A method for determining a threshold value of a dosage of a sediment phosphorus passivator

Abstract

The present application belongs to the technical field of water treatment, and particularly relates to a method for determining the dosage threshold of a sediment phosphorus passivator. The present application discloses a method for determining the dosage threshold of a sediment phosphorus passivator, which comprises the following steps: obtaining a sediment sample from the sediment of a river or lake to be treated; performing a passivation experiment to obtain the dosage A of the phosphorus passivator that has the best passivation effect on the active phosphorus in the sediment sample; performing an in-situ covering experiment to obtain the dosage B of the phosphorus passivator that is lethal to half of the benthic animals in the sediment sample; and adding the dosage C of the phosphorus passivator to the sediment to be treated, wherein the dosage C is the smaller one of the dosage A and the dosage B; and the active phosphorus comprises NH4Cl-P, BD-P and NaOH-nrP. The present application has the beneficial effect of comprehensively considering the passivation effect of the phosphorus passivator on the active phosphorus in the sediment and the potential ecological risk to the benthic animals, thereby avoiding the waste of a large amount of the passivator and the impact on the survival conditions of aquatic organisms.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and specifically relates to a method for determining the threshold of phosphorus passivating agent dosage in sediment. Background Technology

[0002] Phosphorus is one of the main pollutants in surface water bodies such as rivers, lakes, and reservoirs in my country. Even with effective control of exogenous phosphorus input, the continuous release of endogenous phosphorus from the water body makes it difficult to effectively alleviate water pollution. Therefore, technologies such as environmentally friendly dredging, in-situ passivation, and ecological restoration are frequently used to treat endogenous phosphorus pollution. Among these, in-situ passivation is widely used in black and odorous rivers and small eutrophic lakes due to its advantages of ease of operation, significant effects, and low cost. The performance of the passivation material is one of the keys to the success of in-situ passivation technology; therefore, how to prepare high-performance passivation materials has always been a focus of researchers. However, the dosage of passivation material is also a significant factor affecting the effectiveness of in-situ passivation technology. Yet, current researchers have focused on the performance of passivation materials while neglecting the dosage.

[0003] For example, Chinese patent application document 1 (CN202110210974.2) discloses a modified zeolite; Chinese patent application document 2 (CN202010692550.X) discloses a rare earth ion modified clay; Chinese patent application document 3 (CN202210548306.5) discloses a zeolite-kaolin-lanthanum-magnesium-alum mixture; and Chinese patent application document 4 (CN201710371846.X) discloses a zirconium modified bentonite. However, none of the above specifies the dosage of passivating material. Furthermore, Chinese patent application document 5 (CN201510823659.1) discloses an Al-modified sodium-based bentonite, specifying that the passivating agent dosage in water is ≥0.5 g / L, and based on a water depth of 10 meters, the passivating agent dosage is ≥5 kg / m. 2 However, this technical solution has two main drawbacks. First, it lacks an upper limit, making it difficult to determine the dosage in practical applications. Second, it doesn't consider the actual situation of phosphorus pollution in sediments. From the perspective of treatment effectiveness, if the sediment phosphorus pollution is light, excessive dosage may be wasteful; if the sediment pollution is heavy, insufficient dosage will result in poor treatment effects. Therefore, current research and applications primarily focus on excessive application driven by treatment effectiveness. However, from the perspective of aquatic ecological environment protection, the addition of passivating agents alters the water and sediment environment, such as increasing the concentration of suspended solids in the water and raising the pH value of sediments, which has a certain impact on the survival of aquatic organisms.

[0004] Currently, most studies use acute toxicity tests to investigate the effects of passivating agents on aquatic organisms. However, this method cannot simulate the actual effects of passivating agent addition over a certain period. Firstly, sediment phosphorus passivation is a long-term process; secondly, it is almost impossible to achieve the concentrations obtained in acute toxicity tests in real-world situations. Therefore, there is an urgent need for a method to determine the dosage of phosphorus passivating agents for river and lake sediments that comprehensively considers both the passivation effect and potential aquatic ecological risks. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] In existing technologies, it is difficult to determine the dosage of phosphorus passivating agent for river and lake sediments. Excessive dosage may lead to waste, while insufficient dosage will result in poor treatment effects and may also have a certain impact on the survival of aquatic organisms.

[0007] 2. Technical Solution

[0008] To address the aforementioned technical problems, this invention provides a method for determining the threshold dosage of phosphorus passivating agent for bottom sediment, which involves obtaining bottom sediment samples from the river and lake bottom sediment to be treated.

[0009] A passivation experiment was conducted on sediment samples using a phosphorus passivating agent to obtain the optimal phosphorus passivating agent dosage A for the sediment samples.

[0010] An in-situ covering experiment was conducted on sediment samples using a phosphorus passivating agent to obtain the median lethal dose (LD50) of the phosphorus passivating agent on benthic animals in the sediment samples.

[0011] Add phosphorus passivating agent of dosage C to the sediment to be treated;

[0012] in,

[0013] The dosage C is the smaller value between the dosage A and the dosage B;

[0014] The dosage refers to the ratio of the mass of phosphorus passivating agent to the phosphorus content in the bottom sediment at a depth of 0-5cm;

[0015] The phosphorus is active phosphorus, including NH4Cl-P, BD-P and NaOH-nrP.

[0016] Furthermore, the dosage A is obtained as follows:

[0017] Sediment samples were collected and their phosphorus content was measured. Different ratios of the mass of phosphorus passivating agent to the phosphorus content in the sediment samples were set. After the passivation experiment, the phosphorus content in the sediment samples was measured again to obtain the optimal phosphorus passivating agent dosage A for the best phosphorus passivation effect in the sediment samples.

[0018] Furthermore, a gravity sampler was used to collect sediment samples.

[0019] Furthermore, the sampling tube of the gravity sampler is made of acrylic.

[0020] Furthermore, the sampling tube of the gravity sampler is cylindrical in shape.

[0021] Furthermore, when obtaining the dosage A, the collected sediment samples were placed on a sediment separator, and the phosphorus content of the sediment at a depth of 0-5 cm from the sediment-water interface was analyzed.

[0022] Furthermore, before analyzing the phosphorus content, the bottom sediment at a depth of 0-5 cm from the sediment-water interface was dried, weighed, ground, and sieved.

[0023] Furthermore, when the dosage A is obtained, the passivation experiment lasts for 30 days.

[0024] Furthermore, the drying temperature is 100~110℃.

[0025] For example, the drying temperature is 105℃.

[0026] Furthermore, the balance used for weighing has an accuracy of 0.1~0.001g.

[0027] For example, the balance used for weighing has an accuracy of 0.01g.

[0028] Furthermore, the sieve mesh size is 80-120 mesh.

[0029] For example, the sieve mesh size is 100 mesh.

[0030] Furthermore, the method for obtaining the dosage B is as follows:

[0031] Sediment samples were collected and the number of benthic animals in them was determined. Different ratios of the mass of phosphorus passivating agent and the phosphorus content in the sediment samples were set. After in-situ covering experiments, the number of benthic animals in the sediment samples was determined again to obtain the median lethal dose B of phosphorus passivating agent for benthic animals in sediment samples.

[0032] Furthermore, when the dosage B was obtained, the in-situ coverage experiment lasted for 30 days.

[0033] For further information on the determination of active phosphorus, please refer to Rydin and Welch, 1998. Aluminum dose required to inactivate phosphate in lake sediments. Water Res. 32 (10), 2969–2976.

[0034] Furthermore, the sediment samples should be collected at a depth of no less than 10 cm.

[0035] Furthermore, when obtaining the dosage B, the sediment sample collection depth should be no less than 20 cm.

[0036] Furthermore, when obtaining the dosage A, the sampling tube used to collect the sediment sample has an inner diameter of 9~12cm and a length of 30~40cm.

[0037] Furthermore, when obtaining the dosage B, the sampling tube used to collect the sediment sample should have an inner diameter of not less than 25cm and a length of not less than 40cm.

[0038] Furthermore, the number of sediment samples collected when obtaining the dosage B shall not be less than 3.

[0039] Furthermore, the ratio of the mass of the phosphorus passivating agent to the phosphorus content in the sediment sample was set to a range of 50:1 to 500:1 in the passivation and in-situ covering experiments.

[0040] For example, when obtaining the dosage A, the ratio of the mass of phosphorus passivating agent to the phosphorus content in the sediment sample is set as follows: 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1 and 400:1.

[0041] For example, when obtaining the dosage B, the ratio of the mass of the phosphorus passivating agent in the in-situ covering experiment to the phosphorus content in the sediment sample is 100:1, 200:1, 300:1, 400:1 and 500:1.

[0042] Furthermore, the phosphorus passivating agent is one or more of the following: phosphorus-locking agent, aluminum-modified attapulgite, lanthanum-modified attapulgite, and lanthanum-modified zeolite.

[0043] For example, the phosphorus-locking agent could be Phoslock®.

[0044] 3. Beneficial effects

[0045] The beneficial effects of this invention are as follows:

[0046] This invention comprehensively considers the passivation effect of phosphorus passivating agent on active phosphorus in bottom sediment and the potential ecological risks to benthic animals, thus avoiding the waste of large amounts of passivating agent and the impact on the survival of aquatic organisms.

[0047] The method for determining the threshold of phosphorus passivating agent dosage in sediment of the present invention fully considers the dynamic process of the release of endogenous pollutants in river and lake sediments, and determines the effect of phosphorus passivating agent dosage based on the change of bioavailable phosphorus content in sediments, thus avoiding interference caused by the uncertainty of phosphorus concentration changes in overlying water.

[0048] The method for determining the threshold dosage of sediment phosphorus passivating agent of the present invention determines the optimal dosage based on the actual situation of phosphorus pollution in sediments of different water bodies, avoiding situations where insufficient dosage leads to poor phosphorus passivation effect or excessive dosage results in waste.

[0049] The method for determining the threshold of phosphorus passivating agent dosage in sediment of the present invention takes into account the potential actual aquatic ecological risks of phosphorus passivating agent coverage to benthic animals in target rivers and lakes, and will not have a significant impact on the survival of aquatic organisms.

[0050] The method for determining the dosage threshold of phosphorus passivating agent in sediment according to the present invention has wide applicability and can be applied to determining the dosage threshold of various phosphorus passivating agents in different lakes, rivers and other water bodies. Attached Figure Description

[0051] Figure 1 This invention describes the changes in active phosphorus content in sediment samples under different phosphorus passivating agent masses and phosphorus content ratios in sediment samples during passivation experiments when obtaining dosage A in Example 1 of this invention.

[0052] Figure 2 To obtain the dosage B in the in-situ covering experiment of the present invention, the 30-day lethality of benthic animals in the sediment sample under different phosphorus passivating agent masses and phosphorus content ratios in the sediment sample.

[0053] Figure 3 This invention provides an example of how the active phosphorus content in sediment samples changes under different mass levels of phosphorus passivating agent and the proportion of phosphorus content in the sediment sample when a passivation experiment is conducted with a dosage of A.

[0054] Figure 4 To obtain the dosage B for in-situ covering experiments in Example 2 of this invention, the 30-day lethality of benthic animals in the sediment samples under different phosphorus passivating agent masses and phosphorus content ratios in the sediment samples was determined. Detailed Implementation

[0055] Embodiments of this disclosure will now be described in more detail. It should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, implementation methods and embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0056] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0057] This specific embodiment provides a method for determining the threshold of phosphorus passivating agent dosage in sediment, which involves obtaining sediment samples from the sediment of rivers and lakes to be treated;

[0058] A passivation experiment was conducted on sediment samples using a phosphorus passivating agent to obtain the optimal phosphorus passivating agent dosage A for the sediment samples.

[0059] An in-situ covering experiment was conducted on sediment samples using a phosphorus passivating agent to obtain the median lethal dose (LD50) of the phosphorus passivating agent on benthic animals in the sediment samples.

[0060] Add phosphorus passivating agent of dosage C to the sediment to be treated;

[0061] in,

[0062] The dosage C is the smaller value between the dosage A and the dosage B;

[0063] The dosage refers to the ratio of the mass of phosphorus passivating agent to the phosphorus content in the bottom sediment at a depth of 0-5cm;

[0064] The phosphorus is active phosphorus, including NH4Cl-P, BD-P and NaOH-nrP.

[0065] The threshold in this invention refers to the accurate dosage of phosphorus passivating agent. Specifically, it refers to the reasonable value of the dosage of phosphorus passivating agent when considering both the passivation effect of active phosphorus in the sediment and its impact on benthic animals.

[0066] The effective depth of phosphorus passivating agent added to the bottom sediment is about 0~5cm. Based on this, when adding phosphorus passivating agent to the river, the active phosphorus content at a depth of 0~5cm should be the main consideration.

[0067] Since phosphorus passivating agents have a significant effect on reducing the concentration of active phosphorus in sediment, the phosphorus in the technical solution of this invention refers only to active phosphorus.

[0068] The passivation experiment in this invention simulates the passivation process of active phosphorus in river and lake sediments by a phosphorus passivating agent. A certain mass of phosphorus passivating agent is added to the dried sediment sample, followed by the addition of top dressing water and settling. The phosphorus content in the sediment is then analyzed after a period of time. The in-situ covering experiment in this invention simulates the effect of phosphorus passivating agents on the survival status of benthic animals in river and lake sediments. A certain mass of phosphorus passivating agent is directly added to the collected sediment sample, and the survival status of the benthic animals is analyzed after a period of time.

[0069] The method for determining the threshold dosage of phosphorus passivating agent in sediment according to the present invention collects sediment samples from the actual water body to be treated for analysis. It fully considers the dynamic process of endogenous pollutant release from river and lake sediments, and determines the effect of phosphorus passivating agent addition based on changes in the bioavailable phosphorus content of the sediment, avoiding interference caused by the uncertainty of phosphorus concentration changes in the overlying water. Furthermore, the technical solution of the present invention determines the optimal dosage based on the actual phosphorus pollution situation of sediments in different water bodies, avoiding situations where insufficient dosage leads to poor phosphorus passivation effect or excessive dosage results in waste.

[0070] Furthermore, the method for determining the threshold for the dosage of phosphorus passivating agent in sediment in this invention takes into account the potential actual aquatic ecological risks of phosphorus passivating agent coverage to benthic animals in target rivers and lakes.

[0071] Furthermore, the dosage A is obtained as follows:

[0072] Collect sediment samples and determine their phosphorus content, and set different ratios of the mass of phosphorus passivating agent to the phosphorus content in the sediment samples;

[0073] After conducting the passivation experiment, the phosphorus content in the sediment sample was measured again to obtain the optimal phosphorus passivating agent dosage A for the best passivation effect on the sediment sample.

[0074] Using the above technical solution, the changes in phosphorus content before and after passivation experiments were determined under different ratios of phosphorus content in the sediment sample and the mass of the phosphorus passivating agent. This explored the theoretical dosage A of the phosphorus passivating agent with the best phosphorus removal effect, avoiding waste caused by excessive dosage or poor phosphorus removal effect caused by insufficient dosage.

[0075] Furthermore, a gravity sampler was used to collect sediment samples.

[0076] Furthermore, the sampling tube of the gravity sampler is made of acrylic.

[0077] Furthermore, the sampling tube of the gravity sampler is cylindrical in shape.

[0078] Furthermore, when obtaining the dosage A, the collected sediment samples were placed on a sediment separator, and the phosphorus content of the sediment at a depth of 0-5 cm from the sediment-water interface was analyzed.

[0079] Furthermore, before analyzing the phosphorus content, the bottom sediment at a depth of 0-5 cm from the sediment-water interface was dried, weighed, ground, and sieved.

[0080] Furthermore, the drying temperature is 90~120℃.

[0081] Furthermore, the drying temperature is 105°C.

[0082] Furthermore, the balance used for weighing has an accuracy of 0.1~0.001g.

[0083] Furthermore, the balance used for weighing has an accuracy of 0.01g.

[0084] Furthermore, the sieve mesh size is 80-120 mesh.

[0085] Furthermore, the sieve mesh size is 100 mesh.

[0086] Furthermore, the method for obtaining the dosage B is as follows:

[0087] Sediment samples were collected and the number of benthic animals in them was determined. Different ratios of the mass of phosphorus passivating agent and the phosphorus content in the sediment samples were set.

[0088] After conducting an in-situ covering experiment, the number of benthic animals in the sediment samples was measured again to obtain the median lethal dose (LD50) of phosphorus passivator on benthic animals in the sediment samples.

[0089] After exploring the theoretical dosage A of phosphorus passivating agent with the best phosphorus removal effect, we further determined the median lethal dosage B of phosphorus passivating agent for benthic animals in the sediment. We aimed to strike a balance between the effectiveness of the application and the protection of the aquatic ecosystem, avoiding excessive phosphorus passivating agent content that could cause mass mortality of benthic organisms in the water, damage to the aquatic revetment system, loss of its original function, and difficulty in repair.

[0090] The method for counting benthic animals in this invention adopts the provisions of the National Environmental Protection Standard of the People's Republic of China (HJ710.8-2014) issued by the Ministry of Environmental Protection.

[0091] Furthermore, when the dosage B was obtained, the in-situ coverage experiment lasted for 30 days.

[0092] This invention controls the dosage of phosphorus passivating agent to within the 30-day median lethal dose for benthic organisms in the sediment, thus avoiding significant impact on the survival of aquatic organisms and protecting the stability of the aquatic ecosystem.

[0093] For further information on the determination of active phosphorus, please refer to Rydin and Welch, 1998. Aluminum dose required to inactivate phosphate in lake sediments. Water Res. 32 (10), 2969–2976.

[0094] Furthermore, the sediment samples should be collected at a depth of no less than 10 cm.

[0095] Furthermore, when obtaining the dosage B, the sediment sample collection depth should be no less than 20 cm.

[0096] Furthermore, when obtaining the dosage A, the sampling tube used to collect the sediment sample has an inner diameter of 9~12cm and a length of 30~40cm.

[0097] Furthermore, when obtaining the dosage B, the sampling tube used to collect the sediment sample should have an inner diameter of not less than 25cm and a length of not less than 40cm.

[0098] Furthermore, to ensure the randomness of the sediment samples, the number of sediment samples collected when obtaining the dosage B should not be less than 3.

[0099] Furthermore, the ratio of the mass of the phosphorus passivating agent to the phosphorus content in the sediment sample was set to a range of 50:1 to 500:1 in the passivation and in-situ covering experiments.

[0100] For example, when obtaining the dosage A, the ratio of the mass of phosphorus passivating agent to the phosphorus content in the sediment sample in the passivation experiment is set as follows: 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1 and 400:1.

[0101] For example, when obtaining the dosage B, the ratio of the mass of the phosphorus passivating agent to the phosphorus content in the sediment sample is set as follows: 100:1, 200:1, 300:1, 400:1 and 500:1.

[0102] Furthermore, the phosphorus passivating agent is one or more of the following: phosphorus-locking agent, aluminum-modified attapulgite, lanthanum-modified attapulgite, and lanthanum-modified zeolite.

[0103] For example, the phosphorus-locking agent could be Phoslock®. Specific Implementation

[0105] Example 1

[0106] In this embodiment, the treatment of endogenous phosphorus pollution using a phosphorus passivating agent is a black and odorous river in a city in Jiangsu Province. An on-site investigation revealed that the river is 160 meters long, 4.5 meters wide, with an average water depth of 0.3 meters and a mud depth of 1 meter. The selected phosphorus passivating agent is Phoslock®.

[0107] The specific method for determining the threshold dosage of sediment phosphorus passivating agent is as follows:

[0108] (1) A sediment column sample was collected from the polluted river channel using a gravity sampler. The acrylic tube used had an inner diameter of 10 cm, a length of 35 cm, and a sediment height of 15 cm. The sediment column sample was placed on a sediment separator to obtain sediment at a depth of 0-5 cm from the sediment-water interface. The sediment was then dried in an oven at 105°C and weighed using an electronic balance with an accuracy of 0.01 g. The mass of the dried sediment was 235.24 g. The dried sediment was then ground through a 100-mesh sieve for later use.

[0109] (2) According to the method of Rydin and Welch (see Rydin and Welch, 1998. Aluminumdose required to inactivate phosphate in lake sediments. Water Res. 32 (10), 2969–2976), the sum of the contents of NH4Cl-P, BD-P and NaOH-nrP in the sediment is defined as active phosphorus. The active phosphorus content of the sediment in this black and odorous river was measured to be 1431.25 mg / kg. The active phosphorus content in a sediment column sample with a diameter of 10 cm and a height of 5 cm was 336.69 mg. A 30-day passivation experiment was then conducted. 10.00g of ground sediment was added to each of eight 250ml Erlenmeyer flasks. Phosphorus passivating agent was added according to the following ratios (mass ratio) of 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, and 400:1, corresponding to amounts of 0.72g, 1.43g, 2.15g, 2.86g, 3.58g, 4.29g, 5.01g, and 5.73g, respectively. After adding 50mL of water, the mixture was allowed to stand for 30 days, and the active phosphorus content was then measured. The results are shown below. Figure 1 It is evident that the passivation effect is best when the ratio of phosphorus passivator dosage to active phosphorus content in the sediment is 350:1. Therefore, the theoretically optimal dosage for treating endogenous phosphorus pollution in the entire black and odorous river is 10808 kg. To more intuitively represent the dosage of phosphorus passivator in practical applications, the ratio of passivator dosage per unit area of ​​sediment to phosphorus content in the 0-5 cm depth of sediment is used instead of the ratio of phosphorus passivator mass to phosphorus content in the sediment. This is calculated based on the river area, i.e., dosage A is 15 kg / m². 2 .

[0110] The above-mentioned theoretical optimal dosage is calculated as follows: First, based on the active phosphorus content of 336.69 mg in a columnar sample with a diameter of 10 cm and a height of 5 cm, the active phosphorus content in the black and odorous river in this embodiment is calculated proportionally to a length of 160 meters, a width of 4.5 meters, and a depth of 0-5 cm. Then, multiply by the optimal ratio of 350 to obtain the theoretical optimal dosage of phosphorus passivator as 10808 kg.

[0111] (3) Eight sediment column samples were collected from the polluted river using a gravity sampler. The acrylic tubes used had an inner diameter of 30 cm, a length of 35 cm, and a sediment height of 25 cm. Three sediment column samples were selected to analyze the number of benthic animals in the samples. The method in the National Environmental Protection Standard of the People's Republic of China (HJ 710.8-2014) issued by the Ministry of Environmental Protection was adopted, and the average number of benthic animals in the sediment column samples was found to be 10. Phosphorus passivating agent was added to the sediment column samples according to the ratio (mass ratio) of phosphorus passivating agent to active phosphorus content in the sediment at a depth of 0-5 cm: 100:1, 200:1, 300:1, 400:1, and 500:1, respectively. That is, the added masses were 303.02 g, 606.04 g, 909.06 g, 1212.07 g, and 1515.09 g, respectively. The results of a 30-day in-situ coverage experiment showed that, Figure 2 As shown, the 30-day median lethal dose of phosphorus-locking agent for benthic animals is 523.22 g. The corresponding dosage for treating endogenous phosphorus pollution in the entire black and odorous river is calculated to be 5329 kg. To more intuitively represent the amount of phosphorus passivating agent used in practical applications, the mass of passivating agent added per unit area of ​​sediment is used instead of the ratio of phosphorus passivating agent mass to phosphorus content in sediment at a depth of 0-5 cm. This is calculated based on the river area, i.e., dosage B is 7.40 kg / m². 2 .

[0112] The calculation method for the 30-day median lethal dose of the above-mentioned phosphorus-locking agent for benthic animals is as follows:

[0113] The relationship between the dosage of phosphorus passivating agent (in g) and the lethality of benthic animals was statistically analyzed under different dosages. The data were logarithmically transformed. The logarithmic transformation method is referenced from Deng Lisi et al., Study on the toxic effects of rare earth elements ytterbium and neodymium on Daphnia macrocarpa. Journal of Ecotoxicology, 17(3), 2023.

[0114] (4) After comparison, the 30-day median lethal dose is far less than the theoretical optimal dose. Therefore, the actual dose, i.e., the dose C, is 7.40 kg / m³. 2 .

[0115] Example 2

[0116] In this embodiment, the phosphorus passivating agent used for the treatment of endogenous phosphorus pollution is an eutrophic shallow lake in a city in Anhui Province. According to on-site investigation, the lake has an area of ​​0.97 square kilometers, an average water depth of 0.9 meters, and a mud depth of 0.8 meters. The selected phosphorus passivating agent is aluminum-modified attapulgite.

[0117] The specific method for determining the threshold dosage of sediment phosphorus passivating agent is as follows:

[0118] (1) A sediment column sample was collected from the lake using a gravity sampler. The matching acrylic tube had an inner diameter of 9 cm, a length of 40 cm, and a sediment height of 15 cm. The sediment column sample was placed on a sediment separator to obtain sediment at a depth of 0-5 cm from the sediment-water interface. The sediment was then dried in an oven at 105°C and weighed using an electronic balance with an accuracy of 0.01 g. The mass of the dried sediment was found to be 358.42 g. The dried sediment was then ground and passed through a 100-mesh sieve for later use.

[0119] (2) According to the method of Rydin and Welch (see Rydin and Welch, 1998. Aluminumdose required to inactivate phosphate in lake sediments. Water Res. 32 (10), 2969–2976), the sum of the contents of NH4Cl-P, BD-P and NaOH-nrP in the sediment is defined as active phosphorus. The active phosphorus content of the lake sediment was measured to be 268.94 mg / kg. The active phosphorus content in the sediment column sample with a diameter of 9 cm and a height of 5 cm was 96.39 mg. A 30-day passivation experiment was then conducted. 10.00g of ground sediment was added to each of eight 250ml Erlenmeyer flasks. Phosphorus passivating agent was added according to the following ratios (mass ratio) of 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, and 400:1, corresponding to amounts of 0.13g, 0.27g, 0.40g, 0.54g, 0.67g, 0.81g, 0.94g, and 1.08g, respectively. After adding 50mL of water, the mixture was allowed to stand for 30 days, and the active phosphorus content was then measured. The results are shown below. Figure 1 It is evident that the passivation effect is best when the ratio of phosphorus passivating agent dosage to active phosphorus content in the sediment is 150:1. Therefore, the theoretically optimal dosage for treating endogenous phosphorus pollution in the entire black and odorous river is 2204 tons. To more intuitively represent the dosage of phosphorus passivating agent in practical applications, the dosage is calculated using the mass of passivating agent added per unit area of ​​sediment instead of the ratio of phosphorus passivating agent mass to phosphorus content in the sediment at a depth of 0-5 cm. This dosage is then converted according to the lake area, resulting in a dosage A of 2.3 kg / m². 2 .

[0120] The above-mentioned theoretical optimal dosage is calculated as follows: first, based on the active phosphorus content of 96.39 mg in a columnar sample with a diameter of 9 cm and a height of 5 cm, the active phosphorus content in the lake area of ​​0.97 square kilometers and the depth of 0-5 cm in this embodiment is calculated proportionally; then, multiply by the optimal ratio of 150 to obtain the theoretical optimal dosage of phosphorus passivator as 2204 tons.

[0121] (3) Eight sediment column samples were collected from the lake using a gravity sampler. The matching acrylic tube had an inner diameter of 30 cm, a length of 35 cm, and a sediment height of 25 cm. Three sediment column samples were selected to analyze the number of benthic animals in the column samples. The method in the National Environmental Protection Standard of the People's Republic of China (HJ 710.8-2014) issued by the Ministry of Environmental Protection was used, and the average number of benthic animals in the sediment column samples was 18. Phosphorus passivating agent was added to the sediment column samples according to the ratio (mass ratio) of phosphorus passivating agent added to the active phosphorus content in the sediment at a depth of 0-5 cm as 100:1, 200:1, 300:1, 400:1, and 500:1, respectively, i.e., the added masses were 107.10 g, 214.21 g, 321.31 g, 428.42 g, and 535.52 g, respectively. The results of the 30-day in-situ cover experiment showed that, Figure 4 As shown, the 30-day median lethal dose (LD50) of the phosphorus-locking agent for benthic animals is 379.67 g. The corresponding dosage for treating endogenous phosphorus pollution in the entire lake is calculated to be 5210 tons. Based on the lake's area, this translates to a dosage B of 5.4 kg / m². 2 .

[0122] In this embodiment, the calculation method for the 30-day median lethal dose of phosphorus-locking agent for benthic animals is the same as in Example 1.

[0123] (4) After comparison, the 30-day median lethal dose is greater than the theoretical optimal dose. Therefore, the actual dose is, that is, the dose C is 2.3 kg / m³. 2 .

[0124] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or its application areas.

[0125] Comparative Example 1

[0126] Sampling and analysis were conducted in a polluted and odorous river in a city in Jiangsu Province using the same method as in Example 1, and the dosage A was found to be 15 kg / m³. 2 The dosage of B is 7.40 kg / m³. 2 In addition, another sediment sample was taken from the riverbed for an in-situ cover experiment. The dosage of phosphorus passivating agent was A, which is 15 kg / m³. 2The results showed that the mortality rate of benthic animals in the sediment samples reached 100% after 30 days, indicating that when the dosage of phosphating agent is the larger of dosage A and dosage B, it may have a significant negative impact on the survival of benthic animals in the sediment.

[0127] Further theoretical analysis reveals that when sampling and analyzing a polluted river in a city in Jiangsu Province using the same method as in Example 1, if the measured dosage A is less than the dosage B, then selecting dosage B as the dosage of phosphorus passivating agent to be added to the actual water body would result in an over-dosing of phosphorus passivating agent. This is because the ideal treatment effect has already been achieved when the dosage of phosphorus passivating agent reaches dosage A, thus leading to waste.

[0128] Comparative Example 2

[0129] Sampling and analysis were conducted in a eutrophic shallow lake in a city in Anhui Province using the same method as in Example 2, and the dosage A was found to be 2.3 kg / m³. 2 The dosage B is 5.4 kg / m³. 2 In addition, in-situ cover experiments were conducted on sediment samples from the lake, with a phosphorus passivating agent dosage of 5 kg / m³. 2 The results showed that the mortality rate of benthic animals in the sediment samples reached 48% after 30 days, indicating that when the dosage of phosphating agent is between dosage A and dosage B, it may also have a significant negative impact on the survival of benthic animals in the sediment.

[0130] Further theoretical analysis reveals that when sampling and analyzing a shallow, eutrophic lake in a city in Anhui Province using the same method as in Example 2, if the measured dosage A is less than the dosage B, selecting a value between A and B as the dosage of phosphorus passivating agent to be added to the actual water body may result in excessive dosage. This is because the ideal treatment effect is achieved when the dosage of phosphorus passivating agent reaches dosage A, so exceeding dosage A would be wasteful and have a greater impact on the ecological environment of the bottom sediment.

[0131] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

Claims

1. A method for determining the threshold dosage of phosphorus passivating agent for sediment, characterized in that, Sediment samples were obtained from the bottom sediments of rivers and lakes awaiting remediation. A passivation experiment was conducted on sediment samples using a phosphorus passivating agent to obtain the optimal phosphorus passivating agent dosage A for the sediment samples. An in-situ covering experiment was conducted on sediment samples using a phosphorus passivating agent to obtain the median lethal dose (LD50) of the phosphorus passivating agent on benthic animals in the sediment samples. Add phosphorus passivating agent of dosage C to the sediment to be treated; in, The dosage refers to the ratio of the mass of phosphorus passivating agent to the phosphorus content in the sediment at a depth of 0-5 cm; The phosphorus is active phosphorus, including NH4Cl-P, BD-P, and NaOH-nrP; the dosage A is obtained as follows: the collected sediment sample is placed on a sediment separator, sediment from the sediment-water interface at a depth of 0-5 cm is selected, dried, weighed, ground and sieved, and its phosphorus content is analyzed. Different ratios of the mass of the phosphorus passivating agent to the phosphorus content in the sediment sample are set. After the passivation experiment, the phosphorus content in the sediment sample is measured again to obtain the optimal dosage A of phosphorus passivating agent for the best phosphorus passivation effect in the sediment sample. The dosage B is obtained by: collecting sediment samples and measuring the number of benthic animals in them. The sediment sample collection depth is not less than 20 cm. Different ratios of the mass of phosphorus passivating agent and the phosphorus content in the sediment sample are set. After conducting an in-situ covering experiment, the number of benthic animals in the sediment sample is measured again to obtain the median lethal dosage B of phosphorus passivating agent for benthic animals in the sediment sample. The dosage C is the smaller of the dosage A and the dosage B.

2. The method for determining the threshold dosage of sediment phosphorus passivating agent according to claim 1, characterized in that: When the dosage B is obtained, the in-situ coverage experiment lasts for 30 days.

3. The method for determining the threshold dosage of sediment phosphorus passivating agent according to claim 1, characterized in that: The ratio of the mass of the phosphorus passivating agent to the phosphorus content in the sediment sample in the passivation experiment and in-situ covering experiment was set to a range of 50:1 to 500:

1.

4. The method for determining the threshold dosage of sediment phosphorus passivating agent according to any one of claims 1 to 3, characterized in that: The phosphorus passivating agent is one or more of the following: phosphorus-locking agent, aluminum-modified attapulgite, lanthanum-modified attapulgite, and lanthanum-modified zeolite.

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