Table of Contents
Waterborne Coatings: 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), and provides specific standards
of performance to control emissions from various types of coating operations
(40 CFR Part 60). While coating materials
can be formulated with water as a replacement for most of the solvent contained
in conventional solvent-based coatings, VOC and HAP emissions are still
a concern. In high-volume coating operations, the amount of solvent
contained, even in waterborne coatings, may produce sufficient VOC emissions,
and in rare situations HAPs, to subject an operator to major
source requirements and Title
V permitting requirements.
Controlling VOC and HAP emissions can be accomplished in two ways. First, coatings with a lower organic solvent content can be used. Otherwise, air pollution
control equipment is required on application or curing equipment exhaust
systems to recover or incinerate 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 toxic
organics in wastewater streams. Waterborne coatings may contain
materials classified as toxic organics. These materials can enter
the wastewater through the use of water wash spray booths, when cleaning
waterborne coatings from containers or equipment, or following accidental
spills. 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
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). Waterborne coatings may contain constituents listed or
characterized as hazardous wastes, such as solvents. Residual waterborne
coating materials, their containers, and contaminated materials (including
rags, masking material, coveralls, filters, and other process materials.)
may require treatment as hazardous waste depending on the formulation of
the coating material. 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 material 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.
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. Waterborne coatings in sufficient quantities may 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 on-site,
devise emergency response plans for reacting to spills, and notify authorities
of accidental spills and releases (40 CFR Parts 302
and 355). Waterborne coatings stored on-site
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 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?
Do waterborne coatings come in contact with exhaust air streams? If so, do concentrations of VOCs exceed the limits established by facility
Do waterborne coatings 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 waterborne coatings and waterborne coatings wastes properly labeled
and packaged in accordance with 40 CFR part 262,
Are wastes contaminated with waterborne coatings classified as hazardous? If so, are the wastes handled and manifested in accordance with 40
CFR Part 262, Subpart B? Are hazardous wastes segregated from
Has the facility participated in local, regional, or state emergency response
planning activities? Have facility response plans been developed and coordinated
with local authorities?
Waterborne Coatings: Common Causes of Violation
Waterborne coatings contain some amount of solvents classified
as volatile organic compounds and/or hazardous air pollutants that can
evaporate and accumulate above limits allowed by Clean Air Act Title V
permits. Most waterborne coatings have a VOC content of less than
3.0 pounds per gallon; but when large volumes of the material are used,
ambient levels of the volatile organic compounds and hazardous air pollutants
may be a concern.
Waterborne coatings are liquid materials that can easily contaminate water
streams. This contamination may be accidental, as with spilt material
entering a storm sewer, or intentional, as with the use of water wash spray
booths. Contaminated water streams may contain pollutants 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.
Waterborne coatings remaining on rags, filters, masking papers, and coating
containers may be considered hazardous waste which must be properly stored,
manifested and disposed according to 40 CFR Part
Waterborne coatings may contain chemicals defined as hazardous or extremely
hazardous substances. Depending on the quantity of material on-site,
facilities must cooperate with local emergency planning committees, have
an MSDS for each formulation, and maintain records for TRI reporting.
Waterborne Coatings: Sources of Pollution
Waterborne coatings contain some amount of material classified as volatile
organic compounds and hazardous air pollutants.
Waterborne coatings may spill due to improper handling or leaks in containers. The liquid material may enter storm sewers if not properly contained, and
may contaminate water used in spill cleanup.
Waterborne coatings may expire and no longer meet quality standards, thus
becoming waste. In addition, coatings that are not completely used
up in a job and have no use in another job are considered waste as well.
Waterborne coatings come in containers that become solid waste once empty
or when the coating is no longer useable or needed. Containers can
range from small quart or gallon cans to large barrels. Residual
coating material left inside the container adds to the volume of solid
Waterborne coatings may require organic solvents for clean up of mixing
equipment, application equipment, coating containers, or spills. The organic solvents may be classified as volatile organic compounds or
hazardous air pollutants and may be considered hazardous waste.
Waterborne coatings typically require longer and hotter curing cycles than
solvent-based coatings due to the lower volume of organic solvents. These extended periods and higher temperatures may increase energy consumption
for curing processes.
Waterborne coatings may cause flash rusting on water-sensitive substrates,
requiring parts to undergo additional surface preparation steps.
Waterborne Coatings: Pollution Prevention Opportunities
In comparison with traditional solvent-based coatings, waterborne coatings
are a pollution prevention alternative in and of themselves. The
volatile organic compound content is much lower than for solvent-based
coatings, typically less than 3.0 pounds of solvent per gallon of material
(less water, less exempt solvents). In addition, the higher solids
content of waterborne coatings results in a lower volume of material needed
for a given surface area.
Proper scheduling and procurement can reduce the amount of residual coating
material waste. To reduce residual coatings, buy only as much material
as needed to complete a job. Mix remaining light colored coatings
into darker colored coatings where possible. Purchase coating materials
in the largest containers possible for the volume; since the surface area
to volume ratio of the container is lower, less material is left on the
inside of the containers to be thrown away. Work with coating vendors
to have larger containers returned for refilling. Rotate stock of
coatings to use older material first (first in - first out practice). Before discarding expired coatings, test to see if they would still meet
quality requirements. Donate or sell old and unwanted coating materials
as raw material to others or see if vendor will take it back.
Restrict traffic in storage areas to reduce spills and accidents. Keep storage and work areas clean so that spills and leaks are more noticeable
and reaction time to clean up is reduced. Control the temperature
in storage areas to prevent the freezing and heating of coating materials
that cause them to spoil.
Enclose or cover containers of coating material when not in use to minimize
the release of solvent vapors and reduce the possibility of contamination
from facility dust and dirt.
Segregate non-hazardous coating solids from hazardous solvents and thinners,
and label containers to prevent mixing. Separation of the materials
reduces the amount of hazardous wastewater that is produced. Coating
material solids can be dried and treated as a solid waste, allowing for
disposal in a landfill.