A sludge drying bed is a common process developed to dewater sludge by means of filtration and evaporation. Punctured pipes positioned at the foot of the bed are used to drain seepage water or filtrate. A reduction of about 35% or less in moisture content is expected after drying. Sludge drying beds are typically located alongside treatment plants to readily receive and treat incoming sludge from primary or secondary treatment facilities.
The basic design components of the drying bed are composed of a concrete structure for bed and walls, sand and gravel to be used as filter media, splash block, under drain, and inlets. Sludge drying beds are suitable for treatment plants serving a population ranging from 1,000 to 20,000. These facilities exhibit reliability and good process flexibility. However, during the wet season, its efficiency decreases. In terms of its efficiency, while dried sludge is not fully disinfected, the solid content is increased to 50%–70% of total solids.
Sludge drying beds are simple to operate and energy-efficient. They presents as the least cost technology option for dewatering sludge. Among the existing sludge dewatering approaches, the investment costs for sludge drying beds is considered to be then lowest. For operation and maintenance, the only item to be considered is the labour cost.