River channel dredging method
Technical Field
The invention relates to the field of dredging of accumulated mud at the bottom of a water body, in particular to a river channel dredging method.
Background
The town river channel is an important component of the town ecological system, not only has the functions of providing water sources, transportation, flood control, drainage and the like, but also has the ecological environment effects of regulating climate, reducing pollution and the like. However, with the development and progress of society, the river sludge problem has become a prominent problem in urban rivers: the sedimentation of silt and garbage in the river channel influences the flood discharge and landscape of the river channel; a large amount of polluted bottom mud has adverse effects on water quality improvement and ecological restoration; the floating mud layer on the surface layer of the river channel is very easy to float to form a black water hose during low tide, and the mud and the garbage on the high beaches of the two banks are exposed out of the water surface during low tide, so that the sight is obstructed and the landscape is destroyed, therefore, the dredging work of the river channel is very important for improving the environment and building the city.
The geotextile tube bag is a tube strip material which is made of high-strength geotextile and has certain strength and ductility and a filtering effect, is originally used in the dike engineering and is applied to the fields of environmental protection, lake and reservoir dredging and the like at present.
CN101774745A discloses a silt tube bag and a dehydration method for silt dehydration, filling silt into a silt storage bag through a special silt pump system, after the tube bag is filled with a seal, connecting an electrode into a voltage-stabilizing direct-current power supply to start dehydration, utilizing triple functions of gravity, tube bag wall pressure and electroosmosis, collecting moisture in the silt through a cathode and rapidly removing the moisture through filtration of the bag wall, changing the silt in the bag into a plastic body with certain shear strength from fluid, and taking out the dehydrated plastic silt through opening seams of the tube bag wall, thereby realizing silt treatment. CN105000787A discloses a sludge dredging bag and a sludge dredging method, which utilize a sludge dredging bag made of a geotechnical ecological film to carry out dredging, and the concrete steps are as follows: pumping out the water-containing sludge through a mud pump, adding a coagulant, pumping into a dredging bag, and drying the sludge under the action of volatilization and gravity or pressure addition. After the dehydration by the method, the water content of the sludge can be reduced to about 70 percent, and the water content of the sludge can be further reduced to about 50 percent after one week of insolation and natural air drying, so that the treatment capacity of common sludge drying equipment is achieved, and the method has the advantages of low energy consumption, running cost saving and the like.
The method adopted by the common river channel dredging at present is as follows: the method for dredging the river channel comprises the steps of firstly dredging by using a dredger, then dredging out silt by using a ship, then placing the silt in a cofferdam, naturally airing, and then carrying out vehicle loading and transporting for landfill.
CN105399290A discloses a rural river dredging construction method, which comprises the following steps: a. excavating the sludge through a dredger with a cutting head and a pump, wherein the cutting head is placed in a sludge layer of a river channel, then the dredger starts to move forwards, and the cutting head cuts into the sludge layer and conveys the sludge into the pump; b. conveying: the pump sucks water and silt into it together, the mud is sent into the bank buffer pool through the mud pipeline subsequently; c. deodorizing and curing: adding a deodorant and a curing agent into the buffer tank for curing and deodorizing; d. and injecting the slurry subjected to deodorization and curing treatment into the ecological pipe bag through a pipeline by using a pump, curing, precipitating, draining and filtering for one month by using the self weight of the slurry in the ecological pipe bag, and finally using the dewatered and cured sludge as slope protection, landfill or outward transportation. The invention changes the traditional open extensive desilting method, adopts the ecological tube bag for dehydration, avoids the problem of environmental pollution caused by drying sludge in the sun, and has lower cost compared with mechanical dehydration.
However, after the geotextile tube bag is filled to a certain degree, the surface of the geotextile tube bag is covered by a 'filter cake thin layer' formed by fine silt particles, so that the further seepage of water in the geotextile tube bag is hindered, and the water permeation efficiency of the geotextile tube bag is low. Meanwhile, due to the fact that the water content in the soil engineering pipe bag is not uniform, bottom mud is difficult to recycle resources.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a river channel dredging method, which improves the dehydration efficiency of a soil engineering pipe bag by pretreating sludge, and has the advantages of strong operability, small occupied area, low cost and no secondary pollution.
In order to achieve the purpose, the invention adopts the following technical scheme:
a river channel dredging method comprises the following steps:
(1) sludge conveying: conveying water and sludge to a bank side buffer tank together, and uniformly mixing to obtain slurry;
(2) ultrasonic treatment: carrying out ultrasonic treatment on the slurry obtained in the step (1) to obtain slurry liquid;
(3) separating mud and sand: performing air floatation treatment on the mud liquid obtained in the step (2) to obtain heavy gravel and light sludge; cleaning heavy gravel by using raw water in a river channel to obtain gravel and cleaning fluid;
(4) dehydrating the soil engineering pipe bag: and (3) mixing the light sludge obtained in the step (3) with a cleaning solution, adding a flocculating agent, standing, removing a supernatant to obtain a deposition solution, adding diatomite and a modifying agent into the deposition solution to obtain a modified solution, filling the modified solution into an earthen pipe bag for curing and dewatering, and finally recovering the sludge subjected to dehydration and curing as a resource.
Preferably, before the step (1), the method further comprises the following steps: detecting the types and the contents of pollutants in the water body and the bottom mud of the river channel, and determining the dredging depth.
Preferably, the slurry in step (1) has a solids content of 10-15%.
Preferably, the ultrasonic treatment in the step (2) is that the ultrasonic frequency is 20-50kHz and the ultrasonic intensity is 20-75W/cm2The treatment time is 5-10 min.
Preferably, no flocculant and/or coagulant aid is added during the air flotation treatment in the step (3).
Preferably, the air flotation treatment in the step (3) is as follows: the working pressure is 0.3-0.6MPa, the reflux ratio is 8-15%, and the slag scraping period is 0.2-0.5 h.
Preferably, the pore diameter of the geotextile tube bag in the step (4) is 0.1-0.3 mm.
Preferably, the flocculating agent in the step (4) is chitosan and poly ferric chloride, and the addition amount of the flocculating agent is 0.05-0.1% of the mass of the light sludge.
Preferably, the addition amount of the diatomite in the step (4) is 0.1-0.2% of the mass of the deposition solution.
Preferably, the addition amount of the modifying agent in the step (4) is 0.05-0.1% of the mass of the deposition solution.
Preferably, the modifying agent is any one of ethylenediaminetetraacetic acid, citric acid, malic acid and humic acid.
The invention has the beneficial effects that:
(1) the invention realizes the separation of the silt and the gravel by combining ultrasonic treatment and air flotation, the gravel returns to the river channel and is used for restoring the river channel after dredging, simultaneously, the treatment amount of the silt is reduced, and the production cost is reduced.
(2) According to the invention, the diatomite and the modifier are added to pretreat the light sludge, so that a filter cake thin layer formed on the surface of the pipe bag by fine silt particles in the filling process is effectively avoided, and the dewatering efficiency of the self-weight filtration of the geotechnical pipe bag is improved.
(3) The consistency of the water content of the prepared pipe bag sludge is high, and the pipe bag sludge can be directly used for planting soil to realize the resource recycling of bottom sludge.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention are further described below. The sources of the chemical reagents used in the present invention are not particularly limited, and are all common commercial products. The diatomite is 0.1mm in particle size, and the geotechnical pipe bag is a high-strength high-filtration polypropylene geotechnical pipe bag.
A river channel dredging method comprises the following steps:
(1) sludge conveying: conveying water and sludge to a bank side buffer tank by using a pump, and uniformly mixing to obtain slurry with the solid content of 10-15%;
(2) ultrasonic treatment: carrying out ultrasonic treatment on the slurry obtained in the step (1) to obtain slurry liquid; the ultrasonic frequency is 20-50kHz, and the ultrasonic intensity is 20-75W/cm2The treatment time is 5-10 min;
(3) separating mud and sand: performing air floatation treatment on the mud liquid obtained in the step (2) to obtain heavy gravel and light sludge; cleaning heavy gravel by using raw water in a river channel to obtain gravel and cleaning fluid;
a flocculating agent and/or a coagulant aid are not added in the air floatation treatment process; the air floatation treatment comprises the following steps: the working pressure is 0.3-0.6MPa, the reflux ratio is 8-15%, and the slag scraping period is 0.2-0.5 h;
(4) dehydrating the soil engineering pipe bag: mixing the light sludge obtained in the step (3) with a cleaning solution, adding a flocculating agent accounting for 0.05-0.1% of the weight of the light sludge, standing to obtain a deposition solution, adding diatomite accounting for 0.1-0.2% of the weight of the deposition solution and a modifying agent accounting for 0.05-0.1% of the weight of the deposition solution into the deposition solution respectively to obtain a modified solution, blowing the modified solution into a soil engineering pipe bag with the aperture of 0.1-0.3mm for curing and dewatering for 1-3 weeks, and finally recovering the dewatered and cured sludge as resources for landscape planting soil, building materials and the like;
wherein the mass ratio of the flocculating agent is 1: 1 chitosan and poly ferric chloride; the modifier is any one of ethylenediamine tetraacetic acid, citric acid, malic acid and humic acid.
Preferably, the present invention further comprises river damage analysis: detecting the types and the contents of pollutants in the water body and the bottom mud of the river channel, and determining the dredging depth of the river channel; wherein the depth of the sampling point of the bottom mud is 5-10cm, 15-20cm and 25-35cm respectively.
Meanwhile, the sand gravel obtained in the step (3), the supernatant after standing in the step (4) and the filtrate of the geotechnical tube bags are returned to the river channel for restoring the dredging river channel, so that the dredging cost is reduced.
Example 1
A river channel dredging method comprises the following steps:
(1) sludge conveying: conveying water and sludge to a bank side buffer tank by using a pump, and uniformly mixing to obtain slurry with the solid content of 10%;
(2) ultrasonic treatment: carrying out ultrasonic treatment on the slurry obtained in the step (1) to obtain slurry liquid; the ultrasonic frequency is 20kHz, and the ultrasonic intensity is 20W/cm2The treatment time is 10 min;
(3) separating mud and sand: performing air floatation treatment on the mud liquid obtained in the step (2) to obtain heavy gravel and light sludge; cleaning heavy gravel by using raw water in a river channel to obtain gravel and cleaning fluid;
a flocculating agent and/or a coagulant aid are not added in the air floatation treatment process; the air floatation treatment comprises the following steps: the working pressure is 0.3MPa, the reflux ratio is 8 percent, and the slag scraping period is 0.2 h;
(4) dehydrating the soil engineering pipe bag: mixing the light sludge obtained in the step (3) with a cleaning solution, adding a flocculating agent accounting for 0.05% of the weight of the light sludge, standing to obtain a deposition solution, adding diatomite accounting for 0.1% of the weight of the deposition solution and a modifying agent accounting for 0.05% of the weight of the deposition solution into the deposition solution respectively to obtain a modified solution, blowing the modified solution into a geotechnical pipe bag with the aperture of 0.1mm for solidification and dehydration for 3 weeks, and finally, recovering resources by taking the dehydrated and solidified sludge as landscape planting soil;
wherein the mass ratio of the flocculating agent is 1: 1 chitosan and poly ferric chloride; the modifier is prepared from the following components in a mass ratio of 1: 1:2 ethylenediaminetetraacetic acid, citric acid and humic acid.
Example 2
A river channel dredging method comprises the following steps:
(1) sludge conveying: conveying water and sludge to a bank side buffer tank by using a pump, and uniformly mixing to obtain slurry with the solid content of 15%;
(2) ultrasonic treatment: carrying out ultrasonic treatment on the slurry obtained in the step (1) to obtain slurry liquid; the ultrasonic frequency is 50kHz, and the ultrasonic intensity is 75W/cm2The treatment time is 5 min;
(3) separating mud and sand: performing air floatation treatment on the mud liquid obtained in the step (2) to obtain heavy gravel and light sludge; cleaning heavy gravel by using raw water in a river channel to obtain gravel and cleaning fluid;
a flocculating agent and/or a coagulant aid are not added in the air floatation treatment process; the air floatation treatment comprises the following steps: the working pressure is 0.6MPa, the reflux ratio is 15 percent, and the slag scraping period is 0.5 h;
(4) dehydrating the soil engineering pipe bag: mixing the light sludge obtained in the step (3) with a cleaning solution, adding a flocculating agent accounting for 0.1% of the weight of the light sludge, standing to obtain a deposition solution, adding diatomite accounting for 0.2% of the weight of the deposition solution and a modifying agent accounting for 0.1% of the weight of the deposition solution into the deposition solution respectively to obtain a modified solution, blowing the modified solution into a soil engineering pipe bag with the aperture of 0.3mm for curing and dehydrating for 2 weeks, and finally, recovering resources by taking the dehydrated and cured sludge as landscape planting soil;
wherein the mass ratio of the flocculating agent is 1: 1 chitosan and poly ferric chloride; the modifier is prepared from the following components in a mass ratio of 1: 1:2 ethylenediaminetetraacetic acid, citric acid and humic acid.
Example 3
A river channel dredging method comprises the following steps:
(1) sludge conveying: conveying water and sludge to a bank side buffer tank by using a pump, and uniformly mixing to obtain slurry with the solid content of 12%;
(2) ultrasonic treatment: carrying out ultrasonic treatment on the slurry obtained in the step (1) to obtain slurry liquid; the ultrasonic frequency is 35kHz, and the ultrasonic intensity is 50W/cm2The treatment time is 6 min;
(3) separating mud and sand: performing air floatation treatment on the mud liquid obtained in the step (2) to obtain heavy gravel and light sludge; cleaning heavy gravel by using raw water in a river channel to obtain gravel and cleaning fluid;
a flocculating agent and/or a coagulant aid are not added in the air floatation treatment process; the air floatation treatment comprises the following steps: the working pressure is 0.35MPa, the reflux ratio is 12 percent, and the slag scraping period is 0.35 h;
(4) dehydrating the soil engineering pipe bag: mixing the light sludge obtained in the step (3) with a cleaning solution, adding a flocculating agent accounting for 0.08% of the weight of the light sludge, standing to obtain a deposition solution, adding diatomite accounting for 0.15% of the weight of the deposition solution and a modifying agent accounting for 0.08% of the weight of the deposition solution into the deposition solution respectively to obtain a modified solution, blowing the modified solution into a soil engineering pipe bag with the aperture of 0.2mm for solidification and dehydration for 1 week, and finally, recovering resources by taking the dehydrated and solidified sludge as landscape planting soil;
wherein the mass ratio of the flocculating agent is 1: 1 chitosan and poly ferric chloride; the modifier is prepared from the following components in a mass ratio of 1: 1:2 ethylenediaminetetraacetic acid, citric acid and humic acid.
Comparative example 1
This comparative example differs from example 3 in the absence of sonication.
Comparative example 2
This comparative example differs from example 3 in that no diatomaceous earth is added in step (6).
Comparative example 3
The comparative example is different from example 3 in that the modifier is added in the step (6) in a mass ratio of 1:2:1 and the amount of diatomite is 0.2%.
Comparative example 4
The difference between this comparative example and example 3 is that the slurry in step (1) has a solids content of 17%, and the air flotation treatment in step (3) is: the working pressure is 0.6MPa, the reflux ratio is 15 percent, and the slag scraping period is 0.5 h.
Experimental example 1 solid content of sludge after curing
And after the solidification of the sludge in the geotechnical pipe bag is finished, disassembling the pipe bag, sampling according to the height of the solidified sludge in a layering manner, and measuring the solid content of the sludge in the geotechnical pipe bag. Wherein the sampling point A is located 5cm below the upper surface of the consolidated sludge, the sampling point B is located at the horizontal central axis of the consolidated sludge, namely, the distance from the upper surface of the consolidated sludge is 15cm, and the sampling point C is located 5cm above the lower surface of the consolidated sludge.
The detection method comprises the following steps: weighing 5-10g of an analysis sample, putting the analysis sample in a crucible with known weight and dried to constant weight, drying for 4-8h at 105 ℃ to constant weight, and accurately weighing the analysis sample on an analytical balance after drying and cooling. The calculation formula is as follows:
TS%=(W2/W1)×100%
in the formula:
TS-solid content%
W1-sample mass before drying, g;
w2-sample mass after drying, g.
TABLE 1 solidified sludge solids content (TS) data
|
ATS%
|
B TS%
|
C TS%
|
Example 1
|
53.4
|
52.6
|
51.2
|
Example 2
|
53.2
|
51.5
|
50.1
|
Example 3
|
53.0
|
52.9
|
52.3
|
Comparative example 1
|
52.8
|
45.0
|
35.2
|
Comparative example 2
|
50.5
|
42.4
|
31.8
|
Comparative example 3
|
50.2
|
47.5
|
38.0
|
Comparative example 4
|
45.2
|
37.8
|
30.1 |
As can be seen from table 1, the solid contents of the surface layer sludge, the middle layer sludge and the bottom layer sludge of the solidified sludge prepared by the technical solutions of embodiments 1 to 3 of the present application are not very different, which indicates that the present application can effectively improve the consistency of sludge dehydration of the geotextile tube bags, and realize resource utilization of the solidified sludge. Simultaneously, this application has effectively prevented that geotechnological tube bag surface from forming "filter cake thin layer" through the cooperation of ultrasonic treatment, air supporting and diatomaceous earth and modifier, has improved the efficiency of permeating water of tube bag, has shortened the time of silt solidification.
The present invention has been further described with reference to specific embodiments, which are only exemplary and do not limit the scope of the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.