Segregate biological waste
Anything that met a live culture is treated before it leaves the room. Learn which bin each item goes to, and why over-filling the biohazard bag is its own problem.
- A closed plate is still full of living organisms: Putting the lid on stops nothing growing. It only stops you seeing it, and the bag it goes into is not built to hold it.
- Different hazards leave by different routes: One bag cannot serve a point, a live culture and a chemical, because the three are made safe in three different ways.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Now deal with the errors that go the other way, where too much ends up in the hazard stream.
A group clears everything from their bench into the biohazard bag, including the unopened wrapper the slides arrived in. What is wrong with that?
Reviewed- A.The wrapper never met a culture, and clean rubbish weakens the bag
- B.Wrappers must be counted for the inventory record
- C.Nothing is wrong, since over-caution is always the safer choice here
- D.The wrapper is too bulky and will tear the bag on the way out
Show the worked solution ▾
Answer: A. The wrapper never met a culture, and clean rubbish weakens the bag
- Step 1: Ask what put the wrapper at risk: Nothing did. It was never opened and never met a culture.
- Step 2: Ask what the bag is for: It signals that everything inside needs special treatment, and that signal weakens when it is full of ordinary rubbish.
Why it's right: Contact is what sends an item to the hazard stream, and the wrapper had none. Loading the bag with clean rubbish costs money to process and teaches everyone that the bag does not mean what it says.
- B: Consumable wrappers are not inventory items, and counting them would not change which bin they belong in.
- C: Over-caution has a price here, paid in processing cost and in the credibility of the bag itself.
- D: Bulk and tearing are handling annoyances that a second bag solves. They are not the reason this is a mistake.
Aligned to Handling, Preparation, Storage and Disposal · reading level ~grade 9
A tube of leftover broth culture has to be got rid of at the end of the period. What has to happen before it goes anywhere?
Reviewed- A.It is decontaminated by the method the teacher gives
- B.It is poured into the biohazard bag with the used plates
- C.It is left capped on the bench for the next class to deal with
- D.It is diluted with plenty of tap water and then poured away
Show the worked solution ▾
Answer: A. It is decontaminated by the method the teacher gives
- Step 1: Ask what is in the tube: Living organisms suspended in liquid, which spread more easily than a colony fixed on agar.
- Step 2: Ask what the drain and the bag can each do: Neither kills anything, and a bag cannot hold liquid at all.
Why it's right: Broth holds living organisms in a form that spreads easily, and neither a drain nor a sack makes them safe. The kill step comes first, and only then does the container question arise.
- B: A bag is not built to hold liquid, and it does not decontaminate what it holds either way.
- C: Leaving it capped hands a live culture to a class who did not make it and do not know what is in it.
- D: Dilution reduces the concentration and kills nothing. The same organisms reach the plumbing, just in more water.
Aligned to Handling, Preparation, Storage and Disposal · reading level ~grade 9
- A student sorts a cleared bench into four streams rather than sweeping it all into the bag that looks most cautious.
Fill these in as you work through the lesson.
- Segregate (sort into separate streams):
- Autoclave (steam under pressure, kills organisms):
- Over-classifying (putting clean waste in the hazard bag):
- Decontaminate (make safe before it leaves):
Anything that met a live is decontaminated before it leaves, a point always goes to whatever is on it, and clean unused paper is waste.
- Explain why a Petri plate with the lid on cannot go in the classroom bin.
- Give two reasons putting clean paper in the biohazard bag is a problem.
- Name the item that goes to sharps even though it also carries live culture.
Your station holds three streaked plates, a used loop, a snapped glass slide with culture on it, and the wrapper the slides came in. The plates and the loop are decontaminated by your teacher's method. The snapped slide carries culture and can cut, so a point beats a culture and it goes to sharps. The wrapper never met anything and is ordinary waste.