Renovating aging sewers? Improving environment and health or waste of money? (2013-2017)

The sewer system in Sweden is extensive, consisting of about 92,000 km of municipal pipes, with a replacement value of more than 250 billion SEK. Because of the aging sewer system, water leakage into the sewer system is substantial. Much effort is put into renovating these untight pipes but the question is if the efforts are efficient. The inflow and infiltration of water into the sewers have resulted in both increased use of chemicals at the wastewater treatment plant and energy use for pumping as well as discharges of untreated sewage into the receiving waters.

In this project financed by The Swedish Research Council Formas the overall aim is to increase knowledge about measures to improve the management of the sewer system in order to achieve health and environmental benefits. More specific, methods how to identify cross connected sewers as well as sewage in the stormwater pipes are developed. Furthermore, methods to identify and quantify inflow and infiltration (I/I) are evaluated as well as renovation efforts undertaken in the sewer system in order to decrease the I/I.

In this project, field studies are carried out together with the municipalities of Luleå and Skellefteå as well as Norrköping Vatten. In Skellefteå, several methods to identify and quantify I/I are evaluated and compared, e.g. flow and level measurements, turbidity, ammonium and an optic fiber cable (i.e. a DTS Distributed Temperature Sensing cable). This part of the project is performed in cooperation with Delft University and Partners4urbanwater. In Luleå, indicators to identify and localize illicit connections are evaluated. In Norrköping, renovation of sewers by relining is evaluated with respect to decreased amounts of I/I. Furthermore, analyses and modelling of field data are performed with the aim to achieve improved operation and maintenance strategies of the sewers.

The outcomes of this project aim at assisting the municipalities and water utilities in their efforts to prioritize and execute cost efficient measures on the sewer system which could decrease problems with discharges of untreated sewage and increase the resource efficiency within sewerage system in order to improve environment and health.

Annelie Hedström, Oleksandr Panasiuk and Youen Pericault