Transcript ITCHON 2010 Soakpits_0

Soakpits
Gina S. Itchon, Xavier University
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The contents of the SSWM Toolbox reflect the opinions of the respective authors and not necessarily the official opinion of the funding or
supporting partner organisations.
Depending on the initial situations and respective local circumstances, there is no guarantee that single measures described in the toolbox
will make the local water and sanitation system more sustainable. The main aim of the SSWM Toolbox is to be a reference tool to provide
ideas for improving the local water and sanitation situation in a sustainable manner. Results depend largely on the respective situation
and the implementation and combination of the measures described. An in-depth analysis of respective advantages and disadvantages and
the suitability of the measure is necessary in every single case. We do not assume any responsibility for and make no warranty with
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Soakpits
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Contents
1. Concept
2. How it can optimize SSWM
3. Operation and maintenance
4. Applicability
5. Advantages and disadvantages
6. References
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1. Concept
Background
A Soak pit, also known as soakaway or leach pit, is a covered, porouswalled chamber that allows water to slowly soak into the ground.
Pre-settled wastewater or greywater effluent from an upstream
collection and storage/treatment facility or collected stormwater is
discharged to the underground chamber from where it infiltrates into
the surrounding soil.
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1. Concept
Functional Design
• Soak pits can be either left empty and lined with porous material to
provide support and prevent collapse, or they are unlined and filled
with coarse rocks and gravel to provide support and to prevent
collapsing.
• A layer of sand and fine gravel has to be spread across the bottom to
support disperse the flow.
Functional Design of a Soak Pit Source: TILLEY et al. (2008)
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1. Concept
Functional Design
• The depth of a soak pit should be between 1.5 and 4 m. The bottom
of the soak pit has to be more than 1.5 m above the ground water
table.
• As pre-treated wastewater and greywater percolates through the
soil from the soak pit, small particles are filtered out by the soil
matrix and organics are digested by micro-organisms.
• The wastewater effluent is absorbed by soil particles and moves
both horizontally and vertically through the soil pores.
Functional Design of a Soak Pit Source: TILLEY et al. (2008)
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2. How it can optimise SSWM
Implementation and use of Soak Pit can help in optimizing your local
water management and sanitation system and make it more sustainable
by:
• Offering a cost-efficient opportunity for a partial wastewater
treatment
• Providing a relatively safe way of discharging pre-treated
wastewater into the environment
• Recharging groundwater bodies
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3. Operation and Maintenance
• A well-sized soak pit should last for about 3-5 years without
maintenance.
• To extend the life of a soak pit, care should be taken to ensure that
the effluent has been clarified and/or filtered well to prevent
excessive build up of solids.
• The soak pit should be kept away from high-traffic areas so that the
soil above and around it is not compacted.
• To allow for future access, a removable (preferably concrete) lid
should be used to seal the pit until it needs to be maintained.
• Particles and biomass will eventually clog the pit and it will need to
be cleaned or moved.
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4. Applicability
• A soak pit does not provide adequate treatment for raw wastewater
and this technology should only be considered for discharging presettled wastewater or greywater as well as rainwater.
• Soak pits are appropriate for rural and peri-urban settlements.
• They are not appropriate for areas that are prone to flooding or have
high groundwater tables.
• Soak pits are best suited to soils with good absorptive capacity,
whereas clay soils as well as hard packed or rocky soils are not
appropriate.
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5. Advantages and Disadvantages
Advantages:
Disadvantages:
• Can be built and repaired with
locally available materials
•Pre-treatment of the incoming
effluent is required to prevent
clogging,
although
eventual
clogging is inevitable
• Small land area required
• Low capital cost
operating cost
and
low
• Simple technique for all users
•May negatively affect soil and
groundwater properties
(TILLEY et al. 2008)
(TILLEY et al. 2008)
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6. References
AHRENS, B. (2005). A Comparison of Wash Area and Soak pit Construction: The Changing Nature of Urban, Rural, and
Peri-Urban Linkages in Sikasso, USA. Mali. Peace Corp.
TILLEY, E., LÜTHI, C., MOREL, A., ZURBRÜGG, C., SCHERTENLEIB, R. (2008): Compendium of Sanitation Systems and
Technologies, Switzerland, Swiss Federal Institute of Aquatic Science (EAWAG) & Water Supply and Sanitation
Collaborative Council (WSSCC)
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Water Management & Agriculture”
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