Effluent Treatment in the Textile Industry 1 The textile - - PowerPoint PPT Presentation

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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

• ne 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 company concept comprising permanently optimized methods of production integrated wastewater minimization, effluent clearing and waste water recycling. This is nowadays a crucial challenge for the holistic environmental management of a textile finishing company, the importance 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 industry

a) Most relevant effluent impacts by the textile industry

b) Fibre focussed impact: Cellulosic, protein and synthetic fibres c) Make up focussed impact: yarn, knitgood, woven fabric

• 3. Effluent regulations an guidelines for the textile industry

a) Global and municipal governmental effluent regulations

b) 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 company costs

• 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 industry

differentiated by substrate

Most relevant effluent impacts by 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 3 Effluent regulations and guidelines for the textile 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 direct dischargers) 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 step more severe and restrictive

Legal effluent regulations versus effluent guidelines of private organisations

15 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 -

• ften more severly restricted by the law than by

private organizations)

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Chapter 4 Effluent management in the textile industry

Compensation processes Substance separating processes Substance destructing processes Combined processes

Effluent cleaning methods (end of pipe)

Generally accepted rules

• f technology

State of art State of science

Effluent cleaning – Survey of methods

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Hydraulic compensation Compensation

• f concentrations

Compensation

• f temperature

Compensation

• f pH value,

supported by flue gas In case of ventilation: sulphur detoxification

Quantitative compensation Qualitative 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 important for 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 with aerobic biology; since no mineralization but cracking

• f persistent components

 Reduction only useful for Decolorization and removal of Heavy 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 flow waste water Reuse of low contaminated rinsing liquors Reuse of treating liquors

End of pipe effluent clearing Production integrated methods

• f reduction of waste water

E c

• n
• m

y F l e x i b i l i t y

Types of processes for effluent recycling

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New dy es, auxiliaries:

 Dyes with optimized degrees of fixation  Use of ecotoxicologically best dyes, auxil iaries, 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 (T

WINE, IL)  Optimized aftersoaping and –rinsing processes“  Substitution of inecological processes

Production integrated measures of w aste w ater reduction;

• example. dy

eing

Production integrated methods

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Ideal waste water concept

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Questions & Answers

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