Method for reducing inhibition effect of microplastics on anaerobic ammonia oxidation process by using flocculant

Abstract

The invention discloses a method for reducing the inhibiting effect of microplastics on an anaerobic ammonia oxidation process by using a flocculating agent, and relates to the technical field of sewage treatment. The method comprises the following steps: S1, inoculating sludge biomass and simulating domestic sewage; S2, preparing anaerobic ammonia oxidation granular sludge; S3, preparing a ferric sulfate flocculant; and S4, controlling experimental operation conditions. According to the method disclosed by the invention, the ferric sulfate flocculant is added in the process, so that the inhibition effect of the micro-plastics on nitrogen removal of the anaerobic ammonium oxidation process is effectively reduced, the activity of anaerobic ammonium oxidation bacteria is greatly improved, and almost no bacteria is lost; through the process, the adding concentration of the ferric sulfate flocculant can be flexibly regulated and controlled according to the water quality condition and the operation condition, and the process method is flexible to apply and simple to operate; according to the process, the ferric sulfate flocculant does not influence the operation of the anaerobic ammonia oxidation process, but has interaction, so that the denitrification efficiency is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and specifically to a method for reducing the inhibitory effect of microplastics on an anaerobic ammonium oxidation process by utilizing a flocculant. Background Art

[0002] As the problem of excessive nitrogen content in water bodies continues to intensify, anaerobic ammonium oxidation (anammox) technology has gradually become a research hotspot for wastewater nitrogen removal in my country. Anaerobic ammonium oxidation (Anammox) refers to the process in which anaerobic ammonium-oxidizing bacteria use nitrite as an electron acceptor and ammonia nitrogen as an electron donor under anaerobic conditions to eventually convert nitrite and ammonia nitrogen into nitrogen gas at the same time. The microorganisms based on the Anammox process are autotrophic microorganisms that do not require oxygen to participate in the reaction, have zero alkali production, reduce secondary pollution, and do not require the addition of organic carbon sources. For nitrogen pollution treatment, people choose nitrification-denitrification in the traditional treatment process to complete nitrogen removal. In this process, alkali and carbon sources are required, which will cause cost losses and form higher costs. Therefore, compared with the traditional nitrification-denitrification system, the anaerobic ammonium oxidation process is more cost-effective and sustainable, and significantly shortens the traditional nitrogen cycle process, so it has become one of the more economical new biological denitrification processes. At present, many fields have applied the anaerobic ammonium oxidation process; However, with the continuous advancement of science and technology, the living standards of human beings have improved, and new pollutants such as organic matter and microplastics have appeared in domestic sewage. The microplastics in urban domestic sewage are mainly divided into four categories: fiber microplastics, granular microplastics, foam microplastics, and sheet microplastics. Among them, fiber microplastics are the main ones. At present, the anaerobic ammonium oxidation process has not added targeted treatment processes for microplastics, a new type of pollutant. The attachment of microplastics to anaerobic ammonium oxidation granular sludge leads to a decrease in the nitrogen removal efficiency of the anaerobic ammonium oxidation process. However, the impact of microplastics on human life should not be underestimated. The presence of microplastics has also been detected in the human body. Due to their small size, microplastics can easily enter the body of organisms, and most organisms do not have the ability to metabolize microplastics, resulting in the continuous accumulation of microplastics in the body, causing chronic toxicity, which in turn endangers the health of organisms. This hazard will be transmitted step by step in the food chain, eventually causing harm to the human body.

[0003] In response to the above problems, the inventors proposed a method of using flocculants to reduce the inhibitory effect of microplastics on the anaerobic ammonium oxidation process to solve the above problems. Summary of the invention

[0004] The object of the present invention is to provide a method for reducing the inhibitory effect of microplastics on the anaerobic ammonium oxidation process by using a flocculant.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solution: a method for reducing the inhibitory effect of microplastics on anaerobic ammonium oxidation process by using flocculants, comprising the following steps: S1. Inoculation of sludge biomass and simulated domestic sewage The ANAMMOX sludge used in the experiment was taken from the anaerobic ammonium oxidation ASBBR reactor in stable operation in the laboratory (0.5 L was placed in a 2L beaker and mixed for later use), and was mixed with the simulated wastewater for cultivating anaerobic ammonium oxidation sludge to artificially prepare the NH4 + -N and NO2 + -N is provided by ammonium chloride and sodium nitrite, NH4Cl: 40-70mgNH4 + -N / L,NaNO2:50-100mgNO2 - -N / L, other components are KHCO3: 500 mg / L, KH2PO4: 27.2 mg / L, MgSO4·7H2O: 300 mg / L, CaCl2·H2O: 136 mg / L, EDTA: 5 mg / L, FeSO4·7H2O: 9 mg / L, NaCl: 1.0 mg / L, trace elements are 1 mL / L, its main components are ZnSO4·7H2O 430 mg / L, NiCl·6H2O 190 mg / L, CoCl·6H2O 240 mg / L, NaSeO4·10H2O: 210 mg / L, MnCl2·4H2O: 990 mg / L, H3BO4: 14 mg / L, CuSO4·5H2O: 250 mg / L, NaMo4·2H2O: 220 mg / L, the required microplastic content is 0.83 pcs / L; S2. Preparation of anaerobic ammonium oxidation granular sludge First, the anaerobic ammonia oxidizing bacteria liquid and the aqueous polyurethane emulsion are fully mixed in a mold, and then a 0.5% by mass concentration of N,N-methylenebisacrylamide aqueous solution and a 1.0% by mass concentration of potassium persulfate (KPS) aqueous solution are added in sequence, and the mixture is quickly stirred evenly, and allowed to stand for 30 minutes. After the gel is polymerized and formed, it is taken out from the mold, rinsed repeatedly with deionized water for 5-10 times, and then put into a pelletizer and cut into small cubes, and then thoroughly washed with deionized water to wash away the uncrosslinked monomers and unfixed anaerobic ammonia oxidizing bacteria, and then immersed in deionized water and stored at low temperature; The prepared anaerobic ammonium oxidation sludge granules (volume 3×3×3mm) are brick red, smooth in surface, soft and elastic to the touch, good in mechanical strength, and have no obvious odor. The prepared anaerobic ammonium oxidation granular sludge has good fluidity; S3. Preparation of ferric sulfate flocculant At room temperature and pressure, weigh about 20 g of titanium dioxide solid waste (obtained from Beijing Solid Waste Treatment Co., Ltd.), add 30 ml of appropriately prepared sulfuric acid solution, stir evenly, and the self-heating temperature of the reaction is about 70 60~70°C. Then wrap the prepared solution with plastic wrap (to prevent water evaporation) and put it into a 70 °C oven for reaction, and add 10~15 g of appropriate iron powder during this period. After a period of reaction, take out the solution and add 30~35 ml of appropriate water to stir, then filter, and put the solid on the filter paper into an oven set at 70 °C for drying. Add a precipitant to the above liquid, react for 2 h, put the liquid into an electric heating mantle for heating, filter the filtrate before crystallization (the purpose is to remove the incompletely reacted iron powder), and continue to heat the filtrate until a crystal film appears, then stop heating. Cool the solution and filter it, then put the crystals on the filter paper into a vacuum drying oven set at 70 °C, take them out after 2 h and weigh and bag them to obtain ferrous sulfate crystals; At room temperature and pressure, weigh 10g of appropriately prepared ferrous sulfate crystals, add an appropriate amount of deionized water and then a certain amount of concentrated sulfuric acid [w (H2SO4) = 98%], and stir continuously to fully dissolve the ferrous sulfate. Place the solution in a constant temperature heating jacket, heat it to 25°C, and slowly add 5ml of an appropriate amount of hydrogen peroxide. The addition time is controlled at about 6-10 min. Then place it in a 50 °C constant temperature heating jacket to react for a period of time, and take it out after hydrolysis and polymerization reaction. Finally, after aging at room temperature for 24 hours, a reddish-brown viscous liquid is obtained, which is the ferric sulfate flocculant.

[0006] S4. Preparation of ferric sulfate flocculant In order to prevent the influence of improper flocculant treatment on the experimental results, a conical flask with an effective volume of 250 mL was used as the experimental device, and the outside was wrapped with a light-shielding cloth. Before the experiment, water was added to the ASBBR reactor, and the aeration head was placed at the bottom of the reaction bottle. After the cover was added, high-purity nitrogen was used to discharge oxygen for 15 minutes, and then sludge was quickly added to adjust the pH to 7.5-8, and nitrogen aeration was maintained for 2 minutes. The reaction bottle was wrapped with light-proof paper and a black plastic bag and placed in a constant temperature incubator for cultivation; Before the experiment, the prepared ferric sulfate flocculant was prepared into a solution with a concentration of 25 mg / L and a mass fraction of 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.3% respectively for use; S5. Experimental operation condition control A: Operation of ANAMMOX reactor A UASB reactor was used. After deoxygenation treatment, the influent of the UASB reactor was covered and allowed to stand. The operating parameters during the experimental phase were: pH 7.9 ± 0.3; B: Add flocculant A water bath thermostatic system and a sealing device are used to ensure that the temperature is maintained at 30-35°C and in an anoxic and anaerobic state. When the pH is stable between 6.5 and 7.3 in the early stage, 10-25 mg / L ferric sulfate flocculant is added to ensure that the ferric sulfate flocculant can function normally. After 15 minutes, the pH is controlled at 7.5-7.8 to ensure the good growth and reproduction of anaerobic ammonia-oxidizing bacteria, so that the system has an efficient and stable denitrification effect.

[0007] Preferably, in S2, the ratio of the anaerobic ammonia-oxidizing bacteria liquid to the aqueous polyurethane emulsion is: 0.5% N,N-methylenebisacrylamide aqueous solution: 1.0% potassium persulfate (KPS) aqueous solution is 100g: (10-20)g: (0.5-1.0)ml: (1.0-2.0)ml.

[0008] Preferably, in A1 of S4, the UASB reactor is made of mailing glass, the inner diameter of the UASB reactor is 100 mm, the reaction zone is 800 mm high, the effective volume is 6.28 L, and the temperature of the UASB reactor is controlled by a water bath interlayer and maintained at (32±2)°C.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. In the present invention, by adding ferric sulfate flocculant in the process, the inhibitory effect of microplastics on nitrogen removal in the anaerobic ammonium oxidation process is effectively reduced, and the activity of anaerobic ammonium oxidizing bacteria is greatly improved, with almost no loss of sterile amount; 2. In the present invention, through this process, the concentration of ferric sulfate flocculant can be flexibly adjusted according to water quality conditions and operating conditions, and the process method is flexible in application and simple in operation; 3. In the present invention, through this process, the addition of ferric sulfate flocculant does not affect the operation of the anaerobic ammonium oxidation process, but rather has a mutual effect, and the denitrification efficiency is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 This is an improved flow chart of the anaerobic ammonium oxidation granular sludge process of the present invention. DETAILED DESCRIPTION

[0012] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] Example: Figure 1 As shown, the present invention provides a method for reducing the inhibitory effect of microplastics on anaerobic ammonium oxidation process by using flocculants, comprising the following steps: S1. Experimental apparatus and operating conditions The experimental device is a UASB reactor made of organic glass. Figure 1 As shown, the reactor has an inner diameter of 100 mm, a reaction zone height of 800 mm, an effective volume of 6.28 L, and the reactor temperature is controlled by a water bath interlayer and maintained at (32±2)°C. The reactor inlet water is deoxygenated and then covered and allowed to stand. The operating parameters during the experimental phase are: pH 7.9±0.3, HRT 24h; S2. Settings of control and experimental groups The experiment was divided into R1, R2, R3, R4, R5, R6, and R7. R1 was the control group R1 in which no ferric sulfate flocculant was added to the reaction bottle, R2 was the experimental group R2 in which 25 mg / L of ferric sulfate flocculant with a mass fraction of 0.1% was added to the reaction bottle, R3 was the experimental group R3 in which 25 mg / L of ferric sulfate flocculant with a mass fraction of 0.3% was added to the reaction bottle, R4 was the experimental group R4 in which 25 mg / L of ferric sulfate flocculant with a mass fraction of 0.5% was added to the reaction bottle, R5 was the experimental group R5 in which 25 mg / L of ferric sulfate flocculant with a mass fraction of 0.7% was added to the reaction bottle, R6 was the experimental group R6 in which 25 mg / L of ferric sulfate flocculant with a mass fraction of 1.0% was added to the reaction bottle, and R7 was the experimental group R7 in which 25 mg / L of ferric sulfate flocculant with a mass fraction of 1.3% was added to the reaction bottle. In addition, the other conditions of the two groups, such as temperature, pH, time, microplastic content, etc., were the same, and the mud-water ratio was: 150 mL of artificial water was taken from 50 mL of the activated sludge mixed liquor in the ASBBR reactor, and the influent pH value was adjusted to 7.3, and the contents of NH4Cl and NaNO2 were 50 mg / L respectively.

[0014] S3. Experimental operation process When the reaction device was running stably and the pH value was stable at 7.2, 25 mg / L of ferric sulfate flocculant was added to the experimental groups R2, R3, R4, R5, R6, and R7. The experiment was carried out in batches for a total of 10 days. Samples were taken at 12:00 every day to detect the ρ(NH4 + -N) and ρ( NO2+ -N), pH value and microplastic content, and uniformly change the water in the device to observe and analyze NH4 + -N, NO2 - -The changes in N concentration and microplastic content were calculated to calculate the removal rates of ammonia nitrogen and microplastics in the control group and the experimental group; S4. Experimental results During the stable operation stage of the anaerobic ammonium oxidation process, the influent ρ(NH4 + -N)、ρ(NO2 － -N) concentration was 50mg / L, and the NH4 + -N and NO2 － -N concentration and pH value were tested. After adding 25 mg / L of ferric sulfate, the average ammonia nitrogen removal rate of the anaerobic ammonium oxidation process in the experimental group was 86.9%, and the microplastic removal rate was 89.8%, while the average ammonia nitrogen removal rate of the anaerobic ammonium oxidation process in the control group was 56.3%, and the microplastic removal rate was 36.2%, which were significantly lower than those in the experimental group. It can be concluded from the experimental data that after adding 0.7% ferric sulfate flocculant, the anaerobic ammonium oxidation process has a higher ammonia nitrogen removal rate for domestic sewage containing microplastics, and the anaerobic ammonium oxidation process is efficient and environmentally friendly while ensuring the removal of microplastics.

[0015] Working principle: Microplastic flocculation and sedimentation is an effective method to treat microplastics by adding flocculants to water. Flocculants are usually high molecular polymers that can change the surface properties of microplastic particles suspended in water, causing the interaction between these particles to change from repulsion to attraction, thereby forming flocs and settling. Li et al. believe that the aggregation of microplastics is affected by electrostatic repulsion, spatial effects, and coexisting metal ions in water, and found that the aggregation of microplastics is affected by monovalent metal ions (such as K + 、Na + ) compared to divalent metal ions (such as Ca 2+ , Ba 2+ ) has a more obvious inhibitory effect on the aggregation of microplastics. Therefore, in this experiment, ferric sulfate was used as a flocculant. Under the conditions of pH 7.6, flocculant dosage of 25 mg / L, and mass fraction of 0.7%, Fe 2+ As an electron donor, Fe 2+It can reduce NO2--N to N2O under non-biological action, and can also reduce NO3--N to N2 under the participation of microorganisms (NDFO). Therefore, the addition of ferric sulfate flocculant not only effectively inhibits the adsorption of microplastics in activated sludge, but also improves the activity of anaerobic ammonium oxidizing bacteria, greatly improves the nitrogen removal efficiency of the anaerobic ammonium oxidation process, and makes up for the problem that anaerobic ammonium oxidizing bacteria cannot effectively play a role in the anaerobic ammonium oxidation process due to the presence of microplastics and the problem of incomplete denitrification in the anaerobic ammonium oxidation process. At the same time, the ferric sulfate flocculant is put into an anaerobic ammonium oxidation reaction device to strengthen the entire system; At the same time, this process can enable the anaerobic ammonium oxidation process to operate efficiently when treating domestic sewage containing microplastics, and an appropriate amount of ferric sulfate flocculant can be added to the anaerobic ammonium oxidation process according to the actual microplastic content in the sewage to achieve environmentally friendly and green sewage treatment. The process method is flexible in application and simple to operate, and the addition of ferric sulfate can be flexibly adjusted according to actual needs.

[0016] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for reducing the inhibitory effect of microplastics on anaerobic ammonium oxidation process by using flocculants, characterized in that: The following steps are involved: S1. Inoculation of sludge biomass and simulated domestic sewage The ANAMMOX sludge used in the experiment was taken from the anaerobic ammonium oxidation ASBBR reactor in stable operation in the laboratory (0.5 L was placed in a 2L beaker and mixed for later use), and was mixed with the simulated wastewater for cultivating anaerobic ammonium oxidation sludge to artificially prepare the NH4 + -N and NO2 + -N is provided by ammonium chloride and sodium nitrite, NH4Cl: 40-70mgNH4 + -N / L,NaNO2:50-100mgNO2 - -N / L, other components are KHCO3: 500 mg / L, KH2PO4: 27.2 mg / L, MgSO4·7H2O: 300 mg / L, CaCl2·H2O: 136 mg / L, EDTA: 5 mg / L, FeSO4·7H2O: 9 mg / L, NaCl: 1.0 mg / L, trace elements are 1 mL / L, its main components are ZnSO4·7H2O 430 mg / L, NiCl·6H2O 190 mg / L, CoCl·6H2O 240 mg / L, NaSeO4·10H2O: 210 mg / L, MnCl2·4H2O: 990 mg / L, H3BO4: 14 mg / L, CuSO4·5H2O: 250 mg / L, NaMo4·2H2O: 220 mg / L, the required microplastic content is 0.83 pcs / L; S2. Preparation of anaerobic ammonium oxidation granular sludge First, the anaerobic ammonia oxidizing bacteria liquid and the aqueous polyurethane emulsion are fully mixed in a mold, and then a 0.5% by mass concentration of N,N-methylenebisacrylamide aqueous solution and a 1.0% by mass concentration of potassium persulfate (KPS) aqueous solution are added in sequence, and the mixture is quickly stirred evenly, and allowed to stand for 30 minutes. After the gel is polymerized and formed, it is taken out from the mold, rinsed repeatedly with deionized water for 5-10 times, and then put into a pelletizer and cut into small cubes, and then thoroughly washed with deionized water to wash away the uncrosslinked monomers and unfixed anaerobic ammonia oxidizing bacteria, and then immersed in deionized water and stored at low temperature; The prepared anaerobic ammonium oxidation sludge granules (volume 3×3×3mm) are brick red, smooth in surface, soft and elastic to the touch, good in mechanical strength, and have no obvious odor. The prepared granular sludge has good fluidity. S3. Preparation of ferric sulfate flocculant At room temperature and pressure, weigh 20 g of titanium dioxide solid waste, add 30 ml of the prepared sulfuric acid solution thereto, stir evenly, at this time the self-heating temperature of the reaction is 60-70 ° C, then wrap the prepared sulfuric acid solution with plastic wrap and put it into a 70 ° C oven for reaction, and add 10-15 g of iron powder during this period, after the reaction, take out the solution and add 20-30 ml of water to stir, then filter, put the solid on the filter paper into an oven set at 70 ° C for drying, add a precipitant to the above liquid, react for 2 h, put the liquid into an electric heating mantle for heating, filter the filtrate before crystallization, and continue to heat the filtrate until a crystal film appears, then stop heating, cool the solution and filter, then put the crystals on the filter paper into a vacuum drying oven set at 70 ° C, take them out after 2 h and weigh and bag them to obtain ferrous sulfate crystals; At room temperature and pressure, weigh 10g of the prepared ferrous sulfate crystals, add deionized water and then add w (H2SO4) = 98%, stir continuously to fully dissolve the ferrous sulfate, place the solution in a constant temperature heating jacket, heat it to 25°C, slowly add 5ml of hydrogen peroxide, and control the dropwise addition time to 6-10 min. Then place it in a constant temperature heating jacket at 50°C for reaction time, take it out after hydrolysis and polymerization reaction, and finally place it at room temperature for aging for 24 h to obtain a reddish-brown viscous liquid, which is the ferric sulfate flocculant. S4. Preparation of ferric sulfate flocculant In order to prevent the influence of improper flocculant treatment on the experimental results, a conical flask with an effective volume of 250 mL was used as the experimental device, and the outside was wrapped with a light-shielding cloth. Before the experiment, water was added to the ASBBR reactor, and the aeration head was placed at the bottom of the reaction bottle. After the cover was added, high-purity nitrogen was used to deoxygenate for 15 minutes, and then sludge was quickly added to adjust the pH to 7.5-8, and nitrogen aeration was maintained for 2 minutes. The reaction bottle was wrapped with light-proof paper and a black plastic bag and placed in a constant temperature incubator for cultivation; Before the experiment, the chemical flocculant ferric sulfate was prepared into solutions with a concentration of 25 mg / L and mass fractions of 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.3% respectively for use; S5. Experimental operation condition control A: Operation of ANAMMOX reactor A UASB reactor was used. After deoxygenation treatment, the influent of the UASB reactor was covered and allowed to stand. The operating parameters during the experimental phase were: pH 7.9 ± 0.3; B: Add flocculant A water bath thermostatic system and a sealing device are used to ensure that the temperature is maintained at 28-30°C and in an anoxic and anaerobic state. When the pH is stable between 6.5 and 7.3 in the early stage, 5-10 mg / L ferric sulfate flocculant is added to ensure that the ferric sulfate flocculant can function normally. After 15 minutes, the pH is controlled at 7.5-7.8 to ensure the good growth and reproduction of anaerobic ammonia-oxidizing bacteria, so that the system has an efficient and stable denitrification effect.

2. A method for reducing the inhibitory effect of microplastics on anaerobic ammonium oxidation process using a flocculant as claimed in claim 1, characterized in that: In S2, the ratio of the anaerobic ammonia-oxidizing bacteria liquid to the aqueous polyurethane emulsion is: 0.5% N,N-methylenebisacrylamide aqueous solution: 1.0% potassium persulfate (KPS) aqueous solution is 100g: (10-20)g: (0.5-1.0)ml: (1.0-2.0)ml.

3. A method for reducing the inhibitory effect of microplastics on anaerobic ammonium oxidation process using a flocculant as claimed in claim 1, characterized in that: In A1 of S4, the UASB reactor is made of mail glass, the inner diameter of the UASB reactor is 100 mm, the reaction zone height is 800 mm, the effective volume is 6.28 L, and the temperature of the UASB reactor is controlled by a water bath interlayer and maintained at (32±2)°C.

Images