A treatment system and method for industrial boron-containing wastewater

Abstract

This invention discloses a treatment system for industrial boron-containing wastewater, and also discloses a method for treating industrial boron-containing wastewater based on the above treatment system. Boron-containing wastewater with a pH of 6 in a pH adjustment tank flows by gravity into a reaction tank, where sodium ferrate and barium sulfite are simultaneously added. The molar ratio of Na₂FeO₄ to BaSO₃ is 2:1, and the molar ratio of Fe(VI) to boron is 1:1. After the reaction, the liquid flows by gravity to a flocculation tank. In the flocculation tank, flocculant is added to carry out a flocculation reaction, and after sufficient flocculation, the wastewater enters a sedimentation tank. After sedimentation in the sedimentation tank for at least 30 minutes, the concentration of boron in the water at the sedimentation tank outlet is measured. If the boron removal rate reaches 98% or higher, it is directly discharged to the downstream discharge tank. If the boron removal rate is less than 98%, it is returned to the pH adjustment tank inlet for retreatment via a return pump.

Description

TECHNICAL FIELD

[0001] The present application relates to a system for treating industrial boron-containing wastewater, and a method for treating industrial boron-containing wastewater based on the system. BACKGROUND

[0002] Boron is used in many industrial processes, for example, the addition of boron in glass products can enhance their heat resistance and chemical resistance; boron is needed in the synthesis of various products such as fertilizers, pesticides, buffers, dyes, bleaches, etc.; high-concentration boron-containing raw materials are often used in the process of the electronic industry; in the semiconductor industry, boron is used as a dopant for silicon; in the thin-film transistor liquid crystal display industry, boric acid solution is used for the processing of polarizers. The exposure of excess boron can be toxic to humans and animals, so the boron-containing wastewater generated in industry must be effectively removed. Boron in industrial wastewater is mostly in the form of B(OH)3, but when the pH is higher than 9, B(OH)4 - The common methods for removing boron from industrial wastewater at present include chemical precipitation, ion exchange, and reverse osmosis.

[0003] Chemical precipitation method is to add precipitant in wastewater under weak alkaline condition to react with boron in solution, so as to convert boron in wastewater into borate precipitate which is difficult to dissolve in water. After 30 minutes, flocculant is added into the solution, and after heating, stirring, standing and filtering, the optimal boron removal rate is about 70%. The chemical precipitation method has the following disadvantages: (1) when boron removal treatment is performed, the solution pH needs to be adjusted to alkaline state, which often leads to the increase of the salinity of the treated wastewater; (2) when high-concentration boron removal is performed, a large amount of precipitant is consumed, a large amount of sludge is generated, the subsequent sludge treatment load is increased, and the sludge system treatment effect is not ideal. Ion exchange method is to add resin in wastewater, and to use the selective exchange of the polyhydroxy functional group of the resin with the borate ion in the wastewater to form a chelate, and then to generate boric acid by the dissociation of the acid, so as to be adsorbed by the resin to achieve the purpose of boron removal. The ion exchange method has the following disadvantages: (1) ion exchange resin is suitable for low-concentration boron removal, and the removal efficiency of high-concentration boron in industrial wastewater is low, and the operation cost is high; (2) when hydrochloric acid or sulfuric acid is used to regenerate the resin, high-concentration boric acid waste liquid is easily formed, which is not easy to handle; (3) the resin is expensive and has a large consumption, and the investment cost is high. Reverse osmosis method is to use selective semi-permeable membrane as separation medium, and to apply pressure on the side with high concentration to make the raw material components pass through the semi-permeable membrane from the side with high concentration to the side with low concentration, so as to realize the separation of the solution. The reverse osmosis method has the following disadvantages: (1) reverse osmosis method needs to be performed under alkaline condition, and metal ions in the solution are easy to form precipitate under high pH, which leads to the damage and pollution of the reverse osmosis membrane, and the high frequency of membrane replacement increases the process cost; (2) single-stage RO treatment of boron-containing wastewater has low removal rate, and requires higher pressure and more alkali, which further increases the cost of boron removal; (3) multi-stage RO treatment of boron-containing wastewater system is complex and expensive, which leads to high construction cost of the process system. SUMMARY

[0004] The purpose of the present application is to provide an industrial boron-containing wastewater treatment system; another purpose of the present application is to provide an industrial boron-containing wastewater treatment method based on the above-mentioned treatment system, which can achieve a boron removal rate of more than 98% in industrial boron-containing wastewater, and also realize the recycling of boron resources.

[0005] Technical scheme: The industrial boron-containing wastewater treatment system provided by the present application comprises a pH adjusting tank, a reaction tank, a flocculation tank and a sedimentation tank connected in sequence; the drainage outlet of the sedimentation tank is connected with two drainage pipelines, one of which is connected with a rear-end discharge tank, and the other of which is connected with the inlet of the pH adjusting tank; the sludge discharge port of the sedimentation tank is connected with a sludge treatment system; the sludge treatment system comprises a sludge thickening tank and a sludge dewatering area, and the sludge in the sedimentation tank is concentrated and dewatered to obtain sludge crystals; the effluent from the sludge treatment system is delivered to the inlet of the pH adjusting tank by a backflow pump.

[0006] The pH adjusting tank is provided with a pH sensor (a pH probe is arranged in the pH adjusting tank to continuously maintain the pH of the boron-containing wastewater in the pH adjusting tank at 6), and the pH adjusting tank is also provided with a sulfuric acid dosing pump or a liquid alkali dosing pump. The pH sensor collects the pH value of the boron-containing wastewater in the pH adjusting tank in real time. When the pH sensor detects that the pH of the boron-containing wastewater is higher than 6 or lower than 6, the pH value of the boron-containing wastewater in the pH adjusting tank is adjusted through the sulfuric acid dosing pump or the liquid alkali dosing pump, until the pH of the boron-containing wastewater is 6.

[0007] The industrial boron-containing wastewater treatment method based on the above treatment system comprises the following steps:

[0008] (1) The boron-containing wastewater with a pH of 6 in the pH adjusting tank flows into the reaction tank by itself, and sodium ferrate and barium sulfite are added into the reaction tank at the same time; the molar ratio of Na2FeO4 and BaSO3 is 2:1, and the molar ratio of Fe(VI) to boron is 1:1; after reaction, the liquid flows into the flocculation tank by itself;

[0009] (2) In the flocculation tank, a flocculant is added into the flocculation tank to perform a flocculation reaction, and after sufficient flocculation, the liquid enters the sedimentation tank;

[0010] (3) After being deposited in the sedimentation tank for not less than 30 min, the concentration of boron in the water at the drainage outlet of the sedimentation tank is measured. If the boron removal rate reaches 98% or above, the liquid is directly discharged into the discharge tank. If the boron removal rate is less than 98%, the liquid is returned to the inlet of the pH adjusting tank by a reflux pump for reprocessing.

[0011] In step (1), the residence time of the boron-containing wastewater in the reaction tank is 1 h.

[0012] In step (1), the sodium ferrate is prepared by an electrochemical method. Specifically, an iron electrode with a content of 96% of iron is used as the anode of the electrolytic cell, a NaOH solution with a concentration of 16 mol / L is used as the electrolyte in the anode chamber, a copper electrode is used as the cathode, and a NaOH solution with a concentration of 1 mol / L is used as the electrolyte in the cathode chamber. The external voltage is 30 V, and the electrolysis time is 80 min. After electrolysis, a sodium ferrate solution with a concentration of 35 g / L is obtained in the anode chamber.

[0013] The obtained sodium ferrate solution is taken out and placed in a beaker, and the beaker is placed in an ice water bath. In order to make the sodium ferrate precipitate in the form of crystals, 20 g / L of solid sodium hydroxide is slowly added to the sodium ferrate solution, and the ice water bath is continuously stirred for 2 h until the crystals precipitate. After completion, filtration is performed, and the crystals are completely frozen and solidified in a-80℃ refrigerator. Then, the frozen and solidified crystals are placed in a freeze dryer with a refrigeration temperature of-45℃ for freeze drying for 24 h, and a vacuum pump is opened to create a vacuum. After freeze drying, Na2FeO4 crystals are obtained. X-ray diffraction and Raman spectroscopy are used to characterize the purity of the crystals, which is >99.99%.

[0014] The ultra-high purity sodium ferrate crystals (>99.99%) prepared by this invention effectively avoid the formation of impurity phases and have a higher purity than commercially available sodium ferrate (99%). Using the sodium ferrate crystals prepared by this invention to treat boron-containing wastewater has the following advantages: (1) The ultra-high purity crystals contain a higher effective sodium ferrate component and have stronger oxidation performance. When achieving the same boron removal rate, compared to commercially available sodium ferrate, the sodium ferrate crystals prepared by this invention require a lower dosage, produce less sludge, and have a lower overall cost; (2) When the dosage is the same, compared to commercially available sodium ferrate, the sodium ferrate crystals prepared by this invention can achieve a reduction of more than 50% in the effluent boron concentration.

[0015] The electrochemical reactions that occur during electrolysis are as follows:

[0016] Anode: Fe + 8OH - →FeO4 2- +4H2O+6e -

[0017] Cathode: 6H₂O + 6e - →6OH - +3H2

[0018] Overall reaction: Fe + 2OH - +2H₂O→FeO₄ 2- +3H2

[0019] In step (3), the flocculant is PAM, and the concentration of PAM in the flocculation tank is 2 ppm.

[0020] In step (3), the flocculation time is not less than 30 minutes.

[0021] In step (3), the flow rate of the return pump is 75% of the flow rate of the raw water entering the pH adjustment tank.

[0022] The method of this invention involves adding BaSO3 to the sodium ferrate oxidation system and controlling the [Na2FeO4:BaSO3] ratio. mol A ratio of 2:1 is used to achieve efficient boron removal under mild conditions. Since ferrates mainly remain in water as suspended particles, their surfaces carry a negative charge under neutral conditions, making them difficult to rapidly flocculate into larger particles; therefore, their own floc settling performance is poor. However, when ferrates undergo a redox reaction, FeO4... 2-The iron oxides undergo a gradient valence evolution from Fe(VI) to Fe(II) via either a 1e transfer pathway (Fe(VI)→Fe(V)→Fe(IV)→Fe(III)) or a 2e transfer pathway (Fe(VI)→Fe(IV)→Fe(II)), generating a Fe(VI) / Fe(V) / Fe(IV) / Fe(III) / Fe(II) oxidation system, forming a series of positive valence iron oxides. Simultaneously, ferrates can covalently combine with the intermediate valence iron oxides generated in the reaction, forming a complex network structure. This network structure simultaneously functions as a double-layer compressor, adsorption-electroneutralization agent, adsorption bridging agent, and network trapping-sweeping agent, enhancing agglomeration properties and exhibiting excellent sedimentation performance and flocculation effect. Consequently, the barium metaborate precipitate formed in the reaction loses stability under its flocculation and sedimentation action, agglomerating into larger particles that facilitate faster subsequent sedimentation in the settling tank. Furthermore, in the redox reaction process of ferrates, the intermediate valence compounds such as Fe(V) / Fe(IV) / Fe(III) formed have higher reactivity than Fe(VI). Therefore, accelerating the formation of intermediate valence compounds can enhance the oxidizing ability of ferrates; for BaSO3, SO3 2- When reacting with sodium ferrate, it enhances the transfer of single and double electrons during the reaction, accelerates the formation of intermediate valence compounds, and produces SO4· - This enhances the oxidation capacity of the system, while Ba 2+ When it reacts with metaboric acid, it can form a metal precipitate, barium metaborate, which is beneficial for the resource recovery of boron.

[0023] The overall chemical reaction equation is as follows:

[0024] 2FeO4 2- +BaSO3+2H3BO3+H2O→2Fe(OH)3+Ba(BO2)2+SO4 2- +O2+2OH-

[0025] Beneficial effects: Compared with the prior art, the present invention has the following effects: (1) In the method of the present invention, the boron removal reaction process will not generate toxic and harmful byproducts that cause secondary pollution to the environment. Compared with the traditional chemical precipitation method for treating boron-containing wastewater, for the same initial concentration of boron-containing wastewater, the boron removal rate of the present invention can reach more than 98%, while the optimal boron removal rate of the traditional chemical precipitation method is about 70%. (2) The traditional chemical precipitation method requires an operating temperature between 45 and 80°C and a pH between 10 and 11. However, the boron removal reaction temperature of the present invention is maintained at room temperature and the pH is around 6 to achieve a good boron removal effect, which greatly reduces energy consumption and the amount of alkali (Me(OH)2) added. At the same time, it also solves the problem of sludge suspension caused by excessive addition of hydrogen peroxide when using oxidant H2O2 in the existing chemical precipitation method. (3) In the method of this invention, Fe(VI) is converted into intermediate-valence iron oxides via 1e or 2e transfer. These intermediate-valence iron oxides can covalently combine with ferrates to form a complex network structure, which can simultaneously perform the functions of compressing the electric double layer, adsorption-electrode neutralization, adsorption bridging, and net trapping-sweeping, exhibiting excellent sedimentation performance and flocculation effect, thereby reducing the amount of flocculant added and lowering the system operating cost. (4) By adding the two-electron reducing agent BaSO3, the method of this invention enhances the single-electron and two-electron transfer capabilities during the reaction process, accelerating the formation of intermediate-valence compounds such as Fe(V) / Fe(IV) / Fe(III) in the redox reaction of ferrates, and generating SO4· - (5) The sludge obtained by the method of the present invention, after being concentrated and dewatered by the sludge system, mainly consists of barium metaborate and boron-containing crystals, thereby realizing the resource recovery of boron. Attached Figure Description

[0026] Figure 1 This is a flowchart of the processing method of the present invention;

[0027] Figure 2 This is a schematic diagram of the electrolytic cell used for the electrochemical preparation of sodium ferrate. Detailed Implementation

[0028] Example 1

[0029] The boron-containing wastewater from a specialty glass manufacturing plant in Shanghai has the following characteristics: boric acid concentration of 525 ppm, chemical oxygen demand of 350 ppm, pH of 6.4, and flow rate of 12 m³. 3 / h, runtime 24h.

[0030] The method of the present invention for treating the above-mentioned boron-containing wastewater includes the following steps:

[0031] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0032] (2) Boron-containing wastewater was treated at 15m 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0033] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 6 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 6 enter the inlet of the reaction tank by gravity flow.

[0034] (4) Add 8.06 g / L sodium ferrate and 5.28 g / L barium sulfite at the inlet of the reaction tank using a dosing pump. [Fe(VI):Boron] mol = 1:1, [Na2FeO4:BaSO3] mol =2:1; the boron-containing wastewater in the reaction tank undergoes catalytic oxidation, chemical precipitation, and coagulation reactions with the composite material of sodium ferrate and barium sulfite. The residence time of the boron-containing wastewater in the reaction tank is 1 hour.

[0035] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction. The reaction time is 30 min.

[0036] (6) The boron-containing wastewater after flocculation enters the inlet of the sedimentation tank by gravity flow. The sedimentation time is 30 minutes, and the boron concentration at the outlet is measured. At this time, the boron concentration in the effluent is about 9.2 ppm, and the boron removal rate reaches more than 98%. The effluent is transported to the discharge tank for storage by a transfer pump. If the boron removal rate does not reach 98%, the wastewater in the sedimentation tank is transported to the inlet of the pH adjustment tank by a return pump. The transport flow rate is 75% of the original water flow rate (the return ratio is 75%, which can ensure the boron removal efficiency and quality on the one hand, and avoid the return flow rate from increasing the return load on the other hand). The effluent after secondary treatment of the return water is transported together with the effluent after primary treatment to the discharge tank for storage.

[0037] (7) Sludge flow rate in sedimentation tank: 4.25 m³ / h 3 The sludge is pumped to a sludge thickening tank via a screw pump at a rate of 2.13 m³ / h. The thickening tank uses a center-driven scraper, with a thickening time of 12 hours and a sludge flow rate of 2.13 m³ / h. 3 / h, at which point the sludge moisture content is 97%; the sludge produced in the sludge thickening tank is dewatered by a screw press for 8 hours, with a sludge flow rate of 0.14m³ / h. 3 / h, at which point the sludge moisture content is 55%;

[0038] (8) The effluent from the sludge treatment system is pumped back to the inlet of the pH adjustment tank for secondary treatment via a return pump. The return flow rate is 4.11 m³ / s. 3 / h, the effluent after secondary treatment is transported together with the effluent after primary treatment to the discharge tank for storage;

[0039] (9) Collect the sludge crystals after concentration and dehydration. The main components are barium metaborate and boron-containing crystals. Barium metaborate can be used for rust prevention and fire prevention, while boron-containing crystals can be used for strengthening glass. The resource recovery of boron in sludge can minimize the damage of boron to the environment.

[0040] Example 2

[0041] Boron-containing wastewater from a semiconductor factory in Wuxi: boric acid concentration 1120 ppm, chemical oxygen demand 850 ppm, pH 6.5, and volume 17 m³. 3 / h, runtime 24h.

[0042] The method of the present invention for treating the above-mentioned boron-containing wastewater includes the following steps:

[0043] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0044] (2) The boron-containing wastewater was treated at a concentration of 20m³. 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0045] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 6 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 6 enter the inlet of the reaction tank by gravity flow.

[0046] (4) At the inlet of the reaction tank, add 17.2 g / L sodium ferrate and 11.26 g / L barium sulfite using a dosing pump. In the reaction tank, [Fe(VI):Boron] mol = 1:1, [Na2FeO4:BaSO3] mol =2:1; the boron-containing wastewater in the reaction tank undergoes catalytic oxidation, chemical precipitation, and coagulation reactions with the composite material of sodium ferrate and barium sulfite. The residence time of the boron-containing wastewater in the reaction tank is 1 hour.

[0047] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction. The reaction time is 30 min.

[0048] (6) The boron-containing wastewater after flocculation enters the sedimentation tank inlet by gravity flow, and the sedimentation time is 30 minutes. The boron concentration of the effluent at the drain outlet is measured. At this time, the boron concentration of the effluent is about 22 ppm, and the boron removal rate reaches more than 98%. The effluent is transported to the discharge tank for storage by a transfer pump.

[0049] (7) The sludge flow rate in the sedimentation tank is 12.86 m³ / s. 3The sludge is pumped to a sludge thickening tank via a screw pump at a rate of 6.43 m³ / h. The thickening tank uses a center-driven scraper, and the thickening time is 12 hours. 3 / h, at which point the sludge moisture content is 97%; the sludge produced in the sludge thickening tank is dewatered by a screw press for 8 hours, with a sludge flow rate of 0.43m³ / h. 3 / h, at which point the sludge moisture content is 55%;

[0050] (8) The effluent from the sludge treatment system is pumped back to the inlet of the pH adjustment tank for secondary treatment via a return pump. The return flow rate is 12.43 m³ / h. 3 / h, the effluent after secondary treatment is transported together with the effluent after primary treatment to the discharge tank for storage;

[0051] (9) Collect the sludge crystals after concentration and dehydration. The main components are barium metaborate and boron-containing crystals. Barium metaborate can be used for rust prevention and fire prevention, while boron-containing crystals can be used for strengthening glass. The resource recovery of boron in sludge can minimize the damage of boron to the environment.

[0052] Comparative Example 1

[0053] Boron-containing wastewater from a semiconductor factory in Wuxi: boric acid concentration 1120 ppm, chemical oxygen demand 850 ppm, pH 6.5, and volume 17 m³. 3 / h, runtime 24h.

[0054] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0055] (2) The boron-containing wastewater was treated at a concentration of 20m³. 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0056] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 6 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 6 enter the inlet of the reaction tank by gravity flow.

[0057] (4) Controlling [H2O2:Boron] in the reaction tank mol =1.4:1, [Ca 2+ :Boron] mol = 1.5:1, 4.93 g / L H2O2 was added through the H2O2 dosing pump, and 11.52 g / L Ca(OH)2 was added through the Ca(OH)2 dosing pump. The boron-containing wastewater came into full contact with H2O2 and Ca(OH)2 and underwent oxidation and precipitation reactions. The reaction time was 2 hours.

[0058] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction, and the reaction time is 30 min.

[0059] (6) The boron-containing wastewater after flocculation enters the sedimentation tank inlet by gravity flow, the sedimentation time is 30 minutes, and the boron concentration of the effluent at the drain outlet is measured. At this time, the boron concentration of the effluent is about 300 ppm, and the boron removal rate is about 67%. The effluent is transported to the discharge tank for storage by a transfer pump.

[0060] (7) The sludge flow rate in the sedimentation tank is 12.86 m³ / s. 3 The sludge is pumped to a sludge thickening tank via a screw pump at a rate of 6.43 m³ / h. The thickening tank uses a center-driven scraper, and the thickening time is 12 hours. 3 / h, at which point the sludge moisture content is 97%; the sludge produced in the sludge thickening tank is dewatered by a screw press for 8 hours, with a sludge flow rate of 0.43m³ / h. 3 / h, at which point the sludge moisture content is 55%;

[0061] (8) The effluent from the sludge treatment system is pumped back to the inlet of the pH adjustment tank for secondary treatment via a return pump. The return flow rate is 12.43 m³ / h. 3 / h, the effluent after secondary treatment is transported together with the effluent after primary treatment to the discharge tank for storage.

[0062] Comparative Example 2

[0063] The boron-containing wastewater from a specialty glass manufacturing plant in Shanghai has the following characteristics: boric acid concentration of 525 ppm, chemical oxygen demand of 350 ppm, pH of 6.4, and flow rate of 12 m³. 3 / h, runtime 24h.

[0064] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0065] (2) Boron-containing wastewater was treated at 15m 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0066] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 6 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 6 enter the inlet of the reaction tank by gravity flow.

[0067] (4) At the inlet of the reaction tank, add 12.09 g / L sodium ferrate and 5.28 g / L barium sulfite using a dosing pump. [Fe(VI):Boron] mol = 3:2, [Na2FeO4:BaSO3]mol =3:1; the boron-containing wastewater in the reaction tank undergoes catalytic oxidation, chemical precipitation, and coagulation reactions with the composite material of sodium ferrate and barium sulfite. The residence time of the boron-containing wastewater in the reaction tank is 1 hour.

[0068] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction. The reaction time is 30 min.

[0069] (6) The boron-containing wastewater after flocculation enters the sedimentation tank inlet by gravity flow. The sedimentation time is 30 minutes, and the boron concentration at the outlet is measured. At this time, the boron concentration in the effluent is about 20.5 ppm, and the boron removal rate is 96%, which is less than 98%. The effluent is transported to the discharge tank for storage by a transfer pump.

[0070] (7) Sludge flow rate in sedimentation tank: 4.25 m³ / h 3 The sludge is pumped to a sludge thickening tank via a screw pump at a rate of 2.13 m³ / h. The thickening tank uses a center-driven scraper, with a thickening time of 12 hours and a sludge flow rate of 2.13 m³ / h. 3 / h, at which point the sludge moisture content is 97%; the sludge produced in the sludge thickening tank is dewatered by a screw press for 8 hours, with a sludge flow rate of 0.14m³ / h. 3 / h, at which point the sludge moisture content is 55%;

[0071] (8) The effluent from the sludge treatment system is pumped back to the inlet of the pH adjustment tank for secondary treatment via a return pump. The return flow rate is 4.11 m³ / s. 3 / h, the effluent after secondary treatment is transported together with the effluent after primary treatment to the discharge tank for storage.

[0072] Comparative Example 3

[0073] The boron-containing wastewater from a specialty glass manufacturing plant in Shanghai has the following characteristics: boric acid concentration of 525 ppm, chemical oxygen demand of 350 ppm, pH of 6.4, and flow rate of 12 m³. 3 / h, runtime 24h.

[0074] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0075] (2) Boron-containing wastewater was treated at 15m 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0076] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 6 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 6 enter the inlet of the reaction tank by gravity flow.

[0077] (4) At the inlet of the reaction tank, add 8.06 g / L sodium ferrate and 7.92 g / L barium sulfite using a dosing pump. [Fe(VI):Boron] mol = 1:1, [Na2FeO4:BaSO3] mol =2:1.5; the boron-containing wastewater in the reaction tank undergoes catalytic oxidation, chemical precipitation, and coagulation reactions with the composite material of sodium ferrate and barium sulfite. The residence time of the boron-containing wastewater in the reaction tank is 1 hour.

[0078] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction. The reaction time is 30 min.

[0079] (6) The boron-containing wastewater after flocculation enters the sedimentation tank inlet by gravity flow. The sedimentation time is 30 minutes, and the boron concentration at the outlet is measured. At this time, the boron concentration in the effluent is about 25 ppm, and the boron removal rate is 95%, which is less than 98%. The effluent is transported to the discharge tank for storage by a transfer pump.

[0080] (7) Sludge flow rate in sedimentation tank: 4.25 m³ / h 3 The sludge is pumped to a sludge thickening tank via a screw pump at a rate of 2.13 m³ / h. The thickening tank uses a center-driven scraper, with a thickening time of 12 hours and a sludge flow rate of 2.13 m³ / h. 3 / h, at which point the sludge moisture content is 97%; the sludge produced in the sludge thickening tank is dewatered by a screw press for 8 hours, with a sludge flow rate of 0.14m³ / h. 3 / h, at which point the sludge moisture content is 55%;

[0081] (8) The effluent from the sludge treatment system is pumped back to the inlet of the pH adjustment tank for secondary treatment via a return pump. The return flow rate is 4.11 m³ / s. 3 / h, the effluent after secondary treatment is transported together with the effluent after primary treatment to the discharge tank for storage.

[0082] Comparative Example 4

[0083] The boron-containing wastewater from a specialty glass manufacturing plant in Shanghai has the following characteristics: boric acid concentration of 525 ppm, chemical oxygen demand of 350 ppm, pH of 6.4, and flow rate of 12 m³. 3 / h, runtime 24h.

[0084] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0085] (2) Boron-containing wastewater was treated at 15m 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0086] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 6 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 6 enter the inlet of the reaction tank by gravity flow.

[0087] (4) At the inlet of the reaction tank, add 16.12 g / L sodium ferrate and 10.55 g / L barium sulfite using a dosing pump. In the reaction tank, [Fe(VI):Boron] mol = 2:1, [Na2FeO4:BaSO3] mol =2:1; the boron-containing wastewater in the reaction tank undergoes catalytic oxidation, chemical precipitation, and coagulation reactions with the composite material of sodium ferrate and barium sulfite. The residence time of the boron-containing wastewater in the reaction tank is 1 hour.

[0088] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction. The reaction time is 30 min.

[0089] (6) The boron-containing wastewater after flocculation enters the sedimentation tank inlet by gravity flow. The sedimentation time is 30 minutes, and the boron concentration at the outlet is measured. At this time, the boron concentration in the effluent is about 32 ppm, and the boron removal rate is 93.9%, which is less than 98%. The effluent is transported to the discharge tank for storage by a transfer pump.

[0090] (7) Sludge flow rate in sedimentation tank: 4.25 m³ / h 3 The sludge is pumped to a sludge thickening tank via a screw pump at a rate of 2.13 m³ / h. The thickening tank uses a center-driven scraper, with a thickening time of 12 hours and a sludge flow rate of 2.13 m³ / h. 3 / h, at which point the sludge moisture content is 97%; the sludge produced in the sludge thickening tank is dewatered by a screw press for 8 hours, with a sludge flow rate of 0.14m³ / h. 3 / h, at which point the sludge moisture content is 55%;

[0091] (8) The effluent from the sludge treatment system is pumped back to the inlet of the pH adjustment tank for secondary treatment via a return pump. The return flow rate is 4.11 m³ / s. 3 / h, the effluent after secondary treatment is transported together with the effluent after primary treatment to the discharge tank for storage.

[0092] Comparative Example 5

[0093] The boron-containing wastewater from a specialty glass manufacturing plant in Shanghai has the following characteristics: boric acid concentration of 525 ppm, chemical oxygen demand of 350 ppm, pH of 6.4, and flow rate of 12 m³. 3 / h, runtime 24h.

[0094] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0095] (2) Boron-containing wastewater was treated at 15m 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0096] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 5 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 5 enter the inlet of the reaction tank by gravity flow.

[0097] (4) Add 8.06 g / L sodium ferrate and 5.28 g / L barium sulfite at the inlet of the reaction tank using a dosing pump. [Fe(VI):Boron] mol = 1:1, [Na2FeO4:BaSO3] mol =2:1; the boron-containing wastewater in the reaction tank undergoes catalytic oxidation, chemical precipitation, and coagulation reactions with the composite material of sodium ferrate and barium sulfite. The residence time of the boron-containing wastewater in the reaction tank is 1 hour.

[0098] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction. The reaction time is 30 min.

[0099] (6) The boron-containing wastewater after flocculation enters the inlet of the sedimentation tank by gravity flow. The sedimentation time is 30 minutes, and the boron concentration at the outlet is measured. At this time, the boron concentration in the effluent is about 15 ppm, and the boron removal rate is 97%, which is less than 98%. The wastewater in the sedimentation tank needs to be transported to the inlet of the pH adjustment tank by a return pump. The transport flow rate is 75% of the original water flow rate. The effluent after secondary treatment of the return water is transported together with the effluent after primary treatment to the discharge tank for storage.

[0100] Comparative Example 6

[0101] The boron-containing wastewater from a specialty glass manufacturing plant in Shanghai has the following characteristics: boric acid concentration of 525 ppm, chemical oxygen demand of 350 ppm, pH of 6.4, and flow rate of 12 m³. 3 / h, runtime 24h.

[0102] (1) At room temperature, the boron-containing wastewater is collected through the raw water pipe and stored in the wastewater collection tank, and the water quality and quantity are uniformly mixed by the stirring device to reduce the shock load;

[0103] (2) Boron-containing wastewater was treated at 15m 3 A transfer pump with a flow rate of / h transports the contents to the inlet of the pH adjustment tank.

[0104] (3) Add acid and alkali at the inlet of the pH adjustment tank to adjust the pH of the boron-containing wastewater to 6 by adding sulfuric acid dosing pump and liquid alkali dosing pump, and let the boron-containing wastewater with pH 6 enter the inlet of the reaction tank by gravity flow.

[0105] (4) At the inlet of the reaction tank, add 8.06 g / L of commercially available sodium ferrate (99% purity) purchased from a biotechnology company in Hubei Province and 5.28 g / L of barium sulfite via a dosing pump. In the reaction tank,

[0106] [Fe(VI):Boron] mol = 1:1, [Na2FeO4:BaSO3] mol =2:1; the boron-containing wastewater in the reaction tank undergoes catalytic oxidation, chemical precipitation, and coagulation reactions with the composite material of sodium ferrate and barium sulfite. The residence time of the boron-containing wastewater in the reaction tank is 1 hour.

[0107] (5) The boron-containing wastewater after the reaction enters the inlet of the flocculation tank by gravity flow. 2 ppm PAM is added at the inlet of the flocculation tank by a dosing pump to carry out the flocculation reaction. The reaction time is 30 min.

[0108] (6) The boron-containing wastewater after flocculation enters the inlet of the sedimentation tank by gravity flow. The sedimentation time is 30 minutes, and the boron concentration at the outlet is measured. At this time, the boron concentration in the effluent is about 25 ppm, and the boron removal rate is 95%, which is less than 98%. The wastewater in the sedimentation tank needs to be transported to the inlet of the pH adjustment tank by a return pump. The transport flow rate is 75% of the original water flow rate. The effluent after secondary treatment of the return water is transported together with the effluent after primary treatment to the discharge tank for storage.

Claims

1. An industrial boron-containing wastewater treatment method, characterized by, The treatment method is performed by using a treatment system, the treatment system comprising a pH adjusting tank, a reaction tank, a flocculation tank and a sedimentation tank connected in sequence; the sedimentation tank is connected with two drainage pipes, one of which is connected with a back-end discharge tank, and the other is connected with the inlet of the pH adjusting tank; the sludge discharge port of the sedimentation tank is connected with a sludge treatment system; the sludge treatment system comprises a sludge concentration tank and a sludge dewatering area; the effluent produced by the sludge treatment system is transported to the inlet of the pH adjusting tank by a backflow pump; The treatment method comprises the following steps: (1) the boron-containing wastewater with pH 6 in the pH adjusting tank flows into the reaction tank, and sodium ferrate and barium sulfite are simultaneously added into the reaction tank; wherein the molar ratio of Na2FeO4 and BaSO3 is 2:1, and the molar ratio of Fe(VI) and boron is 1:1; the reaction liquid flows into the flocculation tank by itself; (2) in the flocculation tank, a flocculant is added into the flocculation tank for flocculation reaction, and after sufficient flocculation, the flocculation tank enters the sedimentation tank; (3) after the sedimentation tank is precipitated for not less than 30 min, the concentration of boron in the water at the drainage port of the sedimentation tank is determined, if the boron removal rate reaches 98% or above, it is directly discharged to the back-end discharge tank; if the boron removal rate is less than 98%, it is backflowed to the inlet of the pH adjusting tank by a backflow pump for reprocessing; wherein the sodium ferrate is prepared by an electrochemical method, specifically: the anode of the electrolytic cell uses an iron electrode with an iron content of 96%, the anode chamber electrolyte is a NaOH solution with a concentration of 16 mol / L, the cathode uses a copper electrode, the cathode chamber electrolyte is a NaOH solution with a concentration of 1 mol / L, the external voltage is 30 V, and the electrolysis time is 80 min; after electrolysis, the anode chamber obtains a sodium ferrate solution with a concentration of 35 g / L; the obtained sodium ferrate solution is taken out and placed in a beaker, the beaker is placed in an ice water bath, and sodium hydroxide solid is slowly added into the sodium ferrate solution at a concentration of 20 g / L, and the beaker is continuously stirred in the ice water bath for 2 h until crystals are precipitated, and then filtered, frozen and dried for 24 h to obtain Na2FeO4 crystals.

2. The industrial boron-containing wastewater treatment method according to claim 1, characterized by: The pH adjusting tank is provided with a pH sensor, and the pH adjusting tank is also provided with a sulfuric acid dosing pump or a liquid alkali dosing pump. The pH sensor collects the pH value of the boron-containing wastewater in the pH adjusting tank in real time. When the pH sensor detects that the pH of the boron-containing wastewater is higher than 6 or lower than 6, the pH value of the boron-containing wastewater in the pH adjusting tank is adjusted by the sulfuric acid dosing pump or the liquid alkali dosing pump until the pH of the boron-containing wastewater is 6.

3. The industrial boron-containing wastewater treatment method according to claim 1, characterized by: In step (1), the residence time of the boron-containing wastewater in the reaction tank is 1 h.

4. The industrial boron-containing wastewater treatment method according to claim 1, characterized by: In step (2), the flocculant is PAM, and the concentration of PAM in the flocculation tank is 2 ppm.

5. The industrial boron-containing wastewater treatment method of claim 1, wherein: In step (2), the flocculation time is not less than 30 min.

6. The industrial boron-containing wastewater treatment method of claim 1, wherein: In step (3), the delivery flow rate of the backflow pump is 75% of the original water flow rate into the pH adjusting tank.

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