Fly ash landfill leachate treatment device

Abstract

The utility model discloses a fly ash landfill leachate treatment device, and belongs to the technical field of wastewater treatment. The device comprises a feeding unit, a reaction unit, a filter unit, a sludge treatment unit, a concentrated water treatment unit and a dosing unit, the feeding unit, the reaction unit and the filter unit are sequentially connected, and the dosing unit is respectively connected with the reaction unit, the filter unit and the sludge treatment unit. The sludge treatment unit is respectively connected with the reaction unit and the filter unit, the concentrated water treatment unit is connected with the rear end of the filter unit, the device breaks through the treatment mode that membrane treatment + A / O process is used as a pretreatment process section in the traditional process, adopts an efficient electro-catalysis device, is stable in operation, and ensures that the effluent quality meets the requirements of general regions.

Description

Technical Field

[0001] The utility model belongs to the field of wastewater treatment, and more specifically relates to a fly ash landfill leachate treatment device. Background Art

[0002] After incineration, domestic waste will produce fly ash accounting for about 3% of the total amount of waste. Fly ash has been listed as HWI 8 incineration residue hazardous waste in the "National List of Hazardous Wastes" (2021 edition) because it contains a large amount of toxic and harmful substances such as dioxins and heavy metals. It has also been included in the list of hazardous waste exemption management. The exemption links include transportation and disposal. It is clear that if the requirements of the "Pollution Control Standards for Domestic Waste Landfills" (GBl6889) are met, it can be landfilled in domestic waste landfills. At present, most of the fly ash produced by the incineration of domestic waste in my country is landfilled after solidification and stabilization. Common solidification and stabilization methods include cement solidification, asphalt solidification, and chelating agent stabilization. The water quality of the leachate generated by the landfill of solidified fly ash is different from that of general domestic waste leachate. After high-temperature incineration, the organic matter content in the fly ash is greatly reduced, so the leachate is mainly polluted by heavy metals. The leachate has the characteristics of large water quality changes, poor biodegradability, and high heavy metal content. Among them, the five-day biochemical oxygen demand (BOD5), chemical oxygen demand (CODcr), NH3-N and other indicators are far higher than the designed influent water quality. The designed leachate treatment process is difficult to ensure stable operation, and the water quality after treatment is difficult to stably meet the standards. On the other hand, research results show that when the BOD5 and COD content of the leachate is too high, the leachate drainage system is prone to biological clogging, and when the cations such as lead, cadmium, mercury, etc., are too high and the pH is alkaline, chemical clogging is prone to occur.

[0003] Therefore, emergency treatment of leachate from fly ash landfills is one of the main considerations.

[0004] After searching, patents CN109626562A, CN115490375A, and CN111170587A disclose methods for treating wastewater, but the above patents all use ozone and ozone treatment systems, which brings serious safety hazards.

[0005] Patent CN113636702A discloses a process for resource utilization and zero emission of saline organic wastewater. After adjustment and decarbonization, the organic saline wastewater enters a coagulation sedimentation tank, and the effluent enters a multi-media filter; the effluent and the subsequent separation mother liquor are mixed in an intermediate water tank for primary catalytic oxidation, enter a weak acid cation bed, remove impurities and enter ultrafiltration; the ultrafiltration produced water enters a primary nanofiltration device for quality separation and concentration; the concentrated water enters a secondary catalytic oxidation device and a sand filter tank in turn to remove organic matter and residual impurities, and is sent to a concentrated water nanofiltration device and a sodium sulfate evaporation crystallization device; after the produced water is mixed, it enters a high-pressure reverse osmosis, enters a secondary coagulation sedimentation tank and a sand filter tank in turn to remove impurities in the water, and is sent to a sodium chloride evaporation crystallization device; sodium chloride and sodium sulfate with a purity of more than 98% are obtained, and the mother liquor separated by evaporation and crystallization is refluxed to the previous process system, and the evaporated condensate is sent to the reuse water tank. Among them, the catalytic oxidation device adopts electrochemical oxidation. Different from biochemical treatment, it reduces the floor space required for the biochemical pool, and at the same time, through high-efficiency electrocatalytic oxidation, it improves the treatment efficiency of the leachate and improves the treatment efficiency of the leachate. Because biochemical treatment is not used, the treatment of odor generated during the biochemical treatment process is reduced, thereby reducing cost investment. Utility Model Content

[0006] 1. Problem to be solved

[0007] Aiming at the problems of existing fly ash landfill leachate treatment, the utility model provides a fly ash landfill leachate treatment device. Compared with the traditional biochemical treatment system, the treatment process occupies a small area and has low initial investment cost. At the same time, the fly ash landfill leachate can be effectively treated to make the effluent meet the standard.

[0008] 2. Technical solution

[0009] In order to solve the above problems, the technical solution adopted by the utility model is as follows:

[0010] The utility model discloses a fly ash landfill leachate treatment device, which comprises: a feed unit, a reaction unit, a filter unit, a sludge treatment unit, a concentrated water treatment unit and a dosing unit, wherein the feed unit, the reaction unit and the filter unit are connected in sequence, and the dosing unit is respectively connected to the reaction unit, the filter unit and the sludge treatment unit. The sludge treatment unit is respectively connected to the reaction unit and the filter unit, and the concentrated water treatment unit is connected to the rear end of the filter unit.

[0011] The feeding unit, the reaction unit, the filtering unit, the sludge treatment unit, the concentrated water treatment unit and the dosing unit are connected to an automatic control system, and the processing process is controlled by the automatic control system.

[0012] The feeding unit comprises a collecting barrel, in which an air stirring device connected to a blower is provided for pre-treating the leachate, and an online level meter is provided in the collecting barrel for measuring the level of the leachate in the collecting barrel. The air blowing system adopts variable frequency.

[0013] The reaction unit includes a high-efficiency electrocatalytic oxidation tank and a coagulation sedimentation tank. One end of the high-efficiency electrocatalytic oxidation tank is connected to a collecting bucket, and the other end is connected to a coagulation sedimentation tank. An online pH meter is provided between the high-efficiency electrocatalytic oxidation tank and the coagulation sedimentation tank to monitor the pH value of the leachate flowing into the coagulation sedimentation tank. If the pH value does not meet the standard, the dosage of the agent is increased. The coagulation sedimentation tank is provided with a coagulation stirring device to promote the coagulation sedimentation reaction.

[0014] The coagulation sedimentation tank is connected to the raw water barrel and is used for storing the clear liquid flowing out of the coagulation sedimentation tank.

[0015] The raw water barrel is connected to the filter unit, and the clear liquid in the raw water barrel is passed into the filter unit for filtration. In the actual production process, a device without a raw water barrel can also be used, that is, the coagulation sedimentation tank is connected to the filter unit, and the clear liquid flows directly from the coagulation sedimentation tank into the filter unit.

[0016] The filtration unit includes a multi-media filter and an SNF membrane device, which removes the remaining suspended matter that has not been treated cleanly in the coagulation sedimentation tank and reduces the mechanical damage and pollution to the reverse osmosis membrane element.

[0017] The other end is connected to the SNF membrane device, which removes pollutants such as organic matter and heavy metals in the water through nanofiltration membrane.

[0018] Furthermore, the grid of the SNF membrane device adopts a trapezoidal structure.

[0019] The front end of the SNF membrane device is connected to a multi-media filter, and the rear end is connected to a water production tank and a concentrated water tank. The purpose is to reduce the pollutants such as salt and heavy metals contained in the produced water so that the effluent meets the discharge standard. The water that meets the discharge standard enters the water production tank and is discharged in compliance with the standard. The filtered concentrated liquid enters the concentrated water tank for further treatment.

[0020] Furthermore, the SNF membrane device includes a precision filter and an SNF membrane assembly, which are used to remove pollutants such as COD, ammonia nitrogen, and divalent salts in wastewater. The water produced by the SNF membrane system can be reused in compliance with standards after entering the water production tank. Among them, an SNF booster pump is provided in front of the precision filter to boost the water entering the precision filter, and an SNF high-pressure pump is provided in front of the SNF membrane assembly to boost the water entering the SNF membrane assembly.

[0021] The sludge treatment unit includes a sludge thickening barrel, which is respectively connected to a coagulation sedimentation tank and a multi-media filter. The mixture containing sediment filtered from the coagulation sedimentation tank and the multi-media filter is passed into the sludge thickening barrel. The rear end of the sludge thickening barrel is connected to a screw filter press. The front end of the screw filter press is connected to a coagulation tank, and the rear end is connected to a drying evaporation bed. The sludge dehydrated by the screw filter press falls into the drying evaporation bed, and the sewage obtained by filtration enters a concentrated water barrel.

[0022] The concentrated water treatment unit comprises a single-effect evaporator. The sewage collected in the concentrated water tank is passed into the single-effect evaporator for further concentration and precipitation of impurities, and finally water meeting the discharge standards is obtained.

[0023] The dosing unit includes at least one dosing barrel, which includes a first dosing barrel connected to the coagulation sedimentation tank, used for introducing a first flocculant and sodium carbonate; the first flocculant includes PAM anions; a second dosing barrel connected to the multi-media filter, used for introducing a second flocculant, the second flocculant includes PAM cations; a third dosing barrel connected to the coagulation tank, used for introducing an antiscalant, the antiscalant is a complex phosphate salt.

[0024] 3. Beneficial effects

[0025] Compared with the prior art, the beneficial effects of the utility model are:

[0026] (1) The fly ash landfill leachate treatment device of the utility model is provided with a collection unit, a reaction unit, and a filtration unit connected in sequence, wherein the reaction unit adopts a high-efficiency electrocatalytic device, which can make the effluent water quality meet the B grade standard of the "Water Quality Standard for Sewage Discharge into Urban Sewers" (CJ343-2010), and the fecal coliform group meets the general area requirements of Table 2 of the "Pollution Control Standard for Domestic Waste Landfills" (GB16889-2008). The comprehensive utilization of reclaimed water is achieved, creating good economic and environmental benefits;

[0027] (2) The utility model is provided with a sludge treatment unit, which can effectively treat the wastewater and sludge generated during the treatment process by filtering, drying and evaporating the wastewater, thereby achieving green and environmentally friendly treatment of the wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The technical solution of the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for the purpose of explanation and are not intended to limit the scope of the utility model. In addition, unless otherwise specified, these drawings are only intended to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0029] Figure 1 It is a schematic diagram of the structure of a fly ash landfill leachate treatment device;

[0030] Figure 2 It is a schematic diagram of the collection unit structure;

[0031] Figure 3 is a schematic diagram of the reaction unit structure;

[0032] Figure 4 is a schematic diagram of the filter unit structure;

[0033] Figure 5 It is a structural schematic diagram of a concentrated water treatment unit;

[0034] Figure 6 It is a schematic diagram of the structure of the sludge treatment unit;

[0035] Figure 7 It is a schematic diagram of the dosing unit structure;

[0036] In the figure:

[0037] 100. Collection unit: 110. Collection bucket; 120. Online liquid level meter; 130. Air stirring device; 140. Blower;

[0038] 200. Reaction unit: 210. High-efficiency electrocatalytic oxidation tank;

[0039] 220. Coagulation sedimentation tank; 221. Online pH meter; 222. Coagulation stirring device;

[0040] 300. Filter unit: 310. Raw water barrel;

[0041] 320. Multi-media filter;

[0042] 330, SNF membrane device; 331, water production barrel;

[0043] 400. Sludge treatment unit: 410. Drying evaporation bed; 420. Screw filter press; 421. Coagulation tank; 430. Sludge concentration barrel;

[0044] 500. Concentrated water treatment unit: 510. Single-effect evaporator; 520. Concentrated water barrel;

[0045] 600. Dosing unit: 610. Dosing barrel. DETAILED DESCRIPTION

[0046] The following detailed description of exemplary embodiments of the utility model refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments that can be implemented by the utility model are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the utility model, it should be understood that other embodiments can be implemented and various changes can be made to the utility model without departing from the spirit and scope of the utility model. The following more detailed description of the embodiments of the utility model is not intended to limit the scope of the claimed utility model, but is only for illustration and does not limit the description of the characteristics and features of the utility model, so as to propose the best way to perform the utility model, and is sufficient to enable those skilled in the art to implement the utility model. Therefore, the scope of the utility model is limited only by the appended claims.

[0047] The utility model discloses a fly ash landfill leachate treatment method, which is aimed at leachate that meets the following requirements: suspended matter ≤ 100 mg / l, fecal coliform group ≤ 1.7×10 3 mpn / l, BOD5≤375mg / l, COD≤1×10 3 mg / l, hexavalent chromium ≤0.3mg / l, ammonia nitrogen ≤250mg / l, total nitrogen ≤830mg / l, total phosphorus ≤3mg / l, total mercury ≤5×10 -5 mg / l, total cadmium ≤5×10 -5 mg / l, total chromium ≤ 0.8mg / l, total lead ≤ 5×10 -3 mg / l, total arsenic ≤ 0.01 mg / l, the main parameters are shown in Table 1:

[0048] Table 1 Main parameters of influent water quality of leachate system

[0049] Serial number Leachate characteristics unit content 1 Total Phosphorus mg / l ≤3 2 Suspended matter mg / l ≤100 3 Chroma times ≤160 4 Hexavalent Chromium mg / l ≤0.3 5 Fecal coliform bacteria mpn / l <![CDATA[≤1.7×10 3 ]]> 6 Biochemical oxygen demand (BOD5) mg / l ≤375 7 Ammonia nitrogen (as N) mg / l ≤250 8 Total nitrogen (N) mg / l ≤830 9 Total Mercury mg / l <![CDATA[≤5×10 -5 ]]> 10 Total Cadmium mg / l <![CDATA[≤5×10 -5 ]]> 11 Total Chromium mg / l ≤0.8 12 Total Lead mg / l <![CDATA[≤5×10 -3 ]]> 13 Total Arsenic mg / l ≤0.01 14 Chemical oxygen demand (COD) mg / l <![CDATA[≤1×10 3 ]]>

[0050] Example 1

[0051] Embodiment 1 discloses a fly ash landfill leachate treatment device, which includes: a feed unit 100, a reaction unit 200, a filter unit 300, a sludge treatment unit 400, a concentrated water treatment unit and a dosing unit 600, wherein the feed unit 100, the reaction unit 200, the filter unit 300 and the sludge treatment unit 400 are connected in sequence, and the dosing unit 600 is respectively connected to the reaction unit 200, the filter unit 300 and the sludge treatment unit 400. The sludge treatment unit 400 is respectively connected to the reaction unit 200 and the filter unit 300, and the concentrated water treatment unit 500 is connected to the rear end of the filter unit 300.

[0052] The feed unit 100, the reaction unit 200, the filtering unit 300, the sludge treatment unit 400, the concentrated water treatment unit and the dosing unit 600 are connected to an automatic control system, and the processing process is controlled by the automatic control system.

[0053] The feeding unit 100 includes a collecting barrel 110, in which an air stirring device 130 connected to a blower 140 is provided for pre-treating the leachate, and an online level meter 120 is provided in the collecting barrel 110, and the online level meter 120 is used to measure the level of the leachate in the collecting barrel 110. Among them, the air blowing system adopts frequency conversion, and the stirring air volume is adjusted at any time, which reduces power consumption and greatly saves operating costs. Due to this special process combination, the safety and stability of the sewage treatment system are greatly improved, and the volume and floor space of the tank body are reduced. Due to the extensive use of automatic control systems, labor is reduced, management effects are improved, and operating costs are saved.

[0054] The reaction unit 200 includes a high-efficiency electrocatalytic oxidation tank 210 and a coagulation sedimentation tank 220. One end of the high-efficiency electrocatalytic oxidation tank 210 is connected to the collection bucket 110, and the other end is connected to the coagulation sedimentation tank 220. An online pH meter 221 is provided between the high-efficiency electrocatalytic oxidation tank 210 and the coagulation sedimentation tank 220 to monitor the pH value of the leachate flowing into the coagulation sedimentation tank 220. If the pH value does not meet the standard, the dosage of the agent is increased. The coagulation sedimentation tank is provided with a coagulation stirring device 222 to promote the coagulation sedimentation reaction. Removal of ammonia nitrogen NH by using the high-efficiency electrocatalytic oxidation tank 210 3 -N, total nitrogen TN and chromaticity, and effectively improve the pH value of the leachate to make the water quality suitable for the needs of the coagulant. The coagulation sedimentation tank 220 is used to remove the high content of suspended solids in the water to prepare for subsequent pretreatment.

[0055] The coagulation sedimentation tank 220 is connected to the raw water barrel 310 and is used to store the clear liquid flowing out of the coagulation sedimentation tank 220 .

[0056] The raw water barrel 310 is connected to the filter unit 300, and the clear liquid in the raw water barrel 310 is passed into the filter unit 300 for filtration. In the actual production process, a device without the raw water barrel 310 can also be used, that is, the coagulation sedimentation tank 220 is connected to the filter unit 300, and the clear liquid flows directly from the coagulation sedimentation tank 220 into the filter unit 300.

[0057] The filtration unit 300 includes a multi-media filter 320 and a SNF membrane device 330, which removes the remaining suspended matter that has not been cleaned up in the coagulation sedimentation tank 220 and reduces the mechanical damage and pollution to the reverse osmosis membrane element. One end of the multi-media filter 320 is connected to the raw water barrel 310, and the medium filled therein includes quartz sand and activated carbon.

[0058] The other end of the multi-media filter 320 is connected to the SNF membrane device 330. The SNF membrane device 330 removes organic matter, heavy metals and other pollutants in the water through the nanofiltration membrane. It is a new type of structural membrane component specially developed for high-concentration wastewater treatment. It adopts a roll membrane structure, and the membrane adopts an industrial anti-pollution nanofiltration membrane. The grid channel adopts a parallel grid structure that is different from the general roll membrane, so that the general roll membrane can not be used in places where it can operate stably for a long time. The grid of the SNF membrane component adopts a trapezoidal structure. The wastewater / liquid flows in the channel formed by the grid, just like flowing in a tubular membrane. The resistance of the diamond grid is much smaller. At the same time, the internal transverse reinforcement ribs can increase the turbulence of the liquid flow and reduce the concentration polarization of the membrane, so that the pollution resistance of the SNF membrane component is greatly improved. The effluent flows to the water production barrel 331 and is discharged through the water production effluent pump after meeting the standards.

[0059] The present invention adopts a multi-media filter 320 as a pretreatment process for deep treatment. Compared with traditional filters, the filter has the disadvantages of easy plugging and hardening of fillers, large backwashing water volume, and low filtering accuracy. The present invention uses quartz sand and activated carbon as the media, and the multi-media filter 320 is mainly composed of a filter body, supporting pipelines and valves. The filter body includes: a cylinder, a backwashing air pipe, a water distribution component, a support component, and a filter material. While making up for the shortcomings of traditional filters, it reduces energy consumption and saves operating costs.

[0060] The multi-media filter 320 in Example 3 is filled with multiple media, including anthracite, quartz sand and gravel. The anthracite with a small specific gravity and a slightly larger particle size is placed on the top layer of the filter bed, the quartz sand with a moderate specific gravity and a small particle size is placed on the middle layer of the filter bed, and the gravel with a large specific gravity and a large particle size is placed on the bottom layer of the filter bed. While making up for the shortcomings of the traditional filter, it reduces energy consumption and saves operating costs.

[0061] The front end of the SNF membrane device 330 is connected to the multi-media filter 320, and the rear end is connected to the water production tank 331 and the concentrated water tank 520. Its purpose is to reduce the pollutants such as salt and heavy metals contained in the produced water so that the effluent meets the discharge standard. The water that meets the discharge standard enters the water production tank 331 and is discharged in compliance with the standard. The filtered concentrated liquid enters the concentrated water tank 520 for further treatment.

[0062] Preferably, the SNF membrane device 330 includes a precision filter and a SNF membrane assembly, which are used to remove pollutants such as COD, ammonia nitrogen, and divalent salts in the wastewater. The water produced by the SNF membrane system can be reused in compliance with the standards after entering the water production tank. A SNF booster pump is provided in front of the precision filter to boost the water entering the precision filter, and a SNF high-pressure pump is provided in front of the SNF membrane assembly to boost the water entering the SNF membrane assembly.

[0063] The sludge treatment unit 400 includes a sludge thickening barrel 430, which is connected to the coagulation sedimentation tank 220 and the multi-media filter 320 respectively. The mixture containing sediment filtered from the coagulation sedimentation tank 220 and the multi-media filter 320 is passed into the sludge thickening barrel 430. The rear end of the sludge thickening barrel 430 is connected to the stacked screw filter press 420. The front end of the stacked screw filter press 420 is connected to the coagulation tank 421, and the rear end is connected to the drying evaporation bed 410. The sludge dehydrated by the stacked screw filter press 420 falls to the drying evaporation bed 410, and the sewage obtained by the filter press enters the concentrated water barrel 520. The coagulation tank 421 is connected to the dosing unit 600.

[0064] The concentrated water treatment unit 500 includes a single-effect evaporator 510. The sewage collected in the concentrated water tank 520 is passed into the single-effect evaporator 510 to be further concentrated and impurities are precipitated, and finally water that meets the discharge standard is obtained.

[0065] The dosing unit 600 includes three dosing barrels 610, including a first dosing barrel connected to the coagulation sedimentation tank, used to introduce the first flocculant and sodium carbonate, the sodium carbonate is configured into a 5% solution and pumped into the tank; the first flocculant includes PAM anions; the second dosing barrel connected to the multi-media filter 320, used to introduce the second flocculant, the second flocculant includes PAM cations; the third dosing barrel connected to the coagulation tank 421, used to introduce the scale inhibitor, the scale inhibitor is a composite phosphate, which is an organic phosphate. Flow meters are provided on the pipelines of the first dosing barrel, the second dosing barrel, and the third dosing barrel to control the dosing amount.

[0066] Example 2

[0067] The method for treating the leachate from fly ash landfill using the above device is aimed at the leachate that meets the following requirements: suspended matter ≤ 100 mg / l, fecal coliform group ≤ 1.7×10 3 mpn / l, BOD5≤375mg / l, COD≤1×10 3 mg / l, hexavalent chromium ≤0.3mg / l, ammonia nitrogen ≤250mg / l, total nitrogen ≤830mg / l, total phosphorus ≤3mg / l, total mercury ≤5×10 -5 mg / l, total cadmium ≤5×10 -5 mg / l, total chromium ≤ 0.8mg / l, total lead ≤ 5×10 -3 mg / l, total arsenic ≤0.01mg / l.

[0068] The processing method specifically comprises the steps of:

[0069] (1) Pretreatment: The leachate is pumped into the collection tank 110, and the blower 140 is connected to the air stirring device 130 to adjust the water quality and water volume until the water quality is uniform, and the pH is adjusted to 7-8. Preferably, caustic soda flakes are used for adjustment. The components of the leachate are shown in Table 1, including: COD, BOD5, total nitrogen, ammonia nitrogen, total phosphorus, and heavy metals. The flow rate of the blower is adjusted to 1m 3 / min, the delivery pump is adjusted to a flow rate of 5m 3 / h, discharged into the high-efficiency electrocatalytic oxidation tank.

[0070] (2) Electrocatalytic oxidation: The pollutants enter the high-efficiency electrocatalytic oxidation tank 210 to undergo electrochemical reactions on the electrodes to reduce or remove the pollutants in the wastewater; the conditions used in the electrocatalytic oxidation process are: positive and negative electrodes: stainless steel 304; electrolyte: leachate; current is 2A; voltage is 220V, and the residence time is 2h. This treatment can achieve a COD removal rate of 80%, and effectively increase the pH value of the leachate from 7 to 8 to 9 to 10, which is beneficial to the effect of the coagulant, and use the coagulation sedimentation tank to remove the high content of suspended solids in the water, so as to prepare for subsequent pretreatment.

[0071] (3) Coagulation and sedimentation: The sewage entering the system is pretreated by the "sodium carbonate + PAC (polyaluminium chloride) + sodium sulfide + PAM (polyacrylamide) coagulation and sedimentation" method to remove as much as possible the large amount of particulates, suspended matter, heavy metals such as calcium, magnesium, and lead, and colloids contained in the leachate, reduce the content of such substances entering the subsequent system, and ensure that the system can operate in a high-efficiency state; among them, the sodium carbonate input / flow rate is 100 mg / L, the PAC input / flow rate is 100 mg / L, the sodium sulfide input / flow rate is 100 mg / L, and the flocculant is PAM anion, and its input / flow rate is 5 mg / L.

[0072] (4) Adsorption and filtration: The leachate treated in step (3) is passed into the multi-media filter 320; its main function is to remove impurities such as mud, sand, suspended matter, colloids, etc. in the water, reduce mechanical damage and pollution to the reverse osmosis membrane elements, and the multi-media backwash water is regularly discharged to the sludge concentration tank 430, wherein the flow rate of raw water is 2m 3 / h, the multi-media filter 320 contains medium quartz sand and activated carbon, and its backwashing process is specifically to close the water outlet valve, open the drain valve, and use the water pump to pump the backwashing water into the multi-media filter 320, and then discharge it from the drain port.

[0073] (5) SNF filtration: The water is discharged from the multi-media filter 320 to the SNF membrane device 330. The purpose of the SNF membrane device 330 is to remove COD and BOD from the water through the nanofiltration membrane. 5, heavy metal ions and other pollutants. It is a new type of structural membrane component specially developed for the treatment of high COD, BOD and heavy metal wastewater. The SNF membrane device uses PVDF (polyvinylidene fluoride) super nanofiltration membrane to filter out the effluent and flow to the water production bucket 331. After meeting the standards, it is discharged through the water production effluent pump. The flow rate of wastewater in the SNF membrane device is 0.25m 3 / h.

[0074] The debugging process of the SNF membrane device 330 is as follows:

[0075] a. Adjust the pressure control system of the high-pressure pump;

[0076] b. Check whether all pipes in the device are connected properly, whether the pressure gauges are complete, and whether the low-pressure pipe connections are tight;

[0077] c. Fully open the switches of all pressure gauges and the main water inlet valve, concentrated water discharge valve, and produced water discharge valve;

[0078] d. Start the pretreatment equipment and adjust the water supply to be greater than the total water inflow of the device;

[0079] e. When the outlet water has no formaldehyde smell, close the main water inlet valve of the device;

[0080] f. Start the high-pressure pump and slowly open the total water inlet valve of the device, control the total water inlet pressure of the device to be less than 0.5Mpa, flush for 5 minutes, and check whether the high and low pressure pipelines and instruments are normal;

[0081] g. Adjust the water inlet valve and concentrated water discharge valve to make the water inlet pressure reach 1.0~1.4Mpa.

[0082] Open the product water outlet valve and close the product water discharge valve.

[0083] The debugging of SNF membrane device 330 is manual single-step operation. After normal operation, it can be switched to automatic state and automatically controlled by online instruments and PLC. After treatment, the salt removal rate reaches 99%, the effluent water quality meets the B grade standard of "Water Quality Standard for Sewage Discharge into Urban Sewers" (CJ343-2010), and the fecal coliform group meets the general area requirements of Table 2 in "Pollution Control Standard for Domestic Waste Landfill" (GB16889-2008).

[0084] (6) Sludge dehydration: The system uses a screw filter press 420 for sludge dehydration. The sludge in the sludge thickening barrel 430 comes from the coagulation sedimentation tank 220 and the multi-media backwash water. The sludge in the coagulation sedimentation tank 220 can flow into the sludge thickening barrel 430 by gravity and be lifted to the screw filter press 420 by the sludge pump. The front end of the screw filter press 420 is a coagulation tank 421. Flocculant is added to the coagulation pipe through the dosing unit. The dehydrated sludge falls to the drying evaporation bed 410. The type of flocculant is PAM, and its input / flow rate is 0.6% of the absolute dry sludge amount. In the screw filter press, the single filtration time is 2 hours.

[0085] The flocculant is a PAM cation. The principle is that the PAM cation can combine with the particles in the water to form large aggregates, thereby increasing the gap between the particles, reducing the density, and accelerating the sedimentation. At the same time, the PAM cation can reduce the dispersion force in the dispersed phase, enhance the interaction force between the dispersed phases, and improve the stability of the system. It is used to accelerate the sedimentation of sludge and separate the mud and water.

[0086] (7) Drying and evaporation: The drying and evaporation bed 410 is a technology that dries sludge naturally through vertical enhanced infiltration. It is used for sludge dehydration. The dehydration is not only achieved through the sludge's own drainage but also through evaporation from the exposed surface to the air. The sludge is spread flat on the drying bed. A filter cloth is installed on the top of the drying bed, and the surface has a contact surface with good permeability. The electric heater and air mixing fan are used to provide heat to accelerate the evaporation of water in the sludge and the removal of water. After drying and evaporation, the sludge is sent to the sludge truck and transported to outside the factory for disposal. The drying and evaporation temperature is 100°C and the air mixing fan flow rate is 1m 3 / min, 24 hours continuous operation.

[0087] (8) Single-effect evaporation: The concentrate water produced by the SNF membrane device 330 is collected by the concentrate water tank 520, and the concentrate water is transported to the single-effect evaporator 510 by the water inlet pump. The single-effect evaporation temperature is 200°C, negative pressure, and it operates continuously for 24 hours. The input amount / flow rate of the concentrate water is 100L / d.

[0088] This application is aimed at leachate from fly ash landfills. First, the leachate is pumped into a collection bucket to adjust the water quality and quantity, and then quantitatively discharged into a high-efficiency electrocatalytic oxidation tank. In the high-efficiency electrocatalytic oxidation tank, ammonia nitrogen, TN and chroma can be efficiently removed, and the pH value of the leachate can be effectively improved, so that the water quality is suitable for the needs of the coagulant; the effluent flows into the rear-end coagulation sedimentation tank and a coagulant is added for coagulation. The particles, suspended matter and colloids in the leachate react under the action of the agent molecules and enter the sedimentation tank for precipitation. The supernatant discharged after precipitation in the sedimentation tank enters the multi-media filter and SNF membrane device at the back. The SNF membrane device separates the effluent and discharges it in compliance with the standards. The concentrated water, multi-media backwash water and the solid-liquid mixture at the bottom of the sedimentation tank are lifted and discharged into the sludge drying bed, and finally dehydrated and dried before outsourcing for disposal.

[0089] Fly ash landfill leachate refers to a liquid mixed with rainwater and landfill leachate in the fly ash landfill. It contains a large amount of heavy metals and organic matter. Direct discharge of leachate will cause serious pollution to the surrounding environment. The treatment methods for fly ash landfill leachate mainly include physical treatment and chemical treatment. Its components contain fecal coliform bacteria that are difficult to degrade, and the biochemical oxygen demand (BOD5) is high. However, the odor generated during the biochemical treatment process and the safety hazards brought by the odor treatment system, and the biochemical treatment relies on the action of microorganisms. Microorganisms change with the seasons and the environment. Acidification is easily generated during operation, which will bring devastating damage to the flora in the system, thereby affecting the stability of the system. Therefore, the present invention does not use biochemical treatment technology, but adopts high-efficiency electrocatalytic oxidation treatment to remove COD in water, instead of biochemical treatment, which greatly improves the stability of the system and reduces the floor space. Although three-dimensional electrocatalytic devices are used in the prior art to treat fly ash landfill leachate, the three-dimensional electrocatalytic devices are expensive and difficult to maintain in the later stage. Therefore, the present application adopts a conventional electrochemical treatment common rail process to treat fly ash landfill leachate containing difficult-to-degrade fecal coliform bacteria, and uses electrochemical catalysis to reduce or remove pollutants in the wastewater. The COD and BOD in the water that are not removed are 5 , heavy metal ions and other pollutants are removed by multi-media filters and SNF membranes. The effluent quality meets the B grade standard of the "Water Quality Standard for Sewage Discharge into Urban Sewers" (CJ343-2010), and the fecal coliform group meets the general area requirements in Table 2 of the "Pollution Control Standard for Domestic Waste Landfills" (GB16889-2008).

Claims

1. A fly ash landfill leachate treatment device, characterized in that: include: A feeding unit (100), a reaction unit (200), a filtering unit (300), a sludge treatment unit (400), a concentrated water treatment unit (500) and a dosing unit (600); the feeding unit (100), the reaction unit (200) and the filtering unit (300) are connected in sequence; the dosing unit (600) is respectively connected to the reaction unit (200), the filtering unit (300) and the sludge treatment unit (400); the sludge treatment unit (400) is respectively connected to the reaction unit (200) and the filtering unit (300); and the concentrated water treatment unit (500) is connected to the rear end of the filtering unit (300).

2. The device according to claim 1, characterized in that The feeding unit (100), the reaction unit (200), the filtering unit (300), the sludge treatment unit (400), the concentrated water treatment unit (500) and the dosing unit (600) are connected to an automatic control system, and the processing process is controlled by the automatic control system.

3. The device according to claim 1, characterized in that The feeding unit (100) comprises a collecting barrel (110), wherein the collecting barrel (110) is provided with an air stirring device (130) connected to a blower (140) for pre-treating the leachate, and the collecting barrel (110) is provided with an online liquid level meter (120), wherein the online liquid level meter (120) is used to measure the liquid level of the leachate in the collecting barrel (110).

4. The device according to claim 3, characterized in that The reaction unit (200) comprises a high-efficiency electrocatalytic oxidation tank (210) and a coagulation sedimentation tank (220); one end of the high-efficiency electrocatalytic oxidation tank (210) is connected to a collection bucket (110), and the other end is connected to a coagulation sedimentation tank (220); an online pH meter (221) is provided between the high-efficiency electrocatalytic oxidation tank (210) and the coagulation sedimentation tank (220); and a coagulation stirring device (222) is provided in the coagulation sedimentation tank (220).

5. The device according to claim 4, characterized in that It also includes a raw water barrel (310), one end of which is connected to the coagulation sedimentation tank (220), and the other end of which is connected to the filtering unit (300).

6. The device according to claim 1, characterized in that The filtration unit (300) includes a multimedia filter (320) and a SNF membrane device (330).

7. The device according to claim 6, characterized in that The grid of the SNF membrane device (330) adopts a trapezoidal structure.

8. The device according to claim 6, characterized in that The sludge treatment unit (400) comprises a sludge thickening barrel (430), the sludge thickening barrel (430) being connected to a coagulation sedimentation tank and a multi-media filter (320) respectively, the rear end of the sludge thickening barrel (430) being connected to a screw filter press (420), the front end of the screw filter press (420) being connected to a coagulation tank (421), and the rear end being connected to a drying evaporation bed (410), and the sludge dehydrated by the screw filter press (420) falls to the drying evaporation bed (410).

9. The device according to claim 8, characterized in that The concentrated water treatment unit (500) comprises a single-effect evaporator (510), the single-effect evaporator (510) is fed with sewage collected in a concentrated water tank (520), and the concentrated water tank (520) is connected to an SNF membrane device (330) and a screw filter press (420).

10. The device according to claim 1, characterized in that The dosing unit (600) includes at least one dosing barrel (610), and the dosing barrel (610) is respectively connected to the reaction unit (200), the filtering unit (300) and the sludge treatment unit (400).

Images