Industrial wastewater deep denitrification method based on multistage bioelectrochemical system

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses an industrial wastewater deep denitrification method based on a multi-stage bioelectrochemical system, which comprises the following steps: 1) wastewater pretreatment; 2) multi-stage bioelectrochemical treatment; and (3) disinfecting and discharging the treated wastewater through a post-treatment unit. Compared with the prior art, the device has the advantages that the denitrification efficiency of high-concentration ammonia-nitrogen wastewater is improved through the synergistic effect of the multi-stage bioelectrochemical system; the system utilizes organic matters in wastewater to generate electric energy and recycles biogas energy, so that the process energy consumption is reduced; the system adopts a multi-stage modular design and a functional flora enrichment technology, has strong adaptability to water quality fluctuation and impact load, and can still operate stably under the condition of water quality fluctuation; the alkalinity and the carbon source dosage are reduced through the self-adjusting capability of the bioelectrochemical system, and the consumption of chemical agents is reduced compared with the traditional process; the system synchronously recovers energy and fertilizer, and resource utilization in the wastewater treatment process is achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically a method for deep denitrification of industrial wastewater based on a multi-stage bioelectrochemical system, which is particularly suitable for treating industrial wastewater with high concentrations of ammonia nitrogen. Background Technology

[0002] Ammonia nitrogen pollution in industrial wastewater is one of the main causes of eutrophication in water bodies. With increasingly stringent environmental protection requirements, the development of efficient and low-energy-consumption deep denitrification technologies has become a research hotspot in the wastewater treatment field. Currently, traditional biological denitrification processes such as the A / O process and oxidation ditches suffer from problems in practical applications, including large land area requirements, high energy consumption, and sensitivity to water quality changes. While physicochemical treatment technologies such as air stripping and ion exchange offer stable treatment results, they have high operating costs and are prone to generating secondary pollution.

[0003] In recent years, bioelectrochemical systems (BES) have shown promising applications in wastewater treatment and energy recovery as an emerging technology. BES utilizes electroactive microorganisms to catalyze redox reactions, directly converting the chemical energy of organic matter and ammonia nitrogen in wastewater into electrical or hydrogen energy, while simultaneously removing pollutants. However, traditional BES suffers from problems such as low power density, limited treatment efficiency, and poor resistance to shock loads. For example, the power density of microbial fuel cells (MFCs) is typically less than 62.7 mW / m³. 3 Microbial electrolyzers (MECs) require expensive external voltage input. Furthermore, existing BES systems are ineffective at treating high-concentration ammonia nitrogen wastewater (>200 mg / L), with denitrification efficiencies generally below 80%.

[0004] Patent CN119080335B discloses a low-carbon modular biological denitrification treatment system for industrial nitrogen-containing wastewater, employing a combined process of a PNA integrated micro-aerobic reactor, a sludge screening device, and a composite functional bacterial multiplication device. While this system achieves a certain degree of low-carbon denitrification, it still suffers from problems such as unstable denitrification efficiency (60-85%), long system start-up time (>30 days), and complex operation and control.

[0005] Another patent, CN223225927U, discloses a wastewater treatment device that enhances nitrogen removal and phosphorus recovery. It achieves an organic combination of nitrogen removal and phosphorus recovery by incorporating a biological reactor, a rotating disc filter, a phosphorus recovery device, and a high-density sedimentation tank. However, this device is primarily designed for urban wastewater and has limited adaptability to high-concentration industrial wastewater, with high construction and operating costs.

[0006] Therefore, developing an efficient, stable, and low-energy-consumption method for deep denitrification of industrial wastewater, especially a system capable of treating high-concentration ammonia nitrogen wastewater and having the ability to withstand shock loads, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide a method for deep denitrification of industrial wastewater based on a multi-stage bioelectrochemical system, which is particularly suitable for the treatment of industrial wastewater with high concentrations of ammonia nitrogen.

[0008] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a method for deep denitrification of industrial wastewater based on a multi-stage bioelectrochemical system, specifically including the following steps:

[0009] 1) Wastewater pretreatment: Industrial wastewater is pretreated by using screens, equalization tanks, and sedimentation tanks to remove suspended solids and adjust water quality;

[0010] 2) Multi-stage bioelectrochemical treatment: The pretreated wastewater is introduced into a multi-stage system consisting of an anaerobic ammonia oxidation reactor, a short-cut nitrification reactor, and a bioelectrochemical reduction reactor for denitrification treatment;

[0011] 3) The treated wastewater is disinfected and discharged after passing through a post-treatment unit.

[0012] As a preferred embodiment, the multi-stage bioelectrochemical system includes at least one anaerobic ammonia oxidation reactor, a short-path nitrification reactor, and a bioelectrochemical reduction reactor.

[0013] As a preferred embodiment, the multi-stage bioelectrochemical system is filled with a functionalized biomembrane carrier, the carrier having a specific surface area of ​​500-1000 m². 2 / m 3 The pore size distribution is 10-100μm, and the filling rate is 30-50%.

[0014] As a preferred embodiment, the bioelectrochemical reduction reactor employs a graphene-modified cathode and an IrO2-Ta2O5 anode, with the electrodes configured as parallel plates, a plate spacing of 10-20 mm, and a current density of 0.5-1.5 A / cm². 2 .

[0015] As a preferred embodiment, the multi-stage bioelectrochemical system has a hydraulic retention time of 8-24 hours, dissolved oxygen controlled at 0.5-2.0 mg / L, temperature of 25-35℃, and pH value of 7.5-8.5.

[0016] As a preferred embodiment, a specific ratio of anaerobic ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and hydrogen autotrophic denitrifying bacteria is added to the multi-stage bioelectrochemical system, with the amount of bacteria added being 10-20% of the effective volume of the reactor.

[0017] As a preferred embodiment, the multi-stage bioelectrochemical system incorporates an online monitoring and automatic control device to monitor pH, ORP, DO, and ammonia nitrogen concentrations in real time, and automatically adjust the current intensity, aeration rate, and carbon source dosage.

[0018] As a preferred embodiment, the ratio of electrode surface area to reactor volume in the multi-stage bioelectrochemical system is 260-300 cm². 2 / L, the cathode is made of carbon felt material and the anode is made of titanium-based coated electrode.

[0019] As a preferred embodiment, the biogas produced by the multi-stage bioelectrochemical system is collected, purified, and then used for power generation, providing part of the energy consumption for the system.

[0020] The advantages of this invention compared to existing technologies are as follows: High-efficiency nitrogen removal performance: Through the synergistic effect of a multi-stage bioelectrochemical system, the nitrogen removal efficiency for high-concentration ammonia nitrogen wastewater reaches 95-98%, and the total nitrogen removal rate is 90-95%, which is more efficient than traditional biological nitrogen removal processes; Significantly reduced energy consumption: The system utilizes organic matter in wastewater to generate electricity and simultaneously recovers biogas energy, resulting in lower energy consumption compared to traditional nitrogen removal processes; Strong resistance to shock loads: The system adopts a multi-stage modular design and functional microbial enrichment technology, which has strong adaptability to water quality fluctuations and shock loads, and can still maintain stable operation even when water quality fluctuates by 30-50%; Through the self-regulating ability of the bioelectrochemical system, the amount of alkalinity and carbon source added is reduced, reducing the consumption of chemical reagents compared to traditional processes; The system simultaneously recovers biogas energy and ammonium salt fertilizer, realizing resource utilization in the wastewater treatment process. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of the multi-stage bioelectrochemical system of the present invention.

[0023] Figure 3 This is a comparison chart of the processing efficiency of three embodiments of the present invention and two control group processes. Detailed Implementation

[0024] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0025] A method for deep nitrogen removal from industrial wastewater based on a multi-stage bioelectrochemical system, characterized by the following steps:

[0026] (1) Wastewater pretreatment: Industrial wastewater is pretreated by using screens, equalization tanks and sedimentation tanks to remove suspended solids and adjust water quality;

[0027] (2) Multi-stage bioelectrochemical treatment: The pretreated wastewater is introduced into a multi-stage system consisting of an anaerobic ammonia oxidation reactor, a short-cut nitrification reactor and a bioelectrochemical reduction reactor for denitrification treatment;

[0028] (3) Post-treatment: The treated wastewater is disinfected in a disinfection tank before being discharged or reused.

[0029] In a multi-stage bioelectrochemical system, the anaerobic ammonia oxidation reactor is filled with functional biological packing material with a specific surface area of ​​800-1000 m². 2 / m 3 The packing material is enriched with anaerobic ammonia-oxidizing bacteria; the short-cut nitrification reactor uses an aerobic suspended packing biofilm reactor, with dissolved oxygen controlled at 0.5-1.0 mg / L and temperature maintained at 30-35℃; the bioelectrochemical reduction reactor adopts a microbial electrolysis cell (MEC) configuration, with carbon felt as the cathode material and titanium-based coated electrodes (IrO2-Ta2O5) as the anode material, and the electrode surface area to reactor volume ratio is 260-300 cm². 2 / L, current density is 0.8-1.2A / cm 2 .

[0030] The system operating conditions are: hydraulic retention time 8-24 h, pH 7.5-8.5, and temperature 25-35℃. A specific ratio of anaerobic ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and hydrogen autotrophic denitrifying bacteria are added to the system, with the dosage being 10-20% of the effective reactor volume.

[0031] Table 1: Configuration and Operating Parameters of Multi-Stage Bioelectrochemical System

[0032]

[0033]

[0034] This invention also includes an online monitoring and automatic control system that monitors pH, ORP, DO, and ammonia nitrogen concentrations in real time and automatically adjusts the current intensity, aeration rate, and carbon source dosage. The biogas produced by the system is collected, purified, and used for power generation, providing some of the system's energy.

[0035] Example 1: Treatment of high ammonia nitrogen wastewater in a chemical industrial park

[0036] A wastewater treatment plant in a chemical industrial park has an average influent ammonia nitrogen concentration of 350 mg / L, a COD of 600-800 mg / L, and a C / N ratio of approximately 2.0, with significant fluctuations in water quality. The multi-stage bioelectrochemical system provided in this invention is used for deep denitrification treatment.

[0037] System Configuration:

[0038] Pretreatment unit: mechanical bar screen (5mm aperture), equalization tank (HRT = 8h), primary sedimentation tank (surface loading 1.0m). 3 / m 2 ·h).

[0039] Multi-level bioelectrochemical system:

[0040] 1. Anaerobic ammonia oxidation reactor: effective volume 50m³ 3 Functional biological filler (specific surface area 900 m²) 2 / m 3 Add 10m of anaerobic ammonia-oxidizing bacteria agent. 3

[0041] 2. Short-cut nitration reactor: effective volume 50m³ 3 An aerobic suspended packed biofilm reactor was used, with dissolved oxygen controlled at 0.5-0.8 mg / L.

[0042] 3. Bioelectrochemical reduction reactor: effective volume 50m³ 3 The reactor employs a microbial electrolysis cell configuration, with modified carbon felt as the cathode material and titanium-based coated electrodes (IrO2-Ta2O5) as the anode material. The electrode surface area to reactor volume ratio is 280 cm². 2 / L

[0043] Post-treatment unit: Disinfection tank (using ultraviolet disinfection, dosage 40mJ / cm²) 2 )

[0044] Operating parameters: hydraulic retention time 20h, pH controlled at 8.0-8.2, temperature maintained at 32±1℃, current density 1.0A / cm³ 2 .

[0045] Treatment results: After the system is running stably, the ammonia nitrogen removal rate reaches 97.2%, the total nitrogen removal rate reaches 92.8%, the effluent ammonia nitrogen concentration is less than 10 mg / L, and the energy consumption per ton of water is 2.05 kWh / kgN.

[0046] Table 2: Running data of Example 1

[0047]

[0048] Example 2: Food Processing Wastewater Treatment

[0049] The wastewater from a food processing plant has an average ammonia nitrogen concentration of 150 mg / L, a COD of 1000-1200 mg / L, and a C / N ratio of approximately 6.0, exhibiting good biodegradability. The system of this invention is used for deep denitrification treatment.

[0050] System Configuration:

[0051] The pretreatment unit is the same as the previous example, but the scale of the multi-stage bioelectrochemical system is reduced, with a total effective volume of 30m³. 3 (10m at all levels) 3 The ratio of electrode surface area to reactor volume in the bioelectrochemical reduction reactor is 260 cm². 2 / L, current density 0.8A / cm 2 .

[0052] Operating parameters: hydraulic retention time 12h, pH controlled at 7.8-8.0, temperature maintained at 30±1℃.

[0053] Treatment results: After the system stabilized, the ammonia nitrogen removal rate reached 98.5%, the total nitrogen removal rate reached 95.2%, the effluent ammonia nitrogen concentration was below 5 mg / L, and the energy consumption per ton of water was 1.85 kWh / kgN. The biogas produced by the system is used for power generation, which can meet 30% of the system's energy consumption requirements.

[0054] Example 3: Pharmaceutical Wastewater Treatment

[0055] A pharmaceutical factory's wastewater, containing high ammonia nitrogen levels (average concentration 500 mg / L), COD of 1500-2000 mg / L, and trace amounts of inhibitory substances, was treated using the system of this invention for deep denitrification.

[0056] System Configuration:

[0057] The pretreatment process includes an iron-carbon micro-electrolysis unit (to improve the biodegradability of wastewater), and the total effective volume of the multi-stage bioelectrochemical system is 80m³. 3 The ratio of electrode surface area to reactor volume in the bioelectrochemical reduction reactor is 300 cm². 2 / L, current density 1.2A / cm 2 .

[0058] Operating parameters: hydraulic retention time 24h, pH controlled at 8.0-8.5, temperature maintained at 33±1℃.

[0059] Treatment results: After the system is running stably, the ammonia nitrogen removal rate reaches 96.8%, the total nitrogen removal rate reaches 91.5%, the effluent ammonia nitrogen concentration is less than 15 mg / L, and the energy consumption per ton of water is 2.18 kWh / kgN.

[0060] Comparative experiment

[0061] To verify the superiority of the present invention, a comparative experiment was conducted, comparing the present invention with two existing technologies: control group 1 adopted the traditional A / O denitrification process (design parameters refer to a certain brand of sewage treatment equipment, model: AO-2025); control group 2 adopted the SANI sulfur autotrophic denitrification process (refer to patent CN119080335B).

[0062] The experimental water was simulated high-ammonia nitrogen industrial wastewater with an ammonia nitrogen concentration of 300 mg / L and a COD of 600 mg / L, and the operating conditions were the same (HRT = 16 h, T = 30 ℃, pH = 8.0).

[0063] Table 3: Comparison of the processing effects of the present invention and existing technologies

[0064]

[0065] Experimental results show that the present invention is significantly superior to existing technologies in terms of nitrogen removal efficiency, energy consumption, and resistance to shock loads. In particular, regarding the treatment effect on high-concentration ammonia nitrogen wastewater, the ammonia nitrogen removal rate of the present invention is 18.7% higher than the traditional A / O process and 12.0% higher than the SANI process; energy consumption is reduced by 46.9% compared to the traditional A / O process and by 30.5% compared to the SANI process.

[0066] Furthermore, the system of this invention has a short start-up time, requiring only 15-20 days to achieve stable operation, while traditional biological denitrification systems typically require 30-40 days. The system also exhibits strong adaptability to water quality fluctuations; with a 40% fluctuation in water quality, the denitrification efficiency decreases by only 5-8%, compared to 15-20% and 12-18% for control groups 1 and 2, respectively.

[0067] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for advanced nitrogen removal from industrial wastewater based on a multi-stage bioelectrochemical system, characterized in that, Specifically comprising the following steps: 1) wastewater pretreatment: pretreating industrial wastewater by grating, adjusting pool and sedimentation tank to remove suspended solids and adjust water quality; 2) multi-stage biological electrochemical treatment: introducing pretreated wastewater into a multi-stage system composed of an anaerobic ammonia oxidation reactor, a short-cut nitrification reactor and a biological electrochemical reduction reactor for denitrification treatment; 3) the treated wastewater is subjected to a post-treatment unit for disinfection and discharge.

2. The method for advanced nitrogen removal from industrial wastewater based on multi-stage bio-electrochemical system according to claim 1, characterized in that: The multi-stage biological electrochemical system comprises at least one anaerobic ammonia oxidation reactor, one short-cut nitrification reactor and one biological electrochemical reduction reactor.

3. The method for advanced nitrogen removal from industrial wastewater based on multi-stage bio-electrochemical system according to claim 1, characterized in that: The multi-stage bioelectrochemical system is filled with functionalized biofilm carriers, the specific surface area of the carriers is 500-1000 m 2 / m 3 , the pore size distribution is 10-100 μm, and the filling rate is 30-50%.

4. The method for advanced nitrogen removal from industrial wastewater based on multi-stage bio-electrochemical system according to claim 1, characterized in that: The bioelectrochemical reduction reactor adopts a graphene modified cathode and an IrO2-Ta2O5 anode, the electrode is configured as a parallel plate type, the plate spacing is 10-20 mm, and the current density is 0.5-1.5 A / cm 2 .

5. The multi-stage bio-electrochemical system based advanced nitrogen removal process for industrial wastewater as claimed in claim 1 wherein: The hydraulic retention time of the multi-stage biological electrochemical system is 8-24 h, the dissolved oxygen is controlled at 0.5-2.0 mg / L, the temperature is 25-35℃, and the pH value is 7.5-8.

5.

6. The multi-stage bio-electrochemical system based advanced nitrogen removal process for industrial wastewater as claimed in claim 1 wherein: Specific proportions of anaerobic ammonia oxidation bacteria, nitrite oxidizing bacteria and hydrogen autotrophic denitrifying bacteria are added in the multi-stage biological electrochemical system, and the bacterial agent dosage is 10-20% of the effective volume of the reactor.

7. The multi-stage bio-electrochemical system based advanced nitrogen removal process for industrial wastewater as claimed in claim 1 wherein: The multi-stage biological electrochemical system is equipped with an online monitoring and automatic control device, which monitors the pH, ORP, DO and ammonia nitrogen concentration in real time, and automatically adjusts the current intensity, aeration amount and carbon source dosage.

8. The multi-stage bio-electrochemical system based advanced nitrogen removal process for industrial wastewater as claimed in claim 1 wherein: The multi-stage bioelectrochemical system electrode surface area to reactor volume ratio is 260-300 cm 2 / L, the cathode uses carbon felt material, and the anode uses a titanium-based coated electrode.

9. The multi-stage bio-electrochemical system based advanced nitrogen removal process for industrial wastewater as claimed in claim 1 wherein: The biogas produced by the multi-stage biological electrochemical system is collected and purified for power generation, providing part of the energy consumption for the system.

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