Chromium-containing wastewater treatment system

Abstract

The utility model discloses a chromium-containing wastewater treatment system which comprises a concentrated chromium waste liquid treatment unit, a dilute chromium wastewater treatment unit and a recovery treatment unit, a concentrated chromium waste liquid outlet of the unit line is communicated with an inlet of the concentrated chromium waste liquid treatment unit, and a liquid outlet of the concentrated chromium waste liquid treatment unit is communicated with a liquid return port of the unit line; a dilute chromium wastewater outlet of the unit line is communicated with an inlet of the dilute chromium wastewater treatment unit, a concentrated water outlet of the dilute chromium wastewater treatment unit is communicated with an inlet of the concentrated chromium waste liquid treatment unit, and a produced water outlet of the dilute chromium wastewater treatment unit is communicated with an inlet of the recovery treatment unit; a concentrated water outlet of the recovery treatment unit is communicated with an inlet of the concentrated chromium waste liquid treatment unit, and a produced water outlet of the recovery treatment unit is communicated with an industrial water pipeline. The device has the beneficial effects that the concentrated chromium waste liquid treatment unit, the dilute chromium waste water treatment unit and the recovery treatment unit are designed, concentrated chromium waste liquid and dilute chromium waste water are treated in a quality-divided manner, and the treatment manner can reduce the addition of chemicals, improve the utilization rate of the chemicals, reduce the treatment cost, and is green and economical.

Description

Technical Field

[0001] This utility model relates to wastewater treatment technology, specifically to a chromium-containing wastewater treatment system. Background Technology

[0002] Cold rolling is a crucial step in the steel industry. The sodium sulfate electrolysis process in cold-rolled stainless steel production dissolves the iron oxide scale formed on the steel plate surface, primarily removing chromium oxide from the scale. Therefore, the electrolyte has a high salt content and dissolves a large amount of chromium oxide. 6+ Hexavalent chromium compounds can cause significant water pollution; their toxicity is higher than that of chromium. 3+ It is 100 times more potent than other substances and is easily absorbed by the human body, accumulating within it. Related policies apply to newly established Cr enterprises. 6+ Requirements have been set for total chromium emission limits, and many environmentally sensitive areas now require zero discharge of chromium-containing wastewater.

[0003] Typically, cold rolling mills generate dilute chromium wastewater with a total chromium concentration of 13–50 mg / L and concentrated chromium waste liquid with a total chromium concentration of 150–550 mg / L. Existing chromium wastewater treatment processes are as follows: Figure 1 As shown, the dilute chromium wastewater and concentrated chromium waste liquid generated by the cold rolling mill are mixed and then enter the equalization tank. The water in the equalization tank enters the primary and secondary reduction tanks where H2SO4 and NaHSO3 are added to reduce the chromium content. 6+ Reduced to produce Cr 3+ The wastewater then enters the primary and secondary neutralization tanks where NaOH is added for neutralization. Afterward, it enters the flocculation sedimentation tank to remove the generated Cr(OH)3 precipitate. Next, it passes through a multi-media filter to further reduce suspended solids and turbidity. Then, it undergoes ultrafiltration and reverse osmosis to reduce the salt content of the chromium-containing wastewater. The resulting permeate is then reused. The reverse osmosis concentrate has too high a salt content to be reused in the unit or discharged externally, requiring further treatment through evaporation crystallization. When the COD (Chemical Oxygen Demand) content in the wastewater is high, it affects the quality of the evaporated and crystallized salt. Therefore, the COD of the incoming water must be reduced first. This is achieved through ozone oxidation to initially reduce the COD, followed by further reduction in the COD of the influent in an aerated biological filter. Finally, it passes through a hard resin to remove Ca. 2 + Mg 2+ The resulting water is then subjected to evaporation and crystallization to obtain mixed salt Na2SO4, which is then transported off-site for disposal.

[0004] However, existing chromium-containing wastewater treatment processes do not differentiate between different concentrations of chromium-containing wastewater, resulting in high reagent consumption and high wastewater treatment costs. Summary of the Invention

[0005] The purpose of this invention is to provide a chromium-containing wastewater treatment system to address the shortcomings of existing technologies and reduce treatment costs.

[0006] The utility model discloses a technical scheme for a chromium-containing wastewater treatment system, which comprises a concentrated chromium waste liquid treatment unit, a dilute chromium wastewater treatment unit and a recovery treatment unit.

[0007] The concentrated chromium waste liquid outlet of the unit line is communicated with the inlet of the concentrated chromium waste liquid treatment unit through a concentrated chromium waste liquid pipeline, and the liquid outlet of the concentrated chromium waste liquid treatment unit is communicated with the liquid return port of the unit line.

[0008] The dilute chromium wastewater outlet of the unit line is communicated with the inlet of the dilute chromium wastewater treatment unit through a dilute chromium wastewater pipeline, the concentrated water outlet of the dilute chromium wastewater treatment unit is communicated with the inlet of the concentrated chromium waste liquid treatment unit, and the water production outlet of the dilute chromium wastewater treatment unit is communicated with the inlet of the recovery treatment unit.

[0009] The concentrated water outlet of the recovery treatment unit is communicated with the inlet of the concentrated chromium waste liquid treatment unit, and the water production outlet of the recovery treatment unit is communicated with an industrial water pipeline.

[0010] According to the above scheme, the concentrated chromium waste liquid treatment unit comprises a concentrated chromium waste liquid adjusting tank, a reduction tank, a neutralization and precipitation tank, a precipitation tank and a filter pressing device; the inlet of the concentrated chromium waste liquid adjusting tank is communicated with the concentrated water outlet of the dilute chromium wastewater treatment unit, the concentrated water outlet generated by the recovery treatment unit and the concentrated chromium waste liquid pipeline respectively, the outlet of the concentrated chromium waste liquid adjusting tank, the reduction tank, the neutralization and precipitation tank and the precipitation tank are sequentially communicated through pipelines, and the sludge outlet of the precipitation tank is communicated with the inlet of the filter pressing device.

[0011] According to the above scheme, the dilute chromium wastewater treatment unit comprises an adjusting tank, a precipitation tank, a primary raw water tank and a primary electrochemical concentration device; the inlet of the adjusting tank is communicated with a dilute chromium wastewater pipeline, the outlet of the adjusting tank, the inlet of the precipitation tank, the liquid outlet of the precipitation tank, the primary raw water tank and the primary electrochemical concentration device are sequentially communicated through pipelines, the concentrated water outlet of the primary electrochemical concentration device is communicated with the inlet of the concentrated chromium waste liquid treatment unit, and the water production outlet of the primary electrochemical concentration device is communicated with the inlet of the recovery treatment unit.

[0012] According to the above scheme, the dilute chromium wastewater treatment unit further comprises a secondary electrochemical concentration device, the inlet of the secondary electrochemical concentration device is communicated with the water production outlet of the primary electrochemical concentration device, the concentrated water outlet of the secondary electrochemical concentration device is communicated with the primary raw water tank, and the water production outlet of the secondary electrochemical concentration device is communicated with the inlet of the recovery treatment unit.

[0013] According to the above scheme, the recovery treatment unit comprises a secondary water production tank and a chromium removal resin which are communicated through a pipeline, the water production outlet of the secondary electrochemical concentration device is communicated with the inlet of the secondary water production tank, the outlet of the secondary water production tank is communicated with the chromium removal resin, the water production outlet of the chromium removal resin is communicated with the industrial water pipeline, and the concentrated water outlet of the chromium removal resin is communicated with the inlet of the concentrated chromium waste liquid treatment unit.

[0014] According to the above scheme, the liquid outlet of the sedimentation tank is communicated with the liquid return port of the unit line.

[0015] According to the above scheme, the liquid outlet of the pressure filter device is communicated with the liquid return port of the unit line.

[0016] According to the above scheme, the dilute chromium wastewater treatment unit further comprises a filter arranged between the sedimentation tank and the primary raw water tank, and the liquid outlet of the sedimentation tank, the filter and the primary raw water tank are sequentially communicated through pipelines.

[0017] According to the above scheme, the dilute chromium wastewater treatment unit further comprises a pressure filter, the inlet of the pressure filter is communicated with the sludge outlet of the sedimentation tank, the liquid outlet of the pressure filter is communicated with the filter, and the sludge outlet of the pressure filter is communicated with the outside.

[0018] The beneficial effects of the present application are as follows:

[0019] 1. The present application designs a concentrated chromium waste liquid treatment unit, a dilute chromium wastewater treatment unit and a recovery treatment unit, the dilute chromium wastewater treatment unit pre-treats the dilute chromium wastewater of the unit, and the concentrated water generated by the treatment is jointly treated with the concentrated chromium waste liquid from the unit line in the concentrated chromium waste liquid treatment unit, compared with the prior art, the present application can reduce the addition of reagents, improve the utilization rate of reagents, reduce the treatment cost and realize green economy; the water produced by the dilute chromium wastewater treatment unit is treated in the recovery treatment unit, and high-quality industrial water can be obtained for reuse, compared with the prior art, the utilization rate of the produced water is improved.

[0020] 2. The filtered liquid and supernatant liquid (containing impurity salt sodium sulfate) in the concentrated chromium waste liquid treatment unit and the dilute chromium wastewater treatment unit in the present application are reused, compared with the prior art, the utilization rate of reagents is improved, the consumption of reagents is greatly reduced, the treatment cost is reduced, and the reuse of impurity salt is realized.

[0021] 3. No new pollution ions are introduced in the present application, near-zero discharge of chromium-containing wastewater is realized, no external discharge wastewater is generated, and environmental pollution is effectively prevented.

[0022] 4. The present application uses two-stage electrochemical concentration devices to concentrate and reduce the amount of chromium-containing wastewater, has the advantages of good concentration effect and high sedimentation efficiency, and has great significance for the resource utilization of chromium-containing wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application is a process flow chart for existing chromium-containing wastewater treatment technology.

[0024] Figure 2 The present application is a process flow chart for existing chromium-containing wastewater treatment technology.

[0025] Figure 3The flow chart of the present application.

[0026] Figure 2 The reference signs in each drawing are as follows: 1, machine set line; 2, concentrated chromium waste liquid pipeline; 3, concentrated chromium waste liquid adjusting pool; 4, reduction pool; 5, neutralization and precipitation pool; 6, precipitation tank; 7, filter pressing device; 8, dilute chromium waste water pipeline; 9, adjusting pool; 10, precipitation pool; 11, filter; 12, primary raw water pool; 13, primary electrochemical concentration device; 14, secondary electrochemical concentration device; 15, secondary water production pool; 16, chromium removal resin; 17, filter press. DETAILED DESCRIPTION

[0027] In order to better understand the present application, the present application will be further described in detail below in combination with the schematic drawing.

[0028] As shown in Figure 2 and Figure 3 A chromium-containing wastewater treatment system, specifically a chromium-containing wastewater treatment system for a cold rolling machine set line, comprises a concentrated chromium waste liquid treatment unit, a dilute chromium wastewater treatment unit and a recovery treatment unit.

[0029] The concentrated chromium waste liquid outlet of the machine set line 1 is communicated with the inlet of the concentrated chromium waste liquid treatment unit through the concentrated chromium waste liquid pipeline 2, and the liquid outlet of the concentrated chromium waste liquid treatment unit is communicated with the liquid return port of the machine set line 1 through a pipeline.

[0030] The dilute chromium waste water outlet of the machine set line 1 is communicated with the inlet of the dilute chromium waste water treatment unit through the dilute chromium waste water pipeline 8, the concentrated water outlet of the dilute chromium waste water treatment unit is communicated with the inlet of the concentrated chromium waste liquid treatment unit through a pipeline, and the water production outlet of the dilute chromium waste water treatment unit is communicated with the inlet of the recovery treatment unit through a pipeline.

[0031] The concentrated water outlet of the recovery treatment unit is communicated with the inlet of the concentrated chromium waste liquid treatment unit, and the water production outlet of the recovery treatment unit is communicated with an industrial water pipeline.

[0032] The total chromium concentration of the dilute chromium wastewater generated by the cold rolling unit line 1 is 13-50 mg / L, and the total chromium concentration of the concentrated chromium waste liquid generated is 150-550 mg / L. The dilute chromium wastewater generated by the cold rolling unit line 1 firstly enters the dilute chromium wastewater treatment unit through the dilute chromium wastewater pipeline 8 for treatment, the chromium-containing concentrated water (with a total chromium concentration of 50-200 mg / L) generated by the dilute chromium wastewater treatment unit is collected into the concentrated chromium waste liquid treatment unit, mixed with the concentrated chromium waste liquid from the cold rolling unit line 1, and after treatment by the concentrated chromium waste liquid treatment unit, the generated solution (with a total chromium concentration of 0.1-0.5 mg / L) is reused into the cold rolling unit line 1; the water produced by the dilute chromium wastewater treatment unit (with a total chromium concentration of ≤5 mg / L) enters the recovery treatment unit for treatment, the water produced by the recovery treatment unit (with a total chromium concentration of ≤0.05 mg / L) is used as industrial water and enters the industrial water pipeline for reuse, and the concentrated water (with a total chromium concentration of 13-50 mg / L) produced by the recovery treatment unit enters the concentrated chromium waste liquid treatment unit for treatment.

[0033] Preferably, the concentrated chromium waste liquid treatment unit comprises a concentrated chromium waste liquid adjusting tank 3, a reduction tank 4, a neutralization and precipitation tank 5 and a precipitation tank; the inlet of the concentrated chromium waste liquid adjusting tank 3 is communicated with the concentrated water outlet of the dilute chromium wastewater treatment unit (i.e. the concentrated water outlet of the first electrochemical concentration device 13 described below), the concentrated water outlet of the recovery treatment unit (i.e. the concentrated water outlet of the chromium removal resin 16 described below) and the concentrated chromium waste liquid pipeline 2 respectively, and the concentrated chromium waste liquid adjusting tank 3, the reduction tank 4, the neutralization and precipitation tank 5 and the precipitation tank 6 are sequentially communicated by pipelines; the liquid outlet of the precipitation tank 6 is communicated with the liquid return port of the cold rolling unit line 1 by a pipeline.

[0034] Preferably, the concentrated chromium waste liquid treatment unit further comprises a filter pressing device 7, the sludge outlet of the precipitation tank 6 is communicated with the inlet of the filter pressing device 7, the liquid outlet of the filter pressing device 7 is communicated with the liquid return port of the cold rolling unit line 1 by a pipeline, and the filter cake generated by the filter pressing device 7 is transported out.

[0035] Preferably, the reduction tank 4 is provided with an aeration stirring device, and the reduction tank 4 is aerated by using the aeration stirring device to improve the reduction efficiency.

[0036] In the utility model, sulfuric acid is added into the concentrated chromium waste liquid adjusting tank 3, the concentrated chromium waste liquid entering the concentrated chromium waste liquid adjusting tank 3 is adjusted to pH 2.0-3.0 by sulfuric acid, and then enters the reduction tank 4, and NaHSO3 solution is added into the reduction tank 4 to reduce Cr 6+ in the waste liquid into Cr 3+ , and the water produced enters the neutralization and precipitation tank 5 (specifically NaOH neutralization and precipitation tank), and Cr 3+Cr(OH)3is generated in the neutralization and precipitation tank 5, and then enters the precipitation tank 6 for precipitation. After the precipitation, the supernatant of the precipitation tank 6 (including various impurities such as sodium sulfate) is discharged through the liquid outlet into the unit line 1 for reuse; the sludge generated by the precipitation tank 6 is discharged through the sludge outlet into the filter press 7 for filter pressing treatment. The filtered liquid (including impurities such as sodium sulfate, etc.) generated by the filter press 7 is adjusted in concentration by adding sodium sulfate and then reused to the unit line 1. The mud cake generated is transported out for further treatment. 6+ ) is adjusted in concentration by adding sodium sulfate and then reused to the unit line 1. The mud cake generated is transported out for further treatment.

[0037] Preferably, the dilute chromium wastewater treatment unit comprises a conditioning tank 9, a precipitation tank 10, a primary raw water tank 12, and a primary electrochemical concentration device 13. The inlet of the conditioning tank 9 is connected to the dilute chromium wastewater pipeline 8. The conditioning tank 9, the inlet of the precipitation tank 10, the liquid outlet of the precipitation tank 10, the primary raw water tank 12, and the primary electrochemical concentration device 13 are sequentially connected by pipelines. The concentrated water outlet of the primary electrochemical concentration device 13 is connected to the inlet of the concentrated chromium wastewater treatment unit (specifically, the inlet of the concentrated chromium wastewater conditioning tank 3). The water outlet of the primary electrochemical concentration device 13 is connected to the inlet of the recovery treatment unit.

[0038] Preferably, the dilute chromium wastewater treatment unit further comprises a filter 11 arranged between the precipitation tank 10 and the primary raw water tank 12. The liquid outlet of the precipitation tank 10, the filter 11, and the primary raw water tank 12 are sequentially connected by pipelines. The filter 11 comprises a quartz sand filter and a security filter arranged in series.

[0039] Preferably, the dilute chromium wastewater treatment unit further comprises a filter press 17. The inlet of the filter press 17 is connected to the sludge outlet of the precipitation tank 10. The liquid outlet of the filter press 17 is connected to the filter 11. The sludge outlet of the filter press 17 is connected to the outside.

[0040] Preferably, the dilute chromium wastewater treatment unit further comprises a secondary electrochemical concentration device 14. The inlet of the secondary electrochemical concentration device 14 is connected to the water outlet of the primary electrochemical concentration device 13. The concentrated water outlet of the secondary electrochemical concentration device 14 is connected to the primary raw water tank 12. The water outlet of the secondary electrochemical concentration device 14 is connected to the inlet of the recovery treatment unit.

[0041] The utility model discloses, the unit line 1 produces the large water volume of dilute chromium waste water, after the collection is transported to the adjusting pool 9, and the waste water is treated in the homogenization in adjusting pool 9 9, then is transported to the sedimentation tank 10, and the flocculating agent is added in the sedimentation tank 10 for removing the suspended solids in dilute chromium waste water, and the sludge of sedimentation tank 10 is sent into filter press 17, and the mud cake of filter press 17 is transported out, and the filtrate (containing miscellaneous salt sodium sulfate) of filter press 17 is sent into filter 11 again, and the supernatant (containing miscellaneous salt sodium sulfate) after the sedimentation of sedimentation tank 10 is further removed suspended solids after filter 11 and is stored and homogenized in the first raw water pool 12, and the water in the first raw water pool 12 is treated by the capacitive desalination of the first electrochemical concentration device 13, and 70% of the ion (Cr 6+ , Cr 3+ , Na + , SO4 2— ) in it is removed, and the concentrated water (that is, the salt-containing concentrated water, and the total chromium concentration is 50-200mg / L) is entered into the thick chromium waste liquid adjusting pool 3, and the water (that is, the solution after removing the ion) is entered into the secondary electrochemical concentration device 14 and is further desalted, and the concentrated water (that is, the salt-containing concentrated water, and the total chromium concentration is 13-50mg / L) treated by the secondary electrochemical concentration device 14 is entered into the first raw water pool 12, and the water (and the total chromium concentration is ≤5mg / L) obtained by the secondary electrochemical concentration device 14 is entered into the recovery treatment unit.

[0042] Preferably, the recovery treatment unit comprises a secondary water pool 15 and a chromium removal resin 16 communicated by a pipeline, the water outlet of the secondary electrochemical concentration device 14 is communicated with the inlet of the secondary water pool 15, the outlet of the secondary water pool 15 is communicated with the chromium removal resin 16, the water outlet of the chromium removal resin 16 is communicated with the industrial water pipeline, and the concentrated water outlet of the chromium removal resin 16 is communicated with the inlet of the thick chromium waste liquid treatment unit (specifically, the inlet of the thick chromium waste liquid adjusting pool 3).

[0043] In the utility model, the water (and the total chromium concentration is ≤5mg / L) obtained by the secondary electrochemical concentration device 14 is entered into the secondary water pool 15, and then the residual Cr 6+ in the water is treated by the chromium removal resin 16, the water (and the total chromium concentration is ≤0.05mg / L) obtained by the chromium removal resin 16 is used as industrial water (as high-quality industrial water), and the concentrated water (and the total chromium concentration is 13-50mg / L) obtained by the chromium removal resin 16 is entered into the thick chromium waste liquid adjusting pool 3 for treatment.

[0044] In the utility model, the devices are connected by pipelines.

[0045] A method for treating chromium-containing wastewater, the method comprising: providing the chromium-containing wastewater treatment system described above, discharging the dilute chromium wastewater from the unit line 1 into the dilute chromium wastewater treatment unit of the chromium-containing wastewater treatment system, treating the dilute chromium wastewater through precipitation, filtration and desalination to produce water for recycling into the recycling treatment unit, and discharging the concentrated water produced by desalination into the concentrated chromium waste liquid treatment unit; discharging the concentrated water produced by the recycling treatment unit into the concentrated chromium waste liquid treatment unit; discharging the concentrated chromium waste liquid from the unit line 1 into the concentrated chromium waste liquid treatment unit of the chromium-containing wastewater treatment system, mixing with the concentrated water produced by the dilute chromium wastewater treatment unit, adding sulfuric acid for pre-adjustment, and adding NaHSO3 to reduce Cr 6+ to Cr 3+ , precipitating Cr(OH)3 after neutralization and precipitation, discharging the sludge produced by precipitation, and discharging the supernatant into the unit line 1 for reuse. The specific method is as follows:

[0046] After the dilute chromium wastewater is collected, it is introduced into the dilute chromium wastewater treatment unit, and is subjected to homogenization treatment in the adjusting tank 9. The effluent from the adjusting tank 9 is introduced into the precipitation tank 10 to add flocculants to remove the precipitates in the incoming water. The effluent after precipitation is introduced into the filter 11 for filtration (first through a quartz sand filter to remove suspended solids and turbidity in the incoming water, and the effluent from the quartz sand filter is further filtered through a security filter), and then into the primary raw water tank 12. The water in the primary raw water tank 12 is treated by the primary electrochemical concentration device 13 to remove 70% of the ions (Cr 6+ , Cr 3+ , Na + , SO4 2— ) therein. The effluent from the primary electrochemical concentration device 13 is further introduced into the recycling treatment unit for treatment. The effluent from the primary electrochemical concentration device 13 is introduced into the secondary electrochemical concentration device 14 for further capacitive desalination treatment. The effluent is introduced into the secondary water production tank 15. The effluent from the secondary water production tank 15 is further adsorbed by the chromium removal resin 16, and the total chromium concentration is ≤0.05 mg / L, thereby obtaining high-quality industrial water.

[0047] The concentrated water from the primary electrochemical concentration device 13 is introduced into the concentrated chromium waste liquid adjusting tank 3, and is treated simultaneously with the concentrated chromium waste liquid produced by the unit line 1. At this time, waste sulfuric acid from the unit line 1 is added for acid pre-adjustment. The effluent is lifted by a pump and introduced into the reduction tank 4 (the reduction tank 4 is provided with multiple reduction tanks, and the number of stages can be adjusted according to the reduction requirements and the water quality on site). NaHSO3 is added in an environment with a pH of 2.0-3.0 to reduce Cr 6+ to Cr 3+After that, the wastewater enters the neutralization and precipitation tank 5, where NaOH is added to adjust the pH to 7.0-9.0, so that the wastewater reaches the optimal pH value required for the co-precipitation of metal ions; the wastewater that has exited the neutralization and precipitation tank 5 has metal hydroxide Cr(OH)3 precipitated, and the wastewater enters the precipitation tank 6 for precipitation. If the space is sufficient, in order to increase the precipitation efficiency, a coagulation and flocculation tank can be additionally provided to add flocculants to improve the precipitation effect; the supernatant after precipitation is reused to the unit line 1, and the sludge produced by precipitation is sent to the filter press device 7, the filtrate is reused to the unit line 1, and the mud cake is transported out for treatment.

[0048] Embodiment

[0049] The water quantity of the dilute chromium wastewater generated by each unit line 1 of a certain steel plant is 30m 3 / h, the water quantity of the concentrated chromium waste liquid is 5m 3 / h, and the water quality indexes of the two are shown in Table 1.

[0050] Table 1: Water quality of dilute chromium wastewater and concentrated chromium waste liquid

[0051]

[0052]

[0053] The above dilute chromium wastewater and concentrated chromium waste liquid are treated by the above method, and during the treatment process: the concentrated water conductivity of the first-stage electrochemical concentration device 13 is about 40000-50000us / cm, the water quantity is about 6m 3 / h (adjustable), and the total chromium concentration is 50-200mg / L; the water conductivity of the first-stage electrochemical concentration device 13 is about 2000-3000us / cm, and the total chromium concentration is ≤

[0054] 15mg / L; the water conductivity after the second-stage desalination treatment is ≤1000us / cm, and the total chromium concentration is ≤5mg / L; the total chromium concentration in the water after the adsorption of the chromium removal resin 16 is ≤0.05mg / L, and high-quality industrial water is obtained.

[0055] In the utility model, the specific functions of each device are as follows:

[0056] a. The adjustment tank 9: homogenizes the water of the unit line 1;

[0057] b. The precipitation tank 10: used for removing the suspended solids in the water body;

[0058] c. The filter 11: reduces the turbidity of the incoming water, so that it meets the water quality requirements of the electrochemical concentration device;

[0059] d. The primary electrochemical concentration device 13 and the secondary electrochemical concentration device 14: both are capacitive desalination devices based on capacitive desalination technology, the basic principle of which is to apply an external voltage to an electrode-solution interface to form a double-electron layer, raw water flows into the electrode-solution interface from one end of the electrode-solution interface and flows out from the other end; when a positive voltage is applied to the module, the anions and cations in the raw water move towards the anode and the cathode respectively, and are adsorbed on the porous carbon material on the surface of the positive and negative electrodes, so that the concentration of salts (such as Cr 6+ , Cr 3+ , Na + , SO4 2— ), charged colloidal particles and other point substances in the solution is reduced, organic matter is decomposed, and thus desalination and purification of water are achieved; when adsorption saturation is reached, the ions adsorbed on the electrode plate are released into the regenerated solution by applying a reverse external voltage or reversing the power supply, and the electrode plate after desorption can be reused. The core electrode material of the electrode-solution interface is inert carbon material, which is resistant to strong acid and strong base; the desalination device adopts a channel type structure (the channel width is millimeter level), which is not easy to block. In the utility model, the primary electrochemical concentration device 13 and the secondary electrochemical concentration device 14 are mature devices in the industry, and the structure and function are the same as the existing ones, which will not be described here;

[0060] e. The chromium removal resin 16: is a prior art for reducing the concentration of chromium in the produced water to obtain high-quality industrial water;

[0061] f. The concentrated chromium waste liquid adjusting tank 3: uses waste sulfuric acid generated in the factory to adjust the pH of the waste water, saving cost;

[0062] g. The reduction tank 4: NaHSO3 is added to reduce Cr 6+ to Cr 3+ , and an aeration stirring device can also be added in the reduction tank 4;

[0063] h. The neutralization and precipitation tank 5: NaOH is added to react with Cr 3+ to generate Cr(OH)3 precipitation;

[0064] i. The precipitation tank 6: a flocculating agent such as polyacrylamide is added to enhance the precipitation effect;

[0065] j. The filter press device 7: the mud cake generated by the filter press 17 is transported and disposed, and the filtered liquid is reused to the unit line 1.

[0066] Through cost analysis of different chromium-containing waste water treatment processes of the steel plant, as described above, the dilute chromium waste water 30m 3 / h and the concentrated chromium waste liquid 5m 3 / h are mixed and treated by the traditional process, and the total amount is 35m 3The initial investment cost per ton of water is 800,000 yuan, with a total investment cost of 28 million yuan and an operating cost of 20-30 yuan per ton. In contrast, the total investment cost using the technology described in this invention is 12 million yuan, with an operating cost of 10-15 yuan per ton. Comparing investment and operating costs, for the same treatment scale, this invention saves 16 million yuan in investment costs and 10-20 yuan per ton in operating costs. Compared to traditional processes, this invention has significant advantages in both investment and operating costs.

[0067] In this invention, the concentrated chromium waste liquid and dilute chromium wastewater generated by unit line 1 are treated by this process, and the resulting sodium sulfate, filtrate, and supernatant are recycled back to the unit, forming a complete recycling cycle. This achieves near-zero discharge of chromium-containing wastewater, with no external wastewater generated. The system produces no impurities; Cr is reduced using NaHSO3. 6+ The sodium sulfate and Cr produced in the process 3+ , for subsequent Cr 3+ Precipitation creates conditions, and the sodium sulfate generated during the reaction can also be introduced into unit line 1 for reuse, recycling sodium sulfate in wastewater and reducing reagent usage; the permeate from the dilute chromium wastewater in the recycling treatment unit is treated with chromium removal resin 16 to obtain high-quality industrial water for reuse, realizing the resource utilization of chromium-containing wastewater; the concentrated water from the dilute chromium wastewater after treatment by the primary electrochemical concentration unit 13 is mixed with the concentrated chromium waste liquid from unit line 1 for treatment, and the permeate from the dilute chromium wastewater after treatment by the primary electrochemical concentration unit 13 is then treated by the secondary electrochemical concentration unit 14. The concentrated water and dilute water (i.e., permeate) are treated separately, which is green and economical; the highly toxic Cr 6+ Reduced to Cr by NaHSO3 3+ Then it enters the neutralization sedimentation tank 5, without the introduction of new polluting ions, thus reducing environmental pollution; the chromium-containing wastewater is concentrated and reduced by two-stage electrochemical concentration treatment; the system has the advantages of low investment and operating costs, green economy, no introduction of polluting ions, recycling of sodium sulfate in wastewater, good concentration effect, and high sedimentation efficiency, which is of great significance for the resource utilization of chromium-containing wastewater.

[0068] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0069] Finally, it should be noted that the above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A chromium-containing wastewater treatment system, characterized by, The concentrated chromium waste liquid treatment unit, the dilute chromium waste water treatment unit and the recovery treatment unit are included. The concentrated chromium waste liquid outlet of the unit line is communicated with the inlet of the concentrated chromium waste liquid treatment unit through a concentrated chromium waste liquid pipeline, and the liquid outlet of the concentrated chromium waste liquid treatment unit is communicated with the liquid return port of the unit line. The dilute chromium waste water outlet of the unit line is communicated with the inlet of the dilute chromium waste water treatment unit through a dilute chromium waste water pipeline, the concentrated water outlet of the dilute chromium waste water treatment unit is communicated with the inlet of the concentrated chromium waste liquid treatment unit, and the water production outlet of the dilute chromium waste water treatment unit is communicated with the inlet of the recovery treatment unit. The concentrated water outlet of the recovery treatment unit is communicated with the inlet of the concentrated chromium waste liquid treatment unit, and the water production outlet of the recovery treatment unit is communicated with the industrial water pipeline.

2. The chromium-containing wastewater treatment system of claim 1, wherein The concentrated chromium waste liquid treatment unit includes a concentrated chromium waste liquid adjusting tank, a reduction tank, a neutralization and precipitation tank, a precipitation tank and a filter press device; the inlet of the concentrated chromium waste liquid adjusting tank is communicated with the concentrated water outlet of the dilute chromium waste water treatment unit, the concentrated water outlet of the recovery treatment unit and the concentrated chromium waste liquid pipeline respectively, and the outlet of the concentrated chromium waste liquid adjusting tank, the reduction tank, the neutralization and precipitation tank and the precipitation tank are sequentially communicated through pipelines; and the sludge outlet of the precipitation tank is communicated with the inlet of the filter press device.

3. The chromium-containing wastewater treatment system of claim 2, wherein, The dilute chromium waste water treatment unit includes an adjusting tank, a precipitation tank, a primary raw water tank and a primary electrochemical concentration device; the inlet of the adjusting tank is communicated with the dilute chromium waste water pipeline, the outlet of the adjusting tank, the inlet of the precipitation tank, the liquid outlet of the precipitation tank, the primary raw water tank and the primary electrochemical concentration device are sequentially communicated through pipelines, and the concentrated water outlet of the primary electrochemical concentration device is communicated with the inlet of the concentrated chromium waste liquid treatment unit; and the water production outlet of the primary electrochemical concentration device is communicated with the inlet of the recovery treatment unit.

4. The chromium-containing wastewater treatment system of claim 3, wherein The dilute chromium waste water treatment unit further includes a secondary electrochemical concentration device, the inlet of the secondary electrochemical concentration device is communicated with the water production outlet of the primary electrochemical concentration device, the concentrated water outlet of the secondary electrochemical concentration device is communicated with the primary raw water tank; and the water production outlet of the secondary electrochemical concentration device is communicated with the inlet of the recovery treatment unit.

5. The chromium-containing wastewater treatment system of claim 4, wherein The recovery treatment unit includes a secondary water production tank and a chromium removal resin which are communicated through pipelines, the water production outlet of the secondary electrochemical concentration device is communicated with the inlet of the secondary water production tank, the outlet of the secondary water production tank is communicated with the chromium removal resin, the water production outlet of the chromium removal resin is communicated with the industrial water pipeline, and the concentrated water outlet of the chromium removal resin is communicated with the inlet of the concentrated chromium waste liquid treatment unit.

6. The chromium-containing wastewater treatment system of claim 5, wherein, The liquid outlet of the precipitation tank is communicated with the liquid return port of the unit line.

7. The chromium-containing wastewater treatment system of claim 6, wherein The liquid outlet of the filter press device is communicated with the liquid return port of the unit line.

8. The chromium-containing wastewater treatment system of claim 7, wherein, The dilute chromium waste water treatment unit further includes a filter arranged between the precipitation tank and the primary raw water tank, the liquid outlet of the precipitation tank, the filter and the primary raw water tank are sequentially communicated through pipelines.

9. The chromium-containing wastewater treatment system of claim 8, wherein, The dilute chromium waste water treatment unit further includes a filter press, the inlet of the filter press is communicated with the sludge outlet of the precipitation tank, the liquid outlet of the filter press is communicated with the filter, and the sludge outlet of the filter press is communicated with the outside.

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