CPCB, 200 Copies, 2007

Transcription

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2 CPCB, 200 Copies, 2007 Published By : Dr. B. Sengupta, Member Secretary, Central Pollution Control Board, Delhi 32 Printing Supervision & Layout : P.K. Mahendru and Satish Kumar Composing, Laser Typesetting & Cover Page Design : Suresh Chander Sharma Web Version : U.A. Ansari and Shashi Goel Printed at :

3 FOREWORD The release of the Halogenated Organic Compounds in the environment is increasingly becoming a matter of concern due to their carcinogenic/toxic effects. Most of these compounds are adsorbable and the level of their presence in wastewater is assessed in terms of the parameter Adsorbable Organic Halides (AOX). The formation of these compounds is traceable to the use of Chlorine and chlorinated compounds in the various industrial processes including the bleaching process in the pulp and paper industries. The pulp and paper industries also being one of the major consumers of Chlorine and its compounds, need priority attention in the context of controlling AOX discharges in their effluents. The Central Pollution Control board has, therefore undertaken a project for evaluation of the various bleaching techniques used in the Pulp and Paper industries and their relative suitability with respect to the minimum discharges of AOX in the effluents. The present Report covers, a brief description of the pulp bleaching process and its environmental impact, cleaner technologies for the reduction of AOX discharges, details and findings of the studies conducted in the nine pulp and paper units selected for this purpose, and the recommended discharge limits for AOX. The able execution of the project by Central Pulp & paper Research Institute, Saharanpur, is gratefully acknowledged. We hope that the document would be useful to the pulp and paper industries and all those concerned directly or indirectly with the management of the Halogenated Organic Compounds. April, 2007 (J.M. MAUSKAR)

4 Development of AOX Standards for Large Scale Pulp and Paper Industries Project Team Dr. B. Sengupta, Member Secretary : Overall guidance M/s Central Pulp & Paper Research Institute, Saharanpur : Project execution Mr. P. M. Ansari, Additional Director : Project coordination Dr. R. S. Mahawar, Additional Director : Report revision, finalization and editing Mr. H. K. Karforma, Senior Environmental Engineer : Project coordination Mr. S. K. Gupta, Environmental Engineer Mrs. V. Hima Jwala, Senior Research Fellow : Project coordination and follow-up Project coordination and follow-up

5 PREFACE Bleach plant effluents from pulp & paper industries are known to exhibit toxicity to aquatic life. The toxicity is mainly due to discharge of Halogenated Organic Compounds formed during bleaching of pulp with chlorine based chemicals particularly molecular chlorine. The increased environmental pressures including the control of the release of carcinogenic compounds require the paper industries to adopt cleaner technologies such as the Elemental Chlorine Free bleaching techniques (ECF) and Total Chlorine Free (TCF) bleaching techniques for reduction of chlorinated organic compounds. Most of the chlorinated organic compounds that are carcinogenic, are adsorbable and hence the discharge of AOX needs to be controlled. Looking into the problems and limitations of the Indian pulp & paper industries in adoption or up-gradation of their technologies, the Central Pollution Control Board has undertaken a project on Development of AOX Standards for Large Scale Pulp & Paper Industries with an objective to assess the status of the technologies and permissible levels of AOX in effluents in respect of the large scale pulp & paper industries. The studies were conducted in nine selected pulp & paper industries to collect reliable information about level of AOX generation. The studies conducted have provided useful information on the status of the technologies and the levels of AOX discharges in the large-scale pulp and paper industries.

6 CONTENTS Page No. 1.0 INTRODUCTION PULP BLEACHING AND ITS ENVIRONMENTAL IMPACTS Bleaching chemicals and Bleaching sequences Formation of chlorinated compounds Toxic properties of chloro-compounds Chlorophenolics Polychlorinated Dioxins & Furans Carcinogenic and Mutagenic compounds Biological effects of Bleach plant effluents KAPPA NO. AND ITS RELATION TO PULP BLEACHING CLEANER TECHNOLOGIES FOR AOX REDUCTION Technologies for Kappa no. reduction Extended Delignification Improved Pulp Washing Oxygen Delignification Chlorine Dioxide substitution Oxidative alkali extraction bleaching NATIONAL/INTERNATIONAL LIMITS FOR AOX DISCHARGES OBJECTIVE & SCOPE OF THE PROJECT Criteria for Selection of industries Methodology Preliminary Survey of the Selected industries Identification of Sampling Points Analysis of samples Evaluation of Pulp Washing Efficiency Measurement of AOX Measurement of Effluent flow rates INDEPTH STUDIES IN SELECTED INDUSTRIES Writing & Printing paper manufacturing industries Newsprint Paper Industries Rayon Grade Pulp Industries GENERAL OBSERVATIONS Writing and Printing Grade Paper Industries Newsprint Industries Rayon Grade Pulp Industries Effluent Treatment Plants CONCLUSIONS RECOMMENDATIONS FINALIZATION AND NOTIFICATION OF AOX STANDARDS 33

7 1.0 INTRODUCTION The increasing environmental pressures and changing customer preferences in all spheres of life has made it essential that the bleaching techniques adopted by Indian paper industry are also critically evaluated to control and monitor the discharges of chlorinated organics. It is already known that discharge of chlorinated organic compounds through effluents and end products from pulp & paper industries have adverse effect on fauna and flora. The environmental hazards of bleach plant effluent result from the use of chlorine containing bleach chemicals especially molecular chlorine. The developed countries specially Scandinavian countries; Canada and USA have slowly eliminated the use of molecular chlorine over a period of last two decades and now moving towards total chlorine free bleaching (TCF) techniques in a phased manner. The Indian paper industry, which primarily utilises about 20% wood, 60%nonwood and about 20% waste paper, mostly bleach the pulp by chemicals like molecular chlorine, calcium hypochlorite which are responsible for the formation of chloro compounds. The quantity of chlorine required for bleaching one tonne of pulp ranges from 50Kg Kg. The total available chlorine requirement for different raw materials is 6-8% in case of Eucalyptus, 8-10% for Bamboo and 8-10% for Bagasse. It is therefore essential to make an assessment of the existing AOX levels in the effluents and technologies that are suitable for achieving the AOX discharge limits that are acceptable in the Indian Pulp and Paper industries. The present document covers a brief description of the pulp bleaching processes and its environmental impacts, cleaner technologies for the reduction of AOX discharges, details of the studies conducted for the characterization of waste streams in large scale pulp and paper manufacturing industries, and the findings, and the recommended discharge limits for AOX. 2.0 PULP BLEACHING AND ITS ENVIRONMENTAL IMPACTS 2.1 Bleaching chemicals and Bleaching sequences The bleaching chemicals are applied in multistage sequences wherein chemicals are mixed with pulp and allowed a period of retention for bleaching reactions to complete. The spent chemicals and dissolved impurities are removed by washing of pulp. The various bleaching chemicals used in pulp bleaching are given in Table-1. The bleaching sequences can conveniently be broken into two segments namely, Delignification Partial Sequence and Brightening Partial Sequence as given in Table - 2. The delignification partial sequence has the principle function of lignin removal and the brightening partial sequence increases the brightness. 1

8 Table - 1 : Chemicals Used in Pulp Bleaching Oxidants Form Advantages Disadvantages Chlorine Gas Effective, economical delignification. Good practical removal Can cause loss of pulp strength if used improperly. Organochlorine formation. Hypochlorite Ca(OCl 2 ), NaOCl solution 40 gpl as Cl 2 Easy to make and use Can cause loss of pulp strength if used improperly. Cholorform formation Chlorinedioxide 7-10 gpl ClO 2 solution in water Achieves high brightness without pulp degradation. Good particle removal. Must be made on site. Expensive. Some organochlorine formation Oxygen Gas used with NaOH solution Low chemical cost. Provides chloride-free effluent from recovery Used in large amounts requires expensive equipment. Can cause loss of pulp strength. Hydrogen peroxide 2-5% solution Easy to use low capital cost Expensive, poor particle bleaching. Ozone Gas in low concentration in oxygen Effective, provides chloride-free effluent for recovery Expensive, Degrades pulp. Poor particle bleaching Reductant Hydrosulfite (for mechanical pulps only) Solution of Na 2 S 2 O 4 or made onsite from NaBH 4 solution plus SO 2 ) Easy to use. Low capital cost. Decomposes readily. Limited brightness gain Alkali Sodium Hydroxide 5-10% NaOH solution Effective and economical Darkens pulp 2

9 Table - 2 : Bleaching Sequences Delignification Partial Brightening Partial Sequences Sequences CE H CDE D D-CE HD CEO HED OCE HDED DED DEPD C - Chlorine, E - Extraction with sodium hydroxide D - Chlorine dioxide, O - Oxygen, P - Hydrogen peroxide H - Hypochlorite. The traditional mode of delignification uses chlorine followed by extraction and hypochlorite treatment. Oxygen is another effective delignifying agent which is widely used to enhance the extraction stage and it is being used in advance of chlorine in order to reduce the carryover of organic matter to bleach plant. The hypochlorite and ClO 2 are mainly used for brightening of pulp. CEH is the traditional sequence used by the Indian paper industries to produce bleached pulp. But with increasing environmental pressure to reduce or eliminate organo-chlorine, the use of chlorine is decreasing rapidly with oxygen, peroxide and ClO 2 providing more environmentally compatible bleaching. 2.2 Formation of chlorinated compounds The conventional kraft wood pulp bleaching which includes chlorination typically produces kg of chlorinated organic materials per ton of bleached pulp. Approximately 300 different compounds in bleached pulp industries effluents have been identified and about 200 of these are chlorinated organic compounds. The types of chlorinated compounds found in Pulp bleaching effluents are listed in table-3: 3

10 Table - 3 : Chlorinated compounds found in Pulp Bleaching Effluents Type No. of Species Amounts Chlorinated acids 40 upto 500g/t pulp Chlorinated phenolics 40 upto 100g/t pulp Chlorinated aldehydes, Ketones and lactones Chlorinated hydrocarbons Chlorinated others High molecular weight materials -- upto 4 kg. Cl/t pulp It is well established that a series of chlorophenols are formed during bleaching process. The nature and extent of formation of chloro-organics is determined primarily by the residual lignin content in the pulp and the type of bleaching chemicals employed. The discharges of chlorinated organic compounds in paper industries effluents have long been known to exhibit acute, chronic and some mutagenic toxicity to aquatic life. Studies conducted in developed countries reveal that the low molecular weight chlorinated compounds are the major contributors to toxicity and mutagenicity. Most of the chlorine is otherwise bonded with high molecular weight organic compounds, which are stable against biodegradation, and contributes little to toxicity and mutagenicity. However, the past studies conducted indicate that these high molecular weight chloro compounds might also be broken down to smaller more biologically active compounds and can cause long-term toxic effects to the recipients. The relative contribution of the various chlorophenols to AOX is shown in Figure Toxic properties of chloro-compounds Chlorophenolics The Chlorinated compounds present in the alkali extraction bleach effluent are found to be more toxic and contribute more than 90% of acute toxicity. The chloro compounds like trichlorophenol, tri and tetra chloroguaiacols in particular may accumulate in fish and are responsible for acute toxicity Polychlorinated Dioxins & Furans Among the chlorinated phenolics, the dioxins & dibenzofurans are the groups of chlorophenoles found to have toxic effects. The prominent among the dioxins are 2,3,7,8 tetra chloro dibenzo dioxin (TCDD) and 2,3,7,8 tetra chloro dibenzo furan (TCDF). Dioxins are highly lypophyllic and bioaccumulative compounds. Such compounds are formed when unchlorinated dibenzo dioxin (DBD) & dibenzo furan (DBF) present in unbleached pulp are chlorinated in chlorination stage. The oil based pulp industry additives particularly brown stock defoamers 4

11 have been identified as potential sources of such compounds. Laboratory studies indicate a sharp increase in quantity of PCDD and PCDF when elemental chlorine consumption is increased beyond kg Cl 2 /tonne of pulp. The dioxins are quite resistant to degradation and have an elevated potential for bioaccumulation. The toxic effects of dioxins and the risk doses specified in different countries/agencies are given below in table-4. TCDD has been reported to cause cancer in rats but its effect on humans has been the centre of much debate and is still yet to be established. Table - 4 : Toxic Effects and Risk doses of Dioxins Agency / Country Risk dose* Toxic / health effect EPA 6.4 x 10-3 Cancer Germany 1.0 Cancer/reproductive FDA 5.7 x 10-2 Cancer * - Picograms of 2,3,7,8 TCDD/kg of body weight/day AOX 100% Relatively Lipophilic (Fat Soluble). Potentially Toxic. Potentially Bio-accumulable EOX ~ 1% 1% ~20% Low MW Material Low P ow >3 Highly Lypophyllic Bio-accumulative. (e.g. Dioxin 44% Chlorine By weight) ~80% High MW Material Relatively Hydrophilic (Water Soluble). Mainly Non-aromatic, ~ 19% Does not Permeate Cell Walls. 1-10% Chlorine By Weight Relatively Hydorphilic Includes Compounds Which can Easily Be Hydrolysed or Metabolised (e.g. Tricholoroacetic acid) Fig.1. Relative contribution of Chlorophenolic Compounds to AOX 5

12 2.3.3 Carcinogenic and Mutagenic compounds Bleach plant effluents contain chloroform and carbon tetra chloride which have been classified as carcinogens. The hypo-chlorite stage is the major producer of chloroform. The various chlorinated benzenes, phenols, epoxystearic acid and dichloromethane present have also been classified as suspected carcinogens. Some of the chlorinated compounds formed in Cl 2 -stage have been identified as strong mutagens. However, a very limited information regarding the tendency of mutagens to bioaccumulation is available. 2.4 Biological effects of Bleach plant effluents It is well known that bleach plant effluents are toxic to fish and other organisms mainly due to the presence of chloro-compounds. The biological effects of chloro-compounds on fish as characterized in the laboratory studies are: Acute toxicity: - Egg mortality - Percentage of fertilized egg. - Acute toxicity to newly hatched fry. Late effects: Survival and stress tolerance of fry from exposed parents. Effects on behavior: Response to rotary flow. Physiological and Histological sublethal effects: - Growth rate - Histological changes in lever. - Occurrence of parasitic in gills of flounder Bioaccumulation: - Effect on primary production in natural mixed phytoplankton populations. Genotoxic effects: - Mutagenic effects - Carcinogenic effects. 3.0 KAPPA NO. AND ITS RELATION TO PULP BLEACHING The Kappa no. is an index used by the pulp and paper industry to express the lignin content of a pulp. Lignin is responsible for the brown coloration of paper, and is removed by bleaching. Therefore, the lignin content must be well known, so that only a minimum amount of bleach is used. Higher the lignin content more is the kappa no. The pulp having high lignin content termed as hard cooked pulp and the pulp with low lignin content is termed as soft cooked pulp. The hard 6

13 cooked pulp required more bleaching chemicals to attain particular brightness compared to soft cooked pulp. 4.0 CLEANER TECHNOLOGIES FOR AOX REDUCTION 4.1 Technologies for Kappa no. reduction Pulp & paper industries have incorporated various measures to reduce the kappa no. and also to minimize the carry over of organic matter along with pulp as it governs the bleach chemical demand during the bleaching process. Some of these measures include oxygen delignification, extended delignification, improved pulp washing, substitution of elemental chlorine with chlorine dioxide, oxidative alkali extraction stage bleaching etc. 4.2 Extended Delignification The pulp and paper industries normally use kraft process in batch or continuous digesters to remove the lignin as much as possible during pulping of wood based fibrous raw material but the process has limitation that the wood based fibrous raw material can not be delignified to a low kappa number.since the kappa number is the main factor which governs the demand of chemicals for bleaching of the pulp the process was modified to achieve maximum possible delignification during cooking of raw materials and now most of the industries in developed countries are employing RDH, modified continuous cooking, super batch process etc to reduce the kappa number of the unbleached pulp. Modified pulping processes are energy efficient, require less chemicals for cooking of raw materials and produce the pulp of low kappa number with better strength properties as compared to conventional pulping processes. However, the high capital investment and high level of operation restrict the adoption of these technologies in Indian pulp & paper industries. Agro based pulp and paper industries normally use soda pulping process. 4.3 Improved Pulp Washing The pulp mill section of paper industries normally use brown stock washers for extraction of black liquor and for washing of pulp. The washing efficiency of these washers depend on nature and quality of fibrous raw materials. Most of the small industries use brown stock washers for washing of pulp produced from agro residues but the efficiency of these washers are not satisfactory as high carry over of black liquor along with pulp was observed in agro based industries. Since the pulp from agro residues is difficult to dewater so the industries can use the modified washing systems such as belt filter press, double wire washer etc, to minimize the carry over of the black liquor with pulp entering the bleaching section. 7

14 4.4 Oxygen Delignification Oxygen delignification is a well established technology and most of the pulp mill abroad are using this process to reduce the kappa number of pulp before bleaching stage. Single stage oxygen pre bleaching of the pulp reduces the pulp kappa number by % and two stage oxygen pre-bleaching reduces the pulp kappa number by 80%. The process is used in large pulp & paper industries in the developed countries. Indian paper industries have limitations in adopting the process due to high capital investments involved and low scale of their operation. The process needs to develop an economically viable oxygen pressure vessel for low scale of operation as the capacity of small scale pulp mills in the Country varies from ton /day or upgrade capacities of their plants for achieving viability in using these processes. 4.5 Chlorine Dioxide Substitution The elemental chlorine is the major source of toxic chlorinated phenolics and dioxins compounds and contribute more than 70% of total AOX. The chlorine dioxide, because of its high oxidation potential, decreases the formation of chlorinated phenolics, colour, AOX, dioxins etc in addition to improved quality of pulp. Most of the pulp mill in developed countries have substituted or replaced elemental chlorine with chlorine dioxide. The large pulp and paper industries in this Country have now started the use of chlorine dioxide also. 4.6 Oxidative alkali extraction bleaching The addition of small amount of oxygen or peroxide in alkali extraction stage improves the quality of bleach plant effluent by reducing colour & AOX. Most of the large paper industries in India have already started the use of oxygen or hydrogen peroxide in alkali extraction stage. The adoption of modified pulping and bleaching processes in pulp mill developed Countries has resulted in an increased recycling or reuse of the waste water to the internal process and efforts are being continued to achieve zero discharge. These industries are however required to operate the pulp mill under controlled conditions to reduce the kappa number and also to modify their pulp washing system to minimize the carry over of black liquor along with pulp in order to reduce the discharge of chlorinated phenolics compounds. 5.0 NATIONAL/INTERNATIONAL LIMITS FOR AOX DISCHARGES Most of the pulp and paper industries in developed countries have adopted new pulping and bleaching technologies in order to reduce the generation of chloro organics. Environmental Protection Agency (EPA) has issued the guidelines for 8

15 discharge of AOX, Dioxins and 12 numbers of other chlorinated organic compounds in the effluents. In India in the year 1992, Ministry of Environment & Forests (MoEF) has notified the discharge limits for chloro-organic compounds as Total Organic Chlorine (TOCl) 2kg/tonne of paper for large pulp and paper industries. The discharge limits for organo chlorine in some of the developed countries are given in Table-5. Table - 5 : Discharge Limits Of AOX in Different Countries COUNTRY Limits, Kg/tonne of paper MODE Sweden <1.0 TOCI Canada <1.5 AOX Germany <1.0 AOX India 2.0 TOCl 6.0 OBJECTIVE & SCOPE OF THE PROJECT The main objective of the study was to assess/ evaluate and obtain the data on the existing levels of AOX in the effluents from Indian pulp & paper industries producing different grades of paper namely, writing & printing, newsprint and rayon grade pulp using diverse raw materials, and different pulping & bleaching processes. This scope include collection of effluent samples from the identified sampling points to assess the levels of AOX generated & final discharge by Indian pulp & paper industries producing a variety of end products. 6.1 Criteria for Selection of Industries The paper industries were selected on the basis of raw materials used, bleaching practice employed, size of the industries and the type of end products. The types of paper industries selected for the study are: (i) (ii) (iii) Writing & Printing grade of paper; Rayon Grade pulp industries; and Newsprint grade of paper. 6.2 Methodology Preliminary Survey of the Selected industries The preliminary survey of selected pulp and paper industries was conducted through questionnaire requesting the industries to furnish detailed information 9

16 related to the size of industry, usage of raw materials, bleaching process employed, end product, existing effluent treatment facilities, disposal of treated effluent etc. The information thus provided was verified and further updated during the visit to selected pulp and paper industries Identification of Sampling Points The sampling points selected are : (i) Combined bleach plant effluents (ii) Influent to ETP / Primary Clarifier (iii) Overflow of primary clarifier, and (iv) Final treated effluent Analysis of samples The selected pulp and paper industries were visited for indepth study. Two visits were performed in each of the selected units for conducting the in-depth studies in order to generate representative and realistic data based information on AOX level in these category of pulp and paper industries. The sampling and flow measurement were done from identified points for 24 hours composite sampling in order to collect the representative samples. The composite samples collected were preserved and transported for further analysis of the following parameters: (i) ph (ii) Suspended Solids (iii) Chemical Oxygen Demand (iv) Biological Oxygen Demand, and (v) Adsorbable Organic Halides (AOX) Evaluation of Pulp Washing Efficiency The efficiency of existing pulp washing system in selected paper industries was also evaluated by estimation of carryover of black liquor COD along with pulp going to the bleach plant Measurement of AOX The preserved effluent samples (composite) collected from the industries were analysed for AOX as per DIN method 38409H (Flask Procedure) by using DX- 20 DOHRMANN AOX analyser Measurement of Effluent flow rates The flow rates of effluent generated were measured at different time intervals during the sampling period by using measuring devices such as V notch, 10

17 rectangular notch existing in the drain channels and also by using the float velocity method. 7.0 INDEPTH STUDIES IN SELECTED INDUSTRIES 7.1 Writing & Printing paper manufacturing industries Unit-1 Details of the industry and findings of the study are given in Table 6 The industry is mainly based on eucalyptus, bamboo and small amount of pine as the raw materials to produce writing & printing, and Kraft packaging grade papers. The production of these two grades of papers was 110 tpd and 45 tpd respectively. The Kappa no. of unbleached kraft pulp produced ranged 26-30, and it is being used both for writing & printing grade and also for unbleached kraft paper. For the production of writing and printing grade papers the pulp is being bleached by CE P HH bleaching sequence to a targeted brightness level of 75% ISO. The total AOX load generated is 3.58 Kg/t product (555 Kg/day) which is reduced to 1.23 Kg/t product (190 kg/day) in the final effluent discharge. The over-all reduction in AOX in ETP is 65.77%. Table - 6 : Details and findings of study in Unit Installed capacity,t / Year - 46, Raw materials - Bamboo, Eucalyptus, Pine 3. Paper production, T/Day a. Total b. Kraft - 45 c. W & P Grade Pulping process - Sulphate 5. Kappa no. of unbleached pulp Bleaching sequence - CE P HH 7. Bleached pulp brightness,% ISO Characteristics of waste water (Influent to ETP) a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day Contd.

18 e. Suspended solids, Kg/T Paper f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T Paper i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T Paper Characteristics of treated waste water a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l - 90 d. Suspended solids, Kg/ Day e. Suspended solids, Kg/T Paper - 17 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T Paper - 51 i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T Paper Efficiency of ETP a. Reduction in SS,% b. Reduction in COD,% c. Reduction in AOX,% Unit-2 Details of the industry and findings of the study are given in Table 7. The industry is manufacturing writing & printing paper, kraft paper & triplex board from bamboo (50-60%) and mixed hardwoods (40-50%). The unbleached pulp of Kappa is used both for writing and printing grade, and also for kraft packaging & triplex boards. The industry produces 156 t/day writing and printing paper against a total production of 165 t/day. In case of the production of writing and printing grade papers, the pulp is bleached by CEHH/CEHHP bleaching sequence to a brightness level of 78% ISO. The total AOX load generated is 5.03 kg/t of paper (831 kg/day) which is reduced to 2.50 kg/t of paper production (413 kg/day) after secondary treatment. The overall reduction in AOX in the ETP is 50.30%. 12

19 Unit-3 Details of the industry and findings of the study are given in Table 8. The industry is producing fine variety of paper from bamboo (90%) and Eucalyptus (10%). The production of paper during sampling period was 252 tpd. The pulp having kappa no is bleached by C/D EoHHD bleaching sequence to a brightness level of 82-84% ISO. The total AOX load generated is 4.49 kg/t paper production (1131 kg/day), which is reduced to 2.40 kg/t (603 kg/day) paper production after secondary treatment. The overall reduction in AOX during in the ETP is 46.72%. Unit-4 Details of the industry and findings of the study are given in Table 9. This industry is mainly based on bagasse, bamboo, and eucalyptus in addition to little proportion of imported pulp. Presently the industry is producing around 63t/day rayon grade pulp, 110 t/day writing & printing paper from eucalyptus and bamboo, and about 110t/day writing and printing paper from 90% bagasse bleached pulp and 10% imported bleached pulp. Rayon grade pulp (kappa no.16) is bleached by CEHD - SO 2 bleaching sequence to a brightness level of 87% ISO, while Eucalyptus & bamboo pulp of kappa no is bleached by CEHHD-SO 2 bleaching sequence to a brightness level of 83% ISO and bagasse pulp of kappa by C/DE o D bleaching sequence to brightness level of 85% ISO. The total AOX load generated is 2.32 kg/t production (662 kg/day) which is reduced to 1.37 kg/t production (390 kg/day) after secondary treatment and final discharge. The overall reduction of AOX in the ETP is 41%. Table - 7 : Details and findings of study in Unit Installed capacity, T/ Year - 70, Raw materials - Bamboo (50-60%) 3. Paper production, T / Day a. Total b. Kraft c. W & P Grade Mixed Hardwoods(40-50%) 4. Pulping process - Sulphate pulping 5. Kappa no of unbleached pulp Contd.

20 6. Bleaching sequence - CEHHp 7. Bleached pulp brightness,% ISO Characteristics of waste water (Influent to ETP) a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids, Kg/T Paper f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T Paper i. AOX, mg/l j. AOX, g/day k. AOX, Kg/ T Paper Characteristics of treated waste water a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids, Kg/T Paper - 70 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T Paper - 73 i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T Paper Efficiency of ETP a. Reduction in SS,% b. Reduction in COD,% c. Reduction in AOX,%

21 Table - 8 : Details and findings of the study in Unit Installed capacity, T/ Year - 1,00, Raw materials - Bamboo (90 %) - Eucalyptus(10 %) 3. Paper production, T/Day a. Total b. W & P Grade Pulping process - Sulphate 5. Kappa no of unbleached pulp Bleaching sequence - C/DEoHHD 7. Bleached pulp brightness,% ISO Characteristics of waste water (Influent to ETP) a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids, Kg/T Paper f. COD, mg/ g. COD, Kg/Day h. COD, Kg/ T Paper i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T Paper Characteristics of treated waste water a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids, Kg/T Paper - 74 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T Paper - 91 i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T Paper Efficiency of ETP a. Reduction in SS,% b. Reduction in COD,% c. Reduction in AOX,%

22 Table - 9 : Details and findings of the study in Unit Installed capacity,t/year: a. Total - 1,49,900 b. W&P Grade - 36,000 (Eucalyptus &bamboo) 82,500 (bagasse) c. Rayon pulp - 31,200 (Eucalyptus) 2. Raw material - Bamboo, Eucalyptus & bagasse 3. Paper production, T/Day: a. Total b. W & P Grade c. Rayon pulp Pulping process - Sulphate(Eucalyptus & bamboo) Soda (bagasse) 5. Kappa no of unbleached pulp - 16 (Eucalyptus, RG) 13 (bagasse, W & P) 20 (Eucalyptus & bamboo, W & P) 6. Bleaching sequence - CEHD (RG) - CEHH D/SO 2 (E) - C/ DEoD ( B) 7. Bleached pulp brightness,% ISO - 86 (Eucalyptus, RG) 80 (bagasse, W & P) 83 (Eucalyptus, W & P) 8. Characteristics of waste water (Influent to ETP) a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids,kg/t paper - 80 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T Paper i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T Paper Contd. 16

23 9. Characteristics of treated waste water a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids, Kg/T Paper - 52 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T Paper - 84 i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T Paper Efficiency of ETP a. Reduction in SS,% b. Reduction in COD,% c. Reduction in AOX,% Unit-5 Details of the industry and findings of the study are given in Table 10 The industry has installed capacity of 300 tonnes/day of manufacturing high quality bleached paper varieties. The main fibrous raw materials used are bamboo and wood. The mill has employed cleaner technologies like RDH Pulping, Oxygen Delignification with chlorine dioxide bleaching. The CDEoPD bleaching sequence is used for bleaching of the pulp having Kappa No The AOX level in effluent before treatment is 1.92 Kg/tonne of paper while after treatment in ETP its level comes down to 1.07 Kg/tonne of paper. The over-all reduction in AOX in the ETP is 44%. Unit-6 Details of the industry and findings of the study are given in Table 11. The paper industry has installed capacity of t/year for manufacturing writing & printing grade of paper. The main fibrous raw materials used for manufacturing 17

24 of quality paper are bamboo,wood,bagasse and grasses( Sabai,khar & Kai). The industry has two pulping street, new pulp mill is used to produce wood pulp having kappa no While the existing old pulp mill with eight nos. of digestors (32 m 3 each) is used to produce pulp of kappa no from bagasse & grasses. The industry is practicing both conventional bleaching (CHH) for pulp of low kappa no. pulp & CDEDD for wood pulp. The AOX level in effluent before treatment is 4.0 Kg/tonne of paper while after treatment in ETP its level comes down to 1.84 Kg/tonne. The over-all reduction in AOX in the ETP is 54%. 7.2 Newsprint Paper Industries Unit-7 Details of the industry and findings of the study are given in Table 12 The industry is based on bagasse, Eucalyptus and imported Chemi- Mechanical Pulp (CMP) wood. During sampling period, the production of industry was 276 t/d of newsprint and 253 t/d of writing and printing paper. The chemical pulp ( CP) produced from bagasse & Eucalyptus have Kappa 8-10 & respectively. The bagasse & Eucalyptus chemical pulps are bleached by CEH & CEHH bleaching sequences to the brightness level of 75 & 85% ISO respectively. The CMP bagasse is bleached by hydrogen peroxide to brightness level of 65% ISO. The newsprint fibre furnish is 40% bagasse CP, 40% bagasse Chemi Mechanical Pulp ( CMP) & 20% imported CMP of wood pulp while fibre furnish for writing & printing paper is 75% bagasse CP & 25% hardwood CP. The total AOX load generated based on total production of newsprint together with writing & printing paper is 1.79 kg/t(946 kg/day ) production which is reduced to 0.80 kg/t production (424 kg/day) after secondary treatment.. The above AOX level of 1.79 kg/t product is the combined AOX generated from newsprint as well as from writing and printing grades. Out of the total production about 10-12% is the imported CMP wood which does not require any bleaching and about 20-22% is the bagasse CMP where the bleaching done is very mild with hydrogen peroxide and there is no possibility of AOX generation. The AOX generation is mainly due to the bleaching of CP of bagasse and wood. The overall reduction in AOX in the ETP is 55.30%. 18

25 Table - 10 : Details and finding of the study in Unit Exercise Exercise Av.Values I II Installed capacity,t/y 90, Raw materials Bamboo and Hard wood 3. Writing & printing paper production T/D Pulping process RDH (Sulphate) 5. Kappa No. of unbl.pulp Bleaching practice C / DEoPD 7. Bleached Pulp Brightness,% ISO Characteristics of combined waste water (influent to ETP) - Flow,m 3 /d ph Suspended Solids,mg/l Suspended Solids,kg/t paper COD,mg/l COD,Kg/t paper AOX,mg/l AOX,kg/t paper Characteristics of Primary clarifier outlet - ph Suspended Solids,mg/l COD,mg/l AOX,mg/l Characteristics of final discharge -ph Suspended Solids,mg/l Suspended Solids,kg/t paper COD,mg/l COD,kg/t paper AOX,mg/l AOX,kg/t paper Performance of ETP: - Reduction in Suspended Solids,% Reduction in COD,% Reduction in AOX,% Waste water discharge,m 3 /t paper

26 Table - 11 : Details and findings of the study in Unit Exercise Exercise Av.Values I II Installed capacity,t/y Raw materials Wood,Bamboo, Bagasse & Grasses 3. Writing & printing paper production,t/d Pulping process Sulphate process 5. Kappa No. of unbl.pulp - Bamboo/wood Grasses/Bagasse Bleaching practice - Bamboo/wood C/ DEDD - Grasses/Bagasse CHH 7. Bleached Pulp Brightness,% ISO Characteristics of combined waste water (influent to ETP) - Flow,m 3 /d ph Suspended Solids,mg/l Suspended Solids,kg/t paper COD,mg/l COD,Kg/t paper AOX,mg/l AOX,kg/t paper Characteristics of Primary clarifier outlet - ph Suspended Solids,mg/l COD,mg/l AOX,mg/l Characteristics of final discharge - ph Suspended Solids,mg/l Suspended Solids,kg/t paper COD,mg/l COD,kg/t paper AOX,mg/l AOX,kg/t paper Efficiency of ETP: - Reduction in Suspended Solids,% Reduction in COD,% Reduction in AOX,% Wastewater discharge,m 3 /t paper

27 Table 12 : Details and findings of the study in Unit Installed capacity, T/ Year a. Total - 2,00,000 b. Newsprint - 1,00,000 (Bagasse & imported wood pulp) c. W & P Grade - 1,00,000(Eucalyptus & bagasse) 2. Raw materials - Bamboo,Eucalyptus,bagasse Imp. wood pulp 3. Paper production,t/day: a. Total b. Newsprint c. W & P Grade Pulping process - Sulphate (bagasse & Eucalyptus) CMP(bagasse) 5. Kappa no of unbleached pulp - 20 ( Eucalyptus CP) 10 (bagasse CP) 6. Bleaching sequence - CEH(bagasse CP) - CEHH(Euc.CP) - P(bagasse CMP) 7. Bleached pulp brightness, - 85 ( Bagasse, CP) % ISO - 65 (Bagasse, CMP) - 75 (Eucalyptus, CP) 8. Characteristics of waste water (Influent to ETP) a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids,kg/t paper - 97 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T paper i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T paper

28 9. Characteristics of treated waste water a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l - 90 d. Suspended solids, Kg/ Day e. Suspended solids,kg/t paper - 12 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T paper - 23 i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T paper Efficiency of ETP a. Reduction in SS,% b. Reduction in COD,% c. Reduction in AOX,% Unit-8 Details of the industry and findings of the study are given in Table 13. This newsprint industry is based on hardwoods (Eucalyptus & Casurina) CMP, CP of hardwoods and bamboo/reed (70:30) and the imported CP of softwood. The newsprint production was 250t/d during sampling period. The CP produced from hardwoods & bamboo/reed having Kappa no. around 20 is bleached by CH/E sequence to a brightness level around 60-65% ISO. While CMP produced from hardwoods is bleached by Hydrogen peroxide to brightness level around 55% ISO. The newsprint furnish is 70-75% CMP & 25-30% CP including imported CP. The results indicated that generation of total AOX load is 0.53 kg/t of newsprint (133 kg/day) which is reduced to 0.14 kg/t newsprint(36kg/d) production after secondary treatment. The over-all reduction in AOX is about 72.79% during the treatment. 22

29 7.3 Rayon Grade Pulp Industries Unit-9 Details of the industry and findings of the study are given in Table 14 This industry is mainly based on hardwoods (Eucalyptus and Casuarina) for manufacturing about 110t /day rayon grade pulp. The unbleached pulp of kappa no is bleached by CE o HE p D bleaching sequence to a brightness level of 85% ISO. The total AOX load generated is 0.69-kg/t pulp (76 kg/day), which is reduced to 0.2 kg/t pulp (22 kg/day) after secondary treatment. The low level of AOX generation is mainly due to low kappa of the unbleached pulp and use of oxygen in extraction stage and chlorine dioxide in the final stage of bleaching. The overall reduction in AOX level in the ETP is 71.05%. 8.0 GENERAL OBSERVATIONS A summary of the findings of the generation/discharges of AOX, SS and COD in different pulp and paper industries is given in Table Writing and Printing Grade Paper Industries The summary results of the AOX generation and discharge in large scale writing and printing paper industries are given in Table 16. AOX generation in pulp & paper industries producing writing & printing grade paper is found to be generally higher than newsprint and Rayon grade manufacturing industries due to high Kappa no. of the pulp and excessive use of molecular chlorine for achieving high brightness. Therefore, the generation of AOX is comparatively higher for writing and printing paper where final brightness is important. The levels of AOX measured in mill samples vary from 1.92 to 5.32 kg.aox/t paper. In the industries, where chlorine dioxide and oxygen or peroxide reinforced alkali extraction stage are used as bleaching agent, the generation of AOX is on lower side compared to level of AOX generated using conventional CEHH bleaching sequences. 23

30 Table - 13 : Details and findings of the study in Unit Installed capacity,t/ Year - 1,00, Raw materials - Bamboo, Eucalyptus, Casurina, Reed, & Imported wood pulp 3. Paper production, T/Day Pulping process - Sulphate (Eucalyptus,Casurina bamboo and Reed) - CMP (Eucalyptus and Casurina) 5. Kappa no of unbleached pulp - 20 (CP) 6. Bleaching sequence - CH/E(CP) - P(CMP) 7. Bleached pulp brightness,% ISO - 63 (CP) - 50 (CMP) 8. Characteristics of waste water (Influent to ETP) a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids,kg/t paper - 59 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T paper - 73 i. AOX, mg/l j. AOX, Kg/Day k. AOX, Kg/ T paper Characteristics of treated waste water a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids,kg/t paper - 15 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T paper - 39 i. AOX, mg/l j. AOX, Kg/Day - 36 k. AOX, Kg/ T paper Efficiency of ETP a. Reduction in SS,% b. Reduction in COD,% c. Reduction in AOX,%

31 Table - 14 : Details and findings of the study in Unit Installed capacity, T/ Year - 1,00, Raw materials - Eucalyptus & Casurina 3. Pulp production, T/Day Pulping process - Sulphate 5. Kappa no of unbleached pulp Bleaching sequence - CEoHE P D(CP) 7. Bleached pulp brightness,% ISO Characteristics of waste water (Influent to ETP) a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l d. Suspended solids, Kg/ Day e. Suspended solids,kg/t paper - 38 f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T paper i. AOX, mg/l j. AOX, Kg/Day - 76 k. AOX, Kg/ T paper Characteristics of treated waste water a. Flow, M 3 /Day b. ph c. Suspended solids, mg/l - 50 d. Suspended solids, Kg/ Day e. Suspended solids,kg/t paper f. COD, mg/l g. COD, Kg/Day h. COD, Kg/ T paper - 44 i. AOX, mg/l j. AOX, Kg/Day - 22 k. AOX, Kg/ T paper Efficiency of ETP a. Reduction in SS,% b. Reduction in COD,% c. Reduction in AOX,%

32 Table - 15 : AOX Generation in different Pulp & Paper Industries S. No Details of Paper Mill Unit-1 Unit-2 Unit-3 Unit-4 Unit-5 Unit-6 Unit-7 Unit-8 Unit-9 1. Paper production,t/day a. Total b. Kraft c. W & P Grade d. Rayon pulp e. Newsprint Kappa no of unbleached pulp (RG) (W) 10(B) (B) 13-15(B) 20(E) 20(E) 3. Bleaching sequence CE P HH CEHH C/DE O H HD CEDH (RG) CDE OP D CDEDD (W) CEH(B) CHE CE O HE P DSO 2 C/DE O D (B) CHH(B) CEHH (W) CEHHD (W) P(B) 4. Bleached pulp brightness, % ISO Wastewater generated m 3 /T paper

33 S. No Details of Paper Mill Unit-1 Unit-2 Unit-3 Unit-4 Unit-5 Unit-6 Unit-7 Unit-8 Unit-9 6. AOX generated Kg/T paper a. W & P grade b. Rayon pulp c. Newsprint Total AOX at final discharge Kg/T paper SS removal Kg/T paper 8.1 SS in untreated effl SS in treated effl COD removal Kg/T paper 9.1 COD in untreated effl COD in treated effl Efficiency of ETP a. Reduction in TSS, % b. Reduction in COD,% c. Reduction in AOX, % Note : Unit-1; Unit-2; Unit-3; Unit -4; Unit -5; Unit -6; Unit -7; Unit -8; Unit -9 CP- Chemical pulp ; CMP :- Chemi-mechanical pulp ; C - Chlorination; E- Extraction; H- Hypochlorite P - Hydrogen peroxide D - Chlorine dioxide;o - Oxygen (RG)- Rayon grade;(w) Wood,(B) Bagasse,(E) Eucalyptus 27

34 8.2 Newsprint Paper Industries The summary results of the AOX generation and discharge in newsprint paper Industries are given in Table 17. The level of AOX generation in case of chemi-mechanical pulp(cmp) bleached with hydrogen peroxide, is negligible. Therefore, the AOX generation kg/t newsprint mainly depends on the proportion of CMP and CP in the pulp. The level of AOX measured in effluent samples collected from newsprint Industries is less than 1.0 kg AOX/t paper. The pulp furnish used in these industries contains major portion of mechanical pulp which is bleached with Hydrogen peroxide while chemical pulp is given a mild bleaching action with chlorine based chemicals to achieve 60% brightness level. The low degree of brightness in newsprint paper and use of per-oxide in bleaching resulted in low level of AOX in the effluent. 8.3 Rayon Grade Pulp Industries The summary results of the AOX generation and discharge in large scale Rayon Grade Pulp Industries are given in Table 18. The kappa of unbleached in rayon grade pulp is quite low i.e which required less quantity of the bleaching chemicals mainly chlorine and chlorine dioxide resulting in low level of AOX in effluent. The AOX generation level ranges between 1.48 to 1.68 kg/t of pulp. 8.4 Effluent Treatment Plants (i) (ii) (iii) Studies conducted in the industries reveal that biological effluent treatment plants appears to be effective in removal of chlorinated organic compounds. The maximum reduction in AOX i.e. about 70% is observed in newsprint and rayon grade pulp industries while in writing and printing paper industries, the reduction in AOX varies from 41 to 55 %. The high reduction in AOX in newsprint and rayon grade pulp industries may be because of low level of AOX in combined waste water and other reasons may be perhaps because of low molecular weight AOX compounds. There is a wide variation in quantity of wastewater discharged per tonne of paper. The wastewater quality varies from industry to industry depending upon the raw materials used and quality of end product. The lowest figures of m 3 /t were observed in newsprint followed by 155 m 3 /t in rayon grade pulp and m 3 /t in writing and printing paper industries. The generation and discharge of suspended solids in wastewaters also vary from industry to industry and also from product to product. The 28