Black and odorous water body treatment method based on light-driven microalgae remediation

Abstract

The invention relates to a black and odorous water body treatment method based on light-driven microalgae remediation. The method comprises the following steps: preparing at least two immobilized microalgae balls; the two immobilized microalgae balls are arranged in a container, the bottom of the container is embedded into the bottom mud, part of the container is located in the water body, and the two immobilized microalgae balls are located in the areas, corresponding to the bottom mud and the water body, of the container respectively; the lighting module is used for collecting illumination; light is transmitted into the container through the light guide module, and the transmitted light is reflected by the central light diffusion module, so that the two immobilized microalgae balls obtain the light; an interaction channel is arranged on the container, so that oxygen generated by the two immobilized microalgae balls is interacted into bottom mud and water outside the container from the inside of the container. According to the method disclosed by the invention, a spatial layering remediation mode is constructed, and a light guide transmission technology is integrated, so that synergistic and efficient treatment of bottom mud endogenous pollution and overlying water body pollution in the black and odorous water body is realized, and the method belongs to the technical field of environmental engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental engineering, and particularly relates to a black and odorous water treatment method based on light-driven microalgae remediation. BACKGROUND

[0002] Pollutants such as organic matter, sulfides, ferrous and nutrients enriched in the sediment are continuously released to the overlying water under anaerobic or low-oxygen conditions, causing a series of environmental problems such as odor production, dissolved oxygen depletion, abnormal proliferation of algae and degradation of aquatic ecology. Microalgae remediation technology, as a green and sustainable bioremediation method, has shown good application prospects in the treatment of black and odorous water in recent years. The technical principle is to use the photosynthesis characteristics of microalgae, using carbon dioxide in the water as a carbon source, and using nitrogen, phosphorus and other pollutants as a nutrient source, to grow and metabolize under light conditions, thereby realizing the synergistic effect of water quality purification and dissolved oxygen improvement. The oxygen released by microalgae through photosynthesis can directly increase the dissolved oxygen concentration in the water body, inhibit the metabolic activity of anaerobic microorganisms, and at the same time remove organic pollutants and nutrients in the water body through absorption and assimilation, with the technical advantages of complete remediation, environmental friendliness and low cost.

[0003] However, the microalgae remediation technology still has the following key technical bottlenecks in the actual application of black and odorous water treatment engineering: First, due to the limitation of the optical properties of the water body, the transmission efficiency of natural light in the black and odorous water body is significantly reduced. In eutrophic or high-turbidity black and odorous water bodies, abundant suspended solids (TSS) and colored dissolved organic matter (CDOM) have strong absorption and scattering effects on photosynthetically active radiation (PAR), resulting in a sharp attenuation of light in the vertical profile of the water body, producing a significant light gradient of "surface light saturation, deep light starvation", which seriously restricts the photosynthesis efficiency of microalgae in deep water and the sediment-water interface. Second, the microalgae biomass is difficult to stably maintain in an open water environment. Under the influence of external factors such as water flow disturbance and biological predation, free microalgae cells are easily diluted or lost, making it difficult to form and maintain an effective biomass concentration in the target remediation area, directly affecting the stability and sustainability of the remediation effect. Most importantly, the existing microalgae remediation technology lacks effective control means for endogenous pollution in the sediment. Most remediation schemes focus on improving the dissolved oxygen level in the overlying water and removing pollutants in the water, but it is difficult to effectively and continuously deliver the oxygen produced by photosynthesis to the sediment pore space, and it is impossible to form and maintain a stable oxidation front on the surface of the sediment, so it is impossible to inhibit the release of reduced black and odorous substances such as Fe 2+ , H2S from the sediment. SUMMARY

[0004] In view of the technical problems existing in the prior art, the present application aims to provide a black and odorous water body treatment method based on light-driven microalgae remediation, which realizes the synergistic and efficient treatment of endogenous pollution in the sediment and pollution in the overlying water body in the black and odorous water body by constructing a spatially layered remediation mode and integrating light guide transmission technology.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: A black and odorous water body treatment method based on light-driven microalgae remediation comprises the following steps: Preparation of at least two immobilized microalgae balls; The two immobilized microalgae balls are arranged in a container, the bottom of the container is embedded in the sediment, part of the container is located in the water body, and the two immobilized microalgae balls are respectively located in the areas of the corresponding sediment and water body of the container; Collecting light using a light collection module; Transmitting the light to the container through a light guide module, and reflecting the transmitted light using a central light diffusion module to enable the two immobilized microalgae balls to obtain light; An interactive channel is arranged on the container to enable the oxygen generated by the two immobilized microalgae balls to be respectively exchanged from the container to the sediment and the water body outside the container.

[0006] As a preferred embodiment, the immobilized microalgae balls are made by cross-linking and solidifying sodium alginate and calcium chloride, have a diameter of 5-10mm, and the microalgae of the immobilized microalgae balls adopt Trebouxiophyllum, Chlorella kessleri and Tetraselmis obliqua.

[0007] As a preferred embodiment, the container is a hollow cylindrical structure, the top and bottom of the container are provided with connecting holes, the container is connected with the two ends of the light guide module through the connecting holes, the bottom of the container is embedded in the sediment by 1-5cm, and the bottom surface of the container is provided with a porous mesh structure.

[0008] As a preferred embodiment, the container is prepared by using an opal light diffusion grade acrylic plate.

[0009] As a preferred embodiment, the surface of the container is subjected to frosted treatment to form an optical diffusion surface, and the inner wall is coated with a barium sulfate coating.

[0010] As a preferred embodiment, the central light diffusion module is a circular ring structure, the central light diffusion module is made of opal acrylic, the outer surface of the central light diffusion module is subjected to sandblasting treatment with 240-mesh sand particles, and the inner wall is coated with a barium sulfate coating.

[0011] As a preferred embodiment, the light collection module adopts a hemispherical cover structure made of polycarbonate material.

[0012] As a preferred embodiment, the light guide module is a tubular structure, the inner side wall of the tubular structure is provided with a first light reflection layer, the first light reflection layer is an aluminum film or an aluminum cylinder, and the first light reflection layer is attached to the inner side wall of the tubular structure.

[0013] As a preferred, one end of the light guide module protrudes from the container or both ends of the light guide module are flush with both ends of the light collection module.

[0014] As a preferred, the ratio of the oxygen supply of the bottom mud to the water body is 30:70 to 70:30 by adjusting the depth of the bottom mud embedded in the bottom of the container, the density of the immobilized microalgae balls filled in the container and the ratio of the microalgae species of the immobilized microalgae balls.

[0015] Overall, the present application has the following advantages: The method of the present application is to construct a layered repair, by embedding the lower layer of the container into the surface layer of the bottom mud and placing the upper layer in the overlying water body, combined with light guide transmission technology to achieve uniform distribution of light in the bottom mud and water body. The natural light is efficiently guided into the container by the light guide module, and sufficient light is provided for the immobilized microalgae in the upper and lower layers by the double-layer light diffusion device; the microalgae embedded in the bottom mud directly act on the internal pores of the bottom mud, and the oxygen generated by the microalgae forms an oxidation front in the surface layer of the bottom mud, effectively inhibiting the release of black odor substances; the microalgae in the upper water body improve the water quality of the overlying water body, realizing the synergistic treatment of endogenous pollution in the bottom mud and black odor problem in the water body. The method successfully solves the technical problems of uneven light, biomass loss and poor repair effect of the bottom mud in the traditional microalgae repair technology through spatial layering and functional zoning design. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Figure 1 is a structural schematic diagram of the repair device; Figure 2 Figure 2 is a cross-sectional view of the repair device; Figure 3 Figure 3 is a graph of the change of oxidation-reduction state of different treatment groups in the process of repairing the water body.

[0017] Figure 4 Figure 4 is the removal of ferrous iron (Fe 2+ ) by different treatment groups in the process of repairing the water body.

[0018] Figure 5 Figure 5 is the removal of AVS (acid volatile sulfur) by different treatment groups in the process of repairing the water body.

[0019] Figure 6 Figure 6 is the removal of ammonia nitrogen (NH4 + -N) by different treatment groups in the process of repairing the water body.

[0020] In the figure: 1-light collection module, 2-light guide module, 3-center light diffusion module, 4-container, 5-microalgae ball filling area, 6-base, 7-microalgae ball, 8-permeation hole. DETAILED DESCRIPTION

[0021] The present invention will now be described in further detail with reference to specific embodiments.

[0022] like Figures 1-2 As shown in the figure, this embodiment provides a method for treating black and odorous water bodies based on light-driven microalgae remediation, which includes the following steps: Prepare at least two immobilized microalgae spheres 7; Two immobilized microalgae balls 7 are placed inside a container 4. The bottom of the container 4 is embedded in the bottom sediment, and part of the container 4 is located in the water. The two immobilized microalgae balls 7 are located in the areas of the container 4 corresponding to the bottom sediment and the water, respectively. Light is collected using a light-collecting module; Light is transmitted into the container 4 through the light guide module 2, and the transmitted light is reflected by the central light diffusion module 3 so that the two immobilized microalgae balls 7 can obtain light. An interactive channel is set on container 4 so that the oxygen produced by the two immobilized microalgae balls 7 can be exchanged from inside container 4 to the bottom sediment and water outside container 4, respectively.

[0023] The two immobilized microalgae balls 7 are located in the areas of the sediment and water body corresponding to the bottom sediment and water body of container 4, respectively, forming the microalgae ball filling area 5. Oxygen produced by photosynthesis in the microalgae balls 7 of the filling area 5 is released into the water body through the permeation holes 8. In some areas, due to their location in the sediment, oxygen is released into the interstitial water within the sediment for sediment oxidation. Pollutants (nitrogen, phosphorus, and organic pollutants) from the external water body and the interstitial water within the sediment permeate inward through the permeation holes 8, providing the necessary nutrients for microalgae growth and reproduction. The interaction channel is the permeation holes 8 located on the side wall of the container, which facilitate the exchange of oxygen and pollutants in and out of container 4.

[0024] The immobilized microalgae balls 7 are made by cross-linking and solidifying sodium alginate and calcium chloride, with a diameter of 5-10 mm. The microalgae used in the immobilized microalgae balls 7 are Chlorella species (Scenedesmus, Chlorella kJ, Tetracyclina, etc.). The immobilized microalgae technology ensures a biomass retention rate of more than 90%, and can operate stably for more than 30 days without external energy input, significantly extending the maintenance cycle and significantly reducing operating costs.

[0025] The container 4 is a hollow cylindrical structure, and the top and bottom of the container 4 are provided with connecting holes. The container 4 is connected with the two ends of the light guide module 2 through the connecting holes. The bottom of the container 4 is embedded in the bottom mud 1-5 cm (preferably 2-3 cm). The bottom surface of the container 4 is provided with a porous mesh structure, which facilitates direct contact with the bottom mud. The container 4 is prepared by a milky white light diffusion grade acrylic plate. The surface of the container 4 is ground to form an optical diffusion surface, and the inner wall is coated with a barium sulfate coating. Specifically, the end of the container 4 away from the light collection module 1 is connected with a base 6. The base 6 is a conical or disc structure. The conical base 6 is used to embed in the mud, and the disc structure of the base 6 is used to place on the surface of the mud. The function of the base 6 is to keep the device in a stable form in the water body. The conical design is more convenient to embed in the mud. The relative position of the structure is adjusted to realize the distribution of oxygen transmission. The porous mesh structure The central light diffusion module 3 is a circular ring structure. The central light diffusion module 3 is made of milky white acrylic. The outer surface of the central light diffusion module 3 is sandblasted with 240 mesh sand particles, and the inner wall is coated with a barium sulfate coating.

[0026] The light collection module 1 is a hemispherical shell structure made of polycarbonate material. The polycarbonate material has high light transmittance and ultraviolet resistance. The function of the light collection module 1 is that the hemispherical shell covers the top of the light guide module 2, which can effectively capture incident natural light (including direct and scattered light) from multiple angles and effectively converge the captured light to the bottom of the light guide module 2.

[0027] The light guide module 2 is a tubular structure. The inner side wall of the tubular structure is provided with a first light reflection layer. The first light reflection layer is an aluminum film or an aluminum cylinder, which is attached to the inner side wall of the tubular structure. The end of the light guide module 2 connected with the light collection module 1 protrudes from the container 4, or the two ends of the light guide module 2 are flush with the two ends of the light collection module 1. The aluminum film or aluminum cylinder is a high reflection layer with a reflectivity greater than 95%. The function is that the effective light collected by the light collection module 1 enters the light guide module 2 and is reflected by the first light reflection layer. The collected natural light is transmitted from the shallow water body to the deep water body area as much as possible without loss. Through the light guide module, the natural light is efficiently guided into the deep layer of the container, ensuring that the microalgae in the bottom mud layer can obtain sufficient light, and the photosynthesis efficiency is improved by 1.5-2 times, and the "bottom mud light starvation" phenomenon is completely eliminated.

[0028] By adjusting the depth of the container 4 embedded in the bottom mud, the density of the immobilized microalgae ball 7 filled in the container 4, and the species ratio of the immobilized microalgae ball 7, the ratio of oxygen supply to the bottom mud and water body is 30:70 to 70:30. By optimizing the species ratio of microalgae, embedding depth and other parameters, the oxygen in the bottom mud and water body is distributed according to the demand. A stable oxidation layer 1-10 mm thick is formed on the surface of the bottom mud. The oxidation-reduction potential is increased from below -300 mV to above -75 mV within 20 days, effectively inhibiting the release of black and odorous substances.

[0029] Specific application examples: 1. Construction and operation: In a 20cm x 14cm x 14cm transparent glass tank, 3cm thick actual black and odorous river sediment (Fe 2+ 10g / kg, AVS 3g / kg, ammonia nitrogen 375g / kg) was laid at the bottom, and then simulated black and odorous overlying water (DO 0.4mg / L) was slowly injected. The repair device was placed in the center of the tank, and the bottom of the device was kept 2cm away from the interface between the mud and water (buried in the mud) by fixing the base 6.

[0030] Three experimental groups were set up for comparative study: control group: no repair treatment; traditional repair group: immobilized microalgae system with top LED illumination; repair device group of the present embodiment: using the repair device of the present embodiment. Run for 20 days, and take samples every 2 days to measure the following indicators: dissolved oxygen, ammonia nitrogen, oxidation-reduction potential, ferrous iron, and hydrogen sulfide concentration.

[0031] 2. Specific parameters: Center light diffusion module 3: outer diameter 60mm, height 150mm, milky white acrylic material, outer surface sandblasted with 240 mesh sand particles, inner wall coated with barium sulfate coating with reflectivity up to 97%; light guide module 2: diameter 20mm, length 180mm, inner wall vacuum aluminum reflection layer, reflectivity 96%; light collection module 1: 80mm diameter hemispherical PC cover, anti-UV treated; immobilized microalgae ball 7: diameter 6mm, made of 3% sodium alginate and 2% calcium chloride cross-linking and curing, curing time 25 minutes; container 4: outer diameter 100mm, height 160mm, bottom hole diameter 4mm, upper hole diameter 2.5mm, arranged in a regular triangle, hole spacing 10mm; microalgae ball 7 filling density: 70%; 3. Results and analysis: As Figures 3-6 shown, the monitoring data of 20 days of operation shows that the dissolved oxygen changes: DO rises from 0.37mg / L to 5.38mg / L. Pollutant removal effect: Fe 2+ removal rate reaches 30.24%, AVS removal rate reaches 50.43%, and ammonia nitrogen removal rate reaches 46.77%.

[0032] 4. Mechanism verification: Through monitoring, the device of the present embodiment forms a 10mm thick oxidation layer at the sediment-water interface, effectively inhibiting the anaerobic production of black and odorous substances. The internal light uniformity reaches more than 85%, and the microalgae ball 7 biological activity retention rate is more than 95%, confirming the technical advantages of the device of the present embodiment.

[0033] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A method for treating black and odorous water bodies based on light-driven microalgae remediation, characterized in that, Includes the following steps: Prepare at least two immobilized microalgae spheres; Two immobilized microalgae balls were placed inside a container, with the bottom of the container embedded in sediment. Part of the container was located in the water, with the two immobilized microalgae balls located in the corresponding areas of the sediment and water, respectively. Light is collected using a light-collecting module; Light is transmitted into the container through the light guide module, and the transmitted light is reflected by the central light diffusion module, so that the two immobilized microalgae balls can obtain light. An interactive channel is set up on the container so that the oxygen produced by the two immobilized microalgae balls can be exchanged from inside the container to the bottom sediment and the water outside the container.

2. The method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 1, characterized in that: The immobilized microalgae balls are made by cross-linking and solidifying sodium alginate and calcium chloride, with a diameter of 5-10 mm. The microalgae used in the immobilized microalgae balls are Scenedesmus, Chlorella vulgaris, and Tetracyclis obliqueis.

3. The method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 1, characterized in that: The container is a hollow cylindrical structure with connection holes at the top and bottom. The container is connected to the two ends of the light guide module through the connection holes. The bottom of the container is embedded in the bottom mud for 1-5cm, and the bottom surface of the container is provided with a porous mesh structure.

4. A method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 3, characterized in that: The container is made from a milky white light-diffusing grade acrylic sheet.

5. A method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 4, characterized in that: The surface of the container is frosted to form an optically diffused surface, and the inner wall is coated with a barium sulfate coating.

6. A method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 1, characterized in that: The central light diffusion module has a circular structure and is made of milky white acrylic. The outer surface of the central light diffusion module is sandblasted with 240-mesh sand, and the inner wall is coated with barium sulfate.

7. A method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 1, characterized in that: The light acquisition module uses a hemispherical cover structure made of polycarbonate material.

8. A method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 1, characterized in that: The light guide module is a tubular structure. The inner wall of the tubular structure is provided with a first light reflection layer, which is an aluminum film or an aluminum tube. The first light reflection layer is attached to the inner wall of the tubular structure.

9. A method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 8, characterized in that: The end of the light guide module that connects to the light acquisition module protrudes from the container, or both ends of the light guide module are flush with both ends of the light acquisition module.

10. A method for treating black and odorous water bodies based on light-driven microalgae remediation according to claim 1, characterized in that: By adjusting the depth of the bottom sediment embedded in the container, the density of the immobilized microalgae balls filled in the container, and the ratio of microalgae species in the immobilized microalgae balls, the oxygen supply ratio between the bottom sediment and the water is maintained at 30:70 to 70:30.

Images