Biofouling membranes

Biofouling is the irreversible adhesion on a membrane of microorganisms and the extracellular polymeric substances (EPS—aka biofilm) that they produce. The process of adhesion involves three steps  

Bacterial adhesion, which can become irreversible in just hours, even without nutrients present.  

Biofilm maturation with formation of EPS, which serves to protect bacteria from biocides, flow shear, and predators.  

Factors that favor adhesion and biofilm formation include  

Membrane surface roughness. The rougher the surface the more adhesion can occur. (Note that attempts to modify membranes, i.e., change the roughness, or charge, or hydrophilicity, to make adhesion less favorable are not always successful. ) 

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Wisniewski N, Moussy F, Reichert WM. Characterization of implantable biosensor membrane biofouling. Fresenius Journal of Analytical Chemistry 2000, 366, 611-621. 

Wisniewski N, Reichert M. Methods for reducing biosensor membrane biofouling. Colloids and Surfaces B. Biointerfaces 2000, 18, 197-219. 

The clinical utility of electrochemical sensors for continuous glucose monitoring in subcutaneous tissue has been limited by numerous challenges related to sensor component and biocompatibility-based failures.1,2 Sensor component failures include electrical failure, loss of enzyme activity, and membrane degradation,3 4 while examples of biocompatibility-based failures include infection, membrane biofouling (e.g., adsorption of small molecules and proteins to the sensor surface), and bbrous... 

Ivnitsky, H., Katz, I., Minz, D., Shimoni, E., Chen, Y Tarchitzky, J., Semiat, R. and Dosoretz, C.G. (2005) Characterization of membrane biofouling in nanofiltration processes of wastewater treatment. Desalination, 185, 255—268. 

Flemming, H. C. (1997). Reverse osmosis membrane biofouling. Experimental Thermal Fluid Science. 14, 4, 382-391. 

As was described above in a number of MBR processes the membrane, in addition to performing the separation functions previously discussed, also acts as a host for the biocatalysts (whole cells or enzymes) which are immobilized in the membrane s pore structure. Concerns with such MBR configurations include membrane biofouling, mass transport limitations and biocatalyst activity loss and denaturation. In the two sections that follow we discuss further some of the key aspects of MBR for biochemical synthesis. We classify these reactors into two types, namely whole-cell and enzymatic MBR. 

H.-C. Flemming, Mechanistic aspects of reverse osmosis membrane biofouling and prevention, in Z. Amjad (Ed.), Reverse Osmosis, Van Nostrand Reinhold, New York, NY, 1993, pp. 163—209. 

Adequate pretreatment is one of the fundamental keys to successful and cost-effective operation of an RO system. Pretreatment is designed to prevent or minimize membrane fouling, scaling and degradation of membrane performance and materials. This chapter covers mechanical and chemical techniques and technologies that are commonly used to pretreat RO systems. Also included in chapter 8.5 which is a detailed discussion about membrane biofouling and materials to minimize membrane biofouling. 

The following sections discuss the primary biocide used today, chlorine, and alternative physical and chemical techniques to address membrane biofouling control. The most common alternative techniques examined here include chloramine, chlorine dioxide, ozone, UV, and non-oxidizing biocides such as DBNPA and isothiazolone. Table 8.12 summarizes advantages and limitations of these techniques (adapted from Kim, 2009). It is important to note that some of these biocides/disinfectants can contact the membranes, and others must be removed or destroyed before the water is introduced to the membrane system itself. 

Proceedings of the Membrane Biofouling Meeting - Causes and Control, Singapore, 2003. 

Use of warmer seawater may accelerate membrane biofouling, especially if the source water is rich in organics. 

While water permeates through the membrane, the rejected matter accumulates behind the membrane and forms a layer of high concentration of salts that increases the osmotic pressure and reduces the permeability. Also over time, organic and suspended matter adsorb on the membrane and reduce membrane permeability. These materials may also serve as food for bacteria that attach on the membrane surface. The excessive bacterial growth may cause membrane biofouling. Sparingly, soluble salts may precipitate on the membrane surface and impact membrane performance. The phenomenon of the formation of a concentrated layer close to the membrane is called concentration polarization. The ratio... 

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