CN115072933B - Method and system for simultaneously removing brominated pollutants and nitrate in sewage - Google Patents
Method and system for simultaneously removing brominated pollutants and nitrate in sewage Download PDFInfo
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- CN115072933B CN115072933B CN202210691919.4A CN202210691919A CN115072933B CN 115072933 B CN115072933 B CN 115072933B CN 202210691919 A CN202210691919 A CN 202210691919A CN 115072933 B CN115072933 B CN 115072933B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/70—Treatment of water, waste water, or sewage by reduction
- C02F1/705—Reduction by metals
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/34—Biological treatment of water, waste water, or sewage characterised by the microorganisms used
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
- C02F2101/163—Nitrates
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/36—Organic compounds containing halogen
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Abstract
The invention provides a method and a system for simultaneously removing brominated pollutants and nitrate in sewage. The system comprises a reactor main body, a plurality of membrane components and a hydrogen supply unit; the hydrogen supply unit is communicated with the membrane component. The removing method comprises the following steps: 1) Introducing sewage and sludge containing nitrate into a reactor main body, and performing film formation under the condition of hydrogen supply pressure; 2) After the membrane is hung, palladium acid salt is introduced into the reactor main body, and palladium is loaded on the surface of the membrane component under the conditions of hydrogen supply pressure and microbial reduction; 3) The sewage containing brominated pollutants and nitrate is introduced into the reactor main body, and the brominated pollutants are completely mineralized under the conditions of palladium catalysis, microbial reduction and hydrogen supply pressure, and the nitrate is converted into nitrogen. The invention can synergistically promote the degradation efficiency of brominated pollutants and nitrate, the removal efficiency is more than or equal to 99%, the complete mineralization of the pollutants is realized, and meanwhile, the automation degree is high, and the hydrogen utilization rate is more than or equal to 99%.
Description
Technical Field
The invention relates to the technical field of environmental protection, in particular to a method and a system for simultaneously removing brominated pollutants and nitrate in sewage.
Background
In recent years, new pollutants such as brominated pollutants are also widely applied to industrial production and consumer products, so that the brominated pollutants are inevitably released into water environment, and the content of sewage is gradually from ng to ug even mg/L. Because of the highly toxic and low biodegradable nature of these brominated contaminants, conventional wastewater treatment processes cannot completely remove them. These brominated contaminants can be potentially harmful to the human body through biological amplification and the transmission of the food chain. Therefore, ensuring the effective removal of brominated pollutants and nitrate in sewage is a key for ensuring the safety of water environment and the health of human bodies.
At present, hydrodebromination is considered as a very promising method for treating brominated pollutants due to mild reaction conditions and no secondary pollution. Among them, palladium is often used in hydrodebromination because of its strong ability to adsorb and dissociate hydrogen. However, because the gas mass transfer is limited, hydrogen is required to be continuously introduced in the current hydrogenation debromination reaction process, so that accurate hydrogen supply cannot be realized, and serious potential safety hazards are brought. While membrane supported palladium-based reactors may address these disadvantages: palladium is loaded on the surface of the hollow fiber membrane, and hydrogen is spontaneously transferred to the palladium on the surface of the membrane from the inside of the membrane under the action of pressure to carry out hydrogenation debromination reaction. Although hydrodebromination can effectively reduce and debrominate brominated contaminants, it is difficult to carry out ring-opening degradation on benzene rings in degradation products, and thus potential risks to the environment may still be brought. For example, tetrabromobisphenol a is still a persistent organic contaminant of the product bisphenol a after hydrodebromination, requiring further processing. Microorganisms are reported to be capable of effectively carrying out ring-opening degradation on benzene rings, so that complete mineralization of organic pollutants is realized. In addition, palladium has been reported to reduce nitrite to nitrogen, but is unable to catalyze the reduction of nitrate to nitrite. However, nitrate can be reduced to nitrite by microorganisms, thereby providing sufficient nitrite for palladium-catalyzed reduction denitrification. Thus, by coupling hydrodebromination with a membrane bioreactor, complete degradation of brominated organic contaminants and nitrates is possible. However, the coupling process has not been reported at all, and there are a number of uncertain factors in the operation and control of the system, so that the problem of co-existence of denitrifying microorganisms and brominated pollutant degrading microorganisms is needed to be solved. Meanwhile, the intermediate product after debromination may have a certain ecological toxicity, and whether the intermediate product can have adverse effects on microorganisms or not is unknown, so that the degradation efficiency of subsequent pollutants is influenced. In addition, the chemical catalytic reduction rate of palladium is far faster than the degradation rate of microorganisms, and how to realize the rate matching of the two so as to achieve synchronous and efficient degradation of brominated organic pollutants and nitrate is still to be further researched. In addition, in the membrane bioreactor, the thickness of the biological membrane is closely related to the content of hydrogen, but a thicker biological membrane not only reduces the mass transfer efficiency of hydrogen, but also inhibits the activity of microorganisms, so that the degradation effect of the microorganisms on pollutants is reduced, and therefore, how to dynamically control the thickness of the membrane in a coupling system is still a difficult problem to be solved.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method and a system for simultaneously removing brominated pollutants and nitrate in sewage. In this system, brominated organic contaminants are first converted to debrominated intermediates by palladium catalysis, followed by microbial degradation to water and carbon dioxide; the nitrate is firstly reduced into nitrite by microorganisms, and then reduced into nitrogen by palladium catalysis, so that the complete mineralization of brominated organic pollutants is finally realized. Meanwhile, the debrominated product can be used as an electron donor, so that the reduction efficiency of the microorganism on nitrate is further enhanced. In addition, the invention can realize reasonable matching of palladium catalytic rate and microbial degradation rate by regulating and controlling hydrogen pressure and the membrane aeration backwashing system, can dynamically regulate the thickness of the biological membrane, ensures microbial activity and hydrogen mass transfer efficiency, and finally realizes efficient degradation of pollutants. The invention can remove brominated pollutants and nitrate in sewage simultaneously, the removal efficiency is more than or equal to 99%, the complete mineralization of pollutants is realized, and the invention has the advantages of more than or equal to 99% of hydrogen utilization rate, simple and convenient operation, high automation degree and the like.
The technical scheme of the invention is as follows:
the invention firstly provides a system for simultaneously removing brominated pollutants and nitrate in sewage, which comprises:
the system comprises a reactor body, a plurality of membrane assemblies and a hydrogen gas supply unit, wherein the membrane assemblies are arranged in the reactor body, and the hydrogen gas supply unit is communicated with the membrane assemblies, and the membrane assemblies are non-porous hollow fiber membranes;
the system further comprises a contaminant detection unit for detecting a contaminant concentration;
the system also comprises a back flushing aeration head which is positioned at the bottom of the reactor body and is communicated with an aeration system positioned outside the reactor body.
Preferably, the reactor body is also provided with an internal reflux device, and the effluent water of the rear section flows back to the front section through an internal reflux pump.
Preferably, the system further comprises a control unit for controlling the backwash aeration head and the internal reflux device, and controlling the hydrogen supply unit by data of the contaminant detection unit, thereby dynamically adjusting the hydrogen pressure.
Preferably, palladium acid salt solution is introduced into the hollow fiber membrane, and palladium is loaded on the surface of the membrane component under the conditions of hydrogen gas supply pressure and microbial reduction.
The invention also provides a method for simultaneously removing brominated pollutants and nitrate in sewage, which is carried out on the system, and comprises the following steps of:
s1: introducing sewage and sludge containing nitrate into a reactor body, and performing microbial film formation under the condition of hydrogen supply pressure;
s2: after the film is hung, the palladium acid salt solution is led into the reactor body, and palladium is loaded on the surface of the film component under the conditions of hydrogen supply pressure and microbial reduction;
s3: introducing sewage containing brominated pollutants and nitrate into a reactor body, mineralizing brominated organic pollutants into carbon dioxide and water under the conditions of palladium hydrogenation catalysis and microbial reduction, and simultaneously converting nitrate into nitrogen;
s4: detecting the concentration of brominated pollutants and nitrate in the reactor body in real time through a control unit and a pollutant detection unit, dynamically regulating the hydrogen pressure by utilizing a hydrogen control valve, and simultaneously controlling the growth rate of a biological film;
s5: compressed gas is introduced into a back flush aeration head through an aeration system, and aeration flushing is carried out on the membrane surface regularly to control the thickness of the biological membrane.
Preferably, in the step S4, when the concentration of the brominated pollutants and the nitrate in the effluent is respectively lower than 1mmol/L and 0.1mol/L, the regulation and control are not performed; when the bromine pollutant in the effluent is 1-10 mmol/L or the nitrate concentration is 0.1-0.5 mol/L, the hydrogen supply pressure is increased by 0.5-2 psi; when the concentration of the brominated pollutant in the effluent is more than 10mmol/L or the concentration of the nitrate is more than 0.5mol/L, the pressure of the hydrogen supply is increased by 2.5 to 4psi.
Preferably, in step S5, when the film thickness of the biofilm exceeds 3cm, scouring is performed.
Preferably, the method specifically comprises the following steps:
s1: introducing sewage containing nitrate and 6-10 g/L sludge into a reactor body, and forming a film under the condition of hydrogen supply pressure; the hydrogen pressure is 2-6 psi, the film forming time is 8-16 d, and the pH is controlled to be 6-8;
s2: after the film is formed, palladium salt solution with the concentration of 0.5-1.5 mM is led into the reactor body, and palladium is loaded on the surface of the film component under the conditions of hydrogen gas supply pressure and microbial reduction; the hydrogen pressure is 2-6 psi, the loading time is 12-36 h, and the pH is controlled to be 6-8;
s3: introducing sewage containing brominated pollutants and nitrate into a reactor body, completely mineralizing brominated organic pollutants into carbon dioxide and water under the conditions of palladium hydrogenation catalysis and microbial reduction, and simultaneously converting nitrate into nitrogen; the hydrogen supply mode is an intermittent mode, the hydrogen supply/stop time is 0-4 h (not 0), the hydraulic retention time is 4-12 h, and the pH of the inlet water is 6-8;
s4: detecting the concentration of brominated pollutants and nitrate in the reactor body in real time through a control unit and a pollutant detection unit, dynamically regulating the hydrogen pressure by utilizing a hydrogen control valve, and simultaneously controlling the growth rate of a biological film;
s5: compressed gas is introduced into a back flush aeration head through an aeration system, aeration flushing is carried out on the surface of the membrane regularly to control the thickness of the biological membrane, and the microbial activity and the hydrogen mass transfer efficiency are ensured; the aeration scouring strength is 40-60L/(s.m) 2 ) The scouring time is 10-20 min.
Preferably, in step S1, the sludge is secondary sedimentation tank excess sludge from a sewage treatment plant.
Preferably, in the step S1, the sludge TS is 10-15 g/L, and the VS is 6-8 g/L.
Preferably, in step S1, the membrane module is a polyethylene non-porous hollow fiber membrane; a polypropylene non-porous hollow fiber membrane; or other non-porous hollow fiber membranes.
Preferably, in the step S1, the concentration of the sewage containing nitrate is 0.1-10 mol/L.
Preferably, in step S1, the hydrogen pressure is controlled to 4psi, the membrane formation time is controlled to 12d, and the pH is controlled to 7.
Preferably, in step S2, the palladium acid salt is one or more of palladium chloride, palladium sulfate or sodium tetrachloropalladate.
Preferably, in step S2, the palladium salt concentration is controlled to be 1mM; the hydrogen pressure was 4psi, the loading time was 24h, and the pH was controlled at 7.
Preferably, in the step S3, the concentration of the sewage containing the brominated organic pollutants is 1-100 mmol/L.
Preferably, in step S3, the brominated organic contaminants include brominated contaminants such as polybrominated diphenyl ether, tetrabromobisphenol a, hexabromocyclododecane and decabromodiphenylethane.
Preferably, in step S3, the concentration of the nitrate is 0.1-10 mol/L.
Preferably, in step S3, the hydrogen supply/stop time is controlled to be 2 hours, the hydraulic retention time is controlled to be 8 hours, and the pH of the inlet water is controlled to be 7.
Preferably, in step S4, the hydrogen pressure is dynamically adjusted by using the feedback condition, so that the palladium catalytic reduction rate and the microbial degradation rate are matched, the degradation efficiency of the pollutants is ensured, and the biofilm growth rate is controlled.
Preferably, in step S5, the aeration flushing strength is controlled to be 50L/(s.m) 2 ) The flushing time is 15min.
The invention also provides application of the reaction system in sewage treatment.
The beneficial technical effects of the invention are as follows:
(1) In the system of the present invention, brominated organic contaminants are first converted to debrominated intermediates by palladium catalysis, followed by microbial degradation to water and carbon dioxide; the nitrate is firstly reduced into nitrite by microorganisms, then is reduced into nitrogen by palladium catalysis, and finally realizes complete mineralization of brominated organic pollutants.
(2) The brominated pollutant has toxic action on microorganisms and has low biodegradation efficiency. The product obtained after debromination can be used as an electron donor, so that the reduction efficiency of microorganisms on nitrate is further enhanced. Therefore, the degradation effect of brominated organic pollutants is improved, nitrate removal is promoted, complete mineralization of the pollutants is realized, and no environmental secondary pollution risk is caused.
(3) The palladium chemical catalytic reduction rate is far faster than the microbial degradation rate, the invention can realize reasonable matching of the palladium catalytic rate and the microbial degradation rate by regulating and controlling the hydrogen pressure and the membrane aeration backwashing system, can dynamically regulate the thickness of the biological membrane, ensures the microbial activity and the hydrogen mass transfer efficiency, and finally realizes the efficient degradation of pollutants. Meanwhile, the membrane aeration mode is adopted to supply hydrogen, and the hydrogen supply mode is an intermittent mode, so that the invention has the advantages of high hydrogen utilization rate, low hydrogen supply amount and the like compared with the traditional aeration, saves the operation cost, and is safer and more reliable.
(4) The device provided by the invention is simple, small in occupied area and high in automation degree, realizes the integrated reaction of hydrogenation debromination and biodegradation, is safer and more stable than the traditional method, and can be used for synchronously removing the oxidation state composite pollutants.
Drawings
Fig. 1 is a schematic diagram of a system for simultaneously removing brominated contaminants and nitrates in sewage, in which the correspondence between the names of components and the numbers of the drawings is:
the device comprises a 1-reactor body, a 2-membrane component, a 3-hydrogen supply unit, a 4-first hydrogen control valve, a 5-second hydrogen control valve, a 6-pollutant detection unit, a 7-aeration system, an 8-back flushing aeration head, a 9-reflux pump and a 10-control unit.
Detailed Description
The present invention will be described in detail below with reference to the drawings and examples. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The invention firstly provides a system for simultaneously removing brominated pollutants and nitrate in sewage, the structural schematic diagram is shown in figure 1, and the system comprises a reactor body 1, a plurality of membrane assemblies 2 and a hydrogen supply unit 3; the membrane component 2 is arranged inside the reactor body 1; the hydrogen supply unit 3 is communicated with the membrane component 2 through a first hydrogen control valve 4 and a second hydrogen control valve 5; the carrier membrane in the membrane component 2 is a non-porous hollow fiber membrane; the reactor body 1 is also provided with a pollutant detection unit 6 for detecting the concentration of brominated pollutants and nitrate, and dynamically adjusting the hydrogen supply pressure according to the concentration of brominated pollutants and nitrate; the reactor body 1 is also provided with a back flushing aeration head 8 which is communicated with an aeration system 7 positioned outside the reactor body; the reactor body 1 is also provided with an internal reflux device, and effluent water from the rear section is refluxed to the front section through an internal reflux pump 9.
The system is also provided with a control unit 10 which is respectively connected with the hydrogen control unit 3, the first hydrogen control valve 4, the second hydrogen control valve 5, the pollutant detection unit 6, the aeration system 7, the back flushing aeration head 8 and the internal reflux pump 9.
The operation mode and principle of the system of the invention are as follows: firstly, introducing sewage and sludge containing nitrate into a reactor main body, and loading microorganisms on the surface of a membrane under the condition of hydrogen supply pressure; after the biological film grows on the surface of the film steadily, the palladium acid salt solution is introduced into the reactor main body, and bivalent palladium ions are reduced to zero-valent metal palladium to be loaded on the surface of the film component under the conditions of hydrogen gas supply pressure and microorganism; then introducing sewage containing brominated pollutants and nitrate into a reactor main body, wherein brominated organic pollutants are firstly converted into debrominated intermediate products through palladium catalysis, then are degraded and converted into water and carbon dioxide by microorganisms, nitrate is firstly reduced into nitrite by microorganisms, then is reduced into nitrogen through palladium catalysis, and meanwhile, the debrominated intermediate products can be used as electron donors, so that the reduction efficiency of the microorganisms on the nitrate is further enhanced; the system solves the limiting factors of hydrodebromination and biomineralization, synergistically enhances the treatment efficiency of two pollutants, realizes complete mineralization of the pollutants, and has no risk of secondary pollution.
Example 2:
the system of example 1 was used to simultaneously remove brominated contaminants and nitrate from the wastewater.
S1: introducing sewage containing nitrate and 8g/L sludge into a reactor body 1, and forming a film under the condition of hydrogen supply pressure; the hydrogen pressure is 4psi, the film forming time is 12d, and the pH is controlled to be 7;
s2: after the film is formed, sodium tetrachloropalladate solution with the concentration of 1mM is led into the reactor body 1, and palladium is loaded on the surface of the film component under the conditions of hydrogen gas supply pressure and microbial reduction; the hydrogen pressure was 4psi, the loading time was 24h, and the pH was controlled at 7;
s3: introducing sewage containing 50mM tetrabromobisphenol A and 5M nitrate into a reactor body 1, completely mineralizing brominated organic pollutants into carbon dioxide and water under palladium hydrogenation catalysis and microbial reduction conditions, and simultaneously converting the nitrate into nitrogen; the hydrogen supply mode is an intermittent mode, the hydrogen supply/stop time is 2h (2 h for water supply and 2h for stop), the hydraulic retention time is 8h, and the pH of the inlet water is 7;
s4: the concentration of brominated pollutants and nitrate in the reactor body 1 is detected in real time through the control unit 10 and the pollutant detection unit 6, the first hydrogen control valve 4 and the second hydrogen control valve 5 are utilized to dynamically adjust the hydrogen pressure, and when the concentration of the brominated pollutants and nitrate in the effluent is respectively lower than 1mmol/L and 0.1mol/L, the regulation and the control are not carried out; when the bromine pollutant in the effluent is 1-10 mmol/L or the nitrate concentration is 0.1-0.5 mol/L, the hydrogen supply pressure is increased by 1psi; when the concentration of the brominated pollutant in the effluent is more than 10mmol/L or the concentration of the nitrate is more than 0.5mol/L, the hydrogen supply pressure is increased by 3psi, so that the palladium catalytic reduction rate and the microbial degradation rate are matched, the degradation efficiency of the pollutant is ensured, and the growth rate of a biological film is controlled;
s5: compressed gas is introduced into a back flush aeration head 8 through an aeration system 7, aeration flushing is carried out on the surface of the membrane regularly to control the thickness of the biological membrane to be 1-3 cm, and the microbial activity and the hydrogen mass transfer efficiency are ensured; the aeration scouring strength is 50L/(s.m) 2 ) The scouring time is 15min;
detecting the concentration of brominated organic pollutants and nitrate at the outlet, and calculating the removal rate of the brominated organic pollutants and the removal rate of the nitrate, wherein:
brominated contaminant removal = (inlet brominated contaminant concentration-outlet brominated contaminant concentration)/inlet brominated contaminant concentration 100%;
nitrate removal = (influent nitrate concentration-effluent nitrate concentration)/influent nitrate concentration 100%;
gas utilization = 100% - (volume of hydrogen evolved by loaded membrane module at 1h at fixed hydrogen pressure/volume of hydrogen evolved by clean membrane module at 1h at fixed hydrogen pressure).
As a result, it was found that the biological treatment system (conventional sewage treatment A 2 The removal rate of brominated organic pollutants is improved from 40.5% to 99.1% by adopting the method, and 144.7% is enhanced; the nitrate removal rate is improved from 59.8% to 99.5%, and the nitrate removal rate is enhanced by 66.4%; the gas utilization rate is improved from 38.7% to 99.7%, and 157.6% is enhanced.
Comparative example 1 conventional Sewage treatment A 2 O process
The total time of anaerobic-anoxic-aerobic treatment is 10-14 hours, wherein the treatment time of an anaerobic stage is less than or equal to 2 hours, the treatment time of an aerobic stage is more than or equal to 6 hours, the sludge concentration is 3000-4000 mg/L, the sludge residence time is 20-30 days, the temperature is 20-30, the pH of inlet water at the temperature is 6.5-7.5, the dissolved oxygen content of the anaerobic stage is less than or equal to 0.2mg/L, the dissolved oxygen content of the anoxic stage is less than or equal to 0.5mg/L, and the dissolved oxygen content of the aerobic stage is more than or equal to 2.0mg/L.
Comparative example 2:
a single palladium hydrogenation catalytic test comprising the steps of:
s1: the palladium acid salt solution with the concentration of 1mM is led into the reactor body (1), and palladium is loaded on the surface of the membrane component under the conditions of hydrogen gas supply pressure and microbial reduction; the hydrogen pressure was 4psi, the loading time was 24h, and the pH was controlled at 7;
s2: introducing 50mM tetrabromobisphenol A and 5M nitrate into a reactor body (1), wherein the hydrogen supply mode is a batch mode, the hydrogen supply/stop time is 2h, the hydraulic retention time is 8h, and the pH of the inlet water is 7;
after the reaction is finished, the effluent does not detect tetrabromobisphenol A, but the concentration of the degradation product bisphenol A is up to 48.2mM, and the removal rate of tetrabromobisphenol A is up to 96.4 percent, but the degradation product bisphenol A is basically converted into intermediate bisphenol A; meanwhile, the nitrate concentration of the effluent is 4.91M, and the nitrate removal rate is only 1.8%.
Comparative example 3:
a single biodegradation test comprising the steps of:
s1: introducing sewage containing nitrate and 6-10 g/L sludge into a reactor body (1), and forming a film under the condition of hydrogen supply pressure; the hydrogen pressure is 4psi, the film forming time is 12d, and the pH is controlled to be 7;
s2: after the film forming is finished, introducing sewage containing 50mM tetrabromobisphenol A and 5M nitrate into a reactor body (1); the hydrogen supply mode is an intermittent mode, the hydrogen supply/stop time is 2h, the hydraulic retention time is 8h, and the pH of the inlet water is 7;
after the reaction is finished, the concentration of the discharged tetrabromobisphenol A is 38.7mM, and the removal rate of the tetrabromobisphenol A reaches 22.6%; meanwhile, the nitrate concentration of the effluent is 1.38M, and the nitrate removal rate is 72.4%.
Example 3
S1: introducing sewage containing nitrate and 6g/L sludge into a reactor body 1, and forming a film under the condition of hydrogen supply pressure; the hydrogen pressure is 2psi, the film forming time is 8d, and the pH is controlled to be 6;
s2: after the membrane is formed, passing a palladium sulfate solution with the concentration of 0.5mM into the reactor body 1, and loading palladium on the surface of the membrane component under the conditions of hydrogen supply pressure and microbial reduction; the hydrogen pressure was 2psi, the loading time was 12h, and the pH was controlled to 6;
s3: introducing sewage containing 10mM polybrominated diphenyl ether and 1M nitrate into a reactor body 1, completely mineralizing brominated organic pollutants into carbon dioxide and water under palladium hydrogenation catalysis and microbial reduction conditions, and simultaneously converting the nitrate into nitrogen; the hydrogen supply mode is an intermittent mode, the hydrogen supply/stop time is 1h, the hydraulic retention time is 4h, and the pH of the inlet water is 6;
s4: the concentration of brominated pollutants and nitrate in the reactor body 1 is detected in real time through the control unit 10 and the pollutant detection unit 6, the first hydrogen control valve 4 and the second hydrogen control valve 5 are utilized to dynamically adjust the hydrogen pressure, and when the concentration of the brominated pollutants and nitrate in the effluent is respectively lower than 1mmol/L and 0.1mol/L, the regulation and the control are not carried out; when the bromine pollutant in the effluent is 1-10 mmol/L or the nitrate concentration is 0.1-0.5 mol/L, the hydrogen supply pressure is increased by 1.5psi; when the concentration of the brominated pollutant in the effluent is more than 10mmol/L or the concentration of the nitrate is more than 0.5mol/L, the hydrogen supply pressure is increased by 3psi, so that the palladium catalytic reduction rate and the microbial degradation rate are matched, the degradation efficiency of the pollutant is ensured, and the growth rate of a biological film is controlled;
s5: compressed gas is introduced into a back flush aeration head 8 through an aeration system 7, aeration flushing is carried out on the surface of the membrane regularly to control the thickness of the biological membrane to be 1-3 cm, and the microbial activity and the hydrogen mass transfer efficiency are ensured; the aeration scouring strength is 40L/(s.m) 2 ) The scouring time is 10min;
as a result, it was found that the biological treatment system (conventional sewage treatment A 2 The removal rate of brominated organic pollutants is improved to 85.4% from 40.5% by adopting the method, and 110.8% is enhanced; the nitrate removal rate is improved from 59.8% to 81.7%, and 36.6% is enhanced; the gas utilization rate is improved from 38.7% to 94.1%, and the gas utilization rate is enhanced by 143.2%.
Example 4
S1: introducing sewage containing nitrate and 10g/L sludge into a reactor body 1, and forming a film under the condition of hydrogen supply pressure; the hydrogen pressure is 6psi, the film forming time is 16d, and the pH is controlled to be 8;
s2: after the membrane is formed, a palladium chloride solution with the concentration of 1.5mM is led into the reactor body 1, and palladium is loaded on the surface of the membrane component under the conditions of hydrogen supply pressure and microbial reduction; the hydrogen pressure was 6psi, the loading time was 36h, and the pH was controlled at 8;
s3: introducing sewage containing 90mM hexabromocyclododecane and 10M nitrate into a reactor body 1, completely mineralizing brominated organic pollutants into carbon dioxide and water under palladium hydrogenation catalysis and microbial reduction conditions, and simultaneously converting the nitrate into nitrogen; the hydrogen supply mode is an intermittent mode, the hydrogen supply/stop time is 4h, the hydraulic retention time is 12h, and the pH of the inlet water is 8;
s4: the concentration of brominated pollutants and nitrate in the reactor body 1 is detected in real time through the control unit 10 and the pollutant detection unit 6, the first hydrogen control valve 4 and the second hydrogen control valve 5 are utilized to dynamically adjust the hydrogen pressure, and when the concentration of the brominated pollutants and nitrate in the effluent is respectively lower than 1mmol/L and 0.1mol/L, the regulation and the control are not carried out; when the bromine pollutant in the effluent is 1-10 mmol/L or the nitrate concentration is 0.1-0.5 mol/L, the hydrogen supply pressure is increased by 1.5psi; when the concentration of the brominated pollutant in the effluent is more than 10mmol/L or the concentration of the nitrate is more than 0.5mol/L, the pressure of the hydrogen supply is increased by 3.5psi, so that the palladium catalytic reduction rate and the microbial degradation rate are matched, the degradation efficiency of the pollutant is ensured, and the growth rate of a biological film is controlled;
s5: compressed gas is introduced into a back flush aeration head 8 through an aeration system 7, aeration flushing is carried out on the surface of the membrane regularly to control the thickness of the biological membrane to be 1-3 cm, and the microbial activity and the hydrogen mass transfer efficiency are ensured; the aeration scouring strength is 60L/(s.m) 2 ) The scouring time is 20min;
as a result, it was found that the biological treatment system (conventional sewage treatment A 2 The removal rate of brominated organic pollutants is improved to 81.3% from 40.5% by adopting the method according to the O process and comparative example 1), and the removal rate is enhanced by 100.7%; the nitrate removal rate is improved from 59.8% to 83.6%, and the nitrate removal rate is enhanced by 39.8%;the gas utilization rate is improved from 38.7% to 91.2%, and the gas utilization rate is enhanced by 135.6%.
Comparative example 4
If S4 does not dynamically regulate the hydrogen pressure, the original pressure is always kept, other parameter settings are consistent with those of the embodiment 2, and after the reactor runs for a long time, the removal rate can reach 94.8% although the concentration of the tetrabromobisphenol A in the effluent is lower, but 50.3% is converted into an intermediate product bisphenol A, so that the tetrabromobisphenol A is not completely degraded; meanwhile, the nitrate removal rate is 92.4 percent.
Comparative example 5
If S5 does not wash the biological film, other parameter settings are consistent with those of the embodiment 2, and after the reactor is operated for one month, the removal rates of tetrabromobisphenol A and nitrate are respectively reduced to 42.1 percent and 53.7 percent; after two months of operation, the removal rates of the two are respectively reduced to 11.3 percent and 23.8 percent; after three months of operation, the contaminants were hardly degraded.
Although the embodiments of the present invention have been disclosed in the foregoing description and drawings, it is not limited to the details of the embodiments and examples, but is to be applied to all the fields of application of the present invention, it will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
Claims (7)
1. The method for simultaneously removing brominated pollutants and nitrate in sewage is characterized by being performed on a system for simultaneously removing brominated pollutants and nitrate in sewage, wherein the system comprises a reactor body (1), a plurality of membrane assemblies (2) and a hydrogen gas supply unit (3), the membrane assemblies (2) are arranged in the reactor body (1), the hydrogen gas supply unit (3) is communicated with the membrane assemblies (2), and the membrane assemblies (2) are non-porous hollow fiber membranes;
the system further comprises a contaminant detection unit (6) for detecting a contaminant concentration;
the system also comprises a back flushing aeration head (8) which is positioned at the bottom of the reactor body (1) and is communicated with an aeration system (7) positioned outside the reactor body (1);
the method comprises the following steps:
s1: introducing sewage and sludge containing nitrate into a reactor body (1), and performing microbial film formation under the condition of hydrogen supply pressure;
s2: after the film is formed, the palladium acid salt solution is led into the reactor body (1), and palladium is loaded on the surface of the film component (2) under the conditions of hydrogen gas supply pressure and microbial reduction;
s3: introducing sewage containing brominated pollutants and nitrate into a reactor body (1), mineralizing brominated organic pollutants into carbon dioxide and water under palladium hydrogenation catalysis and microbial reduction conditions, and simultaneously converting nitrate into nitrogen;
s4: the concentration of brominated pollutants and nitrate in the reactor body is detected in real time through a control unit (10) and a pollutant detection unit (6), and the hydrogen pressure is dynamically regulated by utilizing a hydrogen control valve, and meanwhile, the growth rate of a biological film is controlled;
s5: compressed gas is introduced into a back flush aeration head through an aeration system (7), and aeration flushing is carried out on the surface of the membrane to control the thickness of the biological membrane at regular intervals;
in the step S4, when the concentration of the brominated pollutants and the nitrate in the effluent is respectively lower than 1mmol/L and 0.1mol/L, the regulation and control are not performed; when the bromine pollutant in the effluent is 1-10 mmol/L or the nitrate concentration is 0.1-0.5 mol/L, the hydrogen supply pressure is increased by 0.5-2 psi; when the concentration of the brominated pollutant in the effluent is more than 10mmol/L or the concentration of the nitrate is more than 0.5mol/L, the pressure of the hydrogen supply is increased by 2.5 to 4psi;
in step S5, when the film thickness of the biofilm exceeds 3cm, scouring is performed.
2. The method according to claim 1, characterized in that the system further comprises a control unit (10) for controlling the backwash aeration head (8) and the hydrogen supply unit (3) is controlled by data of the contaminant detection unit (6) for dynamically adjusting the hydrogen pressure.
3. The method according to claim 1, wherein palladium acid salt solution is filled in the hollow fiber membrane, and palladium is supported on the surface of the membrane component in a reducing way under the conditions of hydrogen gas supply pressure and microorganism.
4. The method according to claim 1, characterized in that it comprises in particular the following steps:
s1: introducing sewage containing nitrate and 6-10 g/L sludge into a reactor body, and forming a film under the condition of hydrogen supply pressure; the hydrogen pressure is 2-6 psi, the film forming time is 8-16 d, and the pH is controlled to be 6-8;
s2: after the film is formed, palladium salt solution with the concentration of 0.5-1.5 mM is led into the reactor body, and palladium is loaded on the surface of the film component under the conditions of hydrogen gas supply pressure and microbial reduction; the hydrogen pressure is 2-6 psi, the loading time is 12-36 h, and the pH is controlled to be 6-8;
s3: introducing sewage containing brominated pollutants and nitrate into a reactor body, completely mineralizing brominated organic pollutants into carbon dioxide and water under the conditions of palladium hydrogenation catalysis and microbial reduction, and simultaneously converting nitrate into nitrogen; the hydrogen supply mode is an intermittent mode, the hydrogen supply/stop time is 0-4 h, wherein the hydrogen supply/stop time is not 0, the hydraulic retention time is 4-12 h, and the pH of the inlet water is 6-8;
s4: detecting the concentration of brominated pollutants and nitrate in the reactor body in real time through a control unit and a pollutant detection unit, dynamically regulating the hydrogen pressure by utilizing a hydrogen control valve, and simultaneously controlling the growth rate of a biological film;
s5: compressed gas is introduced into a back flush aeration head through an aeration system, aeration flushing is carried out on the surface of the membrane regularly to control the thickness of the biological membrane, and the microbial activity and the hydrogen mass transfer efficiency are ensured; the aeration scouring strength is 40-60L/(s.m) 2 ) The scouring time is 10-20 min.
5. The method of claim 4, wherein the membrane module is a polyethylene non-porous hollow fiber membrane; a polypropylene non-porous hollow fiber membrane; or other non-porous hollow fiber membranes.
6. The method according to claim 4 or 5, wherein the palladium acid salt is one or more of palladium chloride, palladium sulfate or sodium tetrachloropalladate.
7. Use of the method according to any one of claims 1 to 6 in sewage treatment.
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