Biological mechanisms in slow sand filters

Weber‐Shirk, Monroe L.; Dick, Richard I.

doi:10.1002/j.1551-8833.1997.tb08180.x

Cited by 66 publications

(38 citation statements)

References 17 publications

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“…The biofilm is credited with the enhanced removal of suspended solids and pathogens through mechanical trapping, adsorption, predation, and natural death. Development of the biofilm results in greater removal of suspended solids and pathogens, but its development also reduces flow rates [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Iron oxide amended biosand filters for virus removal

et al. 2011

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Laboratory studies were performed to determine if the addition of iron oxides throughout biosand filter (BSF) media would increase virus removal due to adsorption.The proposed mechanism is electrostatic adsorption of negatively charged virion particles to positively charged iron oxides formed during the corrosion of zerovalent iron. Initial tests conducted using continuous flow, small-scale glass columns showed high MS2 bacteriophage removal in an iron-amended sand column (5-log 10 ) compared to a sand only column (0.5-log 10 ) over 20 pore volumes. Additionally, two experiments with a column containing iron particles revealed 4 and 5 log 10 removal of rotavirus in the presence of 20 mg/L total organic carbon. Full-scale BSFs with iron particles removed >4-log 10 MS2 for the duration of the experiment (287 days), while BSF with steel wool removed >4-log 10 MS2 for the first 160 days. Plug flow for the BSF was shown to depend on uniformity between the iron oxide material and sand media grains. The results suggest that the duration of effective virus removal by iron-amended biosand filtration depends on source water conditions and the quantity and composition of iron material added. Overall, this study provides evidence that iron-amended BSFs may advance the field of point-of-use technologies and bring relief to millions of people suffering from waterborne diseases.iii ACKNOWLEDGMENTS

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Section: Introductionmentioning

confidence: 99%

Iron oxide amended biosand filters for virus removal

et al. 2011

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“…The action of SSFs against many microorganisms, including some human pathogens and plant pathogens, is still not fully understood but is considered to be a combination of physicochemical and biological processes which remove and consume much of suspended particulate organic carbon from the water passing through the sand column (24,35,65,66). Using traditional microbial methods, the diversity and dynamics of bacteria in SSF used in the water industry have been widely studied (8,13,18).…”

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confidence: 99%

Spatial and Temporal Analysis of the Microbial Community in Slow Sand Filters Used for Treating Horticultural Irrigation Water

Calvo-Bado

Pettitt

Parsons³

et al. 2003

Appl Environ Microbiol

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An experimental slow sand filter (SSF) was constructed to study the spatial and temporal structure of a bacterial community suppressive to an oomycete plant pathogen, Phytophthora cryptogea. Passage of water through the mature sand column resulted in complete removal of zoospores of the plant pathogen. To monitor global changes in the microbial community, bacterial and fungal numbers were estimated on selective media, direct viable counts of fungal spores were made, and the ATP content was measured. PCR amplification of 16S rRNA genes and denaturing gradient gel electrophoresis (DGGE) were used to study the dynamics of the bacterial community in detail. The top layer (1 cm) of the SSF column was dominated by a variable and active microbial population, whereas the middle (50 cm) and bottom (80 cm) layers were dominated by less active and diverse bacterial populations. The major changes in the microbial populations occurred during the first week of filter operation, and these populations then remained to the end of the study. Spatial and temporal nonlinear mapping of the DGGE bands provided a useful visual representation of the similarities between SSF samples. According to the DGGE profile, less than 2% of the dominating bands present in the SSF column were represented in the culturable population. Sequence analysis of DGGE bands from all depths of the SSF column indicated that a range of bacteria were present, with 16S rRNA gene sequences similar to groups such as Bacillus megaterium, Cytophaga, Desulfovibrio, Legionella, Rhodococcus rhodochrous, Sphingomonas, and an uncharacterized environmental clone. This study describes the characterization of the performance, and microbial composition, of SSFs used for the treatment of water for use in the horticultural industry. Utilization of naturally suppressive population of microorganisms either directly or by manipulation of the environment in an SSF may provide a more reproducible control method for the future.Fungal plant diseases are a major problem within the horticultural industry, resulting in reduced yields and occasionally major crop damage. Contaminated irrigation water has long been recognized as an important source of fungal plant pathogens and is an important factor in disease spread on commercial horticultural nurseries (4). Water from many commonly used sources, such as rainwater from glasshouse roofs and, in particular, water stored in open reservoirs and ponds, can often contain large numbers of infective propagules of fungal plant pathogens, such as Pythium and Phytophthora spp. (1,4,34,46,48,53). A particularly high risk of disease spread is associated with the collection, recycling, and reuse of irrigation water, often referred to as recirculation (45,57,58), which is becoming more popular as attempts are increasingly being made to conserve valuable water supplies. Rapid dispersal of the pathogen in water is often achieved by asexual flagellate zoospores, and a key element for pathogen control is the removal of zoospores from water supplies. A wide...

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“…Cette diminution pourrait être liée à une rétention physique et/ou à une adsorption des bactéries coliformes dans les lits filtrants (BELLAMY et al, 1985;ELLIS, 1985;HAARHOFF et CLEASBY, 1991;WEBER-SHIRK et DICK, 1997b). Outre les phénomènes de sorption, la diminution des bactéries coliformes s'effectue principalement par des processus biologiques, notamment la prédation des bactéries par des protistes (BOMO et al, 2004;CHABAUD et al, 2006;CLEASBY et LOGSDON, 1999;HAARHOFF et CLEASBY, 1991;WEBER-SHIRK et DICK, 1997a. Toutefois, la diminution du nombre de colonies est plus importante après l'établissement de la couche biologique (biofilm) et la maturité des filtres (BELLAMY et al, 1985;COMPOS et al, 2002;HUISMAN et WOOD, 1974).…”

Section: Discussionunclassified

Traitement des eaux de consommation par filtration lente sur sable à plusieurs étapes

Disa-Disa

Culot

Lobo

et al. 2014

rseau

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La possibilité d’éliminer la turbidité et les coliformes, en utilisant un système de filtration lente sur sable à plusieurs étapes, a été étudiée à l’échelle du laboratoire. Le but de l’étude était de montrer que cette technologie constitue une solution de traitement efficace de l’eau en milieu rural et dans de petites agglomérations des pays en voie de développement. Dans cette étude, un système a été monté et testé. Ce système était constitué de deux filtres lents à sable en série, lesquels sont précédés de deux filtres à granulométrie grossière à flux ascendant. L’efficacité de cette technologie a été évaluée par la mesure de la turbidité et le dénombrement des coliformes totaux et thermotolérants. Les résultats obtenus ont montré : (i) d’excellents abattements de la turbidité malgré le niveau élevé de celle de l’eau brute (de 20 unités de turbidité néphélométrique (NTU) à plus de 100 NTU); (ii) une bonne élimination des coliformes, en fonction de la maturité biologique des filtres utilisés; (iii) de plus, il a été constaté que la turbidité de l’effluent à la sortie du second filtre lent à sable était largement en dessous de la norme de l’Organisation Mondiale de la Santé (OMS) concernant l’eau potable. Globalement, chaque étape individuelle du système de filtration à plusieurs étapes joue un rôle important dans le processus global de réduction de la turbidité, ainsi que du nombre de coliformes. Il a été remarqué que le filtre à granulométrie grossière, en plus de son rôle protecteur de filtre lent à sable contre les matières en suspension, constitue aussi une barrière importante de traitement dans la diminution du nombre de coliformes. L’addition d’un second filtre lent à sable en série a apporté une efficacité supplémentaire au processus de traitement, en ramenant la turbidité d’effluent proche de 1 NTU et en permettant d’obtenir des abattements additionnels de coliformes.

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Biological mechanisms in slow sand filters

Cited by 66 publications

References 17 publications

Iron oxide amended biosand filters for virus removal

Iron oxide amended biosand filters for virus removal

Spatial and Temporal Analysis of the Microbial Community in Slow Sand Filters Used for Treating Horticultural Irrigation Water

Traitement des eaux de consommation par filtration lente sur sable à plusieurs étapes

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