Method for treating wastewater in iron oxide pigment production process

Abstract

The invention discloses a method for treating wastewater in an iron oxide pigment production process, and belongs to the field of wastewater treatment. According to the method disclosed by the invention, during pretreatment, the waste liquid is sent to ammonia nitrogen stripping towers connected in series, ammonia nitrogen in the waste water is removed in a stripping manner, desulfurization is performed in a chemical precipitation manner, and then mechanical filtration, secondary A / O biochemical treatment, sand filtration, physical adsorption, reverse osmosis and ultraviolet irradiation treatment are performed in sequence, so that the ammonia nitrogen in the waste water is removed. And recycling and treatment of the wastewater can be realized. The method not only solves the problem of treatment of the iron oxide pigment wastewater, but also realizes resource utilization and up-to-standard discharge of the wastewater, and makes positive contributions to sustainable development and environmental protection of enterprises. According to the method, an ammonia nitrogen stripping tower is adopted to pretreat the wastewater generated in the production of ferric oxide, air or steam is used as a carrier, and ammonia nitrogen in the wastewater is transferred into a gas phase in a stripping manner, so that the removal of the ammonia nitrogen in the wastewater is realized.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment, and in particular relates to a method for treating wastewater in the production process of iron oxide pigments. Background Art

[0002] Iron oxide pigments, as the second largest inorganic pigment, are widely used in many industries such as building materials, coatings, plastics, and inks. In its production process, a large amount of wastewater is generated due to the main chemical synthesis methods (such as mixed salt method and sulfate method). These wastewaters mainly contain ammonia nitrogen, ferrous ions, sulfates, nitrates, etc., and the pH value is acidic, which affects the stability of coagulation precipitation and biochemical treatment. Therefore, a series of measures need to be taken to treat these wastewaters.

[0003] Wastewater treatment in the production process of iron oxide pigments involves a variety of methods, including chemical precipitation, biological treatment, and specific process flows to ensure that the wastewater meets discharge standards. For example, after the production wastewater of the red iron oxide plant is treated in an ammonia nitrogen stripping tower, chemical precipitation + pre-anoxic + secondary AO + deep treatment is used to ensure that all indicators of the wastewater meet discharge standards. Among them, chemical desulfurization, as an important pretreatment process, lays the foundation for the normal operation of the subsequent biochemical system. The ammonia nitrogen stripping method of physicochemical denitrification is combined with the pre-anoxic + two-stage AO method of biological denitrification, so that both ammonia nitrogen and total nitrogen in the effluent meet discharge standards.

[0004] In summary, the treatment of iron oxide pigment production wastewater involves a variety of technologies and methods, aiming to ensure that the wastewater is effectively treated and meets discharge standards while reducing the impact on the environment. Summary of the invention

[0005] The purpose of the present invention is to propose a method for treating wastewater in the production process of iron oxide pigments, by transferring ammonia nitrogen in the wastewater to the gas phase by means of stripping before secondary AO+ deep treatment, thereby achieving the removal of ammonia nitrogen in the wastewater.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A method for treating wastewater in the production process of iron oxide pigments, in which the waste liquid is sent to a series of ammonia nitrogen stripping towers in pretreatment, ammonia nitrogen in the wastewater is removed by stripping, and then desulfurization is carried out by chemical precipitation. Subsequently, mechanical filtration, secondary A / O biochemical treatment, sand filtration, physical adsorption, reverse osmosis and ultraviolet irradiation treatment are carried out in sequence to achieve wastewater recovery and treatment.

[0008] Furthermore, the ammonia nitrogen stripping tower includes a conduit, a first stripping tower body, a second stripping tower body, an air outlet, an air inlet and a liquid discharge pipe; the waste liquid enters the first stripping tower body through the conduit and is sprayed downward to fully contact with the rising airflow entering the first stripping tower body from the air inlet in the opposite direction, thereby completing the mass transfer effect and realizing the stripping of ammonia nitrogen.

[0009] Furthermore, the ammonia nitrogen stripping tower also includes a packing layer, which is evenly arranged in the first stripping tower body and the second stripping tower body; the packing layer uses honeycomb phenolic tubes as fillers to increase the contact area between the gas and the waste liquid and improve the mass transfer efficiency.

[0010] Furthermore, the first stripping tower body and the second stripping tower body are connected via a conduit.

[0011] Furthermore, the wastewater after the stripping treatment in the first stripping tower body is discharged from the discharge pipe to the inlet pipe, and the wastewater is pumped by the pump to be transported to the second stripping tower body through the conduit again for secondary stripping treatment.

[0012] Furthermore, a plurality of spraying ports with equal spacing are arranged at the lower ends of the conduits in the tower bodies of the first stripping tower and the second stripping tower.

[0013] Furthermore, the mechanical filtration is between the chemical precipitation and the biochemical treatment, and the mechanical filtration is achieved by using a horizontal screw centrifuge.

[0014] Furthermore, the secondary A / O biochemical treatment includes three stages of biological reactions: anaerobic, facultative anerobic and aerobic. The anaerobic stage removes organic matter and part of COD in the wastewater; the facultative anerobic stage further removes organic carbon and denitrifies; and the aerobic stage aerobically oxidizes the residual COD and removes ammonia nitrogen.

[0015] Furthermore, in the ultraviolet light irradiation treatment, the wavelength of the ultraviolet light is 253.7 nm.

[0016] Furthermore, in the water body finally treated, the ammonia nitrogen content is less than 5 mg / L, and the COD content is less than 100 mg / L.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] 1) The present invention not only solves the problem of iron oxide pigment wastewater treatment, but also realizes the resource utilization of wastewater and its discharge in compliance with standards, making positive contributions to the sustainable development of enterprises and environmental protection.

[0019] 2) The present invention adopts an ammonia nitrogen stripping tower to pre-treat the wastewater produced by the production of iron oxide, uses air or steam as a carrier, and transfers the ammonia nitrogen in the wastewater to the gas phase by stripping, thereby achieving the removal of ammonia nitrogen in the wastewater.

[0020] 3) The wastewater of the present invention is uniformly sprayed downward into the tower by the spraying head at the top of the first nitrogen stripping tower and the top of the second nitrogen stripping tower twice through a pump, and is fully contacted with the countercurrent of the air blown upward from the bottom of the tower. In this process, ammonia nitrogen is transferred from the waste liquid to the gas phase, and is discharged out of the tower with the rising air flow, thereby completing the removal of ammonia nitrogen in the waste liquid.

[0021] 4) In the present invention, a plurality of packing layers are arranged in the ammonia nitrogen stripping tower, and honeycomb phenolic tubes are used as packings to increase the contact area between the gas and the waste liquid and improve the mass transfer efficiency.

[0022] 5) The present invention adopts a two-stage A / O biochemical system to further remove organic matter and ammonia nitrogen in the wastewater through three-stage biological reactions of anaerobic, facultative anaerobic and aerobic. Wastewater with lower concentration of ammonia nitrogen can be directly degraded and absorbed by microorganisms, without the need to take any protective measures for the microorganisms in the pool.

[0023] 6) After microbial degradation, the present invention performs deep treatment on the wastewater, including sand filtration, activated carbon adsorption and reverse osmosis treatment, and finally obtains a clear liquid from which soluble salts, small molecular organic matter and microorganisms are removed.

[0024] 7) The present invention sterilizes the clear liquid with ultraviolet light after reverse osmosis treatment, selects ultraviolet light of a specific wavelength to irradiate the water body, and discharges it into the environmental water body after the ammonia nitrogen content in the water quality is less than 5 mg / L and the COD content is less than 100 mg / L, reaching the first-level discharge standard in the national "Comprehensive Sewage Discharge Standard". BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The process flow chart of wastewater treatment of the present invention is as follows;

[0026] Figure 2 This is a specific process diagram of the wastewater passing through the secondary A / O biochemical system of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of the ammonia nitrogen stripping tower used in the pretreatment of the present invention;

[0028] Among them, 1. liquid inlet pipe; 2. pump; 3. conduit; 4. first blow-off tower body; 5. air outlet; 6. spray outlet; 7. packing layer; 8. air inlet; 9. drain pipe; 10. second blow-off tower body; 11. base. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0030] Example 1

[0031] A method for treating wastewater in the production process of iron oxide pigments, such as Figure 1 As shown, the steps are as follows:

[0032] (1) Wastewater collection and pretreatment: The wastewater from the production of iron oxide pigments is concentrated in the waste liquid pool and pumped into the ammonia nitrogen stripping tower through a pump to remove most of the ammonia nitrogen in the water body. The wastewater collected at the bottom of the tower is discharged into the water collection pool;

[0033] (2) Adjusting the pH value: Adding alkaline substances (in the alkaline substances, quicklime accounts for 30% and sodium hydroxide accounts for 70%) to the water collection pool, adjusting the pH value to 7.5-8.0, so that the iron oxide pigment in the water collection pool precipitates;

[0034] (3) Sedimentation and filtration: Use a horizontal screw centrifuge to filter the wastewater after sedimentation and recover the sediment (i.e., iron oxide pigment); introduce the filtrate into the water distribution tank for temporary storage;

[0035] (4) Biochemical pool treatment: The wastewater in the water distribution pool is pumped into the secondary A / O biochemical system through a pump. The organic matter and ammonia nitrogen in the wastewater are removed through the three-stage biological reaction of anaerobic, facultative aerobic and aerobic. Among them, the anaerobic stage mainly removes organic matter and part of COD in the wastewater; the facultative aerobic stage further removes organic carbon and denitrifies; the aerobic stage aerobically oxidizes the residual COD and removes ammonia nitrogen. The secondary A / O biochemical system treatment is as follows: Figure 2 As shown in the figure, after the filtrate is pumped into the secondary A / O biochemical system, it first enters the anaerobic tank, where it is mixed with the sedimentation wastewater returned from the outside, and the organic matter and part of the COD in the wastewater are removed through the anaerobic environment; then the wastewater enters the anoxic tank for denitrification reaction, reducing nitrate nitrogen to nitrite nitrogen or nitrogen gas, and decomposing some organic matter at the same time; after denitrification, the wastewater flows into the aerobic tank, where aerobic biological reactions are carried out, and organic matter is oxidized and decomposed into carbon dioxide and water. At the same time, ammonia nitrogen is oxidized into nitrate nitrogen under the action of nitrifying bacteria, and part of the effluent in the aerobic tank flows back to the anoxic tank to provide nitrate nitrogen for the denitrification reaction of the anoxic tank. Finally, the sewage discharged from the outlet of the aerobic tank enters the sedimentation tank, where the sediment is separated from the water. The supernatant of the sedimentation tank is discharged from the system for subsequent treatment; the sediment in the sedimentation tank flows into the anaerobic tank by external reflux to maintain the concentration in the reaction tank.

[0036] (5) Advanced treatment: After the wastewater passes through the anaerobic-facultative-aerobic biochemical system, the treated liquid is sand filtered and then introduced into an activated carbon adsorption device. The activated carbon network further adsorbs impurities in the water to obtain a clarified liquid. The clarified liquid is allowed to stand for 6 to 12 hours and then introduced into a reverse osmosis system to remove soluble salts, small molecular organic matter and microorganisms in the clarified liquid to obtain a clear liquid.

[0037] (6) The clear liquid after reverse osmosis treatment is disinfected with ultraviolet light, and the wavelength of ultraviolet light is controlled at 253.7nm to sterilize and disinfect the water body.

[0038] (7) Take samples of the disinfected water for testing. When the ammonia nitrogen content in the water is less than 5 mg / L and the COD content is less than 100 mg / L, and it meets the first-level discharge standard in the national "Comprehensive Sewage Discharge Standard", it is discharged into the environmental water body, thus completing the treatment and recycling of the iron oxide process wastewater.

[0039] Example 2

[0040] The ammonia nitrogen stripping tower used in the pretreatment of the present invention is as follows Figure 3 As shown, it includes a liquid inlet pipe 1, a pump 2, a conduit 3, a first air stripping tower body 4, a second air stripping tower body 10, an air outlet 5, a spray port 6, a packing layer 7, an air inlet 8, a liquid discharge pipe 9 and a base 11; the first air stripping tower body 4, the second air stripping tower body 10 and the pump 2 are all arranged on the ground, the liquid inlet pipe 1 is arranged on one side of the pump 2, and the other end of the pump 2 is provided with a conduit 3 connected to the first air stripping tower body 3, the conduit 3 extends to the inside of the upper end of the first air stripping tower body 4, and spray ports 6 are evenly spaced at the bottom of the conduit 3 in the first air stripping tower body 4.

[0041] The first stripping tower body 4 and the second stripping tower body 10 have exactly the same structure. An air outlet 5 opening upward is provided at the top of the first stripping tower body 4, and packing layers 7 with equal intervals are provided in the first stripping tower body 4. An air inlet 8 is provided at one end of the bottom of the first stripping tower body 4, and a base pedestal 11 is provided at the bottom end of the first stripping tower body 4, and a drain pipe 9 is provided on one side of the base pedestal 11.

[0042] The first stripping tower body 4 is connected to the second stripping tower body 10 through the conduit 3. The wastewater after the stripping treatment in the first stripping tower body 4 is discharged from the discharge pipe 9 to the next inlet pipe 1. The wastewater is pumped by the pump and transported to the second stripping tower body 10 through the conduit 3 again for secondary stripping treatment.

[0043] The process of the present invention through the ammonia nitrogen stripping tower pretreatment is: firstly, the air inlet 8 of the first stripping tower body 4 and the second stripping tower body 10 are connected to the adsorption fan, and a large amount of air or steam is sucked into the first stripping tower body 4 and the second stripping tower body 10 to form a continuous and stable rising airflow; then the liquid inlet pipe 1 is connected to the water outlet of the waste liquid pool, and the water flow is controlled by adding a valve. When the wastewater concentrated in the waste liquid pool is transported to the conduit 3 through the liquid inlet pipe 1 under the action of the pump 2, it is then uniformly sprayed downward from the bottom end spraying port 6 of the conduit 3 in the first stripping tower body 4. The waste liquid sprayed downward is fully contacted with the upward airflow in the packing layer 7. In this process, ammonia nitrogen is transferred from the waste liquid to the gas phase, and is discharged out of the tower with the rising airflow, completing the removal of part of the ammonia nitrogen in the waste liquid, and the waste liquid is concentrated downward in the base 11, and is discharged to the second stripping tower body 10 through the drain pipe 9, and the ammonia nitrogen in the waste liquid is stripped and removed again. Finally, after two stripping treatments, the waste liquid is discharged from the device through the drain pipe 9 in the tower body 10 of the second stripping tower.

[0044] Example 3

[0045] Take a red iron oxide factory as an example. The factory uses a wet mixed acid process to produce red iron oxide. The main raw materials include iron sheets, nitric acid, ferrous sulfate, etc. The wastewater generated during the production process contains a large amount of pollutants such as ferrous ions, ammonia nitrogen, and COD.

[0046] The specific processing methods are as follows:

[0047] (1) The recovered wastewater is concentrated in a waste liquid pool, most of the ammonia nitrogen is removed by the ammonia nitrogen stripping tower in Example 2, and then sulfate ions in the water are removed by chemical precipitation;

[0048] (2) The pretreated wastewater is filtered through a horizontal screw centrifuge and then discharged into a secondary A / O biochemical system for treatment. This system effectively removes organic matter, ammonia nitrogen and total nitrogen in the wastewater through three stages of biological reactions: anaerobic, facultative and aerobic.

[0049] (3) The wastewater after biochemical treatment is treated by sand filtration, activated carbon network and reverse osmosis system to remove dissolved salts, small molecular organic matter and microorganisms in the clarified liquid, and finally obtain clear liquid, and further remove suspended matter and tiny particles;

[0050] (4) After the treated wastewater is disinfected by ultraviolet light irradiation at a wavelength of 253.7nm, the effluent water quality meets the national first-level emission standards and is discharged stably into the municipal pipeline network.

[0051] The successful implementation of the present invention not only solves the problem of iron oxide pigment wastewater treatment, but also realizes the resource utilization of wastewater and its discharge up to standard, making a positive contribution to the sustainable development of enterprises and environmental protection.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating wastewater in the production process of iron oxide pigments, characterized in that: In the pretreatment, the waste liquid is sent to the ammonia nitrogen stripping tower connected in series to remove the ammonia nitrogen in the wastewater by stripping, and then desulfurization is carried out by chemical precipitation. Subsequently, mechanical filtration, secondary A / O biochemical treatment, sand filtration, physical adsorption, reverse osmosis and ultraviolet irradiation treatment are carried out in sequence to achieve wastewater recovery and treatment.

2. The method for treating wastewater in the production process of iron oxide pigment according to claim 1, characterized in that: The ammonia nitrogen stripping tower comprises a conduit (3), a first stripping tower body (4), a second stripping tower body (10), an air outlet (5), an air inlet (8) and a liquid discharge pipe (9); waste liquid enters the first stripping tower body (4) through the conduit (3) and is sprayed downward to fully contact with the rising airflow entering the first stripping tower body (4) from the air inlet (8) in the opposite direction, thereby completing the mass transfer effect and realizing the stripping of ammonia nitrogen.

3. The method for treating wastewater in the production process of iron oxide pigment according to claim 2, characterized in that: The ammonia nitrogen stripping tower further comprises a packing layer (7), wherein the packing layer (7) is evenly arranged in the first stripping tower body (4) and the second stripping tower body (10); the packing layer (7) uses honeycomb phenolic tubes as packing, thereby increasing the contact area between the gas and the waste liquid and improving the mass transfer efficiency.

4. The method for treating wastewater in the production process of iron oxide pigment according to claim 2, characterized in that: The first stripping tower body (4) and the second stripping tower body (10) are connected via a conduit (3).

5. The method for treating wastewater in the production process of iron oxide pigment according to claim 2, characterized in that: The wastewater after the stripping treatment in the first stripping tower body (4) is discharged from the liquid discharge pipe (9) to the liquid inlet pipe (1), and the wastewater is pumped by the pump (2) and transported again from the conduit (3) to the second stripping tower body (10) for secondary stripping treatment.

6. The method for treating wastewater in the production process of iron oxide pigment according to claim 2, characterized in that: The lower ends of the conduits (3) in the first stripping tower body (4) and the second stripping tower body (10) are both provided with a plurality of spraying ports (6) at equal intervals.

7. The method for treating wastewater in the production process of iron oxide pigment according to claim 1, characterized in that: The mechanical filtration is between chemical precipitation and biochemical treatment, and the mechanical filtration is achieved by adopting a horizontal screw centrifuge.

8. The method for treating wastewater in the production process of iron oxide pigment according to claim 1, characterized in that: The secondary A / O biochemical treatment includes three stages of biological reactions: anaerobic, facultative anerobic and aerobic. The anaerobic stage removes organic matter and part of COD in the wastewater; the facultative anerobic stage further removes organic carbon and denitrifies; and the aerobic stage aerobically oxidizes the residual COD and removes ammonia nitrogen.

9. The method for treating wastewater in the production process of iron oxide pigment according to claim 1, characterized in that: In the ultraviolet light irradiation treatment, the wavelength of the ultraviolet light is 253.7 nm.

10. The method for treating wastewater in the production process of iron oxide pigment according to claim 1, characterized in that: The final treated water has an ammonia nitrogen content of less than 5 mg / L and a COD content of less than 100 mg / L.

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