Assessment of an integrated membrane system for surface water treatment

With the promulgation of more stringent regulations to guarantee that the d rinking water presents minimal health risks, nanofiltration (NF) and low pr essure reverse osmosis membrane (RO) processes are nowadays considered for surface water treatment. However, NF and RO spiral wound membranes are sens itive to fouling and an advanced pretreatment such as conventional train, m icrofiltration (MF) and ultrafiltration (UF) may be necessary to control pr oductivity. Consequently, a study was undertaken to evaluate the efficiency of the combined processes, know as Integrated Membrane Systems, for surfac e water treatment. Two IMS were evaluated on polluted low salinity water: U F and conventional train prior low fouling reverse-osmosis membranes (LFRO) . The one-year study has revealed the efficiency of the IMSs for surface tr eatment. Both IMSs tested produced water quality that exceeded the most str ingent water quality proposed in the new European Directives. However, in c ase of blending with the pretreated water for remineralization, clarified w ater has to be disinfected due to its low microorganism removal. In term of hydraulic performances both pretreatments: UF and clarification were found to be effective to control RO fouling. Despite UF reduces the SDI well bel ow the maximum advised by the membrane manufacturer, a slight fouling occur red on the RO membranes at high nux. Organic material plays a role in membr ane fouling and therefore reducing SDI may not guarantee a low fouling rate of the RO membranes. Preliminary cost estimation is on-going in order to i dentify the water cost for both IMSs based on similar final water quality.