text: Simple sludge drying beds can be used for dewatering and drying, as they are a cheap and simple method to dry fecal sludge (they are also widely used to dry sewage sludge). Drainage water must be captured; drying beds are sometimes covered but usually left uncovered. Drying beds are typically composed of four layers (from top to bottom): Sludge, sand, fine gravel, coarse gravel and drainage pipes.
  Fecal sludges behave differently during dewatering processes than wastewater sludges. The amount of extracellular polymeric substances (EPS) can be an important predictor for fecal sludge dewatering performance. Fecal sludge from public toilets took longer to dewater than sludge from other sources, and had turbid supernatant after settling.
  Grass<nowiki/>es with adventitious roots may also be planted in drying beds, allowing for reduction of odor, collection over longer periods, production of forage, and more decomposition of the final biosolids by the time they are extracted. The roots introduce oxygen and maintain the permeability of the sludge. Earthworms may also play an important role in such beds.