Impact of methodological artifact on digested sludge flow curve measurement

Area of Science:

• Environmental Engineering
• Materials Science
• Chemical Engineering

Background:

• Inconsistent experimental procedures in literature lead to non-comparable sludge rheology data and varied rheological models.
• Accurate rheological data is essential for engineers in sludge treatment design and troubleshooting.
• Existing methodologies lack standardization, hindering reliable application of rheological data.

Purpose of the Study:

• To identify and systematically investigate influential parameters affecting sludge rheology data collection.
• To develop a reliable and reproducible procedure for sludge flow curve measurements.
• To provide a framework for characterizing other sludge types.

Main Methods:

• Systematic investigation of parameters including geometry, preshear, equilibrium time, rest time, and storage time.
• Flow curve measurements conducted on digested sludge with total solid concentrations ranging from 2.3% to 6%.
• Analysis of the impact of each parameter on the reliability and reproducibility of rheological data.

Main Results:

• All investigated factors (geometry, preshear, equilibrium, rest, storage time) significantly impact sludge flow curve measurements.
• The influence of these parameters is strongly dependent on the sludge's total solid concentration.
• Recommended protocol includes selecting geometry and allocating equilibrium time based on solid concentration and visual inspection for instabilities.

Conclusions:

• A standardized protocol is necessary for reproducible sludge rheology characterization.
• Sludge solid concentration is a critical factor influencing the selection of experimental parameters.
• The developed protocol offers a customizable method for characterizing various sludge types.