Sludge drying reed beds: full- and pilot-scale study for activated sludge treatment

摘要

Sludge drying reed beds have been used for dewatering and mineralization of sludge since thenbeginning of the 90s, but their insufficient performances in terms of Dry Matter [DM] content andnmineralization of the sludge have made necessary new studies. Therefore, 8 pilots of 2m2 eachnand a full-scale plant (13,000 p.e, 8 beds of 470m2 in operation for 4 years) have been monitorednto examine the influence of the sludge loading rate, the sludge quality and the loading frequencynon the dewatering and mineralization efficiencies. Two filtration layers and two loading rhythmsnwere tested on pilots which were fed at a loading rate of 25–30 kg DMm22 yr21 during the firstnyear of operation (commissioning period). Hydraulic behaviour (infiltration rate, outflow), O2 andnCO2 relative concentrations in the filtration media, redox potential, pollutants removal and drynmatter content were assessed during all the study. The rheological quality of the extracted sludgenfrom full scale beds was assessed and showed that its mechanical behaviour exceed those ofnsludge of comparable dry matter content, making its spreading easier. Therefore, this sludgencould easily claim the status of solid and stabilized sludge according to the French regulation.nDesign and management recommendations (number of beds, loading rates, feeding/rest period)ngained from the experiments results are suggested.