CLEANER PRODUCTION AUDIT IN THE PULP AND PAPER INDUSTRY: A CASE STUDY IN VIETNAM doc

LITERATURE REVIEW 3 2.1 General Production Process of Pulp and Paper Industry 3 2.2 Source of Water Pollution and Its Characteristic 10 2.3 Environmental Problem from Pulping Processes

Asian Institute of Technology Bangkok, Thailand August, 1996

ACKNOWLEDGMENT

First of all I would like to express my profound gratitude and sincerest appreciation to my advisor, Dr C Visvanathan for his encouragement, unending support and valuable advice throughout the study period

My gratitude is extended to Mrs Samorn Muttamara and Dr Nguyen Thi Kim Oanh for their valuable advice and kindly serving as committee members

Appreciation is greatly extended to the Ecumenical Scholarship Program (ESP) for providing financial support for my study at AIT, and to the DANIDA for supporting research grant

Sincere thanks are due to Dr Tran Van Nhan and the Center for Environmental Science and Technology, Hanoi University of Technology for their help and support during my field study in Vietnam

I would like to express my sincere thanks to Dr Mark Radka of UNEP for providing necessary information and sharing his experience with me

My thanks is extended to all staff in the Technical Department of the Van Diem mill for their help in my field study in the mill

I would like to thank all faculty, staff and friends of EEP (SERD) at AIT for their help and cooperation

Finally, I wish to express my extreme gratefulness to my beloved parents and my brother for their unending love and encouragement My sincere thanks is extended to my husband for his helpfulness, encouragement and moral support during my research period I would like to dedicate this piece of work to my beloved parents

ABSTRACT

Van Diem Paper Mill is a small integrated paper mill that uses bagasse and waste paper as raw material The mill manufactures carton board, cover paper, pupil note-book cover It was found that upsets and spills occurred frequently as a result of the old process The production capacity was found to be 9 tons/day when the mill was running normally

Water balance, material balance and energy balance were drawn for the mill The water consumption on an overall basis was found to be 376 m3 per ton of product The suspended solid (SS) in the wastewater was 431.8 kg/ton of product The fiber loss from the paper machines was considerable with the value of 20.8% The total of SS and SS70 (parameter used to assess the fiber loss of a paper mill) discharged to the Red river was 369.7 kg/ton and 211.7 kg/ton respectively

The high concentration of alkaline vapour (0.187 mg/L) in the digestor plant was

a severe source of air pollution in the mill

The cleaner production opportunities for the mill were studied Stream segregation with black liquor collection could reduce pollution load Good-housekeeping was especially recommended such as repairing all leakage, keeping taps closed when they are not in use and cleaning rolls in paper machines

TABLE OF CONTENTS CHAPTER TITLE PAGE

Title Page i

Acknowledgment ii

Abstract iii

Table of Contents iv

List of Figures v

List of Tables vi

List of Illustration vii

I INTRODUCTION

1 1.1 General 1

1.2 Objective 2

1.3 Scope and Limitation of the Study 2

II LITERATURE REVIEW 3

2.1 General Production Process of Pulp and Paper Industry 3

2.2 Source of Water Pollution and Its Characteristic 10

2.3 Environmental Problem from Pulping Processes 11

2.4 Raw Material for Pulping 12

2.5 Cleaner Production for Small Pulp and Paper Mills 15

2.6 An Overview of the Pulp and Paper Industry in Vietnam and Related Environmental Issues 16

2.7 Bench Marks in Pulp and Paper Industry 17

III BACKGROUND INFORMATION OF THE RESEARCH SITE 3.1 General Information 19

3.2 Production Processing 19

3.3 Existing Water Supplied 22

3.4 Existing Wastewater System 22

3.5 Existing Fiber Recovery Unit 26

3.6 Working Environment and Environmental Issues of the Mill 26

3.7 Energy Consumption 26

IV METHODOLOGY 4.1 Study Program 30

4.2 Data Collection 30

4.3 Inplant Monitoring 30

4.4 Material Balance and Energy Balance 30

4.5.2 Wastewater Measurement 31

4.5.4 Water and Wastewater Characterization 33

4.7 Physical Agents in Working Environment 4.7.1 Noise Measurement 33

V RESULTS AND DISCUSSIONS

5.1 Bench Mark of Pulp and Paper Mill 38 5.1.1 Raw Water Used in the Pulp and Paper Mill 38 5.1.2 Wastewater from Production Process 39 5.1.3 Energy Consumption of the Mill 40

5.2 Waste Auditing of Pulp and Paper Mill 40 5.2.1 Unit Operation of the Mill 40

5.4.1 Wastewater Quality and Fiber Recovery Efficiency

54

5.4.2 Determination of Settleable Solid of the Effluent 55

5.5 Noise and Air Pollution in the Work Environment 56

5.5.2 Particulate Matter 55

5.6 Identification for Cleaner Production Oppotunities 58 5.6.1 Causes of Waste Generation 58 5.6.2 Cleaner Production Oppotunities 59

5.7 Options of Cleaner Production Opportunities 60

IV CONCLUSIONS AND RECOMMENDATIONS

6.1 Water and Energy of the Mill 64 6.2 Noise and Air Pollution in the Mill 65 6.3 Recommendation on Cleaner Production Opportunities 65

REFERENCES

APPENDICES

FIGURE TITLE PAGE

2.1 Simplified Diagram of Pulp and Paper Process 4

2.2 Flowchart of Mechanical Pulping Process 5

2.3 Sulphite Pulping Process 7

2.4 Semichemical Pulping Process 9

2.5 Cleaner Production Techniques 15

3.1 Location of the Van Diem Paper Mill

20 3.2 Layout of the Van Diem Paper Mill 21

3.3 Simplified Diagram of Pulp and Paper Production of the Mill 23

3.4 Pulp Production Diagram of the Mill 24

3.5 Paper Production Diagram of the Mill 25

3.6 Water Supplied System of the Mill 26

3.7 Wastewater Drainage System of the Mill 27

3.8 Steam Distribution System of the Mill 29

4.1 General Methodology Outline

31 4.2 Flowrate Measurement Equipment 32

4.3 Wastewater Sampling Points and Wastewater Flow Measurement Points 33

4.4 Raw Water Sampling Points and Water Supplied Flow Measurement Points 34

4.5 Settleable Solid Measurement Using Imhoff Cone 37

4.6 Sound Level Meter Used for Noise Measurement 37

LIST OF TABLES

2.1 Typical Analytical results for Pulp and Paper Mill Waste 10

2.2 Chemical Composition and Fiber Dimension of Agricultural Residue-based

2.3 Wash Filter Loading and Dewatering Properties of Various Sulphate

2.4 Bench Marks for Pulp and Paper Production 17

2.5 Wastewater Pollution Load in Agricultural Residue-based Mill 18

4.1 Analytical Parameters, Locations and Methods Used during the Study 35

ABBREVIATION

BL : Black Liquor

BOD : Biochemical Oxygen Demand

COD : Chemical Oxygen Demand

L/s : Litre per second

Lpm : Litre per minute

P : Pay Back Period

CHAPTER 1 INTRODUCTION

1 General

Paper is becoming an essential commodity of today’s society The pulp and paper industry has been growing with demand of paper The capita consumption has also been steadily increasing over the world

The pulp and paper industry is considered as one of the major potential sources

of pollution in the environment There are two segments, pulping and paper making in the manufacturing process Pulping is the major source of environmental pollution Black liquor from chemical pulping processes is the most significant and troublesome source of pollution Effluent from these pulping processes contains chemicals which are known to cause damage to the flora and fauna Also, bottom deposits of lignin cellulose material near the point of discharge undergoes slow decomposition that leads to depletion of dissolved oxygen in the receiving body

The raw materials for pulp production are those containing cellulose fibers They are divided into two main types: wood and non-wood materials Environmental problems

on a global scale of deforestation is occurring Therefore, using non-wood fiber material for paper production is encouraging Although non-wood fibrous raw material based account for only about 5% of the raw material for pulp and paper manufacture today it is one of the major sources of fibrous raw material for many developing countries (GIERTZ, 1993) Agricultural residues are the most important raw materials of non-wood group that were used in agriculture countries

In developing countries, the small scale mills are more popular than large ones Small scale mills usually cause high level of environmental pollution because of outdated technologies, poor operational and maintenance practices and others On the other hand agricultural residues are especially suitable for small scale mills as their raw materials However, using agricultural residues satisfies in terms of reducing the burden

on forest wood, it has its adverse environmental impacts in term of pollutant discharge

Pulp and paper production is an important contributor to the economy of many nations In Vietnam, the industry accounted for 1.8 per cent of the output value of the manufacturing sectors Despite its increase in production capacity, it has not met the domestic consumption demand

The utilization of sugar cane bagasse as raw material for the pulp and paper industry needs some attention in sugar cane producing countries such as Vienam It contributes to reducing deforestation as well as using by-product from the sugar industry However, small paper mills using sugar cane bagasse as raw material have caused environmental pollution at high levels

Therefore, cleaner production study in the small mill using sugar cane bagasse as raw material for pulp and paper production is useful in terms of economy as well as environmental protection aspect

An essential step in implementing cleaner production is waste audit as it gives a comprehensive look at production process to facilitate the understanding of material flows and to show pollution sources within the process A waste audit points out the points specific area where pollution reduction may be achieved and helps to implement maximum resource optimization and improved process performance (UNEP/IEO and UNIDO,1991)

This study investigated the current environmental status of a pulp and paper mill

in small scale in Vietnam and recommended cleaner production practices for the mill

2 Objectives

The objectives of the study are:

1 To identify and evaluate sources and causes of waste generation of the pulping and paper making processes with a view to find out the extent of all environmental pollution problems, major focus on waste stream

2 To determine the quantity and characteristic of wastewater discharges in pulp and paper mill which use non-wood material as raw material

3 To identify possibilities to conserve water and to minimize pollution load

4 To recommend cleaner production practices to the mill

3 Scope and Limitation of the Study

This study was limited only to a small scale pulp and paper industry using sugar cane bagasse as raw material

Initial investigation of environmental status of the mill included water, air and noise pollution but the major task focused on wastewater

The study on implementing cleaner production was concentrated on process effluent reduction and recovery as well as recycling rather than the process modification

CHAPTER II LITERATURE REVIEW

2.1 General Production Process of Pulp and Paper Industry

The manufacture of paper can be divided into two phases: the pulping and the paper making In the pulping phase the cellulose raw material must be processed to free fibers with suitable properties for paper product The paper making is the continuous process consisting of forming slurried pulp in sheet form then pressing, drying, calendering

The simplified flow diagram of pulp and paper production process is shown in Figure 2.1

1) Stone Groundwood Pulping

The first grinders were built by Voith in 1852 In this method logs of wood are ground against a stone wheel to produce clumps of fiber Stone groundwood does have some favourable characteristics : low energy costs and high fines content which is desirable for printing characteristics

2) Refiner pulping

The first attempt to use disc refiners to produce mechanical pulps was made in the 1950's This demonstrated that it was possible to produce pulp which was stronger than stone groundwood (Mc CUBBIN, 1984) Thermo-mechanical pulping (TMP) process was developed

This technique involves presteaming of chips for a short period, typically about three minutes, at a 110-130oC and 150-210kPa and then performing the first stage of refining under pressure (Mc CUBBIN, 1984)

3) Pressurized Groundwood

Pressurized Groundwood (PGW) is a relatively new development It is similar to the stone groundwood process but logs is ground under pressure Generally speaking, the production of mechanical pulps has been limited to the use of soft woods preferably spruce, balsam and hemlock and , to a lesser extent, jack pine(due to a lower pulp quality) TMP has pulp yield of approximately 94% and the published data on BOD discharge varies from about 15 kg/t to 35 kg/t.(MCCUBBIN, 1984)

Mechanical pulping provides a short pulp fiber due to the considerable fiber damage caused by grinding

Chemical pulping

Chemical pulping is done by digesting to free fibers from the wood chips, wood materials such as bamboo, straw, grass, cotton, in chemical solutions that help to dissolve the lignin binding material Pulp yield is normally in the range of 35 to 57% and about 95% of the lignin is removed in pulping (MCCUBBIN, 1983) Chemical pulps may

non-be subdivided into Kraft (sulphate), sulphite, semi-chemical and soda

The soda pulping was the first chemical process applied in pulp manufacture In the process, sodium hydroxide is used as cooking liquor with adding a mixture of soda ash (Na2CO3) and lime Ca(OH)2 to the digester This process is most suitable for agricultural residues pulping (PALMER et al., 1983)

Sulphite Pulping Process

The sulphite pulping process is one of the major pulping methods This process is most suitable for non-resinous softwood In this method, the fibre-binding lignin is softened and dissolved to a considerable extent in a solution containing dissolved SO2, hydrogen sulphite ions with pH value between 1.5-12 Depending on the cooking degree, the yield varies from 45 to 65%, but normally the yield is about 50% for standard non-bleached pulps If the pulp is bleached, another 4 to 5% of the original wood weight may

be lost in the process (ANONYMOUS, 1982) An advantage of the kraft pulping process is the possibility of recovering both process chemicals and the heat content of the dissolved lignin One drawback is that the process results in pulps with a high kappa number which thus require bleaching for many applications The sulphite pulping process is illustrated in Figure 2.3

3/ Kraft Pulping Process

• Cold soda, in which chips are soaked for several hours in sodium hydroxide at atmospheric pressure without heating

The simplified flow sheet of semi-chemical pulping process is presented in Figure 2.4

5/ Other processes

According to PALMER (1983) recognizing the difficulties of using established

processes on a small scale, a number of alternative processes are being developed which are claimed to be specially suitable for small-scale operation either because they are non-polluting (in at least one case it is claimed that digestion liquor can be used

as fertilizer) or because the recovery process is relatively simple Examples of these processes are:

• Ammonia-based pulping

• Oxygen (air) and alkali processes

• Universal process (acid based)

2.1.2 Paper making

In the paper making process pulp is converted into paper Normally, the process consists of four main steps: stock preparation, sheet preparation, water removal and sheet finishing Pulp in the stock is heated and mixed Some different chemicals and fillers like alum, clay, and starch are added to the pulp stock for enhancement of certain paper properties Next, the pulp is evenly distributed over a travelling belt of fine wire screening, and carried to rolls A small portion of the water contained in the pulp passes through the screen, while the longer fiber are laid down on the wire , pressed through a series of rolls then air dried in a steam-heated dryer section After drying, the sheet may

be surface treated and then finished A considerable portion of the fine fibers and some

fillers also pass through the screen wire with water Because of its colour, this wastewater is called "white water" The main sources of waste from paper mills are beaters and paper machines

2.2 Sources of Water Pollution and Its Characteristics

The pulp and paper industry is one of the largest water- using industries, not only

in terms of the volume specific water use, but also in terms of the volume of output

The sources of the wastewater in the pulp and paper industry come from chipping, pulping, rinsing, chemical recovery, bleaching and paper making process ( STOLL, 1995)

NEMEROW (1978) reviewed the major origins and characteristics of wastes from different pulping processes and paper making Since different types of pulping processes generate somewhat different wastes, each type should be considered separately Typical analytical results of different types of pulp and paper wastes are presented in Table 2.1

Table 2.1 Typical analytical results for pulp and paper mill waste

-7-Toxicity of pulp and paper mill effluent may be caused by sulphur compounds introduced into the pulping process, dissolved organic compounds of the raw materials, resin and fatty acids and some cases heavy metal ( which are used for wood preservation

or raising paper quality) More recent questions have been raised regarding chlorinated dioxins, formed during the bleaching process, that effect water quality for human consumption and other purposes (GELLMAN, 1988)

Colour and turbidity of effluents cause aesthetic problems Colour of the pulp and paper industry's wastewater is caused mainly by lignins of the wood as well as in some cases by dye

2.3 Environmental Problems from Pulp and Paper Production

Preparation of Fibrous Raw Material

There are two types of fibrous raw materials: wood and non-wood material The wood material preparation at mill site include weighing, storage, washing, debarking and chipping The debarking method and equipment is determined by the type of wood, the pulping process, the pulp quality and the debarking capacity The major source of water pollution from the wood preparation is debarking, specially when wet debarking is used The effluent contains large amounts of dissolved as well as suspended pollutants In general, wood has to be washed before chipping to prevent damaging the knives by sand and other impurities Therefore, the wastewater from the process contains coarse materials

For the non-wood material (such as bagasse, bamboo, reed, or cereal and rice straw) preparation, the major source of water pollution is crushing and chipping (bamboo), depithing (bagasse), wet cleaning (rice straw)

Pulping

In this stage, either mechanical or chemical methods are used to produce fibers

In the chemical method , fibrous raw material is treated with chemical cooking liquor which used to dissolve most of lignin and liberate the fibers The effluent is called black liquor containing lignin and hemicellulose as well as toxic waste material like dimethyl sulphite, methyl mercaptan etc The wastewater is highly polluted with brown color and high COD Bottom deposits of lignin cellulosic materials near the discharge point will lead to a DO depletion at the discharge point

Washing and Screening

From an environmental point of view the pulp rinsing after the cooking is one of the most important operations in a pulp mill The rinsing operation aims to separate pulp fiber from spent cooking liquor that contains inorganic cooking chemicals and organic substances dissolved from the fibrous raw materials A thorough washing, that leaves a low residue of black liquor in the washed pulp is also decisive for the amount of polluting discharges from the following process department, i.e screening and bleaching

The screening operation which remove knots, shives, and other impurities is usually integrated in the washing system The water used for dilution in the screens is discharged together with fiber losses and dissolved substance(PER ALSEFELT et al., 1991)

Bleaching

In order to obtain good properties like white and strong paper it must remove remaining lignin and resinous bark as well as knot particles This process is called bleaching The effluent of kraft pulp mill affects spinal deformation in fourhorn sculpin The changes of skeletal composition and strength show a disturbance in the metabolism and onto genetic growth of fish (BENGTSSON, 1988)

SODERGREN (1993) indicated that there are two general types of bleaching sequences: C-E-H-D-E-D and oxygen delignification O-D-EPO-D-EP-D (O=oxygen, C=chlorine, D=chlorine dioxide, H=hypochlorite, E=alkaline extraction, P=hydrogen peroxide) The effluent from a bleaching plant contains large amount of lignin-related chlorinated compounds which have a negative impact on environment in receiving area and further more they are "persistent"/ or degrade very slowly The effluent of bleached pulp affects the diversity, biomass and distribution of fish, invertebrates and plants (SODERGREN et al.1989)

BONSOR et al (1988) reported that kraft mill effluent interacts with a low DO (dissolved oxygen) content and produces synergism effect

2.4 Raw Material for Pulp Production

The fibrous raw materials can be classified as follows:

Wood

• Softwood (spruce, pine, fir, hemlock etc.)

• Hardwood (birch, eucalyptus, mixed tropical hardwoods etc.)

Non-wood

• Agricultural and other residues such as straw from cereals, rice and sorghum

as well as sugar cane bagasse

• Naturally grown plants such as bamboo, reeds, papyrus, esparto and other grasses

• Crops primary grown for their fibers content such as juite, hemp, kenaft, ramie, flax (bast or stem fibers); abaca or Manila hemp, sisal (leaf fibers); cotton (seed hair)

Of these, bagasse, reed, bamboo, cereal (wheat, rye) and rice straw are the most important non-wood fiber raw materials for paper making

-9-Non-wood raw materials

The chemical composition does not differ much between different types of wood fiber and the lignin content is largely the same as that of hardwood The cellulose content and the fibers length vary relatively little between the wood based and non-wood based raw materials However, the ash content of agricultural residues is much higher than that of the wood based raw materials

Chemical characteristics and fiber dimension of different raw materials including

hardwood (common raw material for large mills) and non-wood (raw material for small mills) are given in Table 2.2

Table 2.2 Chemical Composition and Fiber Dimension of Agricultural Residues and

Wood Based Raw Materials (PANNEERSELVAM, 1988)

Raw Material Cellulose

(Alpha) (%)

Lignin (%)

Ash (%)

Fiber Length (Av mm)

Fiber Diameter (Av µm)

10-17 16-20 19-22 18-23 22-32 25-28

14-22 4-11 1-5 3-6 0.5-3 0.4

1.5 1.5 1.6 1.2 1.0 3.5

9

13

20

12 17-32 35-40

Non-wood fibers are easy to be delignified by chemical pulping It is noted that non-wood fiber are delignified much faster than wood This can be explained by the reason of the more open structure of the fiber tissue (UNEP,1986)

GIERTZ (1993) reported that the most widely used pulping method for non-wood raw materials are the soda and the sulphate processes These processes have a relatively short cooking cycle either applied in continuous or in a batch system This means the digester volume can be rather small

Bagasse fairly resembles hardwood in chemical composition and this is reflected

in the yield which is largely the same as that of hardwood but not in cooking time Generally speaking, further processing in the fiber production line such as screening, bleaching and drying is largely the same for the non-wood fibers as for wood

a) Advantages of non-wood pulp:

Non-wood raw materials are cheap

Non-wood fibers are delignified much faster than wood The material is satisfactorily delignified and the pulp obtained is of high quality and can be easily bleached to an acceptable brightness

The cooking time of non-wood raw material is shorter than that of the hardwood Therefore the bagasse cooking time is very short with low alkali requirements and results

in a pulp with low yield

b) Disadvantages of non-wood pulping

- Preparation of fibrous raw material

The problem lies in the preparation of fibrous raw material including collection, transportation, and storage These are bulky material One important thing to note is its seasonal delivery They might deteriorate during storage The dust loads in the handling, storage and cleaning of bagasse, bamboo and straw is high

-Washing

The design of washing equipment has to be more elaborate than for wood pulps due to a slow drainage property of non-wood pulps This is illustrated in the Table 2.3

Table 2.4 Wash filter loadings and dewatering properties of various sulphate and

soda pulps (UNEP, 1986)

Pulp type Wash filter loading

2-4

4 1.5-2 0.5-2

12-13

15-16

20-25 14-16

♦ High viscosity

♦ Low heat value because of lower lignin content and higher carbohydrates content

2.5 Cleaner Production for Small Non-wood Pulp and Paper Mill

-For production process, Cleaner Production includes conserving raw materials

and energy, eliminating toxic raw materials, and reducing the quantity and toxicity of all emissions and wastes before they leave a process

Cleaner Production techniques are shown in Figure 2.5

CLEANER PRODUCTIONTECHNIQUES

MODIFICATION

SOURCE REDUCTION

GOOD HOUSEKEEPING

PROCESS CHANGE

Figure 2.5 Cleaner Production Techniques (NPC, 1995)

The very essential step in implementing cleaner production is waste audit This management tool has been developed to respond to the new environmental management philosophy that of waste prevention and reduction

In UNEP(1991) it is reported that a waste audit enable one to take a comprehensive look at a site or process to facilitate one's understanding of material flows and to focus one's attention on areas where waste reduction and therefore cost saving is possible

2.5.2 Cleaner Production for Small Non-wood Pulp and Paper Mill

It is noted that in the case of small pulp mills a chemical recovery system is uneconomical

PANNERSELVAM, (1988) suggested certain simple pollution abatement measures for small mills Such internal process modifications are less capital intensive and the small mills can more easily afford them, particularly when the associated benefits are considered

Water conservation is performed by using intermittent high pressure, high volume showers or continuous high pressure, low volume showers for felt shower Felt showers provide water for paper machine at the time paper mat is sent to press rolls It is necessary to develop appropriate inexpensive fiber recovery systems to promote the fiber recovery among small mill

It is uneconomical for the small mill to run a conventional chemical recovery system Thus it is essential to develop an alternative simple inexpensive chemical recovery method In tropical countries with very high solar intensity, the feasibility of separating the black liquor and increasing its solid content in a series of solar evaporation ponds should be considered (PANNERSELVAM, 1988)

2.6 An Overview on the Pulp and Paper Industry in Vietnam and Related Environmental Issues

2.6.1 Overview on Pulp and Paper Industry

The number of pulp and paper mill and designed capacity of existing enterprise establishment in Vietnam are presented in Table 1- and Table -2 Appendix A, respectively

The largest mill is Vinh Phu Paper Union (BAPACO) with a production capacity of 55,000 tons per year (t/y) The two intergrated pulp and paper mills Tan Mai (COGIVINA) and COGIDO with production capacities of 45,000 t/y and 15,000 t/y respectively are ranked after BAFACO The other mill are small with capacity varying from 300 t/y to 10,000 t/y At present, there has 9 key-mills which produce 65% of total paper production of the industry The general information of these mill is shown in Table -3 Appendix A

-13-The major pulping process in Vietnam is the soda -13-The soda pulping process is mainly applied for mills which use non-wood as raw material This method is applied to produce more than 50% of the pulp production The pulping methods used in BAPACO, COGIVINA and COGIDO are Kraft, thermo-mechanical and modified soda (cooking liquor is sodium adding 1% of sulphur) respectively

SANH (1996) reported that pulp and paper industry is still in small scale with capacity of 3 kg per capita per year In 1995, pulp and paper production reached 120,000 tons and 200,000 tons respectively Paper demand has increased in Vietnam It is estimated that paper demand will be around 500,000-700,000 tons by the year 2000 (an increasing of 2.5-3 times)

2.6.2 The Related Environmental Issues

Most of the pulp and paper mills in Vietnam are in small scale It is uneconomical

if chemical recovery systems are applied in small mill (with capacity less than 50,000 t/y) Therefore, all the pulp and paper mills have no chemical recovery system except for BAPACO Pollution control facilities for the industry are very poor There are some environmental researches on pulp and paper industry in Vietnam TRUNG (1990) studied the reuse of black liquor from pulp production to produce construction material (concrete) This kind of additive makes stress intensity of cement increasing to 1.5-3 times and reduces 5-10% of water consumption in concrete production

KIM OANH (1994) did a wastewater management in BAPACO The study showed that the effluent of this intergrated kraft pulp and paper mill is mildly acute toxic

A monitoring program for environmental audit of the pulp and paper mill was proposed

DAN (1990) carried out experiments on wastewater treatment of Long Binh pulp and paper mill Physical treatment method (sedimentation), physico-chemical method (neutralization, coagulation, absorbed filtration) and biological method (water hyacinth pond) were studied The results showed that 80-90% of can be removed by settling method, color and turbidity can be decreased by coagulation method with alum coagulant (140 mg/L) and 90% of COD and 80% of lignin was removed in water hyacinth pond

2.7 Bench Marks in Pulp and Paper Industry

WHO, (1993) indicated a bench mark in order to assess the waste discharge of pulp, paper and paperboard manufacturing as in Table 2.4

Table 2.4 Bench mark for Pulp and Paper Production (WHO, 1993)

15 10.5

2 10.5 37.5

30 6.5

Wastewater pollution load of pulp mill section, paper machine and combined these of agicultural residue-based mill is presented in Table 2.7 The total requirement of raw water is about 200-300 m3

Table 2.5: Wastewater Pollution Load in agricutural residue-based mill

60-80 27-41 80-140 61-109 205-394

162-230 161-245 865-1215 192-362 993-1408

CHAPTER III BACKGROUND INFORMATION OF THE RESEARCH SITE

3.1 General Information

Van Diem Paper Mill is a small paper mill It was established in 1962 at Phu Minh district Ha Tay province The mill is bordered by the Red river dike in the East and

a Sugar Mill in the South Figure 3.1 and Figure A-1 in Appendix A shown the location

of Van Diem Paper mill The layout of the mill is shown in Figure 3.2 It shows the location of office, digestor house, depithing house, paper processing, finishing, fiber recovery unit, sedimentation unit for water supply and bagasse storage ground area

Products of the mill are carton board, cover paper and pupil note-book cover All

of them are unbleached products The designed capacity is 3000 tons product per year In

1995 the capacity was 2700 tons of paper

The mill uses sugar cane residue bagasse as raw material based for pulp production Bagasse is bought from neighbour Sugar Mill and transported to bagasse storage ground of the mill through a belt conveyer

The mill has 300 employees Generally, production activities are carried out in 3 shifts (24 hours per day) During the month of December, the mill is closed for machine maintenance

3.2 Production Processing

Production process of the mill is changed depending on raw material state The main raw material of the mill is bagasse which is supplied seasonally During the sugar cane season, bagasse is transported from the sugar cane mill on belt conveyers to material storage site of the pulp mill It has moisture content of 50% Bagasse is incubated in ponds to reduce chemical consumed in cooking process Rest of the bagasse

is heap up in trapezium form on the ground when the ponds are full Therefore, there are two periods of production From January to May (sugar cane season) the mill uses bagasse which is not incubated The bagasse is depithed before cooking In the rest time, the incubated bagasse is used without depithing Incubated bagasse consumes less caustic soda than unincubated bagasse In the first period, bagasse is fed into depithing machine where it is cut into small pieces The piths are carried away by air blower into a pipe going outside

The depithed bagasse is transported to the spherical digestors, where caustic soda solution (white liquor ) with a concentration of 120g/L, water and steam is added The digestors are turn round with a speed of 2.5 circles per minute The delignifying is carried out at approximately 110-125oC and at a pressure of 2.5 atm The cooking is performed

by a batch process and the cooking time is 5 hours Charging and discharging takes

Railway

Figure 3.1 Location of the Van Diem Paper Mill

D D

Toilet 4 Steam Boiler

Entrance

PM Paper Machine 1 Wastewater Pump Station

B Beater 2 Water Supplied Pump Station

P Pump 3 Belt Conveyor of Bagasse

D Digester 4 Water Treatment for Steam Boiler

C Cutting 5 Dilution Tank

Figure 3.2 Layout of the Van Diem Paper Mill

2 SUMP

1 hour and 0.5 hour, respectively Spent liquor and pulp are sent to washing bath In this washing stage ligninand remaining chemicals are removed The depithed pulp is transported to the storage tank then pumped to a beater Waste paper and water are added into beater Here pulp and waste paper is beaten into fine fiber Then it is transported to a sedimentation tank where sand and other coarse materials are removed owing to slope of the tank bottom Rosin and aluminum sulfate are added in beating stage and during the production of pupil note-book cover paper dye is also added

After beating, pulp is sent to a tank for dilution to a consistency of 0.3% and finally fed to three paper machines through a head box Then pulp is passed through a refiner where sand is removed Next, pulp is distributed over a traveling belt of fine wire screening where paper mat is created The paper mat then pass through press rolls and to the vacuum box to remove water and pass drying roll where paper is dried indirectly by steam Finally paper comes to paper rolls Paper then is cut and becomes finished products

A simplified diagram of pulp and paper production process, pulp production, paper production of the mill are presented in Figure 3.3, Figure 3.4, Figure 3.5 respectively

3.3 Existing Water Supply System

Raw water used in this mill is taken from Red river It is pumped from the river into two natural sedimentation tanks then pumped into the mill There are 3 pumps with capacity of 100m3 per hour Normally, only one pump is used This water is used, in all processes, except for the water used in steam boiler and domestic purpose, it is treated with alum and de-hardness is obtained by using chemicals The treated water is also pump to staff housing for domestic used

Currently, the amount of water consumption in the mills is not monitored Water supply system is shown in Figure 3.6

3.4 Existing wastewater system

Wastewater drainage system of the mill is presented in Figure 3.7 There are two wastewater stream: 1 the storm water and domestic wastewater run around the mill wall then come to channel outside the mill; 2 the wastewater from the process is collected into a sump from which wastewater is pump to Red river A part of wastewater flows through a fiber recovery unit before going to the sump In many parts drain is underground The wastewater from staff housing is discharged directly to the cannal located outside the mill

Currently, the wastewater characteristic in the mill is not monitored

RAW MATERIAL

Dilution

PAPER

Figure 3.3 Simplified Diagram of Pulp and Paper Process

in Van Diem Paper Mill

Electricity Depithing Spillage of bagasse in conveying

Figure 3.4 Pulp Production Diagram of the Van Diem Mill

D D

Toilet S 4 Steam Boiler

Entrance

PM Paper Machine 1 Wastewater Pump Station S Sedimentation Unit

B Beater 2 Water Supply Pump Station Domestic Water Pipeline System

P Pump 3 Belt Conveyor of Bagasse

D Digester 4 Water Treatment for Steam Boiler

C Cutting 5 Dilution Tank

2 SUMP

Staff Housing

3.5 Existing Fiber Recovery Unit

Fiber recovery unit is a simple sedimentation unit Its dimension is shown in Figure B-1 AppendixB Wastewater flows naturally through the unit before come to

collection

well The fiber is settled then recovered fiber is used for cover paper production

3.6 Working Environment and Environmental Issues of the Mill

In general, the working environment of the mill is not clean Sugar cane pith dust from depithing unit, fly ash and coal dust surrounding steam boiler, especially black liquor and caustic soda steam from cooking unit are the major environmental problems Based on production process data, the significant environmental pollutants in the mill can

operated during the other break down

Electricity is supplied to unit operations of production process, utilities, and domestic using

- Production process (raw material preparation, pulp mill, paper mill)

- Utilities (steam boiler room, electro-mechanical workshop, wood

- Domestic using (using in office and worker living quater)

The average electricity demand of the factory is 200,000-250,000 kW per month

Electricity loading for the mill is shown in Table 1- Appendix B

D D

Toilet 4 Steam Boiler

Entrance

Note

PM Paper Machine 1 Wastewater Pump Station

B Beater 2 Water Supplied Pump Station

P Pump 3 Belt Conveyor of Bagasse

D Digester 4 Water Treatment for Steam Boiler

C Cutting 5 Dilution Tank

Legend

Storm Water Process Wastewater

Figure 3.7 Wastewater Drainage System

2 SUMP

PM 2

B B

Steam Boiler S

C

Steam Boiler

4.4 Material and Energy Balance

Material balance was carried out for each unit process Since measurement the input raw material quantity was impossible, it was obtained basing on product after each unit operation

Energy balance only was carried out for steam component Measurement of steam amount was also not possible It was calculated from material operation balance

4.5 Water Balance

There is no available record of the water supply as well as wastewater discharge volume of the mill Therefore water balance was carried out in detail It was assumed that water used for office, floor cleaning, hand washing is equal to wastewater generation from those

The total water consumption and wastewater generation were compared with the bench mark available in the literature

4.5.1 Water Supplied Measurement

The mill has not measured the total amount of water used The total water supplied volume only estimated through pump capacity is not accurate because the pump capacity

-31-through pump capacity is not accurate because the pump capacity is not a constant It was decided that the water supplied amount be determined by total water used at all unit operations and domestic used The first step was understanding the water supplied system of the whole mill to find out appropriate water supplied volume measurement points and raw water sampling points

Water supplied to each unit of the pulping process was measured in each batch because the process is batch process Water used at each unit operation was measured by bucket and stop watch using container method (a known volume container to receive the water input during time measurement)

4.5.2 Wastewater Measurement

There are two drain lines leading to collection well (sump) One is open drain line with rectangular shape Another is underground drain line with round shape but its end can be seen at the sump It was very difficult to measure wastewater flow rate in the mill because of the poor drainage system Using weir to measure wastewater flow rate was impossible The following methods were applied to determine wastewater flowrate

-Using flow meter to measure in short drainage parts with constant cross section -Using bucket and stopwatch system

The wastewater volume was measured for each batch operation

The total wastewater flow of the mill was total of two branch flows The flowrate

of each branch was measured by container method A flow meter UKING ”OTT” MOLEN 10615 (Figure 4.2) with calibration curves was used to measure flow rate of the wastewater generated from paper machines Wastewater generation from other units were measured by using bucket and stop watch Wastewater flow measurement locations are illustrated in Figure 4.3

Figure 4.2 Flow Rate Measurement Equipment 4.5.3 Sampling

Raw water sampling was done at before sedimentation unit (Red river water), after sedimentation unit, and after treatment tank for boiler domestic used to obtain water supplied quality Raw water sampling points is presented in Figure 4.4

Wastewater samples were taken at each unit operations Figure 4.3 show sampling location

PM 2

PM 1

B B

B B

PM 3

R

LEGEND:

B: Beater PM: Paper machine

D: Digestor S : Sump R: Fiber Recovery Unit

: Wastewater Sampling Points

Figure 4.3: Wastewater Sampling Points

4.5.4 Water and Wastewater Characterization

The water samples taken from each unit as mentioned in 4.5.3 were analyzed on site for pH, temperature and conductivity parameters The other parameters : turbidity,

SS, TS, SS70, BOD, COD, Total N , total P were analyzed in the laboratory

All the analysis was conducted according to the techniques provided in the

“Standard methods” of examination for the water and wastewater (APHA, AWWA, WPCF, 1985) Method determined suspended solid by using filter wire of 70 µm pore size (SS70) was applied to characterize a large size part of solids consisting of long fiber

in the effluent (Bildberg, G and Rao, 1991)

The parameters analyzed and the corresponding methods used for determination

of water characteristics were shown in Table 4.1

4.6 Fiber Recovery Unit Study

Observation and analysis were done on fiber recovery unit Samples at before and after fiber recovery unit were taken to understand its current problems and the system efficiency

In addition to that the settleable solids were determined using Imhoff cone (Figure4.5) Alum was selected as the coagulant for the settleability study The Jar test was used experimentally to determined the optimum pH and dosage of Alum The wastewater before adding coagulant and the supernatant obtained after experiment from both Imhoff cone test and Jar test were analyzed for COD and SS

4.7 Physical Agents in Working Environment

Table 4.1 Analytical Parameters, Locations and Methods Used during the Study

Parameters Method Equipment and Analytical

Location

COD Dichromate open reflux Reflux apparatus at Lab

BOD5 Azid Modification Incubation chamber 20oC

checker WQC-20A (at site)

checker

at site (at site)

Lab)

Lab) Settleable Solid Volumetric test Imhoff cone (at Lab)

Optimum pH and Alum

dosage for Coagulation

Jar test Imhoff cone (at Lab)

-35-Figure 4.5 Settleable Solids Measurement Using Imhoff Cone

Figure 4.6 Sound Level Meter Used for Noise Measurement