Online analysis of ammonia, nitrate, and nitrite in wastewater

Importance of Nitrogen Monitoring in Wastewater Treatment

Effective removal of ammonia, nitrite and nitrate is essential to prevent eutrophication, protect aquatic ecosystems and comply with regulatory limits. Continuous online monitoring provides real-time data, enabling rapid adjustments to biological nutrient removal processes and safeguarding both environmental and public health.

Objectives and Study Overview

This note presents an online analytical solution for simultaneous measurement of NH₃, NO₂⁻ and NO₃⁻ in industrial and municipal wastewater. It outlines the challenges in nitrification and denitrification, and demonstrates how the Metrohm Process Analytics 2060 TI Process Analyzer addresses the need for robust, drift-free, multi-parameter monitoring.

Methodology and Analytical Approach

The process relies on a chemical colorimetric, drift-free photometric technique that quantifies each nitrogen species within minutes. Samples are automatically preconditioned and routed through reagent modules. The analyzer supports wide concentration ranges—from micrograms per liter to grams per liter—without manual intervention.

Used Instrumentation

• 2060 TI Process Analyzer: A modular online wet-chemistry platform featuring a touchscreen PC, up to five wet-part cabinets, and flexible reagent supply with non-contact level detection.
• Photometric detection system: Drift-free multi-wavelength colorimetry for NH₃/NH₄⁺, NO₂⁻ and NO₃⁻.
• Sample conditioning modules: Filtration, degassing and pressure control to handle solids-laden and high-bacteria streams.

Main Results and Discussion

The analyzer accurately tracks influent and effluent nitrogen levels across all treatment stages. Typical influent concentrations range up to 6000 mg/L for NH₃ and 1400 mg/L for NO₃⁻, decreasing to below 60 mg/L and 88 mg/L, respectively, after treatment. NO₂⁻ is monitored from 160–320 mg/L influent down to 16 mg/L effluent. Continuous data reveal process upsets, such as insufficient aeration or inadequate anoxic conditions, enabling timely corrective action.

Benefits and Practical Applications

• Real-time compliance monitoring ensures effluent quality meets stringent discharge limits.
• Fully automated diagnostics and alarms reduce operator workload and maintenance overhead.
• Simultaneous multi-parameter analysis cuts operational costs by using a single platform for NH₃, NO₂⁻ and NO₃⁻.

Future Trends and Potential Applications

Integration with advanced control systems and predictive analytics will enhance process optimization. Expansion to additional parameters, such as COD, phosphorus and heavy metals, can create comprehensive online monitoring networks. Emerging sensor technologies may further reduce reagent use and energy consumption.

Conclusion

The Metrohm 2060 TI Process Analyzer offers a reliable, drift-free solution for continuous online analysis of ammonia, nitrite and nitrate in wastewater. Its modular design and robust sample conditioning ensure high uptime and accurate data, promoting efficient nutrient removal and regulatory compliance.

References

• AN-PAN-1039 Ortho- and total phosphate phosphorus analysis online (EN ISO 6878)
• AN-PAN-1002 Free, total & WAD cyanide in gold leach slurry & wastewater