Innovative sewer inspection as a basis for an optimised condition-based maintenance strategy

Currently, around 100,000 km of public sewers are operated in Austria, with cleaning as one of the main tasks for a wastewater utility. Due to the precarious financial situation of many cities and municipalities sewer cleaning represents a considerable financial burden, resulting in the extension of cleaning intervals and the delay of required cleaning activities. Different approaches to sewer management can be distinguished. If a selective strategy is adopted, only pipe sections with deposits are cleaned. Thus, detailed information regarding the amount of deposits is required. A simple and quick method to inspect the sewer system and assess the degree of sediments is by means of a manhole-zoom camera. The current research project INNOKANIS investigates the operational condition assessment of sewers by means of different manhole-zoom cameras. So far the data suggest that the majority of investigated pipe sections belongs to the self-cleaning category. Only 1% of the pipe sections of combined sewers and 11% of sanitary sewers require additional cleaning. The example of the city of Salzburg illustrates the potential savings in connection with sewer cleaning if a selective approach is adopted. Following a strategic change, the sewer cleaning expenses decreased by 60% within a year.