Department Process Engineering

As a result of a detailed eco-toxicological risk evaluation agricultural use of sewage sludge will be banned in Switzerland from 2005. In future 100% of the sewage sludge will be incinerated. The dewatered sludge must have minimum dried solids content (DS) 40-45% in order to ensure an energy neutral incineration. In co-operation with the company Bucher Guyer AG and the WWTP Glarnerland full scale trials were accomplished for mechanical de-watering of raw and digested sludge by means of a de-juicing press. Beside sludge from the WWTP Glarnerland sludge from five other WWTP`s were also de-watered. The investigations show that with the tested press system DS contents of 32-41% with a throughput of approximately 5 m³ liquid sludge h-1 could be reached. The de-juicing press system achieved several percentage higher DS contents than other established mechanical dewatering technologies. The research was financially supported by the Swiss Commission for Technology and Innovation (CTI).