RESUMO
Most paper industry waste is in the form of sludge from paper production and recycle process paper. There has been an increasing use of paper sludge in environmental restoration, a practice that requires particular attention. This issue presents a case which demonstrates how the biogas production related to this kind of recovery system can represent a problem for environmental protection and public health. The case history relates to a former quarry area restored by means of paper sludge. After the filling, a substantial quantity of biogas was produced, with an external diffusion to sensible target as well. Initial investigations showed that the area was characterized by a large amount of paper mill sludge made unstable by anaerobic conditions. To date there are no proven technologies for this kind of treatment. In this case, for safety and naturalization as agricultural area, new methods of bioremediation were used and, in particular, an innovative physical, mechanical and biological intervention, based on bio-stabilization of paper mill sludge. The treatment is site-specific, based on the in-site paper sludge biostabilisation. To complete the intervention and in order to demonstrate its validity an important monitoring activity was performed, testing all the phases affected by the biological transformation.