Method for improving self-cleaning capacity of water body by utilizing slow-release particles

Abstract

The invention belongs to the technical field of water body in-situ remediation, and relates to a method for improving the self-cleaning capacity of a water body by utilizing sustained-release particles. According to the method, slow-release particles wrapped by dialysis bags are added into a water body, the release rate of a carbon source is controlled, and the nitrogen and phosphorus removal capacity of native microorganisms is activated. Compared with the prior art, the slow-release particles are wrapped by the dialysis bag, so that microorganisms are prevented from being attached to the particles, the carbon source release rate is controlled, and the microbial community structure is directionally induced; and the method has the remarkable advantages of simplicity, continuous and stable effect, no secondary pollution, environment friendliness and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of in-situ restoration of water bodies, and in particular relates to a method for improving the self-purification ability of water bodies by utilizing slow-release particles. Background Art

[0002] The in-situ water body remediation technology with slow-release particles as the core enhances the activity and metabolic capacity of microorganisms in the water body by introducing slow-release particles, thereby effectively reducing the nutrient load in the water body. It has the characteristics of small secondary pollution, economy and environmental protection, and is an important means to restore the ecological balance of water bodies.

[0003] Slow-release particles use biodegradable materials (such as polyhydroxyalkanoate PHA, etc.) as carriers, and continuously release small molecular carbon sources under the action of hydrolysis and microorganisms, promoting the growth of heterotrophic bacteria such as denitrifying bacteria and polyphosphate bacteria. However, too fast a carbon source release rate will lead to an increase in the organic carbon concentration in the water body, and excessive growth of microorganisms will consume a large amount of oxygen, which may further cause water quality deterioration, water hypoxia and other problems. Therefore, how to effectively control the release rate of the carbon source is the key to water body remediation technology. On the other hand, microorganisms such as bacteria and algae will attach to the particles, forming a film layer and hindering the continuous and stable release of the carbon source.

[0004] In order to solve the above problems, a common method is to adjust the release characteristics of slow-release particles by changing the ratio of different substances in the degradable material, or changing the shape, size and pore structure of the slow-release particles. For example, reducing the surface area and porosity of the particles can help slow down the release rate of the carbon source. However, due to the easy degradability of the material itself, the effect of such methods is limited. With the attachment and accumulation of microorganisms on the particles, the particles may still be rapidly decomposed and released. In addition, a physical barrier can be formed by coating one or more layers of biocompatible materials (such as polyvinyl alcohol, polylactic acid, etc.) on the surface of the particles to reduce the release rate of the carbon source. For example, the stability of the particles is improved by introducing epoxy resin. However, the persistence of such substances in the environment may cause secondary pollution and trigger new environmental problems.

[0005] Therefore, finding a water restoration technology that can effectively control the carbon source release rate and reduce the nutrient load of the water body is of great significance for improving water quality and maintaining the ecological balance of the water body. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems existing in the above-mentioned prior art and provide a method for improving the self-purification ability of water bodies by using slow-release particles. The method can control the release rate of the carbon source and continuously and effectively remove nitrogen and phosphorus nutrients from the water body.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The invention provides a method for improving the self-purification ability of a water body by using slow-release particles, comprising the following steps: adding the slow-release particles wrapped by a semipermeable membrane into the water body.

[0009] Furthermore, the semipermeable membrane comprises a dialysis bag, which has a cutoff molecular weight of not less than 1000Da.

[0010] Furthermore, the dialysis bag is a transparent cellulose membrane.

[0011] Furthermore, the dialysis bag is first boiled in boiling water, and then the sustained-release particles are wrapped with the dialysis bag after cooling.

[0012] Furthermore, the preparation method of the sustained-release granules is: polylactic acid (PLA) and polyhydroxyalkanoate (PHA) in a mass ratio of (0.5-1.5):(0.5-1.5) are mixed and melted, and pelletized to obtain sustained-release granules. The mass ratio of polylactic acid (PLA) and polyhydroxyalkanoate (PHA) is preferably 1:1.

[0013] Furthermore, the density of the sustained-release particles is 0.5-2 g / cm 3 Preferably, the density of the sustained-release particles is 1.25 g / cm 3 .

[0014] Furthermore, the average particle size of the slow-release particles is 2-4 cm. Preferably, the average particle size of the slow-release particles is 3 cm.

[0015] Furthermore, the individual sustained-release particles are wrapped in a layer with an area of ​​38-42 cm 2 Preferably, the single sustained-release particle is completely wrapped in a semipermeable membrane with an area of ​​40 cm 2 in a semipermeable membrane.

[0016] Furthermore, the dosage of the slow-release particles is 1.5-2.5 g / L. Preferably, the dosage of the slow-release particles is 2 g / L.

[0017] Furthermore, the slow-release particles settle to the bottom of the water body, slowing down the release rate of the carbon source and activating the ability of microorganisms in the water body to remove nitrogen and phosphorus.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention provides a method for improving the self-purification capacity of water bodies by using slow-release particles. The method uses dialysis bags to wrap the slow-release particles to prevent microorganisms from directly adhering to the slow-release particles, slow down the release rate of the carbon source, induce the improvement of the microbial community structure, activate the denitrification and phosphorus removal capabilities of native microorganisms, promote the growth of denitrification and phosphorus removal bacteria, improve the self-purification capacity of water bodies, and can continuously and effectively remove nitrogen and phosphorus nutrients from water bodies.

[0020] (2) The present invention provides a method for improving the self-purification ability of water bodies by using slow-release particles. The method is simple and easy to implement, the raw materials are readily available, there is no secondary pollution, the pollutant removal effect is good, and the effect is sustained and stable, which is beneficial to the long-term stability of water quality, is environmentally friendly, and has high social and environmental benefits, economic benefits and broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of a method for improving the self-purification ability of a water body by utilizing slow-release particles. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0023] The present invention provides a method for improving the self-purification ability of a water body by utilizing slow-release particles, comprising the following steps: firstly preparing slow-release particles composed of a degradable material; then completely wrapping the slow-release particles with a dialysis bag to prevent microorganisms from attaching; adding the slow-release particles completely wrapped with the dialysis bag to the bottom of a water body, wherein the slow-release particles slowly release a small molecule carbon source under the action of hydrolysis, thereby promoting the growth of heterotrophic microorganisms in the water body, and thus removing nitrogen and phosphorus substances in the water body.

[0024] The method specifically comprises the following steps:

[0025] 1) Polylactic acid (PLA) and polyhydroxyalkanoate (PHA) in a mass ratio of 1:1 are mixed and melted, and pelletized to obtain sustained-release particles.

[0026] 2) Completely wrap a single sustained-release particle in a layer with an area of ​​40 cm 2 The cellulose dialysis bag can retain substances with a molecular weight greater than 1000 Da.

[0027] 3) Add the slow-release particles to the bottom of the water body at a dosage of 2g / L to activate the nitrogen and phosphorus removal capabilities of the water microorganisms.

[0028] The total nitrogen (TN) concentration of the water body was determined according to the standard method in "Determination of total nitrogen in water quality - alkaline potassium persulfate digestion ultraviolet spectrophotometry". After the restoration, compared with the original water body, the TN concentration dropped from 1 mg / L to 0.5 mg / L and remained stable for a long time.

[0029] In some specific embodiments, the dialysis bag is a transparent cellulose membrane.

[0030] In some specific embodiments, the dialysis bag is first boiled in boiling water, and then the sustained-release particles are wrapped in the dialysis bag after cooling.

[0031] In some specific embodiments, the density of the sustained-release particles is 0.5-2 g / cm 3 Preferably, the density of the sustained-release particles is 1.25 g / cm 3 .

[0032] In some specific embodiments, the average particle size of the slow-release particles is 2-4 cm. Preferably, the average particle size of the slow-release particles is 3 cm.

[0033] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0034] Example 1

[0035] A method for reducing the nutrient load of a small water body in the Siping campus of Tongji University comprises the following steps:

[0036] (1) preparing sustained-release particles composed of polylactic acid (PLA) and polyhydroxyalkanoate (PHA): PLA and PHA are mixed and melted, and pelletized to obtain sustained-release particles;

[0037] The mass ratio of PLA to PHA is 1:1, and the density of the sustained-release particles is 1.25 g / cm 3 The average particle size is 3cm and it can settle to the bottom of the water body.

[0038] (2) Take water samples from water bodies within Tongji University and set up a control group and an experimental group;

[0039] Among them, the total weight of slow-release particles required for the experimental group was calculated based on the dosage of 2g / L. No slow-release particles were added to the control group, and other conditions remained consistent; the initial TN concentration of the water sample was 1.17mg / L, TP concentration was 0.16mg / L, and DO concentration was 6.55mg / L.

[0040] (3) Each particle is completely wrapped with a dialysis bag, and a single sustained-release particle is completely wrapped in a layer with an area of ​​40 cm 2 in the dialysis bag and added to the experimental group;

[0041] Among them, the dialysis bag is a completely transparent cellulose membrane that can intercept substances with a molecular weight greater than 1000Da. It is boiled in 100℃ boiling water for 10 minutes and used after cooling.

[0042] According to the standard method in "Determination of Total Nitrogen in Water Quality by Alkaline Potassium Persulfate Digestion Ultraviolet Spectrophotometry", the TN concentrations of the control group and the experimental group were measured respectively. After 15 days, the TN concentration of the control group was 0.95 mg / L, and the TN concentration of the experimental group was 0.47 mg / L. Compared with the control group, the soluble TN concentration of the experimental group was significantly reduced from 1.03 mg / L to 0.26 mg / L, and the nitrogen nutrients in the water were effectively removed. At the same time, the COD concentration of the experimental group was stable between 11 mg / L-15 mg / L, which was consistent with the level of the control group, and the release rate of the carbon source was effectively controlled.

[0043] Example 2

[0044] A method for reducing the nutrient load of a low-pollution-load water body in Yangpu District, Shanghai, comprises the following steps:

[0045] (1) preparing sustained-release particles composed of polylactic acid (PLA) and polyhydroxyalkanoate (PHA): PLA and PHA are mixed and melted, and pelletized to obtain sustained-release particles;

[0046] The mass ratio of PLA to PHA is 1:1, and the density of the sustained-release particles is 1.25 g / cm 3 The average particle size is 3cm and it can settle to the bottom of the water body.

[0047] (2) Take water samples from a water body in Yangpu District, Shanghai, and set up a control group and an experimental group;

[0048] Among them, the total weight of slow-release particles required for the experimental group was calculated based on the dosage of 2g / L. No slow-release particles were added to the control group, and other conditions remained consistent; the initial TN concentration of the water sample was 0.75mg / L, TP concentration was 0.08mg / L, and DO concentration was 7.15mg / L.

[0049] (3) Each particle is completely wrapped with a dialysis bag, and a single sustained-release particle is completely wrapped in a layer with an area of ​​40 cm 2 in the dialysis bag and added to the experimental group;

[0050] Among them, the dialysis bag is a completely transparent cellulose membrane that can intercept substances with a molecular weight greater than 1000Da. It is boiled in 100℃ boiling water for 10 minutes and used after cooling.

[0051] According to the standard method of "Determination of Total Nitrogen in Water Quality by Alkaline Potassium Persulfate Digestion Ultraviolet Spectrophotometry", the TN concentrations of the control group and the experimental group were measured respectively. After 15 days, the TN concentration of the control group was 0.81 mg / L, and the TN concentration of the experimental group was 0.43 mg / L, and the nitrogen nutrients in the water body were effectively removed. At the same time, the COD concentration of the control group was 10 mg / L, and the COD concentration of the experimental group was stable at about 13 mg / L, the levels were basically the same, and the release rate of the carbon source was effectively controlled.

[0052] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the scope of protection of the present invention.

Claims

1. A method for improving the self-purification capacity of water bodies by using slow-release particles, characterized in that: The method comprises the following steps: adding slow-release particles wrapped with a semipermeable membrane into a water body.

2. A method for improving the self-purification ability of water bodies by using slow-release particles according to claim 1, characterized in that: The semipermeable membrane comprises a dialysis bag, which has a molecular weight cutoff of not less than 1000Da.

3. A method for improving the self-purification ability of water bodies by using slow-release particles according to claim 2, characterized in that: The dialysis bag is a transparent cellulose membrane.

4. A method for improving the self-purification capacity of water bodies by using slow-release particles according to claim 1 or 2, characterized in that: First boil the dialysis bag in boiling water, and then wrap the sustained-release particles with the dialysis bag after cooling.

5. The method of improving the self-purification ability of water body by using slow-release particles according to claim 1, characterized in that: The preparation method of the sustained-release granules comprises: mixing and melting polylactic acid (PLA) and polyhydroxyalkanoate (PHA) in a mass ratio of (0.5-1.5):(0.5-1.5), and pelletizing to obtain sustained-release granules.

6. The method of improving the self-purification ability of water body by using slow-release particles according to claim 1, characterized in that: The density of the sustained-release particles is 0.5-2 g / cm 3 .

7. The method of improving the self-purification ability of water body by using slow-release particles according to claim 1, characterized in that: The average particle size of the sustained-release particles is 2-4 cm.

8. The method of improving the self-purification ability of water body by using slow-release particles according to claim 1, characterized in that: The individual sustained-release particles are encapsulated in a layer with an area of ​​38-42cm 2 in a semipermeable membrane.

9. The method of improving the self-purification ability of water body by using slow-release particles according to claim 1, characterized in that: The dosage of the slow-release particles is 1.5-2.5 g / L.

10. The method of improving the self-purification ability of water body by using slow-release particles according to claim 1, characterized in that: The slow-release particles settle to the bottom of the water body, slowing down the release rate of the carbon source and activating the ability of microorganisms in the water body to remove nitrogen and phosphorus.

Images