Biofilter
A biofilter is designed to remove toxic ammonia and nitrite from
the water. One group of nitrifying bacteria oxidise ammonia to nitrite, and a
second nitrite to nitrate. It should be noted that considerable oxygen is
required for this process. Therefore the biofilter needs to be supplied with
sufficient oxygen for the needs of the nitifying bacteria. This means that the
biofilter should be as close to oxygen saturation as possible.
A routine analysis of the DO (Dissolved Oxygen) in the effluent
is vital since oxidation of ammonia stops below a DO level of 2 mg/l.
Temperature is also important because nitrifying bacteria are slow-growing, the
optimum temperature should be around 28°C - 36°C. The pH should be
about 8.
Nitrifying bacteria must attach to a surface, therefore careful
selection should be given to the selection of the biofilter substrate, we will
use gravel with a diameter of 3-8 mm.
