EPA-R2-73-164
FEBRUARY 1973 Environmental Protection Technology Series
Kraft Pulping Effluent Treatment
and Refuse-State of the Art
Office of Research and Monitoring
U.S. Environmental Protection Agency
Washington, D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
degradation from point and non-point sources of
pollution. This work provides the new or improved
technology required for the control and treatment
of pollution sources to meet environmental quality
standards.
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EPA-R2-73-164
February 1973
PAFT PULPING EFFLUENT TREATMENT AND REUSE - STATE OF THE ART
By
W. G. Timpe
E. Lang
R. L. Miller
Project 12040 EJU
Project Officer
George R. Webster
Office of Water Programs
Environmental Protection Agency
Washington, D.q. 20460
Prepared for
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
For sale by the Superintendent of I>ot(Mh6^," V''S, QOTfjrWMjnt Printing Office, Washington, D.C. 20402
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EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.
Approval does not signify that the contents necessarily
reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommenda-
tion for use.
ii
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ABSTRACT
This report presents a survey of the literature and other sources on
present practices and advanced methods of handling and treatment of
pulp and paper mill effluents, with particular emphasis on the kraft
process, and the use of activated carbon and lime treatment as advanced
methods of treatment. The survey was made as a first step of a devel-
opment program aimed at maximum water reuse in kraft pulp and paper
mills based on effluent treatment using activated carbon.
The results of the survey include information on activated carbon
and its applications in treatment of pulp and paper mill effluents
as well as in treatment of municipal water supplies and effluents.
Information is presented on lime treatment of kraft mill effluent
and on other advanced treatment methods. It also covers the subjects
of in-plant water reuse, effluent collection systems, solids removal,
and biological oxidation.
This report was submitted in partial fulfillment of Grant #12040 EJU
between the Environmental Protection Agency and St. Regis Paper
Company.
iii
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CONTENDS
Section
I CONCLUSIONS 1
Activated Carbon 1
Water Usage and Recycle 1
Present Effluent Treatment Methods 2
Advanced Treatment Methods (other than ketivatel carbon)2
II RECOMMENDATIONS 3
III INTRODUCTION 5
Program Overview 5
Objective and Scope of Survey 5
IV ACTIVATED CARBON 7
General Information 7
Adsorptive Properties 9
Adsorption Processes 14
i
Adsorption Applications 17
V IN-PLANT WATER REUSE IN PULP AND PAPER MILLS 33
Present Water Reuse Practices 33
Potential Reuse and Water Conservation Methods 40
VI EFFLUENT COLLECTION SYSTEMS 43
VII SOLIDS REMOVAL (PRIMARY CLARIFICATION) 45
Removal Requirements and Extent of Practice 45
Process Capabilities 45
Specific Processes and Presetit Applications 46
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CONTENTS (Continued)
Section Page
- '"' .- MI " '"
VIII BIOLOGICAL TREATMENT 53
Treatment Requirements and Extent of Practice 53
Process Capabilities 54
Specific Processes and Present Applications 55
IX PRECIPITATION, COAGULATION, LIME TREATMENT 63
Overview: Extent of Practice 63
Process Capabilities 64
Lime Treatment Development and Demonstration 67
X OTHER TREATMENT METHODS 77
Hyperfiltration (Reverse Osmosis) 77
Ion Exchange (Desal Process) 80
XI ACKNOWLEDGMENTS 83
XII REFERENCES 85
vi
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FIGURES
No. . Page
1 Pore Volume Distribution of Typical Activated
Carbons 11
2 Multiple Column System with Columns Arranged
in Series - 16
3 Divided Feed Application of Powdered Carbon 18
4 Conventional Activated Sludge System X 59
5 Massive Lime Process for Color Removal rQ 69
6 Line Treatment at Interstate Paper Corporation 71
7 Continental Can Company, Inc. - Color Removal
Process 73
8 Georgia-Pacific Color Removal Process 75
vii
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TABLES
No.
I Propertiesof Selected Activated Carbohs
II Activated Carbon Treatment of Water at Nitro, W. Va.
Ill South Tahoe Public Utility District - Overall
Plant Efficiency
IV Average Water Quality Characteristics - Pomona
Pilot Plant
V Results of Run No. 3 - Tucson Pilot Plant
VI Treatment of Primary Effluent by Powdered Carbon,
Lebanon, Ohio
VII Lime and Carbon Treatment of Kraft Mill Bleach
Plant Caustic Extract Effluent
VIII Renovated Water Analysis
IX Renovated Water Analysis
X Renovated Water Analysis
XI Renovated Water Analysis
XII Reuse of "Water in Kraft 6r Soda Mills
XIII Water Requirements In the Bleach Plant
XIV Clean Water Requirements for 340 in. Linerboard
Machine
XV Effectiveness of Stabilization Treatment
XVI Activated Sludge Treatment Data
XVII Summary of Results of Treatment by Reverse
Osmosis
XVIII Water Quality from "DESAL" Ion Exchange
Process
8
18
19
20
21
22
24
26
27
28
!
29
34
36
38
56
61
78
81
viii
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SECTION I
CONCLUSIONS
The following conclusions have been reached:
Activated Carbon
1. Activated carbon is being used commercially and/or tested
in large scale pilot plants for municipal water and effluent
treatment, as well as in diverse industrial applications.
2. Specific information and the extent of current development
activity by others encourages proceeding with the program to
develop the use of activated carbon for water renovation in
kraft pulp and paper mills. '
3. Activated carbon for pulp and paper mill effluent applica-
tion has been and is being studied on a laboratory and small
pilot plant basis by several investigators. Its application is
usually considered as a polishing step. Most of the work has
been with granular activated carbon which necessitates regenera-
tion. Most work is on caustic bleach plant effluent; some on
total effluents and on evaporator cdndensate. No work on
turpentine separator underflow has been reported in the
literature.
4. Carbon selection must be based, -it was confirmed, on specific
test work with actual waste water. Standard carbon characteri-
zation tests are useful only as guidelines, together with recom-
mendations based on experience, to narrow the number of carbons
to be specifically tested and compared for a given application.
A strong contributing factor in this situation appears to be the
incomplete characterization* of most solutions that are to be
treated.
v
Usage and Recycle
1. The pulp and paper industry uses 2,100 billion gallons of
water annually.
2. Reuse of water is extensively practiced in the industry. Re-
use practices consist mostly of in-plant reuse rather than total
mill effluent reuse.
3. In-plant reuse may involve treatments such as solids removal
or cooling, but generally does not involve removal of dissolved
organics.
4. In-plant reuse includes both in-process reuse (such as recycle
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of paper machine white water) and downgrading, process to pro-
cess reuse (such as use of bleach plant effluent in the woodyard).
5. Effluent flows range from 10,000 to about 60,000 gallons
per ton of unbleached kraft.
6. Effluent flows of 4,000 to 6,000 gallons per ton might be
achieved through improved design and increased in-plant reuse,
still without resorting to removal of dissolved organics.
7. One current study is aimed at total mill effluent treatment
and recycle using alum precipitation and biological oxidation.
Present Effluent Treatment Methods
1. Present treatment systems provide for the removal of sus-
pended solids and biologically oxidizable materials. Such
treatment does not remove color bodies from the effluent.
2. Effluent quality obtained by these conventional methods,
even if these methods were employed more fully within their
limits, is not acceptable for most kraft mill feed water require-
ments.
Advanced Treatment Methods (other than activated carbon)
1. Lime treatment (precipitation) is the most actively pursued
advanced treatment method. It is aimed at color removal before
biological oxidation and effluent discharge.
2. Other precipitation-coagulation methods have been investi-
gated, but only alum treatment is still being pursued with some
promise (see conclusion B,7).
3. Reverse osmosis is under active investigation in the sulfite
pulping industry for the concentration of wastes and production of
reusable water.
4. These advanced treatment methods, particularly the lime
treatment, deserve further consideration as part of a treatment
system involving activated carbon to produce reusable treated
effluent.
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SECTION II
RECOMMENDATIONS
Continuation of this program is recommended with the next major
step being a laboratory program to be outlined in detail. The
conclusions of the survey indicate that two approaches should be
pursued to lead to maximum water reuse, i.e. treatment of total mill
effluent and separate treatment of in-plant effluents to extend the
existing trend of in-plant recycle and reuse. The treatment of
total mill effluent and bleach plant effluents by carbon and various
combinations of carbon and biological oxidation and lime treatment
should be investigated, while for the other in-plant effluents,
carbon treatment alone should be investigated for removal of dis-
solved organics.
It is recommended that a broad range of commercial carbons be in-
vestigated since the adsorptive and physical characteristics of the
activated carbon to be produced by the St. Regis recovery process
are as yet unknown. It is recommended that this investigation then
be used to define the desired characteristics which the St. Regis
carbon should have.
It is recommended that effluents from several St. Regis southern
kraft mills be used in the laboratory investigation since effluents
are insufficiently characterized to date and are known to vary in
time and place.
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SECTION III
INTRODUCTION
Program Overview
Under a Federal Water Quality Administration (FWQA) contract,
St. Regis Paper Company has been engaged since July, 1969, in a
program for the development of an economical system for maximum
water reuse in the kraft pulp and paper industry as a means of water
pollution control and water conservation. This program is based on
two key concepts: (1) effluent treatment using activated carbon
and, (2) on-site production of activated carbon from readily avail-
able raw materials, particularly black liquor, with full integration
into the kraft mill recovery and power systems to achieve the lowest
net cost of activated carbon.
An earlier order-of-magnitude economic estimate for an unbleached
kraft pulp and paper mill indicated that effluent treatment and
reuse, based on activated carbon, produced at the mill, promises
to be competitive with treatment and discharge, based on the lime
treatment pioneered by the National Council for Air and Stream
Improvement (NCASI) (63). A premise of this comparison is that
effluents of less than lime-treated quality will become unacceptable
in the foreseeable future.
St. Regis Paper Company made application to the Federal Water Quality
Administration for a Research and Development Grant for this work
as provided in the "Clean Water Restoration Act of 1966".
St. Regis Paper Company on June 23, 1969, accepted an FWQA Research
and Development Grant (12040-EJU) of $878,472, representing an
average of 59% of eligible estimated project costs of $1,483,862.
Under the program, the two key concepts (i.e. of effluent treatment
with activated carbon, and of activated carbon production), are being
pursued in two separate but interdependent programs. Part I is the
program concerned with the development of effluent treatment with
activated carbon. A portion of this program is the subject of this
report. Part II is the program concerned with the production of
activated carbon. This will not be discussed further in this report.
Part I of this program was initiated in July, 1969, with a literature
and very limited industry survey. This survey was completed during
October, 1969 and forms the basis of this report.
Objective and Scope of Survey
This survey was primarily mission oriented. It was intended to
provide, and has provided, for the project team information necessary
or useful in formulating development strategy and determining labora-
tory procedures.
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It is unavoidable in such an effort that information not strictly
pertinent or necessary for the task at hand is included. The short
time allowed for completing the survey, on the other hand, makes it
likely that some pertinent literature has been overlooked, and that
a number of active developments have not been assessed. The "survey"
is therefore of necessity a continuing effort with the objective of
incorporating most up-to-date information in this development. How-
ever, only the initial survey is covered in this report.
The technical coverage included activated carbon, its properties,
methods of application, and utilization, particularly in effluent
treatment. It also included present and proposed paper industry
in-plant water reuse schemes; effluent treatment systems including
collection systems, solids removal, biological treatment, and coagula-
tion and precipitation treatment methods, particularly those involving
lime. To a very limited extent information was included on processes
of potential future interest but not covered in the preceeding cate-
gories, particularly hyperfiltration (reverse osmosis) and ion
exchange.
The literature survey included a search of Chemical Abstracts
V. 45, 1951 through V. 70, 1969; and Water Pollution Abstracts
V. 40, 1967, through V. 42, No. 3, March 1969. The following terms
were searched: Wastes, Water pollution, Water purification, Sulfite
liquor, Sewage, Paper, Pulp and paperboard waste liquors, Ion ex-
change for waste water, Water-potable and industrial. This search
did not include small water purification systems or specific loca-
tions. Emphasis was placed on those items pertaining to the pulp
and paper industry.
The literature survey also included perusal of the Bulletins pub-
lished by the National Council of the Paper Industry for Air and
Water Improvement (NCASI), FWQA reports, and a review of direct
access to pertinent recent technical publications and journals.
A very important part of the survey consisted of personal discussions
with representatives of manufacturers of activated carbon, with
technical personnel involved in the various pilot and commercial
applications of activated carbon in water and effluent treatment,
and with operating and engineering personnel in the paper industry.
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SECTION IV
ACTIVATED CARBON
General Information
1. Manufacture
Activated carbon can be prepared from any carbonaceous material,
but only a limited number of materials are used commercially.
Activation of carbon is accomplished by two general methods (93):
(1) High-temperature controlled oxidation of a previously
charred carbonaceous material.
(2) Lower temperature chemical activation of carbonaceous
raw material.
Most of the production in the United States utilizes the high-
temperature process, however, the chemical activation is favored
in Europe.
2. Types and Physical Properties
Activated carbon is manufactured either in a powdered or granular
form. The powdered form has generally been used for purifying
liquids whereas the granular form has been used for gas purifi-
cation. In recent years, there has been an increasing usage of
granular carbon for liquid purification.
Activated carbon is characterized by an extremely large surface
area (450-1800 sq.m/g) per unit weight. Pore volume and pore
volume distribution are characteristics that affect the use of
a carbon as an adsorbent.
3. Manufacturer's Information
Manufactures generally list several specifications for their
carbons. Common specifications are mesh size, iodine number,
molasses number, methylene blue number (these numbers are a
measure of the adsorptive capacity for these three compounds
under standardized test conditions), abrasion number, ash con-
tent, pH of water extract, and various density measurements.
The specifications given by a manufacturer can only be used as
a very rough guide to carbon selection for a particular applica-
tion. The results of one study show that competent and justifiable
selection can only be achieved by evaluating the carbon on the
particular effluent under consideration (10).
TABLE I lists information on several commercially available
activated carbons.
4. Laboratory Evaluation
Laboratory evaluations of the adsorptive capacity of activated
carbon are generally based on the empirical Freundlich equation
which relates the amount of impurity in the solution phase to the
impurity in the adsorbed phase. The Freundlich equation is as follows:
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TABLE I
Properties of Selected Activated Carbons
oo
Carbon
Aqua Nuchar
(a)
Nuchar C-190
(a)
Bar co S-51
(b)
Darco KB
(b)
Barneby Cheney SC
Norit Poly-C
(c)
Norit A
(c)
Norit F
(c)
Norit SG
(c)
Filtrasorb 100
(d)
Filtrasorb 300
(d)
Filtrasorb 400
(d)
Principal Application
Water Treatment
Chemical Purification,
Sugar Decolorization
Chemical Purification,
Sugar Decolorization
Vegetable Oil Decolor-
ization and Purification
Water Treatment,
Decolorization
Water Treatment
Vegetable Oil Chemical,
Water Purification
Vegetable Oil Chemical,
Water Purification
Vegetable Oil Chemical,
Water Purification
Water Treatment
Municipal Effluent
Municipal Effluent
Base Material
Black Liquor
Black Liquor
Lignite
Wood
Nut Shell
Wood
Wood or Peat
Wood or Peat
Wood or Peat
Coal
Coal
Coal
Stan-
dard
Form6
Powd.
Powd.
Powd.
Powd.
Gran.
Powd.
Powd.
Powd.
Powd.
Gran.
Gran.
Gran.
Pore Mean Nitrogen Iodine
Volume; Pore Size, Areaf> Number
cc/g A° m2/g
0.4 to 20 754 703
0.6
0.9 30 700-900 1071
1.0 30 700 1159
2.2 26 1200 1200
_
1.1 - 400 -
0.5 35 750
0.4 - 640
750
800-900 800
0.8 25 950-1050 900
0.9 35 1000-1100 1000
Moisture^
%
5
3
12
33
5
10
10
10
12
2
2
2
Price in
Car Loadg
Lot, $/lb
0.085
0.14
0.135
0.29
0.32
0.24
0.17
0.115
0.26
_
-
0.29
a) Chemical Div., Westvaco b) Atlas Chemical Ind. c) American Norit Co. d) Calgon Corp. e) Powdered carbons are 907,
minus 325 mesh except S-51 (70%) and KB (50%) f) Dry basis g) "As is" basis.
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/ ,
x/m = kc
where; x = amount of impurity adsorbed
m = weight of carbon
x/m = concentration of impurity in adsorbed
state
c = concentration of impurity in solution at
equilibrium with impurity in adsorbed
state
k,n = constants
A plot of x/m versus c on log-log graph paper yields a
straight line from which the theoretical ultimate capacity of
the carbon may be obtained by extrapolation. A complete descrip-
tion of techniquies used to establish adsorption isotherms is
presented by a number of authors (91, 44, 16).
Adsorptive Properties
1. Surface Area
Adsorption is usually explained in terms of the surface tension
(or energy per unit area) of the solid (15). Molecules in the
interior of any solid are subjected to balanced forces, whereas
surface molecules are subjected to unbalanced forces toward the
interior. The inward forces can only be satisfied if other
molecules, usually liquid or gaseous, become attached on the
surface of the solid. The forces of attraction, or Van der Waal's
forces, are relatively weak, and adsorption due to these forces
is called physical adsorption because the adsorbed species is
easily removed from the adsorbent. A stronger, irreversible type
of adsorption can occur as the result of chemical interaction
between the adsorbate and the adsorbent. Adsorption due to
chemical interaction is called chemisorption. Both physical
and chemisorption are included in the general term sorption.
Although there is presently no method of measuring the surface
tension of a solid directly, it is known that the total sur-
face energy is equal to the product of the surface tension and
the total area. For this reason, high surface area is a pre-
requisite for good adsorption. As mentioned previously,
activated carbons have surface areas ranging from 450 to 1800
sq.m/g.
It is known that activated carbon is effective for removal of
organic substances of relatively low water solubility, pri-
marily because of the large interfacial area on which such
substances may accumulate (97). It is apparent, however, that
an explanation of the adsorptive capacity of activated carbon
based entirely on surface area is far from complete. Equal
9
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weights of two active carbons which have equal surface area,
but have been prepared from different raw materials and/or
by different processes may function quite differently as
adsorbents.
Two phenomena have been presented to account for this dif-
ference in adsorptive ability of carbons having equal surface
area. Part of the explanation is based on relative pore size
distribution while another part of the explanation is based on
the surface chemistry of the carbon.
2. Pore Size Distribution
As shown in Figure 1, gas-phase carbons and liquid phase or
decolorizing carbons exhibit different pore size distributions.
Gas-phase carbons show pore-volume peaks in the microporous
range (3 to 50 A radius) and in the macroporous (1000 to 50,000
8 radius) range, whereas decolorizing carbons exhibit peaks in
these ranges as well as in a transitional (50 to 1000 A radius)
pore range (93). A large amount of transitional pore volume
gives an open structure favorable to access by solutions or
liquids, resulting in rapid attainment of adsorption equilibrium
for smaller adsorbates. The accessibility to larger molecules
and colloidal substances is also improved by pores in this
range. The significant difference in pore volumes associated
with activated carbon made from different raw materials by
different processes is the magnitude of the pore volume con-
centration in the various pore size ranges.
3. Surface Functionality
The nature of the carbon surface is another property that
affects the adsorption capacity. Activated carbon is not an
inert material; it exhibits acid-base properties and it can
undergo several chemical reactions such as halogenation, oxida-
tion, and hydrogenation (93). Several authors have discussed
the surface nature of activated carbon and the effect of
certain functional groups on the sorptive power exhibited by a
carbon (97, 27).
Snoeyink and Weber (97) presented a discussion on the surface
chemistry of activated carbon and how the various functional
groups associated with carbon surfaces can affect adsorption
capabilities. The nature of these functional groups is deter-
mined to a large extent by the method of activation as well as
by the starting raw material. Two major types of surfaces
were postulated for activated carbons: (1) uniform planar
surfaces and (2) heterogeneous edges of planes characterized
by various types of functional groups and vacancies due to
the action of oxidizing gases. Most of the surface area of a
carbon particle is in the micropores and is of the uniform
planar type. Most of the adsorption occurring on this type sur-
10
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1.6
1.4
1.2
e>
1.0
h^H
s
OT
M
i"""*
£
0.8
0.6
CO
0.4
0.2
0.0
GAS CARBON
DECOLORIZING CARBON
I
10 100 1,000 10,000 100,000
r = PORE RADIUS IN ANGSTROMS
Figure 1
Pore Volume Distribution of Typical Activated Carbons (93)
11
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face is due to relatively weak Van der Waals forces. Sorption
processes at the heterogeneous edges of planes are chemical
in nature resulting from electron-sharing reactions.
One of the major noncarbon constituents of activated carbon
is oxygen which may be 2 to 25 percent by weight depending
upon the temperature and method of activation. Oxygen complexes
on the surface of activated carbon have a definite effect on
the sorptive capabilities because their presence increases the
polarity of the surface. Thus, activated carbon having oxygen
on the surface has more affinity for polar adsorbates. Also,
sorbates that have a natural tendency to combine with oxygen
probably sorb more easily on oxygenated surfaces than they do
on nonoxygenated surfaces.
4. Inorganic Impurities
Most commercial carbons contain a significant amount of inorganic
material. It has been suggested (97) that due to the fact that
strong acid removes almost all the ash content of activated carbon,
the inorganic matter exists primarily on the surfaces of the
microcrystallite carbon structure. The presence of inorganic
species on the surface would very likely affect the sorption
capability of a carbon. Possible interactions between the
inorganic salts on the active carbon surface and the sorbate
or other solution components include complex formation, ion-
pair formation, precipitation reactions, and oxidation-reduction
reactions (97).
5. Adsorbate Effects
The nature of the adsorbate also affects the ability of an
activated carbon to adsorb that species from solution. General-
ly, activated carbon is not effective for the adsorption of
inorganic electrolytes from solutions, however, there are
some notable exceptions to this generalization (91). Mercuric
chloride, molybdate, silver salts, gold chloride,
ferric salts, and iodine are examples of inorganic species
which are removed from solution by activated carbon(88). It
is pointed out that certain inorganic compounds such as silver
salts and potassium permanganate are reduced by the carbon to
metallic silver and manganese dioxide, respectively, which
precipitate and are removed by filtration (91). Chlorine is
also adsorbed by activated carbon although the removal of
chlorine from aqueous solution is a combination of catalytic
decomposition and adsorption by the activated carbon. Activated
carbon treatment usually precedes chlorinat^ion in water treat-
ment plants because of its ability to remove chlorine from
water and because it will remove some of the chlorine-consuming
organics.
As a general class, organic compounds are adsorbable. The
12
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higher molecular weight organic compounds are generally more
amenable to adsorption than are low molecular weight com-
pounds. Colloidal organic compounds are riot readily adsorbed
because these compounds cannot penetrate the pores of the
activated carbon particle (10). Strongly hydrophilic (polar)
organic compounds such as carbohydrates or other highly-
oxygenated organic material are generally refractory to carbon
treatment. Sugars and low-molecular weight glycols, amino
acids, hydroxy acids, sulfates, and sulfonates are all very
water soluble and poorly adsorbable on carbon (10). Molecular
configuration also influences the ability of carbon to adsorb
organic molecules and in some cases steric hindrance would
prevent the molecule from entering a pore.
6. Temperature Effect on Equilibrium and Rate
The effect of temperature on adsorption, especially from
liquid solutions, is not easily predicted. Since adosrption
is a thermodynamically exothermic process, increasing the
temperature should decrease adsorption capacity (46). Although
gas-solid systems usually adhere to the predicted behavior,
many solid-liquid systems appear to contradict the predicted
effect of temperature. Substances, such as an aqueous solution
of n-butyl alcohol, that have a negative solubility coefficient
will not be as soluble at higher temperatures and adsorption
will thus be increased. Euchs (46) found that increased tempera-
ture increased the adsorption of color from pulp mill bleach
plant caustic extract on activated carbon. He explained this phe-
nomenon by decreased liquid surface tension at higher temperatures.
The decreased surface tension at higher temperature results in
increased "wetting" or penetration of the liquid into the pores
of the carbon.
The rate of adsorption is also affected by temperature changes.
Investigations by Morris and Weber (77) and by Weber (104) on
the kinetics of adsorption on granular carbon in rapidly stirred
batch systems indicate that the rate of adsorption is controlled
by the rate of diffusion of solutes in the internal capillary
pores of the carbon particles. Assuming that the rate of
adsorption is in fact controlled by the rate of diffusion of
solute particles into carbon capillaries, the effect of tempera-
ture can be shown by the following equation (46):
DAB o< KT/^B
Where; ^AB = Diffusivity of solute A thru solvent B
K = Constant, dependent upon solvent and solute
T = Absolute temperature
/*B = Viscosity of solvent
13
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Thus it is seen that rate of diffusion and, in turn, the rate
of adsorption increases with increasing temperature. The
advantage of increased adsorption rates with increasing tem-
perature can be utilized in laboratory evaluation of adsorption
isotherms. Smith (96) has suggested maintaining solution tem-
peratures (Kraft effluents) near the boiling point for laboratory
isotherm determinations. Using finely ground carbon samples
and high temperatures, equilibrium will be established in two
to three minutes, but there will be little effect on the
equilibrium itself.
7. Effect of Particle Size
Since the controlling factor on the rate of adsorption usually
is the rate of internal diffusion, it would be expected that
adsorption rates would increase with decreasing particle size.
Morris and Weber (77) have experimentally shown that the rate
of adsorption is inversely proportional to the diameter squared.
In laboratory evaluation of granular activated carbon it is
recommended to pulverize the carbon so that 95 to 100% passes
through a 325 mesh screen (16,61). This will eliminate the
variable of particle diameter on adsorption rate studies,
although the equilibrium capacity will be affected slightly.
Pulverizing the carbon will increase the equilibrium capacity
to a small extent because of increased external area and be-
cause previously "blind" pores will become available as adsorp-
tion sites. The effect is quite small because the majority
of the adsorptive capacity is due to internal surface area.
8. Effect of pH
, TT *
The pn of the solution being treated may profoundly affect the
adsorption of solutes. One report (78) says that adsorption is
best when the water is slightly acid or neutral, although
carbon is effective up to pH 9.0. Helbig (60) emphasizes that
the statement "that carbons adsorb more effectively in acid
solutions than in alkaline solutions" should not be used as a
criterion without qualification. The principal effect of pH on
carbon adsorption is probably indirect, due to its influence on
solubility of the adsorbate. Generally, maximum adsorbability
occurs at minimum solubility, a phenomenon which frequently
occurs in the alkaline pH range as it does, for example, with
alkaloids. Increased adsorption of color from pulp and paper
mill caustic extract occurs at decreased pH levels (46). This
is probably accounted for by the decreased solubility of lignin
at lower pH values as evidenced by its precipitation at a pH
of two.
Adsorption Processes
In the next few paragraphs a brief description of the basic
mechanics of utilizing granular and powdered activated carbon
will be given.
14
-------
1. Granular Carbon
Granular carbon is usually used in a vertical cylindrical
column (43). There are two basic types of column systems,
namely, the fixed bed and the moving bed systems. Fixed
bed columns may be used singly or as multiple column systems
arranged either in parallel or in series. Moving bed systems
may be of the continuous or the pulsed bed type.
The simplest arrangement is the single fixed bed column.
Fornwalt and Hutchins (45) indicate that a single-column system
is preferentially used in the following situations:
(1) The breakthrough curve of the carbon is steep.
(2) The carbon charge will last so long at the desired
processing rate that the cost of replacing or regenerating
it becomes a minor part of operating expense.
(3) The capital cost of a second or third column cannot
be justified because carbon savings will not pay for
additional equipment.
(4) For some reason (such as prevention of crystallization
or product deterioration) an unusual temperature, pressure,
or other controlling condition must be maintained in the
column.
Multiple-column systems are used in cases where the process
cannot be interrupted for unloading, reloading, or regeneration,
and a standby column is not available; or if the available space
limits the size or height of the column (45).
Figure 2 is a simple schematic of multiple columns arranged
in series. Series-column systems are used if: (1) the break
through curve is gradual and a highly purified effluent is
desired or (2) it is economically necessary to completely
exhaust each pound of carbon because of a gradual breakthrough
curve and a high carbon requirement per unit of production (45).
These units are operated downflow and each carbon bed is replaced
as a complete batch. As shown in the schematic the effluent
from one column becomes the influent of the next column. An
extra column is required. When breakthrough occurs (some
controlling parameter such as BOD, color, COD, etc. exceeds the
desired value in the purified liquid) the lead column is taken
out of the system and the unused bed becomes the last column.
The carbon in the first column is regenerated and the next time
breakthrough occurs the second column is taken out of service
and the first column containing regenerated carbon is placed
in the series as the last column. In this manner the carbon
beds are used countercurrent to the waste flow so that the
liquid having the lowest level of contaminants is contacted
with the freshest carbon.
15
-------
PURIFIED
LIQUID
Figure 2
Multiple Column System with Columns Arranged in Series
Another multiple column system is the arrangement of
the columns in parallel and the utilization of either upflow
or downflow through the columns. When a high degree of organic
removal is not necessary, this arrangement can be used (70).
The columns are placed into operation at evenly spaced intervals,
thus when one column is nearing exhaustion another is being
started up on freshly-regenerated carbon and the other columns
are at various intermediate stages of exhaustion. Since the
columns discharge into a common manifold, the blended material
from the columns will meet specifications if they are designed
properly. This system requires smaller pumps, less power, and
less stringent pressure requirements for columns and piping
than columns operated in series (45).
Methods of designing granular carbon columns for treating
municipal wastewater were described by Allen (1). Moving bed
systems have a number of advantages over fixed bed series
systems. In the moving bed system the liquid flow is upward,
and fresh carbon is added to the top of the column as spent
carbon is withdrawn from the bottom (45). Thus, the flow of
carbon is countercurrent to the flow of water which provides
a high loading of impurities on the carbon. Also, plugging
of the bed is avoided by the upflow of water (57). The utili-
zation of moving beds is of principal importance in larger
units where the lower capital investment, compared with columns
in series, is of importance. With the possible exception of
instrumentation costs, this system comes the closest to com-
pletely exhausting the carbon with the minimum capital invest-
ment (45).
16
-------
2. Powdered Carbon
Powdered activated carbon is used to treat liquids by the
layer filtration method, batch contact system, multistage
countercurrent flow system, or the divided flow system (43).
Layer filtration involves making a slurry of powdered carbon
in a suitable liquid. A precoat carbon filter cake is then
formed on the filter cloth of a filter and the liquid to be
treated is allowed to flow through the precoat.
In the batch contact system, carbon is added to a tank of
liquid, the contents are agitated, and the carbon is removed
by filtration.
To reduce the amount of powdered carbon needed, multistage
countercurrent and divided flow systems are used. In the
multistage countercurrent system the carbon is used more
than once. For example, in a two stage countercurrent system
two sets of carbon contact tanks and two sets of filters are
used. In the first tank, untreated liquid is mixed with carbon
that has already been used in the second tank. In the second
tank, the partially-purified liquid is contacted with fresh
carbon. This process is best for a product that is made con-
tinuously.
For liquids that have to be treated only intermittently,
countercurrent treatment is not feasible because it is impracti-
cal to store partially-spent carbon. In this system, as shown
in Figure 3, the solution is purified in two stages, using
fresh carbon at each stage.
Adsorption Applications
1. Water Treatment
Hager (55) has described the use of granular activated carbon
for water treatment at Nitro, West Virginia. The water treat-
ment plant treats water from a river heavily polluted with
various organic and industrial wastes and before the use of
activated carbon the odor and carbon-chloroform extracts (CCE)
of the treated water frequently exceeded recommended levels.
Using 14x40 mesh granular carbon beds as combination filter-
adsorption units, an average of 8 mgd of water are treated.
Treatment ahead of the carbon beds consists of double aeration
to remove volatile components, after which the water enters a
24-hour sedimentation basin where alum is added as a coagulant
and chlorine is added as a disinfectant. After coagulated
impurities have settled out, the water is passed through the
carbon beds. Table II depicts the reported capability of the
carbon. On-site regeneration of the spent carbon is accomplished
in a multihearth furnace.
17
-------
UNTREATED
LIQUID FRESH CARBON
ONCE TREATED
LIQUID
FRESH CARBON
I 1
MIX TANK
a
!
i
*-
LIQUID-CARBON
MIXTURE
mammmm
.. I
MIX TANK
|
1 __
TREATED
LIQUID -CARBON LIQUID
MIXTURE 1
FILTER
FILTER
Figure 3
Divided Feed Application of Powdered Carbon
Table II
Activated Carbon Treatment of Water at Nitre, W. Va.
Test
Parameter
Threshold Odor No.
Turbidity (Jackson
units)
Carbon-Chloroform
Extract Value (ppb)
Raw Applied to Recommended Finished
Water Filters Standards Water
66-333 30-50
5-15
200
200
0-3
0.05
50
18
-------
In the last few years that has been intense interest in the
use of activated carbon to treat municipal and industrial
wastewater. Although there are some plant-scale installations,
most of the investigations have been pilot-scale or laboratory
evaluations.
2. Municipal Effluents
One commercial installation for the treatment of municipal
waste by activated carbon is operated by the South Tahoe Public
Utility District in California (29,28). Effluent from a con-
ventional activated sludge process is coagulated with alum and
filtered through mixed-media filters in series. Effluent from
the filters is then passed through two upflow, countercurrent
granular activated columns in parallel Table III depicts the
effectiveness of the plant in removing impurities. The final
effluent was colorless, odorless, and had a turbidity of less
than 0.5 Jackson Units. The granular carbon beds reduced the
Table III
South Tahoe Public Utility District - Overall Plant Efficiency (29)
Test
Parameter
B.O.D., mg/1
C.O.D., mg/1
Total Organic
Carbon, mg/1
Suspended Solids
mg/1
Turbidity, units
Phosphates, mg/1
A.B.S., mg/1
Coliform Bacteria,
MPN/100 ml
Color, units
Odor
Raw Activated Effluent
Waste Sludge Effluent from Filters
200-400
400-600
-
160-350
50-150
15-35
2-4
ISxlO6
High
Odor
20-40
80-160
-
5-20
30-70
25-30
1.1-2.9
ISxlO4
High
Odor
1
30-60
10-18
0.2-3.0
0.2-3.0
0.1-1.0
1.1-2.9
15
10-30
Odor
Chlorinated
Carbon Column
Effluent
1
3-16
1-6
0.5
0.5
0.1-1.0
0.002-0.5
2.2
5
Odorless
19
-------
C.O.D. from the 30 to 60 mg/1 range to the 3 to 16 mg/1 range.
The influent to the carbon column had a total organic carbon (TOG)
content of 10 to 18 mg/1 while the effluent from the carbon
treatment contained 1 to 6 mg/1 TOG. The treatment facilities
also prividefor carbon regeneration in a multiple hearth furnace.
An 0.3 mgd granular activated carbon pilot plant at Pomona,
California has been in operation since 1965 under the direction
of the Federal Water Pollution Control Administration and the
Los Angeles County Sanitation District. The plant uses a four-
stage, packed-bed, downflow, granular activated carbon column
to treat effluent (primarily domestic) from a contact stabiliza-
tion activated sludge treatment (35). The spent carbon is re-
activated in a multihearth furnace. Table IV lists the average
water quality characteristics obtained in more than a year of
operation.
Table IV
Average Water Quality Characteristics - Pomona Pilot Plant (35)
(June ,
Parameter
Suspended Solids, mg/1
C.O.D., mg/1
Dissolved C.O.D.,mg/l
T.O.C., mg/1
Nitrate, as N, mg/1
Turbidity, JTU
Color
Threshold Odor
1965 - August, 1966)
Column Influent
10
47
31
13
6.7
10.3
30
12
Column Effluent
1
9.5
7
2.5
3.7
1.6
3
1
It was observed that dissolved oxygen decreased and carbon
dioxide increased as the effluent passes through the carbon
columns. These observations, plus the fact that the average
nitrate-nitrogen decreased, led investigators to believe that
the column performance was being enhanced by biological activity,
Further tests, using small carbon columns showed that activated
carbon columns can be used to reduce the nitrate in highly
nitrified effluents to less than 10 mg/1. It was found that
supplemental organics would have to be fed to the column to
20
-------
achieve more than the 3 mg/1 that is removed routinely. Methanol
in amounts equivalent to 20 and 40 mg/1 of COD was fed to a small
column receiving -25 mg/1 of nitrate (as nitrogen) for extended
periods. This increased the nitrate removal up to 15 mg/1 (as
nitrogen). '.
Joyce, et al., performed laboratory and pilot scale evaluations
of the use of granular activated carbon to treat secondary
effluent from the activated sludge treatment system at the
Pleasant Hills Treatment Plant in suburban Pittsburgh (2). They
judged the effectiveness of the system by the degree of COD and
ABS removal. The secondary effluent was pretreated by passage
through a sand filter, and downflow columns in series were used
for the carbon treatment. The COD content was reduced from the
50 to 70 mg/1 range to the 12 to 20 mg/1 range under a variety
of operating conditions. Refractory organics such as ABS were
eliminated completely.
Beebe and Stevens (4) investigated the use of powdered activated
carbon in a pilot plant operated at 7 to 9 gallons per minute.
The trials, conducted on activated sludge effluent from the
Tucson Municipal Sewage Treatment Plant, used an Accelator
(trademark of Infilco) recirculating slurry contact treatment
unit having a nominal treatment capacity of five gallons per
minute. To prevent excessive carryover of carbon it was found
necessary to coagulate the carbon particles. A dosage of 15 mg/1
of ferric sulfate and 0.5 mg/1 of cationic polyelectrolyte were
applied to the primary mixing zone and to the coagulating zone
respectively. The effluent from the Accelator was filtered
through sand filters. The following table shows the capability
of the process during a run using a carbon dosage of 138 mg/1.
Effluent from the sand filter was chlorinated and analyzed with
respect to the Public Health Service's 25 physical and chemical
drinking water standards. The product water quality met or ex-
ceeded 23 of 25 drinking water standards.
Table V
Results of Run No. 3 - Tucson Pilot Plant (4)
Test
Parameter
Color, units
C.O.D., mg/1
A.B.S., mg/1
Influent to
Carbon Unit
s
inits 17.6
; 15.7
36
4.2
Effluent from
Sand Filter
1
3.6
14
0.25
21
-------
A ten gallon per minute pilot plant using powdered activated car-
bon is being operated by FWPCA personnel at the Lebanon, Ohio
Municipal Sewage Treatment Plant (70). The powdered carbon
adsorption pilot plant uses two stage countercurrent adsorption
with three tanks per stage (102). The first tank is an agitated
contact tank providing two to seven minutes retention time for
the influent from an activated sludge treatment system. Poly-
electrolyte is added at a dosage of 1 to 3 mg/1 to the effluent
in the pipeline between the first and second tanks. The second
tank is a flocculation tank providing 15 minutes retention time.
The third tank is a sedimentation tank.
Carbon dosages ranged from 100 to 300 mg/1 and a secondary
effluent concentration of 15 ppm total organic carbon was re-
duced to 1.5 ppm. If a primary effluent was used, secondary-
treated quality water was obtained. Table VI presents a summary
of results from several trials of treating primary effluent with
powdered activated carbon (70).
Table VI
Treatment of Primary Effluent by Powdered Carbon,
Lebanon, Ohio (70).
Carbon, Flow, Polymer, mg/1
Run mg/1 gpm 1st Stage 2nd Stage mg/1
Primary Powdered Carbon
Effluent Effluent Filter
T.O.C..Turbid. T.O.C.,Turbid. Run
3
5
6
7
9
200
200
200
200
300
5
5
5
5
5
1.0
1.0
1.5
1.5
1.5
JTU
1.5 69.0 41.7
1.5 41.7 23.4
1.5 46.3 28.5
1.5 48.4 30.5
3.0 67.1 45.0
mg/1
10.2
3.7
4.1
6.7
11.0
JTU
3.3
1.0
2.2
2.9
1.2
Hr.
27
22
29
22
24
In a study of treating municipal waste water with powdered activated
carbon (42), it was found that surface area in pores greater than
14$ in radius gave the best correlation with TOG adsorption capacity
of several commercial carbons. It was concluded that for absorbing
organics from municipal waste water, the carbon should have a broad
spectrum of pore sizes.
A plant designed to treat 10 mgd of municipal waste water at
Rocky River, Ohio, by granular activated carbon following primary
22
-------
clarification has been described (17). This design uses eight
down-flow single-stage columns operated in parallel, each 16 ft.
in diameter and 25 ft. high to reduce BOD by 85%.
3. Pulp and Paper Applications
Several investigators have evaluated the capabilities of activated
carbon in treating various pulp and paper mill effluents. These
investigations have been on a laboratory and small pilot-scale
basis. No commercial applications have been reported.
Hunt (65) investigated nine different activated carbons for
decolorizing a 50/50 mixture of acid and caustic semi-chemical
bleaching wastes. Adsorptive capacities (in terms of volume of
liquid treated per unit weight of carbon) at 100% decolorization
ranged from 180 to 288 ml/g.
Investigations of color removal from a 50/50 mixture of acid and
caustic semi-chemical bleaching wastes by powdered and granular
activated carbon, activated alumina, and mixtures of these absorbents
has also been reported (110). Both powdered and granular activated
carbons were observed to be more effective than powdered and granular
activated alumina. Mixtures of the adsorbents were no more effective
than if the two had been used separately.
Fuchs (46) studied the effects of Ph and temperature on the adsorption
of color from kraft caustic stage effluent, lime process effluent,
chlorination stage effluent, and various combinations of chlorination,
caustic, and hypochlorite stage effluents. He found that the adsorp-
tion of color from bleaching effluents is increased by decreasing pH
and increasing temperature. The pH exerts the greatest effect on
equilibrium, whereas the greatest effect of temperature is on the
rate of adsorption.
McGlasson (72) also studied the treatment of various pulp and paper
mill effluents with activated carbon. For comparative purposes, he
treated kraft mill caustic bleach effluent with 15 g/1 of lime as
specified by Herbert (63) and with 10 g/1 of pulverized activated
carbon. Removal of color was comparable for lime treatment (95%)
and activated carbon (90%). The lime treatment resulted in 45.5%
removal of COD and 39% removal of BOD, whereas the carbon removed
almost 80% of the COD and over 60% of the BOD. Table VII summarizes
the results that were obtained (72).
23
-------
to
Table VII
Lime and Carbon Treatment of Kraft Mill Bleach Plant
Caustic Extract Effluent (72)
Treatment
of
sample
15 g/1 lime
10 g/1 carbon
Before
trtmt .
9 , 750
9,750
Color
After
trtmt.
500
1,250
% Re-
moved
95
87
Before
trtmt .
1,603
1,603
C.O.D.
After
trtmt .
875
348
7o Re-
moved
45
78
Before
trtmt.
260
230
B.O.D.
After
trtmt.
159
91
% Re-
moved
39
60
-------
McGlasson also treated the caustic extract using lime and carbon
treatment in series. The lime treatment was used ahead of the
carbon treatment to remove the bulk of the color, and the carbon
was used as a polishing agent. Using this treatment sequence,
99% of the color was removed as was 88% of the COD and 83% of the
BOD. Studies reported by Smith and Berger (8) using a similar
treatment sequence substantiated the reported capability of this
scheme for removing BOD and color.
McGlasson also compared the capabilities of powdered and granular
activated carbons in treating kraft mill total effluent. He
found that a 10 g/1 application of powdered carbon resulted in
98% color removal and 82% COD removal.
Lueck (68) has issued several reports on the use of granular
activated carbon for treatment of sulfite condensate wastes.
He reported that activated carbon adsorbed volatile organic
acids and high percentages of the COD - causing materials
quite efficiently.
Hansen and Burgess (12) evaluated the capability of granular
activated carbon to treat kraft condensate wastes. Using two
grades of granular carbon, they first pulverized and graded
the carbons to a uniform size by washing through a 325 mesh sieve.
The pulverized samples were then used for establishing batch-
type isotherms on a condensate having an initial COD, BOD, and
TOC of 910, 440, and 185 mg/1 respectively. A dosage of about
2 g/1 of carbon removed a little more than 60% of the COD and
slightly less than 70% of the BOD and TOC. Extrapolation of
Frendlich isotherms showed that the ultimate capacity of one
carbon for COD should be 1.35 mg. COD/mg. carbon while the cap-
acity of the second carbon should be 2.1 mg COD/mg. carbon.
Column studies showed the capacities of the two carbons in the
granular form were 0.7 and 0.96 mg. COD/mg. carbon.
Thibodeaux and Berger (9) have made pilot scale investigations of
renovation of pulp and paper mill effluent in which activated
carbon adsorption is one of the processes used in the treatment
Sequence. They performed trials on total mill effluents from an
unbleached kraft linerboard mill and a bleached kraft mill, and
on a bleached kraft mill caustic extract. The clarified effluents
were subjected to lime treatment followed by biological oxidation
and then adsorption by activated carbbn in granular carbon columns,
Tables VIII through XI summarize the conditions of each trial as
well as the results (9).
The results shown in Tables VIII through XI indicate that the
combined process of massive lime treatment, biological treatment,
and activated carbon treatment is feasible on a pilot scale. The
water produced by this scheme is practically free of all color,
25
-------
NJ
Table VIII
Renovated Water Analysis (9)
nb leached Kraft
lot Plant Run No
Desired Range
5-25
0-80
6.5-7.7
5-200
50-500
10-150
0-12
0-5
_
Linerboard Total
. 1 50 Gallon
Effluent
-
4800
8.7
107
3380
110
-
818
1400
Mill Effluent
Batch
Lime(
-
140
11.5
7.1
2510
140
-
460
1130
Operation
Obtained by
ka) ^k-J
65
200
9.1
86
2650
36
201
8
1600 (d)
Treatment
Carbon (c)
10
10
8.7
61
2500
36
1
2
1400
Constituent
Turbidity, ppm
Color, units
PH
Hardness, ppm CaCOo
Dissolved solids, ppm
Chloride, ppm
COD , ppm
BOD , ppm
Na , ppm
Notes: (a) 8.40 Ibs, reburned lime slaked and added to raw effluent (equivalent to
20,000 ppm Ca(OH)2).
(b) Extended aeration for 10 days. One gallon fertile lake water added as seed
material. NH^OH, HN03 and H?0 added as nutrient. ISO added to Neutralize.
(c) Carbon columns containing 12x40 mesh activated carbon furnished by Pittsburgh
Carbon. Contact time in the carbon bed was 8.2 minutes.
(d) Possible Ntfy interference.
-------
Table IX
Renovated Water Analysis (9)
Unbleached Kraft Linerboard Total Mill Effluent
Pilot Plant Run No. 2 50 Gallon Batch Operation
Constituent
Desired Range
5-25
0-80
6.5-7.7
5-200
Turbidity, ppm
Color, units
PH
Hardness, ppm CaC03
Dissolved Solids, ppm 50-500
Chloride, ppm 10-150
COD, ppm 0-12
B.O.D., ppm 0-5
Na, ppm
Effluent
3000
7.5
4190
160
Obtained by Treatment
Lime
(a)
Bio
(b)
Carbon
(c)
100
12.1
964
2610
200
200
8.2
1000
3070
130
15
8.5
866
2800
130
1430
320
740
230
(135)^'
230
(80)
230
(d)
Notes: (a) 2.87 Ibs. reburhed lime slaked and added to raw effluent (equivalent to 7500 ppm
Ca (OH)2).
(b) Extended aeration for 8 days. One gallon fertile lake water added as seed
material. HN03, H3P04 added as nutrient.H2SQ4 added to neutralize.
(c) Carbon columns containing 12x40 mesh activated carbon furnished by F
Carbon. Contact time in carbon bed was 1.6 minutes.
(d) Estimate, incubator problems.'"
by Pittsburgh
-------
Ni
00
Table X
Renovated Water Analysis (9)
Bleached Kraft Total Mill Effluent
Pilot Plant Run No. 3 50 Gallon Batch Operation
Obtained by Treatment
/ _ \
Constituent
Turbidity, ppm
Color, units
pH
Hardness, ppm CaCOo
Dissolved Solids, ppm
Chlorides, ppm
B.O.D., ppm
Sodium, ppm
Notes: (a) 5.9 Ibs. reburned lime slaked and added to raw effluent (equivalent to
15,000 ppm CaO).
(b) Extended aeration for 6 3/4 days. One gallon fertile lake water added as
seed material. HNOj, H^PO, added as nutrients. H2S04 added to neutralize.
(c) Activated carbon of mesh 12x40 furnished by Pittsburgh Carbon. Contact time
was 1.25 minutes.
(d) Quality data in this column are results of laboratory studies on the water
obtained from the pilot plant after Activated Carbon Treatment.
Desired Range
0-5
0-5
6.8-7.3
5-100
50-250
10-150
0-2
_
Effluent
85
1000
6.75
-
2000
593
225
310
Lime (a)
35
90
11.2
85
1900
593
170
310
Bio(b;
35
60
7.2
75
1790
535
13
310
1 Carbon^0'
35
15
8.0
64
1570
461
0
310
Ion
Exchange ' '
0
5
7.2
-
180
150
0
65
-------
K>
Table XI
Renovated Water Analysis (9)
Bleached Kraft Caustic Extract
Pilot Plant Run No. 4 50 Gallon Batch Operation
Obtained by Treatment
Constituent
Turbidity, ppm
Color, units
PH
Hardness
, ppm CaCOo
Dissolved Solids, ppm
Chlorides, ppm
B.O.D. ,
Sodium,
Notes:
ppm
ppm
Desired Range Effluent Lime'
0-
0-
6.8-
5-
5
5
7.3
100
50-250
10-
0-
-
150
2
310
12000
12.6
-
5820
1150
420
1200
35
1100
11.25
107
4320
1320
210
1200
a) Blo(b)
35
1000
9.2
142
3330
1380
40
1200
ion
Carbon'0' Exchange ' '
35
10
8.7
82
3930
1250
7.6
1220
0
5
3.7
25
250
120
0
20
(a) 5.9 Ibs. reburned lime slaked and added to raw effluent (equivalent to
15,000 ppm CaO).
(b) Extended aeration for 6 days. One gallon fertile lake water added as
seed material. HNO.,, HqPO, added as nutrients. H^SO, added to neutralize.
(c) Activated carbon of mesh 12x40 furnished by Pittsburgh Carbon. Contact
time was 7.12 minutes.
(d) Quality data in this column are results of laboratory studies on the water
obtained from the Pilot Plant after Activated Carbon Treatment.
-------
BOD, and turbidity. It is also evident that this treatment ,
sequence does not materially affect the dissolved solids.
4. Application and Consumption Overview
The first major use of activated carbon in liquid purification
was for the removal of color and other impurities in sugar
refineries. Another major use of activated carbon, as dis-
cussed before, is the treatment of municipal water supplies for
removal of tastes and odors (43). Sugar refining and municipal
water treatment account for over half of the activated carbon
used in liquid-phase processes. It is estimated that 50 million
pounds of activated carbon (mostly powdered) was used in municipal
water treatment plants in the United States during 1968 (105). ?
The decolorization of sugar (both corn and cane) required an -:
estimated 40 million pounds of activated carbon. In the past,
sugar refineries mostly used powedered activated carbon, but the
recent trend has been toward the use of granular activated carbon.
Use of activated carbon for gas adsorption and for solvent
purification in the dry cleaning industry are about equal. The
former is estimated to use 14 million pounds annually while the
latter consumes about 13 million pounds (105).
Activated carbon is also used in reclaimed rubber in the manufacture
of white sedewall tires. The addition of activated carbon to the
black components of the tire prevents migration of the reclaiming
oils into the white sidewalls and thus prevents staining. About
11 million pounds of activated carbon are estimated to be used for
this purpose (105).
About 7 million pounds of activated carbon were used in the
pharmaceutical industry in 1968. The carbon used by this industry
is high purity, high cost, and is used to remove color and harmful
biological materials from antibiotics, intravenous solutions, and
synthetic vitamins.
The food industry uses activated carbons for a number of purposes
(94). The major use is for removal of colored unsaturated polymeric
pigments. Other uses reported for activated carbon in the food
industry are:
(1) Removal of foaming compounds, color precursors and floe.
(2) Removal of impurities which would lower the yield and/or
the purity of the product.
(3) Removal of impurities contributing to objectionable tastes
and odors.
(4) Recovery of a product from a solution or solvent.
(5) Treatment of water or gases which eventually become a
part of the product.
The use of activated carbon for removal of colors and flavors from
scrap candies so that they can be reused is reported (105). Alcoholic
30
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beverages are also purified with activated carbons.
Activated carbon is used in the manufacture of organics other
than Pharmaceuticals and food (43). It is used in the production
of waxes and plasticizers where it aids in meeting color spec-
ifications .
The use of activated carbons in inorganic processes is reported.
Liquid alum is kept clear by mixing activated carbon into the
reacting batch of bauxite from which the alum is made (43). The
electroplating industry uses activated carbon in a filtration-
adsorption treatment to remove from plating solutions the organic
impurities which would otherwise interfere with adhesion or bright-
ness of the plate.
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SECTION V
IN-PLANT WATER REUSE IN PULP AND PAPER MILLS
Present Water Reuse Practices
1. General Overview
Large quantities of water are used by the pulp and paper industry
for cooling, washing, transporting, chemical preparation, and
for other purposes. In fact, the paper industry is the third
largest industrial water user (23). It has been estimated that
approximately 2,100 billion gallons of water are used annually
by the paper industry in the United States (75,14). It has
further been estimated that water usage in terms of the sum of
the water used at all individual water consumption points is
close to 6,000 billion gallons annually. In other words, of
the 6,000 billion gallons needed in the process, only 2,100
billion gallons are fresh water, while the other 65% of the
water requirement is met by reuse. This means water goes through
an average of three use cycles in the mill before being discharged.
Another report indicated the percent of total process water re-
used ranged 63 to 72 percent, with kraft mills at the top of the
range (40). Calculated as a percent reuse factor, that is,
water reused divided by fresh water intake, bleached kraft pulp
and paper had a 320% reuse whereas unbleached kraft pulp and
paper had a reuse factor of 260%.
The fresh water intake by the pulp and paper industry in terms
of gallons per ton of product has decreased significantly
throughout the years. For example, from 1954 to 1964 the total
tonnage of product increased over 52% whereas the total water
intake increased by 16% resulting in a 23% reduction in water
consumed per ton of product (14). It is expected that because of
reuse, recirculation, and other water conservation practices the
water intake per unit of product will continue to decrease.
As the preceding paragraphs point out, the pulp and paper in-
dustry actively practices water reuse. Clouse (23) reports
that there are three apparent reasons for increasing water reuse:
(1) economics; (2) public opinion, and (3) possibility of future
shortage. The ultimate in water reuse would be to have no effluent
at all, a fact that reportedly has been accomplished at one board
mill in the Miami Valley.
Table XII depicts the sources of reuse water and the points of
reuse as practiced in kraft or soda mills (87). The extent of
reuse at any particular mill depends greatly on the product being
made as well as on restrictions on water intake (59).
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Table XII
Reuse of Water in Kraft or Soda Mills (87)
Source Reuse
Digesting, washing, and screening:
Blow tank vapors condensate
Digester colling condensate
Turpentine separator underflow
Decker or thickener water
Pulp mill condensates
Condenser cooling water
Paper machine white water
Evaporator condensates
Causticizing and lime burning:
Lime kiln scrubbing water
Clarifier effluent from lime
sludge
Recovery furnace:
Scrubber liquor following
electrostatic precipitation
Bleaching:
Washer filtrate
Excess washer seal box water
Cooling water
Chlorine dioxide spent liquor
Power house cooling water
Other cooling water
Brownstock washing, shower water
Smelt dissolving, dilution,
deinking pulpers, woodyard
Shower water in lime mud system
Dilution water before screening
and cleaning
Brownstock dilution
Brownstock dilution
Brownstock dilution, washing
and screening, recycled to
machine
Brownstock washing, dregs
washing, mud washing, mud fil-
tration, white liquor filter
backwashing, deinking pulpers,
hot pond debarking, grinders
recovery furnace gas scrubbing
Recycled
Recycled to kiln scrubber
Recycled or returned to dregs or
lime mud washing
Stock dilution
Seal box dilution
Bleaching tower dilution water
Replace salt cake, tall oil
soap acidulation
Process water
Process water
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Major sources of water for reuse in a paper mill have been
identified as the paper machine white water, cooling waters,
decker filtrates, combined condensates, bleach plant washer
filtrate, and water from log flumes and barkers (23,40,80).
Several authors have described and discussed limitations to the
reuse of water (33,40,87,80,67,62,106). The following is a
description of problems encountered when reusing water:
(1) Slime buildup, which slows drainage, causes lost produc-
tion, plugs equipment, and makes dirty paper.
(2) Increased acidity resulting in corrosion, sizing, and
color problems as well as decreased paper strength and poor
aging properties of the paper.
(3) Buildup of dissolved solids causing foam and the problems
attendant with foam.
(4) Deposition of pitch and/or beater size at the water line
and on wires, rolls, and felts.
(5) Starch from broke which contributes to slime and foam,
interferes with wire retention, and hinders saveall operation.
(6) Buildup of fines and colloidal particles which affects
drainage and sheet characteristics.
(7) Temperature increase which may be either good or bad de-
pending on the product.
2. Woodyard
The reuse of wastewater in the woodyard is an accepted practice (40).
Specific usage areas are in log flumes, hot ponds, hydraulic or
wet drum barkers, and for showers before chipping. Heated
effluents such as evaporator condensates, bleach plant washer
filtrate, and paper machine white waters are preferred because
of the beneficial effect of increased temperature on bark removal
efficiency (87). Recycling of woodyard effluent after grit re-
moval is also practiced.
3. Pulp Mill, Recovery
From the pulp mill, combined condensates are increasingly being
reused. In a 1957 survey (80), 23 of 30 southern kraft mills
reported some reuse of this water. Combined condensate represents
a high quality source of supply from the standpoints of heat con-
tent and low suspended and dissolved solids content. The major
reuses of this water are in pulp washing and caustic room makeup
(80,58). Other uses are in the woodyard, bleach plant, condenser
water, and machine water. One report (40) indicated the condensate
may be used in steam generation.
Decker filtrate is reused to a large extent (80). Reuse applica-
tions are many; it may be used for stock dilution, showers, pulp
washing, groundwood grinders, screening, condenser water, fly
ash control, woodyard, and general washup. The major areas of
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reuse of this water are for stock dilution, screening, and as
condenser water makeup.
In the kraft chemical recovery process, water is reused for
dregs washing, green liquor dilution, lime slaking, lime mud
washing, lime kiln scrubbing, white liquor filter back washing,
and as flue gas scrubber water (40). The major source of water
for these uses is the evaporator condensate, although other
sources have been used for these purposes.
4. Bleach Plant
The quantity of water used in bleaching is quite high, the major
volume being used to transport the fiber at low consistency.
Gilmont (52) reported the results of a TAPPI survey of water
requirements for bleaching. Table XIII depicts the water use
in the bleach plant.
Assuming a maximum average consistency of 8% on the washer
drums, theoretically each washing stage would require approxi-
mately 2,800 gallons of water to completely displace the water
in one ton of pulp. Over half of the 52 mills which answered
the TAPPI survey indicated that they used considerably less
fresh water than that theoretically required for one complete
displacement. The reuse of other water was reported to make up
the additional volume.
Table XIII
Water Requirements in the Bleach Plant (52)
Function Gal/ton pulp
Washer vat dilution (37o-l%) 16,000
High density stock dilution (12%-3%) 6,000
Washer showers: 1.0 displacement 2,800
^ 2.0 displacement 5,600
Wire cleaning showers 100-600
Bleach chemical makeup 250-1,100
Heating, per hot stage 250
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Market pulp mills use high quality white water from the paper
machine extensively in the bleach plant, including use as dilu-
tion water for the transport of stock from the bleach plant to
the paper machine. However, some paper mills reported reduced
brightness and increased dirt count when paper machine white
water is used in the bleach plant.
In several cases, tempered water from the heat exchangers is
used for final stage washing in the bleach plant. Uncontaminated
cooling water is sometimes used in the bleach plant with resultant
heat savings (52,58). The heat economy gained can save boiler
feed water lost through direct steam heating of stock.
Low quality water such as solutions from scrubbers used to trap
escaping Cl2 or CIC^ are used on stages where corrosion is un-
likely. Gilmont (52) also reported that filtrate from soda-base
hypochlorite is reused very extensively for dilution on previous
stages, brown stock dilution before chlorination, and for dis-
placement washing.
A large number of mills reported little or no filtrate sewered
from later stages of the bleaching operation. These filtrates
are used countercurrently for dilution or, in some cases, for
displacement washing. Filtrates may be matched by pH and tem-
perature for use on previous stages, or they may be used counter-
currently on preceding stage of different pH.
Gilmont reported that filtrate water is used countercurrently
by various schemes. Overflow of filtrates to the seal box of
the previous stage with all fresh water on displacement showers
is one scheme. Another method is to use fresh water on the first
displacement showers with filtrate on the following showers.
Still another method is the use of filtrate on all showers with
fresh water on wire cleaning showers only.
Although there is considerable interest in the use of chlorination
stage filtrate, its actual use is limited, mostly to brown stock
dilution. Most mills sewer the chlorination filtrate as well as
the first caustic extraction filtrate.
5. Paper Mill
The greatest volume of fresh water in the pulp and paper mills
is used directly on the paper machine and is introduced through
felt and wire cleaning showers (84). Coats reports that water
usage in cleaning press wet felts is the largest single consumer
of fresh water on a new paper machine (24). Smaller amounts of
fresh water are used for stock dilution and washing or cleaning
the stock ahead of the machines. Auxiliary equipment also re-
quires fresh water, and vacuum pump sealing water is the largest
such use. Table XIV illustrates the water requirements of a 900
to 1000 ton/day linerboard machine, and indicates a fair degree of
water reuse (24).
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Table XIV
Clean Water Requirements for 340 tn. Linerboard Machine (24)
Process Recircu-
Demand, Fresh Water, Source, lation Sewer
Application .gal/min gal/min gal/min gal/min gal/min
Gland seal water 595 595 - - 445
Vacuum pumps seal 900 900 - - 120
Press felt washing 1484 1484 -
Grooved roll shower 200 200 -
Miscellaneous 741 741 - -
Cooling water 2360 - - 2360
Miscellaneous paper 2215 - 2215
machine showers
Cleaner dilution 200 - 200 - 200
Total, gal/min 8695 3920 2415 2360 765
Total, MGD 12.50 5.66 3.48 3.36 1.14
The reuse of white water is of economic importance as well as
being an effective method for reducing pollution loads. Reuse
of paper machine white water in stock preparation in integrated
pulping operations is practiced to various degrees in pulp and
paper mills (84).
To obtain maximum economic benefit, the most concentrated white
waters are segregated and reused within their own stock prepara-
tion system. This practice results in maximum recovery of paper-
making materials at the highest level of quality. Examples of
concentrated white water that is reused are tray water, wirepit
water, and couchpit water.
The normal procedure is to recirculate concentrated white water
and use it as dilution water in beaters and consistency regula-
tors and as makeup wateir for additives (90). When the water
demand for these purposes has been satisfied, the remaining
white water is sent to the saveall to reclaim the fiber and
filler content.
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The industry is currently using many types of savealls, filters,
screens, clarifiers, flotation units and similar equipment to
reclaim filler and fiber (14). Drum or disk vacuum savealls are
more flexible than flotation savealls because of their ease of
operation and capacity to take surges during paper breaks (24).
The disk saveall is also proving more satisfactory because of
the higher clarity of the effluent. One author reported re-
ducing the suspended solids from 5-10 lbs/1000 gal to 2 lb/1000
gal on such a unit (106). Installation of such equipment can
usually be justified on the basis of the value of recovered
fibers. Use of the clarified water in showers is possible.
There are certain precautions in white water reuse that should
be observed. Generally, suction box and suction roll discharges
should be excluded from reuse unless measures are taken to pre-
vent slime accumulation (84). White water storage tanks should
be provided with adequate agitation to prevent or minimize the
deposition of solids and formation of slime. Furthermore, the
reuse of white water is not practical where water use is low or
intermittent because of possible pipeline plugging.
As mentioned previously, vacuum pump seal water requirements
account for a large part of the fresh water requirements on the
paper machine. Reuse of vacuum pump seal water can be accom-
plished in two general ways (26). The pump water system may be
considered in series with one or more other water systems or
it may be considered a separate closed cycle.
If the vacuum pump seal water system is considered to be in series
with another system, then reuse may be accomplished by the follow-
ing methods:
(1) Feed the pumps with fresh water and discharge to another
system.
(2) Feed the pumps with pre-used water and sewer the discharge.
(3) Feed the pumps with pre-used water and discharge to another
system.
Vacuum pump seal water is used or may be considered for use on
felt showers, grooved roll showers, process water, pulp mill
(for example, turpentine condenser), woodyard, mill wash water,
and in the white water system (26). Another method of reuse is
to use the discharged high vacuum service seal water to seal low
vacuum service pumps. Despite the 15-20°F increase in tempera-
ture after the first pass through the high vacuum pumps, there
is very little effect on the capacity of the low vacuum service
pumps.
There are several reasons why the reuse of vacuum pump seal
water on felt showers is especially advocated. The felt showers
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frequently use more water than the pumps and can thus utilize
the total discharge. The temperature of the water is beneficial
and the two services are usually close together.
Another water reuse technique mentioned is the reuse of water
from another source for vacuum seal water. Some pre-used
sources are power house condenser cooling water, bearing cooling
water, clarified or fully treated effluent, drainage from log
pile spray, and white water.
Sometimes vacuum pump seal water requirements are reduced by
recirculating the water over a cooling tower or through a heat
exchanger. Some fresh water is required in closed systems to
purge contaminants.
6. Cooling Water
Cooling water is extensively reused and one survey showed that
27 of 30 reporting southern kraft mills employed some recycle
of this stream (80). Cooling water is being reused in the fresh
water system, for stock dilution, pulp washing, wood washing,
flume water, fly ash control, and for recycle.
Potential Reuse and Water Conservation Methods
Fresh water consumption can be considerably reduced by proper
design and maintenance. Thus the installation of inexpensive
flow control and regulating devices in individual supply lines
to packing glands will greatly aid in water conservation (24,90).
Ross (90) advocates a loop system for mill water headers because
of less fluctuation in header pressure even under extreme condi-
tions of flow variations. This is beneficial because operators
will tend to adjust manually controlled valves for the desired
flow at minimum pressure. At maximum pressure, the flow will
be greater and the excess represents waste.
Another aid to conserving water is the use of low-volume, high-
pressure showers. Ross (90) reports the use of saturated steam
on a wire shower to decrease water consumption. Shut-off valves
at the free ends of wash hoses aid in water conservation, and the
use of thermostats on water-cooled equipment such as air compres-
sors would help to conserve water in many cases. The use of an
automatic control on vacuum pumps to make seal water flow inde-
pendent of water supply pressure is also advised (26). On low
vacuum services (12 in. Hg and lower) it is possible and practical
to reduce the flow below manufacturers specifications. A 30%
reduction of water flow on low vacuum service pumps would decrease
the vacuum by two-tenths of one inch Hg.
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Several reuse and recycle possibilities, some of which are
used to a limited extent now, have been suggested for further
consideration (100):
(1) Cooling water, including vacuum pump seal water, pump
bearing water, and air conditioning cooling water to be
recycled to cooling pond or tower.
(2) Use of activated carbon adsorption to control dissolved
organics buildup in closed recycle systems. Use side-
stream treatment to minimize equipment size.
(3) Removal of organics from turpentine underflow, possibly
by steam stripping or activated carbon treatment (see
also ref. 12,33).
(4) Reuse of blowdown stream from white water on pulp washer.
(5) Use of evaporator condensate, after organics removal, in
pulp washing and as make-up water for paper machine
showers.
(6) Possibly close the woodyard water cycle, which"requires
solids separation.
Rapson (39) has suggested the recovery of bleach plant effluents.
His suggested system has three essential components:
(1) Replacement of chlorine by chlorine dioxide in the
chlorination stage to the maximum economically feasible
extent to minimize chloride ion buildup.
(2) Countercurrent washing of the unbleached and bleached
pulp with the minimum amount of water which will give high
quality bleached pulp.
(3) Separation of sodium chloride from sodium sulfate in the
furnace flue gas.
Rapson proposes to wash the bleached pulp with evaporator con-
densate that has been oxidized with chlorine and chlorine dioxide.
Furthermore, the combined bleach plant effluent would be used to
wash unbleached pulp. Some of the bleach plant effluent could be
used to wash the lime mud and dregs and then to dissolve the smelt
to make green liquor.
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SECTION VI
EFFLUENT COLLECTION SYSTEMS
Effluent collection systems in pulp and paper mills are variable,
but an increasingly common practice is to discharge wastes into
separate sewers according to the strength and characteristics of the
wastewater (40). For example, St. Regis' Ferguson mill at Monticello,
Mississippi, has five separate sewers (36):
(1) Surface runoff and cooling waters sewers.
(2) Inert wastes sewer - green liquor dregs and bark boiler ash
are pumped through separate lines to an ash pond.
(3) Low solids sewer
(4) High solids sewer
(5) Sanitary effluent
A Texas bleached kraft mill reports that their wastes leave the mill
in four streams (89). There is a high BOD stream which receives
clarification and biological oxidation. The settleable solids stream
requires clarification and some biological oxidation, while the
bleach plant alkaline stream requires only biological oxidation. The
fourth stream or acid stream requires no treatment other than pH
adjustment.
Four general classifications of kraft mill sewer systems are:
(1) low suspended solids, (2) high suspended solids, (3) strong
wastes, and (4) sanitary sewers (50).
Low suspended solids wastes include bleaching effluents and evapora-
tor condensates which do not require clarification. High suspended
solids wastes are composed mainly of decker, paper machine, and
woodyard effluents. Primary clarification is required after screening
and grit removal. The strong wastes sewer catches floor drains, over-
flows and spills, and strong condensates. Some mills provide strong
waste storage basins or tanks so that these wastes may be metered into
the treatment system at controlled rates in order to prevent an upset
in treatment operations. Sanitary sewage is often not segregated since
it can be effectively treated in the biological oxidation process. Where
local receiving water standards require disinfection of wastes con-
taining sanitary sewage, separate treatment facilities are provided,
normally the packaged activated sludge treatment type. These provide
chlorination for bacteriological control.
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SECTION VII
SOLIDS REMOVAL (PRIMARY CLARIFICATION)
Removal Requirements and Extent of Practice
Pulp and paper mill effluents contain suspended solids such as
fiber, fiber debris, bark particles, shives, grit, and fillers
or coating materials such as clay and calcium carbonate. Al-
though most of the filler and fiber is removed, for economic
reasons, in some type of saveall device before the carrying
stream enters the effluent system, the effluent usually requires
further clarification in order to reduce the pollution waste-
load contributed by the suspended material. Suspended solids
can form bottom deposits in receiving streams (54). These bottom
deposits are harmful to aquatic life, unsightly, and form malodors
upon decomposition, as well as exhibiting an appreciable demand
for dissolved oxygen. Furthermore, highly dispersed materials
such as fiber debris, filler, and coating material limit light
penetration and thus retard the self-purification ability of a
stream.
Solids removal (clarification, primary treatment) is widely
practiced in the pulp and paper industry. Although sedimentation,
filtration, and flotation are all utilized, the process most
commonly used is sedimentation (38). A recent survey of the
kraft industry by the National Council for Air and Stream Improve-
ment showed that 82 of 113 kraft mills in the United States
provide sedimentation facilities for effluent treatment (50).
Clarification is used primarily to treat those streams high in
suspended solids. As indicated in the section on effluent col-
lection systems, it is common to by-pass the solids removal
treatment with effluents such as bleach plant filtrates which
have a low settleable solids content.
Process Capabilities
Before discussing the capabilities of solids removal facilities,
a clear delineation must be made between total suspended solids
and settleable solids. The total suspended solids are all the
solids in suspension in an effluent. The settleable fraction is
defined as that which separates from the liquid in one hour of
quiescent settling in a laboratory vessel, usually an Imhoff
cone. In terms of total suspended solids, the efficiency of any
clarification system will depend on the fraction of settleable
solids present.
45
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Generally, sedimention of paper mill effluents without coagulant
addition removes 70 to 80% of the total suspended solids while
90% or more reduction may be achieved with the aid of coagulants
(49). Although the reduction in total suspended solids is
variable, Edde (38) and Gehm (49) both report that properly de-
signed clarifiers can be expected to remove more than 957o of
the settleable solids.
Primary treatment also results in some reduction of five day
B.O.D. As pointed out by Edde (38), the B.O.D. reduction depends
on the type of mill and type of solids being removed in the primary
treatment. For instance, a white water low in dissolved organic
matter and containing fiber which readily settles will exhibit
high B.O.D. reduction when clarified. Conversely, there would be
little reduction in B.O.D. of a waste containing a large amount,of
dissolved organic matter and containing appreciable quantities of
dispersed organics. In Edde's survey which included several types
of mills, the B.O.D. reduction ranged from 22% for pulp mill
effluents to 84% for tissue mill effluent (38). Gehm reports
that primary clarification results in approximately 15% B.O.D.
reduction (50), while another source reports a reduction of 10
to 40% (40).
Information on C.O.D. reduction and color reduction was not
available; however, estimates were published in one report (40).
The C.O.D. was estimated to be reduced by 10 to 30% and it was
estimated that the "true" or dissolved color was reduced 0 to
10%. True color is not removed unless flocculation has caused
adsorption, so that the color adsorbed on floe particles will
settle out of the wastewater.
Specific Processes and Present Applications.
1. Pretreatment
Due to the nature of pulp and paper mill wastes, it has been found
advisable to perform certain operations, termed pretreatment, be-
fore the clarification process. The presence of large pieces of
debris necessitates the use of bar screens which may be manually
cleaned or automatically cleaned by devices such as traveling
rakes. Bar screens with a spacing of 3/4 to 1-1/2 inches between
bars are normally used for this purpose (40). Fine screening is
not as commonly used as coarse screening for wastewater pretreat-
ment in the pulp and paper industry. Many pulp mills and a large
number of paper mills lose trash in the form of chips, bark, wet
strength paper, and slivers that pass through an ordinary bar
screen (38). Because this type of trash may cause pump and pipe
plugging, it seems desirable to remove it, normally with a screen
having openings of 3/8 to 3/4 inch. Several types of screens are
available for fine screening:
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(1) self-cleaning rotating discs
(2) vibrating screens
(3) traveling screens, and
(4) drum screens.
Where a considerable amount of silt is present in the effluent,
grit removal is practiced as a pretreatment (50). Presently
about 60% of the industry practices grit and debris removal (40).
Grit removal chambers are installed after screening equipment to
trap solids with a particle size of 6 to 150 mesh and a specific
gravity greater than two (69). Grit chambers are designed for
an effective velocity of 0.6 ft/sec and a detention time of
about one minute (50,56). The grit chambers are cleaned periodi-
cally with a clam shell bucket or, in some cases, continuously
by mechanical means.
Deaeration is another pretreatment process which is sometimes
necessary to prevent fiber flotation in the clarifier (38).
This is particularly true when white waters are treated alone,
or when coagulants are used.
2. Sedimentation
Sedimentation is generally accepted for solids removal because
under most circumstances it is less expensive than the other
processes. It is also less sensitive to variations in flow and
solids concentration and less attention and maintenance are
required (38).
Sedimentation is accomplished in earthen-banked clarification
basins and in mechanical clarifiers. Gehm (50) reported that 23
kraft mills in the United States utilize earthen basins while
59 mills employ mechanical clarifiers. The most widely used
mechanical clarifiers are the circular, mechanically cleaned type,
but reactor-type clarifiers, rectangular mechanically cleaned
basins, and conical tanks without collector mechanisms are also
used (49).
Earth embanked basins are generally designed for 12 hrs. deten-
tion when free of sludge (50). When cleaned at proper intervals,
the earth embanked basins yield an effluent which is comparable
to that produced by a mechanical clarifier - that is, it contains
one to two pounds of suspended solids per 1,000 gallons (49).
Earthen basins are difficult to clean and the cost is $10 to
$15 per ton of dry solids removed (50). The use of earthen sedi-
mentation basins is rapidly declining as mechanically cleaned
clarifiers are becoming standard practice.
Although circular, thickener-type clarifiers are most widely
used, excellent results have been achieved with rectangular
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clarifiers (103). Edde (38) reports that in practically all
situations, a design based on a hydraulic loading capable of
removing 95 to 100% of the settleable solids (determined by one
hour quiescent settling in the laboratory) results in adequate
area to accomplish sludge thickening. It is generally agreed
(50,38,30) that rise rates of 600 gal/sq.ft./day will produce
a sufficiently clarified effluent in practically all waste waters.
However, higher hydraulic loadings are reported and one source
reports rise rates of 600 to 1000 gal/sq.ft./day with 800 being
a common value (40).
Theoretical detention time in the clarifier is three to four
hours (50) and, at 700 gal/sq.ft./day rise rate, side wall depths
of 10 to 12 feet provide the necessary detention time as well as
adequate volume for storage of sludge during the thickening
process (38).
Increasing evidence has shown that a minimum clearance between
the stilling well and the floor of the clarifier is necessary
to avoid scouring the solids from the area of the collection
sump (38). This should be about 12 feet in clarifiers 150 feet
or more in diameter. Van Luven (103) believes that it is
necessary to have a minimum side wall depth of 12 feet and a
bottom slope of one to two inches per foot with a substantial
sludge pit in the center of the clarifier. He states that the
sludge pit should be five feet or more in depth and should
occupy at least 25% of the diameter of the clarifier.
Gehm (50) reports that dual unit clarifier installations are
gaining preference because, with one unit down for repairs,
the other clarifier may be operated at a rise rate of 1200
gal/sq.ft./day and still provide reasonably good settleable
solids removal.
Frequently when a single clarifier is used, an equalization
basin is provided after the clarifier to protect the biological
treatment process during periods of abnormal operating conditions
or clarifier shutdown (50). Since the solids load to the
equalization basin is only a fraction of the total solids load,
it generally requires cleaning only once every several years.
The costs of solids removal by a clarifier are categorized by
Edde into three groups as follows: (1) the cost of the clarifier
including collector mechanism, wires, etc., (2) the cost of pumps
and piping and (3) the cost of sludge handling equipment. Clarifier
cost per MGD capacity decreases as the capacity increases. For
instance, a unit for one MGD will cost about $24,000 while a
twenty MGD unit will cost about $7,500 per MGD. Piping cost is
generally about 10% of the total cost when the piping arrange-
ments are simple, but for unusual conditions a generalization
cannot be made.
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Another recent survey (11) indicated capital expenditures in
dollars per ton of capacity per day are $1,000 to $1,500 for
mechanical clarifiers and $1,500 to $1,750 for mechanical
clarifiers and dewatering. Operating charges ranged from 45 to
75 cents per ton for mechanical clarifiers and 55 cents to $1.30
per ton for mechanical clarification plus dewatering. Capital
expenditure for clarification in earthen basins is $500 per
pulp-ton of mill capacity per day, while operating charges are
reported to be 25 to 30 cents per ton of pulp.
3. Filtration and Flotation
Filtration and flotation processes are also used to remove
solids from pulp and paper mill wastes, although not as exten-
sively as the sedimentation process. Filtration savealls utilize
fine screens to recover the fiber and filler contained in white
water. An example of the use of air flotation is the removal of
very fine fibers and solids found in the effluent from some
types of production (40).
4. Sludge Handling
Most of the sludges from the clarification of pulp and paper
mill effluents can be thickened in the primary clarifier to the
point where they can be mechanically dewatered (103). Edde's
survey of the industry in 1964 showed that 30 out of 53 mills
reporting practiced such thickening. Some of the problems that
prevent sludge thickening in the clarifier are: (1) insufficient
storage capacity, (2) lightweight rake mechanism, (3) pump unable
to handle thick sludge, and (4) lack of a torque measuring device.
When sludge thickening is practiced, the clarifier scraper
mechanism is of the heavy duty type designed with a torque rating
of ten times the square of the clarifier diameter (50,38).
Generally the units are equipped with a torque limiting mechanism
to protect against overload.
The type pump used to remove sludge from the primary clarifier
unit depends on the size of the clarifier and the characteristics
of the sludge. Centrifugal pumps are generally used on larger
units, while plunger pumps are used with smaller units (50).
When the sludge tends to compact to high consistencies, screw or
Moyno type pumps are utilized. Both the screw and plunger pumps
require close attention when trash is in the sludge (38). Piping
is arranged for ease of cleaning in case of plugging. A common
problem in sludge drawoff pipes is undersizing which results in
bridging at the entrance or excessively high head loss causing
stoppage when heavy fiber loads are encountered (38). Oversizing
of piping is preferred and pipe sizes for sludge drawoff lines
are generally as follows: (1) 6 inches for 50 to 100 feet diameter
units, (2) 8 in. for 100 to 200 feet diameter units, and (3) 10
inches for clarifiers greater than 200 feet in diameter.
49
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Two recent papers contain excellent information on the handling,
dewatering, and disposal of sludges resulting from solids separa-
tion (primary treatment) and biological oxidation (40,50). Due
to pipe plugging and pump head loss, it is customary to remove
sludge from the primary clarifier at 3 to 67» solids although the
solids concentration at which the sludge can be withdrawn ranges
up to 107..
Sludge from primary clarification units normally does not require
further thickening before dewatering. Several methods are used
to dewater clarifier underflow and the selection of a particular
method depends on the type, concentration and quantity of solids.
These methods include sludge drying basins, vacuum filters,
centrifuges and screw presses.
The underflow from secondary clarifiers is normally withdrawn
at about 1% solids. Gravity thickening of secondary sludges
having a volatile solids of 60 to 90% results in a 2.5 to 37=> solids
concentration at loadings of 10 to 20 pounds per square foot.
If gravity thickening of secondary sludges is not feasible, it
can be mixed and dewatered with primary sludge. Secondary
sludges can also be thickened by dissolved air flotation or cen-
trifugation. The former process yields a sludge of 4 to 5%
solids, whereas the latter process is capable of obtaining 5 to
87o solids.
With certain exceptions, sludges resulting from high rate bio-
logical treatment may be dewatered in combination with sludges
from the primary clarifier.
Where sufficient land of suitable topography is available, the
cheapest method for dewatering primary clarifier underflow is in
sludge drying basins. If sludges from biological oxidation are
present, sludge drying basins cannot generally be used because of
malodors resulting from decomposition of the sludge. Sludge
drying basins are decanted periodically during periods of cold
weather or high stream flow.
When basins become full, the nature of the sludge determines
further treatment. If the underflow is free of fibers, it will
lose more water through evaporation and drainage and will eventual-
ly become friable enough to be removed and used for landfill on
wasteland. Underflows high in filler content drain slowly and
form surface crusts which retard evaporation. Drying basins
containing this type of sludge are frequently abandoned when they
become filled.
Both primary and combined sludges are dewatered by vacuum filtra-
tion. Conditioning chemicals such as lime or polyelectrolytes
are often required. The filter cakes obtained contain from 20 to
307o solids.
50
-------
Horizontal solid bowl centrifuges are also effective dewatering
devices'for pulp and paper mill sludges. Primary sludges can
be easily dewatered on a solid bowl centrifuge to .between 20
and 35% solids. At a feed solids concentration of 5% and de-
pending upon the fiber content, combined sludges can be dewatered
to 15 to 25% solids. Biological sludges usually require the
addition of polyelectrolytes, after which they can be centrifuged
to 12 to 20%.
Compared to the vacuum filter, the centrifuge requires less
operator attention, but is more expensive to operate because of
higher power requirements. Power requirements are approximately
0.7 to 1.0 hp per g.p.m. of feed sludge.
About 30 to 35% of the industry utilizes mechanical dewatering
in one form or another. When incineration is used as a means of
final disposal, pressing of filter or centrifuge cakes is used
as an additional dewatering step to increase the solids content
to 40 to 50%.
Although dewatered sludge is in most cases disposed of by land-
fill, there is increasing interest in other disposal methods.
Incineration of solid wastes resulting from sludge dewatering
is increasing as land costs increase and availability of land
decreases.
51
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SECTION VIII
BIOLOGICAL TREATMENT
Treatment Requirements and Extent of Practice
Pulp and paper mill effluents contain dissolved and suspended
organic substances, primarily in the form of solubilized wood
components and of fibers that are intentionally or inadvertendly
discharged from the processes involved in converting wood or
wood chips into pulp and paper. Most of these substances have
an effect on the ecology of the receiving river or water system.
The effect may take several forms, e.g. depletion of oxygen due
to biological oxidation of these substances; production of foul
odors due to biological reduction in absence of oxygen; effects
on the marine life due to toxicity of some substances or depletion
of oxygen; excessive growth of algae; and others. The ecological
effect is either in fact detrimental, or generally considered so,
making it necessary to exercise control over it.
The most common measures of the actual or potential ecological
effect of a mill discharge today are the biological oxygen demand
(B.O.D.) both of the effluent itself and of the receiving stream
after admixture of the effluent, and the dissolved oxygen (D.O.)
content of the receiving stream at several points downstream from
the effluent admixture point. Other measures are also in use, such
as dissolved and suspended solids, conductivity, turbidity, and
color.
Control measures exercised on the effluent today aim to achieve or
maintain a reasonable ecological balance in the receiving stream
as determined by state regulatory authorities. However, more and
more, restoration and maintenance of the presumed natural state
of the stream is becoming the aim of control measures. Because
of seasonally varying river water flows and assimilation capacity,
early control measures involved primarily regulation of the dis-
charge volume into the receiving stream. This required the use of
storage lagoons to accept a more or less constant mill effluent
flow, while allowing a variable lagoon discharge flow.
The biological treatment of pulp and paper mill effluents is an
outgrowth of the practice of lagooning wastes for controlled
discharge to the receiving stream. It was found that during
53
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storage the B.O.D. was reduced, and subsequent investigations
determined that this phenomenon is due to bacteria utilizing
the organic substances as a food source. It was found that the
oxidation rate in holding ponds is limited mostly by atmospheric
reoxygenation and that fiber deposition in the basins is detrimental
to the B.O.D. reduction. Decomposition of the fibrous material
results in soluble constituents which raise the oxygen demand of
the waste, hence the desirability of suspended solids and fiber
removal as discussed in Section VII.
Several biological treatment processes are utilized by the pulp
and paper industry. These methods are: (1) storage oxidation or
stabilization basins, (2) aerated stabilization basins, (3) act-
ivated sludge, and (4) trickling filter. One report (40) indicated
that in 1967 oxidation ponds were used by about 2070 of the industry,
whereas aerated lagoons and activated sludge were each utilized by
about five percent of the industry. Trickling filters were used
by less than five percent of the industry. i
Gehm (50) reported that 55 out of 113 kraft mills in the United States
are providing some form of biological treatment. The most widely
used processes in the kraft industry are storage oxidation basins
(26 mills treating 432 M.G.D.) and aerated stabilization basins
(17 mills treating 470 M.G.D.). The activated sludge process is
used by 9 kraft mills, whereas the trickling filter is presently
being used by only 2 kraft mills.
Process Capabilities
The primary purpose of biological treatment is to remove soluble
materials exhibiting a biological oxygen demand. Biologically
inert or refractory compounds such as lignin derivatives are not
effectively removed during biological treatment.
The degree of B.O.D. removal depends to a great extent on the
process used as well as on the influent loading. It is reported
(40) that 30 to 95% of the five-day B.O.D. can be removed in the
various biological processes.
Biological treatment also removes some of the chemical oxygen
demand (C.O.D.). The reduction of C.O.D. ranges from 20 to 70%
for the various processes. ;
The true or dissolved color may be reduced to some extent during
biological treatment. This is probably due to adsorption on the
biological solids. It is reported that the activated sludge
process may result in a 10 to 30% decrease in color whereas the
other processes may result in a 0 to 10% removal of color. One
mill reported an exceptional case where slightly more than 40%
reduction in color occurred as a result of aerated stabilization
basin treatment of unbleached kraft effluent (76).
54
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Howard and Walden (64) reported on the pollution and toxicity
characteristics of pulp and paper mill effluents. Laboratory-
scale activated sludge fermentation of bleach plant wastes was
performed. The untreated wastes exhibited 96-hour median tolerance
limit (T.L.m. ) values of 84.8, 77.1 and 77.1% for three samples.
(The median tdlerance limit is the concentration in percent by
volume which will kill 50% of the exposed marine population in a
known exposure time). There was no mortality among fish held in
100% treated effluent. Their study indicated that biological
oxidation would reduce the inherent toxicity of pulp and paper mill
bleach plant wastes.
Pulp and paper mill wastes are generally deficient in nitrogen and
phosphorus, and these nutrients have to be added to obtain effective
biological oxidation of waste. The normal amounts of nutrients per
100 Ib. of B.O.D. are 5 Ib. of nitrogen and 1 Ib. of phosphorus (50).
These nutrients are generally added in the form of ammonia and
phosphoric acid. The ammonia may be added as either a liquid or a
gas, depending upon availability and quantity requirements (40). It
is reported that the presence of large amounts of alum in the waste
water causes a larger demand for phosphoric acid because of the
formation of insoluble aluminum phosphate.
Biological oxidation is generally performed on the total mill
effluent after those streams that are high in settleable suspended
solids have been treated for the removal of these solids. The
desirability of keeping fibrous sedimentation from occuring in
biological treatment facilities is recognized and as explained in
a previous section, an equalization basin is generally provided
ahead of biological oxidation. This basin provides additional
settling and holding capacity to prevent an upset in biological
treatment in the event the clarification system becomes overloaded
or is down.
Specific Processes and Present Applications
1. Storage Oxidation or Stabilization Basins
Storage oxidation basins serve a dual purpose. They are used to
regulate discharge to the receiving stream as well as to reduce the
B.O.D. load. Gehm (50) reports that in some instances the basins
are also used for cooling some of the spent process water being
returned to operate evaporator jet condensers. One mill reportedly
uses the stabilization basin to store process water intermittently
on a seasonal basis.
The design of stabilization basins varies considerably. Some basins
have been built which conform to the topography of the land; others
have been built using dikes. Those basins which have utilized the
land topography are quite variable in depth as well as in storage
period and surface loading (50). Basins which have been built by
dikework have been designed with depths of three to five feet
and large surface areas, thus aiding reoxygenation.
55
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Stabilization basin design basis is usually to pounds of B.O.D. per
acre per day for B.O.D. removal of at least 85% (37). Basins have
been designed for 10 to 300 pounds of B.O.D. per acre per day, with
loadings of less than 50 pounds of B.O.D. providing removal of 90%
or more of the five-day B.O.D. during the summer months. At high
B.O.D. loadings the removal efficiency levels off at approximately
60 to 70%. Removal of up to 150 pounds of B.O.D. per acre per day
have been accomplished by using very shallow multiple basins in
series; however, anaerobic odor production is noted where loadings
result in removal of more than 60 pounds per acre per day. The
retention time in stabilization basins is usually 10 to 30 days.
Table XV lists performance data on several basins (49).
Table XV
Effectiveness of Stabilization Treatment (49)
Type Pond Maximum B.O.D.
Treatment Area, Retention, Influent Effluent Removal
Type Mill System Acres Days mg/1 mg/1 %
Newsprint Multiple 100 20 200 40 80
plus Flowage -
Newsprint Single 140 15 180 110 39
Bleached Single 215 30 299 157 48
Kraft
Bleached Single 175 35 108 36 67
Kraft
|
Unbleached Multiple 350 82 200 20 90
Kraft plus Flowage
Edde (37) reports several reasons for the selection of stabilization
basins as a biological treatment system. Among the reasons are:
(1) responsiveness of effluent to treatment, (2) reliability of the
process, (3) flexibility, and (4) low capital and operation cost.
Gehm (49, 50) also points out that no mechanized quipment or operator
attention is required.
The greatest disadvantage of stabilization basins is the requirement
for large land areas of correct topography and imperviousness.
Typically, 40 to 50 acres of pond area is provided per MGD of mill
waste water (40). Consequently, stabilization basins are generally
56
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limited to southern mills in the United States where large tracts of
suitable land are available. Also, in the South, high ambient temp-
eratures are conducive to microbiological action during most of the
year.
The cost of stabilization basins is dependent upon local land
values (37). Blosser (11) reports a cost of 25 to 35 cents per
ton of pulp production capacity for non-aerated stabilization
bas ins.
i- L~t
2. Aerated Stabilization Basins
The aerated stabilization basin evolved from the need to upgrade
the biological treatment performance of overloaded stabilization
basins. Aerated stabilization basins have been rapidly accepted
and extensive use of this type of biological treatment is found
in the pulp and paper industry. Seventeen kraft mills are using
aerated stabilization basins to treat 450 to 470 MGD of waste
water (50, 37).
The aerated stabilization basin requires much less land than
storage stabilization basins. Typically, land usage may be two
acres per MGD as compared to the 40 acres per MGD generally used
in stabilization basins.
A design parameter that is often used in the construction of aerated
stabilization basins is the Alpha value. The Alpha value is the
relative ease of oxygen transfer in a waste as compared to pure
water. Edde (37) reports that NCASI studies have shown that Alpha
values range from 0.7 to 1.0 for kraft wastes, and generally as
oxidation proceeds, the Alpha value approaches 1.0. If no experi-
mental data are available, an Alpha value of 0.7 will provide a
sufficient margin of safety when designing the aeration system.
Oxygenation is accomplished by mechanical or diffused aeration units
and by induced surface aeration. Although the turbulence level in
aerated basins is quite enough to distribute oxygen throughout the
basin, it is insufficient to maintain all the bacterial solids in
suspension. The aerator also helps to distribute the influent B.O.D.
load throughout the basin (37).
Aerators may be pier-mounted or float-mounted with float-mounting
favored for large basins because of wind effects and for flexibility
(50). Gehm reports that for initial design purposes an aeration
capacity of one to two pounds of oxygen per horsepower hour is generally
employed. This figure takes into consideration the Alpha value, mixing,
oxygen saturation, and effluent temperature.
Aerated basins are usually designed as a completely mixed system, thus
a single basin without baffle walls is all that is required. Gillman
(51) reports that dissolved oxygen levels of 0.5 ppm are adequate to
maintain aerobic conditions.
57
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Optimal ratios of B.O.D. to nitrogen-containing nutrients (as N)
have been found to range from 50:1 with four days aeration to
100:1 with 10 to 15 days aeration (37). If aeration is extended
beyond 10 to 15 days nutrient addition is not normally required.
The biological sludge produced in aerated stabilization basins is
less than in the high rate biological processes. Normally 0.1
to 0.2 pounds of sludge are generated for each pound of B.O.D.
removed (50, 107). Some of the sludge that is formed is consumed
by endogenous respiration, some carries over in the effluent, and
some settles in the basin. That portion which is not destroyed
by endogenous respiration adds 0.1 pound of five day B.O.D. per
pound of volatile suspended solids.
Operating costs of aerated stabilization basins are about $1.50 to
$2.00 per ton of production, or 2.5
-------
S1If ^fxed *l dia&** °f the conventional activated
wth ci f RetU SludSe from the secondary clarifier is mixed
llu* flow f^Wa 6 ^°re 6ntering the aeration tank' Basically,
in fhf ^ f- * liquor with some longitudinal mixing occurs
in the aeration tank (37). As mixed liquor flows through the aeration
nJ?M, h* rem / °rganics occurs Progressively, and the oxygen
utilization rate decreases and approaches the endogenous level at
WASTE
AERATION
TANK
RECYCLE SLUDGE
TREATED
EFFLUENT
SLUDGE TO
DISPOSAL
Figure 4
Conventional Activated Sludge System
The contact-stabilization process consists of mixing the waste with
activated sludge for 15 minutes to one hour during which time organics
are adsorbed. The sludge is then separated from the effluent in a
clarifier and reaerated in a separate tank to stabilize the adsorbed
organic matter. If the sludge is insufficiently aerated, its adsorp-
tion capacity is decreased because of the remaining unoxidized
organics, and the B.O.D. removal efficiency of the system decreases.
Overaeration is also harmful because overaerated sludges disperse
and lose their high initial removal capacity.
The contact-stabilization process was originally developed to treat
waste containing much of the B.O.D. as suspended or colloidal material.
Because the stabilization of these materials occurs at much higher
organism concentrations, the contact-stabilization process requires
less tank volume than the conventional process. Another advantage
is that the mass of biological organisms is outside the main waste
water stream (40). Thus, if toxic or upset conditions occur, the
system can be returned to its original conditions in less time than
required by the conventional system.
59
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The completely mixed activated sludge process mixes the raw waste
uniformly with the entire contents of the aeration tank. The
result is that the aeration tank acts as an equalization basin
to smooth out load variations and dilute slugs and toxic materials
(37). Higher organic loadings can thus be handled in this process
than in the conventional activated sludge system.
It is reported that the conventional activated sludge process is
particularly suited to treat waste water from sulfite mills,
whereas the contact-stabilization process is particularly applicable
to integrated kraft mill effluents (40). Removal of 85% of the
B.O.D. may be attained by the conventional activated sludge process
with a detention time of four to six hours and a mixed liquor
suspended solids of 2000 to 3500 mg/1. The contact-stabilization
process achieves 85% removal of B.O.D. with two to three hours
contact time and two to three hours stabilization time at a mixed
liquor suspended solids concentration of 2000 to 3000 mg/1 in the
contact phase. Both systems require one to two pounds of oxygen
and produce about one-half to one pound of excess sludge per pound
of B.O.D. removed.
Aeration has been accomplished by porous diffusers, spargers, and
turbine aerators in combination, and by mechanical surface aerators.
Mechanical aeration is now favored over diffuse aeration because of
the increased efficiency of the mechanical aerators and because of
the tendency of filter media to clog.
Addition of nutrients in the form of ammonia and phosphoric acid is
generally required. Requirements are generally less than the theo-
retical optimum of 1 mg/1 of nitrogen per 20 mg/1 of B.O.D. and
1 mg/1 of phosphorous per 60 mg/1 of B.O.D., because of traces of
these elements in most effluents (49).
Process loading of up to 150 pounds of B.O.D. per 1000 cubic feet
aeration volume per day are reported. To achieve B.O.D. removals
of 85% or better, loadings should not exceed 125 pounds per 1000
cubic feet per day. Furthermore, optimum sludge settling will occur
in the final clarifier over a loading range of 0.2 to 0.7 pounds of
B.O.D. per day per pound of mixed liquor suspended solids (37).
Table XVI shows typical operating data from mill activated sludge
treatment plants.
The activated sludge process is generally used where suitable land
is not available for stabilization basins. Although the activated
sludge process has been used successfully in treating most pulp
and paper mill wastes, it has certain disadvantages. The capital cost
involved is high, $55,000 to $150,000 per MGD hydraulic load or $50
to $62 per pound of B.O.D. per day (37). Operating costs range from
$1.50 to $2.50 per ton of production or 3 to 5% cents per pound of
B.O.D. removed.
60
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Table XVI
Activated Sludge Treatment Data (37)
Loading
Mill
2
3
4
5
9
Flow,
MGD
25
20
10.5
51
2.9
B.O.D. Detention
#/ day Time, hr.
52,000
33,200
28,400
81,000
5,850
2.5
5.5
7.8
4.0
8.5
#B.O.D./
1000 cu. ft
130
50
52
46
37,5
#B.O.D./
. #MLSS
1.1
0.2
0.3
1.0
0.25
%
B.O.D.
' MLSS Reduc-
ing /,! , ,.
2,500
3,000
3,000
1,000
3,000
tion
88
90
88
89
96
Nutr-
ients
N,P
N,P
N,P
N,P
N,P
Sludge bulking is a common operating problem. Removal of the
biological organisms is accomplished by gravity settling in a clarifier,
generally designed for rise rates of 600 to 800 gallons per day per
square foot. Gehm (50) reports that secondary clarifier rise rates
should not exceed 400 gal. per day per square foot. Sludge bulking
prevents effective settling in the final clarifier and as a result
the final effluent has a high concentration of suspended solids. Edde
(37) has suggested several causes for sludge bulking: (a) excessive
filamentous bacteria, (b) overaeration, (c) underaeration and septicity,
(d) too high or too low aeration solids content, or (e) nitrogen, defi-
cient waste. It is reported (40) that P"^"1-^"^,:^
draw-off clarifiers are being increasingly used as final clanfiers and
that up to 98% of the solids are thus removed from the waste water.
.
S»r eriodl. aloighi^ causes a wide variation in
B.O.D. removal efficiency.
Although tripling
biological "ea^f°f "aap" l-"""'^ <37' ' Reasons f°r
"* " «« 1"1"8 o£ st°M edia
61
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with fiber, high capital cost, and inability to accomplish high
B.O.D. removal at high loading levels.
Trickling filters are capable of removing 40 to 50% of the B.O.D.
at very high volumetric and B.O.D. loading levels. It is reported
that trickling filters have proven useful where only partial B.O.D.
reduction is needed or as a preliminary biological treatment prior
to additional treatment, especially if cooling of the waste is
beneficial. One such application is to use the trickling filter
ahead of the activated sludge process (40).
Costs for plastic media trickling filter units are about $120 per
cubic yard of filter media (37). Operating costs have been reported
to be almost $2.00 per ton of production or 8 to 9<: per pound of
B.O.D. removed depending on amortization period, interest rate, labor
and chemical cost. These costs do not include primary and secondary
clarification.
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SECTION IX
PRECIPITATION,, COAGULATION, LIME TREATMENT
Overview; Extent of Practice
In this section, a general overview of the work and practice in this
area is presented in Part A. The results that have been achieved on
a laboratory or pilot basis, including lime treatment, are discussed
in Part B. The present or planned large scale development and demon-
stration of several lime treatment processes receives additional sepa-
rate coverage in Part C.
Coagulation techniques have been in use for years in water treatment
plants to remove turbidity and colloidal color particles. The coagu-
lants that are commonly used in water treatment are: (a) aluminum
sulfate; (b) ferric sulfate; (c) ferrous sulfate; (d) ferric chloride;
(4) ammonia alum; and (f) sodium aluminate (20,82). In addition to
these materials, other materials known as coagulant aids are often
used. The coagulant aids most often used are: (a) clays; (b) activated
silica, and (c) polyelectrolytes.
Most of the coagulants used in water treatment as well as many other
coagulating or precipitating agents have been investigated for the treat-
ment of pulp and paper mill effluents. Foremost among the chemicals
investigated were alum, ferric sulfate, lime, and various combinations
of these (74). Fuller recently reported the investigation of a number
of salts, mineral acids, waste pickling liquor, waste from alum manufac-
ture, and waste from aluminum ore processing (47).
Coagulation and precipitation techniques are not widely used on a plant-
scale for the treatment of pulp and paper wastes. It is estimated that
approximately 5% of the industry utilizes coagulants (40) . The most
common use for coagulants is in the separation of solids from water for
clarification or reuse purposes. One unbleached kraft mill is removing
color from total effluent by the use of lime (83) .
White water reclamation for reuse is accomplished by magnesium hydroxide
precipitation by one mill having a limited fresh water supply (66). The
process utilizes excess lime to precipitate magnesium hydroxide which
flocculates suspended solids.
It is reported that polyelectrolytes are being used in the paper industry
to improve white water clarification in savealls, to improve vacuum fil-
tration of sludges, and to increase solids removal in mixed pulp and paper
mill wastes (92). Other advantages of polyelectrolytes are claimed to
be simpler handling and feeding equipment, and decreased tonnage of total
sludge (solids plus coagulant).
63
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Process Gapabilities
Although coagulation is not extensively used on a plant scale in the
pulp and paper industry, it has been widely investigated, and the capa-
bilities of the process are fairly well documented. The following para-
graphs describe some of the investigations and results which have been
reported in the literature.
It is reported that investigation of the use of guar gums, synthetic
polymers, and ferric sulfate showed that 20 to 40 mg/1 of the coagulants
was required to produce significant reductions in the color and suspended
solids (25). The maximum B.O.D. reduction reported was 23%.
i
Rebhum, et al. reported that waste water from newsprint production is
easily flocculated with alum and 30 to 40 mg/1 is necessary to obtain
a clear water (86). They also found that wastewater resulting from the
manufacture of offset grade paper could not be flocculated with alum,
sodium aluminate, lime, ferric sulfate, chlroine plus alum, chlorine
plus ferric sulfate or various cationic, anionic, and nonionic poly-
electrolytes. Further study using a synthetic colloidal system con-
taining the components of offset white water showed that the high
stability of the dispersion was due to an interaction between kaolin
and pregelatinized starch. It was found that the addition of sodium
bentonite clay caused a breakdown of the dispersion and brought about
good flocculation and clarification.
The National Council for Air and Stream Improvement has evaluated 42
polyelectrolytes as coagulants in boardmill effluent (79). The most
effective dosage was found to be 0.5 to 2.0 mg/1, and 1.0 mg/1 gave
consistently good results. Suspended solids removal increased from
88% without chemical addition to 94 to 96% with additions, producing
a supernatant suspended solids concentration of 18 to 30 mg/1. The
reported polyelectrolyte cost for treating this type waste water ranged
from $5.50 to $14 per million gallons.
Middlebrooks, et al. reported investigation of alum and six organic poly-
electrolytes, not previously used on pulp and paper mill wastes (25).
The polyelectrolytes tested included anionic, nonionic, and cationic
materials. The effectiveness of the various coagulants was judged by
removal of suspended solids, C.O.D., B.O.D., and color. It was found
that effective coagulation of the wastewater with the organic coagulants
is dependent upon the pH of the effluent. Significant reductions in
C.O.D. (54%), suspended solids (95%) and color (95%) of the kraft mill
wastes were effected by alum and the polyelectrolytes; however, less
than 20% reduction in B.O.D. was achieved.
Stemen (99) reported a unique method for the clarification of white
water with the aid of a coagulating chemical. The process involves
three steps, the first of which is the rapid mixing of white water with
a coagulating chemical and a ferromagnetic powder. In the second step
64
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the mixture is gently agitated to promote the formation of floe, and in
the third step the floe is rapidly removed (5-25 seconds) by passing the
waste over a magnetic drum. The process was tested in a 10 gpm continu-
ous pilot plant using roofing mill waste. Removal of 30 to 507o of the
B.O.D. , 90% of the settleable solids, and 60 to 70% of the total sus-
pended solids were achieved.
Several investigations of color removal by coagulation or chemical tech-
niques have been reported. Moggio (74) reported the treatment of bleach
plant wastes using lime, ferric sulfate-lime, and alum-lime combinations
in the laboratory. Using lime alone, dosages ranged from approximately
860 to 3100 ppm, resulting in B.O.D. reduction of 2 to 15% and color
reduction of 24 to 70%. Ferric sulfate-lime treatment, with the ferric
sulfate application ranging from 172 to 860 ppm and the lime dosages
from 687^to 1720 ppm, resulted in 2 to 18% B.O.D. reduction and color
reduction of 34 to 84%. Alum-lime treatment using the same levels of
dosage resulted in 0 to 18% reduction in B.O.D. and 45 to 80% color
removal.
Moggio also treated mixed bleach plant-pulp mill wastes with the lime,
ferric sulfate-lime, and alum-lime coagulants. Using various concentra-
tions, up to 25% removal of B.O.D. and 91% removal of color were achieved.
The sludges which were obtained were gelatinous in nature and difficult
to dewater. Lime had to be used with ferric sulfate to raise the pH
and prevent the formation of highly colored iron-lignin and iron-tannin
compounds. Lime was used with the alum to furnish the alkalinity neces-
sary to precipitate the aluminum compounds.
Research by the National Council for Air and Stream Improvement and by
several kraft mills further confirmed that color could be successfully
removed from combined kraft and bleach effluents by lime precipitation.
The sludge that was formed was found difficult to dewater to a dryness
suitable for reburning in the kiln. Berger and Brown (7) reported on
an attempt to alleviate the sludge problem resulting from color removal
by lime. In laboratory and bench-scale pilot plant experiments, bleach
plant caustic extract from a kraft mill was treated by application to
a precoat of hydrated lime on a rotary vacuum filter. A reaction be-
tween lime and lignin occurs at the surface of the precoat, thus form-
ing a film that can be doctored off to expose a fresh reactive surface.
Although color removal in excess of 95% was obtained, cracking of the
precoat during full pilot scale trials prevented further development
of this method.
Clarke and Davis (22) investigated color removal from a kraft mill
chlorination stage bleaching waste. Coagulants tested were AlCls,
Alo (SO/,) 7, and Fe2(S04)3. The pH of the A1C13 solution was adjusted
by saturated Ca(OH)2, whereas the PH of the A12(S04)3 was adjusted with
0 IN NaOH. Polyelectrolytes or activated silica were added in some
trials. The removal of total carbon (TC) and color in both systems
65
-------
I f\
using A I"1" was found to be at an optimum in the pH range of 5 to 6, de-
pending on salt dosage. In the A12(804)3 " NaOH system 87% of the c°l°r
and 40% of the TC were removed by a dosage of 61 mg/1 of aluminum ion.
In the A1C13 - Ca(OH)2 system 91% of the color and 42% of the TC were
removed by a dosage of 40 mg/1 of aluminum ion.
The removal of color and TC by Fe2(80^)3 is optimum in the pH range of
3.5 to 4.5 depending upon the salt dosage. At a pH of 4.5, a dosage of
112 mg/1 iron is reported to remove 85% of the color and 48% of the TC.
It was found that neither silica nor organic polyelectrolytes had any
significant effect on TC or color removal. However, both promoted floc-
culation and improved settling.
Smith and Christman (21) have also investigated color removal by coagu-
lation. They investigated the use of alum and ferric chloride without
the use of coagulant aids to treat sulfite waste, kraft waste (hardwood
and softwood) and bleach plant caustic extract from hardwood kraft
bleaching. It was found that both alum and iron coagulation of kraft
wastes resulted in a dense rapidly settling coagulum. Optimum pH was
found to 3.9 for ferric chloride and 5.3 for alum, whereas the optimum
dosage was found to be a linear function of the initial color. Optimum
pH and dosage resulted in about 9270 color removal from the kraft wastes
by alum and about 95% by ferric chloride.
Iron and alum coagulation of sulfite waste was not as effective as it
was for kraft waste. Optimum dosages of alum resulted in only 67% color
removal from sulfite pulping wastes. Trials with ferric chloride greatly
intensified the color. When iron salts are used as coagulants, some of
the color molecules react with iron to produce a highly colored complex.
Although over half the initial color causing substance is removed (based
on carbon measurement), the final effluent is more colored than the
influent.
A recent investigation (47) has utilized various chemicals including
mineral acids, various metal salts, waste pickling liquor, waste from
alum manufacture, waste from aluminum ore processing, and alum. Alum
was preferred by the investigator because of good color and B.O.D. re-
duction possible with it, and because it is present in the water treat-
ment plant and in the paper machine effluents (101). The alum precipi-
tation reduces the color of total mill effluent to a level where reuse,
except perhaps in bleached grades, appears to be possible. Reduction
in five day B.O.D. by alum precipitation was as follows: caustic bleach
effluent, 80%; strong waste effluent 35 to 80% with an average of 50%;
paper mill effluent 25%; size press and coating effluent, 50%; combined
mill effluent, 25 to 80% with an average of 35 to 40%.
Some investigations have been made on the effect of specific white
water components on the capability of coagulation. As mentioned before,
Rebhun, et al. investigated the coagulation and clarification of white
water containing pre-gelatinized starch (86). They found that pre-
gelatinized starch caused a stable colloidal dispersion that could not
66
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be broken by conventional inorganic or polymeric coagulants. Caron (18)
reported the adverse effects on coagulation due to effluents from the
coating operation. Coating room losses counteract the effectiveness of
coagulants and cause increased chemical consumption as well as erratic
results. Various authors have also reported that flocculants and reten-
tion aids were found to be inefficient in the presence of low concentra-
tions of hypochlorite-oxidized starch (109). It is also reported that
black liquor in waste has a dispersing effect on the solids, resulting
in large dosage requirements of coagulants (92).
Lime Treatment Development and Demonstration
1. Review
Interest in the utilization of chemical treatment methods such as coagu-
lation and precipitation for pulp and paper mill wastewater treatment has
generally been aimed at removal of color, which is not amenable to biolog-
ical degradation. Early laboratory investigations utilized coagulants
and adsorbents that are known to be successful in color removal from
natural waters (5).
As described in the preceding part of this section, various chemical
treatment methods have been investigated and varying degrees of color
removal were reported. Critical examination of the results showed that
in all cases the quantity of chemicals needed to achieve the desired
color removal resulted in excessive costs (73). In addition to the costs,
certain technical problems became apparent. The greatest technical prob-
lem proved to be the large volume of gelatinous, difficult-to-dewater
sludge that was formed. In addition to sludge disposal difficulties,
some of the chemicals investigated would require corrosion resistant
equipment.
Of more than 30 coagulants and adsorbents that were screened, it was
determined that hydrated lime offered the best potential as a color re-
ducing chemical for pulp and paper effluents (5). Lime was chosen for
the following reasons: (1) ready availability and low cost; (2) highly-
developed recovery techniques, using conventional recovery equipment
available at kraft mills; and (3) the possession, by kraft operating
personnel, of the necessary background and knowledge to successfully
operate lime and recovery processes.
Further laboratory and pilot plant investigation of color removal from
bleach plant caustic effluent by a minimum lime dose resulted in a gelat-
inous lime-organic sludge which could not be dewatered (73). An attempt
to overcome the poor f ilterability of the lime-organic sludge led to
development of the surface reaction technique. The surface reaction
technique and the problem of precoat cracking were discussed in the
previous section.
Further consideration of the sludge dewatering problem led to the devel-
opment of the massive lime treatment process by the National Council (63).
The massive lime treatment and the limited lime treatment processes
67
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developed by Interstate Paper Company, Continental Can Company, and
Georgia Pacific Corporation will be discussed separately, although
all of these treatments utilize lime for color removal from pulp and
paper waste water.
2. Massive Lime Treatment
The poor dewatering properties of lime-organic sludges resulting from
limited lime dosages are caused by the organic matter that reacts with
the lime to give insoluble calcium-organic compounds or that reacts
and is adsorbed on the surface of the calcium hydroxide particles.
The large lime requirements of the kraft chemical recovery operations
provide a suitable source for obtaining lime concentrations sufficiently
large so that the dewatering properties of the sludge can be enhanced
by the presence of a large amount of Ca(OH)2 particles which make the
sludge denser and more easily filtered (63).
Since most of the lime so used for color removal would still be chem-
ically available, it was suggested that the lime mud from the color re-
moval step could be used in recausticizing green liquor. The available
calcium hydroxide would be utilized for the conversion of the sodium
carbonate to sodium hydroxide, while the lignin color bodies, which are
soluble at the higher pH, would re-dissolve in the white liquor. It
was expected that the dissolved organic matter would not be detrimental
to the cooking properties of the white liquor, since it is common prac-
tice to dilute the concentrated white liquor with black liquor.
The considerations outlined in the previous paragraphs led to the devel-
opment of the massive lime process, which is diagramed in Figure 5.
Basically, the process consists of slaking and reacting the mill's total
lime requirement with the highly colored caustic stage bleach effluent,
settling and dewatering the resulting sludge, then using this sludge
to causticize green liquor (63).
Laboratory and pilot plant tests showed the proposed process to be
capable of removing 88 to 99% of the color, and 36 to 57% of the B.O.D.
Clarification and filtration of the lime-organic sludgewas reported as
good (6).
Recausticizing efficiencies in mill tests ranged from 60 to 887= compared
to normal mill practice of 67 to 8770. Organic-laden white liquor pre-
pared by this process was used to cook pine and hardwood chips in pilot-
scale digesters. The experimental pulps were tested and no significant
differences in pulp quality were found.
/
Over 90% of the calcium in the decolorized filtered effluent was recovered
in laboratory and mill pilot tests by adding C02 to convert the soluble
Ca(OH)2 to insolube CaCOs. The results indicated that commercial clari-
fiers could be used for carbonation with the stack gas from mill lime
kilns. The flocculation of the resulting CaC03 was found to be dependent
on pH; below a pH of 11.5 the CaC03 is colloidal.
68
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o\
vo
BLEACHERY EFFLUENT
WHITE LIQUOR
CLARIFIE
REUSE
WHITE
LIQUOR
TO
PULP MILL
Figure 5
Massive Lime Process for Color Removal (63)
-------
It was estimated in 1969 that the capital expenditure necessary to inte-
grate this process into an existing 500 ton per day bleached kraft mill
would be $600,000 to $700,000 (5). Operating costs, accounted for by
lime loss, soda loss, maintenance labor and materials, additional elec-
trical power for the added equipment, and additional heat requirements,
was estimated to be about 25 to 40 cents per ton of pulp production.
The massive lime process has not been used on a commercial scale but
several investigators have reported the use of it on a laboratory scale
in water renovation studies (9, 95, 6, 8). The International Paper Com-
pany at Springhill, Louisiana, was awarded a demonstration grant by the
Federal Water Pollution Control Administration for the purpose of demon'
strating the process on a commercial scale (71). The treatment plant
is in the construction phase and is scheduled for completion by Decem-
ber, 1969. The plant will handle a maximum wastewater effluent of
530 gpm and 63 tons of lime per day at calcium oxide dosages of 18,000
to 20,000 ppm. Evaluation trials are expected to last for one year.
Caustic stage waste treatment will be evaluated for six months, and
unbleached decker waste and combined waste will each be evaluated for
three months.
3. Lime Treatment at Interstate Paper Company.
The Interstate Paper Company at Riceboro, Georgia has been using lime
for color removal from unbleached kraft total mill effluent for more
than a year (83, 32). It is the first commercial color removal system
in the industry and, because of the unique nature of the process and
industry-wide interest in its application, the Federal.Water Pollution
Control Administration awarded Interstate a research and development
grant to help defray development and demonstration costs.
The 400 ton per day unbleached kraft linerboard mill was required by
the Georgia Water Quality Control Board to meet the following restrictions:
(1) Maximum waste discharge of 10 million gallons per day.
(2) Maximum effluent B.O.D. of 800 pounds per day.
(3) Maximum suspended solids of 10 ppm in the effluent.
(4) Maximum color of 30 APHA units.
The National Council massive lime process was considered but was rejected
on the basis of cost. The limited lime treatment that is being used is
illustrated in Figure 6.
Lime for the treatment system is slaked with evaporator condensate to
form a slurry of calcium hydroxide at about 15% concentration. The lime
slurry is then fed to an in-line mixer where it is mixed proportionally
with the total effluent. The thoroughly mixed effluent and lime slurry
is then sent to a flocculation tank where about 75 minutes detention time
is provided.
70
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AERATOR
t
TO RICEBORO CREEK
T
EFFLUENT OXIDATION POND
LIFT PUMPS
MILL
EFFLUENT
SUMP
IN-LINE
MIXER
SLUDGE
PUMPS
Figure 6
Line Treatment at Interstate Paper Corporation (83, 32)
-------
From the flocculation tank, the waste flews by gravity to a 200-foot
diameter clarifier. In the clarifier, floe from the color removal pro-
cess settles out along with fiber and other solids. The sludge from
the clarifier is presently being pumped to one of the two 20-acre lagoons
for storage until a lime recovery process can be developed.
The decolorized and clarified effluent from the clarifier is sent to
a stabilization basin where reduction of alkalinity is accomplished,by
natural uptake of C0£ from the atmosphere. Ninety to 180 days retention
is provided in this basin before the waste is discharged to a small
final aeration basin where it is mechanically oxygenated.
With a lime dosage of 1650 mg/1 Ca(OH>2, the color was reduced 90 to 95%
from an original 600 to 800 color units (83). The B.O.D. was reduced by
at least 90 to 957=, in the overall treatment, and practically all the
settleable solids were removed. The average lime consumption was 37 tons
per day to treat about 6.5 million gallons of effluent per day.
The construction cost of the color removal process plant was estimated
at $454,100 including plans, specifications, and construction supervision.
First year estimated costs of chemicals, power, and labor were $269,000;
After adding the cost of administration, contingencies, post-construction
studies, and reports, the total first year cost was $833,700.
The effluent from the massive lime process is fully saturated with Ca(OH)2-
Since the solubility of Ca(OH>2 in water at 90°F. is 1500 mg/1, a large
amount of lime would be lost in the effluent unless the water is carbon-
ated with C02 to recover the soluble calcium as CaCO*. The carbonation
of the effluent was studied by Interstate under Grant No. WRD-813-01-68
from the Water Pollution Control Administration but results are not yet
available.
4. Lime Treatment Proposed by Continental Can Company, Inc.
The Continental Can Company mill at Hodge, Louisiana has been awarded
a research and development grant by the Federal Water Pollution Control
Administration (41). The project, which will use limited dosages of
lime ahead of primary clarification, is entitled, "A Color Removal and
Fibrous Sludge Disposal Process for the Kraft Paper Industry".
Still in the preconstruction stage, this is to be a two year project
for the purpose of developing economical design and operational data
applicable to the kraft pulp and paper industry for effluent color re-
moval and fibrous sludge disposal (41). Figure 7 is a flowsheet of the
proposed process. This process will treat the effluent with minimum
dosages of lime ahead of the primary clarifier. The sludge from the
clarifier will then be admixed with lime mud and the mixture will be
dewatered and burned in a kiln (5).
This scheme has been tested in the laboratory as well as in a two gpm
pilot plant. The process has been shown to be feasible but a number of
technical questions relative to organic sludge burning in a lime kiln
have been raised. These questions are under consideration and are being
investigated in the laboratory.
72
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CO
PRIMARY
CIARIFIER
CAUSTICIZING LIME MUD
LIME(MUD TO KILN
TREATED
WATER
VACUUM FILTER
Figure 7
Continental Can Company, Inc. - Color Removal Process (5, 41)
-------
Continental Can found that the inclusion of paper mill wastewater that
contains fiber fines in the water being treated with lime resulted in
good flocculation and satisfactory filtration rates of the sludge (98).
The treated effluent, containing about half of the added lime, is treated
with CC>2 to recover the soluble lime as CaCC^. An addition of 200 mg/1
CaO removed 30% of the color, 300 mg/1 removed 65%, 500 mg/1 removed
86%, and 1000 mg/1 removed 91%.
5. Lime Treatment Process of Georgia Pacific Corporation
Georgia-Pacific Corporation developed a limited lime process similar
to that used by Interstate Paper Company and Continental Can Company,
Inc., for treatment of pulp mill effluents (48, 53). In this process,
covered by U. S. Patent 3,351,370, a dosage of 1000 to 3000 mg/1 of CaO
is used, and the problem with low filtration rates is overcome by inclu-
sion of wastewaters that are high in fiber content. The fiber, which
acts as a filter aid, is obtained by first passing the effluent through
log debarking and by adding bark press water to the effluent. As shown
in Figure 8, the lime treatment is carried out in a reactor-clarifier
which has a clarifier rise rate of about 1000 gal/ft^ per day. The
lime sludge is dewatered on a belt filter and fed to a lime kiln where
about 80% of the lime is recovered. Initial operation on a caustic
bleach effluent achieved 90% removal of color with a lime dosage of
2000 mg/1 of lime.
74
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CAUSTIC
EXTRACTION LIQUOR
LIME
Ui
SIAKER
LOG
DEBARKING
BARK
PRESS
-*~TO RIVER
DEWATERING FILTER
->-TO BARK BOILER
FILTRATE TO PROCESS
Figure 8
Georgia-Pacific Color Removal Process (48, 53)
PROCESS
LIME SLUDGE
FROM
CAUSTICIZING
-------
SECTION X
OTHER TREATMENT METHODS
The purpose of this section is to briefly mention some waste treatment
techniques that might possibly be used in the renovation of pulp and
paper mill wastes for reuse, particularly those processes with poten-
tial application for dissolved inorganic salt removal. This section
is not intended to present a comprehensive report on all the advanced
waste treatment techniques that have been described in the literature,
and as such, this section is a rather limited account of the selected
treatment systems mentioned.
Hyperfiltration (Reverse Osmosis)
Hyperfiltration, or reverse osmosis, has undergone intensive develop-
ment during the past ten years, primarily as a method for desalting
water (85). It is the only membrane process which can be suitably
adapted to the handling of industrial waste water (19). Several re-
cent articles describe progress that has been made in utilizing reverse
osmosis as a waste treatment process in the pulp and paper industry
(108, 81, 3).
The Pulp Manufacturers' Research League has investigated the treatment
of pulp and paper mill wastes by reverse osmosis under a project jointly
sponsored by the League and the Federal Water Pollution Control Adminis-
tration. Their extensive laboratory and pilot scale studies led to the
design and construction of a portable semi-commercial test unit capable
of processing 20,000 to 100,000 gallons daily.
Early laboratory scale investigations included treatment of pulping wash
waters from acid sulfite, neutral sulfite and kraft pulping; sulfite
bleach plant effluents from chlorine bleaching; and chlorine stage efflu-
ent and caustic wash waters from bleaching of kraft pulp; as well as
barking effluents and sulfite process evaporator condensates (3). The
study indicated the capabilities of reverse osmosis as a promising tool
for the treatment of dilute pulp wastes. It was concluded (3) that:
(1) the nature of the waste stream in terms of its content of dis-
solved inorganic salts and of small and large molecular weight
organics will materially affect operating conditions;
(2) as the concentration of the concentrate increase, the osmotic
pressure also increases and the product flow rate decreases;
(3) the minimum linear velocity required for a dilute spent sulfite
liquor increases with an increase in concentration of the concentrate;
(4) increased temperature of feed solution increases the product
water flow rate; and
(5) rejection ratios for the organic components of the solution are
high and stay high over the entire concentration range. The rejec-
tion of inorganic components is good, but the product water rates
are more likely to drop at higher concentrations.
77
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Field tests of the portable commercial-scale unit (108) have been per-
formed at three different sites. The first demonstration was conducted
on dilute pulp washing effluent from a calcium base acid sulfite mill.
The second demonstration was performed on the pulp wash water from on-
machine washing of neutral sulfite semi-chemical pulp, and the third
trial processed wash water from ammonia base acid sulfite pulping.
Table XVII summarizes the results of the trials (108).
TABLE XVII
Summary of Results of Treatment by Reverse Osmosis (108)
Pulp Influent
Wash Concentrations, g/1
Average Rejections, %
Number
of
Water Solids BOD COD Base Solids BOD COD Base OP* Samples
Calcium 11.6 3.9 12.8 0.56CA 87 74 87 96Ca 96 17
Sulfite
Ammonium 15.9 3.7 24.8 0.36NH3 93 70 94 90NH3 99 4
Sulfite
Neutral 8.7 2.5 9.8 l.ONa 95 88 95 88Na 99 12
Sulfite
*0ptical density at 281 run (a measure of the lignosulfonate content).
As can be seen by the results summarized in Table XVII, the reverse osmosis
technique certainly is worthy of further consideration. The field tests
also pointed to certain shortcomings in terms of operating know-how and
in the membranes. It was found in the first trial on calcium base sulfite
wash water that when the concentration was much greater than 7% solids,
there was a problem with CaS04 scaling. In the second demonstration
(NSSC wash water), there was evidence of fouling, and the flux rates could
not be sustained as high as had been expected. This forced a 33% reduction
in feed rate, and it was not possible to sustain a 1070 solids level even
though there were no apparent scaling problems with this particular ef-
fluent. In the third demonstration, a persistent and increasing problem
of membrane module failure occurred. Although there had been some mem- .
brane module failure in the first two trials, the problem became serious
in the third demonstration. After nine months of operation 99 of the
387 modules had failed.
Perona, et al. have reported on the purification of sulfite mill wastes
with a membrane dynamically formed from feed constituents (85). The
dynamic formation of membranes is usually accomplished by circulating,
under pressure, feeds containing additives of a colloidal nature past
membranes having pores in the micron range. The additive concentrates
at the interface and a purified solution permeates through the porous
78
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membrane. Examples of additives that form dynamic membranes are Th(IV),
Fe(III), and humic acid in aqueous solutions. Calcium-base sulfite
liquors also form self-rejecting dynamic membranes, and the use of
dynamic reverse osmosis membranes with such liquors has been studied
and reported (85).
Dynamically formed membranes have the potential advantage of lower
pressure requirements, higher production rates, and the rejection of
neutral organic solutes as well as salts (85). Because of non-repro-
ducibility of results, all the variables affecting the performance of
these membranes are not yet under control, but preliminary laboratory
studies have indicated that the process might be practical.
Cellulose acetate membranes have been used in most studies to date,
and in general it can be said that these membranes reject the high
valency ions better (13). The relative rejection of ions by cellulose
acetate-based membranes has been studied and reported. It is reported
(13) that the order of rejection of anions is as follows: citrate >
tartrate = sulfate >acetate >chloride >bromide >nitrate > iodide > thio-
cyanate; where citrate is the most highly rejected ion. For cations
the relative order of rejection is reported to be: magnesium = barium =
strontium = calcium >lithium > sodium > potassium. It should be noted
that the presence of other ions in solution can interfere with the
relative rejections. For example, if the halides are present as salts
the relative rejections are as listed above, but if they are present
as halogen acids the order is reversed (13).
Reverse osmosis with cellulose acetate membranes does not effectively
remove small water-soluble organic materials such as alcohols, alde-
hydes, low-molecular-weight organic acids, phenol, amines, and nitrites,
as well as dissolved gases such as ammonia and carbon dioxide (19, 13).
Wiley, et al. (108) point out that the B.O.D. removal efficienty is
dependent on the state of the B.O.D. forming components usually present
in the waste. If wood sugars in the waste are allowed to be broken
down by microbiological action during a prolonged processing time of
more than an hour, the resultant low molecular weight degradation
products, such as acetic acid, pass through the membranes and B.O.D.
rejection !is then quite low (108).
The cost of reverse osmosis has been estimated at about $1/1000 gallons
of waste treated. In addition to the high treatment cost, it should be
pointed out that the process not only yields a water suitable for reuse,
but also produces an effluent stream having a concentration of dissolved
substances about ten times greater than the original stream. Thus,
further processing must be applied to the concentrated stream before
any true pollution abatement can be realized.
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Ion Exchange (Desal Process)
Although ion exchange has been widely used for many years in water
treatment, it has been limited generally to waters containing less
than 500 ppm dissolved solids because regeneration costs increase
proportionately with the salinity (34). Thus, at higher dissolved
solids, ion exchange can not economically compete with membrane and
distillation processes. The DESAL process, developed by Rohm and Haas,
is a new deionization technique based upon two weak electrolyte ion
exchange resins. Some of the advantages over conventional ion exchange
processes are claimed to be:
(1) Ability to deionize brackish waters (500 to 3000 ppm
dissolved (solides) with negligible leakage.
(2) Stoichiometric amount of regenerants required for
regeneration (conventional processes required 200 to 3007»
of the Stoichiometric amount); thus regeneration costs
are significantly lower.
(3) High degree of utilization of the theoretical capacity.
The DESAL process is a cyclic deionization process using three beds of
weak electrolyte ion exchange resins. The first bed, which is the alka-
lization unit, contains a weak base anion exchange resin (Amberlite IRA-68)
in the bicarbonate form. The second bed, or dealkalization unit, con-
tains a weak acid cation exchange resin (Amberlite IRC-84); while the
third unit, which is the carbonation unit, also contains Amberlite IRA-68,
but in the free base form. Using the removal of NaCl as an illustrative
example, the reactions which ,occur are as follows:
(1) Unit 1 (Alkalization) : (R-NH)HC03 + Nacl-» (R-NH) Cl+NaHC03
(2) Unit 2 (Dealkalization): RCOOH + NaHC03-*RCOONa + C02 + H20
(3) Unit 3 (Carbonation): R-N + H20 + C02 -» (R-NH)HC03
When breakthrough occurs, the alkalization and dealkalization units
are regenerated, for example with ammonia and sulfuric acid, respectively.
Since the third unit is now in the bicarbonate form, the direction of
flow is reversed and the cycle repeated.
It is reported that successful operation of the DESAL process has been
achieved in two Italian pilot plants (34). A commercial installation
in operation in the United States since September, 1966, has satisfac-
torily functioned in reducing a brackish water from 1000 mg/1 to the
20 to 30 mg/1 range.
Thibodeaux and Berger (9) have reported on laboratory investigations of
this process to deionize partially renovated pulp and paper mill effluents.
They worked with a bleached kraft mill total effluent and caustic stage
extract which had been clarified and then treated successively by lime
and activated carbon. The samples were virtually free of all color,
B.O.D., and turbidity, but were unacceptable from the standpoint of
80
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dissolved solids. Table XVIII shows the results of the trials (9).
Of the parameters used to describe desirable process water require-
ments only the pH of the caustic effluent was out of the acceptable
range. The low pH has been attributed to laboratory operating
conditions and it is felt that under commercial conditions the system
can produce a pH near 7.0.
It has thus been substantiated that this process is technically
feasible for deionization of partially renovated waste water from
pulp and paper mills. Operating costs of this process have been
estimated at 24.0 to 27.5 e/1000 gal. (operating costs only), while
installation costs, including equipment and resin, have been estimated
at 0.8 MM dollars for a 2.0 MM gal/day plant.
TABLE XVIII
Water Quality From "DESAL" Ion Exchange Process (9)
Parameter
Desired Range,
Bleach Mill
Feed
DESAL Product
From From Total Mill
Caustic Extract Effluent (Bleached)
Color
pH
Cl, mg/1
Hardness - CaCO-:
0-5
6.8-7.3
10-150
, 5-100
5
3.7
120
25
5
7.2
150
-
mg/1
Dissolved Solids 50-250
mg/1
B.O.D.,mg/l 0-2
Turbidity, 0-5
J.T.U. "
C.O.D. 0-8
250
0
0
180
0
0
81
-------
SECTION XI
ACKNOWLEDGMENTS
The authors gratefully acknowledge the Invaluable contribution to this
study made by the many people in operations, engineering, and research
and development who made their time freely available early during the
survey which has become part of this report. The list of these silent
contributors is too long to mention specifically. It includes people
from operating companies including St. Regis Paper Co., engineering
firms, manufacturers of activated carbon, academic and federally
sponsored research, development and demonstration facilities.
The National Council of the Paper Industry for Air and Stream Improve-
ment (NCASI), particularly through H. F. Berger, Southern Regional
Engineer, lent its assistance throughout the project.
Mrs. Mary Baldwin, Technical Librarian, St. Regis Technical Center,
went far beyond the call of duty in providing fast and thorough
coverage of the available literature.
Mr. Roy L. Miller, Manager of Research and Development, St. Regis
Technical Center, and Project Director of this project, provided
valuable help based on his long association with the kraft industry.
This survey and report were prepared under his direction in Pensacola,
Florida.
The support of the project by the Environmental Protection Agency,
and the help provided by Mr. William J. Lacy and Mr. George R. Webster,
the Grant Project Officer, is acknowledged with sincere thanks.
83
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SECTION XII
REFERENCES
1. Allen, J. B., Joyce, R. s. and Kasch, R. H., "Process
Design Calculations for Adsorption from Liquids in Fixed
Beds of Granular Activated Carbon", Journal of Water
Pollution Control Federation. _3_2' No. 2, pp 217 (1967).
2. Allen, J. B., Joyce, R. S. and Sukenik, V. A., "Treat-
ment of Municipal Waste Water by Packed Activated Carbon
Beds"» Journal of Water Pollution Control Federation,
3J3, No. 5, pp 813-823 (May, 1966).
3. Ammerlaan, A. C. F., Dubey, G. A. and Wiley, A. J.
"Application of Reverse Osmosis to Processing of Spent
Liquor from the Pulp and Paper Industry", Tappi, 50,
No. 9, pp 455-460 (September, 1967).
4. Beebe, R. L. and Stevens, J. I., "Activated Carbon Sys-
tem for Waste Water Renovation", Water and Wastes Engin-
eering, 4-, No. 1, pp 43-45 (January, 1967) .
5. Berger, H. F., "Development of an Effective Technology
for Pulp and Bleaching Effluent Color Reduction", Paper
for presentation to annual meeting of members, NCASI,
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6. Berger, H. F., "Evaluating Water Reclamation Against Ris-
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No. 8, pp 79A-82A (August, 1966).
7. Berger, H. F. and Brown, R. I., "The Surface Reaction
Method for Color Removal from Kraft Bleaching Effluents",
Tappi, 42, No. 3, pp 245-248 (March, 1959).
8. Berger, H. F. and Smith, D. R., "Waste Water Renovation",
Tappi, 51, No. 10, pp 37A-39A (October, 1968).
9. Berger, H. F. and Thibodeaux, L. J., "Laboratory and
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85
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10. Bishop, D. F., et al., "Studies on Activated Carbon
Treatment", Journal of Water Pollution Control Federation,
39, No. 2, pp 188-203 (February, 1967).
11. Blosser, R. 0., "Result of NCSI Industry Survey of Invest-
ment and Cost of Effluent Treatment", Pulp and Paper Maga-
zine of Canada, 69, No. 3, pp 68-72 (February 2, 1968).
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Kraft Condensate Wastes", Tappi, 51, No. 6, pp 241-246
(June, 1968).
13. Burley, M. J., et al., "Quality Aspects of Water Supply
with Particular Reference to Conventional and Desalina-
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CE408-CE414 (December, 1968).
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the Pulp and Paper Industry", Industrial Process Design
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A
20. Chamberlin, N. S. and Keating, R. J., "Coagulation",
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(1957).
86
-------
21. chnstman, R. F. and Smith, S. E., "Coagulation of Pulp-
ing Wastes for the Removal of Color", Journal of Water
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232 (February, 1969) .
22. Clarke, J. and Davis, M. W. , Jr., "Color Removal from
Kraft Mill Bleaching Waste of the Chlorination Stage" ,
i* ^2, No. 10, pp 1923-1927 (October, 1969).
23. Clouse, J. L., "Need for Water Reuse", Tappi, 47, No. 1,
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24. Coats, J. G., Jr., "Water Conservation in the Design of
New Paper Machine Installations", Tappi, 51, No. 8,
pp 95A-98A (August, 1968) .
25. Coogan, F. J., Middlebrooks, E. J. and Phillips, W. E. ,
Jr., "Chemical Coagulation of Kraft Mill Waste Water",
Water & Sewage Works, 116, No. 3, pp IW/7-IW/9 (March, 1969) .
26. Cooke, R. E. and Mulford, J. E., "Reuse of Nash Vacuum
Pump Seal Water" , Paper presented at Sixth Tappi Air and
Water Conference, Jacksonville, Florida (April, 1969) .
27. Coughlin, R. W. , "Carbon as Adsorbent and Catalyst", I &
EC Product Research and Development, 8, No. 1, pp 12-23
(March, 1969) .
28. Gulp, G. and Slechta, A., "Plant Scale Reactivation and
Reuse of Carbon in Waste Water Reclamation" , Water &
Sewage Works, pp 425-431 (November, 1966) .
29. Gulp, R. L. and Roderick, R. E., "The Lake Tahoe Water
Reclamation Plant" , Journal of Water Pollution Control
Federation, 38, No. 2, pp 147-155 (February, 1966) .
30. Dahlstrom, D. A. and Dlouhy, P. E., "Food and Fermenta-
tion Waste Disposal", Chemical Engineering progress, 6J5,
No. 1, pp 53 (January, 1969) .
31. Davies, D. S. and Kaplan, R. A., "Activated Carbon Elim-
inates organics", Chemical Engineering Progress, £0,
No. 12, pp 46-50 (December, 1964) .
87
-------
32. Davis, C. L., Jr., "Tertiary Treatment of Kraft Mill
Effluent Including Chemical Coagulation for Color Removal
at the interstate Paper Company, Riceboro, Georgia", Paper
presented at the Tappi Sixth Water and Air Conference,
Jacksonville, Florida (April, 1969).
33. DeHaas, G. and Van Vessam, J., "Improved Recovery Tech-
niques for Kraft Volatile Organic Constituents", Presented
at A.l.Ch.E. Sixty-Sixth National Meeting, Portland, Ore-
gon (September, 1969).
34. Downing, D. G., Kunin, R. and Pollio, F. X., "Desal Pro-
cess Economic Ion Exchange System for Treating Brackish
and Acid Mine Drainage Waters and Sewage Waste Effluent",
Chemical Engineering progress Symposium Series No. 90,
64, pp 126-133 (1968).
g
35. Dryden, F. D., English, J., McDermott, G. N. and Park-
hurst, J. D., "Pomona 0.3 MGD Activated Carbon Pilot
Plant", A progress report on a project undertaken jointly
by: U. S. Department of the interior (FWPCA) and The
County Sanitation Districts of Los Angeles County (Janu-
ary, 1967) . .... t
36. Dyer, H., "St. Regis Paper Company Crowns Its New 'Queen1
of the South", Paper Trade Journal, pp 59-78 (November 18,
1968).
37. Edde, H., "A Manual of Practice for Biological Waste
Treatment in the Pulp and Paper Industry", Technical Bulle-
tin, No. 214, National Council for Air and Stream Improve-
ment (April, 1968).
38. Edde, H., "Settleable Solids Removal practices in the
Pulp and Paper Industry", Technical Bulletin, No. 178,
National Council for Air and Stream Improvement (Novem-
ber, 1964).
39. "End All Kraft Pollution and Save Money", Canadian Pulp
and Paper industry, pp 73-75 (November, 1967).
40. Federal Water Pollution Control Administration, The Cost
of Clean Water, Volume III, U. S. Department of the In-
terior, Washington, D. C. (1967). s
88
-------
41. Federal Water Pollution Control Administration, "Research,
Development, and Demonstration Projects, Volume I" (Janu-
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42. Federal Water Pollution Control Administration, "Study
of Powdered Carbons for Waste Water Treatment and Methods
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43. Fornwalt, H. J., Helbig, w. A. and Scheffler, G. H.,
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44. Fornwalt, H. J. and Hutchins, R. A., "Purifying Liquids
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pp 179-184 (April 11, 1968).
45. Fornwalt, H. J. and Hutchins, R. A.,"Purifying Liquids
with Activated Carbon", Chemical Engineering, 73, No. 10,
pp'155-160 (May 9, 1966).
46. Fuchs, R. E., "Decolorization of Pulp Mill Bleaching Ef-
fluents Using Activated Carbon", Technical Bulletin,
NO; 181, National Council for Air and Stream improvement
(May, 1965).
47. . Fuller, R., Paper presented at NCASI Meeing, Atlanta,
Georgia (August 13, 1969).
48. "G-P Develops Lime Recycling System to Effect Removal of
Effluent Color", Pulp and Paper, 44, No. 12, pp 88 (1970).
49. Gehm, H. E., "Pulp and Paper", Chapter 20, Industrial
Waste Water Control, Gurnham, C. F., Ed., Academic Press,
Inc., New York, New York (1965).
50. Gehm, H. W. and Gove, G. W., "Kraft Mill Waste Treat-
ment in the United States A Status Report", Technical
Bulletin, No. 221, National Council for Air and Stream
improvement (December, 1968).
51. Gellman, I., "Aerated Stabilization Basin Treatment of
Mill Effluents", Tappi, 48' No- 6' PP 106A-110A (June,
1965) .
89
-------
52. Gilmont, P. L., "Water Requirements for Pulp Bleach-
ing, Survey of Mill Practice in the United States",
Tappi, 50, No. 10, pp 99A-102A (October, 1967).
53. Gould, M., "Physical-Chemical Treatment of Pulp Mill
Wastes", Twenty-Fifth Annual Purdue Industrial Waste
Conference, Purdue University (May 7, 1970).
54. Gurnham, C. F., Principles of Industrial Waste Treat-
ment, John Wiley & Sons, Inc., New York, New York,
pp 325 (1955).
55. Hager, D. G., "Activated Carbon Used for Large Scale
Water Treatment", Environmental Science and Tech-
nology, _!, No. 4, pp 287-291 (April, 1967) .
56. Hardenbergh, W. A. and Rodie, E. R., Water Supply
and Waste Disposal, International Textbook Company,
Scranton, Pennsylvania (1961).
57. Harris, G., "Liquid Purification with Granular Acti-
vated Carbon", Chemical and process Engineering, 47,
No. 8, pp 45-49.
58. Hawkins, G., "A Ten-Year Program of Fiber Loss Re-
duction and Water Reuse", Tappi, 47, No. 3, pp 158A-
160A (March, 1964).
«'. j "t
« ^
59. Haynes, D. C., "Water Reuse, A Survey of the Pulp
and Paper Industry", Tappi, 49, No. 9, pp 51A-52A
(September, 1966).
60. Helbig,' W. A., "Adsorption from Solution by Activa-
ted Carbon", Colloid Chemistry Theoretical and Ap-
plied, Volume VI, Alexander, J., Ed., Reinhold Pub-
lishing Co., New York, pp 814-839 (1946).
61. Helbig, W. A., "A Symposium on Activated Carbon",
Atlas Chemical Industries, Inc. (1968).
62. Henderson, A. D. and Shotwell, J. S. G., "Water Con-
sumption in the Pulp and Paper Industry", Water Tech-
nology in the Pulp and Paper Industry, Tappi Mono-
graph Series, No. 18, Tappi, New York, New York (1957).
90
-------
63. Herbet, A. j.f »A Process for Removal of Color From
Bleached Kraft Effluents Through Modification of the
Chemical Recovery System", Technical Bulletin, No.157,
National Council for Air and Stream Improvement (June,
1962), u. S. Patent No, 3,120,454 (1964).
64. Howard, T. E. and Walden, C. c., "Pollution and Tox-
icity Characteristics of Kraft Pulp Mill Effluents",
Tappi, 48, No. 3, pp 136-141 (March, 1965).
65. Hunt, R. A., "Decolorization of Semi-Chemical Bleach-
ing Wastes by Adsorption", M.S. Thesis, Purdue Uni-
versity (January, 1962) .
66. LeCompte, A. R., "Water Reclamation by Magnesium Hy-
droxide Precipitation", American Paper Industry,
pp 33-36 (March, 1967).
67. Libby, C. E., Ed., "Paper", Volume II, Pulp and Paper
Science and Technology, McGraw-Hill Book Company, New
York, New York (1962).
f - ,;
68. Lueck, B. F., "Condensate Waste Studies Treatment of
Sulfite Condensate Wastes with Activated Carbon", Pulp
Manufacturers Research League, Inc., Progress Report Nos.
4, 5, 6, 7, 8, 10; Project 815-834.
69. Marks, R. H., "Waste Water Treatment A Special Report",
Power (June, 1967).
70. Masse, A. N., "Removal of Organics by Activated Carbon",
Unpublished Report, U. S. Department of the Interior,
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nati,, Ohio (August, 1968).
71. "Massive Color Removal System Being Constructed by Inter-
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facturers, 32, No. 4, pp 26-30 (April 10, 1969),
72. McGlasson, W. G., "Treatment of Pulp Mill Effluents with
Activated Carbon", Technical Bulletin, No. 199, National
Council for Air and Stream Improvement.
91
-------
73. Moggio, W. A., "Color Removal from Kraft Mill Effluent",
Tappi, 38, No. 9, pp 564-567 (September, 1955).
74. Moggio, W. A., "Experimental Chemical Treatments for
Kraft Mill Wastes", Tappi, 35, No. 4, pp 150A-151A
(April, 1952).
75. Moore, J. G., Jr., Water Quality Criteria, Federal Water
Pollution Control Administration, Washington, D. C.,
pp 188 (April, 1968).
76. Morgan, 0. P., "Extended Aeration Treatment Reduces
High BOD of Pulp Mill Effluent", Pulp and Paper, pp 110-
114 (February, 1969).
j
77. Morris, J. C. and Weber, W. J., Jr., "Adsorption of Bio-
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U. S. Department of Health, Education and Welfare (May,
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78. Morris, J. C. and Weber, W. J., Jr., "Preliminary Ap-
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\
80. National council for Air and Stream Improvement, "Survey
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Bulletin, No. 97 (August, 1957). , ,-
pr -,
81. Nelson, W. R., "Reverse Osmosis Proves Highly Effective",
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'i
82. Nordell, E., Water Treatment for industrial and Other
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83. Olin, J. H., "How Interstate Paper Lowers Color and BOD
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92
-------
84. Palladino, A. j.f "Reducing Effluents for Secondary
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i
85. Perona, J. j.f et al., "Hyperfiltration. Processing of
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-------
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f
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94
-------
106. Whisler, R. c., "A Tight White Water System Its Opera-
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QC au.S. GOVERNMENT PRINTING OFFICE: 1973 514-153/193 1-3
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Kraft Pulping Effluent Treatment & Reuse - State of the Art
W. G. Timpe, E. Lang and R. L. Miller
9. Organization
St. Regis Paper Company
Research and Development Center
Pensacola, Florida
BBS*!*.. ^sSaSss,. . _»«, .* -1'
10. Project Jfo
12040EJU
11 Contract/Grant If o.
12040EJU
"jmt*
« Type- «^ «*.*"££
Penod 4'overed *5ffi vl
Environmental Protection Agency report
number, EPA-R2-73-164, February 1973;
16. A bstract
This report presents a survey of the literature and other sources on present practices
and advanced methods of handling and treatment of pulp and paper mill effluents, with
particular emphasis on the kraft process, and the use of activated carbon and lime
treatment as advanced methods of treatment. The survey was made as a first step of a
development program aimed at maximum water reuse in kraft jmlp and paper mills based
on effluent treatment using activated carbon.
The results of the survey include information on activated carbon and its applications
in treatment of pulp and paper mill effluents as well as in treatment of municipal
water supplies and effluents. Information is presented on lime treatment of kraft
mill effluent and on other advanced treatment methods. It also covers the subjects
of in-plant water reuse, effluent collection systems, solids removal, and-biological
oxidation.
17a. Descriptors
Waste Water Treatment, Industrial Wastes, Pulp Waste, Activated Carbon and Water Reuse
17b. Identifiers
17c.. COWRR Field & Group
IS. A va i7a bility
21.
22. Price '*''»
, >f
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. 2O24O
W. G. Timpe
Institution St. Regis Paper Company
Wf?SiC 102 (REV. JUNE 197O
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