Town of Feldkirch (A): Sewage network turned into reservoir

EU promotes pilot project for active water protection in Feldkirch

Attended by District Administrator Dieter Egger, Mayor Wilfried Berchtold and Town councillor (civil engineering) Manfred Rädler as well as by representatives of the planning and construction firms, the last of five special steel concrete sewers was installed with a 200 tons mobile crane: A “HydroStyx-discharge brake”, a technical innovation which, so far, is little known in Europe, has been integrated into this sewer. The developer of the procedure, Mr. Harald Güthler (Graduated Engineer), came from Germany specifically for this purpose. “It was great pleasure to cooperate with the authorities of the town of Feldkirch ”, he confirmed to the Mayor, Mr. Berchtold.

For more than ten years now, the town of Feldkirch has invested approx. three million euro for the extension and redevelopment of the municipal sewage network which means huge investments for environmental protection. Besides, an additional project for water protection has been in the planning stage for more than three years. The town of Feldkirch has already received pan-European recognition for this project.

The conventional sewers work without problems in normal conditions. During periods of heavy and persistent rainfall, however, large water volumes are carried along with the wastewater to an extent that the sewage purification plants (named “SPP” hereinafter) can no longer cope with. In this case, the SPPs have to “open the sluices”: The wastewater is discharged untreated – although considerably diluted – into the waters.

To solve this problem, retention tanks have previously been built which have stored the accruing water volumes until a controlled discharge into the sewage plants can be effected after the rainfall will have ceased. “However, such retention tanks are very costly and, due to the huge land requirement, can hardly be realized, particularly in residential areas”, the town councillor in charge, Mr. Manfred Rädler (civil engineer) explains.

The “HydrOstyX system allows to use the capacities available in the sewage network as storage volume: In the pilot plant in Feldkirch, a total of five discharge brakes will retard the water in the sewage network as long as possible. At least 4,190 cubic metres of storage volume is available in the main sewer of Gisingen, Altenstadt up to Levis on a distance of about 2.4 kilometres. This will guarantee a sufficient volume to maintain the purification capacity of the SPP in Meiningen in most cases (of rainfall). In any case, the storage volume gained by means of the discharge brakes can be realized considerably more cost-favourable, compared with retention tanks. The town of Feldkirch – the fee-payers, respectively – will thus save investment cost of approx.1.5 million euro. Besides, the pilot project is co-financed by the European Union.