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, built in 1979, had been upgraded several times to the latest technological standards; however, sludge treatment still originated from the “early 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 in a sewage treatment/biogas plant in Austria). In addition, a conventional centrifuge was used as the new dewatering system. Integrating all of this into the existing premises while also retaining the old chamber filter press was a particular challenge.
In addition, the new centrifuge requires a high-performance polymer system – twice the size of the previous one and in an extremely confined space. The VTA subsidiary Eurodos was the only supplier willing and able to adapt a tower system exactly to the conditions on site.
The result is a fully automated two-chamber tower system (2KT4000), which was divided into two levels: The polymer solution is mixed and matured on the ground floor. A pump takes the polymer quantity required for the dewatering operation from the dosing tank in the basement.
“Operation is absolutely faultless and trouble-free,” confirms Managing Director DI Harald Bala, MSc. At present, 100% solid polymer from VTA is used (9.5 kg/t TR with a dewatering result of more than 30% dry residue).
Field report from the VTA Group’s scientific journal “Laubfrosch”, issue 68