Development Document for Effluent Limitations Guideljngp
and New Source Performance Standards for the
PLYWOOD, HARDBOARD,
AND WOOD PRESERVING
Segment of the Timber
Products Processing
Point Source Category
APRIL 1974
U'S ENVIRONMENTAL PROTECTION AGENCY
* Washington, D.C. 20460
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'
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DEVELOPMENT DOCUMENT
for
EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
PLYWOOD, HARDBOARD AND WOOD PRESERVING SEGMENT
OF THE TIMBER PRODUCTS PROCESSING POINT SOURCE
CATEGORY
Russell E. Train
Administrator
Roger Strelow
Acting Assistant Administrator for Air & Water Programs
Allen Cywin
Director, Effluent Guidelines Division
Richard E. Williams
Project Officer
April, 1974
Effluent Guidelines Division
Office of Air and Water Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $3.30
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I
ABSTRACT
A study was made of the plywood, hardboard and wood pre-
serving segment of the timber products processing point source
category. The purpose of the study was to develop information to
assist the Agency in establishing effluent limitation guidelines
for existing sources, new source performance standards and pre-
treatment standards as required by Sections 304, 306, and 307 of
the Federal Water Pollution Control Act Amendments of 1972.
The plywood, hardboard and wood preserving segment of
the industry was divided into 8 subcategories based primarily on
distinctions generated from differences in the type of product
manufactured and the specific processes involved. Best
practicable control technology currently available for six of the
subcategories was determined to be no .discharge of process waste
water pollutants into navigable waters. These subcategories are:
Barking, Veneer, Plywood, Hardboard •*• Dry Process, Wood
Preserving, and Wood Preserving - Boultonizing. Discharges are
allowed for hydraulic barking operations and direct steam
conditioning in the veneer manufacturing operations.
Quantitative limitations are determined for the Hardboard-Wet
Process and the Wood Preserving-Steam subcategories.
Best available technology economically achievable will
result in the elimination of discharge the barking subcategory
and the veneer subcategory.
The new source performance standards for six
subcategories is no discharge of process waste water pollutants
into navigable waters. For the remaining subcategories,
limitations are equivalent to the levels achievable by
application of the best available technology economically
achievable. A discharge is allowed for effluents from hydraulic
barking operations.
The new source performance standards for six subcategories is
no discharge of process waste water pollutants into navigable
waters. For the remaining subcategories, limitations are
equivalent to the levels achievable by application of the best
available technology economically achievable. A discharge is
allowed for effluents from hydraulic barking operations.
Pretreatment standards allow the discharge of process waste
water from these eight subcategories into publicaly owned
treatment works per 40 CFR Part 128, except for Section 128.133.
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CONTENTS
Section Page
I Conclusions 1
II Recommendations 3
III Intro duction 9
Purpose and Authority 9
Basis for Guidelines Development 10
General Description of the Industry 12
Barking 12
Veneer and Plywood 14
Hardboard 28
Wood Preserving 51
IV Industry Subcategorization 61
Introduction 61
Factors in Industry Sufccategorization 61
Summary of Subcategorization 66
V Water Use and Waste Characterization 69
Log Barking 69
Veneer and Plywood 69
Hardboard - Dry Process 86
Hardboard - Wet Process 93
Wood Preserving 113
VI Selection of Pollutant Parameters 135
VII Control and Treatment Technology 149
Barking 149
Veneer 150
Plywood 152
Hardboard - Dry Process 156
Hardboard - Wet Process 158
Wood Preserving
VIII Cost, Energy and Non-Water Quality Aspects 233
Barking 233
Veneer and Plywood Manufacturing 234
Hardboard - Dry Process 241
Hardboard - Wet Process 243
Wood Preserving - Steam 253
Wood Preserving 258
Wood Preserving - Boultonizing 258
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IX The Best Practicable Control Technology 261
Currently Available
Barking 261
Veneer 264
Plywood 268
Hardboard - Dry Process 270
Hardboard - Wet Process 272
Wood Preserving 274
Wood Pregervj-ng - Boultonizing 275
Wood Preserving - Steam 276
X The Best Available Technology Economically 281
Achievable
Barking 282
Veneer 283
Plywood 283
Hardboard - Dry Process 284
Hardboard - Wet Process 284
Wood Preserving 286
wood Preserving - Boultonizing 287
Wood Preserving - Steam 287
XI Standards of Performance for New Sources 291
Barking 291
Veneer 293
Plywood 293
Hardboard - Dry Process 293
Hardboard - Wet Process 294
Wood Preserving 294
Wood Preserving - Boultonizing 295
Wood Preserving - Steam 295
XII Acknowledgements 299
xiil References 301
XIV Glossary 313
VI
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FIGURES
Number Title Pacrg
1 Wet Barking Process Diagram - 13
2 Simplified Process Flow Diagram for Veneer 16
and plywood Production
3 Detailed Process Flow Diagram for Veneer and Plywood 17
4 Distribution of Softwood Veneer and Plywood Mills 23
Throughout the United States
5 Distribution of Hardwood Veneer and Plywood Mills 24
Throughout the United States
6 Distribution of veneer and Plywood Mills in the 32
State of Oregon
7 Distribution of Veneer and Plywood Mills in the 33
State of North Carolina
8 United states Forest Areas 34
9 Growth of the Plywood Industry in the 36
United States
10 Raw Material Handling in the Hardboard Industry 37
11 Typical Dry Process Hardboard Mill 38
12 Typical Wet Process Hardboard Mill 47
13 Geographical Distribution of Hardboard Manufacturing 50
Facilities in the United States
14 Process Flow Diagram for a Typical Wood 53
Preserving Plant
15 Water Balance for a Plywood Mill Producing 9.3 73
Million Square Meters per Year on a
9.53 Millimeter Basis
vi i
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FIGURES (Continued)
Number Title Page
16 Water Balance for a Typical Dry Process 92
Hardboard Mill
17 Water Usage in Raw Materials Handling 94
in the Hardboard Industry
78 Water Use in the Explosion Process 96
19 Effect of Preheating Time and Temperature 99
on Yield
20 The Chemical Components of Wood 101
21 Relation Between Dissolved Lignin and wood 103
22 Process water Recycle in a Typical Wet 105
Process Hardboard Mill
23 Process Water Recycle in a Hardboard Mill Using 107
the Explosion Process
24 Water Balance for a Typical wet Process 112
Hardboard Mill
25 variation in Oil Content of Effluent with Time 115
Before and After Initiating Closed steaming
26 Variation in COD of Effluent with Time Before 117
and After Closed Steaming
27 Variation in COD content and Waste Water 118
Flow Rate with Time
28 Relationship Between BOD and COD for Waste 120
Waste from a Creosote Treating Operation
29 source and Volume of Daily Waste Use and Recycling 133
and Waste Water Source at a Typical Wood-Preserving
Plant
30 Plywood Plant Wash Reuse System 15U
vm
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FIGURES (Continued)
Number Title Page
31 Inplant Treatment and Control Techniques at 160
No, 7
32 Typical Wet Process Hardboard Mill with 162
Pre-Press
33 Inplant Treatment and Control Techniques 163
at Mill No. 3
34 Typical Wet Process Hardboard Mill with Savo System 166
35 Variation of. Effluent BOD and Suspended Solids as 171
a Function of Time for Mill No. 2
36 Variation of Effluent BOD and Suspended Solids as a 172
Function of Time for Mill No. 3
37 Variation of Effluent BOD and Suspended solids as 173
a Function of Time for Mill No. 4
38 Effect of Detention Time on Oil Removal by Gravity 185
Separation
39 Determination of Reaction Rate Constant for a Creosote 202
Waste Water
40 COD Removal from a Creosote Waste water by Aerated 203
Lagoon without Sludge
41 Phenol Content in Weyerhaeuser's Oxidation Pond 212
Effluent Before and After Installation in
June, 1966 of Aerator
42 Relationship Between Weight of Activated Carbon 224
Added, and Removal of COD and Phenols from a
Creosote Waste Water
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FIGURES (Continued)
Number Title Page
43 Waste Water Flow Diagram for Wood Preserving 228
Plant Employing an Extended Aeration Waste
Treatment System in Conjunction with Holding
Lagoons and Soil Irrigation
44 Waste Water Flow Diagram for wood Preserving 229
Plant Employing Chemical Flocculation, Sand
Filtration, and Soil Irrigation
45 Waste Water Flow Diagram for a wood Preserving 230
Plant Employing an Oxidation Pond in Conjunction
with an Aerated Raceway
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TABLES
Number Title Page
1 Current and Projected Adhesive Consumption in the 21
Plywood Industry
2 Summary of Veneer and Plywood Plants in the 25
United States
3 Forest Industries 1968 Plywood Statistics 29
4 Softwood Plywood Production for 1972 30
5 Hardwood Plywood Production in the United States 31
6 Softwood Plywood Production in the United States 31
7 Inventory of Hardboard Manufacturing Facilities 48
8 Consumption of Principal Preservatives and Fire 54
Retardants of Reporting Plants in the United
States, 1967-1971
9 Wood Preserving Plants in the United States by State 56
and Type
10 Materials Treated in the United States by product 58
and Preservatives, 1967-1971
11 Characteristics of Debarking Effluents 70
12 characteristics of Steam Vat Discharges 72
13 Characteristics of Hot Water Steam Vat Discharges 74
14 Analysis of Drier Washwater 76
15 Waste Loads from Veneer Driers 77
16 Ingredients of Typical Protein, Phenolic and Urea 79
Glue Mixes
17 Average chemical Analysis of Plywood Glue 80
18 Average Chemical Analysis of Plywood Glue Washwater 81
19 Characteristics of Glue Washwater 82
20 Amount of Adhesive Washwater Generated in southern 83
Pine Plywood Plants
XI
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TABLES (Continued)
Number Title Page
21 Glue Waste Discharge Measurements 84
22 Dry Process Hardboard - Wastewater Flow and Source 87
23 Average Chemical Analysis of Plywood Resin 89
24 Some Properties of certain United states woods 102
25 Analyses of Some Common Species of Wood 104
26 Waste Water Discharges from wet Process Hardboard 109
27 Raw Waste Water Characteristics from Wet Process 110
Hardboard
28 Progressive Changes in selected Characteristics 117
of Water Recycled in Closed Steaming Operations
29 Phenol and COD Values for Effluents from Thirteen 121
Wood Preserving Plants
30 Ratio Between COD and BOD for Vapor Drying and 122
Cresote Effluent Wastewaters
31 Range of Pollutant Concentrations in Waste Water 122
from a Plant Treating with CCA- and FCAP-Type
Preservatives and A Fire Retardant
32 Raw Waste Loadings for Plant No. 1 124
33 Raw Waste Loadings for Plant No. 2 125
34 Raw Waste Loadings for Plant No. 3 126
35 Raw Waste Loadings for Plant No. 4 127
36 Raw Waste Loadings for Plant No. 5 128
37 Average Raw waste Loadings for Five Wood-Preserving 129
Plants
38 Source and Volume of Water Discharged and Recycled 131
per Day by a Typical Wood-Preserving Plant
39 The Adhesive Mixes U^ed (Cascophen 3566C) 155
40 Representative Process Water Filter Efficiencies 165
41 Primary Settling Tank Efficiency 167
42 Treatment Efficiep-y of Biological Systems 169
XII
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TABLES (Continued)
Number Title Page
43 Example of an ASB System Performance Related 175
To Temperature
44 Method of Disposal of Waste Water by Wood 177
Preserving Plants in the United States
U5 Method of Disposal pf Wood Preserving Waste Water 177
by Region
46 Compliance with State and Federal Water Standards 178
Among wood Preserving Plants in the United States
47 Plans of Wood Preserving Plants not in compliance 178
with Water Standards in the United States
48 Type of Secondary Waste Water Treating Facilities 180
Installed or Planned by Wood Preserving Plants
in the United States
49 Type of Secondary Waste Water Treating Facilities 180
Installed or Planned by Wood Preserving Plants
by Region
50 Efficiencies of Oil Separation Process 184
51 Effect of Lime Flocculation on COD and Phenol 184
Content of Treating Plant Effluent
52 Toxic Constituents in the Principal Salt-Type 189
Preservatives and Fire Retardant Chemicals
Used in the United States
53 Concentrations of Pollutants Before and After 192
Laboratory Treatment of waste Water from Two Sources
54 Concentrations of Pollutants in Plant Waste Water 193
Containing Salt-Type Preservatives and Fire
Retardants Before and after Field Treatment
55 BOD, COD and Phenol Loading and Removal Rates 197
for Pilot Trickling Filter Processing a
Creosote Waste Water
56 Relationship Between BOD Loading and Treatability 198
for Pilot Trickling Filter Processing a Creosote
Waste Water
57 sizing of Trickling Filter for a Wood Preserving Plant 199
xm
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TABLES (Continued)
Number Title Page
58 Substrate Removal at Steady-State Conditions in 199
Activated Sludge Units Containing Creosote
Waste Water
59 Reduction in Pentachlorophenol and COD in Haste Water 204
Treated in Activated Sludge Units
60 Results of Laboratory Tests of Soil Irrigation Method 205
of Waste Water Treatment
61 Reduction of COD and Phenol Content in waste Water 208
Treated by Soil Irrigation
62 Average Monthly Phenol and BOD Concentrations in 211
Effluent from Oxidation Pond at Weyerhaeuser1s
DeQueen, Arkansas Operation: 1968 and 1970
63 Effect of Chlorination on the BOD and Phenolic Content 214
of Pentachlorophenol and Creosote Wastewaters
64 Effect of Chlorination with Calcium Hypochlorite on the 215
Pentachlorophenol Content of Waste Water
65 Effect of Chlorination with Chlorine Gas on the 215
Pentachlorophenol Content of Waste Water
66 Effect of Chlorination of Pentachlolophenol Waste 216
on COD
67 Chlorine Required to Eliminate Taste in Aqueous 218
Solutions of Various Phenolic Compounds
68 Chlorine Demand of M-Cresol After Various Contact 220
Times
69 Chlorophenol Concentration in Creosote Waste Water 222
Treated with Chlorine
70 Summary of Waste Water Characteristics for 17 231
Exemplary wood Preserving Plants
71 Metric Units Conversion Table 325
xiv
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SECTION I
CONCLUSIONS
For the purpose of establishing effluent limitations guidelines
and standards of performance, the plywood, hardboard and wood
preserving segment of the timber products processing category has
been divided into eight subcategories as follows: (1) Barking,
(2) Veneer, (3) Plywood, (4) Hardboard-Dry Process, (5)
Hardboard-Wet Process, (6) Wood Preserving, (7) Wood Preserving-
Steam, and (8) Wood Preserving-Boultonizing.
Readily apparent disparities between the type of products
manufactured and between the different processes employed in the
production of a given product form the primary justification for
the above subcategorization. Distinctions related to raw
material, plant size and age, and air pollution problems are not
contributary to the subcategorization, as the factors involved
are minor non-existent: quantitative differences in wastes
generated serve to reinforce the subcategorization.
Presently, 20 to 30 percent of the veneer and plywood
manufacturing plants are achieving the no discharge limitation as
described herein. Many additional plants are utilizing
manufacturing practices and procedures that result in ' no
discharge of waste water from unit operations within the veneer
and plywood manufacturing process. A small number of mills
utilizing direct steam conditioning may be unable to meet the no
discharge limitation for 1977, and unwilling or unable to make
the change to a different method at this time. The Agency feels
that retention of direct steam conditioning is reasonable for the
present and has thus promulgated quantitative limitations for
these particular operations, for the 1977 standards. 1983
standards, however, recognize that technology is available, the
application of which would result in no discharge of process
waste water. Twenty-five percent of the dry process hardboard
manufacturers and 22 percent of the 9 wet process hardboard
manufacturers are achieving the no discharge limitations set
forth. Of the 390 wood preserving manufacturing operations, at
least 5 are currently meeting the no discharge recommendation in
the Wood Preserving-Boultonizing subcategory, and approximately
10 percent of the Wood Preserving-Steam subcategory manufacturers
are achieving the recommended limitations. It is believed that
all wood preserving operations excluding those in the Wood
Preserving-Steam subcategory can reach the no discharge level by
July 1, 1977.
It is estimated that the capital costs of achieving such
limitations and standards by all plants within this segment of
the timber products processing industry would be less than $38
million.
These costs would result in an increase in capital investment by
approximately $38 million. As a result, the increased costs of
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the products covered in this segment would range from 1-2 percent
under present conditions. The above cost data reflects
conditions where it is assumed no pollution control measures
exist within the industry. Because much of the suggested
technology has already been purchased or is in place, the figures
are higher than the real costs involved.
The increased capital costs would result in an estimated cost
increase of from 0 to 1 percent as compensation for pollution
control measures in all but the hardboard subcategory. Hardboard
prices could rise as much as 8 percent for industrial board, and
4 to 5 percent for other hardboard products, but the rise cannot
be attributed solely or even primarily to the cost of additional
pollution control.
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SECTION II
RECOMMENDATIONS
The recommended effluent limitations guidelines based upon (1)
best practicable control technology currently available, (2) best
available technology economically achievable, and (3) performance
standards for new sources are summarized below. The effluent
limitations as set forth herein are developed in depth in the
following sections of this document.
RECOMMENDED EFFLUENT LIMITATIONS BASED ON BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE
SUBCATEGORY
BARKING
EFFLUENT LIMITATION
A. No discharge of waste water pollutants
to navigable waters for barking operations
excluding those using hydraulic barkers.
B. For barking operations using hydraulic
barkers:
VENEER
BOD5
TSS
30-Day
Average
kg/cu m
(Ib/cu ft)
0.5
(0.03)
2.3
(0.144)
Daily
Maximum
kg/cu m
(Ib/cu ft)
1.5
(0.09)
6.9
(0.431)
A. No discharge of waste water pollutants to
navigable waters, except for those veneer
operations using direct steam conditioning
B For veneer manufacturing operations using
direct steam conditioning:
BOD
30-Day
Average
kg/cu m
(Ib/cu ft)
Softwood 0.24
Veneer (0.015)
Hardwood 0.54
Veneer (0.034)
Daily
Maximum
kg/cu m
(Ib/cu ft)
0.72
(0.045)
1.62
(0.10)
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PLYWOOD
HARDBOARD -DRY
HARDBOARD -WET
WOOD PRESERVING
WOOD PRESERVING-
BOULTONIZING
WOOD PRESERVING-
STEAM
No discharge of waste water pollutants to
navigable waters.
No discharge of waste water pollutants to
navigable waters.
BOD5_
TSS
PH
Range
30- Day
Average
kg/kkg
(Ib/ton)
2.6
(5.2)
5.5
(ii.o)
6.0-9.0
Daily
Maximum
kg/kkg
(Ib/ton)
7.8
(15.6)
16.5
(33.0)
6.0-9.0
No discharge of waste water pollutants
to navigable waters
No discharge of waste waters pollutants to
navigable waters.
COD
Phenols
Oil &
Grease
30-Day
Average
kg/1000 cu m
(lb/1000 cu ft)
550
(34.5)
0.65
(0.04)
12.0
(0.75)
6.0-9.0
Daily
Maximum
kg/1000 cu m
(lb/1000 cu ft)
1100
(68.5)
2.18
(0.14)
24.0
(1.5)
6.0-9.0
RECOMMENDED EFFLUENT LIMITATIONS BASED ON BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE
SUBCATEGORY
BARKING
EFFLUENT LIMITATION
No discharge of waste water pollutants
to navigable waters.
VENEER
No discharge of waste water pollutants
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to navigable waters.
PLYWOOD
HARDBOARD - DRY
HARDBOARD - WET
WOOD PRESERVING
WOOD PRESERVING-
BOULTONIZING
WOOD PRESERVING-
NO discharge of waste water pollutants
to navigable waters.
No discharge of waste water pollutants
to navigable waters.
BOD5_
TSS
pH
Range
30- Day
Average
kg/kkg
(Ib/ton)
0.9
(1.8)
1.1
(2.2)
6.0-9.0
Daily
Maximum
kg/kkg
(Ib/ton)
2.7
(5.4)
3.3
(6.6)
6.0-9.0
No discharge of waste water pollutants
to navigable waters.
No discharge of waste water pollutants
to navigable waters.
COD
Phenols
Oil&
Grease
pH
Range
30-Day
Average
kg/1000 cu m
(lb/1000 cu ft)
110
(6.9)
0.064
(0.004)
3.4
(0.21)
6.0-9.0
Daily
Maximum
kg/1000 cu m
(lb/1000 cu ft)
220
(13.7)
0.21
(0.014)
€.9
(0;42)
6.0-9.0
RECOMMENDED EFFLUENT LIMITATIONS AND NEW SOURCE PERFORMANCE STANDARDS
SUBCATEGORY EFFLUENT LIMITATION
BARKING
A. No discharge of waste water pollutants to
navigable waters for barking operations,
excluding those which use hydraulic barkers.
B. For new sources using hydraulic barkers:
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VENEER
PLYWOOD
HARDBOARD
HARDBOARD
DRY
WET
WOOD PRESERVING
WOOD PRESERVING-
BOULTONIZING
BODS
TSS
30-Day
Daily
kg/cu m
(Ib/cu ft)
0.5
(0.03)
2.3
(0.144)
Daily
Maximum
kg/cu m
(Ib/cu ft)
1.5
(0.09)
6.9
(0.431)
No discharge of waste water pollutants to
navigable waters.
No discharge of waste water
navigable waters.
No discharge of waste water
navigable waters.
30-day
Average
kg/kkg
(Ib/ton)
pollutants to
pollutants to
BODS
TSS
PH
Range
0.9
(1.8)
1.1
(2.2)
6.0-9.0
Daily
Maximum
kg/kkg
(Ib/ton)
2.7
(5.4)
3.3
(6.6)
6.0-9.0
No discharge of waste water
navigable waters.
No discharge of waste water
navigable waters.
pollutants to
pollutants to
WOOD PRESERVING-
STEAM
30-Day
Average
kg/1000 cu m
(lb/1000 cu ft)
COD 110
(6.9)
Phenols 0.064
(0.004)
Maximum
Daily Average
kg/1000 cu m
(lb/1000 cu ft)
220
(13.7)
0.21
(0.014)
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Oil & 3.4 6.9
Grease (0.21) (0.42)
pH 6.0-9.0 6.0-9.0
Range
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SECTION III
INTRODUCTION
PURPOSE AND AUTHORITY
Section 301(b) of the Federal Water Pollution Control Act
requires the achievement, by not later than July 1, 1977, of
effluent limitations for point sources, other than publicly owned
treatment works, which are based on the application of the best
practicable control technology currently available as defined by
the Administrator pursuant to Section 304(b) of the Act. Section
301(b) also requires the achievement by not later than July 1,
1983 of effluent limitations for point sources, other than
publicly owned treatment works, which are based on the
applicat ion of the be st ava ilable technology economically
achievable which will result in reasonable further progress
toward the national goal of eliminating the discharge of all
pollutants, as determined in accordance with regulations issued
by the Administrator pursuant to Section 304(b) of the Act.
Section 306 of the Act requires the achievement by new sources of
a Federal standard of performance providing for the control of
the discharge of pollutants which reflects the greatest degree of
effluent reduction which the Administrator determines to be
achievable through the application of the best available
demonstrated control technology processes, operating methods, or
other alternatives, including, where practicable, a standard per-
mitting no discharge of pollutants.
section 304(b) of the Act requires the Administrator to publish
within one year of enactment of the Act regulations providing
guidelines for effluent limitations setting forth the degree of
effluent reduction attainable through the application of the best
practicable control technology currently available and the degree
of effluent reduction attainable through the application of the
best control measures and practices achievable including
treatment techniques, process and procedure innovations,
operati on method s and other alternatives. Th e regulati ons
proposed herein set forth effluent limitations guidelines
pursuant to Section 304(b) of the Act for selected segments of
the timber products processing category.
Section 306 of the Act requires the Administrator, within one
year after a category of sources is included in a list published
pursuant to Section 306 (b) (1) (A) of the Act, to propose regu-
lations establishing Federal standards of performance for new
sources within such categories. The Administrator published in
the Federal Register of January 16, 1973 (38 F.R. 1624), a list
of 27 source categories. Publication of the list constituted
announcement of the -Administrators intent to establish, under
Section 306, standards of performance applicable to new sources
within the timber products processing category.
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Similar studies will be undertaken and published by the EPA in
future months. Segments of the timber products processing
industry to be covered at that time will include machining
operations, storage of fractionalized wood, insulation board
manufacture, particle board manufacture, storage operations
(including log ponding and wet-decking) , logging camps and
contractors, saw and planing mills, prefabricated wood
structures, special purpose sawmills, millwork, and other wood
products not elsewhere classified.
BASIS FOR GUIDELINES DEVELOPMENT
The effluent limitations guidelines and standards of performance
recommended in this report were developed in the following
manner.
Both detailed and general information was obtained on the
manufacturing plants identified as currently in operation. The
sources and type of information consisted of:
Applications of the Corps of Engineers for Permits to
Discharge under the Refuse Act Permit Program (RAPP),
obtained for exemplary plants. The RAPP applications
provided data on the characteristics of intake and
effluent waters, water usage, waste water treatment and
control practices employed, daily production, and raw
materials used.
Internal reports furnished by the industry and various
manufacturers. The information included: (a) raw
materials utilized and relative amounts, (b) schematic
diagrams of inplant processes (with a definition of
process type) showing waste water discharge and recycle
systems, (c) production rates, (d) definition of sources
of waste water from inplant processes, including flow
and waste water chemical composition, (e) definition of
total waste water flows and chemical composition, (f)
present methods of waste water handling or treatment,
including schematic diagrams of treatment systems with a
definition of chemical composition after each unit
process of the treatment systems, (g) description of
solid wastes resulting from treatment systems and the
methods of handling and disposal of the wastes, (h)
energy requirements per unit of production (i) inplant
methods of waste water reduction or control (reuse,
conservation, etc.) and, (j) effects of waste water
handling on air pollution and solid waste disposal.
On-site visits and interviews at
processing plants throughout the U.S.
timber products
10
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- Other sources of information, including EPA technical
reports and personnel, trade literature, industry
personnel, and special consultants. References used in
this study are tabulated in Section XIII*
This information was compiled by data processing techniques and
analyzed for the following:
Identification of distinguishing features that could
potentially provide a basis for subcategorization of
these selected portions of the timber products
processing category.
- Determination of the waste water usage and waste water
characteristics for each subcategory, as developed in
Section IV and discussed in Section V, including (1) the
source and volume of water used in the particular
process employed and the source of wastes and waste
waters in the plant, and (2) the constituents (including
thermal) of all waste waters, including pollutants, and
other constituents which result in taste, odor, and
color in water or aquatic organisms.
Identification of those constituents discussed in
Section V and Section VI which are characteristic of the
industry and present in measurable quantities, thus
being pollutants subject to effluent limitations
guidelines and standards.
The full range of control and treatment technologies
existing within each subcategory, including an iden-
tification of each distinct control and treatment
technology existent or capable of being designed for
each subcategory, an identification in terms of the
amount of constituents (including thermal) and the
chemical, physical, and biological characteristics of
pollutants, of the effluent level resulting from the
application of each of the treatment and control
technologies, the problems, limitations and reliability
of each treatment and control technology and the re-
quired implementation time.
The non-water quality environmental impact, such as the
effects of the application of such technologies upon
other pollution problems, including air, solid waste,
noise and radiation
The energy requirements of each of the control and
treatment technologies, as well as the cost of the
application of such technologies.
The information outlined above was then evaluated in order to
determine what levels of technology constituted the "best
11
-------
practicable control technology currently available," "best
available technology economically achievable," and the "best
available demonstrated control technology, processes, operation
methods or other alternatives." In identifying such
technologies, various factors were considered, including the
total cost of application of technology in relation to the
effluent reduction benefits to be achieved from such application,
the age of equipment and facilities involved, the process
employed, the engineering aspects of the application of various
types of control techniques (including energy requirements),
process changes, non-water quality environmental impact and other
factors. Consideration of the technologies was not limited to
those presently employed in the industry, but included also those
processes in pilot plant or laboratory research stage and those
used by other industries. The alternative of combined
industrial-municipal treatment, including the compatibility and
economic ramifications, was also examined.
GENERAL DESCRIPTION OF THE INDUSTRY SEGMENT
The timber products processing category includes a broad spectrum
of operations ranging from cutting and removing the timber from
the forest to the processing of the timber into a wide variety of
finished products, encompassing such diverse items as finished
lumber, and cooked, molded, or compressed wood fibers
reconstituted into a number of sheet form flexible and rigid
products. The wide variety of processing steps and products in
the timber products processing industry are, in many instances,
similar only in the fact that the basic raw material is wood.
This development document addresses the segment of the timber
products processing industry which has been estimated to be
responsible for the greatest water pollution problems. The first
segment of the study of the timber products processing industry
includes barking, veneer manufacturing, plywood manufacturing,
hardboard manufacturing, and wood preserving operations.
BARKING
Barking may be the common starting point throughout the (post
harvest, transport and delivery) timber products processing
industry. If barking is required, logs are taken to a barker
where the bark is removed through one of several wet or dry
barking procedures. The logs may be cut to required lengths
before or after barking (figure 1).
Types of barking machines include (1) drum barkers, (2) ring
barkers, (3) bag barkers, (4) hydraulic barkers and, (5)
cutterhead barkers.
Drum barkers range in size from 2.4 to 4.9 m (8 to 16 ft) in
diameter and up to 22.8 m (75 ft) in length. A drum barker
consists primarily of a cylindrical shell rotating on its
12
-------
r
•-
LOG
STORAGE
^
PROCESS
WATER
r *
PROCESS
BACK WATER
1
t
LOG
WASHER
T
i *
-.
WET DRUM
POCKET OR
HYDRAULIC BARKER
DEBARKED
LOGS
OFF GASES
CYCLONE
COARSE
SCREENING
*-^-
FtNE
SCREENING
4--*
^ *<***
4_
-f-
i
BARK PRESS
r*"1!. •
•*4-4»*4H
ASH TO LAND
DISPOSAL
k-*-'
DIVERSION
BOX
I
i
EFFLUENT
PRODUCT AND
RAW MATERIAL
PROCESS WATER
BACK WATER
GASES
BARK ASH
RESIDUE
EFFLUENT
4-^44--
+
t
*
i
f
.J-
FIGURE .1
- WET BARKING PROCESS DIAGRAM
-------
longitudinal axis. Logs are fed into one end and tumbling and
rolling action removes the bark. Water sprays may be used to
reduce dust, promote the thawing of wood in cold climates, or
reduce the bond between the bark and wood.
Ring barkers or rotary barkers consist of a rotating ring on
which several radial arms are pivoted. On the end of each arm is
a tool which abrades or scrapes off the bark. A ring barker
handles only one log at a time, but can handle logs up to 213.4
cm (84 in) in diameter.
Bag barkers or pocket barkers are simple stationary containers in
which the logs are rotated to remove bark by abrasion. Water may
also be used in this process for the same purposes described for
the drum barkers.
Cutterhead barkers remove bark by the milling action of a
cylindrical cutterhead as it rotates parallel to the axis of the
logs which are fed through the unit. No water is employed in
this operation.
The hydraulic barker uses a high pressure water jet to blast bark
from a log. Pressures from 55.4 to 109.9 atm (800 to 1615 psi)
are used with flow in the range of 25.2 to 101 I/sec (400 to 1600
gal/min). Because of the large volumes of low solids content
water required for this operation, there is an apparent inability
to recycle water from this operation, which results in a
relatively large volume waste water discharge. Hydraulic barkers
are slowly being phased out because of water requirements and
because the large diameter logs they process are becoming
unavailable.
VENEER AND PLYWOOD
Plywood is an assembly of layers of wood (veneer) joined together
by means of an adhesive. It is a multi-use material
characterized by its ability to be designed and engineered for
construction and decorative purposes, flat shapes, curves, and
bent shapes. Hardwood plywood is distinguished from softwood
plywood in that the former is generally used for decorative pur-
poses and has a face ply of wood from deciduous or broad leaf
trees. Softwood plywood is generally used for construction and
structural purposes, and the veneers are of wood from coniferous
or needle bearing trees.
Raw Materials
A great assortment of woods are utilized in the manufacture of
veneers. A high percentage of veneer produced in the
northwestern U.S. is manufactured from Douglas fir, with lesser
quantities of veneer made from ponderosa pine and hemlock* In
the southeast U.S., southern pine is the predominant raw
14
-------
material. Veneer is classified as softwood or hardwood.
Softwood veneer is manufactured on the west coast, in the Rocky
Mountain region, and in the southeastern U.S.. The species that
are used in the western U.S. include Douglas fir, sitfca spruce,
western hemlock, balsam fir, western larch, ponderosa pine, sugar
pine, western white pine, and redwood. In the southeastern
states bald cypress and southern pine are most common. The
hardwood species commonly used in the U.S. are beech, birch,
maple, basswood, red gum, yellow poplar, cottonwood, tupelo,
sycamore, oak, walnut, lavan, elm, cherry, hickory, pecan,
cativo, teak, rosewood, and mahogany.
Softwood veneer is almost exclusively used in the manufacturing
of softwood plywood. Small quantities are used as center stock
and cross-banding for panels made with hardwood faces. Hardwood
veneer uses can be categorized as (1) face veneer, (2) commercial
veneers, and (3) veneers for containers. Face veneers are of the
highest quality and are used to make plywood panels employed in
the manufacture of furniture and interior decorative panels.
There are more than 50 such manufacturers throughout the eastern
U.S.. Commercial veneers are those used for cross bands, cores,
and backs of plywood panels and concealed parts of furniture.
Container veneers consist of a large variety of inexpensive
veneers used in the manufacturing of crates, hampers, fruit and
vegetable baskets and kits, boxes and similar container items.
Plywood is manufactured in 36 states. The majority of softwood
plywood is produced on the Pacific Coast while the majority of
the hardwood plywood is manufactured in the southeastern states.
The hardwood plywood industry is made up of a large number of
small factories distributed widely over the eastern U.S..
Manufacturing Process
The various operations for converting roundwood into veneer and
finally into plywood are chiefly mechanical. A simplified
process flow diagram for the production of veneer and plywood
from roundwood is shown in Figure 2. A detailed flow diagram o
the veneer and plywood manufacturing process is shown in Figure
3.
The most important operation in this process is the cutting of
the veneer; the appearance of a plywood panel is greatly de-
pendent upon the manner in which the veneer is cut. Prior to the
cutting of veneer, logs may be heated, or "conditioned"; this
serves to improve the cutting properties of wood, particularly
hardwood. Historically, both hardwood and softwood mills have
practiced log conditioning. There was in recent years a trend
away from log conditioning in the softwood industry, but the
current trend is again toward this practice.
15
-------
LOG
STORAGE
DEBARKER
-
LOG
CONDITIONER
i
VENEER
CUTTER
VENEER
DRIER
VENEER OPERATION
VENEER
PREPARATK>
GLUE
LINE
PRE$S
FINISHING
PLYWOOD OPE RAT ION
FIGURE 2 - SIMPLIFIED PROCESS FLOW DIAGRAM FOR
VENEER AND PLYWOOD PRODUCTION
16
-------
LIQUID WASTE
GREEN END
OVERFLOW FROM
LOG POND
LOG STORAGE
{LOG POND,
COLD DECK
OR BOTH)
GASES
LIQUIDS
DRIER WASH
CONDENSATE AND DELUGE
WATER
EXHAUST
GASES
BARK
SOLID WASTE IS BURNED IN BOILER
CHIPPED FOR REUSE OR SOLD
GLUE
PREPARATION
GLUE WASH
WATER
VENEER
PREPARATION
UE
|
GLUE
LINE
RECYCLf
1 RESSIN(
FINISHING
| UNUSABLE
I VENEER AND
! TRIMMINGS
I
I
i.
TRIM AND
SANDER
DUST
FIGURE 3 - DETAILED PROCESS FLOW DIAGRAM FOR VENEER AND PLYWOOD
-------
When conditioning of logs occurs not only prior to veneering, but
prior to debarking, it facilitates the barking operation. This
has been a common practice in the past. With the increasing use
of ring and cutterhead barkers whose operations are not aided by
prior heating, heating commonly occurs between the barking and
veneering operations.
There are basically two methods of heating logs: (1) by direct-
ing steam onto the logs in a "steam vat" (steam tunnel), and by
(2) heating the logs in a "hot water vat" full of water which is
heated either directly with live steam or indirectly with steam
coils.
Heating in steam vats is generally more violent than in hot water
vats, and steam vats are therefore more applicable to species of
wood that do not rupture under rapid and sudden thermal in-
creases. The times and temperatures of these conditioning
processes vary with species, age, size, and character of veneer
to be cut. The experience has been that the harder (more dense)
the species and the more difficult to cut, the longer the
conditioning period and the lower the temperature required. Some
of the softer woods, such as poplar, bass wood, cottonwood, and
certain conifers, can be cut satisfactorily without such
conditioning.
Veneer Cutting
The principal unit process in the manufacturing of veneers is the
cutting of the veneer. There are four methods used to cut
veneer: (1) rotary cutting, (2) slicing, (3) stay log cutting,
and (4) sawn veneering.
Currently more than 90 percent of all veneer is rotary cut. In
this method of cutting, a log or "bolt" of wood is centered
between two chucks on a lathe. The bolt is turned against a
knife extending across the length of the lathe, and a thin sheet
of veneer is peeled from the log as it turns. Lathes capable of
peeling logs from 3.66 to 4.88 m (12 to 16 ft) in length are not
uncommon, but more often veneer is cut in lengths ranging from
0.61 to 2.4 m (2 to 8 ft). The bolts that are to be veneered are
usually cut from 10 to 15 cm (4 to 6 in) longer than the width of
veneer to be cut from them.
Most slicers consist of a stationary knife. The section of a log
or "flitch" to be cut is attached to a log bed which moves up and
down, and on each downward stroke a slice of veneer is cut by the
knife. Slicers are used primarily for cutting decorative face
veneers from woods such as walnut, mahogany, cherry, and oak.
Stay log cutting produces veneers which are intermediate between
rotary cut and sliced veneers. A flitch is attached to a stay
log or metal beam, mounted off center to a rotary lathe. The
stay log method produces half-round veneer which is generally
used for faces.
18
-------
A small quantity of veneer is cut by sawn veneering. A circular
type saw with a thin, segmented blade, called a segment saw,
turns on an arbor. The thin blade reduces the wastage or saw
kerf. This method generally is used only for certain species
such as oak, red cedar and Spanish cedar in order to achieve
special effects.
Veneers are cut to thicknesses ranging from 0.254 to 9.54 mm
(1/10 to 3/8 in). Most of the rotary cut veneers are either 3.6,
3.2, 2.5, 1.7, or 1.3 mm (1/7, 1/8, 1/10, 1/ 15, or 1/20 in)
thick. Sliced veneer usually ranges from 1.27 to 0.635 mm (1/20
to 1/40 in). Sawn veneers vary from 6.35 to 0.795 mm (1/4 to
1/32 in) in thickness.
After rotary veneers are cut, they may go directly to a clipper
or they may be stored temporarily on horizontal storage decks or
on reels. Usually the veneer coming from the lathe is cut to
rough green size, and defects are removed at the green clipper.
From here the veneers are conveyed to the dryers.
Veneer Drying
Freshly cut veneers are ordinarily unsuited for gluing because of
their wetness. In the undried (green) state, veneers are also
susceptible to attack by molds, blue-stain, and wood-destroying
fungi. It is therefore necessary to remove the excess moisture
rapidly, and veneers are usually dried to a moisture content of
less than 10 percent. This is a level compatible with gluing,
and consistent with the moisture content to which plywood
products will be exposed while in service.
Several methods for drying veneers are in use. The most common
type of dryer is a long chamber equipped with rollers on belts
which advance the veneer longitudinally through the chamber.
Fans and heating coils are located on the sides of the chamber to
control temperature and humidity.
The majority of high-temperature (above 100°C or 212°F) veneer
dryers depend upon steam as a heat source. The heat is trans-
ferred to the air by heat exchangers. However, direct-fired oil
and gas dryers are becoming increasingly common in the industry.
The conventional progressive type and compartment type lumber
kilns are also used in drying veneers. Air drying is practiced
but is quite rare except in the production of low grade veneer
such as that used in crate manufacturing. Air drying is
accomplished by simply placing the veneer in stacks open to the
atmosphere, but in such a way as to allow good circulation of
air.
Veneer Preparation
Between the drying and gluing operations are a series of minor
operations that prepare or repair the veneer stock. These opera-
19
-------
tions may include grading and matching, redrying, dry-clipping,
jointing, taping and splicing, and inspecting. These operations
are self-descriptive and completely mechanical or manual except
for jointing and splicing which may use some sort of adhesive.
The bonding does not have to be as strong as that in the gluing
of plywood, and the amount of adhesive used is kept to a minimum.
Most of these gluing operations do not require washing.
Gluing Operations
A number of adhesives can be used in the manufacture of plywood.
For the purpose of this discussion, distinction is made between
(1) protein, (2) phenol-formaldehyde, and (3) urea-formaldehyde
glues, since these are the classes of glue most often used in the
industry. Protein glue is extracted from plants and animals and
is thermoplastic, while the other two are synthetic,
thermosetting glues. Typical ingredients of protein glues are
water, dried blood, soya flour, lime, sodium silicate, caustic
soda and a formaldehyde doner for thickening. Typical
ingredients of urea-formaldehyde glues are water, defoamer,
extender (wheat flour) and urea formaldehyde resin. Typical
ingredients of phenol-formaldehyde glues are water, furafil,
wheat flour, phenolic formaldehyde resin, caustic soda and soda
ash.
Both protein and urea-formaldehyde glues are chiefly interior
glues, while phenol-formaldehyde is an exterior glue. Urea-
formaldehyde is used almost exclusively in the hardwood plywood
industry when the panels are used for furniture and indoor
panelling. Phenol-formaldehyde is a thermosetting resin like
urea-formaldehyde, but it is waterproof and is practically the
only glue used to make exterior plywood. Phenol-formaldehyde, is
being increasingly used to produce both interior and exterior
plywood so that the use of phenolformaldehyde is increasing
rapidly. Table 1 shows the breakdown of glue usage in 1965 and
the projected usage for 1975. At present, phenolic glues
comprise about 50 percent of all glue consumed while by 1975 it
is projected that about 80 percent of all the glue used in
plywood manufacturing will be phenolic based.
Historically, protein glues had been the only adhesive used in
the plywood industry. However, as a result of synthetic resins
becoming less expensive and their versatility becoming more
recognized, the use of protein glues is disappearing. At the
present time, the main advantage of some protein glues is that
they can be cold pressed. However, while cold pressing is a
simpler and cheaper operation, it is only satisfactory for
interior plywood.
Most plywood manufacturers mix their own glue in large dough-type
mixers. The glue is then applied to the veneer by means of a
spreader, the most common of which consists of two power driven
rollers supplied with the adhesive. Protein glues are usually
applied with steel rollers, while other glues are usually applied
20
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TABLE 1
CURRENT AND PROJECTED ADHESIVE CONSUMPTION IN
THE PLYWOOD INDUSTRY
(Millions of Kilograms)
1965 1975
Plywood Type Phenolic Urea Protein Phenolic Urea Protein
Western
Exterior 37 — — 88
Western
Interior 6.4 — 47 62
Southern
Exterior — •*- — 41 —
Southern
Interior 4.5 — — 39
Hardwood — 25 — — 54
TOTALS 48 25 47 230 54
21
-------
with rubber-covered rollers. More recently the practice of
applying glue by means of sprays and curtain coaters has emerged.
Since all glues harden with time, the glue system must be cleaned
regularly to avoid build-up of dried glue. Some of the more
recent spray curtain-coater glue applicators require less washing
than the conventional rollers.
Pressing
After gluing, the layers of veneer are subjected to pressure to
insure proper alignment and an intimate contact between the wood
layers and the glue. The adhesive is allowed to partially cure
under pressure. Pressing may be accomplished at room temperature
(cold-pressing) or at high temperature (hot-pressing). Cold-
pressing is used with some protein and urea-formaldehyde
adhesives. Hot-pressing equipment is used to cure some protein,
some urea-formaldehyde, and all of the phenol-formaldehyde ad-
hesives.
Most presses are hydraulic and apply pressures from 6.1 to 17 atm
(75 to 250 psi) . Cold presses are operated at room temperatures,
while hot presses are operated at temperatures ranging to 177°C
(350°F) with heat being transferred by means of steam, hot water
or hot oil. Plywood pressing time ranges from two minutes to 24
hours depending upon the temperature of the press and the type of
glue used. Usually, the hotter the press, the shorter the
pressing time.
In recent years, radio-frequency heat has been used to cure
synthetic resin adhesives. This works on the principle that when
an alternating electric current oscillating in the radio
frequency range is applied to a dielectric material, the material
will be heated. It is questionable whether this method of
heating is economically worthwhile, however. It is technically
applicable for curing the resin in plywood as well as edge
gluing.
Finishing
After the pressing operation, any number of a series of finishing
steps, depending upon the operation and the product desired, may
be taken. These operations include (1) redrying, (2) trimming,
(3) sanding, (4) sorting, (5) molding and (6) storing.
Inventory of Veneer and Plywood Manufacturers
There are approximately 500 veneer and plywood mills in the U.S.,
248 of which use softwood, 253 use hardwood, and 27 use a
combination of softwood and hardwood. As shown in Table 2, the
largest concentrations of mills are in Oregon, Washington, and
North Carolina. Figures 2 through 5 show the distribution of
mills throughout the U.S.. Hardwood and softwood mills are
located according to availability of raw materials, and their
22
-------
ro
CO
SOFTWOOD - PLYWOOD
8 VENEER
O SOFTWOOD a HARDWOOD-
PLYWOOD 3 VENEER
NOTE:
OREGON AND WORTH CAROL! NA ABE KI9H
DENSITY AREAS AND ARE SHOWN ON SEPARATE
MAPS
FIGURE 4 - DISTRIBUTION OF SOFTWOOD VENEER AND PLYWOOD MILLS THROUGHOUT THE UNITED STATES
-------
HARDWOOD - PLYWOOD
» VENEER
SOFTWOOD a HARDWOOD
PLYWOOD a VCNEER
NOTE :
OREGON AND NORTH CAROLINA ARE HIQH DENSITY
AREAS AND ARE SHOWN ON SEPARATE MAPS.
Miami
FIGURE 5 - DISTRIBUTION OF HARDWOOD VENEER AND PLYWOOD HILLS THROUGHOUT THE UNITED STATES
-------
TABLE 2
SUMMARY OF VENEER AND PLYWOOD PLANTS IN THE UNITED STATES
SOFTWOOD PLYWOOD
Alabama 6
Arizona 1
Arkansas 8
California 15
Colorado 1
Florida 2
Georgia 5
Idaho 5
Louisiana 12
Maryland 1
Michigan 2
Mississippi 6
Montana 4
New Hampshire 1
North Carolina 6
Oklahoma 1
Oregon 81
South Carolina 3
Texas 9
Virginia 1
Washington 29
TOTAL 199
SOFTWOOD VENEER
Arkansas 1
California 8
Florida 1
Georgia 1
Maryland 1
Minnesota 1
New Jersey 1
North Carolina 6
Oregon 31
South Carolina 1
Texas 1
Virginia 1
Washington 9
Wisconsin 2
TOTAL 65
25
-------
TABLE 2 CONTINUED
HARDWOOD PLYWOOD
HARDWOOD VENEER
Alabama
Arkansas
California
Florida
Georgia
I llinois
Indiana
Louisiana
Maine
Michigan
Minnesota
Miss issippi
9
4
6
3
6
1
6
2
3
4
2
6
Alabama
Florida
Georgia
Illinois
Indiana
Iowa
Kentucky
Maine
Maryland
Michigan
Minnes ota
Miss issippi
4
4
5
1
13
2
4
1
1
3
2
3
New Hampshire 2
New York 2
North Carolina 26
Oregon 9
Pennsylvania 4
South Carolina 16
Tennessee 4
Texas 3
Vermont 5
Virginia 11
Washington 5
West Virginia 1
Wisconsin 16
TOTAL 157
Missouri 2
New Jersey 1
New York 5
North Carolina 19
Ohio 2
Oregon 5
Pennsylvania 5
South Carolina 6
Tennessee 2
Vermont 1
Virginia 7
West Virginia 2
Wisconsin 4
TOTAL
107
26
-------
TABLE 2 CONTINUED
SOFTWOOD & HARDWOOD PLYWOOD
Alabama 2
Florida 1
Michigan 1
New Hampshire 1
North Carolina 1
Oregon 3
South Carolina 1
Texas 1
Washington 4
TOTAL 16
SOFTWOOD & HARDWOOD VENEER
Florida 1
Georgia 1
Minnesota 1
North Carolina 3
Oregon 3
Virginia 1
TOTAL 11
Region
New
England
Middle
Atlantic
East North
Central
West North
Central
South
Atlantic
East South
Central
West South
Central
Mountain
Paci fi c
TOTAL PLYWOOD PLANTS - 340
TOTAL VENEER PLANTS - 161
Total
27
-------
di stributi on, t
in Figure 7. A
presented in Ta
In 1968, a Fo
statistics avai
there were 175
hardwood plyw
installations w
plywood in th
basis (15 billi
hardwood plywo
0.635 cm basis
Table 3 are :
collected as ;
association sh*
1.71 billion sq
3/8 in basis) ,
million sq m on
basis).
During the de<
rose by 150 per<
the world's plyv
the U.S. alone
timber. As the
increase so d<
ago practically
produced in th<
ten years the ir
and the use oj
Nation's softwoc
Hardwood plywooc
past 20 years (1
HARDBOARD
Hardboard is a g
from interfelte
and pressure in
ft) or greater.
properties, sue
resistance to ab
strength, durabi
There are two m
the manner in wh
water is used
distributing the
function in the
developed from a
o
e?
LU
(=»
O
o
3
Q_
(=>
O
C3
32
-------
EGEND
SOFTWOOD
HARDWOOD
SOFT AND HARDWOOD
FIGURE 6 - DISTRIBUTION OF VENEER AND PLYWOOD HILLS IN THE STATE OF OREGON
-------
TABLE 5
HARDWOOD PLYWOOD PRODUCTION IN THE UNITED STATES
Year Square Meters Surface Area
1947 68,700,000
1955 87,000,000
1960 82,500,000
1965 170,500,000
1970 146,600,000
1972 204,765,000
TABLE 6
SOFTWOOD PLYWOOD PRODUCTION IN THE UNITED STATES
Year
1925
1940
1950
1960
1970
1972
Sq. Meters Surface Areas
14,240,000
111,690,000
237,700,000
727,500,000
1,334,700,000
1,707,400,000
No. of Plants
12
25
68
152
179
—
31
-------
TABLE 4
SOFTWOOD PLYWOOD PRODUCTION FOR 1972
State Sq. Meters-9.53 mm Basis
California 140,543,000
Oregon
Washington
Idaho
Others
(Mostly South)
803,700,000
210,443,000
156,366,000
495,066,000
Note: Data obtained from APA
30
-------
TABLE 3
FOREST INDUSTRIES 1968 PLYWOOD STATISTICS
Region
New
Engl and
Middle
Atlantic
East North
Central
West North
Central
South
Atlantic
East South
Central
West South
Central
Mountain
Pacific
Total
Number of
Softwood
Plywood
Plants
-
-
-
-
10
7
.17
11
130
175
Softwood Ply-
'. wood Production
In Square meters
(9.53 rtm Basis)
-
-
-
-
54,730,000
49,500,000
142,500,000
101,720,000
1,063,000,000
1,411,500,000
Number of
Hardwood
Plywood
Plants
- 15
7
41
4
72
24
11
31
205
Hardwood Ply-
wood Production
In Square meters
(6.35 mm - Basis)
7,175,000
1,675,000
29,950,000
4,200,000
42,660,000
30,625,000
4,100,000
-
77,375,000
197,750,000
29
-------
CO
CO
• SOFTWOOD
A - HARDWOOD
• SOFT AND HARDWOOD
WILMINGTON
FIGURE 7- DISTRIBUTION OF VENEER AND PLYWOOD hILLS IN THE STATE OF NORTH CAROLINA
-------
UNITED STATES FOREST AREAS
CO
Softwood timber is indicated by grey
hardwood by black areas.
FIGURE 8
- UNITED STATES FOREST AREAS
-------
Mason during the 1920's. It was the prototype of wet process
hardboard. Other methods of fiber preparation were later
developed. The resulting fibers may be washed, screened, and
refined before being carried in a liquid slurry to a board-
forming machine similar to that used in making paper, a
cylindrical former, or a batch unit. After forming, the wet mat
may be pressed either wet or dry. If the mat is to be pressed
dry, then all of the moisture must be removed by evaporation
after wet-forming.
Fiber preparation in the dry process is similar to that in the
wet process. After fiber preparation, water is removed in a
dryer. The fibers are then transported by an air stream to a
dry-felting machine for mat formation. After formation of the
dry mat, the mat is pressed in a dry state by all but two of the
dry press hardboard mills to" be discussed later. Two mills add
water to the mat after dry formation and in one mill any water
added is evaporated in the pressing operation.
Process Description
The raw material for hardboard production is essentially all
wood. This wood may be in the form of round wood, wood chips
from waste products from saw mills and plywood mills, or other
sources of wood fiber. Raw material handling for both wet and
dry process hardboard mills is shown in Figure 9.
Figure 10 shows a typical process diagram of a dry process
hardboard mill and Figure 11 shows a typical inplant process
diagram of a wet process hardboard mill. The principal
difference between the two processes is the manner in which the
fibers are carried and formed into a mat.
Chipping
Logs or wood scraps must be either processed to chips at the
hardboard manufacturing plant or converted to chips off-site and
hauled to the mill. There are several types of chippers utilized
in the industry with disc chippers being the most common. After
chipping, chips are screened to control size. Screens may be of
the rotating, vibrating, or gyrating types with vibrating and
gyrating screens being the most common.
Chips are stockpiled in the open, under a roof, or enclosed in
chip silos. As least one mill presently washes chips to remove
dirt and other trash which would cause maintenance problems in
the fiber preparation stages. The quantity of dirt in chips
depends upon many factors. In the future/ hardboard mills
project utilizing the complete tree, including bark, limbs, and
leaves, which will cause additional dirt to be brought in with
the chips. There is a general industrial trend toward use of
lower quality fiber because of the increased demand for timber
35
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1.500 -
o
LiJ
t_J
ra
CD
CtL
Q.
to
UJ
-------
LOGS
o
LOG
STORAGE
LOG WASH
DEBARKER
CHIPPER
"*T*
O
TO PROCESS
CHIPS
CHIP
WASH
FIGURE 10 - RAW MATERIAL HANDLING IN THE HARDBOARD INDUSTRY
37
-------
CHI PS
00
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•^1
(30)
— LJ 1 IpiAEfe l^- i-tLi
PREHEATERjZ| REFINER 1DRYER /^l
(60)JZI3 nzj " (7.5)
CHIPS
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FIBER
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rERS| V. J | p „ F e «
i r \ i ,
U (0)
PREPRESS
MAT
** te.
, L_^-x TO
* |—^V FINISHING
BOARD
^
(XX) APPROXIMATE PERCENT MOISTURE
FIGURE 11 - TYPICAL DRY PROCESS HARDBOARD MILL
-------
products, high cost of logs, and their general scarcity. With
the use of lower quality fiber such as tree limbs and bark, it
will become more and more desirable to wash chips. Weather
conditions during logging operations have a significant effect
upon quantity of dirt picked up. Chip washing is also useful in
thawing frozen chips in more northern climates.
Fiber Preparation
Prior to passing wood chips or other fibrous raw materials
through disc pulpers or refiners, it is often expedient to give
the material some form of pre-treatment in order to reduce
subsequent power consumption and improve pulp qualities.
However, the extent of the treatment will again depend upon the
nature of the raw material and the end product desired. Steaming
softens the wood to produce a pulp with fewer broken fibers and
coarse fiber bundles. The fibers of pulp so made are more
flexible and felt together more readily to form a stronger board
than pulp from wood that has not been steamed. However, with
some species, steaming may increase the toughness of the chips
and thereby increase the energy required for defibering. This
pre-treatment operation is carried out in digesters under a
variety of conditions of time and temperature.
There are two basic methods of fiber preparation, but a wide
range of variations exist within each basic method. These two
basic methods are the (1) explosion process, and (2) thermal plus
mechanical refining.
In the explosion process, wood chips are subjected to high
temperature steam in a "gun," or high pressure vessel, and
ejected through a quick opening valve. Upon ejection, the
softened chips burst into a mass of fiber or fiber bundles. The
process is essentially a high temperature acid hydrolysis and
lignin softening procedure, and is adaptable to almost any ligno-
cellulosic material, chips approximately 1.9 cm (3/4 in) square,
prepared in conventional chippers and screened, are fed into 50.8
cm (20 in) caliber guns or high pressure vessels. Each vessel is
filled and closed, and the chips are steamed to 41.8 atm (600
psi) for about one minute. The pressure is then quickly raised
to about 69.0 atm (1000 psi), at 285°C (550°F) and held for about
5 seconds. The time of treatment at this high pressure is
critical, and is dependent upon the species and the desired
quality of the product. The pressure is suddenly released, and
the wood chips burst into a brown, fluffy mass of fiber. The
steam is condensed as it enters the cyclone and the exploded
fiber falls into a stock chest where it is mixed with water and
pumped through washers, refiners, and screens. The yields of
fiber from pulping by the explosion method are lower than those
for other pulping procedures, largely as a result the hydrolysis
of hemicellulosic material under conditions of steaming at high
pressure. The explosion process is used in only two hardboard
mills in the U.S..
39
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By far the most widely used fiber preparation method consists of
a combination of thermal and mechanical pulping. Thermal plus
mechanical refining, as its name implies, involves a preliminary
treatment of the raw material with heat in addition to mechanical
action in order to reduce the raw material to pulp. The
mechanical reduction is carried out in disc refiners or attrition
mills after the wood chips or shredded raw materials have first
been softened by steaming.
One of the advantages of this attrition mill method of pulping
over conventional grinding lies in the fact that a greater
variety of species and forms of raw material may be processed,
including materials from roundwood, slabs, edgings and veneer
residues, as well as materials such as pulp screenings, shavings
and sawdust. furthermore, with the many possibilities of
variation in pre-steaming, of plate pattern, of plate clearances,
and in a number of refining steps, there is considerable
flexibility in the production of pulps which possess a wide range
of properties. In general, attrition mills such as disc pulpers
produce a good quality of pulp. A fast draining pulp can be
readily produced, coarse fiber bundles and few abraded fibers.
In one process the chips are brought to a temperature of 170°c to
190°C (340°C to 375°F) in a period of 20 to 60 seconds by means
of steam pressure between 7.8 and 12.2 atm *(10Q to 165 psi) and
at this temperature are passed through a disc refiner. It is
claimed that because to the short steaming period, little
hydrolysis takes place and that there is little loss of wood
substance, the yield ranging from 90 to 93 percent.
In the dry process, similar equipment can be used. However, the
wood may be subjected to lower steam pressures of 3.1 to 9.2 atm
(31 to 220 psi) for somewhat longer periods (1 to 2 min) and then
passed through a disc refiner. In some cases the resin is added
to the chips while they are being refined, by pumping it through
a hole drilled through the refiner shaft.
Refiners (attrition mills) of the disc type have two discs, one
stationary and one rotating, or both rotating, for defibering and
refining. Various disc patterns are available and choice depends
on species, pre-treatment, and the type of pulp desired. In most
cases, the discs are made of special alloys. The discs are
usually 60 to 100 cm (23 to 40 in) in diameter and operate at 400
to 1,200 revolutions/min.
Double disc attrition mills, with the discs rotating in opposite
directions, do more work on the fiber and result in a higher
stock temperature, such equipment, when operating on wood chips,
produces well fiberized material. Where development of strength
is desired, further refining may be useful.
The single rotating disc mill has certain advantages. The feed
opening is more accessible and can be made very large to
40
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accomodate bulky materials. It has fewer moving parts and fewer
bearings than the double disc mill.
Factors which determine the pulp quality produced by attrition
mills are properties of the raw material, pre—treatment, plate
design, plate clearance, rate of feed, consistency, temperature,
and speed of rotation. The effect of these variables can only be
determined by experiment. Plate clearances usually vary from
1.30 mm (0.050 in) for an initial breakdown of chips to a very
low clearance for the final refining. As the clearance between
the plates is reduced the strength of the pulp is increased.
Also because of the production of more fines, however, the rate
of drainage is reduced. An improved quality of stock may be
obtained by using a plate clearance of about 0.25 mm (0.01 in),
screening out the acceptable stock and recycling the coarse
material. This procedure reduces the power consumption and the
pulp will have a higher percentage of intermediate length fibers
and fewer fines. A certain amount of fines is desirable as they
improve board properties such as rigidity, and provide a smoother
surface.
The power requirements for refiner stock from woods commonly used
vary from about 200 to 800 kw/kkg (100 to 400 hp/ton) depending
on species and pre-treatment.
The consistency of pulp leaving the attrition mill in a wet
process hardboard mill may vary over a wide range, but in general
it is between 30 and 40 percent. Lower consistencies are used
with certain material to prevent feed chokes. High consistencies
tend to produce better pulps by raising the temperature.
After conversion of the raw material to a fibrous pulp in the
attrition mills, the pulp may be screened to remove coarse fiber
bundles, knots, and slivers. Some of the coarse material can be
returned to the system for further breakdown.
There are various attrition mills on the market for the
preparation of pulp. The Asplund system has been used
extensively for preparation of stock for hardboard mills. This
involves the use of a single rotating disc and has the feature of
combining the steaming and defibering in one unit in a continuous
operation. The entire operation is carried out under pressure
and has the advantage that no cooling of the steamed chips takes
place prior to defibering, and foaming difficulties are
substantially reduced. A unit may be expected to process 9 to 45
kkg/day (10 to 50 ton/day) of dry wood, depending on the type of
wood and the degree of defibering required. For hardboard stock,
slight refining may be desirable, especially for the removal of
slivers. When using modern refining equipment, subsequent
screening may be unnecessary. However, when screening is
necessary a vibrating or rotary-type screen may be used.
41
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Forming Hardboard
The manuf act lire of hardboard consists basically of reducing wood
materials to the fibrous state and putting them back together in
the form of sheets or boards having properties and
characteristics not formerly attainable in the natural wood.
Before board formation is started, it is often desirable to
introduce certain chemical additives to the pulp which increase
the strength, water resistance, and other desirable properties of
hardboard. The additives to be used and the amounts depend on
the species of wood, degree of refining, and the final properties
desired. After the inclusion of additives to the refined pulp,
which may be in the form of either a wet slurry or a dry fluff,
the pulp is ready for delivery to the board former, to begin the
process of reassembling fibers into hardboard. The formation or
felting of fibers to form a mat may be done by either the wet-
felting (wet matting) process or the air-felting (dry matting)
process.
Wet-Felting: In the wet process the mat is usually formed on a
fourdrinier type machine similar as those used in making paper.
Refined pulp is pumped to the head box of the machine and diluted
with large quantities of water until the mixture, called "stock,"
contains only about one and one-half percent pulp by weight. The
stock flows rapidly and smoothly from the head box onto an
endless traveling wire screen. Devices control the flow of
stock, allowing it to spread evenly on the screen as an
interlaced fibrous blanket which may be several inches thick,
depending upon the desired thickness of the finished hardboard.
The screen, kept level by tension, and table rolls carry stock
onward for about 9 m (27 ft) while water is withdrawn through the
wire screen. The water is first removed by gravity. As the
screen advances, additional water is removed when it passes over
one or more suction boxes. At this point, the stock has felted
together into a continuous fibrous sheet called "wetlap." The
forming screen extends between a number of pairs of press rollers
which also have an endless screen travelling around a series of
the paired rollers. More water is removed as the press rollers
gradually apply pressure to the wetlap, in a process which is
similar to the wringing action of a washing machine.
When the wetlap emerges from press rollers it still has a high
moisture content (50 to 75 percent), yet it is strong enough to
support its own weight over a small span. At this point, it
leaves the forming screen and continues on a conveyor. The wet
mat is then trimmed to width and cut off to length by a traveling
saw which moves across the traveling mat on a bias, making a
square cut without the necessity of stopping the continuous
wetlap sheet. The thickness of wet mat is normally three or four
times the finished thickness of the hardboard to be produced. It
still contains a great deal of water. The wet mat may be de-
livered directly to a platen press where water is removed by a
combination of pressing and heating or it may be conveyed to a
heated roll dryer where water is evaporated by heating alone.
42
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The direct pressing method is used to produce smooth one-side
hardboard (SIS). The evaporative drying method is used in the
production of smooth two-side hardboard (S2SJ. These operations
will be described later.
Dry-Felting; The main difference between the air-feltingor dry
matting process, and the wet-felting process is that in the dry
process fibers are suspended in air rather than in water. The
unit developed for laying down a continuous mat of dry fibers is
called a felter. The prepared fibers are fed by volumetric
feeders to the felting unit at a controlled rate. A nozzle in
the unit then distributes fibers to the top of the felter chamber
and the fibers fall to the floor of the felter. This snowing
action produces an interwoven mat of fibers,
The floor of the felter is a moving screen which is synchronized
with the volumetric feeders, and air is sucked through the screen
to aid in the felting. As the mat emerges from the felting
chamber, it has attained the height necessary for the thickness
of the board desired.
When a finished board of 0.32 cm (1/8 in) is desired, the height
of the mat as it emerges from the felting chamber may be as much
as 10 to 15 cm (4 to 6 in). Once the mat is formed, the
procedure of compressing, trimming, and sawing of the mat is
similar to that for the wet process. However, air-formed mats
prior to pressing are always thicker and softer than wet-formed
mats and usually require more care in loading the hardboard
press*
Hardboard press
When the reassembly of wood particles is completed, fibers are
welded together into a tough, durable grainless board, on the
hardboard press. Hardboard presses are massive, consisting of
heavy steel heads and bases, each of which may weigh 45 JtJcg (50
ton) or more, held together by steel columns 25 to 30 cm (10 to
12 in) in diameter and as long as 9 to 12 m (30 to 40 ft),
Between the head and the base of the press are suspended a number
of steel platens which are drilled internally to provide
circulating passages for high pressure steam or water which is
used to provide heat necessary to help bond the fibers together.
Several hydraulic rams with a movable head are placed below the
platens and on top of the base to apply pressure upwards toward
the head of the press. When open, the hydraulic rams are at
their lowest position. Each platen, except the top and bottom
platens which are fastened firmly to the press head and moving
base, respectively, is individually suspended, allowing an air
space of 8 to 25 cm (3 to 10 in) between platens. The unpressed
mats are placed one on top of each platen so that there is an
equivalent of a multi-deck sandwich, with the mat located between
the steel platens. When the press is loaded, hydraulic pressure
is applied to the rams. This operation forces the platens up
against the head of the press, squeezing the mats down to a
43
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fraction of their former thickness. Pressures exerted may vary
from 35 to 103 atm (500 to 1500 psi) depending on the process and
density desired in the finished board. Most hardboard presses
have 20 openings and 21 platens, so that 20 boards may be pressed
at the same time. Some presses have as few as ten openings and
some as many as 30. Press sizes vary, but include 1.2 m by 4.9 m
(4 ft by 16 ft), 1.2 m by 2.4 m (4 ft by 8 ft) , 1.2 m by 5.5 m (4
ft by 18 ft), and 1.5 m by 4.9 m (5 ft by 16 ft). The first
press size is the most common production size.
The combination of heat and pressure applied to mats in the press
welds the fibers together. The actual amount of time required
for pressing and the details of temperature and pressure vary
widely, depending on the process and physical properties in the
particular hardboard being produced.
To facilitate loading and unloading the board in the press, most
presses are equipped with loading and unloading racks, which
usually take the form of multi-deck elevators, with one deck for
each opening in the hardboard press. Mats are loaded on all
decks of a loading rack. When the hardboard press is open,
impressed mats are fed into the press at the same time pressed
mats are removed at the other end of the press and placed into an
unloading rack. Then, while the new boards are under pressure,
unpressed mats are placed into the loading rack and pressed mats
are discharged one at a time from the loading rack and conveyed
to subsequent operations*
Pressing Operations: There are two basic types of hardboard,
"smooth one-side" (S1S) and "smooth two-sides" (S2S). In making
S1S hardboard, the cut-to-size mat is delivered from the board
former onto a piece of screen wire slightly larger in overall
dimensions than the piece of wet mat. The wires carrying wet
mats are loaded into the decks of the press loading racks and are
loaded into the press openings. When the press is closed and
pressure applied, a large portion of water is removed. The
remaining water must be evaporated by the heat of the press
platens. Temperatures used in the production of S1S board are
around 190°C (380°F). The entire process of pressing the board
is carefully controlled by automatic electrical equipment.
When a wet-formed mat is to be used to produce S2S hardboard, it
is delivered from the forming machine into a hot air dryer where
surplus moisture is evaporated. This may require from one to
four hours depending upon the weight of board being produced. At
this stage the mat is in large pieces, usually 2 or 3 times as
wide as the hardboard which will ultimately be pressed. The mat
is trimmed to the desired length and width (usually slightly
larger than 1.2 by 4.9 m) and delivered to the S2S hardboard
press. At this point, the board may have less than one percent
moisture content, and it is strong and rigid enough to support
its own weight. Thus, board can be delivered directly into the
press openings and pressed with smooth platens, or caul plates,
directly against both sides. Since moisture does not have to be
44
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squeezed and evaporated, the press cycle, which is from one to
four minutes for common thickness, is much shorter than for
comparable thicknesses of S1S board, which requires a 4 to 12
minute pressing time. The dried board is much harder to compress
than the soft, wet S1S; consequently, hydraulic pressures three
times greater must be applied. Press temperatures in excess of
288°C (550°F) must also be attained.
Dry-formed mat may also be used to produce S2S hardboard. When
this is done, the fibers must be reduced to a desired low
moisture content prior to the board formation. Most dry air-
formed mats are deposited directly on traveling caul plates and
delivered into the press. These traveling caul plates are
necessary because the air-formed mat is too fragile to support
its own weight before pressing* Once in the press however, the
combination of heat, pressure, and time consolidates the soft,
fluffy material into a rigid, durable product.
Oil Tempering
After being discharged from the press, hardboard may receive a
special treatment called tempering. Tempering consists of
impregnating the sheets of hardboard by dipping or roller-coating
them in a bath composed of drying oils and various drying resins
derived from petroleum.
As sheets are removed from the oil bath, they are passed through
a series of pressure rollers which increase absorption of the
oils and removes any excess. The oil is then stabilized by
baking the sheet from one to 4 hours at temperatures ranging from
143° to 171°C (290° to 340°F). Tempering hardboard increases the
hardness, strength, and water resistance, thus making the board
more resistant to abrasion and weathering.
Humidification
Sheets of hardbqard removed from the press or the tempering oven
are very hot and dry, and the boards must be subjected to a
seasoning operation called "humidification." otherwise they may
tend to warp and change dimensions. Humidification is carried
out by conveying boards through a long tunnel humidifier, or
charging them in racks which enter a chamber where a high
relative humidity is maintained. The boards are retained in the
humidifier until they reach the proper moisture content.
Further Processing
The final operation includes trimming the board to the required
size. Hardboard may also be finished by an assortment of
techniques, including simulating wood grain finishes, applying
paint for a variety of uses, embossing, and scoring.
45
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Inventory of Hardboard Industry
In 1973, there were 27 manufacturing facilities which produced
hardboard by some variation of the two basic processes. As shown
in Table 1, 17 of these were variations of the dry process and 10
were variations of the wet process. In addition, some hardboard
is produced at 6 insulation board plants, but the waste water
aspects of these will be considered along with that segment of
the timber products processing category. It has been estimated
that in 1972, the total production of hardboard in the U.S., on a
3.2 mm (1/8 in) basis, was 0.54 billion sq m (518 billion sq ft).
The geographical distribution of the hardboard industry is shown
graphically in Figure 12.
From the viewpoint of total utilization of the forest resource,
those segments of the timber products processing category which
are relatively indiscriminant in terms of the properties of the
wood raw material used are of increasing importance. High
quality lumber and plywood are prized for certain structural
characteristics which are inherent in the structure of the
harvested tree. As the timber products industry becomes more
dependent on smaller, second-growth timber and as the demands for
timber products increase, it becomes more important to develop
those categories of the industry which can use wood and wood
residues in a variety of forms and in large quantities.
In general, the categories of this type include those which can
use wood reduced to small particles or fibers and then
reconstitute them into useful form. In its entirety, this is one
of the most rapidly expanding industrial operations in the United
States. Hardboard production contributes to that growth. It has
been reported that 16 times as much hardboard was used in 1953 as
compared with 1929, The Forest Products Research Society
reported that hardboard production on a 0.32 cm (1/8 in) basis
increase^ from 0.09 billion sq m (0.96 billion sq ft) in 1948 to
0.14 billion sq m (1.5 billion sq ft) in 1955. In 1968, 27
hardboard plants in the U.S. produced approximately 0.39 billion
sq m (4.2 billion sq ft) of product. During the first part of
1973, plans for 3 new dry process plants were completed and
construction was begun.
A U.S. Forest service survey published in 1964, based on
information collected in 1962, established that the amount of
timber consumed in the U.S. has increased to 0.37 billion cu m
(13 billion cu ft) annually. It projected a demand of 0.79
billion cu m (28 billion cu ft) by the year 2000 - more than
twice the 1962 level - based on a population of 325 million. The
increased population must also be sheltered, and experts predict
100 million homes must be built in the next 30 years. If
hardboard manufacture increases at the same rate during the next
decade as in the last two decades, annual production is projected
to be 0.93 billion sq m (10 billion sq ft) by 1980. Ten plants
with an annual capacity of 39 million sq m (420 million sq ft)
each would have to be completed to meet this demand.
46
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CH I PS
FIBER
DILUTION
WATER
CHIPS
SCREW
-FEED
M AT
BOARD
TO ATMOSPHERE
WET FORMING
MACHINE
WET I—T-\
PRESS I—L-,/
' TO
I FINISHING
WATER IN
WATER OUT
(XX) APPROXIMATE PERCENT FIBER
(CONSISTENCY IN PROCESS)
FIGURE 12 - TYPICAL WET PROCESS HARDBOARD MILL
-------
TABLE 7
INVENTORY OF HARDBOARD MANUFACTURING FACILITIES
DRY PROCESS
Anacortes Veneer
Anacortes, Washington
Celotex Corporation
Deposit, New York
Celotex Corporation
Marion, South Carolina
Celotex Corporation
Paris, Tennessee
Evans Products
Doswell, Virginia
Evans Products
Moncure, North Carolina
Evans Products
Phillips, Wisconsin
Georgia-Pacific Corporation
Coos Bay, Oregon
DRY-WET PROCESS
Weyerhaeuser Company
Klamath Falls , Oregon
Georgia Pacific Corporation
Conway, North Carolina
Masonite Corporation
Spring Hope, North Carolina
Masonite Corporation
Towanda, Pennsylvania
Pope and Talbot
Oakridge, Oregon
Superwood (Nu-Ply)
Bemidj i, Minnesota
U.S. Plywood
Champion International
Catawba, South Carolina
U.S. Plywood
Champion International
Lebanon, Oregon
Weyerhaeuser Company
Broken Bow, Oklahoma
WET PROCESS
Abitibi Corporation
Roaring River, North Carolina
Evans Products
Corvallis, Oregon
Forest Fibre
Stimpson Lumber Company
Forest Grove, Oregon
48
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TABLE 7 CONTINUED
(INVENTORY OF HARDBOARD MANUFACTURING FACILITIES)
Masoriite Corporation
Laurel, Mississippi
Masonite Corporation
Ukiah, California
Superior Fibre
Superior, Wisconsin
Superwood
Duluth, Minnesota
Superwood
North Little Rock, Arkansas
U.S. Plywood
Champion International
Dee (Hood River), Oregon
WET-DRY PROCESS
Abitibi Corporation
Alpena, Michigan
WET-DRY HARDBOARD PLANTS
OPERATED IN CONJUNCTION
WITH INSULATION BOARD PLANTS
Boise Cascade
International Falls, Minnesota
Temple Industries
Diboll, Texas
U.S. Gypsum
Danville, Virginia
U.S. Gyps urn
Greenville, Miss issippi
U.S. Gypsum
Pilot Rock, Oregon
Weyerhaeuser Company
Broken Bow. Oklahoma
49
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CJl
o
LEGEND
WET PROCESS
DRY PROCESS
DRY-WET PROCESS
WET- DRY PROCESS
WET-DRY/ INSULATION
FIGURE 13 - GEOGRAPHICAL DISTRIBUTION OF HARDBOARD MANUFACTURING
FACILITIES IN THE UNITED STATES
-------
Somewhat akin to the saw mill part of the timber products
processing industry, hardboard operations are spread nationally
with some production of each kind in each forest region of the
U.S.. The hardboard and particle board industries can use the
residues from other wood working plants and accordingly provide
opportunities to reduce the cost of other products and expand the
development of completely integrated wood industries.
It is anticipated that there will be two major factors which will
influence the location trend of future hardboard plant additions.
The trend toward integrated forest product complexes, which
involve pulp and paper, plywood, hardboard operations, and other
operations all contained at one location is expected to increase.
Installations such as these will be predicated upon the benefits
derived from logistics and economics. Currently, about one-third
of the hardboard plants are owned by one of the major forest
industry companies, and this percentage is expected to increase
moderately in the near future, which will no doubt have some
impact on the location trend.
The other major factor influencing growth trend is that
associated with supply and demand, with new plants being located
where there is demand predicted on the dynamic growth and
expansion areas. Raw material availability and price may have
some impact on the development of this particular growth trend.
By far the most dynamic growth areas are the South Atlantic,
South Central, and Pacific Coast regions. It is anticipated that
the growth trend will intensify in these three areas during the
next decade and probably on into the 1990's.
Due to the anticipated demand for hardboard production, it is not
expected that any operations will be phased out prior to 1980.
After this time, however, wet process plants in the capacity
range of 4.6 to 9.3 million sq m (50 to 100 million sq ft) may
become economically marginal.
WOOD PRESERVING
The wood preserving process is one in which round and sawn wood
products are treated by the injection of chemicals that have
fungistatic and insecticidal properties or impart fire
resistance.
The most common preservatives used in wood preserving are
creosote, pentachlorophenol, and various formulations of water-
soluble, inorganic chemicals, the most common of which are salts
of copper, chromium, and arsenic. Fire retardants are
formulations of salts, the principal ones of which are borates,
phosphates, and ammonium compounds. Eighty percent of the plants
in the U.S. use at least 2 of the 3 types of preservatives. Many
treat with one or 2 preservatives plus a fire retardant .
51
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Treatment is accomplished by either pressure or non-pressure
processes. Pressure processes for treating wood with
preservatives employ a combination of air and hydrostatic
pressure and vacuum. Differences among the various pressure
treating processes used are based mainly on the sequence of
application of vacuum and pressure. Nonpressure processes
utilize open tanks and either hot or cold preservatives in which
the stock to be treated is immersed. Employment of this process
on a commercial scale to treat timbers and poles is largely
confined to the Rocky Mountain and Pacific regions, particularly
the latter. In the East, the process is used to treat lumber and
posts. The conditioning method that must be employed to prepare
stock for preservative treatment is partially dependent on the
species of wood. Some species, such as the southern pines, are
conditioned by a process in which the stock is steamed at
approximately 118°C (245°F) for periods of from 1 to 16 hours
preparatory to preservative treatment. The purpose of this
process, which is normally carried out in the same retort in
which the actual injection of preservative is subsequently
performed, is to reduce the moisture content of green wood and to
render the wood more penetrable, thus improving the quality of
the preservative treatment. Other species, i.e., Douglas fir,
are conditioned for the same purposes by a process called
Boultonizing, in which the wood is heated under vacuum in the
retort at 82° to 104°c (180° to 220°F) prior to preservative
injection. Boultonizing is not used where the preservative is of
the water-borne type.
Waste water generated in steam conditioning is composed of both
steam condensate and water removed from the wood. Waste water
from the Boultonizing process is composed only of water removed
from the wood. Both waste streams are contaminated by the pre-
servative used, and, where the same preservative is used, the
difference between them is primarily a quantitative one.
A process flow diagram for a typical plant using steam condition-
ing is shown in Figure 14.
Consumption data for the principle preservatives for the 5-year
period between 1967 and 1971 are given in Table 8. In terms of
amount used, creosote in its various forms is the most important,
followed in order by pentachlorophenol and salt-type
preservatives. Among the latter, the CCA (copper-chromium-
arsenic) formulations account for most of that used.
The general trend in preservative use is a decrease in creosote
consumption and an increase in the use of pentachlorophenol and
salt-type preservatives. This trend is expected to continue.
Consumption of fire retardants has been relatively stable for the
past five, years, but it is anticipated that it will increase
significantly as existing building codes are modified to permit
the use of fire retardant treated wood in lieu of other
flameproof construction materials.
52
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FIGURE 14 - PROCESS FLOW DIAGRAM FOR A TYPICAL WOOD-PRESERVING PLANT
(COURTESY OF ALBERT H. HALFF ASSOCIATES, INC., DALLAS, TEXAS)
-------
TABLE 8
CONSUMPTION OF PRINCIPAL PRESERVATIVES AND FIRE RETARPANTS
OF REPORTING PLANTS IN THE_UNITED STATES, 1967-1971
Year
Material
(Units) 1967_ 1168 1969 19.70. 1971_
Creosote
Creosote-
Coal Tar
Creosote-
Petroleum
Total
Creos ote
Total
Petroleum
Penta-
chlorophenol
Chromated
Zinc Chloride
CCA
ACC
Pyresote
Non-Com
FCAP
Osmose Flame
Proof
Other
Solids
Million
Liters
Million
Liters
Million
Liters
329 293 274 256 242
216 219
206
229 218
Million
Liters 559
135 121 115 125 118
518 485 475 441
Million
Liters 279
279 258 286 307
Million
Kilograms 11.2 12.0 11.6 12.9 14.5
Million
Kilograms
0.8 0.7 0.6 0.7
Million
Kilograms 1.0 1.4 2.1 2.7
0.6
3.9
Million
Kilograms
0.6 0.5 0.4 0.4 0.5
Million
Kilograms 1.3 1.7 1.1 1.2 1.2
Million
Kilograms 2.4 2.7 3.4 3.1 2.8
Million
Kilograms 2.4 1.8 2.0 1.2 1.0
Million
Kilograms 2.0 1.8 1.8 2.0 2.4
Million
Kilograms 2.7 _ 2.8 2.3 1.7 1.7
Note: Data are based on information supplied by approximately
357 plants for each year.
54
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Inventory of the Wood Preserving Segments
The wood preserving industry in the U.S. is composed of
approximately 390 treating plants, 315 of which use pressure
retorts. Most of the plants are concentrated in two distinct
regions. The larger region extends from East Texas to Maryland
and corresponds roughly to the natural range of the southern pine
which is the major species utilized. The second concentration of
plants is located along the Pacific Coast, where Douglas fir and
western red cedar are the species of primary interest to the
industry. Only 23 percent of the plants in the U.S. are located
outside these two regions. The distribution of plants by type
and location is given in Table 9.
The production of treated wood is very responsive to the general
state of the national economy, particularly the health of the
construction industry. Production overall decreased from 1967 to
1971 (Table 10), but is expected to show a sharp increase for
1972.
The volume of wood treated with creosote showed the largest
decrease during the 1967 to 1971 period, and accounted for most
of the decrease in total production. Wood treated with
pentachlorophenol registered a slight increase during the period,
while that treated with CCA-type preservatives increased almost
four-fold. Production of fire-retardant treated wood remained
essentially constant- These trends are expected to continue,
except that an increase in the production of fire-retardant
treated wood is anticipated.
55
-------
TABLE
WOOD PRESERVING PLANTS IN THE UNITED STATES BY STATE AND TYPE
(1971)
C o mme r c i a1
Railroad and Other
NORTHEAST
Connecticut
Delaware
Dist. of Columb
Maine
Maryland
Massachuset ts
New Hampshire
New Jersey
New York
Pennsylvania
Rhode Island
Vermont
West Virginia
TOTAL
NORTH CENTRAL
Illinois
Indiana
Iowa
Kans as
Kentucky
Michigan
Minnesota
Missouri
Nebraska
North Dakota
Ohio
Wis cons in
TOTAL
SOUTHEAST
Florida
Georgia
North Carolina
South Carolina
Virginia
TOTAL
Pressure
0
1
ia 0
0
6
1
1
4
5
6
1
0
3
28
6
6
0
0
6
4
3
7
0
0
7
3
42
23
24
18
11
15
91
Non-
Pressure
0
0
0
0
0
0
0
2
0
0
0
0
0
2
0
0
0
0
0
2
5
5
0
0
0
0
12
1
1
0
0
1
3
Pressure
and Non-
Pressure
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
2
0
1
0
0
1
4
1
2
0
0
1
4
Pressure
0
0
0
0
0
0
0
0
0
1
0
0
0
1
0
0
0
0
0
0
1
0
0
0
0
1
2
0
0
0
0
0
0
Non-
Pressure
0
0
0
0
0
0
0
0
1
0
0
0
1
2
1
0
1
0
0
0
0
0
0
0
0
1
3
0
0
1
0
0
1
Total
Plants
0
1
0
0
6
1
1
6
6
7
1
0
5
34
7
6
1
0
6
6
11
12
1
0
7
6
63
25
27
19
11
17
99
56
-------
TABLE
CONTINUED
Commercial
Railroad and Other
SOUTH CENTRAL
Al ab a ma
Arkansas
Louisiana
Mississippi
Oklahoma
Tennessee
Texas
TOTAL
ROCKY MOUNTAIN
Arizona
Colorado
Idaho
Montana
Nevada
New Mexico
South Dakota
Utah
Wyoming
TOTAL
PACIFIC
Alaska
California
Hawaii
Oregon
Washington
TOTAL
UNITED STATES
TOTAL
Pressure
22
11
21
18
6
6
27
111
1
2
3
2
0
1
0
0
1
10
0
8
3
6
7
24
306
Non-
Pressure
1
0
0
1
0
1
3
6
0
0
3
3
0
0
0
1
0
7
0
0
0
0
5
5
35
Pressure
and Non-
Pressure
0
1
1
3
0
0
2
7
0
.0
0
1
0
0
1
1
1
4
0
2
0
4
4
10
30
Pressure
0
0
0
0
0
1
2
3
0
0
0
2
0
1
0
0
0
3
0
0
0
0
0
0
9
Non-
Pressure
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
1
0
2
0
0
1
3
10
Total
Plants
23
12
22
22
6
8
34
127
1
2
7
8
0
2
1
2
2
25
0
12
3
10
17
42
390
57
-------
01
CD
TABLE 10
MATERIALS TREATED IN THE_UNITED STATES, BY PRODUCT AND PRESERVATIVE, 1967-1971
(Note:
Pres ervative
Creosote and
Creosote-Coal
Tar
Creosote-
Petroleum
Petroleum-
Pentachloro-
phenol
Chromated
Copper
Ars enate
Components may not add to totals due to rounding.)
Thousand Cubic Meters
Year
1967
1968
1969
1970
1971
1967
1968
1969
1970
1971
1967
1968
1969
1970
1971
1967
1968
1969
1970
Poles
and
Piling
1,636
1,456
1,330
1,315
1,172
30
27
18
18
15
950
927
919
1,074
1,157
5
11
35
42
Railroad
Ties
1,683
1,712
1,497
1,650
1,856
808
125
694
806
775
7
6
5
10
4
1
0.2
1
1
Lumb er
and
Timbers
504
528
451
357
342
82
97
81
62
45
446
54
450
436
430
146
197
254
366
Fence
Posts
184
184
175
181
193
68
45
42
32
27
290
224
212
194
233
3
4
7
9
Other
100
100
93
78
70
12
11
7
9
9
186
168
142
146
143
0.5
4
8
10
Total
4,146
3,980
3,545
3,587
3,6326
1,000
905
849
926
871
1,879
1,846
1,729
1,864
1,967
217
306
306
4287
-------
01
10
T ABL E 10 CONTINUED
Thousand Cubic Meters
Preservative
Fluor Chrome
Arsenate
Phenol
Creosote-
Pentachloro-
phenol
Chromated
Zinc
Chloride
Acid
Copper
Chromate
Year
1967
1968
1969
1970
1971
1967
1968
1969
1970
1971
1967
1968
1969
1970
1971
1967
1968
1969
1970
1971
Poles
and
Piling
2
2
19
0.1
0.3
222
211
187
140
97
0.1
0.6
— —
_ — —
— _
Railroad
Ties
6
2
2
2
2
0.1
—
— —
—
»» —
„ —
— _
— — —
_ —
Lumb er
and
Timbers
346
231
193
128
173
0.9
9
13
11
17
29
29
26
22
20
61
48
37
31
56
Fence
Posts
5
5
3
1
1
0.5
1
0.5
1
0.1
_.__
___
0.1
— _—
0.1
0.1
Other
37
28
28
17
31
1
0.8
0.2
— —
6
0.6
0.2
0.1
__—
___.
Total
397
268
245
142
208
225
222
200
152
114
35
29
27
22
21
61
48
37
31
56
-------
TABLE 10 CONTINUED
Thousand Cubic Meters
Preservative
Fire
Retardants
All
Others
All
Preservatives
Year
1967
1968
1969
1970
1971
1967
1968
1969
1970
1971
1967
1968
1969
1970
1971
Poles
and
Piling
„_
___
12
15
13
12
4
2,857
2,649
2,522
2,600
2,492
Railroad
Ties
3
2
0.3
2
_— -
._—
0.1
0.1
2,508
2,447
2,199
2,469
2,639
Lumber
and
Timbers
99
94
104
10-0
47
18
72
3
19
1,716
1,772
1,687
1,576
1,694
Fence
Posts
1|ti_t
— «.
— -
6
4
3
62
3
595
466
443
428
472
Other
32
42
30
37
7
6
13
6
2
382
360
323
292
305
Total
134
138
134
138
71
43
102
83
28
7,538
7,695
7,175
7,366
7,602
-------
SECTION IV
INDUSTRY SUBCATEGORIZATION
INTRODUCTION
In developing effluent limitations guidelines and standards of
performance for new sources for a.given industry, a judgment must
be made by EPA as to whether effluent limitations and standards
are appropriate for different subcategories within the industry.
The factors considered in determining whether such subcategories
are needed for the segments of the timber products processing
category of point sources are:
1. Products Produced
2. Manufacturing Process Employed
3. Raw Materials .
4. Plant Age
5. Plant Size
.6. Wastes Generated
7. Treatability of Waste Waters
8, Air Pollution Control Equipment
Based upon an intensive literature search, plant inspections, and
communications with the industry, it is the judgment of the
Agency that the timber products processing category should be
subcategorized by product and by the type of manufacturing
process employed. A discussion of these and other factors
considered in this judgment follows.
FACTORS IN INDUSTRY SUBCATEQQRIZATION
Type of Products Produced
As discussed in section III, there are wide differences in the
products manufactured by the segment of the timber products
processing category being considered. Logs are barked to produce
an intermediate product common to most of the timber products
processing category. This intermediate product is further
processed into veneer and plywood, hardboard, and treated or
preserved wood. Because of the readily apparent disparity among
these products it is initially concluded that the timber products
processing category can be subcategorized on the basis of the
61
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type of product produced. Thus, the initial industry
subcategorizations established are: (1) barking, (2) veneer and
plywood manufacture, (3) hardboard manufacture, and (4) wood
preserving. While barking does not produce a commercial product,
it is a necessary initial operation throughout the industry, and
for the purposes of this report is considered to produce an
unfinished or intermediate product.
Manufacturing Process Employed
The manufacturing process used in the production of a given
product have been found to be so different as to support the
previous subcategorization and form a basis for further
subcategorization in certain instances.
The process of barking or removing the bark layer from logs may
be carried out either by mechanical abrasion or hydraulic removal
as previously discussed. These processing operations are
different from those used in any other segment of the category.
Hence, this tends to reinforce the initial segregation of barking
as a subcategory.
The principal processes employed in manufacturing veneer and
plywood are unlike those employed in other segments of the
category. The operations of log conditioning, veneer cutting,
veneer drying, veneer preparation, gluing, pressing and finishing
have been previously described and are unique to this segment of
the category. This reinforces the previous preliminary
conclusion that its veneer and plywood segment should be
considered separately from the other segments of the timber
products category. Also, since the veneer manufacturing process
is a separate operation with waste water quality and quantity
generation differences, and plywood manufacture is a process not
always occurring in the same plant, they logically fall into
distinct subcategories.
One method of log conditioning employs live steam to heat the
logs directly and another uses steam to heat the conditioning
vats resulting in significant discharges of process waste waters.
Other log conditioning methods do not produce large discharges of
process waste waters. Available data indicates that an allowance
may be necessary in the veneer subcategory for those operations
which use direct steam contact to condition wood prior to veneer
cutting, and which are currently unable, or chose not to,
implement other conditioning methods prior to 1983.
The manufacturing processes used to manufacture hardboard are
unique within the timber products category. These processes,
which include chipping, fiber preparation, forming (either wet-
or air-felting), pressing, tempering and finishing, have been
described in detail in Section III. This uniqueness of
manufacturing operations tends to confirm that hardboard
manufacturing should be considered separately within the timber
products processing category.
62
-------
There are two significantly different manufacturing processes in
the\ hardboard industry which afford a basis for further
subcategorization. These are the dry felting process and the wet
felting process. In the dry-felting process the fibers are
suspended in air as the mat is formed, while in the wet-felting
process the fibers are suspended in water. There is little
process waste water generation from the dry-felting process,
while there is a continuous and substantial waste water
generation from the wet-felting process.
Wet-felting (wet process) hardboard mills may press board either
dry or wet. If the board is to be pressed dry it is oven-dried
before pressing, since there is only one existing hardboard mill
which produces hardboard alone by wet-felting and dry pressing,
it does not warrant consideration as a separate category.
There are several insulation board mills which produce hardboard
by the wet process followed by dry pressing. Because insulation
board mills will be considered in a future regulation and because
the interrelationship between the manufacture of insulation board
and hardboard, if any, is unknown at this time, these mills will
be addressed by a future regulation.
In wet process hardboard mills, fiber preparation is a major
factor affecting waste water characteristics. Two mills utilize
the explosion process for fiber preparation, thus causing sub-
stantially more BOD to be released. However, both of these mills
have installed evaporators to handle this high BOD process waste
water and their overall waste discharge is as low or lower than
other wet process mills. All other mills use a combination
thermal-mechanical process for fiber preparation. The degree of
fiber preparation will depend upon many factors including wood
species, inplant processes, and final product. There are even
separate fiber preparation lines for boards that are made up in
layers with the degree of fiber preparation for each layer
dependent upon the product to be produced. The effect of fiber
preparation on waste water flow and composition is not sufficient
in itself to be used as grounds for subcategorizing the industry.
Wood preserving consists of treating round (barked) or sawn wood
products by infusing them with chemicals to protect the wood from
insects, microorganisms, fungi and fire. The chemicals used may
be either oil type or salt (water soluble) type, and may be
infused into the wood by soaking or pressure treatments, indirect
steaming, prior to chemical infusions, the wood may be
conditioned by direct heating, by a vacuum heating process called
Boultonizing, or the wood may not be conditioned at all. The
considerable differences between the processes employed in wood
preserving and the other segments of the timber products category
clearly confirm the preliminary conclusion that wood preserving
should be considered separately from the remainder of the
segment.
63
-------
Water use and waste characterization, related to the process
employed, and discussed in Section V, indicates that the wood
preserving portion should be further divided for the purpose of
establishing effluent guidelines and standards. The waste water
volume generated during the conditioning step prior to infusing
chemicals into the wood appears to offer a logical separation of
the portion. The volume of process waste water generated in the
direct steam conditioning process is relatively large so that
treatment with discharge of the treated effluent appears
necessary. The process waste water volumes generated by the
Boulton conditioning process are relatively small and can be more
readily managed, opportunities for reuse of the small volume of
waste water, generated in the treating of wood with water soluble
preservatives, are available, unless the salts are used with
steam conditioning. The nonpressure treatment methods produce
almost no process waste water and can also be classified along
with Boultonizing in this regard. Therefore, the wood preserving
segment of the timber products category can be subcategorized
into (1) processes using direct steam conditioning of stock to be
treated, (2) processes using Boultonizing, and (3) other wood
preserving processes, inclusively.
Raw Materials
Numerous species of wood are used in the industry and waste water
characteristics may vary somewhat with raw material. Softwoods
in contact with water (particularly hot water), release more wood
sugars than do hardwoods. Within the broad categories of
softwood and hardwood there are also many species with varying
leaching characteristics. In addition, it is known that minor
process variations are often dictated by the type of raw
material. For example, hardwood logs may require a different
type of conditioning than species of softwood do.
While it would be expected that different waste water charac-
teristics result from different raw materials, it is observed
that volumes of waste waters vary only with process variations.
The control and treatment technology applied within these
segments of the industry consist to a large degree of recycle and
containment and is more a function of waste water volume than of
pollutant concentration, Therefore, dif ferences according to
species do not significantly affect the degree to which waste
waters can be treated or controlled.
Thus, while there are a number of distinctions related to raw
material used within the industry, the data generated in this
study indicates that these differences are insufficient to become
a basis for further subcategorization.
Age of Facility
The age of the manufacturing facility has been considered as a
factor for subcategorization of the industry. Barking is
accomplished by a variety of processes and ages of equipment.
64
-------
within the group of processes which use mechanical abrasion to
remove the bark, th^re appears to be no change in the water
pollution vectors attributable to age of equipment. Similarily,
the age of hydraulic barkers has no determinable impact on waste
water pollutants.
The veneer and plywood subcategories include a number of older
manufacturing facilities. The softwood plywood manufacturing
subcategory, however, has been experiencing substantial growth
for the past 20 years, and numerous new facilities have been
constructed. The southeastern U.S., the main area for new
development, contains many of the newer plywood plants. Even
though the ages of plants vary, the ages of various components
within a plant are not necessarily reflected in installation age
as equipment is constantly being modernized and replaced.
A. review of information available and data from the plants in the
hardboard subcategory indicates that plant age has no significant
relationship to waste water generation, quality or quantity.
Within the hardboard subcategory, the major effects of plant age
are higher equipment maintenance costs and possible difficulties
involving the installation of recycle systems, but not in waste
water flows or concentration.
In the wood preserving manufacturing sutcategory, while plants of
varying ages exist, there is no consistently defensible measure
of the effect, of plant age on waste water generation or control.
Plant Size
Plant size has been considered as a basis for subcategorization
of the timber products processing category and this analysis
indicates that no,subcategorization should be made on this basis.
The relative quantity of process waste water pollutants from
barking operations generally are not size-sensitive as the
installation of additional duplicate units is required to handle
larger capacities. The size of mills within the plywood
subcategory can vary drastically from "backyard" operations
producing 200,000 sq m/yr (2 million sq ft/yr) of plywood to a
large plywood mill producing 56 million sq m (600 million sq
ft/yr). Since the volume of waste water produced by a mill is
largely proportional to the size of the mill, control and
treatment are similarly proportional. Hence, plant size is
rejected as a possible element for subcategorization.
within the hardboard subcategory, it has been determined from
existing data and from on-site inspections that, other than in
volumes of process waste water, plant size has no effect upon the
waste water characteristics and, therefore, does not present a
rational base for subcategorization. Plant size will only affect
costs of treatment as economies of scale for larger plants may
show a generally a lower unit cost than for small plants.
65
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Wastes Generated
While there are distinct differences in the quality and
characteristics of the various waste waters generated in the
timber products processing category, a careful examination of the
information in Section V shows that the most significant
differences are quantitative, and are directly related to product
manufactured and manufacturing process employed. As an example,
variation in waste generated in the hardboard portion of the
industry is directly related to the two different manufacturing
processes utilized in making hardboard. The waste water flow,
excluding cooling water, from a typical dry process hardboard
mill will consist of a discharge of less than 1,890 I/day (500
gal/day). This compares with a waste water flow of 1,500,000
I/day (378,000 gal/day) from a typical wet process hardboard
mill. Since wastes generated are similarly related to products
and proce ss es in the remainder of the industry, a
subcategorization on this basis is not indicated, because it is
effectively accomplished by manufacturing process employed.
Treatabilitv of Waste Waters
The waste waters generated by the barking, veneer, plywood r
hardboard-dry process, and hardboard-wet process portions of this
segment contain as major pollutants, BOD and suspended solids.
These parameters are usually treated by biological methods.
waste waters generated by the wood preserving portion of the
segment may include, in addition to the above listed parameters,
pollutants such as COD, heavy metals, phenols, and high
concentrations of oil and grease. This difference is considered
in subcategorization*
Air Pollution Control Equipment
Air pollution is not a major problem in this manufacturing
segment. Air pollution and its control is not a major problem in
this segment of the timber products processing industry. In
situations where air pollution problems exist, the type of
control equipment required may be a venturi type scrubber. This
system can be operated as a closed system with limited
requirements for blowdown, and, therefore, the industry
subcategorization should not be be affected by air pollution
equipment.
66
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SUMMARY OF SUBCATEGORIZATION /
The segments of the timber industry considered in this dpcument
have been separated into the following subcategories for the
purpose of establishing effluent guidelines and standards. These
subcategories are defined as;
1. Barking. The barking subcategory includes the operations
which result in the removal of bark from logs. Barking may be
accomplished by several types of mechanical abrasion or by
hydraulic force.
2. Veneer* The veneer subcategory includes the operations used
to convert barked logs or heavy timber into thinner sections of
wood known as veneer.
3. Plywood. The plywood subcategcry includes the operations of
laminating layers of veneer to form finished plywood.
<*. Hardboard - Dry Process. The dry process hardboard
subcategory includes all of the manufacturing operations
attendant to the production of finished hardboard from chips,
sawdust, logs, or other raw materials, using the dry matting
process for forming the board mat.
5. Hardboard - wet Process. The wet process hardboard
subcategory includes all of the manufacturing operations
attendant to the production of finished hardboard from chips,
sawdust, logs, or other raw materials, using the wet matting
process for forming the board mat.
6. Wood Preserving. The wood preserving subcategory includes
all wood preserving processes in which steaming or boultonizing
is not. the predominant method of conditioning, all non-pressure
preserving processes, and all pressure or non-pressure processes
employing water borne salts, in which steaming or vapor drying is
not the predominant method of conditioning.
7. Wood Preserving - Steam. The wood preserving-steam
subcategory includes all processes that use direct steam
impingement on the wood being conditioned as the predominant
method of conditioning, discharges resulting from wood preserving
processes that use vapor drying as a means of conditioning any
portion of their stock, discharges that result from direct steam
conditioning wood preserving processes that use fluor-chromium-
arsenic-phenol treating solutions (FCAP) , discharges resulting
from direct steam conditioning processes and procedures where the
same retort is used to treat with both salt-type and oil type
preservatives, and discharges from plants which direct steam
condition and apply both salt type and oil type treatments to the
same stock.
67
-------
8* Wood Preserving - Boultonizing. The wood preserving-
boultonizing subcategory covers those wood preserving processes
which use the Boulton process as the method of conditioning
stock.
68
-------
SECTION V
WATER USE AND WASTE CHARACTERIZATION
LOG BARKING
The water employed in hydraulic barking must be free of suspended
solids to avoid clogging nozzles. Results of analyses of the
effluent from a hydraulic barking installation are shown in Table
11. The total suspended solids content in the discharge from
hydraulic barking ranges from 521 to 2,362 mg/1, while BOD values
range between 56 and 250 mg/1.
Results of an analysis of the effluent from a drum barker is also
given in Table 11. Total suspended solids concentrations are
only slightly higher in a drum barker than in a hydraulic barker,
but BOD values are significantly higher. Drum barking waters are
often recycled, which accounts for part of the increase. The
higher BOD values are also due to a longer contact between the
bark and the water and to the grinding action which is absent in
hydraulic barking.
BOD values may also be affected by the species of wood barked and
by the time of the year in which the log is cut.
VENEER AND PLYWOOD MANUFACTURING
Water usage varies widely in the veneer and plywood portion of
the industry, depending on types of unit operations employed and
the degree of recycle and reuse of water practiced. In general,
total water usage is less than 3.15 I/sec (50 gal/min) for a mill
producing 9.3 million sq m/yr (100 million sq ft/yr). There are
plants presently being designed to recycle all waste water,
however, none are now in operation. Considerable effort can, in
any case, be made to reduce the amount of waste water to be
discharged or contained. The amount of information available on
volumes and characteristics of waste waters from the industry is
minimal. Data cited in waste water characterization is based
mostly on data from the literature, information supplied by
individual mills, and sampling and analyses conducted for the
purposes of this study. Because the volumes that are involved
are small, attention has been directed to finding methods for
reducing the volumes and ways of handling process water in such a
way as to eliminate discharges.
In veneer and plywood mills,
operations:
water is used in the following
69
-------
TABLE 11
ANALYSIS OF DEBARKING EFFLUENTS
Total
Suspended
Type of Solids
Mill Debarking (mg/1)
Non-Set
Solids BOD5
(mg/1) (mg/1)
Color Units
1
2
3
4
5
6
7
/
8
9
10
11
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
, i j
Hydraulic
Hydraulic
Drum
Drum
Drum
2,362
889
1,391
550
521
2,017
9 nnn
z , uuu
600
2,017
3,171
2,875
141
101
180
66
53
69
F200
41
69
57
80
85
101
64
99
121
56
Q7
y i
250
480
605
987
Less than 50
Less than 50
Less than 50
Less than 50
Less than 50
Less than 50
35
20
Less than 50
Less than 50
70
-------
(1) Log conditioning
(2) Cleaning of veneer dryers
(3) Washing of the glue lines
and glue tanks
(4) Cooling
Figure 15 presents a detailed process flow diagram.
use and waste characteristics for each operation are
below.
The water
discussed
Log Conditioning
Veneer and plywood manufacturing operations use two distinct
types of log conditioning systems. These systems are discussed
in Section III, and are referred to as steam vats and hot water
vats. In the South about 50 percent of the plants use steam vats
and 50 percent use hot water vats. In the West, however, only
about 30 percent of the plants use any kind of conditioning and
these plants use steam vats almost exclusively.
The only waste water from a steam vat is from condensed steam.
This water carries leachates from the logs as well as wood
particles. Table 12 presents the results of analyses of waste
waters from steam vats. The magnitudes of these flows vary
according to the size and number of vats. A plant producing 9.31
million sq m/yr (100 million sq ft/yr) of plywood on a 9.53 mm
(3/8 in) basis has an effluent of about 1.58 to 3.15 I/sec (25 to
50 gal/min). A southern plywood mill (Plant A, Table 20)
produces a BOD load of 2,500 kg/million sq m (515 Ib/million sq
ft) of production on a 9.53 mm (3/8 in) basis, and a total solids
load of 29,200 kg/million sq m of production on a 9.53 mm (6,000
Ib/million sq ft) (3/8 in) basis.
A hot water vat conditions the log with hot water heated either
directly with steam or by means of heating coils with steam, oil,
or other heat sources. When the vat is heated indirectly, there
is no reason for a constant discharge. Hot water vats are
usually emptied periodically, regardless of heating method, and
the water and the solids that build up in the closed system is
discharged and replaced with clean water, some plants settle the
spent waste water and pump it back into the vats. Chemical
characteristics for hot water vats for a number of veneer and
plywood plants are given in Table 13.
Dryer Washwater
Veneer dryers accumulate wood particles. Volatile hydrocarbons
will also condense on the surface of dryers to form an organic
deposit called "pitch." In order to avoid excessive buildup of
these substances, dryers must be cleaned periodically. Wood
particles can be removed either by flushing with water or by
blowing with air. While some of the pitch can be scraped off,
generally a high pH detergent must be applied to dissolve most of
the pitch and then it must be rinsed off with water.
71
-------
ro
TA-BLE 12
CHARACTERISTICS OF STEAM VAT DISCHARGES
Concentrations
Plant
A
B
C
D
E
F
BOD
470
3,117
2,940
1,499
1,298
476
COD
6,310
4,005
8,670
3,435
3,312
1,668
BS
2^430
. *—
5,080
2,202
2,429
917
SS
2,940
86
370
389
107
.74
TS
5,370
__
5,450
2,591
2,536
991
Turb .
450
__
245
249
30
28
Phenols
0
0
0
0
.69
.57
—
.30
.20
Kjld
-Wv
16.
•-3?>
—
1.
4.
-8
8
5
3
87
?3
T-PO^-P pH
5.70 4.12
14 4.1-6.1
5.38
5,3
.173
1,93
Note: All units are in mg/1 except Turbidity, which is in JTU^s and pH.
-------
47,034(1)
163,440(s)
163,440(1)
44, 220 (s)
1,634(1)
1 ZtA C]\
WATER
IN
LOGS
i
(50)
•
LOG
CONDITIONING
•
(50)
f
VAPORS
OFF
DRYERS
'
(3)
i
DRYER
WASHING
WAT
I-N
PLYW
<
(3)
ER
DOD
k
(7)
VAPORS
OFF
PRESS
<
i
(7.5)
GLUE
WASHUP
' i
i
(7.5)
GLUE
6,583(1)
454(s)
4,222(1)
4,222(1)
4,222(1)
(1) - liquid water
(2) - steam
(XX) - % of moisture by weight
based on dry wood
Water in = 485,800
Water out= 485,800
All units in Kg of water per Day
(Ib. of water per Day)
FIGURE 15 - WATER BALANCE FOR A PLYWOOD MILL PRODUCING
9.3 MILLION SQUARE METERS PER YEAR
ON A 9.53mm BASIS
73
-------
TABLE 13
CHARACTERISTICS OF HOT WATER STEAM VAT DISCHARGES
Concentrations
Plant
A
B
C
D*
E*
BOD
4,
3,
1.
1,
740
100
326
000
900
COD
14,600
9,080
1,492
4,000
DS
3,950
1,570
1,948
319
SS
2,520
460
72
160
1,462
TS Turb. Phenols Kjld-N T-PO.-P pH
6
2
2
1
1
.470 -- 0.40 26.4
,030 -- -- 23.4
,020 800 <1.0 16.? < !.0
,000
,781
5.
3.
6.
4.
4.
4
8
9
5
4
Note: All units are in mg/1 except Turbidity, which is in JTU, and pH
*Analyses for plants 'D' and 'E' were provided by the respective plants and
figures for plant 'E' represent an average for several mills owned by one company
-------
The nature of the dryer wash water varies according to the amount
of water used, the amount of scraping prior to application of
water, condition of the dryer, operation of the dryer, and, to
some extent, the species of wood that is being dried.
The amount of water used varies from plant to plant and from
operator to operator. One drying operation was observed to use
about 23,000 1 (6,000 gal) of water per dryer over a period of 80
hours. At this plant there were six dryers which were washed
every three weeks. The washing operation consisted of removing
the bulk of the wood residue by blowing it out with air and
hauling it away, and then washing the dryer with water for about
three-quarters of an hour to remove more wood particles. After
this water cleaning, caustic detergent was applied. Finally, the
detergent was rinsed off with water for another 45 minutes.
Samples of spent watfjr w$re, tajcen during both applications of
water, and the analyses of these samples are shown in Table 14.
The effluent from this washing operation was averaged over a 7-
day period and expressed on a unit of production basis as shown
in Table 15.
Various industry contacts emphasized that pitch build-up can be
minimized by proper maintenance of the dryers. Jn addition, the
volume of water necessary to wasji the dryers can be greatly
reduced. One Oregon plant of about one-half the size of the one
described previously was observed to use 1/12 as much water per
week to clean its dryers. Waste water characteristics from this
plant are also given in Tables 14 and 15. It must be noted,
however, that this plant provides settling and screening for the
spent wash water before discharge, and samples were taken at the
point of discharge.
Most dryers are equipped with deluge systems to extinguish fires
that might be started inside the dryer. Fires in dryers are
quite common, especially in those that are poorly maintained.
This water is usually handled in a manner similar to the handling
of dryer wash water, and many plants actually take advantage of
fires to clean the dryers. Fire deluge water can add
significantly to the waste water problems in some cases.
In addition to the two waste water sources from veneer dryers
that have been mentioned, water is occasionally used for flooding
the bottom of the dryers. Many operators question the logic
behind this practice, while some claim that it prevents fires and
reduces air pollution problems. In any event, this water does
not have to add to the waste water problems of a mill. Several
plants recycle all flood, wash, and fire water, and because the
flooding results in substantial evaporation of water, these
plants have found that fresh water can be used to clean the
dryers and still keep the system closed.
75
-------
en
TABLE 14
ANALYSIS OF DRYER WASHWATER
Plant
A
Part I
Part B
B
BOD COD DS SS TS Turb .
210 1,131 643 113 756 19
840 6,703 1,095 5,372 6,467 50
60 1,586 1,346 80 1,426 6
Phenols Color Kjld-N T-P04-P
1.31 32 17.7 1.93
0.20 43 211 11.0
4.68 51 2.91 0.495
Note: All units are concentrations in mg/1 except for Turbidity in
JTU's and Color in Pt-Cob'alt Units.
-------
Plant
BOB
TABLE 15
WASTE LOADS FROM VENEER DRYERS
COD DS. SS TS Phenols
Kjld-N
Note; All units are in kilograms per million square meters.
T-P04-P
A
B
60.94
2.33
412
60.6
99.7
52.3
319
3.09
418
55.2
0.018
0.014
13.2
0.112
0.18
0.019
-------
Glue System
Presently there are three types of glues in use in the veneer and
plywood industry; (1) phenolic formaldehyde resin, (2) urea
formaldehyde, and (3) protein glue. Protein glues are slowly
being phased out of the industry, while phenolic glues are
becoming more widely used. The main source of waste water from a
glue system results from the washing of the glue spreaders and
mixing tanks. TabjLe 16 shows a list of the typical ingredients
of the 3 categories of glues already established. The specific
quantities of these ingredients may vary slightly. Table 17
lists the results of chemical analyses of typical mixtures of the
different glues. The waste waters from the washing operations
are diluted at a ratio of about 20:1 with water to yield the
concentrations shown in Table 18-B. Samples of two phenolic and
one urea formaldehyde waste water were collected and are shown in
Table 17. These are in the same range as those in Table 18, so
it is reasonable to assume a 20:1 dilution with water. This
ratio varies considerably, however, according to frequency of
cleaning and amount of water used.
Waste waters from glue systems are presently being handle^ by (1)
direct discharge, (2) lagooning and discharge, (3) evaporators,
(4) partial incineration, and (5) reusing the wash water.
Several studies have been made of waste water flow and reuse in
gluing operations to determine the possibility of complete waste
water recycling. Most plywood mills add about 20 percent water
by weight, and the use of some wash water in the glue mix is,
therefore, possible. Table 20 shows a list of southern plywood
mills along with the waste water generated and the water needed
in glue makeup. Table 21 shows measurement of waste waters
generated by four Oregon plywood plants. It is obvious from this
data that in order to use all of the wash water as glue makeup, a
significant reduction must be made in the wash water generated.
These reductions, however, are feasible and many plants currently
operate with complete recycle.
Cooling Requirements
A typical combined veneer and plywood mill requires a certain
amount of cooling water to dissipate heat from the air compressor
as well as from from machines such as the press and the lathe. A
mill producing 9.3 million sq m/yr (100 million sq ft/yr) of
plywood on a 9.53 mm (3/8 in) basis needs to dissipate about
55,000 kcal/hr (217,000 BTU) from the compressor and 101,000
kcal/hr (400,000 BTU) from the rest of the plant, for a total of
156,000 kcal/hr (617,000 BTU).
78
-------
TABLE 16
INGREDIENTS, OF TYPICAL PROTEIN, PHENOLIC AND UREA GLUE MIXES
Protein Glue for Interior Grade Plywood:
Water
Dried Blood
Soya FLour
Lime
Sodium Silicate
Caustic Soda
Formaldehyde Doner for Thickening
Phenolic Glue for Exterior Grade Plywood
Water
Furafil
Wheat Flour
Phenolic Formaldehyde Resin
Caustic Soda
Soda Ash
Urea Glue for Hardwood Plywood
Water
Defearner
Extender (Wheat Flour)
Urea Formaldehyde Resin
79
-------
00
o
TABLE 17
AVERAGE CHEMICAL ANALYSIS OF PLYWOOD GLUE
Analysis
and Units
GOD,
mg/kg
BOD,
mg/kg
TOG,
tag /kg
Total Phosphate,
mg/kg as P
Total Kjeldahl Nitrogen,
mg/kg as N
Suspended Solids ,
mg/kg
Dissolved Solids ,
mg/kg
Total Solids ,
mg/kg
Total Volatile
Suspended Solids, mg/kg
Total Volatile
Phenolic
Glue
653,000
/ __
176,000
120
1,200
92,000
305,000
397,000
84,000
172,000
Protein
Glue
177,000
88,000
52,000
2*0
12,00*0
59 ,OQO
118,000
177,030 ,
34,000
137,000
Urea
Glue
421,000
195,000
90,000
756
21,300
346,000
304,000
550,000
346,000
550,000
Solids, mg/kg
-------
TABLE 18
AVERAGE CHEMICAL ANALYSIS OF PLYWOOD GLUE WASHWATER
(ASSUMING A 20:1 DILUTION WITH WATER)
Analysis
And Units
COD,
mg/kg
BOD,
mg/kg
TOC,
mg/kg
Total Phosphate,
mg/kg, as P
Total Kjeldahl Nitrogen,
mg/kg as N
Phenols ,
mg/kg
Suspended Solids,
mg/kg
Dissolved Solids,
Total Solids,
mg/kg
Total Volatile
Suspended Solids, mg/kg
Total Volatile
Phenolic
Glue
32,650
—
8,800
6.00
60
25.7
15,250
15,250
19,850
4,200
8,600
Protein
Glue
8,850
440
2,600
13
600
90.5
5,900
5,900
8,850
1,700
6,850
Urea
Glue
21,050
9,750
4,500
37.8
1,065
10,200
10,200
27,500
17,300
27,500
Solids, mg/kg
-------
GO
ro
TABLE 19
CHARACTERISTICS OF GLUE WASHWATER
(mg/D
Plant BOD COD TS DS SS Kjld-N T-PO^-P Phenols pH
A 15,900 16,700 7,910 6,850 21.8 2.46 4.16 9.77
B 8,880 6,310 1,640 20.2 0.14 5.25
C 710 5,670 5,890 3,360 2,530 • 10.8
Note: Plants A and C utilize phenolic glue and Plant C uses urea glue
-------
CO
CO
TABLE 20
AMOUNT OF ADHESIVE WASHWATER GENERATED IN SOUTHERN PINE PLYWOOD PLANTS
Plywood Plant
Production
(million ,sq .
meters/Year)
9 . 53mm basis
2. 7
3.6
4.5
5.4
6.3
7.2
8.1
9.0
Weekly
Adhesive
__. Use (kg)
38,590
51,454
64,316
77,180
90,044
102,906
115,770
128,634
Amount
Glue
Mixers
9,286
9,286
9,286
11,939
23,877
23,877
23,877
23,877
of Washwater
Glue
Hold Tanks
948
1,895
1,895
1,895
1,895
2,843
2,843
2,843
Produced (Liters)
Glue
Spreaders
6,633
13,265
13,265
13,265
19,898
19,898
26,530
26,530
Total
16,866
24,446
24,446
27,099
45,670
45,670
53,250
53,250
Amount of
Adhesive
per week <
7,364
9,820
2,276
14,732
17,188
19,640
22,096
24,552
-------
TABLE 21
GLUE WASTE DISCHARGE MEASUREMENTS
oo
Average Discharge
Plant
1
2
3
4
Days
Measured
212
49
42
42
for Days
Measured (I/sec)
0
1
1
3
.814
.54
.13
.36
1966 Production
(aq.m- 9. 53mm basis)
9
12
9
6
,000
,150
,000
,300
,000
,000
,000
,000
Number of
Spreaders
4
3
4
2
-------
Mass water Balance in a Veneer and. Plywood Mill
An account of water gains and losses that occur in a typical mill
is given in this section*
A combination veneer and plywood mill with an annual production
of 9.3 million sq m {100 million sq ft) of plywood on a 9.53 mm
(3/8 in) basis is used as a basis for the development of the
water balance. Such a mill would be producing plywood equivalent
to 93,980 kg/day (207,000 Ib/day) or 95 kkg/day (104 ton/day) on
a dry wood basis.
Water Inflows
Water inflows from a typical mill include water from the logs,
glue, and from various freshwater intakes that are used
throughout the process without the water becoming incorporated
into the wood.
The moisture content of incoming logs varies according to
species. For the purpose of these calculations, 50 percent
moisture is assumed. Water from incoming logs is thus 47,000
kg/day or 500 kg/kkg (1,000 Ib/ton). The amount of water that is
applied to plywood glue is estimated to be 4,200 kg/day or 43
kg/kkg (86 Ib/ton) of dry plywood.
The freshwater sources of water vary with operation. Based on
data previously given, the following quantities can be estimated;
about 163,000 kg/day (360,000 Ib/day) or 1,750 kg/kkg (3,500
Ib/ton) of steam is used in log conditioning; about 1,620 kg/day
(3,570 Ib/day) or 17*5 kg/kkg (35 Ib/ton) of water is used to
wash veneer dryers; and about 4,200 kg/day (9,300 Ib/day) or 45
kg/kkg (90 Ib/ton) of water is used to wash the glue system.
Water Outflows
Water outflows from a typical mill include the water in the
finished plywood, vapor losses from pressing, and spent water
from log conditioning and washing Operations.
The amount of water that is in the finished plywood can be
calculated to be 6,600 kg/day (14,500 lb/ day or 140 Ib/ton)
based on a 7 percent moisture content.
Vapor losses occur in the dryers and in the press. Based on 3
percent moisture content in dried veneer, approximately 44,000
kg/day (97,400 Ib/day or 940 lb/ ton) of steam must be released.
Similar calculations indicate a steam discharge of 450 kg/day
(1,000 Ib/day or 10 Ib/ton) from the press. Waste water
discharged from log conditioning equals the amount of steam
applied, if coils are not used. This would be equivalent to a
discharge of 163,000 kg/day (360,000 Ib/day or 3,500 Ib/ton).
85
-------
Waste water discharges from the washing operations are equal to
the respective water usage. Dryer wash water is approximately
1,635 kg/day (3,600 Ib/day or 35 lb/ ton), and glue wash water is
approximately 4,200 kg/day (9,300 Ib/day or 90 Ib/ton).
HARDBOARD - DRY PROCESS
Specific Water Uses In A Typical Mill
There are several processes in the dry process hardboard industry
where water might be used. However, due to a wide variety of raw
material handling techniques and inplant processes and
housekeeping practices, no single dry process hardboard mill uses
water in all of the following processes:
(1) Log Washing
(2) Chip Washing
(3) Resin System
(U) Caul Washing
(5) Housekeeping
(6) Humidif ication
(7) Fire Fighting
The quantity of water utilized in any dry process hardboard mill
depends upon water uses in raw materials handling and inplant
processes, the recycle system utilized, housekeeping practices,
and many other factors. Table 22 shows waste water flows from 11
dry process hardboard mills. The quantity of process water
utilized in a typical mill would be approximately 18,900 I/day
(5,000 gal/day). This water is either evaporated in the press or
becomes a part of the final product. A typical waste water flow
from a dry process mill should be less than 1,900 I/day (500
gal/day). Cooling water usage varies widely from mill to mill
but rarely exceeds 280,000 I/day (975,000 gal/day). The water
usage in a dry process hardboard mill is low and waste water
discharges are minimal.
Log Washing
Log washing is practiced by a minority of mills and not neces-
sarily on a continuous basis. Log washing is used to remove dirt
and sand from the log surface, the total amount of dirt varying
according to harvesting and storage techniques. Weather
conditions are a factor in the need for log washing as wet con-
ditions may cause excessive quantities of mud to adhere to the
logs when harvested. Mills may store both whole logs and chips
on-site and the ratio of logs purchased as compared with chips
vary; the quantity of water utilized will vary accordingly. Both
fresh water and cooling water from the inplant processes may be
used for log washing. Quantities of water used for log washing
can be expected to range from 400 1/kkg (105 gal/ton) to 1,250
86
-------
CO
•-J
TABLE 22
DRY PROCESS HARDBOARD
WASTEWATER FLOW AND SOURCE
Mill
A
B
C
D**
E
F
G
H
I
J*A
K
Log
Wash
0
0
0
YES
81,650
0
0
0
0
0
0
Chip
Wash
0
0
0
0
0
0
0
0
0
0
0
Resin*
Wash
0
0
38
0
0
0
5,670
3
0
570
0
Caul*
Wash
0
570
110
300
0
380
0
750
0
0
0
House-
. keeping*
20,000
380
0
YES
-
0
0
0
0
0
-
Cooling
Water
320,000
81,650
227,000
YES
YES
-
189,000
125,000
160,650
283,500
0+
Humidifi-
cation
0
11,340
0
0
0
0
0
0
0
0
0
Note: All flows given in liters per day
* Actual Intermittant Flow Averaged Daily
** Total Waste Contained on Site
+ Cooling Water Used For Boiler Makeup
-------
1/kkg (330 gal/ton). Typical chemical analyses would include a
BOD of 200 mg/1 and suspended solids of 500 mg/1.
Chip Washing
The purpose of chip washing is similar to that of washing logs.
Chips that are brought in from outside sources can contain dirt
and sand which can result in excessive equipment wear. Chip
washing serves not only to remove this unwanted matter, but also
gives the chips a more uniform moisture content and, in northern
climates, helps thaw frozen chips. No dry process hardboard
mills reported the use of chip washing, but the trend is toward
mills having to wash chips. As prime sources of fiber become
increasingly scarce, the trend will be toward whole tree
utilization. This means that whole trees, or just limbs and
branches, might be chipped in the forest and shipped to the mill.
Because to the increased extraneous material, chip washing will
become a necessity.
Fresh water may be used for chip washing or cooling water from
inplant equipment might also be used. Because there are, at the
most, only one known chip washing systems in use, there are no
reliable water usage figures or waste characteristics available
in the dry process hardboard industry.
Resin System
Water is used to make up the resins which are added as binders
for hardboard. The water used for making resin becomes part of
the hardboard and it is evaporated in the press. Some mills
claim it is necessary to clean the resin system, and available
data, as shown in Table 22, indicates that there is no standard
procedure for cleanup as water usage varies widely.
There are two types of resins used in the hardboard industry,
phenol formaldehyde and urea formaldehyde. These resins are
essentially the same as those utilized in the plywood industry
where many mills have already gone to a completely closed resin
system. Table 23 shows typical chemical analysis of plywood
glue,
The chemical analysis of resin washwater will be those
concentrations shown in Table 23 diluted by a factor depending
upon the quantity of water used for wash-up. Several hardboard
mills presently recycle this wash water as resin make-up water or
simply do not wash at all, therefore having no discharge.
Caul and Press Plate Wash Water
Another minor water usage and waste water source in some mills is
caul and press plate wash water. After a period of use, cauls
and press plates acquire a buildup of resin and organics on their
surfaces. This results in sticking in the presses and blemishes
on the hardboard surface. The cauls or press plates must then be
88
-------
TABLE 23
AVERAGE CHEMICAL ANALYSIS OF PLYWOOD RESIN
Analysis and Units
COD, rag/kg
BOD, mg/kg
TOC, mg/kg
Total Phosphate, mg/kg as P
Total Kjeldahl Nitrogen, mg/kg as N
Phenols, mg/kg
Suspended Solids, mg/kg
Dissolved Solids, mg/kg
Total Solids , mg/kg
Total Volatile Suspended Solids, mg/kg
Total Volatile Solids, mg/kg
Phenolic Resin
653,000
—
176,000
120
1,200
514,000
92,000
305,000
397,000
84,000
172,000
Urea Resin
421,000
195,000
90,000
756
21,300
246,000
204,000
550,000
346,000
550,000
-------
cleaned to remove this buildup. The cleaning operation consists
of submerging the cauls in a caustic cleaning solution for a
period of time to loosen the organic matter* Press plates may
also be cleaned with a caustic solution inpiace. After soaking,
cauls are removed, rinsed with fresh water, and then put back in
use. The tanks used for soaking the cauls are emptied as needed,
normally only a few times each year. The soaking water and rinse
water used in a typical dry process hardboard mill ranges from
380 to 950 I/day (100 to 250 gal/day) or approximately 4 1/Jtkg
(1.0 gal/ton) of hardboard production.
Miscellaneous Housekeeping Hater
Water may be used in small quantities for various cleaning pro-
cedures. The frequency and quantity of water used for cleaning
purposes is highly variable as there are generally no scheduled
cleanup procedures. Information gathered from several dry pro-
cess hardboard mills indicates that this water usage can be ex-
pected to range from zero to less than 1,500 I/day (400 gal/day)
in a typical mill. This source of waste water results in such a
minor volume that it can easily be disposed of on-site. Several
mills utilize no water at all for cleaning as all of their house
cleaning is done by sweeping and vacuum cleaning.
Humidification
All dry process hardboard mills humidify board after pressing.
This procedure consists of passing the boards through a room
with a high humidity and temperature to bring the moisture
content to an air dry level. Most mills report no waste water
discharge from this operation.
Fire Water
A. major problem with the dry process for manufacturing hardboard
is the fire hazard. The inside of a dry process hardboard mill
may become coated with dry fibers and an electrical spark or
excessively hot press or other piece of equipment can easily
start a fire. More frequently a fire starts in a refiner and
quickly spreads through the fiber conveying system. Mills have
elaborate fire fighting systems which use large quantities of
water to put fires out quickly. Fires are obviously not
scheduled and their frequency varies from mill to mill. The
water used to control a fire will vary according to the duration
and extent of the fire.
cooling- Water
The largest water usage in a dry process hardboard mill is for
cooling water. This water is used for cooling various inplant
equipment such as refiners and air compressors, and is normally
not changed in quality except for the addition of heat. The
volume of cooling water varies widely from mill to mill depending
upon temperature of freshwater source and the equipment within a
90
-------
mill. Cooling water can be expected to range from 18,900 to
280,000 I/day (5,000 to 75,000 gal/day) with a typical mill
utilizing 190,000 I/day (50,000 gal/day). Cooling water may
become contaminated with lubricating oil and in this event the
oil must be removed before the cooling water is discharged.
Scrubber Water
Air pollution from dry process hardboard mills is a major con-
cern. One method of air pollution control is the use of wet
scrubbers. Although only two hardboard mills report using a wet
scrubber, the future trend appears to be toward the use of wet
scrubbers in dry process hardboard mills. The water usage for
wet scrubbing in a dry process hardboard mill will vary depending
on the individual scrubber design. Since there are only two wet
scrubbers in operation, representative data for the industry is
unavailable. One of the mills using a wet scrubber reportedly
achieves zero discharge by settling and filtering the scrubber
water before recycle. In fact, there is need for water makeup.
Mass Water Balance In A Dry Process Hardboard Mill
For the purpose of illustrating the water requirements in a dry
process hardboard manufacturing plant, presented below is a water
balance. This presentation is not intended to suggest that the
average (or typical) plant in the industry produces 225 kkg/day.
The water intakes and outflows are presented also on a volume of
water per unit of production basis, also, to illustrate the water
requirements and outflows related to the operations involved in
the manufacture of hardboard.
A schematic diagram of the water balance (net inflows and
outflows) for a typical dry process hardboard mill is shown in
Figure 16. Water gains or outflows are shown as 1/kkg of dry
product produced in a typical 225 kkg/day mill.
Water Inflows; Water inflows in a typical dry process hardboard
mill result from incoming raw materials and fresh water intake.
Incoming wood normally has approximately 50 percent moisture
which represents 100 percent of the final product weight.
Water from incoming
(240 gal/ton)
wood = 1,000 1/kJtg (50 percent moisture)
The water usage within a dry process hardboard mill is highly
variable depending upon water usage within an individual process
and plant practices and procedures. A typical dry process mill
uses water only for glue preparation, caul wash, humidification,
and cooling.
Water in glue
product (8.4 gal/ton)
- 35 1/kkg of (3.5 percent of product)
91
-------
ro
6AIN = IOOO
RAW
MATERIALS
HANDLING
COOLING WATER
GAIN = 1250
LOSS=460
SYSTEM
GAIN»35
FIBER
PREPARATION
I
COOLING WATER
LOSS = I250
FIBER
DRYER
FELTER
CAUL WASH
GAIN=4.2-»
LOSS = 4.2
PRESS
FRESH WATER
GAIN*50—*-
LOSS-75
HUMIDIFICATION
FINISHING
PRODUCT
TOTAL GAIN =23392
TOTAL LOSS =2339,2
* GAINS AND LOSSES SHOWN IN LITERS/TON DRY PRODUCT
FIGURE 16 - WATER BALANCE FOR TYPICAL DRY PROCESS HARDBOARD MILL*
-------
Caul wash 950 1/day
product (1 gal/ton)
Humidification
product (12 gal/ton)
Cooling water-284,0 00
product (300 gal/ton)
Total Water Inflows
=
-------
LOGS
O
LOG
STORAGE
1
' \/
LOG WASH
•
'
DEBARKER
CHIPPER
/CH
/STO
ER IN
\
RAGE\
*
i
V
/ CH
/ WA
-
i
IP \
SH \
\
WATER OUT
o
TO PROCESS
FIGURE 17 - WATER USAGE IN RAW MATERIALS HANDLING
IN THE HARDBOARD INDUSTRY
94
-------
hardboard discusses raw materials handling, and the figures and
discussion there also apply to the wet process hardboard segment
of the timber products processing industry.
Fiber Preparation
As previously discussed, there are two principal fiber
preparation processes: (1) thermal plus mechanical refining
process and, (2) the explosion process. Figure 11 showed a
schematic diagram of a typical wet process hardboard mill where
thermal plus mechanical refining is used for fiber preparation.
All but two wet process mills utilize some variation of this
process. Two mills utilize the explosion process as shown in
Figure 18.
The amount of water used in fiber preparation in the wet process
is relatively small as compared to overall water use in a wet
process mill. In general, the only water used in fiber prepara-
tion is the addition of steam into the cooker. This quantity of
steam is approximately equal to one-half the weight of dry chips
processed or approximately 0.5 cu m/kkg (120 gal/ton).
The principal reason for significant waste water flows and
concentrations from the wet process as compared with the dry
process is the fact that the fiber is diluted from approximately
40 percent consistency to 1.5 percent consistency prior to
forming on a wet felting machine. There are limitations on the
concentrations of organics in the process water. This means that
most of the soluble organics released into solution during fiber
preparation must be disposed of in some manner as only a portion
of the solubles may be retained in the hardboard.
The interrelation between fiber preparation processes, variations
of cooking time, and temperature and wood chemistry on waste
water discharge is extremely important. Wood is difficult to
define chemically because it is a complex heterogeneous product
of nature made up of interrelated components, largely of high
molecular weight. The principal components generally are
classified as cellulose, lignin, hemicellulose, and solvent-
soluble substances (extractives). The amounts present are in the
range of 40 to 50 percent, 15 to 35 percent, 20 to 35 percent,
and 3 to 10 percent, respectively. The yield, composition,
purity, and extent of degradation of these isolated components
depend on the exact conditions of the empirical procedures
employed for their isolation. Variations in the chemical
composition of wood influences the quantities and kinds of
chemicals released during fiber preparation.
At normal temperatures wood resists degradation by chemicals and
solvents. This may be attributed to the interpenetrating network
structure of wood comprised of polymers with widely differing
properties. Also, the high crystallinity of the carbohydrate
95
-------
TO ATMOSPHERE
CHIP:
WATER IN
WATER OUT
MAKE-UP
WATER
TO
FINISHING
FIGURE 18 - WATER USE IN THE EXPLOSION PROCESS
-------
system reduces the accessibility of the wood components to
reagents.
Water at room temperature has little chemical effect on wood, but
as temperature rises and pH decreases because of the splitting
off of acetyl groups, wood becomes subject to rapid acid
hydrolysis with the dissolution of carbohydrate material and some
lignin. At temperatures above 140°C, considerable and rapid
removal of hemicelluloses,occurs. Cellulose resists hydrolysis
better than the hemicellulose fractions.
The thermal and explosion pulping processes make use of the
effect of water on wood at high temperatures to prepare fiber for
mechanical refining prior to being formed into hardboard. The
high temperatures soften the lignin-hemicellulose matrix to
permit the separation of fibers with reduced power cost and fiber
damage. Also, carbohydrate and lignin degradation products, and
the lignin softened by high temperature^, facilitate bonding of
the fibrous structure upon drying of the board.
Cooking wood with steam at temperatures of about 180°C causes a
rapid loss in weight. Part of the 'loss is due to thermal
decomposition and simple solution, but the acids released by the
wood hydrolyze appreciable amounts of carbohydrates as well. In
commercial operations, yields of pulp fall to between 75 and 90
percent, and therefore potential waste water problems increase
significantly.
In the explosion process wood chips are exposed to high-pressure
steam in a "gun" or small digester fitted with a quick~opening
valve that allows the chips to disintegrate when the pressure is
abruptly released. In the gun the chips are steamed at 41.8 atm
(600 psi) for 1 minute, and the pressure is then increased to 69
atm (1,000 psi) for an additional 5 seconds before the valve is
opened. Differences in wood species,^ condition, and size of
chips modify the cycle. The high temperature, high pressure
treatment does not remove the lignin but makes it sufficiently
plastic for the chips to burst apart on release. Hemicellulose
is hydrplyzed, becoming pentose sugars. Some of these are
dehydrated and polymerized to form furfural resins as a result of
the steaming and the subsequent high temperature pressing and
tempering involved in manufacturing boards. This process causes
the release of significant quantities of organics which must be
disposed of as a waste stream.
Another representative and more common process makes use of a
screw press to force compressed chips into one end of a
horizontal stainless-steel tube, typically 3m (10 ft) long and
one m (3 ft) in diameter, which the chips traverse in about 30
seconds while exposed to steam at 182°C and 12.9 atm (175 psi).
At the far end they are fiberized in a single-rotating disk mill
while still hot and under pressure. From the disc mill the pulp
is discharged to a cyclone, from which it goes to a surge bin
followed by a second refiner for further processing. Other types
97
-------
of continuous or quick-cycle digesters may be substituted and
give similar results. Because of the lower temperatures and
pressures, the quantity of released organics is considerably less
than in the explosion process, resulting in potentially less
waste.
The yield, chemical composition, and physical properties of the
pulps prepared by any method are dependent upon two sets of
variables:
Variables associated with the wood:
1. Species
2. Density
3. Growth factors
4. Moisture content
5. Length of storage
6. Particle size
Variables associated with the fiber preparation system:
1. pH of liquor (water solution)
2, Temperature and pressure of digestion
3. Time of digestion
4, Method of defibration
The dissolution of the wood substances takes place mainly during
pre-heating and defibration process and is closely related to the
kind of raw material used.
It is difficult to make determinations of the yield of pulp from
wood as a function of the pre-heating conditions, some attempts
have been made, however, and in Figure 19 a graph for beechwood
is shown, where the preheating period was extended to 16 minutes,
These determinations were made with water as "cooking liquor,"
and it is clearly shown that the dissolution proceeds much faster
as the pre-heating temperature is increased.
During the pre-heating two primary reactions take place. One is
the hydrolysis of hemicellulose molecules, whereby oli-
gosaccharides are formed. These short-chain molecules are small
enough to dissolve in water. The other reaction is the hydroly-
sis of acetyl groups, whereby acetic acid is formed, causing an
increase in the hydrogen ion concentration in the raw material.
The higher acidity causes the hydrolytic reactions to proceed
still faster. Thus the reactions can be said to be
autocatalytic. For that reason it is very difficult to calculate
rates of reaction for the dissolution cf wood substances during
the pre-heating stage. The rate of reaction seems to roughly
double with an increase in temperature of about 8°c (14°F), which
is normal for most chemical reactions. So far no exhaustive
investigations seem to have been made on the composition of the
substances dissolved during the pre-heating and defibration
steps. An examination of the composition of the substances
98
-------
YIELD %
100
90
80
I58°C
I72°C
I83°C
70
5 10
PREHEATING TIME
15 20
MINUTES
FIGURE 19
- EFFECT OF PREHEATING TIME AND
TEMPERATURE ON YIELD
99
-------
dissolved in the thermal-mechanical process was made by Edhborg
in 1958. The temperature in the Asplund-Defibrator process is
normally about 180°C and the pre-heating time is usually from one
up to a few minutes. The temperature in the explosion process,
on the other hand, is increased to between 250 and 30Q°C, even if
it is only for a few seconds. This leads to larger amounts of
substances being dissolved in the latter process and also to more
acidic conditions—a pH value of about 3 was obtained in an
extract from an explosion pulp whereas the pH values in extracts
from defibrator pulps'" are usually close to 4. The acidity
depends partly on volatile acids like acetic and formic acid and
partly on non-volatile ones, among which uronic acid is the most
frequent. ;
The investigation on dissolved substances in the explosion
process was based on coniferous wood as raw material. The
dissolved substances in this case consisted of about 70 percent
carbohydrates, 10 percent lignin (partly modified) and 20 percent
"organic resins." The carbohydrates consisted of 35 percent
pentosans (mostly xylans) and 65 percent hexosans.
Corresponding investigations on dissolved substances in the
Asplund-Defibrator process were made with beech as raw material.
In this case 75 percent of the dissolved substances were
carbohydrates and a few percent were lignin type substances. In
addition, about 10 percent acetic acid, partly free and partly
bound as acetyl groups, were found. In this case about 80
percent of the carbohydrates were pentosans (mainly xylans) and
20 percent hexosans.
Tables 24 and 25 relate properties and composition of many common
woods used in this country, and Figure 20 indicates the effects
various treatments have on these components. Figure 21 depicts a
general relationship of lignin dissolution versus percent of wood
dissolved.
Mat Formation and Pressing
Figure 11 shows that from the refiner, fiber is discharged into a
cyclone where the fiber is diluted with process water. Figure 22
shows a typical schematic diagram of the process water flow in
the wet process. From the refiner, fiber is diluted to
approximately 5.0 percent through the cyclone then diluted still
further to approximately 1.5 percent fiber in the stock chest.
A mat is then formed on the wet forming machine where the fiber
concentration is, increased to approximately 35 percent prior to
wet pressing. Water removed from the mat formation flows to a
process water chest where it is recycled as process water. Water
released upon pressing either evaporates to the atmosphere or
flows back to the process water chest or is discharged directly
as a waste water. Process water may be recycled until the
temperature, or the concentration of soluble organics or
suspended solids becomes too high. Normally, fresh makeup water
100
-------
1
TOTAL
WOOD
SUBSTANCE
Neutral
Solvents
and/or
Steam
Soluble
or
Volatile
3
EXTRACTIVES
5%
2
EXTRACTIVE
FREE WOOD
95%
f
INORGANIC
<.05%
Mild
Oxidation
and
Extraction
i
Degraded
Soluble
4
SOLOCELLULOSE
(TOTAL
POLYSACCHARIDE
FRACTION) .
70%
5
LIGNIN
25%
6
Dilute WOOD
Aqueous "" CELLULOSE
Alkali 60o/o
.
Ac
Soluble Hydrc
'
GLUCOS
TRACES
OTHER
CARBOH1
AND IMP
id
)lysis
E +
OF
fDRATES
URITIES
MANNOSE
XYLOSE
GALACTOSE
ARABINOSE
URONIC ACIDS
Acid
Hydrolysis
HEM1CELLULOSE
20%
FIGURE 20
- THE CHEMICAL COMPONENTS OF WOOD
-------
o
-to
TABLE 25
ANALYSES OF SOME COMMON SPECIES OF WOOJ)
(Extractive-free basis, percent of dry wood)
Constituent
Ash
Acetyl
Lignin
a-Cellulose
Heoiicsllulaee
Total (a " ". '
a-Cellulose (b
Mannac (c
Xylan
Uronic anhydride
CH (d
Total (a
Douglas
fir
0.3
0.6
2fi.4
57,2
14,1
100,6
48.3
5.4
6.2
2.8
0.0
92.0
Loblolly
pine
0.3
1.1
29.5
Summation A
55.0
15.3
101.2
Summation B
46.6
4.7
10.1
3.8
0.2
96.3
Black . Southern
spruce red oak
0.4
1.1
28. -Q
51.5
17.4,, ,
98.4
45. ft ...
8.0'
10.5
4,1
0.2
97.9
0.2
3.3
25.2
45.7
23.3
97.7
43.7
_~
20.0
4.5
0.6
97.5
a) Including ash, acetyl, and lignin.
b) Corrected for mannan, xylan, and uronic anhydride.
c) By the phenylhydrazine method; the figures are probably low.
d) Calculated from methoxyl not in lignin.
-------
o
(Jl
CHIPS
STEAM
1
(40)
SCREW
FEED
(XX)
, \ I j CY L— ' STOCK L-1 WET FORMING
.REFINER , : CL nCHES'IS
j 1 1 0 1 I .
r—3 l — i k N. ;(5) A (u
\ /
DILUTION
WATER
MAKE-UP
WATER
MACHINE
J) 1
PROCESS
WATER
CHEST
t !
A
(35)
<*"
*S4-~
S / / s / / /
TO
A ATMOSPHERE
WET I— rA
PRESS I""1"/
1 TO
1
/
/
/
/
>
*
/
/
s
/
/
/
/
>
<
FINISHING
r ^
/SS//////J>
V"
TO
TREATMENT
WATER IN
WATER OUT
ALTERNATE ROUTE
APPROXIMATE PERCENT FI8*R
(CONSISTENCY IN PROCESS)
FIGURE 22 - PROCESS WATER RECYCLE IN A TYPICAL WET PROCESS HARDBOARD MILL
-------
is added at a constant rate to control these parameters and the
overflow is discharged to waste.
In the explosion process considerably more soluble organics are
released. Two plants use process water for fiber washing. Fiber
wash water from the explosion process is a major source of
pollutants. A waste load from this process alone of 40 kg/kkg
(80 Ib/ton) into a flow of 2.5 cu m/kkg (600 gal/ton) is re-
ported. Typical waste water concentrations of this fiber wash
are:
BOD * 22,620 mg/1
COD = 51,100 mg/1
TSS = 32,000 mg/1
Volume =* 2.5 cu m/kkg (600 gal/ton)
Because of these high waste concentrations it has been found that
it is practical to evaporate this waste stream. The concentrated
liquor is sold as cattle feed or incinerated (Figure 23). This
is the normal procedure in the plants that use an explosion
process.
Two other wet process mills which use the thermal-mechanical
cooking process wash fiber prior to mat formation. These mills
do not evaporate this washwater separately as is done by the
explosion process mills, but discharge it directly to waste.
The moisture in the chips entering the wet process is
approximately 50 percent. Assuming that the mat is formed from a
1.5 percent fiber concentration, that the board coming from the
press has a zero percent moisture, and that there is no recycle,
approximately 66.8 cu m/kkg (16,000 gal/ton) of process water
must be disposed of in some form. While a portion of this water
will be disposed of as steam, the majority will be discharged as
a waste stream. The actual volume discharged is a function of
the amount of recycle practiced. There are three principal
factors which limit recycling of process water: temperature,
suspended solids, and soluble solids.
Usually a process water temperature of a certain minimum is
required to avoid excessive use of resin. At lower temperatures
the naturally occurring resins in the fiber will set, thereby
becoming ineffective for bonding. Furthermore, when the board is
formed at low temperature, longer pressing times are required
which can significantly reduce production rates. Most hardboard
mills operate with a process water temperature between 30°c
(86°F) and 63°C (145°F). The more the process system is closed,
the higher its temperature becomes. It has been found that as
temperatures increase, certain corrosion problems are
experienced. Machines become very humid, making working
conditions unpleasant. A critical temperature seems to exist
after which spots will appear on the board, thereby lowering the
106
-------
TO ATMOSPHERE
O
--J
CHIPS
u n
GUN
Vv
)±3 C=T
f 1
WASHEf
\
?
J CHEST | [MACH
Ljf
.
1 " pRncpss
WATER
CHEST
WATER IN
WATER OUT
CONCENTRATED
BY-PRODUCT
CONCENTRATE TO
CATTLE FEED
COMPENSATE
TO
FINISHING
TO TREATMENT
FIGURE 23 - PROCESS WATER RECYCLE IN A HARDBOARD MILL
USING THE EXPLOSION PROCESS
-------
aesthetic quality of the board. This critical temperature varies
with raw material, process and product produced.
Increased recycling of process water increases the concentration
of soluble organics. This increased concentration raises the
risk of spot formation on the board and the chance of sticking in
the press. This is partly due to build-up of volatilized
organics on press plates. The critical concentration of soluble
organics, above which process problems are encountered, is rel-
ated to concentration and type of soluble materials in the
process water.
The effect of suspended solids concentrations relates to the
dewatering characteristics of the board. As suspended solids
concentrations increase with recycling, a certain concentration
is reached after which the board will not exhibit proper water
drainage during mat formation. This can be attributed to a
buildup of fines which cause the mat to dewater slowly. As the
suspended solids level becomes too high in the process water they
must be removed either by blowing down this concentrated water
and diluting it with fresh water, or by removing the solids from
the process water by some other means.
Miscellaneous Waste Water Sources
By far the major waste water discharges from a wet process
hardboard mill are process water from mat formation, pressing,
and fiber washing. Other waste water sources which may be
classified as miscellaneous streams include resin system wash
water, caul wash water, housekeeping water, and cooling water. A
discussion of these sources can be found in the earlier part of
this section relating to dry process hardboard.
Total Waste water Flow
Table 26 is a summary of the total waste water flow from seven
wet process hardboard mills. Table 27 gives a summary of the
average waste water concentrations from these same mills.
Waste water flows vary from about 4.6 to 45.9 cu m/kkg (1,000 to
11,000 gal/ton), BOD concentrations vary from 700 mg/1 to 4,000
mg/1 and suspended solids from 220 to 1,650 mg/1. A comparison
of data reported as raw waste water concentrations from mill to
mill should be made with caution- Several mills report raw waste
water concentrations after primary sedimentation while others do
not. These mills utilize primary clarifiers as part of their
recycle systems while other mills consider primary clarifiers as
part of their waste treatment system. The average discharge of
BOD5 in the raw waste water ranges from 28 to 50 fcg/kfcg (56 to
100 Ib/ton), while average discharge of suspended solids ranges
from 3.2 to 19 kg/kkg (6,4 to 38 Ib/ton).
108
-------
TABLE 26
WASTEWATER DISCHARGES FROM WET PROCESS HARDBOARD
Plant
1
2
3
4+
5
6
7
8*
Production
(metric tons)
91
77
1,356
136
82
127
356
327
Wastewater
(cubic meters /day)
4,164
2,952
16,578
1,590
757
908
1,628
833
Wastewater
(cubic meters/kke
45.9
38.2
12.2
11.7
9.3
7.1
4.6
2.6
+ Chip Wash Included
* Projected Figures
109
-------
TABLE 27
RAW WASTEWATER CHARACTERISTICS FROM WET PROCESS HARDBOARD
Discharge Flow
Plant
1
2
3+*
4
5
6*
7*
8
cu m/D eu
4,164
2,945
16,578
1,589
757
897
1,635
840
m/metric t
45.9
38.2
12.2
11.7
9.3
7.1
4.6
2.6
BOD
on mg/1 kg/kkg
720
1,130
.1,800
3,000
3,500
3,900
—
3,350
33
50
23
28
32
28
—
8.5
S.S.
mg/1 kg/kkg pH
220
—
540
1,650
430
450
—
48
10
—
6.5 5.0
19 4.5
4 4.4
3.21 4.0
—
0.125
* After Primary Treatment
+ Masonite Explosion Process
-------
other representative analyses of raw waste water discharged from
a typical wet process hardboard mill are shown below:
Parameter Concentration (mq/1)
BOD 1,300 - 4,000
COD 2,600 - 12,000
Suspended Solids 400 - 1,100
Total Dissolved Solids 500 - 4,000
Kjeldahl Nitrogen 017 4.0
Phosphates, asp 0.3-3.0
Turbidity 80 - 700
Phenols 0.7 * 1.0
pH Range 4.0 - 5.0
Water Balance for a Typical Wet Process Hardboard Mill For the
purpose of illustrating the water reguirments in a wet hardboard
manufacturing plant, presented below is a water balance. This
presentation is not intended to suggest that the average (or
typical,) plant in the industry produces 127 kkg/day. The water
intakes and outflows are presented also on a volume of water per
unit of production basis, also, to illustrate the water
requirement and outflows related to the operations involved in
the manufacture of hardboard.
A schematic diagram of the water balance (net inflows and
outflows) for a typical mill is shown in Figure 24. Water gains
or losses are shown as liters of water/kkg of product produced in
a 127 kkg/day (140 ton/day) mill.
Water Inflows. Water inflows in a typical wet process hardboard
mill result from incoming raw materials and freshwater makeup.
Incoming wood has approximately 50 percent moisture content which
represents 100 percent of the final product weight.
The volume of miscellaneous housekeeping water, used for such
things as floor and caul washing, is highly variable. There is
little data as this stream is normally discharged to the
treatment system with the process water without monitoring.
Water from incoming chips = 1,000 1/kkg
(50 percent moisture) (240 gal/ton)
Steam to preheater - 500 1/kkg
(120 gal/ton)
Cooling and seal water = 29,840 1/kkg
(7,150 gal/ton)
Additive dilution water ~ 83.5 1/kkg
(20 gal/ton)
111
-------
ro
LOSS = 83.5
STEAM GAIN = 83.5 LOSS* 186 GAIN* 50
SJk.iSS'V A WATER FROM TO STEAM OR
COOLING 8 ' f ADDITIONS ATMOSPHERE WATER
GAIN =50O SEAL WATER A 1 1
STEAM II II If JL
II Jl II JL, v
CHIPS i i " I *"^ 1 lc I~J STOCK '-'wFT FORMING w*T uiiuininirp '"A
r^l^gPREHEATE^ REFINER , I'ci (] CHESTS p| MACHINE PRESS pV
(50) \ (40)1 ' J 1 L 0 /(5) A (1.5
NSCREW FEED ^ V.V
GAINS = I,000 Jl "/^ 17,590 46,6
LOSS =29,6 17
COOI ING AND 1
StAL WATER DILUTION
WATER
MAKE-UP
WATER
55 V 63,911
PROCESS
WATER c^rr™
CHEST r \
1 !_J
I-TON
1.669 PRODUCT
F LOSS= 11,267
A _
TO TREATMENT
> ALTERNATE ROUTE
WATER IN
WATER OUT
MISCELLANEOUS
HOUSEKEEPING
GAIN=42
(XX) PERCENT FIBER (CONSISTENCY IN PROCESS)
ALL NUMBERS* LITERS /METRIC TON
TOTAL GAIN
TOTAL LOSS
41,405
41,405
FIGURE 24 - WATER BALANCE FOR A TYPICAL WET-PROCESS HARDBOARD MILL
-------
Process water makeup
Humidifier
Miscellaneous housekeeping =
Total Water Inflows
9,890 1/kkg
(2,370 gal/ton)
50 1/kkg
(12 gal/ton)
42 1/kkg
(10 gal/ton)
=41,405 1/kkg of product
(9,922 gal/ton)
Water Outflows: Water outflows in a wet process mill result
from:
Press Evaporation
Cooling and Seal Water
discharge)
Steam from cyclone
Discharge of excess pro-
cess water (includes mis-
cellaneous housekeeping
water discharge
Water in product
Total Water Outflows
188 1/kkg
(45 gal/ton)
29,817 1/kkg
(7,145 gal/ton)
83.5 1/kkg
(20 gal/ton)
11,267 1/kkg
(2,700 gal/ton)
50 1/kkg
(12 gal/ton)
= 41,405 1/kkg of product
(9,922 gal/ton)
WOOD PRESERVING SUBCATEGORIES
Waste water characteristics vary with the particular preservative
used, the volume of stock that is conditioned prior to treatment,
the conditioning method used, and the extent to which effluents
from retorts are diluted with water from other sources.
Typically, waste waters from creosote and pentachlorophenol
treatments have high phenolic, COD, and oil contents and may have
a turbid appearance that results from emulsified oils. They are
always acid in reaction, the pH values usually falling within the
range of 4,1 to 6.0. The COD for such wastes frequently exceeds
30,000 mg/1, most of which is attributable to entrained oils and
to wood extractives, principally simple sugars, that are removed
from wood during conditioning.
113
-------
Closed steam Conditioning
The characteristics of wood preserving waste water are different
for plants that practice modified-closed or closed steaming. In
the former process, steam condensate is allowed to accumulate in
the retort during the steaming operation until it covers the
heating coils. At that point, direct steaming is stopped and the
remaining steam required for the cycle is generated within the
retort by utilizing the heating coils. Upon completion of the
steaming cycle, the water in the cylinder is discarded after
recovery of oils. In closed steaming, the water in the retort at
the end of a steaming cycle is returned to a reservoir after re-
covery of free oils, and is reused instead of being discarded.
The principal advantage of modified-closed steaming/ in addition
to reducing the volume of waste released by a plant, is that
effluents from the retorts are less likely to contain emulsified
oils than when open steaming is used. Free oils are readily
separated from the waste water; and as a result of the reduction
of the oily content, the oxygen demand and the solids content of
the waste Water are reduced significantly, relative to the
effluent from plants using open steaming. Typical oil and COD
values from a single plant before and after the plant commenced
modified-closed steaming are shown in Figures 25 and 26,
respectively. The COD of the waste water was reduced by about
two-thirds when this steaming method was initiated. Oil content
was reduced by a factor of ten.
Water used in closed steaming operations increases in oxygen
demand, solids content, and phenol concentration with each reuse.
The high oxygen demand of this waste is attributable primarily to
wood extracts, principally simple sugars, the concentration of
which increases with the reuse of the water. Because practically
all of the solids content of this waste are dissolved solids,
only insignificant reductions in oxygen demand and improvement in
color result from primary treatments involving flocculation. The
progressive changes in the parameters for water used in a closed
steaming operation are shown in Table 28. Although such wastes
are perhaps more difficult to treat, this disadvantage is
counterbalanced in part by the fact that substantial reductions
in the volume of waste water and total weight of pollutants
released can be achieved by using closed steaming.
affect of Time
Because many plants use the same preservatives and follow
essentially the same treating practices, the waste waters they
release are qualitatively similar with respect to a number of
chemical and biochemical properties. Quantitatively, however,
they differ widely from plant to plant, and even from hour to
hour at the same plant, depending upon the time during a treating
cycle that samples for analysis are collected.
114
-------
Avg. oil content
before closed
steaming-1360mg/1
Avg.oil content
after closed
steaming—136 nig/
8
12
TIME ( weeks)
16
20
FIGURE 25 - VARIATION IN OIL CONTENT OF EFFLUENT WITH TIME
BEFORE AND AFTER INITIATING CLOSED STEAMING
-------
10
20
30
40 50
TIME (days)
60
130
FIGURE 26 - VARIATION IN COD OF EFFLUENT WITH TIME BEFORE AND
AFTER CLOSED STEAMING: DAYS 0-35 OPEN STEAMING;
DAYS 35-130 CLOSED STEAMING
-------
TABLE 28
PROGRESSIVE CHANGES IN SELECTED CHARACTERISTICS OF
WATER RECYCLED IN CLOSED STEAMING OPERATIONS
Charge
Number
1
2
3
4
5
7
8
12
13
14
20
Phenol
46
169
200
215
231
254
315
208
230
223
323
NOTE:
COD
15,516
22,208
22,412
49,552
54,824
75,856
99,992
129,914
121,367 1
110,541
Total
Solids
10,156
17,956
22,204
37,668
66,284
66,968
67,604
99,276
04,960
92,092
123,429 114,924
Values expressed
as mg/1
Dissolved
Solids
8,176
15,176
20,676
31,832
37,048
40,424
41,608
91,848
101,676
91,028
88,796
117
-------
CO
8 12 16
TIME ( hours)
24
FIGURE 27 - VARIATION IN COD CONTENT AND WASTEWATER FLOW RATE WITH TIME
-------
Data on the effect of time of sampling during a treating cycle on
the flow rate ancl COD content of effluent from a plant operating
a single retort are shown in Figure 27. Flow rate was measured
and samples for analysis collected at 30 minute intervals, begin-
ning during a steaming cycle and continuing through the treating
cycle and part of the succeeding steaming cycle. The COD of the
effluent varied inversely with flow rate and ranged from 400 mg/1
to 43,000 mg/1 during the 24 hour sampling period, a 100-fold
variation. Plow rate varied from 7570 1/day to 151,400 I/day
(2,000 gal/day to 40,000 gal/day). The pattern of variation for
phenol and solids content was similar to that for COD.
Variation in effluent characteristics among plants is illustrated
by the data in Table 29, which show the phenol and COD values of
raw waste for 13 plants. Also shown in the same table are the
COD values following a treatment consisting of flocculation and
sedimentation. The phenol and COD values for the raw waste vary
over a wide range, as does the efficiency of the treatment as
judged by the percent reduction in COD after flocculation.
Biological Characteristics
Waste water from the wood preserving industry is usually
relatively treatable. Limited experience with bench-scale and
pilot plant activated sludge, trickling filter, and soil
irrigation systems indicate that biological treating methods are
generally effective in reducing the oxygen demand and phenolic
compounds to acceptable levels. Because these waste waters have
a very low nutrient content, the addition of nitrogen and
phosphorus prior to biological treatment is necessary to maintain
a viable bacterial population.
Because of its prolonged exposure to temperatures in the range of
110° to 121°C (230° to 250°F) and its relatively high content of
phenolic compounds, process water is sterile upon its discharge
from retorts. Its successful biological treatment requires the
employment of strains of bacteria that have been acclimated to
concentrations of phenolic compounds of 300 mg/1 or higher. On a
laboratory scale, this requirement renders BOD determinations
difficult to make and almost impossible to interpret, especially
as regards comparisons of results obtained by different analysts.
It is not possible to ascertain whether the differences obtained
are the result of the characteristics of the waste samples or
differences in the bacterial cultures employed and their degree
of acclimation to the waste. Dust and Thompson obtained
differences in BOD values for creosote waste water of 200 percent
among several acclimated cultures of bacteria.
The correlation between BOD and COD for wood preserving waste
water is high. Using creosote waste water with BOD values larger
than 150 mg/1, the above authors found that the equation
BOD=0.497 COD * 60, for which r=0.985, accounted for practically
all of the variation between the two parameters (Figure 28). The
general applicability of this equation was indicated by spot
119
-------
ro
o
10
8
en
o
- 6
x
O
o
CD
I I
Y=0.497X+60
j i
i i
4 6 8 10 12
Influent COD x 103 mg/l
14
16
FIGURE 28 - RELATIONSHIP BETWEEN BOD AND COD FOP WASTEWATER
FROM A CREOSOTE TREATING OPERATION
-------
TABLE 29
PHENOL AND COD VALUES FOR EFFLUENTS FROM
THIRTEEN WOOD PRESERVING PLANTS
COD (mg/1)
Plant
Location
Mississippi
Mississippi
Mississippi
Mississippi
Mississippi
Mississippi
Virginia
Virginia
Georgia
Georgia
Georgia
Tennessee
Louisiana
Phenol
(mg/1)
162
109
-
168
83
50
192
508
119
331
123
953
104
After
Raw Flocculation
6,290
11,490
48,000
42,000
12,300
1,000
9,330
32,300
7,440
3,370
17,100
1,990
10,500
3,700
5,025
2,040
31,500
4,500
-
3,180
8,575
2,360
1,880
3,830
1,990
6,070
Percent
Reduction
41
56
96
25
63
-
66
73
68
44
78
0
42
121
-------
TABLE 30 RATIO BETWEEN COD AND BOD FOR VAPOR DRYING
AND CREOSOTE EFFLUENT WASTEWATERS*
(NOTE: Data provided by the Research Department, Koppers
Company, Inc.)
(ing/liter)
Range of BOD
40 - 75
20 - 35
10 - 15
Average
COD
150
160
300
300
320
450
160
210
180
120
100
210
180
70
—
BOD
45
40
45
75
45
60
25
35
30
20
10
15
10
10
—
Ratio
COD/BOD
3.3
4.0
6.7
4.0
7.1
7.5
6.4
6.0
6.0
6.0
10.0
14,0*
18.0*
7.0
•6.2
*Analysis revealed these values to be statistical aberrants.
They were not included in average.
TABLE 31 RANGE OF POLLUTANT CONCENTRATIONS IN WASTEWATER
FROM A PLANT TREATING WITH CCA- AND FCAP-TYPE
PRESERVATIVES AND A FIRE RETARDANT
(mg/liter) _^_____
Parameter
Range of
Concentrations
COD
As
Phenols
Cu
Cr+6
Cr+3
F
P04
NH3-N
PH
10
13
0.05
0.05
0.23
0
4
15
80
5.0
- 50
- 50
- 0.16
- 1.1
- 1.5
- 0.8
- 20
- 150
- 200
- 6.8
122
-------
checks of the COD:BOD
plants.
ratio for similar wastes from several
The COD;BOD ratio increases rapidly for BOD values smaller than
150 mg/1 (Table 30), and averages 6.2 for values in the range of
20 to 40 mg/1. This ratio is in line with the value of 6.1
reported for the petroleum industry for effluents similar in
composition to those of the wood preserving industry.
Salt Type Preservatives and Fire Retardants
Waste waters resulting from treatments with inorganic salt formu-
lations are low in organic content, but contain traces of heavy
metals used in the preservatives and fire retardants employed.
Average analytical data based on weekly sampling for a year of
the effluent from a plant treating with both preservatives and a
fire retardant are given in Table 31. The presence and concen-
tration of a specific ion in waste water for such treatments de-
pend upon the particular formulation employed and the extent to
which the waste is diluted by washwater and storm water.
Raw Waste Loading Data
Average analytical data for 5 typical wood preserving plants
treating with pentachlorophenol-petroleum solutions and/or creo-
sote are given in Tables 32 through 36. Data for plants 1
through 4 (Tables 32-35) were obtained from 24 samples collected
at hourly intervals at the outfall from each plant and analyzed
separately to obtain information on short-term variation in
effluent quality. These data were later supplemented by analysis
of several grab samples collected over a period of several
months. Data for plant 5 (Table 36) are based on a series of
grab samples collected during 1972. Information on volume of
discharge of process water was obtained either from 24-hour
measurements (plants 1-4) or estimated based on number of
retorts, processing operations used, and other considerations
(plant 5). Waste volume flow data do not include cooling water,
which was recycled at all plants, coil condensate, or boiler
blowdown water. Production figures for 1971 were estimated from
the void volume of the retorts operated by the plants.
Raw waste loadings for each pollutant are expressed in terms of
concentrations (mg/1) and kg/1000 cu m of product treated for
each of the 5 plants. Maximum, minimum, and average raw waste
loadings per day based on analytical data and volume of discharge
are also given. A composite of these data, representing the
average raw waste loadings given in Tables 32-36 is shown in
Table 37. The effluent characteristics represented by these data
are assumed to be representative of the raw waste streams of
plants treating with creosote and pentachlorophenol-petroleum
solutions. Since each of the five plants involved is typical of
the industry, data for the hypothetical plant given in Table 38
will be the basis for an analysis of effluent treatment cost
presented later in this report.
123
-------
TABLE 32
RAW WASTE LOADINGS FOR PLANT NO. 1
Raw Waste Loadings
Raw Waste
Loadings /Day (Kg)
Parenthetical values = Parenthetical values
Pounds/1000 Cubic Feet are in pounds
Parameter
COD
Phenols
Oils and
Grease
Total
Solids
Dissolved
Solids
Suspended
Solids
pH
Kg/1000 Cu-
(mE/1) bic Meters Prod. Max.
28,600 13,723.0
(854.8)
134 48.2
(3.0)
530 188.3
(11.7)
11,963 4,251.6
(264.9)
11,963 3,596.8
(224.1)
1,844 654.8
(40.8)
2,705.5
(5,952.0)
6.7
(14.8)
84.5
(186.0)
836.6
(1,840.5)
673.0
(1,480.6)
163.6
(359.9)
4.6
Min.
317.0
(697.5)
0.1
(.2)
4.2
(9.3)
5.0
(11.1)
2.3
(5.1)
3.3
(7.2)
Avg.
1,631.8
(3,590.0)
5.6
(12.4)
22.4
(49.3)
505.7
(1,112.6)
427.8
(941.1)
78.0
(171.5)
Avg. flow = 42,494 Ipd (11,227 gpd)
Void vol. of cylinders = 293 cubic meters (10,337 cubic feet)
1971 production (est.) = 26,760 cubic meters (945,000 cubic feet)
Avg. work days/yr. = 225
Avg. daily production = 119 cubic meters (4,200 cubic feet)
Preservatives = Creosote
124
-------
TABLE 33
RAW WASTE LOADINGS FOR PLANT NO. 2
Raw
Waste Loadings
Parenthetical values =
Pounds/1000 Cubic Feet
Parameter
COD
Phenols
Oils and
Grease
Total
Solids
Dissolved
Solids
Suspended
Solids
PH
(mg/1).
22,685
258
55
3,504
3,044
460
Kg/1000 Cu- ^
bic Meters Prod
7,712.
(480.
88.
(5.
19.
(1.
1,190.
(74.
1,035.
(64.
155.
(9.
0
5)
3
5)
3
2)
0
2)
2
5)
7
7)
4.9
Raw Waste
Loadings
/Day(Kg)
Parenthetical values
are in pounds
Max.
5,988.
(13,175.
54.
(120.
4.
(10.
728.
(1,603.
645.
(1,419.
95.
(210.
9
6)
7
3)
6
2)
8
4)
3
6)
7
6)
Min.
794
(1,746
9
(19
2
(4
118
(206
106
(234
16
(35
.0
.8)
.0
.9)
.0
.4)
.2
.0)
.5
.4)
.1
.4)
Avg.
1,546.7
(3,402.
17.
(38.
3.
(8.
238.
(525.
207.
(456.
31.
(69.
8)
6
7)
7
2)
9
6)
5
6)
4
0)
Avg. flow = 68,471 Ipd (18,090 gpd)
Void Vol. of cylinders = 427 cubic meters (15,068 cubic feet)
Est. 1971 production = 60,163 cubic meters (2,124,588 cubic feet)
Avg. work days/yr. = 300
Avg. daily production - 201 cubic meters (7,082 cubic feet)
Preservatives - Creosote, Pentachlorophenol
125
-------
TABLE 34
RAW WASTE LOADINGS FOR PLANT NO. 3
Raw Waste Loadings
Parenthetical values =
Pounds/1000 Cubic Feet
Kg/1000 Cu-
Raw^Waste Loadings/Day(Kg)
Parenthetical values
are in pounds
Parameter
COD
Phenols
Oil
Total
Solids
Dissolved
Solids
Suspended
Solids
/mg/1)
12,467
82
150
1,724
1,528
196
bic Meters Prod.
3,295.1
(205.3)
25.7
(1.6)
40.1
(2.5)
455.8
(28.4)
404.5
(25.2)
51.4
(3.2)
Max.
943.2
(2,075.0)
5.9
(12.9)
25.0
(55.0)
130.3
(286.6)
115.5
(254.0)
14.8
(32.6)
Min.
500.0
(1,100.0)
3.5
(7.8)
69.5
(153.0)
61.6
(135.6)
7.9
(17.4)
Avg.
708.4
(1,558.4)
5.6
(12.3)
8.5
(18.8)
98.0
(215.5)
86.8
(191.0)
11.1
(24.5)
pH
4.5
Avg. flow (est.) = 56,775 Ipd (15,000 gpd)
Void vol. of cylinders = 457 cubic meters (16,152 cubic feet)
Est. 1971 production * 64,491 cubic meters (2,277,432 cubic feet)
Avg. work days/yr. = 300
Avg. daily production * 215 cubic meters (7,591 cubic feet)
Preservatives - Creosote, Pentachlorophenol
126
-------
TABLE 35
RAW WASTE LOADINGS FOR PLANT NO. 4
Raw
Waste Loadings
Parenthetical values =
Pounds/1000 Cubic Feet
Parameter
COD
Phenols
Oil
Total
Solids
Dissolved
Suspended
Solids
pH
(mg/1)
9,318
312
580
3,432
2,748
684
Kg/1000 Cu-
bic Meters Prod.
2,291.
(142.
77.
(4.
142.
(8.
844.
(52.
675.
(42.
168.
(42.
9
8)
0
8)
8
9
2
6)
7
1)
5
1)
5.8
Raw Waste
LoadinBs/Day (kg)
Parenthetical values
are in pounds
Max.
1,131.
(2,489.
21.
(46.
45.
(100.
530.
(1,166
383.
(842.
147.
(324.
7
8)
2
6)
8
8)
3
.7)
1
4)
4
2)
Min.
373
(822
14
(32
24
(53
99
(219
93
(206
6
(13
.1
.6)
.6
.2)
.5
.9)
.9
.7)
.8
.4)
.0
.3)
Avg.
563.
(1,239.
18.
(41.
35.
(77.
207.
(456.
166.
(365.
41.
(90.
3
3)
9
5)
0
1)
5
5)
1
5)
3
9)
Avg. flow (est.) = 60,560 Ipd (16,000 gpd)
Void vol. of cylinders = 523 cubic meters (18,470 cubic feet)
Est 1971 production = 73,746 cubic meters (2,604,270 cubic feet)
Avg. work days/yr. - 300
Avg. daily production = 246 cubic meters (8,681 cubic feet)
Preservatives - Creosote, Pentachlorophenol
127
-------
TABLE 36
RAW WASTE LOADINGS FOR PLANT NO. 5
Raw Waste Loadings
Parenthetical values =
Pounds/1000 Cubic Feet
Parameter
COD
Phenols
Oils and
Grease
Total
Solids
Dissolved
Solids
Suspended
Solids
PH
Kg/1000 Cu-
(mg/1) bic Meters Prod.
13,273 3,072.
(191.
126 28.
(1.
172 40.
(2.
5,780 1,338.
(83.
5,416 1,253.
f ~f Q
{. I 0 .
364 83.
(5.
0
4)
9
8)
1
5)
6
*)
5
1)
5
2)
4.5
Raw Waste
Loadings /Bay (kg)
Parenthetical values
are in pounds
Max
593
(1,305
5
(11
9
(21
259
(570
241
(532
—
.2
.0)
.1
.2)
.9
.8)
,5
.9)
.8
.0)
—
Min.
317
(699
3
(7
1
(2
168
(370
137
(303
—
.8
.1)
.4
.4)
.0
.3)
.3
.2)
.9
.4)
—
Avg.
452
(995
4
(9
5
(12
197
(433
184
(406
12
(27
.5
.5)
.3
.4)
.9
.9)
.0
.5)
.6
.2)
.4
.3)
Void vol. of cylinders = 356 cubic meters (12,557 cubic feet)
Est. 1971 production =44,175 cubic meters (1,560,000 cubic feet)
Avg. work days/yr. = 300
Avg. daily production = 147 cubic meters (5,200 cubic feet)
Preservatives - Creosote, Pentachlorophenol
128
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TABLE 37
AVERAGE RAW WASTE LOADINGS FOR FIVE WOOD-PRESERVING PLANTS
Parameter
COD
Phenols
Oils and
Grease
Total
Solids
Dissolved
Solids
Suspended
Solids
pH
Raw Waste Loadings
Parenthetical values =
Pounds/1000 Cubic Feet
Kg/1000 Cu-
(mg/1) bic Meters Prod.
19,269 5,378.4
(335.1)
182 51.4
(3.2)
297 83.5
(5.2)
5,280 1,463.8
(91.2)
4,571 1,276.0
(79.5)
710 199.0
(12.4)
4.9
Raw Waste Loadings/Day (kg)
Parenthetical values
are in pounds
Max.
1,651.9
(3,634.2)
12.8
(28.2)
37.5
(82.5)
470.7
(1,035.5)
387.4
(852.2)
87.2
(191.9)
Min.
502.9
(1,106.3)
6.3
(13.8)
7.5
(16.4)
109.5
(240.9)
93.5
(205.8)
12.2
(26.8)
Avg.
1,016.0
(2,235.2)
9.6
(21.1)
15.6
(34.4)
278.4
(612.5)
241.0
(530.2)
37.5
(82.4)
Avg. flow = 52,990 Ipd (14,000 gpd)
Void vol. of cylinders = 411 cubic meters (14,517 cubic feet)
Est. 1971 Production = 53,867 cubic meters (1,902,258 cubic feet)
Avg. work days/yr. = 285
Avg. daily production = 189 cubic meters (6,674 cubic feet)
Preservatives - Creosote, Pentachlorophenol
129
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Sources of Waste Water
Waste waters from wood preserving operations are of the following
types and contain the contaminants indicated:
a. Condensate from conditioning by steaming: This is the most
heavily contaminated waste water, since it comes into direct
contact with the preservative being used. condensates from
pentachlorophenol and creosote treatments contain entrained oils,
phenolic compounds, and carbohydrates leached from the wood.
Those from salt-type treatments contain traces of the chemicals
present in the preservative formulation used. The oxygen demand
of this waste is high because of dissolved wood extractives and,
in the case of creosote and pentachlorophenol treatments,
entrained oils.
b. Cooling water: Cooling water is used to cool condensers, air
compressors, and vacuum pumps and, in the case of plants that use
it on a once-through basis, accounts for approximately 80 percent
of. the total discharge. Water used with surface condensers, air
compressors, and dry-type vacuum pumps is unchanged in quality.
That used with barometric condensers and wet-type vacuum pumps is
contaminated with the preservative, unless the preservative is of
the water-borne type. In the latter case, the cooling water is
unchanged in quality.
c. Steam condensate from heating coils: Water from this source
is uncontaminated, unless a coil develops a leak through which
preservative can enter.
d. Boiler blowdown water: This water is contaminated with
chemicals, principally chromates and phosphates, used as boiler
compounds.
e. Vacuum water: Water extracted from the wood during the
vacuum cycle following steam conditioning is contaminated with
the preservative employed. In the Boulton process, the waste
water is largely composed of water from this source.
f. Wash water: Water used to clean equipment is contaminated
with the preservative used, with oil and grease, and may also
contain detergents.
g. Water softener brine: Water used for this purpose is
contaminated with various dissolved inorganic materials including
salts of calcium and magnesium.
The source and volume of water used, including recycled water,
and the amount of waste water discharged by a hypothetical wood
preserving plant (Table 37) that employs steam conditioning are
shown in Figure 29. A more complete breakdown of these data is
given in Table 38. A representative plant has an intake of
approximately 121,120 1/day (32,000 gal/day), gross water usage
130
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TABLE 38
SOURCE AND VOLUME OF WATER DISCHARGED AND RECYCLED PER
DAY BY A TYPICAL WOOD PRESERVING PLANT
Source
Cylinder condensate
Coil condensate
Boiler blowdown
Vacuum Water
Cooling water
Other
TOTAL
Volume
Used
51,096
(13,500)
55,640
(14,700)
6,813
(1,800)
-
454,200
(120,000)
1,892
(500)
567,500
(150,500)
Volume Volume
Discharged Recycled
51,098
(13,500)
44,474 (b
(11,750)
6,813
(1,800)
6,434 (a
(1,700)
13,248 (c 440,952
(3,500)(b (116,500)
1,892
(500)
104,277 447,387
(27,550) (118,200)
Open values are in liters.
Parenthetical values are in gallons
a) Water extracted from wood and recycled as cooling water.
b) Approximately 15 percent loss due to flash evaporation.
c) Loss of cooling water by drift and evaporation.
Note: Based on hypothetical plant, data for which are given
in TABLE 3 .
131
-------
of 567,750 1/day (150,000 gal/day), and a discharge of 104,100
1/day (27,500 gal/day). An estimated 13,250 I/day (3,500
gal/day) of cooling water are lost by evaporation. Roughly
446,650 I/day (118,000 gal/day) are recycled as cooling water,
including 6,400 I/day (1,700 gal/day) of water extracted during
the conditioning process (vacuum water)• The amount of vacuum
water recovered averages about 1.9 kg/cu m (4.3 Ib/cu ft) of
green wood that is steam conditioned. Approximately two times
this amount of vacuum water is removed from Boultonized stock.
The actual volume of water used at a plant of this size and type
is not static, but varies depending upon the condition of the
stock (either green or seasoned) being treated and the size of
the individual items. For illustrative purposes only, the data
in Table 38 were computed based on the assumption that the plant
treated stock one-half of which was green and one-half of which
was seasoned. If all green material were treated, the volume of
boiler water and cooling water used would approximately double.
Both the gross water used in a plant and the volume discharged
depends primarily upon whether a plant uses cooling water on a
once through basis or recycles it. To a lesser extent, the
disposition of coil condensate either reused for boiler make-up
water or discharged is also important in determining the volume
of waste water. Nationwide, approximately 75 percent of the
plants recycle their cooling water; only 33 percent reuse their
coil condensate.
Gross water usage is also influenced by cooling water require-
ments. Among plants of the same size and type of operation, the
volume used varies by as much as fourfold. Such variation is
attributable to the operating procedures used. Important
variables in this regard are the length of the vacuum period,
during which cooling water is required for both the condenser and
the vacuum pump, and whether or not the rate of flow to the
condenser is reduced after the initial period of operation when a
high flow rate is needed.
Volume of cooling water used also varies with the conditioning
process used - either steaming or Boultonizing. In the former
process, the condenser is operated only about three hours fol-
lowing a conditioning cycle. In the Boultonizing process, the
condenser is operated for the entire period, which often exceeds
30 hours. Gross cooling water usage at a larger plant employing
the Boulton process may amount to 3.8 million I/day (1 million
gal/day).
Assuming recycling of cooling and coil condensate water, the most
important source of waste water in terms of volume and level of
contamination is cylinder condensate. The amount of waste water
from this source varies with the volume of stock that is green
and must be conditioned prior to preservative treatment. For
plants operating on similar steaming or Boultonizing schedules
132
-------
Intake
9al-
11,166
(2,950)-.--
(Evaporation) 102]
113
(3Q
6,
550 0,
000> 440,952
' (116,500)
J2
"o
s£
^^ ^r
<«
*-
u. 5
^> **
H 0
Wi-
O
• •
102
&.
384
050)
454
(120
813
BOO)
6,434 V
(1,700) (5
200
000)
O
z
-1
O
O
O
4>
**
CO
6
3
3
O
Ml
>
892
00)
CO
(O
UJ
u
O
C£
Q.
^•B
14J248 1,
(3^500) (Evaporation) (s
X
«a»
892
00)
104,277
Waste (27,550)
FIGURE 29 - SOURCE AND VOLUME OF DAILY WATER USE AND RECYCLING AND
WASTEWATER SOURCE AT A TYPICAL WOOD-PRESERVING PLANT
133
-------
the volume of waste does not vary widely among plants of com-
parable size and generally is less than 75,500 I/day (20,000
gal/day) .
134
-------
SECTION VI
POLLUTANT PARAMETERS
Presented below is a discussion of pollutants and pollutant
parameters that may be present in process waters in the portion
of the timber products processing industry that is the subject of
this effluent guidelines and standards development document.
Certain of these parameters are common to all the subcategories
covered by this document, although the concentrations in the
process water and the absolute amounts generated per unit of
production vary considerably among the subcategories.
Review of published information. Refuse Act Permit applications,
industry data, and information generated during the survey and
analysis phase of this effluent guidelines development program
determined that the following pollutants or pollutant parameters
are common to all of the subcategories:
Biochemical Oxygen Demand (BOD5)
Chemical Oxygen Demand
Phenols
Oil and Grease
pH
Temperature
Dissolved Solids
Total Suspended Solids
Phosphorus
Ammonia
The wood preserving subcategories may have the following
pollutants or pollutant parameters present in process water
flows:
Copper
Chromium
Arsenic
Zinc
Flourides
The above listed pollutants or pollutant parameters are, of
course, not present in process water from all the subcategories
for which effluent guidelines and standards are presented in this
document. Their presence depends on a number of factors, such as
processing method, raw materials used, and chemicals added to the
process.
Following is a discussion of the significant pollutants and
pollutant parameters.
135
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Biochemical Oxygen Demand (BODS)
Biochemical oxygen demand (BOD) is a measure of the oxygen
consuming capabilities of organic matter. The Biochemical Oxygen
Demand does not in itself cause direct harm to a water system,
but it does exert an indirect effect by depressing the oxygen
content of the water. Sewage and other organic effluents during
their processes of decomposition exert a Biochemical Oxygen
Demand, which can have a catastrophic effect on the ecosystem by
depleting the oxygen supply. Conditions are reached frequently
where all of the oxygen is used and the continuing decay process
causes the production of noxious gases such as hydrogen sulfide
and methane. Water with a high Biochemical Oxygen Demand
indicates the presence of decomposing organic matter and
subsequent high bacterial counts that degrade its quality and
potential uses.
Dissolved oxygen (DO) is a water quality constituent that, in
appropriate concentrations, is essential not only to keep
organisms living but also to sustain species reproduction, vigor,
and the development of populations. Organisms undergo stress at
reduced DO concentrations that make them less competitive and
able to sustain their species within the aquatic environment.
For example, reduced DO concentrations have been shown to
interfere with fish population through delayed hatching of eggs,
reduced size and vigor of embryos, production of deformities in
young, interference with food digestion^ acceleration of blood
clotting, decreased tolerance to certain toxicants, reduced food
efficiency and growth rate, and reduced maximum sustained
swimming speed. Fish food organisms are likewise affected
adversely in conditions with suppressed DO. Since all aerobic
aquatic organisms need a certain amount of oxygen, the
consequences of total lack of dissolved oxygen as a result or a
high BOD can kill all inhabitants of the affected area.
If a high BOD is present, the quality of the water is usually
visually degraded by the presence of decomposing materials and
algae blooms due to the uptake of degraded materials that form
the foodstuffs of the algal populations.
ChemicaliOxygen Demand (COD)
Chemical oxygen demand (COD) provides a measure of the equivalent
oxygen required to oxidize the organic material present in a
waste water sample, under acid conditions with the aid of a
strong chemical oxidant, such as potassium dichromate, and a
catalyst (silver sulfate). One major advantage of the COD test
is that the results are available normally in less than three
hours. However, one major disadvantage is that the COD test does
not differentiate between biodegradable and nonbiodegradable
organic material. In addition, the presence of inorganic
reducing chemicals (sulfides, etc.) and chlorides may interfere
with the COD test. In certain cases where a definite ratio
136
-------
between BOD5 and COD can often serve as an indicator of organics
that are not readily biodegradable.
Phenols
Phenols and phenolic wastes are derived from petroleum, coke, and
chemical industries; wood distillation; and domestic and animal
wastes. Many phenolic.compounds are more toxic than pure phenol;
their toxicity varies with the combinations and general nature of
total wastes. The effect of combinations of different phenolic
compounds is cumulative.
Phenols and phenolic compounds are both acutely and chronically
toxic to fish and other aquatic animals. Also, chlorophenols
produce an unpleasant taste in fish flesh that destroys their
commercial value.
It is necessary to limit phenolic compounds in raw water used for
drinking water supplies, as conventional treatment methods used
by water supply facilities do not remove phenols. The ingestion
of concentrated solutions of phenols will result in severe pain,
renal irritation, shock and possibly death.
Phenols also reduce the utility of water for certain industrial
uses, notably food and beverage processing, where it creates
unpleasant tastes and odors in the product.
Oil and Grease
Oil and grease exhibit an oxygen demand. Oil emulsions may
adhere to the gills of fish or coat and destroy algae or other
plankton. Deposition of oil in the bottom sediments can serve to
exhibit normal benthic growths, thus interrupting the aquatic
food chain. Soluble and emulsified material ingested by fish may
taint the flavor of the fish flesh. Water soluble components may
exert toxic action on fish. Floating oil may reduce the re-
aeration of the water surface and in conjunction with emulsified
oil may interfere with photosynthesis. Water insoluble
components damage the plumage and coats of water animals and
fowls. Oil and grease in a water can result in the formation of
objectionable surface slicks preventing the full aesthetic
enjoyment of the water.
Oil spills can damage the surface of boats and can destroy the
aesthetic characteristics of beaches and shorelines.
Temperature
Temperature is one of the most important and influential water
quality characteristics. Temperature determines those species
that may be present; it activates the hatching of young,
regulates their activity, and stimulates or suppresses their
growth and development; it attracts, and may kill when the water
137
-------
becomes too hot or becomes chilled too suddenly. Colder water
generally suppresses development. Warmer water generally
accelerates activity and may be a primary cause of aquatic plant
nuisances when other environmental factors are suitable.
Temperature is a prime regulator of natural processes within the
water environment. It governs physiological functions in
organisms and, acting directly or indirectly in combination with
other water quality constituents, it affects aquatic life with
each change. These effects include chemical reaction rates,
enzymatic functions, molecular movements, and molecular exchanges
between membranes within and between the physiological systems
and the organs of an animal.
Chemical reaction rates vary .with temperature and generally
increase as the temperature is increased. The solubility of
gases in water varies with temperature. Dissolved oxygen is
consumed by the decay or decomposition of dissolved organic
substances and the decay rate increases as the temperature of the
water increases reaching a maximum at about 30°C (86°F). The
temperature of stream water, even during summer, is below the
optimum for pollution-associated bacteria. Increasing the water
temperature increases the bacterial multiplication rate when the
environment is favorable and the food supply is abundant.
Reproduction cycles may be changed significantly by increased
temperature because this function takes place under restricted
temperature ranges. Spawning may not occur at all because
temperatures are too high. Thus, a fish population may exist in
a heated area only by continued immigration. Disregarding the
decreased reproductive potential, water temperatures need not
reach lethal levels to decimate a species. Temperatures that
favor competitors, predators, parasites, and disease can destroy
a species at levels far below those that are lethal.
Fish food organisms are altered severely when temperatures
approach or exceed 90°F. Predominant algal species change,
primary production is decreased, and bottom associated organisms
may be depleted or altered drastically in numbers and
distribution. Increased water temperatures may cause aquatic
plant nuisances when other environmental factors are favorable.
Synergistic actions of pollutants are more severe at higher water
temperatures. Given amounts of domestic sewage, refinery wastes,
oils, tars, insecticides, detergents, and fertilizers more
rapidly deplete oxygen in water at higher temperatures, and the
respective toxicities are likewise increased.
When water temperatures increase, the predominant algal species
may change from diatoms to green algae, and finally at high
temperatures to blue-green algae, because of species temperature
preferentials. Blue-green algae can cause serious odor problems.
The number and distribution of benthic organisms decreases as
water temperatures increase above 90°F, which is close to the
138
-------
tolerance limit for the population. This could seriously affect
fish that depend on benthic organisms as a food source.
The cost of fish being attracted to heated water in winter months
may be considerable, due to fish mortalities that may result when
the fish return to the cooler water.
Rising temperatures stimulate the decomposition of sludge,
formation of sludge gasr multiplication of saprophytic bacteria
and fungi (particularly in the presence of organic wastes), and
the consumption of oxygen by putrefactive processes, thus
affecting the esthetic value of a water course.
In general, marine water temperatures do not change as rapidly or
range as widely as those of freshwaters. Marine and estuarine
fishes, therefore, are less tolerant of temperature variation.
Although this limited tolerance is greater in estuarine than in
open water marine species, temperature changes are more important
to those fishes in estuaries and bays than to those in open
marine areas, because of the nursery and replenishment functions
of the estuary that can be adversely affected by extreme
temperature changes.
EM/ Acidity and Alkalinity
Acidity and alkalinity are reciprocal terms. Acidity is produced
by substances that yield hydrogen ions upon hydrolysis and
alkalinity is produced by substances that yield hydroxyl ions.
The terms "total acidity" and "total alkalinity" are often used
to express the buffering capacity of a solution. Acidity in
natural waters is caused by carbon dioxide, mineral acids, weakly
dissociated acids, and the salts of strong acids and weak bases.
Alkalinity is caused by strong bases and the salts of strong
alkalies and weak acids.
The term pH is a logarithmic expression of the concentration of
hydrogen ions- At a pH of 7, the hydrogen and hydroxyl ion
concentrations are essentially equal and the water is neutral.
Lower pH values indicate acidity while higher values indicate
alkalinity. The relationship between pH and acidity or
alkalinity is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works
structures, distribution lines, and household plumbing fixtures
and can thus add such constituents to drinking water as iron,
copper, zinc, cadmium and lead. The hydrogen ion concentration
can affect the "taste" of the water. At a low pH water tastes
"sour". The bactericidal effect of chlorine is weakened as the
pH increases, and it is advantageous to keep the pH close to 7.
This is very significant for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress conditions or
kill aquatic life outright. Dead fish, associated algal blooms,
and, foul stenches are aesthetic liabilities to any waterway.
139
-------
Even moderate changes from "acceptable" criteria limits of pH are
deleterious to some species. The relative toxicity to aquatic
life of many materials is increased by changes in the water pH.
Metalocyanide complexes can increase a thousand-fold in toxicity
with a drop of 1.5 pH units. The availability of many nutrient
substances varies with the alkalinity and acidity. Ammonia is
more lethal with a higher pH.
The lacrimal fluid of the human eye has a pH of approximately 7.0
and a deviation of 0.1 pH unit from the norm may result in eye
irritation for the swimmer. Appreciable irritation will cause
severe pain.
Dissolved Solids
In natural waters the dissolved solids consist mainly of
carbonates, chlorides, sulfates, phosphates, and possibly
nitrates of calcium, magnesium, sodium, and potassium, with
traces of iron, manganese and other substances.
Many communities in the U.S. and in other countries use water
supplies containing 2000 to 4000 mg/1 of dissolved salts, when no
better water is available. Such waters are not palatable, may
not quench thirst, and may have a laxative action on new users.
Waters containing more than 4000 mg/1 of total salts are
generally considered unfit for human use, although in hot
climates such higher salt concentrations can be tolerated whereas
they could not be in temperate climates. Waters containing 5000
mg/1 or more are reported to be bitter and act as bladder and
intestinal irritants. It is generally agreed that the salt
concentration of good, palatable water should not exceed 500
mg/1.
Limiting concentrations of dissolved solids for fresh-water fish
may range from 5,000 to 10,000 mg/1, according to species and
prior acclimatization. Some fish are adapted to living in more
saline waters, and a few species of fresh-water forms have been
found in natural waters with a salt concentration of 15,000 to
20,000 mg/1. Fish can slowly become acclimatized to higher
salinities, but fish in waters of low salinity cannot survive
sudden exposure to high salinities, such as those resulting from
discharges of oil-well brines. Dissolved solids may influence
the toxicity of heavy metals and organic compounds to fish and
other aquatic life, primarily because of the antagonistic effect
of hardness on metals.
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. Dissolved solids in industrial
waters can cause foaming in boilers and cause interference with
cleaness, color, or taste of many finished products. High
contents of dissolved solids also tend to accelerate corrosion.
Specific conductance is a measure of the capacity of water to
convey an electric current. This property is related to the
140
-------
total concentration of ionized substances in water and water
temperature. This property is frequently used as a substitute
method of quickly estimating the dissolved solids concentration.
Total Suspended Solids
Suspended solids include both organic and inorganic materials.
The inorganic components include sand, silt, and clay. The
organic fraction includes such materials as grease, oil, tar,
animal and vegetable fats, various fibers, sawdust, hair, and
various materials from sewers. These solids may settle out
rapidly and bottom deposits are often a mixture of both organic
and inorganic solids. They adversely affect fish by covering the
bottom of the stream or lake with a blanket of material that
destroys the fish-food bottom fauna or the spawning ground of
fish. Deposits containing organic materials may deplete bottom
oxygen supplies and produce hydrogen sulfide, carbon dioxide,
methane, and other noxious gases.
In raw water sources for domestic use, state and regional
agencies generally specify that suspended solids in streams shall
not be present in sufficient concentration to be objectionable or
to interfere with normal /treatment processes. Suspended solids
in water may interfere with many industrial processes, and cause
foaming in boilers, or encrustations on equipment exposed to
water, especially as the temperature rises. Suspended solids are
undesirable in water for textile industries; paper and pulp;
beverages; dairy products; laundries; dyeing; photography;
cooling systems, and power plants. Suspended particles also
serve as a transport mechanism for pesticides and other
substances which are readily sorbed into or onto clay particles.
Solids may be suspended in water for a time, and then settle to
the bed of the stream or lake. These settleable solids
discharged with man's wastes may be inert, slowly biodegradable
materials, or rapidly decomposable substances. While in
suspension, they increase the turbidity of the water, reduce
light penetration and impair the photosynthetic activity of
aquatic plants. _^
Solids in suspension are aesthetically displeasing. When they
settle to form sludge deposits on the stream or lake bed, they
are often much more damaging to the life in water, and they
retain the capacity to displease the senses. Solids, when
transformed to sludge deposits, may do a variety of damaging
things, including blanketing the stream or lake bed and thereby
destroying the living spaces for those benthic organisms that
would otherwise occupy the habitat. When of an organic and
decomposable nature, solids use a portion or all of the dissolved
oxygen available in the area. Organic materials also serve as a
seemingly inexhaustible food source for sludge worms and
associated organisms.
141
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Turbidity is principally a measure of the light absorbing
properties of suspended solids. It may be used as a substitute
method of quickly estimating the total suspended solids when the
concentration is relatively low and a correlation factor is
available.
Phosphorus
During the past 30 years, a formidable case has developed for the
belief that increasing standing crops of aquatic plant growths,
which often interfere with water uses and are nuisances to man,
frequently are caused by increasing supplies of phosphorus. Such
phenomena are associated with a condition of accelerated
eutrophication or aging of waters. It is generally recognized
that phosphorus is not the sole cause of eutrophication, but
there is evidence to substantiate that it is frequently the key
element in all of the elements required by fresh water plants and
is generally present in the least amount relative to need.
Therefore, an increase in phosphorus allows use of other, already
present, nutrients for plant growths. Phosphorus is usually
described, for this reasons, as a "limiting factor."
When a plant population is stimulated in production and attains a
nuisance status, a large number of associated liabilities are
immediately apparent. Dense populations of pond weeds make
swimming dangerous. Boating and water skiing and sometimes
fishing may be eliminated because of the mass of vegetation that
serves as an physical impediment to such activities. Plant
populations have been associated with stunted fish populations
and with poor fishing. Plant nuisances emit vile stenches,
impart tastes and odors to water supplies, reduce the efficiency
of industrial and municipal water treatment, impair aesthetic
beauty, reduce or restrict resort trade, lower waterfront
property values, cause skin rashes to man during water contact,
and serve as a substrate and breeding ground for flies.
Phosphorus in the elemental form is particularly toxic, and
subject to bioaccumulation in much the same way as mercury.
Colloidal elemental phosphorus will poison marine fish (causing
skin tissue breakdown and discoloration). Also, phosphorus is
capable of being concentrated and will accumulate in organs and
soft tissues. Experiments have shown that marine fish will
concentrate phosphorus from water containing as little as 1
microgram/1(ug/1).
Ammonia
Ammonia is a common product of the decomposition of organic
matter. Dead and decaying animals and plants along with human
and animal body wastes account for much of the ammonia entering
the aquatic ecosystem. Ammonia exists in its non-ionized form
only at higher pH levels and is the most toxic in this state.
The lower the pH, the more ionized ammonia is formed and its
142
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toxicity decreases. Ammonia, in the presence of dissolved
oxygen, is converted to nitrate (NO^) by nitrifying bacteria.
Nitrite (NO£), which is an intermediate product between ammonia
and nitrate, sometimes occurs in quantity when depressed oxygen
conditions permit. Ammonia can exist in several other chemical
combinations including ammonium chloride and other salts.
Nitrates are considered to be among the poisonous ingredients of
mineralized waters, with potassium nitrate being more poisonous
than sodium nitrate. Excess nitrates cause irritation of the
mucous linings of the gastrointestinal tract and the bladder; the
symptoms are diarrhea and diuresis, and drinking one liter of
water containing 500 mg/1 of nitrate can cause such symptoms.
Infant methemoglobinemia, a disease characterized by certain
specific blood changes and cyanosis, may be caused by high
nitrate concentrations in the water used for preparing feeding
formulae. While it is still impossible to state precise
concentration limits, it has been widely recommended that water
containing more than 10 mg/1 of nitrate nitrogen (NC)3-N) should
not be used for infants. Nitrates are also harmful in
fermentation processes and can cause disagreeable tastes in beer.
In most natural water the pH range is such that ammonium ions
(NH^+) predominate. In alkaline waters, however, high
concentrations of un-ionized ammonia in undissociated ammonium
hydroxide increase the toxicity of ammonia solutions. In streams
polluted with sewage, up to one half of the nitrogen in the
sewage may be in the form of free ammonia, and sewage may carry
up to 35 mg/1 of total nitrogen. It has been shown that at a
level of 1.0 mg/1 un-ionized ammonia, the ability of hemoglobin
to combine with oxygen is impaired and fish may suffocate.
Evidence indicates that ammonia exerts a considerable toxic
effect on all aquatic life within a range of less than 1.0 mg/1
to 25 mg/1, depending on the pH and dissolved oxygen level
present.
Ammonia can add to the problem of eutrophication by supplying
nitrogen through its breakdown products. Some lakes in warmer
climates, and others that are aging quickly are sometimes limited
by the nitrogen available. Any increase will speed up the plant
growth and decay process.
Copper salts occur in natural surface waters only in trace
amounts, up to about 0.05 mg/1, so that their presence generally
is the result of pollution. This is attributable to the
corrosive action of the water on copper and brass tubing, to
industrial effluents, and frequently to the use of copper
compounds for the control of undesirable plankton organisms.
Copper is not considered to be a cumulative systemic poison for
humans, but it can cause symptoms of gastroenteritis, with nausea
and intestinal irritations,, at relatively low dosages. The
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limiting factor in domestic water supplies is taste. Threshold
concentrations for taste have been generally reported in the
range of 1.0-2.0 mg/1 of copper, while as 5mg/l makes the water
completely unpalatable.
The toxicity of copper to aquatic organisms varies significantly,
not only with the species, but also with the physical and
chemical characteristics of the water, including temperature,
hardness, turbidity, and carbon dioxide content. In hard water,
the toxicity of copper salts is reduced by the precipitation of
copper carbonate or other insoluble compounds. The sulfates of
copper and zinc, and of copper and cadmium are synergistic in
their toxic effect on fish.
Copper concentrations less than 1 mg/1 have been reported to be
toxic, particularly in soft water, to many kinds of fish,
crustaceans, mollusks, insects, phytoplankton and zooplankton.
Concentrations of copper, for example, are detrimental to some
oysters above 0.1 mg/1. Oysters cultured in sea water containing
0.13-0.5 mg/1 of copper deposited the metal in their bodies and
became unfit as a food substance.
Chromium
Chromium, in its various valence states, is hazardous to man. It
can produce lung tumors when inhaled and induces skin
sensitizations. Large doses of chromates have corrosive effects
on the intestinal tract and can cause inflammation of the
kidneys. Levels of chromate ions that have no effect on man
appear to be so low that they are below detectable limits.
The toxicity of chromium salts toward aquatic life varies widely
with the species, temperature, pH, valence of the chromium, and
synergistic or antagonistic effects, especially that of hardness.
Fish are relatively tolerant of chromium salts, but fish 'food
organisms and other lower forms of aquatic life are extremely
sensitive. Chromium also inhibits the growth of algae.
In some agricultural crops, chromium can cause reduced growth or
death of the crop. Adverse effects of low concentrations of
chromium on corn, tobacco and sugar beets have been documented.
Arsenic
Arsenic is found to a small extent in nature in the elemental
form. It occurs mostly in the form of arsenites of metals or as
pyrites.
Arsenic is normally present in sea water at concentrations of 2
to 3 ug/1 and tends to be accumulated by oysters and other
shellfish. Concentrations of 100 mg/kg have been reported in
certain shellfish. Arsenic is a cumulative poison with long-term
chronic effects on both aquatic organisms and on mammalian
species and a succession of small doses may add up to a final
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lethal dose. It is moderately toxic to plants and highly toxic
to animals especially as AsH3.
Arsenic trioxide, whicji also is exceedingly toxic, was studied in
concentrations of 1.96 to 40 mg/1 and found to be harmful in that
range to fish and other aquatic life. Work by the Washington
Department of Fisheries on pink salmon has shown that at a level
of 5.3 mg/1 of As.20.3 for 8 days was extremely harmful to this
species; on mussels, a level of 16 mg/1 was lethal in 3 to 16
days. |
severe human poisoning can result from 100 mg concentrations, and
130 mg has proved fatal. Arsenic can accumulate in the body
faster than it is excreted and can build to toxic levels, from
small amounts taken periodically through lung and intestinal
walls from the airr water and food.
Arsenic is a normal constituent of most soils, with
concentrations ranging up to 500 mg/kg. Although very low
concentrations of arsenates may actually stimulate plant growth,
the presence of excessive soluble arsenic in irrigation waters
will reduce the yield of crops, the main effect appearing to be
the destruction of chlorophyll in the foliage. Plants grown in
water containing 1 mg/1 of arsenic trioxides showed a blackening
of the vascular bundles in the leaves. Beans and cucumbers are
very sensitive, while turnips, cereals, and grasses are
relatively resistant. Old orchard soils in Washington that
contained 4 to 12 mg/kg of arsenic trioxide in the top soil were
found to have become unproductive,
Zinc
&
Occurring abundantly in rocks and ores, zinc is readily refined
into a stable pure metal and is used extensively for galvanizing,
in alloys, for electrical purposes, in printing plates, for dye-
manufacture and for dyeing processes, and for many other
industrial purposes. Zinc salts are used in paint pigments,
cosmetics, Pharmaceuticals, dyes, insecticides, and other
products too numerous to list herein. Many of these salts (e.g.,
zinc chloride and zinc sulfate) are highly soluble in water;
hence it is to be expected that zinc might occur in many
industrial wastes. On the other hand, some zinc salts (zinc
carbonate, zinc oxide, zinc sulfide) are insoluble in water and
consequently it is to be expected that some zinc will precipitate
and be removed readily in most natural waters.
»
In zinc-mining areas, zinc has been found in waters in
concentrations as high as 50 mg/1 and in effluents from metal-
plating works and small-arms ammunition plants it may occur in
significant concentrations. In most surface and ground waters,
it is present only in trace amounts. There is some evidence that
zinc ions are adsorbed strongly and permanently on silt,
resulting in inactivation of the zinc.
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Concentrations of zinc in excess of 5 mg/1 in raw water used for
drinking water supplies cause an undesirable taste which persists
through conventional treatment. Zinc can have an adverse effect
on man and animals at high concentrations.
In soft water, concentrations of• zinc ranging from 0.1 to 1.0
mg/1 have been reported to be lethal to fish. Zinc is thought to
exert its toxic action by forming insoluble compounds with the
mucous that covers the gills, by damage to the gill epithelium,
or possibly by acting as an internal poison. The sensitivity of
fish to zinc varies with species, age and condition, as well as
with the physical and chemical characteristics of the water.
Some acclimatization to the presence of zinc is possible. It has
also been observed that the effects of zinc poisoning may not
become apparent immediately, so that fj.sji removed from zinc-
contaminated to zinc-free water (after 4-6 hours of exposure to
zinc) may die 48 hours later. The presence of copper in water
may increase the toxicity of zinc to aquatic organisms, but the
presence of calcium or hardness may decrease the relative
toxicity.
Observed values for the distribution of zinc in ocean waters vary
widely. The major concern with zinc compounds in marine waters
is not one of acute toxicity, but rather of the long-term sub-
lethal effects of the metallic compounds and complexes. From an
acute toxicity point of view, invertebrate marine animals seem to
be the most sensitive organisms tested. The growth of the sea
urchin, for example, has been retarded by as little as 30 ug/1 of
zinc.
Zinc sulfate has also been found to be lethal to many plants, and
it could impair agricultural uses.
Fluorides
As the most reactive non-metal, fluorine is never found free in
nature but as a constituent of fluorite or fluorspar, calcium
fluoride, in sedimentary rocks and also of cryolite, sodium
aluminum fluoride, in igneous rocks. Owing to their origin only
in certain types of rocks and only in a few regions, fluorides in
high concentrations are not a common constituent of natural
surface waters, but they may occur in detrimental concentrations
in ground waters.
Fluorides are used as insecticides, for disinfecting brewery
apparatus, as a flux in the* manufacture of steel, for preserving
wood and mucilages, for the manufacture of glass and enamels, in
chemical industries, for water treatment, and for other uses.
Fluorides in sufficient quantity are toxic to humans, with doses
of 250 to 450 mg giving severe symptoms or causing death.
There are numerous articles describing the effects of fluoride-
bearing waters on dental enamel of children; these studies lead
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to the generalization that water containing less than 0.9 to 1.0
mg/1 of fluoride will seldom cause mottled enamel in children,
and for adults, concentrations less than 3 or 4 mg/1 are not
likely to cause endemic cumulative fluorosis and skeletal
effects. Abundant literature is also available describing the
advantages of maintaining 0.8 to 1.5 mg/1 of fluoride ion in
drinking water to aid in the reduction of dental decay,
especially among children.
Chronic fluoride poisoning of livestock has been observed in
areas where water contained 10 to 15 mg/1 fluoride.
Concentrations of 30 - 50 mg/1 of fluoride in the total ration of
dairy cows is considered the upper safe limit. Fluoride from
waters apparently does not accumulate in soft tissue to a
significant degree and it is transferred to a very small extent
into the milk and to a somewhat greater degree into eggs. Data
for fresh water indicate that fluorides are toxic to fish at
concentrations higher than 1.5 mg/1.
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
BARKING
Logs are barked by a variety of abrasion and pressure processes
as described in detail in Section III. Ring and cutterhead
barkers produce a solid waste composed of chipped dry bark, which
may be sent to the hog to be shredded and then to the bark boiler
("hog boiler") for use as fuel. Wet drum barkers, bag (pocket)
barkers, and hydraulic barkers, require steps to separate the
abraded bark from the water* The bark is usually pressed to
remove water, and sent to the boiler, again for use as fuel. The
water can be recycled. The volume requirements, in addition to
the quality requirments of supply water to the hydraulic barking
operation, result in a significant difference in procedures and
practices for handling the process contact water generated by
this operation.
Hydraulic Barking
The volume of water used in this method of barking range between
50,000 and 120,000 1/cu m (370 to 890 gal/cu ft) of wood. Raw
effluent from hydraulic barkers ranges between 56 and 250 mg/1
BOD and 500 to 2400 mg/1 suspended solids. Primary settling can
reduce suspended solids to less than 250 mg/1.
Opportunity for disposal of these volumes of waste water are
limited in many segments of the timber products processing
category. With the exception of the pulp and paper, the volumes
generated by hydraulic barking are in excess of the amount that
could be utilized in other unit operations of the manufacturing
process.
Because little information was available on the separate
treatment of hydraulic barker effluent, treatment and control
technology will be applied from another industry, the pulp and
paper industry. It is noted, however, that water from a
hydraulic barker is being sucessfully recycled by at least one
timber products processing plant.
In the pulp industry, modern practice is the use of circular,
heavy-duty type clarifiers or thickeners. These are designed for
a rise rate of 40,700 to 48,900 1/sq m/day (1000 to 1200 gal/sq
ft/day) of surface area and to provide a retention period of
about two hours. They are equipped and piped to handle dense
sludge as well as having a skimmer to collect the floating
materials. The under flow is removed by means of diaphragm,
plunger, or screw pumps and transferred to drying beds or to a
vacuum filter for dewatering. Filter media frequently consists
of 120-mesh stainless steel wire cloth. Filter cake produced
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contains about 30 percent solids and loadings range from 235 to
284 kg/sq m of dry solids. Such cakes are either disposed of on
the land or sold as mulch.
Effluents from clarifiers are usually not treated further
separately but combined with pulp mill and other wastes for
biological treatment, which can be 85% to 95% effective.
VENEER
Treatment and control technology in the veneer manufacturing
industry is not extensive. The major effort made by this segment
of the industry to reduce waste water discharge has been to
reduce the amount of waste water by reuse and conservation of
water and to contain waste waters that cannot be reused. Each
source of potential waste water and methods of treatment is
discussed below.
Log Conditioning
Waste water from log conditioning may be the largest and most
difficult source to handle in a veneer mill.
Although seldom used, biological treatment of the effluent from
hot water vats and steam vats used in log conditioning is
practicable and effective. It has been reported that 85 to 90
percent reduction of BOD is attainable by using lagoons or
aerated lagoons. Other types of biological treatment have not
been reported, but it is obvious that conventional biological
processes such as the activated sludge process are also tech-
nically feasible.
Hot water vats when heated indirectly through coils will not have
a continuous discharge caused by steam condensate. Any discharge
results from spillage when logs are either placed into or taken
out of the vat or from periodic cleaning. Plants operating in
this manner need only to settle the water in settling tanks or
ponds and reuse the water for any makeup that might be required.
There are several plants designed to operate in this manner;
however, the tendency has generally been to operate this system
by injecting live steam into the vats to heat the water to the
desired level and then to use the steam to maintain the
temperature. The reason for the use of steam injection rather
than heating coils is to raise the temperature as quickly as
possible. Quicker indirect heating may also be accomplished by
adding more heating surface to the vats. Plants that use steam
coils in their hot water vats and then settle and reuse the water
have experienced a decreased pH in the vats with time. Addition
of lime or sodium hydroxide may be necessary to control corrosive
activity. The resulting sludge may be trucked to landfill.
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Waste water discharge from steam vats is more difficult to
eliminate. Condensate from the vats must be discharged because
of the difficulty of reusing the contaminated condensate.
Various modifications have been made to steam vats which allow
them to be converted to totally closed systems. Several plants
have converted steam vats to hot water spray tunnels which would
have conditioning effects similar to hot water vats. Hot water
does not heat the logs as rapidly or as violently as direct
steam; however, it is a practical alternative for most plants.
While many mills cannot use hot water vats because of the fact
that some species of logs do not sink, hot water sprays can be
used as an alternative and can be placed in existing steam vats
with only minor modifications. These systems work on the
principle of heating water through heat exchange coils and then
spraying the hot water over the logs. The hot water can then be
collected and reused after settling and screening.
The other possible modification is a technology from the wood
preserving industry called "modified steaming." Modified
steaming works on principles similar to hot water sprays with the
exception that no sprays are used. Coils in the bottom of the
vat are used to produce steam from the water. The steam
conditions the log in much the same manner as in conventional
steam vats, As the steam condenses, it falls to the bottom of
the vat where it is revaporized.
Either the use of hot water sprays or the employment of modified
steaming would allow mills that now use steam vats to operate
similarly to mills that now use hot water vats without direct
steam impingement. All of these methods are closed systems and,
therefore, require some type of solids removal and "flush-outs" a
few times each year. They may also require pH adjustment. The
small volumes of waste water produced during the "flush-outs"
could then be contained or used for irrigation.
Veneer Dryers
The practice of cleaning veneer dryers with water is one that
will necessarily continue. However, the frequency of cleaning
and the volume of wash water can be significantly reduced.
Veneer and plywood mills producing 9.3 million sq m per year (100
million sq ft) on a 9.53 mm (3/8 in) basis may use as much as
57,000 I/week (15,000 gal) of water to clean dryers. There are
many modifications to cleaning procedures which can reduce this
volume. A plywood mill in Oregon has already reduced its veneer
dryer washwater to 8,000 1/weeJc (2,000 gal/week) by manually
scraping the dryer and blowing it out with air prior to the
application of water. Close supervision of operators and the
installation of water meters on water hoses also encourages water
conservation. Most mills can reduce the volume of water to about
12,000 I/week (3,000 gal), and this small volume can be handled
without discharge by containment, or land irrigation.
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For a plant producing 0.465 million sq m/year of hardwood plywood
the veneer dryer wash water will be considerably less than the
flows discussed under veneer dryers serving a 9.3 million sq
m/year softwood plant. Control technology is the same i.e.,
containment, land irrigation, or evaporation.
PLYWOOD
Similar to the veneer manufacturing subcategory, treatment and
control technology is not extensive in the plywood subcategory.
This is true partly because water requirements for the
manufacture of plywood are minimal. In fact water is generated
only in the glue makeup and glue wash-up operations, and in the
veneer drying operations where they occur '-at the plywgod
manufacturing site.
Glue Lines
Current technology in the handling of glue wash water indicates
zero discharge to navigable waters to be achievable throughout
the industry. Recycle systems which eliminate discharge from the
glue lines are now in operation in about 60 percent of all mills
visited during the course of the guidelines development study and
are practicable with all three major types of glue. In 1968>
only one plywood mill had a glue wash water recycle system.
Currently the system is accepted technology in the industry.
Nevertheless, there are still a number of plywood mills that
discharge waste water from their glue operations.
A plywood mill using phenolic glue can reduce the waste water
flow from its glue operation to about 7,570 I/day (about 2,000
gal/day), without altering the process, by conserving water.
Urea formaldehyde glues do not require any more frequent washing
than do phenolic glues and, therefore, can be similarly
controlled. Protein glues, however, normally necessitate more
frequent cleaning because of shorter pot life of the glue. In
order to reduce the flows from a mill that uses protein glue, in-
plant modifications in addition to water conservation are
necessary.
Phenolic glues usually require about 227 kg (500 Ibs) of water
per batch, or 4.5 cu m/day (1200 gal/day). Further reduction of
waste water is then necessary for all of the waste water to be
used in the makeup of glue. Table 26 indicates that most
southern plywood mills generate about twice as much waste water
from glue washing than can be used for glue mixing.
Various inplant operational and equipment modifications can be
used to reduce glue washwater. For example:
(1) Some plants wash glue spreaders several
times a day, and some wash only once a
week. The less frequent washings can
reduce the amount of water to between
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10 and 30 percent of the original volume.
(2) The use of steam to clean the spreaders also
reduces the water usage considerably., While
steam cannot be used for some types of rub-
ber coated roller spreaders commonly used with
phenolic and urea glues, steam would be a
practical modification for protein glue opera-
tions which use steel rollers. This is quite
significant since the frequency of washing for
protein glue lines cannot te reduced to the
same extent as when synthetic resins are used.
(3) The use of high pressure water lines and noz-
zles can reduce the amount of water used to
30 percent of the original volume.
(4) The use of glue applicators which spray the glue
rather than roll it onto the wood can reduce
the volume of washwater, since these do not
require washing as frequently as do the glue
spreaders.
(5) The use of washwater for glue preparation and
the reuse of remaining washwater for washing
the glue system is a simple method of reducing
waste water flows, since a fraction of the
washwater is used to prepare glue, a volume
of fresh water can be added as final rinse in
the washing of the glue spreaders.
These modifications can be used in combination to completely
recycle the washwater and eliminate discharge from the glue
system. A typical recycle system is shown in Figure 30.
There has been no difference in the quality of glue made with
fresh water and that made with washwater. An economic benefit
has been established by using glue waste water, because of the
fact that it contains glue and other chemicals such as sodium
hydroxide, as shown in Table 39.
Complete recycle systems are now in operation for phenolic, urea,
and protein glues. Mills that use several types of glues must
have separate recycle systems to segregate the different wash-
waters. Attempts at mixing washwater from different types of
glues have been unsuccessful.
In addition to washwater recycle, there are plants that contain
and/or evaporate glue washwater, spray the glue water on the bark
that goes into the boiler, or use a combination of these
techniques.
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PLYWOOD PLANT BUILDING
7-1/2 H.R MOTOR
PROVIDING CONTINUOUS
AGITATION
TRASH
REMOVAL
CONVEYOR
BELT
CONCRETE
SETTLING
TANK
2000 GALJ
COLLECTION
TANK
WATER
METERING
TANK
GLUE
MIXER
MIX
HOLD
TANK 1
Uo=!
PUMP
PUMP
GLUING AREA
GLUE
SPREADERS
CONCRETE DRAINAGE TROUGH IN FLOOR
FIGURE 30
- PLYWOOD PLANT WASH WATER REUSE SYSTEM
-------
en
en
TABLE 39
THE ADHESIVE MIXES USED (CASCOPHEN 3566C)
Ingredients
Mix 5 minutes
W-156V Resin
Mix 2 minutes
50% Caustic Soda
Mix 15 minutes
W-156V Resin
Mix 5 minutes
TOTAL
Resin Solids in Mix
Mix 1 (a
220
131
2,178
3,719
25.7%
Mix 2 (b
220
75
2,156.5
3,642.5
25.7%
Mix 3 (c
Water
Phenofil
Wheat
Flour
700
350
140
701
350
140
700
350
140
220
100
2,163.5
3,673.5
25.7%
a) Control mix - clean water used for mix.
b) 20:1 dilution of Mix 1 used for mix water - pH 11.5
c) 30:1 dilution of Mix 1 used for mix water - pH 11.4
-------
HARDBOARD - DRY PROCESS
The small volumes of cprocess waste water discharged from dry
process hardboard mills and the variation of waste sources from
mill to mill have resulted in little new waste treatment
technology being developed. In general, because the small
volumes of waste water generated, the major treatment processes
have been limited to oil-water separation, waste retention ponds,
or perhaps spray irrigation.
The major waste water source in one particular mill may be non-
existent in another mill. Inplant modifications to reduce,
eliminate, or reuse waste water can greatly affect total waste
water discharge from any mill. By inplant modifications and
containment on site, the elimination of discharge can be achieved
throughout the dry process hardboard industry.
Log Wash: At the time of this study, only two mills reported
washing logs. One mill which washes logs has zero discharge of
all its waste through impoundment and land irrigation. The
second mill uses approximately 82 cu m/day (21,600 gal/day) for
log washing with the wash water being discharged directly to a
stream without treatment. Log washwater can be successfully
recycled by settling with only a small percentage of blowdown to
remove accumulated solids. The blowdown from log wash water
recycle systems can be disposed of by impounding or land
spreading.
Chip Wash; At the time of this study, there were no dry process
hardboard mills which reported washing chips, however several
have indicated plans to install chip washing in the future.
Until such time as chip washers are installed and experience
gained, no demonstrated technology is available in the dry
process hardfcoard industry for treatment of this waste stream.
Predicted waste water discharges from a chip wash system are 18.9
to 37.8 cu m/day (5,000 to 10,000 gal/day) for a 227 kkg/day
Dlant.
Resin System
Six mills out of the total of 16 dry process hardboard mills
report no discharge from their resin systems. Several other
mills report a waste discharge of less than 750 I/day (200
gal/day). All hardboard mills use essentially the same types of
resin (phenolic or urea formaldehyde). Taking into consideration
that several mills already have no discharge of waste water
pollutants and that many plywood mills using the same resin have
no discharge of waste water pollutants from the resin (glue)
system, dry process hardboard mills can employ similar practices
and procedures to to achieve no discharge of process waste water
pollutnts from their resin systems.
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Caul Wash: Five (5) mills report no caul wash water discharge.
Those mills reporting discharges of caul washwater average 750
I/day (200 gal/day). This low quality of water can either be
eliminated or neutralized, as necessary, then disposed of by
impounding, land spreading, or disposal of by alternative
methods*
Housekeeping; Housekeeping wash water is a miscellaneous waste
water flow which varies from mill to mill. Several mills report
no housekeeping washwater as all cleaning inplant is done by
sweeping and vacuum cleaning. At least two mills have waste flow
from their press pit which usually contains oil. This waste
water can be eliminated by preventing condensate water from
entering the press pit and by reducing hydraulic fluid leaks.
Housekeeping waste water can be either totally eliminated or, if
water is used, held on site by impounding and spray irrigation,
evaporation, discharge to a municipal system, or discharge to a
treatment system serving a timber processing complex.
Cooling Water: cooling water is by far the major waste water
flow from dry process hardboard mills. Cooling wat,er is used in
such unit processes as refiner seal water cooling systems, and
air compressor cooling systems, erator cooling systems. Use of
cooling water varies widely but is usually less than 380 cu m/day
(100,000 gal/day) Cooling water can be recycled through cooling
towers or cooling ponds.
\
Humidifier: Hardboard must be brought to a standarjd moisture
content after dry pressing. This is done in a humidifier unit in
which a high moisture and temperature is maintained. Nine mills
report no water discharge from humidification units, while one
mill reports a volume of less than 11 cu m/day (3,000 gal/day).
It has been determined that humidifiers can be operated with ,no
discharge of waste water pollutants.
s
Finishing; All dry process hardboard mills report no discharge
from finishing operations. Concern was indicated by industry
with the potential of new technology causing waste water flow
from the finishing operation. For example, air pollution control
regulations may make it necessary to switch from oil based paints
to water based paints in which case a potential waste water
source could exist. At the present time there is no discharge
from finishing operations.
Summary
The water pollution resulting from dry process hardboard
manufacture is directly related to waste water flow and
concentration, which, in turn, is influenced by operation and
maintenance practices and situations in each mill. The decision
to wash logs or chips by a mill is a result of the effect of dirt
and grit on inplant machinery. High maintenance costs resulting
frem abrasion of refiner plates, and other equipment, may make it
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desirable to wash logs and chips. Quantities of extraneous
material on logs depend upon harvesting transportation and
storage operations, and therefore, directly affect waste water
flow and composition.
The operation and maintenance of the resin system affects waste
water flow. Most hardboard mills and numerous plywood mills
using similar resins are able to operate with no discharge from
their resin systems. Modification of inplant equipment or
maintenance procedures should eliminate the resin system as a
source of waste water flow.
Caul washing, a min'or waste water source, is an inplant process
that is affected by operation. Cauls are soaked in tanks con-
taining sodium hydroxide and other cleaning agents. After
soaking they are rinsed and put back into use. The method of
operation of this cleaning system can greatly reduce the water
usage and therefore the quantities of water to be disposed of.
The resulting low volumes of water (less than 750 I/day or 200
gal/day) can be easily disposed of on-site.
Housekeeping practices vary widely from mill to mill with
resulting effects on waste water discharge. Several mills are
able to perform clean up operations without having waste water
being discharged. Other mills use water for clean up operations
because of the ease and efficiency of water cleaning.
Modification of inplant housekeeping procedures can minimize
water usage with resulting elimination of discharge from this
source.
The press pit (a sump under the press) can collect oil, fiber,
and condensate water. The method of clean up of the press pit
can significantly reduce waste from this process. Modifications
can be made to reduce or eliminate condensate water so that an
oil/water emulsion will not be formed.
HARDBOARD - WET PROCESS
As discussed in Section V, the volumes of waste water generated
in wet process hardboard manufacture is sufficient in volume that
the waste water cannot be contained on site. There is no single
scheme currently being used to treat waste water discharges from
wet process hardboard mills. The major treatment and control
methods presently being used include water recycle, filtration,
sedimentation, coagulation, evaporation and biological oxidation
processes such as lagoons, aerated lagoons, and activated sludge
processes.
The treatment and control methods presently utilized in any one
mill have been influenced by pressure from regulatory agencies,
land availability, access to city sewer, individual company
approach to waste water control, and other factors.
Inplant Control Measures and Technology
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Raw Materials Handling; There were no mills reporting washing
logs, however, if logs were washed, a simple recirculation system
could be installed to eliminate discharge from this source. This
recirculation system would consist of a sedimentation basin or
pond to catch the washwater and allow the removal of settleable
solids. Pumps preceded by screens would recirculate the water
for log washing. Accumulated deposits in the sedimentation basin
or pond would be removed as needed and disposed of as landfill.
Chip washing, if practiced, could be eliminated as a waste water
source in a similar manner.
Process Water: The major source of waste water flow and concen-
tration comes from discharging the process water. This includes
water from fiber preparation, mat formation, and pressing
operations. As has been previously discussed, the source of
organic material in the process water is from the solution of
wood chemicals. The quantity of organics released is directly
dependent upon wood species, cooking time, pressure, temperature,
and degree and nature of refining.
It has been suggested that a decrease in BOD load can be made by
reducing the cooking or preheating temperature at the expense of
higher energy consumption in the refiners. Little research has
been done in this area, however, only a portion of the BOD can be
eliminated in this manner.
Assuming that chips contain 50 percent fiber and must be diluted
to 1.5 percent fiber prior to mat formation, for every kkg of dry
fiber processed, 60.5 cu m (16,000 gal) of water is needed for
dilution. The obvious procedure to obtain this quantity of water
and reduce or eliminate the discharge of organic material is to
recycle a portion or all of the process water.
There are several limiting factors preventing total recycle of
process water, including temperature, soluble organics, and build
up of suspended solids (fines)* Temperature of process water can
be controlled by the installation of a heat exchanger. At least
two mills report the use of shell and tube heat exchangers to
control process water temperature.
Soluble organics are the most difficult to control in the wet
process. The explosion process utilized by two mills produces
greater quantities of soluble organics (pollutants) than other
processes because of the higher temperature and pressure.
Because of the large quantities of organic material released from
the wood, these plants installed evaporation systems to reduce
the quantities of organics discharged in their waste water.
Figure 31 shows a schematic diagram of one of these systems. In
this system countercurrent washers are used to remove a major
portion of the organics from the fiber prior to dilution and mat
formation. This waste stream passes through a darifier is then
evaporated. The concentrated organic stream from the evaporator
is sold as cattle feed or it can be incinerated, and the
condensate is either reused as process makeup water or discharged
159
-------
TO ATMOSPHERE
CHI
O)
O
WATER IN
WATER OUT
CONCENTRATED
BY-PRODUCTS
STOCK
CLARIFIED
| CHEST) (MACHINE |
-------
as a waste water stream. Process water from the felter and the
press pass through a clarifier to remove settleable solids. All
solids are reused to make board, while the overflow is used for
fiber wash or dilution water. The total BODS discharge from this
mill without biological treatment is only 3.25 kg/kkg (6.5
Ib/ton) .
The thermal-mechanical pulping process releases less organics and
it is questionable whether or not process water soluble
concentrations can be increased to a high enough level to make
evaporation economical without inplant modifications. However,
at least one mill in Sweden is presently evaporating excess
process water. One possibility to decrease the volume of waste
water without increasing the concentration of soluble substances
in the process water system at the same time is to arrange some
kind of prepressing of the pulp to remove the concentrated
organics before they enter the refining and formation process
water stream. An arrangement of this type is shown in Figure 32,
where a pre-press has been inserted after the cyclone. If the
process water system is completely closed, all soluble substances
with the exception of those deposited in the hardboard would be
contained in the waste water leaving the pre-press. The
concentration of soluble substances in this waste water depends
on the amount of substances dissolved during the pre-heating, on
the volume of waste water leaving the pre-press, and finally on
the efficiency of the pre-press, i.e., the consistency of the
pulp leaving the press. The efficiency of such a system can be
increased by installing two or three presses in series. A system
of this type can significantly reduce the concentration of
soluble organics in the process water, allowing increased
recirculation rates.
Suspended Solids: Suspended solids within the process stream
must be controlled to limit the build up of fines which reduce
water drainage during mat formation and to limit the suspended
solids discharged in the raw waste water. If treatment methods
such as evaporation are used, the suspended solids concentrations
entering these processes must be controlled. Suspended solids
removal systems are usually of gravity settling, screening,
filtration, or flotation.
Only 2 mills utilize sedimentation tanks for removal of suspended
solids in process water prior to recycle, and both use the
explosion process. These systems are shown in Figures 31 and 33.
Process water from both mat formation and final pressing is
passed through a clarifier and reused in the process. Other
mills utilize gravity separators in their final waste water
treatment scheme, but do not recycle back to process. In one of
the mills utilizing gravity separators to remove solids from the
process water, the settled solids are returned to the process and
become part of the board. The other mill has not been able to do
this because of differences related to raw material.
161
-------
STEAM
01
no
(XX)
WATER IN
WAT ER OUT
APPROXIMATE PERCENT FIBER
(CONSISTENCY IN PROCESS)
STOC K
WET FORMING
WET
* J«5)
f
•
1
1
v
"' 1 -••-•»•- I I MAiniN-t I
(30) >
r\
k (1-5)
r
1
PROCESS
WATER
CHEST
(35)
KKtS3
^
'
y//s////y////y///////?//////y////y///tf^^^^
TO TREATMENT
FIGURE 32 - TYPICAL WET-PROCESS HARDBOARD MILL WITH PRE-PRESS
-------
TO ATMOSPHERE
CHIPS^'GUN
WATER IN
WATER OUT
CONCENTRATED
BY-PRODUCTS
FIGURE 33 - INPLANT TREATMENT AND CONTROL TECHNIQUES AT MILL NO. 3
-------
Filters can accomplish the same liquid solid separation as
gravity separation. The efficiency of such filters varies widely
depending upon flow rates, suspended solids concentrations, and
types and sizes of solids. Representative data for filter
efficiency may be found in Table 40.
One system utilized for controlling suspended solids is a
patented process developed in Finland at the Savo Oy Mill. This
system is a chemical treatment system followed by sedimentation
and/or flotation. The chemical treatment includes adjustment of
the pH, addition of chemicals for coagulation, followed by
removal of suspended solids and some dissolved and colloidal
solids^
There are 2 mills in the U.S. presently using this system to some
degree. Typical data from the Savo system from one of these
mills is shown below:
COD
Total suspended solids
Total dissolved solids
Soluble organics
Volatile suspended solids
Influent
(mq/1)
7775
750
5525
4285
740
Effluent
(ma/1)
4745
48
4788
3362
46
Percent
Reduction
39
94
13
22
94
An advantage reported from the use of the Savo'system is that all
sludge from the system can be reused in the board. One mill has
been able to reduce its waste water flow to 2.3 cu m/ton (611
gal) and BOD discharge to 8.5 kg/kkg (17 Ib/ton). This rate and
concentration is the result of inplant modifications and does not
include end of line treatment. Figure 34 shows a schematic
diagram of this process.
End of Line Waste water Treatment
The existing end of line waste treatment facilities consist
primarily of screening followed by primary and biological
treatments. All of the wet process hardboard mills utilize
primary settling basins either within the process or as part of
their final waste treatment facilities. In order to protect the
primary settling units from sludge loading and to remove as much
fiber as possible, screens are generally placed ahead of the
primary units. Fiber removed by screening is disposed of by
landfill or returned to process.
Three of nine wet process mills were either sampled or the mill
reported treatment efficiencies across their primary clarifiers.
This data is shown in Table 41. Although this data may be
typical of the treatment efficiency that existing facilities are
achieving, it is not representative of the efficiency that can be
obtained through proper design and operation. The three mills
164
-------
TABLE 40
REPRESENTATIVE PROCESS WATER FILTER EFFICIENCIES
Suspended Solids (mg/1)
Mill . Before Filter After Filter
0 1000 - 3500 80 - 250
P 170 - 1000 30 - 150
Q 1000 T 1300 280 - 330
R 230 - 620 90 - 145
165
-------
STEAM
CHIPS
WATER IN
WATER OUT
TO
.ATMOSPHERE
DREH EATER— REFINER
WET FORMING
MACHINE
FIBER
TO
PROCESS
PROCESS
WATER
CHEST
WET
PRESS
TO
FINISHING
i
^
S AVO
1
DISCHARGE
FIGURE 34 - TYPICAL WET-PROCESS HARDBOARD MILL WITH SAVO SYSTEM
-------
TABLE 41
PRIMARY SETTLING TANK EFFICIENCY
BOD IN
Mill
BOD Out
mg/1 k/kkg mg/1 k/kkg
Percent
Removal
SS In
mg_/l k/kkg
SS Out
mg/1 k/kkg
Percent
Removal
2400 28.5
3500 32
6000 42.2
2400 28.5
3300 30.5
3900 28
0
5
35
1650 19
430 4
1440 10
178 2
154 1.4
450 3.25
89
69
68
-------
listed1 in Table 41 utilized settling ppnds as primary clarifiers.
These ponds are allowed to fill with, solids before being dredged
for solids 'removal. Accumulated solids undergo anaerobic
decomposition causing an increase in BOD5 and suspended solids
(SS) in the effluent.
A properly designed clarifier with a mechanical sludge collector
and continuous sludge removal can be expected to obtain
approximately 75 to 90 percent SS reinoval and 10 to 30 percent
BODIJ removal.
The pH of wet process waste water varies from 4.0 to 5.0. ^?he pH
must be adjusted to near 7.0 to obtain satisfactory biological
degradation. The pH may be adjusted by the addition of lime or.
sodium hydroxide.
wet process hardboard mill waste water is deficient in nitrogen
and phosphorus. These nutrients must be added in some form to
obtain rapid biological degradation of the waste. The most
commonly used source of nitrogen is anhydrous ammonia, and the
most commonly use£ source of phosphorus is phosphoric acid-
Existing biological treatment systems consist of lagoons, aerated
lagoons, activated sludge, or a combination of these. The type
of system presently used at each mill is shown below:
Mill No. End^ Of Line Treatment System
1 Primary settling pond - aerated lagoon -
secondary settling pond.
2 Primary settling pond - aerated lagoon -
secondary settling pond.
3 Primary clarifier - activated sludge -
aerated lagoon
4 Primary settling pond - activated sludge -
aerated lagoon
5 Primary settling pond - activated sludge -
lagoon or spray irrigation.
6 Primary settling pond.
7 NO treatment.
8 (No^ treatment.
9 Aerated lagoon.
Table 42 shows the treatment efficiency of the five mills whicli
presently have bioligical treatment systems in operation. The
values shown are average values and do not define the variations
in effluent that can be expected from biological systems. It
should be noted that the values shown for mills No. 1,2, and 5
include the efficiency of the primary settling units while for
mills No. 3 and 4 the efficiency is across the biological unit
alone.
168
-------
TABLE 42
TREATMENT EFFICIENCY OF BIOLOGICAL SYSTEMS
Mill No.
*+i
*+2
*3
*4
*+5
**+!
**+2
*3
*4
*5
Influent
33
50
23
28.5
32
720
1310
1800
2400
3500
BOD, kg/kkg
Effluent
7
15
0.6
6.45
1.55
151
393
54
552
175
Percent
Removal
79
70
97
77
95
79
70
97
77
95
Influent
10
_-
1.4
0.7
1.4
220
—
114
60
151
\
SS, kg/kkg
Effluent
9
--
3.6
4.2
3.6
bb, mg/x
198
— —
295
360
388
Percent
Removal
10
--
0
0
L,^
10
_»
0
0
0
— *. f
+ Includes efficiency of primary settling
** Aerated lagoons
* Activated sludge
-------
Mills No. 1 and 2 utilize! Werated lagoons. Their treatment
efficiencies for BOD removal hnvj averaged 70 and 79 percent,
respectively. Mills 3, 4, atra 5 utilize some variation of the
activated sludge process and their average efficiencies for BOD
removal are ^7,77, and 95 percent, respectively. Mill No. 4,
whose activated sludge system averages only 77 percent efficiency
for BOD removal is actually not operated as an activated sludge
system as theare is no sludge wastes from the system. Therefore,
the system is more representative of an aerated lagoon system.
The efficiency of solids removal across the biological system for
all mills is essentially zero. There are several reasons for
this. Biological solids produced in waste treatment systems
treating hardfcoard waste water are difficult to settle and
dewater. There is presently no economical method that is
satisfactory for handling waste activated sludge from these
biological systems. one mill attempts to utilize a centrifuge
for sludge thickening prior to incineration, however, the system
is highly variable in its efficiency and 'frequently excess sludge
has to be hauled by tank trucks to a land spreading area.
Several mills in the U.S. and Europe have put excess sludge back
into the process water to become part of the board. The quantity
of sludge which can be reclaimed in this manner is variable from
mill to mill depending upon a variety of factors. It is known
that the addition of sludge to the board increases the water
absorption, reduces the drainage rates, and make it necessary to
add additional chemicals to compensate for the sludge addition.
At least one mill (mill No. 5) is disposing of its waste sludge
by spray irrigation. Waste sludge is pumped to an aerobic di-
gester, then the digested sludge is pumped to a nearby spray
irrigation field. Land irrigation or sludge lagooning has the
advantage of making it unnecessary to dewater the sludge prior to
disposal.
The difficulty in handling waste sludge from the activated sludge
treatment of wet process hardboard waste water leads to a build
up of solids within the system with a resulting discharge of
solids in the effluent. Weather conditions (temperature) are
also reported to have an effect on the settling rate of
biological solids in both aerated lagoon systems and the acti-
vated sludge system.
Figures 35, 36, and 37 show the variations in effluent BOD and
suspended solids for mills No. 2, 3, and 4, respectively. Values
shown are monthly averages and do not necessarily indicate a di-
rect relationship between suspended solids and seasonal
temperature variations. The main information presented by these
graphs is that for either the aerated lagoon or activated sludge
average, suspended solids in the effluent can be expected to be
250 mg/1.
170
-------
1/72 2/72 3/72 4/72 5/72 6/72 7/72 8/72 9/72 tO/72 11/72 12/72 1/73
FIGURE 35 - VARIATION OF EFFLUENT BOD AND SUSPENDED SOLIDS
AS A FUNCTION OF TIME FOR MILL NO. 2
-------
BOD
ro
1/72 2/72 3/72 4/72 5/72 6/72 7/72 8/72 9/72 10/72 11/72
12/72
FIGURE 36 - VARIATION OF EFFLUENT BOD AND SUSPENDED SOLIDS
AS A FUNCTION OF TIME FOR MILL NO. 3
-------
OJ
1/72
2/72
3/72
4/72
5/72
6/72
7/72
8/72
9/72
10/72
11/72
FIGURE 37 - VARIATION OF EFFLUENT BOD AND SUSPENDED SOLIDS
AS A FUNCTION OF TIME FOR MILL NO. 4
-------
Table 43 shows an example of an aerated stabilization basin (ASB)
or aerated lagoon performance related to tempe rat tire. This table
is for a biological system treating paperboard waste. Similar
effects are experienced in the wet process hardboard industry.
The main difference, however, is that the quantity of solids can
be expected to be several times greater.
Summary
Water Reuse; The 9 wet process hardboard mills presently
practice considerable recycle of waste water. These systems
include:
(1) process water recycle with blowdown to control suspended
solids and dissolved organics. This blowdown may occur in a pre-
press, from the wet or hot press, or from the process water
chest. (2) Process water recycle through a primary clarifier
with blowdown of some clarifier effluent and recycle of some or
all sludge to the stock chest. (3) Process water recycle
through a primary clarifier with falowdown being evaporated and
some evaporator condensate being utilized for makeup. In the
explosion process all fiber washwater is discharged through a
primary clarifier prior to evaporation. (4) Process water
recycle with blowdown passing through chemical coagulation
system. Part of coagulated waste recycled back to process and
all sludge returned to stock chest.
Waste water Treatment: End of pipe treatment technol-
ogy presently consists of one or more of the following practices:
(1) Screening
(2) Primary clarification
a. settling ponds
b. mechanical clarifiers
(3) pH control
(4) Nutrient addition
(5) Aerated lagoons
(6) Activated sludge process
(7) Oxidation lagoons
Sludge Handling: Systems utilized for disposal of waste
sludge include:
(1) Reuse in manufacture of hardboard
(2) Landfill
(3) Spray irrigation
(4) Incineration
174
-------
TABLE 43
EXAMPLE OF AN ASB SYSTEM PERFORMANCE RELATED TO TEMPERATURE
PAPERBOARD*
Average
Monthly
Temperature
(°C)
21
21
19
17
17
11
7
5
5
3
Effluent
BODS
(mg/1)
11
17
22
17
11
20
40
29
38
42
Cone .
SS
(mR/1)
22
21
23
17
16
29
56
61
31
42
* Includes long-term
settling
175
-------
WOOD PRESERVING
The technological base for waste control in the wood preserving
industry is generally quite weak by comparison with most other
industrial subcategories. Relatively few companies have
employees with the engineering and other technical skills needed
to utilize effectively current or potential developments in waste
treatment and management, or to adopt processing methods that
would minimize waste loads. Engineering services required by
individual plants are most commonly performed by consulting
firms. This situation is ameliorated somewhat by the American
Wood-Preservers' Association through the activities of its
technical committees and publication of its Proceedings, both of
which serve to keep its members advised of current developments.
Membership in the association represents plants that account for
an estimated 90 percent of the total production of the industry.
The comments and data which follow summarize the status of
pollution control activities in the wood preserving industry, as
revealed by a recent <1973) survey by Thompson of 377 plants.
The data are based on the results on a questionaire survey from
207 plants.
Disposition of Waste water
The approach to the pollution problem taken by many treating
plants is to store their waste water on company property (Table
44). This is by far the most popular method of handling waste
water, accounting for 42 percent of the plants reporting.
Seventeen percent are still releasing their waste water with no
treatment, while 14 percent of the plants are discharging to
sanitary sewer systems. Of the latter group, 63 percent are
discharging raw waste to sewers, while 37 percent are giving the
waste a partial treatment before releasing it. Only 9 percent of
the 207 plants responding to the survey presently are giving
their waste the equivalent of secondary treatment before
releasing it. Eighteen percent either have no waste water or are
disposing of it by special methods such as evaporation or
incineration.
There are no unusual trends when the data on methods of disposal
of waste water were broken down by region (Table 45). However,
it is of interest to note that a high proportion of the plants in
the West dispose of their waste by special methods, or have no
waste stream.
Compliance With Standards
Sixty percent of the plants surveyed in 1973 indicated that they
currently meet state and federal water pollution standards (Table
46). Twenty-five percent stated that they do not meet these
standards and 15 percent do not know whether they do or not. A
higher portion of plants in the West and Southwest currently meet
176
-------
TABLE 44 METHOD OF DISPOSAL OF WASTEWATER BY WOOD
PRESERVING PLANTS IN THE UNITED STATES
Disposal Method
Release - No Treatment
Store in Ponds
To Sewer - Untreated
To Sewer - Partial Treatment
Secondary Treatment
Other*
*No wastewater, incineration
Number
of
Plants
35
86
19
11
18
38.
, etc.
Percent
of
Plants
17
42
9
5
9
18
TABLE 45 METHOD OF DISPOSAL OF WOOD PRESERVING
WASTEWATER BY REGION
Region
Southeast
Southwest
Atlantic Coast
Lake and Northeast
Release
Untreated
13
5
9
2
Store
29
20
10
17
Sewer
12
6
4
6
Treat
5
4
4
5
Other
17
5
4
2
177
-------
TABLE 46. COMPLIANCE WITH STATE AND FEDERAL WATER STANDARDS
AMONG WOOD PRESERVING PLANTS IN THE UNITED STATES
Compliance
Yes
Don't Know
No
Number
of
Plants
126
29*
52
Percent
of
Plants
60
15
25
*Includes Non-Responses
TABLE 47. PLANS OF WOOD PRESERVING PLANTS NOT IN COMPLIANCE
WITH WATER STANDARDS ~ UNITED STATES
Plan
Number
of
Plants
None
Discharge To Sewer - Raw
Discharge to Sewer - ui I Removal
Discharge To Sewer - Oil + Phenol Removal
Construct On-Site Treating System
Other
TOTAL
29
5
6
4
25
IL
81
178
-------
standards than in other regions of the country. However, the
differences among regions are not great, ranging from 57 percent
of the plants in the Atlantic Coast region to 73 percent in the
West.
Table 47 gives a breakdown of what the plants that did not meet
the 1973 standards plan to do with the their waste water.
Nationally, roughly onethird of the plants have made no plans.
Most of the remainder plan either to construct on-site treatment
facilities for their waste water (31 percent) or discharge it to
sewer systems (19 percent). Twelve of the 81 plants involved
indicated that they would dispose of their waste by other means.
Incineration and evaporation were two of the "other" methods
mentioned.
Over a third of the plants not meeting standards are located in
the southeast. Most of these plants are planning to treat their
waste on site or discharge it to a sewer system. Half of the
plants in the West and Lake and Northeast states indicated that
they have made no plans to meet applicable standards.
Of the plants that have installed or plan to install secondary
treating facilities, 70 percent will use either oxidation ponds
or soil percolation (Table 48). Only 14 plants (about 15
percent) have elected to use trickling filters or activated
sludge. The choices of the various methods of treatment were
generally uniform among regions, with no single region showing a
strong preference of one method over another (Table 4.9) .
Plant Sanitation
Plant sanitation covers those aspects of plant housekeeping which
reduce or eliminate the incidence of water contamination
resulting from equipment and plumbing leaks, spillage of
preservative, and other similar sources. Lack of attention to
these sources of pollution is a serious problem at many plants
that will require remedial action. Its origin lies in the lack
of appreciation of the fact that even small losses of
preservative can largely negate waste management practices
directed toward collecting and treating process water.
179
-------
TABLE 48 TYPE OF SECONDARY WASTEWATER TREATING FACILITIES
INSTALLED OR PLANNED BY WOOD PRESERVING PLANTS IN U.S.
Number
of
Plants
Oxidation Pond
Trickling Filter
Activated Sludge
Soil Percolation
Chemical Oxidation
Other (incineration)
TOTAL
31
8
6
31
3
10
89
TABLE 49 TYPE OF SECONDARY WASTEWATER TREATING FACILITIES INSTALLED
OR PLANNED BY WOOD PRESERVING PLANTS BY REGION
Treatment
Oxidation Pond
Trickling Filter
Activated Sludge
Soil Percolation
Chemical Oxidation
Other
SE
12
3
1
12
1
0
sw
9
3
2
2
0
4
AC
3
0
1
9
1
0
w
2
1
1
2
1
6
L&NE
5
1
1
6
0
0
SE - Southeast
SW - Southwest
AC - Atlantic Coast
W - Western
L - Lake and Northeast
180
-------
Preservative Loss From Retorts
Areas under and in the immediate vicinity of retorts are the most
important from the standpoint of plant sanitation. The camber in
some retorts prevents the complete drainage of preservative from
the retort upon completion of a charge. Consequently, when the
retort door is opened to remove the charge, a quantity of
preservative drains into pipe trenches or sumps under the retort
where it becomes contaminated with dirt, storm water, and other
types of preservatives. Most plants process the preservative
through oil separators and thereby recover most of it. The
better managed and equipped plants collect it in troughs as it
drains from the retorts and transfer it to underground storage
tanks.
Losses of preservative in the vicinity of the retort are of
particular importance in salt-type treatments because they
represent the major source of pollution. Many such plants are
equipped to collect preservative spillage and wash water and
reuse it as make-up water for fresh treating solutions.
Storm Water
Storm water becomes contaminated as it flows over areas saturated
with preservative from spills and leaks. Areas of particular
concern are those around and in the vicinity of treating
cylinders, storage tanks, and separators. Because these areas
are usually not large, it is practical to reduce the volume of
storm water that must be treated by constructing dikes and
drainage ditches around the areas to prevent uncontaminated water
from flowing across them.
Preservative accumulation in the soil where treated stock is
stored, although unavoidable, is another potential source of
contaminated storm water. Storage yards frequently encompass
large areas.
Equipment Leaks
Preservative losses from pipes and pumps contribute to the
pollution problem at many plants. The early detection of leaks
from these sources can best be ; accomplished by periodic and
systematic checks of all pumps and plumbing employed in the
transfer of preservatives.
Treatment and Control Technology
Waste water treating facilities have been installed and are in
operation at only about 9 percent of the estimated 390 plants in
the U.S. (Table 44). Most of these facilities have been in
181
-------
operation for only a relatively short period of time. It follows
that both experience in the treatment of waste water from the
wood preserving industry and the backlog of data on such
operations is limited. This problem is lessened somewhat by
studies and field experience in the treatment of petroleum
wastes. Data from this industry are frequently directly
applicable to the wood preserving industry because of the
similarity of the effluents involved, particularly as regards
phenol content, oil content and other parameters. Likewise,
within the past three years laboratory and pilot-plant studies
have supplied useful information on the treatment of effluents
from wood preserving operations. Review of these sources, as
well as information obtained from visits to and analyses of
effluent samples from wood preserving plants that have effective
waste treatment and management programs, provided the data on
which this section is based.
Primary Treatments
Primary treatments for creosote and pentachlorophenol-petroleum
waste waters usually include flocculation and sedimentation.
This process, as currently practiced at a number of plants, is
normally carried out for one of two purposes: (1) to remove
emulsified oils and other oxygendemanding substances preparatory
to secondary treatment, and (2) to render waste water acceptable
to municipal authorities prior to releasing it into sanitary
sewers. A few plants discharging their waste into city sewers
apply primary treatments to reduce sewer charges levied by
municipal authorities, rather than to meet specific influent
limitations.
One of the principal benefits of primary treatments of oily waste
water is the reduction of the oil content of the waste water to a
level compatible with the secondary treating process that is
employed. This is particularly important with those waste waters
containing emulsified oils, which normally cannot be removed by
mechanical means. Flocculation treatments employing a suitable
polyelectrplyte are quite effective in breaking emulsions and
precipitating the oil. Reductions in oil content on the order of
95 percent are not unusual. Where the oil content of waste water
is not a serious problem, however, flocculation treatments
preparatory to secondary treatment may not be necessary. The
decision in this regard must be based on the relative cost of
such treatments and that of providing sufficient secondary
treating capacity to accommodate the additional COD loading that
would normally be removed during primary treatment of the waste
water.
Primary treatments of waste waters containing salt-type
preservatives and fire retardants serve to precipitate heavy
metals and thus make the waste amenable to biological treatment.
Waste Waters Containing Entrained Oils - It is the intermingling
of the oils and water from the treating cycle and the condensate
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I
from conditioning operations that is responsible for most of the
waste water pollution in the industry. Oils account for most of
the oxygen demand of the waste water, serve as carriers for
concentrations of pentachlorophenol far in excess of those
attainable in oil-free water, and create emulsion problems.
Recovery Of Free Oils - Most wood preserving plants have oil-
recovery systems for reclaiming a high percentage of the oil that
may become entrained in water during treating operations. Apart
from environmental considerations, this practice is and always
has been done for economic reasons: it is less expensive to
recover and reuse this oil than to buy new oil. With the passage
of the Federal Water Pollution Control Act of 1965 and subsequent
amendments, the contribution of non-recovered oils to the cost of
treating waste water has become an important consideration.
Within the past 5 years many plants have added new oil-recovery
systems or revamped existing ones.
Free oils are recovered from waste water by gravity-type
separators. Various designs are used. The most common ones are
patterned after the separator developed by the American Petroleum
Institute. These are equipped to recover oils both lighter and
heavier than water. Basically they consist of a horizontal tank
divided into three or more compartments by strategically placed
baffles which decrease turbulence. Heavy oils sink to the bottom
where they are removed by a pump to a dehydrator, and thence
transferred to storage. Floating oils are removed by a skimmer.
For pentachlorophenol-petroleum solutions, a simple tank or
series of tanks with provisions for drawing off the oil that
collects at the top and the water from the bottom is all that is
required. Good practice dictates the installation of separate
oil removal systems for each preservative. However, many plants
are not so equipped.
A few plants have installed air-flotation equipment to effect
oil-water separation. In these units, all oil is brought to the
surface of the water by bubbles created by saturating a portion
of the waste water with air under pressure and releasing it at
the bottom of the flotation chamber. The oil is removed at the
surface by a skimming device. Mechanical oil scavengers are also
sometimes used to remove surface oils.
The percentage of entrained oils removed by oil-water separation
equipment varies widely, depending in part upon whether or not
the oil is in a free or emulsified form. Data on the percent
efficiencies of several oil-separation processes, including the
API separator, are given in Table 50. These data are based upon
the treatment of petroleum refinery waste water, but are
applicable to other oily wastes. Separator efficiency is of
course a function of detention time. The effect of this variable
on oil removal is shown in Figure 38.
Only free oils are removed in conventional oil-water separators.
However, emulsions are broken by rotary vacuum filters and by
183
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TABLE 50 EFFICIENCIES OF OIL SEPARATION PROCESSES
API Separator
Air Flotation without
Chemicals
Air Flotation with
Chemicals
Chemical Coagulation and
Sedimentation
TABLE 51 EFFECT OF
CONTENT OF
Lime
(Sin /I) pH
0.0 5.3
0.25 6.8
0.50 7.9
0.75 9.7
1.00 10.5
1.25 11.4
1.50 11.8
Source Of Percent Removal
Influent Free Oils Emulsified Oils
Raw Waste 60-99 ^ Not applicable
API 70 - 95 10 - 40
Effluent
API 75 - 95 50 - 90
Effluent
API 60 - 95 50 - 90
Effluent
LIME FLOCCULATION ON COD AND PHENOL
TREATING-PLANT EFFLUENT
COD
Cone. Percent Phenol
(mg/1) Removal (mg/1)
11,800 -- 83
9,700 23 81
7,060 39 72
5,230 56 78
5,270 55 80
5,210 56 84
5,210 56 83
184
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AVERAGE TEMPERATURE-38°C
INITIAL OIL CONCENTRATION-45P.P.M.14P.P.M.
0 40 80 120 160
SEPARATION TIME IN MINUTES
200
FIGURE 38
EFFECT OF DETENTION TIME ON OIL
REMOVAL BY GRAVITY SEPARATION
185
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centrifuges, both of which have been tested on wood preserving
waste water at a few plants in the South- Waste waters
containing emulsified oils frequently have oil contents in excess
of 100Q mg/1 after passing through gravity-type separators. Oils
in this form normally must be removed by primary treatments
invoIving flocculation.
The formation of oil-water emulsions is a particular problem
where conventional steam conditioning is used and apparently
results from agitation of retort condensate as it is expelled
from the retort through a steam trap. Thompson analyzed
condensate samples collected alternately from a hole drilled near
the bottom of a retort and from a pipe leading from the trap and
found that only those samples that had passed through the trap
contained emulsified oils. Some plants treating with
pentachlorophenol-petroleum solutions have greatly reduced the
problems of emulsion by replacing high-speed pumps involved in
preservative transfer with low-speed, high-volume models.
Breaking Of Oil-Water Emulsions - Emulsions may be broken
chemically, physically, or electrically. Chemical methods
involving flocculation and. sedimentation are the most widely
used, generally are the least expensive, and are effective with
effluents from wood preserving plants. For these reasons, the
discussion below is directed towards, chemical methods of
breaking emulsions.
Chemicals that have been used to break oil-water emulsions either
in the laboratory or field, include metallic hydroxides,
principally lime, ferric chloride and other salts of iron, alum,
bentonite clay, and various types of polyelectrolytes. The same
material or combination of materials does not work equally well
with waste waters from all plants (Table 29, Section V). COD and
BOD reductions of up to 83 percent have been achieved in creosote
waste water by using a single cationic polymer at a rate of 40
mg/1. Similar results were observed at a plant treating with
both creosote and pentachlorophenol that flocculated its waste
prior to routing it to a sanitary sewer.
Oil reductions in refinery waste water of more than 95 percent
were obtained by using both anionic and cationic polyelectrolytes
in combination with bentonite clay. . There was no difference be~
tween the two types of polymers in the results obtained.
However, only cationic polyelectrolytes broke oil^water emulsions
from wood preserving plants in work reported in 1971. Aluminum
chloride, alum, activated-silica, clay and lime have been
employed with refinery wastes, and reductions in BOD, COD, and
oil content on the order of 50 percent were reported from this
treatment.
Ferric chloride has been found to be an effective flocculating
agent for both creosote and pentachlorophenol waste waters.
However, floe formation occurred only within very narrow pH
186
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lirrtits. This feature would pose serious problems in field
applications of this chemical.
Much of the research work on flocculating wood preserving waste
waters has involved the use of lime either singly or in
combination with a polyelectrolyte. Thompson and Dust reported
that the optimum dosage of lime, as judged from COD reductions,
varied from 0.75 to 2.0 g/1, depending upon waste water
characteristics. Percent reduction in this parameter increased
with increasing dosage up to a maximum, and then was unaffected
by further lime additions (Table 51). Phenol content, exclusive
of pentachlorophenol, was not decreased by flocculation of the
waste water. However, pentachlorophenol was regularly reduced to
a concentration of about 15 mg/1 in waste waters containing this
chemical. It was surmised from this result that
pentachlorophenol, unlike other phenolic compounds, is primarily
associated with the oil phase in oil-water emulsions and is
precipitated with the oils when the emulsion is broken. The
residual concentration of pentachlorophenol remaining in the
filtrate was reported by Thompson and Dust to correspond
approximately to the solubility of this chemical in water.
Typical data showing the reduction of pentachlorophenol resulting
from lime additions to a waste water are shown below:
Residual PCP
Lime Dosage Concentration
(mq/11 (mq/1)
0 150
1.0 45
1.5 25
2.0 17
Lime, in dosages of 2.0 g/1, has been shown to obtain reductions
in COD of up to 70 percent in a creosote waste water. Similar
results have been achieved with alum, and both chemicals have
been used successfully to treat creosote and vapor-drying waste
water previously de-emulsified with sulfuric acid. Lime and
caustic soda have been reported to be effective in flocculating
oily waste water after treatment with polyelectrolytes failed to
produce a floe.
Among numerous polyelectrolytes tested by Thompson and Dust rela-
tively few were found that in the absence of lima were effective
with wood preserving waste water. The primary contributions that
many of the test materials made to the flocculation process were
the agglomeration of minute floe particles, which promoted rapid
settling, and reduction in sludge volume. Only a few of them
were effective in initiating floe formation in samples of waste
water from 20 plants, and none increased COD removal beyond that
obtained with lime alone. The few that were effective in
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listing of the principal water-soluble preservatives and fire
retardants currently marketed in the U.S., and the harmful
constituents in each, is given in Table 52.
The procedure used to precipitate heavy metals from wood
preserving effluents was adopted from the electroplating
industry. Dodge and Reams compiled a bibliography of over 700
references dealing with the processing and disposal of waste from
this industry, and it is been estimated that 50 additional
articles on the subject have been published annually since this
bibliography first appeared. A detailed treatment of the subject
has been prepared by Bliss. The basic procedure followed, while
modified to reflect the specific preservative salts involved, is
described below.
With the exception of boron, hexavalent chromium is the only ion
shown in Table 52 which will not precipitate from solution when
the pH of the waste water is raised to 7 or 8 with lime. Since
trivalent chromium will precipitate from neutral or slightly
alkaline solutions, the first step in treating waste waters
containing this metal is to reduce it from the hexavalent to the
trivalent form. The use of sulfur dioxide for this purpose has
been reported on in detail by Chamberlin and Day. Chromium
reduction proceeds most rapidly in acid solution. Therefore, the
waste water is acidified with sulfuric acid to a pH of 4 or less
before introducing the sulfur dioxide. The latter chemical will
itself lower the pH to the desired level, but it is less
expensive to use the acid.
When the chromium has been reduced, the pH of the waste water is
increased to 8.5 or 9.0 to precipitate not only the trivalent
chromium, but also the copper and zinc. If lime is used for the
pH adjustment, fluorides and most of the arsenic will also be
precipitated. Care must be taken not to raise the pH beyond 9.5,
since trivalent chromium is slightly soluble at higher values.
Additional arsenic and most of any residual copper and chromium
in solution can be precipitated by treating the waste with hydro-
gen sulfide gas, or by adding sodium sulfide. Ammonium and
phosphate compounds are also reduced by this process.
This procedure is based on the fact that most heavy metals are
precipitated as relatively insoluble metal hydroxides at alkaline
pH. The theoretical solubilities of some of the hydroxides are
quite low, ranging down to less than 0.01 mg/1. However,
theoretical levels are seldom achieved because of unfavorable
settling properties of the precipitates, slow reaction rates,
interference of other ions in solution, and other factors. Among
the ions shown in Table 52, copper, zincr and chromium can be
reduced to levels substantially lower than 1.0 mg/1 by the above
procedure. Fluorides have a theoretical solubility at a pH of
8.5 to 9.0 of 8.5 mg/1, but residual concentrations on the order
of 10 to 20 mg/1 are more usual because of slow settling of
calcium fluoride. The use of additional lime, alum coagulation
190
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and filtration through bone char are reported to reduce fluoride
concentrations to 1.0 mg/1 or less.
The most difficult ion to reduce to acceptable concentration
levels is arsenic. Treatment of water containing arsenic with
lime generally removes only about 85 percent of the metal.
Removal rates in the range of 94 to 98 percent have been reported
for filtration through ferric sulfide beds, coagulation with
ferric chloride, and precipitation with ferric hydroxide.
However, none of these methods is entirely satisfactory,
particularly for arsenic concentrations above 20 mg/1.
Information on treatment processes for removing boron from waste
waters is not available.
The sludge resulting from the precipitation process contains the
heavy metals formerly in solution, along with the excess lime.
It may also contain various organic materials of wood origin that
are flocculated and precipitated with the lime. The sludge can
be filtered to reduce its volume and disposed of in a suitable
manner. The supernatant may be routed to a holding basin, as is
currently being done by several plants, given a secondary
treatment, or released, depending upon its oxygen demand and
content of residual metals. Work is in progress to determine if
the sludge can be acidified and reused in the treating solution.
Representative data on the laboratory treatment of waste water
containing CCA-type salt preservatives and a proprietary fire-
retardant formulation composed mainly of ammonium and phosphate
compounds are given in Table 53. Data for both concentrated
solutions and diluted waste water from a holding pond are given.
Average results of treatments conducted daily over a period of a
year on effluent from a plant are given in Table 54. The latter
data were obtained by analyzing effluent from equipment designed
by Russell to process waste water automatically.
Waste waters from salt-type treatments frequently are heavily
diluted and, consequently, may contain very low metal
concentrations. The importance of subjecting the waste to a
primary treatment to remove the metals, even when present in only
trace quantities, was referred to earlier. Numerous studies have
shown that copper, chromium, zinc, and arsenic have a toxic
effect on biological waste treatment systems.
Ion exchange resins of the sulfonated-polystyrene and
quaternaryamine types have been employed on a commercial scale
for purification and recovery of metals used in the
electroplating industry. The technology involved in ion exchange
has application to the wood preserving industry, but the
economics of the process in the purification of preservative
waste waters containing metal contaminants are unknown. It has
been suggested that inert sulfate and sodium ions and organic ma-
terials in these waste waters would lower the metal-removing
191
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capacity of the exchangers sufficiently to make the process
impractical under mos.t circumstances.
Plant experience in treating waste water from salt-type
treatments is limited. This situation arises from the fact that
steam conditioning of stock prior to preservative injection is
not widely practiced among plants that use preservative and fire-
retardant salts. Consequently, only a small volume of waste
water is generated. The better managed plants use the waste
water that is available as make-up water in preparing fresh
batches of treating solution.
Secondary Treatments
Biological treatments, chemical oxidation, activated-carbon
adsorption and various combinations of these basic methods of
waste water treatment have been used commercially, proposed for
such use, or tested in laboratory and pilot-plant investigations
of wood preserving effluents. Each of these methods is discussed
below in terms of: (a) characteristics relating to sensitivity
to shock loadings, availability of equipment, and maintenance
requirements; (b) efficiency with phenolic-type wastes, as
revealed by the literature; and (c) effluent characteristics of
wood preserving waste resulting from treatment. Because of the
limited number of wood preserving plants that are currently
providing secondary treatment for their waste, data for item (c)
is, in some instances, based on grab samples collected in
connection with this study, or on results of pilot-plant
investigations.
Biological. Treatments - Where a substantial volume of waste with
a high organic load is involved, cost considerations usually
dictate that biological oxidation be used as the major component
in the waste treatment program. Polishing treatments involving
chlorination, and possibly activated-carbon filtration, may or
may not be required, depending upon the design of the biological
system and the waste loads involved. Each of the several
biological waste treating systems that have present or potential
application in the wood preserving industry is covered in this
section.
Characteristics - According to Besselieure, trickling filters are
not unduly susceptible to disruption fay shock loads and recover
quickly if disruption occurs. Their operation does not require
constant attention, and, when equipped with plastic media, they
are capable of handling high loading rates. The latter feature
minimizes the land area required. For package units sized for
the relatively small volume of discharge at the average wood
preserving plant, an area of 186 sq m (2,000 sq ft) should be
adequate for the tower (approximately 6 m (20 ft) in diameter)
and associated equipment, including settling tank.
Processing Efficiency for Phenolic Wastes - The literature
contains many references concerning waste water treatment using
194
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trickling filters in the petroleum and by-product coal
industries.
Most of the references report on efforts to reduce phenol
concentrations to acceptable levels. Sweets, Hamdy and Weiser
studied the bacteria responsible for phenol reductions in
industrial waste and reported good phenol removal from
synthesized waste containing doncentrations of 400 mg/1.
Reductions of 23 to 28 percent were achieved in a single pass of
the waste water through a pilot trickling filter having a filter
bed only 30 cm (12 in) deep.
Waters containing phenol concentrations of up to 7500 mg/1 have
been successfully treated in laboratory tests conducted by Reid
and Libby. Phenol removals of 90 to 90 percent were obtained for
concentrations on the order of 400 mg/1. Their work confirmed
that of others who found that strains of bacteria isolated from a
trickling filter could survive phenol concentrations of 1600 mg/1
and were able to oxidize phenols in concentrations of 450 mg/1 at
better than 99 percent efficiency. Reid, Wortman, and Walker
found that many pure cultures of bacteria were able to live in
phenol concentrations of up to 200 mg/1, but few survived
concentrations above 900 mg/1, although some were grown in
concentrations as high as 3700 mg/1.
Harlow, Shannon, and Sercu described the operation of a
commercial- size trickling filter containing "Dowpac" filter
medium that was used to process waste water containing 25 mg/1
phenol and 450 to 1,900 mg/1 BOD. Reductions of 96 percent for
phenols and 97 percent for BOD were obtained in this unit. Their
results compare favorably with those reported by other
researchers. BOD reductions of 90 percent in a trickling filter
using a 1:2 recycle ratio. Dickerson and Laffey obtained phenol
and BOD reductions of 99.9 and 96.5 percent, respectively, in a
trickling filter used to process refinery waste water.
Davies, Biehl, and Smith reported on a combination biological
waste-treatment system employing a trickling filter and an
oxidation pond. The filter, which was packed with a plastic
medium, was used for a roughing treatment of tO.6 million I/day
(2.8 million gal/day) of waste water, with £inal treatment
occurring in the oxidation pond. Removal rates of 95 percent for
phenols and 60 percent for BOD were obtained in the filter,
notwithstanding the fact that the pH of the influent averaged
9.5.
Biological treatment of refinery waste waters, using a series of
4 trickling filters has been studied. Each filter was operated
at a different recycle ratio. The waste contained 22 to 125 mg/1
of oil. BOD removal was adversely affected by the oil, the
lowest removal rates corresponding to the periods when the oil
content of the influent was highest. Phenol removal was unaf-
fected by oil concentrations within the range studied.
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Prather and Gaudy found that significant reductions in COD, BOD,
and phenol content of refinery waste water were achieved by
simple aeration treatments. They concluded that this phenomenon
accounted for the high allowable loading rates for biological
treatments such as trickling filtration.
Treatment of Wood Preserving Effluents - The practicality of
using the trickling filters for secondary treatment of waste
waters from the wood preserving industry was explored by Dust and
Thompson. A pilot unit containing a 6.4 m (21 ft) filter bed of
plastic media was used in their study. Creosote waste water was
applied at BOD loading rates of from 400 to 3050 kg/1000 cu m/day
(25 to 190 lb/ 1000 cu ft/day). The corresponding phenol
loadings were 1.6 to 54.6 kg/1000 cu m/day (0.1 to 3.4 lb/1000 cu
ft/day). Raw feed-to-recycle ratios varied from 1:7 to 1:28.
The pilot unit was operated and daily samples collected and
analyzed over a period of 7 months that included both winter and
summer operating conditions.
Because of waste water characteristics at the particular plant
cooperating in the study, the following pretreatment steps were
necessary: (a) equalization of wastes; (b) primary treatment by
coagulation for partial solids removal; (c) dilution of the waste
water to obtain BOD loading rates commensurate with the range of
raw flow levels provided by the equipment; and (d) addition to
the raw feed of supplementary nitrogen and phosphorus. Dilution
ratios of 0 to 14 were used.
The efficiency of the system was essentially stable for BOD
loadings of less than 1200 kg/1000 cu m/day (75 lb/1000 cu
ft/day). . The best removal rate was achieved when the hydraulic
application rate was 2.851/min/sq m (0.07 gal/min/sq ft) of raw
waste and 40.7 1/min/sg m (1.0 gal/min/sq ft) of recycled waste.
The COD, BOD, and phenol removals obtained under these conditions
are given in Table 55. Table 56 shows the relationship between
BOD loading rate and removal efficiency. BOD removal efficiency
at loading rates of 1060 kg/1000 cu m/day (66 lb/1000 cu ft/day)
was on the order of 92 percent, and was not improved at reduced
loadings. Comparable values for phenols at loading rates of 19.3
kg/1000 cu m/ day (1.2 lb/1000 cu ft/day) were about 97 percent.
Phenol content was more readily reduced to levels compatible with
existing standards than was BOD content. Consequently, the
sizing of commercial units from data collected from the pilot
unit was based on BOD removal rates. Various combinations of
filter-bed depths, tower diameters, and volumes of filter media
that were calculated to provide a BOD removal rate of 90 percent
for influent having a BOD of 1500 mg/1 are shown in Table 57 for
a plant with a flow rate of 75,700 I/day (20,000 gal/day).
Activated Sludge and Aerated Lagoon - Characteristics - Activated
sludge treatments which employ the complete-mix alternative to
the conventional process are very resistant to disruptions caused
by shock loads, offer low operation and maintenance costs, low
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TABLE 55 BOD, COD, AND PHENOL LOADING AND REMOVAL RATES FOR
PILOT TRICKLING FILTER PROCESSING A CREOSOTE WASTEWATER
Measurement Characteristic
BOD COD Phenol
Raw Flow Rate (gpm/ sq ft) 0.07 0.07 0.07
Recycle Flow Rate (gpm/sq ft) 1.0 1.0 1.0
Influent Concentration (mg/1) 1698 3105 31
Loading Rate (IbAOOO cu ft) 66.3 121.3 1.2
Effluent Concentration (mg/1) 137 709 1.0
Removal (%) 91.9 77.0 99+
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TABLE 56 RELATIONSHIP BETWEEN BOD LOADING AND TREATABILITY
FOR PILOT TRICKLING FILTER PROCESSING A CREOSOTE WASTEWATER
BOD
Loading Removal Treatability*
(Ib/cu ft/day) <%) Factor
23 91
26 95
37 92
53 93
66 92
76 82
85 80
115 75
156 62
0.0301
0.0383
0.0458
0.0347
0.0312
0.0339
0.0286
0.0182
0.0130
*Based on the equation:
Le = e^/QO.S (Germain, 1966)
Lo
in which Le = BOD concentration of settled effluent, Lo =
BOD of feed, Q = hydraulic application rate of raw waste
in gpm/ft , D = depth of media in feet, and K = treatability
factor (rate coefficient).
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TABLE 57 SIZING OF TRICKLING FILTER FOR A WOOD PRESERVING PLANT
(NOTE: Data are based on a flow rate of 20,000 gallons per
day, with filter influent BOD of 1500 and effluent
BOD of 150.)
Depth of Raw flow Recycle flow Filter Volume
filter (gpm/ sq ft) (gpm/ sq ft) Surface Tower of
bed filter filter area dia. media
(ft) surface) surface) (sq ft) (ft) (cu ft)
10.7 0.019
12.5 0.026
14.3 0.034
16.1 0.044
17.9 0.054
19.6 0.065
21.4 0.078
TABLE 58 SUBSTRATE
SLUDGE
Aeration Time, Days
COD Raw, mg/1
COD Effluent, mg/1
% COD Removal
COD Raw/COD Effluent
0.73 708 30.0 7617
0.72 520 25.7 6529
0.71 398 22.5 5724
0.70 315 20.0 5079
0.69 255 18.0 4572
0.68 210 16.3 4156
0.67 177 15.0 3810
REMOVAL AT STEADY-STATE CONDITIONS IN ACTIVATED
UNITS CONTAINING CREOSOTE WASTEWATER
5.0 10.0 14.7 20.1
447 447 442 444
178 103 79 67
60.1 76.9 82.2 84.8
2.5 4.3 5.6 6.6
199
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initial cost, and have small land requirements. Package units
designed to £*eat the waste water from an average wood preserving
plant could be located on an area pf approximately 93 sq m (1000
sq ft). Additional space would be required for a pretreatment
equalization reservoir and, where required, flocculation tanks.
A system will occupy an area of approximately 140 sq m (1500 sq
ft), including equipment for pre- and post-treatment
chlorination. •
An aerated lagoon is a special type of complete-mix, activated
sludge system, without sludge recycle. It normally is operated
in conjunction with a polishing pond into which waste from the
lagoon is discharged. Both the lagoon and polishing pond are
usually constructed with earthen embankments, a feature which
reduced the cost of the system compared with the activated sludge
process. This method of treatment has essentially the same
advantages as the conventional complete-mix, activated sludge
system, but does require more land area.
Processing Efficiency for Phenolic Wastes - Treatment of
municipal and mixes of municipal and industrial wastes by the
activated sludge process is common practice. In recent years the
process has also been adapted to industrial wastes similar in
composition to that of effluents from wood preserving plants.
Ninety nine percent oxidation efficiency for BOD5 has been
obtained in petrochemical wastes. Coe reported reductions of
both BODji and phenols of 95 percent from petroleum wastes in
bench-scale tests of the activated sludge process. Optimum BOD5
loads of 2247 kg/1000 cu m/day (140 lb/1000 cu ft/ day) were
obtained in his work* Coke plant effluents were successfully
treated by Ludberg and Nicks (87) , although they experienced some
difficulty: in start-up of the activated sludge system because of
the high phenol content of the water.
The complete mixed, activated sludge process was employed to
process a high-phenolic waste water from a coal-tar distilling
plant in Ontario. Initial phenol and COD concentrations of 500
and 6,000 mg/1, respectively, were reduced in excess of 99
percent for phenols and 90 percent for COD.
Cooke and Graham employed the complete-mixed, activated sludge
system to treat waste containing phenols, organic acids,
thiocyanates, and ammonia using detention times of 8 to 50 hours.
At feed rates of 144 to 1605 kg/1000 cu m/day (9 to TOO lb/1000
cu ft/day), phenol content was reduced from 281 mg/1 to 62 mg/1,
for a removal rate of 78 percent.
The employment of aerated reaction units on a continuous flow
basis has been used to treat coke gasification plant waste.
Badger and Jackson have found that a two-day detention period was
sufficient to remove 90 percent of the phenol from a waste stream
containing up to 5,000 mg/1 of the chemical.
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Nakashio successfully treated coal gas washing liquor containing
1,200 mg/1 of phenols in a study that lasted more than a year.
Phenol concentration was reduced by more than 99 percent.
Similar phenol removal rates have been obtained by Reid and
Janson in treating waste water containing cresols by the
activated sludge process.
In a report of pilot and full-scale studies performed by
Bethlehem steel Corporation, phenol removal efficiencies greater
than 99.8 percent were obtained using the complete-mixed,
activated sludge process. Loading rates of 0.86 kg phenol/kg
MLSS/day were used successfully. Phenol influent concentrations
of 3,500 mg/1 were reduced to 0.2 mg/1 in the effluent.
Treatment of Wood Preserving. Effluents - Dust and Thompson
conducted bench-scale tests of complete-mixed, activated sludge
treatments of creosote and pentachlorophenol waste waters using
5-liter units and detention times of 5, 10, 15, and 20 days. The
operational data collected at steady state conditions of
substrate removal for the creosote waste are shown in Table 58.
A plot of these data showed that the treatability factor, K =
0.30 days-1 (Figure 39). The resulting design equation, with t
expressed in days, is:
Le = Lo
1 + 0.30t
where: Lo = COD in raw waste
Le = COD in effluent
A plot of percent COD removal versus detention time in the
aerator, based on the above equation, is shown in Figure 40. The
figure shows that an oxidation efficiency of about 85 percent can
be expected with a detention time of 20 days in units of this
type.
Work done with pentachlorophenol waste was conducted to determine
the degree of biodegradability of this chemical. Cultures of
bacteria, prepared from soil removed from a drainage ditch
containing pentachlorophenol waste, were used to inoculate the
treatment units. Feed to the units contained 10 mg/1 of
pentachlorophenol and 2,400 mg/1 COD. For the two 5-liter units
(A and B) the feed was 500 and 1000 ml/day and detention times
were, in order, 10 and 5 days.
Removal rates for pentachlorophenol and COD are given in Table
59. For the first 20 days Unit A removed only 35 percent of the
pentachlorophenol added to the unit. However, removal increased
dramatically after this period and averaged 94 percent during the
remaining ten days of the study. Unit B consistently removed
over 90 percent of the pentachlorophenol added. Beginning on the
46th day and continuing through the 51st day, pentachlorophenol
loading was increased at two-day intervals to a maximum of about
201
-------
no
o
rsj
Slope= K =0*30 day
-1
Le =
Lo
1+0.301
5 10
Aeration Time (Days)
15
FIGURE 39
DETERMINATION OF REACTION RATE CONSTANT
FOR A CREOSOTE WASTEWATER
-------
o
o
x 90
tt»
ro
o
CO
(0
80
70
O
8 50
d) |
a
40
Lo
1+0.301
10
Aeration Time (Days)
15
20
FIGURE 40
- COD REMOVAL FROM A CREOSOTE WASTEWATER BY
AERATED LAGOON WITHOUT SLUDGE RETURN
-------
TABLE 59 REDUCTION IN PENTACHLOROPHENOL AND COD IN
WASTEWATER TREATED IN ACTIVATED SLUDGE UNITS
DAYS
1-5
6-10
11-15
16-20
21-25
26-30
31-35
1-5
6-10
11-15
16-20
21-25
26-30
31-35
36-40
41-45
46-47
48-49
50-51
RAW
WASTE
(mg/1)
COD
2350
2181
2735
2361
2288
2490
2407
PENTACHLOROPHENOL
7.9
10.2
7.4
6.6
7.0
12.5
5.8
10.3
10.0
20.0
30.0
40.0
EFFLUENT FROM UNIT
a
"A"
78
79
76
82
90
—
83
20
55
33
30
—
94
94
Removal)
"B"
78
79
75
68
86
84
80
77
95
94
79
87
94
91
91
96
95
97
99
204
-------
TABLE 60 RESULTS OF LABORATORY TESTS OF SOIL IRRIGATION
METHOD OF WASXEWATER TREATMENT*
Loading Rate
(Liters/ha/day)
32,800
(3,500)
49,260
(5,250)
82,000
(8,750)
Loading
Length
Test
(Week)
31
13
14
rates in
COD REMOVAL
of Avg. % COD Last Week
Removal to of Test
Breakthrough %
99.1 (22 wks) 85.8
99.6 99.2
99.0 (4 wks) 84.3
parentheses in gallons/acre/day
Phenol
Avg. %
Removal
(All Weeks)
98.5
99.7
99.7
*Creosote wastewater containing 11,500 mg/liter of COD and 150 mg/liter
of phenol was used.
205
-------
40 mg/1. Removal rates for the three two-day periods of
increased loadings were 94, 97, and 99 percent.
COD removal for the two units averaged about 90 percent over the
duration of the study.
Also working with the activated sludge process, Kirsh and Etzel
obtained removal rates for pentachlorophenol in excess of 97
percent using an 8-hour detention time and a feed concentration
of 150 mg/1. The pentachlorophenol was supplied to the system in
a mixture that included 100 mg/1 phenol. Essentially complete
decomposition of the phenol was obtained, along with a 92 percent
reduction in COD.
Soil Irrigation - Characteristics - The principal feature of the
soil irrigation method of waste water treatment is its
simplicity. Water that has been freed of surface oils and,
depending upon the presence of emulsified oils, treated with
flocculated chemicals and filtered through a sand bed is simply
sprayed onto a prepared field. Soil microorganisms decompose the
organic matter in the water in much the same fashion as occurs in
more conventional waste treatment systems.
In addition to its simplicity, soil irrigation has the advantage
of low capital investment, exclusive of land costs, low operating
and maintenance costs, requires a minimum of mechanical
equipment, and produces a high quality effluent in terms of
color, as well as oxygen demand and other pertinent parameters.
Its chief disadvantage is that its use requires a minimum area of
approximately one ha/33,000 1 of discharge/day (one ac/3500 gal
of discharge/day). This requirement makes the method impractical
in locations where space is at a premium. However, it is not a
major problem for the many plants in rural areas where land is
relatively inexpensive.
Processing Efficiency For Phenolic Wastes - Effluents from a
number of different types of industries have been successfully
disposed of by soil irrigation. At least 20 types of industrial
wastes that have been treated by this method. Among these are
several wastes high in phenol content. Removal efficiencies as
high as 99.5 percent for both BOD and phenols were reported.
Fisher reported on the use of soil irrigation to treat waste
waters from a chemical plant that had the following
characteristics:
pH 9.0 to 10.0
Color 5,000 to 42,000 units
COD 1,600 to 5,000 mg/1
BOD 800 to 2,000 mg/1
Operating data from a 0.81 ha (2 ac) field, when irrigated at a
rate of 18,690 1/ha/day (2000 gal/ac/day) for a year, showed
206
-------
color removal of 88 to 99 percent and COD removal of 85 to 99
percent.
The same author reported on the use of this method to treat
effluent from two tar plants that contained 7,000 to 15,000 mg/1
phenol and 20,000 to 54,000 mg/1 COD. The waste was applied to
the field at a rate of about 23,400 1/ha/day (2500 gal/ac/day).
Water leaving the area had COD and phenol concentrations of 60
and 1 mg/1, respectively. Based on the lower influent
concentration for each parameter, these values represent
oxidation efficiencies of well over 99 percent for both phenol
and COD.
Bench-scale treatment of coke plant effluent by soil irrigation
has also been studied. Wastes containing BOD5 and phenol
concentrations of 5,000 and 1,550 mg/1, respectively, were
reduced by 95 and 99 percent when percolated through 0.9 m (36
in) of soil. Fisher pointed out that less efficient removal was
achieved with coke-plant effluents using the activated sludge
process, even when the waste was diluted with high-quality water
prior to treatment. The effluent from the units had a color
rating of 1,000 to 3,000 units, compared to 150 units for .water
that had been treated by soil irrigation.
v
Treatment of Wood Preserving Effluents - Both laboratory and
pilot scale field tests of soil-irrigation treatments of wood
preserving waste water were conducted by Dust and Thompson. In
the laboratory tests, 210 liter (55 gal) drums containing a heavy
clay soil 60 cm (24 in) deep were loaded at rates of 32,800,
49,260, and 82,000 1/ha/day (3,500, 5,250, and 8,750 gal/ac/day).
Influent COD and phenol concentrations were 11,500 and 150 mg/1,
respectively. Sufficient nitrogen and phosphorus were added to
the waste to provide a COD:N:P ratio of 100:5:1. weekly effluent
samples collected at the bottom of the drums were analyzed for
COD and phenol.
Reductions of 99+ percent in COD content of the waste water were
attained from the first week in the case of the two highest
loadings and from the fourth week for the lowest loading. A
breakthrough occurred during the 22nd week for the lowest loading
rate and during the fourth week for the highest loading rate.
The COD removal steadily decreased thereafter for the duration of
the test. Phenol removal showed no such reduction, but instead
remained high throughout the test. The average test results for
the three loading rates are given in Table 61. Average phenol
removal was 99+ percent. Removal of COD exceeded 99 percent
prior to breakthrough and averaged over 85 percent during the
last week of the test.
The field portion of Dust and Thompson's study was carried out on
an 0.28 ha (0.7 ac) plot prepared by grading to an approximately
uniform slope and seeded with grasses. Wood preserving waste
water from an equalization pond was applied to the field at the
rate of 32,800 1/ha/day (3,500 gal/ac/day) for a period of nine
207
-------
TABLE £1 REDUCTION OF COD AND PHENOL CONTENT IN WASTEWATER
TREATED BY SOIL IRRIGATION
Soil Depth (centimeters)
Month Raw Waste 0
July
August
September
October
November
December
January
February
March
April
2235
2030
2355
1780
2060
3810
2230
2420
2460
2980
COD (mg/1)
1400
1150
1410
960
1150
670
940
580
810
2410
30
— —
—
—
150
170
72
121
144
101
126
60
__
—
—
—
170
91
127
92
102
—
120
66
64
90
61
46
58
64
64
68
76
Average % Removal
(weighted)
July
August
September
October
November
December
January
February
March
April
235
512
923
310
234
327
236
246
277
236
55.0
Phenol (ms/l)
186
268
433
150
86
6
70
111
77
172
94.9
ta—
—
4.6
7.7
1.8
1.9
4.9
2.3
1.9
95.3
w— _
—
—
—
3.8
9.0
3.8
2.3
1.9
0.0
97.4
1.8
0.0
0.0
2.8
0.0
3.8
0.0
1.8
1.3
0.8
Average % Removal
(weighted) 55.4 98.9 99.2 99.6
208
-------
months. Average monthly influent COD and phenol concentrations
ranged from 2,000 to 3,800 mg/1 and 235 to 900 mg/1,
respectively. Supplementary nitrogen and phosphorus were not
added. samples for analyses were collected weekly at soil depths
of G (surface), 30, 60, and 120 cm (1, 2, and 4 ft).
The major biological reduction in COD and phenol content occurred
at the surface and in the upper 30 cm (1 ft) of soil. A COD
reduction of 55.0 percent was attributed to overland flow. The
comparable reduction for phenol content was 55.4 percent (Table
61). Average COD reductions at the three soil depths, based on
raw waste to the field, were 94.9, 95.3, and 97.4 percent,
respectively, for the 30-, 60-, and 120 cm (1-, 2-, and 4-ft)
depths. For phenols, the reductions were, in order, 98.9, 99.2,
and 99.6 percent.
Color of the waste water before and after treatment was not
measured. However, the influent to the field was dark brown and
the effluent was clear. Samples taken from the 6C and 120 cm (2
and 4 foot) depths showed no discoloration.
The application of the waste water to the study area did not
interfere with the growth of vegetation. On the contrary, the
area was mowed several times during the summer months to control
the height of native grasses that became established.
The soil percolation method for treating the creosote waste water
from the wood preserving plant consistently showed a greater
percentage removal of COD and phenol than either the activated
sludge or the trickling filter methods.
Oxidation Ponds - Characteristics - Oxidation ponds are
relatively simple to operate and, because of their large volume,
difficult to disrupt. Operation and maintenance costs are
usually lower than for other waste treating methods. Their
disadvantages are numerous. Included among these are; (a) low
permissible loading rate, which necessitates large land areas;
(b) abrupt changes in efficiency related to weather conditions;
(c) difficulty of restoring a pond to operating condition after
it has been disrupted; (d) tendency to become anaerobic, thus
creating odor problems, and (e) effluents containing algal cells,
themselves a pollutant.
Processing Efficiency for Phenolic Wastes - Only a few cases of
the use of oxidation ponds to treat phenolic wastes are recorded
in recent literature. The American Petroleum Institute's "Manual
on Disposal of Refinery Wastes" refers to several industries that
have successfully used this method.
Montes reported on results of field studies involving the
treatment of petrochemical wastes using oxidation ponds. He
obtained BOD reductions of 90 to 95 percent in ponds loaded at
the rate of 84 kg/ha/day of .BOD (75 Ib/ac/day) .
209
-------
Phenol concentrations of 990 mg/1 in coke oven effluents were
reduced to about 7 mg/1 in field studies of oxidation ponds
conducted by Biczysko and Suschka. Similar results have been
reported by Skogen for a refinery waste.
Treatment of Wood Preserving Effluents - Oxidation ponds rank
high among the various methods that wood preserving companies
plan to use to treat their waste water (Table 48). However, the
literature contains operating data on only one pond used for this
purpose.
As originally designed and operated in the early 1960's, this
waste treatment system consisted of holding tanks into which
water from the oil-recovery system flowed. From the holding
tanks the water was sprayed into a terraced hillside from which
it flowed into a mixing chamber adjacent to the pond. Here it
was diluted 1:1 with creek water, fortified with ammonia and
phosphorus, and discharged into the pond proper. Retention time
in the pond was 45 days. The quality of the effluent was quite
variable, with phenol content ranging up to 40 mg/ 1.
In 1966 the system was modified by installing a raceway
containing a surface aerator and a settling basin in a portion of
the pond. The discharge from the mixing chamber now enters a
raceway where it is treated with a flocculating agent. The floe
formed collects in the settling basin. Detention time is 48
hours in the raceway and 18 hours in the settling basin. From
the settling basin, the waste water enters the pond proper.
These modifications in effect changed the treating system from an
oxidation pond to a combination aerated lagoon and polishing
pond. The effect on the quality of the effluent was dramatic.
Figure 41 shows the phenol content at the outfall of the pond
before and after installation of the aerator. As shown by these
data, phenol content decreased abruptly from an average of about
40 mg/1 to 5 mg/1.
Even with the modifications described, the efficiency of the
system remains seasonally dependent. Table 62 gives phenol and
BOD5 values for the pond effluent by month for 1968 and 1970.
The smaller fluctuations in these parameters in 1970 as compared
with 1968 indicate a gradual improvement in the system.
chemic al Oxidation - Phenolic compounds, in addition to
contributing to the oxygen demand of wood preserving waste
waters, largely account for the toxic properties of effluents
from creosote and pentachlorophenol treatments. These compounds
can be destroyed by chemical oxidation. Oxidizing agents that
have been successfully used for this purpose are chlorine and
ozone.
chlorine - Many references to the chlorination of phenol-bearing
waters exist in the literature. Chlorine gas and calcium and
210
-------
TABLE 62 AVERAGE MONTHLY PHENOL AND BOD CONCENTRATIONS IN EFFLUENT
FROM OXIDATION PQND
(mg/ liter)
1968
Month
January
February
March
April
May
June
July
August
September
October
November
December
Phenol
26
27
25
11
6
5
7
7
7
16
7
11
BOD
290
235
190
150
100
70
90
70
110
150
155
205
1970
Phenol
7
9
6
3
1
1
1
1
1
—
—
__
BOD
95
140
155
95
80
60
35
45
25
—
—
__
211
-------
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sodium hypochlorite have been used most extensively for this
purpose. Direct treatment with gaseous chlorine using a
continuous-flow system is simpler and less expensive than
hypochlorite where large volumes of waste water must be treated.
However, for batch-type treatments involving small waste water
volumes, hypochlorite is probably the more practical.
Chlorine dioxide may also be used to oxidize phenols. It has the
advantage over other sources of chlorine of short reaction time,
does not require close control of pH and temperature, does not
produce chlorophenols, and is effective at ratios of chlorine to
phenol of 1:1 or 2:1. Its primary disadvantages are its lack of
stability, which requires that it be produced as used, and its
relatively high cost.
The theoretical ratio of chlorine to phenol required for complete
oxidation is about 6:1. For m-cresol the ratio is 3.84:1.
However, because of the presence in waste water of other
chlorine-consuming compounds, much higher ratios are required.
Thompson and Dust found that the minimum concentration of calcium
hypochlorite needed to destroy all phenols in creosote waste
water was equivalent to a chlorine:phenol ratio of from 14:1 to
65:1. The exact ratio varied with the pH, COD content, and
source of the waste water. Comparable ratios for
pentachlorophenol ranged as high as 300:1 when calcium
hypochlorite was used to 700:1 for chlorine gas. Generally,
approximately two times as much gaseous chlorine was required to
oxidize a given weight of pentachlorophenol as chlorine from
calcium hypochlorite.
In other work. Dust and Thompson analyzed waste water samples for
COD, phenol, and pentachlorophenol content following chlorination
with quantities of calcium hypochlorite equivalent to 0 to 3.0
g/1 of chlorine. Typical results are shown in Table 63.
Treatment of creosote waste water achieved a reduction in phenol
content of 95 to 100 percent, as determined by procedures
recommended by APHA (NOTE: This qualification is necessary,
since the 4-amino antipyrine test for phenols does not detect all
chlorinated phenols and cresols). However, as illustrated in
Table 63, a residual phenol content of 5 to 10 mg/1 that was
resistant to oxidation remained in some samples. Substantial
reductions in COD were also obtained by the treatments. However,
practically all of the reduction in COD occurred at chlorine
doses of 2 g/1 or less.
In the same study, both chlorine gas and calcium hypochlorite
were used to treat pentachlorophenol waste water adjusted to pH
levels of 4.5, 7.0, and 9.5. The results, which are summarized
in Tables 64 and 65, showed that the efficiency of the
treatments, in terms of the ratio of weight of chlorine used to
weight of pentachlorophenol removed, varied with the pH of the
waste water, the source of chlorine, and whether or not the waste
was flocculated prior to chlorination.
213
-------
TABLE 63 EFFECT OF CHLORINATION ON THE COD AND PHENOLIC CONTENT
OF PENTACHLOROPHENOL AND CREOSOTE WASTEWATERS
Ca(OCl)2 as
Chlorine
(g/liter)
0
0.5
1.0
1.5
2.0
3.0
PCP Wastewater
(mg/liter)
COD
—
8150
7970
8150
7730
7430
PCP
40.7
17.3
13.1
12.0
10.4
0.0
Creosote Wastewater
(mg/liter)
COD
5200
4800
4420
4380
4240
3760
Phenol
223.1
134.6
65.3
15.4
10.0
5.4
214
-------
TABLE 64 EFFECT OF CHLORINATION WITH CALCIUM HYPOCHLORITE
ON THE PENTACHLOROPHENOL CONTENT OF WASTEWATER
Pentachlorophenol (mg/liter)
Ca(PCl)2 as
Chlorine
(g/liter)
0
0.5
1.0
1.5
2.0
3.0
4.0
5.0
TABLE 65
Unflocculated
PH
4.5 7.0 9.5
21.5 19.0 20.5
10.0 14.0 10.0
8.0 10.0 8.0
6.0 8.0 8.0
6.0 7.5 8.0
3.5 6.0 5.0
2.0 6.0 4.0
2.0 5.8 4.0
4.5
12.0
6.0
4.0
2.0
0.0
0.0
0.0
0.0
EFFECT OF CHLORINATION WITH CHLORINE
THE PENTACHLOROPHENOL CONTENT
Flocculated
PH
7.0
12.0
9.0
8.0
5.0
3.6
0.0
0.0
0.0
GAS ON
9.5
14.0
11.0
9.0
6.0
7.0
4.0
0.0
0.0
OF WASTEWATER
Pentachlorophenol (mg/liter)
Chlorine
(g/liter)
0.0
0.5
1.0
1.5
2.0
3.0
4.0
5.0
10.0
Unflocculated
PH
4.5 7.0 9.5
22.0 20.0 18.0
13.0 14.0 16.0
10.0 12.5 15.0
9.0 9.0 11.5
8.0 8.0 11.5
8.0 8.0 8.0
10.0 8.0 11.0
14.0 11.5 12.0
14.0 11.5 14.0
4.5
18.0
16.0
14.0
10.0
8.0
7.5
2.0
0.0
0.0
Flocculated
PH
7.0
17.0
14.0
13.0
14.0
10.0
8.0
6.0
2.0
2.0
9.5
19.5
16.5
11.0
11.0
8.0
8.0
6.0
4.0
2.0
215
-------
TABLE 66 EFFECT OF CHLORINATION OF PENTACHLOROPHENOL.WASTE ON COD
Test Conditions
Calcium Hypochlorite
pH - 4.5
Calcium Hypochlorite
Chlorine Gas
pH - 4.5
Chlorine- 6s
pH = 7.0
Available Chlorine
(g/liter)
0.0
0.5
1.0
1.5
2.0
3.0
4.0
5.0
0.0
0.5
1.0
1.5
2.0
3.0
4.0
5.0
0.0
0.5
1.0
1.5
2.0
3.0
4.0
5.0
10.0
0.0
0.5
1.0
1.5
2.0
3.0
4.0
5.0
10.0
COD
(mg/liter)
24,200
10,650
10,600
10,300
23,800
10,300
10,200
10,050
20,400
10,250
10,500
10,200
23,600
9,760
10,700
11,250
216
-------
A large proportion of the chlorine added to the waste water in
the above studies was consumed in oxidizing organic materials
other than phenolic compounds. This is indicated by the major
reductions in COD that occurred coincident to the chlorination
treatments. For unflocculated waste, the COD averaged 24,000
mg/1 before and 10,300 mg/1 after treatment with calcium
hypochlorite, a reduction of 58 percent (Table 66) . The com-
parable reduction for samples treated with chlorine gas was 55
percent. These reductions were obtained at the maximum dose of
chlorine employed; that is, 5 g/1 for calcium hypochlorite and 10
g/1 for chlorine gas. However, practically all of the reduction
in COD occurred at chlorine doses of 1 g/1 or less, in the case
of samples treated with the hypochlorite, and 2 g/1 or less for
those treated with chlorine gas. For example, a typical sample
of raw waste treated with chlorine gas had an initial COD of
20,400 mg/1. This value was reduced to 10,250 mg/1 by a chlorine
dose of 2 g/1. The addition of 10 g/1 of chlorine further
reduced the COD to only 10,200 mg/1. These data indicate that a
portion of the organic content of the waste water was resistant
to chemical oxidation.
The reduction in COD caused by chlorination of raw waste water
was practically the same as that achieved by flocculation with
lime and a polyelectrolyte.
Chlorination of phenol-bearing waters has long been associated
with odor and taste problems in municipal water supplies. Phenol
itself apparently does not impart taste to water in
concentrations below about 60 mg/1. its significance as a taste
and odor problem arises from its reaction with chlorine to
produce chlorophenols. Some of the latter group of chemicals are
reported to impart taste in concentrations as low as 0.00001
mg/1.
Ingols and Ridenour postulated that a quinone-like substance was
responsible for the taste and odor problem of chlorinated water,
and that this substance was an intermediate product in a
succession of chlorinated products produced by chlorine
treatments of phenol. A ratio of 5 to 6 g of chlorine/g of
phenol was found to eliminate the taste problem. They
hypothesized from this result that high levels of chlorination
rupture the benzene ring to form maleic acid. Later studies by
Sttinger and Ruchoft largely substantiated earlier work which
showed that taste intensity increases with chlorine dosage and
then decreases with further chlorination, until no taste remains.
Results of work by these authors on the chlorination of various
phenolic compounds and the quantities of chlorine required to
eliminate taste are given in Table 67. These data indicate that
a chlorine-to-phenol ratio of 5:1 would be adequate to form
chlorination end products. Work reported by others show that for
m-cresol this ratio is 3.84:1. A ratio of 5:1 resulted in a free
chlorine residual after a reaction time of 2 hours.
217
-------
TABLE 67 CHLORINE REQUIRED TO ELIMINATE TASTE IN AQUEOUS
SOLUTIONS OF VARIOUS PHENOLIC COMPOUNDS
Chlorine Required To
Eliminate Taste
(mg/1)
Phenol
0-Cresol
M-Cresol
P-Cresol
2-Chlorphenol
4-Chlorophenol
2-, 4-Dichlorophenol
2-, 4-, 6-Trichlorophenol
2-, 4-, 5-Trichlorophenol
2-, 3-, 4-, 6-Tetrachlorophenol
Pentachlorophenol
4
5
5
3
3
3
2
*
*
*
*
Chlorine Added
To Produce Free
Residual (mg/1)
7
5
5
4
5
6
6
3
2
1.5
1.0
*Could not be tasted
218
-------
More recent work by the Manufacturing Chemists Association shows
that the reaction between chlorine and phenolic compounds
proceeds at a rapid rate for the first 15 minutes and is
essentially complete after 2 hours contact time. For
concentrations of m-cresol of 10 and 20 mg/1, the application of
50 and 100 mg/1 of chlorine produced a free chlorine residual
after 2 hours. A residual chlorine content after 2 hours contact
time was obtained for phenol only when chlorine was applied at
ten times the level of phenol. The relationship among m-cresol
concentration, chlorine dosage, contact time, and chlorine
residual is shown in Table 68.
In related studies, phenol in concentrations of 25 mg/1 was
treated with levels of chlorine calculated to provide an excess
of phenol. Gas chromatographic analyses of samples withdrawn
after a contact time of 0.5 hour revealed the presence of 0-
chlorophenol, p-chlorophenol, 2,6, dichlorophenol, 2,4
dichlorophenol, and 2,4,6 trichlorophenol. Similar tests with m-
cresol showed the formation of a number of reaction products,
which were assumed to be a mixture of chloro-m-cresols. Positive
identification was not made because chlorine-substituted cresols
for use as standards are not available commercially.
The authors proposed that the reaction proceeds in part
sequentially by the stepwise substitution of the 2,4, and 6 ring
positions, and in part simultaneously, resulting in the formation
of a complex mixture of chlorphenols and their oxidations
products. Ring oxidation was assumed to follow the formation of
2,4^6 trichlorophenol. Other authors have postulated that the
reaction proceeds only by a stepwise substitution.
Burttschell has indicated that the progression of chlorinated
products occurs as follows:
Phenol
2-Chlorophenol
4-Chlorophenol
2,4-Dichlorophenol
2,6-Dichlorophenol
2,4,6-Trichlorophenol
4,4-Dichloroquinone
Organic Acids
Destruction of the benzene ring was found to occur at a chlorine-
to-phenol ratio of 10:1. Burttschell attributed the taste
problem associated with chlorophenols to 2,6-dischlorophenol.
The development of taste was reported not to occur at pH values
of less than 7.0.
Results of a study by Eisenhauer supported earlier work of other
investigators that non-aromatic products are formed when phenols
are treated with high levels of chlorine.
219
-------
TABLE 68 CHLORINE DEMAND OF M-CRESOL AFTER VARIOUS
CONTACT TIMES
m-Cresol Contact
Concentration Chlorine Time
(mg/1) (mg/1) (hr)
0.25
10 20 0.5
1.0
2.0
0.25
10 50 0.5
1.0
2.0
0.25
10 100 0.5
1.0
2.0
0.25
20 50 0.5
1.0
2.0
0.25
20 100 0.5
1.0
2.0
Chlorine
Residual
(mg/1)
3.3
1.5
0.5
0.2
30.8
30.8
28.3
17.0
81.4
77.0
61.6
61.6
16.3
11.1
8.0
8.0
61.6
58.2
56.6
46.0
Net
mg/1
16.7
18.5
19.5
19.8
19.2
19.2
21.7
33.0
18.6
23.0
38.4
38.4
33.7
38.9
42.0
42.0
38.4
41.8
43.4
54.0
Chlorine
Demand
m mol cl?
m mol m-Cresol
2.5
2.8
3.0
3.0
2.9
2.9
3.3
5.0
2.8
3.5
5.9
5.9
2.6
3.0
3.2
3.2
2.9
3.2
3.3
4.1
220
-------
Oxidation products resulting from the chlorination of
pentachlorophenol have not been studied intensively. However,
Thompson and Dust reported the presence of chloranil in samples
of chlorinated waste water analyzed using a gas chromatograph.
with the exception of the last reference cited, the studies
described in the foregoing paragraphs have dealt with phenolic
compounds in solutions not contaminated with other substances.
Because of other chlorine-consuming materials in wood preserving
waste water, a question arises concerning the levels of chlorine
required to fully oxidize phenols in such wastes. Unpublished
results of a recent study (1970) at the Mississippi Forest
Products Laboratory provide a partial answer.
Creosote waste water with phenol and COD contents of 508 and
13,500 mg/ 1, respectively, were flocculated and samples of the
filtrate adjusted to pH values of U.5, 7.0, and 9.5. The samples
were treated with quantities of calcium hypochlorite calculated
to yield a gradient series of chlorine concentrations. The pH
readings of the samples were adjusted to the original values
after a contact period of 30 minutes. After 8 hours, the samples
were filtered, analyzed for phenols by the 4-aminantipyrine
method, and then analyzed for di- and tri-chlorophenols using an
electron capture detector. Chloro-cresols and other
chlorophenols were not included because reagent-grade materials
for use as standards could not be found. The results are given
in Table 69.
Trichlorophenol was present in all samples, but the concentration
decreased rapidly with increasing levels of chlorine. However,
traces remained in samples treated with the highest levels of
chlorine. The rate of oxidation was highest at pH 4.5 and
decreased with increasing alkalinity, although the difference
between pH 7.0 and 9.5 was not great. The relationship between
results of the APHA test for phenols and levels of chlorophenols
determined using an electron capture detector was generally poor
at low chlorine levels. However, low values for the APHA test
always corresponded with low concentrations of chlorophenols.
Ozone Treatments - Ozone is a powerful oxidizing agent, but its
employment in waste treatment is a relatively recent development.
Its principal disadvantages are its lack of stability, which
requires that it be produced as used, and its high cost both in
terms of capital investment in equipment and operating costs.
The major cost of producing ozone is electricity. It requires
19.8 kwh of electricity to produce one kilogram of ozone with air
feed to the generating equipment and 9.9 kwh with oxygen feed.
The high initial cost of ozonation is offset in part by the fact
that the equipment has a useful life expectancy of 25 years.
Treatment of waste water with ozone may be either by batch or
continuous flow methods. Ozone reacts rapidly with phenols at
all pH levels, but the optimum pH observed by Niegowski was 12.0.
Ozone demand at pH 12 was less than one-half that at pH 7 in
221
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TABLE 69 CHLOROPHENOL CONCENTRATION IN CREOSOTE WASTEWATER
TREATED WITH CHLORINE
As
PH
4.5
7.0
9.5
Ca(PCl)2
Chlorine
(8/D
0
0.5
1.0
1.5
2.0
3.0
5.0
0.5
1.0
1.5
2.0
3.0
5.0
0.5
1.0
1.5
2.0
3.0
5.0
Residual
Phenols (mg/1)
by
APHA Method
438.5
256.1
30.8
0.0
0.0
0.0
0.0
300.0
101.5
7.7
0.0
0.0
0.0
315.4
101.5
11.5
0.0
0.0
0.0
ECD Analysis
2-, 4-dichloro-
phenol
—
161.0
9.9
0.0
0.0
0.0
0.0
122.0
0.0
0.0
0.0
0.0
0.0
198.0
0.0
0.0
0.0
0.0
0.0
(mg/1)
2-, 4-, 6-tri-
chlorophenol
—
910.0
6.7
1.5
1.0
0.3
0.3
316.0
35.0
6.4
2.8
1.5
1.3
264.0
27.0
25.0
3.7
3.8
1.9
222
-------
treating petroleum waste waters. However, the difference in
demand was manifested only in oxidizing the last 30 percent of
the phenol in the waste. During two-thirds of the oxidation, the
reaction was so rapid that pH had very little effect.
A ratio of ozone:phenol of about 2:1 normally is required to
destroy the phenols in a solution. However, ratios as low as 1:1
and as high as 10:1 were reported by Niegowski for waste waters
from different sources. According to Gloyna and Malina, only
about I/TO as much ozone is required as chlorine to oxidize the
same amount of phenol.
Because of its high energy requirements and the resulting high
operating costs, ozonation does not lend itself to the treatment
of wood preserving waste waters, and hence will not be considered
further in this report,
Activated Carbon Filtration - Activated carbon is used
commercially to treat petroleum and other types of industrial
waste waters. It can also be used effectively to remove phenolic
compounds from wood preserving waste streams. Although carbon
has a strong affinity for nonpolar compounds such as phenols,
adsorption is not limited to these materials. Other organic
materials in waste water are also adsorbed, resulting in a
decrease in the total oxygen demand of the waste. Because the
concentration of the latter substances exceeds that of phenols in
effluents from wood preserving plants, the useful life of
activated carbon is determined by the concentration of these
materials and the rate at which they are adsorbed.
Results of carbon-adsorption studies conducted by Dust and
Thompson on a creosote waste water are shown in Figure 42.
Granular carbon was used and the contact time was 24 hours. The
waste water was flocculated with ferric chloride and its pH
adjusted to 4.0 prior to exposure to the carbon. As shown in the
figure, 96 percent of the phenols and 80 percent of the COD were
removed from the waste water at a carbon dosage of 8 g/1. The
loading rate dropped off sharply at that point, and no further
increases in phenol removal and only small increases in COD
removal occurred by increasing carbon dosage to 50 g/1. Similar
results were obtained in tests using pentachlorophenol waste
water.
Results of adsorption isotherms that were run -on
pentachlorophenol waste water, and other samples of creosote
waste water followed a pattern similar to that shown in Figure
42. In some instances a residual content of phenolic compounds
remained in waste water after a contact period of 24 hours with
the highest dosage of activated carbon employed, while in other
instances all of the phenols were removed. Loading rates of 0.16
kg of phenol and 1.2 kg COD/carbon were typical, but much lower
rates were obtained with some waste waters.
Other Process Waste Water Handling Methods
223
-------
100
(0
s
Q>
CC
Q.
•o
C
(Q
O
o
o
Activated Carbon (gm / liter)
FIGURE 42
RELATIONSHIP BETWEEN WEIGHT OF ACTIVATED
CARBON ADDED AND REMOVAL OF COD AND PHENOLS
FROM A CREOSOTE WASTEWATER
224
-------
Containment arid Spray Evaporation - Forty-two percent of the
plants responding to the survey referred to in Section V
indicated that they currently are storing their waste water on
company property, and therefore have no discharge (Table 44).
The popularity of this method of waste handling undoubtedly is
attributable to its low cost, in the case of plants with ample
land area, and its simplicity. The practicality of the method is
questionable in areas of high rainfall and low evaporation rate,
unless the rate of evaporation is increased by the application of
heat or by spraying. The latter alternative is being employed by
a number of plants in the Gulf coast region of the South.
The use of spray ponds to dispose of waste water by evaporation
requires that a diked pond of sufficient .capacity to balance
annual rainfall and evaporation be constructed. The pond is
normally equipped with a pump and the number of spray nozzles
necessary to deliver to the air the volume of water calculated to
provide the desired amount of evaporation, assuming a given
evaporation efficiency.
The feasibility of spray evaporation depends upon the
availability of a land area of such size that a pond large enough
to permit a balance between inflow and evaporation can be
constructed, pond size and number of spray heads are determined
by waste volume and the ratio of rainfall to surface evaporation.
Where rainfall and evaporation in a region are approximately
equal, the effect of both can be neglected, if sufficient storage
capacity is provided. For areas with higher annual rainfall or
lower evaporation rate, the design of a spray evaporation system
must account for a net annual increase in water volume in the
pond due to rainfall.
Pan Evaporation - A few plants with small volumes of waste water
are evaporating it directly by application of heat. Basically,
the procedure involved is to channel the effluent from the oil-
separation system into an open vat equipped with steam coils.
The water is then vaporized by boiling, or, as in one instance,
heated to approximately 71°C (160°F) and the rate of evaporation
increased by circulation of air across the surface of the water.
The method is expensive, and is based on using natural gas as
fuel, assuming an overall efficiency of 65 percent for the
process.
Evaporation in Cooling Towers - In this process, effluent from
the :oilseparation system is discharged to the basin of a cooling
tower and reused as cooling water. Normal evaporation associated
with the operation of the tower accounts for an average loss of
approximately 7,570 I/day (2000 gal/day) for a typical tower.
Evaporation of excess water is expedited by the intermittent
operation of a heat exchanger or other heating system in
conjunction with a fan. The efficiency of the condensers, both
tube type and barometric, are reported to be unaffected by water
temperatures of up to 38°C (100°F) and by light oils that
225
-------
accumulate in the water. The owner of one plant stated that oil
concentrations as high as 10 percent could be tolerated in the
cooling water. However, problems with condenser efficiency were
reported at another plant in which the oil content of the process
water used for cooling was less than 100 mg/1.
Incineration - Two plants in the U.S. are known to operate
incinerators for waste water disposal. The one plant for which
data are available currently operates a unit capable of "burning"
5,676 1/hr {1500 gal/hr) of waste water. Fuel cost alone for
this unit, which is fired with Bunker C oil, is $15.00/3,785 1
(1000 gal) of waste.
Data reported by the American Wood Preservers' Association
indicates that incineration of waste water is economical only
when the oil content of the waste is 10 percent or higher. Such
high oil contents are not common for waste water from the wood
preserving industry.
Required Implementation Time
Because of the relatively small volume of waste water at most
wood preserving plants, "off-the-shelf" equipment should
ordinarily meet the requirements of the individual plants with
regard to the application of treatment technology required to be
achieved by July 1, 1977 and July 1, 1983, respectively. It is
not anticipated, therefore, that either equipment availability,
or (because of the simplicity of the equipment) availability of
construction manpower will seriously affect implementation time.
For the same reason, it is not anticipated that the time required
to construct new treatment facilities or modify existing ones
will affect implementation time for any of the treatment and
control technologies that are likely to be employed in the
industry.
Land availability will influence the choice of treatment and
control technology at many wood preserving plants located in
urban areas. For example, the employment of oxidation ponds,
soil irrigation, and possible aerated lagoons will not be
feasible in areas where all company land is in use and additional
acreage cannot be purchased at a reasonable price. Plants thus
located will have to select other treating methods, the land
requirements of which conform to the space that is available.
Effect of Treatment Technology on Other Pollution Problems - None
of the treatment and control technologies that are currently
feasible for use in the wood preserving segment of the industry
will have an effect on other pollution problems.
Solid Waste - Solid wastes resulting from treatment and control
technologies that have potential use in the wood preserving
industry are of two types: sludge from coagulation of waste
water and bacterial sludges originating from biological
226
-------
treatments. The former material contains oil and dissolved
phenolic compounds originally in the preservative, along with the
flocculating compound used. In the case of water-soluble
preservatives, the sludge will contain traces of the metals used
in the particular preservative or fire retardant formulation
involved. Bacterial sludges contain the biomass from biological
treatments, but are of importance from the standpoint of disposal
only in the case of treatments that employ activated sludge and
trickling filter units.
The volume of sludge involved with both types is small. Plants
currently are disposing of these materials in sanitary landfills.
Incineration of organic waste and burial of inorganic salts are
possible disposal methods that could be used.
Plant Visits
A number of wood preserving plants judged to be exemplary in
terms of their waste management programs and practices were
visited in conjunction with this study. Selection of plants for
visits was based on the type of waste water treating disposal
system employed or both, and, insofar as possible, geographic
location. Plants that dispose of their raw waste by discharging
it to a sewer were not represented among the plants visited.
Exclusion of these plants limited the number considered for a
visit to the approximately 30 plants in the U.S. that either give
their waste the equivalent of a secondary treatment before
discharging it, or which have no discharge, only four of this
number were found both to treat their waste on site and discharge
it directly to a stream. The remainder either channel their
treated water to an irrigation field or to a sewer, or have no
discharge because of reuse of waste water, evaporation, or both.
Plant visits were used to obtain samples, the analyses of which
permitted an evaluation of the efficiency of the waste water
treating system employed. Performance data provided by the
plants themselves were used in this evaluation when available.
Information was also obtained on flow rate, annual production,
and other parameters needed for the development of effluent
guidelines. Cost data on waste water treating systems were
requested of all plants and provided by some.
A summary of the data obtained for each plant visted is presented
in Table 70. Flow diagrams illustrating waste treatment systems
employing extended aeration, soil percolation, and combination
aerated lagoon and oxidation pond are shown in Figures 43, 44,
and 45 respectively.
227
-------
PCP
Secondary PCP
ft Creo. Separation
Catch Pond
Overflow and Run-off Water
Holding Ponds
Final Separation
WASTEWATER FLOW DIAGRAM FOR
A WOOD-PRESERVING PLANT EM-
PLOYING AN OXIDATION POND IN
CONJUNCTION WITH AN AERATED
RACEWAY
-------
TABLE 70 SUMMARY OF WASTEWATER CHARACTERISTICS FOR 17 EXEMPLARY WOOD PRESERVING PLANTS
ro
OJ
Plant
No,
1
2*
3
4*
5
6
7
8
9
10
11
12
13
14
15
16
17J j
Average
Phenol
(mg/1)
6.00
0.00
0.50
35.96
—
—
3.30
0.40
—
—
—
—
—
—
—
—
2.50
2.50
COD
(mg/1)
845
10
10
1695
—
—
523
435
—
—
—
—
—
—
—
—
240
240
Oil and
Grease
(mg/D
7
7
0
83
—
—
55
158
—
—
—
—
—
—
—
—
12
46
Suspended
Solids
(mg/1)
100
253
60
724
—
—
103
270
—
—
—
—
—
—
—
—
82
123
Volume
of
Effluent
,' Ipd)
73,800
49,200
49,200
34,100
3,800
34 , 100
567,800
98,400
15,100
22,700
49,200
18,900
4,700
9,500
7,600
19,700
63,200
34,600
Volume
of
Discharge
(Ipd)
0
0
0
0
0
0
492,100
87,100
0
0
49,200
0
0
0
0
0
63,200
—
Daily
Produc-
tion
(cu m)
283
283
266
436
210
403
708
425
178
204
93
210
62
125
34
190
223
255
Cost
($)
42,000
90,000
30,000
17,000
40,000
25,000
85,000
46,000
38,000
85,000
—
120,000
5,500
6,000
50,000
39,000
—
47,900
Final
Disposition
of
Waste
Sewer
Field
Field
Field
Field
Field
Stream
Stream
Pond
Evaporated
Ditch
Evaporated
Evaporated
Evaporated
Evaporated
Sewer
Stream
*Data not included in average.
-------
-------
SECTION VIII
COST, ENERGY, AND NON-WATER QUALITY ASPECTS
BARKING
Cost and Reduction Benefits of Alternative Treatment and Control
Technologies
Only wet barking techniques result in any discharge of process
waste waters. An elimination of the discharge of pollutants can
be accomplished by all but hydraulic barkers through the recycle
of process water.
A hydraulic barking operation servicing a 9.3 million sq m/yr
will typically have a waste load of about 13,100 kg/day (100
million sq ft/yr) plant (28,800 Ib/day) of suspended solids and
660 kg/day (1,450 Ib/day) of BOD5, and a flow of approximately
6500 cu m/day (1.73 million gal/day). Recycle of this effluent
has not been shown to be practicable technology. In the pulp and
paper industry, however, hydraulic barker effluent is commonly
treated biologically along with other waste waters.
One hydraulic barker such as the one presented here can handle
the barking operation of mill producing 9.3 million sq m (100
million sq ft/yr) of plywood on a 9.5 mm (3/8 in) basis.
Alternative A; No Waste Treatment or Control
Effluent waste load is estimated at 660 kg/day of BOD5_ and 13,100
kg/day of suspended solids for the selected plant.
Costs: None
Reduction Benefits: None
Alternative B_: Clarification and Biological Treatment
This alternative includes clarification of waste waters and then
combination with other wastes for biological treatment. An
activated sludge system can achieve 95 percent BOD5 removal with
a resulting effluent load of 35.0 kg/day (77 Ib/day) for a 100
million sq ft/yr plywood on 3/8 in basis plant.
INVESTMENT AND OPERATING COST ESTIMATE
ALTERNATIVE B
Clarification and Biological Treatment
.Item Cost
1. Installed Equipment $1,070,500
2. Yearly Operating Costs 138,200
233
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TOTAL COST/YR $ 196,300
VENEER AND PLYWOOD MANUFACTURING SUBCAT.EGQR1ES
Reduction Benefits of Alternative Treatment And Control
Technologies For A Selected Plant
The typical combination veneer and plywood mill selected to
represent the veneer and plywood subcategories is a mill
producing 9.3 million sq m/yr on a 9.53 mm basis (100 million sq
ft/yr on a 3/8 in basis) . It is assumed to have the following:
(1) Log conditioning by means of hot water
vats with direct steam
impingement and a resulting discharge;
(2) No containment of dryer washwater;
(3) A phenolic glue system without recycle
of washwater.
This is a hypothetical mill and is not typical in the sense that
it represents the average mill. It is typical of a softwood
plywood mill built in the past twenty years, but without any
degree of waste water treatment and control. This hypothetical
plant might be located in a number of places throughout the U.S.,
however, it is more likely that it will be located in the
southeast because of the fact that hot water vats are used.
A single mill has been chosen to represent both the veneer and
plywood subcategories, as the two manufacturing operations often
take place in the same plant, and the costs would thus be
applicable to a combination operation. In a plant producing only
plywood, however, only the costs of alternative treatment B (glue
wash water recycle) would apply.
Basis of. Assumptions Employed In Cost Estimation
Investment costs are based on actual engineering cost estimates
as described in the following paragraph.
Yearly operating costs are based on actual engineering cost
estimates using $7.00/hr for salaries and $0.01 kwh for
electricity. The annual interest rate for capital cost was
estimated at 8%. Salvage value was set at zero over 20 years for
physical facilities and equipment. The total yearly cost equals:
(investment cost/2) X (0.08) + (investment cost) X (0.05) *
yearly operating cost.
234
-------
Alternative A: No Waste Treatment Or Control
Effluent waste load is estimated at 485 Kg/day of BOD (1080
Ib/day) for the selected plant.
Costs: None
Reduction Benefits: None
Alternative B: Complete Retention of Glue Washwater
This alternative includes complete retention of glue wastes by
recycle and reuse in glue preparation. This practice has now
become standard in the industry although four years ago only one
mill practiced complete recycle. Collection, holding, and
screening is now practiced in 60 percent of the mills surveyed.
In 1972, 50 mills practiced recycling and it is believed that
more than 50 percent of the softwood plywood mills now recycle or
plan to recycle glue wash water. BOD waste load is estimated at
410 kg/day (900 Ib/day) for the selected typical plant at this
control level,
Recycling of glue wash water is the most significant pollution
control step in the reduction of phenolic compounds; free phenols
are reduced by 73 percent. Associated costs for a 9.3 million sq
m/yr plant on a 9.53 mm basis (100 million sq ft/yr on a 3/8 in
basis) are described below.
INVESTMENT COST ESTIMATE
ALTERNATIVE B
Item Cost
1. 3785 1 (1000 gal) concrete sump $ 1,300
2. 18925 1 (5,000 gal) holding tank 1,000
3. 1080 1 (285 gal) pressure tank 350
4. Rotating screen 1,800
5. Pumps 3,700
6. Valves, fittings, controls and
engineering costs 9. 350
TOTAL COST $17,500
OPERATING COST ESTIMATE
Item Cost
1. Operation and Maintenance $ 2,200
2. Electricity 800 rii
TOTAL COST/YR $ 3,000
Summary:
Costs: Incremental costs are approximately
$17,500 over Alternative A, thus
total costs are $17,500.
235
-------
Reduction Benefits: An incremental reduction
in plant BOD is approximately 77 kg/day
(170 Ib/day). Total plant reduction in BOD
would be 15.8 percent.
Alternative C: Complete Retention of Waste Water From Log
Conditioning
Alternative C would result in complete recycle of water from hot
water vats with containment of excess waste waters. Modification
of hot water vats to provide heat by means of coils rather than
direct steam impingement is assumed.
INVESTMENT COST ESTIMATE
ALTERNATIVE C
Item Cost
1. 320 cu m (85,000 gal) settling tank $ 1,900
2. Pump and motor 1,300
3. Containment pond, 30.5 m x 30.5 m
(100 ft x 100 ft) 4,300
4. Piping, contingencies and labor 4,500
TOTAL COST $12,000
OPERATING COST ESTIMATE
ALTERNATIVE C
Item Cost
1. Operation and Maintenance $ 6,300
2. Electricity 2.200
TOTAL COST/YR $ 8,500
Summary
Costs: Incremental costs of approximately
$12,000 over Alternative B would be
incurred, thus producing total costs
of $29,500.
Reduction Benefits: An incremental reduction
in plant BOD of 406 kg/day (894 Ib/day)
is evidenced when compared to
Alternative B. Total plant reduction
in BOD is 99.3 percent.
Alternative D: Complete Retention of Dryer Wasnwater
Alternative D would result in the complete retention of dryer
washwater. Modification of washing operations to reduce the
volume of water used assumes reduction of water by scraping,
pneumatic cleaning and general water conservation with complete
retention of waste water by irrigation or containment on site.
Effluent waste load is estimated at 0 kg/day of BOD for the
236
-------
selected typical plant at this control level. Complete control
of wastes without discharge to receiving waters is effected.
INVESTMENT COST ESTIMATES
ALTERNATIVE D
Alternative p-1; Spray Irrigation.
Associated Costs:
Item Cost
1. 37850 1 (10,000 gal) storage tank $ 2,700
2. Pump and motors 1,200
3. Piping 2,600
4. Labor and contingencies 3,200
TOTAL COST ~$ 9,700
Alternative P-2 - Containment by Lagooning
A conservative estimate of 76.2 cm/yr (30 in/yr) of evaporation
is assumed.
Item - Total Cost
30.5 m x 30.5 m pond $ 4,300
OPERATING COST ESTIMATES
ALTERNATIVE D
Item Cost
1. Operation and Maintenance $ 7,900
2. Electricity 2,300
TOTAL CQST/YR $10,200
Summary:
Costs: Investment'costs of $5,000 to $10,000
over Alternative c would be incurred,
thus producing total costs of about
$37,000 ($35,000 to $40,000).
Reduction Benefits: An incremental reduction
in plant BOD of 3 Jcg/day (6 Ib/day) is
evidence when compared to Alternative C,
producing a total plant reduction in BOD discharge
of 100 percent.
SUMMARY OF ALTERNATIVE COSTS
BOD Investment Yearly Total Yearly
Alternative Removal cost Operating Cost
237
-------
A
B
C
D
OX
15.8%
99.3%
100.0%
0
17,500
29,500
37,000
0
3,000
5,000
7,700
0
4,575
7,655
9,030
TABLE 72
SUMMARY OF HASTE LOADS FROM TREATMENT ALTERNATIVES (kg/day)
BOD
TSS
RWL
485
352
A
485
352
B
412
330
C
3
11
D
C
0
Phenols
0.25
0.25
0.09
0.07 0
HARDWOOD VENEER AND PLYWOOD MANUFACTURING CONSIDERATIONS
Hardwood veneer and plywood manufacture normally occurs at a
plant considerably smaller in size than a softwood manufacturing
facility. As discussed above, the softwood plant has a
production rate of about 9,290,000 sq m/year (1000,000,000 sq
ft/yr) whereas a hardwood veneer and plywood mill of average size
will produce about 464,500 sq m/year (5,000,000 sq ft/yera) of
veneer and plywood.
Because of the significantly lower production (or throughput
rate) less water is used and as a result, treatment and control
schemes necessary to reduce or eliminate the discharge of waste
water pollutants are on a smaller scale than those applicable to
waste waters generated by a softwood manufacturing facility.
Presented below in tabular format is information showing the
pollutants generated, the pollutant reduction achievable by
application of technology and the costs associated with these
technologie s.
RAW WASTE
Conditioning
Vats
Dryer
Washwater
Flow Waste Load
LI m/day
(mgd)
0.043
(0.0115)
0.429
(0.000 14)
Concentration
mg/1
BOD
700
750
SS
600
3000
Loading,
kg/ day
(Ib/day)
BOD SS
30 26
(67) (58)
0.4 1.6
(0.9) (3.5)
238
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TREATMENT Investment Yearly TOTAL BOD
Cost Operating Annual Removal
<$) <$> <$)
Conditioning Vats
Lagoon 3,000 600 870 30
Activated Sludge 32,500 8,500 11,025 90
Glue Wash Water
Recycle System 2,000 300 480 100
Dryer Wash Water
Lagoon 50 50 50 32
As can be seen from the information presented in the table above
it is, from an economic viewpoint, more feasible to modify the
manufacturing procedures to accomplish the elimination of the
discharge of pollutants than it is to install treatment
technologies to reduce the level of discharge.
Mills With Existing Steam Vats
In Sections I, II, and IX of this report, a variance is
recommended for mills with existing steam vats. In Section VII,
it is noted that existing technology for treatment and control of
waste waters from steam vats consists of biological treatment
which is capable of 85 to 90 percent removal of BOD. Two
modifications of steam vats (modified steaming and hot water
sprays) which make zero discharge feasible are also discussed in
Section VII. These modifications will not be required for best
practicable control technology as defined by the Act.
As discussed in Section VII, biological treatment is applicable
to waste waters from steam vats. A summary of costs and effluent
levels for biological treatment of waste waters from mills with
existing steam vats is presented below;
1. A system consisting of a vacuum separator
followed by an aerated lagoon would cost
approximately $81,000 for the selected
mill utilizing a steam vat and
would reduce the load to around 41 kg/day
(90 Ib/day) of BOD.
2. An activated sludge plant may result in
slightly higher BOD removals for a cost of
about $138,000 and a resulting BOD discharge of
about 20 kg/day (45 Ib/day) for the
239
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selected mill.
Related Energy Requirements of Alternative Treatment and Control
Technologies
It is estimated that 180 kwh of electricity is required to
produce 93 sg m (1000 sq ft) of plywood. This electrical energy
demand is affected by the following factors: (1) type of wood,
(2) whether or not logs are conditioned, (3) type of dryer, and
(4) amount of pollution control devices.
For a typical mill producing 9,3 million sq m/yr (100 million sq
ft/yr) of plywood on a 9.53 mm (3/8 in) basis, total energy is
estimated at 4500 kw. At a cost of one cent/kwh the plant would
have a yearly energy cost of $180,000. Associated with the
control alternatives are annual energy costs. These are
estimated to be:
For Alternative A: $0
For Alternative B: $800
For Alternative C: $900
For Alternative D: $1000
Nonwater Quality Aspects of Alternative Treatment and Control
Technologies
Air Pollution; While there are no appreciable air pollution
problems associated with any of the -treatment and control alter-
natives, in veneer and plywood manufacturing operations there are
air pollution problems presently in existence that may cause
water pollution problems. The main source of air pollution is
from the veneer dryers as the stack gases from the dryers contain
volatile organics.
Veneer Dryers: Since there are currently no emission control
systems installed on any veneer dryers, it is not possible to
cite typical applications or technology. There are, of course,
methods operating on similar processes which would be suitable
and applicable for controlling emissions from veneer dryers.
If particulate emissions were excessive, they could be adequately
controlled by utilizing inertial collectors of the cyclone or
mechanical type. Volatile and condensable hydrocarbon emissions
could be effectively controlled by one of the several following
methods:
(1) Condensation, utilizing tube con-
densers with air or water for cooling.
(2) Absorption (scrubbing) , utilizing
water or a selective solvent.
(3) Incineration or thermal oxidation.
(4) Adsorption
(5) A combination of the above.
240
-------
The water pollution potential of these control methods are not
great. Only condensation and scrubbing use water. Water used in
condensation is only cooling water and thus not contaminated.
The most efficient scrubber appears to be that using a selective
solvent rather than water for absorption. Scrubbing water can
usually be recycled.
Odors: Odors presently associated with veneer and plywood are
not considered to be a pollution problem. Since the control and
treatment technology of this industry is greatly dependent on
containment ponds, there is always the danger of ponds becoming
anaerobic. Frequently anaerobic ponds will promote growth of
organisms which biochemically reduce compounds to sulfur dioxide,
hydrogen sulfide and other odor causing gases.
Solid waste; The bulk of the solid waste from veneer and plywood
mills is comprised of wood residues and bark. These wastes are
commonly used as fuel in the boiler.
In addition to wood wastes are the settleable solids that
accumulate in ponds and those that are separated in screening
devices. Disposal of this material may be at the plant site or
the waste material may be collected by the local municipality
with disposal by landfill. While the amount of solids generated
is not expected to be great/ consideration must be given to a
suitable site for landfill and, in turn, to protection of
groundwater supplies from contamination Isy leachates.
HARDBOARD - DRY PROCESS
Cost and Reduction Benefits of Alternative Treatment and Control
Technologies
The following cost estimates are based upon actual preliminary
cost estimates for a waste treatment system for the dry process
industry. The waste water volume from this industry is low and
the major approach for further reducing waste flow is by inplant
modifications and changes in inplant procedures. The mill
selected to represent the dry process hardboard industry has a
production of 227 kkg/day (250 ton/day), and a waste water flow
of 945 I/day (250 gal/day). The waste water discharges result
only from caul washing. The basic results are summarized in the
paragraphs below.
241
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Basis o£ Assumptions Employed in Cost Estimates
Investment costs are based on actual engineering cost estimates.
Yearly operating costs are based on engineering cost estimates
using $10.00/hr for salaries, $0.01 kwh for electricity and 1973
market cost for chemicals. Annual interest rate for capital cost
is estimated at 856, a salvage value of zero over 20 years for
physical facilities and equipment, and a straight line
depreciation cost are assumed. The total yearly cost equals:
(investment cost/2) X (0.08) + (investment cost) X (0.05) +
yearly operating cost.
Alternative A; No Waste Treatment or Control
Effluent consists of 945 I/day (250 gal/day) of. caul wash water.
There is no log or chip wash, no resin wash water, humidifier
water or housekeeping water discharge.
Costs: None
Reduction Benefits: None
Alternative B: Retention of Caul Washwater
This alternative includes the collecting of caul washwater in a
holding tank and trucking to land disposal after pH
neutralization. There are no provisions in the following cost
estimates for handling water from fire fighting. As the number
of fires and the amount of water used vary so widely, no
estimation was made for handling this potential source of water.
There are new techniques being developed to limit the oxygen
concentrations in the air stream which will greatly reduce, if
not eliminate, future fire problems in the dry process hardboard
industry.
INVESTMENT COST ESTIMATE
ALTERNATIVE B
Item Cost
.(May, 1973)
1. 18,925 1 (5,000 gal) storage tank
(includes installation and fittings) $ 4,000
2. 1892 1 (500 gal) storage tank (acid resistant)
(includes installation and fittings) 1,500
3. Chemical feed pump 500
4. Pumps and piping 6,000
5. Instrumentation (pH) and controls 1,000
6. Chemical mixer 500
7. Tank Truck 7570 1 (2,000 gal) 8,500
8. Land 3,000
TOTAL $25,000
242
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OPERATING COST ESTIMATE
ALTERNATIVE B
Item
1. Labor (4 man hr/wk)
2. Electricity
3. Chemicals
4. Maintenance
Costs:
Cost
$ 2,080
65
500
355
TOTAL COST/YR
$ 3,000
Incremental costs are approximately
$21,500 over Alternative A, thus total
costs are $21,500.
Reduction Benefits: Elimination of caul wash-
water as a discharge stream.
Factors Involved In The Installation Of Treatment
The only treatment system involved in the representative dry
process mill is the disposal of caul wash water by hauling to
land disposal. There are no problems concerning the reliability
of the system as caul wash water will be put into a storage tank,
neutralized, then hauled by truck to a disposal area. This
system is not sensitive to shock loads, and startup and shutdown
procedures do not cause a problem. This system can be designed
and installed within one year and requires little or no time to
upgrade operational and maintenance practices. There are no air
pollution, noise, or radiation effects from the installation of
this treatment system. The quantities of solid waste generated
from this system are insignificant as are the additional energy
requirements.
HARDBOARD-WET PROCESS
Basis Of Assumptions Employed In Cost Estimation
Investment costs are based on actual engineering cost estimates.
Yearly operating costs are based on actual engineering cost
estimates using $10,00/hr for salaries, $0.01 Jcw/hr for
electricity and present market cost for chemicals. The annual
interest rate for capital cost is estimated to be Q%r and a
salvage value of zero over 20 years for physical facilities and
equipment, and straight line depreciation cost are assumed. The
total yearly cost equals (investment cost/2) (0.08) plus
(investment cost) (0.05) plus yearly operating cost.
. and Reduction Benefits of Alternative Treatment and Control
Technologies
The mill selected to represent the wet process industry has a
production of 127 kkg/day (140 tons/day) , a waste water flow of
1,432 cu m/day(0.378 million gal/day), a BOD of 33.75 kg/kkg
243
-------
production (67.5 Ib/ton) f and a suspended solids concentration of
9 Jcg/kkg production (18 Ib/ton) . The results of the cost
estimates are shown below.
Alternative A: Screening and Primary Clarification
Raw waste water characteristics for the typical mill having a BOD
of 33.75 kg/kkg production (67.5 Ib/ton) represents a mill with
recirculation but no inplant treatment facilities.
INVESTMENT COST ESTIMATE
ALTERNATIVE A
Primary Treatment
Item
1. Drum Screen, installed
2. Clarifier - 7.6 m diam x 3.05 m deep
(25 ft diameter - 10 ft deep)
3. Sludge Pond - 0.405 ha - 2.44 m deep
(1 ac - 8 ft deep)
with liner - including land cost
4. Alum System
5. Miscellaneous
Subtotal
Cost
(May 19731
$ 8,000
36,000
43,000
10,000
10,000
$107,000
20% Engineering and
Contingencies 22,000
TOTAL COST $129,000
OPERATING COST ESTIMATE
ALTERNATE A
Primary Treatment
Item
1. Manpower
2. Electricity
3. Steam
4. Water
5. Chemicals
6. Maintenance
Summary:
TOTAL COST/YR
Cost
$ 8,000
2,000
18,000
3,000
$31,000
Costs: $129,000
Reduction Benefits: A BOD reduction of 3.4 kg/ ton (ten
percent) and a suspended solids re-
duction of 6.8 kg/kkg (75 percent) would result.
244
-------
Alternative B-l; Addition of Activated Sludge Process
This alternative includes the addition of an activated sludge
process including pH adjustment and nutrient addition to Al-
ternative A. The effluent from this system would average 3.4
kg/kkg (6.8 Ib/ton) BOD and 2.25 kg/kkg (4.5 Ib/ton) suspended
solids.
The excess water is taken from the process water chest and put
through a rotating drum type screen to remove the larger
particles of fiber and suspended solids. The filtered effluent
is discharged to the feed well of a primary clarifier. The
underflow is pumped to a sludge digester. A portion of this
sludge may be returned to the process water chest. The sludge
from the sludge disgester is pumped to a holding lagoon.
The overflow from the primary clarifier is discharged into an
activated sludge system consisting of an aerated lagoon followed
by a secondary clarifier. The underflow from the secondary
clarifier is transferred to the sludge digester and the overflow
is discharged to waste.
\
INVESTMENT COST ESTIMATE
ALTERNATIVE B-1
Primary Treatment with Activated sludge
Item Cost
(May 1973)
1. Primary Treatment $130,000
2. Activated Sludge 503.000
TOTAL COST $633,000 *
*Includes 20% for engineering and contingencies
OPERATING COST ESTIMATE
ALTERNATIVE B-1
Primary Treatment with Activated sludge
Item Cost
1. Manpower $233,000
2. Electricity 28,000
3. Steam
4. Water
5. Chemicals 29,000
6. Maintenance 24.000
Yearly Costs $314,000
Alternative B-2: Addition of Aerated Lagoon to Alternative A
245
-------
Here, -the excess water is taken from the process water chest and
put through a rotating drum type screen to remove the larger
particles of suspended fiber and solids. The filtered effluent
is discharged into the feed well of a clarifier.
The under flow from the clarifier is pumped to a 0.405 ha (one
acre) pond for sludge dewatering. A portion of this sludge is
returned to process. The clarifier overflow is discharged into
an aerated lagoon for 20 days retention and the aerated effluent
is transferred into a lagoon of 5 days retention time. Effluent
from the 5 day lagoon is discharged to the environment.
246
-------
INVESTMENT COST ESTIMATE
ALTERNATIVE B-2
Screen, Clarifier, and Aeration Lagoon
Item
1.
2.
3.
4.
5.
6.
Rotating Drum Screen installed
Glarifier 7.6 m diam x 3.05 m depth
25 ft diam - 10 ft depth
Sludge Pond - 0.045 ha - 3.05 m depth
(1ac - 10 ft depth )
Aerated Lagoon - 20 day retention
Lagoon - 5 day retention
Miscellaneous ,
Subtotal
20% Engineering and
Contingencies
TOTAL
.OPERATING COST ESTIMATE
ALTERNATIVE B-2
Cost
(May 1973)
$ 8,000
36,000
41,000
225,000
50,000
40,000
$400,000
80yOOQ
$480,000
Item
1. Manpower
2. Electricity
3. Steam
4. Water
5. Chemicals
6. Maintenance
Cost
$ 87,000
21,000
29,000
24.000
TOTAL COST/YR
$161,000
Summary:
Costs: Incremental costs are approximately
$435,000 over Alternative A, thus the
total costs are $544,000.
Reduction Benefits: A BOD reduction of 27 kg/kkg
(90 percent) and a suspended
solids increase from 200 mg/1 to 250 mg/1
Alternative
Addition of An Aerated Lagoon Treatment System to
the Activated Sludge Treatment (B-11 .
— -w^» *— ^«-^v^B«*^W-W^ ^W-^^B-^B^^^— ^••^••i • I • ^—^m***-^l£ ^»— * A_X_^^
This alternative includes the addition of a five day detention
time aerated lagoon to the preceding treatment system in
Alternative B. The effluent from this system would average 1.6
kg/kkg (3.2 Ib/ton) BOD and 2.8 kg/kkg (5.6 Ib/ton) of suspended
solids. The excess water is taken from the process water chest
247
-------
and put through a rotating drum type screen to remove the larger
particles of fiber and suspended solids. The filtered effluent
is discharged into the feed well of a clarifier. Underflow from
the clarifier is pumped to a sludge digester with a portion of
this flow returned to the process water chest. Supernate from
the sludge digester is transferred to a lagoon. The primary
clarifier overflow is treated toy the activated sludge process
consisting of an aerated lagoon and a secondary clarifier. After
activated sludge treatment, the processes effluent is transferred
to a secondary aeration lagoon where after treatment it is
discharged to waste.
INVESTMENT COST ESTIMATE
ALTERNATIVE C
Primary Treatment, Activated Sludge, Aeration Lagoon
Item . Cost
fMay, 1973)
1. Primary Treatment $130,000
2. Activated Sludge Treatment , 500,COO
3. Aerated Lagoon 350,000
TOTAL* $980, 000"
includes 20% for engineering and
contingencies ' . •
OPERATING COST ESTIMATE
ALTERNATIVE C
Primary Treatment, Activated Sludge, Aeration Lagoon
Item ' . Cost
1. Manpower $233,000
2. Electricity 48,000
3. Steam
4. water
5. Chemicals , 29,000
6. Maintenance 49,000
TOTAL COST/YR $359,000
Summary:
Costs: Incremental costs of $299,000 over
Alternative B would be incurred, thus
producing a total cost of $843,000.
Reduction Benefits: A BOD reduction of 1.8 kg/kkg
(150 mg/1) (overall reduction of 95£), and
a suspended solids reduction of 0 percent.
(overall reduction of 69 percent.)
Alternative p-J: Installation of Pre-Press Evaporation of
Process Water Discharge to Lagoon
248
-------
Summary:
This alternative is a new process separate from those discussed
previously. Alternative D consists of the addition of a pre-
press inplant which results in waste water discharges totaling
7.4 I/sec (117 gal/min) being discharged from the pre-press and
the hot press. The total waste flow would be passed through a
screen, primary clarifier, and evaporator. The evaporator
condensate is then discharged.
INVESTMENT COST ESTIMATE
ALTERNATIVE D-1
PRE-PRESS EVAPORATION, LAGOON
Cost
Item (May 19? 3)
1. Davenport Press with Auxiliaries $172,000
2. Rotating Drum Screens installed 8,000
3. Clarif ier 26,0*00
4. Liquor Holding Tank (8 hours) 30,000
5. Quadruple Effect Evaporators with
surface Condensers (304 SS wetbed parts) 250,000
6. Cooling Tower with Transfer Pumps (2) 30,000
7. Sludge Lagoon (100 days) 22,500
8. Alum Storage and Metering System 10,000
Subtotal $546,000
20% Engineering and
Contingencies 109TOOQ
TOTAL $655,000
OPERATING COST ESTIMATE
ALTERNATIVE D-1
PRE-PRESS EVAPORATION, LAGOON
Item Cost
1. Manpower $175,000
2. Electricity 8,000
3. Steam 92,000
4. Water 1,000
5. Chemicals 18,000
6. Product Worth (deduct) 89,000
7. Maintenance 36,000
TOTAL COST/YR 241,000
Costs; Total cost of this system would
be $655,000.
Reduction Benefits: The BODfi of this system would
average 2.0 kg/kkg production (4.0 Ib/ton)
and the suspended solids would average 0.46 kg/kkg
production (1.0 Ib/ton) for an overall reduction
of 99.4 percent and 86 percent, respectively.
249
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ACTIVATED SLUDGE TREATMENT OF CONDENSATE PRIOR TO DISCHARGE
ALTERNATIVE D-2
Approximately 90 percent of the contaminated condensate flow from
the evaporators is treated biologically in an activated sludge
process. The pH is first adjusted with lime and polymers are
added to assist settling in the clarifier. The treated flow
enters an aeration lagoon of approximately one day retention
time. The flow is transferred to the feed well of a clarifier
designed for 16,300 1/sq m/day (400 gal/sq ft/day) The overflow
from the clarifier is discharged to the environment.
The underflow is pumped back to the inlet of the aeration lagoon
with part of this flow sent to a sludge digester and on to a
holding lagoon.
INVESTMENT COST ESTIMATE
ALTERNATIVE D-2
Activated Sludge Treatment Of Evaporator Condensate
Item Cost
(May, 1973)
1. Neutralization System - Lime with Bucfcet
Elevator, Lime Storage Tank Feeder, Shutoff
Gate, Slurry Holding Tank with Agitator. Slurry
Pumps $23,000
2. Aeration Basin-621 cu m (164,000 gal) with
Aerator, Pumping Station 39,400
3. Clarifier - 1.7.6 m diam (25 ft diam) - Steel with
Feed Well Rake Mechanism and Drive, 3 sludge pumps
(100 gal/min 3 50 ft TDH) 36,000
4. Waste Sludge Handling
a. Aerobic Digester Basin - 140 cu m
(37,000 gal)
3.6 m(12-ft) deep with liner - Aerator 37,400
b. Two ha (five acre) lagoon with liner 15,000
1.8 m (6-ft) deep
Subtotal $150,800
20% Engineering and
Contingencies 30,200
TOTAL $181,bo5
OPERATING COST ESTIMATE
ALTERNATIVE D-2
ACTIVATED SLUDGE TREATMENT OF EVAPORATOR CONDENSATE
Item Cost
250
-------
1. Manpower $233,000
2. Electricity 5,000
3. Steam - -
4. Water
5. Chemicals 11,000
6. Maintenance 8,000
TOTAL COST/YR $257,000
Summary:
Costs: The add on cost for this
system is $181,000.
Reduction Benefits: The BODS of this system would
average 0.2 kg/kfcg production (0.4 Ib/ton)
and the suspended solids would average
0.46 kg/kkg (0.9 Ib/ton) .
SUMMARY OF TREATMENT EFFICIENCIES OF ALTERNATIVES
Flow (cu m/day) 1,432 1,432 1,432 1,432 627 627
Alternatives
Parameters A B-1 B-2 C D-1 D-2
Raw BOD mg/1 3,000 3,000 3,000 3,000 6,825 6,825
Eff. BOD mg/1 2,700 300 600 150 450 45
Raw SS mg/1 800 800 800 800 200 200
Eff. SS mg/1 200 250 250 250 100 250
Raw BOD kg/kkg 33.8 33.8 33.8 33.8 33.8 33.8
Eff BOD kg/kkg 26.7 2.8 6.8 1.7 2.0 0.2
Raw SS kg/kkg 9.0 9.0 9.0 9.0 0.9 0.9
Eff. SS kg/kkg 2.1 2.5 2.5 2.5 0.5 1.3
SUMMARY OF ALTERNATIVE COSTS, AUGUST 1971
% BOD Investment Yearly Operating Total Yearly
Alternative Removal Cost Cost Cost $&
A
B-1
B-2
C
D-1
D-2
10
90
80
95
93.5
99.4
$109,000
544,000
413,000
843.000
566.000
722.000
$ 26,700
270,000
138T500
308,800
207,000
428,000
$36,500
319,000
175,000
385.000
258,000
493,000
251
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Factors Involved in the Installation of Alternative A
All existing wet process hardboard mills presently have screening
and settling or the equivalent of primary settling as part of
their treatment systems. Several mills utilize a single lagoon
or pond for both settling and sludge storage. The use of a
settling and storage pond in one unit is not desirable because of
anaerobic decomposition which resuspends solids and releases
dissolved organics into the effluent. The primary clarifier
recommended in Alternative A consists of a mechanical clarifier
with continuous sludge wasting to a sludge lagoon.
Mechanical clarifiers are one of the simplest and most dependable
waste treatment systems available. They are not sensitive to
shock loads and shutdown and start-up of manufacturing processes
have little or no effect. Primary clarifiers and screening
devices are readily available on the market and an estimated time
of one year would be required for the design and construction of
such a facility. It is estimated that an area less than 0.6 ha
(1.5 ac) would be required for this system. The additional
energy required to operate this system is estimated to be 22 kwh.
There are no noise or radiation effects related to this process;
however, the disposal of 285 kg/day of solids into a sludge
lagoon may be a source of odor problems.
Factors involved in the Installation of Alternative B
Alternative B consists of an activated sludge system following
the facilities previously discussed in Alternative A. Activated
sludge treatment of wet process hardboard mill waste can be quite
effective. However, the system has all of the problems
associated with activated sludge treatment of domestic plus
several more. These include the necessity for pH control and
nutrient addition. Another major problem is that the sludge pro-
duced does not readily settle. This can frequently cause high
suspended solids in the effluent. Temperature apparently has an
effect not only in reducing the biological reaction rates during
cold weather, but also in affecting the settling rates of the
mixed liquor suspended solids.
Activated sludge systems require constant supervision and
maintenance. They are quite sensitive to shock loads and to
shut-down and start-up operations of the manufacturing process.
The equipment needed for activated sludge systems is available on
the market; however, up to two years may be required from
initiation of design until beginning of plant operation. The
energy requirements as high as approximately 320 kilowatts are
needed to operate the process. There is essentially no noise or
radiation effects associated with the process; however, the
disposal of waste solids each day can cause odor problems.
252
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factors Involved in The Installation Of Alternative c
Alternative C consists of an aerated lagoon following the process
described in Alternative B. Similar problems associated with the
operation of an activated sludge process hold true with this
system. Sludge loadings are not a problem. Temperature does
affect the system as it does any biological system.. The only
additional equipment necessary for this system is aeration
equipment of which an additional 225 Kw of energy is required.
The estimated time of construction of this facility is one year
from initiation of design. No noise or radiation problems are
associated with this process, nor are there any odor problems.
Factors involved in the Installation of Alternative b
Alternative D is a completely different system from those
described in Alternatives A through C and may involve process
modifications. This system consists of the installation of a
pre-press inside the wet process mill to dewater the stock
betwe'en the cyclone and the .stock chest. This allows a projected
decrease in waste water flow from 1,432 cu m/day (0.378 million
gal) to 629 cu m/day (0.166 million gal). Waste water from the
pre-press and the wet press will first be treated through a
screening and clarification system as described in Alternative A.
Next, instead of using a biological system to remove organics, an
evaporation system is used. This system produces a saleable by-
product (being produced at two mills) . A portion of the
condensate is recycled back inplant and the remaining process
water is treated in an activated sludge" system similar to the
system described in Alternative B.
Evaporation systems must be fed at a relatively constant rate as
they are sensitive to shock loads. Maintenance requirements are
high because of the nature of the material being evaporated. The
evaporator must be cleaned out weekly, if not more frequently.
Evaporation equipment can be obtained on the market; however, a
two year period from initiation of design until start-up is not
unreasonable. Noise and radiation effects are minor, but energy
requirements for steam and electricity are significant. For
example, approximately 150 kw are required to operate the system
in addition to steam requirements. Air pollution factors are
related to the energy requirement as fuel must be burned to
produce both steam and electricity.
WOOD PRESERVING-STEAM
Alternative Treatment and Control Technologies
253
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Cost figures which have been obtained for wood preserving plants
vary widely for a number of reasons. In order to attempt to
provide a reasonable common basis for comparison, a hypothetical
waste treatment facility was devised to meet the suggested
standards and costs estimated based on May 1973 construction
data.
The treatments to be provided are; A - Oil separation; B -
Coagulation and filtration; Biological treatment in aerated
lagoons; - Biological treatment by or activated sludge; D -
Chlorination as a polishing treatment. The two biological
treatments are alternates, and either one or the other is
intended to be used. For estimating purposes, a waste water flow
of 53,000 I/day (14,000 gal/day) was used. The waste loading and
quality of effluent which is expected from each stage of
treatment suggested is as follows;
QUALITY OF EFFLUENT FROM EACH STAGE OF A WASTE TREATMENT SYSTEM
Parameter
Raw
Waste
Treatments
(mg/1)
B C
D
COD
40,000
7,260
3,630
410
300
Phenols 190
Oil 6 Grease 1,500
190
225
190
80
2.5
45
0.5
25
ENGINEERING ESTIMATES FOR A WOOD PRESERVING - STEAM PLANT
Alternative A: Oil Separation
Standard oil separation equipment, equipped for both surface and
bottom removal, can be used for this purpose. Depending on the
treating preservatives used, provisions must be made for both
surface and bottom removal creosote tends to settle while
pentachlorophenol in oil will rise to the surface.
INVESTMENT COST ESTIMATE
ALTERNATIVE A
Oil Separation
Item
1. Land including clearing
2, Oil separator, installed
Cost
$ 2,000
18,000
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3. Pumps, motors, starters, lighting 1,200
4. Pipe, valves, fittings 2,500
5. Piping labor 600
6. Electrical labor 500
Subtotal $24,800
Engineering contingencies 4,960
TOTAL $29,760
Summary:
Capital cost $29,760
Annualized cost including operation and
and maintenance $0.31/1000 1
Alternative B^ Coagulation and Filtration
The coagulation and filtration system would also serve to
equalize variations in rate of flow. Several possibilities
present themselves, but to economize on space a multi-compartment
tank or several tanks, rather than lagoons were selected.
Basically, the waste water would enter a tank from which a
constant flow could be admitted to a rapid mix tank where a
proportioning pump would add the coagulant chemical.
Approximately one half hour of rapid mixing would be followed by
one hour of slow mixing of the waste water/coagulant. This would
be followed by about 6 hours of sedimentation. The filtration
system would be slow sand filters with a total area of about 93
sq m (1000 sq ft).
INVESTMENT COST ESTIMATE
ALTERNATIVE B
Coagulation and Filtration
Item Cost
1. Land including clearing $10,000
2. Equalization tank 2,000
3. Coagulation tank . 15,000
4. Pumps, motors, starters, lighting 1,500
5. Sand filters 4,000
6. Pipe, valves, fittings 2,000
7. Piping labor 1,000
8. Electrical labor 600
Subtotal $36,100
Engineering and contingencies 7,220
Total for B $42,320
Summary:
Capital cost $42,320
Annualized cost including operation
and maintenance $0.70/1000 1
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Alternative C-l^_ Biological Treatment, Aerated Lagoon
This treatment should result in a waste water having a BOD of
about 3000 mg/1 or about 375 Ib/day. Assuming a normal aeration
efficiency, an aerated lagoon would require an input of about 15
hp to provide the necessary treatment. The necessary detention
time would require a volume of 1.06 million 1 (280,000 gal). For
about a 3 m depth (10 ft), 353 sq m (less than 0.1 ac) of surface
area will be required. Two aerators of 7.5 hp each were selected
and are sufficient to provide the necessary aeration.
Item
1. Land including clearing
2. Liner, installed 3 $0.50 per sq ft
3. Two 7.5 hp aerators, installed
4. Pumps, motors, starters, lighting
5. Pipes, valves, fittings
6, Piping labor
7. Electrical labor
Subtotal
Engineering and contingencies
Total for C-l
Summary:
Capital cost
Annualized cost including operation
and maintenance
Alternative C-^i Biological Treatment, Activated Sludge
Cost
$3,000
3,000
7,600
1,500
. 1,200
800
500
$17,600
3f520
$21,120
$21,120
$0.70/1000 1
The proposed activated sludge plant design is based on the same
influent BOD loading of about 3000 mg/1 or about 375 Ib/day.
Assuming 0.2 Ib BOD will produce one Ib of mixed liquor suspended
solids (MLSS) and assuming a desirable concentration of 2500 mg/1
of MLSS, an aeration tank volume of 341,000 1 '{90,000 gal) is
required. Therefore a 378,000 I/day (100,000 gal/day) activated
sludge package plant was selected.
256
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INVESTMENT COST ESTIMATE
ALTERNATIVE C-2
Biological Treatment, Activated Sludge
Item Cost
1. Land, package plant and installation $100,000
2. Engineering and contingencies 20,000
TOTAL COST $120,000
Summary:
Capital cost $120,000
Annualized cost including
operation and maintenance $1.75/1000 1
Alternative D: Polishing Treatment, Chlorination
The chlorination facility is intended to provide for a chlorine
dosage of up to 500 mg/1. For a design flow of 53,000 I/day
(14,000 gal/day) this will require up to 27 kg (60 Ib) of
chlorine per day. A detention time of 3 to 6 hours will be
provided. For ease of handling, 200 Ib cylinders were selected.
INVESTMENT COST ESTIMATE
ALTERNATIVE D
Polishing, Chlorination
Item Cost
1. Chlorinator, installed $4,000
2. Detention tank, installed 1,000
3. Automatic sampler, installed 1,200
4. Truck hand stand 800
Subtotal $7,000
Engineering and contingen-
cies 1,400
TOTAL COST $8,400
Summary:
Capital cost $8,400
Annualized cost including
operation and maintenance $0.64/1000 1
Alternative E:. Effluent Measurement
A recording flow measurement device was selected.
INVESTIMATE COS! ESTIMATE
ALTERNATIVE E
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Flow Recording Device
Item Cost
1. Measuring element with recorder $2500
2. Installation 500
Subtotal $3,000
Engineering and contingen-
cies 600
TOTAL COST $3,600
Summary:
Capital cost $3,600
Annualized cost including $0.16/1000 1
operation and maintenance
Total capital costs for complete treatment
with lagoons: $106,200
Annualized cost for same system: $3.45/1000 1
WOOD PRESERVING
As discussed in Section III through VII, discharge of waste water
pollutants can be controlled by wood preserving plants in this
sufacategory by implementation of in-process control technologies.
Therefore there are no costs directly related to pollution
control.
Non-Water Quality Aspects
None of the waste water treatment and control technologies
discussed above has a significant effect on non-water
environmental quality. The limited volume of sludge generated by
coagulation and biological treatments of waste water is currently
being disposed of in approved landfills by most plants. Because
the organic components of these sludges are biodegradable, this
practice should present no threat to the environment.
WOOD PRESERVING - BOULTONIZING
The most common method of waste disposal in this subcategory is
evaporation. Following oil separation the waste water is pumped
to a cooling tower for reuse as cooling water. For an average
waste flow of 15,100 I/day {4,000 gal/day), approximately one-
half of the water is evaporated during the normal operation of
the tower. The excess water, about 7,600 I/day (2,000 gal/day),
is evaporated by raising the temperature of the water in the
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tower reservoir using a small heat exchanger. Pan evaporation
may also be used. However, since the volume of water involved
and the heat energy required for evaporation is about the same
for the two methods, the calculations which follow are based on
using a cooling tower.
The cost of a cooling tower of a size needed at an average plant
is $24,000, including heat-exchanger and overhead fan to expedite
evaporation. Because a tower would be required regardless of
pollution control activities, the total investment cannot
legitimately be charged to those activities. Thus, in computing
capital investment only 50 percent of the tower cost was used.
This percentage was selected because the tower is used as a
pollution-control device to evaporate only one-half of the waste
water from a typical plant. Tiie balance is ^ost regardless of
pollution-control objectives.
Capital investment in other equipment directly concerned with
pollution-control is estimated to be $20,000. All of this sum is
for oil separation, storage and transport of recovered oil, and
holding tanks and pumps for handling oil separator effluent. The
total investment amounts to $32,000.
Operating costs, exclusive of energy requirroents, are estimated
to be $2,595/yr, or about $T,14/1000 1 ($4.32/1000 gal). This
item is broken down as follows:
Item Cost
1. Labor $1800
2. Repair Parts 795
TOTAL $2595
Labor cost is based on 300 man-hr/yr and an hourly wage rate of
$6.00.
Energy is the most expensive item in disposing of wastewater by
evaporation. Fuel cost to evaporate 7,600 I/day (2,000 gal/day)
is estimated to be $14.54, for an annual cost of $4,361. This
estimate is based on using natural gas for fuel, a heat of
vaporization at 38°C(100°F) of 1739 kg cal/fcg (1035' BTU/lb), an
overall heating efficiency of 65 percent, and gas costing
$19.42/1000 cu m ($.55 1000 cu m) . Electric power to operate an
overhead fan is estimated to cost $150 annually.
The total annual cost of this scheme for waste disposal is
approximately $12,228 or about $5,38/1000 1 ($20.38/1000 gal) of
excess water evaporated. If water evaporated because Of the
normal operation of the cooling tower is included, the per unit
cost would be only one-half as great.
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SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
The effluent limitations which must be achieved by July 1, 1977*
are to specify the degree of effluent reduction attainable
through the application of the best practicable control
technology currently available. Best practicable control
technology currently available is generally based upon the
average of the best existing performance by plants of various
sizes, ages, and unit processes within the industrial category or
subcategory. This average is not based upon a broad range of
plants within the timber products processing category, but rather
based upon performance levels achieved by exemplary plants or
best operating unit operations.
Consideration must also be given to;
(a) The total cost of application of technology
in relation to the effluent reduction bene-
fits to be achieved from such application;
(b) The size and age of equipment and facilities
involved;
(c) The processes employed;
(d) The engineering aspects of the application
of various types of control techniques;
(e) Process changes, and;
(f) Nonwater quality environmental impact,
including energy requirements.
Best Practicable Control Technology Currently Available
emphasizes treatment facilities at the end of a manufacturing
process but includes the control technologies within the process
itself when the latter are considered to be normal practice
within an industry.
A further consideration is the degree of economic and engineering
reliability which must be established for the technology to be
"currently available." As a result of demonstration projects,
pilot plants, and general use, there must exist a high degree of
confidence in the engineering and economic practicability of the
technology at the time of commencement of construction or
installation of the control facilities.
BARKING
Identification of Best Practicable
Control Technology Currently Available
Barking is an almost industry-wide pre-processing operation which
has been treated as a separate subcategory for the reasons given
in Sections III and IV of this document. The barking operation
consists solely of removing bark by pressure or abrasion
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Summary
Based upon the ipformation contained in Sections III through VIII
of this document and summarized above, a determination has been
made that the degree of effluent reduction attainable and the
maximum allowable discharge in the Barking subcategory thorugh
the application of the best practicable technology currently
available is no discharge of waste water pollutants to navigable
waters.
A variance shall be allowed for those barking operations
utilizing a hydraulic barker. Based upon the information
contained in Section III through VIII of this document and
summarized above, a determination has been made that the degree
of effluent reduction attainable and the maximum allowable
discharge in the Barking subcategory for hydraulic barkers in
preparation for veneer or plywood manufacture, is through the
application of the best practicable control technology currently
available, as follows:
30-day Average Daily Maximum
(Ib/cu ft) (Ib/cu ft^
kg/cu m Jcg/cu m
BOD5 0.5 1.5
(0.03) (0.09)
Total
Suspended 2.3 6.9
Solids (0.14) (0.43)
pH Within the range 6.0 to 9.0
VENEER
Identification of Best Practicable Control Technology' Currently
Available
The manufacture of veneer may or may not result in the generation
of process waste water, depending on the types of manufacturing
procedures used. The unit operations required in veneer
manufacture have been discussed in detail in Section III, the
wastes derived from each of the operations characterized in
Section V, and treatment and control technology, when applicable,
detailed in Section VII.
An extensive technology exists which, when applied to each of the
unit operations in this subcategory, will result in no discharge
of waste water pollutants. While the technology exists, it is
not, however, uniformly applied.
To meet this standard of" no discharge requires the implementation
of the following control technologies:
1. Substituting, for direct steam conditioning of logs, (a)
hot water spray tunnels, (b) indirect steaming or (c) modified
264
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steaming with the use of steam coils. Hot water spray tunnels
where water is heated and then sprayed on the logs can be
placed in existing steam vats with only minor modifications,
and the hot water collected and reused after settling and
screening. Modified steaming produces, after the steam
contacts the wood, a condensate which may be revaporized and
reused. The small volume wood based sludge that is generated
can be disposed or the procedures discussed in Section VII.
2. Discharge of contaminated waste water from hot water vats,
where the water is heated indirectly, to a settling basin, with
possible pH adjustment, and later reuse.
3. Manual removal of a portion of solid waste in the veneer
dryer, the use of air to blow out dust before using water,
installation of water meters on water hoses used for washing
and the disposal of excess veneer dryer washing water by
irrigation, or containment and evaporation. At least one 9.3
million sq m plant has reduced its water use for this purpose
to 2,000 1/wk (530 gal/wk). By limiting water use to 3,000
1/wk, this water can be handled by containment or irrigation.
Rationale for the Selection of Best Practicable Control Technolocry
Currently Available
Age and Size of Equipment and Facilities
As discussed in Section IV, the age and size of a veneer
manufacturing plant do not bear directly on the quantity or quality
of the waste water pollutants generated. The age of a plant may,
however, be a factor in the type of log conditioning procedure
used, and thus in the selection of a variance and its associated
waste water control technology.
Processes Employed and Engineering Aspects
All plants in this subcategory use essentially the same or similar
production methods and equipment. Sections III and VII treat these
process aspects in great detail.
Each of the technologies outlined above have been identified as
being in use in some portion of the veneer subcategory of the
timber products processing industry. No plant, however, has been
found to utilize all of these control procedures. About 100 of the
500 veneer and plywood plants have retention of water from log
conditioning, and 90 plants have control systems which eliminate
the discharge of dryer wash water.
Process Changes
Certain peripheral process modifications will inevitably be
necessary in the veneer manufacturing subcategory, in order to meet
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the no discharge regulation. As indicated in the economic analysis
in Section VIII, a modification of log conditioning procedures is
more economically feasible than the addition of the biological
-treatment units necessary to reduce BOD and solids loading from the
open steaming conditioning process.
Employing the processes above, a softwood veneer plant supplying a
9.31 million sq m/yr plywood on a 0.53 mm basis production facility
that uses steam vats with direct steaming would have a continuous
effluent of about 1.9 I/ sec (30 gal/min) with a BOD loading of
about 410 kg/ day at 2500 mg/1 concentration and a suspended solids
loading of 325 kg/day at 2000 mg/1 concentration. Applying 85
percent BOD removal efficiency can reduce BOD to 61 kg/day, or 2.3
kg/1000 sq m of production, on a 9.53 mm
A hardwood veneer plant supplying a 0.465 million sq m/yr (5
million sq ft/yr) plywood production plant using steam vats with
direct steaming would have a continuous effluent of about 0.5 I/sec
( 8 gal/mi n) with a BOD loading of 30 kg/day at 200 mg/1
concentration and a suspended solids loading of 26 kg/day at a
concentration of 700 mg/1. Applying 85 percent BOD removal
efficiency can reduce BOD to 4.5 kg/day, or 3.4 kg/1000 cu m.
As discussed earlier, alternative procedures for conditioning of
logs exist and indications are that the more practical procedures
would be the selection of those methods that eliminate the
discharge of pollutants.
The volumes of water required for cleaning of veneer dryers have
been determined to be relatively small. Softwood veneer dryer
waste water is in the range of 2600 I/day and hardwood about 530
I/day. BOD5 waste loads are, for softwood 2.0 kg/day and for
hardwood 0.5 kg/day. Softwood plant production base is 9.5 million
sq m/yr. Hardwood plant production base is 0.46 million sq m/yr.
Because of the small volumes of water the relative ease of disposal
on land, and the impracticality of application of biological
treatment to this waste water a discharge will not be allowed,
except to an existing biological treatment system. The small waste
loads attributed to dryer wash water will have no effect on the
operation and efficiency of the treatment system. The pollutant
discharge from the biological treatment system serving a timber
products processing complex will not be increased to allow credit
for the veneer dryer cleaning input.
Nonwater Quality Impact and Energy Requirements
There are potentially three nonwater related pollutants: (1)
emission of particulates from the veneer dryer, (2) odors released
from anaerobic containment ponds, and (3) solid wastes.
There are currently no emission control systems installed on veneer
dryers. There is, however, transferrable technology applicable.
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Particulates can be controlled utilizing inertial collectors of the
cyclone or mechanical type. Volatile and condensable hydrocarbons
can be controlled by condensation, adsorption or scrubbing,
incineration, or combinations of the three. As air emission
standards become more stringent, control of particulate matter may
require the use of wet scrubbers, thus resulting in a waste water
relatively high in solids content.
The bulk of the solid waste from veneer mills is comprised of wood
residues and bark. These wastes are commonly used as fuel in the
boiler. In addition to wood wastes are the settleable solids that
accumulate in ponds and those that are separated in screening
devices. Disposal of the small amounts of this material which
result may be at the plant site or the waste material may be
collected by the local municipality with eventual disposal by
landfill. The proper disposal of these wastes will ensure that
they present no significant non-water quality environmental
problem.
In terms of energy requirements, a 9.3 million sq m/year veneer and
plywood plant will have a total energy demand of 4500 kw and a
manufacturing energy cost of $180,000. Additional costs for
implementation of the pollution control technology discussed here
and in section VII range from $0 to $2300/yr. These figures are
more closely examined in Section VIII.
Summary
Based upon the information contained in Sections III through VIII
of this document and summarized above, a determination has been
made that the degree of effluent reduction attainable for all
sources in the veneer manufacturing subcategory excluding those
which use direct steam conditioning as described below, through the
application of the Best Practicable Control Technology Currently
Available is no discharge of process waste water pollutants to
navigable waters.
A variance will be allowed for those plants that both (1) as part
of their existing equipment use a log conditioning method rhat
injects steam directly into the conditioning vat, and (2) find it
infeasible to implement the technology discussed above.
Based upon the information contained in Sections III through VIII
of this document and summarized above, a determination has been
made that the degree of effluent reduction attainable for all
sources in the Veneer manufacturing subcategory which use the
direct steam conditioning as described above, through the
application of the Best Practicable Control Technology Currently
Available is as follows:
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BOD
Softwood
Veneer:
Hardwood
Veneer:
30-Day
Average
kg/cu m
(Ib/cu ft)
0.24
(0.015)
0.54
(0.034)
Daily
Maximum
kg/cu m
(Ib/cu ft)
0.72
(0.045)
1.62
(0.10)
6.0-9.0
6.0-9.0
PLYWOOD
Identification of the Best Practicable Control Technology Currently
Available
Plywood may include several distinct process steps. Alternatively
some of these may take place in the veneer manufacturing and
processing location. These steps are: (1) drying, (2) clipping,
(3) gluing, (4) pressing, and (5) trimming and packaging.
The unit operations required in plywood manufacturing have been
discussed in detail in Section III, the waste derived from each of
the operations characterized in Section V, and treatment and
control technology, as applicable, detailed in Section VII.
Technologies exist which, when applied to the unit operations
in this subcategory, will result in no discharge of pollutants.
While the technology exists, it is not uniformly applied. To meet
this standard of no discharge requires the implementation of a
portion or all of the following control technologies:
1. The use of steam to clean spreaders where applicable
and the use of high pressure water for cleaning;
2.
3.
4.
The use of glue applicators that spray
rather than rollers;
the glue on
The use of glue washwater for glue makeup; and
Evaporation and spray application of glue water on
bark going to the incinerator.
Rationale for the Selection of Best Practicable Control Technology
Currently Available
Age and Size of Equipment and Facilities
As discussed in section IV, the age and size of a plywood
manufacturing plant do not bear directly on a quantity or quality
of the waste water pollutants generated.
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Processes Employed and Engineering Aspects
All plants in this subcategory use essentially the same or similar
production methods and equipment. Sections III and VII treat these
process aspects in great detail.
Each of the technologies outlined above have been identified as
being in use in some portion of the plywood subcategory of the
timber products processing industry. Yet no plant has been found
which utilizes all of these control procedures. About 100 of the
500 veneer and plywood plants have retention of water from log
conditioning, and aboul: 90 plants have control systems which
eliminate the discharge of dryer wash water.
Process Changes
Certain peripheral process modifications will inevitably be
necessary in the plywood manufacturing subcategory, in order to
meet the no discharge regulation. These are discussed in detail in
section VII and summarized, above.
Nonwater Quality Impact and Energy Requirements
The bulk of the solid waste from plywood mills is comprised of wood
residues. These wastes are commonly used as fuel in the boiler.
In addition to wood wastes are ,the settleable solids that
accumulate in ponds and those that are separated in screening
devices. Disposal of this material may be at the plant site or the
waste material may be collected by the local municipality with
eventual disposal by landfill. The amount of solids generated from
these procedures is not expected to be great and proper disposal
will ensure that they present no significant nonwater quality
environmental problem,
In terms of energy requirements, a 9.3 million sq m/yr veneer and
plywood manufacturing planti will have a total energy demand of
45,COO lew and a yearly energy^cost of $180,000. Additional costs
for implementation of the pollution control technology discussed
here and in section VII range from $0 to $2300/yr. These figures
are more closely examined in Section VIII.
Summary
Based upon , the information contained in Sections III through VIII
of this document and summarized above, a determination has been
made that the degree of .effluent reduction attainable in the
Plywood manufacturing subcategory through the application of the
Best Practicable Control Technology Currently Available is no
discharge of process waste water pollutants to navigable waters.
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HARDBOARD-DRY PROCESS
Identification of. Best Practicable
Control Technology Currently Available
The manufacture of hardboard using the dry process, as discussed in
Sections III and IV is accomplished through a series of operations
that for the purposes of developing effluent guidelines and
standards were considered on a unit operation basis. Water
requirements, waste water generation and quality, and opportunities
for reuse and disposal, either within the unit operation or in
other operations in the dry process hardboard manufacturing
process, were determined from this information. Dry process
hardboard manufacturing focuses on seven primary unit operations:
(1) log washing, (2) chipping, <3) fiber preparation, (4) dry-
felting, (5) pressing and tempering, (6) humidification, and (7)
trimming and packaging.
It has been demonstrated that technologies exist (discussed in
Section VII) which, when applied to each of the unit operations,
will result in no discharge of pollutants. To meet the standard of
no discharge requires the iimplementation of the following control
technologies:
1. Recycle of log wash and chip wash water and disposal of
the solids by landfill or use as boiler fuel.
2. Operation of the resin system as a closed system, with
wash water being recycled as make-up in the resin
solution.
3. Neutralization of caul water, and disposal by impoundment
or spray irrigation.
4. Elimination of discharge from humidification by the
implementation of in-plant control, including reasonable
operating and process management processes.
Rationale for the Selection of Best Practicable Control Technology
Currently Available
Processes Employed and Engineering Aspects
Log washing in the dry process hardboard manufacturing subcategory
is practiced by about 15 percent of the mills. The volume and the
characteristics of the waste waters vary depending on harvesting,
transportation and storage practices and conditions. Wash water
may be fresh, process, or cooling water and can be recycled after
settling. Slowdown is required only infrequently and one of the
two plants currently washing logs is disposing of the small volume
of water by land irrigation. Settled sludge may be disposed of by
landfill.
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Water used in the formulation of binders for hardboard can be
incorporated in the hardboard and disposed of by evaporation in the
pressing operation. Waste water is generated only during cleaning
of the resin system, and the opportunity for use of the washwater
in makeup of resin solutions exists. For these reasons the resin
system can be operated on a closed system, and 6 out of 16 dry
process hardboard mills are currently achieving no discharge from
their resin systems.
Caul washwater is a relatively small volume of water, amounting to
approximately 4 1/kkg of production. This water is a caustic
solution used to loosen the organic buildup on the cauls or press
plates. It is replaced periodically when the concentration of
dissolved organics builds up to a level that inhibits cleaning of
the plates. Before disposal the washwater is usually neutralized
and the relatively small volume disposed of by impoundment or spray
irrigation.
There are no waste water losses in fiber preparation other than
evaporative losses, no waste water is generated in the forming and
pressing operations, and more than half of the mills report no
discharge of process water from the humidification operation.
Process Changes
There are no process changes necessary in order to eliminate the
discharge of waste water pollutants, but rather the implementation
of recycle and careful water management procedures. Settling ponds
may be necessary in some instances as indicated.
The primary costs and changes associated with achieving no
discharge of waste water pollutants are related to the removal of
caul washwater as a pollutant. Waste water generation from this
operation in normal operating practice is about 41/kkg (1 gal/ton)
of production. A system including volume retention of one week's
caul washwater (6,700 1) and transportation costs to a land
disposal site would cost about $25,000/yr. Operation and
maintenance costs for this system would be about $3,000/yr.
Nonwater Quality Impact and Energy Requirements
The single nonwater quality environmental impact from the treatment
and control technologies presented is the problem of disposal of
minor volumes of sludges. Proper disposal will ensure that solid
waste presents no significant non-water quality impact.
Energy costs are limited to pumping and instrument operation and
are estimated to be less than $100/yr. About 50 percent of the
plants in this subcategory will be required to add treatment and
control systems to comply with this alternative.
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Summary
Based upon the information contained in Sections III through VIII
of this document and summarized above, a determination has been
made that the degree of effluent reduction attainable in the
Hardboard-Dry Process manufacturing subcategory through the
application of the Best Practicable Control Technology Currently
Available is no discharge of process waste water pollutants to
navigable waters.
No limit is established for fire control water. This effluent will
be collected and should receive at least primary screening before
discharge.
HARDBOARP-WET PROCESS
Identification of Best Practicable Control Technology Currently Available
Wet process hardboard is manufactured using seven distinct process
steps or unit operations: (1) log washing, (2) chipping, (3) fiber
preparation, (4) wet-felting (mat formation), (5) drying and
pressing, (6) numidification, and (7) trimming and packaging. Each
of these unit operations has been discussed in detail in section
III, the wastes derived and characterized in Section V, and
treatment and control technologies detailed in"Section VII.
Technology is currently available and demonstrated which can reduce
the level of pollutants to zero in all of the unit operations, with
the exception of those singular to the fiber preparation and mat
forming process. Treatment and control schemes are in use in
individual plants within this subcategory, which reduce pollutant
discharge to the best practicable control technology limits as set
forth herein.
To meet the limitation in wet process hardboard manufacturing
requires the implementation of the recycle and water management
policies described in Section VII and summarized in the following
paragraphs on the wet process hazdboard sutcategory.
The best practicable control technology currently available which
will result in reduced pollutant loading requires the
implementation of all or part of the following:
1. Recycle of process water as dilution water, utilization of
heat exchangers to reduce temperature, and gravity
settling, screening, filtration, or flotation to reduce
suspended solids.
2. Treatment of total waste water flow by primary settling
combined with screening, and followed by aerated lagoons
or activated sludge or both, with probable pH adjustment
prior to biological treatment.
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3. Disposal of sludge by aerobic digestion in sludge lagoons,
recycle inplant, or as land fill.
Rationale for the Seletion of Best Practicable Control Technology
Currently Available
Processes Employed and Engineering Aspects
The level of technology summarized above, and the effluent
reductions suggested are being attained by 22 percent of the
manufacturing plants in this subcategory. Four (U) mills are
reaching 60 to 90 percent efficiencies for suspended solids removal
through the use of filters and gravity separators. One mill has
reduced its discharge, by inplant modifications without end of line
treatment, to 2.3 cu m/kkg of production (630 gal/ton) and BOD
discharge to 8.5 kg/kkg (17 Ib/ton). Two (2) plants are known to
use chemical treatment combined with sedimentation and flotation to
reduce solids, COD, and soluble organics. All of the ten wet
process plants have screening and primary clarification/ 3 mills
have activated sludge systems, 2 use activated sludge followed by
an aerated lagoon, and 2 plants evaporate process water and dispose
of the solids by land disposal or selling the concentrated solids
as cattle feed.
Information obtained from 5 wet process plants showed an average
waste water discharge of 9.0 cu m/kkg of production (2376 gal/ton).
Raw waste water characteristics were 27.8 kg/kkg (61.1 Ib/ton) BOD,
and 8.4 kg/kkg (18.5 Ibs/ton) suspended solids.
The treatment and control technologies summarized above are each in
use in at least one manufacturing plant in this subcategory, and
each has a demonstrated high degree of engineering reliability.
Process Changes
There are no significant process changes required; rather the
addition of certain treatment capabilities and implementation of
water recycle and conservation practices will be needed to meet
these limitations.
Non-Water Quality Impact and Energy Requirements
Sludge generated in the treatment systems must be disposed of, and
as land fill is one suggested means of disposal, there may be some
minor environmental impact. Proper disposal techniques will ensure
that the non-water quality impact is minimal.
Energy costs for alternative technologies are: screening and
primary settling, $2,000/yr; activated sludge after screening and
clarification, $28,000/yr; aerated lagoon after screening and
clarification, $21,000/yr; and aerated lagoon after screening,
clarification and activated sludge, $48,000/yr (based on an
electricity cost of $0.01/kwh).
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Summary
Based upon the information contained in sections III through VIII
of this document, a determination has been made that the degree of
effluent reduction attainable and the maximum allowable discharge
in the wet process hardboard subcategory through the application of
the best practicable control technology currently available is as
set forth in the following table:
30-Day Daily
Average Maximum
kg/kkg kg/kkg
(Ib/ton) (Ib/ton)
BODS
Total
Suspended Solids
pH
2.6
(5.2)
5.5
(11.0)
6.0-9.0
7.8
(15.6)
16.5
(33.0)
6.0-9.0
WOOD PRESERVING
Identification of Best Practicable Control Technology Currently
Available
The manufacturing, process in this subcategory consists primarily of
indirect heat conditioning and preservative injection operations.
There are numerous differences in specific processes and types of
preservatives, but waste water characteristics, as detailed in
Section V, are similar and thus subject to the same treatment
methods. Many of the pollutants superficially characteristic of
this subcategory are traceable to nonprocess wastes which shall be
discussed in future studies. Sections VII and VIII detail specific
technology and the costs associated with the technologies.
The discharge of waste water pollutants may be eliminated through
the implementation of the following control technologies:
1. Elimination of equipment and piping leaks, and
minimization of spills by the use of good housekeeping
techniques:
2. Recovery and reuse of contaminated water, generated in
processes employing salt-type preservatives and fire-
retardant formulations, as make-up water for treating
solutions;
3. Modification of existing nonpressure processing equipment
in order to eliminate the introduction of water from
precipitation in the treating tanks, and;
4. Segregation of contaminated and uncontaminated water
streams. The latter includes condensate from heating
coils and heat exchangers, and noncontact cooling water.
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Rationale for Best Practicable Control Technology Currently
Available
Process Changes
No significant process changes are necessary to meet these
standards but control techniques would have to be implemented.
This technology is based on the fact that there exist opportunities
to reuse the limited amount of waste water generated; the recycling
of process water from salt type treatment is practicable and is
being practiced in at least one plant in the subcategory; and,
there is no process waste water generated in nonpressure processes.
Non-Water Quality Impact and Energy Requirements
The suggested technologies are based primarily on modification of
iriplant practices and controls, and as a result have little impact
on other environmental considerations. Limited amounts of sludge
would be generated from the suggested biological systems. Sludge,
however, is readily biodegradable and thus presents no great
environmental problem if disposed of properly.
The cost associated with achieving the effluent limitations are
minimal for this subcategory.
Oil separation, already in place at 95% of wood preserving plants
has a cost of $0.31/1000 1 for annualized cost including operating
and maintenance. Evaporation for 7,600 I/day for a hypothetical
plant may be expensive and is related to the cost of natural gas.
The total annual cost would be about $6.00/1000 1.
Summary
Based upon the information contained in Sections III through VIII
of this document, a determination has been made that the degree of
effluent reduction attainable in the Wood Preserving subcategory
through the application of the best practicable control technology
currently available is no discharge of process waste water
pollutants to navigable waters.
WOOD PRESERVING - BOULTONIZING
Identif ication of Best Practicable Control Technology Currently
Available
Wood conditioning by the Boulton process involves five distinct
process steps: 1) placing wood to be treated into a treating
cylinder, 2) sealing the cylinder, 3) putting treating chemical
into the cylinder, 4) applying heat and pressure (by steam coils or
heat exchanger) and 5) drawing a vacuum to remove moisture. The
extracted water passes through a condenser and goes to a hot well.
The waste water volume is only that amount removed from the wood
itself.
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The best practicable control technology currently available which
will result in no discharge of waste water pollutants includes:
1. The elimination of equipment and piping leaks, and
minimization of spills by the use of good housekeeping
techniques, and;
2. Disposal of the small volumes of water removed from the
wood, by evaporation or percolation.
This technology is currently utilized in at least 4 plants which
are now achieving no discharge of waste water pollutants. Sections
VII and VIII detail specific technology and cost analyses.
Rational For Best Practicable Control Technology Currently
Available
The waste water generated by this manufacturing procedure is in the
range of 100 1/cu m of wood treated. This volume of waste water
can be disposed of by evaporation, possibly assisted by the heat
available from auxiliary operations. The volume or ability to
dispose of the waste water is not influenced by the age or size of
the facility.
The capital cost of achieving no discharge of pollutants from this
subcategory ranged between $5,500 and $112,000 depending on the
practices and methods used at four different plants. These costs
were obtained from plants that have installed the technology that
achieves no discharge, technology.
Summary
Based upon the information contained in sections III through VIII
of this document and summarized above, a determination has been
made that the degree of effluent reduction attainable in the Wood
Preserving - Boultonizing subcategory through the application of
the best practicable control technology currently available is no
discharge of process waste water pollutants to navigable waters.
WOOD PRESERVING - STEAM
Identification of Best
Available
Practicable Control Technology
Conditioning and preservative injection are the primary sources of
waste water pollutant generation in this subcategory. Condensate
from steaming is the most heavily contaminated since it comes in
contact with the preservative in the treating vessel; vacuum cycle
water following steam conditioning, and water used to clean
equipment are also heavily contaminated. These operations have
been discussed in detail in Section III, wastes derived and
characterized in Section V, and treatment and control technologies,
when applicable, discussed in Section VII.
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To meet the standards set forth herein will require the use of the
following inplant control and treatment technologies:
1. Installation of oil recovery equipment (oil separators) to
reduce influent to biological systems to less than 100
mg/1;
2. Minimization of waste water volume by the implementation
of rigorous inplant water conservation practices;
3. Elimination of equipment and plumbing leaks;
4. Segregation of contaminated and uncontaminated waste
streams, and;
5. Use of one or a combination of the following: biological
treatment (tricking filter, activated sludge), soil
irrigation, oxidation ponds, chemical oxidation,
containment and spray evaporation, pan evaporation,
evaporation in cooling towers, and incineration of high
concentration oily waste waters.
Rational for the Selection of the Best Practicable Control
Technology Currently Available
Age and Size of equipment and facilities
As discussed in Section VI, the age and size of the wood preserving
plants in this subcategory bear little relation to the quantity or
quality of the process waste water generated and because the
treatment and control methods indicated as best practicable control
technology currently available are "end-of-the-line" processes.
Processes Employed and Engineering Aspects
Inplant procedures which are currently in use in the industry, and
which will minimize the volume of waste water that must be treated,
include the recirculation of direct-contact cooling water and
segregation of contaminated and uncontaminated waste streams. All
of the methods proposed are standard in that they are used by a
number of plants. None present unique problems from an engineering
point of view.
Most wood preserving operations using oily based preservatives have
oil-recovery systems. Apart from environmental considerations, it
is economically feasible to recover and reuse oil rather than
discharge it. Chemical methods involving flocculation and
sedimentation on the oil separator effluent are most widely used,
generally are least expensive, and are effective with wood
preserving waste water.
Trickling filter treatment efficiency on a creosote plant waste
water has been shown to achieve 91 percent BOD removal, 77 percent
COD removal and at least 99 percent phenol removal. Activated
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sludge has been demonstrated to reduce COD by 90 percent and
phenols by 99 percent. Aerated lagoon systems can accomplish the
same efficiency, the main disadvantage being the necessity for more
extensive land area.
Land disposal has relatively simple operating procedures, low
capital investment, minimum equipment needs, low operating and
maintenance costs, and good quality effluent in terms of color and
oxygen demand. Its chief disadvantage is the land requirement (in
the range of 1 ha/3000 I/day). BOD and phenol removal efficiencies
as high as 99.5 percent are reported.
Chlorine and ozone have been used successfully to remove phenols
from wood preserving waste water. Chlorine dioxide can also be
used. Chlorination will reduce COD to the same degree as
flocculation with lime and a polyelectrolyte. carbon adsorption
will remove 96 percent of the phenols and 80 percent of the COD
from a creosote waste water at an 8:1 dosage.
Effluent from the oil separation system can be discharged to a
cooling tower. Normal evaporation rates for a cooling tower
accounts for a loss of 7,500 I/day (2000 gal/day). Problems with
condenser efficiency are associated with the presence of oil in the
cooling water.
Non-Water Quality Aspects and Energy Requirements
None of the waste water treatment and control technologies
discussed above have a significant effect on nonwater environmental
quality. The limited volume of sludge generated by coagulation and
biological treatments of waste water is currently being disposed of
in approved landfills by most plants. Because the organic
components of these sludges are biodegradable, proper disposal will
ensure that these wastes should present no threat to the
environment,
Summary
Based upon the information contained in Sections III through VIII
of this document and summarized above, a determination has been
made that the degree of effluent reduction attainable in the Wood
Preserving-Steam subcategory through the application of the best
practicable control technology currently available is as set forth
in the following table;
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30-Day Daily
Average Maximum
kg/1000 cu m kg/1000 cu m
(lb/1000 cu ft) {1b/1000 cu ft)
COD 550 1100
(34.5) (68.5)
Phenols 0.65 2.18
(0.04) (0.13)
Oil and Grease 12.0 24.0
(0.75) (1.5)
pH 6.0-9.0 6.0-9.0
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SECTION X
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
INTRODUCTION
The effluen-t limitations which must be achieved by July 1, 1983,
are to specify the degree of effluent reduction attainable through
the application of the best available technology economically
achievable. The best available technology economically achievable
is not based upon an average of the best performance within an
industrial category, but is to be determined by identifying the
very best control and treatment technology employed by a specific
point source within the industrial category or subcategory, or
transfer of technology from one industry process to another. A
specific finding must be made as to the availability of control
measures to eliminate the discharge of pollutants, taking into
account the cost for such elimination.
Consideration must also be given to:
(a) the age of equipment and facilities involved;
(b) the process employed;
(c) the engineering aspects of the application
of various types of control techniques;
(d) process changes;
(e) cost of achieving the effluent reduction
resulting from application of the best
available technology economically achievable, and
(f) nonwater quality environmental impact
(including energy requirements).
In contrast to the best practicable control technology currently
available, the best available technology economically achievable
assesses the availability in all cases of in-process modifications
and controls as well as control or additional treatment techniques
employed at the end of a production process.
Those plant processes and control technologies which at the pilot
plant, semi-works, or other levelt have demonstrated both
-technological performances and economic viability at a level
sufficient to reasonably justify investing in such facilities may
be considered in assessing the best available technology
economically achievable. The best available technology
economically achievable is the highest degree of control technology
that has been achieved or has been demonstrated to be capable of
being designed for plant scale operation up to and including no
discharge of process waste water pollutants. Although economic
factors are considered in this development, the costs for this
level of control are intended to be the top-of-the-line of current
technology subject to limitations imposed by economic and
engineering feasibility. However, -the best available technology
economically achievable may be characterized by some technical risk
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with respect to performance and with respect to certainty of costs.
Therefore, the best available technology economically achievable
may necessitate some industrially sponsored development work prior
to its application.
BARKING
Identification of the Best Available Technology Economically
Achievable
As summarized in Section IX, the best practicable control
technology currently available is no discharge of waste water
pollutants into navigable waters. Therefore, the best available
technology economically achievable in the Barking subcategory is no
discharge of waste water pollutants to navigable waters.
This limitation can be achieved by:
1. Selection of a barking method that does not have a waste
water effluent;
2. Selection of a barking method that has a relatively low
volume of water use, and treating and reusing that water
either within the unit operation or within the total
manufacturing operation, or;
3. Application of treatment of hydraulic barker effluent and
recycle of that water to the degree that eliminates the
discharge of pollutants to navigable waters.
As noted in sections VII and IX of this document, treatment of
hydraulic barker effluent is already in place in one plant and is
currently resulting in the achievement of almost 100 percent
recycle of process water in that plant.
This recycle is being achieved by a treatment process that includes
screening, coagulation, clarification, pH control, and algae
control.
Effluent Reduction Attainable Through the Application of. the Best
Available Technology Economically Achievable
Based upon the information contained in. Sections III through IX of
this document, and consistent with the discussion presented above,
a determination has been made that the effluent limitation
representing the degree of effluent reduction attainable in the
Barking subcategory through the application of the best available
technology economically achievable is no discharge of process waste
water pollutants to navigable waters* Application of the factors
listed in Section IX does not allow variation from the no discharge
limitation set forth in this section for any point source subject
to such effluent limitation.
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VENEER
Identification of the Best Available Technology
Achievable
Economically
The best practicable control technology currently available, as
defined in Section IX, is no discharge of waste water pollutants.
The best available technology economically achievable in the Veneer
subcategory is:
1. The substitution, for direct steam conditioning of logs
(a) hot water spray tunnels, (b) indirect steaming, or (c)
modified steaming with the use of steam coils;
2. Discharge of contaminated waste water from hot water vats
to settling ponds for reuse, and;
3. The use of dry veneer dryer cleaning methods or proper
land disposal of the quantities of waste water generated
from wet cleaning procedures.
Effluent Reduction Attainable Through the Application of
Available Technology Economically Achievable
the Best
Based upon the information contained in Sections III through VIII
of this document, and consistent with the discussion in Section IX
a determination has been made the the effluent limitation
representing the degree of effluent reduction attainable in the
Veneer manufacturing subcategory through the application of the
best available technology economically achievable is no discharge
of process waste water pollutants to navigable waters. Application
of the factors listed in Section IX does not require variation from
the effluent limitation set forth in this section for any point
source subject to such effluent limitation.
PLYWOOD
Identification of Best Available Technology Economically Achievable
As summarized in Section IX, best practicable control technology
currently available is no discharge of process waste water
pollutants to navigable waters, waters. Therefore, best available
technology economically achievable is no discharge of waste water
pollutants into navigable waters. This limitation can be achieved
by:
1. Elimination of discharge from the gluing operation in the
plywood subcategory including reduction of the amount of
fresh water used by the use of waste water for glue
formulation, monitoring of glue and glue waste water
concentrations, the use of steam to clean spreaders where
applicable, the use of high pressure water for cleaning
operations, and the use of spray applicators for glue.
2. Dry housekeeping procedures and judicious use of wet
cleaning water.
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Effluent Reduction Attainable Through the Application of the Best
Available Technology Economically Achievable
Based upon the information contained in Sections III through VIII
of this document, and consistent with the discussion in Section IX
a determination has been made that the effluent limitation
representing the degree of effluent reduction attainable in the
Plywood manufacturing subcategory through the application of the
best available technology economically achievable is no discharge
of process waste water pollutants to navigable waters.
HARDBOARD - DRY PROCESS
Identification of the Best Available Technology
Achievable
Economically
As summarized in Section IX, the best practicable technology
currently available in the Hardboard - Dry Process subcategory
consists of:
1. Recycle of log wash and chip wash or disposal by landfill;
2. The operation of resin system as a closed system, with
recycle and reuse of resin wash water as make-up in the
resin solution;
3. Neutralization of caul wash water and disposal by
impoundment or spray irrigation, and;
U. Elimination of discharge from humidification by the
implementation of inplant control, including operating and
process management procedures.
Effluent Reduction Attainable Through the Application of the Best
Available Technology Economically Achievable
Based upon the information contained in Sections III through IX of
this document, and consistent with the discussion in Section IX, a
determination has been made that the effluent limitation
representing the degree of effluent reduction attainable in the
Hardboard - Dry Process subcategory through the application of the
best available technology economically achievable is no discharge
of process waste water pollutants to navigable waters.
HARDBOARD - WET PROCESS
Identif ication of the Best Available Technology
Achievable
Economically
The best available technology economically achievable in the
Hardboard-Wet process subcategory includes:
1. Recycle of process water as dilution water utilizing
temperature control and suspended solids control to reduce the
total plant discharge to 4.5 cu m/kkg {1186 gal/ton), the BOD5
to 33.8 kg/kkg (67.5 Ib/ton) and the suspended solids to 9
fcg/kkg (18 Ib/ton);
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2. Installation of a pre-press and evaporation system;
3. Discharge of process water only from the pre-press and the
wet press;
4. Treatment of the total waste water flow by screening,
primary settling, and evaporation;
5* Recycle of a portion of the condensate back to the
process;
6. Activated sludge treatment of the excess condensate, and;
7. Sludge disposal by appropriate means*
Processes Employed and Engineering Aspects
The press system has been used on semi-chemical pulp and on a
calcium bisulphite system. Presses have been designed and operated
to take pulp from 10-15 percent up to 55 percent consistently (by
weight). The filtrate removes a higher percentage of the dissolved
solids to treatment and results in a cleaner pulp going through the
stock system thus reducing the .rate of dissolved solids buildup in
the system. Full scale trials run on a semi-chemical pulp mill in
Scandinavia showed a waste liquor recovery of 85 percent on a
weight basis.
The discharge water from the press is passed over a screen to
remove fiber clumps, which are returned to the process. The screen
effluent is diverted to a clarifier feedwell where liquid alum is
added to aid flocculation. The clarifier is expected to remove 75
to 90 percent of the suspended solids. Waste liquor is then
evaporated to 65 percent solids and disposed of by incineration or
as a byproduct, contaminated condensate from the evaporators may
be treated in an activated sludge system.
Screening and primary clarification (for 10 percent BOD5 removal)
would cost $109,000 initial investment and $26,700 for added yearly
operating expenses. All existing plants currently have screening
and primary clarification in place. A prepress and evaporation
system would initially cost $566,000 with a yearly operating cost
of $207,000 for a 93.5 percent BOD5 removal. And a prepress
combined with evaporation and activated sludge treatment of the
condensate would accomplish 99.4 percent BOD5 removal for an
initial cost of $722,000 and yearly operating cost of $428,000.
Effluent Reduction Attainable Through the Application of the Best
Available Technology Economically Achievable
Based upon the information contained in sections III through VIII
of this document a determination has been made that the effluent
limitation representing the degree of effluent reduction attainable
in the Hardboard-wet Process subcategory through the application of
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the best available technology economically achievable is a maximum
discharge as follows:
BODS,
Total
Suspended Solids
PH
WOOD PRESERVING
30-Day
Average
kg/kkg
tlb/ton)
0.9
(1.8)
1.1
(2.2)
6.0-9.0
Daily
Maximum^
kg/kkg
(Ib/ton)
2.7
(5-4)
3.3
(6.6)
6.0-9.0
Identification of the Best Available Technology Economically Achievable
As summarized in section IX and developed earlier in the document,
the best available technology economically achievable in the Wood
Preserving subcategory includes:
1. Minimization of waste water volume by the implementation
of rigorous inplant water conservation practices;
segregation
streams;
of cont aminat ed and uncontaminated water
2. Installation of oil recovery equipment to reduce influent
to treatment system;
4. Elimination of equipment and plumbing leaks, and;
5. Use of one or a combination of the following biological
treatment (trickling filter, activated sludge), soil
irrigation, oxidation ponds, chemical oxidation,
containment and spray evaporation, pan evaporation,
evaporation in ccoling towers, and incineration of high
concentration oily waste waters.
Effluent Reduction Attainable Through the Application of the Best
Available Technology Economically Achievable
Based upon the information contained in Sections III through IX of
this document, and consistent with the discussion above, a
determination has been made that the effluent limitation
representing the degree of effluent reduction attainable in the
Wood Preserving sufccategory through the application of the best
available technology economically achievable is no discharge of
process waste water pollutants into navigable waters.
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WOOD PRESERVIKG-BOULTQNIZING
I denti f icati on of the Bes-t Available Technology Economically
Achievable
As summarized in section IX and developed earlier in this document,
the best available technology economically achievable in the Wood
Preserving-Boultonizing subcategory includes:
1. Minimization of waste water volume by the implementation of
rigorous inplant water conservation practices;
2. segregation of contaminated and uncontaminated water
streams.
3. Installation of oil recovery equipment to improve the
quality of the influent to treatment system;
4. Elimination of equipment and plumbing leaks;
5. Use of one or a combination of the following treatments:
soil irrigation, oxidation ponds, containment and spray
evaporation, pan evaporation, evaporation in cooling
towers.
Effluent Reduction Attainable Through the Application of the Best
Available Technology Economically Achievable
Based upon the information contained in Sections III through IX of
this document, and consistent with the discussion above, a
determination has been made that the effluent limitation
representing the degree of effluent reduction attainable in the
Wood Preserving-Boultonizing subcategory through the application of
the best available technology economically achievable is no
discharge of process waste water pollutants to navigable waters.
WOOD PRESERVING-STEAM
Identification of the Best Available Technology Economically
Achievable
The low waste water flow rate that must be achieved to conform with
1983 requirements will necessitate a high level of water reuse,
changes in steaming technique among plants using open steaming,
efficient oil recovery systems, and the initiation of an effective
preventive maintenance and housekeeping program. The following
technologies related to these factors have been considered in
determining the best available technology economically achievable:
1. Minimization of the volume of discharge by (a) recycling
all direct contact cooling water, (b) reuse of a portion
of the process water for cooling purposes, (c) insulation
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of retorts and steam pipes to reduce the volume of
cylinder condensate, (d) use of closed steaming or
modified-closed steaming to reduce the volume of cylinder
condensate and to lessen the incidence of oil-water
emulsion formation, (e) reuse of all water contaminated
with heayy metals in preparing treating solutions of
salt-type preservatives and fire retardants, and (f)
segregation of contaminated and uncontaminated water
streams;
2. Modification of oil-recovery systems or replacement, as
required, to insure efficient removal of oils; and
3. implementation of preventive maintenance and good
housekeeping programs to reduce spills and leaks and
provide a standard procedure for cleaning up those that
occur.
Rationale for the Selection of the Best Available Technology
Economically Achievable
Processes Employed and Engineering Aspects
Some of the methods of reducing waste flow are standard industry
practice, and would normally be adopted earlier than 1983. These
include waste stream segregation and recycling of contaminated
cooling water.
Closed steaming is applicable to virtually all plants using steam
conditioning. It is the single most important inplant process
change that a plant can make from the standpoint of both reducing
the volume of waste water that must be disposed of and also
reducing emulsion formation. Modified-closed steaming, while
reducing the volume of waste water to a lesser extent than closed
steaming, also lessens emulsion formation. In addition, this
method substantially reduces steam requirements by retaining the
hot steam condensate in the retort rather than discharging it as it
forms.
Like closed steaming, insulation of treating cylinders and pipes
used in steam transfer potentially can reduce both the volume of
condensate formed and the energy requirements for steam generation.
The heat loss from an uninsulated metal vessel amounts to 7.3 kcal/
hr/sq in of surface area (2.7 BTU/hr/sq ft) for each degree of
temperature difference between the inside and outside of the
vessel. For an uninsulated retort 2.13 m (7 ft) in diameter and
36.57 m (120 ft) long, the daily heat loss would be 7.56 million
kcal (30 million BTU) if the inside and ambient temperatures were
121°C and 27°c (250°F and 80°F), respectively. This loss can be
cut by 70 percent by proper insulation. As a result, , steam
requirements and, the volume of condensate produced would be
reduced significantly.
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A well executed preventive maintenance and housekeeping program is
an integral part of the treatment and control technology required
to achieve best available technology economically achievable
limitations. Spills and leakages can largely negate the efforts
directed toward other, more obvious aspects of waste water
management if they are ignored. The areas around and in the
immediate vicinity of retorts and storage tanks are of particular
importance because of the opportunity for storm water contamination
from preservative drips and spills associated with freshly pulled
charges and loss of preservative from plumbing and pump leaks-
Consideration should be given to paving the area in front of
retorts to permit channeling of drips and spills to a sump from
which the oil can be recovered.
In addition to the inplant controls described above, polishing
treatments may be required to achieve the best available technology
economically achievable limitations. Treatments such as chemical
oxidation and carbon filtration have been used in treatment of wood
preserving waste waters or petroleum waste waters. Chlorination of
pentachlorophenol waste water has reduced phenol content 95 to 10QS
at dosages up to 3.0 g/1 of CaOC12 as chlorine. At a dosage of 8
g/1 and 24 hour contact time, 96% of phenols and 80% of COD was
removed from creosote waste water. Dosages over 8 g/1 showed
little additional improvement. Similar results were obtained in
tests using pentachlorophenol waste water.
Effluent Reduction Attainable Through the Application of the Best
Available Technology Economically Achievable
Based upon the information contained in Sections III through IX of
this document, and consistent with the discussion above, a
determination has been made that the effluent limitation
representing the degree of effluent reduction attainable in the
Wood Preserving-Steam subcategory through the application of the
best available technology economically achievable is a maximum
discharge as follows;
289
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COD
Phenols
Oil and Grease
30-Day
Average
kg/1000 cu m
(lb/100 cu ft)
110
(6.9)
0.064
(0.003)
3-4
(0.2)
Daily
Maximum
kg/1000 cu m
(lb/1000 cu ft)
220
(13.7)
0.21
(0.014)
6.8
(0.4)
PH
6.0-9.0
6.0-9.0
_
290
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SECTION XI
STANDARDS OF PERFORMANCE FOR NEW SOURCES
INTRODUCTION
This level of effluent reduction is to be achieved by new sources.
The -term. "new source" is defined in the Act to mean "any source,
the construction of which is commenced after the publication of
proposed regulations prescribing a standard of performance." New
source technology shall be evaluated by adding to the consideration
underlying the identification of best available technology
economically achievable a determination of what higher levels of
pollution control are available thj:pugh the use of improved pro-
duction processes and/or treatment techniques.
In addition to considering the best in-plant and end-of-process
control technology, identified in best available technology
economically achievable, new source technology is to be based upon
an analysis of how the level of effluent may be reduced by changing
the production process itself. Alternative processes, operating
methods or other alternatives must be considered. However, the end
result of the analysis will be to identify effluent standards which
reflect levels of control achievable through the use of improved
production processes (as well as control technology), rather than
prescribing a particular type of process or technology which must
be employed. A further determination which must be made for new
source technology is whether a standard permitting no discharge of
pollutants is practicable.
Specific Factors to be Taken Into Consideration
At least the following factors should be considered with respect to
production processes which are to be analyzed in assessing new
source technology:
a. The type of process employed and process changes;
b. Operating methods;
c. Batch as opposed to continuous operations;
d. Use of alternative raw materials and mixes of raw materials;
e. Use of dry rather than wet processes (including substitution
of recoverable solvents for water) ; and
f. Recovery of pollutants as by-products.
BARKING
Effluent Reduction, Identification and Rationale for Selection of
New Source Performance Standards
291
-------
Based on the information contained and developed in sections III
through IX of this document, a determination has been made that the
standard of performance representing the degree of effluent
reduction attainable for new sources in the Barking subcategory,
excluding hydraulic barking operations, through the application of
the best practicable demonstrated control technology, processes,
operating methods, or other alternatives is no discharge of process
waste water pollutants to navigable waters.
The standard of performance for new sources is based on the
following production raw waste and waste water flow assumptions.
These assumptions are based on information presented in Section V:
Production (veneer or plywood)
Effluent from the Barker
BOD5 concentration
Total Suspended solids (TSS)
concentration
252 cu m/day
6,540 cu m/day
100 mg/1
2000 mg/1
The limitations are based on the following treatment
efficiencies:
Primary screening and settling 75% Removal SS
Biological treatment
BOD5 Removal
Available information indicated that variation in the effluent from
a biological treatment system processing wastes from the timber
products processing industry is 300 percent.
Based upon the information contained in sections III through VIII
of this document and summarized above, a determination has been
made that the standard of performance representing the degree of
effluent reduction attainable and the maximum allowable discharge
for new sources in the Barking subcategory that use the hydraulic
barking process shall be as follows:
BODS
Total Suspended
Solids
30-Day
Average
kg/cu m
(Ib/cu ft)
0.5
(0.03)
2.3
(0.14)
Daily
Maximum
kg/ cu m
(Ib/cu ft)
1.5
(0.09)
6.9
(0.43)
292
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VENEER
Effluent Reduction,, Identification, and Rationale for Selection
New Source Performance Standards
of
Limitations prescribed for new sources are applicable to all plants
in the veneer segment of the timber products processing industry.
No variation will be allowed for log conditioning by open steaming.
As discussed in section IX, alternative procedures to conditioning
by open steaming exist and are in use in the industry currently.
Based on the information contained and developed in Sections III
through VIII of this document, a determination has been made that
the standard of performance representing the degree of effluent
reduction attainable for new sources in the Veneer subcategory
through the application of the best available demonstrated control
technology, processes, operating methods, or other alternatives is
no discharge of process waste water pollutants to navigable waters.
PLYWOOD
Effluent Reduction. Identification. and Rationale for Selection of
New Source Performance Standards
As summarized in section IX, there currently exists treatment and
control technologies applicable and in practice in this subcategory
that are capable of eliminating the discharge of pollutants.
Based on the information contained and developed in Section III
through VIII of this document, a determination has been made that
the standard of performance representing the degree of effluent
reduction attainable for new sources in the Plywood manufacturing
subcategory through tiie application of the best available
demonstrated control technology, processes, operating methods, or
other alternatives is no discharge of process waste water
pollutants to navigable waters.
HARDBOARD - DRY PROCESS
Effluent Reduction, Identification, and Rationale for Selection
of New Source performance Standards
As summarized in section IX, there currently exist treatment and
control technologies applicable and in practice in this subcategory
that are capable of eliminating the discharge of pollutants.
Based on the information contained and developed in Sections III
through IX of this document, a determination has been made that the
standard of performance representing the degree of effluent
reduction attainable for new sources in the Hardboard-Dry
subcategory through the application of the best available
demonstrated control technology, processes, operating methods, or
293
-------
other alternatives is no discharge of process waste water
pollutants to navigable waters.
HARDBOARD ~^WET PROCESS
Effluent Reduction,. Identification, and Rationale for the Selection
of New Source Performance Standards
The waste loadings generated by the manufacture of hardboard by the
wet process come mainly from dissolved organics released during the
fiber preparation process. Section VII discusses and sections IX
and X summarize technologies which will result in a significant
reduction of process waste water pollutants.
Based on the information contained and developed in sections III
through VIII of this document, a determination has been made that
the standard of performance representing the degree of effluent
reduction attainable for new sources in the Hardboard-wet
subcategory through the application of the best available
demonstrated control technology, processes, operating methods, or
other alternatives is as defined below:
BOD 5
Total
Suspended Solids
pH Range
WOOD PRESERVING
30-Day
Average
kg/kkg
(]b/ton)
0.9
(1.8)
1.1
(2.2)
6.0 - 9.0
Daily
Maximum
kg/kkg
Ob/ton)
2.7
(5.4)
3.3
(6.6)
6.0 - 9.0
Effluent Reduction, Identification, and Rationale for the
Selection of New Source Performance Standards
As described in section IX, there currently exist treatment and
control technologies applicable and in practice in this subcategory
that are capable of eliminating the discharge of pollutants.
Based on the information contained and developed in Sections III
through VIII of this document, a determination has been made that
the standard of performance representing the degree of effluent
reduction attainable by the Wood Preserving subcategory through the
application of the best available demonstrated control technology,
processes, operating methods, or other alternatives is no discharge
of process waste water pollutants to navigable waters.
294
-------
WOOD PRESERVING-BOULTONIZING
Effluent Reduction, identification, and Rationale for the Selection
9.L New Source Performance Standards
As described in section IX, there currently exist treatment and
control technologies applicable and in practice in this subcategory
that are capable of eliminating the discharge of pollutants.
Based on the information contained and developed in Section III
through IX of this document, a determination has been made that the
standard of performance representing the degree of effluent
reduction attainable by the Wood Preserving-Boultonizing
subcategory through the application of the best available
demonstrated control technology, processes, operating methods, or
other alternatives is no discharge of process waste water
pollutants to navigable waters.
WOOD PRESERVING-STEAM
Effluent Reduction, Identification, and Rationale for the
Selection of New Source Performance_Standards
The process by which wood is treated by plants in this subcategory
is direct and simple. Basically, it consists of placing the stock
in a pressure retort, conditioning it using steam or vapors of an
organic solvent, and impregnating it with a preservative or fire
retardant. The opportunity for change in the production process of
an operation of this type is limited. Alternative raw materials
are not available, and the replacement of existing preservatives
with new or different chemicals is not anticipated in the
foreseeable future. ,
A consideration of the overall operation reveals only two
processing steps in which the opportunity exists for changes that
can lead to reduced discharge. Both are related to preparation of
stock: for preservative treatment, and both are expensive in terms
of the capital investment required. One of the methods is to treat
dry stock, and thereby abrogate the need to steam condition it.
The other method is to steam condition or vapor dry stock in a
separate retort from the one in which the preservative treatment is
applied. Both methods, which are used to some extent by existing
plants, serve to separate conditioning operations from treating
operations and thereby prevent contamination of water with
preservatives.
Approximately 30 percent of the plants in the U.S.
dry a portion of their stock prior to treatment.
percent use kiln drying for all their stock.
investment is high for this technology, amounting
kiln. A minimum of 5 kilns would be required if all
treated by a typical three-retort plant were
preservative treatment. Total investment would
Including $47,000 for each kiln and $13,000
currently kiln
Only about 10
The capital
to $60,000 per
the material
dried prior to
be $300,000,
for accessory
295
-------
equipment, gas and electric service and the laying of tracks.
Total operating costs for the system would be approximately $98,000
per year. Kiln drying also darkens the surface of poles so that
some poles do' not meet the color standards under which an
increasing percentage of the ones treated with pentachlorophenol
are sold.
A reduction in the volume of discharge can also be obtained by air
seasoning stock before treating it. Some air seasoning takes place
on the yeard, in the normal processing of material and most plants
ordinarily maintain an inventory of untreated stock in open stacks
to expedite the filling of orders. Any seasoning that occurs here
lessens the conditioning time required when the material is
treated. , To air season thoroughly, certain items, such as poles
and piling, take up to six months. The large inventory required
for this imposes a financial burden on the owners and is not
practical during a prolonged period of high demand. Furthermore,
deterioration is a problem in the South when stock is stored for
the time required for it to air season.
Steam conditioning or vapor drying in a separate retort would
require three additional retorts for the typical three retort
plant. Capitol investment would be $150,000, with an additional
cost of $110,000 for accessory equipment and installation. Total
operating costs would be about $64,000/yr.
It is apparent from the foregoing discussion that there is no
simple, economically viable method to reduce the volume of
discharge from plants in this subcategory other than that based on
the best available technology economically achievable.
Energy Requirements
Kiln drying all stock would have a fuel cost of $72,000/yr for the
typical plant, based on a gas consumption of 99 cu m/hr for 312
days/yr operation.
Fuel and electricity costs for a separate retort system for
conditioning.would be $30,000 and $500, respectively.
Summary
Based on the information contained and developed in Sections III
through VIII of this document and summarized above, a determination
has been made that the standard of performance representing the
degree of effluent reduction attainable for new sources in the wood
Preserving -Steam subcategory through the application of the best
available demonstrated control technology, processes, operating
methods, or other alternatives is as defined below:
296
-------
COD
Phenols
Oil and Grease
30-Day
Average
kg/1000 cu m
(lb/1000 cu ft)
110
(6.9)
0.064
(0.003)
3.4
(0.21)
Daily
Maximum
kg/1000 cu m.
(lb/1000 cu ft)
220
(13.7)
0.21
(0.014)
6.8
(0.4)
pH Range
6.0-9.0
6.0-9.0
297
-------
-------
SECTION XII
ACKNOWLEDGEMENTS
The information presented in this document was developed
input and assistance of many persons and organizations.
with the
The data base and current state of pollution control in this
segment of the timber products processing industry was developed
and presented by Environmental Science and Engineering, Inc.,
Gainesville, Florida, Richard H. Jones, vice president; and John D.
Crane, project manager, organized and directed the activity; Robert
A. Morrell and Leonard P. Levine served as project leaders for the
veneer and plywood, and Jjarflboard portions of the industry,
Recognition is given to the ••secretarial staff of Environmental
Science and Engineering for their efforts in providing the Agency
with a draft report within a limited time schedule. Dr. John
Meiler also served as a consultant to Environmental Science and
Engineering for the hardboard industry.
The wood preserving portion of this document was developed by Dr.
Warren s. Thompson, Director, Forest Products Utilization
Laboratory, Mississippi State University. Appreciation is extended
to him and his staff.
Industry associations and organizations that were involved in the
development of information and commenting included: The National
Forest Products Association, The American Plywood Association, The
Hardwood Plywood Assocation, The American Hardboard Association.
The American Wood Preservers Association, The American Wood
Preservers Institute, The Society of American wood Preservers, The
southern Pressure Treaters Association, and the Quality Wood
Preservers Society.
It is not possible to list the industry individuals who have worked
with the Agency and its contractors in the development of the
guidelines and standards presented in this document. However,
their assistance and cooperation is appreciated.
The Timber Products Processing Working Group/steering committee
provided insight and constructive criticism of the support document
in its various stages of development. The committee was composed
of the following EPA personnel; Ernst P. Hall, chairman. Effluent
Guidelines Division, Al Swing.,. Corvallis NERC, G. William Frick,
Office of Enforcement and General Counsel, Arthur Mallon, Office of
Research and Development, Robert MCManus, Office of Enforcement and
General Counsel, D. Robert Quartel, Effluent Guidelines Division,
Willard Smith and Irving Susel, Office of Economic Development,
Reinhold Thieme, Office of Enforcement and General Counsel, and
Kirk Willard, Corvallis NERC.
Special thanks are expressed to Ernst Hall, Effluent Guidelines
Division for his guidance and support. Rob Quartel formerly of
299
-------
the Effluent Guidelines Division, served as project officer during
the formative stages of this document.
Special appreciation is extended to the women of the Effluent
Guidelines Division who maintained their composure and charm during
the long and arduous task of typing, retyping and revising this
document during its development. Thank you, in particular to Linda
Rose, Chris Miller, Darlene Miller and Fran Hansborough.
300
-------
SECTION XIII
REFERENCES
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3» Forest Products Industry Directory, Miller Freeman Publications,
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4. Market profile - Softwood and Hardwood Plywood, U.S.A. and Canada,
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5. Panshin, Alexis John et al* Forest Products; Their Sources, Produc-
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6- Market Profile - Hardboard, Forest Industries, Portland, Oregon.
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303
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305
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68. Gilbert, L., Morrison, W. S., and Kahler, F. H., "Use of Ion
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71. Sweets, W. H., Hamdy, M. K. , and Weiser, H. H., "Microbiological
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Petroleum Phenolic Wastewater," Proceedings, 10th Industrial Waste
Conference, Purdue University, pp 106-119,
74. Reid, G. W. , Wortman, R. and Walker, R., "Removal of Phenol with
Biological Slimes," Proceedings, llth Industrial Waste Conference,
Purdue University, pp 354-357, 1956.
75. Harlow, H. W., Shannon, E. S., and Sercu, C. L., "A Petro-Chemical
Waste Treatment System," Proceedings, 16th Industrial Waste Con-
ference, Purdue University, pp 156-166, 1961.
76. Montes, G. E., Allen, D. L., and Showell, E. B., "Petrochemical
Waste Treatment Problems," Sewage Ind. Wastes, 28, pp 507-512,
1956.
77. Dickerson, B. W. and Laffey, W. T., "Pilot Plant Studies of
Phenolic Wastes from Petrochemical Operations," Proceedings,
13th Industrial Waste Conference^ Purdue University, pp 780-799,
1958.
306
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78. Davies, R. W., Biehl, J. A., and Smith, R. M.t "Pollution Control
and Waste Treatment at an Inland Refinery," Proceedings, 21st
Industrial Waste Conference, Purdue University, pp 126-138, 1967.
79. Austin, R. H., Meehan, W. G., and Stockham, J. D., "Biological
Oxidation of Oil-Containing Wastewaters," Ind. Eng. Chem.,
46, pp 316-318, 1954.
80. Prather, B. V., and Gaudy, A. F., Jr., "Combined Chemical, Physical,
and Biological Processes in Refinery Wastewater Purification,11
Proceedings, American Petroleum Institute, 44(111), pp 105-112, 1964,
81. Davies, J. J., "Economic Considerations of Oxidation Towers,"
Proceedings, Conference on Pollution Abatement and Control
in the Wood Preserving Industry, (W. S. Thompson, Editor)
Mississippi Forest Products Laboratory, Mississippi State
University, State College, Mississippi, pp 195-205, 1971.
82. Ullrich, A. H., and Smith M. W., "The Biosorpiton Process of
Sewage and Waste Treatment," Sewage and Ind. Wastes, 23,
pp 1248-1253, 1951.
83. Ullrich, A. H., and Smith, M. W., "Operation Experience with
Activated Sludge Biosorption at Austin, Texas," Sewage and
Industrial Wastes, 29 pp 400-413, 1957.
84. Besselieure, E. B., The Treatment of Industrial Wastes, McGraw-
Hill, New York, 1969.
85. Preussner, R. D., and Mancini, J., "Extended Aeration Activated
Sludge Treatment of Petrochemical Waste at the Houston Plant
of Petro-Tex Chemical Corporation," Proceedings, 21st Industrial
Waste Conference, Purdue University, pp, 591-599, 1967.
86. Coe, R. H., "Bench-Scale Method for Treating Waste by Activated
Sludge," Petroleum Processing, 7, pp 1128-1132, 1952.
87. Ludberg, J. E., and Nicks, G. D., "Phenols and Thiocyanate
Removed from Coke Plant Effluent,11 Ind. Wastes (November) pp 10-
13, 1969.
88. American Wood Preservers' Association, Report of Wastewater
Disposal Committee, Proceedings, American Wood Preservers'
Association, Washington, D. C., 56, pp 201-204, 1960.
89. Cooke, R., and Graham, P. W., "The Biological Purification
of the Effluent from a Lurgi Plant Gasifying Bituminous Coal,"
Int. Jour. Air Water Pollution, 9(3), pg. 97, 1965.
90. Badger, E.H.M. and Jackman, M. I., "Loading Efficiencies in the
Biological Oxidation of Spent Gas Liquor,11 Journal and Proceedings,
Inst. Sewage Purification, 2:159, 1961.
307
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91. Nakashio, M., "Phenolic Waste Treatment by an Activated-Sludge
Process," Hakko Kogaku Zasshi 47:389, Chem. Abs_. 71(8):236, 1969.
92. Reid, 6. W., and Janson, R. J., "Pilot Plant Studies on Phenolic
Wastes at Tinker Air Force Base," Proceedings, 10th Purdue
Industrial Waste Conference, p 28, 1955.
93. Kostenbader, P. 0. and Flacksteiner, J. W. (Bethlehem Steel
Corporation), "Biological Oxidation of Coke Plant Weak Ammonia
Liquor," J. WPCF, 41(2):199, 1969.
94. Kirsh, E. J. and Etzel, J. E., "Microbial Decomposition of
Pentachlorophenol," (Submitted for Publication, J. WPCF)
Personal Correspondence from E. J. Kirsh to Warren S. Thompson,
1972.
95. Fisher, C. W., "Hoppers' Experience Regarding Irrigation of
Industrial Effluent Waters and Especially Wood Treating Plant
Control in the Wood Preserving Industry (W. S. Thompson, Editor),
Mississippi Forest Products Laboratory, Mississippi State
University, State College, Mississippi, pp 232-248, 1971.
96. American Petroleum Institute, Manual on Disposal of Refinery
Wastes. Vol. I_. Wastewater Containing Oil (6th Edition), 92 pp,
1960.
97. Montes, G. E., Allen, D. L., and Showell, E, B., "Petrochemical
Waste Treatment Problems," Sewage Ind. Wastes, 28:507-512, 1956.
98. Biczysko, J. and Suschka, J., "Investigations on Phenolic
Wastes Treatment in an Oxidation Ditch," in Advances in Water
Pollution Research, Munich Conference, Vol. 2, pp 285-289, Pergamon
Press, New York, N.Y, 1967,
99. Skogen, D. B., "Treat HPI Wastes with Bugs," Hydrocarbon Pro-
cessing, 46(7):105, 1967.
100. Crane, L. E., "An Operational Pollution Control System for
Abatement and Control in the Wood Preserving Industry, (W. S.
Thompson, Editor) Mississippi Forest Products Laboratory,
Mississippi State University, State College, Mississippi, pp 261-
270, 1971.
101. Gaudy, A. F., Jr., Scudder, R., Neeley, M. M., and Perot, J. J.,
"Studies on the Treatment of Wood Preserving Wastes," Paper
presented at 55th National Meeting, Amer. Inst. Chem. Eng.,
Houston, Texas, 1965.
102, Gaudy, A. F., Jr., "The Role of Oxidation Ponds in A Wood
Treating Plant Waste Abatement Program," Proceedings, Conference
On Pollution Abatement and Control i_n_ the Wood Preserving Industry
TW". S. Thompson, Editor) Mississippi Forest Products Laboratory,
Mississippi State University, State College, Mississippi, pp 150-
164, 1971.
308
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103. Vaughan, J. C., "Problems in Water Treatment," Jour., American
Water Works Association, 56(5):521, 1964.
104. Woodward, E. R., "Chlorine Dioxide for Water Purification!11
Jour. Pennsylvania Water Works Operators' Assoc., 28:33, 1956.
105. Glabisz, 0., "Chlorine Dioxide Action on Phenol Wastes," Chem.
Abs., 65:10310, 1966.
106. Manufacturing Chemists Association, "The Effect of Chlorination
on Selected Organic Chemicals," Environmental Protection Agency,
Water Pollution Control Research Series. Project 12020 EXE, 104
pages, 1972.
107. Thompson, W. S. and Dust, 0. V., "Pollution Control in the Wood
Preserving Industry. Part 2. Inplant Process Changes and Sanita-
tion," Forest Prod. J.. 22(7):42-47, 1972.
108, American Public Health Association, Standard Methods for the
Examination of Water and Vlastewater, 12th Ed., New York, 1965.
109. Corbitt, R. A., "The Wood Preserving Industry's Water Pollution
Control Responsibility in Georgia and Neighboring States," Pro-
Wood Preserving Industry, (W. S. Thompson, Editor) Mississippi
Forest Products Laboratory, Mississippi State University, State
College, Mississippi, pp 19-35, 1971.
110. Inhols, R. S. and Ridenour, G. M., "The Elimination of Phenolic
Tastes by Chloro-Oxidation," Mater and Sewage Works, 95:187, 1949,
111. Ettinger, M. B., and Ruchoft, C. C.» "Effect of Stepwise
Chlorination on Taste-and-Color-Producing Intensity of Some
Phenolic Compounds," Jour. American Water Works Association.
43:651, 1951.
112. Burttschell, R. H., "Chlorine Derivatives of Phenol Causing Taste
and Odor," Jour. American Water Works Assoc., 51:205-214, 1959.
113. Eisenhaeur, H. R., "Oxidation of Phenolic Wastes," Jour. Water
Pollution Control Federation. 36(9):1H6-1128, 1964.
114. Niegowski, S. J., "Destruction of Phenols by Oxidation with
Ozone," Ind. Eng. Chem., 45(3):632-634, 1953.
115. Niegowski, S. J., "Ozone Method for Destruction of Phenols
in Petroleum Wastewater," Sewage and Ind. Wastes, 28(10):
1266-1272, 1956.
116. Gloyna, E. F. and Malina, J. F., Jr., "Petrochemical Wastes
Effects on Water, Part 3. Pollution Control," Ind. Water and
Wastes (January - February, pp 29-35, 1962.
117. Gloyna, E. F., and Malina, J. F., Jr., "Petrochemical Waste
309
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Effects on Water, Part 2. Physiological Characteristics/1
Ind. Water and Wastes, (November-December) pp 157-161, 1962.
118. Gould, M. and Taylor, J., "Temporary Water Clarification System,"
Chem. Eng. Progress, 65(12):47-49, 1969.
119. Thomas E. Gates & Sons, Inc., Personal Correspondence to
Environmental Engineering, Inc., Gainesville, Florida, June,
1973.
120. Effenberger, Herman K., Gradle, Don D. and Tomany, James P.,
Division Conference of TAPPI, Houston, Texas, May, 1972.
121. Powell, S. T., Water Conditioning.ForJndustry, McGraw-Hill
York, 1954.
New
122. Patterson, J. W., and Minear, R, A., "Wastewater Treatment
Technology," Illinois Institute for Environmental Quality, Report
No. PB-204521, 280 pages, 1971.
ADDITIONAL REFERENCES
Back, Ernst, L. and Larsson, Stig A,, "Increased Pulp Yield as Means
Means of Reducing the BOD of Hardboard Mill Effluent," Swedish
Paper Journal, October 15, 1972.
Boydston, James R., "Plywood and Sawmill Liquid Waste Disposal," Forest
Products Journal, Vol. 21, No. 9, September 1971.
Fisher, C. W., "Soil Percolation and/or Irrigation of Industrial Effluent
Waters—Especially Wood Treating Plant Effluents," Forest Products
Journal, Vol. 21, No. 9, September 1971.
Freeman, H. G. and Grendon, W. C., "Formaldehyde Detection and Con-
trol in the Wood Industry," Forest Products Journal, Vol. 21, No.
9, September, 1971.
Gehm, Harry, State-of-the-Art Review of Pulp and Paper Waste Treatment
Office of Research and Monitoring, U. S. Environmental
Protection Agency, Washington, D. C., April, 1973.
Gehm, Harry W. and Lardieri, Nicholas J., "Waste Treatment in
the Pulp, Paper, and Paperboard Industries," Sewage and
Industrial Wastes, Vol. 28, No. 3, March, 1956.
Glossary - Water and Waste Water Control Engineering, Prepared by
Editorial Board representing American Public Health Association,
American Society of Civil Engineers, American Water Works
Association, Water Pollution Control Federation, 1969.
Gould, M. and Taylor» J., "Temporary fcater Clarification System,"
Chemical Engineering Progress, Vol. 65, No. 12, December, 1969.
Groth, Bertil, Wastewater from Fiberboard Mills, Annual Finnish Paper
310
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Engineers' Association Meeting, Helsinki, April 12, 1962.
Hansen, George, (Task Force Chairman) Log Storage and Rafting in
Public Waters. Pacific Northwest Pollution Control Council,
August, 1971.
Hoffbuhr, Jack, Blanton, Guy, and Schaumburg, Frank, "The Character
and Treatability of Log Pond Waters," Industrial Waste, July-
August, 1971.
Kleppe, Peder J., and Rogers, Charles N., Survey of Water Utilization
and Waste Control Practices in the Southern Pulp and Paper
Industry, Water Resources Research Institute, University of
North Carolina, June, 1970.
Leker, James E., and Parsons, Ward C.s "Recycling Water - A Simple
Solution?," Southern Pulp and Paper Manufacturer, January,
1973.
Luxford, R. F., and Trayer, George W., (Forest Products Laboratory,
University of Wisconsin) Wood Handbook, U. S. Department of
Agriculture, Washington, D.C. 1935.
Malo, Bernard A., "Semichemical Hardwood Pulping and Effluent
Vol. 39, No. 11, November 1967.
McHugh, Robert A., Miller, LaVerne SI, and Olsen, Thomas E., The
In the Pacific Northwest, Division of Sanitation and Engineer-
ing, Oregon State Board of Health, Portland, 1964.
Parsons, Ward C., "Spray Irrigation of Wastes from the Manufacture
of Hardboard," Purdue Wastewater Conference, 1967.
Parsons, Ward C., and Woodruff, Paul H., "Pollution Control: Water
Conservation, Recovery, and Treatment," TAPPI, 53:3, March,
1970.
Quirk, T. P., Olson, R. C., and Richardson, G., "Bio-Oxidation of
Concentrated Board Machine Effluents," Journal, Water Pollu-
tion Control Federation, Vol. 38, No. 1, 1966.
Reinhall, Rolf, and Vardheim, Steinar, Experience with the DKP Press,
Appit'a Conference, Australia, March, 1965.
Robinson, J. G., "Dry Process Hardboard," Forest Products Journal,
July, 1959.
Sawyer, Clair N., Chemistry for Sanitary Engineers, Second Edition,
McGraw-Hill, New York, 1967.
Shreve, Norris, Chemical Process Industries, McGraw-Hill, New York,
1967.
Timpe, W. G., Lang, E., and Miller, R. L., Kraft Pulping Effluent
311
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Treatment and Refuse -State-of-the-Art," Office of Research and
Monitoring, U. S. Environmental Protection Agency, Washington,
D. C., 1973.
Tretter, Vincent J., Or., "Pollution Control Activities at Georgia-
Pacific," Forest Products Journal. Vol. 21, No. 9, September,
1971.
Wood Products Sub-Council, "Principal Pollution Problems Facing
the Solid Wood Products Industry," Forest Products Journal.
Vol. 21, No. 9, September, 1971.
312
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SECTION XIV
GLOSSARY
"Act" - The Federal Water Pollution Control Act Amendments of 1972.
Activated Sludge - Sludge floe produced in raw or settled waste
water by the growth of zoogleal bacteria and other organisms in the
presence of dissolved oxygen and accumulated in sufficient
concentration by returning floe previously formed.
Activated Sludge Process - A biological waste water treatment
process in which a mixture of waste water and activated sludge is
agitated and aerated. The activated sludge is subsequently
separated from the treated waste water (mixed liquor) by
sedimentation and wasted or returned to the process as needed.
Aerated Lagoon - A natural or artificial waste water treatment pond
in which mechanical or diffused-air aeration is used to supplement
the oxygen supply.
Aerobic - condition in which free, elemental-, oxygen is present,
Additive - Any material introduced prior to the final consolidation
of a board to improve some property of the final board or to
achieve a desired effect in combination with another additive.
Additives include binders and other materials. Sometimes a
specific additive may perform more than one function. Fillers and
preservatives are included under this term.
Air Drying - Drying veneer by placing the veneer in stacks open to
the atmosphere, in such a way as to allow good circulation of air.
It is used only in the production of low quality veneer.
Air-felting - Term applied to the forming of a fiberboard from an
air suspension of wood or other cellulose fiber and to the arrange-
ment of such fibers into a mat for board.
Anaerobic - Condition in which free elemental oxygen is absent.
Asplund Method - An attrition mill which combines the steaming and
defibering in one unit in a continuous operation.
Attrition Mill - Machine which produces particles by forcing coarse
material, shavings, or pieces of wood between a stationary and a
rotating disk, fitted with slotted or grooved segments.
Back - The side reverse to the face of a panel, or the poorer side
of a panel in any grade of plywood that has a face and back.
Bag Barker - See debarker.
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Blue Stain - A biological reaction caused by a stain producing
fungi which causes a blue discoloration of sapwood, if not dried
within a short time after cutting.
Biological Waste water Treatment - Forms of waste water treatment
in which bacterial or biochemical action is intensified to
stabilize, oxidize, and nitrify the unstable organic matter
present. Intermittent sand filters, contact beds, trickling
filters, aerated lagoons and activated sludge processes are
examples.
Slowdown - The removal of a portion of any process water to
maintain the constituents of the solution at desired levels.
BODS - Biochemical Oxygen Demand is a measure of biological
decomposition of organic matter in a water sample. It is
determined by measuring the oxygen required by microorganisms to
oxidize the organic contaminants of a water sample under standard
laboratory conditions. The standard conditions include incubation
for five days at 20°C.
Bolt - A short log cut to length suitable for peeling in a lathe.
Boultonizing - A conditioning process in which unseasoned wood is
heated under a partial vacuum to reduce its moisture content prior
to injection of the preservative.
Casein - A derivative of skimmed milk used in making glue.
Caul - A steel plate or screen on which the formed hardboard wetlap
mat is placed for transfer to the press, and on which the mat rests
during the pressing process.
CCA-Type Preservative - Any one of several inorganic salt formula-
tions based on salts of copper, chromium, and arsenic.
Chipper - A machine which reduces to chips.
Clarifier - A unit of which the primary purpose is to reduce the
amount of suspended matter in a liquid.
Clipper - A machine which cuts veneer sheets to various sizes and
also may remove defects.
Closed Steaming - A method of steaming in which the steam required
is generated in the retort by passing steam through heating coils
that are covered with water. The water used for this purpose is
recycled.
COD - Chemical Oxygen Demand. Its determination provides a measure
of the oxygen demand equivalent to that portion of matter in a
sample which is susceptible to oxidation by a strong chemical
oxidant.
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Coil Condensate - The condensate formed in steam lines and heating
coils.
Cold .Pressing - See pressing.
Commercial Veneer - See veneer; hardwood.
Composite Board - Any combination of different types of board,
either with another type board or with another sheet material. The
composite board may be laminated in a separate operation or at the
same time as the board is pressed. Examples of composite boards
include veneer-faced particle board, hardboard-faced insulation
board and particle board, and metal-faced hardboard.
Conditioning - The practice of heating logs prior to cutting in
order to improve the cutting properties of the wood and in some
cases to facilitate debarking.
Container Veneer - See veneer.
Cooling Pond - A water reservoir equipped with spray aeration
equipment from which cooling water is drawn and to which it is
returned.
£ore - Also referred to as the center
plywood panel.
The innermost segment of a
Creosote - A complex mixture of organic materials obtained as a by-
product from coking and petroleum refining operations that is used
as a wood preservative.
Crossband, v - To place the grain of the layers of veneer at
angles in order to minimize swelling and shrinking.
right
Crossband, n - The layers of veneer whose grain direction is at
right angles to that of the face piles, applied particularly to
five-ply plywood and lumber core panels, and more generally to all
layers between the core and the faces.
Curing - The physical-chemical change that takes place either to
thermosetting synthetic resins (polymerization) in the hot presses
or to drying oils (oxidation) used for oil-treating board. The
treatment to produce that change.
Cutterhead Barker - See debarker.
Cylinder - See retort.
Cylinder Condensate - Condensation that forms on the walls of the
retort during steaming operations. Also, of process in which
unseasoned wood is subjected to exposure to aft atmosphere of steam
to reduce its moisture content and improve its pereability.
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Debarker - Machines which remove bark from logs. Debarkers may be
wet or dry, depending on whether or not water is used in the opera-
tion. There are several types of debarkers including drum barkers,
ring barkers, bag barkers, hydraulic barkers, and cutterhead
barkers. With the exception of the hydraulic barker, all use
abrasion or scraping actions to remove bark. Hydraulic barkers
utilize high pressure streams of water. All types may utilize
water, and all wet debarking operations may use large amounts of
water and produce effluents with high solids concentrations.
Decay - The decomposition of wood caused by fungi.
Defiberization - The reduction of wood materials to fibers.
Delamination - Separation of the plies of a piece of plywood.
Digester - 1) Device for conditioning chips using high pressure
steam, 2) A tank in which biological decomposition (digestion) of
the organic matter in sludge takes place.
Disc Pulpers - Machines which produce pulp or fiber through the
shredding action of rotating and stationary discs.
DO - Dissolved Oxygen is a measure of the amount of free oxygen in
a water sample.
Drum Barker - See debarker.
Dry-clipping - Clipping of veneer which takes place after drying.
Dryers - Most commonly long chambers equipped with rollers on belts
which advance the veneer longitudinally through the chamber. Fans
and heating coils are located on the sides to control temperature
and humidity. Lumber kilns are also sometimes used. See also
veneer drying.
Dry*felting - see air-felting.
Durability - As applied to wood, its lasting qualities or perma-
nence in service with particular reference to decay. May be
related directly to an exposure condition.
Snd-checking - Cracks which form in logs due to rapid drying out of
the ends.
Exterior - A term frequently applied to plywood, bonded with highly
resistant glues, that is capable of withstanding prolonged exposure
to severe service conditions without failure in the glue bonds.
Face - The better side of a panel in any grade of plywood calling
for a face and back; also either side of a panel where the grading
rules draw no distinction between faces.
Face Veneer - see veneer; hardwood.
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Fiber - The slender thread-like elements of. wood or similar
cellulosic material, which, when separated by chemical and/or
mechanical means* as in pulping, can be formed into fiberboard.
Fiberboard - A sheet material manufactured from fibers of wood or
other ligno-cellulosie materials with the primary bond deriving
from the arrangement of the fibers and their inherent adhesive
properties. Bonding agents or other materials may be added during
manufacture to increase strength, resistance to moisture, fire,
insects, or decay, or to improve some other property of the
product. Alternative spelling: fibreboard.
Fiber .Preparation - The reduction of wood to a fibrous condition
for . hardboard.. manufacture, utilising mechanical, thermal, or
explosive methods.
Figure -- Decorative natural designs in wood which are valuable in
the furniture and cabinet making industries.
Finishing *• The final preparation of the product. Finishing may
include redrying, trimming, sanding,.sorting, molding, and storing,
depending On the operation and product desired.
Fire Retardant - A formulation of inorganic salts that imparts firo
resistance when injected into wood in high concentrations. Flitch
- A part of a log which has been so sectioned as to best display a
particular grain configuration or figure ,in the resulting veneer.
Flotation * The raising of suspended matter to the surface of the
liquid, in a tank as scum1—by aeration, the evolution of gas,
chemicals, electrolysis, heat, or bacterial decomposition.
Formation fForming) - The felting of Wood or other cellulose fibers
into a mat for hardboard. Methods employed: airfelting and wet
felting.
Glue - Adhesive which is used to join
plywood.. There are three types most
,o£ plywood, depending on raw material
They are 1) protein, 2) phenol
formaldehyde. The first is extracted
thermoplastic while the other two are
veneer sheets together into
often used in the manufacture
and intended product usage.
formaldehyde, and 3) urea
from plants and animals and
synthetic and thermosetting.
Glue Spreaders - Means of applying glue to veneer, either by use of
power driven rollers or spray curtain-coater applicators.
J3lue_ Line - The part of the plywood production process where the
glue is applied to the veneer and the plywood layers assembled.
GPP - Gallons per day.
GPM - Gallons per minute.
317
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Grading — The selection and categorization of different woods and
wood products as to its suitability for various uses. Criteria for
selection include such features of the wood as color, defects, and
grain direction.
Grain - The direction, size, arrangement, and appearance of the
fibers in wood or veneer.
Green Clipper - A clipper which clips veneer prior to being dried.
Green Stock - Unseasoned wood.
Hardboard - A compressed fiberboard of 0.80 to 1.20 g/cm3 (50 to 75
pounds per cubic foot) density. Alternative term: fibrousfelted
hardboard.
Hardboard Press - Machine which completes the reassembly of wood
particles and welds them into a tough, durable, grainless board.
Hardwood - wood from deciduous or broad-leaf trees.
Hardwoods
include oak, walnut, lavan, elm, cherry, hickory, pecan, maple,
birch, gum, cativo, teak, rosewood, and mahogany.
Heartwood - The inner core of a wood stem composed of nonliving
cells and usually differentiated from the outer enveloping layer
(sapwood) .
Heat-treated Hardboard - Hardboard that has been subjected to
special heat treatment after hot-pressing to increase strength and
water resistance.
Holding Ponds — See impoundment.
Hot Pressing - See pressing.
Humidif ication - The seasoning operation to which newly pressed
hardboard are subjected to prevent warpage due to excessive
dryness.
Hydraulic Barker - See debarker.
Impoundment - A pond, lake, tank, basin, or other space, either
natural or created in whole or in part by the building of
engineering structures, which is used for storage, regulation, and
control of water, including waste water.
Kiln Drying - A method of preparing wood for treatment in which the
green stock is dried in a kiln under controlled conditions of
temperature and humidity.
KIld-N - Kjeldahl Nitrogen - Total organic nitrogen plus ammonia of
a sample.
Lagoon - A pond containing raw or partially treated waste water in
which aerobic or anaerobic stabilization occurs.
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Leaching - Mass transfer of chemicals to water from wood which is
in contact with it.
Log.Bed - Device which holds a log and moves it up and down past a
stationary blade which slices sheets of veneer,
MGD - Million gallons per day.
mg/1 - Milligrams per liter (equals parts per million, ppm, when
the specific gravity is 1.0) .
Modified Steaming - A technique for conditioning logs which is a
variety of the steam vat process in that steam is produced by
heating water with coils set in the bottom of the vat.
Moisture - water content of wood or a timber product expressed as a
percentage of total weight or as percentage of the weight of dry
wood.
Non-Pressure Process p- A method of treating wood at atmospheric
pressure in which the wood is simply soaked in hot or cold pre-
servative.
Nutrients - The nutrients in contaminated water are routinely
analyzed to characterize the food available for microorganisms to
promote organic decomposition. They are:
Nitrogen. Ammonia (NH^) , mg/1, as N
Nitrogen, Total Kleldahl (NH3^ and Organic N) ,
mg/1, as N
Nitrogen Nitrate (NO3j , mg/1, as N
Total Phosphate, mg/1 as P
Ortho Phosphate, mg/1 as P
Oil-Recovery System - Equipment used to reclaim oil from waste
water.
Oily Preservative — Pentachlorophenol-petroleum solutions
creosote in the various forms in which it is used.
and
Open steaming - A method of steam conditioning in which the steam
required is injected directly into the cylinder.
Pearl Benson Index '- A measure of color producing substances.
Pentachlorophenol - A chlorinated phenol with the formula c6ci5_OH
and formula weight of 266.35 that is used as a wood preservative.
Commercial grades of this chemical are usually adulterated with
-tetrachlorophenol to improve its solubility.
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2H - pH is a measure of the acidity or alkalinity of a water
sample. It is equal to the negative log of the hydrogen ion
concentration.
Phenol - The simplest aromatic alcohol.
Pitch - An organic deposit composed of condensed hydrocarbons which
forms on the surface of dryers.
Plant Sanitation - Those aspects of plant housekeeping which reduce
the incidence of water contamination resulting from equipment
leaks, spillage of preservative, etc.
Plywood - An assembly of a number of layers of wood, or veneers,
joined together by means of an adhesive. Plywood consists of two
main types:
1) hardwood plywood - has a face ply of hardwood and is generally
used for decorative purposes.
2) softwood plywood — the veneers typically are of softwood and
the usage is generally for construction and structural purposes.
Plywood Pressing Time - The amount of time that plywood is in a
press. The time ranges from two minutes to 24 hours, depending on
the temperature of the press and the type of glue used.
Point Source - A discrete source of pollution.
Pressing - The step in the production operation in which sheets are
subjected to pressure for the purpose of consolidation. Pressing
may be accomplished at room temperature (cold pressing) or at high
temperature (hot pressing).
Press Pit — A sump under the hardboard press.
Pressure Process - A process in which wood preservatives and fire
retardants are forced into wood using air or hydrostatic pressure.
Radio Frequency Heat - Heat generated by the application of an al-
ternating electric current, oscillating in the radio frequency
range, to a dielectric material. In recent years this method has
been used to cure synthetic resin glues.
Resin - Secretions of saps of certain plants or trees. It is an
oxidation or polymerization product of the terpenes, and generally
contains "resin" acids and ethers.
Retort - A steel vessel in which wood products are pressure impreg-
nated with chemicals that protect the wood from biological
deterioration or that impart fire resistance. Also called -treating
cylinder.
Ring barker - See detarfcer.
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Rotary lathing - See veneer cutting.
Roundwood - Wood that is still in the form of a log, i.e. round.
Saw Kerf - Wastage of wood immediately adjacent to a saw blade due
to the cut-cleaning design of the blade, which enlarges the cut
slightly on either side.
Sawn Veneer - See veneer cutting,
Sedimentation Tank - A basin or tank in which water or waste water
containing settleable solids is retained to remove by gravity a
part of the suspended matter.
Segment Saw - A modern veneer saw which consists of a heavy metal
tapering flange to which are bolted several thin, steel saw
segments along its periphery. The segment saw produces
considerably less kerf than conventional circular saws.
Semi-Closed Steaming - A method of steam conditioning in which the
condensate formed during open steaming is retained in the retort
until sufficient condensate accumulates to cover the coils. The
remaining steam required is generated as in closed steaming.
Settling Ponds - A basin or tank in which water or waste water
containing settable solids is retained to remove by gravity a part
of the suspended matter. Also called sedimentation basin,
sedimentation tank, settling tank.
Slicing - See veneer cutting.
Sludge - The accumulated solids separated from liquids,
water or waste water, during processing.
such as
jimooth-two-sides (S-2-Si - Hardboard, or other fiberboard or
particle board produced when a board is pressed from a dry mat to
give a smooth surface oh both sides.
Softwood - Wood from evergreen or needle bearing trees.
Soil, Irrigation - A method of land disposal in which waste water is
sprayed on a prepared field. Also referred to as soil percolation.
Solids - Various types of solids are commonly determined on water
samples. .These types of solids are:
Total Solids (TS) - The material left after eva-
poration and drying a sample at 103-105°C.
Total suspended solids (TSS) - The material removed from
a sample filtered through a standard glass fiber
filter. Then it is dried at 1G3-105°C.
Dissolved Solids (PS) - The difference between
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the total and suspended solids.
Volatile Solids (VS1 - The material which is lost
when the sample is heated to 550°C.
Settleable solids - The material which
settles in an Immhoff cone over a period of time.
Spray Evaporation - A method of waste water disposal in which water
is sprayed into the air to expedite evaporation.
Spray Irrigation - A method of disposing of some organic waste
waters by spraying them on land, usually from pipes equipped with
spray nozzles.
Steam Conditioning - A conditioning method in which unseasoned wood
is subjected to an atmosphere of steam at about 120°C (249°F) to
reduce its moisture content and improve its permeability pre-
paratory to preservative treatment.
Steaming - Treating wood material with steam to soften it.
Sump - (1) A tank or pit that receives drainage and stores it
temporarily, and from which the drainage is pumped or ejected, (2)
A tank or pit that receives liquids.
Synthetic Resin (Thermosetting) - Artificial resin (as opposed to
natural) used in board manufacture as a binder. A combination of
chemicals which can be polymerized, e.g. by the application .of
heat, into a compound which is used to produce the bond or improve
the bond in a fiberboard or particle board. Types usually used in
board manufacture are phenol formaldehyde, urea formaldehyde, or
melamine formaldehyde.
Tapeless Splicer - A machine which permits the joining of
individual sheets of veneer without the use of tape. Individual
sheets are glued edge to edge, and cured, thus saving on tape costs
and sanding time during finishing.
Taping Machine - A machine which joins indivdual sheets of veneer
by taping them together. The tape is later sanded off during the
finishing operations.
Tempered Hardboard - Hardboard that has been specially treated in
manufacture to improve its physical properties considerably.
Includes, for example, oil-tempered hardboard. Synonym:
superhardboard.
Thermal Conductivity - The quantity of heat which flows per unit
time across unit area of the subsurface of unit thickness when the
temperature of the faces differs by one degree.
Thermosetting - See synthetic resin.
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TOC - Total Organic carbon is a measure of the organic con-
tamination of a water sample. It has an empirical relationship
with the biochemical and chemical oxygen demands,
T-PO4-P _ Total phosphate as phosphorus.
Turbidity - (1) A condition in water or waste water caused by the
presence of suspended matter, resulting in the scattering and
absorption of light rays. (2) A measure of the fine suspended
matter in liquids. (3) An analytical quantity usually reported in
arbitrary turbidity units determined by measurements of light
diffraction.
vacuum period
Vacuum water - Water extracted from wood during
following steam conditioning.
Vapor_ Drying - A process in which unseasoned wood is heated in the
hot vapors of an organic solvent, usually xylene, to season it
prior to preservative treatment.
Vat - Large metal container in which logs are "conditioned," or
heated prior to cutting. The two basic methods for heating are by
direct steam contact in "steam vats," or by steam heated water in
"hot water vats."
Veneer - A thin sheet of wood of uniform thickness produced by
peeling, slicing, or sawing logs, bolts, or flitches. Veneers may
be categorized as either hardwood or softwood depending on the type
of woods used and the intended purpose.
softwood veneer is used in the manufacture
of softwood plywood and in some cases the
inner plies of hardwood faced plywood.
Hardwood Veneer can be categorized according
to use, the three most important being:
(1) face veneer - the highest quality used
to make panels employed in furniture
and interior decoration.
(2) commercial veneer - used for crossbands,
cores, backs of plywood panels and con-
cealed parts of furniture.
(3) container veneer - inexpensive veneers
used in the making of crates, hampers,
baskets, kits, etc.
Veneer Cutting - There are four basic methods:
(1) rotary lathing - cutting continuous strips
by the use of a stationary knife and a lathe.
(2) slicing - consists of a stationary knife and
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an upward and downward moving log bed. On
each down stroke a slice of veneer is cut.
(3) stay log - a flitch is attached to a "stay
log," or a long, flanged, steel casting
mounted in eccentric chucks on a conventional
lathe.
(4) sawn veneer - veneer cut by a circular type
saw called a segment saw. This method
produces only a very small quantity of veneer
(see also "segment saw").
Veneer Drying - Freshly cut veneers are ordinarily unsuited for
gluing because of their wetness and are also susceptible to molds,
fungi, and blue stain. Veneer is usually dried, therefore, as soon
as possible, to a moisture content of about 10 percent.
Vene'er Preparation - A series of minor operations including grading
and matching, redrying, dry-slipping, joining, taping, and
splicing, inspecting, and repairing. These operations take place
between drying and gluing.
Water-Borne Preservative - Any one of several formulations of
inorganic salts, the most common which are based on copper,
chromium, and arsenic.
Water Balance - The water gain (inflows) of
loss (outflows) .
Wet Barkers - See debarker.
a mill versus water
Wet-Felting - Term applied to the forming of a fiberboard from a
suspension of pulp in water usually on a cylinder or Fourdrinier
machine; the interfelting of wood fibers from a water suspension
into a mat for board.
Wet Process - see Wet Felting.
Wet Scrubber - An air pollution control device which involves the
wetting of particles in an air stream and the impingement of wet or
dry particles on collecting surfaces, followed by flushing.
Wood Extractives - A mixture of chemical compounds, primarily
organics, removed from wood.
Wood Preservatives - A chemical or mixture of chemicals with
fungistatic and insecticida'l properties that is injected into wood
to protect it from biological deterioration.
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TABLE 71
CONVERSION TABLE
CO
ro
tn
MULTIPLY
acre
acre - feet
board foot
British Thermal
Unit
British Thermal
Unit/pound
cubic feet/minute
cubic feet/second
cubic feet
cubic feet
cubic inches
degree Fahrenheit
feet
gallon
gallon/minute
horsepower
inches
inches of mercury
pounds
pounds/cubic ft
million gallons/day
mile
pound/square inch
(guage)
square feet
square inches
1000 board ft
tons (short)
yard
ABBREVIATION
ac
ac ft
bd ft
BTU
BTU/lb
by
CONVERSION
0.405
1233.5
12.0
0.252
0.555
TO OBTAIN
ABBREVIATION
ha
cu m
cu ft
kg cal
kg
cfm
cfs
cu ft
cu ft
cu in
OF
ft
gal
gpn
hp
in
in Hg
Oto
Ib/cu ft
mgd
mi
psig
sq ft
sq in
1000 bd ft
ton
0.028
1.7
0.028
28.32
16.39
0.555 <°F-32}*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
16.05
3,785
1.609
(0.06805 psig +1)*
0.0929
6.452
2.36
0.907
cu nyfriin
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
on
atm
kg
kg/cu m
cu m/day
km
atm
sq m
sq cm
cu m
kkg
yd
0.9144
m
hectares
cubic meters
cubic feet
kilogram-calories
kilogram calories/
kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
kilowatts
centimeters
atmospheres
kilograms
kilograms/cubic meters
cubic meters/day
kilometer
atmospheres
(absolute)
square centimeters
square centimeters
cubic meters
metric tons
(1000 kilograms)
meters
*Actual conversion, not a multiplier
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