Sludge Drying Bed
It is a rectangular pit excavated to the required depth. The beds are filled with gravel and coarse sand as a filter. Open joints underdrain pipes are laid below the gravel layer.
The beds are about 15 m x 30m in plan and are surrounded by brick walls rising about 1 m above the sand surface.
The sewage sludge from the digestion tank is brought and spread over the top of the drying beds to a depth of about 20 to 30 cm.
A portion of the moisture drains through the bed, while most of it is evaporated to the atmosphere. It usually takes about 2 weeks to 2 months for drying the sludge. After drying, the sludge cakes are removed and used as manure.