Pit emptying systems
Practical Action
There should also be consideration for national regulations and what requirements these put
on emptying services. In the absence of such regulation an appreciation of the entire faecal
sludge management chain would bring significant benefits to environmental health.
Faecal Sludge Management
The term given to the management of waste through collection, haulage, disposal and
treatment is faecal sludge management (FSM). Figure 1 shows the chain with examples of
possible activities at each stage.
Figure 1: The FSM process, from generation to by-products [Illustrator: Niall Boot 2007]
An appreciation of the full FSM process can result in successful achievement of the core
goals i.e. preventing excreta from entering the urban environment and being used
inappropriately in agriculture. Although this technical brief discusses possibilities for
emptying it cannot be emphasised enough that it should not be tackled in isolation. For
example, if one vacuum tanker indiscriminately dumps faecal sludge into the environment it
is comparable to 5,000 people defecating openly (Strauss et al, 2006); effectively negating
the very purpose of on-site sanitation systems. A number of recent studies have identified
haulage distances as a possible area for reducing overall expenditure on FSM services
(Strauss and Montangero, 2002).
Demand Responsive Services
Many emptying systems have become demand responsive whereby customers are requesting
their facility to be emptied. The service provider will then travel from a previous household (or
a disposal point) to the requested place, resulting in very disaggregated demand. This
generally means that the services are more costly, partially as a result of treatment plants (or
disposal points) being centralised and the large transport distances involved. Some attempts
have been made in the past to aggregates this demand by serving customer living close to one
another.
Organising customers into clusters to be serviced on a regular basis (and possibly for a set
fee) may reduce overall emptying costs. However, the benefits brought would be dependent
on (i) the distance to a safe disposal point and (ii) the volume of faecal sludge being removed
per visit i.e. if the volume exceeds one tanker then organising customers near to one another
may be less beneficial.
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