Microalgae-tidal flow subsurface wetland enhanced water body pollutant purification device and method

Abstract

The application discloses a kind of microalgae-tidal flow subsurface wetland enhanced water body pollutant purification device and method, comprising the following steps: when treating contaminated water, contaminated water is introduced from the top of microalgae growth area, when flowing through microalgae growth area, microalgae assimilates and absorbs pollutants, and provides oxygen-rich environment;When the contaminated water flows through the wetland substrate filling area, the fresh high-activity microalgae carried in the water flow and the bacteria form algal-bacterial symbiotic film, and the contaminated water is intensively purified;The purified water flows out from the water outlet;During the purification process of the contaminated water, the water flow velocity of the microalgae growth area is periodically adjusted, and the attached microalgae is periodically flushed, so that it enters the wetland substrate with water flow to replenish microalgae.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sewage purification, in particular to a microalgae-tidal flow subsurface wetland enhanced pollutant purification device and method. BACKGROUND

[0002] The statements herein are provided only to enhance understanding of the present application and are not necessarily intended to constitute the prior art.

[0003] The artificial wetland system is to purify sewage by using the physical, chemical and biological triple synergistic effect of substrate, plants and microorganisms. The traditional artificial wetland includes three water passing modes of surface flow, horizontal subsurface flow and vertical subsurface flow. At the same time, in order to solve the problems of phosphorus adsorption saturation, dissolved oxygen and carbon source limitation of nitrogen removal in the nitrification and denitrification process of the traditional artificial wetland, the new combined artificial wetland begins to be used to optimize the removal of nitrogen and phosphorus and other pollutants. The tidal flow combined subsurface wetland provides high dissolved oxygen nitrification and trace pollutant oxidation conditions, and also provides anaerobic conditions to realize multi-stage purification of pollutants. However, the current tidal flow combined subsurface wetland has poor total nitrogen removal effect when facing low carbon-nitrogen ratio of the influent, and the two types of artificial wetlands arranged in front and back have large operation engineering quantity, low economic benefit and wide occupation.

[0004] Microalgae are a kind of eukaryotic microorganisms with photosynthetic ability. The resource / energy microalgae cultivation and sewage deep purification coupling technology combines the growth characteristics of microalgae and the composition characteristics of sewage, utilizes the photosynthesis of microalgae to fix carbon, and at the same time absorbs nitrogen, phosphorus and other pollutants to convert into microalgae biomass, thereby realizing the purification of sewage and the recycling of biomass resources. Although the microalgae oxidation pond has low cost and high economic benefit, it occupies a large area and cannot realize small-scale and decentralized sewage treatment alone. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a microalgae-tidal flow subsurface wetland enhanced pollutant purification device and method. The device is used for small-scale and low-cost application of artificial wetlands, and realizes efficient and deep purification of sewage and recycling of biomass resources.

[0006] In order to achieve the above purpose, the present application is realized by the following technical scheme:

[0007] In the first aspect, the present application provides a microalgae-tidal flow subsurface wetland enhanced pollutant purification device, which is internally provided with a microalgae growth area and a wetland substrate filling area from top to bottom, the wetland substrate filling area is provided with a water outlet, and the water outlet is provided with a valve to adjust and control the water flow speed.

[0008] The top of the microalgae growth area is open to light, and a plurality of support and attachment members are arranged inside, which include rigid support members and attachment materials wound on the surfaces of the rigid support members for biofilm formation of microalgae on the surfaces.

[0009] In some embodiments, a baffle is arranged in the middle of the shell to divide the shell into a first chamber and a second chamber, the baffle is spaced apart from the bottom of the shell, the first chamber is arranged from top to bottom with a microalgae growth area and a wetland substrate filling area, and the second chamber is filled with wetland substrate, and the side wall of the second chamber is provided with a water outlet.

[0010] In some embodiments, the support and attachment members are arranged vertically or obliquely relative to the top of the wetland substrate filling area.

[0011] The top of the microalgae growth area is open, on one hand, to allow sunlight to normally enter the microalgae growth area and ensure normal growth of microalgae, and on the other hand, to form a contaminated water inlet for the contaminated water to be treated to enter from the top of the microalgae growth area.

[0012] The support and attachment members include rigid support members and attachment materials wound on the surfaces of the rigid support members, and the microalgae can grow on the surfaces of the attachment materials. The support and attachment members are arranged vertically or obliquely relative to the top of the wetland substrate filling area, which is conducive to the entry of sunlight and thus the growth of microalgae. When the contaminated water to be treated enters from the top of the microalgae growth area, the flow direction of the water is the microalgae growth area of the first chamber → the wetland substrate filling area → the second chamber → the water outlet. The pre-microalgae biofilm oxidation pond assimilates and absorbs nitrogen and phosphorus, and the photosynthesis increases the dissolved oxygen, which promotes the removal of NH4-N in the subsurface wetland nitrification zone. During the water flow, the opening degree of the water outlet valve is controlled to adjust the water flow speed. When the water flow speed increases, the microalgae growing on the support and attachment members in the microalgae growth area can be flushed away, and the microalgae can enter the wetland substrate below under the action of the water flow. Fresh and high-activity microalgae can better play the role of biological stimulant compared with the microalgae biomass harvested by means of algal powder carbon source or centrifugation and filtration, and can form algal-bacterial symbiotic film with bacteria to jointly purify the contaminated water, which has a better purification effect. Moreover, the separation of microalgae and water in the middle of the series microalgae pond-artificial wetland is not needed, which reduces the process flow and cost.

[0013] Since there is no sunlight in the wetland substrate to provide a favorable environment for the reproduction of microalgae, it is necessary to supplement the microalgae to the wetland substrate by periodically flushing the microalgae growth area.

[0014] A baffle is arranged in the middle of the shell, and the lower part of the microalgae growth area and the inside of the second chamber are filled with wetland substrate, and the microalgae entering the wetland substrate with the water flow can be effectively intercepted, the algae and water are separated, and the process of high-cost separation of microalgae and purified water can be omitted.

[0015] In some embodiments, the depth of the microalgae growth area is 15-30 cm. This ensures that sunlight can reach the microalgae at the bottom of the microalgae growth area, and ensures the normal growth of microalgae in the microalgae growth area.

[0016] In some embodiments, the rigid support is a rod-shaped structure made of high-boron silicon material, which is inserted into the substrate to maintain its upright state.

[0017] In some embodiments, the attachment material is a cotton hydrophilic fiber chain rope.

[0018] The soft fiber rope has a large specific surface area and good water retention, which is beneficial to the attached growth of microalgae.

[0019] In some embodiments, the height of the water outlet is higher than the height of the bottom of the microalgae growth area. This ensures that the water at the bottom of the microalgae growth area is not emptied, and the attachment material can absorb water to ensure the normal growth of the microalgae biofilm.

[0020] Preferably, the attachment material is wrapped around the length direction of the rigid support. This ensures that the microalgae grow on the surface of the entire rigid support.

[0021] In some embodiments, the wetland substrate is Φ4-8mm quartz sand.

[0022] In a second aspect, the present application provides a method for strengthening the purification of pollutants by microalgae-tidal flow subsurface wetlands, comprising the following steps:

[0023] Water is introduced into the microalgae growth area, and microalgae are inoculated and cultured, so that the microalgae grow on the surface of the support and attachment member;

[0024] When treating contaminated water, the contaminated water is introduced from the top of the microalgae growth area, and when flowing through the microalgae growth area, the microalgae assimilate and absorb pollutants and provide an oxygen-rich environment; when the contaminated water flows through the wetland substrate filling area, the microalgae and bacteria carried in the water flow form a symbiotic film, which purifies the contaminated water; and the purified water flows out from the water outlet.

[0025] During the purification process of the contaminated water, the water flow velocity in the microalgae growth area is periodically adjusted to periodically flush the attached microalgae, so that they enter the wetland substrate with the water flow to replenish the microalgae.

[0026] In some embodiments, the microalgae are Chlorella vulgaris or Scenedesmus dimorphus.

[0027] In some embodiments, the method further comprises the step of periodically harvesting the microalgae in the microalgae growth area.

[0028] In some embodiments, when the periodically flushing of the attached microalgae causes the microalgae to fall off, the water flow rate in the microalgae growth area is 1-2 cm / s, and the flushing time is 3-5 min.

[0029] The beneficial effects achieved by one or more embodiments of the present application are as follows:

[0030] Part of the attached microalgae enters the matrix interstice with the water flow, and compared with the separation of suspended microalgae, the attached microalgae do not need to be filtered by membrane or centrifuged, which can reduce the operation cost and avoid the damage to the microalgae cells caused by the separation of algae water, and is beneficial to maintain the high activity of the microalgae. The algal-bacterial symbiotic membrane is formed under the continuous supplement of high-activity microalgae, and the extracellular polysaccharides and other components released by the microalgae are microbial growth stimulants, which promote the purification of conventional and trace pollutants by microorganisms.

[0031] Compared with the series process of suspended microalgae culture-artificial wetland, artificial wetland-microalgae, the present application solves the problem of high-cost separation of suspended microalgae and purified water, and reduces the land occupation area, and realizes the substantial coupling of the two types of biological water purification through the quantitative delivery of high-activity microalgae into the wetland matrix.

[0032] The combination of the attached culture form and the tidal drainage can realize the regulation of the microalgae entering rate into the matrix, so as to play a better water purification role. The wetland controls the drainage period and the drainage amount through the electromagnetic valve (continuous water inlet and outlet, when the system microalgae content needs to be improved, a certain time is flushed quickly through the electromagnetic valve to realize the supplement of microalgae in the matrix; periodic tidal operation). Through the regulation of the water level height setting, the drainage rate and the period parameters in the wetland, the growth rate of the attached microalgae and the amount of the attached microalgae entering the wetland matrix can be changed, the removal of pollutants can be strengthened, and the matrix blockage can be avoided.

[0033] The high-efficiency removal of phosphorus by microalgae, and the slow adsorption saturation of phosphorus by the matrix in the process of rapid flushing of water in the wetland can ensure the removal effect of phosphorus and prolong the service life of the wetland.

[0034] The attached microalgae replace the wetland plants, and the attached microalgae have stronger and more direct ability to release oxygen and carbon into water than the plants through the root system. The assimilation rate of the microalgae growth to the pollutants is significantly higher than the water purification rate of the plant growth, which can improve the resource conversion efficiency of the wetland to the pollutants under the condition of the same land occupation area. The microalgae have more efficient carbon sequestration than the plants.

[0035] The attached microalgae biofilm creates an oxygen-rich environment, increases the number of microenvironments for various organisms, and enhances the system's biodiversity and water purification stability. It offers better stability than suspended microalgae, is more resistant to fluctuations in water quality and quantity, and is easier to operate and maintain. Excess microalgae in the microalgae zone need to be harvested periodically and the carrier reused to maintain the microalgae's high nitrogen and phosphorus assimilation activity and achieve the resource utilization of pollutants. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0037] Figure 1 This is a schematic diagram of the structure of the microalgae-tidal flow subsurface wetland enhanced pollutant purification device according to an embodiment of the present invention.

[0038] In the diagram, 1. Rigid support; 2. Microalgae; 3. Attachment material; 4. Attached microalgae community; 5. Wetland inlet water; 6. Wetland substrate; 7. Baffle plate; 8. Outlet pipe; 9. Solenoid valve. Detailed Implementation

[0039] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] The present invention will be further described below with reference to the embodiments.

[0041] like Figure 1 As shown, a tidal vertical subsurface flow wetland is constructed, with an underwater forest of attached microalgae built within a certain space above the substrate surface to assimilate and absorb pollutants. Fresh attached microalgae can be washed into the wetland substrate by the water flow, forming an algae-bacteria symbiotic biofilm and enhancing the wetland's water purification efficiency. The attachment material 3 required for the formation of the attached microalgae community 4 is made of materials such as absorbent microfiber, which has a high specific surface area and strong water retention. The attached microalgae community 4 is supported by a support material 1, made of high borosilicate glass or other materials, which is sturdy, durable, and resistant to oxidation. Its height ranges from 15-30 cm, ensuring sunlight can reach the attached microalgae at the bottom. The height of the underwater forest is adjustable, determined according to the characteristics of the influent pollutants. When the nitrogen and phosphorus ratio of the influent is low (i.e., high phosphorus content), the height of the underwater forest can be appropriately increased to improve the overall phosphorus assimilation and removal performance of the system. The attached microalgae species 2 are selected from non-toxic, pollution-resistant, and high-oil-content species such as Chlorella and Scenedesmus.

[0042] like Figure 1As shown, the wetland water flow control system allows for continuous water intake 5. When it is necessary to increase the microalgae content in the substrate, the microalgae in the substrate can be replenished by rapidly flushing for a certain period of time through the electromagnetic valve 9. It can also operate in a periodic tidal manner, controlled by the electromagnetic valve 9. The lowest point of the liquid level in the wetland, that is, the horizontal position of the outlet of the water outlet pipe 8, is at the bottom of the attached microalgae community 4 to prevent the attached microalgae community from dying because it cannot absorb water from the bottom when the water level is low.

[0043] The outlet point is far from the inlet. A middle baffle plate 7 can be installed, or the bottom can be connected to an overflow weir to reduce the content of microalgae and other organic matter in the outlet water.

[0044] The harvesting cycle of attached microalgae is guided by the maximization of nitrogen and phosphorus removal in the effluent, so as to realize the resource conversion of pollutants, while renewing the attached microalgae biofilm and improving its metabolic rate of pollutants.

[0045] Specifically, such as Figure 1 The small-scale attached microalgae-tidal subsurface flow wetland device shown is made of plexiglass. A baffle plate in the middle divides the interior into two chambers, each 0.15m long, 0.15m wide, and 0.8m high. A 0.10m gap is left between the bottom of the baffle plate and the bottom of the device for water passage. The total effective volume of the wetland is 0.036m³. 3 The wetland's internal substrate is Φ4-8mm quartz sand. The space occupied by the attached microalgae community is the inlet area, which has dimensions of 0.15m (length), 0.15m (width), and 0.10m (height). The initial water volume of the entire device is 15860ml. The wetland adopts a uniform and continuous water inflow, with an inflow rate of 3L / d and a hydraulic retention time of 4.5d.

[0046] The attached microalgae community was constructed using glass rods wound with ultrafine fiber chains, with a mixed species of *Chlorella* and *Scenedesmus* attached to the surface. The attachment carrier density was 8.9 cells / dm³. 2 The illumination is provided by a full-spectrum solar lamp with a light intensity of 3000 lux and a light-to-dark ratio of 12h:12h. The ambient temperature is 20-25℃.

[0047] The conventional pollutants in the wetland influent were based on the secondary effluent concentrations from the municipal wastewater treatment plant: 100 mg / L COD; 25 mg / L NH4-N; 15 mg / L NO3-N; and 3 mg / L TP.

[0048] When the small attached microalgae-tidal flow subsurface wetland is operated for 120 days until the effluent water quality is stable, the effluent water quality is: 1.60±0.85 mg / L COD; 4.72±0.63 mg / L NH4-N; 12.08±1.12 mg / L NO3-N; 17.02±1.61 mg / L TN; 1.44±0.23 mg / L TP. Among them, the effluent TP reaches the Class B standard of the first level standard of urban sewage treatment plant, and the NH4-N, TN and COD reach the Class A standard of the first level standard of urban sewage treatment plant.

[0049] When the water in the attached microalgae group area of the device is saturated, the dissolved oxygen can reach 10.2 mg / L or more, and the minimum level of dissolved oxygen in the internal substrate of the wetland is 0.9 mg / L, which is beneficial to the oxidative degradation of pollutants.

[0050] The maximum removal of effluent TN is used as a guide. The biomass harvesting cycle of the attached microalgae group is 6 days, and the dry weight of the biomass harvested from each wetland device is 0.04817 g / d.

[0051] The present application has the advantages of small occupation and low cost, and can be used for water purification and pollutant resourceization simultaneously, and has potential for wide application in urban areas.

[0052] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for enhancing pollutant purification by microalgae-tidal flow subsurface wetland, characterized in that: a device for enhancing pollutant purification by microalgae-tidal flow subsurface wetland is used, which is internally provided with a microalgae growth zone and a wetland substrate filling zone from top to bottom, and the wetland substrate filling zone is provided with a water outlet, and the water outlet is provided with a valve; the top of the microalgae growth zone is open to light, and the inside is provided with a plurality of support and attachment parts, which include rigid support parts and attachment materials wound on the surface of the rigid support parts, for the formation of biofilms of microalgae on their surfaces; the height of the water outlet is higher than the height of the bottom of the microalgae growth zone; the method for enhancing pollutant purification by microalgae-tidal flow subsurface wetland comprises the following steps: when treating contaminated water, the contaminated water is introduced from the top of the microalgae growth zone, and when flowing through the microalgae growth zone, the microalgae assimilate and absorb pollutants and provide an oxygen-rich environment; when the contaminated water flows through the wetland substrate filling zone, fresh and highly active microalgae and bacteria carried in the water flow form a symbiotic film, which purifies the contaminated water; the purified water flows out of the water outlet; periodically adjusting the water flow velocity of the microalgae growth zone to periodically flush the attached microalgae and make them enter the wetland substrate with the water flow to supplement the microalgae; and further comprising the step of periodically harvesting microalgae in the microalgae growth zone. The middle part of the shell is provided with a baffle, which divides the inside of the shell into a first chamber and a second chamber, and the baffle is left with a set distance from the bottom of the shell, and the first chamber is internally provided with a microalgae growth zone and a wetland substrate filling zone from top to bottom; the second chamber is filled with wetland substrate, and the side wall of the second chamber is provided with a water outlet.

2. The microalgae-tidal flow constructed wetland enhanced contaminant removal method according to claim 1, wherein: The support and attachment part is vertically arranged on the top of the wetland substrate filling zone or is inclined relative to the top of the wetland substrate filling zone.

3. The microalgae-tidal flow constructed wetland enhanced contaminant removal method according to claim 1, wherein: Or, the depth of the microalgae growth zone is 15-30 cm. The rigid support part is a rod-shaped structure made of high boron silicon material.

4. The microalgae-tidal flow constructed wetland enhanced contaminant removal method according to claim 1, wherein: Or, the attachment material is a chain rope of cotton hydrophilic fibers. The attachment material is wrapped and wound along the length direction of the rigid support part.

5. The microalgae-tidal flow constructed wetland enhanced pollutant removal method according to claim 1, wherein: Chlorella 6. The microalgae-tidal flow constructed wetland enhanced pollutant removal method according to claim 1, wherein: The microalgae are Scenedesmus Chlorella vulgaris or When flushing the attached microalgae to make them fall off, the water flow velocity in the microalgae growth zone is 1-2 cm / s, and the single flushing time is 3-5 min. Scenedesmus sp.

7. The microalgae-tidal flow constructed wetland enhanced pollutant removal method according to claim 1, wherein: ​

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