Method for rapidly starting shortcut nitrification of algal-bacterial symbiotic system

Abstract

The invention discloses a method for rapidly starting short-cut nitrification of an algal-bacterial symbiotic system. The method comprises the following steps: constructing calcified nitrified sludge with high calcium carbonate content through long-term high-alkalinity treatment, introducing the calcified nitrified activated sludge as a functional flora into an algal-bacterial symbiotic system, and dispersing high-intensity incident light into multiple beams of moderate-intensity light under high light intensity by using a light scattering effect driven by CaCO3, and soluble polysaccharide and humic acid in the extracellular polymer are induced to enhance the light buffering capability, and meanwhile, by promoting intracellular and extracellular electron transfer and enhancing an antioxidant defense system, dissipation of photo-induced electrons is accelerated, oxidative stress damage is relieved, the ammoxidation activity is maintained, and short-cut nitrification is rapidly started. According to the method disclosed by the invention, the nitrification rate as high as 18.17 mg.NH4 < + >-N.L <-1 >. H <-1 > can be realized under high light intensity, and the nitrite accumulation rate as high as 100% can be realized.

Description

Technical Field

[0001] This invention belongs to the field of wastewater biological treatment technology, and relates to a method for rapidly starting up short-cut nitrification in a bacterial-algae symbiotic system. Background Technology

[0002] In recent years, algae-microbe symbiotic systems have attracted much attention as an energy-saving and low-carbon wastewater treatment technology due to their ability to utilize the natural synergistic effects between microorganisms and microalgae. Theoretically, this system can significantly reduce aeration energy consumption and external carbon source requirements, while achieving carbon fixation and biomass resource recovery. However, in practical engineering applications, the stable operation of algae-microbe symbiotic systems still faces a series of challenges, among which system fluctuations caused by light conditions are particularly prominent. Specifically, microalgae cause the system pH to rise during photosynthesis, typically reaching above 9.0. This alkaline environment interferes with the transmembrane proton gradient of nitrifying bacteria and inhibits the activity of their key enzymes, thus adversely affecting ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Meanwhile, strong light conditions induce the generation of large amounts of reactive oxygen species, causing oxidative damage to cell membranes, functional proteins, and nucleic acids, further disrupting the electron transport chain and interfering with energy metabolism, ultimately inhibiting chemoautotrophic nitrification (Yang M, Qiu S, Wang L, et al. Effect of short-term light irradiation with varying energy densities on the activities of nitrifiers in wastewater [J]. Water Research, 2022, 216: 118291.). Therefore, how to improve the stress resistance of nitrifying bacteria under the dual stress of strong light and high pH has become a key issue in promoting the practical application of algal-microbe symbiosis technology.

[0003] In traditional understanding, calcium carbonate precipitation in activated sludge systems is generally considered a detrimental factor, as it is believed to occupy microbial niches, hinder substrate-oxygen mass transfer, and reduce the abundance of functional microbial communities. However, current research on the role of calcium carbonate in activated sludge systems mainly focuses on its inhibitory effect on microbial activity. For example, calcium carbonate deposition occupies space available for microbial attachment, reduces the density of functional microorganisms, and impedes substrate-oxygen diffusion, thus hindering the maintenance of functional bacterial activity (Yu T, Tian L, You X, et al. Deactivation mechanism of calcified anaerobic granule: Space occupation and pore blockage [J]. WaterResearch, 2019, 166: 115062.). However, the potential for activated sludge to enhance its resistance to light stress through bacterial self-mineralization lacks systematic exploration. Therefore, conducting research on the enhancement of algal-microbe symbiotic systems based on biomineralization strategies is not only of significant scientific importance but also provides a new solution for the stable operation of this technology under high light intensity environments. Summary of the Invention

[0004] To address the problem of decreased nitrogen removal efficiency of nitrifying bacteria in algae-microbe symbiotic systems due to strong light inhibition, this invention provides a method for rapidly initiating short-cut nitrification in such systems. This method involves acclimating the activated sludge system to a highly alkaline environment to obtain high-performance calcified nitrifying activated sludge. This calcified nitrifying activated sludge is then introduced into the algae-microbe symbiotic system as a functional microbial community. Utilizing the light scattering effect of CaCO3, strong light is dispersed. Furthermore, the light buffering capacity enhanced by soluble polysaccharides and humic acid in the extracellular polymeric substances is improved. Through accelerated electron transfer and effective ROS regulation, antioxidant defense is strengthened, collectively mitigating photo-induced oxidative damage. This significantly improves the system's stability under high light intensity, maintains the structural and functional integrity of the AOB community, and ultimately achieves 18.17 mg·NH4. + -N·L -1 ·h -1 High nitrification rate and 100% high nitrite accumulation rate.

[0005] The technical solution of the present invention is as follows:

[0006] A method for rapidly initiating short-cut nitrification in a microbial-algae symbiotic system is as follows:

[0007] (1) In the nitrification reactor, the activated sludge system is acclimated to a high alkaline environment to induce the accumulation of calcium carbonate in the sludge and obtain calcified nitrified activated sludge. The pH value of the high alkaline environment system is above 9.0.

[0008] (2) Calcified nitrified activated sludge is introduced into the bacterial-algae symbiotic system as a functional microbial community and operated in the sequencing batch reactor mode; during the aeration stage of the sequencing batch reactor, light is applied to the system to achieve rapid start-up of short-range nitrification in the in-situ bacterial-algae symbiotic system.

[0009] Preferably, in step (1), the calcium carbonate content in the calcified nitrified activated sludge is not less than 26% based on calcium element, and the content is an elemental mass percentage (wt%).

[0010] Preferably, in step (1), the influent is synthetic domestic sewage without carbon source, with the following composition: 229.28 mg / L NH4Cl, 21.95 mg / L K2HPO4, 91.2 mg / L MgSO4·7H2O, 11.1 mg / L CaCl2, and 1 mL / L trace element solution; the trace element solution composition is: 1.5 g / L FeCl3·6H2O, 0.18 g / L KI, 0.15 g / L H3BO3, 0.12 g / L LmnCl2·4H2O, 0.12 g / L ZnSO4·7H2O, 0.06 g / L NaMoO4·2H2O, 0.03 g / L CuSO4·5H2O, and 10 g / L LEDTA-2Na.

[0011] Preferably, in step (2), the influent is municipal sewage.

[0012] Preferably, in step (2), the single operating cycle of the sequencing batch reactor is 4.5 hours, and its specific stages include: 5 minutes of water inlet, 1 hour of anoxic stirring, 3 hours of aeration, 20 minutes of settling, and 5 minutes of water outlet.

[0013] Preferably, in step (2), the light intensity is 1.81 kJ·mg. -1 VSS.

[0014] Preferably, in step (2), the initial concentration of calcified and nitrified activated sludge is 1000~2000 mg / L.

[0015] Preferably, in step (2), the dissolved oxygen concentration in the system is maintained at 3.0~4.0 mg / L.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) This invention successfully prepared calcified nitrifying activated sludge with a calcium carbonate content of 26.53% (calculated as elemental calcium) by inducing microbial biomineralization in a long-term highly alkaline environment. A large amount of CaCO3 in this activated sludge adheres to the surface of the bacterial flocs, which can significantly reduce the sensitivity of the functional bacterial community to light intensity through the scattering and shielding effect of incident light, fundamentally improving its light tolerance. At 1.81 kJ·mg -1 Even under high light intensity stress, VSS can maintain a concentration as high as 18.17 mg·L⁻¹. -1 ·h -1 The ammonia nitrogen removal rate is 13.27 times that of traditional activated sludge systems.

[0018] (2) This invention successfully constructed a photosensitive algal symbiotic system based on high-performance calcified nitrifying activated sludge. Under high light intensity, the system simultaneously enhances treatment efficiency and stress resistance by synergistically enhancing intracellular and extracellular electron transfer, improving energy metabolism, and activating an antioxidant defense network. The ammonia nitrogen removal rate during system operation remains above 95%, and it can quickly achieve short-cut nitrification, reaching 100% nitrite accumulation rate within only 8 operating cycles.

[0019] In summary, this invention utilizes the biomineralization process of microorganisms to construct calcified nitrifying sludge with high light tolerance, and rapidly constructs a short-range bacterial-algae symbiotic system using high light intensity. This not only solves the light inhibition bottleneck of the bacterial-algae symbiotic system, but also achieves a significant increase in the denitrification rate, laying a solid foundation for the practical engineering application of this technology. Attached Figure Description

[0020] Figure 1 EDS surface elemental distribution maps of (a) ordinary sludge and (b) calcified sludge, showing the spatial distribution of C, N, O, Al, Si, and Ca; (c) transmission electron microscope image of calcified sludge (scale bar: 1.0 μm); (d) scattering efficiency factor (Q) of ordinary sludge and calcified sludge in the visible light band. sca )distributed.

[0021] Figure 2 The ordinary sludge group, calcified sludge group, and decalcified sludge group were subjected to high light conditions (1.81 kJ·mg). -1 (a) NH4 under VSS irradiation + -N removal rate and the amount of reduction in (b) ammonia monooxygenase (AMO) and (c) nitrite oxidoreductase (NXR) activity.

[0022] Figure 3The changes in extracellular (a) protein, (b) polysaccharide, and (c) total extracellular polymeric substances (EPS) before and after intense light stress; (df) spectra of the three fluorescent components extracted based on three-dimensional fluorescence spectroscopy-parallel factor analysis; (gi) maximum fluorescence intensity of each component (F). max (Changes).

[0023] Figure 4 Before and after intense light stress, the intracellular (a) electron transport system activity (ETSA), (b) adenosine triphosphate (ATP) content, and (c) NAD content were observed in the ordinary sludge group, calcified sludge group, and decalcified sludge group. + The changes in the NADH / NADH ratio, as well as (d) reactive oxygen species (ROS) levels, (e) malondialdehyde (MDA) content, (f) superoxide dismutase (SOD) activity, (g) catalase (CAT) activity, and (h) lactate dehydrogenase (LDH) release rate.

[0024] Figure 5 To determine the concentration of NH4+ in the effluent of the ordinary sludge group and the calcified sludge group systems under continuous strong light irradiation, + -N、(b)NO2 - -N and nitrite accumulation rate (NAR), (c)NO3 - Changes in the concentration of -N. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0026] The reagents used in the following examples are all commercially available.

[0027] Example 1

[0028] Preparation of calcified nitrifying activated sludge with resistance to light stress:

[0029] A continuous flow nitrification reactor was established, with the pH value maintained above 9.0 by an automatic pH controller. Both influent and effluent flow rates were controlled by peristaltic pumps. The reactor influent consisted of carbon-free synthetic domestic wastewater with the following composition: 229.28 mg / L NH4Cl, 21.95 mg / L K2HPO4, 91.2 mg / L MgSO4·7H2O, 11.1 mg / L CaCl2, and 1 mL / L trace element solution. The trace element solution consisted of: 1.5 g / L FeCl3·6H2O, 0.18 g / L KI, 0.15 g / L H3BO3, 0.12 g / L LnCl2·4H2O, 0.12 g / L ZnSO4·7H2O, 0.06 g / L NaMoO4·2H2O, 0.03 g / L CuSO4·5H2O, and 10 g / L LEDTA-2Na. Under long-term operation, high-performance calcified nitrifying activated sludge containing a large amount of calcium carbonate can be obtained through the biomineralization process of microorganisms in a highly alkaline environment. For example... Figure 1 As shown in (a)-(b), the Ca content in calcified nitrifying activated sludge is as high as 26.53%, while the Ca content in ordinary activated sludge is only 0.40%. Figure 1 As shown in (b), a wide CaCO3 coating layer exists on the surface and inside the calcified and nitrified activated sludge flocs, while Figure 1 (c) Transmission electron microscopy imaging further demonstrates the close association between mineral deposits and the extracellular layer. Mie scattering model results in the visible spectral range indicate that the core-shell structure of calcified nitrifying activated sludge produces a higher scattering factor Q at most wavelengths. sca ( Figure 1 (d) Enhanced light scattering and internal shielding effects can effectively reduce the peak irradiance reaching embedded cells.

[0030] Example 2

[0031] Performance verification of calcified and nitrified activated sludge under high light intensity:

[0032] The performance changes and biological responses of ordinary activated sludge, calcified nitrifying activated sludge, and calcified nitrifying activated sludge after decalcification treatment (hereinafter referred to as decalcified sludge) under high light intensity were compared. Specifically, the three types of sludge were washed three times with deionized water to thoroughly remove residual substrate, and 200 ml of each type of sludge was placed in an Erlenmeyer flask. NH4Cl (NH4Cl) was added to each group of sludge. + -N 60 mg / L), aeration should begin immediately after adding the drug, and the concentration should be 1.81 kJ·mg. -1The sludge was treated with high light intensity VSS for 10 h. The decalcified sludge was obtained by vortex rinsing the calcified and nitrified activated sludge sample three times with deionized water (pH 8.0), followed by ultrasonic treatment at a frequency of 20 kHz, power of 2500 W, amplitude of 50%, duration of 5 minutes, and pulse duration of 6 seconds, using a 6 mm diameter needle-shaped titanium probe. After ultrasonic treatment, CaCO3 rapidly precipitated under gravity, while the cells remained suspended in the solution, thus separating the CaCO3 crystals.

[0033] Figure 2 It was shown at 1.81 kJ·mg -1 The changes in nitrification performance of these three types of sludge under high light intensity conditions (VSS). Calcified nitrifying activated sludge showed significantly improved light tolerance, maintaining 18.17 mg·L⁻¹ light intensity even after 3 hours of strong light exposure. -1 ·h -1 The high ammonia nitrogen degradation rate was achieved, with complete ammonia nitrogen removal within 4 hours, while AMO activity remained stable. In contrast, the AMO and NXR activities of ordinary activated sludge and decalcified calcified nitrifying activated sludge both showed a significant decrease, indicating that their nitrification function was severely inhibited under strong light. After 10 hours of strong light stress, as shown... Figure 3 As shown, the EPS content of calcified nitrifying activated sludge remains stable, and the CaCO3 coating on the floc surface effectively maintains structural integrity and reduces the demand for EPS synthesis. Furthermore, calcified nitrifying activated sludge can stably form photoprotective components (such as humic acid) within tightly bound EPS (TB-EPS), thereby mitigating the direct interference of strong light on the sludge system. Meanwhile, as... Figure 4 As shown, the ETSA and ATP contents of the calcified nitrifying activated sludge were significantly higher than those of the other two groups, indicating that it had a stronger energy metabolism maintenance capacity. According to... Figure 4 As can be seen from (d) to (h), the ROS level in the calcified nitrified activated sludge system is low, and the LDH release is significantly less than that of ordinary activated sludge and decalcified sludge, indicating that the sludge structure can effectively alleviate cell damage caused by light stress and maintain the overall stability of the system.

[0034] Table 1. NH4 content of ordinary activated sludge, calcified nitrified activated sludge, and decalcified sludge under strong light. + -N degradation rate and removal rate

[0035]

[0036] Example 3

[0037] Rapid start-up of short-cut nitrification in calcified algal symbiotic systems:

[0038] To establish an in-situ algal symbiotic system, comparative experiments were conducted using both conventional activated sludge and calcified nitrified activated sludge. The initial concentration of both sludge types was 2000 mg / L, the effective reactor volume was 1.0 L, and a sequencing batch reactor (SBR) was used. Each operating cycle was set as follows: 5 min influent, 1 h anaerobic stirring, 4 h aeration, 30 min settling, and 5 min effluent. During the aeration phase, 1.81 kJ·mg / L of activated sludge was applied. -1 Under high-intensity light, the dissolved oxygen concentration was maintained at 3.0~4.0 mg / L. The influent was synthetic municipal wastewater with the following composition: 115.4 mg / L C2H3NaO2, 229.28 mg / L NH4Cl, 21.95 mg / L K2HPO4, 91.2 mg / L MgSO4·7H2O, 11.1 mg / L CaCl2, and 1 mL / L trace element solution. The trace element solution consisted of: 1.5 g / L FeCl3·6H2O, 0.18 g / L KI, 0.15 g / L H3BO3, 0.12 g / L MnCl2·4H2O, 0.12 g / L ZnSO4·7H2O, 0.06 g / L NaMoO4·2H2O, 0.03 g / L CuSO4·5H2O, and 10 g / L EDTA-2Na.

[0039] like Figure 5 As shown, after applying high-intensity light starting on day 16, the conventional activated sludge system immediately experienced a decline in function, with an increase in effluent NH4. + -N concentration gradually increased, reaching 13.75 mg / L by day 24, NH4+ + The -N removal rate dropped to 54.17%, indicating that its nitrification function was severely impaired under light stress. In contrast, the calcified nitrifying activated sludge system showed excellent tolerance under the same light conditions, with lower effluent NH4 levels. + -N remained at a low level, and the system's ammonia nitrogen removal efficiency remained stable, verifying the effectiveness of calcification treatment in protecting the sludge from light. Further observation revealed that the calcified nitrification activated sludge system not only maintained high ammonia oxidation activity under strong light conditions but also exhibited significant inhibition of NOB. Since starting under high light conditions, the system's effluent NO2... - The -N concentration continued to rise, reaching 31.98 mg / L by day 24, and the nitrite accumulation rate could be stably reached and maintained at 100%. This state could be maintained for more than 35 days, achieving rapid start-up and stable maintenance of the short-cut nitrification process.

[0040] In summary, this invention effectively solves the technical challenges of inhibited nitrification and unstable operation of algae-bacterial symbiotic systems under strong light conditions by constructing a calcified nitrifying activated sludge system with high resistance to light stress. This method utilizes calcification treatment to form a stable photoprotective layer on the sludge surface, which not only significantly improves the system's tolerance to high-intensity light and maintains efficient ammonia oxidation activity, but also selectively inhibits NOB activity, achieving rapid start-up and long-term stable operation of the short-cut nitrification process. This invention provides clearly defined process conditions and strong operability, offering a reliable technical solution for enhancing efficient and energy-saving wastewater treatment using short-cut algae-bacterial symbiotic systems under high light intensity conditions.

[0041] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the specific embodiments described above. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0042] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0043] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for rapidly initiating short-cut nitrification in a microbial-algae symbiotic system, characterized in that, Specifically as follows: (1) In the nitrification reactor, the activated sludge system is acclimated to a high alkaline environment to induce the accumulation of calcium carbonate in the sludge and obtain calcified nitrified activated sludge. The pH value of the high alkaline environment system is above 9.

0. (2) Calcified and nitrified activated sludge is introduced as a functional microbial community into the bacterial-algae symbiotic system and operated in the sequencing batch reactor mode; During the aeration stage of the sequencing batch reactor, light is applied to the system to construct a calcified short-range in-situ bacterial-algal symbiotic system.

2. The method according to claim 1, characterized in that, In step (1), the calcium carbonate content in the calcified and nitrified activated sludge is not less than 26% based on calcium element, and the content is an elemental mass percentage.

3. The method according to claim 1, characterized in that, In step (1), the influent is synthetic domestic sewage without carbon source, with the following composition: 229.28 mg / L NH4Cl, 21.95 mg / L K2HPO4, 91.2 mg / L MgSO4·7H2O, 11.1 mg / L CaCl2, and 1 mL / L trace element solution; the trace element solution composition is: 1.5 g / L FeCl3·6H2O, 0.18 g / L KI, 0.15 g / L H3BO3, 0.12 g / L MnCl2·4H2O, 0.12 g / L ZnSO4·7H2O, 0.06 g / L NaMoO4·2H2O, 0.03 g / L CuSO4·5H2O, and 10 g / L EDTA-2Na.

4. The method according to claim 1, characterized in that, In step (2), the influent is municipal sewage.

5. The method according to claim 1, characterized in that, In step (2), the single operating cycle of the sequencing batch reactor is 4.5 hours, and its specific stages include: 5 minutes of water inlet, 1 hour of anoxic stirring, 3 hours of aeration, 20 minutes of settling, and 5 minutes of water effluent.

6. The method according to claim 1, characterized in that, In step (2), the light intensity is 1.81 kJ·mg. -1 VSS.

7. The method according to claim 1, characterized in that, In step (2), the initial concentration of calcified and nitrified activated sludge is 1000~2000 mg / L.

8. The method according to claim 1, characterized in that, In step (2), the dissolved oxygen concentration in the system is maintained at 3.0~4.0 mg / L.

Images