A bacteria-algae synergistic photoelectric denitrification wastewater treatment system and a wastewater treatment method

Abstract

The application provides a bacteria-algae synergistic photoelectric denitrification wastewater treatment system and a wastewater treatment method. The treatment system comprises a bacteria-algae reactor, a flocculation tank and a photoelectric denitrification treatment device. The light guide fiber and light reflection material of the bacteria-algae reactor can enhance the penetration of light in sewage. The photoelectric denitrification treatment device is in an inner-outer sleeve structure. The outer sleeve is used for the reaction of wastewater and the activated product of a photosensitizer, which is conducive to the treatment of organic carbon in the wastewater. The photo-generated electrons generated by the activation of the photosensitizer are transmitted to the inner sleeve through the conductive material as the electron donor of the photoautotrophic denitrifying bacteria. Therefore, the photoelectric denitrification treatment device has the dual functions of organic carbon decomposition and denitrification, and the inner-outer sleeve structure design is conducive to simplifying the process design and reducing the floor area. The wastewater treatment system combines the bacteria-algae reactor, the flocculation tank and the photoelectric denitrification treatment device, and can realize the comprehensive treatment of aquaculture tail water, so that the aquaculture tail water meets the discharge standard.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a bacterial-algae synergistic photoelectric denitrification wastewater treatment system and wastewater treatment method. Background Technology

[0002] Aquaculture wastewater refers to the treated wastewater discharged during the aquaculture process. It contains waste products, metabolic byproducts, feed residues, and other organic loads generated during the aquaculture process. Intensive aquaculture models involve high stocking densities and large feed inputs, resulting in over 70%–80% of the feed not being absorbed and utilized by aquatic animals. Under normal circumstances, fish absorb less than 35% of total phosphorus (TN) and 30% of total nitrogen (TP). The decay and decomposition of these leftover feed and excrement produce harmful substances, leading to water quality deterioration; among these factors, the discharge of aquaculture wastewater is a significant cause of eutrophication.

[0003] The main characteristics of aquaculture wastewater can be summarized as follows: high organic load, high concentrations of nitrogen and phosphorus, high solubility and suspension, low pollutant concentration, large volume, and uneven discharge. Aquaculture wastewater is generally slightly polluted, with low chemical oxygen demand (COD), typically between 40 and 100 mg / L, and ammonia nitrogen content below 3 mg / L. Therefore, traditional biological technologies, such as activated sludge processes, biological filtration, and biofilm processes, cannot effectively remove pollutants from aquaculture wastewater. Therefore, there is an urgent need to find a highly efficient and economical treatment method for aquaculture wastewater.

[0004] Currently, extensive research and application have been conducted on aquaculture wastewater treatment technologies. Some farms use bio-balls or filters to filter and treat wastewater, but this method can only remove large particulate impurities and does not achieve the goal of pollution removal. A few farms use equipment such as protein skimmers to purify wastewater. Currently, this wastewater is usually discharged directly after passing through several purification devices. Even after treatment, a significant amount of toxic and harmful substances remain in the wastewater, causing considerable environmental pollution. The "three-pond, two-dam" process (sedimentation tank—filtration dam—aeration tank—filtration dam—ecological purification tank) is a commonly used process for aquaculture wastewater with large discharge volumes and low concentrations; however, this process has disadvantages such as large footprint and low treatment efficiency.

[0005] Existing wastewater treatment methods include photoelectric denitrification and algae-bacterial symbiotic treatment. Patents CN113845208A (a photoelectric microbial coupled denitrification and carbon removal system) and CN110642375A (a photocatalytic coupled autotrophic denitrification reactor) mention using photoelectric electrode plates for photoelectric denitrification, but these require excessive equipment, including anode chambers, cathode chambers, and wiring. Patent CN110282831A (algae-bacterial symbiotic photobioreactor coupled with constructed wetland wastewater treatment device and its treatment method) discloses a wetland wastewater treatment device combining algae and bacteria with a photoreactor, but the light source of this device cannot penetrate deeply into the wastewater tank, resulting in high energy consumption and low treatment efficiency. Furthermore, there are currently no reported solutions combining photoelectric denitrification and algae-bacterial symbiotic treatment for treating aquaculture wastewater. Summary of the Invention

[0006] To overcome the problems existing in the prior art, one objective of this invention is to provide a bacterial-algae synergistic photoelectric denitrification wastewater treatment system. Another objective of this invention is to provide a wastewater treatment method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of this invention provides a bacterial-algae synergistic photoelectric denitrification wastewater treatment system, comprising:

[0009] The bacterial and algae reactor is equipped with a bacterial and algae reactor inlet and a bacterial and algae reactor outlet, and contains optical fibers, light-reflecting materials, activated sludge and Chlorella vulgaris.

[0010] The flocculation tank is divided into a flocculation reaction zone and a sedimentation zone. The flocculation tank is equipped with a flocculation tank inlet and a flocculation tank outlet. The flocculation tank inlet is connected to the outlet of the bacteria and algae reactor.

[0011] A photoelectric denitrification treatment device includes an outer cylinder made of a light-transmitting material. The outer cylinder has an inlet and an outlet. The inlet is connected to a wastewater inlet pipe, and the outlet is connected to the inlet of a bacterial and algal reactor. An inner cylinder is fitted inside the outer cylinder. The inner cylinder is made of a conductive material and is filled with a porous medium with a biofilm attached to its surface. The biofilm is formed by photoautotrophic denitrifying bacteria. The inner cylinder has an inlet and an outlet, and the inlet is connected to the outlet of a flocculation tank.

[0012] Algae-bacteria systems are a technology that utilizes the interaction between algae and bacteria to treat wastewater. In this system, algae produce oxygen through photosynthesis, providing a favorable living environment for bacteria. Simultaneously, bacteria decompose organic matter in the wastewater through metabolism, providing nutrients for the algae. This symbiotic relationship effectively removes pollutants such as organic matter, nitrogen, and phosphorus from wastewater. Furthermore, addressing the problem of light sources failing to penetrate deep into wastewater in traditional algae-bacteria systems, this invention employs two methods to enhance light penetration: firstly, by adding light-reflecting materials to disperse the light source throughout the wastewater; and secondly, by adding transparent light-guiding fibers to the system, thereby directing light to the depths of the wastewater pool, significantly improving the utilization rate of the light source.

[0013] Photovoltaic denitrification is a denitrification process driven by light and electricity, which can reduce nitrates in wastewater to nitrogen gas, thereby removing nitrogen pollutants from the wastewater. This technology is characterized by high efficiency and low energy consumption, and has broad application prospects in the treatment of aquaculture wastewater. Addressing the shortcomings of traditional photovoltaic denitrification systems (which only perform denitrification), this invention uses an inner and outer cylinder structure for the photovoltaic denitrification treatment device, forming a continuous flow for simultaneous wastewater treatment. The outer cylinder is used for the reaction between wastewater and the activation products of the photosensitizer, which is beneficial for treating organic carbon in the wastewater. The photogenerated electrons generated by the photosensitizer activation are transferred to the inner cylinder through a conductive material as electron donors for photoautotrophic denitrifying bacteria. Therefore, the photovoltaic denitrification treatment device has the dual functions of organic carbon decomposition and denitrification.

[0014] This invention combines three technologies—bacterial and algal systems, flocculation, and photoelectric denitrification—to achieve comprehensive wastewater treatment, including the removal of organic matter, nitrogen and phosphorus, and suspended solids. This integrated treatment process can effectively improve the water quality of aquaculture effluent, enabling it to meet discharge or reuse standards.

[0015] Preferably, the algae-bacterial reactor is lined with optical fibers and light-reflecting materials, and is inoculated with domesticated activated sludge and Chlorella.

[0016] Preferably, the light-reflecting material is selected from at least one of zinc oxide, titanium oxide, and calcium oxide.

[0017] Preferably, the particle size of the light-reflecting material is 10-100 nm.

[0018] Preferably, the amount of light-reflecting material in the algae and bacteria reactor is 0.05–1% (v / v).

[0019] Preferably, the light guide fiber is an acrylic light guide fiber.

[0020] Preferably, the inoculum amount of Chlorella in the algal reactor is 8% to 12%.

[0021] In this invention, the Chlorella inoculum amount refers to the ratio of the volume of the Chlorella culture medium to the volume of the algal-bacterial reactor.

[0022] Preferably, the inoculum amount of activated sludge in the algae-bacteria reactor is 0.5% to 2%.

[0023] In this invention, the activated sludge inoculation amount refers to the ratio of the activated sludge volume to the volume of the algae and bacteria reactor.

[0024] More preferably, the activated sludge is sludge from the secondary sedimentation tank of a wastewater treatment plant.

[0025] More preferably, the bacterial phyla of the activated sludge include Bacteroidetes, Chlorobacteria, Proteobacteria, and Actinobacteria.

[0026] Preferably, the light-transmitting material is light-transmitting glass or light-transmitting plastic.

[0027] More preferably, the light-transmitting plastic is selected from plexiglass or polycarbonate.

[0028] Preferably, the outer cylinder is used for the reaction of wastewater with the activation products of the photosensitizer.

[0029] Preferably, the conductive material is selected from at least one of iron, titanium, iron alloy, and graphite.

[0030] More preferably, the ferroalloy is stainless steel.

[0031] Preferably, the photoelectric denitrification treatment device is composed of nested double cylindrical reactors, wherein the wall material of the outer cylindrical reactor is plexiglass and the wall material of the inner cylindrical reactor is iron alloy.

[0032] Preferably, the photosensitizer is selected from at least one of cadmium sulfide nanomaterials, anthraquinone-2,6-disulfonic acid, and sodium anthraquinone-2-sulfonate.

[0033] Preferably, the porous medium is selected from activated carbon, plastic balls, porous ceramics, sponges, or carbon felt.

[0034] Preferably, the photoautotrophic denitrifying bacteria are denitrifying thiobacilli.

[0035] Preferably, the method for preparing the porous medium with a biofilm attached to its surface includes the following steps: immersing the porous medium in a mixture of photoautotrophic denitrifying bacteria and culturing it to obtain the porous medium with a biofilm attached to its surface.

[0036] More preferably, the culture time is 2-3 days.

[0037] Preferably, the algae and bacteria reactor is equipped with a stirring device.

[0038] Preferably, the flocculation tank is equipped with a stirring device.

[0039] Preferably, the inner cylinder is equipped with a stirring device.

[0040] A second aspect of the present invention provides a wastewater treatment method, which employs the bacteria-algae synergistic photoelectric denitrification wastewater treatment system described in the first aspect, and includes the following steps:

[0041] S1. Wastewater flows into the outer cylinder through the inlet of the outer cylinder. A photosensitizer is added and stirred. Under light, the photosensitizer is excited to generate photogenerated electrons and holes. The wastewater reacts with the holes in an oxidation reaction.

[0042] S2. Wastewater flows into the bacteria and algae reactor and is treated under light. The wastewater treated by the bacteria and algae reactor flows into the flocculation tank, and flocculant is added to the flocculation tank. The flocculant mixes with the suspended solids in the wastewater to carry out a flocculation reaction. After the flocculation reaction, flocculants are obtained in the sedimentation zone for sedimentation.

[0043] S3. Wastewater treated in the flocculation tank flows into the inner cylinder through the inlet of the inner cylinder, while untreated wastewater flows into the outer cylinder for treatment in S1, forming a simultaneous internal and external flow of wastewater treatment. Photogenerated electrons from the outer cylinder are transferred to the inner cylinder as electron donors for photoautotrophic denitrifying bacteria, which then perform denitrification treatment on the wastewater.

[0044] Preferably, the wastewater undergoes preliminary filtration before flowing into the outer cylinder.

[0045] Using preliminary filtration helps reduce light scattering caused by large suspended particles.

[0046] Preferably, the water quality parameters of the wastewater are selected from at least one of the following:

[0047] a) COD concentration is 20–150 mg / L;

[0048] b) TP concentration is 0.1–1 mg / L;

[0049] c) TN concentration is 5–15 mg / L.

[0050] Preferably, the photosensitizer is added by first mixing it with wastewater and / or by adding the photosensitizer into the outer cylinder.

[0051] Preferably, the concentration of the photosensitizer in the wastewater is 0.1–10 mol / L.

[0052] Preferably, the illumination in step S1 uses a xenon lamp light source with an illumination intensity of 50–200 mW / cm². 2 .

[0053] Preferably, the illumination in step S2 is natural illumination.

[0054] Preferably, the flocculant comprises polyaluminum chloride, polyacrylamide, and Bacillus polymyxa.

[0055] More preferably, the method for preparing the flocculant includes mixing polyaluminum chloride, polyacrylamide, and Bacillus polymyxa powder.

[0056] Preferably, the amount of flocculant added is 5%.

[0057] Preferably, step S2 further includes adding a chemical phosphorus removal agent to the flocculation tank.

[0058] Preferably, step S3 involves forming a vertical inward and outward flow to simultaneously treat wastewater.

[0059] Preferably, the hydraulic retention time of the wastewater in the algae and bacteria reactor is 1 to 3 days.

[0060] Preferably, the hydraulic retention time of the wastewater in the flocculation tank is 0.5 to 2 days.

[0061] Preferably, the hydraulic retention time of the wastewater in the inner cylinder is 0.5 to 2 days.

[0062] The beneficial effects of this invention are:

[0063] (I) This invention provides a bacterial-algae synergistic photoelectric denitrification wastewater treatment system, including a bacterial-algae reactor, a flocculation tank, and a photoelectric denitrification treatment device. The bacterial-algae reactor uses algae photosynthesis to generate oxygen, which, combined with bacteria in activated sludge, can effectively remove pollutants such as organic matter, nitrogen, and phosphorus from the wastewater. In addition, optical fibers and light-reflecting materials can enhance the light transmittance in the wastewater. The photoelectric denitrification treatment device has an inner and outer sleeve structure. The outer sleeve is used for the reaction between wastewater and the activation products of photosensitizer, which is beneficial for treating organic carbon in the wastewater. The photogenerated electrons generated by the activation of the photosensitizer are transferred to the inner sleeve through a conductive material as electron donors for photoautotrophic denitrifying bacteria. Therefore, this photoelectric denitrification treatment device has the dual functions of organic carbon decomposition and denitrification. Moreover, the inner and outer sleeve structure design has significant advantages in terms of simplified process design and floor space. The wastewater treatment system of this invention combines three technologies: algae and bacteria reactor, flocculation tank, and photoelectric denitrification treatment device. It can achieve comprehensive treatment of aquaculture wastewater, including the removal of organic matter, nitrogen and phosphorus, and suspended solids, so that the aquaculture wastewater meets the discharge standards or reuse standards.

[0064] (II) The present invention also provides a wastewater treatment method, which uses a bacterial-algae synergistic photoelectric denitrification wastewater treatment system to treat wastewater. The wastewater is treated sequentially through an inner cylinder, a bacterial-algae reactor, a flocculation tank, and an outer cylinder. The bacterial-algae reactor uses algae photosynthesis to produce oxygen. The system can operate without power aeration, reducing power consumption and saving aeration power consumption compared with traditional aquaculture wastewater treatment processes. The photoelectric denitrification device uses photoelectric materials to provide denitrification electrons, eliminating the need for additional carbon sources. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the processing technology of the present invention;

[0066] Figure 2 This is a schematic diagram illustrating the carbon and nitrogen removal principles in the inner and outer cylinders. Detailed Implementation

[0067] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial channels or prepared and isolated through simple synthesis; unless otherwise specified, the processes employed are conventional processes in the art.

[0068] Example 1

[0069] This embodiment provides a bacterial-algae synergistic photoelectric denitrification wastewater treatment system and a method for treating aquaculture wastewater.

[0070] 1. The setup of the bacteria-algae synergistic photoelectric denitrification wastewater treatment system should refer to... Figure 1 The specific settings are as follows:

[0071] (1) The photoelectric denitrification device consists of nested double cylindrical reactors. The outer reactor is made of transparent acrylic, and the inner reactor is made of stainless steel. The outer cylinder has a diameter of 30cm and a height of 40cm, while the inner cylinder has a diameter of 25cm and a height of 50cm. The inner cylinder is filled with porous spheres with a biofilm attached to their surface. The biofilm is composed of photoautotrophic denitrifying bacteria.

[0072] The biofilm is prepared by immersing a porous medium in a mixture of photoautotrophic denitrifying bacteria and culturing it to obtain a porous medium with a biofilm attached to its surface.

[0073] The photoautotrophic denitrifying bacteria described were *Thiobaci* denitrificans, Td. The culture method for Td was as follows: the culture medium consisted of a basal medium and a mixture of glucose (5-10 g), NaCl (10-20 g), and elemental sulfur (2-5 g). The basal medium was composed of a solution of microvitamins and trace elements. The culture conditions were: temperature: 30℃, pH: 7.0, salt concentration: 1%, shaking speed: 150 r / min, and culture time: 24 hours.

[0074] (2) The algae-bacterial reactor is a cylindrical reactor with a diameter of 0.5m and a height of 0.3m, and an effective volume of approximately 50L. The algae source in the algae-bacterial system is *Chlorella vulgaris* (purchased from the Institute of Hydrobiology, Chinese Academy of Sciences), with an inoculum of 10% at 5L (OD=300). The bacterial strains are derived from the sludge of the secondary sedimentation tank of the Fuzhou Chengbei Wastewater Treatment Plant (mainly composed of *Bacteroidota*, *Chloroflexi*, *Proteobacteria*, *Actinobacteria*, and *Patescibacteria*), with an inoculum of 2% at 1L (OD=300). Simultaneously, nano-zinc oxide (30-50nm) is added to the system as a light dispersant at a concentration of 0.2%; dendritic acrylic optical fibers are used as the substrate for algae and bacterial attachment, with a total surface area of ​​approximately 5m². 2 .

[0075] (3) The biological flocculation tank has a diameter of 0.3m and a height of 0.8m. The upper two-thirds of the biological flocculation tank is the flocculation reaction zone, and the lower one-third of the depth is the sedimentation zone.

[0076] (4) The algae reactor is provided with an algae reactor inlet and an algae reactor outlet, the flocculation tank is provided with a flocculation tank inlet and a flocculation tank outlet, and the flocculation tank inlet is connected to the algae reactor outlet; the outer cylinder is provided with an outer cylinder inlet and an outer cylinder outlet, the outer cylinder inlet is connected to a sewage inlet pipe, and the outer cylinder outlet is connected to the algae reactor inlet; the inner cylinder is provided with an inner cylinder inlet and an inner cylinder outlet, and the inner cylinder inlet is connected to the flocculation tank outlet.

[0077] 2. The specific methods for treating aquaculture wastewater are as follows:

[0078] S1. Influent water quality parameters are: COD concentration 25.59–30.6 mg / L, average 28.4 mg / L; TP concentration 0.35–0.53 mg / L, average 0.45 mg / L; TN concentration 7.1–10.5 mg / L, average 8.6 mg / L. The aquaculture wastewater is filtered to remove large suspended solids and reduce light scattering. The wastewater enters the outer cylinder from the elevated tank through the outer cylinder inlet. The photosensitizer, sodium anthraquinone-2-sulfonate (AQS), is added at a concentration of 2 mol / L. A solar-simulated xenon lamp (illuminance 100 mW / cm²) is used as the light source. 2 When the outer cylinder is irradiated, the photosensitive material generates photoelectrons and holes under the excitation of light. The generated holes act as a strong oxidizing agent to oxidize the organic matter in the wastewater.

[0079] S2. Wastewater treated by the outer cylinder is continuously fed into the algae and bacteria reactor. Natural light is used to irradiate the algae and bacteria reactor. The algae and bacteria reactor is equipped with a stirring device with a rotation speed of 150 rpm. The wastewater retention time is 2 days.

[0080] S3. Preparation of bioflocculant: Using liquid LB medium, *Bacillus polymyxa* (1 mL bacterial solution, 200 mL medium) was inoculated and cultured at pH 7.0, 30℃, and on a shaker (300 rpm) for 3 days. The medium was centrifuged, the supernatant was removed, and dilute hydrochloric acid (0.5 mol / L) was added, stirred evenly, and allowed to stand for 10 min. Then, it was centrifuged at low speed (5000 rpm) and dried at room temperature to obtain bacterial powder A. Bacterial powder A was mixed evenly with PAC (1%) and PAM (1%) in a specific mass ratio to obtain the bioflocculant.

[0081] Wastewater treated by the algae and bacteria reactor flows into the flocculation tank. The bio-flocculator prepared above is introduced into the flocculation tank. The flocculant mixes with the suspended solids in the wastewater and undergoes a flocculation reaction. After the reaction, the flocculants in the wastewater are precipitated. The amount of bio-flocculator added is 5%, and the wastewater retention time is 1 day.

[0082] S4. Wastewater treated in the flocculation tank flows into the inner cylinder through the inlet. The inlet TN concentration is approximately 6.3 mg / L. Simultaneously, the outer cylinder undergoes treatment in step S1, forming a vertical, synchronous inward and outward flow of wastewater treatment. The photosensitive material absorbs photon energy and generates photoelectrons, which are then transferred via stainless steel to photoautotrophic denitrifying bacteria in the inner cylinder for photoelectrotrophic metabolism. If nitrate is used as the electron acceptor, it can drive microbial photoelectrotrophic denitrification to remove nitrogen, ultimately removing inorganic nitrogen from the wastewater in gaseous form. The mechanism is as follows: Figure 2 As shown.

[0083] Example 2

[0084] The bacterial-algae synergistic photoelectric denitrification wastewater treatment system and the method for treating aquaculture tailwater in Example 2 are similar to those in Example 1, except that zinc oxide is not added as a photodispersant in the bacterial-algae reactor.

[0085] Example 3

[0086] The bacterial-algae synergistic photoelectric denitrification wastewater treatment system and the method for treating aquaculture tailwater in Example 3 are similar to those in Example 1, except that: (1) the influent water quality parameters are: COD concentration 23.5-26.6 mg / L, average 24.4 mg / L; TP concentration 0.5-1.0 mg / L, average 0.43 mg / L; TN concentration 6.6-10.1 mg / L, average 7.3 mg / L; (2) no zinc oxide is added as a photodispersant in the bacterial-algae reactor.

[0087] Example 4

[0088] The bacterial-algae synergistic photoelectric denitrification wastewater treatment system and the method for treating aquaculture tailwater in Example 4 are similar to those in Example 1, except that: (1) the influent water quality parameters are: COD concentration 80.5~148.4mg / L, average 106.3mg / L; TP concentration 0.17~0.43mg / L, average 0.32mg / L; TN concentration 6.4~12.4mg / L, average 10.6mg / L; (2) no optical fiber is added to the bacterial-algae reactor.

[0089] Comparative Example 1

[0090] Based on the setup of Example 1, only the bacterial-algae system and bioflocculation process are used, without a denitrification system, and the other settings are the same as in Example 1.

[0091] Comparative Example 2

[0092] Based on the setup of Example 1, only the bioflocculation process and photoelectric denitrification system are used, without the bacterial and algal system, and the other settings are the same as in Example 1.

[0093] Comparative Example 3

[0094] The traditional "three ponds and two dams" aquaculture wastewater treatment process is adopted. Specifically: the sedimentation pond is 0.5m in size and 0.3m in height, with an effective volume of approximately 50L. The aeration pond is 0.5m in size and 0.3m in height, with an effective volume of approximately 50L. The ecological purification pond is 1.0m in size and 0.3m in height, with an effective volume of approximately 100L. The ecological pond measures 0.8m × 0.5m × 0.5m, with an effective volume of 200L, and is filled from top to bottom with 15cm of fine sand, 15cm of cinder, and 15cm of gravel, with a water surface and overflow height of 5cm. Water hyacinth and similar plants are selected for the ecological purification pond, with a plant density of 100 plants / m² and a hydraulic load of 0.2m / d. The influent water quality parameters are as follows: COD concentration 29.5–36.6 mg / L, average 32.4 mg / L; TP concentration 0.12–0.73 mg / L, average 0.53 mg / L; TN concentration 5.3–13.8 mg / L, average 8.3 mg / L.

[0095] Water effluent testing

[0096] The effluent from Examples 1-4 and Comparative Examples 1-3 were tested for COD, TP, and TN, and the removal rates of COD, TP, and TN were calculated. The results are shown in Table 1.

[0097] Table 1

[0098] Example COD removal rate TN removal rate TP removal rate Example 1 92～98％ 82～95％ 76～83％ Example 2 78～83％ 82～89％ 80～85％ Example 3 81～86％ 82～91％ 81～89％ Example 4 80～88％ 78～88％ 82～90％ Comparative Example 1 82～88％ 42～58％ 44～57％ Comparative Example 2 44～57％ 42～57％ 35～57％ Comparative Example 3 82～86％ 34～49％ 37～57％

[0099] As shown in Table 1, when the influent water quality changes, the removal rates of COD, TN, and TP in the effluent treated by the aquaculture wastewater treatment system of this embodiment are relatively stable, with most changes within 10%. In the small-scale experiment, the aquaculture wastewater treatment system of this embodiment operated stably for more than 180 days.

[0100] A comparison of the data from Example 1 and Example 2 shows that adding zinc oxide can improve the removal efficiency of organic matter.

[0101] In the comparative example, the effluent efficiency was lower than that of the aquaculture wastewater treatment system in the embodiment of this invention, with TN and TP removal rates around 50%, showing significant fluctuations and poor operational stability. In the small-scale experiment, the water quality of the comparative system deteriorated after 55 days of operation, rendering it unusable.

[0102] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A synergistic bacterial-algae photoelectric denitrification wastewater treatment system, characterized in that, include: The bacterial and algae reactor is equipped with a bacterial and algae reactor inlet and a bacterial and algae reactor outlet, and contains optical fibers, light-reflecting materials, activated sludge and Chlorella vulgaris. The flocculation tank is divided into a flocculation reaction zone and a sedimentation zone. The flocculation tank is equipped with a flocculation tank inlet and a flocculation tank outlet. The flocculation tank inlet is connected to the outlet of the bacteria and algae reactor. A photoelectric denitrification treatment device includes an outer cylinder made of a light-transmitting material. A photosensitizer is added inside the outer cylinder, and a xenon lamp simulating sunlight is used to irradiate the outer cylinder. The outer cylinder has an inlet and an outlet. The inlet is connected to a wastewater inlet pipe, and the outlet is connected to the inlet of a bacterial and algal reactor. An inner cylinder is fitted inside the outer cylinder. The inner cylinder is made of a conductive material and is filled with a porous medium with a biofilm attached to its surface. The biofilm is formed by photoautotrophic denitrifying bacteria. The inner cylinder has an inlet and an outlet, and the inlet is connected to the outlet of a flocculation tank.

2. The bacteria-algae synergistic photoelectric denitrification wastewater treatment system according to claim 1, characterized in that, The light-reflecting material is selected from at least one of zinc oxide, titanium oxide, and calcium oxide; And / or, the particle size of the light-reflecting material is 10-100 nm.

3. The bacteria-algae synergistic photoelectric denitrification wastewater treatment system according to claim 1, characterized in that, The inoculum amount of Chlorella in the algae reactor is 8%~12%; And / or, the inoculum amount of the activated sludge in the algae reactor is 0.5% to 2%.

4. The bacteria-algae synergistic photoelectric denitrification wastewater treatment system according to claim 1, characterized in that, The light-transmitting material is light-transmitting glass or light-transmitting plastic; And / or, the conductive material is selected from at least one of iron, titanium, iron alloy, and graphite.

5. The bacteria-algae synergistic photoelectric denitrification wastewater treatment system according to claim 1, characterized in that, The photosensitizer is selected from at least one of cadmium sulfide nanomaterials, anthraquinone-2,6-disulfonic acid, and sodium anthraquinone-2-sulfonate. And / or, the photoautotrophic denitrifying bacteria are denitrifying thiobacilli.

6. The bacteria-algae synergistic photoelectric denitrification wastewater treatment system according to claim 1, characterized in that, The method for preparing the porous medium with a biofilm attached to its surface includes the following steps: the porous medium is immersed in a mixture of photoautotrophic denitrifying bacteria and cultured to obtain the porous medium with a biofilm attached to its surface.

7. A wastewater treatment method, characterized in that, The treatment method employs the synergistic algae-bacterial photoelectric denitrification wastewater treatment system described in any one of claims 1-6, and includes the following steps: S1. Wastewater flows into the outer cylinder through the inlet of the outer cylinder. A photosensitizer is added and stirred. Under light, the photosensitizer is excited to generate photogenerated electrons and holes. The wastewater reacts with the holes in an oxidation reaction. S2. Wastewater flows into the bacteria and algae reactor and is treated under light. The wastewater treated by the bacteria and algae reactor flows into the flocculation tank, and flocculant is added to the flocculation tank. The flocculant mixes with the suspended solids in the wastewater to carry out a flocculation reaction. After the flocculation reaction, flocculants are obtained in the sedimentation zone for sedimentation. S3. Wastewater treated in the flocculation tank flows into the inner cylinder through the inlet of the inner cylinder, while untreated wastewater flows into the outer cylinder for treatment in S1, forming a simultaneous internal and external flow of wastewater treatment. Photogenerated electrons from the outer cylinder are transferred to the inner cylinder as electron donors for photoautotrophic denitrifying bacteria, which then perform denitrification treatment on the wastewater.

8. The wastewater treatment method according to claim 7, characterized in that, The concentration of the photosensitizer in the wastewater is 0.1~10 mol / L.

9. The wastewater treatment method according to claim 7, characterized in that, The flocculant comprises polyaluminum chloride, polyacrylamide, and Bacillus polymyxa.

10. The wastewater treatment method according to claim 7, characterized in that, The hydraulic retention time of the wastewater in the algae and bacteria reactor is 1-3 days. And / or, the hydraulic retention time of the wastewater in the flocculation tank is 0.5 to 2 days; And / or, the hydraulic retention time of the wastewater in the inner cylinder is 0.5 to 2 days.

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