When human excreta collects in a pit latrine, the solids settle at the bottom and form a slurry called faecal sludge. Over time the sludge accumulates and periodically needs to be removed and disposed of. This process presents several challenges because the sludge is offensive, a potential danger to human health and highly polluting if dumped indiscriminately into the environment. Faecal sludge management (FSM) is a set of processes designed to ensure that people and the environment are protected from these hazards. It includes the storage, collection, transport, treatment and safe end use or disposal of faecal sludge (Strande et al., 2014). FSM is a significant problem in towns and cities in many developing countries. Key issues are who is responsible for collecting sludge and where and how it is disposed of.
The next section describes some of the methods for removing faecal sludge from pit latrines. These methods also apply to sludge removal from septic tanks, which are described in detail in Section 6.3.