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Figure 3. Schematic representation of different separation methods of oil particles from wastewater cum oil. on their density differences. Common gravity-based separators include gravity settlers, centrifuges, hydro- cyclones, and inclined plate separators [41]. Gravity settlers allow oil droplets to rise to the surface and form a distinct oil layer, which can then be skimmed off. Centrifuges utilize centrifugal force to accelerate the separation process, while hydrocyclones leverage centrifugal and gravitational forces to separate oil from water. Inclined plate separators use inclined plates to enhance the coalescence and settling of oil droplets [42]. These methods are widely employed due to their simplicity, reliability, and cost-effective- ness in treating wastewater contaminated with oil, contributing to the preservation of water resources and compliance with environmental regulations in the oil industry [43].

Figure 3 Schematic representation of different separation methods of oil particles from wastewater cum oil. on their density differences. Common gravity-based separators include gravity settlers, centrifuges, hydro- cyclones, and inclined plate separators [41]. Gravity settlers allow oil droplets to rise to the surface and form a distinct oil layer, which can then be skimmed off. Centrifuges utilize centrifugal force to accelerate the separation process, while hydrocyclones leverage centrifugal and gravitational forces to separate oil from water. Inclined plate separators use inclined plates to enhance the coalescence and settling of oil droplets [42]. These methods are widely employed due to their simplicity, reliability, and cost-effective- ness in treating wastewater contaminated with oil, contributing to the preservation of water resources and compliance with environmental regulations in the oil industry [43].

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The management of oil-contaminated water and wastewater in the oil industry remains a critical challenge due to its environmental and economic implications. This manuscript provides a comprehensive review of separation and removal techniques for oil from water and wastewater. It gives an overview of the origins and compositions of oil in wastewater, including natural and anthropogenic sources, as well as variations in physical states such as free, emulsified, and dissolved oil. The review delves into various separation methods, ranging from traditional gravity-based techniques to advanced technologies like membranes and recent developments in wastewater treatment systems. Furthermore, it discusses the application of new technologies specifically designed for the unique challenges faced in Middle East oil fields. The manuscript explores factors influencing oil-water separation efficiency, including operating conditions, chemical additives, equipment design, and environmental considerations. Additionally, it highlights current aspects and future directions in oily wastewater treatment, emphasizing the need for sustainable and effective solutions in the oil industry. 1. Introduction and grease are harmful to water life and can even and grease are harmful to water life and can even harm humans [3]. They get into the water from different sources, forming a layer on the surface that reduces the amount of oxygen in the water. As the industry grows, more oil is used, leading to more pol- lution. Petrochemical industries produce a lot of oily wastewater during production. Also, extracting oil results in a lot of wastewater containing oil com- ponents [4]. Oil extraction typically results in large volumes of petroleum industry wastewater In today's world of industry, the oil industry plays a big role in ensuring we have enough energy world- wide. Oil companies operate in many different places and do various tasks. One crucial job they have is cleaning up water that has oil or dirt in it [1]. This is important because when oil mixes with water, it can harm the environment. So, keeping water clean not only helps oil companies run smoothly but also protects nature [2] because oil
The management of oil-contaminated water and wastewater in the oil industry remains a critical challenge due to its environmental and economic implications. This manuscript provides a comprehensive review of separation and removal techniques for oil from water and wastewater. It gives an overview of the origins and compositions of oil in wastewater, including natural and anthropogenic sources, as well as variations in physical states such as free, emulsified, and dissolved oil. The review delves into various separation methods, ranging from traditional gravity-based techniques to advanced technologies like membranes and recent developments in wastewater treatment systems. Furthermore, it discusses the application of new technologies specifically designed for the unique challenges faced in Middle East oil fields. The manuscript explores factors influencing oil-water separation efficiency, including operating conditions, chemical additives, equipment design, and environmental considerations. Additionally, it highlights current aspects and future directions in oily wastewater treatment, emphasizing the need for sustainable and effective solutions in the oil industry. 1. Introduction and grease are harmful to water life and can even and grease are harmful to water life and can even harm humans [3]. They get into the water from different sources, forming a layer on the surface that reduces the amount of oxygen in the water. As the industry grows, more oil is used, leading to more pol- lution. Petrochemical industries produce a lot of oily wastewater during production. Also, extracting oil results in a lot of wastewater containing oil com- ponents [4]. Oil extraction typically results in large volumes of petroleum industry wastewater In today's world of industry, the oil industry plays a big role in ensuring we have enough energy world- wide. Oil companies operate in many different places and do various tasks. One crucial job they have is cleaning up water that has oil or dirt in it [1]. This is important because when oil mixes with water, it can harm the environment. So, keeping water clean not only helps oil companies run smoothly but also protects nature [2] because oil
Figure 1. A concise summary of the current stage of development of treatment approaches, the following factors have been con- sidered: Examples of gravity-based separation techniques include skimmer tanks, API separators, coalescers, and newer techniques for wastewater treatment systems. In the pursuit of making things more efficient anc sustainable, finding better ways to separate oil from water is crucial [14]. This review explores different techniques, from simple physical methods like gravity separation to more advanced chemical methods like electrocoagulation and membrane filtration. Studies have been summarized for the Oil in wastewater is a significant environmental concern with far-reaching implications for ecosys- tems, human health, and the economy. It primarily stems from industrial activities, such as oil refineries, petrochemical plants, and transportation [20]. When oil contaminates wastewater, it poses serious threats due to its toxicity, persistence, and potential for eco- logical disruption [21]. One of the major challenges with oil in wastewater is its tendency to form slicks on the surface, which can inhibit oxygen exchange,
Figure 1. A concise summary of the current stage of development of treatment approaches, the following factors have been con- sidered: Examples of gravity-based separation techniques include skimmer tanks, API separators, coalescers, and newer techniques for wastewater treatment systems. In the pursuit of making things more efficient anc sustainable, finding better ways to separate oil from water is crucial [14]. This review explores different techniques, from simple physical methods like gravity separation to more advanced chemical methods like electrocoagulation and membrane filtration. Studies have been summarized for the Oil in wastewater is a significant environmental concern with far-reaching implications for ecosys- tems, human health, and the economy. It primarily stems from industrial activities, such as oil refineries, petrochemical plants, and transportation [20]. When oil contaminates wastewater, it poses serious threats due to its toxicity, persistence, and potential for eco- logical disruption [21]. One of the major challenges with oil in wastewater is its tendency to form slicks on the surface, which can inhibit oxygen exchange,
Figure 2. (a) Oil particles dispersed in water to make the emul- sion (b) Oil particles containing water. An emulsion is a thermo- dynamically unstable system that tends to separate over time. The volume ratio of the two materials plays a significant role in determining the type of emulsion that forms, with the phase that is present in greater abundance producing the con- tinuous phase (both water & oil phase).
Figure 2. (a) Oil particles dispersed in water to make the emul- sion (b) Oil particles containing water. An emulsion is a thermo- dynamically unstable system that tends to separate over time. The volume ratio of the two materials plays a significant role in determining the type of emulsion that forms, with the phase that is present in greater abundance producing the con- tinuous phase (both water & oil phase).
Figure 4. Gravity-based oils diagram in which the lighter fluid, which is an oil, rises to the top and then leaps over the stationary plate. By removing the removable plate, it can be used with only one compartment when in operation [45]. compliance within industrial wastewater manage- ment practice [50]. clogged with oily water. When water encounters the first baffle, water's turbulence is reduced because most of the solids settle down in the separator, and oil droplets float to the surface of the water. As the wastewater runs to the second chamber towards the middle of the separator but is blocked from exiting by a second baffle, any remaining solids settle [46].
Figure 4. Gravity-based oils diagram in which the lighter fluid, which is an oil, rises to the top and then leaps over the stationary plate. By removing the removable plate, it can be used with only one compartment when in operation [45]. compliance within industrial wastewater manage- ment practice [50]. clogged with oily water. When water encounters the first baffle, water's turbulence is reduced because most of the solids settle down in the separator, and oil droplets float to the surface of the water. As the wastewater runs to the second chamber towards the middle of the separator but is blocked from exiting by a second baffle, any remaining solids settle [46].
Figure 5. Schematic representation of vertical skimmers. easier to bring the oil particles to the top for separ- ation. Merging oil particles in the region between he water outflow and the effluent input is possible, and the larger particles created can easily be carried o the surface [54,55] Controlling the oil’s depth can be done via various methods, including interface control, a water leg configuration analogous, or a bucket and weir arrangement Figure 5.
Figure 5. Schematic representation of vertical skimmers. easier to bring the oil particles to the top for separ- ation. Merging oil particles in the region between he water outflow and the effluent input is possible, and the larger particles created can easily be carried o the surface [54,55] Controlling the oil’s depth can be done via various methods, including interface control, a water leg configuration analogous, or a bucket and weir arrangement Figure 5.
Figure 6. Schematic representation of horizontal skimmers. o the surface and form a distinct oil layer. Meanwhile, suspended solids and heavier contaminants settle at he bottom of the tank. Skimmers or scrapers are hen used to collect and remove the accumulated oil layer, while sludge is periodically removed from he bottom of the tank [60]. API separators are renowned for their high efficiency in removing oil and suspended solids from wastewater, making them indispensable in ensuring compliance with environmental regulations and maintaining the integ- rity of water resources. Moreover, API separators can be integrated into larger wastewater treatment systems or used as standalone units, providing versa- tility and adaptability to various industrial appli- cations [59]. According to the API, basin performance is deter- mined by fluid retention duration, basin design, oil characteristics, operating conditions, and flocculation, (if added). This pond is ineffective in removing small particles. The retention time required increases sub- stantially as the size of the oil particles decreases, therefore, it is often not cost-effective to employ them to separate small particles [63].
Figure 6. Schematic representation of horizontal skimmers. o the surface and form a distinct oil layer. Meanwhile, suspended solids and heavier contaminants settle at he bottom of the tank. Skimmers or scrapers are hen used to collect and remove the accumulated oil layer, while sludge is periodically removed from he bottom of the tank [60]. API separators are renowned for their high efficiency in removing oil and suspended solids from wastewater, making them indispensable in ensuring compliance with environmental regulations and maintaining the integ- rity of water resources. Moreover, API separators can be integrated into larger wastewater treatment systems or used as standalone units, providing versa- tility and adaptability to various industrial appli- cations [59]. According to the API, basin performance is deter- mined by fluid retention duration, basin design, oil characteristics, operating conditions, and flocculation, (if added). This pond is ineffective in removing small particles. The retention time required increases sub- stantially as the size of the oil particles decreases, therefore, it is often not cost-effective to employ them to separate small particles [63].
Figure 7. API separator for oil-water separator. which involves the merging of smaller oil droplets into larger ones to facilitate their separation from water [64]. Coalescer separators typically consist of a series of specialized media, such as coalescing plates or fibrous materials, engineered to promote he coalescence of oil droplets. As wastewater flows hrough the separator, oil droplets adhere to the coa- escer media and coalesce into larger droplets, even- ually rising to the surface due to their lower density 65]. Meanwhile, treated water exits the separator hrough an outlet at the bottom. Coalescer separators offer high efficiency in oil removal, even in the pres- ence of emulsified oils or fine droplets, making them ideal for applications where stringent oil dis- charge limits must be met. Additionally, these separa- tors are compact, easy to maintain, and can be integrated into existing wastewater treatment systems, providing a cost-effective solution for oil- water separation challenges across various industries [66]. facilitate the combination of smaller oil particles into larger ones, enhancing the efficiency of separation processes.
Figure 7. API separator for oil-water separator. which involves the merging of smaller oil droplets into larger ones to facilitate their separation from water [64]. Coalescer separators typically consist of a series of specialized media, such as coalescing plates or fibrous materials, engineered to promote he coalescence of oil droplets. As wastewater flows hrough the separator, oil droplets adhere to the coa- escer media and coalesce into larger droplets, even- ually rising to the surface due to their lower density 65]. Meanwhile, treated water exits the separator hrough an outlet at the bottom. Coalescer separators offer high efficiency in oil removal, even in the pres- ence of emulsified oils or fine droplets, making them ideal for applications where stringent oil dis- charge limits must be met. Additionally, these separa- tors are compact, easy to maintain, and can be integrated into existing wastewater treatment systems, providing a cost-effective solution for oil- water separation challenges across various industries [66]. facilitate the combination of smaller oil particles into larger ones, enhancing the efficiency of separation processes.
Figure 8. Combination of a membrane bioreactor (MBR) and a photocatalytic reactor (PCR) for the treatment of shipboard sewage [93]. used in the wastewater treatment of various indus- tries, including the oil industry, to effectively remove organic pollutants and contaminants [96]. These pro- cesses involve the generation of highly reactive hydroxyl radicals (*OH) to oxidize and degrade organic compounds into simpler, less harmful sub- stances [97,98]. Photocatalytic is one of the powerful AOP processes, which involve the use of semiconduc- tor photocatalysts such as titanium dioxide (TiO), zinc oxide (ZnO), Haematite (a-Fe2O3), that become activated under UV light, generating electron-hole pairs. These electron-hole pairs then react with oxygen and water to produce hydroxyl radicals, which oxidize organic pollutants in the wastewater [99-102]. In contrast, the microelectrolysis process offers several advantages, including rapid treatment rates, versatility in treating various types of contami- nants, and the potential for simultaneous removal of oil and other pollutants. Additionally, this method can be integrated with other treatment processes to enhance overall efficiency, making it a promising sol- ution for addressing oil-contaminated wastewater in industrial settings [103,104]. For high concentrations of oily wastewater. micro in a single process [108], known as microelectrolysis. A variety of treatment procedures might be accom- plished utilizing this single approach [109], including discoloration, better flocculation, refractory organic oxidation, and enhancement in biodegradability. Figure 9 illustrates the integrated treatment process for wastewater containing both oil and organic con- taminants. This combined approach combines the principles of micro-electrolysis and MBR technologies to achieve efficient and effective treatment outcomes. The influent wastewater enters the micro-electrolysis reactor, where metal particles, typically iron or iron alloys, serve as electrodes submerged in the waste- water. Through electrochemical reactions, the metal particles undergo corrosion, releasing metal ions and generating reactive species such as hydroxyl rad- icals. These reactive species oxidize organic pollutants and break down oil and grease into smaller, more bio- degradable compounds, improving the treatability of the wastewater. wep Ho rr ee a |
Figure 8. Combination of a membrane bioreactor (MBR) and a photocatalytic reactor (PCR) for the treatment of shipboard sewage [93]. used in the wastewater treatment of various indus- tries, including the oil industry, to effectively remove organic pollutants and contaminants [96]. These pro- cesses involve the generation of highly reactive hydroxyl radicals (*OH) to oxidize and degrade organic compounds into simpler, less harmful sub- stances [97,98]. Photocatalytic is one of the powerful AOP processes, which involve the use of semiconduc- tor photocatalysts such as titanium dioxide (TiO), zinc oxide (ZnO), Haematite (a-Fe2O3), that become activated under UV light, generating electron-hole pairs. These electron-hole pairs then react with oxygen and water to produce hydroxyl radicals, which oxidize organic pollutants in the wastewater [99-102]. In contrast, the microelectrolysis process offers several advantages, including rapid treatment rates, versatility in treating various types of contami- nants, and the potential for simultaneous removal of oil and other pollutants. Additionally, this method can be integrated with other treatment processes to enhance overall efficiency, making it a promising sol- ution for addressing oil-contaminated wastewater in industrial settings [103,104]. For high concentrations of oily wastewater. micro in a single process [108], known as microelectrolysis. A variety of treatment procedures might be accom- plished utilizing this single approach [109], including discoloration, better flocculation, refractory organic oxidation, and enhancement in biodegradability. Figure 9 illustrates the integrated treatment process for wastewater containing both oil and organic con- taminants. This combined approach combines the principles of micro-electrolysis and MBR technologies to achieve efficient and effective treatment outcomes. The influent wastewater enters the micro-electrolysis reactor, where metal particles, typically iron or iron alloys, serve as electrodes submerged in the waste- water. Through electrochemical reactions, the metal particles undergo corrosion, releasing metal ions and generating reactive species such as hydroxyl rad- icals. These reactive species oxidize organic pollutants and break down oil and grease into smaller, more bio- degradable compounds, improving the treatability of the wastewater. wep Ho rr ee a |
Figure 9. Wastewater cum oil treatment using a combination of micro electrolysis and membrane bioreactor (MBR) technology [107,110].
Figure 9. Wastewater cum oil treatment using a combination of micro electrolysis and membrane bioreactor (MBR) technology [107,110].
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