1. Application advantages of UVC-LED for water disinfection
2. Main interference factors in water and typical effects (with a data table)
3. Prevention and control measures against water interference factors
4. Conclusion
I. Application Advantages of UVC-LED Water Disinfection
UVC LED (Ultraviolet-C Light-Emitting Diode), as the third-generation ultraviolet disinfection light source, demonstrates significant application potential in terminal drinking water treatment, building secondary water supply, industrial recirculating aquaculture systems, medical process water, emergency water supply assurance, and industrial circulating cooling water, owing to its mercury-free design, compact solid-state packaging structure, excellent frequent start-stop tolerance, millisecond-level dimming response characteristics, long operational lifespan, and highly modular system integration advantages[1].
The core wavelength band of its photochemical disinfection action is concentrated at 260–280 nm, which highly coincides with the maximum absorption peak of microbial nucleic acid base pairs. This enables effective inactivation of pathogenic microorganisms through direct photolysis of pyrimidine dimer structures without reliance on chemical agents[1][4]. Meanwhile, this band exhibits a relatively low optical path attenuation coefficient in aqueous media and possesses strong penetration tolerance against light scattering and absorption caused by turbidity, color, and dissolved organic matter, making it suitable for conventional water disinfection conditions. By comparison, although the 222 nm band achieves higher nucleic acid disruption efficiency due to its proximity to protein absorption peaks, its molar extinction coefficient in water is significantly elevated, resulting in an extremely short optical path and limited penetration depth, which makes it difficult to meet the disinfection requirements of water with a certain optical path or turbidity. Therefore, for conventional water disinfection, the 260–280 nm band remains the preferred choice; for water bodies with complex microbial loads and high biofilm proliferation risks, a multi-wavelength synergistic irradiation strategy combining 260–280 nm and 222 nm can be adopted to achieve a coupled effect of broad-spectrum inactivation and deep disinfection.
UV photons at 260–280 nm directly photolyze pyrimidine dimers in microbial nucleic acids, achieving pathogen inactivation without chemical agents.
II. Main Interference Factors in Water and Typical Effects
The optical characteristics of water and the medium in water are the two core constraints determining the effective delivery of disinfection dose. The current main interference factors include the following aspects:
Strong UV absorption at 260–280 nm by conjugated structures; photon thermal dissipation
At humic acid 10 mg/L, UV transmittance at 265 nm decreases to 52%
Suspended solid particles (SS)
Mie scattering alters optical path and light intensity distribution; microbial encapsulation forms shielding
At SS 10 mg/L (≈5 NTU), transmittance decreases to 58%
Synergistic attenuation of organic matter + SS
DOM adsorbs onto particle surfaces, intensifying absorption-scattering coupling
Composite system transmittance drops sharply to 29%
Calcium and magnesium ion scaling
Ca⊃2;⁺, Mg⊃2;⁺ precipitate as carbonates under high temperature and UV-promoted oxidation, covering lenses/quartz sleeves
At hardness 300 mg/L with 30 days continuous operation, transmittance attenuates 32% without cleaning
pH-mediated scaling
At pH > 8.3, carbonate proportion increases, accelerating scaling
Scaling rate increases 2.7-fold; pH 6.5–7.5 is the stable operating range
Packaging material differences
Inorganic window density and chemical stability
Quartz glass/sapphire packaging outperforms organic silicone in scale resistance and chemical cleaning durability
III. Prevention and Control Measures Against Water Interference Factors
To address the main interference factors, the following engineering measures should be adopted:
1. Photoabsorption Interference from Dissolved Natural Organic Matter (NOM)
The conjugated double bond systems in molecules such as humic acid and fulvic acid exhibit strong characteristic absorption at the 260–280 nm band, converting photon energy into heat and directly reducing the effective irradiation dose. Studies have shown that when the UV transmittance (UVT) of water decreases, microbial inactivation efficiency declines significantly. Enhanced pretreatment processes such as coagulation, sedimentation, or activated carbon adsorption can be employed to reduce the dissolved organic carbon (DOC) concentration; in reactor design, computational fluid dynamics (CFD) simulation can be used to optimize the hydraulic retention time in the irradiation zone to compensate for light attenuation losses.
2. Scattering and Shielding Effects of Suspended Solids (SS)
Suspended particles alter the photon propagation path through Mie scattering, prolonging the optical path and causing uneven spatial distribution of irradiance; simultaneously, they can adsorb or encapsulate microorganisms, forming a physical shielding layer that prevents UV photons from directly acting on nucleic acids. Under high turbidity conditions (e.g., turbidity 4–10 NTU, high TSS), the system's disinfection efficacy is significantly limited. Countermeasures include: installing pre-filtration units to control influent turbidity below 5 NTU; adopting multi-point array LED arrangements or annular flow channel designs to reduce shadow zones; and dynamically increasing the irradiation dose redundancy based on real-time UVT monitoring data.
3. Multi-Factor Synergistic Attenuation
When dissolved organic matter and suspended solids coexist, the adsorption of organic matter onto particle surfaces further intensifies the coupling of light absorption and scattering, resulting in UV transmittance lower than the additive value of single-factor attenuation. Therefore, engineering design must adopt comprehensive pretreatment as the core approach, ensuring that the influent UVT of the disinfection unit is maintained at a high level (e.g., >70%), rather than optimizing for only a single indicator.
4. Scaling Interference Mediated by Hardness and pH
Ca⊃2;⁺ and Mg⊃2;⁺ in water readily precipitate as calcium carbonate, magnesium carbonate, and other insoluble salts on LED lens or quartz sleeve surfaces under conditions of temperature >30 °C and UV-promoted oxidative synergy, forming dense scale layers that cause continuous transmittance attenuation. This can be mitigated by: controlling the total hardness of influent water; maintaining pH within the relatively stable range of 6.5–7.5 to avoid carbonate supersaturation; prioritizing inorganic packaging modules with quartz glass or sapphire windows, whose surface density and chemical stability are significantly superior to organic silicone packaging; and configuring automatic cleaning structures (mechanical scraping or periodic chemical cleaning) to restore the optical window transmittance.
Figure 2. Water Interference Factors Affecting UVC-LED Disinfection
Schematic of three major interference mechanisms: dissolved organic matter (DOM) UV absorption, suspended solid (SS) Mie scattering and microbial shielding, and calcium/magnesium carbonate scaling on optical windows.
Key Takeaway: The core wavelength band of 260–280 nm remains the preferred choice for conventional water disinfection. For complex water bodies with high biofilm proliferation risks, a multi-wavelength synergistic strategy combining 260–280 nm and 222 nm should be considered to achieve coupled broad-spectrum inactivation and deep disinfection.
Figure 3. Engineering Countermeasures Against Water Interference Factors
Four-axis prevention framework mapping each interference factor to its engineering countermeasure, from pretreatment and reactor design to anti-scaling and automatic cleaning strategies.
IV. Conclusion
As a new generation of environmentally friendly UV disinfection technology, UVC-LED has achieved large-scale application in terminal water purification, secondary water supply, and aquaculture. However, shortcomings such as complex water quality adaptation, long-term stability, and standardization systems remain to be overcome. With the future development of multi-wavelength synergy, intelligent regulation, and novel anti-scaling technologies, UVC-LED water disinfection technology will evolve toward higher efficiency, greater intelligence, and lower cost, gradually becoming the mainstream technical route in the field of water disinfection.
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