Degradable wastewater treatment process based on coupling of EBIS and improved BAF

Abstract

The application discloses a refractory wastewater treatment process based on coupling of EBIS and improved BAF, relates to the technical field of wastewater treatment, and discloses the following technical scheme: EBIS effluent is introduced into an intermediate sedimentation tank for solid-liquid separation, part of the sludge is backflowed to the inlet of the EBIS reactor to maintain high biological concentration, and the remaining sludge is discharged; the supernatant is introduced into an improved BAF tank by gravity, the improved BAF tank is filled with porous modified composite filter material, and a pulse intermittent aeration and air-water backwashing linkage mode is adopted to form a stable biological membrane activated carbon composite functional layer on the surface of the filter material, so that the intermediate metabolites in the EBIS effluent are subjected to deep adsorption and simultaneous nitrification and denitrification biological mineralization. Through the efficient coupling of EBIS and improved BAF, the application realizes the staged treatment and deep purification of refractory industrial wastewater, and effectively solves the problems of low treatment efficiency, poor stability and high energy consumption of single process and traditional coupling process.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a recalcitrant wastewater treatment process based on the coupling of EBIS and modified BAF. Background Technology

[0002] With the rapid development of industrial sectors, the total amount of recalcitrant industrial wastewater discharged from industries such as pharmaceuticals, coking, petrochemicals, and dyes continues to increase. This type of wastewater has complex composition and high pollutant concentration, containing a large number of organic pollutants with stable structure and poor biodegradability. It is also characterized by high toxicity and long degradation cycle, making it difficult for conventional biological treatment processes to achieve effective degradation.

[0003] Currently, the treatment of recalcitrant industrial wastewater mainly employs single advanced oxidation processes, traditional biological treatment processes, or simple coupled processes, but these methods have many limitations. Single advanced oxidation processes are costly, easily generate toxic intermediate metabolites during the oxidation process, and lack of effective subsequent advanced treatment units can easily lead to substandard effluent. Traditional biological treatment processes have extremely low degradation efficiency for recalcitrant organic matter, microorganisms are easily inhibited by toxic pollutants, and the system has poor operational stability, making it difficult to meet increasingly stringent emission standards.

[0004] Existing coupled processes often suffer from insufficient synergy. The front-end pretreatment unit cannot effectively break down the stable structure of recalcitrant organic matter and improve the biodegradability of wastewater, while the back-end deep treatment unit struggles to efficiently remove intermediate metabolites generated at the front end. Furthermore, the system's operating parameters are fixed and cannot be dynamically adjusted according to changes in water quality, resulting in unstable treatment effects, large sludge discharge, and high energy consumption. These processes are ill-suited to the treatment needs of different types of recalcitrant industrial wastewater. Therefore, developing a highly efficient, stable, energy-saving, and adaptable coupled process for treating recalcitrant wastewater has become an urgent need in the field of industrial wastewater treatment. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a recalcitrant wastewater treatment process based on the coupling of EBIS and a modified BAF. The technical solution adopted is as follows: The recalcitrant wastewater treatment process based on the coupling of EBIS and modified BAF includes the following steps: Step 1: The recalcitrant industrial wastewater is homogenized in terms of water quality and quantity by passing through a screen and equalization tank, and the pH and temperature are adjusted to the set pH range and the set temperature range. Step 2: Pump the effluent from Step 1 into the EBIS reactor. Under the step control of dissolved oxygen (DO) concentration, use the high-concentration complex functional bacteria cultured and domesticated in the reactor to adsorb, enrich, and catalyze the degradation of recalcitrant organic matter by extracellular enzymes. Step 3: The effluent from the EBIS enters the intermediate sedimentation tank for solid-liquid separation. Part of the settled sludge is returned to the inlet of the EBIS reactor to maintain a high biological concentration, and the remaining sludge is discharged. Step 4: The supernatant from Step 3 is allowed to flow by gravity into the modified BAF tank. The modified BAF tank is filled with porous modified composite filter media, and a pulse intermittent aeration and air-water backwashing linkage mode is adopted to form a stable biofilm activated carbon composite functional layer on the surface of the filter media, which performs deep adsorption and simultaneous nitrification and denitrification biomineralization of intermediate metabolites in the EBIS effluent. Step 5: After the BAF-treated effluent meets the standards, it is discharged; periodically, based on the BAF pressure difference or operating time, the air-water combined backwashing program is started, and the backwash effluent is returned to the equalization tank.

[0006] Optionally, step 6 is also included, which involves real-time monitoring of the biodegradability index (B / C) and characteristic intermediate product concentration of the EBIS effluent, as well as the total organic carbon (TOC) and total nitrogen (TN) of the BAF effluent. Based on a preset algorithm model, the DO concentration and HRT of the EBIS in S2, and the pulse aeration frequency and air-to-water ratio of the BAF in S4 are dynamically adjusted.

[0007] Optionally, the high-concentration composite functional microbial community in the EBIS reactor in step 2 is prepared by adding and acclimating the following functional microbial agents to the inoculated sludge in a certain proportion: Actinobacterial strains with strong adsorption and secretion capabilities for non-specific extracellular enzymes account for 15%-25% of the total bacterial abundance; Rhodococcus and Pseudomonas strains, which are obligate degraders of recalcitrant organic matter, account for 20%-30% of the total bacterial abundance. Strains of the genus *Aeromonas*, which have a strong ability to produce EPS to enhance biosorption, account for 10%-15% of the total bacterial abundance. The remainder consists of the inherent microbial community in the activated sludge.

[0008] Optionally, the stepwise control of dissolved oxygen (DO) concentration in step 2 is as follows: at least three dissolved oxygen control zones are set from the inlet to the outlet of the EBIS reactor. The DO in the first zone is controlled at 0.5 mg / L-1.0 mg / L to promote adsorption and facultative hydrolysis. The DO in the second zone is controlled at 1.2 mg / L-1.8 mg / L to promote aerobic decomposition. The DO in the third zone is controlled at 1.8 mg / L-2.0 mg / L to stabilize the effluent quality.

[0009] Optionally, the porous modified composite filter media in step 4 is formed by high-temperature sintering of the following components in the indicated mass percentages: Modified diatomaceous earth 40%-50%, with nano-iron oxides loaded on the surface; powdered activated carbon 20%-30%; lightweight ceramsite 20%-30%; rare earth element catalyst 1%-3%; The filter media has a hierarchical pore structure. Macropores with a pore size greater than 50 μm are used for biofilm attachment and mass transfer, mesopores with a pore size of 2 μm-50 μm are used for retention and adsorption, and micropores with a pore size less than 2 nm and surface-supported catalysts are used for catalytic oxidation.

[0010] Optionally, the pulse intermittent aeration and air-water backwashing linkage mode in step 4 is as follows: During operation, low-frequency pulse aeration is used, with alternating cycles of 5-10 minutes of aeration followed by 20-30 minutes of aeration, and an air-to-water ratio of (3:1)-(5:1). During the backwashing period, when the head loss of the filter bed increases to 0.05 MPa or after 24-48 hours of operation, first perform air-only backwashing with a backwash intensity of 15 L / (m²·s)-20 L / (m²·s) for 2-3 minutes. Then perform combined air-water backwashing with a backwash intensity of 15 L / (m²·s)-20 L / (m²·s) and a water intensity of 8 L / (m²·s)-10 L / (m²·s) for 5-8 minutes. Finally, perform water-only rinsing with a rinsing intensity of 6 L / (m²·s)-8 L / (m²·s) for 3-5 minutes.

[0011] Optionally, the biofilm activated carbon composite functional layer structure formed in step 4 is as follows: a primary adsorption layer is formed by using porous modified composite filter media as the framework, with the powdered activated carbon contained in the filter media and the organic matter adsorbed from the water; microorganisms grow on the surface of the adsorption layer and in the macropores of the filter media, forming a composite biofilm layer mainly composed of nitrifying bacteria, denitrifying bacteria and bacteria that degrade recalcitrant organic matter; microbial metabolites and aging biofilm further fill the pores, forming a dynamic composite layer with continuous adsorption and biological regeneration capabilities.

[0012] Optionally, the EBIS effluent B / C value can be collected in real time and recorded as follows: The concentration value of the characteristic intermediate product is denoted as The TOC value of BAF effluent is recorded as follows: The TN value is denoted as ; like If the value is less than the preset B / C threshold, it is determined that the degradation of recalcitrant organic matter is insufficient. Therefore, the HRT of EBIS is increased by 10%-20%, and the DO setting value in the second zone is increased by 0.2 mg / L. like Greater than the preset If the threshold is reached, the accumulation of intermediate products is determined, and the DO setting value in the third zone of the EBIS is increased by 0.1 mg / L-0.3 mg / L simultaneously, while the BAF pulse aeration frequency is increased by 20%. like Exceeding the standard but If the standard is met, it is determined that the organic load of BAF is high, and the backwashing frequency of BAF is temporarily increased, and the sludge return ratio of some EBIS is increased to the upper limit. like Exceeding the standard but If the target is met, it is determined that the BAF denitrification is insufficient. The BAF pulse aeration is adjusted to a short duration, high frequency mode, and it is checked whether a carbon source needs to be added. The corresponding judgment results are converted into control commands and sent to the blower and inlet pump of EBIS and the pulse aeration valve and backwash controller of BAF.

[0013] Optionally, a chemically enhanced oxidation step can be added between steps 3 and 4, achieved by adding a chemically enhanced oxidation buffer tank. When the EBIS effluent B / C value is consistently below 0.2, a trace amount of Fenton's reagent is added to the buffer tank for emergency enhanced oxidation. The dosage is based on... The concentration is calculated to be 10 mg / L-50 mg / L, and the effluent after oxidation is then fed into the BAF.

[0014] Optionally, the recalcitrant industrial wastewater is at least one of the following: pharmaceutical wastewater, coking wastewater, petrochemical wastewater, and dye wastewater.

[0015] In summary, the present invention has at least one of the following beneficial technical effects: This invention provides a wastewater treatment process for recalcitrant wastewater based on the coupling of EBIS and a modified BAF. Through the efficient coupling of EBIS and the modified BAF, it achieves graded treatment and deep purification of recalcitrant industrial wastewater, effectively solving the problems of low efficiency, poor stability, and high energy consumption associated with single processes and traditional coupled processes. The front-end EBIS reactor, through the action of a high-concentration composite functional microbial community and dissolved oxygen stepwise control, can efficiently adsorb, enrich, and catalyze the breakdown of recalcitrant organic matter, significantly improving the biodegradability of the wastewater and laying the foundation for subsequent deep treatment. The sludge recirculation design in the intermediate sedimentation tank maintains a high biological concentration within the EBIS reactor, ensuring reaction stability and reducing sludge discharge.

[0016] The improved BAF tank at the back end uses porous modified composite filter media and a pulse intermittent aeration and air-water backwashing linkage mode to form a stable biofilm activated carbon composite functional layer on the surface of the filter media. This layer can efficiently adsorb and mineralize intermediate metabolites in the EBIS effluent through simultaneous nitrification and denitrification, effectively reducing the total organic carbon and total nitrogen content of the effluent and ensuring that the effluent meets the discharge standards.

[0017] The dynamic parameter adjustment step allows for flexible adjustment of process operating parameters based on real-time water quality monitoring data, further enhancing system adaptability and treatment stability. An optional chemically enhanced oxidation step can address emergency situations with extremely low wastewater biodegradability, ensuring treatment effectiveness. The entire process is simple, stable in operation, and has controllable energy consumption and treatment costs. It is suitable for treating various recalcitrant industrial wastewaters, demonstrating good practicality and widespread application value. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process for treating recalcitrant wastewater based on the coupling of EBIS and modified BAF according to the present invention. Figure 2 This is a schematic diagram of the dissolved oxygen stepped control and functional zoning structure inside the EBIS reactor according to a specific embodiment of the present invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings.

[0020] This invention discloses a recalcitrant wastewater treatment process based on the coupling of EBIS and modified BAF.

[0021] Reference Figure 1 and Figure 2 Example 1, a recalcitrant wastewater treatment process based on EBIS coupled with modified BAF, includes the following steps: Step 1: The recalcitrant industrial wastewater is homogenized in terms of water quality and quantity by passing through a screen and equalization tank, and the pH is adjusted to 6.5-7.5 and the temperature to 25-35℃. Step 2: Pump the effluent from Step 1 into the EBIS reactor. Under the step control of dissolved oxygen (DO) concentration, use the high-concentration complex functional bacteria cultured and domesticated in the reactor to adsorb, enrich and catalyze the degradation of recalcitrant organic matter. The hydraulic retention time (HRT) is 4-8 hours. Step 3: The effluent from the EBIS enters the intermediate sedimentation tank for solid-liquid separation. Part of the settled sludge is returned to the inlet of the EBIS reactor to maintain a high biological concentration, and the remaining sludge is discharged. Step 4: The supernatant from Step 3 flows by gravity into the modified BAF tank. The modified BAF tank is filled with porous modified composite filter media, and a pulse intermittent aeration and air-water backwashing linkage mode is adopted to form a stable biofilm activated carbon composite functional layer on the surface of the filter media. This allows for deep adsorption and simultaneous nitrification, denitrification and biomineralization of intermediate metabolites in the EBIS effluent. The empty bed contact time of BAF is 2-4 hours. Step 5: After the BAF-treated effluent meets the standards, it is discharged; periodically, based on the BAF pressure difference or operating time, the air-water combined backwashing program is started, and the backwash effluent is returned to the equalization tank.

[0022] Example 2 also includes step 6, which involves real-time monitoring of the biodegradability index (B / C) and characteristic intermediate product concentration of the EBIS effluent, as well as the total organic carbon (TOC) and total nitrogen (TN) of the BAF effluent. Based on a preset algorithm model, the DO concentration and HRT of the EBIS in S2, and the pulse aeration frequency and air-to-water ratio of the BAF in S4 are dynamically adjusted.

[0023] By adopting the above technical solution, the gradual purification of recalcitrant industrial wastewater is achieved through the staged synergistic effect of the EBIS reactor and the modified BAF tank. The pretreatment in step 1, involving the screen and equalization tank, focuses on eliminating fluctuations in water quality and quantity, as well as interference from solid impurities, and adjusting the pH and temperature to provide stable environmental conditions for subsequent biological reactions, thus avoiding the inhibition of microbial activity by extreme parameters.

[0024] In step 2, the EBIS reactor relies on the stepwise control of dissolved oxygen concentration to adapt to the metabolic needs of different functional microorganisms. Combined with the effect of high-concentration composite functional bacterial communities, the recalcitrant organic matter is rapidly fixed in the bacterial community system through the adsorption and enrichment of microorganisms. Then, the extracellular enzymes secreted by the bacterial community are used to catalyze the decomposition of the stable chemical structure of the organic matter, breaking its recalcitrant characteristics. Extending the hydraulic retention time can ensure that the decomposition reaction is fully carried out, creating conditions for subsequent biodegradation.

[0025] The solid-liquid separation in the intermediate sedimentation tank in step 3 can effectively separate sludge from treated wastewater. Sludge recirculation can maintain a high biological concentration in the EBIS reactor, ensure a stable number of bacteria, and improve reaction efficiency. Discharging excess sludge can prevent excessive sludge accumulation from causing abnormal reactor operation.

[0026] Step 4 improves the BAF tank by using porous modified composite filter media as a carrier. Its hierarchical pore structure enables multi-level interception and adsorption of organic matter. The pulse intermittent aeration mode provides sufficient oxygen to the biofilm while avoiding energy waste caused by excessive aeration. The air-water backwash linkage prevents filter media clogging and maintains filter media activity. The biofilm activated carbon composite functional layer formed on the filter media surface achieves synergy between adsorption and biological metabolism. Through the simultaneous nitrification and denitrification process, the intermediate metabolites of EBIS effluent are further mineralized and decomposed. The control of empty bed contact time ensures a deep purification effect.

[0027] In step 5, monitoring the BAF effluent to ensure that it meets the discharge standards can guarantee that the treatment effect meets environmental protection requirements. The backwash effluent is returned to the equalization tank to realize the recycling of wastewater, reduce water waste, and at the same time avoid the direct discharge of pollutants in the backwash water, which would cause secondary pollution.

[0028] Example 2, based on Example 1, adds a dynamic parameter adjustment step. By monitoring key water quality indicators in real time, a linkage mechanism between water quality changes and process operating parameters is established to achieve adaptive adjustment of the process. The biodegradability index and characteristic intermediate product concentration at the EBIS effluent directly reflect the effectiveness of breaking down recalcitrant organic matter, while the total organic carbon and total nitrogen at the BAF effluent directly reflect the deep purification and denitrification effects. These indicators can comprehensively characterize the operating status of each unit of the process.

[0029] Based on a pre-set algorithm model, the monitored real-time indicators are compared and analyzed with preset thresholds to identify operational deficiencies in each treatment unit. Targeted adjustments are then made to the dissolved oxygen concentration and hydraulic retention time of the EBIS reactor, and the pulse aeration frequency and air-to-water ratio of the BAF tank, ensuring that process operating parameters consistently adapt to changes in water quality. This dynamic adjustment avoids insufficient treatment or energy waste caused by fixed parameters, further improving the stability and efficiency of the process and ensuring that the effluent quality consistently meets standards.

[0030] Example 3: The high-concentration composite functional microbial community in the EBIS reactor in step 2 was prepared by adding and acclimating the following functional microbial agents to the inoculated sludge in a certain proportion: Actinobacterial strains with strong adsorption and secretion capabilities for non-specific extracellular enzymes account for 15%-25% of the total bacterial abundance; Rhodococcus and Pseudomonas strains, which are obligate degraders of recalcitrant organic matter, account for 20%-30% of the total bacterial abundance. Strains of the genus *Aeromonas*, which have a strong ability to produce EPS to enhance biosorption, account for 10%-15% of the total bacterial abundance. The remainder consists of the inherent microbial community in the activated sludge.

[0031] Example 4, the stepwise control of dissolved oxygen (DO) concentration in step 2 is as follows: at least three dissolved oxygen control zones are set from the inlet to the outlet of the EBIS reactor. The DO in the first zone is controlled at 0.5 mg / L-1.0 mg / L to promote adsorption and facultative hydrolysis. The DO in the second zone is controlled at 1.2 mg / L-1.8 mg / L to promote aerobic decomposition. The DO in the third zone is controlled at 1.8 mg / L-2.0 mg / L to stabilize the effluent quality.

[0032] By adopting the above technical solutions, Example 3 enhances the adsorption and degradation capabilities of the EBIS reactor for recalcitrant organic matter through the scientific formulation and domestication of high-concentration composite functional microbial communities, ensuring the stability and synergy of the microbial community system. Inoculated sludge provides a basic survival carrier for the microbial community, and different functional microbial agents are added in proportion. Each strain has a clear division of labor and works synergistically to construct a highly efficient microbial community system adapted to the treatment of recalcitrant wastewater.

[0033] Actinobacteria strains possess strong adsorption capacity and non-specific extracellular enzyme secretion ability, enabling them to rapidly adsorb recalcitrant organic matter in water while simultaneously secreting extracellular enzymes to provide catalytic conditions for subsequent organic matter degradation. Rhodococcus and Pseudomonas strains specifically degrade recalcitrant organic matter, capable of specifically breaking down the degraded organic matter molecules and improving degradation efficiency. Agrobacterium strains can secrete large amounts of EPS, enhancing the biosorption performance of the bacterial community, promoting bacterial aggregation, reducing bacterial loss, and simultaneously improving the enrichment effect on recalcitrant organic matter.

[0034] The inherent microbial community in activated sludge, as a supplement to the microbial system, can adapt to the living environment within the reactor and synergistically coexist with the added functional microbial agents, further optimizing the microbial community structure, enhancing the community's adaptability to water quality fluctuations, and ensuring the continuous and stable adsorption, enrichment, and catalytic degradation functions of the EBIS reactor. Through the acclimatization process, various strains can quickly adapt to the recalcitrant wastewater environment, improving strain activity and tolerance, and fully leveraging the functional advantages of each strain.

[0035] Example 4 uses a stepwise control of dissolved oxygen concentration in the EBIS reactor to adapt to the oxygen demand of different metabolic stages of the complex functional microbial community, thereby achieving efficient and phased adsorption, decomposition, and stable effluent of recalcitrant organic matter, and improving reaction efficiency and effluent stability.

[0036] The EBIS reactor is equipped with three dissolved oxygen control zones from the inlet to the outlet, corresponding to different stages of recalcitrant organic matter treatment. The first zone controls a lower dissolved oxygen concentration to meet the metabolic needs of facultative microorganisms, focusing on promoting the adsorption and facultative hydrolysis of recalcitrant organic matter by microorganisms, laying the groundwork for subsequent aerobic decomposition, while avoiding interference from high dissolved oxygen levels in the adsorption process.

[0037] The second zone controls an appropriate medium-to-high dissolved oxygen concentration to meet the metabolic needs of aerobic microorganisms. It focuses on promoting the secretion of extracellular enzymes by functional bacteria to efficiently and aerobically break down the stable chemical structure of recalcitrant organic matter, thereby breaking down its recalcitrant characteristics and decomposing large organic molecules into easily biodegradable small molecules.

[0038] The third zone maintains a high and stable dissolved oxygen concentration, further enhancing aerobic degradation to degrade residual organic matter and intermediate metabolites. Simultaneously, it stabilizes the activity of the microbial community within the reactor, ensuring stable effluent quality and providing high-quality feedwater for subsequent solid-liquid separation in the intermediate sedimentation tank and advanced treatment in the BAF tank, thus guaranteeing the overall treatment effect of the coupled process.

[0039] Example 5: The porous modified composite filter material in step 4 is formed by high-temperature sintering of the following components in mass percentage: Modified diatomaceous earth 40%-50%, with nano-iron oxides loaded on the surface; powdered activated carbon 20%-30%; lightweight ceramsite 20%-30%; rare earth element catalyst 1%-3%; The filter media has a hierarchical pore structure. Macropores with a pore size greater than 50 μm are used for biofilm attachment and mass transfer, mesopores with a pore size of 2 μm-50 μm are used for retention and adsorption, and micropores with a pore size less than 2 nm and surface-supported catalysts are used for catalytic oxidation.

[0040] Example 6, the pulse intermittent aeration and air-water backwashing linkage mode in step 4 is as follows: During operation, low-frequency pulse aeration is used, with alternating cycles of 5-10 minutes of aeration followed by 20-30 minutes of aeration, and an air-to-water ratio of (3:1)-(5:1). During the backwashing period, when the head loss of the filter bed increases to 0.05 MPa or after 24-48 hours of operation, first perform air-only backwashing with a backwash intensity of 15 L / (m²·s)-20 L / (m²·s) for 2-3 minutes. Then perform combined air-water backwashing with a backwash intensity of 15 L / (m²·s)-20 L / (m²·s) and a water intensity of 8 L / (m²·s)-10 L / (m²·s) for 5-8 minutes. Finally, perform water-only rinsing with a rinsing intensity of 6 L / (m²·s)-8 L / (m²·s) for 3-5 minutes.

[0041] Example 7: The biofilm activated carbon composite functional layer structure formed in step 4 is as follows: a porous modified composite filter material serves as the framework, and the powdered activated carbon contained in the filter material itself, together with the organic matter adsorbed from the water, constitutes the primary adsorption layer; microorganisms grow on the surface of the adsorption layer and in the macropores of the filter material, forming a composite biofilm layer mainly composed of nitrifying bacteria, denitrifying bacteria, and bacteria that degrade recalcitrant organic matter; microbial metabolites and aged biofilm further fill the pores, forming a dynamic composite layer with continuous adsorption and biological regeneration capabilities.

[0042] By adopting the above technical solution, Example 5 prepared a porous modified composite filter material with hierarchical pore structure and multiple functions by scientifically proportioning the components and sintering at high temperature. This provides an efficient carrier for improving the deep purification of BAF pools, enhances the synergistic effect of adsorption, catalysis and bio-attachment, and meets the needs of deep treatment of intermediate metabolites.

[0043] The modified diatomaceous earth surface loaded with nano-iron oxides can enhance catalytic oxidation capacity, enabling the catalytic decomposition of recalcitrant intermediate metabolites. Its porous nature can also assist in adsorption. Powdered activated carbon has extremely strong adsorption performance, which can quickly adsorb small molecule organic matter and intermediate products in water, thereby increasing the adsorption capacity of the filter media. Lightweight ceramic particles can optimize the pore structure and mechanical strength of the filter media, reduce the bulk density of the filter media, and facilitate gas-water mass transfer and biofilm adhesion. Rare earth element catalysts can accelerate the catalytic reaction rate and enhance the oxidative degradation effect. The components are matched in proportion and sintered at high temperature to form a structurally stable and functionally complementary composite filter media.

[0044] The hierarchical pore structure of the filter media corresponds to different purification functions. Macropores provide ample space for microbial growth, ensure stable biofilm adhesion, and facilitate gas-water mass transfer, creating favorable conditions for biological metabolism. Mesopores can effectively trap suspended particles and some organic matter in the water, improving the pretreatment effect. Micropores and surface-loaded catalysts can play a highly efficient role in adsorption and catalytic oxidation, further decomposing recalcitrant pollutants, achieving synergistic effects of physical adsorption, chemical catalysis, and biodegradation, and enhancing the deep purification capacity of the BAF pool.

[0045] Example 6 uses a pulse intermittent aeration and air-water backwashing linkage mode to improve the biodegradation efficiency of the BAF tank and the operational stability of the filter media. While reducing energy consumption, it avoids filter media clogging and ensures that the filter media can continuously perform adsorption and biodegradation functions.

[0046] During operation, low-frequency pulse aeration is used. Through the alternating cycle of aeration and aeration stop, sufficient oxygen is provided to the biofilm on the filter media surface during the aeration stage to meet the metabolic needs of microorganisms such as nitrifying bacteria and denitrifying bacteria, ensuring the smooth progress of simultaneous nitrification and denitrification reactions. At the same time, a brief anaerobic environment is provided for microorganisms during the aeration stop stage to promote the further degradation of recalcitrant organic matter. Meanwhile, the energy waste caused by continuous aeration is avoided. The appropriate air-to-water ratio can optimize the air-to-water mass transfer efficiency and improve the contact effect between the biofilm and pollutants.

[0047] During the backwashing period, by setting dual trigger conditions of filter bed head loss and operating time, excess sludge, aged biofilm, and trapped pollutants adhering to the filter media surface can be removed in a timely manner, preventing filter media clogging and a decrease in treatment efficiency. Air-only backwashing can loosen the filter bed and remove loose pollutants from the surface; combined air-water backwashing can efficiently remove blockages in the filter media pores by utilizing the synergistic effect of air and water flow, while avoiding filter media wear or incomplete cleaning caused by single backwashing methods; water-only rinsing can wash away residual backwash pollutants, restore the adsorption and bio-attachment performance of the filter media, and ensure the long-term stable and efficient operation of the BAF tank.

[0048] Example 7: A layered and synergistic biofilm activated carbon composite functional layer was constructed on the surface of porous modified composite filter media, integrating physical adsorption, biological metabolism and pore interception functions to achieve efficient and continuous purification of intermediate metabolites in EBIS effluent.

[0049] The primary adsorption layer uses powdered activated carbon from the filter media itself as its core, combined with organic matter adsorbed from the water, to rapidly adsorb intermediate metabolites, small molecule organic matter and other pollutants in the water, forming an initial purification barrier. At the same time, it provides a nutrient basis for the subsequent growth of microorganisms. Its adsorption effect can quickly reduce the concentration of pollutants in the water and reduce the degradation load on the biofilm.

[0050] The composite biofilm layer grows based on the macroporous structure of the filter media, mainly composed of nitrifying bacteria, denitrifying bacteria, and bacteria that degrade recalcitrant organic matter. These microorganisms can use the pollutants adsorbed by the primary adsorption layer as a nutrient source and mineralize and decompose them through biological metabolism, thus achieving the complete degradation of pollutants. At the same time, the synergistic effect of nitrifying bacteria and denitrifying bacteria can effectively remove nitrogen from the water and improve the denitrification effect.

[0051] The dynamic composite layer is formed by microbial metabolites and aging biofilm filling the pores. It can not only further intercept fine pollutants in the water, but also realize the biological regeneration of adsorption function. The microbial active substances released during the degradation of aging biofilm can help enhance the adsorption and biodegradation effect, forming a "adsorption-degradation-regeneration" cycle mechanism to ensure that the composite functional layer can play a stable purification role in the long term and improve the treatment efficiency and operational stability of BAF pool.

[0052] Example 8: Real-time acquisition of EBIS effluent B / C values, denoted as... The concentration value of the characteristic intermediate product is denoted as The TOC value of BAF effluent is recorded as follows: The TN value is denoted as ; like If the value is less than the preset B / C threshold, it is determined that the degradation of recalcitrant organic matter is insufficient. Therefore, the HRT of EBIS is increased by 10%-20%, and the DO setting value in the second zone is increased by 0.2 mg / L. like Greater than the preset If the threshold is reached, the accumulation of intermediate products is determined, and the DO setting value in the third zone of the EBIS is increased by 0.1 mg / L-0.3 mg / L simultaneously, while the BAF pulse aeration frequency is increased by 20%. like Exceeding the standard but If the standard is met, it is determined that the organic load of BAF is high, and the backwashing frequency of BAF is temporarily increased, and the sludge return ratio of some EBIS is increased to the upper limit. like Exceeding the standard but If the target is met, it is determined that the BAF denitrification is insufficient. The BAF pulse aeration is adjusted to a short duration, high frequency mode, and it is checked whether a carbon source needs to be added. The corresponding judgment results are converted into control commands and sent to the blower and inlet pump of EBIS and the pulse aeration valve and backwash controller of BAF.

[0053] Example 9: Between steps 3 and 4, a chemically enhanced oxidation step is added, implemented by adding a chemically enhanced oxidation buffer tank. When the EBIS effluent B / C value is consistently below 0.2, a trace amount of Fenton's reagent is added to the buffer tank for emergency enhanced oxidation. The dosage is... The concentration is calculated to be 10 mg / L-50 mg / L, and the effluent after oxidation is then fed into the BAF.

[0054] By adopting the above technical solution, the real-time collected EBIS effluent B / C value, characteristic intermediate product concentration, and BAF effluent TOC and TN values ​​correspond to the breakdown effect of the EBIS reactor and the deep purification and denitrification effect of the BAF tank, respectively. These four indicators can comprehensively and accurately reflect the operating status of the entire coupled process and provide reliable data support for parameter adjustment.

[0055] Differentiated adjustment strategies are adopted for different monitoring anomalies, aligning with the core functional logic of each treatment unit. A low B / C value indicates insufficient breakdown of recalcitrant organic matter. Increasing the hydraulic retention time of the EBIS to prolong the reaction time and enhancing aerobic breakdown by increasing the dissolved oxygen concentration in the second zone can improve the efficiency of organic matter breakdown. A high concentration of characteristic intermediate products indicates accumulation during the degradation process. Increasing the dissolved oxygen concentration in the third zone of the EBIS to enhance subsequent degradation and simultaneously increasing the frequency of BAF pulse aeration to enhance the mineralization of intermediate products can rapidly reduce the accumulation.

[0056] If the TOC in the BAF effluent exceeds the standard while the TN meets the standard, it indicates that the organic load in the BAF tank is too high. Increasing the backwashing frequency to restore the adsorption and degradation capacity of the filter media and increasing the EBIS sludge return ratio to enhance front-end adsorption and degradation can reduce the treatment pressure on the BAF tank. If the TN exceeds the standard while the TOC meets the standard, it indicates insufficient denitrification. Adjusting the BAF pulse aeration mode to suit the metabolic needs of nitrifying and denitrifying bacteria, and supplementing with carbon sources if necessary to ensure the denitrification reaction, can improve denitrification efficiency. The judgment results are converted into control commands and sent to the corresponding equipment to achieve automated and precise parameter adjustment, ensuring the process quickly returns to its optimal operating state.

[0057] Example 9 adds an emergency chemical enhancement oxidation step to address extreme situations where the EBIS reactor is not performing well and the wastewater has extremely low biodegradability, breaking through the process bottleneck and ensuring the stable and reliable treatment effect of the entire coupled process.

[0058] The chemically enhanced oxidation buffer tank provides a dedicated reaction space for emergency treatment, preventing Fenton's reagent from inhibiting the activity of the complex functional bacteria community within the EBIS reactor, while ensuring the oxidation reaction proceeds fully. Using a B / C ratio in the EBIS effluent consistently below 0.2 as the emergency trigger condition accurately indicates extremely poor degradation of recalcitrant organic matter. In this case, biological action alone cannot meet the advanced treatment requirements of the subsequent BAF tank, necessitating auxiliary chemical oxidation.

[0059] The core of adding trace amounts of Fenton's reagent is to utilize the strong oxidizing free radicals it generates to quickly break down the stable chemical structure of recalcitrant organic matter, decompose large recalcitrant organic molecules into small, easily biodegradable substances, reduce wastewater toxicity, significantly improve wastewater biodegradability, and create favorable conditions for subsequent biosorption and mineralization in the BAF tank.

[0060] Controlling the Fenton reagent dosage to 10 mg / L to 50 mg / L (based on hydrogen peroxide) ensures effective oxidation and degradation while avoiding increased treatment costs and secondary pollution caused by excessive reagent dosage. The effluent after oxidation then enters a BAF (Biodegradable Aerated Concentrate) tank for further treatment. This fully utilizes the adsorption and biodegradation functions of the BAF to thoroughly remove small-molecule organic matter generated after oxidation, ensuring that the final effluent meets discharge standards and further expanding the process's adaptability to recalcitrant industrial wastewater.

[0061] Example 10: The recalcitrant industrial wastewater is at least one of pharmaceutical wastewater, coking wastewater, petrochemical wastewater, and dye wastewater.

[0062] By adopting the above technical solutions, pharmaceutical wastewater, coking wastewater, petrochemical wastewater, and dye wastewater, although from different sources, all share common characteristics such as complex composition, high content of recalcitrant organic matter, poor biodegradability, and strong toxicity. This is also the core reason why conventional treatment processes are difficult to adapt. The front-end EBIS reactor of this process, through the multi-faceted effects of a high-concentration composite functional microbial community, can specifically adsorb and enrich characteristic recalcitrant pollutants in various wastewaters. It utilizes extracellular enzyme catalysis to break down their stable chemical structures, combined with dissolved oxygen stepwise control, to adapt to the degradation requirements of different types of pollutants, effectively improving the biodegradability of various wastewaters.

[0063] The porous modified composite filter media of the back-end improved BAF pool has a hierarchical pore structure and multi-element catalytic adsorption function, which can efficiently intercept and adsorb intermediate metabolites generated by various wastewaters after EBIS treatment. The biofilm activated carbon composite functional layer on the surface of the filter media achieves deep mineralization of pollutants through simultaneous nitrification and denitrification. It can adapt to the deep purification needs of different types of wastewater and effectively remove various characteristic pollutants and indicators such as nitrogen and carbon.

[0064] The optional dynamic parameter adjustment steps and emergency chemical enhancement oxidation steps in the process can further adapt to the water quality fluctuation characteristics of various wastewaters. Based on the differences in pollutant concentrations and biodegradability of different wastewaters, operating parameters can be flexibly adjusted or emergency treatments can be initiated to ensure stable treatment results. In summary, the hierarchical synergy and multi-adaptive design of this coupled process enable it to be widely applied to the treatment of recalcitrant industrial wastewater in industries such as pharmaceuticals, coking, petrochemicals, and dyes, without requiring significant modifications for a single wastewater type, demonstrating strong versatility and adaptability.

[0065] The following specific embodiments illustrate the implementation principle of the present invention: The treatment of pharmaceutical wastewater is carried out according to the following steps.

[0066] The recalcitrant pharmaceutical wastewater is first screened to remove suspended solids, and then enters the equalization tank to complete the homogenization treatment of water quality and quantity, adjusting the pH value of the wastewater to 7.0 and controlling the temperature at 30℃, so as to provide stable environmental conditions for subsequent biological treatment.

[0067] After homogenization and conditioning, the wastewater is pumped into the EBIS reactor, where a three-stage stepped dissolved oxygen concentration control system is employed. In the first inlet zone, the dissolved oxygen concentration is controlled at 0.8 mg / L, primarily for organic matter adsorption and facultative hydrolysis. In the second middle zone, the dissolved oxygen concentration is controlled at 1.5 mg / L, enhancing the extracellular enzyme secretion of functional bacteria and the aerobic breakdown of recalcitrant organic matter. In the third effluent zone, the dissolved oxygen concentration is controlled at 1.9 mg / L, stabilizing bacterial activity and ensuring effluent quality. A high-concentration complex of functional bacteria is added to and acclimated within the reactor. Actinobacteria account for 20% of the total bacterial abundance, Rhodococcus and Pseudomonas strains together account for 25%, and Zoogloea strains account for 12%, with the remainder being the inherent microbial community of the activated sludge. The hydraulic retention time is set to 6 hours. Through bacterial adsorption and enrichment, and extracellular enzyme catalysis, the structural breakdown and initial degradation of recalcitrant organic matter are achieved.

[0068] The effluent from the EBIS reactor flows by gravity into the intermediate sedimentation tank for solid-liquid separation. 70% of the settled sludge is returned to the inlet of the EBIS reactor to maintain a high biological concentration in the reactor. The remaining sludge is periodically discharged into the sludge treatment system.

[0069] The supernatant from the sedimentation tank flows by gravity into the modified BAF treatment tank, which is filled with porous modified composite filter media. The filter media is made of 45% modified diatomaceous earth, 25% powdered activated carbon, 28% lightweight ceramsite, and 2% rare earth element catalyst, sintered at high temperature. Nano-iron oxides are loaded onto the surface of the modified diatomaceous earth, forming a hierarchical structure of macropores, mesopores, and micropores. The BAF tank operates in a pulsed intermittent aeration mode, alternating between 8 minutes of aeration and 25 minutes of aeration stoppage, with an air-to-water ratio controlled at 4:1. This forms a biofilm activated carbon composite functional layer on the surface and within the pores of the filter media. This functional layer uses the filter media as a framework; the inner layer consists of powdered activated carbon and adsorbed organic matter forming a primary adsorption layer, while the outer layer is a composite biofilm formed by nitrifying bacteria, denitrifying bacteria, and characteristic degradation bacteria. Microbial metabolites and aged biofilm fill the pores, forming a dynamic composite layer. The empty bed contact time is set to 3 hours. Through simultaneous adsorption and biomineralization, deep degradation of intermediate metabolites and simultaneous nitrification and denitrification are achieved.

[0070] The treated effluent from the BAF tank is discharged directly after meeting the online water quality standards. When the filter head loss reaches 0.05 MPa or after 36 hours of continuous operation, the air-water combined backwashing program is automatically activated. First, a backwash is performed for 2.5 minutes with an air intensity of 18 L / (m²・s), followed by a combined air-water backwash for 6.5 minutes with the same air intensity and a water intensity of 9 L / (m²・s). Finally, a separate rinse is performed for 4 minutes with a water intensity of 7 L / (m²・s). All wastewater generated during backwashing is returned to the equalization tank for retreatment.

[0071] The system collects the B / C ratio of the EBIS effluent, the concentration of characteristic intermediate products, and the total organic carbon and total nitrogen (TOC) in the BAF effluent in real time. When the B / C ratio is below the set threshold, the hydraulic retention time of the EBIS is extended by 15%, and the dissolved oxygen concentration in the second zone is increased by 0.2 mg / L. When the concentration of characteristic intermediate products exceeds the threshold, the dissolved oxygen concentration in the third zone of the EBIS is increased by 0.2 mg / L, and the pulse aeration frequency of the BAF is increased by 20%. When the TOC in the BAF effluent exceeds the standard but the TNO is within the standard, the BAF backwashing frequency is increased, and the EBIS sludge return ratio is increased to the upper limit of operation. When the TNO in the BAF effluent exceeds the standard but the TOC is within the standard, the pulse aeration is switched to a short-duration, high-frequency mode, and an external carbon source is supplemented if necessary to ensure the denitrification effect. All adjustment commands are automatically sent to the blower, influent pump, aeration valve, and backwash controller through the control system, realizing dynamic adaptive adjustment of operating parameters.

[0072] If the EBIS effluent B / C ratio remains below 0.2, initiate an emergency chemically enhanced oxidation procedure. Add Fenton's reagent to the buffer tank between the sedimentation tank and the BAF tank, with the dosage controlled at 30 mg / L (calculated as hydrogen peroxide). This strong oxidation further breaks down the structure of recalcitrant organic matter, improving the wastewater's biodegradability. The oxidized effluent then enters the BAF tank for further purification, ensuring the final effluent consistently meets standards.

[0073] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A recalcitrant wastewater treatment process based on the coupling of EBIS and modified BAF, characterized in that, Includes the following steps: Step 1: The recalcitrant industrial wastewater is homogenized in terms of water quality and quantity by passing through a screen and equalization tank, and the pH and temperature are adjusted to the set pH range and the set temperature range. Step 2: Pump the effluent from Step 1 into the EBIS reactor. Under the step control of dissolved oxygen (DO) concentration, use the high-concentration complex functional bacteria cultured and domesticated in the reactor to adsorb, enrich, and catalyze the degradation of recalcitrant organic matter by extracellular enzymes. Step 3: The effluent from the EBIS enters the intermediate sedimentation tank for solid-liquid separation. Part of the settled sludge is returned to the inlet of the EBIS reactor to maintain a high biological concentration, and the remaining sludge is discharged. Step 4: The supernatant from Step 3 is allowed to flow by gravity into the modified BAF tank. The modified BAF tank is filled with porous modified composite filter media, and a pulse intermittent aeration and air-water backwashing linkage mode is adopted to form a stable biofilm activated carbon composite functional layer on the surface of the filter media, which performs deep adsorption and simultaneous nitrification and denitrification biomineralization of intermediate metabolites in the EBIS effluent. Step 5: After the BAF-treated effluent meets the standards, it is discharged; periodically, based on the BAF pressure difference or operating time, the air-water combined backwashing program is started, and the backwash effluent is returned to the equalization tank. It also includes step 6, which involves real-time monitoring of the biodegradability index (B / C) and characteristic intermediate product concentration of the EBIS outlet, as well as the total organic carbon (TOC) and total nitrogen (TN) of the BAF outlet. Based on a preset algorithm model, the DO concentration and HRT of the EBIS in step 2, and the pulse aeration frequency and air-to-water ratio of the BAF in step 4 are dynamically adjusted. The high-concentration complex functional microbial community in the EBIS reactor in step 2 was prepared by adding and acclimating the following functional microbial agents to the inoculated sludge in a certain proportion: Actinobacterial strains with strong adsorption and secretion capabilities for non-specific extracellular enzymes account for 15%-25% of the total bacterial abundance; Rhodococcus and Pseudomonas strains, which are obligate degraders of recalcitrant organic matter, account for 20%-30% of the total bacterial abundance. Strains of the genus *Aeromonas*, which have a strong ability to produce EPS to enhance biosorption, account for 10%-15% of the total bacterial abundance. The remainder consists of the inherent microbial community within the activated sludge; The specific steps for controlling dissolved oxygen (DO) concentration in step 2 are as follows: at least three dissolved oxygen control zones are set up from the inlet to the outlet of the EBIS reactor. In the first zone, DO is controlled at 0.5 mg / L-1.0 mg / L to promote adsorption and facultative hydrolysis. In the second zone, DO is controlled at 1.2 mg / L-1.8 mg / L to promote aerobic decomposition. In the third zone, DO is controlled at 1.8 mg / L-2.0 mg / L to stabilize the effluent quality.

2. The recalcitrant wastewater treatment process based on EBIS and modified BAF coupling according to claim 1, characterized in that, The porous modified composite filter media in step 4 is formed by high-temperature sintering of the following components in the indicated mass percentages: Modified diatomaceous earth 40%-50%, with nano-iron oxides loaded on the surface; powdered activated carbon 20%-30%; lightweight ceramsite 20%-30%; rare earth element catalyst 1%-3%; The filter media has a hierarchical pore structure. Macropores with a pore size greater than 50 μm are used for biofilm attachment and mass transfer, mesopores with a pore size of 2 μm-50 μm are used for retention and adsorption, and micropores with a pore size less than 2 nm and surface-supported catalysts are used for catalytic oxidation.

3. The recalcitrant wastewater treatment process based on EBIS and modified BAF coupling according to claim 2, characterized in that, The pulse intermittent aeration and air-water backwashing linkage mode in step 4 is as follows: During operation, low-frequency pulse aeration is used, with alternating cycles of 5-10 minutes of aeration followed by 20-30 minutes of aeration, and an air-to-water ratio of (3:1)-(5:1). During the backwashing period, when the head loss of the filter bed increases to 0.05 MPa or after 24-48 hours of operation, first perform air-only backwashing with a backwash intensity of 15 L / (m²·s)-20 L / (m²·s) for 2-3 minutes. Then perform combined air-water backwashing with a backwash intensity of 15 L / (m²·s)-20 L / (m²·s) and a water intensity of 8 L / (m²·s)-10 L / (m²·s) for 5-8 minutes. Finally, perform water-only rinsing with a rinsing intensity of 6 L / (m²·s)-8 L / (m²·s) for 3-5 minutes.

4. The recalcitrant wastewater treatment process based on EBIS and modified BAF coupling according to claim 3, characterized in that, The biofilm activated carbon composite functional layer structure formed in step 4 is as follows: the porous modified composite filter material serves as the framework, and the powdered activated carbon contained in the filter material itself, together with the organic matter adsorbed from the water, constitutes the primary adsorption layer; microorganisms grow on the surface of the adsorption layer and in the macropores of the filter material, forming a composite biofilm layer mainly composed of nitrifying bacteria, denitrifying bacteria, and bacteria that degrade recalcitrant organic matter; microbial metabolites and aging biofilm further fill the pores, forming a dynamic composite layer with continuous adsorption and biological regeneration capabilities.

5. The recalcitrant wastewater treatment process based on EBIS and modified BAF coupling according to claim 4, characterized in that, Real-time acquisition of EBIS effluent B / C values, recorded as The concentration value of the characteristic intermediate product is denoted as The TOC value of BAF effluent is recorded as follows: The TN value is denoted as ; like If the value is less than the preset B / C threshold, it is determined that the degradation of recalcitrant organic matter is insufficient. Therefore, the HRT of EBIS is increased by 10%-20%, and the DO setting value in the second zone is increased by 0.2 mg / L. like Greater than the preset If the threshold is reached, the accumulation of intermediate products is determined, and the DO setting value in the third zone of the EBIS is increased by 0.1 mg / L-0.3 mg / L simultaneously, while the BAF pulse aeration frequency is increased by 20%. like Exceeding the standard but If the standard is met, it is determined that the organic load of BAF is high, and the backwashing frequency of BAF is temporarily increased, and the sludge return ratio of some EBIS is increased to the upper limit. like Exceeding the standard but If the target is met, it is determined that the BAF denitrification is insufficient. The BAF pulse aeration is adjusted to a short duration, high frequency mode, and it is checked whether a carbon source needs to be added. The corresponding judgment results are converted into control commands and sent to the blower and inlet pump of EBIS and the pulse aeration valve and backwash controller of BAF.

6. The recalcitrant wastewater treatment process based on the coupling of EBIS and modified BAF according to claim 5, characterized in that, Between steps 3 and 4, a chemically enhanced oxidation step is added, achieved by adding a chemically enhanced oxidation buffer tank. When the EBIS effluent B / C value is consistently below 0.2, a trace amount of Fenton's reagent is added to the buffer tank for emergency enhanced oxidation. The dosage is as follows: The concentration is calculated to be 10 mg / L-50 mg / L, and the effluent after oxidation is then fed into the BAF.

7. The recalcitrant wastewater treatment process based on EBIS and modified BAF coupling according to claim 6, characterized in that, Recalcitrant industrial wastewater is at least one of the following: pharmaceutical wastewater, coking wastewater, petrochemical wastewater, and dye wastewater.

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