CN111453961A

CN111453961A - Integrated process for continuously dredging sediment in situ

Info

Publication number: CN111453961A
Application number: CN202010475033.7A
Authority: CN
Inventors: 王昶
Original assignee: Shijiazhuang Hangquan Mineral Products Co ltd
Current assignee: Shijiazhuang Hangquan Mineral Products Co ltd
Priority date: 2020-05-29
Filing date: 2020-05-29
Publication date: 2020-07-28

Abstract

The invention relates to a substrate sludge continuous in-situ dredging integrated process, which comprises the steps of enabling sludge water (the mass percentage of dry sludge in the sludge water is 5-5.5%) sucked up by a dredging sludge ship to enter a first rapid stirring tank through a sludge water extraction pipeline, mixing the sludge water with an inorganic mineral flocculant in the first rapid stirring tank, rapidly stirring the mixture, staying for a certain time, entering a second rapid stirring tank, mixing the mixture with a coagulant aid in the second rapid stirring tank, rapidly stirring the mixture, staying for a certain time, entering a sedimentation tank, sinking sludge in the sedimentation tank to the bottom of the tank, returning upper clear water to a lake again through a clear water extraction pipeline, extracting substrate sludge at the bottom of the tank, entering a dehydrator, further dehydrating, allowing the dehydrated substrate sludge to enter a substrate sludge storage tank, conveying the dehydrated substrate sludge to a sludge barge through a sludge conveying device, conveying the dehydrated substrate sludge onto a bank, and returning the water extracted from the dehydrator to the first rapid stirring tank again. The invention integrates the ecological dredging of the underwater suction of the sediment, the agglomeration, the flocculation and the concentration and the dehydration into a whole, realizes the continuous operation and does not cause secondary pollution.

Description

Integrated process for continuously dredging sediment in situ

Technical Field

The invention belongs to the field of completion engineering of rivers, lakes and seas, relates to a mud-water separation technology, and particularly relates to a bottom mud continuous in-situ dredging integrated process.

Background

The river and lake sediment is structural soil with microbial action deposited in still water or water environment with very slow flow rate, and is an extremely complex heterogeneous body mainly comprising an extremely fine clay colloidal substance, and the river and lake sediment mainly comprises organic debris, bacterial thalli, inorganic particles, colloids and the like and is a comprehensive solid substance. Not only the central link of the nutrient substance circulation of rivers and lakes, but also the main gathering bank of persistent organic pollutants, nutrients, heavy metals and the like. Lakes such as the Dian Pond, the nested lake and the lake of the white lake and the bottoms of main rivers of cities are deposited with a large amount of bottom mud to different degrees. Even if the external source is effectively controlled, the release of the sediment caused by the action of physical or biological factors can still cause the water quality to continue to deteriorate or maintain the poor state of eutrophication and the like in a considerable period of time.

Dredging of rivers, lakes and seas is an effective means for effectively removing bottom mud containing heavy metals, toxic and harmful organic matters, high nitrogen and phosphorus contents and the like, and among them, the trailing suction type, the cutter suction type and the suction-lift type dredge ships have been widely used in practical engineering at home and abroad. By environment-friendly dredging, the pollutants in the bottom mud can be removed out of the water body together with the bottom mud, so that the toxic threat of the pollutants to the water body and water body organisms is relieved. However, the sludge and water pumped in the dredging process need to be quickly separated to realize continuous operation without causing secondary pollution, so that the technical problems are solved by considering the flocculation mechanism, and more importantly, the problems are solved by utilizing the rules of the nature, and the self non-toxicity, the high efficiency of the flocculation process and the rapidness of the sedimentation process are realized by an ecological method. The existing inorganic high molecular polymer polyaluminium chloride (PAC), polyferric sulfate (PFS) and the like have biotoxicity due to the properties of the inorganic high molecular polymer polyaluminium chloride (PAC), the polyferric sulfate (PFS) and the like, are difficult to be directly used for the dredging engineering of rivers, lakes and seas, and the development of a flocculating agent which is nontoxic, good in flocculating effect, high in settling speed and good in separating effect is urgently needed for the continuous dredging process.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a substrate sludge continuous in-situ dredging integrated process, which realizes the rapid separation of sludge and water and does not cause secondary pollution.

The technical scheme adopted by the invention for solving the technical problem is as follows:

an integrated process device for continuous in-situ dredging of bottom mud is characterized in that two rapid stirring tanks, a flocculant mixing tank, a coagulant aid mixing tank, a sedimentation tank, a dehydrator and a bottom mud storage tank are installed on a dredging sludge ship, wherein the first rapid stirring tank is provided with three inlets which are respectively connected with a dredging mud water extraction pipeline, a dehydration mud water backflow pipeline and a flocculant injection pipeline, the dehydration mud water backflow pipeline is connected with the dehydrator, the flocculant injection pipeline is connected with the flocculant mixing tank, the outlet of the first rapid stirring tank is connected with the inlet of the second rapid stirring tank through a pipeline, the other inlet of the second rapid stirring tank is connected with the coagulant aid injection pipeline, the coagulant aid injection pipeline is connected with the coagulant aid mixing tank, the outlet of the second rapid stirring tank is connected with the middle mud water inlet of the sedimentation tank through a pipeline, the top of the side wall of the sedimentation tank is provided with a clear water outlet, and the clear water outlet is connected with a, clear water is adopted in the pipeline leads to outboard lake, and the sedimentation tank bottom silt is through silt extraction pipe connection to hydroextractor import, and the outlet of hydroextractor is connected to first rapid mixing tank through dehydration muddy water backflow pipeline, and the mud discharging mouth of hydroextractor is through defeated mud pipe connection to sediment storage tank, and the sediment is carried to transport mud barge through carrying mud device.

And, a flow vibrator is installed at the upper part in the sedimentation tank.

And the mud water sucked up by the dredging silt boat enters a first rapid mixing tank, is mixed with an inorganic mineral flocculating agent in the mixing tank, is rapidly mixed, stays for a certain time and then enters a second rapid mixing tank, is mixed with a coagulant aid in the second rapid mixing tank, is rapidly mixed, stays for a certain time and then enters a sedimentation tank, the mud sinks into the bottom of the sedimentation tank, the upper clear water returns to the lake again, the bottom mud at the bottom of the tank enters a dehydrator after being extracted, the dehydrated bottom mud enters a bottom mud storage tank, then is conveyed to a mud conveying barge through a mud conveying device and is conveyed to the shore, and the water extracted from the dehydrator returns to the first rapid mixing tank again.

And the mass percentage of the dry mud in the muddy water is 5-5.5%.

And the inorganic mineral flocculant is one or a mixture of more than two of an acid modified montmorillonite flocculant, an acid modified vermiculite flocculant, an acid modified volcanic rock flocculant and an acid modified medical stone flocculant.

The inorganic mineral flocculating agent is powder with the grain diameter less than 74 microns.

The dosage of the inorganic mineral flocculating agent per ton of water is 1.0 kg-1.4 kg, and the optimal dosage is 1.2kg per ton of water.

Moreover, the coagulant aid is C-PAM or A-PAM.

Moreover, the coagulant aid is an aqueous solution with the mass percentage of 0.1-0.3%.

The addition amount of the coagulant aid per ton of water is 2-8 g.

And the rotation speed of the rapid stirring is 180 rpm-250 rpm, and the retention time is 0.4 min-1.0 min.

The invention has the advantages and positive effects that:

1. the invention integrates the ecological dredging of the underwater suction of the sediment, the agglomeration, the flocculation and the concentration as well as the dehydration, realizes the continuous operation, does not cause secondary pollution, and has the characteristics of high efficiency, small volume, land occupation saving and the like.

2. The invention adopts inorganic mineral as flocculant, can realize the rapid separation of mud and water, has no biotoxicity, and the separated bottom mud can be directly used as fertilizer.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a schematic diagram of flocculation according to the present invention;

FIG. 3 shows the effect of different amounts of MTSF on turbidity and Zeta potential of the bottom sludge water;

FIG. 4 shows the different amounts of MTSF added to the sediment water NH₄ ⁺-influence of N and TP.

FIG. 5 shows the effect of different amounts of MTSF on COD and SS of the sediment water.

FIG. 6 shows the effect of 1.2kg/t MTSF in combination with C-PAM of various concentrations on turbidity and Zeta potential of the bottom sludge water.

FIG. 7 shows the matching of 1.2kg/t MTSF and C-PAM with different concentrations for the sediment waterNH₄ ⁺The influence of N and COD.

In FIG. 8, (a) is a photograph of a water sample left standing for 30min at 1.2kg/t MTSF, and (b) is a photograph of a water sample left standing for 30min at 1.2kg/t MTSF +8 g/tC-PAM.

FIG. 9 shows (a) a 10-fold micrograph of MTSF flocs at 1.2kg/t and (b) a 10-fold micrograph of MTSF flocs at 1.2kg/t +8g/tC-PAM flocs.

Detailed Description

The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.

A substrate sludge continuous in-situ dredging integrated process device is characterized in that two rapid stirring tanks, a flocculating agent mixing tank 5, a coagulant aid mixing tank 6, a sedimentation tank 4, a dehydrator 8 and a substrate sludge storage tank 9 are installed on a dredging sludge ship, wherein a first rapid stirring tank 2 is provided with three inlets which are respectively connected with a dredging mud water extraction pipeline 1, a dewatering mud water backflow pipeline 7 and a flocculating agent injection pipeline, the dewatering mud water backflow pipeline is connected with the dehydrator, and the flocculating agent injection pipeline is connected with the flocculating agent mixing tank. The outlet of the first rapid stirring tank is connected with the inlet of the second rapid stirring tank 3 through a pipeline, the other inlet of the second rapid stirring tank is connected with a coagulant aid injection pipeline, and the coagulant aid injection pipeline is connected with a coagulant aid blending tank. The outlet of the second rapid stirring tank is connected with the middle muddy water inlet of the sedimentation tank through a pipeline, the top of the side wall of the sedimentation tank is provided with a clear water outlet, the clear water outlet is connected with a clear water extraction pipeline 12, and the clear water extraction pipeline is communicated into a lake outside the ship. The sedimentation tank bottom sediment mud is connected to the hydroextractor through sediment mud extraction pipeline, and the outlet of hydroextractor is connected to first rapid mixing groove through dehydration muddy water backflow pipeline, and the mud discharging mouth of hydroextractor is connected to the sediment storage tank through defeated mud pipeline, and the sediment is carried to fortune mud barge through carrying mud device 11, transports it to the bank.

In order to achieve a higher sedimentation effect, a flow vibrator 10 is installed at the upper portion in the sedimentation tank.

A continuous in-situ dredging integrated process for bottom mud includes such steps as pumping the mud from sludge dredger into the first fast stirring tank, mixing it with inorganic flocculant, fast stirring for 0.4-1.0 min, flowing into the second fast stirring tank, mixing it with coagulant aid, fast stirring for 0.4-1.0 min, flowing into settling tank, depositing the sludge in settling tank, and returning the upper clean water back to lake via clean water pipeline. And the sediment at the bottom of the pool is extracted through a sediment extraction pipeline and then enters a dehydrator for further dehydration, the dehydrated sediment enters a sediment storage tank and is conveyed to a sediment barge through a sediment conveying device to be conveyed to the bank. The water extracted from the dewatering machine returns to the first rapid stirring tank again.

The inorganic mineral flocculating agent is an acid modified montmorillonite flocculating agent, an acid modified vermiculite flocculating agent, an acid modified volcanic rock flocculating agent and an acid modified medical stone flocculating agent. Preparing aqueous solution with certain concentration in a flocculating agent mixing tank. The mass percentage content is 1-3%.

The coagulant aid is C-PAM or A-PAM. Preparing aqueous solution with a certain concentration in a coagulant aid mixing tank. The mass percentage content is 0.1-0.3%.

The flocculation effect of MTSF on the bottom sludge and water is given by taking acid modified montmorillonite flocculant (MTSF) as an example, and the Zeta potential, turbidity, pH, conductivity and NH of the supernatant liquid before and after flocculation₄ ⁺N, TP, change in Chemical Oxygen Demand (COD), analysis of flocculation effect, sedimentation rate and giving optimum dosage.

The inorganic mineral Montmorillonite (MTS) is from Lingshou county of Hebei province, and the main chemical component of Montmorillonite (MTS) is SiO₂、Al₂O₃And Fe₂O₃. The preparation method comprises the following steps of crushing MTS into powder with a certain particle size through a crusher, adding sulfuric acid modified montmorillonite powder with a certain mass ratio, fully mixing sulfuric acid and montmorillonite at room temperature, drying and crushing to obtain an acid modified montmorillonite flocculant, wherein the specific experimental steps can be referred to documents (preparation and application research of clay minerals used as raw material flocculants. proceedings of Tianjin scientific and technical university 2015,30(1): 62-66).

TABLE 1 major chemical composition of MTS

Table 2 water quality indexes of raw water produced from a dredging mud water production line

As can be seen from Table 2, the turbidity of the slurry raised by the siphon process was high and reached 622 NTU. The mud water not only contains a large amount of granular silt, but also contains a large amount of colloid and soluble pollutants, wherein the mass percentage of the dry mud is 5.01 percent, and the dry mud is separated from the water and settled by a physical and chemical flocculation method.

1) Influence on turbidity and Zeta potential of supernatant

FIG. 3 shows the effect of different amounts of MTSF added on turbidity and Zeta potential of the bottom sludge water. As can be seen from FIG. 3, the turbidity of the supernatant after the flocculation and sedimentation shows a tendency of a sharp decrease with an increase in the amount of the added sediment water, and when the amount of the added sediment water is 1.2kg/t, the turbidity of the supernatant is only 9.07NTU, which corresponds to the turbidity of a natural river, and then even if the amount of the added sediment water is further increased, the change in the turbidity is small, and when the amount of the added sediment water is 2.4kg/t, the turbidity is 7.22 NTU. While the Zeta potential of the supernatant increased from-1.61 mV to 1.35mV through zero point with increasing dosage, and the solution also changed from original turbidity to clear and transparent. Generally, turbid muddy water contains a large amount of solid particles and colloids, the Zeta potential of the turbid muddy water is negative, and after MTSF is added, soluble metal ions in the turbid muddy water are electrically neutralized with colloids in an aqueous solution to reduce repulsive force among the colloids, so that the colloids are destabilized to generate flocculation; as the addition amount of MTSF is increased, the Zeta potential is correspondingly increased. When the Zeta potential is close to zero, the supernatant reaches clear and transparent from the flocculation effect of the experiment, the turbidity removal rate is as high as 98.8%, and the 1.2kg/t dosage can be regarded as the optimal dosage at the moment.

As can be seen from Table 2, the soluble contaminants TP and NH in the bottom sludge water₄ ⁺Concentration of-NThe degree is respectively as high as 2.90 mg. L^-1And 2.18 mg. L^-1If the water quality and the living of organisms cannot be reduced effectively in the process of dredging rivers and lakes, the water quality and the living of the organisms can be seriously influenced. FIG. 4 shows TP and NH of the sediment water in different amounts of MTSF₄ ⁺FIG. 4 shows that MTSF has a good selectivity for soluble phosphorus-containing compounds, that about 25% of the metal ions Al and Fe and small amounts of Ca and Mg in soluble substances of MTSF can be separated from phosphorus by forming salts which are difficult to dissolve, and that the phosphorus content in the supernatant is from 2.90Mg L when MTSF is added in an amount of 1.2kg/t^-1Reduced to 0.01 mg-L^-1The removal rate is as high as 99.6%. And MTSF to NH₄ ⁺The removal of-N is not very high, only 29.8% at a 1.2kg/t addition, due to NH₄ ⁺NH in-N₄ ⁺Form NH with water₄OH, stably dispersed in the form of molecules in aqueous solution, is not colloid by itself, but in the flocculation process, the molecules are possibly adsorbed, entrained and captured by formed flocs and removed from water; the more MTFS added, NH₄ ⁺The higher the-N removal rate, but after all is a physical process, so the removal rate is limited. This result indicates that MTSF is responsible for NH₄ ⁺The removal selectivity of-N is poor, but the selectivity to TP is very high. In addition, the pH decreased with increasing MTSF addition, but the change was small, fluctuating only about 0.5 in the neutral range.

3) Effect on supernatant SS and COD

After the bottom sludge is siphoned and stirred, the Suspended Solid (SS) in the bottom sludge and a large amount of escaped pollutant COD respectively reach 1364 mg-L^-1And 119.55mg L^-1FIG. 5 shows the influence of different amounts of MTSF added on the SS and COD of the sludge and water, and it can be seen from FIG. 5 that the SS and COD of the supernatant decreased sharply with the increase of the amount of MTSF added, and when the amount of MTSF added was 1.2kg/t, the SS and COD of the supernatant were 32mg L mg, respectively^-1And 51.6 mg. L^-1The removal rates were 97.7% and 56.9%, respectively. Effective removal of SS allows the supernatant to be clearClearing; the reduction of COD also obviously improves the water quality of the supernatant, and when the dredging engineering is continuously operated, the supernatant flows back to the water body, so that the secondary pollution of the water environment can not be caused. As the adding amount is increased continuously, SS and COD of the supernatant can still be reduced, but the amplitude is relatively slow, and in consideration of the economical efficiency of practical application, when the adding amount of MTSF is 1.2kg/t, the Zeta potential of the supernatant is approximately zero, the colloid is basically neutralized by electricity, and all indexes are relatively good.

4) Effect of coagulant aid C-PAM on turbidity and Zeta potential of supernatant

In order to further prove the synergistic effect between the montmorillonite flocculant and the coagulant aid C-PAM, 1.2kg/t MTSF dosage when the Zeta potential is close to zero is selected to be compounded with the C-PAM with different concentrations. As can be seen from FIG. 6, the turbidity of the supernatant was further reduced on the basis of the condition that no C-PAM was added, and when the addition amount of C-PAM was 8g/t, the turbidity of the supernatant was reduced to 4.7NTU, as can be seen from the experimental effect observed, the supernatant was clearer, the floc was larger and denser, and the settling rate was also faster. The C-PAM has a bridging function, so that suspended fine particles in water can be gathered into large particles, the adsorption and net-catching capabilities are improved, and the sedimentation speed is accelerated. The amount added continues to increase, and the change in turbidity slows down. Furthermore, since cationic C-PAM is added, the Zeta potential of the supernatant fluid is increased with the addition amount, and the range of the Zeta potential is 0-0.25 mV.

5) Coagulant aid C-PAM for supernatant NH₄ ⁺Influence of-N and COD

From the above experimental results, it can be seen that 1.2kg/t MTSF of soluble pollutant NH in the bottom sludge water after being added₄ ⁺N and COD values of 1.54 mg-L, respectively^-1And 51.62 mg. L^-1According to the regulations of the surface water environment quality standard GB 3838-2002 water outlet standard, the content of COD is more than the limitation of the type I standard of 15 mg-L^-1. If COD can not be effectively reduced in the dredging process of rivers and lakes, the water quality of the river and lake can be seriously influenced, and even the survival of organisms is influenced. However, when C-PAM was further added, it is understood from FIG. 7 that NH was added as the amount of C-PAM added increased₄ ⁺of-NThe change amount was not so large that the removal rate was 17.4% at 8g/t, but the COD was decreased to a large extent at 8g/t of 15 mg-L, as compared with that before the addition of C-PAM^-1Compared with 1.2kg/t MTSF, the removal rate is improved by 70.9 percent, and the total removal rate of the two is 87.4 percent. The reason is that the addition of the C-PAM increases the conglomeration of the flocs, and simultaneously, the water in the flocs is further extruded and becomes dense, and the flocs have affinity to organic matters, so that the adsorption of the flocs to the organic matters is increased, the flocculation effect is effectively promoted, and the synergistic effect of the flocs and the organic matters is realized.

6) Comparison of the effects of C-PAM on flocculation and sedimentation

FIG. 8 shows photographs taken at 1.2kg/t MTSF (a) and 1.2kg/t MTSF +8g/tC-PAM (b) for 30 min. As can be seen from FIG. 8, the water sample on the right side is clearer than that on the left side, and the settling speed of the flocculated flocs is higher when the water sample is 1.2kg/t MTSF +8g/tC-PAM in the experimental process, and the flocs are completely settled along with slow stirring. The settled flocs were observed by a microscope, and the results are shown in FIG. 9. As can be seen from FIGS. 8 and 9, 1.2kg/t MTSF flocculated flocs were fine, while 1.2kg/t MTSF +8g/t C-PAM flocs were further enlarged and agglomerated; under a microscope, the particle size of the floc is small and no larger lump is formed when only MTSF is used, and the floc agglomeration is obviously increased when 1.2kg/t MTSF +8g/tC-PAM is used, so that the rapid sedimentation is realized. Thus, the C-PAM coagulant aid can further coagulate fine flocs again to form coarse flocs to form agglomerates, thereby enhancing the entrainment adsorption effect and clarifying water; the agglomerated floc particles are large and compact, the relative diameter is large, the sedimentation resistance is small, and the sedimentation speed is improved. As can be seen from the measurement of the sedimentation velocity at the experimental site, complete sedimentation was achieved in the case of MTSF alone, which took about 5 min. However, after the coagulant aid C-PAM is added, the smaller flocs are quickly agglomerated and settled while stirring, and the flocculation is basically completed after the stirring. Therefore, the addition of the coagulant aid C-PAM can not only reduce the using amount of MTSF, but also improve the flocculation effect in the flocculation process.

The MTSF has good flocculation effect on the bottom mud water, when the MTSF is 1.2kg/t, the Zeta potential of the supernatant is almost zero, and the turbid mud water becomes clear and transparent and is turbidity and NH₄ ⁺-N、TP、The removal rates of SS and COD were 98.8%, 29.8%, 99.6%, 97.7% and 56.9%, respectively. The optimum amount of addition was confirmed from the zeta zero potential of the supernatant, and the amount of addition had little effect on the pH of the system.

2, a small amount of C-PAM coagulant aid is added to contribute to the flocculation process and further improve the water quality of the supernatant, when the MTSF is 1.2kg/t and the C-PAM is 8g/t, the turbidity and the COD of the supernatant are further reduced from 9.0NTU and 51.6 mg-L respectively^-1Reduced to 4.7NTU and 15 mg-L^-1。

The C-PAM coagulant aid can further agglomerate flocs to form larger flocs, promote the quick sedimentation of the flocs and simultaneously help to further remove pollutants in a water phase. The combination of the two can reduce the dosage of MTSF and achieve better effect.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept, and these changes and modifications are all within the scope of the present invention.

Claims

1. The integrated process device for continuously dredging the sediment in situ is characterized in that: two rapid stirring tanks, a flocculating agent mixing tank, a coagulant aid mixing tank, a sedimentation tank, a dehydrator and a bottom mud storage tank are arranged on a dredging sludge ship, wherein the first rapid stirring tank is provided with three inlets which are respectively connected with a dredging sludge water extraction pipeline, a dehydration sludge water backflow pipeline and a flocculating agent injection pipeline, the dehydration sludge water backflow pipeline is connected with the dehydrator, the flocculating agent injection pipeline is connected with the flocculating agent mixing tank, the outlet of the first rapid stirring tank is connected with the inlet of the second rapid stirring tank through a pipeline, the other inlet of the second rapid stirring tank is connected with the coagulant aid injection pipeline, the coagulant aid injection pipeline is connected with the coagulant aid mixing tank, the outlet of the second rapid stirring tank is connected with the middle sludge water inlet of the sedimentation tank through a pipeline, the top of the side wall of the sedimentation tank is provided with a clear water outlet, the clear water outlet is connected with a clear water extraction pipeline, and the clear water extraction pipeline is, the sedimentation tank bottom sediment mud is connected to the hydroextractor import through sediment mud extraction pipeline, and the outlet of hydroextractor is connected to first rapid mixing groove through dehydration muddy water backflow pipeline, and the mud discharging mouth of hydroextractor is connected to the sediment storage tank through defeated mud pipeline, and the sediment is carried to fortune mud barge through carrying mud device.

2. The apparatus of claim 1, wherein: the upper part in the sedimentation tank is provided with a flow vibrator.

3. A substrate sludge continuous in-situ dredging integrated process method is characterized in that: the mud water sucked up by a dredging mud boat enters a first rapid mixing tank, is mixed with an inorganic mineral flocculating agent in the mixing tank, is rapidly mixed, stays for a certain time and then enters a second rapid mixing tank, is mixed with a coagulant aid in the second rapid mixing tank, is rapidly mixed, stays for a certain time and then enters a sedimentation tank, sludge in the sedimentation tank sinks to the bottom of the tank, upper clear water returns to the lake again, bottom mud at the bottom of the tank enters a dehydrator after being extracted, the dehydrated bottom mud enters a bottom mud storage tank, and then is conveyed to a mud conveying barge and conveyed to the shore through a mud conveying device, and the water extracted from the dehydrator returns to the first rapid mixing tank again.

4. The method of claim 3, wherein: the mass percentage of the dry mud in the muddy water is 5-5.5%.

5. The method of claim 3, wherein: the inorganic mineral flocculating agent is one or a mixture of more than two of an acid modified montmorillonite flocculating agent, an acid modified vermiculite flocculating agent, an acid modified volcanic rock flocculating agent and an acid modified medical stone flocculating agent.

6. The method according to claim 3 or 5, characterized in that: the dosage of the inorganic mineral flocculating agent per ton of water is 1.0 kg-1.4 kg.

7. The method of claim 3, wherein: the coagulant aid is C-PAM or A-PAM.

8. The method according to claim 3 or 7, characterized in that: the coagulant aid is an aqueous solution with the mass percentage of 0.1-0.3%.

9. The method according to claim 3 or 7, characterized in that: the dosage of the coagulant aid per ton of water is 2 g-8 g.

10. The method of claim 3, wherein: the rotating speed of the rapid stirring is 180 rpm-250 rpm, and the retention time is 0.4 min-1.0 min.