The sludge coming from the first clarifiers (primary sludge) is thickened mechanically by a rotating drum. The sludge is now eliminated from secondary clarifiers and thickened mechanically by screencloth. The pre-thickened sludges are now reached at a temperature of 38°C approx and digested into an anaerobic digestion chamber. The sludges, now stabilized and neutrals, are dried with a Strain press.
During the digestion process, the microorganisms transforming the organic compounds on CO2 and methane with high energetic content, available for thermal heating of digestion chambers and for factory heating. To take a solution at the gas over production, in the ARA Pustertal plant is provided a storage gas tank.
The gas line is composed by:
Gasometer, gas flare, 2 heaters and 1 cogeneration groups.