Germany – Engineering services – Sammelkläranlage des Abwasserzweckverbands Kläranlage Kirnautal in Rosenberg - Objektplanung Ingenieurbauwerke / Fachplanung TA / Gebäudeplanung

The four currently operated smaller wastewater treatment plants in Rosenberg, Altheim (Walldürn), Hohenstadt-Eubigheim, and Schillingstadt (Ahorn) are in a very different, partially dilapidated condition. In light of the upcoming renewal of water rights for individual plants, the responsible district offices suggested an examination of the possibilities for centralising wastewater disposal. As part of a structural assessment, several variants for a reorganisation of wastewater disposal at the four locations were investigated. Variant 3 with stream relocation – the connection of the wastewater treatment plants Altheim, Hohenstadt-Eubigheim, and Schillingstadt to the wastewater treatment plant Rosenberg – proved to be the preferred variant both from an economic point of view and taking into account non-monetary criteria. Required conversion and expansion measures (extract from Part 1 of the Structural Assessment for the future wastewater treatment of the municipality of Rosenberg (Baden), page 143): [1] Storm overflow tank: The calculation of the pollutant load is currently being prepared and shows a need for expansion at the STO. [2] Inlet area (incl. gravel trap): The inlet area (channel) incl. gravel trap is to be expanded for the increased water volume in the event of mixed water inflow (QM = 90.5 l/s). [3] Screen (building): The screen incl. channel and bypass is to be expanded for the increased water volume in the event of mixed water inflow (QM = 90.5 l/s). [4] Sand and grease trap: The existing circular sand trap is to be replaced by an aerated sand and grease trap, which is also to be dimensioned for the mixed water inflow QM = 90.5 l/s. The new sand and grease trap is to be placed in front of the screen building. [5] Aeration tank: For the load of approx. 5,800 EWCSB, an aeration tank volume of approx. VBB = 2,650 m³ at a TS content of TSBB = 3.4 g/l is required for simultaneous aerobic sludge stabilisation. Compared to the existing aeration tank volume (VBB,IST = 380 m³), an expansion of approx. 2,300 m³ is required. The relatively high excess volume results from the fact that the wastewater treatment plant is currently designed only for simultaneous aerobic partial stabilisation, with aerobic post-stabilisation in the aerated sludge storage tank. It would be advisable to construct the aeration tank in 2 construction phases and to dismantle the existing combined tank. Three aeration tanks with the dimensions (BxLxT) 11 m x 18 m x 4.5 m (Vges = 2,673 m³) would be conceivable. This would provide three lanes for maintenance work and inspections. Distributor structures are to be erected in the inlet and outlet of the aeration tanks. [6] Blower station: With intermittent denitrification and an injection depth of hD = 4.50 m, the required air volume is approx. QL,N = 150 – 1,350 mN³/h. The blowers are to be adjusted accordingly. [7] Secondary settling tanks: Three rectangular secondary settling tanks with the dimensions (BxLxT) 4.5 m x 23 m x 4.0 m (Vges = 1,242 m³) are to be erected (also conceivable as circular tanks in further planning). This would provide three lanes for maintenance work and inspections. A return sludge and excess sludge pump station is to be attached to the secondary settling tank. The return sludge pumps are to be designed with a return ratio of RV = 1.0 (according to DWA-A 131, 2016) for a maximum mixed water inflow of QM = 90.5 l/s. Investment costs: Wastewater treatment plants: Total costs approx. 10 million € gross.