1.1 Preparing the Biofilter

Our first objective is to start up a biofilter for the recirculation system. Therefore we need a tank, a filtering mechanism, heating and water. In this virtual labwork we assume that we already have a suitable tank at our disposal, but before we actually can start filling it, we need something to filter the water... 

1.1.1 Choice of the Substrate

Many biofilters can be constructed and all have their own advantages and limitations (biodrums, trickling filters, beat filters, fluidised bed filters). For our project we will construct a submerged biofilter which is probably not the most efficient or most compact biofilter, but easy to construct and able to support high flow rates without releasing floccules or bacterial mats.

For constructing the biofilter our tank needs an aeration system on the bottom (for instance perforated PVC tubing).

PVC tubing at the bottom of the biofilter (click to enlarge)	PVC tubing - detailed (click to enlarge)

This tubing will be covered with inert material on which a biological film of nitrifying bacteria will develop. This biofilm contains nitrifying bacteria that will oxidise the toxic organic ammonium compounds to the less toxic nitrate, and hence produce on a continuous basis a less toxic environment for the rotifers.

Now we will have to decide what material (substrate) is best suitable for filtering the water. The choice of inert material will be essential since it forms the substrate for the bacteria.

DO THE EXERCISE...

HOME                                             PREVIOUS STEP| EXERCISE | NEXT STEP                                              INDEX