Introducing Kaldnes Biomedia In Hozelock Trinamic Pond Filter Design & Operation
The primary job of a biofilter is to convert ammonia (or ammonium) to nitrites
and then to nitrates using specific bacteria types. In practical terms this
requires that ammonia, which is dissolved in the circulating water, must make
contact with bacteria at an interface and in conjunction with oxygen in such a
way that a chemical reaction can take place.
Take a look at our diagram again.
Once the chemical reaction has taken place then the product of the reaction
which is nitrite or nitrate must be able to be transferred back into the body of
the circulating water and removed from the immediate presence of the bacteria to
make way for the next bit of ammonia.
If you go back to our coffee examples what do you think would happen if there
was
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only a small area for contact with the bacteria or
-
the rate of flow through the filter was slow or
-
if the temperature was say only 5 degrees centigrade or
-
if there was insufficient oxygen in the water.
All of these things happen to be bad for biofiltration and all can be explained
by an understanding of the principles of mass transfer.
Therefore a
well-designed biofilter MUST have:
-
A large surface area on which bacteria can grow and to which a maximum amount
of pond water can be exposed
-
Biofilters work best at higher flow rates/lower residence times - ie
turbulent flows are best.
-
The presence of large amounts of oxygen at the interface also creates the
concentration differences required for good mass transfer. This is why top class
koi keepers have vortex filters and blow massive amounts of air around the biomedia that is generally Japanese matting.
-
The Hozelock Trinamic products (by far the
best so get as much information as you can from Bradshaws) and before this
most types of pressurized pond filters (and especially the FishMate series
which contain Alfagrog biomedia) are excellent examples of good use of mass
transfer principles
-
On a much larger scale and used extensively in
large koi ponds the biomedia Kaldnes (as used in the Trinamic) allows small
footprint biofilters to replace massive underground vortex filter
installations. The reason is the dramatic increase in turbulence and surface
area contact made possible by the properties of Kaldnes. Before Kaldnes came
along all biofilter media were static and relied upon turbulent flow passing
a static concentration of bacteria. With Kaldnes and the Trinamic the
bacteria are in a continuous state of agitation and they love it.
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