Bio‐refractory wastewater treatment is compulsory for a safe discharge into the environment. This paper aims to study the use of membrane processes to concentrate wastewater to be then treated by a hydrothermal process such as wet air oxidation for advanced and intensified wastewater treatment. The work focused on three different synthetic wastewaters of public or industrial interest: pharmaceutical wastewater, grey wastewater, and bilge wastewater. Membrane processes operated at the pilot scale enabled retentions as high as 100% of total organic carbon, more than 99% of turbidity, and 70% of hydrocarbon, respectively. High concentration factors were obtained. Membrane foulings were chemically reversible whatever the type of wastewater or the membrane process. Thanks to membrane filtrations, the volumes to be treated by wet air oxidation were drastically reduced, leading to high energy savings. Membrane retentates were then treated by wet air oxidation (300°C, 15 MPa) and resulted in more than an 83% mineralization rate, regardless of the effluent. The hybrid intensified process presented in this work strongly increased the possibility of discharging into the environment by mixing the process outputs or greatly reducing the discharge volume and ultimately the waste load.

This work aims to analyse the performances of a new hybrid process: membrane filtration to concentrate biorefractory wastewater before treatment by a hydrothermal process such as wet air oxidation. The aim is to obtain a complete discharge of the effluent in the environment. The three different synthetic wastewaters under study were pharmaceutical wastewater, grey wastewater and bilge wastewater. The results of the membrane filtration showed high retention rates as it could reach between 75% and 100% of total organic carbon retention, more than 99% of turbidity removal and more than 70% of hydrocarbon retention. Moreover, it was possible to achieve high concentration factors comprised between 17 and 40 times. Membrane fouling was chemically reversible regardless of the type of pollution. Then, the treatment of the membrane retentates by wet air oxidation process (300 °C, 15 MPa) could eliminate more than 83% of organic pollution for all the tested effluents. In summary, the hybrid intensified process could finally decrease the volume and the waste load of wastewater before possibly discharging it into the environment.