Unep/Chw/Oewg/4/Inf/9

UNEP/CHW/OEWG/2/12

/

BC

UNEP/CHW/OEWG/4/INF/9

/ Distr.: General
26 April 2004
English only

1

UNEP/CHW/OEWG/4/INF/9

Open-ended Working Group of the Basel Convention

on the Control of Transboundary Movements of

Hazardous Wastes and Their Disposal

Fourth session

Geneva, 4–8 July 2005

Item 5 (l) of the provisional agenda[*]

Implementation of the decisions adopted by the Conference

of the Parties at its seventh meeting: preparation of

technical guidelines on the environmentally sound

management of wastes resulting from surface treatment

of metals and plastics (Y17) (decisionVII/15)

Draft technical guidelines on the environmentally sound

management of wastes resulting from surface treatment

of metals and plastics (Y17)

Attached is the draft technical guidelines on the environmentally sound management

of wastes resulting from surface treatment of metals and plastics (Y17) as prepared by Australia.

1

UNEP/CHW/OEWG/4/INF/9

Contents

1PREAMBLE

2THE WASTE AND THE INDUSTRY THAT GENERATES THE WASTE

2.1Background

2.2Current Consumption and Emission Levels

2.2.1Input materials

2.2.2Utilities

2.2.3Gaseous Emissions

2.2.4Effluent Emissions

2.2.5Solid Waste

3ENVIRONMENTAL HAZARDS

3.1Key Environmental Issues in the Surface Finishing Industry

3.1.1Hazardous Air Pollutants (HAP)

3.1.2Liquid Discharge

3.1.3Priority Pollutants

3.2Overview of Environmental and Health Effects and Impacts of Wastes

3.2.1Health Effects

3.3Hazards in Surface Preparation/Pre-treatment

3.3.1Mechanical Processes (for metals)

3.3.2Chemical Processes – Cleaning

3.3.3Electrolytic Processes

3.3.4Conditioning of Plastics

3.4Hazards in Surface Coating and Painting

3.4.1Specialist Pre-coats

3.4.2Chemical Processes – Dip Coating and Flow Coating

3.4.3Physical Processes – Painting and Coating

3.4.4Electro-deposition and Anodising

3.4.5Solvent-based Coatings

3.4.6High-solids Coatings

3.4.7Water-borne Coatings

3.4.8Electrostatic Powder Coatings

3.4.9Radiation-cured Coatings

3.4.10Wet Spray Application

3.4.11Roller Application

3.4.12Surface-Coating-Free Materials

3.5Hazards in Post Treatment including Curing

3.5.1Conversion Coatings

3.5.2Top Coatings

3.5.3Colouring and Sealing of Aluminum

3.5.4Drying for Barreled and Racked Components

3.6Equipment Cleaning

3.7Medical Plastics

4IDENTIFICATION OF OPPORTUNITIES FOR WASTE AVOIDANCE

4.1Waste Avoidance and Minimization – General Considerations

4.1.1Designated Area

4.1.2Empty Containers/Packaging

4.1.3Pre-cleaning

4.1.4Reduction of Drag-Out

4.1.5Acid and Alkaline Wastes

4.1.6Acid and Alkaline Wastewater Streams (Rinse Waters)

4.1.7Sludges

4.1.8Paints, Inks

4.1.9Water Conservation

4.1.10Improving Existing Process Conditions and Practices

4.1.11Segregation of Waste at Source

4.2Dealing with Surface Preparation Wastes

4.2.1Abrasive Blasting Wastes

4.2.2Halogenated de-greasing Wastes

4.2.3Chemical Cleaners and Specialist Pre-coats Wastes

4.3Dealing with Coating Application Wastes

4.3.1Dip and Flow coating

4.3.2Electro-deposition and Anodising

4.3.3Spray Application

4.3.4Electrostatic Powder Coats

4.3.5Roller Application

4.4Dealing with Curing Wastes

4.4.1Product Finishing

4.5Alternative Processes: Surface Preparation

4.5.1Alternative Stripping Processes

4.5.2Alterntive Pickling and Descaling

4.5.3Alternative Etching

4.5.4Alternative Cleaning Equipment

4.5.5Alternative Cleaning

4.6Alternative Surface Finishing Process & Coating Techniques

4.6.1Alternative Anodizing

4.6.2Organic Coatings

4.6.3Alternative Vapour Deposition

4.6.4Thermal Spray

4.6.5Hardfacing

4.6.6Porcelain Enameling

4.6.7Metal Cladding and Bonding

4.6.8UV and electron beam technology

4.7Alternative Solvents

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

5identification of opportunities for recovery

5.1Recovery of Solids

5.2Recovery and purification of Process Solution

5.2.1Diffusion Dialysis

5.2.2Microfiltration

5.2.3Membrane Electrolysis

5.2.4Acid (Resin) Sorption

5.2.5Electrowinning

5.2.6Other Technologies

5.3Recovery of Concentrate or Rinse Purification

5.3.1Reverse Osmosis

5.3.2Electrodialysis

5.3.3Ion Exchange

5.3.4Vacuum Evaporation

5.3.5Atmospheric Evaporation

5.3.6Other Technologies

5.4Recycling of Spent Solvents

5.4.1On-site Recycling

5.4.2Off-site Recycling

6WASTE TREATMENT AND DISPOSAL TECHNOLOGIES

6.1Aqueous liquids

6.1.1Rinsing waters

6.1.2Acid and Alkali Solutions

6.1.3Water based coatings

6.2Solvent-Based Wastes

6.2.1Non-halogenated solvents

6.2.2Chlorinated Hydrocarbon Cleaning Solvent

6.2.3Mixed VOC Solvent Wastes

6.2.4Mixed Hydrocarbon and Aqueous Solutions

6.3Specific Wastewater Treatment Technologies

6.3.1Alkaline Chlorination

6.3.2Electrolytic Destruction

6.3.3High-pressure and high-temperature hydrolysis

6.3.4Chromium Reduction

6.3.5Neutralization and Hydroxide Precipitation

6.3.6Sedimentation

6.4Solid Hydrocarbon Coatings

6.5Control of Air Emissions

6.5.1Particulate Matter (PM)

6.5.2Solvent Vapour, VOCs

6.5.3Stacks for spray painting and coating

6.6Hazardous Waste Disposal options

6.6.1On-site Disposal: Solvent-based Cleaner

6.6.2On-site Disposal: Paint Removal

6.6.3Off-site Disposal

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

7ECONOMIC ASPECTS OF SUITABLE WASTE MANAGEMENT OPTIONS

7.1Pre-treatment Evaluation

7.2Coating Application Waste Evaluation

7.3Product Finishing Waste Evaluation

8CRITERIA FOR THE SOUND OPERATION OF TECHNOLOGY AND SAFETY

8.1Generators’ Responsibilities

8.2Collection & Storage Responsibilities

8.3Transport Responsibilities

8.4Disposal Responsibilities

9GLOSSARY OF TERMS

10REFERENCES

11CONTACTS

12Annex I Proposal for new chapter: degreasing, cleaning, impregnating………………………………..41

13Annex II Best available technologies………………………..……………………………53

1PREAMBLE

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.

1. Theprimary 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.

1. 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.

1. 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)

2THE WASTE AND THE INDUSTRY THAT GENERATES THE WASTE

2.1Background

1. 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.

1. 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.

1. 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.

1. Surfacepreparation 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.

2.2Current Consumption and Emission Levels

1. 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

2.2.1Input materials

2.2.2Utilities

2.2.3Gaseous Emissions

2.2.4Effluent Emissions

2.2.5Solid Waste

3ENVIRONMENTAL HAZARDS

3.1Key Environmental Issues in the Surface Finishing Industry

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

3.1.1Hazardous Air Pollutants (HAP)

1. 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.

3.1.2Liquid Discharge

1. 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.).

1. 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.

3.1.3Priority Pollutants

1. 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.

3.2Overview of Environmental and Health Effects and Impacts of Wastes

3.1 Environmental impacts

1. 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.

3.2.1Health Effects

1. 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.

3.3Hazards in Surface Preparation/Pre-treatment

3.3.1Mechanical Processes (for metals)

1. 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

1. 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.

1. 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.

1. 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).

1. 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.

3.3.2Chemical Processes – Cleaning

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

1. 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.

1. 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.

1. 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.

1. 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.

1. 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.

1. 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.

1. 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.

3.3.3Electrolytic Processes

1. 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.

3.3.4Conditioning of Plastics

1. 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.

3.4Hazards in Surface Coating and Painting