Proper Disposal of School Chemicals
Several options are available for schools when deciding how to dispose of unneeded or unusable chemical wastes. These disposal methods are dependent on the type of chemical and it’s hazardous characteristics.
For no-longer-useful pure chemical compounds in the science laboratories, search for the chemical’s name in the school chemicals database and, once the search is complete, click on the chemical’s name for in-depth information on its hazards and proper disposal method.
For the three most commonly generated waste mixtures from school science labs - heavy metals solutions, corrosive liquid wastes, and organic solvent wastes:
- Heavy Metals Solutions: Collect waste liquids containing heavy metals in a single large wide-mouthed container lined with a sliding lock plastic bag. Leave the bag open so most of the water can be evaporated in a fume hood. When the bag is full of settled solids, zip it closed and place it in a five-gallon bucket labeled “Hazardous Waste – Heavy Metals” and snap the lid closed. When this five-gallon bucket is full of bags of sludge, dispose of it as hazardous waste. Keep a log sheet listing the name and amount of the waste solutions that are placed in the bags and the date they were added. An inventory of what the waste is made of can save you the expense of testing for identification by the hazardous waste disposal vendor or site when it is disposed. Contact the Business Waste Line at 206-263-8899 for guidance on your disposal options.
- Organic Solvents: Collect waste solvents in a glass or metal container with a tight-sealing lid. Label this container with the words Hazardous Waste. Keep a log of the amount and type of organic compounds added to the container on a log sheet with the date they were added. If you have chlorinated solvent waste, store it in a separate container labeled “Chlorinated Solvents” to reduce costs. When the containers are full, contact the Business Waste Line at 206-263-8899 for guidance on best disposal options. Waste solutions containing over 24 percent alcohol are ignitable hazardous waste and cannot be disposed down the drain nor evaporated in the fume hood.
- Corrosive Liquids: Concentrated acids and bases must be disposed as hazardous waste. Contact the Business Waste Line at 206-263-8899 for guidance on your disposal options. Dilute inorganic acid and base solutions (1.0 molar or less) can be neutralized to a pH between 6.0 and 11.0 and discharged to the sanitary sewer, provided they’ve not been contaminated with heavy metals. Keep a log sheet that tracks the amount of acidic or basic waste generated and the date it was neutralized on a log sheet. When the pH is correct, the solution can be drained to the sanitary sewer with a water rinse of 50 times the acid or base’s volume.
Schools with 220 pounds of chemical waste (art, science or maintenance) or less per month may qualify for no-charge hazardous waste disposal.
For schools with more hazardous waste requiring disposal, the No-Charge Business Hazardous Waste Disposal can help reduce the cost of disposal and assist with purchasing needed hazardous material management supplies.