Effect of influent organic content on digested sludge extracellular polymer content and dewaterability

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Sludge dewaterability is a critical factor in wastewater treatment efficiency and cost.
• The organic composition of feed sludge can significantly impact sludge properties.
• Microbial extracellular polymers (ECP) are known to influence sludge characteristics.

Purpose of the Study:

• To investigate the effect of altering feed sludge organic composition on digested sludge dewaterability.
• To determine the relationship between extracellular polymer (ECP) content and sludge filtrability.
• To identify optimal ECP levels for improved sludge dewaterability.

Main Methods:

• Laboratory-scale anaerobic digesters were used to process sludge with varied organic compositions.
• Primary sludge was substituted with glucose or propionic acid solutions.
• Sludge dewaterability was assessed using the capillary suction time test.
• Extracellular polymer (ECP) yield was extracted and quantified from digested sludge.

Main Results:

• Substitution with glucose significantly increased ECP content in digested sludge.
• Increased ECP levels led to altered particle size distribution and reduced sludge dewaterability.
• Substitution with propionic acid did not significantly alter sludge dewaterability compared to the control.
• A significant inverse relationship (P = 0.01) was found between ECP yield and sludge filtrability.
• An optimal ECP level of 17.2 mg g(-1) SS was calculated for maximum sludge dewaterability.

Conclusions:

• The organic composition of influent sludge, particularly the addition of glucose, directly impacts ECP production and subsequent sludge dewaterability.
• Understanding and controlling ECP levels is essential for optimizing downstream sludge treatment processes.
• The findings provide a basis for predicting the effects of changes in sewage composition on wastewater treatment plant operations.