When wastewater can produce power

In future, wastewater will flow from the municipality of Zumikon down into the wastewater treatment plant of the municipality of Küsnacht on Lake Zurich. The plan is to use the height difference of 180 m to produce alternative energy in a small hydropower plant via a turbine. The wastewater from Zumikon is taken to the power plant by a pressure pipeline.

The approx. 3 km long pressure pipeline runs partly through a landscape which is difficult to access and geologically challenging; in large sections it has been installed using an underground driving process, the directional drilling technique.
The high tensile forces expected during the installation of the pipes on account of the geological conditions as well as the high internal pressures under the operation of the wastewater pressure pipeline required the use of a robust, flexible and easy-to-handle pipe system. Based on experience with similar projects, the client (the municipalities of Zumikon and Küsnacht) decided in favour of ductile iron pipes from Duktus/Hagenbucher with BLS^® restrained push-in joints, cement mortar coating and a cement mortar lining based on high-alumina cement.

In total, 2,918 m of DN 300 ductile iron pipes with restrained push-in joints, type BLS^® with cement mortar coating and cement mortar lining were installed. Of these, two sections with lengths of 748 m and 655 m were laid using the directional drilling technique and the remaining 1515 m with the open trench technique.

Figure 2:
Assembling the pipes with socket guards before pulling in

Figure 4:
Upsizing head with the first pipe in the target pit