Method for reinforcing organic nitrogen in electroplating wastewater based on fungi

Abstract

The application discloses a method for treating organic nitrogen in electroplating wastewater based on fungus reinforcement, and belongs to the technical field of electroplating wastewater biological treatment, and comprises the following steps: after wastewater is pretreated by Fenton, the wastewater enters a fungus reinforcement unit, organic nitrogen is converted by using the ability of fungus to crack organic nitrogen carbon-nitrogen bonds and the tolerance of fungus to heavy metals; after treatment, the wastewater enters an A / O biochemical system for anoxic-oxygenated deep denitrification. The application solves the biological inhibition problem of organic nitrogen and heavy metal residues in Fenton effluent, realizes total nitrogen up to standard and stable operation, and breaks through the technical bottleneck of traditional biochemical method for treating high organic nitrogen electroplating wastewater.

Description

Technical Field

[0001] This invention relates to a method for enhancing the treatment of organic nitrogen in electroplating wastewater using fungi, belonging to the field of biological treatment technology for electroplating wastewater. Background Technology

[0002] Electroplating wastewater mainly originates from pickling, electroplating rinsing solutions, chemical plating, and post-treatment processes. It is characterized by large fluctuations in water volume, complex pollutant composition, and high total nitrogen concentration, facing increasingly stringent emission standards and the challenge of zero discharge. Meanwhile, the market for novel electroplating processes (such as zinc-nickel alloys) is developing rapidly and is expected to become the industry mainstream. These processes are characterized by high organic nitrogen concentrations (originating from organic additives in the electroplating tank) and a high content of bioinhibitory substances such as metal complexes. Existing Fenton-biochemical processes have significant limitations in treating novel electroplating wastewater containing organic nitrogen (organic amines, etc.), primarily because the organic nitrogen concentration in the effluent after Fenton pretreatment is still far higher than the tolerance threshold of the biochemical system. Taking a zinc-nickel wastewater as an example, after Fenton-flocculation pretreatment, the total nitrogen concentration is as high as 350 mg / L, of which organic nitrogen accounts for more than 20% (far exceeding the tolerance threshold of the biochemical system by 3 times). The main components are triethanolamine (TEOA), tetraethylenepentamine (TEPA) and N,N-dimethylformamide (DMF), which cannot directly enter the biochemical system, leading to frequent collapse of the biochemical system and a significant gap in organic nitrogen degradation.

[0003] Studies have shown that these organic nitrogen compounds impair microbial metabolic function by disrupting microbial cell membrane structure, interfering with key enzyme activity, and inducing oxidative stress. When coexisting with heavy metals, the synergistic effect of the two further exacerbates toxicity, leading to damage to cell membrane integrity and decreased denitrification efficiency. Organic complexing agents such as ethylenediaminetetraacetic acid (EDTA) can form stable complexes with heavy metals such as copper and zinc, making it easier for heavy metals to penetrate the microbial cell barrier and increasing the risk of microbial toxicity. Specifically, the complex carbon-nitrogen bonds in organic nitrogen wastewater are the main cause of its poor biodegradability. Traditional biochemical systems have low efficiency in treating organic nitrogen. Studies have shown that under high organic nitrogen loads, the denitrification efficiency of traditional A / O (anoxic / aerobic) systems decreases by more than 30%, and the system frequently collapses.

[0004] Currently, the Fenton oxidation + AO (anaerobic-aerobic) combined process dominates in electroplating wastewater treatment. However, the traditional Fenton process faces a double bottleneck in treating wastewater containing organic nitrogen: the organic nitrogen conversion rate is only about 24%. This process suffers from high reagent costs and poor economic efficiency. Furthermore, the pretreatment focuses on heavy metal removal, with limited effect on the pre-degradation of organic nitrogen, making it difficult to alleviate the high load pressure on the biological system at the source. This results in long system start-up cycles, poor operational stability, and low resistance to shock loads. This leads to key bottlenecks for subsequent traditional biological methods in treating novel electroplating wastewater: firstly, the microbial community is "intolerant." The high concentration of organic nitrogen in novel electroplating wastewater causes a decrease in activity in existing biological methods, such as AO, UASB-SBR (upflow anaerobic sludge blanket-sequencing batch reactor), and biological contact oxidation, frequently leading to system collapse risks; secondly, degradation "failure." Organic amines in the wastewater originate from organic additives in the electroplating process. These additives contain a large number of CN bonds and branched structures, exhibiting stable chemical properties. However, traditional biological methods lack enzymes to cleave these complex groups, resulting in "failure" in degradation.

[0005] Therefore, the inhibitory effect of organic nitrogen on biological systems severely restricts the treatment capacity and volume of wastewater treatment facilities for electroplating wastewater. There is an urgent need to develop a bio-enhanced technology that can simultaneously and efficiently degrade organic nitrogen, solving the problem that effluent from Fenton pretreatment cannot directly enter the biological system, in order to meet the challenges and market opportunities presented by the upgrading of surface treatment industry standards. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects of the prior art and provide a method for the treatment of organic nitrogen in electroplating wastewater based on fungal enhancement. This method addresses the biological inhibition problem of organic nitrogen and heavy metal residues in Fenton effluent, achieves total nitrogen compliance and stable operation, and breaks through the technical bottleneck of traditional biochemical methods for treating high organic nitrogen electroplating wastewater.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for enhancing the treatment of organic nitrogen in electroplating wastewater based on fungi includes the following steps:

[0009] Zinc-nickel electroplating wastewater was pretreated using Fenton's method.

[0010] The zinc-nickel electroplating wastewater after Fenton pretreatment was transported to a fungal enhancement unit containing fungi. Through the synergistic effect between different enzyme systems produced by the fungi, the carbon-nitrogen bonds of the organic nitrogen-metal complexes remaining after Fenton pretreatment were cleaved in a targeted manner to degrade some of the organic nitrogen.

[0011] The zinc-nickel electroplating wastewater treated by the fungal enhancement unit is transported to the A / O biological system for anoxic and aerobic denitrification treatment.

[0012] The organic nitrogen pollutants targeted by this invention are broad in scope, referring to nitrogen-containing organic compounds in electroplating wastewater that have a significant inhibitory effect on microorganisms in the biochemical system, including but not limited to at least one of the categories of aniline, alkanolamine and amide. Specifically, organic nitrogen can be triethanolamine (TEOA), tetraethylenepentamine (TEPA) and N,N-dimethylformamide (DMF), etc.

[0013] Fenton pretreatment includes the following steps:

[0014] Prepare 350 g / L ferrous sulfate heptahydrate and 30% hydrogen peroxide by mass, then add them to zinc-nickel electroplating wastewater. Connect the zinc-nickel electroplating wastewater to a DC power supply and control the current to 0.2 A for 4 h.

[0015] After adjusting the pH of the zinc-nickel electroplating wastewater to 8-9, add 4.9 g PAC and 0.1 g PAM for flocculation for 30 min.

[0016] The supernatant obtained after flocculation was acidified to pH 2.5, and then 3 g of zinc-nickel complex-breaking agent was added and reacted for 30 min.

[0017] Then adjust the pH of the supernatant to 8-9 for secondary flocculation.

[0018] The total nitrogen content in the zinc-nickel electroplating wastewater after Fenton pretreatment is 10~400 mg / L, the total nickel ion concentration is 0.1~1.0 mg / L, and the conductivity is 1~3 mS / cm.

[0019] The fungi in the fungal enhancement unit possess a carbon-nitrogen bond cleaving enzyme system, including but not limited to at least one of laccase (Lac), manganese peroxidase (MnP), lignin peroxidase (LiP), multifunctional peroxidase (VP), amide hydrolase (ami), and cytochrome P450 (CYP450), capable of efficiently degrading organic nitrogen pollutants. The fungi in the fungal enhancement unit are filamentous fungi, selected from at least one of white-rot fungi (Trametes versicolor, Phanerochaete chrysosporium, Coriolusversicolor, Pleurotus sajor-caju, and Pleurotus ostreatus).

[0020] The hydraulic retention time of the fungal enhancement unit is 12–24 h to ensure sufficient biological contact and reaction time. This allows the fungi to continuously exert their highly efficient degradation performance until the removal rate of total nitrogen (mainly organic nitrogen) in the actual electroplating wastewater is stably maintained above 60%. The aeration flow rate is 0.1–0.3 L / min to ensure dissolved oxygen supply and maintain the fluidized state of the particles. The dissolved oxygen concentration is maintained at 2–6 mg / L. Through the above parameter settings, the fungi can continuously exert their highly efficient degradation performance until the removal rate of total nitrogen (mainly organic nitrogen) in the actual electroplating wastewater is stably maintained above 60%.

[0021] The fungal addition methods in the fungal enhancement unit include: culturing fungi to form fungal bioparticles with a diameter of 3 mm to 7 mm and then adding them to the reactor, or using carrier immobilization technology, mixing the mycelial suspension obtained from the expanded culture with a carrier, immobilizing it to form fungal immobilized particles, and then adding them to the reactor.

[0022] There are two ways to add fungi in the fungal enhancement unit: one is to take advantage of the fungal’s own growth characteristics towards the external interface and culture them into fungal biological particles with a diameter of 3 mm to 7 mm, which have good mechanical strength; the other is to use carrier immobilization technology, which can mix the mycelial suspension obtained from the expanded culture with the carrier and then immobilize it under suitable conditions to enhance the loading of the fungi and form fungal immobilized particles before adding them into the reactor.

[0023] The reactor is a fluidized bed reactor or a biofilm reactor. The reactor is equipped with a gas collection hood and a perforated baffle at the top and bottom, respectively, so as to retain fungal biological particles or fungal immobilized particles in the reaction zone. The treated effluent achieves efficient solid-liquid separation, which greatly simplifies the subsequent treatment process.

[0024] The addition volume of fungal bioparticles or immobilized fungal particles accounts for 10% to 40% of the reactor volume, which can achieve economical and efficient degradation, with 20% to 30% being the preferred range.

[0025] The method for expanding the culture of fungi in a fungal enhancement unit includes the following steps:

[0026] Inoculate the preserved strains onto potato dextrose agar plates or slants and incubate at 20–30°C for 4–7 days.

[0027] Mycelial balls were collected and mycelial suspension was prepared. Then, the mycelial balls were inoculated into PD liquid medium and cultured at an inoculation rate of 0.5% to 5% by volume. The culture was carried out for 4 to 7 days under shaking conditions of 25°C and 135 rpm to obtain mycelial suspension.

[0028] The system after addition is adapted to a short period of time using diluted actual wastewater. This process only takes 1 to 2 days. Thanks to the high activity and strong adaptability of the fungal strain, the system can skip the long traditional acclimatization stage and start up quickly.

[0029] The beneficial effects of this invention are:

[0030] (1) Overcoming the bottleneck of organic nitrogen degradation. This invention places the fungal enhancement unit after the physicochemical pretreatment processes such as Fenton flocculation and before the traditional biochemical treatment system. Through the synergistic effect of enzymes such as laccase, cytochrome P450, and amide hydrolase produced by the fungi in the fungal enhancement unit, targeted carbon-nitrogen bond cleavage of residual organic amine-metal complexes after Fenton treatment is achieved, whereas traditional activated sludge processes are almost ineffective against such pollutants. The fungi used in this invention (such as *Trametes versicolor*) achieve a degradation rate of over 90% for complex organic amines such as triethanolamine (TEOA) and tetraethylenepentamine (TEPA) through the synergistic effect of their rich enzyme system, significantly outperforming the traditional activated sludge process (degradation rate less than 30%), thus solving the system failure problem caused by residual organic nitrogen in traditional biochemical processes. Furthermore, the ability of the fungi in this invention to degrade aromatic compounds such as aniline and nitroaniline further expands the applicability of this invention, providing a reliable solution for high-concentration organic nitrogen wastewater (10~400 mg / L).

[0031] (2) Excellent environmental tolerance and adaptability to highly inhibitory wastewater conditions. The fungi selected in this invention exhibit significant resistance to heavy metal residues and high-salt environments, and can operate stably under harsh conditions, with tolerance far exceeding that of ordinary microorganisms. This characteristic enables them to directly treat zinc-nickel alloy wastewater pretreated by Fenton (typically containing 0.1~1.0 mg / L of nickel and with a conductivity of 1~3 mS / cm) without additional treatment steps, significantly reducing treatment costs. Furthermore, the fungi maintain activity within a pH range of 4.5~7.0, eliminating the need to adjust the wastewater pH and simplifying the operation process.

[0032] (3) Significant advantages in process simplification and rapid start-up. The treatment system of this invention achieves rapid start-up by using pre-formed biological particles or immobilized bacteria, and can adapt to water quality in just 1-2 days, shortening the start-up cycle by several times compared to the traditional activated sludge process. The system has simple and reliable solid-liquid separation, and does not require sludge return, pH adjustment or secondary sedimentation tank. It can operate under normal temperature (20-30℃) conditions. In addition, the aeration flow rate is 0.1-0.3 L / min and the hydraulic retention time is 12-24h, which enables the fungi to continuously exert their efficient degradation performance.

[0033] (4) Potential for cost-effective large-scale application. The compatibility of fixed-bed or moving-bed reactors further enhances the versatility of the technology, making it suitable for centralized treatment in electroplating parks or decentralized treatment in enterprises. By enhancing degradation through bioparticle reactors, the amount of reagents added in the front-end Fenton process is significantly reduced, effectively alleviating the operating load and pressure of the pretreatment stage, and providing a sustainable green solution for the treatment of highly challenging organic nitrogen wastewater.

[0034] (5) Achieving efficient removal of organic nitrogen and rapid conversion to ammonia nitrogen. The fungi used in this invention can efficiently and rapidly convert organic nitrogen into bioavailable ammonia nitrogen, providing an ideal substrate for the subsequent nitrification-denitrification denitrification process. Kinetic studies show that under shake-flask experimental conditions, the ammonia nitrogen conversion rate of a specific fungus to a 100 mg / L triethanolamine standard solution reaches over 65% within 24 hours. This rapid and high-proportion directional conversion capability effectively avoids the accumulation of organic nitrogen in the system, ensuring the stable removal of organic nitrogen from zinc-nickel wastewater by the overall process. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a fungal-enhanced biological treatment tandem process provided in an embodiment of the present invention;

[0036] Figure 2 This is a diagram illustrating the long-term operational effect of the fungal-A / O combined process used in this invention to treat actual zinc-nickel wastewater.

[0037] Figure 3 This is a comparison chart showing the degradation performance of specific fungi and domesticated activated sludge in treating actual triethanolamine-containing zinc-nickel wastewater (total nitrogen 200 mg / L) under the shake-flask experimental conditions of this invention.

[0038] Figure 4 This is a kinetic diagram illustrating the degradation of 100 mg / L triethanolamine aqueous solution by specific fungi under the shake-flask experimental conditions of this invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0040] Example 1

[0041] This invention utilizes a biologically enhanced organic nitrogen degradation system for electroplating wastewater, consisting of a "fungal enhancement unit + A / O" architecture, to verify the enhanced degradation effect of fungi on organic nitrogen. Figure 1 As shown in the figure, the influent direction, pretreatment system, fungal enhancement unit, A / O biological system, and effluent destination are marked. This invention discloses a method for treating organic nitrogen in electroplating wastewater based on fungal enhancement, comprising the following steps:

[0042] Step 1: The zinc-nickel electroplating wastewater was pretreated using Fenton chromatography. The Fenton pretreatment process is as follows: The experiment used actual wastewater from an electroplating company in the industrial park. The wastewater underwent electro-Fenton flocculation pretreatment (preparing 350 g / L ferrous sulfate heptahydrate and 30% hydrogen peroxide, controlling the current at 0.2 A for 4 h; adjusting the pH to 8-9, adding 4.9 g PAC and 0.1 g PAM for flocculation for 30 min; acidifying the supernatant to pH 2.5, adding 3 g of zinc-nickel complex-breaking agent, and reacting for 30 min; then adjusting the pH to 8-9 for secondary flocculation). The resulting supernatant showed a significant reduction in nickel concentration, a COD removal rate exceeding 96%, and a 93% decrease in conductivity.

[0043] Step two involves transferring the pretreated zinc-nickel plating wastewater from the Fenton process to a fungal enhancement unit to remove some organic nitrogen. The pretreated wastewater was diluted and ammonium tartrate (organic nitrogen) was added to prepare a simulated reactor influent (COD 460.2 mg / L, TN 150 mg / L, total nickel 0.1 mg / L, conductivity 0.36 mS / cm), as shown in Table 1. In this embodiment, the fungus was purchased from the China Industrial Microbial Culture Collection Center and selected as *Trametesversicolor* (accession number: CICC 14001), exhibiting significant laccase activity and cytochrome P450 expression.

[0044] The hydraulic retention time of the fungal enhancement unit is 12–24 h, preferably 24 h in this embodiment. The aeration flow rate is 0.1–0.3 L / min, preferably 0.2 L / min in this embodiment, maintaining a dissolved oxygen concentration of 2–6 mg / L. The fungal enhancement unit uses a fluidized bed reactor or a biofilm reactor, preferably a fluidized bed reactor in this embodiment. The fungal cells are added to the fungal enhancement unit by culturing fungi to form fungal bioparticles with a diameter of approximately 3 mm–7 mm, or by using carrier immobilization technology, mixing the mycelial suspension obtained from the expanded culture with a carrier and then immobilizing it to form immobilized fungal particles. In this embodiment, fungal bioparticles are used. The filling volume ratio of fungal bioparticles in the fluidized bed reactor is 10–40%, preferably 10–30% in this embodiment.

[0045] Step 3: The zinc-nickel electroplating wastewater treated by the fungal enhancement unit was transferred to the A / O biological system for anoxic / aerobic denitrification treatment. The prepared wastewater was continuously fed into the A / O biological system and run for 92 days as a control experiment; subsequently, a fungal enhancement unit was added at the front end of the A / O biological system (93-125 days). The fungal mycelial balls added in the fungal enhancement unit were prepared as follows: four 1 cm... 2Trametes versicolor agar blocks of the size were inoculated into 500 mL of potato dextrose (PD) medium and cultured with shaking at 25°C and 135 rpm for 5 days. After isolation, mycelial balls (i.e. fungal bioparticles) were collected and directly added to the fungal enhancement unit.

[0046] Table 1. Water quality parameters before and after Fenton pretreatment and influent to the reactor

[0047]

[0048] Note: The TN of the Fenton pretreated effluent after dilution was 60.0 mg / L. Ammonium tartrate (organic nitrogen) was added to adjust it to about 150 mg / L as the reactor influent.

[0049] Heavy metal ions such as zinc and nickel in electroplating wastewater can penetrate microbial cell membranes, interfering with enzyme activity and electron transport chains, leading to inhibition of nitrifying bacteria, decreased sludge settling performance, and the risk of system collapse. Establishing a functional microbial community with heavy metal resistance is a core element in ensuring the stable operation of biological treatment of zinc- and nickel-containing wastewater. To explore the synergistic enhancement effect of fungi, this embodiment uses the Fenton pretreatment effluent as a substrate and sets up a control experiment of the A / O biochemical system (92 days) and a fungal-A / O combined process (93 days to 125 days) for comparison.

[0050] Figure 2 The study demonstrated the high tolerance of fungi to organic nitrogen and heavy metal residues under continuous operation for 125 days, as well as the synergistic removal efficiency and operational stability of the system for total nitrogen (TN) and organic nitrogen in wastewater. Figure 2 This also reflects the performance difference between the A / O process operating alone (days 1–92) and the fungal-A / O combined process stage after the introduction of the fungal enhancement unit (days 93–125).

[0051] As shown in Table 2 and Figure 2 As shown, the monitoring results indicate that the A / O biological system alone is susceptible to water quality fluctuations. After introducing fungal enhancement, the system's resistance to shocks is significantly improved. Compared with the A / O biological system alone, the addition of a fungal treatment unit to form a fungal-A / O biological system significantly improves the total nitrogen removal rate: the average removal rate of the A / O biological system is 50.4%, while the average removal rate of the fungal-A / O biological system reaches 64.8%, with the highest removal rate increasing to 74.4%. This confirms the enhanced removal effect of fungal treatment units with oxidoreductase (laccase, cytochrome P450, etc.) activity on organic nitrogen.

[0052] Table 2 Comparison of total nitrogen removal efficiency of different treatment systems in zinc-nickel wastewater

[0053]

[0054] This invention provides a method for fungal-enhanced treatment of organic nitrogen in electroplating wastewater. Using zinc-nickel wastewater as influent, the wastewater first undergoes a Fenton flocculation and sedimentation pretreatment system to remove some pollutants. Subsequently, the pretreated wastewater, containing organic nitrogen and heavy metal residues, enters a fungal-enhanced treatment unit, where fungi further degrade organic nitrogen and treat heavy metal residues. The treated water then flows into an A / O biological system for deep degradation of pollutants. The fungi efficiently cleave the carbon-nitrogen bonds of organic nitrogen using enzymes such as laccase and cytochrome P450 (degradation rate ≥ 90%), while also exhibiting significant tolerance to the toxicity of organic nitrogen-metal complexes (1 mg / L total nickel and 2 mS / cm conductivity), thus precisely addressing the problem of residual organic nitrogen.

[0055] Example 2

[0056] This invention utilizes a biologically enhanced organic nitrogen degradation system for electroplating wastewater, consisting of a "fungal enhancement unit + A / O" approach, to verify the enhanced degradation effect of fungi on organic nitrogen. Figure 1 As shown in the figure, the influent direction, pretreatment system, fungal enhancement unit, A / O biological system, and effluent destination are marked. This invention discloses a method for treating organic nitrogen in electroplating wastewater based on fungal enhancement, comprising the following steps:

[0057] Step 1: The zinc-nickel electroplating wastewater was pretreated using Fenton chromatography. The Fenton pretreatment process is as follows: The experiment used actual wastewater from an electroplating company in the industrial park. The wastewater underwent electro-flocculation pretreatment (preparing 350 g / L ferrous sulfate heptahydrate and 30% hydrogen peroxide, controlling the current at 0.2 A for 4 h; adjusting the pH to 8-9, adding 4.9 g PAC and 0.1 g PAM for flocculation for 30 min; acidifying the supernatant to pH 2.5, adding 3 g of zinc-nickel complex-breaking agent, and reacting for 30 min; then adjusting the pH to 8-9 for secondary flocculation). The resulting supernatant showed a significant reduction in nickel concentration, a COD removal rate exceeding 96%, and a 93% decrease in conductivity.

[0058] Step two involves transferring the pretreated zinc-nickel electroplating wastewater to a fungal enhancement unit to remove some organic nitrogen. The pretreated effluent was diluted and ammonium tartrate (organic nitrogen) was added to prepare a simulated reactor influent (COD 460.2 mg / L, TN 150 mg / L, total nickel 0.1 mg / L, conductivity 0.36 mS / cm), as shown in Table 1. In this embodiment, the fungus selected was *Trametes versicolor* (accession number: CICC 50001), which exhibits significant laccase activity and cytochrome P450 expression.

[0059] The hydraulic retention time of the fungal enhancement unit is 12-24 h, preferably 12 h in this embodiment. The aeration flow rate is 0.1-0.3 L / min, preferably 0.1 L / min in this embodiment, and the dissolved oxygen concentration is maintained at 2-6 mg / L. The fungal enhancement unit adopts a fluidized bed reactor or a biofilm reactor, preferably a fluidized bed reactor in this embodiment. The fungal cells are added to the fungal enhancement unit by culturing fungi to form fungal bioparticles with a diameter of approximately 3 mm-7 mm, or by using carrier immobilization technology, mixing the mycelial suspension obtained from the expanded culture with a carrier and then immobilizing it to form fungal immobilized particles. In this embodiment, fungal bioparticles are used. The filling volume ratio of fungal bioparticles in the fluidized bed reactor is 10-40%, preferably 30-40% in this embodiment.

[0060] Step 3: The zinc-nickel electroplating wastewater treated by the fungal enhancement unit was transferred to the A / O biological system for anoxic / aerobic denitrification treatment. The prepared wastewater was continuously fed into the A / O biological system and run for 92 days as a control experiment; subsequently, a fungal enhancement unit was added at the front end of the A / O biological system (93-125 days). The fungal mycelial balls added in the fungal enhancement unit were prepared as follows: four 1 cm... 2 Trametes versicolor agar blocks of the size were inoculated into 500 mL of potato dextrose (PD) medium and cultured with shaking at 25°C and 135 rpm for 5 days. After isolation, mycelial balls (i.e. fungal bioparticles) were collected and directly added to the fungal enhancement unit.

[0061] Example 3

[0062] This invention utilizes a biologically enhanced organic nitrogen degradation system for electroplating wastewater, consisting of a "fungal enhancement unit + A / O" approach, to verify the enhanced degradation effect of fungi on organic nitrogen. Figure 1 As shown in the figure, the influent direction, pretreatment system, fungal enhancement unit, A / O biological system, and effluent destination are marked. This invention discloses a method for treating organic nitrogen in electroplating wastewater based on fungal enhancement, comprising the following steps:

[0063] Step 1: The zinc-nickel electroplating wastewater was pretreated using Fenton chromatography. The Fenton pretreatment process is as follows: The experiment used actual wastewater from an electroplating company in the industrial park. The wastewater underwent electro-flocculation pretreatment (preparing 350 g / L ferrous sulfate heptahydrate and 30% hydrogen peroxide, controlling the current at 0.2 A for 4 h; adjusting the pH to 8-9, adding 4.9 g PAC and 0.1 g PAM for flocculation for 30 min; acidifying the supernatant to pH 2.5, adding 3 g of zinc-nickel complex-breaking agent, and reacting for 30 min; then adjusting the pH to 8-9 for secondary flocculation). The resulting supernatant showed a significant reduction in nickel concentration, a COD removal rate exceeding 96%, and a 93% decrease in conductivity.

[0064] Step two involves transferring the pretreated zinc-nickel electroplating wastewater to a fungal enhancement unit to remove some organic nitrogen. The pretreated effluent was diluted and ammonium tartrate (organic nitrogen) was added to prepare a simulated reactor influent (COD 460.2 mg / L, TN 150 mg / L, total nickel 0.1 mg / L, conductivity 0.36 mS / cm), as shown in Table 1. In this embodiment, the fungus selected was *Phanerochaete chrysosporium* (accession number: CICC 14076), which exhibits significant laccase activity and cytochrome P450 expression.

[0065] The hydraulic retention time of the fungal enhancement unit is 12–24 h, preferably 18 h in this embodiment. The aeration flow rate is 0.1–0.3 L / min, preferably 0.3 L / min in this embodiment, and the dissolved oxygen concentration is maintained at 2–6 mg / L. The fungal enhancement unit adopts a fluidized bed reactor or a biofilm reactor, preferably a fluidized bed reactor in this embodiment. The fungal cells are added to the fungal enhancement unit by culturing fungi to form biological particles with a diameter of approximately 3 mm–7 mm, or by using carrier immobilization technology, mixing the mycelial suspension obtained from the expanded culture with a carrier and then immobilizing it to form fungal immobilized particles. In this embodiment, fungal biological particles are used. The filling volume ratio of fungal biological particles in the fluidized bed reactor is 10–40%, preferably 30–40% in this embodiment.

[0066] Step 3: The zinc-nickel electroplating wastewater treated by the fungal enhancement unit was transferred to the A / O biological system for anoxic / aerobic denitrification treatment. The prepared wastewater was continuously fed into the A / O biological system and run for 92 days as a control experiment; subsequently, a fungal enhancement unit was added at the front end of the A / O biological system (93-125 days). The fungal mycelial balls added in the fungal enhancement unit were prepared as follows: four 1 cm... 2 Phanerochaete chrysosporium agar blocks of a certain size were inoculated into 500 mL of potato dextrose (PD) medium and cultured with shaking at 25°C and 135 rpm for 5 days. After isolation, mycelial balls (i.e. fungal bioparticles) were collected and directly added to the fungal enhancement unit.

[0067] This invention also provides a comparative study on the biodegradation performance of fungal mycelial balls and activated sludge under zinc-nickel stress on high-concentration organic nitrogen wastewater. Specifically, to eliminate the interference of complex matrices in actual wastewater, the degradation efficiency of fungi on typical organic nitrogen pollutants (triethanolamine) was directly verified under controlled shake-flask conditions, and compared with that of traditional activated sludge. Zinc-nickel complexed wastewater, i.e., the pretreated water sample, still retains high concentrations of organic pollutants and trace amounts of heavy metals, posing a continuous toxicity pressure on traditional activated sludge systems. This embodiment systematically evaluates the total nitrogen removal efficiency of fungal mycelial balls and activated sludge in tank A under the same high-load influent conditions through parallel controlled experiments.

[0068] The experiment used the following method: four 1 cm pieces 2 Trametes versicolor (accession number: CICC14001) agar blocks were inoculated into 500 mL of PD medium and cultured with shaking at 25℃ and 135 rpm for 5 days. Mycelial balls were then collected after separation. Simultaneously, the sludge-water mixture from the A / O process's A tank was centrifuged and the sludge was collected. Using the pretreated effluent as the raw water, triethanolamine (100 mg / L, TN = 9.4 mg / L) was added to prepare a shake flask simulating the influent with COD = 2685 mg / L, TN = 200 mg / L, total nickel = 1.0 mg / L, and conductivity = 1.2 mS / cm. 100 mL of this wastewater was measured and placed in four Erlenmeyer flasks. Two flasks contained 2 g of the centrifuged A tank activated sludge, and the same mass of fungal mycelial balls were added to the other two flasks. All flasks were placed in a constant temperature shaking incubator at 25℃ and 135 rpm for 24 hours. Analysis of relevant indicators using h and 48h sampling.

[0069] As shown in Table 3, the results indicate that within 48 hours, the TN removal rate of the mycelial ball group reached 70.8%, while that of the activated sludge group reached 32.6%. Trametes versicolor mycelial balls exhibit superior pollutant removal capacity and environmental adaptability compared to traditional activated sludge under conditions of high organic nitrogen and trace nickel coexistence, making them particularly suitable for the advanced biological treatment stage of wastewater after electro-Fenton pretreatment. Therefore, in this embodiment, mycelial balls are preferred as the core functional material for subsequent enhanced biological units, and their dosage and cultivation conditions can serve as reference parameters for engineering scale-up.

[0070] Table 3 Comparison of the degradation performance of fungi and sludge on total nitrogen in zinc-nickel wastewater

[0071]

[0072] In addition, this invention also provides an analysis of the degradation performance of specific fungi on pure triethanolamine (organic nitrogen) solutions. The experimental method is the same as in the foregoing examples, except that: a 100 mg / L triethanolamine aqueous solution was prepared in an Erlenmeyer flask, inoculated with 2 g *Trametes versicolor* mycelial balls, and cultured in a constant temperature shaking incubator at 25°C and 135 rpm. Samples were taken at 0 h, 5 h, and 24 h to determine the concentrations of triethanolamine and ammonia nitrogen in the supernatant. Figure 3 As shown, fungi have a significant advantage in degrading high concentrations of organic nitrogen in highly inhibitory wastewater.

[0073] As shown in Table 4 and Figure 4 As shown, the results indicate that *Trametes versicolor* achieved a 24-hour removal rate of 99.1% ± 1.1% for 100 mg / L triethanolamine (14.3% ± 3.0% at 5 hours), with degradation mainly occurring between 5 and 24 hours. Ammonia nitrogen increased from 0.025 mg / L to 6.1 mg / L, indicating that organic nitrogen was inorganicized during degradation, providing substrate for subsequent A / O stage nitrification-denitrification. This experiment eliminated interference from actual wastewater substrates and confirmed the direct degradation ability of fungi for organic nitrogen.

[0074] Table 4. Data on fungal degradation of triethanolamine and ammonia nitrogen conversion.

[0075]

[0076] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for enhancing the treatment of organic nitrogen in electroplating wastewater based on fungi, characterized in that: Includes the following steps: Zinc-nickel electroplating wastewater was pretreated using Fenton's method. The zinc-nickel electroplating wastewater pretreated with Fenton's enzymes was transported to a fungal enhancement unit containing fungi. Through the synergistic effect of different enzyme systems produced by the fungi, targeted carbon-nitrogen bond cleavage of residual organic nitrogen-metal complexes after Fenton pretreatment was performed, thereby degrading some of the organic nitrogen. The fungi added in the fungal enhancement unit are white-rot fungi. The fungi added in the fungal enhancement unit include: culturing the fungi to form fungal bioparticles with a diameter of 3 mm to 7 mm and then adding them to the reactor; or using carrier immobilization technology, mixing the mycelial suspension obtained from the expanded culture with a carrier and then immobilizing it to form fungal immobilized particles before adding them to the reactor; the reactor is a fluidized bed reactor or a biofilm reactor. The zinc-nickel electroplating wastewater treated by the fungal enhancement unit is transported to the A / O biological system for anoxic and aerobic denitrification treatment.

2. The method for treating organic nitrogen in electroplating wastewater based on fungal enhancement according to claim 1, characterized in that: Fenton pretreatment includes the following steps: Prepare 350 g / L ferrous sulfate heptahydrate and 30% hydrogen peroxide by mass, then add them to zinc-nickel electroplating wastewater. Connect the zinc-nickel electroplating wastewater to a DC power supply and control the current to 0.2 A for 4 h. After adjusting the pH of the zinc-nickel electroplating wastewater to 8-9, add 4.9 g PAC and 0.1 g PAM for flocculation for 30 min. The supernatant obtained after flocculation was acidified to pH 2.5, and then 3 g of zinc-nickel complex-breaking agent was added and reacted for 30 min. Then adjust the pH of the supernatant to 8-9 for secondary flocculation.

3. The method for treating organic nitrogen in electroplating wastewater based on fungal enhancement according to claim 1, characterized in that: The total nitrogen content in the zinc-nickel electroplating wastewater after Fenton pretreatment is 10~400 mg / L, the total nickel ion concentration is 0.1~1.0 mg / L, and the conductivity is 1~3 mS / cm.

4. The method for treating organic nitrogen in electroplating wastewater based on fungal enhancement according to claim 1, characterized in that: The hydraulic retention time of the fungal enhancement unit is 12-24 h, the aeration flow rate is 0.1-0.3 L / min, and the dissolved oxygen concentration is maintained at 2-6 mg / L.

5. The method for treating organic nitrogen in electroplating wastewater based on fungal enhancement according to claim 1, characterized in that: The volume of fungal bioparticles or immobilized fungal particles added accounts for 10% to 40% of the reactor volume.

6. The method for treating organic nitrogen in electroplating wastewater based on fungal enhancement according to claim 1, characterized in that: The method for expanding the culture includes the following steps: Inoculate the preserved strains onto potato dextrose agar plates or slants and incubate at 20–30°C for 4–7 days. Mycelial balls were collected and mycelial suspension was prepared. Then, the mycelial balls were inoculated into PD liquid medium and cultured at an inoculation rate of 0.5% to 5% by volume. The culture was carried out for 4 to 7 days under shaking conditions of 25°C and 135 rpm to obtain mycelial suspension.

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