CN109943377B - Method for synchronously purifying and enhancing sewage denitrification by using nitrite as electron acceptor - Google Patents
Method for synchronously purifying and enhancing sewage denitrification by using nitrite as electron acceptor Download PDFInfo
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Abstract
A method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor relates to a treatment method for synchronously denitrifying sewage and desulfurizing methane. Aims to solve the problem of high cost of methane desulfurization and sewage denitrification. The method comprises the following steps: injecting sewage into a reaction zone of the gas stripping type EGSB reactor, inoculating sludge into the reaction zone, and conveying nitrite, nutrient elements and methane into the reaction zone to complete starting; stopping conveying methane, conveying methane into the reaction zone through the aeration pipe, continuously conveying sewage, and synchronously coupling sewage denitrification and methane desulfurization after running for 40 days; after 41, biogas desulfurization and sewage denitrification are carried out. The invention combines autotrophic denitrification and denitrification type anaerobic methane oxidation processes, takes nitrite as an electron acceptor, realizes methane desulfurization and strengthens the denitrification process of sewage at the same time, does not add an external carbon source, and has the highest denitrification and desulfurization efficiency reaching 100 percent. The invention is suitable for synchronously strengthening sewage denitrification during biogas purification.
Description
Technical Field
The invention relates to a treatment method for synchronously denitrifying sewage and desulfurizing methane.
Background
The problem of energy shortage can be greatly relieved by using the biogas as a novel energy material, so that biogas engineering relying on anaerobic digestion of sludge is vigorously developed in China. Biogas generated by anaerobic digestion contains not only methane as a main energy substance, but also impurity gases such as hydrogen sulfide, and the concentration of hydrogen sulfide in biogas is reduced to below 0.0013% by the national regulation, so that the biogas can be used for energy utilization such as power generation, and the like, and therefore biogas desulfurization is gradually becoming an important technical means. The current commonly used biogas desulfurization technologies comprise wet desulfurization and dry desulfurization, wherein the wet desulfurization utilizes a specific solvent to contact biogas to absorb hydrogen sulfide in the biogas, and the solvent passes through the biogas after losing efficacyThe regeneration is reused, but the generation of harmful substances requires continuous supplement and replacement of absorption liquid, so that the treatment cost and the possibility of secondary pollution are increased, and the requirement on the corrosion resistance of equipment is higher; dry desulfurization is generally carried out by reacting metal oxide with hydrogen sulfide to produce sulfide, removing hydrogen sulfide, and then using O2The method reacts with the generated sulfide to generate elemental sulfur and simultaneously completes the regeneration of metal oxide, however, the method has limitation in the engineering with larger methane production capacity, and is generally suitable for the projects with small methane quantity and H2The situation that the concentration of S is low is easy to cause the insufficient utilization of the filler; at present, most of biogas desulfurization is carried out by the method, the cost of required reagents is high, and tail gas of some small biogas plants is not treated at all, so that the biogas is difficult to achieve high-efficiency recycling.
With the continuous development of science and technology in China, the problem of water pollution is increasingly prominent. The discharge of agricultural, industrial and domestic sewage causes a great amount of nitrogen-containing pollutants to enter water bodies, causes eutrophication of the water bodies and also directly influences the daily life of citizens and the normal production activities of industrial enterprises. The existing sewage discharge standard is more and more severe, most sewage plants need upgrading and modification, and the problem of deep removal of nitrogen-containing pollutants is still a technical difficulty generally faced by the existing sewage plants, and is an important technical bottleneck for construction and modification of the sewage plants. At present, the traditional activated sludge method is adopted in the denitrification modes of most sewage treatment plants, the traditional denitrification technology firstly converts ammonia nitrogen, organic nitrogen and the like into nitrate nitrogen by exposing excessive air, organic nitrogen in wastewater is converted into nitrate by a nitrification process, namely, the excessive oxidation or the complete oxidation of the organic nitrogen is realized, the condition of resource waste exists, then the nitrate nitrogen is converted into nitrogen by a denitrification process, thereby realizing the removal of the nitrogen in the sewage, the denitrification process is mainly completed by heterotrophic bacteria, an organic carbon source is required to be used as an electron acceptor, the nitrate nitrogen and the nitrite nitrogen are used as the electron acceptor for denitrification under the anaerobic condition, therefore, for the sewage with low carbon-nitrogen ratio, the carbon source substances in the sewage are insufficient, the nitrogen removal efficiency is low, generally, in order to ensure the nitrogen removal effect, an additional carbon source is usually required, this increases the processing cost.
Disclosure of Invention
The invention provides a method for synchronously strengthening sewage denitrification by using nitrite as an electron acceptor for biogas purification, aiming at solving the problem of high cost of the existing biogas desulfurization and sewage denitrification.
The method for synchronously purifying and enhancing sewage denitrification by using the nitrite as the electron acceptor comprises the following steps:
step one, starting the anaerobic oxidation of methane by taking nitrite as a substrate:
continuously injecting sewage into a reaction zone (6) of the gas stripping type EGSB reactor from a water inlet pipe (9), sieving secondary sedimentation tank sludge of a common sewage treatment plant to be used as inoculation sludge, inoculating the inoculation sludge into the reaction zone (6) of the gas stripping type EGSB reactor to form a sludge-water mixture, injecting nitrite and nutrient elements into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), continuously conveying methane into the sludge-water mixture in the reaction zone (6) through an aeration pipe (8), and operating for at least 230 days to finish starting;
step two, synchronously coupling sewage denitrification and biogas desulfurization:
stopping conveying methane into the sludge-water mixture in the reaction zone (6), continuously conveying the methane into the sludge-water mixture in the reaction zone (6) through the aeration pipe (8), continuously conveying the sewage into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), and operating for 40 days to realize synchronous coupling of sewage denitrification and methane desulfurization; and after the 41 th day, continuously conveying the marsh gas and the sewage into the mud-water mixture in the reaction zone (6) for marsh gas desulfurization and sewage denitrification, thus completing the process.
The principle of the invention is as follows: the invention adds an aeration pipe (8) on the basis of the existing gas stripping type EGSB reactor, inputs methane and biogas into a reaction zone (6) by utilizing the aeration pipe (8) in an aeration mode, and maintains the temperature required by the reaction by utilizing a temperature control system (4) arranged on the outer wall of the reaction zone (6).
The first step is an anaerobic oxidation starting stage of methane with nitrite as a substrate, the running time is 230 days totally, the second step is a synchronous coupling stage of sewage denitrification and methane desulfurization, the synchronous coupling of the sewage denitrification and the methane desulfurization is realized after the running for 40 days, and the sewage denitrification and the methane desulfurization are continuously carried out after the 41 th day; the anaerobic oxidation starting stage of methane using nitrite as a substrate and the synchronous coupling stage of sewage denitrification and biogas desulfurization need to continuously inject sewage into a reaction zone (6) of the gas stripping type EGSB reactor through a water inlet pipe (9), the treated sewage is discharged from an overflow weir of the gas stripping type EGSB reactor, and the purified biogas is discharged from a gas separation zone of the gas stripping type EGSB reactor.
In the anaerobic oxidation starting stage of methane with nitrite as a substrate, firstly, taking nitrite as an electron acceptor, taking methane as a simple electron donor, carrying out acclimatization culture on methane denitrifying bacteria in an atmosphere containing methane, and simultaneously carrying out sewage denitrification; after the reactor operates stably, when the denitrification efficiency reaches a higher level, the reactor enters a synchronous coupling stage of sewage denitrification and methane desulfurization, methane containing hydrogen sulfide is introduced into the stage, the hydrogen sulfide is used as an electron donor to provide a good environment for the growth of autotrophic denitrifying bacteria, so that the two stages are coupled, and the coupled anaerobic methane oxidizing bacteria and the autotrophic denitrifying bacteria coexist and play a role together, thereby realizing sewage denitrification and methane desulfurization; nitrite is a nitrogen source in the synchronous coupling stage of sewage denitrification and biogas desulfurization, and the nitrite reacts with methane and hydrogen sulfide to generate nitrogen, carbon dioxide and sulfate; the nitrite is obtained from sewage or partial oxidation of sewage.
The invention has the beneficial effects that:
the invention combines autotrophic denitrification and denitrification type anaerobic methane oxidation processes, takes nitrite as an electron acceptor, realizes methane desulfurization and strengthens the denitrification process of sewage, and partial nitrification is adopted in the nitrification process, namely, a part of oxygen is provided, so that ammonia nitrogen is converted into nitrite nitrogen without excessive oxidation, resources are greatly saved, and the influence of greenhouse gas methane can be reduced.
The traditional activated sludge method utilizes an organic carbon source to denitrify, for example, a sewage plant generally needs to add a carbon source such as sodium acetate or methanol behind a nitrification tank to change methanol or acetate into carbon dioxide and change nitrogen-containing pollutants into nitrogen; the method utilizes the effect of replacing a carbon source by methane and hydrogen sulfide, namely, the method only introduces methane without adding an external carbon source, and utilizes the methane and the hydrogen sulfide in the methane to remove nitrogen-containing pollutants, so that the methane is changed into carbon dioxide, the nitrite is changed into nitrogen, and the hydrogen sulfide is changed into sulfate, thereby saving the cost. The invention can ensure the high-efficiency denitrification of the sewage on the basis of not adding carbon sources, can realize the desulfurization and purification of the methane, and has the highest denitrification and desulfurization efficiency reaching 100 percent.
Drawings
FIG. 1 is a schematic structural diagram of a gas stripping EGSB reactor, in which FIG. 1 is an overflow weir, 2 is a gas separation zone, 3 is a sludge settling zone, 4 is a temperature control system, 5 is a sampling port, 6 is a reaction zone, 8 is an aeration pipe, 9 is a water inlet pipe, 10 is an internal reflux pipe, and 11 is a water outlet pipe;
FIG. 2 is a graph showing the effect of the operation of the process in example 1, wherein
Represents the concentration of nitrite in the feed water; o represents the effluent nitrite concentration; tangle-solidup represents the yield of sulfate;
FIG. 3 is a graph showing the main pollutant removal efficiency and the change in hydraulic retention time in example 1, wherein Δ represents the nitrite removal efficiency; x represents the removal efficiency of hydrogen sulfide; and a is a hydraulic retention time change curve.
The specific implementation mode is as follows:
the technical scheme of the invention is not limited to the specific embodiments listed below, and any reasonable combination of the specific embodiments is included.
The first embodiment is as follows: referring to fig. 1, the present embodiment is described, which is a method for synchronously enhancing sewage denitrification by biogas purification using nitrite as an electron acceptor, and is characterized in that: the method comprises the following steps:
step one, starting the anaerobic oxidation of methane by taking nitrite as a substrate:
continuously injecting sewage into a reaction zone (6) of the gas stripping type EGSB reactor from a water inlet pipe (9), sieving secondary sedimentation tank sludge of a common sewage treatment plant to be used as inoculation sludge, inoculating the inoculation sludge into the reaction zone (6) of the gas stripping type EGSB reactor to form a sludge-water mixture, injecting nitrite and nutrient elements into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), continuously conveying methane into the sludge-water mixture in the reaction zone (6) through an aeration pipe (8), and operating for at least 230 days to finish starting;
step two, synchronously coupling sewage denitrification and biogas desulfurization:
stopping conveying methane into the sludge-water mixture in the reaction zone (6), continuously conveying the methane into the sludge-water mixture in the reaction zone (6) through the aeration pipe (8), continuously conveying the sewage into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), and operating for 40 days to realize synchronous coupling of sewage denitrification and methane desulfurization; and after the 41 th day, continuously conveying the marsh gas and the sewage into the mud-water mixture in the reaction zone (6) for marsh gas desulfurization and sewage denitrification, thus completing the process.
The principle and the beneficial effects of the implementation mode are as follows:
in the embodiment, an aeration pipe (8) is added on the basis of the existing gas stripping type EGSB reactor, methane and methane are input into a reaction zone (6) by the aeration pipe (8) in an aeration mode, and the temperature required by the reaction is maintained by a temperature control system (4) arranged on the outer wall of the reaction zone (6).
The first step is an anaerobic oxidation starting stage of methane with nitrite as a substrate, the running time is 230 days totally, the second step is a synchronous coupling stage of sewage denitrification and methane desulfurization, the synchronous coupling of the sewage denitrification and the methane desulfurization is realized after the running for 40 days, and the sewage denitrification and the methane desulfurization are continuously carried out after the 41 th day; the anaerobic oxidation starting stage of methane using nitrite as a substrate and the synchronous coupling stage of sewage denitrification and biogas desulfurization need to continuously inject sewage into a reaction zone (6) of the gas stripping type EGSB reactor through a water inlet pipe (9), the treated sewage is discharged from an overflow weir of the gas stripping type EGSB reactor, and the purified biogas is discharged from a gas separation zone of the gas stripping type EGSB reactor.
In the anaerobic oxidation starting stage of methane with nitrite as a substrate, firstly, taking nitrite as an electron acceptor, taking methane as a simple electron donor, carrying out acclimatization culture on methane denitrifying bacteria in an atmosphere containing methane, and simultaneously carrying out sewage denitrification; after the reactor operates stably, when the denitrification efficiency reaches a higher level, the reactor enters a synchronous coupling stage of sewage denitrification and methane desulfurization, methane containing hydrogen sulfide is introduced into the stage, the hydrogen sulfide is used as an electron donor to provide a good environment for the growth of autotrophic denitrifying bacteria, so that the two stages are coupled, and the coupled anaerobic methane oxidizing bacteria and the autotrophic denitrifying bacteria coexist and play a role together, thereby realizing sewage denitrification and methane desulfurization; nitrite is a nitrogen source in the synchronous coupling stage of sewage denitrification and biogas desulfurization, and the nitrite reacts with methane and hydrogen sulfide to generate nitrogen, carbon dioxide and sulfate; the nitrite is obtained from sewage or partial oxidation of sewage.
The embodiment combines autotrophic denitrification and denitrification type anaerobic methane oxidation processes, uses nitrite as an electron acceptor, realizes methane desulfurization and strengthens the denitrification process of sewage, and partial nitrification is adopted in the nitrification process, namely, a part of oxygen is provided, so that ammonia nitrogen is converted into nitrite nitrogen without excessive oxidation, resources are greatly saved, and the influence of greenhouse gas methane can be reduced.
The traditional activated sludge method utilizes an organic carbon source to denitrify, for example, a sewage plant generally needs to add a carbon source such as sodium acetate or methanol behind a nitrification tank to change methanol or acetate into carbon dioxide and change nitrogen-containing pollutants into nitrogen; the embodiment utilizes the effect of replacing a carbon source by methane and hydrogen sulfide, namely, no additional carbon source is added, only methane is introduced, and the nitrogen-containing pollutants are removed by utilizing the methane and the hydrogen sulfide in the methane, so that the methane is changed into carbon dioxide, the nitrite is changed into nitrogen, and the hydrogen sulfide is changed into sulfate, thereby saving the cost. The embodiment can ensure the efficient denitrification of the sewage on the basis of not adding carbon sources, can realize the desulfurization and purification of the methane, and has the highest denitrification and desulfurization efficiency reaching 100 percent.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: in the stage of starting the anaerobic oxidation of methane by taking nitrite as a substrate, the hydraulic retention time of 187 days before operation is 4-8 days, and the hydraulic retention time of 188-230 days after operation is 7-15 days. Other steps and parameters are the same as in the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: step one, the reflux ratio of the methane anaerobic oxidation starting stage with nitrite as a substrate is (5-10): 1. other steps and parameters are the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: step one, the reaction temperature of the methane anaerobic oxidation starting stage with nitrite as a substrate is 30-40 ℃. Other steps and parameters are the same as in one of the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: firstly, nutrient elements in the reaction zone (6) comprise potassium dihydrogen phosphate, calcium chloride dihydrate, magnesium sulfate heptahydrate, sodium bicarbonate, acid trace element concentrated solution and alkaline trace element concentrated solution; the acid microelement concentrated solution contains one or more of ferrous sulfate heptahydrate, zinc sulfate heptahydrate, cobalt chloride hexahydrate, manganese chloride tetrahydrate, copper sulfate pentahydrate, nickel chloride hexahydrate, boric acid and hydrochloric acid; the alkaline microelement concentrate contains one or more of sodium hydroxide, sodium tungstate dihydrate, sodium molybdate and selenium dioxide. Other steps and parameters are the same as in one of the first to fourth embodiments.
The sixth specific implementation mode: the fifth embodiment is different from the fifth embodiment in that: in the first step, the concentration of the potassium dihydrogen phosphate in the reaction zone (6) is 60-80 mg/L, the concentration of the calcium chloride dihydrate is 250-350 mg/L, the concentration of the magnesium sulfate heptahydrate is 150-300 mg/L, the concentration of the sodium bicarbonate is 800-1200 mg/L, the concentration of the acidic trace element concentrated solution is 0.5mL/L, and the concentration of the alkaline trace element concentrated solution is 0.2 mL/L;
the concentration of ferrous sulfate heptahydrate, the concentration of zinc sulfate heptahydrate, the concentration of cobalt chloride hexahydrate, the concentration of manganese chloride tetrahydrate, the concentration of copper sulfate pentahydrate, the concentration of nickel chloride hexahydrate, the concentration of boric acid and the concentration of hydrochloric acid in the acid trace element concentrated solution are respectively 2.085g/L, 0.068g/L, 0.12g/L, 0.5g/L, 0.32g/L, 0.095g/L and 100mmol/L, respectively;
the concentration of sodium hydroxide in the alkaline microelement concentrate is 0.4g/L, the concentration of sodium tungstate dihydrate is 0.05g/L, the concentration of sodium molybdate is 0.242g/L, and the concentration of selenium dioxide is 0.067 g/L. Other steps and parameters are the same as those in the fifth embodiment.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: in the stage of synchronously coupling the sewage denitrification and the biogas desulfurization, the reflux ratio of the sewage denitrification and the biogas desulfurization in the first 40 days of operation is (5-10): 1, the reflux ratio after the 41 th day of operation is (100-300): 1. other steps and parameters are the same as in one of the first to sixth embodiments. The reflux ratio is improved in the synchronous coupling stage of sewage denitrification and methane desulfurization so as to increase the ascending flow velocity and make the back mixing of the reaction zone more uniform.
The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: and in the stage of synchronously coupling the sewage denitrification and the biogas desulfurization, the hydraulic retention time of the first 84 days of operation is 7-15 days, and the hydraulic retention time of the second 85 days of operation is 4-8 days. Other steps and parameters are the same as in one of the first to seventh embodiments.
The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: the sewage in the first step and the second step is sewage with low carbon-nitrogen ratio, and the carbon-nitrogen ratio is less than 5/8. Other steps and parameters are the same as in one of the first to eighth embodiments.
The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: in the stage of starting the anaerobic oxidation of methane by using nitrite as a substrate, the concentration of nitrite in the sewage is 100-150 mgN/L in 0-84 days of operation, and the concentration of nitrite in the sewage is 30-100 mgN/L in 85-230 days. Other steps and parameters are the same as in one of the first to ninth embodiments.
The concrete implementation mode eleven: the present embodiment differs from one of the first to tenth embodiments in that: and in the stage of synchronously coupling the sewage denitrification and the methane desulfurization, the concentration of nitrite in the sewage is 50-100 mgN/L. Other steps and parameters are the same as in one of the first to ninth embodiments.
The specific implementation mode twelve: this embodiment is different from one of the first to eleventh embodiments in that: and step two, the reaction temperature of the sewage denitrification and biogas desulfurization synchronous coupling stage is 30-40 ℃. The other steps and parameters are the same as in one of the embodiments one to eleven.
The specific implementation mode is thirteen: the present embodiment differs from the first to twelfth embodiments in that: and step one, adopting a 30-50 mesh sieve during sieving. Other steps and parameters are the same as in one to twelve of the embodiments.
The specific implementation mode is fourteen: the present embodiment is different from one to thirteen embodiments in that: in the first step, the gas inlet rate of the methane is 7.5-8.5 mL/min. Other steps and parameters are the same as in one to thirteen embodiments.
The concrete implementation mode is fifteen: the present embodiment is different from the first to the fourteenth embodiment in that: the purity of the methane in the first step is 99.99%. Other steps and parameters are the same as in one to fourteen embodiments.
The specific implementation mode is sixteen: the present embodiment differs from one of the first to fifteenth embodiments in that: and step two, the gas inlet rate of the biogas is 5-10 mL/min. Other steps and parameters are the same as in one of the first to fifteenth embodiments.
The beneficial effects of the invention are verified from the following examples:
example 1:
the embodiment is a method for synchronously enhancing sewage denitrification by biogas purification with nitrite as an electron acceptor, which is characterized by comprising the following steps: the method comprises the following steps:
step one, starting the anaerobic oxidation of methane by taking nitrite as a substrate:
continuously injecting sewage into a reaction zone (6) of the gas stripping type EGSB reactor from a water inlet pipe (9), sieving secondary sedimentation tank sludge of a common sewage treatment plant to be used as inoculation sludge, inoculating the inoculation sludge into the reaction zone (6) of the gas stripping type EGSB reactor to form a sludge-water mixture, injecting nitrite and nutrient elements into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), continuously conveying methane into the sludge-water mixture in the reaction zone (6) through an aeration pipe (8), and operating for 230 days to finish starting;
step one, in the stage of starting the anaerobic oxidation of methane by taking nitrite as a substrate, the hydraulic retention time of 187 days before operation is 5 days, and the hydraulic retention time of 188-230 days after operation is 10 days;
step one, the reflux ratio of the anaerobic oxidation starting stage of the methane using the nitrite as the substrate is 6: 1;
step one, the reaction temperature of the anaerobic oxidation starting stage of the methane using the nitrite as the substrate is 35 ℃.
Firstly, the nutrient elements in the reaction zone (6) are potassium dihydrogen phosphate, calcium chloride dihydrate, magnesium sulfate heptahydrate, sodium bicarbonate, acid trace element concentrated solution and alkaline trace element concentrated solution; the concentrated solution of the acid trace elements contains ferrous sulfate heptahydrate, zinc sulfate heptahydrate, cobalt chloride hexahydrate, manganese chloride tetrahydrate, copper sulfate pentahydrate, nickel chloride hexahydrate, boric acid and hydrochloric acid; the alkaline microelement concentrated solution contains sodium hydroxide, sodium tungstate dihydrate, sodium molybdate and selenium dioxide;
in the first step, the concentration of the potassium dihydrogen phosphate in the reaction zone (6) is 70mg/L, the concentration of the calcium chloride dihydrate is 300mg/L, the concentration of the magnesium sulfate heptahydrate is 200mg/L, the concentration of the sodium bicarbonate is 1050mg/L, the concentration of the acidic trace element concentrated solution is 0.5mL/L, and the concentration of the alkaline trace element concentrated solution is 0.2 mL/L;
the concentration of ferrous sulfate heptahydrate, the concentration of zinc sulfate heptahydrate, the concentration of cobalt chloride hexahydrate, the concentration of manganese chloride tetrahydrate, the concentration of copper sulfate pentahydrate, the concentration of nickel chloride hexahydrate, the concentration of boric acid and the concentration of hydrochloric acid in the acid trace element concentrated solution are respectively 2.085g/L, 0.068g/L, 0.12g/L, 0.5g/L, 0.32g/L, 0.095g/L and 100mmol/L, respectively; the concentration of sodium hydroxide in the alkaline microelement concentrated solution is 0.4g/L, the concentration of sodium tungstate dihydrate is 0.05g/L, the concentration of sodium molybdate is 0.242g/L, and the concentration of selenium dioxide is 0.067 g/L;
step one, the sewage is sewage with low carbon-nitrogen ratio, and the carbon-nitrogen ratio is less than 5/8;
in the stage of starting the anaerobic oxidation of methane by using nitrite as a substrate, the concentration of nitrite in the sewage is 100mgN/L in 0 th to 40 th days of operation, the concentration of nitrite in the sewage is 150mgN/L in 41 th to 84 th days of operation, the concentration of nitrite in the sewage is 100mgN/L in 85 th to 202 th days of operation, and the concentration of nitrite in the sewage is 50mgN/L in 202 th to 230 th days of operation;
step one, a 40-mesh sieve is adopted during sieving;
the gas inlet rate of the methane in the first step is 8 mL/min;
in the first step, the purity of the methane is 99.99 percent;
step two, synchronously coupling sewage denitrification and biogas desulfurization:
stopping conveying methane into the sludge-water mixture in the reaction zone (6), continuously conveying the methane into the sludge-water mixture in the reaction zone (6) through the aeration pipe (8), continuously conveying the sewage into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), and operating for 40 days to realize synchronous coupling of sewage denitrification and methane desulfurization; after the 41 th day, continuously conveying the biogas and the sewage into the mud-water mixture in the reaction area (6) for biogas desulfurization and sewage denitrification to finish;
in the stage of synchronously coupling the sewage denitrification and the biogas desulfurization, the reflux ratio of the sewage denitrification and the biogas desulfurization in the first 40 days is 6: 1, reflux ratio after 41 days of operation 160: 1; the reflux ratio is improved in the synchronous coupling stage of sewage denitrification and methane desulfurization so as to increase the ascending flow velocity and make the back mixing of the reaction zone more uniform;
in the stage of synchronously coupling the sewage denitrification and the biogas desulfurization, the hydraulic retention time of the first 84 days of operation is 10 days, and the hydraulic retention time of the second 85 days of operation is 5 days;
step two, the sewage is sewage with low carbon-nitrogen ratio, and the carbon-nitrogen ratio is less than 5/8;
in the stage of synchronously coupling the sewage denitrification and the biogas desulfurization, the concentration of nitrite in the sewage is 50mgN/L in 231 th to 248 th days of operation, the concentration of nitrite in the sewage is 100mgN/L in 249 th to 380 th days of operation,
step two, the reaction temperature of the sewage denitrification and biogas desulfurization synchronous coupling stage is 35 ℃;
the gas inlet speed of the biogas in the step two is 8 mL/min;
1. in the embodiment, an aeration pipe (8) is added on the basis of the existing gas stripping type EGSB reactor, methane and methane are input into a reaction zone (6) by the aeration pipe (8) in an aeration mode, and the temperature required by the reaction is maintained by a temperature control system (4) arranged on the outer wall of the reaction zone (6). 2. The embodiment combines autotrophic denitrification and denitrification type anaerobic methane oxidation processes, uses nitrite as an electron acceptor, realizes methane desulfurization and strengthens the denitrification process of sewage, and partial nitrification is adopted in the nitrification process, namely, a part of oxygen is provided, so that ammonia nitrogen is converted into nitrite nitrogen without excessive oxidation, resources are greatly saved, and the influence of greenhouse gas methane can be reduced. 3. The traditional activated sludge method utilizes an organic carbon source to denitrify, for example, a sewage plant generally needs to add a carbon source such as sodium acetate or methanol behind a nitrification tank to change methanol or acetate into carbon dioxide and change nitrogen-containing pollutants into nitrogen; the embodiment utilizes methane to replace the carbon source, does not add extra carbon source promptly, just lets in methane, utilizes methane to carry out the desorption to the nitrogenous pollutant for methane becomes carbon dioxide, and nitrite becomes nitrogen gas, consequently can practice thrift the cost. The embodiment can ensure the high-efficiency denitrification of the sewage on the basis of not adding carbon sources, can realize the desulfurization and purification of the methane, and has the highest denitrification and desulfurization efficiency reaching 100 percent.
FIG. 2 is a graph showing the effect of the operation of the process in example 1, wherein
Represents the concentration of nitrite in the feed water; o represents the effluent nitrite concentration; tangle-solidup represents the yield of sulfate; the operation of the process of the embodiment is divided into two stages, the start stage of anaerobic methane oxidation with nitrite as a substrate is 0-230 days, 0-84 days in the start stage are the internal carbon source removal part, and the synchronous coupling stage of sewage denitrification and biogas desulfurization is 231-380 days. Before the reactor is started, the concentration of nitrite is 100mgN/L, in the internal carbon source removing part of the initial starting stage, the concentration of nitrite in effluent is 0, because sludge contains internal carbon source substances, the concentration is increased to 150mgN/L, the concentration of nitrite in effluent is increased firstly and then reduced, the removal rate also shows the trend of decreasing firstly and then increasing, which shows that the action of the internal carbon source is gradually weakened, and the anaerobic methane oxidation process is gradually strengthened. And then, after the concentration of nitrite in the inlet water is reduced to 100mgN/L, the nitrite content in the outlet water tends to be stable and is about half of the original concentration, and because the generation period of the methane anaerobic oxidizing bacteria is longer, the removal efficiency of the nitrite is gradually enhanced by carrying out acclimatization culture for a longer time. After the nitrite concentration in the inlet water is reduced to 50mgN/L again, the nitrite concentration in the outlet water is reduced again, and then the second stage is carried out. In the second stage, the original 99.99% pure methane was replaced with a simulated biogas containing 75% methane, 0.3% hydrogen sulfide and 24.7% carbon dioxide. As can be seen from FIG. 1, in the second stage, after the hydrogen sulfide is introduced, the amount of sulfate produced is gradually increased, which indicates that the autotrophic denitrification process plays a role in the system, and the effect of denitrification by using the hydrogen sulfide as an electron donor is more remarkable. After the concentration is increased to 100mgN/L again, the nitrite concentration of the effluent is still lower, and the nitrite removal efficiency is higher compared with that under the same condition before the introduction of hydrogen sulfide.
FIG. 3 is a graph showing the main pollutant removal efficiency and the change in hydraulic retention time in example 1, wherein Δ represents the nitrite removal efficiency; x represents the removal efficiency of hydrogen sulfide; and a is a hydraulic retention time change curve. As can be seen from fig. 3, the removal efficiency of hydrogen sulfide after the second stage can reach 100%, and the concentration of hydrogen sulfide in the tail gas is lower than the detection limit (13 ppm). Therefore, the coupling system can purify the methane and enhance denitrification by taking nitrite as an electron acceptor under the condition of no external carbon source. The nitrite removal efficiency remained 100% after the second stage, which remained 100% even when the feed water concentration was increased to 100mgN/L, and was reduced after the hydraulic retention time was subsequently changed to 5 days.
Claims (12)
1. A method for synchronously enhancing sewage denitrification by biogas purification with nitrite as an electron acceptor is characterized by comprising the following steps: the method comprises the following steps:
step one, starting the anaerobic oxidation of methane by taking nitrite as a substrate:
continuously injecting sewage into a reaction zone (6) of the gas stripping type EGSB reactor from a water inlet pipe (9), sieving secondary sedimentation tank sludge of a common sewage treatment plant to be used as inoculation sludge, inoculating the inoculation sludge into the reaction zone (6) of the gas stripping type EGSB reactor to form a sludge-water mixture, injecting nitrite and nutrient elements into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), continuously conveying methane into the sludge-water mixture in the reaction zone (6) through an aeration pipe (8), and running for at least 230 days to finish starting;
step two, synchronously coupling sewage denitrification and biogas desulfurization:
stopping conveying methane into the sludge-water mixture in the reaction zone (6), continuously conveying the methane into the sludge-water mixture in the reaction zone (6) through the aeration pipe (8), continuously conveying the sewage into the sludge-water mixture in the reaction zone (6) from the water inlet pipe (9), and operating for 40 days to realize synchronous coupling of sewage denitrification and methane desulfurization; after the 41 th day, continuously conveying the biogas and the sewage into the mud-water mixture in the reaction zone (6), and finishing;
partial nitrification is adopted in the nitrification process.
2. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: in the stage of starting the anaerobic oxidation of methane by taking nitrite as a substrate, the hydraulic retention time of 187 days before operation is 4-8 days, and the hydraulic retention time of 188-230 days after operation is 7-15 days.
3. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: step one, the reflux ratio of the methane anaerobic oxidation starting stage with nitrite as a substrate is (5-10): 1.
4. the method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: step one, the reaction temperature of the methane anaerobic oxidation starting stage with nitrite as a substrate is 30-40 ℃.
5. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: firstly, nutrient elements in the reaction zone (6) comprise potassium dihydrogen phosphate, calcium chloride dihydrate, magnesium sulfate heptahydrate, sodium bicarbonate, acid trace element concentrated solution and alkaline trace element concentrated solution; the acid microelement concentrated solution contains one or more of ferrous sulfate heptahydrate, zinc sulfate heptahydrate, cobalt chloride hexahydrate, manganese chloride tetrahydrate, copper sulfate pentahydrate, nickel chloride hexahydrate, boric acid and hydrochloric acid; the alkaline microelement concentrate contains one or more of sodium hydroxide, sodium tungstate dihydrate, sodium molybdate and selenium dioxide.
6. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production system as claimed in claim 5, wherein: in the first step, the concentration of the potassium dihydrogen phosphate in the reaction zone (6) is 60-80 mg/L, the concentration of the calcium chloride dihydrate is 250-350 mg/L, the concentration of the magnesium sulfate heptahydrate is 150-300 mg/L, the concentration of the sodium bicarbonate is 800-1200 mg/L, the concentration of the acidic trace element concentrated solution is 0.5mL/L, and the concentration of the alkaline trace element concentrated solution is 0.2 mL/L;
the concentration of ferrous sulfate heptahydrate, the concentration of zinc sulfate heptahydrate, the concentration of cobalt chloride hexahydrate, the concentration of manganese chloride tetrahydrate, the concentration of copper sulfate pentahydrate, the concentration of nickel chloride hexahydrate, the concentration of boric acid and the concentration of hydrochloric acid in the acid trace element concentrated solution are respectively 2.085g/L, 0.068g/L, 0.12g/L, 0.5g/L, 0.32g/L, 0.095g/L and 100mmol/L, respectively;
the concentration of sodium hydroxide in the alkaline microelement concentrate is 0.4g/L, the concentration of sodium tungstate dihydrate is 0.05g/L, the concentration of sodium molybdate is 0.242g/L, and the concentration of selenium dioxide is 0.067 g/L.
7. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: in the stage of synchronously coupling the sewage denitrification and the biogas desulfurization, the reflux ratio of the sewage denitrification and the biogas desulfurization in the first 40 days of operation is (5-10): 1, the reflux ratio after the 41 th day of operation is (100-300): 1.
8. the method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: and in the stage of synchronously coupling the sewage denitrification and the biogas desulfurization, the hydraulic retention time of the first 84 days of operation is 7-15 days, and the hydraulic retention time of the second 85 days of operation is 4-8 days.
9. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: the sewage in the first step and the second step is sewage with low carbon-nitrogen ratio, and the carbon-nitrogen ratio is less than 5/8.
10. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: in the stage of starting the anaerobic oxidation of methane by using nitrite as a substrate, the concentration of nitrite in the sewage is 100-150 mgN/L in 0-84 days of operation, and the concentration of nitrite in the sewage is 30-100 mgN/L in 85-230 days of operation.
11. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: and in the stage of synchronously coupling the sewage denitrification and the methane desulfurization, the concentration of nitrite in the sewage is 50-100 mgN/L.
12. The method for synchronously purifying and enhancing sewage denitrification by using nitrite as an electron acceptor in the biogas production process as claimed in claim 1, wherein: and step two, the reaction temperature of the sewage denitrification and biogas desulfurization synchronous coupling stage is 30-40 ℃.
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