Electrical conductivity is one of the most efficient parameters for continuous water quality monitoring. It measures the ability of water to conduct electrical current and is directly related to the concentration of dissolved ions such as salts, minerals, and inorganic impurities.
Unlike individual analyses, conductivity provides a quick overall indicator of ion content, allowing for immediate assessment of system conditions.
Why Conductivity is Crucial
Conductivity correlates directly with the amount of total dissolved solids (TDS). As ion concentration increases, so does conductivity. This allows for immediate detection of changes in water composition.
Sudden increases typically indicate contamination, dosing errors, or leaks. In stable systems, constant conductivity is an indicator of process safety.
Typical value ranges:
- Ultrapure water: <1 µS/cm
- Drinking water: 50–500 µS/cm
- Seawater: ~50,000 µS/cm
Conductivity in Drinking Water
In drinking water, conductivity serves as an indirect quality parameter. High values indicate elevated concentrations of dissolved substances, which may contain undesirable components.
The WHO recommends guideline values for TDS of around 500 mg/L to ensure taste and quality. Due to the strong correlation, conductivity is practically used for monitoring.
Industrial Applications
In technical systems, conductivity is a central control parameter:
- Boiler systems: Control of impurities and prevention of deposits
- Cooling towers: Control of blowdown cycles
- Membrane systems (RO/EDI): Monitoring of permeate quality and early detection of defects
- Pharmaceutical and semiconductor industry: Control of ultrapure water at extremely low conductivity levels
Measurement and Control
Inline sensors:
Enable continuous real-time monitoring.
Temperature compensation:
Since conductivity is temperature-dependent, standardization to 25°C is performed.
Calibration:
Regular calibration with reference solutions is absolutely necessary.
Automation:
Integration into control systems enables automatic reactions to deviations.
Limitations of Conductivity
Conductivity does not provide information about the type of dissolved substances. Identical values can conceal different chemical compositions.
Conclusion
Conductivity is a key real-time indicator for water quality and process stability. However, its informative value depends on correct measurement and interpretation.
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