space
About UNEP UNEP offices News centre Publications Calendar Awards Milestones UNEP Store
space
space
United Nations Environment Programme
Division of Technology, Industry and Economics
 top image
  space
space space space
  UNEP>DTIE>IETC space
space
Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

3.3 Settled sewerage

Settled sewerage refers to sewerage for conveying wastewater that has been settled, for example in a septic tank. The origin of settled sewerage is to convey overflow from septic tanks where the soil cannot cope or absorb the overflow. This usually occurs when the groundwater table is high, or where the soil permeability is low, or where there are rock outcrops. It can also be used when effluent from septic tanks pollutes groundwater and it is necessary to convey the effluent off-site and treat it. Because there are no solids that can potentially sediment in the sewerage pipes, there is no requirement for the self-cleansing velocity. Smaller pipes and lower gradients can be used. The cost of settled sewerage is between a third and a half of conventional sewerage. Originally developed in South Australia to overcome problems with failing septic tanks, it has been used quite widely worldwide to upgrade septic tank systems.

Where there is no existing septic tank, an interceptor box or tank can be used. It functions like a septic tank and designed in the same way (Figure 2.14). To reduce cost the wastewater from a group of houses can be connected to one interceptor tank. Just like in a septic tank, accumulation of sludge has to be removed regularly from an interceptor tank.


Figure 2.14: Interceptor tank in settled sewerage

 

      Main Menu

          

  • Major Projects
  • DEBRI Project
  • DEBRI Project
  • Iraqi Marshlands Project
  • Iraqi Marshlands Project
  • IETC's Tools
  • Environmentally Sound Technology Information System
  • ESTIS facilitates creation and management of websites on the Internet, sharing and searching of information across multiple ESTIS websites, publishing of information by non-web designers and decentralized management of content.
  • WiseWater
  • WiseWater is a spreadsheet application for projecting reductions in Water Consumption Patterns after application of Environmentally Sound Technologies. It is included as part of the publication "Every Drop Counts: Environmentally Sound Technologies for Urban and Domestic Water Use Efficiency".
  • Pamolare
  • PAMOLARE is an environmental modelling tool to forecast the changes in water quality leading to the eutrophication of Lakes and Reservoirs.
    The versatility of PAMOLARE allows for its use in decision making process as well as for training purposes.