After the gravel traps six screw pumps raise the wastewater to the six fine screen (6mm) lines followed by rectangular grit chambers. The degritted waste water is divided into two symmetric treatment lines consisting of primary and biological treatment. Mechanical treatment consists of eight rectangular settling tanks with a volume of 28.500 m3.
The primary effluent discharges to four aeration tanks with a total volume of 42.000 m3. The activated sludge is aerated by 32 cone aerators. The activated sludge is evenly distributed to 16 rectangular secondary settling tanks with scrapers, where the sludge is separated from the treated effluent. Two screw pumps return the settled sludge to the aeration tanks.
The effluent is discharged into the Danube Canal. Primary and secondary sludge from the mechanical and biological treatment process are pumped to four thickeners.
Expansion of the Main Treatment Plant of Vienna
(under construction)
Due to a new emission regulation which was issued in 1996 by the Austrian Federal Ministry for Agriculture and Forestry in accordance with the EU Guideline for Municipal Waste Water 91/271 the following minimum requirements have to be met by the year 2005:
| Parameter | Dim. | _ |
| BOD5 | mg/l | 15 |
| COD | mg/l | 75 |
| NH4-N | mg/l | 5 |
| Tot N-removal | % | 70 |
| Tot P | mg/l | 1,0 |
In order to meet these requirements it is necessary to change the treatment concept and to enlarge the capacity.
| mean dry weather flow | 680.000 | m³/d |
| maximum wet weather flow | 18 | m3/s |
| BOD-load | 240 | t/d |
| PE | 4,0 | million |
A novel two stage activated sludge process concept was selected which combines the advantages of two stage process for reliable nitrification with optimal use of the volume for denitrification in both stages. The concept does only little affect the existing plant and enables different operational modes (Bypass and Hybrid process).
The second stage activated sludge plant consists of 15 lines with one aeration tank and one secondary sedimentation tank each. The total aeration tank volume is 171.000 m3.
The aeration tanks are subdivided into three main cascades. The first cascade is not aerated and acts as pre-denitrification tank. The following two cascades of the aeration tank can be operated as simultaneous nitrification/denitrification tanks.
The 15 circular secondary clarifiers with a total volume of 200.000 m3 have a diameter of 64 meters each. The clarifiers are equipped with double scrapers and submerged outlet pipes. (Source: Dipl.Ing. Miklós Papp / EBS)
Information & Contact:
Entsorgungsbetriebe Simmering G.m.b.H.
11. Haidequerstrasse 6
A-1110 Vienna
Phone +43 1 76099-5812
Fax +43 1 76099-5800
