Page 9
Copyright Wet Paper Publications 2010
Materials
For each filter you will need (See Figure 9.2)
• One 10mm X 100mm PET sample tube with plastic screw
top. See page 120 for equipment supplier details.
• One flat bottom 10ml clear polystyrene cylindrical test tube
with screw top
• Quantity of 3mm (1/8”) clear PVC plastic tubing
• One sterile cotton wool ball
• Hand drill and 3 mm drill bit
Procedure
Step 1 Hold the tube securely and drill a 3 mm hole in the
centre of the cap and the bottom of the tube as shown
in Figure 9.1.
Step 2 Now unscrew the plastic lid off the sample tube and
remove any drill shavings.
Step 3 Sterilise the tube and lid in bleach (see box below).
Step 4 Place a sterile cotton wool ball in the tube (Figure 18.1,
Page 18).
Step 5 Insert the required length of plastic into the outlet and
inlet holes (Figure 18.1).
Discussion
1. Explain why a filter is needed on the inlet air line.
2. Explain why a filter is needed on the outlet air line.
3. Discuss the benefits of making the filter out of clear plastic
specimen tubes that can readily be pulled apart.
4. Explain the reasons for growing micro algae in ‘closed’
containers rather than open fish tanks.
5. Explain why sterilization is needed for equipment.
Hand drill
3 mm drill bit
1 flat bottom 10ml clear
polystyrene cylindrical test
tube with screw top
Figure 9.1 Drill a 3 mm hole in the centre of the cap and the
bottom
Cap
3mm (1/8”) clear PVC plastic
tubing
Figure 9.2 Parts ready for assembly
Mick O'Connor
Mick O'Connor
Sterilizing
A simple method of sterilization is
to use household bleach.
• Follow the instructions on the
bottle for nappies - dilution is
usually 1/5 dilution
• Fill acontainerofknownvolume
that will fit all the tubes and lids
with water and use one part
bleach to five parts water
• Immerse all equipment to be
sterilized for one hour.
- be careful of your clothing
with bleach as it can leave
nasty white marks on school
uniforms!!
1 3,4,5,6,7,8,9,10