Effects of sewage effluent on soil constraints in the Tamworth Region of New South Wales

Cameron, Adrian (2020) Effects of sewage effluent on soil constraints in the Tamworth Region of New South Wales. [USQ Project]

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The Tamworth Regional Council area has experienced many challenges during 2020 – drought, fires, floods, and an unprecedented global pandemic. Council staff and especially engineers have had to be at the forefront of addressing issues arising from the natural disasters and pandemic. Amid the crises water use has had huge political and social repercussions regarding acceptable outcomes within a changing climate.

Councils have for many years disposed of municipal effluent from their sewage treatment schemes in land-based disposal areas. The ability to grow agricultural crops from this effluent has only become viable as treatment systems have improved with the subsequent lowering of health and environmental risks.

Tamworth Regional Council has an effluent reuse farm utilizing pivot irrigation. Control areas can be sourced on soils outside the irrigation area to determine before and after condition of the soil. To be fully representative of the soils where sewage effluent has or has not been applied this study identified appropriate testing sites at the Tamworth Effluent Reuse Farm (TERF). The research involved classifying the study soils on the farm using the Australian Soil Classification (ASC), (Isbell & NCST, 2016). The quality and quantity of effluent applied to each of the soils was determined using data provided by Tamworth Regional Council in relation to ANZECC guidelines.

Irrigation data for each pivot showed insufficient effluent had been applied to push the salts through the profile. This was highlighted in a chemical analysis that had been performed for EPA compliance. To determine how the effluent was affecting the physical characteristics of the best and worst performing vertosol, sampling of irrigated and control soil was collected according to Australian guidelines. Testing was performed at a National Australian Testing Authority (NATA) registered laboratory. Physical soil tests were carried out in each identified horizon of excavated soil pits, as part of this report, and the results showed the irrigated soils are displaying signs of dispersion, compaction and reduced hydraulic conductivity.

To fully understand all the constraints and spatial covariates of interest further, an Electro Magnetic (EM) and gamma survey was conducted on the worst yielding pivots. Ground truthing of the spatial survey was then carried out with soil cores and constraint maps produced. Soils were found to have high dispersion, reduced permeability and increased salt levels compared to control areas, which are symptoms of salinity and sodicity caused by effluent irrigation at levels that significantly affect yield.

The findings revealed alternative spatial management of the irrigation and cropping regime will be required to ensure the sustainability of the TERF soils in the long term. The effluent, even at medium strength salt load, requires a leaching factor to be applied to ensure salts are pushed through the profile as even exceptionally good agricultural soils will be adversely affected if adequate leaching does not occur over time.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Current - Institute for Life Sciences and the Environment - Centre for Sustainable Agricultural Systems (1 Aug 2018 -)
Supervisors: Bennett, John McLean; Banks, Robert
Qualification: Bachelor of Engineering (Honours) (Environmental)
Date Deposited: 25 Aug 2021 23:02
Last Modified: 26 Jun 2023 03:53
Uncontrolled Keywords: sewage; soil constraints
URI: https://sear.unisq.edu.au/id/eprint/43078

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