Rapid culture method of aerobic granular sludge

Abstract

The invention discloses a rapid culture method of aerobic granular sludge, and belongs to the technical field of sewage treatment. According to the invention, pharmaceutical factory sludge is used as a raw material to prepare pharmaceutical factory sludge biochar; an SBR reactor is constructed and operates in a water inlet-anoxic-aeration-precipitation-drainage mode, and pharmaceutical factory sludge biochar is added in the sludge inoculation process to promote rapid formation of system particles and stable operation. According to the method disclosed by the invention, the mature aerobic granular sludge with the capabilities of removing organic matters and synchronously denitrifying can be obtained by culturing for 30 days on average, so that the granulation process of the sludge is effectively improved, the forming time of the aerobic granular sludge is remarkably shortened, and the aerobic granular sludge has higher long-term operation stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a method for rapidly culturing aerobic granular sludge. Background Art

[0002] In most provinces and cities in China, due to problems such as rainwater dilution and sewer leakage, low COD concentrations are relatively common. An overly low influent load not only slows down the granulation process but also inhibits the ability to remove organic matter. On the other hand, filamentous bacteria are extremely likely to compete with other microorganisms for limited substrates when the influent load is low, and multiply in large numbers, resulting in a decline in the stability of the granules, making it difficult to maintain the stability of the granules. Adding external carbon sources is a common method for treating low-carbon wastewater at present, but adding carbon sources will not only increase the treatment cost but also emit more CO2, polluting the environment.

[0003] Treating wastewater with aerobic granular sludge has the characteristics of high pollutant removal efficiency, small floor area, and strong shock load and toxicity resistance. However, the disadvantages of long system startup time and poor long-term operation stability limit the application of this technology in the wastewater treatment industry. A large number of studies have shown that adding carriers to SBR, such as activated carbon, biochar, Fe 2+ , Ca 2+ and other metal ions, etc., can provide a core for the attachment of suspended sludge, thereby accelerating sludge aggregation and forming granular sludge.

[0004] Pharmaceutical sludge refers to the sludge generated during the pharmaceutical production process and the pharmaceutical wastewater treatment process. The composition of pharmaceutical sludge is complex, containing not only a large amount of refractory organic matter but also toxic and harmful substances, with bad odor and corrosiveness, and is highly harmful to the environment and organisms. Traditional methods for disposing of pharmaceutical sludge (such as landfilling, incineration) face problems such as high costs, risks of secondary pollution (such as the generation of dioxins during incineration), and waste of resources. In recent years, some countries have included part of the pharmaceutical sludge in the list of hazardous wastes. Therefore, promoting resource-based technologies and harmless treatment has become a research hotspot, but there are still challenges in its technical and economic feasibility and large-scale application. However, there is still relatively little research on the role of sludge-like pharmaceutical sludge biochar in the aerobic granular sludge system at present, and the long-term operation stability of most aerobic granular sludge systems added with pharmaceutical sludge biochar remains to be further studied. Summary of the Invention

[0005] Aiming at the technical problems of long granulation time and unstable long-term operation under low-carbon conditions, the present invention provides a method for rapidly culturing aerobic granular sludge, which can rapidly culture aerobic granular sludge. The cultured aerobic granular sludge has strong growth and reproduction ability and can maintain stability for a long time.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A rapid cultivation method for aerobic granular sludge, specifically including the following steps:

[0008] (1) Using pharmaceutical factory sludge as raw material, drying it in a constant temperature air blast drying oven, cooling it to room temperature, manually pulverizing it through a 100-mesh sieve, then storing it at a constant temperature, and then pyrolyzing it in a nitrogen atmosphere to prepare pharmaceutical factory sludge biochar at different temperatures;

[0009] (2) Inoculating the pharmaceutical factory sludge biochar prepared in step (1) into activated sludge, constructing an SBR experimental device, starting the reactor to add the pharmaceutical factory sludge biochar and then inoculating the activated sludge, and culturing aerobic granular sludge to obtain aerobic granular sludge.

[0010] Preferably, in step (1), the drying temperature is 103°C - 105°C, and the drying time is 24 - 72 h.

[0011] Preferably, in step (1), the pyrolysis conditions are: heating from room temperature to the pyrolysis temperature at a heating rate of 0.4 - 0.6 L / min.

[0012] Preferably, in step (1), the pyrolysis temperature is 400 - 600°C, and the pyrolysis time is 2 h.

[0013] Preferably, in the present invention, the optimal dosage of the pharmaceutical factory sludge biochar is determined by simulating the combination experiment of the pharmaceutical factory sludge biochar and the activated sludge; the dosage of the pharmaceutical factory sludge biochar is added according to the mass ratio of pharmaceutical factory sludge biochar:activated sludge = 1:3, the optimal particle size of the added pharmaceutical factory sludge biochar is <50 μm, 6 g / L of activated sludge is inoculated in the reactor at startup, and at the same time 2 g / L of the prepared pharmaceutical factory sludge biochar is added for culturing aerobic granular sludge.

[0014] Preferably, in step (2), the SBR experimental device is composed of a water inlet system, an organic glass column reactor, an aeration system and a water outlet system. The influent is transported from the bottom by a peristaltic pump, and the effluent is discharged from the middle of the reactor by a peristaltic pump; aeration is carried out through a microporous aeration stone at the bottom of the reactor, and the aeration volume is controlled by a rotameter.

[0015] Preferably, in step (2), the wastewater is pumped into the reactor, the height-diameter ratio of the reactor is 20 - 25, the reactor operates in the mode of influent - anoxic - aeration - sedimentation - water discharge, the influent pH is controlled between 7 - 8, and the operating environmental temperature of the reactor is controlled at 24 - 26°C throughout the process; among them, the influent time is 5 min, the anoxic time is 55 min, the aeration time is 145 - 170 min, the sedimentation time is 5 - 30 min, the effluent time is 5 min, the cycle operation time is 4 h, 6 cycles are operated every day, the reactor volume exchange rate is maintained at 10 - 50%, the hydraulic retention time is 8 h, and the aeration flow rate is 1.2 - 2.0 L / min.

[0016] Preferably, during the formation of aerobic granular sludge in the early stage, regular tests are carried out on the physical properties of the sludge, and the physical properties of the sludge include:

[0017] MLSS, MLVSS, SVI30, SVI30 / SVI5, F / M, effluent SS and particle size, changes in influent and effluent concentrations (COD, ammonia nitrogen, NO x -N and phosphorus), and the sludge morphology is observed using an electron microscope; under normal cultivation conditions: SVI5 and SVI30 will gradually decrease from the initial 100-150 mL / g to below 60 mL / g; it can be observed under the microscope that the flocs in the system gradually decrease, replaced by oval small particles wrapped in biochar similar to pharmaceutical factory sludge; the SVI30 / SVI5 ratio will gradually tend to 1.

[0018] Preferably, when the above indicators are monitored and activated sludge and biochar of pharmaceutical factory sludge are successfully added to the reactor, the sedimentation time is directly adjusted from 30 min to 25 min, and then for every 10-15 mL / g decrease in SVI30, the sedimentation time is shortened by 5 min, and the aeration time is correspondingly increased by 5 min.

[0019] Preferably, when it is monitored that the sludge concentration MLSS of the system continuously drops below 1 g / L or the effluent SS concentration is as high as 250 mg / L, it indicates that the sludge loss inside the system is serious, and the sedimentation time is adjusted to 8-15 min; if the sludge concentration MLSS is between 0.8-1 g / L, the sedimentation time is adjusted back to 8 min; if MLSS is below 0.8 g / L, the sedimentation time can be adjusted back to 15 min; when it is found that the sludge concentration begins to rise back to greater than or equal to 1 g / L and remains for at least 7 days, the sedimentation time is restored by 5 min; when it is monitored that the sludge volume of the system continuously drops, that is, the system is in a declining period, it indicates that aerobic granulation enters the most critical sludge selection period. During this period, the system will discharge a large amount of flocculent sludge with poor sedimentation performance, resulting in fluctuations in the overall pollutant removal capacity of the system. As an important period for particle formation, the reduction in sludge volume is a normal phenomenon. When the pollutant removal performance of the system is stable, SVI30 / SVI5 is stable at about 1, and particles with a particle size greater than 200 um appear significantly inside the system and this state lasts for at least 10 days, it indicates the successful formation of aerobic granular sludge in the system.

[0020] Preferably, when the system continuously and stably achieves a COD removal rate of 85% and an ammonia nitrogen removal rate of 90% for at least one week, and small aerobic granular sludge with a particle size > 200 um begins to appear inside the system, the sedimentation time is directly adjusted to 5 min.

[0021] Preferably, after the aerobic granules are successfully cultivated, the sludge is used for the treatment of low-carbon wastewater and wastewater with a low carbon-nitrogen ratio; the low-carbon wastewater uses artificial simulated domestic wastewater, and the wastewater with a low carbon-nitrogen ratio is the domestic sewage of a certain factory.

[0022] Preferably, the influent COD load of the low-carbon wastewater is 50 - 250 mg / L, and the ammonia nitrogen load is 10 mg / L. After 200 days, compared with the operating system without adding pharmaceutical sludge biochar, in the SBR experimental operating system with the addition of pharmaceutical sludge biochar, the removal rates of COD and ammonia nitrogen are increased to more than 20%.

[0023] Preferably, the influent COD load of the low-carbon and low-nitrogen ratio wastewater is 50 - 250 mg / L, and the ammonia nitrogen load is 30 - 80 mg / L. At this time, the removal rates of both COD and ammonia nitrogen can reach more than 90%.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] (1) The method for culturing aerobic granular sludge in the present invention has gone through three stages: inoculation, appearance, and maturity. Under the action of the selection pressure, the flocculent sludge gradually agglomerates, the structure becomes gradually dense, and the color changes from dark brown to yellowish brown. More importantly, the addition of pharmaceutical sludge biochar can significantly shorten the particle formation time of the particles under low-strength wastewater conditions. Stable aerobic granular sludge can be formed in only 63 days, which is 36 days faster than without adding the biochar.

[0026] (2) During the particle formation period of the present invention, the granular sludge that has undergone slight disintegration can be re-formed through its own regulation. It recovers faster compared to the group without adding the biochar, indicating that the pharmaceutical sludge biochar can accelerate the formation process of the granular sludge. After the particles are formed and mature, the system officially enters the operation period, and it can treat low-carbon wastewater for a long time, and relevant research on the sewage treatment performance and long-term stability of the particles can also be carried out.

[0027] (3) The aerobic granular sludge cultured in the present invention can also be used for the treatment of low-carbon and low-nitrogen ratio wastewater, and the removal of COD and ammonia nitrogen can also be achieved. On the other hand, the present invention is further used to treat the actual domestic wastewater of the factory and has obtained remarkable effects, providing an important basis for subsequent industrial applications. Description of the Drawings

[0028] Figure 1 It is a general electron microscope photograph of the aerobic granular sludge obtained after culturing for 30 days in Example 1. Figure (a) is the general electron microscope photograph of the aerobic granular sludge obtained after culturing for 30 days with the addition of pharmaceutical sludge biochar, and Figure (b) is the general electron microscope photograph of the sludge obtained after culturing for 30 days without adding pharmaceutical sludge biochar.

[0029] Figure 2 It is a general electron microscope photograph of the mature aerobic granular sludge obtained during the culturing of Example 2 for 168 days. Detailed Embodiments

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the described content.

[0031] Example 1

[0032] The method for culturing aerobic granular sludge for treating low-carbon wastewater in this example uses the sludge from the secondary sedimentation tank of a pharmaceutical factory in Kunming as the raw material. The influent sewage is artificial simulated domestic wastewater with a COD concentration of 50 - 250 mg / L, an ammonia nitrogen concentration of 10 mg / L, and a TP concentration of 5 mg / L. The pH is adjusted to be between 7.5 - 8.5, and the operating environment temperature of the reactor is maintained between 24 - 30 °C. The method includes the following steps:

[0033] (1) Using the sludge from the pharmaceutical factory as the raw material, it is dried in a constant-temperature blast drying oven at 105 °C, cooled to room temperature after 36 h, manually crushed through a 100-mesh sieve, and then stored at a constant temperature. It is heated from room temperature to 500 at a heating rate of 0.5 L / min in a nitrogen atmosphere and pyrolyzed for 2 h to obtain the biochar of the pharmaceutical factory sludge.

[0034] (2) An organic glass column sequencing batch reactor (SBR) is used; the parameters of the reactor are: the inner diameter of the reactor is 50 mm, the effective working volume is 2 L, the effective height is 1150 mm, and the height-diameter ratio (H / D) is 23; the influent is transported from the bottom by a peristaltic pump, and the effluent is discharged from the middle of the reactor by a peristaltic pump to maintain a volume exchange rate (VER) of 50%; during the aerobic aeration stage, an air pump provides sufficient air flow to fully mix the mud and water in the reactor and the oxygen required for the growth of microorganisms. The aeration volume is controlled by a rotameter, and the air flow is controlled at 2 L / min. The entire experiment is carried out under the condition of 25 °C, and all electrical appliances are controlled by a time relay.

[0035] (3) The reactor cultivation method is operated according to the following process: Two identical SBR experimental devices are constructed and named R1 and R2 respectively; the activated sludge from Jingyuan Domestic Sewage Treatment Plant of Kunming University of Science and Technology is used as the inoculated sludge, which is dark black in color and flocculent in shape.

[0036] (4) According to the results of regularly measuring the particle sedimentation ability, the sedimentation time is reasonably adjusted. The initial sedimentation time is 30 min, and it is shortened by 5 - 10 min every once in a while until the final 5 min. The reactor operates 6 cycles per day, corresponding to a cycle time of 4 h and a hydraulic retention time of 8 h; the specific operation mode of each cycle is as follows: 5 min for influent, 55 min for anoxic, 145 - 170 min for aerobic, 5 - 30 min for sedimentation, and 5 min for effluent.

[0037] (5) In the initial stage of starting the SBR experimental device named R1, the inoculation dosage of activated sludge in the reactor was 6 g / L, and at the same time, 2 g / L of pharmaceutical sludge biochar was added for the cultivation of AGS; the SBR experimental device named R2 was used as a control group. In the initial stage of starting, 6 g / L of activated sludge was inoculated in the reactor, and pharmaceutical sludge biochar was not added for the cultivation of AGS.

[0038] Through the simulation of the binding experiment between pharmaceutical sludge biochar and activated sludge, it was obtained that the dosage of pharmaceutical sludge biochar was 1:3 (pharmaceutical sludge biochar concentration / activated sludge concentration), and the particle size of the added pharmaceutical sludge biochar was <50 μm.

[0039] Through elemental analysis, BET analyzer and atomic absorption spectrometry to characterize the elemental composition, specific surface area, microporous surface area and metal ion content of the pharmaceutical sludge biochar obtained in Example 1 of the present invention. Compared with the other two types of sludge biochars, the contents of Ca 2+ , Mg 2+ , Fe 2+ in the pharmaceutical sludge biochar were relatively high, being 24.0%, 8.1%, and 3.8% respectively. The specific surface area and microporous surface area were the largest, with the specific surface area and microporous surface area being 52.54 m 2 / g and 35.81 m 2 / g respectively. At the same time, the O / C ratio in the pharmaceutical sludge biochar was 0.92, and the hydrophilicity was relatively low.

[0040] During the cultivation process, aerobic granular sludge gradually formed in both reactors. Among them, when R1 was cultivated to 17 days, small particles were observed through a microscope, and mature aerobic granular sludge was formed on the 30th day.

[0041] Sludge flocs did not appear in the system, replaced by dark brown particles. At this time, the average particle size of the particles was 200 μm; while only small particles appeared in R2 on the 30th day, and during the formation process, filamentous bacteria gradually multiplied in large numbers, and the particle structure was loose. As Figure 1 shown, it shows that adding pharmaceutical sludge biochar can significantly improve the granulation process of aerobic granular sludge. For R1 with added pharmaceutical sludge biochar, after 160 days of cultivation, the main elemental composition changes of aerobic granular sludge are shown in Table 1.

[0042] Table 1 Main elemental changes of aerobic granular sludge in the R1 group with added pharmaceutical sludge biochar.

[0043]

[0044]

[0045] According to Table 1, the effect of pharmaceutical sludge biochar on particles is long-term, and it can also improve particle strength to maintain long-term stability of the system. After constructing two identical SBR experimental devices R1 and R2, it was found that after particles were formed in the two reactors, the system's pollutant removal performance was stabilized to 90%. After that, the system was operated for 200 days. At the end of the operation, the ammonia nitrogen removal performance of R2 dropped to 70%, and the total nitrogen removal performance was only 50%. In the R1 reactor, the removal efficiency was 90% and 70%, respectively, and the COD removal efficiency was 90%.

[0046] As a control, this example also replaces the pharmaceutical sludge with municipal sludge and chicken manure, prepares municipal sludge biochar and chicken manure biochar under the same conditions, and then uses the municipal sludge biochar and chicken manure biochar for low-carbon wastewater and low carbon-nitrogen ratio wastewater treatment.

[0047] Under the same conditions, it was found that the biochar prepared with municipal sludge and chicken manure as raw materials had a longer culture time when used for low-carbon wastewater, and the aerobic granular sludge had filamentous bacteria and a loose structure. After testing and analysis, the possible reason is that the composition of pharmaceutical sludge is complex and contains a large amount of discarded drugs. After testing, the pharmaceutical sludge biochar prepared by the present invention contains Ca 2+ Mg 2+ , Fe 2+ In addition, the O / C of the pharmaceutical factory sludge biochar itself is relatively large, so during the cultivation of activated sludge, the particle formation time of particles under low-intensity wastewater conditions can be shortened, and it is conducive to the formation of stable aerobic granular sludge. In addition, the activated pharmaceutical factory sludge biochar also has a higher specific surface area and micropore surface area.

[0048] Example 2

[0049] This embodiment is used for the aerobic granular sludge cultivation method for treating actual domestic wastewater from a factory. The system influent is domestic wastewater from a factory, and the influent COD is 50-250 mg / L, ammonia nitrogen is 30-60 mg / L, TP is 2-6 mg / L, and SS is 100-200 mg / L. The method comprises the following steps:

[0050] A cylindrical sequencing batch reactor is used, with an inner diameter of 1.2m, an effective height of 2m, and an effective volume of 2.3m 3 , height-to-diameter ratio (H / D) is 1.7, fan frequency is 30Hz, which is used to represent aeration intensity; water enters the reactor from the bottom and drains from the middle, and the volume exchange law is 50%, wherein water intake, aeration, sedimentation, drainage, standing and other processes are set according to test needs and automatically controlled by the controller; the reaction device operates outdoors, the temperature is not controlled, and changes with the ambient temperature.

[0051] The system operates in the SBR mode, running 8 cycles per day, with each cycle lasting 3 hours. The specific operation mode for a single cycle is as follows: influent for 10 minutes, anoxic for 50 minutes, aerobic (aeration) for 79 minutes, sedimentation for 30 minutes, drainage for 10 minutes, and static settling for 1 minute. The inoculated sludge is activated sludge, presenting a yellow, loose flocculent structure.

[0052] In the initial startup stage of the system, 2.5 g / L of activated sludge was inoculated into the reactor, and 1 kg of pharmaceutical plant sludge biochar was added for the cultivation of AGS.

[0053] During the cultivation process, aerobic granular sludge wrapped by pharmaceutical plant sludge biochar was formed in the reactor on the 20th day. The granular structure was dense. On the 30th day, it was found that large granules occupied the entire reactor, indicating the maturity of aerobic granular sludge. By the 134th day, a large number of filamentous bacteria were found to multiply, and the granular structure became loose. Subsequently, 1 kg of pharmaceutical plant sludge biochar was added to the system. On the 168th day, aerobic granular sludge was observed under an electron microscope to be ellipsoidal in shape, with a clear outline and the disappearance of filamentous bacteria. The granular morphology was as Figure 2 shown.

[0054] In the initial stage of reactor operation, the pollutant removal performance of the system fluctuated greatly. Among them, the COD removal rate was 50 - 80%, the ammonia nitrogen removal rate was 0 - 20%, and the TP removal rate was 100%. When the granules matured, the ammonia nitrogen removal rate was relatively low. The system cycle time was extended to 4 hours, and it ran 6 cycles per day. The specific operation mode for a single cycle was as follows: influent for 8 minutes, anoxic for 49 minutes, aerobic (aeration) for 149 minutes, sedimentation for 24 minutes, drainage for 7 minutes, and static settling for 3 minutes. At the same time, 1 kg of pharmaceutical plant sludge biochar was added to the system. At this time, the COD and ammonia nitrogen removal efficiencies of the system reached 90% and 100% respectively. The effluent COD concentration was 30 mg / L, and the ammonia nitrogen was 0 mg / L, both meeting the first-class A standard of the National Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants.

[0055] By the 360th day of stable operation of the system, under low-temperature conditions (average winter temperature below 10°C), the activities of bacteria such as AOB and NOB were inhibited, and the ammonia nitrogen removal performance was affected. However, the granular morphology remained dense. The addition of pharmaceutical plant sludge biochar could form granules under the condition of a low carbon-nitrogen ratio and improve the shock resistance ability of the system.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A rapid cultivation method for aerobic granular sludge, characterized in that: The method includes the following steps: (1) Using pharmaceutical factory sludge as raw material, after drying and pulverizing, pyrolyzing in a nitrogen atmosphere to prepare pharmaceutical factory sludge biochar; (2) Inoculating the pharmaceutical factory sludge biochar prepared in step (1) into activated sludge, constructing an SBR experimental device, starting the reactor to add the pharmaceutical factory sludge biochar and then inoculating the activated sludge, and culturing aerobic granular sludge to obtain aerobic granular sludge; The dosage of the pharmaceutical factory sludge biochar is added according to the mass ratio of pharmaceutical factory sludge biochar:activated sludge = 1:3, and the particle size of the added pharmaceutical factory sludge biochar is <50μm.

2. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The temperature of the drying is 103℃ - 105℃.

3. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The pyrolysis conditions in step (1) are: heating from room temperature to the pyrolysis temperature at a heating rate of 0.4 - 0.6L / min.

4. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The pyrolysis temperature is 400 - 600℃, and the pyrolysis time is 2h.

5. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The SBR experimental device consists of a water inlet system, a reactor main body, an aeration system and a water outlet system. The influent is transported from the bottom by a peristaltic pump, and the effluent is discharged from the middle of the reactor by a peristaltic pump; aeration is carried out through the microporous aeration stone at the bottom of the reactor, and the aeration volume is controlled by a rotameter.

6. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: Pump the wastewater into the reactor. The height-diameter ratio of the reactor is 20 - 25, and the reactor operates in the mode of influent - anoxic - aeration - sedimentation - drainage. Pump the low-carbon ratio wastewater into the reactor.

7. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The influent pH is controlled between 7 and 8, and the operating environment temperature of the reactor is controlled at 24 - 26℃ throughout the process.

8. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The influent time is 5min, the anoxic time is 55min, the aeration time is 145 - 170min, the sedimentation time is 5 - 30min, and the effluent time is 5min.

9. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The cycle operation time is 4h, and it operates 6 cycles per day.

10. The rapid cultivation method of aerobic granular sludge according to claim 1, characterized in that: The volume exchange rate of the reactor is 10 - 50%, the hydraulic retention time is 8h, and the aeration flow rate is 1.2 - 2.0L / min.

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