Effect of various design and operation parameters on performance of pilot-scale Sludge Drying Reed Beds

Thirteen pilot-scale Sludge Drying Reed Bed units have been constructed and operated under various design and operational characteristics. All the beds included a cobbles bottom layer, where perforated PVC aeration tubes were placed. One bed did not contain aeration tubes. Two gravel layers were placed above the cobbles layer. The setup included planted beds with common reeds and control units. Three sludge loading rates were examined: 30, 60 and 75 kg dm/m2/yr. The dewatering efficiency of the planted units exceeded 95% volume reduction. The final dry matter content varied between 50 and 64%, depending on the applied SLR. Mineralization of the residual sludge also took place. VS content of the planted units decreased up to 20%, while nutrient concentration was also reduced. The presence of reeds, aeration tubes and a fine-grained material improved the system efficiency, while the material composition did not have any effect on efficiency. Moreover, the units were able to treat sludge with high concentration of Cr.