Rheology of sludge from purification plants: preliminary studies for controlling storage and spreading

Abstract

Soft residual sewage sludge behaves in a complex way. It is too liquid to form into a heap but too solid to be spread properly using current machinery. A study of the mechanical behaviour of this sludge has been undertaken recently to remove these two major obstacles to agricultural recycling, other than various psychological reservations. After a preliminary description of sewerage treatment processes, we have attempted to highlight the characteristics considered to be the most relevant. Parallels are drawn with other materials in several fields, bearing in mind the specific characteristics of sludge. Finally, in order to finalise our experimental approach, we illustrate our proposal with a specific case.