Characterization and Innovative Process of Oily Wastewater from Substations

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In the context of today's carbon emission reduction, more and more people are be-ginning to pay attention to the treatment of oily wastewater generated from substations. The specific traits such as the complicated components and rapid change in the raw wastewater quality make it rather hard to be degraded thoroughly and economically. In response to this challenge, we introduce a novel solution that combines pre-treatment, dissolved air flotation, and fine multi-stage filtration techniques to efficiently remove oil and suspended solids from oily wastewater discharge. This study comprehensively summarizes the characteristics of oil-containing wastewater in substations and invents a novel process for treating oil-containing wastewater from substations. It exhibits notable advantages in terms of energy efficiency and cost-effectiveness compared to conventional treatment methods. This research not only promotes the technical advances in the field of wastewater treatment but also provides a practical and sustainable solution for industries grappling with the conundrum of oily wastewater manage-ment. The findings presented here can be supposed to serve as a stepping stone towards the development of more efficient and environmentally friendly wastewater treatment strategies. Substations Oily wastewater treatment New process Economic benefits Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Highlights The characteristics of oily wastewater in substation were further studied. A new combined process was created to treat oily wastewater. The new filter material modified by itself has better filtration effect. 1. Introduction Substations play a vital role in electricity distribution, ensuring a continuous and reliable power supply. The treatment of wastewater from substations presents a mul-tifaceted challenge at the intersection of environmental protection and technological advancement[ 1 ]. Substation wastewater often contains oil and other hydrocarbon-based contaminants, making its treatment complex and multifaceted. However, the treatment of oily wastewater in substation is more complicated mainly in the following aspects. First and foremost, the treatment of oil-contaminated wastewater from substations is inherently complex due to the diverse and often intricate nature of the pollutants involved. These contaminants can range from insulating oils and lubricants to hydro-carbons, creating a mixture with varying physical and chemical properties[ 2 ]. As a result, conventional wastewater treatment processes may struggle to efficiently remove these substances, necessitating new specialized techniques. Furthermore, a noteworthy challenge in substation wastewater treatment stems from the potential formation of emulsified oils. Emulsified oil not only hinders the ef-fective aggregation of oily droplets and detachment from the water but also complicates the treatment process, as traditional separation methods may prove ineffective. As such, developing efficient means to destabilize these emulsions and facilitate oil-water sep-aration is a critical step of substation wastewater treatment[ 3 ]. Additionally, the lack of well-established treatment technologies for substation wastewater further exacerbates the overall challenge. Unlike other wastewater types compatible with more established treatment methodologies, substation wastewater's unique composition demands innovative solutions[ 4 ]. When treating oily wastewater from substations, the efficiency, cost and sustainability of these methods usually need to be considered comprehensively. In the treatment of substation oily wastewater, people have tried many different processes. In the daily treatment of oily wastewater in sub-station, people often consider methods such as gravity separation, electrocoagulation, and adsorption. However, gravity separation has drawbacks including a large footprint, high infrastructure investment, poor performance in treating emulsified oil, and a long retention time for wastewater. While electrocoagulation has advantages such as a small footprint, effective treatment, and relatively low sludge generation, it has high energy consumption, significant electrode wear, and higher operating costs[ 5 ]. On the other hand, adsorption methods require a large amount of adsorbent material, resulting in high costs, making them unsuitable for routine processes[ 6 ]. Therefore, the absence of standardized, efficient, and cost-effective treatment processes urgently calls for more efforts to bridge this technological gap. In conclusion, substation wastewater treatment is a complex endeavor, character-ized by the intricate nature of oil contamination, the potential for emulsified oils, and the absence of well-defined treatment technologies. Overcoming these challenges is essential not only to ensure environmental compliance but also to maintain the integrity and sustainability of the power infrastructure[ 7 ]. However, due to the fact that substa-tions are typically situated in relatively remote areas, far from urban centers, the oil-contaminated wastewater from substations is typically discharged into nearby small villages after treatment. This necessitates the implementation of more stringent regu-latory standards and higher water quality requirement for substation effluent. With this in mind, we need to further study more novel techniques to address this concern. 2. Wastewater characteristics and methods 2.1. Current Status of Oil Content in Substations Based on factors such as voltage level and operational duration of substations within Hubei province, 31 substations were selected as the subjects of investigation. These included 6 substations with a voltage level of 500 kV, 9 substations with a voltage level of 220 kV, and 16 substations with a voltage level of 110 kV. Among these, there were 11 substations with an operational duration of 0 to 10 years, 9 substations with an operational duration of 10 to 20 years, and 11 substations with an operational duration exceeding 20 years. In this study, the oil-contaminated wastewater in the oil pools of these 31 substations was stratified sampled. Sampling points were determined based on the water level and the presence of floating oil in the oil pools, with samples taken from shallow layers (at distances of approximately 10cm, 20cm, and 50cm from the water surface), middle layers, and the bottom layer (approximately 20cm above the bottom of the oil pool)[8]. The petroleum content in the water samples was analyzed. The average petroleum content in samples from oil pools with noticeable surface oil layers ranged from 12.6 to 31.1 mg/L. In samples from oil pools with a small amount of surface-floating oil, the average petroleum content ranged from 0.8 to 12.2 mg/L, and in samples from oil pools with minimal surface-floating oil, the average petroleum content ranged from 0.4 to 1.1 mg/L. In oil pools with surface-floating oil, the petroleum content in samples from the shallow layer was generally higher than in the middle and bottom layers. The closer the sample was to the floating oil layer, the higher the petroleum content in the wastewater. Conversely, the closer the sample was to the bottom layer, the lower the petroleum content in the wastewater. In oil pools with virtually no surface-floating oil, the overall petroleum content in the wastewater was lower, and there was no apparent distribution pattern in petroleum content among the different layers. When the oil pools were at full water level and experienced continuous rainfall, the petroleum content in the wastewater discharged from the oil pools initially increased slowly, peaked at around 20 minutes, and then began to decline, eventually stabilizing. Substation oily wastewater contains different kinds of oil, such as cooling oil, in-sulating oil, lubricating oil, etc., and some of them will form emulsified oil. Emulsified oils are those that have formed stable mixtures with water, creating a challenging scenario for efficient phase separation and removal. These emulsions can be particularly stubborn, as they resist conventional separation methods. Based on this, we also carried out GCMS analysis(Figure 1)on some emulsified water samples of substation oily wastewater, and found that the emulsified oil mainly contained long-chain alkanes (mineral oil), alcohols and fatty acid esters. 2.2. Feeding water The experimental water used is oily wastewater separated from the oil-water separation process of a three-phase separator at a certain substation in Hubei Province, China. 2.3. New integrated air flotation device This integrated air flotation device (Figure 2) was mainly composed of five parts as follows: aeration zone, diffusion air flotation reaction zone, pressurized dissolved air flotation reaction zone, scum scraping system and drainage system. The core reaction zone includes two parts: the diffusion air flotation was applied in the front section where inorganic coagulants was input, followed by a pressurized dissolved air flotation. 2.4. Fine Filtration Device The designed multipolar fine filtration tank integrates three-stage treatment de-vices into one, adopting a fully symmetrical arrangement. The schematic diagram of the device is as follows（Figure 3）. 2.5. Analytical methods Inlet and outlet oil content: The domestic measurement methods are quite complex. In this study, the JDS-106U infrared spectrophotometer manufactured by Beiguang Analysis Instrument Factory in Jilin City was utilized for determination. The primary principle of this instrument involves using tetrachloroethylene to extract oil substances from water, measuring the total extracted substances, and subsequently adsorbing the extraction liquid with magnesium silicate to remove polar substances such as animal and plant oils. The petroleum content is then determined. The content of both total ex-tracted substances and petroleum is calculated using the absorbance values (A2930, A2960, and A3030) corresponding to the wavenumbers 2930 cm -1 (stretching vibration of C-H bonds in CH2 groups), 2960 cm -1 (stretching vibration of C-H bonds in CH3 groups), and 3030 cm -1 (stretching vibration of C-H bonds in aromatic hydrocarbons). The content of animal and plant oils is calculated based on the difference between the total extracted substances and petroleum content. SS measurement: Turbidity meter model TD-2 is employed. COD determination: The Hashi digestion method is used. 3. Innovative Approach for Transformer Substation Oily Wastewater Treatment This research introduces a groundbreaking method for addressing the treatment of oily wastewater originating from transformer substations. Presently, a spectrum of techniques is disposed in managing such wastewater, but each exhibiting its inherent merits and demerits. Nevertheless, the utilization of a single-process methodology frequently falls short in achieving the desired water quality standards. In response to this question, the article advocates using a combination of multiple processes to replace a single process for treating such wastewater. By judiciously integrating different pro-cesses, this novel approach leverages the strengths of individual methods while miti-gating their respective limitations. Following a comprehensive phase of rigorous research and experimentation, a more efficacious treatment process has emerged, which incorporates preliminary treatment, flotation, and fine filtration. This innovative process not only conserves energy but also attains superior treatment effects. Within this article, a comprehensive elucidation is presented, encompassing the intricate stages of the treatment process and the precise determination of critical parameters. 3.1. Pretreatment Preceding the commencement of industrial processes, pretreatment of oily wastewater stands as a requisite procedure. The pretreatment of such wastewater confers manifold advantages. It not only serves to enhance the quality of efficiency, but also mitigates the subsequent treatment burden while concurrently augmenting treatment efficiency. In this study, the latest and timely method was employed: utilizing 185nm far-ultraviolet light oxidation as a pre-treatment for oil-containing wastewater [9]. The most significant feature of this method is its ability to disrupt conventional oil removal techniques such as precipitation and coagulation. From a molecular perspective, it breaks down the long chains of oil molecules, leading to the complete degradation of lipids. This approach exhibits a notably high removal rate of fats, thereby enhancing the biodegradability of the wastewater for subsequent biological treatment. 3.2. Flotation Process 3.2.1. Introduction to Flotation The flotation process, a recently developed technology that has gained global at-tention, leds a new trend in the field of sewage treatment. Originating in the 1990s, this method demonstrates proficiency in the separation of solid particulates, particularly dispersed and emulsified oils, characterized by particle dimensions ranging from 10 to 60 nanometers, which persist in aqueous mediums post-separation processes [10]. It re-lies on the chemical interaction of air generated within water, leading to the formation of minute air bubbles. These bubbles effectively entrap suspended particles in the aqueous matrix, ascend to the water-air interface, and create an oil-laden froth layer. Subsequent removal of this froth layer is accomplished through the utilization of an oil skimmer device. Compared to alternative treatment methodologies, this approach distinguishes itself through its inherent simplicity, cost-effectiveness in terms of construction and operation, and its remarkable oil removal efficiency, which can attain levels as high as 95%. Additionally, it plays a pivotal role in elevating oil recovery rates and concurrently curbing environmental pollution. Compared to alternative treatment methodologies, this approach distinguishes itself through its inherent simplicity, cost-effectiveness in terms of construction and operation, and its remarkable oil removal efficiency, which can attain levels as high as 95%. Additionally, it plays a pivotal role in elevating oil recovery rates and concurrently curbing environmental pollution. 3.2.2. Operating Principle In this study, the vortex impeller flotation method is employed. Vortex impeller flotation belongs to the category of dispersed-air flotation. The vortex impeller flotation device comprises an aeration zone, flotation zone, recirculation system, scraper system, and drainage system. The device primarily utilizes the high-speed rotation of the aeration impeller at the bottom of the air distribution pipe to create a vacuum region in the water [11]. Air at the liquid surface is introduced into the water through the aeration machine to fill the vacuum, leading to the formation of microbubbles, which spiral upward to the water surface. The oxygen in the air is dissolved into the water. The pre-treated wastewater enters the small inflatable section of the vortex impeller flotation machine, where the air at the water surface is transferred to the water column through an air suction pipe, allowing the wastewater to mix and come into contact with the microbubbles generated by the flotation machine. Microbubbles adhere to oil and suspended solids in the water, forming a buoyant fraction with a lower density than water. This fraction quickly rises to the water surface and is subsequently scraped into a sludge collection tank using a scraper, completing the purification of wastewater. Coagulants are added at the front end of the coagulation reaction tank. Through primary and secondary stirring within the tank, water and chemicals undergo thorough coagulation reactions. Then, the water enters the vortex impeller flotation tank, where coagulants are added to the wastewater before it enters the tank. The effluent from the vortex impeller flotation is sent to a lift pump and transported to subsequent treatment systems. An open return pipe extends along the bottom of the flotation tank. While generating microbubbles, the vortex aeration machine forms a negative pressure zone at the bottom of the tank with the return flow pipe [12, 13]. This negative pressure effect causes wastewater to flow back to the aeration zone from the tank bottom, then return to the flotation section. This process ensures that approximately 40% of the wastewater recirculates, allowing the flotation section to operate without incoming water. 3.2.3. Determination of Process Parameters 3.2.3.1 Dosage Determination Prior to initiating the flotation system, the introduction of coagulants, conventionally represented by polyacrylamide (PAM), is executed within the coagulation re-action vessel. Ensuring the effective amalgamation of PAM with the wastewater or sludge is of paramount importance, a procedure typically consummated within a temporal range of 10 to 30 seconds, with a prescribed upper limit not exceeding 2 minutes. The quantification of PAM is intricately linked to the concentration, attributes, and treatment apparatus of colloidal and suspended solids prevalent within the wastewater or sludge matrix. The precise determination of the optimal dosage necessitates com-prehensive empirical investigations tailored to the distinctiveness of transformer sub-station oily wastewater. Following a series of methodical comparative experiments designed to accommodate the idiosyncratic attributes of transformer substation oily wastewater, the ensuing dataset was acquired as Figure 4 and Table 1. Table 1. Effect table of different dosage. Dosage (mg/L) SS Removal Rate COD Removal Rate O il Removal Rate PAC 15mg/L+PAM 1mg/L 41.06% 9.58% 31.45% PAC 30mg/L+PAM 1.5mg/L 54.17% 15.6% 42.51% PAC 45mg/L+PAM 2mg/L PAC 60mg/L+PAM 2.5mg/L 72.91% 70.88% 39.34% 34.12% 50.62% 46.38% 3.2.3.2 Aeration Volume Determination Aeration equipment is crucial to the operation of the flotation system. It supplies oxygen to the flotation tank and provides mixing and agitation, enhancing mass transfer conditions in the water treatment system and improving treatment efficiency. Different aeration volumes yield different effects on flotation. Through experiments conducted with commonly used aeration volumes, the following results were obtained as Figure 5 and Table 2. Table 2. Effect table of different aeration rate. Aeration Rate （ m 3 /L ） SS Removal Rate COD Removal Rate Oil Removal Rate 5 56.81% 39.97% 45.97% 6 57.63% 48.74% 51.26% 7 72.45% 58.82% 68.55% 8 59.27% 48.21% 51.84% 3.2.3.3 Determination of pH Value According to the literature, the pH value significantly impacts the efficiency of air flotation treatment. This influence can be categorized into two primary aspects: 1.When the pH value is 6.8, the interfacial tension of oily wastewater reaches its maximum. Regardless of an increase or decrease in pH value, the interfacial tension decreases. To enhance the disruption speed of the water film and increase adhesion, it is necessary to reduce interfacial tension. Thus, the pH value should deviate from 6.8. 2.Within the pH range of 6 to 9, the coagulant PAC demonstrates optimal coagu-lation effects. Therefore, it is essential to conduct experiments considering the impact of pH value on interfacial tension, coagulation effectiveness, and changes in oil droplet diameters to determine the best pH utilization range. Employing dissolved air flotation while maintaining other conditions constant, only the pH value was altered. The water's oil content at different pH values was measured using a spectrophotometer, and the measured data is presented in the table below as Figure 6 and Table 3. Table 3. Effect table of different pH value. Pressure （ MPa ） Inlet Oil Content （ mg/L ） pH Value Outlet Oil Content （ mg/L ） Oil Removal Rate 0.32 100.93 4 37.17 63.17% 0.32 100.93 5 27.9 72.36% 0.32 100.93 6 17.52 82.64% 0.32 100.93 7 14.91 85.23% 0.32 100.93 8 19.15 81.03% 0.32 100.93 9 23.36 76.86% 0.32 100.93 10 32.72 67.58% The data from the chart demonstrates a pronounced influence of pH value on air flotation treatment. The treatment effect is optimal within the pH range of 6 to 8. Hence, when handling oily wastewater using air flotation technology, it is recommended to control the pH value within the range of 6 to 8. In summary, when the dosage is PAC 45mg/L + PAM 2mg/L, and the aeration volume is 7m³/L, the vortex concave air flotation exhibits the best effects. The vortex concave air flotation machine exhibits a strong adaptability to changes in wastewater quantity and water quality. By adjusting the height of the effluent weir easily, it can adapt to varying circumstances[14]. 3.3. Fine Filtration Device 3.3.1. Experimental Device Design Filtration is a critical process in treating oily wastewater and serves as the final stage of wastewater treatment. Various oil fields and design production units consider filtration technology and equipment as a focal point of research. However, so far, there have been deficiencies in achieving the relevant emission standards. Conventional filters cannot meet the relevant emission standards for oily wastewater. Thus, a concept of a multi-stage fine filtration device is proposed based on conventional filters. This device is an intermittent counter-granularity filtration de-vice[15]. Each stage utilizes homogeneous filter media. Although the particle sizes of the filter media in each stage differ, there is an overall gradation from large to small, en-suring a more uniform distribution of pollutant interception across the filter layers, while also guaranteeing the attainment of emission standards under high-speed filtra-tion conditions. The device adopts a sealed pressure filtration, ensuring water pressure. The device is divided into symmetrical halves, each subdivided into three segments, ensuring each filter layer receives thorough backwashing, thereby saving energy [16].. 3.3.2. Determination of Process Parameters 3.3.2.1 Selection of Filter Media Surface modified B2, C5, C7 ceramic filter media and unmodified filter media were used under the same conditions to treat wastewater of the same concentration to de-termine the oil removal rate through each filter media. The wastewater is treated with the water sample after the best effect air flotation treatment. The experimental data is presented below as Figure 7 and Table 4. Table 4. Effect table of different filter material model. Filter Material Model Oil Content Before Filtration (mg/L) Oil Content After Filtration (mg/L) Oil Content Removal Rate （ % ） Untreated 14.91 6.93 53.52% B2 3.68 75.31% C5 2.64 82.29% C7 0.08 99.46% It is evident from the data that the C7 model of filter media exhibits the most effective oil removal, characterized as a surface-modified hydrophilic ceramic filter. The C7-type filter described in this study is specially modified, primarily utilizing 202 silicone oil-modified porous ceramic filter balls. Silicone compounds exhibit two notable characteristics: (1) a lower surface energy and (2) wear resistance. Consequently, they have found widespread applications in surface modification, such as waterproofing agents, surface treatment of textiles, and corrosion protection of metal surfaces, re-placing environmentally polluting processes like phosphating and chromating. However, research on the surface modification of ceramic filter media with organosilicon compounds is relatively scarce. The surface energy of ceramic filter balls is relatively high, rendering them hydrophilic. To make them oleophilic, it is necessary to reduce the surface energy of the filter balls, increasing the wetting angle for oil adsorption [17]. This allows the formation of an oil film on the filter ball surface, completing the wetting aggregation. Additionally, gaps exist between filter materials, and there are large pores within the filter material [18]. Collision and aggregation of small oil droplets occur in these spaces, and both theoretical and practical evidence demonstrate that the best results are achieved when both types of aggregation are present. In this study, we applied 202 silicone oil-modified porous ceramic filter balls. The Si-H in 202 undergoes hydrolysis to form Si-OH, which then undergoes condensation with hydroxyl groups on the filter ball surface, forming a reticulated structure. This rearranges the orientation of oleophilic groups (methyl) toward the external surface of the filter ball, altering the surface properties from hydrophilic to oleophilic [19, 20]. The schematic diagram illustrating the mechanism is presented in the figure below as Figure 8. This type of ceramic filter outperforms traditional filter media like quartz sand and walnut shells, demonstrating longer filtration cycles, lower filtered water turbidity, greater pollutant interception capacity, a shorter maturation period, and enhanced resistance to impact loads, among other qualities. 3.3.2.2 Determination of Filter Media Gradation Combinations The particle gradation and suitable porosity of filter media are vital for filtration devices. Large particle sizes with high porosity yield low filtration resistance when dealing with minute suspended particles. Conversely, smaller particles with low po-rosity lead to the reverse. Therefore, for a specific water quality, meticulous gradation experiments are necessary to determine the appropriate filter media gradation and porosity [21]. With artificial preparation of raw water and addition of clay in tap water, the removal rates of SS for each stage, COD removal rates, oil removal rates, etc., were measured. According to literature and experiments conducted by others, three types of gradation were determined: Gradation 1: Particle size of filter media between 1.60-1.80mm, a layer thickness of 900mm; particle size between 1.0-1.60mm, a layer thickness of 800mm; particle size between 0.8-1.0mm, a layer thickness of 700mm. Gradation 2: Particle size between 1.25-1.60mm, a layer thickness of 800mm; parti-cle size between 0.8-1.25mm, a layer thickness of 700mm; particle size between 0.6-0.8mm, a layer thickness of 600mm. Gradation 3: Particle size between 1.25-1.40mm, a layer thickness of 700mm; parti-cle size between 0.6-1.0mm, a layer thickness of 700mm; particle size between 0.4-0.6mm, a layer thickness of 700mm. Different filter media gradations exhibit distinct removal effects on different pol-lutants, as detailed in the table below as Figure 9 and Table 5. Table 5. Effect table of different particle size distribution. Particle Size Distribution Turbidity Removal SS Removal COD Removal Oil Removal Particle Size Distribution 1 60.52% 73.66% 42.12% 89.21% Particle Size Distribution 2 70.84% 79.87% 48.89% 90.73% Particle Size Distribution 3 80.32% 84.36% 54.30% 96.88% Based on experiments conducted on raw water, it's evident that after filtration using gradation three, the best filtration efficiency is achieved, thereby establishing the required gradation conditions for fine filtration. After extensive research and experimentation, the use of ceramic filter media with a filtration rate of 15m/h, a gradation of particle sizes between 1.25-1.40mm, a layer thickness of 700mm, particle sizes between 0.6-1.0mm, and particle sizes between 0.4-0.6mm yielded relatively better treatment outcomes. 4. The comprehensive effect of Effluent treatment 4.1. Evaluation of effluent effect After confirming various parameters of the aforementioned process, in order to further validate the effectiveness of this technique, experiments were conducted to access the treatment efficiency of oily wastewater. This study examines the effectiveness of a wastewater treatment process for actual substation oily wastewater. The process involves pretreatment, flotation, and multi-stage fine filtration. The removal efficiency of turbidity, oil, and COD was evaluated through a week-long sampling and testing period. The detailed experimental data can be found in the table below as Table 6. Table 6. Effect table of combined process for water treatment. water sample Sample Turbidity (NTU) Turbidity Removal Oil Content (mg/L) Oil Removal COD Removal First Data Second Data Average Data water sample1 8.915 96.89% 100.62 100.33 100.475 67.21% 87.33% water sample2 10.487 98.35% 100.23 100.66 100.445 83.92% 96.41% water sample3 10.355 98.79% 101.38 102.32 101.85 95.89% 88.67% water sample4 10.286 99.03% 99.73 100.12 99.925 87.92% 92.91% water sample5 10.598 96.21% 99.12 98.96 99.04 96.24% 99.55% water sample6 9.431 97.27% 100.87 100.99 100.93 96.83% 86.92% water sample7 9.33 97.91% 100.99 101.77 100.38 88.76% 89.81% water sample8 10.234 98.52% 101.28 100.83 101.055 80.64% 88.71% water sample9 9.202 98.72% 102.43 101.64 102.035 86.22% 89.41% The results demonstrate that this combined treatment process effectively removes turbidity and oil from the wastewater, meeting regulatory standards. The efficiency of turbidity, oil removal, and COD reduction was investigated to assess the performance of this treatment system. The experimental data reveals a significant reduction in turbidity achieved by the combined treatment process[22]. Over a continuous operation period of 5 hours, the lowest turbidity removal rate observed was 96.21%, and the effluent tur-bidity consistently remained below 1 mg/L, meeting A1 standards. Furthermore, the removal of oil content was highly effective, with the effluent oil concentration con-sistently below 5 mg/L, also meeting A1 standards. 4.2. Financial analysis Cost analysis of the novel process indicates that, in comparison to alternative methods, it boasts both lower costs and superior efficacy. The overall cost of the process for treating this wastewater is shown in the following table(Table 7). Table 7. Financial analysis. Process Electricity Pharmaceutical costs Labor costs pretreatment 0.1 0 0.1 air flotation 0.1 0.2 0.1 Fine Filtration 0.2 0.1 0.1 total cost 1 5. Conclusion Once the combined treatment process of pretreatment, flotation, and fine filtration was stabilized, During continuous operation over several days, the minimum turbidity removal rate reached 96.21%, and the effluent turbidity consistently remained below 1 mg/L. The removal efficiency for oil was also significant, with the effluent oil concentration showing a notable decrease and consistently staying below 5 mg/L. These values fully comply with the national emission standard. The combination of this treatment process demonstrates its capability to effectively remove oil and organic contaminants from oily wastewater, exhibiting strong shock resistance and stable performance with low operational costs. It has the potential to become the mainstream technology for oily wastewater treatment and can serve as a reference for engineering design in this field. Declarations Declaration of Interest Statement We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and company that could be construed as influencing the position presented in, or the review of, the manuscript entitled. Author Contribution Yan HUANG and Shangyong Wen put forward the innovation of the article, wrote the manuscript content；Zhengdong WAN, Hongyan Xin drew a picture and changed the format of the article. Kaiman Li conducted an article review and contributed papers. Data Availability Data is provided within the manuscript or supplementary information files References Wang, H., B. Zhou, and X. 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Wang, C., et al., Separation of emulsified crude oil from produced water by gas flotation: A review. Science of The Total Environment, 2022. 845. Romphophak, P., et al., Prediction Model for the Treatment of Stabilized Oily Wastewater by Modified Induced Air Flotation (MIAF). Engineering Journal, 2016. 20(3): p. 11-21. Loh, Z.Z., et al., Shifting from Conventional to Organic Filter Media in Wastewater Biofiltration Treatment: A Review. Applied Sciences, 2021. 11(18). Qing, C., et al., Filtration of oil from oily wastewater via hydrophobic modified quartz sand filter medium. Journal of Water Reuse and Desalination, 2018. 8(4): p. 544-552. Jin, Z., et al., 3D-printed controllable gradient pore superwetting structures for high temperature efficient oil-water separation. Journal of Materiomics, 2021. 7(1): p. 8-18. Ding, D., et al., Underwater superoleophobic-underoil superhydrophobic Janus ceramic membrane with its switchable separation in oil/water emulsions. Journal of Membrane Science, 2018. 565: p. 303-310. Cheng, X., et al., Finely tailored pore structure of polyamide nanofiltration membranes for highly-efficient application in water treatment. Chemical Engineering Journal, 2021. 417. Kaetzl, K., et al., Slow sand filtration of raw wastewater using biochar as an alternative filtration media. Scientific Reports, 2020. 10(1). Alquraish, M., et al., Development of Environment-Friendly Membrane for Oily Industrial Wastewater Filtration. Membranes, 2021. 11(8). Druskovic, M., et al., The application of electrochemical processes in oily wastewater treatment: a review. Journal of Environmental Science and Health, Part A, 2021. 56(13): p. 1373-1386.Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 11 Jul, 2024 Reviews received at journal 01 Jul, 2024 Reviewers agreed at journal 26 Jun, 2024 Reviewers agreed at journal 26 Jun, 2024 Reviews received at journal 25 Jun, 2024 Reviewers agreed at journal 25 Jun, 2024 Reviews received at journal 30 May, 2024 Reviewers agreed at journal 26 May, 2024 Reviewers invited by journal 26 May, 2024 Editor assigned by journal 23 May, 2024 Submission checks completed at journal 23 May, 2024 First submitted to journal 16 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4429410","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":309127507,"identity":"e8469c62-1d98-4ed3-8ab8-87a30fab34d8","order_by":0,"name":"Yan HUANG","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAuElEQVRIiWNgGAWjYBACAxiDn3Qtkg0kazE4QKwWc4nkZw+/ttnlGR8//vgFQ80dwlosZ6SZG8u2JRebnckxs2A49owIh91IMJOWbGNO3HaDh82AseEwMVrSvwG11CdunsH+jFgtOWaSH9sOJ26QYDB+QJyWM2/KpBnOHU+cAfQLQ8IxYrQcT98m+aOsOrG//fjjDx9qiNACAsy8bGCaTSKBOA0MDIw//kC0fiBWxygYBaNgFIwsAABPkD13RqzGewAAAABJRU5ErkJggg==","orcid":"","institution":"China Southern Power Grid","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Yan","middleName":"","lastName":"HUANG","suffix":""},{"id":309127508,"identity":"8df4999f-5275-404f-b267-d839b178c634","order_by":1,"name":"Shangyong Wen","email":"","orcid":"","institution":"China Southern Power Grid","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Shangyong","middleName":"","lastName":"Wen","suffix":""},{"id":309127509,"identity":"007f1dc2-a268-4e8c-ae57-7dd33ca23f3d","order_by":2,"name":"Zhengdong WAN","email":"","orcid":"","institution":"China Southern Power Grid","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhengdong","middleName":"","lastName":"WAN","suffix":""},{"id":309127510,"identity":"85dc1eeb-38f6-4c7e-a19f-7fa041ab8009","order_by":3,"name":"Hongyan Xin","email":"","orcid":"","institution":"China Southern Power Grid","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hongyan","middleName":"","lastName":"Xin","suffix":""},{"id":309127511,"identity":"1a2fc109-448e-4840-b75e-f5f325220bdd","order_by":4,"name":"Kaiman Li","email":"","orcid":"","institution":"China Southern Power Grid","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Kaiman","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2024-05-16 08:02:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4429410/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4429410/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":57762394,"identity":"783a23ff-dcac-420d-bf92-68b652e44734","added_by":"auto","created_at":"2024-06-05 09:48:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":31873,"visible":true,"origin":"","legend":"\u003cp\u003eThis is a GCMS analysis figure.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/9667a17fcd25cf383a741717.png"},{"id":57762393,"identity":"e7bae813-2b3e-4264-89bd-7524c2fdf406","added_by":"auto","created_at":"2024-06-05 09:48:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":59288,"visible":true,"origin":"","legend":"\u003cp\u003eThis Structure composition of air flotation machine.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/d7430730d70487c5f9869dce.png"},{"id":57763997,"identity":"021326b7-2119-4b68-960e-e6995419ee59","added_by":"auto","created_at":"2024-06-05 10:12:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":130338,"visible":true,"origin":"","legend":"\u003cp\u003eFine filtration device diagram.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/13b6176cb0937740cd498b7b.png"},{"id":57762398,"identity":"97236f25-4f03-48fc-ac01-1d3aef64a59a","added_by":"auto","created_at":"2024-06-05 09:48:38","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":13575,"visible":true,"origin":"","legend":"\u003cp\u003eEffect figure of different dosage.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/57ebea17d34fb8a3931823fc.png"},{"id":57763649,"identity":"09c654c2-4414-4f0e-9d2e-b721e38dcc7d","added_by":"auto","created_at":"2024-06-05 10:04:38","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":34752,"visible":true,"origin":"","legend":"\u003cp\u003eEffect figure of different aeration rate.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/c02fd81210eede9b1572ce57.png"},{"id":57763186,"identity":"bfca3ef7-b405-4401-bfb5-b3ffb98df73c","added_by":"auto","created_at":"2024-06-05 09:56:38","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":49684,"visible":true,"origin":"","legend":"\u003cp\u003eEffect figure of different pH value.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/e0cdcb934a6bed2d2c9f6739.png"},{"id":57762399,"identity":"eb1f4b05-e643-42c7-84cd-2792bb98eb1b","added_by":"auto","created_at":"2024-06-05 09:48:38","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":48864,"visible":true,"origin":"","legend":"\u003cp\u003eEffect figure of filter material model.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/260c50383c43890e303b6277.png"},{"id":57762401,"identity":"d40acfb9-90ba-471b-935a-1142bfa1305d","added_by":"auto","created_at":"2024-06-05 09:48:38","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":71268,"visible":true,"origin":"","legend":"\u003cp\u003eMaterial modification mechanism diagram.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/ad34563783d4ddf69be3f4ed.png"},{"id":57762402,"identity":"61c3e5a9-e293-4d01-89d8-7e1366f13251","added_by":"auto","created_at":"2024-06-05 09:48:38","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":46483,"visible":true,"origin":"","legend":"\u003cp\u003eEffect figure of particle size distribution.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/afdb847748f912999ae15013.png"},{"id":57764377,"identity":"cb03561c-cc19-41c2-8978-600f1be1080e","added_by":"auto","created_at":"2024-06-05 10:20:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1114703,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4429410/v1/a02554e5-0e31-4b9c-b93e-6ce0e43f4263.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characterization and Innovative Process of Oily Wastewater from Substations","fulltext":[{"header":"Highlights","content":"\u003col\u003e\n \u003cli\u003eThe characteristics of oily wastewater in substation were further studied.\u003c/li\u003e\n \u003cli\u003eA new combined process was created to treat oily wastewater.\u003c/li\u003e\n \u003cli\u003eThe new filter material modified by itself has better filtration effect.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eSubstations play a vital role in electricity distribution, ensuring a continuous and reliable power supply. The treatment of wastewater from substations presents a mul-tifaceted challenge at the intersection of environmental protection and technological advancement[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Substation wastewater often contains oil and other hydrocarbon-based contaminants, making its treatment complex and multifaceted. However, the treatment of oily wastewater in substation is more complicated mainly in the following aspects.\u003c/p\u003e \u003cp\u003eFirst and foremost, the treatment of oil-contaminated wastewater from substations is inherently complex due to the diverse and often intricate nature of the pollutants involved. These contaminants can range from insulating oils and lubricants to hydro-carbons, creating a mixture with varying physical and chemical properties[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. As a result, conventional wastewater treatment processes may struggle to efficiently remove these substances, necessitating new specialized techniques.\u003c/p\u003e \u003cp\u003eFurthermore, a noteworthy challenge in substation wastewater treatment stems from the potential formation of emulsified oils. Emulsified oil not only hinders the ef-fective aggregation of oily droplets and detachment from the water but also complicates the treatment process, as traditional separation methods may prove ineffective. As such, developing efficient means to destabilize these emulsions and facilitate oil-water sep-aration is a critical step of substation wastewater treatment[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditionally, the lack of well-established treatment technologies for substation wastewater further exacerbates the overall challenge. Unlike other wastewater types compatible with more established treatment methodologies, substation wastewater's unique composition demands innovative solutions[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. When treating oily wastewater from substations, the efficiency, cost and sustainability of these methods usually need to be considered comprehensively. In the treatment of substation oily wastewater, people have tried many different processes. In the daily treatment of oily wastewater in sub-station, people often consider methods such as gravity separation, electrocoagulation, and adsorption. However, gravity separation has drawbacks including a large footprint, high infrastructure investment, poor performance in treating emulsified oil, and a long retention time for wastewater. While electrocoagulation has advantages such as a small footprint, effective treatment, and relatively low sludge generation, it has high energy consumption, significant electrode wear, and higher operating costs[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. On the other hand, adsorption methods require a large amount of adsorbent material, resulting in high costs, making them unsuitable for routine processes[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Therefore, the absence of standardized, efficient, and cost-effective treatment processes urgently calls for more efforts to bridge this technological gap.\u003c/p\u003e \u003cp\u003eIn conclusion, substation wastewater treatment is a complex endeavor, character-ized by the intricate nature of oil contamination, the potential for emulsified oils, and the absence of well-defined treatment technologies. Overcoming these challenges is essential not only to ensure environmental compliance but also to maintain the integrity and sustainability of the power infrastructure[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, due to the fact that substa-tions are typically situated in relatively remote areas, far from urban centers, the oil-contaminated wastewater from substations is typically discharged into nearby small villages after treatment. This necessitates the implementation of more stringent regu-latory standards and higher water quality requirement for substation effluent. With this in mind, we need to further study more novel techniques to address this concern.\u003c/p\u003e"},{"header":"2. Wastewater characteristics and methods","content":"\u003cp\u003e\u003cem\u003e2.1. Current Status of Oil Content in Substations\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eBased on factors such as voltage level and operational duration of substations within Hubei province, 31 substations were selected as the subjects of investigation. These included 6 substations with a voltage level of 500 kV, 9 substations with a voltage level of 220 kV, and 16 substations with a voltage level of 110 kV. Among these, there were 11 substations with an operational duration of 0 to 10 years, 9 substations with an operational duration of 10 to 20 years, and 11 substations with an operational duration exceeding 20 years. In this study, the oil-contaminated wastewater in the oil pools of these 31 substations was stratified sampled. Sampling points were determined based on the water level and the presence of floating oil in the oil pools, with samples taken from shallow layers (at distances of approximately 10cm, 20cm, and 50cm from the water surface), middle layers, and the bottom layer (approximately 20cm above the bottom of the oil pool)[8]. The petroleum content in the water samples was analyzed. The average petroleum content in samples from oil pools with noticeable surface oil layers ranged from 12.6 to 31.1 mg/L. In samples from oil pools with a small amount of surface-floating oil, the average petroleum content ranged from 0.8 to 12.2 mg/L, and in samples from oil pools with minimal surface-floating oil, the average petroleum content ranged from 0.4 to 1.1 mg/L.\u003c/p\u003e\n\u003cp\u003eIn oil pools with surface-floating oil, the petroleum content in samples from the shallow layer was generally higher than in the middle and bottom layers. The closer the sample was to the floating oil layer, the higher the petroleum content in the wastewater. Conversely, the closer the sample was to the bottom layer, the lower the petroleum content in the wastewater. In oil pools with virtually no surface-floating oil, the overall petroleum content in the wastewater was lower, and there was no apparent distribution pattern in petroleum content among the different layers. When the oil pools were at full water level and experienced continuous rainfall, the petroleum content in the wastewater discharged from the oil pools initially increased slowly, peaked at around 20 minutes, and then began to decline, eventually stabilizing.\u0026nbsp;\u003c/p\u003e\n\u003c!--[endif]--\u003e\n\u003cp\u003eSubstation oily wastewater contains different kinds of oil, such as cooling oil, in-sulating oil, lubricating oil, etc., and some of them will form emulsified oil. Emulsified oils are those that have formed stable mixtures with water, creating a challenging scenario for efficient phase separation and removal. These emulsions can be particularly stubborn, as they resist conventional separation methods. Based on this, we also carried out GCMS analysis(Figure 1)on some emulsified water samples of substation oily wastewater, and found that the emulsified oil mainly contained long-chain alkanes (mineral oil), alcohols and fatty acid esters.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2. Feeding water\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe experimental water used is oily wastewater separated from the oil-water separation process of a three-phase separator at a certain substation in Hubei Province, China.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.3. New integrated air flotation device\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis integrated air flotation device (Figure 2) was mainly composed of five parts as follows: aeration zone, diffusion air flotation reaction zone, pressurized dissolved air flotation reaction zone, scum scraping system and drainage system. The core reaction zone includes two parts: the diffusion air flotation was applied in the front section where inorganic coagulants was input, followed by a pressurized dissolved air flotation.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.4. Fine Filtration Device\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe designed multipolar fine filtration tank integrates three-stage treatment de-vices into one, adopting a fully symmetrical arrangement. The schematic diagram of the device is as follows（Figure 3）.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.5. Analytical methods\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eInlet and outlet oil content: The domestic measurement methods are quite complex. In this study, the JDS-106U infrared spectrophotometer manufactured by Beiguang Analysis Instrument Factory in Jilin City was utilized for determination. The primary principle of this instrument involves using tetrachloroethylene to extract oil substances from water, measuring the total extracted substances, and subsequently adsorbing the extraction liquid with magnesium silicate to remove polar substances such as animal and plant oils. The petroleum content is then determined. The content of both total ex-tracted substances and petroleum is calculated using the absorbance values (A2930, A2960, and A3030) corresponding to the wavenumbers 2930 cm\u003csup\u003e-1\u003c/sup\u003e (stretching vibration of C-H bonds in CH2 groups), 2960 cm\u003csup\u003e-1\u003c/sup\u003e (stretching vibration of C-H bonds in CH3 groups), and 3030 cm\u003csup\u003e-1\u003c/sup\u003e (stretching vibration of C-H bonds in aromatic hydrocarbons). The content of animal and plant oils is calculated based on the difference between the total extracted substances and petroleum content.\u003c/p\u003e\n\u003cp\u003eSS measurement: Turbidity meter model TD-2 is employed. COD determination: The Hashi digestion method is used.\u003c/p\u003e"},{"header":"3. Innovative Approach for Transformer Substation Oily Wastewater Treatment","content":"\u003cp\u003eThis research introduces a groundbreaking method for addressing the treatment of oily wastewater originating from transformer substations. Presently, a spectrum of techniques is disposed in managing such wastewater, but each exhibiting its inherent merits and demerits. Nevertheless, the utilization of a single-process methodology frequently falls short in achieving the desired water quality standards. In response to this question, the article advocates using a combination of multiple processes to replace a single process for treating such wastewater. By judiciously integrating different pro-cesses, this novel approach leverages the strengths of individual methods while miti-gating their respective limitations.\u003c/p\u003e\n\u003cp\u003eFollowing a comprehensive phase of rigorous research and experimentation, a more efficacious treatment process has emerged, which incorporates preliminary treatment, flotation, and fine filtration. \u0026nbsp; This innovative process not only conserves energy but also attains superior treatment effects. Within this article, a comprehensive elucidation is presented, encompassing the intricate stages of the treatment process and the precise determination of critical parameters.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.1. Pretreatment\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePreceding the commencement of industrial processes, pretreatment of oily wastewater stands as a requisite procedure. The pretreatment of such wastewater confers manifold advantages. It not only serves to enhance the quality of efficiency, but also mitigates the subsequent treatment burden while concurrently augmenting treatment efficiency.\u003c/p\u003e\n\u003cp\u003eIn this study, the latest and timely method was employed: utilizing 185nm far-ultraviolet light oxidation as a pre-treatment for oil-containing wastewater\u0026nbsp;[9]. The most significant feature of this method is its ability to disrupt conventional oil removal techniques such as precipitation and coagulation. From a molecular perspective, it breaks down the long chains of oil molecules, leading to the complete degradation of lipids. This approach exhibits a notably high removal rate of fats, thereby enhancing the biodegradability of the wastewater for subsequent biological treatment.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2. Flotation Process\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2.1. Introduction to Flotation\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe flotation process, a recently developed technology that has gained global at-tention, leds a new trend in the field of sewage treatment. Originating in the 1990s, this method demonstrates proficiency in the separation of solid particulates, particularly dispersed and emulsified oils, characterized by particle dimensions ranging from 10 to 60 nanometers, which persist in aqueous mediums post-separation processes\u0026nbsp;[10]. It re-lies on the chemical interaction of air generated within water, leading to the formation of minute air bubbles. These bubbles effectively entrap suspended particles in the aqueous matrix, ascend to the water-air interface, and create an oil-laden froth layer. Subsequent removal of this froth layer is accomplished through the utilization of an oil skimmer device.\u003c/p\u003e\n\u003cp\u003eCompared to alternative treatment methodologies, this approach distinguishes itself through its inherent simplicity, cost-effectiveness in terms of construction and operation, and its remarkable oil removal efficiency, which can attain levels as high as 95%. Additionally, it plays a pivotal role in elevating oil recovery rates and concurrently curbing environmental pollution.\u003c/p\u003e\n\u003cp\u003eCompared to alternative treatment methodologies, this approach distinguishes itself through its inherent simplicity, cost-effectiveness in terms of construction and operation, and its remarkable oil removal efficiency, which can attain levels as high as 95%. Additionally, it plays a pivotal role in elevating oil recovery rates and concurrently curbing environmental pollution.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2.2.\u003c/em\u003e \u003cem\u003eOperating Principle\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eIn this study, the vortex impeller flotation method is employed. Vortex impeller flotation belongs to the category of dispersed-air flotation. The vortex impeller flotation device comprises an aeration zone, flotation zone, recirculation system, scraper system, and drainage system. The device primarily utilizes the high-speed rotation of the aeration impeller at the bottom of the air distribution pipe to create a vacuum region in the water\u0026nbsp;[11]. Air at the liquid surface is introduced into the water through the aeration machine to fill the vacuum, leading to the formation of microbubbles, which spiral upward to the water surface. The oxygen in the air is dissolved into the water. The pre-treated wastewater enters the small inflatable section of the vortex impeller flotation machine, where the air at the water surface is transferred to the water column through an air suction pipe, allowing the wastewater to mix and come into contact with the microbubbles generated by the flotation machine. Microbubbles adhere to oil and suspended solids in the water, forming a buoyant fraction with a lower density than water. This fraction quickly rises to the water surface and is subsequently scraped into a sludge collection tank using a scraper, completing the purification of wastewater.\u003c/p\u003e\n\u003cp\u003eCoagulants are added at the front end of the coagulation reaction tank. Through primary and secondary stirring within the tank, water and chemicals undergo thorough coagulation reactions. Then, the water enters the vortex impeller flotation tank, where coagulants are added to the wastewater before it enters the tank. The effluent from the vortex impeller flotation is sent to a lift pump and transported to subsequent treatment systems. An open return pipe extends along the bottom of the flotation tank. While generating microbubbles, the vortex aeration machine forms a negative pressure zone at the bottom of the tank with the return flow pipe\u0026nbsp;[12, 13]. This negative pressure effect causes wastewater to flow back to the aeration zone from the tank bottom, then return to the flotation section. This process ensures that approximately 40% of the wastewater recirculates, allowing the flotation section to operate without incoming water.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2.3.\u003c/em\u003e \u003cem\u003eDetermination of Process Parameters\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2.3.1\u003c/em\u003e \u003cem\u003eDosage Determination\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePrior to initiating the flotation system, the introduction of coagulants, conventionally represented by polyacrylamide (PAM), is executed within the coagulation re-action vessel. Ensuring the effective amalgamation of PAM with the wastewater or sludge is of paramount importance, a procedure typically consummated within a temporal range of 10 to 30 seconds, with a prescribed upper limit not exceeding 2 minutes. The quantification of PAM is intricately linked to the concentration, attributes, and treatment apparatus of colloidal and suspended solids prevalent within the wastewater or sludge matrix. The precise determination of the optimal dosage necessitates com-prehensive empirical investigations tailored to the distinctiveness of transformer sub-station oily wastewater. \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFollowing a series of methodical comparative experiments designed to accommodate the idiosyncratic attributes of transformer substation oily wastewater, the ensuing dataset was acquired as Figure 4 and Table 1.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eTable 1.\u0026nbsp;\u003c/strong\u003e Effect table of different dosage.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"660\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e\u003cstrong\u003eDosage (mg/L)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSS Removal Rate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e\u003cstrong\u003eCOD Removal Rate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003cstrong\u003eil\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Removal Rate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003ePAC 15mg/L+PAM 1mg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e41.06%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e9.58%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e31.45%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003ePAC 30mg/L+PAM 1.5mg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e54.17%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e15.6%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e42.51%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003ePAC 45mg/L+PAM 2mg/L\u003c/p\u003e\n \u003cp\u003ePAC 60mg/L+PAM 2.5mg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e72.91%\u003c/p\u003e\n \u003cp\u003e70.88%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e39.34%\u003c/p\u003e\n \u003cp\u003e34.12%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e50.62%\u003c/p\u003e\n \u003cp\u003e46.38%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2.3.2\u003c/em\u003e \u003cem\u003eAeration Volume Determination\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAeration equipment is crucial to the operation of the flotation system. It supplies oxygen to the flotation tank and provides mixing and agitation, enhancing mass transfer conditions in the water treatment system and improving treatment efficiency. Different aeration volumes yield different effects on flotation. Through experiments conducted with commonly used aeration volumes, the following results were obtained as Figure 5 and Table 2.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eTable 2.\u0026nbsp;\u003c/strong\u003e Effect table of different aeration rate.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"650\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.725038402457756%\"\u003e\n \u003cp\u003e\u003cstrong\u003eAeration Rate\u003c/strong\u003e\u003cstrong\u003e（\u003c/strong\u003e\u003cstrong\u003em\u003csup\u003e3\u003c/sup\u003e/L\u003c/strong\u003e\u003cstrong\u003e）\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.50537634408602%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSS Removal Rate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.806451612903224%\"\u003e\n \u003cp\u003e\u003cstrong\u003eCOD Removal Rate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.963133640552996%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOil Removal Rate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.725038402457756%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.50537634408602%\"\u003e\n \u003cp\u003e56.81%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.806451612903224%\"\u003e\n \u003cp\u003e39.97%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.963133640552996%\"\u003e\n \u003cp\u003e45.97%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.725038402457756%\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.50537634408602%\"\u003e\n \u003cp\u003e57.63%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.806451612903224%\"\u003e\n \u003cp\u003e48.74%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.963133640552996%\"\u003e\n \u003cp\u003e51.26%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.725038402457756%\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.50537634408602%\"\u003e\n \u003cp\u003e72.45%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.806451612903224%\"\u003e\n \u003cp\u003e58.82%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.963133640552996%\"\u003e\n \u003cp\u003e68.55%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.725038402457756%\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.50537634408602%\"\u003e\n \u003cp\u003e59.27%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.806451612903224%\"\u003e\n \u003cp\u003e48.21%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.963133640552996%\"\u003e\n \u003cp\u003e51.84%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003e3.2.3.3\u003c/em\u003e \u003cem\u003eDetermination of pH Value\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the literature, the pH value significantly impacts the efficiency of air flotation treatment. This influence can be categorized into two primary aspects:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e1.When the pH value is 6.8, the interfacial tension of oily wastewater reaches its maximum. Regardless of an increase or decrease in pH value, the interfacial tension decreases. To enhance the disruption speed of the water film and increase adhesion, it is necessary to reduce interfacial tension. Thus, the pH value should deviate from 6.8.\u003c/p\u003e\n\u003cp\u003e2.Within the pH range of 6 to 9, the coagulant PAC demonstrates optimal coagu-lation effects. Therefore, it is essential to conduct experiments considering the impact of pH value on interfacial tension, coagulation effectiveness, and changes in oil droplet diameters to determine the best pH utilization range. Employing dissolved air flotation while maintaining other conditions constant, only the pH value was altered. The water\u0026apos;s oil content at different pH values was measured using a spectrophotometer, and the measured data is presented in the table below as Figure 6 and Table 3.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3.\u0026nbsp;\u003c/strong\u003e Effect table of different pH value.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"639\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePressure\u003c/strong\u003e\u003cstrong\u003e（\u003c/strong\u003e\u003cstrong\u003eMPa\u003c/strong\u003e\u003cstrong\u003e）\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e\u003cstrong\u003eInlet Oil Content\u003c/strong\u003e\u003cstrong\u003e（\u003c/strong\u003e\u003cstrong\u003emg/L\u003c/strong\u003e\u003cstrong\u003e）\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e\u003cstrong\u003epH Value\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOutlet Oil Content\u003c/strong\u003e\u003cstrong\u003e（\u003c/strong\u003e\u003cstrong\u003emg/L\u003c/strong\u003e\u003cstrong\u003e）\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOil Removal Rate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e37.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e63.17%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e27.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e72.36%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e17.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e82.64%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e14.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e85.23%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e19.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e81.03%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e23.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e76.86%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.561815336463223%\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.50078247261346%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.67605633802817%\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.604068857589983%\"\u003e\n \u003cp\u003e32.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.657276995305164%\"\u003e\n \u003cp\u003e67.58%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe data from the chart demonstrates a pronounced influence of pH value on air flotation treatment. The treatment effect is optimal within the pH range of 6 to 8. Hence, when handling oily wastewater using air flotation technology, it is recommended to control the pH value within the range of 6 to 8. In summary, when the dosage is PAC 45mg/L + PAM 2mg/L, and the aeration volume is 7m\u0026sup3;/L, the vortex concave air flotation exhibits the best effects. The vortex concave air flotation machine exhibits a strong adaptability to changes in wastewater quantity and water quality. By adjusting the height of the effluent weir easily, it can adapt to varying circumstances[14].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.3. Fine Filtration Device\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.3.1. Experimental Device Design\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eFiltration is a critical process in treating oily wastewater and serves as the final stage of wastewater treatment. Various oil fields and design production units consider filtration technology and equipment as a focal point of research. However, so far, there have been deficiencies in achieving the relevant emission standards.\u003c/p\u003e\n\u003cp\u003eConventional filters cannot meet the relevant emission standards for oily wastewater. Thus, a concept of a multi-stage fine filtration device is proposed based on conventional filters. This device is an intermittent counter-granularity filtration de-vice[15]. Each stage utilizes homogeneous filter media. Although the particle sizes of the filter media in each stage differ, there is an overall gradation from large to small, en-suring a more uniform distribution of pollutant interception across the filter layers, while also guaranteeing the attainment of emission standards under high-speed filtra-tion conditions. The device adopts a sealed pressure filtration, ensuring water pressure. The device is divided into symmetrical halves, each subdivided into three segments, ensuring each filter layer receives thorough backwashing, thereby saving energy\u0026nbsp;[16]..\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.3.2.\u003c/em\u003e \u003cem\u003eDetermination of Process Parameters\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.3.2.1\u003c/em\u003e \u003cem\u003eSelection of Filter Media\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eSurface modified B2, C5, C7 ceramic filter media and unmodified filter media were used under the same conditions to treat wastewater of the same concentration to de-termine the oil removal rate through each filter media. The wastewater is treated with the water sample after the best effect air flotation treatment. The experimental data is presented below as Figure 7 and Table 4.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4.\u0026nbsp;\u003c/strong\u003e Effect table of different filter material model.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"680\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.735294117647058%\"\u003e\n \u003cp\u003e\u003cstrong\u003eFilter Material Model\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.441176470588236%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOil Content Before Filtration (mg/L)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.61764705882353%\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;Oil Content After Filtration (mg/L)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.205882352941178%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOil Content Removal Rate\u003c/strong\u003e\u003cstrong\u003e（\u003c/strong\u003e\u003cstrong\u003e%\u003c/strong\u003e\u003cstrong\u003e）\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.735294117647058%\"\u003e\n \u003cp\u003e\u0026nbsp;Untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.441176470588236%\" rowspan=\"4\"\u003e\n \u003cp\u003e14.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.61764705882353%\"\u003e\n \u003cp\u003e6.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.205882352941178%\"\u003e\n \u003cp\u003e53.52%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.810650887573964%\"\u003e\n \u003cp\u003eB2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"35.700197238658774%\"\u003e\n \u003cp\u003e3.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"36.489151873767256%\"\u003e\n \u003cp\u003e75.31%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.810650887573964%\"\u003e\n \u003cp\u003eC5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"35.700197238658774%\"\u003e\n \u003cp\u003e2.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"36.489151873767256%\"\u003e\n \u003cp\u003e82.29%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.810650887573964%\"\u003e\n \u003cp\u003eC7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"35.700197238658774%\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"36.489151873767256%\"\u003e\n \u003cp\u003e99.46%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eIt is evident from the data that the C7 model of filter media exhibits the most effective oil removal, characterized as a surface-modified hydrophilic ceramic filter.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe C7-type filter described in this study is specially modified, primarily utilizing 202 silicone oil-modified porous ceramic filter balls. Silicone compounds exhibit two notable characteristics: (1) a lower surface energy and (2) wear resistance. Consequently, they have found widespread applications in surface modification, such as waterproofing agents, surface treatment of textiles, and corrosion protection of metal surfaces, re-placing environmentally polluting processes like phosphating and chromating.\u0026nbsp;However, research on the surface modification of ceramic filter media with organosilicon compounds is relatively scarce.\u003c/p\u003e\n\u003cp\u003eThe surface energy of ceramic filter balls is relatively high, rendering them hydrophilic. To make them oleophilic, it is necessary to reduce the surface energy of the filter balls, increasing the wetting angle for oil adsorption\u0026nbsp;[17]. This allows the formation of an oil film on the filter ball surface, completing the wetting aggregation. Additionally, gaps exist between filter materials, and there are large pores within the filter material\u0026nbsp;[18]. Collision and aggregation of small oil droplets occur in these spaces, and both theoretical and practical evidence demonstrate that the best results are achieved when both types of aggregation are present.\u003c/p\u003e\n\u003cp\u003eIn this study, we applied 202 silicone oil-modified porous ceramic filter balls. The Si-H in 202 undergoes hydrolysis to form Si-OH, which then undergoes condensation with hydroxyl groups on the filter ball surface, forming a reticulated structure. This rearranges the orientation of oleophilic groups (methyl) toward the external surface of the filter ball, altering the surface properties from hydrophilic to oleophilic\u0026nbsp;[19, 20]. The schematic diagram illustrating the mechanism is presented in the figure below as Figure 8.\u003c/p\u003e\n\u003cp\u003eThis type of ceramic filter outperforms traditional filter media like quartz sand and walnut shells, demonstrating longer filtration cycles, lower filtered water turbidity, greater pollutant interception capacity, a shorter maturation period, and enhanced resistance to impact loads, among other qualities.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.3.2.2\u003c/em\u003e \u003cem\u003eDetermination of Filter Media Gradation Combinations\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe particle gradation and suitable porosity of filter media are vital for filtration devices. Large particle sizes with high porosity yield low filtration resistance when dealing with minute suspended particles. Conversely, smaller particles with low po-rosity lead to the reverse. Therefore, for a specific water quality, meticulous gradation experiments are necessary to determine the appropriate filter media gradation and porosity\u0026nbsp;[21]. With artificial preparation of raw water and addition of clay in tap water, the removal rates of SS for each stage, COD removal rates, oil removal rates, etc., were measured. According to literature and experiments conducted by others, three types of gradation were determined:\u003c/p\u003e\n\u003cp\u003eGradation 1: Particle size of filter media between 1.60-1.80mm, a layer thickness of 900mm; particle size between 1.0-1.60mm, a layer thickness of 800mm; particle size between 0.8-1.0mm, a layer thickness of 700mm.\u003c/p\u003e\n\u003cp\u003eGradation 2: Particle size between 1.25-1.60mm, a layer thickness of 800mm; parti-cle size between 0.8-1.25mm, a layer thickness of 700mm; particle size between 0.6-0.8mm, a layer thickness of 600mm.\u003c/p\u003e\n\u003cp\u003eGradation 3: Particle size between 1.25-1.40mm, a layer thickness of 700mm; parti-cle size between 0.6-1.0mm, a layer thickness of 700mm; particle size between 0.4-0.6mm, a layer thickness of 700mm.\u003c/p\u003e\n\u003cp\u003eDifferent filter media gradations exhibit distinct removal effects on different pol-lutants, as detailed in the table below as Figure 9 and Table 5.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5.\u0026nbsp;\u003c/strong\u003e Effect table of different particle size distribution.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"734\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.337874659400544%\"\u003e\n \u003cp\u003e\u003cstrong\u003eParticle Size Distribution\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.798365122615802%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTurbidity Removal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.029972752043598%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSS Removal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.713896457765667%\"\u003e\n \u003cp\u003e\u003cstrong\u003eCOD Removal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.11989100817439%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOil Removal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.337874659400544%\"\u003e\n \u003cp\u003e\u0026nbsp;Particle Size Distribution 1\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.798365122615802%\"\u003e\n \u003cp\u003e60.52%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.029972752043598%\"\u003e\n \u003cp\u003e73.66%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.713896457765667%\"\u003e\n \u003cp\u003e42.12%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.11989100817439%\"\u003e\n \u003cp\u003e89.21%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.337874659400544%\"\u003e\n \u003cp\u003e\u0026nbsp;Particle Size Distribution 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.798365122615802%\"\u003e\n \u003cp\u003e70.84%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.029972752043598%\"\u003e\n \u003cp\u003e79.87%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.713896457765667%\"\u003e\n \u003cp\u003e48.89%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.11989100817439%\"\u003e\n \u003cp\u003e90.73%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.337874659400544%\"\u003e\n \u003cp\u003e\u0026nbsp;Particle Size Distribution 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.798365122615802%\"\u003e\n \u003cp\u003e80.32%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.029972752043598%\"\u003e\n \u003cp\u003e84.36%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.713896457765667%\"\u003e\n \u003cp\u003e54.30%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.11989100817439%\"\u003e\n \u003cp\u003e96.88%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eBased on experiments conducted on raw water, it\u0026apos;s evident that after filtration using gradation three, the best filtration efficiency is achieved, thereby establishing the required gradation conditions for fine filtration. After extensive research and experimentation, the use of ceramic filter media with a filtration rate of 15m/h, a gradation of particle sizes between 1.25-1.40mm, a layer thickness of 700mm, particle sizes between 0.6-1.0mm, and particle sizes between 0.4-0.6mm yielded relatively better treatment outcomes.\u003c/p\u003e"},{"header":"4. The comprehensive effect of Effluent treatment","content":"\u003cp\u003e\u003cem\u003e4.1.\u003c/em\u003e \u003cem\u003eEvaluation of effluent effect\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAfter confirming various parameters of the aforementioned process, in order to further validate the effectiveness of this technique, experiments were conducted to access the treatment efficiency of oily wastewater.\u003c/p\u003e\n\u003cp\u003eThis study examines the effectiveness of a wastewater treatment process for actual substation oily wastewater. The process involves pretreatment, flotation, and multi-stage fine filtration. The removal efficiency of turbidity, oil, and COD was evaluated through a week-long sampling and testing period. The detailed experimental data can be found in the table below as Table 6.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 6.\u0026nbsp;\u003c/strong\u003e Effect table of combined process for water treatment.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"649\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003e\u003cstrong\u003ewater sample\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSample Turbidity (NTU)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTurbidity Removal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"38%\" colspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eOil Content (mg/L)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOil Removal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e\u003cstrong\u003eCOD Removal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003eFirst Data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003eSecond Data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003eAverage Data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e8.915\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e96.89%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e100.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.475\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e67.21%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e87.33%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e10.487\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e98.35%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e100.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.445\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e83.92%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e96.41%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e10.355\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e98.79%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e101.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e102.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e101.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e95.89%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e88.67%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e10.286\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e99.03%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e99.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e99.925\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e87.92%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e92.91%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e10.598\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e96.21%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e99.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e98.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e99.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e96.24%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e99.55%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e9.431\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e97.27%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e100.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e96.83%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e86.92%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e9.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e97.91%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e100.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e101.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e88.76%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e89.81%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e10.234\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e98.52%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e101.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e100.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e101.055\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e80.64%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e88.71%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.307692307692308%\"\u003e\n \u003cp\u003ewater sample9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.076923076923077%\"\u003e\n \u003cp\u003e9.202\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.153846153846153%\"\u003e\n \u003cp\u003e98.72%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e102.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e101.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.384615384615385%\"\u003e\n \u003cp\u003e102.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e86.22%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23076923076923%\"\u003e\n \u003cp\u003e89.41%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe results demonstrate that this combined treatment process effectively removes turbidity and oil from the wastewater, meeting regulatory standards. The efficiency of turbidity, oil removal, and COD reduction was investigated to assess the performance of this treatment system. The experimental data reveals a significant reduction in turbidity achieved by the combined treatment process[22]. Over a continuous operation period of 5 hours, the lowest turbidity removal rate observed was 96.21%, and the effluent tur-bidity consistently remained below 1 mg/L, meeting A1 standards. Furthermore, the removal of oil content was highly effective, with the effluent oil concentration con-sistently below 5 mg/L, also meeting A1 standards.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e4.2.\u003c/em\u003e \u003cem\u003eFinancial analysis\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCost analysis of the novel process indicates that, in comparison to alternative methods, it boasts both lower costs and superior efficacy. The overall cost of the process for treating this wastewater is shown in the following table(Table 7).\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eTable 7.\u0026nbsp;\u003c/strong\u003e Financial analysis.\u003c/em\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"657\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"22.831050228310502%\"\u003e\n \u003cp\u003e\u003cstrong\u003eProcess\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\"\u003e\n \u003cp\u003e\u003cstrong\u003eElectricity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.4855403348554%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePharmaceutical costs\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.461187214611872%\"\u003e\n \u003cp\u003e\u003cstrong\u003eLabor costs\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"22.831050228310502%\"\u003e\n \u003cp\u003epretreatment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.4855403348554%\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.461187214611872%\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"22.831050228310502%\"\u003e\n \u003cp\u003eair flotation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.4855403348554%\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.461187214611872%\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"22.831050228310502%\"\u003e\n \u003cp\u003eFine Filtration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.4855403348554%\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.461187214611872%\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"22.831050228310502%\"\u003e\n \u003cp\u003etotal cost\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"77.1689497716895%\" colspan=\"3\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eOnce the combined treatment process of pretreatment, flotation, and fine filtration was stabilized, During continuous operation over several days, the minimum turbidity removal rate reached 96.21%, and the effluent turbidity consistently remained below 1 mg/L. The removal efficiency for oil was also significant, with the effluent oil concentration showing a notable decrease and consistently staying below 5 mg/L. These values fully comply with the national emission standard. The combination of this treatment process demonstrates its capability to effectively remove oil and organic contaminants from oily wastewater, exhibiting strong shock resistance and stable performance with low operational costs. It has the potential to become the mainstream technology for oily wastewater treatment and can serve as a reference for engineering design in this field.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of Interest Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and company that could be construed as influencing the position presented in, or the review of, the manuscript entitled.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eYan HUANG and Shangyong Wen put forward the innovation of the article, wrote the manuscript content；Zhengdong WAN, Hongyan Xin drew a picture and changed the format of the article. Kaiman Li conducted an article review and contributed papers.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData is provided within the manuscript or supplementary information files\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWang, H., B. Zhou, and X. Zhang, Research on the Remote Maintenance System Architecture for the Rapid Develop-ment of Smart Substation in China. IEEE Transactions on Power Delivery, 2018. 33(4): p. 1845-1852.\u003c/li\u003e\n\u003cli\u003eYu, L., M. Han, and F. He, A review of treating oily wastewater. Arabian Journal of Chemistry, 2017. 10: p. S1913-S1922.\u003c/li\u003e\n\u003cli\u003eWang, M., et al., Effective purification of oily wastewater using lignocellulosic biomass: A review. Chinese Chemical Letters, 2022. 33(6): p. 2807-2816.\u003c/li\u003e\n\u003cli\u003eAlmutairi, M., Evaluate the effectiveness technology for the treatment of oily wastewater. Journal of Water and Health, 2022. 20(8): p. 1171-1187.\u003c/li\u003e\n\u003cli\u003eBalasubramanian, N., N. Sakthipriya, and D.S. Ibrahim, Electro-coagulation treatment of oily wastewater with sludge analysis. Water Science and Technology, 2012. 66(12): p. 2533-2538.\u003c/li\u003e\n\u003cli\u003eMedeiros, A.D.L.M.d., et al., Oily Wastewater Treatment: Methods, Challenges, and Trends. Processes, 2022. 10(4).\u003c/li\u003e\n\u003cli\u003eAbuhasel, K., et al., Oily Wastewater Treatment: Overview of Conventional and Modern Methods, Challenges, and Future Opportunities. Water, 2021. 13(7).\u003c/li\u003e\n\u003cli\u003eZhang, H., S.C. Bukosky, and W.D. Ristenpart, Low-Voltage Electrical Demulsification of Oily Wastewater. Industrial \u0026amp; Engineering Chemistry Research, 2018. 57(24): p. 8341-8347.\u003c/li\u003e\n\u003cli\u003eDruskovic, M., et al., The Influence of Pretreatment on the Efficiency of Electrochemical Processes in Oily Wastewater Treatment. Water, 2022. 14(19).\u003c/li\u003e\n\u003cli\u003eHanafy, M. and H.I. Nabih, Treatment of Oily Wastewater Using Dissolved Air Flotation Technique. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2007. 29(2): p. 143-159.\u003c/li\u003e\n\u003cli\u003eZhang, H., S. Liu, and S. Yuan, Molecular dynamics simulation of oily wastewater treatment by air floatation. Journal of Molecular Liquids, 2023. 385.\u003c/li\u003e\n\u003cli\u003eSaththasivam, J., K. Loganathan, and S. Sarp, An overview of oil\u0026ndash;water separation using gas flotation systems. Chem-osphere, 2016. 144: p. 671-680.\u003c/li\u003e\n\u003cli\u003eWang, C., et al., Separation of emulsified crude oil from produced water by gas flotation: A review. Science of The Total Environment, 2022. 845.\u003c/li\u003e\n\u003cli\u003eRomphophak, P., et al., Prediction Model for the Treatment of Stabilized Oily Wastewater by Modified Induced Air Flotation (MIAF). Engineering Journal, 2016. 20(3): p. 11-21.\u003c/li\u003e\n\u003cli\u003eLoh, Z.Z., et al., Shifting from Conventional to Organic Filter Media in Wastewater Biofiltration Treatment: A Review. Applied Sciences, 2021. 11(18).\u003c/li\u003e\n\u003cli\u003eQing, C., et al., Filtration of oil from oily wastewater via hydrophobic modified quartz sand filter medium. Journal of Water Reuse and Desalination, 2018. 8(4): p. 544-552.\u003c/li\u003e\n\u003cli\u003eJin, Z., et al., 3D-printed controllable gradient pore superwetting structures for high temperature efficient oil-water separation. Journal of Materiomics, 2021. 7(1): p. 8-18.\u003c/li\u003e\n\u003cli\u003eDing, D., et al., Underwater superoleophobic-underoil superhydrophobic Janus ceramic membrane with its switchable separation in oil/water emulsions. Journal of Membrane Science, 2018. 565: p. 303-310.\u003c/li\u003e\n\u003cli\u003eCheng, X., et al., Finely tailored pore structure of polyamide nanofiltration membranes for highly-efficient application in water treatment. Chemical Engineering Journal, 2021. 417.\u003c/li\u003e\n\u003cli\u003eKaetzl, K., et al., Slow sand filtration of raw wastewater using biochar as an alternative filtration media. Scientific Reports, 2020. 10(1).\u003c/li\u003e\n\u003cli\u003eAlquraish, M., et al., Development of Environment-Friendly Membrane for Oily Industrial Wastewater Filtration. Membranes, 2021. 11(8).\u003c/li\u003e\n\u003cli\u003eDruskovic, M., et al., The application of electrochemical processes in oily wastewater treatment: a review. Journal of Environmental Science and Health, Part A, 2021. 56(13): p. 1373-1386.Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Substations, Oily wastewater treatment, New process, Economic benefits","lastPublishedDoi":"10.21203/rs.3.rs-4429410/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4429410/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe increasing demand for electrical power has led to a surge in the construction of substations worldwide. In the context of today's carbon emission reduction, more and more people are be-ginning to pay attention to the treatment of oily wastewater generated from substations. The specific traits such as the complicated components and rapid change in the raw wastewater quality make it rather hard to be degraded thoroughly and economically. In response to this challenge, we introduce a novel solution that combines pre-treatment, dissolved air flotation, and fine multi-stage filtration techniques to efficiently remove oil and suspended solids from oily wastewater discharge. This study comprehensively summarizes the characteristics of oil-containing wastewater in substations and invents a novel process for treating oil-containing wastewater from substations. It exhibits notable advantages in terms of energy efficiency and cost-effectiveness compared to conventional treatment methods. This research not only promotes the technical advances in the field of wastewater treatment but also provides a practical and sustainable solution for industries grappling with the conundrum of oily wastewater manage-ment. The findings presented here can be supposed to serve as a stepping stone towards the development of more efficient and environmentally friendly wastewater treatment strategies.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e","manuscriptTitle":"Characterization and Innovative Process of Oily Wastewater from Substations","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-05 09:48:33","doi":"10.21203/rs.3.rs-4429410/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-07-11T15:49:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-01T06:39:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"324878385218115245112440786534040805665","date":"2024-06-26T19:21:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"77208156299697112116387380965165709098","date":"2024-06-26T14:44:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-25T12:03:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"183760667685240921285599087120386330970","date":"2024-06-25T07:36:25+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-05-30T05:34:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"92092956111892642876439751806261202782","date":"2024-05-26T14:00:59+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-26T13:54:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-23T12:37:23+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-05-23T12:36:08+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Applied Sciences","date":"2024-05-16T08:01:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"39eb9b81-978f-4690-9cc2-88b6689ad7a0","owner":[],"postedDate":"June 5th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-03-04T06:38:06+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-05 09:48:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4429410","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4429410","identity":"rs-4429410","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}