A method and system for deep removal of COD in wastewater of super-heavy oil

Abstract

The present application relates to the technical field of high-difficult-degradation sewage discharge treatment of thick oil field, and particularly discloses a method for deep removal of COD in super-thick oil sewage, which comprises integrated adjustment and settlement treatment, series air floatation treatment and gradient peat collaborative treatment in sequence, wherein the integrated adjustment and settlement tank is used to carry out homogenization settlement treatment on the super-thick oil sewage to obtain primary oil-removed sewage; the flocculant and treatment agent are added to carry out settlement, demulsification, gel breaking and pre-oxidation treatment on the primary oil-removed sewage to obtain intermediate treatment sewage; and the activated sludge process is used to carry out microbial treatment and adsorption on the intermediate treatment sewage to obtain final treatment sewage. The present application uses integrated adjustment and settlement to realize homogenization and equalization of fluctuating sewage and primary oil removal; uses series air floatation to realize effective demulsification and gel breaking of high-emulsified sewage, and preliminarily reduces the COD value by means of physicochemical method; and uses gradient peat collaborative treatment to deeply remove COD, and effectively improves the biochemical treatment efficiency of difficult-biodegradation sewage.

Description

Technical Field

[0001] This invention relates to the field of treatment technology for highly resistant wastewater from heavy oil fields, specifically to a method and system for deep COD removal from ultra-heavy oil wastewater. Background Technology

[0002] Heavy oil (heavy asphalt crude oil) is characterized by high viscosity, high density and difficulty in extraction, while my country generally uses thermal recovery and steam injection for heavy oil extraction.

[0003] In the 1980s and 1990s, heavy oil was extracted using steam injection and steam drive. Large-scale heavy oil development led to an imbalance between production and injection, with produced water volume far exceeding the water consumption for steam injection.

[0005] Extra-heavy oily wastewater is difficult to treat due to factors such as the properties of the oil, the extraction method, the gathering and transportation method, and the dehydration method. It has the following seven main characteristics.

[0006] (1) Small density difference between oil and water Crude oil has a high density, with a relative density of 982.6–995.4 g / cm³. 3 The density difference between oil and water is small.

[0007] (2) High viscosity The produced water has high viscosity, with asphalt and gum content as high as 42-48%, poor fluidity, and high pollution level, especially at low water temperatures.

[0008] (3) High temperature In order to reduce the viscosity of crude oil during the development, gathering and transportation and dehydration process of heavy oil, the temperature is often raised to 70~80℃, which results in a relatively high temperature of the produced water.

[0009] (4) Severe emulsification Heavy oil produced water tends to form oil-in-water emulsions. This is because heavy oil contains a large amount of gums and asphaltenes, which are excellent natural emulsifiers, and because it undergoes multiple centrifugal shearing processes during crude oil production, the emulsification of heavy oil produced water is quite severe.

[0010] (5) Complex and variable composition Heavy oil produced water is complex. It is not only polluted by crude oil and contains a large amount of organic matter, but also carries many suspended solids in the high-temperature and high-pressure reservoir, and dissolves various salts and gases. Various chemical agents are added during the oil extraction and oil and gas gathering and transportation process, which makes the heavy oil produced water contain a variety of impurities.

[0011] (6) The inflow of water is highly volatile. The wastewater contains filter press water, acid and alkali wastewater, well washing wastewater, oil well operation wastewater, etc., and these wastewaters are discharged intermittently, which greatly increases the fluctuation of the incoming water.

[0012] (7) Poor biochemical properties Through tracking and analysis of BOD and COD values, the B / C ratio of ultra-heavy oily wastewater has remained at around 0.1 to 0.2 for a long time, indicating poor biodegradability and lack of nutrients.

[0013] Currently, the COD value of wastewater discharged from heavy oil fields in China, such as Xinjiang Oilfield and Henan Oilfield, is generally above 100 mg / L. The treatment process is relatively simple, with the main process being pretreatment oil removal followed by biological treatment. The pretreatment mainly uses oil removal tanks and flotation machines, adding conventional demulsifiers and water purification agents. The biological process uses conventional biological contact oxidation, utilizing the biofilm on the packing material to degrade organic pollutants in the wastewater.

[0014] For ultra-heavy oily wastewater, conventional processes and technologies cannot effectively achieve deep demulsification and oil-water separation of highly emulsified wastewater with low density difference. At the same time, due to biological toxicity and low biodegradability, general biological treatment processes are difficult to achieve effective degradation of organic matter. The COD degradation efficiency of biological systems for ultra-heavy oily wastewater is difficult to exceed 70%, and the final COD index cannot be treated to below 50 mg / L.

[0015] In summary, achieving compliant discharge and developing a novel, suitable method for deep COD removal from ultra-heavy oily wastewater, addressing its water quality characteristics and treatment challenges, has become an urgent problem to be solved. Summary of the Invention

[0016] To address existing technical problems, this invention proposes a deep COD removal method applicable to the water quality characteristics of the region. This method solves the problems of deep demulsification and degelatinization in ultra-heavy oily wastewater, as well as the problem of removing large amounts of chemical agents and other recalcitrant organic matter from ultra-heavy oily wastewater. It significantly improves the treatment efficiency of the biochemical system and ultimately achieves a COD of less than 50 mg / L after treatment of recalcitrant ultra-heavy oily wastewater, enabling wastewater to meet discharge standards.

[0017] According to one aspect of the present invention, a method for deep removal of COD from extra-heavy oily wastewater is provided, comprising sequentially performing integrated conditioning and sedimentation treatment, series-connected air flotation treatment, and cascaded peat co-treatment, wherein: Integrated regulating and settling treatment includes using an integrated regulating and settling tank to homogenize and settle the extra-heavy oily wastewater to obtain pre-de-oiled wastewater; The series air flotation treatment includes sedimentation, demulsification, degelatinization and pre-oxidation of the pre-degreased oil-removed wastewater by adding flocculants and treatment agents to obtain intermediate treated wastewater; The cascade peat co-treatment involves using activated sludge technology to treat intermediate wastewater with microorganisms, followed by adsorption treatment to obtain the final treated wastewater.

[0018] According to one embodiment of the present invention, the series air flotation treatment includes a first stage air flotation and a second stage air flotation. The first stage air flotation involves adding a first flocculant to perform a first stage sedimentation treatment on the pre-degreased oil-removed wastewater. The second stage air flotation involves adding a treatment agent to perform demulsification, degelatinization, and pre-oxidation treatment on the wastewater after the first stage sedimentation treatment. Then, a second flocculant is added to perform a second stage sedimentation treatment to obtain intermediate treated wastewater.

[0019] According to one embodiment of the present invention, the cascade peat co-treatment includes a first-stage cascade treatment and a second-stage cascade treatment. The first-stage cascade treatment uses activated sludge technology to treat intermediate wastewater with microorganisms. The second-stage cascade treatment adds water purification materials to the wastewater after the first-stage cascade treatment for adsorption, and then returns the water purification materials to the first-stage cascade treatment. The high concentration of active bacteria in the first-stage cascade treatment is used to biologically regenerate the returned water purification materials.

[0020] According to one embodiment of the present invention, the integrated regulating settling tank is divided into three zones in the vertical direction, which are, from top to bottom, a regulating buffer zone, a settling and clarification zone and a sludge discharge zone. The preliminarily degreased wastewater is discharged from the sludge outlet of the sludge discharge zone.

[0021] According to one embodiment of the present invention, a pontoon is provided in the tank of the regulating buffer zone near the water surface of the oil layer, and a fixed weir is provided on the downstream side of the pontoon. The integrated regulating settling treatment also includes oil collection by combining the pontoon and the fixed weir.

[0022] According to one embodiment of the present invention, a high and low weir is provided near the outlet of the sedimentation clarification zone for collecting and guiding the flow of clarified water, and the integrated sedimentation regulation also includes switching the drainage through the high and low weir.

[0023] According to one embodiment of the present invention, a funnel-shaped opening for sludge sedimentation is provided at the center of the bottom of the sludge discharge zone, and the integrated regulating sedimentation treatment also includes sludge discharge through negative pressure at the funnel-shaped opening.

[0024] According to one embodiment of the present invention, the integrated regulating sedimentation treatment further includes adding a reverse demulsifier into the integrated regulating sedimentation tank.

[0025] According to one embodiment of the present invention, the reverse demulsifier includes one or more of alkoxylated amines, alkoxylated phenolic resins, polyamine glycol esters, polyalkoxylated glycol esters, polyoxyethylene glycol esters, fatty acid esters, alkoxylated polyols, low molecular weight alkoxylated resins, and polyoxyalkylene glycols.

[0026] According to one embodiment of the present invention, when a reverse demulsifier is added, the pH value in the integrated settling tank is adjusted to a range of 6 to 9.

[0027] According to one embodiment of the present invention, the first flocculant comprises polyaluminum chloride and polyacrylamide, and the second flocculant comprises polyacrylamide.

[0028] According to one embodiment of the present invention, the treatment agent comprises polyferric sulfate produced by the persulfate process.

[0029] According to one embodiment of the present invention, the water purification material includes powdered activated carbon, the specific surface area of ​​which is between 500 and 1700 m² / g.

[0030] According to one embodiment of the present invention, the integrated regulating sedimentation treatment further includes adding a coagulant aid in the sedimentation clarification zone, wherein the coagulant aid is added by dry addition and / or wet addition.

[0031] According to one embodiment of the present invention, the coagulant aid includes acid-base regulators and / or inorganic particles and / or polymers and / or enzyme preparations.

[0032] According to one embodiment of the present invention, a stirring mechanism for preventing clumping is provided in the regulating buffer.

[0033] According to one embodiment of the present invention, the activated sludge process further includes the addition of highly efficient degrading bacteria and / or biological enzymes.

[0034] According to one embodiment of the present invention, the series flotation process includes a first-stage flotation and a second-stage flotation using a dissolved air flotation machine and / or a pressurized dissolved air flotation machine.

[0035] According to another aspect of the present invention, a system for deep COD removal from ultra-heavy oily wastewater is provided, comprising: An integrated regulating and settling device is used to homogenize and settle ultra-heavy oily wastewater to obtain pre-de-oiled wastewater. A series-connected air flotation unit, comprising air flotation zones connected in series, is used to add flocculants and treatment agents to pre-treated oil-removed wastewater for sedimentation, demulsification, degelatinization, and pre-oxidation to obtain intermediate-treated wastewater; and The cascade peat co-treatment device uses activated sludge technology to treat intermediate wastewater through microbial and adsorption processes to obtain the final treated wastewater.

[0036] According to one embodiment of the present invention, the integrated regulating settling device includes an integrated regulating settling tank, which forms three zones in the vertical direction, namely, a regulating buffer zone, a settling and clarification zone, and a sludge discharge zone from top to bottom; The series-connected air flotation device includes a first-stage air flotation zone and a second-stage air flotation zone connected in series. The outlet of the first-stage air flotation zone is connected to the inlet of the second-stage air flotation zone. The first-stage air flotation zone is used to perform a first-stage sedimentation treatment on the pre-de-oiled wastewater when a first flocculant is added. The second-stage air flotation zone is used to perform demulsification, degelatinization, and pre-oxidation treatment on the wastewater after the first-stage sedimentation treatment when a treatment agent is added, and to perform a second-stage sedimentation treatment when a second flocculant is added, so as to obtain intermediate-treated wastewater. The cascade peat co-treatment device includes a primary cascade treatment zone and a secondary cascade treatment zone. The primary cascade treatment zone uses activated sludge technology to treat intermediate wastewater with microorganisms. The secondary cascade treatment zone is used to adsorb the wastewater after the primary cascade treatment. The adsorption treatment includes adsorbing the remaining non-biodegradable components by adding water purification materials. The discharge port of the primary cascade treatment zone is connected to the inlet of the secondary cascade treatment zone. A return pipe is also installed between the primary and secondary cascade treatment zones.

[0037] Due to the adoption of the above technical solutions, this invention has the following advantages compared with the prior art: For ultra-heavy oily wastewater, integrated regulation and sedimentation are used to achieve homogenization and quantity of fluctuating wastewater and preliminary oil removal; series air flotation and the addition of treatment agents are used to effectively demulsify and break down highly emulsified wastewater, while initially reducing the COD value through physicochemical methods; and a cascaded peat co-treatment method is used to deeply remove COD, effectively improving the biochemical treatment efficiency of recalcitrant wastewater. Through the complete set of ultra-heavy oily wastewater COD deep removal methods, the oil content of ultra-heavy oily wastewater can be reduced from 1000 mg / L to 3 mg / L, suspended solids from 2000 mg / L to 5 mg / L, and COD from 1000 mg / L to below 50 mg / L, ultimately achieving wastewater discharge that meets standards. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some implementation examples of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A process flow diagram of a method for deep COD removal from ultra-heavy oily wastewater according to an embodiment of the present invention is shown. Detailed Implementation

[0040] The following detailed description of the embodiments is intended to exemplify the principles of the present invention, but should not be construed as limiting the scope of the invention. The present invention can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0041] These embodiments are provided to make this disclosure thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0042] It should be noted that, in the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0043] It should also be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0044] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0045] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0046] This invention provides a method for deep COD removal from ultra-heavy oily wastewater. Figure 1 A process flow diagram of an exemplary method for deep COD removal from extra-heavy oily wastewater according to the present invention is shown, which includes sequentially performed integrated conditioning and settling treatment, series air flotation treatment, and cascade peat co-treatment, wherein: In response to the characteristics of extra-heavy oily wastewater, which contains multiple water sources such as formation produced water, filter press water, acid and alkali wastewater, well washing wastewater and oil well operation wastewater, and has large fluctuations in water flow and complex and variable composition, the integrated regulating and settling treatment includes using an integrated regulating and settling tank to homogenize and settling the extra-heavy oily wastewater to obtain preliminary oil-removed wastewater; In response to the characteristics of ultra-heavy oily wastewater, such as low density difference, high viscosity, and high degree of emulsification, the series of air flotation treatment includes sedimentation, demulsification, degelatinization, and pre-oxidation treatment of the initially de-oiled wastewater by adding flocculants and treatment agents to obtain intermediate treated wastewater; In response to the characteristics of ultra-heavy oily wastewater, such as low B / C ratio and poor biodegradability, the cascade peat co-treatment method involves using activated sludge technology to treat intermediate wastewater with microorganisms, followed by adsorption treatment to obtain the final treated wastewater.

[0047] The series air flotation treatment includes a first-stage air flotation and a second-stage air flotation. The first-stage air flotation involves adding a first flocculant to perform a first-stage sedimentation treatment on the pre-de-oiled wastewater. The second-stage air flotation involves adding a treatment agent to perform demulsification, degelatinization, and pre-oxidation treatment on the wastewater after the first-stage sedimentation treatment. Then, a second flocculant is added for a second-stage sedimentation treatment to obtain intermediate-treated wastewater.

[0048] The cascade peat co-treatment includes a primary cascade treatment and a secondary cascade treatment. The primary cascade treatment uses activated sludge technology to treat intermediate wastewater with microorganisms. The secondary cascade treatment adds water purification materials to the wastewater after the primary cascade treatment for adsorption. The water purification materials are then returned to the primary cascade treatment, where the high concentration of active bacteria from the primary cascade treatment biologically regenerates the returned water purification materials.

[0049] The primary function of cascade treatment processes is to enhance the role of microbial treatment. Whether using activated sludge or biofilm processes, both require contact between pollutants and microorganisms within the biological treatment tank for the microorganisms to degrade the pollutants. The treatment efficiency largely depends on the contact time, i.e., the hydraulic retention time of the wastewater in the biological treatment tank. However, when dealing with highly viscous oily wastewater containing recalcitrant organic matter, the microorganisms often haven't completed the effective decomposition of the pollutants before they flow into the next unit. Therefore, it's necessary to increase the hydraulic retention time of the biological treatment tank, which means larger tanks and higher investment.

[0050] The first stage of the cascade treatment in this invention employs an activated sludge process to degrade readily biodegradable organic matter within the conventional retention time. To maximize the contact time between microorganisms and pollutants, porous powdered activated carbon is introduced. The porous space within the powdered carbon adsorbs bacteria and recalcitrant organic matter, allowing them to continuously contact and interact within the carbon. This shifts the contact time of recalcitrant organic matter from hydraulic retention time to solid-state retention time, extending it to 15 days for ultra-heavy oily wastewater. Through solid-liquid separation in a sedimentation tank and subsequent reflux, peat retention is achieved, resulting in a contact time 15 times longer than conventional processes. These two processes at the beginning of the cascade treatment stage remove the vast majority of recalcitrant organic matter, leaving the remaining COD primarily composed of non-biodegradable organic matter, thus reducing the COD value of ultra-heavy oily wastewater to 110-130 mg / L.

[0051] In some specific embodiments, the integrated regulating settling tank is vertically divided into three zones: a regulating buffer zone, a settling and clarification zone, and a sludge discharge zone, from top to bottom. Initially degreased wastewater is discharged from the sludge outlet in the sludge discharge zone. The regulating buffer zone, located at the top, buffers the impact of incoming water flow, allowing the water to flow smoothly into subsequent zones and facilitating orderly subsequent treatment. The settling and clarification zone, in the middle, allows suspended particles in the water to settle sufficiently, effectively improving water clarity. The sludge discharge zone at the bottom facilitates the collection of settled sludge, enabling regular cleaning and ensuring the tank's continuous and efficient operation. The three zones work synergistically to improve overall regulating and settling efficiency, making wastewater treatment processes smoother, more stable, and more efficient.

[0052] Based on the above embodiments, a pontoon is installed near the oil layer surface within the tank of the regulating buffer zone, and a fixed weir is installed downstream of the pontoon. The integrated regulating settling treatment also includes oil collection through a combination of the pontoon and the fixed weir. The pontoon can flexibly float according to changes in oil layer thickness, precisely conforming to the oil surface to ensure maximum collection of floating oil and avoid leakage. The fixed weir provides stable support and auxiliary blocking, and together with the pontoon, it can effectively prevent the outflow of floating oil, improving oil collection efficiency. The combination of the two can adapt to different operating conditions, ensuring a stable and continuous oil collection process, reducing oil loss, improving resource recovery rate, and also helping to reduce the adverse impact of oily wastewater on the surrounding environment.

[0053] In some specific embodiments, high and low weirs are set near the outlet of the settling and clarification zone to collect and guide the outflow of clarified water. Integrated settling regulation also includes switching drainage through high and low weirs. The high and low weirs can selectively drain water according to the water quality at different heights in the settling and clarification zone. Generally, after sedimentation, the clarified water closer to the surface has relatively better quality and lower impurity content. By reasonably setting the height of the high and low weirs, the higher-quality upper layer of clarified water is discharged first from the higher weir, which can better ensure the stability and good quality of the final discharged water and reduce the possibility that water with slightly more impurities in the lower layer may mix into the discharged water due to accidental water disturbances, thus affecting the overall effluent water quality.

[0054] Based on the above embodiments, a funnel-shaped inlet for sludge sedimentation is provided at the center of the bottom of the sludge discharge zone. The integrated regulating sedimentation treatment also includes sludge discharge through negative pressure at the funnel. The negative pressure formed at the funnel generates a strong suction force. Compared with conventional sludge discharge methods that rely on gravity or other natural forces, this negative pressure suction can more effectively extract the sludge settled at the bottom. Especially for some thicker, more viscous sludge, gravity flow may be difficult to discharge smoothly, while the negative pressure at the funnel can overcome the resistance of this sludge, ensuring that it is smoothly removed from the sedimentation zone, improving sludge discharge efficiency, and preventing excessive sludge accumulation at the bottom from affecting the sedimentation effect.

[0055] In some specific embodiments, the integrated conditioning and settling treatment also includes adding a reverse demulsifier into the integrated conditioning and settling tank. Many oily wastewater systems form stable emulsions, with oil droplets uniformly dispersed in the aqueous phase and encapsulated by emulsifiers, making natural separation difficult. Reverse demulsifiers, through their unique chemical structure, interact with emulsifiers, altering their properties and disrupting the original stable structure of the emulsion, allowing oil droplets to coalesce and grow.

[0056] Based on the above embodiments, the reverse demulsifier includes one or more of alkoxylated amines, alkoxylated phenolic resins, polyamine glycol esters, polyalkoxylated glycol esters, polyoxyethylene glycol esters, fatty acid esters, alkoxylated polyols, low molecular weight alkoxylated resins, and polyoxyalkylene glycols.

[0057] In some specific embodiments, when adding the reverse demulsifier, the pH value in the integrated settling tank is adjusted to a range of 6-9. Within this relatively mild pH range of 6-9, the active groups in the demulsifier molecules maintain a good active state, allowing them to effectively interact with the emulsifier in the emulsion, thereby disrupting the emulsion's stability and achieving oil droplet coalescence.

[0058] Based on the above embodiments, the first flocculant includes polyaluminum chloride and polyacrylamide, and the second flocculant includes polyacrylamide.

[0059] In some specific embodiments, the treatment agent includes polyferric sulfate produced by the persulfate process, which achieves a high-intensity demulsification and degelatinization effect.

[0060] Based on the above embodiments, the water purification material includes powdered activated carbon. Powdered activated carbon has a highly developed pore structure, containing pores of different sizes such as micropores, mesopores, and macropores, which gives it a huge specific surface area, enabling it to effectively remove various organic pollutants from water through physical adsorption.

[0061] In some specific embodiments, the specific surface area of ​​the powdered activated carbon is between 500 and 1700 m² / g.

[0062] Based on the above embodiments, the integrated sedimentation treatment also includes adding a coagulant aid in the sedimentation clarification zone. The coagulant aid itself can adsorb onto the surface of suspended particles in water and the initially formed micro flocs. By changing the surface properties of these particles and flocs, such as surface charge and hydrophilicity, it makes them more likely to collide and adhere to each other, thereby promoting the formation of larger and more stable floc structures.

[0063] In some specific embodiments, the coagulant aid includes acid-base regulators and / or inorganic particles and / or polymers and / or enzyme preparations. When the above-mentioned coagulant aids are used in combination with flocculants, they can improve the utilization efficiency of flocculants, allowing for a suitable reduction in the amount of flocculant used while achieving the same or even better flocculation and sedimentation effects.

[0064] Based on the above embodiments, the coagulant aid can be added by dry dosing and / or wet dosing. Dry dosing is simple and flexible to operate, requires no complicated preparation, and can be added in emergencies; it saves storage space and is suitable for places with limited space; it has high stability and a long shelf life; wet dosing has good mixing uniformity, can avoid local uneven concentration, and solution dosing can quickly take effect, accelerate flocculation and sedimentation, and is applicable to a variety of coagulant aids.

[0065] In some specific embodiments, a stirring mechanism is provided in the regulating buffer to prevent clumping. The continuous operation of the stirring mechanism ensures that the material in the regulating buffer remains in a uniform state at all times, avoiding the phenomenon of material stratification or local component aggregation and clumping caused by prolonged standing, thus ensuring that the material flowing out of the buffer is stable in properties and uniform in composition, providing a reliable guarantee for the stable operation of subsequent processes.

[0066] Building upon the above embodiments, the activated sludge process further includes the addition of highly efficient degrading bacteria and / or bioenzymes. Highly efficient degrading bacteria often possess a strong ability to decompose specific organic pollutants, such as strains that specifically degrade recalcitrant organic matter (like polycyclic aromatic hydrocarbons). Their addition accelerates the decomposition of these substances, converting them into harmless substances like carbon dioxide and water. Similarly, bioenzymes catalyze specific biochemical reactions, promoting the rapid hydrolysis of complex organic matter. The combined effect of both significantly enhances the overall removal efficiency of organic matter from wastewater by activated sludge, effectively improving effluent quality.

[0067] In some specific embodiments, tandem dissolved air flotation (DAF) treatment includes primary and secondary flotation using a dissolved air flotation (DAF) machine and / or a pressurized DAF machine. Both DAF and pressurized DAF machines generate a large number of microbubbles, which, as they rise, attach to suspended particles in the water. These bubbles, relying on buoyancy, carry the particles quickly to the surface, forming scum that is then removed. For fine suspended particles in wastewater that are difficult to remove through natural sedimentation, DAF treatment can achieve highly efficient separation, significantly reducing the suspended solids content in the water and improving water clarity.

[0068] One stage of air flotation incorporates polyaluminum chloride and polyacrylamide, reducing the oil content of the treated wastewater to 20 mg / L and suspended solids to 50 mg / L. The core second stage air flotation uses polyferric sulfate produced by persulfate treatment to achieve a high-intensity demulsification and degelatinization effect, while pre-oxidizing complex organic matter. Polyacrylamide is added again for flocculation, and the pollutants are transformed into scum and separated by the floating action of small-sized bubbles in the flotation machine. Through a series of comprehensive effects of demulsification, degelatinization, oxidation, and flocculation, the oil content and suspended solids in the wastewater are reduced to below 10 mg / L, and the COD of wastewater with oil content below 10 mg / L is reduced from 800-1000 mg / L to 400-600 mg / L.

[0069] Based on the above embodiments, the cascade peat co-treatment also includes sending the adsorbed and saturated water purification material to the first-stage cascade treatment through a reflux process via a two-stage cascade treatment; the high concentration of active bacteria in the first-stage cascade treatment biologically regenerates the refluxed water purification material.

[0070] The two-stage cascade treatment with peat co-treatment targets the remaining non-biodegradable components by adsorbing them with freshly added powdered activated carbon, reducing the COD of the wastewater to below 50 mg / L. The activated carbon dosage is adjusted according to the B / C ratio of the influent of the extra-heavy oily wastewater, ranging from 500 to 700 mg / L. The activated carbon saturated in the two-stage treatment is returned to the first-stage treatment for biological treatment, utilizing its remaining adsorption capacity to further enrich pollutants and bacteria. Simultaneously, the high concentration of active bacteria in the first-stage treatment biologically regenerates the returned carbon. For extra-heavy oil, the COD treatment efficiency of this invention with peat co-treatment can reach 90-95%, far exceeding the 70% treatment efficiency of conventional biological treatment.

[0071] If water purification materials are discarded directly after they become saturated with adsorption, it not only wastes resources but also increases usage costs. This reflux and biological regeneration method restores some of their adsorption capacity, allowing them to be recycled and used multiple times in the water purification process. This significantly extends the lifespan of the water purification materials, reduces the need for frequent replacements, and substantially lowers long-term costs related to material procurement.

[0072] After biological regeneration, the water purification materials can be reintroduced into the water purification process to continue adsorbing pollutants (such as organic matter and heavy metals) in the water. This ensures that the entire water purification system can function continuously and stably without experiencing a decline in treatment efficiency due to the adsorption saturation of the water purification materials. It helps maintain a stable and efficient level of water purification and meets continuous water purification needs.

[0073] The saturated water purification materials that are returned to the system often have contaminants that were not completely removed before. These substances are like additional substrates for the high-concentration active bacteria in the first-stage treatment process, enriching the nutrients available to the bacteria, stimulating their growth and reproduction, and further enhancing the activity and efficiency of the biological treatment process. This creates a virtuous cycle between biological treatment and the adsorption effect of the water purification materials, improving the overall water treatment effect.

[0074] The present invention also provides a system for deep removal of COD from ultra-heavy oily wastewater, comprising: An integrated regulating and settling device is used to homogenize and settle ultra-heavy oily wastewater to obtain pre-de-oiled wastewater. A series-connected air flotation unit, comprising air flotation zones connected in series, is used to add flocculants and treatment agents to pre-treated oil-removed wastewater for sedimentation, demulsification, degelatinization, and pre-oxidation to obtain intermediate-treated wastewater; and The cascade peat co-treatment device uses activated sludge technology to treat intermediate wastewater through microbial and adsorption processes to obtain the final treated wastewater.

[0075] In some specific embodiments, the integrated regulating settling device includes an integrated regulating settling tank, which forms three zones in the vertical direction, namely, a regulating buffer zone, a settling and clarification zone, and a sludge discharge zone from top to bottom; The series-connected air flotation device includes a first-stage air flotation zone and a second-stage air flotation zone connected in series. The outlet of the first-stage air flotation zone is connected to the inlet of the second-stage air flotation zone. The first-stage air flotation zone is used to perform a first-stage sedimentation treatment on the pre-de-oiled wastewater when a first flocculant is added. The second-stage air flotation zone is used to perform demulsification, degelatinization, and pre-oxidation treatment on the wastewater after the first-stage sedimentation treatment when a treatment agent is added, and to perform a second-stage sedimentation treatment when a second flocculant is added, so as to obtain intermediate-treated wastewater. The cascade peat co-treatment device includes a primary treatment zone and a secondary treatment zone. The primary treatment zone uses activated sludge technology to treat intermediate wastewater using microorganisms. The secondary treatment zone is used for adsorption treatment of the wastewater after the primary treatment. Adsorption treatment includes adding water purification materials to adsorb remaining non-biodegradable components. The discharge port of the primary treatment zone is connected to the inlet of the secondary treatment zone, and a return pipe is also provided between the two zones. This invention has the following advantages compared to existing technologies: For ultra-heavy oily wastewater, an integrated regulating sedimentation system is employed to achieve homogenization and initial oil removal of fluctuating wastewater. A series of air flotation processes and the addition of a treatment agent (polyferric persulfate) are used to effectively demulsify and break down highly emulsified wastewater, while simultaneously reducing COD values ​​through physicochemical methods. A tiered peat co-treatment system is then used for deep COD removal, effectively improving the biochemical treatment efficiency of recalcitrant wastewater. This comprehensive COD removal method for ultra-heavy oily wastewater reduces oil content from 1000 mg / L to 3 mg / L, suspended solids from 2000 mg / L to 5 mg / L, and COD from 1000 mg / L to below 50 mg / L, ultimately achieving wastewater discharge that meets standards.

[0076] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for deep COD removal from ultra-heavy oily wastewater, characterized in that, This includes sequential integrated conditioning and settling treatment, tandem air flotation treatment, and cascade peat co-treatment, wherein: The integrated regulating and settling treatment includes using an integrated regulating and settling tank to homogenize and settling the extra-heavy oily wastewater to obtain pre-de-oiled wastewater. The series flotation treatment includes sedimentation, demulsification, degelatinization and pre-oxidation of the preliminary oil-removed wastewater by adding flocculants and treatment agents to obtain intermediate treated wastewater; The cascade peat co-treatment includes using activated sludge technology to treat the intermediate wastewater with microorganisms, followed by adsorption treatment to obtain the final treated wastewater.

2. The method for deep COD removal from ultra-heavy oily wastewater according to claim 1, characterized in that, The series flotation treatment includes a first-stage flotation and a second-stage flotation. The first-stage flotation involves adding a first flocculant to perform a first-stage sedimentation treatment on the pre-degreased oil-removed wastewater. The second-stage flotation involves adding a treatment agent to perform demulsification, degelatinization, and pre-oxidation treatment on the wastewater after the first-stage sedimentation treatment. Then, a second flocculant is added for a second-stage sedimentation treatment to obtain the intermediate-treated wastewater.

3. The method for deep COD removal from ultra-heavy oily wastewater according to claim 1, characterized in that, The cascade peat co-treatment includes a first-stage treatment and a second-stage treatment. The first-stage treatment uses activated sludge technology to treat the intermediate wastewater with microorganisms. The second-stage treatment adds water purification materials to the wastewater after the first-stage treatment for adsorption, and then returns the water purification materials to the first-stage treatment. The high concentration of active bacteria in the first-stage treatment is used to biologically regenerate the returned water purification materials.

4. The method for deep COD removal from ultra-heavy oily wastewater according to claim 1, characterized in that, The integrated regulating sedimentation tank is divided into three zones along the vertical direction, which are, from top to bottom, a regulating buffer zone, a sedimentation and clarification zone, and a sludge discharge zone. The preliminary oil-removed wastewater is discharged from the sludge outlet of the sludge discharge zone.

5. The method for deep COD removal from ultra-heavy oily wastewater according to claim 4, characterized in that, A pontoon is installed in the tank of the regulating buffer zone near the water surface of the oil layer, and a fixed weir is installed on the downstream side of the pontoon. The integrated regulating settling treatment also includes oil collection through the combination of the pontoon and the fixed weir.

6. The method for deep COD removal from ultra-heavy oily wastewater according to claim 4, characterized in that, The sedimentation clarification zone is equipped with high and low weirs near the outlet for collecting and guiding the clarified water outflow. The integrated sedimentation regulation also includes switching the drainage through the high and low weirs.

7. The method for deep COD removal from ultra-heavy oily wastewater according to claim 4, characterized in that, The bottom center of the sludge discharge zone is provided with a funnel-shaped opening for sludge sedimentation, and the integrated regulating sedimentation treatment also includes sludge discharge through the negative pressure of the funnel-shaped opening.

8. The method for deep COD removal from ultra-heavy oily wastewater according to claim 1, characterized in that, The integrated regulating sedimentation treatment also includes adding a reverse demulsifier into the integrated regulating sedimentation tank.

9. The method for deep COD removal from ultra-heavy oily wastewater according to claim 8, characterized in that, The reverse demulsifier includes one or more of alkoxylated amines, alkoxylated phenolic resins, polyamine glycol esters, polyalkoxylated glycol esters, polyoxyethylene glycol esters, fatty acid esters, alkoxylated polyols, low molecular weight alkoxylated resins, and polyoxyalkylene glycols.

10. The method for deep COD removal from ultra-heavy oily wastewater according to claim 8, characterized in that, When a reverse demulsifier is added, the pH range in the integrated settling tank is 6 to 9.

11. The method for deep COD removal from ultra-heavy oily wastewater according to claim 2, characterized in that, The first flocculant includes polyaluminum chloride and polyacrylamide, and the second flocculant includes polyacrylamide.

12. The method for deep COD removal from ultra-heavy oily wastewater according to claim 1, characterized in that, The treatment agent includes polyferric sulfate produced by the persulfate process.

13. The method for deep COD removal from ultra-heavy oily wastewater according to claim 3, characterized in that, The water purification material includes powdered activated carbon, and the specific surface area of ​​the powdered activated carbon is between 500 and 1700 m² / g.

14. The method for deep COD removal from ultra-heavy oily wastewater according to claim 4, characterized in that, The integrated sedimentation regulation treatment also includes adding a coagulant aid to the sedimentation clarification zone, wherein the coagulant aid is added by dry addition and / or wet addition.

15. The method for deep COD removal from ultra-heavy oily wastewater according to claim 14, characterized in that, The coagulant aid includes acid-base regulators and / or inorganic particles and / or polymers and / or enzyme preparations.

16. The method for deep COD removal from ultra-heavy oily wastewater according to claim 4, characterized in that, The regulating buffer zone is equipped with a stirring mechanism to prevent clumping.

17. The method for deep COD removal from extra-heavy oily wastewater according to claim 1, characterized in that, The activated sludge process also includes the addition of highly efficient degrading bacteria and / or biological enzymes.

18. The method for deep COD removal from ultra-heavy oily wastewater according to claim 2, characterized in that, The series flotation process includes a first-stage flotation and a second-stage flotation using a dissolved air flotation machine and / or a pressurized dissolved air flotation machine.

19. A system for deep COD removal from ultra-heavy oily wastewater, comprising: An integrated regulating and settling device is used to homogenize and settle ultra-heavy oily wastewater to obtain pre-de-oiled wastewater. A series-connected air flotation device, comprising air flotation zones connected in series, is used to add flocculants and treatment agents to perform sedimentation, demulsification, degelatinization and pre-oxidation treatment on the pre-treated oily wastewater to obtain intermediate-treated wastewater; as well as A tiered peat co-treatment device, wherein the tiered peat co-treatment device uses activated sludge process to perform microbial treatment and adsorption treatment on the intermediate wastewater to obtain the final treated wastewater.

20. The COD deep removal system for ultra-heavy oily wastewater according to claim 19, characterized in that: The integrated regulating settling device includes an integrated regulating settling tank, which forms three zones along the vertical direction, namely, a regulating buffer zone, a settling and clarification zone, and a sludge discharge zone, from top to bottom. The series-connected air flotation device includes a first-stage air flotation zone and a second-stage air flotation zone connected in series. The outlet of the first-stage air flotation zone is connected to the inlet of the second-stage air flotation zone. The first-stage air flotation zone is used to perform a first-stage sedimentation treatment on the pre-de-oiled wastewater when a first flocculant is added. The second-stage air flotation zone is used to perform demulsification, degelatinization, and pre-oxidation treatment on the wastewater after the first-stage sedimentation treatment when a treatment agent is added, and to perform a second-stage sedimentation treatment when a second flocculant is added, to obtain intermediate-treated wastewater. The cascade peat co-treatment device includes a first-stage treatment zone and a second-stage treatment zone. The first-stage treatment zone uses activated sludge technology to treat the intermediate wastewater with microorganisms. The second-stage treatment zone is used to adsorb the wastewater after the first-stage treatment. The adsorption treatment includes adsorbing the remaining non-biodegradable components by adding water purification materials. The discharge port of the first-stage treatment zone is connected to the inlet of the second-stage treatment zone. A return pipe is also provided between the first-stage treatment zone and the second-stage treatment zone.

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