Digester circulation
In 2008, an agitator for the circulation of the digested sludge was installed in digestion tower 1 of the Tobl wastewater treatment plant, which has a digestion tower size of 2000m³. The agitator weighed 2,200 kg, was 18.2 m long and equipped with two propellers. One of them had a diameter of 4.3m, the other 2.5m. The agitator achieved a consistently good mixing of the digested sludge, but clogging was still a problem and the static load on the gas dome showed its effects over the years and cost-intensive repairs had to be carried out.
