Most middle and high school science laboratories produce chemical hazardous waste, but what exactly is it, and how do you dispose of it appropriately?
Chemical waste is a substance that poses a hazard to human health or the environment, including toxins, corrosive liquids, and organic solvents. A school’s chemical hygiene plan or lab safety plan should include instructions for properly disposing chemical hazardous waste, as well as offer strategies for implementing alternatives to traditional chemistry lab activities or provide more teachers laboratory demonstrations. Both would ultimately reduce the amount of chemical hazardous waste.
The Environmental Protection Agency defines hazardous waste as a waste that is ignitable, corrosive, reactive, or toxic. According to the EPA,
• Ignitable hazardous waste could cause a fire during handling. Examples include acetone, ethanol, ethyl ether, hexane, and methanol.
• Corrosive hazardous waste could corrode containers. Examples include strong acids with pH less than 2 or strong bases with pH higher than 12.5.
• Reactive hazardous waste could explode with air, water, or other chemicals. Examples include picric acid, dinitro and trinitro compounds, and ethers with peroxides.
• Toxic hazardous waste contains toxic components such as carcinogens, mutagens, teratogens, and heavy metals.
The first step in disposing of chemical hazardous waste involves determining its location. Usually, chemistry laboratories produces waste, but biology laboratories may also produce biological or medical waste as the result of biotechnology and microbiology course work.
The second step involves determining whether the waste is hazardous or nonhazardous. This will dictate how to handle the waste. A generator in school laboratories can make the determination based on information supplied by the manufacturer’s Safety Data Sheet. Alternatively, you can check if the chemical is listed in the Resource, Conservation and Recovery Act (RCRA).
In addition, all waste containing chemical solids, liquids, or containerized gases should be treated as hazardous chemical waste. A laboratory chemical is considered to be “waste” when you no longer plan to use it. Spilled chemicals and materials used to clean them up are hazardous waste. In addition to stock chemicals, items containing chemicals (e.g., solvents, glues, disinfectants) are hazardous waste.
Collecting and disposing hazardous waste
The American Chemical Society’s book titled Guidelines for Chemical Laboratory Safety in Secondary Schools provides the following series of steps in planning for hazardous waste collection and disposal:
1. Spend time planning and preparing for the activity.
2. Select laboratory activities that are tailored to your science standards:
a) Review the properties of the chemicals required and the products generated using resources such as the SDS. If the reactants or products require special disposal or create unique hazards, then modify the experiment to use safer materials.
b) Use small-scale or microscale procedures. These reduce waste, save on resources, and reduce preparation time. Know and review the federal, state, and local regulations for disposal of the chemicals involved.
3. Incorporate disposal instructions into your laboratory activity. By making waste disposal a routine in every activity, students will develop a culture of concern for the environment and accept it as part of their responsibility. Note: Many laboratory explosions have occurred from inappropriate mixing of wastes, such as mixing nitric acid waste with organic wastes, so be sure that waste materials are compatible. Mixing nitric acid with any organic materials may result in an over pressurization of the waste container and release of the chemical into the workspace.
4. Collect all compatible waste solutions with similar properties in a centrally located, well labeled container.
5. Dispose of waste immediately, following the regulations appropriate for your area. Disposal of small amounts of waste is easier and quicker than disposal of larger, stockpiled amounts.
The following is a suggested safety disposal protocol that can help you dispose of hazardous lab chemicals. Specific protocols are determined by the needs of each laboratory based on the types of hands-on activities and/or demonstrations.
Glastonbury Public Schools (CT) Laboratory Waste Disposal Safety Procedure
Over the past few years, waste-reducing strategies in science labs have been adopted to reduce the amount of hazardous chemical waste being produced. However, to prevent safety incidents resulting from mixing reactive chemical products, science teachers need to be vigilant when disposing and removing solid and liquid waste produced in laboratories.
The following safety procedure will help reduce or eliminate the danger of unexpected reactions and also help foster proper waste disposal:
a. Proper receptacles: Appropriate waste containers should be made available in the labs to prevent cross contamination of chemical products from lab activities. The use of each container will depend on the number of students and how many times the same lab is conducted. These plastic containers with lids need to be HDPE-rated (High-density polyethylene) as chemical resistant. The containers are to be labeled and color coded for liquid chemical waste or solid chemical waste. Before the end of each class period, students must return any chemicals (excess reagent, product, or waste) to the appropriate location, or dispose of them as instructed by their teacher in chemical waste disposal containers. For instructions on disposal of specific hazardous chemicals, check out: http://mdk12.msde.maryland.gov/instruction/curriculum/science/safety/chemicals.html.
b. Tag it: Each hazardous waste container from the lab needs to display the following information. This information can be completed by the teacher or lab paraprofessional.
• name of chemical waste components;
• known hazard (e.g., GHS pictograms); and
• date, school building, lab room, and science teacher.
c. Storing waste: If you add waste to a container until it is full, make sure it is segregated into compatibility groups. Also remember to add the additional contents to the tag. Keep the containers closed while being stored. They can be temporarily stored in the laboratory if additional use is anticipated within two weeks and if there is space in the container. Waste ultimately will be stored in the chemical storeroom, but again, make sure it is segregated from other chemicals and is clearly labeled and tagged. Also, have the Safety Data Sheets available.
d. Removing waste: The waste removal process will depend on the type of waste. Some forms of waste will be processed and neutralized on site by the science paraprofessional or teacher. Most waste must be picked up and removed from the site. If removed, make sure to record the day it was removed on a document—the school owns the chemical. Always plan ahead—either process it or have the waste removed in an environmentally responsible way via the maintenance hazardous waste disposal program vendor. In addition:
• Chemical storage areas shall be equipped with spill control and containment equipment, and fire extinguishers (types A, B, and C).
• Any storage area containing flammable metals must have a type-D extinguisher available.
• All chemical materials to be recycled shall be recorded on a document.
• The district will provide an annual collection for chemicals to be recycled.
Submit questions regarding safety to Ken Roy at firstname.lastname@example.org or leave him a comment below. Follow Ken Roy on Twitter: @drroysafersci.