Types of toilet and their suitability
Figure 6: Septic tank layout (Source: Harvey et al, 2002)
The system reduces the level of odour and flies
The user has the convenience of a WC which
can be located indoors
The system comes at a high cost – including
the cost of land
Water is required (both in quantity and
Permeable soil is required for drainage
Requires regular emptying
Other Forms of On-Site Sanitation
There are other forms of sanitation which are less used or unsanitary. Borehole latrines are often
used in emergency situations but adopted less elsewhere. Unsanitary forms would include
overhung latrines which will dispose directly into a watercourse, or bucket latrines where users
defecate into a bucket which is routinely emptied.
An important consideration when employing on-plot sanitation systems is that of groundwater
pollution. Due to the nature of on-site systems shallow groundwater can be exposed to the
pathogens within faeces and become contaminated. In urban areas this can be particularly
problematic especially is shallow groundwater is used for drinking. In general it is possible to
reduce this risk by locating a latrine at least 10m horizontally from a groundwater source. There
is often debate as to the costs associated with alternative sanitation systems as oppose to
alternative water sources. An alternative means to reduce the risk of contamination to
groundwater is to employ a raised pit latrine.
Decomposition of waste takes place to some extent but eventually the superstructure will have to
be located and a new pit excavated, or the pit will need to be emptied. The biggest problems
become apparent in urban locations where there is little space to relocate or access a latrine and
where increased population density increases loading on latrines and thus increases filling rates.
The waste must also be safely disposed of, or else the very pollution sanitation was designed to
avoid will still take place.