Low-energy-consumption photocatalysis-bacterium-alga symbiosis integrated biogas slurry treatment device and method

Abstract

The application discloses a kind of low-energy consumption photocatalysis-bacteria-algae symbiosis integrated biogas liquid treatment device and method, belong to sewage treatment technical field.The device includes sequence intermittent activated sludge reactor and the photobioreactor in its inner layer;The photobioreactor that can rotate along shaft is arranged in the inner chamber of sequence intermittent activated sludge reactor;Annular region between sequence intermittent activated sludge reactor and photobioreactor is as first reaction zone, the inner chamber of photobioreactor is as second reaction zone, and first reaction zone is communicated with second reaction zone by the passage with water inlet solenoid valve;Bacteria-algae are built-in in first reaction zone, and the microporous aeration disc that can be aerated upwards is arranged in bottom;Second reaction zone is communicated with the drainage port opened in the side wall of sequence intermittent activated sludge reactor by pipeline.The application has the characteristics such as high microalgae proportion, low sludge light shielding, high biogas liquid treatment efficiency, low energy consumption, low carbon emission, strong impact resistance etc..

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a low-energy-consumption photocatalysis-bacteria-algae symbiosis integrated biogas slurry treatment device and method. BACKGROUND

[0002] The conventional SBR reactor sewage treatment method can be divided into physical methods (adsorption method, ionizing radiation method, etc.), chemical methods (catalysis method, oxidation method, etc.), but in actual sewage treatment, the physical method and the chemical method have high treatment cost, are easy to cause secondary pollution, and are difficult to achieve standard treatment of high ammonia-nitrogen biogas slurry. In the process of removing pollutants, a large amount of greenhouse gases CO2, CH4 and N2O is easily discharged, and the electric energy consumption in the aeration and stirring process also indirectly produces carbon emissions, which aggravates the greenhouse effect. Compared with the conventional activated sludge method, the photocatalysis-bacteria-algae symbiotic system sewage treatment process can meet the sustainability requirements of reducing energy consumption and recycling biomass. Therefore, it is of great significance to develop a method with low cost, low energy consumption, no secondary pollution and high removal rate of high ammonia-nitrogen biogas slurry.

[0003] Biological enhancement treatment, as an environmentally friendly, low-cost and effective wastewater treatment method, has obvious advantages in pollution control. Studies have found that due to strong mechanical aeration, the gas flow in the influent and aeration stages of the traditional SBR is the highest in the entire SBR process, and the carbon dioxide emission is the largest. The greenhouse gas emission of SBR is usually higher than that of AAO, and the aeration part accounts for a large proportion of the greenhouse gas emission in AAO and SBR sewage treatment plants. At present, the technology of using microalgae and bacteria to form a bacteria-algae symbiotic system to treat sewage has become the main direction. Bacteria-algae symbiosis is to utilize the mutualistic symbiotic relationship between bacteria and microalgae. However, in the existing technology, the colority of the biogas slurry is high, which leads to insufficient light for the bacteria-algae symbiotic system in the equipment, and thus the photosynthesis is poor, and the nitrogen and phosphorus elements in the biogas slurry cannot be efficiently utilized. In addition, the dissolved oxygen in the water body is insufficient, which cannot provide sufficient light energy and oxygen for the bacteria-algae symbiotic system, and an aeration device is also needed, which increases the energy consumption pressure of sewage treatment and the cost, and causes poor sewage treatment effect of the bacteria-algae symbiotic system, incomplete purification, and even due to insufficient dissolved oxygen, bacteria will undergo anaerobic decomposition, causing continuous water pollution. That is, the current bacteria-algae symbiotic system has low microalgae proportion, serious loss, and the light-shielding property of sludge affects the biomass accumulation of microalgae, which limits the popularization and application of the bacteria-algae symbiotic sewage treatment system in the field of sewage treatment.

[0004] In view of this phenomenon, the present application improves the traditional SBR process, and selects biological and chemical treatment devices for deep treatment of aquaculture biogas liquid. In the early 1970s, the photocatalytic method was widely used due to its low cost, low energy consumption, high efficiency, simple assembly and low price, but it is important to select a suitable photocatalyst. Compared with the traditional bacteria-algae symbiotic system, the photocatalytic coupling bacteria-algae symbiotic system has the characteristics of high microalgae proportion, low sludge light shielding, high biogas liquid treatment efficiency, low energy consumption, low carbon emission and strong impact resistance, which lays a good foundation for promoting the development of sewage treatment process to high efficiency, green and low consumption, and realizes the "energy neutralization" and "carbon neutralization" of sewage treatment. SUMMARY

[0005] The existing bacteria-algae symbiotic system has problems such as insufficient bacteria-algae illumination, insufficient dissolved oxygen, high energy consumption, and is not conducive to carbon emission reduction. The purpose of the present application is to overcome the defects in the prior art and provide a low-energy photocatalytic-bacteria-algae symbiotic integrated biogas liquid treatment device and method.

[0006] The specific technical solutions adopted by the present application are as follows:

[0007] In a first aspect, the present application provides a low-energy photocatalytic-bacteria-algae symbiotic integrated biogas liquid treatment device, comprising a sequencing batch reactor and a photobioreactor located in the inner layer thereof.

[0008] The lower part and the upper part of the side wall of the sequencing batch reactor are respectively provided with a water inlet and an overflow port communicating with the inner cavity, and the inner cavity is provided with a photobioreactor capable of rotating along the shaft; the photobioreactor comprises a heat dissipation cylinder and an illumination column coaxially arranged from outside to inside, and the outer wall of the heat dissipation cylinder is circumferentially provided with a plurality of stirring paddles; the annular region between the sequencing batch reactor and the photobioreactor serves as a first reaction zone, the inner cavity of the photobioreactor serves as a second reaction zone, and the first reaction zone is communicated with the second reaction zone through a passage provided with a water inlet electromagnetic valve; the first reaction zone is internally provided with bacteria-algae, and the bottom is provided with a microporous aeration disc capable of upward aeration; the second reaction zone is communicated with a drainage port provided in the side wall of the sequencing batch reactor through a pipeline.

[0009] As a preferred, the microporous aeration disc is circumscribed by an aeration pump, and a gas flow meter is arranged on the gas pipeline of the aeration pump.

[0010] As a preferred, a plurality of sampling ports are arranged on the sequencing batch reactor along the length direction at intervals, and a valve is arranged on each sampling port.

[0011] As a preferred, the water inlet is connected with a water inlet bucket through a water inlet pipe provided with a peristaltic pump and a rotor flow meter.

[0012] Further, the rotor flow meter is connected with a first timer, and the first timer can control the operation of the peristaltic pump according to the data of the rotor flow meter.

[0013] As preferred, the drain port is connected with the water bucket through a drain pipe provided with a second timer and a drain electromagnetic valve.

[0014] As preferred, the first reaction zone is further provided with a temperature probe, a pH probe and a DO probe for measuring water quality indexes.

[0015] Further, the temperature probe, the pH probe and the DO probe are all connected with a PLC automatic control device, and the PLC automatic control device can feedback control the operation of the valves and the microporous aeration disc and the heat dissipation cylinder according to the results obtained by the temperature probe, the pH probe and the DO probe.

[0016] As preferred, an external power supply for supplying power to the electric devices is further included.

[0017] In the second aspect, the present application provides a biogas slurry treatment method using the low-energy-consumption photocatalysis-bacteria-algae symbiosis integrated biogas slurry treatment device according to any one of the first aspect, and the method is specifically as follows:

[0018] The biogas slurry to be treated is pretreated and then used as the bacteria-algae water, which enters the first reaction zone of the sequencing batch activated sludge reactor; the sequencing batch activated sludge reactor is intermittently operated in the mode of water inflow-oxygenation-deposition-drainage-rest, and at the same time, the light column is turned on to preliminarily purify the biogas slurry; in the preliminary purification process, the aerobic bacteria degrade the carbon-containing organic matter into carbon dioxide and water, and at the same time, the nitrogen-containing organic matter is ammoniated and then nitrified to generate ammonia nitrogen, nitrite and nitrate, and the phosphorus-containing organic matter is finally degraded into orthophosphate; the energy generated by the oxidation degradation provides energy for the metabolic activity of the bacteria, and the carbon dioxide generated by the bacterial degradation of the organic matter becomes the main carbon source of the algae to promote the photosynthesis of the algae; in the process of the metabolism of the algae, the substances generated in the bacterial metabolism are absorbed and converted into the cell substances of the algae, the oxygen released by the photosynthesis of the algae increases the dissolved oxygen in the water, promotes the metabolic activity of the aerobic bacteria and enables the aerobic bacteria to maintain normal life activities; then, after the deposition stage, the bacteria-algae are deposited in the lower part of the first reaction zone;

[0019] The biogas slurry preliminarily purified in the first reaction zone is controlled by the water inlet electromagnetic valve, and the supernatant enters the second reaction zone, and meanwhile, the C3N4 photocatalytic material is added into the second reaction zone, the light column is controlled to alternately operate in light and dark, so that the bacteria and algae simultaneously perform the photocatalytic reaction in the light reaction stage, and the dark reaction stage is used as the photocatalytic standing process; in the photocatalytic reaction, the photocatalytic material acts as a light trapping agent to assist the bacteria and algae to treat the wastewater, meanwhile, the photocatalytic function of the photocatalytic material activates the algae spores to make them rapidly split in the water, promote the cell growth, and make the algae in-situ enrichment and adhere to the outer surface of the bacteria group and the reactor wall, and naturally form the algae immobilization, in addition, the photocatalytic material can also assist the fixation of carbon dioxide; the biogas slurry treated by the second reaction zone is discharged from the treatment device.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application benefits from the combination of the photocatalysis and the bacteria-algae symbiotic device, so that the light column can contact the biogas slurry in the first reaction zone and the second reaction zone in a larger area, improve the removal efficiency of the organic matter in the biogas slurry, reduce a large amount of energy consumption, and utilize the bacteria-algae symbiotic mechanism, the oxygen generated by the photosynthesis of the microalgae is used as the respiratory degradation of the aerobic bacteria to degrade the water pollutants, meanwhile, the carbon dioxide produced by the bacterial respiration can also be used for the photosynthesis of the microalgae, in terms of material metabolism, under the eutrophic state, the microalgae synthesize their own materials by absorbing and utilizing the nitrogen and phosphorus elements through the photosynthesis, and release organic matter to the environment, the decomposition of the microalgae cells is also an important source of dissolved organic carbon, and the bacteria can utilize the oxygen to decompose the secretions and the dead algal cells of the microalgae, and the decomposition products are in turn absorbed and utilized by the microalgae. The light column in the photobioreactor is provided with a heat dissipation cylinder on the side wall, which is beneficial to reduce the heat generated in the photocatalysis process, maintain the bacteria and algae in the suitable temperature operation, and add stirring paddles on the outer wall for stirring, which is more conducive to the uniform and efficient photocatalytic reaction, the algae absorb the CO2 generated by the microbial decomposition of the organic matter, thereby reducing the emission of greenhouse gases in the reaction process, and having the environmental protection benefit.

[0022] The present application benefits from the setting of the PLC (timer, electromagnetic valve), so that the water discharge time of the first reactor can be controlled in real time, the water is controlled to be discharged at a time, and the bacteria and algae can simultaneously perform the photocatalytic reaction in the light reaction stage, and the dark reaction stage can be used as the photocatalytic standing process, so that the biogas slurry in the device is deeply treated, the emission is avoided to be over standard, and the energy consumption is saved. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to explain the present application, and for those skilled in the art, other drawings can be obtained without creative work on the premise of the provided drawings.

[0024] Figure 1 It is a schematic diagram of the overall structure of the low-energy-consumption photocatalysis-bacteria-algae symbiosis integrated biogas slurry treatment device of the present application.

[0025] Figure 2 It is a schematic diagram of the structure of the sequence batch activated sludge reactor (SBR reactor) of the present application.

[0026] Figure 3 It is a schematic diagram of the overall structure of the photobioreactor of the present application.

[0027] Figure 4 It is a schematic diagram of the growth conditions of bacteria and algae with different inoculation concentrations.

[0028] Figure 5 It is a schematic diagram of the removal changes of water quality indicators. (a) is a schematic diagram of ammonia nitrogen concentration and removal rate, (b) is a schematic diagram of COD concentration and removal rate, (c) is a schematic diagram of phosphate concentration and removal rate, (d) is a schematic diagram of nitrite nitrogen concentration change, and (e) is a schematic diagram of pH value change during operation.

[0029] In the figure, the reference numerals are: 1, water inlet bucket; 2, peristaltic pump; 3, external power supply; 4, first timer; 5, PLC automatic control device; 6, aeration pump; 7, gas flow meter; 8, microporous aeration disc; 9, pH probe; 10, water inlet; 11, stirring paddle; 12, heat dissipation cylinder; 13, light column; 14, overflow; 15, water inlet electromagnetic valve; 16, water outlet; 17, second timer; 18, DO probe; 19, sampling port; 20, drainage electromagnetic valve; 21, water outlet bucket. DETAILED DESCRIPTION

[0030] The present application will be further described and explained with the accompanying drawings and specific embodiments. The technical features of each embodiment in the present application can be combined accordingly without conflict.

[0031] For example, Figure 1As shown, this invention provides a low-energy photocatalytic-algal symbiosis integrated biogas slurry treatment device, which mainly includes a sequential intermittent activated sludge reactor (SBR) and a photobioreactor. Both the SBR and photobioreactor are cylindrical structures, with the SBR coaxially mounted on the outside of the photobioreactor. A light column is installed inside the photobioreactor, ensuring that the lighting conditions meet both the photosynthetic requirements of the bacteria and algae and the photocatalytic requirements. This achieves carbon reduction with low energy consumption and further treats the biogas slurry, improving the utilization efficiency of nutrients in the slurry. This invention allows for more uniform regulation of bacteria and algae growth and photocatalysis through individual lamps (i.e., light columns), making it easier to control the reaction operation, reducing energy consumption, and facilitating biogas slurry treatment.

[0032] The specific structures and connection methods of sequential intermittent activated sludge reactors and photobioreactors are as follows:

[0033] In this invention, such as Figure 2 As shown, the sequential intermittent activated sludge reactor located in the outer layer has a cylindrical inner cavity, with an inlet 10 and an overflow 14 respectively opened on the side wall. Both the inlet 10 and the overflow 14 are connected to the inner cavity, and the height of the inlet 10 is lower than the height of the overflow 14.

[0034] In a preferred embodiment of the present invention, the sequential intermittent activated sludge reactor can be made of transparent acrylic sheet, with multiple sampling ports 19 spaced apart along its length (i.e., height). Each sampling port 19 is equipped with a valve, allowing for sampling as needed during operation to monitor the sludge treatment status. The inlet 10 can be connected to the inlet tank 1 via an inlet pipe, which is equipped with a peristaltic pump 2 and a rotor flowmeter. The rotor flowmeter can be externally connected to a first timer 4. In actual use, the first timer 4 controls the operation of the peristaltic pump 2 based on the received data from the rotor flowmeter. The outlet 16 can be connected to the outlet tank 21 via a drain pipe, which is equipped with a second timer 17 and a drain solenoid valve 20.

[0035] In this invention, a photobioreactor capable of rotating along an axis is provided within the inner cavity of the sequential intermittent activated sludge reactor. The sequential intermittent activated sludge reactor and the photobioreactor are coaxially arranged and spaced apart. Figure 3As shown, the photobioreactor comprises a heat dissipation cylinder 12 and a light column 13 coaxially arranged from outside to inside, and the outer wall of the heat dissipation cylinder 12 is circumferentially provided with a plurality of stirring paddles 11. The annular area between the sequencing batch reactor and the photobioreactor serves as a first reaction zone, the inner cavity of the photobioreactor serves as a second reaction zone, and the first reaction zone is communicated with the second reaction zone through a passage provided with a water inlet electromagnetic valve 15. The first reaction zone is internally provided with bacteria-algae, and the bottom is provided with a microporous aeration disc 8 capable of upward aeration. The second reaction zone is communicated with a water outlet 16 provided in the side wall of the sequencing batch reactor through a pipeline.

[0036] In actual use, the stirring paddles 11 can rotate with the heat dissipation cylinder 12 to realize stirring and disturbance of the biogas slurry in the first reaction zone, which is more conducive to the photocatalytic reaction. In order to optimize the device, the light column 13 can be arranged as a fixed structure, only the heat dissipation cylinder 12 can rotate around the shaft, and the light column 13 should be able to realize uniform irradiation in the circumferential direction.

[0037] As a preferred embodiment of the present application, the microporous aeration disc 8 is externally connected with an aeration pump 6, and a gas flow meter 7 is arranged on the gas conveying pipeline of the aeration pump 6. The first reaction zone is also provided with a temperature probe, a pH probe 9 and a DO probe 18 for measuring water quality indicators. In addition, the treatment device of the present application also comprises a PLC automatic control device 5 and an external power supply 3 for supplying power to each electrical equipment, wherein the temperature probe, the pH probe 9 and the DO probe 18 are connected with the PLC automatic control device 5, and the PLC automatic control device 5 can feedback control each valve and the operation of the microporous aeration disc 8 and the heat dissipation cylinder 12 according to the results obtained by the temperature probe, the pH probe 9 and the DO probe 18.

[0038] In actual operation, the biogas slurry is preliminarily treated by the bacteria-algae symbiotic system of the first reaction zone, and the effluent is used as the influent of the photobioreactor (i.e. the second reaction zone), which is controlled by the water inlet electromagnetic valve 15. Then, under the condition of ultraviolet-visible light reaction, the SBR treated biogas slurry is further treated by photocatalysis, and the reactor is provided with a PLC automatic control system (electromagnetic valve, timer, heat dissipation cylinder, stirring paddle, aeration disc, etc.), which controls the intermittent operation (influent-reaction-settlement-drainage-rest) of the SBR. The pH, DO and temperature sensors inside the reactor are connected with the PLC control end for online monitoring of changes and automatic regulation and control through feedback programs.

[0039] As a preferred embodiment of the present application, the light column 13 is also externally connected with a timer, which can realize the timing of the light column according to the preset period, and the light column can adopt an LED integrated lamp tube. The light condition of the light column should be able to meet the photosynthesis of bacteria-algae and completely meet the photocatalysis requirements, so as to realize carbon emission reduction under low energy consumption, further treat the biogas slurry and improve the utilization efficiency of nutrients in the biogas slurry.

[0040] The reactor column (i.e. the sequencing batch activated sludge reactor) of the present application is intermittently operated, keeps the bacteria-algae in the starvation-saturation condition, closely links the CO2 circulation and the O2 circulation, is beneficial to reduce the carbon emission, makes the microalgae growth no longer rely on the external carbon source, saves the setting of the aeration tank and the aeration system in the prior art, and makes the production cost relatively low; the photosynthesis assembly (i.e. the photobioreactor) promotes the light illumination in the aeration tank (i.e. the first reaction zone) to be fully beneficial to the photosynthesis of the microalgae. In the co-culture system, the metabolites of the bacteria can provide the nutrients for the microalgae, which cannot be obtained in the single culture of the microalgae.

[0041] The present application also provides a biogas slurry treatment method using the above low-energy-consumption photocatalysis-bacteria-algae symbiosis integrated biogas slurry treatment device, and specifically as follows.

[0042] The biogas slurry to be treated is pretreated and used as the bacteria-algae influent, and enters the first reaction zone of the sequencing batch activated sludge reactor. The sequencing batch activated sludge reactor is intermittently operated in the mode of influent-oxygenation-precipitation-drainage-resting, and simultaneously the light illumination column 13 is turned on to preliminarily purify the biogas slurry. In the preliminary purification process, the aerobic bacteria degrade the carbon-containing organic matters into carbon dioxide and water, and at the same time, ammonify the nitrogen-containing organic matters and then nitrify the ammonified nitrogen-containing organic matters to generate ammonia nitrogen, nitrite and nitrate, and finally degrade the phosphorus-containing organic matters into orthophosphate. The energy generated by the oxidative degradation provides the energy for the metabolic activity of the bacteria, and the carbon dioxide generated by the bacterial degradation of the organic matters becomes the main carbon source for the photosynthesis of the algae, which promotes the photosynthesis of the algae. In the process of the metabolism of the algae, the substances generated in the bacterial metabolism are absorbed and converted into the cell substances of the algae, the oxygen released by the photosynthesis of the algae increases the dissolved oxygen in the water, and promotes the metabolic activity of the aerobic bacteria to enable the aerobic bacteria to maintain the normal life activities. Subsequently, the bacteria-algae are precipitated in the lower part of the first reaction zone through the settling stage.

[0043] The biogas slurry preliminarily purified in the first reaction zone enters the second reaction zone through the control of the influent electromagnetic valve 15, and at the same time, the C3N4 photocatalysis material is added into the second reaction zone, and the light illumination column 13 is controlled to alternately operate in light and dark, so that the bacteria-algae perform the photocatalysis reaction in the light reaction stage and the photocatalysis resting process in the dark reaction stage. In the photocatalysis reaction, the photocatalysis material acts as a light trapping agent to assist the bacteria-algae to treat the wastewater, and at the same time, the photocatalysis function of the photocatalysis material activates the algae spores to make them rapidly split in the water, promote the cell growth, and make the algae in-situ enrichment and adhere to the outer surface of the bacteria colony and the reactor wall to naturally form the algae immobilization. In addition, the photocatalysis material can also assist the fixation of carbon dioxide. The biogas slurry treated in the second reaction zone is discharged from the treatment device.

[0044] The application adds a photocatalytic material in water, which can efficiently capture light energy and produce photo-generated electrons to reduce CO2 under light conditions due to its photocatalytic properties. Therefore, the photocatalytic material put into water can be used as a light trapping agent to assist bacteria and algae in wastewater treatment, thereby making up for the shortcomings of bacteria and algae in capturing light energy. At the same time, it also contributes to carbon dioxide fixation to some extent; and due to the photocatalytic function of the photocatalytic material, the spores of algae are activated to rapidly split in water, promote cell growth, and make the algae in-situ enrichment and adhere to the outer surface of the bacteria group and the reactor wall, naturally forming algae immobilization, which saves the algae immobilization process of traditional bacteria-algae symbiotic filling filler carrier and saves economic cost. The application preferably uses C3N4 as a photocatalytic material and a light trapping agent, and further preferably uses nanoscale C3N4. As a semiconductor photocatalytic material with a suitable electronic energy band structure, C3N4 has good thermal stability and chemical stability, low price, low preparation cost, and good biocompatibility, and will not have toxic effects on the growth of microorganisms. Compared with other photocatalytic materials, the system performance of C3N4 nanoparticles is better, which can quickly build a more efficient and stable photocatalytic-bacteria-algae symbiotic integrated system.

[0045] As a preferred embodiment of the application, the pretreatment method for the biogas slurry to be treated can adopt coagulation sedimentation (or bleaching powder) + color removal agent operation, specifically as follows:

[0046] Considering the dual needs of bacteria-algae symbiosis and biogas slurry purification, the pretreatment must meet the following requirements: (1) the cost of drugs, equipment, and measurement method energy consumption should be low; (2) the treated biogas slurry should not affect the growth and reproduction of bacteria and algae in the later stage. Because the livestock breeding wastewater contains a large amount of feces and a small amount of food, the suspended solids concentration is high, and the coagulation sedimentation method can be used to treat the livestock breeding wastewater, which can reduce the difficulty of biological treatment, and has low cost and simple operation. Specifically, the coagulation sedimentation method used in this embodiment uses chitosan as a coagulant. As an organic coagulant, chitosan has a long molecular weight, strong adsorption bridging effect, good coagulation effect, and low dosage, and is non-toxic.

[0047] The example also uses 0 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L of bleaching powder (such as calcium hypochlorite) to pretreat the biogas slurry, and it is found that 40 mg / L of bleaching powder can basically kill the pig biogas slurry in the algae-eating pests, but the pig biogas slurry after treatment cannot be directly used as the algae reaction inlet water, because the hypochlorite in the bleaching powder is harmful to the algae, but considering that the hypochlorite is easily decomposed in the open environment, it only needs to be placed for 4-6 days to inoculate and culture the algae; this pretreatment method has relatively low cost, and the measurement cost of each ton of pig biogas slurry is only 0.050 yuan; this pretreatment method is simple to operate, and has less damage to the nutrient elements in the pig biogas slurry, which solves a thorny problem of realizing large-scale algae symbiosis by using pig biogas slurry.

[0048] Uniformly adding 0.5%-1% of a color removal agent (such as polyaluminum chloride) to the biogas slurry can have a good flocculation and color removal effect on the biogas slurry, providing a good growth environment for the growth of chlorella.

[0049] The device and effects of the present application will be specifically described below through examples.

[0050] Example 1

[0051] The example provides a low-energy-consumption photocatalysis-algae symbiosis integrated biogas slurry treatment device, and the specific structure is not described again. The sequencing batch activated sludge reactor is an organic glass cylinder with an inner diameter of 160 mm, a height of 1000 mm, and an effective volume of 4 L; the operation cycle of the sequencing batch activated sludge reactor is 6 h, wherein the water inlet time is 10 min, the aeration time is 228-255 min, the anaerobic time is 360 min, the standing and sedimentation time is 30-3 min, and the water outlet time is 2 min, and 2 L of water is discharged per cycle, that is, the specific operation time change of each stage is shown in Table 1; the device is provided with dissolved oxygen, pH, and temperature probes, and the DO, temperature, and pH are monitored online and automatically started and closed by the PLC automatic control device to control the pH to be maintained in the range of 7.5-8.5, and the water inlet temperature is maintained at 25-30°C during the experiment; the photobioreactor is an organic glass cylinder with an inner diameter of 80 mm, a height of 900 mm, and an effective volume of 2 L, and a timer is used to control the light column 13 to provide light for the algae granular sludge: dark reaction = 12:12 h, and in this process, the algae granular sludge performs photocatalysis reaction in the light reaction stage, and the dark reaction stage can be used as a photocatalysis standing process, and the whole light-dark alternating reaction process. The water inlet of the photobioreactor is arranged at a position of 450 mm, so that the supernatant in the first reaction zone enters the subsequent reaction.

[0052] Table 1 Change of time length of each process in the cycle

[0053]

[0054] Example 2

[0055] Based on the low-energy consumption photocatalysis-bacteria-algal symbiosis integrated biogas slurry treatment device provided in Example 1, the experimental conditions are optimized, specifically as follows:

[0056] The quality of the aquaculture wastewater to be treated is: COD 3360 mg / L, ammonia nitrogen 2000 mg / L, total phosphorus (TP) 65 mg / L, suspended solids SS 6753 mg / L. Coagulation and sedimentation are carried out on a six-union stirrer, the pH of the wastewater is adjusted to 7.1-8.1 with HCl and NaOH, 2 g / L of flocculant chitosan is added under stirring at 150 rpm, 30 s later, 0.3 g / L of CaCl2 is added and stirring is continued for 30 s, then stirring at 50 rpm for 15 min, and standing for 10 min to discharge the water. The quality of the pretreated water is: COD 1522 mg / L, ammonia nitrogen 1085 mg / L, total phosphorus (TP) 36 mg / L.

[0057] During the treatment process, through orthogonal test, the light time is set to 18-24 h / d (for example, 18 h / d, 20 h / d, 21 h / d, 24 h / d, etc.), the light intensity is set to 2000-2500 lx (for example, 2000 lx, 2100 lx, 2200 lx, 2400 lx, 2500 lx, etc.), and the aeration amount is set to 0.38-0.5 L / min (for example, 0.38 L / min, 0.39 L / min, 0.4 L / min, 0.43 L / min, 0.46 L / min, 0.5 L / min, etc.) to treat the aquaculture wastewater by using the symbiosis of microalgae and activated sludge. In the second reaction zone, 150-200 mg / L of C3N4 material is added, and the light parameters are controlled (the total light-dark time ratio is set to 12 h:12 h, and the light intensity is adjusted to 4000-6000 lx).

[0058] Among them, the microalgae is Chlorella pyrenoidosa, which is purchased from the Chinese Academy of Sciences Freshwater Algae Library, and the strain is transferred to BG11 (Blue-Green Medium 11) for 20-day activation culture by sterile operation. Specifically, the Chlorella pyrenoidosa includes the separation and purification and the expansion culture stages: a) the culture medium for Chlorella pyrenoidosa purification culture is BG11 culture medium, and the Chlorella pyrenoidosa is diluted to 10 -5The Chlorella vulgaris was inoculated into BG11 liquid medium at a ratio of 20%, and cultured under the conditions of 26°C, light intensity of 2500 lx, and light time of 12 h. After the Chlorella vulgaris was cultured to the logarithmic growth phase, it was centrifuged at 8000 rpm for 10 min, resuspended with ultrapure water, repeated three times, and concentrated for use.

[0059] The activated sludge was taken from the biological pool aeration stage of a sewage treatment plant, and the common freshwater Chlorella vulgaris was used as the inoculated algae under laboratory conditions. The inoculation amount of the common freshwater Chlorella vulgaris was 40 mL and 0.3 g / L. The mass ratio of the bacteria-algae symbiont to the biogas liquid was 0.8-5.2:1000 (for example, 0.8:1000, 1:1000, 5.2:1000), and the mass ratio of the Chlorella vulgaris to the mixed bacteria was 1:150. After 40 days of culture, the granular sludge with a particle size greater than 0.5 mm was obtained. The MLSS was about 5000 mg / L when the reactor was started. In the initial stage of inoculation of the sludge, the sludge with poor settling performance was eliminated in a large amount due to a short settling time, and the MLSS was reduced to 3500 mg / L. With the formation of the granules, the sludge settling performance became good, the concentration gradually increased, and finally stabilized at about 3800 mg / L.

[0060] During the operation of the test device, the average air temperature was 25°C, the hydraulic retention time (HRT) was 2 d, and the water was continuously fed for 24 h. After the system was normally operated, the influent and effluent samples were taken once a day, and the sampling time was fixed at 10:00 am. The water quality indexes were analyzed on the same day after sampling.

[0061] It was found that the treatment effect of the wastewater was the best under the conditions of light time of 20 h / d, light intensity of 2500 lx, aeration amount of 0.4 L / min, initial inoculation ratio of the bacteria-algae of 1:150, mass ratio of the bacteria-algae symbiont to the biogas liquid of 1:1000, and light time of 20 h / d. This is because, according to the variance analysis, the aeration amount and the initial inoculation ratio of the bacteria-algae have a significant relationship with the removal of ammonia nitrogen, but have no significant influence on the removal of COD and phosphate. Therefore, when the optimal levels of the two influencing factors are selected, the influence on the removal of ammonia nitrogen should be mainly considered. Therefore, the optimal levels of the aeration amount and the initial inoculation ratio of the bacteria-algae should be selected as 0.4 L / min and 1:150. As for the light time factor, it has a significant influence on the removal of COD and ammonia nitrogen, but considering that the optimal level of the removal of phosphate is the same as that of the removal of ammonia nitrogen, and the range R of the different light time levels on the removal of COD is small, the optimal level of the light time is selected as 20 h / d.

[0062] In the process, the appropriate ratio of microalgae and bacteria in the symbiotic system is conducive to better symbiosis of microalgae and bacteria, and the oxygen produced by microalgae photosynthesis is used by bacteria, and the carbon dioxide produced by bacteria is used by microalgae for photosynthesis. In the bacteria-algae granular sludge coupling system (ABGS), granular sludge (AGS) and algae play an indispensable role. AGS has the characteristics of good settling performance, large specific surface area, high proportion of dominant microbial population, high biomass, high nitrogen removal efficiency, strong toxicity resistance, etc., and algae grow attached to the surface of granular sludge, and the surface of algae is distributed with hydrophobic substances such as proteins and polysaccharides, which can efficiently separate sludge and water, and quickly settle with granular sludge, while achieving good nitrogen and phosphorus removal effect; on the other hand, algae provide oxygen for the system, which can greatly reduce or even replace aeration, relieve the huge energy consumption pressure of sewage, save costs, and at the same time provide a guarantee for stable operation of the system. Algae absorb CO2 produced by microbial decomposition of organic matter, thereby reducing greenhouse gas emissions from sewage plants and having environmental benefits. Therefore, ABGS has considerable development prospects.

[0063] Example 3

[0064] Based on the optimal reaction parameters obtained in Example 2:

[0065] 1) Measure the OD value of bacteria-algae at 680 nm on the ultraviolet spectrophotometer, and count microscopically, count the microalgae less than 10 μm with a blood cell counting plate, and count the algae greater than 10 μm with a 0.1 mL plankton counting frame. Plot the OD value against the cell density, and calculate the light absorption coefficient. Then convert the light absorption coefficient to biomass using the formula (lg(m) = -1.0465ln(x) + 4.255, where m is the biomass and x is the light absorption coefficient). Measure the accumulation of biomass in bacteria-algae after 15 days according to the above method.

[0066] The results are shown in Figure 4 From the figure, it can be seen that the OD 680 value of Chlorella pyrenoidosa did not change significantly within the first 24 hours after inoculation, and was in the lag phase of growth. After 48 hours of inoculation, Chlorella pyrenoidosa began to grow rapidly. By the 9th day of culture, the cell density of Chlorella pyrenoidosa reached a maximum. After the 9th day, the growth of Chlorella pyrenoidosa was affected due to the gradual consumption of nutrients and the possible decline of some Chlorella pyrenoidosa, so the cell density gradually decreased.

[0067] 2) Refer to the national standard "Determination of ammonia nitrogen in water - flow injection-salicylic acid spectrophotometric method" (HJ 666-2013), the ammonia nitrogen content before and after sewage treatment is determined, and the removal rate is calculated; refer to the national standard "Determination of total nitrogen in water - flow injection-hydrochloric acid naphthalene ethylenediamine spectrophotometric method" (HJ 668-2013), the total nitrogen content before and after sewage treatment is determined, and the removal rate is calculated; refer to the national standard "Determination of nitrite nitrogen and nitrate nitrogen and through flux analysis (CFA and FIA) - Spectral determination" (NF T90-012-1996 (R2002)), the nitrate nitrogen content before and after sewage treatment is determined, and the removal rate is calculated; refer to the national standard "Determination of total phosphorus in water - ammonium molybdate spectrophotometric method" (GB / T 11893-1989), the total phosphorus content before and after sewage treatment is determined, and the removal rate is calculated; refer to the national standard "Chemical oxygen demand (COD) meter" (GB / T 32208-2015), the COD value before and after sewage treatment is determined, and the removal rate is calculated.

[0068] The results are shown in Figure 5 As can be seen from the figure, the removal rates of ammonia nitrogen, COD and phosphate gradually increase and finally tend to be stable with the formation of bacterial-algal particles, and the change of the removal rate conforms to the growth trend of bacteria-algae. It can be shown that under the culture conditions of aquaculture wastewater, bacteria-algae have strong pollution resistance and impact resistance, can better remove nitrogen and phosphorus, degrade organic matter, and have good purification effect on the water quality of the culture system. The efficiency of removing nitrogen and phosphorus is high, the residence time is 40d, the ammonia nitrogen removal rate is more than 80%, the nitrite nitrogen does not accumulate, the COD removal rate is more than 85%, and the phosphate removal rate is more than 75%.

[0069] The above-described embodiments are only a preferred scheme of the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, any technical solutions obtained by equivalent replacement or equivalent transformation fall within the protection scope of the present application.

Claims

1. A method for treating biogas slurry using a low-energy photocatalytic-bacterio-algal symbiotic integrated biogas slurry treatment device, characterized by, The low-energy-consumption photocatalysis-bacteria-algae symbiosis integrated biogas slurry treatment device comprises a sequencing batch activated sludge reactor and a photobioreactor located in the inner layer of the sequencing batch activated sludge reactor; The lower part and the upper part of the side wall of the sequencing batch activated sludge reactor are respectively provided with a water inlet (10) and an overflow port (14) which are in communication with the inner cavity, and the inner cavity is provided with a photobioreactor which can rotate along an axis; the photobioreactor comprises a heat dissipation cylinder (12) and an illumination column (13) which are coaxially arranged from outside to inside, and the outer wall of the heat dissipation cylinder (12) is circumferentially provided with a plurality of stirring paddles (11); the annular region between the sequencing batch activated sludge reactor and the photobioreactor serves as a first reaction zone, the inner cavity of the photobioreactor serves as a second reaction zone, and the first reaction zone is in communication with the second reaction zone through a passage provided with a water inlet electromagnetic valve (15); the first reaction zone is internally provided with bacteria and algae, and the bottom is provided with a microporous aeration disc (8) which can aerate upward; the second reaction zone is in communication with a drainage port (16) provided in the side wall of the sequencing batch activated sludge reactor through a pipeline; The biogas slurry treatment method is as follows: After being pretreated, the biogas slurry to be treated is used as the bacteria and algae water inlet and enters the first reaction zone of the sequencing batch activated sludge reactor; the sequencing batch activated sludge reactor is intermittently operated in a water inlet-oxygenation-precipitation-drainage-resting mode, and the illumination column (13) is turned on at the same time to preliminarily purify the biogas slurry; in the preliminary purification process, the aerobic bacteria degrade the carbon-containing organic matter into carbon dioxide and water, and at the same time, the nitrogen-containing organic matter is ammoniated and then nitrified to generate ammonia nitrogen, nitrite and nitrate, and the phosphorus-containing organic matter is finally degraded into orthophosphate; the energy generated by the oxidative degradation provides energy for the metabolic activity of the bacteria, and the carbon dioxide generated by the bacterial degradation of the organic matter becomes the main carbon source for the photosynthesis of the algae, thereby promoting the photosynthesis of the algae; in the process of metabolism of the algae, the substances generated in the bacterial metabolism are absorbed and converted into cell substances of the algae, the oxygen released by the photosynthesis of the algae increases the dissolved oxygen in the water, thereby promoting the metabolic activity of the aerobic bacteria and enabling the aerobic bacteria to maintain normal life activities; then, after the settling stage, the bacteria and algae are precipitated in the lower part of the first reaction zone; After being preliminarily purified in the first reaction zone, the biogas slurry enters the second reaction zone through the control of the water inlet electromagnetic valve (15), and at the same time, C3N4 photocatalytic material is added into the second reaction zone, and the illumination column (13) is controlled to alternately operate in light and dark, so that the bacteria and algae perform photocatalytic reaction in the light reaction stage and the dark reaction stage is used as the photocatalytic resting process; in the photocatalytic reaction, the photocatalytic material acts as a light trapping agent to assist the bacteria and algae in wastewater treatment, and at the same time, the photocatalytic function of the photocatalytic material activates the algae spores to make them rapidly split in the water, promote cell growth, and enable the algae to in-situ enrich and adhere to the outer surface of the bacterial population and the reactor wall, thereby naturally forming algae immobilization, in addition, the photocatalytic material can also assist in fixing carbon dioxide; the biogas slurry treated in the second reaction zone is discharged from the treatment device.

2. The method of claim 1, wherein, The microporous aeration disc (8) is externally connected with an aeration pump (6), and a gas flow meter (7) is arranged on the gas conveying pipeline of the aeration pump (6).

3. The method of claim 1, wherein, The sequence intermittent activated sludge reactor is provided with a plurality of sampling ports (19) spaced apart along the length direction, and each sampling port (19) is provided with a valve.

4. The method of claim 1, wherein, The water inlet (10) is connected with the water inlet barrel (1) through a water inlet pipe provided with a peristaltic pump (2) and a rotor flowmeter.

5. The method of claim 4, wherein the biogas slurry is treated by a method comprising: The rotor flowmeter is connected with a first timer (4), and the first timer (4) can control the operation of the peristaltic pump (2) according to the data of the rotor flowmeter.

6. The method of claim 1, wherein, The water outlet (16) is connected with the water outlet barrel (21) through a water outlet pipe provided with a second timer (17) and a water outlet electromagnetic valve (20).

7. The method of claim 1, wherein, The first reaction zone is further provided with a temperature probe, a pH probe (9) and a DO probe (18) for measuring water quality indexes.

8. The method of claim 7, wherein the biogas slurry is treated by a method comprising: The temperature probe, the pH probe (9) and the DO probe (18) are connected with a PLC automatic control device (5), and the PLC automatic control device (5) can feedback control the operation of each valve, the microporous aeration disc (8) and the heat dissipation cylinder (12) according to the results obtained by the temperature probe, the pH probe (9) and the DO probe (18).

9. The method of claim 1, wherein, Further comprising an external power supply (3) for supplying power to each electrical equipment.

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