&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-78-150
July 1978
Research and Development
Water Reuse
in a Wet Process
Hardboard
Manufacturing
Plant
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental 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.
-------
EPA-600/2-78-150
July 1978
WATER REUSE IN A
WET PROCESS HARDBOARD MANUFACTURING
PLANT
by
Richard L. Coda
Superior Fiber Products, Inc.
Superior, Wisconsin 54880
Grant No. S-804306-01
Project Officer
Victor Gallons
Food and Wood Products Branch
Industrial Environmental Research Laboratory
Corvallis, Oregon 97330
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publi-
cation. 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 endorsement
or recommendation for use.
-------
FOREWORD
When ertergy 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
control methods be used. The Industrial Environmental Research Laboratory-
Cincinnati (lERL-Ci) assists iii developing and demonstrating new and impro-
ved methodologies that will meet these needs both efficiently and econo-
mically.
Hardboard mills generally discharge large quantities of biological,
oxygen demand (BOD) causing materials to the receiving waters near where
they are located. Biological treatment of these BOD causing materials is
only partially effective and is expensive. This report describes how one
mill dramatically reduced their BOD and suspended solids discharge by re-
using all of their process waters. Other hardboard mills should find the
material Contained in this report useful to greatly reduce the quantity
of BOD causing materials being discharged from their mills.
For further information regarding this report contact H. Kirk Willard,
Food and Wood Products Branch, Industrial Environmental Research Laboratory-
Cincinnati, Ohio 45268.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati, Ohio
111
-------
PREFACE
With increasing pressure from public concerns, and with local, state,
and federal agencies promulgating new and tougher water pollution regulations,
a successful manufacturing operation must find methods of economically re-
ducing pollution loads to the environment. The wastes discharged by Superior
Fiber Products, Inc., a wet process hardboard manufacturing plant, were
colored and carried a high pollution load. This discharge into Superior Bay
of Lake Superior was to be stopped or greatly reduced. Superior Fiber's
aim was to maintain the quality of Lake Superior.
In searching for ways to reduce the pollution load to Lake Superior,
numerous known treatment methods were evaluated both in Superior Fiber's
laboratory and in other laboratories. Both biological and physical chemical
methods were looked at and plants with interesting processes were visited.
All methods evaluated were either economically unfavorable or involved too
many unsolved problems. The severe winter climate in Wisconsin posed problems
with biological treatment processes which are successful in1 warmer climates.
Because the waste treatment systems investigated were not applicable to
Superior Fiber's situation, efforts were focused in the direction of white
water (process water) reuse and mill close-up.
All close-up attempts in the past resulted in a severe drop in product
quality along with other operational problems. In October of 1974 a totally
closed white water system in operation at the Isorel hardboard mill iff
Casteljaloux, France, was located. Representatives of Superior Fiber Products
visited the mill and found the system to be compatible with the require-
ments of the Superior Fiber mill. On September 5, 1975, an agreement was
signed with Isel S.A., a division of Isorel which deals only with the closed
white water system, further referred to as the "Isel process", for detailed
information on how to go about the close-up and avoid the product quality
problems that were experienced in the past.
IV
-------
ABSTRACT
Superior Fiber Products, Inc., a manufacturer of smooth on one side
wet process hardboard, undertook a project to eliminate any discharge of pro-
cess water through a program of increasing the reuse of process water until
there was none left fo discharge. Before implementation of the process
water reuse Superior Fiber was>.discharging around 757,000 I/day of white
water with a BODs loading of 2,710 Kg/day. Today they are discharging
about 18,925 I/day with a'loading of about 340 Kg/day BODs. This residual
flow consists of wash water and a small amount of white water leakage from
pump seals. Further work will be done to eliminate or reduce this remaining
discharge.
White water total solids concentration went from 1% to about 7% when
white water was reused. Physical properties of the hardboard were watched
closely during the close-up process. Board strength was equal to or better
than the strength before cTosing the system. Water absorption and linear
expansion of the board increased after close-up. Close-up of the processes
reduced chemical usage, both in the board manufacturing and in wastewater
treatment. Production was reduced in the early phases of the close-up due
to then unsolved production problems. The stock drained slower. Altera-
tion of the formation line brought production to its normal level. Some
of the drawbacks of the closed system are a darker board color and overall
reduced cleanliness of the mill. The highly concentrated white water leaves
much more residue when spilled or spattered. This report was submitted in
fulfillment of grant S-804306-01 by Superior Fiber Products. This report
covers a period from 1-23-76 to 7-22-77 and was completed as of 5-12-78.
-------
CONTENTS
Foreword iii
Preface iv
Abstract v
Figures viii
Tables x
Acknowledgments xi
1. Introduction 1
2. Conclusions 2
3. Recommendations 4
4. Process Description and Modifications 5
Process description 5
Process dates, - 7
Mill modifications 8
Water balance 13
Cost comparisons 15
5. Effects of Closure on the Process
and Product quality 17
White water characteristics 17
Effects of process water reuse on
white water properties 21
6. Results and Discussion 27
Product quality 27
7. Effluent Characteristics 38
References 42
-------
FIGURES
Number Page
1 Process flow diagram of existing production facilities. . , 6
2 Diagram of cyclone to remove steam from fiber ....... 10
3 Process flow diagram and water balance for a totally
closed system ...................... 14
4 Correlation between monthly average total solids
and monthly average dissolved solids ........... 18
5 Correlation between monthly average total solids
and monthly average suspended solids ........... 20
6 Percent dissolved solids tn the white water as a
function of the discharge flow .............. 22
7 Percent suspended solids in the white water as a
function of the discharge flow .............. 23
8 White water BOD concentration as a function of the
discharge flow ...................... 23
9 Average white water pH ................... 24
10 Average white water total acidity ............. 25
11 Average temperature of slurry ............... 26
12 Hardboard MOR as a function of the white water
total dissolved solids ........... ....... 28
13 Resin usage as a function of the white water
total dissolved solids .................. 29
14 Board water adsorption as a function of the
white water total dissolved solids ............ 31
15 Linear expansion of the board as a function of the
white water total dissolved solids ....... ..... 32
vm
-------
Number
16 Wax usage as a function of the white water
total dissolved solids 33
17 Board density as a function of the white water
dissolved solids 34
18 Hot press stainless steel plate life as a function of
white water total dissolved solids and pH 36
19 Polymer usage 38
20 BOD discharged as a function of process water discharge . . 40
21 Suspended solids discharged as a function of
process water discharge 41
IX
-------
TABLES
Number Page
1 Chronological Waste Load Reduction 8
2 Mill water Balance 13
3 Itemized Cost for the Closed Water System .... 15
4 Internal Process Equipment for Zero Discharge . . 16
-------
ACKNOWLEDGMENTS
The firm of Isel S.A., B.P. 25, 47700 Casteljaloux, France, was in-
strumental in adoption of the closed system, in project engineering, and
in guiding the staff through to completion of the project. Mr. Bernard
Marechal, Director, and Mr. Stig Selander, Marketing, are particularly
acknowledged with sincere thanks.
The cooperation and assistance of the firm of Eder, Connors and As-
sociates of Long Island, New York, are gratefully acknowledged with parti-
cular debt to Mr. Leonard J. Eder.
The success of close-up and ensuing improvement in Lake Superior water
quality were achieved in spite of severe technical difficulties. The dif-
ficulties proved surmountable with intense effort by engineering and ma-
nagement staff of Superior Fiber Products, Inc. The support ,of the project
by the U.S. Environmental Protection Agency and the help of Mr. Victor
Gallons is gratefully acknowledged.
-------
SECTION 1
INTRODUCTION
Superior Fiber Products, Inc., undertook a project to eliminate any
discharge of process water through a program of increasing reuse of pro-
cess water until there was none left to discharge. Reuse of water was pre-
dicated by a close watch of the mill water balance and the elimination of
all fresh water inputs to the system. Furthermore, to achieve a closed
water system in this mill, evaporation of process water was encouraged.
Evaporation of process water served two objectives, to remove excess water
from the process, and to remove excess heat from the process. Evaporation
was encouraged in the cyclone following primary refining by not using a
water spray in the cyclone and at the hot press.
-------
SECTION 2
CONCLUSIONS
Based upon eight months of full scale investigations on white water
close-up, the following conclusions were drawn.
One hundered percent white water reuse is technically and economi-
cally feasible in a wet process SIS mill. Balancing incoming water with
water evaporated in the process is a necessity for close-up. Board strength
can be maintained or improved when close-up is instigated, although some
problems have to be overcome. Less resin is required after close-up so
chemical costs are lower. There is no odor problem.
Prior to close-up, white water had a pH ranging between 3.5-4.0.
Since close-up it is necessary to maintain a range of 5.0-5.5. Operation
at a higher white water concentration resulted in shorter stainless steel
plate life due to solids depositing on the plates and the resultant hard-
board surface irregularities. When the pH was raised to 5.0-5.5 the de-
posits formed much more slowly. Stainless steel press plate life is now
equivalent to that normal before close-up.
The white water temperature will continue to rise to an intolerable
level as process water is reused unless some control is put on it. The main
control is at the cyclones. Allowing steam to escape to the atmosphere
at the cyclone rather than condensing it into the process water reduces
the heat input into the white water system. Heat exchangers are also used
to remove heat from the white water.
White water storage capacity must be at least equal to stock storage
capacity and must also be kept in reasonable balance. White water dissolved
solids concentration will increase as more process water is reused. The
final concentration will depend on solubility of raw material, amount of
steaming at grinding section, evaporation at press, and fresh water addi-
tions to the system. The white water concentration can be controlled quite
precisely through metered additions of fresh water when partial close-up is
being practiced.
The ratio of total dissolved solids and BOD concentrations to total
solids concentrations remains constant. No appreciable increased biological
growth or plugging of piping systems occurred from increased white water
concentration.
-------
Stock drainage becomes slower as the white water total solids concen-
tration increases. A coarser forming line screen increases drainage upon
close-up. This coarser screen also helps in reducing the moisture content
of the mat going to the press.
Hardboard production did not decrease significantly because of the
closed system.
There are no hidden secrets or totally new techniques in the Isel pro-
cess and no extra personnel are necessary. Capital and operating costs for
the close-up system are lower than for conventional wastewater treatment faci-
lities. Closure of the hardboard mill's water system resulted in additional
power requirements for pumps, agitation, filters, etc., but power costs
would have increased with conventional biological treatment.
The board color has -a tendency to become darker and blotchy looking,
but can be controlled by more careful operation of the press and forming
line. Much more residue is left from spills, leaks, etc., therefore the
plant equipment has to be cleaned more often.
-------
SECTION 3
RECOMMENDATIONS
Eliminating the discharge from a hardboard mill by process water reuse
may have several discouraging pitfalls. A hardboard mill desiring to take
the closed water system approach to reducing or eliminating their water
pollution problems should heed the following recommendations to avoid some
of the pitfalls that may be encountered.
Maintain a 100% positive attitude that the closed system will work
and the problems experienced can be solved. Strong upper management
commitments are a necessity.
Make all employees aware of what you are going to do, how you are
going to do it, and why you chose this method. Keep them periodically
up-to-date on what is happening, and if any changes are made, make
sure the people involved know about it and what to do differently.
Mill employees have control of large quantities of water and their
cooperation is a necessity in a successful close-up.
Make sure you have a handle on all incoming and outgoing water, install
ing flow meters where necessary. Keep a daily flow balance sheet.
Make changes slowly and observe results; proceed in a step by step
procedure that has been well thought over. Do not close all the
valves at once or major problems may occur.
Take maximum advantage of any means of evaporating process water.
This does not mean buying evaporators but using your present equipment.
It is always much better to have a negative water balance than to have
excess water.
Try to maintain forming machine temperature at a maximum of 51 °C
(125°F). At higher white water temperatures resins set prematurely
resulting in board strength losses.
i°" chi!e-W?ter P? ValU6S tends t0 result in builduP of deposits on the
press stainless plates and in boards sticking to the plates in the press
" ^ ^^^ ** th« ^
0.
and as
-------
SECTION 4
PROCESS DESCRIPTION AND MODIFICATIONS
Superior Fiber Products, Inc. produces approximately 140 tons/day
of hardboard for use in the automotive, television, furniture and construc-
tion industries. Located in Superior, Wisconsin, the mill is on the shore of
Superior Bay and discharges its wastewater via five settling ponds into
this bay.
The hardboard is produced from wood fiber pulped from locally cut aspen
logs. The mill production process is classified as a "wet smooth one side
(SIS) process" designed to utilize water in the manufacturing system.
PROCESS DESCRIPTION
The production of hardboard basically involves reducing trees to
fibers, and reforming these fib'ers into boards with new properties not
available to the raw unprocessed wood. Chemical additives are mixed with
the pulp prior to board formation to increase strength, water resistance,
and to add other desirable qualities.
The process flow diagram is illustrated in Figure 1. The logs, which
are all aspen, are debarked with a rotary ring debarker. The bark, along
with hardboard scrap, is burned in a waste fired boiler to produce process
steam.
The debarked logs are then sent to the chipper where they are reduced
to flat chips about 3/4-inch square. The chips are then fed into chip bins.
From the chip bins the chips are fed via a screw feeder to a vertical pre-
heater or cooker where they are steamed by 7.03 Kgf/cm? (100 psi) steam for
2-3 minutes. The preheater condenses steam onto the chips. The screw feeder
squeezes water out of the chips. This water enters the white water system.
After the preheater, wax is added to the chips which then enter two
600 HP defibrators or primary grinders for reduction to fiber. The fiber
is then blown to two cyclones for steam release and cooling. No water is
added to these cylones. Almost all other mills add water to the top of the
cyclone to prevent bridging and plugging; the added water condenses the steam
which causes higher white water temperatures and an additional source of
water to'the system. Superior Fiber's process permits the maximum amount
of steam to escape.
-------
BARK TO
WASTE BURNER
STEAM I
STEAM-
CORD
WOOD
DEBARKER
PRE-HEATER
^EVAPORATION
MACHINE
CHEST
ALUM, WAX
ACID, RESIN
o
PRESS
Ol
ooooooooo
PRESS
SQUEEZE
SUCTION
BOXES
STOCK CHEST
DEFIBERATOR
CYCLONE \/
SQUEEZE OUT
WATER
RAFINATOR
WHITE-WATER
CHEST
OVERFLOW
1
r
SETTLING
LAGOONS
DISCHARGE
Figure 1. Process flow diagram of existing production facilities.
-------
After the cyclones, white water is added to the fiber to bring the
consistency to 10-20% and then is screw fed to two raffinators or secondary
grinders for final fiber preparation. At this point white water is added
to bring the pulp concentration down to 4% solids. This pulp is then
stored in stock chests. Sulfuric acid is added at times to these chests.
No alum is used at Superior Fiber Corporation. When the pulp is removed from
the stock chest more white water is added to bring the consistency to between
2.0-2.5%.
The stock, with phenolic resin added, is sent to the forming machine
where the fiber is laid down in mat form. Water is sequentially removed
from the mat by gravity, suction, and pressure, and is returned to the white
water system. The mat (wet-lap) is then trimmed and sent to the press.
The moisture content is still about 65-70% (total weight basis) prior
to pressing. The press, operating under high temperature and pressure ,
squeezes out water until the wet-lap is about 45% moisture. This remaining
moisture is then evaporated during pressing. When the board is dry, it is
removed from the press and sent on for humidification and finishing which
are both water free operations.
PROCESS DATES
Superior Fiber has gone through a long process in reducing the pollu-
tion load to Lake Superior. Listed below is the sequence of events that
led to the implementation of a no discharge process.
February 21, 1968, D.N.R. issued order #1-68-27 requiring that Superior
Fiber Products process water be treated to meet state water quality stan-
dards by October 1, 1970.
August 14, 1969, advised the Mayor of the City of Superior that joint
municipal treatment was not in the best interests of the company.
January 1970, separation of all cooling waters from process waters.
June 1970, visited plants in Finland and Sweden to investigate water
treatment methods.
July 1970, forming line spray water system completely recycled.
July 15, 1972, the Company entered into a stipulation agreement with
the State D.N.R. requiring 85% BOD removal by December 1, 1974, with in-
terim dates.
August 18, 1972, State D.N.R. approved plans of waste treatment fa-
cility. Completion date moved to August 1, 1973, with 60% BOD removal,
90% suspended solids.
May 1973, met August 1st requirements by debarking, polymer addition,
and some close-up.
-------
September 28, 1973, EPA issued NPDES permit number WI 0002798 to
Superior Fiber.
July 1975, plans and specifications sent to State D.N.R. outlining how
we would meet the EPA permit by close-up. The plans were accepted.
September 1975, Superior Fiber entered into agreement with Isel to close-
up the process water system.
November 1975, applied for $100,000 grant from EPA. Grant approved
early in 1976.
Each step resulted in some reduction of waste loads discharged to
Lake Superior. Table 1 lists the chronological waste load reduction.
TABLE 1. CHRONOLOGICAL WASTE LOAD REDUCTION^1)
Date
4-1-72
6-20-72
8-30-72
11-30-72
5-30-73
7-1-77
Method
Existing
Reduce chip cook
close-up
lagoon upgrading
Debarking
Polymer
More close-up
Isel
Kg/ day
20,350
13,150
8,160
4,080
2,890
(BOD5#/day)
(44,865)
(29,000)
(18,000)
(9,000)
(6,380)
(550)
Kg/day
9650
3630
1360
450
285
61
(SS #/day)
(21,278)
(8,000)
(3,000)
(1,000)
( 630)
(135)
MILL MODIFICATIONS
To attain a no discharge mill, modifications of the process equipment
were required. Some of these modifications were to allow greater control
of the mill water balance, while others were made to maintain the product
quality. These modifications are discussed below.
Pulping Section
Digester Feed Screw--
The digester is a steaming vessel used before the pulping section which
softens the chips for grinding. This steaming vessel is capable of opera-
8
-------
p
ting between 5.62-10.55 Kgf/cm (80-150 psi) steam pressure, but is maintained
at 7.03 Kgf/cm2 (100 psi). In order to maintain the pressure in the vessel
the chips enter as a continuous plug formed by a screw feeder. As the chips
are compressed, wood water is squeezed out. This water discharge varies
with the wood moisture content, anywhere from 0 to 34 l/min(0 to 9 gal/
min). This water has a BOD5 average of 13,000 ppm and passes over a side
mill filter to remove shives and chips before entering the white water sys-
tem. Previously the screw water went to the discharge without any screening.
Cyclone—
Before adding the cyclones, Superior Fiber used both pressurized pri-
mary and secondary refining with no steam escape. Water was added to the
pulp between the primary and secondary refiners to control the consistency
in the secondary refiners. This water addition would condense the steam
into the pulp resulting in an addition of both heat and water to the pro-
cess. The condensing steam added approximately 75,700 liters (20,000 gal)
per day of water to the system).
Installation of the cyclones has reduced the white water temperature
by 11-17°C (20-30°F) and has resulted in not only the release of the 75,700
liters (20,000 gal) per day of steam added to the preheaters, but also
in an additional 13,250 liters (3,500 gal) per day of water entering
the system as wood moisture.
These cyTones are a very Important part of the closed system. The
principle of operation is that the fibers enter the top of the cyclone and
immediately create a vortex. The fiber follows the cyclone wall downward
to the bottom. The steam meanwhile is separating from the fiber and es-
capes out the top of the cyclone. Immediately after the fiber falls out
the bottom of the cyclone, water is introduced and the resulting pulp is
then transported by screw conveyor to the secondary grinders as shown in
Figure 2.
It is very important that the cyclone and cyclone exhaust pipes be
kept clean of fiber build-up. They are cleaned at least every two weeks.
Main Shaft Sealing Waters-
Fresh water used on the packing seals on primary grinders was replaced
with steam. Savings accrued is of about 7570 liters (2,000 gal) per day per
machine. Fresh water was completely shut off on the secondary grinders
reducing water usage by an additional 7570 liters (2,000 gal) per day.
Miscellaneous--
Steam flow indicators were added to the preheaters to measure amount
of steam being added so that steam use could be minimized. Stock tempera-
ture indicators were also added after secondary grinding consistency. The
overall grinding procedure was modified to optimize the cyclone efficiency
and temperature control. All the power possible was applied before the
cyclones to further heat the stock, thereby enabling more evaporation in
the cyclones.
-------
K\\\\\\\
STEAM
FIBER FROM
\ \ V \ \ \ \
\\X\\\\\
,1,
FIBER TO
PRIMARY
GRINDERS
•WATER SPRAYS
SECONDARY GRINDERS
Figure 2. Diagram of cyclone to remove steam from fiber.
10
-------
Forming Section
Forming Machine Screen Cleaning--
Screen sprays were mostly eliminated by use of a vacuum screen cleaning
arrangement. The vacuum system was chosen over white water sprays because
it is more efficient.
Forming Machine Screen--
The screen open area had to be increased from 25% open to about 50%
open to facilitate the slower draining stock.
Machine Cleaning--
The forming machine was previously cleaned with low pressure high volume
fresh water but has been changed to high pressure low volume fresh water.
Vacuum Boxes--
The forming line vacuum dewatering previously consisted of moving
"rotobelts" over vacuum boxes. Fresh water was used to lubricate the
rotobelts. These rotobelts have since been removed and replaced with sta-
tionary perforated plastic tops which need no water for lubrication and
last longer.
White Mater and Stock Systems
Three additional vats of 75,700 liters (20,000 gal) apiece were added to
the white water system. This gives the mill a total of five white water
vats and four stock vats. The storage capacity is necessary to avoid white
water overflows due to unbalanced conditions between the grinding section
and forming line. Agitators were installed in all white water vats to pre-
vent settling out of solids. Level indicators were installed in all vats
including stock vats to assist operators in preventing overflows.
Stock and White Water Pumps—
Fresh sealing water has been shut off on many pumps. These pumps now
run with no sealing water, permitting water savings amounting to approxi-
mately 18,900 liters (5,000 gallons) per day.
Hot Press Section
Hot Press Squeeze Out Water—
This water was discharged directly to the lagoons but is now pumped
back to the white water system after passing through an oil skimmer and
down hill screen to remove large pieces.
Transport Screens--
Transport screens are now cleaned and changed every eight hours where
before they were cleaned and changed every twenty-four hours.
11
-------
Press Cleaning—
A high pressure pump has been purchased to keep the press clean.
With the closed water system the residue from evaporation builds up much
more rapidly than with an open system. The previous method of cleaning,
which was scraping the press about every thirty days, was not sufficient.
A high pressure water spray is now used and cleaning is done once a day.
Press Operations-
Experience has shown it to be necessary to reduce press temperature
from about 204°C (400 °F) to 196°C (385°F). The temperature reduction
was required to avoid discoloration and sticking in the press. As a result
press cycles are a little longer. The press pressures have not been affected.
Miscellaneous
Water Sampling and Recording--
Before the close-up, wastewater samples were composited proportional
to flow only at the lagoon discharge to Superior Bay. In addition to
the lagoon effluent sample, composite samples are now taken of total mill
discharge to the lagoons and of the white water system. Prior to close-up,
flow was recorded only at the lagoon discharge to the bay, but no additional
white water overflows nor total mill discharge to the lagoons were recorded.
All flows were measured over 90 degree V notch weirs.
Lagoons—
Prior to close-up, five lagoons were used with a total volume of around
five million gallons. Use of three lagoons has been discontinued leaving
a total volume of around one and one-half million gallons. Eventually
the remaining lagoons may be eliminated altogether. The three lagoons were
filled to prevent possible odor problems in the future caused by the exces-
sively long detention time, as well as for aesthetic reasons.
Debarking—
Tighter controls were put on bark removal to prevent the white water
total solids concentration from becoming too high.
Phenolic Resin--
The resin addition point was changed from the defibrator section to
the forming line area. Mill trials showed that addition of resin closer
to the formation line improved the board strength. The resin was also
diluted 3:1 with water before close-up, but it is now used as is (42$ solids),
Sulfuric Acid-
Addition of sulfuric acid to the process was discontinued after close-
up.
Polymer—
Polymer addition to the effluent prior to the settling lagoons to
settle waste waters, suspended, and colloidal matter has been discontinued.
12
-------
WATER BALANCE
In order to achieve no discharge, the water balance was carefully con-
trolled. All unnecessary water additions were eliminated and process water
was used in place of fresh water wherever possible. When this high degree
of water control had been achieved, the major sources of water input to the
process were to the water contained in the wood and the water put into the sys-
tem as steam. Other fresh water uses were minimal. Table 2 shows the water
input to the system.
Removal of water from the system by evaporation is very important.
There is more water entering the system in the wood than there is in the
product. Wood moisture is around 50% total weight basis while the hardboard
leaves the process bone dry. All the water entering the system in the wood
plus all the miscellaneous water additions must be evaporated from the sys-
tem to achieve a zero discharge.
Evaporation takes place at two major points, at the cyclone and at
the hot press. Table 2 shows how much water leaves the process at what
location. When the press closes, about 57% of the water is squeezed from
the mat. The water remaining in the mat is evaporated. The amount of water
evaporated in the hot press is less than the amount of water coming into
the process in the wood. There the amount of water being evaporated at
the cyclone must be greater than the amount of steam added to the process.
This extra evaporation of water" at the cyclone is effected by utilizing
the energy put into the primary refiner to evaporate wood water at the
cyclone. Figure 3 shows the water and energy balance for the mill.
When the amount of water being evaporated in the process is the same
as the water input to the process, there is no discharge.
TABLE 2. MILL WATER BALANCE
Source
Water Input
Kl/KKg Gal/Ton
Board
Exit
Total
1.45
346.4
Water Out.
Kl/KKg Gal/Ton
Board
Wood water
Steam condensate
Pump sealing
Wet- lap saws
Resin
Misc.
0.80
0.45
0.06
0.12
0.01
0.01
193
107
14.3
28.6
2.1
1.4
Cyclone evap.
Press evap.
Pump leaks
Misc. evap.
0.60
0.79
0.03
0.03
143
189
7.1
7.1
1.45
346.2
13
-------
CHIPS
STEAM
S:0.45
at I65°C
E:237
0.17 KWH
E:I45
RESIN
WiO.Ol
PM.OO
| W:0.80
op'Otruu ccm
ot/KtW rttu
iP:I.OO E
W:0.62
TOOK
\S\J\Jl\
1
nFFIRFRATOR
L» Q r i DC.r\M i \jr\
IP: i.oo
W:0.53
5:0.54
OVPI r»MF
L/TL»1_L/I\J C.
ip: 1.00
W:0.39
S.'O.OS
r* A n m AT^Q
RArlNATOR
I
C'T/'N/*!/ r*LJCOT
STOCK LMtbl
J
^
OIIPTIOM RHYFC
OUU 1 lUlM DUAC.O
1
urvT DDtrcc
MU 1 rr\ too
1:75
E:5I6
j
S:0.60
E:383
Etl33
-^ *
W:O.I8
LEGEND
P:KKg pulp/KKg board
W.KI water/KKg board
S:KKgsteam/KKg board
E: Kcal energy/KKg board
STEAM
^
\
^ WHITF WATER CHEST
k
STEAM
^
BOARD
Figure 3. Process flow diagram and water balance for a
totally closed system.
14
-------
COST COMPARISONS
Capital costs for a conventional biological treatment system were esti-
mated to be about $608,600 in July 1975, by Leonard J. Eder Engineers (1).
The system consisted of a primary settling lagoon, followed by an aerated
lagoon, followed by a final settling lagoon. The system was designed to
handle 938,800 I/day (248,000 gal/day) or about 7.45 1/KKg (1772 gal/Ton)
production.
The cost of the totally closed water system as of May 1977 was $620,644.
This cost includes a $111,500 contract to Isel Corp. of France for informa-
tion on how to set up and operate a closed cycle hardboard mill. The itemized
costs are listed in .Table 3.
TABLE 3. ITEMIZED COST FOR THE CLOSED WATER SYSTEM
Item Cost
Equipment $285,136
Installation labor (including
fringes) 125,273
Isel , 115,000
Installation (outside contractors) 82,114
Supplies 13.121
Total $620,644
Grant -$100,000
Net $520,644
The estimated costs for each piece of equipment installed are listed
in Table 4.
Annual operating costs for conventional treatment would have been
about $60,300. We estimate annual operating costs for the Isel system to
be: Power, $2,000; Maintenance, $3,000; Supplies, $1,000; and Chemicals
for cleaning, $3,000; or a total of $9,000.
15
-------
TABLE 4. INTERNAL PROCESS EQUIPMENT FOR ZERO DISCHARGE
Item Description Estimate Cost
1
2
3
4
5
6
7
8
9
Cyclones (2)
White water chests
Agitators
White water pumps
Piping
Drum screens
Instruments and control equipment
Spray cutting arrangements
Contingencies
$ 40,000
25,000
20,000
35,000
40,000
40,000
30,000
20,000
25,000
$275,000
16
-------
SECTION 5
EFFECTS OF CLOSURE ON THE PROCESS AND PRODUCT QUALITY
As water reuse is increased in a hardboard mill, water proper-
ties are changed. These changes in white water properties result in changes
in product quality and production methods. A close record of the changes
in white water characteristics and the hardboard quality were kept. Pro-
blems in production and board quality, and their solutions, were related
to white water properties.
WHITE WATER CHARACTERISTICS
Sampling
Samples from the white water system are taken from a common in-line
water valve. They are taken twice every eight hours and are composited
daily. These samples are then stored at 35-40°F in a refrigerator until
testing. Some tests require grab samples and immediate testing.
All testing is done in accordance with the applicable procedure set
forth in "Standard Methods" 13th Edition (3).
Discharge Flow--
All discharges out of the white water system are metered over a 90
degree V-notch weir with a Leopold-Stevens level recorder. The system
is designed so that any overflow from the white water system will always
overflow from the same vat. On occasions, certain systems have malfunc-
tioned causing discharges other than the normal vat overflow. These acci-
dental discharges are then recorded by another 90 degree V-notch weir and
level recorder. This weir measures total mill discharge just before it is
pumped to the lagoons. Samples are also taken proportional to flow there.
Total Solids-
Total solids is tested every four hours. This test provides data
used as an indicator on close-up performance. The reason total solids
was chosen instead of the more commonly used dissolved solids is that
it is faster and easier. There is a good correlation between total solids
and dissolved solids (Figure 4).
17
-------
oo
E
to 40000
Q
O
CO
O
LU
32000
co 24000
CO
-------
Dissolved Solids--
The dissolved solids of the white water is tested every 24 hours.
Many of the operating and board quality problems can be related to the white
water dissolved solids.
Suspended Solids--
The suspended solids of the white water is tested every 24 hours. The
white water suspended solids concentration is closely related to the total
solids concentration as shown in Figure 5.
Other Parameters--
The biochemical oxygen demand of the white water is monitored every 24
hours and the pH is^monitored continuously. Total acidity is tested
every 4 hours. The*white water temperature is monitored continuously.
Parameters Affecting White Hater Properties
Extraneous Factors--
Numerous factors, other than increased process water reuse, can affect
the properties of white water. Some of these factors are discussed below.
White water temperature--A high white water temperature will tend to
dissolve more soluble material from the pulp, resulting in a slightly higher
white water concentration. A lab test has shown that a 8.3°C (15 °F) rise
in stock temperature will give a 0.5% increase in white water concentration
in one hour. This test was performed on stock with a high white water total
solids concentration (8%) to start with; therefore, white water temperature
might have a more dramatic effect at lower concentration levels.
Cooking Time--Cooking time is the length of time chips are subject
to steam pressure in the vertical preheater. Longer cooking times result
in more solids being dissolved out of the wood. The cooking time is main-
tained by adjusting chip level in the preheater to correspond with different
speeds of the grinders. Cook time is held constant at about 2.5 minutes
and, therefore, does not tend to vary white water concentration.
Cooking Pressure—Changes in the preheater steam pressure will vary
white water dissolved solids concentration. Higher pressures result in
more solids being dissolved from the wood. Continuous pressure of 7.03
Kgf/cm2 (100 psig) is maintained; therefore, this factor is not a variable
in the'system.
Bark Content—The amount of bark that enters the system could also
have an effect on white water concentration. Bark is more soluble than
wood. Higher bark content in the raw material would result in a higher
white water total solids concentration. All logs are debarked and a maxi-
mum of 1.5% bark is allowed in the chips. This variable is controlled
efficiently.
19
-------
rsa
o
14000
^ 12000
en
Si 10000
8000
C/5
in
i-
o
6000
4000
2000
0
o ex,
i
o
o
o
(O
o
o
o
CJ
SUSPENDED SO LIDS =.2028 TOTAL SOLIDS
O
o
o
GO
o
o
o
o
o
o
o
ro
O
O
O
(0
ro
O
O
O
CM
O
o
o
CO
o
o
o
si-
If)
o
o
o
o
MONTHLY AVERAGE TOTAL SOLIDS mg/l
Figure 5. Correlation between monthly average total solids and
monthly average suspended solids.
-------
Cyclone Steam Removal Efficiency—The ability of the cyclone to remove
steam from the pulp affects the temperature of the white water. Greater
steam removal at the cyclone results in less steam condensing into the white
water and, hence, less heat addition to the process and lower process tempera-
tures.
EFFECTS OF PROCESS WATER REUSE ON WHITE WATER PROPERTIES
Increasing the reuse of white water and press pit water changes the
properties of the white water. To follow the changes in white water pro-
perties and any possible product quality or operational problems, the amount
of water reuse was increased slowly, in steps. To maintain a steady refer-
ence, the white water total solids was controlled by the addition of fresh
water. For example, total solids of 2.0%-2.5% were run for two to four
weeks and then raised to 2.5%-3.0%, etc. This procedure has performed
efficiently. Reduction of fresh water additions reduced the quantity of
water discharged. The parameters discussed below are in terms of the amount
of water discharged from the mill.
Dissolved Solids
Figure 6 shows that when the quantity of water discharged is smaller,
the concentration of dissolved solids is larger. The concentration of dis-
solved solids in the whitewwater and effluent increases rapidly when the
last bit of discharge is eliminated.
Suspended Solids
As less water was discharged, the concentration of suspended solids in
the white water remained constant at about 0.3% until less than 1.0 Kl/KKg
water was discharged. At less than 1.0 Kl/KKg discharge, the dissolved solids
concentration rose rapidly to 1.3% dissolved solids at zero discharge as shown
in Figure 7.
Biochemical Oxygen Demand (BOD)
The BOD5 of the white water has continued to climb along with white
water solids. Figure 8 illustrates this steady climb in terms of the quantity
of discharge. BOD concentrations have increased about tenfold as the amount
of discharge was decreased.
White Water pH
Two conditions exist which contribute to the acidic nature of the
vhite water. The first is the hydrolysis of acetyl groups present in the
wood furnish which causes the formation of acetic acid during the preheating
of the chips. This source of acid or hydrogen ions is relatively constant
because of debarked aspen chips and uniform cooking time. The other source
is the addition of sulfuric acid to the process to precipitate the phenolic
resin. Sulfuric acid usage was reduced as the amount of recycle was increased
and was discontinued in the last two months of the study. Before close-up,
21
-------
the pH was between 3.5 and 4.0. Today a pH between 5.0 and 5.5 is maintained,
although at times it has gone as high as 6.2. In the past, management felt
that good strong hardboard could never be made at such a high pH. Figure 9
illustrates white water pH for the last year.
12345
DISCHARGE KI/KKg
Figure 6. Percent dissolved solids in the white water as a
function of the discharge flow.
22
-------
o
O
I 23456
DISCHARGE KI/KKg
Figure 7. Percent suspended solids in the white water as a function of the
discharge flow.
40
Figure 8.
456
DISCHARGE KI/KKg
White water BOD concentration as a function of the discharge flow.
23
-------
3
2
T 1 1 T
T T
J I I
J I I I I I I I I
CD
LJ
LJ_
a:
o_
1976
Figure 9. Average white water pH.
1977
Total Acidity
There seems to be no definite trend in total acidity as the effluent is
decreased, as illustrated by Figure 10. What can be seen is that it varied
considerably when sulfuric acid was used, but has since leveled off and
slowly climbed along with other parameters.
White Water Temperature
As the quantity of water discharged decreases, the quantity of heat that
accompanies it decreases. Heat continues to be added to the stock due to the
cooking and refining of the chips. This results in an increase in the tem-
perature of the stock unless the temperature is controlled.
In this system stock temperature is controlled basically three ways.
One way is to add fresh water to the system to cool it; however, with a
closed system this method is not available. Another way is with the heat
exchanger in which white water is cooled with bay water. This exchanger
has been running at capacity so there is no added help there. The last
and most important control for use in a closed system is regulation of the
amount of heat entering the white water system from the grinding section.
Much of the heat released from the grinding section is contained in the
steam escaping from the cyclone. When this steam is condensed by water addi-
tion to the cyclone or refiners, as was done prior to the system close-up,
the heat is added directly to the white water. The amount of steam passing
24
-------
from the grinding section to the white water is carefully controlled. More
steam passage results in higher white water temperature. This steam
entering the white water system is controlled by the blow-valve (the valve
which passes the fiber from the pressurized primary grinder to the cyclone)
and the cyclone efficiency. This means optimum conditions must be kept at
the grinding section along with clean cyclones. If not, too much steam
will condense into the white water and the temperature will climb. Figure 11
shows the stock temperature throughout the recycle effort.
1976
1977
Figure 10. Average white water total acidity.
25
-------
80
70
60
50
O
0 40
30
20
10
0
i
i
i
O
=> ID
~3 ~3
Q.
UJ
CO
O
O
>
O
O
UJ
O
CD
UJ
U_
I
or o:
< Q.
s <
1976
1977
Figure 11. Average temperature of slurry.
26
-------
SECTION 6
RESULTS AND DISCUSSION
PRODUCT QUALITY
Strength Properties
One of the major questions dealt with before deciding to use the Isel
system concerned board strength. In all previous close-up attempts, serious
strength problems appeared. Other industry and research leaders also
doubted if high strength standards could be met with high white water dis-
solved solids concentration as characteristic of the closed system. The
Isorel Mill in France has somewhat lower strength standards than are cus-
tomary here. They also heat treat all their hardboard to give strength,
a process which is not practiced by Superior Fiber. They even had to add
phenolic resin to some of their more critical boards to get the required
strength. After many discussions with Isel, they convinced Superior Fiber
that if strength problems occurred, available technology could provide ready
solutions. After eight months of close-up experience and with a white water
total solids concentration of up to 8.5%, strengths are running slightly bet-
ter than before close-up.
Modules of Rupture--
Modules of Rupture of (MOR) is the strength property most used. It
is tested every two hours in accordance with the applicable test in Part B
of American Society for Testing and Materials (ASTM) D 1037-72a, (a) Stan-
dard Methods of Evaluating the Properties of Wood - Base Fiber and Particle
Panel Materials. It is also referred to as bending strength. As stated
earlier in this report, the MOR has been equal to or slightly better than
before the close-up (Figure 12).
Phenolic Resin--
Phenol -formaldehyde resin, more often called phenolic resin, is used
in the manufacturing of hardboard to impart added strength to the finished
board. Superior Fiber uses anywhere from 0.5% to 1.5% resin (dry on dry)
depending on the type of product. When strength problems occur, resin
usage normally is increased; therefore, resin usage is a good indicator
of strength properties. Figure 13 illustrates resin usage equal to or slightly
less than before, after the close-up.
27
-------
8500
8000
g" 7500
7000
6500
6000
O
O
WHITE WATER TOTAL DISSOLVED SOLIDS %
Figure 12. Hardboard MOR as a function of the white water
total dissolved solids.
Early in the close-up attempt the MOR began to drop off and about
40% more resin had to be added to maintain the board strength. The forming
line temperature had increased to 65-71°C (150-160°F). When the tempera-
ture of the forming line was reduced to 50-52°C (120-125°F) by venting
more steam from the cyclone, the resin usage returned to normal.
Stock or furnish temperature plays a part in MOR results. Hotter
stock temperature tends to pre-cure the phenolic resin before the hot press
resulting in lower MOR values. This phenomenon seems to be more pronounced
with a closed system than with an open system. Stock temperature is now
running cooler than before (Figure 11).
28
-------
175
o
D
•o
O
150
E
CT
O
O
O
LU
100
75
LU
o:
50
o _
o 0 o o
WHITE WATER TOTAL DISSOLVED SOLIDS %
Figure 13. Resin usage as a function of the white water
total dissolved solids.
Resin is purchased containing 42% solid material. Previous to September
1976, the resin was further diluted to a consistency of 14% solids and
86% water. It was added to slurry immediately after coming out of the
refiner. The high solids content in the purchased resin required the addi-
tion of 8330 liters (2,200 gal) of water per day to the white water system.
Higher temperatures of the slurry also caused the presetting of the resin.
After experimenting with several addition points we found that the
addition of the resin just prior to the consistency regulators produced
the best results. The addition here meant that the stock would normally
be on the forming line within 15-20 minutes after resin addition. This
reduced the possibility of any pre-setting of the resin. Finally, using
resin undiluted at 42% solids was tried and found workable.
29
-------
Hot Press Adjustments-
Hot press temperature, time, and pressures have a noticable effect on
the MOR of the hardboard. Although many tests were made changing the press
variables, the same press cycle exists as did before. In an effort to
clear up the surface of the board and to prevent sticking in the press,
press temperatures are between 196-199°C (385-390°F) instead of 204-210°C
(400-410°F).
Water Properties
Various uses of hardboard require that the board exhibit certain de-
grees of water resistance. Tests performed on water properties are ex-
plained below and are also tested in accordance with the applicable test of
ASTM Methods (2). In only a few of Superior Fiber's products is water
resistance critical.
Water Absorption—
The water absorption test is performed every four hours. The board is
submerged in a water bath for 24 hours. The weight of water pick-up is
determined and the water absorption value is calculated. The water absorp-
tion of Superior Fiber's board has increased since the close-up as is evi-
dent in Figure 14. Research is continuing to find a method to bring it
back down. Testing is being done with different types of wax.
Dimensional Stability
Dimensional stability or linear variation is a parameter showing the
expansion or contraction of the board along with plane of the surface.
It is tested in accordance with the applicable procedure in ASTM Methods
(2) with the exception of conditioning. Superior Fiber's test conditions
the board for 24 hours in a 21 °C (70°F) water bath and then for 24 hours in
an oven at approximately 100°C (212°F). This method then gives both linear
expansion and contraction. The dimensional stability of the board has
decreased with the closed-up system as is indicated by the increase in linear
expansion as shown in Figure 15.
Wax Usage
A low grade paraffin wax, often called "slack wax", is used to impart
water resistance to the hardboard. Wax usage varies from 1% to 2% depending
on the type of board being made. Figure 16 illustrates wax usage during
the close-up effort.
Density
Board density or specific gravity has increased slightly as is shown
in Figure 17.
30
-------
40
.o 35
O
I- 30
Q_
a:
o
c/>
Q
< 25
o:
UJ
<
^ 20
15
CD
WHITE WATER TOTAL DISSOLVED SOLIDS %
Figure 14.
Board water adsorption as a function of the
white water total dissolved solids.
Surface Quality
Running with a closed system has resulted in darker board surface.
Due to the high white water concentration, surface defects appear much more
rapidly and are normally much more pronounced than when running with an open
system. Process variables must be closely controlled or unacceptable board
can be produced.
31
-------
40
« 35
^
2
O
CO 30
CL
X
LU
25
~f
LU
^20
I5(
1— 1 I i
^H
O
0
o
o -
o o
0
0
CD O
O
o
— —
1 1 1 1
) 1 2345
WHITE WATER TOTAL DISSOLVED SOLIDS %
Figure 15. Linear expansion of the board as a function of the
white water total dissolved solids.
Color
The board color progressively became darker as the white water concen-
tration increased. The fact that the board is darker is really not a pro-
blem for Superior Fiber because their customers can use a dark board as
well as a light board.
Color variations across a board are sometimes quite extreme. This
color variation is caused by white water evaporation in the hot press where
in some places more white water evaporates than it does in other places.
Upon evaporation this white water leaves a very dark residue. This problem
originates at the forming line.
32
-------
100
80
o
o
D>
60
LU
g 40
O)
D
X
20
O o
O
OQ
0
0 12 3 4 5
WHITE WATER TOTAL DISSOLVED SOLIDS %
Figure 16. Wax usage as a function of the white water
total dissolved solids.
Some areas of the stock contain more fiber than other areas due to
fiber bundles and high stock consistency. When this stock is pressed in
the hot press the white water from the denser areas will tend to flow to
the less dense areas to equalize the density. This water then evaporates
leaving much darker areas. Superior Fiber refers to these areas as dewa-
tering patterns. To illustrate further, a fracture is an actual break or
pulling apart of the wet-lap. With an open white water system this fracture
appears lighter after pressing than the surrounding board simply because it
is less dense. In a closed white water system it will be just the oppo-
site, a very dark area, because the water from the surrounding area enters
this break and evaporates.
33
-------
To prevent this problem the forming line must be watched and monitored
closely, and the wet-lap must be kept as dry as possible before pressing.
Lowering press temperature also helps to some degree. The dewatering patterns
or discolorations always occur predominantly along the edges of the board
because the water from the board has to work its way out the edges.
65
3
O
63
CO
UJ 62
Q
Q
o:
O 61
GO
60
O
O
0
00
0
1
1
1
1
0 I 2345
WHITE WATER TOTAL DISSOLVED SOLIDS %
Figure 17. Board density as a function of the white water
dissolved solids.
34
-------
Roughness
Even before white water close-up, Superior Fiber never produced what
could be called a smooth surface board. Although the board always had a
glossy surface, it generally exhibited an "orange peel" or hill and valley
effect. This was evident by feel and also by sight in the right light.
This inherent property of the board is not any different now after the
white water close-up than before, but to maintain this characteristic it
must be watched and controlled more. Without close control, density blisters
may occur.
This orange peel effect is related to slower draining stock. The
drainage time of the stock increased as the white water concentration
became higher. A fiber solution that used to take 20 defibrator seconds to
drain will now take between 24 and 26 seconds to drain. Therefore, to
compensate for the slower draining stock Superior Fiber now grinds a little
coarser fiber and also runs at a.higher fiber concentration (less water)
on the forming line. The forming line wire was changed from a 30% open to
an approximately 50% open mesh to improve drainage.
Paintability
Superior Fiber also runs a small paint line where they prime some
garage door stock and stock of other limited applications using a simple
roller coater. Paint hold down and drying have not changed between pre-'
close and post-close-up. Because of darker colored board and color varia-
tions, paint hiding is not as good as with the Tighter colored board.
Surface wax tests indicate no lessening in paintability after close-up.
Production Problems
Stainless Steel Plates--
A major concern with the closed system was the length of time the
stainless steel plates could be used before they required cleaning. Isel
advised that they did not see any major change in the life of their stain-
less steel plates; their normal change was every 10 days, much less than
Superior Fiber's usual 30-day interval.
Superior Fiber's initial close-up effort was not a slow procedure.
All fresh water valves were closed and the white water concentration in-
creased rapidly. After about two weeks the white water total solids con-
centration went over 5%. Severe plate shedding problems began to occur.
Plate life as low as six days was experienced. Using a wax emulsion spray
on the surface of the wet-lap helped very little.
The problem of short plate life was resolved by polishing the plates
and maintaining a white water pH between 5.0 and 5.5. Figure 18 illustrates
the effect of pH and total dissolved solids on the plate life. By control-
ling the pH to remain above 5.0, stainless steel plate lives of approximately
30 days can be maintained with white water concentrations up to 7.5%.
35
-------
o
T3
UJ
I]
UJ
H
Q.
4O
35
30
25
20
15
10
3
1 1 i i 1
*
•••
O *
X ^
o
0
— —
D
A
0 IDS = 0.5- 1.0
A IDS =1.0-2.0 °
- DTDS = 2.0-3.0
X TDS = 3.0-4.0
*TDS = 4.0-5.0 D
I i i i I
.0 3.5 4.0 4.5 5.0 5.5
pH
Figure 18. Hot press stainless steel plate life as a function of
white water total dissolved solids and pH.
Other problems exist with the stainless steel plates which can be related
to the closed system. One such problem is build-up of material on the sur-
face of the plates. This is caused by a short wet-lap going into the press
or one that is just about pulled apart. This condition causes the water
being squeezed out of the wet-lap to evaporate on an unused area of the stain-
less steel plate, leaving a deposit. This deposit then has to be scraped
off the plate or the board produced will have a dull recessed area on its
surface.
Another lesser problem is the build-up of material along the edges of
the stainless steel plate. If set-down is not monitored closely, the boards
will stick to this build-up. Set-down refers to the exact placing of the
wet-lap on the transport plate. Ideally, exact sized wet-lap should set
in exactly the same spot in the press every time.
36
-------
Drainage--
Because a forming line screen with sufficient open area to properly
drain the wet-lap has yet to be found, the mat goes into the hot press with
excess moisture. The result is poor quality board surface. Experimentation
with screens containing 42-44% open area proved unsatisfactory because
they failed to hold up. The larger open areas seemed to weaken screen
strength. Equipment using a vacuum to remove the water is now being in-
stalled for a new forming line. It will not now be necessary to use a more
open screen. The goal is to move wet-lap into the hot press with a moisture
content of between 68 and 71%.
Hardboard Production
Hardboard production has dropped off slightly with the closed system.
This is probably due to lack of experience with the closed system. As
experience increases, it should be possible to regain a higher production
level.
Production per month has dropped 1.6% since close-up. This figure
compares nine months before close-up to nine months after. Production
per hour, which is the production per running hour, downtime excluded,
dropped only 0.25%. The difference between the two figures is a result of
more down time after the closed system than before.
37
-------
SECTION 7
EFFLUENT CHARACTERISTICS
Until May 1977, Superior Fiber utilized five lagoons with a total ca-
pacity of approximately 19 million liters (5 million gal) of water. The
lagoons served basically as primary settling ponds. A cationic guar gum
polymer was added to the influent to aid in the settling of suspended and
colloidal material (Figure 19) prior to close-up. Today because of low
flow discharges, addition of polymer is not necessary to meet requirements
of the NPDES permit. Superior Fiber is filling in three of their five
lagoons because the long detention time is not needed and for aesthetic
reasons. A complication caused by the low flows during the winter months
was freezing. Normal drainage channels from the lagoons to Superior Bay
completely froze last winter and the discharge had to be pumped directly
into the bay.
I
T
I I
O
3
TJ
O
u_
CL
E
O
O
O
1976
Figure 19. Polymer usage.
1977
38
-------
Sampling
Samples are taken by a flow proportional automatic sampler. Samples
are then stored at 17°C (35°F) until testing.
Discharge Flow
Measurement—
The lagoon discharge flows over a 90 degree V-notch weir. Level over
the weir is recorded with a Leopold-Stevens level recorder.
Volume--
Before the Isel system, close-up discharge was somewhere between 568,000
and 757,000 liters (150,000 and 200,000 gal) per day. Now discharge is
less than 19,000 1 (5,000 gal) per day.
During the months of April and May 1977 lagoons number 1,2, and 3
were emptied and land filled. For this reason all data for these months
show much higher flows than if the flow due to pumping ponds 1, 2, and 3
into 4 and 5 had been excluded from the data.
Test Results
As the quantity of water discharged from the mill decreased, the quan-
tity of BOD5 discharged also decreased as shown in Figure 20. Prior to the
qlose-up, BODs were in the range of 22 Kg/KKg (44 Ib/Ton) production.
After the close-up the BODs were about 3 Kg/KKg production. The small
flows and BODs after close-up were due to leaks, spills, and wash water.
BODs decrease significantly with close-up because the BOD causing materials
become part of the hardboard.
The quantity of suspended solids discharged also decreases with de-
creasing effluent flow as shown in Figure 21.
39
-------
25
v: 20
P»
O
S is'
O
o:
u
Q 5
Q
03
i r i i I
o
o
o
.0
-o
I 1 1 1
0 I 23456
DISCHARGE KI/KKg
Figure 20. BOD discharged as a function of process water discharge.
40
-------
CO ^2.0
Q N
o £
Q Q
UJ id
Q CD
1.5
Q- X
CO O
ID CO
CO ~
0.5
2345
DISCHARGE Kl/KKg
Figure 21. Suspended solids discharged as a function of
process water discharge.
41
-------
REFERENCES
1. Eder, L. J., and Connors, J. E. Engineers report describing proposed
waste load reduction facilities in accordance with NPDES Permit require1-
ments for Superior Fiber Products, Locust Valley, New York.
2. American Society for Testing and Materials 1970 Annual Book of ASTM
Standards, Part 16. Page 12-14.
3. APHA AWWA WPCF; Standard Methods for the Examination of Mater and
Wastewater, Thirteenth Edition. Page 18.
42
-------
TECHNICAL REPORT DATA
/Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-150
4. TITLE AND SUBTITLE
WATER REUSE IN A WET PROCESS HARDBOARD
MANUFACTURING PLANT
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
July 1978 Issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Richard L. Coda
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Superior Fiber Products, Inc.
North Fifth Street and Bay Front
Superior, WI 54880
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
S804306-01
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab,
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati. OH 45268
- Cinn, OH
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Superior Fiber Products, Inc., a manufacturer of smooth on one side wet
process hardboard, undertook a project to eliminate any discharge of process water
through a program of increasing process water reuse. All but wash up water and
some pump seal leak water discharges were eliminated. White water total solids
concentration went from 1% to about 7%. Physical properties of the hardboard
were watched closely during the close up process. Water absorption and linear
expansion of the board increased after close up. Close up of the process reduced
chemical usage. Board strength problems were eliminated through control of the
white water temperature. Slower drainage of the stock was countered by formation
line alterations. Some remaining draw backs to the system are a darker board
color and overall reduced cleanliness of the mill.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Water Pollution, Industrial Wastes
Hardboard Mills
68D
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
55
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
43
HUS. GOVDSMOITPR*™*OfFlCL 1978—757-140/1403
------- |