MICROBIAL DETERIORATION OF MATERIALS - BI OFILM AND BIOFOULING - BIOFOULING

The undesired deposition of microorganisms and the formation of biofil ms is called ''biofouling''. In water systems, biofilms are contaminat ion sources for the water phase and support rapid microbial regrowth. Biofilms cover surfaces. In membrane processes, this leads to an incre ase of the hydraulic membrane resistance. Biofilms are viscoelastic an d display a more or less rough surface. Thus, they consume kinetic ene rgy and cause an increased pressure drop when water is pumped. In poro us filter media, membrane systems, heat exchangers, water pipelines an d on ship bottoms, thus, the energy demand is increased while the perf ormance is decreased. In heat exchangers, biofilms represent a gel lay er between medium and surface. This allows only diffusive but no conve ctive heat transport and, thus, decreases the effectivity of the heat transfer process. The loss of performance and product quality as well as by cleaning efforts due to biofouling causes high technical and fin ancial damage. This is increased indirectly by countermeasures such as the application of biocides, because these may promote corrosion proc esses and contaminate the environment.