Bacteria-algae synergistic photoelectric denitrification wastewater treatment system and wastewater treatment method

Abstract

The invention 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 basin and a photoelectric denitrification treatment device, and a light guide fiber and a light reflection material of the bacteria-algae reactor can enhance the penetration rate of light in sewage; the photoelectric denitrification treatment device is of an inner-outer sleeve type structure, an outer sleeve is used for reacting wastewater with an activation product of a photosensitizer, and organic carbon in the wastewater is favorably treated; photo-induced electrons generated by activation of the photosensitizer are transmitted to the inner cylinder through the conductive material to serve as electron donors of photoautotrophic denitrifying bacteria, so that the photoelectric denitrification treatment device has dual functions of organic carbon decomposition and denitrification at the same time, and the inner and outer sleeve type structural design is beneficial to simplifying the process design and reducing the occupied area. According to the wastewater treatment system disclosed by the invention, the bacteria-algae reactor, the flocculation basin and the photoelectric denitrification treatment device are combined, so that comprehensive treatment on the aquaculture tail water can be realized, and the aquaculture tail water reaches the discharge standard.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a bacteria-algae collaborative photoelectric denitrification wastewater treatment system and a wastewater treatment method. Background Art

[0002] Aquaculture tailwater refers to the wastewater discharged after treatment during the aquaculture process. It contains wastes, metabolites, feed residues and other organic loads generated during the aquaculture process. Intensive aquaculture models have high aquaculture density and large feed inputs, and more than 70% to 80% of the feed is not absorbed and utilized by aquatic animals. Under normal circumstances, the absorption rate of total phosphorus (TN) and total nitrogen (TP) by fish is less than 35% and 30% respectively. The decay and decomposition of these residual feed and excrement produce harmful substances, leading to water quality deterioration; among them, the discharge of aquaculture tailwater is an important cause of eutrophication of water bodies.

[0003] The main characteristics of aquaculture tailwater can be summarized as: rich in organic load, high concentration of nitrogen and phosphorus, highly soluble and suspended, low concentration of pollutants, large water volume, uneven discharge, etc. Aquaculture tailwater is generally slightly polluted water, in which the chemical oxygen demand (COD) is low, usually between 40 and 100 mg / L, and the ammonia nitrogen content is also below 3 mg / L. Therefore, traditional biotechnology, such as activated sludge method, biofiltration method and biofilm method, cannot effectively remove pollutants in aquaculture tailwater. Therefore, it is urgent to find an efficient and economical treatment method for aquaculture tailwater.

[0004] At present, a lot of research and application has been carried out on aquaculture tailwater treatment technology. Some farms use bio-balls or filters to filter and treat tailwater, but this method can only filter out large particles of impurities in the tailwater and cannot achieve the purpose of removing pollution. A few farms use equipment such as protein separators to purify the tailwater. At present, these tailwaters are usually discharged directly after passing through several purification equipment in sequence. There are still many toxic and harmful substances in the treated tailwater, which will still cause great pollution to the environment. The "three pools and two dams" (sedimentation tank-filtration dam-aeration tank-filtration dam-ecological purification tank) process is a commonly used process for aquaculture wastewater with large discharge volume and low concentration. However, this process has the disadvantages of large footprint and low treatment efficiency.

[0005] Existing wastewater treatment methods have been reported to use photoelectric denitrification technology and algae-bacteria symbiotic treatment methods. Patent CN113845208A, a photoelectric microbial coupling denitrification and carbon removal system and CN110642375A, a photocatalytic coupling autotrophic denitrification reactor, mention the use of photoelectric electrode plates for photoelectric denitrification, but too many equipment are required, and an anode chamber, a cathode chamber, and wires need to be set up; Patent CN110282831A, a bacteria-algae symbiotic photobioreactor coupled with an artificial wetland sewage treatment device and its treatment method, discloses a wetland sewage device combining bacteria-algae and a photoreactor, but the light source of the device cannot penetrate deeply into the sewage pool, and there are problems of high energy consumption and low treatment efficiency. In addition, there is currently no report on the scheme of combining photoelectric denitrification technology and algae-bacteria symbiotic treatment methods for treating aquaculture tail water. Summary of the invention

[0006] In order to overcome the problems existing in the prior art, one of the purposes of the present invention is to provide a bacteria-algae synergistic photoelectric denitrification wastewater treatment system. The second purpose of the present invention is to provide a wastewater treatment method.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

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

[0009] A bacteria-algae reactor, wherein the bacteria-algae reactor is provided with a bacteria-algae reactor water inlet and a bacteria-algae reactor water outlet, and wherein the bacteria-algae reactor is provided with a light-guiding fiber, a light-reflecting material, activated sludge and Chlorella;

[0010] A flocculation tank, wherein the flocculation tank is divided into a flocculation reaction zone and a sedimentation zone, and the flocculation tank is provided with a flocculation tank water inlet and a flocculation tank water outlet, and the flocculation tank water inlet is connected to the water outlet of the bacteria-algae reactor;

[0011] The photoelectric denitrification treatment device comprises an outer cylinder, which is made of a light-transmitting material, and is provided with an outer cylinder water inlet and an outer cylinder water outlet, wherein the outer cylinder water inlet is connected to a sewage inlet pipe, and the outer cylinder water outlet is connected to the water inlet of the bacteria-algae reactor; an inner cylinder is sleeved inside the outer cylinder, and the inner cylinder is made of a conductive material, and is filled with a porous medium with a biofilm attached to the surface, wherein the biofilm is formed by photoautotrophic denitrifying bacteria, and the inner cylinder is provided with an inner cylinder water inlet and an inner cylinder water outlet, and the inner cylinder water inlet is connected to the water outlet of the flocculation tank.

[0012] The bacteria-algae system is a technology that uses the interaction between algae and bacteria to treat wastewater. In this system, algae produce oxygen through photosynthesis, providing a good living environment for bacteria. At the same time, bacteria decompose organic matter in wastewater through metabolism, providing nutrients for algae. This symbiotic relationship can effectively remove pollutants such as organic matter, nitrogen and phosphorus in wastewater. At the same time, in view of the problem that the light source in the traditional bacteria-algae system is difficult to penetrate the depth of sewage, the present invention adopts two methods to enhance the penetration of light. On the one hand, light reflective materials are added so that the light source can be dispersed into the sewage; on the other hand, transparent light-guiding fibers are added to the system so that the light can be guided to the depth of the sewage pool, greatly improving the utilization rate of the light source.

[0013] Photoelectric denitrification is a denitrification process driven by light energy and electrical energy, which can reduce nitrates in wastewater to nitrogen gas, thereby removing nitrogen pollutants in wastewater. This technology has the characteristics of high efficiency and low energy consumption, and has broad application prospects in aquaculture tailwater treatment. It aims at the shortcomings of traditional photoelectric denitrification systems with a single function (only denitrification). In the present invention, the photoelectric denitrification treatment device is an inner and outer sleeve structure to form an inner and outer continuous flow to synchronously treat wastewater, wherein the outer cylinder is used for the reaction of wastewater with the activation product of the photosensitizer, which is beneficial to the treatment of organic carbon in the wastewater; the photogenerated electrons generated by the activation of the photosensitizer are transferred to the inner cylinder through the conductive material as an electron donor for photoautotrophic denitrifying bacteria. Therefore, the photoelectric denitrification treatment device has the dual functions of organic carbon decomposition and denitrification.

[0014] The present invention combines the three technologies of bacteria-algae system, flocculation and photoelectric denitrification to achieve comprehensive treatment of wastewater, including removal of organic matter, nitrogen and phosphorus, and suspended solids. This comprehensive treatment process can effectively improve the water quality of aquaculture tail water to meet the discharge standard or reuse standard.

[0015] Preferably, optical fibers and light reflecting materials are laid in the bacteria-algae reactor, and the bacteria-algae reactor 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 reflective material is 10-100 nm.

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

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

[0020] Preferably, the inoculation amount of Chlorella in the bacteria-algae reactor is 8% to 12%.

[0021] The Chlorella inoculation amount in the present invention refers to the ratio of the volume of the Chlorella culture solution to the volume of the bacteria-algae reactor.

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

[0023] The activated sludge inoculation amount in the present invention refers to the ratio of the volume of activated sludge to the volume of the bacteria-algae reactor.

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

[0025] More preferably, the bacterial phyla of the activated sludge include Bacteroidetes, Chloroflexi, 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 organic glass or polycarbonate.

[0028] Preferably, the outer cylinder is used for the wastewater to react with the excited product 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 ferrous alloy is stainless steel.

[0031] Preferably, the photoelectric denitrification treatment device is formed by nesting two cylindrical reactors, wherein the wall material of the outer cylindrical reactor is organic glass, 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 anthraquinone-2-sodium sulfonate.

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

[0034] Preferably, the photoautotrophic denitrifying bacteria is Thiobacillus denitrifying.

[0035] Preferably, the method for preparing the porous medium with biofilm attached to the surface comprises the following steps: immersing the porous medium in a mixed solution of photoautotrophic denitrifying bacteria for culturing, thereby obtaining the porous medium with biofilm attached to the surface.

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

[0037] Preferably, the bacteria-algae reactor is provided with a stirring device.

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

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

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

[0041] S1. Wastewater flows into the outer cylinder through the water inlet of the outer cylinder, and photosensitizer is added and stirred. Under light, the photosensitizer is stimulated to generate photogenerated electrons and holes, and the wastewater and holes undergo oxidation reaction;

[0042] S2, the wastewater flows into the bacteria-algae reactor and is treated under light; the wastewater treated by the bacteria-algae reactor flows into the flocculation tank, and a flocculant is added to the flocculation tank, the flocculant is mixed with the suspended matter in the wastewater to perform a flocculation reaction, and after the flocculation reaction, the floccules are obtained in the sedimentation area for precipitation;

[0043] S3. The sewage treated in the flocculation tank flows into the inner cylinder through the water inlet, and the untreated wastewater flows into the outer cylinder for treatment in S1, forming a synchronous treatment of wastewater in and out. The photogenerated electrons in the outer cylinder are transferred to the inner cylinder as electron donors for photoautotrophic denitrifying bacteria, and the sewage is denitrified by photoautotrophic denitrifying bacteria.

[0044] Preferably, the wastewater is preliminarily filtered before flowing into the outer cylinder.

[0045] The use of preliminary filtration helps to reduce the scattering of light caused by large suspended particles.

[0046] Preferably, the water quality parameter of the wastewater is 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 the wastewater and / or 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 as a light source, and the illumination intensity is 50-200 mW / cm 2 .

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

[0054] Preferably, the flocculant comprises polyaluminium chloride, polyacrylamide and Paenibacillus polymyxa.

[0055] More preferably, the method for preparing the flocculant comprises: mixing polyaluminium chloride, polyacrylamide and Paenibacillus polymyxa powder.

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

[0057] Preferably, step S2 further comprises: adding a chemical dephosphorization agent into the flocculation tank.

[0058] Preferably, step S3 is to form vertical internal and external flows to synchronously treat wastewater.

[0059] Preferably, the hydraulic retention time of the wastewater in the bacteria-algae 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 drum is 0.5 to 2 days.

[0062] The beneficial effects of the present invention are:

[0063] (I) The present invention provides a bacteria-algae collaborative photoelectric denitrification wastewater treatment system, comprising a bacteria-algae reactor, a flocculation tank and a photoelectric denitrification treatment device, wherein the bacteria-algae reactor uses algae photosynthesis to produce oxygen, which combined with bacteria in activated sludge can effectively remove pollutants such as organic matter, nitrogen and phosphorus in wastewater, and in addition, optical fibers and light-reflecting materials can enhance the penetration rate of light in sewage; the photoelectric denitrification treatment device is an inner and outer sleeve structure, wherein the outer sleeve is used for the reaction of wastewater with the activated product of photosensitizer, which is beneficial to the treatment of organic carbon in wastewater; the photogenerated electrons generated by the activation of the photosensitizer are transferred to the inner sleeve through the conductive material as electron donors for the photoautotrophic denitrifying bacteria, so the photoelectric denitrification treatment device has the dual functions of organic carbon decomposition and denitrification, and the inner and outer sleeve structure design has great advantages in streamlining process design and floor space. The wastewater treatment system of the present invention combines three technologies, namely, a bacteria-algae reactor, a flocculation tank and a photoelectric denitrification treatment device, to achieve comprehensive treatment of aquaculture tail water, including removal of organic matter, nitrogen and phosphorus, and suspended solids, so that the aquaculture tail water meets the discharge standard or reuse standard.

[0064] (ii) The present invention also provides a wastewater treatment method, which uses a bacteria-algae collaborative photoelectric denitrification wastewater treatment system to treat wastewater. The wastewater is treated in sequence through an inner cylinder, a bacteria-algae reactor, a flocculation tank, and an outer cylinder. The bacteria-algae reactor uses algae photosynthesis to produce oxygen. The system can operate under unpowered aeration conditions, reducing power consumption. Compared with traditional aquaculture tail water treatment processes, it saves power consumption for aeration. The photoelectric denitrification device uses photoelectric materials to provide a source of denitrification electrons, and there is no need to add additional carbon sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic diagram of the treatment process flow of the present invention;

[0066] Figure 2 Schematic diagram of the carbon removal and nitrogen removal principles in the inner and outer cylinders. DETAILED DESCRIPTION

[0067] The present invention is further described in detail below through specific examples. The raw materials used in the following examples, unless otherwise specified, can be obtained from conventional commercial sources or prepared and separated by simple synthesis; the processes used, unless otherwise specified, are conventional processes in the art.

[0068] Example 1

[0069] This embodiment provides a bacteria-algae collaborative photoelectric denitrification wastewater treatment system and a method for treating aquaculture tail water.

[0070] 1. Reference for the setting of bacteria-algae synergistic photoelectric denitrification wastewater treatment system Figure 1 , the specific settings are as follows:

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

[0072] The preparation method of the biofilm is as follows: the porous medium is immersed in a mixed solution of photoautotrophic denitrifying bacteria and cultured, so as to obtain the porous medium with the biofilm attached to the surface.

[0073] The photoautotrophic denitrifying bacteria are laboratory cultured ThiobaciUus denitrificans, Td. The culture method of Td bacteria is as follows: the culture medium is composed of a basic culture medium, glucose (5-10g), NaCl (10-20g) and elemental sulfur (2-5g); the basic culture medium is composed of a microvitamin and trace element solution; the culture conditions are as follows: temperature: 30°C, pH: 7.0, salt concentration: 1%, shaking speed: 150r / min, and culture time: 24-hours).

[0074] (2) The bacteria-algae reactor adopts a cylindrical reactor with a diameter of 0.5m, a height of 0.3m, and an effective volume of about 50L. The algae source in the bacteria-algae system is Chlorella vulgaris (purchased from the Institute of Hydrobiology, Chinese Academy of Sciences), with an inoculation amount of 10%, 5L (OD=300). The bacteria are derived from the sludge in the secondary sedimentation tank of the Chengbei Sewage Treatment Plant in Fuzhou (mainly composed of Bacteroidota, Chloroflexi, Proteobacteria, Actinobacteria and Patescibacteria), with an inoculation amount of 2%, 1L (OD=300). At the same time, nano zinc oxide (30-50nm) is added to the system as a light dispersant with a concentration of 0.2%; a tree-shaped acrylic optical fiber is used as a carrier for the attachment of bacteria and algae, and the total surface area of ​​the optical fiber is about 5m 2 .

[0075] (3) The size of the biological flocculation tank is 0.3m in diameter and 0.8m in height. About two-thirds of the upper part of the biological flocculation tank is the flocculation reaction zone, and about one-third of the lower part is the sedimentation zone.

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

[0077] 2. The specific methods for treating aquaculture tail water 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 particles and reduce the scattering effect of light. The aquaculture wastewater enters the outer cylinder from the high-level water tank through the outer cylinder water inlet, and the photosensitive substance anthraquinone-2-sodium sulfonate (AQS) is added. The concentration of AQS in the aquaculture wastewater is 2 mol / L, and the light source is a xenon lamp imitating sunlight (the light intensity is 100 mW / cm 2 ) is irradiated on the outer cylinder, and the photosensitive substance generates photoelectrons and holes under the excitation of light. The generated holes act as a strong oxidizing substance to oxidize the organic matter in the wastewater.

[0079] S2. The wastewater treated in the outer cylinder is continuously fed into the bacteria-algae reactor. The bacteria-algae reactor is irradiated with natural light. A stirring device is provided in the bacteria-algae reactor with a rotation speed of 150 rpm. The wastewater retention time is 2 days.

[0080] S3. Preparation of biological flocculant: liquid LB medium was used, and Bacillus polymyxa (1 mL bacterial solution, 200 mL culture medium) was inoculated, and the culture temperature was 30°C, and the culture was carried out on a shaker (300 rpm) at a pH of 7.0 for 3 days. The culture medium was centrifuged, the supernatant was removed, and dilute hydrochloric acid (concentration 0.5 mol / L) was added, stirred evenly, and allowed to stand for 10 minutes; then, the culture medium was centrifuged at a low speed (5000 rpm), and dried at room temperature to obtain bacterial powder A; bacterial powder A was evenly mixed with PAC (1%) and PAM (1%) according to the mass ratio to obtain a biological flocculant;

[0081] The wastewater treated by the bacteria-algae reactor flows into the flocculation tank, and the biological flocculant prepared above is introduced into the flocculation tank. The flocculant is mixed with the suspended matter in the sewage to produce flocculation reaction. After the reaction, the flocculants in the wastewater are precipitated. The addition amount of the biological flocculant is 5%, and the wastewater retention time is 1 day.

[0082] S4, the wastewater treated by the flocculation tank flows into the inner cylinder through the inner cylinder water inlet, and the inlet TN concentration is about 6.3mg / L. At the same time, the outer cylinder is undergoing the treatment of step S1, forming a vertical inner and outer flow to synchronously treat the wastewater. The photosensitive substance can generate photoelectrons after absorbing photon energy, and then transfer them to the photoautotrophic denitrifying bacteria in the inner cylinder through stainless steel for photoelectrotrophic nutrition metabolism. If nitrate is used as an electron acceptor, it can drive the microbial photoelectrotrophic denitrification reaction for denitrification, and finally remove the inorganic nitrogen in the wastewater in gaseous form. The mechanism is as follows Figure 2 shown.

[0083] Example 2

[0084] The bacteria-algae collaborative photoelectric denitrification wastewater treatment system and the method for treating aquaculture tail water in Example 2 are similar to those in Example 1, except that zinc oxide is not added as a light dispersant in the bacteria-algae reactor.

[0085] Example 3

[0086] The bacteria-algae collaborative photoelectric denitrification wastewater treatment system and the method for treating aquaculture tail water in Example 3 are similar to those in Example 1, except that: (1) the inlet 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) zinc oxide is not added as a light dispersant in the bacteria-algae reactor.

[0087] Example 4

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

[0089] Comparative Example 1

[0090] Based on the settings of Example 1, only the bacteria-algae system and the biological flocculation process are adopted, and no denitrification system is provided. Other settings are the same as those of Example 1.

[0091] Comparative Example 2

[0092] Based on the configuration of Example 1, only the biological flocculation process and the photoelectric denitrification system are adopted, and the bacteria and algae system is not provided. The other configurations are the same as those of Example 1.

[0093] Comparative Example 3

[0094] The traditional "three pools and two dams" aquaculture tailwater treatment process is adopted. The details are as follows: the size of the sedimentation tank is 0.5m, the height is 0.3m, and the effective volume is about 50L. The size of the aeration tank is 0.5m, the height is 0.3m, and the effective volume is about 50L. The size of the ecological purification pool is 1.0m, the height is 0.3m, and the effective volume is about 100L. The size of the ecological pool is 0.8m×0.5m×0.5m, with an effective volume of 200L. From top to bottom, it is filled with 15cm of fine sand, 15cm of coal slag, and 15cm of gravel, and the water surface and super height are 5cm. Water hyacinth is selected as the plant in the ecological purification pool, with a plant density of 100 plants / m2 and a hydraulic load of 0.2m / d. The influent water quality parameters are: COD concentration 29.5~36.6mg / L, average 32.4mg / L; TP concentration 0.12~0.73mg / L, average 0.53mg / L; TN concentration 5.3~13.8mg / L, average 8.3mg / L.

[0095] Water outlet detection

[0096] The effluents of 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 COD, TN, and TP removal rates of the effluent treated by the aquaculture tailwater treatment system of the embodiment of the present invention are relatively stable, and the variation range is mostly within 10%. In the pilot experiment, the aquaculture tailwater treatment system of the embodiment of the present invention operated stably for more than 180 days.

[0100] From the comparison of the data of Example 1 and Example 2, it can be seen that the addition of zinc oxide can improve the removal efficiency of organic matter.

[0101] In the comparative example, the water effluent efficiency is lower than that of the aquaculture tailwater treatment system of the embodiment of the present invention, the TN and TP removal rates are about 50%, the variation range is large, and the operation stability is poor. In the small-scale experiment, after the comparative example was operated for 55 days, the water quality of the system deteriorated and could not be operated.

[0102] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A bacteria-algae synergistic photoelectric denitrification wastewater treatment system, characterized in that: include: A bacteria-algae reactor, wherein the bacteria-algae reactor is provided with a bacteria-algae reactor water inlet and a bacteria-algae reactor water outlet, and wherein the bacteria-algae reactor is provided with a light-guiding fiber, a light-reflecting material, activated sludge and Chlorella; A flocculation tank, wherein the flocculation tank is divided into a flocculation reaction zone and a sedimentation zone, and the flocculation tank is provided with a flocculation tank water inlet and a flocculation tank water outlet, and the flocculation tank water inlet is connected to the water outlet of the bacteria-algae reactor; The photoelectric denitrification treatment device comprises an outer cylinder, which is made of a light-transmitting material, and is provided with an outer cylinder water inlet and an outer cylinder water outlet, wherein the outer cylinder water inlet is connected to a sewage inlet pipe, and the outer cylinder water outlet is connected to the water inlet of the bacteria-algae reactor; an inner cylinder is sleeved inside the outer cylinder, and the inner cylinder is made of a conductive material, and is filled with a porous medium with a biofilm attached to the surface, wherein the biofilm is formed by photoautotrophic denitrifying bacteria, and the inner cylinder is provided with an inner cylinder water inlet and an inner cylinder water outlet, and the inner cylinder water inlet is connected to the water outlet of the flocculation tank.

2. The bacteria-algae synergistic photoelectric denitrification wastewater treatment system according to claim 1 is 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 reflective material is 10-100 nm.

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

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

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 biofilm attached to the surface comprises the following steps: the porous medium is immersed in a mixed solution of photoautotrophic denitrifying bacteria for culturing, thereby obtaining the porous medium with biofilm attached to the surface.

7. A method for treating wastewater, characterized in that: The treatment method adopts the bacteria-algae synergistic photoelectric denitrification wastewater treatment system according to any one of claims 1 to 6, and comprises the following steps: S1. Wastewater flows into the outer cylinder through the water inlet of the outer cylinder, and photosensitizer is added and stirred. Under light, the photosensitizer is stimulated to generate photogenerated electrons and holes, and the wastewater and holes undergo oxidation reaction; S2, the wastewater flows into the bacteria-algae reactor and is treated under light; the wastewater treated by the bacteria-algae reactor flows into the flocculation tank, and a flocculant is added to the flocculation tank, the flocculant is mixed with the suspended matter in the wastewater to perform a flocculation reaction, and after the flocculation reaction, the floccules are obtained in the sedimentation area for precipitation; S3. The sewage treated in the flocculation tank flows into the inner cylinder through the water inlet, and the untreated wastewater flows into the outer cylinder for treatment in S1, forming a synchronous treatment of wastewater in and out. The photogenerated electrons in the outer cylinder are transferred to the inner cylinder as electron donors for photoautotrophic denitrifying bacteria, and the sewage is denitrified by photoautotrophic denitrifying bacteria.

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 polyaluminium chloride, polyacrylamide and Paenibacillus polymyxa.

10. The wastewater treatment method according to claim 7, characterized in that: The hydraulic retention time of the wastewater in the bacteria-algae reactor is 1 to 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 drum is 0.5 to 2 days.

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