A method for treating nitrogen-containing phosphorus-containing cleaning wastewater

Abstract

This invention relates to a method for treating nitrogen- and phosphorus-containing cleaning wastewater, which involves adding residual activated sludge, activated carbon, and a nitrogen- and phosphorus-removing bacterial agent to the treatment system, performing a simmering and aeration treatment, and periodically adding an organic carbon source; the nitrogen- and phosphorus-removing bacterial agent contains at least *Microbacterium chrysogenum* (…). Microbacterium kitamiense PR and aerobic bacteria ( Aeromicrobium tamlense The patent is registered in CGMCC No. 25182 and CGMCC No. 25183 respectively. After the aeration process, the water intake is started, and the wastewater is continuously treated. This invention can achieve efficient removal of total nitrogen, total phosphorus and COD from wastewater simultaneously in one structure, avoiding the burden of subsequent biological treatment units. The process is simple and the cost is low.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control technology, specifically relating to a method for treating nitrogen and phosphorus-containing cleaning wastewater. Background Technology

[0002] During shutdowns and maintenance, refining and chemical enterprises use chemical cleaning agents to clean their equipment. These agents mainly include cleaning builder and surfactants. Surfactants include cationic, anionic, amphoteric, and nonionic surfactants, with anionic surfactants primarily including carboxylates, sulfates, sulfonates, and phosphates. Cleaning builder primarily softens hard water, buffers pH, and prevents redeposition during the degreasing process, and synergistically enhances degreasing performance with surfactants. Phosphorus-containing cleaning builder includes sodium tripolyphosphate, trisodium phosphate, and sodium pyrophosphate. Sodium tripolyphosphate provides both alkali and emulsification, exhibiting excellent performance, but its use can lead to phosphorus contamination.

[0003] The use of nitrogen- and phosphorus-containing cleaning agents results in cleaning wastewater with high COD, high nitrogen and phosphorus concentrations, complex chemical composition, high metal ion content, and poor biodegradability. This easily impacts wastewater treatment plants, causing anything from substandard effluent to activated sludge poisoning or death, with biological activity difficult to recover in the short term. Most existing enterprises use a method of first storing and then centrally treating the wastewater, typically employing simple methods to treat metal ions, but the treated wastewater still contains organic matter, nitrogen, phosphorus, and other pollutants, posing a continued risk of impact when discharged into the biological treatment units of subsequent wastewater treatment plants.

[0004] In traditional biological nitrogen and phosphorus removal processes, ammonia nitrogen in wastewater is first oxidized to nitrite or nitrate nitrogen through autotrophic nitrification under aerobic conditions, and then reduced to nitrogen gas through heterotrophic denitrification under anaerobic conditions. Meanwhile, phosphate in wastewater is excessively absorbed into the cells of heterotrophic polyphosphate-accumulating bacteria under aerobic conditions and stored as polyphosphate particles. Under anaerobic conditions, these polyphosphate particles are decomposed to release phosphate, which is then removed from the system through sludge discharge. The differences in the biological nitrogen and phosphorus removal mechanisms make it difficult to unify these two processes. Competition for carbon sources between phosphorus-removing bacteria and denitrifying bacteria is constant; the different ages of nitrifying, denitrifying, and phosphorus-removing bacteria, along with the mutual constraints among various bacterial communities, make it difficult to achieve optimal system operating conditions. Therefore, traditional processes require segmented treatment of anaerobic phosphorus release, anoxic denitrification, and aerobic nitrification, which not only increases equipment complexity but also increases floor space and operating costs.

[0005] Therefore, with increasingly stringent environmental protection requirements, the treatment of chemical cleaning wastewater is a major challenge faced by refineries during shutdown and maintenance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for treating nitrogen- and phosphorus-containing cleaning wastewater. This invention enables the simultaneous and efficient removal of total nitrogen, total phosphorus, and COD from wastewater within a single structure, avoiding the burden of subsequent biological treatment units. The process is simple and cost-effective.

[0007] The present invention provides a method for treating nitrogen- and phosphorus-containing cleaning wastewater, comprising the following:

[0008] The remaining activated sludge, activated carbon, and denitrifying and phosphorus-removing bacteria are added to the treatment system for aeration treatment, with organic carbon sources added periodically. The denitrifying and phosphorus-removing bacteria contain at least Microbacterium kitamiense PR and Aeromicrobacterium tamlense PW, with preservation numbers CGMCC No. 25182 and CGMCC No. 25183, respectively. After the aeration is completed, the influent is started for continuous treatment of the cleaning wastewater.

[0009] In this invention, the excess activated sludge is added at a sludge concentration of 10%-40%, preferably 15%-20%. The excess activated sludge mainly comes from the waste sludge discharged from the enterprise's wastewater treatment plant.

[0010] In this invention, activated carbon is added at 5%-30% of the effective volume of the reactor, preferably 10%-15%. The activated carbon is in powder form, with a particle size of 0.2-0.5 mm and a specific surface area of ​​200-1000 m². 2 / g, iodine value 600-1000m 2 / g.

[0011] In this invention, *Microbacterium kitamiense* PR and *Aeromicrobium tamlense* PW were deposited on June 27, 2022, at the China General Microbiological Culture Collection Center (CGMCC), with accession numbers CGMCC No. 25182 and CGMCC No. 25183, respectively; the deposit address is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing. *Microbacterium kitamiense* PR and *Aeromicrobium tamlense* PW can simultaneously perform heterotrophic nitrification and aerobic denitrification for nitrogen and phosphorus removal, as well as aerobic denitrification for nitrogen and phosphorus removal. The main morphological characteristics of *Microbacterium kitamiense* PR are: when cultured on TSA medium at 30°C for 3 days, the colonies are yellow, round, moist, opaque, and have neat edges. Under a microscope, the bacteria appear as short rods, 0.4-0.6 μm × 0.7-1.6 μm, arranged singly or in pairs, and are Gram-positive. The main morphological characteristics of *Aeromicrobium tamlense* PW are: when cultured on TSA medium at 30°C for 3 days, the colonies are yellow, round, moist, opaque, and have regular edges. Under a microscope, the bacteria appear as short rods, 0.4-0.6 μm × 0.6-1.3 μm, arranged singly or in pairs, and are Gram-positive.

[0012] In this invention, the denitrifying and phosphorus-removing bacterial agent contains Microbacterium kitamiense PR and Aeromicrobacterium tamlense PW in a bacterial mass ratio of 1-5:1, preferably 2-3:1.

[0013] In this invention, the denitrifying and phosphorus-removing bacterial agent contains 30%-60% bacteria by mass, and is added at a volume of 0.01%-0.05% of the effective volume of the wastewater treatment system. The bacterial agent may also contain nutrients, preservatives, and other substances required by the bacteria.

[0014] In this invention, the conditions for simmering and aeration are: dissolved oxygen concentration of 2-6 mg / L, pH of 7-9, temperature of 25-40℃, and simmering time of 5-7 days.

[0015] In this invention, the organic carbon source can be selected from at least one of glucose, acetic acid, methanol, urea, etc., with glucose being preferred. The organic carbon source is added at a COD concentration of 300-500 mg / L after addition, once every 12-24 hours, until the simmering and aeration process is completed.

[0016] In this invention, the continuous operating conditions are as follows: the hydraulic residence time is set to 0.5-3h, preferably 1-2h; the dissolved oxygen concentration is 0.5-3mg / L; the pH is 7-9; and the temperature is 15-40℃.

[0017] In this invention, the water quality of the cleaning wastewater is as follows: ammonia nitrogen concentration not higher than 400 mg / L, preferably 50-200 mg / L; total phosphorus concentration not higher than 50 mg / L, preferably 20-30 mg / L; COD concentration not higher than 2000 mg / L, preferably 500-1000 mg / L.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) In view of the water quality characteristics of chemical cleaning wastewater, the present invention rapidly constructs an efficient treatment system in a reactor by using residual sludge, activated carbon and the denitrification and phosphorus removal bacteria provided by the present invention. This system integrates organic matter enrichment and degradation, and denitrification and phosphorus removal, realizing the efficient and simultaneous removal of total nitrogen, total phosphorus and COD in wastewater, reducing the burden of subsequent biochemical unit treatment, and the process is simple and efficient.

[0020] (2) The denitrification and phosphorus removal bacterial agent of the present invention is prepared from two strains of different species with similar living environment and industrial performance. It is not affected by different growth environment and generation time. In particular, it can achieve rapid enrichment culture after being treated with residual sludge and activated carbon by simmering and aeration, and exhibits excellent denitrification and phosphorus removal performance. Detailed Implementation

[0021] The following examples further illustrate the method and effects of the present invention in detail. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following examples.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples can be purchased from biochemical reagent stores.

[0023] In this embodiment of the invention, COD concentration was determined using GB11914-89 "Water Quality - Determination of Chemical Oxygen Demand - Dichromate Method"; ammonia nitrogen concentration was determined using GB7478-87 "Water Quality - Determination of Ammonium - Distillation and Titration Method"; total nitrogen concentration was determined using GB11894-89 "Water Quality - Determination of Total Nitrogen - Alkaline Potassium Persulfate Digestion Ultraviolet Spectrophotometric Method"; and total phosphorus concentration was determined using GB11893-89 "Ammonium Molybdate Spectrophotometric Method".

[0024] In this embodiment, the cleaning wastewater was taken from the cleaning wastewater of a chemical plant undergoing maintenance during shutdown. Testing revealed an ammonia nitrogen concentration of 200 mg / L, a total phosphorus concentration of 30 mg / L, and a COD concentration of 1000 mg / L. The excess activated sludge mainly came from the wastewater treatment plant of the same company. The activated carbon was in powder form with a particle size of 0.2-0.3 mm and a specific surface area of ​​500-700 m². 2 / g, iodine value 600-700m 2 / g.

[0025] Example 1

[0026] Preparation of nitrogen- and phosphorus-removing bacterial agents: (1) Strain activation: *Microbacterium praecoxibrio* PR and *Aerobicum praecoxibrio* PW were inoculated onto LB solid medium, spread evenly, and placed in a constant temperature incubator at 30℃ for activation. (2) Seed culture: Colonies of the two strains on the plate were taken with an inoculation loop and inoculated into LB liquid culture medium. The culture was shaken at 30℃ and 150 rpm for 48 hours until the logarithmic growth phase to obtain liquid bacterial agent seed culture. (3) Scale-up culture: The above seed culture was scaled up in a reactor with an aeration device. The culture temperature was 30℃, dissolved oxygen was 2.5 mg / L, pH was 7.0-7.5, and the culture time was 72 hours to obtain concentrated bacterial solutions of the two strains. The LB liquid medium formula used to prepare the bacterial agent was: NaCl 10 g / L, peptone 10 g / L, yeast extract 5 g / L; the solid medium was the liquid medium with 20 g / L agar added.

[0027] The concentrated bacterial solution obtained after the above-mentioned amplification culture was collected and prepared according to the proportions described in Table 1. The mass content of the two bacteria in the bacterial agent was 50%, as shown in Table 1.

[0028] Table 1 Composition and ratio of the microbial agent

[0029]

[0030]

[0031] Example 2

[0032] The remaining activated sludge was added to the treatment system at a concentration of 20%, activated carbon at 10% of the reactor's effective volume, and No. 1 denitrification and phosphorus removal bacterial agent at 0.02% of the system's effective volume. A simmering treatment was then performed with dissolved oxygen at 2-3 mg / L, pH at 7-9, and temperature at 25-30℃ for 5 days. Glucose was added every 24 hours to achieve a post-addition COD concentration of 400 mg / L until the simmering period ended. The influent was then started for continuous wastewater treatment under the following conditions: hydraulic retention time of 2 hours, dissolved oxygen concentration of 0.5-3 mg / L, pH at 7-9, and temperature at 25-35℃. During continuous operation, effluent samples were collected daily for pollutant concentration analysis. The average treatment effect over 10 days is shown in Table 2.

[0033] Example 3

[0034] The remaining activated sludge was added to the treatment system at a concentration of 10%, activated carbon at 30% of the reactor's effective volume, and No. 1 denitrification and phosphorus removal bacterial agent at 0.01% of the system's effective volume. A simmering treatment was then performed with dissolved oxygen at 2-3 mg / L, pH at 7-9, and temperature at 25-30℃ for 5 days. Glucose was added every 18 hours to achieve a post-addition COD concentration of 500 mg / L until the simmering period ended. The influent was then started for continuous wastewater treatment under the following conditions: hydraulic retention time of 1 hour, dissolved oxygen concentration of 0.5-3 mg / L, pH at 7-9, and temperature at 25-35℃. During continuous operation, effluent samples were collected daily for pollutant concentration analysis. The average treatment effect over 10 days is shown in Table 2.

[0035] Example 4

[0036] The remaining activated sludge was added to the treatment system at a concentration of 40%, activated carbon at 5% of the reactor's effective volume, and No. 1 denitrification and phosphorus removal bacterial agent at 0.05% of the wastewater treatment system's effective volume. A simmering treatment was then performed with dissolved oxygen at 2-3 mg / L, pH at 7-9, and temperature at 25-30℃ for 5 days. Glucose was added every 12 hours to achieve a post-addition COD concentration of 300 mg / L until the simmering period ended. The influent was then started, and wastewater was continuously treated under the following conditions: hydraulic retention time of 2 hours, dissolved oxygen concentration of 0.5-3 mg / L, pH at 7-9, and temperature at 25-35℃. During continuous operation, effluent samples were collected daily for pollutant concentration analysis. The average treatment effect over 10 days is shown in Table 2.

[0037] Example 5

[0038] The remaining activated sludge was added to the treatment system at a concentration of 20%, activated carbon at 10% of the reactor's effective volume, and No. 2 denitrification and phosphorus removal bacterial agent at 0.02% of the system's effective volume. A simmering treatment was then performed with dissolved oxygen at 2-3 mg / L, pH at 7-9, and temperature at 25-30℃ for 5 days. Glucose was added every 24 hours to achieve a post-addition COD concentration of 300 mg / L until the simmering period ended. The influent was then started, and wastewater was continuously treated under the following conditions: hydraulic retention time of 2 hours, dissolved oxygen concentration of 0.5-3 mg / L, pH at 7-9, and temperature at 25-35℃. During continuous operation, effluent samples were collected daily for pollutant concentration analysis. The average treatment effect over 10 days is shown in Table 2.

[0039] Example 6

[0040] The remaining activated sludge was added to the treatment system at a concentration of 20%, activated carbon at 10% of the reactor's effective volume, and No. 3 denitrification and phosphorus removal bacterial agent at 0.02% of the effective volume of the wastewater treatment system. A simmering treatment was then performed with dissolved oxygen concentration of 2-3 mg / L, pH of 7-9, and temperature of 25-30℃ for 5 days. Glucose was added every 24 hours to achieve a post-addition COD concentration of 300 mg / L until the simmering period ended. The influent was then started for continuous wastewater treatment under the following continuous operating conditions: hydraulic retention time of 2 hours, dissolved oxygen concentration of 0.5-3 mg / L, pH of 7-9, and temperature of 25-35℃. During continuous operation, effluent samples were collected daily for pollutant concentration analysis. The average treatment effect over 10 days is shown in Table 2.

[0041] Example 7

[0042] The remaining activated sludge was added to the treatment system at a concentration of 20%, activated carbon at 10% of the reactor's effective volume, and No. 3 denitrification and phosphorus removal bacterial agent at 0.02% of the effective volume of the wastewater treatment system. Aeration was then performed with dissolved oxygen concentration of 2-3 mg / L, pH of 7-9, and temperature of 25-30℃ for 5 days. Acetic acid was added every 24 hours to achieve a post-addition COD concentration of 300 mg / L until the eration was complete. The influent was then started for continuous wastewater treatment under the following conditions: hydraulic retention time of 2 hours, dissolved oxygen concentration of 0.5-3 mg / L, pH of 7-9, and temperature of 25-35℃. During continuous operation, effluent samples were collected daily for pollutant concentration analysis. The average treatment effect over 10 days is shown in Table 2.

[0043] Comparative Example 1

[0044] Same as Example 1, except that the phosphorus removal agent contained only PW. During continuous operation, effluent samples were collected daily for pollutant concentration analysis, and the average treatment effect over 10 days is shown in Table 2.

[0045] Comparative Example 2

[0046] Same as Example 1, except that the phosphorus removal agent contained only PR. During continuous operation, effluent samples were collected daily for pollutant concentration analysis, and the average treatment effect over 10 days is shown in Table 2.

[0047] Comparative Example 3

[0048] Same as Example 1, except that the treatment system did not use residual activated sludge. During continuous operation, effluent samples were collected daily for pollutant concentration analysis, and the average treatment effect over 10 days is shown in Table 2.

[0049] Comparative Example 4

[0050] Same as Example 1, except that activated carbon was not used in the treatment system. During continuous operation, effluent samples were collected daily for pollutant concentration analysis, and the average treatment effect over 10 days is shown in Table 2.

[0051] Comparative Example 5

[0052] Similar to Example 1, except that the treatment system did not undergo a steaming treatment. During continuous operation, effluent samples were collected daily for pollutant concentration analysis, and the average treatment effect over 10 days is shown in Table 2.

[0053] Table 2. Treatment effects of the examples and comparative examples (unit: mg / L)

[0054]

[0055] As shown in Table 2, the method of this invention significantly reduces total phosphorus, ammonia nitrogen, and total nitrogen in chemical cleaning wastewater after treatment. However, under the same conditions, treatment with a single bacterium or without activated sludge and activated carbon results in relatively higher concentrations of nitrogen and phosphorus pollutants in the water. Therefore, the scheme of this invention achieves simultaneous and efficient removal of total nitrogen and total phosphorus in a single system.

Claims

1. A method for treating nitrogen- and phosphorus-containing cleaning wastewater, characterized in that... The process includes the following: adding residual activated sludge, activated carbon, and denitrifying and phosphorus-removing bacteria to the treatment system, performing a simmering and aeration treatment, and periodically adding organic carbon sources; the denitrifying and phosphorus-removing bacteria contain at least *Microbacterium chrysogenum* (…). Microbacterium kitamiense PR and aerobic bacteria ( Aeromicrobium tamlense PW; the preservation numbers are CGMCC No.25182 and CGMCC No.25183 respectively; after the simmering and aeration is completed, the water inlet is started and the cleaning wastewater is continuously treated; the simmering and aeration conditions are: dissolved oxygen concentration of 2-6 mg / L, pH of 7-9, temperature of 25-40℃, and simmering time of 5-7 days.

2. The method according to claim 1, characterized in that: The remaining activated sludge is added at a concentration of 10%-40%.

3. The method according to claim 2, characterized in that: The remaining activated sludge is added at a concentration of 15%-20%.

4. The method according to claim 1, characterized in that: Activated carbon is added at a rate of 5%-30% of the effective volume of the reactor.

5. The method according to claim 4, characterized in that: Activated carbon is added at a rate of 10%-15% of the effective volume of the reactor.

6. The method according to claim 1, 4, or 5, characterized in that: The activated carbon is in powder form, with a particle size of 0.2-0.5 mm, a specific surface area of 200-1000 m 2 / g, and an iodine value of 600-1000 m 2 / g.

7. The method according to claim 1, characterized in that: Kitami Microbacterium ( Microbacterium kitamiense PR and aerobic bacteria ( Aeromicrobium tamlense PW was deposited on June 27, 2022, at the China General Microbiological Culture Collection Center (CGMCC) with accession numbers CGMCC No. 25182 and CGMCC No. 25183, respectively. The deposit address is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

8. The method according to claim 1, characterized in that: The denitrifying and phosphorus-removing bacterial agent contains *Microbacterium urinaria* (… Microbacterium kitamiense PR and aerobic bacteria ( Aeromicrobium tamlense PW is mixed at a bacterial mass ratio of 1-5:

1.

9. The method according to claim 8, characterized in that: The denitrifying and phosphorus-removing bacterial agent contains *Microbacterium urinaria* (… Microbacterium kitamiense PR and aerobic bacteria ( Aeromicrobium tamlense PW was mixed at a bacterial mass ratio of 2-3:

1.

10. The method according to claim 1, 7, 8, or 9, characterized in that: The denitrification and phosphorus removal bacterial agent contains 30%-60% bacteria by mass, and is added at a rate of 0.01%-0.05% of the effective volume of the wastewater treatment system.

11. The method according to claim 1, characterized in that: The organic carbon source is selected from at least one of glucose, acetic acid, methanol, and urea.

12. The method according to claim 11, characterized in that: The organic carbon source is glucose.

13. The method according to claim 1, 11, or 12, characterized in that: Add the organic carbon source at a COD concentration of 300-500 mg / L after addition, once every 12-24 hours, until the simmering and aeration is completed.

14. The method according to claim 1, characterized in that: The continuous operating conditions are as follows: hydraulic retention time is set to 0.5-3h, dissolved oxygen concentration is set to 0.5-3mg / L, pH is set to 7-9, and temperature is set to 15-40℃.

15. The method according to claim 14, characterized in that: The hydraulic residence time is set to 1-2 hours.

16. The method according to claim 1, characterized in that: The water quality of the cleaning wastewater is as follows: ammonia nitrogen concentration not exceeding 400 mg / L, total phosphorus concentration not exceeding 50 mg / L, and COD concentration not exceeding 2000 mg / L.

17. The method according to claim 16, characterized in that: The water quality of the cleaning wastewater is as follows: ammonia nitrogen concentration of 50-200 mg / L; total phosphorus concentration of 20-30 mg / L; and COD concentration of 500-1000 mg / L.

Images