It is more than clear that during the last decades the interest in environmental issues is constantly increasing and environmental issues have gradually been broadened, including economic and social responsibilities. Among several issues, the treatment of wastewater, and consequently, the handling of sewage sludge generated, are of the most significant challenges in environmental management. The properties of sludge depend on the contents of the wastewater treated and also on the operational characteristics of the wastewater and sludge treatment facilities. Treated sludge can be recycled or...