CN115974288A - Method for reinforcing dissimilatory reduction process of nitrate into ammonium by electric field coupling magnetic field - Google Patents
Method for reinforcing dissimilatory reduction process of nitrate into ammonium by electric field coupling magnetic field Download PDFInfo
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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 relates to a method for strengthening dissimilatory reduction of nitrate into ammonium by using an electric field coupling magnetic field, which promotes quick start of a DNRA reactor and improves the stability of a system by using the coupling effect of the electric field and the magnetic field, and simultaneously improves the activity of DNRA bacteria and the abundance of a functional gene nrfA. Meanwhile, the application of the electric field and the magnetic field promotes the activity of DNRA bacteria, shortens the period of enrichment culture and achieves the aim of quickly starting the reactor. The equipment for generating the electric field and the magnetic field has low energy consumption, particularly the magnetic field generated by the permanent magnet does not need to consume energy, has long duration, is safe and harmless to the environment and is convenient for engineering application.
Description
Technical Field
The invention relates to a method for strengthening the dissimilatory reduction of nitrate into ammonium by using an electric field coupled magnetic field, belonging to the technical field of sewage treatment.
Background
In the biological denitrification process of sewage, the nitrate produced in the nitrification stage is subjected to denitrificationReducing the nitrogen into nitrogen, thereby achieving the aim of denitrification. However, it is also possible for nitrates to be reduced to ammonium (CH) in addition to nitrogen 3 COO - +NO 3 - +2H + →CO 2 +NH 4 + +HCO 3 - ) I.e. the DNRA procedure. The DNRA process not only can reduce the greenhouse gas N 2 The emission of O, and the NO which is difficult to utilize 3 - Conversion of-N to NH more readily available to microorganisms 4 + N, and therefore its role in the nitrogen cycle is of increasing interest and acceptance. However, most of the current research on the DNRA process is focused on soil systems, and relatively few on water systems. In natural water, the DNRA process cannot reduce the total nitrogen to a certain level, but can reduce the greenhouse gas N by competing with the denitrification process 2 And (4) discharging O. In artificial waters, such as sewage treatment plants, the DNRA process may remove NO from the wastewater 3 - Reduced to emission standard with the production of NH-containing gas 4 + The waste water can be processed into nutrient fertilizer through secondary treatment, thereby realizing the reclamation of the waste water.
The activated sludge process is a commonly used process in sewage treatment, and ammonia nitrogen is very lacking as a commonly used nitrogen source for microbial growth in regions such as denitrification part of a three-stage process, high nitrate nitrogen industrial wastewater treatment and the like. The three-stage method comprises three parts of decarbonization, nitrification and denitrification, and is respectively provided with a corresponding sedimentation tank and a corresponding sludge backflow system, and the three systems run relatively independently. The post denitrification process for denitrification usually encounters the problem of insufficient carbon source or nitrogen source, and needs to add nitrogen source and carbon source to ensure the growth of microorganisms and the proceeding of denitrification. The industrial wastewater of explosives, polysilicon batteries and the like contains high-concentration nitrate nitrogen, and ammonia nitrogen needs to be added to maintain the normal growth of the activated sludge. Factors such as temperature, C/N, pH and the like have an influence on the denitrification of the activated sludge, and the factors are directly related to the DNRA process. Through the adjustment of key factors, a certain proportion of nitrate nitrogen can generate DNRA effect to generate ammonia, a nitrogen source is provided for the normal growth of denitrifying functional bacteria, and the rest nitrate nitrogen passes through denitrificationRemoving, and saving the adding cost of the nitrogen source under the condition of ensuring higher denitrification efficiency; but if there is more NO 3 - Is not removed from the water by denitrification, but is converted to NH by DNRA action 4 + The denitrification efficiency of the process is affected. Therefore, it is very important to control the rate at which nitrate nitrogen acts on DNRA. At present, the research on DNRA in China is still in an exploration stage, the influence mechanism of relevant factors in a denitrification system on DNRA is not clear, and a reactor for enriching DNRA bacteria needs to be established to further research a transformation way. However, the long startup time of DNRA and unstable reactor performance have been the bottleneck in DNRA research.
Disclosure of Invention
Aiming at the defects of the prior art, in particular to the problems of long DNRA starting time, unstable system and the like, the invention provides a method for strengthening the process of dissimilatory reduction of nitrate into ammonium by using an electric field coupling magnetic field.
The invention changes the permeability of the cell membrane of the microbial flora through the coupling of the electric field and the magnetic field, has influence on the growth and the reproduction of the microbial flora, has obvious influence on both intracellular enzyme and extracellular enzyme, can specifically promote various reactions in the microbial flora through stimulating the enzyme, and greatly improves the performance and the stability of the bioreactor. The method can effectively accelerate the initiation of DNRA, promote the growth of DNRA functional bacteria and the abundance of functional enzymes, and improve the stability of the DNRA reactor.
The invention is realized by the following technical scheme:
a method for strengthening the dissimilatory reduction of nitrate into ammonium by using an electric field coupled magnetic field comprises the following specific steps:
(1) Cleaning flocculent sludge with tap water until the cleaning solution is transparent, pouring out the cleaning solution, adding phosphate buffer solution to seal the sludge, standing overnight, and transferring to a sequencing batch biofilm reactor the next day;
(2) The permanent magnet is arranged outside the reactor, the magnetic field intensity in the center of the reactor is 20-100mT, the constant voltage electric field is arranged inside the reactor, and the voltage intensity of the adjusting polar plate is controlled to be-2.2-0.6V SCE To (c) to (d);
(3) Introducing synthetic wastewater from the top of the reactor, wherein the inflow water is divided into two strands, the first strand is nitrogen source inflow water, the second strand is carbon source inflow water, the flow rates of the two strands of inflow water are kept consistent, the rotation speed of a peristaltic pump is adjusted to control the inflow water flow rate, meanwhile, a water outlet pipe connected with a membrane module is connected with the peristaltic pump, 24 hours of continuous inflow water is carried out, the hydraulic retention time is 10-48 hours, the rotation speed of the peristaltic pump is adjusted to control the outflow water flow rate, and a time control switch is used for controlling the peristaltic pump, so that the liquid level of the reactor is maintained at a specified height;
(4) The pH value in the reactor is kept at 7.1 +/-0.1, the temperature is kept at 23 +/-1 ℃, a mechanical stirrer is arranged at the top of the reactor, the reactor is sealed and runs in a dark place, and the DNRA process is started quickly by continuous operation for 24 hours.
Preferably, in the step (1), the flocculent sludge is a mixed solution with a suspended solid concentration of 4.0-8.0 g/L.
Preferably, in step (1), the phosphate buffer has a pH =7.2 and a concentration of 0.1-0.3mol/L.
Preferably, in step (1), the amount of the sludge inoculated in the sequencing batch biofilm reactor accounts for 1/5 to 1/2 of the volume of the reactor.
Preferably, in step (2), the reactor is a sequencing batch biofilm reactor using a non-woven fabric membrane as a membrane material, and a water bath layer is arranged.
According to the invention, in step (2), the magnet used in the invention is a common commercial ferromagnetic material, and an electromagnetic field and a magnetic field intensity are measured at the center of the reactor, and a Wett WT103 permanent magnet surface magnetic field tester is used. The electric field intensity of the invention is controlled by a constant voltage instrument, a carbon felt (3 cm multiplied by 3 cm) is used as a working electrode, a graphite flake is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode.
Preferably, in step (2), the permanent magnet is arranged outside the reactor, so that the magnetic field intensity in the center of the reactor is 35-45mT.
Preferably, in step (2), a constant voltage electric field is arranged in the reactor, and the voltage intensity of the adjusting plate is controlled to be 0.01-0.5V SCE 。
Preferably, in step (3), the membrane module in the reactor is made of polymethyl methacrylate, the pore diameter of the non-woven fabric is 0.1mm, the membrane module is tightly fixed around the membrane support by the non-woven fabric and is symmetrically arranged in the reactor.
Preferably, in step (3), the nitrogen source feed water comprises the following components: per liter of feed water, 0.197g MgSO 4 ·7H 2 O，1.254g NaNO 3 ，1.999g KH 2 PO 4 ，0.04g NaOH，0.021g MnCl 2 ·4H 2 O，0.02g FeSO 4 ·7H 2 O，0.022g CaCl 2 0.01g of yeast powder and 4mL of trace elements; the water inflow ingredients per liter of trace elements are as follows: 20g of EDTA-2Na,2.2g of ZnSO 4 ·7H 2 O，1.75g CuSO 4 ·5H 2 O，5.54g CoCl 2 ·6H 2 O，1.1g(NH 4 ) 6 Mo 7 O 24 ·4H 2 O。
Preferably, in step (3), the carbon source feed water is ethanol with a concentration of 0.964mL/L and a COD concentration of 1400mg/L.
According to the invention, in the step (3), the nitrogen source inflow water and the carbon source inflow water are aerated for 30min by pure nitrogen (99.9%), and then are aerated for 30min every 24h and then are introduced into the reactor.
Preferably, in step (4) according to the present invention, the pH in the reaction is controlled by an in-line pH meter and the temperature is controlled by a constant temperature circulator.
The monitoring of the water quality is realized by measuring the concentration of nitrate nitrogen, ammonium nitrogen and nitrite nitrogen in the reactor, the monitoring of the functional genes is realized by measuring the abundance of DNRA functional gene nrfA by qPCR technology, and the determination of the DNRA potential rate is realized by using 15 And N isotope tracing technology.
Compared with the prior art, the invention has the following advantages:
1. the permeability of the cell membrane of the microbial flora is changed through coupling of the electric field and the magnetic field, the growth and the propagation of the microbial flora are also influenced, both intracellular enzymes and extracellular enzymes are obviously influenced, various reactions in the microbial flora can be specifically promoted through the stimulating enzymes, and the performance and the stability of the bioreactor are greatly improved. The method can effectively accelerate DNRA starting, promote the growth of DNRA functional bacteria and the abundance of functional enzymes, and improve the stability of the DNRA reactor.
2. According to the invention, the ammonia nitrogen conversion efficiency of the DNRA reactor is effectively improved through electric and magnetic field coupling, the enrichment of DNRA bacteria is promoted, the stability of the system is improved, the biomembrane reactor taking non-woven fabrics as a membrane component provides an attachable biomembrane for the growth of flora, the loss of effective strains can be reduced, the biomass retention capacity is improved, the number of microorganisms in the reactor is increased by the interception effect of the membrane, the stability of the system is improved, and the high sludge concentration in the equipment is ensured. The mixing system promotes the mixing of matrix and flora, improves the mass transfer efficiency, forms a sludge-membrane symbiotic system with higher microorganism concentration, realizes that the biomass is intercepted, simultaneously makes the microorganism fully contact with raw water, builds a stable habitat suitable for DNRA bacteria to live, and ensures the activity of DNRA functional microorganisms. The enrichment of DNRA bacteria is faster, and an attachable biological film is provided for the growth of the flora, and the radiation effect of the magnetic field is enhanced.
3. The method of the invention has low operation cost, low energy consumption of the constant voltage instrument, long duration time, safety and harmlessness to the environment and convenient engineering application, and the magnetic field generated by the permanent magnet does not need to consume energy.
Drawings
FIG. 1 shows the nitrogen conversion performance of the reactor in the application test example in the long-term operation. (A) a control group Rck; (B) Experimental group R1; (C) Experimental group R2; (D) Experimental group R3.
FIG. 2 shows the potential DNRA rates during steady state operation of the reactor (80 days) in the application test examples.
FIG. 3 shows the abundance of the nrfA gene in the reactor of the application test example.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
A method for strengthening the dissimilatory reduction of nitrate into ammonium by using an electric field coupled magnetic field comprises the following specific steps:
(1) Washing flocculent sludge for several times by using tap water, pouring out the washing liquid until the washing liquid is transparent, then adding phosphate buffer (pH =7.2, 0.2M) to seal the sludge, standing overnight, transferring to a sequencing batch biofilm reactor in the next day, wherein the inoculated sludge accounts for about one fifth of the volume of the reactor;
(2) The permanent magnet is arranged outside the reactor, the magnetic field intensity in the center of the reactor is 40mT, the constant voltage electric field is arranged inside the reactor, and the voltage intensity of the adjusting polar plate is controlled to be 0.01-0.5V SCE ；
(3) Introducing synthetic wastewater from the top of the reactor, wherein the inflow water is divided into two strands, the first strand is nitrogen source inflow water, the second strand is carbon source inflow water, the flow rates of the two strands of inflow water are kept-controlled, the rotating speed of a peristaltic pump is adjusted to control the inflow water flow rate, meanwhile, a water outlet pipe connected with a membrane module is connected with the peristaltic pump, 24 hours of continuous inflow water are carried out, and the hydraulic retention time is 24 hours. The nitrogen source feed water comprises the following components per liter: 0.197gMgSO 4 ·7H 2 O，1.254g NaNO 3 ，1.999g KH 2 PO 4 ，0.04g NaOH，0.021g MnCl 2 ·4H 2 O，0.02gFeSO 4 ·7H 2 O，0.022g CaCl 2 0.01g of yeast powder and 4ml of trace elements. The trace elements per liter are as follows: 20g of EDTA-2Na,2.2g of ZnSO 4 ·7H 2 O，1.75g CuSO 4 ·5H 2 O，5.54g CoCl 2 ·6H 2 O，1.1g(NH 4 ) 6 Mo 7 O 24 ·4H 2 And O. The carbon source inlet water is anhydrous sodium acetate, the concentration is 5.4g/L, and the COD concentration is 1400mg/L. Aerating nitrogen source inlet water and carbon source inlet water for 30min by using pure nitrogen (99.9%), then aerating for 30min every 24h, and then introducing into the reactor;
(4) The rotation speed of the peristaltic pump is adjusted to control the water outlet flow rate, the peristaltic pump is controlled by a time control switch, the water outlet time is set to be 10min, the water outlet frequency is set to be 1 time/4 h, and the liquid level of the reactor is maintained at the height of 27.5-32.5 cm. And controlling the pH to be kept at 7.1 +/-0.1 by using an online pH meter, keeping the temperature at 23 +/-1 ℃, installing a mechanical stirrer at the top of the reactor, sealing the reactor to operate in a dark place, and continuously working for 24 hours to realize the quick start of the DNRA process.
Application test example
4 reactors were set, a control Rck and experimental R1, R2, R3. The control group Rck is not provided with the influence of an electric field and a magnetic field, the experimental group R1 is provided with a magnetic field, the experimental group R2 is provided with an electric field, and the experimental group R3 is provided with the influence of the coupling effect of the magnetic field and the electric field (embodiment 1); the test was carried out by referring to the method of example 1.
The magnets used (12 cm. Times.6 cm. Times.1.5 cm) are the most common ferromagnetic materials, the magnetic field strength is measured at the center of the reactor, and a Wett WT103 permanent magnet surface magnetic field tester is used, the magnetic field strength being about 40mT. The electric field is controlled by a constant voltage instrument, a carbon felt (3 cm multiplied by 3 cm) is used as a working electrode, a graphite flake is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, and the voltage of the working electrode is controlled to be 0.01 to 0.5V by the constant voltage instrument SCE 。
And continuously monitoring parameters such as water quality, functional gene abundance, DNRA potential rate and the like in the running process of the reactor. The monitoring of water quality is to measure the concentration of nitrate nitrogen, ammonium nitrogen and nitrite nitrogen in the reactor, the monitoring of functional gene is to measure the abundance of DNRA functional gene nrfA, and the determination of DNRA potential rate is to use 15 And N isotope tracing technology.
And (3) test results:
from the figure 1 shows the change trend in the starting process of 4 reactors, the starting time of the experimental group is greatly shortened, the effect of applying the magnetic field and the electric field is most obvious, and then the magnetic field and the electric field are independently applied. This may be that suitable magnetic and electric fields facilitate the DNRA process so that the DNRA can dominate in a short time. In the long-term operation process of the reactor under the influence of different electromagnetic effects, the reactor does not show obvious difference in ammonia nitrogen conversion efficiency during stable operation, but under the influence of magnetic field and electric field coupling effect, the reactor shows relatively high ammonia nitrogen conversion efficiency and overall stability of the system, the conversion rate of R3 is always maintained at about 64.02% in nearly three months after successful start-up, and the effluent quality is stable, which indicates that the appropriate electric field and magnetic field strength can promote the start-up of the DNRA process, the coupling effect of the two electromagnetic effects can further promote the DNRA process, and the stability of the DNRA system is improved to a certain extent.
As shown in FIG. 2, the potential rates of DNRA for Rck, R1, R2, and R3 were 52.07, 88.49, 160.17, and 174.30. Mu. Mol/(kg. H), respectively. In substantial agreement with the water quality data, the experimental groups, which were affected by both magnetic and electric fields, showed higher DNRA rates than the control group, with the reactor effect most evident with the effect of coupling the magnetic field by the electric field. The DNRA process being NO 3 - -N reduction to NH in one step 4 + N, so in the R1 reactor with the highest potential rate of DNRA, the DNRA bacteria show the highest activity, namely the highest ability to convert nitrate nitrogen into ammonia nitrogen. From the results, it is likely that the combined action of the electric field and the magnetic field promotes the succession of microbial communities, so that the DNRA process in the system is dominant in a shorter time.
As shown in FIG. 3, nrfA is a gene encoding nitrite reductase in DNRA. At 40 days, the nrfA gene abundance of the R3 reactor was highest, reaching 3.54X 10 6 copies/ng DNA, rck abundance 1.80X 10 6 copies/ng DNA, R1 abundance 2.0X 10 6 copies/ng DNA, R2 abundance 3.24X 10 6 copies/ng DNA. At 80 days, the nrfA gene in the reactor continued to be multiplied, and the nrfA gene abundance of the R3 reactor was still the highest, reaching 4.72X 10 6 copies/ng DNA, the abundance of Rck is 2.91X 10 6 copies/ng DNA, R1 abundance of 3.23X 10 6 copies/ng DNA, R2 abundance of 4.33X 10 6 copies/ng DNA. According to qPCR data, the abundance of DNRA functional species can be effectively improved by applying an electric field and a magnetic field, and the abundance can be improved by coupling the two magnetic effectsGood promoting effect.
(9) In summary, various data show that the application of both electric field and magnetic field can shorten the DNRA start-up time, and the effect of electric field coupling magnetic field is most obvious. The long-term experiment results show that the coupling effect of the electric field and the magnetic field also has a certain promotion effect on the stability of the system. The potential rate of DNRA and the qPCR result also show that the coupling effect of the electric field and the magnetic field promotes the activity of DNRA bacteria and the abundance of functional genes.
Claims (9)
1. A method for strengthening the dissimilatory reduction of nitrate into ammonium by using an electric field coupled magnetic field comprises the following specific steps:
(1) Washing flocculent sludge by using tap water, pouring out the washing liquid until the washing liquid is transparent, adding phosphate buffer solution to seal the sludge, standing overnight, and transferring to the sequencing batch biofilm reactor the next day;
(2) The permanent magnet is arranged outside the reactor, the magnetic field intensity in the center of the reactor is 20 mT to 100mT, the constant voltage electric field is arranged inside the reactor, and the voltage intensity of the adjusting polar plate is controlled to be minus 2.2V to 0.6V SCE In the middle of;
(3) Introducing synthetic wastewater from the top of the reactor, wherein the inflow water is divided into two strands, the first strand is nitrogen source inflow water, the second strand is carbon source inflow water, the flow rates of the two strands of inflow water are kept consistent, the rotation speed of a peristaltic pump is adjusted to control the inflow water flow rate, meanwhile, a water outlet pipe connected with a membrane module is connected with the peristaltic pump, 24 hours of continuous inflow water is carried out, the hydraulic retention time is 10-48 hours, the rotation speed of the peristaltic pump is adjusted to control the outflow water flow rate, and a time control switch is used for controlling the peristaltic pump, so that the liquid level of the reactor is maintained at a specified height;
(4) The pH value in the reactor is kept at 7.1 +/-0.1, the temperature is kept at 23 +/-1 ℃, a mechanical stirrer is arranged at the top of the reactor, the reactor is sealed and runs in a dark place, and the DNRA process is started quickly by continuous operation for 24 hours.
2. The method according to claim 1, wherein in the step (1), the flocculent sludge is a mixed liquor with a suspended solid concentration of 4.0-8.0 g/L.
3. The method according to claim 1, wherein in step (1), the phosphate buffer has a pH =7.2 and a concentration of 0.1-0.3mol/L.
4. The method of claim 1, wherein in step (1), the amount of the inoculated sludge in the sequencing batch biofilm reactor accounts for 1/5 to 1/2 of the volume of the reactor.
5. The method according to claim 1, wherein in the step (2), permanent magnets are disposed outside the reactor so that the magnetic field strength in the center of the reactor is 35-45mT.
6. The method of claim 1, wherein in the step (2), a constant voltage electric field is provided inside the reactor, and the voltage intensity of the adjusting plate is controlled to be 0.01-0.5V SCE 。
7. The method of claim 1, wherein in step (3), the nitrogen source influent water has the following composition: per liter of feed water, 0.197g MgSO 4 ·7H 2 O，1.254g NaNO 3 ，1.999g KH 2 PO 4 ，0.04g NaOH，0.021gMnCl 2 ·4H 2 O，0.02g FeSO 4 ·7H 2 O，0.022g CaCl 2 0.01g of yeast powder and 4mL of trace elements; the water inflow ingredients per liter of trace elements are as follows: 20g of EDTA-2Na,2.2g of ZnSO 4 ·7H 2 O，1.75g CuSO 4 ·5H 2 O，5.54g CoCl 2 ·6H 2 O，1.1g(NH 4 ) 6 Mo 7 O 24 ·4H 2 O。
8. The method of claim 1, wherein in the step (3), the carbon source feed water is ethanol with a concentration of 0.964mL/L and a COD concentration of 1400mg/L.
9. The method of claim 1, wherein in step (3), the nitrogen source feed water and the carbon source feed water are aerated for 30min by pure nitrogen (99.9%), and then are introduced into the reactor after being aerated for 30min every 24h.
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