Fully automated water analysis

Significance of the topic

The comprehensive monitoring of water and wastewater is critical for environmental protection, public health and regulatory compliance. Reliable data on conductivity, pH, alkalinity, hardness, chloride, fluoride, chemical oxygen demand (COD) and permanganate index (PMI) guide treatment processes and ensure safe water distribution. Automating these analyses reduces human error, improves throughput and enables real-time decision making in industrial and research settings.

Aims and overview of the application bulletin

This application bulletin demonstrates a fully automated workflow for the simultaneous determination of key physical and chemical water parameters. The system integrates measurements of conductivity, pH, alkalinity (p- and m-value), total and individual hardness (calcium, magnesium), chloride, fluoride, PMI (EN ISO 8467) and COD (DIN 38409-44) within a single analytical sequence. The aim is to illustrate method setup, calibration, sample handling and data interpretation for high-precision routine water analysis.

Methodology and instrumentation

The automated platform consists of a swing-head sample changer, two external titration stands, titrators with DET mode and a conductivity module. Key sensors include five-ring conductivity cell, combined titration electrodes (Ca ISE, Ag-Titrode, Pt-Titrode, F-ISE) and reference electrodes. Reagent delivery uses burettes (50 mL, 20 mL, 10 mL, 5 mL) and a triburette for multiplex dosing.

Sample preparation is minimal: raw samples are placed in beakers on the rack, covered to prevent evaporation. The conductivity cell is preconditioned by immersion, then conductivity is measured. Automated dosing transfers aliquots to titration vessels for sequential pH, alkalinity, hardness, chloride and fluoride titrations. PMI and COD determinations use separate vessels with heating and redox titration protocols.

Main results and discussion

The integrated process achieves:

• Conductivity and pH measurement in seconds.
• Alkalinity and hardness combined titrations in ~15 minutes.
• Chloride and fluoride titrations without cross-interference.
• PMI by back-titration in ~30 minutes.
• COD by digestion and titration in 2 hours.

The system delivers high reproducibility (relative standard deviations <1 % for most parameters) and accurate titer correction via standardization steps. Covering titration vessels prevents sample oxidation and ensures stability over extended runs.

Benefits and practical applications

The fully automated setup offers:

• High sample throughput with minimal operator intervention.
• Consistent titration endpoints via dual DET titrimetry and fixed pH points.
• Broad parameter coverage in a single workflow.
• Reduced reagent consumption and waste management through precise dosing.
• Compliance with international standards (EN ISO 8467, DIN 38409-44).

This approach is suited for water utilities, industrial process control, environmental laboratories and QA/QC facilities requiring rapid, multiplexed analysis.

Used instrumentation

• Sample changer with swing head
• External titration stands (2 ×)
• Titrators with DET mode and multiple interfaces
• Conductivity module and five-ring conductivity cell
• Combined titration electrodes: Ca ISE, Ag-Titrode, Pt-Titrode, F-ISE, reference electrodes
• Burettes and triburette for reagent dosing
• Thermostat jacketed vessel for PMI and COD digestion

Future trends and applications

Advances in sensor miniaturization, integrated ion chromatography modules and real-time data analytics will further streamline water quality monitoring. Implementation of machine learning algorithms could optimize titration endpoints and predictive maintenance. Remote operation and cloud-based reporting will enable decentralized networks of automated analyzers for smart water infrastructure.

Conclusion

This application bulletin demonstrates a robust, fully automated platform for multi-parameter water analysis. By combining conductivity, pH, alkalinity, hardness, chloride, fluoride, PMI and COD in a single sequence, laboratories can achieve reliable, high-throughput results in compliance with international standards, reducing manual workload and improving data consistency.

References

• EN ISO 8467: Water quality – Determination of permanganate index.
• DIN 38409-44: German standard methods for the examination of water – COD determination.
• Metrohm Application Bulletin AB-221: Standard methods in water analysis.