Full Description

Application of membrane filtration in water treatment enables the production ofmicrobiologically safe and biologically stable drinking water by removingmicroorganisms and inorganic and organic compounds, respectively. However,fouling may cause serious operational problems. Fouling mechanisms ofnanofiltration (NF) and reverse osmosis (RO) membranes include scaling(inorganic, organic and colloidal) and biofouling. Different types of fouling canoccur simultaneously, influencing each other. Controlling biological fouling isconsidered to be a major challenge in operating membrane filtrationinstallations. Biofouling, defined as accumulation of biomass on a surface bygrowth and/or deposition to such a level that it causes operational problems, isdifficult to quantify. However, the diagnosis "biofouling" is only justified whena relation is found between the encountered operational problems and biomassaccumulation as determined with an adequate parameter. Biofouling may cause fluxreduction (normalized flux: MTC) and/or increased pressure drops (normalizedpressure drop: NPD) leading to increased costs. A suite of biomass parameters andanalytical tools are available, but the question remains which parameter(s) atwhich level is conclusive for identifying biofouling as the cause of theoperational problems and at what level biofilm densities are acceptable.Chemicals such as antiscalants and acids used for scale control in NF and ROmembranes differ greatly in their ability to promote growth of microorganisms andcertain commercially available antiscalants can cause biofouling. Criteria and ameasuring strategy are needed to detect biofouling in an early stage or forevaluation of the risks of biofouling (water type, chemicals dosed,pre-treatment). Curative or preventive measures against biofouling are not alwayseffective. Methods are needed for evaluation of the effects of cleaning methodsand chemicals. This report describes the development of investigations aiming atachieving methods and strategies for the diagnosis, prediction, and prevention ofbiofouling. Includes 14 references, tables, figures.

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Edition: Vol. - No. Published: 05/01/2001 Number of Pages: 7 File Size: 1 file , 360 KB