A good example comes from the Ecoespanso plant of Santa Croce, which is entirely dedicated to the treatment of sewage sludge produced by the Aquarno Consortium and the Tanning Consortium of Fucecchio. The final product of the recovery treatment is the Sintered Granulate (KEU) which, after being mixed with calcium carbonate, is used for the production of inert granulates for the construction industry (HSC) and bituminous conglomerates (HCB) for asphalts.
The sewage sludge of the Aquarno Consortium arrive to Ecoespanso through a special puddle and flows into the plant tank which has a capacity of 3,000 cubic metres. This is where the process starts, which is divided into 5 phases: dehydration (centrifugation), drying, pyrosintering of dried sludge, energy recovery and fume treatment, production of plastofill (HSC and HBC) containing the KEU (sintered granulate).
From sludge to fertilisers
Not just inert material. Since the 1980s, the Consorzio Cuoio-Depur, which manages the centralised urban waste water treatment plant at Ponte a Egola, studies possible forms of reuse in agriculture of its sludge with high organic protein content.
In particular, efforts have been focused on identifying possible formulations made by mixing the protein sludge obtained by the tannery purification with products deriving from the same production cycle and in any case already recognised as fertilisers.
Considerable investments have been made parallel to the studies to improve the production process through the use of the most advanced processing technologies, with the aim of making the material as homogeneous and stable as possible.