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[[Image:Settled_sewerage_small_icon.png|right]]
Settled sewerage, also called small diameter or small-bore sewerage is designed to prevent solids in wastewater from entering a communal small bore sewer network. An important condition for the functioning of these sewer networks is that a minimum average of 25 litres per person per day enters the system. First wastewater settles in a small interceptor tank. Later, wastewater is conveyed via small (50 200 mm) diameter sewers of PVC or other durable material. Pipes are laid at various gradients from 0% to 10%. Inspection manholes are limited to minimise unauthorised opening and disposal into the system. Costs can be reduced if a group of households shares one interceptor tank. Although settled sewerage is mainly used to transport wastewater, small diameter sewers are also appropriate to transport urine.
[[Image:Settled_sewerage.PNG|thumb|right|150px|[[Dry toilet |Dry toilet]], in Egypt (for credits, click the picture)]]
{| border="1" cellpadding="5" cellspacing="0" align="center"
|-
! width="50%" style="background:#efefef;" | Advantages
! style="background:#ffdead;" | Disadvantages
|-
| valign="top" | Less dependent on active user involvement. <br>
All kind of wastewater can be transported. <br>
Little water needed to transport excreta through the small diameter pipe. <br>
Sewers can be laid at flat gradients. <br>
Excreta `out of sight'.
| valign="top" | Institutional operation and maintenance required. <br>
Interceptor tanks need to be desludged periodically. <br>
Potential risk of blockages due to illegal connections that by-pass the interceptor tank. <br>
High water consumption for excreta removal.
|}
== Costs ==
* Investment per household US$ 150 500 (Honduras, 1990).
* Investment per person US$ 35 85 (North East Brazil).
* Investment 20%-50% less than conventional sewerage in rural areas.
* Where septic tanks already exist, the cost reduction can be 40%70% (USA).
== Applying conditions ==
<ul>
<li>The system can be appropriate in high- and low-density areas. </li>
<li>In areas where elevation differences do not permit gravity flow, pump stations are required. </li>
<li>The system is appropriate for areas where septic tanks already exist, but effluent is causing public health or environmental risks. </li>
<li>Understanding of the system hydraulics is required. </li>
<li>The system needs to be flushed periodically to avoid blockages.</li>
</ul>
== External links ==
* General information about Settled sewarage [http://www.sanicon.net www.sanicon.net ]
* General information [http://www.efm.leeds.ac.uk/CIVE/Sewerage http://www.efm.leeds.ac.uk/CIVE/Sewerage ]
* General information [http://wedc.lboro.ac.uk http://wedc.lboro.ac.uk ]
Settled sewerage, also called small diameter or small-bore sewerage is designed to prevent solids in wastewater from entering a communal small bore sewer network. An important condition for the functioning of these sewer networks is that a minimum average of 25 litres per person per day enters the system. First wastewater settles in a small interceptor tank. Later, wastewater is conveyed via small (50 200 mm) diameter sewers of PVC or other durable material. Pipes are laid at various gradients from 0% to 10%. Inspection manholes are limited to minimise unauthorised opening and disposal into the system. Costs can be reduced if a group of households shares one interceptor tank. Although settled sewerage is mainly used to transport wastewater, small diameter sewers are also appropriate to transport urine.
[[Image:Settled_sewerage.PNG|thumb|right|150px|[[Dry toilet |Dry toilet]], in Egypt (for credits, click the picture)]]
{| border="1" cellpadding="5" cellspacing="0" align="center"
|-
! width="50%" style="background:#efefef;" | Advantages
! style="background:#ffdead;" | Disadvantages
|-
| valign="top" | Less dependent on active user involvement. <br>
All kind of wastewater can be transported. <br>
Little water needed to transport excreta through the small diameter pipe. <br>
Sewers can be laid at flat gradients. <br>
Excreta `out of sight'.
| valign="top" | Institutional operation and maintenance required. <br>
Interceptor tanks need to be desludged periodically. <br>
Potential risk of blockages due to illegal connections that by-pass the interceptor tank. <br>
High water consumption for excreta removal.
|}
== Costs ==
* Investment per household US$ 150 500 (Honduras, 1990).
* Investment per person US$ 35 85 (North East Brazil).
* Investment 20%-50% less than conventional sewerage in rural areas.
* Where septic tanks already exist, the cost reduction can be 40%70% (USA).
== Applying conditions ==
<ul>
<li>The system can be appropriate in high- and low-density areas. </li>
<li>In areas where elevation differences do not permit gravity flow, pump stations are required. </li>
<li>The system is appropriate for areas where septic tanks already exist, but effluent is causing public health or environmental risks. </li>
<li>Understanding of the system hydraulics is required. </li>
<li>The system needs to be flushed periodically to avoid blockages.</li>
</ul>
== External links ==
* General information about Settled sewarage [http://www.sanicon.net www.sanicon.net ]
* General information [http://www.efm.leeds.ac.uk/CIVE/Sewerage http://www.efm.leeds.ac.uk/CIVE/Sewerage ]
* General information [http://wedc.lboro.ac.uk http://wedc.lboro.ac.uk ]