Una nuova procedura per ridurre i valori di elementi potenzialmente tossici contenuti in fanghi di depurazione urbana

[Autom. eng. transl.] The purpose of this work is to present the results of a study concerning the development of a new chemical-physical procedure (patent No. PC2012A000008 of 03/22/2012) designed to reduce the concentrations of some potentially toxic elements in urban sewage sludge obtained through anaerobic digestion and to dehydrate them efficiently, removing the water contained in them with an increase in total solids, in order to reduce the total volume of the final sludge and to recover useful nutrients in view of their direct re-use, or to use them as components and / or precursors of new fertilizing products to be used in agriculture. A Fenton-like treatment (classic Fenton + further acidification at pH 2) has proved to be more suitable than the classic Fenton treatment (pH 3.5) to reduce the metal content, except Pb, with average reduction values of Zn ( 77%), Ni (63%), Cd (15%) and Cr (10.5%), to remove water from the sludge thus increasing the proportion of total solids (44%) and to allow to maintain acceptable values of Corg in the mud (26.4 g / kg) compared to an initial Corg value of 28.1 g / kg. The results of the tests carried out in a laboratory-scale pilot plant have all the peculiarities to be able to be extended satisfactorily to an industrial scale.