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< prev - next > Water and sanitation Sanitation KnO 100425_Types of toilet and their suitability (Printable PDF)
Toilet types can be broadly split into two categories; on-site and off-site systems. Off-site
systems are associated more with the developed world, cities and high density areas and often
take on the form of sewerage systems which require a reliable water supply and the provision of
wastewater treatment. Alternative on-site systems are isolated and provide some level of
treatment or containment at the toilet location and avoid the need for further treatment.
However, a number of on-site systems need regular emptying.
This technical brief outlines different types of toilets, whilst highlighting some advantages and
disadvantages which will facilitate their planning and selection.
Off-site sanitation systems
Off-site systems are widely acknowledged as systems that are only suited to developed and
affluent areas, whose water resources are plentiful and reliably delivered to household
connections in enough quantities. In low income and less developed areas where water is often
collected from a stand-post or well, dry (on-site) systems are the only possibilities. Despite this,
there are alternatives to conventional sewerage that may sometimes be applicable.
One major consideration with sewerage systems is the required provision of wastewater
treatment. This is a significant distinction from on-site systems which should treat waste in-situ
or have no need to treat the waste as it is contained within the ground (although in some cases
the faecal sludge within the latrine will be removed, after which it should be treated and
disposed of safely).
Off-site sanitation systems generally involve the construction of long lengths of permanent
infrastructure. Land ownership issues may result in investments of this level being unrealistic if
government institutions do not back the development. The requirement to provide treatment
means such involvement is likely to be necessary unless decentralised community operated
facilities could realistically be established. In order to recover the costs of construction,
operation and maintenance users of the system need to pay for a connection, this makes the
likelihood of adopting such systems being restricted to densely populated urban areas where the
number of connections per unit area is highest.
Conventional Sewerage
Conventional sewerage (employed widely in high income areas) is acknowledged to be based on
criteria (such as minimum gradients and minimum cover levels) that must meet very
conservative values (UNEP, 2002). This often results in deeper pipes which results in the
necessity for pumping and thus increased operation costs.
In order to construct a sewerage network each property should have a toilet, the contents of
which discharge to a household connection sewer, which will often include an inspection
chamber to clear blockages. The waste will then discharge to a main sewer, on which manholes
should be installed at set intervals. The size of the sewer pipes will get progressively larger until
the waste is discharged to a treatment works; the sludge by-product from this will require further
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