Effects of Different Solid Loading Rates of Faecal Sludge on the Dewatering Performance of Unplanted Filter Bed.

Abstract

The aim of this study was to investigate which Solid Loading Rate (SLR) of faecal sludge will best improve the dewatering performance of selected sand with particle sizes range of (? 0.1 ? 0.5) mm raised on bench scale filter beds. Public toilet sludge  and septage collected from suction trucks discharging at Dompoase stabilisation  ponds in Kumasi , Ghana, mixed in the ratio of 1:1, 1:2 and 1:3 by volume representing SLR1, SLR2 and SLR3 respectively, were used for the dewatering. Percolate volume was measured every 24 hour. The faecal sludge of SLR1, SLR2 and SLR3 dewatered at average dewatering times of 7, 5 and 4 days respectively. Removal efficiencies of the different solid loading rates though very high for TS, SS, TVS, COD, DCOD, NH₃-N, did not show any significant difference. Organic matter build up in the top 10cm of the filter bed was least in SLR3. Again SLR3 showed the highest potential for annual generation of biosolids at 438, 421 and 379 (kg/m² year) for SL3, SLR2 and SLR1 respectively. Therefore SLR3 of faecal sludge is recommended for dewatering on the selected filter bed.

Key words: Faecal sludge, solid loading rate, dewatering time, filter bed, percolate.