Chromium removal reaction device for chromium-containing wastewater treatment of textile printing and dyeing wastewater

Abstract

The utility model provides a chromium removal reaction device for treating chromium-containing wastewater such as textile printing and dyeing wastewater. The chromium removal reaction device comprises an acidification tank, a reduction filtering tank, a precipitation reaction tank, a flocculation tank, a communication area and a precipitation tank which are sequentially connected and communicated. According to the utility model, the filter material of the reducing agent is stored in the filter material filling frame of the reducing filter tank for filling, and the hoisting tool is arranged at the top of the reducing filter tank, so that the filter material is convenient to replace, the time required for replacing the filter material is reduced, the labor is saved, and the building is convenient. Filtered filtrate returns to the water inlet area through the circulating pump and enters the reduction filter layer of the filter material area again, and part of ferrous ions in the filtrate can be recycled, so that excessive reducing power is prevented from entering a subsequent precipitation reaction tank to cause waste; the circulating pump also provides a regulation and control means for reducing and filtering operation, and the reduction reaction rate of the reducing and filtering tank is changed by regulating the reflux quantity; the reaction liquid is circulated, so that the flow speed of the reduction filter layer is increased, and the filter layer is not easy to block.

Description

Technical Field

[0001] The utility model relates to the technical field of chromium-containing wastewater treatment, in particular to a chromium removal reaction device for treating chromium-containing textile printing and dyeing wastewater. Background Art

[0002] Chromium is a transition metal element primarily used in the industrial production of stainless steel and other metal materials, as well as in electroplating. Chromium compounds are also commonly used as catalysts, grinding agents, colorants, leather softeners, and fabric mordants. Therefore, wastewater and waste residues associated with the production and use of these products often contain high concentrations of chromium. Chromium exists primarily in trivalent and hexavalent forms. Trivalent chromium is relatively stable in the environment and readily reacts with alkali to form insoluble Cr(OH)3, which is essentially non-toxic or has very low toxicity. Hexavalent chromium, on the other hand, is highly toxic and a typical carcinogen and mutagen. It is also highly mobile and easily migrates through the environment, posing a significant threat to the environment.

[0003] The country has established corresponding emission standards for various types of chromium-containing wastewater. For example, for tanning wastewater, the national standard GB30486-2013, "Emission Standard of Water Pollutants for Leather and Fur Processing Industries," stipulates that the total chromium concentration in wastewater discharged from workshops or production facilities shall not exceed 1.5 mg / L, and the hexavalent chromium concentration shall not exceed 0.1 mg / L. The special emission limits for water pollutants also stipulate that the total chromium concentration in wastewater discharged from workshops or production facilities shall not exceed 0.5 mg / L, and the hexavalent chromium concentration shall be below 0.05 mg / L. With the increasing demand for environmental protection, the treatment of chromium-containing wastewater has become more demanding.

[0004] The existing chromium-containing wastewater treatment processes are mainly as follows:

[0005] 1. Chemical reduction precipitation method, that is, adding reducing agent to chromium-containing wastewater under acidic conditions to reduce Cr 6+ Reduction to Cr 3 + , and then add slaked lime or sodium hydroxide to generate chromium hydroxide Cr(0H)3 precipitation under alkaline conditions to remove chromium.

[0006] 2. Electrolytic reduction method: the chromium-containing wastewater is passed into the electrolytic cell, and the Cr 6+ Reduction to Cr 3 + , and Cr 3+ It is precipitated as hydroxide Cr(OH)3.

[0007] 3. Adsorption analysis method, which uses special adsorbents to adsorb chromium ions in wastewater.

[0008] 4. Ion exchange method, that is, using ion exchange resin to remove Cr from wastewater 6+Selective adsorption is carried out to achieve the purpose of chromium removal.

[0009] CN2208883607U discloses a chromium removal system for electroplating wastewater, comprising a chromium-containing wastewater regulating tank, a chromium reaction tank, and a chromium precipitation tank, all interconnected by pipelines. The chromium reaction tank utilizes a three-tank structure, with acid and reducing agent, alkali solution, and flocculant added separately. This utility model combines chemical reduction, chemical precipitation, chemical flocculation, and precipitation to enhance chromium removal. CN211471070U discloses a treatment device for chromium-containing electroplating wastewater, comprising a first reaction chamber, a second reaction chamber, and a precipitation tank. Sodium metabisulfite and ferrous sulfate are added separately, pH is adjusted, and chromium is removed through co-precipitation. CN117466485A relates to a chromium-containing wastewater treatment system, comprising a reduction unit, a neutralization unit, a flocculation unit, and a filtration unit. The reduction unit is used to reduce hexavalent chromium in the wastewater to trivalent chromium, using sodium sulfite as the reducing agent. The neutralization unit is used to adjust the wastewater pH, the flocculation unit is used to agglomerate particulate matter in the wastewater, and the filtration unit is used to filter out precipitates. Through the coordinated action of these units, the chromium ions in the wastewater are fully reacted to form trivalent chromium ion precipitates, which are then removed by filtration. CN112499825B discloses a triple treatment method for chromium-containing wastewater. The method first uses modified coal ash to adsorb chromium in the wastewater; then uses ferrous salts to reduce high-valent chromium to low-valent chromium, which is then precipitated; and finally, adds barium salts to remove residual chromium through a precipitation reaction between barium ions and chromium ions. Each step specifically removes different concentrations of chromium. The above Chinese patents all use chemical reduction methods for chromium removal, and use soluble reducing agents in the reduction step. However, these reaction systems use completely mixed reaction tanks, and the reducing agent needs to be added continuously. The amount added is difficult to adjust in time according to changes in water quality, and the treatment effect is bound to fluctuate.

[0010] CN101519241B discloses a method for reducing hexavalent chromium in wastewater using dewatered sludge from a sewage treatment plant as a reducing agent. The dewatered sludge from the sewage treatment plant is dried and crushed, and then protonated with a 0.1 mol / L hydrochloric acid or sulfuric acid solution to produce a reducing agent. This sludge reducing agent reacts with wastewater to reduce the hexavalent chromium in the wastewater to trivalent chromium. This utility model addresses the high cost and secondary pollution issues of traditional chemical reducing agents by using dewatered sludge from sewage treatment plants as a reducing agent, leveraging the reducing power of organic matter in the sludge to reduce hexavalent chromium in the wastewater. This method offers the advantages of low cost, wide availability, simple equipment, and minimal secondary pollution, making it highly practical and enabling waste treatment with waste. However, this method requires a large amount of sludge, and its reduction effect is inferior to that of traditional reducing agents. Furthermore, the introduction of sludge introduces other inorganic and organic pollutants into the wastewater.

[0011] CN104150651B provides a method for removing hexavalent chromium from water by chemical reduction assisted electrochemical method, comprising adding a reducing agent (selected from Na2S205, Na2S03, NaHS03 or FeS04) to raw water with a pH value of 2-4 to carry out a chemical reduction reaction, so that part of the Cr 6+ Reduction to Cr 3+ , and then enters the electrochemical reactor with iron as the electrode material to undergo electrochemical reaction, so that the remaining Cr 6+ Reduction to Cr 3+ , while the pH value of water increases, Cr 3+ It is converted into Cr(OH)3, and then passed through a solid-liquid separation unit and a sand filtration unit to remove hexavalent chromium from the water. CN117326759A relates to a method for treating electroplating chromium-containing wastewater. After adjusting the pH value of the chromium-containing wastewater to 0-4, a first electrolytic reduction reaction and a first chemical reduction reaction are performed, followed by a second chemical reduction reaction, and then flocculation and sedimentation. By combining electrolytic reduction and chemical reduction, hexavalent chromium can be efficiently removed from electroplating chromium-containing wastewater with less reducing substances, avoiding the generation of secondary pollution. CN 214781255 discloses a device for recovering heavy metal chromium from tanning wastewater. After the chemical precipitation reaction, the filtrate enters a filter press for solid-liquid separation. The filtrate enters an electrolytic device for reaction with an aging stirring tank, and then enters a second filter press for filtration. This utility model device has a high chromium recovery rate, low effluent chroma, and low reagent consumption. The chromium removal units described in these patents all incorporate electrochemical chromium removal, which consumes significant current and requires frequent electrode lubrication, making operation more complex. Furthermore, the use of iron-based electrodes produces a large amount of ferric hydroxide (Fe(OH)3) precipitate, which has low utility value. Dehydration using a filter press can only be performed intermittently, not continuously.

[0012] CN 219058624 U and CN 218435417 disclose an integrated chromium-containing wastewater treatment and chromium resource recovery system. The system includes a chromium-containing wastewater regulating tank, a wastewater lift pump, a multi-media filter, and a two-stage high-efficiency chromium removal exchanger, thereby deeply removing hexavalent chromium and trivalent chromium from the wastewater. The regeneration subsystem includes a device for eluting and regenerating the first and second ion exchange columns in the high-efficiency chromium removal exchanger, as well as a device for collecting and storing the regenerated liquid containing hexavalent chromium obtained during elution and regeneration. The recycling subsystem includes a device for recycling the regenerated liquid containing hexavalent chromium, and a sequentially connected sodium removal ion exchange column, an evaporation and concentration device, a barium sulfate reaction device, and a chromium plating tank. This system is relatively complex in composition. While it can reduce chromium environmental pollution and utilize chromium sludge, the processing cost is high.

[0013] As can be seen from this, currently disclosed industrial wastewater chromium removal systems mostly use chemical reduction precipitation, electrochemical reduction, and ion exchange, or a combination of these methods. The chemical reduction reaction uses a soluble salt reducing agent such as sodium metabisulfite, sodium sulfite, sodium bisulfite, or ferrous sulfate to reduce hexavalent chromium to trivalent chromium under acidic conditions, which is then removed by reacting with an alkali to form a chromium hydroxide precipitate. The chemical reduction reaction requires a relatively low pH acidic condition (generally in the pH range of 0-4), and the addition of the reducing agent also introduces sodium ions and sulfate ions, thereby increasing the salt concentration in the effluent. These methods are based on chemical reaction formulas, so when the chromium concentration in the wastewater changes, it is difficult to adjust the amount of reducing agent added in a timely manner. CN 101519241B uses protonated sludge as a reducing agent, which has the advantage of low reducing agent cost. However, using sludge as a reducing agent will inevitably add new organic and inorganic pollutants to the wastewater, increasing the burden and difficulty of subsequent treatment. The electrochemical reduction method uses an iron-based positive electrode to generate reducing power in water, thereby reducing hexavalent chromium. However, due to the relatively small specific surface area of ​​the electrode, part of the electrical energy will be consumed in the electrolysis of water, resulting in a large amount of electrical energy consumption. At the same time, the consumed positive electrode needs to be replaced frequently, which is troublesome. This method also produces a large amount of iron hydroxide Fe(0H)3 in the precipitate, which has low utilization value. The ion exchange method uses cationic exchange resin to perform ion exchange reaction on free chromium ions. However, after the resin exchange capacity is saturated, the resin needs to be regenerated, which requires the consumption of strong alkali and is more troublesome to operate. Utility Model Content

[0014] The purpose of the utility model is to provide a chromium removal reaction device which is easy to operate, low in operating cost and reliable in operation, so as to overcome the shortcomings of the prior art.

[0015] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0016] A chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater comprises an acidification tank, a reduction filtration tank, a precipitation reaction tank, a flocculation tank, a communication zone and a sedimentation tank which are connected and communicated with each other in sequence; an agitator is provided in each of the acidification tank, the precipitation reaction tank and the flocculation tank; a water inlet pipe and an acid addition pipe are connected to the acidification tank; a filter material is provided in the reduction filtration tank; an alkali addition pipe and a coagulant pipe are connected to the precipitation reaction tank; a flocculant pipe is connected to the flocculation tank; the flocculation tank is connected to the sedimentation tank via the communication zone; a water inlet zone, a water outlet zone and a sedimentation zone are provided in the sedimentation tank; the water outlet zone is located above the water inlet zone and is connected to the water outlet pipe for discharging clear liquid; the sedimentation zone is located between the water outlet zone and the water inlet zone and is used for settling flocs; a mud discharge port is provided at the bottom of the water inlet zone, and the mud discharge port discharges sludge via a mud discharge pipe through a mud discharge pump.

[0017] Preferably, a filter material filling frame is provided in the reduction filtration tank via a filter material supporting bracket, and the filter material is filled in the filter material filling frame.

[0018] Preferably, a filter material filling frame hoisting device is provided above the reduction filtration tank, and the filter material filling frame hoisting device is used to hoist the filter material filling frame for easy installation and replacement.

[0019] Preferably, the reduction filtration tank comprises, from top to bottom, a post-filtration zone, a filter material zone, and a water inlet zone, the post-filtration zone being above the filter material zone, and the water inlet zone being below the filter material zone;

[0020] The filter material filling frame is arranged in the filter material area; the post-filtration area is provided with a reduction filter pool outlet channel, and a circulation pump is provided on the top of the reduction filter pool. The post-filtration area above the filter material filling frame in the reduction filter pool is connected to the water inlet area below the filter material filling frame through the circulation pump inlet pipe and the circulation pump outlet pipe.

[0021] Preferably, an outlet channel is provided in the outlet area of ​​the sedimentation tank, and the outlet channel is connected to the outlet pipe for guiding the clean water in the outlet area to be discharged from the outlet pipe.

[0022] Preferably, the sedimentation area of ​​the sedimentation tank includes a plurality of sedimentation inclined tubes laid between the water outlet area and the water inlet area, and the wastewater with flocs enters the plurality of sedimentation inclined tubes through the water inlet area to precipitate the flocs.

[0023] Preferably, a scraper is provided at the bottom of the sedimentation tank, and the scraper is externally connected to a driving mechanism for scraping the mud deposited at the bottom of the sedimentation tank.

[0024] Preferably, a sludge hopper with an inverted cone or columnar structure is provided at the bottom center of the water inlet area of ​​the sedimentation tank, and the sludge discharge port is provided at the bottom of the sludge hopper, through which sludge is collected centrally.

[0025] Preferably, pH probes are provided in the acidification tank and the precipitation reaction tank for detecting the pH values ​​in the acidification tank and the precipitation reaction tank respectively.

[0026] Preferably, the acidification tank, reduction filtration tank, sedimentation reaction tank, flocculation tank and communication area are separated by partition walls, and a No. 1 communication hole with a gate valve for communication is provided between the acidification tank and the reduction filtration tank; a No. 2 communication hole for communication is provided between the reduction filtration tank and the sedimentation reaction tank; a No. 3 communication hole for communication is provided between the sedimentation reaction tank and the flocculation tank, and a No. 4 communication hole for communication is provided between the flocculation tank and the communication area.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The utility model stores the filter material of the reducing agent in a filling frame for filling, and installs a lifting device on the top of the reduction filter tank, which can facilitate the replacement of the filter material, reduce the time required for replacing the filter material, and save labor.

[0029] (2) The utility model uses a circulation pump to allow the filtered filtrate to return to the water inlet area and re-enter the reduction filter layer in the filter material area, so that a part of the divalent iron ions in the filtrate can be reused, preventing excessive reducing power from entering the subsequent precipitation reaction tank and causing waste; the addition of a circulation pump also increases the means of regulating the reduction filtration operation, and by adjusting the reflux volume, the reduction reaction rate of the reduction filter tank can be changed; in addition, the circulation of the reaction liquid can also increase the flow rate through the reduction filter layer, and the filter layer is less likely to be blocked.

[0030] (3) The utility model adopts an integrated combined pool structure, which can save the floor space of the treatment structure.

[0031] (4) The utility model can provide an efficient, reliable and economical chromium removal treatment device for the discharge treatment of chromium-containing wastewater to meet the discharge standards.

[0032] In summary, the utility model can be used as a pretreatment device for wastewater to effectively remove the chromium contained therein, providing conditions for subsequent treatment steps such as biochemical treatment. It can also be used to remove chromium alone, so that the concentrations of total chromium and hexavalent chromium are lower than 1.5 mg / L and 0.15 mg / L, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic structural diagram of a chromium removal reaction device for treating chromium-containing wastewater in textile printing and dyeing wastewater provided in an embodiment of the present utility model;

[0034] Figure 2 for Figure 1 Schematic diagram of the structure of the filter material filling frame.

[0035] The serial numbers in the figure are as follows:

[0036] 1. Acidification tank; 2. Reduction filter tank; 201. Filter media support bracket; 202. Filter media filling frame; 2021. Filter media filling frame side wall; 2022. Filter media filling frame bottom mesh plate; 2023. Filter media filling frame top reinforcement rib; 2024. Filter media filling frame bottom reinforcement rib; 203. Filter media; 204. Reduction filter tank outlet channel; 3. Sedimentation reaction tank; 4. Flocculation tank; 5. Sedimentation tank; 501. Inlet perforated wall; 502. Inlet area; 503. Outlet area; 504. Outlet channel; 505. Sedimentation inclined pipe; 506. Sludge scraper; 507. Sludge hopper; 6. Connecting area; 7. , agitator; 8. Circulating pump; 801 Circulating pump inlet pipe; 802 Circulating pump outlet pipe; 9. Filter material filling frame lifting equipment; 901. Gantry column; 902. Gantry beam; 903. Pulley; 904. Electric hoist; 905. Hook; 906. Cable; 10. pH probe; 11. Water inlet pipe; 12. Connecting hole No. 1; 1201. Gate valve; 13. Connecting hole No. 2; 14. Connecting hole No. 3; 15. Connecting hole No. 4; 16. Water outlet pipe; 17. Mud discharge port; 18. Acid addition pipe; 19. Alkali addition pipe; 20. Coagulant pipe; 21. Flocculant pipe. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0038] like Figure 1 As shown, a chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater disclosed in the present invention comprises an acidification tank 1, a reduction filtration tank 2, a precipitation reaction tank 3, a flocculation tank 4, a communication area 6 and a sedimentation tank 5 which are sequentially connected and communicated.

[0039] The acidification tank 1, the reduction filtration tank 2, the sedimentation reaction tank 3, the flocculation tank 4 and the connecting area 6 are separated by a partition wall, and a No. 1 connecting hole 12 with a gate valve 1201 for connecting is provided between the acidification tank 1 and the reduction filtration tank 2, which is used to connect the acidification tank 1 and the reduction filtration tank 2; a No. 2 connecting hole 13 is provided between the reduction filtration tank 2 and the sedimentation reaction tank 3, which is used to connect the reduction filtration tank 2 and the sedimentation reaction tank 3; a No. 3 connecting hole 14 is provided between the sedimentation reaction tank 3 and the flocculation tank 4, which is used to connect the sedimentation reaction tank 3 and the flocculation tank 4; a No. 4 connecting hole 15 is provided between the flocculation tank 4 and the connecting area 6, which is used to connect the flocculation tank 4 and the connecting area 6.

[0040] Agitators 7 are provided in the acidification tank 1 , the sedimentation reaction tank 3 and the flocculation tank 4 .

[0041] Acidification tank 1 is connected to a water inlet pipe 11 and an acid addition pipe 18. The function of the acidification tank 1 is to adjust the pH to an acidic range of 1-5, with an optimal pH of 2-4. The reaction time is 10-20 minutes. This allows the colloid or organic components to be protonated under acidic conditions, changing their surface electrical properties and thus releasing chromium ions. The acidic pH also facilitates the subsequent reduction reaction.

[0042] The function of the reduction filter tank 2 is to reduce the hexavalent chromium in the wastewater to trivalent chromium. The residence time in the filter layer is 0.5-2 hours. In this embodiment, an iron-based reduction filter material is used as a reducing agent. Since the reduced iron can lose electrons under acidic conditions, the electrons can be transferred to the hexavalent chromium, reducing it to trivalent chromium. Figure 2 As shown, a filter material filling frame 202 is provided in the reduction filter pool 2 through a filter material supporting bracket 201 , and the filter material filling frame 202 is filled with filter material 203 serving as a reducing agent.

[0043] In this embodiment, the filter media filling frame 202 is formed by a rectangular frame comprising four filter media filling frame side walls 2021. The bottoms of the four filter media filling frame side walls 2021 are connected to the filter media filling frame bottom mesh plate 2022. Furthermore, cross-structured filter media filling frame top reinforcement ribs 2023 and filter media filling frame bottom reinforcement ribs 2024 are respectively installed at the top and bottom of the filter media filling frame side walls 2021. Granular iron-based reducing filter media is used as a reducing agent in a two-phase reaction system to undergo a reduction reaction, and the filter media 203 is stored within the filling frame. Compared to existing methods that use salt reducing agents, this method eliminates the need for continuous addition of reducing agent, resulting in reduced reducing agent usage, convenient filter media replacement, low increased salt concentration, good removal efficiency, and low processing costs.

[0044] Furthermore, in this embodiment, the reducing power of the iron-based reducing filter material will gradually be consumed over time. At this time, a filter material filling frame hoisting device 9 is provided above the reduction filter tank 2. The filter material filling frame hoisting device 9 is used to hoist the filter material filling frame 202, which can facilitate the hoisting and replacement of the filter material filling frame 202.

[0045] The filter material loading frame hoisting equipment 9 includes a gantry column 901, a gantry beam 902, a pulley 903, an electric hoist 904, a hook 905, and a cable 906. The two gantry columns 901 are connected by the gantry beam 902. The electric hoist 904 is movably mounted on the gantry beam 902 and connected to the hook 905 via a cable 906. The electric hoist 904 drives the cable 906 to hoist the filter material loading frame 202 via the hook 905.

[0046] The bottoms of the two gantry columns 901 are connected to pulleys 903 with brakes, so as to facilitate the horizontal movement of the filter material filling frame hoisting device 9.

[0047] Furthermore, in this embodiment, the reduction filter tank 2 is divided into a post-filtration area, a filter material area and a water inlet area. The area above the filter material area is the post-filtration area, and the area below the filter material area is the water inlet area.

[0048] Above the filter material loading frame 202 is the post-filtration area, which is provided with a reduction filter tank outlet channel 204. A circulation pump 8 is provided at the top of the reduction filter tank 2. The post-filtration area above the filter material loading frame 202 in the reduction filter tank 2 is connected to the water inlet area below the filter material loading frame 202 via a circulation pump inlet pipe 801, a circulation pump 8, and a circulation pump outlet pipe 802. The filtered filtrate is returned to the water inlet area by the circulation pump 8 and re-enters the reduction filter layer of the filter material area. In this way, a portion of the divalent iron ions in the filtrate can be reused, preventing excessive reducing power from entering the subsequent precipitation reaction tank and causing waste. The addition of the circulation pump 8 also increases the means of regulating the reduction filtration operation. By adjusting the reflux rate, the reduction reaction rate of the reduction filter tank 2 can be changed. In addition, the circulation of the reaction liquid can also increase the flow rate through the reduction filter layer, making the filter layer less prone to clogging.

[0049] The precipitation reaction tank 3 primarily allows the trivalent chromium formed by the reduction reaction to react with alkali under alkaline conditions to form a Cr(OH)3 precipitate. This precipitate then undergoes a coagulation reaction under the action of a coagulant to form a coagulant. The residence time in the precipitation reaction tank is 5-15 minutes. An alkali addition tube 19 and a coagulant tube 20 are connected to the precipitation reaction tank 3. Furthermore, in this embodiment, pH probes 10 are installed in both the acidification tank 1 and the precipitation reaction tank 3 to monitor the pH values ​​therein, respectively.

[0050] The primary function of flocculation tank 4 is to allow the coagulants formed in the sedimentation tank to flocculate under the action of a flocculant, producing larger flocs that facilitate better sedimentation in the subsequent sedimentation tank. The retention time in the flocculation tank is 5-15 minutes. A flocculant tube 21 is connected to flocculation tank 4, which is connected to sedimentation tank 5 via a connecting area 6. The primary function of sedimentation tank 5 is to allow the flocs to settle.

[0051] The sedimentation tank 5 is provided with an inlet area 502, an outlet area 503 and a sedimentation area; the outlet area 503 is located above the inlet area 502 and is connected to the outlet pipe 16 for discharging clear liquid; the sedimentation area is located between the outlet area 503 and the inlet area 502, and a number of sedimentation inclined pipes 505 are laid in the sedimentation area. The wastewater with flocs enters the sedimentation inclined pipes 505 through the inlet area 502 to precipitate the flocs.

[0052] A sludge hopper 507 with an inverted cone or columnar structure is provided at the central bottom of the water inlet area 502, and a sludge discharge port 17 is provided at the bottom of the sludge hopper 507. Sludge is collected by the sludge hopper 507 and then discharged from the sludge discharge port 17 through a sludge discharge pipe by a sludge discharge pump.

[0053] Furthermore, in this embodiment, an outlet channel 504 is provided in the outlet area 503 of the sedimentation tank 5 . The outlet channel 504 is connected to the outlet pipe 16 and is used to guide the clean water in the outlet area 503 to be discharged from the outlet pipe 16 .

[0054] Furthermore, in this embodiment, a scraper 506 is provided at the bottom of the sedimentation tank 5 . The scraper 506 is externally connected to a driving mechanism and is used to scrape the mud deposited at the bottom of the sedimentation tank 5 .

[0055] Furthermore, in this embodiment, the stirrer 7 is vertically arranged, and the stirrer 7 includes a stirring rod and stirring blades. One end of the stirring rod is connected to an external driving unit through a gearbox; the stirring blades are symmetrically arranged as a group of stirring paddles.

[0056] An embodiment of the present invention is as follows:

[0057] The flow rate of chromium-containing wastewater discharged from a metal complex dye workshop is 15m 3 / h, the total chromium concentration is 56 mg / L. After treatment, the total chromium concentration needs to be reduced to below 1.5 mg / L.

[0058] The chromium-containing wastewater first enters the acidification tank 1 through the water inlet pipe 11. Under the action of the agitator 7, it mixes and reacts with sulfuric acid added from the acid addition pipe 18. The addition of sulfuric acid is controlled by pH. The pH of the wastewater in the acidification tank 1 is monitored using a pH probe 10 to maintain the pH within the range of 2.5-3.5. Here, the wastewater is retained for 15 minutes. The surface electrical properties of the colloid in the wastewater are changed, causing the chromium ions to be released. The wastewater then enters the water inlet area below the filter media area of ​​the reduction filter tank 2 through the No. 1 connecting hole 12 and its gate valve 1201 on the partition wall between the acidification tank 1 and the reduction filter tank 2. It then passes through the filler support bracket 201 and the filter media area to enter the post-filtration area above the filter media and enter the outlet channel 204. In the reduction filter tank 2, the wastewater remains for 1 hour. The hexavalent chromium in the wastewater receives electrons released from the filter media and is reduced to trivalent chromium. At this time, the pH of the wastewater rises to 3.0-4.0.

[0059] The circulation flow of the circulation pump 8 accounts for 50% of the wastewater inlet flow; the wastewater entering the outlet channel 204 enters the precipitation reaction tank 3 through the second connecting hole 13; in the precipitation reaction tank 3, the wastewater stays for 10 minutes, and the trivalent chromium in the wastewater reacts with the sodium hydroxide lye added through the alkali addition pipe 19 to form a chromium hydroxide precipitate, which then undergoes a coagulation reaction with the polyaluminum chloride added through the coagulant pipe 20 to form a coagulant. The agitator 7 provides power to cause the reaction liquid to undergo a mixing reaction; the reacted mixed liquid then enters the flocculation tank 4 through the third connecting hole 14, and the mixed liquid in the flocculation tank 4 undergoes a flocculation reaction with the flocculant polyacrylamide (PAM) added through the flocculant pipe 21. The stirring paddle 7 provides power for the flocculation reaction. Under the action of PAM, the coagulants in the mixed liquor gradually aggregate into larger, more easily precipitated flocs. The wastewater remains in flocculation tank 4 for 10 minutes, after which the reaction mixture enters communication zone 6 through connecting hole 15. In communication zone 6, the reaction mixture passes through perforated wall 501 of sedimentation tank 5 and enters inlet zone 502 of the sedimentation tank. It then passes through inclined sedimentation pipe 505 into outlet zone 503, and then into outlet channel 504, before entering outlet pipe 16 for discharge or further treatment. Accumulated sludge deposited in inclined pipe 505 slides to the bottom of the sedimentation tank. Sludge scraper 506 directs the sludge into sludge hopper 507 in the middle of the tank bottom and is discharged through sludge outlet 17 for dewatering. Through the above wastewater treatment device, the chromium in the chromium-containing wastewater is converted into Cr(OH)3 precipitate, which enters the precipitated sludge and is removed. The total chromium concentration in the sedimentation tank effluent reaches 1.3 mg / L.

[0060] After running for a period of time, when the reduction effect of the reduction filter material deteriorates and the total chromium concentration of the effluent increases significantly, it indicates that the reduction filter material needs to be replaced. At this time, stop the water intake, close the gate valve 1201 on the No. 1 connecting hole 12, and use a temporary water pump to evacuate the wastewater in the reduction filter pool 2 until the filter material 203 of the reducing agent is exposed to the water surface. Use the filter material filling frame hoisting equipment 9 on the top of the reduction filter pool 2 to lift the filter material filling frames 202 one by one and move them to the surrounding open space to replace the filter material 203. Then move the filter material filling frames 202 filled with new filter material 203 back to their original places one by one for stacking. After completing the filter material replacement operation, open the gate valve 1201 on the No. 1 connecting hole 12 and re-introduce water for treatment.

[0061] The water quality of the inlet water and the outlet water of the pre-reactor and the main reactor in this example is shown in Table 1.

[0062] Table 1 Changes in total chromium concentration in the inlet and outlet water of the chromium removal device of this embodiment

[0063] COD (mg / L) TCr (mg / L) Water ingress 2000 56 Sedimentation tank effluent 1700 1.3

[0064] The wastewater undergoes a reduction reaction through an iron-based reduction filter under acidic conditions, reducing hexavalent chromium to trivalent chromium. After chemical precipitation, flocculation reaction and sedimentation tank treatment steps, the total chromium concentration in the wastewater reaches below 1.5 mg / L.

[0065] Unlike existing chromium-containing wastewater treatment systems that use soluble reducing agents such as sodium metabisulfite, sodium sulfite, sodium bisulfite, and ferrous sulfate, and whose reactions are liquid homogeneous reactions, the present invention uses granular reducing filter material as the reducing agent, and the reaction adopts a solid-liquid two-phase reaction. This eliminates the need for continuous addition of the reducing agent and prevents the problem of overdosage or underdosage, resulting in stable and reliable treatment results. The use of reducing filter material requires a slightly higher pH than that required for dissolved salt reducing agents, thus reducing the amount of acid consumed for pH adjustment. Furthermore, the reducing agent is a simple material such as reduced iron, which does not introduce anionic components into the wastewater. Furthermore, the pH of the solution increases during the reduction process, thus reducing the amount of alkali required during pH adjustment after treatment. Therefore, the use of reducing granular filter material reduces the amount of reducing agent, acid, and alkali used, thereby reducing the salt concentration in the treated water, which greatly benefits subsequent biochemical treatment or reclaimed water reuse.

[0066] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0068] The above are only preferred specific implementation methods of the present invention, but the protection scope of the present invention is not limited to them. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater, characterized in that: It comprises an acidification tank (1), a reduction filtration tank (2), a precipitation reaction tank (3), a flocculation tank (4), a communication area (6) and a sedimentation tank (5) which are sequentially connected and communicated with each other; The acidification tank (1), the precipitation reaction tank (3) and the flocculation tank (4) are all provided with a stirrer (7); the acidification tank (1) is connected to a water inlet pipe (11) and an acid addition pipe (18); the reduction filtration tank (2) is provided with filter material (203); the precipitation reaction tank (3) is connected to an alkali addition pipe (19) and a coagulant pipe (20); and the flocculation tank (4) is connected to a flocculant pipe (21); The flocculation tank (4) is connected to the sedimentation tank (5) through the communication area (6); the sedimentation tank (5) is provided with a water inlet area (502), a water outlet area (503) and a sedimentation area; the water outlet area (503) is located above the water inlet area (502) and is connected to the water outlet pipe (16) for discharging clear liquid; the sedimentation area is located between the water outlet area (503) and the water inlet area (502) and is used for settling flocs; a mud discharge port (17) is provided at the bottom of the water inlet area (502), and the mud discharge port (17) discharges sludge through a mud discharge pipe via a mud discharge pump.

2. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 1, characterized in that: A filter material filling frame (202) is provided in the reduction filter pool (2) via a filter material supporting bracket (201), and filter material (203) is filled in the filter material filling frame (202).

3. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 2, characterized in that: A filter material filling frame hoisting device (9) is provided above the reduction filter tank (2). The filter material filling frame hoisting device (9) is used to hoist the filter material filling frame (202) to facilitate installation and replacement.

4. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 2, characterized in that: The reduction filter pool (2) comprises, from top to bottom, a post-filtration zone, a filter material zone, and a water inlet zone, wherein the post-filtration zone is located above the filter material zone, and the water inlet zone is located below the filter material zone; The filter material filling frame (202) is arranged in the filter material area; a reduction filter pool outlet channel (204) is provided in the post-filtration area; a circulation pump (8) is provided on the top of the reduction filter pool (2); and a circulation pump inlet pipe (801) is used to connect the post-filtration area above the filter material filling frame (202) in the reduction filter pool (2) to the water inlet area below the filter material filling frame (202) through the circulation pump (8) and the circulation pump outlet pipe (802).

5. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 1, characterized in that: An outlet channel (504) is provided in the outlet area (503) of the sedimentation tank (5), and the outlet channel (504) is connected to the outlet pipe (16) for guiding the clean water in the outlet area (503) to be discharged from the outlet pipe (16).

6. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 1, characterized in that: The sedimentation area of ​​the sedimentation tank (5) includes a plurality of sedimentation inclined pipes (505) arranged between the outlet area (503) and the inlet area (502). Wastewater with flocs enters the plurality of sedimentation inclined pipes (505) through the inlet area (502) to precipitate the flocs.

7. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 1, characterized in that: A scraper (506) is provided at the bottom of the sedimentation tank (5), and the scraper (506) is externally connected to a driving mechanism for scraping mud deposited at the bottom of the sedimentation tank (5).

8. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 1, characterized in that: A sludge hopper (507) with an inverted cone or columnar structure is provided at the bottom center of the water inlet area (502) of the sedimentation tank (5). The sludge discharge port (17) is provided at the bottom of the sludge hopper (507), and sludge is collected centrally through the sludge hopper (507).

9. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 1, characterized in that: The acidification tank (1) and the precipitation reaction tank (3) are both provided with pH probes (10) for respectively detecting the pH values ​​in the acidification tank (1) and the precipitation reaction tank (3).

10. The chromium removal reaction device for treating chromium-containing wastewater from textile printing and dyeing wastewater according to claim 1, characterized in that: The acidification tank (1), the reduction filtration tank (2), the precipitation reaction tank (3), the flocculation tank (4), and the communication zone (6) are separated by partition walls, and a No. 1 communication hole (12) with a gate valve (1201) for communication is provided between the acidification tank (1) and the reduction filtration tank (2); a No. 2 communication hole (13) for communication is provided between the reduction filtration tank (2) and the precipitation reaction tank (3); a No. 3 communication hole (14) for communication is provided between the precipitation reaction tank (3) and the flocculation tank (4); and a No. 4 communication hole (15) for communication is provided between the flocculation tank (4) and the communication zone (6).

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