Table of Contents
Chemical Coatings Removal: Regulatory Requirements
The Clean Air Act regulates the emission of
compounds (VOCs) (40 CFR Part 60) and hazardous
air pollutants (HAPs) (40 CFR Part 61 and
40 CFR Part 63). Chemical coatings removal
operations often use organic solvent based chemicals. Evaporation
of the solvents from tanks and spray systems may produce sufficient VOC
and HAP emissions to subject an operator to major
source requirements and Title
V permitting requirements. Under the standards for the aerospace
industry (40 CFR Part 63 Subpart GG), there are
specific requirements for chemical depainting operations.
Controlling VOC emissions can be completed in several ways. Evaporation
can be minimized by covering tanks, keeping a lower volume level of solvent
solution in tanks, or providing a barrier layer of water or cold air above
the organic solvent solution. Otherwise, air
pollution control equipment is required on exhaust systems to recover
the VOCs and HAPs before they are released from the facility.
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. Several components of chemical coatings removal
operations are classified as water pollutants including organic solvent
solutions, caustic solutions, or salt solutions. Also, the residual
coating solids or sludge in the solutions may contain metals. These
materials can enter the wastewater through liquid dripping off of parts,
when cleaning equipment, and from accidental spills or leaks in equipment. Actual limits for effluent constituents are dependent 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
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). Used chemical coatings removal solutions may contain constituents
listed or characterized as hazardous wastes. The residual coatings
materials remaining in the solutions will also contribute to the volume
and determination of hazardous wastes. 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
The Emergency Planning and Community Right-to-Know
Act (EPCRA) requires facilities to notify employees, customers and
the surrounding community of certain hazardous chemicals and materials
(40 CFR Parts 355 and 370)
that are present on-site. Large chemical coatings removal operations
may use hazardous materials in sufficient quantities to subject a facility
to several EPCRA requirements. Facilities may be required to inform
emergency planning committee (LEPC) and the state
emergency response commission (SERC) of the materials stored and used
on-site, devise emergency
response plans for reacting to spills, and notify authorities of accidental
spills and releases (40 CFR Parts 302 and 355). The materials used in chemical coatings removal solutions may also require
facilities to submit Material
Safety Data Sheets (MSDS) for these materials to state, regional, and
local organizations, while disposed volumes of the material may have to
be documented on annual Toxic
Release Inventory reports (40 CFR Part 372).
Do chemical coatings removal solutions come in contact with water streams? If so, do concentrations of pollutants exceed limits established by the
facility NPDES permit or POTW discharge agreement?
Are all chemical coatings removal solutions and wastes labeled and packaged
in accordance with 40 CFR Part 262, Subpart C? Are manifest forms completed for wastes to be shipped for disposal?
Has the facility participated in local, regional, or state emergency response
planning activities? Have facility response plans been developed
and coordinated with local authorities?
Chemical Coatings Removal: Common Causes of Violations
Emission of volatile organic compounds from chemical coatings removal solutions
may occur and exceed limits established in a Clean Air Act Title V permit. The harmful emissions can be captured and treated to prevent their release
to the atmosphere. Common air pollution control tactics include solvent
recovery, solvent incineration, and solvent concentration.
Chemical coatings removal solutions are liquid materials that can contaminate
water streams. This may occur accidentally, as with spilt material
entering a storm sewer. Contaminated water streams may contain pollutants,
including solvents, residual sludges, and oils, in concentrations that
exceed the limits established by facility NPDES or POTW permits. Effluent, then, may not be directly released to water systems or to publicly
owned treatment works without pretreatment.
Used chemical stripping solutions containing oils, grease, coating sludges,
and other contaminants may be classified as hazardous waste according to
RCRA. These materials must be labeled, stored, and disposed of properly.
Chemical coatings removal solutions may contain chemicals defined as hazardous
or extremely hazardous substances. Depending on the quantity of material
on-site, facilities must have an MSDS for each solution, maintain records
for TRI reporting, and cooperate with local emergency planning committees.
Chemical Coatings Removal: Sources of Pollution
Chemical coatings removal solutions contain materials classified as volatile
organic compounds, hazardous air pollutants, and/or ozone-depleting chemicals.
Chemical coatings removal solutions may spill due to improper handling
or leaks in tanks, pipes, hoses, etc. The liquid material may enter
storm sewers if not properly contained.
In addition to the solvents, used chemical coatings removal solutions may
contain coating solids, grease, oils, and heavy metals that would classify
the material as a hazardous substance.
Coating residue and metal particulates may be separated from chemical coatings
removal solutions as a sludge. Depending on the constituents of the
coating material, the sludge may be classified as a hazardous waste.
Heat (required for some chemical coatings removal solutions) consumes energy.
Chemical Coatings Removal: Pollution Prevention Alternatives
Chemical 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. However, other concerns make it less acceptable
than other coatings removal methods.
Use mechanical coatings removal methods (or a combination of mechanical
methods and less hazardous chemical coatings removal methods) to eliminate
or reduce the use of hazardous materials.
Substitute waterborne chemicals, semi-aqueous chemicals or organic solvents
with lower vapor pressures for chemical coatings removal solutions. Compared to traditional chemical coatings removal solutions, waterborne
chemicals and low vapor pressure solvents release fewer volatile organic
Restrict traffic in chemical storage areas to reduce spills and accidents. Keep storage and work areas clean so that spills and leaks are more noticeable
and reaction time is reduced.
Optimize process to strip properly with minimal solution and with lower
concentrations. Proper adjustment of operating parameters, such as
time, agitation, solution concentration, and temperature, will improve
coatings removal without requiring stronger solvents. Modify part
arrangement to ensure that cleaner reaches all surfaces.
Conserve energy by operating at optimum temperature, and by covering baths,
using insulated tanks, or using waste heat from other processes to heat
Enclose or cover containers of chemical coating removal solutions when
not in use to minimize the release of solvent vapors and lower contamination
from facility dust and dirt. Turning off spray systems and maintaining
a cool barrier zone above chemical tanks can also reduce the evaporation
Minimize water consumption by utilizing counter-current rinse baths. Backflow water from final rinse, to pre-rinse, to stripping baths before
Remove contaminants from chemical coatings removal solutions to retain
cleaning effectiveness. Separate coating residue, dirt, oils, and
other contaminants using filtration, gravity separation, or membrane technologies
(crossflow filtration). Reducing heat and stopping agitation will
promote separation of contaminants in batch systems.
Segregate non-hazardous wastewater and other materials from hazardous organic
solvents, and label containers to prevent mixing. Separation of the
materials reduces the amount of hazardous waste that is produced.
Recycle spent solvents with recovery units. Use semi-dirty solvent
materials for other cleaning jobs - paint spills, application equipment,
accessory clean-up, where some contaminants will not matter.
Check chemical coatings removal equipment regularly for leaks and repair
them. Items to check include tanks, pumps, pipes, hoses, valves,
fittings, and storage containers.
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 chemical coatings removal.
Train employees on safe handling of materials and wastes and encourage
continuous improvement. Training familiarizes workers with their
responsibilities, which reduces spills and accidents.