Post-denitrification using alginate beads containing organic carbon and activated sludge microorganisms

Area of Science:

• Environmental Science
• Microbiology
• Biotechnology

Background:

• Nitrate concentration in wastewater effluent is a critical concern for biological treatment systems.
• Pre-denitrification systems often struggle with complete nitrate removal, necessitating advanced treatment strategies.
• Post-denitrification offers a potential solution for polishing effluent quality.

Purpose of the Study:

• To investigate the efficacy of post-denitrification using alginate beads with immobilized microorganisms and organic carbon sources.
• To identify optimal carbon sources for enhanced nitrate removal and bead stability.
• To evaluate the performance of selected beads in a coupled bioreactor system treating dairy farm wastewater.

Main Methods:

• Batch studies were conducted to screen carbon sources (acetate, glucose, calcium tartrate, starch, canola oil) for nitrate removal and bead stability.
• Alginate beads immobilized with activated sludge and carbon sources were tested.
• Post-denitrification was implemented in the final clarifier of a lab-scale coupled upflow bioreactor and aerobic system.

Main Results:

• Starch and canola oil beads demonstrated superior denitrification rates, stability, and lower nitrite accumulation compared to acetate, glucose, and tartrate.
• Post-denitrification with starch and canola oil beads achieved >90% nitrate removal efficiency.
• Alginate beads degraded within 12 days, indicating a limitation for long-term treatment.

Conclusions:

• Alginate beads immobilized with starch or canola oil are effective for post-denitrification, significantly improving nitrate removal.
• Bead stability and longevity are critical factors for practical application, suggesting the need for stronger materials.
• Further research is required to optimize bead formulations and scale up the process for real-world wastewater treatment systems.