Test for assessing shear sensitivity of activated sludge flocs: a feasibility study

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Microbiology

Background:

• Sludge deflocculation, often due to filamentous bacteria, can lead to activated sludge wastewater treatment failure.
• Currently, no standardized tool exists to quantify activated sludge flocculation or predict deflocculation.
• Accurate assessment is crucial for maintaining efficient wastewater treatment processes.

Purpose of the Study:

• To develop and validate a novel test procedure for assessing activated sludge flocculation sensitivity to shear.
• To establish a reliable method for predicting potential sludge deflocculation and treatment failure.
• To provide a practical framework for routine assessment in wastewater treatment plants.

Main Methods:

• A shear-SV test procedure was developed, involving subjecting sludge samples to controlled shear treatment.
• Sludge volume after 30 minutes (SV(30)) was measured for both sheared and control samples.
• Shear sensitivity was quantified using the ratio of SV(30) of the sheared sample to the control sample.

Main Results:

• The shear-SV test successfully ranked sludge samples according to their shear sensitivity.
• The test differentiated between amorphous sludges (SV(30) ratio ≥ 100%) and normal sludges (SV(30) ratio < 100%).
• The procedure demonstrated repeatability, simplicity, and cost-effectiveness, requiring only basic laboratory equipment.

Conclusions:

• The shear-SV test is a reliable and practical tool for assessing activated sludge shear sensitivity.
• This method can aid in predicting and preventing sludge deflocculation and subsequent wastewater treatment failures.
• The test offers a valuable framework for routine monitoring in activated sludge systems.