Waste stabilisation ponds are a widely accepted and proven technology to treat wastewater. It is often stipulated (and also practised) that the design of ponds for faecal sludges (FS), septage in particular, should follow the same principles as for wastewater. Field research conducted by SANDEC and its partners at the Water Research Institute in Ghana, and information gathered from the scarce literature on FS treatment, however, has shown that design principles should be taken into consideration, which are specific to the treatment of FS. These principles depend on the type of FS to be treated and on the type of pond system envisaged. Issues dealt with in this article are the handling of FS solids; the role of anaerobic ponds in FS treatment; the anaerobic degradability of septage; and ammonia (NH3–N) toxicity.

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