Harmless treatment process for bottom mud of rivers and lakes

Abstract

The invention relates to the technical field of chemical reagent treatment of bottom mud, in particular to an innocent treatment process for bottom mud of rivers and lakes. The treatment process provided by the invention overcomes the problems that the metal content of the bottom mud treated by the traditional treatment process is high, and organic compounds, pesticides and other substances exceed the standard. The method comprises the following steps: firstly, measuring and investigating to obtain bottom mud and caching, and removing inorganic solid wastes and sand grains through size screening; carrying out primary flocculation by utilizing a Venturi structure pipeline and a six-way valve type sample injector, and carrying out primary dehydration by virtue of spiral extrusion and crawler-type filter pressing; after detection and analysis, chemicals are added to substances exceeding the standard, and the content of pollutants is reduced by means of the oxidation-adsorption-chelation synergistic effect; finally, carrying out secondary dehydration, molding and steam hydrothermal curing; various indexes of the treated bottom mud reach the standard, the metal migration amount is low, the treated bottom mud can be used for landscaping, and harmlessness and recycling are achieved; through process innovation, the reaction efficiency of the reagent and the bottom mud is optimized, and the environmental protection benefit is remarkable.

Description

Technical Field

[0001] The invention relates to the technical field of chemical reagent treatment of sediment, and in particular to a harmless treatment process for sediment in rivers and lakes. Background Art

[0002] As urbanization and industrialization accelerate, river and lake sediment pollution has become an environmental problem that needs to be solved urgently. As an important part of the aquatic ecosystem, river and lake sediments have become a "repository" for harmful substances such as heavy metals, organic pesticides, organic matter and E. coli because they accept a large amount of pollutants from industrial wastewater, domestic sewage and surface runoff.

[0003] At present, existing sediment treatment technologies have many limitations. Conventional physical treatment methods, such as simple screening and dehydration, can only remove large particles of impurities and some water in the sediment, but are powerless against the large amount of heavy metals and organic pollutants in the sediment. As a result, the treated sediment will still pollute the soil, water and other environmental elements during the subsequent disposal process.

[0004] In terms of chemical treatment technology, some methods use a large amount of chemical reagents to remove pollutants. For example, some methods that use acid and alkali to adjust the pH value can change the existence form of heavy metals to a certain extent, but they are likely to cause drastic changes in the chemical properties of the sediment, affecting its subsequent resource utilization; excessive oxidants will react with minerals, humus, etc. in the sediment. Complex chemical reactions. These reactions will not only consume a large amount of reagents, but may also destroy the original structure of the sediment, release the originally fixed heavy metal ions, and increase the pollution risk of the sediment. At the same time, some intermediate products generated by the reaction, such as organic free radicals, metal complexes, etc., are unstable in nature and may be further converted into more toxic substances, causing secondary pollution to the environment. In addition, the large amount of chemical reagents remaining after the reaction will also affect the subsequent resource utilization of the sediment, reducing its application value in agriculture, landscaping and other fields.

[0005] In addition, the existing technology lacks systematicity and coordination in the overall design of the sediment treatment process. Each treatment link is independent of each other, and the advantages of different treatment methods cannot be fully utilized, resulting in low treatment efficiency and difficulty in achieving the dual goals of harmless treatment and resource utilization of sediment. Therefore, it is urgent to develop a sediment treatment technology that is efficient, environmentally friendly and can achieve resource utilization.

[0006] Therefore, a harmless treatment process for river and lake sediments is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a harmless treatment process for river and lake sediments, which comprises obtaining sediments through measurement and survey and caching, removing inorganic solid waste and sand particles through size screening; then using a Venturi structure pipeline and a six-way valve type sample injector for preliminary flocculation, and then dehydrating once through spiral extrusion and crawler filter press; after detection and analysis, adding drugs to the substances exceeding the standard, reducing the pollutant content by means of the synergistic effect of oxidation-adsorption-chelation; finally, secondary dehydration, molding and hydrothermal solidification; the treated sediments meet the standards in various indicators, with a low metal migration amount, and can be used for landscaping to achieve harmlessness and resource utilization; through process innovation, the reaction efficiency between reagents and sediments is optimized, and the environmental protection benefits are remarkable.

[0008] To achieve the above object, the present invention provides the following technical solutions: The present invention provides a harmless treatment process for river and lake sediments, and the process is as follows: S1 sediment collection and caching; S2 size screening; S3 flocculation screening; The interfaces of the six-way valve injector are A, B, C, D, E and F in clockwise order. In working mode one, the polyethylene oxide solution is pumped in; in working mode two, the polyacrylamide solution is pumped in to react and obtain the pre-treated sludge. S4 one-time dehydration; S5 detection and analysis; S6 dosing; S61 one-time dosing; At pH 6.0, hydrogen peroxide solution and ferrous sulfate solution were added; composite NH 2 -MIL-101 suspension, dithiocarbamate solution, thiocarboxylic acid chitosan solution and activated carbon suspension, the reaction pH was adjusted to 7.0; S62 secondary dosing; Calcium chloride solution, calcium hydroxide suspension, sodium hypochlorite solution and potassium permanganate solution were added at the same time, and after reacting for 1 hour, polyaluminium chloride solution was added; after the reaction, polyacrylamide solution was added to obtain chemically treated sludge; S7 secondary dehydration; S8 molding treatment; S9 hydrothermal curing.

[0009] Preferably, in milligrams per liter of chemically treated sludge; The ratio of polyethylene oxide solution to chemically treated sludge in S61 is 10-15:1; the ratio of polyacrylamide solution to chemically treated sludge is 150-250:1; the ratio of hydrogen peroxide solution to chemically treated sludge is 180-220:1; the ratio of ferrous sulfate solution to chemically treated sludge is 450-500:1; the ratio of composite NH 2-The ratio of MIL-101 suspension to chemically treated sludge is 260-320:1; the ratio of dithiocarbamate solution to chemically treated sludge is 4800-5100:1; the ratio of thiocarboxylic acid chitosan solution to chemically treated sludge is 800-1050:1; In S62, the ratio of calcium chloride solution to chemically treated sludge is 90-150:1; the ratio of calcium hydroxide suspension to chemically treated sludge is 45-60:1; the ratio of sodium hypochlorite solution to chemically treated sludge is 3500-4000:1; the ratio of potassium permanganate solution to chemically treated sludge is 1800-2200:1; the ratio of polyaluminum chloride solution to chemically treated sludge is 130-150:1; the ratio of polyacrylamide solution to chemically treated sludge is 40-60:1.

[0010] Preferably, in S3 flocculation screening, in working mode one, the polyethylene oxide solution is pumped in from F, passes through A and D in sequence, and is pumped into the venturi structure pipeline from E; switching to working mode two, the polyacrylamide solution is pumped in from C, and is pumped into the venturi structure pipeline from C.

[0011] Preferably, in S61, in working mode one, hydrogen peroxide solution is pumped in by F. After initially pumping in 10 L, it passes through A and D in sequence and is sealed by E. Then, working mode two is switched to that in which ferrous sulfate solution is pumped in by C. The hydrogen peroxide solution and ferrous sulfate solution between A and D are mixed in C and finally pumped into the tapered section and throat connection of the Venturi structure pipeline.

[0012] Preferably, in S62, in working mode one, polyaluminium chloride solution is pumped in by F, passes through A and D in sequence, and is sealed by E; switching to working mode two, polyacrylamide solution is pumped in by C, the polyaluminium chloride solution and the polyacrylamide solution are mixed in C, and finally pumped into the venturi structure pipeline to obtain chemically treated sludge.

[0013] Preferably, the S2 size screening step is as follows: use a vibrating screen screening device to size screen the sludge in the buffer pool to separate the inorganic solid waste, and screen out stones, branches, and plastic inorganic solid waste with a diameter greater than 15 mm; use a sieve hole size of 1.5 mm to screen out sand particles to obtain the primary screened sludge.

[0014] Preferably, the conditions for hydrothermal curing in S9 are: curing the die-casting sludge with water vapor for 3 hours at 280° C. to obtain a cured sludge.

[0015] Preferably, the composite NH 2 -MIL-101 suspension is composed of composite NH 2 -MIL-101 and deionized water are mixed to obtain composite NH 2-MIL-101 is obtained by reacting terephthalic acid, 2-aminoterephthalic acid and ferrosoferric oxide nanoparticles, or the product with commercial information CAS 1189182-85-1 is directly purchased.

[0016] Preferably, the thiocarboxylate chitosan solution is obtained by mixing thiocarboxylate chitosan and deionized water; and the thiocarboxylate chitosan is obtained by reacting chitosan with a deacetylation degree of 90% with thioacetic acid.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Through S2 size screening, it can effectively separate stones, branches, plastic inorganic solid waste larger than 10-20mm and sand particles of 0.1-2mm, reducing the interference of impurities on subsequent treatment; S3 flocculation screening and S4 primary dehydration are combined to reduce the moisture content of the sludge from 85% to 45%, creating good conditions for subsequent treatment. In the S6 dosing link, by accurately controlling a variety of chemical reagents, such as hydrogen peroxide, ferrous sulfate, and composite NH 2 -MIL-101 and other dosages and addition sequence, using oxidation-adsorption-chelation synergy, precipitation-flocculation synergy and disinfection oxidation mechanism, effectively reduced the content of heavy metals, organic compounds and E. coli in the sludge; after treatment, the total zinc content was 380-442 mg / kg, the total cadmium was 3.2-4.1 mg / kg, the glyphosate was 65-84 mg / kg, the coliform value was 0.004-0.007 mg / kg, etc., all of which were in line with the GB / T23486 standard "Mud for Landscaping and Sewage Treatment Plant Sludge Disposal", achieving the harmless treatment of the sludge and greatly reducing the risk of sludge pollution to the environment.

[0018] 2. Reagents are added to the tapered section and throat through a Venturi structure pipeline in conjunction with a six-way valve injector. The high-speed, low-pressure environment and special flow state are used to quickly disperse the reagents and fully mix them with the sediment, thereby improving the treatment efficiency. This design optimizes the reaction process of the chemical reagents and the sediment. In the S9 steam hydrothermal curing stage, the 280°C steam curing condition converts the metals in the cured sediment from an unstable state to a residual state, significantly reducing the amount of metal migration. The migration amount of metallic zinc is 21.1 mg / Kg and that of cadmium is 0.12 mg / Kg. The process of the present invention effectively stabilizes the metals in the sediment, reduces their migration and release in the environment, and avoids secondary pollution to the soil and water. The treated cured sediment can be directly used for the greening of woodlands, nursery gardens, grasslands, and roadside slopes, thus realizing the resource utilization of the sediment, which is of great significance in terms of environmental protection and resource recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a process diagram for harmless treatment of river and lake sediments according to the present invention; Figure 2It is a working mode one state diagram of the six-way valve type sample injector of the present invention; Figure 3 This is a state diagram of the second working mode of the six-way valve injector of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] See also Figures 1 to 3 The present invention provides a harmless treatment process for river and lake sediments, and the technical scheme is as follows:

[0022] Example 1 like Figure 1 As shown, the processing process is as follows: S1 Sediment Collection and Cache According to the design method of patent CN106638456B, measurement, investigation, testing, dredging project quantity determination and ecological dredging are carried out step by step to obtain bottom mud, which is temporarily stored in a buffer pool; the volume of the buffer pool is 100 cubic meters.

[0023] S2 size screening Vibrating screen screening equipment is used to size-screen the sludge in the buffer pool to separate the inorganic solid waste for subsequent separate treatment (stones, branches, and plastic inorganic solid waste with a diameter greater than 15 mm are screened out, and sand is removed by screening with a sieve size of 1.5 mm); the moisture content of the initial sludge after preliminary screening is 85%; the screening frequency is maintained in the range of 15-30 Hz.

[0024] S3 Flocculation Screening A Venturi structure pipeline is arranged in front of the pretreatment tank. The pipeline is divided into a gradually contracting section, a throat and a gradually expanding section. A six-way valve injector is arranged at the connection between the gradually contracting section and the throat. The interfaces are A, B, C, D, E and F in clockwise order. In working mode 1, the drag reducer polyethylene oxide solution (dosing concentration 12 mg / L) is pumped into the Venturi structure pipeline by F, and after the initial pumping of 10L, it is switched to working mode 2, and the cationic polyacrylamide solution (dosing concentration 150 mg / L) is pumped into the Venturi structure pipeline by C; the flow rate at the inlet of the gradually contracting section is 1.2 m / s, the flow rate of the throat is 3.5 m / s, and the flow rate at the outlet of the gradually expanding section is 0.6 m / s.

[0025] Working mode 1: Figure 2As shown, B is connected to C, A is connected to F, E is connected to D, and A is connected to D; the pipeline connecting A and D is a transparent pipeline, and the state and situation of the chemical reagents in it can be observed at any time; it flows in from F, passes through A and D in turn, and finally flows out from E. Working mode 2: As shown in Figure 3 As shown, B is connected to A, A is connected to F, A is connected to D, D is connected to C, and E is connected to F.

[0026] The flocculated sludge that flows out and flocculates through the gradually expanding section is screened for the second time and filtered to remove the flocculated substances to obtain the pre-treated sludge.

[0027] S4 one-step dehydration The pre-treated sludge is passed through a screw extrusion dewatering machine and a crawler filter press in turn. The speed of the screw extrusion dewatering machine in the feeding section is 12r / min, the pressure is 0.5MPa, the speed of the extrusion section is 10r / min, the pressure is 0.8MPa, the speed of the pressing section is 6r / min, and the pressure is 1.2MPa; the pressure in the gravity dehydration zone of the crawler filter press is 0.2MPa, the filter belt speed is 5m / min, the pressure in the wedge pre-pressing zone is 0.7MPa, the filter belt speed is 3m / min, the pressure in the high-pressure pressing zone is 1.5MPa, and the filter belt speed is 1.5m / min; the filter belt mesh number is 500 meshes. After being treated by the screw extrusion dewatering machine, the moisture content of the sludge is 68%. After passing through the crawler filter press again, the moisture content of the once dehydrated sludge is 45%.

[0028] S5 Detection Analysis If the standard is met, it will go directly to S7, and if it is not met, it will go to S6 for treatment. The heavy metal, organic matter, organic pesticide and E. coli content will be tested and analyzed, and the sample will be tested and analyzed after processing; among them, referring to the material limit requirements specified in GB / T23486-2009 "Municipal Sewage Treatment Plant Sludge Disposal Landscaping Mud", for total zinc <500mg / kg, total nickel <200mg / kg, total copper <400mg / kg, total cadmium <5mg / kg, total mercury <5mg / kg, total arsenic <50mg / kg, total lead <300mg / kg, total chromium <400mg / kg kg, hexavalent chromium <10mg / kg, DDT <2mg / kg, BHC <2mg / kg, glyphosate <100mg / kg, dichlorvos <1.0mg / kg, polychlorinated biphenyls <0.5mg / kg, toluene <50mg / kg, benzo(a)pyrene <0.3mg / kg and coliform value <0.01mg / kg. The primary dewatered sludge is squeezed by a plate and frame press and mixed with inorganic solid waste, digested and mixed, mechanically formed and hydrothermally solidified, and directly used in the greening of forest land, nursery gardens, grasslands and road slopes; The actual detected contents of sediment substances are as follows: total zinc 1126 mg / kg, total nickel 80 mg / kg, total copper 125 mg / kg, total cadmium 276 mg / kg, total mercury 14 mg / kg, total arsenic 32 mg / kg, total lead 125 mg / kg, total chromium 316 mg / kg, hexavalent chromium 8 mg / kg, DDT not detected, Benzene 0.5 mg / kg, Glyphosate 324 mg / kg, Dichlorvos 1.6 mg / kg, Polychlorinated biphenyls 0.1 mg / kg, Toluene 175 mg / kg, Benzo(a)pyrene 0.8 mg / kg; E. coli value 0.16 mg / kg; The contents of some substances did not meet the requirements and were processed in the next step.

[0029] The six-way valve injector is equipped with a PID controller, which establishes a relationship model between the pollutant content and the reagent dosage through the initial detection content of pollutants in the sediment and the treatment target. The forward feedback controller calculates the amount of chemical reagent that needs to be increased based on the model, and controls the pump of the corresponding interface of the dynamic reagent injector to increase the dosage.

[0030] S6 Dosing S61 one-time dosing The pH of the sludge was adjusted to 6.0, and then hydrogen peroxide solution (dosing concentration 200 mg / L) and ferrous sulfate solution (dosing concentration 480 mg / L) were added. The temperature was maintained at 45°C before the addition of ferrous sulfate solution. The mixed composite NH 2 -MIL-101 suspension (dosing concentration 320 mg / L), dithiocarbamate solution (dosing concentration 4800 mg / L), react for 20 minutes, then add thiocarboxylic acid chitosan solution (dosing concentration 800 mg / L), react for 10 minutes, and finally add activated carbon suspension (dosing concentration 6000 mg / L), react at room temperature for 5 hours, and adjust the pH to 7.0 after the reaction is completed; The hydrogen peroxide solution is pumped in by F. After the initial pumping of 10L, it is sealed by E and then switched to working mode 2. The ferrous sulfate solution is pumped in by C. The hydrogen peroxide solution and the ferrous sulfate solution are mixed in equal volumes at the outlet of C. Finally, they are pumped into the venturi structure pipeline by C. The adding positions of the above reagents are all at the interface between the tapered section and the throat; S62 Secondary Dosing Calcium chloride solution (dosing concentration 130 mg / L), calcium hydroxide suspension (dosing concentration 50 mg / L), sodium hypochlorite solution (dosing concentration 3500 mg / L), potassium permanganate solution (dosing concentration 1800 mg / L) were added at the same time. After fully reacting for 1 hour, polyaluminium chloride solution (130 mg / L) was added. After reacting for 20 minutes, polyacrylamide solution (40 mg / L) was added. After flocculation, the flocculated precipitate was removed by filtration, and the composite NH 2-MIL-101 and oxidized iron, the resulting flocculants and composite NH 2 -MIL-101 separation, and finally chemically treated sludge is obtained; magnetic separation intensity is 400mT, and magnetic separation time is 20min; The polyaluminium chloride solution is pumped in by F, passes through A and D in sequence, and is finally sealed by E. After initially pumping in 10L, it is switched to working mode two, and the polyacrylamide solution is pumped in by B. Before being pumped into the venturi structure pipeline by C, the polyaluminium chloride solution and the polyacrylamide solution are mixed in equal volumes at the inlet of C, and finally pumped into the venturi structure pipeline by C to obtain the chemically treated sludge; when the reagent stored between the feedback ends A and D after the PID controller is less than 300mL, the treatment is stopped and switched to working state one, and then switched to working state two after replenishing the reagent.

[0031] S7 secondary dehydration After adding calcium oxide suspension (dosing concentration 60 mg / L) to the chemically treated sludge, a plate and frame press was used to remove water and discharge the remaining water. The water content of the secondary dehydrated sludge was 36.8%; S8 Forming Process The inorganic solid waste in S2 is added to the secondary dewatered sludge, and mixed to obtain a material to be molded; the material to be molded is placed in a die-casting machine, and die-casting is performed to obtain a die-casting sludge; S9 hydrothermal curing At 280°C, the die-casting sludge is cured by steam for 3 hours to obtain cured sludge. The cured sludge can be directly used for landscaping, such as woodlands, nursery gardens, grasslands, and road slope greening.

[0032] The following chemical reagent concentrations are the concentrations added into the Venturi structure pipeline. The following chemical reagents are dissolved or dispersed after mixing with water. Among them, the concentration of hydrogen peroxide solution is 20g / L, the concentration of ferrous sulfate solution is 50g / L, and the concentration of compound NH 2 -The concentration of MIL-101 suspension is 100g / L, the concentration of dithiocarbamate solution is 100g / L, the concentration of thiocarboxylic acid chitosan solution is 100g / L, the concentration of activated carbon suspension is 2000g / L; the concentration of calcium chloride solution is 111g / L; the concentration of calcium hydroxide suspension is 37g / L; the concentration of sodium hypochlorite (available chlorine) solution is 50g / L; the concentration of potassium permanganate solution is 30g / L; the concentration of polyaluminium chloride solution is 100g / L; the concentration of polyacrylamide solution is 10g / L; the concentration of polyethylene oxide solution is 20g / L; the concentration of cationic polyacrylamide solution is 5g / L; the concentration of calcium oxide suspension is 35g / L.

[0033] Embodiment 2-4 Different from Example 1, the concentrations of the following chemical reagents were changed, as shown in Table 1 and Table 2. The concentration units in the table are the mass of the chemical reagents per liter of dewatered sludge.

[0034] Table 1 Dosage concentration of chemical reagents during primary and secondary dosing

[0035] Table 2 Dosing concentration of chemical reagents during primary and secondary dosing

[0036] Comparative Example 3 The difference from Example 1 is that the composite NH 2 -MIL-101 was replaced with a sodium persulfate aqueous solution with a dosing concentration of 320 mg / L, and the concentration of the sodium persulfate aqueous solution itself was 5 g / L.

[0037] Comparative Example 4 The difference from Example 1 is that the thiocarboxylic acid chitosan solution is replaced by a carboxylic acid chitosan solution of the same addition concentration.

[0038] Comparative Example 5 Different from Example 1, no thiocarboxylic acid chitosan solution was added.

[0039] Preparation Example 1 Compound NH 2 -MIL-101 was prepared as follows: 0.1 mol of terephthalic acid and 0.1 mol of 2-aminoterephthalic acid were weighed and dissolved in 1000 mL of N,N-dimethylformamide to form a mixed solution A; 0.1 mol of ferric chloride hexahydrate ( ) was dissolved in 50 mL DMF to form solution B; solution B was slowly added to solution A, stirred evenly, and then transferred to a reactor to react at 180°C for 36 h; after the reaction was completed, it was naturally cooled to room temperature to obtain NH 2 -MIL-101 crystals were centrifuged, washed three times with DMF and ethanol, and dried to obtain NH 2 -MIL-101; Weigh 10 g of NH 2 -MIL-101 and 20 g of ferroferric oxide nanoparticles (100 nm) were dispersed in 1000 mL of deionized water and ultrasonicated for 45 min to make the ferroferric oxide nanoparticles uniformly adsorbed on the NH 2 -MIL-101 surface; then add 0.15g of sodium persulfate; The mixed solution was stirred at 40 °C for 18 h to allow sodium persulfate to react with NH 2-MIL-101 surface amino groups or other active sites undergo chemical bonding reactions, while the FeO nanoparticles also react with NH 2 -MIL-101 combined to form a composite product; after the reaction, the product was separated by centrifugation, washed with deionized water and ethanol three times each, and dried at 70°C to obtain a composite NH 2 -MIL-101.

[0040] Preparation Example 2 The preparation method of thiocarboxylic acid chitosan is as follows: 65g of chitosan with a deacetylation degree of 90% is dissolved in 1000mL of acetic acid solution with a mass concentration of 5% to obtain a chitosan solution; 76.2g of thioacetic acid is dissolved in methanol to obtain a thioacetic acid solution with a mass fraction of 1mol / L; the chitosan solution is added dropwise into 200mL of thioacetic acid solution at a rate of 5 drops / s, and reacted at 45°C for 5h to obtain a thiocarboxylic acid chitosan solution; then filtered, washed with water, and dried to obtain thiocarboxylic acid chitosan.

[0041] Experimental Example 1 The chemically treated sludge obtained by the above schemes was tested for metal content, organic matter content and coliform value, and the final test results are shown in Tables 3 and 4. The concentration units of the substances in the table are all mg / kg.

[0042] Table 3 Test results of Examples 1-4 and Comparative Example 1

[0043] Table 4 Test results of comparative examples 2-5

[0044] By adjusting the dosage of chemical reagents, the content of substances in the sludge is changed. In addition to the substances that have met the requirements, the content of substances that originally exceeded the standard is also reduced to within the standard range. Under the conditions of Examples 1-4, the total zinc content is 380-442 mg / kg, the total cadmium is 3.2-4.1 mg / kg, the total mercury is 1.5-2.0 mg / kg, the glyphosate is 65-84 mg / kg, the dichlorvos is 0.4-0.6 mg / kg, the toluene is 28-36 mg / kg, the benzo(a)pyrene is 0.1-0.2 mg / kg, and the coliform value is 0.004-0.007 mg / kg. By adding hydrogen peroxide solution, ferrous sulfate solution, and composite NH 2 -The concentrations of MIL-101 suspension, dithiocarbamate solution, thiocarboxylic acid chitosan solution, activated carbon suspension, calcium chloride solution, calcium hydroxide suspension, sodium hypochlorite solution and potassium permanganate solution were adjusted to achieve good removal of metals, organic matter and E. coli. +Catalyze hydrogen peroxide to generate hydroxyl radicals, whose oxidation potential is as high as 2.8V, which can non-selectively degrade organic pollutants; composite NH 2 -MIL-101 high specific surface area (>1000m 2 / g) and amino-modified channels selectively adsorb heavy metals and hydrophobic organic matter, while the sodium persulfate contained in them releases SO after activation. 4 - Free radicals degrade the adsorbed organic matter on the MOF surface, avoiding the oxidation caused by the direct addition of sodium persulfate, which would affect the Fenton reaction; the amino groups (-NH 2 ) Enhanced Cr 6+ The reduction adsorption (C 6+ →Cr 3+ ), and after thiolation, the degradation capacity of organic compounds increases; sodium hypochlorite oxidizes organochlorine pesticides (hexachlorocyclohexane, DDT) to CO 2 and Cl - Potassium permanganate degrades the stubborn organic matter of benzo(a)pyrene and inactivates Escherichia coli (oxidizing the cell membrane). In addition, it oxidizes the previously added divalent iron to facilitate subsequent magnetic separation and removal; Al 3+ The double electric layer is compressed, and the long chain structure of polyacrylamide bridges the particles to form dense flocs (size>500μm). The flocs wrap the residual heavy metals and organic matter, which is convenient for filter pressing and separation. In Comparative Example 1, the content of the substance is increased, and the removal efficiency of the substance is improved, but too many unnecessary components are easily introduced into the sediment, and it is difficult to be effectively removed in the sediment; in Comparative Example 2, the content of the chemical reagent is reduced, and the removal effect of metals, organic compounds and Escherichia coli is reduced; in Comparative Example 3, the composite NH 2 -MIL-101 was replaced with a sodium persulfate aqueous solution with a concentration of 320 mg / L, which had no significant effect on the removal of heavy metals, but reduced the removal of organic compounds such as glyphosate and dichlorvos, and reduced the removal ability of E. coli; Comparative Example 4 was replaced with carboxylic acid chitosan (without -SH group), and the adsorption and removal effect of metals and organic compounds was reduced; Comparative Example 5 did not add thiocarboxylic acid chitosan, and the adsorption and removal effect was further reduced. Through oxidation-adsorption-chelation synergy, precipitation-flocculation synergy and disinfection oxidation, good removal of metals, organic compounds and E. coli was achieved together.

[0045] Example 5 and Example 6 Different from Example 1, the dosage of flocculant in flocculation screening and secondary dosing is changed, as shown in Table 5.

[0046] Table 5 Dosage concentration of flocculant and drag reducer

[0047] Comparative Example 6 Different from Example 1, in the second dosing of S62, the polyaluminium chloride solution and the polyacrylamide solution were added after reacting for 10 minutes.

[0048] Comparative Example 7 Different from Example 1, in S3, the drag reducer polyethylene oxide solution and cationic polyacrylamide solution are not added to the primary screening sludge through a six-way valve injector, but the drag reducer polyethylene oxide solution and cationic polyacrylamide solution are mixed in equal volumes and then added to the primary screening sludge.

[0049] Comparative Example 8 Different from Example 1, in the one-time dosing process of S61, the ferrous sulfate solution and the hydrogen peroxide solution are not added to the primary screening sludge through a six-way valve injector, but are mixed in advance and then added.

[0050] Comparative Example 9 The difference from Example 1 is that the ferrous sulfate solution is not added to the primary screening sludge through a six-way valve injector, but is first introduced into the pipeline in advance, and the hydrogen peroxide solution is introduced 10 minutes later while the ferrous sulfate solution is still introduced.

[0051] Comparative Example 10 Different from Example 1, during the treatment process, the inlet of the chemical reagent is not located at the connection between the tapered section and the throat of the venturi structure pipeline, but is arranged at the front end of the tapered section.

[0052] Comparative Example 11 The difference from Example 1 is that in the secondary dosing of S62, the polyaluminium chloride solution is first added, the polyacrylamide solution is added after reacting for 5 minutes, and finally the calcium chloride solution, calcium hydroxide suspension, sodium hypochlorite solution and potassium permanganate solution are added simultaneously.

[0053] Comparative Example 12 Different from Example 1, the order of the secondary dosing in S62 and the primary dosing in S61 is replaced, and the specific adding conditions remain unchanged.

[0054] Comparative Example 13 The difference from Example 1 is that S3 flocculation and screening and S4 primary dehydration are not performed, and the process directly enters the dosing stage.

[0055] Comparative Example 14 Different from Example 1, the S9 steam hydrothermal curing step is not performed, but air drying and curing are performed in the sun.

[0056] Experimental Example 2 The chemically treated sludge obtained in Examples 1, 5, 6 and Comparative Examples 6-13 was tested for chemical composition, and the test results are shown in Tables 6 and 7.

[0057] Table 6 Chemical treatment sediment material content of Examples 1, 5, 6 and Comparative Examples 7-8

[0058] Table 7 Comparative Examples 9-13 Chemically treated sediment material content

[0059] The sludge obtained by the process of the present invention has the required material content under the conditions of Examples 1, 5 and 6. In S62, the oxidant is reacted for a sufficient time first, so that the subsequently added polyaluminium chloride solution and polyacrylamide solution can play a good flocculation effect, and the fine particles in the sludge are condensed and settled through adsorption bridging, electrical neutralization and other effects. Metal ions will be removed as these particles flocculate and settle; the flocs formed by the flocculant can adsorb organic compounds and precipitate them with the flocs; they can also condense the tiny particles containing Escherichia coli together and remove them through subsequent filtration and other operations; the reaction time in Comparative Example 6 is too short, and the oxidant produces an oxidative decomposition effect on the flocculant, so the removal effect of metals, pesticides, organic matter and Escherichia coli is reduced. In Comparative Example 7, the drag reducer polyethylene oxide solution and the cationic polyacrylamide solution are mixed in equal volumes and then added, which destroys the synergistic effect of step-by-step addition through a six-way valve injector. When the two are mixed in advance, their polymer chains will entangle with each other. The cationic groups of cationic polyacrylamide will attract the polyethylene oxide molecular chains through electrostatic action, so that the distance between the molecular chains is shortened, and then flocculation occurs. In the treatment of sediment, this flocculation may cause the flocs to form too early and too large, which is not conducive to uniform dispersion in the sediment, and reduces the wrapping and flocculation effect on the sediment particles; the cationic groups of cationic polyacrylamide will hydrolyze in the aqueous solution to produce an acidic environment. The presence of metal ions in the sediment after one-time dosing will catalyze the degradation reaction of polyethylene oxide. The acidic environment produced by the hydrolysis of cationic polyacrylamide may also accelerate the breakage of polyethylene oxide molecular chains, reduce its molecular weight, and thus weaken the drag reduction performance of polyethylene oxide. The flocculation and sedimentation of metal ions are affected, and the metal contents of total zinc, total cadmium, total mercury, etc. are increased. This addition method makes the flocculant unable to effectively adsorb organic compounds, resulting in an increase in the content of organic compounds, such as glyphosate, dichlorvos, etc. The content increases. Comparative Example 8 Because the Fenton reagent is mixed in advance, hydrogen peroxide and ferrous ions produce hydroxyl radicals in advance, and organic compounds cannot be effectively oxidized subsequently, so the removal effect of organic compounds decreases, and the removal of metal elements has little effect. In Comparative Example 9, ferrous sulfate solution was first introduced, and then hydrogen peroxide solution was introduced, which changed the process of the Fenton reaction. Excessive ferrous ions consumed the oxidant in the system, reducing the removal effect of organic matter such as glyphosate and dichlorvos.In comparative example 10, the sample inlet is set at the front end of the tapered section, which changes the mixing and reaction environment of the chemical reagents in the Venturi structure pipeline, and the removal effect of the substance is reduced; in the Venturi structure, when the fluid flows through the tapered section, the flow rate gradually increases and the pressure gradually decreases; at the throat, the flow rate reaches the maximum and the pressure reaches the minimum; adding reagents in the tapered section and the throat can utilize this high-speed, low-pressure environment to quickly disperse the reagents, and the low-pressure environment helps the reagents to fully contact with the bottom mud and avoid local aggregation of the reagents; the special flow state at the tapered section and the throat can produce strong turbulence and shear force, which can quickly break up the added reagents and fully mix them with the bottom mud, thereby improving the contact treatment effect between the chemical reagents and the bottom mud. In Comparative Example 11, polyaluminium chloride solution was first added, and polyacrylamide solution was added after reacting for 5 minutes. The two formed a complex, and the flocculation ability decreased. Then, oxidants and other substances were added, which reduced the removal effect of the substance. The added calcium ions preferentially precipitated some heavy metals to reduce the consumption of oxidants. PAC was added after the oxidation reaction to avoid oxidation and decomposition. The addition order in Comparative Example 11 was opposite to that in Example 1, so the removal effect of the substance decreased. Comparative Example 12 had the worst removal effect on the substance. The S61 stage removed organic matter and exchangeable heavy metals through Fenton reaction and chelation. S62 was first performed, Ca(OH). 2 The precipitation encapsulates the pollutants, hinders the oxidation / chelation reaction, and the treatment efficiency drops sharply. Comparative Example 13 does not perform S3 flocculation screening and S4 primary dehydration, and directly enters the dosing stage, which interferes with the removal of metals, organic pesticides, organic compounds and E. coli.

[0060] Experimental Example 3 Metal migration content test: The solidified sludge obtained in Example 1 and Comparative Example 14 was crushed and ground, and passed through a 200-mesh sieve. An acetic acid solution with a pH of 2.88 was used as the extracting solution, and the solid-liquid ratio (w / v) was 1:20. The extraction was performed by oscillation for 18 hours. The obtained metal substance contents are shown in Table 8. The migration limits of zinc, chromium, cadmium, nickel and lead in SW-846 are 25 mg / Kg, 5 mg / Kg, 0.5 mg / Kg, 1 mg / Kg and 5 mg / Kg, respectively.

[0061] Table 8 Metal migration test results

[0062] Through steam hydrothermal curing in the harmless treatment process of river and lake bottom mud, under the conditions of Example 1, the migration amount of metal zinc is 21.1 mg / Kg, the migration amount of chromium is 3.74 mg / Kg, the migration amount of cadmium is 0.12 mg / Kg, the migration amount of nickel is 0.64 mg / Kg and the migration amount of lead is 2.8 mg / Kg. Comparative Example 14 does not perform thermal curing, and the migration amount of metal increases. By setting the water vapor curing condition of 280°C, the metals in the cured bottom mud are converted from the acetic acid extractable state, the reducible state and the oxidizable state to the residual state, and the stable metals are not easy to migrate out of the cured bottom mud, thereby reducing the pollution to the environment.

[0063] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A harmless treatment process for river and lake sediments, characterized in that: The harmless treatment process comprises: Flocculation screening: The interfaces of the six-way valve injector are A, B, C, D, E and F in clockwise order. Working mode 1: pump in polyethylene oxide solution; working mode 2: pump in polyacrylamide solution to obtain pre-treated sludge by reaction. One-time dosing: adding hydrogen peroxide solution and ferrous sulfate solution; adding composite NH2-MIL-101 suspension, dithiocarbamate solution, thiocarboxylic acid chitosan solution and activated carbon suspension in sequence; Secondary dosing: adding calcium chloride solution, calcium hydroxide suspension, sodium hypochlorite solution and potassium permanganate solution at the same time, and adding polyaluminium chloride solution after the reaction; and adding the polyacrylamide solution after the reaction to obtain chemically treated sludge.

2. A harmless treatment process for river and lake sediments according to claim 1, characterized in that: Measured in milligrams per liter of chemically treated sediment; In the one-time dosing, the ratio of the polyethylene oxide solution to the chemically treated sludge is 10-15:1; the ratio of the polyacrylamide solution to the chemically treated sludge is 150-250:1; the ratio of the hydrogen peroxide solution to the chemically treated sludge is 180-220:1; the ratio of the ferrous sulfate solution to the chemically treated sludge is 450-500:1; the ratio of the composite NH2-MIL-101 suspension to the chemically treated sludge is 260-320:1; the ratio of the dithiocarbamate solution to the chemically treated sludge is 4800-5100:1; the ratio of the thiocarboxylic acid chitosan solution to the chemically treated sludge is 800-1050:1; In the secondary dosing, the ratio of the calcium chloride solution to the chemically treated sludge is 90-150:1; the ratio of the calcium hydroxide suspension to the chemically treated sludge is 45-60:1; the ratio of the sodium hypochlorite solution to the chemically treated sludge is 3500-4000:1; the ratio of the potassium permanganate solution to the chemically treated sludge is 1800-2200:1; the ratio of the polyaluminium chloride solution to the chemically treated sludge is 130-150:1; the ratio of the polyacrylamide solution to the chemically treated sludge is 40-60:

1.

3. The harmless treatment process for river and lake sediments according to claim 1 is characterized in that: In the flocculation screening, in the working mode one, the polyethylene oxide solution is pumped in by F, passes through A and D in sequence, and is pumped into the venturi structure pipeline by E; switching to the working mode two, the polyacrylamide solution is pumped in by C, and is pumped into the venturi structure pipeline by C.

4. A harmless treatment process for river and lake sediments according to claim 1, characterized in that: In the one-time dosing, in the working mode one, the hydrogen peroxide solution is pumped in by F, and after the initial pumping, it passes through A and D in sequence, is sealed by E, and then switches to the working mode two, and the ferrous sulfate solution is pumped in by C, the hydrogen peroxide solution and the ferrous sulfate solution between A and D are mixed at C, and finally pumped into the tapered section and throat connection of the venturi structure pipeline.

5. The harmless treatment process for river and lake sediments according to claim 1 is characterized by: In the secondary dosing, in the working mode one state, the polyaluminium chloride solution is pumped in by F, passes through A and D in sequence, and is sealed by E; switching to the working mode two, the polyacrylamide solution is pumped in by C, the polyaluminium chloride solution and the polyacrylamide solution are mixed in C, and finally pumped into the venturi structure pipeline to obtain the chemically treated sludge.

6. A harmless treatment process for river and lake sediments according to claim 1, characterized in that: The harmless treatment process also includes hydrothermal curing; the conditions of the hydrothermal curing are: using water vapor to thermally cure the die-casting sludge to obtain cured sludge.

7. The harmless treatment process for river and lake sediments according to claim 1 is characterized by: The composite NH2-MIL-101 suspension is obtained by mixing the composite NH2-MIL-101 and deionized water; the composite NH2-MIL-101 is obtained by reacting terephthalic acid, 2-aminoterephthalic acid and ferrosoferric oxide nanoparticles.

8. The harmless treatment process for river and lake sediments according to claim 1 is characterized by: The thiocarboxylate chitosan solution is obtained by mixing thiocarboxylate chitosan and deionized water; the thiocarboxylate chitosan is obtained by reacting chitosan with a deacetylation degree of 90% with thioacetic acid.

Images