CN116002938A - Conditioning agent for dehydration and synchronous fermentation of river and lake dredging bottom soil working pipe bags 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 synchronous fermentation of river and lake dredging bottom soil working pipe bags and preparation method thereof

Technical Field

The invention relates to the technical field of treatment and disposal of river and lake bottom mud, in particular to a conditioner for dehydration and synchronous fermentation of a river and lake dredging bottom mud work pipe bag and a preparation method thereof.

Background

Ecological dredging is an important means for removing endogenous pollution of river and lake, but dredging inevitably generates a large amount of sediment with high water content. The common treatment method is to safely landfill the sediment after dehydrating and reducing the volume, but the treatment method not only occupies limited storage capacity of a landfill, but also causes waste of sediment resources, and most of river and lake sediment is rich in organic matters and nitrogen and phosphorus nutrient salts, and can be used as greening planting soil after fermentation treatment, so that resource utilization is realized.

At present, there is a related study on preparing greening soil from river and lake sediment, mainly simply connecting a sediment dehydration process and a sediment fermentation greening technology process in series, namely, firstly dehydrating the sediment to a design water content requirement, then transporting to a designated place for fermentation treatment, as disclosed in Chinese patent publication No. CN113142014A, a basic river mud-based garden green plant soil and a preparation method thereof are disclosed, and materials such as furfural residue, straw powder, chitosan and the like are mixed with the sediment after plate-frame filter pressing dehydration, and composting fermentation is carried out. Chinese patent publication No. CN110604031A discloses a method for producing soilless culture substrate for garden plants by using riverway sediment compost, which comprises the steps of adding garden solid waste, mushroom residue, chinese medicine residue and other materials into dewatered sediment, carrying out aerobic fermentation by strip pile type or forced ventilation type compost, and finally adding perlite, vermiculite and other auxiliary materials to obtain the soilless culture substrate. The two methods are both aimed at the fermentation of the dehydrated sediment, and do not consider the mutual reinforcement benefits of the sediment dehydration and synchronous fermentation treatment, so that the problems of long construction period, high cost and difficult large-scale application exist.

The inventor finds that if the geotechnical pipe bag dehydration technology is adopted, the fermentation material is directly filled into the geotechnical pipe bag, and two links of dehydration and fermentation of the bottom mud can be synchronously processed, wherein the fermentation material can promote the reduction of the water content of the bottom mud, the geotechnical pipe bag for dehydration of the bottom mud can provide a bottom mud fermentation place, the whole technology can greatly shorten the construction period, and the cost for preparing greening soil from the bottom mud is reduced. The key to realize the synchronous treatment process is to find a fermentation material which can adapt to the dehydration of the sediment, and no related research exists at home and abroad at present.

Disclosure of Invention

In order to realize the bottom mud dehydration and synchronous fermentation technology, the invention aims to provide a conditioner for river and lake dredging bottom mud work pipe bag dehydration and synchronous fermentation, which is simple in process, environment-friendly and cost-saving.

It is another object of the present invention to provide a process for preparing the conditioning agent described above.

Therefore, the invention provides the following technical scheme:

the conditioner for dehydration and synchronous fermentation of soil engineering bags at the bottom of river and lake dredging 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 volume ratio of the shell to the inner core is about 0.65:0.35); 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.

Preferably, the conditioning agent particles have a diameter of 4 to 6mm and a density of 1.1 to 1.2g/cm ³ 。

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 (salt content) of 1.30-2.60mS/cm; and cleaning the coconut husk fiber powder with clear water for 3-5 times, controlling the EC value of the coconut husk to be less than or equal to 0.5mS/cm, and then drying until the water content is less than or equal to 15%.

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%.

Preferably, the water content of the composite microbial inoculum is less than or equal to 8wt percent, and the effective viable count is more than or equal to 20 hundred million CFU/g.

Preferably, the conditioner particles have a density of from 1.1 to 1.2g/cm ³ Thus, the density of the dredging slurry is closest to that of the dredging slurry, the conditioner can be uniformly distributed in the slurry, and the uniformity and the sufficiency of the later fermentation process are ensured.

The preparation method of the conditioner comprises the following steps:

s1, kernel manufacturing: delivering the coconut coir into a twin-roll shredding granulator, and pressing into balls under the pressure of 2.5-3Mpa for 5-10 min. The twin-roll shredding granulator can reduce the volume of coconut coir to 1/4-1/3 of the original volume, and the diameter of a roll die can be adjusted within the adjustment range of 2 mm-20 cm.

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.

The conditioner can be used for dredging river and lake sediment (water content of about 95% and density of 1.12 g/cm) ³ ) Preparing greening soil by geotechnical pipe bag dehydration and synchronous fermentation, wherein the water content of river and lake dredging substrate sludge is about 95%, and the density is 1.08g/cm ³ ) Dredging river and lake in each sideThe dosage of the conditioner for dredging the sediment is 1-1.6 kg. When in use, the flocculant and the conditioner are added into the river and lake dredging sediment in sequence.

According to the requirements of sediment dehydration and greening soil preparation, the conditioner is divided into three layers, and each layer plays different roles, and the conditioner is specifically as follows:

the inner core selects compressed compact coconut husk body, on one hand, the coconut husk body can expand sharply when meeting water, absorbs water with the volume of 5-10 times, can condition the sediment water content from 85% to within 70%, meets the subsequent sediment fermentation water content condition, and meanwhile, due to the expansion effect of the coconut husk, the air permeability of the sediment in the geotechnical pipe bag can be increased, and the subsequent sediment fermentation ventilation condition is improved. On the other hand, the C/N ratio of the coconut coir is about 120, so that the problem of insufficient carbon source of the bottom sludge in the fermentation process can be solved.

The shell consists of sand, starch and a composite microbial inoculum, wherein the sand can be used for improving the index of the infiltration rate of the greening soil prepared from the sediment, and the reason is that the dredging sediment is mainly composed of silt clay, the natural infiltration rate is low, and the grain size distribution of the soil body after the sand is introduced is more similar to that of natural planting soil. The starch in the outer shell layer plays a role of an adhesive on one hand, and the outer shell material is wrapped on the inner core, and on the other hand, the starch can provide nutrients for the composite microbial inoculum. The composite microbial inoculum of the outer shell layer is used for fermenting mud in a geotechnical pipe bag.

The polyvinyl alcohol is modified by adopting the vinyl acetate-ethylene copolymer, so that the water resistance of the film is effectively improved, the permeability is about 0.66%, and the main function is to control the water in the bottom mud to slowly enter the inner core layer, so that the inner core is ensured to absorb water and expand after about 2-3 days, and the conditioner is cracked.

Compared with the existing conditioner, the invention has the following beneficial effects:

1. the conditioner fully utilizes the strong water absorbability and high carbon nitrogen ratio of the coconut husk material, and realizes the functions of dewatering and synchronous fermentation of dredging substrate sludge. The conditioner and the mud are synchronously filled into the geotechnical pipe bags, so that the dehydration period of the bottom mud is obviously shortened, and meanwhile, the bottom mud fermentation is completed in the geotechnical pipe bags, and additional fermentation equipment is not needed. The total construction period of the tandem construction process for preparing greening soil by dehydrating and fermenting the conventional geotechnical tube bags is at least 3-4 months, and the conditioner can shorten the total construction period to within 2 months.

2. The conditioner fully utilizes the bag volume released by tail water discharge after the filling of the geotechnical pipe bags, takes the inner space released by the geotechnical pipe bags as a substrate sludge fermentation place, and compared with the traditional substrate sludge fermentation preparation greening soil engineering, the conditioner does not need civil engineering and factory building part investment, obviously reduces the engineering cost of comprehensive treatment of the substrate sludge, and enhances the market viability and the competitiveness of the substrate sludge preparation greening soil technology.

3. On one hand, the sand in the conditioner can promote the survival of strains, and the quality guarantee period is more than 1 year under the conditions of drying and normal temperature, on the other hand, the physical structure of greening soil prepared by the sediment is improved, the permeability is increased, and the quality of the greening soil can be further improved.

4. The conditioner can be applied to geotechnical pipe bag dehydration engineering, and can be filled into the geotechnical pipe bag synchronously with mud, so that the dehydration period of the bottom mud can be shortened obviously, and meanwhile, the bottom mud fermentation is completed in the geotechnical pipe bag without additional fermentation equipment.

Drawings

Fig. 1 is a schematic structural diagram of a conditioner of the present invention.

Detailed Description

The following specific examples further illustrate the conditioning agents of the present invention and are not meant to limit the scope of the invention to the examples set forth.

Example 1

Depending on a dredging project of a river in Harbin city of Heilongjiang province, carrying out dehydration and synchronous fermentation test work of a bottom soil work pipe bag, wherein the water content of bottom mud before dehydration is 95%, and the carbon-nitrogen ratio (C/N) in the bottom mud is 2.5:1, the effective utilization bag capacity of the geotechnical pipe bag for test is 60m ³ 60m of filling slurry ³ 240kg of conditioner is added in a cumulative way in the filling process. The total period of dehydration and fermentation of the sediment is 45 days.

The conditioner for dehydration and synchronous fermentation of the substrate sludge of this example was prepared by the following method:

(1) and (3) kernel manufacturing: firstly, washing coconut coir with clear water for 5 times, controlling the EC value not to exceed 0.5mS/cm, and then dryingThe coconut coir after drying is sent into a twin-roll shredding granulator until the water content is 15 percent, pressed into spheres with the diameter of 2 to 4mm under the pressure of 2.5Mpa for 8 minutes, and the density of the compressed coconut coir is about 0.45g/cm ³ ；

(2) And (3) manufacturing a shell: uniformly mixing 6 parts of sand, 2 parts of starch and 0.5 part of composite microbial inoculum according to the proportion, and then placing 1 part of core material and 6 parts of shell material into a shot blasting granulator for shell-wrapping granulation, wherein the particle diameter is 4-6 mm;

(3) and (3) coating preparation: vinyl acetate-ethylene copolymer and polyvinyl alcohol are prepared according to the mass parts of 0.6: mixing uniformly in a proportion of 0.15, adding the granules obtained in the step (2), and placing the granules into a coating machine for coating, wherein the thickness of the coating is 20 mu m.

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

The action mechanism of the conditioner of the invention is as follows:

the conditioner is mainly used in geotechnical pipe bag dehydration engineering and mainly plays a role in two stages.

The first stage: and a sediment dehydration stage. The flocculant and the conditioner enter the geotechnical pipe bag along with dredging mud, the flocculant plays a role in 2-3 after the geotechnical pipe bag is filled, the bottom mud is dehydrated by means of the self water filtering effect of the geotechnical pipe bag, the water content of the bottom mud can be reduced to about 85%, and the surface of the geotechnical pipe bag body is not obviously drained. After entering the geotechnical pipe bag for 3-5 days, the coating on the surface of the conditioner is gradually melted, the coconut husk kernel starts to contact with water and absorb water to expand, and the conditioner is rapidly disintegrated. The coconut husk after water absorption can be expanded to 5-10 times of the original volume, each kilogram of conditioner can absorb about 20L of water theoretically, and the water content of the sediment is reduced to be within 70 percent.

And a second stage: and (3) a bottom mud fermentation stage. The coconut husk absorbs water and establishes a supporting framework in soil, so that the air permeability of dredging sediment can be effectively improved, and an environment is created for aerobic fermentation of the composite microbial inoculum. Because the density of the conditioner is close to that of the dredging mud, the conditioner in the geotechnical pipe bag is uniformly dispersed in the bottom mud, and the uniformity of fermentation can be ensured. After 30-45 days, the dredging substrate sludge can be fermented into greening planting soil, and finally the bag is broken and screened.

After the mud filling of the geotechnical pipe bags is finished, periodically collecting columnar soil samples from cuffs of the geotechnical pipe bags, and detecting the water content of the bottom mud and the state of the conditioner, wherein the sampling frequency is 1 day, 2 days, 3 days, 5 days, 15 days, 30 days and 45 days, and the results are shown in table 1. Compared with the traditional geotechnical pipe bag dehydration technology, the sediment dehydration efficiency is remarkably improved (3-6 months are needed for the traditional geotechnical pipe bag dehydration to the water content of 60%), and the sediment water content meets the requirements of external transportation and loading at 30 days.

TABLE 1 detection results

Sampling time (Tian)	Sediment moisture content (%)	Conditioning agent status
			1	90.2	Not disintegrated
2	88.5	Not disintegrated
			3	85.1	Not disintegrated
5	72.3	Completely disintegrate
			15	61.5	Completely disintegrate
30	50.5	Completely disintegrate
			45	45.6	Completely disintegrate

After 45 days, the geotechnical tube bags were broken, the products were crushed and sampled for greening soil index detection as shown in table 2. All indexes of the greening soil prepared by adopting the dredging sediment meet the requirements of CJ/T340-2016 in greening planting soil. Compared with the traditional dredging sediment fermentation process (the soil infiltration rate is 60-80 mm/h), the soil infiltration rate is obviously improved and is 152.44mm/h.

TABLE 2 detection results

Sequence number	Detection index	Unit (B)	Treated greening soil
				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	Hydrolytic nitrogen	mg/kg	145
6	Available phosphorus	mg/kg	9.5
				7	Quick-acting potassium	mg/kg	201.3
8	Effective magnesium	mg/kg	163.1
				9	Effective calcium	mg/kg	301.32
10	Effective iron	mg/kg	121.12
				11	Copper availability	mg/kg	1.24
12	Effective zinc	mg/kg	2.49

Example 2

Depending on a dredging project of a white lake test point in a xiaoan new area, carrying out dehydration and synchronous fermentation test work of a bottom soil work tube bag, wherein the water content of bottom mud before dehydration is 90%, and the average C/N ratio of the bottom mud is 3.5:1, the effective utilization bag capacity of the geotechnical pipe bag for test is 90m ³ Filling mud 90m ³ 450kg of conditioner is added according to the accumulation in the filling process. The total period of dehydration and fermentation of the sediment is 42 days.

The conditioner for dehydration and synchronous fermentation of the substrate sludge of this example was prepared by the following method:

(1) and (3) kernel manufacturing: firstly, washing coco coir with clear water for 5 times, controlling the EC value not to exceed 0.5mS/cm, then drying until the water content is 15%, feeding the dried coco coir into a twin-roll shredding granulator, pressing the coco coir into spheres with the diameter of 2-4 mm under the pressure of 2.6Mpa for 10min, and the density of the coco coir after compression is about 0.48g/cm ³ ；

(2) And (3) manufacturing a shell: uniformly mixing sand, starch and a composite microbial inoculum according to the proportion of 7 parts, 2.5 parts and 0.9 part, and then placing 1 part of inner core material and 6 parts of outer shell material into a shot blasting granulator for coating granulation, wherein the particle diameter is 4-6 mm;

(3) and (3) coating preparation: vinyl acetate-ethylene copolymer and polyvinyl alcohol are prepared according to the mass parts of 0.6: mixing uniformly in a proportion of 0.15, adding the granules obtained in the step (2), and placing the granules into a coating machine for coating, wherein the thickness of the coating is 20 mu m.

After the mud filling of the geotechnical pipe bags is finished, periodically collecting columnar soil samples from cuffs of the geotechnical pipe bags, and detecting the water content of the bottom mud and the state of the conditioner, wherein the sampling frequency is 1 day, 2 days, 3 days, 5 days, 15 days, 30 days and 45 days, and the results are shown in Table 3.

TABLE 3 detection results

Sampling time (Tian)	Sediment moisture content (%)	Conditioning agent status
			1	89.2	Not disintegrated
2	87.5	Not disintegrated
			3	84.6	Not disintegrated
5	68.4	Completely disintegrate
			15	59.1	Completely disintegrate
30	53.5	Completely disintegrate
			42	41.6	Completely disintegrate

Compared with the traditional geotechnical pipe bag dehydration technology, the sediment dehydration efficiency is remarkably improved (3-6 months are needed for the traditional geotechnical pipe bag dehydration to the water content of 60%), and the sediment water content is 30 days so as to meet the requirements of external transportation and loading.

After 42 days, the geotechnical tube bags were broken, the products were crushed and sampled for greening soil index detection as shown in table 4.

TABLE 4 detection results

Sequence number	Detection index	Unit (B)	Treated greening soil
				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	Hydrolytic nitrogen	mg/kg	121
6	Available phosphorus	mg/kg	7.7
				7	Quick-acting potassium	mg/kg	185.1
8	Effective magnesium	mg/kg	173.3
				9	Effective calcium	mg/kg	255.14
10	Effective iron	mg/kg	110.32
				11	Copper availability	mg/kg	1.05
12	Effective zinc	mg/kg	2.15

All indexes of the greening soil prepared by adopting the dredging sediment meet the requirements of CJ/T340-2016 in greening planting soil. Compared with the traditional dredging sediment fermentation process (the soil infiltration rate is 60-80 mm/h), the soil infiltration rate is obviously improved and is 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.

Images