Method for improving in-situ bacteria and algae biofilm formation and nitrogen and phosphorus removal efficiency by high light intensity synchronization

Abstract

The application discloses a method for improving in-situ bacteria and algae biofilm formation and nitrogen and phosphorus removal efficiency by high light intensity synchronization. The method irradiates the suspended in-situ bacteria and algae and the suspended filler under high light intensity, carries out photoassimilation reaction, reduces the total interfacial energy of the suspended in-situ bacteria and algae, and excessively secretes extracellular polymeric substances. The application greatly improves the adhesion of the suspended in-situ bacteria and algae on the filler, promotes the initial colonization of the suspended in-situ bacteria and algae on the filler, and makes the biomass of the biofilm on the filler increase by an average of 548%. Meanwhile, the ammonia nitrogen and phosphorus removal rates of the in-situ bacteria and algae biofilm system are increased by 72.1% and 90.3% respectively. The method has important significance for promoting low-carbon resource treatment of sewage.

Description

Technical Field

[0001] This invention belongs to the field of wastewater resource treatment technology, and relates to a method for simultaneously improving the efficiency of in-situ bacterial and algal biofilm formation and nitrogen and phosphorus removal. Specifically, it relates to a method for simultaneously improving the efficiency of in-situ bacterial and algal biofilm formation and nitrogen and phosphorus removal by utilizing high light intensity. Background Technology

[0002] Algal-microbe symbiotic systems utilize the interaction of functional microorganisms to achieve nutrient recovery, increase system carbon sequestration, and generate high-value-added biological products, representing a promising wastewater resource treatment technology. In-situ algal-microbe systems enriched based on target wastewater exhibit greater adaptability to complex wastewater environments. While flocculent in-situ algal-microbe systems are currently the most widely used form, they suffer from drawbacks such as poor settling properties, long hydraulic retention time, and poor resistance to shock loads. In contrast, in-situ algal-microbe biofilm systems formed by adding suspended packing materials to flocculent in-situ algal-microbe systems show greater application potential.

[0003] Rapid start-up of in-situ algal biofilm systems is one of the key technical challenges in improving their performance. Generally, biofilm formation can be divided into three stages: (i) colonization, where microbial cells move to the carrier surface driven by flowing liquid and subsequently attach to the carrier through various mechanisms (such as non-covalent intermolecular forces); (ii) accumulation, during which the attached cells aggregate through extracellular polymers (EPS) and further grow; and (iii) maturation, where the biofilm matures and stabilizes. EPS (mainly composed of extracellular proteins (PN) and extracellular polysaccharides (PS)) is widely considered to play a crucial role in biofilm development due to its initial adhesion to the surface and subsequent cell aggregation. EPS secretion is primarily influenced by water quality and environmental conditions, and light is a significant environmental factor for in-situ algal biofilm systems. Therefore, it is reasonable to speculate that regulating light intensity can alter the EPS secretion characteristics of in-situ algae and bacteria, thereby affecting their biofilm formation process.

[0004] Currently, research on the effect of light intensity on biofilm formation has yielded inconsistent conclusions. For example, reference 1 indicates that within the studied light intensity range (22–10¹¹ μmol / (m²),... 2High light intensity resulted in the highest biomass of biofilms (Schultze Larissa K.P., Simon Marie-Victoria, Li Tong, et al. High light and carbon dioxide optimize surface productivity in a Twin-Layer biofilm photobioreactor[J]. Algal Research, 2015, 8:37-44). Reference 2 found that biofilm biomass increased with light intensity (approximately 18–144 μmol / (m²)). 2The light intensity initially increased and then decreased (Liao Qiang, Wang Ye-Jun, Wang Yong-Zhong, et al. Formation and hydrogen production of photosynthetic bacterial biofilm under various illumination conditions[J]. Bioresoure Technology, 2010, 101(14):5315-5324). This can be attributed to the varying responses and adaptations of different microbial species to light intensity. Therefore, for complex in-situ bacterial and algal systems, it remains unclear which light intensity control strategy can promote the formation of in-situ bacterial and algal biofilms. Furthermore, most studies use fixed packing materials (such as cellulose ester membranes, carbonated membranes, and polyurethane foam plates) (Wang Yi, Jiang Zeyi, Lai Zhijian, et al. The self-adption capability of microalgae biofilm under different light intensities: Photosynthetic parameters and biofilm microstructures[J]. Algal Research, 2021, 58: 102383; Ye Yangli, Ma Shiyan, Peng Hongyan, et al. Insight into the comprehensive effect of carbon dioxide, light intensity and glucose on heterotrophic-assisted phototrophic microalgae biofilm growth: A multifactorial kinetic model[J]. Journal of Environmental Management, 2023, 325: 116582). However, the hydraulic conditions and light field distribution of biofilm systems containing mobile packing materials are more complex, therefore the conclusions of the above studies are not applicable. More importantly, achieving stable and efficient removal of nitrogen and phosphorus is a key factor affecting the performance of biofilm systems. None of the above studies focused on the effect of light intensity on nitrogen and phosphorus removal, while the light intensity range studied by Zhu Lin et al. (approximately 0–94.75 μmol / (m²)) 2The ammonia nitrogen removal rate of the bacterial-algal biofilm in the ·s)) did not change significantly (about 0.4 mg / L / d), and the effect on phosphorus removal has not yet been reported (Zhu Lin, Che Xuan, Liu Xingguo, et al. Effect of light intensity on bacterial community structure of bacterial-algal symbiotic biofilm [J]. Transactions of the Chinese Society of Agricultural Engineering, 2020, 36(11):241-247). Summary of the Invention

[0005] To address the issues of low efficiency in in-situ algal biofilm formation and inefficient nitrogen and phosphorus removal, this invention provides a method for simultaneously improving the efficiency of in-situ algal biofilm formation and nitrogen and phosphorus removal using high light intensity. This method utilizes high light intensity to irradiate in-situ algal bacteria, simultaneously achieving rapid biofilm formation and efficient nitrogen and phosphorus removal.

[0006] The technical solution of the present invention is as follows:

[0007] The specific steps of the method to simultaneously improve the efficiency of in-situ bacterial and algal biofilm formation and nitrogen and phosphorus removal by utilizing high light intensity are as follows:

[0008] Suspended in-situ bacteria and algae and suspended packing material are introduced into the wastewater, and the mixture is placed under a light intensity ≥180 μmol / (m²). 2 Irradiation under high light intensity (·s) induces photosynthetic reactions, reducing the total interfacial energy of suspended in-situ bacteria and algae and causing excessive secretion of extracellular polymers.

[0009] Preferably, the method for obtaining in-situ bacteria and algae is as follows: actual domestic sewage is mixed with sterilized synthetic domestic sewage at a volume ratio of 1:10, with a light:dark cycle of 14:10 and a light intensity of 54 μmol / (m²) during the light-dark cycle. 2 ·s), and cultured at 25±2℃ to obtain in situ bacteria and algae.

[0010] Preferably, the composition of the synthetic domestic wastewater is as follows: NaAc (230.77 mg / L), NH4Cl (114.64 mg / L), K2HPO4 (21.95 mg / L), and trace element solution (1 mL / L). The trace element solution consists of: 1.5 g / L FeCl3·6H2O, 0.38 g / L MgSO4·7H2O, 0.01 g / L CaCl2, 0.18 g / L KI, 0.15 g / L H3BO3, 0.15 g / L CoCl2·6H2O, 0.12 g / L MnCl2·4H2O, 0.12 g / L ZnSO4·7H2O, 0.06 g / L Na2MoO4·2H2O, 0.03 g / L CuSO4·5H2O, and 10 g / L EDTA.

[0011] Preferably, the synthetic domestic sewage is sterilized at 121°C for 30 minutes.

[0012] Preferably, the biomass concentration of the suspended in-situ bacteria and algae is 580–4080 mg / L, and the total suspended chlorophyll concentration is 4.92–92.89 mg / L.

[0013] Preferably, the filling rate of the suspended packing is 30% (v / v).

[0014] Preferably, the suspended filler is industrial high-density polyethylene, with a diameter of 25 mm, a height of 10 mm, and a density of 0.96 g / cm³. 3 .

[0015] Preferably, the irradiation time under high light intensity is 14 hours.

[0016] Preferably, the photosynthetic reaction is carried out using an SBR process; the SBR process includes influent,

[0017] The process includes light-induced reaction, sedimentation, and drainage.

[0018] The method of this invention exposes suspended in-situ bacteria and algae to high light intensity, reducing their total interfacial energy by 33.8%. No energy barrier was observed at any separation distance between the suspended in-situ bacteria / algae and the packing material, indicating that high light intensity significantly enhances the adhesion of suspended in-situ bacteria and algae to the packing material, inducing faster microbial colonization, i.e., the initial stage of biofilm formation. In the subsequent biomass accumulation stage, the biomass of the biofilm on the packing material increased by an average of 548% under high light intensity. The in-situ bacteria and algae biofilm system formed by high light intensity irradiation using the method of this invention increased the average removal rates of ammonia nitrogen and phosphorus by 72.1% and 90.3%, respectively.

[0019] In summary, this invention utilizes light within a specific intensity range to accelerate the initial colonization of biofilms and promote biomass accumulation, while simultaneously improving nitrogen and phosphorus removal efficiency and significantly reducing reaction costs. This is of great significance for advancing the low-carbon resource utilization of wastewater. Attached Figure Description

[0020] Figure 1 The in-situ bacterial and algal biofilm formation rate under different light intensities.

[0021] Figure 2 This shows the growth of in-situ bacterial and algal biofilm on the surface of the packing material.

[0022] Figure 3 The free energy of adhesion between (a) suspended in-situ bacteria and algae and the packing material, and the interaction energy between (b) the control group and (c) the high light intensity group.

[0023] Figure 4 Linear regression analysis was performed on EPS and biomass of suspended biomass (a, c) and biofilm (b, d).

[0024] Figure 5 PN function annotations for (a) control group and (b) high light intensity group.

[0025] Figure 6 Atomic force microscopy images of the PS molecular structure in the control group (a, c) and the high-intensity light group (b, d), and parameters of the polysaccharide chain molecular conformation in (e). AVH, AVW, and DB represent the average chain height (n=30), average chain width (n=30), and degree of branching, respectively. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0027] The reagents used in the following examples are all commercially available.

[0028] Example 1

[0029] In situ enrichment culture of bacteria and algae:

[0030] Actual domestic sewage was collected from a local wastewater treatment plant in Nanjing and mixed with sterilized (121℃, 30min) synthetic domestic sewage at a ratio of 1:10 (v / v). The mixture was then subjected to a light-to-dark cycle of 14:10 (the light intensity of the light cycle was 54 μmol / (m²)). 2 In situ bacteria and algae were obtained by culturing at 25±2℃.

[0031] The composition of the synthetic domestic wastewater is as follows: NaAc (230.77 mg / L), NH4Cl (114.64 mg / L), K2HPO4 (21.95 mg / L), and trace element solution (1 mL / L). The trace element solution composition is: 1.5 g / L FeCl3·6H2O, 0.38 g / L MgSO4·7H2O, 0.01 g / L CaCl2, 0.18 g / L KI, 0.15 g / L H3BO3, 0.15 g / L CoCl2·6H2O, 0.12 g / L MnCl2·4H2O, 0.12 g / L ZnSO4·7H2O, 0.06 g / L Na2MoO4·2H2O, 0.03 g / L CuSO4·5H2O, and 10 g / L LEDTA.

[0032] Example 2

[0033] The effects of light intensity control on in-situ bacterial and algal biofilm formation and nitrogen and phosphorus removal:

[0034] This experiment consisted of two groups: a control group and a high-intensity group, with light intensities of 54 and 180 μmol / (m²), respectively. 2•s). Illumination is provided using a cold photodiode board, eliminating the temperature rise caused by illumination. The cold photodiode board is connected to an integrated control box to control the light intensity and illumination time.

[0035] The experiment was divided into two phases: (1) Baseline period (20 days). No suspended packing was added to the photobioreactors (PBRs), and the PBRs in both experimental groups were kept under the same light intensity (54 μmol / (m²). 2 The test was conducted in a batch mode, including 5 minutes of influent, 14 hours of illumination, 10 hours of sedimentation, and 5 minutes of effluent, until stable nutrient removal performance was achieved. The influent was the synthetic domestic sewage from Example 1. The same agitator was used during illumination to maintain the same mixing conditions for both groups, and the stirring speed was 600 rpm. (2) Experimental period (180 days): Suspended packing material (filling rate 30% (v / v)) was added, and the illumination intensity of the high light intensity group was switched to 180 μmol / (m²) through the integrated control box. 2 The experiment aimed to study the effects of light intensity on biofilm growth and nitrogen and phosphorus removal, with all other operating conditions remaining consistent with the baseline phase. The experimental period was further divided into three phases with varying intervals between phases to assess the stability of the high-light-intensity irradiation strategy. The suspended packing material was industrial high-density polyethylene, 25 mm in diameter, 10 mm in height, and with a density of 0.96 g / cm³. 3 .

[0036] Figure 1 The formation of biofilms by suspended in-situ bacteria and algae on packing materials was compared under two different light intensities. Clearly, high light intensity significantly promoted biofilm growth, as its biofilm attachment rate (biofilm biomass / suspended in-situ bacteria and algae biomass) was 73.7-1154% higher than the control group (p<0.001, t-test). Figure 2 As shown in the visual comparison of the packing materials, the higher in-situ bacterial and algal biomass on the packing material in the high light intensity group is clearly demonstrated. Table 1 compares the nitrogen and phosphorus removal rates during the experimental period. The nitrogen and phosphorus removal rates in the high light intensity group are significantly improved, with the average removal rates of ammonia nitrogen and phosphorus increasing by 72.1% and 90.3%, respectively.

[0037] Table 1. Nitrogen and phosphorus removal rates during the experimental period

[0038]

[0039] Figure 3 A comparison of the surface thermodynamic properties and interfacial interactions between suspended in-situ bacteria and algae and the packing material shows that high light intensity is beneficial to the adhesion of suspended in-situ bacteria and algae to the packing material. Figure 3 As shown in (a), compared with the control group, the total interfacial energy of suspended in-situ bacteria and algae in the high light intensity group was reduced by 33.8%, making them easier to adhere to the packing material. Figure 3As shown in (b), no energy barrier was observed at any separation distance in the high light intensity group, indicating that the adhesion process of suspended in-situ bacteria and algae on the packing material can occur spontaneously. These results suggest that high light intensity promotes the initial adhesion of suspended in-situ bacteria and algae to the packing material. Figure 4 The correlation between EPS (expanded biofilm) levels and biofilm biomass was compared, and the results showed that biofilm growth was more strongly correlated with the EPS of suspended in-situ bacteria and algae. Therefore, an in-depth study was conducted on the EPS of suspended in-situ bacteria and algae. Figure 5 It can be seen that the high-intensity group has more PN molecules with signal transduction capabilities, thereby promoting EPS secretion. Specifically, the increased secretion of PN molecules with binding capabilities (proteins, polysaccharides, nucleic acids, and metal ions) helps form a tightly connected EPS network, thus promoting cell aggregation and biomembrane accumulation. Figure 6 It can be seen that the branching degree, height, and width of the PS chains increased by 473%, 63.4%, and 28.9%, respectively, which helps maintain the structural integrity of the biofilm matrix. Therefore, the PN and PS secreted by in-situ bacteria and algae induced by high light intensity promote the accumulation of biofilm biomass on the packing material.

[0040] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the specific details of the above embodiments. 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.

[0041] 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.

[0042] 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 simultaneously improving in-situ bacterial and algal biofilm formation and nitrogen and phosphorus removal efficiency using high light intensity, characterized in that, The specific steps are as follows: Suspended in-situ bacteria and algae and suspended packing material are introduced into the wastewater, and the mixture is placed under a light intensity ≥180 μmol / (m²). 2 Irradiation under high light intensity (·s) induces photosynthetic reactions, reducing the total interfacial energy of suspended in-situ bacteria and algae and causing excessive secretion of extracellular polymers. The method for obtaining in-situ bacteria and algae involves mixing actual domestic sewage at a volume ratio of 1:10 with sterilized synthetic domestic sewage, using a light-to-dark cycle of 14:10, with a light intensity of 54 μmol / (m²) during the illumination period. 2 ·s), cultured at 25 ± 2 ℃, to obtain in situ bacteria and algae, with a biomass concentration of 580~4080 mg / L and a total suspended chlorophyll concentration of 4.92~92.89 mg / L.

2. The method according to claim 1, characterized in that, The composition of the synthetic domestic wastewater is as follows: 230.77 mg / L NaAc, 114.64 mg / L NH4Cl, 21.95 mg / L K2HPO4, and 1 mL / L trace element solution; the trace element solution consists of: 1.5 g / L FeCl3·6H2O, 0.38 g / L MgSO4·7H2O, 0.01 g / L CaCl2, 0.18 g / L KI, 0.15 g / L H3BO3, 0.15 g / L CoCl2·6H2O, 0.12 g / L MnCl2·4H2O, 0.12 g / L ZnSO4·7H2O, 0.06 g / L Na2MoO4·2H2O, 0.03 g / L CuSO4·5H2O, and 10 g / L EDTA.

3. The method according to claim 1, characterized in that, Synthetic domestic sewage is sterilized at 121 ℃ for 30 minutes.

4. The method according to claim 1, characterized in that, The volumetric filling rate of the suspended packing is 30%.

5. The method according to claim 1, characterized in that, The suspended filler is made of industrial high-density polyethylene, with a diameter of 25 mm, a height of 10 mm, and a density of 0.96 g / cm³. 3 .

6. The method according to claim 1, characterized in that, The irradiation time under high light intensity was 14 hours.

7. The method according to claim 1, characterized in that, The photosynthesis reaction described herein employs the SBR process; the SBR process includes water inlet, photoreaction, sedimentation, and drainage steps.

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