Effluent Treatment in the Textile Industry 1
“ … 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. … “ 2
Wolfgang Höhn (Dipl. Ing. (FH)) Senior technical consultant and Owner Hoehn Textile Engineering “ .... 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 3 importance of which is permanently increasing over the years. …”
What will you learn now? Find your position in the textile chain! 1. Effluent minimization within the textile production… 2. Effluent minimization after the textile production... 4
Table of contents 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 5
Chapter 1: Situation of worldwide textile industry effluent 6
Textile industry effluent – situation report 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) 7
Chapter 2: Effluent impact by the textile industry differentiated by substrate 8
Most relevant effluent impacts by the textile industry 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 9
Origins of COD contribution by the textile industry 50 - 60% Sizes, Preparation agents, Fibre impurities Pretreatment agents (Detergents) Auxiliaries for dyeing/finishing Colorants < 10% 15 - 20% 15 - 20% 10 Source: 3031ke.ppt
Fibre specific impact to effluent (apart of preparations) Native cellulosic fibres: Native fibre impurities->COD Mainly washing auxiliaries/sequestrants->COD Salt->Electrolyte Alkali->pH value Polyamide fibres: Dyestuff (reactive and sulphur dyeings)->Color See protein fibres but without fibre impurities Quaternary polyammonia compounds->aquatoxic Polyester: Washing and dyeing auxiliaries->COD Regenerated cellulosic fibres: Alkali-> pH value Same as native ones but without native fibre Org. and inorg. sulphur->Sulfite, Sulfide, Sulphate impurities and washing auxiliaries/sequestrants Polyacrylnitrile: Washing and dyeing auxiliaries ->COD Protein fibres: Acid-> pH value Native fibre impurities->COD Washing and dyeing auxiliaries->COD Fibre blends: Cr, Co ->toxicity See individual fibre impacts Acid->pH value 11
Make up specific impact to effluent (preparations) 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 12
Chapter 3 Effluent regulations and guidelines for the textile industry 13
Global and regional governmental effluent regulations 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 14
Legal effluent regulations versus effluent guidelines of private organisations Waste water limits by legal regulations Waste water limits by guidelines of (government); e.g. App. 38 AbV, Germany 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 In average the guidelines are more severe and less more feasible feasible Details: Details: - Clear differentiation between indirect and direct - Mostly no clear differentiation between indirect and discharge direct discharge - Only the really relevant parameters are regulated - Often much more parameters are regulated - Mostly the limit values are higher to much higher - Often the limit values are lower to much lower compared with private guidelines - 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 - 15 often more severly restricted by the law than by private organizations)
Chapter 4 Effluent management in the textile industry 16
Effluent cleaning – Survey of methods Generally accepted rules State of art State of science of technology Effluent cleaning methods (end of pipe) Substance Substance Compensation Combined separating destructing processes processes processes processes 17
Effluent cleaning – Compensation processes Compensating processes (in buffer, neutralization basins and tanks Quantitative Qualitative compensation compensation Compensation In case of ventilation: Hydraulic Compensation Compensation of pH value, sulphur compensation of concentrations of temperature supported by flue gas detoxification � 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 18
Effluent cleaning – separating processes Substance separating and concentrating processes Other technologies of Coagulation/Precipitation Adsorption and filtration Substance separation (Flocculation) Course filtration Ion pair extraction Conventional inorg. coagulants Evaporation Adsorption/Ion exchange Freezing out Modern inorganic coagulants Emulsion separation Membrane filtration Foaming out Modern organic coagulants Cheap Expensive Less important Universal Direct discharge for textile industry Recycling For indirect discharge Much sludge generation 19
Effluent cleaning – Destructive processes Substance destructive processes Reductive processes: Oxidative processes: Simultaneous oxidative and reductive processes: Inaerobic biology Aerobic biology Chemical reduction Chemical oxidation (e.g. ozone) Electrocoagulation - sulphur based Chemical oxidation with pressure - sulphur free (wet oxidation) Aerobic biology: good COD Anaerobic biology always Combines oxidative, reduction but poor decolorization combined with reductive and flocculation/ aerobic biology; since no flotation processes Chemical oxidation: mineralization but cracking Only for decolorization and of persistent components Well modularly expendable cracking of persistent (eg by membrane filtration) for Reduction only useful for components waste water recycling/reuse Decolorization and removal of Wet oxidation: Total mineralization Heavy metal ions 20
Effluent cleaning – combined processes 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) 21
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