Fenton Reactor
Refractory wastewater from pharmaceutical, printing and dyeing, chemical, and landfill leachate sources often contains highly toxic, highly colored, and poorly biodegradable organic matter. As the most mature homogeneous advanced oxidation process in application, Fenton oxidation involves dosing ferrous salts and hydrogen peroxide into acidic wastewater to generate highly active hydroxyl radicals (·OH) in situ, which break molecular chains and mineralize organic matter—the process is mature, fast to start, low in investment, and easily integrated with existing facilities. It remains one of the most commonly used and most reliable means for advanced treatment and pretreatment of refractory wastewater.
I. Product Positioning
The Fenton reactor is a homogeneous advanced oxidation unit that doses soluble Fe²⁺ (such as ferrous sulfate) and H₂O₂ (hydrogen peroxide) to carry out the Fenton reaction under acidic conditions. It typically integrates chemical dosing, pH adjustment, rapid mixing, oxidation reaction, neutralization and flocculation, and sludge-water separation into a single system, supplied as a skid-mounted unit of "Fenton oxidation + coagulation sedimentation." It is used for advanced oxidation and pre-biochemical pretreatment of refractory wastewater, and is the chemical oxidation equipment with the richest engineering case history and the easiest operation to master.
II. Working Principle (Brief)
Acidification: Acid is added to the wastewater to adjust it to acidic conditions (pH approximately 2–4), creating a suitable environment for the Fenton reaction.
Chemical dosing and mixing: Fe²⁺ and H₂O₂ are dosed and rapidly mixed to ensure uniform contact between chemicals and wastewater.
Fenton reaction: Fe²⁺ reacts with H₂O₂ to generate Fe³⁺ and highly active ·OH; ·OH non-selectively breaks molecular chains, mineralizes organic matter, and achieves decolorization and detoxification.
Reaction maturation: Sufficient residence time is provided in the oxidation stage for complete reaction; chemicals may be supplemented in stages if necessary to enhance oxidation efficiency.
Neutralization and pH adjustment: Alkali is added to adjust pH back to neutral, causing Fe³⁺ to hydrolyze and form ferric hydroxide flocs.
Flocculation and sedimentation: PAM is dosed for flocculation, iron sludge is separated by sedimentation, and the clear liquid proceeds to subsequent processes.
Process flow: Wastewater → Acidification (pH 2–4) → Dosing of Fe²⁺ + H₂O₂ → Fenton reaction (·OH mineralization) → Maturation → Neutralization and pH adjustment → Flocculation and sedimentation (iron sludge) → Clear liquid to subsequent processes
The core lies in "the chemicals themselves generate the active species": Fe²⁺ catalytically decomposes H₂O₂ to generate ·OH, which has extremely strong oxidizing power and no selectivity; after the reaction, Fe³⁺ is neutralized and flocculated to form iron sludge for separation. The process is mature and reliable, operating at ambient temperature and pressure, but the iron salt is dosed in dissolved form, which is the fundamental reason for its relatively high iron sludge production (this is also the key difference from electro-Fenton, which features "iron cycling and low sludge").
III. Core Advantages
① Mature process: A century of application experience, clear mechanism, abundant engineering cases, and controllable operational risk.
② Fast start-up: Ambient temperature and pressure, immediate reaction upon dosing, no complex start-up or biofilm cultivation period required.
③ Strong oxidation: ·OH non-selectively breaks chains and mineralizes, simultaneously reducing COD, decolorizing, and breaking biological toxicity.
④ Low investment: Simple equipment, no special electrodes or ozone generation systems required, cost-friendly.
⑤ Wide adaptability: Easily coupled with coagulation sedimentation, aeration, and biochemical systems; can serve as an advanced polishing unit.
⑥ Flexible and adjustable: Chemical ratio, pH, and dosing points can be optimized according to water quality; multi-point dosing improves efficiency.
IV. Main Technical Parameters (Reference Ranges)
Item | Parameter Range / Description | Remarks |
|---|---|---|
Treatment capacity | 1 – 200 m³/h | Skid-mounted to engineered scale, typical range reference |
Influent COD (applicable) | ≤ 2000 mg/L | Pretreatment or advanced stage, typical range reference |
COD removal rate | 20% – 60% | Varies with water quality and operating conditions, typical range reference |
Operating pH (oxidation stage) | 2 – 4 | Weak acid Fenton window, typical range reference |
H₂O₂ dosage | 0.5 – 3 mol / mol COD | Or based on actual water quality, typical range reference |
Fe²⁺ / H₂O₂ molar ratio | 1/10 – 1/4 | Optimized according to water quality, typical range reference |
Reaction residence time | 30 – 120 min | Oxidation + maturation, typical range reference |
Iron sludge yield | Approximately 0.5 – 1.5 kg DS / kg COD removed | Higher than electro-Fenton, requires supporting disposal, typical range reference |
* The above are typical reference ranges. Actual scale, removal rate, chemical consumption, and iron sludge quantity shall be determined by design calculations and on-site bench tests/commissioning.
V. Typical Application Scenarios
Scenario / Industry | Adaptability Description / Main Function |
|---|---|
Pharmaceutical wastewater | Detoxification and mineralization of antibiotic mother liquor and highly toxic refractory organics |
Printing and dyeing wastewater | Efficient decolorization, TOC reduction, and breakdown of chromophoric groups |
Chemical / pesticide wastewater | Advanced oxidation pretreatment of poorly biodegradable toxic organics |
Landfill leachate | Advanced COD reduction of NF/RO concentrate or raw liquid |
Coking wastewater | Chain scission and mineralization of phenols, cyanides, and polycyclic aromatic hydrocarbons |
Electroplating / PCB | Advanced polishing combined with complex breaking and COD reduction |
Industrial park comprehensive wastewater | Advanced upgrading after biochemical treatment to ensure stable compliance |
VI. Applicable Boundaries and Selection Recommendations
This product is suitable for pretreatment and advanced oxidation of refractory toxic wastewater. Operation requires acidification, neutralization, and supporting iron sludge dewatering and disposal; high concentrations of carbonates and strong complexing agents in water will quench ·OH or lock up iron, and must be pre-removed or conditioned. Ultra-high-concentration organic raw water should first undergo biochemical/physicochemical load reduction.
Selection is based on water volume, influent COD and biodegradability, and target removal rate to determine chemical dosage and reaction volume; it is recommended to first conduct bench tests with water samples to determine the H₂O₂/Fe²⁺ ratio, optimal pH, and dosing method (single-point/multi-point), and then scale up accordingly. Compared with electro-Fenton, this equipment is homogeneous Fenton with externally dosed chemicals (non-electrochemical, no electrodes), with higher iron sludge production but a mature process and low investment; the iron sludge disposal unit must be planned simultaneously.
Give refractory wastewater a "Fenton" treatment first
Rihong Environmental can provide process selection, chemical dosage ratio design, and complete equipment solutions for "Fenton + coagulation sedimentation" for Fenton reactors. Welcome to call or leave a message for a customized design.
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