BIOFILMS AND FLOW

"An integrative study on the distribution, morphology and composition of biofilms under the influence of secondary flows around flow obstructions"

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 Obiettivo del progetto (Objective)

'Biofilms are bacteria consortia, embedded in a self-secreted 'gel' matrix which provides bacteria with significant advantages for their survival and proliferation. Owing to this successful strategy, biofilms may be found virtually anywhere, provided some nutrients are available. Beneficial examples include biofilm-based wastewater treatment systems. On the 'negative' side, biofilms may cause disease transmission or trigger infections from medical implants; biofilms are a cause for increased resistance of heat-exchange equipment and clogging of filtration columns, water distribution pipes, drip-irrigation emitters and, the focus of this study - membrane separation modules. The latter are of particularly great importance as state-of-the-art technology for water treatment and desalination. Owing to this wide range of applications, biofilms have been extensively studied. In spite of these efforts, the interplay between the characteristics of a velocity field and biofilm distribution and composition remain largely illusive, particularly in complex velocity fields, such as those arising in the presence of flow obstructions. The overreaching goal of this project is to develop a mechanistic, quantitative approach to understanding the effect of hydrodynamics on bacterial deposition and biofilm development in the presence of a flow obstruction; a micro-fluidic approach will be developed for characterizing biofilm development under various hydrodynamic and physico-chemical conditions. Concurrently, two- and three-dimensional simulations of the flow field will be performed, so as to connect hydrodynamic characteristics, such as secondary flows, to the deposition patterns as well as biofilm morphology and composition. The model system to be considered will have direct implication for the design and operation of membrane-based desalting. However, in a wider context, the methodology developed may be applied to study biofilms in any other flowing systems.'

Descrizione progetto (Article)

When bacteria are under stress, which is often, they team up and form this collective called a biofilm. If you look at naturally occurring biofilms, they have a very complicated network. They are like cities with channels for nutrients to go in and waste to go out.

The BIOFILMS AND FLOW research project is an integrative study on the distribution, morphology and composition of biofilms under the influence of secondary flows around flow obstructions.

Bacterial biofilms are responsible for several chronic diseases that are difficult to treat. Examples include cystic fibrosis, endocarditis, cystitis and infections caused by in-dwelling medical devices. Biofilm bacteria show much greater resistance to antibiotics than their free-living counterparts. A beneficial example is a biofilm-based wastewater treatment system.

In this project, a model has been developed to describe the development and growth of a biofilm in a large-scale reverse-osmosis desalination system. The model accounts for bio growth in the presence of nutrients, its effect on mass transfer and its interplay with hydrodynamics in the membrane channels. It also provides a tool for assessing conditions leading to an increased resistance to permeation versus channel clogging. Both factors are of paramount importance in the energy efficiency of real operation.

The research is providing important new knowledge on the fundamental aspects of bacterial deposition. Further research goals for the next phase will be consolidation of the theoretical and experimental work. Also, elaborate experimental characterisation with some additional new skills will be learned and applied. Microfluidic designs already developed, using purely physical 'surrogates', with added 3D image reconstruction using confocal microscopy will be used. Concurrent, higher-resolution characterisation of the biofilm will be made using staining techniques.