Biofouling Processes in Industry - Fouling on artificial substrata

From the initial adsorption of organic molecules, to the colonisation by microorganisms, to the development of complex and diverse sessile assemblages, fouling affects most man-made surfaces. Fouling affects the hulls of ships, oilrigs, mariculture cages, pipelines, heat exchangers and seawater intakes in general, resulting in significant economic costs. Fouled ships, for instance, need 40% more fuel in order to maintain the same speed. This leads to a global cost of about $7.5 billion per year and to related environmental issues due to 20 million tons of CO2 more that are emitted annually. The US Office of Naval Research estimated that the periodical cleaning and restoring of ship hulls cost to the US Navy about $1000 million per year (Alberte et al. 1992). The costs of fouling are clearly not limited to ship hulls nor to the marine environment. Control of fouling in water intakes, piping systems and desalinisations plants cost over $15 billion per year (Meesters at al. 2003). In food industry, the formation of fouling layer within food processing equipment for pasteurization and sterilization costs to the US industrial community about $10 billion per year (Jun & Puri 2005). Biofilm-associated infections extend hospital stays of an average of about three days and it is estimated that up to 65% of nosocomial infections are biofilm-based with an associated treatment cost in excess of $1 billion per year. Up to 82% of nosocomial bacteremias are the result of bacterial contamination of intravascular catheterizations (Archibald & Gaynes 1997). Biofouling has been described as a four-step sequential ecological process (Wahl 1989). The first two steps, which produce a microbial biofilm, occur similarly whether on a surface in the sea or on a catheter in a hospital room. The following two steps are unique to aquatic habitats and involve the attachment of unicellular and multicellular eukaryotes to an inorganic or living surface. The multi-step process results from the web of interactions in the initial biofilm and subsequent community of colonizers, culminating in the establishment of a mature community composed of prokaryotes, fungi, protists and adult invertebrates. Biofouling assemblages on artificial substrata is a complex phenomenon resulting from several processes, the rate and extent of which are influenced by numerous physical, chemical and biological factors in the immediate proximity of the surface and cannot be defined as distinct and univocal entities. The major structuring factors influencing the development of biofouling communities on artificial substrates are here considered. An emphasis is given on how the interaction between biological systems (micro and macrofouling) can interplay with the nature of substrate in regulating patterns of species settlement and assemblage development. Some guidelines on the use of artificial substrata in the management strategies for controlling fouling in industrial plans are also provided.

Biofouling on artificial substrata results from several processes, whose rate and extent are influenced by the intertwining of numerous physical, chemical and biological factors in the immediate proximity of the surface. The importance of substratum features in influencing species settlement is considered here. An emphasis is given on how biological systems (micro- and macrofouling) can interplay with the nature of substratum in regulating patterns of biofouling development. The environmental issues related to the deployment of man-made structures in coastal waters are also discussed, and some guidelines on the use of artificial substrata in the management strategies for controlling fouling in industry are provided.