Apart from waste water, rainwater can also be conducted to the treatment plant. Rainwater is collected in a retention basin as a first step, in order to prevent subsequent stages from overloading. At the same time, the basin must not overflow. Ultrasonic sensors detect the fill level inside the basin, transmitted to the control room by transmitter power supplies or field barriers.
The measuring values serve as a basis to control the pumps that conduct rainwater to the plant. Those pumps are equipped with rotational speed monitors as well, enabling switching to reserve pumps. This ensures that there is always enough water flowing into the plant and that there are no disturbances, such as a burst pipe, for instance.