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CHAPTER 1: INTRODUCTION

1.1 Abstract

Textile industries of Bangladesh are large growing industries where the people are contributing efficiently for the growth of better economy. Development of the textile industries calls for preparation of a pragmatic road map with synchronized strategic action plans in respect of technology, inputs, HRD, quality, productivity, compliances and other trade promotion aspects.

Textile Wet processing industries may be a bright future in the economic growth of our Country but pollution in textile is a big issue of concern. Here in our literature we discussed about pollution; different forms of pollution; pollution related to textile wet processing industries. Many articles are provided in here as examples of waste reduction techniques, successfully implemented at textile mills. Also there are articles consists of clear concepts and benefits of pollution prevention. We also discussed about situation of Bangladesh in case of pollution and action of Bangladesh Government to reduce the hazardous affect of pollution. In the study we also showed that the pollution prevention audit on four textile mills located in Gazipur and Bhaluka. The intention of the companies towards pollution prevention has been observed carefully and their action has been analyzed thoroughly. The study was also consists of modern pollution prevention techniques and their implementation as well as the responsibility of ours for the environment to protect.

1.2 INTRODUCTIONTEX 400 1

Practice of Pollution Prevention in Textile Wet Processing Industries of Bangladesh

The textile industries of Bangladesh have a major impact not only on the nation’s economy but also on the economic and environmental quality of life in many communities. In Bangladesh, textile is the leading provider of the manufacturing jobs. Only 5% of the established textile mills are owned by the foreigners where it is the sector which is the result of Bangladeshi investor’s new ideas and hard leadership.

Textile wet processing industry is a complex one where the main objective is to coloring the material with appropriate dyes and chemicals. Textile wet processing industry requires vast amount of water, dyes and chemicals, so therefore they have important effect on environment quality in the textile manufacturing regions. It is very much believed that the textile wet processing industry is one of the pollutant industry where careful monitoring of the pollution is must necessary. The most suitable idea of reducing the dyes & chemicals related to pollution is to reduce their amount of use. Less toxic material is less pollution.

Air quality is also an issue in textile where the toxicity of our air is increasing day by day. In addition to air toxicity concerns, textile factories should take some incentives, some of the mills are very aware but most of them are ignoring the case. In addition now a day’s indoor air quality of the textile industries are also an emerging issue.

1.3 Objectives

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1. To study the pollution in Textile Wet Processing Industries.

2. To investigate Pollution Prevention opportunities in the Textile Wet Processing Industries.

3. Ideas on the scope of modern Pollution Prevention Techniques

4. To study the policies of Textile Wet Processing Industries of Bangladesh against Pollution Prevention.

.

CHAPTER 2: LITERATURE REVIEW

2.1 Pollution:TEX 400 3


It is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat, or light. Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels. Pollution is often classed as point source or nonpoint source pollution.

Also we can define pollution as it is the discharge of unwanted materials, residue and energy into the environment. Some of these residues are unconverted raw materials, some are converted products and some are by products produce during the manufacturing or processing. In other words, pollution is a sign of inefficiency in industrial production & it can be considered as money that is going up the chimney, down the sewerage and out of the plant in waste truck, thus causing loss to the manufacturer.

Pollution is a very concerning area for the environmental structure. Day by day the pollution is increasing and it is destroying the natural balance of the environment, causing it to breakdown as a natural disaster every year around the globe. Bangladesh is a delta, situated near the Bay of Bengal. For a third world country like us we do not have the luxury to play with the environment that causes pain to us in various forms of natural disaster each year. As a result Bangladesh government has created pollution prevention law. Country like Bangladesh there is various sources of pollution. Industrial pollution is the area of our concern in here and to highlight exactly the Textile Wet Processing is going to be the theme of our topic.

2.2 Forms of Pollution:

There are different types of pollution around the world, in the different sectors of industries. In general pollution mainly divided into following categories

2.2.1 Water Pollution: By the discharge of wastewater from commercial and industrial waste (intentionally or through spills) into surface waters; discharges of untreated domestic sewage; release of waste and contaminants into surface runoff flowing to surface waters (including urban runoff); waste disposal and leaching into groundwater; and littering.

2.2.2 Air Pollution: The release of chemicals and particulates into the atmosphere. Common gaseous air pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFC) and nitrogen oxide produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight.

2.2.3 Noise Pollution: This encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.

2.2.4 Soil Contamination: It occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, herbicides, pesticides and chlorinated hydrocarbons.

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2.2.5 Light Pollution: This includes light trespass, over-illumination and astronomical interference.

2.2.6 Littering: Leaving litter here & there is not an environmental friendly option, causes to degrade the environmental condition of the industry.

2.2.7 Radioactive Contamination: Resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment. 2.2.8 Thermal Pollution : It is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.

2.2.9 Visual Pollution: This can refer to the presence of overhead power lines, motorway billboards, and scarred landforms (as from strip mining), open storage of trash or municipal solid waste.

2.3 Affects of Pollution:

Pollution around the world is a name of big burden. Day by day the increasing affect of pollution in our daily life, making it more miserable to tolerate. Affects of pollution cannot be described totally in short words but we are trying to give a brief idea of its hazardous affect.

2.3.1 Affects of Pollution in Human Health:

1. Adverse air quality is very dangerous not only for humans but also many organisms. Many diseases are the result of this obnoxious air quality like; respiratory diseases, cardiovascular disease, throat inflammation, chest pain, and congestion. Air pollution is so threatening in Bangladesh that it is called that Dhaka is the most air polluted metropolitan city of the world.

2. Approximately 14,000 deaths per day are caused by water pollution, mostly due to contaminated drinking water from untreated sewage in developed countries. An estimated 15 million Bangladeshis have no access to a proper toilet. The availability of safe drinking water in the rural area of Bangladesh is a hard catch.

3. Oil spills is also dangerous for human health, it can causes skin irritations and rashes.4. Noise pollution can cause hearing loss, high blood pressure, stress and sleep

disturbance.5. Children and infants are also at serious risk. Lead and other heavy metals have been

shown to cause neurological problems. Chemical and radioactive substances can cause cancer and as well as birth defects.

2.3.2 Affects of Pollution in Environment:

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Pollution has been found to be present widely in the environment. There are a number of effects of this:

1. Biomagnifications describes situations where toxins (such as heavy metals) may pass through tropic levels, becoming exponentially more concentrated in the process.

2. Carbon dioxide emissions cause ocean acidification, the ongoing decrease in the pH of the Earth's oceans as CO2 becomes dissolved.

3. The emission of greenhouse gases leads to global warming which affects ecosystems in many ways.

4. Invasive species can outcompete native species and reduce biodiversity. Invasive plants can contribute debris and bimolecular (allelopathy) that can alter soil and chemical compositions of an environment, often reducing native species competitiveness.

5. Nitrogen oxides are removed from the air by rain and fertilize land which can change the species composition of ecosystems.

6. Smog and haze can reduce the amount of sunlight received by plants to carry out photosynthesis and leads to the production of tropospheric ozone which damages plants.

7. Soil can become infertile and unsuitable for plants. This will affect other organisms in the food web.

8. Sulphur dioxide and nitrogen oxides can cause acid rain which lowers the pH value of soil.

2.4. Textile Wet Processing Technology & Pollution

Textile Wet Processing Technology is a process where the material is passed through various steps like desizing, singeing, scouring, bleaching etc and finally dyed or printed to obtain desired color.

In the following flow chart a simple structure of wet processing is delivered followed by the brief idea on the process steps.

2.4.1 Textile Wet Processing Technology:

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Heat set Dry

Printing

Pre dry & dryPre dryingFixing (Stream)Dyeing padWashWashingPre dry & dryMercerize

Wash

WashBleachingWashingScouring

White cotton or blend fabricSingeingDesizing

Material from weaving

knits

Dyed synthetic

Fig:2.4.1 Sequence of textile Wet Processing Source: Snowden-swan

2.4.1.1 Singeing:

Singeing is a processing step that removes surface fibers from woven fabric. These surface fibers form small fiber balls on the cloth after being washed several times. Many different systems are available but usually the goods pass through gas-fired burners at high speed. For woven materials, this is the first processing step.

2.4.1.2 Desizing:

After the weaving process, the sizes have to be removed from the fabric because they interfere with subsequent processing steps. Sizes have, in general, a high Biological Oxygen Demand (BOD) and will contribute significantly to the waste load of the mill’s effluent. In 1990, W. B. Achwal reported that waste stream of the desizing operation can contribute up to 50% of the total pollution load of a mill’s wastewater.Three methods frequently used in textile processing are acid desizing, enzyme desizing and oxidative desizing. The goal of these different methods is to hydrolyze the starch. Unlike starch, synthetic starches stay intact during desizing, can be recovered and reused.

2.4.1.3 Scouring:

Scouring is typically performed in an alkaline solution and high temperature environment. The removal of natural impurities is based upon saponification at high pH.

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Knits enter here enter

Finished fabric

Cure& heat set

Pre dry

Finish

Pre wet

Cure

Soaps and detergents added during scouring may precipitate with calcium, magnesium and iron3+ if present. These metals are therefore removed by the addition of reducing and sequestering agents. The sequesterants will form strong complexes with calcium, magnesium and iron2+ at high pH. The reducing agents are added to reduce Fe3+ to Fe2+. The removal of natural impurities can be done in a single process or can be combined with desizing and/or bleaching. The use of sequestering and reducing agents can be avoided when softened water is used. Scouring is usually the first step in the processing of knitted goods and will remove the knitting oils which were applied to the yarn prior to knitting.

2.4.1.4 Bleaching:

Almost all fabric containing cellulose are being bleached to remove the natural colored matter. Three chemicals are commonly used: hydrogen peroxide, sodium hypochlorite and sodium chlorite. In sodium hypochlorite bleaching, the washed and scoured fabric is passed through a dilute sodium hypochlorite bath for impregnation (saturator) and stored in a J-box or a large pit. After bleaching, the goods are washed and treated with antichlor (NaHSO3) to remove any traces of bleach. Bleaching with sodium chlorite is most efficient at pH 4.0. However, chlorine dioxide, a gas with a low threshold limit value for inhalation, is formed at this pH. Sufficient care must be taken to protect operators from chlorine dioxide fumes. Hydrogen peroxide bleaching is carried out under alkaline conditions. As a result, scouring and peroxide bleaching can often be conducted in one step. During peroxide bleaching, stabilizers are added for two reasons. Stabilizers inactivate metal impurities that may cause catalytic decomposition of hydrogen peroxide. They also act as buffers. A stabilizer frequently used is colloidal sodium silicate.

2.4.1.5 Mercerization:

Mercerization is the treatment of pure cotton fabrics or yarn with a strong caustic soda solution to improve strength, dye substantivity, strength and smoothness. Sufficient washing is required after this step to remove any traces of caustic soda.

2.4.1.6 Dyeing:

For thousands of year dyeing has been used by humans to decorate clothing or fabrics for other uses, the primary source of dye has been nature, with the dyes being extracted from animals or plants. In the last 150 years, humans have produced artificial dyes to achieve a broader range of colors, and to render the dyes more stable to resist washing and general use. Different classes of dyes are used for different types of fiber and at different stages of the textile production process, from loose fibers through yarn and cloth to completed garments.

Dyeing is the process of adding color to textile products like fibers, yarns, and fabrics. Dyeing is normally done in a special solution containing dyes and particular chemical material. After dyeing, dye molecules have uncut chemical bond with fiber molecules. The temperature and time controlling are two key factors in dyeing where mainly two classes of dye, natural and man-made are used.

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http://en.wikipedia.org/wiki/Dyes

http://en.wikipedia.org/wiki/Natural_dyes

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Chemical_bond

http://en.wikipedia.org/wiki/Molecules

http://en.wikipedia.org/wiki/Material

http://en.wikipedia.org/wiki/Material

http://en.wikipedia.org/wiki/Dye

http://en.wikipedia.org/wiki/Solution

http://en.wikipedia.org/wiki/Fabric

http://en.wikipedia.org/wiki/Yarn

http://en.wikipedia.org/wiki/Fiber

http://en.wikipedia.org/wiki/Textile

http://en.wikipedia.org/wiki/Plant

http://en.wikipedia.org/wiki/Animal

http://en.wikipedia.org/wiki/Nature

http://en.wikipedia.org/wiki/Clothing

2.4.1.7 Printing:

Printing is also a coloring process but the difference with dyeing is that here instead of coloring the whole material only impression of a design is printed on the fabric through various process steps.

2.4.1.8 Finishing:

Finishing operations change the properties of the fabric or yarn. They can increase the softness, luster, and durability of textiles. Finishing can also improve the water repelling and flame resistant properties of the fabric. The characteristics of textiles can be altered by physical techniques (dry finishing processes) or by application of chemicals (wet finishing processes). Luster can be added by both physical and chemical methods. Characteristics like flame or water repellency can only be obtained by wet finishing.

2.5. Pollution in Wet Processing Industries:

Among all of the different forms of pollution the most important for textile wet processing industry in our country are following these

5.1 Water pollution.5.2 Air Pollution.5.3 Noise & Vibration pollution.

Of this water pollution is more significant compared to other pollution.

F IGURE 2.5.1

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2.5.1 Water Pollution:

Textile industry is one of the leading consumers of water. It consumes about 3.2% of total consumption of water for various processes such as sizing, scouring, bleaching, dyeing, printing and other finishing process. The used water containing various constitutions such as dyes, chemicals is directly released into the sources of water which gets contaminated & thus resulting into water pollution. Nowadays the use of synthetic fibers, polymers & finishes by textile industry is increasing at rapid rate. Since many of these products are resistant to biological degradation, it causes water pollution when released as effluent into the water sources.

The seriousness of water pollution depends upon how effectively the above processes are carried out and also the quantity of water as well as the substrate or the chemicals used in the processes.

F IG 2.4.1 1 SOURCE: BURIGANGA-RIVER.BLOGSPOT.COM

2.5.1.1 Sources of water pollution:

Water pollution can be result of various sources. Here in the following table an idea is presented on the source of water pollution in textile wet processing industry

Table: 2.5.1

Process Possible pollutants Nature of effluentDesizing Starch, glucose, CMC, PVA, resins,

fats & waxes not exert a high BODVery small volume, High BOD:

(30%-50% of total)CMC & PVA

Kiering Caustic Soda, waxes & grease, soda ash, sodium silicate & fragments of

cloth

Small volume, Strongly alkaline, dark color, high BOD: (30% of

total)

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Bleaching Hypochlorite, Chlorine, caustic soda, hydrogen peroxide ,acids

Small volume, Strongly alkaline, Low BOD: (5% of total)

Mercerization Caustic soda Small volume, strongly alkaline, low BOD: (less than 1% of total)

Dyeing Dyestuff, mordant and reducing agents like sulphides , acetic acid &

soap

Large volume, strongly colored, fairly high BOD: (6% of total)

Printing Dyes, Starch, gums oil, china clay, mordant, acid & metallic salts

Very small volume, oily appearance, fairly high BOD.

Finishing Traces of starch, tallow , salts , special finishes etc

Very small volume, less alkaline, low BOD

The polluted water is very harmful for human life as well as for various living organisms on earth due to its odors, colors, turbidity and toxic chemicals present in it. Therefore these waste streams from different processing operation causing the pollution will have to be isolated & treated by either physical, chemical or biological methods or by combination of these methods in order to control water pollution.

2.5.1.2 Effects of important effluent characteristics :

1. P H : High alkalinity of waste water has an adverse effect on aquatic life. It also causes incrustation in sewers and damages crops by impairing their growth. High acidity causes corrosion of sewers, sewage treatment plant and machinery.

2. Color: Colors in the stream does not allow the penetration of sunlight at water surface, essential for photosynthesis which nature follows for self purification of rivers.

3. Suspended solids : The suspended solids present in an effluent along with colors & oily scum increase the turbidity & gives it a bad appearance and foul smell. Oily scum interferes with oxygen transfer mechanism at air water interface. Colloidal matters clog the pores of soil forming a mat, which reduces water-holding capacity of soil.

4. Dissolved solids: High amount of dissolved matter increases the incrustation in sewers. If most of the dissolved matter is in the form of salts of sodium then it hardens the soil and thus penetration of air to roots is prevented.

5. Oxygen demand : Dissolved oxygen is very much essential for the marine life. The oxygen demand is in the amount of oxygen required to correct the effluent, expressed in form of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD).

2.5.2 Air Pollution:

Ambient air is a mixture of gases i.e. 78% nitrogen, 20% oxygen, about 1% argon, 0.03% carbon dioxide and a number of minor gaseous elements such as neon, helium, methane, krypton etc. When there is disturbance in the composition of air due to the particulate matter or gases let out from the industries into atmosphere, it is considered as air pollution. The

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particulate matter may be in the form of fine dust, aerosols, fumes and gases in significant qualities.

F IG 2.4.1 2 SOURCE: UNIVERSETODAY.COM

2.5.2.1 Sources of air pollution:

Some of the pollutants causing air pollution are sulphur dioxide, metal sulphates, and exhaust gases emitting from polycondensation, melt spinning fiber lines and the fluff generated during spinning and weaving processes etc.Steam which is the energy media has an important role in textile mill and in processing houses-both coal and water are used to generate steam and in the process carbon, carbon dioxide, carbon monoxide and sulphur are produced which again cause air pollution.

2.5.2.2 Hazards of air pollution:

Air pollution is injurious to human being as well as animals. Air pollution results to mortality to eye, respiratory problems, irritation, diminishing visibility, obscuration of sunlight, persistence of fog etc.

Table: 2.5.2

Pollutants Effects of human being SourcesSulphur dioxide Irritates respiratory system and causes

bronchitisBoiler flue gas, rayon plant

etc.Aldehydes Irritates all parts of respiratory system Polyester plantChlorine Causes lung irritation and also irritation

in eyesProcessing house

Carbon dioxide Deprives body cells of oxygen and cause unconsciousness by CO combining with

hemoglobin

Boiler house

2.5.3 Noise and Vibration Pollution:

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Both of these cause hazards to health. Noise is all time irritating to people as it also causes damages to our ear when it is beyond the limitation range. Vibration is another case where people may easily get hurt so it is very much avoidable.

2.5.3.1 Sources of noise:

There can be two possible sources1. Dynamic sources : These are due to air jet, intermittent or periodic discharge of gas,

fan noise, hydraulic pump noise, combustion flow generated noise.2. Mechanical sources : These are due to impact of bearings and slide ways, tooth

engagement of gears, electronically induced vibration in electric machines, stick-slip motion due to friction and impact generate as a part of machine process.

2.6. Major Environmental Problem for the Wet Processing Industries:

It is important for each source of waste to be carefully identified for a textile processing operation. This can be done by

1) Inventory control and knowledge of potential pollutants in purchased products or2) Process analysis.

This section we will concentrate on the identification of pollutant sources in textile processing. Specific types of pollutants that will be considered in detail are:

6.1 BOD.6.2 Acidity/Alkalinity/pH.6.3 Toxicity.6.4 Air Emissions.6.5 Metals.

2.6.1 BOD:

In order to identify processes and their contributions to BODs in waste streams, each textile wet processing step will be listed with appropriate general comments concerning the potential BOD contributions.

The first wet processing step is desizing of woven fabrics except for singeing, which does not produce a significant wastewater stream. The BOD values of size materials listed in several sources range from 20,000–650,000 mg/l.

Starch size has BOD of 500,000–600,000 mg/l; alginates and modified starches, 100,000–500,000 mg/l; and synthetic sizes, 10,000–30,000 mg/l. In addition, starch is generally removed with enzymes that have BOD over 10,000 mg/l. The removal of synthetic

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sizes is accomplished with hot water and alkali (depending on the situation) so that the removal system does not normally contribute to BOD load. In a typical operation, desizing would contribute approximately 50 percent of the total BOD load from preparation for woven fabric but not knits.

Other factors are auxiliary components of size mixtures that are commonly used in the operation. Components of commercial mixed-size formulations include:

1. Size (starch, CMC, PVOH, PVA etc.);2. Humectants (urea, di-ethylene glycol, etc.); 3. Lubricant (wax or oil); 4. Antis tat; 5. Biocide; 6. Glycerin; and 7. Wetter.

In the following table we tried to provide the BOD contribution in the various textile processes:

Table: 2.6.1 BOD contribution in various textile processing

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Process BOD per 100 fabric

Singeing(Woven only) None

Desizing (woven only)Enzyme/starch

Starch/CMC mixPVOH or CMC only

Scouring

67200

40-50

BleachingPeroxide

Hypochlorite3-48

Mercerizing(no caustic recovery)(with caustic recovery

156

Heat setting (synthetic only) 0

Table: 2.6.2 BODs of Dyeing Assistants (ppm)

Class Fiber Machines Chemicals Bod contribution towaste

Acid WoolNylon

StockSkeinPackageJigBeckJetBeam

SurfactantLevelerRetarderAcidDyeLubricantSalt

Moderate(varies)Varies (may exhaust)VariesLowLOWVaries (may exhaust)Nil

Basic AcrylicOtherpolymers

StockPackageBeckJetBeam

SurfactantLevelerRetarderAcidDyeLubriantSaltCarrier

Moderate (varies)Varies (may exhaust)VariesLowLOWVaries (may exhaust)NilVaries (may be high)

Direct Cellulose StockPackageJetBeck

Alkali (weak)SurfactantRetarder/levelerSaltLubricantFixativeDye

NilVaries (moderate)Varies (moderate)NilVaries (may exhaust)Low (exhausts)Low

Disperse Synthetic StockPackageBeckJetBeam

Acid (weak) DispersantDyeCarrierLubricantReductive/After scour

LowHighHigh (dispersant)High (varies)Varies (may exhaust)Moderate to high

FiberReactive

Cellulose(wool)

stockJig

Alkali (strong)Salt

NilNil

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2.6.2 Acidity/Alkalinity

Textile mills have several sources of acids and alkalis. Normally the effluent gives an overall pH around 10–11. Desizing only contributes marginally to alkalinity/acidity of waste streams. The contribution of these continuous desizing processes can be a significant portion of total alkalinity. Scouring and bleaching of synthetics use small quantities of alkali, but scouring of cotton requires large amounts. For continuous process, it is possible to neutralize or reuse waste streams. The dyeing process varies in acidity/alkalinity depending on the substrate and dye class.

2.6.3 Toxicity

The toxic materials generated or used in the textile process include: Metals; Non-biodegradable surfactants; and Toxic organic materials.

2.6.4 Air Emissions

There are several places in textile operations where air emissions are generated: 1. Hot air dryers; 2. Dyeing machines; 3. Storage tanks; 4. Warehouse areas;5. Fugitive emissions.

The finishing process generates air emissions from high temperature drying and curing ovens. Emissions typically contain volatile compounds of finishing mix or volatile residues remaining in fabrics from prior processing. Proper preparation of dyeing and finishing agents can reduce the waste. The emphasis has been on air emission abatement equipment rather than source reduction. Abatement equipment operation can be combined with heat recovery from air exhaust to provide a return on investment.

Acetic acid is sometimes emitted from bulk storage tanks, dyeing machines, or dryers.

Formaldehyde may be emitted from resin storage tanks, finished fabric warehouses, dryers and curing ovens.

2.6.5 Metals

According to the America Dyestuff Manufacturers Institute, metals can be present in varying amounts in different dyes. Common metals include arsenic, chrome, copper, cadmium, cobalt, lead, mercury and zinc. Thai manufacturers have predominately shifted to dyes containing no heavy metals.

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2.7. Pollution Prevention

Pollution Prevention (P2) describes activities that reduce the amount of pollution generated by a process, whether it is consumer consumption, driving or industrial production. In contrast to most pollution control strategies, which seek to manage a pollutant after it is formed and reduce its impact upon the environment, the pollution prevention approach seeks to increase the efficiency of a process, thereby reducing the amount of pollution generated at its source. Although there is wide agreement that source reduction is the preferred strategy, some professionals also use the term pollution prevention to include recycling or reuse.

As an environmental management strategy, pollution prevention shares many attributes with cleaner production, a term used more commonly in the third world country like Bangladesh. Pollution prevention encompasses more specialized sub-disciplines including green chemistry and green design.

Pollution prevention is simply not treating the waste (or pollutant) in the first place. But also it means doing what we can do to reduce the amount and toxicity of the pollution we generate. Preventing pollution may be something as simple as using a catch basin to prevent spills, or something as complex as redesigning your operation to increase efficiency and reduce waste. Simple things like choosing non-hazardous solvents can protect the environment and reduce the number of environmental regulations you are faced with. Pollution prevention means thinking about the environmental impact of your actions, and trying to limit that impact.

Pollution prevention is defined as those measures that eliminate or reduce pollution prior to off-site recycling or treatment. Pollution prevention does not only reduce water pollution, but also minimizes the release of pollutants to land and air. In the Pollution Prevention Act of US, the Congress defines a multimedia waste management hierarchy. Source reduction stands at the top of the waste management hierarchy and is followed by reuse and on-site recycling. Off-site recycling is not considered a pollution prevention measure.

Pollution Prevention uses source reduction techniques and practices to reduce or eliminate the amount of hazardous substances, pollutants or contaminants entering any waste stream or being released into the environment. In short, pollution prevention means not creating waste in the first place while reducing risks to public health, welfare, and the environment.

2.7.1 Necessity of Pollution Prevention:

When we generate waste or pollution, we must safely and legally manage that waste or pollution. Whether it is household trash or waste from a business, managing wastes costs money. And usually the things we discard are materials we paid for when we got them. A good example is paper towels. We buy them, use them once and then pay again to dispose of them. If we reduce the amount of waste we generate, we save money. It's as simple as that. Reducing costs is a major reason to prevent pollution. Here are a few others:

Improved work environment and worker safety. Reduced liability.

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Increased efficiency. Fewer regulatory requirements. Better environmental protection. Enhanced marketing and public relations opportunities.

2.8. Pollution Abatement Techniques in Different Steps of Wet Processing Technology:

The wet processing of textiles is considered the major pollutant source in the textile industry, due to the many different chemicals used in the different finishing processes. Most of the used chemicals are considered hazardous pollutants to air and wastewater. 2.8.1 Purchasing Policy for Raw Materials: The textile company should deal with suppliers having less-polluting raw materials. The quality of raw material is controlled by prescreening and testing shipments as they are received to determine the proper type with least pollution impact. Some suppliers may change the chemicals to be delivered without notifying their customers, and if the material is not checked by testing, the company may have more hazardous pollution.The chemicals to be used in the wet finishing processes are recommended to be purchased in returnable, reusable containers to eliminate waste packing materials, and reduce spillage and worker exposure to chemicals.

2.8.2 Pollution Abatement in Desizing: Desizing operations represent large contribution to pollution, accounting for 40-50 % of

the total pollution load from preparatory processing. The use of acrylates as a size in place of starch reduces the BOD, due to the recovery of size. The efficient sizes are degradable, recoverable, water soluble (for staple fibers), and universally applicable. Starches can be partially substituted by polyvinyl alcohol to reduce pollution in effluents.

The use of hydrogen peroxide instead of enzymes, to desize starch (known as oxidative desizing) reduces the pollution in effluents, because in this case the starch degraded to carbon dioxide and water.

The use of low viscosity sizes, such as PVA, CMC enables the recovery instead of up to 50% of the size in the effluents of the desizing process.

The use of newer enzymes which degrade the starch size to ethanol of anhydroglucose, enables the recovery of ethanol by distillation, thereby reducing the BOD load in the desized effluent considerably.

Recovery of sizes from the desizing plant should be considered as this technique is universally applicable using high pressure or vacuum technology in a pre-wash stage.

Wastewater from cleaning the machines should be purified by biological treatment or concentrated by ultrafilteration. Chemical coagulation or thermal precipitation transfers the environmental problem to the produced sludge.

If recovery of size is not possible and degradation of the size is required, an integrated chemical pretreatment (scouring, desizing, bleaching all in one) is preferred; this will reduce the consumption of water and energy and minimize pollution.

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Acids should be replaced by enzymatic and/or oxidative desizing to render the vegetable or animal size water soluble (hydrolysis); starch from all sources can be removed.

For PVA, PES, PAC and CMC membrane filtration should be carried out, if reuse is possible

For starch and derivatives, galactmannate and PVA, biological treatment should be carried out (after sludge adaptation).

For all polyacrylates, chemical coagulation (e.g. by iron) plus an appropriate waste treatment of the produced sludge should be carried out.

2.8.3 Pollution Abatement in Scouring:

The optimum amounts of alkaline recipes should not be exceeded. Alkalis should be recycled and reused as much as possible; rinsing water should be

reused for preparing the scouring bath. Combining the desizing and scouring processes can save water and energy and reduce

processing time. Rinse water can be reused following mercerizing rather than dumping the bath water

after each use. The spent rinse water can be processed in an evaporator and concentrated caustic soda can be used in mercerizing. This technique reduces the wastewater drastically.

Using continuous horizontal washers, which operate by spraying clean wash water on the top pass of fabric as it makes a series of horizontal traverses upward in the machine. The unprocessed fabric enters of the bottom traverse, and the water enters at the top. This method conserves energy and water, thus reduces pollutant effluents.

A reduction of 25% in sodium hydroxide can be obtained by substitution with sodium carbonate.

The use of sodium acetate is recommended for neutralizing scoured goods so as to convert mineral acidity into volatile organic acidity.

Surfactants should have a high degree of ultimate biodegradability without producing metabolites that are toxic to aquatic species.

Alkylphenolethoxylates (APEO) in detergents and dispersants should be substituted by readily biodegradable surfactants, or should at least not reach the final effluent. Similar restrictions for other non-readily biodegradable surfactants should be considered.

Solvents having environmental impact that is more damaging than available alternatives should be avoided.

Alkalis should be recycled and reused as much as possible, rinsing water should be reconstituted (upgraded).

Mineral acids (sulphuric acid, hydrochloric acid) should only be used for neutralization when no better options are available.2.8.4. Pollution Abatement in Bleaching:

Fabrics that need to be colored in deep shades should not be bleached extensively, thus reducing the consumption of bleach and consequently reducing the pollution load.

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The use of continuous knit bleaching ranges, to replace batch preparation of knitted fabrics reduces the water and chemical consumption, and consequently contributes to less pollution load.

Peroxide bleaches should be used instead of reductive sculpture, containing bleaches which are more hazardous.

Hydrogen peroxide (H2O2) should be used as the bleaching agent in preference to chlorine containing compounds, such as hypochlorite. This will take the factory one step closer to obtaining an “eco label”. Also, the use of hypochlorite is banned by many certifying agencies. Hydrogen peroxide also minimizes the content of hazardous organohalogen substance in the final effluent, and eliminates a toxic and hazardous chemical from the workplace and improve working environment.

The use of the enzyme Terminox Ultra (of Novo) in place of a reducing agent such as thiosulphate can reduce the processing time by half, and reduce the water and energy considerably.

The wetting agents, emulsifiers, surfactants and all other organic chemicals should be readily biodegradable without producing metabolites, which are toxic to aquatic species.

The installation of holding tanks for bleach bath reuse, where the bath is reconstituted to correct strength after analysis by titration. Using this technique decreased BOD over 50%, and reduced the water use.

In case of bluish and bright qualities (76% on Berger-scale) of fabrics, alternatives for chlorine bleach are not always available. Hazardous organohalogen substances production needs to be reduced or treated adequately.

Precursors (proteins and pectines) should be removed in order to prevent the formation of hazardous organohalogen substances in bleaching with chlorine.

Hydrogen peroxide (H2O2) in effluents from bleaching can be reused in the treatment of the (combined) wastewaters as a clean oxidant in the activated sludge process or chemical oxidation processes.

2.8.5 Pollution Abatement in Mercerizing:

Dilute alkali from mercerizing should be reused in scouring, bleaching or dyeing operations, so that discharges from alkaline treatment can be minimized, resulting less polluted effluents.

Liquid ammonia is a low pollution substitution for conventional mercerization (NaOH) Heavy cotton fabrics treated with liquid ammonia require less dye for a given depth of

shade, and consequently contribute to pollution abatement due to using less chemical for the same requirement.

Alkali should be recovered and recycled or reused after regenerative treatment to remove dirt (coagulation, flotation, microfiltration, nanofiltration) and after concentration.

The non-recoverable fraction of the mercerizing wastewater should be neutralized by mixing with acid effluents or by CO2 as acid.

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2.8.6. Pollution Abatement in Dyeing:

2.8.6.1 The use of low-liquor ratio dyeing The bath ratio is defined as the ratio of bath weight to the fabric weight. The lower the bath ratio, the less the amounts of chemicals required in the dye bath, and the less the pollution impact. So, low liquor dyeing machines are recommended for pollution abatement

2.8.6.2 Salt management Although salt is cheap, effective and has very low toxicity, it has to be used with optimum dosage for each individual for each dyeing. It is recommended to select dyes which exhaust with minimum salt, e.g. Cibachrone LS dye.

2.8.6.3 Dye bath temperature The temperature of dye bath should be optimized to avoid overheating, and excess consumption of dye which helps to reduce pollution. If dye bath is heated by direct steam, the heating should be gently, to avoid overflowing and subsequent loss of dye bath solution, which causes pollution.

2.8.6.4 Reuse of dye baths After the fabric is dyed, the dye bath is pumped to a holding tank and then the dyed fabric is rinsed in the same machine, and after removing the rinsed fabric, the dye bath is returned back to the dye machine. This technique reduces pollution concentrations, and effluent volume.

2.8.6.5 Substitution of harmful dyestuffs - Black dyeing is often carried out using sodium sulphide (the reducing agent) and

dichromate (the oxidizing agent), and these two chemicals are toxic, hazardous to handle, generate effluents that damage the environment and they leave harmful residues in the finished fabric. So these chemicals should be substituted with glucose (for reduction) and sodium perborate (for woven fabrics) and hydrogen peroxide (for knitted fabrics) as oxidation agent.

- Aniline black dyes, which require large quantities of potassium dichromate and sodium chlorate can be replaced by sulphur dyes, using glucose as a reducing agent and either sodium perborate or hydrogen peroxide as oxidizing agent. This substitution can reduce hazardous pollution considerably.

- In vat dyeing, potassium dichromate, which is toxic and hazardous, can be satisfactorily replaced by peroxides or periodates for pollution abatement.

2.8.6.6 Banned dyes A number of dyes should be banned from use due to their potentially toxic, mutagenic or carcinogenic properties. These dyes release amines during processing that are hazardous. These dyes are listed in the following table

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Table 2.8.1: Banned dyes

No Banned Amine No Banned Amine

1 4- Aminodiphenyl 11 3,3- Dimethylbenzidine

2 Benzidine 12 3,3- Dimethoxybenzidine

3 4- Chloro –o- toluidine 13 3,3-Dimethyl1-4,4

diaminodiphenylmethane

4 2- Naphthylamine 14 p-kresidin

5 o-Aminoazotoluidine 15 4,4 Methyene- bis-

(2-chloraniline)

6 2- amino-4 nitroluene 16 4,4 Oxydianiline

7 p-Chloraniline 17 4,4 Thiodianiline

8 2,4- Diamonoanisol 18 o- Toluidine

9 4,4- Diaminodiphenylmethane 19 2,4- Toluylendiamine

10 3,3- Dichlorobenzidine 20 2,4,5- Trimethylaniline

2.8.6.7 Minimizing machine cleaning: In dyeing operations, startups, stop offs, and color changes cause intensive cleanings and pollution in effluents. The ideal sequence is to run the same color repeatedly on a particular machine, or to group colors within families (red, yellow, blue), and then run the dyes within one color family from lighter to darker values and from brighter to duller chromes.

2.8.6.8 Handling of powder dyes The manual transfer of powder dyes from bulk containers to smaller process containers generates significant amounts of dust. All operations concerning manual handling of powdered dyes should be in small special room and blow the current of sucked air for dust. A protective mask provided with filter must be used. This pollution causes breathing and skin diseases such as asthma, eczema, and severe allergic reactions. Ventilation booths are recommended. A vertical air shower pushes airborne dust out of the worker’s breathing zone, until the dust is captured and exhausted from the work area to a filter. All tasks associated with manual transfer of powdered dyes should be performed inside the booth under the air shower. Most powder dyes are shipped in drums that range in height from 75 to 90 cm. When manually transferring dye from these drums, workers must lean forward and place their heads inside the drum to scoop out dye near the bottom. In this position, the worker is greatly exposed to airborne dye dust, even in a ventilated booth. So, shorter drums should be used to eliminate the need for workers to place their heads inside the drum. The drum height should be limited to 60cm.

2.8.6.9 Safer alternatives for banned dyes. Environmental Quick Scan Textiles, compiled for CBI and SIDA by Consultancy and Research for Environmental Management, published by CBI, SIDA, VIVO, 1996. This

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authority published lists for banned dyes and the corresponding safer alternative dye which contributes to pollution abatement. The lists are available for acid dyes, direct dyes, and disperse dyes.

2.8.6.10 Important precautions in dyeing for pollution abatement - Dyes found to be containing PCBs (e.g. certain sources of Cu-phtalocyanine)

should be substituted immediately. - Cadmium containing pigments should not be used. - Benzidine-based azo-dyes should not be used at all.- Carriers containing chlorine should not be used.- Reduction of dyes by sulphide should be avoided. Dichromate oxidation of vat

dyes and sulphur dyes should be substituted by peroxide oxidation.- Azo-dyes which can, under reductive conditions, release aromatic amines, which

are suspected carcinogens, should not be used.- Halogenated solvents and dispersants for dyes and chemicals should be

substituted where possible by water-based systems.- Metal containing dyes (Cu, Cr, Ni, Co, etc.) should be substituted by other dyes

or techniques.- In order to minimize the discharges of BOD, COD, etc. as well as of colored

substances in case of repeated dyeing, the rinsing bath should be used as next dye bath, if the after-treatment chemicals are compatible with the dye bath chemicals.

- Wastewater generated from dyeing, should receive a dedicated treatment to remove the persistent pollutants.

2.8.7 Pollution Abatement In Printing : The following are some recommendations contributing to pollution abatement in printing: The excess printing pastes can be recovered through optimized paste preparation and

supplying systems, and they should be recycled and reused to reduce the pollution in effluents.

The use of urea in printing with reactive dyes should be reduced by (or in combination with) other techniques (e.g. pre- wetting of fabric) so that the nitrogen emissions do not increase. The printing paste should contain no more than 30 gm. of urea/kg of textile. Some approaches to eliminate or replace urea in cellulose printing are: - Adoption of two-phase flash printing.- Complete or partial substitution of urea with an alternative Chemical like

Methaxyl FN-T.- Mechanical application of moisture to printed fabric prior to entering the steamer.

Full or partial substitution of gum thickening by emulsion thickening in textile printing. Replacement of the use of white spirit kerosene by water-based system. The use of biodegradable natural thickening auxiliaries or highly degradable synthetic

thickeners. Minimizing the use of copper and chrome salts to the extent possible. Avoiding use of solvent-based pastes in pigment printing.

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Recovery of acetic acid, which is used to bond the two components of azoic dyes. The use of pigments, which give improved absorption and lower effluents for reducing

COD. Some of the pigments are suspected to have toxic/ carcinogenic properties, and these

are listed and the safer alternatives corresponding to each pigment is given. CBI, SIDA, VIVO, and Compiled publish this list by consultancy and Research for Environmental Management.

When feasible, pigmentation is preferred over dyeing because this may reduce dyeing and printing operations, saving energy, water and chemicals.

Biodegradable natural thickening auxiliaries or highly degradable synthetic thickeners should be chosen.

Printing screens should be replaced by non-contact techniques (e.g. ink-jet printing). Automation may lead to less pollution.

2.8.8 Pollution Abatement In Finishing:

The following are recommendations for pollution abatement in chemical finishing: Finishing chemicals should be reused whenever possible. Reducing the use of formaldehyde releasing chemicals as much as possible.

Formaldehyde should be replaced with polycarboxylic. Alkylphenol should be replaced with fatty alcoholethoxylates.

Replacement of acetic acid (used for pH adjustment in resin finishing bath) with formic or mineral acids to reduce BOD load.

Using formaldehyde- free cross-linking agents for cellulose textiles and formaldehyde-free dye-fixing agents.

Using formaldehyde scavengers during application and storage of resin finished goods. Dimethylol or dihydroxythlene urea used in anti-wrinklefinishing should be substituted

by polycarboxylic acids, mainly 1,2,3,4-butanetetracarboxylic acid or glyoxales. MAC Complexing agents like DTDMAC, DSDMAC, DHTDMAC used in softening

finishing should be replaced with cellulose enzymes. Asbestos, halogenated Compounds like bromated diphenylethers and heavy metal

containing compounds used in flame retardant finishing should be replaced by inorganic salts and phosphonates.

Biocides such as chlorinated phenols, metallic salts (As, Zn, Cu, or Hg), DDE, DDT and benzothiazole used in preservation finishing should be substituted by UV treatment and, or mechanical processes or by enzymatic finishing.

In case of using fireproofing chemicals, the best technique is that which consumes minimal amounts of water (such as Vacuum, back coating, foam) or techniques leading to minimal of residues particularly (e.g. foam).

The use of hazardous chemicals for the conservation of textiles should be minimized, either through substitution or through “tailor-made” selective use to only those textiles which are exposed to possible environmental degradation.

Limitation of the chlorination stage in wool shrink proofing by substitution of other techniques (e.g. peroxygen treatment).

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It is more recommended to build in the finishing chemicals into the fiber during production or during spinning than applying the finish at a later stage.

Concentrated residues from finishing should not be discharged. They should be reused or treated as waste.

In case of mothproofing agent-contaminated water, the volume of bath should be reduced by employing e.g. mini-bowls, modified centrifuges or foam treatment during back coating laminating or carpets.

In case of mothproofing finish, wastewater should be treated in such a way that excessive sludge is avoided. This sludge should preferably be incinerated as chemical waste or detoxified by wet (catalyzed) oxidation.

2.9. Waste Minimization Options for the Textile Industry

2.9.1 Reducing water consumptionWater consumption in a textile factory can be reduced by implementing various changes ranging from simple procedures such as fixing leaks, to more complex options such as optimizing water use and reducing the number of process steps. Some suggestions are outlined in this section.

2.9.1.1 Repair leaks, faulty valves, etc.A simple method of determining if leaks exist is to take incoming water meter readings before and after a shut-down period when no water is being used. A difference in the readings could indicate a leak.

2.9.1.2 Turn off running taps and hosesEncourage workers to turn off taps and hoses when water is not required. The fixing of hand triggers to hoses also reduces water consumption.

2.9.1.3 Turn off water when machines are not running Encourage workers to turn off machines and water during breaks and at the end of the day. Avoid circulating cooling water when machines are not in use.

2.9.1.4 Reduce the number of process stepsThis involves a study of all the processes and determining where changes can be made. For example, fewer rinsing steps may be required if a dye with high exhaustion is used.

2.9.1.5 Optimize process water useExamples include using batch or stepwise rinsing rather than overflow rinsing, introducing counter-current washing in continuous ranges, and installing automatic shut-off valves.

2.9.1.6 Recycle cooling waterCooling water is relatively uncontaminated and can be reused as make-up or rinse water. This will also save energy as this water will not require as much heating.

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2.9.1.7 Re-use process waterThis requires a study of the various processes and determining where water of lower quality can be used. For example, final rinse water from one process can be used for the first rinse of another process.

2.9.1.7 Using water efficient processes and equipmentAlthough replacing outdated equipment with modern machines which operate at lower liquor ratios and are more water efficient requires capital investment, the savings that can be made ensure a relatively short pay-back period.

2.9.1.8 Sweeping floorsInstead of washing the floors of the dye house and kitchens, rather sweep up any spillages and wash down only when essential. Not only will this reduce water use, but also the concentration of contaminants to drain as the waste is disposed of as solids.

2.9.1.9 Reusing water from auxiliary processesThe water used in the rinsing of ion-exchange columns and sand filters can be reused elsewhere in the factory.

2.9.2. Reducing Chemical ConsumptionThe majority of chemicals applied to the fabric are washed off and sent to drain. Therefore, reducing chemical consumption can lead to a reduction in effluent strength and therefore lower treatment costs, as well as overall savings in chemical costs. Various options for reducing chemical use are listed below:

2.9.2.1 Recipe OptimizationRecipes are generally fail-safing designed which results in the over-use of chemicals. Optimizing the quantity of chemicals required will lead to more efficient chemical use and lower costs. Continual updating of recipes should be carried out when new dyestuffs enter the market as, in general, less of these chemicals are required.

2.9.2.2 Dosing ControlOverdosing and spillages can be reduced by mixing chemicals centrally and pumping them to the machines. Check that manual measuring and mixing is carried out efficiently and automatic dispensers are properly calibrated.

2.9.2.3 Pre-screen Chemicals and Raw MaterialsAvoid dyestuffs containing heavy metals, solvent-based products and carriers containing chlorinated aromatics. Safety data sheets should be obtained from the chemical manufactures to obtain information such as toxicity, BOD and COD. Check that raw materials do not contain toxic substances. Check that companies will accept expired raw materials for disposal.

2.9. 2.4 Chemical SubstitutionReview chemicals used in the factory and replace those hazardous to the environment with those that have less of an impact. Use dyes that have high exhaustion rates and require less salt specifically:

a) Replace metal-containing dyesb) Use bi-reactive dyes in place of mono-reactive

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c) Avoid the use of APEO detergents and replace with more biodegradable alternatives

d) Replace stilbene optical brighteners with alternatives, or eliminate altogethere) Dye wool with dyes that do not require after-chroming

2.9.2.5 Correct Storage and HandlingMore effective control of the storage and handling of chemicals will results in less spillage reaching the drains.

2.9,2.6 Chemical Recovery and ReuseChemical use may be reduced through recovery and reuse. For example, sodium hydroxide from mercerizing can be recovered through evaporation. Dye baths may be reused and size can be recovered for reuse.

2.9.2.7 Process ModificationsChemical application methods (e.g. process parameters such as time, temperature, wet pickup/liquor ratio, and machine speed) can often have substantial effects on waste loads resulting from a process. For example, fiber reactive dyes can be applied from batch dyeing equipment with an amount of salt on the order of the weight of the goods, thousands of pounds per day for a typical dye house. Alternatively, pad batch dyeing uses no salt at all for the same fiber reactive dyes and same shade on the same fabric. The manner of application of chemicals to substrate is clearly an important factor.

2.9.2.8 Equipment ModificationIn many cases, modifying equipment can provide source reduction such as reducing “drag out” or reducing liquor to goods ratio. Reduced liquor to goods ratio results in less water use and thus less alkali or acid required for pH adjustments, less stabilizer, lubricants, etc. Recycling waste streams within a process can also be effective. Examples such as reusing once through non-contact cooling water and counter current washing are discussed in other parts of this document

2.9.2.9 Improve SchedulingReview the scheduling of continuous processes such as sizing, desizing, padding etc. to ensure that the same chemical bath is used as many times as possible, thus reducing the number of dumps to drain per day.

2.9.3 Energy ConservationAs with water conservation, reductions in energy use can result in substantial savings and lower emissions from boilers or generating plants. Some energy efficient options are listed below.

2.9.3.1 Compressed Air

2.9.3.1.1 Optimize compressed air generation To keep generation costs to a minimum:

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a) Pressure control should be based on the pressure at the most sensitive / critical of machinery.b) Compressor sequencing should be based on a narrow pressure band in order to achieve the minimum generation pressure at all times. Care should be taken, however to avoid excessive cycling.Reducing generation pressure by 10% will yield savings of 5% of annual compressor operating cost.

2.9.3.1.2 Fix compressed air leaksNo-load tests should be carried out regularly, approximately every 2 to 3 months. All air leaks should be tagged and repaired at the earliest opportunity. Ultrasonic detection devices are available to assist in leak detection.

2.9.3.1.3 Optimize compressor sizingCompressors should be sized as closely as possible to the duty. It is not economical to run any machine for long periods at low loads; the off-load power consumption can be between 15% to 70% of on-load power once motor inefficiencies have been taken into account. In general, reciprocating compressors offer the highest part-load operating efficiently, if it is well maintained.

2.9.3.1.4 Install compressor control systemsFor multiple compressor installations, a modern compressor control system can save between 5% and 20% of total generation costs for a modest capital outlay. Many modern controllers comprise cascade control, run-on timers and pressure control. The latter is important in installations where the demand for air fluctuates significantly. It enables a lower generation pressure at times when air demand (and therefore system pressure drops) is reduced.

2.9.3.1.5 General housekeepingThe following general items should be considered when addressing compressed air efficiency:a) Ensure that the air fed to compressors is as cool as practicable. A 4ºC drop in inlet temperature will give savings of 1% of generation efficiency. Air-cooled compressors should be fitted with ductwork to atmosphere, such that the exiting warm air does not overheat the plant room.b) Ensure that air dryers are installed downstream of the air receiver. The receiver acts as a pre-drier. Only dry (or treat) compressed air for processes that require it. If air lines are subject to condensate problems, fit appropriate drainage points.

2.9.3.2 Refrigeration2.9.3.2.1 Reduce Cooling LoadsThe most common application of refrigeration in Southern African textiles industries is for the provision of air conditioning of production areas. There are two issues here.

a) Ensure that heat gains (from machinery, unnecessary air ingress, lighting, etc.) are kept to a minimum. Bear in mind that heat gains from electrical machinery operating when not needed is paid for twice: once to operate the machine and again to remove the heat gain.

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b) Ensure that the control temperature is set to an acceptably high level. Do not over-cool.

2.9.3.2.2 Decrease Condensing TemperatureCauses of unnecessarily high condensing temperatures include:

a) Non-condensable gas build-up in the condenserb) Liquid refrigerant backing-up into the condenserc) Head pressure control set too highd) Fouling of the condenser heat exchangere) Fan and pump malfunctionAs a guideline, reducing condensing temperature by 1ºC will yield savings of between 2% and 4% of annual refrigeration cost

2.9.3.2.3 Increase Evaporating TemperatureCauses of unnecessarily low evaporating temperatures include:

a) Low refrigerant charge. Excessively low refrigerant charge can lead to gas by-passing of the expansion valve, increasing costs by 30 % or more.

b) Fouling of the evaporator heat exchanger.c) Control temperature set too low.d) Poor expansion valve performance.As a guideline, increasing evaporator temperature by 1ºC will yield savings of

between 2% and 4% of annual refrigeration cost

2.9.3.2.4 Compressor ControlThe type of control strategy adopted can have a significant effect on operating costs.An effective control strategy could be adopted using the following guidelines:

a) Avoid excessive part-load operation.b) Ensure that compressors are sequenced to avoid operating more than one compressor at part-load at any one time.c) Use reciprocating compressors for part-load operation, in preference to screw or centrifugal types.d) Avoid the use of compressor capacity control mechanisms that throttle the inlet gas flow, raise the discharge pressure or use gas by-pass.e) Ensure that all auxiliaries are switched off when the compressor is off.Incorrect control of compressors can increase costs by 20%, or more. Poor control of auxiliaries can increase costs by 20%, or more.

2.9.3.3 Steam Generation2.9.3.3.1 Boiler blow downIt is necessary to control the build-up of total dissolved solids (TDS) within any steam-raising boiler, through periodic blowing-down. It is essential that boiler TDS is monitored regularly in order that excessive blowing down is avoided. Increasing blow down by 5% will increase fuel consumption by between 1% and 1.5%.

2.9.3.3.2 Economizers

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Boiler efficiency may be increased by preheating feed water through the use of an economized installed within the boiler flue. In general, an increase in feed water temperature will result in 1% less fuel being burned at the boiler.

2.9.3.3.3 Combustion air temperatureBoiler efficiency can be increased by recovering waste heat from the flue gas and preheating combustion air. An increase in combustion air temperature will result in about 2% efficiency increase.

2.9.3.3.4 Firing rate and load variationHighest boiler efficiencies generally occur over the range of firing rates from 70% to 90% of rated capacity. Boiler efficiency can be optimized, therefore, by ensuring, as far as possible, that equipment is used within this range. Fluctuating loads have adverse effects on boiler efficiency, especially if frequent periods of low load are a characteristic. There are several ways to improve this situation:a) Rationalization of the load demand, if possible. Steam accumulators enable a

damping effect of load variation.b) Rationalization of boiler firing schedule.c) Improvements to the firing control system.d) Installation of a flue-gas shut-off damper to eliminate the circulation of cold air in

the event of boiler shut-down.e) Installation of a number of smaller boilers as opposed to a single large one.

2.9.3.4 Steam Distribution and Use2.9.3.4.1 InsulationAll hot surfaces of a steam distribution system must be insulated. Justification can be made on the grounds of a reduction of heat loss, improvement in steam quality (through reduced condensate formation) and health and safety issues. Heat loss charts are available for various combinations of pipe work diameters and surface temperatures over a range of insulation thicknesses. As a rough guide, insulation can be economically justified to reduce bare pipe losses by 90%.

2.9.3.4.2 Flash steam recoveryFlash steam is generated when hot condensate is allowed to reduce in pressure, allowing a certain amount of condensate to evaporate (flash). The total heat content of the new system at equilibrium is the same at the total heat content of the original condensate. The quantity of flash steam generated may be calculated using a flash steam chart, or from steam tables. Wherever the generation of flash steam occurs, it is important to consider alternative possible uses for it (this includes the use of flash steam from boiler blow down).

2.9.3.4.3 Good housekeepingThe following guidelines should be used to ensure good housekeeping of steam distribution systems:a) All steam traps should be surveyed annually to ensure their correct operation.b) Ensure that all steam leaks are attended to at the earliest opportunity

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c) Reduce temperature levels to the minimum required by the process.d) Optimize end-user requirements by ensuring that the plant is fully loaded when possible and shut down (isolated) when not operational.

e) Ensure that end-user heat exchanger surfaces are maximized by provision of adequate air venting (during start-up only) and steam trapping.

f) Valve off steam supply lines that are out of use for considerable periods.g) Consider heating small, distant or occasional users by other means.

2.9.3.5 Install Heat ExchangersThe installation of heat exchangers on the high temperature effluent streams to recover energy and heat incoming water results in substantial savings.

2.9.3.6 Optimize Plant Environmental ConditionsOptimize the temperature, humidity etc., of the factory so that only the required amount of energy is used.

2.9.3.7 Shutting off of Lighting, Air-conditioning, etc.Shutting off the lights in areas not in use and during shut down periods will reduce electricity costs, as will turning off the air-conditioning over weekends and shut-downs. Shutting off machines when not in use also results in savings.

2.9.4. Reducing Air Pollution Some steps to reduce the emissions to air include:a) Decreasing emissions of organic solvents by changing to water-based products.b) Using scrubbers to collect particulate matter.c) Optimizing boiler operations to reduce the emissions of nitrous and sulphur oxides.d) Pre-screening chemicals using the Material Safety Data Sheets to ensure that chemicals

are not toxic.e) Identifying sources of air pollution and quantifying emissions.f) Designing and manufacturing products that do not produce toxic or hazardous air

pollutants.g) Avoiding fugitive air emissions from chemical spills through improved work practices.

2.9.5 Reducing Solid WasteIn terms of volume, solid waste is the second largest waste stream in the textile industry next to liquid effluent. There are a number of waste minimization options available to reduce solid waste, and these include:

a) Reducing the amount of packaging material by improved purchasing practices such as ordering raw materials in bulk or returnable intermediate bulk containers (IBCs).

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This reduces spillages, handling costs, exposure of workers to chemicals and the amount of storage space required.b) Purchasing chemicals in returnable drums. Enquire if vendors will accept unwashed drums as this will reduce the waste water generated in the factory.c) If possible, ordering chemicals in IBCs rather than bags as these are easily broken, causing spillages.d) Purchasing yarn on reusable plastic cones rather than cardboard cones.e) Reducing seam waste through effective training programmes.f) Selling waste fibers, sweeps, rags, yarn and cloth scraps.g) Selling used pallets to a recycler.h) Donating damaged pallets to institutions (e.g. schools) for the wood.

2.9.6 Reducing ToxicityCompounds that contribute to the aquatic toxicity of textile effluent include salt, metals, surfactants, toxic organic chemicals, biocides and toxic anions. Some methods of reducing the use of these compounds are to:

a) Reduce metal content through careful pre-screening of chemicals and dyes for metal content and using alternatives where possible.b) Eliminate galvanized plumbing as reactions with brass fittings can take place in the presence of acids, alkalis or salt and lead to the release of zinc.c) Reduce the amount of salt in the effluent by optimizing recipes, using low-salt dyes, reusing dye baths and optimizing dyeing temperatures.d) Use biodegradable surfactants such as linear alcohol ethoxylates.e) Replace chlorinated solvents with unchlorinated alternatives.f) Replace the use of biocides with ultraviolet light as a disinfectant for cooling towers.g) Carefully pre-screen chemicals for their toxic nature using MSDS.

2.9.7 Reducing Noise Pollution The following steps can be implemented to reduce noise pollution:

a) Install screens and sound baffles on fans,b) Regular maintenance of machinery,c) Fit anti-vibration mounts on machines, andd) Fit walls with sound-absorbing material.

2.10 Some Pollution Prevention Tips:

There are some general ideas which comes into action from our general knowledge, general intention, and some usual carefulness these are

Make sure hoses are not left running. Replace broken or missing valves.

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Don't leave cooling water running when machinery is shut down. Replace defective toilets and water coolers. Reuse noncontact cooling water by sending it back to a clear well or influent water

line to the mill. Use countercurrent washing techniques. Practice rapid inverse dyeing (RID). Remove water from waste liquids with a water evaporator, (a hot evaporation system)

which is a natural gas fired, air assisted evaporator for the removal of water from waste liquids. The purpose of the unit is to safely concentrate and contain hazardous waste liquids.

Look for marketability in waste products. For example, waste print paste has significant potential for improved market value as a concrete additive for colored concrete.

Consider speaking to liaisons available for materials exchange between generator and potential users of the wastes. The materials exchange may analyze and treat the waste to make it a suitable raw material for buyers to use. The type of exchange actively seeks buyers for the wastes.

Eliminate phosphates wherever possible. Explore solvent processing techniques. Use bathless washers. Use liquid-ammonia mercerization instead of caustic. Replace all chromates used for oxidation of vat dyes. Evaluate all maintenance chemicals for metals and toxicity. Save energy by removing water by centrifugal means, rather than evaporation

2.11 Modern Pollution Prevention Techniques:

In modern days pollution is a big area of concern. Modern technologies have great influences on this case. New improved & eco friendly technologies are opening new opportunities for us every day. Here in next some articles we are going to give some brief idea on this.

2.11.1 New Generation Dyestuffs

As indicated above, the textile industry needs a new generation of dyestuffs based on better treatability, higher exhaustion thus-less color residue in wastewater, and safer intermediates, while maintaining desirable tinctorial, cost and fastness properties. The application properties of these dyes of the future should be adequate in terms of repeatability, compatibility with existing equipment, controllability, etc. This new generation of dyes should require fewer chemical dyeing assistants, especially salt, retarders and accelerants. Fiber reactive dyes for cotton, which are the fastest growing class of dyes over the last 20 years, are promising for this major opportunity to reduce or eliminate some of the most intractable emerging problems enumerated above, i.e.

Color residues in dyeing and printing wastewater,

Massive electrolyte discharges,

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Aquatic toxicity,

Toxic air emissions,

Improving treatability of wastes,

Elimination of low levels of metals from wastewater.

2.11.2 New Application Methods

There is also the need to develop new application methods especially for existing fiber reactive dyes on cotton. One successful approach is pad batch dyeing, which is well known. Other methods are also needed, especially for tubular knits and other substrates not adaptable to pad batch dyeing. Using alternative electrolytes or other methods to control dye affinity and exhaustion via solubility control and fiber zeta potential is another opportunity which begs investigation.

2.11.3 Chemical Specialties

Specialty textile processing assistants are a unique group of products, which are not understood very well by outsiders to the textile industry. They are used in large quantities with relatively little information about their pollution potential. A recent listing contained over 5000 products in 100 categories which were marketed by 175 companies under 1800 trade names. Each product is a proprietary blend of chemical commodities. The composition is not revealed to the user, nor is the pollution characteristics (e.g. aquatic toxicity).

There is a clear need for disclosure of user information, which is in a sense a business issue, including potential incompatibilities with upstream process residues. But there are also technical needs of better data on these mixtures, as well as more accurate aquatic toxicity data. Toxicity reduction programs are often frustrated because comparative evaluation of substitute chemicals is almost impossible. Test results for aquatic toxicity often correlate poorly between labs due to non standardized test conditions, species variations, etc.

The incentive to establish a good pollution prevention program is often economic. These programs are often justified through a “pollution prevention pays profits” type of thinking. The need for better risk/benefit assessment and more realistic waste goals, as well as realistic forecasting of benefits and liabilities therefore is critical. The challenge is to eliminate the barrier of poor technical information described above. This also contributes to the better technical understanding of processes discussed earlier.

2.11.4 Chemical Commodities

In addition to specialties, textiles uses massive amounts of commodity chemicals, e.g. acid, alkali, salt, warp size, fiber, water. A typical cotton production facility might use commodities that are greater that the weight of product produced. It is not unusual to find cotton dye houses which discharge 3000 ppm of salt in the wastewater. There are two needs in this area:

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1. The first challenge is to reduce the amounts of commodities, especially salt, required for dyeing. The second is to determine the trace impurities in commodities and to seek better sources of commodities, or better methods of manufacturing commodities, which reduce or eliminate offensive trace materials.

2. The second major need, to identify and eliminate trace impurities from commodity raw materials, is crucial. Tests of textile wastewater have clearly shown the presence of toxic materials which also have been detected as impurities in fibers and chemical commodities. Further work shows that these toxic wastewater pollutants are present in significant amounts in high volume raw materials (e.g. fibers) as well as salt and alkalis. Major needs exist in this area, especially related to zinc in salt, low level impurities in fibers (I.e. monomer, catalyst, delusterants), metals in caustic, and impurities (e.g. metals, organics) in raw water supplies.

2.11.5 ECO-FRIENDLY DYEING:

2.11.5.1 Background:

Increasing awareness for a cleaner & greener living standard. Enforcement of stricter guidelines and rulings from various associations and

Government bodies. Challenges faced by Textile Dyeing companies around the world alike.

2.11.5.1 Dyeing process:

Fig: 2.11.1 source: Matex

2.11.5.1.1 Desizing:

• Traditional Desizing Methods – Acidic: Sulphuric or hydrochloric acid – Oxidative: Persulphate plus alkali orbromite and alkaliThese treatments reduce the tensile strength of the fabric.

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• Desizing with biocatalyst

• Advantages:

– Less chemicals involved– Eco-friendly– Efficient in wide range temperature– Specific, no damage to cellulose fibres– Better strength retention– Softer fabric feel

– Shorter process time

2.11.5.1.2 Scouring:

Conventional in highly alkaline condition

fabric

input alternative no neutralization/low alkalinity pH 8.5


Advantages of bioscouring :

– Eco-friendly (less harsh chemical – caustic soda)

– Less rinse water needed

– Reduce effluent load

– Reduce water consumption

– Save energy

– Save cost

– Fully retain cellulose structure

Table 2.11.1 Comparison between alkaline scouring & bioscouring:

Measurement Bioscouring Alkaline scouringpH 8-9.5 13-14

Temperature 50-60®c(extract at 75-95®c) 95-100®cResidual pectin 22-30% 10-15%

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Alkaline scouring

Bioscouring

Neutralization

Washing Dyeing

Weight loss <1.5% 4-10%Wet ability, drop test <1 second <1 secondBrightness increase +1-5% points +5-10% points

Bleach ability Same SameDye ability Same Same

Rinse water consumption 35-50% 100%Total dissolved solid( TDS) 20-50% 100%

BOD 20-45% 100%COD 20-45% 100%

Source: November, 4 December 2006

2.11.5.1.3 Bleach Clean Up:

• Removal of H2O2 residual to ensure leveled dyeing

• Bleach Clean Up Alternatives

– By rinsing only


– By reducing agent


– With biocatalyst

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Bleaching Rinsing Rinsing Rinsing Rinsing Dyeing

Bleaching Rinsing Reducing agent Rinsing Dyeing

Bleaching Rinsing Biocatalyst Dyeing


Advantages of using biocatalyst:

- Save water- No rinsing required. Can proceed in the same bath with dyeing process- Save energy- No more hot rinse, cold rinse, hot rinse.- Save time- As short as 10 min to complete the job.- Safe- H2O2 complete removal without affecting dyestuff or textile materials

Bleach Clean Up with Biocatalyst:

Temperature®

100

80 - Adjust pH as desired for subsequent dyeing-,Add biocatalyst

60 check peroxide level

40

20 -drain Bleach clean up Dyeing

-fill cold

0 5 10 15 20 25 30 35 40 45 50 55 60 65 Time(min)


Water usage in various bleach cleanup method:

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4.5

4.0

No. 3.5

Of 3.0

rinse 2.5

bath 2.0

1.5

1.0

0.5

0

water reductive biocatalyst


2.11.5.1.4 Cold pad batch dyeing:

• A more environmentally sound and higher quality dyeing method• Process steps:

Padding Roll Batching Washing Soaping Washing

Fig: 2.11.7

Fig: 2.11.8 source: matex

Total volume of pad-trough 10 / 15 litres per metre of width of fabric (example 2 metres; volume 20 to 30 litres)• Immersion time 1.5sec• Bath temperature 25 –30°C• Pick up 70 – 80%

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F IG: 2.11.9 SOURCE: MATEX

• Fabric speed such as the time to completely renew the trough should not exceed 10 minutes• Batching time: 8 – 16hrs

• Advantages of Cold Pad Batch Dyeing:

– Simplicity in process of dyestuff application

– Reduction in water consumption by 50 to80%

– Reduction in energy consumption by up to60%

– Reduction in chemical costs, other than dyestuff, by up to 50% due to elimination of salt and reduction of alkali requirements

– Reduction in labor costs by 40 to 60%

– Minimum fabric abrasion

– Excellent shade reproducibility from lot to lot

So we tried to give a brief idea on eco friendly dyeing as a modern pollution free greener technology for textile wet processing technology

2.12 Textile Effluent & Treatment Technology

Effluent in the man-made sense is generally considered to be pollution originated from waste water, such as the outflow from a sewage treatment facility or the wastewater discharge from industrial facilities.

Here is a flow chart in the waste water treatment

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FIG: 2.12.1

F IG 2.12.2 ETP SOURCE: GETIT.IN

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2.12.1 Effluent Treatment Technologies

There are 2 possible locations for treating the effluents, namely, at the textile factory or at the sewage works. The advantage of treatment at the factory is that it could allow for partial or full re-use of water. The following technologies have all been used:

11.1.1 Coagulation and / or flocculation11.1.2 Membranes (microfiltration, nanofiltration, reverse osmosis),11.1.3 Adsorbents (granular activated carbon, silica, clays, fly ash, synthetic ion-

exchange media, natural bioadsorbants, synthetic bioadsorbants),11.1.4 Oxidation (Fenton's reagent, photo catalyst, advanced oxidation processes,

ozone)11.1.5 Biological treatment (aerobic and anaerobic).

2.12.1.1 Coagulation and/or Flocculation

Chemicals are added that form a precipitate which, either during its formation or as it settles, collects other contaminants. This precipitate is then removed either through settling or by floating it to the surface and removing the sludge. This is a well-known method of purifying water. Both inorganic (alum, lime, magnesium and iron salts) and organic (polymers) coagulants have been used to treat dye effluent to remove colour, both individually and in combination with one another. With the changes in dyes and stricter discharge limits on colour, inorganic coagulants no longer give satisfactory results. They have the added disadvantage of producing large quantities of sludge. Organic polymers show improved colourremoval and produce less sludge, but then may have detrimental effects on the operation of the sewage works. Cationic polymers have also been shown to be toxic to fresh water fish.

Alum is effective in removing colour from textile effluent containing disperse, vat and sulphur dyes, but is ineffective against reactive, azoic, acid and basic dyes. However, it does have the advantage of reducing phosphorous levels, thereby improving the operation of sewage works.

2.12.1.2 Membranes

The membrane methods that are available for effluent treatment are microfiltration, ultrafiltration, nanofiltration and reverse osmosis. In general, nanofiltration or reverse osmosis are the most effective processes for removing colour and recovering water. The drawbacks of these processes are the high capital costs, the fact that the concentrated effluent still has to be treated, and membrane fouling.

The most frequently tested method is reverse osmosis. The effluent is forced under moderate pressure (1.5 to 4 MPa) across a semi-permeable membrane to produce a purified permeate and a concentrate. This process can remove up to 99% of salts and the complete removal of most organic compounds. The concentrate will require further treatment prior to disposal as the level of impurities are up to six times that of the original effluent stream.

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In nanofiltration, the membrane acts as a molecular filter, retaining polyvalent ions and compounds with a molecular mass greater than 200. The concentrate contains almost all of the organic impurities and a large proportion of the polyvalent inorganic salts and requires further treatment prior to disposal. The permeate contains the monovalent ions (e.g. Sodium and chloride ions). This method of effluent treatment has been found to be effective in the treatment of dyebaths from reactive dyeing where sodium chloride is used as the electrolyte, as the permeate produced contains the salt and is virtually colourless, and therefore, suitable for reuse in the reactive dyeing process, saving both water and the cost of the salt.

Ultrafiltration and microfiltration as stand-alone treatment methods are only suitable for reducing COD and suspended solids from solution. They are effective in combination with other treatment methods such as coagulation or flocculation. They are also useful for the partial removal of colour and organics prior to discharge to sewer. Microfiltration removes colloidal material such as disperse and vat dyes.

2.12.1.3 Oxidation

Oxidants decolourise dyes by breaking down the dye molecule. Commonly used processes are ozone and Fenton's Reagent.

Ozone has been investigated in a number of studies. It has been found that dye wastewaters react differently depending on the composition. Effluent containing sulphur and disperse dyes are difficult to decolourise, whereas colour due to reactive, basic, acid and direct dyes is removed fairly easily. The main drawback with installing an ozonation plant is the high capital and operating costs. However, improvements in generator and contacting equipment design, together with increasingly strict environmental legislation will probably lead to a more widespread application.

Fenton's Reagent consists of ferrous salt (usually sulphate) and hydrogen peroxide. The reaction is carried out at a pH of 3 and involves the oxidation of ferrous ion to ferric ion with the simultaneous production of the hydroxyl radical. This radical is a powerful oxidizing agent and will attack organic compounds and cleave the bonds. In the case of dye molecules, this would lead to decolourisation. A disadvantage (in terms of costs for the discharger) is the production of ferric hydroxide sludge, but it is thought that this sludge is advantageous to the biological treatment system.

Other oxidation methods include the use of ultraviolet light in conjunction with a photo catalyst (titanium dioxide), or other chemical agents such as hypochlorite (the use of which is not encouraged as chlorinated organic species may be formed which are themselves toxic to the environment).

The main drawback of these above methods is that it is not known what degradation products are formed from the oxidation process and it may be the case that these end products, although colorless, may be more toxic than the original dye molecules.

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2.12.2Biological Treatment

2.12.2.1 Aerobic treatment

The majority of sewage works are based on the principle of aerobic treatment, where the incoming effluent is exposed to bacteria which convert the components into carbon dioxide and sludge, which is then sent to an anaerobic digester for further treatment. It has been found by a number of researchers that aerobic treatment methods are not sufficiently able to treat the colour from the textile industry and any colour removal that does take place is due to adsorption onto the sludge, rather than degradation of the dye molecule.

2.12.2.2 Anaerobic digestion

Anaerobic digestion is the biodegradation of complex organic substances in the absence of oxygen to yield carbon dioxide, methane and water. It is an effective process for treating high COD wastes (e.g. size, desize washing and scouring) and the methane that is produced can be utilized as energy for heating etc. The reducing conditions in an anaerobic digester have been found to cause decolourisation of azo dyes through cleavage of the azo bond and subsequent destruction of the dye chromophore. Complete mineralization of these degradation products does not take place and aromatic amines may be present in the effluent from the digester.

Table2.12.1 the characteristics of effluent of textile industry :

Cotton Synthetic Wool scouring (Dyeing)PH 8 – 12 7 – 9 3 – 10 (5 – 10)

BOD 150 – 750 150 - 200 5000 – 8000 (500-600)COD 200 – 2400 400 – 650 104 – 2×104 (1700 – 2400)

Alkalinity 180 – 7300 550 – 630 80 – 100 (240 – 300)Phenol 0.03 - 1 - -

Oils and grease 4.5 - 30 - 2000 – 2500 (400-500)TDS 2100 – 7700 1060 – 1080 104 – 1.3×106 (800 – 1000)

2.12.3 Control of Effluent Quality:

11.3.1. Equalization 11.3.2. Recovery of By-products11.3.3. Loss of chemicals 11.3.4. Process modification 11.3.5. Segregation

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2.12.3.1 Equalization

Effluent characteristics like PH, BOD, Alkalinity etc. vary widely from time to time, depending on the textile wet processes carried out at different times. In order to even out such dynamic characteristics, the effluents are held for duration as long as several hours (8 – 16 hours) or a few days, depending on the capacity of the treatment plant and the quality of effluent generation. Equalization also brings about self-neutralization of different alkaline and acidic streams. Pollution may also be diluted when concentration and dilute streams are mixed together. The effluent may be optionally screened to remove floating matters like fibers and linters before taking into an equalization tank.

2.12.3.2 Recovery of By-products

The effluent load can be reduced considerably if some of the polluting chemicals present in the effluents can be recovered e.g. recovery of caustic soda from mercerization waste. Costly dyes can be recovered from the dye-house waste by dialysis, reverse osmosis and other techniques. Heat from the wastewater can be used for preheating, thereby reducing the temperature of discharge water.

2.12.3.3 Loss of chemicals

Many a time, spillage and leakage may cause several raw materials to spread into the drain. Reduction of such wastage will reduce the pollution load significantly.

2.12.3.4 Process modification

By suitable modification of the processes and by using more eco-friendly chemicals, the quality of wastewater can be removed.

Using carboxymethylcellulose and polyvinyl alcohol instead of starch in sizing, mineral acids instead of enzymes in desizing, mineral acids and ammonium sulphate instead of acetic acid, synthetic detergents instead of soap, emulsions instead of gums in printing, durable finishes instead of temporary finishes, the BOD load can be reduced considerably. Dyes having high exhaustion power minimize residual dye in the effluent.

2.12.3.5 Segregation

Sometimes it is beneficial to segregate waste streams containing highly toxic or specific chemicals that can be treated separately and more efficiently.

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CHAPTER 3: STRATEGIES OF BANGLADESH GOVERNMENT AGAINST POLLUTION3.1 Acts and Rules Concerning Environment

3.1.1 Bangladesh Environmental Conservation Act 1995 (Eca 1995):

The main strategies of the act are-

a) Declaration of ecologically critical areas, and restriction, on the operation and process which can be carried or cannot be initiated in the ecologically critical area.b) Regulation in respect of vehicles emitting smoke harmful for the environment.c) Environment clearance.d) Regulation of the industries and other development activities-discharge permit.e) Promulgation of standards for quality of air, water, noise and soil for different areas for different purposes.f) Promulgation of standard limit for discharging and emitting waste.g) Promulgation and declaration of environmental guidelines.

Some of the important acts concerning industrial sectors are discussed below

3.1.1.1 Environmental clearance: 3.1.1.2 Environmental Standards: 3.1.1.3 Discharge permit: 3.1.1.4 Limits for discharging or emitting Environmental pollutants:

3.1.2 Environment Conservation Rules, 1997 (ECR, 1997):

These are the first set of rules, promulgated under the Environmental Conservation Act 1995. These rules set-(1) the National Environmental Quality Standards for ambient air, various types of water, industrial effluent, emission noise, vehicular exhaust etc.,(2) Requirement for and procedures to obtain environment clearance,(3) Requirement for IEE/EIA according to categories of industrial and other development interventions.

3.1.3 The Penal Code 1860:

3.1.3.1 Article 277; Failing Water or Public Spring or Reservoir: Sentenced to 3 months jail or 500 taka.

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3.1.3.2 Article 278; Making Atmosphere Noxious to Health: Punishment with live hundred taka.

3.1.3.3 Article 284; Negligent Conduct with Respect to Poisonous Substance: Punishment with imprisonment of either description for a term which may extend to 6 months, or with fine, which may extend to 1000 taka, or with both.

3.1.3.4 Article 285; Negligent Conduct with respect to fire or Combustible matter: Punishment with imprisonment of either description for a term which may extend to 6 months, or with fine, which may extend to 1000 taka, or with both.

3.1.3.5 Article 286, Negligent Conduct with respect to Explosive Substances: Punishment with imprisonment of either description for a term which may extend to 6 months, or with fine, which may extend to 1000 taka, or with both.

3.1.4 Obtaining Environmental Clearance:For any proponent planning an industrial project it is currently mandatory under

Paragraph 12 of the Environmental Protection Act, 1995 to obtain an & quot; Environmental Clearance Letter and quot ; from DOE is essential. The application should include feasibility study report of the project, EIA, NOC of local authority, mitigation plan of minimizing the impact of environmental pollution and a Treasury chalan of Taka 10,000. Clause-9 of the ECR, 1997 ensures the right of the aggrieved to appeal.

3.1.5 Green, Orange And Red List Industry:Green list industries are considered relatively pollution free and therefore do not

require an environmental clearance certificate from the DOE.Orange list industries fall into two categories. Category A industries are required to

submit general information, a feasibility report, a process flow diagram and schematic diagrams of waste treatment facilities along with their application for obtaining DOE environmental clearance. Category B industries are required to submit an Initial Environmental Examination (IEE) report, along with their application are the information specified for Category A industries.

Red list industries are those that can cause significant adverse environmental impacts and are therefore required submitting an EIA report.

3.2 Environmental StandardsThe operating environmental standards are promulgated under the Environmental

Conservation Rules 1997. There are standards prescribed for varying water resources, ambient air, noise, odor, industrial effluent and emission discharges, vehicular emission.

In order to find out the approach of Bangladeshi textile factory for pollution prevention we did some research on few renowned textile factories. The result of the that

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research will be introduced in the following chapter of my presentation according to different

case study.

CHAPTER 4: CASE STUDIES

4.1 Case study 1:

Intramex Textile Ltd.

4.1.1 Company Profile:Intramex Textile Ltd is producing 100% export high quality fabrics with modern and computerized looms, also have facilities of modern dyeing and rotary printing.

Address:Corporate Office : House # 115, Road # 4, Block - B, Banani,Dhaka – 1213, BangladeshTel : +880 2 989 5917, 986 2242FAX : +880 2 988 9226Factory : Laxmipura, Chandona, Joydebpur, Gazipur.(Near Bangladesh Rice Research Institute)Tel : +880 2 925 6892,925 6898.Fax : +880 2 925 6816Administration Board:Managing Director : A. T. M. Anayet Ullah.Director : Nazneen Ahmed.Factory Contact Person : 1) Md. Nurul Amin. [Deputy General Manager]2) Abdur Rouf. [Factory Manager]Products: Twill, Canvas, Bedford, Dobby, Herring Bone, Ribstop, Ottoman, Poplin & Sheeting for Garment & Home Textile.Company information:Year of Establishment: 2004Sizing & Warping: 2, 50,000 lbs / monthWeaving: 3, 00,000 meter / monthDyeing: 5, 00,000 meter / monthPrinting: 10, 00,000 meter / monthSpace: 94,000 sqft.Number of loom: 30Manpower: 200

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Discharge effluent: 1440m3/day

Main Customers: 1. Lahalle – France2. Creeks – France3. OBS – Italy4. Gemo – France5. Monoprix – France

4.1.2 General Policies of Intramex Textile Against Pollution:

Intramex group is one of the leading groups of companies who established their strong role in the textile industry by their new & improved innovative ideas. Textile Wet Processing is one of their important sectors being the soul of the company; it is also a huge source of textile waste. In order to continue our research we are going to find about the policies of intramex group for pollution prevention.

4.1.2.1 Housekeeping:

All steam traps are surveyed annually for the correct operation. All steam leaks are attended to at earliest opportunity. End-user heat exchanger surfaces are maximized by provision of steam trapping. Valve of steam supply is considered out of date after certain period. Air fed to the compressor is much cool. Adequate facility to isolate the supply line when not in use. Air dryers are installed downstream of the receiver.

4.1.2.2 Machine modification:

As we did a thorough audit on the machine modification of the Intramex textile we saw not that much of an effort. The dyeing machines all are running manually where the total process is controlled by the operator. If the automation in the machines was implemented that would be case of less pollution.

4.1.2.3 Water consumption:

Any existing leaks, faulty valves are repaired immediately and proper maintenance and observation is continued.

Running taps and hoses are remained turned off when they are not in use. Water remains turn off when machines are not running. Effort is always there to include as less as possible process steps.

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Instead of washing the floors of the dye house and kitchen sweeping of any spillage is preferred.

4.1.2.4 Chemical consumption:

4.1.2.4.1 Recipe optimization: In the Inramex textile ltd. Optimization of quantity of chemical is maintained which leads to more efficient chemical use and lower costs. In case of entry of new dyestuff in the market; updated recipe is not practiced rather than they preferred to use the old practiced recipes. 4.1.2.4.2 Dosing control: In order to control the dosing to prevent overdosing and spillage central mixing and pumping of the chemicals into the machine is not use rather than manual mixing is carried out. Here automatic dispensing system would do the job more efficiently. 4.1.2.4.3 Pre-screen Chemicals and Raw Materials: Dyestuff containing heavy metals, solvent-based products are not used in a large base. Safety data is obtained from the chemical manufacturers. Also they tend to avoid using expired materials.4.1.2.4.4 Correct storage & handling: Control of the storage and handling of the chemicals are done efficiently resulting in less spillage reaching the drain.4.1.2.4.5 Chemical recovery & reuse: No chemical recovery & reuse of the chemicals are practiced in the Intramex textile industry.4.1.2.4.6 Scheduling: Scheduling of continuous processes such as desizing, mercerization, padding etc are ensured that the chemical bath is used as many times as possible to reduce the number of dumps to drain per day.

4.1.2.5 Process modification:The process modification is not a case in here. Feasibility of environmental friendly process is not a fact rather the cheaper one is considered

4.1.2.6 Steam distribution & use:All hot surfaces of a steam distribution system are insulated. Justification can be made on the grounds of a reduction of heat loss, improvement in steam quality (through reduced condensate formation) and health and safety issues.

4.1.2.7 Heat exchanger:Heat exchanger is added to each machine to recover heat and energy.

4.1.2.8 Optimize plant environmental condition:The plant condition of the Intramex textile is quite satisfactory. Proper maintenance of the factory is a big achievement. They modified the factory according to environmental friendly condition.

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4.1.2.9 Shutting off of lighting, air condition etc : When not necessary it is a environmental friendly factor to shut of light, air condition etc, though it is completely not practiced but personal motivation is present in there.

In the following paragraph we mention the policies of Intramex textile’s on water pollution prevention.

4.1.3 Effluent Treatment Strategy :

To mention about pollution in textile wet processing industry the most important part is the water pollution. In textile wet processing industry in order to treat the waste water ETP plant is must necessary. According to Bangladesh environment regularizations ETP is must necessary to be present in any wet processing industry. Also buyer of different renowned organization prefers the presence of ETP.

4.1.3.1 Effluent Treatment Plant (ETP):

We may include that there are various number of ETP plant which can be settled for textile wet processing industry. It may be biological, chemical or electrical. Intramex group is very conscious about their action in the pollution free Bangladesh, that’s why they have established latest technology for effluent treatment plant. The TRIDENT ECR (Electro Contaminant Removal) technology system (Singapore) is practiced for waste water treatment. It is a very much a modern technology which may be little expensive in the initial cost comparison but in the further long time running of the system seems to be very much a profitable investment. The initial cost is 7 million BDT but the later running cost of the system is lower. In this technology we can easily remove fats, oils, grease, complex organics, metal oxides, color, TSS, colloidal solid; reducing COD, BOD; breaking oil emulsion, destroying bacteria and viruses.

A valid scientific principle is involved in this TRIDENT ECR technology in which the water contaminants are getting on with the action against strong electric fields results in electrically induced oxidation and reduction reactions which in turn creates generated coagulation.

ECR machine consists of 2 units which contain 344 pieces of iron plate, 172 pieces each.There are 3 mm spaces between the each iron plates. Water is flowed from below & DC voltage is supplied from side 90-95 amp current and 300-500 v voltage is given. Iron plates are act as cathode and anode. As a result, plates are damaged & have to be changed after two month.

4.1.3.2 Capacity of ECR:

Capacity of this ECR machine is 60 cubic meter per hour, But average capacity used is 45 cubic meter per hour.

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4.1.3.3 Advantages of ECR machine:

Maintenance cost is low. Initial cost is higher but the long term cost is reduced to 50%. Power required is less. No chemical is needed. Minimum attention is needed. The produced sludge is minimum. Result is efficient and reliable.

FIG 4.1.1 ETP OF INTRAMEX GROUP

4.1.3.4 Flow chart of ETP plant:

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Fig 4.1.2

4.2 Case study 2:TEX 400 54


Storage tank

Equalization tank (pH=6)

ECR machine

Primary clarifier (little amount of sludge is removed in here)

Aeration tank (BOD is controlled here)

Secondary clarifier (excess amount of sludge are removed in here)

Outlet

DBL GROUP

(Hamza & Mymun Textile)

4.2.1 Company Profile:

DBL group as we know one of the biggest institutions of our country whose strong footstep has improved the economic growth of our country significantly. As we may know that DBL was a garments factory at the early stage of its foundation. But as the day progresses it has increased its ambition towards bigger goal. Nowadays DBL group is also renowned for their various textile factories. Hamza & Mymun textile is one of them which are used for the textile wet processing technology.

Managing Director: Mr. BABUL HOSSAIN

Corporate Office: BGMEA Complex, 12th Floor, 23/1 Panthapath Link Road. Kawran Bazar, Dhaka-1215, Bangladesh.

Telephone : + 880-2-8140207 to 12

Fax: + 880-2-8140214

Email: [email protected]

Factory: Nayapara, Kashimpur, Gazipur, Bangladesh.

Production oriented department:

Spinning. Knitting. Batching. Pretreatment. Dyeing lab. Dyeing floor. Chemical house Finishing. Quality control. Finished ware house. Garments. Maintenance. Utility

Supporting department:

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mailto:[email protected]

Procurement. Marketing. HRD. Finance & accounting. Personnel administration. Security.

Factory Information:

1. Total area (sqft): 122,000 (Sqft) Production arca: 80,000 (Sqft)2. Total Number of employee on pay roll (Last Month): 497 3. Number of working hours shift, working hour & break: Shaft -03 Nos, working 08

hours, Break-01 hour.4. Minimum wage, highest wage and average wage at worker level : 3000/-, 14,500/-,

10,000/-5. Type of production (woven, knit, sweater) & Process: Knit dyeing & Finishing6. Discharged effluent: 4000m3/day

Vision:

To establish as a one stop source for the Global knit Apparel market and to satisfy and meet customers expectation by developing and providing products and services on time, which offer value in terms of Quality, Price, Safety and Environmental impact. To assure complete compliance with the international quality standards and also provide the employees internationally acceptable working condition and standards, to promote the development and to use human talent and equal opportunity of employment & DBL group is firmly resolved.

Mission:

DBL group realizes the need to take out a competitive segment in the changing global market of today through technological excellence and human expertise. DBL group is committed to transpose its local success to the world scene.

4.2.2 General Policies of Hamza & Mymun Textile Against Pollution:

As we are going further ahead on our survey we are trying to submit a brief idea of these two factories in the pollution prevention practices. In the following different articles we are going to present some pictures of these two factories.


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In order to maintain a good housekeeping Hamza & Mymun textiles follows these techniques:

All steam traps are surveyed annually. All steam leaks are repaired by time. They tend to use minimum temperature for the process. When the necessity isn’t there the machines remain shutdown. Heat exchanger end use is maximized. Valve of the steam supplies are replaced periodically. Air dryers are installed downwards. Hose pipe, water pipes doesn’t remain open when in not use The floors are dry, no water, chemicals or dyes spillage


The machines the Hamza & Mymun textile uses are all imported. These machines arrived in the factory as in modified conditions & they do not modify the machine for further improvement.

4.2.2.3 Water Consumption:

All kinds of leaks & faulty valves are repaired immediately. Running taps & hoses remain turned off during no use. In case of machine stoppage water is not supplied. Process steps are reduced time to time like fewer rinsing steps in use of high

exhaustion of dyes. Cooling water is used. Instead of washing the floor of the dye house & the kitchen they sweep the

spillages & wash down when it is necessary. It will reduce the water wastage.

4.2.2.4 Chemical Consumption:

4.2.2.4.1 Recipe optimization: In the Hamza & Mymun textiles optimization of quantity of chemical is maintained which leads to more efficient chemical use & lower costs. In case of entry of new dyestuff in the market; updated recipe is not practiced rather than they preferred to use the old practiced recipes. 4.2.2.4.2 Dosing control: In order to control the dosing to prevent overdosing & spillage central mixing & pumping of the chemicals into the machine is present in Hamza & Mymun textiles but due to some technical difficulties they do not use it rather than manual mixing is carried out.

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FIG 4.1.1 AUTO DISPENSING SYSTEM

4.2.2.4.3 Pre-screen Chemicals and Raw Materials: Dyestuff containing heavy metals, solvent-based products are not used in a large base. Safety data is obtained from the chemical manufacturers. Also they tend to avoid using expired materials.4.2.2.4.4 Correct storage & handling: Control of the storage & handling of the chemicals are done efficiently resulting in less spillage reaching the drain.4.2.2.4.5 Chemical recovery & reuse: No chemical recovery & reuse of the chemicals are practiced in the Hamza & Mymun textile industries.4.2.2.4.6 Scheduling: Scheduling of continuous processes such as desizing, mercerization, padding etc are ensured that the chemical bath is used as many times as possible to reduce the number of drums to drain per day.

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4.2.2.5. Process modification: The process modification is not a case in here. Feasibility of environmental friendly process is not a fact rather the cheaper one is considered.

4.2.2.6 Steam distribution & use:

4.2.2.6.1 InsulationAll hot surfaces of the steam distribution system are insulated. Justification is done on the grounds of reduction of heat loss, improvement in steam quality (through reduced condensate formation) and health and safety issues.

4.2.2.6.2 Flash steam recoveryFlash steam is recovered in the Hamza & Mymun Textiles. Flash steam is generated when hot condensate is allowed to reduce in pressure, allowing a certain amount of condensate to evaporate (flash). In Hamza & Mymun textiles the recovered steam is collected in PPE pump and condensed in the Condenser then the condensed steam turned into water and it is used as feed water of the Boiler.

F IG 4.2.2 STEAM RECOVERY SYSTEM

.

4.2.2.7 Heat exchanger:Heat exchanger is added to each machine to recover heat & energy.

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4.2.2.8 Optimize plant environmental condition: The plant condition of Hamza & Mymun textiles is quite satisfactory. Proper maintenance of the factory is a big achievement. They modified the factory according to environmental friendly condition.

4.2.2.9 Shutting off of lighting, air condition etc:When not necessary it is an environmental friendly factor to shut of light, air condition etc, though it is completely not practice but personal motivation is present in there.

4.2.2.10 Electrostatic Precipitator (Power generator) :

In the power generator they use electrostatics precipitator. When the gas which will produce electricity it will passes through water, in the presence of this Electrostatic Precipitator; sulphur , carbon, nitrogen cannot reach to the operating panel of the generator. If this Electrostatic Precipitator is absent in there than we would face pollution due to the presence of those unwanted gasses.

Now we are going to give a brief idea on the strategies of Hamza & Mymun textile on water pollution prevention.

4.2.3 Effluent Treatment Strategy

As we know water is the most important source of waste in the textile wet processing industry so the treatment of water waste is must necessary in the wet processing technology. The waste water contains different kinds of chemicals, dyes and much other toxic material releasing of these material in the open environment is a deadlier option. So the treatment of these are must necessary. Because releasing of this waste water in the local pond, rivers will destroy the ecological balance. The released toxic material will destroy the living organism of those ponds, lakes; rivers also if the toxicity reaches to much dangerous condition it may destroy the life of the fertile agricultural land.

So in order to prevent the pollution from waste water, ETP plant is must necessary in any wet processing industry due to the strict law of Bangladesh environment regularizations act. The establishment of ETP is not only necessary according to the law but also according to the recommendation of the buyer.

4.2.3.1 Effluent Treatment Plant:

As we know there are different kinds of ETP plant. Different company follows different strategies when it comes to the ETP plant. Lots of important issues comes in front that needed to be solved. That’s why it is no surprise that in the Hamza & Mymun textile both use same ETP plant & that one is Biological. We may declare it as it is not the latest technology but according to their thought it is their strategy because of its capacity.

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Biological waste water treatment consists of treating the water waste with bacteria in order to treat the water from their harmful agents by creating sludge and disposing them off, also recovering the bacteria for the further treatment.

F IG4.2.3 ETP OF HAMZA & MYMUN TEXTILE

In the following flow chart we are going to give an idea about the ETP plant of the Hamza & Mymun textile

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4.2.3.2 Flow chart of ETP:

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Waste water from dyeing & finishing (incoming raw effluent)

By drain

Cooling unitBy drain

Collection sump tank

By under drain

Screening unit

Lifting sump

By under drain

By lifting pump

Storage & Homogenization Tank

Neutralization unit

H2SO4 tank

H2SO4 auto dosing by pump

By under hole

By pump

Sludge recirculation pit

Sedimentation or clarifiers

Biological oxidation tank

Distribution unit

Sedimentation feeding tank

Treated water out

Manually feeding bacteria for proper living on

Decolorant dosing for removing color

Antifoam feeding for removing foam

By under drain

By under hole

By overflow

By overflow

By pump

Sludge thickener tank

Polyelectrolyte feeding for flocculation

By collection pipe

By pump

Fig4.2.4

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Sludge collection bed

Sludge drying bed Sludge store room

Sludge dumping

Waste water

By pump

4.3 Case study 3

Masco Dyeing Ltd


Masco Industries Limited is totally committed to its products and customers have helped it grow from a knit fabric manufacturer to a composite and garment manufacturer. Masco Industries Limited is a pioneer in introducing European technology in knit fabric manufacturing in this country. Masco dyeing is a part of this organization which is textile wet processin industry.

Address:

Masco Industries LtdHead Office: Masco Center, House-06, Road-01, Sector-03, Jashimuddin Avenue Uttara, Dhaka-1230, Bangladesh.Tel : 88-02-8814081, 9891008, 9862686 Fax : 88-02-8821822 E-mail: [email protected] [email protected]: 23, Shataish Road, Gazipura, Tongi, GazipurTel: 88-02-9813362-3, 88-02-9810791Fax: 88-02-9810790 E – Mail: [email protected]

Administration board:

M. A. SABUR: Group ChairmanAHMED ARIF BILLAH: Managing DirectorMS. FAHIMA AKHTER: DirectorMS. FARHANA AKHTER: DirectorCompany information:Year of establishmentArea

: 199940,000 sqft.

Men power : 350 Production Capacity

: 12,000 Kg/per day

Discharged Effluent

: 1080m3/day

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Buyer:Present Buyers: New Wave (Sweden), Umbro (UK), Aldi (Germany),

Zara, Stradivarius, Bershka (Spain), Big Star (Poland), TK International (Germany), Lonsdale (UK)

Countries of Exports: A) GermanyC) SwedenE) ItalyG) United KingdomI) PolandK) AustriaM) Belgium

B) SpainD) The Netherlands F) France H) Norway J) Finland L) Denmark

Countries of Imports: A) Hong KongB) ChinaC) KoreaD) ThailandE) Taiwan

4.3.2 General Policies of Masco dyeing Ltd Against Pollution:

Masco dyeing ltd is one of the most renowned textile wet processing industries of Bangladesh. They have established their influences in the economy of Bangladesh. Now is the time to audit their action against pollution prevention.

In the below we tried to give a brief idea of the practiced pollution prevention tactics of Masco textile


In order to maintain a good housekeeping Masco dyeing ltd. follows these techniques:

All steam traps are surveyed annually. All steam leaks are repaired by time. When the necessity isn’t there the machines remain shutdown. Heat exchanger end use is maximized. Valve of the steam supplies are replaced periodically. The used temperature remains as cool as possible.

In general the housekeeping of Masco dyeing ltd. isn’t a satisfactory one. The floors are not dry, waters are everywhere seems that they do not care about the dryness of the floor; also the fabric is left here and there in the floor.


The machines the Masco dyeing ltd. uses are all imported. These machines arrived in the factory as in modified conditions & they do not modify the machine for further improvement.

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All kinds of leaks & faulty valves are repaired immediately. Running taps and hoses remain turned off during no use. In case of machine stoppage water is not supplied. Process steps are reduced time to time like fewer rinsing steps in use of high

exhaustion of dyes.


4.3.2.4.1 Recipe optimization: In the Masco dyeing ltd. optimization of quantity of chemical is maintained which leads to more efficient chemical use & lower costs. In case of entry of new dyestuff in the market; updated recipe is not practiced rather than they preferred to use the old practiced recipes.

4.3.2.4.2 Dosing control: In order to control the dosing to prevent overdosing & spillage central mixing & pumping of the chemicals into the machine is not present in Masco dyeing ltd. but as in our interview with the administration they told us that they are planning to establish an auto dosing system of dyes & chemicals4.3.2.4.3 Pre-screen Chemicals and Raw Materials: Dyestuff containing heavy metals, solvent-based products are not used in a large base. Safety data is obtained from the chemical manufacturers. Also they tend to avoid using expired materials.4.3.2.4.4 Correct storage & handling: Control of the storage & handling of the chemicals are done efficiently resulting in less spillage reaching the drain.4.3.2.4.5 Chemical recovery & reuse: No chemical recovery & reuse of the chemicals are practiced in the Masco dyeing ltd.4.3.2.4.6 Scheduling: Scheduling of continuous processes such as desizing, mercerization, padding etc are ensured that the chemical bath is used as many times as possible to reduce the number of drums to drain per day.

4.3.2.5 Process modification: The process modification is not a case in here. Feasibility of environmental friendly process is not a fact rather the cheaper one is considered.


4.3.2.6.1 Insulation: All hot surfaces of the steam distribution system are insulated. Justification is done on the grounds of reduction of heat loss, improvement in steam quality (through reduced condensate formation) and health and safety issues.

4.3.2.6.2 Flash steam recovery: Flash steam is partially recovered in the Masco dyeing ltd. Flash steam is generated when hot condensate is allowed to reduce in

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pressure, allowing a certain amount of condensate to evaporate (flash). In Masco textile the flash steam are used as an extra heating energy for hot water.


4.3.2.8 Optimize plant environmental condition: The plant condition of Masco textile isn’t quite satisfactory. Proper maintenance of the factory is a big step where there negligence is not quite expected.


4.3.2.10 Employee motivation:

As we did the interview of the operators & the workers seems that they are not properly aware about the pollution, means less motivation. Proper motivation among the employee can increase the awareness about pollution, than there simple steps may restrict the wastage within the limited range.

Now in order to prevent the pollution from water wastage their policies are mentioned in followings.

4.3.3 Effluent Treatment Strategy:

We know it is mandatory according to Bangladesh Government’s pollution prevention strategy to establish a ETP in order to treat the water waste to a minimum level, so it is must necessary for every textile wet processing industry to have a ETP. That’s why ETP is necessary & it is present in the masco dyeing ltd.

We are going to give a brief idea about this ETP plant we observed in there.

4.3.3.1 Effluent treatment plant:

The ETP plant we observed in the Masco dyeing ltd. is a chemical and biological mixed effluent treatment plant. Here three types of chemicals are used. Ferrous sulphate, it produce sludge; polymer it makes the sludge bigger and lime powder it changes the water color.

At first all the efflunt water from the processing zone comes to the equalization tank. In here the temperature of the effluent is controlled and air is passed below the water into yhe equalization tank through a blower. Then the water goes to the flash tank, here lime powder & ferrous sulphate are addedd.

In the the next case the water goes to the flocculation tank where polymer is added. Then it goes to the tube settler-1, here some amount of fresh water rises at top and sludge

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precipitate and this sludge goes to the sludge tank. Now the raised water goes to the biological tank-1 where the pH is controlled by adding hcl. Then it goes to the Biological tank-2. In this two tanks Urea & Di Ammonium Phosphate is used as the food of bacteria.

The water than goes to the tube settler-2 where again the fresh water rises and goes to the delivery tank from where the fresh water is disharged to the munucipality drain & the precipitated sludge goes to the sludge tank where hydrose are use to make the sludge as in solid form. Then those sludges are dumped into the deepwell

In the following we tried to give a flow chart on their effluent treatment process

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4.3.3.2 Flow chart of ETP:

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Water effluent from processing zone

Sludge

Fresh water

Sludge EXTRA WATER

Fresh water

Fig 4.3.1

Equalization tank

Flash tank

Flocculation

Tube settler-1

Tube settler-2

Biological tank-2

Biological tank-1 Sludge tank (Here sludge is collected)

Delivery Tank

Sludge are dumpedWater discharged

4.4 Case study 4

Shabab Fabrics Ltd

Shabab fabrics ltd introduced a new era in the production of home textile in Bangladesh. Their aim is to satisfy the high value consumer with world class quality of yarn dyed fabric. The professional management, state-of-the art machineries to-gather with the expertise of highly trained employees will meet the increasing demand of choosy customer. They maintain all demanded standard recommended by the buyers.


Business Type: ManufacturerProduct/Service: Terry Towel,all Type of towelCategory: Home & Garden - Home TextileBrands: SFL Number of Employees: 101 - 500 People

Trade & MarketMain Markets: North America

South AmericaEastern EuropeWestern EuropeCentral AmericaNorthern EuropeSouthern Europe

Main Customers: Valley Forge Inc, Tissages Denantes, Eurodiff, Richard Haworth Limited, H&M, Laredout, Li & Fung,OTTO int, Carrefour etc

Total Annual Sales Volume: US$5 Million - US$10 Million Export Percentage: 91% - 100%

Factory InformationFactory Size (Sq.meters): Above 100,000 square meters Factory Location: Bhaluka , Mymensingh, Dhaka.QA/QC: In House Number of Production Lines: 10Number of R&D Staff: 11 - 20 People Number of QC Staff: 31 - 40 PeopleManagement Certification: Others

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http://www.gmdu.net/list-22-1079-p1.html

http://www.gmdu.net/list-22-p1.html

4.4.2 General Policies of Shabab fabrics Ltd against pollution:

Shabab fabrics ltd is a new and fast-growing textile industries of Bangladesh. Already they have established their influences in the economy of Bangladesh. But now here we are going to audit their action against pollution prevention.

In the below we tried to give a brief idea of the practiced pollution prevention tactics of Masco textile.


In order to maintain a good housekeeping Shabab fabrics follows these techniques:

All steam traps are surveyed annually. All steam leaks are repaired by time.. When the necessity isn’t there the machines remain shutdown. Heat exchanger end use is maximized. Valve of the steam supplies are replaced periodically. Hose pipe, water pipes doesn’t remain open when in not use. The floors are dry, no water, chemicals or dyes spillage.

In general the housekeeping of Shabab Fabrics is a satisfactory one. The floors are dry, the maintenance and the cleanliness of the factory id a good model.


All the machines in the Shabab fabrics are not installed properly as it is a new factory going through its starting phase. All the machines are imported where no extra modification is done rather than expert opinion is used from the foreigner engineers to install the machine effectively.


All kinds of leaks and faulty valves are repaired immediately. Running taps and hoses remain turned off during no use. In case of machine stoppage water is not supplied. Process steps are reduced time to time like fewer rinsing steps in use of high

exhaustion of dyes.


4.4.2.4.1 Recipe optimization: In the Shabab fabrics optimization of quantity of chemical is maintained which leads to more efficient chemical use & lower costs. In case

TEX 400 71


of entry of new dyestuff in the market; updated recipe is not practiced rather than they preferred to use the old practiced recipes.

4.4.2.4.2 Dosing control: In order to control the dosing to prevent overdosing & spillage central mixing & pumping of the chemicals into the machine is not present in Shabab fabrics rather than they use manual dosing system.4.4.2.4.3 Pre-screen Chemicals and Raw Materials: Dyestuff containing heavy metals, solvent-based products are not used in a large base. Safety data is obtained from the chemical manufacturers. Also they tend to avoid using expired materials.4.4.2.4.4 Correct storage & handling: Control of the storage & handling of the chemicals are done efficiently resulting in less spillage reaching the drain.4.4.2.4.5 Chemical recovery & reuse: No chemical recovery & reuse of the chemicals are practiced in the Masco textile industry.

4.4.2.5 Process modification: The process modification is not a case in here. Feasibility of environmental friendly process is not assessed that much.


4.4.2.6.1 Insulation: All hot surfaces of the steam distribution system are insulated. Justification is done on the grounds of reduction of heat loss, improvement in steam quality (through reduced condensate formation) and health and safety issues.

4.4.2.6.2 Flash steam recovery: Flash steam is partially recovered in the Shabab fabrics. Flash steam is generated when hot condensate is allowed to reduce in pressure, allowing a certain amount of condensate to evaporate (flash). In Shabab fabrics the flash steam are used in the heat exchanger to heating the water without wasting extra energy.


4.4.2.8 Optimize plant environmental condition: The plant condition of Shabab fabrics is satisfactory. Proper maintenance of the factory is a big step where the factory seems to be quite successful.


4.4.2.10 Employee motivation:

As we did the interview of the operators & the workers seems that they are aware about the pollution, means motivation is there but proper utilization is the big case. Proper motivation

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among the employee can increase the awareness about pollution, than there simple steps may restrict the wastage within the limited range.

Now in order to prevent the pollution from water wastage their policies is mentioned in followings.

4.4.3 Effluent Treatment Strategy

In order to treat the waste water & releasing it into the environment after minimizing the toxic material into a minimum level ETP plant is needed to be established which is ruled by Bangladesh Government. Shabab fabric does have a ETP.

We are going to give a brief idea about this ETP plant we observed in there.

4.4.3.1 Effluent treatment plant:

At first the raw waste water is collected into the screen chamber where the floating materials are screened, as well as the oil and grease in the oil & grease trap. Then the water goes to the equalization tank where H2SO4 is added in order to control the PH. The water then goes to the Flash mixer where De-coloring material is added also with the polyelectrolyte. Now the waste water goes to the primary clarifier-1 & some sludge are produced that goes to the sludge thickener. It then goes to the Aeration tank from the primary clarifier-2 where DAP/Urea is added as food of the Bacteria. From this chamber Bacterial activity started.

The waste water than goes to the secondary clarifier-1, from this tank Bio-sludge is produced and later excluded. Also from the secondary clarifier-2 also some bio-sludge is produced. The effluent then goes to the trickling filter and from there it is dispose to the nature. The bio sludge from the secondary clarifier-1 goes to the sand filter from where some extra waste water return to the equalization tank and the sludge is collected then disposed safely in later.

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F IG4.4.1 ETP OF SHABAB FABRICS

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4.4.3.2Flow chart of ETP:

Fig 4.4.2

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Raw waste water in

Screen chamber

Equalization

Oil& grease trap

Primary clarifier-1

Aeration tank

Secondary clarifier -1

Flash mixer

Primary clarifier-2

H2SO4

Secondary clarifier -2

Trickling filter

Dispose to nature (Treated effluent)

Waste water

Alum/De-colorant

Polyelectrolyte

Floating course material

Oil & grease scan

Sludge thickener

Air DAP/Urea

Sludge collect

Bio-sludge

Sand filter

Dispose safely

Ex sludge

Air

4.5 Characteristics of Discharged Water from Audited Textile Industries:

In the textile industry the discharged water has to maintain a certain quality according to the Bangladesh government ruled these factors are:

4.5.1 P H : pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at 25 °C (77 °F). Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline.

4.5.2 BOD: Biological Oxygen Demand or BOD is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. It is most commonly expressed in milligrams of oxygen consumed per liter of sample during 5 days of incubation at 20 °C.

4.5.3 COD : In environmental chemistry, the Chemical Oxygen Demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water (e.g. lakes and rivers), making COD a useful measure of water quality. It is expressed in milligrams per liter (mg/L), which indicates the mass of oxygen consumed per liter of solution. Older references may express the units as parts per million (ppm).

4.5.4 DO: Dissolved Oxygen analysis measures the amount of gaseous oxygen (O2) dissolved in an aqueous solution. Oxygen gets into water by diffusion from the surrounding air, by aeration (rapid movement) and as a waste product of photosynthesis. When performing the dissolved oxygen test, only grab samples is used, and the analysis is performed immediately. Therefore, this is a field test that needed to be performed on site.

4.5.5 TDS: Total Dissolved Solids (often abbreviated TDS) is a measure of the combined content of all inorganic and organic substances contained in a liquid in molecular, ionized or micro-granular (colloidal sol) suspended form.

Here in the following table the result of analyzed water sample of the four textiles wet processing industries is mentioned.

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http://en.wikipedia.org/wiki/Sol_(colloid)

http://en.wikipedia.org/wiki/Organic_compound

http://en.wikipedia.org/wiki/Inorganic

http://en.wikipedia.org/wiki/Parts_per_million

http://en.wikipedia.org/wiki/Solution

http://en.wikipedia.org/wiki/Mass

http://en.wikipedia.org/wiki/Litre

http://en.wikipedia.org/wiki/Milligram

http://en.wikipedia.org/wiki/Water_quality

http://en.wikipedia.org/wiki/River

http://en.wikipedia.org/wiki/Lake

http://en.wikipedia.org/wiki/Surface_water

http://en.wikipedia.org/wiki/Pollutant


http://en.wikipedia.org/wiki/Water


http://en.wikipedia.org/wiki/Environmental_chemistry

http://en.wikipedia.org/wiki/Oxygenation_(environmental)

http://en.wikipedia.org/wiki/Alkaline

http://en.wikipedia.org/wiki/Base_(chemistry)

http://en.wikipedia.org/wiki/Acidic

http://en.wikipedia.org/wiki/Fahrenheit

http://en.wikipedia.org/wiki/Celsius

http://en.wikipedia.org/wiki/Aqueous_solution

http://en.wikipedia.org/wiki/Base_(chemistry)

http://en.wikipedia.org/wiki/Acid

Sample location PH BOD

mg/l

COD

mg/l

DO

mg/l

TDS

mg/l

Intramex textile ltd(outlet of

ETP)

8.2 44 134 4.8 1870

Hamza & Mymun

textile(outlet of ETP)

8.5 43 140 4.9 1900

Masco dyeing ltd(outlet of

ETP)

8.8 35 125 4.6 1750

Shabab Fabrics ltd(inlet of ETP)

10.0 104 312 0 2122

Shabab Fabrics ltd(outlet of

ETP)

8.0 4.8 160 4.6 880

Bangladesh standard for Waste Water

from industrial units, discharge to inland surface

water as per ECR 1997

6.0 – 9.0 50 200 4.5 - 8.0 2100

Table 4.1 Comparative data of the effluent from the audited textile industries

NOTE: BOD5 temperature at 250 c

Table 4.2 Comparison between audited textile industries :

Here in the following table we did a comparison among the audited textile industry according to a checklist.

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checklist Textile industry

Intramex textile Ltd.

DBL Group Masco Dyeing Ltd.

Shabab Fabrics Ltd.

Mymun textile

Hamza textile

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Storing dry materials

Practiced partially

Practiced partially

Practiced well Practiced partially

Practiced well

Drainage in storage floor

Available Available Available Available Available

Curbs in storage area Not available Not available Not available Not available Not available

Removal of water supply in storage

area

Successful, dry

Slightly wet Successful, dry Slightly wet Successful, dry

Dry cleanup method Not used Not used Not used Not used Not used

Providing suitable work areas

Not available Not available Available Not available Available

Recipe for each chemistry

Optimized Optimized Optimized Optimized Optimized

Providing measuring equipment

Yes Yes Yes Yes Yes

Optimize chemistry Yes Yes Yes Yes Yes

Separation of dyeing machine according

to lot

Yes Yes Yes Yes Yes

Placing spring loaded nozzle

No No Yes No No

Selecting pipe and valve to minimize

corrosion

Yes Yes Yes Yes Yes

Avoiding water in process equipment

Yes Yes Yes Yes Yes

Using counter current rinsing

No No No No No

Reuse waste water from water

No No No No No

Testing of the incoming water

Yes Yes Yes Yes No

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Housekeeping Not satisfactory

Not satisfactory

Satisfactory Not satisfactory

Satisfactory

CHAPTER 5: OBSERVATION5.1 Benefits of Pollution Prevention

• Loss reduction.• Reduction of chemical, water and energy consumption, thereby resulting in savings,

sometimes even increased production.• Reduced liability for waste produced.• Improved compliance with regulations.

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• Cleaner and healthy working environment.

5.2 Limitation Of pollution prevention :

Pollution prevention research is an ongoing case where the total success is not achieved.

The eco friendly materials are not that much available. The available materials are quite expensive. The quality of the product may be not desirable. Proper awareness increasing among the people is a hard task.

5.3 Our ideas on pollution prevention:

By assessing the literature we see that the largest waste stream from most textile mills involved in washing, bleaching, and dyeing is wastewater. Textile mill wastewater is often contaminated with process chemicals (dye, salt, bleach, detergent, etc.), oil, and energy from hot water discharges. As a result, wastewater discharge permit limits, such as BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), aquatic toxicity, and metals content, are often difficult to meet. According to a research in Thailand, water usage in a typical mill can easily top 40,000 gallons per day costing more than $30,000 annually in water and sewer fees. Here some of our ideas to reduce water pollution, air pollution etc. Spills and cleanup can be a major source of water pollution. Process chemicals are stored, mixed, transported, and spilled in most mills. Seemingly minor spills can have major impacts on wastewater. A spill of 5 pounds of salt will contaminate 2,700 gallons of water. If a 50-pound bag of salt bursts in handling, 27,000 gallons of water would be contaminated. The best solution is to avoid the spill. The next best solution is to sweep up the spill and reuse the salt. If the floor is reasonably dry when the spill first happened, dry cleanup and reuse is usually easy to achieve. If a liquid product is spilled, dry cleanup, using absorbent clay and sweeping, is a better solution than washing it down the floor drain.

Another area where waste can be reduced is in chemical mixing. Adding excessive chemicals to recipes will increase cost and may cause quality problems. Different dye mixtures will require varying amounts of salt to achieve complete exhaustion. Adding too much salt may cause few quality problems, but will result in increased salt in the wastewater discharge. Adding too little salt will reduce the amount of dye fixing to the cloth; this will result in an overuse of dye, dye in the wastewater, and quality problems. Following specific recipes each time can avoid problems such as these. All parameters, including the temperature and amount of water added to a bath, should be documented and provided to mill operators responsible for mixing chemistry. Measuring equipment, such as scales and measuring cups, must also be provided to avoid "eyeball" measurements and errors.

Water usage can be reduced in mills by making simple housekeeping changes in addition to process modifications. It is very common for garden hoses to be left running continuously in textile mills. Usually a hose is allowed to discharge into a floor drain between uses rather than being turned off because the hose end may be 50 feet from the valve. A very simple solution is to attach a spring loaded nozzle, costing less than $5, to the hose. The

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operator is happier, and water usage is reduced. Leaks are another major problem in mills. Heavy use of salt, acid, and caustic results in valve and piping failure. Replacing steel valves and piping with plastic is a low-cost way to reduce leaks.

Process changes can make substantial reductions in water and energy use. Water flow through a rinsing process can be reduced by 50% if counter current or two-stage rinsing is used. Counter current rinsing is a process where the "dirtiest" fabric contacts the "dirtiest" water first; clean water rinses the fabric as it leaves the process. Continuous rinsing processes are usually designed with counter current rinsing. Batch processes can be modified to use two-stage or multi-stage rinsing; water used for rinsing the previous bath is used to provide initial rinsing of the next batch. This water is then discharged and clean water is used to provide final rinsing. A two-stage process like this one may replace three separate rinsing cycles using clean water to achieve the same level of cleanliness.

There are many opportunities to reuse wastewater in a textile mill. For example, final rinse water from dyeing can be used as make-up water for the dye bath. Final rinses from scouring and bleaching may be used for makeup water in desizing. Wastewater from many sources may be suitable for washing process equipment and floors (after sweeping or other dry cleanup). As an example we may add, in Viyellatex Group they do not discharged the treated effluent into the sewerage or local pond or river rather than they use that water as flash water in the toilet. This type of little steps can help to reduce the wastage of water where the process is very easy but the only lacking is a noble intention. Some mills have reduced operating costs substantially by installing water reuse systems.

Air pollution is also a concerning factor; where discharged polluted air infecting our environment. In case of releasing air into the environment, filtering is a possibility where the harmful gases like sulphur, Carbon mono oxide, ozone can be extracted. In some process steps we use harmful solvents, oils, chemicals which can degrade the air quality into dangerous level. Here more bio friendly option is suggested,

Noise pollution although not a big option in textile wet processing industries but in power generator or in boiler noise level can be out of range, silencer in this case may be an option, also according to the safety factor of the employees ear plug use is also suggested.

5.3.1 Pollution Prevention Check List for Textile MillsIn order to pollution prevention we needed to be concerned about some points. The

factors that needed to be checked in pollution prevention are mention in the below

1. Store dry materials, such as bags of salt or dye drums, off of the floor and away from liquids by placing catch pans beneath the material.

2. Plug floor drains in material storage areas.3. Build curbs around storage areas to keep spills in and water out.4. Remove water supplies from storage areas.5. Use dry cleanup methods; provide brooms, vacuums, and absorbent.

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6. Provide suitable work areas, handling tools, and training to operators so they can avoid creating spills.

7. Provide recipes for each chemistry.8. Provide measuring equipment, in addition to recipes, to operators.9. Optimize chemistry; correct temperature can reduce the use of salt and dye.10. One size does not fit all; use small volume equipment for small production runs.11. Place spring loaded nozzles or timers on all water supplies to turn off when not used.12. Select valve and piping material to minimize corrosion and leaks.13. Avoid filling process equipment with water from unmetered hoses; place meters on

water supplies feeding process equipment.14. Use counter current or multi-stage rinsing to reduce water use. 15. Reuse wastewater from processes in other processes that do not require high quality

water.16.Test incoming water supply for minerals or chemicals that negatively affect the process.

CHAPTER 6: FINAL DISCUSSION

6.1 Key Findings:

Our project work was based on the practice of pollution prevention in textile wet processing industries of Bangladesh. We tried our best to make this project work to be a successful one. At the final stage of our project we may include in our comments on the subject is that being a third world country, people of Bangladesh seems not really care about pollution prevention. Unfortunately the action of the Bangladesh Government is not that much convincing. Here strict regulation is necessary also the Government have to ensure that whether the industries are following the rules or not. As we audited four textile

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wet processing industries where huge amount of waste water is discharged everyday; treatment of this waste is practiced regularly in those textile wet processing industry, which is a light for a better hope. Also further initiative is necessary, because not only water pollution, but also air pollution, noise pollution, soil pollution these are increasing day by day. Action against this is very necessary but unfortunately it is very much absent in textile wet processing industry. In the finale we may say that the action of wet processing industries seems to be effective but the real scenario is different where more initiative is must necessary.

6.2 Limitation of the project work:

1. The factories that we audited are very secretive about some of their information which they do not prefer to share.

2. As we audited only four textile factories which do not give a clear idea about the scenery of textile wet processing industry of Bangladesh on pollution prevention.

3. The people of the audited industries have lack of knowledge on pollution prevention.

4. The opportunity to observe the industries was limited.

6.3 Conclusion :

Project work consists of a huge research and a vast analysis. But due to lack of opportunities, we tried our best to complete this project with a maximum analysis and research. Under these circumstances, we tried to find out the incentives on pollution prevention to textile wet processing industries of Bangladesh. At last we may hope for the best, that our project work will be acknowledged by everyone.

References:

Books & Journals

1. Ms. Ilse Hendrickx & Gregory D. Boardman; Pollution Prevention studies in the Textile Wet Processing Industry, Department of Environmental Quality, May 1995

2. Achwal, W. B., 1990 a. “Environmental aspects of textile chemical processing (partI).” Colourage, vol 37, September 1990,

3. Cooper, S. G,. The textile industry. Environmental control and energy conservation. Noyes Data Corporation, Park Ridge, New Jersey, 1978

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4. Smith, B, Identification and reduction of pollution sources in textile wet processing. Pollution Prevention Program, North Carolina Department of Environment, Health and Natural Resources. Raleigh, North Carolina, 1986.

5. Matex, EFD SFW07, Eco Friendly Dyeing, 20076. Brent Smith, The Future of Pollution Prevention An Alternative to Costly Waste, NC

State University, October, 19947. Brent Smith, A Workbook For Pollution Prevention By Source Reduction In Textile

Wet Processing, October 19888. DPPEA FY02-08 – North Carolina Division of Pollution Prevention and

Environmental Assistance.9. Susan Barclay and Chris Buckley, Waste Minimization Guide for the Textile, For The

South African Water Research Commission, Volume I, Appendix 1, 199710. Best Management Practices for Pollution Prevention in the Textile Industry, U.S.

Environmental Protection Agency, National Technical Information Service, September 1996

11. R.M. Christie, Environmental aspect of Textile Dyeing, European legislation relating to textile dyeing, CRC.

12. Brent Smith, Identification And Reduction Of Toxic Pollutants In Textile Mill Effluents, Office of Waste Reduction, N.C. Department of Environment, Health, and Natural Resources

13. Environmental Guidelines For The textile Dyeing And Finishing Industry, Environment Protection Authority, Australia Publication 621, June 1998

Web pages:

1. www.pollutionprevention.com 2. www.fibre2fashion.com3. www.p2pays.org4. www./u.se/IIIEE/publications/theses-98/xir_abst.htm15. www.scribd.com 6. www.wikipedia.org

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http://www.scribd.com/

http://www.p2pays.org/

http://www.fibre2fashion.com/

http://www.pollutionprevention.com/