Sludge

International audienceWater treatment residuals, sewage sludge and dredged sediments, hereinafter referred to as sludge, share common features, like inherent high moisture content, high organic and mineral pollutant load and above all a pasty consistency. Several recovery opportunities exist. However, sludge composition is closely correlated with human activity and the design of the recovery processes requires knowledge of physical, thermal or biological characteristics of the sludge that will be processed, often even before the specific sludge exists. Therefore, sludge characterization is a key challenge for the process design, control and optimization and further valorization. The present chapter is divided into four parts dedicated to the composition, the material properties, the dynamic processing properties and the environmental assessments, respectively. Standard tests methods for the characterization of solids and water distribution in sludge are introduced first. Then, the fate of organic constituents, inorganic nonmetallic and metallic constituents as well as pathogenic organism. In the second part, standard and state-of-the-art methods for the characterization of chemical, physical and thermal properties of sludge are described. Dynamic tests, required for the selection and design of conventional processes for sludge concentration and conveying, are detailed in the third part. Finally, methods for assessing the environment impacts of sludge and secondary raw materials derived from sludge are addressed