Problems of operation and main reasons for failure of membranes in tertiary treatment systems.

This paper presents the results of the long-term operation and monitoring of membrane fouling at several full-scale MF/RO water recycling facilities operated by Agbar in Spain. It was demonstrated that membranes give very reliable treatment enabling the production of high-grade recycled water, well disinfected and with the removal of all priority substances. The high organic and salt concentrations of raw wastewater combined to extremely high variations justified the implementation of sand filtration to protect MF/RO membranes. Membrane autopsy was used to better understand the predominant fouling mechanisms and optimise down-stream operation and membrane cleaning strategy. The main membrane pathologies are described with recommendation of an adequate cleaning strategy.