Table of Contents
Mechanical Coatings Removal: Regulatory Requirements
The Clean Air Act regulates particulate
matter in exhaust air (40 CFR Part 50). Large mechanical coatings removal operations can create a sufficient amount
of particulate matter consisting of dry blast media and coatings residue
to subject a facility to Title
V permitting requirements. In addition, specific standards have
been established for Mechanical Coatings removal operations at aerospace
manufacturing and rework facilities (40 CFR Part 63,
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 heavy
metals, toxic organics, and
in wastewater streams. Residue from mechanical coatings removal methods
including residual coatings, blast media, and blast water, may contaminate
the water stream, especially when wet-abrasive blasting is used. 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). Waste from mechanical coatings removal operations
may be classified as hazardous depending on the type of coating material
removed. 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 at 40 CFR
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). Contact state environmental agencies for specific
information and guidance.
Health and Safety
Mechanical coatings removal creates adverse conditions inside facilities
which, while not regulated by EPA, should be addressed. Suspended
particulates in confined areas and excessive noise created by equipment
can impact worker health and are regulated by the Occupational
Safety and Health Administration. Also, workers should be trained
properly to avoid accidents
and injuries when working with mechanical coatings removal equipment. For example, blasting systems produce a high-pressure stream of dry or
wet media that is capable of severely damaging or even severing limbs.
Do dry residual coatings and blast media come in contact with exhaust air
streams? If so, do concentrations of particulate matter exceed limits
established by facility air permits?
Do mechanical coatings removal media or residual coatings come in contact
with water streams? If so, do concentrations of pollutants exceed
limits established by the facility NPDES
permit or POTW
Are all mechanical coatings removal media or residual coatings wastes labeled
and packaged in accordance with 40 CFR Part 262,
Are wastes contaminated with residual coatings classified as hazardous? If so, are the wastes handled and manifested in accordance with 40
CFR Part 262, Subpart B? Are the hazardous wastes segregated
from non-hazardous wastes?
Mechanical Coatings Removal: Common Causes of Violations
Blast media, coating material, and substrate residue form dust in the blast
area. Some particles may be small enough to qualify as respirable
particulates capable of penetrating lung tissue. Typical hazards
include exposure to silica and lead.
Mechanical coatings removal technologies generate a high level of noise. Equipment used to compress and pump air or water, the exhaust of the air
or water stream, and the media striking the substrate create sufficient
decibel levels to require process engineering controls and hearing protection.
Wet-abrasive blasting and waterjet blasting create a waste of coating residue
and water, which can contaminate water streams. Water streams may also
become contaminated accidentally, as with spilt material entering a storm
sewer. Contaminated water streams may contain pollutants, including
the solvents, residual sludges, and oils in concentrations that exceed
the limits established by facility NPDES permits or POTW discharge agreements. As a result, effluent, may not be directly released to water systems or
to publicly owned treatment works without pretreatment.
Dry-abrasive blasting creates a waste of blast media and coatings residue. Wet-abrasive blasting creates a sludge of coatings residue. Based
on the coating constituents, the waste may be classified as hazardous according
to RCRA (40 CFR Part 261).
Mechanical Coatings Removal: Sources of Pollution
- Dry-abrasive blasting creates a waste of spent blast media, dislodged
coating materials and other contaminants. This material can create
a fine dust containing respirable particles in the work area.
Wet-abrasive blasting creates a waste of spent blast media, dislodged coating
materials and other contaminants, and water. The blast media and
dislodged contaminants may be segregated from the water as a sludge.
Waterjet blasting creates a waste of dislodged coating materials and other
contaminants, as well as water. The dislodged contaminants may be
segregated from the water as a sludge.
Depending on the constituents of the coating material and other contaminants,
the coatings residue or coating sludge may be considered to be a hazardous
Noise is created from the equipment used to compress and pump the air and
solid carbon dioxide, from the exhaust of the carbon dioxide stream, and
from the blast media striking the substrate.
Mechanical Coatings Removal: Pollution Prevention Alternatives
Mechanical coatings removal may be considered a pollution prevention alternative
since it aids in the proper application of coating materials thereby reducing
rework or reject parts. It also eliminates or reduces the use of
hazardous materials used in chemical coatings removal.
Substitute carbon dioxide blasting for dry-abrasive blasting and wet-abrasive
blasting to eliminate the need for solid blast media, water, and their
Perform mechanical coatings removal in enclosed areas such as blast booths
or workcells to contain noise, dust, and water. The enclosures must
have adequate ventilation systems to reduce levels of dust, and drainage
systems to capture wastewater.
Optimize process to strip properly with minimal aggression. Proper
adjustment of operating parameters, such as media size and media exhaust
velocity, will improve coatings removal without damaging the substrate. Modify part arrangement to ensure that blast media reaches all surfaces.
Remove residual coatings and other contaminants from blast media so that
it can be reused. Dry-abrasive blast media and water from wet-abrasive
blasting and waterjet blasting can be separated from coatings through filtration.
Recycle water from wet-abrasive blasting to other processes such as rinse
baths, facility clean-up, or other uses where small contaminants will not
Segregate non-hazardous blast media and wastewater from hazardous coatings
residue or other facility chemicals, and label containers to prevent mixing. Separation of the materials reduces the amount of hazardous waste that
Minimize need for coatings removal by improving other process steps. Reduce coating failure by handling parts carefully, and by performing good
cleaning, coating application and curing. Determine if time between
rework can be lengthened to reduce need for mechanical coatings removal.
Train employees on safe operation of equipment and handling of wastes and
encourage continuous improvement. Training familiarizes workers with
their responsibilities, which reduces accidents and spills.