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Oscillation characteristics of biofilm streamers in turbulent flowing water as related to drag and pressure drop

Oscillation characteristics of biofilm streamers in turbulent flowing water as related to drag and pressure drop
Oscillation characteristics of biofilm streamers in turbulent flowing water as related to drag and pressure drop
Mixed population biofilms consisting of Pseudomonas aeruginosa, P. fluorescens, and Klebsiella pneumoniae were grown in a flow cell under turbulent conditions with a water flow velocity of 18 cm/s (Reynolds number, Re, =1192). After 7 days the biofilms were patchy and consisted of cell clusters and streamers (filamentous structures attached to the downstream edge of the clusters) separated by interstitial channels. The cell clusters ranged in size from 25 to 750 microm in diameter. The largest clusters were approximately 85 microm thick. The streamers, which were up to 3 mm long, oscillated laterally in the flow. The motion of the streamers was recorded at various flow velocities up to 50.5 cm/s (Re 3351) using confocal scanning laser microscopy. The resulting time traces were evaluated by image analysis and fast Fourier transform analysis (FFT). The amplitude of the motion increased with flow velocity in a sigmoidal shaped curve, reaching a plateau at an average fluid flow velocity of approximately 25 cm/s (Re 1656). The motion of the streamers was possibly limited by the flexibility of the biofilm material. FFT indicated that the frequency of oscillation was directly proportional to the average flow velocity (u(ave)) below 9.5 cm/s (Re 629). At u(ave) greater than 9.5 cm/s, oscillation frequencies were above our measurable frequency range (0.12-6.7 Hz). The oscillation frequency was related to the flow velocity by the Strouhal relationship, suggesting that the oscillations were possibly caused by vortex shedding from the upstream biofilm clusters. A loss coefficient (k) was used to assess the influence of biofilm accumulation on pressure drop. The k across the flow cell colonized with biofilm was 2.2 times greater than the k across a clean flow cell.
0006-3592
536-544
Stoodley, Paul
08614665-92a9-4466-806e-20c6daeb483f
Lewandowski, Z.
1f3f2a52-af00-4d39-99b9-cb4a372959ce
Boyle, J.D.
368bdeb9-d77b-42e8-811a-09fb24a33c12
Lappin-Scott, H.M.
fa1948ea-97cd-47a8-9fea-4f67567a50c8
Stoodley, Paul
08614665-92a9-4466-806e-20c6daeb483f
Lewandowski, Z.
1f3f2a52-af00-4d39-99b9-cb4a372959ce
Boyle, J.D.
368bdeb9-d77b-42e8-811a-09fb24a33c12
Lappin-Scott, H.M.
fa1948ea-97cd-47a8-9fea-4f67567a50c8

Stoodley, Paul, Lewandowski, Z., Boyle, J.D. and Lappin-Scott, H.M. (1998) Oscillation characteristics of biofilm streamers in turbulent flowing water as related to drag and pressure drop. Biotechnology and Bioengineering, 57 (5), 536-544. (doi:10.1002/(SICI)1097-0290(19980305)57:5<536::AID-BIT5>3.0.CO;2-H).

Record type: Article

Abstract

Mixed population biofilms consisting of Pseudomonas aeruginosa, P. fluorescens, and Klebsiella pneumoniae were grown in a flow cell under turbulent conditions with a water flow velocity of 18 cm/s (Reynolds number, Re, =1192). After 7 days the biofilms were patchy and consisted of cell clusters and streamers (filamentous structures attached to the downstream edge of the clusters) separated by interstitial channels. The cell clusters ranged in size from 25 to 750 microm in diameter. The largest clusters were approximately 85 microm thick. The streamers, which were up to 3 mm long, oscillated laterally in the flow. The motion of the streamers was recorded at various flow velocities up to 50.5 cm/s (Re 3351) using confocal scanning laser microscopy. The resulting time traces were evaluated by image analysis and fast Fourier transform analysis (FFT). The amplitude of the motion increased with flow velocity in a sigmoidal shaped curve, reaching a plateau at an average fluid flow velocity of approximately 25 cm/s (Re 1656). The motion of the streamers was possibly limited by the flexibility of the biofilm material. FFT indicated that the frequency of oscillation was directly proportional to the average flow velocity (u(ave)) below 9.5 cm/s (Re 629). At u(ave) greater than 9.5 cm/s, oscillation frequencies were above our measurable frequency range (0.12-6.7 Hz). The oscillation frequency was related to the flow velocity by the Strouhal relationship, suggesting that the oscillations were possibly caused by vortex shedding from the upstream biofilm clusters. A loss coefficient (k) was used to assess the influence of biofilm accumulation on pressure drop. The k across the flow cell colonized with biofilm was 2.2 times greater than the k across a clean flow cell.

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Published date: 5 March 1998
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 157463
URI: http://eprints.soton.ac.uk/id/eprint/157463
ISSN: 0006-3592
PURE UUID: 3a6db553-4e10-40d0-8b82-36427652b52c
ORCID for Paul Stoodley: ORCID iD orcid.org/0000-0001-6069-273X

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Date deposited: 15 Jun 2010 14:11
Last modified: 14 Mar 2024 02:55

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Contributors

Author: Paul Stoodley ORCID iD
Author: Z. Lewandowski
Author: J.D. Boyle
Author: H.M. Lappin-Scott

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