Pilot scale study on retrofitting conventional activated sludge plant for biological nutrient removal

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Wastewater Management

Background:

• Eutrophication from nitrogen and phosphorus in wastewater effluent is a growing environmental concern.
• Conventional activated sludge processes often require retrofitting for effective nutrient removal.
• Biological nutrient removal (BNR) strategies are crucial for mitigating water pollution.

Purpose of the Study:

• To evaluate a biological nutrient removal process for retrofitting existing activated sludge systems.
• To determine the effectiveness of anoxic/anaerobic zones in enhancing nutrient removal.
• To investigate the impact of operational parameters on nutrient removal efficiency.

Main Methods:

• A pilot-scale research program was conducted.
• The study focused on modifying conventional activated sludge plants.
• Key parameters evaluated included anoxic/anaerobic zone implementation and return sludge ratio.

Main Results:

• Creating an anoxic/anaerobic zone before the aeration basin significantly enhanced total phosphorus (TP) and total nitrogen (TN) removal.
• Optimal conditions achieved approximately 80% removal for both TP and TN without internal cycling.
• Phosphorus and nitrogen removal decreased with varying return sludge ratios and decreasing BOD5 concentrations.

Conclusions:

• Retrofitting existing activated sludge plants with anoxic/anaerobic zones is an effective strategy for biological nutrient removal.
• Operational parameters, such as return sludge ratio and influent BOD5 concentration, influence removal efficiency.
• The modified system demonstrated improved sludge settling and reduced foaming, offering additional operational benefits.