Abstract
The increasing worldwide population and industrialization engender great pressure on available water resources. One of the solutions to the water scarcity is to no longer consider wastewater as mere waste, but rather as a potential alternative resource for various applications, after appropriate treatment. Nevertheless, urban wastewater is increasingly contaminated with organic micropollutants (OMP) such as biocides and pharmaceutical substances that are refractory to conventional treatment. Safe and sustainable reuse of this resource requires the use of appropriate tertiary treatment processes. With this in mind, membrane processes, especially nanofiltration and reverse osmosis, have recently attracted considerable interest, as they ensure good removal of micropollutants and the production of high-quality permeate. However, these separation processes still face the challenges of membrane fouling and concentrate management. In addition, advanced oxidation processes such as ozonation degrade micropollutants well but are likely to lead to the formation of by-products that are potentially more toxic than the parent compounds. The objective of this study was therefore to develop an integrated and innovative system coupling nanofiltration (NF) and ozonation (O3) applied to a membrane bioreactor (MBR) secondary effluent. The ozonation process degrades micropollutants and organic matter well. The nanofiltration process provides a satisfactory retention of micropollutants and ozonation by-products and produces a very good quality effluent. Pre-ozonation mitigates membrane foulinf in nanofiltration. This study demonstrates the synergistic operation of the hybrid process to efficiently treat secondary effluents containing priority substances targeted by legislation in order to provide safe and sustainable urban wastewater reuse.