Oxygen-producing cyanobacteria symbiotic granular sludge and rapid cultivation method thereof

Abstract

The present application relates to sewage biological treatment technical field, specifically relates to a kind of self-production oxygen bacteria algae symbiosis granular sludge and its rapid culture method.The present application includes the following sequentially performed steps: taking activated sludge of municipal wastewater treatment plant aeration tank, after pretreatment, obtain homogeneous activated sludge suspension;The activated sludge suspension is placed in transparent sealed container, and the activated sludge suspension is subjected to light treatment under static state, and self-production oxygen bacteria algae symbiosis granular sludge is obtained.The technical scheme can solve the problems of high energy consumption of mechanical aeration or stirring in the process of granular sludge formation, long-term operation instability of system, etc., and can overcome the technical bottlenecks of weak solid-liquid separation capacity, biomass loss, etc.in bacteria-algae symbiotic system.The self-production oxygen bacteria algae granular sludge cultured by the present application has the characteristics of significant energy-saving benefit, compact granular structure, excellent settling performance, outstanding stress resistance, etc., has the advantages of fast granular formation speed and strong granular structure stability, and has great popularization value.

Description

Technical Field

[0001] This invention relates to the field of wastewater biological treatment technology, specifically to a self-oxygenating bacteria-algae symbiotic granular sludge and its rapid cultivation method. Background Technology

[0002] Aerobic granular sludge (AGS) is a granular microbial aggregate formed by the self-aggregation of activated sludge under selective pressure. It possesses advantages such as compact structure, excellent settling performance, and simultaneous nitrogen and phosphorus removal. However, AGS has a long cultivation time and stringent requirements for cultivation conditions, necessitating energy-intensive mechanical aeration to provide sufficient hydraulic shear and dissolved oxygen. Therefore, effectively shortening the start-up period of AGS systems and further developing energy-saving and energy-efficient system construction technologies are current research priorities.

[0003] Algal-bacterial aerobic granular sludge (ABGS) is a novel wastewater treatment system that couples the self-coagulation of aerobic sludge (AGS) with the advantageous characteristics of a bacterial-algae symbiotic system, and has become a cutting-edge technology in wastewater treatment. This novel coupled system can fully utilize the symbiotic relationship between bacteria and algae, such as gas exchange, energy cycling, and metabolic complementarity, to significantly improve wastewater treatment efficiency and restore aquatic ecosystems. However, although this technology can utilize in-situ oxygen production by algae to reduce aeration energy consumption, it still does not escape dependence on external water or airflow shear forces. How to break through conventional methods of cultivating algal-bacterial granular sludge, how to cultivate self-oxygenating algal-bacterial granular sludge under "zero aeration" still water conditions (i.e., conditions without mechanical aeration to provide shear forces), and thus develop an energy-saving and consumption-reducing ABGS system, are urgent problems to be solved in this field. Summary of the Invention

[0004] This invention aims to provide a rapid cultivation method for self-aerobic algae-bacterial symbiotic granular sludge, solving the technical problems of excessive energy consumption and complex operation caused by hydraulic shearing required in existing technologies for cultivating self-aerobic algae-bacterial symbiotic granular sludge. Specifically, this solution breaks through conventional cultivation methods, cultivating self-aerobic algae-bacterial symbiotic granular sludge under "zero aeration" still water conditions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A rapid cultivation method for self-oxygenating bacteria-algae symbiotic granular sludge includes the following steps performed sequentially:

[0007] S1: Take activated sludge from the aeration tank of a municipal wastewater treatment plant and obtain a homogeneous activated sludge suspension after pretreatment.

[0008] S2: Place the activated sludge suspension in a transparent sealed container, and apply light treatment to the activated sludge suspension while it is in a static state to obtain self-oxygenating bacteria and algae symbiotic granular sludge.

[0009] This solution also provides a rapid cultivation method for self-aerobic algae symbiotic granular sludge to obtain self-aerobic algae symbiotic granular sludge.

[0010] The principles and advantages of this scheme are:

[0011] This technical solution proposes a method for the spontaneous formation and rapid cultivation of self-aerobic algae-bacterial symbiotic granular sludge from flocculent activated sludge under still water conditions (i.e., zero aeration) and by controlling external factors. This method enables the rapid cultivation of algae-bacterial symbiotic granular sludge under aeration or agitation-free conditions. The self-aerobic algae-bacterial symbiotic granular sludge cultivated by this method has significant advantages, including no need for mechanical aeration or agitation, compact granular structure, large average particle size, and strong oxygen production capacity. This has positive implications for reducing energy consumption and improving biomass resource recovery, aligning with the green and low-carbon development concept.

[0012] In self-aerobic algae symbiotic granular sludge, the granules possess a unique granulation process and layered structure. Oxygen produced by algal photosynthesis provides dissolved oxygen to the surrounding substrate and also creates a dissolved oxygen concentration gradient within the granules, supplying nitrifying bacteria, polyphosphate-accumulating bacteria, and other microorganisms to degrade organic matter, achieving simultaneous nitrogen and phosphorus removal. Simultaneously, secondary metabolites and inorganic carbon produced by bacterial respiration can maintain the algal growth, metabolic activity, and photosynthesis. The complex interactive network between bacteria and algae enables microbial growth and sludge granulation under still water conditions through the exchange and utilization of substances. This synergistic symbiotic relationship between bacteria and algae lays an important foundation for improving wastewater treatment efficiency and reducing energy consumption.

[0013] Under closed-circuit lighting conditions, after several days of static cultivation, filamentous cyanobacteria in the flocculent sludge system intertwine and connect, forming a cushion-like active layer around the originally loose activated sludge flocs. During the cultivation process, the microbial community structure undergoes succession, and the filamentous cyanobacteria gradually grow and accumulate. A thin layer of sticky extracellular polymers adheres to the surface of the filamentous cyanobacteria, which not only maintains the structural stability of the photosynthetically active cushion-like interwoven layer but also facilitates the sliding movement and entanglement of the filamentous cyanobacteria. Ultimately, through the contraction and entanglement of the filamentous cyanobacteria and the coagulation-promoting effect of the extracellular polymers, a compact, well-settling, and oxygen-producing self-oxygenating algae-bacterial symbiotic granular sludge is formed. In this scheme, the formation process of the self-oxygenating algae-bacterial symbiotic granular sludge is divided into four stages: sludge compaction period, photosynthetic organism reproduction period, cushion layer contraction period, and granule formation period.

[0014] In summary, by cultivating self-aerobic algae-bacterial symbiotic granular sludge in a closed, light-illuminated photobioreactor, rapid granulation of flocculent sludge can be achieved in an aeration-free environment. The beneficial effects of this technical solution are:

[0015] (1) This solution provides a rapid cultivation method for self-oxygenating bacteria and algae symbiotic granular sludge under static water conditions, which will help promote the substantial transformation of the continuous flow bacteria and algae granular sludge cultivation process from "requiring mechanical energy consumption" to "zero mechanical energy consumption", and has significant energy-saving effects.

[0016] (2) The self-oxygenating bacteria-algae symbiotic granular sludge cultivated using this scheme is conducive to the aggregation of microorganisms due to the entanglement of filamentous cyanobacteria and the adhesion of extracellular polymers produced by algae and bacteria, thus achieving rapid granulation of the self-oxygenating bacteria-algae symbiotic granular sludge (20-30 days).

[0017] (3) The self-aerobic algae symbiotic granular sludge cultivated using this method has a relatively large average particle size (10-20 mm), compact particle structure (integrity coefficient 10-40%), and excellent settling performance (SVI). 30 It has advantages such as a production capacity of 20-60 mL / g and a strong oxygen production capacity (oxygen production rate of 10-25 mg O2 / g biomass-h).

[0018] (4) The self-oxygenating bacteria-algae symbiotic photobioreactor and cultivation system of this scheme have a simple structure and are easy to operate, which can achieve the purpose of energy saving and consumption reduction. The self-oxygenating bacteria-algae symbiotic granular sludge cultivated by the above method using this system is expected to be used as inoculated sludge to quickly start the continuous flow bacteria-algae symbiotic system, which is easy to apply in engineering technology.

[0019] Furthermore, in S1, the pretreatment method includes: passing the mixture through an 80-100 mesh sieve 3-5 times; adjusting the pH value to 6.5-8.5; stirring at 60-100 r / min for 5-10 min at 20-35℃ to obtain a homogeneous mixed liquor with a suspended solids concentration of 1.0-4.5 g / L.

[0020] Furthermore, in S1, the water quality indicators for the activated sludge suspension are: COD: 10-40 mg / L, NH4+: 10-40 mg / L. + -N: 5-20 mg / L, NO2 — -N: 2-5 mg / L, NO3 — -N: 2-8 mg / L, PO4 3- -P: 1-6 mg / L.

[0021] Furthermore, in S1, the method for measuring the water quality indicators of the activated sludge suspension is as follows: first, filter the solution using filter paper with a pore size of 0.45 μm, and then measure COD and NH4. +-N, NO2 - -N, NO3 - -N,PO4 3- -P content.

[0022] The realization of granulation of flocculent sludge under still water conditions is an important discovery in granular sludge technology research. The concentration of activated sludge and water quality conditions have a significant impact on the formation process and particle size of granular sludge with symbiotic aerobic bacteria and algae. Too low or too high concentrations will affect the competition for nutrients between filamentous cyanobacteria and other symbiotic bacteria, affect the enrichment of filamentous cyanobacteria, and thus affect the formation rate of granular sludge.

[0023] Furthermore, in S2, the transparent sealed container is a photobioreactor with an effective volume of 15-30 mL; the inoculum amount of activated sludge suspension is 50-60% of the effective volume.

[0024] In their extensive preliminary experiments, the inventors discovered that, under closed, still-water conditions with illumination, the sludge inoculum size of the photobioreactor needs to be manually controlled to achieve rapid granulation of flocculent sludge. By altering the sludge inoculum size, the food-to-microbe ratio (F / M) within the reactor is balanced, utilizing the nutrients in the wastewater to create an environment suitable for microbial growth and the enrichment of filamentous cyanobacteria, ultimately achieving rapid granulation of the flocculent sludge.

[0025] Furthermore, in S2, the light treatment applies a full-day light intensity of 3000-8000 Lux to the activated sludge suspension.

[0026] Furthermore, the ambient temperature during the light treatment is 20-35℃, and the light treatment time is 20-30 days.

[0027] The operating conditions of the reactor, namely light intensity, have a significant impact on the growth status and motility of filamentous cyanobacteria. By selecting an appropriate parameter range, the rapid formation of self-oxygenating bacteria-algae symbiotic granular sludge can be achieved.

[0028] Furthermore, the self-oxygenating bacteria-algae symbiotic granular sludge consists of compact granules with an outer layer of intertwined filamentous cyanobacteria, and an average particle size of 10-20 mm.

[0029] Furthermore, the settling performance (SVI) of the self-oxygenating bacteria-algae symbiotic granular sludge is improved. 30 The concentration is 20-60 mL / g, the integrity coefficient is 10-40%, and the oxygen production rate is 10-25 mg O2 / g biomass-h.

[0030] In summary, the rapid cultivation method of this technical solution is roughly as follows: Fresh activated sludge is taken from the aeration tank of an urban wastewater treatment plant, pretreated to obtain a homogeneous sludge suspension with a mixed liquor suspended solids concentration (MLSS) of 1.0-4.5 g / L, and the water quality is recorded using standard methods, and then used as inoculum for the reaction; several photobioreactors are prepared, and the inoculum biomass volume is controlled within the optimal range (the inoculum volume is 50-60% of the photoreactor volume); under undisturbed still water conditions, i.e., in a static environment where mechanical aeration is not required to provide hydraulic shear force, external factors are controlled, and the photobioreactors are operated to obtain fully granulated self-oxygenating algae symbiotic granular sludge. This invention breaks through conventional methods of cultivating granular sludge from bacteria and algae. It cultivates self-aerobic bacteria-algae symbiotic granular sludge under "zero aeration" static water conditions (i.e., without the need for mechanical aeration to provide shear force), solving problems such as high energy consumption from mechanical aeration or stirring during granular sludge formation and long-term system instability. It also overcomes technical bottlenecks such as weak solid-liquid separation and easy biomass loss in bacteria-algae symbiotic systems. This technical solution cultivates self-aerobic bacteria-algae symbiotic granular sludge in a closed, light-illuminated photobioreactor, utilizing the symbiotic relationship between bacteria and algae to achieve a substantial shift from "high energy consumption" to "zero energy consumption." The self-aerobic bacteria-algae granular sludge cultivated using this method exhibits significant energy-saving benefits, compact granular structure, excellent settling performance, and outstanding stress resistance, demonstrating high granular stability and strong pollutant removal efficiency, making it highly valuable for widespread application.

[0031] Those skilled in the art generally believe that activated sludge granulation cannot be achieved without providing hydraulic shear force. However, this solution treats fresh flocculent activated sludge in the aeration tanks of municipal wastewater treatment plants. It discovers that under still water conditions, by utilizing the microbial community within the activated sludge and adjusting appropriate conditions, aerobic granular sludge with symbiotic bacteria and algae can be formed, achieving still-water granulation of the flocculent sludge. This technical solution breaks through traditional thinking and technical biases in the field, discovering that activated sludge can be granulated under long-term closed, low-light, and starved conditions, offering significant advantages in pollution reduction, carbon reduction, energy conservation, and consumption reduction.

[0032] While still-water granulation is achievable, inappropriate cultivation methods can lead to slow or even impossible granulation. This solution not only presents an innovative cultivation method as described above but also reveals that adjusting suspended solids concentration (MLSS), water quality conditions (COD and NH4) can significantly impact granulation. + By controlling the nitrogen (N) and external conditions (such as light) within the optimal range, the granulation process can be accelerated. Using this technique, granulation can be achieved in approximately 20 days, with very significant results; no similar reports have been found to date. Attached Figure Description

[0033] Figure 1This is a schematic diagram of the self-oxygenating bacteria-algae symbiotic granular sludge cultivation system of Example 1 of the present invention.

[0034] Figure 2 The images show the state changes at different stages during the cultivation of self-oxygenating bacteria-algae symbiotic granular sludge in Examples 1-4 of this invention. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art: the materials, reagents, etc. used can all be obtained commercially.

[0036] Example 1:

[0037] This example discusses the effect of sludge concentration on granulation, using Test 1 as an example to illustrate the process of preparing aerobic granular sludge with bacterial-algae symbiosis:

[0038] Step 1: Preparation of activated sludge suspension

[0039] (1) Fresh flocculent activated sludge from the aeration tank of a municipal wastewater treatment plant was collected and filtered three times using a 100-mesh sieve to obtain activated sludge with uniform texture. Activated sludge is a general term for microbial communities and the organic and inorganic matter they adhere to; the microbial community mainly includes bacteria, protozoa, and algae. Activated sludge collected from the aeration tank of a municipal wastewater treatment plant is generally flocculent (non-granular), a relatively common sludge form. The inventors collected activated sludge from the aeration tank of a municipal wastewater treatment plant in different seasons (summer, autumn, and winter) for experiments. The results showed that no additional algae (or bacteria) were needed; the microbial community inherent in the activated sludge already met the initial requirements for bacteria and algae to form aerobic granular sludge with bacterial-algae symbiosis. In the subsequent cultivation process, only the reaction environment, such as wastewater concentration, sludge concentration, and light intensity, needs to be controlled to achieve the enrichment of the target filamentous cyanobacteria, thereby achieving static water granulation. The flocculent activated sludge samples used in subsequent experiments of this technical solution were from the same source to ensure experimental parallelism.

[0040] (2) Transfer the filtered activated sludge to a beaker and adjust the sludge concentration according to the optimal MLSS range (1.0-4.5 g / L). Here, the MLSS is selected as 1.2 g / L. Adjust the pH to the optimal concentration range of 6.5-8.5 using HCl and NaOH. Here, it is adjusted to 7.5. Stir the sludge thoroughly at a temperature of 25±3℃ and a stirring speed of 80 r / min to restore its activity, finally obtaining a homogeneous activated sludge suspension. Take a portion of the sludge suspension and filter it through 0.45 μm filter paper. Determine the main water quality indicators using standard methods, according to COD: 10-40 mg / L, NH4+: + -N: 5-20 mg / L, NO2 — -N: 2-5 mg / L, NO3 — -N: 2-8 mg / L, PO4 3- -P: The optimal concentration range of 1-6 mg / L is used to adjust the activated sludge suspension. For example, sodium acetate is added to adjust the carbon source, ammonium chloride is added to adjust the nitrogen source, and dipotassium hydrogen phosphate is added to adjust the phosphorus source. The water quality conditions of the activated sludge suspension can be controlled through conventional artificial adjustments using existing technology, which will not be elaborated further here. If the concentration of a specific substance in the raw water is too high, it can be diluted first and then added according to specific requirements to achieve the desired effect. The nutrient environment in the reactor is adjusted using artificial water distribution; the specific data after adjustment are shown in Table 1.

[0041] Step 2: Inoculate the above-mentioned activated sludge suspension into the photobioreactor.

[0042] Prepare several dry, clean, sealable photobioreactors (e.g., transparent bottles with lids), each with an effective volume of 25 mL. An aerobic algae-bacterial symbiotic granular sludge cultivation system is a standard existing technology; simply place the aforementioned photobioreactors in an incubator with controllable light and temperature (see [reference]). Figure 1 Avoid excessive shaking of the reactor during inoculation. After inoculation, use a rubber stopper or a threaded cap to ensure the reactor is sealed.

[0043] The inoculation volume of the activated sludge suspension is 50-60% of the reactor volume. In this example, 15 mL of sludge-water mixture (activated sludge suspension) was inoculated. After inoculation, the photobioreactor was sealed, and the reactor was kept free from vibration.

[0044] Step 3: Operation of the photobioreactor

[0045] The inoculated photobioreactor was operated in a closed, still-water environment with a temperature of 25±3℃ and a light intensity of 5500 Lux (full-day illumination, without light-dark alternation). The experimental results were observed and recorded periodically until the self-generating aerobic bacteria and algae granular sludge was completely granulated. The granulation process includes the following stages (see...). Figure 2 , Figure 2 The samples shown were prepared according to the method of Test 1): (1) Sludge compaction period (the sludge is yellowish-brown flocculent, goes through two stages of sludge floating and sinking, and is compacted; time 0-3 days); (2) Photosynthetic organism reproduction period (green fluorescent substances appear on the surface of the compacted yellowish-brown flocculent sludge, at which time green algae begin to reproduce, and then filamentous blue algae gradually appear on the outer layer of the sludge, and the sludge is green and compacted; time 4-9 days); (3) Mat shrinkage period (green algae lose their competitive advantage, filamentous blue algae continue to grow and reproduce, wrap around the outer layer of the particles, causing the sludge to shrink inward and separate from the reactor wall, and the sludge is mat-like; time 10-18 days); (4) Particle formation period (filamentous blue algae are enriched in large quantities, and the sludge gradually becomes granular, with good settling performance, compact and stable particle structure, and not easy to loosen or break; the standard for complete granulation: forming particle shape, particle integrity coefficient of 10-40%, SVI 30 The concentration is 20-60 ml / g; the time is 19-22 days. The particle integrity coefficient refers to the ratio of the supernatant concentration to the initial total biomass concentration after centrifuging the granular sludge at 12000 rpm. The smaller the value, the higher the particle integrity coefficient and the more compact the particle structure.

[0046] In Test 1 of Example 1, after 20 days of cultivation, granular sludge had formed and settled to the bottom of the liquid matrix in the photobioreactor. The average particle size was 12 mm, with a compact structure and the granules were covered with a large number of intertwined green filamentous cyanobacteria. In this example, COD, suspended solids concentration (MLSS), average particle size, nitrogen, phosphorus, and other technical indicators were all measured using national standard analytical methods.

[0047] Tests 2, 3, and 4 follow the same steps as Test 1, except for the parameter settings for sludge concentration, as detailed in Table 1.

[0048] Table 1: Parameter settings and product performance test results for tests 1-4 in Example 1.

[0049]

[0050] As shown in Table 1, the self-aerobic algae symbiotic granular sludge prepared by the above method has advantages such as larger particle size, compact particle structure, and smaller integrity coefficient. It overcomes the technical bottlenecks of aerobic granular sludge systems and suspended algae symbiotic systems, such as the need for high-energy-consumption aeration to provide hydraulic shear force, stringent requirements for particle formation, and easy loss of biomass. Under the sliding motion of filamentous cyanobacteria and in a closed, light-filled environment, initial coagulation nuclei are rapidly formed, accelerating the sludge granulation process.

[0051] In the data in Table 1, Test 1 first formed dense, self-oxygenating algal granular sludge, which had excellent settling performance and could greatly reduce the problem of easy loss of biomass. Its high oxygen production rate made a great contribution to the removal of pollutants. Within the optimal sludge concentration range (1.0-4.5 g / L, more preferably 1.2-3.5 g / L), Test 2, due to its higher sludge volume, formed larger granular sludge, but at the same time, it required more enrichment and entanglement of filamentous cyanobacteria to achieve the effect of sludge aggregation. The algae were covered by sludge, resulting in a lower oxygen production rate than Test 1.

[0052] Excessively high or low sludge concentrations significantly impact the rapid formation of granules. In Test 3, the low initial biomass necessitated a longer growth time for filamentous cyanobacteria to accumulate. While granulation was eventually achieved, this increased the time required for granule formation, negatively affecting sludge settling performance and increasing the risk of biomass loss. Furthermore, the lower extracellular polymeric content resulted in a higher granule integrity coefficient in Test 3, which is detrimental to long-term granule stability. In Test 4, while excessively high sludge concentrations led to earlier algal blooms, the high concentration also resulted in the algae being encased in sludge, preventing them from receiving sufficient light and ultimately hindering granular sludge formation.

[0053] Example 2

[0054] This example study investigated the impact of wastewater quality on granulation. Test 1 in this example is the same as Test 1 in Example 1. Tests 2-7 in this example involved different settings of wastewater quality parameters based on Test 1. See Table 2 for details.

[0055] Table 2: Parameter settings and product performance test results for tests 1-7 in Example 2.

[0056]

[0057] Wastewater quality serves as a primary nutrient source for the growth of microorganisms within sludge, providing abundant nutrients for the growth and reproduction of bacteria and algae. Through extensive preliminary experiments, the applicant discovered that COD and ammonia nitrogen in wastewater have a significant impact on the rapid formation of granules.

[0058] In Test 1, the earliest formation of bacterial-algal granular sludge aggregates was observed. Within the optimal wastewater concentration range, appropriate changes in COD and ammonia nitrogen concentrations did not significantly affect the success of granulation or the performance of the bacterial-algal granules; oxygen production rate and sludge settling performance were not significantly affected. A moderately increased COD concentration (Test 2) promoted microalgal growth to some extent, stimulating bacteria to secrete more extracellular polymers, thus leading to an increase in the granulation integrity coefficient. A moderately increased ammonia nitrogen concentration (Test 5) also put filamentous cyanobacteria at a disadvantage in competition with microalgae, slightly prolonging the granulation process, but within an acceptable range. However, if water quality conditions exceed or fall below the optimal wastewater concentration range (COD: 10-40 mg / L, preferably 20-35 mg / L; NH4+), the formation of granulation may be significantly affected. + -N (5-20 mg / L, preferably 10-20 mg / L) has a significant impact on the process of particle formation.

[0059] In tests 4 and 7, excessively high COD or ammonia nitrogen concentrations prevented granulation. The inventors analyzed that these conditions put filamentous cyanobacteria at a disadvantage in competition with microalgae, preventing the accumulation of self-aggregating filamentous cyanobacteria and ultimately failing to form granular sludge. In tests 3 and 6, lower COD or ammonia nitrogen concentrations resulted in excessively long granulation times or failure to achieve granulation. The inventors analyzed that this was due to a lack of sufficient growth substrate for microorganisms, requiring a very long start-up phase for granulation, or the loss of a dominant ecological niche for filamentous cyanobacteria, leading to a lower oxygen production rate. Data showed that carbon and nitrogen sources are crucial for algal growth. Within the optimal concentration range, lower or higher COD and ammonia nitrogen concentrations did not significantly affect granulation formation, but they did hinder rapid granulation. Excessive or insufficient COD or ammonia nitrogen concentrations prevented granulation, making proper water quality control essential for rapid granulation formation.

[0060] Example 3

[0061] This example studies the effect of light intensity on granulation. Test 1 differs from Test 1, Test 2, 3, 4, and 5 of Example 1 in the setting of the light intensity parameter, as detailed in Table 3.

[0062] Table 3: Parameter settings and product performance test results for tests 1-5 in Example 3

[0063]

[0064]

[0065] Light intensity, as a crucial indicator of algal growth, significantly regulates the enrichment of different algae. Suitable light intensity is essential for the growth of filamentous cyanobacteria. Within the optimal light range, slightly lower or higher light intensities do not significantly affect granulation. Granular sludge was formed in tests 1, 2, and 3, with no significant difference in the number of days. Higher or lower light intensities did not cause filamentous cyanobacteria to lose their competitive advantage over other algae; in fact, they stimulated the oxygen production rate of the granular sludge and encouraged the microorganisms to produce more extracellular polymers, enhancing granule integrity. However, once the optimal light range (3000-8000 Lux) is exceeded, both excessively low and high light intensities severely impact the granulation process and the achievement of active granules. In tests 4 and 5, excessively high or low light intensities significantly slowed the granulation process. Although granules with a diameter of 25-30 mm could be formed after 50-60 days, the granule integrity coefficient and SVI (Special Viable Index) remained low. 30 The oxygen production rate and other parameters are far from ideal; granulation can be barely achieved, but the cycle is too long and the performance of the active particles is unsatisfactory, failing to meet application requirements. The inventors analyzed the reasons as follows: excessively low light intensity leads to extremely slow growth of filamentous cyanobacteria, greatly reducing the granulation process, while excessively high light intensity causes filamentous cyanobacteria to grow into the interior of the particles, resulting in poor particle performance, especially with an integrity coefficient far exceeding that of granular sludge cultivated under optimal light intensity.

[0066] Based on Examples 1-3, this solution proposes a novel process for granulating flocculent sludge under static, light-only conditions without aeration. In the transition from activated sludge to granular sludge technology in wastewater treatment, while technological upgrades continuously improve processing capacity, all processes require extensive aeration to ensure quality. For example, activated sludge requires significant aeration to maintain normal microbial function, and granular sludge requires substantial aeration as selective pressure to achieve granulation. This has created a technological bias in the field that granular sludge cultivation must involve aeration or be conducted under non-static conditions. However, through extensive experimental research, the inventors unexpectedly discovered that for flocculent sludge, by controlling certain light and other parameters, relatively rapid granulation can be achieved under static, non-aeration, non-stirring conditions, forming aerobic granular sludge with symbiotic bacteria and algae. This technical solution overcomes the existing technological bias and solves problems such as high energy consumption and long-term system instability associated with mechanical aeration or stirring.

[0067] This technical solution enables the granulation of sludge from various sources in general social sectors under still water conditions. During the cultivation process, the key technical factors determining the granulation speed and particle quality performance are: sludge concentration (MLSS of activated sludge suspension), light intensity, and nutrients (water quality conditions). These three factors are controllable and adjustable, offering strong operability and controllability. Still water granulation is achieved by artificially controlling the environment during cultivation to enrich filamentous cyanobacteria (the key to still water granulation). Since activated sludge is a microbial complex containing algae, bacteria, and other types of microorganisms, this technical solution allows for granulation without the addition of any algae or other microorganisms, further reducing future investment. The optimal light intensity range used in this solution enables spontaneous enrichment of filamentous cyanobacteria. Outside of this optimal light intensity range, granulation is achieved very slowly (the enrichment effect is extremely slow), or even impossible. Among the nutrient concentration ranges (water quality conditions), carbon source (reflected in COD value) and ammonia nitrogen concentrations had the most significant impact on the enrichment of filamentous cyanobacteria, thus affecting the granulation process. Simultaneously, the concentration of flocculent sludge suspension also significantly affected the granulation process.

[0068] The inventors discovered the phenomenon of still-water granulation, overcoming the biases of existing technologies. Through extensive research, the inventors also discovered that the process and quality of this still-water granulation can be artificially controlled, making it highly operable and practical. Therefore, the commonly used continuous flow activated sludge process (which is generally considered to lack sufficient hydraulic shear to form granular sludge) can also achieve granulation of flocculent sludge using this method, significantly reducing the footprint of wastewater treatment equipment and the consumption of energy (such as electrically powered aeration) in wastewater treatment. Therefore, the main innovations of this technology are: the discovery that flocculent sludge can be granulated without aeration (i.e., without hydraulic shear); and the establishment of a method for controlling external conditions to achieve still-water granulation.

[0069] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for rapid cultivation of a self-oxygen-producing cyanobacterial granular sludge, characterized by, The method comprises the following steps in sequence: S1: taking activated sludge from an aeration tank of a municipal wastewater treatment plant, and obtaining homogeneous activated sludge suspension after pretreatment; The pretreatment method comprises the following steps: passing through a 80-100 mesh sieve for 3-5 times; adjusting the pH value to 6.5-8.5, stirring at 20-35 ℃ and 60-100 r / min for 5-10 min, and obtaining the activated sludge suspension with a homogeneous mixed liquid suspended solid concentration of 1.0-4.5 g / L; S2: placing the activated sludge suspension in a transparent sealed container, and applying light treatment to the activated sludge suspension in a static state to obtain the oxygen-producing bacteria and algae symbiotic granular sludge; The sealed container is a photobioreactor with an effective volume of 15-30 mL; and the inoculation amount of the activated sludge suspension is 50-60% of the effective volume; The light treatment applies full-day light with a light intensity of 3000-8000 Lux to the activated sludge suspension; the environmental temperature during the light treatment is 20-35 ℃, and the light treatment time is 20-30 days; The obtained oxygen-producing bacteria and algae symbiotic granular sludge is a compact structure granule with an outer layer covered by interwoven filamentous cyanobacteria.

2. The method according to claim 1, wherein the method is characterized by, In S1, the water quality indicators of the activated sludge suspension are: COD: 10-40 mg / L, NH4 + -N: 5-20 mg / L, NO2 - -N: 2-5 mg / L, NO3 - -N: 2-8 mg / L, PO4 3- -P: 1-6 mg / L.

3. The method according to claim 1, wherein the method is characterized by, In S1, the method for measuring the water quality index of the activated sludge suspension is: first, filter using filter paper with a pore size of 0.45 μm, and then measure COD, NH4 + -N, NO2 - -N, NO3 - -N, PO4 3- -P content.

4. The oxygen-producing bacteria and algae symbiotic granular sludge obtained by the method according to any one of claims 1-3.

5. The self-producing oxygen bacteria and algal symbiotic granular sludge obtained by the rapid culture method of self-producing oxygen bacteria and algal symbiotic granular sludge according to claim 4, characterized in that, The oxygen-producing bacteria and algae symbiotic granular sludge is a compact structure granule with an outer layer covered by interwoven filamentous cyanobacteria, and the average particle size is 10-20 mm.

6. The self-producing oxygen bacteria and algal symbiotic granular sludge obtained by the rapid culture method of self-producing oxygen bacteria and algal symbiotic granular sludge according to claim 5, characterized in that, Its settling performance SVI 30 was 20-60 mL / g, the integrity factor was 10-40%, and the oxygen production rate was 10-25 mg O2 / g biomass-h.

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