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Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems.

Publication ,  Journal Article
Mercer, E; Usher, SP; McAdam, EJ; Stoner, B; Bajón-Fernández, Y
Published in: Journal of environmental management
December 2021

In order to obviate the economic issues associated with pit latrine emptying and transport such as high water additions and rheologically difficult sludge properties, the implications of prompt solid/liquid separation were investigated. This was achieved through rheological characterisation of fresh human faeces and synthetic faeces, and comparison with aged faecal sludges. Shear yield stress, thixotropy and post-shear structural recovery were characterised for a total solids (TS) concentration range of 5-35% total solids (TS) and stickiness yield stress was determined for concentrations up to 100% TS. Fresh faeces rheology proved to be favourable when compared to aged matrices, evidenced by a lower shear yield stress and higher gel point solids concentration, suggesting that aging could alter the physico-chemical properties of faecal sludge. Fresh and synthetic faeces exhibited similar shear thinning, thixotropic behaviour with the majority of structural breakdown occurring at a low shear rate of 10 s-1, and the extent increasing with higher solids concentrations. At 32% TS, fresh faeces shear yield stress was permanently reduced by 80%, suggesting that low shear pumping could reduce the energy demand required for faeces transport. The sticky phase, which represents the region to avoid faecal transport and mechanical drying processes, was identified to range from 30 to 50% TS, with 25% TS as ideal to commence dewatering processes. This also coincides with the average solids concentration of faeces, which is achievable by source separation. This study has identified that handling of fresh faeces as opposed to aged faecal sludges would result in economic and environmental benefits, with energy, water and labour savings.

Duke Scholars

Published In

Journal of environmental management

DOI

EISSN

1095-8630

ISSN

0301-4797

Publication Date

December 2021

Volume

300

Start / End Page

113730

Related Subject Headings

  • Toilet Facilities
  • Sewage
  • Sanitation
  • Rheology
  • Humans
  • Feces
  • Environmental Sciences
  • Aged
 

Citation

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ICMJE
MLA
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Mercer, E., Usher, S. P., McAdam, E. J., Stoner, B., & Bajón-Fernández, Y. (2021). Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems. Journal of Environmental Management, 300, 113730. https://doi.org/10.1016/j.jenvman.2021.113730
Mercer, Edwina, Shane P. Usher, Ewan J. McAdam, Brian Stoner, and Yadira Bajón-Fernández. “Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems.Journal of Environmental Management 300 (December 2021): 113730. https://doi.org/10.1016/j.jenvman.2021.113730.
Mercer E, Usher SP, McAdam EJ, Stoner B, Bajón-Fernández Y. Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems. Journal of environmental management. 2021 Dec;300:113730.
Mercer, Edwina, et al. “Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems.Journal of Environmental Management, vol. 300, Dec. 2021, p. 113730. Epmc, doi:10.1016/j.jenvman.2021.113730.
Mercer E, Usher SP, McAdam EJ, Stoner B, Bajón-Fernández Y. Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems. Journal of environmental management. 2021 Dec;300:113730.
Journal cover image

Published In

Journal of environmental management

DOI

EISSN

1095-8630

ISSN

0301-4797

Publication Date

December 2021

Volume

300

Start / End Page

113730

Related Subject Headings

  • Toilet Facilities
  • Sewage
  • Sanitation
  • Rheology
  • Humans
  • Feces
  • Environmental Sciences
  • Aged