Photochemical oxidation combining UV photolysis with hydrogen peroxide to generate hydroxyl radicals that mineralise recalcitrant organics, dyes, and micropollutants.
UV/H2O2 AOP uses ultraviolet light (typically 254 nm) to photolyse hydrogen peroxide, generating hydroxyl radicals (OH →) with an oxidation potential of 2.8 V. These radicals non-selectively attack and break down complex organic molecules including pharmaceuticals, pesticides, dyes, and endocrine disruptors. The process is particularly effective for water reuse applications, pharmaceutical wastewater, and effluents with variable organic composition.
Unlike Fenton AOP, UV/H2O2 produces no iron hydroxide sludge – only H2O2 and UV are consumed.
254 nm UV provides simultaneous disinfection achieving 4-6 log pathogen reduction alongside oxidation.
Effluent contains only water, CO2, and trace salts – ideal for direct reuse without further polishing.
H2O2 dose automatically adjusted based on online UV transmittance (UVT) monitoring.
Step-by-step breakdown of the treatment process from influent to effluent.
Optimal pH for UV/H2O2 is neutral to mildly acidic. pH adjustment with CO2 or sulphuric acid ensures maximum OH → generation efficiency.
If influent UVT <65%, pre-treatment (coagulation or filtration) improves UV penetration. Online UVT analyser triggers automatic adjustments.
Hydrogen peroxide (technical grade 35-50%) dosed via metering pump at 200-2,000 mg/L depending on target COD reduction. Static mixer ensures uniform distribution.
Medium-pressure UV lamps (1-5 kW per m3/h) provide 254 nm photons for H2O2 photolysis. Residence time 5-30 minutes. UV fluence 400-1,500 mJ/cm2.
Any residual H2O2 quenched with sodium bisulfite (1:1 stoichiometric) or allowed to decompose naturally in holding tank. Final effluent H2O2 <0.1 mg/L.
Explore the equipment components that make this process effective.
Medium-pressure UV system with quartz sleeves, automatic wiping, 254+185 nm option.
Day tank, metering pump, static mixer, online residual monitor.
Online UV transmittance analyser for automatic dose adjustment.
CO2 or acid dosing for optimal UV/H2O2 pH range.
Destroy active pharmaceutical ingredients in wastewater to prevent environmental contamination.
Break down reactive dyes and colour compounds resistant to advanced biological treatment.
Polish biological effluent to reuse quality by removing trace organics and pathogens.
Treat effluents containing phenols, solvents, and chlorinated organics.
This treatment stage is engineered to achieve specific contaminant removal targets while providing stable, predictable performance across variable inlet conditions. Design parameters are calculated from wastewater characterisation data, regulatory requirements, and site-specific constraints including footprint, energy availability, and operator capability.
Design validated by CFD modelling and pilot testing to confirm performance guarantees.
Equipment selected for 20-year design life with minimal wearing parts and easy access.
Automated dosing and feedback control minimise reagent consumption and sludge production.
Online monitoring and data logging demonstrate continuous consent compliance.
| Design Flow | 10 – 5,000 m³/h (application specific) |
| Inlet Variability | Designed for 1:3 peak-to-average flow ratio |
| Removal Efficiency | 85 – 99% depending on target contaminant |
| Hydraulic Retention | Calculated from kinetic constants and safety factors |
| Power Consumption | 0.5 – 5.0 kWh/100 m³ (process dependent) |
| Chemical Dose | Auto-controlled based on online analysers |
| Sludge Production | 0.2 – 1.5 kg DS/kg contaminant removed |
| Materials | SS304, SS316L, or carbon steel with coating |
No treatment stage operates in isolation. This process is designed to receive conditioned influent from upstream stages and deliver effluent quality suitable for downstream processes. Hydraulic and organic loading rates are balanced across the complete treatment train to prevent bottlenecking and ensure overall plant efficiency. Our engineers model the complete flowsheet to optimise Capital expenditure and Operating expenditure across the plant lifecycle.
Screening, equalisation, and pre-treatment protect this stage from damage and overload.
Effluent quality ensures downstream biology, filtration, or disinfection performs optimally.
Reject streams, filtrate, and centrate are routed back to appropriate upstream points.
Fluence, quantum yield and dose-response calculations for validated AOP performance.
Fluence H = I0 × t × Tf, where I0 = incident irradiance (mW/cm2), t = exposure time (s), and Tf = transmittance factor. Target H = 400–1,500 mJ/cm2 for AOP; 40–100 mJ/cm2 for disinfection alone.
H2O2 photolysis quantum yield Φ ≈ 0.5 mol/E at 254 nm. Second-order rate constant for OH• + organics: 108–1010 M−1s−1. Pseudo-first-order decay constant kobs = 0.05–0.5 min−1 for typical industrial effluents.
Theoretical demand = 2.1 g H2O2 per g COD. In practice, dose 1.2–2.5 × theoretical. Excess >500 mg/L scavenges OH• and raises residual quenching cost.
Reactor validation requires chemical actinometry (iodide/iodate, ferrioxalate or uridine). Delivered fluence must be within ±10 % of design value for consent compliance.
| Attribute | UV/H2O2 | O3/UV | Photo-Fenton | O3 Only |
|---|---|---|---|---|
| Sludge | None | None | Medium–high | None |
| pH window | 5.5–7.0 | 6–9 | 2.5–3.5 | 6–9 |
| HRT | 5–30 min | 10–30 min | 30–120 min | 10–30 min |
| Energy (kWh/kg COD) | 4–8 | 3–6 | 1.5–4.0 (solar) | 2.5–5.0 |
| Best for | Low TSS, water reuse | Micropollutants, pharma | High COD, coloured effluent | Decolourisation, disinfection |
Influent UVT drops due to humics or colour. Pre-treat with coagulation or GAC if UVT <55 %. Online UVT analyser triggers automatic H2O2 dose reduction to avoid excess residual.
Low-pressure Hg lamps lose 10–15 % output per 8,000 h; medium-pressure 20–30 % per 5,000 h. Replace at 80 % of nominal output. Calibrate UV intensity sensor quarterly.
If quench system fails, residual >0.1 mg/L can corrode downstream stainless steel. Install redundant bisulfite dosing with ORP feedback control.
Reactor temperature >35 °C accelerates H2O2 thermal decomposition and reduces UV lamp efficiency. Provide ventilation or cooling water for medium-pressure lamps.
German technical rule for UV disinfection — dose validation, sensor placement and monitoring protocols.
U.S. UV Guidance Manual for validated dose calculation, reactor certification and RED testing.
Water quality — determination of the inhibitory effect of water samples on V. fischeri (luminescent bacteria test) for AOP effluent toxicity screening.
Safety of UV reactor electrical systems, including earth-fault and emergency-stop interlocks.
Our engineers design and commission complete treatment systems including all equipment, automation, and commissioning support.
Our expertise spans multiple industries with sector-specific water treatment solutions.