Anion exchange resin-duckweed coupling treatment system and treatment method for rapid denitrification and phosphorus removal in water

Abstract

The present invention discloses an anion exchange resin-duckweed coupling treatment system and treatment method that can quickly denitrify and remove phosphorus from water bodies. The system includes an interconnected water purification reactor and a resin regeneration reactor. Both reactors are provided with stirring paddles and anion exchange resin. Duckweed is located on the water surface of the two reactors, and an inclined plate is provided between the duckweed and the resin. The anion exchange resin can be transported to each other in the water purification reactor and the resin regeneration reactor. In the present invention, the anion exchange resin and duckweed are the purification bodies of the system. The coupling system of the resin and duckweed strengthens the denitrification and phosphorus removal to achieve the purpose of water quality improvement. At the same time, in the resin regeneration reaction, the resin is regenerated by desorption of low-concentration salt water and absorption of nitrogen and phosphorus by duckweed. The regenerated resin is returned to the water purification reactor for reuse, realizing the recycling of the resin. The present invention achieves efficient removal of nitrogen, phosphorus, and organic matter in eutrophic water bodies.

Description

Technical Field

[0001] The invention belongs to the field of eutrophic water body restoration, and particularly relates to an anion exchange resin-duckweed coupling treatment system and a treatment method for rapidly removing nitrogen and phosphorus from water bodies. Background Art

[0002] Currently, commonly used water denitrification and phosphorus removal processes include coagulation and sedimentation, membrane technology, and adsorption. Coagulation and sedimentation primarily involves the addition of flocculants to flocculate pollutants in the water into larger flocs, which then settle by gravity. In practice, coagulation and sedimentation are effective for phosphorus removal, but less effective for nitrogen removal. Membrane technology is an effective and selective wastewater nutrient recovery technology, capable of separating and concentrating nutrients such as nitrogen and phosphorus from different water streams. However, membrane fouling is a major challenge for nutrient recovery from wastewater, thus reducing its economic viability. Adsorption is a purification technology that utilizes the physical and chemical properties of adsorbents to interact physically and chemically with pollutants, separating and removing them from wastewater. Common adsorbents include activated carbon, fly ash, and zeolites, but they also present desorption difficulties and the influence of interfering ions. In recent years, ion exchange resins have gained widespread application due to their ability to selectively remove pollutants from water through functional groups on their surfaces (such as quaternary ammonium, sulfonic acid, carboxylic acid, and phosphate groups). They offer advantages such as large processing capacity, high adsorption efficiency, and ease of desorption and regeneration. Strong-base anion exchange resins, with their quaternary ammonium groups, can efficiently remove electronegative pollutants by exchanging ions with them. Therefore, anion exchange resins can be used to effectively remove nitrogen and phosphorus from water. However, traditional resin regeneration methods require the use of highly concentrated brine, and the resulting highly concentrated brine desorption solution is also harmful to the environment and requires further treatment. Existing technologies often use 8% to 15% NaCl solutions to desorb anion exchange resins. Patent CN112266050 A improves on this approach by using a strong-base anion exchange material to deeply remove nitrate nitrogen from water. This strong-base anion exchange material can effectively adsorb nitrate nitrogen from water, and the regeneration process uses a 3% to 5% NaCl solution. However, the subsequent treatment of the regenerated wastewater requires the use of multiple membrane technologies, which can easily lead to membrane fouling problems, and the regeneration wastewater treatment process is cumbersome.

[0003] At present, the existing technology directly introduces aquatic plants into eutrophic lakes for ecological restoration. During their growth, aquatic plants need to absorb large amounts of nutrients such as nitrogen and phosphorus and assimilate them into their own structural components, thereby purifying the eutrophic water bodies. Among them, floating plants have attracted attention because they have high productivity and are easy to harvest. They can be directly salvaged to remove nutrients such as nitrogen and phosphorus from water bodies, thereby reducing the degree of eutrophication of water bodies. In related studies, water hyacinth has a good effect on removing nitrogen and phosphorus in water bodies, but due to its strong reproductive capacity, it can occupy the entire water area in a short period of time, which is not conducive to the healthy development of the ecosystem. Duckweed can absorb a large amount of pollutants and can tolerate low concentrations of salinity. It can also be an excellent poultry and livestock feed and fish bait, and has broad application prospects in the field of sewage purification. Summary of the Invention

[0004] Purpose of the invention: In response to the problems existing in the prior art, the present invention provides an anion exchange resin-duckweed coupling treatment system that can quickly remove nitrogen and phosphorus from water bodies. This system addresses the problem of excessive nitrogen and phosphorus content in eutrophic water bodies. Through the coupling effect of anion exchange resin and duckweed, it quickly adsorbs and absorbs nitrogen and phosphorus in the water body. Duckweed is particularly capable of absorbing ammonia nitrogen, which is difficult to remove by anion exchange resin. Low-concentration salt water is then used to regenerate the adsorption-saturated resin. At the same time, the desorption of anion exchange resin by salt water is a dynamic equilibrium process. The absorption of high-concentration nitrogen and phosphorus enriched during desorption by duckweed can make the desorption dynamic equilibrium tend to complete desorption. Therefore, coupling the desorption process with duckweed absorption can greatly reduce the regeneration cost, and no high-concentration salt water is produced, thereby realizing the recycling of resin.

[0005] The present invention also provides an anion exchange resin-duckweed coupling treatment method capable of rapidly removing nitrogen and phosphorus from water bodies.

[0006] Technical solution: In order to achieve the above-mentioned purpose, the present invention provides an anion exchange resin-duckweed coupling treatment system capable of rapidly removing nitrogen and phosphorus from water, comprising a water purification reactor and a resin regeneration reactor connected to each other, wherein stirring paddles and anion exchange resin are provided in both reactors, duckweed is located on the water surface of the two reactors, and an inclined plate is provided between the duckweed and the resin to prevent resin loss; the anion exchange resin (8) can be transported between the water purification reactor and the resin regeneration reactor.

[0007] The water purification reactor is provided with a water inlet at the bottom and a water outlet at the top side, and is connected to the resin regeneration reactor through a resin regeneration pipeline and a resin return pipeline.

[0008] The anion exchange resin is a polyacrylic acid or polystyrene strong base anion exchange resin, including one or more of A520E, A300, D201, IRA900, and IRA958.

[0009] The volume of the water purification reactor is 10L to 1000m 3 The ratio of the reactor height to the diameter of the water surface at the top of the reactor is 0.1:1 to 2:1, and the amount of resin used is 1% to 10% of the volume of the water purification reactor; the volume of the resin regeneration reactor is 2L to 200m 3 The amount of resin in the resin regeneration reactor is 5% to 20% of the volume of the resin used in the water purification reactor. Usually, 5% to 20% of the resin that is saturated with adsorption in the water purification reactor is input into the resin regeneration reactor every 2 to 24 hours.

[0010] The duckweed in the two reactors is one or more of D. purpurogenum, D. sparsely veined, D. green, D. truncatum, and D. pauciflora, preferably D. purpurogenum, when the temperature is below 10° C. The light-shielding effect of the duckweed on the water surface can prevent the resin from being oxidized during long-term use.

[0011] Preferably, the duckweed in the two reactors is one of Lemna purpurogena and Lemna natans, or a combination of the two.

[0012] The pH value of the wastewater in the water purification reactor is 5.5 to 8.5. Under the condition of pH 7.0 to 8.0, duckweed grows best. The entire treatment system is kept at a temperature of about 10 to 30° C. during the wastewater treatment process, and duckweed grows well.

[0013] Wherein, the desorbent in the resin regeneration reactor is NaCl solution with a concentration of 0.01wt% to 0.5wt%.

[0014] The duckweed coverage in the two reactors is 40-80%, that is, the area ratio of the water surface covered. Preferably, the duckweed coverage is 80%.

[0015] Furthermore, excessive duckweed in the water purification reactor can be salvaged and transferred to the resin regeneration reactor to further absorb nitrogen and phosphorus in the desorption liquid. The duckweed coverage in the two reactors is about 40% to 80%. When the system is continuously running, 5% to 20% of the duckweed in the two reactors is salvaged every day to maintain the duckweed coverage in the reactor at about 80%, leaving a certain growth space, thereby ensuring that the duckweed grows vigorously and absorbs nitrogen and phosphorus more.

[0016] The resin in the resin purification reactor is the adsorption-saturated resin transported from the water purification reactor, which can be returned to the water purification reactor after desorption. This process realizes the recycling of the resin, and the resin desorption time is 2 to 8 hours.

[0017] The reaction time for treating nitrogen- and phosphorus-containing wastewater and desorbing the resin in the two reactors is 2 to 24 hours.

[0018] The treatment method of the anion exchange resin-duckweed coupling treatment system for rapidly removing nitrogen and phosphorus from water bodies of the present invention comprises the following steps:

[0019] (1) Inputting nitrogen and phosphorus-containing wastewater into a water purification reactor through a water inlet of the water purification reactor;

[0020] (2) The stirring paddle in the water purification reactor is stirred, and the nitrogen and phosphorus in the wastewater are fully adsorbed by the anion exchange resin in the water purification reactor (1). The duckweed also absorbs the nitrogen and phosphorus in the wastewater at the same time. The adsorption purification time is 2 to 24 hours. The purified water is further treated or discharged;

[0021] (3) The anion exchange resin with a volume fraction of 5% to 20% adsorption saturation in the water purification reactor is input into the resin regeneration reactor through the resin regeneration pipeline (usually transported every 2-24 hours). The resin regeneration reactor contains a desorbent to desorb the resin. The agitator in the resin reactor is stirred to desorb the anion exchange resin in the resin regeneration reactor by the desorbent. At the same time, the duckweed covering the water surface of the resin regeneration reactor can further improve the desorption efficiency of the resin by adsorbing nitrogen and phosphorus in the desorption liquid;

[0022] (4) The anion exchange resin that has been completely desorbed in the resin regeneration reactor can be fed back into the water purification reactor through the resin return pipe for recycling.

[0023] In the step, nitrogen- and phosphorus-containing wastewater having a pH adjusted to between 5.5 and 8.5 is input into the water purification reactor through the water inlet of the water purification reactor, the duckweed coverage on the water surface is 40 to 80%, and the resin amount is 1 to 10% of the reactor volume.

[0024] During the entire treatment process, 5% to 20% of the duckweed in the two reactors is salvaged every day while the system is in continuous operation. The salvaged duckweed can be used as feed. During the wastewater treatment process, the entire reaction system is kept at a temperature of 10 to 30°C to ensure that the duckweed in the system grows well.

[0025] Preferably, the anion exchange resin-duckweed coupling treatment method for rapidly removing nitrogen and phosphorus from water comprises the following steps:

[0026] (1) Nitrogen and phosphorus-containing wastewater adjusted to a pH between 5.5 and 8.5 is introduced into a water purification reactor through the water inlet, with duckweed covering approximately 80% of the water surface and the amount of resin being 1% to 10% of the reactor volume;

[0027] (2) The stirring paddle in the water purification reactor is constantly stirring, and the nitrogen and phosphorus in the wastewater are fully adsorbed by the anion exchange resin in the water purification reactor. Duckweed also absorbs nitrogen and phosphorus in the wastewater, especially ammonia nitrogen, for its own growth. The adsorption and purification time is 2 to 24 hours. The purified water is further treated or discharged;

[0028] (3) Every 2 to 24 hours, 5% to 20% of the resin in the water purification reactor is input into the resin regeneration reactor. At the same time, the excessive duckweed in the water purification reactor can also be salvaged into the resin regeneration reactor. The resin regeneration reactor contains 0.01 wt% to 0.5 wt% of NaCl solution as a desorbent to desorb the resin. The resin regeneration reactor also has duckweed with a water surface coverage of 80% to adsorb nitrogen and phosphorus in the desorption solution, which can improve the desorption efficiency of the resin. During this process, the stirring paddle is continuously stirred, and the desorption time is 2 to 8 hours.

[0029] (4) The resin completely desorbed from the resin regeneration reactor can be input into the water purification reactor for recycling;

[0030] (5) When the system is in continuous operation, 5% to 20% of the duckweed in the two reactors is salvaged every day. The salvaged duckweed can be used as feed. The entire reaction system is kept at a temperature of about 10 to 30°C during the wastewater treatment process to ensure good growth of the duckweed in the system.

[0031] The anion exchange resin-duckweed coupling treatment system capable of rapidly removing nitrogen and phosphorus from water bodies according to the present invention can also be applied to urban sewage treatment plants for deep sewage treatment.

[0032] The anion exchange resin-duckweed coupled treatment system and method, described herein, can rapidly remove nitrogen and phosphorus from eutrophic water bodies. They are specifically targeted at eutrophic water bodies with excessively high nitrogen and phosphorus contents. This treatment system and method achieve a removal rate of over 96% for ammonia nitrogen, over 95% for total nitrogen, and over 85% for total phosphorus, effectively removing nitrogen and phosphorus from eutrophic water bodies. Since organic matter in water is generally negatively charged, the resin can simultaneously adsorb electronegative organic pollutants in the eutrophic water. Furthermore, duckweed requires a carbon source during its growth, allowing this system to remove COD from water at a removal rate of over 40%. Furthermore, the duckweed can be harvested for feed, providing both water purification and biomass energy.

[0033] Mechanism: When the present invention utilizes a strong base anion exchange resin to treat wastewater, the exchangeable ions on the resin are replaced with anions in the water body, thereby achieving the removal of nitrogen and phosphorus in the water body. On the other hand, duckweed prefers to grow in nutrient-rich water bodies, and the structural components such as the stems and leaves of duckweed disappear, and most of them are able to photosynthesize. They have a strong metabolism, grow rapidly, and have a strong ability to absorb nitrogen and phosphorus, making them very suitable for nitrogen and phosphorus wastewater purification. In the treatment system of the present invention, the resin in the water purification reactor fully adsorbs nitrogen and phosphorus in the water body, and duckweed assists in denitrification and phosphorus removal. At the same time, duckweed will preferentially absorb ammonia nitrogen in the sewage that cannot be removed by anion exchange resin to synthesize amino acids and proteins, etc. Only when the ammonia nitrogen is consumed will it absorb a large amount of other forms of nitrogen, thereby greatly improving the removal efficiency of nitrogen and phosphorus in the water purification reactor. In the resin regeneration reactor, low-concentration brine is used to desorb the resin, and nitrogen and phosphorus nutrients are enriched and concentrated in the desorption liquid, which is conducive to the growth of duckweed in the desorption liquid. In this process, the nitrogen and phosphorus in the desorption liquid are absorbed by the duckweed, which can further desorb the undesorbed nitrogen and phosphorus in the resin, ultimately achieving complete desorption of the resin and reducing the salt concentration in the desorbent.

[0034] The present invention utilizes anion exchange resin to rapidly remove nitrogen and phosphorus from water, and uses duckweed to assist in denitrification and phosphorus removal. During the resin regeneration process, duckweed absorbs and promotes the desorption of low-concentration saltwater from the anion exchange resin. This not only reduces salt usage and enables efficient resin reuse, but also generates biomass energy. Excess duckweed grown in the two reactors can be harvested and used as feed. Compared to other aquatic plants, duckweed has higher crude protein and starch content, lower cellulose and lignin content, and is easily digestible, making it an excellent livestock feed.

[0035] This method not only treats water but also significantly improves ammonia nitrogen removal rates, reduces the salt concentration of the resin desorbent, and reduces the difficulty of subsequent treatment. It also produces no desorption wastewater and eliminates secondary pollution. Furthermore, the innovative use of duckweed for water purification allows for the recovery of duckweed biomass as feed, enabling the process to achieve both water purification and biomass energy recovery.

[0036] This invention, for the first time, couples duckweed with a water purification reactor and applies it to resin desorption, significantly reducing salt concentration. The use of duckweed allows biomass synthesis using nitrogen and phosphorus in wastewater, or nitrogen and phosphorus desorbed by resin, effectively recovering nutrients from wastewater, thus achieving dual functions of water purification and nutrient recovery. Furthermore, duckweed can remove ammonia nitrogen, which is difficult for resin to remove, thereby enhancing the water purification effect.

[0037] The present invention is a circulation system in which resin is provided in both a water purification reactor and a resin regeneration reactor. A portion of the resin is extracted from the water purification reactor and introduced into the regeneration reactor for resin regeneration, and then returned to the water purification reactor to ensure the resin purification efficiency in the water purification reactor. The present invention is designed with duckweed in both reactors so that it can grow. The duckweed in the purification reactor can absorb pollutants to purify water quality. The duckweed in the regeneration reactor is tolerant to low salt concentrations and can absorb pollutants concentrated after desorption from the resin. Since desorption is a dynamic equilibrium, the pollutants desorbed by the resin are absorbed by the duckweed, and the resin will further desorb them until they are completely desorbed, thereby reducing the required desorbent salt concentration. The present invention is the first to use duckweed in the resin desorption process, which can regenerate the resin at a low cost. The desorption of anion exchange resin by salt water is a dynamic equilibrium process. The duckweed's absorption of high-concentration nitrogen and phosphorus enriched during desorption can make the desorption dynamic equilibrium tend towards complete desorption.

[0038] By coupling with duckweed, the present invention enhances the resin's adsorption and purification effectiveness, particularly for ammonia nitrogen, and allows for low-cost resin regeneration. The duckweed biomass is also recovered and can be used as feed. Conventional anion exchange resins barely remove ammonia nitrogen, but coupling with duckweed achieves an ammonia nitrogen removal rate exceeding 96%. Furthermore, the salt concentration of the desorbent is significantly reduced, and the desorbent can be recycled, easing the difficulty of subsequent desorption liquid processing. For example, while desorption resin without duckweed requires a NaCl concentration of over 8 wt%, using duckweed requires a NaCl concentration of 0.01 wt% to 0.5 wt%.

[0039] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0040] 1. The present invention provides an anion exchange resin-duckweed coupling treatment system and treatment method for rapid denitrification and phosphorus removal in water. Compared with traditional denitrification and phosphorus removal methods, anion exchange resin has a large treatment capacity, high adsorption efficiency, and is easy to desorb and regenerate, making denitrification and phosphorus removal in water more efficient. At the same time, duckweed has a strong ability to remove nitrogen and phosphorus in water, especially ammonia nitrogen that cannot be removed by anion exchange resin. Therefore, the coupled system enhances the denitrification and phosphorus removal effects.

[0041] 2. In the present invention, duckweed is present in both the water purification reactor and the resin regeneration reactor. The duckweed in the water purification reactor assists in denitrification and phosphorus removal to purify water through absorption, while the duckweed in the resin regeneration reactor absorbs highly concentrated nitrogen and phosphorus nutrients in the resin desorption solution, shifting the desorption equilibrium toward complete desorption. This also reduces the required desorbent salt concentration to only 0.01 to 0.5 wt%, far below the commonly used salt concentration of 8 to 12 wt%. Furthermore, excess duckweed in both reactors can be used as feed, thus providing biomass energy while achieving water purification and resin regeneration.

[0042] 3. In the present invention, the resin is regenerated under low-concentration salt water conditions, and the duckweed absorbs nitrogen and phosphorus in the desorption solution, avoiding the problem of high-concentration desorption salt water requiring further subsequent treatment. This simplifies the difficulty of resin regeneration, and the desorption solution can be reused multiple times without generating secondary pollution. The resin can be almost completely regenerated in this process, and the adsorption capacity can still be maintained at more than 95% of the initial value after 10 regenerations.

[0043] 4. The anion exchange resin-duckweed coupled treatment system and treatment method of the present invention, which can rapidly remove nitrogen and phosphorus from water bodies, is low-cost, simple to operate, and environmentally friendly. It can remove ammonia nitrogen from eutrophic water bodies by more than 96%, total nitrogen by more than 95%, and total phosphorus by more than 85%. In addition, the resin and duckweed can also remove COD from the water, with a COD removal rate of more than 40%, thereby achieving deep purification of eutrophic water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a structural schematic diagram of an anion exchange resin-duckweed coupling treatment system of the present invention that can quickly remove nitrogen and phosphorus from water. The symbols in the figure are: 1-water purification reactor, 2-resin regeneration reactor, 3-water inlet of water purification reactor, 4-water outlet of water purification reactor, 5-inclined plate, 6-duckweed, 7-stirring paddle, 8-resin, 9-resin return pipe, 10-resin regeneration pipe. DETAILED DESCRIPTION

[0045] The present invention can be better understood based on the following examples. Those skilled in the art will readily appreciate that the contents described in the examples are merely illustrative of the present invention and should not and will not limit the present invention described in detail in the claims. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources. Experimental methods for which specific conditions are not specified in the examples are generally performed under conventional conditions or under conditions recommended by the manufacturer.

[0046] Example 1

[0047] This embodiment provides an anion exchange resin-duckweed coupled treatment system and method for rapidly removing nitrogen and phosphorus from water. The water purification reactor 1 has a volume of 10 L, and the resin regeneration reactor 2 has a volume of 2.5 L. The total nitrogen concentration in the eutrophic water of a particular lake is 26 mg / L, the total phosphorus concentration is 1.4 mg / L, and the COD concentration is 83 mg / L. The ratio of the height of the water purification reactor 1 to the diameter of the reactor top at the water surface is 0.5:1. The resin dosage is 1% of the volume of the water purification reactor 1; the resin content in the resin regeneration reactor 2 is 15% of the volume of the resin used in the water purification reactor 1.

[0048] like Figure 1As shown, the anion exchange resin-duckweed coupled treatment system includes an interconnected water purification reactor 1 and a resin regeneration reactor 2. Both reactors are equipped with a stirring paddle 7 and an anion exchange resin 8. Duckweed 6 is located on the water surface of both reactors, and an inclined plate 5 is provided between the duckweed 6 and the resin 8. A desorbent is also provided in the resin regeneration reactor 2. The anion exchange resin 8 can be transported between the water purification reactor 1 and the resin regeneration reactor 2. The resin in the water purification reactor 1 enters the resin regeneration reactor 2 through the resin regeneration pipe 10. The regenerated resin returns to the water purification reactor 1 through the resin return pipe 9. A water purification reactor water inlet 3 is provided at the bottom of the water purification reactor 1, and a water purification reactor water outlet 4 is provided on the top side.

[0049] The specific processing steps are as follows:

[0050] (1) The pH of the eutrophic lake water was adjusted to 7.0-7.5, and the wastewater was input into the water purification reactor 1 through the water inlet 3 of the water purification reactor. At the same time, 100 mL of A520E resin 8 and 80% coverage of duckweed 6 were added. The water surface coverage ratio of duckweed and purple-backed duckweed was 1:2, and the wastewater temperature was about 25°C.

[0051] (2) The stirring paddle 7 in the water purification reactor 1 continuously stirs the wastewater, the wastewater is fully contacted with the anion exchange resin, the nitrogen and phosphorus are fully adsorbed, and the duckweed also absorbs the nitrogen and phosphorus in the wastewater for its own growth. The adsorption purification time is 2 hours, and the purified water is further discharged or treated through the water outlet 4 of the water purification reactor;

[0052] (3) After adsorption, 15% of the volume of the resin in the water purification reactor 1 that is close to adsorption saturation is input into the resin regeneration reactor 2 through the resin regeneration pipeline 10. The desorbent in the reactor is 2 L of 0.2 wt% NaCl solution, the temperature is 25°C, and the duckweed coverage, species, and proportion are the same as those in the water purification reactor. The duckweed absorbs nitrogen and phosphorus in the desorption solution, accelerates the desorption of the resin, and purifies the desorption solution. The stirring paddle 7 is continuously stirred, and the desorption time is 4 hours.

[0053] (4) The system is operated continuously for 3 days. During the above process, the resin 8 after complete desorption in the resin regeneration reactor 1 can be re-input into the water purification reactor 1 through the resin return pipe 9. The resin can be recycled, and the desorbent can be applied multiple times without replacement. When the system is continuously running, the excessive duckweed (5% to 20%) grown in the two reactors can be salvaged every day and used as poultry feed, fish bait, etc., and the duckweed coverage is maintained at 80%.

[0054] According to the test, in the water outputted by the system and method of the present invention, the total nitrogen removal rate is 96%, the total phosphorus removal rate is 88%, and the COD removal rate can reach 43%.

[0055] Example 2

[0056] This embodiment describes a coupled anion exchange resin-duckweed treatment system and method for rapidly removing nitrogen and phosphorus from water. The water purification reactor 1 has a volume of 20 L, and the resin regeneration reactor 2 has a volume of 4.5 L. Wastewater from a pig farm, diluted 10 times, has a total nitrogen concentration of 60 mg / L, a total phosphorus concentration of 1.7 mg / L, and a COD concentration of 274 mg / L. The ratio of the height of the water purification reactor 1 to the diameter of the reactor top at the water surface is 0.5:1. The resin dosage is 5% of the volume of the water purification reactor; the resin content in the resin regeneration reactor 2 is 20% of the volume of the resin in the water purification reactor 1. The components of the treatment system of this invention are the same as those in Example 1.

[0057] The specific processing steps are as follows:

[0058] (1) The pH of the pig farm wastewater was adjusted to between 6.5 and 7.5, and the pig farm wastewater was input into the water purification reactor through the water inlet 3 of the water purification reactor. At the same time, 1 L of IRA900 resin 8 was added, the coverage of duckweed 6 was 80%, the duckweed species was purple-backed duckweed, and the wastewater temperature was about 10°C;

[0059] (2) The stirring paddle 7 in the water purification reactor 1 continuously stirs the wastewater, the wastewater is fully contacted with the anion exchange resin, the nitrogen and phosphorus are fully adsorbed, and the duckweed also absorbs the nitrogen and phosphorus in the wastewater for its own growth. The adsorption purification time is 4 hours, and the purified water is further discharged or treated through the outlet of the water purification reactor 4;

[0060] (3) After adsorption, 20% of the volume of the saturated resin in the water purification reactor 1 is fed into the resin regeneration reactor 2 through the resin regeneration pipeline 10. The desorbent in the reactor is 4 L of a 0.5 wt% NaCl solution at 15°C. The duckweed coverage and species are the same as those in the water purification reactor. The duckweed absorbs nitrogen and phosphorus in the desorption solution, accelerates the desorption of the resin, and purifies the desorption solution. The stirring blade 7 continuously stirs the solution for 4 hours.

[0061] (4) The system is operated continuously for 5 days. During the above process, the resin after complete desorption in the resin regeneration reactor 2 can be re-input into the water purification reactor through the resin return pipe 9. The resin can be recycled, and the desorbent can be applied multiple times without replacement. When the system is continuously running, the excessive duckweed (5% to 20%) grown in the two reactors can be salvaged every day and used as poultry feed, fish bait, etc., and the duckweed coverage is maintained at 80%.

[0062] According to the test, in the water outputted by the system and method of the present invention, the total nitrogen removal rate is 97.3%, the total phosphorus removal rate is 87%, and the COD removal rate can reach 41%.

[0063] Example 3

[0064] This embodiment provides an anion exchange resin-duckweed coupled treatment system and method for rapidly removing nitrogen and phosphorus from water. The water purification reactor 1 has a volume of 10 L, the resin regeneration reactor 2 has a volume of 2.5 L, the laboratory-prepared wastewater has a total nitrogen concentration of 50 mg / L and a total phosphorus concentration of 1.5 mg / L, and the wastewater contains a carbon source that can be utilized by duckweed. The ratio of the height of the water purification reactor 1 to the diameter of the water surface at the top of the reactor is 0.5:1, and the resin dosage is 5% of the volume of the water purification reactor; the volume of the resin regeneration reactor 2 is 2 L to 200 m 3 The volume of resin in the resin regeneration reactor 2 is 20% of the volume of resin in the water purification reactor 1. The composition of the treatment system of the present invention is the same as that of Example 1.

[0065] The specific processing steps are as follows:

[0066] (1) The pH of the prepared wastewater was adjusted to between 6.5 and 7.5, and the wastewater was input into the water purification reactor 1 through the water inlet 3 of the water purification reactor. At the same time, 500 mL of D201 resin 8 was added, the coverage of duckweed 6 was 80%, and the duckweed species was Lemna nodosum. The wastewater temperature was about 25°C.

[0067] (2) The stirring paddle 7 in the water purification reactor 1 continuously stirs the wastewater, the wastewater is fully contacted with the anion exchange resin, the nitrogen and phosphorus are fully adsorbed, and the duckweed also absorbs the nitrogen and phosphorus in the wastewater for its own growth. The adsorption purification time is 8 hours. The purified water is further discharged or treated through the outlet of the water purification reactor 4;

[0068] (3) After adsorption, 20% of the volume of the saturated resin in the water purification reactor 2 is input into the resin regeneration reactor 2 through the resin regeneration pipeline 10. The desorbent in the reactor is 2 L of 0.1 wt% NaCl solution, the temperature is 25 ° C, the duckweed coverage and species are the same as those in the water purification reactor, and the duckweed absorbs nitrogen and phosphorus in the desorption liquid, accelerates the desorption of the resin, and purifies the desorption liquid. The stirring paddle 7 continuously stirs, and the desorption time is 4 hours;

[0069] (4) The system operates continuously for 24 hours. During the above process, the resin completely desorbed from the resin regeneration reactor 2 can be re-input into the water purification reactor through the resin return pipe 9. The resin can be recycled, and the desorbent can be applied multiple times without replacement. When the system is in continuous operation, the excess duckweed (5% to 20%) grown in the two reactors can be salvaged every day and used as poultry feed, fish bait, etc., to maintain the duckweed coverage at 80%.

[0070] According to the test, in the water outputted by the system and method of the present invention, the total nitrogen removal rate was 98.5%, and the total phosphorus removal rate was 92%.

[0071] Example 4

[0072] This embodiment provides an anion exchange resin-duckweed coupled treatment system and method for rapidly removing nitrogen and phosphorus from water. The water purification reactor 1 has a volume of 10 L, the resin regeneration reactor 2 has a volume of 2.5 L, the laboratory-prepared wastewater has a total nitrogen concentration of 130 mg / L and a total phosphorus concentration of 3.2 mg / L, and the wastewater contains a carbon source that can be utilized by duckweed. The ratio of the height of the water purification reactor 1 to the diameter of the water surface at the top of the reactor is 0.5:1, and the resin dosage is 5% of the volume of the water purification reactor; the volume of the resin regeneration reactor 2 is 2 L to 200 m 3 The amount of resin in the resin regeneration reactor 2 is 10% of the volume of the resin in the water purification reactor (1).

[0073] The composition of the processing system of the present invention is the same as that of Example 1.

[0074] The specific processing steps are as follows:

[0075] (1) adjusting the pH of the prepared wastewater to between 6.5 and 7.5, inputting the wastewater into the water purification reactor through the water inlet 3 of the water purification reactor, and adding 500 mL of D213 resin 8, with the coverage of duckweed 6 being 80%, the duckweed species being Lemna minor and Spirodela dal, the ratio of Lemna minor to Spirodela dal being 1:2, and the wastewater temperature being about 25° C.;

[0076] (2) The stirring paddle 7 in the water purification reactor 1 continuously stirs the wastewater, the wastewater is fully contacted with the anion exchange resin, the nitrogen and phosphorus are fully adsorbed, and the duckweed also absorbs the nitrogen and phosphorus in the wastewater for its own growth. The adsorption purification time is 2 hours, and the purified water is further discharged or treated through the water outlet 4 of the water purification reactor;

[0077] (3) After adsorption, 10% of the volume of the saturated resin in the water purification reactor is fed into the resin regeneration reactor 2 through the resin regeneration pipeline 10. The desorbent in the reactor is 2 L of a 0.1 wt% NaCl solution at 25°C. The duckweed coverage, species, and proportion are the same as those in the water purification reactor. The duckweed absorbs nitrogen and phosphorus in the desorption solution, accelerates the desorption of the resin, and purifies the desorption solution. The stirring blade 7 continuously stirs the solution, and the desorption time is 4 h.

[0078] (4) The system operates continuously for 24 hours. During the above process, the resin 8 completely desorbed from the resin regeneration reactor 2 can be re-input into the water purification reactor through the resin return pipe 9. The resin can be recycled, and the desorbent can be applied multiple times without replacement. When the system is running continuously, the excess duckweed (5% to 20%) grown in the two reactors can be salvaged every day and used as poultry feed, fish bait, etc., to maintain the duckweed coverage at 80%.

[0079] According to the test, in the water outputted by the system and method of the present invention, the total nitrogen removal rate was 95.5%, and the total phosphorus removal rate was 86.7%.

[0080] Example 5

[0081] This embodiment provides a coupled anion exchange resin-duckweed treatment system and method for rapidly removing nitrogen and phosphorus from water. The water purification reactor 1 has a volume of 100 L, and the resin regeneration reactor 2 has a volume of 25 L. The eutrophic water of a certain urban river has a total nitrogen concentration of 8.4 mg / L, a total phosphorus concentration of 0.9 mg / L, and a COD concentration of 47 mg / L. The ratio of the height of the water purification reactor 1 to the diameter of the reactor top at the water surface is 0.5:1. The resin dosage is 1% of the volume of the water purification reactor; the resin content in the resin regeneration reactor 2 is 10% of the volume of the resin in the water purification reactor 1. The components of the treatment system of the present invention are the same as those of Example 1.

[0082] The specific processing steps are as follows:

[0083] (1) The pH of the eutrophic water body is adjusted to between 7.0 and 8.5, and the wastewater is input into the water purification reactor through the water inlet 3 of the water purification reactor. At the same time, 1000 mL of IRA900 resin 8 is added, and the coverage of duckweed 6 is 80%. The duckweed species are Lemna minor and Spirodela dalbergia, and the ratio of Lemna minor to Spirodela dalbergia is 1:2. The wastewater temperature is about 25°C.

[0084] (2) The stirring paddle 7 in the water purification reactor 1 continuously stirs the wastewater, the wastewater is fully contacted with the anion exchange resin, the nitrogen and phosphorus are fully adsorbed, and the duckweed also absorbs the nitrogen and phosphorus in the wastewater for its own growth. The adsorption purification time is 2 hours, and the purified water is further discharged or treated through the water outlet 4 of the water purification reactor;

[0085] (3) After adsorption, 10% of the volume of the saturated resin in the water purification reactor 1 is fed into the resin regeneration reactor through the resin regeneration pipeline 10. The desorbent in the reactor is 2 L of a 0.3 wt% NaCl solution at 25°C. The duckweed coverage, species, and proportion are the same as those in the water purification reactor. The duckweed absorbs nitrogen and phosphorus in the desorption solution, accelerates the desorption of the resin, and purifies the desorption solution. The stirring blade 7 continuously stirs the solution, and the desorption time is 4 h.

[0086] (4) The system is operated continuously for 2 days. During the above process, the resin that has been completely desorbed in the resin regeneration reactor can be re-input into the water purification reactor through the resin return pipe 9. The resin can be recycled, and the desorbent can be applied multiple times without replacement. When the system is continuously running, the excess duckweed (5% to 20%) grown in the two reactors can be salvaged every day and used as poultry feed, fish bait, etc., and the duckweed coverage is maintained at 80%.

[0087] According to the test, in the water outputted by the system and method of the present invention, the total nitrogen removal rate is 98.8%, the total phosphorus removal rate is 93.7%, and the COD removal rate can reach 56%.

[0088] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An anion exchange resin-duckweed coupling treatment system capable of rapidly removing nitrogen and phosphorus from water, characterized in that: The invention comprises a water purification reactor (1) and a resin regeneration reactor (2) connected to each other, wherein a stirring paddle (7) and an anion exchange resin (8) are provided in both reactors, duckweed (6) is located on the water surface of both reactors, and an inclined plate (5) is provided between the duckweed (6) and the resin (8); the anion exchange resin (8) can be transported between the water purification reactor (1) and the resin regeneration reactor (2); The resin in the water purification reactor (1) adsorbs nitrogen and phosphorus in the water body, and duckweed assists in denitrification and phosphorus removal. At the same time, duckweed preferentially absorbs ammonia nitrogen in the sewage that cannot be removed by the anion exchange resin to synthesize amino acids and proteins. Only when the ammonia nitrogen is consumed will it absorb other forms of nitrogen, thereby improving the removal efficiency of nitrogen and phosphorus in the water purification reactor; in the resin regeneration reactor (2), low-concentration salt water is used to desorb the resin, and nitrogen and phosphorus nutrients are enriched and concentrated in the desorption liquid, which is conducive to the growth of duckweed in the desorption liquid. In this process, the nitrogen and phosphorus in the desorption liquid are absorbed by the duckweed, which can further desorb the nitrogen and phosphorus that have not been desorbed in the resin, ultimately achieving complete desorption of the resin and reducing the salt concentration in the desorbent; The desorbent in the resin regeneration reactor (2) uses a NaCl solution with a concentration of 0.01 wt% to 0.5 wt%.

2. The anion exchange resin-duckweed coupling treatment system for rapid denitrification and dephosphorization of water according to claim 1, characterized in that: The water purification reactor (1) is provided with a water purification reactor water inlet (3) at the bottom and a water purification reactor water outlet (4) at the top side, and is connected to the resin regeneration reactor (2) via a resin regeneration pipeline (10) and a resin return pipeline (9).

3. The anion exchange resin-duckweed coupling treatment system for rapid denitrification and dephosphorization of water according to claim 1, characterized in that: The anion exchange resin is a polyacrylic acid or polystyrene strong base anion exchange resin, including one or more of A520E, A300, D201, IRA900, and IRA958.

4. The anion exchange resin-duckweed coupling treatment system for rapid denitrification and dephosphorization of water according to claim 1, characterized in that: The volume of the water purification reactor (1) is 10 L~1000 m 3 The ratio of the reactor height to the diameter of the water surface at the top of the reactor is 0.1:1~2:1, and the amount of resin used is 1%~10% of the volume of the water purification reactor; the volume of the resin regeneration reactor (2) is 2 L~200 m 3 The amount of resin in the resin regeneration reactor (2) is 5% to 20% of the volume of the resin in the water purification reactor (1).

5. The anion exchange resin-duckweed coupling treatment system for rapid denitrification and dephosphorization of water according to claim 1, characterized in that: The duckweed in the two reactors is one or more of the group consisting of D. purpurogenum, D. sparsely veined, D. green, D. truncatum, and D. pauciflora.

6. The anion exchange resin-duckweed coupling treatment system for rapid denitrification and dephosphorization of water according to claim 1, characterized in that: The duckweed coverage in the two reactors ranged from 40 to 80%.

7. A treatment method using the anion exchange resin-duckweed coupled treatment system for rapid nitrogen and phosphorus removal from water according to claim 1, comprising the following steps: (1) Nitrogen and phosphorus-containing wastewater is fed into the water purification reactor (1) through the water inlet (3) of the water purification reactor; (2) The stirring paddle (7) in the water purification reactor (1) is stirred, and the nitrogen and phosphorus in the wastewater are fully adsorbed by the anion exchange resin (8) in the water purification reactor (1). The duckweed (6) also absorbs the nitrogen and phosphorus in the wastewater at the same time. The adsorption purification time is 2 to 24 hours. The purified water is further treated or discharged through the outlet (4) of the water purification reactor; (3) The anion exchange resin (8) with a volume fraction of 5% to 20% adsorption saturation in the water purification reactor (1) is input into the resin regeneration reactor (2) through the resin regeneration pipeline (10). The resin regeneration reactor (2) contains a desorbent to desorb the resin. The stirring paddle (7) in the resin reactor (2) is stirred to desorb the anion exchange resin (8) in the resin regeneration reactor (2). At the same time, the duckweed (6) covering the water surface of the resin regeneration reactor (2) further improves the desorption efficiency of the resin by adsorbing nitrogen and phosphorus in the desorption liquid. The inclined plate (5) is provided to prevent the loss of the resin. (4) The anion exchange resin (8) completely desorbed from the resin regeneration reactor (2) is fed back into the water purification reactor (1) through the resin return pipe (9) for recycling.

8. The processing method according to claim 7, characterized in that: In step (1), the nitrogen- and phosphorus-containing wastewater having a pH adjusted to between 5.5 and 8.5 is fed into the water purification reactor (1) through the water inlet (3) of the water purification reactor, the coverage of duckweed (6) on the water surface is 40% to 80%, and the amount of resin is 1% to 10% of the volume of the reactor.

9. The processing method according to claim 7, characterized in that: During the entire treatment process, 5% to 20% of the duckweed in the two reactors is salvaged every day while the system is running continuously. The salvaged duckweed is used as feed. The entire reaction system is kept at a temperature of 10 to 30°C during the wastewater treatment process to ensure good growth of the duckweed in the system.

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