Sludge drying reed beds: recall of technical key points

Abstract

Sludge drying reed beds exist in France since the early 1990s. These facilities often consisting of 4 beds each being alternately fed during a week have inadequate performance with a dryness around only 15% against 30 or 35% in Denmark where this technology is widespread. A higher number of beds (6 to 8, or more for stations above 15 000 inhabitants) sized globally for 50 kg of MES.m2.an-1, allowing longer rest periods between each feeding, would be a progress. But the essential point lies in respect of a period of acclimatization-development of reeds at mid-load, up to what the density is at least 250 stems per m2. An acceptable dry-matter content of approximately 25% should be obtained if the loadings of the bed(s) to be withdrawn are stopped 4 months before being emptied in summer (between mid July and the end of August). The beds emptied are fed at half load until the end of October considering that the sludge production of the treatment plant should be distributed on all beds during winter.