The RHV Trattnachtal, an association of 13 municipalities in Upper Austria, operates a central sewage treatment plant in Wallern with a capacity of 70,000 PE. The plant, which was built in 1979, has been adapted to the state of the art several times; however, the sludge treatment still dates back to the "founding days". It was therefore time to replace the existing chamber filter press.
Those responsible finally decided in favour of a technologically new sludge thickening process, membrane ultrafiltration (incidentally the first on a sewage/biogas plant in Austria). A conventional centrifuge was added as a new dewatering unit. A particular challenge was to integrate all of this into the existing premises and also to retain the old chamber filter press.
What's more, the new centrifuge required a high-performance polymer plant - twice as large as the previous one, and with extremely limited space. VTA subsidiary Eurodos was the only supplier willing and able to customise a tower system precisely to the conditions on site.
The result is a fully automatic two-chamber tower system (2KT4000), which is divided into two levels: The polymer solution is prepared and matured on the ground floor. The amount of polymer required for dewatering is taken by a pump from the dosing tank in the basement.
"Operation is absolutely error-free and trouble-free," confirms Managing Director DI Harald Bala, MSc. Currently, 100% solid polymer from VTA is used (9.5 kg/t TR with a dewatering result of more than 30% dry residue).
Practical report from the VTA Group's knowledge magazine "Der Laubfrosch", issue 68
