A method and system for removing trace contaminants from wastewater plant effluent using biomass ash

Abstract

This invention relates to the field of advanced wastewater treatment and biomass ash reuse, and discloses a method and system for removing trace pollutants from wastewater treatment plant effluent using biomass ash. The method is carried out in a system including an equalization tank, an ozone catalytic reaction tank, and a biochemical buffer tank, and includes: (1) introducing the effluent into the equalization tank for homogenization to obtain reclaimed water I; (2) introducing the reclaimed water I into the ozone catalytic reaction tank for ozone catalytic reaction to obtain reclaimed water II; (3) introducing the reclaimed water II into the biochemical buffer tank to contact with biofilm-coated microbial carriers for biochemical treatment to obtain effluent. The method provided by this invention can achieve efficient removal of trace organic pollutants from effluent, without the addition of chemical reagents, making it environmentally friendly and free from secondary pollution; at the same time, it can improve the biodegradability of the effluent.

Description

Technical Field

[0001] This invention relates to the field of advanced wastewater treatment and biomass ash reuse, specifically to a method and system for removing trace pollutants from wastewater treatment plant effluent using biomass ash. Background Technology

[0002] Frequent pandemics of influenza have highlighted the widespread concern about water pollution caused by the large-scale production and use of pharmaceuticals. Wastewater treatment plants, as the first recipients of drug residues, determine the pathways and fates of various drugs after human ingestion through their treatment processes. As emerging, persistent trace pollutants, antibiotics and antiviral drugs have been widely detected in surface water, sediments, and wastewater treatment plant effluents, with concentrations reaching ng·L⁻¹. -1 -μg·L -1 However, conventional wastewater treatment processes cannot effectively degrade recalcitrant trace pollutants in municipal wastewater, and the high detection rate of trace pollutant residues in effluent remains a thorny issue in the wastewater treatment field.

[0003] Furthermore, due to increasingly stringent requirements for the development of a circular economy and ecological environmental protection in the industry, the large-scale storage of ash has become a bottleneck restricting the upgrading and sustainable development of the biomass power generation industry. Most of my country's biomass power plants are located in underdeveloped areas, where the development of ash resource utilization is late and the utilization rate is low. Whether such a large volume of ash is directly landfilled or used in building materials, agriculture, forestry, or environmental protection, it poses a significant challenge to ecological environmental protection and the industry's development needs.

[0004] Biomass ash has an alkaline surface and carries a negative charge, making it suitable as an adsorbent for purifying domestic sewage. Functional filter media / fillers produced from biomass ash are applied to the treatment of black and odorous water bodies or wetland projects in sewage treatment plants, showing significant effects on improving water quality and promoting wetland plant growth. However, they have minimal effect on the degradation of trace pollutants in the effluent, and the biodegradability of the effluent is not high.

[0005] Therefore, how to expand the high-value utilization of ash in the wastewater field and achieve efficient removal of trace pollutants in wastewater effluent and significant improvement in ecological safety is of great practical significance in the process of deep treatment of effluent. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low removal rate of trace pollutants in the effluent of sewage treatment plants and low biodegradability of the effluent in the prior art.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for removing trace pollutants from wastewater treatment plant effluent using biomass ash, the method being carried out in a system including an equalization tank, an ozone catalytic reaction tank, and a biological buffer tank, comprising:

[0008] (1) The tailwater is introduced into the equalization tank for homogenization to obtain greywater I;

[0009] (2) The greywater I is introduced into the ozone catalytic reaction tank to carry out ozone catalytic reaction, and greywater II is obtained;

[0010] (3) The greywater II is introduced into the biochemical buffer tank and contacted with the biofilm-coated microbial carrier for biochemical treatment to obtain effluent;

[0011] The tetracycline content in the tailwater is 0.01-50 mg / L;

[0012] The catalyst used in the ozone catalytic reaction has a specific surface area of ​​45-65 m². 2 Modified ash residue with a content of not less than 80 wt% of m(SiO2+CaO+Al2O3+Fe2O3); the amount of catalyst used is 50-300 g relative to each 1 L of the tailwater.

[0013] The microbial carrier is ash slag I with an average volume diameter of 0.6-8.0 mm;

[0014] The modified ash is the product obtained by modifying ash II with citric acid and chitosan.

[0015] The second aspect of the present invention provides a system for removing trace pollutants from wastewater treatment plant effluent using biomass ash residue. The system is applied to the method described in the first aspect and is provided with an equalization tank, an ozone catalytic reaction tank and a biochemical buffer tank arranged sequentially along the liquid phase flow direction.

[0016] The equalization tank is used to introduce the effluent into the equalization tank for homogenization to obtain greywater I;

[0017] The ozone catalytic reaction tank is connected to the conditioning tank so that the greywater I undergoes an ozone catalytic reaction with the catalyst filled in the ozone catalytic reaction tank to obtain greywater II;

[0018] The biochemical buffer tank is connected to the ozone catalytic reaction tank so that the reclaimed water II comes into contact with the biofilm-coated microbial carrier filled in the biochemical buffer tank for biochemical treatment to obtain effluent.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] (1) The method provided by the present invention can improve the adsorption behavior of biomass ash on different trace pollutants in the tailwater by enhancing adsorption, interception and other processes, including heavy metals, antibiotics, antiviral drugs, etc.

[0021] (2) The method provided by the present invention can utilize the interception and enrichment behavior of modified biomass ash residue on pollutants while combining ozone to construct a heterogeneous catalytic oxidation system, thereby achieving efficient removal of trace organic pollutants in the tailwater. The process does not require the addition of chemical reagents, is environmentally friendly and does not cause secondary pollution; at the same time, it forms oxygen-rich tailwater, which improves the biodegradability of the tailwater.

[0022] (3) The method provided by the present invention can increase the amount of beneficial bacteria in the effluent, thereby enhancing the ecological value of the effluent as “ecological replenishment”.

[0023] (4) In this invention, modified ash with small particle size is used as a heterogeneous catalyst and ash with large particle size is used as a microbial carrier, which expands the application of large-volume ash in the field of wastewater and can achieve the purpose of waste reuse. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of a preferred method for removing trace pollutants from wastewater treatment plant effluent using biomass ash, provided by the present invention.

[0025] Figure 2 This is a SEM image of ash II in a preferred embodiment provided by the present invention;

[0026] Figure 3 This is an EDX image of ash II in a preferred embodiment provided by the present invention;

[0027] Figure 4 This is an FTIR image of ash II and catalyst in a preferred embodiment of the present invention;

[0028] Figure 5 This is a SEM image of the catalyst in a preferred embodiment of the present invention;

[0029] Figure 6 This is an EDX image of the catalyst in a preferred embodiment of the present invention;

[0030] Figure 7 This is a preferred embodiment and a comparative example of the TOC removal rate curve in the effluent provided by the present invention;

[0031] Figure 8 This is a preferred embodiment and a comparative example of the TOC removal rate curve in the effluent provided by the present invention;

[0032] Figure 9 This is a degradation rate curve of tetracycline, enrofloxacin, sulfamethoxazole, and amantadine in a preferred embodiment of the present invention;

[0033] Figure 10This is a dilution curve of the microbial carrier after the system has been running for one week in a preferred embodiment of the present invention;

[0034] Figure 11 This is a classification diagram of the microbial community on the biofilm carrier at the gate level after the system has been running for one week in a preferred embodiment of the present invention. Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] As mentioned above, this invention provides a method for removing trace pollutants from wastewater treatment plant effluent using biomass ash. This method is carried out in a system comprising an equalization tank, an ozone catalytic reaction tank, and a biological buffer tank, and includes:

[0037] (1) The tailwater is introduced into the equalization tank for homogenization to obtain greywater I;

[0038] (2) The greywater I is introduced into the ozone catalytic reaction tank to carry out ozone catalytic reaction, and greywater II is obtained;

[0039] (3) The greywater II is introduced into the biochemical buffer tank and contacted with the biofilm-coated microbial carrier for biochemical treatment to obtain effluent;

[0040] The tetracycline content in the tailwater is 0.01-50 mg / L;

[0041] The catalyst used in the ozone catalytic reaction has a specific surface area of ​​45-65 m². 2 Modified ash residue with a content of not less than 80 wt% of m(SiO2+CaO+Al2O3+Fe2O3); the amount of catalyst used is 50-300 g relative to each 1 L of the tailwater.

[0042] The microbial carrier is ash slag I with an average volume diameter of 0.6-8.0 mm;

[0043] The modified ash is the product obtained by modifying ash II with citric acid and chitosan.

[0044] It should be noted that, in this invention, m(SiO2+CaO+Al2O3+Fe2O3) represents the sum of the mass fractions of SiO2, CaO, Al2O3 and Fe2O3 in the catalyst.

[0045] Preferably, the effluent also contains enrofloxacin, sulfamethoxazole, and amantadine, and the content of enrofloxacin, sulfamethoxazole, and amantadine in the effluent is 0.01-50 mg / L.

[0046] Preferably, both ash residue I and ash residue II are products obtained by sequentially screening, washing, and drying biomass ash residue until the moisture content does not exceed 4 wt%; and

[0047] The biomass ash is a solid waste generated from biomass power plant combustion power generation. In the biomass ash, the content of SiO2 is 35-60wt%, the content of CaO is 5-20wt%, the content of Al2O3 is 5-15wt%, and the content of Fe2O3 is 5-15wt%, and the sum of the contents of SiO2, CaO, Al2O3 and Fe2O3 is not less than 80wt%.

[0048] In a preferred embodiment, the modification reaction includes the following steps:

[0049] S1. The ash residue II is reacted with citric acid solution I in a first reaction, and then dried to obtain mixture I; wherein the volume average diameter of the ash residue II is 0.15-0.60 mm, and the concentration of citric acid in the citric acid solution I is 5-20 wt%.

[0050] S2. The chitosan is mixed with citric acid solution II to obtain a chitosan-citric acid solution; the concentration of citric acid in citric acid solution II is 2-5 wt%.

[0051] S3. The mixture I is reacted with the chitosan-citric acid solution in a second reaction. The pH is adjusted to 9-10, and after standing for 8-12 hours, the mixture is pyrolyzed at low temperature, washed, and dried to obtain modified ash. The inventors have found that under this preferred condition, the removal rate of trace pollutants in the final effluent can be improved.

[0052] Preferably, in step S1, the conditions for the first reaction are at least: rotation speed of 100-120 rpm, temperature of 22-28°C, and time of 6-8 h.

[0053] Preferably, in step S2, the mixing conditions at least satisfy: a rotation speed of 100-120 rpm and a time of 5-15 min.

[0054] In a preferred embodiment, the drying temperature in steps S1 and S3 is independently 80-110°C.

[0055] In a preferred embodiment, in step S3, the conditions for the second reaction are at least: a rotation speed of 100-120 rpm, a temperature of 35-45°C, and a time of 8-12 h.

[0056] Preferably, in step S1, the weight ratio of the ash residue II to the volume ratio of the citric acid solution I is 1:10-15.

[0057] It should be noted that in this invention, the unit of weight is g and the unit of volume is mL.

[0058] In a preferred embodiment, in step S2, the chitosan concentration in the chitosan-citric acid solution is 5-10 g / L.

[0059] Preferably, in step S3, the low-temperature pyrolysis is carried out in a nitrogen atmosphere at a temperature of 300-500°C for 1-2 hours.

[0060] In a preferred embodiment, in step S3, the pH is adjusted using a 1 mM NaOH solution.

[0061] Preferably, in step S3, the weight ratio of the mixture I to the volume ratio of the chitosan-citric acid solution is 1:18-22.

[0062] According to a preferred embodiment, the method of the present invention further includes: in step (2), ozone is introduced upward from the lower part of the ozone catalytic reaction tank using an aeration disc, and the ozone inlet flow rate is 0.2-2 L / min.

[0063] Preferably, the ozone introduction mode is continuous and / or intermittent, and in the intermittent mode, the time interval between each two adjacent ozone introductions is independently 1-12h, and the ozone introduction time for each time is independently 20-120min.

[0064] Preferably, the homogenization time is 0.5-1 hour.

[0065] Preferably, the ozone catalytic reaction time is 20-120 min.

[0066] Preferably, the biochemical treatment time is 0.5-2 hours.

[0067] The following combination Figure 1 A preferred method for removing trace pollutants from wastewater treatment plant effluent using biomass ash is provided, comprising:

[0068] (1) The tailwater is introduced into the equalization tank for homogenization to obtain greywater I;

[0069] (2) The reclaimed water I is pressurized by a peristaltic pump and introduced into the ozone catalytic reaction tank to undergo ozone catalytic reaction with the catalyst. At the same time, ozone is introduced from the bottom to the top of the ozone catalytic reaction tank using an aeration disc, and the ozone inlet flow rate is 0.5-2 L / min. The resulting reclaimed water II is drawn out from the top of the ozone catalytic reaction tank.

[0070] (3) The reclaimed water II is introduced into the biochemical buffer tank and comes into contact with the biofilm-coated microbial carrier for biochemical treatment to obtain effluent.

[0071] It should be noted that, in this invention, there are no specific limitations on the other parameters of the homogenization and the biochemical treatment, and conventional techniques and parameters in the art can be used.

[0072] As mentioned above, the second aspect of the present invention provides a system for removing trace pollutants from wastewater treatment plant effluent using biomass ash residue. This system is applied to the method described in the first aspect and is provided with an equalization tank, an ozone catalytic reaction tank, and a biochemical buffer tank arranged sequentially along the liquid phase flow direction.

[0073] The equalization tank is used to introduce the effluent into the equalization tank for homogenization to obtain greywater I;

[0074] The ozone catalytic reaction tank is connected to the conditioning tank so that the greywater I undergoes an ozone catalytic reaction with the catalyst filled in the ozone catalytic reaction tank to obtain greywater II;

[0075] The biochemical buffer tank is connected to the ozone catalytic reaction tank so that the reclaimed water II comes into contact with the biofilm-coated microbial carrier filled in the biochemical buffer tank for biochemical treatment to obtain effluent.

[0076] Preferably, an aeration disc is provided at the bottom of the ozone catalytic reaction tank to introduce ozone into the ozone catalytic reaction tank from bottom to top.

[0077] Preferably, a peristaltic pump is provided between the equalization tank and the ozone catalytic reaction tank to pressurize the greywater I drawn from the equalization tank.

[0078] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products.

[0079] Preparation of tailwater I:

[0080] Dissolve 1g of tetracycline in deionized water to obtain tailwater I with a tetracycline concentration of 10mg / L.

[0081] Preparation of tailwater II:

[0082] Dissolve 1g tetracycline, 1g enrofloxacin, 1g sulfamethoxazole, and 1g amantadine in deionized water to obtain tailwater II with a tetracycline concentration of 10mg / L, an enrofloxacin concentration of 10mg / L, a sulfamethoxazole concentration of 10mg / L, and an amantadine concentration of 10mg / L.

[0083] Biomass ash residue: solid waste derived from biomass power generation at a biomass power plant in Anhui Province. Its parameters and composition are shown in Table 1.

[0084] Table 1

[0085] project Content / Value Volume diameter / mm 0.15-8.0 <![CDATA[Specific surface area / m 2 ·g -1 > 1.560-37.398 <![CDATA[SiO2 / wt%]]> 38.15-56.46 <![CDATA[Al2O3 / wt%]]> 8.69-13.30 <![CDATA[Fe2O3 / wt%]]> 5.94-7.88 CaO / wt% 9.54-17.63

[0086] Unless otherwise specified, the following examples use Figure 1 The process shown is carried out, and the flow rate of the effluent is 0.2 L / min.

[0087] Preparation Example A-1

[0088] Preparation of Ash Slag I:

[0089] The biomass ash residue was screened, then rinsed with deionized water for 120 seconds, and dried to a moisture content of 4wt% to obtain ash residue I with an average volume diameter of 3.0 mm.

[0090] Preparation Example A-2

[0091] Preparation of Ash Slag II:

[0092] The biomass ash residue was screened, then rinsed with deionized water for 120 seconds, and dried to a moisture content of 4 wt% to obtain ash residue II with an average volume diameter of 0.5 mm.

[0093] Preparation Example B-1

[0094] S1. At 25°C and 120 rpm, 100 g of the ash residue II was added to 1000 mL of citric acid solution I (concentration of 10 wt%) for a first reaction for 7 h, and then dried at 105°C to constant weight to obtain mixture I.

[0095] S2. At 25℃ and 120 rpm, chitosan was added to citric acid solution II (concentration of 4 wt%) and mixed for 10 min to obtain a chitosan-citric acid solution with a chitosan concentration of 8.0 g / L.

[0096] S3. At 35℃ and 120 rpm, 100 g of the mixture I was added to 2000 mL of the chitosan-citric acid solution for a second reaction for 9 h. The pH was then adjusted to 9 using a 1 mM NaOH solution. After standing for 8 h, the mixture was pyrolyzed at 500℃ for 1 h under a nitrogen atmosphere. It was then washed with deionized water for 120 s and dried at 105℃ to constant weight to obtain a specific surface area of ​​59.59 m². 2 The concentration of SiO2 + CaO + Al2O3 + Fe2O3 is 86.56 wt%, and the pore volume is 0.022 cm³. 3 / g, modified ash residue with an average pore size of 3.088nm, is named catalyst I;

[0097] Figure 2 The SEM image (scanning electron microscope image) of ash II is shown. Figure 3 The EDX (energy dispersive X-ray) spectrum of ash II is shown. Figure 4 The FTIR (infrared spectrum) of ash II and catalyst I is shown. Figure 5 The SEM image of catalyst I is shown. Figure 6 The EDX image of catalyst I is shown. It can be seen that the surface structure of catalyst I after citric acid washing modification becomes rougher and the pore structure is richer. The surface carbon content is increased, and the introduced carbon functional groups can be more stably loaded on the ash surface, which is beneficial for the interception and adsorption of trace organic pollutants in water.

[0098] Preparation Example B-2

[0099] This preparation example is carried out using a method similar to that of preparation example B-1. The difference is that in step S1, an equal volume of deionized water is used instead of citric acid solution I for the first reaction.

[0100] The final specific surface area was 28.21 m². 2 The concentration of SiO2 + CaO + Al2O3 + Fe2O3 is 88.29 wt%, and the pore volume is 0.015 cm³. 3 The modified ash residue with an average pore size of 2.841 nm per g was named Catalyst II.

[0101] Preparation Example B-3

[0102] This preparation example is carried out using a method similar to that of preparation example B-1. The difference is that step S2 is not performed, and in step S3, an equal volume of citric acid solution II is directly used instead of citric acid-chitosan solution to carry out the second reaction with mixture I.

[0103] The final specific surface area was 52.81 m². 2The concentration of SiO2 + CaO + Al2O3 + Fe2O3 is 80.17 wt%, and the pore volume is 0.041 cm³. 3 The modified ash residue with an average pore size of 4.120 nm per g was named Catalyst III.

[0104] Example 1

[0105] This embodiment illustrates that the method for removing trace pollutants from wastewater treatment plant effluent using biomass ash provided by the present invention is carried out according to the following steps:

[0106] (1) The tailwater (tailwater I) is introduced into the equalization tank and homogenized for 1 hour to obtain greywater I;

[0107] (2) The reclaimed water I is pressurized by a peristaltic pump and introduced into the ozone catalytic reaction tank to undergo an ozone catalytic reaction with the catalyst for 120 min. At the same time, ozone is continuously introduced into the ozone catalytic reaction tank from the bottom to the top using an aeration disc, and the ozone inlet flow rate is 0.5 L / min. The resulting reclaimed water II (named Q1) is drawn out from the top of the ozone catalytic reaction tank. The amount of catalyst used is 100 g per 1 L of the tailwater.

[0108] (3) After the ash residue I is used as a microbial carrier to form a biofilm, it is contacted with the reclaimed water II in a biochemical buffer tank for biochemical treatment for 1 hour; the effluent is obtained and named P1.

[0109] The system was run for a week, during which microbial diversity analysis was performed on the microbial carriers within it.

[0110] Figure 10 The dilution curve of the microbial vector after one week of operation in this embodiment is shown. As can be seen from the figure, the curve becomes flat as the number of sequences increases, indicating that the sequencing method is feasible. Based on a similarity of 97%, it can be found that the number of OUT can reach about 1500, indicating a high species richness, which allows for subsequent sequencing.

[0111] Figure 11 This diagram shows the microbial community classification of the biofilm carrier at the gate level after one week of operation in this embodiment. Figure 11 The figure shows the weight percentage of each bacterial group. It can be seen from the figure that at the phylum level, Proteobacteria and Nitrifying Spirochetes account for 39.2% and 33.9% of the weight, respectively. They can play a role in nitrification and denitrification, and actively promote the further purification of water bodies and nitrogen cycling by degrading organic pollutants and nitrogen compounds in the effluent.

[0112] Example 2

[0113] This embodiment uses a method similar to that of Embodiment 1, except that in step (1), the tailwater used is tailwater II;

[0114] We obtained medium-grade water II, which was named Q2;

[0115] The water that was eventually extracted was named P2.

[0116] Comparative Example 1

[0117] This comparative example was carried out using a method similar to that of Example 1. The difference is that in step (2), an equal mass of catalyst III was used instead of catalyst I to carry out an ozone catalytic reaction with water I.

[0118] We obtained medium-grade water II, which was named DQ1;

[0119] The water that eventually emerged was named DP1.

[0120] Comparative Example 2

[0121] This comparative example was conducted using a method similar to that of Example 1, except that in step (2), catalyst I was not added; only ozone and greywater I were introduced to carry out an ozone oxidation reaction. Specifically:

[0122] (2) In the ozone catalytic reaction tank, ozone is continuously introduced from the bottom to the top of the ozone catalytic reaction tank using an aeration disc, and the ozone inlet flow rate is 0.5L / min. The greywater I is pressurized by a peristaltic pump and introduced into the ozone catalytic reaction tank for reaction for 120min, and greywater II (named DQ2) is drawn out from the top of the ozone catalytic reaction tank.

[0123] The water that eventually emerged was named DP2.

[0124] Comparative Example 3

[0125] This comparative example was carried out using a method similar to that of Example 1. The difference was that in step (2), an equal mass of ash residue II was used directly to replace catalyst I and to carry out an ozone catalytic reaction with wastewater I; wastewater II was obtained and named DQ3.

[0126] The water that was eventually produced was named DP3.

[0127] Comparative Example 4

[0128] This comparative example was carried out using a method similar to that of Example 1. The difference was that in step (2), an equal mass of catalyst II was used instead of catalyst I to carry out an ozone catalytic reaction with greywater I to obtain greywater II, which was named DQ4.

[0129] The water that was eventually produced was named DP4.

[0130] Comparative Example 5

[0131] This comparative example was carried out using a method similar to that of Example 1, except that in step (2), the amount of catalyst used was 20g relative to 1L of the tailwater;

[0132] The resulting medium-grade water II was named DQ5;

[0133] The water that was eventually produced was named DP5.

[0134] Test Example 1

[0135] The dissolved oxygen in the wastewater II obtained in the examples and comparative examples was measured, and the dissolved oxygen results for Q1 and Q2 are shown in Table 2.

[0136] Table 2

[0137] Control Indicators Q1 Q2 Dissolved oxygen concentration (mg / L) 15.21 13.36

[0138] Test Example 2

[0139] The adsorption capacity of pollutants in the effluent obtained from the examples and comparative examples was tested and recorded.

[0140] The TOC removal rate curves of the effluent from P1 and DP3 were obtained. See the results below. Figure 7 ;

[0141] The TOC removal rate curves of the effluent from DP1, DP2, DP4, and DP5 were obtained. See the results below. Figure 8 ;

[0142] The degradation rate curves of tetracycline, enrofloxacin, sulfamethoxazole, and amantadine in P2 were obtained. See the results below. Figure 9 .

[0143] The results above show that the method provided by this invention can achieve efficient removal of trace organic pollutants in effluent, without the addition of chemical reagents, making it environmentally friendly and free from secondary pollution; at the same time, it forms oxygen-rich effluent, improving the biodegradability of the effluent; finally, the effluent is rich in microorganisms, with a large proportion of nitrification-related phyla such as Proteobacteria and Nitrifying Spirochetes, which can release more beneficial bacteria into the environment, facilitating further biological purification.

[0144] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for removing trace pollutants from wastewater treatment plant effluent using biomass ash, characterized in that, This method is carried out in a system including a conditioning tank, an ozone catalytic reaction tank, and a biochemical buffer tank, and includes: (1) The tailwater is introduced into the equalization tank for homogenization to obtain greywater I; (2) The greywater I is introduced into the ozone catalytic reaction tank for ozone catalytic reaction to obtain greywater II; (3) The reclaimed water II is introduced into the biochemical buffer tank and brought into contact with the biofilm-coated microbial carrier for biochemical treatment to obtain effluent; The tetracycline content in the tailwater is 0.01-50 mg / L; The catalyst used in the ozone catalytic reaction has a specific surface area of ​​45-65 m². 2 Modified ash residue with a content of not less than 80 wt% of m(SiO2+CaO+Al2O3+Fe2O3); the amount of catalyst used is 50-300 g relative to each 1 L of the tailwater. The m(SiO2+CaO+Al2O3+Fe2O3) represents the sum of the mass fractions of SiO2, CaO, Al2O3, and Fe2O3 in the catalyst. The microbial carrier is ash slag I with an average volume diameter of 0.6-8.0 mm; The modified ash residue is the product obtained by modifying ash residue II with citric acid and chitosan. The modification reaction includes the following steps: S1. The ash residue II is reacted with citric acid solution I in a first reaction, and then dried to obtain mixture I; wherein the volume average diameter of the ash residue II is 0.15-0.60 mm, and the concentration of citric acid in the citric acid solution I is 5-20 wt%. S2. The chitosan is mixed with citric acid solution II to obtain a chitosan-citric acid solution; the concentration of citric acid in citric acid solution II is 2-5 wt%. S3. The mixture I is reacted with the chitosan-citric acid solution in a second reaction. The pH is adjusted to 9-10. After standing for 8-12 hours, the mixture is pyrolyzed at low temperature, washed, and dried to obtain modified ash residue.

2. The method according to claim 1, wherein, In step S1, the conditions for the first reaction are at least: a rotation speed of 100-120 rpm, a temperature of 22-28°C, and a time of 6-8 h; and / or In step S3, the conditions for the second reaction are at least: a rotation speed of 100-120 rpm, a temperature of 35-45°C, and a time of 8-12 h; and / or In step S3, the low-temperature pyrolysis is carried out in a nitrogen atmosphere at a temperature of 300-500°C for 1-2 hours.

3. The method according to claim 2, wherein, In step S1, the weight ratio of the ash residue II to the volume ratio of the citric acid solution I is 1:10-15; and / or In step S3, the weight ratio of the mixture I to the volume ratio of the chitosan-citric acid solution is 1:18-22.

4. The method according to claim 1 or 2, wherein, In step S2, the chitosan concentration in the chitosan-citric acid solution is 5-10 g / L.

5. The method according to any one of claims 1-3, wherein, Both ash residue I and ash residue II are products obtained by sequentially screening, washing, and drying biomass ash residue until the moisture content is no higher than 4 wt%; and The biomass ash is a solid waste generated from biomass power plant combustion power generation. In the biomass ash, the content of SiO2 is 35-60wt%, the content of CaO is 5-20wt%, the content of Al2O3 is 5-15wt%, the content of Fe2O3 is 5-15wt%, and the sum of the contents of SiO2, CaO, Al2O3 and Fe2O3 is not less than 80wt%.

6. The method according to any one of claims 1-3, wherein, The method further includes: in step (2), using an aeration disc to introduce ozone from the bottom of the ozone catalytic reaction tank upwards, and the ozone inlet flow rate is 0.2-2 L / min.

7. A system for removing trace pollutants from wastewater treatment plant effluent using biomass ash, characterized in that, The system is applied to the method described in any one of claims 1-6, and is provided with an equalization tank, an ozone catalytic reaction tank and a biochemical buffer tank in sequence along the liquid phase flow direction; The equalization tank is used to introduce the effluent into the equalization tank for homogenization to obtain greywater I; The ozone catalytic reaction tank is connected to the conditioning tank so that the greywater I and the catalyst filled in the ozone catalytic reaction tank can undergo an ozone catalytic reaction to obtain greywater II; The biochemical buffer tank is connected to the ozone catalytic reaction tank so that the reclaimed water II comes into contact with the biofilm-coated microbial carrier filled in the biochemical buffer tank for biochemical treatment to obtain effluent.

8. The system according to claim 7, wherein, An aeration disc is installed at the bottom of the ozone catalytic reaction tank to introduce ozone into the ozone catalytic reaction tank from bottom to top.

9. The system according to claim 8, wherein, A peristaltic pump is installed between the equalization tank and the ozone catalytic reaction tank to pressurize the greywater I drawn from the equalization tank.

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