System and method for treating landfill leachate through combination of high-energy wave, electrochemistry and RO (Reverse Osmosis) membrane

Abstract

The invention provides a high-energy wave-electrochemistry-RO membrane combined landfill leachate treatment system and method, and relates to the technical field of landfill leachate treatment. Aiming at the problems of low biochemical treatment efficiency, serious secondary pollution caused by advanced oxidation, easy blockage of a membrane and the like in a traditional process, a three-stage coupling process is provided: firstly, macromolecular organic matters are crushed through high-energy wave cavitation, and bound ammonia nitrogen is released; then, in the electrochemical unit, ammonia nitrogen is selectively oxidized into nitrogen by adopting a chlorine evolution active anode, and hydroxyl free radicals are synchronously generated to degrade organic matters; finally, residual pollutants are intercepted through the anti-pollution RO membrane. The method has the advantages of high efficiency, low consumption, high impact resistance and the like, is suitable for advanced treatment of the leachate, and is a landfill leachate treatment technology with great application and development prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of landfill leachate treatment, and specifically relates to a system and method for efficiently removing organic matters and ammonia nitrogen in landfill leachate by using a high-energy wave pretreatment, electrochemical oxidation and reverse osmosis (RO) membrane integrated process. Background Art

[0002] Landfill leachate refers to the water contained in the garbage itself in the landfill, rain and snow water entering the landfill, water leaked from the garbage piled up for incineration, and other water. After deducting the saturated water holding capacity of the garbage and the covering soil layer, and passing through the garbage layer and the covering soil layer, a high-concentration organic wastewater is formed. Landfill leachate wastewater has the characteristics of high organic matter concentration, large water quality variation, high ammonia nitrogen content, and imbalance in the proportion of microbial nutrient elements. The treatment of landfill leachate from urban landfills has always been a very difficult problem in the design, operation and management of landfills.

[0003] The current mainstream processes generally adopt a combined mode of "biochemical treatment + advanced treatment": in the biochemical stage, nitrification-denitrification or anaerobic ammonium oxidation for nitrogen removal is mostly relied on, but problems such as imbalance in the carbon-nitrogen ratio of leachate and inhibition by toxic substances often lead to a decrease in microbial activity, and the ammonia nitrogen removal rate is less than 60%; in the advanced treatment link, advanced oxidation technologies such as Fenton oxidation and ozone catalysis are relied on. Although some refractory organic matters can be degraded, there are defects such as large dosage of chemicals, secondary pollution of iron sludge and high operation cost.

[0004] Therefore, it is urgent to develop an integrated process with high efficiency, low consumption and short process to achieve the synchronous and advanced removal of organic matters and ammonia nitrogen. Summary of the Invention

[0005] The present invention aims to provide a system and method for jointly treating landfill leachate by high-energy wave - electrochemistry - RO membrane, and through the synergistic effect of high-energy wave pretreatment, electrochemical directional oxidation and RO membrane interception, achieve the efficient and synchronous removal of organic matters and ammonia nitrogen in landfill leachate, simplify the process flow and avoid secondary pollution.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a system for jointly treating landfill leachate by high-energy wave - electrochemistry - RO membrane, which system comprises: a high-energy wave generating device, an electrochemistry reaction device and an RO membrane module that are connected in sequence; the high-energy wave generating device is used for performing high-energy wave treatment on the landfill leachate to break macromolecular organic matters in the landfill leachate and release bound ammonia nitrogen, and then conveying the treated landfill leachate to the next treatment process; the electrochemistry reaction device is used for performing electrochemistry oxidation treatment on the landfill leachate to oxidize and degrade organic matters and simultaneously electrolyze to produce active chlorine for efficient denitrification, and then conveying the treated landfill leachate to the next treatment process; the RO membrane module is used for intercepting residual pollutants in the landfill leachate through the membrane and then discharging the tail water.

[0008] Further, a high-energy wave generator is provided at the top of the high-energy wave generating device; the operating frequency of the high-energy wave generating device is 20 - 40 kHz, and the energy density per unit area is 300 - 400 W / CM 2 。

[0009] Further, the number of the high-energy wave generating devices is at least two, and at least two high-energy wave generating devices are arranged in series and operate in a periodically alternating manner; wherein, the longest operating time of each high-energy wave generating device is 8 - 12 h, and the intermittent time is 1 - 2 h.

[0010] Further, an anode and a cathode are arranged in the electrochemistry reaction device, the anode is a titanium-based ruthenium-iridium coated electrode, the cathode adopts a stainless steel mesh, and the current density is 10 - 50 mA / cm 2 。

[0011] Further, the RO membrane module adopts an anti-pollution spiral wound RO membrane, and the operating pressure is 1.5 - 3.0 MPa.

[0012] Further, the system comprises a controller connected to the high-energy wave generating device and the electrochemistry reaction device, and the controller is used for controlling the start-stop operation of the high-energy wave generating device and the electrochemistry reaction device and adjusting the operating parameters.

[0013] Further, the system further comprises a grille and an adjustment tank arranged before the high-energy wave generating device; the grille is used for intercepting suspended impurities in the landfill leachate to be treated; the adjustment tank is used for adjusting the pH value of the landfill leachate and balancing the water quality and water quantity.

[0014] Further, a first feed pump is arranged between the adjustment tank and the high-energy wave generating device; a second feed pump is arranged between the high-energy wave generating device and the electrochemistry reaction device; a third feed pump is arranged between the electrochemistry reaction device and the RO membrane module.

[0015] The present invention also provides a method for jointly treating landfill leachate by high-energy wave-electrochemistry-RO membrane, which is applied to the system for jointly treating landfill leachate by high-energy wave-electrochemistry-RO membrane as described above; the method includes the following steps: the landfill leachate to be treated enters the regulation tank through grid interception of suspended impurities to adjust the pH value to 6.5-8.5 and balance the water quality and quantity; the regulated landfill leachate is pumped into the high-energy wave generating device by the first inlet water pump for high-energy wave treatment; the treated liquid is pumped into the electro-chemical reaction device by the second inlet water pump for electro-chemical oxidation; the landfill leachate after electro-chemical treatment is pumped into the anti-pollution RO membrane module by the third inlet water pump, and the tail water is discharged after the residual pollutants are intercepted by the membrane.

[0016] Further, the hydraulic retention time of the landfill leachate in the high-energy wave generating device is 5-30 min, and the hydraulic retention time in the electro-chemical reaction device is 1.5-3 h. Among them, the service life of the high-energy wave generating device and the RO membrane module is greater than 3 years, and the service life of the electro-chemical reaction device can reach 2-4 years.

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

[0018] First, through the high-energy wave cavitation pretreatment, the macromolecular organic matter is effectively broken and the bound ammonia nitrogen is released, solving the problem of insufficient cavitation oxidation ability of traditional ultrasonic waves, and greatly improving the subsequent electro-chemical treatment efficiency; second, the electro-chemical oxidation process using a chlorine-evolving active anode realizes the selective oxidation of ammonia nitrogen to nitrogen at a low current density, and simultaneously generates hydroxyl radicals to degrade organic matter, avoiding the reagent dependence and secondary iron sludge pollution of processes such as Fenton oxidation; in addition, through the synergistic pretreatment of high-energy waves and electro-chemistry, the colloid and organic matter load in the RO membrane inlet water is significantly reduced, the membrane life is extended and the cleaning frequency is reduced.

[0019] The whole set of processes realizes efficient treatment with short process and low energy consumption through three-stage coupling. The ammonia nitrogen removal rate can reach more than 90%, and the organic matter removal rate exceeds 94%. Moreover, the system has strong anti-shock load capacity through periodic alternating operation of the high-energy wave device and dynamic controller adjustment, and is suitable for the advanced treatment of landfill leachate with high concentration and large water quality fluctuations, having significant economic and environmental benefits. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of a system for jointly treating landfill leachate by high-energy wave-electrochemistry-RO membrane provided by an embodiment of the present invention.

[0021] In the figure: 1, grille; 2, regulating tank; 3, first inlet water pump; 4, high-energy wave generating device; 5, high-energy wave generator; 6, controller; 7, second inlet water pump; 8, electrochemical reaction device; 9, anode; 10, cathode; 11, third inlet water pump; 12, RO membrane module. Detailed implementation mode

[0022] The inventor's research found that the ultrasonic cavitation effect can effectively break down macromolecular organic matter, but lacks the ability of directional oxidation and makes little contribution to ammonia nitrogen removal. When electrochemistry is used to treat high-ammonia-nitrogen wastewater alone, the anodic oxidation of ammonia nitrogen requires an extremely high current density, resulting in a sharp increase in energy consumption costs; the RO membrane technology can effectively intercept pollutants, but when directly treating the original solution, the membrane surface is easily blocked by substances such as colloids and humic acids, and the flux decay rate reaches 40% / month. Frequent chemical cleaning further shortens the membrane life, seriously restricting its engineering application.

[0023] Taking the above situation into comprehensive consideration, the present invention breaks down macromolecular organic matter through the high-energy wave cavitation effect and releases bound ammonia nitrogen; the electrochemical anodic oxidation degrades organic matter, and at the same time electrolyzes to produce active chlorine for efficient denitrification; the RO membrane intercepts residual pollutants, and the triple coordination realizes short-process and efficient treatment.

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings and embodiments in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0025] The present invention provides a system for jointly treating landfill leachate by high-energy wave - electrochemistry - RO membrane, as Figure 1 shown. The system includes: a high-energy wave generating device 4, an electrochemical reaction device 8, and an RO membrane module 12 that are connected in sequence.

[0026] The high-energy wave generating device 4 is used to perform high-energy wave treatment on landfill leachate to break down macromolecular organic matter in the landfill leachate and release bound ammonia nitrogen, and then convey the treated landfill leachate to the next treatment process; the electrochemical reaction device 8 is used to perform electrochemical oxidation treatment on landfill leachate to oxidize and degrade organic matter and at the same time electrolyze to produce active chlorine for efficient denitrification, and then convey the treated landfill leachate to the next treatment process; the RO membrane module 12 is used to discharge the tail water after intercepting residual pollutants in the landfill leachate through the membrane.

[0027] Specifically, a high-energy wave generator 5 is provided at the top of the high-energy wave generating device 4; the working frequency of the high-energy wave generating device 4 is 20 - 40 kHz, and the energy density per unit area is 300 - 400 W / CM 2 .

[0028] The number of the high-energy wave generating devices 4 is at least two. At least two high-energy wave generating devices 4 are arranged in series and operate in a periodically alternating manner. Among them, the longest operation time of each high-energy wave generating device 4 is 8 - 12 h, and the intermittent time is 1 - 2 h.

[0029] An anode 9 and a cathode 10 are arranged in the electrochemical reaction device 8. The anode 9 is a titanium-based ruthenium-iridium coated electrode, and the cathode 10 is made of a stainless steel mesh. The current density is 10 - 50 mA / cm 2 。

[0030] The RO membrane module 12 uses an anti-pollution spiral wound RO membrane, and the operating pressure is 1.5 - 3.0 MPa.

[0031] The system includes a controller 6 connected to the high-energy wave generating device 4 and the electrochemical reaction device 8. The controller 6 is used to control the start-stop operation of the high-energy wave generating device 4 and the electrochemical reaction device 8 and adjust the operating parameters.

[0032] The system further includes a grille 1 and an adjustment tank 2 arranged before the high-energy wave generating device 4. The grille 1 is used to intercept suspended impurities in the landfill leachate to be treated. The adjustment tank 2 is used to adjust the pH value of the landfill leachate and balance the water quality and quantity.

[0033] A first inlet pump 3 is arranged between the adjustment tank 2 and the high-energy wave generating device 4. A second inlet pump 7 is arranged between the high-energy wave generating device 4 and the electrochemical reaction device 8. A third inlet pump 11 is arranged between the electrochemical reaction device 8 and the RO membrane module 12.

[0034] Example 1:

[0035] The leachate of a certain landfill (COD 8000 mg / L, ammonia nitrogen 1200 mg / L) is treated by this technology. First, after the leachate intercepts suspended impurities through the grille, it enters the adjustment tank, where the pH is adjusted to 7.5 and the water quality and quantity are balanced. Subsequently, it is sent into the series-connected high-energy wave generating devices through the first inlet pump. The devices operate in a periodically alternating mode, ensuring that one high-energy wave generating device is operating while two high-energy wave generating devices are resting (the longest operation time of a single device is 10 hours, and the intermittent time is at least 1.5 hours). The working frequency of the device is 30 kHz, and the energy density per unit area is 350 W / cm 2 , The hydraulic retention time is 20 minutes, and the cavitation effect is used to break macromolecular organic matter and release bound ammonia nitrogen. The treated liquid enters the electrochemical reaction device through the second inlet pump. A titanium-based ruthenium-iridium coated anode and a stainless steel mesh cathode are used, and the current density is 30 mA / cm 2, with a hydraulic retention time of 2 hours, realizes the selective oxidation of ammonia nitrogen to nitrogen gas and simultaneously degrades organic matter. Finally, the leachate is sent into the anti-pollution spiral RO membrane module by the third inlet water pump, with an operating pressure of 2.0 MPa to intercept residual pollutants.

[0036] The COD of the treated effluent is reduced to below 200 mg / L (removal rate: 97.5%), and the ammonia nitrogen is reduced to below 50 mg / L (removal rate: 95.8%). The membrane cleaning cycle is extended from 7 days to 30 days, and the service life reaches 4 years. The system operates stably with low energy consumption.

[0037] Example 2:

[0038] For the leachate of a certain incineration plant (ammonia nitrogen 2500 mg / L, COD 6000 mg / L, containing high-concentration humic acid), this technology realizes efficient treatment by optimizing parameters. After pretreatment, the leachate is sent into the series-connected high-energy wave generating device by the first inlet water pump. The device adopts a periodic alternating operation mode to ensure that two high-energy wave generating devices are operating while one high-energy wave generating device is resting when treating the leachate. The working frequency is 40 kHz, and the energy density is 400 W / cm 2 , with a hydraulic retention time of 30 minutes, fully releases the bound ammonia nitrogen and breaks the macromolecules of humic acid. Subsequently, the electrochemistry reaction device increases the current density to 50 mA / cm 2 , uses the titanium-based ruthenium-iridium anode to generate active chlorine to strengthen the oxidation of ammonia nitrogen to nitrogen gas, and the hydraulic retention time is extended to 3 hours. The RO membrane module adopts an anti-pollution membrane, with an operating pressure of 2.5 MPa, effectively avoiding the blockage of humic acid.

[0039] After treatment, the ammonia nitrogen concentration is reduced to below 75 mg / L (removal rate: 97%), and the COD is reduced to 300 mg / L (removal rate: 95%). The RO membrane flux decay rate is controlled within 10% per month, significantly reducing the operation and maintenance costs.

[0040] Example 3:

[0041] The water quality of the leachate in a landfill during the rainy season (instantaneous peak value of COD 15000 mg / L, peak value of ammonia nitrogen 1800 mg / L) fluctuates violently. This system monitors the influent water quality in real time through a controller and dynamically adjusts the operation parameters. The device adopts a periodic alternating operation mode to ensure that two high-energy wave generating devices are operating while one high-energy wave generating device is resting when treating the leachate. The working frequency of the device is 30 kHz, and the energy density of the high-energy wave device is automatically adjusted to 300 - 400 W / cm 2 , with a hydraulic retention time of 20 minutes. The current density of the electrochemistry unit is dynamically switched to 20 - 50 mA / cm 2 , with a hydraulic retention time of 2.5 hours, ensuring the effective degradation of high-concentration pollutants. The operating pressure of the RO membrane module is adjusted to 1.5 MPa to reduce the membrane surface pollution rate.

[0042] The COD of the treated effluent is stably below 900 mg / L (removal rate > 94%), the ammonia nitrogen concentration is below 180 mg / L (removal rate > 90%), the membrane flux decay rate is < 15% / month, the system has a significant ability to resist shock loads, and it is suitable for scenarios with large water quality fluctuations.

Claims

1. A system for treating landfill leachate by combining high energy wave, electrochemical and RO membrane, characterized in that: The system comprises: a high-energy wave generating device (4), an electrochemical reaction device (8) and an RO membrane assembly (12) connected in sequence; The high-energy wave generating device (4) is used to perform high-energy wave treatment on the landfill leachate to break up the macromolecular organic matter in the landfill leachate and release the bound ammonia nitrogen, and then transport the treated landfill leachate to the next treatment process; The electrochemical reaction device (8) is used to perform electrochemical oxidation treatment on the landfill leachate to oxidatively degrade organic matter and simultaneously electrolyze to produce active chlorine for efficient nitrogen removal, and then transport the treated landfill leachate to the next treatment process; The RO membrane assembly (12) is used to discharge tail water after the residual pollutants in the landfill leachate are intercepted by the membrane.

2. The system for treating landfill leachate by high energy wave-electrochemical-RO membrane combination according to claim 1 is characterized in that: A high-energy wave generator (5) is provided on the top of the high-energy wave generating device (4); the operating frequency of the high-energy wave generating device (4) is 20 to 40 kHz, and the energy density per unit area is 300 to 400 W / CM 2 .

3. The system for treating landfill leachate by high energy wave-electrochemical-RO membrane combination according to claim 1 is characterized in that: The number of the high-energy wave generating devices (4) is at least two, and at least two of the high-energy wave generating devices (4) are arranged in series and operate in a periodic alternating manner; The maximum operating time of each high-energy wave generating device (4) is 8 to 12 hours, and the intermittent time is 1 to 2 hours.

4. The system for treating landfill leachate by high energy wave-electrochemical-RO membrane combination according to claim 1 is characterized in that: The electrochemical reaction device (8) is provided with an anode (9) and a cathode (10), wherein the anode (9) is a titanium-based ruthenium-iridium coated electrode, and the cathode (10) is a stainless steel mesh, and the current density is 10 to 50 mA / cm 2 .

5. The system for treating landfill leachate by high energy wave-electrochemical-RO membrane combination according to claim 1 is characterized in that: The RO membrane assembly (12) adopts an anti-pollution rolled RO membrane, and the operating pressure is 1.5-3.0 MPa.

6. The system for treating landfill leachate by high energy wave-electrochemical-RO membrane combination according to claim 1 is characterized in that: The system comprises a controller (6) connected to the high-energy wave generating device (4) and the electrochemical reaction device (8), wherein the controller (6) is used to control the start and stop operation of the high-energy wave generating device (4) and the electrochemical reaction device (8) and to adjust the operating parameters.

7. The system for treating landfill leachate by high energy wave-electrochemical-RO membrane combination according to claim 1 is characterized in that: The system also includes a grid (1) and a regulating pool (2) arranged before the high-energy wave generating device (4); The grid (1) is used to intercept suspended impurities in the landfill leachate to be treated; The regulating tank (2) is used to adjust the pH value in the landfill leachate and balance the water quality and quantity.

8. The system for treating landfill leachate by combining high energy wave, electrochemistry and RO membrane according to claim 1 is characterized in that: A first water inlet pump (3) is provided between the regulating tank (2) and the high-energy wave generating device (4); a second water inlet pump (7) is provided between the high-energy wave generating device (4) and the electrochemical reaction device (8); and a third water inlet pump (11) is provided between the electrochemical reaction device (8) and the RO membrane assembly (12).

9. A method for treating landfill leachate by combining high energy wave, electrochemical and RO membrane, characterized in that: The method is applied to a system for treating landfill leachate by combining high energy wave-electrochemical-RO membrane as claimed in any one of claims 1 to 8; The method comprises the following steps: The landfill leachate to be treated passes through a screen (1) to intercept suspended impurities and then enters a regulating tank (2) to adjust the pH value to 6.5 to 8.5 and balance the water quality and quantity; The regulated landfill leachate is pumped into the high-energy wave generating device (4) through the first water inlet pump (3) for high-energy wave treatment; The treated liquid is pumped into the electrochemical reaction device (8) through the second water inlet pump (7) for electrochemical oxidation; The electrochemically treated landfill leachate is pumped into the anti-pollution RO membrane assembly (12) by the third water inlet pump (11), and the tail water is discharged after the residual pollutants are intercepted by the membrane.

10. The system for treating landfill leachate by high energy wave-electrochemical-RO membrane combination according to claim 9 is characterized in that: The hydraulic retention time of the garbage leachate in the high-energy wave generating device (4) is 5 to 30 minutes, and the hydraulic retention time in the electrochemical reaction device (8) is 1.5 to 3 hours.

Images