By engaging in forward-looking, visionary, prospective thinking, the challenge was to create a project that valorizes sewage sludge waste while generating a long-term social dynamic involving and affecting local communities.

How, for such a project, to revalue the architectural action capable of promoting the openness and acceptability of these new types of equipment for the general public?

Which architecture for a sewage sludge valorization Center, which could combine both the purely technical function and the recreational and attractive function for the general public ?

For a country where the agricultural component is not only dominant but also promising. The central idea is to forge a link between the project and its immediate environment, to achieve community integration and to meet functional requirements. Hence, the idea of THE GREEN HILL, which divides the building in two parts, functional and playful, thinking of the landscape side and taking the public on a walk that guides them to organic farming activities at the end of the route.

This green hill path with the two organic gardens , from an environmental point of view, will regulate the temperature differences by absorbing heat and favour the environmental footprint. Socially, this pathway will create a general atmosphere that will be a recreational area for the city's residents and a public meeting place for workers and visitors.

Thus, each project must be committed to sustainability, but being part of a playful hedonistic sustainability while addressing the issue of responsible and attractive urban living is an asset.

After an analysis of the sites of the wastewater treatment plants was carried out, a choice stopped on the plant "El Attar" on the basis of the following logic : as the project, with agricultural valorization of sludge, has as output product the compost, an organic amendment, the criterion of the nearness of the potential agricultural perimeters proves to be important, where the site of plant "El Attar" happens to be upstream of the perimeter of several thousand hectares. Also, the sewage treatment plant "El Attar" has implemented an environmental management plan with initiations on the theme of sludge. Giving the terrain, the parcel selected is chosen in consideration of the ease of access.

The main components of the project are a unit for recreational activities, the green hill and the two organic gardens at extremities and the composting unit. Underneath the green hill, there is a rainwater reservoir that will feed part of the green spaces, in addition to the purified water produced by the wastewater treatment plant, producing a progressive watering system.

For the recreational block, the program is spread over three floors. On the ground floor, the administration, a reception area plus an exhibition space, and a compost sales room are distributed around one of the two curves of the hill. In addition, a discovery gallery located below the hill is discovered as the user advances. This gallery creates a place between factory, work space and public space. In addition, two peripheral staircases that go up the hill, create a complete entertaining circulation path from the ground floor. A multimedia room, a library and a double height art workshop occupy the first floor. Access to the green hill is available from the art workshop. The upper floor serves as a restaurant and event space.

For the composting unit, the organization of the valorization process has been developed according to a precise alignment that effectively responds to its internal logic following these steps: the arrival of the trucks, unloading of the sludge in the ditch, pre-treatment/grinding, fermentation, maturation and finally storage of the final product "the compost". Once standardized, the compost is marketed to local farmers. The program of the composting unit also includes a control and monitoring office, a maintenance workshop, labs, a packaging room...

Thus, a progressive discovery of the plant is offered from the green hill. On the other side, this route is completed by a panoramic tower with a wide view of the plant overlooking the treatment plant El Attar. In addition, secure visits of the treatment plants will be organized.

Moving towards sustainability thinking, specifically bioclimatic architecture, a second skin placed upstream of the South façade is used as an energy regulator.

Composting Unit is completely compact (closed tunnels) to ensure containment of treatment and deodorization.