OPTIMISCH - Optimized Design of Combined Sewer Facilities

The new ÖWAV Guideline 19 (Guideline for the design of combined sewer overflows) released in November 2007 presents new requirements for the design of combined sewer overflows (CSOs) in Austria. In future, hydrological long term simulations will be used for verification of CSO design and function. According to the guideline, an efficiency factor that is defined as part of the rainfall runoff that reaches the waste water treatment plant in long-time yearly average has to be reached. Within the OPTIMISCH project a guide for planners and sewer network operators will be created to show possibilities, advantages and limitations of the new guideline. On the basis of real case studies (existing sewer networks), hydrological model simulations combined with a thorough sensitivity-analysis will be carried out. A comparison of the obtained results with alternative design rules (ÖWAV guideline 19 (1987), ATV guideline A 128) will let us conclude what results we have to expect when CSOs designed according to the older rules are re-designed using the new ÖWAV guideline 19. In addition a comparison of planning and investment costs will be carried out. To increase universality of the results obtained within the OPTIMOSCH project, the selected case studies represent catchments with different properties (rural zones, urban zones, extensive sewer network....)