Method for inhibiting the generation of an odor in a water source using submerged plants

Abstract

This invention relates to a method for suppressing odor generation in water sources using submerged plants. The specific steps are as follows: S1. Determine the cause of odor problems in lake / reservoir type water sources. If the odor problem is caused by odor-producing filamentous cyanobacteria, measure the concentration of odor-causing substances and the transparency of the raw water in the lake / reservoir type water source. S2. Construct a flexible submerged plant odor control module, which is divided into a high-efficiency odor control zone and a stable zone. S3. Select fine-leaved submerged plants and plant them in the high-efficiency odor control zone, and select broad-leaved and fine-leaved submerged plants and plant them in the stable zone. S4. Introduce raw water from the lake / reservoir type water source containing a high concentration of odor-causing substances into the flexible module, and set the hydraulic residence time of the raw water to be treated in each flexible module. S5. Based on the water supply and odor-causing substance concentration of the lake / reservoir type water source, connect multiple odor control flexible modules in series or parallel. The treated water is then returned to the lake / reservoir type water source or directly transported to a water treatment plant. This invention is highly flexible and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of water source quality protection and aquatic ecosystem restoration, and in particular to a method for using submerged plants to suppress the generation of odors in water sources. Background Technology

[0002] Algal-induced odor problems in water bodies are a common issue faced by lake and reservoir-type drinking water sources globally. Odor-producing filamentous cyanobacteria proliferate seasonally, generating large amounts of odor-causing substances (such as dimethyl isobathrol) through metabolism, becoming a key factor affecting the quality of lake and reservoir-type drinking water sources. Lake and reservoir-type water sources are important drinking water sources and strategic water resource reserves in my country. The generation of odors not only significantly reduces the sensory appeal of drinking water sources but also increases the difficulty of advanced drinking water treatment.

[0003] Unlike algal bloom algae, odor-producing filamentous cyanobacteria are usually filamentous and do not easily aggregate. They can tolerate low nutrient and low light environments. A small amount of odor-producing filamentous cyanobacteria can produce a large amount of odor substances. Therefore, conventional methods for controlling algal bloom algae may not be effective against odor-producing filamentous cyanobacteria.

[0004] Currently, traditional odor control in drinking water still primarily relies on end-of-pipe treatment at water plants. Methods combining ozone oxidation and activated carbon adsorption are not only costly but also have limited effectiveness. Therefore, in-situ suppression of odor-producing algae and their generation at lake and reservoir water sources is crucial for solving the odor problem. Among in-situ odor control methods, physical methods such as mechanical removal and aeration suffer from high energy consumption and low removal rates, and have not been proven effective against odor-producing algae. Chemical methods, such as algaecides, raise safety and health concerns. Biological methods, on the other hand, are relatively green, ecological, and safe, and have garnered significant attention. Summary of the Invention

[0005] The purpose of this invention is to provide a method for inhibiting the generation of odors in water sources using submerged plants. This method specifically suppresses the proliferation of odor-producing algae and reduces the generation of odor-causing substances in water bodies. Without harming other aquatic organisms and ensuring water quality safety, this invention utilizes the nutrient competition, shading effect, and allelopathy of submerged plants to inhibit the growth and production of odor-producing algae, thus addressing the odor problem at its source. This effectively reduces the concentration of algal-derived odor-causing substances and odor-producing filamentous cyanobacteria in lakes and reservoirs, thereby effectively controlling algal-induced odor problems in water bodies. By selectively inhibiting the proliferation of odor-producing algae, the cost of drinking water treatment is reduced. Furthermore, this invention proposes a submerged plant optimization process, utilizing fine-leaved submerged plants to achieve higher odor suppression efficiency. Compared with existing technologies, the algae suppression and odor control method provided by this invention is highly flexible, ecologically green and pollution-free, highly efficient and safe, achieving a comprehensive odor suppression rate of over 90% in water sources, which helps in-situ control of algal-derived odor problems in water sources.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for suppressing the generation of odors in water sources using submerged plants, the specific steps of which are as follows:

[0008] S1. Determine the cause of odor problems in lake and reservoir type water sources. If the odor problem is caused by odor-producing filamentous cyanobacteria, measure the concentration of odor substances and the transparency of the raw water in the lake and reservoir type water source.

[0009] S2. Construct a flexible module for controlling odor with submerged plants, wherein the flexible module is divided into a high-efficiency odor control zone and a stable zone;

[0010] S3. Select small-leaved submerged plants for planting in the high-efficiency odor control zone, and select broad-leaved and small-leaved submerged plants for planting in the stability zone;

[0011] S4. Introduce raw water from a lake or reservoir containing a high concentration of odorous substances into the flexible module, and set the hydraulic residence time of the raw water to be treated in each flexible module.

[0012] S5. Based on the water supply and odor concentration of the lake / reservoir type water source, multiple odor control flexible modules are connected in series or in parallel. The treated water is then returned to the lake / reservoir type water source or directly transported to the water plant.

[0013] Furthermore, in step S1, odor-producing filamentous cyanobacteria are a class of cyanobacteria known to produce odorous substances, such as *Anabaena*, *Pseudo-Anabaena*, *Oscillatoria*, and *Hylocereus*. If a large number of one or more of these cyanobacteria appear in a water source with an odor, it can be considered that the odor is caused by odor-producing filamentous cyanobacteria. Conversely, if there is an odor even without odor-producing filamentous cyanobacteria, it is generally caused by actinomycetes. In practice, the correlation between the algal density of odor-producing filamentous cyanobacteria and the concentration of odorous substances is used for verification. Alternatively, the method of using algal odor-producing genes can also be used for verification.

[0014] Furthermore, in step S1, the odor substances include dimethylisoborneol and geosmin, as specified in the "Standards for Drinking Water Quality" (GB 5749-2022).

[0015] Furthermore, in step S1, the odor-producing filamentous cyanobacteria is distinct from bloom cyanobacteria; it is a filamentous cyanobacteria that can produce large amounts of dimethyl isoborneol or geosmin even in small quantities.

[0016] Furthermore, the odor-producing filamentous cyanobacteria are selected from any one or more combinations of Anabaena pseudoaquatica, Oscillatoria, Floating filamenta, Bungeiformia, Sheath filamenta, or Rhynchus, with Anabaena pseudoaquatica being the sole odor-producing source.

[0017] Furthermore, in step S1, the concentration of odor substances in the raw water of the lake-reservoir type water source is determined by headspace solid phase microextraction gas chromatography-mass spectrometry, specifically referring to the national standard GB / T 5750.8-2023 "Standard Examination Methods for Drinking Water - Part 8: Organic Matter Indicators".

[0018] Furthermore, in step S2, the area of ​​the high-efficiency olfaction control region is greater than 1 / 2 of the flexible module, preferably, the ratio of high-efficiency olfaction control region to stable region is 7:3.

[0019] Furthermore, in step S2, the flexible module is a shallow, enclosed water area with a design water depth of less than 2 meters. The ratio of the raw water transparency to the design water depth in the lake / reservoir type water source is >0.5, preferably 0.55. This determination method ensures that most submerged plants can grow and reproduce healthily under this water depth condition. [1,2] .

[0020] [1]Yang C, Shi 20;808:152199.doi:10.1016 / j.scitotenv.2021.152199.Epub 2021Dec 7.PMID:34890676.

[0021] [2]Cui Z, Huang Q, Sun J, Wan B, Zhang S, Shen J, Wu J, Li J, Yang C. TheSecchi disk depth to water depth ratio affects morphological traits ofsubmerged macrophytes:Development patterns and ecological implications.SciTotal Environ.2024Jan 10;907:167882.doi:10.1016 / j.scitotenv.2023.167882.Epub2023Oct 18.PMID:37858823.

[0022] Furthermore, in step S2, the flexible module is a closed water body suitable for the growth of aquatic plants, and the bottom of the flexible module is sand or mud, and is free of harmful substances.

[0023] Furthermore, in step S2, the flexible module can be installed inside a lake or reservoir type water source area, or in a fixed area outside the lake or reservoir type water source area;

[0024] The size and number of the flexible modules are determined according to the size of the site where the flexible modules are fixed and the water supply.

[0025] Furthermore, in step S3, the narrow-leaved submerged plant is a submerged plant with smaller leaves and a larger specific surface area; the broad-leaved submerged plant is a submerged plant with larger leaves, and the broad-leaved submerged plant is used to improve the stability of the submerged plant community.

[0026] Furthermore, the fine-leaved submerged plant is selected from any one or more of the following: *Ceratophyllum demersum*, *Hydrilla verticillata*, or *Myriophyllum spicatum*.

[0027] The broad-leaved submerged plants mentioned are selected from any one or more of Vallisneria natans, Potamogeton crispus, or Potamogeton malaianus.

[0028] Furthermore, in step S3, the planting density within the high-efficiency odor control zone and the stable zone is greater than 5 kg wet weight / m². 2 Planting density refers to the biomass of submerged plants planted per unit area within the high-efficiency odor control zone or stable zone. The total planting density of broad-leaved and narrow-leaved submerged plants in the stable zone is greater than 5 kg wet weight / m². 2 .

[0029] Preferably, after the submerged plant community has matured, the density in the highly efficient odor-controlling zone and the stable zone reaches 10-15 kg wet weight / m³. 2 .

[0030] Furthermore, in step S3, the submerged plant is planted in spring, from April to May, so that the submerged plant can grow and reproduce rapidly in summer, thus inhibiting the production of odorous filamentous blue-green algae. The better the submerged plant grows, the less odorous substances are produced.

[0031] Furthermore, in step S4, the raw water from the lake-type water source flows in from the high-efficiency odor control zone and flows out from the stable zone, and the hydraulic residence time in the flexible module is controlled by controlling the inflow rate.

[0032] Furthermore, in step S4, the hydraulic residence time of the raw water to be treated in the flexible module is 5-7 days.

[0033] Furthermore, in step S4, a higher concentration is defined as a concentration of odorous substances in the raw water of the lake-reservoir type water source when the concentration is greater than 100 ng / L.

[0034] Furthermore, in step S5, when the concentration of odorous substances in the raw water of a lake or reservoir-type water source ranges from 100 to 300 ng / L, multiple flexible modules are connected in parallel, which can greatly improve the processing capacity.

[0035] When the concentration of odorous substances in the raw water of a lake or reservoir-type water source exceeds 300 ng / L, multiple flexible modules are connected in series. The series connection of flexible modules can greatly improve the effect of algae suppression and odor control.

[0036] Furthermore, the inlet of the flexible module is connected to a lake-reservoir type water source, and the outlet of the flexible module flows into a collection channel, which is connected to the water plant and the lake-reservoir type water source through pipelines.

[0037] Multiple flexible modules are arranged side by side. One end of each flexible module is connected to a lake or reservoir-type water source through a first parallel pipe, and the other end of each flexible module is connected to a water collection channel through a second parallel pipe. Adjacent flexible modules are connected end to end through a second series pipe. The outermost flexible module on one side is connected to the lake or reservoir-type water source through a first series pipe, and the outermost flexible module on the other side is connected to the water collection channel through a third series pipe.

[0038] When connected in parallel, the second series pipe between adjacent flexible modules is closed, the first parallel pipe connecting the flexible module to the lake / reservoir type water source is opened, the second parallel pipe connecting the flexible module to the water collection channel is opened, and the first and third series pipes are closed.

[0039] When connected in series, the second series pipe between adjacent flexible modules is opened, the first series pipe connecting the outermost flexible module on one side to the lake-type water source is opened, the third series pipe connecting the outermost flexible module on the other side to the water collection channel is opened, and the first parallel pipe and the second parallel pipe are closed.

[0040] Furthermore, after step S5, there is step S6: when the submerged plants wither, the dead submerged plants need to be harvested in time. If the concentration of odor substances is very low at this time, all flexible modules can be deactivated and reactivated in the following year when the odor substances are more concentrated.

[0041] The principle of this invention is as follows:

[0042] The growth and reproduction period of odor-producing filamentous cyanobacteria in drinking water sources is generally from summer to early autumn, which basically coincides with the rapid growth period of submerged plants. This invention first utilizes the fact that submerged plants absorb a large amount of nutrients from the water during their growing season, reducing the concentration of nutrients available to odor-producing algae in the water. In particular, phosphorus concentration has a significant impact on the growth and odor production of odor-producing algae, thus inhibiting their growth and odor production from the perspective of nutrients. The canopy or bottom plant bed formed by submerged plants effectively blocks solar radiation, reducing the light available to odor-producing filamentous cyanobacteria. Light is equally important for the growth and odor production of odor-producing algae, and the shading effect of submerged plants creates light limitation for them. In addition, some submerged plants (such as the fine-leaved Ceratophyllum demersum and Myriophyllum sp.) can release allelochemicals that specifically attack the photosynthetic system of odor-producing filamentous cyanobacteria, reducing their photosynthetic activity and electron transfer efficiency in the second stage of photosynthesis. Under the combined effect of the above three mechanisms, the nutrient salt utilization efficiency, photosynthetic efficiency and photosynthetic activity of odor-producing filamentous cyanobacteria in water sources are significantly reduced, thereby enhancing the odor control effect by inhibiting the growth and reproduction of odor-producing filamentous cyanobacteria in water sources.

[0043] Submerged plants reduce the production of odor-producing substances by inhibiting the growth and odor production of odor-producing filamentous cyanobacteria. Firstly, they reduce the amount of nutrients available for odor production, algal growth, and odor generation through their absorption of nutrients. Secondly, they block light from the lower water layers, limiting the photosynthesis of odor-producing algae and inhibiting their growth. Furthermore, narrow-leaved submerged plants can release allelochemicals that inhibit the photosynthetic activity of odor-producing filamentous cyanobacteria, damage their photosynthetic systems, and promote cell apoptosis.

[0044] The unique features of this invention lie in the design of the flexible modules, the selection method of submerged plants, and the arrangement of the flexible modules. First, the water depth of the flexible modules in this invention ensures the healthy growth and reproduction of most submerged plants, preventing their death due to poor underwater light conditions. The design of the high-efficiency odor control zone and the stability zone balances algae suppression and odor control effectiveness with the stability of the submerged plant community. Second, the submerged plant selection method of this invention effectively suppresses both the growth and odor production of odor-producing filamentous cyanobacteria, with a community dominated by slender-leaved algae exhibiting the highest algae suppression and odor control efficiency. Finally, the flexible module arrangement method proposed in this invention offers high flexibility, strong applicability, and excellent odor control without causing secondary pollution.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] When odor outbreaks occur in the same body of water, the concentration of odor substances in areas with abundant submerged plants is significantly lower than in areas without submerged plants. This invention explores the inhibitory effects of different types of submerged plants on the growth and odor production of characteristic odor-producing algae through simulation experiments, and finds that submerged plants have a significant ability to inhibit algae and control odor.

[0047] Compared with existing methods, the submerged plant odor control method provided by this invention can effectively inhibit the growth and reproduction of odor-producing algae in the long term, thereby reducing the generation of odor substances. Under the premise of adopting this method and proper management, the goal of long-term odor control of water sources can be achieved, improving the quality of drinking water sources, reducing the treatment costs of drinking water plants, and enhancing the landscape effect of drinking water source areas. Attached Figure Description

[0048] Figure 1 These are the inhibition effects of different submerged plants on dimethyl isoborneol in Examples 2-6;

[0049] Figure 2 These are the inhibition effects of different submerged plants on *Houttuynia cordata* produced in Examples 2-6;

[0050] Figure 3 This is a diagram illustrating the shading effect of submerged plants on *Houttuynia cordata*, as described in Example 7.

[0051] Figure 4 Example 8 illustrates the adsorption of nutrients by submerged plants;

[0052] Figure 5 These are the allelopathic inhibition effects of different submerged plants on the photosynthetic activity and growth of *Anabaena odorata* in Examples 9-12.

[0053] Figure 6 This is a schematic diagram of the connection of the flexible module of the present invention;

[0054] The following are the diagram labels: 1. Flexible module; 2. Lake / reservoir type water source; 3. Water plant; 4. Water collection channel; 5. First series pipe; 6. Second series pipe; 7. First parallel pipe; 8. Second parallel pipe; 9. Third series pipe. Detailed Implementation

[0055] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0056] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0057] Example 1

[0058] like Figure 6 As shown in the figure, this embodiment provides a method for suppressing the generation of odors in water sources using submerged plants. The specific steps are as follows:

[0059] S1. Determine the cause of the odor problem in Lake-type Water Source 2. If the odor problem is caused by odor-producing filamentous cyanobacteria, measure the concentration of odor substances and the transparency of the raw water in Lake-type Water Source 2.

[0060] S2. Construct a flexible submerged plant odor control module 1, wherein the flexible module 1 is divided into a high-efficiency odor control zone and a stable zone;

[0061] S3. Select small-leaved submerged plants for planting in the high-efficiency odor control zone, and select broad-leaved and small-leaved submerged plants for planting in the stability zone;

[0062] S4. Introduce raw water from a lake-type water source 2 containing a high concentration of odor substances into the flexible module 1, and set the hydraulic residence time of the raw water to be treated in each flexible module 1.

[0063] S5. Based on the water supply and odor concentration of the lake-type water source 2, multiple odor control flexible modules 1 are connected in series or in parallel, and the treated water is returned to the lake-type water source 2 or directly transported to the water plant 3.

[0064] In this embodiment, the odor substances in step S1 include dimethylisoborneol and geosmin.

[0065] In this embodiment, in step S1, the odor-producing filamentous cyanobacteria is different from algal bloom cyanobacteria; it is a filamentous cyanobacteria that can produce large amounts of dimethyl isoborneol or geosmin even in small quantities.

[0066] In this embodiment, the odor-producing filamentous cyanobacteria are selected from any one or more combinations of Anabaena pseudoaquatica, Oscillatoria, Floating filamenta, Bungeiformia, Sheath filamenta, or Rhynchus, with Anabaena pseudoaquatica being the sole odor-producing source.

[0067] In this embodiment, in step S1, the concentration of odor substances in the raw water of the lake-reservoir type water source 2 is determined by headspace solid phase microextraction gas chromatography-mass spectrometry.

[0068] In this embodiment, in step S2, the ratio of high-efficiency snoring control region to stable region is 7:3.

[0069] In this embodiment, in step S2, the flexible module 1 is a shallow enclosed water area. The designed water depth of the flexible module 1 is less than 2 meters, and the transparency of the raw water to be treated in the lake-reservoir type water source 2 is 0.55. The water depth determination method can ensure that most submerged plants can grow and reproduce healthily under this water depth condition.

[0070] In this embodiment, in step S2, the flexible module 1 is a closed water body suitable for the growth of aquatic plants, and the bottom of the flexible module 1 is sand or mud, and is free of harmful substances.

[0071] In this embodiment, in step S2, the flexible module 1 can be located inside the lake-reservoir type water source 2 or in a fixed area outside the lake-reservoir type water source 2;

[0072] The size and number of the flexible modules 1 are determined according to the size of the site where the flexible modules 1 are fixed and the water supply.

[0073] In this embodiment, the fine-leaved submerged plant is selected from any one or more of the following: *Ceratophyllum demersum*, *Hydrilla verticillata*, or *Myriophyllum spicatum*.

[0074] The broad-leaved submerged plants mentioned are selected from any one or more of Vallisneria natans, Potamogeton crispus, or Potamogeton malaianus.

[0075] In this embodiment, in step S3, the planting density in the high-efficiency odor control zone and the stable zone is greater than 5 kg wet weight / m². 2 Planting density refers to the biomass of submerged plants planted per unit area within the high-efficiency odor control zone or stable zone. The total planting density of broad-leaved and narrow-leaved submerged plants in the stable zone is greater than 5 kg wet weight / m². 2 .

[0076] Furthermore, once the submerged plant community has matured, the density within the highly efficient odor-controlling zone and the stable zone reaches 10-15 kg wet weight / m³. 2 .

[0077] In this embodiment, in step S3, the submerged plant is planted in spring, from April to May, so that the submerged plant can grow and reproduce rapidly in summer, becoming a suppressor of odor-producing filamentous blue-green algae. The better the submerged plant grows, the less odorous substances are produced.

[0078] In this embodiment, in step S4, the raw water from the lake-type water source 2 flows in from the high-efficiency odor control zone and flows out from the stable zone. The hydraulic residence time in the flexible module 1 is controlled by controlling the inflow rate.

[0079] In this embodiment, in step S4, the hydraulic residence time of the raw water to be treated in the flexible module 1 is 5-7 days.

[0080] In this embodiment, in step S4, a higher concentration is defined as a concentration of odorous substances in the raw water of the lake-reservoir type water source 2 when the concentration is greater than 100 ng / L.

[0081] In this embodiment, in step S5, when the concentration of odorous substances in the raw water of the lake-reservoir type water source 2 is in the range of 100 to 300 ng / l, multiple flexible modules 1 are connected in parallel, and the parallel flexible modules can greatly improve the processing capacity.

[0082] When the concentration of odorous substances in the raw water of the lake-reservoir type water source 2 is greater than 300 ng / L, multiple flexible modules 1 are connected in series. The series connection of flexible modules can greatly improve the algae suppression and odor control effect.

[0083] In this embodiment, the inlet of the flexible module 1 is connected to the lake-reservoir type water source 2, and the outlet of the flexible module 1 flows into the collection channel 4. The collection channel 4 is connected to the water plant 3 and the lake-reservoir type water source 2 through pipelines.

[0084] Multiple flexible modules 1 are arranged side by side. One end of each flexible module 1 is connected to the lake-reservoir type water source 2 through a first parallel pipe 7. The other end of each flexible module 1 is connected to the water collection channel 4 through a second parallel pipe 8. Adjacent flexible modules 1 are connected end to end through a second series pipe 6. The outermost flexible module 1 on one side is connected to the lake-reservoir type water source 2 through a first series pipe 5, and the outermost flexible module 1 on the other side is connected to the water collection channel 4 through a third series pipe 9.

[0085] When connected in parallel, the second series pipe 6 between adjacent flexible modules 1 is closed, the first parallel pipe 7 connecting the flexible module 1 to the lake-reservoir type water source 2 is opened, the second parallel pipe 8 connecting the flexible module 1 to the water collection channel 4 is opened, and the first series pipe 5 and the third series pipe 9 are closed.

[0086] When connected in series, the second series pipe 6 between adjacent flexible modules 1 is opened, the first series pipe 5 connecting the outermost flexible module 1 on one side to the lake-type water source 2 is opened, the third series pipe 9 connecting the outermost flexible module 1 on the other side to the water collection channel 4 is opened, and the first parallel pipe 7 and the second parallel pipe 8 are closed.

[0087] In this embodiment, step S6 is provided after step S5. When the submerged plants wither, the dead submerged plants need to be harvested in time. If the concentration of odor substances is very low at this time, all flexible modules 1 can be deactivated and reactivated in the following year when the odor substances are more concentrated.

[0088] Example 2

[0089] This embodiment provides a method for inhibiting the density of *Anabaena spp.* and the concentration of the odor compound dimethyl isoborneol using the submerged plant *Vallisneria natans*. The specific steps are as follows:

[0090] After 7 days of cultivation, an initial algal density of 2.51 × 10⁻⁶ was selected. 8 Samples of *Anabaena* were collected at a concentration of 1.7% (v / L) of live *Vallisneria natans* (no such addition was made to the control group). The samples were then cultured for 7 days at 25°C under light conditions of 1800–2200 lx.

[0091] The density of *Anabaena pseudoanthraceae* in the control group was 5.8 × 10⁻⁶. 8 The concentration of dimethyl isoborneol was 5190 ng / L; after being co-cultured with Vallisneria natans for 7 days, the density of *Anabaena pseudocaryophylla* was measured to be 4.9 × 10⁻⁶. 7 Units / L ( Figure 1 The concentration of dimethylisoborneol was 1017 ng / L. Figure 2 Compared with the control group, the algal density decreased by 90.2% and the dimethyl isofensteinol concentration decreased by 80.4%.

[0092] Example 3

[0093] This embodiment provides a method for inhibiting the density of *Anabaena simulans* and the concentration of the odor compound dimethyl isoborneol using the submerged plant *Potamogeton crispus*. The specific steps are as follows:

[0094] After 7 days of cultivation, an initial algal density of 2.51 × 10⁻⁶ was selected. 8 Samples of *Anabaena* were prepared by adding 1.7% (by volume) of live *Potamogeton crispus* (the control group was not included) to the samples, and then incubating for 7 days at 25°C under light conditions of 1800–2200 lx.

[0095] The density of *Anabaena pseudoanthraceae* in the control group was 5.8 × 10⁻⁶. 8 The concentration of dimethyl isoborneol was 5190 ng / L; after being co-cultured with *Potamogeton crispus* for 7 days, the density of *Pseudohae* was measured to be 1.0 × 10⁻⁶.8 Units / L ( Figure 1 The concentration of dimethylisoborneol was 762 ng / L. Figure 2 Compared with the control group, the algal density decreased by 79.2% and the dimethyl isofensteinol concentration decreased by 84.8%.

[0096] Example 4

[0097] This embodiment provides a method for inhibiting the density of *Anabaena simulans* and the concentration of the odor compound dimethyl isobathol using the submerged plant *Myriophyllum spicatum*. The specific steps are as follows:

[0098] The initial algal density was selected as 2.51 × 10⁻⁶. 8 The sample contained 1.7% (v / L) of live *Myriophyllum spicatum* (no such addition was made to the control group), and was then cultured for 7 days at 25°C under light conditions of 1800–2200 lx.

[0099] After 7 days of cultivation, the density of *Anabaena pseudoanthraceae* in the control group was 5.8 × 10⁻⁶. 8 The concentration of dimethyl isoborneol was 5190 ng / L; after 7 days of co-culturing with *Myriophyllum spicatum*, the density of *Pseudo-Anabaena* was measured to be 1.3 × 10⁻⁶. 7 Units / L ( Figure 1 The concentration of dimethylisoborneol was 23 ng / L. Figure 2 Compared with the control group, the algal density decreased by 97.4% and the dimethyl isofensteinol concentration decreased by 99.5%.

[0100] Example 5

[0101] This embodiment provides a method for inhibiting the density of *Hydrilla verticillata* and the concentration of the odor compound dimethyl isobathol using the submerged plant *Hydrilla verticillata*. The specific steps are as follows:

[0102] The initial algal density was selected as 2.51 × 10⁻⁶. 8 Samples of *Anabaena* were prepared by adding 1.7% (by volume) of live *Hydrilla verticillata* (no such addition was made to the control group) to the samples, and then incubating for 7 days at 25°C under light conditions of 1800–2200 lx.

[0103] After 7 days of cultivation, the density of *Anabaena pseudoanthraceae* in the control group was 5.8 × 10⁻⁶. 8 The concentration of dimethyl isoborneol was 5190 ng / L; after 7 days of co-culturing with *Hydrilla verticillata*, the density of *Pseudo-Anabaena* was measured to be 1.2 × 10⁻⁶. 7 Units / L ( Figure 1 The concentration of dimethylisoborneol was 18 ng / L. Figure 2 Compared with the control group, the algal density decreased by 97.6% and the dimethyl isofensteinol concentration decreased by 99.5%.

[0104] Example 6

[0105] This embodiment provides a method for inhibiting the density of *Hypericum pseudocaryophyllum* and the concentration of the odor compound dimethyl isobathol using the submerged plant *Ceratophyllum demersum*. The specific steps are as follows:

[0106] The initial algal density was selected as 2.51 × 10⁻⁶. 8 The sample contained 1.7% (by volume) of live *Ceratophyllum demersum* (the control group did not receive any addition) and was then cultured for 7 days at 25°C under light conditions of 1800–2200 lx.

[0107] After 7 days of cultivation, the density of *Anabaena pseudoanthraceae* in the control group was 5.8 × 10⁻⁶. 8 The concentration of dimethyl isoborneol was 5190 ng / L; after co-culturing *Ceratophyllum demersum* for 7 days, the density of *Pseudo-Anabaena* was measured to be 3.0 × 10⁻⁶. 7 Units / L ( Figure 1 The concentration of dimethylisoborneol was 25 ng / L. Figure 2 Compared with the control group, the algal density decreased by 94.0% and the dimethyl isofensteinol concentration decreased by 99.1%.

[0108] Example 7

[0109] This embodiment provides a method for suppressing the density of *Anabaena simulans* using submerged plants. The specific steps are as follows:

[0110] The initial algal density was selected as 6.5 × 10⁻⁶. 8 Samples of *Anabaena* were collected at a concentration of 1.7% per L. Submerged plastic plants (not added to the control group) were added to the samples, and the samples were then cultured for 7 days at 25°C under light conditions of 1800–2200 lx.

[0111] After adding the plastic submerged plant material, the light intensity at the bottom of the sample increased from 25.3 μmol photons·m –2 ·s –1 Reduced to 11.8 μmol photons·m –2 ·s –1 After 7 days of cultivation, the algal density in the control group was 1.5 × 10⁻⁶. 9 The algae density in the plastic submerged plant treatment group was 9.6 × 10⁶ cells / L. 8 algae / L, algal density decreased by 36% ( Figure 3 This indicates that the shading effect of submerged plants can inhibit the growth of olfactory algae.

[0112] The purpose of this embodiment is to study the shading effect of submerged plants on algae. In order to eliminate other influences, plastic submerged plants are used instead of living submerged plants.

[0113] Example 8

[0114] This embodiment provides a method for inhibiting *Anabaena simulans* by utilizing submerged plants to adsorb nutrients. The specific steps are as follows:

[0115] The initial algal density was selected as 2.51 × 10⁻⁶. 8 The initial dissolved total nitrogen (DNT) of the *Anabaena* sample was 217.64 mg / L, and the initial dissolved total phosphorus (PTP) was 7.63 mg / L. 1.7% (by volume) of live submerged plants (no such plants were added to the control group) were added to the sample, and the samples were then cultured for 7 days at 25°C under light conditions of 1800–2200 lx.

[0116] After 7 days of cultivation, the total dissolved nitrogen in the control group was 212.86 mg / L and the total dissolved phosphorus was 6.39 mg / L. In the submerged plant treatment group, the total dissolved nitrogen was 202.48 mg / L and the total dissolved phosphorus was 0.48 mg / L. Figure 4 Compared with the control group, the dissolved total nitrogen and dissolved total phosphorus in the submerged plant treatment group decreased by 4.9% and 92.5%, respectively. This example illustrates that the absorption of phosphorus by submerged plants is one of the basic principles for inhibiting algae and controlling odor.

[0117] Example 9

[0118] This embodiment provides a method for inhibiting the photosynthetic activity of *Anabaena pseudoacacia* by releasing allelochemicals from the submerged plant *Vallisneria natans*. The specific steps are as follows:

[0119] The initial algal density was selected as 1.9 × 10⁻⁶. 7 The photosynthetic activity of *Anabaena spp.* samples was 0.42, as measured by a phytoplankton fluorometer. *Vallisneria natans* was cultured in source water for 48 hours, then filtered through 0.45 μm pore size filter paper. The filtrate was then used to treat the *Anabaena spp.* samples (the control group was treated with pure water).

[0120] Under conditions of 25℃ and dark cultivation, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.30 after 3 hours and 0.26 after 24 hours; for samples treated with *Vallisneria natans* filtrate, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.53 after 3 hours and 0.37 after 24 hours, showing a significant increase compared to the control group. Figure 5 ).

[0121] Then, the algae were cultured for another 7 days at 25°C and 1800–2200 lx light. The algal density increase in the control group was 7.92 × 10⁻⁶. 7 The concentration of cells / L in the *Vallisneria natans* filtrate treatment group increased to 8.81 × 10⁻⁶. 7 Units / L ( Figure 5 ).

[0122] This example illustrates that the allelopathic effect of Vallisneria natans on olfactory algae is relatively weak.

[0123] Example 10

[0124] This embodiment provides a method for inhibiting the photosynthetic activity of *Anabaena simulans* by releasing allelochemicals from the submerged plant *Myriophyllum spicatum*. The specific steps are as follows:

[0125] The initial algal density was selected as 1.9 × 10⁻⁶. 7 The photosynthetic activity of *Anabaena* samples with a density of cells / L was measured to be 0.42 using a phytoplankton fluorometer. *Myriophyllum spicatum* was cultured in source water for 48 hours, then filtered through 0.45 μm filter paper. The filtrate was then used to treat *Anabaena* samples (the control group was treated with pure water).

[0126] Under conditions of 25℃ and dark cultivation, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.30 after 3 hours and 0.26 after 24 hours. For samples treated with *Myriophyllum spicatum* filtrate, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.07 after 3 hours and 0.01 after 24 hours, representing decreases of 76.7% and 96.7% respectively compared to the control group at 3 hours and 24 hours. Figure 5 ).

[0127] Then, the algae were cultured for another 7 days at 25°C and 1800–2200 lx light. The algal density increase in the control group was 7.92 × 10⁻⁶. 7 The algae density in the Myriophyllum sp. filtrate treatment group decreased to 0 cells / L, a 100% reduction compared to the control group. Figure 5 ).

[0128] This example illustrates the strong allelopathic effect of *Myriophyllum spicatum* on the growth of olfactory algae.

[0129] Example 11

[0130] This embodiment provides a method for inhibiting the photosynthetic activity of *Anabaena pseudoacacia* by releasing allelochemicals from the submerged plant *Hydrilla verticillata*. The specific steps are as follows:

[0131] The initial algal density was selected as 1.9 × 10⁻⁶. 7 The photosynthetic activity of *Hydrilla verticillata* samples was 0.42, as measured by a phytoplankton fluorometer. *Hydrilla verticillata* was cultured in source water for 48 hours, then filtered through 0.45 μm pore size filter paper. The filtrate was then used to treat *Hydrilla verticillata* samples (the control group was treated with pure water).

[0132] Under conditions of 25℃ and dark cultivation, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.30 after 3 hours and 0.26 after 24 hours. For samples treated with *Hydrilla verticillata* filtrate, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.12 after 3 hours and 0.01 after 24 hours, representing a decrease of 60% and 96.7% respectively compared to the control group at 3 hours and 24 hours. Figure 5 ).

[0133] Then, the algae were cultured for another 7 days at 25°C and 1800–2200 lx light. The algal density increase in the control group was 7.92 × 10⁻⁶. 7 The algae density in the *Hydrilla verticillata* filtrate treatment group decreased to 0 cells / L, representing a 100% reduction compared to the control group. Figure 5 ).

[0134] This example illustrates the strong allelopathic effect of *Hydrilla verticillata* on the growth of olfactory algae.

[0135] Example 12

[0136] This embodiment provides a method for inhibiting the photosynthetic activity of *Anabaena pseudocaryophylla* by releasing allelochemicals from the submerged plant *Ceratophyllum demersum*. The specific steps are as follows:

[0137] The initial algal density was selected as 1.9 × 10⁻⁶. 7 The photosynthetic activity of *Anabaena* samples with a density of cells / L was measured to be 0.42 using a phytoplankton fluorometer. *Ceratophyllum demersum* was cultured in source water for 48 hours, then filtered through 0.45 μm filter paper. The filtrate was then used to treat *Anabaena* samples (the control group was treated with pure water).

[0138] Under conditions of 25℃ and dark cultivation, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.30 after 3 hours and 0.26 after 24 hours. For samples treated with *Ceratophyllum demersum* filtrate, the photosynthetic activity of *Anabaena pseudocaryophylla* in the control group was 0.12 after 3 hours and 0.01 after 24 hours, representing a decrease of 60% and 96.7% respectively compared to the control group at 3 hours and 24 hours. Figure 5 ).

[0139] Then, the algae were cultured for another 7 days at 25°C and 1800–2200 lx light. The algal density increase in the control group was 7.92 × 10⁻⁶. 7 The concentration of *Ceratophyllum demersum* filtrate in the treatment group decreased to 0.37 × 10⁶ cells / L. 7 The algal density was reduced by 95.3% compared to the control group (number of algae / L). Figure 5 ).

[0140] This example illustrates the strong allelopathic effect of Ceratophyllum demersum on the growth of olfactory algae.

[0141] Therefore, submerged plants reduce the production of odor substances by inhibiting the growth and odor production of odor-producing filamentous cyanobacteria. Firstly, they reduce the amount of nutrients available for odor production, algal growth, and odor generation through their absorption of nutrients. Secondly, they block light from the lower water layers, limiting the photosynthesis of odor-producing algae and inhibiting their growth. Furthermore, narrow-leaved submerged plants can release allelochemicals that inhibit the photosynthetic activity of odor-producing filamentous cyanobacteria, damage their photosynthetic systems, and promote cell apoptosis.

[0142] Example 13

[0143] This embodiment provides a method for suppressing the density of *Anabaena simulans* and the concentration of the odor compound dimethyl isobathol using submerged plants. The specific steps are as follows:

[0144] An algae-suppressing and odor-controlling flexible module 1 experimental device was constructed around a lake-type water source 2 affected by false hyacinth algae. The inlet end of the flexible module 1 is connected to the lake-type water source 2, and the outlet end of the flexible module 1 flows into a water collection channel 4. The water collection channel 4 is connected to the lake-type water source 2 through a pipeline.

[0145] Multiple flexible modules 1 are arranged side by side. The first parallel pipe 7 connecting the flexible module 1 to the lake-type water source 2 is opened, and the second parallel pipe 8 connecting the flexible module 1 to the water collection channel 4 is opened. Each flexible module 1 is a square with a length and width of 2m*2m.

[0146] The flexible module 1 is 1m deep and is divided into a high-efficiency odor control zone and a stable zone with an area ratio of 1:1. The high-efficiency odor control zone is planted with submerged plants such as Myriophyllum spicatum and Ceratophyllum demersum, while the stable zone is planted with submerged plants such as Vallisneria natans, Potamogeton malaianus, and Ceratophyllum demersum.

[0147] When the density of submerged plants reaches 10 kg wet weight / m³ 2 At approximately 10:00 AM, the submerged plant community was considered to be mature. Raw water from the lake-type water source 2 and treated water taken from the stable zone after hydraulic retention in the flexible module 1 were collected to replace the water in the experimental device for a static test lasting 7 days.

[0148] The experimental results showed that the density of *Houttuynia cordata* in the raw water of the initial lake-reservoir type water source 2 was 5.31 × 10⁻⁶. 7 The concentration of dimethyl isoborneol (2-MIB) was 112 ng / L. After 7 days of hydraulic retention in flexible module 1, the density of *Anabaena pseudocaryophylla* was measured to be 0.45 × 10⁻⁶. 7 With a concentration of 7 ng / L of dimethyl isoborneol (2-MIB), the concentrations of *Anabaena pseudocaryophylla* and dimethyl isoborneol (2-MIB) decreased by 91.5% and 93.8%, respectively.

[0149] Example 14

[0150] This embodiment provides a method for determining the optimal planting depth of submerged plants by planting them at different water depths. The specific steps are as follows:

[0151] In a water body with a transparency of 0.7 m, devices were suspended at water depths of 0.60 m, 1.07 m, 1.16 m, 1.27 m, 1.40 m, 1.55 m, 1.75 m, and 2.00 m to cultivate Vallisneria natans and Hydrilla verticillata. The corresponding transparency / depth values ​​were 1.17, 0.65, 0.60, 0.55, 0.50, 0.45, 0.40, and 0.35, respectively.

[0152] The initial biomass of *Vallisneria natans* and *Hydrilla verticillata* planted in each group were 2.80 g and 2.6 g, respectively. After 24 days of cultivation, the biomass and number of propagules of *Vallisneria natans* decreased significantly when the transparency / depth value was 0.50 and 0.45, respectively, while the biomass and stability-related indicators of *Hydrilla verticillata* decreased significantly when the transparency / depth value was 0.40 and 0.50, respectively. These results show that when the transparency / depth value is below a certain value, the growth and reproduction capacity of submerged plants is inhibited.

[0153] In this embodiment (with a transparency of 0.7m), to ensure the healthy growth and reproduction of both broad-leaved and narrow-leaved submerged plants, the lightness / water depth value should be greater than 0.50, and the designed water depth should be greater than 1.4m.

[0154] Examples 13 and 14 illustrate the design of the flexible module 1, the method for selecting submerged plants, and the arrangement of the flexible module 1 in this invention. First, the water depth of the flexible module 1 in this invention ensures the healthy growth and reproduction of most submerged plants, preventing death due to poor underwater light conditions. The design of the efficient odor control zone and the stable zone balances algae suppression and odor control effectiveness with the stability of the submerged plant community. Second, the method for selecting submerged plants in this invention effectively suppresses both the growth and odor production of odor-producing filamentous cyanobacteria, with a community dominated by slender-leaved algae exhibiting the highest algae suppression and odor control effectiveness. Finally, the flexible module arrangement method proposed in this invention is highly flexible, widely applicable, and provides excellent odor control without causing secondary pollution.

[0155] The results of the above embodiments demonstrate that by using the method of the present invention to treat samples containing odor-producing filamentous cyanobacteria with different submerged plants, the growth and reproduction of odor-producing filamentous cyanobacteria can be effectively inhibited, thereby achieving the purpose of ecological and green odor control. In particular, the odor control effect of narrow-leaved submerged plants (such as Elodea, Hydrilla verticillata, and Myriophyllum spicatum) is much better than that of broad-leaved submerged plants (such as Vallisneria natans and Potamogeton crispus).

[0156] The submerged plants added in this invention primarily achieve in-situ odor control through nutrient absorption and light shading. The reason why narrow-leaved submerged plants are more effective at odor control than broad-leaved ones is that they can release allelochemicals, which reduce the photosynthetic activity of odor-producing filamentous cyanobacteria through allelopathic effects, thus achieving a stronger odor control effect. Using the odor control method described in this invention to treat lake and reservoir water sources can reduce the concentration of odor-causing substances by more than 80%, and when using narrow-leaved submerged plants, the concentration can be reduced by more than 99%, demonstrating a significant odor control effect.

[0157] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for suppressing the generation of odors in water sources using submerged plants, characterized in that, The specific steps are as follows: S1. Determine the cause of the odor problem in the lake-reservoir type water source (2). If the odor problem is caused by odor-producing filamentous blue-green algae, measure the concentration of odor substances and the transparency of the raw water in the lake-reservoir type water source (2). S2. Construct a flexible module (1) for controlling the odor of submerged plants, wherein the flexible module (1) is divided into a high-efficiency odor control zone and a stable zone; S3. Select small-leaved submerged plants for planting in the high-efficiency odor control zone, and select broad-leaved and small-leaved submerged plants for planting in the stability zone; S4. Introduce raw water from a lake-type water source (2) containing a high concentration of odor substances into the flexible module (1), and set the hydraulic residence time of the raw water to be treated in each flexible module (1). S5. Based on the water supply and odor concentration of the lake-reservoir type water source (2), multiple odor control flexible modules (1) are connected in series or in parallel, and the treated water is returned to the lake-reservoir type water source (2) or directly transported to the water plant (3). The flexible module (1) is a shallow, enclosed water area, and the designed water depth of the flexible module (1) is less than 2 meters. The substrate of the flexible module (1) is sand or mud, and is free of harmful substances; The inlet end of the flexible module (1) is connected to the lake-reservoir type water source (2), and the outlet end of the flexible module (1) flows into the collection channel (4). The collection channel (4) is connected to the water plant (3) and the lake-reservoir type water source (2) through pipelines. Multiple flexible modules (1) are arranged side by side. One end of each flexible module (1) is connected to the lake-reservoir type water source (2) through a first parallel pipe (7). The other end of each flexible module (1) is connected to the water collection channel (4) through a second parallel pipe (8). Adjacent flexible modules (1) are connected end to end through a second series pipe (6). The outermost flexible module (1) on one side is connected to the lake-reservoir type water source (2) through a first series pipe (5), and the outermost flexible module (1) on the other side is connected to the water collection channel (4) through a third series pipe (9). When connected in parallel, the second series pipe (6) between adjacent flexible modules (1) is closed, the first parallel pipe (7) connecting the flexible module (1) to the lake-type water source (2) is opened, the second parallel pipe (8) connecting the flexible module (1) to the water collection channel (4) is opened, and the first series pipe (5) and the third series pipe (9) are closed. When connected in series, the second series pipe (6) between adjacent flexible modules (1) is opened, the first series pipe (5) connecting the outermost flexible module (1) on one side to the lake-type water source (2) is opened, the third series pipe (9) connecting the outermost flexible module (1) on the other side to the water collection channel (4) is opened, and the first parallel pipe (7) and the second parallel pipe (8) are closed.

2. The method for suppressing the generation of odors in water sources using submerged plants according to claim 1, characterized in that, In step S1, the odor substances include dimethylisoborneol and geosmin. The odor-producing filamentous cyanobacteria are selected from any one or more combinations of Anabaena pseudoanthellae, Oscillatoria, Floating filaments, Thymicolae, Sheath filaments, or Sylvae. The concentration of odor substances in the raw water of the lake-reservoir type water source (2) was determined by headspace solid phase microextraction gas chromatography-mass spectrometry.

3. The method for suppressing the generation of odors in water sources using submerged plants according to claim 1, characterized in that, In step S2, the area of ​​the high-efficiency olfaction control region is greater than 1 / 2 of the area of ​​the flexible module (1). (2) The raw water to be treated has a transparency / design depth > 0.

5.

4. The method for suppressing the generation of odors in water sources using submerged plants according to claim 1, characterized in that, In step S3, the planting density in the high-efficiency odor control zone and the stable zone is greater than 5 kg wet weight / m². 2 .

5. A method for suppressing the generation of odors in water sources using submerged plants according to claim 4, characterized in that, The fine-leaved submerged plants are selected from any one or more of the following: *Ceratophyllum demersum*, *Hydrilla verticillata*, or *Myriophyllum spicatum*. The broad-leaved submerged plant is selected from any one or more of Vallisneria natans, Potamogeton crispus, or Potamogeton malaianus. After the submerged plant community has matured, the density in the highly efficient odor-controlling zone and the stable zone reaches 10-15 kg wet weight / m³. 2 .

6. A method for suppressing the generation of odors in water sources using submerged plants according to claim 1, characterized in that, In step S4, the raw water of the lake-reservoir type water source (2) flows in from the high-efficiency odor control zone and flows out from the stable zone. The hydraulic residence time in the flexible module (1) is controlled by controlling the inflow rate. The hydraulic residence time of the raw water to be treated in the flexible module (1) is 5-7 days.

7. A method for suppressing the generation of odors in water sources using submerged plants according to claim 1, characterized in that, In step S4, a higher concentration is defined as the concentration of odorous substances in the raw water of the lake-reservoir type water source (2) is greater than 100 ng / L.

8. A method for suppressing the generation of odors in water sources using submerged plants according to claim 1, characterized in that, In step S5, when the concentration of odorous substances in the raw water of the lake-reservoir type water source (2) is in the range of 100~300 ng / L, multiple flexible modules (1) are connected in parallel. When the concentration of odorous substances in the raw water of the lake-reservoir type water source (2) is greater than 300 ng / L, multiple flexible modules (1) are connected in series.

9. A method for suppressing the generation of odors in water sources using submerged plants according to claim 1, characterized in that, Step S5 is followed by step S6, where the dead submerged plants are harvested when they wither.

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