CN116002938A - Conditioning agent for geotechnical tube bag dehydration and simultaneous fermentation of river and lake dredging bottom mud and preparation method thereof - Google Patents

Abstract

The invention discloses a conditioner for dehydration and synchronous fermentation of bottom mud and a preparation method thereof, wherein the conditioner is granular and sequentially comprises an inner core, an outer shell and a coating from inside to outside, wherein: the mass portion of the inner core is 1.5-2 portions, the inner core is formed by pressing coconut husk, and the density of the pressed coconut husk is 0.45-0.50g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the The shell consists of 6-8 parts by weight of natural sand, 2-2.5 parts by weight of corn cob powder and 0.5-1 part by weight of composite microbial inoculum, wherein the fineness modulus of the natural sand is 2.5-3.0, and the mass part ratio of the inner core to the shell is 1 (5-6); the composite microbial inoculum consists of streptococcus thermophilus and actinomycetes thermophilus, and the mass ratio of the streptococcus thermophilus to the actinomycetes thermophilus is 1:1, a step of; the coating consists of 0.6-0.8 part by weight of vinyl acetate-ethylene copolymer and 0.15-0.2 part by weight of polyvinyl alcohol. The method comprisesThe regulator can obviously shorten the dehydration period of the bottom mud and reduce the comprehensive treatment cost of the bottom mud.

Description

Conditioning agent for dehydration and simultaneous fermentation of river and lake dredging bottom mud geotechnical tube bag and preparation method thereof

technical field

The invention relates to the technical field of river and lake bottom mud treatment and disposal, in particular to a conditioner for dehydration and simultaneous fermentation of river and lake bottom mud geotechnical tube bags and a preparation method thereof.

Background technique

Ecological dredging is an important means to remove endogenous pollution in rivers and lakes, but dredging will inevitably produce a large amount of sediment with high water content. The usual treatment method is to dehydrate and reduce the volume of the sediment and then landfill it safely. However, this treatment method not only occupies the limited storage capacity of the landfill, but also causes a waste of the sediment resource itself, because most river and lake sediments are rich in Containing organic matter and nitrogen and phosphorus nutrients, it can be used as green planting soil after fermentation treatment to realize resource utilization.

At present, there have been related studies on the preparation of greening soil from river and lake sediments, mainly through the simple connection of the dehydration process of the sediment and the process of preparing the greening soil from the fermentation of the sediment, that is, dehydrating the sediment to the design moisture content requirement first, and then transporting it to the Fermentation treatment is carried out at a designated place, such as the Chinese Invention Patent Publication No. CN113142014A discloses an alkaline river mud-based garden green planting soil and its preparation method, after materials such as furfural residue, straw powder, and chitosan are dehydrated with plate and frame press filtration The bottom mud is mixed for compost fermentation. Chinese Invention Patent Publication No. CN110604031A discloses a method of using river bottom mud compost to produce soilless culture substrates for garden plants. Materials such as garden solid waste, mushroom slag, and traditional Chinese medicine slag are added to the dehydrated bottom mud. Or forced ventilation compost aerobic fermentation, and finally add perlite, vermiculite and other auxiliary materials to obtain a soilless cultivation substrate. Both methods are aimed at the fermentation of the dehydrated bottom sludge, without considering the mutually reinforcing benefits of bottom sludge dehydration and simultaneous fermentation treatment, which have the problems of long construction period, high cost, and difficulty in large-scale application.

The inventor found through research that if the geotechnical tube bag dehydration process is used, the fermentation material can be directly filled into the geotechnical tube bag, and the two links of sediment dehydration and fermentation can be simultaneously processed, wherein the fermentation material can promote the decline of the moisture content of the sediment, and the The geotube bag for sediment dehydration can provide a fermentation place for sediment, and the whole process can greatly shorten the construction period and reduce the cost of preparing green soil from sediment. The key to realizing the synchronous treatment process is to find a fermentation material that can adapt to the dehydration of the sediment, and there is no related research at home and abroad.

Contents of the invention

In order to realize the above-mentioned sediment dehydration and synchronous fermentation technology, an object of the present invention is to provide a conditioner for dehydration and synchronous fermentation of river and lake dredging sediment geotube bags with simple process, environmental friendliness and cost saving.

Another object of the present invention is to provide a process for the preparation of the above conditioner.

For this reason, the present invention provides following technical scheme:

A conditioner used for dehydration and synchronous fermentation of river and lake dredged geotechnical tube bags, the conditioner is in the form of granules, and includes an inner core, an outer shell and a coating from the inside to the outside, wherein:

The mass fraction of the inner core is 1.5-2 parts, which is formed by pressing coconut bran, and the density of the pressed coconut bran is 0.45-0.50g/cm ³ ;

The shell is composed of natural sand, corn cob powder, and composite microbial agent, and the mass parts of the three are 6-8 parts, 2-2.5 parts, and 0.5-1 part respectively, wherein the fineness modulus of the natural sand is 2.5-3.0, the mass fraction ratio of the inner core and the shell is 1:(5-6) (the volume ratio of the shell and the inner core is about 0.65:0.35); Composed of actinomycetes, the mass ratio of the two is 1:1;

The coating is composed of vinyl acetate-ethylene copolymer and polyvinyl alcohol, and the mass parts of the two are 0.6-0.8 parts and 0.15-0.2 parts respectively.

Preferably, the conditioner particles have a diameter of 4-6 mm and a density of 1.1-1.2 g/cm ³ .

The coconut peat is prepared from coconut shell fiber powder, the decomposition degree of the coconut shell fiber powder is medium, the ash content ratio is 6% to 8%, the bulk density is 0.1 to 0.15g/cm ³ , and the EC value (salt content) It is 1.30-2.60mS/cm; after cleaning the coconut shell fiber powder with clean water for 3-5 times, the EC value of coconut peat is controlled to be ≤0.5mS/cm, and then dried until the moisture content is ≤15%.

The corn cob powder is obtained by grinding corn cobs after removing kernels through a 120-mesh sieve, and the water content is 3-5 wt%.

Preferably, the water content of the composite bacterial agent is ≤8wt%, and the number of effective viable bacteria is ≥2 billion CFU/g.

Preferably, the conditioner particles have a density of 1.1-1.2g/cm ³ , which is closest to the density of dredging mud, which can ensure that the conditioner is evenly distributed in the mud and ensure the uniformity and adequacy of the later fermentation process.

A preparation method of the above conditioning agent, comprising the following steps:

S1, making the inner core: send the coconut peat into a double-roll shredding granulator, and press it into a spherical shape after 5-10 minutes under a pressure of 2.5-3Mpa. The double roller shredding granulator can reduce the volume of coconut peat to 1/4~1/3 of the original volume, and the diameter of the roller mold can be adjusted, and the adjustment range is 2mm~20cm.

S2, shell production: mix sand, starch, and composite bacterial agent uniformly according to the above-mentioned raw material ratio to obtain shell materials; then put the core and shell materials into a shot blasting granulator in proportion to shell granulation, and granulate The diameter is 4~6mm;

S3, coating production: mix the vinyl acetate-ethylene copolymer and polyvinyl alcohol uniformly according to the ratio, then add the granules obtained in step S2, put them into a coating machine for coating, and the coating thickness is 15-20 μm.

The above-mentioned conditioner can be used for the dehydration of river and lake dredging sediment (moisture content is about 95%, density is 1.12g/cm ³ ) geotube bag and synchronous fermentation to prepare greening soil, wherein the water content of river and lake dredging sediment is about 95% , with a density of 1.08g/cm ³ ), the amount of conditioner used for each square of river and lake dredged sediment is 1-1.6kg. When in use, the flocculant and the conditioning agent are sequentially added to the dredged bottom mud of rivers and lakes.

The present invention divides the conditioning agent into three layers according to the needs of bottom mud dehydration and preparation of landscaping soil, and each layer plays a different role, specifically as follows:

The inner core is made of compressed and dense coconut bran body. On the one hand, it will expand rapidly when it encounters water, absorbing 5 to 10 times its own volume of water, and can adjust the moisture content of the sediment from 85% to less than 70%, which meets the moisture content conditions of the subsequent sediment fermentation. At the same time, due to the expansion of coconut peat, the air permeability of the bottom mud in the geotube bag will be increased, and the aeration conditions for subsequent bottom mud fermentation will be improved. On the other hand, the C/N ratio of coconut peat is about 120, which can solve the problem of insufficient carbon source in the sediment during the fermentation process.

The outer shell is composed of sand, starch, and compound bacterial agent. The sand can be used to improve the infiltration rate index of the green soil prepared from the bottom mud. The reason is that the dredged bottom mud is mainly silty clay, and the natural infiltration rate is low. The particle size distribution of sanded soil is closer to the natural planting soil. The starch in the shell layer, on the one hand, acts as an adhesive to wrap the shell material on the inner core, and on the other hand, it can provide nutrients for the compound bacterial agent. The composite microbial agent of the shell layer is used for the fermentation of the bottom mud in the geotechnical pipe bag.

Vinyl acetate-ethylene copolymer is used to modify polyvinyl alcohol, which effectively improves the water resistance of the membrane, and the permeability is about 0.66%. The inner core absorbs water and swells, and the conditioner crumbles.

Compared with existing conditioning agents, the present invention has the following beneficial effects:

1. The conditioner of the present invention fully utilizes the strong water absorption and high carbon-to-nitrogen ratio of the coconut bran material, and realizes the dehydration and synchronous fermentation functions of dredging bottom sludge. The conditioner is filled into the geotechnical tube bag synchronously with the mud, which significantly shortens the dehydration period of the sediment, and at the same time completes the fermentation of the sediment in the geotechnical tube bag without additional fermentation equipment. The traditional geotechnical pipe bag dehydration and fermentation process for preparing landscaping soil requires a total construction period of at least 3 to 4 months. The conditioner of the present invention can shorten the total construction period to within 2 months.

2. The conditioning agent of the present invention makes full use of the bag capacity released by the tail water discharge after the geotechnical tube bag is filled, and uses the internal space released by the geotechnical tube bag as the bottom mud fermentation place, which is more than the traditional bottom mud fermentation to prepare green soil projects, without civil engineering Partial investment in plants and workshops has significantly reduced the engineering cost of comprehensive treatment of sediment and enhanced the market viability and competitiveness of the technology of preparing green soil from sediment.

3. On the one hand, the sand in the conditioner can promote the survival of the bacteria. Under dry and normal temperature conditions, the shelf life is more than one year. On the other hand, it improves the physical structure of the green soil prepared from the bottom mud, increases the permeability, and can further improve Quality of landscaping.

4. The conditioner of the present invention can be applied to geotechnical tube bag dehydration projects, and the conditioner and mud are filled into the geotechnical tube bag synchronously, which can significantly shorten the dehydration period of the bottom sludge, and at the same time complete the fermentation of the bottom sludge in the geotechnical tube bag without additional fermentation equipment.

Description of drawings

Figure 1 is a schematic diagram of the structure of the conditioning agent of the present invention.

Detailed ways

The following specific examples further illustrate the conditioning agent of the present invention, and do not mean that the content of the invention is limited to the scope of the examples.

Example 1

Relying on a river dredging project in Harbin City, Heilongjiang Province, the geotube bag dehydration and simultaneous fermentation experiments of the bottom mud were carried out. The moisture content of the bottom mud before dehydration was 95%, and the carbon-nitrogen ratio (C/N) in the bottom mud was 2.5:1. The geotechnical tube bag used in the test has an effective utilization bag capacity of 60m ³ , and is filled with 60m ³ of mud, and 240kg of conditioning agent is added during the filling process. The total duration of sediment dehydration and fermentation is 45 days.

The conditioning agent used for bottom sludge dehydration and simultaneous fermentation of the present embodiment is prepared by the following method:

① Kernel production: first wash the coconut peat with water for 5 times, control the EC value not to exceed 0.5mS/cm, then dry it to a moisture content of 15%, and send the dried coconut peat into the double-roller shredding granulator, After 8 minutes under the pressure of 2.5Mpa, it is pressed into a spherical shape with a diameter of 2-4mm, and the density after compression is about 0.45g/cm ³ ;

②Shell production: mix sand, starch, and compound bacterial agent according to the ratio of 6 parts, 2 parts, and 0.5 parts, and then put 1 part of core material and 6 parts of shell material into the shot blasting granulator for shell making Granules, particle diameter 4 ~ 6mm;

③ Coating production: Mix vinyl acetate-ethylene copolymer and polyvinyl alcohol evenly at a ratio of 0.6:0.15 by mass, then add the particles obtained in step ②, put them into a coating machine for coating, and the thickness of the coating is 20 μm.

The structure of the conditioner prepared by the above method is shown in Figure 1.

The mechanism of action of conditioning agent of the present invention is as follows:

The conditioning agent of the present invention is mainly used in geotechnical tube bag dehydration engineering, and mainly functions in two stages.

The first stage: sediment dehydration stage. The flocculant and conditioner enter the geotube bag along with the dredging mud, and the flocculant will play a role within 2 to 3 hours after the geotube bag is filled. It can be reduced to about 85%. At this time, the surface of the geotube bag body is no longer obviously drained. After entering the geotechnical tube bag for 3 to 5 days, the coating on the surface of the conditioner gradually melts, the inner core of the coconut peat begins to contact with water and swells after absorbing water, and the conditioner disintegrates rapidly. After absorbing water, the coconut peat can expand to 5-10 times of its original volume. Each kilogram of conditioning agent can theoretically absorb about 20L of water, and the moisture content of the sediment will drop to less than 70%.

The second stage: bottom mud fermentation stage. While absorbing water, coconut peat also builds a supporting framework inside the soil, which can effectively improve the air permeability of the dredged sediment and create an environment for the aerobic fermentation of the compound bacterial agent. Since the density of the conditioner is close to that of dredging mud, the conditioner inside the geotube bag is evenly dispersed in the bottom mud, which can ensure the uniformity of fermentation. After 30 to 45 days, the dredged bottom mud can be fermented into green planting soil, and finally the bags can be broken and screened.

After the geotechnical tube bag is filled with mud, regularly collect columnar soil samples from the cuff of the geotechnical tube bag to detect the moisture content of the bottom mud and the state of the conditioning agent. The sampling frequency is 1 day, 2 days, 3 days, 5 days, 15 days, and 30 days , 45 days, the results are shown in Table 1. Compared with the traditional geotechnical tube bag dewatering process, the dewatering efficiency of the sediment is significantly improved (the dehydration of the traditional geotechnical tube bag to a moisture content of 60% takes 3-6 months), and the moisture content of the sediment has met the loading requirements for foreign shipments in 30 days .

Table 1 Test results

Sampling time (days) Sediment moisture content (%) conditioner status 1 90.2 not disintegrated 2 88.5 not disintegrated 3 85.1 not disintegrated 5 72.3 completely disintegrated 15 61.5 completely disintegrated 30 50.5 completely disintegrated 45 45.6 completely disintegrated

After 45 days, the geotechnical pipe bag was broken open, the product was crushed, and samples were taken for greening soil index detection, as shown in Table 2. All indicators of greening soil prepared by dredging bottom mud meet the requirements of "Green Planting Soil" CJ/T340-2016. Compared with the traditional dredging and sediment fermentation process (soil infiltration is 60-80mm/h), the soil infiltration rate is significantly increased to 152.44mm/h.

Table 2 Test results

serial number Detection Indicator unit Green soil after treatment 1 pH dimensionless 7.82 2 Salt content g/kg 4.36 3 organic matter mg/kg 45 4 soil infiltration rate mm/h 152.44 5 Hydrolyzable nitrogen mg/kg 145 6 available phosphorus mg/kg 9.5 7 Available Potassium mg/kg 201.3 8 available magnesium mg/kg 163.1 9 available calcium mg/kg 301.32 10 available iron mg/kg 121.12 11 Effective copper mg/kg 1.24 12 available zinc mg/kg 2.49

Example 2

Relying on the Baiyangdian pilot dredging project in Xiong'an New District, the dehydration and simultaneous fermentation experiments of the bottom mud geotube bag were carried out. The moisture content of the bottom mud before dehydration was 90%, and the average C/N ratio of the bottom mud was 3.5:1. The effective bag capacity is 90m ³ , and 90m ³ of mud is filled, and 450kg of conditioner is added accumulatively during the filling process. The total duration of sediment dehydration and fermentation is 42 days.

The conditioning agent used for bottom sludge dehydration and simultaneous fermentation of the present embodiment is prepared by the following method:

① Kernel production: first wash the coconut peat with water for 5 times, control the EC value not to exceed 0.5mS/cm, then dry it to a moisture content of 15%, and send the dried coconut peat into the double-roller shredding granulator, After 10 minutes under the pressure of 2.6Mpa, it is pressed into a spherical shape with a diameter of 2-4mm, and the density after compression is about 0.48g/cm ³ ;

②Shell production: mix sand, starch, and compound bacterial agent according to the ratio of 7 parts, 2.5 parts, and 0.9 parts, and then put 1 part of core material and 6 parts of shell material into the shot blasting granulator for shell making Granules, particle diameter 4 ~ 6mm;

③ Coating production: Mix vinyl acetate-ethylene copolymer and polyvinyl alcohol evenly at a ratio of 0.6:0.15 by mass, then add the granules obtained in step ②, put them into a coating machine for coating, and the thickness of the coating is 20 μm.

After the geotechnical tube bag is filled with mud, regularly collect columnar soil samples from the cuff of the geotechnical tube bag to detect the moisture content of the bottom mud and the state of the conditioning agent. The sampling frequency is 1 day, 2 days, 3 days, 5 days, 15 days, and 30 days , 45 days, the results are shown in Table 3.

Table 3 Test results

Sampling time (days) Sediment moisture content (%) conditioner status 1 89.2 not disintegrated 2 87.5 not disintegrated 3 84.6 not disintegrated 5 68.4 completely disintegrated 15 59.1 completely disintegrated 30 53.5 completely disintegrated 42 41.6 completely disintegrated

Compared with the traditional geotechnical tube bag dewatering process, the dewatering efficiency of the sediment is significantly improved (it takes 3-6 months for the traditional geotechnical tube bag to dehydrate to a moisture content of 60%), and the moisture content of the sediment within 30 days can meet the loading requirements for foreign transportation .

After 42 days, the geotechnical pipe bag was broken open, the product was crushed, and samples were taken for greening soil index detection, as shown in Table 4.

Table 4 Test results

serial number Detection Indicator unit Green soil after treatment 1 pH dimensionless 7.62 2 Salt content g/kg 3.36 3 organic matter mg/kg 53 4 soil infiltration rate mm/h 115.13 5 Hydrolyzable nitrogen mg/kg 121 6 available phosphorus mg/kg 7.7 7 Available Potassium mg/kg 185.1 8 available magnesium mg/kg 173.3 9 available calcium mg/kg 255.14 10 available iron mg/kg 110.32 11 Effective copper mg/kg 1.05 12 available zinc mg/kg 2.15

All indicators of greening soil prepared by dredging bottom mud meet the requirements of "Green Planting Soil" CJ/T340-2016. Compared with the traditional dredging and sediment fermentation process (soil infiltration is 60-80mm/h), the soil infiltration rate is significantly increased to 115.13mm/h.

Claims (7)

1. A conditioner for dehydration and synchronous fermentation of soil engineering bags at the bottom of river and lake dredging is characterized in that: the conditioner is granular and sequentially comprises an inner core, an outer shell and a coating from inside to outside, wherein:

the mass portion of the inner core is 1.5-2 portions, the inner core is formed by pressing coco coir, and the density of the pressed coco coir is 0.45-0.50g/cm ³ ；

The shell consists of 6-8 parts by mass of natural sand, 2-2.5 parts by mass of corn cob powder and 0.5-1 part by mass of composite microbial inoculum, wherein the fineness modulus of the natural sand is 2.5-3.0, and the mass part ratio of the inner core to the shell is 1 (5-6); the composite microbial inoculum consists of streptococcus thermophilus and actinomyces thermophilus, wherein the mass ratio of the streptococcus thermophilus to the actinomyces thermophilus is 1:1, a step of;

the coating consists of 0.6-0.8 part by weight of vinyl acetate-ethylene copolymer and 0.15-0.2 part by weight of polyvinyl alcohol.

2. The conditioner of claim 1, wherein: the diameter of the conditioning agent particles is 4-6 mm, and the density is 1.1-1.2 g/cm ³ 。

3. The conditioner of claim 1, wherein: the coconut husk is prepared from coconut husk fiber powder, the decomposition degree of the coconut husk fiber powder is medium, the ash content ratio is 6-8%, and the volume weight is 0.1-0.15 g/cm ³ EC value is 1.30-2.60mS/cm; after cleaning for 3-5 times by adopting clear water, controlling the EC value of the coco coir to be less than or equal to 0.5mS/cm, and then drying until the water content is less than or equal to 15%.

4. The conditioner of claim 1, wherein: the corn cob powder is obtained by grinding corn cobs from which seeds are removed and sieving the corn cobs with a 120-mesh sieve, and the water content is 3-5 wt%.

5. The conditioner of claim 1, wherein: the water content of the composite microbial inoculum is less than or equal to 8wt%, and the effective viable count is more than or equal to 20 hundred million CFU/g.

6. The conditioner of claim 1, wherein: the density of the conditioning agent particles is 1.1-1.2 g/cm ³ 。

7. A process for preparing the conditioning agent of any of claims 1 to 6 comprising the steps of:

s1, kernel manufacturing: delivering the coconut coir into a twin-roll shredding granulator, and pressing the coconut coir into balls under the pressure of 2.5-3Mpa for 5-10 min;

s2, manufacturing a shell: uniformly mixing sand, starch and a composite microbial inoculum according to the proportion of the raw materials to obtain a shell material; then the inner core and the outer shell materials are put into a shot blasting granulator according to the proportion for shell wrapping granulation, and the particle diameter is 4-6 mm;

s3, coating preparation: and (2) uniformly mixing the vinyl acetate-ethylene copolymer and the polyvinyl alcohol according to a proportion, adding the particles obtained in the step (S2), and placing the particles into a coating machine for coating, wherein the coating thickness is 15-20 mu m.

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