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234 Safety Reference
Review of Chemical Disposal Procedures
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Responsible management of the chemical resources of school science labs encompasses best practices for the purchase, storage, use, and disposal of chemicals. It is a shared responsibility of the admin- istration, faculty, and staff. Chemical disposal procedures require compliance with a variety of federal, state, and local laws and regu- lations, and are therefore a particular challenge for many science departments.
The Resource Conservation and Recovery Act
The Resource Conservation and Recovery Act, or RCRA, is the key law dealing with the identification, management, and disposal of hazardous waste. All institutions are required to have a policy for identifying hazardous waste and complying with the requirements of RCRA, which was enacted in 1976. The overarching goals of the law are to reduce the amount and toxicity of hazardous waste and thus protect human health and the environment. In writing the regulations to ensure that the goals of RCRA are achieved, the Environmental Protection Agency (EPA) also has the mandate to promote methods to minimize the amount of hazardous waste and reduce its environmental impact. These methods include source reduction, reuse and recycling of wastes, and chemical treatment that will eliminate hazardous waste characteristics.
Knowing Your RCRA Status and Requirements
In most cases authority for implementing and enforcing the law has been delegated to individual states that have adopted the RCRA guidelines. Some states may be more restrictive or impose additional conditions than federal guidelines require. Federal EPA recognizes three classes of hazardous waste generators, based on the amount and kinds of hazardous waste generated in one month. The storage and reporting regulations become increasingly more stringent as the amount of hazardous waste increases. Schools that generate less than 100 kg (220 lbs) of hazardous waste per month, and no more than 1 kg of acutely hazardous waste in any month, would fall into the least regulated, “conditionally exempt small quantity generator,” class. (The definitions for these types of waste are summarized below.) The EPA defines hazardous waste as a subset of solid waste, where solid waste is anything that will be discarded or may enter the environment—by burn- ing, for example. (It’s confusing, but the term solid waste thus includes solids, liquids or gases!) Obviously, all schools and other institutions produce solid waste. Regardless of their RCRA status, all schools are required to determine which types of solid waste must be classified as hazardous waste.
Identifying Hazardous Waste
The first step in managing chemical disposal is identifying which discarded chemicals, as well as chemical reaction mixtures or byprod- ucts that will not be reused, must be considered hazardous waste. There are two broad categories of hazardous waste—characteristic wastes and listed wastes. Characteristic wastes have one or more of the following properties:
• Ignitable wastes include flammable or combustible liquids (flash point <140 °F) as well as flammable compressed gases and solid oxidizers. Organic solvents such as acetone or toluene, compressed gases such as hydrogen, and solid ammonium nitrate are examples of ignitable wastes.
• Corrosive wastes are acidic or basic solutions that have a pH <2 or >12.5, respectively.
• Reactive wastes are substances that react violently with air or water, are capable of detonation, or can generate toxic gases under rela- tively neutral conditions. Examples include the alkali metals sodium and potassium, diethyl ether and other peroxide-forming organic compounds, and cyanides or sulfides.
• Toxic chemical wastes are substances that, if disposed in a landfill, are capable of leaching threshold amounts of specific chemicals into groundwater. There are 40 substances in this category (also known as toxicity characteristic wastes). Although many of the substances on this list are pesticides, the list includes common heavy metals, including lead, barium, and silver.
There are four categories of listed wastes. Two categories include chemical byproducts from manufacturing processes and do not generally apply to schools. The other two categories, designated by the codes P and U, identify by name specific discarded commercial chemical products. All academic institutions should be aware of the chemicals on the P- (acutely toxic) and U- (toxic) lists. The P-listed, or acutely toxic, wastes are especially important because any school generating more than 1 kg (2.2 pounds or approx. one quart of liquid) of acutely hazardous waste per month will be subject to the most stringent generator requirements for listing, storing, and reporting all their hazardous waste. Most institutions do not use many P-list chemicals. The exceptions, which some schools might use, are sodium cyanide, potassium cyanide, arsenic trioxide, sodium azide, ammo- nium vanadate, and carbon disulfide. Recall that listed wastes refer to discarded or unused commercial chemical products where the chemi- cal is the sole active ingredient. Make sure your school has effective chemical purchasing and inventory controls in place if you use P-listed chemicals in your science labs. This will prevent the school from accu- mulating excess chemicals that must be discarded.
Treating Chemicals in the Lab
The EPA encourages all waste generators, including academic institu- tions and laboratories, to minimize the amount of hazardous waste. Treating materials in the lab to reduce or eliminate chemical and physical hazards is one strategy for accomplishing this goal. Chemicals or chemical byproducts that are stored in the lab or remain in the lab after a lab activity is finished are not generally regulated as solid waste. The treatment of hazardous waste without a permit is generally not allowed. To avoid restrictions on treating hazardous waste, always incorporate treatment or disposal of excess reagents or chemical byproducts from a chemical reaction into the lab procedure itself. The Flinn Suggested Disposal Methods described on pages 239–260 may frequently be used to treat chemicals and eliminate potential hazards. Before undertaking any of these methods it is important to read, review, and understand the general principles and guidelines governing the disposal of laboratory chemicals:
• Check all federal, state, and local guidelines that may apply.
• All procedures should be carried out by skilled and trained personnel who are familiar with the physical and chemical properties of the chemicals and understand the procedure.
• Observe all safety precautions, including the requirements for personal protective equipment.
• Carry out all reactions that may generate gases in the hood.
• Provide secondary containment to protect against spills.
• Consult current Safety Data Sheets for storage, handling, and
disposal information.
• Wear chemical splash goggles, chemical-resistant gloves, and a lab coat or chemical-resistant apron.
Examples of generally allowed chemical treatment methods include
neutralization of acids and bases (Flinn Suggested Disposal Methods #24a, b and #10, respectively); redox reactions for oxidizing agents and reducing agents (Flinn Suggested Disposal Methods #12a and 12b); and precipitation reactions for metals (Flinn Suggested Disposal Methods #11 and 27h).
REVIEW OF CHEMICAL DISPOSAL PROCEDURES continued on next page.