A method and system for efficient denitrification and n2o recovery from sewage

Abstract

The present application relates to sewage treatment and resource recycling technical field, disclose a kind of wastewater efficient denitrification and N2O recovery method and system.The method is carried out in the system including ammonia nitrogen ion exchange regeneration unit, short nitrification unit, incomplete denitrification unit and N2O gas stripping unit.Based on the combined process of short nitrification-incomplete denitrification, by coupling ammonia nitrogen ion exchange regeneration and N2O gas stripping technology, the method provided by the present application realizes the enrichment and recovery of N2O in the side stream simultaneously with the main stream separation denitrification, and can reuse the regeneration liquid and improve the regeneration efficiency of ion exchanger, finally realizes the zero discharge of side stream system wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment and resource recovery, and particularly relates to a method and system for efficient denitrification and N2O recovery of sewage. BACKGROUND

[0002] The nitrogen recovered from sewage is not only one of the important ways to reduce the emission of nitrogen-containing pollutants and control water eutrophication, but also can provide various nitrogen-containing products for industrial and agricultural production, directly serving the social nitrogen cycle. At present, there are related reports on the technology and process for recovering nitrogen from domestic sewage, and the main recovered products include nitrate and struvite, etc. However, considering the difficulty of subsequent salting-out and purification of nitrate and the cost of reagent addition of struvite, the two types of conventional recovered products cannot realize the high-value recovery of nitrogen.

[0003] On the one hand, in the process of biological denitrification or nitrogen conversion of sewage, N2O is a typical intermediate product, and its greenhouse effect potential is 256 times that of CO2. The carbon emission caused by the release of N2O in sewage treatment accounts for 83% of the total emission of sewage treatment plants, and the N2O released in the process of microbial denitrification accounts for more than 90% of the total amount of N2O in the atmosphere. Therefore, the recovery of N2O is conducive to reducing the generation of greenhouse gases. On the other hand, N2O is a potential renewable energy and a more powerful oxidant than oxygen. The energy generated by the complete combustion of N2O and methane (1219 kJ / mol) is 1.3 times that of oxygen and methane (890 kJ / mol). N2O is easier to store than other oxidants, and its decomposition products are harmless nitrogen and oxygen, and is often used as a combustion aid for cars and a strong oxidant for hybrid rockets. Therefore, the recovery of nitrogen in the form of N2O from sewage has obvious economic benefits.

[0004] At present, the process of realizing N2O enrichment and recovery by biological method still has certain limitations. First, in order to maintain a high level of N2O conversion rate, high-concentration nitrogen sources (NO3-N, NO2-N and NO, etc.) are usually needed as reaction substrates, and inhibitors (such as free nitrous acid) are also needed to prevent further reduction of N2O. However, the ammonia nitrogen concentration of the influent of the municipal sewage plant is usually 20-60 mg N / L, which is far lower than the feasible range (500-1100 mg N / L) of N2O high-efficiency production and recovery technology. Therefore, the free nitrous acid concentration produced by direct short-cut nitrification of low-concentration nitrogen source in municipal sewage is usually lower than 0.005 mg N / L, and the pH value needs to be controlled below 6.0 to achieve good inhibition effect (free nitrous acid > 0.1 mg N / L). However, this pH value range will affect the activity of denitrifying bacteria, reduce the production of N2O, and also affect the purity of N2O, increasing the recovery cost. Finally, N2O dissolved in the sludge mixture is difficult to be directly recovered and utilized, and has biological toxicity, which affects the long-term operation of the N2O enrichment and recovery device.

[0005] Based on this, it is of great significance to provide a method and device which neither need high-concentration nitrogen source as reaction substrate nor benefit N2O enrichment recovery. SUMMARY

[0006] The purpose of the present application is to overcome the problems in the prior art that the process of N2O enrichment recovery needs high-concentration nitrogen source as reaction substrate, N2O dissolved in sludge mixed liquor is difficult to be directly recovered and utilized, and has biological toxicity, affecting the long-term operation of the N2O enrichment recovery device.

[0007] To achieve the above-mentioned purpose, the first aspect of the present application provides a method for efficient denitrification and N2O recovery of sewage, which is carried out in a system comprising an ammonia nitrogen ion exchange regeneration unit, a short-cut nitrification unit, an incomplete denitrification unit and an N2O stripping unit, comprising:

[0008] (1) introducing domestic sewage after coagulation and sedimentation into the ammonia nitrogen ion exchange regeneration unit for ion exchange to obtain main stream ion exchange effluent, and using regeneration liquid I to backwash the ion exchange column used in the ion exchange to obtain ammonia nitrogen-containing backwash water;

[0009] (2) introducing the ammonia nitrogen-containing backwash water into the short-cut nitrification unit for short-cut nitrification to obtain nitrosation effluent;

[0010] (3) introducing a part of the nitrosation effluent into the incomplete denitrification unit for incomplete denitrification to obtain gas I and incomplete denitrification effluent;

[0011] (4) introducing the incomplete denitrification effluent into the N2O stripping unit for stripping to obtain gas II and regeneration liquid II;

[0012] (5) backflowing the gas II to the incomplete denitrification unit for aeration of the incomplete denitrification;

[0013] (6) introducing another part of the nitrosation effluent and the regeneration liquid II into the ammonia nitrogen ion exchange regeneration unit together with the regeneration liquid I for the backwashing;

[0014] The water amount of the part of the nitrosation effluent is controlled so that the concentration of nitrite nitrogen in liquid phase stream I composed of the another part of the nitrosation effluent, the regeneration liquid II and the regeneration liquid I is 0.01-6.0 g N / L.

[0015] The second aspect of the present application provides a system for efficient denitrification and N2O recovery of sewage, which is used for applying the method of the first aspect and comprises an ammonia nitrogen ion exchange regeneration unit, a short-cut nitrification unit, an incomplete denitrification unit and an N2O stripping unit connected in sequence.

[0016] The ammonia-nitrogen ion exchange regeneration unit is used for ion exchange of the coagulation and sedimentation treated domestic sewage to obtain main stream ion exchange effluent, and is used for backwashing of the ion exchange column used in the ion exchange by using regeneration liquid I to obtain ammonia-nitrogen containing backwashing water;

[0017] The short-cut nitrification unit is used for short-cut nitrification of the ammonia-nitrogen containing backwashing water to obtain nitrosation effluent;

[0018] The incomplete denitrification unit is used for incomplete denitrification of the nitrosation effluent to obtain gas I and incomplete denitrification effluent, and is used for aeration by using gas II;

[0019] The N2O stripping unit is used for stripping of the incomplete denitrification effluent to obtain gas II and regeneration liquid II.

[0020] Compared with the prior art, the method and system provided by the application not only have high treatment efficiency, but also have at least the following advantages:

[0021] (1) The method provided by the application breaks through the bottleneck of efficient production of N2O from low nitrogen-containing wastewater by adopting main stream ammonia-nitrogen ion exchange regeneration coupled with side stream short-cut nitrification and concentration cycle;

[0022] The ammonia-nitrogen ion exchange regeneration unit can rapidly remove NH4 + -N from the main stream under short HRT, has the advantages of small occupation area and low NH4 + -N concentration in effluent; NH4 + -N in the regeneration liquid is converted into NO2 - -N in the regeneration liquid is converted into NO2 2- -O by short-cut nitrification, and NaNO2 is generated to continue to be used for regeneration of ion exchange materials, realizing nitrogen conversion and NO + Concentration phase coupling, while providing high concentration of free nitrous acid at a pH suitable for survival of denitrifying microorganisms (6.5-8.0) to provide necessary conditions for efficient production of N2O;

[0023] (2) The method provided by the application solves the problem that NH4 + -N regeneration liquid cannot be reused, and compared with the existing ammonia-nitrogen ion exchange regeneration process and main stream NH4 + -N recovery process, the application has the advantages of low ion exchange material regeneration cost, efficient nitrogen recovery, and finally realizes zero discharge of wastewater in the side stream system, in line with the concepts of circular economy and sustainable development;

[0024] (3) The method provided by the application adopts short-cut nitrification-incomplete denitrification-N2O stripping combined technology, and through incomplete denitrification, part of NO2- N is oriented to high-purity N2O product and is recovered; the hollow fiber membrane-based technology in N2O gas stripping can increase the N2O recovery rate to 90% compared with the traditional exposure recovery technology, and can reduce the purge gas demand by 70%, thereby increasing the N2O yield and further enhancing the incomplete denitrification process;

[0025] (4) Compared with the traditional biological denitrification and physical and chemical denitrification, the method provided by the application provides alkalinity for biological short-cut nitrification by adding carbonates and bicarbonates, and the acetic acid added in the incomplete denitrification stage can not only serve as a carbon source but also as an acidic substance to complement the alkaline generated by incomplete denitrification, so as to achieve acid-base balance, save the dosage of acid-base reagents, save the amount of carbon source and aeration energy consumption compared with the traditional complete nitrification-denitrification denitrification process, reduce the operation cost, and obtain high-value N2O product, and realize the high-value recovery process of nitrogen in wastewater;

[0026] (5) The gas after N2O stripping provided by the application can be directly used or purified by one or more of gradient cooling, pressure swing adsorption or alkali absorption. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a process flow diagram of a wastewater efficient denitrification and N2O recovery method provided by the application.

[0028] REFERENCE NUMERALS

[0029] 1, wastewater inlet pump; 2, coagulation sedimentation tank;

[0030] 3, stirrer; 4, dosing port;

[0031] 5, coagulation sedimentation outlet pump; 6, ammonia nitrogen ion exchange regeneration unit;

[0032] 7, main flow ion exchange outlet pump; 8, membrane-biological reactor;

[0033] 9, aeration pipe; 10, membrane module;

[0034] 11, outlet pump; 12, side flow nitritation inlet pump;

[0035] 13, short-cut nitrification unit; 14, oxygen aeration pipe;

[0036] 15, dosing port; 16, nitritation outlet diversion pump;

[0037] 17, incomplete denitrification inlet pump; 18, incomplete denitrification unit;

[0038] 19, self-circulation aeration pipe; 20, stirrer;

[0039] 21, dosing port; 22, gas collection port;

[0040] 23, hollow fiber membrane water inlet pump; 24, hollow fiber membrane contactor;

[0041] 25, safety valve; 26, hollow fiber membrane vacuum pump;

[0042] 27, vacuum gauge; 28, hollow fiber membrane water outlet pump;

[0043] 29, regenerated liquid backflow pump; 30, regenerated liquid storage barrel;

[0044] 31, regenerated liquid water inlet pump. DETAILED DESCRIPTION

[0045] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are provided as approximate descriptions of the ranges and are understood to be open-ended. Each range is a continuum of values between the upper and lower limits of that range and each intervening value. The endpoints of the ranges and any values are not provided to limit the described ranges and values. Each intervening value between the upper and lower limits of that range and each value within that range, to the extent that there are any, are equally

[0046] As described above, the present application provides a method for efficient nitrogen removal and N2O recovery from sewage, which is carried out in a system comprising an ammonia-nitrogen ion exchange regeneration unit, a partial nitrification unit, an incomplete denitrification unit, and an N2O stripping unit, comprising:

[0047] (1) introducing domestic sewage after coagulation and sedimentation into the ammonia-nitrogen ion exchange regeneration unit for ion exchange to obtain main stream ion exchange effluent, using regenerated liquid I to backwash the ion exchange column used in the ion exchange to obtain ammonia-nitrogen-containing backwash water;

[0048] (2) introducing the ammonia-nitrogen-containing backwash water into the partial nitrification unit for partial nitrification to obtain nitrosation effluent;

[0049] (3) introducing a portion of the nitrosation effluent into the incomplete denitrification unit for incomplete denitrification to obtain gas I and incomplete denitrification effluent;

[0050] (4) introducing the incomplete denitrification effluent into the N2O stripping unit for stripping to obtain gas II and regenerated liquid II;

[0051] (5) backflowing the gas II to the incomplete denitrification unit to aerate the incomplete denitrification;

[0052] (6) introducing another part of the nitrosation effluent and the regeneration liquid II into the ammonia ion exchange regeneration unit together with the regeneration liquid I to perform the backwashing;

[0053] controlling the water amount of the part of the nitrosation effluent so that the concentration of nitrite nitrogen in the liquid phase stream I composed of the other part of the nitrosation effluent, the regeneration liquid II and the regeneration liquid I is 0.01-6.0 g N / L.

[0054] Preferably, the content of N2O in the gas I and / or the gas II is 60-99 vol%.

[0055] Preferably, the method further comprises: performing the method in cycles, and through at least 2 cycles, so that the nitrite concentration of the incomplete denitrification is 0.5-4.0 g N / L.

[0056] Preferably, the pH of the incomplete denitrification is 6.5-7.5.

[0057] Preferably, based on the total water amount of the part of the nitrosation effluent and the other part of the nitrosation effluent, the water amount of the part of the nitrosation effluent accounts for 50-95 vol%, and the water amount of the other part of the nitrosation effluent accounts for 5-50 vol%. It is found that in this preferred case, sufficient nitrite for eluting NH4 + + on the ion exchange column in the upstream can be obtained, and further sufficient NH4 + -N is provided to ensure the progress of the nitrosation reaction, thereby facilitating the incomplete denitrification to obtain continuous and stable high-concentration NO2 - -N as a reaction substrate.

[0058] Preferably, in step (1), the regeneration liquid I is selected from at least one of sodium nitrite and other monovalent cation solutions, and

[0059] In the regeneration liquid I, the concentration of nitrite nitrogen is 0.01-6.0 g N / L.

[0060] Preferably, in step (1), the coagulant used in the coagulation sedimentation is selected from at least one of ferric chloride, aluminum sulfate, polyaluminum chloride and polyaluminum ferric sulfate.

[0061] Preferably, in step (1), the coagulant aid used in the coagulation sedimentation is selected from at least one of polyacrylamide and polydimethyl diallyl ammonium chloride.

[0062] Preferably, in step (1), an alkali is added in the coagulation sedimentation, and the alkali is sodium hydroxide and / or sodium bicarbonate.

[0063] Preferably, in step (1), the coagulation sedimentation is carried out in a coagulation sedimentation tank, and the hydraulic retention time of the liquid phase stream in the coagulation sedimentation tank is 0.1-2h.

[0064] Preferably, in step (1), the ion exchanger used in the ion exchange is selected from at least one of zeolite, molecular sieve, ion exchange resin.

[0065] Preferably, the ion exchange is carried out by using 4-6 ion exchange columns connected in parallel, and each ion exchange column is enabled according to actual conditions, so that the method of the present application can continuously treat the domestic sewage.

[0066] It should be noted that, in the present application, the operation mode of the ion exchange column is a conventional technical means in the art, which can be exemplarily up-in and down-out or down-in and up-out.

[0067] Preferably, in step (1), the ion exchange time is 6-12h.

[0068] It should be noted that, in the present application, the regeneration mode of the ion exchanger is a conventional technical means in the art, which can be exemplarily forward-flow regeneration or counter-flow regeneration.

[0069] Preferably, the backwashing time is 0.1-10.0h.

[0070] Preferably, the liquid phase stream I is heated or cooled so that the temperature of the liquid phase stream I is 15-50℃.

[0071] Preferably, the liquid phase stream I is first introduced into a regeneration liquid storage barrel and then introduced into the ammonia nitrogen ion exchange regeneration unit for the backwashing.

[0072] Preferably, the method of the present application further comprises, in step (1), subjecting the main stream ion exchange effluent to a membrane-biological reaction by using a membrane assembly to obtain a main stream effluent, and controlling the conditions of the membrane-biological reaction so that the water quality of the main stream effluent at least meets: ammonium nitrogen≤1.5mg / L, TN≤10mg / L, TP≤0.5mg / L, COD≤30mg / L.

[0073] Preferably, the material of the membrane assembly is selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, polysulfone.

[0074] Preferably, the membrane-biological reaction time is 4-15h.

[0075] According to a preferred embodiment, in step (2), the conditions of the short-cut nitrification at least satisfy: pH is 6.0-10.0, temperature is 15-40℃, dissolved oxygen concentration is 0.5-8 mg / L, and concentration of nitrite nitrogen is 100-6000 mg N / L. Research shows that, under the preferred conditions, when the influent of nitrite nitrogen is continuously and stably provided at 500-2000 mg N / L for incomplete denitrification, the conversion rate of N2O for the incomplete denitrification is more than 80%, and the N2O yield is stably at 0.8-1.5 mg N / h.

[0076] Preferably, in step (2), the concentration of ammonium nitrogen in the ammonia-nitrogen-containing backwash water is 25-1000 mg N / L.

[0077] Preferably, in step (2), carbonate and / or bicarbonate are added in the short-cut nitrification.

[0078] Preferably, the hydraulic retention time of the short-cut nitrification is 1-48 h.

[0079] Preferably, the sludge age in the short-cut nitrification is 10-150 d.

[0080] Preferably, the dissolved oxygen concentration of the incomplete denitrification is not more than 3.0 mg / L.

[0081] Preferably, in step (3), a carbon source is added in the incomplete denitrification.

[0082] More preferably, the carbon source is at least one selected from acetic acid, sodium acetate, sodium propionate, pyruvic acid, ethanol and fatty acid.

[0083] Further preferably, the carbon source is sodium acetate.

[0084] Preferably, in step (3), acetic acid and / or hydrochloric acid is used to adjust the pH to 6.0-8.0 in the incomplete denitrification.

[0085] Preferably, the gas stripping is performed using a hydrophobic polypropylene hollow fiber membrane, and

[0086] The porosity of the hydrophobic polypropylene hollow fiber membrane is 40-50%, and the inner diameter of the fiber is 100-300 μm.

[0087] Preferably, the membrane pore size of the hydrophobic polypropylene hollow fiber membrane is (0.1±0.02) μm.

[0088] Preferably, the number of the membrane filaments of the hydrophobic polypropylene hollow fiber membrane is 2000-2500.

[0089] As described above, the second aspect of the present application provides a system for efficient denitrification and N2O recovery of sewage, which is used for applying the method of the first aspect and comprises an ammonia-nitrogen ion exchange and regeneration unit, a short-cut nitrification unit, an incomplete denitrification unit and an N2O stripping unit connected in sequence.

[0090] The ammonia-nitrogen ion exchange and regeneration unit is used for ion exchange of the sewage after coagulation and sedimentation to obtain main stream ion exchange effluent, and is used for backwashing of an ion exchange column used in the ion exchange with regeneration liquid I to obtain ammonia-nitrogen-containing backwashing water.

[0091] The short-cut nitrification unit is used for short-cut nitrification of the ammonia-nitrogen-containing backwashing water to obtain nitrosation effluent.

[0092] The incomplete denitrification unit is used for incomplete denitrification of the nitrosation effluent to obtain gas I and incomplete denitrification effluent, and is used for aeration with gas II.

[0093] The N2O stripping unit is used for stripping of the incomplete denitrification effluent to obtain gas II and regeneration liquid II.

[0094] Preferably, the system of the present application further comprises a membrane assembly arranged downstream of the ammonia-nitrogen ion exchange and regeneration unit in the direction of liquid phase flow, which is used for membrane-biological reaction of the main stream ion exchange effluent to obtain main stream effluent, and the conditions of the membrane-biological reaction are controlled so that the water quality of the main stream effluent at least meets: ammonium nitrogen ≤ 1.5 mg / L, TN ≤ 10 mg / L, TP ≤ 0.5 mg / L, and COD ≤ 30 mg / L.

[0095] Preferably, the short-cut nitrification reactor is selected from at least one of a membrane-biological reactor, a moving bed biological membrane reactor, and an aerobic tank + sedimentation tank + membrane treatment reactor.

[0096] Preferably, the incomplete denitrification unit comprises an incomplete denitrification reactor, and the N2O stripping unit comprises a hollow fiber membrane contactor, and

[0097] The incomplete denitrification reactor is provided with an aeration pump, a stirrer, a gas collection port and a connection port of the hollow fiber membrane contactor.

[0098] Preferably, the hollow fiber membrane contactor is provided with a water inlet pump, a vacuum gauge, a vacuum pump and a gas valve.

[0099] The following will be described in combination with Figure 1 to provide a preferred embodiment, which comprises:

[0100] (1) the domestic sewage is introduced into the coagulation sedimentation tank 2 through the sewage inlet pump 1, coagulated and precipitated, and then introduced into the ammonia nitrogen ion exchange regeneration unit 6 through the coagulation sedimentation outlet pump 5 to perform ion exchange, so as to obtain main stream ion exchange effluent, and coagulants, coagulant aids and alkalis are added through the dosing port 4; the coagulation sedimentation tank 2 is provided with a stirrer 3 for stirring;

[0101] The ion exchange column used in the ion exchange is backwashed using the regeneration liquid I, and ammonia nitrogen-containing backwash water is obtained;

[0102] (2) the ammonia nitrogen-containing backwash water is introduced into the short-cut nitrification unit 13 through the side stream nitrosation inlet pump 12 to perform short-cut nitrification, so as to obtain nitrosation effluent; the short-cut nitrification unit 13 is provided with an oxygen aeration pipe 14 for aeration; carbonates and / or bicarbonates are added through the dosing port 15;

[0103] (3) a part of the nitrosation effluent is introduced into the incomplete denitrification unit 18 through the incomplete denitrification inlet pump 17 to perform incomplete denitrification, acetic acid and a carbon source are added from the dosing port 21, and mixing is performed using the stirrer 20, so as to obtain incomplete denitrification effluent, and gas I is collected through the gas collection port 22;

[0104] (4) the incomplete denitrification effluent is introduced into the N2O stripping unit's hollow fiber membrane contactor 24 through the hollow fiber membrane inlet pump 23, and gas stripping is performed using the hydrophobic polypropylene hollow fiber membrane therein, so as to obtain regeneration liquid II and gas II, and the safety valve 25 can perform emergency discharge;

[0105] (5) the gas II is returned to the incomplete denitrification unit 18 through the hollow fiber membrane vacuum pump 26 and is used to aerate the incomplete denitrification through the self-circulation aeration pipe 19; a vacuum gauge 27 is arranged downstream of the hollow fiber membrane vacuum pump 26 to maintain negative pressure and ensure stable flow of the gas II, and the running state of the vacuum fiber membrane is judged at the same time;

[0106] (6) another part of the nitrosation effluent from the nitrosation effluent diversion pump 16 and the regeneration liquid II from the hollow fiber membrane effluent pump 28 are pumped to the regeneration liquid storage barrel 30 using the regeneration liquid return pump 29, and then introduced into the ammonia nitrogen ion exchange regeneration unit 6 through the regeneration liquid inlet pump 31 to perform the backwashing together with the regeneration liquid I;

[0107] (7) the main stream ion exchange effluent is subjected to membrane-biological reaction using a membrane assembly, so as to obtain main stream effluent, including introducing the main stream ion exchange effluent into the membrane-biological reactor (MBR tank) 8 through the main stream ion exchange effluent pump 7, removing residual organic matter through the membrane assembly 10 to obtain the main stream effluent, and returning the main stream effluent to the main stream treatment system through the effluent pump 11; the membrane-biological reactor is provided with an aeration pipe 9.

[0108] The present application is described in detail below by way of examples, and the raw materials used in the examples are all commercially available unless otherwise specified.

[0109] Coagulant: polyaluminum chloride;

[0110] Coagulant aid: polyacrylamide;

[0111] Alkali: sodium hydroxide;

[0112] Carbonate: sodium bicarbonate;

[0113] Carbon source: sodium acetate;

[0114] Ion exchanger: zeolite, average volume diameter 1 mm;

[0115] Regeneration liquid I: sodium nitrite, concentration of nitrite nitrogen 2.0 g N / L;

[0116] The water quality parameters of the domestic sewage are shown in Table 1.

[0117] Membrane module: polyvinylidene fluoride;

[0118] Hydrophobic polypropylene hollow fiber membrane:

[0119] Hydrophobic polypropylene hollow fiber membrane I: porosity 40%, fiber inner diameter 100 μm, membrane pore size 0.1 μm, number of membrane fibers 2500;

[0120] Hydrophobic polypropylene hollow fiber membrane II: porosity 60%, fiber inner diameter 50 μm, membrane pore size 0.2 μm, number of membrane fibers 1500.

[0121] The following examples are carried out by the process shown in Figure 1 Table 3 unless otherwise specified, and the influent flow rate of the domestic sewage is 6 m 3 / h.

[0122] Example 1

[0123] This example is used to illustrate the method for efficient denitrification and N2O recovery of sewage provided by the present application, which is carried out according to the operation comprising the following steps and referring to the parameters in Table 2, and the method is carried out in a system comprising an ammonia nitrogen ion exchange regeneration unit, a short-cut nitrification unit, an incomplete denitrification unit and an N2O stripping unit, comprising:

[0124] (1) the domestic sewage is introduced into the coagulation sedimentation tank 2 through the sewage inlet pump 1, coagulated and precipitated, and then introduced into the ammonia nitrogen ion exchange regeneration unit 6 through the coagulation sedimentation outlet pump 5 to perform ion exchange, so as to obtain the main stream ion exchange effluent, and coagulants, coagulant aids and alkalis are added through the dosing port 4; the coagulation sedimentation tank 2 is provided with a stirrer 3 for stirring; the ion exchange is performed by using five ion exchange columns connected in parallel, and a downward-inward operation mode is adopted;

[0125] The ion exchange column used in the ion exchange is backwashed using the regeneration liquid I, so as to obtain ammonia nitrogen-containing backwashing water with the concentration of ammonium nitrogen being 150 mg N / L;

[0126] (2) the ammonia nitrogen-containing backwashing water is introduced into the short-cut nitrification unit 13 through the side stream nitrosation inlet pump 12 to perform short-cut nitrification, so as to obtain the nitrosation effluent; the short-cut nitrification unit 13 is provided with an oxygen aeration pipe 14 for aeration; carbonates and / or bicarbonates are added through the dosing port 15;

[0127] (3) a part of the nitrosation effluent is introduced into the incomplete denitrification unit 18 through the incomplete denitrification inlet pump 17 to perform incomplete denitrification, acetic acid and a carbon source are added from the dosing port 21, the pH is adjusted to 7.0 by using acetic acid, and a stirrer 20 is used for mixing, so as to obtain the incomplete denitrification effluent, and gas I is collected through the gas collection port 22;

[0128] (4) the incomplete denitrification effluent is introduced into the hollow fiber membrane contactor 24 of the N2O stripping unit through the hollow fiber membrane inlet pump 23, and gas stripping is performed by using the hydrophobic polypropylene hollow fiber membrane (hydrophobic polypropylene hollow fiber membrane I) therein, so as to obtain the regeneration liquid II and gas II, and the safety valve 25 can be used for emergency discharge;

[0129] (5) the gas II is backflowed to the incomplete denitrification unit 18 through the hollow fiber membrane vacuum pump 26 and is used for aeration of the incomplete denitrification through the self-circulation aeration pipe 19; a vacuum gauge 27 is arranged downstream of the hollow fiber membrane vacuum pump 26 to maintain negative pressure and ensure stable flow of the gas II, and the running state of the vacuum fiber membrane is judged at the same time;

[0130] (6) another part of the nitrosation effluent from the nitrosation effluent diversion pump 16 and the regeneration liquid II from the hollow fiber membrane effluent pump 28 are pumped to the regeneration liquid storage barrel 30 by using the regeneration liquid backflow pump 29, and then introduced into the ammonia nitrogen ion exchange regeneration unit 6 through the regeneration liquid inlet pump 31 to perform the backwashing together with the regeneration liquid I;

[0131] (7) the main stream ion exchange effluent water is subjected to membrane-biological reaction through a membrane assembly to obtain main stream effluent water, including that the main stream ion exchange effluent water is pumped into a membrane-biological reactor (MBR tank) 8 through a main stream ion exchange effluent water pump 7, residual organic matter is removed, and the main stream effluent water is obtained through a membrane assembly 10, and then is returned to the main stream treatment system through an effluent water pump 11, and an aeration pipe 9 is arranged in the membrane-biological reactor;

[0132] The water quality of the main stream effluent water is: ammonium nitrogen 0.3 mg N / L, TN 2.0 mg N / L, TP 0.08 mg P / L, and COD 13.0 mg / L;

[0133] Based on the total water quantity of the one part of the nitrosation effluent water and the another part of the nitrosation effluent water, the water quantity of the one part of the nitrosation effluent water accounts for 80-90 vol%, and the water quantity of the another part of the nitrosation effluent water accounts for 10-20 vol%;

[0134] The system is continuously operated for 24 hours, 1100 L of gas I and 550 L of gas II are obtained, and in the gas I, the content of N2O is 88 vol%; and in the gas II, the content of N2O is 92 vol%.

[0135] Example 2

[0136] In this embodiment, the similar method of example 1 is adopted, except that the parameters of each step are referred to table 2;

[0137] The system is continuously operated for 24 hours, 1100 L of gas I and 550 L of gas II are obtained, and in the gas I, the content of N2O is 88 vol%; and in the gas II, the content of N2O is 92 vol%.

[0138] Example 3

[0139] In this embodiment, the similar method of example 1 is adopted, except that based on the total water quantity of the one part of the nitrosation effluent water and the another part of the nitrosation effluent water, the water quantity of the one part of the nitrosation effluent water accounts for 98 vol%, and the water quantity of the another part of the nitrosation effluent water accounts for 2 vol%;

[0140] The system is continuously operated for 24 hours, 1100 L of gas I and 550 L of gas II are obtained, and in the gas I, the content of N2O is 88 vol%; and in the gas II, the content of N2O is 92 vol%.

[0141] Example 4

[0142] This example was carried out in a similar manner to Example 1, except that the short-cut nitrification was carried out at a pH of 8.0, a temperature of 20°C, a dissolved oxygen concentration of 4.0 mg / L, and a nitrite nitrogen concentration of 600 mg N / L;

[0143] The system was continuously operated for 24 h, and 400 L of gas I and 150 L of gas II were obtained. In the gas I, the content of N2O was 65 vol%; in the gas II, the content of N2O was 85 vol%.

[0144] Example 5

[0145] This example was carried out in a similar manner to Example 1, except that in step (4), the hydrophobic polypropylene hollow fiber membrane used was hydrophobic polypropylene hollow fiber membrane II;

[0146] The system was continuously operated for 24 h, and 400 L of gas I and 150 L of gas II were obtained. In the gas I, the content of N2O was 65 vol%; in the gas II, the content of N2O was 85 vol%.

[0147] Comparative Example 1

[0148] This comparative example was carried out in a similar manner to Example 1, except that the operation in step (6) was not carried out. Specifically, in step (3), all of the nitrited effluent was introduced into the incomplete denitrification unit for incomplete denitrification, and gas I and incomplete denitrification effluent were obtained for subsequent treatment;

[0149] The system was continuously operated by replenishing the NaNO2 regeneration solution with a nitrite nitrogen concentration of 2.0-6.0 g N / L in the regeneration solution storage barrel;

[0150] Finally, the system was continuously operated for 24 h, and 1.5 L of gas I and 0.2 L of gas II were obtained. In the gas I, the content of N2O was 60 vol%; in the gas II, the content of N2O was 83 vol%.

[0151] Table 1

[0152] Item Value COD Cr (mg / L) 200 BOD5 (mg / L) 150 SS (mg / L) 250 [NH3-N (mg N / L)] 50 TN (mg N / L) 75 TP (mg P / L) 15 pH 7.0

[0153] Table 2

[0154]

[0155]

[0156] The application is based on a short-range nitrification-incomplete denitrification combined process, and realizes main stream ion exchange regeneration-side stream biological short-range nitrification-biological incomplete denitrification-N2O gas stripping of main stream separation denitrification and synchronous side stream enrichment and recovery of N2O by coupling ammonia ion exchange regeneration and N2O gas stripping technology without the need of high-concentration nitrogen source as a reaction substrate. In the process, NH4 + -N in wastewater is removed by an ion exchange unit, and the effluent NH4 + -N and TN concentration can reach the first level A discharge standard of Urban Sewage Treatment Plant Pollutant Discharge Standard (GB18918-2002) or even more stringent "quasi-IV" standard.

[0157] Biological short-range nitrification converts NH4 + -N in the ammonia-containing backwash water into NO2 - -N, which cleverly realizes enrichment of NO2 - -N and avoids inhibition of NH4 + -N on the ion exchange regeneration process, realizes reuse of the regeneration liquid and efficient regeneration of the ion exchanger, and finally realizes zero discharge of wastewater in the side stream system.

[0158] The above describes the preferred embodiments of the application, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the application and belong to the protection scope of the application.

Claims

1. A method for efficient denitrification and N2O recovery in sewage, characterized in that: The method is carried out in a system including an ammonia nitrogen ion exchange regeneration unit, a short-cut nitrification unit, an incomplete denitrification unit and an N2O stripping unit, and includes: (1) introducing the domestic sewage into the ammonia nitrogen ion exchange regeneration unit after coagulation and sedimentation to perform ion exchange to obtain mainstream ion exchange effluent, and using regeneration liquid I to backwash the ion exchange column used in the ion exchange to obtain ammonia nitrogen-containing backwash water; (2) introducing the ammonia nitrogen-containing backwash water into the short-cut nitrification unit for short-cut nitrification to obtain nitrite effluent; (3) introducing a portion of the nitrite effluent into the incomplete denitrification unit for incomplete denitrification to obtain gas I and incomplete denitrification effluent; (4) introducing the incomplete denitrification effluent into the N2O stripping unit for stripping to obtain gas II and regeneration liquid II; (5) refluxing the gas II to the incomplete denitrification unit to aerate the incomplete denitrification; (6) introducing another portion of the nitrite effluent and the regeneration liquid II into the ammonia nitrogen ion exchange regeneration unit to perform backwashing together with the regeneration liquid I; The amount of the portion of the nitritation effluent is controlled so that the concentration of nitrite nitrogen in the liquid phase stream I composed of the other portion of the nitritation effluent, the regeneration liquid II, and the regeneration liquid I is 0.01-6.0 g N / L.

2. The method according to claim 1, wherein Based on the total water volume of the part of the nitrosation effluent and the other part of the nitrosation effluent, the water volume of the part of the nitrosation effluent accounts for 50-95 vol%, and the water volume of the other part of the nitrosation effluent accounts for 5-50 vol%.

3. The method according to claim 1 or 2, wherein: The method further includes, in step (1), subjecting the mainstream ion exchange effluent to a membrane-biological reaction using a membrane assembly to obtain mainstream effluent, and controlling the conditions of the membrane-biological reaction so that the water quality of the mainstream effluent at least meets the following conditions: ammonium nitrogen ≤ 1.3 mg N / L, TN ≤ 5 mg N / L, TP ≤ 0.3 mg P / L, and COD ≤ 26 mg / L.

4. The method according to claim 1 or 2, wherein: In step (2), the conditions for the short-range nitrification at least meet the following requirements: pH 6.0-10.0, temperature 15-40° C., dissolved oxygen concentration 0.5-8 mg / L, and nitrite nitrogen concentration 100-6000 mgN / L.

5. The method according to claim 1 or 2, wherein: In step (3), the pH of the incomplete denitrification is 6.5-7.

5.

6. The method according to claim 1 or 2, wherein: The gas stripping is performed using a hydrophobic polypropylene hollow fiber membrane, and The porosity of the hydrophobic polypropylene hollow fiber membrane is 40-50%, and the inner diameter of the fiber is 100-300 μm.

7. A system for efficient denitrification and N2O recovery of sewage, characterized by: The system is used to apply the method according to any one of claims 1 to 6, and comprises an ammonia nitrogen ion exchange regeneration unit, a short-cut nitrification unit, an incomplete denitrification unit and an N2O stripping unit connected in sequence; The ammonia nitrogen ion exchange regeneration unit is used to perform ion exchange on the domestic sewage after coagulation and sedimentation to obtain mainstream ion exchange effluent; and is used to backwash the ion exchange column used in the ion exchange using the regeneration liquid I to obtain ammonia nitrogen-containing backwash water; The short-cut nitrification unit is used to perform short-cut nitrification on the ammonia nitrogen-containing backwash water to obtain nitrite effluent; The incomplete denitrification unit is used to perform incomplete denitrification on the nitrite effluent to obtain gas I and incomplete denitrification effluent; and is used to perform aeration using gas II; The N2O stripping unit is used to strip the incomplete denitrification effluent to obtain gas II and regeneration liquid II.

8. The system according to claim 7, wherein: The system also includes a membrane assembly arranged downstream of the ammonia nitrogen ion exchange regeneration unit in the direction of liquid phase flow, for subjecting the mainstream ion exchange effluent to a membrane-biological reaction to obtain mainstream effluent, and controlling the conditions of the membrane-biological reaction so that the water quality of the mainstream effluent at least meets the following requirements: ammonium nitrogen ≤1.3 mgN / L, TN ≤5 mgN / L, TP ≤0.3 mgP / L, and COD ≤26 mg / L.

9. The system according to claim 7 or 8, wherein: The short-cut nitrification unit includes a short-cut nitrification reactor, and an aeration pump and a reflux pump are arranged in the short-cut nitrification reactor.

10. The system according to claim 9, wherein: The short-cut nitrification reactor is selected from at least one of a membrane-bioreactor, a moving bed biofilm reactor, and an aerobic tank+sedimentation tank+membrane treatment reactor.

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