Treatment methods for emulsified oil wastewater

With the continuous enhancement of environmental awareness, the treatment effect of production measures residue is also receiving more and more attention, especially the treatment of emulsified oil residue, which is urgent. Because emulsified oil contains oil, general physical filtration methods are not effective and are the most difficult type of oily residue to treat. The current methods for treating emulsified oil residue mainly include flocculation, adsorption, membrane separation, magnetic separation, etc. The study of these processing techniques lays a solid theoretical foundation for future research on better processing methods.

1. Analysis of the basic situation of emulsified oil wastewater
Emulsified oil is mainly an oily mixture discharged during the dehydration process of crude oil
Due to the presence of surfactants in this residual liquid, the crude oil in the liquid is emulsified, which enhances the stability and adsorption of the oil. Therefore, it is difficult to treat it using general physical and chemical methods. After oil emulsification, the types and contents of organic compounds in the emulsion increase. For example, CODCr is usually tens of thousands of mg/L, and its composition is no longer just emulsified oil. It contains a large amount of surfactants and other additives, which increase the difficulty of treating emulsified oil wastewater. At present, the methods used in wastewater treatment, such as oil separation, centrifugation, demulsification, flotation, and electrolysis, have certain limitations on the treatment of emulsified oil wastewater. It is not possible to treat emulsified oil wastewater that meets purification requirements. However, combining the above methods has a significant effect on improving the treatment of emulsified oil wastewater. Therefore, further research and innovation in emulsified oil wastewater treatment technology are still needed.
2. Research on Emulsified Oil Wastewater Treatment Technology
2.1 Flocculation method
The flocculation method mainly involves adding flocculants to wastewater to exert their electrostatic, adsorption bridge, and net trapping and sweeping effects, causing the stability of emulsified oil droplets to be disrupted, reducing their adhesion, and then using floc settling or floating to achieve oil-water separation. Researchers have added an appropriate amount of phosphoric acid to polyaluminum chloride and polymeric ferric sulfate, which react to produce polyaluminum chloride and polymeric ferric sulfate. Their emulsified oil flocculation effect is significantly higher than that of polyaluminum chloride and polymeric ferric sulfate, and the wastewater treatment cost of these two substances is also lower. With the application and research of flocculation method, more and more researchers have conducted further research on the treatment principle of this method. Some scholars have obtained amphiphilic cationic chitosan based flocculants through grafting copolymerization of chitosan and acryloyloxyethyl dimethylbenzylammonium chloride, and then used the obtained amphiphilic cationic chitosan based flocculants for emulsified oil wastewater treatment, It was found that the treatment effect of this flocculant is even more ideal than that of polyphosphate aluminum chloride and polyphosphate iron sulfate, and relevant scholars were encouraged to study the innovation of flocculants. Although the flocculation method is relatively simple in terms of process, it mainly uses chemical reactions to obtain flocculants, and their wastewater treatment capacity is also very good. However, this method still has shortcomings, such as requiring a long waiting time to put the flocculants into the wastewater. If floating flocs are formed, it is easy to cause them to be difficult to separate, which affects the purification effect.
2.2 Adsorption method
Adsorption method is a method that can be understood by its name. It mainly involves adding adsorption materials to wastewater and then adsorbing pollutants in the wastewater.
The key to applying adsorption method is how to choose adsorption materials. If the selection of adsorption materials is appropriate, the treatment of emulsified oil wastewater can be said to have been successful for a large part. The most common adsorption method currently used is activated carbon, which has a strong ability to adsorb oil. However, it not only adsorbs oil, but also other organic substances in wastewater. However, the amount of activated carbon used in wastewater is limited, and the recycling and utilization of activated carbon is also relatively difficult. Considering its high treatment cost and limited adsorption capacity, activated carbon is also limited. If the control is not good, other organic substances may be adsorbed while oil is adsorbed very little, which completely fails to achieve the purpose of emulsified oil treatment. Therefore, the application of adsorption method to treat emulsified oil wastewater requires the development of targeted adsorbents for oil, and the application cost should be low, which is also the main direction of adsorption method application research. In recent years, adsorption resins have been gradually developed and applied. As a new type of adsorption material, some wastewater treatment enterprises have relatively few applications, but its adsorption capacity is still good. Unlike activated carbon, which is expensive and difficult to recover, its manufacturing cost is still acceptable. It is renewable and avoids the problem of difficult recovery. It can be said to be a very good adsorbent. In order to better innovate the adsorption method, some scholars have developed a macroporous adsorption resin containing benzene rings and good hydrophilicity through suspension polymerization. This can effectively improve the absorption capacity of the adsorption resin, and its regeneration principle is mainly obtained through extraction, which is relatively simple and easy to operate.
2.3 Membrane separation method
Membrane separation method is a newly developed physical separation method in recent years, which mainly uses filter membranes made of special materials to analyze pollutants in wastewater. The principle of separation is to use the size of pollutants for filtration and separation.
There is still a certain difference between this and traditional separation membranes. Traditional separation membranes mainly include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes, which use the size of ion diameter to achieve rough separation. However, for separation membranes that are easily contaminated by oil substances or have poor chemical and physical properties, their application in emulsified oil wastewater not only fails to purify but may also aggravate the pollution level of wastewater, So using membrane separation method requires a new type of material separation membrane that is suitable for oil-water separation to be feasible. Now researchers have studied the characteristics of oil-water separation membranes with special wettability to separate oil and water from oil-water mixtures. Among them, superhydrophilic oleophobic membranes are particularly suitable for the treatment of emulsified oil wastewater. This type of separation membrane utilizes the superhydrophobicity of the membrane surface to make oil droplets stay on the surface of the separation membrane, while water can penetrate to the other side of the separation membrane, achieving the purpose of oil-water separation. The membrane separation method is relatively simple, but the requirements for the production and material selection of the separation membrane are relatively high. It is necessary to meet the requirements of oil-water separation and ensure the stability of the chemical and physical properties of the separation membrane. Therefore, attention should be paid to the research and application of new materials in the membrane separation process.
2.4 Magnetic Separation Method
Magnetic separation method can be said to be a relatively new wastewater treatment method in emulsified oil wastewater treatment technology, and this treatment method is relatively energy-saving in terms of energy consumption
Compared to other treatment methods, the area occupied is relatively small, the operation process is relatively simple and flexible, and the separation efficiency is high. It is easy to recover and meet the current environmental protection policy requirements for recycling and reuse, greatly reducing environmental pollution. Therefore, the development and application prospects of this method in the future treatment of emulsified oil wastewater are quite promising. The Fe3O4 nanoparticles used in the magnetic separation method for wastewater treatment are relatively easy to obtain, which can effectively reduce the cost of emulsified oil wastewater treatment. The surface modification of this material is very strong, and the surface wettability of magnetic nanoparticles can be adjusted to improve the separation of oil containing substances in emulsified oil wastewater by nanoparticles, thereby achieving the purpose of purifying emulsified oil wastewater.
2.5 Microbial detachment method
The reason why wastewater discharge pollutes the environment is because the organic matter contained in wastewater can easily breed bacteria in mixed environments, and promote the growth of some microorganisms in the wastewater. Over time, the wastewater will emit an unpleasant odor. Based on this principle, the microbiological separation method can be used to separate the organic matter in wastewater, reducing the incidence of organic matter breeding bacteria. Nowadays, many industrial wastewater treatment processes are using this method. In addition to being able to separate organic matter from wastewater, the microbial separation method can also use the chemical reaction between microorganisms and organic matter to obtain certain chemical substances required by industry. For the wastewater treatment industry, this not only achieves the goal of wastewater purification but also obtains the substances required for industrial production, Especially for the emulsified oil wastewater discharged from petroleum production, the effect of using microbial separation method is still quite significant, because the wastewater discharged from petroleum production contains more organic compounds. In addition, the cost of microbial detachment method is relatively low, and its impact on the environment is also very small, making it an advanced sewage treatment method at present.
3. Conclusion
Through the analysis of the basic situation of emulsified oil wastewater generation and the technology of emulsified oil wastewater treatment, it is known that the treatment of emulsified oil wastewater is much more difficult compared to other types of wastewater treatment. However, with the rapid development of the petroleum industry, machinery manufacturing, and food production enterprises, the discharge of emulsified oil wastewater is increasing. Although flocculation and adsorption methods have achieved certain results, the separation efficiency is still low, and recycling and utilization are difficult, The requirements for environmental protection and recycling policies are still lacking, so further research and development of emulsified oil wastewater treatment technology is an important task for effectively treating industrial wastewater today.