5.7
5.1
5.3
5.3
4.1
4.1
4.2
4.3
4.2
4.1
4.0
4.0
4.3
Basis
weight
(g/M2)
516
474
529
499
508
495
495
478
504
491
516
487
478
478
495
491
461
499
483
499
Caliper
(mil)
70.0
65.0
71.0
70.0
68.5
67.5
67.0
67.0
68.5
66.5
74.5
70.5
71.0
65.0
68.0
68.0
65.0
71.0
68.0
67.0
Mullen
(pt)
36.0
40.0
44.0
38.5
41.0
44.0
38.5
40.5
38.0
37.5
35.0
35.5
35.0
35.0
37.5
37.0
40.5
35.5
41.0
34.5
-------
APPENDIX A-2. TEST RESULTS ON INDIVIDUAL SAMPLES OF ROOFING FELT PAPER
(85% WATER REUSE)
Tensile strength
Sample
No.
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
(g/cm)
MD
7232
6661
6875
7322
7286
7679
7661
8411
6893
7179
8179
7857
8250
7411
7054
6107
7090
6393
7018
5928
CMD
4143
4625
3786
4232
4179
4143
4232
4322
4053
4410
4322
3839
3929
4625
4286
4697
4467
4714
4322
4268
Elongation
MD CMD
6.4
6.4
6.6
6.4
6.6
6.6
6.4
6.6
6.6
6.6
6.8
6.4
6.2
6.6
6.6
6.4
6.6
6.6
6.4
6.4
7.4
7.6
7.6
8.4
7.0
8.0
7.4
7.0
7.4
7.2
8.0
6.6
7.2
8.0
7.6
7.6
7.8
7.6
7.2
7.8
Tear,
MD
272
256
280
264
328
320
368
288
288
328
320
304
312
320
288
296
296
376
336
272
Elmendorf
(g)
CMD
288
384
328
312
352
352
385
400
416
408
448
392
368
408
344
320
304
304
352
328
Porosity,
Gurley
(sec/lOOcc)
4.0
4.4
5.6
5.3
4.9
4.6
5.0
4.6
4.1
5.3
4.7
5.0 •
4.6
4.8
5.1
4.3
4.0
4.4
4.2
4.7
Basis
weight
(g/M2)
504
512
516
487
546
508
499
495
512
497
516
499
508
483
461
521
495
521
508
508
Caliper
(mil)
68.5
68.5
69.5
67.0
72.0
70.0
68.5
67.0
68.0
66.0
71.5
68.5
70.5
65.5
63.5
71.0
68.5
70.5
69.0
68.5
Mullen
(pt)
36.5
39.0
36.5
38.5
45.0
37.0
39.5
37.5
38.0
34.5
38.5
38.0
39.5
33.5
35.5
38.0
41.5
38.0
39.0
38.5
-------
APPENDIX B-l. WASTEWATER CHARACTERISTICS
(NO WATER REUSE)
•vj
Cn
Machine Chest
Parameter
COD, mg/1 02
Chloride, mg/1
TDS, mg/1
Filterable fixed
— i j j ~ / 1
Mean
1811
50
403
459
Standard
deviation
392
20
172
172
Cylinder Vat Cylinder Water
Mean
1544
54
412
337
Standard ..
, . . Mean
deviation
250 1778
51
110 418
193 349
Standard
deviation
317
13
105
170
Filterable
volatile solids, 1584
mg/1
Nonfilterable
fixed solids,
mg/1
Nonfilterable
volatile solids,
mg/1
Alkalinity, 271
mg/1 CaCO-
257
1342
232
286
1215
152
265
255
319
21
36
97
-------
APPENDIX B-2. WASTEWATER CHARACTERISTICS
(NO WATER REUSE)
Filtered Water
Parameter
COD, mg/1 02
Chloride, mg/1
TDS, mg/1
Mean
1269
55
360
Standard
deviation
—
—
—
Hydrasieve Influent
_. Standard
Mean , . . .
deviation
1351 213
60 22
376 73
Hydrasieve Effluent
„ Standard
Mean . , ^.
deviation
1485 350
46 12
372 74
Filterable fixed
solids, mg/1
Filterable
volatile solids,
mg/1
Nonfilterable
fixed solids,
mg/1
Nonfilterable
volatile solids,
mg/1
Alkalinity,
mg/1 CaCO-
350
760
153
268
268
268
1075
239
242
296
153
331
76
21
63
323
1045
208
188
273
133
362
76
26
97
-------
APPENDIX C-l. WASTEWATER CHARACTERISTICS
(85 PERCENT WATER REUSE)
Parameter
COD, mg/1 02
Chloride, mg/1
TDS, mg/1
Filterable fixed
— ~\ j j ~ «~ / 1
Machine
Mean
—
—
1350
1296
Chest
Standard
deviation
—
—
76
179
Cylinder Vat
.. Standard
Mean ,
deviation
—
—
1310 95
1151 146
Cylinder
Mean
5730
92
1317
1189
Water
Standard
deviation
592
6
147
189
Filterable
volatile solids,
mg/1
Nonfilterable
fixed solids,
mg/1
Nonfilterable
volatile solids,
mg/1
Alkalinity,
mg/1 CaCO
4302
502
4225
385
570
60
580
62
4100
226
348
575
349
87
73
61
-------
oo
APPENDIX C-2. WASTEWATER CHARACTERISTICS
(85 PERCENT WATER REUSE)
Parameter
COD, mg/1 02
Chloride, mg/1
TDS, mg/1
Filterable fixed
solids, mg/1
Filterable
volatile solids,
mg/1
Nonfilterable
fixed solids,
mg/1
Nonfilterable
volatile solids,
mg/1
Alkalinity,
mg/1 CaC03
Hydras ieve
influent
Mean
5600
90
1306
1092
3825
202
426
565
Standard
deviation
453
11
108
134
409
43
71
71
Hydrasieve
effluent
Mean
5469
90
1306
1074
3937
146
359
574
Standard
deviation
571
6
118
143
407
30
72
67
Zurn
Mean
5590
91
1243
1075
3887
134
315
572
effluent
Standard
deviation
407
15
137
93
256
25
76
83
Zurn reject
Mean
5369
91
1310
1122
3719
253
963
621
Standard
deviation
224
10
108
121
295
20
80
42
-------
APPENDIX D-l. WASTEWATER CHARACTERISTICS
(100 PERCENT WATER REUSE)
Paper Chest
Parameter
COD, mg/1 02
Chloride, mg/1
TDS, mg/1
Filterable fixed
.~ i -: j ~ / 1
Mean
9104
193
1983
2034
Standard
deviation
2437
63
561
602
Machine Chest
Mean
9160
193
2066
2137
Standard
deviation
2360
58
583
740
Cylinder Vat
Mean
8640
183
1950
1919
Standard
deviation
2202
47
556
561
Filterable
volatile solids,
mg/1
Nonfilterable
fixed solids,
mg/1
Nonfilterable
volatile solids,
mg/1
Alkalinity,
mg/1 CaC03
6511
1085
6594
1386
6241
1538
1086
244
1099
251
1071
245
-------
APPENDIX D-2. WASTEWATER CHARACTERISTICS
(100 PERCENT WATER REUSE)
oo
o
Cylinder Water
Parameter
COD, mg/1 02
Chloride, mg/1
TDS, mg/1
Filterable fixed
solids, mg/1
Filterable
volatile solids,
mg/1
Nonf ilterable
fixed solids,
mg/1
Nonfilterable
volatile solids,
mg/1
Alkalinity,
mg/1 CaGO-
Mean
8700
184
1950
1814
6502
386
874
1069
Standard
deviation
2150
52
606
484
1670
82
214
257
Hydrasieve Influent
Mean
8726
180
1917
1938
6123
416
849
1079
Standard
deviation
2137
52
603
592
1679
73
126
253
Hydrasieve Effluent
Mean
8685
183
1967
2006
5978
385
811
1073
Standard
deviation
2174
48
633
623
1556
55
205
245
-------
APPENDIX D-3. WASTEWATER CHARACTERISTICS
(100 PERCENT.WATER REUSE)
oo
Parameter
COD, mg/1 02
Chloride, mg/1
TDS, mg/1
Filterable fixed
i^j^ ^ / 1
Zurn
Mean
8710
179
2000
1867
Effluent
Standard
deviation
2101
43
589
542
Zurn Reject
Mean
8599
178
1917
2002
Standard
deviation
2216
47
633
670
Filtered Water
Mean
8709 -
177
1900
1929
Standard
deviation
2322
45
638
668
Filterable
volatile solids,
mg/1
Nonfilterable
fixed solids,
mg/1
Nonfilterable
volatile solids,
mg/1
Alkalinity,
mg/1
6202
350
698
1090
1982
75
229
252
5994
388
1140
1083
1737
56
223
261
6109
298
609
1080
1593
76
285
254
-------
APPENDIX E-l. CORROSION RATES
NO WATER REUSE
(mg/M /day)
Coupon material
Number
Rate
Brass
Stainless steel
Mild steel
Cast iron
B-l
S-l
M-3
M-4
C-l
C-2
1.87
0.02
37.70
27.80
29.60
30.70
82
-------
APPENDIX E-2. CORROSION RATES, 85% WATER REUSE
(mg/M2/day)
Coupon material
Brass
Stainless steel
Mild steel
Cast iron
Number
B-21
B-22
B-23
B-24
B-25
S-20
S-21
S-22
S-23
S-24
M-2
M-3
M-4
M-5
M-20
M-22
M-23
M-24
M-25
M-26
M-27
M-28
C-3
C-4
C-5
C-6
C-22
C-26
C-27
C-28
C-29
C-30
C-32
C-33
Rate
8.29
- 1.53
5.00
5.30
5.39
0.05
0.08
0.05
0.00
0.00
38.02
41.45
30.51
27.43
50.05
116.50
99.50
100.89
65.11
103.31
135.69
84.84
38.53
35.01
35.74
35.86
82.05
58.34
43.00
75.20
46.16
53.19
52.19
56.11
83
-------
APPENDIX E-3. CORROSION RATE, 100% WATER REUSE
2
(mg/M /day)
Coupon material
Brass
Stainless steel
Mild steel
Cast iron
Number
B-l
B-2
B-3
B-4
B-5
S-l
S-2
S-3
S-4
S-5
M-l
M-2
M-3
M-4
M-5
M-8
M-9
C-l
C-2
C-3
C-4
.C-5
C-7
C-9
Rate
27.60
27.17
26.66
21.70
16.87
0.00
0.00
0.08
0.08
0.09
115.47
99.67
115.22
99.20
75.66
79.50
77.41
87.58
81.08
105.73
88.86
96.80
58.23
65.02
Number
B-6
B-7
B-8
B-10
B-26
S-6
S-7
S-8
S-10
M-10
M-ll
M-l 2
M-14
M-l 5
M-25
C-10
C-ll
C-12
C-l 3
C-14
C-15
Rate
17.77
21.53
22.64
18.97
12.70
0.09
0.09
0.13
0.13
74.08
81.72
68.01
68.61
72.92
89.75
66.56
48.10
75.19
56.92
66.94
52.67
84
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-76-232
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
WATER REUSE IN A PAPER REPROCESSING PLANT
5. REPORT DATE
October 1976 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Leale E. Streebin*, George W. Reid*, Paul Law*,
and Charles Hogan**
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
**Big Chief Roofing Company
Ardmore, Oklahoma 73401
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
S-801206
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory-Gin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
*School of Civil Engineering
Norman, Oklahoma 73069
Environmental Science, University of Oklahoma,
16. ABSTRACT
This project was undertaken to determine the feasibility of water reuse in a paper
reprocessing plant with the goal being to "close the loop" or to demonstrate zero dis-
charge technology. Before the project began, Big Chief Roofing Company at Ardmore, OK,
was discharging 7.89 I/sec (125 gpm). Normal operation is now zero discharge with
approximately 0.76 I/sec (12 gpm) fresh water make-up replacing evaporative losses. Ho
ever, weekly clean-ups still result in an effluent of approximately 15.14 M3 (4000 gal)
a week. Additional clear water storage capacity could eliminate this weekly discharge.
Project scope included identifying and solving problems resulting from increased re-
cycle of process water, and determining costs, benefits, and effect on product quality.
The favorable cost/benefit ratio experienced at the plant demonstrated an economic ad-
vantage of in-plant control over end-of-pipe treatment. Attaining zero discharge opera
tion has the further benefit of eliminating the problems, cost, and liabilities assoc-
iated with operation under a discharge permit. Economic benefits observed during zero
discharge operation included reduced water supply costs, reduced wastewater treatment
costs improved yield, improved drainage and greater dryer section production. The bene
fits were partially offset by shorter felt lives, increased corrosion control cost, and
process modification cost. No degradation of product quality was observed.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COS AT I Field/Group
Industrial waste treatment, Industrial
wastes, Roofing, Materials recovery, Paper
mills, Paper industry, Water conservation
Wastewater treatment,
Water reuse, Slime contro}.
Paper quality, Physical
treatment, Paper
reprocessing, Product
recovery, By-product
recovery, Corrosion contrdl
13B
18. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
93
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
85
*U.S. GOVERNMENT PRINTING OFFICE: 1977-757-056/5495
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