Solid–liquid separation of faecal sludge using drying beds in Ghana: Implications for nutrient recycling in urban agriculture

Abstract

This study investigated the possibility of recycling nutrients in human excreta and municipal solid waste for use in agriculture. It reports on the use of drying beds in separating solid and liquid fractions of faecal sludge (FS) so that the solids can be co-composted and the organic matter and part of the nutrients captured for urban agriculture. Sludge influent onto drying beds, percolate effluent, and dewatered sludge (biosolids) were monitored over eight loading cycles in 2002. The unplanted drying beds were made of 15 cm of sand (0.2–0.6 mm diameter) and 25 cm gravel (10 and 19 mm diameter). The loading rate of sludge ranged from 196 to 321 kg total solids (TS) /m 2 y. Biosolids with TS ⩾20% were obtained after an average drying time of 2 weeks. The drying beds retained 80% of solids and 100% of helminth eggs. The biosolids had average organic matter content of 61%; hence, allowing for co-composting with biodegradable organic solid waste for hygienisation. The process is being investigated further to attain higher efficiency and reliability.