Department of
Environmental Quality

A spent solvent is a type of spent material, which is defined as "any material that has been used and as a result of contamination can no longer serve the purpose for which it was produced without processing." Spent solvent is considered solid waste and may be hazardous, depending on its content. Examples of spent solvents include mineral spirits, chlorinated solvent, paint-related waste, and alcohol that is no longer useful.

Under the federal Resource and Recovery Act (RCRA) which Idaho has adopted by reference into state rules, owners and/or operators of facilities where spent materials are generated must be able to demonstrate they have adequately determined if the solvents are hazardous prior to shipping offsite for disposal.

How to Determine if a Spent Solvent is Hazardous

A spent solvent is hazardous if it meets certain ignitability, corrosivity, or toxicity characteristics, or meets the definition of a listed hazardous waste.

To determine if the spent solvent is...

...ignitable, you will need to know if it has a flash point below 140° D. If so, it must be managed as a hazardous waste. Solvents which exhibit this characteristic carry the D001 hazardous waste code.

...corrosive, you will need to know if the material is aqueous and has a pH less than or equal to 2 or greater than or equal to 12.5 or is a liquid that corrodes steel at a specific rate under specific conditions as prescribed in 40 CFR 261.22.

...reactive, you will need to know if the material is explosive, unstable or undergoes violent change without detonative, reacts violently or generates toxic gases, vapors or fumes when mixed with water. Solvents which exhibit this characteristic carry the D003 hazardous waste code.

...toxic, you will need to know if the material contains any organic or inorganic chemicals in excess of allowable concentrations listed under 40 CFR 261.24.

...listed, you will need to know if it meets the definition of an F-listed hazardous waste under 40 CFR 261.31, which means it must contain 10% by volume of one or more of the constituents in the listing description for waste codes F001 - F005.

Disposing of Hazardous Spent Solvents

Regulated spent solvents may be at a recycled for reuse either at the generator facility or off-site or disposed of off-site at a permitted hazardous waste Treatment, Storage, and Disposal facility (TSD). DEQ recommends that businesses recycle as much spent solvent as possible. To avoid ground water contamination, do not dispose of any regulated spent solvent down any drain or on the ground, and don't put spent solvents into a garbage dumpster on the ground.

Regulated spent solvents count toward to the facility's generator status.

Solvent-Contaminated Rags

Solvent-contaminated rags may be laundered on-site or sent to a regulated commercial laundering facility. If a business is using launderable, reusable cloth rags or wipes, the contaminated cloth rags are not subject to generator, transporter, and permitted treatment, storage, and disposal facility requirements and are not “counted” as a hazardous waste if free liquids are properly removed, rags are stored and transported properly and kept away from sources of ignition, containers holding used rags are properly labeled, contaminated rags from more than one process with incompatible solvents are not stored in the same container, and on-site documentation is maintained and available for review.

If a business is using rags and wipes that are not laundered for reuse, a different set of requirements applies. When these rags become too dirty to use, they are considered a solid waste subject to a waste determination and applicable hazardous waste regulations, depending upon the type of solvent the rag contains.

Air-drying solvent-contaminated rags to allow volatile constituents to evaporate is not a permissible form of treatment or disposal. Evaporation merely transfers the hazardous constituents from the rag to the air.

In many instances, it is possible to eliminate the generation of hazardous waste rags. Nonhazardous solvents may replace F-listed and characteristic solvents or a generator may consider mechanical methods of cleaning such as power washing or steam cleaning using non-hazardous detergents.

Alternative Cleaning Solvents and Processes

In recent years, environmental concerns have made traditional solvent cleaning products and processes increasingly regulated and expensive. Some ozone-depleting chemicals are being phased out, while emission and operating standards have been placed on the use of others. DEQ encourages businesses to consider switching to safer, less toxic alternative products or processes when cleaning criteria can continue to be met. Popular alternatives include:

• aqueous cleaning solutions that use water as the primary solvent
• semi-aqueous solutions that use a mix of water and natural or synthetic organic solvents or other additives
• carbon dioxide blasting using pellets shot at a surface with air or other gases to strip paints and to remove grease and oil or soft "snow flakes" of frozen gas to clean surfaces
• media blasting combining an abrasive media, a pressurized delivery system, and one of a variety of cleaning chambers
• solvent recycling units. These units can reduce waste generated and the amount of solvent purchased. This option also may be cost-effective, depending on your operation
• automated aqueous parts washers. These units use a soap/hot water mixture to clean parts and work much like a large dishwasher. Costs for solvents and waste management are reduced. Employees spend less time cleaning parts and more time doing other work. May have payback in 1 to 2 years.

Best Management Practices

Switching to different products or processes can require capital investment. The following recommendations identify cost-effective ways to reduce solvent use and employee exposure to solvent vapors:

• Keep vapors contained. Keep doors to mixing/storage areas closed at all times, properly label all solvent containers, and store and transport solvents only in approved safety containers. Read container labels and follow directions. Keep containers tightly closed when not in use.
• Minimize chances of spills and leaks. Use secondary containment whenever possible, and develop and follow safety procedures for storing and using solvents. Inspect equipment and storage containers frequently. Clean up spills and leaks quickly, and repair leaky containers immediately. Be sure employees are properly trained.
• Minimize solvent use. Evaluate cleaning needs and establish guidelines to reduce excessive cleaning. Avoid cross-contamination and water contamination of solvents. Use solvent only for designated purpose.