Short process sewage treatment process with low dissolved oxygen operation

Abstract

The application discloses a short-process sewage treatment process with low dissolved oxygen operation, which adopts two-stage biochemical treatment to realize simultaneous nitrification and denitrification under the conditions of micro-dissolved oxygen (DO 0.5-1.5 mg / L) and low-dissolved oxygen (DO 1.5-2.5 mg / L); a new aeration mode combining cyclone aeration and micropore aeration is adopted to promote the fluidization of fillers, strengthen mass transfer, make the dissolved oxygen concentration controllable and not cause the abrasion of fillers; the mud film mixed mode is adopted to operate, and a low activated sludge concentration is set to guarantee that the ammonia nitrogen in the effluent meets the standard under the short process, and the residual sludge is reduced. The process greatly shortens the traditional denitrification process flow, significantly improves the denitrification efficiency, effectively reduces the aeration energy consumption under the low-dissolved oxygen operation, reduces the unnecessary aeration amount through fine aeration control, realizes energy saving and efficiency increase, and further reduces the number of process units, reduces the land occupation and construction cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sewage treatment, in particular to a short process sewage treatment process with low dissolved oxygen operation. BACKGROUND

[0002] At present, the process flow of sewage treatment plant is still relatively long, and the aeration energy consumption is an important part of carbon emission of sewage treatment plant. Therefore, it is necessary to construct a short process sewage treatment process with low dissolved oxygen operation to realize the low-carbon development of sewage treatment technology.

[0003] The moving bed biofilm reactor (MBBR) is a new sewage treatment technology which utilizes the biofilm of pollutant degrading bacteria enriched on the surface of filler. Through adsorption, interception and degradation on the surface of biofilm, it realizes efficient removal of pollutants. MBBR has the advantages of high volumetric loading, more than 50% reduction in land occupation, high treatment efficiency, simple process, strong impact resistance and easy automation control, and has been widely used in expansion and reconstruction of sewage treatment plants, and has shown broad application prospects in the field of sewage treatment.

[0004] In recent years, more and more studies have found that operating MBBR under low dissolved oxygen conditions can not only greatly reduce energy consumption, but also realize simultaneous nitrification and denitrification and short-cut nitrification and denitrification, thereby realizing short process and efficient nitrogen control. However, MBBR has high requirements for aeration quantity and mixing intensity. If the filler is completely fluidized by aeration, it is difficult to accurately control the dissolved oxygen concentration, and will result in high energy consumption; if the aeration and mechanical stirring are combined, the stirring blade and the filler are easy to be worn, which brings high operation cost. To some extent, this problem restricts the popularization and application of the technology.

[0005] Therefore, it is of great significance to develop a more efficient, low-consumption and sustainable MBBR aeration control strategy for constructing a short process sewage treatment process with low dissolved oxygen operation. This not only helps to further improve the performance and economy of MBBR process, but also provides a new idea and direction for realizing the low-carbon and sustainable development of sewage treatment process. SUMMARY

[0006] The present application is to overcome the shortcomings of the prior art, and provides a short process sewage treatment process with low dissolved oxygen operation.

[0007] The technical scheme of the present application is as follows: a short process sewage treatment process with low dissolved oxygen operation, comprising the following steps:

[0008] S1. The system used in the short process sewage treatment process is composed of a pool body, an aeration system and an aeration control system;

[0009] The pool body comprises a first-stage micro-dissolved oxygen reaction zone and a second-stage low-dissolved oxygen reaction zone, the aeration system comprises a blower, an aeration main pipe, a micro-porous aeration branch pipe, a liftable cyclone aeration branch pipe, a micro-porous aerator, a liftable cyclone aerator, the aeration control system comprises dissolved oxygen sensors in each biochemical section, an ammonia nitrogen sensor at a water outlet, a gas flow meter, a pressure sensor, a data acquisition and transmission unit, automatic control valves, and a controller.

[0010] S2. Ammonia nitrogen-containing wastewater A at an influent end flows into the first-stage micro-dissolved oxygen reaction zone (1.5 mg / L≥DO≥0.5 mg / L), and the residence time is (3-5 h), to obtain sludge-water mixture A;

[0011] Low-C / N municipal wastewater flows into the first-stage micro-dissolved oxygen reaction zone, and organic matter in the influent is utilized by heterotrophic denitrification functional bacteria as a denitrification carbon source, to occur simultaneous nitrification and denitrification and short-cut nitrification and denitrification.

[0012] S3. The sludge-water mixture A flows into the second-stage low-dissolved oxygen reaction zone (2.5 mg / L≥DO≥1.5 mg / L), and the residence time is (1-3 h), to obtain sludge-water mixture B;

[0013] Wastewater flows into the second-stage low-dissolved oxygen reaction zone, residual organic matter is oxidized into carbon dioxide, and residual ammonia nitrogen is further oxidized into nitrate nitrogen, to ensure that COD, NH4 + -N and TN meet the standards;

[0014] S4. The sludge-water mixture B enters a sedimentation tank, sludge is separated from water, and then the sludge is returned to the process influent end, and the effluent enters a subsequent advanced treatment unit;

[0015] The sludge-water mixture containing suspended sludge and aged biofilm enters a sedimentation tank, sludge is separated from water, and then the sludge is returned to the process influent end, to reduce the amount of residual sludge and maintain the stability of the biomass in the MBBR;

[0016] S5. The aeration control system monitors the dissolved oxygen levels in each section of the process and the ammonia nitrogen level at the effluent end during operation. Under normal temperature operation (water temperature≥15℃), when the effluent ammonia nitrogen abnormally rises to more than 3.0 mg / L due to the impact of the influent water quality, the valve opening of the micro-porous aerator in the second-stage low-dissolved oxygen reaction zone is increased by 5%-10%, and at the same time, the valve opening of the cyclone aerator is reduced by 5%-10%. When the effluent ammonia nitrogen is stably below 1.5 mg / L, if the DO in the first-stage micro-dissolved oxygen reaction zone frequently fluctuates by more than 1.5 mg / L within a single day, the micro-porous aeration valve opening is reduced by 5%-10%, and at the same time, the cyclone aeration valve opening is increased by 5%-10%, to maintain the DO below 1.0 mg / L.

[0017] Further, the pool body is filled with suspended filler, the first-stage micro-dissolved oxygen reaction zone filler filling rate is 40%~60%, the second-stage low-dissolved oxygen reaction zone filling rate is 15%~30%, the filler is selected from the B-class filler specified in "High-density polyethylene suspended carrier filler for water treatment" (CJ / T 461-2014), the material is HDPE, the effective specific surface area is 500<SV<800 m2 / m3, the filler biofilm biomass is greater than or equal to 2000 mg MLSS / L, and the sludge concentration is 1000 mg MLSS / L~2000 mg MLSS / L.

[0018] Further, the first-stage micro-dissolved oxygen reaction zone filler filling rate is 50%, the second-stage low-dissolved oxygen reaction zone filling rate is 15%, the filler SV is 800 m 2 3 , the filler biofilm biomass is 2000 mg MLSS / L, and the sludge concentration is controlled at 1000 mg MLSS / L.

[0019] Further, the first-stage micro-dissolved oxygen reaction zone and the second-stage low-dissolved oxygen reaction zone both contain partitions, the number of partitions n is greater than or equal to 2, the length-width ratio of a single partition is controlled at 1:2~2:1, 1:1 is appropriate, three-dimensional columnar stainless steel interception screens with a pore size of 0.5~2.0 cm are arranged at the water inlet and outlet of the partitions, so as to avoid filler accumulation and blockage at the interception screens.

[0020] Further, the first-stage micro-dissolved oxygen reaction zone is mainly subjected to cyclone aeration, the gas amount accounts for 60%~100%, so as to ensure complete fluidization of the filler; the second-stage low-dissolved oxygen reaction zone has a lower filler stirring requirement, and is mainly subjected to micropore aeration, the gas amount accounts for 60%~100%, so as to ensure that the DO concentration is greater than or equal to 1.5 mg / L.

[0021] Further, the micropore aerator and the liftable cyclone aerator are combined and installed, the installation ratio is 4:1~6:1, the micropore aerator has a pore size of 0.5~1.0 mm, the installation height is 0.3~0.5 m from the bottom, the liftable cyclone aerator has a pore size of 1~3 mm, the gas-water ratio is 10:1~20:1, the aeration head inclination angle is 45°, the center is arranged in a rectangular or plum blossom shape, and the installation height is 0.5~1.0 m.

[0022] Further, the micropore aerator has a pore size of 0.5 mm, the liftable cyclone aerator has a pore size of 3 mm, and the gas-water ratio is 10:1, so that the stirring efficiency is higher.

[0023] Further, the sludge reflux ratio is 50%~100%.

[0024] Further, the ammonia nitrogen concentration of the sewage inlet water is 30~100 mg / L, the COD and NH4 + ​- N, TN reaches the first level A standard of Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002).

[0025] Advantages of the present application:

[0026] 1. Short process and high efficiency of denitrification. The present application adopts two-stage biochemical treatment process to realize simultaneous nitrification and denitrification and short-cut nitrification and denitrification under the conditions of micro-dissolved oxygen (DO 0.5-1.5 mg / L) and low-dissolved oxygen (DO 1.5-2.5 mg / L); the process is operated in the mode of mixed activated sludge and biofilm, and a relatively low activated sludge concentration is set, so that the competition and inhibition of suspended sludge to biofilm are reduced under the short process, and the ammonia nitrogen in the effluent meets the standard. Overall, the process greatly shortens the traditional denitrification process flow and significantly improves the denitrification efficiency.

[0027] 2. Energy saving and consumption reduction. Low-dissolved oxygen operation can effectively reduce the aeration energy consumption, and the partitioned addition and fine control of the filler also reduce unnecessary aeration amount, thereby realizing energy saving and efficiency improvement. In addition, the short process also reduces the number of process units and the construction cost.

[0028] 3. Small filler abrasion. The combination of micro-porous aerator and lift-type cyclone aerator can accurately control the dissolved oxygen concentration, realize low-dissolved oxygen operation, and meet the mixing demand of the filler while avoiding the abrasion of the mechanical stirring blade to the filler, thereby prolonging the service life of the filler and reducing the operation cost.

[0029] 4. Intelligent control. The online monitoring and automatic control system is equipped, the aeration amount and aeration mode are adjusted in real time according to the DO at each stage and the ammonia nitrogen in the effluent, and energy saving and consumption reduction, cost reduction and efficiency improvement are realized.

[0030] 5. Sludge backflow. The sludge and aged biofilm are backflowed to the front end, thereby ensuring the biomass and degradation efficiency. The three-dimensional columnar screen is set in the grid to prevent the filler from being blocked and ensure long-term stable operation.

[0031] 6. Wide applicability. The present process adopts the mixed mode of activated sludge and biofilm, has the advantages of activated sludge method and biofilm method, has strong adaptability to the influent water quality, and can effectively cope with different types of wastewater; the lift-type cyclone aerator is easy to install and disassemble, so the present application is not only suitable for new projects, but also suitable for upgrading and operation optimization.

[0032] In summary, the present application constructs a new low-dissolved oxygen short process wastewater treatment process through process flow optimization, aeration system innovation and intelligent control means, significantly improves the denitrification and phosphorus removal efficiency, helps energy saving and consumption reduction and carbon emission reduction, and provides a new solution for the green and sustainable development of wastewater treatment plants. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1is a short process core process unit configuration schematic diagram of the present application.

[0034] Figure 2 is a short process process flow schematic diagram of the present application. DETAILED DESCRIPTION

[0035] The present application will be described in detail below in conjunction with the drawings and specific embodiments.

[0036] As shown in Figure 2 , a short process sewage treatment process with low dissolved oxygen operation includes the following steps:

[0037] S1. The system used by the short process sewage treatment process is composed of a pool body, an aeration system, and an aeration control system;

[0038] The pool body comprises a first-stage micro-dissolved oxygen reaction zone 1 and a second-stage low-dissolved oxygen reaction zone 2, the aeration system comprises a blower 3, aeration main pipes, micro-porous aeration branch pipes, micro-porous aerators 4, and a liftable cyclone aerator 5, and the aeration control system comprises dissolved oxygen sensors 6 in each biochemical section, an effluent ammonia nitrogen sensor 7, a gas flow meter, a pressure sensor, a data acquisition and transmission unit, an automatic control valve 8, and a controller 9, as shown in Figure 1 ;

[0039] S2. Ammonia nitrogen-containing wastewater A flows into the first-stage micro-dissolved oxygen reaction zone (1.5 mg / L≥DO≥0.5 mg / L), with a residence time of (3-5 h), to obtain sludge-water mixture A;

[0040] The wastewater flows into the first-stage micro-dissolved oxygen reaction zone, and the organic matter in the influent is utilized by heterotrophic denitrification functional bacteria as a denitrification carbon source, and synchronous nitrification and denitrification and short-cut nitrification and denitrification occur;

[0041] S3. The sludge-water mixture A flows into the second-stage low-dissolved oxygen reaction zone (2.5 mg / L≥DO≥1.5 mg / L), with a residence time of (1-3 h), to obtain sludge-water mixture B;

[0042] The wastewater flows into the second-stage low-dissolved oxygen reaction zone, and the residual organic matter is oxidized into carbon dioxide, and the residual ammonia nitrogen is further oxidized into nitrate nitrogen, to ensure that COD, NH4 + -N, and TN meet the standards;

[0043] S4. The sludge-water mixture B enters a sedimentation tank, and after sludge-water separation, the sludge is returned to the process influent end, and the effluent enters a subsequent advanced treatment unit;

[0044] The sludge-water mixture containing suspended sludge and aged biofilm enters a sedimentation tank, and after sludge-water separation, the sludge is returned to the process influent end, to reduce the amount of residual sludge and maintain the stability of the biomass in the MBBR;

[0045] S5. The aeration control system monitors the dissolved oxygen level of each section of the process and the ammonia nitrogen level of the effluent end. When the effluent ammonia nitrogen is abnormally increased to more than 3.0 mg / L due to the impact of the influent water quality under normal temperature operation (water temperature ≥ 15℃), the valve opening of the microporous aerator in the second low-dissolved oxygen reaction zone is increased by 5% to 10%, and the valve opening of the cyclone aerator is reduced by 5% to 10% at the same time. When the effluent ammonia nitrogen is stably below 1.5 mg / L, if the DO in the first micro-dissolved oxygen reaction zone frequently fluctuates more than 1.5 mg / L within a single day, the microporous aeration valve opening is reduced by 5% to 10%, and the cyclone aeration valve opening is increased by 5% to 10% at the same time, so that the DO is maintained below 1.0 mg / L.

[0046] The low-dissolved oxygen short-flow wastewater treatment process configuration of the application comprises:

[0047] The short-flow process comprises an MBBR tank (divided into two sections), two sets of microporous aeration devices (including 2 groups of 12 aerators), two sets of liftable cyclone aeration devices, and a control system. The MBBR filler adopts K3 type filler, the effective specific surface area is 800 m 2 / m 3 , the carrier filling rate of the first micro-dissolved oxygen reaction zone is 40%, the carrier filling rate of the second low-dissolved oxygen reaction zone is 15%, the sludge concentration in the MBBR tank is 1500 mg / L MLVSS, and the sludge return ratio is 100%. The microporous aeration device is installed at the bottom of the MBBR reactor, which is used to generate fine bubbles to improve the dissolved oxygen level in the tank; the liftable cyclone aeration device is installed 0.3 m above the microporous aerator, which generates rotating air flow to suck water under negative pressure, realizes air-water mixing, and provides power to make the carrier in a fluidized state. The control system is used to adjust the operating parameters of the aeration device according to the dissolved oxygen in the reactor and the effluent ammonia nitrogen, so as to achieve the best nitrogen control effect under low energy consumption.

[0048] The operation effect of the low-dissolved oxygen short-flow process:

[0049] The low-dissolved oxygen high-efficiency nitrogen control MBBR aeration system described in the application is applied to treat municipal sewage with a treatment scale of 50 m 3 / d. The system operates in a sludge-membrane mixed mode, and the water quality parameters of the influent are as follows: COD concentration is about 250 mg / L, NH + -N concentration is about 27 mg / L, TN concentration is about 30 mg / L, and TP concentration is about 3 mg / L.

[0050] The operation is divided into two stages, each for 30 days, the first stage simulates the traditional MBBR operation mode, only the micro-porous aerator is turned on in the two-stage reaction zone, the air blower power is adjusted until the filler is completely fluidized; the second stage uses the operation method described in the application, the micro-porous aeration and the cyclone aeration are cooperated, the filler is also completely fluidized, according to the monitoring of the DO level of the first-stage micro-dissolved oxygen reaction zone and the second-stage low-dissolved oxygen reaction zone and the change of the effluent ammonia nitrogen during the operation, the aeration device is adjusted and controlled, the DO concentration of the first-stage micro-dissolved oxygen reaction zone is kept in the range of 0.5-1.5 mg / L, the DO concentration of the second-stage low-dissolved oxygen reaction zone is kept in the range of 1.0-2.5 mg / L. After the debugging operation, the operation results of the two stages of the MBBR of the embodiment are shown in Table 1, compared with the operation mode of the traditional MBBR, the operation mode of the low-dissolved oxygen MBBR proposed in the application has more advantages in energy saving and denitrification efficiency.

[0051] Table 1 Comparison of MBBR two-stage operation

[0052]

[0053] It should be noted that for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the application.

Claims

1. A low dissolved oxygen operated short process wastewater treatment process characterized by: It comprises the following steps: S1. The system used by the short process sewage treatment process is composed of a pool body, an aeration system and an aeration control system; The pool body comprises a first-stage micro-dissolved oxygen reaction zone and a second-stage low-dissolved oxygen reaction zone, the aeration system comprises a blower, a main aeration pipe, a micro-porous aeration branch pipe, a liftable cyclone aeration branch pipe, a micro-porous aerator and a liftable cyclone aerator, and the aeration control system comprises a dissolved oxygen sensor for each biochemical section, an ammonia nitrogen sensor at a water outlet, a gas flow meter, a pressure sensor, a data acquisition and transmission unit, an automatic control valve and a controller; S2. Ammonia nitrogen-containing wastewater A flows into the first-stage micro-dissolved oxygen reaction zone, 1.5 mg / L≥DO≥0.5 mg / L, the residence time is 3-5 h, and sludge-water mixture A is obtained; Low-C / N municipal wastewater flows into the first-stage micro-dissolved oxygen reaction zone, and the organic matter in the influent is used as a denitrification carbon source by heterotrophic denitrification functional bacteria to cause simultaneous nitrification and denitrification and short-cut nitrification and denitrification; S3. The sludge-water mixture A flows into the second-stage low-dissolved oxygen reaction zone, 2.5 mg / L≥DO≥1.5 mg / L, the residence time is 1-3 h, and sludge-water mixture B is obtained; The wastewater flows into the second-stage low-dissolved oxygen reaction zone, residual organic matters are oxidized into carbon dioxide, and residual ammonia nitrogen is further oxidized into nitrate nitrogen, so as to ensure that COD, NH4 + - N and TN reach the standard; S4. The sludge-water mixture B enters a sedimentation tank, the sludge is separated from the water, the sludge is returned to the process influent end, and the effluent enters a subsequent advanced treatment unit; The sludge-water mixture containing suspended sludge and aged biofilm enters a sedimentation tank, the sludge is separated from the water, the sludge is returned to the process influent end, the amount of residual sludge is reduced, and the biomass in the MBBR is maintained stable; S5. The aeration control system monitors the dissolved oxygen levels of each section of the process and the ammonia nitrogen level at the effluent end during operation, under normal temperature operation, when the water temperature is ≥15℃, and the effluent ammonia nitrogen abnormally rises to above 3.0 mg / L due to the impact of the influent water quality, the valve opening of the micro-porous aerator in the second-stage low-dissolved oxygen reaction zone is increased by 5%-10%, and at the same time, the valve opening of the cyclone aerator is reduced by 5%-10%; when the effluent ammonia nitrogen is stably below 1.5 mg / L, if the DO in the first-stage micro-dissolved oxygen reaction zone frequently fluctuates by more than 1.5 mg / L within a single day, the micro-porous aeration valve opening is reduced by 5%-10%, and at the same time, the cyclone aeration valve opening is increased by 5%-10%, so that the DO is maintained below 1.0 mg / L.

2. A low dissolved oxygen operated short process wastewater treatment process according to claim 1, characterized in that: The pool is filled with suspended filler, the filler filling rate of the first stage micro-dissolved oxygen reaction zone is 40% to 60%, the filler filling rate of the second stage low-dissolved oxygen reaction zone is 15% to 30%, the filler is selected from the B type filler specified in the "High-density polyethylene suspended carrier filler for water treatment" CJ / T 461-2014, the material is HDPE, the effective specific surface area is 500<SV<800m 2 / m 3 , the biomass of the filler after biofilm formation is greater than or equal to 2000mg MLSS / L, and the sludge concentration is 1000mg MLSS / L to 2000mg MLSS / L.

3. A low dissolved oxygen operated short flow wastewater treatment process according to claim 2, characterized in that: The first-stage micro-aeration reaction zone has a packing filling rate of 50%, and the second-stage low-aeration reaction zone has a packing filling rate of 15% and a packing SV of 800 m 2 / m 3 , and the biomass of the biofilm on the packing reaches 2000 mg MLSS / L, while the sludge concentration is controlled at 1000 mg MLSS / L.

4. A low dissolved oxygen operated short flow wastewater treatment process according to claim 3, characterized in that: Both the first-stage micro-dissolved oxygen reaction zone and the second-stage low-dissolved oxygen reaction zone contain compartments, the number of compartments n≥2, the length-width ratio of a single compartment is controlled to be 1:2-2:1, and three-dimensional columnar stainless steel intercepting screens with a pore size of 0.5-2.0 cm are arranged at the inlet and outlet of the compartments.

5. A low dissolved oxygen operated short flow wastewater treatment process according to claim 4, characterized in that: The first-stage micro-dissolved oxygen reaction zone mainly uses cyclone aeration, and the air volume accounts for 60%-100%; the second-stage low-dissolved oxygen reaction zone mainly uses micro-porous aeration, and the air volume accounts for 60%-100%, so as to ensure that the DO concentration is above 1.5 mg / L.

6. A low dissolved oxygen operated short flow wastewater treatment process according to claim 5, characterized in that: The micro-porous aerator is combined with the liftable cyclone aerator, the installation ratio is 4:1-6:1, the pore diameter of the micro-porous aerator is 0.5-1.0 mm, the installation height is 0.3-0.5 m from the bottom, the pore diameter of the liftable cyclone aerator is 1-3 mm, the air-water ratio is 10:1-20:1, the inclination angle of the aeration head is 45°, the rectangular or plum blossom shape is arranged in the center, and the installation height is 0.5-1.0 m.

7. A low dissolved oxygen operated short flow wastewater treatment process according to claim 6, characterized in that: The pore diameter of the micro-porous aerator is 0.5 mm, the pore diameter of the liftable cyclone aerator is 3 mm, and the air-water ratio is 10:

1.

8. A low dissolved oxygen operated short flow wastewater treatment process according to claim 7, characterized in that: The sludge reflux ratio is 50%-100%.

9. A low dissolved oxygen operated short flow wastewater treatment process according to claim 8, characterized in that: The ammonia nitrogen concentration of sewage inflow is 30-100 mg / L, and the effluent COD, NH4 + - N, TN reaches the first level A standard of "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" GB 18918-2002.

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