Effect of hydraulic loading on the performance of unplanted drying beds treating low-concentrated faecal sludge

Abstract

To optimize faecal sludge (FS) treatment plants in operation in Dakar (Senegal), this study was conducted to test the effectiveness of the solid/liquid separation on unplanted drying beds under different loading rates and two operation strategies (one or two feedings per campaign). Clogging, purification performances, dryness and hygienic quality were monitored. Results have shown that the load fractionation has reduced the clogging. Only removals of total solids (TS) and slightly those of total Kjeldahl nitrogen and chemical oxygen demand are influenced by the loading rate and the feeding mode. The reduction of faecal coliforms (FC) and helminth eggs (HE) in leachates is, respectively, 1 log unit and 100%. Two to nine days were sufficient to obtain a dryness higher than 80% TS with nominal loads of 13.7–122 kg/m2*year. Concentrations of the dried sludge in FC and HE were, respectively, about 7.104 FCU/100 g and 46 eggs/g with a reduction of 3 log unit after 15 days of drying and 32% in the sludge stored during 30 days. Unplanted beds are not effective for the treatment of low concentrated FS. The use of other technologies such as planted drying beds could be advisable in these types of sludge.

Fecal sludge treatment in a pilot-scale vertical-flow constructed wetland for the removal of helminth eggs

“…Several operational variables and design factors have been found to affect the reduction of helminth eggs in VFCW. Indeed, Sonko et al (2015) pointed out the reduction of helminth eggs in FS to be affected by hydraulic loading. Manga et al (2016) revealed the effect of sand filter media thickness on the removal performance of helminth eggs in FS drying beds.…”