Biofouling and biofilm formation outside naturally occurring ecosystems constitute a nuisance. The accumulation of bacterial colonies, typically in industrial settings, degrades the underlying material, causing corrosion and material failure.
This leads to production losses and increased costs. Furthermore, it can also cause health risks by, for example, degrading filtration membrane performance, affecting membrane throughput and thus drinking water quality.
Biofilms occur in abundance as part of larger ecosystems, but these bundles of microorganisms also live and thrive in man-made constructions that offer moist and nutritious settings for the microorganisms. Waste runoffs, production facilities that use water cooling pipes, other piping systems such as water piping or oil pipelines, and membrane systems such as membrane bioreactors and reverse osmosis membranes for wastewater filtration are typically affected. The costs of damage due to biofouling are enormous, and the consequences that pose a risk to human life and health are severe. Therefore, it is of great interest to understand and prevent the biofouling phenomenon.
Characterization of biofouling, biofilm formation and antifouling coatings
Biofilms comprise a major hurdle to the effectiveness of membrane and filtration processes. For example, one of the most important factors affecting membrane bioreactor performance is membrane fouling induced by the extracellular polymeric substances secreted by the microorganisms. Membrane cleaning has been extensively studied but approaches that completely prevent fouling are even more attractive. To secure the optimal long-term performance of the membranes it is, therefore, of interest to understand and characterize the conditions that minimize and prevent fouling and biofilm formation. Information that allows for an increased understanding of the relationship between membrane surface properties and fouling propensity can be collected with QSense® QCM-D – a technology that can be used to characterize both scale buildup and fouling processes, and to detect biofilm formation (pdf) by measuring bacterial attachment and growth. The technology can also be used to evaluate antiscalant and antifouling strategies, as well as helping in the design of, for example, antifouling membrane coatings.
Contact angles are used for the characterization of membranes
Membrane fouling is caused by pore blocking due to foulants such as inorganics (salts, precipitations such as metal hydroxides and carbonates) organics, colloids (suspended particles such as silica), microbial contamination and particles on the membrane surface, or by cake formation. As most of the foulants are hydrophobic in nature, it is generally accepted that hydrophilic membranes are needed. Different types of coatings and surface treatments are utilized to render the membrane more hydrophilic. Contact angle measurements are routinely used to evaluate surface hydrophilicity.
