In collaboration with the laboratory for microbiological ecology of the University of Gent, Kelma has developed the Nitrox 2000. It is an on-line toxicity analyser. It measures, rapidly and extremely accurately, the activity of the nitrifying bacteria in active sludge. The activity of these bacteria is very rapidly suppressed whenever water carrying concentrated toxic burdens flows into the installation through the inflow. In all industrial and household water purification plants, the nitrification process is also the most fragile step, which with the aid of the Nitrox 2000, can now be checked and protected better than before.To be able to measure the activity of the nitrifying bacteria, the Nitrox analyser determines the oxygen use of these bacteria. First the reactor is filled with wastewater, then the nitrifying sludge is added and finally the oxygen use of the bacteria is measured. Low activity indicates the presence of toxic components in the wastewater. If the toxicity alarm threshold is exceeded, then the operator of the water purification plant can take appropriate measures on time. Keeping up to standard is no longer problematic and the costs are limited because the water purification process can be modified more rapidly than previously.