Wastewater ozonation is a modern method of deep treatment used as a final stage before discharge to water bodies or water reuse. Ozone is a powerful oxidizer that effectively breaks down complex organic compounds, providing disinfection without forming toxic chlorinated organics.
The method is especially effective for treating industrial effluents containing phenols, oil products, surfactants (SAS), pesticides and other hard-to-oxidize organic compounds. After ozonation, water is safe for discharge to water bodies without long dechlorination.
Effluent disinfection methods comparison
| Parameter | Ozonation | Chlorination |
|---|---|---|
| Disinfection effectiveness | 99.9% | 99% |
| Organic oxidation | High | Low |
| Byproducts | O₂ (safe) | Chlorinated organics (toxic) |
| Dechlorination required | No | Yes |
| Effect on COD/BOD | Reduces by 50-95% | Minimal |
| Color removal | Yes (up to 80%) | No |
| Odor removal | Yes | Masks |
| Safety for water bodies | High | Requires monitoring |
Wastewater ozonation technical parameters
| Wastewater type | Ozone dose, mg/L | Contact time, min |
|---|---|---|
| Domestic (after biological treatment) | 5-15 | 10-15 |
| Industrial (organic) | 20-50 | 15-30 |
| Oil-containing effluents | 30-100 | 20-40 |
| Phenol-containing effluents | 15-30 | 15-20 |
| Surfactant-containing effluents | 10-25 | 10-20 |
| Food industry effluents | 10-20 | 10-15 |
Wastewater treatment process
Mechanical treatment
Removal of coarse impurities, sand, suspended solids. Mandatory stage before ozonation.
Biological treatment
Aerobic or anaerobic biological treatment to reduce BOD to 15-30 mg/L. Ozonation is applied after this stage.
Ozone generation
Production of ozone from oxygen by corona discharge method. Ozone concentration in gas: 6-12%.
Contact chamber
Mixing ozone-air mixture with effluents through bubbling system. Contact time: 10-30 minutes depending on contamination level.
Clarification
Settling or filtration to remove oxidized insoluble compounds.
Quality control
Analysis of treated water for compliance with discharge standards: BOD, COD, suspended solids, coliform index.
Pollutants removed by ozonation
- Phenols and nitrophenols: oxidation to CO₂ and H₂O, reduction to MPC levels
- Oil products: destruction to simple organic acids
- Surfactants (SAS): molecular structure breakdown
- Pesticides and herbicides: oxidation to non-toxic compounds
- Dyes and pigments: complete effluent decolorization
- Pathogenic microflora: inactivation of bacteria, viruses, helminth eggs
- Ammonium nitrogen: oxidation to nitrates
- Hydrogen sulfide and mercaptans: elimination of unpleasant odors
Wastewater ozonation results
| Parameter | Before ozonation | After ozonation | Efficiency |
|---|---|---|---|
| Color, degrees | 70-100 | 10-20 | 80-85% |
| Turbidity, mg/L | 30-50 | 5-10 | 75-80% |
| BOD₅, mg/L | 20-30 | 3-5 | 85-90% |
| COD, mg/L | 50-80 | 15-25 | 65-70% |
| Coliform index | 10,000 | < 1,000 | > 90% |
| Odor | Swamp-fecal | Absent | 100% |
Data obtained when treating effluents with ozone dose of 50 mg/L in contact chamber with contact time of 15 minutes. At ozone doses above 50 mg/L, color, turbidity and odor disappear, coliform index decreases to regulatory values.
Benefits of wastewater ozonation
Waste-free process
Ozone is synthesized from air oxygen and decays back to oxygen. No reagent purchase or storage required.
Universality
Effective against any organic pollutants: phenols, oil products, surfactants, pesticides.
Ecological safety
Does not form toxic byproducts. Water is safe for discharge to water bodies without dechlorination.
Reuse
After ozonation, water can be used for technical purposes: irrigation, washing, cooling.
Applications
| Industry | Main pollutants | Ozone dose, mg/L |
|---|---|---|
| Oil refineries | Oil products, phenols, sulfides | 50-100 |
| Chemical plants | Organic solvents, surfactants | 30-80 |
| Food production | Fats, proteins, organic acids | 15-30 |
| Textile factories | Dyes, surfactants | 20-50 |
| Pulp and paper mills | Lignin, resins | 30-60 |
| Municipal treatment plants | Domestic effluents after biological treatment | 10-20 |
Discharge regulatory requirements
- SanPiN 2.1.5.980-00 «Hygienic requirements for surface water protection»
- MPC of harmful substances in water bodies for domestic and drinking water use
- Ministry of Natural Resources Order No. 333 dated 17.12.2007 «On approval of MPD development methodology»
- GOST 17.1.3.13-86 «Nature protection. Hydrosphere. General requirements for surface water protection from pollution»