Evaluating the Effects of Nitrite on Nitrogen Removal Efficiency and Energy Optimization in Wastewater Treatment Plants

Abstract

This study examines the optimization of nitrogen removal and energy efficiency in wastewater treatment plants (WWTPs) through the simultaneous nitrification and denitrification (SND) process. The research focuses on comparing the efficiency of ammonia removal in two reactors, with one receiving an additional 20 mg N/L of nitrite for 55 days. Results indicated that nitrite addition significantly enhanced ammonia removal efficiency, reducing effluent NH4+ concentrations from 14.50 ± 0.34 mg N/L to 0.12 ± 0.06 mg N/L in the treated reactor. This led to a substantial increase in total nitrogen removal efficiency, achieving 99.0% in the nitrite-supplemented reactor compared to 74.5% in the control reactor. Further analysis revealed that nitrite supplementation also positively impacted ammonia removal rates, which were 4.5 times higher in the treated reactor. Inhibitor tests demonstrated a significant reduction in ammonia removal efficiency with NaClO3 and ATU + NaClO3, while COD removal efficiency remained high across conditions. Gene copy analysis showed a notable increase in ammonia oxidizer populations and enhanced nitrite reduction, indicating the effectiveness of nitrite in optimizing microbial communities. Operational challenges such as high total suspended solids (TSS) and variable dissolved oxygen levels were observed, highlighting the need for improved aeration and process adjustments to manage TSS buildup and enhance treatment efficiency. The study underscores the importance of integrating advanced technologies and optimizing energy use in WWTPs to achieve better environmental sustainability and operational performance. The findings suggest that continued innovation and adaptation are essential for balancing energy consumption with environmental impact, providing a foundation for future advancements in wastewater treatment practices.