How to remove reverse osmosis fouling in wastewater reuse applications: a combination of process recovery and water cleaning

Many publications focus on domestic wastewater reuse. Nevertheless, most of them are based on synthetic effluent experiments, or on robust full scale experiments in which only few filtration operating parameters can be studied. In order to go beyond these limitations, a mobile pilot plant combining a membrane bioreactor and a reverse osmosis (RO) unit has been designed to operate continuously with any kind of preliminary treated domestic effluent. The impacts of RO unit parameters such as volume reduction factor (VRF), feed crossflow velocity and water cleaning are investigated without any use of antiscalant or pH regulators. MBR effluent filtration causes severe fouling mainly due to scaling by calcium phosphate and calcium carbonate. VRF seems to affect the final scaling structure since the final flux is four times higher at VRF equal to 2 (50% recovery) compared to VRF equal to 5 (80% recovery). Once the scaling structure is set, increasing the feed crossflow velocity does not enable permeability recovery. On the contrary, deionised water cleaning enables total recovery of the initial permeability without altering the RO membrane retention performance.