Sediment basins

Sediment basins — Key considerations

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• Overview
• Key considerations
• Planning and design
• Construction and operation
• Links and references

What makes an effective sediment basin?

• Sufficiently sized to intercept and retain run-off long enough for the target sediments to settle out of the water column (water regime/hydrology and area) and sediment type (see sizing in planning and design), with sufficient storage so that desilting is only needed about once every five years[4].
• Ideally contains a high-flow bypass to prevent trapped sediment being resuspended and exported during high flows.
• An elongated shape, with a length to width ratio between 3:1 and 10:1 to avoid short-circuiting and improve sediment trapping[2].
• Easy access for maintenance to clean out accumulated sediment (desilting).
• Used in combination with farm best management practices - so that the sediment basin doesn’t fill up too quickly and require frequent desilting.

Treatment processes

Suitability and limitations

Sediment basins have been used in a range of agricultural production systems and locations throughout Queensland, particularly where there is a high risk of sediment loss, i.e. during tillage, land preparation, planting or harvesting and where crops are grown on slopes.

A type of sediment basin, called sedimentation or settlement ponds, are commonly used to treat aquaculture wastewater. These ponds often take up a significant proportion of the productive area on a farm, with up to 30% of the productive land on a prawn farm dedicated to these ponds[1]. They have been shown to be effective at reducing total suspended solids (by up to 60%) in prawn farm discharge in Queensland[3]. They can also remove some particulate nutrients, but these may get remineralised into dissolved forms back into the water, leading to little overall reduction in total nitrogen and phosphorus[3].

The cost-effectiveness of a sediment basin in removing the target pollutant/s needs to be considered relative to other treatment structures or management intervention options. Refer to cost considerations for more information.

References

1. ^ Australian Prawn Farmers Association (2022), Sustainable Farming (Education & Resources) – APFA.
2. ^ Department of Land and Water Conservation (1998), The constructed wetlands manual: Volume 2, Department of Land and Water Conservation, New South Wales.
3. ^ a b Jackson, CJ, Preston, N, Burford, MA & Thompson, PJ (October 2003), 'Managing the development of sustainable shrimp farming in Australia: the role of sedimentation ponds in treatment of farm discharge water', Aquaculture. [online], vol. 226, no. 1-4, pp. 23-34. Available at: https://linkinghub.elsevier.com/retrieve/pii/S0044848603004642 [Accessed 27 November 2022].
4. ^ Moreton Bay Waterways and Catchment Partnership (2006), Water sensitive urban design technical design guidelines for South East Queensland. [online], Healthy Waterways, Brisbane. Available at: https://www.redland.qld.gov.au/download/downloads/id/1406/wsud_technical_design_guidelines.pdf.

Last updated: 5 November 2022