Collecting Algae with a Microstrainer
There is very little head to force the fluid through a
microstrainer, so the mesh size of the screen must be coarse
to get a practical filtration rate. Consider the screen shown
in the sketch and some alage of different sizes and shapes.
Some algae have beautiful spiral components, but this was too
hard to draw.
The alga marked A is only slightly larger than the mesh opening.
It is likely to clog the mesh, and some may pass through if the
screen is not uniform. Compression of the filtered material is
not likely to be too bad because that is the idea of the microstrainer
- to minimize forces.
Some of the shapes and sizes should collect well while others will
pass the screen easilty. The cylindrical organisms are of particular
interest because their orientation is important. If they hit the
screen on their long side, they are captured easily. When they
approach lengthwise, they go right through.
The points to remember are:
Algal species change with the seasons. Sometimes they may be collected
very well with the microstrainer. At other times, the sizes or shapes
may result in poor or no collection.
If some algae are recycled to the system, they have a great competitive
advantage. It is the same as inculating with the ones that are
captured well while the ones that are not captured escape from the system.
while on sabbatical leave in Porto, Sept. 96