Environmental impacts, management and potential recovery of residual sludge from stone industry: the Piedmont case.

Residual sludge (EWC 010413, according with Commission Decision 2000/532/EC and its Italian implementation Legislative Decree 152/2006 Annex D Part IV) produced during dimension stone working activities still represent a big concern for Stone industry. Even if in the last 10-12 years (from 2006 up to now) the total production, at national and local level, has been decreasing, due to the global market crisis which negatively influenced both building industry and infrastructure realization their management still represent a problem (in term of economic, environmental and social impacts) for the companies interested in slabs, tiles and manufactured production (from dimension stones’ blocks), and for the citizen at large. The main challenges to deal with for their correct management are: - The huge volume produced in quite limited areas (eg. Ossola Valley or Pietra di Luserna quarry basin, considering Piedmont Region – object of the present research). - The very fine particles distribution of the sludge (leads to a behavior similar to the silt clay; it is to say low permeability and axphyxit condition that make it not completely suitable for the production of substrates. . - The chemical properties of the waste due to the presence of heavy metal and TPH contents, sometimes over the threshold values, which can polluted water and soil if residual sludge are not properly managed. The present research investigates several aspects connected to residual sludge: from the estimation of the volumes at Piedmont Region scale, to its chemical and physical characterization, to the impacts potentially connected to its management. Moreover, at laboratory scale the treatments to separate heavy metals and/or to decrement the TPH content, up to the potential reuses of treated sludge are tested. Its potential recover is in line with the circular economy approach, which can lead, on the one side, to the decrement of costs for its disposal in dumps, and, on the other side, to the quality improvement of the material (and of its environmental characteristics)