SRT contributes significantly to sludge reduction in the OSA-based activated sludge process

Area of Science:

• Environmental Science
• Environmental Engineering
• Microbiology

Background:

• Activated sludge systems are crucial for wastewater treatment but generate excess sludge.
• Oxic-settling-anaerobic (OSA)-based processes show potential for sludge reduction.
• The exact mechanisms behind sludge reduction in OSA processes remain unclear.

Purpose of the Study:

• To elucidate the sludge reduction mechanisms in OSA-based wastewater treatment.
• To quantify the contribution of different factors to sludge reduction.

Main Methods:

• Investigated four different conditions within the OSA process.
• Analyzed sludge reduction percentages and attributed contributions to specific factors.
• Assessed the impact on nutrient removal efficiency.

Main Results:

• Achieved a 42% sludge reduction in the OSA process with side hydrolysis and acidification.
• Identified sludge retention time (SRT) as the main contributor (33%) to sludge reduction.
• Quantified contributions from energy uncoupling (7.7%) and hydrolysis/acidification (1.1%).

Conclusions:

• The OSA process effectively reduces excess sludge during wastewater treatment.
• Long SRT is the predominant factor driving sludge reduction in OSA systems.
• Optimizing OSA processes based on these clarified mechanisms can improve wastewater treatment efficiency without compromising nutrient removal.