Treatment Methods for Oil-containing Wastewater in Shale Oil Production
For the oil-containing wastewater in shale oil production, the following treatment methods can be applied:
1. Oil Separation:
Floating oil is removed from the wastewater through oil separation tanks or oil-water separators. In the oil separation tank, the difference in specific gravity between oil and water causes the floating oil to rise to the surface, from where it is discharged through a drainage pipe. An oil-water separator, on the other hand, uses physical principles to separate floating oil and suspended solids from the wastewater.
2. Demulsification and Flotation Treatment:
After oil separation, emulsified oil in the wastewater needs further treatment through a demulsification flotation tank. By adding demulsifiers and flotation agents, the emulsified oil is broken and floats to the surface, allowing for its removal.
3. Biological Treatment:
Microbial metabolism is used to convert organic substances in the wastewater into harmless materials. Common biological treatment methods include activated sludge and biological film processes. However, it is important to note that because the wastewater contains substances that can inhibit microbial activity, the effectiveness of biological treatment may be limited.
4. Physical and Chemical Treatment:
This includes methods such as adsorption, oxidation, and reduction to remove pollutants from the wastewater. These methods offer high treatment efficiency and stable results, but it is important to select appropriate treatment agents and control the treatment conditions.
5. Advanced Treatment:
Wastewater that still does not meet discharge standards after the above treatments requires advanced treatment. Methods for advanced treatment include advanced oxidation and membrane separation. Advanced oxidation uses oxidants to degrade the organic substances in the wastewater, while membrane separation utilizes the membrane’s separation properties to remove pollutants from the wastewater.
Disadvantages of Traditional Processes
1. Limited Oil-Water Separation Effect:
The oil-water separation effect is often limited because the concentration of chemicals and the temperature during the settling process sometimes do not meet the required standards. Additionally, the inability to regularly clean the inclined plate tank and failure to control the clear water according to standards also lead to oil and solids remaining in the produced water, increasing the difficulty of subsequent treatment.
2. Equipment Corrosion and Clogging Issues:
The high content of sulfides and bacteria in the produced water causes severe corrosion of wastewater treatment equipment, shortening the lifespan of the equipment. If calcium carbonate precipitates are not dealt with in time, they form hard lime scale that can block pipelines over time, reducing the flow rate of produced water and affecting the normal operation of equipment.
3. Insufficient Treatment Efficiency:
As the volume of produced water increases over time, the treatment capacity becomes inadequate, requiring an expansion of the produced water system, which increases investment and operating costs. Delays in oil recovery in the oil separator lead to filter pipe blockages, further affecting oil-water separation efficiency. In filtration tanks, compaction of filter media reduces the filtration effect, which impacts the water quality and its ability to meet discharge standards.
4. Environmental Pollution Issues:
After treatment, large amounts of oily sludge are produced. Due to insufficient sludge reinjection treatment capacity, the sludge cannot be processed quickly, posing environmental and safety risks. If the treated water does not meet quality standards and is directly discharged into the environment, it can cause pollution to soil and water bodies, impacting the ecological environment.
5. Technical Limitations:
For heavy oil produced water, due to its high viscosity, both extraction and treatment are very challenging. While high-pressure steam extraction methods can be used for heavy oil, the main challenge in subsequent produced water treatment is the high oil content, which increases the difficulty of wastewater purification. For low-permeability oil produced water, formation clogging is a major issue. To optimize produced water technology, adjustments to the filtration membrane coefficient for low-permeability oil are required, which increases technical complexity and costs.
High molecular polymers in polymer flooding wastewater increase the viscosity of the produced water, making it difficult to effectively separate oil and water, further increasing the treatment difficulty.
SINOKLE Patent Treatment Process
Through the patented technologies CDFU, CDOF, and the patented product KFM active filter media filter, the emulsified oil, suspended liquids, and solids in shale oil produced water can be significantly reduced. Different processes are selected based on discharge requirements, achieving efficient wastewater treatment and compliance with discharge standards. The process has the following advantages:
1. Strong resistance to shock conditions, with stable and reliable performance;
2. No chemical additives, purely physical demulsification, no aging oil, no secondary pollution, and good environmental benefits;
3. Short process flow, small footprint, fewer moving equipment, simple operation, and low operating costs;
4. Closed container design, overcoming the drawbacks of traditional flotation tanks influenced by environmental factors, ensuring efficient, continuous, and stable operation.
