Lotito, A.M.1, Fratino, U.1, Lotito, V.2, Mininni, G.2, Blonda, M.3, 1Politecnico di Bari, 2CNR-IRSA, Water Research Institute, National Research Council, 3ARPA-Puglia, Apulian Regional Agency for Environmental Protection (Italy)(free)
Agricultural use is one of the best options for sewage sludge management, whenever sludge quality is suitable with respect to established law limits and if local situations (field availability, climate, specific constraints) are favourable. This practice is recognized to be the most economical one and allows recovering nutrients and organic matter with benefits to crops and land.
Beside general rules issued at European level (Directive 86/278/EEC) and transposed in Italy with D.Lgs. 99/1992, regional authorities can establish other restrictions to better protect environment, preserve population from nuisance and defend specific areas.
Through GIS elaborations, we have analysed different scenarios, computing available land in Apulia region with present and new revised constraints and evaluating sludge quantities to be potentially recovered for land application in the light of current legislative limits, nitrogen requirements by crops and cultivation cycles.
This study has showed that available land can face the total sludge production in the area even in the most conservative hypothesis. The used methodology represents a powerful tool to move the focus of political decisions from general law constraints towards specific ones closely related to the environmental and agricultural context and to plan new investments to completely satisfy sludge disposal needs.
Keywords: agricultural sludge use, GIS analysis, sludge disposal management, strategic planning
Sewage sludge disposal represents one of the most urgent environmental issues nowadays, as, while on the one hand the different disposal routes are becoming less feasible (see for example landfill), on the other hand huger amounts of sludge are produced as a result of the implementation of Directive 91/271/EEC.
According to the figures provided to the European Commission for the period 2003-2006, about 10 million tons of dry matter (DM) of sewage sludge were annually produced in the European Union (8.7 million t DM in the EU-15 and further 1.2 million t DM for the 12 new Member States), a value which is probably even underestimated (Milieu Ltd et al. 2010).
Figure 1 shows mean annual sewage sludge production in Europe in the period 1996 – 2007, based on Eurostat data. As Italy is one of the states with wider amounts of sludge yearly generated, the correct evaluation of sludge production and quality, along with current outlet available routes and disposable quantities, is necessary for an effective planning of sludge management strategies to avoid future emergencies.
The common options for sludge outlet are agricultural sludge use (direct or as compost), landfilling and incineration. Other routes, such as innovative thermal treatments, land reclamation or incorporation in building materials (Meeroff and Bloetscher 1999, Monzò et al. 1999, Weng et al. 2003), play only a marginal role. Figure 2 shows the incidence of every disposal route in Europe for the period 1996 – 2007, on the base of Eurostat data.