On the compressional rheology of fresh faeces: evidence for improving community scale sanitation through localised dewatering

Simple item page
dc.contributor.authorMercer, Edwina
dc.contributor.authorUsher, Shane P.
dc.contributor.authorMcAdam, Ewan J.
dc.contributor.authorStoner, Brian
dc.contributor.authorBajón Fernández, Yadira
dc.date.accessioned2021-08-13T11:04:39Z
dc.date.available2021-08-13T11:04:39Z
dc.date.issued2021-08-06
dc.description.abstractNon-sewered sanitation is currently dependent upon pit latrine emptying, the safety of which is compromised by the high costs of faecal sludge transport to centralised treatment facilities. Transport in turn is hindered by the complex rheology of pit latrine sludge. This study therefore characterised the compressional rheology of fresh faeces and modelled the implications for passive (gravity) or mechanical (forced) solid/liquid separation. This informs on the viability of decentralising dewatering for more efficient volume reduction and improve the economics of transportation. The gel point (ϕg) is the solids concentration where the material has a networked structure and signifies the point when mechanical intervention is required for further solid-liquid separation. For fresh faeces, ϕg ranged between 6.3 and 15.6% total solids (TS) concentration. This is significantly higher than the ϕg observed for wastewater sludge at centralised facilities, and it implies that passive gravity driven processes can suffice to improve localised dewatering. The kinetics of passive sedimentation of faecal material were modelled and illustrate thickening from 3 to 10% TS concentration in <0.5h. This highlights that early intervention to thicken faeces while fresh can improve solid/liquid separation efficiency. Filtration of fresh faeces was characterised by lengthy cake filtration times and comparably short compression times, more similar to mineral slurries than to wastewater sludge. Consequently, fresh faeces presented improved dewatering characteristics, supporting higher final cake solids concentrations and improved dewatering kinetics. By complementing thickening with 300kPa filtration, a 1.4 cm thick 25% TS product could be achieved in <24h. Investigation of matrix properties highlighted that increased conductivity (e.g. exposure to urine) negatively influenced dewaterability, an effect which could be mitigated by introducing solid-liquid separation earlier. The thermodynamically favourable compressional rheology of fresh faeces has identified that focussing on localised dewatering could radically improve the economics of faecal sludge management, primarily through reducing transport costs.en_UK
dc.identifier.citationMercer E, Usher SP, McAdam EJ, et al., (2021) On the compressional rheology of fresh faeces: evidence for improving community scale sanitation through localised dewatering. Water Research, Volume 204, October 2021, Article number 117526en_UK
dc.identifier.issn0043-1354
dc.identifier.urihttps://doi.org/10.1016/j.watres.2021.117526
dc.identifier.urihttp://dspace.lib.cranfield.ac.uk/handle/1826/16994
dc.language.isoenen_UK
dc.publisherElsevieren_UK
dc.rightsAttribution 4.0 International
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectThickeningen_UK
dc.subjectcompressive yield stressen_UK
dc.subjectsolids diffusivityen_UK
dc.subjecthindered settling functionen_UK
dc.subjectpressure filtrationen_UK
dc.titleOn the compressional rheology of fresh faeces: evidence for improving community scale sanitation through localised dewateringen_UK
dc.typeArticleen_UK

Files

Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
On_the_compressional_rheology_fresh faeces-2021.pdf
Size:
1.5 MB
Format:
Adobe Portable Document Format
Description:
Download

Collections

Staff publications (SWEE)