Investigating mechanisms for effluent pond sealing: the effect of suspended organic particulate on soil hydraulic conductivity

Warren, Bradley (2012) Investigating mechanisms for effluent pond sealing: the effect of suspended organic particulate on soil hydraulic conductivity. [USQ Project]

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Feedlot regulating authorities have proposed a pond seepage infiltration rate guideline of 1.0x10^-9 m/s (31.54 mm/year) in an effort to control environmental degradation.
This project aims to investigate the effect of the organic particulates in feedlot effluent upon physical pore blockage and a reduction in soil hydraulic conductivity (HC). Two soils, a heavy clay and clay loam were treated with four solutions, calcium chloride, synthetic effluent, filtered effluent and raw effluent, and the hydraulic conductivity was calculated over an extended time period. The soils were compacted to 98% maximum dry density (MDD) to ensure the best chance at achieving the guideline
infiltration rate. Hydraulic conductivity was calculated using a falling pressure head method. Calcium chloride application caused a slight increase in HC, likely due to an
osmotic effect reducing the diffuse double layer. Synthetic effluent was compared against actual effluent, results showed actual effluent caused a much slower flow rate,
from this observation it was concluded that accumulation of suspended solids was the major reason for a reduction in HC, not dispersion or swelling. The raw and filtered
effluent samples were also compared and as expected the raw effluent produced a slower HC, due to the higher amount of total suspended solids (TSS) in the solution, although it was determined that particulate <3 μm was primarily responsible for pore blockage. A reduction in TSS from the percolating solution to leachate meant that
solid organic matter has accumulating within the soil profile. It was concluded that the organic particulate in feedlot effluent does contribute to pore blockage and a
reduction in HC. Regarding the guideline rate, the heavy clay achieved this target after approximately 500 hours of leaching with a final HC of 9.39x10^-10 m/s. The
clay loam was unable to reach this rate during the time period finishing with a HC of 1.52x10^-9. However, HC trends indicate that given time the clay loam HC could be
expected to achieve the guideline rate. This potential for a large cost saving, due to negation of the requirement for expensive plastic liners to limit HC, was identified.
This project provides the groundwork for a more comprehensive study, involving a wider range of soils and effluent sources, which have the potential to ensure the
sustainable operation of beef feedlot ponds by restricting pond seepage through organic particulate pore blockage.

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Item Type: USQ Project
Refereed: No
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering (Up to 30 Jun 2013)
Supervisors: Mclean-Bennett, John
Date Deposited: 26 Feb 2013 23:39
Last Modified: 26 Feb 2013 23:39
Uncontrolled Keywords: effluent pond sealing; soil; feedlot
Fields of Research (2008): 05 Environmental Sciences > 0503 Soil Sciences > 050305 Soil Physics
Fields of Research (2020): 41 ENVIRONMENTAL SCIENCES > 4106 Soil sciences > 410605 Soil physics

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