Biofilter design for clean healthy pond water
biofilter, bacteria, water, ammonia, flow, mass transfer, chemical reaction, Biofilters work, amount, temperature, presence, interface, circulating water, nitrates, nitrites.
Summary:
The primary job of a biofilter is to convert ammonia (or ammonium) to nitrites and then to nitrates using very 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.
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 there was insufficient oxygen in the water.
All of these things happen to be very bad for biofiltration and all can be explained by an understanding of the principles of mass transfer.
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 create the concentration differences required for good mass transfer.