EPA 440/1-73/023
Development Document for
Proposed Effluent Limitations Guidelines
New Source Performance Standards
for the
PLYWOOD,HARDBOARD
and WOOD PRESERVING
Segment of the L
Timber Products Processing
Point Source Category
UNITED STATES ENVIRONMENTAL PROTECTION AGF^MC Y
DECEMBER 1973
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Publication Notice
This is a development document for proposed effluent limitations
guidelines and new source performance standards. As such, this
report is subject to changes resulting from comments received
during the period of public comments of the proposed regulations.
This document in its final form will be published at the time
the regulations for this industry are promulgated.
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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
Dr. Robert L. Sansom
Assistant Administrator for Air & Water Programs
Allen Cywin
Director, Effluent Guidelines Division
Richard E. Williams
Project Officer
December, 1973
Effluent Guidelines Division
Office of Air and Water Programs
United States Environmental Protection Agency
Washington, D.C. 20460
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ABSTRACT
A study was made of the plywood, hardboard and wood preserving
segment of the timber products processing point source category by
Environmental Science and Engineering, Inc., Gainesville, Florida, for
the U. S. Environmental Protection Agency. 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 pretreatment standards as required by Section 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 fcr 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 Wood
Preserving-Steam subcategories.
Best available technology economically achievable will result in
the elimination of discharge for hydraulic barking and direct steam
conditioning in 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.
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CONTENTS
Section
I
II
III
IV
V
VI
VII
VIII
Conclusions
Recommendations
Introduction
Purpose and Authority
Basis for Guidelines Development
General Description of the Industry
Barking
Veneer and Plywood
Hardboard
Wood Preserving
Industry Subcategorization
Introduction
Factors in Industry Subcategorization
Summary of Subcategorization
Water Use and Waste Characterization
Log Barking
Veneer and Plywood
Hardboard - Dry Process
Hardboard - Wet Process
wood Preserving
Selection of Pollutant Parameters
Introduction
Discussion of Pollutant Parameters
Control and Treatment Technology
Barking
Veneer
Plywood
Hardboard - Dry Process
Hardboard - Wet Process
wood Preserving
Cost* Energy and Non-Water Quality Aspects
Barking
1
3
9
61
69
135
139
223
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Veneer and Plywood Manufacturing
Hardfcoard - Dry Process
Hardboard - Wet Process
Wood Preserving - Steam
Wood Preserving
Wood Preserving - Boultonizing
IX The Best Practicable Control Technology 251
Currently Available 251
Introduction
Barking
Veneer
Plywood
Hardboard - Dry Process
Hardboard - Wet Process
Wood Preserving
Wood Preserving - Boultonizing
Wood Preserving - steam
X The Best Available Technology Economically
Achievable 271
Introduct ion
Barking
Veneer
Plywood
Hardboard - Dry Process
Hardboard - Wet Process
Wood Preserving
Wood Preserving - Boultonizing
Wood Preserving - steam
XI Standards of Performance for New Sources 281
Introduction
Barking
Veneer
Plywood
Hardboard - Dry Process
Hardboard - Wet Process
Wood Preserving
Wood Preserving - Boultonizing
Wood Preserving - steam
XII Acknowledgements 288
XIII References 291
XIV Glossary 303
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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 23
United States
3 Forest Industries 1968 Plywood Statistics 32
4 Softwood Plywood Production for 1972 33
5 Hardwood Plywood Production in the United States 34
6 Softwood Plywood Production in the United States 34
7 Inventory of Hardboard Manufacturing Facilities 47
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 73
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
via
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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 101
25 Analyses of Some Common Species of Wood 102
26 Wastewater Discharges from Wet Process Hardboard 109
27 Raw Wastewater Characteristics from Wet Process Hardboard 110
28 Progressive Changes in Selected Characteristics of Water 117
Recycled in Closed Steaming Operations
29 Phenol and COD Values for Effluents from Thirteen Wood 119
Preserving Plants
30 Ratio Between COD and BOD for Vapor Drying and Cresote 122
Effluent Wastewaters
31 Range of Pollutant Concentrations in Wastewater from a 122
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 per Day 130
by a Typical Wood-Preserving Plant
39 The Adhesive Mixes Used (Cascophen 3566C) 131
40 Representative Process Water Filter Efficiencies 154
41 Primary Settling Tank Efficiency 157
42 Treatment Efficiency of Biological Systems 159
Vlll
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TABLES (Continued)
Number Title Page
43 Example of an ASB System Performance Related to 164
Temperature
44 Method of Disposal of Wastewater by Wood Preserving 167
Plants in the United States
45 Method of Disposal of Wood Preserving Wastewater by 167
Region
46 Compliance with State and Federal Water Standards 168
Among Wood Preserving Plants in the United States
47 Plans of Wood Preserving Plants not in Compliance with 168
Water Standards in the United States
48 Type of Secondary Wastewater Treating Facilities 170
Installed or Planned by Wood Preserving Plants in the
United States
49 Type of Secondary Wastewater Treating Facilities 170
Installed or Planned by Wood Preserving Plants by Region
50 Efficiencies of Oil Separation Process 174
51 Effect of Lime Flocculation on COD and Phenol Content of 174
Treating Plant Effluent
52 Toxic Constituents in the Principal Salt-Type Preservatives 179
and Fire Retardant Chemcials Used in the United States
53 Concentrations of Pollutants Before and After Laboratory 182
Treatment of Wastewater from Two Sources
54 Concentration of Pollutants in Plant Wastewater Containing 183
Salt-Type Preservatives and Fire Retardants Before and
After Field Treatment
55 BOD, COD and Phenol Loading and Removal Rates for Pilot 187
Trickling Filter Processing a Creosote Wastewater
56 Relationship Between BOD Loading and Treatability for 188
Pilot Trickling Filter Processing a Creosote Wastewater
57 Sizing of Trickling Filter for a Wood Preserving Plant 189
58 Substrate Removal at Steady-State Conditions in Activated 189
Sludge Units Containing Creosote Wastewater
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TABLES (Continued)
Number Title Page
59 Reduction in Pentachlorophenol and COD in Wastewater 194
Treated in Activated Sludge Units
60 Results of Laboratory Tests of Soil Irrigation Method 197
of Wastewater Treatment
61 Reduction of COD and Pehnol Content in Wastewater Treated 198
by Soil Irrigation
62 Average Monthly Phenol and BOD Concentrations in Effluent 202
from Oxidation Pond at Weyerhaeuser1s DeQueen, Arkansas
Operation: 1968 and 1970
63 Effect of Chlorination on the BOD and Phenolic Content of 204
Pentachlorophenol and Creosote Wastewaters
64 Effect of Chlorination with Calcium Hypochlorite on the 205
Pentachlorophenol Content of Wastewater
65 Effect of Chlorination with Chlorine Gas on the 205
Pentachlorophenol Content of Wastewater
66 Effect of Chlorination of Pentachlolophenol Waste 206
on COD
67 Chlorine Required to Eliminate Taste in Aqueous Solutions 208
of Various Phenolic Compounds
68 Chlorine Demand of M-Cresol After Various Contact Times 209
69 Chlorophenol Concentration in Creosote Wastewater Treated 211
with Chlorine
70 Summary of Wastewater Characteristics for 17 Exemplary 218
Wood Preserving Plants
71 Metric Units Conversion Table 3T7
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FIGURES
Number Title Page
1 Wet Barking Process Diagram 14
2 Simplified Process Flow Diagram for 16
Veneer and Plywood Production
3 Detailed Process Flow Diagram for Veneer 17
and Plywood
4 Distribution of Softwood Veneer and 26
Plywood Mills Throughout the United
States
5 Distribution of Hardwood Veneer and 27
Plywood Mills Throughout the United
States
6 Distribution of Veneer and Plywood Mills 28
in the State of Oregon
7 Distribution of Veneer and Plywood Mills 29
in the State of North Carolina
8 United States Forest Areas 31
9 Growth of the Plywood Industry in the 35
United States
10 Raw Material Handling in the Hardboard 37
Industry
11 Typical Dry Process Hardboard Mill 38
12 Typical Dry Process Hardboard Mill 39
13 Geographical Distribution of Hardboard 50
Manufacturing Facilities in the United
States
14 Process Flow Diagram for a Typical 53
Wood Preserving Plant
15 Water Balance for a Plywood Mill Pro- 72
ducing 9.3 Million Square Meters per
Year on a 9.53 Millimeter Basis
xa
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FIGURES (Continued)
Number Ti11e Page
16 Water Balance for a Typical Dry Process 92
Hardboard Mill
17 Water Usage in Raw Materials Handling 94
in the Hardboard Industry
18 Water Use in the Explosion Process 96
19 Effect of Preheating Time and Tempera- 99
ture on Yield
20 The Chemical Components of Wood 103
21 Relation Between Dissolved Lignin and 104
Wood
22 Process Water Recycle in a Typical 105
Wet Process Hardboard Mill
23 Process Water Recycle in a Hardboard 107
Mill Using the Explosion Process
24 Water Balance for a Typical Wet 112
Process Hardboard Mill
25 Variation in Oil Content of Effluent 115
with Time Before and After Initiating
Closed Steaming
26 Variation in COD of Effluent with Time 116
Before and After Closed Steaming
27 Variation in COD Content and Waste- 118
water Flow Rate with Time
28 Relationship Between BOD and COD 121
for Wastewater from a Creosote
Treating Operation
29 Source and Volume of Daily Waste Use 132
and Recycling and Wastewater Source
at a Typical Wood-Preserving Plant
30 Plywood Plant Wash Water Reuse System 144
Xll
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FIGURES (Continued)
Number Title Page
31 Inplant Treatment and Control Techniques 150
at Mill No. 7
32 Typical Wet Process Hardboard Mill with 152
Pre-Press
33 Inplant Treatment and Control Techniques 153
at Mill No. 3
34 Typical Wet Process Hardboard Mill with 156
Savo System
35 Variation of Effluent BOD and Suspended 161
Solids as a Function of Time for Mill
No. 2
36 Variation of Effluent BOD and Suspended 162
Solids as a Function of Time for Mill
No. 3
37 Variation of Effluent BOD and Suspended 163
Solids as a Function of Time for Mill
No. 4
38 Effect of Detention Time on Oil Removal 175
by Gravity Separation
39 Determination of Reaction Rate Constant 191
for a Creosote Hastewater
40 COD Removal from a Creosote Wastewater 193
by Aerated Lagoon without Sludge
41 Phenol Content in VJeyerhaeuser's 201
Oxidation Pond Effluent Before and
After Installation in June, 1966 of
Aerator
42 Relationship Between Weight of Activated 213
Carbon Added, and Removal of COD and
Phenols from a Creosote Wastewater
Xlll
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FIGURES (Continued)
Number Title
43 Wastewater Flow Diagram for Wood
Preserving Plant Employing an
Extended Aeration Waste Treatment
System in Conjunction with Holding
Lagoons and Soil Irrigation
4-4 Wastewater Flow Diagram for Wood 220
Preserving Plant Employing Chemical
Flocculation, Sand Filtration, and
Soil Irrigation
45 Wastewater Flow Diagram for a Wood 221
Preserving Plant Employing an
Oxidation Pond in Conjunction with
an Aerated Raceway
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,
(U) 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 and other non-
existant: 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. 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 expenditure to 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 recommended quantitative limitations for
these particular operations, for the 1977 standards. 1983 standards,
however, recognize that better 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, 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 pro-
cessing 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 the
products covered in this segment would range from 1-2 percent under
present conditions. The above cost data reflects conditions where it is
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assumed no pollution control measures exist within the industry. Since
much of the suggested technology has already been purchased or is in
place, the figures are considerably higher than the real costs involved.
The increased capital costs above 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 high 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:
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)
VENEER
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:
Softwood Veneer
Hardwood Veneer
30-Day
Average
kg/cu m
(Ib/cu ft)
0.24
(0.015)
0.54
(0.034)
BOD
Daily
Maximum
kg/cu m
(Ib/cu ft)
0.72
(0.045)
1.62
(0.10)
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PLYWOOD
No discharge of waste water pollutants to
navigable waters.
HARDBOARD -DRY
No discharge of waste water pollutants to
navigable waters.
HARDBOARD - WET
BODC
TSS
pH Range
30-Day
Average
kg/kkg
(Ib/ton)
2.6
(5.2)
5.5
(11.0)
6.0-9.0
Daily
Maximum
kg/kkg
(Ib/ton)
7.8
(15.6)
16.5
(33.0)
6.0-9.0
WOOD PRESERVING
No discharge of waste water pollutants
to navigable waters
WOOD PRESERVING-
BOULTONIZING No discharge of waste waters pollutants to
navigable waters.
WOOD PRESERVING-
STEAM
COD
Phenols
Oil and
Grease
30-Day
Average
kg/1000 cu m
(lb/1000 cu ft)
550
(34.5)
0.65
(0.04)
12_0
(0.75)
Daily
Maximum
kg/1000 cu m
(lb/1000 cu ft)
1100
(68.5)
2.18
(0.14)
24.0
(1.5)
pH Range
6.0-9.0
6.0-9.0
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RECOMMENDED EFFLUENT LIMITATIONS BASED ON BEST AVAILABLE
TECHNOLOGY ECONOMICALLY ACHIEVABLE
SUBCATEGORY
EFFLUENT LIMITATION
BARKING
No discharge of waste water pollutants
to navigable waters.
VENEER
No discharge of waste water pollutants
to navigable waters.
PLYWOOD
No discharge of waste water pollutants
to navigable waters.
HARDBOARD - DRY
No discharge of waste water pollutants
to navigable waters.
HARDBOARD - WET
BODc
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
WOOD PRESERVING
No discharge of waste water pollutants
to navigable waters.
WOOD PRESERVING-
BOULTONIZING
No discharge of waste water pollutants
to navigable waters.
WOOD PRESERVING-
COD
30-Day
Average
kg/1000 cu m
(lb/1000 cu ft)
110
(6.9)
Phenols
0.064
(0.004)
Daily
Maximum
kg/1000 cu m
(lb/1000 cu ft)
220
(13.7)
0.21
(0.014)
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Oil and
Grease
pH Range
3.4
(0.21)
6.0-9.0
6.9
(0.42)
6.0-9.0
RECOMMENDED EFFLUENT LIMITATIONS AND SEW 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:
BODt
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)
VENEER
No discharge of waste water pollutants to
navigable waters.
PLYWOOD
No discharge of waste water pollutants to
navigable waters.
HARDBOARD - DRY
No discharge of waste water pollutants to
navigable waters.
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HARDBOARD - WET
WOOD PRESERVING
WOOD PRESERVING-
BOULTONIZING
BODC
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.
WOOD PRESERVING-
STEAM
COD
Phenols
Oil and
Grease
30-Day
Average
kg/1000 cu m
(lb/1000 cu ft)
110
(6.9)
0.064
(0.004 )
3.4
(0.21)
Maximum
Daily Average
kg/1000 cu m
(lb/1000 cu ft)
220
(13.7)
0.21
(0.014)
6.9
(0.42)
pH Range
6.0-9.0
6.0-9.0
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SECTION III
INTRODUCTION
PyRPQSE_AND_AyTHORITY
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 nor
later than July 1, 1983 of effluent limitations for point sources, other
than publicly owned treatment works, which are based on the application
of the best available 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 permitting 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, operation methods and other alternatives. The
regulations 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 regulations 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 Administrator's 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 log transport and 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 compositon, (e) definition of total waste
water flows and chemical compositon, (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 exemplary plants through the U.S.
Other sources of information, including EPA technical reports and
personnel, trade literature, industry personnel, and special
consultants. All references used in this study are tabulated in
Section XIII.
10
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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 segments 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
waste 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 sutcategory, including an identification 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 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
11
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•the application of various types of control techniques process changes,
non-water quality environmental impact (including energy requirements)
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^DESCRIPTIQN^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. While a greater total volume of
wastes may be discharged from other liquid waste generating factories of
the industry, the strength is lower and total flow is distributed over a
substantially larger number of installations. At any given location the
environmental impact of the relatively higher strength wastes from the
processes described here will be considerably greater. Therefore, the
first segment of the long-range study of the timber products processing
industry includes barking, veneer manufacturing, plywood manufacturing,
hardboard manufacturing, and wood preserving operations.
BARKIJSK3
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.
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 longitudinal axis. Logs are fed
into one end and tumbling and rolling action removes the bark. Water
12
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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.
sers 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.
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 h^draulic_barker uses a high pressure water jet to blast bark from a
log. Pressures" from 55.4 to 109.9 atm (800 to 1550 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 clean 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 oversize logs they process are
becoming unavailable.
All of the wet barkers use large amounts of water and it requires a
moderately complex operation (Figure 1) to separate the bark from the
water and dry it for disposal. In spite of the recovery operations, the
effluent from wet barkers may have a high solids concentration.
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 purposes 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 coniforous 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 United States
is manufactured from Douglas fir, with lesser quantities of veneer made
from ponderosa pine and hemlock. In the Southeast, southern pine is the
13
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PROCESS
WATER
PROCESS
BACK WATER
LOG
STORAGE
-
LOG
WASHER
WET DRUM
POCKET OR
HYDRAULIC BARKER
DEBARKED
LOGS
OFF GASES
CYCLONE
COARSE
SCREENING
FINE
SCREENING
-n--
ASH TO LAND
DISPOSAL
BARK BOILER
^
4
4
•t
+
4-
4-4-
4
i
-J
DIVERSION
BOX
I
i
EFFLUENT
PRODUCT AND
RAW MATERIAL
PROCESS WATER -—•
BACK WATER
GASES
BARK ASH
RESIDUE
EFFLUENT
FIGURE 1
- WET BARKING PROCESS DIAGRAM
-------
predominant raw 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 United States. The species that are
used in the western United states include Douglas fir, sitka 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 United States 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 United states, 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 in the Union. The majority of
softwood plywood is produced on the Pacific Coast while the bulk 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 United States.
Manufactur ing Proces s
The various operations for converting roundwood into veneer and finally
into plywood are relatively simple and 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, since the appearance of a plywood panel is greatly dependent
upon the manner in which the veneer is cut. Prior to the cutting of
veneer, logs may be heated, or "conditioned" as this serves to improve
the cutting properties of wood, particularly hardwood. Historically,
both hardboard 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
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LOG
STORAGE
DEBARKER
LOG
CONDITIONER
VENEER
CUTTER
VENEER
DRIER
VENEER OPERATION
VENEER
PREPARATION
GLUE
LINE
PRESS
FINISHING
PLYWOOD OPERATION
FIGURE 2 -
SIMPLIFIED PROCESS FLOW DIAGRAM FOR
VENEER AND PLYWOOD PRODUCTION
16
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LIQUID WASTE
"GREEN END" ' STEAM DR1ER WASH
OVERFLOW FROM CONDENSATE AND DELUGE
LOG POND WATER
: j
1 EXHAUST
GASES
LOG STORAGE ;
(LOG POND. _ LOG LOG VENEER VENEER |
COLD DECK UbBAKKING *' SIEAMING '"*" LATHt "*" DRIER ~
OR BOTH)
GASES
SOLIDS
BARK
LIQUIDS
1
VENEE
PREPAR/S
^^
GLUE
PREPARATION/^
GLUE
i
R _ GLUE .
TION "* ulNE
GLUE WASH
WATER
RECYCLE
1 1
PRESSING^ FINISHING
r
1 1
UNUSABLE TRIM AND
VENEER AND SANDER
TRIMMINGS DUST
:• — L - J1
SOLID WASTE IS BURNED IN BOILER
CHIPPED FOR REUSE OR SOLD
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 to
the same degree as the wet barking methods, heating commonly occurs
between the barking and veneering operations.
There are basically two methods of heating logs: (1) by directing 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 increases. 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.
Vene e r C utting
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 usu-
ally ranges from 1.27 to 0.635 mm (1/20 to 1/UO 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 transferred 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.
Yeneer^Preparation
Between the drying and gluing operations are a series of minor
operations that prepare or salvage veneer. These operations may include
grading and matching, redrying, dry-clipping, jointing, taping and
19
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splicing, and inspecting and repairing. 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^Operationg
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, 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
usually 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 with rubber-covered
rollers. More recently the practice of applying glue by means of sprays
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
Wes tern
Exterior 37 — -- 88
Wes tern
Interior 6.4 -- 47 62
S ou them
Exterior — — — 41 — —
S outhern
Interior 4.5 -- — 39
Hardwood — 25 — — 54 —
TOTALS 48 25 47 230 54
21
-------
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 adhesives.
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
edgegluing.
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 United
States, 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 United
States. Hardwood and softwood mills are located according to
availability of raw materials, and their distribution, therefore,
22
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TABLE 2
SUMMARY OF VENEER AND PLYWOOD PLANTS IN THE UNITED STATES
SOFTWOOD PLYWOOD
Alab ama
Ariz ona
Arkansas
California
C olorado
Florida
Georgia
Idaho
L ouis iana
Maryland
Mi chi gan
Mis s iss ippi
Mont ana
New Hampshire
North Carolina
Oklahoma
0 regon
South Carolina
Texas
Virginia
Washington
TOTAL
6
1
8
15
1
2
5
5
12
1
2
6
4
1
6
1
81
3
9
1
29
199
SOFTWOOD VENEER
Arkans as
California
Florida
Georgia
Maryland
Minnes ot a
New Jersey
North Carolina
Oregon
South Carolina
Texas
Virginia
Wash ingt on
Wis cons in
TOTAL
1
8
1
1
1
1
1
6
31
1
1
1
9
2
65
23
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TABLE 2 CONTINUED
HARDWOOD PLYWOOD
HARDWOOD VENEER
Alabama
Arkansas
California
Florida
Georgia
Illinois
Indiana
Louisiana
Maine
Michigan
Minnesota
Mississippi
9
4
6
3
6
1
6
2
3
4
2
6
Alabama
Florida
Georgia
Illinois
Indiana
Iowa
Kentucky
Maine
Maryland
Michigan
Minnes o t a
Miss iss ippi
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
24
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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
Ore gon 3
Virginia 1
TOTAL 11
TOTAL PLYWOOD PLANTS - 340
TOTAL VENEER PLANTS - 161
25
-------
..^
aitnown ( \ m^
'Cf.ajlowfi-..- "^^ \ ,/Z^y
L__— ScrorronS-^^
-------
NJ
A HARDWOOD - PLYWOOD
8 VENEER
SOFTWOOD a HARDWOOD-
PLYWOOD S VENEER
NOTE :
CREGON AND NC«TH CAROLINA ARE HIGH DENSITY
AREAS ANB ARE SHOWN ON SEPARATE MAPS.
FIGURE 5 - DISTRIBUTE OF HARDHOOD VENEER AND PLYWOOD HILLS THROUGHOUT THE UNITED STATES
-------
c~>
8
NJ
CO
LEGEND
§ SOFTWOOD
A HARDWOOD
Q SOFT AtO HARDA'OCD
FIGURE 6 - DISTRIBUTION OF VEHEER AND PLYWOOD MILS IN THE STATE OF OREGON
-------
NJ
• SOFTWOOD
A HARDWOOD
• SOFT AND HARDWOOD
WILMINGTON
FIGURE 7- DISTRIBUTION OF VENEER AND PLYWOOD hi US IN THE STATE OF NORTH CAROLINA
-------
follows the timber distribution as shown in Figure 8« A summary
inventory of the mills in the United States is presented in Table 2.
In 1968, a Forest Industry survey resulted in the most complete
statistics available for the plywood industry. At that time there were
175 softwood and 242 hardwood plywood mills. Although hardwood plywood
mills were more numerous, individual installations were smaller. In
1968, the production of softwood plywood in the United States was about
1.4 billion sq m on a 0.953 cm basis (15 billion sq ft on a 3/8 in
basis), while that of hardwood plywood was slightly more than 186
million sq m on a 0,635 cm basis (2 billion sq ft on a 1/4 in basis).
Included in Table 3 are statistics from the 1968 survey. More recent
data collected as a result of correspondence with the industry
association shows that in 1972, softwood plywood production was 1.71
billion sq m on a 0.953 cm basis (18.3 billion sq ft on a 3/8 in basis),
that of hardwood plywood was estimated as 205 million sq m on a 0.635 cm
basis (2.2 billion sq ft on a 1/1 in basis).
During the decade 1950-1960, the world's production of plywood rose by
150 percent. The United States accounted for about 50 percent of the
world's plywood production. More importantr however, is that the United
States along with Canada was the major source of softwood timber. As
the demand for construction materials continues to increase so does the
demand for softwood plywood. Twenty years ago practically all of the
softwood plywood in the United States was produced in the Pacific
Northwest from Douglas fir. In the past ten years the industry has
expanded into the southeastern United States and the use of southern
pine now accounts for 30 percent of the Nation's softwood plywood
production (Table 4) .
Hardwood plywood production has remained fairly constant over the past
20 years (Tables 5 and 6, and Figure 9)•
HARDBOARD
Hardboard is a generic term for a panel manufactured primarily from
interfelted ligno-cellulosic fibers consolidated under heat and pressure
in a hot press to a density of 0.5 g/cu cm (31 Ib/cu ft) or greater.
Other materials may be added to improve certain properties, such as
stiffness, hardness, finishing properties, resistance to abrasion and
moisture, as well as to increase strength, durability and utility.
There are two major hardboard manufacturing processes based upon the
manner in which the board is formed. In the wet process, water is used
as the medium for carrying the fibers and distributing them in the
forming machine. Air serves that function in the dry process. The
hardboard industry in the United States developed from a defiberization
process originated by William H. Mason during the 19206s, It was the
30
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UNITED STATES FOREST AREAS
Softwood timber is indicated by grey,
hardwood by black areas.
FIGURE 8
- UNITED STATES FOREST AREAS
-------
TABLE 3
FOREST INDUSTRIES 1968 PLYWOOD STATISTICS
Hardwood Ply-
Number of Softwood Ply- Number of wood Production
Softwood wood Production Hardwood In Square meters
Plywood In Square meters Plywood (6.35 mm - Basis)
Region Plants (9.53 mm Basis) Plants
New
England
Middle
Atlantic
East North
Central
West North
Central
South
Atlantic 10
East South
Central 7
West South
Central 17
Mountain 11
Pacific 130
Total
U.S.A. 175
15 7,175,000
7 1,675,000
41 29,950,000
4 4,200,000
54,730,000 72 42,660,000
49,500,000 24 30,625,000
142,500,000 11 4,100,000
101,720,000
1,063,000,000 31 77,375,000
1,411,500,000 205 197,750,000
32
-------
TABLE 4
SOFTWOOD PLYWOOD PRODUCTION FOR 1972
State Sq. Meters-9.53 mm Basis
California 140,543,000
Oregon 803,700,000
Washington 210,443,000
Idaho 156,366,000
Others 495,066,000
[Mostly South)
Note: Data obtained from APA.
33
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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
Note: Data obtained from Hardwood Plywood Manufacturing
Association - April 1, 1973.
TABLE 6
SOFTWOOD PLYWOOD PRODUCTION IN THE UNITED STATES
Year Sq . Meters
1925
1940
1950
1960
1970
1972
14
111
237
727
1,334
1,707
Surface Areas
,240
,690
, 700
,500
,700
,400
,000
,000
,000
,000
,000
,000
No. of Plants
12
25
68
152
179
--
Note: Data obtained from APA.
34
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OH
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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 10.
Figure 11 shows a typical inplant process diagram of a dry process
hardboard mill and Figure 12 shows a typical inplant process diagram of
a wet process hardboard mill. The principle 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 products, high cost of logs, and their general scarcity.
36
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LOGS
o
LOG
STO R AGE
LOG WASH
DEBARKER
CHIPPER
CHIP
rSTORAGE>
O
TO PROCESS
CHIP
WASH
FIGURE 10 - RAW MATERIAL HANDLING IN THE HARDBOARD INDUSTRY
37
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CHI PS
(50)
U)
QO
PREHEATERlZ REFINER
o
(7.5)
CHIPS
FIBER
*(J
FINISHING
(0)
PREPRESS
MAT
BOARD
(XX) APPROXIMATE PERCENT MOISTURE
FIGURE 11 - TYPICAL DRY PROCESS HARDBOARD MILL
-------
CH I PS
CHIPS
CO
UD
SCREW
-FEED
FIBER
DILUTION
WATER
PREHEATER ___ REFINER
MAT
BOARD
TO ATMOSPHERE
AT
1J
n
STOCK «—' WET FORMING
CHESTS I—I MACHINE
0.5)
(35)
TO
FINISHING
WATER IN
WATER OUT
(XX) APPROXIMATE PERCENT FIBER
(CONSISTENCY IN PROCESS)
FIGURE 12 - TYPICAL WET PROCESS HARDBOARD MILL
-------
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.
FiberJP reparation
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) calibre 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 or 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, due largely to the hydrolysis of hemicellulosic material
under conditions of steaming at high pressure. The explosion process is
used in only two hardboard mills in the United States.
By far the most widely used fiber preparation method consists of a
combination of thermal and mechanical pulping. Thermal plus mechanical
40
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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 or 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 posses 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,
having few abraded fibers and coarse fiber bundles.
In one process the chips are brought to a temperature of 170°C to 190°C
(3UO°C to 375°F) in a period of 20 to 60 seconds by means of steam
pressure between 7.8 and 12.2 atm (100 to 165 psi) and at this
temperature are passed through a disc refiner. It is claimed that due
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 sta-
tionary 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 UO
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 accomodate bulky
materials. It has fewer moving parts and fewer bearings than the double
disc mill.
41
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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 varies
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 vibratory or
rotary-type screen may be used.
42
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Forming Hardboard
The manufacture of hardboard consists basically of reducing wood
materials to fibers, 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 process or
the dry-felting (air-felting) process.
Wet-Felting: In the wet process the mat is usually formed on a
fourdrinier type machine such 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. The stock flows rapidly and
smoothly from the bottom of the head box onto an endless traveling wire
screen. Special 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 delivered
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. 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 (S2S).
These operations will be described later.
43
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Dry-Felting: The main difference between the dry, or airfelting
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_Pregs
The reassembly of wood particles is completed, and 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 kkg (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 impressed 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 plat-fens. 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 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 f t) ,
44
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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 back together. The actual amount of time required for
pressing and the details of temperature and pressure vary widely,
depending upon 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, unpressed 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.
E£§^§ilia_2£§£Sti2IlS: There are two basic types of hardboard, "smooth
one-side11 (S1S) arid "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
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.
45
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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^Temger ing
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
removing any excess. The oil is then stabilized by baking the sheet
from one to 4 hours at temperatures ranging from 113° 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.
Humidif icatign
Sheets of hardboard removed from the press or the tempering oven are
very hot and dry, and the boards must be subjected to a seasoning
operation called "humidif ication." 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 _ Pro cess ing
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.
Inventory of Hardboar (^Industry
In 1973, there were 27 manufacturing facilities which produced hardboard
by some variation of the two basic processes. As shown in Table 7, 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
46
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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)
Bemidji, 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
47
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TABLE 7 CONTINUED
(INVENTORY OF HARDBOARD MANUFACTURING FACILITIES)
Masonite Corporation
Laurel, Mississippi
Masonite Corporation
Ukiah, California
Superior Fibre
Superior, Wisconsin
S uperwood
Duluth, Minnesota
S up erwood
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, Mississippi
U.S. Gypsum
Pilot Rock, Oregon
Weyerhaeuser Company
Broken Bow. Oklahoma
48
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category. It has been estimated that in 1972, the total production of
hardboard in the United States, on a 3.2 nun (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 13.
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
wastes 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 increased 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 United States 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 United States Forest Service survey published in 1964, based on
information collected in 1962, established that the amount of timber
consumed in the United states 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 during the next 7 years to meet this
demand.
Somewhat akin to the saw mill part of the timber products processing in-
dustry, hardboard operations are spread nationally with some production
of each kind in each forest region of the United States. 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.
49
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tn
o
LEGEND
WET PROCESS
DRY PROCESS
DRY-WET PROCESS
WET- DRY PROCESS
fl) WET-DRY/ INSULATION
FIGURE 13 - GEOGRAPHICAL DISTRIBUTION OF HARDBOARD MANUFACTURING
FACILITIES IN THE UNITED STATES
-------
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, particle board and hardboard 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, 33 percent 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 two 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 due to operating performance and environmental capital
expenditures.
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 United States use at least 2 of the 3 types
of preservatives. Many treat with one or 2 preservatives plus a fire
retardant .
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
51
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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 preservative 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 conditioning 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.
Inventory of the Wood Preserving Segments
The wood preserving industry in the United States 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
52
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U)
R-CHlh-CHlHS
o o-
o &~ a ~
r
LO»RT TO£*tmnT IS S*UE WITHOUT «IH
Y
I
I
L.
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 RETARDANTS
OF REPORTING PLANTS IN THE UNITED STATES, 196
7-19
71
Year
Mat er ial
C reos o te
Cr eos o te-
Coal Tar
Creoso te-
Pe t roleum
Total
Creosote
Total
Petroleum
Penta-
chlorophenol
Chromat ed
Zinc Chloride
CCA
ACC
Pyresote
Non-Coin
FCAP
Osmose Flame
Proof
Other
Solids
(Units)
Million
Liters
Million
Liters
Million
Liters
Million
Liters
Million
Liters
Million
Kilograms
Million
Kilograms
Million
Kilograms
Million
Kilograms
Million
Kilograms
Million
Kilograms
Million
Kilograms
Million
Kilo grams
Million
Kilo grams
1967
329
216
135
559
279
11.2
0 .8
1.0
0.6
1.3
2.4
2.4
2.0
2. 7
1968
293
219
121
518
279
12.0
0 .7
1.4
0.5
1. 7
2. 7
1 .8
1.8
2.8
1969
274
206
115
485
258
11.6
0 .6
2.1
0.4
1.1
3.4
2.0
1.8
2.3
1970
256
229
125
475
286
12.9
0.7
2. 7
0.4
1.2
3.1
1 .2
2.0
1 . 7
19
242
218
118
441
307
14
0
3
0
1
2
1
2
1
71
.5
.6
.9
.5
. 2
.8
.0
.4
. 7
Note: Data are based on information supplied by approximately
357 plants for each year.
54
-------
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 United states 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
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TABLE
WOOD PRESERVING PLANTS IN THE UNITED STATES BY STATE AND TYPE
(1971)
Commercial
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
Kansas
Kentucky
Michigan
Minneso ta
Missouri
Neb raska
North Dakota
Ohio
Wis consin
TOTAL
SOUTHEAST
Florida
Georgia
North Carolina
South Carolina
Virginia
TOTAL
Press ure
0
1
ia 0
0
6
1
1
4
5
6
1
0
3
28
6
6
0
0
6
4
3
7
0
X)
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
JO
0
0
0
0
0
Non-
Press ure
0
0
0
0
0
0
0
0
1
0
0
0
1
2
1
0
1
0
0
a
0
0
0
0
0
i
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
Alab ama
Arkans as
Lo uisiana
Miss is sippi
Oklahoma
Tenness ee
Texas
TOTAL
ROCKY MOUNTAIN
Arizona
Colorado
Idaho
Mont ana
Nevada
New Mexico
South Dakota
Utah
Wyoming
TOTAL
PACIFIC
Alaska
Cali f ornia
Hawaii
Oregon
Washington
TOTAL
UNITED STATES
TOTAL
Press ure
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-
Press ure
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
Press ure
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
Press ure
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-
Press ure
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
-------
Ln
CO
TABLE 10
MATERIALS TREATED IN THE UNITED STATES, BY PRODUCT AND PRESERVATIVE, 1967-1971
(Note:
Pres ervative
Creosote and
Creosote-Coal
Tar
Creos ote-
Petroleum
Petroleum-
Pent achloro-
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
-------
TABLE 10 CONTINUED
I-"
Thousand C
Pres ervative
Fluor Chrome
Ars enate
Phenol
Creosote-
Pent achloro-
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
ubic Meters
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
CTl
O
Thousand Cubic Meters
Preservative
Fire
Re tardants
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
Lumb er
and
Timb ers
99
94
104
100
47
18
72
3
19
1,716
1,772
1,687
1,576
1,694
Fence
Posts
_„
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 segments (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
H. 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 this 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.SUBCATEGQRIZATIQN
Tyjpg_ofr Products Produced
As discussed in Section III, there are wide differences in the products
manufactured by the segments 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,
61
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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 type of product produced. Thus, the initial industry
subcategorizations established are: (1) barking, (2) veneer and plywood
manufacture, (3) hardboard manufacture, and (U) 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 entirely
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 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 a variance 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 nature of the waste waters from this process are
such as to warrant note of the differences within the subcategory.
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),
62
-------
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.
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 or no process waste water discharge from the
dry-felting process, while there is a continuous and substantial waste
water discharge 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 also be
addressed by a future regulation.
In the 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 substantially 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 base or salt (water soluble) type, and may be infused into
the wood by soaking or under pressure. Prior to treatment, the wood may
be conditioned by direct steam 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
63
-------
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 category.
Water use and waste characterization, related to the process employed,
and discussed in Section V, indicates that the wood preserving segment
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 segment. 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 Boultonizing
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. In the processing
of veneer and plywood,for example, it is known that 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
conditioning while some species of softwood do not.
While it would be expected that different waste water characteristics
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, differences 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.
64
-------
Agg^Qf .Facility
The age of the manufacturing facility has been rejected as a determining
factor for subcategorization of the industry. Barking is accomplished
by a variety of processes and ages of equipment. Within the group of
processes which use mechanical abrasion to remove the bark, there
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 United States, 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.
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 subcategory, 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 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
65
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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.
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 processes in the remainder of the industry, a
subcategorization on this basis is not indicated, because it is
effectively accomplished by manufacturing process employed.
Treatability^of^Waste Waters
Treatability of waste waters in not a justified basis for further
subcategorization, as waste waters may be easily dealt with and treated
within the framework already established.
Air, Pollution__Control^Equipment
Air pollution is not a major problem in this manufacturing segment. Air
pollution control equipment is not a major factor affecting waste water
discharge elsewhere in the timber products processing category and,
therefore, the industry subcategorization should not be be affected by
air pollution equipment.
SUMMARY OF SUBCATEGORIZATION
The segments of the timber industry considered in this document 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. The product
from the barking subcategory is normally used as a raw or feed material
to other subcategories in the timber products processing category rather
than sold as a finished product.
66
-------
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 subcategory includes the operations of
laminating layers of veneer to form finished plywood.
U. Hardboard - Dry Process. The dry process hardboard subcategory
includes all of the manufacturing operations attendant to the production
of finished hardboard from chips, dust, 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.
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.
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.
67
-------
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
hydraulic barking are shown in Table 11. The total suspended solids
content in the discharge from hydraulic barking ranges from 521 to 2,362
mg/lr 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 reused, which
accounts for part of the increase. The high 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.
YENEER_AND_PLYWOgp_MANyFACTyRING
Water usage varies widely in the veneer and plywood segment 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. Since 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, water is used in the following operations:
69
-------
TABLE 11
ANALYSIS OF DEBARKING EFFLUENTS
Mill
1
2
3
4
5
6
7
8
9
10
11
Type of
Debarking
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Drum
Drum
Drum
Total
Suspended
Solids
(mg/1)
2,362
889
1,391
550
521
2,017
2,000
600
2,017
3,171
2,875
Non-Set
Solids
(mg/1)
141
101
180
66
53
69
F200
41
69
57
80
BODS
(mg/1)
85
101
64
99
121
56
97
250
480
605
987
Color Units
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. The water use and
waste characteristics for each operation are discussed below.
Log Conditioning JStearning)^
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 sg 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 board on a 9.53 mm (3/8 in) basis, and a total solids load of 29,200
kg/million sq m of board 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 is discharged and replaced
with clean water. Some plants settle spent waste water and pump it back
into the vats. Chemical characteristics for hot water vats for a series
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
-------
47,034(1)
163,440(s)
163,440(1)
44, 220 (s)
1,634(1)
i fi-^4 n \
WATER
IN
LOGS
1
WATER
I.N
PLYWOOD
(
(50)
»
LOG
CONDITIONING
1
(50)
»
VAPORS
OFF
DRYERS
1
(3)
t
DRYER
WASHING
(3)
1
(7)
VAPORS
OFF
PRESS
<
t
(7.5)
GLUE
WASHUP
i
>
(7.5)
GLUE
6,583(1)
454 (s)
4,222(1)
4,222(1)
4,222(1)
Water in = 485,800
Water out= 485,800
(1) - liquid water
(2) - steam
(XX) - \ of moisture by weight
based on dry wood
All units in Kg of water per Day
(lb. 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
72
-------
UJ
TABLE 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
8,310
4,005
8,670
3,435
3,312
1,668
DS
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 . Phenols
450 0.69
—
245 0.57
249
30 0.30
28 0.20
Kjld-N
56.8
16.5
39 .3
—
1.87
4.73
T-P04-P pH
5.70 4.12
14 4.1-6.1
5.38
5.3
.173
1.93
No
te: All units are in mg/1 except Turbidity, which is in JTU's and pH.
-------
TABLE 13
CHARACTERISTICS OF HOT WATER STEAM VAT DISCHARGES
Concentrations
Plant
A
B
C
D*
E*
BOD
4,740
3,100
326
1,000
1,900
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
6
2
2
1
1
TS Turb. Phenols
,470 -- 0.40
,030
,020 800 <1.0
,000
,781
Kjld-N T-P04-P pH
26.4 -- 5
23.4 -- 3
16. 2 < 1.0 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 water were taken 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. In addition, the volume
of water necessary to wash 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 generated 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
-------
CTl
TABLE 14
ANALYSIS OF DRYER WASHWATER
Plant
A
Part I
Part B
B
BOD
210
840
60
COD DS
1,131 643
6,703 1,095
1,586 1,346
SS
113
5,372
80
TS Turb . Phenols Color
756 19 1.31 32
6,467 50 0.20 43
1,426 6 4.68 51
Kjld-N T-P04-P
17.7 1.93
211 11.0
2.91 0.495
Note: All units are concentrations in mg/1 except for Turbidity in
JTU's and Color in Pt-Cobalt Units.
-------
TABLE 15
WASTE LOADS FROM VENEER DRYERS
Plant
A
B
BOD
60 .94
2.33
COD
412
60 .6
DS
99 .7
52.3
SS
319
3.09
TS
418
55.2
Phenols
0.018
0.014
Kjld-N
13.2
0.112
T-P04-P
0.18
0.019
Note: All units are in kilograms per million square meters.
-------
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. Table 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 is. 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 19, 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 handled 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 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).
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 schematic diagram of water balance is given in
Figure 16.
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
Defoamer
Extender (Wheat Flour)
Urea Formaldehyde Resin
79
-------
TABLE 17
AVERAGE CHEMICAL ANALYSIS OF PLYWOOD GLUE
Analysis
and Units
COD,
mg/kg
BOD,
mg/kg
00
o TOG,
mg/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
260
12,000
59 ,000
118,000
177,000
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
-------
CO
TABLE 18
AVERAGE CHEMICAL ANALYSIS OF PLYWOOD GLUE WASHWATER
(ASSUMING A 20:1 DILUTION WITH WATER)
Analys is
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,
mg/kg
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
-------
TABLE 19
CHARACTERISTICS OF GLUE WASHWATER
(mg/D
Plant
A
B
oo C
to
BOD COD TS
15,900 16,700 7,910
8,880
710 5,670 5,890
DS SS Kjld-N T-P04-P
6,850 21.8 2.46
6,310 1,640 20.2
3,360 2,530
Phenols pH
4.16 9.77
0.14 5.25
10.8
Note: Plants A and C utilize phenolic glue and Plant C uses urea glue
-------
CO
TABLE 20
AMOUNT OF ADHESIVE WASHWATER GENERATED IN SOUTHERN PINE PLYWOOD PLANTS
Plywood Plant
Production
(million sq. Weekly
meters/Year) Adhesive
9.53mm basis Use (kg)
2
3
4
5
6
7
8
9
. 7
.6
.5
.4
.3
.2
.1
.0
38
51
64
77
90
102
115
128
,590
,454
,316
,180
,044
,906
,770
,634
Amount of Washwater
Glue
Mixers
9
9
9
11
23
23
23
23
,286
,286
,286
,939
,877
,877
,877
,877
Glue
Hold Tanks
1
1
1
1
2
2
2
948
,895
,895
,895
,895
,843
,843
,843
Produced (Liters)
Glue
Spreaders
6,
13,
13,
13,
19,
19,
26,
26,
633
265
265
265
898
898
530
530
Total
16,866
24,446
24,446
27,099
45,670
45,670
53,250
53,250
Amount of
Adhes ive
per week
7,364
9,820
2,276
14,732
17,188
19,640
22,096
24,552
-------
TABLE 21
GLUE WASTE DISCHARGE MEASUREMENTS
Average Discharge
00
>£>.
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
(sq . m -
9
12
9
6
Production
9 .53mm basis)
,000
,150
,000
,300
,000
,000
,000
,000
Number of
Spreaders
4
3
4
2
-------
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 (85 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 equi-
valent to a discharge of 163,000 kg/day (360,000 Ib/day or 3,500
Ib/ton) .
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).
85
-------
HARDBOA.RD - 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
(14) 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 necessarily 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 conditions 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 (100 gal/ton) to 1,250 1/kkg (300 gal/ton).
Typical chemical analyses would include a BOD of 200 mg/1 and suspended
solids of 500 mg/1.
86
-------
CO
TABLE 22
DRY PROCESS HARDBOARD
WASTEWATER FLOW AND SOURCE
Mill
A
B
C
D**
E
F
G
H
I
J**
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
-------
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
may cause 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 supposedly 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. Due 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 presently no chip
washing systems in use, there are no water usage figures or waste
characteristics available in the dry process hardboard industry.
Resinugystem
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. Due to the small quantity of water and
ease of reuse, there should be no discharge from the resin system in a
dry process hardboard mill.
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 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
88
-------
TABLE 23
AVERAGE CHEMICAL ANALYSIS OF PLYWOOD RESIN
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, 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
-------
inplace. After soaking, cauls are removed, rinsed with fresh water,
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/kkg (1.0 gal/ton)
of hardboard production.
MiscellaneousrjHousekeeping Water
Water may be used in small quantities for various cleaning procedures.
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 process hardboard mills indicates
that this water usage can be expected 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.
Humidificatipn
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 process.
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 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
90
-------
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 concern. 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^InmA^Dry Process Hardboard^.Mill
An account of water gains and losses in a typical dry process hardboard
mill is given in this section. 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/Jckg 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 wood = 1,000 1/kkg
(50 percent moisture) (240 gal/ton)
The water usage within a dry process hardboard mill is highly variable
depending upon water usage within an individual process and plant
operation. A typical dry process mill uses water only for glue
preparation, caul wash, humidification, and cooling.
Water in glue = 35 1/kkg of
(3.5 percent of product) product (8.4 gal/ton)
Caul wash 950 1/day =4.2 1/kkg of
(250 gal/day) product (1 gal/ton)
Humidification = 50 1/kkg of
(5.0 percent of product) product (12 gal/ton)
Cooling water-284,000 = 1,250 1/kkg of
I/day (75,000 gal/day) product (300 gal/ton)
91
-------
N)
6AIN = IOOO
1
RAW
MATERIALS
HANDLING
COOLING WATER
GAIN = I250 RESIN LOSS = 460
SYSTEM
GAIN=3
1 = 1
FIBER
PREPARATION
I
COOLING WATER
LOSS=I250
FIBER
DRYER
FELTER
CAUL WASH
GAIN=4.2-*
LOSS = 4.2
PRESS
FRESH WATER
GA!N=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*
-------
W.2.ter_0utflows: Water outflows in a dry process hardboard mill result
from:
Fiber drying to 7.5 = 960 1/kkg of
percent moisture product (230.4 gal/ton)
Press evaporation = 75 1/kkg of
(0.0 percent moisture) product (18 gal/ton)
Water in product = 50 1/kkg of
(5.0 percent moisture) product (12 gal/ton)
Caul wash (950 I/day) =4.2 1/kkg of
(250 gal/day) product (1.0 gal/ton)
Cooling water = 1,250 1/kkg of
(284,000 I/day) product (300 gal/ton)
HARDBOARD __- WET PRQCESg
Specific Water_Uses
There are several processes in the wet process hardboard industry where
water is used. Wet process mills have similar overall water uses and
waste water sources; however, due to variations from mill to mill there
will be variations in water use in the following processes:
1. Raw materials handling
2. Fiber preparation
3, Mat formation and pressing
4. Miscellaneous
Raw_Materials_Handling
There are two potential sources of water usage and waste discharge in
the raw materials handling process; (1) log washing and (2) chip
washing (see Figure 17 for schematic diagram of the raw materials
handling processes). The section on dry process hardboard discusses raw
materials handling, and the figures and discussion 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) the explosion process, and (2) thermal plus mechanical
refining 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
93
-------
LOGS
o
LOG
STORAGE
LOG WASH
DEBARKER
CHIPPER
WATER IN
WATER OUT
o
TO PROCESS
FIGURE 17 - WATER USAGE IN RAW MATERIALS HANDLING
IN THE HARDBOARD INDUSTRY
94
-------
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 preparation 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 hard-
board. All solubles released during fiber preparation in the dry
process are retained in the board.
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 interpenetrating 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 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 1UO°C, considerable and rapid removal of hemicelluloses occurs.
Cellulose resists hydrolysis better than the hemicellulose fractions.
95
-------
CHIP1
WATE R IN
4%2ZZL WATER OUT
V
TO ATMOSPHERE
STOCK rz WET FORMING
jl MACHINE
MAKE-UP
WATER
1*
V
TO
FINISHING
FIGURE 18 - WATER USE IN THE EXPLOSION PROCESS
-------
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
temperatures, 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 hydrolyzed, 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 3 m (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 of continuous or quick-cycle digesters may be substituted and give
similar results. Due to 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, i.e.:
Variables associated with the wood:
97
-------
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 as, in general, the pre-heating
periods used in practice are fairly short in comparison to the time it
takes for the chips to reach the final temperature in the pre-heater.
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 oligosaccharides are
formed. These short-chain molecules are small enough to dissolve in
water. The other reaction is the hydrolysis 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 of wood substances
during the pre-heating stage. The rate of reaction seems to roughly
double with an increase in temperature of about 8°C (1t°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 preheating and defibration steps. An examination of the com-
position of the substances 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 300°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 con-
ditions—a pH value of about 3 was obtained in an extract from an
98
-------
YIELD %
100
90
80
I58°C
I72°C
I83°C
70
5 IO
PREHEATING TIME
15 20
MINUTES
FIGURE 19
- EFFECT OF PREHEATING TIME AND
TEMPERATURE ON YIELD
99
-------
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 t 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 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 recycle and 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
100
-------
TABLE 24
SOME PROPERTIES OF CERTAIN UNITED STATES WOODS
Snliiliiliiij. %
Spitiec
Kii»i'!matin
Krc'l
Silka
Wliilc
Kir
Alpine
HaKain
Grand
Noble
Silver
While
l)ou«;l;is fir, coast type
Pine"
Jack
Loblolly
Lodge pi ilc
Ixwglciif*
Pomlerosa
Red
Shorlleaf
Slash
Sugar
While eastern
White western
Hemlock
Eastern
Western
Inarch
Tamarack
Western
Cypress, l«ild
Ash, white
llasswood
Beech
liirch
Paper
Yellow
Rultcmnr
Chcslmil
Cucimilicr live
Elm, American
Gum
lilack
S\vivt
Maple
IU-d
Silver
Su\;a r
Poplar
Quaking a^prn
I!.ik.m
K:i\lein i-iillimwuixl
l.:iri;r-(iMlli a.vpcn
Sycamine
Yclliiw- pnpl.ir
Sjirri/ir
SliruiK-
Ituik.
Kile
Eml
Crlliihsr.
tipmn.
Hot
irnlfr
F.llwr
Conifers
0.3)
0.3S
0.37
0.37
0.31
0.34
0.37
0.35
0.35
0.35
0.45'
0.39
0.47
0.38
0,5-1
0.3S
0.44
0.46
0.50
0.35
0.3-1
0.36
0.38
0.3S
0.49
0.48
0.42
0.55
0.32
0.50
0.48
0.55
0.36
0.40
0.44
0.40
0.46
0.44
0.49
0.44
0.50
0.3.')
0.30
O.:i7
O..T)
O.-IO
o.as
10.4
11.8
11.5
13.7
9.0
10.8
10.6
12.5
14.1
9.4
11.8
10.4
12.3
11.5
12.2
9.6
11.5
12.3
12.2
7.9
8.2
11.8
9.7
11.9
13.6
13.2
10.5
13.3
15.8
1G.3
16.2
10.7
10.2
ll.fi
13.6
1-1.6
13.9
15.0
13.1
' 12.0
14.5)
11.5
10.5
1-1.1
ll.S
14.2
)2.3
11.1
—
—
12.4
—
9.1
15.9
10.6
9.S
10.5
7.5
ll.fi
_
11.9
15.0
12.5
18.9
9.7
—
S.S
-
lltinln.:
_
_
13.2
,
_
9.(>
J2.4
__
13.7
IS.4
—
1-1.7
—
—
240
350
350
320
220
29(1
3GO
290
310
330
4SO
370
450
3.3d
590
310
340
410
630
310
310
310
400
430
3SO
450
390
900
250
850
500
7SO
390
420
520
620
6)0
520
700
5'.i()
970
3(X>
2.10
310
37(1
6!()
310
250
410
430
350
280
290
420
330
3GO
380
510
3.SO
420
320
5-50
330
360
410
GdO
320
310
310
500
520
400
470
4 -in
1,010
25)0
970
470
810
4)0
530
(i(K)
aso
790
(iill
7SO
(i7(l
1 .070
2MI
24(1
3SU
•KXI
7(x>
3
-------
TABLE 25
ANALYSES OF SOME COMMON SPECIES OF WOOD
(Extractive-free basis, percent of dry wood)
Constituent
Ash
Acetyl
Lignin
a-Cellulose
Hemicellulose
Total
(a
a-Cellulose (b
Mannac
Xylan
Uronic
CH (d
Total
(c
anhydride
(a
Douglas
fir
0.
0.
28.
57.
14.
100.
48.
5.
6.
2.
0.
92.
3
6
4
2
1
6
3
4
2
8
0
0
Loblolly
pine
2
Summat
5
1
0.
1.
9.
3
1
5
Black
spruce
0.
1.
28.
4
1
0
Southern
red oak
0.
3.
25.
2
3
2
ion A
5.
5.
101.
Summat
4
1
9
0
3
2
51.
17.
98.
5
4
4
45.
23.
97.
7
3
7
ion B
6.
4.
0.
3.
0.
6.
6
7
1
8
2
3
45.
8.
10.
4.
0.
97.
6
0
5
1
2
9
43.
—
20.
4.
0.
97.
7
0
5
6
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
(jj
1
TOTAL
WOOD
SUBSTANCE
Neutral
Solvents
and/or
Steam
i
i
i
Soluble
or
Volatile
*
3
EXTRACTIVES
5%
2
EXTRACTIVE
FREE WOOD
95%
?
INORGANIC
<.05%
Mild
Oxidation
and
Extraction
i
i
t
t
i
i
Degraded
Soluble
*
4
SOLOCELLULOSE
(TOTAL
POLYSACCHARIDE
FRACTION)
70%
5
LIGNIN
25%
So
6
Dilute WOOD
Aqueous CELLULOSE
Alkali 60%
Ac
luble Hydrc
i
GLUCOSI
TRACES
OTHER
CARBOHT
AND IMF
id
(lysis
i
E +
OF
ITDRATES
'URITIES
MANNOSE
XYLOSE
GALACTOSE
ARABINOSE
URONIC ACIDS
Acid
Hydrolysis
HEMICELLULOSE
20%
FIGURE 20
- THE CHEMICAL COMPONENTS OF WOOD
-------
100
S 80
o
CO
CO
a
CD
Q:
o
H-
Z
UJ
O
or
UJ
o_
60
40
20
0
0
20
w
40
60
80
100
PERCENT WOOD DISSOLVED
FIGURE 21
- RELATION BETWEEN DISSOLVED LIGNINS AND WOOD
104
-------
STEAM
CHIPS
(50)
PREHEATER ._. REFINER
(40)
\SCREW
FEED
WATER IN
WATER OUT
r_T''^> ALTERNATE ROUTE
TO
ATMOSPHERE
STOCK
CHESTS
(5) A (1-5)
WET FORMING
MACHINE
(35)
WE
PRESS
T — r-\
SS [""^V
DILUTION
WATER
PROCESS
WATER
CHEST
TO
FINISHING
V
s///////
MAKE-UP
WATER
TO
TREATMENT
APPROXIMATE PERCENT FIB^R
(CONSISTENCY IN PROCESS)
FIGURE 22 - PROCESS WATER RECYCLE IN A TYPICAL WET PROCESS HARDBOARD MILL
-------
Ib/ton) into a flow of 2.5 cu m/kkg (600 gal/ton) is reported. Typical
waste water concentrations of this fiber wash are shown below:
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
simply 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 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 hot press.
This is partly due to build-up of volatilized organics on press plates.
The critical concentration of soluble organics, above which process
106
-------
TO ATMOSPHERE
CHIPS
STOCK J^WETFORMING
WATER IN
WATER OUT
CONCENTRATED
BY-PRODUCT
CONCENTRATE TO
CATTLE FEED
[MACHINE
i
SS 1 ......
WUOLt
PROC
a
/
i
i
i
\
|
'iiii/nirrll
TO
FINISHING
-UP WATER
Z#> TO TREATMENT
FIGURE 23 - PROCESS WATER RECYCLE IN A HARDBOARD MILL
USING THE EXPLOSION PROCESS
-------
problems are encountered, is related to the wood species used as raw
material.
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 highly
concentrated water and diluting it with fresh water, or by removing the
solids from the process water by some other means.
Water Sources
By far the major waste water discharge from a wet process hardboard mill
is 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 kg/kkg (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) .
Other representative analyses of raw waste water discharged from a
typical wet process hardboard mill are shown below:
Parameter Concentration
BOD 1,300 - 4,000
COD 2,600 - 12,000
Suspended Solids 400 - 1,100
108
-------
TABLE 26
WASTEWATER DISCHARGES FROM WET PROCESS HARDBOARD
Plant
I
2
3
4+
5
6
7
8*
Production
(metric tons)
91
77
1,356
136
82
127
356
327
Was tewa ter
(cubic meters/day)
4,164
2,952
16,578
1,590
757
908
1, 628
833
Was tewa ter
(cubic meters/kka
45.
38.
12.
11.
9.
7.
4.
2.
9
2
2
7
3
1
6
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 ro/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
-------
Total Dissolved Solids
Kjeldahl Nitrogen
Phosphates, as P
Turbidity
Phenols
ph Range
500 -
0.17 -
0.3 -
80 -
0.7 -
4,000
3.0
700
1.0
4.0 - 5.0
Waterj3alance_f or a Typical Wet Process ; Hardboard, Mill
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 typical 127 kkg/day (140
ton/day) mill.
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
(50 percent moisture)
Steam to preheater
Cooling and seal water
Additive dilution water
Process water makeup
Humidifier
Miscellaneous housekeeping
Total Water Inflow
= 1,000 1/kkg
(240 gal/ton)
=500 1/kkg
(120 gal/ton)
= 29,840 1/kkg
(7,150 gal/ton)
=83.5 1/kkg
(20 gal/ton)
= 9,890 1/kkg
(2,370 gal/ton)
= 50 1/kkg
(12 gal/ton)
= 42 1/kkg
(10 gal/ton)
= 41,405 1/kkg
(9,922 gal/ton)
111
-------
LOSS = 83.5
STEAM GAIN = 83 5 LOSS=I88 GAIN= 50
GAIN = 29,840 A WATER FRQM T0 STEAM OR
COOLING a «> ADDITIONS ATMOSPHERE WATER
GAIN =500 SEAL WATER A ,i
STEAM II 1! m Jl
Z-TONS Jl V V 1 — 1 | ~ 1
^'^ " ,1 T^i |_JC ^ STOCK UWET FORMING WET 1 H,,MiniFiir» ""A
n£>[2£*PREHEATERjlj REFINER JZ± YC nCHtSISjl MACHINE PRESS pV
i Jj U / \ ^ ^ w ^ i ~t \ ^ / \^ ) y\ v 1 .0 v l/jj \ O v /
XSCREW FEED K| \_V Jl
GAINS = I,000 Kl A 17,590 46,655 V 63,91'
v ir
LOSS-29617 PROCESS
LOSS-29,617 WATER «
COOLING AND 1 -• -. (-UL-&-T 1
SEALWAltH n.iimnN ^t:"
WATER A 'ft
'
1-TON
l|669 PRODUCT
LOSS= 11,267
?„ ^
WATER A
GAIN = 9,890 if TO TREATMENT
ALTERNATE ROUTE
WATER IN
WATER OUT
(XX) PERCENT FIBER (CONSISTENCY IN PROCESS )
ALL NUMBERS* LITERS /METRIC TON
MISCELLANEOUS
HOUSEKEEPING
GAIN=42
TOTAL GAIN
TOTAL LOSS
41,405
41,405
FIGURE 24 - WATER BALANCE FOR A TYPICAL WET-PROCESS HARDBOARD MILL
-------
Water Outflows: Water outflows in a wet process mill result
from:
Press Evaporation = 188 1/kkg
(45 gal/ton)
Cooling and seal Water = 29,817 1/kkg
discharge) (7,145 gal/ton)
Steam from cyclone = 83.5 1/kkg
(20 gal/ton)
Discharge of excess pro-
cess water (includes mis-
cellaneous housekeeping
water discharge = 11,267 1/kkg
(2,700 gal/ton)
Water in product = 50 1/kkg
(12 gal/ton)
Total Water Outflows = 41,405 1/kkg
(9,922 gal/ton)
WOOD .PRESERVING.SUECATEGORIES
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.
Closed Steam_conditioninq
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
recovery of free oils, and is reused instead of being discarded.
113
-------
The principal advantage cf modified-closed steaming, aside from 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 kg of pollutants released can be
achieved by using closed steaming.
Ef_fect_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.
Data on the effect of time of sampling during a treating cycle on the
flow rate and 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, beginning 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. Flow 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
114
-------
Avg. oil content
before closed
steaming-1360mg/l
Ln
Avg.oil content
after closed
steaming—136
8
12
TIME ( weeks)
16
20
FIGURE 25 - VARIATION IN OIL CONTENT OF EFFLUENT WITH TIME
BEFORE AND AFTER INITIATING CLOSED STEAMING
-------
65
55-
E
a
a
045-
Q
o
o
25
15
-rfe
5 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
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
110,541
123,429
STEAMING OPERATIONS
Total
Solids
10,156
17,956
22, 204
37,668
66,284
66,968
67,604
99,276
104,960
92,092
114, 924
Dissolved
Solids
8,176
15,176
20,676
31,832
37,048
40,424
41,608
91,848
101,676
91,028
88,796
Values expressed as mg/1
117
-------
CO
0
FIGURE 27
12
TIME ( hours)
- VARIATION IN COD CONTENT AND WASTEWATER FLOW RATE WITH TIME
-------
TABLE 29
PHENOL AND COD VALUES FOR EFFLUENTS FROM
THIRTEEN WOOD PRESERVING
PLANTS
COD (mg/1)
Plant
Location
Mississippi
Missis sippi
Missis sippi
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
Raw
6,
11,
48,
42,
12,
1,
9,
32,
7,
3,
17,
1,
10,
290
490
000
000
300
000
330
300
440
370
100
990
500
After
Flocculation
3,
5,
2,
31,
4,
3,
8,
2,
1,
3,
1,
6,
700
025
040
500
500
-
180
575
360
880
830
990
070
Percent
Reduc t ion
41
56
96
25
63
-
66
73
68
44
78
0
42
119
-------
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.
Bioloqical^Characteristies
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 due to the characteristics of the waste
samples or to 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=O.U97 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 checks of the COD:BOD ratio for similar wastes from
several plants.
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 formulations
are low in organic content, but contain traces of heavy metals used in
120
-------
10-
8
o>
CO
O
- 6
x
Q
O
m
3
•***
C
Y=0.497X + 60
i i
8
10
12
14
16
Influent COD x 103 mg/|
FIGURE 28 - RELATIONSHIP BETWEEN BOD AND COD FOP WASTEWATER
FROM A CREOSOTE TREATING OPERATION
-------
TABLE 30 RATIO BETWEEN COD AND BOD FOR VAPOR DRYING
AND CREOSOTE EFFLUENT WASTEWATERS*
(NOTE: Data provided by the Research Department, Koppers
Company, Inc.)
(mg/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
-------
the preservatives and fire retardants employed. Averaqe analytical data
based on weekly sampling for a year of the effluent from a plant
treatinq with both preservatives and a fire retardant are qiven in Table
31, The presence and concentration of a specific ion in waste water for
such treatments depend upon the particular formulation employed and the
extent to which the waste is diluted by washwater and storm water.
Raw^Waste Loading Data
Averaqe analytical data for 5 typical wood preservinq plants treatinq
with pentachlorophenol-petroleum solutions and/or creosote are qiven in
Tables 33 throuqh 37. Data for plants 1 throuqh U (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 qrab samples collected over a period of several
months. Data for plant 5 are based on a series of qrab samples
collected during 1972. Information on volume of discharqe of process
water was obtained either from 24-hour measurements (plants 1-4) or
estimated based on number of retorts, processinq operations used, arid
oth^r considerations (plant 5). waste volume flow data do not include
coolinq water, which was recycled at all plants, coil condensate, or
boiler blowdown water. Production fiqures for 1971 were estimated from
the void volume of the retorts operated by the plants.
Raw waste loadinqs for each pollutant are expressed in terms of
concentrations (mq/1) and kq/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 averaqe raw waste loadinqs
qiven 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 treatinq with creosote
and pentachlorophenol-petroleum solutions. Since each of the five
plants involved is typical of the industry, data for the hypothetical
plant qiven in Table 38 will be the basis for an analysis of effluent
treatment cost presented later in this report,
.Sources qf Waste Water
Waste waters from wood preservinq operations are of the followinq types
and contain the contanrinants indicated:
a. Condensate from conditioninq by steaminq: This is the most heavily
contaminated waste water, since it comes into direct contact with the
preservative beinq 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 oxyqen demand of this waste is high because of dissolved wood
123
-------
TAIH.K V.'
HAW WASTI-: LOAD! NCS I'OK I'l.ANT NO. I
I'M rM me I i- r
COD
1' ll C MO 1 II
0 1 1 H M 11(1
C r I'M MI'
To 1 M 1
Sol lM UMW Wiiiilr l.o/id 1 ii£»i / DM y ( K £ )
I'M i' i'n I lu> I 1 c n 1 vnliicM - I'M r en 1 lie 1 leal vnlncii
I'o 11 n tl M / 1 000 Cubic Keel M re In poundii
"K y.7 i ooT) c n --
(UIK/ 1 ) !l ' c' Me tern Prod. MIIX. M 1 n . A v^ .
:>»,(> oo n,/:n.o I'./os.s 'U/.o I.I.II.H
(HVi.H) ('),<)',?.())((,')/.'.) (•),')')().())
1 'l/i /iH . 1' (> . 7 O.I '> . f>
( •) . o ) ( i '• . H ) ( - 7 ) ( i :• . ft )
')•)() IHH.'J H/i.1) /i.:' I'?. /i
( 1 1 . /) ( 1 «(,.()) («).'») (/!'). 'I)
1 1 ,«)<>•» /i , 7') 1 . d H'U) .(> '» .0 '•()', . /
O'M .')) ( I ,H/.O. '. ) ( I I . I ) ( I , I I :' . r, )
II ,<)()'l ') , r)«)().H d7'l .0 •> . 'J /i 77 . H
(:':'/i.i) (I ,/. HO.*)) C>. i ) (•)/. i . i )
1 , H/I/I rir)/i . M Id"). (> ') . '» /H . 0
( /. 0 . M ) (') 'i ').')) ( / . 7 ) ( 1 / 1 . 'i )
/I .(>
AVK. n»w - /!';.,/«»)/( ipd (ii,'r;v ^pd)
Void vol. ol cyllnilrrH - 20') cnhli- nu-lcrH ( I 0 , VI7 ctihlc ti-cl)
1<)7! product' I on («Ht.) - ?.fi,7f>0 ruble. nuMiTM (<)/i r>, 000 cubic lc<-t)
Avy.. work dnyn/yr. •• 2 7 r>
A VK . d/i II y p rod tic l I on - 1 1 (> c till f c mt-1 <• r n (/i , ? 00 c cih I c ICc I )
1'rcncrvMl Ivi'H •• (Ir
-------
TABLE 33
RAW WASTE LOADINGS FOR PLANT NO. 2
Raw Waste Load
ings 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-
(mg/1). bic Meters Prod. Max.
22,685 7,712
(480
258 88
(5
55 19
(1
3,504 1,190
(74
3,044 1,035
(64
460 155
(9
.0
.5)
. 3
.5)
.3
.2)
.0
.2)
.2
.5)
. 7
.7)
5,9
(13,1
(1
<
7
88.
75.
54.
20.
4.
10.
28.
(1,603.
645.
(1,4
(2
4.9
19.
95.
10.
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.
(3,402
17
(38
3
(8
238
(525
207
(456
31
(69
7
.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
Parameter
COD
Phenols
Oil
Total
Solids
Dissolved
Solids
Suspended
Solids
pH
Kg/1000
Cu-
.(mg/1) bic Meters Prod.
12,467 3,295.
(205.
82 25.
(1.
150 40.
(2.
1,724 455.
(28.
1,528 404.
(25.
196 51.
(3.
1
3)
7
6)
1
5)
8
4)
5
2)
4
2)
4.5
Raw Waste Loadings /Day (Kg)
Parenthetical values
are in pounds
Max .
943.
(2,075.
5.
(12.
25.
(55.
130.
(286.
115.
(254.
14.
(32.
2
0)
9
9)
0
0)
3
6)
5
0)
8
6)
Min.
500
(1,100
3
(7
69
(153
61
(135
7
(17
.0
.0)
.5
.8)
.5
.0)
.6
.6)
.9
.4)
Avg.
708.
(1,558.
5.
(12.
8.
(18.
98.
(215..
86.
(191 .
11.
(24.
4
4)
6
3)
5
8)
0
5)
8
0)
1
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 Load
ings
Parenthetical values =
Pounds/1000 Cubic Feet
Parameter
COD
Phenols
Oil
Total
Solids
Dissolved
Suspended
Solids
pH
Kg/1000 Cu-
(mg/1) bic Meters Prod.
9,318 2,291
(142
312 77
(4
580 142
(8
3,432 844
(52
2,748 675
(42
684 168
(42
.9
.8)
.0
.8)
.8
.9
.2
.6)
. 7
.1)
.5
.1)
5.8
Raw Waste
Loadings /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
Avg.
.1 563
.6) (1,239
.6
.2)
.5
.9)
.9
.7)
.8
.4)
.0
.3)
1
(4
3
(7
20
(45
16
(36
4
8
1
5
7
7
6
6
5
1
(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 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-
(mg/1) bic Meters Prod. Max.
13,273 3,072.
(191.
126 28.
(1.
172 40.
(2.
5,780 1,338.
(83.
5,416 1,253.
(78.
364 83.
(5.
0
4)
9
8)
1
5)
6
4)
5
1)
5
2)
59
3
(1,305
(1
(2
5
1
9
1
259
(570
24
1
(532
_
4.5
_
.2
.0)
.1
.2)
.9
.8)
.5
.9)
.8
.0)
—
Min
317
(699
(
(
3
7
1
2
168
(370
137
(30
—
3
—
.8
.1)
.4
.4)
.0
.3)
.3
.2)
.9
.4)
—
Avg .
45
(99
<
(1
19
(43
18
(40
1
(2
2.
5.
4.
9.
5.
2 .
7 .
3.
4.
6.
2.
7.
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
-------
TABLE 37
AVERAGE RAW WASTE LOADINGS FOR FIVE WOOD-PRESERVING PLANTS
Raw Waste Loadings Raw
Waste Load
ings/Day (kg)
Parenthetical values = Parenthetical values
Pounds/1000 Cubic Feet are in pounds
Parameter
COD
Phenols
Oils and
Greas e
Total
Solids
Dissolved
Solids
Suspended
Solids
PH
Kg/1000 Cu-
(mg/1) bic Meters Prod. Max.
19,269 5,378
(335
182 51
(3
297 83
(5
5,280 1,463
(91
4,571 1,276
(79
710 199
(12
.4
.1)
.4
.2)
. 5
.2)
. 8
.2)
. 0
.5)
.0
.4)
1,65
1.
(3,634.
1
(2
3
(8
47
2.
8.
7.
2.
0.
(1,035.
38
(85
8
(19
4.9
7.
2.
7.
1.
9
2)
8
2)
5
5)
7
5)
4
2)
2
9)
Min
50
2.
(1,106.
(1
(1
10
(24
9
(20
1
(2
6.
3.
7.
6.
9.
0.
3.
5.
2.
6.
9
3)
3
8)
5
4)
5
9)
5
8)
2
8)
Avg
1,0
(2,2
(
(
2
(6
2
(5
(
•
16
35
9
21
15
34
78
12
41
30
37
82
.0
.2)
.6
.1)
.6
.4)
.4
.5)
.0
.2)
.5
.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, Pentachloropheno1
129
-------
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 .
130
-------
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 Boultcn process, the wastewater 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 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
131
-------
11,166
(2,950)^----
(Evaporatfon) 102,
Intake
gal.
113,
(3Q
6,
550 0.
000)
"5
SE •£•
^w ^kr
^ 2
u 5
So S
o
•t
102,
(27
384
050)
440,952
(116,500)
454,
(12Q
813
800)
6,434 1.
(1,700) (5
200
000)
O
z
0
o
u
0)
+*
to
E
3
U
892
00)
(0
(0
UJ
o
O
QC
ft.
1&J248 T
(3,1 500) (Evaporation) (s
892
°0) 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
132
-------
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 requirements.
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 cr Boultonizing. In the former process, the
condenser is operated only about three hours following a conditioning
cycle. In the Boult.onizing 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 tc preservative treatment. For plants operating on
similar steaming or Boultonizing schedules the volume of waste does not
vary widely among plants of comparable size and generally is less than
75,500 I/day (20,000 gal/day).
133
-------
SECTION VI
POLLUTANT PARAMETERS
INTRODUCTION
Presented below are the major pollution parameters considered to be of
significance to the segments of the timber products processing industry
for which effluent guidelines and standards are developed at this time.
Listed below are the parameters that are common to all segments:
Biochemical Oxygen Demand (BOD5)
Chemical Oxygen Demand (COD)
Phenols
Oil and Grease
PH
Temperature
Dissolved Solids
Total Suspended Solids
Phosphorus
Parameters more commonly found in the wood preserving segment of the
industry include:
Nitrogen Zinc
Copper Florides
Chromium Ammonia
Arsenic
All of these parameters are not present in the raw waste streams of each
plant in the timber products processing industry. The inorganics listed
under wood preserving occur only in waste water from plants treating
with salt-type preservatives. The particular ions present in the
discharges from these plants depend upon the preservative or fire
retardant formulation used.
DISCUSSION OF^POLLUTANT^PARAMETERS
BOD5: Biochemical Oxygen Demand^ 5 day at 20°C
BOD5 is the parameter used to determine degradable organic matter in a
waste water, and as such, it is one of the standard criteria used in
pollution control regulations. BOD^ concentrations are an indication of
soluble and suspended organics, including simple wood sugars as well as
long chain and cyclic hydrocarbons. Wastes with a high BOD5 may cause
serious oxygen depletion problems in receiving waters with relatively
low assimilative capacities.
135
-------
CQDi_Chemical_Oxygen Demand
The COD of a waste water is another measure for organic matter con-
centration. It is a chemical analysis used to augment the BOD5
analysis, and, in certain cases where a definite ratio between BOD5 and
COD has been established, it can substitute for the BOD5 analysis.
Furthermore, COD can often serve as an indicator of organics that are
not readily biodegradable.
Phenol
Phenols are natural constituents found in wood. Therefore, water
contacting wood can be expected to obtain some concentration of phenols.
Resin, another potential source of phenols, might also be found in waste
water discharges. Phenol is a cyclic hydrocarbon which can be degraded
biochemically by the EOE5 test but not chemically by standard COD
analysis.
Phenol concentrations in receiving waters are potentially toxic to
receiving water biota, and may, in very low concentrations, cause taste
and and odor problems in drinking water supplies, as well as the
potential of toxicity tc receiving water biota.
Oi1 and Grease
Oil and grease (hexane extractables) are standard lubricating chemicals
used in a variety of. inplant machinery. These lubricating chemicals can
find their way into cooling water, wash water, and other miscellaneous
waste streams. Creosote is an oil, and various petroleum products are
used as carriers for pentachlorophenol. These oils are invariably
present in waste water from wood preserving treatments employing oily
preservatives and they create a serious pollution problem. Values for
wood preserving raw waste water range from less than 50 to over 1000
mg/1. High oil and grease concentrations have deleterious effects upon
domestic water supplies and toxicity toward fish, and this parameter is
also esthetically undesirable.
EM
The pH of a liquid is by definition the negative log of the hydrogen ion
concentration. It is an important parameter in that most reactions in
water are a function of hydrogen ion concentrations from an equilibrium
as well as from a kinetic standpoint.
Waste waters from hardboard manufacture and oily based wood preserving
treatments are invariably acid in reaction, the pH ranging between 3. 8
and 6.0. The waste waters from salt-type treatments may be either acid
or basic, depending upon the particular formulation used. Not only is
the hydrogen ion a potential pollutant in itself, it can also affect the
toxicity of other substances, such as ammonia.
136
-------
Temperature
Temperature is also an important parameter in reaction kinetics and
equilibria. Large heat loads on a receiving stream can cause
significant temperature increases which in turn can result in serious
imbalance in ecosystems.
Dissolved solids
Total dissolved solids is defined as a chemical analysis measurement
which, when added to the total suspended solids concentrations, gives
the total solids in a waste stream. It is also an indication of the
soluble organics that are leached from wood. In the case of salt-type
treatments in wood preserving plants, inorganic preservatives contribute
to the dissolved solids content of waste waters. In any recycle system
dissolved solids accumulate even though suspended solids may be removed.
Dissolved solids concentrations as low as 50 mg/1 are harmful to some
industrial operations. The U.S. Public Health Service (USPHS) has set a
standard of 500 mg/1 if more suitable supplies are, or can be made,
available. This limit was set primarily on the basis of taste
thresholds. Limiting concentrations of dissolved solids for fresh water
fish may range from 5,000 to 10,000 mg/1. Concentrations exceeding
2,100 mg/1 in irrigation waters have proved to be harmful to crops.
Total^Suspended^SQlids
Waste waters can carry substantial suspended solids concentrations due
to the presence of wood fibers, fiber fragments, and other residue.
Suspended solids may kill fish and shellfish by causing abrasive
injuries, by clogging the gills and respiratory passages of various
aquatic fauna, and by blanketing the stream bottom, killing eggs, young
and food organisms, and destroying spawning beds. Indirectly, suspended
solids are inimical to aquatic life because they screen out light and
because, by carrying down and trapping bacteria and decomposing organic
wastes on the bottom, they promote and maintain the development of
noxious conditions and oxygen depletion, thereby killing fish, shellfish
and fish food organisms, and reducing the economic and recreational
value of the water.
Phosphorus
The only source of phosphorus from these segments of the timber products
processing industry is the wood itself. Phosphorus is a nutrient and
can have a significant effect on the eutrophication of receiving waters.
However, the waste waters from this industry are nutrient deficient, and
phosphorus is not considered a problem.
137
-------
Nitrogen
The main forms of nitrogen in water are organic nitrogen, ammonia,
nitrites, and nitrates. Nitrate is the lowest oxidation level of these.
Biochemical reactions will oxidize ammonia to nitrite and finally to
nitrate, exerting an oxygen demand in water. Nitrates have been found
to be toxic at high levels to infants, and to interfere with
disinfection by halogens. Nitrogen is a nutrient and can affect
eutrophication in receiving waters. Urea formaldehyde glue and protein
glues are responsible for introducing organic nitrogen to the process
water.
Inorganics
All of the inorganics listed for the wood preserving industry occur in
one or more salt-type preservatives and fire retardants. As indicated
previously, the particular ions present depend upon the salt formulation
used. Concentrations in raw waste water range from 5 to 100 mg/1.
138
-------
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 of water used in
hydraulic barking, however, is significantly larger than that used in
other wet processes, and therefore necessitates a different treatment
before disposal. Opportunities for reuse within the hydraulic barking
operation may be limited because of the relatively low suspended solids
requirement.
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 category, 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 veneer 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 3/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
139
-------
120-mesh stainless steel wire cloth. Filter cake produced 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 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.
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
and COD 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 technically 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 small 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 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
140
-------
hydroxide may be necessary to reduce resulting corrosion problems. The
resulting sludge may be trucked to landfill.
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 due to 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 (100 million sq ft)
on a 9.53 mm (3/8 in)'basis presently use approximately 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 I/week
(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
141
-------
12,000 I/week (3,000 gal), and this small volume can be handled without
discharge by containment, or land irrigation.
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 plywood 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 glue pot
life. In order to reduce the flows from a mill that uses protein glue,
inplant 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 produce 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:
142
-------
(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
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 be 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, due to 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 washwaters. Attempts at
mixing washwater from different types of glues have been unsuccessful.
143
-------
PLYWOOD PLANT BUILDING
7-1/2 H.P. MOTOR
PROVIDING CONTINUOUS
AGITATION
TRASH
REMOVAL
CONVEYOR
BELT
CONCRETE
SETTLING
TANK
2000 GAL
COLLECTION
TANK
| WATER
METERING
TANK
GLUE
MIXER
MIX
HOLD
TANK
PUMP
PUMP
GLUING AREA
GLUE
SPREADERS
CONCRETE DRAINAGE TROUGH IN FLOOR
FIGURE 30
- PLYWOOD PLANT WASH WATER REUSE SYSTEM
-------
01
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,J.63.5
3,673.5
25.71
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
-------
In addition to washwater recycle, -there are plants that contain and
evaporate glue washwater, spray the glue water on the bark that goes
into the boiler, or use a combination of these techniques.
HARDBQARD - DRY PROCESS
The small volumes of 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, due
to 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 flow 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: Only two mills out of 16 existing 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 reused 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.
ChiB_Wash: At the present time, there are 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 hardboard 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
plant.
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, it is obvious that
all dry process hardboard mills can achieve no discharge from their
resin systems.
146
-------
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 quantity of water can be neutralized as needed, then
disposed of by impounding or land spreading.
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.
Cooling Water: Cooling water is by far the major waste water flow from
dry process hardboard mills. Cooling water is used in such unit
processes as refiner seal water cooling systems, air compressor cooling
systems, and resonance frequency generator cooling systems. Use of
cooling water varies widely but is consistently 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 standard 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 documented that
humidifiers can be operated with no discharge of waste water pollutants.
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. Until such time as
technology changes create waste water discharges from this source there
should be a no discharge limitation.
Summary
The water pollution resulting from dry process hardboard mills is
directly related to waste water flow and concentration, which, in turn,
is influenced by operation and maintenance practices and problems in
each mill. The decision to wash logs or chips by a mill is a result of
the effect of dirt and sand on inplant machinery. High maintenance
costs resulting from abrasion of refiner plates, etc., may make it
desirable to wash logs and chips. Quantities of extraneous material on
147
-------
logs depend upon harvesting 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 minor waste water source, is an inplant process that is
affected by operation. Cauls are soaked in tanks containing 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 ro
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 or
discharge from this source.
The press pit (a sump under the press) can colleqt 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^PROC ESS
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 CgntrolirMeasures and Technology
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
148
-------
system would consist of a sedimentation basin or pond to catch the
washwater and allow the removal of settleable solids. Pumps preceeded
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.
_ Welter- The major source of waste water flow and concentration
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, and temperature.
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 prevent discharge
of organic material is to recycle 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 tc control in the wet process.
The explosion process utilized by two mills produces greater quantities
of soluble organics than other processes because of the higher
temperature and pressure. Due to 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 clarifier is then evaporated. The concen-
trated 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 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
149
-------
TO ATMOSPHERE
CHIPS
M
Ul
O
TO
FINISHING
WATER IN
WATER OUT
CONCENTRATED
BY-PRODUCTS
CLARIFIER
+ J
SLUDGE (FIBER)
TO PROCESS
FIGURE 31 - INPLANT TREATMENT AND CONTROL TECHNIQUES AT MILL NO. 7
-------
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 more conventional cooking processes release 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 main 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 con-
trolled. Suspended solids removal systems consist primarily of gravity
settling, screening, filtration, and 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
due to differences related to raw material.
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.
151
-------
STEAM
WET FORMING
(XX)
WATER IN
WATER OUT
APPROXIMATE PERCENT FIBER
(CONSISTENCY IN PROCESS)
WET
•k 1
N yes)
\j
i
\
tf
— i *•••*--' iw • • mmmrac i
(30) >
f\
\ (1.5)
r
1
PROCESS
WATER
CHEST
(35)
^7//j^//////y/7////7/////7y/y^//^7^///'77/'^//y/7/'y/^77^////7///7j
rrtt a a
^
I
*^
77S//S////t
TO TREATMENT
FIGURE 32 - TYPICAL WET-PROCESS HARDBOARD MILL WITH PRE-PRESS
-------
TO ATMOSPHERE
CHIPS
I-1
Ul
U)
WATER IN
WATER OUT
CONCENTRATED
BY-PRODUCTS
STOCK
-H I 1 rwirVr
C=j CHEST
WET
FORMING I 1
MACHINE J ^ROCE;
/ \
1 1
1
' LP
t
t
t
SSJSS f f {
\
SLUDGE TO
LANDFILL
FIGURE 33 - INPLANT TREATMENT AND CONTROL TECHNIQUES AT MILL NO. 3
-------
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 - 1300 280 - 330
R 230 - 620 90 - 145
154
-------
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 United states presently using this system to
some degree. Typical data from the Savo system from one of these mills
is shown below:
COD 7775 4745 39
Total suspended solids 750 48 94
Total dissolved solids 5525 4788 13
Soluble organics 4285 3362 22
Volatile suspended solids 740 _ 46 _ 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 any 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 treatment. 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 the 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 listed in Table 41 utilized
settling ponds 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.
155
-------
STEAM
CHIPS
PREHEATER— REFINER
WATER IN
WATER OUT
WET FORMING
MACHINE
FIBER
TO
PROCESS
PROCESS
WATER
CHEST
TO
* ATMOSPHERE
WET LrA.
PRESS
JTO
FINISHING
{
7
SAVO
1
1
DISCHARGE
FIGURE 34 - TYPICAL WET-PROCESS HARDBOARD MILL WITH SAVO SYSTEM
-------
TABLE 41
PRIMARY SETTLING TANK EFFICIENCY
M
Ul
Mill
4
5
6
BOD
mg/1
2400
3500
6000
IN
k/kkg
28.5
32
42.2
BOD
mg/1
2400
3300
3900
Out
k/kkg
28.5
30.5
28
Percent
Removal
0
5
35
SS
mg/1
1650
430
1440
In
k/kkg
19
4
10
SS
mg/1
178
154
450
Out
k/kkg
2
1.4
3.25
Percent
Removal
89
69
68
-------
A properly designed clarifier with a mechanical sludge collector and
continuous sludge removal can be expected to obtain approximately 75 to
90 percent SS removal and 10 to 30 percent BOD5 removal.
The pH of wet process waste water varies from 4,0 to 5.0. The 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 used 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 which
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.
Mills No. 1 and 2 utilize aerated lagoons. Their treatment efficiencies
for BOD removal have averaged 70 and 79 percent, respectively. Mills 3,
4, and 5 utilize some variation of the activated sludge process and
their average efficiencies for BOD removal are 97,77, and 95 percent.
158
-------
Ln
TABLE 42
TREATMENT EFFICIENCY OF BIOLOGICAL SYSTEMS
Mill No.
•«
*+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
BOD, mg/1
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
SS, mg/1
198
--
295
360
388
Percent
Removal
10
--
0
0
0
10
--
0
0
0
+ Includes efficiency of primary settling
** Aerated lagoons
* Activated sludge
-------
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 there 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 hardboard
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 United states 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 digester, 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 activated 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 direct 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.
Table 43 shows an example of an aerated stabilization basin (ASB) or
aerated lagoon performance related to temperature. This table is for a
biological system treating paperboard waste. Similar effects are
experienced in the wet process hardboard industry. The main difference.
160
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30 -
1/72 2/72 3/72 4/72 5/72 6/72 7/72 8/72 9/72 10/72 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
CTi
fO
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
-------
GJ
30 H
251
o
20
Q
O
m
104
5
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
EXAMPLE &F 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
(mg/1)
22
21
23
17
16
29
56
61
31
42
* Includes long-term
set tling
164
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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 cf some or all sludge to the stock chest. (3)
Process water recycle through a primary clarifier with blowdown 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:
(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
Incineration
WOOD PRESERVING
The technological base for waste control in the wood preserving industry
is generally quite weak by comparison with most other industrial
165
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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-Preservers1 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 survey by Thompson of 3.77 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 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 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.
166
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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
Southeas t
Southwes t
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
167
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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 of
_ _ Plants
None 29
Discharge To Sewer - Raw 5
Discharge to Sewer - in 1 Removal 6
Discharge To Sewer - Oil + Phenol Removal 4
Construct On-Site Treating System 25
Other 12
TOTAL 81
168
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Table 47 gives a breakdown of what the plants that do not now meet the
standards plan to do with their waste water. Nationally, roughly one-
third 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 tc 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 49) .
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.
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.
169
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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
170
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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.
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 United states
(Table 44). Most of these facilities have been in 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. Perusal 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-pe.troleum 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 oxygen-
demanding 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.
171
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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 polyelectrolyte 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_Containinq Entrained^oils - It is the intermingling of the
oils and water from the treating cycle and the condensate 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 OJLLs - 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 effluent
172
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handling 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 cham-
ber. The oil is removed at the surface by a skimming device. Mechani-
cal oil scavengers are also sometimes used to remove surface oils.
The percentage of entrained oils removed by oil-water separation equip-
ment 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 probably 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
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 1000 mg/1 after passing
through gravity-type separators. Oils in this form normally must be
removed by primary treatments involving f locculation.
The formation of oil-water emulsions is a particular problem where con-
ventional steam conditioning is used and apparently results from agita-
tion 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.
2f. Oil- Water Emulsions - Emulsions may be broken chemically,
physically7 or electrically. Chemical methods involving flocculation
and sedimentation are the most widely used, generally are the least ex-
pensive, and are effective with effluents from wood preserving plants.
For these reasons, the remarks which follow are confined to processes
which are based on the use of chemicals.
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 vari-
ous types of polyelectrolytes. The same material or combination of ma-
terials does not work equally well with waste waters from all plants
173
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TABLE 50 EFFICIENCIES OF OIL SEPARATION PROCESSES
Source Of
Influent
Percent Removal
Free Oils
Emulsified Oils
API Separator
Air Flotation without
Chemicals
Air Flotation with
Chemicals
Chemical Coagulation and
Sedimentation
Raw Waste
API
Effluent
API
Effluent
API
Effluent
60 - 99
70 - 95
75 - 95
60 - 95
Not applicable
10 - 40
50 - 90
50 - 90
TABLE 51 EFFECT OF LIME FLOCCULATION ON COD AND PHENOL
CONTENT OF TREATING-PLANT EFFLUENT
Lime
(Rffl/1)
0.0
0.2
0.5
0. 7
5
0
5
1.00
1.2
1.5
5
0
pH
5
6
7
9
10
11
11
.3
.8
.9
.7
.5
.4
.8
COD
Cone .
(lHR/1)
11
9
7
5
5
5
5
,800
,700
,060
,230
,270
,210
,210
Percent
Removal
--
23
39
56
55
56
56
Phenol
(mg/1)
83
81
72
78
80
84
83
174
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AVERAGE TEMPERATURE- 38°C
INITIAL OIL CONCENTRATION-45P.P.M. ±4 P.P.M.
0 40 80 120 160 200
SEPARATION TIME IN MINUTES
FIGURE 38
- EFFECT OF DETENTION TIME ON OIL
REMOVAL BY GRAVITY SEPARATION
175
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(Table 29, section V). COD and BOD reductions of up to 83 percent have
been achieved creosote waste water by using a single cationic polymer at
a rate of 40 mg/1. Similar results were observed by Thompson 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 ob-
tained by Simonsen who used both anionic and cationic polyelectrolytes
in combination with bentonite clay. There was no difference between the
two types of polymers in the results obtained. However, only cationic
polyelectrolytes broke oil-water emulsions from wood preserving plants
in work reported by Jones and Frank. 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 limits. 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 lima 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/lr
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 pentachlcrophenol, was nor 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
snowing the reduction of pentachlorophenol resulting from lime additions
to a waste water are shown below:
176
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Residual PGP
Lime Dosage Concentration
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 polyelectrolytes alone
failed to produce a floe.
Among numerous polyelectrolytes tested by Thompson and Dust relatively
few were found that in the absence of lime 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 initiating floe formation in the absence of lime are
relatively new products currently marketed by a large chemical company.
Reductions in COD for individual polyelectrolytes in this group ranged
from UO to 7U percent and averaged 62 percent. Several wood preserving
plants currently use them in primary treatments of their waste water.
Lime in combination with polyelectrolytes is used by other plants.
Vacuum and pressure filtration has also been used to break oil-water
emulsions, permitting the recovery of the oil. Halff, in commenting on
work with vacuum filtration through diatomaceous earth, reported that a
precoated rotary vacuum filter efficiently broke oil-water emulsions
from wood preserving operations. The same author tested sand filtration
of composited waste water from several wood preserving plants and
concluded that the method was not practical, although a 99 percent
reduction in turbidity was achieved by the process.
Sluckte, Dewatering - The availability of effective polyelectrolytes for
-flocculation treatments lessens considerably the problem of sludge
handling and disposal. Using lime alone, a volume of sludge equal to 30
percent of the waste water is produced by flocculation. This value is
reduced to about 7 percent when lime is used in combination with a
177
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suitable polyelectrolyte, and is reduced still further when other
polyelectrolytes are used alone.
Sludge drying beds similar to those employed with domestic., sewage have
been used successfully to. dewater sludge resulting from primary treat-
ments of wood preserving waste water. Recent tests conducted by Dust
have shown that the dewatering characteristics of beds Of this type are
unaffected by adding a total of 41 cm (16 in) of sludge from creosote
waste water to them in two applications during a 24-hour period. Upon
drying, the sludge can be easily removed from the beds using a garden
rake. Drying beds are currently in use at a number of plants in the
southern states.
Sludge dewatering can also be accomplished mechanically with equipment
currently available. Results of tests of the effectiveness of one
machine in processing sludge from creosote waste water were promising.
The sludge was dewatered to a solids content of 25 percent.
Waters Containimj Heavy. Metals - Because heavy metals contained in
waste water from plants that treat with salt-type preservatives and fire
retardants may be toxic to microorganisms in low concentrations, they
must be removed before subjecting the waste water to secondary
treatments involving biological oxidation. Unlike primary treatments of
oily waste waters in which recovery of oil is primarily a physical
problem the removal of preservative salts from solution is a chemical
problem and is related to the properties of the specific ions present.
A listing of the principal water-soluble preservatives and fire
retardants currently marketed in the United States, and the harmful
constituents in each, is given in Table 52.
The procedure used to precipitate heavy metals from wood preserving ef-
fluents 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
178
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TABLE 52 TOXIC CONSTITUENTS IN THE PRINCIPAL SALT-TYPE PRESERVATIVES
AND FIRE RETARDANT CHEMICALS USED IN THE UNITED STATES
Dinitro
Cu Zn Cr B As F phenol
Fluor-Chrome Arsenate Phenol X XX X
Chromated Zinc Chloride X X
Copperized Chromated Zinc
Chloride XXX
Chromated Copper Arsenate X XX
Chromated Zinc Arsenate XX X
Acid Copper Chromate X X
Ammoniacal Copper Arsenite X X
Fire Retardant
Type A XX
Type B XXX
Type D XXX
179
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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 hydrogen sulfide gas, or by adding sodium sulfide.
Ammonium and phosphate compounds are also reduced by this process.
This procedure is based on the well-known 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,
zinc, 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 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 re-
moves 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 are entirely
satisfactory, particularly for arsenic concentrations above 20 mg/1.
Literature 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.
L80
-------
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 im-
portance of subjecting the waste to a primary treatment to remove the
metals, even when present in only trace quantities, was alluded 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 re-
covery 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 capacity of
the exchangers sufficiently to make the process impractical under most
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 prepar-
ing fresh batches of treating solution.
Secondary^Tr eatments
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 labora-
tory 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 num-
ber of wood preserving plants that are currently providing secondary
treatment for their waste, data for item (c) is, in some instances,
181
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TABLE 53 CONCENTRATIONS OF POLLUTANTS BEFORE AND AFTER LABORATORY
TREATMENT OF WASTEWATER FROM TWO SOURCES
Concentration Solution
COD
As
Phenols
Cu
+6
Cr
+3
Cr
F
PO
4
influent
1700
300
Nil
170
375
0
590
640
Effluent
400.
15
Nil
25
0
0
80
90
Dilute Pond Waste
Influent
112
20.8
0.03
0.35
0.52
0
19
80
Effluent
20
1.0
Nil
0.25
0
0
9.5
25
NOTE: Values expressed as mg/1.
182
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TABLE 54 CONCENTRATION OF POLLUTANTS IN PLANT WASTEWATER CONTAINING
SALT-TYPE PRESERVATIVES AND FIRE RETARDANTS
BEFORE AND AFTER FIELD TREATMENT
Influent Ranges Effluent Averages
COD 10 - 50 25
As 13-50 8.9
Phenols 0.050 - 0.160 0.048
Cu 0.05 - 1.1 0.35
Cr+6 0.23 - 1.5 0.1
Cr+3 0.0-0.8 0.02
4-20 5.8
P04 15 - 150 15
NH3-N 80 - 200 75
Values expressed as ing/liter
183
-------
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 bio-
logical 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 by 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 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 concentrations 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 80 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.
184
-------
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 10.6 million I/day (2.8 million gal/day) of
waste water, with final treatment occurring in the oxidation pond.
Removal rates of 95 percent for phenols and 60 percent for BOD were ob-
tained in the filter, notwithstanding the fact that the pH of the influ-
ent 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 unaffected by oil concentrations within the
range studied.
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 coopera-
ting 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.
185
-------
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/sq 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 exist-
ing standards than was EOD content. Consequently, the sizing of commer-
cial units from data collected from the pilot unit was based on BOD
removal rates. Various combinations of filter-bed depths, tower
diameters, and volumes cf 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 initial cost, and have small
land requirements. Package units designed to treat the waste water from
an average wood preserving plant could be located on an area of approxi-
mately 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 mo 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 BOD5 and phenols of 95 percent from petroleum wastes in bench-
scale tests of the activated sludge process. Optimum BOD5 loads of 22U7
186
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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 (lb/1000 cu ft) 66.3 121.3 1.2
Effluent Concentration (mg/1) 137 709 1.0
Removal (%) 91.9 77.0 99+
187
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TABLE 56 RELATIONSHIP BETWEEN BOD LOADING AND TREATABILITY
FOR PILOT TRICKLING FILTER PROCESSING A CREOSOTE WASTEWATER
BOD
Loading
(Ib/cu ft/day)
23
26
37
53
66
76
85
115
156
Removal
(%)
91
95
92
93
92
82
80
75
62
Treatability*
Factor
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).
188
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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
filter
bed
(ft)
10.7
12.5
14.3
16.1
17.9
19.6
21.4
Raw flow
(gpm/ sq ft)
filter
surface)
0.019
0.026
0.034
0.044
0.054
0.065
0.078
Recycle flow
(gpm/ sq ft)
filter
surface)
0.73
0.72
0.71
0.70
0.69
0.68
0.67
Filter
Surface
area
(sq' ft)
708
520
398
315
255
210
177
Tower
dia.
(ft)
30.0
25.7
22.5
20.0
18.0
16.3
15.0
Volume
of
media
(cu ft)
7617
6529
5724
5079
4572
4156
3810
TABLE 58 SUBSTRATE REMOVAL AT STEADY-STATE CONDITIONS IN ACTIVATED
SLUDGE UNITS CONTAINING CREOSOTE WASTEWATER
Aeration Time, Days
COD Raw, mg/1
COD Effluent, mg/1
% COD Removal
COD Raw/COD Effluent
5.0
447
178
60.1
2.5
10.0
447
103
76.9
4.3
14.7
442
79
82.2
5.6
20.1
444
67
84.8
6.6
189
-------
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, respec-
tively, 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 100 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.
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 eresols 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
190
-------
~ 4
flC IU
00
oo
o
®
Slope =K=0.30 day
-1
Le =
Lo
1+0.30t
5 10
Aeration Time (Days)
15
20
FIGURE 39
- DETERMINATION OF REACTION RATE CONSTANT
FOR A CREOSOTE WASTEWATER
-------
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 bicdegradability 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 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.
192
-------
CO
o
o
x 90
«H
_
I
o
80
70
o
cc
g 5Q
k.
0
Q.
40
Le =
Lo
l+0.30t
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"
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
194
-------
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
7570 1/ac/day (2000 gal/ac/day) for a year, showed 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.
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
195
-------
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 60. 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 (0.8 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 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 0 (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 60 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 re-
moval of COD and phenol than either the activated sludge or the trick-
ling filter methods.
196
-------
TABLE 60 RESULTS OF LABORATORY TESTS OF SOIL IRRIGATION
METHOD OF WASTEWATER 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.
197
-------
TABLE 61 REDUCTION OF COD AND PHENOL CONTENT IN WASTEWATER
TREATED BY SOIL IRRIGATION
Soil Depth (centimeters)
/Mbnth 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 (mg/1)
186
268
433
150
86
6
70
111
77
172
94.9
—
—
4.6
7.7
1.8
1.9
4.9
2.3
1.9
95.3
—
—
—
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
198
-------
Oxidation Ponds - Characteristics - Oxidation ponds are relatively
simple to operate and, because of their large volume, difficult to dis-
rupt. 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 due to weather con-
ditions; (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 lit-
erature. 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) .
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*3, 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 phosphates, and discharged into the pond
proper. Retention time in the pond was 45 days. The quality of the
effluent was guite 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.
199
-------
These modifications in effect changed the treating system from an oxi-
dation 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 re-
mains 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.
Chemical__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 use'd 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 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 involv-
ing small waste water volumes, hypochlorite is probably the more
practical.
Chlorine dioxide may also be used to oxidize phenols. It has the advan-
tage over other sources of chlorine of short reaction time, does not re-
quire 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 oxi-
dation 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 com-
pounds, 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.
200
-------
O
I-1
45
40
35
30
o>
^20
0)
«M
c
o
15
c
0)
10
JAN FEB MAR APR
MAY JUNE JULY AUG SEPT OCT NOV
Month
DEC
FIGURE 41 - PHENOL CONTENT IN WEYERHAEUSER'S OXIDATION POND EFFLUENT
BEFORE AND AFTER INSTALLATION IN JUNE, 1966 OF AERATOR
-------
TABLE 62 AVERAGE MONTHLY PHENOL AND BOD CONCENTRATIONS IN EFFLUENT
FROM OXIDATION POND
(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
—
—
202
-------
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 qual-
ification 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 6H 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.
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 comparable 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 in-
dicate that a portion of the organic content of the waste water was re-
sistant to chemical oxidation.
The reduction in COD caused by chlorination of raw waste water was prac-
tically the same as that achieved by flocculation with lime and a poly-
electrolyte.
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
203
-------
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
PGP Wastewater
(rag/liter)
COD
—
8150
7970
8150
7730
7430
PGP
40.7
17.3
13.1
12.0
10.4
0.0
Creosote Wastewater
(rag/liter)
COD
5200
4800
4420
4380
4240
3760
Phenol
223.1
134.6
65.3
15.4
10.0
5.4
204
-------
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
EFFECT OF CHLORINATION WITH
4.5
12.0
6.0
4.0
2.0
0.0
0.0
0.0
0.0
CHLORINE
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
THE PENTACHLOROPHENOL CONTENT 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
205
-------
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 • Its
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
10,20.0
23,600
9,760
10,700
11,250
206
-------
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 Ettinger 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 tc 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.
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:
207
-------
TABLE 67 CHLORINE REQUIRED TO ELIMINATE TASTE IN AQUEOUS
SOLUTIONS OF VARIOUS PHENOLIC COMPOUNDS
Chlorine Required To
Eliminate Taste
(mg/D
Phenol
0-Cresol
M-CresoT
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
208
-------
TABLE 68 CHLORINE DEMAND OF M-CRESOL AFTER VARIOUS
CONTACT TIKES
m-Cresol
Concentration Chlorine
(mg/1) (me/1)
10 20
10 50
10 100
20 50
20 100
Contact
Time
(hr)
0.25
0.5
1.0
2.0
0.25
0.5
1.0
2.0
0.25
0.5
1.0
2.0
0.25
0.5
1.0
2.0
0.25
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
209
-------
Phenol
2-Chlorophenol
U-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.
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-con-
suming materials in wood preserving waste water, a question arises con-
cerning 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 4.5, 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 de-
creased rapidly with increasing levels of chlorine. However, traces re-
mained 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
210
-------
TABLE 69 CHLOROPHENOL CONCENTRATION IN CREOSOTE WASTEWATER
TREATED WITH CHLORINE
As
pH
4.5
7.0
9.5
Ca(PCl)2
Chlorine
(8/1)
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 Analys
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
is (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
211
-------
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 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 1/10 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 tc 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 efflu-
ents 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
212
-------
100
CO
5
0)
cc
"o
0)
CO
a
o
o
10 20 30 40
Activated Carbon (gm/liter)
70
FIGURE 42
- RELATIONSHIP BETWEEN WEIGHT OF ACTIVATED
CARBON ADDED AND REMOVAL OF COD AND PHENOLS
FROM A CREOSOTE WASTEWATER
213
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carbon. A.S 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 penxachlorophenol 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 Waste, Handling^Methods
Containment: and Spray Evaporation - Forty-two percent of the plants re-
sponding to the survey referred to in Section V indicated that they cur-
rently are storing their waste water on company property, and therefore
have no discharge (Table 44). The popularity of this method of wasre
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 be-
tween 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
214
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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 per-
cent for the process.
Evaporation in Cooling Towers - In this process, effluent from the oil-
separation system is discharged to the basin of a cooling tower and re-
used 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
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.
ReguiredmImglementation_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.
215
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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 oxidaticn 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.
E£l§Qi 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 tech-
nologies 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 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 cculd 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 due to reuse of
waste water, evaporation, or both.
216
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Cool. Pond
Overflow
Boiler
Back
Wash
Jj
Condenser
Drain
Tanks (3)
Solvent
Tank
Pit
Pumps (3)
Cylinder Pit
Treating Room
OH Drips
Cylinder Vent
And
Slowdown
To Ditch
Equalizing
Tank
Flow Splitter
lorinator
Control Valv
@ 10 6PM
Nutrient Feede
— 9
Duplex Ext. Aer. Tank Clar.
Weir & Sludge Return
1/4 Acre Lagoon
1/4 Acre Lagoon
1/3 Acre
Lagoon
Irrigation
Field
FIGURE 43 - WASTEWATER FLOW DIAGRAM FOR WOOD-PRESERVING PLANT EMPLOYING
AN EXTENDED AERATION WASTE TREATMENT SYSTEM IN CONJUNCTION
WITH HOLDING LAGOONS AND SOIL IRRIGATION
-------
(VJ
NJ>
O
Penta
Storage
Tank
(t
31
Barometric
Condenser
Water Cooling
Pond
_y
m
2,000 Gat*.
5,500 Gals.
1,000 Gal*.
Gravimetric Penta
Separation Tank
Steaming Water
Transfer Pump
Float Control Valve
(Normal Open) Sump
(Normal Open)
' '(Norn ,
j .Closed))
^^glne Bark Filter
Oil &
Separation Tank
ft
a
Sludge To
Landfill
Sludge Dewaterlng Bed
P^^JI^
Holding. Tank
Transfer
Pump
(Normal!
Closed) *
Spr«v«
Soil Percolation
Field
FIGURE 44 - WASTEWATER FLOW DIAGRAM FOR WOOD-PRESERVING PLANT EMPLOYING
CHEMICAL FLOCCULATION, SAND FILTRATION, AND SOIL IRRIGATION
To Stream
-------
To PCP
Recovery
to
to
Secondary PCP
• Creo. Separation
PCP Separation
Tank
Catch Pond
Overflow and Run-off Water
Light Oil
Recovery
Creo.
Dehydration
Tank
Creo. Separation,-
Tanks ^
To Creo.
Recovery
Holding Ponds
Final Separation
To PCP
Recovery
Emergency Catch
Pond
Mixing
Chamber
Recycle Pump
FIGURE 45
Aerator/^ W —
Oxidation Pond
WASTEWATER FLOW DIAGRAM FOR
A WOOD-PRESERVING PLANT EM-
PLOYING AN OXIDATION POND IN
CONJUNCTION WITH AN AERATED
RACEWAY
-------
SECTION VIII
COST, ENERGY, AND NON-WATER QUALITY ASPECTS
BARKING
and Reduction Benefits of Alternative Treatment and Control
Technolpgi e s
Only wet barking techniques result in any discharge of process waste
waters, A no discharge can be accomplished by all but hydraulic barkers
through the recycle of process water*
A hydraulic barking operation will typically have a waste load of about
13,100 kg/day production (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 producting 100 million sq ft/yr of plywood on
a 3/8 in basis, for example.
AiiSiSSiive Aj. No Waste Treatment or Control
Effluent waste load is estimated at 660 kg/day of BOD5 and 13,100
kkg/day of suspended solids for the selected typical plant.
Costs: None
Reduction Benefits: None
itive B:_ Clarification and BioJLocfical 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.
INVESTMENT AND OPERATING COST ESTIMATE
ALTERNATIVE B
Clarification and Biological Treatment
Item Cost
1. Installed Equipment $1,070,500
223
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2. Yearly Operating Costs __ 138,200
TOTAL COST/YR $ 196,300
VENEER AND PLYWQQD^MANUFACTURING^SyBCATEGQRIES
Cost kQ
-------
Effluent waste load is estimated at 485 kg/day of BOD (1080 Ib/day) for
the selected typical plant.
Costs: None
Reduction Benefits: None
Alternative ^ _Bim__ Complete Retention^of Glue Wash water
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. Effluent 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 Qost
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 2x.350
TOTAL COST $17,500
The above information was based on cost data for an individual mill.
OPERATING COST ESTIMATE
Item Cost
1. Operation and Maintenance $ 2,200
2. Electricity 80Q_
TOTAL COST/YR $ 3,000
Summary:
Costs: Incremental costs are approximately
$17,500 over Alternative A, thus
225
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total costs are $17,500.
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,
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. Effluent waste load is estimated as 2.7 kg/day
(6 Ib/day) of BOD for the selected typical plant at this control level.
INVESTMENT COST ESTIMATE
ALTERNATIVE C
Jit em 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 iixlLP.0
TOTAL COST $12,000
OPERATING COST ESTIMATE
ALTERNATIVE C
Item Cost
1. Operation and Maintenance $ 6,300
2. Electricity 2^.20 0_
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_Drver Washwater
226
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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 selected typical plant at this control level. Complete
control of wastes without discharge to receiving waters is effected.
INVESTMENT COST ESTIMATES
ALTERNATIVE D
Alternative D-l; Spray^irrigation.
Associated Costs:
jEtem £°..§t
1. 37850 1 (10,000 gal) storage tank $ 2,700
2. Pump and motors 1/200
3. Piping 2,600
U. Labor and contingencies 3,200
TOTAL COST $~9,700
Alternative^D-2 :_ Containment_bv^Lacrooning
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
NOTE: For the purpose of the report an average investment cost
of $7,500 has been assumed to represent the cost of Alternative D.
OPERATING COST ESTIMATES
ALTERNATIVE D
Item Cost
1. Operation and Maintenance $ 7,900
2. Electricity 2^30 0_
TOTAL COST/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).
227
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Reduction Benefits: An incremental reduction
in plant BOD of 3 kg/day (6 Ib/day) is
evidence when compared to Alternative C,
producing a total plant reduction in BOD of 100 percent.
SUMMARY OF ALTERNATIVE COSTS
BOD Investment Yearly Total Yearly
Alternative Removal Cost Operating Cost
A 0% 0 0 0
B 15.8% 17,500 3,000 4,575
C 99.3% 29,500 5,000 7,655
D 100.0% 37,000 7,700 9,030
SUMMARY OF WASTE LOADS FROM TREATMENT ALTERNATIVES jfkg/dayj
RWL A BCD
BOD
SS
Total Suspended
Solids
Phenols 0.25 0.25 0.09 0.07 0
Mills With^Existingosteam,Vats
In Sections I, II, and IX of this report, a variance is recommended for
mills with existing direct steam vats. Since there are a number of mills
with steam vats, it is felt that these should not be treated as rare
cases to be dealt with as the occasion arises. 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:
485
352
1105
485
352
1105
412
330
1008
3
11
19
0
0
0
228
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1. A system consisting of a vacuum separator
followed by an aerated lagoon would cost
approximately $81,000 for the selected
typical 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 EOC removals for a cost of
about $138,000 and a resulting BOD load of
about 20 kg/day (45 Ib/day) of BOD for the
selected typical mill.
SQ§2r2Y. Requirements of Al£j£rna£iy.e_ Treatment and Control
Technology
It is estimated that 180 kwh of electricity is required to produce 93 sq
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 E: $800
For Alternative C: $900
For Alternative D: $1000
Nonwater Quality Aspects of Alternative Treatment and Control Technology
Air __ Pollution: While there are no appreciable air pollution problems
associated~with any of the treatment and control alternatives, 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
229
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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.
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.
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 by leach-
ates.
HARDBOARD - DRY PROCESS
_ and Reduction Benefits of Alternative Treatment and Control
Te chnologies
230
-------
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 typical mill selected to represent the dry
process hardboard industry has a production of 227 kkg/day (250
ton/day) , 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.
§§sis of Assumptions EmglOYgd In Cosj: 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 present market cost for
chemicals. Annual interest rate for capital cost is estimated at 8%, 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 925 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
18,925 1 (5,000 gal) storage tank
(includes installation and fittings) $ 4,000
23i
-------
3,
4,
5.
6,
7.
8.
1892 1 (500 gal) storage tank (acid resistant)
(includes installation and fittings) 1,500
Chemical feed pump 500
Pumps and piping 6,000
Instrumentation (pH) and controls 1,000
Chemical mixer 500
Tank Truck 7570 1 (2,000 gal) 8,500
Land 3,000
TOTAL $25,000
OPERATING COST ESTIMATE
ALTERNATIVE B
Item
1. Labor (4 man hr/wk)
2. Electricity
3. Chemicals
U. Maintenance
TOTAL COST/YR
Cost
$ 2,080
65
500
355_
$ 3"7ooo
Costs: 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 InstajLlati.cn Of Treatment Systems
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,
HARDBQARD-WET PROCESS
Basis Of Assumptions Employed Iri Cojst 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 kw/hr for electricity and present
232
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market cost, for chemicals. The annual interest rate for capital cost is
estimated to be 8%, 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.
Cost and Reduction Benefits of Alternative Treatment and Control
Technologies "~ ~"
The typical 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 production (67.5
Ib/ton), and a suspended solids concentration of 9 kg/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 Cost
JMay_1973).
1. Drum Screen installed $ 8,000
2. Clarifier - 7.6 m diam x 30.5 m deep
(25 ft diameter - 10 ft deep) 26,000
3. Sludge Pond - 0.405 ha - 2.44 m deep
(1 ac - 8 ft deep)
with liner - including land cost 43,000
4. Alum System 10,000
5. Miscellaneous _UQ*JLQ.O
Subtotal $107,000
20% Engineering and
Contingencies 22,OOP
TOTAL COST $129,000
OPERATING COST ESTIMATE
ALTERNATE A
Primary Treatment
Item Cost
1. Manpower $ 8,000
233
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2. Electricity 2,000
3. Steam
4. Water
5. Chemicals 18,000
6. Product Worth (deduct)
7. Maintenance 3^000,
TOTAL COST/YR $31,000
Summary:
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.
Alternative_B^lj __ Addition^of Activated Sludge Process
This alternative includes the addition of an activated sludge process
including pH adjustment and nutrient addition to Alternative 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
1. Primary Treatment $130,000
2. Activated Sludge __ 503, OOP
TOTAL COST $633,000
^Includes 20% for engineering and contingencies
234
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OPERATING COST ESTIMATE
ALTERNATIVE B- 1
Primary Treatment with Activated Sludge
Item Cost
1. Manpower $233,000
2. Electricity 28,000
3. Steam
i*. Water
5. Chemicals 29,000
6. Product (deduct)
7. Maintenance 2U
< _
Yearly Costs $314,000
Alternative B- 2i_ Addition of Aerated Laaoon to -Alternative A
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 waste.
235
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INVESTMENT COST ESTIMATE
ALTERNATIVE B-2
Screen, Clarifier, and Aeration Lagoon
Cost
Item
1. Rotating Drum Screen installed $ 8,000
2. Clarifier 7.6 m diam x 3.05 m depth
25 ft diam - 10 ft depth 36,000
3. Sludge Pond - 0.045 ha - 3.05 m depth
(1ac - 10 ft depth ) 41,000
4. Aerated Lagoon - 20 day retention 225,000
5. Lagoon - 5 day retention 50,000
6. Miscellaneous _ 40,000
Subtotal $400,000
20% Engineering and
Contingencies _ 80,000
TOTAL $480,000
OPERATING COST ESTIMATE
ALTERNATIVE B-2
Item Cost
1. Manpower $ 87,000
2. Electricity 21,000
3. Steam
4. Water
5. Chemicals 29,000
6. Product Worth (deduct)
7. Maintenance ______ 24j.0_0p
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 Cj_ Addition of An Aerated Lagoon Treatment System to the
Activated Sludge Treatment JB-_1J_._
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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 lb/ton) BOD and
2.8 kg/kkg (5.6 lb/ton) of 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 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 by 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
1. Primary Treatment $130,000
2. Activated Sludge Treatment 500,000
3. Aerated Lagoon 350, OOP
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. Product Worth (deduct)
7. Maintenance _ 4 9, 00 0
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.
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Reduction Benefits: A BOD reduction of 1.8 kg/kkg
(150 mg/1) (overall reduction of 9555} r and
a suspended solids reduction of 0 percent.
(overall reduction of 69 percent.)
Alternative D-1_j_ JjVaEorati.on of Process Water Discharge to Lagoon
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.U 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.
238
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INVESTMENT COST ESTIMATE
ALTERNATIVE D-1
Item
1. Davenport Press with Auxiliaries
2. Rotating Drum Screens installed
3. Clarifier
4. Liquor Holding Tank (8 hours)
5. Quadruple Effect Evaporators with
surface Condensers (304 SS wetbed parts)
6. Cooling Tower with Transfer Pumps (2)
7, Sludge Lagoon (100 days)
8. Alum Storage and Metering System
Subtotal
20% Engineering and
Contingencies
TOTAL
OPERATING COST ESTIMATE
ALTERNATIVE D-1
Item
1. Manpower
2. Electricity
3. Steam
4. Water
5. Chemicals
6. Product Worth (deduct)
7. Maintenance
TOTAL COST/YR
Summary:
Cost
(May 1973)
$172,000
8,000
26,000
30,000
250,000
30,000
22,500
10X000
$546,000
109,000
"$655,000
Cost
$175,000
8,000
92,000
1,000
18,000
89,000
36X000
241,000"
Costs: Total cost of this system would
be $655,000.
Reduction Benefits: The BODj> 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.
Alternative D-2^ Activated Sludge Treatment of Condensate Prior to
Discharge
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
239
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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 waste.
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
rtem Cost
19731
1. Neutralization System - Lime with Bucket
Elevator, Lime Storage Tank Feeder, Shutof f '
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 S 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«__Q.QO
1.8 m (6-ft) deep
Subtotal $150,800
20% Engineering and
Contingencies __ 30X200
TOTAL $181,000"
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
240
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A
Bzl
B-2
C
D-1
D-2_
10
90
80
95
93.5
99.4
$109^000 $
544^000
ors^ooo
843,000
566^000
722,000
26^700
270,000
138,500
308,800
207,000
428,000
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 kg/kkg 9.0 9.0 9.0 9.0 0.9 0.9
Eff. 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.
$36^50^0
'" ~319,QOO
175,000
^385,000
258,000
493.000
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 consis-cs
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 potential odor problems.
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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 produced 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 approximately 3.3 kkg (3 ton) of waste solids each day can
cause odor problems.
Factors Involved In The Installatign^Qf Alternatiye 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 biolcgical 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^D
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 between 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
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(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 due to
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
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
Raw Treatments
(mg/1)
Parameter Waste A B C D
COD 40,000 7,260 3,630 410 300
Oil & Grease 1,500 255 80 45 25
Phenols 190 190 190 2.5 0.5
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ENGINEERING__ESTIMATE S_FO]R_A_WOOiD_PRESERVING_- STEAM PLANT
£ii§£Dsi£iy§ hL Qii Separation
Standard oil separation equipment, equipped for both surface and bottom
removal, can be used for this purpose. Provisions must be made for both
surface and bottom removal since creosote tends to settle while
pentachlorophenol in oil will rise to the surface.
INVESTMENT COS1 ESTIMATE
ALTERNATIVE A
Oil Separation
Item
1. Land including clearing
2. Oil separator, installed
3. Pumps, motors, starters, lighting
^. Pipe, valves, fittings
5. Piping labor
6. Electrical labor
Subtotal
Engineering contingencies
Total for A
Summary:
Capital cost
Annualized cost including operation and
and maintenance
Alternative B:
and Filtration
Cost
$ 2,000
18,000
1,200
2,500
600
50 0
$24,800
$29,760
$29,760
$0.31/1000 1
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
244
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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 _60p_
Subtotal $36,100
Engineering and contingencies 7, 220
Total for B $42,320
Summary:
Capital cost $42,320
Annual!zed cost including operation
and maintenance $0.70/1000 1
^U^iH^iiZS. C^Ll. 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 Cost
1. Land including clearing $3,000
2. Liner, installed a $0.50 ft 3,000
3. Two 7.5 hp aerators, installed 7,600
4. Pumps, motors, starters, lighting 1,500
5. Pipes, valves, fittirgs 1,200
6. Piping labor 800
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7. Electrical labor _ 5_00
Subtotal $177600
Engineering and contingencies 3X52_0
Total for C-l $21,120
Summary:
Capital cost 21,120
Annualized cost including operation
and maintenance $0.70/1000 1
Alternative C-2^. Biological Treatmentft Activated Sludge
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.
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 Dj_ E2ii§iiilJ3 Treatment^ Chlorinatign
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 £2§t
T7~"chlorinator, installed $4,000
2. Detention tank, installed 1,000
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3. Automatic sampler, installed
4. Truck hand stand
Subtotal
Engineering and contingen-
cies
TOTAL COST
Summary:
Capital cost
Annualized cost including
operation and maintenance
Alternative E:. Effluent Measurement
A recording flow measurement device was selected.
INVESTIMATE COST ESTIMATE
ALTERNATIVE E
Flow Recording Device
Item
1. Measuring element with recorder
2. Installation
Subtotal
Engineering and contingen-
cies
TOTAL COST
Annualized cost for D summarized in Table A-5.
Summary:
Capital cost
Annualized cost including
operation and maintenance
Total capital costs for complete treatment
with lagoons:
Annualized cost for same system:
1,200
800.
'$7,000
$8,400
$8,400
$0.64/1000 1
cost
$2500
500.
$3,000
5.00
$3,600
$3,600
$0. 16/1000 1
$106,200
$3.45/1000 1
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WOOD PRESERVING
As discussed in Section III through VII, discharge of waste water
pollutants can be controlled by wood preserving plants in this
subcategory 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 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 wastewater from a typical plant. The balance is
lost regardlesss 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.
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Operating costs, exclusive of energy requirments, are estimated to be
$2r595/yr, or about $1.14/1000 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/kg (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 due to 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
THE 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.
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_Ayailable
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
251
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removing bark by pressure or abrasion processes. These processes may be
further broken down into "wet" and "dry11 methods. None of the processes
identified create significant water pollution problems, with the
exception of the hydraulic barking process.
Technology exists which can significantly reduce the waste discharge
loading from hydraulic barker operations. This technology consists of:
1. The application of primary screening and settling followed by;
2. Biological treatment.
Selection of Best Practicable Control Technology
~"
Age and .Size of Equipment and Facilities
The primary factor involved is the age of equipment and the raw
materials used, as discussed in Section IV. As noted therein, hydraulic
barkers are being phased out throughout the industry due to a decrease
in the number of over-size logs, and the associated water pollution
control problems.
Engineering Aspects
As discussed in Sections III through VIII of this document, the volume
of process waste water generated by the hydraulic barking operation is
estimated to be in the range of 5,860 to 7,600 cu m/day for a 9.31
million sq m/yr on a 0,953 cm basis, plywood plant.
The pollutants present in this water are suitable for application of
biological treatment. Certain segments of the timber products
processing industry may find uses for this process water while others
may chose to dispose of the hydraulic barker effluents into existing
biological treatment systems. The veneer and plywood subcategories
usually do not have this option available.
Biological treatment of hydraulic barker effluent alone is not
practiced. However, in the pulp and paper industry the effluent may be
treated biologically with other process waste waters. Application of
primary settling and biological treatment to the waste can remove from
70 to 90 percent of suspended solids and 80 to 85 percent of BOD5.
At least one hydraulic barking system applies physical-chemical
treatment to its effluent and accomplished nearly 10055 recycle.
However, this system has been in operation only since June, 1973 and is
not considered to be sufficiently proven to be defined as best
practicable control technology for hydraulic barker effluents at this
time.
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The best practicable control technology currently available for
hydraulic barker effluents is based on a 100 mg/1 BOD5 concentration and
a 2000 mg/1 suspended solids concentration, 80 percent BOD5 removal
efficiency, 50 percent suspended solids removal efficiency, a 6,5UO cu
m/day effluent from the hydraulic barker operation, and a throughput
rate of 252 cu m/day of wood.
Available information indicates that variation in the effluent from a
biological treatment system processing wastes from the wood based
industries is 300 percent.
Non-Water Quality Impact^and Energy Requirements
There is no significant non-water quality impact as the result of the
use of this technology. Solid wastes generated are currently burned as
fuel in the bark boiler, or disposed of as with other barking
technologies, including use as mulch or disposal by landfill.
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 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 requiring the
use of 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 is, through the application of the
best practicable control technology currently available, as follows:
30-day Average Daily Maximum
kg/cu m kg/cu m
llb/cu_f t]_ (Ib/cu
BOD5 0.5 1.5
(0.03) (0.09)
Total
Suspended 2.3 6.9
Solids -(0.144) (0.431)
VENEER
Identification of Best Practicable Control Te_chQ2i29y_ Currently
Available
253
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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 the unit
operations in this subcategory, will result in no discharge of
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
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
of waste can be disposed of by land disposal methods.
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.
12! 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 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.
254
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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 veneer subcategory of the
timber products processing industry. No plant, however, has been
found to utilize all of these control procedures. One hundred
(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 venaer manufacturing subcategory, in order to meet
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 U10 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 basis.
A hardwood veneer plant supplying a O.U65 million sq m/yr plywood
production plant using steam vats with direct steaming would have a
continuous effluent of about 0.5 I/sec (8 gal/min) 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, on a 6.35 mm basis.
As discussed earlier, alternative procedures for conditioning of
logs exist and indications are that the more practical procedures
would be those methods that do not result in the discharge of
pollutants.
The volumes of water required for cleaning of veneer driers have
been determined to be relatively small. Softwood veneer drier
255
-------
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 is 9.5 million sq m/yr.
Hardwood plant is O.U6 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 tc drier wash water will have no effect on the
operation and efficiency of the treatment system.
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.
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 plant will
have a total energy demand of 4500 kw 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.
256
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Summary
Based upon the information contained
of this document and summarized above,
made that the degree of effluent
sources in the Veneer manufacturing
which use direct steam conditioning as
application of the Best Practicable
Available is no discharge of process
navigable waters.
in Sections III through VIII
a determination has been
reduction attainable for all
subcategory excluding those
described below, through the
Control Technology Currently
waste water pollutants to
A variance will be allowed for those plants that both (1) as part
of their existing equipment use a log conditioning method that
injects steam directly into the conditioning vat, and (2) find it
infeasible to implement the technology listed- 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:
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)
PLYWOOD
Available
°i £h® !§§£ P^icticable Control Technology Currently
Plywood may include several distinct process steps. Alternatively
some of these may take place in the veneer manufacturing and
processing location
(3) gluing, (4)
. These steps are: (1) drying, (2)
pressing, and (5) trimming and packaging.
clipping,
The unit operations required in plywood manufacturing have been
discussed in detail in section III, the waste derived form each of
257
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the operations characterized in Section V, and treatment and
control technology, when 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 the
following control technologies:
1. The use of steam to clean spreaders where applicable and
the use of high pressure water for cleaning;
2. The use of glue applicators that spray the glue on rather
than rollers;
3. The use of glue washwater for glue makeup and disposal of
glue water, and;
1. Evaporation and spray application of glue water on bark
going to the incinerator.
fog the Selection of Best Practicable Control. Technology
s
Age ard Size of Equipment and Facilities
As discussed in section IV, the age and size of a plywood
manufacturing plant dc not bear directly on a quantity or quality
of the waste water pollutants generated.
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. One hundred (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 plywood manufacturing subcategory, in order to
258
-------
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 plant will
have a total energy demand of 45,000 kw 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.
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.
259
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It has been demonstrated that technologies exist which, when
aoplied to each of the unit operations, will result in no discharge
of pollutants. To meet the standard of no discharge requires the
implementation 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 humidif ication by the
implementation of in-plant control, including reasonable
operating and process management processes.
tionale for the Selection of Best Practicable control Technology
~ ~ - -
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. Biological treatment of this water is also possible
although it is not currently being practiced in any of the mills in
the subcategory.
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
260
-------
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 seme 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 UVkkg (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.
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 to navigable
waters.
261
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NOTE: No limit is established for fire control water. This
effluent will be collected and received at least primary screening
before discharge,
HARDBQAR|>WET_PROCESS
Identification of Best Practicable^ContrQl^
Wet process hardboard is manufactured using seven distinct process
steps or unit operations: (1) log washing, (2) chipping, (3) fiber
preparation, (U) wet-felting (mat formation) , (5) drying and
pressing, (6) humidification, 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 wet-felting 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 hardboard subcategory.
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.
3. Disposal of sludge by aerobic digestion in sludge lagoons,
recycle inplant, or as land fill.
Rationale for the Selction of Best Practicable Control Technology
Available
Processes Employed and Engineering Aspects
262
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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 (4) 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 reguired; rather the
addition of certain treatment capabilities and implementation of
water recycle and conservation practices will be needed to meet
these reductions.
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 technigues will ensure
that the non-water guality 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).
263
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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/tonX (Ib/tonl
BODS
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
Available
Practicable Control Technology Currently
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 a cost analysis.
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 cf 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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f2£ §§§£ PE12ticable Control Technology Currently
Available
Process Changes
No significant process changes are necessary to meet these
standards but treatment and control techniques would have to be
implemented. This technology is all based on the fact that there
exist opportunities to reuse the limited amount of waste water
generated; the recycling of waste 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 QuaJity. Impact and Energy Requirements
The suggested technologies are based primarily on modification of
inplant 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 $5.98/1000 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.
PRESERVING - BQULTONIZING
2l §§s£ Practicable Control Techno logy 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
265
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into the cylinder, U) 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.
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 U plants which
are now achieving no discharge of waste water pollutants. Sections
VTI and VIII detail specific technology and cost analyses.
Egr §§§£ 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 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.
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 Practicable Control Technology. Currently
Available
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Log conditioning and preservative injection are the primary unit
processes from which waste water pollutants may be derived in this
subcategory. Condensate from steaming is the most heavily
contaminated since it ccmes in contact with the preservative and
the wood; 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.
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 IV, 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
267
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number of plants. None present unique problems from an engineering
point of view.
Mosr wood preserving operations using oily based preservatives have
oil-recovery systems. Apart from environmental considerations, it
is less expensive to recover and reuse oil than to replace it.
Chemical methods involving flocculaticn 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
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 Enercjy 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.
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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 this wood
preserving subcategory through the application of the best
practicable control technology currently available is as set forth
in the following table:
COD
Phenols
Oil and Grease
30-Day
Average
kg/1000 cu m
550
(34.5)
0.65
(0:04)
12.0
(0.75)
Daily
Maximum
kg/1000 cu m
(lb/1QOO cu
1100
(68.5)
2.18
(0.14)
24.0
(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 effluent limitations which must be achieved by July I, 1983,
are to specify the degree of effluent reduction attainable through
the application of the best available technology economically
achievable. The besr 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 conrrol
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 control 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 level, 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
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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
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 T®£]}22i23Y Economically
Achievable
As summarized in section IX, 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 manufacturinq
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.
Attainable Through the Application of the Best
Available Technologj£""Ecgnomically_ 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 require variation from the no
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discharge limitation set forth in this section for any point source
subject to such effluent limitation.
VENEER
Identification of the Best Available Technology. Economically
Achievable ~
The best practicable control technology currently available 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 Ap.p_lication o_f the Best
ky.
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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 ho\isekeeping procedures and judicious use of wet. cleaning
water.
Effluent Reduction Attainable Through the Application of the Best
Technology IsojQSIBically. 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 subcat.egory through the application of the
best available technology economically achievable is no discharge
of process waste water pollutants to navigable waters.
HARDBOARD - DRY PROCESS
I d e n t i f j. ca t i on of the Best Technology Economically Achievable
As summarized in Section IX, the best available technology
economically achievable in the Hardboard - Dry Process subcategory
consist 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;
4. Elimination of discharge from humidification by the
implementation of inplant control, including operating and
process management procedures.
Reduction Attainable Through the Application of the Best
Avail.able 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
Id en t if i ca t i on of the Best Technology Economically Achievable
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As discussed in section VII, the best available technology
economically achievable in the Hardboard-Wet 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 kg/kkg
(18 Ib/tonj ;
2. Installation of a pre-press and evaporation system;
3. Discharge of process water only from the pre-press and the wet
press;
U. 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 consistency. 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
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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. U percent BOD^ removal for an
initial cost of $722,000 and yearly operating cost of $428,000.
iHf-flu®!!!; Seduction Artainabl.e Through the Application of_ the Best
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 subcategory through the application of the
best available technology economically achievable is a maximum
discharge as follows:
30-Day Daily
Average Maximum
kg/kkg kg/kkg
Jlb/t°Dl lib/ton).
BOD5 0.9 2.7
(1.8) (5.U)
Total
Suspended Solids 1.1 3.3
(2.2) (6.6)
pH 6.0-9.0 6.0-9.0
WOOD .PRESERVING
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;
2; Segregation of contaminated and uncontaminated water streams;
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 sludges), soil
irrigation, oxidation ponds, chemical oxidation, containment
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and spray evaporation, pan evaporation, evaporation in cooling
towers, and incineration of high concentration oily waste
waters.
Effluent Reduction Attainable Through the Application of the Best
Ay,siii§.bi§ 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 subcategory through the application of the best
available technology economically achievable is no discharge of
process waste water pollutants into navigable waters,
WOOD PRESERVIN6-BOULTQNIZING
Identification of the Best 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 cil recovery equipment to reduce influent to
treatment system;
4. Elimination of equipment and plumbing leaks;
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 cooling
towers, and incineration of high concentration oily waste
waters.
Eff.luenr 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
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the best, available technology economically achievable is no
discharge of process waste water pollutants to navigable waters.
PRESERVI2IG- STEAM
2f. £h§ l§£t AZ§i_lsble Technology EconomicallY
.Achievable
The low wast=? water flow rate and limitations on discharges that
must be achieved to conform with 1983 requirements will necessitate
a high level of water reuse, changes in steaming rechnique amonq
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 to be the best available technology
economically achievable:
1. Minimization of the volume of discharge by (a) recycling all
directcontact cooling water, (b) reuse of a portion of the
process water for cooling purposes, (c) insulation 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 heavy 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 ensure 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
278
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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 m 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. In addition, the volume of
condensate produced would also be reduced significantly.
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 th^
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 100%
ar dosages up to 3.0 g/1 of CaOCl2 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.
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E§^ii£tl2Ii Attainable Through the Application of_ the Best
Av=iiiai2i£. 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:
30-Day Daily
Average Maximum
kg/1000 cu m kg/1000 cu m
ilb/l£00_cu_ftl_ (lb/1000 cu ft)
COD 110 220
(6.9) (13.7)
Phenols 0.064 0.21
(0.004) (0.014)
Oil and Grease 3.U 6.9
(0.21) (0.42)
pH 6.0-9.0 6.0-9.0
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SECTION XI
STANDARDS OF PERFORMANCE FOR NEW SOURCES
INTRODUCTION
This level of technology 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 through 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 03: 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__IntQ_CQnsideratign
?^t least the following factors should be considered with respect +-.0
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.
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BARKING
5§!Sii££i9ELt Identification and E§ti2DSl® Jo^ Selection of
New Source Performance Standards
Based or. 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 effluents tc navigable waters.
The standard of performance for new sources using hydraulic barkers
will be varied from the above effluent standard, and is based or. a
100 mg/1 BOD and a 2000 mg/1 suspended solids concentration, 80
percent BOD and 50 percent suspended solids removal efficiency, and
6,540 cu m/day effluent from the hydraulic barkers operation, at a
throughout rate of 2, 520 cu m/day of wood.
Available information indicated that variation in the effluent from
a biological treatment system processing wastes from the wood based
industry is 300 percent.
Based upon the information contained in sections ill through VIII
of this document and summarized above, a determination has been
made that the standard of performance representing the dearee of
effluent reduction attainable and the maximum allowable discharge
for new sources ir. the Barking subcategory that use the hydraulic
barking process shall be as follows:
30-Day Daily
Average Maximum
kg/cu m kg/cu m
BOD5 0.5 1.5
(0.03) (0.09)
Total Suspended
Solids 2.3 6.9
(0.144) (0.431)
VENEER
Effluent Reduction^ Identif ication^. and Rationale for Selection of
New Source Performance Standards
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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 discunsed 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 vni 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
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 for new sources in the Plywood manufacturing
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.
H&PDBOARD - DRY PROCESS
Sf f J.Tjgnt^Rgducr ion ^Identification f._and>rRationale_jor^ select ion
of-New_Source_Perf ormance 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 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
other alternatives is no discharge of process waste water
pollutants to navigable waters.
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HARDBOARD - WET PROCESS
Effluent BeductipILji. I^D^iJLiSaSionji, and Rationale Jgr the Selection
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-wer
subcategory through the apolication of the best available
demonstrated control technology, processes, operating methods, or
other alternatives is as defined below:
30-Day Daily
Average Maximum
kg/kkg kg/kkg
BOD5 0.9 2.7
(1.8) (5.U)
Total
Suspended solids 1.1 3.3
(2.2) (6.6)
pH Range 6.0-9.0 6.0-9.0
WOOD_PRESERVING
Ef f_luent_Reduct4onx_ld_entif i cation x _ and Rationale for the
Selection of New Source Perf or ma nee _ Standards
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 to navigable waters.
WOQD_ PRESERVING- BO ULTONI ZI NG
Effluent Reduction^ Identification^ and Rationale for the selection
of New source Performance Standards
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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 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 feasible 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
3ry 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 United States
currently kiln dry a portion of their stock prior to treatment.
Only about 10 percent use kiln drying for all their stock. The
capital investment is high for this technology, amounting to
$60,000 per kiln. A minimum of 5 kilns would be required if all
the material treated by a typical three-retort plant were dried
prior to preservative treatment. Total investment would be
$300,000, including $47,000 for each kiln and $13,000 for accessory
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
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increasinor 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. Seme air seasoning takes place
in the normal processing of material on the yard, 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
Cor 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 cr vapor drying in a separate retort woulri
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,QOO/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:
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30-Day 30-Day
Average Average
kg/1000 cu m kg/1000 cu m
Jlb/J0_00_cu_ftl JiJS£2MO_S
COD 110 220
(6.9) (13.7)
Phenols 0.064 0.21
(0.004) (0.014)
Oil and Grease 3.4 6.9
(0.21) (0.42)
pH Range 6.0-9.0 6.0-9.0
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SECTION XII
ACKNOWLEDGEMENTS
The preparation and writing of this document for the veneer and
plywood, and the hardboard subcategories of the industry was
accomplished principally through the efforts of Dr. Richard H.
Jones, Mr. John D. Crane, Mr. Robert A. Morrell, and Mr. Leonard P.
Levine all of Environmental Science and Engineering, Inc. (ESE).
Dr. John Meiler was a consultant to ESE and provided guidanqe
during the preparation of the report. The Mississippi Forest
Products Laboratory was responsible for the preparation and writing
of the sections on the wood preserving industry.
Industrial Advisory Groups for both the plywood/veneer and the
hardboard industry were established and these groups assisted this
project by supplying information and making recommendations. The
plywood/veneer advisory group consisted of:
Mr. Bruce Greforth - National Forest Products
Association
Mr. J. Tait Hardaway - Memphis Plywood Corporation
Mr. Wallace N. Corry - Boise Cascade
Mr. W. D. Page - American Plywood Association
Mr. Carl Erb - American Plywood Association
Mr. Mac Donald - Hardwood Plywood Association
Mr. John Stover - The Mortenson Company
Mr. Matt Gould - Georgia-Pacific Corporation
Mr. Roger Sherwood - Georgia-Pacific Corporation
Mr. Don Deardorf - Agnew Plywood
Mr. Harry Bartels - Champion International
Mr. O. B. Burns, Jr. - Westavco
Mr. Ron Presley - U. S. Plywood
The hardboard advisory group consisted of:
Mr. Ken R. Peterson - American Hardboard Association
Mr. James E. Leker - Masonite Corporation
Mr. Fred E. Blattner - Celotex Corporation
Mr. Greg M. Schaefer - Boise Cascade Institute
Mr. John M. Sims - Abitibi Corporation
Mr. Steven Myers - Abitibi Corporation
Several industrial trade associations and individual corporations
provided assistance and cooperation to the wood preserving study.
Among these were:
American Wood-Preservers* Association
American Wocd-Preservers1 Institute
288
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J. H. Baxter and Company
Cascade Pole Company
Fernwood Industries
Koppers Company, Inc.
L. D. McFarland Company
Moss-American, Inc.
Sheridan Pressure Treated Lumber, Inc.
W. J. Smith Wood-Preserving Company
Society of American Wood Preservers
Weyerhaeuser Company
Wyckoff Company
Ak.cn owl edge men t is also expressed for the assistance of the
Industry Coordinating Committee and the many individuals who
contributed the data for use in the study of wood preserving.
Specific appreciation is extended to:
Mr. C. W. Best - J. H. Baxter and Company
Mr. C. A. Burdell - Southern Wood Piedmont Company
Mr. L. E. Crane - Weyerhaeuser Company
Mr. P. C. Gaskin - Moss-American, Inc.
Mr. C. D. Hudson - Wyckoff Company
Mr. M. D. Miller - Koppers Company, Inc.
Dr. J. N. Roche - Koppers Company, Inc.
/
Intra-agency review, analysis, and assistance was provided by the
Timber Products Processing Working Group/Steering Committee
comprised of the following EPA personnel:
Mr. Ernst P. Hall, Effluent Guidelines Division
(Committee Chairman)
Mr. Al Ewing, National Environmental Research
Center, Corvallis
Mr, Arthur Mallon, Office of Research and Development,
Headquarters
Mr. Robert McManus, Office of Enforcement and
General Council, Headquarters
Mr. Robert Quartel, Effluent Guideline Division,
Headquarters
Mr. William Smith, Office of Economic Development,
Headquarters
Mr. Reinhold Thieme, Office of Enforcement and
General Council, Headquarters
Mr. Kirk Willard, National Environmental Research
Center, Corvallis
Mr. Richard Williams, Effluent Guidelines
Division, Headquarters, (Project Officer)
289
-------
Mr. Richard Williams of the EPA Effluent Guidelines Division was
the Project Officer and Mr. Robert Quartel participated in the
preparation of this document. Mr. Ernst P. Hall was a source of
invaluable guidance during the final preparation of the document.
Acknowledgement and appreciation is given to the secretarial staffs
of Environmental Science and Engineering, Inc. the Mississippi
Forest Products Laboratory, and the Effluent Guidelines Division,
EPA with special thanks to Ms. Fran Hansborough on the EGD/EPA
staff for the many hours of overtime and good typing.
290
-------
SECTION XIII
REFERENCES
1. Thompson, W. S., "Status of Pollution Control in the Wood Preserving
(in press) .
2. American Wood Preservers* Association, P£oceedinc[s, vol. 68, pg. 275,
286, 287, 1972.
3. Forest Products Industrv_DirectorY* Miller Freeman Publications,
San Francisco, 1972. ~"
U. Market_Profile — Softwood and_Hardwood PlvwgodA^CJ._S.A._and Canada,
Forest Industries, Portland, Oregon, 1969.
5. Panshin, Alexis Jchn et al, Forest rProductsi Their_Sourcesx_Produc-
tion, and Utilization, McGraw-Hill, New York, First Edition, 1950.
6. Market_Profi_le_-_Hardboard, Forest Industries, Portland, Oregon.
7. MacDonald, Ronald G., Editor, and Franklin, John N. , Technical
Editor, The Pulping of Wood, Second Edition, Volume I, McGraw-Hill,
New York, 1969.
8. Gehm, Harry, Industrial Waste^Study of _the_Paper rand Allied Products
Industries, Environmental Protection Agency, July, 1971.
9. "Plywood and Other Wood-Based Panels," Food and Agricultural
Organization of the United Nations, Rome, 1966.
10. Bodien, Danforth G., PlYwood_Plant_Glue_Wastes_DiS2osal, Federal
Water Pollution Ccntrol Administration, Northwest Region, Pacific
Northwest Water Laboratory, U. S. Department of the Interior,
1969.
11. "Fiberboard and Particle Board," Food and Agricultural Organization
of the United Nations, Rome, 1958.
12. Asplund, A., The_Origin_and Deyelgpmer.t_of^the_Defibrator Process,
FAO/ECE/Board Cons., Paper 5.2.
13. Watts, E. W., Industrial Experience in the Manufacture_of_Smooth-
2~Sides_Hardboard, FAO/ECE/Board Cons., Paper 5.11.
14. Gettle, Karl, A Guide for the Study^of the Manufacturing_of
Hardboard, American Hardboard Association and American Indus-
trial Arts Association.
291
-------
1 5. gasic^Hardbgard^-^Proggsed yoluntajry^Product,
.American Hardboard Association, Revision of CS 251-63 Hardbpard,
February 13, 1973.
16. Statistical Policy Division of the Office of Management and
Budget, U.S. Government Printing Office, Washington, D. C.,
1972.
17. stephenson, J. Newell, Editor, Preparation,and Treatment of
Wood_Pul£, Vol. 1, McGraw-Hill, New YorkT 1950.
18. Schaumburg, Frank D., The_Inf_luence_of_Log_Handling_on_Water
O_uali_ty_, Office of Research and Monitoring, U. S. Environmental
Protection Agency, Washington, D.C., 1973.
19. Haskell, Henry H., "Handling Phenolic Resin Adhesive Wash Water
in Southern Pine Plywood Plants," Forest_Products_Journal, Vol.
21, No. 9, September, 1971.
20. Mortenson, A. W., Private Communications (Inferno Steam Systems,
Portland, Oregon) April - June, 1973.
21. Gran, Gunnar, Wastewater_from_Fi1ber;board_Mills, Stockholm, Sweden.
22. Leker, James E. , Masonite Corporation, Private Coinmunication,
January - June, 1973.
23. Thompson, W. S. and Dust, J. V., "Pollution Control in the Woo3
Preserving Industry. Part 1. Nature and Scope of the Problem,"
Forest Products Journal, 21(9), pp 70-75, 1971.
2M. Mississippi Forest Products Laboratory, Ungubli.shed_Data,
Mississippi State University, State College, Mississippi,
1970.
25. Dust, J. V. , and Thompson, W. S., "Pollution Control in the
Wood Preserving Industry, Parr 4. Biological Methods of Treat-
ing Wastewater." Forest, Products Journal, in press, 1973.
26. Sohlman, L., "Measures Taken by the Wallboard Mill of Skinn-
skatteberg to Control Water Pollution," International Congress
on Industrial Wastewater, Stockholm, Sweden.
Effect of Inlet Conditions on Oil-Water Separators at SOHIO's
Conference, pp. 618-625, 1965.
31. Thompson, W. s., "Pollution Abatement by Inplant Process Changes
and Sanitation," Proceedings, Conference on^ PollutionAbatement
and Control in the Wood Preserving Industry, Mississippi Forest
292
-------
Products Laboratory, Mississippi State University, State College,
Mississippi, pp. 116-129, 1971.
35. Jones, R. H., and Frank, W. JU, "Wastewater Treatment Methods
in the Wood Preserving Industry,11 Proceedings, Conference_on
W. S. Thompson, Editor, Mississippi Forest Products Laboratory,
Mississippi State University, State College, Mississippi, 1971,
pp. 206-216.
36. Simonsen, R. N., "Oil Removal by Air Flotation at SOHIO Refin-
pp. 399-406, 1962.
37. Weston, R. F. and Merman, R. G., "The Chemical Flocculation
of a Refinery Waste," Proceedings, American_Petroleum_Insti-
tute, 34(111), pp 207-224, 1954.
38. Middlebrook, E. J., "Wastes from the Preservation of Wood,"
^2ii£0§i/ Sanitary Engineering Division, ASCE, 9Jir PP 41-56,
1968.
39. Gaskin, P. C., "A Wastewater Treating Plant for the Wood
Preserving Industry," Proceedings, Conferencemgn_Pollution
Abatement and Control in the Wood Preserving Industry, (W. S,
Thompson, Editor) Mississippi Forest Products Laboratory,
Mississippi State University, State College, Mississippi, pp
271-281, 1971.
40. Van Frank, A. J. and Eck, J. C., "Warer Pollution Control in
rhe Wood Preservation Industry," Proceedings, American wood
Preservers1 Association, Washington, D. C., 52, pp 187-194,
1956.
41. American wood Preservers' Association, Report on Information
and Technical Development Committees, Proceedings, American
Wood_Preservers_Association, Washington, D. C., 52, pp 187-194,
1956.
42. Halff, A. H., "Slow Sand Filtration of Wood Treating Plant
55, pp 184-188, 1959.
43. Halladay, W. B. and Crosby, R. H., "Current Techniques of Treat-
ing Recovered Oils and Emulsions," Proceedings, Americanu Petro-
leiiELJiQStitute, 44 (III) , pp 68-73, 1964.
44. Dust, J. V., "Sludge Production and Dewatering," Proceedings
c.2S£££gS£g.-QP _Pgllution_Abjiteme_nt_and^C9ntrol_Tin the Wood Pre-
serving ^Industry (W. S. Thompson, Editor), Mississippi Forest
Products Laboratory, Mississippi State University, State College
Mississippi, pp 85-95, 1971.
293
-------
45. Schwoyer, W., "The Permutit DCG Unit," Proceedings, Conference
on Pollution Abatement and Control in the Wood Preserving In-
dustry,, (W. S. Thompson, Editor), Mississippi Forest Products
46. Jones, R. H., "Toxicity in Biological Waste Treatment Processes,"
the^Wgod. Preserving Industry, {W. S. Thompson, Editor) Missis-
sippi Forest Products Laboratory, Mississippi State University,
State College, Mississippi, pp 217-231, 1971.
47. Dodge, B. F., and Reams, D. C., Jr., "Disposing of Plating
Room Waste," Research Report No. 9, American Electroplaters
Society, New York, New York, 1949.
48. American Wood Preservers* Association, Report on Information
and Technical Development Committees, Proceedings, Washington,
D. C. , 54, pp 188-190, 1958.
49. Bliss, H. , "Developing a Waste Disposal Process," Chern. Eng.
PI22I-/ I*** PP 887-894, 1948.
50. Chamberlin, N. S. , and Day, R. V., "Technology of Chrome Re-
duction with Sulfur Dioxide," Proceedings, llthTIndustrial_waste
QSHf^E^HS-Sr Purdue University, pp 129-156, 1956.
51. Nyquist, O. W. and Carroll, H. R., "Design and Treatment of
Metal Processing Wastewaters," Sew. Indus, wjast.es, 31, pp 941-
948, 1959.
52. Stone, E.H.F., "Treatment of Non-ferrous Metal Process
Waste of Kynoch Works, Birmingham, England," Proceedings, 25rh
Industrial Waste Conference, Purdue University, pp 848-855,
1967.
53. Hansen, N.H., and Zabban, W., "Design and Operation Problems
of a Continuous Automatic Plating Waste Treatment Plant at the
Data Processing Division, IBM, Rochester, Minnesota,"
249, 1959.
54. Anderson, J. S. and lobst, E. H., Jr., "Case History of Waste
water Treatment at a General Electric Appliance Plant," Jour.
Water Pollution Control Federation, 10, pp 1786-1795, 19687
55. Zabban, W. and Jewett, H. W., "The Treatment of Fluoride Waste"
716, 1967.
56. Culp, R. L. and Stoltenburg, H. A., "Fluoride Reduction at La
Crosse, Kansas," Jour. AWWA, 50, pp 423-437, 1958.
57. Wamsley, R. and Jones, W. F., "Fluoride Removal," Water_and
Sewa2e_Works, 94, pp 372-376, 1947.
294
-------
58. Magnusen, L. M., Waugh, T. C,, Galle, 0. K., and Bredfeldt, J.,
"Arsenic in Detergents, Possible Danger and Pollution Hazard,"
Science, 168, pp 398-390, 1970.
59. Shen, Y. s. and Chen, C. S., "Relation Between Black-Foot
Disease and the Pollution of Drinking Water by Arsenic in
Pollution Research, Tokoyo, Pergamon Press, New York,
pp 173-190, 1964.
60. Irukayama, K., Discussion of Paper "Relation Between Black-
Foot Disease and the Pollution of Drinking Water by Arsenic
in Taiwan," 1964. (See Shen and Chen, Reference 59).
61. Cherkinski, S. N. and Genzburg, F. I., "Purification of Arsen-
ious Wastewaters," Water Pollution ^ Abstracts^ 14, pp 315-316,
1941.
62. Russell, L. V., "Heavy Metals Removal from Wood Preserving
Wastewater," Proceedings, 27th Purdue Industrial Waste Con-
ference, 1972, in pressT
63. Russell, L. V, "Treatment of CCA-, FCAP-, and FR-type Wastewaters,"
Proceedings, Conference on Pollution Abatement and Control in the
wood Preserving Industry, (W. S. Thompson, Ed.) Mississippi Forest
Products Laboratory, Mississippi State University, State College,
Mississippi, pp 249-260, 1971.
64. Earth, E. P., Salotto, B.V., English, J. N., and Ettinger, M. B.,
"Effects of a Mixture of Heavy Metals on Sewage Treatment pro-
cesses," Proceedings, 18th Industrial Waste Conference, Purdue
UniversityT Lafayette, pp 616-635, 1964.
65. Kucjelman, I. J. , and Mccarty, P. L. , "Cation Toxicity and
Stimulation in Anaerobic Waste Treatment," Journal, WPCF, 37{1):
97-116, 1965.
66. McDermott, G. N., Earth, E. F., Salotto, B. V., and Ettinger,
M. B., "Zinc in Relation to Activated sludge and Anaerobic
Digestion Process," Proceedings,_17th^Industrial__Waste Conference,
Purdue University, pp 461-475, 1964.
67. Young, "Anionic and Cationic Exchange for Recovery and Puri-
fication of chrome from Plating Process Wastewaters," Pro-
ceedings, 18th_Industrial._Waste_Con£erence, Purdue University,
pp 454-4647~~1964.
68. Gilbert, L., Morrison, W. S., and Kahler, F. H., "Use of Ion
Exchange Resins in Purification of Chromic Acid solutions,"
Proceedings, Amer. Electroplating Soc., 39, pp 31-54, 1952.
295
-------
69. Costa,R. L., "Regeneration of Chromic Acid Solutions by Ion
Exchange," Ind^_Eng_._Chem. , 42, pp 308-311, 1950.
70. .American Wood Preservers' Association, Report on Information
and Technical Development Committees, Proceedings, American
Woood Preservers' Association, Washington, D. C., 53, pp 215-
220, 1957.
71. Sweets, w. H., Hamdy, M. K., and Weiser, H. H., "Microbiological
Studies on the Treatment of Petroleum Refinery Phenolic Wastes,,"
Sewage^lncUjWas tes, 26, pp 862-868, 1954.
72. Reid, 3. W. and Libby, R. W., "Phenolic Waste Treatment Studies,"
Processings, 12th Industrial__Wasta^Confergnce, Purdue University,
pp 250-258, 1957.
73. Ross, w. K., and sheppard, A. A., "Biological Oxidation of
Petroleum Phenolic Wastewater," Proceedings, 10th Industrial Waste
Conference, Purdue University, pp 106-119, 1955.
74. Reid, G. W., Wortman, R. and Walker, R,, "Removal of Phenol with
Biological Slimes," Proceedings, llth Inaustrial_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_Industria1_Waste_Con-
ference, Purdue University, pp 156-166, 1961.
76. Montes, G. E., Allen, D. L., and Showell, E. B., "Petrochemical
Waste Treatment Problems," SewaQ§_Indi_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."
78. Davies, R. W., Biehl, J. A., and Smith, R. M., "Pollution Control
and Waste Treatment at an Inland Refinery," Proceedings, 2^st.
Industrial Waste Conference, Purdue University, pp 126-138, 1967.
79. Austin, R. H., Meehan, W. G., and Stockham, J. D., "Biological
Oxidation of Oi1-Ccntaining Wastewaters," Ind. Enq. Chem.,
46, op 316-318, 1954.
80. Prather, B. V., and Gaudy, A. F., Jr., "Combined Chemical, Physical,
and Biological Processes in Refinery Wastewater Purification,"
P£2C§§dings, American Petroleum_Institute, 44(111), pp 105-112, 1964,
296
-------
81. Davies, J. J. , "Economic Considerations of Oxidation Towers,"
i Conference on Pollution Abatement and Control
in_the^Wood^Pre serving^ 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 ; , 2_1_st Industrial
£2Qf §£§D£S • Purdue University, pp, 591-599, 1967.
86. Coe, R. H., "Bench-Scale Method for Treating Waste by Activated
Sludge," PetrQleum_Processing, 7, pp 1128-1132, 1952.
87. Ludberg, J. E., and Nicks, G. D., "Phenols and Thiocyanate
Removed from Coke Plant Effluent," Ind. __ Wastes (November) pp 10-
13, 1969.
88. American Wood Preservers1 Association, Report of Wastewater
Disposal Committee, Proceedings, Ameri1can_Wood_Pre serve rs •
£§§Q£i3ti°.!l» 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._JQur. _.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," Journal_and_Proceedinqs ,
S-PJiSif i£ail2Q t 2:159, 1961.
91. Nakashio, M. , "Phenolic Waste Treatment by an Activated-Sludge
Process," Hakko Kogaku Zasshi 47:389, Chem. Abs. 71(8) :236, 1969.
92. Reid, G. W. , and Janson, R. J. , "Pilot Plant Studies on Phenolic
Wastes at Tinker Air Force Base," Proceedings, IQth Purdue
Industrial Waste Conference, p 28, 1955.
93. Kostenbader, P. O. and Flacksteiner , J. W. (Bethlehem Steel
Corporation) , "Biological Oxidation of Coke Plant Weak Ammonia
297
-------
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., "Koppers* Experience Regarding Irrigation of
Industrial Effluent Waters and Especially wood Treating Plant
Cgntrol_J.n_the_Wood_Preserying_Industri (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 gf Refinery
W§.§fees_. 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," Sewaa§_Indi_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, 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 -Indu§try, (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.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
(W. S. Thompson, Editor) Mississippi Forest Products Laboratory,
Mississippi State University, State College, Mississippi, pp 150-
164, 1971.
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,"
Jour. Pennsylvania Water Works Operators' Assoc., 28:33, 1956.
298
-------
105. Glabisz, O., "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, J. 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 Wastewater, 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, " Water_and_Sewage_ Works, 95:187, 19*49,
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,
U3:651, 1951.
112. Burttschell, R. H., "Chlorine Derivatives of Phenol Causing Taste
and Odor," Jgur^American^Water^Works^AssQC.., 51:205-214, 1959.
113. Eisenhaeur, H. R. , "Oxidation of Phenolic Wastes," Jour_.__Water
Pollution Control Federation, 36 (9) : 1116-1128, 1964."
114. Niegowski, S. J., "Destruction of Phenols by Oxidation with
Ozone," Ind-.^nSi.Chem., 45 (3) : 632-634, 1953.
115. Niegowski, S, J., "Ozone Method for Destruction of Phenols
in Petroleum Wastewater," Sewa3e_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," In d_._ Water _ and
Wastes (January - February, pp 29-35, 1962.
117. Gloyna, E. F., and Malina, J. F., Jr., "Petrochemical Waste
Effects on Water, Part 2, Physiological Characteristics,"
Ind. Water and Wastes, (November-December) pp 157-161, 1962.
299
-------
118. Gould, M. and Taylor, J. , "Temporary Water Clarification System,"
Qhgm..._Eng.._Prog.ress, 65 ( 12) : 47-49, 1969.
119. Thomas E. Gates 8 Sons, Inc., Personal Correspondence to
Environmental Enaineering, 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 For Industry* McGraw-Hill, New
York, 1954.
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
r October 15, 1972.
Boydston, James R. , "Plywood and Sawmill Liquid Waste Disposal," Forest
J?roducts_ Jour na 1 , Vol. 21, No. 9, September 1971.
Fisher, C. W. , "Soil Percolation and/or Irrigation of Industrial Effluent
Waters--Esoecially Wood Treating Plant Effluents," Fore s t_ Produ c ts
Journal, Vol. 21, No. 9, September 1971.
Freeman, H. G. and Grendon, W. C. , "Formaldehyde Detection and Con-
trol in the wood Industry," Fores t_Products_ Journal, Vol. 21, No.
9, September, 1971.
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
IHdustrial_Wastes, Vol. "2 8, No. 3, March, 1956.
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 Water Clarification System,"
Chemical Enqineering_PrQgress, Vol. 65, No. 12, December, 1969.
Groth, Bertil, Wastewater from Fiberboard Millg, Annual Finnish Paper
300
-------
Engineers' Association Meeting, Helsinki, April 12, 1962.
Hansen, George, (Task Force Chairman) Log Storaqe^and^Raftinq,in
Public Waters, Pacific Northwest Pollution Control Council,
August, 1971.
Hoffbuhr, Jack, Blanton, Guy, and Schaumburg, Frank, MThe Character
and Treatability of Log Pond Waters," IndustrialmWaste, July-
August, 1971.
Kleppe, Peder J., and Rogers, Charles N. , SuryeyTOf_Water Uti 1izatign
and Waste Contrgl^Practices in the Southern_Pulp and Pager
iliilusjry. Water Resources Research Institute, University of
North Carolina, June, 1970.
Leker, James E., and Parsons, Ward C., "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," Journalx_Water__Pollu-
ti.Q.n Control Federation, Vol. 38, No. 1, January, 1966.
Reinhall, Rolf, and Vardheim, Steinar, Experience_with_the_DKP_jPressf
Appita 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.
301
-------
Shreve, Norris, Chemical Process^Industries, McGraw-Hill, New York,
1967.
Timpe, W. G., Lang, E., and Miller, R. L,, Kraft Pulging^Effluent
Treatment and Refuse - State-of-the-Art," Office of Research and
Monitoring, U. S. Environmental Protection Agency, Washington,
D. C., 1973.
Tre-cter, Vincent J., Jr., "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.
302
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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
orocess in which a mixture of waste water and activated sludge is
agirated 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.
~ 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.
~ 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.
- 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.
kttrition_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.
303
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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.
Bl.ue_Staini - 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 tr ea truer -
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.
~ 'rne removal of a portion of any process water to
maintain the constituents of the solution at desired levels.
BOD5 - 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 ccntaminants of a water sample under standard
laboratory conditions. The standard conditions include incubation
for five days at 20°C.
Bo3.t - A. short log cut to length suitable for peeling in a lathe.
Boultoni_zi.ng_ - A conditioning process in which unseasoned wood is
heated under a partial vacvium to reduce its moisture content prior
to injection of the preservative.
Q'l§§lG ~ 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 rest.s
during the pressing process.
CCA-_Ty_p_e __ P r e s er va t i v e - Any one of several inorganic salt formula-
tions based on salts cf copper, chromium, and arsenic.
Chij2£er - A machine which reduces to chips.
Clarif^ier - A unit of which the primary purpose is to reduce the
amount of suspended matter in a liquid.
CjLi££er - A machine which cuts veneer sheets to various sizes and
also may remove defects.
304
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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.
Coil ^Condensate - The condensate formed in steam lines and heating
coils.
Cold_Pres_sing - 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.
Q9Jl^iii.2Ili23 ~ Tne 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.
Core - Also referred to as the center. The innermost segment of a
plywood panel.
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.
j^y - To place the grain of the layers of veneer at right
angles in order to minimize swelling and shrinking.
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.
305
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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.
Quiterhead_Barker - See debarker.
- See retort.
Cylinder _ Condensate - Condensation that forms on the walls of th-
retort during steaming operations. Also, of process in which
unseasoned wood is subjected to exposure to an atmosphere of steam
to reduce its moisture content and improve its pereability.
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 curterhead
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.
D§f iberization - The reduction of wood materials to fibers.
D"lS2]il^ii2D ~ 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.
pisc_Pul£ers - 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.
Dr y- cli pping - Clipping of veneer which takes place after drying.
DrYgrs - 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.
306
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Dry- felting - See air-felting. Dry Process - 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.
End-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.
?
-------
Flotation - The raising of suspended matter to the surface of the
liquid in a tank as scum — by aeration, the evolution of gas,
chemicals, electrolysis, heat, or bacterial decomposition.
Formation __ (Forming) - 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 veneer sheets together in*.'.
plywood. There are three types most often used in the manufactu; ~
of plywood, depending on raw material and intended product usage.
They are 1) protein, 2) phenol formaldehyde, and 3) urea
formaldehyde. The first is extracted from plants and animals and
thermoplastic while the other two are synthetic and thermosetting.
§luie_Spreaders - Means cf applying glue to veneer, either by use of
power driven rollers or spray curtain-coater applicators.
Glue _Line - The part of the plywood production process where the
glue is applied to the veneer and the plywood layers assembled.
GPD - Gallons per day.
GPM - Gallons per minute.
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.
~ Unseasoned wood.
Hardboard - A compressed fiberboard of 0.80 to 1.20 g/cm3 (50 to 75
pounds per cubic foot) density. Alternative term: f ibrousf elted
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.
S§.SE£S[225 " The inner cere of a wood stem composed of nonliving
cells and usually differentiated from the outer enveloping layer
(sapwood) .
308
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Heat-treated Hardboard - Hardboard that has been subjected to
special heat treatment after hot-pressing to increase strength and
water resistance.
22i^ii3S_£o,QiI§ - see impoundment
Hot_Pressing - See pressing.
- The seasoning operation to which newly pressed
hardboard are subjected to prevent warpage due to excessive
dryness.
Hy_draulic_Barker - See debar ker,
~ 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.
Kil,n_DrYin.c[ - A method of preparing wood for treatment in which the
green stock is dried in a kiln under controlled conditions of
temperature and humidity.
Kjld-N - Kjeldahl Nitrogen - Total organic nitrogen plus ammonia of
a sample.
Lag.oon - A pond containing raw or partially treated waste water in
which aerobic or anaerobic stabilization occurs.
Leaching - Mass transfer of chemicals to water from wood which is
ir. contact with it.
ii29_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 __ - Milli grams per liter (equals parts per million, ppm, when
the specific gravity is 1.0).
Modi fie d 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.
309
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Non-Pressure __ Process _ - 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 (NH3) , mg/1, as N
Nitrogen^^gta^Kjel.dahl (NH3 and Organic N) ,
mg/1, as N
Nitro2en_ Nit rate (NO 3) , mg/1, as N
Total Phosphate, mg/1 as P
Qrtho Phosphate/ mg/1 as P
°ii::B£cJ2y.§£y. __ Sy.§tem ~ Equipment used to reclaim oil from waste
water.
Oily. _ Preservative - Pentachlorophenol-petroleum solutions ana
creosote in the various forms in which it is used.
Ogen __ Steaming - A method of steam conditioning in which the ste=»m
required is injected directly into the cylinder.
p£arl_Benson_lndex - A measure of color producing substances,
~ A chlorinated phenol with the formula Cl C 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.
£H - 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.
310
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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 an=5
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.
ce ~ A discrete source of pollution.
step in the production operation in which sheets are
subjected to pressure fcr 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.
~ A process in which wood preservatives and fire
retardants are forced into wood using air or hydrostatic pressure.
Radi.o __ 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.
5§sin - 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 debarker.
Rotary ^ lathing - See veneer cutting.
Roundwpod - 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.
311
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~ 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 s« v
segments along its periphery. The segment saw produce
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 wat^r
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, such as
water or waste water, during processing.
tSninS) ~ Hardboard, or other fiberboard or
particle board produced when a board is pressed from a dry mat to
give a smooth surface on both sides.
Softwood - Wood from evergreen or needle bearing trees.
~ A method of land disposal in which waste water is
sprayed on a prepared field. Also referred to as soil percolation.
~ 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.
Suspended Solids (SS) - The material removed from
a sample filtered through a standard glass fiber
filter. Then it is dried at 103-105°C.
Piss_olved_Sglid^ __ [DSJ^ - The difference between
the total and suspended solids.
Volatile_Solids__(VSJ_ - The material which is lost
when the sample is heated to 550°C.
312
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Settleable Solids - The material which
settles in an Immhoff cone in one hour.
SpraY_Eva_9oration - A method of waste water disposal in which water
is sprayed into the air to expedite evaporation.
SgraY^Irrigation_- A method of disposing of some organic waste
waters by spraying them on land, usually from pipes equipped wirh
spray nozzles.
- A conditioning method in which unseasoned wood
is subjected to an atmosphere of steam at 120°C (2<49°F) to reduce
its moisture content and improve its permeability preparatory to
preservative treatment.
Steaming^ - Treating wood material with steam to soften it.
_Sump_ - (1) A tank or pit that receives drainage and stores ir
temporarily, and from which the drainage is pumped or ejected, (2)
A tank or pit that, receives liquids.
Sy.nthetic_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.
TsL2i.H3_M§£^illS ~ 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._ConductiyitY - 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.
313
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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 suspencu i
matter in liquids. (3) An analytical quantity usually reported ir.
arbitrary turbidity units determined by measurements of light
diffraction.
Underflow - (wet decking) - water which runs off the logs.
y.acu.um_Water ~ Water extracted from wood during the vacuum period
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,
Sof twood__Veneeir 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.
314
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Veneer_Cutting ~ There are four basic methods:
(1) rotary lathing - cutting continuous strips
by the use of a sationary knife and a lathe.
(2) slicing - consists of a stationary knife and
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.
(U) 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") .
- 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.
Veneer 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 cooper,
chromium, and arsenic.
Water_Balance - The water gain (inflows) of a mill versus water
loss (outflows) .
Wet Barkers - see debarker.
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.
315
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Wood Extractives - A mixture of chemical compounds, primarily
organics, removed from vcood.
Wood_Preservatives - A chemical or mixture of chemicals with
fungistatic and insecticidal properties that is injected into wood
to protect it from biological deterioration.
316
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TABLE 71
METRIC UNITS
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS)
by
TO OBTAIN • (METRIC UNITS)
ENGLISH UNIT
acre
acre - feet
British Thermal
Unit
British Thermal
Uni t/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
million gallons/day
mile
pound/square inch
(gauge)
square feet
square inches
tons (short)
yard
ABBREVIATION
CONVERSION ABBREVIATION METRIC UNIT
ac
ac f t
BTU
BTU/lii
cf m
cf s
cu f t
cu f t
cu in
op
ft
gal
gpm
hp
in
in Hg
Ib
mgd
mi
psig
sq f t
sq in
ton
yd
0.405
1233.5
0.252
0.555
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
3, 785
1.609
(0.06805 psig 4-1)
0.0929
6.452
0.907
0.9144
ha
cu m
kg cal
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/ sec
kw
cm
a tm
kg
cu in/day
km
*atm
sq m
sq cm
kkg
m
hectares
cubic meters
kilogram-calories
kilogram calories/
kilogram
cubic meters/minute
cubic me t er s /tninu te
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
killowa 1 1 s
cent imet er s
atmospheres
kilograms
cubic meters/day
kilometer
a tmospher es
(absolute)
square meters
square centimeters
me trie tons
(1000 kilograms)
meters
* Actual conversion, not a multiplier
317
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