Page 8
Copyright Wet Paper Publications 2010
Figure 8. 1 Completed air filter
P
ROJECT
1.2 M
AKING
AN
AIR
FILTER
FOR
ALGAL
CULTURES
Background
Micro algae like all plants require carbon dioxide (CO
2
) for
photosynthesis.
• They obtain this gas from the air that is dissolved in thewater
in which they live.
When micro algae are grown in containers they have to have
enough air to provide the carbon dioxide they need.
• This is not a problem when a small amount of liquid is put
into a large container - the air can diffuse in and out through
a cotton wool or specially designed filter plug as shown in
Figure 8.2.
It does become a problem when algae are grown in containers
with little free air, providing insufficient carbon dioxide for the
algae to make food.
Figure 8.2 A small amount of liquid put into a large container is
not a problem for a time
(Illustration Mick O'Connor)
A solution
To overcome this air must be pumped into the container
as described in Figure 8.3 (below)
• Normal air will contain minute particles of dust and
may also contain micro organisms such as bacteria
and fungi that may be harmful to the algae or what the
algae will be fed to.
• To minimise the risk of infecting the algal culture, the
air being pumped in is filtered. A cotton wool filter is
placed on the inlet tube, filtering the air coming in to
remove micro organisms. Another similar filter is
placed on the outlet tube to prevent microorganisms
entering the culture as the excess air escapes.
• The double filter acts as a barrier. Air containing the
needed carbon dioxide is provided continuously to the
algae allowing them to growwhile excluding airborne
micro organisms coming back through the outlet tube.
Figure 8.3 Algal growth container
Project 1.3 over
describes how to
make this
container
Mick O'Connor
Mick O'Connor
See page 116 for equipment
supplier details.
1 2,3,4,5,6,7,8,9,10