A Soak Pit, also known as a
soakaway or leach pit, is a covered, porous-walled chamber that allows water to
slowly soak into the ground. Pre-settled effluent from a Collection and
Storage/Treatment or (Semi-) Centralized Treatment technology is discharged to
the underground chamber from where it infiltrates into the surrounding soil. (Popular for discharge of the household wastewater in Rural Areas)
The Soak Pit can be left
empty and lined with a porous material (to provide support and prevent
collapse), or left unlined and filled with coarse rocks and gravel. The rocks
and gravel will prevent the walls from collapsing, but will still provide
adequate space for the wastewater. In both cases, a layer of sand and fine
gravel should be spread across the bottom to help disperse the flow. The soak
pit should be between 1.5 and 4m deep, but never less than 1.5m above the ground
water table.
As wastewater (pre-treated
greywater or blackwater) percolates through the soil from the Soak Pit, small
particles are filtered out by the soil matrix and organics are digested by
micro-organisms. Thus, Soak Pits are best suited to soils with good absorptive
properties; clay, hard packed or rocky soils are not appropriate.
Advantages
|
Disadvantages/limitations
|
- Can be built and repaired with locally
available materials.
- Small land area required. - Low capital cost; low operating cost. - Can be built and maintained with locally available materials. - Simple technique for all users. |
- Pretreatment is
required to prevent clogging, although eventual clogging is inevitable.
- May negatively affect soil and groundwater properties. |
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