Follow-up of a nanofiltration drinking water treatment plant during the third year of operation

摘要

The Méry-sur-Oise drinking water treatment plant consists in two parallel treatment paths: aconventional biological path and a nanofiltration path, that has been operating since September 99,producing 37 MGD, and that is equipped with NF200B-400 8-inch spiral elements (DOW).Part of the challenge was the operation of a large nanofiltration unit on treated surface water,containing high levels of particles and dissolved materials. Indeed, since the full-scale step wasbrought in service, a slight loss in water permeability has been observed and the effectiveness of thecleaning has not been constant. In order to understand this phenomenon, a statistical modelling ofthe fouling has been carried out. The input parameters are the running time after cleaning and thefeedwater characteristics.The water quality after each treatment step and the water permeability of each stage of the eightunits are recorded in a database. The running time since the last cleaning was also added to thesedata. On this basis, a model of water permeability (PLS regression) has been calculated for each ofthe eight units.For all models, the running time after cleaning was the main influent parameter on the membranefouling. An increase in particle counts and Total Organic Carbon content accelerated the foulingphenomenon, while changes in chemical parameters such as hardness, sulphate content, seemedto have a slight impact on the membrane clogging.The modelling of the membrane fouling will be useful to estimate the lifetime of the membranes andto program their replacement.