UV-C sensitivity measurement
When you use water for drinking or in critical (production) processes, in terms of clean and safe water only 100% certainty counts. By monitoring the flow through and UV-C intensity in the UV-C system, you can guarantee the operational safety of your disinfection system. This allows for optimization of energy consumption and guarantees safety. If the system deviates from the set certified/validated working range, the system can generate alarms and the water flow can be shut off.
Measurement of performance
Measurement of performance is about continuously verifying that the system is operating as designed and that microbial safety is maintained over time. Monitoring takes place at two complementary levels: operational monitoring of the UV system itself, and analytical verification of biological performance in the treated water. In this article we focus on operational monitoring.
Monitoring during system operation
In UV-C systems, disinfection performance depends directly on delivered dose. Dose is a function of UV intensity and exposure time. UV intensity is determined by lamp output and water quality. Exposure time is determined by flow rate and reactor hydraulics. Therefore, operational monitoring focuses on 3 parameters:
1 UV-C intensity
2 Temperature management
3 Electronical monitoring
1. UV-C intensity measurement
The core measurement in modern UV systems is the UV intensity sensor. This sensor measures the actual UV-C irradiance inside the reactor under operating conditions. It is calibrated to reflect the germicidal wavelength range and compensates for fouling and aging effects. The measured value is continuously compared to a validated setpoint. If intensity drops below a defined threshold, alarms are triggered. These alarms can be tiered, for example:
- Warning alarm at reduced intensity indicating lamp aging, contamination or fouling
- Critical alarm when the minimum validated intensity is no longer measured and dose can’t be guaranteed
- Automatic shut-off or diversion when dose compliance cannot be ensured
Many systems also include dump valves or diversion valves. When a critical alarm occurs — for example low UV intensity, lamp failure, or power interruption — the system can automatically divert untreated water away from the distribution line. This prevents potentially under-treated water from reaching downstream processes or users. In validated installations, this fail-safe concept is a central compliance feature.
2. Temperature protection
Temperature protection is an additional operational safeguard. UV lamps operate within a defined temperature window for stable output and lifetime. Excessive temperature may damage components or reduce output. Therefore temperature sensors are often integrated into the reactor. If temperature exceeds safe limits, the system can reduce power, shut down, or trigger alarms to prevent unsafe operation.
3. Electrical monitoring
Electrical monitoring through the lamp ballast or power supplies provides another layer of control. Modern electronic ballasts continuously monitor lamp current, voltage, ignition behavior and operating stability. Deviations indicate lamp end-of-life, failure, or electrical malfunction. These parameters are logged and can generate remote alarms. Remote access allows operators to monitor system status in real time, review trends, and intervene before performance drops below validated conditions.
Conclusion
This combination of UV sensor feedback, temperature protection, electrical diagnostics and automated diversion creates a closed control loop that protects dose delivery during operation.
The measured UV-C intensity can be affected by the aging of the lamp(s), the transmittance of the water, the water temperature (in case of low pressure lamps) and fouling of the quartz sleeves and/or measuring window of the UV sensor. In case lamp power control is used the UV sensor is essential to monitor and control the process. Depending on you process a low UV-C intensity alarm, in case the setpoint is not reached, can be used the signal the operator and stay in operation or stop the process.