Understanding the risk of enhanced particle penetration into slow sand filter beds when using underwater skimming techniques

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dc.contributor.authorElemo, Tolulope
dc.contributor.authorChipps, Michael
dc.contributor.authorGraham, Nigel
dc.contributor.authorTurner, Andrew
dc.contributor.authorJefferson, Bruce
dc.contributor.authorHassard, Francis
dc.date.accessioned2025-05-30T11:55:52Z
dc.date.available2025-05-30T11:55:52Z
dc.date.freetoread2025-05-30
dc.date.issued2025-06-01
dc.date.pubOnline2025-05-17
dc.description.abstractThis study evaluated abiotic slow sand filters (SSFs) to understand the risk of particle penetration during underwater skimming (UWS), focusing on clogging, headloss development, and particle breakthrough. Pilot-scale filters containing clean sand were challenged with dispersed kaolin particles to simulate surface accumulation, and the sand surface was agitated to mimic UWS procedures. The study was undertaken with no maturation period to consider the worst-case scenario corresponding to the period just after filter skimming. Agitating the surface and restarting flow released captured particles, some moving downward through the filter. Shallow filter depths resulted in particles appearing in the filtrate, but increasing the media depth beyond 500 mm minimized this effect. Since 90 % of headloss occurred in the upper layers, deeper particle penetration was insignificant. Increasing the hydraulic loading rate from 0.3 to 0.5 m/h reduced particle retention by 0.72 log, yet all abiotic SSFs achieved over 2 log particle capture. Small particles (2–10 μm) were removed by 2 logs, indicating sufficient non-viral pathogen retention under routine conditions. Effective capture of particles sized 2–125 μm suggested minimal risk to water quality and public health during UWS on full-scale SSFs. Using clean sand and kaolin represented a worst-case scenario, excluding biological maturation and particles. The findings suggest that under normal conditions, UWS does not increase deep particle penetration or breakthrough, supporting its safe implementation to enhance filter maintenance without compromising water quality.
dc.description.journalNameJournal of Environmental Management
dc.description.sponsorshipEngineering and Physical Sciences Research Council (EPSRC)
dc.description.sponsorshipThe authors acknowledge the financial support of the Engineering and Physical Sciences Research Council (ESPRC), through the STREAM Industrial Doctorate Centre (EP/L015412/1), and financial support from Thames Water and Northumbrian Water Group.
dc.format.mediumPrint-Electronic
dc.identifier.citationElemo T, Chipps M, Graham N, et al., (2025) Understanding the risk of enhanced particle penetration into slow sand filter beds when using underwater skimming techniques. Journal of Environmental Management, Volume 386, June 2025, Article number 125845
dc.identifier.eissn1095-8630
dc.identifier.elementsID673309
dc.identifier.issn0301-4797
dc.identifier.paperNo125845
dc.identifier.urihttps://doi.org/10.1016/j.jenvman.2025.125845
dc.identifier.urihttps://dspace.lib.cranfield.ac.uk/handle/1826/23951
dc.identifier.volumeNo386
dc.languageEnglish
dc.language.isoen
dc.publisherElsevier
dc.publisher.urihttps://www.sciencedirect.com/science/article/pii/S0301479725018213
dc.relation.isreferencedbyhttps://doi.org/10.6084/m9.figshare.27094813
dc.rightsAttribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectParticle penetration
dc.subjectSlow sand filter (SSF)
dc.subjectUnderwater skimming (UWS)
dc.subjectWater treatment
dc.titleUnderstanding the risk of enhanced particle penetration into slow sand filter beds when using underwater skimming techniques
dc.typeArticle
dc.type.subtypeJournal Article
dcterms.dateAccepted2025-05-14

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