Wastewater treatment in the oil industry encompasses the wastewater management of vegetable oil refineries, margarine production, olive oil (black water), and cooking oil packaging facilities. Although this sector has one of the lowest water consumption rates, it has the highest levels of wastewater concentration.
The BOD value in oil wastewater is extremely high, ranging from 2,000-10,000 mg/L, COD from 5,000-30,000 mg/L, and oil-grease content from 500-15,000 mg/L. The pH of saponification (caustic neutralization) wastewater fluctuates between 11-13, while the pH of fatty acid wastewater ranges from 2-3. Therefore, flow separation and balancing are essential.
Arsistek's oil sector solutions include a combination of API oil separator, DAF (dissolved air flotation), neutralization, balancing tank, anaerobic UASB, and aerobic biological treatment. The recovered oil-grease becomes a marketable biofuel or raw material for soap.
Wastewater Structure in the Oil Sector
Five main processes in vegetable oil production generate wastewater: pressing, extraction, neutralization, bleaching, deodorization. Each stage has a different composition.
Neutralization wastewater contains caustic (NaOH) and soap (sodium salts) — pH 11-13, COD 10,000+ mg/L. This is the most challenging effluent. Deodorization wastewater carries high temperature (80-90°C) and volatile free fatty acids.
Additionally, in the olive oil sector, karasu (vegetation water) is produced — COD 100,000-200,000 mg/L. This is seasonal (October-February) and a toxic effluent. Before standard biological treatment, evaporation, anaerobic or membrane concentration is required.
DAF + Oil Recovery
Dissolved Air Flotation (DAF) is an indispensable pre-treatment step in this sector. %95+ oil-grease removal efficiency is achieved.
The collected flotation sludge contains %20-40 oil. This sludge can be centrifuged and sold as crude oil — serving as a raw material for biodiesel or soap.
Anaerobic UASB Reactor
Post-DAF flow is treated in the UASB anaerobic reactor with 80-90% COD removal.
The produced biogas (source: 0.5 m³/kg COD removal) is used in the facility's steam boiler or dryer energy. The carbon footprint is reduced.
Olive Oil (Karasu) Special Condition
Olive oil production wastewater (black water) is one of the most difficult industrial wastewaters to treat in the world. BOD 100,000-200,000 mg/L, high polyphenol content, pH 4-5, and high toxicity level.
A 3-stage approach is recommended:
- Evaporation: Reduces concentration by 5-10 times
- Two-stage anaerobic: Acidogenic + methanogenic separation, over 85% BOD removal
- Aerobic post-treatment: Polyphenol biodegradation, compliance with discharge standards
Due to seasonal operation (October-February), biomass storage or feeding with hybrid plant wastewater strategy is implemented.
Advantages of Solutions in the Oil Sector
Oil Industry Reference Projects
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Frequently Asked Questions
DAF (dissolved air flotation) is the most effective technology for oil removal. It reduces from 15,000 mg/L inlet to <50 mg/L outlet with over 95% efficiency. Chemical breaking is combined with DAF for stable emulsions.
Yes. The float sludge collected from the DAF contains 20-40% oil. It can be purified using a centrifuge or hot/cold separator and sold to biodiesel producers or soap factories.
The Karasu COD is 100,000-200,000 mg/L — which is 20-100 times that of standard industrial wastewater. Additionally, polyphenols are bacterial inhibitors. Standard biological treatment does not work; evaporation + two-stage anaerobic treatment is required.
Approximately 0.5 m³ of biogas (CH4 ~75%) is obtained per 1 kg of COD removed in oil wastewater. Wastewater with a COD of 10,000 mg/L and a flow rate of 500 m³/day produces about 2,000 m³/day of biogas.
The olive season lasts for 4-5 months between October and February. Biomass is preserved using 3 methods: 1) Low load feeding (granulation is preserved), 2) Hybrid feeding — contribution with other organic wastewaters, 3) Granule storage (80% viability at 4°C for 6 months).
Engineering 1-2 months, manufacturing 3-4 months, on-site assembly 1-2 months, commissioning + biological adaptation 1-2 months. Total 6-10 months. Karasu projects require an additional pilot plant period.