The challenges of Process Engineering fo

The reuse of wastewater aims to mobilize and treat, for certain uses and under certain conditions, water that has already been used. Rather than discharging wastewater into the natural environment, this practice aims to recover it by replacing the mobilization of water withdrawn from the environment. By moving from a linear logic of the mobilization and use of water to a circular approach, the objective pursued is to reduce the pressure, qualitative then quantitative, on the resources while limiting, as far as possible, the usage conflicts. It is in fact a question of passing from a simple competitive mode which strongly mobilizes resources, to a complex mode, known as 'circular', of putting in complementarity of uses. This approach initially mainly concerned agricultural uses insofar as agricultural needs represent the majority of the water mobilized, including developed countries. Cities integrate specific issues that are characterized by significantly different options from those that can be found in rural areas. In the city, the recovery of wastewater has both material aspects (water, nutrients, critical metals, biopolymers, etc.) and energy aspects (recovery of heat from the networks, production of energy by biological means and/or thermal) which should be integrated.