Method for hydrolyzing urea and recovering nitrogen in urea waste liquid

Abstract

The invention belongs to the field of resource recovery, and particularly relates to a method for hydrolyzing urea and recovering nitrogen in urea waste liquid, which comprises the following steps: a) performing urea decomposition and air stripping treatment on the urea waste liquid step by step or synchronously to respectively obtain treated waste liquid and air stripping gas; and b) introducing the stripping gas into a collecting device filled with an ammonia nitrogen collector to obtain an ammonia nitrogen product. According to the method provided by the invention, urea is rapidly decomposed at normal temperature and normal pressure by using urease-producing microorganisms, then the waste liquid is adjusted to be alkaline, and ammonia nitrogen is recovered through air stripping under mild conditions. The method is easy and convenient to operate, low in requirements for equipment and working conditions, low in production and operation cost and suitable for various high-concentration urea waste liquid systems (such as urea industrial wastewater and urine), and the content of urea and ammonia nitrogen in treated effluent is low; meanwhile, the ammonia nitrogen recovered by the method is high in purity, and subsequent product processing is facilitated.

Description

Technical Field

[0001] The invention belongs to the field of resource recovery, and in particular relates to a method for hydrolyzing urea and recovering nitrogen from urea waste liquid. Background Art

[0002] Urea is an important nitrogen-containing compound that is widely used in agriculture, industry, medicine and other fields. Due to the large demand for urea in these fields, a large amount of waste liquid containing urea is generated during its use and treatment. In addition, urine produced by human metabolism also contains high concentrations of urea. If these urea waste liquids are directly discharged into the wastewater treatment system without proper treatment, it will not only have a negative impact on the environment, but also lead to the loss of precious nitrogen resources. Therefore, the effective removal and recovery of urea in waste liquid is particularly important.

[0003] Depending on the concentration of urea in the waste liquid, the treatment method of urea is also different. When the urea concentration is low, ion exchange, reagent reaction and other methods are usually used to remove or convert urea; when the concentration is high, the industry often uses the method of "ammonia nitrogen stripping-urea hydrolysis-re-stripping" to recover urea. This method is easy to operate and has a high nitrogen recovery capacity. However, this method needs to be carried out in multiple steps, the overall process is complicated and the operation time is long; in addition, since it needs to be operated under high temperature and high pressure conditions, it is energy-intensive and requires high durability of the equipment. Therefore, although this method is effective, it still has many limitations. In order to overcome the shortcomings of the above methods, the industry has developed technologies such as reverse osmosis, multi-stage flash evaporation, and membrane distillation. Although these technologies have simplified the process and shortened the recovery process to a certain extent, the equipment requirements are more stringent, and the energy consumption problem has not been fundamentally solved. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for hydrolyzing urea and recovering nitrogen in urea waste liquid, which achieves rapid decomposition of urea and high recovery rate of nitrogen through simple and efficient process and low-cost equipment, and at the same time has wide applicability and long-term stable operating performance.

[0005] The present invention provides a method for hydrolyzing urea and recovering nitrogen from urea waste liquid, comprising the following steps:

[0006] a) performing urea decomposition and stripping treatment on the urea waste liquid step by step or simultaneously to obtain treated waste liquid and stripping gas respectively;

[0007] The process of carrying out urea decomposition and stripping treatment step by step specifically includes:

[0008] a1) decomposing urea waste liquid in the presence of a microorganism that can produce urease to obtain an enzymatic waste liquid; adjusting the enzymatic waste liquid to alkaline, and performing a stripping treatment to obtain a treated waste liquid and a stripping gas, respectively;

[0009] The process of simultaneously performing urea decomposition and stripping treatment specifically includes:

[0010] a2) Under alkaline conditions, urea waste liquid is subjected to synchronous urea decomposition and stripping treatment in the presence of microorganisms that can produce urease, to obtain treated waste liquid and stripping gas respectively;

[0011] b) introducing the stripping gas into a collecting device containing an ammonia nitrogen collection material to obtain an ammonia nitrogen product.

[0012] Preferably, in step a), the urea concentration of the urea waste liquid is 5 to 50 g / L.

[0013] Preferably, in step a), the type of the microorganism includes one or more of Proteus, modified Proteus, Pseudomonas, modified Pseudomonas, Klebsiella, modified Klebsiella, Sporosarcina, modified Sporosarcina, Nocardia, modified Nocardia, Escherichia and modified Escherichia; the OD of the microorganism in the urea wastewater is 600 It is 0.02~0.2.

[0014] Preferably, in step a), the alkalinity has a pH value of 9 to 13; the alkalinity is provided by an alkaline agent, and the alkaline agent is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, sodium oxide and potassium oxide.

[0015] Preferably, in step a), the stripping gas used in the stripping treatment is nitrogen or air, and the gas-liquid volume ratio is (100-10000):1.

[0016] Preferably, in step a1), the urea decomposition is carried out in a decomposition device, which is a barrel-shaped device having a bacteria adding port, a stirrer, a liquid adding port and a liquid outlet; and the urea decomposition time is 2 to 12 hours.

[0017] Preferably, in step a1), the stripping treatment is carried out in a stripping device, which is a tower-shaped device having a liquid inlet, an air inlet, a liquid outlet, an air outlet and a heater; the stripping treatment temperature is 20 to 50° C., and the time is 3 to 12 hours.

[0018] Preferably, in step a2), the synchronous urea decomposition and stripping treatment is carried out in a comprehensive device having urea decomposition and stripping functions, and the comprehensive device is a stripping tower containing a hydrolysis module; the temperature of the synchronous urea decomposition and stripping treatment is 20 to 50° C., and the time is 5 to 15 hours.

[0019] Preferably, in step b), the ammonia nitrogen collection material is one or more of sulfuric acid, hydrochloric acid, water and acidic diatomaceous earth.

[0020] Preferably, in step b), the collecting device is a barrel-shaped device having an air inlet, a collecting tank and an air outlet.

[0021] Compared with the prior art, the present invention provides a method for recovering nitrogen resources from high-concentration urea waste liquid, comprising the following steps: a) urea waste liquid is subjected to urea decomposition and stripping treatment step by step or simultaneously to obtain treated waste liquid and stripping gas respectively; the process of carrying out urea decomposition and stripping treatment step by step specifically comprises: a1) urea waste liquid is subjected to urea decomposition in the presence of a microorganism that can produce urease to obtain enzymatic waste liquid; the enzymatic waste liquid is adjusted to alkaline and stripped to obtain treated waste liquid and stripping gas respectively; the process of carrying out urea decomposition and stripping treatment simultaneously specifically comprises: a2) under alkaline conditions, urea waste liquid is subjected to synchronous urea decomposition and stripping treatment in the presence of a microorganism that can produce urease to obtain treated waste liquid and stripping gas respectively; b) the stripping gas is introduced into a collection device containing ammonia nitrogen collection material to obtain an ammonia nitrogen product. The method provided by the present invention utilizes a urease-producing microorganism to rapidly decompose urea at normal temperature and pressure, then adjusts the waste liquid to alkaline, and recovers ammonia nitrogen by stripping under mild conditions. The method is easy to operate, has low requirements on equipment and working conditions, and has low production and operation costs. It is applicable to a variety of high-concentration urea waste liquid systems (such as urea industrial wastewater, urine, etc.), and the urea and ammonia nitrogen content in the treated effluent is low; at the same time, the ammonia nitrogen recovered by the method has a high purity, which is conducive to the processing of subsequent products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 It is a schematic diagram of a process flow and device for urea hydrolysis and nitrogen recovery in urea waste liquid provided by an embodiment of the present invention;

[0024] Figure 2 It is a schematic structural diagram of an integrated air stripping tower containing a hydrolysis module provided in an embodiment of the present invention.

[0025] Description of the accompanying drawings: 1 is a cylindrical urea decomposition device, 11 is a liquid inlet of the urea decomposition device, 12 is a bacteria adding port of the urea decomposition device, 13 is a liquid outlet of the urea decomposition device, 14 is a stirrer of the urea decomposition device, 2 is an ammonia nitrogen stripping tower, 21 is a liquid inlet of the ammonia nitrogen stripping tower, 22 is an air inlet of the ammonia nitrogen stripping tower, 23 is a liquid outlet of the ammonia nitrogen stripping tower, 24 is an air outlet of the ammonia nitrogen stripping tower, 25 is a heater of the ammonia nitrogen stripping tower, 3 is an ammonia nitrogen collecting device, 31 is an air inlet of the ammonia nitrogen collecting device, 32 is an air outlet of the ammonia nitrogen collecting device, 33 is an ammonia nitrogen collection, 4 is a hydrolysis mold containing The integrated stripping tower has an integrated stripping tower, 401 is a cleaning port of the integrated stripping tower, 402 is a liquid inlet of the integrated stripping tower, 403 is an air inlet of the integrated stripping tower, 404 is an air pump of the integrated stripping tower, 405 is a heater of the integrated stripping tower, 406 is a guide plate of the integrated stripping tower, 407 is a bacteria adding port of the integrated stripping tower, 408 is a partition screen of the integrated stripping tower, 409 is a liquid outlet of the integrated stripping tower, 410 is a safety port of the integrated stripping tower, 411 is a reflux port of the integrated stripping tower, 412 is a dryer of the integrated stripping tower, and 413 is an air outlet of the integrated stripping tower. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The present invention provides a method for hydrolyzing urea and recovering nitrogen from urea waste liquid, comprising the following steps:

[0028] a) performing urea decomposition and stripping treatment on the urea waste liquid step by step or simultaneously to obtain treated waste liquid and stripping gas respectively;

[0029] The process of carrying out urea decomposition and stripping treatment step by step specifically includes:

[0030] a1) decomposing urea waste liquid in the presence of a microorganism that can produce urease to obtain an enzymatic waste liquid; adjusting the enzymatic waste liquid to alkaline, and performing a stripping treatment to obtain a treated waste liquid and a stripping gas, respectively;

[0031] The process of simultaneously performing urea decomposition and stripping treatment specifically includes:

[0032] a2) Under alkaline conditions, urea waste liquid is subjected to synchronous urea decomposition and stripping treatment in the presence of microorganisms that can produce urease, to obtain treated waste liquid and stripping gas respectively;

[0033] b) introducing the stripping gas into a collecting device containing an ammonia nitrogen collection material to obtain an ammonia nitrogen product.

[0034] In the method provided by the present invention, in step a), the urea concentration of the urea waste liquid is preferably 5-50 g / L, specifically 5 g / L, 8.1 g / L, 10 g / L, 15 g / L, 18 g / L, 20 g / L, 22 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 41 g / L, 45 g / L or 50 g / L.

[0035] In the method provided by the present invention, in step a), the type of the microorganism includes one or more of Proteus, modified Proteus, Pseudomonas, modified Pseudomonas, Klebsiella, modified Klebsiella, Sporosarcina, modified Sporosarcina, Nocardia, modified Nocardia, Escherichia and modified Escherichia; the OD of the microorganism in the urea wastewater is 600 It is preferably 0.02 to 0.2, specifically 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.2.

[0036] In the method provided by the present invention, in step a), the pH value of the alkalinity is preferably 9 to 13, specifically 9, 9.5, 9.7, 10, 10.5, 10.6, 11, 11.5, 11.9, 12, 12.4, 12.5 or 13; the alkalinity is provided by an alkaline agent, and the alkaline agent is preferably one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, sodium oxide and potassium oxide.

[0037] In the method provided by the present invention, in step a), the stripping gas used in the stripping treatment is preferably nitrogen or air, and the gas-liquid volume ratio is preferably (100-10000):1, specifically 100:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, 3000:1, 3500:1, 4000:1, 4500:1, 5000:1, 6000:1, 7000:1, 8000:1, 9000:1 or 10000:1.

[0038] In the method provided by the present invention, in step a1), the urea decomposition is preferably carried out in a decomposition device, which is a barrel-shaped device having a bacteria adding port, a stirrer, a liquid adding port and a liquid outlet; the urea decomposition time is preferably 2 to 12 hours, specifically 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0039] In the method provided by the present invention, in step a1), the stripping treatment is preferably carried out in a stripping device, which is a tower-shaped device having a liquid inlet, an air inlet, a liquid outlet, an air outlet and a heater; the temperature of the stripping treatment is preferably 20-50°C, specifically 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C; the time of the stripping treatment is preferably 3-12h, specifically 3h, 3.5h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h.

[0040] In the method provided by the present invention, in step a2), the synchronous urea decomposition and stripping treatment is carried out in an integrated device with urea decomposition and stripping functions, and the integrated device is preferably a stripping tower containing a hydrolysis module; the temperature of the synchronous urea decomposition and stripping treatment is preferably 20-50°C, and can be specifically 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C; the time of the synchronous urea decomposition and stripping treatment is preferably 5-15h, and can be specifically 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h. In the present invention, the integrated device is preferably a continuous treatment device, and the above treatment time is the hydraulic retention time of the urea waste liquid in the continuous treatment device.

[0041] In the method provided by the present invention, in step b), the ammonia nitrogen collection material is preferably one or more of sulfuric acid, hydrochloric acid, water and acidic diatomaceous earth.

[0042] In the method provided by the present invention, in step b), the collecting device is preferably a barrel-shaped device having an air inlet, a collecting tank and an air outlet.

[0043] The method provided by the present invention achieves rapid decomposition of urea and high recovery rate of nitrogen through simple and efficient process and low-cost equipment, and has wide applicability and long-term stable operation performance. More specifically, the method has the following advantages and positive effects:

[0044] (1) The present invention can simplify the process flow, complete urea decomposition and ammonia nitrogen stripping at normal temperature and pressure, reduce the pressure and temperature resistance requirements of the equipment, reduce operating energy consumption, and thus reduce the equipment construction and process operation costs of high-concentration urea waste liquid;

[0045] (2) The present invention is applicable to a variety of complex urea waste liquid systems. The concentrations of urea and ammonia nitrogen in the treated waste liquid are low, which simplifies the subsequent sewage treatment process and reduces the cost of denitrification.

[0046] (3) The strain used in the present invention has long-lasting activity, can quickly decompose urea for a long time under mild conditions, and has high environmental tolerance, thereby improving the overall stability of the process;

[0047] (4) The present invention shows high urea removal rate and ammonia nitrogen recovery rate in different urea waste liquid systems, reduces the waste of nitrogen resources, and promotes the recycling of nitrogen resources;

[0048] (5) The ammonia nitrogen product recovered by the present invention has high purity, which simplifies the subsequent processing steps and is conducive to further processing and production.

[0049] For the purpose of greater clarity, the invention is described in detail through the following examples.

[0050] Example 1

[0051] use Figure 1 The process flow and device shown are used to hydrolyze urea and recover nitrogen from urea waste liquid. The specific steps are as follows:

[0052] S1) introducing high-concentration urea waste liquid into a barrel-shaped urea decomposition device 1, adding urease-producing microorganisms to decompose urea, and obtaining a waste liquid with high ammonia nitrogen and low urea;

[0053] The urea concentration of the high-concentration urea waste liquid is 22 g / L, the microorganism is of the genus Proteus, and the OD of the microorganism in the waste liquid is 600 is 0.11 and the processing time is 3h.

[0054] S2) adjusting the high ammonia nitrogen and low urea waste liquid obtained in step S1 to alkalinity, and introducing the waste liquid into the ammonia nitrogen stripping tower 2 for stripping treatment to obtain the low ammonia nitrogen and low urea waste liquid and the gas generated by the stripping;

[0055] The pH value of the waste liquid after being adjusted to alkaline is 9.7, and the alkaline adjusting agent added is magnesium oxide; the stripping treatment temperature is 25° C., the treatment time is 12 hours, the stripping gas is air, and the gas-liquid volume ratio is 500:1.

[0056] S3) introducing the gas produced by the stripping in step S2 into an ammonia nitrogen collecting device 3 containing an ammonia nitrogen collection material to obtain an ammonia nitrogen product; the ammonia nitrogen collection material is dilute sulfuric acid.

[0057] Example 2

[0058] use Figure 1 The process flow and device shown are used to hydrolyze urea and recover nitrogen from urea waste liquid. The specific steps are as follows:

[0059] S1) diluting high-concentration urea waste liquid and introducing it into a barrel-shaped urea decomposition device 1, adding urease-producing microorganisms to decompose urea, and obtaining a waste liquid with high ammonia nitrogen and low urea;

[0060] The urea concentration of the high-concentration urea waste liquid is 82 g / L, and the urea concentration after dilution is 41 g / L; the microorganism is Nocardia, and the OD of the microorganism in the waste liquid is 600 is 0.15 and the processing time is 8h.

[0061] S2) adjusting the high ammonia nitrogen and low urea waste liquid obtained in step S1 to alkalinity, and introducing the waste liquid into the ammonia nitrogen stripping tower 2 for stripping treatment to obtain the low ammonia nitrogen and low urea waste liquid and the gas generated by the stripping;

[0062] The pH value of the waste liquid after being adjusted to alkaline is 12.4, and the alkaline adjusting agent added is potassium hydroxide; the stripping treatment temperature is 40°C, the treatment time is 3.5h, the stripping gas is nitrogen, and the gas-liquid volume ratio is 7000:1.

[0063] S3) introducing the gas produced by the stripping in step S2 into an ammonia nitrogen collecting device 3 containing an ammonia nitrogen collection material to obtain an ammonia nitrogen product; the ammonia nitrogen collection material is water.

[0064] Example 3

[0065] use Figure 2 The integrated stripping tower 4 containing the hydrolysis module is combined Figure 1 The ammonia nitrogen collection device 3 in the urea waste liquid is used to hydrolyze urea and recover nitrogen. The specific steps are as follows:

[0066] S1) High concentration urea waste liquid is introduced into Figure 2 In the integrated stripping tower 4 containing a hydrolysis module shown, urease-producing microorganisms are added to the waste liquid, and the waste liquid is adjusted to alkaline, and urea decomposition and ammonia nitrogen stripping are carried out simultaneously and continuously, and finally low ammonia nitrogen, low urea waste liquid and gas generated by stripping are obtained;

[0067] The urea concentration of the high-concentration urea waste liquid is 18 g / L; the microorganism is Klebsiella spp. cultured to the stationary phase for one week, and the OD of the microorganism in the waste liquid is 600 is 0.05; the pH value of the waste liquid after being adjusted to alkaline is 10.6, and the alkali adjusting agent added is sodium hydroxide; the temperature for the simultaneous urea decomposition and ammonia nitrogen stripping is 30°C, the stripping gas is air, and the gas-liquid volume ratio is 2500:1; the hydraulic retention time of the waste liquid in the integrated stripping tower 4 is 10h, and the total operation time is 100h.

[0068] S2) introducing the gas produced by the stripping in step S1 into an ammonia nitrogen collecting device 3 containing an ammonia nitrogen collection material to obtain an ammonia nitrogen product; the ammonia nitrogen collection material is dilute hydrochloric acid.

[0069] Example 4

[0070] use Figure 2 The integrated stripping tower 4 containing the hydrolysis module is combined Figure 1 The ammonia nitrogen collection device 3 in the urea waste liquid is used to hydrolyze urea and recover nitrogen. The specific steps are as follows:

[0071] S1) High concentration urea waste liquid is introduced into Figure 2 In the integrated stripping tower 4 containing a hydrolysis module shown, urease-producing microorganisms are added to the waste liquid, and the waste liquid is adjusted to alkaline, urea decomposition and ammonia nitrogen stripping are carried out simultaneously, and finally low ammonia nitrogen, low urea waste liquid and gas generated by stripping are obtained;

[0072] The urea concentration of the high-concentration urea waste liquid is 8.1 g / L; the microorganism is a sporosarcina, and the OD of the microorganism in the waste liquid is 600 is 0.09; the pH value of the waste liquid after being adjusted to alkalinity is 11.9, and the alkali adjusting agent added is calcium oxide; the temperature for simultaneous urea decomposition and ammonia nitrogen stripping is 35°C, the stripping gas is air, and the gas-liquid volume ratio is 4000:1; the hydraulic retention time of the waste liquid in the integrated stripping tower 4 is 6h, and the total operation is 24h.

[0073] S2) introducing the gas produced by the stripping in step S1 into an ammonia nitrogen collecting device 3 containing an ammonia nitrogen collection material to obtain an ammonia nitrogen product; the ammonia nitrogen collection material is acidic diatomaceous earth.

[0074] Effect evaluation

[0075] In Examples 1 to 4, the urea concentration is detected by substrate colorimetric method (the substrate is p-dimethylaminobenzaldehyde, PDAB). Under acidic conditions, PDAB reacts with urea to generate a lemon-yellow p-diaminobenzaldehyde urea product to determine the urea concentration. The ammonia nitrogen concentration is detected by Nessler's reagent spectrophotometry. Under strong alkaline conditions, ammonia reacts with Nessler's reagent to generate a yellow-brown colloidal product for determining the ammonia nitrogen concentration. Table 1 shows the concentration of urea after decomposition, the concentration after ammonia nitrogen stripping, as well as the urea decomposition rate, urea nitrogen recovery rate and the main ammonia nitrogen products in each embodiment.

[0076] Table 1 Urea concentration and decomposition rate before and after urea waste liquid treatment

[0077] Experimental example Urea concentration in wastewater before decomposition (g / L) Urea concentration in wastewater after decomposition (g / L) Urea decomposition rate Example 1 22 0.18 99.2％ Example 2 41(82)* 3.53 91.4％ Example 3 18 1.42 92.2％ Example 4 8.1 0.25 96.9％

[0078] In Table 1, *: The area in brackets indicates the concentration of urea in the undiluted influent water.

[0079] Table 2 Urea decomposition products in urea wastewater and ammonia nitrogen concentration and recovery rate after stripping

[0080]

[0081] As can be seen from Tables 1 and 2, the effect of biological decomposition of urea is excellent. In urea waste liquids of different concentrations, the urea decomposition rate is above 90%, and the lowest residual concentration can reach 0.2 g / L; the ammonia nitrogen stripping efficiency is also high. In the embodiments of "urea decomposition-ammonia nitrogen stripping" being carried out separately and simultaneously, the ammonia nitrogen stripping rate exceeds 85%. In summary, this method can achieve efficient decomposition and ammonia nitrogen recovery in urea waste liquids of different concentrations.

[0082] In addition, the total treatment time of this method is relatively short. Under appropriate bacterial quantity, ambient temperature and stripping conditions, the total treatment process can be completed in as little as 6 hours, meeting the demand for rapid treatment of urea waste liquid. The operating conditions are mild, the process temperature does not exceed 50°C, and the equipment requirements are low; the bacterial strain activity lasts for a long time, can be maintained for more than 100 hours, and subsequent replenishment is simple; the nitrogen recovery product is mainly ammonium salt or ammonia water, which is convenient for subsequent processing.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for hydrolyzing urea and recovering nitrogen from urea waste liquid, characterized in that: The following steps are involved: a) performing urea decomposition and stripping treatment on the urea waste liquid step by step or simultaneously to obtain treated waste liquid and stripping gas respectively; The process of carrying out urea decomposition and stripping treatment step by step specifically includes: a1) decomposing urea waste liquid in the presence of a microorganism that can produce urease to obtain an enzymatic waste liquid; adjusting the enzymatic waste liquid to alkaline, and performing a stripping treatment to obtain a treated waste liquid and a stripping gas, respectively; The process of simultaneously performing urea decomposition and stripping treatment specifically includes: a2) Under alkaline conditions, urea waste liquid is subjected to synchronous urea decomposition and stripping treatment in the presence of microorganisms that can produce urease, to obtain treated waste liquid and stripping gas respectively; b) introducing the stripping gas into a collecting device containing an ammonia nitrogen collection material to obtain an ammonia nitrogen product.

2. The method according to claim 1, characterized in that In step a), the urea concentration of the urea waste liquid is 5 to 50 g / L.

3. The method according to claim 1, characterized in that In step a), the type of the microorganism includes one or more of Proteus, modified Proteus, Pseudomonas, modified Pseudomonas, Klebsiella, modified Klebsiella, Sporosarcina, modified Sporosarcina, Nocardia, modified Nocardia, Escherichia and modified Escherichia; the OD of the microorganism in the urea wastewater is 600 It is 0.02~0.

2.

4. The method according to claim 1, characterized in that: In step a), the alkalinity has a pH value of 9 to 13; the alkalinity is provided by an alkaline agent, and the alkaline agent is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, sodium oxide and potassium oxide.

5. The method according to claim 1, characterized in that In step a), the stripping gas used in the stripping treatment is nitrogen or air, and the gas-liquid volume ratio is (100-10000):

1.

6. The method according to claim 1, characterized in that In step a1), the urea decomposition is carried out in a decomposition device, which is a barrel-shaped device having a bacteria adding port, a stirrer, a liquid adding port and a liquid outlet; the urea decomposition time is 2 to 12 hours.

7. The method according to claim 1, characterized in that In step a1), the stripping treatment is carried out in a stripping device, which is a tower-shaped device having a liquid inlet, an air inlet, a liquid outlet, an air outlet and a heater; the stripping treatment temperature is 20 to 50° C., and the time is 3 to 12 hours.

8. The method according to claim 1, characterized in that In step a2), the synchronous urea decomposition and stripping treatment is carried out in a comprehensive device with urea decomposition and stripping functions, and the comprehensive device is a stripping tower containing a hydrolysis module; the temperature of the synchronous urea decomposition and stripping treatment is 20 to 50° C., and the time is 5 to 15 hours.

9. The method according to claim 1, characterized in that: In step b), the ammonia nitrogen collected is one or more of sulfuric acid, hydrochloric acid, water and acidic diatomaceous earth.

10. The method according to claim 1, characterized in that In step b), the collecting device is a barrel-shaped device having an air inlet, a collecting pool and an air outlet.

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