Dewatering mechanisms in pilot-scale Sludge Drying Reed Beds: Effect of design and operational parameters

Abstract

Eleven pilot-scale Sludge Drying Reed Beds (SDRBs) have been constructed, and operated treating municipal activated sludge. Quantification of the dewatering mechanisms in these systems (i.e., evapotranspiration and draining) is attempted here, and the effects of different parameters, i.e., the level of sludge loading, the presence of reeds, the gradation of substrate materials etc., on these mechanisms are presented. Results reveal that evapotranspiration is the major dewatering process that takes place in SDRB systems, accounting for 58–84% of total water losses, depending on unit characteristics, sludge loading, season and other parameters. Draining follows in significance, with respective values varying from 13% to 41% of total water losses, while 1% to 4% of water remains in the sludge layer. The presence of reeds was found necessary, since it improved the dewatering efficiency. Precipitation and temperature were also found to affect the dewatering process under temperate climate conditions.