Originally, the raw sludge from the wastewater treatment plant in Vienna was incinerated in the neighbouring incineration plant. Due to the high water content of the raw sludge, this had disadvantages in terms of energy yield. At the same time, the control system was outdated and had to be completely renewed in line with the increasing demands on the operation of such a large critical infrastrucure. Thefore, the customer wanted to migrate the systems while the plant was in full operation. Moreover, Siemens had to make sure that the standardized PCS 7 solutions have the same functionality and visualization as the former solution which the operators were used to.

The order included the migration and expansion of a SIMATIC PCS 7 process control system to the latest version 8.1. The conversion took place parallel to ongoing operations. All functions were already tested during engineering with the SIMIT simulation software, which ensured quality and shortened commissioning times. In addition, Siemens supplied SITRANS process instruments, devices for gas analysis (ULTRAMAT/OXIMAT) and SCALANCE network components including cabling, assembly and commissioning. For the safe and highly available power supply of around 450 motors and drives in the sewage treatment plant, Siemens installed a redundant 20 kV medium-voltage switchgear of the NXAir type (28 fields), low-voltage switchgear of the SIVACON S8 type (about 80 fields), a busbar distribution system and 14 transformers. Siemens equips the protection devices of the existing plants as well as those of the new plants with Ethernet-based communication interfaces.

With a design for four million population equivalents the wastewater treatment plant Vienna is one of the largest in Europe. Covering an area of 460,000 square meters, Vienna's central sewage treatment plant treats all of the Austrian capital's municipal wastewater. The microorganisms that remove the pollutants from the wastewater - roughly 6,000 liters per second - require around two thirds of the energy consumption of the wastewater treatment plant. With one of the largest environmental projects in the city of Vienna, a milestone has now been set in terms of reducing the energy consumption of Vienna's sewage treatment plant. After completion of the project "E_OS - Energy_Optimization of Sludge Treatment" more than the energy required for wastewater treatment can now be generated through the energetic use of biogas from the sewage sludge. The sewage treatment plant was thus transformed from a major energy consumer into an eco-power plant. In the project Siemens supplied the control, measurement, analysis and switchgear control technology as well as low-voltage and medium-voltage switchgear and lately even an operator training system (OTS).