Microbial Biofouling: Unsolved Problems, Insufficient Approaches, and Possible Solutions

Microbial biofouling is a very costly problem, keeping busy a billion dollar industry providing biocides, cleaners, and antifouling materials worldwide. Basically, five general reasons can be identified, which continuously compromise the efficacy of antifouling strategies: 1. Biofouling is detected by its effect on process performance or product quality and quantity. Early warning systems are very rare, although they could save costly countermeasures necessary for removing established fouling. 2. Usually, biofouling is diagnosed only indirectly, when other explanations fail. The common practice is to take water samples, which give no information about site and extent of biofouling deposits. 3. When finally the diagnosis “biofouling” is established, biocides are used which, in many cases, for the best kill microorganisms but do not really remove them. Killing, however, is not cleaning while frequently the presence of biomass and not its physiological activity is the problem. 4. Biofouling is a biofilm phenomenon and based on the fact that biofilms grow at the expense of nutrients; oxidizing biocides can make things even worse by breaking recalcitrant molecules down into biodegradable fragments. Nutrients have to be considered as potential biomass. 5. Efficacy control is performed again by process performance or product quality and not optimized by meaningful biofilm monitoring, verifying successful removal.