Final clarification tanks

The 15 secondary clarifiers look like small lakes and mark the last step of the cleaning process. In these huge tanks, each of them 64 metres in diameter, the wastewater is left to settle for a period of four hours. The clarifiers are among the largest in Europe and have a holding capacity of 13 million litres each. The 67-metre-long scraper bridges with their lightweight steel frame design weigh only 22 tonnes each. This reduces the wear and tear of the mechanical components and helps to cut energy consumption and operating costs.

The wastewater and the activated sludge from the aeration tanks of the second biological cleaning stage reach the secondary clarifiers via a central structure, in a non-turbulent, steady flow. The activated sludge settles to the tank bottom where scrapers push the sludge into a hopper underneath the central structure. The purified effluents are drained through submersible pipes to a collecting channel and from here flow to the outlet structure and into the Danube Canal.

Technical parameters

  • 15 tanks
  • Inner diameter: 64 m
  • Mean depth: 4.1 m
  • Total surface: 43,500 m²
  • Total volume: 200,000 m³

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