MSC Presentation 1312

7/30/2019 MSC Presentation 1312

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Pollutants of Textile Wastewater

and Their Effects on Environment

ByProf. Dr. Engr. Md Mahbubul Haque


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IntroductionLot of textile processing industries was established to

cater the RMG sector of Bangladesh.

Most of the installed factories are spinning, weaving,

denims, knitting and knit dyeing, garments and garment

washing plants.

Some of these plants generate huge amount of wastewater,

which find their way into the environment.

These wastewaters are polluted and may cause various

types of consequences and complicacies.


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Many factories have already installed Effluent Treatment Plants

(ETP).

Lot of ETPs are in various stages of their commissioning /operation.

Setting up of ETP does not and will not always ensure a safe

environment.

It is a collective and social responsibility to monitor and ensure cleanenvironment.

In order to make it a collective issue it will be necessary to make

awareness about the harmfulness of environmental pollution.It is also important to know the characteristics of effluent generated

by various types of textile processes and plants.


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Sl.

No.

Water quality

parameters

Unit Standard value for discharging into *

Inland river On land for

irrigation

1 PH ---- 6-9 6-9

2 BOD mg/L


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Name of the factory Type of thefactory

/plantConcentration of pollutants present in the wastewater

BODmg/L COD

mg/LTD

Smg/L

TSS

mg/LOil &

Greasemg/L

ColourCo-pt. Temp0C PH

1 2 3 4 5 6 7 8 9 10Ahsan Composite Knit

dyeing 300 437 2210 82 ND* ND ND 9.39Reedisha Knitex Ltd. Knit

dyeing 300 449 3380 3118 ND ND ND 9.01Fakhruddin Textile Mills

LtdKnit

dyeing

450 1000 3500

100 ND Dark ND 9-11Grameen knitwear Knit

dyeing

600 1200 - 1000 10 Dark ND 10Southeast Knit

dyeing

450 1000 3500 100 --- Dark ND 11

Epyllion Knit Ltd. Knitdyeing 450 1400 3500 200 60 600 60 9

Aboni Textiles Ltd. Knitdyeing 350 1050 3500 200 40 140 35 11

Greenland garments ltd. Knitdyeing 450 1000 4500 100 ND Dark ND 6-9

Ha-Meem Denim Denim 850 2150 - 350 20


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Table-2: Characteristics generated by various textile

processs


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Effect of pH of the effluent

Table 3: Comparison of pH with Bangladesh standard.Name of the

factory Type of the

factory/plant

pH Standard value for discharging intoInland river On land for

irrigation

1 2 3 4 6Ahsan Composite Knit dyeing 9.39 6-9 6-9Southeast Knit dyeing 11 6-9 6-9

Ha-Meem Denim

Denim

9

6-9

6-9

Jamuna denim Denim 11 6-9 6-9

Various standards suggest that pH greater than 9.5 or less than 4.5 areunsuitable for most aquatic organisms.


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Effect of pH on aquatic life

All submerged plants and animals, are constantly removing dissolved

oxygen from the water and excreting carbon dioxide during normal

respiration.

During daylight hours all plants, which include all algal forms, actively

involve in photosynthesis.

Young fish and immature stages of aquatic insects are extremely sensitiveto pH levels out side (58) and may die beyond these pH values.

High pH levels like (9-14) can harm fish by denaturing cellular

membranes.

Rapid changes in pH are stressful to fish and should be avoided.

Changing the pH by more than 3 units per day is known to stress fish.


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Biochemical Oxygen demand (BOD):

The amount of Dissolved oxygen (DO) required to degrade organic matters

of certain wastewater is regarded as Biochemical Oxygen Demand (BOD).

It is measured as ppm or mg/lMicroorganisms such as bacteria are responsible for decomposing organic

waste.

When organic matter such as dead plants, leaves, grass clippings, cellulose

components, manure, sewage, organic waste like dyes, fats and oils, or even

food waste is present in a body of water, the bacteria will begin the process

of breaking down this waste.

In degrading the organic waste, the bacteria rob the available dissolved

oxygen necessary to survive by the other aquatic organisms like fishes and

aquatic insects.


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BOD (Contd)

The higher the organic waste the higher will be the number of

bacteria to degrade. Higher will be the oxygen consumption.Under this circumstance there will be an additional demand fordissolved oxygen (DO).

This additional demand for DO is regarded as BOD.

As the waste is consumed gradually or dispersed through the water,

BOD levels will begin to decline.Table 3: Comparison of (BOD) with Bangladesh standard.Name of the factory Type of the

factory /plant BODmg/

L

Standard value for discharging intoInland river

(mg/L) On land for

irrigation (mg/L)

1 2 3 4 6Ahsan Composite Knit dyeing 300


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BOD (Cont..)

The presence of Nitrogen and phosphates in a body of water can also

contribute to high BOD levels.

Nitrates and phosphates are plant nutrients and can cause plant life and

algae to grow quickly.

When plants grow quickly, they also die quickly.

This contributes to the organic waste in the water, which is then

decomposed by bacteria. This also results in a high BOD level.

The temperature of the water can also contribute to high BOD levels.

Warmer water usually will have a higher BOD level than colder water.

As water temperature increases, the rate of photosynthesis by algae and

other plant life in the water also increases.

Therefore, increased water temperatures will speed up bacterial

decomposition and result in higher BOD levels.


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Table-4: Sizing ingredients used for various types of denim fabricsQuality Water

(Litre) Starch(Kg) PVA(Kg) Size CA(Kg) Wax(Kg)7R,9K

410

40

7

6

4

7Rs 400 40 7 7 512Rs + K 400 40 8 7 420Rs 380 40 10 7 510Rs 400 40 10 7 430 Rs + K 380 40 10 7 5BOD and DO (Dissolved oxygen)The amounts of oxygen present in a certain amount of water in dissolved

state are known as Dissolved Oxygen or simply DO.

DO is normally expressed as mg/l, and varies from 0 to 18 mg/l

In most cases of normal waters, DO lies between 7-9 mg/l.


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Chemical Oxygen Demand (COD):The organic compounds of the textile dyes and auxiliaries may be

oxidized by means of the dissolved oxygen present in the water

As a result the level of DO falls and there will be demand for oxygen,which is termed as Chemical Oxygen Demand (COD).COD accounts for all oxidisable organic compounds while, BOD refers

to only biodegradable organics.

Table 5: Comparison of COD with Bangladesh standard.Name of the factory Type of the

factory

/plantCODMg/L


(mg/L) On land forirrigation(mg/L)



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Table 9: COD of some selected dyes

Dye Structure COD (g O2)/g of dyeVat Blue 4 Anthraquinone 1600Vat green 1 Anthraquinone 1800

Direct Blue 199 Phtalocynanine 700Disperse Blue 56 Anthraquinone 1500

Reactive Blue 204 Oxazine (MFT) 650Reactive Blue-209 Formazan (FCP) 800

Sulfur ----- 650


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Total suspended Solids (TSS):

TSS is mainly organic in nature, is visible and can be removed from the

wastewater by physical/ mechanical means e.g. screening and

sedimentation.

The pore size of the filter paper is very important in estimating the TSS,

the nominal pore size 1.58 micro metre.Table 6: Comparison of TSS with Bangladesh standard.Name of the factory Type of the

factory

/plantTSSMg/l


(mg/l) On land forirrigation (mg/l)1 2 3 4 6

Ahsan Composite Knit dyeing 82


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Total Dissolved Solids (TDS):

TDS -is the sum total of all of the dissolved things in a given body of

water.

Hardness, alkalinity, cyanuric acid, potassium, chlorides and sodium,bromides, sulfates, silicates, and all manner of organic compounds.

Textile effluent inherits TDS from dyes, chemicals and auxiliaries that are

used in processing.

Table 7: Comparison of TDS with Bangladesh standard.Name of the factory Type of the

factory

/plantTDSMg/L


(mg/L) On land forirrigation(mg/L)



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Dyes and the Environment:Dyes are present in the effluent at concentrations of 10 mg/l to 50 mg/l

with 1 mg/l being visible to the naked eye.

Photochemical reactions may be important, as dyes are good absorbers of

solar energy.

Aquatic plants will not be able to produce food by the process of

photosynthesis. As a result their life will be endangered.Table-8: Comparison of Color point with Bangladesh standard.Name of the factory Type of the

factory

/plantColourCo.pt


(Co.pt) On land forirrigation(Co.pt)1 2 3 4 6

Grameen knitwear Knit dyeing Dark


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Table 5: Typical fixation of various dyes (Source-www.e-textile.org)


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Effect of temperature on Environment:Temperature controls the rate of metabolic and reproductive activities, and

determines which aquatic species can survive.

Different aquatic species require different quantity of DO to survive in the

water.

Temperature inversely affects the rate of transfer of gaseous oxygen into

dissolved oxygen.

At higher temperature the metabolic rate of aquatic plants and animals

increases producing an increase in oxygen demand.

Related International regulations classifies water, as "Class 1 Cold Water

Aquatic Life" max. temp. 20C, as "Class 2 Warm Water Aquatic Life"

max temp. 30C.

Generally, a max. 3 C increase over a minimum of a 4-hr period, lasting

12 hrs maximum, is deemed acceptable.

(C td ) Eff t f t t


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(Contd) Effect of temperature

Respiration rates can increase by 10% or more per 1 C temperature rise.

Increase in temp. of textile wastewater reduces oxygen availability, and

increases oxygen demand.The onsite test shows that effluent temperature is around 50-600C which is

quite harmful for aquatic species.Oil and greases

The term oil and grease, as commonly used, includes the fat, oils, waxes,

and other related constituents found in wastewater.

Oils and fats are mainly due to the sizing process and also as oils and

grease comes in contact with the fabric during processing. Small amountoils is found in the cellulose fibres.

Oils and fats form a layer at the top surface of the wastewater. As a result

the oxygen cannot come in contact with the water and becomes difficult to

increase DO level.

OIL & G


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OIL & Grease

Research show that oil is toxic to fish. In greater quantities, it limits

oxygen transfer, hindering biological activity.

Oils and grease affect respiration of fish by adhering to the gills, it adhereto and destroy algae and plankton.

Feeding and reproduction of water life are affected by oils and fat.Table 7: Comparison of oil and grease with Bangladesh standard.Name of the factory Type of the

factory /plant Oil andgrease(mg/l)

Standard value for discharging

Inland river

(mg/L) On landforirrigation

1 2 3 4 6Grameen knitwear Knit dyeing 10 < 10 < 10Epyllion Knit Ltd. Knit dyeing 60 < 10 < 10Ha-Meem Denim Denim 20 < 10 < 10Partex denims Denim ND < 10 < 10


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CONCLUSION/SUGGESTIONSProper management of wastewater will reduce the overall volume of

effluent.

All the factories should install and run ETP.

Setting up industries far away from the crowded greater Dhaka will

at least reduce the pollution burden on the Dhaka dwellers to some

extent.

Starch based sizes should be replaced with synthetic sizes.Government should reduce or exempt the tariffs and taxes on the

synthetic sizes.

Reconstitution of processed effluent should be examined.

CONCLUSION/SUGGESTIONS (C td )


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CONCLUSION/SUGGESTIONS (Contd._)Attempt should be made to expand woven sector. Woven account for

less m:l ratio, less energy higher profit. In knit the m:l ratio is nearly

1:200.

Selection of dyes, chemicals and auxiliaries that generate lower

pollutants will reduce ultimate pollution load.

Like many developed countries, Government can offer free water

and wastewater test facilities.

Environment is also violated by slaughtering houses, sweet

manufacturers, bakeries, poultry farms etc.

Research is necessary to study the effect and toxicity of various dyes,

chemicals and auxiliaries used in our country.Research is also necessary to reduce the operating cost of the existing

plants.

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