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ChE 2G03
Wastewater Treatment in the Pulp and Paper Industry
Name: Rexem Lally Pinzon
Student Number: 1302834
Word Count: 1892 words
November 3, 2014

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Abstract
Wastewater treatment is essential to pulp and paper (P&P) industry because it contributes
a significant amount of pollutants in the environment and is one of the heaviest users of water in
the world. Wastewater treatments commonly used today involve two to three processes, namely
primary, secondary, or tertiary treatment. The common goal of these treatments is to reduce
wastewater’s toxicity by removing suspended solids and chemical compounds. Because of these
wastewater treatments, pulp and paper industry has reduced 80-90% of its waste products. In
addition, since P&P industry consumes a large amount of freshwater, wastewater management that
pulp and paper industry can use to reuse and recycle wastewater is also discussed. Hence, watering
salt-tolerant crops and using two-step nanofiltration process are presented as solutions to reduce
high production of wastewater and high consumption of water.

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Table of Contents
Abstract....................................................................................................................................................... ii
1. Introduction......................................................................................................................................... 1
2. Process Description............................................................................................................................. 1
2.1. Pulping........................................................................................................................................ 2
2.2. Papermaking ............................................................................................................................... 3
3. Wastewater and its Environmental Effect ........................................................................................... 3
3.1. Characteristics of Wastewater..................................................................................................... 3
3.2. Environmental Effect .................................................................................................................. 5
4. Wastewater Treatment Process ........................................................................................................... 5
4.1. Primary Treatment ...................................................................................................................... 5
4.2. Secondary Treatment .................................................................................................................. 7
4.3. Tertiary Treatment ...................................................................................................................... 8
5. The Future of Wastewater Management ............................................................................................. 8
5.1. Achieving Zero Discharge .......................................................................................................... 9
5.2. Nanofiltration Process................................................................................................................. 9
6. Conclusion and Discussions.............................................................................................................. 10
References ................................................................................................................................................ 11

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Table of Figures
Figure 1. Specific water usage. Adapted from [4]....................................................................................... 2
Figure 2. Wastewater compounds at various processing units. ................................................................... 4
Figure 3. Generalized schematic diagram of the plant for treatment of paper mill effluent. Reproduced
from [4]....................................................................................................................................................... 6
Figure 4. Performance of a full-scale anaerobic digester treating paper mill wastewater. Reproduced from
[4]. .............................................................................................................................................................. 8
Table of Tables
Table 1. The performance of physicochemical treatment processes. Reproduced from [1]. ....................... 9

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1. Introduction
P&P industry is ranked third in the world in terms of water usage making wastewater
treatment essential. Pulping and papermaking, the two main processes of P&P making, use a
significantly large amount of water. However, the usage of water varies from different types of
paper products produced as shown in Figure 1. Between 20 000 and 60 000 gallons of water per
ton of product is used in the P&P industry, and approximately 85% of this is used as process water
[1]. As a result, large quantities of contaminated water are produced which led to a lot of issues
regarding wastewater treatment. Fortunately, wastewater treatment solutions have been made
through making use of advanced technologies and strategic techniques for reusing water and
recovering resources from P&P making. These include primary treatment which involves
removing suspended solid and small amount of organic compounds; secondary (biological)
treatment which is responsible for decreasing effluent toxicity by removing organic matter; or the
tertiary which further treat the effluent to higher qualities. Because of these treatments, P&P
industry has reduced 80-90% of its waste products [2]. Moreover, this paper discusses the different
processes involved P&P making, characteristics and effect of its wastewater, wastewater
treatments commonly used in the industry, as well as the future of wastewater management.
2. Process Description
P&P making involves two main processes, namely pulping and papermaking. These
processes convert raw materials, such as wood, recycled paper, agricultural residues, and other
substances that contain cellulose fibers, to all different kinds of paper.

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Figure 1. Specific water usage (mean values). Adapted from [4].
2.1. Pulping
Pulping is the stage that provides the processed material of the P&P making. It is also
where most of the waste products and pollutants are produced. About 75-225 m3
/ ton of product
of wastewater is generated in this process [3]. Pulping is carried out after handling and preparing
raw materials. In this stage, prepared raw materials turn into cellulose-rich pulp through removing
their lignin and hemicellulose [4]. Furthermore, there are various methods that can carry out
pulping, particularly mechanical, chemical, and chemo-mechanical pulping.
 Mechanical pulping - fibers from raw materials are extracted and suspended in water [5].
This type of pulping yields 90-95% but produces low quality, high colored pulp [1].
 Chemical pulping - combines chemicals in aqueous solution, high temperature and pressure
to break down raw materials and produce pulp with a yield of about 40-50% [1].
0 10 20 30 40 50 60 70
Specialty
Tissue
Printing and writing
Newsprint
Corrugated
Packaging and board
Specific use (m3/tonne)

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 Chemo-mechanical pulping - a method in which chemicals are used to soften raw materials
and then use mechanical treatment to separate fibers. This type of pulping yields 85-90%
and has a better quality of pulp compared to mechanical [1].
2.2. Papermaking
Papermaking is the process in which paper products are finally produced. It is not as
elaborate as pulping since the only thing that is left to do is to transform the pulp into paper. The
pulp that is produced in the previous process is diluted with water, china clay, chalk and other
substances such as optical brighteners and polyvinyl alcohol [5]. Then, this treated pulp undergoes
through a pumping head box that evenly distributes the pulp into the machine and passes through
a continuous wire to form wet paper sheet. Finally, this wet paper undergoes through a vacuum
drier where it is dried and press to produce a dry one.
3. Wastewater and its Environmental Effect
3.1. Characteristics of Wastewater
The characteristics of wastewater depend on the raw materials used and the types of process
technology applied. Since wood is the primary raw material used in P&P making, compounds such
as lignin, carbohydrates and extractives are produced [1]. These compounds are hard to biodegrade
making them parts of the effluent. Moreover, different processing units in P&P making produces
different types of wastewater and other waste products because each one of them has a unique
function. In general, about 220-320 m3
of wastewater per ton of paper are produced [6]. Most
pollutants and compounds from the said wastewater come from pulping because it is a process in
which most water is used. Toxic chemicals such as resin acids, diterpene alcohols, fatty acids, and
others are mostly produced in the digester house which is a part of the pulping process. Figure 2

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shows the different processing units and their respective pollutants and compounds from
wastewater.
Figure 2. Wastewater compounds at various processing units.
Wood Handling
and Preparation
Papermaking
Pulping
Digester house
Washing
Bleaching
-Suspended solids
-Dirt -Color -Fibers
-Biochemical Oxygen Demand (BOD)
-Resins -BOD
-Color -fatty acids
-Volatile Organic Compounds (VOC)
-Adsorbable Organohalogens (AOX)
-Chemical Oxygen Demand (COD)
-High pH -COD -BOD
-Suspended solids
-Dissolved lignin -COD
-Carbohydrate -AOX
-Chlorinated Compounds
-VOCs
-Organic compounds
-Color -COD
-Acetone
PROCESSING UNIT WASTEWATER COMPOUNDS

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3.2. Environmental Effect
Pollutants and other toxic compounds from the wastewater affect the environment
significantly, especially in water. Fishes and other aquatic animals that were exposed in P&P
effluent suffered from diseases and abnormalities such as respiratory stress, liver damage, mixed
function oxygenase activity, genotoxicity, and mutagenicity [1]. These pollutants are dangerous
not only to aquatic animals but to human beings as well. In India, people that were exposed to P&P
effluent experienced negative health effects such as diarrhea, vomiting, headaches and eye
irritation [1]. Thus, it is important that the wastewater should be treated so that the discharge from
P&P does not affect the environment as well as the living organisms.
4. Wastewater Treatment Process
Over the years, toxic chemicals and other harmful compounds in wastewater have been
continuously decreasing because of the advancement in technology and recent developments in
pulp and paper wastewater treatment. Primary and secondary treatments are the main treatments
used in P&P industry today. Tertiary treatment, however, is for further processing and may also
become necessary for legislative purposes. Figure 3 shows the generalized schematic diagram of
the plant for wastewater treatment.
4.1. Primary Treatment
Suspended solids, such as bark particles, fillers, fibers, coating materials and some of the
organic compounds from the raw materials used are removed in this treatment. Sedimentation and
flotation are mainly used in this process. Sedimentation is carried out by lowering the velocity of
the water until the suspended particles settle out of the water due to gravitational force. Flotation
process, on the other hand, is carried out after sedimentation. Unsettled lightweight, small particles

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are attached to bubbles causing them to rise to the surface where they are removed from the top of
the flotation unit. About 80% of suspended solid is removed using sedimentation, and 65-95% of
total suspended solids (TSS) is removed using air flotation [1].
Figure 3. Generalized schematic diagram of the plant for treatment of
paper mill effluent. Reproduced from [4].

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4.2. Secondary Treatment
Secondary (biological) treatment mainly removes organic compounds (BOD, COD, VOC,
etc.) and decreases the toxicity of the effluent by using enzymes, bacteria, algae and fungi. In this
treatment, the microorganisms digest the organic compounds to remove them from the wastewater.
Activated sludge process (aerobic treatment) and anaerobic treatment are most commonly used
in secondary treatment.
 Activated Sludge Process – a process that involves oxygen and suspended growth of
microorganisms to remove organic compounds, such as BOD, COD, AOX, chlorinated
phenolics, etc. This process is widely used in wastewater treatment and is also known for
its flexibility since it can be tailored to meet specific needs. However, this process requires
a constant energy supply and frequent system monitoring since bulking may occur which
can result in excessive concentrations of solids in the final discharge.
 Anaerobic Treatment – utilizes anaerobic bacteria to remove organic compounds, most
especially COD. The COD removal efficiency of this treatment is about 80% as shown in
Figure 4. Moreover, it lowers sludge production, chemical and energy consumption, and
only requires smaller land because anaerobic treatment uses smaller reactors [7].

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4.3. Tertiary Treatment
Tertiary treatment is the next treatment process after secondary in which remaining
inorganic compounds and substances are removed. This treatment may be expensive, but this final
treatment stage raise the effluent quality that can be almost as good as drinking-water. This
treatment can be carried out by various physicochemical methods such as coagulation, adsorption,
oxidation, ozonation, and membrane filtration. These methods remove color, Total Organic
Carbon (TOC), COD, AOX, etc. as shown in Table 1.
5. The Future of Wastewater Management
Many studies are being conducted to improve efficiency on pulp and paper process without
negatively affecting the environment. Thus, researchers are focusing more on biological
applications to P&P process and achieving zero discharge.
Figure 4. Performance of a full-scale anaerobic digester treating paper mill
wastewater. ●, Effluent COD; ▲, Removal efficiency (%). Reproduced
from [4].

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5.1. Achieving Zero Discharge
Achieving zero discharge from P&P making seems impossible but believe it or not, studies
have been conducted to prove that it is possible. To address socio-environmental concern about
mill effluents, Singh, Ladwani, Deshbhratar and Ramteke conducted a study on the impact of paper
mill wastewater on soil properties and crop yield. The main idea of this study is to recycle and
reuse mill effluents that may benefit not only P&P industry, but others as well. Based on their
result, treated effluents can be used for irrigation of salt-tolerant crops with special farm
management practices [6]. In relation to this, another study was conducted by Asghar and Mushtaq
having the same positive result.
5.2. Nanofiltration Process
Since P&P making requires high consumption of water, several P&P mills are facing
problems regarding water scarcity. Hence, consumption of freshwater and production of effluents
should be reduced. Two-step nanofiltration process was investigated to solve the water scarcity
Table 1. The performance of physicochemical treatment processes. Reproduced from [1].

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problem. According to Gönder, Arayici and Barlas, this process can convert wastewater from the
secondary treatment to process water. The first step of this process is the conditioning of the pH,
temperature, transmembrane pressure and volume reduction factor on the membrane fouling. This
is then followed by the second step which is the use of FM NP030 membrane for a better permeate
quality that is almost as good as actual process water [8]. Based on their result, two-step
nanofiltration process is a success for recycling wastewater.
6. Conclusion and Discussions
This paper has shown the mechanism behind P&P making and proved that wastewater
treatment is a very crucial aspect on pulp and paper industry. Two main treatments are commonly
used in P&P sites today, namely primary and secondary treatment. Primary treatment is mainly for
removing large suspended solids while secondary treatment is for removing organic compounds
and substances. Tertiary treatment is also effective and is used in some P&P sites, but since it may
cost large amount of money, some sites cannot afford this type of treatment. In my opinion, instead
of using tertiary treatment, P&P industry and farmers of salt-tolerant crops should partner up so
that P&P mill effluents is reused and recycled. Hence, not only that they will benefit from it, but
the environment as well because P&P sites will be achieving almost zero discharge. In addition,
two-step nanofiltration process can also be a good solution to the water scarcity problem. Through
using this process, not only do they reduce their consumption of freshwater, but they will also
reduce their production of effluent. Thus, P&P sites should consider using the two-step
nanofiltration process because it will benefit both the industry and the environment.

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References
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[2] M. N. Asghar, S. Khan, and S. Mushtaq, “Management of treated pulp and paper mill effluent to
achieve zero discharge.,” J. Environ. Manage., vol. 88, no. 4, pp. 1285–99, Oct. 2008.
[3] R. Sridhar, V. Sivakumar, V. Prince Immanuel, and J. Prakash Maran, “Treatment of pulp and
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[4] M. Ali and T. Sreekrishnan, “Aquatic toxicity from pulp and paper mill effluents: a review,” Adv.
Environ. Res., vol. 5, no. 2, pp. 175–196, May 2001.
[5] G. Thompson, J. Swain, M. Kay, and C. F. Forster, “The treatment of pulp and paper mill
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[6] P. K. Singh, K. Ladwani, P. B. Deshbhratar, and D. S. Ramteke, “Impact of paper mill wastewater
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pp. 599–606, 2013.
[7] T. Meyer and E. a Edwards, “Anaerobic digestion of pulp and paper mill wastewater and sludge.,”
Water Res., vol. 65, pp. 321–49, Nov. 2014.
[8] Z. Beril Gönder, S. Arayici, and H. Barlas, “Advanced treatment of pulp and paper mill
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Purif. Technol., vol. 76, no. 3, pp. 292–302, Jan. 2011.