Method for deeply denitrifying petrochemical wastewater and quickly starting sulfur autotrophic denitrification process

Abstract

The invention relates to a method for rapidly starting a sulfur autotrophic denitrification process for deep denitrification of petrochemical wastewater, and belongs to the technical field of sewage treatment.The method comprises the steps that a sulfur autotrophic denitrification deep bed filter is constructed, a sulfur-iron composite filler is filled, salt-tolerant sulfur autotrophic denitrification bacteria are inoculated, and the nitrogen concentration, hydraulic retention time (HRT) and the pH value of inflow nitrate are adjusted in stages; according to the method, rapid starting of the sulfur autotrophic denitrification function of the deep bed filter for treating the petrochemical high-salinity wastewater is achieved, the starting condition is optimized, the starting period is shortened to be within 14 days, the denitrification efficiency and stability of the system are remarkably improved, meanwhile, the method is suitable for high-salinity wastewater treatment, high salinity resistance and impact load resistance are achieved, and the method is suitable for popularization and application. The method has the advantages of simplicity and convenience in operation, high starting efficiency, stability in operation and the like, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater. Background Art

[0002] As a commonly used wastewater treatment process, the deep bed filter is widely used in the solid-liquid separation and pollutant removal of wastewater due to its high filter media filling height, long residence time, high treatment efficiency, etc. The deep bed filter can provide a large biological attachment area, which is conducive to the formation of a dense microbial biofilm, thereby improving the reaction efficiency.

[0003] Petrochemical high-salt wastewater is difficult to treat due to its high salt content and complex pollutant concentration. However, under high-salt conditions, the attachment and reproduction of microorganisms in the deep bed filter are significantly affected by salinity stress, resulting in problems such as long start-up periods and low denitrification efficiency in the actual application of the deep bed filter. In addition, the high-salt environment will change the physicochemical properties of the filter media surface, further affecting the attachment performance of microorganisms. Therefore, developing a rapid start-up method based on salt-tolerant denitrifying bacteria is of great significance for improving the treatment efficiency of petrochemical high-salt wastewater. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention proposes a method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater, which highlights the use of salt-tolerant denitrifying bacteria as the core and realizes the rapid start-up of the filter through scientific process parameter regulation, and is applicable to the deep nitrogen removal treatment of petrochemical wastewater in a high-salt environment.

[0005] The present invention adopts the following technical solutions to solve the above problems:

[0006] A method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater, the method comprising the following steps:

[0007] S1: Construct a sulfur autotrophic denitrification deep bed filter and fill it with sulfur-iron composite packing:

[0008] S2: Domesticate salt-tolerant sulfur autotrophic activated sludge and inoculate salt-tolerant sulfur autotrophic denitrifying bacteria:

[0009] S3: Start up the sulfur autotrophic denitrification deep bed filter and adjust the parameters in stages: Adjust the influent nitrate nitrogen concentration, hydraulic retention time (HRT) and pH value in stages to realize the rapid start-up of the sulfur autotrophic denitrification function of the deep bed filter for treating petrochemical high-salt wastewater;

[0010] S4: Stable operation.

[0011] Further, in S1, the deep bed filter internally includes a supporting layer and a packing layer. The supporting layer includes pebbles and gravel, and the packing layer is composed of sulfur-iron composite particles. The height of the packing layer is 1.5 - 1.8 meters.

[0012] Further, the pebbles selected in the supporting layer have a particle size of 8 - 10 mm, the gravel has a particle size of 6 - 8 mm, and the sulfur-iron composite particles used in the packing layer have a particle size of 4 - 6 cm.

[0013] Further, in S2, the salt-tolerant sulfur autotrophic denitrifying bacteria inoculated are Thiobacillus, and the main denitrifying bacteria are Thauera. The bacteria are evenly inoculated into the deep bed filter in the form of suspended bacteria, and their attachment and reproduction are promoted by means of circulating flow.

[0014] Further, in S2, the salt-tolerant sulfur autotrophic denitrifying bacteria are inoculated into the deep bed filter at a sludge concentration of 4000 mg / L, the influent nitrate nitrogen concentration is 50 mg / L, the salinity is 3000 mg / L, and the influent pH is 6.5 - 7.5.

[0015] Further, in S3, the parameter regulation specifically includes the following steps:

[0016] S301: Control the influent nitrate nitrogen concentration at 30 - 50 mg / L to provide sufficient denitrification substrates;

[0017] S302: Maintain the influent salinity at 5 - 10‰ to ensure the activity of salt-tolerant denitrifying bacteria;

[0018] S303: Optimize the sulfur source supply amount, and supplement a trace amount of organic carbon source when the total nitrogen removal rate is lower than 50% to improve the startup efficiency;

[0019] S304: Control the influent pH at 7.0 - 7.5 by adding alkali or acid;

[0020] S305: The initial flow rate during startup is 0.5 - 1.0 m / h, and maintain an internal circulation for 72 h to reduce the risk of microbial shedding, and supplement the substrate regularly during this period.

[0021] S306: Judgment of startup completion: When the nitrate nitrogen removal rate in the effluent is stable above 85%, the sulfate production amount is approximately equal to the theoretical value of the nitrate nitrogen removal amount, and the population of salt-tolerant denitrifying bacteria is stable, it is determined that the startup is completed.

[0022] Further, the start-up period of the deep bed filter is within 14 days, and the dissolved oxygen concentration is controlled below 0.5 mg / L; during the domestication period of the deep bed filter, internal circulation is carried out twice, with each operation cycle being 3 days, and the flow rate is controlled at 0.5 - 1.0 m / h to promote the rapid attachment and proliferation of microorganisms; the indicators for the completion of the domestication of the deep bed filter are that the nitrate nitrogen concentration in the effluent is below 5 mg / L and the TN is below 10 mg / L. During the stable operation stage of the deep bed filter, the nitrate nitrogen removal rate is stable above 90%.

[0023] Further, the method is applicable to the treatment of high-salt wastewater generated in the petrochemical industry, and the influent salinity range is 1% - 5%.

[0024] Further, the method also includes regularly monitoring the nitrate nitrogen concentration and sulfide concentration in the effluent, and adjusting the influent load and HRT according to the effluent quality to prevent the inhibition of the system caused by the accumulation of sulfide.

[0025] Further, after the stable operation of this process, zero carbon source addition can be achieved, and the sulfur autotrophic denitrifying bacteria are autotrophic bacteria, effectively reducing the input of sludge treatment.

[0026] Advantages of the present invention:

[0027] By inoculating salt-tolerant denitrifying sludge and combining the strategy of gradually increasing the influent load in stages (HRT is shortened from 24 hours to 6 hours), the start-up period of the denitrifying deep bed filter for treating high-salt petrochemical wastewater is significantly shortened to within 21 days, and the start-up efficiency is increased by more than 50%; with the inoculated sludge whose dominant genera are Thiobacillus and Thauera, the microorganisms in the denitrifying deep bed filter can maintain high activity under the condition of salinity of 5 - 10‰, overcoming the defect that the traditional denitrifying deep bed filter is prone to inactivation in a high-salt environment, and the filter has a strong anti-shock load capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The exemplary embodiments of the present invention will be described in more detail in conjunction with the accompanying drawings, making the above objects, features, and advantages of the present invention more obvious. In the exemplary embodiments of the present invention, the same reference numerals generally represent the same components.

[0029] Figure 1 is the flow chart of this method;

[0030] Figure 2 is the bar chart of the nitrate nitrogen removal rate of the denitrifying deep bed filter in Example 1;

[0031] Figure 3 is the diagram of the system flora composition (at the genus level) before and after the start-up in Example 1;

[0032] Figure 4Bar chart of nitrate nitrogen removal rate in the denitrifying deep bed filter in Comparative Example 1. Detailed implementation manners

[0033] The following describes the detailed implementation manners of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed implementation manners. For those of ordinary skill in the art of the present technology, various changes are obvious within the spirit and scope of the present invention defined and determined by the appended claims. All inventions made using the concept of the present invention are within the scope of protection.

[0034] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be obtained through market purchases or prepared by existing methods.

[0035] The present invention selects a sulfur-based material with a high specific surface area (such as sulfur particles or modified sulfur-based fillers) to ensure the sulfur source required for sulfur autotrophic denitrification reaction.

[0036] The salt-tolerant bacteria selected in the present invention are Thiobacillus, and the main denitrifying and nitrogen-removing bacteria are Thauera. The bacteria are evenly inoculated into the deep bed filter in the form of suspended bacteria, and their attachment and reproduction are promoted by means of circulating flow.

[0037] As Figure 1 shown, the method for rapid start-up of the sulfur autotrophic denitrification process for advanced nitrogen removal of petrochemical wastewater in this solution includes the following steps:

[0038] S1: Construct a sulfur autotrophic denitrifying deep bed filter and fill it with sulfur-iron composite fillers:

[0039] S2: Domesticate salt-tolerant sulfur autotrophic activated sludge and inoculate salt-tolerant sulfur autotrophic denitrifying bacteria:

[0040] S3: Start up the sulfur autotrophic denitrifying deep bed filter and adjust the parameters in stages: Adjust the influent nitrate nitrogen concentration, hydraulic retention time (HRT), and pH value in stages to achieve the rapid start-up of the sulfur autotrophic denitrification function of the deep bed filter for treating petrochemical high-salt wastewater;

[0041] S4: Stable operation.

[0042] The above steps are described in detail below in conjunction with embodiments:

[0043] Example 1

[0044] Two sets of high-salt wastewater treatment devices were built in the laboratory, and columnar deep-bed filters (with a diameter of 10 cm, a total height of 200 cm, and a packing height of 100 cm) were used.

[0045] For Device 1, sulfur-iron granular packing was added, and the sulfur autotrophic denitrification process was adopted. Using domesticated salt-tolerant sulfur autotrophic activated sludge, the bacteria were mainly Thiobacillus and Thauera. The initial influent salinity was 10‰, and the nitrate nitrogen concentration was 30 mg / L.

[0046] Initial startup: In the first 7 days, the flow rate was controlled at 0.5 m / h, and the changes in nitrate nitrogen and total nitrogen concentrations were monitored daily.

[0047] Mid-term startup: From the 8th to the 12th day, the flow rate was gradually increased to 1.0 m / h, and the pH was maintained at 6.8.

[0048] Late-term startup: On the 13th - 14th day, the nitrate nitrogen removal rate reached a maximum of 92%.

[0049] Stable operation: From the 15th to the 30th day, the nitrate nitrogen removal rate was stable above 82%.

[0050] During the mid-late startup of Device 1, backwashing was carried out once every 3 days, adopting the air-water backwashing method.

[0051] Comparative Example 1

[0052] For Device 2, traditional ceramsite packing was added, and the traditional heterotrophic denitrification process was adopted. Using traditional activated sludge for inoculation, the initial influent salinity was 10‰, the nitrate nitrogen concentration was 30 mg / L, and sodium acetate was used as the carbon source.

[0053] Initial startup: In the first 7 days, the flow rate was controlled at 0.5 m / h, the carbon-nitrogen ratio was 5, and the changes in nitrate nitrogen and total nitrogen concentrations were monitored daily.

[0054] Mid-term startup: From the 8th to the 12th day, the flow rate was gradually increased to 1.0 m / h, the carbon-nitrogen ratio was 6, and the pH was maintained at 6.8. Air-water backwashing was carried out every day.

[0055] Late-term startup: On the 13th - 14th day, the carbon-nitrogen ratio was 6.5, the nitrate nitrogen removal rate reached a maximum of 92%, and air-water backwashing was carried out every day.

[0056] Stable operation: From the 15th to the 30th day, the carbon-nitrogen ratio was 6, the nitrate nitrogen removal rate was stable above 82%, and air-water backwashing was carried out every day.

[0057] The nitrate nitrogen removal rate of the traditional heterotrophic denitrification deep-bed filter at the laboratory scale is as Figure 3 shown.

[0058] Example 1 and Comparative Example 1 are compared as follows: The device 1 adopts the sulfur autotrophic denitrification process. As Figure 2 shown, for the nitrate nitrogen removal rate of the laboratory-scale sulfur autotrophic denitrification deep bed filter, the start-up speed is fast, and a relatively high nitrate nitrogen removal rate can be achieved within a short time. The composition of the system flora (at the genus level) before and after start-up is as Figure 3 shown; The device 2 adopts the traditional heterotrophic denitrification process. As Figure 4 shown, the start-up period is long, the system needs to add external carbon sources, the operating cost is high, and when the carbon source in the system is insufficient, the nitrate nitrogen removal rate decreases, and at the same time, nitrite nitrogen accumulates in the system; In addition, the doubling period of heterotrophic bacteria is short, and the traditional heterotrophic denitrification process requires frequent backwashing.

[0059] Example 2

[0060] In a centralized wastewater treatment plant in a coastal petrochemical park, the influent of the sulfur autotrophic denitrification deep bed filter is the wastewater after secondary treatment. The water quality characteristics are high salinity (chloride 3000 - 4000 mg / L), and it contains a certain amount of refractory organic matter, mainly trace amounts of grease and benzene series compounds (≤10 mg / L, TOC concentration 30 - 50 mg / L).

[0061] (1) Construction of the reactor and configuration of the packing

[0062] The sulfur autotrophic denitrification deep bed filter has a diameter of 1.5 m and an effective height of 3 m, and the height of the packing layer is 1.5 m.

[0063] The packing is composed of sulfur-iron particles (particle size 3 - 5 mm, purity ≥99%), and pebble supports are provided at the bottom.

[0064] An on-line pH / ORP monitor, a nitrate nitrogen sensor (range 0 - 500 mg / L) and a microporous aeration system (aeration intensity 0.1 - 0.3 m 3 / h) are equipped.

[0065] (2) Sludge inoculation

[0066] Domesticated salt-tolerant sulfur autotrophic activated sludge is adopted. The bacteria are mainly Thiobacillus and Thauera. The inoculation amount is 10% of the effective volume of the filter. After inoculation, internal circulation is carried out to make the sludge form a film.

[0067] (3) Phased start-up control

[0068] Phase 1: From the 1st to the 7th day, the influent nitrate nitrogen concentration is about 30 mg / L, the HRT is 24 hours, and the pH is 7.2 - 7.5.

[0069] The second stage (days 8 - 14): The influent nitrate nitrogen concentration is about 30 mg / L, HRT is 18 hours, and pH is 7.0 - 7.5.

[0070] The third stage (days 15 - 18): The influent nitrate nitrogen concentration is about 30 mg / L, HRT is 12 hours, and pH is 7.0 - 8.0.

[0071] (3) Stable operation

[0072] After the start - up stage, continuous operation is carried out for 30 days. The average effluent total nitrogen is 6.8 mg / L (removal rate ≥ 95%), meeting the first - level discharge requirements of the "Pollutant Discharge Standard for Municipal Wastewater Treatment Plants" (GB 18918 - 2002) (total nitrogen ≤ 15 mg / L).

[0073] After the stable operation of this process, zero carbon source addition can be achieved, and sulfur - autotrophic denitrifying bacteria are autotrophic bacteria, effectively reducing the sludge treatment and disposal cost. Compared with the traditional denitrification deep - bed filter process, the comprehensive operation cost of this process can be reduced by more than 40%.

[0074] The present invention has been described in detail through the embodiments, but the content is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. Any equivalent changes and improvements made according to the scope of the application of the present invention shall still fall within the scope covered by the patent of the present invention.

Claims

1. A method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater, characterized in that: The method includes the following steps: S1: Construct a sulfur autotrophic denitrification deep bed filter and fill it with sulfur-iron composite packing: S2: Domesticate salt-tolerant sulfur autotrophic activated sludge and inoculate salt-tolerant sulfur autotrophic denitrifying bacteria: S3: Start up the sulfur autotrophic denitrification deep bed filter and adjust parameters in stages: Adjust the influent nitrate nitrogen concentration, hydraulic retention time (HRT), and pH value in stages to achieve a rapid start-up of the sulfur autotrophic denitrification function of the deep bed filter for treating petrochemical high-salt wastewater; S4: Operate stably.

2. The method for rapidly starting the sulfur autotrophic denitrification process for deep denitrification of petrochemical wastewater according to claim 1, characterized in that: In S1, the inside of the deep bed filter includes a support layer and a packing layer. The support layer includes pebbles and gravel. The packing layer is composed of sulfur-iron composite particles, and the height of the packing layer is 1.5 - 1.8 meters.

3. A method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater according to claim 2, characterized in that: The pebbles selected in the support layer have a particle size of 8 - 10 mm, and the gravel has a particle size of 6 - 8 mm. The sulfur-iron composite particles used in the packing layer have a particle size of 4 - 6 cm.

4. A method for rapidly starting the sulfur autotrophic denitrification process for deep denitrification of petrochemical wastewater according to claim 1, characterized in that: In S2, the inoculated salt-tolerant sulfur autotrophic denitrifying bacteria are Thiobacillus, and the main denitrifying bacteria are Thauera. The bacteria are evenly inoculated into the deep bed filter in the form of suspended bacteria, and their attachment and reproduction are promoted by means of circulating flow.

5. A method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater according to claim 1, characterized in that: In S2, the salt-tolerant sulfur autotrophic denitrifying bacteria are inoculated into the deep bed filter at a sludge concentration of 4000 mg / L, the influent nitrate nitrogen concentration is 50 mg / L, the salinity is 3000 mg / L, and the influent pH is 6.5 - 7.

5.

6. A method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater according to claim 1, characterized in that: In S3, the parameter adjustment specifically includes the following steps: S301: Control the influent nitrate nitrogen concentration at 30 - 50 mg / L to provide sufficient denitrification substrates; S302: Maintain the influent salinity at 5 - 10‰ to ensure the activity of salt-tolerant denitrifying bacteria; S303: Optimize the supply amount of sulfur source and supplement trace organic carbon source when the total nitrogen removal rate is lower than 50% to improve the start-up efficiency; S304: Control the influent pH at 7.0 - 7.5 by adding alkali or acid; S305: The initial flow rate during start-up is 0.5 - 1.0 m / h, and an internal circulation is maintained for 72 h to reduce the risk of microbial shedding, and the substrate is supplemented regularly during this period. S306: Judgment of start-up completion: When the nitrate nitrogen removal rate in the effluent is stable above 85%, the sulfate production amount is approximately equal to the theoretical value of the nitrate nitrogen removal amount, and the population of salt-tolerant denitrifying bacteria is stable, it is judged that the start-up is completed.

7. A method for rapidly starting the sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater according to claim 6, characterized in that: The start-up period of the deep bed filter is within 14 days, and the dissolved oxygen concentration is controlled below 0.5 mg / L; during the domestication period of the deep bed filter, the internal circulation is carried out twice, each operation cycle is 3 days, and the flow rate is controlled at 0.5 - 1.0 m / h to promote the rapid attachment and proliferation of microorganisms; the indication of the completion of the domestication of the deep bed filter is that the nitrate nitrogen concentration in the effluent is lower than 5 mg / L and the TN is lower than 10 mg / L. During the stable operation stage of the deep bed filter, the nitrate nitrogen removal rate is stable above 90%.

8. A method for rapidly starting the sulfur autotrophic denitrification process for deep denitrification of petrochemical wastewater according to any one of claims 1-7, characterized in that: The method is applicable to the treatment of high-salt wastewater generated in the petrochemical industry, and the influent salinity range is 1% - 5%.

9. A method for rapidly starting a sulfur autotrophic denitrification process for deep nitrogen removal of petrochemical wastewater according to any one of claims 1-7, characterized in that: The method also includes regularly monitoring the nitrate nitrogen concentration and sulfide concentration in the effluent, and adjusting the influent load and HRT according to the effluent quality to prevent the inhibition of the system caused by sulfide accumulation.

10. A method for rapidly starting the sulfur autotrophic denitrification process for deep denitrification of petrochemical wastewater according to any one of claims 1-7, characterized in that: After the process operates stably, zero carbon source addition can be achieved, and sulfur autotrophic denitrifying bacteria are autotrophic bacteria, effectively reducing the investment in sludge treatment.

Images