AWWA MTC69764

The Mery-sur-Oise water treatment plant (France), operated by Veolia Water on the behalf of the Syndicat des Eaux d'Ile de France (SEDIF), has used nanofiltration (NF) membranes to produce safe drinking water since 1999. However, significant fouling has been observed according to seasonal conditions, even with several types of pretreatment including conventional surface water treatment followed by ozonation, acid injection, antiscalant addition and microfiltration. The objective of this study was to characterize and identify the nature of foulants responsible for flux declines and higher pressure drop, and to monitor the membranes' performance after 9 years of operation. Since 2002, several membrane autopsies were performed each year on NF modules extracted from the first and the third stages of the Mery-sur-Oise nanofiltration unit. Several analytical tools such as FT-IR (Fourier Transformed Infra Red) spectroscopy, LCUV- COD (Liquid Chromatography coupled with UV_{254 nm} and Organic Carbon Detectors), SEM (Scanning Electron Microscopy) and TOC (Total Organic Carbon) measurements have been used to extensively characterize the fouling layer. Feedwater quality parameters (organic, inorganic and microbiological compositions) were also monitored continuously. The different analyses show that fouling results mainly from the formation of a biofilm on the membrane surface. Significant variations are observed between the two stages: the amount and the composition of the deposit differ. Includes figures.