1. Put the WWTP into the flow phase, if the flow phase is not just running. (Switch on the blower and take up the end piece of the controlling float so, that increased water level in accumulation will be simulated).

2. If the mixture in the activation chamber is aerated (the chamber swirls), take a sample of the mixture into the prepared container.

3. Put aside the container for 30 min and let it settle. The optimal amount of sludge is approx. 1/3 of the taken mixture. If the amount of sludge is bigger than 1/3, there is probably an excess of sludge in the WWTP and it is necessary to pump out the content of the sludge tank. It is possible to do it either partly by an air-lift pump, or better to pump out all the volume of the sludge tank by a sludge pump. If the sludge concentration is too high, then it is necessary to repeat pumping out of sludge after few days.