Insight into the stickiness of faecal sludge from dry sanitation technologies: a path toward sustainable and efficient FSM via thermal processes

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dc.contributor.authorMupinga, Ratidzaishe T.
dc.contributor.authorMercer, Edwina
dc.contributor.authorRayavellore Suryakumar, A.
dc.contributor.authorPocock, Jonathan
dc.contributor.authorSeptien, Santiago
dc.date.accessioned2025-06-19T12:25:43Z
dc.date.available2025-06-19T12:25:43Z
dc.date.freetoread2025-06-19
dc.date.issued2025-06
dc.date.pubOnline2025-06-06
dc.description.abstractThis study explores the stickiness behaviour of faecal sludge (FS) during thermal drying—an operational challenge that hampers the performance of faecal sludge management (FSM) systems. Samples were collected from ventilated improved pit (VIP) latrines and urine diversion dry toilets (UDDTs) in Durban, South Africa, and analysed using a texture analyser to measure adhesive and cohesive forces over a temperature range of 25–80 °C and moisture contents between 20–90 wt.%. Complementary tests were conducted to assess water activity, drying kinetics, rheological properties, and plastic behaviour. Maximum stickiness occurred in the 50–60 wt.% moisture range. In this region, FS transitioned from a viscoelastic fluid to lumpy and plastic consistency dominated by interstitial moisture, and eventually to a granular solid at the end of the sticky region, as interstitial water was depleted. The sticky phase coincided with the transition from the first to the second falling-rate period of drying, reflecting a shift from surface to internal moisture evaporation. Cohesive forces were consistently greater than adhesive forces and increased modestly at 80 °C. UDDT sludge was slightly stickier than VIP sludge under similar conditions. The results highlight the strong dependence of FS stickiness on moisture content and its binding properties. To address this issue, the study proposes mitigation strategies such as bypassing the sticky range, using bulking agents, or applying pre-treatments to improve drying performance. These findings provide practical guidance for the design and operation of sludge treatment systems and contribute to more sustainable FSM practices.
dc.description.journalNameResults in Engineering
dc.description.sponsorshipThe authors gratefully acknowledge the Bill and Melinda Gates Foundation for their financial support, which made this research possible.
dc.identifier.citationMupinga RT, Mercer E, Rayavellore Suryakumar A, et al., (2025) Insight into the stickiness of faecal sludge from dry sanitation technologies: a path toward sustainable and efficient FSM via thermal processes. Results in Engineering, Volume 26, June 2025, Article number 105453en_UK
dc.identifier.elementsID673554
dc.identifier.issn2590-1230
dc.identifier.paperNo105453
dc.identifier.urihttps://doi.org/10.1016/j.rineng.2025.105453
dc.identifier.urihttps://dspace.lib.cranfield.ac.uk/handle/1826/24056
dc.identifier.volumeNo26
dc.languageEnglish
dc.language.isoen
dc.publisherElsevieren_UK
dc.publisher.urihttps://www.sciencedirect.com/science/article/pii/S2590123025015233?via%3Dihub
dc.rightsAttribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subject4004 Chemical Engineeringen_UK
dc.subject40 Engineeringen_UK
dc.subject40 Engineeringen_UK
dc.subjectAdhesionen_UK
dc.subjectCohesionen_UK
dc.subjectThermal dryingen_UK
dc.subjectPlastic limiten_UK
dc.subjectBound moistureen_UK
dc.subjectRheologyen_UK
dc.titleInsight into the stickiness of faecal sludge from dry sanitation technologies: a path toward sustainable and efficient FSM via thermal processesen_UK
dc.typeArticle
dcterms.dateAccepted2025-05-22

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