Measuring the Rheological, Textural, Geotechnical and Viscoelastic Behaviour of Dewatered Sludge: Including Adhesiveness and Cohesiveness

Mechanical properties such as viscoelastic, rheological, and textural properties, particularly adhesiveness and cohesiveness, play a significant role in the optimization of handling, processing and drying of dewatered sludge. However, there is no currently standardized methodology for quantifying these properties, leading researchers to adopt various techniques based on economic feasibility, equipment availability, and research objectives. This review systematically compiles and analyzes the most relevant experimental methodologies for evaluating the mechanical properties of dewatered sewage sludge (DSS). This work presents a general overview of the composition and structure of DSS, followed by a comprehensive bibliometric analysis that revealed literature gaps (particularly in adhesiveness evaluation) and identified regulatory frameworks that incremented interest in researching DSS’ properties in the broader push for sustainability. Consequently, a discussion of the experimental set-ups, data treatment and visualization, advantages and disadvantages, and mathematical models with their physical significance is presented for the different techniques identified. The methods analyzed include oscillatory rheology, penetrometry (cylinder and cone), uniaxial compression tests (TPA), shear testing (e.g., Jenike shear test, Atterberg limit test, direct box shear test, triaxial shear test, unconfined shear test, and vane shear test), tomography and slump tests. By comparing these techniques, this study provides insights into the most appropriate approaches for sludge characterization, emphasizing the need for a unified framework to standardize the evaluation of viscoelastic and textural properties in DSS.