A method and system for denitrification of wastewater based on a bacteria-algae symbiotic system

Abstract

The application provides a wastewater denitrification method and system based on a bacteria-algae symbiotic system, and relates to the technical field of biological denitrification of wastewater.The wastewater denitrification method based on the bacteria-algae symbiotic system comprises the steps of sludge activation treatment, preparation of the bacteria-algae symbiotic system and wastewater denitrification treatment, wherein the sludge is secondary sedimentation tank sludge of a wastewater treatment plant, and the sludge activation treatment is aeration and sedimentation treatment.The application takes green algae and the secondary sedimentation tank sludge of the wastewater treatment plant as main raw materials, prepares the bacteria-algae symbiotic system, improves the wastewater treatment efficiency through specific green algae culture and activated sludge activation process, reduces the wastewater treatment cost, realizes efficient recovery of biomass in low carbon-nitrogen ratio wastewater and resource utilization of wastewater treatment, and provides a beneficial solution for environmental protection and sustainable development.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biological nitrogen removal of sewage, and particularly relates to a sewage denitrification method and system based on a bacteria-algae symbiotic system. BACKGROUND

[0002] Municipal wastewater refers to domestic wastewater, wastewater from government offices, schools, hospitals, commercial service institutions, and various public facilities, as well as industrial wastewater and initial rainwater allowed to be discharged into the municipal wastewater collection system. These wastewaters need to be treated to remove pollutants before being safely discharged or reused. Effective treatment and management of municipal wastewater is a very important link in urban management and environmental protection.

[0003] Nitrogen in water exists in various forms, including ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen. Ammonia nitrogen is an important pollutant that causes water eutrophication and environmental pollution. Excessive ammonia nitrogen discharge can cause a large amount of dissolved oxygen consumption in water, promote the reproduction of algae and microorganisms, and eventually form black and smelly water, destroying the water ecosystem. The other two inorganic nitrates also cause direct or indirect harm to water bodies, so efficient removal of nitrogen from municipal wastewater is crucial. However, the low carbon-nitrogen ratio of municipal wastewater makes it difficult to meet the total nitrogen discharge standard after treatment.

[0004] Currently, biological treatment, physical-chemical treatment, advanced oxidation treatment, and membrane separation technology are common methods for wastewater treatment. Among them, biological treatment uses microorganisms in a biological reactor to degrade organic matter into harmless substances, purifying water quality. Common biological treatment methods include biological filter, activated sludge method, and biofilm method. Physical-chemical treatment is usually used to remove suspended solids, sediments, and heavy metals in wastewater. Advanced oxidation treatment can oxidize and degrade organic matter into harmless substances, including ozone oxidation and ultraviolet light oxidation. Membrane separation technology uses the retention effect of membranes to remove microorganisms, colloids, and particulate matter, improving water quality. These technologies can be used as pretreatment or enhanced processes to improve wastewater treatment efficiency.

[0005] However, for municipal wastewater with a low carbon-nitrogen ratio, traditional treatment methods generally have the following shortcomings: (1) Insufficient carbon source limits the process of reducing nitrate to nitrogen gas by denitrifying bacteria; (2) To improve denitrification efficiency, a large amount of oxygen and energy is consumed, increasing the treatment cost; (3) Multiple process combinations such as short-cut nitrification and denitrification, simultaneous nitrification and denitrification, and anaerobic ammonia oxidation are required to improve denitrification efficiency; (4) Excessive or insufficient carbon source addition can easily cause secondary pollution. These difficulties make denitrification of low carbon-nitrogen ratio wastewater a complex and challenging process.

[0006] Therefore, how to overcome these problems, provide a method for treating low carbon-nitrogen ratio municipal wastewater, improve the treatment efficiency of low carbon-nitrogen ratio municipal wastewater, reduce the treatment cost, realize the efficient recovery of biomass in wastewater and resource utilization of wastewater treatment is one of the technical problems to be solved at present. SUMMARY

[0007] To solve the above problems, the present application provides a wastewater denitrification method and system based on a bacteria-algae symbiotic system. The present application uses Chlorella vulgaris and sewage treatment plant secondary sedimentation tank sludge as the main raw material to prepare a bacteria-algae symbiotic system. Through specific Chlorella vulgaris culture and activated sludge activation process, the treatment efficiency of low carbon-nitrogen ratio municipal wastewater is improved, the efficient recovery of biomass in low carbon-nitrogen ratio municipal wastewater and resource utilization of wastewater treatment are realized, and a beneficial solution is provided for environmental protection and sustainable development.

[0008] The wastewater denitrification method based on the bacteria-algae symbiotic system provided by the present application comprises the following steps:

[0009] S1, inoculate the sludge into the wastewater after natural sedimentation to form a sludge mixed solution, activate the sludge mixed solution to obtain aerobic sludge;

[0010] S2, mix the Chlorella vulgaris in the logarithmic growth phase and the aerobic sludge after centrifugation in a certain proportion to obtain a bacteria-algae symbiotic system;

[0011] S3, add the bacteria-algae symbiotic system to the wastewater to realize wastewater denitrification treatment.

[0012] Further, the sludge is the secondary sedimentation tank sludge of a sewage treatment plant.

[0013] Further, the natural sedimentation time of the sludge is 30 min, and the volume ratio of the sludge to the wastewater is 1:2.

[0014] Further, the activation treatment is aeration for 6-24 h and sedimentation for 15-45 min. Preferably, the activation treatment is aeration for 12 h and sedimentation for 30 min.

[0015] Further, the Chlorella vulgaris is preserved in the General Microbiological Center of the China Microbial Culture Collection Committee, the preservation number is CGMCC No. 41189, the preservation address is No. 3, Beichen West Road, Chaoyang District, Beijing, the preservation date is April 3, 2024, and the classification name is Cladophora aegagrophila.

[0016] Further, the culture method of the Chlorella vulgaris is as follows:

[0017] The Chlorella vulgaris culture medium is sterilized at high temperature, and the Chlorella vulgaris is inoculated and cultured to the logarithmic growth phase.

[0018] Further, the Chlorella vulgaris culture medium is BG11 culture medium.

[0019] Further, the high-temperature sterilization temperature is 120 DEG C, and the high-temperature sterilization time is 20 min.

[0020] Further, the culture temperature is 25 DEG C to 30 DEG C, the culture time is 15 to 20 days, the light intensity is 5000 to 8000 lux, and the light-dark ratio is 12 h:12 h. Preferably, the culture temperature is 25 DEG C, the culture time is 15 days, and the light intensity is 5000 lux.

[0021] Further, the centrifugation speed is 5000 to 8000 r / min, the centrifugation time is 5 to 15 min, and the centrifugation times is 1 to 3 times. Preferably, the centrifugation speed is 6000 r / min, the centrifugation time is 10 min, and the centrifugation times is 2 times.

[0022] Further, the weight ratio of the Chlorella vulgaris and the activated sludge is 1:(1 to 10) on a dry weight basis. Preferably, the weight ratio of the Chlorella vulgaris and the activated sludge is 1:(1 to 3) on a dry weight basis. More preferably, the weight ratio of the Chlorella vulgaris and the activated sludge is 1:1 on a dry weight basis.

[0023] Further, the carbon-nitrogen ratio of the sewage is 1 to 5.

[0024] Further, the weight-volume ratio of the Chlorella vulgaris and the activated sludge to the sewage is 2 g / L on a dry weight basis.

[0025] Further, the sewage denitrification treatment is performed under the conditions of a temperature of 25 DEG C to 30 DEG C, a light intensity of 5000 to 8000 lux, a light-dark ratio of 12 h:12 h, and a treatment time of 3 to 8 days. Preferably, the sewage denitrification treatment is performed under the conditions of a temperature of 25 DEG C, a light intensity of 5000 lux, a light-dark ratio of 12 h:12 h, and a treatment time of 5 days.

[0026] The application also provides a sewage denitrification system based on a bacteria-algae symbiotic system, which comprises a real-time control system, an inlet water system, an aeration, illumination, and sedimentation system, and an outlet water system.

[0027] The operation method of the sewage denitrification system is as follows:

[0028] The real-time control system starts the inlet water pump, and the untreated sewage in the inlet water tank is transported to the reactor inlet through the inlet water pipe. When the reactor inlet water volume reaches the working volume, the real-time control system stops the inlet water pump, and the inlet water stage ends.

[0029] The real-time control system controls to open the aeration device and the lamp tube, and after ammonia nitrogen is completely removed in the reactor in the aerobic and photosynthesis stages, the real-time control system controls to close the aeration device and the lamp tube, and after the aerobic-photosynthesis process in the reactor ends, precipitation occurs;

[0030] The real-time control system opens the water outlet pump, and the treated water is transported to the water outlet tank through the water outlet pipe, and when the water discharge reaches 50% of the working volume of the reactor, the real-time control system closes the water outlet pump, and the water outlet stage ends;

[0031] According to actual needs, the system automatically enters the next cycle, and repeats water inlet, aeration and illumination, precipitation and water outlet or stops running.

[0032] Compared with the prior art, the beneficial technical effects of the present application are:

[0033] The present application utilizes the synergistic effect of chlorella and activated sludge, avoids the investment and use of a large amount of aeration equipment, saves energy consumption, improves the nitrogen removal efficiency in low carbon-nitrogen ratio municipal wastewater and reduces the removal cost.

[0034] The present application finds a high-efficiency denitrification microbial system by controlling the ratio of chlorella and activated sludge, improves the efficiency of low carbon-nitrogen ratio municipal wastewater treatment, promotes chlorella enrichment, realizes efficient recovery of biomass in low carbon-nitrogen ratio municipal wastewater and resource utilization of wastewater treatment, and provides a beneficial solution for environmental protection and sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0035] The present application will be further described below in combination with the description of the accompanying drawings.

[0036] Figure 1 It is a structural schematic diagram of the sewage denitrification system of the present application;

[0037] Figure 2 It is a diagram of the change of chlorophyll a concentration in microalgae in the different bacteria-algae ratio bacteria-algae symbiotic system;

[0038] Figure 3 It is a diagram of the change of ammonia nitrogen with time in the different bacteria-algae ratio bacteria-algae symbiotic system in the stable period;

[0039] Figure 4 It is a column chart of the total inorganic nitrogen concentration of the effluent of the sewage treated by the different bacteria-algae ratio bacteria-algae symbiotic system. DETAILED DESCRIPTION

[0040] The present application provides a sewage denitrification method based on a bacteria-algae symbiotic system, comprising the following steps:

[0041] S1, inoculate the sludge after natural sedimentation into sewage to form a sludge mixed solution, activate the sludge mixed solution to obtain aerobic sludge;

[0042] S2, centrifuging the green algae and the aerobic sludge in the logarithmic growth phase respectively, mixing them in proportion, and then adding water to obtain a bacteria-algae symbiotic system;

[0043] S3, adding the bacteria-algae symbiotic system to sewage to achieve sewage denitrification treatment.

[0044] In one embodiment, the sludge is secondary sedimentation tank sludge from a sewage treatment plant.

[0045] Generally in sewage treatment, primary sedimentation tank sludge adopts the principle of free sedimentation to remove settleable and floating substances, reducing the load of subsequent treatment facilities. Unlike the primary sedimentation tank, the secondary sedimentation tank utilizes the principle of laminar settling and compression sedimentation, and the flocculated suspended solids form a layered material, which is in the form of bulk sedimentation, forming a relatively obvious solid-liquid interface to clarify the mixed liquid and recover and concentrate the activated sludge, ensuring the water quality of the effluent and the concentration of the return sludge. The final activated sludge has the characteristics of high concentration (2000-4000 mg / L), flocculation, light quality, and slow settling velocity.

[0046] In the present application, the secondary sedimentation tank sludge contains a large number of active microorganisms, which have been activated during the sewage treatment process and can efficiently decompose organic matter and transform nitrogen. Secondly, the secondary sedimentation tank sludge contains rich nutritional ingredients, which can promote the growth of algae and microorganisms in the bacteria-algae symbiotic system, thereby improving the denitrification efficiency. In addition, the microorganisms in the secondary sedimentation tank sludge have adapted to various pollutants and operating conditions in the sewage treatment environment, have strong environmental adaptability, and can quickly play a role in denitrification treatment. Furthermore, the secondary sedimentation tank sludge is a byproduct of the sewage treatment process, which is widely available and easy to obtain, can reduce costs and operational difficulties. Finally, using secondary sedimentation tank sludge for denitrification treatment helps to recycle resources and reduces the pressure of sludge treatment and disposal, which has environmental and economic benefits. Therefore, the present application uses the rich microbial resources and nutritional ingredients of the secondary sedimentation tank sludge to improve the efficiency and effectiveness of denitrification treatment, and is also an environmentally friendly measure of resource recycling.

[0047] In one embodiment, the sludge natural sedimentation time is 30 min, and the volume ratio of the sludge to sewage is 1:2.

[0048] In one embodiment, the activation treatment is aeration for 6-24 h and sedimentation for 15-45 min.

[0049] In one embodiment, the activation treatment is aeration for 12 h and sedimentation for 30 min.

[0050] In one embodiment, the Chlorella vulgaris is preserved in the China General Microbiological Culture Collection Center, with the preservation number CGMCC No. 41189.

[0051] Chlorella vulgaris Cladophora aegagrophila ) and Chlorella pyrenoidosa Chlorella ) are both green algae, but they have significant differences in morphology, ecological habits, and applications. Both of them live in freshwater environments and produce organic matter through photosynthesis. Chlorella vulgaris is single-cell spherical, near-spherical, oval, and heart-shaped. It is commonly found in flowing water bodies and attached to rocks. Chlorella pyrenoidosa belongs to the Chlorellales and is a single-cell alga. The cell is spherical or oval and suspended in water, with a faster growth rate. Chlorella vulgaris grows relatively slowly and adapts to colder water bodies, while Chlorella pyrenoidosa is highly adaptable and grows rapidly in warm conditions.

[0052] Currently, Chlorella pyrenoidosa and activated sludge are commonly used together for wastewater treatment because the bacteria-algae system prepared by Chlorella pyrenoidosa and activated sludge can quickly start up. However, Chlorella pyrenoidosa is less resistant and stable than Chlorella vulgaris, and is not suitable for projects that require long-term stable operation. Therefore, in the case of long-term stable operation, Chlorella vulgaris is more suitable for preparing a bacteria-algae system.

[0053] In one embodiment, the culture method of Chlorella vulgaris is as follows:

[0054] The Chlorella vulgaris culture medium is autoclaved at high temperature, and Chlorella vulgaris is inoculated and cultured to the logarithmic growth phase of Chlorella vulgaris.

[0055] In one embodiment, the Chlorella vulgaris culture medium is BG11 medium.

[0056] In one embodiment, the high-temperature sterilization temperature is 120°C, and the high-temperature sterilization time is 20 min.

[0057] In one embodiment, the culture temperature is 25°C-30°C, the culture time is 15-20 d, the light intensity is 5000-8000 lux, and the light-dark ratio is 12 h:12 h.

[0058] In one embodiment, the culture temperature is 25°C, the culture time is 15 d, and the light intensity is 5000 lux.

[0059] In one embodiment, the centrifugation speed is 5000-8000 r / min, the centrifugation time is 5-15 min, and the centrifugation number is 1-3 times.

[0060] In one embodiment, the centrifugation speed is 6000 r / min, the centrifugation time is 10 min, and the centrifugation number is 2 times.

[0061] In one embodiment, the weight ratio of Chlorella vulgaris to activated sludge is 1:(1-10) by dry weight.

[0062] In one embodiment, the weight ratio of the Chlorella vulgaris and the activated sludge is 1:(1~3) by dry weight.

[0063] In one embodiment, the weight ratio of the Chlorella vulgaris and the activated sludge is 1:1 by dry weight.

[0064] In one embodiment, the carbon-nitrogen ratio of the sewage is 1~5.

[0065] In one embodiment, the weight-volume ratio of the Chlorella vulgaris and the activated sludge to the sewage is 2 g / L by dry weight.

[0066] Compared with Chlorella, the preparation of the bacteria-algae system using Chlorella vulgaris and the activated sludge needs to overcome many difficulties, for example, the slow growth rate of Chlorella vulgaris, the thick cell structure, the high requirement for environmental conditions, and the difficulty in ensuring the stability of the system. Therefore, the weight ratio of the Chlorella vulgaris and the activated sludge is strictly controlled in the present application. At the same time, the culture mode of the Chlorella vulgaris is strictly controlled. In combination with the activation of the activated sludge, the problems existing in the preparation of the bacteria-algae system using Chlorella vulgaris are overcome, and finally the effective application of the Chlorella vulgaris and the activated sludge system in the fields of sewage treatment and ecological restoration is realized.

[0067] In one embodiment, the sewage denitrification treatment is carried out under the conditions of a temperature of 25℃~30℃, a light intensity of 5000~8000 lux, a light-dark ratio of 12 h:12 h, and a treatment time of 3~8 d.

[0068] In one embodiment, the sewage denitrification treatment is carried out under the conditions of a temperature of 25℃, a light intensity of 5000 lux, a light-dark ratio of 12 h:12 h, and a treatment time of 5 d.

[0069] The present application also provides a sewage denitrification system based on a bacteria-algae symbiotic system, which comprises a real-time control system, a water inlet system, an aeration, illumination, and sedimentation system, and a water outlet system.

[0070] The operation method of the sewage denitrification system is as follows:

[0071] The real-time control system starts the water inlet pump, and the sewage to be treated in the water inlet tank is transported to the reactor inlet through the water inlet pipe. When the water inlet amount of the reactor reaches the working volume, the real-time control system stops the water inlet pump, and the water inlet stage ends.

[0072] The real-time control system controls the start of the aeration device and the lamp, and after the complete removal of ammonia nitrogen in the aerobic and photosynthetic stages in the reactor, the real-time control system stops the aeration device and the lamp, and the aerobic-photosynthetic process in the reactor ends.

[0073] The real-time control system starts the effluent pump, and the treated water is transported to the effluent tank through the effluent pipe via the effluent outlet. When the volume of the effluent reaches 50% of the working volume of the reactor, the real-time control system stops the effluent pump, and the effluent stage ends.

[0074] According to the actual demand, the system automatically enters the next cycle, and repeats the water inlet, aeration and light, sedimentation, effluent or stops running.

[0075] The technical solutions provided by the present application are further described below in combination with examples.

[0076] Example 1: Sewage denitrification method based on a bacteria-algae symbiotic system

[0077] (1) Cultivation of Chlorella vulgaris:

[0078] The Chlorella vulgaris was centrifuged three times with deionized water at a speed of 6000 r / min for 15 min each time. After centrifugation, the supernatant was discarded, and the enriched Chlorella vulgaris was obtained.

[0079] BG11 medium with a concentration of 1.7 g / L was prepared, sterilized at 120℃ for 20 min, and then cooled down for standby. The inoculation operation was performed on a clean bench, and the inoculation amount of the enriched Chlorella vulgaris was 6.67 g / L.

[0080] After inoculation, the logarithmic phase Chlorella vulgaris was obtained after being cultured at a temperature of 25℃, an illumination intensity of 5000 lux, and a light-dark ratio of 12 h:12 h for 15 d, and was used to prepare a bacteria-algae symbiotic system.

[0081] (2) Activation of activated sludge:

[0082] The sludge in the secondary sedimentation tank of a sewage treatment plant was collected, and after natural sedimentation for 30 min, the sludge was inoculated into the sewage at a volume ratio of 1:2 to form a sludge mixed liquid. The sludge mixed liquid was aerated for 12 h in the dark and then settled for 30 min to complete the activation.

[0083] Preparation of a bacteria-algae symbiotic system:

[0084] The logarithmic phase Chlorella vulgaris and the activated sludge were mixed in a dry weight ratio of 1:1, 1:3, 1:5, and 1:10 to obtain a bacteria-algae symbiotic system.

[0085] The dry weight was determined as follows: The weight of the dried filter paper was measured, and the centrifuged Chlorella vulgaris and activated sludge were dropped onto the dried filter paper, which was then placed in a 105℃ oven for 24 h. After taking out, the weight was measured, and the dry weight of the Chlorella vulgaris and the activated sludge was obtained by the difference method.

[0086] The mixed bacteria-algae symbiotic system with different bacterial-algae ratios (i.e., the dry weight ratio of activated sludge and Chlorella vulgaris) was mixed with the wastewater to be treated at an initial dry weight to water volume ratio of 2 g / L. The mixture was then placed under the conditions of 25℃, 5000 lux light intensity, and 12 h:12 h light-dark ratio for 5 days of wastewater treatment, with samples taken and measured every 12 hours.

[0087] The wastewater to be treated has a carbon-to-nitrogen ratio of 5, a COD concentration of 275 mg / L, and an ammonia nitrogen concentration of 55 mg / L; it includes 352.56 mg / L NaAc, 90 mg / L MgSO4, 14 mg / L CaCl2, 211.54 mg / L NH4Cl, 46 mg / L Na2HPO4, 10 mg / L yeast extract, and 1 mL / L trace elements; the trace elements include 120 mg / L ZnSO4·7H2O, 150 mg / L H3BO3, 30 mg / L CuSO4·5H2O, 120 mg / L MnCl2·4H2O, 180 mg / L KI, 60 mg / L Na2MoO4, 10000 mg / L EDTA, 1540 mg / L FeSO4·7H2O, and 150 mg / L CoCl2·6H2O.

[0088] This invention uses changes in chlorophyll a to represent changes in Chlorella vulgaris. Figure 2 The graph shows the changes in chlorophyll a concentration in microalgae within symbiotic systems with different bacterial-algae ratios. It can be seen that the microalgae enrichment is highest in the system with a bacterial-algae ratio of 1:1. The system enters a stable period after 20 days of operation, and the average concentration of chlorophyll a during the stable period (20-60 days) is 11 mg / L.

[0089] Figure 3 This graph shows the change of ammonia nitrogen over time in algal symbiotic systems with different bacteria-to-algae ratios during the stable phase. Figure 3 It can be observed that the system with a bacteria-to-algae ratio of 1:1 has the highest ammonia nitrogen removal efficiency compared to the other three groups, achieving a 100% ammonia nitrogen removal rate.

[0090] Figure 4 A bar chart showing the total inorganic nitrogen concentration in the effluent from wastewater treated by algal symbiotic systems with different bacteria-to-algae ratios. Figure 4 As can be seen from this, the treated water meets the Class A discharge standard for wastewater in the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB 18918-2002)".

[0091] Example 2: Wastewater denitrification system based on a bacterial-algae symbiotic system:

[0092] (1) The fungus-alga symbiotic system with a fungus-alga ratio of 1:1 in Example 1 was added to the reactor, and the initial dosage was 2 g / L of the initial dry weight to the volume of the water;

[0093] (2) The water inlet pump was started by the real-time control system to transport the synthetic sewage in the water inlet tank to the reactor. When the water inlet amount of the reactor reached 100% of the working volume of the reactor, the water inlet control system was closed, and the water inlet was completed.

[0094] (3) After the water inlet was completed, the anaerobic stage reaction was completed after 4 h (including the water inlet time), the aeration device and the lamp were started synchronously by the real-time control system, and the aerobic-photosynthetic stage reaction was completed after 12 h. The aeration device and the lamp were closed synchronously by the real-time control system, and the sedimentation was 4 h.

[0095] (4) After the sedimentation was completed, the water outlet pump was started by the real-time control system to transport the treated sewage in the reactor from the water outlet to the water outlet tank through the water outlet pipe. When the drainage amount reached 50% of the working volume of the reactor, the water outlet pump was automatically closed, the drainage stage was completed, and the sample was taken for determination.

[0096] (5) The system automatically entered the next cycle, and steps (2) to (4) were repeated.

[0097] After the system was operated for 15 d, the ammonia nitrogen concentration in the reactor tended to be stable, and the average effluent concentration was 5 mg / L. Then, the reactor had an ammonia nitrogen concentration of 0 mg / L (below the detection limit, not detected) for 55 d of continuous operation, the average removal rate of ammonia nitrogen was 100%, the average removal rate of total nitrogen was 87.96%, and the treated effluent met the first level A discharge standard of the "Urban Sewage Treatment Plant Pollutant Discharge Standard (GB 18918-2002)". The system entered the stable period when it was operated for 15 d, and the stable period lasted for 55 d (15-70 d).

[0098] Comparative Example 1

[0099] The same as Example 2, except that the Chlorella in the fungus-alga symbiotic system was replaced with an equal amount of Chlorella vulgaris.

[0100] After the system was stably operated for 55 d, the average removal rate of ammonia nitrogen was 97%, and the average removal rate of total nitrogen was 87.6%.

[0101] Comparative Example 2

[0102] The same as Example 2, except that the activated sludge was not activated.

[0103] The start-up time is long, and the system enters the stable period on the 24th day of operation. The time to enter the stable period is 160% of that of Example 2. After the system stably operates for 55 days, the average removal rate of ammonia nitrogen is 78.27%, and the average removal rate of total nitrogen is 72.68%.

[0104] The principles and implementation manners of the present application are described herein by using specific examples, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present description should not be understood as a limitation of the present application.

Claims

1. A wastewater denitrification method based on a bacterial-algae symbiotic system, characterized in that, Includes the following steps: S1. After the sludge settles naturally, it is inoculated into the sewage to form a sludge mixture. The sludge mixture is then activated to obtain aerobic sludge. S2. After centrifuging the logarithmic growth stage of Chlorella and the aerobic sludge separately, they are mixed in proportion to obtain a bacterial-algae symbiotic system. S3. Add the aforementioned bacteria-algae symbiotic system to the wastewater to achieve wastewater denitrification treatment; The sludge is sludge from the secondary sedimentation tank of a sewage treatment plant. The activation treatment consists of aeration for 6-24 h and sedimentation for 15-45 min. The *Cladophora aegagrophila* species is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 41189, located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, on April 3, 2024, and is classified as *Cladophora aegagrophila*. The method for culturing Chlorella is as follows: sterilize the Chlorella culture medium at high temperature, inoculate Chlorella, and then culture until the logarithmic growth phase of Chlorella; On a dry weight basis, the weight ratio of the green algae to the aerobic sludge is 1:1; The carbon-to-nitrogen ratio of the wastewater is 1 to 5.

2. The wastewater denitrification method based on a bacterial-algae symbiotic system according to claim 1, characterized in that, The activation treatment consisted of aeration for 12 hours and sedimentation for 30 minutes.

3. The wastewater denitrification method based on a bacterial-algae symbiotic system according to claim 1, characterized in that, The culture temperature of the *Chlorella vulgaris* is 25℃~30℃, the culture time is 15~20 days, the light intensity for the culture is 5000~8000 lux, and the light-dark ratio is 12 h:12 h.

4. The wastewater denitrification method based on a bacterial-algae symbiotic system according to claim 1, characterized in that, On a dry weight basis, the ratio of the total weight of the green algae and aerobic sludge to the volume of the wastewater is 2 g / L.

5. The wastewater denitrification method based on a bacterial-algae symbiotic system according to claim 1, characterized in that, The wastewater denitrification treatment is carried out at a temperature of 25℃~30℃, a light intensity of 5000~8000 lux, and a light-dark ratio of 12 h:12 h, for a treatment time of 3~8 days.

Images