Evapotranspiration Systems
Domestic Wastewater Reuse in Remote Aboriginal Communities, through the use of Evapotranspiration Trenches
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There are many instances of sewage ponding in Aboriginal settlements due to the inappropriate design of septic tanks and their associated leach drains. Over the past 10 years, in an attempt to alleviate this problem, reticulated sewer to lagoon systems have been installed as the funds become available. However these systems are not water wise and are expensive to install and maintain. Up to 85% of the cost involved can be in capital and maintenance costs associated with the pipes and pumps required to transport sewage to the treatment plant (Newman & Mouritz 1996). The potential to reuse treated effluent is limited as it is concentrated in one area.
Evapotranspiration systems offer an alternative to the above two approaches to domestic wastewater treatment. By using evapotranspiration trenches wastewater effluent can be reused for revegetation and food production, this allows for a holistic approach to service delivery in remote aboriginal communities.
Domestic Wastewater Reuse in Remote Aboriginal Communities, through the use of Evapotranspiration Trenches |
EPA: Evapotranspiration and Evapotranspiration/Infiltration Fact Sheet
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Onsite evapotranspiration wastewater treatment systems are designed to disperse effluent exclusively by evapotranspiration. Evapotranspiration (ET) is defined as the combined effect of water removal from a medium by direct evaporation and by plant transpiration. The evapotranspiration/infiltration (ETI) process is a subsurface system designed to dispose of effluent by both evapotranspiration and infiltration into the soil. Both of these systems are preceded by primary pretreatment units (e.g., septic tank) to remove settleable and floatable solids. The influent to the ET or ETI units enters through a series of distribution pipes to a porous bed. In ET systems, a liner is placed below the bed to prevent water loss via infiltration unless the soil is impermeable. The surface of the sand bed is planted with water-tolerant plants. Effluent is drawn up through fine media by capillary wicking and evaporated or transpired into the atmosphere. In ETI systems, effluent is allowed to percolate into the underlying soil.Modifications to ET and ETI systems include mechanical evaporating devices and a broad array of different designs and means of distribution, storage of excess influent, wicking, and containment or infiltration prevention. Some newer studies are using drip irrigation with distribution to forested areas with purported success.
EPA: Evapotranspiration and Evapotranspiration/Infiltration Fact Sheet |
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