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Water treatment technology
UV disinfection & advanced oxidation.
Ultraviolet light destroys pathogens at the DNA level: no chemicals, no residuals, no taste or odour. Combined with advanced oxidation, it destroys even pharmaceuticals, PFAS and emerging organic pollutants.
- Peak germicidal wavelength
- 254 nm
- Inactivation at a 4-log target
- 99.99%
- Chemical by-products added
- 0
- Most powerful oxidant in water treatment
- ·OH
How UV light destroys pathogens.
UV-C radiation, 200 to 280 nm, penetrates microbial cell walls and damages nucleic acids directly, stopping replication without adding any chemical.
DNA and RNA photodamage
UV-C photons are absorbed by the pyrimidine bases thymine, cytosine and uracil. Adjacent bases fuse into cyclobutane pyrimidine dimers, lesions that block the cell's replication machinery. The organism cannot reproduce and is effectively dead.
Why 254 nm?
DNA absorbs most strongly at 253 to 260 nm, almost exactly the 253.7 nm emission of low-pressure mercury lamps, which maximises germicidal effect per unit of energy. Medium-pressure lamps emit across 200 to 400 nm, useful against some UV-resistant organisms.
Unlike chlorine or ozone, UV forms no disinfection by-products: no trihalomethanes, no haloacetic acids, no bromate. That matters in water reuse, food production and high-purity applications where DBPs are regulated.
Because UV adds nothing, it offers no lasting protection against re-contamination downstream. Municipal networks often pair UV for primary disinfection with a low-dose chlorine residual for distribution: each technology where it is strongest.
Three UV system architectures.
They differ in lamp technology, spectral output, energy efficiency and fit. The right choice depends on flow rate, water quality and target organisms.
| Low-pressure (LP) | Medium-pressure (MP) | UV-LED | |
|---|---|---|---|
| Source | Mercury lamp, monochromatic | Mercury lamp, polychromatic | Solid-state, tunable |
| Output wavelength | 253.7 nm | 200–400 nm | 255–285 nm |
| Power | 25–1,000 W per lamp | 1–30 kW per lamp | 1–10 mW per LED |
| Life | 8,000–12,000 h | 4,000–8,000 h | 20,000–50,000 h |
| Germicidal efficiency | ~35–38% | ~10–15% | 3–10%, improving |
| Character | Aligned almost perfectly with DNA's absorption peak. The industry standard for drinking and wastewater. | Very high power per lamp, so fewer lamps per flow. More effective against organisms that resist monochromatic UV (photoreactivation). | Mercury-free, instant on and off, long life, compact. Higher capital cost today, improving fast. |
| Best for | Municipal drinking water, wastewater effluent, residential point of use | High-flow municipal plants, ballast water, recalcitrant pathogens | Point of use, food and beverage, pharmaceutical, compact on-demand systems |
One molecule in, two radicals out.
AOP combines UV with an oxidant, usually hydrogen peroxide or ozone, to generate hydroxyl radicals (·OH). They destroy contaminants that UV or chemicals alone cannot.
- UV/H₂O₂
The most common configuration. H₂O₂ is dosed before the UV reactor, and photolysis (bond energy 200 kJ/mol) cleaves each molecule into two hydroxyl radicals. Typical doses are 5 to 20 mg/L, set by the target contaminant and UV fluence.
- O₃/UV
Ozone is a stronger direct oxidant than H₂O₂ and also yields ·OH under UV, with very high radical yields. Higher capital and operating cost, as ozone is generated on site, but extremely effective for recalcitrant pollutants and high-TDS water.
- Radical power
The hydroxyl radical has a standard reduction potential of +2.80 V, second only to fluorine. It reacts with virtually all organic molecules at near diffusion-limited rates (k ≈ 10⁸–10¹⁰ M⁻¹s⁻¹).
What does your dose reach?
UV dose, or fluence, is measured in mJ/cm². Set a dose and see which organisms reach 3-log (99.9%) inactivation with low-pressure UV. Regulatory targets are typically 3 to 4 log.
| Organism group | Examples | 3-log dose | At this dose |
|---|---|---|---|
| Gram-negative bacteria | E. coli, Salmonella, Vibrio cholerae | 3–6 | |
| Protozoa (oocysts) | Cryptosporidium parvum, Giardia lamblia | 3–10 | |
| Gram-positive bacteria | Staphylococcus, Bacillus (vegetative), Listeria | 6–10 | |
| RNA viruses | Rotavirus, norovirus, hepatitis A, SARS-CoV-2 | 12–40 | |
| Fungi and moulds | Aspergillus, Fusarium, Candida | 45–100 | |
| Bacterial spores | Bacillus anthracis spores, Clostridium | 80–150 | |
| DNA viruses | Adenovirus, reovirus | 40–200 |
Doses for low-pressure UV at 253.7 nm. Medium-pressure UV can reach similar inactivation at lower nominal doses for some organisms. Water quality (UVT, turbidity, suspended solids) strongly affects the dose actually delivered. Reference points: 4-log (99.99%) Cryptosporidium inactivation at 22 mJ/cm²; typical reactor residence time under 10 ms.
Delivering the dose to every drop.
Dose depends on irradiance, contact time, water quality and reactor geometry. Getting the right dose to every water molecule is the central engineering challenge.
- 01
UV dose (fluence)
Dose = Irradiance × Time
Irradiance (W/cm²) times exposure time (s), in mJ/cm². In a flow-through reactor, time is set by flow rate and reactor volume. Minimums: 16 mJ/cm² for US EPA drinking water (Cryptosporidium 2-log); 40 mJ/cm² for wastewater reuse in many jurisdictions.
- 02
UV transmittance (UVT)
UVT = T₂₅₄ × 100%
How much 254 nm light passes through 1 cm of water. High-quality drinking water: 90 to 98%. Secondary wastewater effluent: 55 to 75%. Iron, natural organic matter, turbidity and UV-absorbing compounds lower it, demanding pre-treatment or more lamp output.
- 03
Sleeve fouling & ageing
UVT × lamp age × fouling
Quartz sleeves foul with scale, iron and biofilm, and lamps lose 20 to 30% of output over their life. UV sensors and automatic dose monitoring correct for it; sleeve cleaning with chemical or mechanical wipers and lamp replacement are the key O&M tasks.
- 04
Reactor hydraulics
CFD + biodosimetry
Flow patterns mean not every molecule gets the same dose. Reactors are validated by biodosimetry and computational fluid dynamics, establishing a Reduction Equivalent Dose for each validated flow rate.
In the US, drinking-water UV systems are validated under the UV Disinfection Guidance Manual using Tier 1 or Tier 2 protocols with MS2 phage or Cryptosporidium parvum. European systems are tested under DVGW W294 or equivalent national standards. Validation must be done at maximum design flow and minimum UVT.
What AOP can destroy.
Its non-selective radical chemistry makes AOP uniquely effective against contaminants of emerging concern: micropollutants present at ng/L to µg/L with documented effects on ecosystems and health.
Pharmaceuticals & hormones
- Antibiotics (ciprofloxacin, erythromycin): a driver of antimicrobial resistance
- Oestrogens (17α-ethinylestradiol, estrone): endocrine disruption in aquatic life
- Anti-epileptics (carbamazepine): highly resistant to biodegradation
- NSAIDs (ibuprofen, diclofenac): detected in drinking water sources worldwide
- Antidepressants, cytostatics, contrast agents
Pesticides & herbicides
- Atrazine: endocrine disruptor, highly persistent in groundwater
- Glyphosate and its AMPA metabolite
- Chlorpyrifos, imidacloprid: neonicotinoids affecting invertebrates
- Organochlorine pesticides (lindane, DDT metabolites)
- Fungicides (azoxystrobin, tebuconazole)
PFAS, “forever chemicals”
- PFOA: linked to cancer and immunotoxicity
- PFOS: persistent, bioaccumulative
- Short-chain PFAS replacements, increasingly regulated
- High-energy UV/AOP is one of few processes able to break C–F bonds
- Vacuum UV (185 nm) is particularly effective
Industrial & household chemicals
- 1,4-dioxane: solvent stabiliser, UV/AOP is the primary treatment
- NDMA: disinfection by-product and carcinogen
- MTBE: fuel additive in groundwater
- TCE and PCE: chlorinated solvents
- Bisphenol A: plasticiser with endocrine effects
Completely resistant to activated carbon and biodegradation, 1,4-dioxane is a canary for groundwater contamination, and UV alone does not remove it. UV/H₂O₂ is the primary recommended treatment in drinking water and remediation, and many AOP specifications are sized around a target dioxane reduction as proof of radical capacity.
Where UV and AOP are deployed.
From municipal plants to beverages and semiconductors.
- Primary disinfection
Municipal drinking water
The dominant technology for Cryptosporidium and Giardia in surface water, often with chloramination for the network. AOP controls micropollutants in indirect potable reuse.
- AOP for CECs
Wastewater reuse
Advanced reclamation plants, such as Singapore's NEWater and Orange County's GWRS, rely on UV/AOP as a cornerstone barrier for potable reuse.
- Chemical-free
Food & beverage
Disinfection of process, rinse and bottle-wash water in brewing, soft drinks, dairy and juice, where chemical residuals would affect taste or status.
- RAS systems
Aquaculture
Inactivates fish pathogens such as VHS and IHN viruses in recirculating systems. Essential for salmonid hatcheries and high-value species.
- 185 nm VUV
Pharma & semiconductor
Ultra-pure water with TOC below 10 ppb. Vacuum UV at 185 nm breaks trace organics down to CO₂.
- IMO D-2
Ballast water
UV-based systems are the dominant IMO type-approved technology, treating thousands of m³ per hour to stop invasive species transfer.
- FSMA
Agricultural water
Disinfection of irrigation water against E. coli O157:H7 and Listeria as produce safety rules tighten (FSMA, EU Reg. 2020/741).
- Chloramines
Pools & spas
Medium-pressure UV destroys the chloramines behind “pool smell” and irritation, cutting levels by 50 to 80% and allowing less chlorine.
- PFAS, 1,4-dioxane
Groundwater remediation
The primary treatment for groundwater carrying 1,4-dioxane, PFAS, chlorinated solvents and MTBE at pump-and-treat sites.
UV and AOP questions.
The questions we are asked most, answered briefly.
Does UV leave anything in the water?
No. UV adds no chemicals and forms no disinfection by-products such as trihalomethanes, haloacetic acids or bromate. The flip side is that it leaves no residual, so distribution networks often add a low chlorine dose after UV.
What UV dose do I need?
It depends on the target organism and regulation. For example, 16 mJ/cm² meets the US EPA 2-log Cryptosporidium requirement for drinking water, 40 mJ/cm² is common for wastewater reuse, and 3-log adenovirus inactivation needs about 186 mJ/cm² with low-pressure UV.
What is advanced oxidation?
AOP combines UV with an oxidant, usually hydrogen peroxide or ozone, to generate hydroxyl radicals: the most powerful oxidant used in water treatment. They destroy micropollutants that UV or chemicals alone cannot, such as 1,4-dioxane, pharmaceuticals and some PFAS.
Low-pressure, medium-pressure or UV-LED?
Low-pressure lamps are the efficient standard for drinking and wastewater. Medium-pressure lamps suit high flows and resistant organisms. UV-LEDs are mercury-free and compact, best for point-of-use and on-demand systems, and improving fast.
The right dose, validated.
Tell us your flow rate, water quality and regulatory target. Book a meeting and we will confirm within minutes, or write to us on WhatsApp.
Denmark and Saudi Arabia. Serving the European Union and the Middle East, in English and Arabic.
- WhatsApp+966 55 455 4158
- Phone+966 55 455 4158
- Phone+966 53 968 6765
- Emailcontact@aggregatorsolutions.com
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Technical data is provided for reference only. Regulatory requirements vary by jurisdiction. System sizing and validation should be performed by qualified engineers in accordance with applicable standards (UVDGM, DVGW W294, ÖNORM M 5873 and others). UV dose requirements depend on water quality characterisation at the point of installation.