Managing waste properly in a science laboratory is vital to protect the environment and avoid endangering living things. Not all substances can simply be poured down the sink or thrown into regular dustbins.
Compare the four biological waste categories and the action steps for chemical versus mercury spills.
Biological waste substances are disposed materials that can cause serious harm or biological hazards.
Laboratories deal with dangerous substances requiring strict safety protocols. Strong chemicals, reactive compounds, and solids cannot go into the sink because they can corrode piping, cause explosions, or poison waterways; only weak acids, weak alkalis, and neutral liquids of low concentration are permissible.
Biological wastes must never be mixed together. Sharps (Category A) go directly into dedicated puncture-proof sharps bins without autoclaving to prevent puncture hazards; solid non-sharps (Category B) must be autoclaved at 121°C under 15 psi for 20 minutes; animal carcasses (Category C) must be wrapped in absorbent paper and frozen; and biological liquids (Category D) must be autoclaved before sink/toilet disposal.
In emergencies, quick action is essential. Isolate the area and call staff first, then use sand to dam normal chemical spills or sulphur powder to react with toxic mercury before fire authorities take over.
Not every substance can be poured down the sink.
Substances with low concentrations and that are non-hazardous.
Examples: neutral substances (e.g., distilled water), weak acids, and weak alkalis.
Substances that pollute the environment and are hazardous to living things.
Examples: solid waste, substances with a pH value lower than 5 or more than 9, organic solvent compounds, chemical substances (acid, grease, oil, oil paint, hydrogen peroxide), toxic substances, heavy metals, organic waste substances (microbes, carcasses), radioactive waste, volatile substances, and reactive substances.
Biological waste is managed through a specific Standard Operating Procedure (SOP).
Biological waste substances include tissues, carcasses, culture medium, plastic containers, glass, and gloves. They are managed through a specific Standard Operating Procedure (SOP).
1. Separation at source: Carry out the separation of waste at the source correctly.
• Category A: Temporarily stored in a safe place.
• Category B: Placed in a leak-proof autoclave bag and autoclaved at 121°C, 15 psi, for 20 minutes.
• Category C: Packaged carefully and temporarily stored in a freezer.
2. Decontamination: Waste that has been decontaminated is placed into a biohazard bag.
3. Storage & Disposal: Packaged waste is labelled and placed in biohazard bins. Biohazard bins are temporarily stored in a safe, controlled condition and cooled before centralised disposal is carried out.
Accidents occur due to carelessness, negligence, unexpected events, or lack of skills/knowledge.
Common accidents include cuts from glass splinters, splashes of concentrated acid/alkali, small fires, reactive metal residues, broken thermometers, gas leaks, and electric shocks.
When a chemical substance spills on the bench:
1. Inform the teacher or the laboratory assistant immediately.
2. Make the spillage area a restricted zone.
3. Stop the spillage from spreading by using sand to form a boundary.
4. Scoop the chemical spillage.
5. Dispose of it safely.
Mercury is dangerous because mercury poisoning can occur via skin absorption or touch. It attacks the nervous system, digestive tract, reproductive system, and kidneys.
When mercury spills:
3. Sprinkle sulphur powder onto the spillage.
4. Call the Fire Department.
Answer in your mind, then press “Check Answer”.
Can a solution of concentrated hydrochloric acid with a pH of 3 be disposed of directly into a laboratory sink? Explain why.
How should an animal carcass from an experiment be prepared and handled for disposal?
State the specific substance that must be sprinkled over spilled mercury from a broken thermometer, and state who must be contacted afterwards.
All biological wastes can be thrown into the regular laboratory dustbin if they are sealed in a plastic bag.
Biological wastes carry hazardous pathogens and biological risks; they must follow the specific SOP (Category A in sharps bins, Category B autoclaved in biohazard bags, Category C frozen, Category D autoclaved liquids).
Category A sharps should be autoclaved to sterilise them before putting them in bins.
The SOP specifically states that Category A waste is not autoclaved; sharps are stored directly in rigid sharps containers to prevent needle-stick injuries during handling.
Mercury spills can be scooped up with sand just like other chemical spills.
Mercury releases toxic fumes and easily absorbs through the skin. It requires sulphur powder to chemically bind/coat it, and the Fire Department must be summoned.
1 Which of the following biological waste substances must NOT be autoclaved before disposal according to the Standard Operating Procedure?
2 What is the correct action to take immediately after restricting the area during a mercury spillage caused by a broken thermometer?
3 Under Category B waste management, non-sharp solids are autoclaved at a temperature of 121°C and a pressure of 15 psi for minutes.
4 To stop an ordinary chemical spill from spreading on a laboratory table, is used to form a boundary.
Drag each waste item to its correct Standard Operating Procedure disposal category. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.
Write the correct waste item next to each disposal category.
Answer choices: Syringe needle • Used gloves and culture medium • Experimental animal carcass • Blood and serum
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