Production and characteristics of sewage sludge in Italy

Results of an extended survey on the production and quality of sewage sludge produced in Italy are herewith reported and discussed. Data are relevant to 2015. They were provided by 84 Italian water utilities responsible for municipal wastewater treatment serving approximately 35 million persons. Total production was estimated at about 395,000 t dry solids/year, of which 9.9% is used in agriculture without further treatments, 26.4% is sent to external plants for compost production, 5.6% is sent to external plant for production of a soil conditioner called 'chalk of defecation', 17.2% is disposed to landfill, and 5.9% is sent to incineration or co-incineration plants. The rest (35%) is sent to external sludge centres for further treatments (manly chemical and physical processes) before recovery/disposal. Regarding chemical characterization the following parameters were investigated: TOC, total nitrogen, total phosphorus, potassium, arsenic, cadmium, copper, nickel, lead, zinc, mercury, total chromium, chromium VI, selenium, hydrocarbons C10-C40, sum of polycyclic aromatic hydrocarbons, sum of polychlorinated biphenyls, sum of polychlorinated dibenzo-p-dioxins/ dibenzo-p-furanes (toxic equivalent) salmonella, faecal coliforms, sulphur, sum of absorbable halogenated organic compounds, nonylphenol and nonylphenolethoxylates with one or two ethoxy groups, and di(2-ethylhexyl)phthalate. All the parameters showed that the quality of Italian sewage sludge is consistent with a typical sludge in Europe, Asia and America and the maximum concentrations of pollutants are well below the fixed standards of the European Directive 86/278 and the third draft of the European Commission's Working Document on Sludge.