TNb determination in tre monitoring and control of the municipal wastewater treatment plants

Significance of TNb Determination in Wastewater Treatment

The monitoring and control of total bound nitrogen (TNb) is critical for municipal wastewater treatment plants to comply with increasingly stringent environmental regulations. Conventional methods focusing on individual inorganic nitrogen species (NH4-N, NO3-N, NO2-N) can underestimate total nitrogen load due to unmeasured organic fractions. Real-time TNb analysis offers a comprehensive view of nitrogen pollution and removal efficiency, enabling rapid operational adjustments and ensuring effluent quality meets legal guidelines.

Study Objectives and Overview

This study examined the application of a chemiluminescence-based TNb analyzer (Shimadzu TOCN-4100) in a large municipal wastewater treatment facility serving 2 million inhabitants. The main goals were to validate online TNb monitoring against laboratory methods, to assess its ability to track nitrogen removal across process stages, and to demonstrate operational benefits over traditional offline techniques.

Methodology and Instrumentation

A TNb analyzer TOCN-4100 was installed to measure incoming and outgoing wastewater streams at key points: initial clarification, biological treatment influent and effluent, and sludge processing concentrate. Sample streams passed through integrated online filtration, followed by chemiluminescence detection of oxidized nitrogen species and organic nitrogen derivatives. Parallel laboratory validation used a manual homogenization protocol with an Ultraturrax and a TN-5 Abimed analyzer for comparison. Key instrumentation:

• Shimadzu TOCN-4100 TNb analyzer with three-flow online sampling
• Ultraturrax homogenizer for laboratory TNb pretreatment
• TN-5 Abimed laboratory TNb analyzer

Main Results and Discussion

Online TNb measurements correlated closely with laboratory values (differences generally <1 mg/L) once calibration issues were resolved. Real-time data revealed dynamic nitrogen removal performance, including rapid responses to changes in sludge concentrate dosing. Traditional inorganic nitrogen monitoring would have missed up to 10–20 mg/L of organic nitrogen present at the plant inlet. The TNb analyzer tracked hourly and daily trends, providing early detection of denitrification delays and influent load spikes.

Benefits and Practical Applications

Online TNb monitoring enables process engineers to:

• Obtain a complete nitrogen balance in real time
• Optimize chemical and biological treatment stages
• Respond quickly to fluctuations in influent quality or sludge recirculation
• Ensure compliance with EU directive 91/271/EWG discharge limits

These advantages support cost-effective operation, reduce risk of permit violations, and improve overall plant performance.

Future Trends and Potential Applications

Advances in sensor integration and data analytics will further enhance TNb monitoring by enabling predictive control and automated adjustments. Expansion of chemiluminescence and optical detection technologies to smaller decentralized plants can democratize access to comprehensive nitrogen monitoring. Coupling TNb data with multi-parameter probes (e.g., TOC, COD, ammonia) promises holistic process insight and digital twin implementations.

Conclusion

The implementation of online TNb determination using the Shimadzu TOCN-4100 at a major municipal plant demonstrated superior sensitivity to organic and inorganic nitrogen compared to conventional methods. Rapid, continuous measurement allowed immediate operational interventions and ensured adherence to discharge regulations. TNb monitoring represents a significant step forward in wastewater analytics, offering robust process control and environmental compliance.