Adaption of the main waste water treatment plant in Vienna to meet Austrian emission regulations

The modification of the main waste water treatment plant in Vienna will take place in accordance with the minimum efficiences laid down in the emission regulations as issued in 1991 by the Austrian Federal Office for Agriculture and Forestry. To meet these figures it is necessary to adapt the plant by 2001. The studies on several variants and the evaluation process showed a 2-step technology with partial by-passing of the 1st step to be the optimal solution. For this flexible system a new aeration tank volume of only 210,000 m³ is sufficient. Test-runs with a semi-commercial plant confirmed the correctness of all calculations. Possibilities for further modifications have been considered, e.g. dimensioning of all relevant hydraulic installations up to 24 m³/sec, final purification by sand or flocculant filtration and spare areas for measures after 2015.