Winery wastewater, an environmental problem
Wineries generate liquid effluents during the cleaning of tanks, presses, floors, and equipment. These wastewaters are characterized by a high organic load, strong seasonal variability (especially during the harvest), and the presence of phenolic compounds and residues from oenological products. Their treatment is essential to limit environmental impact and comply with discharge regulations.
Among advanced processes, ozonation has proven to be an effective technique to improve wastewater quality prior to discharge or reuse.
Characteristics of winery wastewater
- High organic load: COD ranging from 2,000 to 15,000 mg/L depending on the period.
- Presence of colored and phenolic compounds, which are difficult to biodegrade.
- Seasonal variability: pollution peaks during the harvest season.
- Variable pH (often acidic after fermentation).
These characteristics make conventional biological treatments sometimes insufficient.
Principle of ozonation
Ozone (O₃) is a powerful oxidant (redox potential +2.07 V). When injected into water, it:
- Directly oxidizes organic matter,
- Degrades phenolic compounds responsible for color and toxicity,
- Generates hydroxyl radicals (•OH) in aqueous media, further enhancing oxidative action.
Advantages of ozonation for winery effluents
Winemaking generates large volumes of wastewater, particularly during harvest and cleaning operations. These effluents are typically acidic, strongly colored, and rich in organic matter, with chemical oxygen demand (COD) ranging from 2,000 to 15,000 mg/L. The high variability in composition and flow poses challenges for wastewater treatment.
- Reduction of COD and BOD: improves biodegradability.
- Decolorization through oxidation of anthocyanin pigments.
- Odor removal and reduction of toxicity.
- Compatibility with other processes: ozone can be used as pretreatment before a biological stage (lagooning, activated sludge), or as post-treatment to refine water quality.
- On-site production: ozone is generated by an ozonizer, eliminating the need for hazardous storage.
Applications and Reported Results
Studies have shown that:
- COD can be reduced by 40–70%, depending on operating conditions.
- Biodegradability (BOD₅/COD ratio) improves significantly after ozonation, facilitating subsequent biological treatment.
- When combined with biological treatment, effluents can meet European discharge standards (< 125 mg/L COD).
Conclusion
Ozonation is a highly effective solution for the treatment of winery wastewater, particularly in degrading phenolic compounds and improving effluent biodegradability. It is most often integrated into a combined treatment process (physico-chemical pretreatment + ozonation + biological stage).
Ozone remains a sustainable technology, well suited to high-strength winery effluents and increasingly strict environmental requirements.
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