CN112624508B - Slow-release Fenton-like system based on immobilized enzyme and method for in-situ remediation of groundwater pollution by using slow-release Fenton-like system - Google Patents
Slow-release Fenton-like system based on immobilized enzyme and method for in-situ remediation of groundwater pollution by using slow-release Fenton-like system Download PDFInfo
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Abstract
The invention discloses a slow-release Fenton-like system based on immobilized enzyme and provides a method for in-situ remediation of groundwater pollution, which mainly comprises the following steps: 1) Selecting a central well and a plurality of peripheral medicine adding wells in a pre-repaired underground water pollution area; 2) Adding the green rust into the medicine adding well, pumping water into the central well, and recharging the water into underground water through the medicine adding well; pumping water continuously until green rust appears; 3) Arranging an immobilized enzyme reactor in each medicine adding well, aerating, and introducing a glucose solution; pumping water with small water amount in the central well and recharging to underground water through the medicine adding well; pumping water until the concentration of the effluent pollutants reaches the standard. The slow-release Fenton-like system has a pH range close to the environment of underground water, can realize the lasting slow release of free radicals in the whole process and the controllability of a degradation area, can not introduce other pollutants into the underground water, and can realize non-toxicity and harmlessness.
Description
Technical Field
The invention belongs to the technical field of groundwater pollution remediation, and particularly relates to a slow-release Fenton-like system based on immobilized enzyme and a method for in-situ remediation of groundwater pollution by using the slow-release Fenton-like system.
Background
Water resources are one of the most important environmental resources of people, and not only influence the life and production of people, but also influence the physical health and life safety of people to a great extent. The stacking of harmful wastes generated in industrial production, the residue of a large amount of organic pesticide and fertilizer in soil in agricultural production, the accumulation of mining gangue and the like, and pollutants contained in the substances enter underground water in a large amount under the action of rainwater and underground runoff thereof. So that most cities in China are more or less polluted by ground water.
At present, the repair technology of groundwater pollution is mainly divided into in-situ repair and ex-situ repair, wherein the most widely applied in the in-situ repair technology is Permeable Reactive Barrier (PRB) technology, and in the engineering practice process, a PRB system may fail due to loss of activity of a reaction medium, change of hydraulic conditions, even errors in process design and other factors, and a blocking phenomenon is very easily generated. The ectopic repair technology generally has the problems of high economic cost, complex operation management and the like.
The Fenton reaction utilizes Fe 2+ And H 2 O 2 The reaction generates hydroxyl free radical with strong oxidizing property, and the pollutant is decomposed into small molecular substance or further mineralized into CO under the action of the hydroxyl free radical 2 And H 2 And (O). Meanwhile, a series of Fenton-like systems are generated in the subsequent development process, such as the change of an electron donor and H in reaction 2 O 2 In situ generation. In the Fenton reaction, reactants and products are friendly to the groundwater environment, so that the Fenton reaction has certain potential in groundwater pollution remediation.
The conventional Fenton reaction is difficult to be applied to groundwater pollution remediation due to the characteristics of the reaction (a large amount of OH is generated simultaneously, the OH cannot be rapidly and sufficiently contacted with pollutants in groundwater, and the OH is quenched), reaction conditions and a reaction generating device. Chinese patent CN 106966484A discloses a method for utilizing Fe 3 O 4 /CaO 2 A method for degrading benzene series in underground water by a heterogeneous Fenton-like reaction system. The method is that calcium peroxide and nano ferroferric oxide are added into benzene series polluted water at normal temperature and pH is controlled to be 4-7. The method has the disadvantages that the reaction of the agent after contacting with water is too violent, the utilization efficiency of the agent is low, and the pH range of the method is difficult to realize in-situ groundwater remediation.
Chinese patent CN 110759319A discloses a method for removing chlorinated hydrocarbons and benzene series in underground water by activating slow-release nano calcium peroxide with ferrous sulfide. The method takes calcium chloride, 30 percent of hydrogen peroxide and ammonia water as raw materials, adds different dispersing agents and then adds polyethylene glycol400 (PEG 400) in nCaO 2 Forming a film on the surface to obtain the slow-release nano calcium peroxide advanced oxidation material embedded by the macromolecular polymer, and realizing the slow-release contact of the calcium peroxide and water to generate H 2 O 2 . However, this method introduces sulfides, as well as some macromolecular organics, into the groundwater.
Therefore, the current Fenton-like reaction system has a plurality of defects in the groundwater pollution remediation process, such as the introduction of other pollutants, H 2 O 2 Low utilization rate, low in-situ generation rate and the like, and has the problems that the movement of the underground water is random under the natural condition, the oxidant is difficult to control after being added and the like.
Disclosure of Invention
The invention aims to solve the technical problem of providing a sustained-release Fenton-like system based on immobilized enzyme and a method for in-situ remediation of underground water pollution by the same, aiming at the defects in the prior art. The slow-release Fenton-like system of the immobilized enzyme has a pH (7.2-7.8) range closer to the environment where underground water is located, and the whole process can realize the lasting slow release of free radicals and the controllability of a degradation region; in addition, other pollutants can not be introduced into underground water in the whole system, and non-toxicity and harmlessness can be realized.
The technical scheme adopted by the invention for solving the problems is as follows:
a slow-release Fenton-like system based on immobilized enzyme comprises sulfate Rust GR (SO 4) 2- ) The glucose solution and the immobilized glucose oxidase.
According to the scheme, the immobilized glucose oxidase is gel particles, the diameter of the immobilized glucose oxidase is 2-4 mm, and the enzyme activity is 100-120U/g. Preferably, the preparation method of the immobilized glucose oxidase comprises the following steps: and (3) fixing the glucose oxidase by adopting an embedding method to obtain the immobilized glucose oxidase. The preparation method comprises the following steps:
(1) Preparing a Glucose Oxidase (GOD) solution with a certain concentration range; the concentration of the GOD solution is 130-160U/ml;
(2) Preparing a mixed solution A of sodium alginate and gellan gum with a certain concentration, stirring and dissolving in a boiling water bath, and cooling to room temperature; wherein, the mass fraction of the sodium alginate in the mixed solution is 1.0 to 1.5 percent, and the mass fraction of the gellan gum is 0.4 to 0.7 percent;
(3) Mixing the mixed solution A obtained in the step (2) with the GOD solution obtained in the step (1) according to a volume ratio of 1: 25-40 to obtain mixed liquid B;
(4) Preparing CaCl with a certain concentration 2 A solution; caCl 2 The mass fraction is 10-13%;
(5) Dropping the mixed solution B into CaCl 2 And (3) standing the solution after the dripping is finished to obtain gel beads, namely the immobilized glucose oxidase, and controlling the dripping speed (for example, 5 drops/s) and the dripping height (for example, the dripping height is 15 cm) to ensure that the diameter of the gel beads is 2-4 mm.
The method for in-situ remediation of groundwater pollution by adopting the slow-release Fenton-like system based on the immobilized enzyme mainly comprises the following steps:
1) Selecting a central well and a plurality of peripheral medicine adding wells in a pre-repaired underground water pollution area;
2) In the first stage, green rust is added into a medicine adding well, then a central well pumps water with large water volume (the water pumping volume per minute is 1/400-1/2000 of the water volume in a pre-repaired underground water pollution area), and the water pumped by the central well is re-pumped to underground water through the medicine adding well;
3) The water pumping in the step 2) is continued until the central well is rusted, and the central well is stopped to pump water;
4) In the second stage, arranging immobilized enzyme reactors in each medicine adding well, aerating the immobilized enzyme reactors, and simultaneously introducing a glucose solution; pumping water with a small amount of water in the central well (the pumping amount per minute is 1/3000-1/6000 of the water in the underground water pollution area to be repaired), and recharging the water pumped by the central well to the underground water through a chemical feeding well;
5) And 4) in step 4), when the concentration of the pollutants in the effluent of the central well is below a target value, the reaction is terminated, and the remediation of the underground water polluted area is completed.
According to the scheme, the pre-repaired underground water polluted area surface is treated in the step 1)A central well is selected at the position of the accumulation center, the central well is used as the center of a circle, medicine adding wells are approximately distributed on the periphery of the repair area, the wells are all complete wells (namely, the wells are dug to the water-proof bottom layer), and the size of the wells is based on meeting the actual water pumping quantity requirement. Preferably, in practical engineering, the pre-remediated groundwater pollution area should be less than 0.25km 2 Every 0.03km 2 A medicine feeding well is arranged in the repair area, and the repair area is large and can be repaired by a plurality of blocks.
According to the scheme, the adding amount of the patina in the step 2) is 0.15-0.3 mol/m 3 The ferrous iron equivalent of (2) is calculated by ferrous iron, and the addition amount of the green rust is 0.15-0.3 mol per cubic meter of the water amount in the underground water polluted area to be repaired, and is preferably added in the form of solution.
According to the scheme, the immobilized enzyme reactor is a reactor loaded with immobilized glucose oxidase; the reactor is provided with a hollow cavity, wherein an up-down alternative guide plate is arranged in the hollow cavity and used for circulating reflux of liquid in the hollow cavity (ensuring the hydraulic retention time (generally more than 30 min) of glucose solution in the hollow cavity), a stainless steel filter screen is arranged in the middle of the outer side wall of the reactor, a three-phase separator is arranged at an outlet of the hollow cavity of the reactor, an aerator pipe is positioned at the end part inside the reactor and is provided with an aerator head, a gas discharge pipe is inserted into the three-phase separator, and a glucose feeding pipe and the head part of the aerator pipe are inserted into the hollow cavity through the three-phase separator.
According to the scheme, the aeration rate in the step 4) is 3-4 m calculated according to the volume of the solution in the reactor 3 /(m 3 H), the ratio of the flow rate of the glucose solution fed to the central well pumping in step 4) is 1:20 to 30. Preferably, the concentration of the glucose solution should be in the range of 0.05 to 0.2mol/L.
The working principle of the invention mainly comprises the following two stages:
in the first stage, the green rust is added into the peripheral drug adding wells, and large-water-volume water pumping is carried out through the central well, so that the directional migration of the green rust in the water-containing layer is realized, the added green rust is ensured to reach the position of the preset water-containing layer, and the pumped water is re-pumped to the underground water through the peripheral wells. The process is shown in figure 5. When the central well has the green rust, the green rust is indicated to be fully distributed in the aquifer, and the water pumping of the central well is stopped. The patina can realize the adsorption of a large amount of organic pollutants through the adsorption effect of the patina in the movement stage, realize enrichment and directly provide basic guarantee for high efficiency of subsequent degradation and oxidation.
And in the second stage, the immobilized enzyme reactor is arranged in a peripheral medicine adding well, aeration is realized through an aeration pipe respectively, and a glucose adding pipe is used for adding a glucose solution. And pumping water with small water amount by using a central well (pumping water and recharging by using peripheral wells). The enriched contaminants are fixed within the intercalation layer of patina by the adsorption of the first stage patina. In this case, the glucose is oxidized by the enzyme to release H 2 O 2 Under the action of free diffusion and water flow movement generated by pumping small amount of water, the Fe (II) in the structure state in the green rust is in contact with the green rust to H 2 O 2 Activating to generate OH, oxidizing and degrading pollutants in situ to mineralize. The gluconic acid generated by the reaction can react with iron ions to form a complex, and natural adsorption and sedimentation are carried out in the water-containing layer. In the whole reaction process, the non-toxicity of the externally-added reagent is realized.
Patina acts as a layered double metal hydroxide (LDH) and thus patina has good adsorptive capacity, which can adsorb contaminants by ligand exchange and surface complexation or anion exchange. In low concentration solutions, the internal anion exchange occurs predominantly in a high proportion of adsorbate/LDH. Furthermore, the patina interlayer contains many exchangeable anions, and thus can adsorb heavy metal cations, organic anions, and inorganic ions to form an inner layer complex on the patina. In the case of micro-pollution of groundwater, the adsorption enrichment of the pollutants can be realized during the migration process of the patina in the foregoing.
Fe (II) in the patina is structural divalent iron, and compared with dissolved divalent iron, the patina surface has electrons flowing at a high speed, so that the electron flowing efficiency is enhanced, the electron transfer is promoted, and the patina surface has higher catalytic activity. Meanwhile, because the content of Fe (II) in the patina is higher, the efficiency of catalyzing and generating active intermediate products (hydroxyl free radicals, superoxide radical and high-valence iron species) can be greatly improved, and the catalytic oxidation system has higher degradation rate.
Compared with the prior art, the invention has the following beneficial effects:
(1) The slow-release Fenton-like system based on the immobilized enzyme has a pH value range closer to the environment where underground water is located, and the whole process can realize the lasting slow release of free radicals and the controllability of a degradation region. In addition, other pollutants can not be introduced into the underground water in the whole system, and the non-toxicity and harmless treatment can be realized. Meanwhile, the invention combines well group water pumping to realize the control of degradation area, carries out in-situ removal on underground water pollutants, realizes the mineralization degradation of organic pollutants, and converts the organic pollutants into H 2 O and CO 2 And other pollutants for polluting water bodies are not introduced in the whole process.
(2) The directional migration of the underground water is realized by using a well group pumping test as a starting material, so that the added medicament can migrate in a water-containing layer towards a designated area and direction and reach a designated position, and meanwhile, the area range of the reaction can be controlled.
(3) The invention adopts a glucose-glucose oxidase system to produce H 2 O 2 : no external energy initiation is required; producing H in situ with other groundwater 2 O 2 Compared with the prior art, the substances in the system have the characteristics of no toxicity and no harm. In addition, the glucose oxidase has high specificity, can avoid side reaction with other substances in underground water, and can efficiently and gradually convert glucose into H 2 O 2 。
(4) The immobilized enzyme reactor adopted in the invention can realize the repeated utilization of the enzyme and provide proper guarantee for economy. Glucose oxidase catalyzes the oxidation of glucose in the presence of oxygen to produce H 2 O 2 The process has the characteristic of continuous and mild property, and the slow release property effectively avoids the generation of H at local part due to adding or medicament reaction 2 O 2 Too high a concentration leads to local too high OH concentration, self-quenching occursA phenomenon.
Drawings
FIG. 1 is a longitudinal sectional view of an immobilized enzyme reactor;
FIG. 2 is a schematic cross-sectional view taken in the direction 2-2 of FIG. 1;
FIG. 3 is a schematic cross-sectional view taken in the direction 3-3 of FIG. 1;
FIG. 4 is a schematic plan view of a well group arrangement;
FIG. 5 is a schematic diagram of green rust migration;
FIG. 6 is a schematic diagram of the reaction stage.
Wherein, (1) is a glucose adding pipe; (2) is an aeration pipe; (3) is a gas discharge pipe; (4) is a three-phase separator; (5) is a fixed support; (6) immobilized glucose oxidase; (7) a stainless steel filter screen with 0.1mm aperture; (8) an aeration head; (9) is a central well; charge well for medicine in charge well (charge well);
is an immobilized enzyme reactor;
is the added patina;
a contaminant.
Detailed Description
In order to better understand the present invention, the following examples are further provided to illustrate the content of the present invention, but the present invention is not limited to the following examples.
In the following examples, sulfate patina having suitable adsorbability and reducing power was selected while satisfying both the requirements of adsorbability and electron donating ability. Preparation of wet green rust GR (SO 4) by coprecipitation method 2- ) The method comprises the following specific steps:
1) Weighing a certain amount of Fe by using an analytical balance 2 (SO 4 ) 3 And FeSO 4 ·7H 2 And O (the quantity ratio of Fe (II) to Fe (III) is 2) 2 (SO 4 ) 3 And FeSO 4 The solution is ready for use;
2) Under the condition of no oxygen, taking a three-neck flask as a reactor, and adding FeSO 4 Putting the solution into a three-neck flask; will produce Fe 2 (SO 4 ) 3 Transferring the solution and the 1.0mol/L NaOH solution into a constant pressure funnel, and arranging the constant pressure funnel at two side openings of the flask; to FeSO simultaneously 4 Dripping Fe into the solution 2 (SO 4 ) 3 And NaOH solution, and performing magnetic stirring; the pH value of the reaction is maintained to be about 7.8 to 8.2 by adjusting the dropping speed of the NaOH solution; after the dropwise addition, the pH value is stabilized at 8.0, and stirring is continued for 1h; after stirring, obtaining serous fluid, placing the serous fluid in a serum bottle and sealing;
3) The prepared liquid green rust is aged in a constant temperature water bath box for 12 hours at the temperature of 40 ℃, and then is sealed and stored under anaerobic condition, the water content is 96.0-96.9 percent, and the liquid green rust is used for subsequent examples.
In the following examples, the preparation of immobilized glucose oxidase comprises the following steps:
(1) Preparing 150U/ml Glucose Oxidase (GOD) solution;
(2) Preparing a mixed solution A of sodium alginate and gellan gum, stirring and dissolving in a boiling water bath, and cooling to room temperature; wherein the mass fraction of the sodium alginate in the mixed solution is 1.2 percent, and the mass fraction of the gellan gum is 0.5 percent;
(3) Mixing the mixed solution A obtained in the step (2) with the GOD solution obtained in the step (1) according to a volume ratio of 1:30 to obtain a mixed solution B;
(4) Preparing 10 percent of CaCl by mass fraction 2 A solution;
(5) Putting the mixed solution B into a constant-pressure funnel, and fixing the funnel to ensure that the opening of the funnel is spaced from CaCl 2 Dripping CaCl into the solution beaker at a rate of 5 drops/s at a liquid level of about 15cm 2 In solution; after the dropwise addition is finished, standing the gel for 1h; filtering, washing the gel beads by using deionized water; absorbing the surface moisture with absorbent paper, and storing in a refrigerator at 4 ℃ to obtain immobilized glucose oxidase; wherein the size of the gel bead is 2-4 mm, and the enzyme activity is 100-120U/g.
In the following examples, the immobilized enzyme reactors are shown in FIGS. 1 to 3. The immobilized enzyme reactor is a cylinder made of stainless steel, and an opening on the side wall is covered with a stainless steel filter screen (7) to realize the outflow of reaction mixed liquid; immobilized glucose oxidase (6) is loaded in the cylinder; a cylindrical up-down alternating guide plate is arranged in the cylinder body, and the circulating reflux is realized under the action of aeration pushing force; a fixed support (5) is arranged between the guide plate and the outer wall of the cylinder body; the three-phase separator (4) is arranged at an outlet at the center of the top of the cylinder body, and separated gas is discharged into the external environment; the aeration pipe (2) and the glucose adding pipe (1) are introduced into the bottom of the cylinder body through a three-phase separator (4).
In the following examples, a aquifer-underground model was constructed using a scale (length scale is 350) and glass fiber reinforced plastic as a material according to the platinum-han theorem, and a degradation test of pollutants was performed by simulating regional underground water distribution using the model. The model is of a cubic structure, clay is arranged on a bottom water-proof bottom layer, and the clay is tamped to be a fine sand bedding; and filling coarse crushed stones in the middle of the model water-bearing stratum as a water-bearing stratum, paving fine crushed stones on the tops of the coarse crushed stones, paving fine sand on the tops of the fine crushed stones, paving clay on the tops of the fine sand and tamping the clay, reserving a central well and peripheral medicine feeding wells in the center and the peripheral positions, filling water containing pollutants in the model water-bearing stratum by using trichloroethylene as pollutants (the concentration of the trichloroethylene is 5 mg/L).
The experimental process is divided into two stages, wherein in the first stage, the green rust is added into the medicine adding well, then the central well pumps water with large water volume (the water pumping volume per minute is 1/400-1/2000 of the water volume in the repaired area), and the water pumped by the central well is refilled into underground water through the medicine adding well; arranging an immobilized enzyme reactor in each medicine feeding well, aerating the immobilized enzyme reactor, and introducing a glucose solution; and pumping small water amount to the central well (the water pumping amount per minute is 1/3000-1/6000 of the water amount in the repaired area), and recharging the water pumped by the central well to the underground water through a medicine adding well.
The slow-release Fenton-like system of the immobilized enzyme is subjected to pollutant simulated degradation experiments in a designed underground water simulation device, so that the method and the effect of the system for repairing underground water pollution in situ are proved.
Example 1
A slow-release Fenton-like system based on immobilized enzyme comprises three parts, namely sulfate patina, a glucose solution and immobilized glucose oxidase; wherein the sulfate patina is in a wet state (the water content is 96.0-96.9%), and is added in a liquid state when in use; the concentration range of the glucose solution is 0.1mol/L; the diameter of the immobilized glucose oxidase gel particle is 2-4 mm, and the enzyme activity is 100-120U/g.
The method for in-situ remediation of groundwater pollution by adopting the immobilized enzyme-based slow-release Fenton-like system mainly comprises the following steps:
1) The water filling amount in the underground water simulation device is 2m 3 Selecting a central well at the center of the simulation device, and arranging a medicine adding well around the restoration area by taking the central well as the circle center (the area of the pre-restored underground water pollution area is 2 m) 2 Calculating according to the Kingham's theorem, setting 8 medicine adding wells in total), wherein the wells are all complete wells (namely, the wells are drilled to the water-proof bottom layer);
2) Adding green rust into the medicine adding well, then pumping water with large water volume by the central well at the speed of 5L/min, and recharging the water pumped by the central well to underground water through the medicine adding well; the total content of ferrous iron of green rust added is 0.5mol, and the green rust is added at one time;
3) The water pumping in the step 2) is continued until the central well generates green rust, and the central well is stopped pumping water; at the moment, the water pumping time is 3 hours;
4) An immobilized enzyme reactor (wherein, the immobilized glucose oxidase gel particles in the immobilized enzyme reactor are 2000g, the enzyme content is calculated by the enzyme activity, and the total amount is 2.0 multiplied by 10) 5 U), aerating the immobilized enzyme reactor, and simultaneously pumping 0.1mol/L glucose solution at the speed of 15ml/min (the effective volume of the reactor is 5L to ensure that the hydraulic retention time of the reaction solution is more than 30 min); pumping water with a small water amount of 0.5L/min by using a central well until the reaction is finished, and recharging the water pumped by the central well to underground water through a medicine adding well;
5) And (3) after 1h, 3h, 6h, 12h, 24h, 48h, 72h, 96h and 168h start in the step 4) (namely when the reaction time is respectively 1h, 3h, 6h, 12h, 24h, 48h, 72h, 96h and 168 h), respectively monitoring the concentration of pollutants in the water pumped out from the small water volume of the central well, wherein the test result is shown in table 1, and the time when the water pumped out from the central well reaches the corresponding groundwater quality standard is taken as the reaction finishing time, namely the remediation of the groundwater pollution area is finished.
TABLE 1 degradation Rate Change of trichloroethylene
Example 2
The difference from example 1 is that: the green rust is added according to the content of Fe (II), and the total content of ferrous iron of the green rust added is 0.10mol, 0.25mol, 0.50mol and 1.00mol respectively.
When the reaction time is 168h, the pollutant concentration of water extracted from the small water amount of the central well is respectively monitored, and the test result is shown in table 2.
TABLE 2 influence of the total amount of patina added on the degradation of trichloroethylene
Example 3
The difference from example 1 is that: the total enzyme content in the immobilized enzyme reactor is 1.0 × 10 in total based on enzyme activity 5 U、1.5×10 5 U、2.0×10 5 U、2.5×10 5 U, monitoring the pollutant concentration of the water extracted from the small water volume of the central well at the reaction time of 24h, 72h and 168h under the condition of the total enzyme amount, and the test result is shown in Table 3.
TABLE 3 Effect of enzyme amount on trichloroethylene degradation
The results in table 1 show that the Fenton-like system established by the invention can effectively realize degradation in 7 days aiming at the underground water pollution of low-concentration trichloroethylene. The data result in table 2 shows that the efficient degradation of trichloroethylene can be realized by adding the green rust to a certain extent. The results in Table 3 show that the amount of enzyme in the immobilized enzyme reactor affects the degradation rate of the contaminant, and that the increasing tendency of the degradation rate shows a decreasing state as the amount of enzyme increases.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and changes can be made without departing from the inventive concept of the present invention, and these modifications and changes are within the protection scope of the present invention.
Claims (4)
1. The method for in-situ remediation of groundwater pollution based on the slow-release Fenton-like system of immobilized enzyme is characterized by mainly comprising the following steps:
1) Selecting a central well in a pre-repaired underground water pollution area, and arranging a plurality of medicine feeding wells around the central well;
2) In the first stage, sulfate patina is added into a medicine adding well, then large-water-volume water pumping is carried out on a central well, and water pumped by the central well is re-filled into underground water through the medicine adding well; stopping pumping water to the central well when the water pumping is continued until the central well is rusted;
3) In the second stage, arranging an immobilized enzyme reactor in each medicine adding well, aerating the immobilized enzyme reactor, and introducing a glucose solution; pumping a small amount of water to the central well, and recharging the water pumped by the central well to the underground water through the medicine feeding well; pumping water until the concentration of effluent pollutants of the central well is below a target value, and taking the reaction as a reaction end point to finish the repair of the underground water pollution area;
the slow-release Fenton-like system based on the immobilized enzyme comprises three parts, namely sulfate patina, a glucose solution and immobilized glucose oxidase;
the dosage of the green rust in the step 2) is 0.15-0.3 mol/m 3 The equivalent of ferrous iron is added in the form of solution;
the ratio of the flow rate of the glucose solution introduced in the step 3) to the central well pumping flow rate in the step 3) is 1:20 to 30, the concentration range of the glucose solution is 0.05 to 0.2mol/L;
the immobilized enzyme reactor is a reactor loaded with immobilized glucose oxidase; wherein the immobilized glucose oxidase is gel particles with the diameter of 2-4 mm and the enzyme activity of 100-120U/g; the reactor is provided with a hollow cavity, an upper and lower alternative guide plate is arranged in the hollow cavity and used for circulating reflux of liquid in the hollow cavity, a filter screen is arranged in the middle of the outer side wall of the reactor, a three-phase separator is arranged at the outlet of the hollow cavity of the reactor, an aerator is arranged at the end part inside the reactor and provided with an aerator head, a gas discharge pipe is inserted into the three-phase separator, and a glucose adding pipe and the head part of the aerator pipe are inserted into the hollow cavity through the three-phase separator.
2. The method for in-situ remediation of groundwater pollution of the immobilized enzyme-based slow-release fenton-like system according to claim 1, wherein the preparation method of the immobilized glucose oxidase comprises the following steps:
(1) Preparing a glucose oxidase solution with the concentration of 130-160U/ml;
(2) Preparing a mixed solution A of sodium alginate and gellan gum, stirring and dissolving in a boiling water bath, and cooling to room temperature; wherein the mass fraction of the sodium alginate is 1.0-1.5%, and the mass fraction of the gellan gum is 0.4-0.7%;
(3) Mixing the mixed solution A obtained in the step (2) with the glucose oxidase solution obtained in the step (1) according to a volume ratio of 1: 25-40 to obtain a mixed solution B;
(4) Preparing 10-13% of CaCl by mass fraction 2 A solution;
(5) Dropping the mixed solution B into CaCl 2 And (3) standing the solution after the dropwise addition is finished to obtain gel beads with the diameter of 2-4 mm, namely the immobilized glucose oxidase.
3. The method for in-situ remediation of underground water pollution by the immobilized-enzyme-based slow-release Fenton-like system according to claim 1, wherein in the step 2), when large-volume water is pumped, the pumping volume per minute is 1/400 to 1/2000 of the volume of water in the underground water pollution area to be remediated; in the step 3), when small-volume water is pumped, the water pumping amount per minute is 1/3000-1/6000 of the water amount in the underground water pollution area to be repaired.
4. The method for in-situ remediation of groundwater contamination of the immobilized enzyme-based slow release fenton-like system of claim 1, wherein the pre-remediated groundwater contamination area is less than 0.25km 2 Every 0.02-0.04 km 2 A medicine feeding well is arranged in the area of the repair area; the pre-remediated groundwater contaminated area is greater than 0.25km 2 Sometimes, it is divided into multiple repairs.
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