SLUDGE TREATMENT
Sludge is the end product of wastewater treatment. Sludge treatment is a crucial issue that affects both the environment and the economic stability of the different treatment sectors. It is a problem that brings several factors into play: firstly, the quantities produced, secondly, the treatment processes used and, thirdly, the different reprocessing sectors involved: energy and biological.
Degrémont provides all types of sludge treatment: incineration in dense fluidized-bed furnaces, such as those in operation in Valence and Elbeuf (France), and in several locations in the United States; co-incineration in household refuse incinerators, such as those used in Monaco, Amsterdam and Besançon; an alternative to incineration, the wet oxidation process (WOP), mineralizes sludge; lastly, drying is necessary when the sludge is destined for agricultural re-use, although this doesn't preclude its thermal conversion or placing in landfills. Three processes are available: indirect drying, Naratherm™, which produces stabilized and sanitized sludge solids with a dryness of 90 %, for agricultural use; direct drying combined with centrifugal separation, Centridry™, which achieves 65 % dryness without stabilizing or sanitizing the sludge; and, finally, two-stage drying with Innodry™. As for the Héliantis™ process, this enables solar drying of purification sludge up to a dryness of between 45 % and 80 %, depending on requirements.