Evaluating sludge minimization caused by predation and viral infection based on the extended activated sludge model No. 2d

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies
• Bioprocess modeling

Background:

• The Activated Sludge Model No. 2d (ASM2d) is a standard for simulating wastewater treatment processes.
• Understanding factors influencing sludge minimization is crucial for efficient wastewater treatment.
• Polyphosphate-accumulating organisms (PAOs) play a key role in biological nutrient removal.

Purpose of the Study:

• To extend the ASM2d model to include predation and viral infection processes.
• To quantify the contributions of predation and viral infection to sludge minimization in a sequencing batch reactor (SBR) system.
• To analyze the impact of these processes on system stability and effluent quality.

Main Methods:

• Extension of the ASM2d model to incorporate predation and viral infection.
• Calibration and validation of the extended model using experimental data.
• Simulation of SBR systems to evaluate sludge minimization potentials.

Main Results:

• Predation contributes approximately twice as much to sludge minimization as viral infection in PAO-enriched SBRs.
• Sensitivity analyses revealed thresholds for predation and viral infection rates, beyond which effluent quality and sludge retention time degrade.
• The maximal contribution of predation and viral infection to sludge minimization was estimated at 21% and 9%, respectively.

Conclusions:

• Predation and viral infection can significantly contribute to sludge minimization in SBRs, but their impact is limited by critical rate thresholds.
• Further research is needed to accurately determine parameters for predation and especially viral infection, potentially through independent experimental methods.
• The findings highlight the importance of considering these biological processes in optimizing wastewater treatment designs for sludge reduction.