ANAEROBIC DIGESTION AS A PROCESS FOR THE DECONTAMINATION AND VALORIZATION OF ACTIVATED SLUDGES RESULTING FROM PLANTS TREATING WASTEWATERS CONTAMINATED BY XENOBIOTIC COMPOUNDS

Xenobiotic compounds accumulate in sewage sludges resulting from wastewater treatment plants serving both civil and industrial areas. The opportunity to use anaerobic digestion for the decontamination and beneficial disposal of the contaminated sludge from the Fusina’s wastewater treatment plant (Italy) was investigated in mesophilic and thermophilic microcosms monitored through an integrated chemical, microbiological and ecotoxicological procedure. The 10 months sludge incubation at 35°C resulted in an extensive production of a methane-rich biogas, a marked reduction of pathogenic cultivable bacteria and, importantly, a marked biodegradation of the sludge-carried organic pollutants, including some polychlorinated biphenyls and polycyclic aromatic hydrocarbons, to which corresponded a relevant sludge detoxification. The sludge decontamination seemed strictly correlated to the activity of methanogenic bacteria and was not affected by the presence of exogenous yeast extract or molasses. Lower sludge bioremediation and biomethanisation extents were observed under thermophilic conditions.