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An investigation into the environmental and chemical aspect of sugarcane paper and wood fiber paper Bakhurji, Ammar; Leung, Auburn; Kim, William; Wang, Yu Chen Apr 4, 2013

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UBC Social Ecological Economic Development Studies (SEEDS) Student Report       An Investigation into the Environmental and Chemical Aspect of Sugarcane Paper and Wood Fiber Ammar Bakhurji, Aburn Leung, William Kim, Yu Chen Wang  University of British Columbia APSC 262 April 4, 2013           Disclaimer: ?UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report?.   1 An Investigation into the Environmental and Chemical Aspect of Sugarcane Paper and Wood Fiber Paper               Ammar Bakhurji  Auburn Leung  William Kim  Yu Chen Wang     Instructor: Dr.Mills April 4th,2013  Applied Science 262 Technology and Society II University of British Columbia  2 Abstract The University of British Columbia is a leader in the sustainability movement. With the increasing demand for paper in the developing countries such as China and India, the growing concerns for the environmental impacts are expected to accumulate over time. Our report investigates the environmental concerns in the production stages of both types of paper. The investigation focuses on various categories such as chemicals used in bleaching, different types of bleaching processes, quantitative analysis on wastewater, and alternative methods of bleaching process. This report includes a case study in Iran, academic journals, and data collected from past production reports. Based on the findings from the investigation, it is environmentally prominent to opt for bagasse (sugar cane) paper when it is challenged with wood fiber paper due to the quantity of wastes generated, and the amount of water required to effectively treat the said wastes.    3 Table of Contents Contents Abstract ....................................................................................................................................................... 2 Table of Contents .................................................................................................................................... 3 List of Illustrations ................................................................................................................................. 4 Glossary ...................................................................................................................................................... 5 List of abbreviations .............................................................................................................................. 6 1.0 Introduction............................................................................................................................. 7 2.0 Chemical use for Bleaching ..................................................................................................... 7 2.1 Bleaching Chemical .................................................................................................................... 7 3.0 Bleaching process .................................................................................................................... 10 3.1 Bleaching methods .................................................................................................................. 11 3.1.1 Elemental chlorine-free ..................................................................................................... 11 3.1.2 Total chlorine-free ............................................................................................................... 11 3.1.3 Processed chlorine-free ..................................................................................................... 11 3.2 Cost of different methods ..................................................................................................... 12 4.0 Alternative Bleaching Technology .................................................................................... 13 4.1 Adsorbable Organic Halides (AOX) ................................................................................... 13 4.2 Alternative Methods of Bleaching ..................................................................................... 13 4.3 Case Study in Iran .................................................................................................................... 14 5.0 Environmental Assessment of Waste Water ................................................................. 15 5.0.1 Where Are These Wastes Coming From? .................................................................... 15 5.0.2 COD and BOD? ....................................................................................................................... 15 5.0.3 AOX Content ........................................................................................................................... 16 5.1 Water Consumption for Diluting Water Wastes .......................................................... 16 5.2 Possibility of Alternative Methods for Bleaching? ...................................................... 17 6.0 Conclusions and Recommendation ................................................................................... 18 References .............................................................................................................................................. 19     4 List of Illustrations  Figure 1: Water used, and the generated wastewater (K. Ranganathan, 2007)    5 Glossary Alkaline condition ? The pH value has to high than 7. Bagasse ? Fiber material that remains after sugarcane juice is being extracted.  Bleaching ? Chemical process that decrease the color of the pulp or bagasse. Dioxin ? A diverse range of chemical compounds which are known to exhibit dioxin-like toxicity Elemental Chlorine Free (ECF) ? A technique that is using the chlorine dioxide for bleaching. Environmental Protection Agency (EPA) -an agency created for protecting human health and the environment by enforcing regulations and laws passed by Congress Lignin ? Complex chemical compound that is taken out from wood. Total Chlorine Free (TCF) ? A technique that is complete not using any chlorine                                                    chemical for bleaching. COD- The standard method for indirect measurement of the amount of pollution (that cannot be oxidized biologically) in a sample of water. BOD- The amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water, such as that polluted by sewage. It is used as a measure of the degree of water pollution. AOX- refers to a family of stable compounds produced when halogens (for example, chlorine) are used for bleaching, such as chlorine, bromine, and iodine, react with organic matter TSS- A measure of the suspended solids in waste water, effluent, or water bodies.    6 List of abbreviations  AOX-Adsorbable Organic Halides C ? Chloride  COD- Chemical Oxygen Demand BOD- Biochemical Oxygen Demand D - Chloride dioxide E - Extraction with sodium hypochlorite ECF -Elemental chlorine free ECT ? Elemental Chlorine Free EPA- Environmental Protection Agency  H - Sodium Hypochlorite O ? Oxygen P - Alkaline Hydrogen peroxide PAA - Peroxy acids PCF -Processed Chlorine Free  TCF ? Total Chlorine Free TCF- Totally chlorine free TSS- Total Suspended Solids X ? Enzymes Y - Sodium hydrosulfite Z ? Ozone    7 1.0 Introduction  The world demand for paper is expected to grow 2.1% by 2020. Due to this increase of demand, the growing concern over the environmental effect of paper mills is expected to increase, as well. Moreover, the increase cost of pulpwood and the constraints of fiber supply in the paper industry have led to the development of competitive alternatives to the wood fiber paper. One of these alternatives is sugarcane paper, or bagasse paper. Processes of producing paper are similar in all types of fiber raw materials13. The differences, if existent, only arise due to the availability of different process options for each section of the paper mills. This paper investigates the environmental effects caused by producing paper from wood, or sugar cane and compares the effects of both in order to provides the more environmentally cleaner option. 2.0 Chemical use for Bleaching  After researching, we found out that the chemical uses for bleaching process are not quite different from the sugarcane paper and wood fiber paper. The purpose of the bleaching process is to decrease the color of the pulp from the wood fiber or sugar cane bagasse. The brightness and whiteness is very important to make papers, therefore the bleaching process are necessary for such purpose. However the chemical that is used in the bleaching process has a great negative impact on the environmental.  2.1 Bleaching Chemical     The most common chemical use in a bleaching process are, Chloride with letter C, Sodium Hypochlorite with letter H, Chloride dioxide with letter D, Extraction with sodium hypochlorite with letter E, Oxygen with letter O, Alkaline Hydrogen peroxide with letter P, Ozone with letter Z, Enzymes with letter X, Peroxy acids with letter PAA, and Sodium hydrosulfite with letter Y.  Different bleaching methods uses different chemical to bleach. For example the bleaching sequence CEHEH has an effect of exposing the pulp to chlorine, and ?extract with the a sodium hydroxide solution to remove lignin fragmented by the chlorination, treated with sodium hypochlorite, washed with sodium hydroxide again and given a final treatment with hypochlorite?.   8 Chlorine dioxide is used alone in the elemental chlorine-free (ECF) bleaching sequence, but the chlorine dioxide usually is used combining the chlorine. The reason for using the chlorine dioxide is to ?minimize the amount of organochlorine compounds produced? (E.Sjostrom,1993). Chlorine dioxide is the most common use round the world. However chlorine dioxide is very explosive and unstable in high concentration. Therefore this chemical is used immediately after it is been produced.  In order to produce the chlorine dioxide, sodium chlorate needs to react with sulfur dioxide.  2 NaClO3 + H2SO4 + SO2 ? 2 ClO2 + 2 NaHSO4 (E.Sjostrom,1993 )  Chloride is also the most common used chemical in bleaching process. The reason is that the characteristic of strong electrophilic and oxidizing. The principle is to remove the lignin from the cellulose fibers, though ?aromatic substitution?  The chloride reacts with water will replace hydrogen atom on the ?aromatic rings of lignin? with chloride atom and hypochlorous acid.  Cl2 + H2O ? H+ + Cl- + HClO (Fari, G.M.;J.C. Morris, S.L. Chang, I. Weil, and R.P. Burden,1948)  All the bleaching chemicals that are used to de-lignify are going to smaller and oxygen-container molecules. These breakdown materials need to be removed, before these chemicals react again, from the bleaching process. These chemicals are easily removed because the materials are soluble in water.    Since the chemical chloride has negative impact to the environment, a total chlorine free bleach process has been discovered, TCF. Ozone is the additional method of bleaching sequence to chloride dioxide, and not using any ECF. The benefit of using the ozone in the bleaching process is to decrease the use of other chemical in the bleaching process, so that to decrease the negative impact to the environment from the waste of using the chemical. The disadvantages of ozone bleaching are that the ozone has a very low water solubility, which means that the disposal of the ozone waste would be a  9 problem, and the ozone is toxic even in a very low level. During the bleaching process, ozone will ?reach with the carbon carbon double bonds in lignin, including those within aromatic rings?, (?the original?, 2007) and the cleaved aromatic rings form muconic acid.   Hydrogen peroxide requires many dynamic conditions for removing the lignin. The hydrogen peroxide is firstly being degraded to superoxide and hydroxide radicals, and which would remove the lignin. The pH value and the temperature for this chemical reaction are very high. The pH value requires to be larger than 9, and the temperature needs to be larger than 90 degree Celsius. Before using the hydrogen peroxide, chelating agents is used to remove the metals that would decompose hydrogen peroxide. Compare to Chloride or Chloride dioxide, hydrogen peroxide is less selective under the lignin removal condition.   Another chemical that is used in bleaching, which produces less chlorinated organic to waste is Oxygen. The cost of oxygen is much lower than chlorine dioxide, resulting many paper manufactory choose oxygen over chlorine dioxide. Also the oxygen has lower corrosiveness than the other chemicals. On the other hand, there are many disadvantage of oxygen bleaching. Using oxygen bleaching can only remove fifty percent of lignin; the process will lose selectivity after removing fifty percent of lignin in order to improve the selectivity of oxygen bleaching, magnesium can be added for that purpose. The oxygen has very low water solubility therefore the treatment for the waste would be very expensive.  Because the oxygen is used in the bleaching process as a gas, therefore the oxygen is not very reactive. And in order for it to react with ionized phenolic hydroxyl group, the beaching process has to carry out under alkaline condition.      10 3.0 Bleaching process  Woodchips are raw material for producing wood pulp. They are produced by woodchipper, which are machines powered by internal combustion engine ranging from three to a thousand horsepower. After woodchips are made by cutting larger pieces of wood, they are graded and the leftover woodchips are to be used as a solid fuel for heating in buildings or in energy plants for generating electricity.  The raw material is not naturally white; the appearance of pure whiteness is a result of multi-phase bleach processes. Wood comprises of lignin and cellulose; Cellulose is the structural component for making pulp and paper, and lignin is a natural adhesive that binds wood fibers together. During the pulping process, the lignin and cellulose are separated, and up to about 90 percent of the lignin are dissolved without degrading the cellulose fiber (Reeve,1987).  The objective of removing lignin from the pulp is to lighten the color of the pulp, ensure paper remains brighter longer, and improve quality (Gerholdt, 2007, para. 3). The pulp is bleached in a combination of alternating bleaching and washing phases, the pulp can be very bright without degrading its structure and strength. When the last of the lignin is removed from the pulp after repetitive bleaching processes, the chemicals used in bleaching effectively dissolve any extractives contained in the pulp and dissolves remaining bark debris.     11 3.1 Bleaching methods  Chlorine is the most commonly used whitening agent for bleaching. There are three common methods of bleaching processes: elemental chlorine-free (ECF), processed chlorine-free (PCF), and totally chlorine-free (TCF) (Gerholdt, 2007, para. 4).   3.1.1 Elemental chlorine-free  The most common method used in North American pulp mills is Elemental Chlorine Free bleaching because it is due to mandates put on pulp mills by US EPA 1 regulation to eliminate the use of elemental chlorine gas (Gleason,2009). However, ?ECF does not preclude the use of chlorine compound and derivatives of chlorine, such as chlorine dioxide? (Gerholdt, 2007, para. 5). ECF only reduces the potential of dioxin2, carcinogens and toxic compound formation; they are disposed from pulp mill?s waste water to waterways, affecting the aquatic ecosystem. 3.1.2 Total chlorine-free   Total Chlorine-free bleaching does not use any chlorine chemicals; it utilizes Hydrogen peroxide, oxygen and ozone promoting a zero-discharge system where all possible solid and liquid waste is recycled. Ozone removes residual lignin from pulp more effectively than peroxide, but the ozone requires special equipment. However, the quality of the paper is competitive to chlorine bleached paper (Gleason,2009). 3.1.3 Processed chlorine-free   Recycled papers are typically processed by chlorine-free method.  Typical chemicals used include peroxide, oxygen and hydrosulfite, but no chlorine or derivatives are used in the process. The quality of these papers is often compatible to TCF or ECF paper.                                                           1 Environmental Protection Agency (EPA) 2 Dioxin is extremely harmful to the environment and human health  12 3.2 Cost of different methods  Chlorine free bleaching methods are more cost beneficial than elemental chlorine because chlorine free can result in costs savings in pollution control, safety equipment, security and workplace safety costs (Gerholdt, 2007, para.14). Paper mills are not adopting these environmentally and socially preferable bleaching alternative is because the capital cost in investment can be substantial, but in the long term these mills will save money (Environment America, 2007).  In 2000, Samoa mill is the first mill in the world that operates on total chlorine free process, which required an additional of $7.2million. However, the long term benefits are: ?2% increase in pulp production, 12% reduction in total mill waste, including a 31% reduction in bleach plant effluent, and a 19% decrease in water use?; this lowers the mill?s operating cost by $1.1 million (Environment America, 2007).     13 4.0 Alternative Bleaching Technology  The main environmental concerns of the paper production are dioxin level in both air and water wastes, and the organic load of Adsorbable Organic Halides (AOX). These concerns arise mainly from the bleaching process13. Due to the increase demand and pressure to reduce the emission and release of those compounds, research has been focused in obtaining the most environmentally process available.   4.1 Adsorbable Organic Halides (AOX)  Adsorbable Organic Halides are a family of chemicals produced from halogens, such as chlorine, reaction with organic materials. AOX has a unique property of adsorption on activated carbon. Although the introduction of AOX is a recent subject of research, the effect on marine life and aquatic environment is well documented. In fact, AOX has been reported as carcinogenic chemical.  4.2 Alternative Methods of Bleaching  Dioxin and AOX arise from the use of chlorine gas, and chlorine dioxide as bleaching agents in the bleaching process. Chlorine use has been decreasing rapidly in the industry and substituted with chlorine dioxide14. No bleaching substitute to chlorine dioxide, with the same potential has been found. However, research has been focusing on other ways to eliminate the problems of both AOX and dioxin levels. Due to the fact that each wood or bagasse fiber differs in content that any other same fiber, bleaching requirements, in terms of amounts, differ. In other words, each fiber used in every industry is unique and requires different amounts of bleaching than other fibers, although not substantially different3. Thus, in order to reduce AOX and dioxin levels, experimental data on different bleaching sequences are done for different plants in literature13. In India, an analysis was made that recorded a reduction in AOX content by 10-65% by adhering to a certain bleaching sequence that uses chlorine dioxide13.   14 4.3 Case Study in Iran  A case study in Iran was conducted to investigate the Pars paper factory in Iran. The plant is 1500 km from Tehran, the capital city. Hafttapeh Sugarcane Factory, which is the supplier of the raw materials of the paper plant, is near the Pars factory. This analysis of the plant included a life cycle analysis of sugarcane paper. The government of Iran owns the Pars Paper Factory. It has a production capacity of 40,000 metric tonnes of paper produced solely from bagasse.  One of the conclusions of the study is that energy and water consumption, Chlorine and raw materials used, and Greenhouse Gases emitted are less for sugarcane paper than in virgin wood paper. In other words, producing one tonne of paper from bagasse can save 17 trees, 360L of water, 100L of gasoline, 60 pounds of air pollutants, 10401 kilowatts of electricity, and 3.3 cubic meter of landfill space (Poopak & Reza, 2012).     15 5.0 Environmental Assessment of Waste Water Waste water that is streamed down from large hard-wood paper mills and sugarcane (bagasse) mills contain very high levels of BOD and COD contents, toxic substances, acids, and recalcitrant organics (organic and synthetic). Exposure to these wastes has been known to cause or can result in carcinogenic, Endocrine disruptor, diarrhea, intense vomiting, nausea, eye irritation, respiratory stress, oxidative stress and liver damage. These wastes carry life-threatening risks to the locals around the factory and for the organisms that live in nearby lakes and rivers.  5.0.1 Where Are These Wastes Coming From? Paper machine waste water is generated from large factory mills, where shredded wood or bagasse is cooked with white liquor, and bleaching units, where the partially-organic pulp is treated with chemicals such as chlorine dioxide. About 40-45% of the raw materials for paper are recovered as cellulose fibers, and the remaining parts are discharged as waste water (Ranganathan, 2007), which contains organic compounds and pulp fiber. These organic compounds are referred to as BOD, COD, Adsorbable Organic Halides (AOX), and Total Suspended Solids (TSS).   5.0.2 COD and BOD? Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are indirect measurements of the quantity of organic material in a sample of waste water. COD refers to the amount of water required (mg/L) to break down an organic compound by converting it to carbon dioxide, ammonia, and water through oxidation. Similarly, BOD refers to the amount of water required (mg/L) for biological organisms in a body of sample water to break down the organic material within a specific temperature and time period.      16 5.0.3 AOX Content  AOX refers to a family of stable compounds produced when halogens (for example, chlorine) are used for bleaching, such as chlorine, bromine, and iodine, react with organic matter. AOX has a unique property of adsorption on activated carbon. Although the introduction of AOX is a recent subject of research, the effect on marine life and aquatic environment is well documented. AOX compounds are reported to be carcinogenic and bio-accumulative, and cause ?chronic toxicity in aquatic organisms when they are discharged in large quantities as waste water.? (Ranganathan, 2007).   5.1 Water Consumption for Diluting Water Wastes After bleaching process and the actual paper manufacturing process, there is a large quantity of ?black liquor? released. This is the embodiment of COD and BOD content. To remove a substantial amount of COD and BOD, large quantity of water is used to dilute the solution. The distilled water help to stabilize and help remove as much COD and BOD as possible. The problem is the amount of water used in the diluting process; for this process to effectively remove contaminated waste water, substantial amount of water is used.  Figure 1: Water used, and the generated wastewater In the figure above, it is important to note that the waste water generated through the process is 87~93% of the actual distilled water used. For one ton of paper, 250 m^3 of water is used for the production. The amount of waste water pollution generated through the paper production is very large. In comparison to wood fiber paper, the production of bagasse paper requires less water, and generates less waste water as a result.    17 5.2 Possibility of Alternative Methods for Bleaching? The main environmental concerns of the paper production are dioxin level in both air and water wastes, and the organic load of Adsorbable Organic Halides (AOX). These concerns arise mainly from the bleaching process13. Due to the increase demand and pressure to reduce the emission and release of those compounds, research has been focused in obtaining the most environmentally process available.  Dioxin and AOX arise from the use of chlorine gas, and chlorine dioxide as bleaching agents in the bleaching process. Chlorine use has been decreasing rapidly in the industry and substituted with chlorine dioxide14. No bleaching substitute to chlorine dioxide, with the same potential has been found. However, research has been focusing on other ways to eliminate the problems of both AOX and dioxin levels. Due to the fact that each wood or bagasse fiber differs in content that any other same fiber, bleaching requirements, in terms of amounts, differ. In other words, each fiber used in every industry is unique and requires different amounts of bleaching than other fibers, although not substantially different3. Thus, in order to reduce AOX and dioxin levels, experimental data on different bleaching sequences are done for different plants in literature13. In India, an analysis was made that recorded a reduction in AOX content by 10-65% by adhering to a certain bleaching sequence that uses chlorine dioxide13.      18 6.0 Conclusions and Recommendation  Although bagasse and wood paper production have similar processes, the investigation of the environmental effect of bagasse and wood paper production has yielded that bagasse, in general, have less environmental effects that wood paper. Nevertheless, this analysis resulted from excluding transportation effects as well as using recycled wood in the production of wood-based paper. It is recommended that a life cycle analysis to be done that focuses on a specific plant with specific customers.         19 References   1.      Allister Maclean, Jae Yeong Bae, Ting Hin Wan. (2012). An investigation into wheat paper. This paper compares the Wheat Paper with wood fiber paper in three different aspect, Social, environmental, and economic. This triple bottom line assessment suggests that the wheat paper is more sustainable than the wood base paper. This reading is very helpful to our report because this report provide us a format of an official report.  2. Liliana Beatriz Molina Tirdo. (2009). Optimizing Alkaline sizing in Sugar cane bagasse paper  recycling. This paper investigates the recycling process of the  sugar cane paper. This paper is very technical to the recycling if the sugar cane paper. It has very detailed graph and data to show the energy use in recycling sugar cane paper. 3. Ricoh Canada Inc. (2012). TreeFrog Paper This article provided us some of the basic information about the sugar cane paper. We were able to draw in some of the key pros and cons in using sugar cane paper vs. wheat paper 4.  Kiatkittipong, W., Wongsuchoto, P., & Pavasant, P. (2009). Life cycle assessment of bagasse waste management options.Waste Management, 29(5), 1628-1633. doi: 10.1016/j.wasman.2008.12.006 This paper highlights that paper production is the most environmentally choice of utilizing bagasse in sugar cane industry  5. Ekvall, T. (1999). Key methodological issues for life cycle inventory analysis of paper recycling. Journal of Cleaner Production, 7(4), 281-294. doi: 10.1016/S0959-6526(99)00149-3 This paper discusses the best method to investigate the life cycle of wood-fiber paper. We were able to use this analysis to foretell some of the struggles using wheat and sugar cane papers.  6. Liang, S., Zhang, T., & Xu, Y. (2012). Comparisons of four categories of waste recycling in China?s paper industry based on physical input?output life-cycle assessment model. Waste Management, 32(3), 603-612. doi: 10.1016/j.wasman.2011.10.020 This paper compares the waste recycling process of wood-fiber paper with bagasse paper. Recycling is a big factor in deciding which paper is more durable and efficient.  7.Shapley, D. (2007, October 2).15 facts about the paper industry, global warming and the environment. http://www.thedailygreen.com/environmental-news/latest/7447 This short article states numerical facts about the environment impact of the paper industry.  20 8. Reddy, N., Yang, Y. (2005). Biofibres from agricultural byproducts for industrial applications.Trends in Biotechnology, 23, 22-27. This paper discusses the properties of fibre and the extraction process in detail, the structure and composition is thoroughly investigated. 9. Miles,K.B;Karnis,A (1995). Wood characteristics and energy consumption in refiner pulps. Journal of Pulp and Paper Science, v 21, n 11, p J383-J389. This is an analysis on the wood quality and energy consumption with respect to different coarseness and length and ways to minimize the energy consumption on certain types of fibre.  10. Grace Lee (2010). Sugarcane pulp as paper-making mat?l. http://ecop.pbworks.com/w/page/18520850/Sugarcane%20pulp%20as%20paper-making%20mat%E2%80%99l%200809 This is a simple summary of sugarcane paper production using the pulp; harvest methods, pros and cons in using sugarcane to produce paper for the people.  11. Walford S.N. (2008) SUGARCANE BAGASSE:HOW EASY IS IT TO MEASURE ITS CONSTITUENTS? Sugar Milling Research Institute Proc S Afr Sug Technol Ass (2008) 81: 266 - 273. http://www.sasta.co.za/wp-content/uploads/Proceedings/2000s/2008_%20Walford_sugarcane%20bagasse.pdf This report demonstrates the chemical composition of sugarcane, as well as whether it?s beneficial to use sugarcane as a biomass material aside from just paper.  13 Ranganathan, K., Jeyapaul, S., & Sharma, D. C. (2007). Assessment of water pollution in different bleaching based paper manufacturing and textile dyeing industries in india.Environmental Monitoring and Assessment, 134(1), 363-372. doi: 10.1007/s10661-007-9628-z Retrieved  from http://link.springer.com.ezproxy.library.ubc.ca/content/pdf/10.1007%2Fs10661-007-9628-z   This paper summarizes all the aspects of pollution resulting from bleaching by both bagasse and wood fiber paper.     21 14 Environment America. (2007). Pulp Fiction: Chemical Hazard Reduction At Pulp And Paper Mills Retrieved from http://www.environmentamerica.org/reports/ame/pulp-fiction-chemical-hazard-reduction-pulp-and-paper-mills Citation in text: (Environment America, 2007)  15 Gerholdt,J. (2007). Environmentally Friendly Bleaching Agents: How Papers Can Be Whitened Without Chlorine Retrieved from http://betterpaper.ning.com/profiles/blogs/environmentally-friendly Citation in text: (Gerholdt, 2007)  16 Princeton. (1987). Pulp Bleaching Technology Retrived from http://www.princeton.edu/~ota/disk1/1989/8931/893106.PDF  Citation in text: (Princeton, 1987)  17 Pradeep Kumar, Tjoon Tow Teng, Shri Chand, and Kailas L. Wasewar (2011). Treatment of Paper and Pulp Mill Effluent by Coagulation Retrieved from http://www.waset.org/journals/ijcee/v3/v3-4-36.pdf   18 Vaidhegi, K, (March 2013). Treatment Of Bagasse Based Pulp And Paper Industry Effluent Using Moving Bed Biofilm Reactor  Retrieved from http://www.sphinxsai.com/2013/vol_5_3/pdf/CT=29%281313-1319%29IPACT.pdf  

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