Process for reducing hardness of industrial wastewater

Abstract

The invention belongs to the technical field of metallurgy, and discloses a production technology for reducing hardness of industrial wastewater. In a wastewater treatment section, a sodium carbonate auxiliary material dosing point is changed at an outlet of a lime reaction tank, so that sodium carbonate fully reacts with the wastewater, the hardness in the wastewater is reduced, a small amount of suspended sludge is settled in sludge through settling, and the produced qualified wastewater is subjected to a reverse osmosis process to be recycled. Recycled water which reaches the discharge standard of industrial pollutants of lead and zinc can return to a production system, a zinc system and a lead system for use again, and the purposes of water circulation and zero discharge are achieved.

Description

Technical Field

[0001] The invention relates to the field of metallurgical technology, and more specifically to a production process technology for reducing the hardness of industrial waste water. Background Art

[0002] With the improvement of environmental protection requirements in water basins, the discharge standards of wastewater in the smelting industry have also been significantly improved. Industrial wastewater refers to water that is seriously polluted during use, and most of them are seriously harmful. According to the chemical properties of the main pollutants contained in industrial wastewater, it can be divided into inorganic wastewater containing mainly inorganic pollutants, organic wastewater containing mainly organic pollutants, mixed wastewater containing both organic and inorganic substances, heavy metal wastewater, wastewater containing radioactive substances, and cooling water that is only thermally polluted. Therefore, it is necessary to adopt corresponding treatment methods for different types of wastewater.

[0003] At present, the industrial wastewater discharged from the lead and zinc smelting system has great differences in water quality and quantity due to differences in production processes, auxiliary materials added, equipment water conditions, etc., with high salt concentration, high calcium and magnesium ions, poor wastewater clarity, deviations in various indexes, and trace amounts of heavy metals. Since wastewater has multiple characteristics, it is necessary to use different process flows or processes for treatment according to different production conditions, so that the water quality is qualified and meets the reuse standards, and all of it is reused in the system.

[0004] Therefore, developing a method suitable for reducing the hardness of lead-zinc industrial wastewater is an urgent problem to be solved by technicians in this field. Summary of the invention

[0005] In view of this, the present invention provides a method for reducing the hardness of industrial wastewater. In the wastewater treatment section, the sodium carbonate auxiliary material dosing point is changed to the outlet of the lime reaction tank, so that the sodium carbonate reacts fully with the wastewater to reduce the hardness of the wastewater.

[0006] In order to achieve the above object, the present invention provides a process for reducing the hardness of industrial wastewater, specifically:

[0007] (1) Adjust the temperature of industrial wastewater in the regulating tank so that the inlet temperature of the water entering the lime reaction tank is 20℃~35℃;

[0008] (2) First, adjust the pH value of industrial wastewater to 10.5-11.5 with sodium hydroxide, then add flocculant polyferric sulfate, let the wastewater and flocculant mix to form granular flocs and settle, and finally add industrial grade sodium carbonate to the outlet of the lime reaction tank pipeline to remove calcium and magnesium in the water, and then enter the soda ash reaction tank;

[0009] (3) Adding industrial grade PAM (polyacrylamide) to industrial wastewater to settle the particle flocs and discharge them into a mechanical clarification and stirring tank;

[0010] (4) Add non-oxygen bactericide to the mechanical clarification stirring tank, and then use the mechanical accelerated clarification filter tank equipment to pump the flocculants settled in the lower layer to the filter press through a high-pressure pump for pressure filtration. The effluent after pressure filtration is returned to the regulating tank, and the upper clear water is discharged into the gravity valveless filter tank by overflow;

[0011] (5) Add sulfuric acid (concentration>90%) to the water inlet of the gravity valveless filter, adjust the pH value of the upper layer of clear water to 6-9, and filter again;

[0012] (6) The filtered water enters the clean water tank for storage, and then is filtered through a multi-media filter and an activated carbon filter in turn. The active surface of the activated carbon is used to remove free chlorine, organic matter, etc. in the water, so as to reduce the contamination of the organic matter on the strong alkaline anion exchange resin, and effectively remove 60% to 80% of the colloidal substances, 50% of the iron and 50% to 60% of the organic matter in the water;

[0013] (7) The effluent after the above treatment enters the ultrafiltration device, ultrafiltration pool, safety filter and reverse osmosis device in sequence, and finally the recycled water returns to the original industrial system, achieving the effect of zero discharge of water circulation.

[0014] The beneficial effects of using the above-mentioned multiple filtering methods are:

[0015] Maintain clear water turbidity <1NTU, effectively remove 60%-80% of colloids, 50% of iron and 50%-60% of organic matter in water.

[0016] Preferably, in step (2), the amount of the polyferric sulfate is 2.5-5% of the mass of the industrial wastewater, and the amount of the industrial-grade sodium carbonate is such that the hardness of the effluent from the lime reaction tank is less than 1500 μmol / L.

[0017] Furthermore, the dosage of the industrial grade sodium carbonate is calculated according to the inlet water hardness and flow rate, and the calculation process is:

[0018] Assuming that the inlet water hardness is mainly caused by calcium hardness (calculated as calcium carbonate CaCO3), the reaction formula is: Ca 2+ +Na2CO3=CaCO3↓+2Na +

[0019] Assume that the inlet water hardness is H (mg / L in terms of CaCO3), the flow rate is Q (L / h), and the purity of sodium carbonate is P (%).

[0020] According to the chemical reaction formula, 1 mol of sodium carbonate can react with 1 mol of calcium or magnesium ions. The molar mass of calcium carbonate is 100 g / mol, and the molar mass of sodium carbonate is 106 g / mol.

[0021] For calcium hardness, the amount of sodium carbonate required is:

[0022] n1=H×Q / 1000×106 / 100

[0023] For magnesium hardness, the amount of sodium carbonate required is:

[0024] n2=H×Q / 1000×106 / 84 (considering the reaction of magnesium ions converting into magnesium hydroxide)

[0025] The total amount of sodium carbonate added (in terms of pure sodium carbonate) is: n = n1 + n2

[0026] The actual mass of industrial grade sodium carbonate added is: m = n × 106 / P

[0027] Preferably, in step (3), the amount of PAM used is 1 to 2‰ of the mass of the industrial wastewater.

[0028] Preferably, in step (4), the amount of the non-oxygen fungicide used is 5-10% of the mass of the industrial wastewater, and the non-oxygen fungicide is organic bromine.

[0029] The technical effects of using the above non-oxygen fungicide are:

[0030] Destroy the cell structure or physiological activities of microorganisms, mainly eliminating inorganic and organic matter.

[0031] Preferably, in step (4), the turbidity of the upper clear water is <1NTU.

[0032] Preferably, in step (6), the turbidity of the effluent is <0.9NTU and COD is <60mg / L.

[0033] Preferably, in step (7), the effluent turbidity of the ultrafiltration device is <0.5NTU, and SDI is <1; and the recycled water complies with the "Lead and Zinc Industrial Pollutant Emission Standard" GB25466-2010.

[0034] It can be seen from the above technical scheme that compared with the prior art, the present invention uses sodium carbonate as an auxiliary material to remove calcium and magnesium ions in wastewater, and settles a small amount of suspended sludge in the mud residue through sedimentation. The qualified wastewater generated is then passed through a reverse osmosis process, and the recycled water that meets the "Lead and Zinc Industrial Pollutant Emission Standards" can be returned to the production system, zinc system and lead system for use again, achieving the purpose of water circulation and zero emission.

[0035] The present invention solves the technical problem that it is difficult to completely remove the calcium and magnesium hardness in the industrial wastewater generated during the production process of the smelting system. At the same time, after the application of this technology, the wastewater treatment system returns the treated water that meets the standards to the system for recycling. The current daily replenishment of the circulating water pool is 200-400m 3, treated water that meets the standards can replace new water, solving the problem of reuse of recycled water, and indirectly solving the problems faced in water resource protection and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 The accompanying drawing is a process flow chart of the present invention.

[0038] Figure 2 This is the process flow chart before changing the dosing point. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] A process for reducing the hardness of industrial wastewater is provided, specifically:

[0042] (1) Adjust the temperature of industrial wastewater in the regulating tank so that the inlet temperature of the lime reaction tank is 20℃~35℃;

[0043] (2) firstly adjust the pH value of industrial wastewater to 10.5-11.5 with sodium hydroxide, then add 2.5-5% polyferric sulfate, let the wastewater mix with the flocculant to form granular flocs and settle, finally add 10-15% industrial grade sodium carbonate at the outlet of the lime reaction tank pipeline, react for 40-60 minutes, remove calcium and magnesium in the water, make the outlet water hardness less than 1500 μmol / L, and then enter the soda ash reaction tank;

[0044] (3) Add 1-2‰ industrial grade PAM (polyacrylamide) to industrial wastewater to settle the particle flocs and discharge them into a mechanical clarification stirring tank;

[0045] (4) Add 5-10% non-oxygen bactericide organic bromine into the mechanical clarification stirring tank, and then use the mechanical accelerated clarification filter tank equipment to pump the flocculants settled in the lower layer to the filter press through a high-pressure pump for pressure filtration. The effluent after pressure filtration is returned to the regulating tank, and the upper clear water with turbidity <1NTU is discharged into the gravity valveless filter tank through overflow;

[0046] (5) Add sulfuric acid (concentration>90%) to the water inlet of the gravity valveless filter, adjust the pH value of the upper layer of clear water to 6-9, and filter again;

[0047] (6) The turbidity of the filtered water is less than 0.9 NTU, and the COD is less than 60 mg / L. The water enters the clean water tank for storage, and then is filtered through a multi-media filter and an activated carbon filter in turn. The active surface of the activated carbon is used to remove free chlorine, organic matter, etc. in the water to reduce the contamination of the organic matter on the strong alkaline anion exchange resin, and effectively removes 60% to 80% of the colloidal substances, 50% of the iron and 50% to 60% of the organic matter in the water;

[0048] (7) The effluent after the above treatment enters the ultrafiltration device. The effluent turbidity of the ultrafiltration device is <0.5NTU and SDI is <1. It then enters the ultrafiltration pool, the safety filter and the reverse osmosis device in sequence. The recycled water obtained complies with the "Lead and Zinc Industrial Pollutant Emission Standard" GB25466-2010. Finally, the recycled water is returned to the original industrial system to achieve the effect of zero discharge of water circulation.

[0049] In the first half of 2022, the technical scheme of Example 1 was implemented on the lead and zinc wastewater of smelters in Inner Mongolia. The hardness of industrial wastewater was tested according to the hardness determination method of boiler water and cooling water analysis method GB / T 6909-2008. The specific implementation conditions are shown in Table 1.

[0050]

[0051]

[0052] Example 1: Change the sodium carbonate auxiliary material addition point in the process flow to the outlet of the lime reaction tank: The hardness removal rate of lead-zinc wastewater can reach up to 85%, and the hardness can meet the control requirements.

[0053] <1500μmol / L.

[0054] Comparative Example 1

[0055] In the prior art, the dosing point of the sodium carbonate auxiliary material is at the outlet of the regulating tank, and the rest of the process flow is the same as this application. The specific implementation conditions are shown in Table 2: The hardness removal rate of lead-zinc wastewater can reach up to 70%, and the hardness index does not meet the process.

[0056]

[0057] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for reducing the hardness of industrial wastewater, characterized in that: The specific steps include: (1) Adjust the temperature of industrial wastewater so that the inlet temperature of the lime reaction tank is 20℃~35℃; (2) First, adjust the pH value of industrial wastewater with sodium hydroxide, then add flocculant, and finally add sodium carbonate at the outlet of lime reaction tank to enter the soda ash reaction tank; (3) Add PAM to industrial wastewater and discharge it into a mechanical clarification and mixing tank; (4) Add non-oxygen bactericide to the mechanical clarification stirring tank, filter press to separate the lower flocculants and settle them, return the effluent after filter press to the regulating tank, and discharge the upper clear water into the gravity valveless filter tank; (5) Adjust the pH value of the upper clear water and filter it again; (6) The filtered water enters the clean water tank for storage, and then is filtered and discharged through the multi-media filter and activated carbon filter in turn; (7) The effluent enters the ultrafiltration device, ultrafiltration water tank, safety filter and reverse osmosis device in sequence, and finally the recycled water returns to the original industrial system.

2. A process for reducing the hardness of industrial wastewater according to claim 1, characterized in that: In step (2), the pH value is 10.5-11.5, the mass concentration of the flocculant in the industrial wastewater is 2.5-5%, and the amount of sodium carbonate used makes the hardness of the water out of the lime reaction tank less than 1500 μmol / L.

3. A process for reducing the hardness of industrial wastewater according to claim 2, characterized in that: The flocculant is polyferric sulfate.

4. A process for reducing the hardness of industrial wastewater according to claim 1, characterized in that: In step (3), the mass concentration of PAM in the industrial wastewater is 1-2‰.

5. A process for reducing the hardness of industrial wastewater according to claim 1, characterized in that: In step (4), the mass concentration of the non-oxygen bactericide in the industrial wastewater is 5-10%, and the non-oxygen bactericide is organic bromine.

6. A process for reducing the hardness of industrial wastewater according to claim 1, characterized in that: In step (4), the turbidity of the upper clear water is <1NTU.

7. A process for reducing the hardness of industrial wastewater according to claim 1, characterized in that: In step (5), the pH value of the industrial wastewater is adjusted by adding sulfuric acid to the water inlet of the gravity valveless filter, and the pH value is 6 to 9.

8. A process for reducing the hardness of industrial wastewater according to claim 1, characterized in that: In step (6), the turbidity of the effluent is <0.9NTU and COD is <60mg / L.

9. A process for reducing the hardness of industrial wastewater according to claim 1, characterized in that: In step (7), the effluent turbidity of the ultrafiltration device is <0.5NTU, and the SDI is <1; the recycled water complies with the "Lead and Zinc Industrial Pollutant Emission Standard" GB25466-2010.

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