Nitrogen removal and simultaneous nitrification and denitrification in a fluidized bed step-feed process

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Microbiology

Background:

• Urban wastewater treatment faces challenges in efficiently removing chemical oxygen demand (COD) and nitrogenous pollutants.
• Conventional systems may struggle with high nutrient loads, necessitating advanced treatment strategies.

Purpose of the Study:

• To evaluate the performance of a novel four-stage step-feed wastewater treatment system coupled with a fluidized bed reactor.
• To assess the removal efficiencies of COD, ammonium (NH4+-N), and total nitrogen (TN).
• To analyze biomass characteristics and bacterial activity within the treatment system.

Main Methods:

• Implementation of a four-stage step-feed wastewater treatment system.
• Integration of a fluidized bed reactor for enhanced treatment.
• Laboratory-scale experiments to measure pollutant concentrations and bacterial activity.
• Monitoring of nitrogen species to identify nitrification and denitrification processes.

Main Results:

• Achieved high removal rates: 88.2% for COD, 95.7% for NH4+-N, and 86.4% for TN.
• Effluent concentrations met stringent standards: <50 mg/L COD, <8 mg/L NH4+-N, and <10 mg/L TN.
• Observed significant simultaneous nitrification and denitrification, indicating efficient nitrogen cycling.
• Identified higher nitrobacteria counts in activated sludge compared to biofilm, with comparable overall bacterial activity.

Conclusions:

• The novel four-stage step-feed system with a fluidized bed is highly effective for urban wastewater treatment.
• The system demonstrates excellent pollutant removal, achieving low effluent concentrations for COD and nitrogen.
• Simultaneous nitrification and denitrification are key processes contributing to the system's high nitrogen removal efficiency.