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Recovery of microbial biomass and purification performance after scraping of full-scale slow sand filters

Journal Article (2024)
Author(s)

S.A. Trikannad (TU Delft - Sanitary Engineering)

Valentina Attiani (Wageningen University & Research)

Paul W.J.J. van der Wielen (Wageningen University & Research, KWR Water Research Institute)

Hauke Smidt (Wageningen University & Research)

Jan Peter van der van der Hoek (TU Delft - Sanitary Engineering, Waternet)

Doris van Halem (TU Delft - Sanitary Engineering)

Research Group
Sanitary Engineering
Copyright
© 2024 S.A. Trikannad, Valentina Attiani, Paul W.J.J. van der Wielen, Hauke Smidt, J.P. van der Hoek, D. van Halem
DOI related publication
https://doi.org/10.1016/j.jwpe.2024.105101
More Info
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Publication Year
2024
Language
English
Copyright
© 2024 S.A. Trikannad, Valentina Attiani, Paul W.J.J. van der Wielen, Hauke Smidt, J.P. van der Hoek, D. van Halem
Research Group
Sanitary Engineering
Volume number
60
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Abstract

Slow sand filters (SSFs) are widely used in drinking water production to improve microbial safety and biological stability of water. Full-scale SSFs are maintained by scraping the biomass-rich top layers of sand. The period of downtime required for filter recovery after scraping is a major challenge due to limited knowledge of the re-stabilisation of purification processes. This study examined the recovery of microbial biomass, and removal of dissolved organic carbon (DOC) and ammonium (NH4+) in water phase and/or on sand along the depth of a scraped full-scale SSF. Scraping reduced microbial biomass on sand in the top layers, while the main prokaryotic taxa remained unaltered. Cellular ATP (cATP) and intact cell counts (ICC) in water sampled from the top layers increased, indicating a temporary disruption in functionality for 37 days. However, stable concentrations of cATP and ICC and similar microbial community composition in the effluent after scraping revealed that deeper layer biofilms offset any scraping effect. Consistent DOC and NH4+ removal after scraping showed that deeper layers effectively performed the role of the top layer. These findings highlight the resilience and robustness of microbial communities in mature full-scale SSFs and their contribution to water treatment efficiency after disturbances caused by scraping.