Impact of sludge mechanical behaviour on spatial distribution parameters obtained with centrifugal spreader: Preliminary study

In France, more than half of the production of sewage sludge is spread on agricultural fields as a fertilizer. However, these biosolids contain nutrients that can pollute the soil if their distribution on field is heterogeneous: it is then necessary to optimize the spreading in order to limit their environmental impacts. In that purpose, this study focuses on the impact of pasty materials rheological behaviour on spatial distribution parameters obtained with a centrifugal spreader, i.e. a spinning disc system. Kaolin suspensions were employed. To model their rheological properties, a Herschel-Bulkley equation was used, which is consistent with the literature. Experiments were performed with a specific spreading device (a vane with no disc) and with the CEMOB, a bench dedicated to the analysis of organic fertilisers spreading. Results showed that radial distribution of the 3D spread patterns is clearly dependent on the size and the density of the particles, both of them being related to the material consistency. Angular distribution also tends to follow similar tendencies. Eventually, advanced imaging shows a relation between fragmentation process and material consistency. This study presents a new approach to analyse organic spreading and opens the way to more developments.