Experimental analysis of sludge processing in an EFT Cartigliano drying plant

The following paper is aimed at exposing the research work carried out in the analysis of both civil and industrial sewage sludge. More specifically the text deals with the path that was carried out between the laboratory of the DII (Department of Industrial Engineering) and the company "Officine di Cartigliano S.p.a". The latter, from the various activity, deals with the design and production of machines for the drying of the depuration sludge. The purpose of the dryer is reducing the volume and the weight of the sludge. In order to increase the heat exchange during drying phase, the material, before entering the unit, is extruded and spread uniformly in the working area of the machine. It is precisely in this first extrusion phase that the problems that lead to the realization of this paper arise. In some cases, non-homogeneous extrusion was noted, with the formation of areas in which there is a greater presence of material compared to the other zones; this then causes a heterogeneous humidity in the output material during the drying phase. If from a physical point of view, over the years the company has developed a series of parameters that indicate whether the sludge can be processed or not, from a chemical point of view it was not yet clear which parameters made a sludge suitable for drying in the plant. Sludge samples were therefore collected from customers who relied on OCD and, after an initial joint phase of bibliographic research and analysis of the processes from which these different sludges were derived, the study began in the laboratory. We opted for the use of infrared spectroscopy and ESEM, two techniques that manage to identify the functional groups and elements present within the sample. In this way it was possible to compare the composition of correctly processable samples and those that gave rise to problems during the extrusion and subsequent drying phase. The comparison between bibliographic analysis and practical tests made it possible to identify the presence of EPS as the possible cause of these problems in the mud mechanics. The extracellular polymeric substances are organic molecules that can be found in different quantities within sludge of biological origin. This research could be a first step for a collaborative relationship between the University of Padua and the Officine di Cartigliano S.p.a. company.