High-iron manganese backwashing wastewater treatment method

Abstract

The present application relates to the application field of water purification plant production wastewater treatment, in particular to a high-iron-manganese backwashing wastewater treatment method. The high-iron-manganese backwashing wastewater treatment method provided by the present application integrates coagulation, reaction, sedimentation and concentration, and magnetic powder is added in the coagulation sedimentation tank. The magnetic powder serves as a crystal nucleus, more easily forms alum flowers, greatly improves the specific gravity of the alum flowers, speeds up the sedimentation speed, and can improve the sedimentation efficiency of the high-iron-manganese backwashing wastewater. In combination with the addition of coagulants and coagulant aids, the treatment efficiency of the high-iron-manganese backwashing wastewater is further improved, the content of iron, manganese and SS in the effluent is reduced, and the solid content of the sludge is improved. The high-iron-manganese backwashing wastewater treatment method provided by the present application has the characteristics of small land occupation, high surface load, short hydraulic retention time and good treatment effect, improves the effluent water quality, the formed sedimentation sludge has a lower water content, the sludge discharge is more conducive to dewatering, and the subsequent sludge treatment pressure is reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment in water purification plants, specifically a method for treating high-iron-manganese backwashing wastewater. Background Technology

[0002] In my country's water plants, 3% to 8% of the total water production constitutes filter backwash wastewater. Discharging this type of wastewater without any treatment will result in resource waste, energy consumption, and environmental pollution. Efficiently treating and reusing high-ferrous-manganese backwash wastewater is of significant economic and social importance for conserving water resources and achieving sustainable water resource development.

[0003] Currently, most groundwater treatment plants in my country discharge backwash wastewater directly after slight sedimentation, while some discharge it into municipal sewers. However, due to the high concentration of iron sludge in the wastewater, it exhibits a distinct iron-red color. When the water flow is low and the dilution capacity decreases, it can display obvious red bands or large areas turning red, wasting water resources and causing environmental pollution. A few water plants use coagulation-sedimentation-concentration-dewatering or concentration-dewatering processes; however, these traditional processes are inefficient, require numerous structures, and occupy a large area. Therefore, there is an urgent need to develop a suitable technology for treating high-iron-manganese backwash wastewater sludge, improving the treatment effect of conventional processes, reducing direct discharge pollution, and enhancing water resource utilization.

[0004] Magnetic concrete technology originated at MIT and was engineered by Cambridge Water Technology. Figure 1 As shown, Figure 1 This is a schematic diagram of the magnetic coagulation process. The principle of the magnetic coagulation sedimentation tank process: This process adds magnetic powder to conventional coagulation sedimentation, allowing the flocs produced during coagulation to effectively combine with the magnetic powder. Since the specific gravity of the magnetic powder is 5.2~5.3, it significantly increases the specific gravity of the coagulated flocs, thereby greatly accelerating the settling speed of the flocs. Simultaneously, a sludge return system is installed, allowing most of the magnetic powder in the sludge to be directly recycled. The remaining sludge is discharged from the system after magnetic powder recovery, with a magnetic powder recovery rate of approximately 99%. However, the effectiveness of this method in controlling the suspended solids (SS), iron, and manganese concentrations in high-iron and manganese backwash wastewater still needs improvement. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for treating high-iron and manganese backwash wastewater. The treatment method provided by the present invention utilizes magnetic coagulation process to treat high-iron and manganese backwash wastewater. Based on the characteristics of high turbidity, high iron and high manganese in the backwash wastewater, the method optimizes the addition of magnetic coagulation agents, and achieves high removal efficiency of suspended solids (SS), iron and manganese in the high-iron and manganese backwash wastewater.

[0006] This invention provides a method for treating backwash wastewater containing iron and manganese, comprising the following steps: mixing backwash wastewater from an iron and manganese removal filter, polyaluminum chloride, polyacrylamide, and magnetic powder, and performing magnetic coagulation, flocculation, and sedimentation treatment under alkaline conditions.

[0007] Specifically, the method for treating backwash wastewater of iron and manganese removal filter provided by the present invention includes the following steps: adjusting the backwash wastewater of iron and manganese removal filter, then mixing it with polyaluminum chloride and magnetic powder in sequence, then simultaneously adding polyacrylamide and alkaline solution and mixing for 60 s to 120 s, and then performing magnetic coagulation flocculation sedimentation treatment.

[0008] In some embodiments of the present invention, the method for treating high-iron and manganese backwash wastewater provided by the present invention includes the following steps: collecting backwash wastewater from the iron and manganese removal filter into a wastewater equalization tank, and discharging the high-iron and manganese backwash wastewater in the wastewater equalization tank at a rate of 100 m³ / min. 3 / h~150 m 3 The flow rate is increased to the mixing tank area of ​​the magnetic coagulation sedimentation tank and mixed with the coagulant. Then it is transferred to the magnetic mixing tank area and mixed with the magnetic powder. Then it is transferred to the flocculation tank area and mixed with the coagulant aid and magnetic powder for 60 s to 120 s. Then it undergoes magnetic coagulation flocculation sedimentation treatment.

[0009] The concentration of polyaluminum chloride in the system according to this invention is 25 mg / L to 35 mg / L; the concentration of polyacrylamide in the system is 4 mg / L to 6 mg / L. The dosage of magnetic powder according to this invention is 1 mg / L to 2 mg / L. The alkaline conditions according to this invention are formed by an alkaline solution in the system; specifically, the alkaline solution is selected from one or more of sodium hydroxide and calcium oxide. Preferably, the concentration of the effective component of the alkaline solution in the system is 8 mg / L to 12 mg / L. The magnetic coagulation flocculation sedimentation treatment time according to this invention is 10 min to 20 min; the sedimentation separation surface loading in the magnetic coagulation flocculation sedimentation treatment is 10 m / h to 15 m / h.

[0010] The backwash wastewater from the iron and manganese removal filter described in this invention has an SS concentration of 1500 mg / L to 2500 mg / L, an iron concentration of 80 mg / L to 100 mg / L, and a manganese concentration of 2 mg / L to 5 mg / L. In some embodiments of this invention, the backwash wastewater originates from the iron and manganese removal filter backwash wastewater at the Jiamusi Jiangbei Groundwater Purification Plant. This source water is characterized by high iron and manganese content, resulting in backwash wastewater with high iron and manganese content and poor natural settling performance. Addressing the problems of large volume, high iron and manganese content, and poor natural settling performance of the backwash wastewater from the aforementioned water source, the inventors of this application have creatively discovered that adding polyaluminum chloride coagulant and polyacrylamide coagulant aid under alkaline conditions for magnetic coagulation and flocculation sedimentation treatment can achieve better SS, iron, and manganese removal effects.

[0011] After magnetic coagulation and flocculation sedimentation treatment, the present invention obtains a mixture of supernatant and magnetic mud; the supernatant is reused in the water treatment system; the magnetic mud mixture is subjected to magnetic mud separation, so that the separated magnetic powder is returned to participate in the magnetic coagulation and flocculation sedimentation treatment, and the separated sludge is subjected to subsequent sludge treatment.

[0012] In some embodiments of the present invention, after magnetic coagulation and flocculation sedimentation treatment, a mixture of supernatant and magnetic sludge is obtained; the supernatant is collected in a recycled water equalization tank, and the supernatant in the recycled water equalization tank is returned to the front end of the water supply treatment system; the magnetic sludge mixture is subjected to magnetic sludge separation to obtain recycled magnetic powder and sludge, the recycled magnetic powder is reused in the magnetic coagulation sedimentation tank, and the sludge is transported to the sludge treatment system.

[0013] This invention provides a method for treating high-iron and manganese backwash wastewater. The method provided is a treatment technology for high-iron and manganese backwash wastewater from iron and manganese removal filters in underground water source purification plants. It is applicable to the field of wastewater treatment in water purification plants and includes: collecting backwash wastewater into a wastewater equalization tank; pumping the suspension from the equalization tank to a magnetic coagulation sedimentation tank; adding coagulant, flocculant aid, and magnetic powder to the magnetic coagulation sedimentation tank for flocculation and sedimentation; recycling the treated supernatant into a water treatment system for reprocessing; and discharging sludge into a sludge system for further treatment.

[0014] The high-iron and manganese backwash wastewater treatment method provided by this invention integrates coagulation, reaction, sedimentation, and concentration into one process. Magnetic powder is added to the coagulation and sedimentation tank; the magnetic powder acts as crystal nuclei, facilitating floc formation and significantly increasing the specific gravity of the flocs, thus accelerating sedimentation and improving the sedimentation efficiency of the high-iron and manganese backwash wastewater. Combined with the addition of coagulants and flocculants, the treatment efficiency of the high-iron and manganese backwash wastewater is further improved, reducing the content of iron, manganese, and suspended solids (SS) in the effluent and increasing the solids content of the discharged sludge. The high-iron and manganese backwash wastewater treatment method provided by this invention features a small footprint, high surface loading, short hydraulic retention time, and excellent treatment effect, improving effluent quality, resulting in lower moisture content in the formed precipitated sludge, and facilitating dewatering during sludge discharge, thereby reducing the pressure on subsequent sludge treatment.

[0015] The high-iron-manganese backwash wastewater treatment method provided by this invention is simple and efficient, reducing the pollution problem caused by direct discharge of backwash wastewater and effectively recovering water resources. Although conventional mechanical mixing + mechanical flocculation + inclined tube sedimentation can also treat backwash wastewater, its treatment efficiency is not as high as that of this invention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the magnetic concrete coagulation process;

[0017] Figure 2 This is a schematic diagram of the high-iron-manganese backwash wastewater treatment system of the present invention;

[0018] Figure 3 This is a schematic diagram illustrating the operation of the high-iron-manganese backwashing wastewater treatment method provided by the present invention. Detailed Implementation

[0019] This invention discloses a method for treating high-ferrous manganese backwash wastewater. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The method and application of this invention have been described through preferred embodiments, and those skilled in the art can obviously make modifications or appropriate alterations and combinations to the method and application described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0020] The high-ferrous manganese backwash wastewater treatment method provided by this invention is carried out in a high-ferrous manganese backwash wastewater treatment system, such as... Figure 2 As shown, Figure 2 This is a schematic diagram of the high-iron-manganese backwash wastewater treatment system of the present invention, which includes:

[0021] The equalization tank 1 for backwash wastewater is used to collect and regulate the backwash wastewater of high iron and manganese from the filter, mainly to regulate the water volume.

[0022] Submersible pump 2 is used to lift backwash wastewater to magnetic coagulation sedimentation tank 3.

[0023] The first dosing pump 4 is used to add coagulant to the first dosing tank 7, the second dosing pump 5 is used to add alkali solution to the second dosing tank 8, and the third dosing pump 6 is used to add coagulant aid to the third dosing tank 9.

[0024] The magnetic coagulation sedimentation tank 3 includes a mixing tank 16, a magnetic mixing tank 17, a flocculation tank 18, and a sedimentation tank 19. The outlet pipe of the submersible pump 2 is directly connected to the mixing tank 16. The coagulant is rapidly mixed with the incoming ferrous manganese backwash wastewater in the mixing tank. Magnetic powder recovered by the magnetic mud separation device is added to the magnetic mixing tank 17 and mixed with the backwash wastewater in the magnetic mixing tank. Coagulant aid and alkali are added to the flocculation tank 18. Under the combined action of the agents and magnetic powder, the tiny suspended matter in the ferrous manganese backwash wastewater aggregates into larger flocs. The sedimentation tank 19 is equipped with inclined tubes made of polypropylene. The flocs settle in the tubes, achieving mud-water separation.

[0025] The inlet of the recycled water equalization tank 14 is directly connected to the effluent of the magnetic coagulation sedimentation tank 3, and the treated supernatant is stored and collected in the recycled water equalization tank 14.

[0026] The booster pump 15 is used to lift the supernatant in the recycled water equalization tank 14 to the front end of the water treatment system. In this application example, it is in the drop aeration tank of the water purification plant.

[0027] The sludge screw pump 10 is activated according to the sludge level change in the sedimentation tank 19, and the settled magnetic sludge is returned to the magnetic sludge separation device 11 for separation of magnetic powder and sludge. The magnetic powder is recycled after separation, and the sludge is discharged to the sludge storage tank 12.

[0028] The sludge storage tank 12 is used to collect and store the sludge discharged from the system; a sludge pump 13 is installed therein to lift the sludge to the sludge dewatering system. For this application example, a centrifugal dewatering machine is used.

[0029] like Figure 3 As shown, Figure 3 This is a schematic diagram illustrating the operation of the high-iron-manganese backwash wastewater treatment method provided by the present invention. Figure 3As can be seen, the wastewater generated during the backwashing process of the iron and manganese removal filter is collected in a wastewater equalization tank. The backwash wastewater collected in the wastewater equalization tank is then pumped to a magnetic coagulation sedimentation tank at a certain flow rate using a submersible pump. Coagulants, flocculants, and magnetic powder are added to different zones of the magnetic coagulation sedimentation tank to flocculate and settle the backwash wastewater. After sufficient sedimentation in the magnetic coagulation sedimentation tank, the supernatant flows through an overflow weir into the subsequent recovery water equalization tank. A lift pump is installed in the recovery water equalization tank to recover the supernatant to the front end of the water supply treatment system according to the liquid level in the recovery water equalization tank. The magnetic sludge mixture discharged from the magnetic coagulation sedimentation tank is separated by a magnetic sludge separation device. The magnetic powder is recovered and enters the magnetic mixing tank of the magnetic coagulation sedimentation tank. The sludge is discharged to a sludge storage tank. After a short period of storage and equalization, it is pumped to a sludge dewatering system for further dewatering treatment.

[0030] This invention focuses on the treatment of backwash wastewater from the Jiamusi Jiangbei underground water source water purification plant. This plant uses groundwater, which is characterized by high iron and manganese content. The backwash wastewater from the filters is large in volume and has high iron and manganese content. The water treatment in this project primarily targets the suspended solids (SS) and iron and manganese levels in the backwash wastewater. Based on relevant experimental results, considering the characteristics of the plant's discharged wastewater, the backwash wastewater exhibits poor natural settling properties and is difficult to treat. Adding coagulants and flocculants under alkaline conditions can achieve better treatment results.

[0031] In this project, the reaction sedimentation process is a crucial component. The effectiveness of coagulation and sedimentation directly affects the content of suspended solids (SS), iron, and manganese in the supernatant, which is essential for the reuse of backwash wastewater.

[0032] The present invention will be further described below with reference to the embodiments:

[0033] Comparative Example 1

[0034] Backwash wastewater from the iron and manganese removal filter is collected and placed in a wastewater recovery tank. It is then pumped at a rate of 150 m³ / h. 3 A flow rate of [flow rate] / h was introduced into the magnetic coagulation sedimentation tank. Polyaluminum chloride (PAC) was added to the mixing tank at a dosage of 60 mg / L. Pure sodium hydroxide solution was added to the flocculation tank at a dosage of 10 mg / L, with a mixing time of 60 s. Magnetic powder was added to the magnetic mixing tank at a dosage of 1 mg / L, with a flocculation time of 15 min. The surface loading rate of the sedimentation tank was 12.4 m³ / h. The water quality entering and leaving the magnetic coagulation sedimentation tank was monitored, and the results are shown in Table 1 below.

[0035] Table 1. Water quality testing data during the treatment process in the magnetic coagulation sedimentation tank of Comparative Example 1.

[0036]

[0037] Comparative Example 2

[0038] Backwash wastewater from the iron and manganese removal filter is collected and placed in a wastewater recovery tank. It is then pumped at a rate of 150 m³ / h. 3 A flow rate of [flow rate] / h was introduced into the magnetic coagulation sedimentation tank. PAM (20 mg / L) was added to the mixing tank, and pure sodium hydroxide solution (10 mg / L) was added to the flocculation tank. The mixing time was 60 s. Magnetic powder (10 mg / L) was added to the magnetic mixing tank, and the flocculation time was 15 min. The surface loading rate of the sedimentation tank was 12.4 m³ / h. The water quality entering and leaving the magnetic coagulation sedimentation tank was monitored, and the results are shown in Table 2 below.

[0039] Table 2. Water quality test data during the treatment process in the magnetic coagulation sedimentation tank of Comparative Example 2.

[0040]

[0041] Example 1

[0042] Backwash wastewater from the iron and manganese removal filter is collected and placed in a wastewater recovery tank. It is then pumped at a rate of 150 m³ / h. 3 A flow rate of [flow rate] / h was introduced into the magnetic coagulation sedimentation tank. Polyaluminum chloride (PAC) was added to the mixing tank at a dosage of 30 mg / L. Pure sodium hydroxide solution was added at a dosage of 5 mg / L to the flocculation tank, along with PAM at a dosage of 5.0 mg / L. The mixing time was 60 s. Magnetic powder was added to the magnetic mixing tank at a dosage of 1 mg / L, with a flocculation time of 15 min. The surface loading rate of the sedimentation tank was 12.4 m³ / h. The water quality entering and exiting the magnetic coagulation sedimentation tank was monitored, and the results are shown in Table 3 below.

[0043] Table 3. Water quality testing data during the magnetic coagulation sedimentation process in Example 1.

[0044]

[0045] Comparative Example 3

[0046] Backwash wastewater from the iron and manganese removal filter is collected and placed in a wastewater recovery tank. It is then pumped at a rate of 150 m³ / h. 3 A flow rate of [flow rate] / h was introduced into the magnetic coagulation sedimentation tank. Polyaluminum chloride (PAC) was added to the mixing tank at a dosage of 30 mg / L, and PAM (PAM) at a dosage of 5.0 mg / L was added to the flocculation tank. The mixing time was 60 s. Magnetic powder was added to the magnetic mixing tank at a dosage of 1 mg / L. The flocculation time was 15 min, and the surface loading rate of the sedimentation tank was 12.4 m³ / h. The water quality entering and leaving the magnetic coagulation sedimentation tank was monitored, and the results are shown in Table 4 below.

[0047] Table 4. Water quality test data during the treatment process in the magnetic coagulation sedimentation tank of Comparative Example 3.

[0048]

[0049] Comparative Example 4

[0050] Backwash wastewater from the iron and manganese removal filter is collected and placed in a wastewater recovery tank. It is then pumped at a rate of 150 m³ / h. 3 A flow rate of [flow rate] / h was introduced into the magnetic coagulation sedimentation tank. Aluminum sulfate (60 mg / L) was added to the mixing tank, and PAM (5.0 mg / L) was added to the flocculation tank. The mixing time was 60 s. Magnetic powder (1 mg / L) was added to the magnetic mixing tank, and the flocculation time was 15 min. The surface loading rate of the sedimentation tank was 12.4 m³ / h. The water quality entering and leaving the magnetic coagulation sedimentation tank was monitored, and the results are shown in Table 5 below.

[0051] Table 5. Water quality testing data during the treatment process in the magnetic coagulation sedimentation tank of Comparative Example 4.

[0052]

[0053] Comparative Example 5

[0054] Backwash wastewater from the iron and manganese removal filter is collected and placed in a wastewater recovery tank. It is then pumped at a rate of 150 m³ / h. 3 A flow rate of [flow rate] / h was introduced into the magnetic coagulation sedimentation tank. Aluminum sulfate (60 mg / L) was added to the mixing tank. Pure sodium hydroxide solution (5 mg / L) was added to the flocculation tank. PAM (5.0 mg / L) was added to the flocculation tank, with a mixing time of 60 s. Magnetic powder (1 mg / L) was added to the magnetic mixing tank, with a flocculation time of 15 min. The surface loading rate of the sedimentation tank was 12.4 m³ / h. The water quality entering and leaving the magnetic coagulation sedimentation tank was monitored, and the results are shown in Table 6 below.

[0055] Table 6 Water quality test data during the treatment process in the magnetic coagulation sedimentation tank of Comparative Example 5

[0056]

[0057] Based on the above data, Comparative Examples 1 and 2 show that a relatively large dosage is required to ensure the treatment effect when only alkali solution and coagulant PAC are added, or when alkali solution and coagulant aid PAM are added. It should be noted that although using a high dosage of PAM can achieve a certain effluent effect in a short time, the high viscosity of PAM will cause the flocs to be firmly wrapped by the polymer, making magnetic powder recovery difficult. Moreover, long-term operation can easily cause blockage of inclined tubes and sludge pumps. Therefore, even if the same treatment effect can be achieved in actual operation, the dosage of PAM should not be too high.

[0058] Example 1 shows that when alkaline solution, coagulant PAC, and coagulant aid PAM are added simultaneously, a better treatment effect can be achieved with a smaller amount of reagents added.

[0059] Comparative Example 3 shows that, without adding alkali solution, only adding coagulant PAC and coagulant aid PAM, it is difficult to achieve a better treatment effect with the same dosage as in Example 3.

[0060] Comparative Example 4 shows that without adding alkali, replacing the coagulant with aluminum sulfate, and adding both coagulant and coagulant aid PAM, the treatment effect is not good.

[0061] Comparative Example 5 shows that when alkaline solution, aluminum sulfate coagulant, and PAM coagulant aid are added simultaneously, the treatment effect is not as good as when PAC is used as the coagulant.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for treating high-ferrous-manganese backwash wastewater, characterized in that, Includes the following steps: The backwash wastewater from the iron and manganese removal filter, polyaluminum chloride, polyacrylamide, and magnetic powder are mixed and subjected to magnetic coagulation, flocculation, and sedimentation treatment under alkaline conditions.

2. The method according to claim 1, characterized in that, The concentration of the polyaluminum chloride in the system is 25 mg / L to 35 mg / L.

3. The method according to claim 1, characterized in that, The concentration of the polyacrylamide in the system is 4 mg / L to 6 mg / L.

4. The method according to claim 1, characterized in that, The amount of magnetic powder added is 1 mg / L to 2 mg / L.

5. The method according to claim 1, characterized in that, The alkaline conditions are formed by an alkaline solution in the system; The alkaline solution is selected from one or more of sodium hydroxide and calcium oxide.

6. The method according to claim 5, characterized in that, The concentration of the effective component in the alkaline solution in the system is 8 mg / L to 12 mg / L.

7. The method according to claim 1, characterized in that, The magnetic coagulation flocculation sedimentation treatment time is 10 min to 20 min.

8. The method according to claim 1, characterized in that, The sedimentation separation surface load in the magnetic coagulation flocculation sedimentation treatment is 10 m / h to 15 m / h.

9. The method according to claim 1, characterized in that, The SS concentration of the backwash wastewater from the iron and manganese removal filter is 1500 mg / L to 2500 mg / L, the iron concentration is 80 mg / L to 100 mg / L, and the manganese concentration is 2 mg / L to 5 mg / L.

10. The method according to any one of claims 1 to 9, characterized in that, Specifically, the following steps are included: The backwash wastewater from the iron and manganese removal filter is conditioned and then mixed with polyaluminum chloride and magnetic powder in sequence. Polyacrylamide and alkaline solution are then added to the mixture for magnetic coagulation, flocculation and sedimentation treatment to obtain a mixture of supernatant and magnetic mud. The supernatant is reused in the water treatment system; The magnetic mud mixture is subjected to magnetic mud separation, and the separated magnetic powder is returned to participate in the magnetic coagulation flocculation sedimentation treatment, and the separated sludge is subjected to subsequent sludge treatment.

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