Proper waste management and disposal procedures for sorting and handling hazardous waste will ensure a safe school and protect human health and the environment.
Advice for Handling Hazardous Waste in Schools
The general advice for handling hazardous waste in school laboratories is in line with the hierarchy of waste management.
- Optimize the process to reduce or avoid waste and hazards (more about Green Chemistry).
- Replace hazardous substances with less hazardous substances (more about Substitution).
- Make the waste less hazardous by e.g. neutralization, dilution, evaporation, oxidation, decomposition, precipitation or filtration.
- Hazardous waste that cannot be treated and made harmless in the laboratory, must be collected and disposed according to applicable regulations for sorting and handling hazardous waste.
- Label and store your waste properly prior to disposal or recycling.
Classification of Hazardous Waste
Hazardous waste may pose a risk to human health and the environment, and thus requires a control regime. Waste which displays one or more of the hazardous properties listed in Annex III of the Waste Framework Directive is considered hazardous waste. The table below gives an overview of some hazard classes that are highly relevant for school chemistry. The complete list of chemicals is found in Annex III.
The hazard statements for a chemical and information about the hazard classes can for example be found in the safety data sheet (SDS) section 2.1. Be aware that a solution that is not classified as a hazardous chemical can be classified as hazardous waste.
The following example shows how to use the table to determine whether 1 mol/L HCl is classified as hazardous waste: In the SDS of concentrated HCl, it is stated that this solution is classified as skin corrosive 1B (H314). According to the table below the concentration limit is then 1 % (mass/mass). Since 1 mol/L HCl is approximately 3.6 %, this solution is classified as hazardous waste, and needs to be handled as such. Furthermore, concentrated HCl is classified in other hazard classes. However, we do not need to consider them because we already have classified 1 mol/L HCl as hazardous waste.
|Hazard pictogram||Hazard Class and Category||Hazard Statements||Concentration Limit||Examples|
|Flammable liquid 2||H225||Propan-1-ol|
|Flammable liquid 3||H226||Pentan-1-ol|
|Flammable solid 1||H228||Iron powder|
|Flammable reactant 1||H260||Magnesium, sodium, calcium carbide|
|Skin corrosive 1A/B/C||H314||1 %||Hydrochloric acid|
|Eye damage 1||H318||10 %||Zink sulfate|
|Skin irritant and/or eye irritant||H315 and/or H319||20 %||Sodium carbonate|
|Acute toxicity 3 (oral)||H301||5 %||Barium chloride, methyl orange|
|Acute toxicity 4 (oral)||H302||25 %||Ammonium chloride|
|Acute toxicity 3 (dermal)||H311||15 %||Methanol|
|Acute toxicity 4 (dermal)||H312||55 %|
|Acute toxicity 3 (inhalation)||H331||3.5 %||Nitric acid|
|Acute toxicity 4 (inhalation)||H332||22.5 %|
|Aquatic acute 1||H400||25 %|
|Aquatic chronic 1||H410||0.25 %||Copper(II) sulfate, silver chloride|
|Aquatic chronic 2||H411||2.5 %||Manganese(II) chloride|
|Aquatic chronic 3||H412||25 %|
How to Dispose of Laboratory Waste
School science and chemistry laboratories should have waste disposal stations for hazardous waste that complies with the applicable requirements. The waste containers must be labelled with appropriate pictograms and stored in cabinets according to the hazards of the content. The school needs routines for what to do with the waste when it needs to be disposed of. Local and national regulations are often stringent; for this reason, you should contact the local authorities to get guidance.
Advice for Waste Disposal Stations
Designate a hazardous waste storage area that is out of the way of normal activities, yet easily accessible and recognizable for the users.
The containers at a waste disposal station should:
- be chemically compatible with the waste they will hold (e.g. acidic and alkaline solutions in high-density polyethylene containers)
- be sturdy and leak-proof
- have screw-on caps
- be placed in a secondary container (e.g. polyethylene retention tray) in the case of liquid waste to prevent leaks and spills
- be labelled in accordance with local and national requirements
The tables below suggest how to organize chemical waste and other laboratory waste. Below the tables there is a decision tree that can be helpful to determine which container to use for different hazardous waste.
If a professional company is handling the waste, consult with this company on the choice of containers and what to dispose of in the different containers.
E.g. hydrochloric acid
E.g. sodium hydroxide
Solutions of toxic inorganic salts
E.g. heavy metal salts, copper salts
Non-halogenated organic substances
E.g. ethyl acetate, methanol, heptane
All halogenated organic substances and waste from halogenation reactions of organic substances
E.g. chlorobenzene, bromopropane
Solid metals should be reused (e.g. copper electrode) or reacted to completion (e.g. magnesium in acid when making hydrogen gas).
Small amounts of liquid fats and oils can be put in a sealed container (e.g. a milk carton) and disposed with the regular waste. Larger amounts should be collected and delivered along with the hazardous waste.
Contaminated pointed and/or sharp objects
E.g. heavily contaminated Pasteur pipettes, broken laboratory glass
Contaminated solid waste
E.g. heavily contaminated gloves, paper towels, filter paper
Uncontaminated laboratory glass
E.g. uncontaminated laboratory glass non defined as recyclable glass (broken or not)