Co-treatment process and system for fly ash washing wastewater from leachate treatment plant of waste incineration plant

Abstract

This invention belongs to the field of municipal solid waste incineration technology, specifically relating to a co-treatment process and system for fly ash washing wastewater from a leachate treatment station in a waste incineration plant. The system includes: a leachate pretreatment unit for pretreating the leachate; a chemical softening system for treating the mixed wastewater after the pretreated leachate and fly ash washing wastewater are mixed; a post-treatment unit for further treating the mixed wastewater after treatment by the chemical softening system; and a dewatering system for dewatering the sludge generated by the chemical softening system and sending it to the incinerator. By redesigning and replacing the leachate treatment process within the leachate treatment station, the system effectively removes suspended solids, COD, SS, and salt from the leachate, as well as pollutants such as high salt content, high calcium ion concentration, and a certain amount of heavy metals from the fly ash washing wastewater. The effluent quality is excellent and stable, meeting standards for reuse.

Description

Technical Field

[0001] This invention belongs to the field of municipal solid waste incineration technology, specifically relating to a co-treatment process and system for fly ash and washing wastewater from leachate stations in waste incineration plants. Background Technology

[0002] Landfill leachate is a secondary pollutant produced during the storage and disposal of landfills through extraction, hydrolysis, and fermentation. It is a complex wastewater containing high concentrations of organic pollutants, ammonia nitrogen, suspended solids (SS), and high salinity. Fly ash washing wastewater is the wastewater produced after three stages of countercurrent washing of fly ash generated from the incineration of municipal solid waste in an incinerator. It is small in scale and low in output, and is characterized by high salinity, high calcium ion concentration, and a certain amount of heavy metals.

[0003] Currently, among the many leachate treatment processes designed for municipal solid waste incineration leachate treatment plants, the "pretreatment system + anaerobic treatment system + MBR system + NF system + RO system" process is the most commonly used and has good results. However, when using this process to co-treat fly ash washing wastewater, it suffers from drawbacks such as severe scaling in nanofiltration and reverse osmosis, and low permeate recovery rate, making it unsuitable for co-treating fly ash washing wastewater. If separate process packages are designed for the two wastewater streams, it results in large land area requirements, high investment costs, and high operating costs. How to achieve technically feasible and economically reasonable simultaneous treatment of leachate and fly ash washing wastewater within a limited space is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a process and system for the co-treatment of fly ash washing wastewater from leachate treatment plants in waste incineration plants.

[0005] To address the aforementioned technical problems, this invention provides a co-treatment system for fly ash washing wastewater from a waste incineration plant leachate station, comprising:

[0006] The leachate pretreatment unit is used to pretreat the leachate.

[0007] A chemical softening system is used to treat mixed wastewater after pretreated leachate and fly ash washing wastewater are mixed.

[0008] The post-treatment unit is used to further treat the mixed wastewater after it has been treated by the chemical softening system; and

[0009] The dewatering system is used to dewater the sludge produced by the chemical softening system and send it to the incinerator.

[0010] In one embodiment of this application, the chemical softening system includes a first reaction tank, a second reaction tank, a softened sludge tank, a TUF circulation tank, and a TUF membrane system connected in sequence; wherein

[0011] The first reaction tank is used to receive mixed wastewater and remove hardness ions such as calcium and magnesium from the mixed wastewater;

[0012] The second reaction tank is used to receive the mixed wastewater from the first reaction tank and remove heavy metal ions from the mixed wastewater;

[0013] The softened sludge tank is used to receive the mixed wastewater from the second reaction tank, where it settles to form sludge and is then transported to the dewatering system.

[0014] The TUF membrane system is connected to the softened sludge tank and the post-treatment unit. Its permeate flows into the post-treatment unit, and the concentrate is returned to the softened sludge tank.

[0015] In one embodiment of this application, the leachate pretreatment unit includes an equalization tank, an anaerobic reactor, an A / O system, and an ultrafiltration system connected in sequence.

[0016] The ultrafiltration system is connected to the first reaction tank.

[0017] In one embodiment of this application, the post-processing unit includes a material membrane system, an RO system, an ultra-high pressure RO system, and an evaporation system connected in sequence;

[0018] The material membrane system is used to separate organic matter from the permeate of the TUF membrane system. After the permeate is reduced by the RO system and the ultra-high pressure RO system, the permeate meets the standards for reuse, and the concentrate enters the evaporation system.

[0019] The purified water from the evaporation system is returned to the RO system.

[0020] Accordingly, the present invention also provides a co-treatment process for fly ash washing wastewater from a waste incineration plant leachate station, comprising:

[0021] Pretreatment of leachate;

[0022] The pretreated leachate and fly ash washing wastewater are mixed to form mixed wastewater;

[0023] Chemical softening treatment is applied to the mixed wastewater;

[0024] Post-treatment of mixed wastewater after chemical softening system treatment; and

[0025] The sludge generated from the chemical softening system is dewatered and then sent to the incinerator.

[0026] In one embodiment of this application, the method for pretreating leachate includes:

[0027] The leachate was homogenized and its quantity was uniformly measured in the equalization tank.

[0028] Removal of major organic matter such as COD and ammonia nitrogen in anaerobic and A / O systems;

[0029] The ultrafiltration system further removes pollutants such as large molecular COD and suspended solids.

[0030] In one embodiment of this application, the method for chemically softening mixed wastewater includes:

[0031] The mixed wastewater, under the action of the first reaction tank and the added caustic soda and soda ash, removes hardness ions such as calcium and magnesium.

[0032] It then flows by gravity to the second reaction tank to react with added sodium sulfide to remove heavy metal ions;

[0033] The precipitates generated in the first and second reaction tanks settle in the softened sludge tank and are then transported to the dewatering system for separation.

[0034] The mixed wastewater in the softened sludge tank continues to overflow into the TUF circulation tank and is pumped to the TUF membrane system.

[0035] The TUF membrane system produces and concentrates water. The concentrate is returned to the softened sludge tank and settled by gravity to remove the precipitate. The produced water is then subjected to further treatment.

[0036] In one embodiment of this application, the method for post-treating the mixed wastewater after treatment by a chemical softening system includes:

[0037] The permeate from the TUF membrane system enters the material membrane system. Under the separation action of the material membrane, organic matter is discharged with the concentrate and then utilized.

[0038] After the permeate from the membrane system is reduced in volume by the RO system and the ultra-high pressure RO system, the permeate is reused and the concentrate enters the evaporation system.

[0039] The evaporation system further concentrates the concentrate, and the clear liquid produced by evaporation is returned to the front-end RO system. The salt mud produced by evaporation is packaged in ton bags for comprehensive utilization.

[0040] The beneficial effects of this invention are that the co-treatment process and system for fly ash washing wastewater from the leachate station of the waste incineration plant of this invention, by redesigning and replacing the leachate treatment process in the leachate station, not only effectively removes pollutants such as suspended solids, COD, SS, and salt from the leachate, but also effectively removes pollutants such as high salt content, high calcium ion concentration, and a certain amount of heavy metals from the fly ash washing wastewater; the effluent quality is excellent and stable, and can be reused in compliance with standards.

[0041] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0043] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the co-treatment of fly ash and washing wastewater from the leachate station of a waste incineration plant according to the present invention;

[0045] Figure 2 This is a schematic diagram of the chemical softening system of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] See Figure 1 and Figure 2 A first aspect of the present invention provides a co-treatment system for fly ash washing wastewater from a leachate station in a waste incineration plant, comprising: a leachate pretreatment unit for pretreating the leachate; a chemical softening system for treating the mixed wastewater after the pretreated leachate and fly ash washing wastewater are mixed; a post-treatment unit for post-treating the mixed wastewater after treatment by the chemical softening system; and a dewatering system for dewatering the sludge generated by the chemical softening system and feeding it into the incinerator.

[0048] Specifically, the leachate pretreatment unit is connected to the chemical softening system, which in turn is connected to the dewatering system and the post-treatment unit.

[0049] See Figure 2 In this embodiment, preferably, the chemical softening system includes a first reaction tank, a second reaction tank, a softened sludge tank, a TUF circulation tank, and a TUF membrane system connected in sequence; wherein

[0050] The first reaction tank is connected to the leachate pretreatment unit and the fly ash washing wastewater regulating tank, and is used to receive the mixed wastewater and remove hardness ions such as calcium and magnesium from the mixed wastewater.

[0051] The second reaction tank is used to receive the mixed wastewater from the first reaction tank and remove heavy metal ions from the mixed wastewater; optionally,

[0052] The softened sludge tank is used to receive the mixed wastewater from the second reaction tank, settle it to form sludge, and transport it to the dewatering system; the first reaction tank and the second reaction tank can be connected at the bottom, so that the mixed wastewater from the first reaction tank can flow into the second reaction tank by gravity.

[0053] The TUF membrane system is connected to the softened sludge tank and the post-treatment unit. Its permeate flows into the post-treatment unit, and the concentrate is returned to the softened sludge tank.

[0054] As an optional embodiment of the leachate pretreatment unit, the leachate pretreatment unit includes an equalization tank, an anaerobic reactor, an A / O system, and an ultrafiltration system connected in sequence; the ultrafiltration system is connected to the first reaction tank.

[0055] The post-treatment unit includes a material membrane system, an RO system, an ultra-high pressure RO system, and an evaporation system connected in sequence. The material membrane system is used to separate organic matter from the permeate of the TUF membrane system. After the permeate is reduced in volume by the RO system and the ultra-high pressure RO system, the permeate meets the standards for reuse, and the concentrate enters the evaporation system. The purified water from the evaporation system is returned to the RO system.

[0056] See Figure 1 and Figure 2 Based on the above embodiments, a second aspect of the present invention provides a co-treatment process for fly ash washing wastewater from a leachate station in a waste incineration plant, comprising: pretreatment of leachate; mixing the pretreated leachate and fly ash washing wastewater to form mixed wastewater; chemically softening the mixed wastewater; post-treating the mixed wastewater after treatment by the chemical softening system; and dewatering the sludge generated by the chemical softening system and sending it to the incinerator.

[0057] See Figure 1 The method for pretreating leachate includes: homogenizing and equalizing the quantity of leachate in an equalization tank; removing major organic matter such as COD and ammonia nitrogen in an anaerobic system and an A / O system; and filtering in an ultrafiltration system to further remove pollutants such as macromolecular COD and suspended solids.

[0058] See Figure 2The method for chemically softening mixed wastewater includes: removing hardness ions such as calcium and magnesium from the mixed wastewater under the action of added caustic soda and soda ash in a first reaction tank; the mixed wastewater then flows by gravity to a second reaction tank to react with added sodium sulfide to remove heavy metal ions; the mixed wastewater overflows from the second reaction tank into a softening sludge tank, where the precipitates generated in the first and second reaction tanks settle and can be pumped to a dewatering system for separation; the mixed wastewater in the softening sludge tank continues to overflow into a TUF circulation tank and is pumped to a TUF membrane system; the TUF membrane system produces water and concentrates it, the concentrate is returned to the softening sludge tank and precipitates under gravity to remove the precipitates, and the produced water undergoes post-treatment.

[0059] See Figure 1 Optionally, the method for post-treatment of the mixed wastewater after chemical softening includes: the permeate from the TUF membrane system enters the material membrane system; organic matter in the wastewater that cannot be treated by biochemical methods can be discharged with the concentrate and utilized under the separation action of the material membrane; the permeate from the material membrane system is reduced in volume by the RO system and the ultra-high pressure RO system, and the permeate is reused after meeting the standards, while the concentrate enters the evaporation system; the evaporation system further concentrates the concentrate, and the clear liquid produced by evaporation is returned to the front-end RO system to ensure that the final permeate meets the standards for reuse, and the system permeate recovery rate is not less than 80%; the salt mud produced by evaporation is packaged in ton bags and then utilized comprehensively.

[0060] In summary, the co-treatment process and system for fly ash washing wastewater from the leachate station of the waste incineration plant of the present invention, through the redesign and replacement of the leachate treatment process in the leachate station, not only effectively removes pollutants such as suspended solids, COD, SS, and salt from the leachate, but also effectively removes pollutants such as high salt content, high calcium ion concentration, and a certain amount of heavy metals from the fly ash washing wastewater; the effluent quality is excellent and stable, and meets the standards for reuse.

[0061] This process has the following advantages:

[0062] 1) For the two streams of water, leachate and fly ash washing wastewater, a co-treatment method is adopted, which has the advantages of small footprint, low construction cost and convenient operation;

[0063] 2) By redesigning and replacing the conventional leachate process, a higher system permeate recovery rate can be obtained (the system recovery rate is increased from 63.75% to over 80%).

[0064] All the devices (parts whose specific structures are not specified) selected in this application are general standard parts or parts known to those skilled in the art. Their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0065] In the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0066] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0067] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A co-treatment process for fly ash washing wastewater from a waste incineration plant leachate station, characterized in that, For use in a co-treatment system for fly ash washing wastewater from leachate stations in waste incineration plants; The co-treatment system for fly ash washing wastewater from the leachate station of the waste incineration plant includes: The leachate pretreatment unit is used to pretreat the leachate. A chemical softening system is used to treat mixed wastewater after pretreated leachate and fly ash washing wastewater are mixed. The post-treatment unit is used to further treat the mixed wastewater after it has been treated by the chemical softening system; and The dewatering system is used to dewater the sludge produced by the chemical softening system and send it to the incinerator. The chemical softening system includes a first reaction tank, a second reaction tank, a softened sludge tank, a TUF circulation tank, and a TUF membrane system connected in sequence. The first reaction tank receives mixed wastewater and removes calcium and magnesium hardness ions from it. The second reaction tank receives the mixed wastewater from the first reaction tank and removes heavy metal ions from it. The softened sludge tank receives the mixed wastewater from the second reaction tank, settles it to form sludge, and transports it to a dewatering system. The TUF membrane system is connected to the softened sludge tank and a post-treatment unit; its permeate flows into the post-treatment unit, and the concentrate is returned to the softened sludge tank. The leachate pretreatment unit includes an equalization tank, an anaerobic reactor, an A / O system, and an ultrafiltration system connected in sequence; the ultrafiltration system is connected to the first reaction tank. The post-treatment unit includes a material membrane system, an RO system, an ultra-high pressure RO system, and an evaporation system connected in sequence. The material membrane system is used to separate organic matter from the permeate of the TUF membrane system. After the permeate is reduced in volume by the RO system and the ultra-high pressure RO system, the permeate meets the standards for reuse, and the concentrate enters the evaporation system. The purified water from the evaporation system is returned to the RO system. The co-treatment process for fly ash washing wastewater from the leachate station of the waste incineration plant includes: Pretreatment of leachate; The pretreated leachate and fly ash washing wastewater are mixed to form mixed wastewater; Chemical softening treatment is applied to the mixed wastewater; Post-treatment of mixed wastewater after chemical softening system treatment; and The sludge generated from the chemical softening system is dewatered and then sent to the incinerator.

2. The collaborative processing technology according to claim 1, characterized in that, The method for pretreating the leachate includes: The leachate was homogenized and its quantity was uniformly measured in the equalization tank. Removal of major COD, ammonia nitrogen, and organic matter in anaerobic and A / O systems; The ultrafiltration system further removes large molecular COD and suspended solids.

3. The collaborative processing technology according to claim 2, characterized in that, The method for chemically softening mixed wastewater includes: The mixed wastewater, under the action of the first reaction tank and the added caustic soda and soda ash, removes calcium and magnesium hardness ions; It then flows by gravity to the second reaction tank to react with added sodium sulfide to remove heavy metal ions; The precipitates generated in the first and second reaction tanks settle in the softened sludge tank and are then transported to the dewatering system for separation. The mixed wastewater in the softened sludge tank continues to overflow into the TUF circulation tank and is pumped to the TUF membrane system. The TUF membrane system produces and concentrates water. The concentrate is returned to the softened sludge tank and settled by gravity to remove the precipitate. The produced water is then subjected to further treatment.

4. The collaborative processing technology according to claim 3, characterized in that, The method for post-treatment of mixed wastewater after treatment by a chemical softening system includes: The permeate from the TUF membrane system enters the material membrane system. Under the separation action of the material membrane, organic matter is discharged with the concentrate and then utilized. After the permeate from the material membrane system is reduced in volume by the RO system and the ultra-high pressure RO system, the permeate is reused after meeting the standards, and the concentrate enters the evaporation system. The evaporation system further concentrates the concentrate, and the clear liquid produced by evaporation is returned to the front-end RO system. The salt mud produced by evaporation is packaged in ton bags and then used for comprehensive utilization.

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