[[Image:Icon_sedimentation_thickening_ponds.png |right|80px]]
'''Sedimentation or thickening ponds are settling ponds that allow sludge to thicken and dewater. The effluent is removed and treated, while the thickenedsludge can be further treated in a subsequent technology.'''
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Faecal sludge is not a uniform product and, therefore, its treatment must be specific to the characteristics of the sludge. Sludge, which is still rich in organics
and has not undergone significant degradation, is difficult to dewater. Conversely, sludge that has undergone significant anaerobic degradation, is more easily
dewatered. In order to be properly dried, fresh sludge rich in organic matter (e.g., latrine or public toilet sludge) must first be stabilized. Allowing the sludge to degrade anaerobically in sedimentation/thickening ponds can do this. The same type of pond can be used to thicken sludge which is already partially stabilized (e.g., originating from [[Septic Tank|Septic Tanks]], S.9), although it undergoes less degradation and requires more time to settle. The degradation process may actually hinder the settling of sludge because the gases produced bubble up and re-suspend the solids. As the sludge settles and digests, the supernatant must be decanted and treated separately. The thickened sludge can then be dried or further composted.
===Design Considerations===