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Effluent Treatment

in the Textile Industry

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“ … The textile industry is one of the most wastewater

intensive industries - if not the most wastewater relevant

one at all worldwide. …”

� “ … Therefore there is hardly a sector of industry known which needs

more to consider and to take care for providing measures of

sustainability in terms of the aquatic environment. … “

Wolfgang Höhn (Dipl. Ing. (FH))

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“ .... Sustainability of waste water management in the textile industry:

It can be confidently achieved only by a well organized companyconcept comprising permanently optimized methods ofproduction integrated wastewater minimization, effluentclearing and waste water recycling.

This is nowadays a crucial challenge for the holisticenvironmental management of a textile finishing company, theimportance of which is permanently increasing over the years. …”

Senior technical consultant and Owner Hoehn Textile Engineering

What will you learn now?

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1. Effluent minimization within the textile production…

2. Effluent minimization after the textile production...

Find your position in the textile chain!

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1. Textile industry effluent - situation report

2. Effluent impact by the textile industrya) Most relevant effluent impacts by the textile industryb) Fibre focussed impact: Cellulosic, protein and synthetic fibresc) Make up focussed impact: yarn, knitgood, woven fabric

3. Effluent regulations an guidelines for the textile industrya) Global and municipal governmental effluent regulationsb) Governmental regulations vs. guidelines of private organizations

4. Effluent management in the textile industry

a) Survey of processes for effluent cleaning

b) Types of processes for effluent recycling

c) Textile effluent reduction by production integrated methods

e) Ideal waste water concept

Table of contents

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Chapter 1:Situation of worldwide textile industry effluent

Textile industry effluent – situation report

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The textile industry is the most effluent relevant industry segment worldwide

The effluent costs amount currently in average 10% of the total textile companycosts

• Effluent fees• Effluent treatment costs

Continuously more restrictive effluent laws and pressure by private regulations-> Efficient effluent management more and more important-> Permanently increasing price of textile product

Effluent discharge types• Direct discharge: appr. 5-10 % (tendency increasing)• Indirect discharge: appr. 90-95 % (tendency decreasing)

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Chapter 2:Effluent impact by the textile industrydifferentiated by substrate

Most relevant effluent impactsby the textile industry

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Color

High COD (DOC) value

Low bioeliminable (persistent/refractory) substances

Aquatoxic substances, inclusive

- Heavy metal ions (particularly Cr(III), Co(III) and Cu(II))

- AOX contributing substances

- APEO

- Sulphur containing substances

Bioaccumulating substances

Eutrophicating substances: Inorganic and organic N and P

Extreme pH values

High electrolyte concentrations

CMR (carcinogenic, mutagenic, reproduction toxic) substances

Origins of COD contribution by the textile industry

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Sizes, Preparation agents, Fibre impurities

Pretreatment agents (Detergents)

Auxiliaries for dyeing/finishing

Colorants

50 - 60%

< 10%15 - 20%

Source: 3031ke.ppt

15 - 20%

Fibre specific impact to effluent(apart of preparations)

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Native cellulosic fibres:

Native fibre impurities->COD

Mainly washing auxiliaries/sequestrants->COD

Salt->Electrolyte

Alkali->pH value

Dyestuff (reactive and sulphur dyeings)->Color

Quaternary polyammonia compounds->aquatoxic

Regenerated cellulosic fibres:

Same as native ones but without native fibre

impurities and washing auxiliaries/sequestrants

Protein fibres:

Native fibre impurities->COD

Washing and dyeing auxiliaries->COD

Cr, Co ->toxicity

Acid->pH value

Polyamide fibres:

See protein fibres but without fibre impurities

Polyester:

Washing and dyeing auxiliaries->COD

Alkali-> pH value

Org. and inorg. sulphur->Sulfite, Sulfide, Sulphate

Polyacrylnitrile:

Washing and dyeing auxiliaries ->COD

Acid-> pH value

Fibre blends:

See individual fibre impacts

Make up specific impact to effluent (preparations)

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Yarn:

Lower amounts of mineral oil based

and synthetic preparations -> Low COD contribution

Knitgoods:

Higher amounts of mineral oil based and

synthetic preparations inclusive silicone -> Medium COD contribution

Woven fabrics:

High amounts of sizes:

- Synthetic sizes and warp waxes: -> High COD contribution

-> Bad bioleliminability

- Native sizes (starch and starch derivatives): -> Very high COD contribution

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Chapter 3Effluent regulations and guidelines for thetextile industry

Global and regional governmental effluent regulations

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In most countries the legal bases for discharge of waste water are defined in a general waste water law of government

This law is usually concretized for textile plants in a legal decree (for directdischargers) or by municipal statutes (for indirect dischargers) by definition of

- Commandments- Prohibitions- Limit values for different waste water parameters (ingredients)- Waste water fees

There are different regulations for direct and indirect discharge

Worldwide there is a tendency for these regulations to become step by stepmore severe and restrictive

Legal effluent regulations versus effluentguidelines of private organisations

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Waste water limits by legal regulations

(government); e.g. App. 38 AbV, Germany

Waste water limits by guidelines of

private organizations (e.g. ZDHC,

Bluesign, GOTS, Li & Fung)

Reflect high expertise in waste water management Reflect usually minor expertise in waste water

management

In average the regulations are less severe and much

more feasible

In average the guidelines are more severe and less

feasible

Details:

- Clear differentiation between indirect and direct

discharge

- Only the really relevant parameters are regulated

- Mostly the limit values are higher to much higher

compared with private guidelines

Details:

- Mostly no clear differentiation between indirect and

direct discharge

- Often much more parameters are regulated

- Often the limit values are lower to much lower

- Some private organizations don’t claim that if their

limit values are higher than those of the government,

the lower limit values of the government have to be

followed->legal danger for dyehouses (e.g. pH value of

indirect or direct discharge being – exceptionally -

often more severly restricted by the law than by

private organizations)

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Chapter 4Effluent management in the textile industry

Compensation

processes

Substance

separating processes

Substancedestructing

processes

Combined

processes

Effluent cleaning methods

(end of pipe)

Generally accepted

rulesof technology

State of art State of science

Effluent cleaning – Survey of methods

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Hydraulic compensation

Compensation of concentrations

Compensation of temperature

Compensation of pH value,

supported by flue gas

In case of ventilation:sulphur

detoxification

Quantitative

compensationQualitative compensation

� Elementary and cheap „cleaning“ step against load peaks

� Minimum equipment for every indirect discharger

� No real cleaning effect apart of partial sedimentation of suspended particles

Compensating processes (in buffer, neutralization basins and tanks

Effluent cleaning –Compensation processes

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Substance separating and concentrating processes

Coagulation/Precipitation

(Flocculation)

Conventional inorg. coagulants

Modern inorganic coagulants

Modern organic coagulants

Adsorption and filtration

Course filtration

Adsorption/Ion exchange

Membrane filtration

Other technologies of

Substance separation

Ion pair extraction

Evaporation Freezing out

Emulsion separation

Foaming out

Cheap Universal For indirect discharge Much sludge generation

Expensive Direct discharge Recycling

Less importantfor textile industry

Effluent cleaning – separating processes

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Substance destructive processes

Oxidative processes:

Aerobic biology Chemical oxidation (e.g. ozone)

Chemical oxidation with pressure(wet oxidation)

Reductive processes:

Inaerobic biology

Chemical reduction- sulphur based

- sulphur free

Simultaneous oxidative

and reductive processes:

Electrocoagulation

Aerobic biology: good COD reduction but poor decolorization

Chemical oxidation:

Only for decolorization and cracking of persistent

components

Wet oxidation: Total mineralization

Anaerobic biology always

combined withaerobic biology; since no

mineralization but crackingof persistent components

Reduction only useful for

Decolorization and removal ofHeavy metal ions

Combines oxidative,reductive and flocculation/

flotation processes

Well modularly expendable (eg by membrane filtration) for

waste water recycling/reuse

Effluent cleaning – Destructive processes

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Combination of processes

Best state of art for

- Direct discharge

- Recycling of effluent

Basic Scheme

1. Compensating processes

2. Substance destructing processes

3. Substance separating processes(polish steps)

Effluent cleaning – combined processes

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Recycling of waste water mix

Recycling methods(intermediate position)

Recycling of partial flowwaste water

Reuse of low contaminated rinsing liquors

Reuse of treating liquors

End of pipe effluent clearing

Production integrated methods

of reduction of waste water

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Types of processes foreffluent recycling

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New dyes, auxiliaries:

Dyes with optimized degrees of fixation

Use of ecotoxicologically best dyes, auxiliaries, chemicals and recipes for the individual application;

as far as no inherent technical and economical disadvantages

New/improved finishing processes:

Plasma pretreatment without water (GRINP, IT)

Pretreatment for better dyestuff fixation

Dyeing at low liquor ratio

Combination of preparation/dyeing and finishing in one bath

Dyeing systems free of water-CO2 fabric dyeing (DYCOO, NL)- Digital yarn dyeing (TWINE, IL)

Optimized aftersoaping and –rinsing processes“

Substitution of inecological processes

Production integrated measures of

waste water reduction;

example. dyeing

Production integrated methods

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Ideal waste water concept

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Questions & Answers

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