EPA Self-Audit and Inspection Guide
Organic Finishing of Metals

Table of Contents

Powder Coating Methods: Regulatory Requirements

Air
The Clean Air Act regulates the emission of particulate matter of various sizes (40 CFR Part 50). Small dry powder particles can be suspended in exhaust air streams in amounts that would subject an operator to Title V permitting requirements. Filtration systems are typically included with powder coating application systems to capture particulates prior to their release in exhaust air. Due to the very low solvent content of powder coating materials, regulations concerning volatile organic compounds (VOCs) or hazardous air pollutants (HAPs) are typically not a concern. However, if large quantities of the material are used, then these air emissions may cause a problem. VOCs or HAPs should be monitored during curing stages when the materials would be released.

Water
As part of the Clean Water Act, Effluent Guidelines and Standards for Metal Finishing (40 CFR Part 433) have been established that limit concentrations of suspended solids in wastewater streams. Powder coating particles may be classified as suspended solids if found in large quantities in wastewater streams. Powder coatings can enter the wastewater stream when cleaning containers or equipment, or as the result of a spill. Actual limits for effluent constituents depend on the size of the operation and the amount of wastewater generated from the facility. If the facility discharges directly to receiving waters, these limits will be established through the facility's National Pollutant Discharge Elimination System (NPDES) permit (40 CFR Part 122). Facilities which are indirect dischargers releasing to a POTW must meet limits in the POTW's discharge agreement. Wastewater streams with concentrations exceeding permit limits will require pretreatment prior to discharge to receiving waters or to a publicly owned treatment works. Pretreatment may include separation of liquid wastes to remove solvents, and settling or precipitation of solid materials.

Solid and Hazardous Waste
Under the Resource Conservation and Recovery Act (RCRA), organic finishing facilities are required to manage listed and characteristic hazardous wastes (40 CFR Part 261). Powder coatings used in the various powder coating application systems may contain constituents listed or characterized as hazardous wastes. Materials contaminated with the coatings, such as spray booth air filters, masking materials for booth light fixtures and floors, and rags or containers used for cleaning, may require treatment as hazardous waste depending on their formulation. Hazardous waste management (40 CFR Part 262) includes obtaining permits for the facility in order to generate wastes, meeting accumulation limits for waste storage areas, and manifesting waste containers for off-site disposal. Responsibilities will vary according to the amount of hazardous waste generated; facilities generating at least 100 kilograms of hazardous waste per month must comply with the hazardous waste generator requirements of 40 CFR Part 262.

Each state and/or region is primarily responsible for the regulation of non-hazardous solid wastes (those not governed by the hazardous waste provisions of RCRA). Check with state environmental agencies for specific information or guidance.

Health and Safety
While not directly regulated by the EPA, several conditions exist that should be considered when using powder coatings application methods. Workers should be aware of their responsibilities when handling coating materials equipment during preparation and cleaning activities. Workers should also know the risks associated with inhaling the respirable coating particles. Finally, workers should be trained properly to avoid accidents and injuries when working with powder application equipment.

Self-Audit/Inspection

• Do exhaust air streams have air pollution control equipment attached? Is that air pollution control equipment working properly? Does final exhaust air have concentrations of pollutants below required levels?

Does the powder application system produce a liquid waste stream? Do concentrations of pollutants in the waste stream exceed limits established by the facility NPDES permit or POTW discharge agreement? Are wastes contaminated with powder coatings classified as hazardous? If so, are the wastes handled and manifested in accordance with 40CFR Part 262, Subpart B are the materials segregated from non-hazardous wastes?

Powder Coating Methods: Common Causes of Violation

• Powder spray methods suspend powder coating materials in the coating area. Some particles may be small enough to qualify as respirable particulates capable of penetrating lung tissue. Ventilation and exhaust systems must operate properly to ensure the particles are removed from the coating area. Also, powder coating materials in exhaust systems may accumulate above limits for particulate matter allowed by Clean Air Act Title V permits. Particulate filtration devices must not be clogged.
Powder systems utilize powder coating materials which can contaminate water streams. Contamination may occur from cleaning equipment and coating areas or from accidental spills or leaks from equipment. Contaminated water streams may contain suspended particulate solids in concentrations that exceed the limits established by facility NPDES permits or POTW discharge agreements. In such cases, effluent, may not be directly released to water systems or to publicly owned treatment works without pretreatment. Powder spray application systems can deposit coating materials on filters, masking paper, rags, and clothing which may need to be stored, manifested and disposed of according to RCRA standards for hazardous waste (40 CFR Part 262).

Powder Coating Methods: Sources of Pollution Powder coating applications can suspend particulates and create a fine dust containing respirable particles in the work area. Powder coating spray application systems create a flow of particles which do not all deposit on the part. Fluidized bed application systems require extra powder coating materials to maintain proper levels in the dip chamber. The excess coating materials may become waste. Powder coating application systems may require preheating of work piece which consumes extra energy. Powder coating application systems create solid waste in the form of filters, masking materials, clothing, personnel protective equipment, and other materials. Liquid waste can be created from the water and solvents used for cleaning equipment such as coating receptacles, pumps, valves, and hoses.

Powder Coating Methods: Pollution Prevention Alternatives

Powder coating application systems provide pollution prevention over traditional spray application systems due to the higher transfer efficiency (above 90%), and very low volatilization of organic solvents. Install a booth recovery system for electrostatic spraying and flocking applications. Booth recovery systems collect overspray powder particles from the exhaust air so that they may be reused. Reduce or eliminate contamination of coatings by enclosing and covering work areas. Surround systems with a semi-open structure which allows operation of the process but does not fully expose the coatings to the air and contaminants from the rest of the facility. Schedule paint jobs to minimize changing colors in powder application equipment. Paint with light colors first, then darker ones; lighter coating does not need to be completely removed from the equipment, but can blend into the darker coating. Modify consecutive powder coating systems applying different coating materials. Increase the distance between the streams and have separate recovery systems for each to keep the different coating materials separate, thereby allowing them to be reused. Clean powder coating application equipment regularly to prevent build-up of coating materials. Use water in cleaning steps to reduce the amount of organic solvents used and the amount of hazardous waste generated. Segregate non-hazardous coating solids and water from hazardous solvents and thinners, and label containers to prevent mixing. Separation of the materials reduces the amount of hazardous waste that is produced. Coating material solids can be dried and treated as a solid waste, allowing for disposal in a landfill. Maintain powder coating application equipment to sustain proper operation. Make sure valves, gauges, pumps, and filters are in proper working order. Keep powder coating application areas clean so that problems with equipment can be found and fixed quickly, and accidents can be prevented. Train employees on safe handling of materials and wastes and encourage continuous improvement. Training familiarizes workers with their responsibilities, which reduces spills and accidents.