Dynamic response of biofilm to pipe surface and fluid velocity

Cloete, T.E.; Westaard, D.; Vuuren, S.J. van

doi:10.2166/wst.2003.0280

Cited by 45 publications

(30 citation statements)

References 9 publications

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“…The same study showed that there was no significant difference in the viable counts on PE and PVC. Different results were obtained by Cloete et al (2003), where biofilm formation was higher on the PVC surfaces than on galvanized steel piping. van der Kooij and Veenendaal (2001) and Clark et al (1994) observed that PE supports biofilm formation in a higher degree than PVC, while Wingender and Flemming (2004), Pedersen (1990) and Zacheus et al (2000) concluded that there was no significant difference in the colonization of the investigated materials (stainless steel, PVC and PE), in some cases after decades of operation.…”

Section: Article In Pressmentioning

confidence: 76%

“…In most fixed biomass systems, stable and higher flow rates have the advantage of limiting biofilm growth (Peyton and Characklis, 1993;Melo and Vieira, 1999;Cloete et al, 2003), since they produce thinner and more cohesive layers less prone to release bacteria into the bulk water. However, these conditions are not always feasible to maintain in drinking water networks.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of drinking water biofilm in flow/non-flow conditions

2007

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A B S T R A C TDrinking water biofilm formation on polyvinyl chloride (PVC), cross-linked polyethylene (PEX), high density polyethylene (HDPE) and polypropylene (PP) was followed in three different reactors operating under stagnant or continuous flow regimes. After one week, a quasi-steady state was achieved where biofilm total cell numbers per unit surface area were not affected by fluctuations in the concentration of suspended cells. Metabolically active cells in biofilms were around 17-35% of the total cells and 6-18% were able to form colony units in R 2 A medium. Microbiological analysis showed that the adhesion material and reactor design did not affect significantly the biofilm growth. However, operating under continuous flow (0.8-1.9 Pa) or stagnant water had a significant effect on biofilm formation: in stagnant waters, biofilm grew to a less extent. By applying mass balances and an asymptotic biofilm formation model to data from biofilms grown on PVC and HDPE surfaces under turbulent flow, specific growth rates of bacteria in the biofilm were found to be similar for both materials (around 0.15 day À1) and much lower than the specific growth rates of suspended bacteria (around 1.8 day À1 ).

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Section: Article In Pressmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Dynamics of drinking water biofilm in flow/non-flow conditions

2007

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“…The results obtained for coaggregation and community population dynamics therefore can be considered to relate to occurrences within polymicrobial freshwater communities. Shear rates have been suggested to be important in the development of biofilm community structure (3) and govern the abilities of individual species to immigrate to biofilms and to colonize new surfaces (9,45). Other factors include substratum composition, concentrations of solutes, and nutrient availability (6,19).…”

Section: Discussionmentioning

confidence: 99%

“…Few published articles have described the effect of shear on the bacterial composition and diversity of freshwater biofilms. Evidence is emerging, however, that at high fluid velocities with associated high shear rates, multispecies communities are less diverse than those developed at lower shear rates (9,23,35,42). In order to adhere to surfaces or surface-attached cells and subsequently to form biofilms, bacteria in high-velocity flowing systems must overcome shear stress at the fluid-surface interface (7, 11).…”

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confidence: 99%

Shear Rate Moderates Community Diversity in Freshwater Biofilms

Rickard

McBain

Stead

et al. 2004

Appl Environ Microbiol

149

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The development of freshwater multispecies biofilms at solid-liquid interfaces occurs both in quiescent waters and under conditions of high shear rates. However, the influence of hydrodynamic shear rates on bacterial biofilm diversity is poorly understood. We hypothesized that different shear rates would significantly influence biofilm diversity and alter the relative proportions of coaggregating and autoaggregating community isolates. In order to study this hypothesis, freshwater biofilms were developed at five shear rates (<0.1 to 305 S ؊1 ) in a rotating concentric cylinder reactor fed with untreated potable water. Eubacterial diversity was assessed by denaturing gradient gel electrophoresis (DGGE) and culturing on R2A agar. Fifty morphologically distinct biofilm strains and 16 planktonic strains were isolated by culturing and identified by partial 16S rRNA gene sequencing, and their relatedness was determined by the construction of a neighbor-joining phylogenetic tree. Phylogenetic and DGGE analyses showed an inverse relationship between shear rate and bacterial diversity. An in vitro aggregation assay was used to assess the relative proportions of coaggregating and autoaggregating species from each biofilm. The highest proportion of autoaggregating bacteria was present at high shear rates ( Microorganisms colonize a wide range of environments as spatially organized, taxonomically diverse, multispecies biofilm communities (1,20,44). In potable water distribution systems, many bacterial species, including members of the Proteobacteria, Actinobacteria, low-GϩC-content gram-positive bacteria, and Cytophaga-Flavobacterium-Bacterioides group, readily adhere to surfaces to form multispecies biofilms (29,41). The abilities of these taxonomically diverse organisms to attach to surfaces and codevelop within multispecies biofilms are imperative for their survival and persistence within flowing environments (4,33,44). Few published articles have described the effect of shear on the bacterial composition and diversity of freshwater biofilms. Evidence is emerging, however, that at high fluid velocities with associated high shear rates, multispecies communities are less diverse than those developed at lower shear rates (9,23,35,42). In order to adhere to surfaces or surface-attached cells and subsequently to form biofilms, bacteria in high-velocity flowing systems must overcome shear stress at the fluid-surface interface (7, 11). Attachment is facilitated by the expression of cell surface polymers that alter cell surface properties (3, 15). Properties that enhance attachment include increases in whole-cell hydrophobicity (14) and the abilities to coaggregate (25, 36) and autoaggregate (17). Recently, it was shown, using a simple recirculating tank model (35), that freshwater biofilms formed at high shear rates contained a high proportion of bacterial species that were not detectable in the surrounding fluid phase. In addition, a larger proportion of biofilm strains than of their planktonic counterparts were able to coaggr...

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“…The formation of biofilms increases with the flow velocity of water due to the increase of nutrient mass transfer [15]. Nevertheless, specific velocities between 3-4 m/s may favor its release [4].…”

Section: Case-studymentioning

confidence: 99%

Ensemble of naïve Bayesian approaches for the study of biofilm development in drinking water distribution systems

Ramos-Martínez

Herrera

Izquierdo

et al. 2013

International Journal of Computer Mathematics

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The survival and regrowth of microorganisms in drinking water distribution systems (DWDSs) can be affected not only by biological aspects but also by the interaction of various other factors. Some of these factors have been found to be clearly related to biofilm development in DWDSs. However, the complexity of the microenvironment under study and the biofilm growth characteristics have so far led the various methodologies applied to produce ambiguous or not easily comparable, and thus not very useful, results. In this study we compile the information currently available on biofilm ecology in DWDSs and apply various machine learning algorithms based on naïve Bayesian networks. In addition, as a step forward, we also use ensemble methods. These methods have been widely adopted to improve the robustness and the overall prediction accuracy of single models through their accumulative experience on the performance of multiple applications in learning systems. We claim that they also reduce the high uncertainty associated with the process of biofilm development in DWDSs. Specifically, we propose alternatives for the base naïve Bayesian model to outperform its individual results while maintaining its simplicity. These alternatives include augmentation of the arcs in the graph and bagging initial approaches. Then, both ideas are combined by a hybrid algorithm that produces explanatory decision trees. As a result, it is possible to achieve a deeper understanding of the consequences that the interaction of the relevant hydraulic and physical factors of DWDSs has for biofilm development.

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Dynamic response of biofilm to pipe surface and fluid velocity

Cited by 45 publications

References 9 publications

Dynamics of drinking water biofilm in flow/non-flow conditions

Dynamics of drinking water biofilm in flow/non-flow conditions

Shear Rate Moderates Community Diversity in Freshwater Biofilms

Ensemble of naïve Bayesian approaches for the study of biofilm development in drinking water distribution systems

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