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The application of membrane filtration in the production of drinking and process water issteadily increasing. The use of spiral wound membranes for nanofiltration (NF) and reverseosmosis (RO) is often hampered by biofouling which leads to operational problems such as anincrease in normalized pressure drop (NPD) and a decrease in production rate (Ridgway andSafarik, 1991). Biofouling can be limited by pretreatment of the feed water of the membraneinstallation, but this approach increases the total investment cost of the water treatment process.Another option is to use periodical cleaning in place (CIP) for biofouling control, in which thenegative effects of biofouling are (temporarily) reversed.For a cost-effective application of membrane filtration in practice, extensive knowledgeis required of the influence of cleaning methods on biomass removal. Partly due to thecomplexity of biofouling the determination of the optimal CIP strategy is based on "trial anderror". Furthermore, data from scientific literature in many cases gives incomplete informationabout the interactions between the feed water quality, the type of membrane, the resulting typeof membrane fouling, the cleaning method and the effect of membrane cleaning on themembrane process. An important step in elucidating the effect of membrane cleaning processesis to develop a protocol for a systematic analysis. Two approaches can be followed for evaluatingthe effects of a cleaning procedure: the use of operational parameters (Graham et al, 1989);and, the application of a test procedure under standardized conditions in the laboratory or in apilot set up (Whittaker et al, 1981).Indications of effective cleaning procedures for biofouling control were obtained from asystematic approach to evaluate CIP procedures from both literature and full-scale membraneplant experience. In some cases, biofouling was effectively controlled with mixtures ofcomplexing agents, surface active components and denaturating agents. Apart from this, theeffect of a hydraulic action, e.g. by using air-water flushing, proved to be very promising inbiofouling control (Cornelissen et al, 2007). The biomass removal efficacy of the air-waterflushing strategy was verified with a newly developed laboratory test procedure and described inthis paper. Includes 6 references, figures.

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Edition: Vol. - No. Published: 03/01/2007 Number of Pages: 4File Size: 1 file , 270 KB