1. Introduction
The urban wastewater treatment plant has a role to eliminate the pollution contained in the domestic and industrials effluents before their rejection in the natural environment. If water, at the end of the treatment, was purified, initial pollution was found stored and concentrated in sludge resulting from the various water treatment stages. This sludge can be considered like a recyclable waste and must be eliminated in laws respect. Sludge management, valorization and elimination, were problematic as well as the other waste (OMS) [1]. Several paths exist for sludge treatment and valorization, but the choice must be tributary of the installation cost, sludge origin, the added value of the product which results from it and of the environment impact that could have the retained path.