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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
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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?
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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?
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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
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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.
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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.
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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
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Powder coating applications can suspend particulates and create a fine
dust containing respirable particles in the work area.
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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.
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Powder coating application systems may require preheating of work piece
which consumes extra energy.
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Maintain powder coating application equipment to sustain proper operation. Make sure valves, gauges, pumps, and filters are in proper working order.
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Keep powder coating application areas clean so that problems with equipment
can be found and fixed quickly, and accidents can be prevented.
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Train employees on safe handling of materials and wastes and encourage
continuous improvement. Training familiarizes workers with their
responsibilities, which reduces spills and accidents.
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