North italian wastewater sludges characterisation before biotreatment for agriculture applications

Heavy metals and pathogens appear as the main hindrance to the reuse of wastewater sludges (WWS) in agriculture. The further utilization of WWS may be evaluated by reliable sampling and a complete characterisation of the material. According to the work programme of an INCO-COPERNICUS 2 Project, the Institute of Environmental Geology and Geoengineering has worked out a wide activity devoted to sludge collection and characterisation. The aim of the work was to set out and to develop international procedures for the characterisation of North Italy WWS, originated from a wastewater treatment plant of Brescia. According to CEN (European Committee for Standardisation) procedures (prEN procedures), the main physical-chemical-biological determinations have been achieved; especially nutrients (N, P, K, Ca and Mg), heavy metals (Al, As, Cd, Cr etc.), pathogens, polychlorodibenzo-p-dioxins (PCDD) and polychlorodibenzofuran (PCDF) concentration. Fecal Coliform bacteria have been determined by Most Probably Number (MPN) technique, while viruses have been enumerated by plaque assay technique, after elution according to the United Stated Environmental Protection Agency (USEPA) method. Chemical determinations of PCDD and PCDF have been accomplished by official method 8280A. The evaluation of the toxicity equivalent concentration (TEQ) of each sample was performed by means of toxicity equivalence factors (TEFs) The experimental results of the work have been satisfactory due to the repeatability and reliability. The through characterisation of the material and the technical and scientific literature acquired, will allow to develop a biological process for the utilization of WWS in agriculture.