Generation and Treatment of Oil-Containing Wastewater from Waste Tire Pyrolysis

Generation and Treatment of Oil-Containing Wastewater from Waste Tire Pyrolysis

I. Sources of Oil-Containing Wastewater

Oil-containing wastewater from waste tire pyrolysis mainly originates from the following stages:

Oil Refining Process: Wastewater containing oil, acids, alkalis, and organic compounds is generated during the acid washing, alkali washing, or water washing of crude pyrolysis oil.

Condensation and Cooling Stage: Partially separated oil mixes with cooling water during the condensation of pyrolysis gas, forming oil-containing wastewater.

Equipment Cleaning: Cleaning of pyrolysis furnaces, oil storage tanks, and other equipment produces wastewater with residual oil.

Tail Gas Treatment: Washing acidic tail gas with water or alkali generates wastewater containing sulfur and oil.

II. Mainstream Treatment Methods

1. Pre-Treatment: Oil-Water Separation

Gravity Separation: Using the density difference between oil and water, a gravity oil separator removes approximately 60%–80% of floating oil.

Dissolved Air Flotation (DAF): Microbubbles are introduced to attach to fine oil droplets, making them float for removal of emulsified and dispersed oil.

Demulsification: Demulsifiers, ultrasound, or electrolysis break the emulsified state of oil droplets, improving subsequent treatment efficiency.

2. Advanced Treatment: Pollutant Degradation

Biological Treatment: Anaerobic and aerobic biological processes degrade organic pollutants such as COD and BOD, serving as the mainstream advanced treatment technology.

Membrane Separation: Ultrafiltration and nanofiltration membranes precisely intercept oil and organic matter, ensuring stable effluent quality but with higher membrane costs.

Advanced Oxidation Process (AOP): Strong oxidants like ozone or Fenton reagents decompose refractory organic compounds, suitable for pre-treatment of high-concentration wastewater.

3. Recycling and Discharge Compliance

Treated wastewater must meet the Integrated Wastewater Discharge Standard (GB 8978-1996) or stricter local standards. Qualified effluent can be recycled for cooling, cleaning, etc., to achieve efficient water resource utilization.