TY - JOUR
T1 - Recovery of microbial biomass and purification performance after scraping of full-scale slow sand filters
AU - Trikannad, Shreya Ajith
AU - Attiani, Valentina
AU - van der Wielen, Paul W.J.J.
AU - Smidt, Hauke
AU - van der Hoek, Jan Peter
AU - van Halem, Doris
PY - 2024
Y1 - 2024
N2 - 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.
AB - 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.
KW - Slow sand filters
KW - Schmutzdecke
KW - Scraping
KW - Ripening period
KW - Dissolved organic carbon
KW - Ammonium
UR - http://www.scopus.com/inward/record.url?scp=85187390485&partnerID=8YFLogxK
U2 - 10.1016/j.jwpe.2024.105101
DO - 10.1016/j.jwpe.2024.105101
M3 - Article
SN - 2214-7144
VL - 60
JO - Journal of Water Process Engineering
JF - Journal of Water Process Engineering
M1 - 105101
ER -