Pit emptying systems
Practical Action
Emptying Methodologies
It is generally accepted that a pit should be emptied when the sludge is half a metre from the
top of the pit. Compaction of sludge at depth may result in a need to add water in order to
liquefy the sludge. The methods used to empty pit latrines can be categorised into four main
groups; manual, manually driven mechanical systems, specifically designed mechanical
systems and large vacuum tankers. Each of these categories will now be described in turn.
Manual Methods
In many urban areas of the world manual
emptying methods dominate the sector.
Manual emptying occurs most frequently
where large vacuum tankers are unable to
access sanitation facilities. It is also
generally the cheapest way of removing
enough waste to keep a pit operational,
although it is usually the most expensive per
unit volume.
Figure 2: Manual emptiers operating in
Kibera, Nairobi [Photo Credit: WSP/Sabine
Bongi 2005]
There are numerous types of manual
emptying. Often it entails two workers using a
rope and bucket (figure 2), if the waste
becomes too solidified at the bottom of the
pit a worker will have to climb in to remove
the waste by hand. Sometimes pits will be
emptied using gravitational emptying,
whereby a hole is made in the side of the pit
and excreta flow out under gravity (either into
a nearby stream or an adjacent hole). In
some cases residents allow flood waters to
carry away the top level of sludge making it
functional for a short period of time.
Often manual emptying causes environmental pollution because there is no safe place (such
as a transfer station) for workers to dispose of waste. In some areas (such as Nairobi, Kenya)
workers suffer from a significant stigma that forces them to operate at night. This not only
increases the likelihood of worker injury, but also increases spillage. The stigma originates
from a community dislike of the odour and spillage resulting from the work. Workers health
could be affected by direct contact with faeces containing dangerous pathogens and gas build
up in latrines.
If there is no other realistic option than to empty manually it is important to remember that
fresh excreta will contain pathogens that could cause worms or diarrhoea. Furthermore, flies
attracted to this may spread such diseases to local communities. It is important that no one
should enter the pit without a safety rope and colleagues on the surface with the ability to
pull the worker out. The risk of fumes and pit collapse are the two primary drivers for this.
Workers should be provided with safety clothes and nearby washing facilities. Furthermore,
pits should be adequately ventilated when a worker is inside (Scott and Reed, 2006).
5