BASEL CONVENTION

Draft technical guidelines on the environmentally sound management of wastes resulting from surface treatment of metals and plastics (Y17)

Contents

1 PREAMBLE..................................................................................................................................................6

2 THE WASTE AND THE INDUSTRY THAT GENERATES THE WASTE.........................................6

2.1 Background 6

2.2 Current Consumption and Emission Levels72.2.1 Input materials.................................................................................................................................7

2.2.2 Utilities.............................................................................................................................................7

2.2.3 Gaseous Emissions...........................................................................................................................7

2.2.4 Effluent Emissions............................................................................................................................7

2.2.5 Solid Waste.......................................................................................................................................7

3 ENVIRONMENTAL HAZARDS...............................................................................................................7

3.1 Key Environmental Issues in the Surface Finishing Industry 73.1.1 Hazardous Air Pollutants (HAP).....................................................................................................7

3.1.2 Liquid Discharge..............................................................................................................................7

3.1.3 Priority Pollutants............................................................................................................................8

3.2 Overview of Environmental and Health Effects and Impacts of Wastes 83.2.1 Health Effects...................................................................................................................................8

3.3 Hazards in Surface Preparation/Pre-treatment 83.3.1 Mechanical Processes (for metals)..................................................................................................8

3.3.2 Chemical Processes – Cleaning.......................................................................................................9

3.3.3 Electrolytic Processes......................................................................................................................9

3.3.4 Conditioning of Plastics.................................................................................................................10

3.4 Hazards in Surface Coating and Painting 103.4.1 Specialist Pre-coats........................................................................................................................10

3.4.2 Chemical Processes – Dip Coating and Flow Coating..................................................................11

3.4.3 Physical Processes – Painting and Coating...................................................................................11

3.4.4 Electro-deposition and Anodising..................................................................................................11

3.4.5 Solvent-based Coatings..................................................................................................................12

3.4.6 High-solids Coatings......................................................................................................................12

3.4.7 Water-borne Coatings....................................................................................................................13

3.4.8 Electrostatic Powder Coatings.......................................................................................................13

3.4.9 Radiation-cured Coatings..............................................................................................................13

3.4.10 Wet Spray Application....................................................................................................................13

3.4.11 Roller Application..........................................................................................................................13

3.4.12 Surface-Coating-Free Materials....................................................................................................14

3.5 Hazards in Post Treatment including Curing 143.5.1 Conversion Coatings......................................................................................................................14

3.5.2 Top Coatings..................................................................................................................................14

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3.5.3 Colouring and Sealing of Aluminum..............................................................................................14

3.5.4 Drying for Barreled and Racked Components...............................................................................14

3.6 Equipment Cleaning 14

3.7 Medical Plastics 14

4 IDENTIFICATION OF OPPORTUNITIES FOR WASTE AVOIDANCE.........................................14

4.1 Waste Avoidance and Minimization – General Considerations 144.1.1 Designated Area.............................................................................................................................15

4.1.2 Empty Containers/Packaging.........................................................................................................15

4.1.3 Pre-cleaning...................................................................................................................................15

4.1.4 Reduction of Drag-Out...................................................................................................................15

4.1.5 Acid and Alkaline Wastes...............................................................................................................15

4.1.6 Acid and Alkaline Wastewater Streams (Rinse Waters).................................................................16

4.1.7 Sludges............................................................................................................................................16

4.1.8 Paints, Inks.....................................................................................................................................16

4.1.9 Water Conservation........................................................................................................................16

4.1.10 Improving Existing Process Conditions and Practices..................................................................17

4.1.11 Segregation of Waste at Source......................................................................................................17

4.2 Dealing with Surface Preparation Wastes 174.2.1 Abrasive Blasting Wastes...............................................................................................................17

4.2.2 Halogenated de-greasing Wastes...................................................................................................17

4.2.3 Chemical Cleaners and Specialist Pre-coats Wastes.....................................................................18

4.3 Dealing with Coating Application Wastes 184.3.1 Dip and Flow coating.....................................................................................................................18

4.3.2 Electro-deposition and Anodising..................................................................................................19

4.3.3 Spray Application...........................................................................................................................19

4.3.4 Electrostatic Powder Coats............................................................................................................19

4.3.5 Roller Application..........................................................................................................................20

4.4 Dealing with Curing Wastes 204.4.1 Product Finishing...........................................................................................................................20

4.5 Alternative Processes: Surface Preparation 204.5.1 Alternative Stripping Processes.....................................................................................................20

4.5.2 Alterntive Pickling and Descaling..................................................................................................20

4.5.3 Alternative Etching.........................................................................................................................20

4.5.4 Alternative Cleaning Equipment....................................................................................................20

4.5.5 Alternative Cleaning.......................................................................................................................20

4.6 Alternative Surface Finishing Process & Coating Techniques 204.6.1 Alternative Anodizing.....................................................................................................................20

4.6.2 Organic Coatings...........................................................................................................................21

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4.6.3 Alternative Vapour Deposition.......................................................................................................21

4.6.4 Thermal Spray................................................................................................................................21

4.6.5 Hardfacing......................................................................................................................................21

4.6.6 Porcelain Enameling......................................................................................................................21

4.6.7 Metal Cladding and Bonding.........................................................................................................21

4.6.8 UV and electron beam technology.................................................................................................21

4.7 Alternative Solvents 21

4.8 Coating Alternatives Guide: CAGE Expert System (U.S. EPA) 21

5 IDENTIFICATION OF OPPORTUNITIES FOR RECOVERY..........................................................21

5.1 Recovery of Solids 21

5.2 Recovery and purification of Process Solution 215.2.1 Diffusion Dialysis...........................................................................................................................21

5.2.2 Microfiltration................................................................................................................................21

5.2.3 Membrane Electrolysis...................................................................................................................21

5.2.4 Acid (Resin) Sorption.....................................................................................................................21

5.2.5 Electrowinning...............................................................................................................................21

5.2.6 Other Technologies........................................................................................................................21

5.3 Recovery of Concentrate or Rinse Purification 215.3.1 Reverse Osmosis.............................................................................................................................21

5.3.2 Electrodialysis................................................................................................................................21

5.3.3 Ion Exchange..................................................................................................................................22

5.3.4 Vacuum Evaporation......................................................................................................................22

5.3.5 Atmospheric Evaporation...............................................................................................................22

5.3.6 Other Technologies........................................................................................................................22

5.4 Recycling of Spent Solvents 225.4.1 On-site Recycling...........................................................................................................................22

5.4.2 Off-site Recycling...........................................................................................................................22

6 WASTE TREATMENT AND DISPOSAL TECHNOLOGIES.............................................................22

6.1 Aqueous liquids 236.1.1 Rinsing waters................................................................................................................................23

6.1.2 Acid and Alkali Solutions...............................................................................................................23

6.1.3 Water based coatings.....................................................................................................................24

6.2 Solvent-Based Wastes 246.2.1 Non-halogenated solvents..............................................................................................................24

6.2.2 Chlorinated Hydrocarbon Cleaning Solvent..................................................................................25

6.2.3 Mixed VOC Solvent Wastes............................................................................................................25

6.2.4 Mixed Hydrocarbon and Aqueous Solutions..................................................................................26

6.3 Specific Wastewater Treatment Technologies 26

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6.3.1 Alkaline Chlorination.....................................................................................................................26

6.3.2 Electrolytic Destruction.................................................................................................................27

6.3.3 High-pressure and high-temperature hydrolysis...........................................................................27

6.3.4 Chromium Reduction......................................................................................................................27

6.3.5 Neutralization and Hydroxide Precipitation..................................................................................27

6.3.6 Sedimentation.................................................................................................................................27

6.4 Solid Hydrocarbon Coatings 27

6.5 Control of Air Emissions 286.5.1 Particulate Matter (PM).................................................................................................................28

6.5.2 Solvent Vapour, VOCs....................................................................................................................28

6.5.3 Stacks for spray painting and coating............................................................................................28

6.6 Hazardous Waste Disposal options 286.6.1 On-site Disposal: Solvent-based Cleaner......................................................................................28

6.6.2 On-site Disposal: Paint Removal...................................................................................................28

6.6.3 Off-site Disposal.............................................................................................................................28

6.7 Monitoring of multimedia emissions (air, water, solid wastes) 28

7 ECONOMIC ASPECTS OF SUITABLE WASTE MANAGEMENT OPTIONS...............................28

7.1 Pre-treatment Evaluation 28

7.2 Coating Application Waste Evaluation 29

7.3 Product Finishing Waste Evaluation 29

8 CRITERIA FOR THE SOUND OPERATION OF TECHNOLOGY AND SAFETY........................29

8.1 Generators’ Responsibilities 29

8.2 Collection & Storage Responsibilities 30

8.3 Transport Responsibilities31

8.4 Disposal Responsibilities 32

9 GLOSSARY OF TERMS...........................................................................................................................33

10 REFERENCES...........................................................................................................................................38

11 contacts.........................................................................................................................................................40

1 2 AN N E X I P roposal for new chapter: degreasing, cleaning, impregnating………………………………..42

1 3 An n e x I I B e s t a v a i l a b l e t e c h no l o g i e s … … … … … … … … … . . … … … … … … … … … … 5 6

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1 PREAMBLE

1. These technical guidelines are principally intended to provide guidance to countries who are building their capacity to manage waste in an environmentally sound and efficient way. They provide information on waste avoidance and the management of wastes in the surface coating of metals and plastics. The guidelines briefly describe the industries that are the major waste generators from surface coating, the situations in which these industries generate wastes, the commonly occurring waste treatments and best practice waste treatment methods.

2. The primary reasons for applying surface coatings to metal and plastic surfaces are for corrosion resistance and aesthetic decoration. Coating methods include spray and electrodeposition for small parts, while dip processes and roller coating operations are commonly used for high-volume continuous sheet coating, and for the coating of larger work pieces.

3. In most cases the surfaces to be coated require preparation prior to application, and this is usually performed with chemical cleaners and converters. Common application methods for surface cleaning are dipping and vapour de-greasing. Both surface preparation and application of the final coating have potential for release of chemical agents during application and curing operations, and also from the release of residues (e.g. sludge) resulting from the cleaning and coating operations.

4. This document is intended to offer guidelines on the environmentally appropriate management practices for the wastes generated from these activities.

General comments from Germany: The surface treatment of metals and plastics covers a wide range of different production technologies which cannot be classified easily. Nevertheless we think that it might be better to differentiate the guideline in two main parts:

- Surface treatment of metals and plastics using electrolytic or chemical means

- Surface treatment of metals and plastics using solvents

Concerning the further development of the guideline we propose

- to include a new chapter on degreasing, cleaning and impregnation (see Annex I)

- to take into consideration the work done by Germany on the BAT of Surface Treatment (German BAT - report, Annex II)

2 THE WASTE AND THE INDUSTRY THAT GENERATES THE WASTE

2.1 Background

5. Major industry sectors which perform surface coating as a major component of their overall manufacturing processes include the:

Metal finishing industry;

Metal products fabrication industry;

Automotive component manufacture;

Automotive manufacture and repair industry;

Printing; and

Aircraft manufacture and maintenance.

6. The types of substrate coated in these industries are plastics (various types), metals and paper products. While waste streams resulting from paper coating and printing are not specifically dealt with in this guidance document, the liquid waste streams are commonly treated in substantially the same way as those resulting from certain metal and plastic coating operations.

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7. In most circumstances, to ensure acceptable performance of the final coating it is necessary to rigorously clean the surface of the substrate prior to application of the final coating or – when applicable - of the pre-treatment. The guidance note application includes the following three steps employed by each of the above industries:

Surface preparation or cleaning;

Application of the coating; and

Curing of the coating.

8. Surface preparation may include abrasive blasting, chemical cleaning or de-greasing, specialist coating and/or rinsing activities. Coating application may be by electrodeposition, spray, dip or roller application. Coating curing may utilize heat, U V light or air drying to remove solvent and set lacquer and varnishes. Buffing and polishing as finishing operations may also result in high dust load activities. Each operation has a high potential to contaminate the work area and environment if not appropriately managed.

2.2 Current Consumption and Emission Levels

9. This section provides information (as available) on raw chemicals consumption and emission levels of surface finishing industries in many parts of the world, giving a perspective of the typical pollution levels for this industry

2.2.1 Input materials

2.2.2 Utilities

2.2.3 Gaseous Emissions

2.2.4 Effluent Emissions

2.2.5 Solid Waste

3 ENVIRONMENTAL HAZARDS

3.1 Key Environmental Issues in the Surface Finishing Industry

10. These subsections describe the overall sources of pollutants from the surface treatment of metals and plastics and the reasons for health and environmental concerns.

3.1.1 Hazardous Air Pollutants (HAP)

11. Fugitive emissions from the curing of organic solvent based coatings are a substantial contribution to the VOC load, and recognition of the role of these chemicals in the formation of photochemical smog has prompted exploration of substitute solvents and alternative (water based) coating technologies.

3.1.2 Liquid Discharge

12. Due to the diverse nature of the surface preparation and coating industry, a variety of liquid waste streams are generated. Aqueous wastes from the preparation (cleaning) of metal prior to application of final coats, will usually contain a high concentration of dissolved metals (eg. iron, copper, nickel), but may also contain emulsified oils, grease and fats together with suspended particulate matter (eg derived from scale and rust etc.).

13. Liquid wastes from the application of final coats or other treatments may also contain dissolved heavy metals, but are also likely to contain suspended particles of polymer, paints and pigments etc. The waste streams from both cleaning and final coating application may be acidic or basic, and due to high level of contamination must be comprehensively treated before they can be discharged to the environment.

3.1.3 Priority Pollutants

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14. Includes “priority pollutants” (as identified by the U.S. Environmental Protection Agency), used in the metal finishing industry. e.g. benzene, carbon tetrachloride, phenol, lead, zinc, silver etc.

Comments from Germany: The “priority pollutants” benzene, carbon tetrachloride, phenol, and lead are not used in Europe any more. They can be substituted completely with the exception of electroplated lead alloy of friction bearings.

3.2 Overview of Environmental and Health Effects and Impacts of Wastes

3.1 Environmental impacts

15. To identify adverse environmental impacts arising from inadequate collection, transport or improper disposal of wastes generated from surface treatment, such as air pollution, unpleasant odours, photochemical smog, acid rain from acid precipitation, fire hazard and possible dust explosions; and fine powders which can damage nearby objects and properties.

3.2.1 Health Effects

16. To identify potential health effects, when exposed to solvents such as toluene, xylene, and isocyanates, as well as dust fallout, which may cause respiratory, eye and lung irritation, asthma, irritation and metabolic toxicity. It is noted that removal of old paints also poses health risks, odour and toxic dusts some of which may contain chromium and lead salts.

3.3 Hazards in Surface Preparation/Pre-treatment

3.3.1 Mechanical Processes (for metals)

17. Process descriptions include: sandblasting, grinding, barrel finishing, polishing and buffing, and the types of wastes generated include:

solid wastes (metal shavings, fines, and contaminated coolants, used grinding wheels, drills, and other tools),

air emission (fine metal and abrasive dust from polishing and buffing),

liquid waste (waste rinse water, lubricants wastes, oils, chemical additives), waste machining oils containing halogens, and spent waxes and fats

18. Abrasive blasting is commonly used to prepare large steel articles that have either been previously coated or have a significant layer of oxidised surface that will affect the expected service of subsequent surface coatings. High silica content sands have created local and off-site adverse effects, particularly where articles are of a size to require abrasive blasting “out of doors”. The very fine crystalline silica dusts resulting from the use of these sands creates a threat to workers and the human health of neighbouring activities, as well as nuisance dust. Uncontrolled blasting with silica sand is banned in many areas even where the used material is extracted and collected in fabric filter baghouse units.

19. Recent past practice in some countries has been to use metallurgical slag from copper, lead and zinc refining as the abrasive medium. While these slags are substantially silica, they also contain significant levels of metals, and particularly of copper and lead. The presence of these metals in the slags present additional hazards to human and environmental health.

20. The use of garnet (fabric filter) materials in equipment that captures the used abrasive material from the work piece is best-practice operation. Wet blasting may also be advantageous for extreme cleaning and reduction of air-borne particulate material. The collection of used blasting medium reduces the high health and environmental risk from the older technology “free” sand blasting. Collected garnet may be reused following size screening and contaminant removal (screening).

21. Cleaned areas are free from the oxide surface layer and are ready for coating. Primers, undercoats and topcoats generally follow and the finish is often rough due to the pitting of the surface during blasting. Primary environmental hazards are air pollution and generation of heavy metal and pigment contaminated solid waste.

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3.3.2 Chemical Processes – Cleaning

22. Process descriptions include: solvent cleaning, alkaline cleaning, acid pickling/etching/bright dipping, salt bath pot cleaning, quenching/cyaniding, degreasing.

23. Chlorinated solvents including trichloroethylene, perchloroethylene, trichloroethane, methylene chloride and trichlorotrifluoroethane have been used with great success as solvent de-greasers for cleaning of oils and greases from the surface of metals.

24. Cold cleaning (liquid state) and vapour de-greasing are the two common methods used. Cold cleaning is performed by direct application of the solvent to the surface by wiping, brushing, spraying, flushing or dipping the work piece. However, vapour degreasing utilises a heated bath of solvent, a vapour space and a cooled area where vapour condenses. Pieces to be cleaned are lowered into the vapour area where cleaning occurs as the chlorinated solvent vapour condenses on the surface of the article, and dissolved adhering grease and grime.

25. The use of chlorinated solvents to dissolve hydrocarbon compounds was introduced to overcome flammability issues associated with hydrocarbon based cleaning solvents. Over time the halogenated solvents have increasingly been identified as toxic to both humans and the environment. Trichloroethylene and methylene chloride are confirmed carcinogens and require stringent control over releases to the work area and the environment. Trichloroethane is an ozone depleting substance and the use of this material is banned in most circumstances.

Comments from Germany: In Germany only the use of trichloroethylene, perchloroethylene and methylene chloride as halogenated solvents is permitted.

26. Primary environmental hazards are air pollution and generation of a chlorinated hydrocarbon waste solvent and sludge. Liquid wastes include the condensed solvent containing dissolved grease and other contaminants.

Comments from Germany: The degreasing with organic solvent has been substituted nearly completely by water-based methods. Therefore the degreasing with organic solvents especially by using chlorinated hydrocarbon is BAT. only in completely encapsulated units.

27. Caustic and slightly acidic rinses may also be used to remove dirt, scale and grime. The resultant waste solutions may not be directly disposed to sewer due to extreme pH levels (>9 for caustic rinses and < 4 for acid) and contaminants removed from the surface of the articles cleaned.

Comments from Germany: The high risk of ground water contamination should also be mentioned.

28. Special gels containing a high content of caustic or methylene chloride are used in vigorous paint stripping operations generally required to remove previously cured coatings during rejuvenation or restoration of previously painted articles. Typically these cleaners and solutions are rinsed or pressure washed from the clean surface carrying with the wash water sludge and dissolved contaminants collected for further treatment. The primary environmental hazards resulting from this process are water, groundwater and land pollution and the generation of an aqueous solution requiring treatment. Sludges are also produced which require pre-treatment for disposal into landfill.

29. Steam cleaning is also used in some applications. While this is not strictly a chemical cleaning method, it produces an aqueous waste stream containing dissolved and suspended contaminants, and may not be released to the environment before these have been removed.

Comments from Germany: The treatment described in this chapter has been used for the paint stripping of airplanes. Due to the high contamination of the environment this technology has been substituted by several physical treatments.

3.3.3 Electrolytic Processes

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30. Process descriptions include: electrolytic activating (electrolytic degreasing), electrocleaning and electropolishing. In essence this method of cleaning metal objects consists of making the metal the anode in an electrolytic cell, where the electrolyte is an aqueous solution of an “inert” salt, or possibly a dilute acid or alkali solution. When a current from an external power source is applied between the anode and cathode of the cell the metal near the surface of the object is oxidised to metal ions, which then dissolve in the water. Any adhering particles of metal oxide or grease etc. will slough off the metal surface and will become suspended in the electrolyte, or are dissolved. Wastes generated include liquid waste containing dissolved metal, and a sludge.

3.3.4 Conditioning of Plastics

31. Where plastics are to be coated with a polymer formulation (eg paint) or are to be “metallised”, certain surface preparations may be required. Apart from cleaning the surfaces, it may be necessary to “activate” them so that the final polymer or metal coat forms a uniform film over the surface and is firmly bonded to the surface. Since different plastic types have quite different chemistries a variety of activating reagents may be used in the role of activator, and the resultant waste streams – consisting of unreacted reagent and reaction products – would be industry (plastic) specific. Both organic and inorganic (eg. oxidising agents) may be used, and so many of the associated waste steams are likely to be toxic to human and/or environmental health if released without appropriate treatment.

3.4 Hazards in Surface Coating and Painting

32. For continued protection from corrosion the surface to be coated must be cleaned and dried by one of the techniques outlined in Section 3.3, and after appropriate cleaning, the coating is then applied to the cleaned substrate. There are many methods of application, and the particular method used will be determined by the chemical nature of the coating, the economics and the scale of the operation.

33. Coating chemistry will effectively determine the environmental and waste consideration issues. A heat set coating applied with the aid of high quantities of solvent will generate significant VOC air discharge relative to a high solids UV ink coat or thermoplastic powder. Significant variation in the equipment used in applying and curing the coating will be effected by the size of the job and the eventual use of the component, part or product.

3.4.1 Specialist Pre-coats

34. Phosphates and chromium coatings are widely used as slightly alkaline metal surface etchers and binders to improve the adhesion of organic coatings to the metal surface. For example, aqueous phosphate solutions are used to pre-coat extruded aluminium, while steel components are extensively phosphate coated as a pre-treatment to surface coating. Aluminium is treated with chromate for corrosion protection and is applied, as are phosphate pre-coats by either immersion of the parts, conveyor dipping or by spray application. These coatings are generally oven cured prior to application of subsequent decorative coatings (paint).

Comments from Germany: The use of chromium VI containing coatings in automobiles, electrical and electronic devices is banned from 2007 in the European Union, also for imported goods.

The use of chromium VI containing coatings on aluminum has been substituted completely by other methods.

35. Hexavalent chrome and phosphate baths require continual replenishment or periodic change over. Although solution concentrations are low, municipal sewer authorities generally will not permit direct discharge of the waste solutions unless treated heavy metals are either substantially removed, or reduced to specified concentration levels. A newer technology intended to replace the chromium pre-coat is based on a zinc and/or titanium formulation offers lower environmental toxicity, but result in poorer performance of the final coating over the working life of the component or item.

36. Primary environmental hazards associated with discharge of these solutions are water, groundwater and land pollution. Treatment of the contaminated liquor to remove heavy metals results in sludges, and these may not be directly disposed of into unsecured landfill (e.g. if they contain chromium).

Comments from Germany: Waste water containing Cr(VI) is treated in two steps:

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1. Reduction of Cr (VI) to Cr(III) 2. Precipitation of Cr(III) as hydroxide

Concerning the substitution of chromium VI several other alternatives are existing.Instead of chromium mentioned in the bracket at the end of this chapter it should read chromium(VI).

3.4.2 Chemical Processes – Dip Coating and Flow Coating

37. In dip coating, the article is immersed in solution of the treatment chemical, and on removal from the bath excess coating is allowed to drain into drip trays, and then returned to the main dip tank. A transfer efficiency of ~85% is usual, and the coating solution (or emulsion) may be either water or solvent based. Drag out and solvent evaporation is replenished by fresh material. Dip coatings are not high quality finishes and production run changes are rare. Primers and undercoats used to protect against corrosion are often applied in this manner for high volume production runs.

38. Overhead flow of coating over the article on a conveyor, with the excess coating solution dripping and returning to the tank, has the same transfer efficiency as dip coating. Phosphate and chromium conversion coatings are commonly applied via these methods.

39. Odour and chemical vapours will be emitted from the main tank and drag out areas (organic coatings). Periodic replacement of the tank contents is sometimes necessary, and this may generate a sludge containing heavy metals.

3.4.3 Physical Processes – Painting and Coating

40. Process description includes plastic and paint coating.

3.4.4 Electro-deposition and Anodising

41. This method (sometimes also called electro-plating) is only generally applicable to the coating of metal objects because it is essential that the object to be coated is able to conduct an electric current. In this method the metal part to be coated is made the cathode of an electrolytic cell, while the electrolyte is an aqueous solution of a salt of the metal which is to be plated onto the surface. When a DC current is applied to the cell, the metal ions in the solution are attracted to the cathode (ie. the work piece) and are reduced to the metal on the surface of the work piece, forming a tightly adhering metal film. Metals which are commonly electro-deposited include copper, nickel, chromium, zinc and alloy, tin and alloy, copper and alloy and precious metals. Transfer of the coating to the metal parts is typically performed at ~95% current efficiency.

Comments from Germany: The efficiency of 95   % mentioned at the end of para 42 is not of general nature, because some coating systems are remarkable lower.

42. Anodising is essentially the reverse of electro-deposition, and in many ways is similar to the electrolytic cleaning process described in 3.3.3. However, the chemical composition of the electrolyte and the voltage applied to the cell are such that the surface of the metal is not dissolved (as with electrolytic cleaning), but is instead converted to a thin film of metal oxide. For some metals (eg. aluminium) the oxide film is very tough and inert, and therefore acts as a protective barrier to mechanical damage to the surface, and as a protection against corrosion in most environments. In some cases the metal oxide has an attractive colour, and so anodising is used to produce an oxide “patina”.

43. After either electrodeposition or anodising is performed on a metal work piece, it must be thoroughly rinsed before further coating applications or processing occurs.

Comments from Germany: Rinsing occurs after every single (only some exceptions exist) step of the process: pickling, coating, after-treatment, …

44. Acid baths are utilized in both anodising and electroplating applications, and may generate an acid mist in the workplace as air emissions. Bath replenishment and rinsing water and drag out will generate an aqueous heavy metal waste stream requiring treatment before it can be released. A variety of water soluble metal salts

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may be used as the source of the metal which is to be plated, but industry has found that many metals are very successfully plated from solutions of their cyanide salts.

45. Wastes generated include:

cyanidic (alkaline) wastes containing heavy metals other than chromium,

cyanidic (alkaline) wastes which do not contain heavy metals,

cyanide-free wastes containing chromium,

nickel/chromium wastes from double layer nickel and “microdiscontinuous” chromium electroplating of plastics, and

wastes from plastics resins for electroplating.

Comments from Germany: The enumeration of waste types seems to be arbitrary. We therefore propose to change No. 46 as follows:Wastes generation includes: wastes from chemical surface treatment and coating of metals and other materials (for example galvanic processes, zinc coating processes, pickling processes, etching, phosphating, alkaline degreasing, anodizing):

pickling acids acids not otherwise specified pickling bases phosphatising sludges sludges and filter cakes containing hazardous substances aqueous rinsing liquids containing hazardous substances degreasing wastes containing hazardous substances eluate and sludges from membrane systems or ion exchange systems containing hazardous

substances saturated or spent ion exchange resins cyanide-free wastes containing chromium, nickel/chromium wastes from double layer nickel and “microdiscontinuous” chromium

electroplating of plastics, and wastes from plastics resins for electroplating.

3.4.5 Solvent-based Coatings

46. The waste streams are primarily solvent containing diminished concentrations of the coating polymers and pigments if included in the formulation. Such waste streams have potential to be hazardous to both human and environmental health, although the degree of hazard will depend on the exact formulation used.

47. Common examples of such coatings include oil based paints often used in decoration of houses and buildings. Evaporation of the solvents from these paints as they dry will release VOC to the atmosphere. Such coatings are applied to the surfaces by brush, roller or spray gun.

3.4.6 High-solids Coatings

48. High solids coatings may be based on either organic or aqueous solvent systems. As in 3.4.5 the hazardous status of waste streams from use of these coating formulations will depend on the nature of the solvents and the chemistry of the actual coating material.

3.4.7 Water-borne Coatings

49. Common examples of water borne coatings include acrylic latex paints, which are used in high volumes for decorative purposes (houses and other buildings). These paint formulations are increasingly replacing the solvent based paints, and consequently their use decreases VOC release to the atmosphere. These are usually applied through brush, roller or spray gun.

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3.4.8 Electrostatic Powder Coatings

50. In this method the coating material (usually a ceramic material, or a pigmented polymer) is ground into a very finely divided powder, which may then be sprayed from a reservoir by a blast of air through a nozzle aimed at the work piece. The Nozzle of the spray unit is charged to a high positive potential (several thousand volts) relative to the work piece, and as the particles leave the nozzle they become positively charged, and once having struck the work piece are attracted to it through electrostatic interactions. Once coated the work piece is placed in an oven where the applied heat sets (cures) the coating chemical to a tough even finish.

51. The use of an electric potential between a fine powder and the surface to be coated increases the transfer efficiency and reduces the need for particulate control, and so the use of such methods generates little waste. Collected overspray particulate can be reused if uncontaminated with other pigmented materials and extraneous solids.

3.4.9 Radiation-cured Coatings

52. These are specialist coatings used in fairly low volumes. The actual coating of the article is formed by cross-linking (curing) individual polymer molecules – previously pre-coated onto the work piece through dipping or spraying. The formation of the crosslinks is promoted through exposure to high energy UV radiation, or in some cases to radioactivity. Apart from waste streams generated during the pre-coating, little waste generated by the radiation curing process itself.

Comments from Germany: This section describes that in some cases radioactivity is used for the hardening. This seems to be rather scare. To our knowledge the curing reaction is initiated by energy-rich radiation (ultra-red or ultraviolet radiation) but not by radioactivity-

3.4.10 Wet Spray Application

53. Four basic methods are employed:

Air-atomized;

Airless;

Electrostatic spray; and

High volume, low pressure spray.

54. Atomization of the coating within the gun creates a fine mist that is directed at the surface to be coated. The transfer efficiencies vary greatly depending upon the piece to be coated, the operator skill, etc and typically may range from only around 10% for air “birdcage” type pieces to better than 60% for large “flat pieces. As with electrostatic powder coating, application of a high voltage between the spray nozzle and the work piece aids the overall transfer efficiency, efficiencies up to 95% may be achieved with electrostatic sprays.

55. A spray booth is used to protect the work, confine and collect overspray and supply good ventilation for the spray painter. Water wall spray booths are commonly used within the booth to capture overspray. Solvents associated with the overspray are released as air emissions. High pH wastewater is often generated as a result of this coating technique, and this also contains some of the unused coating. Sludges also result from spray booth cleaning.

3.4.11 Roller Application

56. Coating of continuous reels or sheets using a system of rollers with one roller partially immersed in a bath of coating transferring the coating to a second parallel roller is the basis for flexographic and coil coating applications. The sheets or strip from a reel passes between the second roller and a third drive roller. High solvent proportions are required for good application, and large quantities of solvent may be lost from the roller bath and during the drying stage.

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57. Contaminated solvent solutions as waste in roller cleaning activities are generated. Air emissions to the work and external environment are problematic.

3.4.12 Surface-Coating-Free Materials

3.5 Hazards in Post Treatment including Curing

58. Except for powder and radiation cured coatings most surface coatings utilize large quantities of solvents for the best coating application. The proportion and type of solvents used depends on the coating methods employed. For example, spray applied paints require fast evaporating solvents, where brushing, dipping and roller coating applications require slow evaporating solvents to maximize coating coverage. To allow the curing of the applied coatings the solvent must initially be vaporized.

59. Air, heat set, UV and thermoplastic resins are typically used to offer the abrasive resistance required for the coatings. The end use of the coated material and the volume to be coated will determine the production techniques employed, and in turn will determine the solvent requirements.

60. Treatment of all solvent emissions is required and the necessity for this has been a major impetus for the development of high performance, low VOC formulations. A major effect from the discharge of VOCs to the lower atmosphere is the promotion of formation of photochemical smog. VOC emissions from solvent evaporation, particularly in summer when UV light and ozone are present in the lower atmosphere contribute to the generation of photochemical smog, and the compounds formed from reactions within the smog can be highly reactive within the human respiratory system. In industrialized cities there are increasing movements to replace traditional coating methods with low VOC formulations and coating technologies.

61. The evaporation of solvent, heat setting and drying of coatings also contributes to the generation of greenhouse gases through direct combustion of fossil fuel or indirect use of electricity. The reduction of greenhouse gases may be important for the development of coating formulation in the future, and may indirectly affect the choice of application and heat usage for coatings application and curing.

3.5.1 Conversion Coatings

3.5.2 Top Coatings

3.5.3 Colouring and Sealing of Aluminum

3.5.4 Drying for Barreled and Racked Components

3.6 Equipment Cleaning

62. Equipment, e.g. spray guns, needs to be cleaned between application runs. The wastes associated with cleaning include spent solvent, liquid waste from line cleaning, sludges etc., and each waste stream must be appropriately treated prior to discharge into the environment.

3.7 Medical Plastics

63. Processes descriptions include: Ion-beam processing, light-activated surface modification, plasma surface engineering, antimicrobial/antibiotic coatings, and thromboresistant (heparin) coatings. Waste generated will be discussed.

4 IDENTIFICATION OF OPPORTUNITIES FOR WASTE AVOIDANCE

4.1 Waste Avoidance and Minimization – General Considerations

64. Short summaries of process-specific Pollution Prevention and Waste Minimization ideas are included in this Section.

4.1.1 Designated Area

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65. This subsection discusses the importance of working in designated areas to minimize impacts on the environment. For example, spray painting must be done in a spray booth for control of emissions of particles and solvents, thus avoiding soil contamination, vegetation damage and fallout on to other objects and surfaces.

66. Where large volumes of corrosive chemicals (eg acids or alkali solutions) are to be used for cleaning the surfaces of metal (eg. steel pickling), this operation must be conducted in an area specifically designed for the processing, and operated to standards adequate to prevent release of the corrosive liquids and to present no hazards to the health of the plant operators. Such a plant should be built to high engineering standards with proper bunding to contain the largest possible spill of corrosive liquid, pumps adequate to return the spilt liquid to storage tanks or waste treatment facilities and adequate ventilation and/or fume extraction equipment to prevent the build up of hazardous or irritating levels of fumes and mist. Equipment in all such treatment facilities should be subject to regular inspection, testing and maintenance regimes.

4.1.2 Empty Containers/Packaging

67. Most well run operations will have instituted sensible regimes for the purchase of raw materials and other necessary operating supplies, and this should optimize the generation of waste packaging and other sundry wastes. On occasions some empty drums, pallets and other heavy packaging materials may be beneficially re-used within the operation. However, the potential for such re-use will be dependant on the specific operations performed by a given plant and site specific considerations.

4.1.3 Pre-cleaning

68. Discussion of alternatives such as use of

mechanical methods instead of chemical degreasing;

alternative solvents for cleaning;

plastic beads for abrasive media stripping; and

initial flushing of equipment dirty solvent before final cleaning with virgin solvent.

4.1.4 Reduction of Drag-Out

69. The volume of liquid lost during drag out is a function of the time taken to remove the item from the bath and the viscosity of the liquid in the bath. In general the slower the article is removed from the bath the more adhering liquid drains back into the bath, and is not lost from the system. Higher bath temperatures also reduce liquid viscosity and assist drainage, and hence decrease drag-out losses.

4.1.5 Acid and Alkaline Wastes

70. General considerations of minimizing acid and alkaline wastes, such as:

recycle/recovery of resources,

improvements in purchasing and inventory procedures to reduce the amount of expired chemicals being dumped,

material substitution (e.g. replacing cyanide process with non-cyanide),

review of the bath life recovery system procedures;

use of DI water for make-up baths, etc.

4.1.6 Acid and Alkaline Wastewater Streams (Rinse Waters)

71. This subsection discusses general considerations for the minimizing of acid and alkaline wastewater streams which include:

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keeping work area clean to prevent spills of concentrated chemicals;

installation of drip trays and splash guards around processing equipment to contain spills and leaks;

regular inspections of plating rack;

drag out reductions;

improving rinsing practice through air/mechanical agitation to improve rinsing efficiency, etc.

4.1.7 Sludges

72. Sludge production is unavoidable in most chemical industry operations, including the surface preparation and coating sectors. Waste sludge usually contains a large volume of entrained liquid, and this significantly increases the weight and volume of the sludge. While the liquid content may be reduced through filtering and/or drying in electric or gas fired drying ovens, these operations are usually expensive, and the degree to which waste sludge volume may be reduced will depend very much on the overall economics of the whole plant operation.4.1.8 Paints, Inks

73. Good practices for minimizing wastes related to paints and ink usages include

minimising overspray and unused coating materials. This is best addressed through good planning of work programs (eg. so far as is possible, dedicating particular equipment to a single type of production activity), maintaining good regimes for the cleaning and maintenance of equipment, and employment of skilled personnel to perform necessary manual functions.

reducing solvent content in coatings. The higher the solids content of a coating solution, the less solvent needs to be removed through evaporation during drying (curing) of the final coat. In the case of solvent based coatings this reduces VOC emissions. For water based coatings less energy will be required for the evaporation.

Comments from Germany: It is stated that "For water based coatings less energy will be required for the evaporation." We question this statement due to the high evaporation enthalpy of water.

use of water-based coatings and powder coatings. If practicable, these techniques will reduce the release of waste VOCs, and since overspray in powder coating systems is re-usable, and only water is released during curing of water based coatings, overall waste generation should be substantially reduced.

4.1.9 Water Conservation

74. Specific suggestions for conservation of water usage include the use of solenoid valves and timers on rinse tanks, pressure regulators on incoming water pipes and the use of counter-current series reaction and rinsing systems. A properly designed and maintained plant should incorporate these engineering measures, all of which if properly serviced and maintained should help avoid loss of expensive chemical reagents and make up water.

75. Most industrial plants are periodically washed down to remove dust, grit and other small foreign matter from the equipment and work areas. The wash water is normally discharged to metropolitan sewers or, in larger facilities to on site waste treatment plants. A careful study of the wash down procedures may result in a reduction in the frequency of these wash downs, and the volume of wash water used.

Comments from Germany: The second sentence of this para states: " The wash water is normally discharged to metropolitan sewers or,…. This is not environmental sound for galvanic processes. Especially for metal containing wash waters a pre treatment is necessary

4.1.10 Improving Existing Process Conditions and Practices

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76. To properly understand the waste issues associated with a particular facility a full waste audit must be undertaken. Determination of the waste flow and material balance for each operation should be completed, and subsequent evaluation of the audit results may then indicate areas of greatest cost or environmental impact. Appreciation of these results should indicate processing areas or techniques with potential for improvement.

77. To develop a waste reduction program the specific details of location, volume and concentration of each waste stream; the labour and activities associated with the collection and segregation of the waste stream; any testing or quality imposed requirements; and costs for disposal are required. The options offered by alternative processes to minimise the waste generation volume and prevent health and safety hazards and the economic risks should be evaluated.

4.1.11 Segregation of Waste at Source

78. Wastes with different chemical natures should be kept separated unless deliberately mixed to achieve an intended and well defined final outcome. For example it may be sensible to mix an acidic waste containing dissolved iron from a steel pickling operation with an alkaline waste from another operation in order to neutralise both the acid and alkali and precipitate an iron hydroxide sludge. However it would be irresponsible to mix an acidic waste stream with a waste stream containing cyanide (eg. certain waste electroplating solutions) with a waste acid stream, since this has potential to release highly toxic hydrogen cyanide gas. The design of plants using highly corrosive or potentially toxic reagents should be such that there is no possibility for the unintentional accidental mixing of “incompatible” reagents or waste streams.

4.2 Dealing with Surface Preparation Wastes

4.2.1 Abrasive Blasting Wastes

79. Abrasive blasting has progressed from the use of primarily ungraded high silica sands used in outdoor operations to the current technologies which utilise internally operated self-extracting equipment and recyclable low silica materials. The current trend is to efficiently collect the spent blast material. Separation of contaminants from the spent grit will likely give rise to small quantities of metal oxides from the surface metal, and polymer pieces including metals possibly associated with the pigments (e.g. copper, chromium, cadmium, lead) within the coatings. These materials should be segregated from the environment and typically disposed of into a licensed containment facility.

80. All blasting material purchased by the operator is eventually converted to a waste product. Increased the re-use of the abrasive medium will save direct expenditure and lower the cost of disposal. Waste re-use practices for the higher cost abrasive grits may be economically practical (multi-use blasting) but for cheaper raw materials, re-use as a raw material in an alternative manufacturing process is a good option to reduce the volume of used medium which would otherwise have to be sent to landfill.

81. Particle size and coating contamination will determine the potential for re-use. Depending on the level and type of any contamination of the spent blasting medium, it may be possible to blend this material into road base, other construction materials, packing sands, soil additives, or other blends suitable for cement and glass manufacture, etc.

4.2.2 Halogenated de-greasing Wastes

Comments from Germany: The installations described in this section destined for the use of chlorinated solvents seems to be open, eventually with a unit for condensation. Such installations should not be used because they emit relevant amounts of chlorinated solvents. See the description of BAT in Annex II.

82. Solvent degreasers are designed to remove hydrocarbon contamination from the surface of metals thus producing a dry hydrocarbon free surface ready for coating. Dissolved and suspended hydrocarbon contaminants leave the work piece with the condensing solvent collected in the sump of the degreaser. Water vapour is also collected within the condensate.

83. The chlorinated solvents are continually evaporated from the collection sump area at rates compatible with the condensation capacity in the upper sections of the equipment; and therefore solvent loss should be low. Control of the work entering and exiting the vapour zone should not overly disturb the area otherwise solvent

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loss will be high. Ventilation extraction with further condensation of the air flow around the vapour degreaser may be appropriate for the further recovery of fugitive solvent emissions.

84. De-sludging and dewatering of the collected non-volatile hydrocarbons, water and dirt must be completed on a regular basis, and each stream should be segregated if further treatment off-site is to occur. Distillation of the recovered hydrocarbon waste may be undertaken on site to recover the chlorinated hydrocarbon from the oil/water and residue material. Separated liquid fractions may then be recovered for appropriate downstream re-use activities where available (hydrocarbons to energy recovery, waste waters to biological treatment). The segregation of chlorinated hydrocarbons from non-chlorinated hydrocarbons will allow the re-use of chlorinates on site and for the non-chlorinated hydrocarbons the option for energy recovery in approved burner applications.

85. Waste streams associated with de-greasing are unlikely to contain high levels of heavy metal contamination.

4.2.3 Chemical Cleaners and Specialist Pre-coats Wastes

86. In general these solutions are required to be rinsed from the work piece and therefore contaminated rinse water will be the waste stream to be collected and treated. Typically this would be treated for removal of contaminants, and then directed to sewer disposal. Where off-site disposal is required the increased cost will offer distinct economic impetus for minimising waste generation. Reduction in volumes of treated materials indicates a maximising of the chemical use, and therefore a reduction in raw material expenditure. Drag-out from dip and spray application areas will contaminate the rinse water tanks, and so any reduction in drag-out losses or other losses of liquids will reduce the overall liquid waste volume.

87. Reduction of rinse water volume may also reduce the energy required to dry the parts prior to coating application, as well as reduce the contamination and therefore the frequency of replenishment.

88. Recovery of pre-coat formulations is most unlikely and therefore lower volume usage will generate savings for waste disposal.

4.3 Dealing with Coating Application Wastes

89. As final coatings are expensive it is important from the economic perspective to minimise losses. Indirect savings may also be obtained through evaluation of the total coating process, and a single coating type utilising a simple solvent system may have advantages for materials re-use or recovery over more complex systems. The use of alternative coating types with similar performance should be reviewed with respect to the possible savings through waste minimization and waste treatment cost reduction, energy requirements, or environmental emissions. Each individual processing step has associated has direct and indirect costs, and evaluation of the most cost effective overall process will require significant consideration of all alternative process options.

90. Wastes generated from solvent based coating are likely to be flammable, and hence present potential fire hazards in the workplace. An appropriate system of labelling, separation and recording is required.

4.3.1 Dip and Flow coating

91. Drag out reduction techniques are the most significant areas of waste generation and correspondingly the minimization activities. Where wastes are generated the appropriate collection and segregation techniques that minimise any additional materials requiring disposal is important for economic disposal. Air emissions from open vessels may be substantial if volatile solvents are used. These may also create health and safety hazards in the workplace if not carefully managed.

92. Wastes are likely to be heavy sludges of uncured coatings. Reformulation is not often practicable and best practice disposal will include energy recovery activities in appropriate industrial burners such as cement kilns or purpose built incinerators.

4.3.2 Electro-deposition and Anodising

93. Heavy metal contamination and strong acid/alkali levels in the waste stream will give rise to increased treatment costs. Recovery and re-use options for heavy metal sludges are few, and in general heavy metal waste treatments are not specifically differentiated. A shift to lower toxicity formulations will benefit workers and the environment.

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94. Acid solutions produced must be neutralized to precipitate dissolved metals from solution. Where available spent caustic solution should be utilised if the precipitated sludge can be safely and economically handled, otherwise the appropriate waste disposal option is off-site treatment.

4.3.3 Spray Application

95. High transfer efficiency spray equipment is commonly available and should be used. High solids electrostatic coatings are also commonly available. These coating technologies reduce the VOC laden air discharged and also minimise the waste sludge collected in spray booths, and the subsequent necessity to change dry filter medium when used in the spray booth. Excessive overspray of coatings must be avoided to save raw material and disposal costs, while colour changes and gun washouts should be minimised through appropriate production planning.

4.3.4 Electrostatic Powder Coats

96. Very efficient transfer efficiencies are generally observed, but effective capture of overspray may improve the cost effectiveness. However, colour changes should be minimised between successive runs, while recovery of powders and re-use activities may reduce the cost of the application.

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4.3.5 Roller Application

97. Colour and coating changes should be minimised and where possible the use of darker coatings in a multi-component coating operation should be progressively used. Running lighter coatings between heavier and darker coatings should be avoided.

98. Wastes are generated from coating changes and roller clean-ups. High efficiency automatic roller washers can be employed to reduce health and safety issues. The wash solvent should be carefully chosen, so as to maximise potential for re-use. In-house recovery operations may also be cost effective, with only high molecular weight polymers or solid resins constituting the final waste streams.

4.4 Dealing with Curing Wastes

99. Since the major wastes generated during curing of the coatings are emissions of VOC solvents used in the coating, final choice for this coating method should be only after careful consideration of all alternative methods. Greenhouse gas generation and photochemical smog issues should be considered when deciding between different coating technologies. Stationary source emissions may play a significant role in the formation of photochemical smog and for this reason must be minimized by regulation.

100.Recovery operations for the VOC solvents may be economic in some circumstances, although where the emission of VOC is in excess of legislative limits, discharge treatment may be required by regulations. In descending order of merit, the recovery options should be

recovery for on-site use,

recovery for off-site use,

energy recovery,

incineration or disposal by other means.

4.4.1 Product Finishing

101.Following curing, on occasion application of wax or cleaning solvents to a surface coated area is undertaken, and this may generate rub down rags that need disposal, and may also lead to VOC emissions. Buffing of surface coatings to smooth the surface area may also generate a particulate stream that may be either air or water borne. Minimization of fugitive emissions should be a goal with the efficient collection and further recovery/disposal options evaluated for environmental impact.

4.5 Alternative Processes: Surface Preparation

102.In these sections, advances in alternative surface finishing processes and coatings, and limitations and economic consideration are presented. Most of the alternative surface finishing processes/techniques discussed here can result in substantial reductions in discharges compared to traditional processes. (EPA, 2000)

4.5.1 Alternative Stripping Processes

4.5.2 Alterntive Pickling and Descaling

4.5.3 Alternative Etching

4.5.4 Alternative Cleaning Equipment

4.5.5 Alternative Cleaning

4.6 Alternative Surface Finishing Process & Coating Techniques

4.6.1 Alternative Anodizing

103.Discusses alternatives to chromic acid anodizing

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4.6.2 Organic Coatings

104.Discusses alternatives to electroplating

4.6.3 Alternative Vapour Deposition

105.Process such as Chemical vapor deposition (CVD) can produce a variety of high-density, high-strength and high-purity coatings.

4.6.4 Thermal Spray

4.6.5 Hardfacing

4.6.6 Porcelain Enameling

4.6.7 Metal Cladding and Bonding

4.6.8 UV and electron beam technology

4.7 Alternative Solvents

106.Discusses alternative low VOC solvents

4.8 Coating Alternatives Guide: CAGE Expert System (U.S. EPA)

107.The Coatings Alternatives Guide (CAGE) offers coatings users a compliance assistance tool to aid identification of compliant coating options for their coating processes.

5 IDENTIFICATION OF OPPORTUNITIES FOR RECOVERY

5.1 Recovery of Solids

108.Discusses technology used to recover dusts (metal, etc), e.g. use of a cyclone separator.

5.2 Recovery and purification of Process Solution

5.2.1 Diffusion Dialysis

5.2.2 Microfiltration

5.2.3 Membrane Electrolysis

5.2.4 Acid (Resin) Sorption

5.2.5 Electrowinning

5.2.6 Other Technologies

5.3 Recovery of Concentrate or Rinse Purification

5.3.1 Reverse Osmosis

109.To recover metal salts and organic solutes

5.3.2 Electrodialysis

110.To recover metal ions from rinsewater

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5.3.3 Ion Exchange

111.To recover metal ions from rinsewater

5.3.4 Vacuum Evaporation

112.To recover plating chemicals from rinsewater

5.3.5 Atmospheric Evaporation

5.3.6 Other Technologies

5.4 Recycling of Spent Solvents

5.4.1 On-site Recycling

113.Discussion of common methods of on-site recycling of used solvents (settling, filtering and distilling)

5.4.2 Off-site Recycling

114.Discussion of methods of proper handling of waste solvents such as toluene and xylene for off-site recycling.

6 WASTE TREATMENT AND DISPOSAL TECHNOLOGIES

115.Industrial waste management techniques operated by the private sector, are in general, designed and operated to a minimum standard to allow for lowest process costs. Traditionally wastes have been treated to meet the acceptance criteria for disposal to landfill or discharged into sewer systems. These disposal options are now regarded as unacceptable, and with the development of the principle of intergenerational equity will ensure the trend away from these techniques is continued.

116.The generation of significantly reduced waste volumes or the transformation of wastes into usable by-products is increasingly required by regulators, and being adopted by industry through Industry Codes of Practice. However, implementing higher order treatment technologies (beyond landfill and sewer disposal) may add considerable cost to the overall manufacturing activity.

117.Activities within the surface coating industry pose difficult treatment problems due to the manner in which the industry undertakes its production processes, and because of the diverse nature of the waste streams. The volumes and variety of waste streams makes for a complex waste management regime on most individual sites.

118.The following are guidance notes for actions.

Where an on-site waste treatment activity is developed it is important to approach the treatment activity as a production operation, with all raw materials stored under appropriate conditions (Dangerous Goods and Hazardous Substances), intermediates processed immediately; and all activities planned to fit the production requirements.

Where off-site treatment is required the selection of the waste disposer and therefore the treatment activity is the responsibility of the waste producer. The treatment process to be employed should be understood by the waste producer, who should receive an undertaking from the disposer that the contaminant concentrations in the waste stream will be treated to appropriate levels using techniques acceptable to both parties. A Certificate of Destruction for the waste material is commonly issued by responsible treatment operators.

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6.1 Aqueous liquids

119.Pre-treatment coating activities will generate acid, alkali and other contaminated rinse waters, and/or water/oil emulsions depending on the process. Water borne coating washes may also contain hydrophilic resin materials, water miscible solvents and other organics such as resin polymers, and may also contain insoluble sludges. A great range of chemical compounds are used in the industry, and therefore recovery options from the aqueous waste streams may be limited.

120.Soluble metal components within low pH solutions from cleaning activities restrict disposal options and alternate recovery operations involving the concentration of acids are problematic (costly) from a process viewpoint. The most straightforward method for removing heavy metals from aqueous waste streams and overcoming the pH issue is through neutralization and precipitation. Raising the solution pH with a suitable base (eg. Lime, caustic or soda ash) will precipitate a metal hydroxide sludge, which is subsequently dewatered and may possibly require stabilisation within cement or other inorganic matrix prior to landfill disposal. Disposal to sewer of the filtrate is usually via a multi-step waste water treatment plant. Knowledge of the limiting contaminant levels for acceptance to the treatment plant or sewer should indicate the treatment activity.

121.When evaluating the off-site treatment options the associated costs include a significant component for transport. The addition of excess water to the mixture will increase this cost and therefore must be avoided.

122.Where organics are present in solution the contaminant mix must be analysed with respect to use as an additive to composting or green waste treatment processes. Nitrogen, potassium and phosphorus are beneficial to these processes. Inclusion of heavy metals and sodium to these processes must however be avoided.

6.1.1 Rinsing waters

123.Where possible the most effective treatment of rinse solutions is undertaken on the site of generation where the chemistry of the solution is best understood.

124.The chemical composition of the rinse waters should be ascertained in detail to select the most appropriate treatment and/or recovery method. Rinse waters from coating operations will in general contain only low levels of heavy metal contamination, and after appropriate adjustment of pH and, if necessary, removal of suspended solids may be re-used for rinsing, or other appropriate wash down, raw material or cleaning activities within a plant.

125.Water re-use must be carefully controlled, with batch tracking and quality testing. Options for on site re-use of rinse water should be carefully investigated for their potential for reducing overall plant effluent volume. As mentioned above the use of quality controlled rinse waters for green waste or for horticultural activities for rinse waters may be a viable and beneficial option in some circumstances.

126.Where off site treatment of the effluent is the preferred option, it may be advantageous to reduce the volume requiring treatment through processes such as ion exchange, reverse osmosis, ultrafiltration, with re-use of most of the processed water. However, these concentration techniques are often expensive to operate and implementation of this strategy would be dependant on the results of a rigorous cost benefit analysis.

6.1.2 Acid and Alkali Solutions

127.As with rinse and washwaters, treatment of waste acidic and basic solutions should be simplest at the site of generation. High strength acid and basic solutions should be used in the production process until the plant quality system deems otherwise, and then batch neutralized and where necessary further treated to allow for reuse or discharge from the plant. Batch activities minimise the potential for cross contamination but may be too small for separate treatment activities.

128.Neutralisation is generally a simple process, but requires installation of appropriately sized and constructed dosing, mixing and precipitate separation equipment. Specific training of staff in the activity is required as the neutralization may generate hot solutions, or have other associated hazards. Extra labour may be required to operate and maintain dosing pumps, reagent levels and monitor/control any solids/liquids separations in the process.

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129.Products of the neutralization will be a solid or sludge and a neutral or slightly basic liquid. In some instances the solid (or sludge) residue may contain valuble components which may be marketable as raw materials for other industrial processes. The suspended solids are required to be filtered from the solution prior to solid or liquid disposal. Re-use options for the solid or filtered liquor may depend on the choice of neutralizing agent.

130.As with the treatment of rinse water, when off-site treatment is deemed appropriate minimization of the volume will reduce transport and treatment economics and a pre-concentration stage may be advantageous.

6.1.3 Water based coatings

131.Water based coatings have become an alternative to solvent based coatings as a result of VOC reduction requirements by regulators. Replacement of the volatile solvents does require more energy for the curing of these coatings but VOC emissions are dramatically reduced. The recovery of these coatings is impractical and residues are generally considered waste materials requiring off-site disposal.

132.Waste uncured coatings and equipment requiring cleaning may be washed clean in water, but this typically creates large volumes of wastewater. These solutions are generally unacceptable for sewer discharge. Solids separated are recovered as a wet sludge, which may be mixed into cement dust or other suitable solidification medium, allowed to air cure and set. The cured stabilised mass is directed to specialised landfill for disposal. Solidification does not bind the organic matter well and is likely to leach from the mass within the landfill. Leachate contamination over time would be expected within the landfill and therefore specialised controls for leachate collection and treatment are imposed. The alternate mechanism to degradation within the landfill is via microbial degradation that will generate methane or other greenhouse gases over time.

133.The above issues make on-site treatment of waste water-based coatings difficult and in general these materials require off-site treatment within established treatment programs. The disposal options are simplified where the residues are non-flammable.

134.The most appropriate off-site treatment method for water based coating wastes is as an addition to a multi-component Waste-to-Energy operation. The sludge and coating liquids would in general be collected manually or mechanically without dilution with water and will therefore have sufficient organic content to sustain combustion when blended with fuels or other high organic content waste. Their inclusion in such a program must however add value to the program.

135.Waste-to-Energy operations are an alternative solution that should offer reduced treatment costs and added environmental value for water based coating wastes. This is covered in greater detail in the next section as per organic wastes.

6.2 Solvent-Based Wastes

136.The separation of the hydrocarbon solvent from solvent based coating wastes via distillation will after condensation of the gas phase result in high purity low boiling point solvent compounds and semi-solid or solid residues. Distillation residues will include heavy metal pigments and the resin and additive formulations. The resin material will set to a solid when cooled unless re dissolved within a suitable hydrocarbon. Residues suspended or dissolved in oil or other recovered solvent may be used as a waste derived fuel in approved burner installations. Where distillation residues are solidified and a solid or liquid fuel program is unavailable; the landfill option is an alternative as a final disposal option. Solvents separated in this fashion may be further refined to high quality raw materials or used as general purpose thinners and cleaning solvents. These materials are generally flammable and carry a Dangerous Goods classification; therefore the re-use must be carefully controlled from a safety perspective.

Comments from Germany: From our point of view the possible use of a landfill is no environmental sound method. The alternative to be used is the hazardous waste incineration, not the landfill. In most cases a regeneration of organic solvent is technical possible and economical acceptable..

6.2.1 Non-halogenated solvents

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137.Both recovery and disposal options are available for non-halogenated surface coating solvent based wastes. Any treatment though is relatively expensive due to the flammability of the materials.

138.On-site distillation may be a viable option but capital expenditure for equipment is high due to the safety and environmental control requirements. The long term continual use of solvents, or high volume usage and potential for economic solvent recycling are critical business issues which should be well understood before committing to operation of a stand alone site treatment unit. Consequently, prior to a decision to build an on-site dedicated plant for solvent recovery, a cost benefit analysis should be undertaken to ensure sustainability from an operational and economic perspective. In respect of this, factors to be considered include:

the volume of waste solutions generated;

applicable waste minimisation techniques;

personnel skill levels available to sustain quality finished products from recovery operations;

cost and quality of replacement solvent; and

all safety and management issues associated with on-site re-processing.

139.Off-site treatment options are recovery via distillation, disposal via waste-to-energy programs or direct incineration of the flammable coating wastes. Distilled product may be of acceptable quality for reformulation or down-graded to a simple wash solvent used for cleaning and therefore demands a relatively high resale value.

140.Destruction of the solvent in a dedicated incineration unit is a high cost activity that usually has little benefit other than raising steam; whereas a Waste-to Energy program will use the high energy waste as a substitute for non-renewable and often costly fossil fuel use. Energy, greenhouse gas and economic benefits stem from the latter option. A Waste-to-Energy program will utilise existing off-site combustion infrastructure and will require only slight increases in maintenance and operational costs if developed and managed appropriately. For this reason this option has economic advantages for waste disposal that should be reflected in reduced cost for the waste producer.

141.A successful solvent based waste treatment activity will be based on an end product quality management system. The distilled or blended product specification in the respective case will limit the raw materials combined as feedstock for the process. The flexibility offered by the proposed solvent waste stream for the recovery program should also influence the cost for treatment. That is, a relatively uncontaminated solvent stream will be used as diluent stock for either distillation or Waste-to Energy/incineration operations in allowing a greater proportion of more heavily contaminated waste (higher cost items) into the respective program.

6.2.2 Chlorinated Hydrocarbon Cleaning Solvent

142.Recovery of chlorinated cleaning solvent (vapour degreaser solution) is a simple activity, and should ideally be undertaken as a unit operation at the degreasing facility. In general only a relatively small distillation unit will be required to recover solvent from the oily waste stream from the de-greaser units, and this would normally be operated on batches of used de-greasing fluid. The boiling and subsequent condensation of the degreasing solvent will allow the recovered solvent to be returned to the degreasing process, possibly after addition of stabilising chemicals. Residue that has been stripped of the chlorinated solvent can be blended with waste oil or other waste hydrocarbon liquid and supplied to a Waste-to-Energy recovery program if the halogenated level is low.

143.Filtered solids (where collected) may in turn be solvent washed, dried and be included as inert solids in acceptable applications from soil additives to landfill as approved by the regulators. A recovery program for off-site treatment and return for re-use can also be an economic alternative when compared with the purchase of virgin material.

6.2.3 Mixed VOC Solvent Wastes

144.Coating solvents are typically multi-component mixture that offers application, curing or commercial advantages over an alternate system, and this may complicate or prevent the recycling of recovered solvent. To

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gain the most advantage from a waste recovery method a clear understanding of the system requirements must be obtained.

145.Wash down solvents or condensed solvents from a drying or curing activity may be re-used as a mixture in subsequent maintenance cleaning or solvent top up operations if the appropriate formulation is recovered. Where the formulation is deficient (usually in the most volatile components) the addition of a proportion of the volatile solvent will ensure appropriate re-use performance.

146.Low molecular weight solvents such as acetone and ethyl acetate may be required to be added to boost the solvency in some cases. The recovered and topped up solvent can be used as a replacement solvent during coating application rather than a gun wash or roller cleaning and maintenance solvent.

147.To optimise recovery options, wastes from different coating formulations should be kept segregated and treated separately.

148.Where the solvent recovery by distillation is not a viable economic option (eg. mixed high boiling point solvent stream) the waste volume should be minimised and kept free of other contaminants to increase potential for re-use (downgrading of coating application) and reduce disposal costs. Mixed and complex wastes may be best suited to disposal in a Waste-to-Energy program.

149.In a program that supplies liquid or solid fuel to a large industrial burner such as a cement kiln, or a coal/oil fired power station, the calorific value within the waste is consumed and supplements the energy normally supplied by non-renewable fossil fuels. In general the minor contaminants associated with the coating pigments do not adversely effect the production of cement, steel or other production process but must be managed as a raw material supply to the process to prevent quality, health and safety, or environmental problems. A supply of fuel from coatings waste blended with other waste hydrocarbons has been successfully employed in many countries including Australia, Belgium, Canada, France, Germany, Japan, Korea, Norway, Thailand, UK, USA, and others.

150.Mixed hydrocarbon solutions and solids are processed to fuels in purpose built facilities that are tolerant to relatively high levels of water within the fuel. Water based coatings are readily included with other oils, solvent based paints and organic liquids and used as an economic replacement fuel. Contamination of coating wastes by halogenated organics must be avoided. Combustion processes will have a low level of acceptance (between 1 and 3%) for halogenated contaminants within the fuel because of the process problems and products of incomplete combustion eg. dioxins/furans and acid gas formation.

151.Energy recovery operations should be considered where the cross contamination of the recovered waste streams does not allow the direct recycling of the waste to the original use. It is a higher value adding activity than incineration and landfill disposal options.

152.High temperature incineration (plasma arc) and dechlorination techniques are often the only solution for disposal of high concentration halogenated waste stream. This option is limited and in general expensive. These wastes are more commonly being restricted from landfill and waste generators are looking to other options such as microbial degradation for halogenated waste treatment. These activities require specialist management skills but are likely to become more commonly available in the future.

6.2.4 Mixed Hydrocarbon and Aqueous Solutions

153.Separation of the aqueous and hydrocarbon fractions by gravity or via mechanical (centrifuge) and/or chemical methods should be sufficient to separate mixed components. Soluble organics such as alcohols, ketones and acetate materials may meet the acceptance criteria in an off-site waste to energy program or as above for VOC contaminated rinse waters within green waste treatments. It is practical to include materials with calorific values as low as 10 MJ/kg in a managed Waste-to-Energy program without detriment to the overall product.

6.3 Specific Wastewater Treatment Technologies

6.3.1 Alkaline Chlorination

154.This technique is often used to oxidise toxic cyanide (CN-) in a waste stream to less toxic cyanate(CNO-). Chlorine gas or hypochlorite (OCl-) are the oxidising agents. Although the waste stream will be depleted in toxic cyanide, it will still contain dissolved solids which may need to be removed prior to discharge.

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Metal cyanide solutions are often used in electroplating operations (eg. silver and nickel plating), and electroplating plants are most likely to use this technique.

6.3.2 Electrolytic Destruction

155.In this technique, oxidation of toxic contaminants is accomplished at the anode of a specially designed electrochemical cell, and is used primarily for removal of certain organic contaminants and cyanides. The design of the electrochemical cell is such that the anode area (where the oxidation actually takes place) is made as large as possible so as to maximise the contact between the electrode and solution.

156.This technique is not universally applicable, and should be thoroughly tested on the waste stream before it is implemented. Capital costs are likely to be large, and it is likely that this technique would be used only by large coating plants.

6.3.3 High-pressure and high-temperature hydrolysis

157.Because of the extreme operating conditions employed, this technique is potentially capable of destruction of a wide range of organic contaminants, including polymers commonly used in the coating industry. However, it is expensive and likely to be used only by large plants.

6.3.4 Chromium Reduction

158.To reduce hexavalent chrome to trivalent chrome. This is commonly performed by addition of ferrous sulphate solution to the waste chromate solution.

6.3.5 Neutralization and Hydroxide Precipitation

159.To neutralize acidic effluents generated during acid cleaning/rinses and plating rinses; and to precipitate metals trivalent chrome, phosphates

6.3.6 Sedimentation

160.To remove suspended solids (generated from hydroxide precipitation). This is performed in specially designed sedimentation tanks or thickeners. Larger particles tend to settle more quickly than small ones in the settling tanks, and often special proprietary polymers called flocculants are added to the waste stream to coagulate the small suspended particles into larger “flocks”, which have a higher sedimentation velocity. This technique usually produces a clear overflow solution which may be reused in the plant, or if necessary sent for further treatment prior to discharge, and a sludge which would normally be placed into a landfill.

6.4 Solid Hydrocarbon Coatings

161.Solid coating wastes may be a variable mixture of flammable and sludgy materials separated from solution due to sedimentation in storage; coatings that have “set” during exposure to the atmosphere or over time/heat; and process bath sludges. All are difficult to handle due to the volatile and odorous nature of emissions and require specialised equipment to decant, process and treat.

162.In general the solid waste is out dated chemical mixes, or a combination of many materials and recovery as a raw material is not practicable. Recovery in liquid Waste-to-Energy programs requires high volumes of solvents to liquefy the solids and specialised handling and firing systems. Where available the wastes are best utilised in solid energy recovery programs that blend and shred the materials to the appropriate size. Only a limited number of these programs exist and most often landfill disposal is the only available commercial option.

163.Collection in drums is the most common scenario for ease of storage and handling. Disposal to landfill for most of these wastes is not safe due to flammability issues and the materials are required to be distilled in specialized equipment or autoclaved in drums to remove the flammable component prior to landfill disposal.

164.The phasing out of organic sludges and similar materials from landfill is a desired outcome for many communities and regulators but the alternatives are only as above and require significant management and specialised equipment. Avoiding of the generation of these wastes is a high priority.

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6.5 Control of Air Emissions

6.5.1 Particulate Matter (PM)

165.Sources of PM and air pollution control technology that can capture PM such as cyclone and dust collectors, filters, and mist eliminators.

6.5.2 Solvent Vapour, VOCs

166.Technologies to treat or capture solvent emissions such as afterburners, wet scrubbers, etc.

6.5.3 Stacks for spray painting and coating

167.Discusses requirements for stack height, discharge velocity, etc.

6.6 Hazardous Waste Disposal options

6.6.1 On-site Disposal: Solvent-based Cleaner

6.6.2 On-site Disposal: Paint Removal

6.6.3 Off-site Disposal

168.Options for off-site disposal of sludge and dust collected by filters

6.7 Monitoring of multimedia emissions (air, water, solid wastes)

169.Short review of monitoring techniques in the appropriate medium

7 ECONOMIC ASPECTS OF SUITABLE WASTE MANAGEMENT OPTIONS

170.The management of waste at a surface coating plant should be regarded as an essential part of the manufacturing process. The appropriate management can dramatically increase the business profitability through savings in waste minimization. Waste generation consumes raw materials, energy, machine time and labour, and attracts direct costs in disposal or treatment and transport. All costs associated with waste generation and the capital and operating costs associated with waste treatment must be viewed as unavoidable components of overall production costs, and these costs factored into final product sale price. Given this motivation, thoughtful process design and constant management will minimise the generation of waste.

7.1 Pre-treatment Evaluation

171.These activities are the basis for the longevity of the surface coating in final service. Inappropriate pre-treatment will shorten the life of the component and final product. The application method must maximise the chemical use but minimise product failure due to poor substrate preparation. An efficient, economic and accurate method for determining the pre-treatment solution quality must be established and regularly applied to ensure valuable pre-treatment solution is not directed to waste streams.

172.Effective collection and segregation of the individual waste streams is the key to minimizing waste management costs in this area. Keeping cross contamination to a minimum increases the possible re-use as an alternate raw material and offers best opportunity for recycling on site.

173.Chromate based pre-coats have traditionally been used in production of cars and trucks etc., but concerns centred around the toxicity of chromium have lead to adoption of alternative formulations. The current alternatives do not have the performance of the chromate based pre-coats and effectively shorten the life of the part, but are environmentally more acceptable.

174.Aqueous solution disposal costs in an off-site treatment facility are generally more expensive than the costs for pre-treatment followed by on-site discharge to the sewer system.

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7.2 Coating Application Waste Evaluation

175.Coating alternatives are many and varied. The choice of the coating system is often influenced by the existing equipment, capital expenditure restrictions and the need to utilise existing systems. Improvements may be made in sourcing more efficient transfer equipment but there may be other issues that effect the economics of the coating system.

176.High solvent coatings and coatings requiring high heat curing actions will become increasingly less attractive due to energy associated greenhouse and VOC emissions and should be reviewed with the intent to replacement when practicable.

177.Collection and re-use of coating wastes are issues that should influence the selection of the type of coatings and the management of the production at a facility.

178.Segregation of the component materials is extremely important to enable the re-use for energy recovery systems where available. The cost of segregated materials in appropriate vessels for storage and transport is likely to reduce the cost of waste treatment. Long term waste recovery processes may utilise returnable transport/storage vessels to reduce handling, warehousing and packaging waste generation.

7.3 Product Finishing Waste Evaluation

179.Rub-down rags and buffing waste solids, contaminated by solvents, are generally disposed of to landfill. The solvent rags should be autoclaved prior to disposal to remove any flammability. Laundering of these materials is more expensive but is economically available if landfill costs are high or the waste is excluded from landfill. Energy recovery is possible but may also require shredding or sizing in addition to emission controls.

8 CRITERIA FOR THE SOUND OPERATION OF TECHNOLOGY AND SAFETY

8.1 Generators’ Responsibilities

180.As stated above, waste management activities should be undertaken as an integral part of the production process. All associated waste activities should be understood, tracked, recorded and reported. Activities should be written up as Standard Operating Procedures and Risk Management assessments should be completed in a systematic manner.

181.Off-site transporters and disposal facility operators will require the same information as employees handling the wastes. The waste disposer will require a more rigorous tracking system for received and processed materials because of the complexities of receiving wastes from a multitude of sources.

182.Best practice activities start with the accurate description of the waste. The best method of description is in the form of a standard Material Safety Data Sheet (MSDS). This document may be developed from the relevant MSDS information for the waste component ingredients.

183.Waste materials must be evaluated with regard to the Dangerous Goods and Hazardous Substances requirements. Many coating raw materials and pre-coat materials are classified as either or both under most regulations, and these regulatory requirements will apply to the wastes generated from these materials.

184.On-site storage and handling requirements will be required for those materials destined for off-site treatment activities. Every package must be labelled at source by employees who understand the handling requirements, before the material leaves the production area. Bulk materials should be stored in placarded tanks.

185.To simplify all downstream activities the segregation of the waste must be a high priority. Unlike materials or contaminants should not be combined. By keeping the waste mixture as simple as possible, identification and handling will be made easier and downstream recycling potential will be maximised.

186.Potential value-adding programs for waste materials should be sourced by the waste generator to ensure a minimum liability for any treatment option. When wastes are re-used in another process this may remove the waste liability from the generator but any recycling activity must be quality controlled and acknowledged by local authorities as a viable and sustainable activity.

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187.Collection and storage of waste materials can be done most efficiently and effectively if the waste disposal operation has been identified and its limitations acknowledged. For example, if the disposal facility only accepts liquids, it will be very important to segregate liquid and solid wastes. Full knowledge of the disposal operation will also reduce the liability that is the responsibility of the waste generator.

188.Labelling of tanks and vessels; and particularly packages for storage, is essential; and should reflect the standard DG format including the following information:

Dangerous Goods Class diamond (where appropriate);

The material common name;

Waste generator name;

Waste generator contact details;

UN #, HAZCHEM Code, Packaging Group;

Drum identification reference number (Regulatory tracking document number if used);

Safety & Risk Messages (PPE);

Spill, Leak and Disposal Information; and

Fire Information.

189.It is advisable to have pre-printed labels available in the waste generation area is advisable.

190.The cradle to grave reporting system requirements should indicate the generator authorizing the transporters and the disposer for their respective actions. The waste generator authorises the disposal activity but remains responsible for the subsequent disposal of the waste. Waste transport and waste disposal activities should be well understood by the waste generator to ensure the liability of the waste is minimised through the best practicable treatment and recovery or disposal techniques.

191.The waste generator is responsible for:

the generation of a Material Safety Data Sheet for the waste material;

the description of the waste;

the selection of the appropriate storage and transport containers;

the labelling of the packages and containers; and

the subsequent treatment re-use or disposal of the waste.

192.Records of off-site transfers should be accurately kept by the generator and referenced to the process so that the true operational cost can be allocated.

8.2 Collection & Storage Responsibilities

193.Coating wastes should be collected in good quality 205L drums approved by the local Dangerous Goods authorities. This will allow safe storage, and transport for off-site treatment.

194.The collected waste materials will be a by-product or combination of the process raw materials and/or products. Each raw material supplied to a workplace must have available a Material Safety Data Sheet (MSDS) from the manufacturer or supplier of the material. All MSDSs must be available in the workplace. The information within these documents will indicate to the waste generator the requirements for subsequent

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handling, storage, labelling and waste disposal of the material. It will also allow the storage containers to be properly specified and labelled.

195.Where the MSDS indicates that a raw material is a Dangerous Good or Hazardous Substance the waste should be assumed to be the same. Tanks and storage containers must be labelled in accordance with any associated regulations.

196.Where a waste contains a combination of raw materials, the most stringent requirements for a particular material in the process should, as a minimum, be used for the subsequent waste materials. Toxicity and other hazardous values are unlikely to be available for mixed waste materials; and therefore specifications for worker safety (Personal Protective Equipment) during handling of the waste streams should be set at conservative (or precautionary) levels.

197.Containers must be made using materials that are compatible with all materials and combinations of materials within the waste stream. Relevant information must be made available and passed on to the waste transporters and the waste disposer. Advice from an industrial chemist or toxicologist will confirm any reduced storage and handling requirements.

198.The area for storing packaged wastes should be in a location obvious to all personnel. It should be under cover on hardstand and bunded to prevent possible drainage or soil contamination. Collection of stormwater falling within the waste storage area should be automatic, and runoff should be prevented. The collected water should be treated as contaminated water and treated as waste water. The collected water should not be discharged to the stormwater system.

199.Bulk stored waste materials should be close to the generation area to avoid increased maintenance relating to drains or pipework, but also in a location easily accessible by waste transport vehicles. Bulk storage vessels should be fitted with take-off points to decant the liquid waste stream from above settled solids, and the sludge should be removed through large bore pipework in conical bottomed tanks where required.

200.The generator should have the minimization of waste as a key performance indicator for operators and managers; and offer incentives for savings in waste expenditure. However, the generator should also be aware of the possibility of short cuts being taken in this area, and should operate with random audits as appropriate.

201.In relation to the off-site treatment of wastes the waste generator should request a copy of the operating licence for the waste disposer to ensure that the approved disposal methodology is suitable for the waste materials in question.

202.The waste generator should also request a copy of a Certificate of Destruction from the waste disposer for each delivery of waste material to assure closure of the activity. A site visit to the treatment facility and observation of the destruction activity should be completed before contracting a waste disposal service.

8.3 Transport Responsibilities

203.The transporters of the waste material are responsible for the safe transfer from the generation site to the disposal site. The transporters may be contracted by either party but it is essential that all the information is available for review prior to the movement of the waste.

204.This includes:

an understanding of the waste material and specific safety and handling requirements;

the requirements at the generator site; and

the requirements at the waste disposal site.

205.Where wastes are transported from the site there are also the associated transport and labelling regulations requirements to be met. These will include Dangerous Goods notifications and depending on the regulatory regime the likelihood of waste tracking and reporting requirements. In most circumstances the wastes may only be transferred on approved and permitted/licensed vehicles that carry emergency spill equipment and with drivers suitably trained in emergency contingencies. The permitting of vehicles and drivers is to ensure that the

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operator of the vehicle is fully conversant with the mechanisms of safe handling and tracking of the waste materials. Vehicles also may be required to be fitted with spill trays and collection sumps depending on the regulatory requirements.

206.Most often the generator will report to the regulator the waste type, volume, treatment method and the location of the treatment facility for wastes transported from site. Waste generators should be aware of the service a transporter offers and audit the actions at least annually.

8.4 Disposal Responsibilities

207.Upon arrival at the disposal facility the disposer must only accept the waste for treatment if it is accurately described. The disposer will complete receipt tests to confirm the material and verify the waste generator the acceptance of the material to the disposal program thus closing the loop. The waste disposer is responsible for the safe and environmentally sustainable disposal of the wastes received. The disposer will carry a licence or permit, issued by the regulators, to specifically store and treat the waste materials.

208.A waste disposer will request a representative sample or information sufficient to describe the waste prior to offering a quotation for the treatment. Waste description is aided by the use of codes that are internationally and nationally standardised to allow an initial classification.

209.A comprehensive management and safety system will be employed by the waste disposer to track, treat and report on the associated commercial and environmental activities. This will include environmental monitoring and a system of to record continual improvement at the disposal site.

210.The waste disposer should readily supply the appropriate information in relation to received wastes to the individual waste generators, the regulators and the community within the constraints of confidentiality. Environmental reporting should be open and honest and available for external auditing.

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9 GLOSSARY OF TERMS

Abrasive blastingThe compressed air entrainment of fine particulate to strip extraneous material, via high velocity impact, the surface of metal exposing a clean surface.

AfterburnerA painting process that uses the particle-attracting property of electrostatic charges to reduce overspray

AnodizingA coating process in which a metal part is coated with a film by making the part, the anode, in an electrolytic cell.

BaghouseHigh efficiency particulate collector incorporating long cylindrical bags to separate air streams from the entrained particles.

Bright DippingA metal surface finishing process in which the metal is immersed in a liquid, such as a mixture of sulfuric and nitric acid, to give it a clean, bright surface. The liquid removes oxides and mild scratches.

CAGE Expert System The Coatings Alternatives Guide (CAGE) developed in corporation with U.S. EPA offers coatings users a compliance assistance tool to aid identification of compliant coating options for their coating processes

Chemical conversion coatingCoating of a surface by using a decorative or protective conversion coating material produced by a chemical reaction of the base metal with some other reactant.

CondensationLiquefying of gas phase compounds by contact with a cool surface.

CVD Chemical vapour deposition. Vapor deposition in which heat or a gaseous reduction initiates a chemical reaction of the vapor present, causing its condensation on the substrate.

CuringThe application of heat to evaporate free solvent and heat set or oxidise the coating polymer to a hard thin coating layer.

DGDangerous Goods

De-greasingRemoval of extraneous hydrocarbon and dirt from the surface of the material.

DescalingA process in which scales or metallic oxides are removed from the surface of a metal object, such as a pipe or boiler.

Drag-OutDrag-out" is the plating solution that "clings" to parts as they are removed from a bath. This solution then either ends up dripping onto the floor or mixing into the next bath or rinse.

Electrocleaning Electrolytic cleaning employs DC current and a specially formulated electrolyte to descale a surface by continuous oxidation and reduction at the surface.

ElectrodepositionThe depositing of a metal to a surface by the application of electric current through a solution of the metal.

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Electroless platingElectroless plating is a chemical reduction process which depends upon the catalyticreduction process of metal (nickel or copper) ions in an aqueous solution (containing a chemical reducing agent) and the subsequent deposition of nickel metal without the use of electrical energy.

Electrolytic Activating (electrolytic degreasing)Electrolytic activation is used to remove the rest of unwanted residues from the surface after surface pickling. The basic composition of the solution is similar to alkaline degreasers. Wetting agents are left out to prevent foaming, however, cyanides or other complexing agents may be added to improve the activation of steel items. For normal applications, cyanide and chelator free electrolytes are sufficient.

Electrolytic ColouringElectrolytic colouring is a process, whereby metal is electrodeposited in the bottom of the pores of the oxide film. By applying an alternating current, metal oxides will be deposited in the porous structure in a thickness of 1 – 5 µm. The film obtains a colour characteristic of the metal salts used. The metal salts most commonly used are tin, nickel, cobalt and copper.

Electrophoretic coatingsOrganic coatings may be applied from aqueous media to a conductive substrate by a processknown as electrophoresis. Upon application of a direct current, charged paint polymer will migrate electrophoretically to the electrode of opposite charge, and form an insulating film that limits further deposition.

ElectroplatingA process in which a metal coating (plating) is electrodeposited on the surface of an object. The object is either immersed in an electrolytic solution, or the solution is applied by some other means, such as spraying. The object to be coated is the cathode.

ElectropolishingA metal polishing process where a surface is polished by making it an anode in an appropriate electrolyte

ElectrostaticThe changed electric charge on a surface caused by the loss of electrons. Attractive and repulsive forces are induced dependent on the proximity of the charged surfaces.

Electrostatic precipitator (ESP) An air pollution control device that removes particles from a gas stream (smoke) after combustion occurs. The ESP imparts an electrical charge to the particles, causing them to adhere to metal plates inside the precipitator. Rapping on the plates causes the particles to fall into a hopper for disposal.

Electrostatic PaintingFuel burning equipment (usually a gas burner arrangement) designed for destroying, by combustion, organic vapours before they are released to the atmosphere

EmulsionA colloidal dispersion of one liquid in another

Environmentally sound managementTaking all practicable steps to ensure that hazardous wastes or other wastes are managed in a manner which will protect human health and the environment against the adverse effects which may result from such wastes

EtchingA chemical finishing process in which the surface of a material, such as glass, metal, or silicon, is eroded in specific, designated areas by an etchant such as an acid.

FlexographicTerm used to describe the coating of a flexible continuous web by transfer of coating from rollers.

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Fugitive emissionsAir pollutants that enter the atmosphere without first passing through a stack or duct designed to direct or control their flow

Green wasteFresh plant, crop and other vegetation cuttings.

Greenhouse gasGases that within the lower atmosphere trap absorb solar radiation with the net effect to warm the surface of the earth.

HalogenatedChemical compounds containing chlorine, or bromine or iodine.

HAP Hazardous Air Pollutants. The 1990 Clean Air Act (CAA) directs the U.S. Environmental Protection Agency (EPA) to regulate emissions into the air 189 toxic chemicals. These chemicals, called Hazardous Air Pollutants (HAPs), are known or suspected carcinogens, and have high usage and emissions in a wide variety of industries, including printing, metal fabrication, autobody repair, automotive repair, wood finishing, dry cleaning and others.

Hazardous SubstanceA substance that is potentially hazardous to peoples health as defined by regulations

Heavy metalsMetallic elements including arsenic, cadmium, chromium, copper, lead, mercury, and zinc.

High temperatureTemperatures of at least 1400 oC.

HydrophilicWater tolerant or miscible.

LacquerFast drying, hard, high gloss surface coating

LandfillMulti- stream deposition of waste into a lined or unlined cell without or without leachate collection at below natural ground surface level.

LeachateLiquid solution extracted from landfill due to infiltration of water or the microbial degradation within the landfill.

Metabolic ToxicityToxics that affect the chemical and physical processes whereby the body functions.

MSDSMaterial Safety Data Sheet.

Neutralization The combining of solutions of acids and bases to result in a solution of pH between 6.5 and 7.5. Most commonly, a chemical reaction that produces a resulting environment that is neither acidic nor alkaline. Also, the addition of a scavenger chemical to an aqueous system in excess concentration to eliminate a corrosive factor, such as dissolved oxygen.

OrganicContaining principally hydrocarbon compounds.

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OversprayPaint, powder and solvent that misses the item being coated

PicklingThe process of removing scale or other compounds from a metal surface by immersion in a suitable liquid (usually an acid or an alkaline solution). Pickling of plastic is a precondition for sufficient metal adhesion.

PaintA mixture of a pigment and a vehicle that togheter form a liquid that can be applied to a surface, providing an adherent coating that imparts colour and often protects the surface

Paint vehicleThe liquid constituent of paint, consisting of solvent or thinner and resin (film-forming component)

Powder coatingA coating that contains no organic solvents. These coating are either thermoplastic or thermosetting powders.

Porcelain EnamelingA glassy coating which is often applied to metal surfaces to improve appearance and protect the surface. Common applications of porcelain enamels are for major appliances, water heaters, cookware, etc.

Priority PollutantsThe priority pollutants are a subset of "toxic pollutants" as defined in the Clean Water Act (USA). These 126 pollutants were assigned a high priority for development of water quality criteria and effluent limitation guidelines because they are frequently found in wastewater. Many of the heavy metals, pesticides, and other chemicals listed here are on the priority pollutant list

SealingPrior to placing surface treatments on a surface, the surface is sealed first in order to extend the life of the coating. Sealing improves the corrosion and stain resistance of the oxide layers. It also prevents organic dyes from leaching out and improves the light fastness. Sealing may be carried out in hot or cold processes.

SedimentationLetting solids settle out of waste water by gravity during waste water treatment/

SludgeSemi-solid, deformable conglomeration of particulate and paste material settled or physically separated from a liquid suspension.

SmogAir pollution associated with oxidants

SolidificationThe addition of an additive to a liquid or sludge material to obtain a spadeable solid.

Solvent recoveryRecovery of vapours from solvents, for example by use of a solid adsorbent material that holds the vapour molecules on its surface, from which they can be regenerated for recycling. This is desirable if cost is a major consideration or if incineration is impractical, as with chlorinated solvents.

Spray paintingA spray coating process in which a fine, even coat of paint is applied to an object or material

SubstratePlastic or metal surface to be coated

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Surface coatingCoating of surfaces for decoration and/or protection. A number of basic coating operations are used, including spraying, dip coating, flow coating, roller coating and electrocoating. Variations and combinations of these operations may be used, each designed for a special task. For example, articles may be coated by spraying using air-atomised, airless-electrostatic or hot-spray methods. The composition and physical properties of these coatings vary widely. Organic solvents and thinners are required for many of these operations

Surface TreatmentThe removal, conversion and deposition of layers. Surface treatments create a composite structure by changing the properties of the structure.

Stripping ProcessesRemoval of an undesirable material, especially a coating.

UVUltra violet electromagnetic radiation.

Vapour DepositionA deposition method involving the formation of a vapor which subsequently condenses on and coats the surface of an object.

VarnishTransparent coating applied as a liquid and dries to a solid.

VOCs Volatile organic compound; family of highly evaporative organic materials used in a variety of industrial applications, such as paints and solvents. VOC emissions are a component in the formation of ground-level ozone (smog).

Waste-to-energyGeneration of a form of energy from the combustion of wastes.

Wet scrubberA piece of pollution-control equipment designed for removing particles from gas by capturing the particles on or in liquid (usually water) droplets and separating the droplets from the gas stream.

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10 REFERENCES

1. Air & Waste Management Association, Air Pollution Engineering Manual, Van Nostrand, 1992

2. Air & Waste Management Association. “Air pollution engineering manual”. 2nd edition. Edited by Wayne T. Davis. John Wiley & Sons, Inc. New York, 2000.

3. Guidance Document on the Preparation of Technical Guidelines for the Environmentally Sound Management of Wastes Subject to the Basel Convention

4. Centre for Excellence in Cleaner Production, Curtin University of Technology, WA. 2002. “Waste minimization in metal surface finishing”. Internet: http://cleanerproduction.curtin.edu.au/industry/metals/waste_minimisation-metalfinishing.pdf

5. CETS. European Committee for Surface Treatment (Comité Européen des Traitements de Surfaces) 2002. “Reference Document on best available techniques: Surface Treatment of Metals and Plastic Materials using electrolytic or chemical process (volume of treatment vats > 30 m3)”. Internet: http://www.sits.fr/htm/Anglais/

6. Coatings GuideTM. “Coating Alternatives Guide”. Internet: www.cage.rti.org. Last Update: November 2002.

7. Colorado Department of Public Health & Environment. 2001. “Pollution prevention ideas for surface coating”. Internet: www.cdphe.state.co.us/el/documents/chemical/

8. Environment Canada. 1987. “Overview of the Canadian Súrface Finishing Industry. Status of the Industry and Measures for Pollution Control”. Report EPS 2/SF/1. Chemical Industries Division, Environmental Protection Conservation and Protection, Environment Canada and J.E. Hanna Associates Inc.

9. EnviroSense. “Massachusetts Toxics Use Reduction: Alternatives to Solvent-Based Coatings: Fact Sheet 5”. Internet: http://es.epa.gov/

10. EPA Office of Compliance Sector Notebook, Profile of the Fabricated Metal Products Industry, Sept 1995.

11. EPCRA - Reporting Guidance for Spray Application and Electro-deposition of Organic Coatings, USEPA, Dec 1998.

12. Hart, Anthony et al. “Electroplating of Plastics” Source: Materials World, Vol. 4 No. 5 pp. 265-67 May 1996. Internet: http://www.azom.com/details.asp?ArticleID=525

13. Hazardous Waste List. Special Waste. Appendix 2. Section 15.

14. http://www.epa.nsw.gov.au/mao/spraypaintingsurfacecoating.htm#sources

15. Jon Katz. 1997. “Medical Plastics: Coating and Surface Treatment Technology”. Medical Devicelink.

16. McGraw-Hill Concise Encyclopaedia of Science, Fourth Edition, 1998

17. Moreton, Janet and N.A.R. Falla. 1980. “Analysis of Airborne Pollutants in Working Atmospheres: The Welding and Surface Coatings Industries”. The Chemical Society. London.

18. Simpson, W.Gordon (editor). 1993. “Plastics: Surface and Finish”. 2nd edition. The Royal Society of Chemistry. Cambridge.

19. Surface Engineering Association. 2001. “Code of best practice for the surface finishing industry”. Developed in association with Environment Agency, Scottish Environmental Protection Agency (SEPA), Environment and Heritage Service, Health & Safety Executive. Published by Environment Agency. Almondsbury, Bristol.

20. U.S. EPA. Environmental Protection Agency. “Pollution prevention in painting and coating operations”. 2001 Internet: http://www.epa.state.oh.us/opp/paints/fact23.html

21. U. S. EPA (Environmental Protection Agency) and SEDESOL Pollution Prevention Group. 1993. “Pollution Prevention: Waste minimization for the metal finishing industry”. Internet: http://www.p2pays.org/ref/03/02383/02383.pdf

22. U.S. EPA. Environmental Protection Agency. 1982. “Development Document for Effluent Limitations Guidelines and Standards for the Metal Finishing Point Source Category”. (EPA 440/1-82/091-b).

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23. U.S. EPA. United States Environmental Protection Agency. “Spray painting and surface coating”. Internet:

24. U.S. EPA. United States Environmental Protection Agency. 2000. “Capsule Report: Approaching Zero Discharge in Surface Finishing”. EPA/625/R-99/008. Washington, DC.

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11 CONTACTS

Name Web Address Phone No./E-mail Fax. No.1 The powder coating institute www.powdercoating.org2 Chemical Coaters Association International,

Cincinnatihttp://www.arcat.com aygoyer@one.net

3 Journal of coatings technology http://www.coatingstech.org/Publications/JCT.html4 The society for protective coating (SSPC) http://www.sspc.org 5 Metal finishing association www.finishes.org.uk6 The surface engineering assoication www.sea.org.uk/mfapubs.htm7 Canadian plastic association www.cpia.ca/scriptcontent/index.cfm8 American Electroplaters and Surface Finishers

Society http://www.aesf.org

9 European Committee for Surface Treatment10 Home Page of the Finishing Industry www.finishing.com11 National paint and coatings association www.paint.org12 British Coatings Federation http://www.bcf.co.uk13 Environmental Industries Commission http://www.eic-uk.co.uk14 Friends of the Earth, International organization http://www.foe.org/ 15 Scottish Environmental Protection Agency -SEPA www.sepa.org.uk/16 Surface Engineering Association http://www.sea.org.uk17 Society of Motor manufactureres and Traders Ltd.18 The Association for Finishing Processes of the

Society of Manufacturing Engineers (AFP/SME)http://www.sme.org/afp/ (800) 733-4763.

19 American Galvanizers Association 12200 E. Iliff Ave., Aurora, CO 80014-1252, USA 303/750-2900 303/750-2909 20 Chemical Coaters Association International ,

(CCAI)http://www.ccaiweb.com, P.O. Box 54316, Cincinnati, OH 45254, USA

513/624-6767 513/624-0601

21 Electrochemical Society (Electrodeposition Div) 10 S. Main St., Pennington, NJ 08534, USA 609/737-1902 609/737-2743 22 The Institute of Corrosion 4 Leck House, Lake Street, Leighton Buzzard,

Bedfordshire LU7 9TQ, UK01525 851771 01525 376690

23 Institute of Metal Finishing Exeter House, 48 Holloway Head, Birmingham, UK 121/622-7387 121/666-631624 International Lead Zinc Research Organization,Inc. P.O. Box 12036, Research Triangle Park, NC 27709, 919/361-4647 919/361-1957

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Name Web Address Phone No./E-mail Fax. No.USA

25 National Association of Metal Finishers http://www.namf.org/26 Society of Vacuum Coaters http://www.svc.org, 71 Pinon Hill Place, Albuquerque,

NM 87122-1914, USA 505/856-7188 505/856-6716

27 Metal Finishing Magazine http://www.elsevier.nl:80/locate/inca/52293128 Canadian Centre for Pollution Prevention http://www.c2p2online.com/29 Products Finishing Magazine http://www.pfonline.com/30 Institute of Waste Management, UK www.iwm.co.uk/31 Institute of Waste Management, Poland www.igo.katowice.pl/eng/32 Institute of Waste Management, New Zealand www.wasteminz.org.nz33 QM Technologies: Ion Beam Surface Treatment http://www.qminc.com/Applications.htm34 Greenpeace International www.greenpeace.org

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12 ANNEX I. Proposal from Germany for a new chapter: Degreasing, Cleaning, Impregnating

1 Degreasing, cleaning and impregnating

1.1 General information

1.2 Apllied processes and techniques

1.2.1 Continuous cleaning systems

1.2.2 Multi-chamber plants

1.2.3 Single-chamber plants

1.2.4 Typical treatments

1.2.4.1 Immersion

1.2.4.2 Spraying

1.2.4.2.1 Ultrasonics

1.2.4.2.2 Circuit filtration

1.2.4.3 Vapour degreasing

1.2.4.4 Convection drying

1.2.4.5 Vacuum drying

1.2.5 Water-based systems

1.2.6 Solvent-based systems

1.2.7 Replacement of solvent systems

1.3 Current emission and consumption levels

1.4 Techniques to consider in the determination of BAT for industrial cleaning with chlorinated Solvents/CHC/Hydrocarbons

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General information

Nowadays, a large number of parts constructed from the most widely varied material are cleaned. These parts come from a wide range of industries, such as mechanical engineering, plant engineering and construction, vehicle construction and instrument manufacturing in the aerospace industry, medical technology, optics industry, furniture manufacturing, household goods etc.

Work-pieces for cleaning include raw materials, semi-finished products, finally-assembled units and finished products; ranging from tiny electronic parts, which can hardly be seen with the naked eye, to car bodies and aircraft components. Demands on the cleanness of surfaces are laid down by the user and mostly based on experience. There are no universally applicable quality specifications.

Three cleaning agents are mainly used in the cleaning of parts: non-halogenated hydrocarbons (HC), chlorinated hydrocarbons (chlorin.HC) and aqueous cleaning systems. Other cleaning processes have only a negligible market share.

Figure 1: Market shares of different cleaning processes

The parameters for the cleaning procedure (for example, number of baths, volumes, temperatures, type of application, treatment times, cleaning agent etc.) are generally determined by means of tests with original parts at plant suppliers. There are usually no standardized procedures for different purity demands (determined by the user or conditional on the following operational step), since a large number of exit parameters, such as the geometry of parts, auxiliary agents, batch size, packaging, throughput etc. considerable influence the choice of procedure.

Cleaning is carried out either as (repeated) intermediate cleaning or final cleaning.

Applied processes and techniques

Cleaning installations are nowadays constructed in modular form and can thus be easily adapted to the respective cleaning task. In installation assembly a distinction is made between

▪ continuous cleaning systems▪ multi-chamber plants▪ single-chamber plants

or a combination of them.

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Cleaning processed generally comprise the following steps:▪ cleaning▪ rinsing▪ drying

or a combination of them.

Each cleaning step can be variedly conducted according to plant configuration. The most common procedures and additional processes are:

▪ immersion▪ spraying▪ circuit filtration▪ ultrasonics▪ vacuum drying▪ convection drying

or a combination of them.

Continuous cleaning systems

Figure 2: Continuous cleaning plant

An exemplary continuous cleaning plant is described in Figure 2. The individual sections perform the following tasks:

1. Pre-cleaning with a spraying process 2. Cleaning with a spraying process 3. Rinsing with a spraying process4. Draining and blowing off5. Drying (hot air)

The work-piece basket passes through the unit on a conveyor belt. The conveyor belt can move continuously or be synchronized. In-line-units are used, as a rule, for simple cleaning operations in intermediate cleaning.

In-line-units are nearly always aqueous cleaning systems.

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Multi-chamber plants

Figure 3: Aqueous multi-chamber plant with a trolley

An exemplary multi-chamber plant is described in Figure 3. Here, the work-piece container is moved from bath to bath by means of a trolley. The individual treatment basins perform in this case the following tasks:

1. pre-treatment2. cleaning3. rinsing4. Rinsing (with demineralized water)5. drying with hot air6. treatment, recycling of cleaning systems

Treatment in the individual baths is frequently supplemented with additional processes such as circuit filtration and/or ultrasonics.

Multi-chamber plants can operate with both solvents and water.

Single chamber plants

Figure 4: Single-chamber plant

An exemplary single-chamber plant is described in Figure 4. It comprises the following elements:

1. work chamber

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2. flood tank 1 (cleaning)3. flood tank 2 (rinsing)4. drying (convection and/or vacuum)5. processing of the cleaning agent (distillation)

The main difference to the multi-chamber plant is that only one batch can be cleaned at a time. All processing steps take place one after the other in a work chamber. As a result of this set-up the throughput of single-chamber plants is limited, but they offer distinct advantages due to the processing steps that are possible and low-emission operation.

Single-chamber plants can be operated with all cleaning agents, but are frequently found in solvent-based cleaning plants.

Typical treatments

I m m e r s i o n

Figure 5: Flooding

The work-piece is completely surrounded by the cleaning agent. This can occur through immersion in a treatment basin (multi-chamber plants) or by flooding from an additional storage tank (single-chamber plants).

Sp r a y i n g

Figure 6: Spraying

With spraying, the cleaning agent is distributed over the work-piece by means of nozzles. Depending on the geometry of the work-piece, this form of cleaning can be sufficient.

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Ultrasonics

Figure 7: Utrasonics

Better cleaning of surfaces (particles and pastes) can be achieved with additional ultrasound. The energy is introduced into the cleaning agent by means of oscillators. Typical frequencies of these ultrasonic oscillators are in the kHz range (typically 25-40 kHz).The principle of ultrasonic cleaning has to do with the tiny steam pockets on the work-piece surface, which suddenly collapse and release high mechanical energy (cf. cavitation).

Circuit filtration

Figure 8: Circuit filtration

With circuit filtration, the cleaning agent is withdrawn from the bath, passed through a filter and then returned to the bath. Depending on the filter system used, good to very good bathing quality can be realized.

V a p o u r d e g r e a s i n g

Figure 9: Vapour degreasing

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As a rule, vapour degreasing is only applied in solvent plants. Here, solvent vapour is applied to cold work-pieces, where the vapour condenses all over the surface and then drains off. Since the condensate has a very purity, a high degree of degreasing can be ensured.

1. Vapour2. Condensate

Co n v e c t i o n D r y i n g

Figure 10 Convection drying

With convection drying, pre-heated or hot air is passed over the work-piece. The liquid evaporates on the work-piece surface and is absorbed by the air stream. In the case of environmentally-relevant or valuable cleaning agents the air can be circulated. The air stream has then to be additionally dried before it is passed again over the work-piece. With very high temperatures (hot-air drying) this is useful for energetic reasons.Drying takes place almost exclusively on the surface. Geometrically complex work-pieces, such as bore holes or blind holes are very difficult to dry in this way. Convection drying is advantageous when the work-piece to be dried can hardly emit heat (for example, thin sheet metal and plastics), since the energy required for the evaporation of the liquid can be obtained from the drying air.

V a c u u m D r y i n g

Figure 21 Vacuum drying

With vacuum drying, work-piece drying is achieved by reducing the pressure below the steam pressure of the liquid (cleaning agent) to be dried. The energy required for evaporation stems exclusively from the work-piece to be dried. Vacuum drying enables optimum drying of geometrically complex parts. .

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Solvent based systemsFor cleaning purposes different hydrocarbons – in part, halogenated – are available on the market..

Chlorinated HydrocarbonsChlorinated Hydrocarbons have a very high cleaning performance. Chlorofluorocarbons (CFC) or hydrochlorofluorocarbons (HCFC) are compounds that destroy ozone (cf. Montreal Protocol) and may no longer be used (or used only for a transitional period). The most common solvents are perchloroethylene and trichlorethylene. Because they represent a particular potential risk to human health and the environment, they are only used in German in completely enclosed plants, in order to minimize the possibility of release as much as possible. Beyond that, demands are made on the collection and separate storage of waste solvents, in order to ensure reprocessing and recycling.

F - Fluorinated hydrocarbonsFluorinated hydrocarbons are generally very stable compounds with, in part, a very high global warming potential (GWP). They may be used in Germany to only a limited extent and then only in completely enclosed plants. Unfortunately, they have only a poor cleaning performance and are used, as a rule, as a (azeotropic) mixture with other solvents (for example, with isopropyl alcohol, trans-dichloroethylene, ethanol).

Non-halogenated Hydrocarbons (HC)Non-halogenated Hydrocarbons are, as a rule, inflammableand inflammable solvents. Their cleaning performance depends on the respective formulation. Typical solvents of this type are:

▪ Pure hydrocarbons (for example, isoparaffin)▪ Oxygenous hydrocarbons (for example, alcohol, ester, ketone)

Pure hydrocarbons, in comparison with halogenated solvents, have a lower cleaning performance than chlorinated hydrocarbons. This can be greatly increased in modern plants, however, and in the meantime is equivalent to that of chlorinated hydrocarbons. Alcohol, ester and similar compounds are primarily used in manual cleaning, since they clean well in a cold state and still dry quickly.

Water-based systems

▪ Alkaline, neutral, acidic▪ Typical component of cleaners ▪ Stainless drying through the use of demineralized water▪ Complex cleaning = multi-chamber plants▪ Simple cleaning = single-chamber plants

Demulsifying 1-component (mainly applied by spraying) and 2-component (surfactant, builder; mainly applied by immersion) cleaner systems available on the market have been continually advanced over the last ten years or so, and today represent best available techniques. They are supplied in liquid form and can be dosed automatically via conductivity, or according to batch requirements. The products have been optimised in terms of the number of individual raw materials, quality of raw materials, cleaning performance and material compatibility.

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Material compatibility is becoming more and more important in the development of cleaner systems, as parts made of different materials or composite materials are increasingly being cleaned together in a single process. Examples are:

▪ stainless steel▪ steel, cast iron▪ brass and its alloys▪ aluminium and its alloys▪ magnesium▪ die-cast zinc▪ electroplated (zinc, chromium) and chromated steel▪ anodised and chromated aluminium▪ plastic▪ glass▪ composite materials

2-component systems have been developed for the purpose of extending bath lifetimes in plants equipped with oil separation, membrane (or micro) filtration (MF) or ultra-filtration (UF). This means that they do not cause membrane blockage or a reduction of permeation performance or have a demulsifying effect, and they are liquid. The builder component permeates almost completely. Permeation of the surfactant component is about 10% for spray surfactants and up to about 80% for immersion surfactants. The rate of permeation depends, however, on the auxiliary agents used in the manufacture of the work pieces.

Achievable residual oil concentrations are normally < 1% for oil separators, < 100 mg/l for MF and < 10 mg/l for UF.

A few cleaner components, together with the appropriate plant technology, can tackle many different cleaning jobs within a plant. Two different surfactant systems (spray, immersion) and a builder are sufficient in most cases. This reduces storage costs and conserves resources.

Replacement of solvent systems

The various systems are not fully compatible or exchangeable. A change is not always possible or expedient (cost-benefit, complexity). The results of a research project funded by the Federal Ministry for Education and Research and carried out by the Institute for Technical and Environmental Chemistry of the Friedrich-Schiller University in Jena in cooperation with the DGO Technical Committee on Cleaning provide a basis for the comparative assessment of cleaning systems.

The tables below show the differences between cleaning media in terms of removal of different kinds of contamination, the effectiveness of mechanical support and possibilities of drying and of emission reduction.

Contamination Example Water-based Hydrocarbons ChlorinatedSolvents

Organic, non-polar oil, grease poor Good-very good

very good

Organic, polar colophony moderate moderate-good moderate-goodInorganic, non-polar pigments good moderate-good moderate

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Inorganic, polar

Salts very good poor poor

Figure 3 Cleaning performance

211. Cleaning efficiency can be considerably improved through mechanical support (energy) such as ultrasonics, pressure flooding, movement of the work pieces being cleaned etc..

Ultrasonics Pressure flooding SprayingWater-based ++ ++ ++/+Hydrocarbons - + +Chlorinated solvents + + +Figure 4 Effectiveness of mechanical support

Expenditure for drying Emission reduction

Water-basedHigh

hot air / forced convectionvacuum

not necessary

HydrocarbonsLow

warm air / forced convectionvacuum

condensationadsorption

Chlorinated solventsvery low

forced convectionvacuum

condensationadsorption

Figure 5 Drying

Current emission and consumption levels

Automated cleaning processes are especially to be found with metal degreasing, precision cleaning and special industrial applications, which are carried out in enclosed plants. Table 1 shows emissions and consumption of non-halogenated solvents in the cleaning sector as a whole, in which the above-mentioned cleaning of industrial parts represents just one area.

Table 1: Surface cleaning with non-halogenated organic solvents in Germany in 1998, by subsector; solvent consumption, VOC emissions to air, disposal of spent solvents

Subsector Solvent consumption

in t/aVOC emissions

in t/a

Waste solventsin t/a

Non-industry service sector 11000 6200 4800Car de-waxing 6600 1225 5375Industrial metal degreasing, total;- manual cleaning- plant cleaning

27200250002200

1200011100900

15200139001300

Special industrial applications;of which, manual finishing of

120004500

86003500

34001000

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productsPrecision cleaning 4400 2755 1645Coating removal 2500 370 2130Total 63700 31150 32550

The consumption of solvents in modern cleaning plants using chlorinated hydrocarbons fell in German from 32,000 Tonnes in 1986 to 6,500 Tonnes in 1995. This represents a decline of about 80% (Source: BIA-Report 3/03). In isolated cases, in particular in large plants, solvent consumption was reduced by over 95% (Source: Dürr Ecoclean).

In totally enclosed plants diffuse emissions are hardly significant. With open applications, almost all solvent lost is attributable to diffuse emissions.

Besides obvious differences in equipment construction, open plants often have inadequate drying systems. This leads to additional losses due to work-pieces that are not completely dry, in particular in the case of complex geometry.

In addition, fugitive emissions occur during the filling and emptying of plant. Fully enclosed filling and emptying systems with vapour recovery have gained acceptance and are regulated by certain countries – for the abatement of emissions.

General composition of emission levels:Per plant:

▪ Captured emissions (waste gas) none▪ Fugitive emissions via air change during loading/unloading concentration level

prior to opening of work chamber < 1 g/m3 of work-chamber volume▪ Fugitive emissions via housing of the plant below odour threshold (< 5 ppm)▪ Emissions during servicing operations (filter change, solvent change) very low▪ The plants are generally equipped with a vacuum filter drier so that virtually no

emissions arise during removal of the filter bags▪ They also generally have additional exhaust ventilation which can be switched on

during servicing operations and which draws off emissions and feeds them to the process-air treatment unit

▪ Change of solvent is carried out using a safety system with vapour recovery (e.g. Safetainer), involving no dripping

▪ "Contaminated" solvent can be recovered almost completely prior to removal through distillation. The solvent content in the distillation residue is 1 – 5% (depending on the type of oil contamination)

HC plant:▪ Captured emissions (waste gas) yes ▪ Fugitive emissions via air change during loading/unloading 2 – 10 g/m³, depending

on the geometry of the parts and the drying time set▪ Fugitive emissions via housing of the plant low (exhaust ventilation)▪ Emissions during servicing operations sometimes distinctly noticeable by the

unpleasant odour of many A-III products▪ These plants also have vacuum filter driers, but due to the poor drying behaviour of

these solvents, the filter bags cannot be removed without odour nuisance▪ The exhaust ventilation that can be switched on during servicing operations protects

the operator, but only transfers emissions to the waste-gas side of the process.

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▪ As safety systems with vapour recovery (e.g. Safetainer) cannot be supplied, feeding of A-III solvents into the plant normally takes place from open vats, generating additional emissions

▪ "Contaminated" solvent can be recovered almost completely prior to removal through distillation. The solvent content in the distillation residue is about 10 % (depending on the type of oil contamination)

The quantity of solvent circulated in the plant/distilled depends very much on the amount of contamination/oil that enters the system via the work-pieces to be cleaned. A certain quantity needs to be distilled, however, to achieve the required cleanness/quality of the work-pieces. If input of oil/contamination is high, a large quantity of solvent will have to be distilled to achieve the same degree of cleanness.

A minimal distillation rate, of only 60 litres per hour, with operation in three shifts would already produce a quantity of just under 250 t per year. In most cases, however, the distillation rate can be assumed to be significantly higher, since solvent systems are used mainly where the surface of the parts to be cleaned are heavily contaminated by dirt/oil.

Techniques such as vacuum bypass residue distillation, and are designed to minimise the solvent content in the bottoms to be disposed of to be disposed of, help maintain the internal solvent cycle. Their primary purpose, however, is to minimize the generation of waste and solvent consumption.

Solvent consumption in different plant systems is generally difficult to estimate, since it is mainly determined by the solvent content in the bottoms to be disposed of. The bottoms volume is, in turn, dependent on the amount of oil entering the plant via the parts, on the one hand, and on the type of reprocessing (with or without internal vacuum bypass residue distillation), on the other.

The emission levels of such plant systems vary greatly as a function of throughput, batch size and geometry of the parts. As a guideline for Per plants, a range of 5 – 20 grams per hour can be assumed.

Oil input[l/h] Quantity disposed of

[kg/a]Quantity of Per therein

[kg]Emissions

[kg/a]Total Per

[kg]

DifferenceWith/without

[kg]

Plant with residue distillation

1 4000 120 67 187 + 1480

3 12000 360 67 427 + 4440

5 20000 600 67 667 + 7400

Same plant without residue distillation

1 4000 1600 67 1667

3 12000 4800 67 4867

5 20000 8000 67 8067

Example:

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Same plant system, same cleaning quality, with and without residue distillation, at different oil inputs

Oil input of 1 l per hour, corresponding to about 4000 kg per year in 3-shift operation. Solvent content in the bottoms: 3% with residue distillation, 40% without. Emissions 15 g/h.

In the case of CHC plants, residue distillation can reduce the solvent content in the bottoms to less than 3%. For CHC plants not equipped with a residue distillation unit, the solvent content in the bottoms is 40-50%.

In the case of HC plants, vacuum bypass residue distillation usually reduces the residual solvent content to about 10 – 15%. As a guideline, emissions can be assumed to be 20 – 50 g/h.

Techniques to consider in the determination of BAT for industrial cleaning with chlorinated Solvents/CHC/Hydrocarbons

Solvent-based cleaning plants are generally full-vacuum plants, so that the process as such does not differ for CHC solvents (perchloroethylene, Per) and for A-III products (HC solvents).

CHC plants do not generate any waste gases that are discharged from the plant. Solvent-containing process air from drying is cleaned in an activated-carbon filter and fed into an in-plant "storage tank". It is re-used to ventilate the chamber following vacuum drying.

Figure 1: Cleaning plant of the Höckh company (CHC and A-III products)

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Hydrocarbons in vacuum machines Cleaning plants that operate wholly under vacuum have been specially designed for the use of inflammable hydrocarbons. All cleaning stages proceed under vacuum and thus constitute primary explosion protection. Furthermore, hydrocarbons can be used that would otherwise be difficult to dry.

These plants are single-chamber plants in which the solvent is continually processed (distillation). As a result, very long lifetime is achieved with constant cleaning quality.

Additional equipment such as - ultrasonics- circuit filtration- injection flooding- heat recovery- continuous oil discharging

have already been incorporated and can be easily retrofitted.

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Comments from Germany:

13 ANNEX II - Best available techniques for paint and adhesive application in Germany

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