Evaluation of several respirometry-based activated sludge toxicity control strategies

Area of Science:

• Environmental Engineering
• Wastewater Treatment
• Biotechnology

Background:

• Activated sludge processes are vital for wastewater treatment but vulnerable to toxic influent events.
• Effluent quality deterioration during toxic events poses significant environmental risks.
• Effective control strategies are needed to maintain process stability under toxicity.

Purpose of the Study:

• To evaluate four distinct strategies for mitigating toxic influent events in activated sludge systems.
• To assess the efficacy of influent storage and reintroduction, step-feeding, rapid sludge recycle, and waste sludge storage.
• To enhance the IWA simulation benchmark for evaluating toxicity impacts.

Main Methods:

• Simulations were conducted using the IWA activated sludge model benchmark.
• Four strategies were evaluated: influent storage/reintroduction, step-feeding, rapid sludge recycle, and waste sludge storage.
• Maximum specific respiration rate (Rmax) was used as a controlled variable; a pseudo-online respirometer simulated toxicity detection.

Main Results:

• Influent storage and reintroduction demonstrated the most effective mitigation of toxic effects.
• Step-feeding, rapid sludge recycle, and waste sludge storage strategies were unable to adequately reduce effluent quality deterioration.
• The success of influent storage and reintroduction was contingent on the reintroduction flow rate, enabling estimation of treatment time.

Conclusions:

• Influent storage and reintroduction is a promising strategy for managing toxic influent events in wastewater treatment.
• The developed simulation approach enhances the ability to assess activated sludge process resilience to toxicants.
• Further research should focus on optimizing reintroduction flow rates for storage-based mitigation strategies.