A method for treating pathogenic bacteria in reclaimed water using biochar-microalgae biofilm granules
By leveraging the synergistic effect of biochar and microalgae biofilm particles, the problems of easy loss and difficult separation of microalgae in reclaimed water treatment are solved, achieving efficient and low-cost pathogen removal and improving treatment efficiency and photosynthetic efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2025-04-07
- Publication Date
- 2026-08-04
AI Technical Summary
In existing technologies, microalgae are easily lost when treating pathogens in reclaimed water. Separation after treatment is difficult and costly. Conventional methods also suffer from high energy consumption and byproduct pollution.
The biochar-microalgae biofilm particle treatment method uses the synergistic effect of biochar and microalgae to immobilize microalgae and form biochar-microalgae biofilm particles. The porous structure of biochar and the extracellular secretions of microalgae are used to achieve efficient adsorption of pathogens. Aeration drives the particles to flow in the water, simplifying the separation process.
It effectively immobilizes microalgae, prevents loss, reduces separation costs, increases adsorption capacity and processing efficiency, significantly improves photosynthetic efficiency and shear resistance, reduces energy consumption, and enhances adsorption capacity for Escherichia coli.
Smart Images
Figure CN120229821B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wastewater treatment and reclaimed water reuse safety technology, specifically relating to a method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles. Background Technology
[0002] Urban landscape water bodies are one of the main pathways for reclaimed water reuse. However, the residual problem of pathogens such as E. coli in reclaimed water is currently prominent, making the safe reuse of reclaimed water particularly important. Common methods for treating E. coli include chlorination, ultraviolet disinfection, ozone oxidation, and adsorption. Traditional chlorination easily produces carcinogenic byproducts such as trihalomethanes, with byproduct concentrations reaching 50-100 μg / L. Ultraviolet disinfection is sensitive to turbidity; when NTU>5, the disinfection efficiency decreases by 40%, and it cannot sustain bacterial inhibition. Ozone oxidation technology is energy-intensive, consuming 0.8-1.2 kWh of electricity per ton of water, and it also produces bromate pollution. Although microalgae adsorption has attracted attention due to its environmentally friendly characteristics, single microalgae suffer from problems such as easy loss (loss rate >30% when hydraulic retention time >6h), low adsorption capacity (usually <50 mg / g), and microalgae are usually in a suspended growth state, easily lost from the reactor. Furthermore, the separation of microalgae from water after treatment is costly.
[0003] Therefore, there is an urgent need to develop a method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles that combine high adsorption capacity and strong carrier binding stability. Summary of the Invention
[0004] To overcome the problems of easy loss of microalgae from the reactor, high cost, and low activity of microalgae in the treatment of pathogenic microorganisms in reclaimed water by microalgae adsorption in existing technologies, the present invention aims to provide a method for treating pathogenic bacteria in reclaimed water using biochar-microalgae biofilm particles. This method can effectively fix microalgae, prevent microalgae from being lost from the reactor, and facilitate the separation of microalgae from water after treatment with low separation cost. The present invention utilizes the synergistic effect of biochar and microalgae, resulting in high activity of microalgae, strong secretion of extracellular secretions, and high overall treatment efficiency.
[0005] The objective of this invention is achieved by including the following steps: S1. Chlorella cultivation: Chlorella ( Chlorella vulgaris The microalgae were placed in a liquid culture medium and cultured. The culture medium was then centrifuged to obtain concentrated microalgae. S2. Preparation of biochar-microalgae biofilm particles: Chlorella cultured in step S1 is diluted, and biochar is added to the Chlorella solution. Microalgae are adsorbed onto the surface and inside of the carrier by static or flowing biofilm attachment to form biochar-microalgae biofilm particles. S3. Adsorption: Biochar-microalgae biofilm particles are added to the reclaimed water, and aeration is introduced into the reclaimed water to cause the biochar-microalgae biofilm particles to flow in the water. The biochar-microalgae biofilm particles adsorb pathogens in the water. Afterwards, the biochar-microalgae biofilm particles are retrieved, which reduces the difficulty of separating microalgae from wastewater.
[0006] Preferably, the liquid culture medium in step S1 is BG11 liquid culture medium, the centrifugation rate is 2000 rpm to 6000 rpm, and the centrifugation time is 5 min to 10 min.
[0007] Preferably, in step S2, sterile water is used to dilute the Chlorella and adjust the OD of the concentrate. 680 The activity is high within the range of 1.0-1.5, therefore Chlorella has high adsorption activity for pathogens in sewage.
[0008] Preferably, the biochar in step S2 is prepared by the following method: coconut shells are washed and crushed into 2cm~5cm particles, dried at 60℃~105℃ to remove moisture, placed in a pyrolysis furnace, and pyrolyzed at 300℃~700℃ for 1h~4h under anaerobic conditions to promote the carbonization of organic matter and form a porous structure. After cooling, it is ground and sieved.
[0009] Preferably, the biochar from step S2 has a specific surface area of 200 m² / g to 600 m² / g, a pore size greater than 25 micrometers, and a microalgal biomass of 1.0 × 10⁻⁶. 6 cell / g ~5.0×10 6 cell / g; Biochar, with its well-developed microporous, mesoporous, and macroporous structure and high specific surface area, provides a large number of adsorption sites for microalgae, resulting in a high concentration of microalgal biomass.
[0010] Preferably, the adsorption process in step S2 involves shaking at room temperature for 2 to 3 days, with an adsorption temperature of 25°C to 30°C and a pH value of 6 to 8.
[0011] Preferably, the adsorption process in step S3 is carried out at a temperature of 25°C, a stirring speed of 150 rpm, and a light intensity of 300 μmol•m. -2 •s -1 The pH value is 6.0.
[0012] The beneficial effects of this invention are: 1. This invention utilizes the adsorption combination of biochar and microalgae to enhance the resistance to water flow shear force and completely solve the problem of microalgae loss. 2. Biochar-microalgae particles have higher solid-liquid separation efficiency than simple microalgae systems, and their energy consumption is much lower than that of traditional centrifugation. 3. The persistent free radicals generated during the biochar pyrolysis process of this invention can stimulate and enhance the activity of microalgal antioxidant enzyme systems (SOD, CAT); 4. This invention utilizes the oxygen-containing functional groups (-COOH, -OH) on the surface of biochar to form a semi-interpenetrating network with EPS secreted by microalgae, so that the pH gradient in the biofilm is maintained at 6.8-7.2, at which time the adsorption rate is high, and compared with the traditional suspension culture system, the photosynthetic efficiency of this invention is significantly improved. 5. Enhanced adsorption through quorum sensing: The micropore confinement effect allows algal cell density to reach 10. 6 The cells / mL triggers the microalgae QS (Quorum Sensing) system to secrete EPS, which increases the adsorption capacity for E. coli compared to the pure microalgae system. Attached Figure Description
[0013] Figure 1 The effect of biochar-Chlorella on the adsorption of Escherichia coli at different temperatures in Example 1; Figure 2 The effect of biochar-Chlorella on the adsorption of Escherichia coli under different mechanical shear forces in Example 1; Figure 3 The effect of biochar-Chlorella on the adsorption of Escherichia coli under different light conditions in Example 1; Figure 4 Example 1 illustrates the effect of biochar-Chlorella on the adsorption of Escherichia coli at different pH levels. Detailed Implementation
[0014] The present invention will be further described below with reference to the embodiments and accompanying drawings, but this does not limit the present invention in any way. Any changes or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.
[0015] Example 1 The method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles in this embodiment is as follows: S1. Chlorella was placed in BG11 liquid medium (containing 1500 mg / L NaNO3, 75 mg / L MgSO4·7H2O, 40 mg / L K2HPO4·3H2O, 36 mg / L CaCl2·2H2O, and 20 mg / L Na2CO3) and cultured. The culture medium was centrifuged at 4000 rpm for 10 min, and the supernatant was discarded to obtain the lower layer of concentrated microalgae. S2. Preparation of biochar-microalgae biofilm particles: The Chlorella cultured in step S1 is diluted with sterile water and the OD is adjusted. 680For a value of 1.0, biochar was added to the Chlorella algal solution, and the microalgae were adsorbed onto the surface and inside of the carrier by static or flowing biofilm method. The treatment lasted for 2 days, while shaking was performed to form biochar-microalgae biofilm particles. S3. Adsorption: Biochar-microalgae biofilm particles are added to the reclaimed water, and aeration is introduced to move the biochar-microalgae biofilm particles in the water while continuously stirring. The treatment temperature is 25℃, the stirring speed is 150 rpm, and the light intensity is 300 μmol•m. -2 •s -1 The pH gradient is maintained at 6.8-7.2, and pathogens in the water are adsorbed by biochar-microalgae biofilm particles.
[0016] Example 2 This embodiment describes a method for treating pathogenic bacteria and removing OD from reclaimed water using biochar-microalgae biofilm particles. 680 Except for 1.5, the rest is the same as in Example 1.
[0017] Example 3 This embodiment describes a method for treating pathogenic bacteria and removing OD from reclaimed water using biochar-microalgae biofilm particles. 680 Except for 1.25, the rest is the same as in Example 1.
[0018] Example 4 The method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles in this embodiment is based on Example 1. The preparation method of biochar is as follows: coconut shells are washed and crushed into 2cm~5cm particles, dried at 105℃ to remove moisture, placed in a pyrolysis furnace, and pyrolyzed at 700℃ for 1 hour under anaerobic conditions to promote the carbonization of organic matter and form a porous structure. After cooling, the biochar is ground and sieved. The specific surface area of the biochar is 200-600m² / g, and the pore size is greater than 25 micrometers.
[0019] Example 5: Comparative Experiment (1) Effect of biochar-Chlorella on the adsorption of Escherichia coli at different temperatures Based on Example 1, step S3 involved the adsorption of Escherichia coli in water by biochar-microalgae biofilm particles at temperatures of 10°C, 15°C, 20°C, 25°C, 30°C, and 37°C, with a Chlorella density of 1×10⁻⁶. 6 The concentration of E. coli was 1 × 10⁻⁶ cells / mL. 8 CFU / mL, samples were taken 10 min after the reaction. Bound Escherichia coli and free Escherichia coli in the water were separated by filtration. The free Escherichia coli was then diluted with sterile water and counted. The adsorption rate of biochar-microalgae biofilm particles on Escherichia coli in the water was calculated using the following formula. In the formula, N1 is E. coli Total amount, CFU / mL; N2 is biochar-microalgae adsorption E. coli The number of cells; The results are as follows Figure 1 As shown, biochar-microalgae biofilm particles have an effect on... E. coli It exhibits high adsorption rates, all exceeding 80%; under temperature conditions between 15~35℃, the biochar-microalgae biofilm particles show good adsorption efficiency. E. coli The adsorption efficiency began to increase at 10℃, and at 25℃, the biochar-microalgae biofilm particles adsorbed 9.36 × 10⁻⁶ ppm. 7 CFU / mL E. coli Biochar-microalgae biofilm particles E. coli The adsorption rate of cells reached its highest level, at 93.6%; no significant difference in adsorption effect was observed with further increases in temperature; appropriately increasing the temperature is beneficial for stimulating the growth and accumulation of metabolically active substances in microalgae, thereby enhancing the microalgae's ability to... E. coli Physicochemical adsorption; (2) Effect of biochar-Chlorella on the adsorption of Escherichia coli under different mechanical shear forces Based on Example 1, step S3 involved the adsorption of Escherichia coli in the water by biochar-microalgae biofilm particles at rotation speeds of 0, 50, 100, 150, 175, 200, 250, and 300 rpm, with a Chlorella algal density of 1 × 10⁻⁶. 6 The concentration of E. coli was 1 × 10⁻⁶ cells / mL. 8 CFU / mL samples were taken at 10 min of reaction time. Bound E. coli and free E. coli in the water were separated by filtration. The free E. coli were then diluted with sterile water and counted. The adsorption rate of biochar-microalgae biofilm particles on E. coli in the water was calculated. Results are as follows: Figure 2 As shown, with the gradual increase of rotational speed (from 0 rpm to 300 rpm), the effect of biochar-microalgae biofilm particles on... E. coli The adsorption capacity of the biochar-microalgae biofilm particles first increases and then decreases; the lowest values are observed at rotation speeds of 0 rpm and 300 rpm. E. coli The adsorption rate was even less than 65%. At a rotation speed of 150 rpm, the biochar-microalgae biofilm particles adsorbed 9.43 × 10⁻⁶ ppm. 7 CFU / mL E. coli The adsorption rate reached 94.3%; when the rotation speed was increased to 200 revolutions per minute, the biochar-microalgae biofilm particles... E. coli The adsorption efficiency decreased significantly to 81.8%; at a rotation speed of 300 rpm, the adsorption efficiency of biochar-microalgae biofilm particles on... E. coliThe adsorption efficiency is approximately 43.2%; appropriate stirring speed can increase the adsorption efficiency of biochar-microalgae biofilm particles. E. coli The degree of mixing between biochar-microalgae biofilm particles and E. coli The presence of sufficient energy and collision opportunities between biochar-microalgae biofilm particles promotes their interaction. E. coli The collisions and contacts achieve the optimal adsorption rate; (3) Effect of biochar-Chlorella on the adsorption of Escherichia coli under different light conditions Based on Example 1, step S3 was performed at light intensities of 0, 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 μmol•m. -2 •s -1 Under specific conditions, the adsorption of Escherichia coli in water by biochar-microalgae biofilm particles was carried out, with the Chlorella density being 1×10⁻⁶. 6 The concentration of E. coli was 1 × 10⁻⁶ cells / mL. 8 CFU / mL samples were taken at 10 min of reaction time. Bound E. coli and free E. coli in the water were separated by filtration. The free E. coli were then diluted with sterile water and counted. The adsorption rate of biochar-microalgae biofilm particles on E. coli in the water was calculated. Results are as follows: Figure 3 As shown, with increasing light intensity, the biochar-microalgae biofilm particles have a greater effect on... E. coli The adsorption rate increases at 300 μmol•m -2 •s -1 At that time, the biochar-microalgae biofilm particles adsorbed 9.59 × 10⁻⁶ mg / L. 7 CFU / mL E. coli The adsorption rate reached a maximum of 96.0%; with further increase in light intensity, only a slight decrease in adsorption efficiency was observed; within a certain range of light intensity, the photosynthetic rate of biochar-microalgae biofilm particles increases with the increase of light intensity, which helps the secretion of metabolites from biochar-microalgae biofilm particles, thereby increasing the adhesion of biochar-microalgae biofilm particles to the surface. (4) Effect of biochar-Chlorella adsorption on Escherichia coli at different pH levels Based on Example 1, step S3 involved the adsorption of *E. coli* in the water by biochar-microalgae biofilm particles under pH gradients of 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, respectively, with a *Chlorella* algal density of 1 × 10⁻⁶. 6 The concentration of E. coli was 1 × 10⁻⁶ cells / mL. 8CFU / mL samples were taken at 10 min of reaction time. Bound E. coli and free E. coli in the water were separated by filtration. The free E. coli were then diluted with sterile water and counted. The adsorption rate of biochar-microalgae biofilm particles on E. coli in the water was calculated. Results are as follows: Figure 4 As shown, biochar-microalgae biofilm particles adsorb... E. coli The ability of biochar-microalgae biofilm particles to initially increase and then gradually decrease with rising pH; when the pH is 4.0-5.0, the ability of these particles to... E. coli The cell adsorption rate was as low as 80.9%; when the pH value rose to 6.0, the biochar-microalgae biofilm particles showed a higher adsorption rate. E. coli Cellular adsorption reached its maximum value (9.62 × 10⁻⁶). 7 The adsorption rate was 96.2% (CFU / mL). When the pH value was further increased to 10.0, the adsorption efficiency decreased to 64%-75%. Because the pH value was too low, it would lead to an overly acidic environment, resulting in poor growth of biochar-microalgae biofilm particles. However, when the pH value was 5.0-6.0, the dissociation of acidic functional groups such as carboxyl groups on the cell surface was inhibited, the degree of protonation increased, and the cell surface became positively charged or the charge density decreased, thereby reducing the electronegativity and stability of algal cells. At this time, the zeta potential on the surface of biochar-microalgae biofilm particles was positively charged. As the absolute value of the zeta potential decreased, the repulsive force between cells also weakened, and cells were more likely to adsorb, thereby improving the adsorption of microalgae and bacteria.
Claims
1. A method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles, characterized in that... Includes the following steps: S1. Chlorella cultivation: Chlorella is placed in a liquid culture medium and cultured. The culture medium is then centrifuged to obtain concentrated microalgae. S2. Preparation of Biochar-Microalgae Biofilm Particles: Chlorella cultured in step S1 is diluted, and biochar is added to the Chlorella solution. Microalgae are adsorbed onto the carrier surface and interior via static or flowing attachment, forming biochar-microalgae biofilm particles. The biochar is prepared as follows: Coconut shells are washed, crushed into 2-5 cm particles, dried at 60-105℃ to remove moisture, and placed in a pyrolysis furnace. Under anaerobic conditions, the particles are pyrolyzed at 300-700℃ for 1-4 hours to promote carbonization of organic matter and form a porous structure. After cooling, the particles are ground and sieved. The biomass of microalgae in the biochar is 1.0 × 10⁻⁶. 6 cell / g ~5.0×10 6 cell / g; S3. Adsorption: Biochar-microalgae biofilm particles are added to the reclaimed water, and aeration is introduced into the reclaimed water to drive the biochar-microalgae biofilm particles to flow in the water. Pathogens in the water are adsorbed by the biochar-microalgae biofilm particles; the pH gradient in the biofilm is maintained at 6.8-7.
2.
2. The method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles according to claim 1, characterized in that... The liquid culture medium mentioned in step S1 is BG11 liquid culture medium, with a centrifugation rate of 2000 rpm to 6000 rpm and a centrifugation time of 5 min to 10 min.
3. The method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles according to claim 1, characterized in that... Step S2 involves diluting the Chlorella with sterile water and adjusting the OD of the concentrate. 680 It is 1.0-1.
5.
4. The method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles according to claim 1, characterized in that... The specific surface area of the biochar from the S2 step is 200 m² / g to 600 m² / g, and the pore size is greater than 25 micrometers.
5. The method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles according to claim 1, characterized in that... During the S2 step adsorption process, the device is continuously oscillated and treated for 2 to 3 days.
6. The method for treating pathogens in reclaimed water using biochar-microalgae biofilm particles according to claim 1, characterized in that... During the S3 step adsorption process, the treatment temperature was 25℃, the stirring speed was 150 rpm, and the light intensity was 300 μmol•m. -2 •s -1 .