Comparison between two techniques for sludge dewatering – trials at Sjölunda and Klagshamn WWTPs
The cost for disposal of the dewatered sludge is dominating among the operational costs for sludge handling at municipal wastewater treatment plants. This, in turn, is affected by the dryness of the sludge. In this paper the results from parallel trials with two different dewatering techniques, at two different wastewater treatment plants (Sjölunda and Klagshamn in Sweden), are presented and discussed. The dewatering equipment tested is a high-speed centrifuge and a hydraulic filter press.
In general, at both treatment plants, the press delivered drier sludge than the centrifuge, about 30 % DS contra 28 % DS at Sjölunda and 33 % contra 29 % DS at Klagshamn, at relatively moderate polymer doses (7–10 g polymer /kg DS).
Another general observation was that both the press and the centrifuge delivered drier sludge at Klagshamn than at Sjölunda. It was noted, during the trials with the press at both plants, that the dewatered sludge cake needed more or less manual help to detach from the press and fall into the collecting tray under the press.