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Water Usage in the Pulp and Paper Processes
CHAPTE R 4
Water Usage in the Pulp and Paper Processes Water is one of the key components of papermaking. Without water, the production of paper is unthinkable. The pulp and paper industry is a water-intensive consumer (Buyukkamaci and Koken, 2010); consequently, several drivers impulse this sector to reduce its water consumption. Among others, water stress, legal requirements, environmental concerns, and, indeed, the potential benefits are the main ones. Water scarcity is, however, more important in countries that suffer from water shortages. The industry uses large volumes of water as a fiber carrier and as a solvent. Much water is lost to evaporation during production, between 0.5 and 2 m3/ton, resulting in high demand for freshwater. The industry has made steady progress over the past 3 decades in reducing its relative water footprint, dropping from 300 m3/ton to about 50 m3/ton, a reduction of 80%. A growing market for equipment and services in pulp and paper water and wastewater treatment, especially in disinfection and filtration systems, is seen by Frost and Sullivan (Bredenberg, 2013). According to the group’s study, the global market should grow at 6.0% compound annual growth rate from $984 million in 2012 to about $1.57 billion in 2020. North America and Europe each represent about one-third of the market and the Asia–Pacific region about one-quarter, with high growth expected. Most of the water used in the paper production life cycle is used during the production process, basically for conveyance of the fibers when they are extracted from the logs as wood chips, and through the pulping process. During the last decades, increased attention has been given to the overall efficiency of paper mills and also to the environmental footprint of the industry. Water management has become a very important factor in the industry. Reasons include the following: • limited water resources • need for cost savings • environmental impacts • legislation The industry has seen an increase in energy costs, environmental legislation tightening all around the world, and shortages of water resources becoming a growing concern in different parts of the world. These trends have led to a reduction in the use of freshwater in the paper industry and an increase in water recycling. Expanding water recycling by adding treatment units in a paper mill appears to be a relatively simple task, but it is not that easy in reality. Addition of water recycling processes, and at the same time, handling possible risks and Pulp and Paper Industry. http://dx.doi.org/10.1016/B978-0-12-811099-7.00004-6 Copyright © 2017 Elsevier Inc. All rights reserved.
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38 Chapter 4 pitfalls, needs an overall understanding of the different types of processes, chemistry, and conditions, not only in the paper industry in general, but also of the particular mill in question. A particular risk in water recycling is that certain impurities and substances will concentrate in process waters, causing serious problems in processes, equipment, and product quality. Still, with the correct technology and knowhow, many opportunities exist for water recycling at paper mills. A high level of water consumption, in turn, results in high consumption of energy and also generation of a high volume of effluent, as 90% of the water intake is discharged as effluent in pulp and the papermaking process (CPPRI, 2008). Because of this, high levels of effluent require adequate effluent treatment plants (ETPs) for treatment to stipulated discharge norms. In India also, since the mills have slowly increased the production capacity without a corresponding increase in effluent handling capacity, most of the ETPs are overloaded and most of the mills find difficulty in treating their effluent to stipulated discharge norms (APIC, 2003). Water consumption varies from >5 m3/ton up to >100 m3/ton between mills. This actually depends on production, raw materials, and technologies used in pulp, papermaking, and related processes (Olli et al., 2012). In tissue production, water consumption is higher than in many other grades like newsprint or fine paper and usually ranges from 8 to 100 m3/ton. This is because tissue products have very high quality standards in brightness, texture, and also odor. This leads to washings and higher demand of freshwater. Tissue mills using recycled paper as raw material have a lot of challenges in handling quality problems, and therefore, water management is critical. By using suitable technology, freshwater can be replaced with recycled process water in many production points, even in the case of tissue mills, without compromising quality or runnability. Usual points where freshwater can be replaced are, for example, different dilution waters in pulping and stock preparation, and shower and washing waters in the machine area. Over the years, the mills abroad have been successful in reducing the consumption of water in the papermaking process by adoption of modern fiber line technologies and also methods for increased recycling, resulting in minimal discharge of effluent. However, this has not been so in the case of Indian pulp and paper mills. The water consumption in the Indian paper industry is significantly higher as a result, compared to the developed countries (CPPRI, 2008; Table 4.1). In pulp and paper production, reduction in the use of water consumption implies a strategic management. It is aimed at water conservation and the reuse and recycling of used process waters in an attempt to reduce both water consumption and effluent discharge (Gavrilescu et al., 2008; Table 4.2). More restrictive legislation has increased efforts toward better preservation of water and effluent load reduction in the manufacturing process. The work during the last decades has been focused on the identification of the most economically effective processes, the development of wastewater treatment, and the optimization of the
Water Usage in the Pulp and Paper Processes 39 Table 4.1: Water consumption in the mills with best available techniques (BAT). Water Consumption, m3/ton Paper Pulping Process Kraft Rayon grade Recycled fiber End product Newsprint Writing and printing Industrial and packaging
Mills with BAT 42 36 8
Indian mills 110–220 130–180 25–75
11 m3/ton paper 38 m3/ton paper 15 m3/ton paper
90–160 100–220 60–150
Based on CPPRI, 2008. Water Conservation in Pulp and Paper Industry, www.dcpulppaper.org/gifs/report17.pdf.
Table 4.2: Total water management. Conservation Reduction of water consumption, improving operation of existing equipment and process Reuse Reuse of water with no change in quality Recycled Reuse of water in process after improving its quality Reclaimed Reuse of mill effluent after improving its quality Zero effluent Increased investment Based on Gavrilescu, M., Teodosiu, C., Gavrilescu, D., Lupu, L., 2008. Strategies and practices for sustainable use of water in industrial papermaking processes. Engineering in Life Sciences 8 (2), 99–124.
process design (Cuevas, 2014). In order to reduce the water consumption, two basic strategies have been used. These are: • modification of the individual processes and its units to reduce the inherent water requirement; and • water reuse; looking for opportunities to reuse the outlet stream of one operation process as the inlet stream of the same operation process or of another one. In this way, more than 40% water intake reduction has been obtained since 1990 (CEPI, 2013). In spite of all the efforts carried out to reduce water consumption, this sector is still water-intensive. According to Ordoñez et al. (2009), water is required for following purpose: • dispersion and transport of the fibrous raw materials and additives throughout the different stages of the production process • as heat exchange fluid • as sealant in vacuum systems • as steam • as lubricant
40 Chapter 4 In modern mills where best available technologies are applied, the average water use range is from 3 to 10 m3/ton, depending on the product quality, although some paper products, such as tissue, have a higher range. 1.5- 1.5-3 m3/ton is required for board products in closed systems, 5–15 m3/ton for newsprint, 15–20 m3 for tissue, and more than 20 m3/ton for high-quality printing grades and speciality papers (IPPC, 2013). Although the closure of circuits has several advantages, such as less water consumption, less freshwater pretreatment, decreased fiber and filler losses, lower volume to effluent treatment, and reduced energy demand, this implies the accumulation of pollutants in the process water. There is actually a break point in the accumulation of contaminants, which limits the closure of the water circuits (Miranda et al., 2009). Contaminants must be removed before further closing the water circuit for avoiding the following problems: • corrosion • clogging of equipment • scaling • slime forming in the process or in the final product In order to reuse process water, internal treatments are installed for removing these substances (CAR/PL, 2005). The major advantage of inline treatment is that only a part of the chemical oxygen demand (COD) load from the purge of white water requires being eliminated to keep the level of contaminants in the circuit low, making the treatment economically attractive (IPPC, 2013). Several processes are being used to treat the internal streams and the final effluents in the pulp and paper industry. Every paper mill has a distinctive water profile because of its location and the origins of its water, the destination of its effluent, and the origin of its fibrous and nonfibrous raw materials being used. The paper industry is continuously working on reducing its effect on water consumption. In the 1970s, producing 1 ton of pulp required as much as 250 m3 of water, and now, it only takes 5–50 m3 (Kemira, 2014; www.cepi.org). The last decade saw water consumption of paper machines being reduced by one-third as a result of more efficient water circulation. According to the Confederation of European Paper Industries (CEPI, 2011), in 2008, the pulp and paper industry took out approximately 4000 million m3 of water from surface and groundwater sources, of which about 92% of water was returned back to surface water supplies. Water used for paper production is usually circulated within the manufacturing system. The water that is discharged is purified in high-end wastewater treatment facilities. In actuality, water coming out of a paper production mill is cleaner than when it goes in. The paper industry has actually become an active partner in the development of water stewardship and water footprinting. It is developing comprehensive water reporting guidelines for the sector, and in recent years, the industry has been an active partner in the development of a globally harmonized understanding of water stewardship.
Water Usage in the Pulp and Paper Processes 41 Water consumption by the pulp and paper industry is affected by production conditions, such as grade changes, equipment used, and water management practices (Bajpai, 2008). Quantifying the consumption of freshwater in a mill is often the first step in taking an analytical approach to saving water. Identifying all the instances when water is discharged at various stages of production can lead to savings in both raw materials and energy. In practice, half of the total flow of effluent from pulp and paper production comes from the process itself and contains most of the dissolved solids. The remainder is flushing, leakages, vacuum system seal water, and cooling water, fractions that are all roughly uncontaminated with dissolved substances from the process. The characteristics of the waste liquid to be treated depend on the type of wood and the process, the technology used and the selected management practices, raw material and the process involved, and the amount of water that the mill is able to circulate. Untreated waste fluids can have high biochemical oxygen demand, COD, suspended solids that are mainly fibers, fatty acids, tannins, resin acids, lignin, and its derivatives (Covinich et al., 2014). Some of them are naturally occurring pollutants and others are xenobiotics, which are produced during the pulp and paper manufacturing process (Area et al., 1998; Ali and Sreekrishnan, 2001). Some substances are recalcitrant to biological degradation and toxic to aquatic species. Some bleaching processes even produce bioaccumulative compounds (Bajpai, 2012; Karrasch et al., 2006; Kovacs et al., 2002). The wastewaters of high yield pulping processes are characterized by their suspended solids content, which includes the following: • bark particles; • organic substances; • chromophoric compounds, mainly labile extractives and lignin fragments; and • inorganic compounds: nitrogen and phosphorus, as result of the effluent treatment and salts. Semichemical processes contain lignosulfonates derived from lignin in addition to the previous. The kraft process wastewaters are characterized by their content of solids, including bark particles, dissolved organics, and chromophoric compounds, mainly derived from lignin. If kraft pulps are bleached with chlorine compounds, they produce organochlorine compounds (dioxins and furans) (IPPC, 2001; Bajpai, 2012). The National Council for Air and Stream Improvements (US) conducted a survey in 1989. In the US, a reduction in water use between 1985 and 1988 of 7–8% and a reduction between 1975 and 1988 of 27–34% were reported by Miner and Unwin (1991). In 1988, about 16,500– 17,500 gallons of water to produce a ton of paper or board (68–73 m3/ton) in the US was required. This is about 70% less than was required to produce a ton of paper in 1959. Reductions in wastewater treatment are of the same magnitude as that reported for water use. Untreated wastewater flows were reduced by around 8% between 1985 and 1988, whereas the reductions obtained between 1975 and 1988 were 26–29%. In 1988, wastewater going for treatment was 63–69 m3/ton of paper. Biological oxygen demand (BOD) and total suspended solids loads were reduced by about 10% between 1975 and 1988. The amount of BOD discharged in final
42 Chapter 4 Table 4.3: Average specific water consumption in large wood-based pulp and paper mills. United States Europe Australia Canada Finland Spain
64 40 28.7 67 40 30
APIC, 2003. APIC Public Eco-friendly Report 2003; Dudley N., Stolton S., Jeanrenaud J.P., 1996. Pulp Fact – Environmental Implications of the Paper Cycle. WWF International; National Productivity Council, 2006. Final Report on Development of Guidelines for Water Conservation in Pulp and Paper Sector. New Delhi, India.
effluents per unit of production in 1988 was one-third to one-quarter that discharged in 1975, and less than 5% of that in 1943. Available data show that in 1988, total suspended solids discharges in final effluents per unit of production had been reduced by around 40% since 1975 and by over 80% since 1965. Even in the short period between 1985 and 1988, it was found that final discharges of BOD and total suspended solids per unit of production were reduced by around 5%. National Productivity Council (2006) has compiled from different sources average water consumption for large, wood-based pulp and paper industries, basically producing paper and board products in Europe, Canada, the US, Australia, Finland, and Spain (Table 4.3). The average water consumption varies from 30 to 67 m3/ton of product for large, wood-based pulp and paper mills primarily producing paper and paperboard products, whereas average water consumption in wastepaper-based pulp and paper mills in developed countries varies from 8–10 m3/ton of product (NPC, 2006). According to a study conducted in 2003 by the Department of International Development of the UK government, average water consumption in different pulp and paper mills is presented in Table 4.4. There are huge variations in the water consumption data because of the differences in raw materials, the production processes used, and the quality of products produced by different mills. Integrated mills producing chemical pulp from wood and high-quality papers may consume much larger quantities of water. Some mills might produce simple boards from recycled paper and consume very little water. Water consumption in the developed markets is much lower than in developing countries like India, Pakistan, and China. The best performances have been observed in paper mills using closed cycles, where specific water consumption of around 20 m3/ton of paper has been obtained. Nowadays, the trend has been a shift to recycled paper, i.e., producing paper from wastepaper because of the huge costs in terms of energy, water, and chemicals, and the impact on the environment of virgin paper production. Saving trees and making new paper from old paper uses a fraction of the energy and chemicals used in virgin paper production. Therefore, expanding the recycling of used paper has great potential to bring environmental and economic benefits. Specific water consumption in Europe and Scandinavia varies from 8 to 10 m3/ton of paper. In fact, a few producers in the Netherlands claim to use only
Water Usage in the Pulp and Paper Processes 43 Table 4.4: Average water consumption in different pulp and paper mills. Mill
Production (tons/day)
1 2 3 4 5
650 1200 290 900 145
Water Intake (m3/day)
Water Consumption (m3/ton)
Integrated pulp and paper mills 44,840 39,320 20,000 122,400 2700
67 33 69 136 19
Nonintegrated pulp and paper mills 1 2 3 4 5 6
120 900 22 185 15 148
1000 32,600 230 145 740 2800
9 36 11 1 49 19
Based on Gavrilescu, M., Teodosiu, C., Gavrilescu, D., Lupu, L., 2008. Strategies and practices for sustainable use of water in industrial papermaking processes. Engineering in Life Sciences 8 (2), 99–124.
4.4 m3 of water per ton of paper produced from wastepaper. A brief summary of the pulp and paper industries in a number of developed countries is presented in the following paragraphs. The US has more than 300 pulp mills and more than 550 paper mills, and is one of the largest producers of pulp and paper and accounts for around 38% of world production. Because of tough competition in the pulp and paper industry, several companies have merged, resulting in fewer pulp and paper mills, but substantially increased production capacity per mill. Mills are not allowed to “run a river through their plant” and dump the processed water back into the environment without first cleaning it. There is a clear trend toward reducing the volume of process water by recycling and reusing water in closed-loop systems, then cleaning it before releasing it back into the environment (Bajpai, 2008). A typical pulp mill used about 64 m3 of water per ton of bleached pulp in 2000, down from about 379 m3/ton in the 1940s. Water consumption data for different types of pulp and paper mill in the US was reported by Bryant et al. (1996). The data, based on a survey of 664 manufacturing facilities, are presented in Table 4.5. Tables 4.6–4.9 contain data for freshwater requirements in a typical bleached kraft mill. The table shows water consumption for older mills (10–20 years), for newer mills (less than 10 years old), and for mills being designed in 1997 (Chandra, 1997). In Europe, more than 60% of the pulp and paper produced comes from mills that are certified under one of the main ecomanagement schemes. Recovered paper forms more than 60% of the raw materials used in paper production in Europe, with the packaging sector being the biggest consumer. Newsprint, household papers, and sanitary papers are produced from recovered paper. However, printing and writing papers, which represent 40% of all paper and board production, mostly are produced from virgin fibers. Paper recycling levels have increased in Europe, but performance varies greatly from one country to another because of
44 Chapter 4 Table 4.5: Water consumption in US pulp and paper mills. Water Consumption (m3/ton) Mill Category
No. of Mills
Range
Average
Integrated, bleached Integrated, unbleached Paper mill >100 tons/day Paper mill <100 tons/day Bleached market kraft pulp Newsprint (mechanical pulp) Corrugating medium neutral sulfite semichemical (NSSC) Newsprint (mechanical and high yield) Deinked secondary fiber Dissolving pulp Market sulfite, bleached chemi- thermomechanical pulp, and others
104 44 218 135 32 40 21
37.1–200.8 14.2–102.5 0.5–188.3 1.3–364.6 47.1–141.7 13.8–113.8 29.1–87.9
90.0 14.2–102.5 33.3 58.8 91.7 41.3 27.5
17 36 8 9
37.1–296.0 0.5–91.3 105.4–351.7 1.3–206.3
82.1 43.8 185.4 67.5
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.6: Freshwater consumed by different processes in bleached kraft mills. Water Consumption (m3/ton) Process Area
Older Mills
Newer Mills
New Design Mills
Total fiber line Total pulp machine Total recovery/power Grand total
60.8 6.5 10.3 77.6
34.6 6.2 3.4 44.2
10.6 0.4 1.2 12.2
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.7: Freshwater consumed in fiber line in bleached kraft mills. Water Consumption (m3/ton)
Process Area
Older Mills
Newer Mills
New Design Mills
Digesting Washing and screening Bleach plant
1.1 4.2
1.0 1.8
0.2 0.2
• Acid • Alkaline Chemical preparation
25.0 30.0 0.5
21.0 10.0 0.8
5.0 5.0 0.2
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Water Usage in the Pulp and Paper Processes 45 Table 4.8: Freshwater consumed in pulp machine in bleached kraft mills. Water Consumption (m3/ton) Process Area
Older Mills
Newer Mills
New Design Mills
Rejects General
1.3 5.2
1.3 4.9
0.2 0.2
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.9: Freshwater consumed in chemical recovery in bleached kraft mills. Water Consumption (m3/ton) Process Area
Older Mills
Newer Mills
New Design Mills
Evaporators Recovery Hog/power boiler Recausticizing
0.7 2.1 4.9 2.6
0.6 0.6 0.9 1.3
0.2 0.2 0.5 0.3
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.10: Discharge of water pollutants in CEPI (Confederation of European Paper Industries) countries. Pollutant (kg/ton) Biological oxygen demand (BOD) Chemical oxygen demand (COD) Adsorbable organic halides (AOX)
1990
2003
2003
2004
2005
5.28
1.51
1.25
0.84
0.83
27.28
7.29
6.95
5.76
5.83
0.60
0.05
0.04
0.03
0.03
Based on Gavrilescu M., Teodosiu C., Gavrilescu D., Lupu L., 2008. Strategies and practices for sustainable use of water in industrial papermaking processes. Engineering in Life Sciences 8 (2), 99–124.
the differences in market and industry structures, population density, education, and transportation distances. The discharge of water pollutants in the CEPI countries has reduced substantially since 1990 (Table 4.10; Gavrilescu et al., 2008). Canada is a producer of high-quality recycled content paper products and has 22 mills, which are capable of recycling, and 62 mills use recovered paper in whole or in part as a source of fiber. Water consumption per ton of pulp is less than half what it was 20 years ago (Bajpai, 2008). Since 1990, the pulp and paper industry has invested in pollution prevention
46 Chapter 4 technologies, which resulted in the virtual elimination of dioxins and furans. The concentration of these compounds reached unmeasurable levels in 1995 (Bajpai and Bajpai, 1999). Total suspended solids and BOD, two leading indicators of mill effluent pollution, have also reduced significantly. Since 2000, levels of BOD have dropped 10-fold and total suspended solids by more than half. The use of elemental chlorine in bleaching dropped to 87% between 1988 and 1999. Further, the level of dioxins and furans in mill effluent has reduced by 99%. The Australian paper industry is strongly aware of the requirement to reduce its water use. In Australia, there are five major papermaking facilities, four large saw mills, and several smaller wood processing plants. In 2001–02, the industry used an average of 28.7 m3 of water per ton of paper production, a 62% reduction in water use since 1990. The Australian paper industry’s water use compares favorably with industries elsewhere in the world (Bajpai, 2008). In the Netherlands, freshwater consumption in wastepaper-based pulp and paper mills is 8.4 m3/ton of production in 2008. The production process operates a closed water system, whereby the water system is divided into two large process water cycles, which are separated by the thickener: the stock preparation cycle with comparatively contaminated water, and the paper machine cycle with comparatively clean water. The production process is improved by inserting an extra thickener in the process. As a result, an extra water cycle is created between refiner and cleaner. The new cycle comprises refiner and thickener, while the paper machine cycle comprises cleaner and paper machine. The improved process reduces freshwater consumption to 4.4 m3/ton of production. The German paper industry reduced its specific effluent volumes from 46 m3/ton of paper in 1974 to around 11 m3/ton in 2002. Specific effluent volumes for mills producing paper and board from recycled fiber range from 3–8 m3/ton (Bajpai, 2008). Four German mills now operate integrated closed circuit water treatment, producing no effluent (Neidhardt, 2004). Stock preparation and paper machine circuits are separated to reduce effluent volumes in mills producing packaging papers, with freshwater added only to the cleanest circuit on the paper machine. Clear filtrate is passed through filters to replace freshwater used in jets to control consistency. In fact, specific water consumption in Germany has reduced significantly during the past 30 years, starting at about 50 m3/ton of paper produced and reducing to almost 10 m3/ton of paper in 2004 (Schabel and Hamm, 2007). Jaakko Poyry (2002) has reported that Indian pulp and paper mills consumed much more water per ton of product and discharged more pollutants compared to their European counterparts (Table 4.11). However, the water consumed and effluent discharged by Indian papermakers had reduced significantly by 2005 because of economic and environmental pressures, which has been confirmed in a study conducted by the National Productivity Council in association with the Central Pollution Control Board of India (NPC, 2006). The specific water consumption data are presented in Tables 4.12–4.14. To calculate the effluent discharge, it is assumed that about 21% of the water is lost through evaporation and as moisture in the final product. From
Water Usage in the Pulp and Paper Processes 47 Table 4.11: Effluent benchmarking of Indian pulp and paper mills.
Mill Type Indian agro-based integrated mills Indian forest-based integrated mills European forestbased integrated mills Indian wastepaperbased mills European wastepaperbased mills
Flow (m3/ton)
Total Suspended Solids (TSS) (kg/ton)
Chemical Oxygen Demand (COD) (kg/ton)
Biological Oxygen Demand (BOD) (kg/ton)
Adsorbable Organic Halides (AOX) (kg/ton)
120
40
47
10
n/a
175
11
37
3.7
0.4
40
1.5
12.0
1.5
0.1
32
2.6
8.7
1.3
n/a
10
1.0
5.0
1.0
n/a
Based on Poyry J., 2002. Report on Global Competitiveness of Indian Paper Industry.
Table 4.12: Water consumption in large-scale Indian mills. Raw Material
End Product
Water Consumption (m3/ton)
Wood and wastepaper Wood and wastepaper Wood, agro residue, and wastepaper
Newsprint Cultural–high grade Cultural–high grade
80 77 67
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
Table 4.13: Water consumption in medium-scale Indian mills. Raw Material
End Product
Water Consumption (m3/ton)
Agro residue and wastepaper Agro residue and wastepaper Wastepaper
Cultural—high grade Industrial grade Cultural—high grade
80 47 48
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
Table 4.14: Water consumption in small-scale Indian mills. Raw Material
End Product
Water Consumption (m3/ton)
Agro residue and wastepaper Agro residue and wastepaper Wastepaper Wastepaper
Cultural—high grade Industrial grade Cultural—low grade Cultural—low grade
110 93 13 129
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
48 Chapter 4 Table 4.15: Cluster rule (bleach plant effluent discharge). Adsorbable organic halides
Dioxin and 12 chlorinated phenolics Trichlorodibenzofuran (TCDF) Chloroform Color, acetone, methyl ethyl ketone, methylene dioxide
0.623 kg/ton (Monthly Average) 0.512 kg/ton (Annual Average) 0.951 kg/ton (Daily Maximum) Non detect TCDF 31.9 pg/L (daily maximum) Chloroform 4.14 g/ton No limit
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
this detailed field study, it is clear that water consumption varies significantly, depending upon the raw material used, the scale of the operation, and the end product produced. There are no standards for the quantities of water consumed and effluent discharged in most developed countries. However, it is controlled indirectly by standards for the discharge of pollutants per ton of product. In the US, it is governed by the cluster rules (Anon, 1997; Table 4.15). The limit of COD discharge used to be 25.4 kg/ton. In addition, efforts are being made to close water cycles in mills to reduce freshwater consumption and the discharge of effluents in the US and in Europe (IPPC Directive, 1996). The EU Integrated Pollution Prevention and Control (IPPC) directive to obtain high environmental standards by considering effluents, air emissions, and solid waste was adopted in September 1996 and legislated into national laws in October 1999. All pulp and paper mills with a production capacity of more than 20 tons/day come under the scope of the IPPC directive. The concept of best available techniques (BAT) plays a central role in the IPPC directive. BAT is considered the best tool to achieve IPPC by providing a basis for emission limit values. The definition of BAT for the pulp and paper industry was started in 1997, and the final document was published in July 2000 (http://eippcb.jrc.es). Corporate Responsibility for Environmental Protection (CREP) was formulated jointly by the Central Pollution Control Board, New Delhi, and the Ministry of Environment and Forests in close association with the industry in March 2003. It addresses issues common to both large and small pulp and paper mills in India, and also issues particular to large mills and small mills. The following water discharge standards (Table 4.16) were agreed by the different pulp and paper manufacturing associations of India (CPCB, 2003). While this standard is discharge-specific, it also takes into account the size and age of the mill. It does not differentiate between the pulping process, the raw material used, and the end product. The Centre for Science and Environment (CSE), New Delhi, India, through its Green Rating Project, has reported a significant reduction in water consumption in large-scale Indian paper mills. In 2002, the average fell to 135 m3/ton paper due to increased awareness of the need for water conservation, increasing pressure from government regulatory agencies and water scarcity in many regions. The CSE findings indicate that most mills are already achieving the water consumption standards set by the CREP program (NPC, 2006).
Water Usage in the Pulp and Paper Processes 49 Table 4.16: Emission standards in the Indian pulp and paper industry. Effluent discharge, m3/Adt paper
150, from April 1, 2005
Chemical oxygen demand (COD) (mg/L) Biological oxygen demand (BOD) (mg/L) AOX (kg/Adt paper)
350
<140, from April 1, 2005 <120, from April 1, 2007 <100, from April 1, 2007 for Mills Set Up After 1992 350
30 (100a)
30 (100a)
AOX (kg/ton pulp) Upgrading of ETP Utilization of treated effluent for irrigation
<2.0 from April 1, 2006 <1.5 from April 1, 2005 <1.0 from April 1, 2008 <1.0 from April 1, 2008 AOX (kg/ton pulp) 20% higher than that based on paper Before April 1, 2004 N/A Wherever possible Wherever possible
Adt, air-dried ton; AOX, adsorbable organic halides; ETP, effluent treatment plant. aBOD for land discharge, 100 mg/L. Based on CPCB, 2003. Corporate responsibility for environmental protection [cross ref., Panwar, S., Endlay, N., Gupta, M.K., Mishra, S., Mathur, R.M., Kulkarni, A.G., 2006. Charter on corporate responsibility for environmental protection in pulp and paper industry – implication and compliance. IPPTA Journals 18 (4), 63–69].
Average water consumption for large, wood-based pulp and paper mills, primarily water consumption producing paper and paperboard products, in developed countries varies from 30 to 67 m3/ton of product. It varies from 8 to 10 m3/ton of product in wastepaper-based pulp and paper mills. In addition, efforts are being made to reduce it further by introducing closed water cycles. Exact knowledge on water consumption and quality in different uses forms the basis for good water management. In paper mills that have implemented BAT, freshwater is mainly introduced to the process as shower waters and chemical handling. The more efficient fiber and filler recovery technique has made it possible to use the resulting clear water in less critical showers of the paper machine and thus to increase recycling of water. The recycling rate of clear filtrates can be further increased by adopting ultrafiltration as a technique for the internal treatment of white water. However, due to only partial removal of dissolved materials by use of ultrafiltration, further increase of recycling (for example, for press section showers) is not yet considered feasible. Closed water circulation of paper machine waters would require more efficient separation techniques like nanofiltration, reverse osmosis, or other complementary techniques. For closing up the water systems, knowledge, awareness, and proper actions for controlling the water system are required. Control of microorganisms, proper design of the piping and storage systems, and material selection actually help to keep the surfaces in clean condition and reduce the requirement for washing. Recycling stream monitoring by measurements and laboratory analysis can be used to determine the actual performance of separation processes and the quality of shower waters and other process waters (Bajpai, 2008). Data gathering on water flows and the chemical state of the water systems makes it possible to study and control the water behavior of
50 Chapter 4 the whole mill and to determine the best running conditions for quality changes, startups, and shutdowns. For example, operation procedures with large pH or temperature gradients should be omitted because they lead to harmful deposit and scaling formations. Online measurements and accurate process control are important for effective and stable papermaking. Recycling of cooling and sealing waters can be increased by using heat exchangers or a cooling tower. However, microbial and water quality monitoring and control methods are required to ensure disturbance-free performance of the system. In cases where recovery and reuse of coating colors from coating wastewater by membrane technique is not possible, flocculation of this concentrated partial wastewater stream is considered as the best available technique. The ultrafiltration separation technique is mentioned as a measure for reducing the solid waste. The removal efficiency after wastewater treatment and the environmental impact as a whole can be improved by using nontoxic and biodegradable products and process chemicals. In developing countries, water consumption per ton of product is much higher. The paper industry and the regulatory agencies are trying to reduce water consumption. Water consumption varies significantly, depending upon the raw material used, the scale of the operation, and the end product. Recognizing these variations, it was clear that one or two general standards would not be enough for the entire pulp and paper sector. Accordingly, considering the characteristics of India’s pulp and paper mills, six types of pulp and paper mills in respect of water consumption patterns are proposed for the formulation of standards (NPC, 2006): Three levels of standards have been formulated considering the previously mentioned factors (Table 4.17). The consolidated proposed water consumption/wastewater discharge standards for each category of the pulp and paper mills are presented in Tables 4.18 and 4.19. Table 4.17: Standards formulated. Benchmark Standard: Refers to minimum water consumption required after implementation of best available technology (economically viable and currently practiced/demonstrated in India), recycle, and reuse practices. This standard has been developed by identifying the various mill operations involved in each category and identifying the least water consumption achieved by any of the mills studied in that category. The total water consumption in each mill operation/process will be the benchmark standard for that specific category. Best Achieved Standard: Refers to the minimum water consumption already achieved by a mill (or can be achieved by implementing simple recycling/reuse measures) in a specific category. Relaxed Standard: Provides 20% relief over the best achieved standard in each category. This standard is proposed for immediate reduction in water consumption by most of the high water-consuming industries, thus bridging the gap between the best performing and worst performing mills in a short time. It is estimated that this standard can be achieved by other industries by implementing simple reuse, recycling, and other minor modification
Water Usage in the Pulp and Paper Processes 51 Table 4.18: Proposed water consumption standards. Water Consumption, m3/ton of Product
Large-scale wood-based and integrated pulp and paper mills manufacturing newsprint Cultural-grade paper and paper board Small/medium–scale agro-based pulp and paper mills manufacturing cultural-grade paper Small/medium–scale agro-based pulp and paper mills manufacturing industrial grade All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper and/or newsprint with deinking All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper without deinking All medium/small–scale wastepaper-based pulp and paper mills manufacturing industrial-grade paper
Benchmark
Best Achievable
Relaxed
63
67
80
38
80
95
18
47
56
19
41
49
9
13
15
6
6
7
Based on National Productivity Council, 2006. Final Report on Development of Guidelines for Water Conservation in Pulp and Paper Sector. New Delhi, India.
Table 4.19: Proposed wastewater discharge standards. Wastewater Discharge Standards, m3/ton of Product
Large-scale wood-based and integrated pulp and paper mills manufacturing newsprint Cultural-grade paper and paper board Small/medium–scale agro-based pulp and paper mills manufacturing cultural-grade paper Small/medium–scale agro-based pulp and paper mills manufacturing industrial grade All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper and/or newsprint with deinking All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper without deinking All medium/small–scale wastepaper-based pulp and paper mills manufacturing industrial grade paper
Benchmark
Best Achievable
Relaxed
50
53
63
30
63
75
15
37
44
15
32
38
7
10
12
5
5
6
Based on National Productivity Council, 2006. Final Report on Development of Guidelines for Water Conservation in Pulp and Paper Sector. New Delhi, India.
52 Chapter 4
References Ali, M., Sreekrishnan, T.R., 2001. Aquatic toxicity from pulp and paper mill effluents: a review. Advances in Environmental Research 5 (2), 175–196. Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14. APIC, 2003. APIC Public Eco-friendly Report 2003. . Area, M.C., Valade, J.L., 1998. Revisión de los procesos de pulpado con acción química, El papel. La revista papelera para Espeña y América Latina 69, 47–51. Bajpai, P., 2008. Water Recovery in Pulp and Paper Making. Pira technology report. Pira International, UK. Bajpai, P., 2012. Environmentally Benign Approaches for Pulp Bleaching, second ed. Elsevier, Amsterdam. Bajpai, P., Bajpai, P.K., 1999. Recycling of Process Water in a Closed Mill System – An Introduction. Pira International, UK. ISBN: 1 85802 277 0. Bredenberg, A., 2013. Pulp and Paper Industry Strives to Reduce Its Water Impact. news.thomasnet.com/imt/.../ pulp-and-paper-industry-strives-to-reduce-its-water-impact. Bryant, S.P., Woitkovich, C.P., Malcolm, E.W., 1996. Pulp and Paper Mill Water Use in North America. Proc. Tappi 1996 Environmental Conference. Tappi Press, Atlanta, p. 451.. Buyukkamaci, N., Koken, E., 2010. Economic evaluation of alternative wastewater treatment plant options for pulp and paper industry. Science of the Total Environment 408, 6070–6078. CAR/PL, 2005. Prevención de la contaminación en el sector papelero. Centro de actividad regional para la producción limpia (CAR/PL), Barcelona. CEPI, Paper Production Uses Too Much Water – CEPI. www.cepi.org/system/files/public/.../myths.../too%20 much%20water.pdf. CEPI, 2011. Sustainability Report 2011. CEPI, 2013. Sustainability Report. Chandra, S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42. Covinich, L.G., Bengoechea, D.I., Fenoglio, R.J., Area, M.C., 2014. Advanced oxidation processes for wastewater treatment in the pulp and paper industry: a review. American Journal of Environmental Engineering 4 (3), 56–70. CPCB, 2003. Corporate responsibility for environmental protection [cross ref., Panwar, S., Endlay, N., Gupta, M.K., Mishra, S., Mathur, R.M., Kulkarni, A.G., 2006. Charter on corporate responsibility for environmental protection in pulp and paper industry – implication and compliance. IPPTA Journals 18 (4), 63–69]. CPPRI, 2008. Water Conservation in Pulp and Paper Industry. www.dcpulppaper.org/gifs/report17.pdf. Cuevas, N.M., 2014. Development and Assessment of Advanced Oxidation Processes for the Treatment of Pulp and Paper Mill Effluents. Doctoral thesis in chemical engineering. Universidad Complutense De Madrid, Spain. Dudley, N., Stolton, S., Jeanrenaud, J.P., 1996. Pulp Fact – Environmental Implications of the Paper Cycle. WWF International. Gavrilescu, M., Teodosiu, C., Gavrilescu, D., Lupu, L., 2008. Strategies and practices for sustainable use of water in industrial papermaking processes. Engineering in Life Sciences 8 (2), 99–124. Integrated Pollution Prevention and Control (IPPC), 2001. Reference Document on Best Available Techniques in the Pulp and Paper Industry. European Commission. IPPC, 2013. Best Availables Techniques (BAT). Reference Document for the Production of Pulp, Paper and Board. European Commission. IPPC Directive, 1996. European Union Directive No. 96/61/EC. Karrasch, B., Parra, O., Cid, H., Mehrens, M., Pacheco, P., Urrutia, R., Valdovinos, C., Zaro, C., 2006. Effects of pulp and paper mill effluents on the microplankton and microbial self-purification capabilities of the Biobío River, Chile. Science of The Total Environment 359 (1–3), 194–208 (1–3). Kemira, 2014. Water Reuse. www.kemira.com/en/newsroom. Kovacs, T.G., Martel, P.H., Voss, R.H., 2002. Assessing the biological status of fish in a river receiving pulp and paper mill effluents. Environmental Pollution 118 (1), 123–140.
Water Usage in the Pulp and Paper Processes 53 Miner, R., Unwin, J., 1991. Progress in reducing water use and wastewater loads in U.S. paper industry. Tappi Journal 74 (8), 127–131. Miranda, R., Blanco, A., Negro, C., 2009. Accumulation of dissolved and colloidal material in papermakingApplication to simulation. Chemical Engineering Journal 148 (2–3), 385–393. National Productivity Council, 2006. Final Report on Development of Guidelines for Water Conservation in Pulp and Paper Sector. New Delhi, India. Neidhardt, T., 2004. Water systems in the production of packaging paper from recycled fibers. Wochenblatt für Papierfabrikation 132 (8), 422–426 428 (German). Olli, K., Petri, P., Mikko, S., 2012. Advanced Water Treatment, Recycling Lower Paper Mill Water Consumption, Industrial Water World. www.waterworld.com/.../advanced-water-treatment-recycling. Ordoñez, R., Hermosilla, D., Fuente, E., lanco, A., 2009. Influence of water quality on the efficiency of retention aids systems for the paper industry. Industrial & Engineering Chemistry Research 48 (2009), 10247–10252. Poyry, J., 2002. Report on Global Competitiveness of Indian Paper Industry. Schabel, S., Hamm, U., 2007. Effluent-free papermaking: industrial experience in the German and European paper industry. In: Proc. 8th International Technical Conference on Pulp, Paper, Conversion & Allied Industry (Paperex 2007), New Delhi, 7–9 December 2007, pp. 43–54.
Water Usage in the Pulp and Paper Processes Water is one of the key components of papermaking. Without water, the production of paper is unthinkable. The pulp and paper industry is a water-intensive consumer (Buyukkamaci and Koken, 2010); consequently, several drivers impulse this sector to reduce its water consumption. Among others, water stress, legal requirements, environmental concerns, and, indeed, the potential benefits are the main ones. Water scarcity is, however, more important in countries that suffer from water shortages. The industry uses large volumes of water as a fiber carrier and as a solvent. Much water is lost to evaporation during production, between 0.5 and 2 m3/ton, resulting in high demand for freshwater. The industry has made steady progress over the past 3 decades in reducing its relative water footprint, dropping from 300 m3/ton to about 50 m3/ton, a reduction of 80%. A growing market for equipment and services in pulp and paper water and wastewater treatment, especially in disinfection and filtration systems, is seen by Frost and Sullivan (Bredenberg, 2013). According to the group’s study, the global market should grow at 6.0% compound annual growth rate from $984 million in 2012 to about $1.57 billion in 2020. North America and Europe each represent about one-third of the market and the Asia–Pacific region about one-quarter, with high growth expected. Most of the water used in the paper production life cycle is used during the production process, basically for conveyance of the fibers when they are extracted from the logs as wood chips, and through the pulping process. During the last decades, increased attention has been given to the overall efficiency of paper mills and also to the environmental footprint of the industry. Water management has become a very important factor in the industry. Reasons include the following: • limited water resources • need for cost savings • environmental impacts • legislation The industry has seen an increase in energy costs, environmental legislation tightening all around the world, and shortages of water resources becoming a growing concern in different parts of the world. These trends have led to a reduction in the use of freshwater in the paper industry and an increase in water recycling. Expanding water recycling by adding treatment units in a paper mill appears to be a relatively simple task, but it is not that easy in reality. Addition of water recycling processes, and at the same time, handling possible risks and Pulp and Paper Industry. http://dx.doi.org/10.1016/B978-0-12-811099-7.00004-6 Copyright © 2017 Elsevier Inc. All rights reserved.
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38 Chapter 4 pitfalls, needs an overall understanding of the different types of processes, chemistry, and conditions, not only in the paper industry in general, but also of the particular mill in question. A particular risk in water recycling is that certain impurities and substances will concentrate in process waters, causing serious problems in processes, equipment, and product quality. Still, with the correct technology and knowhow, many opportunities exist for water recycling at paper mills. A high level of water consumption, in turn, results in high consumption of energy and also generation of a high volume of effluent, as 90% of the water intake is discharged as effluent in pulp and the papermaking process (CPPRI, 2008). Because of this, high levels of effluent require adequate effluent treatment plants (ETPs) for treatment to stipulated discharge norms. In India also, since the mills have slowly increased the production capacity without a corresponding increase in effluent handling capacity, most of the ETPs are overloaded and most of the mills find difficulty in treating their effluent to stipulated discharge norms (APIC, 2003). Water consumption varies from >5 m3/ton up to >100 m3/ton between mills. This actually depends on production, raw materials, and technologies used in pulp, papermaking, and related processes (Olli et al., 2012). In tissue production, water consumption is higher than in many other grades like newsprint or fine paper and usually ranges from 8 to 100 m3/ton. This is because tissue products have very high quality standards in brightness, texture, and also odor. This leads to washings and higher demand of freshwater. Tissue mills using recycled paper as raw material have a lot of challenges in handling quality problems, and therefore, water management is critical. By using suitable technology, freshwater can be replaced with recycled process water in many production points, even in the case of tissue mills, without compromising quality or runnability. Usual points where freshwater can be replaced are, for example, different dilution waters in pulping and stock preparation, and shower and washing waters in the machine area. Over the years, the mills abroad have been successful in reducing the consumption of water in the papermaking process by adoption of modern fiber line technologies and also methods for increased recycling, resulting in minimal discharge of effluent. However, this has not been so in the case of Indian pulp and paper mills. The water consumption in the Indian paper industry is significantly higher as a result, compared to the developed countries (CPPRI, 2008; Table 4.1). In pulp and paper production, reduction in the use of water consumption implies a strategic management. It is aimed at water conservation and the reuse and recycling of used process waters in an attempt to reduce both water consumption and effluent discharge (Gavrilescu et al., 2008; Table 4.2). More restrictive legislation has increased efforts toward better preservation of water and effluent load reduction in the manufacturing process. The work during the last decades has been focused on the identification of the most economically effective processes, the development of wastewater treatment, and the optimization of the
Water Usage in the Pulp and Paper Processes 39 Table 4.1: Water consumption in the mills with best available techniques (BAT). Water Consumption, m3/ton Paper Pulping Process Kraft Rayon grade Recycled fiber End product Newsprint Writing and printing Industrial and packaging
Mills with BAT 42 36 8
Indian mills 110–220 130–180 25–75
11 m3/ton paper 38 m3/ton paper 15 m3/ton paper
90–160 100–220 60–150
Based on CPPRI, 2008. Water Conservation in Pulp and Paper Industry, www.dcpulppaper.org/gifs/report17.pdf.
Table 4.2: Total water management. Conservation Reduction of water consumption, improving operation of existing equipment and process Reuse Reuse of water with no change in quality Recycled Reuse of water in process after improving its quality Reclaimed Reuse of mill effluent after improving its quality Zero effluent Increased investment Based on Gavrilescu, M., Teodosiu, C., Gavrilescu, D., Lupu, L., 2008. Strategies and practices for sustainable use of water in industrial papermaking processes. Engineering in Life Sciences 8 (2), 99–124.
process design (Cuevas, 2014). In order to reduce the water consumption, two basic strategies have been used. These are: • modification of the individual processes and its units to reduce the inherent water requirement; and • water reuse; looking for opportunities to reuse the outlet stream of one operation process as the inlet stream of the same operation process or of another one. In this way, more than 40% water intake reduction has been obtained since 1990 (CEPI, 2013). In spite of all the efforts carried out to reduce water consumption, this sector is still water-intensive. According to Ordoñez et al. (2009), water is required for following purpose: • dispersion and transport of the fibrous raw materials and additives throughout the different stages of the production process • as heat exchange fluid • as sealant in vacuum systems • as steam • as lubricant
40 Chapter 4 In modern mills where best available technologies are applied, the average water use range is from 3 to 10 m3/ton, depending on the product quality, although some paper products, such as tissue, have a higher range. 1.5- 1.5-3 m3/ton is required for board products in closed systems, 5–15 m3/ton for newsprint, 15–20 m3 for tissue, and more than 20 m3/ton for high-quality printing grades and speciality papers (IPPC, 2013). Although the closure of circuits has several advantages, such as less water consumption, less freshwater pretreatment, decreased fiber and filler losses, lower volume to effluent treatment, and reduced energy demand, this implies the accumulation of pollutants in the process water. There is actually a break point in the accumulation of contaminants, which limits the closure of the water circuits (Miranda et al., 2009). Contaminants must be removed before further closing the water circuit for avoiding the following problems: • corrosion • clogging of equipment • scaling • slime forming in the process or in the final product In order to reuse process water, internal treatments are installed for removing these substances (CAR/PL, 2005). The major advantage of inline treatment is that only a part of the chemical oxygen demand (COD) load from the purge of white water requires being eliminated to keep the level of contaminants in the circuit low, making the treatment economically attractive (IPPC, 2013). Several processes are being used to treat the internal streams and the final effluents in the pulp and paper industry. Every paper mill has a distinctive water profile because of its location and the origins of its water, the destination of its effluent, and the origin of its fibrous and nonfibrous raw materials being used. The paper industry is continuously working on reducing its effect on water consumption. In the 1970s, producing 1 ton of pulp required as much as 250 m3 of water, and now, it only takes 5–50 m3 (Kemira, 2014; www.cepi.org). The last decade saw water consumption of paper machines being reduced by one-third as a result of more efficient water circulation. According to the Confederation of European Paper Industries (CEPI, 2011), in 2008, the pulp and paper industry took out approximately 4000 million m3 of water from surface and groundwater sources, of which about 92% of water was returned back to surface water supplies. Water used for paper production is usually circulated within the manufacturing system. The water that is discharged is purified in high-end wastewater treatment facilities. In actuality, water coming out of a paper production mill is cleaner than when it goes in. The paper industry has actually become an active partner in the development of water stewardship and water footprinting. It is developing comprehensive water reporting guidelines for the sector, and in recent years, the industry has been an active partner in the development of a globally harmonized understanding of water stewardship.
Water Usage in the Pulp and Paper Processes 41 Water consumption by the pulp and paper industry is affected by production conditions, such as grade changes, equipment used, and water management practices (Bajpai, 2008). Quantifying the consumption of freshwater in a mill is often the first step in taking an analytical approach to saving water. Identifying all the instances when water is discharged at various stages of production can lead to savings in both raw materials and energy. In practice, half of the total flow of effluent from pulp and paper production comes from the process itself and contains most of the dissolved solids. The remainder is flushing, leakages, vacuum system seal water, and cooling water, fractions that are all roughly uncontaminated with dissolved substances from the process. The characteristics of the waste liquid to be treated depend on the type of wood and the process, the technology used and the selected management practices, raw material and the process involved, and the amount of water that the mill is able to circulate. Untreated waste fluids can have high biochemical oxygen demand, COD, suspended solids that are mainly fibers, fatty acids, tannins, resin acids, lignin, and its derivatives (Covinich et al., 2014). Some of them are naturally occurring pollutants and others are xenobiotics, which are produced during the pulp and paper manufacturing process (Area et al., 1998; Ali and Sreekrishnan, 2001). Some substances are recalcitrant to biological degradation and toxic to aquatic species. Some bleaching processes even produce bioaccumulative compounds (Bajpai, 2012; Karrasch et al., 2006; Kovacs et al., 2002). The wastewaters of high yield pulping processes are characterized by their suspended solids content, which includes the following: • bark particles; • organic substances; • chromophoric compounds, mainly labile extractives and lignin fragments; and • inorganic compounds: nitrogen and phosphorus, as result of the effluent treatment and salts. Semichemical processes contain lignosulfonates derived from lignin in addition to the previous. The kraft process wastewaters are characterized by their content of solids, including bark particles, dissolved organics, and chromophoric compounds, mainly derived from lignin. If kraft pulps are bleached with chlorine compounds, they produce organochlorine compounds (dioxins and furans) (IPPC, 2001; Bajpai, 2012). The National Council for Air and Stream Improvements (US) conducted a survey in 1989. In the US, a reduction in water use between 1985 and 1988 of 7–8% and a reduction between 1975 and 1988 of 27–34% were reported by Miner and Unwin (1991). In 1988, about 16,500– 17,500 gallons of water to produce a ton of paper or board (68–73 m3/ton) in the US was required. This is about 70% less than was required to produce a ton of paper in 1959. Reductions in wastewater treatment are of the same magnitude as that reported for water use. Untreated wastewater flows were reduced by around 8% between 1985 and 1988, whereas the reductions obtained between 1975 and 1988 were 26–29%. In 1988, wastewater going for treatment was 63–69 m3/ton of paper. Biological oxygen demand (BOD) and total suspended solids loads were reduced by about 10% between 1975 and 1988. The amount of BOD discharged in final
42 Chapter 4 Table 4.3: Average specific water consumption in large wood-based pulp and paper mills. United States Europe Australia Canada Finland Spain
64 40 28.7 67 40 30
APIC, 2003. APIC Public Eco-friendly Report 2003; Dudley N., Stolton S., Jeanrenaud J.P., 1996. Pulp Fact – Environmental Implications of the Paper Cycle. WWF International; National Productivity Council, 2006. Final Report on Development of Guidelines for Water Conservation in Pulp and Paper Sector. New Delhi, India.
effluents per unit of production in 1988 was one-third to one-quarter that discharged in 1975, and less than 5% of that in 1943. Available data show that in 1988, total suspended solids discharges in final effluents per unit of production had been reduced by around 40% since 1975 and by over 80% since 1965. Even in the short period between 1985 and 1988, it was found that final discharges of BOD and total suspended solids per unit of production were reduced by around 5%. National Productivity Council (2006) has compiled from different sources average water consumption for large, wood-based pulp and paper industries, basically producing paper and board products in Europe, Canada, the US, Australia, Finland, and Spain (Table 4.3). The average water consumption varies from 30 to 67 m3/ton of product for large, wood-based pulp and paper mills primarily producing paper and paperboard products, whereas average water consumption in wastepaper-based pulp and paper mills in developed countries varies from 8–10 m3/ton of product (NPC, 2006). According to a study conducted in 2003 by the Department of International Development of the UK government, average water consumption in different pulp and paper mills is presented in Table 4.4. There are huge variations in the water consumption data because of the differences in raw materials, the production processes used, and the quality of products produced by different mills. Integrated mills producing chemical pulp from wood and high-quality papers may consume much larger quantities of water. Some mills might produce simple boards from recycled paper and consume very little water. Water consumption in the developed markets is much lower than in developing countries like India, Pakistan, and China. The best performances have been observed in paper mills using closed cycles, where specific water consumption of around 20 m3/ton of paper has been obtained. Nowadays, the trend has been a shift to recycled paper, i.e., producing paper from wastepaper because of the huge costs in terms of energy, water, and chemicals, and the impact on the environment of virgin paper production. Saving trees and making new paper from old paper uses a fraction of the energy and chemicals used in virgin paper production. Therefore, expanding the recycling of used paper has great potential to bring environmental and economic benefits. Specific water consumption in Europe and Scandinavia varies from 8 to 10 m3/ton of paper. In fact, a few producers in the Netherlands claim to use only
Water Usage in the Pulp and Paper Processes 43 Table 4.4: Average water consumption in different pulp and paper mills. Mill
Production (tons/day)
1 2 3 4 5
650 1200 290 900 145
Water Intake (m3/day)
Water Consumption (m3/ton)
Integrated pulp and paper mills 44,840 39,320 20,000 122,400 2700
67 33 69 136 19
Nonintegrated pulp and paper mills 1 2 3 4 5 6
120 900 22 185 15 148
1000 32,600 230 145 740 2800
9 36 11 1 49 19
Based on Gavrilescu, M., Teodosiu, C., Gavrilescu, D., Lupu, L., 2008. Strategies and practices for sustainable use of water in industrial papermaking processes. Engineering in Life Sciences 8 (2), 99–124.
4.4 m3 of water per ton of paper produced from wastepaper. A brief summary of the pulp and paper industries in a number of developed countries is presented in the following paragraphs. The US has more than 300 pulp mills and more than 550 paper mills, and is one of the largest producers of pulp and paper and accounts for around 38% of world production. Because of tough competition in the pulp and paper industry, several companies have merged, resulting in fewer pulp and paper mills, but substantially increased production capacity per mill. Mills are not allowed to “run a river through their plant” and dump the processed water back into the environment without first cleaning it. There is a clear trend toward reducing the volume of process water by recycling and reusing water in closed-loop systems, then cleaning it before releasing it back into the environment (Bajpai, 2008). A typical pulp mill used about 64 m3 of water per ton of bleached pulp in 2000, down from about 379 m3/ton in the 1940s. Water consumption data for different types of pulp and paper mill in the US was reported by Bryant et al. (1996). The data, based on a survey of 664 manufacturing facilities, are presented in Table 4.5. Tables 4.6–4.9 contain data for freshwater requirements in a typical bleached kraft mill. The table shows water consumption for older mills (10–20 years), for newer mills (less than 10 years old), and for mills being designed in 1997 (Chandra, 1997). In Europe, more than 60% of the pulp and paper produced comes from mills that are certified under one of the main ecomanagement schemes. Recovered paper forms more than 60% of the raw materials used in paper production in Europe, with the packaging sector being the biggest consumer. Newsprint, household papers, and sanitary papers are produced from recovered paper. However, printing and writing papers, which represent 40% of all paper and board production, mostly are produced from virgin fibers. Paper recycling levels have increased in Europe, but performance varies greatly from one country to another because of
44 Chapter 4 Table 4.5: Water consumption in US pulp and paper mills. Water Consumption (m3/ton) Mill Category
No. of Mills
Range
Average
Integrated, bleached Integrated, unbleached Paper mill >100 tons/day Paper mill <100 tons/day Bleached market kraft pulp Newsprint (mechanical pulp) Corrugating medium neutral sulfite semichemical (NSSC) Newsprint (mechanical and high yield) Deinked secondary fiber Dissolving pulp Market sulfite, bleached chemi- thermomechanical pulp, and others
104 44 218 135 32 40 21
37.1–200.8 14.2–102.5 0.5–188.3 1.3–364.6 47.1–141.7 13.8–113.8 29.1–87.9
90.0 14.2–102.5 33.3 58.8 91.7 41.3 27.5
17 36 8 9
37.1–296.0 0.5–91.3 105.4–351.7 1.3–206.3
82.1 43.8 185.4 67.5
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.6: Freshwater consumed by different processes in bleached kraft mills. Water Consumption (m3/ton) Process Area
Older Mills
Newer Mills
New Design Mills
Total fiber line Total pulp machine Total recovery/power Grand total
60.8 6.5 10.3 77.6
34.6 6.2 3.4 44.2
10.6 0.4 1.2 12.2
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.7: Freshwater consumed in fiber line in bleached kraft mills. Water Consumption (m3/ton)
Process Area
Older Mills
Newer Mills
New Design Mills
Digesting Washing and screening Bleach plant
1.1 4.2
1.0 1.8
0.2 0.2
• Acid • Alkaline Chemical preparation
25.0 30.0 0.5
21.0 10.0 0.8
5.0 5.0 0.2
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Water Usage in the Pulp and Paper Processes 45 Table 4.8: Freshwater consumed in pulp machine in bleached kraft mills. Water Consumption (m3/ton) Process Area
Older Mills
Newer Mills
New Design Mills
Rejects General
1.3 5.2
1.3 4.9
0.2 0.2
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.9: Freshwater consumed in chemical recovery in bleached kraft mills. Water Consumption (m3/ton) Process Area
Older Mills
Newer Mills
New Design Mills
Evaporators Recovery Hog/power boiler Recausticizing
0.7 2.1 4.9 2.6
0.6 0.6 0.9 1.3
0.2 0.2 0.5 0.3
Based on Chandra S., 1997. Effluent minimization – a little water goes a long way. Tappi Journal 80 (12), 37–42.
Table 4.10: Discharge of water pollutants in CEPI (Confederation of European Paper Industries) countries. Pollutant (kg/ton) Biological oxygen demand (BOD) Chemical oxygen demand (COD) Adsorbable organic halides (AOX)
1990
2003
2003
2004
2005
5.28
1.51
1.25
0.84
0.83
27.28
7.29
6.95
5.76
5.83
0.60
0.05
0.04
0.03
0.03
Based on Gavrilescu M., Teodosiu C., Gavrilescu D., Lupu L., 2008. Strategies and practices for sustainable use of water in industrial papermaking processes. Engineering in Life Sciences 8 (2), 99–124.
the differences in market and industry structures, population density, education, and transportation distances. The discharge of water pollutants in the CEPI countries has reduced substantially since 1990 (Table 4.10; Gavrilescu et al., 2008). Canada is a producer of high-quality recycled content paper products and has 22 mills, which are capable of recycling, and 62 mills use recovered paper in whole or in part as a source of fiber. Water consumption per ton of pulp is less than half what it was 20 years ago (Bajpai, 2008). Since 1990, the pulp and paper industry has invested in pollution prevention
46 Chapter 4 technologies, which resulted in the virtual elimination of dioxins and furans. The concentration of these compounds reached unmeasurable levels in 1995 (Bajpai and Bajpai, 1999). Total suspended solids and BOD, two leading indicators of mill effluent pollution, have also reduced significantly. Since 2000, levels of BOD have dropped 10-fold and total suspended solids by more than half. The use of elemental chlorine in bleaching dropped to 87% between 1988 and 1999. Further, the level of dioxins and furans in mill effluent has reduced by 99%. The Australian paper industry is strongly aware of the requirement to reduce its water use. In Australia, there are five major papermaking facilities, four large saw mills, and several smaller wood processing plants. In 2001–02, the industry used an average of 28.7 m3 of water per ton of paper production, a 62% reduction in water use since 1990. The Australian paper industry’s water use compares favorably with industries elsewhere in the world (Bajpai, 2008). In the Netherlands, freshwater consumption in wastepaper-based pulp and paper mills is 8.4 m3/ton of production in 2008. The production process operates a closed water system, whereby the water system is divided into two large process water cycles, which are separated by the thickener: the stock preparation cycle with comparatively contaminated water, and the paper machine cycle with comparatively clean water. The production process is improved by inserting an extra thickener in the process. As a result, an extra water cycle is created between refiner and cleaner. The new cycle comprises refiner and thickener, while the paper machine cycle comprises cleaner and paper machine. The improved process reduces freshwater consumption to 4.4 m3/ton of production. The German paper industry reduced its specific effluent volumes from 46 m3/ton of paper in 1974 to around 11 m3/ton in 2002. Specific effluent volumes for mills producing paper and board from recycled fiber range from 3–8 m3/ton (Bajpai, 2008). Four German mills now operate integrated closed circuit water treatment, producing no effluent (Neidhardt, 2004). Stock preparation and paper machine circuits are separated to reduce effluent volumes in mills producing packaging papers, with freshwater added only to the cleanest circuit on the paper machine. Clear filtrate is passed through filters to replace freshwater used in jets to control consistency. In fact, specific water consumption in Germany has reduced significantly during the past 30 years, starting at about 50 m3/ton of paper produced and reducing to almost 10 m3/ton of paper in 2004 (Schabel and Hamm, 2007). Jaakko Poyry (2002) has reported that Indian pulp and paper mills consumed much more water per ton of product and discharged more pollutants compared to their European counterparts (Table 4.11). However, the water consumed and effluent discharged by Indian papermakers had reduced significantly by 2005 because of economic and environmental pressures, which has been confirmed in a study conducted by the National Productivity Council in association with the Central Pollution Control Board of India (NPC, 2006). The specific water consumption data are presented in Tables 4.12–4.14. To calculate the effluent discharge, it is assumed that about 21% of the water is lost through evaporation and as moisture in the final product. From
Water Usage in the Pulp and Paper Processes 47 Table 4.11: Effluent benchmarking of Indian pulp and paper mills.
Mill Type Indian agro-based integrated mills Indian forest-based integrated mills European forestbased integrated mills Indian wastepaperbased mills European wastepaperbased mills
Flow (m3/ton)
Total Suspended Solids (TSS) (kg/ton)
Chemical Oxygen Demand (COD) (kg/ton)
Biological Oxygen Demand (BOD) (kg/ton)
Adsorbable Organic Halides (AOX) (kg/ton)
120
40
47
10
n/a
175
11
37
3.7
0.4
40
1.5
12.0
1.5
0.1
32
2.6
8.7
1.3
n/a
10
1.0
5.0
1.0
n/a
Based on Poyry J., 2002. Report on Global Competitiveness of Indian Paper Industry.
Table 4.12: Water consumption in large-scale Indian mills. Raw Material
End Product
Water Consumption (m3/ton)
Wood and wastepaper Wood and wastepaper Wood, agro residue, and wastepaper
Newsprint Cultural–high grade Cultural–high grade
80 77 67
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
Table 4.13: Water consumption in medium-scale Indian mills. Raw Material
End Product
Water Consumption (m3/ton)
Agro residue and wastepaper Agro residue and wastepaper Wastepaper
Cultural—high grade Industrial grade Cultural—high grade
80 47 48
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
Table 4.14: Water consumption in small-scale Indian mills. Raw Material
End Product
Water Consumption (m3/ton)
Agro residue and wastepaper Agro residue and wastepaper Wastepaper Wastepaper
Cultural—high grade Industrial grade Cultural—low grade Cultural—low grade
110 93 13 129
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
48 Chapter 4 Table 4.15: Cluster rule (bleach plant effluent discharge). Adsorbable organic halides
Dioxin and 12 chlorinated phenolics Trichlorodibenzofuran (TCDF) Chloroform Color, acetone, methyl ethyl ketone, methylene dioxide
0.623 kg/ton (Monthly Average) 0.512 kg/ton (Annual Average) 0.951 kg/ton (Daily Maximum) Non detect TCDF 31.9 pg/L (daily maximum) Chloroform 4.14 g/ton No limit
Based on Anon, 1997. Industry news: cluster rule signed. Tappi Journal 80 (12), 14.
this detailed field study, it is clear that water consumption varies significantly, depending upon the raw material used, the scale of the operation, and the end product produced. There are no standards for the quantities of water consumed and effluent discharged in most developed countries. However, it is controlled indirectly by standards for the discharge of pollutants per ton of product. In the US, it is governed by the cluster rules (Anon, 1997; Table 4.15). The limit of COD discharge used to be 25.4 kg/ton. In addition, efforts are being made to close water cycles in mills to reduce freshwater consumption and the discharge of effluents in the US and in Europe (IPPC Directive, 1996). The EU Integrated Pollution Prevention and Control (IPPC) directive to obtain high environmental standards by considering effluents, air emissions, and solid waste was adopted in September 1996 and legislated into national laws in October 1999. All pulp and paper mills with a production capacity of more than 20 tons/day come under the scope of the IPPC directive. The concept of best available techniques (BAT) plays a central role in the IPPC directive. BAT is considered the best tool to achieve IPPC by providing a basis for emission limit values. The definition of BAT for the pulp and paper industry was started in 1997, and the final document was published in July 2000 (http://eippcb.jrc.es). Corporate Responsibility for Environmental Protection (CREP) was formulated jointly by the Central Pollution Control Board, New Delhi, and the Ministry of Environment and Forests in close association with the industry in March 2003. It addresses issues common to both large and small pulp and paper mills in India, and also issues particular to large mills and small mills. The following water discharge standards (Table 4.16) were agreed by the different pulp and paper manufacturing associations of India (CPCB, 2003). While this standard is discharge-specific, it also takes into account the size and age of the mill. It does not differentiate between the pulping process, the raw material used, and the end product. The Centre for Science and Environment (CSE), New Delhi, India, through its Green Rating Project, has reported a significant reduction in water consumption in large-scale Indian paper mills. In 2002, the average fell to 135 m3/ton paper due to increased awareness of the need for water conservation, increasing pressure from government regulatory agencies and water scarcity in many regions. The CSE findings indicate that most mills are already achieving the water consumption standards set by the CREP program (NPC, 2006).
Water Usage in the Pulp and Paper Processes 49 Table 4.16: Emission standards in the Indian pulp and paper industry. Effluent discharge, m3/Adt paper
150, from April 1, 2005
Chemical oxygen demand (COD) (mg/L) Biological oxygen demand (BOD) (mg/L) AOX (kg/Adt paper)
350
<140, from April 1, 2005 <120, from April 1, 2007 <100, from April 1, 2007 for Mills Set Up After 1992 350
30 (100a)
30 (100a)
AOX (kg/ton pulp) Upgrading of ETP Utilization of treated effluent for irrigation
<2.0 from April 1, 2006 <1.5 from April 1, 2005 <1.0 from April 1, 2008 <1.0 from April 1, 2008 AOX (kg/ton pulp) 20% higher than that based on paper Before April 1, 2004 N/A Wherever possible Wherever possible
Adt, air-dried ton; AOX, adsorbable organic halides; ETP, effluent treatment plant. aBOD for land discharge, 100 mg/L. Based on CPCB, 2003. Corporate responsibility for environmental protection [cross ref., Panwar, S., Endlay, N., Gupta, M.K., Mishra, S., Mathur, R.M., Kulkarni, A.G., 2006. Charter on corporate responsibility for environmental protection in pulp and paper industry – implication and compliance. IPPTA Journals 18 (4), 63–69].
Average water consumption for large, wood-based pulp and paper mills, primarily water consumption producing paper and paperboard products, in developed countries varies from 30 to 67 m3/ton of product. It varies from 8 to 10 m3/ton of product in wastepaper-based pulp and paper mills. In addition, efforts are being made to reduce it further by introducing closed water cycles. Exact knowledge on water consumption and quality in different uses forms the basis for good water management. In paper mills that have implemented BAT, freshwater is mainly introduced to the process as shower waters and chemical handling. The more efficient fiber and filler recovery technique has made it possible to use the resulting clear water in less critical showers of the paper machine and thus to increase recycling of water. The recycling rate of clear filtrates can be further increased by adopting ultrafiltration as a technique for the internal treatment of white water. However, due to only partial removal of dissolved materials by use of ultrafiltration, further increase of recycling (for example, for press section showers) is not yet considered feasible. Closed water circulation of paper machine waters would require more efficient separation techniques like nanofiltration, reverse osmosis, or other complementary techniques. For closing up the water systems, knowledge, awareness, and proper actions for controlling the water system are required. Control of microorganisms, proper design of the piping and storage systems, and material selection actually help to keep the surfaces in clean condition and reduce the requirement for washing. Recycling stream monitoring by measurements and laboratory analysis can be used to determine the actual performance of separation processes and the quality of shower waters and other process waters (Bajpai, 2008). Data gathering on water flows and the chemical state of the water systems makes it possible to study and control the water behavior of
50 Chapter 4 the whole mill and to determine the best running conditions for quality changes, startups, and shutdowns. For example, operation procedures with large pH or temperature gradients should be omitted because they lead to harmful deposit and scaling formations. Online measurements and accurate process control are important for effective and stable papermaking. Recycling of cooling and sealing waters can be increased by using heat exchangers or a cooling tower. However, microbial and water quality monitoring and control methods are required to ensure disturbance-free performance of the system. In cases where recovery and reuse of coating colors from coating wastewater by membrane technique is not possible, flocculation of this concentrated partial wastewater stream is considered as the best available technique. The ultrafiltration separation technique is mentioned as a measure for reducing the solid waste. The removal efficiency after wastewater treatment and the environmental impact as a whole can be improved by using nontoxic and biodegradable products and process chemicals. In developing countries, water consumption per ton of product is much higher. The paper industry and the regulatory agencies are trying to reduce water consumption. Water consumption varies significantly, depending upon the raw material used, the scale of the operation, and the end product. Recognizing these variations, it was clear that one or two general standards would not be enough for the entire pulp and paper sector. Accordingly, considering the characteristics of India’s pulp and paper mills, six types of pulp and paper mills in respect of water consumption patterns are proposed for the formulation of standards (NPC, 2006): Three levels of standards have been formulated considering the previously mentioned factors (Table 4.17). The consolidated proposed water consumption/wastewater discharge standards for each category of the pulp and paper mills are presented in Tables 4.18 and 4.19. Table 4.17: Standards formulated. Benchmark Standard: Refers to minimum water consumption required after implementation of best available technology (economically viable and currently practiced/demonstrated in India), recycle, and reuse practices. This standard has been developed by identifying the various mill operations involved in each category and identifying the least water consumption achieved by any of the mills studied in that category. The total water consumption in each mill operation/process will be the benchmark standard for that specific category. Best Achieved Standard: Refers to the minimum water consumption already achieved by a mill (or can be achieved by implementing simple recycling/reuse measures) in a specific category. Relaxed Standard: Provides 20% relief over the best achieved standard in each category. This standard is proposed for immediate reduction in water consumption by most of the high water-consuming industries, thus bridging the gap between the best performing and worst performing mills in a short time. It is estimated that this standard can be achieved by other industries by implementing simple reuse, recycling, and other minor modification
Water Usage in the Pulp and Paper Processes 51 Table 4.18: Proposed water consumption standards. Water Consumption, m3/ton of Product
Large-scale wood-based and integrated pulp and paper mills manufacturing newsprint Cultural-grade paper and paper board Small/medium–scale agro-based pulp and paper mills manufacturing cultural-grade paper Small/medium–scale agro-based pulp and paper mills manufacturing industrial grade All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper and/or newsprint with deinking All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper without deinking All medium/small–scale wastepaper-based pulp and paper mills manufacturing industrial-grade paper
Benchmark
Best Achievable
Relaxed
63
67
80
38
80
95
18
47
56
19
41
49
9
13
15
6
6
7
Based on National Productivity Council, 2006. Final Report on Development of Guidelines for Water Conservation in Pulp and Paper Sector. New Delhi, India.
Table 4.19: Proposed wastewater discharge standards. Wastewater Discharge Standards, m3/ton of Product
Large-scale wood-based and integrated pulp and paper mills manufacturing newsprint Cultural-grade paper and paper board Small/medium–scale agro-based pulp and paper mills manufacturing cultural-grade paper Small/medium–scale agro-based pulp and paper mills manufacturing industrial grade All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper and/or newsprint with deinking All wastepaper-based pulp and paper mills manufacturing high-grade cultural paper without deinking All medium/small–scale wastepaper-based pulp and paper mills manufacturing industrial grade paper
Benchmark
Best Achievable
Relaxed
50
53
63
30
63
75
15
37
44
15
32
38
7
10
12
5
5
6
Based on National Productivity Council, 2006. Final Report on Development of Guidelines for Water Conservation in Pulp and Paper Sector. New Delhi, India.
52 Chapter 4
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