A sewage treatment method for degrading low-concentration drugs and simultaneously removing nitrogen

Abstract

The present invention provides a sewage treatment method for degrading low-concentration drugs and synchronously denitrifying, belonging to the technical field of sewage treatment. The sewage treatment method for degrading low-concentration drugs and synchronously denitrifying provided by the present invention comprises the following steps: inoculating sludge into an anaerobic tank provided with a biofilm carrier, and introducing the sewage to be treated to carry out film formation treatment, iron autotrophic anaerobic denitrification domestication and degradation-denitrification treatment in sequence; wherein, no external organic carbon source is added during both the iron autotrophic anaerobic denitrification domestication and the degradation-denitrification treatment, and an iron source is added during both the iron autotrophic anaerobic denitrification domestication and the degradation-denitrification treatment; the sewage to be treated contains low-concentration drug pollutants, and the concentration of each drug pollutant in the sewage to be treated is independently ≤ 300 μg / L. By adopting iron autotrophic anaerobic denitrification domestication, the present invention can achieve efficient degradation of low-concentration drug pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a sewage treatment method for degrading low-concentration drugs and synchronously denitrifying. Background Art

[0002] A large number of pharmaceuticals and personal care products (PPCPs) cannot be completely absorbed by the human body or animals. A part of them is excreted into the environment, which has an impact on environmental organisms and ecosystems, and may ultimately have an adverse impact on human health and survival. In particular, the problems of drug resistance and drug residues have attracted the attention of countries around the world. For example, the residues of antibiotic drugs in the aquaculture environment may induce the generation of drug-resistant bacteria, cause toxicity to non-target organisms, and pose a health threat to aquatic product consumers, etc.

[0003] For pharmaceutical pollutants in urban domestic sewage, in the prior art, the pharmaceutical pollutants are mainly removed by biodegradation after the activation sludge domestication in the sewage treatment process of urban domestic sewage treatment plants. Sodium acetate is usually used as the carbon source and electron donor during the treatment process. However, the concentration of pharmaceutical pollutants in urban domestic sewage is relatively low, usually at the μg / L and ng / L levels (the concentration of pharmaceutical pollutants in pharmaceutical factory wastewater is usually at the mg / L level). The above method has an unsatisfactory degradation effect on low-concentration pharmaceutical pollutants. Summary of the Invention

[0004] The purpose of the present invention is to provide a sewage treatment method for degrading low-concentration drugs and synchronously denitrifying. By using the method of the present invention, the high-efficiency degradation of low-concentration pharmaceutical pollutants can be achieved.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a sewage treatment method for degrading low-concentration drugs and synchronously denitrifying, comprising the following steps:

[0007] Inoculate sludge into an anaerobic tank provided with a biofilm carrier, and introduce the sewage to be treated to carry out biofilm formation treatment, iron autotrophic anaerobic denitrification domestication and degradation-denitrification treatment in sequence; wherein, no external organic carbon source is added during the iron autotrophic anaerobic denitrification domestication and degradation-denitrification treatment, and an iron source is added during the iron autotrophic anaerobic denitrification domestication and degradation-denitrification treatment; the sewage to be treated contains low-concentration pharmaceutical pollutants, and the concentration of each pharmaceutical pollutant in the sewage to be treated is independently ≤300 μg / L.

[0008] Preferably, the material of the biofilm carrier is polyurethane sponge, and the volume filling rate of the biofilm carrier in the anaerobic tank is 20-60%.

[0009] Preferably, the sludge is the return sludge from the secondary sedimentation tank. Before inoculation, the following steps are also included: subjecting the sludge to aeration with closed air supply and static sedimentation in sequence, and the aeration with closed air supply is carried out under aerobic conditions.

[0010] Preferably, the conditions for the biofilm formation treatment include: dissolved oxygen content ≤ 0.5 mg / L; pH value is 6.0 - 7.0; the volume ratio of the sewage to be treated to the sludge is 0.6 - 4:1; the water change period is 24 - 72 h; the time for the biofilm formation treatment is 3 - 14 days.

[0011] Preferably, the iron source includes divalent soluble iron salts and / or zero-valent iron.

[0012] Preferably, the divalent soluble iron salts include ferrous sulfate and / or ferrous chloride.

[0013] Preferably, the conditions for the iron autotrophic anaerobic denitrification domestication include: dissolved oxygen content ≤ 0.5 mg / L; pH value is 6.0 - 7.0; based on the volume of the sewage to be treated, the dosage of the iron source is 0.3 - 0.5 g / L; the influent reaction period is 18 - 30 h, and the water change ratio for each water change is 20 - 60%; the end indexes for the iron autotrophic anaerobic denitrification domestication include: nitrate removal rate in the effluent ≥ 90%, no nitrite accumulation, and iron source utilization rate ≥ 90%.

[0014] Preferably, the conditions for the degradation-denitrification treatment include: dissolved oxygen content ≤ 0.5 mg / L; pH value is 6.0 - 7.0; based on the volume of the sewage to be treated, the dosage of the iron source is 0.3 - 0.5 g / L; the influent reaction period is 18 - 30 h, and the water change ratio for each water change is 20 - 60%.

[0015] Preferably, the sewage to be treated is urban domestic sewage, and the pharmaceutical pollutants in the sewage to be treated include sulfonamide antibiotics and non-steroidal anti-inflammatory drugs; the concentration of each pharmaceutical pollutant in the sewage to be treated is independently 1.3 - 2.5 μg / L.

[0016] Preferably, the sulfonamide antibiotics include sulfamethoxazole, and the non-steroidal anti-inflammatory drugs include ketoprofen.

[0017] The present invention provides a sewage treatment method for degrading low-concentration drugs and synchronously denitrifying, comprising the following steps: inoculating sludge into an anaerobic tank provided with a biofilm carrier, introducing the sewage to be treated to perform film formation treatment, iron autotrophic anaerobic denitrification domestication, and degradation-denitrification treatment in sequence; wherein, no external organic carbon source is added during both the iron autotrophic anaerobic denitrification domestication and the degradation-denitrification treatment, and an iron source is added during both the iron autotrophic anaerobic denitrification domestication and the degradation-denitrification treatment; the sewage to be treated contains low-concentration drug pollutants, and the concentration of each drug pollutant in the sewage to be treated is independently ≤ 300 μg / L. By adopting iron autotrophic anaerobic denitrification domestication, the present invention can achieve efficient degradation of low-concentration drug pollutants.

[0018] In addition, for the treatment of sewage, the conventional water quality improvement function cannot be ignored. For example, it is usually necessary to remove carbon source pollutants and nitrogen source pollutants in the sewage. By adopting iron autotrophic anaerobic denitrification domestication, the present invention can achieve efficient removal of drug pollutants on the basis of maintaining a high removal rate of carbon source pollutants and nitrogen source pollutants, and the process has good stability.

[0019] Furthermore, for the degradation of drug pollutants, the activated sludge enhanced degradation process in the prior art is mostly developed for a certain type of specific drug, while the drug pollutants in sewage often include different types and properties of drugs. By adopting iron autotrophic anaerobic denitrification domestication, the present invention can achieve efficient degradation of different types of drug pollutants (such as sulfonamide antibiotics and non-steroidal anti-inflammatory drugs), and has a wide application range.

[0020] Furthermore, the organic carbon source content in some sewage (such as urban domestic sewage) is low, and the microbial electron donor supply is insufficient, resulting in incomplete removal of nitrogen during the denitrification and anaerobic phosphorus release processes. It is often necessary to add an external organic carbon source to achieve the treatment target. By adopting iron autotrophic anaerobic denitrification domestication, the present invention can achieve efficient degradation of drug pollutants and efficient removal of nitrogen source pollutants without adding an external organic carbon source. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of a suspended biofilm carrier reactor for experiments and a physical diagram of a polyurethane sponge biofilm carrier. Detailed Embodiments

[0022] The present invention provides a sewage treatment method for degrading low-concentration drugs and synchronously denitrifying, comprising the following steps:

[0023] The sludge is inoculated into an anaerobic tank equipped with a biofilm carrier, and the sewage to be treated is introduced to carry out film formation treatment, iron autotrophic anaerobic denitrification domestication, and degradation-denitrification treatment in sequence; wherein, no external organic carbon source is added during the iron autotrophic anaerobic denitrification domestication and degradation-denitrification treatment, and an iron source is added during both the iron autotrophic anaerobic denitrification domestication and degradation-denitrification treatment; the sewage to be treated contains low-concentration pharmaceutical pollutants, and the concentration of each pharmaceutical pollutant in the sewage to be treated is independently ≤ 300 μg / L.

[0024] Through the adoption of iron autotrophic anaerobic denitrification domestication, the present invention can achieve the efficient degradation of low-concentration pharmaceutical pollutants. The concentration of each pharmaceutical pollutant in the sewage to be treated applicable to the method of the present invention is independently ≤ 300 μg / L, preferably independently 1 - 200 μg / L, more preferably independently 2 - 100 μg / L, further preferably independently 3 - 50 μg / L, and even more preferably independently 4 - 20 μg / L. In the present invention, the sewage to be treated is preferably domestic sewage in urban areas; the pharmaceutical pollutants in the sewage to be treated preferably include sulfonamide antibiotics and non-steroidal anti-inflammatory drugs; the concentration of each pharmaceutical pollutant in the sewage to be treated is preferably independently 1.3 - 2.5 μg / L. In the present invention, the sulfonamide antibiotics preferably include sulfamethoxazole, and the non-steroidal anti-inflammatory drugs preferably include ketoprofen. Current research findings show that the risk coefficients of sulfonamide antibiotics and non-steroidal anti-inflammatory drugs in the effluent of sewage treatment plants are relatively large, which is comprehensively caused by the relatively high concentration in the influent and the low degradation efficiency. Therefore, in the present invention, the two types of drugs, sulfonamide antibiotics and non-steroidal anti-inflammatory drugs, with relatively high concentration and poor degradation performance are specifically selected for mixed degradation to verify the feasibility of the method of the present invention. In the present invention, other water quality indicators of the sewage to be treated include: the chemical oxygen demand is preferably 30 - 500 mg / L, more preferably 65 - 250 mg / L; the concentration of nitrogen sources (including nitrate and nitrite) is preferably 0 - 30 mgN / L, more preferably 18 - 20 mgN / L; the carbon-nitrogen ratio is preferably 1 - 50:1, more preferably 1 - 20:1, and further preferably 5 - 10:1; the pH value is preferably 5 - 7, more preferably 6 - 7. The method of the present invention will be described in detail below.

[0025] In the present invention, unless otherwise specified, the raw materials used are commercially available products well-known to those skilled in the art, and the equipment used is equipment well-known to those skilled in the art. In the present invention, unless otherwise specified, the conditions of the sewage treatment method include: the temperature is preferably 22 - 26 °C, and the air pressure is preferably 1008 Pa; an anaerobic environment is maintained, and the anaerobic environment means that the dissolved oxygen content in the influent is ≤ 0.5 mg / L and no aeration is carried out during the treatment process.

[0026] In the present invention, sludge is inoculated into an anaerobic tank provided with a biofilm carrier, and the sewage to be treated is introduced for biofilm formation treatment. In the present invention, the material of the biofilm carrier is preferably polyurethane sponge. As a biofilm carrier, polyurethane sponge has the advantages of large specific surface area, low density, good suspension, good stability, resistance to biodegradation and aging, and high mechanical strength. The volume filling rate of the biofilm carrier in the anaerobic tank is preferably 20-60%, more preferably 30-50%, and further preferably 40%. In the embodiments of the present invention, a suspended biofilm carrier reactor is specifically used to verify the feasibility of the method of the present invention. Figure 1 FIG. Figure 1 is a schematic diagram of the suspended biofilm carrier reactor used in the embodiments of the present invention and a physical diagram of the polyurethane sponge biofilm carrier. Specifically, a capped serum bottle is selected as the experimental reactor (to simulate the anaerobic tank). The bottle body is made of high borosilicate glass, and the four-hole joint is made of 316L stainless steel. The inner diameter of the bottle body is 100 mm, the maximum height is 218 mm, the working volume is 1000 mL, and 250 pieces of polyurethane sponge with a side length of 10 mm are loaded into each reactor as the biofilm carrier (that is, the volume filling rate of the biofilm carrier in each reactor is 40%). The four-hole joint of the reactor serves as the water inlet, water outlet, gas balance and collection port respectively, and the water outlet is connected to a countersunk head and immersed in the bottom of the reactor. A peristaltic pump is used to control the inflow and outflow of water, and an electrical device uses a Bull timer socket (GND-1) to control the running time to achieve automatic operation of power on and off. Each reactor is placed on a magnetic stirrer, and the magnetic stirrer is used to simulate the push flow device of the anaerobic tank to ensure the circulation of the liquid in the reactor.

[0027] In the present invention, the sludge is preferably the return sludge from the secondary sedimentation tank. Before inoculation, it preferably further includes: subjecting the sludge to aeration and static sedimentation in sequence, and the aeration is carried out under aerobic conditions. In the embodiments of the present invention, the return sludge from the secondary sedimentation tank is specifically the return sludge from the secondary sedimentation tank of Shenzhen Buji Water Quality Purification Plant. In the present invention, the time of the aeration is preferably 1-3 days, more preferably 2 days; the aeration is preferably carried out under aerobic conditions, and the aerobic conditions specifically refer to a dissolved oxygen content greater than 2.0 mg / L. In the present invention, between the aeration and the static sedimentation, it preferably further includes cultivation. The time of the cultivation is preferably 7-14 days, more preferably 10 days. The cultivation is preferably carried out under aerobic conditions, and after cultivation, the ammonia nitrogen content of the sludge is preferably less than 2 mg / L; the time of the static sedimentation is preferably 1-24 h, more preferably 20-24 h. After the static sedimentation, the present invention preferably removes the supernatant, and the precipitate is collected and sieved (the mesh number of the sieve is preferably 35 meshes) and then inoculated into the anaerobic tank, and the sewage to be treated is introduced for biofilm formation treatment.

[0028] In the present invention, the conditions for the biofilm formation treatment include: the dissolved oxygen content is preferably ≤ 0.5 mg / L; the pH value is preferably 6.0 - 7.0, more preferably 6.4 - 7.0; the volume ratio of the sewage to be treated to the sludge is preferably 0.6 - 4:1, more preferably 1 - 3:1, and further preferably 1.5:1; the MLSS value of the sludge is preferably 2000 - 30000 mg / L, more preferably 20000 - 25000 mg / L, and further preferably 23080 mg / L; the water change period is preferably 24 - 72 h, more preferably 48 h; the time for the biofilm formation treatment is preferably 3 - 14 days, more preferably 10 - 14 days. The present invention preferably determines whether to externally add an organic carbon source according to the time of the biofilm formation treatment. Specifically, when the time of the biofilm formation treatment is short, no organic carbon source is externally added, and when the time of the biofilm formation treatment is long, an organic carbon source is externally added. The organic carbon source is preferably sodium acetate, and the addition amount of the sodium acetate can be determined according to the time of the biofilm formation treatment by routine selection in the art. In the present invention, the biofilm formation treatment is preferably carried out under stirring conditions, and the rotation speed of the stirring is preferably 400 - 500 r / min, more preferably 450 r / min. Specifically, in the present invention, the sludge is circulated inside the anaerobic tank for the biofilm formation treatment, and a relatively stable biofilm is obtained on the surface of the biofilm carrier in the anaerobic tank. In the embodiments of the present invention, specifically, a culture medium is prepared to simulate the sewage to be treated, and in order to facilitate the accurate measurement of the drug removal rate, the culture medium used for the biofilm formation treatment does not contain drugs (when actually treating the sewage to be treated containing low-concentration drug pollutants, the presence of the low-concentration drug pollutants basically has no adverse effect on the effect of the biofilm formation treatment and the subsequent iron autotrophic anaerobic denitrification domestication); specifically, the components of the culture medium preferably include 320 mg / L of sodium acetate, 150 mg / L of KNO 3 150 mg / L, 200 mg / L of NaHCO 3 200 mg / L of CaCl 2 ·2H 2 O, 100 mg / L of MgCl 2 ·6H 2 O, 5 mg / L of KH 2 PO 4 5 mg / L, and 1 mL / L of trace element solution (that is, 1 L of the culture medium contains 1 mL of the trace element solution); the components of the trace element solution preferably include: 0.43 g / L of ZnSO 4 ·7H 2 O, 0.24 g / L of CoCl 2 ·6H 2 O, 1.00 g / L of MnCl 2 ·4H 2 O, 0.25 g / L of CuSO 4 ·5H 2 O, 0.25 g / L of NaMoO 4·2H 2 O 0.22 g / L, NiCl 2 ·6H 2 O 0.19 g / L, H 3 BO 4 0.014 g / L, NaSeO 4 ·10H 2 O 0.21 g / L and EDTA 6.25 g / L. Wherein the sodium acetate is used as an organic carbon source to simulate the organic carbon source present in the wastewater to be treated and meet the requirements of biofilm formation treatment; the KNO 3 is used to simulate the nitrogen source in the wastewater to be treated (the nitrogen source available for the denitrification process is nitrate nitrogen); the NaHCO 3 is used to control the pH value of the culture medium to 6.0 - 7.0; CaCl 2 ·2H 2 O, MgCl 2 ·6H 2 O, KH 2 PO 4 and the trace element stock solution are used to provide the elements required during the growth of microorganisms.

[0029] After the biofilm formation treatment, the present invention adjusts the influent conditions for iron autotrophic denitrification acclimation (i.e., acclimating a specific autotrophic denitrifying community), and an iron autotrophic denitrifying biofilm is obtained on the surface of the biofilm carrier. In the present invention, no external carbon source is added during the iron autotrophic anaerobic denitrification acclimation, and an iron source is added; the iron source preferably includes divalent soluble iron salts and / or zero-valent iron, more preferably divalent soluble iron salts; the divalent soluble iron salts preferably include ferrous sulfate and / or ferrous chloride, and specifically may be FeSO 4 ·7H 2 O, FeCl 2 ·4H 2 O, FeSO 4 and FeCl 2 one or more of them. The iron autotrophic denitrification nitrogen removal process includes zero-valent iron autotrophic denitrification, nitrate-type anaerobic ferrous oxidation, and nitrite-type anaerobic ferrous oxidation, which is a biochemical process that uses iron as an electron donor to reduce nitrate (NO 3 - ) and nitrite (NO 2 - ) into nitrogen gas (N 2 ). Compared with the heterotrophic process, iron autotrophic denitrification is more direct and efficient in providing an electron donor. By regulating the iron source concentration, the growth conditions of microorganisms can be optimized, and the denitrification rate and nitrogen removal efficiency can be improved. During the iron autotrophic denitrification nitrogen removal process, reduced iron compounds, such as zero-valent iron and ferrous ions (Fe 2+) etc. provide electrons, which promotes the growth and metabolism of denitrifying bacteria. The present invention preferably uses divalent soluble iron salts as the iron source, which is easily soluble in water and thus easily utilized by microorganisms, facilitating the guarantee of good treatment effects.

[0030] In the present invention, the conditions for iron autotrophic anaerobic denitrification domestication include: the dissolved oxygen content is preferably ≤0.5 mg / L; the pH value is preferably 6.0 - 7.0, more preferably 6.4 - 7.0 (under lower pH value conditions, the solubility of the iron source is higher and it is easily utilized by microorganisms, but if the pH value is too low, it is not conducive to the growth of iron autotrophic denitrifying bacteria, and if the pH value is too high, it will cause precipitation of the iron source); based on the volume of the sewage to be treated, the dosage of the iron source is preferably 0.3 - 0.5 g / L, more preferably 0.4 - 0.5 g / L (if the dosage of the iron source is too much, it will be toxic to microorganisms); the influent reaction cycle is preferably 12 - 30 h, more preferably 24 h (specifically including 15 min of influent, 23.5 h of reaction, and 15 min of effluent); the water change ratio for each water change is preferably 20 - 60%, more preferably 30 - 50%, and further preferably 40%. The water change ratio in the present invention specifically refers to the proportion of the effluent volume at the end of each reaction cycle to the working volume of the reactor. In the examples of the present invention, the specific water change volume is 400 mL. In the present invention, the iron autotrophic anaerobic denitrification domestication is preferably carried out under stirring conditions, and the rotation speed of the stirring is preferably 400 - 500 r / min, more preferably 450 r / min. In the examples of the present invention, taking the iron source as FeSO 4 ·7H 2 O as an example, specifically, a culture medium is prepared to simulate the sewage to be treated. The difference between the culture medium used for iron autotrophic anaerobic denitrification domestication and the culture medium used for biofilm formation treatment is that "sodium acetate 320 mg / L" is replaced with "FeSO 4 ·7H 2 O 0.5 g / L". In the present invention, the end indicators for iron autotrophic anaerobic denitrification domestication preferably include: the nitrate removal rate of the effluent ≥90%, no nitrite accumulation, and the iron source utilization rate ≥90%; the so-called no nitrite accumulation in the present invention means that the concentration of nitrite ions in the effluent is less than 0.02 mgN / L.

[0031] In the present invention, at the end of the iron autotrophic anaerobic denitrification domestication, an iron autotrophic denitrification biofilm is obtained on the surface of the biofilm carrier in the anaerobic tank. Then, the sewage to be treated is introduced into the anaerobic tank for degradation-denitrification treatment. In the present invention, no external carbon source is added during the degradation-denitrification treatment, and an iron source is added. The optional types of the iron source are preferably the same as those used during the iron autotrophic anaerobic denitrification domestication, which will not be elaborated herein. In the present invention, the degradation-denitrification treatment is preferably carried out under stirring conditions, and the rotation speed of the stirring is preferably 180-250 r / min, more preferably 230 r / min. In the present invention, the dosage of the iron source and other operating conditions during the degradation-denitrification treatment are preferably the same as those of the iron source and other operating conditions during the iron autotrophic anaerobic denitrification domestication, which will not be elaborated herein. In the examples of the present invention, specifically, a culture medium is prepared to simulate the sewage to be treated. The difference between the culture medium used for the degradation-denitrification treatment and the culture medium used for the iron autotrophic anaerobic denitrification domestication is that sulfamethoxazole (2441.80 ng / L) and ketoprofen (1300.01 ng / L) are added.

[0032] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the examples in the present invention. Obviously, the described examples are only a part of the examples of the present invention, rather than all the examples. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] The following experiments used Figure 1 the suspended biofilm carrier reactor shown. The names, models and manufacturers of other main instrument equipment used during the experiment are shown in Table 1.

[0034] Table 1 Main instruments used in the experiment

[0035] Equipment Name Instrument Model Manufacturer Muffle Furnace SX-G07122 Tianjin Zhonghuan Electric Furnace Co., Ltd. Centrifuge DT5-1 Beijing Shida Beili Centrifuge Co., Ltd. Peristaltic Pump LHZW005 United Zhongwei Technology Co., Ltd. Electronic Balance ML503 / 02 METTLER TOLEDO Instruments (Shanghai) Co., Ltd. Magnetic Stirrer 84-1A Shanghai Sile Instruments Co., Ltd. Hot Air Blower Drying Oven — Shanghai Yiheng Scientific Instruments Co., Ltd. Vertical Constant Temperature Oscillator IS-RSV1 Shanghai Huyue Ming Scientific Instruments Co., Ltd. Vortex Mixer NMSG-12 Taizhou Nuomi Medical Technology Co., Ltd. UV-Vis Spectrophotometer DR6000 HACH Company, USA Ion Chromatograph IC Thermo Fisher Scientific Co., Ltd.

[0036] During the following experimental process, water samples from the inlet and outlet of the reactor were collected. After filtration through a 0.45 μm aqueous filter membrane, relevant water quality indicators were immediately measured (the relevant detection methods are shown in Table 2), or stored in a -20 °C refrigerator for future measurement. The main measurement indicators and measurement methods refer to "Methods for Monitoring and Analysis of Water and Wastewater" (Fourth Edition) and the National Standard Information Public Service Platform (https: / / std.samr.gov.cn / ); the sample storage method refers to the national environmental protection standard "Technical Regulations for the Preservation and Management of Water Quality Sampling Samples" (HJ493-2009); among them, the detection method for sulfamethoxazole refers to the group standard (T / GDSES2-2022) issued by the Guangdong Provincial Society for Environmental Sciences. The sampling method and pretreatment method for ketoprofen are the same as those in the above standard, and the instrument detection method is as follows:

[0037] Run in negative mode, using ibuprofen-d3 as the internal standard; Mass spectrometry parameters: the parent ion m / z of ketoprofen is 253.1, the daughter ion m / z is 209.1, the fragmentation voltage is 70V, and the collision energy is 1V; the parent ion m / z of ibuprofen-d3 is 208.1, the daughter ion m / z is 164.1, the fragmentation voltage is 70V, and the collision energy is 0V; the chromatographic column used is ZORBAX SBC18 column (RRHD2.1×100mm, 1.8μm, Agilent), mobile phase A is ultrapure water, and mobile phase B is acetonitrile; Gradient elution program: 0 - 1 min, the volume fraction of mobile phase B is 20%, 1 - 10 min; the volume fraction of mobile phase B is linearly increased from 20% to 90%; 10 - 13 min, the volume fraction of mobile phase B remains 90%; 13 - 13.1 min, the volume fraction of mobile phase B is decreased from 90% to 20%; The detection limit and quantification limit are 0.38 ng / L and 1.13 ng / L respectively; the standard curve range is 1 - 2000 μg / L, and the standard curve R 2 is greater than 0.999; when the spiked concentrations are 5 ng / L and 50 ng / L, the matrix spiked recovery rates are 67.66 ± 10.47% and 76.66 ± 10.74% respectively.

[0038] Table 2 Detection methods for water quality indicators

[0039]

[0040] Unless otherwise specified, the temperature is 22 - 26 °C and the air pressure is 1008 Pa during the following experimental process; maintain an anaerobic environment, and the anaerobic environment means that the dissolved oxygen content in the influent is ≤ 0.5 mg / L and no aeration is carried out during the treatment process.

[0041] Example 1

[0042] The return sludge from the secondary sedimentation tank (collected from Buji Water Quality Purification Plant in Shenzhen) was aerated statically for 2 days under aerobic conditions (dissolved oxygen content greater than 2.0 mg / L), and then cultured for 10 days under aerobic conditions. At this time, the ammonia nitrogen content in the sludge was lower than 2 mg / L. Then, it was allowed to stand and settle for 24 h, the supernatant was poured out, the precipitate was sieved (the sieve mesh size was 35 mesh), and the obtained activated sludge was inoculated into the suspended biofilm carrier reactor; Prepare a culture medium, and the components of the culture medium include 320 mg / L of sodium acetate, KNO 3 150 mg / L, NaHCO 3 200 mg / L, CaCl 2 ·2H 2 O 100 mg / L, MgCl 2 ·6H 2 O 100 mg / L, KH 2 PO4 5 mg / L and 1 mL / L of trace element solution (i.e., 1 L of the culture medium contains 1 mL of trace element solution). The composition and content of the trace element solution are shown in Table 3;

[0043] Table 3 Composition and content of the trace element solution

[0044]

[0045]

[0046] Add the culture medium to the reactor inoculated with the activated sludge. The inoculation amount of the activated sludge in each reactor is 400 mL (the MLSS value of the activated sludge is 23080 mg / L), and the addition amount of the culture medium is 600 mL. Before adding the culture medium to the reactor, it is aerated with high-purity nitrogen in advance to remove excessive dissolved oxygen (DO) to ensure an anoxic environment in the reactor (DO < 0.5 mg / L). Turn on the magnetic stirrer and keep its rotation speed at 450 r / min. The activated sludge is circulated inside the reactor for biofilm formation treatment. During the biofilm formation treatment, the water change cycle is 48 h. After 14 days, a relatively stable biofilm attachment state is observed, and the biofilm formation treatment ends; then, the influent conditions are adjusted to domesticate a specific autotrophic denitrification community. Specifically, simulated municipal sewage is introduced into the reactor (basically the same as the formula of the culture medium, the only difference is that "320 mg / L of sodium acetate" is replaced by "FeSO 4 ·7H 2 O 0.5 g / L", that is, 1 L of the simulated municipal sewage contains 0.5 g of the iron source FeSO 4 ·7H 2 O, replacing sodium acetate as the electron donor) for iron autotrophic anaerobic denitrification domestication. Each influent reaction cycle is 24 h (each influent reaction cycle is defined as 1T), including 15 min of influent, 23.5 h of reaction, and 15 min of effluent. The amount of water changed each time is 400 mL, and the water change ratio is 40%; domesticate according to the above conditions. When the nitrate removal rate of the effluent is greater than 90%, there is no nitrite accumulation (the concentration of nitrite ions in the effluent is less than 0.02 mgN / L), and the electron donor utilization rate reaches 90%, the domestication ends, and the iron autotrophic denitrification biofilm system in each reactor is constructed;

[0047] Adjust the rotation speed of the magnetic stirrer to 230 r / min, and introduce simulated municipal sewage containing the mixed drugs (i.e., add the mixed drugs to the simulated municipal sewage used for iron autotrophic anaerobic denitrification domestication) into the reactor for the degradation - denitrification treatment of the mixed drugs. The mixed drugs are sulfamethoxazole and ketoprofen; each influent reaction cycle is 24 h (each influent reaction cycle is defined as 1T), including 15 min of influent, 23.5 h of reaction, and 15 min of effluent. The amount of water changed each time is 400 mL, and the water change ratio is 40%; the reactor operates continuously for 20 days, and the effluent is collected every two days for the measurement of the substance concentration to evaluate the performance of the reactor for the long - term stable degradation of the mixed drugs and denitrification. The influent indexes, effluent indexes (specifically, the average value of the effluent indexes at different times), and the related removal rates of the iron autotrophic denitrification biofilm reactor are shown in Table 4. The concentration of sulfamethoxazole detected in the influent is 2441.80 ng / L, and the concentration of ketoprofen is 1300.01 ng / L; the results of the drug effluent concentration and removal rate at different times are shown in Table 5. The results show that the iron autotrophic activated sludge domesticated in Example 1 can efficiently degrade the mixed drugs in the wastewater with a low carbon - nitrogen ratio (carbon - nitrogen ratio is 5:1) and synchronously denitrify.

[0048] Table 4 Substance concentrations and average removal rates in the influent and effluent of the iron autotrophic denitrification biofilm reactor in Example 1

[0049]

[0050]

[0051] Table 5 Results of the continuous operation of the iron autotrophic denitrification biofilm reactor in Example 1 for the degradation of the mixed drugs

[0052]

[0053] Comparative Example 1

[0054] Operate according to the method of Example 1, with the difference that after the film - hanging treatment in this comparative example, 0.320 g of sodium acetate is added to every 1 L of simulated municipal sewage to replace 0.5 g of FeSO 4 ·7H 2 O as the electron donor for the heterotrophic denitrification domestication of sodium acetate; and when performing the degradation - denitrification treatment of the mixed drugs, 0.320 g of sodium acetate is added to every 1 L of simulated municipal sewage to replace 0.5 g of FeSO 4 ·7H 2O serves as the electron donor. The reactor operates continuously for 20 days, and the effluent is collected every two days for substance concentration testing to evaluate the performance of the reactor in stably degrading mixed drugs and denitrifying over a long period. The influent indexes, effluent indexes (specifically, the average effluent indexes at different times), and related removal rates of the denitrification reactor simulating a municipal sewage treatment plant are shown in Table 6; the effluent drug concentrations and removal rate results at different times are shown in Table 7. The results show that the effect of the denitrification reactor simulating a municipal sewage treatment plant in degrading mixed drugs in Comparative Example 1 is average.

[0055] Table 6 Substance Concentrations and Removal Rates in the Influent and Effluent of the Denitrification Reactor Simulating a Municipal Sewage Treatment Plant in Comparative Example 1

[0056] Substance Name Inlet Concentration Average Outlet Concentration Average Removal Rate Nitrate 18.85mgN / L 0.03mgN / L 99.84％ Nitrite 0.00mgN / L 0.00mgN / L / Chemical Oxygen Demand 250mgO / L 8.5mgO / L 96.6％ pH Value 7.00 7.33 /

[0057] Table 7 Results of the Denitrification Reactor Simulating a Municipal Sewage Treatment Plant in Comparative Example 1 in Continuously Operating and Degrading Mixed Drugs

[0058]

[0059] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A wastewater treatment method for degrading low-concentration drugs and simultaneously removing nitrogen, comprising the following steps: Inoculating the sludge into an anaerobic tank provided with a biofilm carrier, wherein the volume filling rate of the biofilm carrier in the anaerobic tank is 40-60%; Access The wastewater to be treated is subjected to biofilm treatment, iron autotrophic anaerobic denitrification acclimation and degradation-denitrification treatment in sequence; wherein no organic carbon source is added to the iron autotrophic anaerobic denitrification acclimation and degradation-denitrification treatment, and an iron source is added to the iron autotrophic anaerobic denitrification acclimation and degradation-denitrification treatment, and the iron source includes a divalent soluble iron salt; The sewage to be treated is urban domestic sewage, the pharmaceutical pollutants in the sewage to be treated include sulfonamide antibiotics and non-steroidal anti-inflammatory drugs, the sulfonamide antibiotic is sulfamethoxazole, the non-steroidal anti-inflammatory drug is ketoprofen, and the concentration of each pharmaceutical pollutant in the sewage to be treated is independently 1.3-2.5 μg / L; the chemical oxygen demand in the sewage to be treated is 65-250 mg / L; the concentration of the nitrogen source is 18-20 mgN / L, and the nitrogen source includes nitrate and nitrite; The biofilm treatment conditions include: dissolved oxygen content ≤ 0.5 mg / L; pH value 6.0-7.0; volume ratio of sewage to be treated to sludge 0.6-4:1; water exchange cycle 24-72 hours; biofilm treatment time 3-14 days; The conditions for the iron autotrophic anaerobic denitrification acclimation include: based on the volume of the sewage to be treated, the amount of the iron source is 0.3-0.5 g / L; the dissolved oxygen content is ≤0.5 mg / L; the pH value is 6.0-7.0; the water inlet reaction cycle is 18-30 hours, and the water change ratio of each water change is 20-60%; The end indicators of the iron autotrophic anaerobic denitrification acclimation include: effluent nitrate removal rate ≥ 90%, no nitrite accumulation and iron source utilization rate ≥ 90%; The conditions for the degradation-denitrification treatment include: based on the volume of the sewage to be treated, the amount of the iron source is 0.3-0.5 g / L; the dissolved oxygen content is ≤0.5 mg / L; the pH value is 6.0-7.0; the water inlet reaction cycle is 18-30 hours, and the water change ratio of each water change is 20-60%.

2. The sewage treatment method according to claim 1, characterized in that: The sludge is the return sludge from the secondary sedimentation tank, and before the inoculation, the method further includes: subjecting the sludge to aeration and static sedimentation in sequence, wherein the aeration is performed under aerobic conditions.

3. The sewage treatment method according to claim 1, characterized in that: The divalent soluble iron salt includes ferrous sulfate and / or ferrous chloride.

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