AU2022400828A1

AU2022400828A1 - Stepped sediment modifier for ecological restoration of deepwater rivers and lakes

Info

Publication number: AU2022400828A1
Application number: AU2022400828A
Authority: AU
Inventors: Xianfeng Dong; Baoan HU; Jiayin Huang; Jing Liu; Zepeng QIAN
Original assignee: Cccc Tianjin Eco Environmental Protection Design & Research Institute Co Ltd
Current assignee: Cccc (tianjin) Eco-Environmental Protection Design & Research Institute Co Ltd
Priority date: 2021-12-01
Filing date: 2022-11-29
Publication date: 2023-12-21
Also published as: CN113845284B; LU504481B1; CN113845284A; WO2023098663A1

Abstract

Disclosed in the present invention is a stepped sediment modifier for the ecological restoration of deepwater rivers and lakes. The modifier is composed of a flocculation layer, an oxidation layer, a nutrition layer and an oxygenation layer. The flocculation layer is formed by uniformly and proportionally mixing polyacrylamide, polyaluminum chloride, disodium ethylene diamine tetraacetate and polyvinylpyrrolidone and then pre-tabletting the mixture. The oxidation layer is formed by uniformly and proportionally mixing citric acid, humic acid and composite potassium hydrogen persulfate and then pre-tabletting the mixture on the basis of the flocculation layer. The nutrition layer is formed by uniformly and proportionally mixing calcium bentonite, magnesium chloride, calcium chloride, anhydrous sodium sulfate, an alkali-activated modified mineral powder and diatomite and then pre-tabletting the mixture on the basis of the flocculation layer and the oxidation layer. The oxygenation layer is formed by uniformly and proportionally mixing a porous biological polymerization agent, sodium percarbonate, percarbamide and polyvinylpyrrolidone and then tabletting the mixture on the basis of the flocculation layer, the oxidation layer and the nutrition layer. The modifier has both biological and chemical effects, and has no secondary pollution and low investment.

Description

STEPPED TYPE SUBSTRATE IMPROVER FOR ECOLOGICAL REMEDIATION OF DEEP-WATER RIVERS AND LAKES FIELD OF TECHNOLOGY

The present invention relates to the fields of ecological remediation of substrates of

rivers and lakes and water purification of rivers and lakes, and specifically relates to a

stepped type substrate improver for ecological remediation of deep-water rivers and lakes.

BACKGROUND

At present, many reports have been carried out on sediment remediation agents applied

in aquaculture, while few sediment remediation agents have been used for ecological

remediation of sediment of rivers and lakes. As the aquatic ecology and the river and lake

ecology have different environments, contents and categories of sediment substances are

also different, and two kinds of sediment remediation agents cannot be mixed and need to be

used specifically for different cases.

Most of existing ecological remediation agents of sediment are chemical compound

type and microbial compound type remediation agents prepared by direct mixing. Such

sediment remediation agents have certain effects on ecological remediation of rivers and

lakes, but have the disadvantages such as low utilization rate in a short time, low reaction

efficiency and low follow-up effects when being used in a direct addition method. As a

result, functions of each component in a corresponding stage cannot be fully exerted, a

certain effect will be achieved by adding a large number of the sediment remediation agents,

and the risk of secondary pollution is caused.

However, during application in deep-water rivers and lakes, the case happens that

effective components specially acting on the sediment are rapidly dispersed and floated in a

water environment in a descending process and thus are unable to further act on the

sediment. An expected effect can only be achieved by increasing the quantity, so that

secondary pollution will be caused.

SUMMARY

In order to solve the problems of the prior art, one purpose of the present invention is to provide a stepped type substrate improver for ecological remediation of deep-water rivers and lakes. The stepped type substrate improver has a high utilization rate, and functions of each component in various stages of a sediment remediation process can be fully exerted, so that the use amount of a sediment remediation agent is decreased, the investment of an ecological remediation project for sediment is effectively reduced, and the risk of secondary pollution in an ecological remediation process is reduced.

Another purpose of the present invention is to provide a method for preparing the

stepped type substrate improver.

For this purpose, the present invention provides the following technical solutions.

A stepped type substrate improver for ecological remediation of deep-water rivers and

lakes includes a flocculation layer, an oxidation layer, a nutrient layer and an oxygenation

layer which are arranged in sequence. The flocculation layer is obtained by uniformly

mixing polyacrylamide, polyaluminum chloride, disodium ethylenediamine tetraacetate and

polyvinylpyrrolidone at a mass ratio of 1:1:(1-2):1 and then conducting pre-tableting. The

oxidation layer is obtained by uniformly mixing citric acid, humic acid and compound

potassium hydrogen persulfate (such as a potassium hydrogen peroxymonosulfate

compound salt (such as potassium monopersulfate and potassium hydrogen monopersulfate))

at a mass ratio of (1-2):(1-2):(2-4) and then conducting pre-tableting on the basis of the

flocculation layer. The nutrient layer is obtained by uniformly mixing calcium-based

bentonite, magnesium chloride, calcium chloride, anhydrous sodium sulfate, an

alkali-excited modified mineral powder and diatomite at a mass ratio of

(2-3):1:1:1:(2-3):(2-3) and then conducting pre-tableting on the basis of the flocculation

layer and the oxidation layer. The oxygenation layer is obtained by uniformly mixing a

porous biological polymerization agent, sodium percarbonate (with a high release rate),

percarbamide (with a low release rate) and polyvinylpyrrolidone at a mass ratio of

(2-4):(2-3):(2-3):1 and then conducting tableting on the basis of the flocculation layer, the

oxidation layer and the nutrient layer.

The improver includes the following mass percent of the flocculation layer, the

oxidation layer, the nutrient layer and the oxygenation layer:

5-30% of the flocculation layer;

10-40% of the oxidation layer;

20-70% of the nutrient layer; and

5-35% of the oxygenation layer.

Most preferably, the improver includes the following mass percent of the flocculation

layer, the oxidation layer, the nutrient layer and the oxygenation layer:

7-25% of the flocculation layer;

15-30% of the oxidation layer;

25-55% of the nutrient layer; and

10-25% of the oxygenation layer.

Preferably, before use, the alkali-excited modified mineral powder is washed with

water for 3-4 times and then dried at 105 C.

Preferably, the total thickness of the flocculation layer and the oxygenation layer is not

greater than 0.2 cm, the total thickness of the flocculation layer and the oxygenation layer is

proportional to the water depth, and the total thickness of the oxidation layer and the nutrient

layer is proportional to the severe pollution situation of sediment.

Preferably, the substrate improver has a length of 5-11 cm, a width of 5-11 cm and a

thickness of 0.3-0.8 cm as a whole.

In a preparation process, the mixing uniformity and the tableting sequence need to be

ensured. The oxidation layer is required to be positioned between the flocculation layer and

the nutrient layer, and the nutrient layer is required to be positioned between the oxidation

layer and the oxygenation layer.

According to the present invention, a product is divided into four layers according to an

ecological remediation process of water, and the layers have different main functions. In the

process of descending from the surface of a deep-water river or lake to the bottom, the layers

mainly having functions include the flocculation layer and the oxygenation layer, which can

effectively flocculate suspended colloids and other substances in the water and finally make

the substances settled to the bottom of the river or lake. In the process of descending,

beneficial microorganisms will be retained by the porous biological polymerization agent in

the oxygenation layer, so that the self-remediation sustainability of the water environment is

ensured while the self-purification ability of the water environment is strengthened. In the process of descending to the bottom, a small part of the components in the flocculation layer and the oxygenation layer are retained for acting on the sediment continuously and flocculating and compressing the sediment, so that a basis is provided for exerting functions of the oxidation layer while the capacity of the water environment of the river or lake is increased.

In the present invention, the various layers can keep stable without reactions when

being dry, and will rapidly act on harmful substances in the water after placing in the water.

Moreover, various substances have a certain synergistic effect, and specific functions are as

follows.

The flocculation layer and the oxygenation layer mainly have the functions of

flocculation and complexation, and oxygenation and stabilization, respectively. The

polyaluminum chloride, the polyacrylamide and the porous biological polymerization agent

have the functions of chemical flocculation and biological flocculation. In the process of

descending in a deep-water river or lake, a part of suspended substances and colloids in the

water environment can be removed. The flocculation layer without the porous biological

polymerization agent is used for preventing an oxidizing substance in the oxidation layer

from destroying a part of biological structures. The polyvinylpyrrolidone has the functions

of antioxidant synergism and stabilization. On the one hand, a certain firmness after

tableting and forming can be ensured. On the other hand, an oxidizing substance and a

corrosive substance in the oxidation layer can be prevented from destroying the structure of

a substance in the flocculation layer. The disodium ethylenediamine tetraacetate (EDTA) in

the flocculation layer is an antioxidant and a complexing agent, and can be used for

complexing heavy metal ions in the water environment in the process of descending in a

deep-water river or lake. The sodium percarbonate and the percarbamide in the oxygenation

layer have the functions of rapidly releasing oxygen and slowly releasing oxygen,

respectively, so that the instantaneity and sustainability of oxygen in the water are ensured.

The oxidation layer mainly has the functions of conducting disinfection, removing

macromolecular organic substances and converting other substances. Under the action of the

citric acid and the humic acid, harmful microorganisms in the sediment can be effectively

removed, so that harm caused by viruses and bacteria is reduced. Under the action of the compound potassium hydrogen persulfate, the redox potential of a sediment-water interface can be improved, and the purpose of eliminating harmful bacteria is achieved by reducing the permeability of microbial cells in the sediment. Bivalent iron and aluminum atoms in the water can be oxidized into trivalent atoms by an oxidation effect, so that a flocculation effect is promoted, the transparency of the water is improved, and diffusion of heavy metal ions in the sediment is reduced. Nitrites and hydrogen sulfide in the sediment can be oxidized into nitrates and sulfates, respectively, so that organic pollutants which are toxic and difficult to degrade are removed, and hepatotoxin and other kinds of algal toxins produced by the death of deposited algae are degraded.

The nutrient layer is mainly used for providing nutrients and nutrient elements required

by plants and microorganisms. The alkali-excited modified mineral powder and the

diatomite can also be used for reducing heavy metal ions in the water and the sediment

under the action of ion exchange and adsorption.

Compared with similar products, the present invention has the following

beneficial effects.

1. According to the present invention, as the porous biological polymerization agent is

combined with other effective chemical substances under the action of layering, the same

sediment remediation agent has a biological effect and a chemical effect simultaneously, so

that not only can a rapid and good effect on the current environment be ensured effectively

under the action of a chemical reagent, but also a continuous effect can be maintained under

the action of microorganisms, and meanwhile, the self-purification ability of the water

environment and the sediment is strengthened.

2. According to the present invention, a layered structure is designed for the sequence

of different stages of ecological remediation based on a conventional ecological remediation

method, so that the maximum utilization rate of corresponding effective substances at

different stages under different aging conditions is ensured, the problem of secondary

pollution caused by excessive addition is avoided, and the investment of an ecological

remediation project is effectively reduced. The added amount is about 1/2 of that of a similar

product in the market to achieve the same effect.

3. According to the present invention, through the addition of a variety of substances with a stabilization effect, it is ensured that the product has certain stability at normal temperature under dry conditions, and the shelf life is as long as 3.5 years, which is 2 years longer than that of a similar product in the market.

DESCRIPTION OF THE EMBODIMENTS An improver of the present invention is described in detail in the following embodiments. A porous biological polymerization agent used in the present invention is an efficient water purification product including a variety of natural mineral powders, a special compound microorganism extracted from the nature and a metabolite thereof. The product includes a variety of minerals and a variety of microorganisms such as mold, yeast and actinomyces according to a specific formula. A preparation method of the porous biological polymerization agent is recorded in a Chinese invention patent with the public number of CN111018282A titled "POROUS BIOLOGICAL POLYMERIZATION AGENT FOR DEWATERING OF SEDIMENT IN ECOLOGICAL DREDGING OF RIVERS AND LAKES", and the contents of which are included in the present invention, where a porous biological polymerization agent used in Embodiment 1 and Embodiment 2 is the porous biological polymerization agent prepared in Embodiment 1 of the invention patent. Polyaluminum chloride used in the present invention is a commercially available solid product, and the mass fraction of aluminum chloride may be 26%, 28%, or 30%. Calcium-based bentonite used in the present invention is a commercially available product with Ca 2as an interlayer cation. An alkali-excited modified mineral powder used in the present invention is a commercially available product which is modified based on an alkali excitation principle.

Embodiment 1 An outdoor medium-sized container with a length of 1m, a width of 1 m and a height of 1.5 m was used for simulating a river and lake environment. Water and sediment in a Qilu lake in Tonghai county, Yunnan province and seeds of eel grass having strong adaptability were used as experimental materials. The container was placed outdoors to ensure natural conditions. Then, the black smelly sediment was spread at the bottom of the container, and the seeds of eel grass were added at fixed points, where the total thickness of the sediment was 0.2 m, and the total water depth was 0.8 m (excluding the sediment). Three instruments for monitoring dissolved oxygen were distributed at fixed points in a triangular shape in the middle of a water environment. A stepped type substrate improver for ecological remediation of deep-water rivers and lakes in this embodiment was prepared by the following method. First, an alkali-excited mineral powder in a nutrient layer was washed with water for 3-4 times and then dried and pre-treated at 105 C. Then, components of various layers were prepared according to the following mass ratios, and mixed uniformly, respectively: (1) the mass ratio of polyacrylamide to polyaluminum chloride (the mass fraction of aluminum chloride was 26%) to disodium ethylenediamine tetraacetate to polyvinylpyrrolidone was 1:1:2:1; (2) the mass ratio of citric acid to humic acid to compound potassium hydrogen persulfate was 1:1:2; (3) the mass ratio of calcium-based bentonite to magnesium chloride to calcium chloride to anhydrous sodium sulfate to an alkali-excited modified mineral powder to diatomite was 2:1:1:1:2:2; and (4) the mass ratio of a porous biological polymerization agent to sodium percarbonate to percarbamide to polyvinylpyrrolidone was 2:2:2:1. Quantitative samples of a flocculation layer, an oxidation layer, a nutrient layer and an oxygenation layer were taken out according to the mass percent of 15%, 20%, 50% and 15%, respectively. Then, substances of the flocculation layer were pre-tableted, substances of the oxidation layer were pre-tableted on the basis of the flocculation layer, and pre-tableting was conducted in this sequence to obtain a formed improver, where the improver had a length of 7 cm and a width of 7 cm, the thickness of the flocculation layer, the oxidation layer, the nutrient layer and the oxygenation layer was about 0.1 cm, 0.15 cm, 0.2 cm and 0.1 cm, respectively, and the total thickness was about 0.55 cm. When the sediment improver with the above proportions was added from a water surface, the improver slowly settled to the bottom of the container due to great buoyancy produced by a large surface area, effective components for flocculation and increasing dissolved oxygen in the upper and lower layers were rapidly dissolved in the settling process, and the process was observed that floating substances in the water were slowly flocculated and further flocculated. The overall water environment required 6 days to become clear and transparent, and was kept clear continuously within the following 5 days. According to display of dissolved oxygen detectors, the content of dissolved oxygen was also slowly increased. When the sediment improver settled to the bottom of the container to get full contact with the sediment, the processes of dissolution of the sediment improver and improvement of the sediment were carried out simultaneously. Under the action of a slow release effect and the biological polymerization agent, the sediment gradually turned yellow after 7 days, and the seeds of eel grass germinated and grew after 8 days.

Embodiment 2

An outdoor medium-sized container with a length of 1m, a width of 1 m and a height

of 1.5 m was used for simulating a river and lake environment. Water and sediment in a Qilu

lake in Tonghai county, Yunnan province and seeds of eel grass having strong adaptability

were used as experimental materials. The container was placed outdoors to ensure natural

conditions. Then, the black smelly sediment was spread at the bottom of the container, and

the seeds of eel grass were added at fixed points, where the total thickness was 0.2 m, and

the total water depth was 1.2 m. Three instruments for monitoring dissolved oxygen were

distributed at fixed points in a triangular shape in the middle of a water environment.

lakes in this embodiment was prepared by the following method.

First, an alkali-excited mineral powder in a nutrient layer was sequentially washed with

water for 3-4 times and then dried and pre-treated at 105 C. Then, components of various

layers were prepared according to the following mass ratios, and mixed uniformly,

respectively:

(1) the mass ratio of polyacrylamide to polyaluminum chloride (the mass fraction of

aluminum chloride was 26%) to disodium ethylenediamine tetraacetate to polyvinylpyrrolidone was 1:1:2:1;

(2) the mass ratio of citric acid to humic acid to compound potassium hydrogen

persulfate was 1:1:2;

(3) the mass ratio of calcium-based bentonite to magnesium chloride to calcium

chloride to anhydrous sodium sulfate to an alkali-excited modified mineral powder to

diatomite was 2:1:1:1:2:2; and

(4) the mass ratio of a porous biological polymerization agent to sodium percarbonate

to percarbamide to polyvinylpyrrolidone was 2:2:2:1.

Quantitative samples of a flocculation layer, an oxidation layer, a nutrient layer and an

oxygenation layer were taken out according to the mass percent of 20%, 28%, 28% and 22%,

respectively.

Then, substances of the flocculation layer were pre-tableted, substances of the

oxidation layer were pre-tableted on the basis of the flocculation layer, and pre-tableting was

conducted in this sequence to obtain a formed improver, where the improver had a length of

cm and a width of 10 cm, the thickness of the flocculation layer, the oxidation layer, the

nutrient layer and the oxygenation layer was about 0.11 cm, 0.17 cm, 0.18 cm and 0.13 cm,

respectively, and the total thickness was about 0.59 cm.

When the sediment improver with the above proportions was added from a water

surface, the improver slowly settled to the bottom of the container due to great buoyancy

produced by a large surface area, effective components for flocculation and increasing

dissolved oxygen in the upper and lower layers were rapidly dissolved in the settling process,

and the process was observed that floating substances in the water were slowly flocculated

and further flocculated. The overall water environment required 3 days to become clear and

transparent, and was kept clear continuously within the following 5 days. According to

display of dissolved oxygen detectors, the content of dissolved oxygen was also slowly

increased. When the sediment improver settled to the bottom of the container to get full

contact with the sediment, the processes of dissolution of the sediment improver and

improvement of the sediment were carried out simultaneously. Under the action of a slow

release effect and the biological polymerization agent, the sediment gradually turned yellow

after 9 days, and the seeds of eel grass germinated and grew after 10 days.

Comparative Example 1

the total water depth was 0.8 m. Three instruments for monitoring dissolved oxygen were

As a blank control group, restoration was carried out under natural ecological

conditions without adding any sediment improver in this example. Timing was conducted

when necessary conditions were provided. Under the action of self-generation of beneficial

microorganisms and gravity settling, partial floating substances in the water environment

were dissolved in a small part and settled in a large part. The overall water environment

required 15 days to become clear and transparent. However, after 15 days, small particles

still floated in the water environment. Due to full integration of dissolved oxygen in the air,

a sediment environment was gradually improved and loosened, some harmful substances in

the sediment were released, and beneficial microorganisms were gradually activated and

varied. Under the action of slow remediation of microorganisms, the sediment gradually

turned yellow after 25 days. However, the seeds of eel grass were not provided with required

nutrients within the natural restoration time of a small ecosystem and thus were eroded by

harmful substances around the sediment. As a result, it was found that the seeds of eel grass

were rotten when being taken out after 25 days.

Comparative Example 2

were used as experimental materials. The container was placed outdoors to ensure natural conditions. Then, the black smelly sediment was spread at the bottom of the container, and the seeds of eel grass were added at fixed points, where the total thickness was 0.2 m, and the total water depth was 0.8 m. Three instruments for monitoring dissolved oxygen were distributed at fixed points in a triangular shape in the middle of a water environment. 100 g of a commercially available powdered sediment improver was uniformly poured. Flocculent substances were produced in a settling process. The overall water environment became clear rapidly within 6 days. However, after 8 days, the sediment floated upward at a sediment-water interface, and some insoluble substances continued to float in the water environment. The phenomenon of a three-layer coexistence of a water layer, a sediment layer and a sediment-water mixed layer was found, where the height of the sediment-water mixed layer was about 4 cm. After 10 days, the whole environment reached a balanced state. When the sediment improver settled to the bottom of the container to get full contact with the sediment, the sediment gradually turned yellow after 7 days, and the seeds of eel grass germinated and grew after 8 days.

Table 2 Addition differences in various examples Time for a Type of a water Time for Time for sediment Water environment black Ratio of various eel grass to remediation depth, to become sediment to layers (wto) germinate, agent meter clear and turn yellow, transparent, day day day Embodiment Present 1 invention Embodiment Present 2 invention Comparative No addition No Example 1 germination Comparative Commerciall Example 2 y available

From the above table, it can be seen that when the flocculation layer and the

oxygenation layer have larger proportions of flocculation and oxygenation components

under the same conditions, the time required for the water environment to become clear and transparent is shorter. Meanwhile, it is also indicated that when other effective components are reduced, the time for remediation and yellowing of the sediment is longer. The percent of each layer is required to be adjusted according to the actual water depth and the pollution degree of the sediment.

Claims

WHAT IS CLAIMED IS:

1. A stepped type substrate improver for ecological remediation of deep-water rivers and lakes, comprising a flocculation layer, an oxidation layer, a nutrient layer and an oxygenation layer which are arranged in sequence, wherein the flocculation layer is obtained by uniformly mixing polyacrylamide, polyaluminum chloride, disodium ethylenediamine tetraacetate and polyvinylpyrrolidone at a mass ratio of 1:1:(1-2):1 and then conducting pre-tableting; the oxidation layer is obtained by uniformly mixing citric acid, humic acid and compound potassium hydrogen persulfate at a mass ratio of (1-2):(1-2):(2-4) and then conducting pre-tableting on the basis of the flocculation layer; the nutrient layer is obtained by uniformly mixing calcium-based bentonite, magnesium chloride, calcium chloride, anhydrous sodium sulfate, an alkali-excited modified mineral powder and diatomite at a mass ratio of (2-3):1:1:1:(2-3):(2-3) and then conducting pre-tableting on the basis of the flocculation layer and the oxidation layer; the oxygenation layer is obtained by uniformly mixing a porous biological polymerization agent, sodium percarbonate, percarbamide and polyvinylpyrrolidone at a mass ratio of (2-4):(2-3):(2-3):1 and then conducting tableting on the basis of the flocculation layer, the oxidation layer and the nutrient layer; and the improver comprises the following mass percent of the flocculation layer, the oxidation layer, the nutrient layer and the oxygenation layer: 5-30% of the flocculation layer; 10-40% of the oxidation layer; 20-70% of the nutrient layer; and 5-25% of the oxygenation layer.

2. The stepped type substrate improver according to claim 1, wherein the improver comprises the following mass percent of the flocculation layer, the oxidation layer, the nutrient layer and the oxygenation layer: 7-25% of the flocculation layer; 15-30% of the oxidation layer; 25-55% of the nutrient layer; and 10-25% of the oxygenation layer.

3. The stepped type substrate improver according to claim 1, wherein before use, the alkali-excited modified mineral powder is washed with water for 3-4 times and then dried at 105°C.

4. The stepped type substrate improver according to claim 1, wherein the thickness of the flocculation layer and the oxygenation layer is not greater than 0.2 cm, the total thickness of the flocculation layer and the oxygenation layer is proportional to the water depth, and the total thickness of the oxidation layer and the nutrient layer is proportional to the severe pollution situation of sediment.

5. The stepped type substrate improver according to claim 4, wherein the substrate improver has a length of 5-11 cm, a width of 5-11 cm and a thickness of 0.3-0.8 cm as a whole.