Spatio-temporal dynamics of virus and bacteria removal in dual-media contact-filtration for drinking water

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2016-03-05Department
Ingeniería Química y Tecnología de AlimentosSource
Water Research 156 (2019) 9-22Abstract
Microorganism removal efficiencies in deep bed filters vary with time and depth in the filter bed as the
filter collects particles. Improved knowledge of such dynamics is relevant for the design, operation and
microbial risk assessment of filtration processes for drinking water treatment. Here we report on a highresolution
spatio-temporal characterization of virus and bacteria removal in a pilot-scale dual-media
filter, operated in contact-filtration mode. Microorganisms investigated were bacteriophage Salmonella
typhimurium 28B (plaque assay, n ¼ 154)), fRNA phage MS2 (plaque assay/RT-qPCR, n ¼ 87) and E. coli
(Colilert-18, n ¼ 73). Microscopic and macroscopic filtration models were used to investigate and
characterize the removal dynamics.
Results show that ripening/breakthrough fronts for turbidity, viruses and E. coli migrated in a wavelike
manner across the depth of the filter. Virus removal improved continuously throughout the filter
cycle and viruses broke through almost simultaneously with turbidity. Ripening for E. coli took longer
than ripening for turbidity, but the bacteria broke through before turbidity breakthrough. Instantaneous
log-removal peaked at 3.2, 3.0 and 4.5 for 28B, MS2 and E. coli, respectively. However, true average logremoval
during the period of stable effluent turbidity was significantly lower at 2.5, 2.3 and 3.6,
respectively. Peak observed filter coefficients l were higher than predicted by ideal filtration theory. This
study demonstrates the importance of carefully designed sampling regimes when characterizing
microorganism removal efficiencies of deep bed filters.
Subjects
Drinking water; Filtration; Virus; Dynamics; ModelingCollections
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