AWWA MTC57542

The M¿ry-sur-Oise drinking water treatment plant produces daily 90 MGD treated surface water. The plant consists of two parallel treatment units: a conventional biological unit and a nanofiltration unit, that has been operating since September 1999, producing 37 MGD. Part of the challenge was the operation of a large nanofiltration unit on treated surface water, containing high levels of particles and dissolved materials. Since the full-scale step was brought in service, a slight loss in water permeability has been observed and the effectiveness of the cleaning has not been constant. In order to understand this phenomenon, a statistical modelling of the fouling has been carried out. The input parameters are the running time after cleaning and the feedwater characteristics. This paper presents the results of the statistical modelling. For all models, the running time after cleaning is the main influent parameter on the membrane fouling. This study also underlined seasonal effects: the lower the temperature, the greater the fouling. An increase in particle count, Silt Density Index and Total Organic Carbon content accelerate the fouling phenomenon, while the change in chemical parameters such as hardness, sulphate content, seems to have a slight impact on the membrane clogging. Includes reference, tables, figures.