Linz – CSO management

The SUDPLAN pilot of Linz will develop planning tools for dimensioning of water sewer systems, to mitigate future spill behaviour of combined sewer overflows (CSO).

The Linz pilot focuses on the problem of combined sewer overflows into receiving waters. Proper strategic adaptations can be developed within the catchment area, by comparing the results of today’s and of future scenarios possible effects and changes.

The Linz pilot will explore the suitability and applicability of an innovative sensor, communication and information system for the improved operation of the sewerage system under possible climate change conditions.

Mainly because of historical aspects most European cities are operating combined sewer systems which mean that waste water and storm water is drained in one sewerage system.

Due to the hydraulic limitation of waste water treatment plants it is not possible to treat the whole amount of the drained water during heavy rainfalls. Therefore, the storm water runoff in combined sewer systems has to be either spilled out at combined sewer overflows into receiving waters or stored temporarily in reservoirs.

Since it can be assumed that during more frequent and heavier rainfalls the overflow duration of these facilities and the spilled out pollution loads to receiving waters will also increase, possible climate changes might have crucial impacts to the aquatic environment.

Estimating CSO and sedimentation efficiency

Within this pilot two main tasks will be carried out:

- Estimation of overall combined sewer overflow efficiency rates for dissolved pollutants and for particulate pollutants in the catchment area of the waste water treatment plant of Linz, based on long-term simulations with historical and predicted rain data provided by the common services of the SUDPLAN project.

- Estimation of the sedimentation efficiency rate for the primary clarifiers of the treatment plant in Linz by the installation and operation of a novel sensor network in the inflow and outflow of the clarifiers in order to quantify the total suspended solid and chemical oxygen demand retention efficiency under different storm water flow regimes. The sedimentation efficiency rate of these clarifiers is crucial for calculating the overall efficiency rate of the combined sewer overflows for particulate pollutants of the whole catchment area.