Aluminum-free cyanobacteria rapid sedimentation and recycling process based on natural polymer composite modified clay

Abstract

The invention discloses an aluminum-free cyanobacteria rapid sedimentation and recycling process, which comprises the following steps: mixing clay loaded with bacillus subtilis and cationic starch according to a weight ratio of 10: (1-5), dissolving with deionized water, and stirring at 60-80 DEG C for reaction to form modified clay particles with the charge density of more than or equal to 20mC / g; mixing the modified clay particles with chitosan according to a weight ratio of 7: (1-5), adding 0.1 wt% of a nonionic polyacrylamide solution, stirring to prepare a turbid liquid in which the total mass concentration of the modified clay particles and the chitosan is 5-10%, and adjusting the pH value to 6.5-7.5 to obtain a composite flocculant; 2-3 kg of the composite flocculant is splashed to the cyanobacteria water body per mu, and cyanobacteria floc sedimentation is achieved within 5-15 min; and long-acting prevention and control and recycling: decomposing algae remains by using bacillus subtilis loaded in the modified clay particles, collecting floc, and dehydrating to prepare the organic fertilizer.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection, and in particular to a method for rapid settling of blue-green algae using natural high molecular material modified clay and bioflocculants, which is especially suitable for emergency treatment and resource utilization of blue-green algae in eutrophic water bodies. BACKGROUND

[0002] Cyanobacterial blooms are an important environmental problem faced by global freshwater ecosystems. In traditional treatment methods, chemical flocculants such as polyaluminum chloride (PAC) are widely used due to their fast-acting nature, but they have significant drawbacks: 1. Aluminum residue risk: Aluminum ions can harm human health through the food chain and cause damage to aquatic organisms, which does not meet the aluminum ion limit requirements in the "Surface Water Environmental Quality Standard" (GB3838-2002).

[0003] 2. Secondary pollution: Traditional flocculants can easily cause algae cells to rupture and release toxins, and the settled flocs need to be treated.

[0004] 3. Process limitations: Existing patents use chitosan modified clay, but do not address issues such as low carbon source utilization rate, insufficient flocculation strength, and lack of microbial synergistic control mechanism.

[0005] The deficiencies of the prior art are: 1. Urgent need for aluminum-free treatment: There is an urgent need for aluminum-free flocculation technology in sensitive scenarios such as drinking water sources, aquaculture, and landscape water bodies.

[0006] 2. Lack of long-term prevention and control: Traditional processes only focus on emergency settling and do not consider blue-green algae recovery inhibition and resource recycling.

[0007] After searching, the following prior art is found: The patent specification with publication number CN113287626A discloses an algal removal agent based on activated monopersulfate composite modified attapulgite and its application. The algal removal agent is prepared by the following steps: 1) Take attapulgite, immerse it in a 0.5-1.5 mol / L hydrochloric acid solution at 60-75°C for 12-18 h, wash, filter, and dry, then place it in a muffle furnace and calcine it at 300-800°C for 30-120 min, cool it, and grind it to pass through a sieve; 2) Mix chitosan solution and PMS solution in a ratio to form a mixed solution; 3) Add the attapulgite obtained in step 1) to the mixed solution prepared in step 2), and stir for 30-60 min to make the attapulgite uniformly dispersed in the mixed solution; 4) Ultrasonically treat the mixed solution, then stir, centrifuge, dry, cool, and grind. The algal removal agent has fast-acting and long-lasting effects, and can both rapidly settle and effectively control algae.

[0008] The patent specification with publication number CN112520860A discloses an ecological remediation agent of natural adsorption material loaded with microorganisms, which comprises the following components by weight: chitosan-Zr-clay material composite 10-40 parts; microbial liquid 200-400 parts; wherein the clay material in the chitosan-Zr-clay material composite is composed of clay minerals and modified humic acid, green tea; the total number of viable bacteria in the microbial liquid is ≥5.0×10 9 The patent technology loads the microbial bacteria on the chitosan-Zr-clay material composite, so that the obtained ecological remediation agent has good anion and cation adsorption performance and ion exchange capacity, and will not quickly sink to the bottom of the water, which has the effect of "weighting agent" of clay and has enough time to coagulate with pollutants in the water body to strengthen the water purification effect of the microbial community.

[0009] The patent specification with publication number CN101508505A discloses a method for removing blue-green algae in water and eliminating its odor. The method can not only remove blue-green algae existing in lakes, rivers or other water bodies, but also make the water body with blue-green algae not smell. The blue-green algae is flocculated by a flocculating agent, and the flocculated blue-green algae is decomposed and odor is eliminated by an algae-removing and odor-eliminating agent. The water quality is purified by spraying microbial water preparation, planting elodea or water hyacinth, and planting snail and shellfish, so that the blue-green algae is sequentially flocculated, decomposed and deodorized, and the blue-green algae contaminated water area is purified by biological purification technology. The method has the advantages of: being able to remove blue-green algae before the blue-green algae outbreak, eliminating the odor of blue-green algae, improving the ecological and environmental quality of the water area, being non-toxic and harmless to aquatic animals and humans, and being low in use cost. SUMMARY

[0010] The present application provides an aluminum-free and high-efficiency blue-green algae treatment process, which realizes the synergistic effect of rapid sedimentation, low greenhouse gas emission and resource recovery, and solves the problems of aluminum pollution and long-term effectiveness in the prior art.

[0011] The specific technical solutions are as follows: An aluminum-free blue-green algae rapid sedimentation and resource utilization process comprises: Preparation of cationic starch modified clay: clay loaded with bacillus subtilis and cationic starch are mixed in a weight ratio of 10:1-5 (for example, 10:2, 10:3, 10:4, etc.), dissolved in deionized water, and stirred and reacted at 60-80°C to form modified clay particles (i.e., cationic starch modified clay) with a charge density ≥20 mC / g (for example, 25 mC / g, 27 mC / g, etc.); Preparation of composite flocculant: mix modified clay particles and chitosan at a weight ratio of 7:(1-5) (for example 7:1.05, 7:2, 7:3, 7:4, etc.), add 0.1wt% non-ionic polyacrylamide (NPAM) solution, stir to prepare a suspension with a total mass concentration of 5%-10% (for example 6%, 7%, 8%, 9%, etc.) of modified clay particles and chitosan, adjust the pH to 6.5-7.5, and obtain a composite flocculant; Targeted addition and sedimentation: spray the composite flocculant into the cyanobacterial water at a dose of 2-3 kg / acre, and achieve cyanobacterial floc sedimentation within 5-15 minutes; Long-term prevention and resource utilization: use Bacillus subtilis loaded in the modified clay particles to decompose algal residues, collect the flocs and dehydrate to prepare organic fertilizer.

[0012] The aluminum-free cyanobacterial rapid sedimentation and resource utilization process has the following advantages: the cationic starch modified clay has a positive charge and is the core of electrostatic neutralization, can neutralize the negative charge on the surface of cyanobacteria through electrostatic neutralization, provides support for the sedimentation density, cooperates with the high molecular chains of chitosan and NPAM to agglomerate cyanobacterial particles and enhance the floc strength, accelerates the sedimentation rate, and cooperatively generates bridging and netting effects, and the purpose of adjusting the pH to 6.5-7.5 is to enhance the charge matching.

[0013] In some preferred examples, the aluminum-free cyanobacterial rapid sedimentation and resource utilization process, the clay used in the preparation of the cationic starch modified clay is bentonite and / or attapulgite, which has a high specific surface area and adsorption performance.

[0014] The aluminum-free cyanobacterial rapid sedimentation and resource utilization process, the clay loaded with Bacillus subtilis in the preparation of the cationic starch modified clay can be prepared according to the prior art, and the inoculation method of Bacillus subtilis can use conventional technical means in the art, such as adsorption and membrane hanging.

[0015] In some preferred examples, the aluminum-free cyanobacterial rapid sedimentation and resource utilization process, the number of Bacillus subtilis loaded on the clay used in the preparation of the cationic starch modified clay is ≥10 8 CFU / g.

[0016] The aluminum-free cyanobacterial rapid sedimentation and resource utilization process, the cationic starch used in the preparation of the cationic starch modified clay is in the prior art, and the positive charge group can be introduced through etherification grafting reaction, for example, it can be referred to the patent specification with the publication number CN113583184A, etc., and it can also be obtained through commercial channels.

[0017] In some preferred examples, the aluminum-free cyanobacterial rapid sedimentation and resource utilization process, the mass of the deionized water used in the preparation of the cationic starch modified clay is 5-10 times the total mass of the clay and the cationic starch, for example, 6 times, 7 times, 8 times, 9 times, etc.

[0018] In some preferred examples, in the preparation of the cationic starch modified clay in the aluminum-free cyanobacteria rapid sedimentation and resource utilization process, the stirring reaction time is 2-4 hours.

[0019] In some preferred examples, in the preparation of the composite flocculant in the aluminum-free cyanobacteria rapid sedimentation and resource utilization process, the molecular weight of the chitosan is 5-100,000 Da, and the degree of deacetylation is ≥85%.

[0020] In some preferred examples, in the preparation of the composite flocculant in the aluminum-free cyanobacteria rapid sedimentation and resource utilization process, the stirring speed is 200-300 rpm, and the time is 5-10 min.

[0021] In some preferred examples, in the preparation of the composite flocculant in the aluminum-free cyanobacteria rapid sedimentation and resource utilization process, the pH is adjusted to 6.5-7.5 with citric acid.

[0022] In some preferred examples, in the targeted dosing and sedimentation in the aluminum-free cyanobacteria rapid sedimentation and resource utilization process, the composite flocculant is uniformly sprayed to the cyanobacteria aggregation area of the cyanobacteria water body through a spraying system of a drone, a shipborne or a cooperative group of both.

[0023] The aluminum-free cyanobacteria rapid sedimentation and resource utilization process can be used in real lakes and river water bodies, at which time the flocs can not be collected, but allowed to settle, the water transparency is improved, and the light can reach the conditions for subsequent ecological restoration engineering (such as planting submerged plants).

[0024] In some embodiments, in the long-acting prevention and control and resource utilization in the aluminum-free cyanobacteria rapid sedimentation and resource utilization process, the flocs are collected by a siphon pump.

[0025] The aluminum-free cyanobacteria rapid sedimentation and resource utilization process of the present application can be used for emergency treatment, and the preparation of the composite flocculant requires a short time, can be prepared synchronously, and the cyanobacteria flocs settle to the bottom within 5-15 minutes after targeted dosing, and the algae removal rate is ≥90%.

[0026] The aluminum-free cyanobacteria rapid sedimentation and resource utilization process of the present application also has the characteristics of long-acting inhibition, and the Bacillus subtilis (inoculation amount preferably ≥10 8 CFU / g) loaded in the modified clay particles decomposes the algal debris, and the algal cell mortality rate is ≥95% within 72 hours, and the recovery is inhibited.

[0027] Compared with the prior art, the present application has the following beneficial effects: 1. Aluminum-free and environmentally friendly: aluminum ion residue <0.1 mg / L, far lower than the national standard limit, suitable for sensitive scenes such as drinking water sources.

[0028] 2. High efficiency, fast algae removal speed: flocculation is completed within 5-15 minutes, which is more than 50% higher than traditional aluminum salt process.

[0029] 3. Ecological synergy: biodegradable materials reduce carbon emissions, and bacillus subtilis inhibits the recurrence of cyanobacteria. DETAILED DESCRIPTION

[0030] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application.

[0031] The operation method in the following examples without specific conditions is usually according to the conventional conditions or according to the conditions suggested by the manufacturer.

[0032] Example 1: Small-scale test verification (laboratory simulation).

[0033] Water sample conditions: Fresh water containing microcystis (chlorophyll a = 100 μg / L, pH = 7.2, turbidity = 50 NTU), volume 10 L.

[0034] Preparation of cationic starch modified clay: bentonite with bacillus subtilis inoculation amount ≥10 8 CFU / g is mixed with cationic starch at a weight ratio of 10:2, dissolved with deionized water, stirred and reacted at 60-80°C for 2 hours to form modified clay particles with a charge density of 25 mC / g. Among them, the mass of deionized water used is 6 times the total mass of bentonite and cationic starch used.

[0035] Preparation of composite flocculant: modified clay particles and chitosan (molecular weight 5-10 million Da, degree of deacetylation ≥85%) are mixed at a weight ratio of 7:1.05, 0.1wt% non-ionic polyacrylamide solution is added, and 200~300 rpm stirring for 5 minutes to prepare a suspension with a total mass concentration of 6% of modified clay particles and chitosan. Adjust the pH to 6.5~7.5 with citric acid to obtain a composite flocculant.

[0036] 10 mL of the composite flocculant is added to 10 L of water sample, and after 5 minutes, the detection shows: chlorophyll a = 8.2 μg / L, turbidity = 3.8 NTU, aluminum ions are not detected, and the survival rate of bacillus subtilis is 92%.

[0037] Example 2: Pilot application (a city landscape lake).

[0038] Water body profile: area 50 mu, cyanobacteria coverage 60%.

[0039] Preparation of cationic starch modified clay: bentonite with bacillus subtilis inoculation amount ≥10 8The attapulgite and cationic starch are mixed in a weight ratio of 10:4, dissolved in deionized water, stirred and reacted at 60-80°C for 4 hours to form modified clay particles with a charge density of 27 mC / g. The mass of deionized water used is 10 times the total mass of attapulgite and cationic starch used.

[0040] The composite flocculant is prepared by mixing the modified clay particles and chitosan (molecular weight 50-100 thousand Da, degree of deacetylation ≥85%) in a weight ratio of 7:3, adding 0.1wt% non-ionic polyacrylamide solution, stirring at 200-300 rpm for 10 minutes to prepare a suspension with a total mass concentration of 10% of the modified clay particles and chitosan, and adjusting the pH to 6.5-7.5 with citric acid to obtain the composite flocculant.

[0041] Targeted addition and sedimentation: The composite flocculant is uniformly sprayed onto the cyanobacterial aggregation area of the cyanobacterial water body by a drone and / or shipborne spraying system at a dose of 2.5 kg / acre, and the cyanobacterial flocs are settled within 15 minutes.

[0042] Long-term prevention and control and resource utilization: Bacillus subtilis loaded in the modified clay particles is used to decompose algal debris, and the flocs are collected by a siphon pump and dehydrated to produce organic fertilizer.

[0043] 12 hours after the end of the targeted addition and sedimentation stage, the cyanobacterial coverage on the lake surface is always <5%, and 30-day long-term monitoring shows that the water body chlorophyll a is stable at <15 μg / L, and no secondary outbreak occurs.

[0044] In summary, the present application has the following characteristics: 1. Triple innovation mechanism: Non-aluminum modification: Cationic starch is used instead of aluminum salt to solve the problem of aluminum residue.

[0045] Composite flocculation: Chitosan and NPAM synergistically enhance the strength of the flocs, and the settling speed is increased by 50%.

[0046] Microbial control: Bacillus subtilis is loaded to inhibit the recovery of cyanobacteria, breaking through the limitations of traditional processes that only deal with emergencies.

[0047] 2. Process integration innovation: The composite flocculant can be prepared simultaneously when cyanobacterial outbreak is predicted, simplifying the process.

[0048] Targeted addition by a drone and / or shipborne spraying system + resource recovery by a siphon pump, forming a closed-loop system.

[0049] 3. None of the existing technologies simultaneously involves the complete technical chain of non-aluminum modification + biological flocculation + microbial regulation + resource utilization.

[0050] It is to be understood that even though numerous characteristics and embodiments of the application have been set forth in the foregoing disclosure, the details can be varied without departing from the application, which is defined by the following claims.

Claims

1. An aluminum-free cyanobacteria rapid sedimentation and resource recovery process, characterized in that, The method comprises the following steps: Preparation of cationic starch modified clay: mix the clay loaded with bacillus subtilis and cationic starch at a weight ratio of 10:1-5, dissolve in deionized water, stir and react at 60-80℃ to form modified clay particles with a charge density of ≥20 mC / g; Preparation of composite flocculant: mix the modified clay particles and chitosan at a weight ratio of 7:(1-5), add 0.1wt% non-ionic polyacrylamide solution, stir to prepare a suspension with a total mass concentration of 5%-10% of modified clay particles and chitosan, adjust the pH to 6.5~7.5 to obtain the composite flocculant; Targeted addition and sedimentation: sprinkle the composite flocculant into the cyanobacterial water body at a dose of 2-3 kg / acre, and the cyanobacterial flocs are settled within 5-15 minutes; Long-term prevention and resource utilization: use the bacillus subtilis loaded in the modified clay particles to decompose the algal debris, collect the flocs and dehydrate to produce organic fertilizer.

2. The aluminum-free, blue-green algae rapid settling and resource recovery process of claim 1, wherein, In the preparation of cationic starch modified clay, the clay used is bentonite and / or attapulgite.

3. The aluminum-free, blue-green algae rapid settling and resource recovery process of claim 1, wherein, In the preparation of cationic starch modified clay, the number of Bacillus subtilis loaded on the clay is ≥ 10 8 CFU / g.

4. The aluminum-free, blue-green algae rapid settling and resource recovery process of claim 1, wherein, In the preparation of cationic starch modified clay, the stirring reaction time is 2-4 hours.

5. The aluminum-free, blue-green algae rapid settling and resource recovery process of claim 1, wherein, In the preparation of composite flocculant, the molecular weight of chitosan is 5-100 million Da, and the degree of deacetylation is ≥85%.

6. The aluminum-free, blue-green algae rapid settling and resource recovery process of claim 1, wherein, In the preparation of composite flocculant, the stirring speed is 200~300 rpm, and the time is 5~10 min.

7. The aluminum-free, blue-green algae rapid settling and resource recovery process of claim 1, wherein, In the preparation of composite flocculant, the pH is adjusted to 6.5~7.5 with citric acid.

8. The aluminum-free, blue-green algae rapid settling and resource recovery process of claim 1, wherein, In the targeted addition and sedimentation, the composite flocculant is uniformly sprinkled into the cyanobacterial aggregation area of the cyanobacterial water body through the spraying system of unmanned aerial vehicles, shipborne or their collaborative groups.