Evaluation of aeration energy saving in two modified activated sludge processes

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Energy Efficiency in WWTPs

Background:

• Activated sludge processes are crucial for removing organics and nutrients (N and P) in wastewater treatment plants (WWTPs).
• Aeration basins represent the largest energy consumers in WWTPs, driving the need for energy-saving strategies.
• Modified activated sludge processes offer potential for enhanced nutrient removal and energy reduction.

Purpose of the Study:

• To evaluate energy-saving potentials of two modified activated sludge processes: ABA(2) (temporal air adjustment) and MB-A(2)O (spatial volume ratio change).
• To assess the impact of reduced aeration on effluent quality (COD, TN, NH4+, TP) in nutrient removal.

Main Methods:

• Pilot-scale testing of the ABA(2) process with a fixed air on/off period (60min/45min) and aerobic fraction of 0.57.
• Pilot-scale testing of the MB-A(2)O process with a reduced aerobic/anoxic volume ratio (from 0.58 to 0.42).
• Monitoring of effluent quality parameters including Chemical Oxygen Demand (COD), Total Nitrogen (TN), Ammonium (NH4+), and Total Phosphorus (TP).

Main Results:

• Both ABA(2) and MB-A(2)O processes demonstrated significant energy savings through reduced aeration time and volume.
• Effluent concentrations of COD, TN, NH4+, and TP remained within acceptable limits after implementing energy-saving modifications.
• This study represents the first attempt to reduce aeration energy in these specific modified activated sludge processes.

Conclusions:

• Adjusting air on/off periods (ABA(2)) and aerobic/anoxic volume ratios (MB-A(2)O) are effective strategies for reducing aeration energy consumption in WWTPs.
• Energy reduction can be achieved without compromising the nutrient removal efficiency of modified activated sludge systems.
• These findings have significant implications for optimizing operational costs and sustainability in wastewater treatment.