To make wastewater useable again or to discharge it into the environment, it has to cleaned in a multistage process of a wastewater treatment plant.

There are three major cleaning steps, located between inlet and outlet of a plant: mechanical cleaning, biological cleaning, chemical cleaning.

An additional part is the treatment of the sludge, which is produced during the cleaning. In all areas, process monitoring is required to take corrective action if needed. This monitoring can be ensured by measuring the respective parameters. The measuring location can be critical for proper monitoring.