Pit emptying systems
Practical Action
Figure 3: UN-HABITAT Vacutug.
Photo Credit: UN-HABITAT, n.d.
Figure 4: Vacutug Mk II mother tank.
Photo Credit: GHK, 2005
The Vacutug project is still awaiting the scaling up phase. Currently a number of machines
are on trial throughout the world, and governments are being encouraged to take the lead on
purchasing. The machine has a capacity of 500 litres, has a maximum speed of 5 km/hour,
and comes at an approximate cost of US$5,000 – 7,000 (dependent on shipping costs). It
can be difficult to completely empty deep pits, partially due to pit depth and partially due to
sludge compaction.
One significant problem with the Vacutug Mk I is the low speed and the need for a localised
disposal point. This was one driver behind the development of the Vacutug Mk II which uses a
small satellite tank (200 litres) and a larger mother tank (1,900 litre) towed by a vehicle to
take large volumes to disposal.
Table 4: Advantages and Disadvantages of the Vacutug
Advantages
Disadvantages
Removes waste safely for both workers and Slow max speed means localized emptying
public health
point such as sewer or tank are needed
It is a low odour technology
Costs too much for many SSIPs
Faster to empty than either manual or
Is having some access problems in Kibera,
manually driven mechanical systems
Nairobi, despite its small size
Reduces social stigma on workers
Maintenance costs are potentially high
Some of the disadvantages listed above have been overcome with the development of the
Vacutug Mk II. However, this increases costs due to the necessity to purchase a vehicle to tow
the mother tank. More up-to-date information on the Vacutug systems can be acquired from
UN-HABITAT (http://www.unhabitat.org/categories.asp?catid=548).
Large Vacuum Tankers
Large vacuum tankers (figure 5) are very widely used for emptying of sanitation facilities
throughout the world. They are generally the most economic means (apart from sewerage
systems) of moving large volumes of excreta. Their volume can vary between 5 and 10 m3. It
is generally agreed that they can operate effectively up to about 60m from an installation
(although connecting and disconnecting these sections can be a time consuming process),
and to a depth of 2 to 3 m. The large capacity means that to empty a pit to its practical limit
may only take one or two visits. (Note: despite strong pumps a pit can often not be emptied
completely due to sludge compaction and pit depth).
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