Evaporation Transpiration Absorption Beds (ETA Beds)
ETA Beds under construction
With this type of waste water disposal system the effluent is piped by gravity where possible into specially constructed beds or trenches below the ground within an assigned disposal area.
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Cross Section ETA Bed for clay loams, light to heavy clay |
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Self supporting arch trench for gravels, sandy soils and loam |
Evaporation takes place by capillary action as water will be thrown up between the soil ‘peds’ to the surface and than evaporates assisted by the sun and wind, that is why it’s important that the beds have good exposure.
Transpiration is achieved through the foliage growing on top of the Beds, which should only be grass, larger plants will shade out the beds and slow down evaporation.
Absorption takes place into the surrounding soil, where the waste water is further processed by cultures of decaying bacteria and organisms.
The most important factor for the sizing of the Bed is the Daily Loading Rate(DLR) and the limitations of the soil. Once established, this system is mostly maintenance free, it is also considered the safest way of disposing of effluent, as it guaranties complete separation of humans and animals from waste water, regardless of whether it has been disinfected.
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On site construction of ETA Beds |
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Owners of ETA Beds should establish appropriate vegetation, in addition to grassing the Beds, shrubs can be planted around the Beds (never on) generally as far from the Bed as the grow in height.
Traffic, tractors, cars etc must be kept off the Beds as must all hoofed animals to avoid damage and compaction of the ETA Beds.
Appropriate vegetation for around ETA Beds
SUITABLE NUTRIENT ANDWATER SCAVENGING PLANT SPECIES FOR PLANTING AROUND DISPOSAL FIELDS |
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Angoizanthus flavidus
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Kangaroo Paw
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NB: Plants should be placed a little further away from the edge of the Beds as they grow in height |
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