A method for improving the treatment effect of a high-pollutant wastewater treatment process

Abstract

The present application relates to the field of industrial wastewater treatment, and a method for improving the treatment effect of high-pollutant wastewater treatment process, which develops effective technical means such as a denitrification filter material expansion control method, a nitrification filter material agglomerate melting method, a non-surge fan annular air supply pipeline, a biochemical+physicochemical dual-effect phosphorus removal control method and the like. The method effectively eliminates the problems of denitrification filter material expansion, nitrification filter agglomeration and aerobic tank oxygen supply fan surge during operation, ensures the dissolved oxygen concentration of the aerobic tank, and makes the denitrification filter effluent smooth, so that the system phosphorus removal is stably above 95%, further realizing water resource recycling, achieving the standard ultra-low discharge standard of TISCO wastewater, and realizing the resource utilization of wastewater.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment, and in particular to a method for improving the treatment effect of high-pollutant wastewater treatment processes. Background Technology

[0002] The industrial wastewater treatment system of Shanxi Taigang Stainless Steel Co., Ltd. treats a total of 160,000 tons / day of production wastewater. The treated wastewater is mainly reused in the plant's industrial circulating water system and in the preparation of desalinated water using membrane systems (MERS and MER). The membrane system's chemical cleaning water, mixed-bed reclaimed water, and denitrification water from the neutralization station are all substandard water sources containing large amounts of chemical agents. Originally, this water entered the Phase V system and, after pretreatment, entered the advanced treatment system. Some pollutants were difficult to remove, impacting the effluent quality and permeate flow of the membrane system. After the implementation of the new renovation project (Phase VI), this substandard water will be recycled, treated, and discharged in compliance with standards, eliminating the circulating pollution to the membrane system. The Phase VI system mainly relies on biological phosphorus removal and chemical precipitation phosphorus removal to achieve phosphorus reduction and compliant discharge (system phosphorus removal rate 89%, discharge index P≤0.4mg / l). Total phosphorus, as one of the main elements of eutrophication, can cause water pollution and imbalance in the distribution of aquatic species if its content is too high, resulting in serious environmental problems. Reducing the total phosphorus concentration in the Phase VI system's effluent and improving the system's total phosphorus removal rate to achieve compliant water quality discharge is closely related to the entire ecosystem.

[0003] The purpose of this invention is to control the expansion of the denitrification filter media, eliminate the risk of media leakage, dissolve the caking of the filter media, restore the normal filtration of the system, optimize the air supply pipeline of the blower, stabilize the dissolved oxygen key parameter of the aerobic tank, reduce the total phosphorus concentration in the effluent of the sixth-phase system, improve the total phosphorus removal rate of the system, and ensure that the water quality meets the discharge standards. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a method to improve the treatment effect of high-pollutant wastewater treatment processes.

[0005] The purpose of this invention is achieved as follows: A method to improve the treatment effect of high-pollutant wastewater treatment process, (I) taking the following measures to address the expansion of filter media in denitrification filters: daily regular inspections, paying attention to the filter media layer in denitrification filters, increasing the backwashing frequency of denitrification filters to 2-3 times a week; adjusting the backwashing method: water and air cleaning time is 23-25 ​​minutes, and the down-discharge valve is opened for 6-8 minutes after each cleaning to fully release the interstitial gas in the filter media layer. The adjusted backwashing is as follows: down-discharge 1-2 minutes - air washing 5-7 minutes - water and air washing 23-25 ​​minutes - down-discharge 8-10 minutes. When filter media backwashing is not performed, the down-discharge valve is opened for 5-8 minutes daily; (II) addressing the caking problem in denitrification filters, salt is used in each filter. To eliminate acid, the following measures should be taken: (1) Put industrial hydrochloric acid into a ton box and place it on the south side of the nitration filter; (2) Lower the liquid level of the nitration filter to 20-23 cm below the surface of the filter material, and the liquid level should just submerge the filter material layer during aeration; (3) Use a long rubber tube to guide hydrochloric acid to the filter, monitor the pH test paper in real time, control the amount of hydrochloric acid added through the valve, and keep the pH of the acid solution in the filter > 2; (4) Use the static + aeration method in the reaction, static for 2-2.5 hours and aeration for 2-2.5 hours; (5) Add 1-1.2 tons of hydrochloric acid, and backwash the filter when the pH reaches 6.5-7, and then add hydrochloric acid according to the above steps. When the reaction foam on the surface of the filter material changes from brown to off-white, it can be considered that the caking material has been completely dissolved; (6) Put After backwashing the filter, it is put into use; (III) Optimize the blower air supply pipeline, stabilize the dissolved oxygen of the key parameter of the aerobic tank, and take the following measures: the aerobic reaction tank is aerated by aeration pipe, the air source is supplied by four blowers, the blower outlet pipe is on a main pipeline, and then the branch pipe is distributed to each aerobic tank A, B, C and D, 2 on standby; (1) Add DN700 valve between the main outlet pipes of blowers 1#, 2# and 3#, 4#; (2) Add DN500 valve between the main inlet pipes of aerobic tanks A, B and C, D; (3) Lay DN500 pipeline, connect from the port of blower 4# to the section between aerobic tanks A, B and C, D to form a ring air supply pipeline; (IV) Develop the biochemical + physicochemical dual-effect phosphorus removal control method and take the following measures: (1) Source analysis: through Source analysis revealed that the total phosphorus content in the secondary membrane brine, the overflow of the thickener, and the effluent from the screw press was relatively high; 1) The secondary membrane brine source was domestic sewage. The domestic sewage was treated by biochemical methods, which increased the discharge time of the remaining sludge from the domestic sewage and shortened the sludge age. Each tank was sludge discharged for 35-38 minutes every 1 hour to reduce the total phosphorus content in the secondary membrane brine; 2) The thickener discharged 5-6 truckloads of sludge per day, which is 45-54 tons. The thickener was observed every 4-4.5 hours to avoid the activated sludge overflowing back into the system and causing secondary pollution; (2) Biochemical phosphorus removal: the dissolved oxygen in the aerobic tank was 4-10 mg / l, the sludge concentration was 2000-3000 mg / l, and the total phosphorus in the effluent was reduced to 0.3-0.7 mg / l; (3) Chemical precipitation phosphorus removal.

[0006] (iv) In (3) chemical precipitation for phosphorus removal, polyferric sulfate is used for phosphorus removal, with an addition amount of 40-45 ppm.

[0007] The beneficial effects of this invention are: 1. After operation and adjustment, the gas in the gaps between the filter layers is removed in time, thus eliminating the problem of filter media expansion in the denitrification filter.

[0008] 2. The caking problem in the nitrification filter has been greatly improved, and the effluent from the denitrification filter flows smoothly. The hourly flow rate of a single filter has increased by approximately 30 m³ / h. The daily flow rate of ten filters has increased by approximately 7000 m³.

[0009] 3. The blower surge phenomenon has been eliminated, enabling 2-3 blowers to operate continuously and stably simultaneously, ensuring oxygen supply to the aerobic tanks, with dissolved oxygen concentrations reaching over 6 mg / L. System control methods have also been enhanced. When valves #1 and #2 are closed, blowers #1 and #2 correspond to aerobic tanks C and D, while blowers #3 and #4 correspond to aerobic tanks A and B, allowing for adjustments based on individual conditions in each aerobic tank.

[0010] 4. The total phosphorus removal rate reached 95.16%.

[0011]

[0012] Through the implementation of the project, Phase VI will achieve a daily wastewater treatment capacity of 50,000 tons. The treated wastewater will meet the special discharge limits in Table 3 of the "Water Pollutant Discharge Standard for Iron and Steel Industry," with the main indicators reaching Class V standards in the "Surface Water Environmental Quality Standard" (specifically, effluent COD ≤ 30 mg / L, ammonia nitrogen ≤ 2 mg / L, total nitrogen ≤ 15 mg / L, and total phosphorus ≤ 0.4 mg / L), placing it at an industry-leading level. Attached Figure Description

[0013] The present invention will now be further described with reference to the accompanying drawings.

[0014] Figure 1 This is a bar chart of chemical phosphorus removal in a high-density sedimentation tank.

[0015] Figure 2 This is a diagram of the blower aeration system for the sixth-phase aerobic tank.

[0016] Figure 3 This is a diagram of the improved sixth-phase aerobic tank blower aeration system.

[0017] Among them: 1. Aerobic tank A, 2. Aerobic tank B, 3. Aerobic tank C, 4. Aerobic tank D, 5. Blower 4, 6. Blower 3, 7. Blower 2, 8. Blower 1. Detailed Implementation

[0018] Due to the low ratio of carbon to nitrogen sources in the water, methanol was added to the denitrification filter to enhance the function of denitrifying bacteria. During operation, it was found that the filter media periodically expanded, overflowing the filter boundaries and even spilling out of the filter, causing filter media loss and blockage of the effluent system, while also posing a significant safety hazard.

[0019] (I) The following measures will be taken to address the expansion of the filter media in the denitrification filter: Regular daily inspections will be conducted, paying close attention to the filter media layer. If the filter media shifts, the backwash intensity will be reduced if there is only a slight change (the water-air wash time can be reduced by 3 minutes depending on the actual situation). If the shift is severe, a shutdown for maintenance will be requested, and the filter media will be rearranged. Simultaneously, the backwash frequency of the denitrification filter will be increased from once a week to 2-3 times a week. The backwash method will be adjusted: the water-air wash time will be extended from 20 minutes to 25 minutes to enhance the cleaning of the filter media layer; the opening time of the drain valve after each wash will be extended from 5 minutes to 8 minutes to fully release the interstitial gas in the filter media layer. The adjusted backwash sequence is as follows: 1 minute drain – 5 minutes air wash – 25 minutes water-air wash – 8 minutes drain; even when the filter media is not being backwashed, the drain valve will be opened for 5 minutes daily.

[0020] (II) To address the caking problem in denitrification filters, hydrochloric acid is used to eliminate it in each filter. Specific measures are as follows: 1. Industrial hydrochloric acid is placed in a ton-sized container on the south side of the denitrification filter; 2. The liquid level in the denitrification filter is lowered to approximately 20cm below the surface of the filter media (the liquid level should just submerge the filter media layer during aeration); 3. Hydrochloric acid is channeled into the filter using a long rubber hose, with real-time pH monitoring using pH test paper. The amount of hydrochloric acid added is controlled by a valve to maintain the pH of the acid solution in the filter > 2; 4. A static + aeration method is used during the reaction. Static for 2 hours (to allow hydrochloric acid to better penetrate the filter media layer), followed by 2 hours of aeration (to promote rapid reaction); 5. For every ton of hydrochloric acid added, the filter is backwashed when the pH reaches approximately 7. Then, hydrochloric acid is added again following the above steps. When the reaction foam on the surface of the filter media changes from brownish-white to off-white, the caking is considered completely dissolved; 6. The filter is put into use after backwashing.

[0021] (III) Optimize the blower air supply pipeline to stabilize dissolved oxygen, a key parameter in the aerobic tank: The aerobic reactor is the main stage of the microbial biochemical reaction. The aerobic reactor uses aeration pipes for aeration, supplied by four blowers. The blower outlet pipes are connected to a DN700 main pipeline, and then branch pipes supply air to each aerobic tank A, B, C, and D (e.g., ...). Figure 1 Generally, 2 are open and 2 are on standby.

[0022] Transformation ( Figure 2(Bolded section): 1. Add DN700 valves between the main air outlet pipes of blowers 1#, 2# and 3#, 4#; 2. Add DN500 valves between the main air inlet pipes of aerobic tanks A, B and C, D; 3. Lay DN500 pipelines from the port of blower 4# to the section between aerobic tanks A, B and C, D to form a ring-shaped air supply pipeline.

[0023] (iv) Development of a biochemical + physicochemical dual-effect phosphorus removal control method: 1. Source analysis: The main water sources for Phase VI are concentrated brine from various membrane systems, denitrification water from the neutralization station, overflow from the thickener, and effluent from the screw press. Total phosphorus testing results for each water source are shown in Table 1.

[0024]

[0025] Source analysis revealed high total phosphorus content in the brine from the second membrane reactor, the overflow from the thickener, and the effluent from the screw press.

[0026] (1) The source of the concentrated brine for the second membrane is domestic sewage (Phase IV), and the water quality of Phase IV is treated by biological methods. Increase the discharge time of the excess sludge in Phase IV and shorten the sludge age. Increase the sludge discharge time from 20 minutes every hour per tank to 35 minutes to reduce the total phosphorus content of the concentrated brine for the second membrane.

[0027] (2) The thickening tank stores a large amount of activated sludge. Increase the amount of sludge discharged from the thickening tank from 4-5 truckloads per day to 5-6 truckloads. Observe the thickening tank once every 4 hours to avoid the activated sludge overflowing back into the system and causing secondary pollution.

[0028] (3) The screw press is a sludge thickening treatment device with a small amount of effluent, which will not have a significant impact on the system.

[0029] 2. Biological Phosphorus Removal: The growth curve of microorganisms is divided into the lag phase, logarithmic growth phase, stationary phase, and death phase. Microorganisms utilize phosphorus to synthesize polyphosphates and nucleic acids, etc. Microorganisms in the logarithmic growth phase reproduce the fastest and have the highest demand for phosphorus. Through long-term operation data, it was found that when the dissolved oxygen in the aerobic tank is 4-10 mg / L and the sludge concentration is 2000-3000 mg / L, the activated sludge is in the logarithmic growth phase, and the system has a better phosphorus removal effect, which can reduce the total phosphorus in the influent from 1-5 mg / L to 0.3-0.7 mg / L.

[0030] 3. Chemical precipitation for phosphorus removal: Phosphorus mainly exists in wastewater as phosphate. Adding chemical agents causes it to become an insoluble precipitate, thus removing it. Commonly used chemical agents include iron-based and aluminum-based agents. The reaction chemical equations are shown below.

[0031]

[0032] Commonly used industrial phosphorus removal agents such as polyaluminum chloride (PAC), polyferric sulfate (PFS), polyferric chloride (PFC), and polyaluminum ferric chloride (PAFC) were selected and added at concentrations of 30 ppm, 40 ppm, 50 ppm, and 60 ppm, respectively, followed by the addition of 1 ppm of polyacrylamide (PAM). The results are shown in the table below.

[0033]

[0034] Depend on Figure 1 It can be seen that PFS has the best phosphorus removal effect, and when the dosage of the agent is 40 ppm, the phosphorus removal rate reaches 66%.

[0035] Taiyuan Iron & Steel Group Phase VI wastewater treatment system.

[0036] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for improving the treatment effect of high-pollutant wastewater treatment processes, characterized in that: (I) To address the expansion of the filter media in the denitrification filter, the following measures should be taken: Regularly inspect the filter media layer in the denitrification filter daily, increase the backwashing frequency of the denitrification filter to 2-3 times a week; adjust the backwashing method: the water and air cleaning time should be 23-25 ​​minutes, and the drain valve should be opened for 6-8 minutes after each cleaning to fully release the interstitial gas in the filter media layer. The adjusted backwashing is as follows: drain 1-2 minutes - air washing 5-7 minutes - water and air washing 23-25 ​​minutes - drain 8-10 minutes. When the filter media is not being backwashed, the drain valve should be opened for 5-8 minutes daily. (II) To address the problem of caking in the denitrification filter, hydrochloric acid was used to eliminate it in each filter. The following measures were taken: (1) Industrial hydrochloric acid was placed in a ton box and placed on the south side of the nitrification filter; (2) The liquid level in the nitrification filter was lowered to 20-23 cm below the surface of the filter media, and the liquid level was just enough to submerge the filter media layer during aeration; (3) Hydrochloric acid was diverted to the filter using a long rubber tube, and pH was monitored in real time with pH test paper. The amount of hydrochloric acid added was controlled by a valve to keep the pH of the acid solution in the filter > 2; (4) The reaction was carried out by a combination of static and aeration. The static solution was left to stand for 2-2.5 hours and then aerated for 2-2.5 hours; (5) For every 1-1.2 tons of hydrochloric acid added, the filter was backwashed when the pH reached 6.5-7. Then, hydrochloric acid was added again according to the above steps. When the reaction foam on the surface of the filter media changed from brown to off-white, it could be considered that the caking material had been completely dissolved; (6) The filter was put into use after backwashing. (III) Optimize the blower air supply pipeline and stabilize the dissolved oxygen, a key parameter of the aerobic tank. The following measures are taken: the aerobic reaction tank is aerated by aeration pipes. The air source is supplied by four blowers. The blower outlet pipes are connected to a main pipeline and then distributed to each aerobic tank A, B, C and D through branch pipes. Two are open and two are on standby. (1) Add DN700 valves between the main outlet pipes of blowers 1#, 2# and 3#, 4#. (2) Add DN500 valves between the main inlet pipes of aerobic tanks A, B and C, D. (3) Lay DN500 pipelines from the port of blower 4# to the section between aerobic tanks A, B and C, D to form a ring air supply pipeline. (iv) Develop a biochemical + physicochemical dual-effect phosphorus removal control method and take the following measures: (1) Source analysis: Through source analysis, it was found that the total phosphorus content of the secondary membrane brine, the overflow of the thickener and the effluent of the screw press was high; 1) The source of the secondary membrane brine is domestic sewage. The domestic sewage is treated by biochemical method, increasing the discharge time of the remaining sludge of domestic sewage and shortening the sludge age. Each tank discharges sludge for 35-38 minutes every 1 hour to reduce the total phosphorus content of the secondary membrane brine; 2) The thickener discharges 5-6 truckloads of sludge per day, which is 45-54 tons. The thickener is observed once every 4-4.5 hours to avoid the activated sludge overflowing back into the system and causing secondary pollution; (2) Biochemical phosphorus removal: The dissolved oxygen in the aerobic tank is 4-10 mg / l, the sludge concentration is 2000-3000 mg / l, and the total phosphorus in the effluent will be reduced to 0.3-0.7 mg / l; (3) Chemical precipitation phosphorus removal.

2. The method for improving the treatment effect of high-pollutant wastewater treatment process according to claim 1, characterized in that: (iv) In (3) chemical precipitation for phosphorus removal, polyferric sulfate is used for phosphorus removal, with an addition amount of 40-45 ppm.

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