Method for planting vallisneria natans based on hydrophilic sludge ceramsite

Abstract

The invention belongs to the technical field of soil improvement, and relates to a hydrophilic sludge ceramsite-based vallisneria natans planting method, which comprises the following steps of: 1, preparing fermented sludge; 2, mixing the fermented sludge with an acid solution, aerating, and granulating to obtain spherical particles; 3, sintering the modifier to obtain modified sludge ceramsite; 4, adding a calcium chloride solution into the modified sludge ceramsite matrix to obtain a vallisneria natans matrix; 5, transplanting the eel grass plants into the eel grass substrate to obtain substrate-fixed eel grass plants; 6, directly putting the matrix-fixed vallisneria natans plants into the polluted water body to be treated; the core of the method lies in that sludge recycling and ecological restoration technologies are deeply fused, efficient fixation, long-acting fertilizer supply, pollution adsorption and low cost of eel grass planting are achieved through material modification and functional design, and compared with the prior art, the method has remarkable advantages in the fields of water body restoration and sludge recycling.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollution control and relates to a method for planting Vallisneria natans based on hydrophilic sludge ceramsite. Background Art

[0002] As a submerged plant, Vallisneria natans is widely used in water body ecological restoration. However, the traditional planting method has the following technical problems:

[0003] 1) In the prior art, the matrix has poor stability and lacks physical fixation ability, making it difficult to adapt to the dynamic water environment. Ordinary bottom mud or sand and gravel are used as the matrix, with a loose structure, and are easily washed away by water flow, resulting in root detachment and low plant survival rate.

[0004] 2) The prior art relies on natural nutrients in the bottom mud or artificial fertilization, which is prone to nutrient loss or local enrichment, resulting in slow growth of Vallisneria natans, unable to achieve slow-release fertilization, and affecting the long-term ecological restoration effect.

[0005] 3) The prior art lacks targeted pollutant adsorption function, restricting the application of Vallisneria natans in severely polluted water bodies. Ordinary matrices have limited adsorption capacity for pollutants such as heavy metals and organic matters, and may also release harmful substances (such as secondary pollution of bottom mud).

[0006] 4) The prior art relies on commercial matrices (such as vermiculite and perlite), which are costly and do not fully utilize waste resources (such as sludge), resulting in poor economy.

[0007] Therefore, providing a method for planting Vallisneria natans based on sludge ceramsite has become an urgent problem to be solved. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides a method for planting Vallisneria natans based on hydrophilic sludge ceramsite, which specifically includes the following steps:

[0009] Step 1: Crush plant straws and diatomite respectively, pass through a 70-80 mesh sieve, mix them evenly with the dewatered sludge from a sewage treatment plant, ferment at 25-35°C, humidity 60-70%, oxygenate for 10-15 minutes every 2-3 hours, with an oxygenation amount of 0.3-0.4 m 3 / h, and ferment for 2-3 days to obtain fermented sludge after fermentation is completed.

[0010] Preferably, the mass ratio of the dewatered sludge from the sewage treatment plant, plant straws, and diatomite is 20:1:1. Most preferably, the moisture content of the dewatered sludge is 55-60%.

[0011] Step 2: Mix the fermented sludge and acid solution at a mass ratio of 1:5, then aerate for 2 - 3 h with an air-water volume ratio of 3:1. After aeration, filter to remove the filtrate, and dry the filter residue at 100 - 120 °C until the water content ≤ 10%, then granulate to obtain spherical particles with a diameter of 6 - 8 mm.

[0012] Preferably, the acid solution is a citric acid solution with a mass fraction of 10 - 12% or a citric acid solution with a mass fraction of 8 - 10%.

[0013] Step 3: Sinter the spherical particles in three stages.

[0014] In the first stage, heat up to 600 - 650 °C at a rate of 10 °C / min, then keep the temperature for 1 - 1.5 h with an air flow rate of 3 - 4 m 3 / h;

[0015] In the second stage, heat up to 1000 - 1100 °C at a rate of 5 °C / min, then keep the temperature for 20 - 30 min with a nitrogen flow rate of 2 m 3 / h;

[0016] In the third stage, quench with water spray, cool down to 400 - 450 °C at a rate of 30 °C / s, then naturally cool to room temperature to obtain sludge ceramsite.

[0017] Step 4: Mix the sludge ceramsite and modifier at a mass ratio of 1:3, and perform ultrasonic treatment at 50 - 60 °C and 30 - 40 kHz for 20 - 30 min to obtain modified sludge ceramsite.

[0018] Preferably, the modifier is sodium alginate, potassium humate, and deionized water with a mass ratio of 10:1:100.

[0019] Step 5: Lay three layers of planting substrates in the planting container. Lay a 5 - 8 cm thick layer of modified sludge ceramsite at the bottom, lay a 3 - 5 cm thick mixture of modified sludge ceramsite, earthworm castings, and bentonite in the middle layer, and lay a 2 - 3 cm thick layer of diatomite on the surface. Then add calcium chloride solution with a solid-liquid mass ratio of 1:2, and let it stand for 0.5 - 1 h to obtain a substrate for Vallisneria natans.

[0020] Preferably, the mass ratio of the modified sludge ceramsite, earthworm castings, and bentonite is 10:3:2.

[0021] Preferably, the mass fraction of the calcium chloride solution is 5 - 8%.

[0022] Step 6: Immerse the roots of Vallisneria natans plants in the composite gel for 10 - 15 s, then transplant the Vallisneria natans plants into the substrate for Vallisneria natans with a planting density of 100 - 120 cm 2 / plant, with the root contact area with the substrate for Vallisneria natans > 90%. Then add sodium alginate solution and water retention agent, and let it stand for 1 - 1.5 h to obtain substrate-fixed Vallisneria natans plants.

[0023] Preferably, the mass ratio of the Vallisneria natans substrate, sodium alginate solution and water retaining agent is 20:10:3. Most preferably, the mass fraction of the sodium alginate solution is 1.5-2%. Most preferably, the water retaining agent is chitosan, gelatin and water, and the mass ratio is 1:1:50.

[0024] Preferably, the composite gel comprises sodium carboxymethylcellulose, sodium naphthylacetate and water, and the mass ratio is 1:0.01:100.

[0025] Step seven, directly put the substrate-fixed Vallisneria natans plants into the polluted water body to be treated.

[0026] Preferably, the putting density is 2.5-3m 2 / piece.

[0027] The present invention has the following advantages:

[0028] (1) The sludge ceramsite is sintered in three stages to form a porous spherical structure. Combining ultrasonic modification to enhance hydrophilicity, the three-layer substrate design (ceramsite bottom layer + mixed middle layer + diatomite surface layer) provides gradient support, improves the mechanical strength of the ceramsite, enhances the ability of the substrate to resist water flow scouring, and enhances the plant fixing effect.

[0029] (2) The mixed layer of earthworm manure (containing humic acid) and bentonite (high cation exchange capacity) provides continuous nutrient release. The calcium alginate generated by sodium alginate and calcium chloride will tightly bond the ceramsite particles, and the dissolved calcium alginate will not affect the original water ecosystem. Chitosan and gelatin form a three-dimensional network structure with the gel, significantly improving the water retention rate and significantly extending the nutrient slow release period.

[0030] (3) After the sludge ceramsite is activated by citric acid, the specific surface area is significantly increased, and the adsorption capacity for heavy metal ions is improved. In the polluted water body, the ceramsite can simultaneously realize the fixation of pollutants and the growth of Vallisneria natans, avoiding secondary pollution.

[0031] (4) Using dehydrated sludge as the main raw material, while reducing costs, realizing the harmless resource utilization of sludge. Both the composite gel and the water retaining agent are made of biodegradable materials, which are environmentally friendly. Specific embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] Example 1

[0034] Step 1: Crush corn straw and diatomite respectively, sieve them through a 75-mesh sieve, mix them evenly with the dewatered sludge from a sewage treatment plant with a water content of 58%, aerate for 10 minutes every 2 hours at 30°C and a humidity of 65%, with an aeration volume of 0.3 m 3 / h, and ferment for 3 days. After fermentation, the fermented sludge is obtained. The mass ratio of the dewatered sludge from the sewage treatment plant, corn straw, and diatomite is 20:1:1.

[0035] Step 2: Mix the fermented sludge with the acid solution at a mass ratio of 1:5, then aerate for 2.5 hours with a gas-water volume ratio of 3:1. After aeration, filter to remove the filtrate. Dry the filter residue at 120°C until the water content ≤ 10%, and then granulate to obtain spherical particles with a diameter of 6 - 8 mm. The acid solution is a 10% citric acid solution by mass fraction.

[0036] Step 3: Sinter the spherical particles in three stages.

[0037] The first stage: Heat up to 650°C at a rate of 10°C / min, then hold for 1.5 hours with an air flow rate of 3 m 3 / h;

[0038] The second stage: Heat up to 1050°C at a rate of 5°C / min, then hold for 20 minutes with a nitrogen flow rate of 2 m 3 / h;

[0039] The third stage: Quench by spraying water, cool down to 400°C at a rate of 30°C / s, and then naturally cool to room temperature to obtain sludge ceramsite.

[0040] Step 4: Mix the sludge ceramsite with the modifier at a mass ratio of 1:3, and perform ultrasonic treatment at 55°C and 40 kHz for 30 minutes to obtain modified sludge ceramsite. The modifier is sodium alginate, potassium humate, and deionized water, with a mass ratio of 10:1:100.

[0041] Step 5: Lay three layers of planting substrates in the planting container. Lay 8 cm thick modified sludge ceramsite at the bottom layer, lay a mixture of 5 cm thick modified sludge ceramsite, earthworm castings, and bentonite at the middle layer, and lay 3 cm thick diatomite at the surface layer. Then add a 6% calcium chloride solution by mass fraction with a solid-liquid mass ratio of 1:2. After standing for 45 minutes, obtain the Vallisneria natans substrate. The mass ratio of the modified sludge ceramsite, earthworm castings, and bentonite is 10:3:2.

[0042] Step 6: Immerse the roots of Vallisneria natans plants in the composite gel for 15 seconds, and then transplant the Vallisneria natans plants into the Vallisneria natans substrate with a planting density of 100 cm 2 / plant, the contact area between the root system and the Vallisneria natans substrate is > 90%. Then, a 2% sodium alginate solution and a water-retaining agent are added. After standing for 1 - 1.5 h, the substrate-fixed Vallisneria natans plants are obtained. The mass ratio of the Vallisneria natans substrate, the sodium alginate solution, and the water-retaining agent is 20:10:3. The water-retaining agent is chitosan, gelatin, and water, with a mass ratio of 1:1:50. The composite gel includes sodium carboxymethylcellulose, sodium naphthylacetate, and water, with a mass ratio of 1:0.01:100.

[0043] Step seven, directly put the substrate-fixed Vallisneria natans plants into the polluted water body to be treated, and the putting density is 3m 2 / piece.

[0044] Test example 1

[0045] Experimental group: Put the substrate-fixed Vallisneria natans plants into the circulating water tank according to the method of Example 1.

[0046] Control group: Directly plant Vallisneria natans plants in ordinary bottom mud, and then put them into the circulating water tank. The planting density, light, and water temperature conditions are the same as those in the experimental group.

[0047] Environmental parameters: water temperature, 25 ± 2 °C; pH, 7.0 - 7.5; dissolved oxygen, 5 - 6 mg / L.

[0048] The water in the circulating water tank is simulated polluted water: containing 200 mg / L of COD, 15 mg / L of NH3-N, Pb 2+ 5 mg / L and Cd 2+ 2 mg / L.

[0049] 1. Anti-water flow scouring experiment

[0050] Equipment setting: Adjust the flow rate of the circulating water tank to 0.5 m / s to simulate a dynamic water environment.

[0051] Experimental process: Continuously scour for 24 hours, and record the number of plants toppling and root system detachment.

[0052] Calculate the loss rate: Loss rate (%) = (number of detached plants / total number of plants) × 100%.

[0053] 2. Observation of plant stability

[0054] Measurement of inclination angle*: Use a protractor to measure the proportion of plants with an inclination angle > 15°.

[0055] 3. Survival rate statistics

[0056] Standard: Determine survival when the leaves remain green, the root system is not rotten, and the new root growth > 1 cm.

[0057] Recording frequency: Count the number of surviving plants every 10 days.

[0058] 4. Water quality detection

[0059] Sampling method: Take 500 mL of water sample from the middle of the water tank every 15 days and filter it through a 0.45 μm filter membrane.

[0060] Detection items:

[0061] COD: Potassium dichromate method (HJ 828-2017).

[0062] NH3-N: Nessler reagent spectrophotometry (HJ 535-2009).

[0063] Heavy metals: Determination of Pb 2+ 、Cd 2+ concentration by atomic absorption spectrometry.

[0064] 5. Adsorption efficiency calculation

[0065] Formula: Adsorption rate (%) = (Initial concentration - Residual concentration) / Initial concentration × 100%.

[0066] Table 1

[0067] Experimental group Control group Root contact area (%) 95±2.5 60±10 Anti-scouring loss rate (%) 3±1 45±8 Plant inclination rate (%) 1±0.5 18±5 New root growth length (cm) 5.2±0.8 1.5±0.6 Survival rate (%) 92±3 68±7 COD removal rate (%) 85±5 50±10 <![CDATA[NH3-N removal rate (%)]]> 78±4 42±8 <![CDATA[Pb 2+ Removal rate (%)]]> 93±4 25±12 <![CDATA[Cd 2+ Removal rate (%)]]> 87±5 35±10

[0068] As can be seen from Table 1, the plant fixation effect of the experimental group is significantly better than that of the control group. The pollution treatment efficiency of COD, NH3-N, Pb 2+ and Cd 2+ removal rates and the survival rate of Vallisneria natans in the experimental group are all significantly higher than those in the control group. Therefore, the method for planting Vallisneria natans of the present invention is significantly better than the prior art.

[0069] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for planting Vallisneria based on hydrophilic sludge ceramsite, characterized in that: The following steps are involved: Step 1: crushing plant straw and diatomaceous earth respectively, mixing with dewatered sludge for fermentation, and obtaining fermented sludge after fermentation is completed; Step 2, mixing the fermented sludge with the acid solution, aerating, filtering, removing the filtrate, drying the filter residue to a moisture content of ≤10%, and then granulating to obtain spherical particles; Step 3, sintering the spherical particles, and then mixing and soaking them with a modifier to obtain modified sludge ceramsite; Step 4: laying three layers of planting substrate in a planting container, with modified sludge ceramsite on the bottom layer, a mixture of modified sludge ceramsite, vermicompost and bentonite on the middle layer, and diatomaceous earth on the surface layer, and then adding calcium chloride solution and letting it stand to obtain Vallisneria substrate; Step 5: Immerse the roots of the Vallisneria plant in the composite gel, and then transplant the Vallisneria plant into the Vallisneria substrate with a planting density of 100-120cm 2 / plant, the root system and the Vallisneria substrate contact area> 90%, then add sodium alginate solution and water retaining agent, after standing, the substrate fixed Vallisneria plants; Step six, placing the substrate-fixed Vallisneria plants directly into the polluted water body to be treated.

2. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The mass ratio of the dewatered sludge, plant straw and diatomaceous earth in step 1 is 20:1:

1.

3. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The acid solution in step 2 is a citric acid solution with a mass fraction of 10-12% or a citric acid solution with a mass fraction of 8-10%.

4. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: In step 3, the spherical particles are sintered in three stages. In the first stage, the temperature is raised to 600-650℃ at 10℃ / min, and then kept at this temperature for 1-1.5h, with an air flow rate of 3-4m 3 / h; In the second stage, the temperature was raised to 1000-1100℃ at 5℃ / min, and then kept at this temperature for 20-30min, with a nitrogen flow rate of 2m 3 / h; In the third stage, the temperature is lowered to 400-450°C at 30°C / s, and then naturally cooled to room temperature to obtain sludge ceramsite.

5. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The modifiers described in step three are sodium alginate, potassium humate and deionized water, with a mass ratio of 10:1:

100.

6. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The mass ratio of the modified sludge ceramsite, earthworm castings and bentonite described in step 4 is 10:3:

2.

7. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The mass fraction of the calcium chloride solution in step 4 is 5-8%.

8. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The mass ratio of the Vallisneria substrate, the sodium alginate solution and the water retaining agent in step 5 is 20:10:

3.

9. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The water-retaining agent described in step five is chitosan, gelatin and water, and the mass ratio is 1:1:

50.

10. The method for planting Vallisneria based on hydrophilic sludge ceramsite according to claim 1, characterized in that: The composite gel in step five includes sodium carboxymethyl cellulose, sodium naphthylacetate and water in a mass ratio of 1:0.01:100.