" />[lead]
Ultraviolet (UV) light is a common water treatment technology that effectively removes microbes from water. However, the effectiveness of UV light can be affected by several factors, including water quality. Although it is generally understood that water quality affects the performance of UV systems, some contaminants, such as iron and manganese, can significantly reduce the effectiveness of UV light even at low concentrations.
Over time, iron and manganese accumulate and adhere to the quartz sleeve surrounding the UV lamp, resulting in visible staining of the quartz. This staining effect can prevent UV light from penetrating the quartz sleeve, leading to inadequate microbial inactivation. Since iron and manganese are commonly found in well water and groundwater systems, it is critical to know the concentrations of these contaminants in the municipal water supply before applying UV radiation, especially in applications where UV radiation is used as a “firewall” and pre-treatment technologies are not available before the UV system.
[/lead]
How to ensure optimal UV performance
As a rule of thumb, concentrations greater than 0.3 ppm of iron or 0.05 ppm of manganese are enough to create concern regarding ensuring reliable UV disinfection. If levels are greater than these recommended limits, facilities can consider a few different options to ensure optimal UV performance:
- Implement pretreatment technology such as sequestration or cation exchange, or use an oxidation and filtration technique to reduce iron and manganese levels considerably.
- Ensure the UV equipment includes a UV intensity monitor for the quartz sleeve fouling issue. When reductions in UV intensity occur, conduct a CIP of the UV equipment to clean the fouling from the quartz sleeve. The required CIP frequency will depend on the severity of the fouling, which in turn depends on the concentrations of iron and manganese in the water.
- Consider installing UV equipment with a chemical wiping system built into the chamber. Although a physical wiper will help with some quartz sleeve fouling issues such as total suspended solids (TSS), minerals, and hardness, physical removal of the iron and manganese staining is not highly effective due to the chemical bond that forms with the quartz sleeve. Using a chemical wiper such as Nuvonics’ (Aquionics) UltraWipe can effectively clean the iron/manganese staining without requiring the downtime associated with a full CIP.
- If possible, consider implementing UV further downstream in the process, where iron/manganese will have already been removed through filtration or other processes.
[hr][/hr]
Conclusion
In conclusion, iron and manganese fouling can significantly reduce the effectiveness of UV systems, even at low concentrations. To ensure optimal UV performance, facilities should know the concentrations of these contaminants in the municipal water supply before implementing UV technology and consider applying pre-treatment technologies or other options, such as using a chemical cleaning system or installing UV equipment later in the process. In addition, installing a UV intensity monitoring system that can detect sleeve fouling problems is crucial to ensure that the system delivers the dosage required for adequate water purification. By taking these steps, facilities can ensure that their UV systems operate as intended and effectively remove microbes from the water.
Brian Grochowski
Date 01/02/2023
- Share this
