A system and method for removing nano-microplastics by enhancing benthic animals in artificial wetlands

Abstract

The present invention discloses a system and method for removing nano-microplastics by using benthic animals to enhance artificial wetlands. The system includes an artificial wetland, and the matrix filler of the artificial wetland includes a river sand layer doped with benthic animals. The particles of the river sand layer intercept nano-microplastics in the water. The benthic animals ingest and degrade the nano-microplastics, and cooperate with microorganisms and plants in the artificial wetland to remove the nano-microplastics in the water. The present invention uses common benthic animals in nature as matrix fillers for artificial wetlands, utilizes the pollution resistance of benthic animals, and changes the microbial community structure of the water ecosystem through the benthic animals' own activities and the parasitic and predatory relationships with microorganisms. The interaction between the benthic animals and various environmental factors of the ecosystem achieves pollutant removal and environmental optimization, thereby changing pollutant conversion, realizing biological circulation, and improving the ability to remove nano-microplastics.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technology, and in particular to a system and method for removing nano-microplastics by enhancing benthic animals in artificial wetlands. Background Art

[0002] Nanoplastics (NPs), plastic particles smaller than 100 nanometers in diameter, are a major source of pollution. Most NP pollution originates from textiles, tires, and urban dust, accounting for over 80% of all nanoplastic pollution in the environment. Some chemicals contained in nanoplastics can disrupt the endocrine system, leading to various physiological diseases and neurological damage. They are also difficult to metabolize and absorb by the human body. The unexcreted particles accumulate in the body, causing cellular damage, local inflammation, and immune system compromise. Furthermore, compared to "white pollution" plastics, the harmful effects of NPs are primarily due to their tiny particle size, which contributes to their greater environmental harm compared to conventional non-degradable plastics. The small size of NPs translates to a higher specific surface area (specific surface area per unit mass of a porous solid). This greater specific surface area enhances their ability to absorb pollutants, thereby attracting persistent organic matter, heavy metals, and other pollutants, forming aggregates that exert a stronger synergistic toxicity and disrupt the balance of ecosystems. Traditional sewage treatment plants have extremely low removal rates, and commonly used recycled water deep treatment technologies, such as adsorption, membrane filtration, advanced oxidation and other physical and chemical technologies, can remove NPs from water, but they are expensive, require harsh reaction conditions, have low removal efficiency, are complex to operate and manage, and are prone to secondary pollution, making them difficult to promote in river basin water environments.

[0003] Constructed wetlands are an ecological treatment technology that treats wastewater by simulating the purification process of natural wetland environments. Pollutants in nature are removed by constructing a multi-factor synergistic ecological treatment system consisting of "plants, substrates, and microorganisms." Constructed wetlands are characterized by low construction and operation costs, ease of maintenance, and convenient operation and management. The substrate, serving as the skeleton of the constructed wetland, adsorbs pollutants from the water during operation. Once the substrate's adsorption capacity reaches saturation, the pollutants are released back into the water, causing secondary pollution. Furthermore, most substrate fillers are expensive and easily lost, making them difficult to apply on a large scale in constructed wetlands. Microorganisms are components of constructed wetland systems, and microbial metabolism is an important way to decompose pollutants. Due to the difficulty of degrading NPs, microorganisms have poor degradation performance, which reduces the removal efficiency of constructed wetlands. Furthermore, NPs have a small specific surface area and can easily synergize with other pollutants to cause more severe toxicity to cells, resulting in poor pollutant removal. Summary of the Invention

[0004] In response to the problems existing in the existing technology, the present invention provides a system and method for enhancing the removal of nano-microplastics by artificial wetlands using benthic animals. Common benthic animals in nature are used as matrix fillers in artificial wetlands to enhance the performance of artificial wetlands in removing nano-microplastics.

[0005] The technical solutions of the present invention are as follows:

[0006] In the first aspect of the present invention, a system for removing nano-microplastics by using benthic animals to enhance artificial wetlands is provided, comprising an artificial wetland, wherein the matrix filler of the artificial wetland comprises a river sand layer doped with benthic animals, the particles of the river sand layer intercept nano-microplastics in the water, the benthic animals ingest and degrade the nano-microplastics, and cooperate with the microorganisms and plants in the artificial wetland to remove the nano-microplastics in the water.

[0007] In the second aspect of the present invention, a method for enhancing the removal of nano-microplastics in water by artificial wetlands is provided. Inlet water enters the artificial wetland through a peristaltic pump, and passes through the river sand layer and the gravel layer from top to bottom. Nano-microplastics in the water are intercepted in the river sand layer, and benthic animals ingest and degrade the nano-microplastics, thereby removing the nano-microplastics in the water. The purified water is discharged through a drain pipe.

[0008] In the third aspect of the present invention, a system for removing nano-microplastics by using benthic animals in artificial wetlands and / or the method for removing nano-microplastics in water by using enhanced artificial wetlands are provided for use in sewage purification. Benthic animals can cooperate with microorganisms and plants to improve the removal efficiency of nano-microplastics in water.

[0009] One or more technical solutions of the present invention have the following beneficial effects:

[0010] (1) The present invention uses common benthic animals in nature as matrix fillers for artificial wetlands, and utilizes the pollution resistance of benthic animals. Through the activities of benthic animals themselves, as well as the parasitic and predatory relationships with microorganisms, the structure of the microbial community in the aquatic ecosystem is changed, and the interaction between benthic animals and various environmental factors in the ecosystem is achieved to achieve pollutant removal and environmental optimization, thereby changing the transformation of pollutants, realizing biological circulation, and improving the ability to remove nano-microplastics.

[0011] (2) The present invention utilizes the effect of benthic animals on promoting the abundance of microbial communities that can degrade microplastics in the environment, thereby achieving microbial degradation of pollutants and improving the pollutant degradation capacity of the artificial wetland system. While achieving the degradation of nano-scale microplastics by benthic animals in the matrix, it also produces a synergistic effect with microorganisms to enhance the degradation effect of nano-scale microplastics.

[0012] (3) The present invention adopts a specific artificial wetland system with a simple structure and easy assembly. Moreover, there are no other special requirements for the device in the process of removing nano-microplastics from sewage, which greatly reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The process of ingestion and accumulation of nano-scale microplastics by benthic animals in the present invention;

[0014] Figure 2 This is the process of nano-plastic accumulation by artificial wetland plants under the synergistic action of different benthic animals in the present invention;

[0015] Figure 3 A comparison chart of the nanoscale plastic removal rates of the embodiment of the present invention and the comparative example;

[0016] Figure 4 This is a comparison chart of the effluent concentration of nano-scale microplastics in the embodiment of the present invention and the comparative example;

[0017] Figure 5 To demonstrate the mechanism by which benthic animals promote microbial degradation of microplastics. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Example 1

[0020] At present, due to the toxicity of nano-microplastics themselves and their difficulty in degradation in the environment, and due to their large specific surface area, they easily adsorb other pollutants in the environment to produce more serious synergistic toxicity, causing more serious damage to the ecological environment. In addition, due to their small particle size, the existing artificial wetland systems have poor removal efficiency for nano-microplastics in pollutants.

[0021] In a typical embodiment of the present invention, a system for removing nano-microplastics by using benthic animals to enhance artificial wetlands is proposed, comprising an artificial wetland, wherein the matrix filler of the artificial wetland comprises a river sand layer doped with benthic animals, the particles in the river sand layer intercept nano-microplastics in the water, the benthic animals ingest and degrade the nano-microplastics, and cooperate with the microorganisms and plants in the artificial wetland to remove nano-microplastics in the water.

[0022] Benthic animals are a crucial component of aquatic ecosystems, playing a key role in maintaining ecosystem balance and purifying water quality. This embodiment leverages the widespread distribution of benthic animals, their strong resistance to toxicity and pollution, and their ability to accumulate, stabilize, or degrade water pollutants. This allows for multi-factor synergistic degradation of nanoplastics, enhancing the nanoplastic degradation capacity of constructed wetland systems. While enabling the degradation of nanoplastics by benthic animals within the matrix, they also synergize with aquatic plants and microorganisms to enhance the degradation of nanoplastics.

[0023] Furthermore, the river sand layer is screened using a 100-mesh sieve. The thickness of the river sand layer is 40-45 cm. If the river sand thickness is too thin, it will affect the self-disturbance and living habits of benthic animals, thereby affecting the activity of benthic animals and reducing the degradation of nano-microplastics. If the river sand layer is too thick, the dissolved oxygen will gradually decrease with depth, affecting the activity of benthic animals. The thickness of the river sand layer is preferably 40 cm deep. The use of river sand helps benthic animals grow better and maintain their optimal activity. At the same time, due to its small particle size, river sand can more easily intercept the loss of nano-microplastics, improving removal efficiency.

[0024] Furthermore, the matrix filler also includes a gravel layer, which is disposed below the river sand layer to prevent clogging of the water outlet. Furthermore, the gravel layer has a particle size of 2-3 cm and a thickness of 10-12 cm. Since the gravel layer is not suitable for benthic animals, the gravel layer should not be too thick. However, if the gravel layer is too thin, river sand may be trapped in the gaps between the gravel, causing clogging of the water outlet and thus affecting the pollutant removal efficiency of the entire constructed wetland system. Preferably, the gravel layer is set to a thickness of 10 cm.

[0025] In this embodiment, the benthic animals are one of water earthworms, chironomid larvae, and river clams. Since these three benthic animals have high population density in normal wetland environments, strong pollution resistance, good environmental indication, pollutant removal, food chain enrichment, and easy interaction with microorganisms, these three benthic animals are selected as experimental dosing organisms.

[0026] In this embodiment, the density of benthic animals in river sand is: 12000-13000 water earthworms / m 2 、Clams 900-1000 / m 2 , Chironomid larvae 13000-15000 / m 2 , preferably, 12800 water earthworms / m 2 、Clams 1000 / m 2 、Chironomid larvae 4000 / m 2This density was set because research has found that benthic animals have the highest survival rates in river sand environments at this density. It also maximizes their feeding and pollutant degradation, and is the optimal density for achieving maximum pollution tolerance. Densities above or below this range will affect the efficiency of benthic wetlands in removing nano-microplastics.

[0027] In this embodiment, a porous PVC tube is provided in the middle of the matrix layer of the system for monitoring the physical and chemical parameters of the matrix environment, such as in situ monitoring of dissolved oxygen (DO), pH, etc. The diameter is 3-5 cm. By monitoring the matrix environment at any time, the optimal removal efficiency of nano-scale microplastics is guaranteed.

[0028] The artificial wetland system can be used to plant the common wetland plant Acorus calamus. It adopts a continuous flow operation mode, with water entering from the upper part of the device and discharging from the lower part, ensuring the continuous flow of the water to be treated in the matrix, so that the artificial wetland system maintains a stable environment.

[0029] In another typical embodiment of the present invention, a method for removing nano-microplastics by using benthic animals to enhance artificial wetlands is provided. Inlet water enters the artificial wetland through a peristaltic pump, and passes through the gravel layer and the river sand layer from bottom to top. Nano-microplastics in the water are intercepted in the river sand layer, and benthic animals ingest and degrade the nano-microplastics, thereby removing the nano-microplastics in the water. The purified water is discharged through a drain pipe.

[0030] Furthermore, the hydraulic retention time is 2-5 days and the influent load is 0.15-0.4 m 3 (m 2 • cycle), under this influent load environment, it helps to maintain the stable progress of the reaction in the constructed wetland system.

[0031] Benthic animals can directly ingest and accumulate nano-sized microplastics, such as Figure 1 As shown, the nano-scale microplastics are fluorescently labeled polystyrene microplastics. Figure 1 As can be seen in the figure, confocal imaging was performed on a biological section of a benthic organism. Figure 1 (ah) are confocal images of longitudinal sections of benthic animals exposed to 80 nm fluorescently labeled PS microspheres. Fluorescent signals from polystyrene microspheres were detected in all benthic animals exposed to polystyrene. (a)(c)(e)(g) are bright-field images, and (b)(f)(d)(h) are fluorescent images, indicating that benthic animals ingested microplastics and that microplastics accumulated in their bodies. By ingesting and degrading microplastics, benthic animals prevent secondary contamination.

[0032] At the same time, benthic animals will have a synergistic effect with wetland plants, thereby affecting the accumulation of nano-scale microplastics by wetland plants. Figure 2 It can be seen that confocal imaging was performed on plant sections under different dosing conditions. Figure 2 (ah) are confocal images of longitudinal sections of 80nm fluorescent microplastics in plants under different addition conditions, (a)(c)(e)(g) are fluorescence images, and (b)(f)(d)(h) are bright field images, among which (a)(c)(e) are the fluorescence signal intensities of nanoscale microplastics in plants under the cooperation of different benthic animals, and (g) is the fluorescence signal intensity of nanoscale microplastics in plants without the cooperation of benthic animals. It can be seen that the fluorescence signal intensity of nanoscale microplastics in plants with the cooperation of benthic animals is greater than that without the cooperation of benthic animals, so the synergistic effect between benthic animals and wetland plants will enhance the accumulation of nanoscale microplastics by wetland plants.

[0033] In addition, benthic animals can also change the microbial community structure of the aquatic ecosystem through their own activities, as well as parasitic and predatory relationships with microorganisms, and interact with various environmental factors in the ecosystem to achieve pollutant removal and environmental optimization, thereby changing pollutant transformation.

[0034] In another typical embodiment of the present invention, a system for enhancing the removal of nano-microplastics by artificial wetlands using benthic animals and / or a method for enhancing the removal of nano-microplastics in water by artificial wetlands are provided for use in sewage purification. Benthic animals cooperate with microbial plants to improve the removal efficiency of nano-microplastics in water. During application, benthic animals can increase the removal efficiency of polystyrene microplastics in the effluent water of the system by approximately 43.1%, 49.3% and 54.7%.

[0035] In order to enable those skilled in the art to more clearly understand the technical solution of the present disclosure, the technical solution of the present disclosure will be described in detail below with reference to specific embodiments.

[0036] The experimental device used influent from a wastewater treatment plant, Class B effluent (GB 18918-2002), and was dosed with a specific concentration of polystyrene (PS), a typical nanoplastic. This influent was pumped into a pilot-scale constructed wetland via a peristaltic pump. The water then flowed through the constructed wetland from top to bottom, and the purified water was discharged through a drainpipe. A total of eight groups were set up in the benthic constructed wetland: a blank control, a group treated with water earthworms, a group treated with chironomid larvae, and a group treated with river clams.

[0037] Example 1

[0038] Add water earthworm group 1

[0039] The small-scale artificial wetland test device was constructed using inorganic glass columns with an inner diameter of 15 cm and a height of 60 cm to construct a laboratory-scale artificial wetland experimental device. The aquatic plant was the common Acorus calamus. The substrate consisted of two layers: a 10-cm-deep layer of gravel with a particle size of 2-3 cm to prevent clogging of the water outlet; and an upper layer of 40 cm of river sand sieved through a 100-mesh sieve. The common benthic animal, water earthworms, were also added.

[0040] During operation, wastewater containing nanoplastics was introduced into the pilot constructed wetland system via a peristaltic pump. The hydraulic retention time (HRT) was set to three days. The influent pollutant concentration was adjusted based on the system's operational status, with a focus on quantitative and qualitative analysis of nanoplastics in the effluent.

[0041] Add water earthworm group 2

[0042] The addition of water earthworms to group 2 was the same as that to group 1.

[0043] Example 2

[0044] Group 1 with chironomid larvae

[0045] The small-scale artificial wetland test device was constructed using inorganic glass columns with an inner diameter of 15 cm and a height of 60 cm to construct a laboratory-scale artificial wetland experimental device. The aquatic plants used were common calamus. The substrate consisted of two layers: a 10-cm-deep layer of gravel with a particle size of 2-3 cm to prevent clogging of the water outlet; and an upper layer of 40-cm-thick river sand sieved through a 100-mesh sieve. Chironomid larvae, a common benthic animal, were also added.

[0046] During operation, wastewater containing nanoplastics was introduced into the pilot constructed wetland system via a peristaltic pump. The hydraulic retention time (HRT) was set to three days. The influent pollutant concentration was adjusted based on the system's operational status, with a focus on quantitative and qualitative analysis of nanoplastics in the effluent.

[0047] Group 2 with chironomid larvae

[0048] The dosage of group 2 with chironomid larvae is the same as that of group 1 with chironomid larvae.

[0049] Example 3

[0050] Adding Clams Group 1

[0051] The small-scale artificial wetland test device was constructed using inorganic glass columns with an inner diameter of 15 cm and a height of 60 cm. The aquatic plants used were common calamus. The substrate consisted of two layers: a 10-cm-deep layer of gravel with a particle size of 2-3 cm to prevent clogging of the water outlet; and an upper layer of 40 cm of river sand sieved through a 100-mesh sieve. Common benthic animals, such as river clams, were also added.

[0052] During operation, wastewater containing nanoplastics was introduced into the pilot constructed wetland system via a peristaltic pump. The hydraulic retention time (HRT) was set to three days. The influent pollutant concentration was adjusted based on the system's operational status, with a focus on quantitative and qualitative analysis of nanoplastics in the effluent.

[0053] Adding Clams Group 2

[0054] The addition of river clams to group 2 was the same as that to group 1.

[0055] Two groups are set up for each experiment, one of which is a parallel group. The purpose is to ensure that there is no randomness in the data of the device operation results and to improve the accuracy of the nano-microplastic removal efficiency.

[0056] Comparative Example 1

[0057] Blank group 1

[0058] The small-scale artificial wetland test device was constructed using inorganic glass columns with an inner diameter of 15 cm and a height of 60 cm. The aquatic plants used were common calamus. The substrate consisted of two layers: a 10-cm-deep layer of gravel with a particle size of 2-3 cm to prevent clogging of the water outlet; and an upper layer of 40 cm of river sand sieved through a 100-mesh sieve.

[0059] During operation, wastewater containing nanoplastics was introduced into the pilot constructed wetland system via a peristaltic pump. The hydraulic retention time (HRT) was set to three days. The influent pollutant concentration was adjusted based on the system's operational status, with a focus on quantitative and qualitative analysis of nanoplastics in the effluent.

[0060] Blank group 2

[0061] Blank group 2 was the same as blank group 1.

[0062] After 180 days of stable operation, Figure 3 As shown in the figure, the removal rates of nano-microplastics in water by different benthic artificial wetland systems were 80.8%, 86.9% and 92.3%, respectively, which were 43.1%, 49.3% and 54.7% higher than those in the blank control group. The experimental results show that benthic animals have a good feeding and accumulation effect on nano-microplastics ( Figure 1 Benthic animals ingest nano-scale microplastics). Different benthic animals cooperate with plants to enhance the accumulation effect of plants on nano-scale microplastics ( Figure 2 The accumulation effect of plants on nano-microplastics under different addition conditions), so the artificial wetland system uses benthic animals as a matrix and cooperates with plants and microorganisms to have a good effect on removing nano-microplastics from water.

[0063] like Figure 4As shown, the concentration of nano-microplastics in the effluent of artificial wetlands with different benthic animals after purifying microplastic-containing wastewater, among which the content of nano-microplastics in the effluent of artificial wetlands containing river clams is 769.97 μg / L, the content of nano-microplastics in the effluent of artificial wetlands containing chironomid larvae is 522.28 μg / L, the content of nano-microplastics in the effluent of artificial wetlands containing water earthworms is 306.2 μg / L, and the content of nano-microplastics in the effluent of artificial wetlands without benthic animals is 2493.7 μg / L. It can be seen that by placing benthic animals in artificial wetlands, the removal rate of nano-microplastics in artificial wetlands can be effectively improved.

[0064] like Figure 5 As shown in the figure, in the artificial wetlands with different benthic animals, the interaction between different benthic animals and microorganisms in the wetland environment leads to differences in the abundance of microorganisms in the artificial wetlands with different benthic animals, which results in different abundances of enzymes that can degrade microplastics in different microorganisms, affecting the performance of microorganisms in degrading microplastics in the entire wetland system. In the bar chart in the figure, G1 (containing river clams), G2 (containing chironomid larvae), G3 (containing water earthworms) and G4 (blank) represent different artificial wetlands. It can be seen from the figure that the abundance of key microbial enzymes for degrading microplastics in each step is different, which proves that the ability of each artificial wetland system to degrade nano-scale microplastics is different, and that the interaction between different benthic animals and microorganisms will promote the degradation of nano-scale microplastics.

[0065] The experimental results show that three benthic animals, earthworms, river clams and midge larvae, have a good feeding and accumulation effect on nano-microplastics, and will promote the accumulation of nano-microplastics in wetland plants. ( Figure 1 、 2 The ingestion of nano-microplastics by benthic animals and the accumulation of nano-microplastics by plants under different dosing conditions). In artificial wetland systems, benthic animals are used as a matrix in conjunction with plants and microorganisms, which has a good effect on removing nano-microplastics from water ( Figure 3 、 4 , 5. Effluent concentration, removal efficiency and microbial degradation mechanism of nano-microplastics in benthic constructed wetlands).

[0066] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A system for removing nano- and micro-plastics by enhancing benthic animals in artificial wetlands, characterized in that: The artificial wetland comprises a matrix filler comprising a river sand layer doped with benthic animals, the particles of the river sand layer intercept nano-scale microplastics in the water, the benthic animals ingest and degrade the nano-scale microplastics, and cooperate with the microorganisms and plants in the artificial wetland to enhance the removal of nano-scale microplastics in the water; The benthic animal is one of water earthworms, chironomid larvae and river clams.

2. The benthic animal-enhanced constructed wetland system for removing nano- and microplastics according to claim 1, characterized in that: The river sand in the river sand layer is screened using a 100-mesh sieve, and the thickness of the river sand layer is 40-45 cm.

3. The benthic animal enhanced artificial wetland system for removing nano-microplastics according to claim 1, characterized in that: The matrix filler further includes a gravel layer, which is arranged below the river sand layer.

4. The benthic animal-enhanced constructed wetland system for removing nano- and microplastics according to claim 3, characterized in that: The gravel particle size of the gravel layer is 2-3 cm, and the thickness of the gravel layer is 10-12 cm.

5. The benthic animal enhanced artificial wetland system for removing nano- and microplastics according to claim 1, characterized in that: The density of benthic animals in river sand is: 12,000-13,000 earthworms / m 2 、Clams 900-1000 / m 2 , Chironomid larvae 13000-15000 / m 2 .

6. The benthic animal-enhanced constructed wetland system for removing nano- and microplastics according to claim 1, characterized in that: A porous PVC pipe is provided in the middle of the system for monitoring the physical and chemical parameters of the matrix environment.

7. A method for enhancing the removal of nano- and micro-plastics from water using artificial wetlands, implemented using the system according to any one of claims 1 to 6, characterized in that: The incoming water enters the artificial wetland through a peristaltic pump, passing through the river sand layer and gravel layer from top to bottom. Nano-scale microplastics in the water are intercepted in the river sand layer, and benthic animals eat and degrade the nano-scale microplastics, removing the nano-scale microplastics in the water. The purified water is discharged through the drain pipe.

8. The method for removing nano- and micro-plastics from water using an enhanced artificial wetland according to claim 7, wherein: The hydraulic retention time is 2-5 days and the influent load is 0.15-0.4 m 3 / (m 2 •cycle).

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