Short-cut nitrification and denitrification system and process method

Abstract

The application discloses a short-range nitrification and denitrification system and a process method, and the system comprises a primary denitrification tank, a primary nitration tank, a secondary denitrification tank, a secondary nitration tank and a UF unit which are sequentially connected in communication, and the UF unit is connected with a drainage pipe, a sludge external return pipe and a sludge discharge pipe; sludge in the primary nitration tank enters the primary denitrification tank through a sludge internal return pipe, and sludge generated by the UF unit enters the primary denitrification tank through the sludge external return pipe; a gas supply machine provides dissolved oxygen for the primary nitration tank and the secondary nitration tank through an aeration head, and the primary denitrification tank and the secondary denitrification tank are each provided with a stirrer. The application adopts a phased starting and running mode and corresponding control conditions without increasing fillers, biofilms and artificial addition of inhibitors, and establishes a system and a technical process for starting, cultivating and running of short-range nitrification and denitrification, and has the effects of fast starting and cultivating speed, good effect, low energy consumption and low cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to a short-cut nitrification and denitrification system and process method. BACKGROUND

[0002] With the continuous expansion of urbanization, the scale of sewage treatment is also increasing. Sewage denitrification is an important link in the process of sewage treatment, and research and development of economic and efficient denitrification technology and realization of carbon emission reduction are the research focus in the field of sewage treatment in the future. The most mature and widely used sewage biochemical treatment technology at present is the nitrification and denitrification technology as the core, but the high operation energy consumption and high carbon emission are unavoidable problems.

[0003] In the activated sludge, there are various microorganisms, and AOB bacterial flora and NOB bacterial flora are two common denitrification microbial bacteria. The nitrification and denitrification technology is to realize NH4 + oxidation to NO3 - , and then to reduce NO3 - to N2 through denitrification. The short-cut nitrification and denitrification technology is a new type of sewage denitrification process, which controls NH4 + oxidation to NO2 - , and then reduces NO2 - to N2 by taking NO2 - as an electron acceptor and providing electrons for organic matter. Compared with the traditional nitrification and denitrification process, the short-cut nitrification and denitrification process can theoretically save 25% of aeration energy consumption and 40% of carbon source requirement. The biochemical reaction formulas of nitrification and denitrification and short-cut nitrification and denitrification are as follows:

[0004] NH4 + + 2O2→ NO3 - + H2O + 2H + (nitrification reaction)

[0005] 6NO3 - + 5CH3OH→ 3N2↑ + 5CO2↑ + 7H2O + 6OH - (denitrification reaction, CH3OH represents carbon source)

[0006] NH4 + + 1.5O2→ NO2 - + H2O + 2H + (nitrosation reaction)

[0007] 6NO2 - + 3CH3OH→ 3N2↑ + 3CO2↑ + 3H2O + 6OH - (short-cut denitrification reaction, CH3OH represents carbon source)

[0008] At present, the technical methods for short-cut nitrification and denitrification start-up, cultivation and operation have the following problems:

[0009] (1) The existing method is difficult to maintain a high nitrosation degree, and the system has poor continuous operation stability, especially in dynamically maintaining AOB genus dominance and dynamically eliminating NOB genus, which easily leads to cultivation operation failure.

[0010] (2) The existing method including adding inhibitors and strain screening has high cost for short-cut nitrification strain cultivation and domestication.

[0011] (3) There are many inconveniences in sludge preservation and transportation, and how to use the existing pool and start-up and domestication in situ and put into operation is a big problem to be solved. SUMMARY

[0012] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a short-cut nitrification and denitrification system and process method which has fast cultivation rate, good effect, low cost, high automation degree and uses existing pool and conventional sludge for self-cultivation.

[0013] To solve the above technical problems, the present application adopts the following technical scheme:

[0014] A short-cut nitrification and denitrification system, comprising a first denitrification tank, a first nitrosation tank, a second denitrification tank, a second nitrosation tank and a UF unit which are sequentially connected, the first denitrification tank and the first nitrosation tank are connected through the bottom, the first nitrosation tank and the second denitrification tank are connected through the upper part, the second denitrification tank and the second nitrosation tank are connected through the bottom, the bottom of the second nitrosation tank and the UF unit are connected, and the UF unit is connected with a drainage pipe, a sludge external reflux pipe and a sludge discharge pipe; the sludge in the first nitrosation tank enters the first denitrification tank through a sludge internal reflux pipe, and the sludge generated by the UF unit enters the first denitrification tank through the sludge external reflux pipe; a gas supply machine provides dissolved oxygen for the first nitrosation tank and the second nitrosation tank through an aeration head, and the first denitrification tank and the second denitrification tank are each provided with a stirrer.

[0015] As a further improvement of the present application, an alkalinity tank and a carbon source tank are further included, the alkalinity tank is connected with the first nitrosation tank, the carbon source tank is connected with the first denitrification tank, and the first denitrification tank and the first nitrosation tank are both connected with a wastewater pipe and switch the water inlet point through a switch valve.

[0016] As a further improvement of the present application, the gas supply machine adopts a Roots blower, a magnetic suspension blower or a jet aeration; and the stirrer adopts a double-curved surface stirrer, a stirring paddle or a submersible plug flow stirrer.

[0017] As a further improvement of the present application, a cooling device is arranged on the sludge external reflux pipe to realize overall temperature control of the system, and the cooling device adopts a closed cooling tower or a plate heat exchanger.

[0018] As a further improvement of the present application, the short-cut nitrification-denitrification system adopts a PLC control system for automatic control and operation; the primary nitritation tank and the secondary nitritation tank are both provided with an online pH detector and a DO detector, wherein the pH detector is interlocked with an alkalinity tank to realize automatic addition of alkali liquid, so as to reach the pH parameter range set in the PLC control system; the DO detector is interlocked with a gas supplier to realize automatic adjustment of the gas supplier frequency, so as to reach the DO parameter range set in the PLC control system; the primary denitrification tank is provided with an online NO 2- detector, and the wastewater pipe and the outlet end of the carbon source tank are both provided with an online flow meter, and the online NO 2- detector and the online flow meter are interlocked in the PLC control system.

[0019] As a general technical concept, the present application further provides a process method based on the short-cut nitrification-denitrification system, which comprises the following steps:

[0020] Step S1, starting short-cut nitrification:

[0021] Step S11, inoculating the primary nitritation tank and the secondary nitritation tank with nitrifying activated sludge, and controlling the MLSS of the system at 5g / L-10g / L and the MLVSS / MLSS at more than 60% after inoculation;

[0022] Step S12, switching the valve on the wastewater pipe to feed water into the primary nitritation tank to perform an aeration nitrification reaction;

[0023] Step S13, adjusting the gas supplier to control the DO of the primary nitritation tank at 2.0 mg / L-2.5 mg / L, the DO of the secondary nitritation tank at 1.5 mg / L-2.0 mg / L, and not adding carbon source to the primary denitrification tank;

[0024] Step S14, maintaining the MLSS of the system at 5g / L-10g / L by sludge discharge to inhibit the growth of NOB bacteria, until c(NO2 - ) / c(NH4 + )>1.0 and c(NO2 - ) / c(NO3 - )>5;

[0025] Step S2, starting short-cut denitrification:

[0026] Step S21, keep the influent of the first stage nitritation tank, set the C / N ratio parameter in the control system to realize automatic carbon source adding of the first stage denitrification tank, and the first stage nitritation tank does not add alkalinity;

[0027] Step S22, adjust the air supply machine to control the DO of the first stage nitritation tank at 2.0 mg / L-2.5 mg / L, and control the DO of the second stage nitritation tank at 1.5 mg / L-2.0 mg / L;

[0028] Step S23, when the NO2 - Concentration of the first stage denitrification tank drops below 10 mg / L, it indicates that the short-cut denitrification domestication is successful.

[0029] Step S3, cultivation operation:

[0030] Step S31, the wastewater pipe cuts the wastewater into the influent of the first stage denitrification tank, in the first stage denitrification tank, the ratio of the sludge internal return flow to the influent is 100%-200%, and the ratio of the sludge external return flow to the influent is 200%-400%;

[0031] Step S32, according to the change of the ammonia nitrogen and nitrite nitrogen concentration in the first stage denitrification tank, gradually increase the influent load on the basis of step S2, and set the C / N ratio to 3.0 in the control system, and keep the NO2 - Concentration in the first stage denitrification tank below 10 mg / L.

[0032] Step S33, adjust the air supply machine to control the DO of the first stage nitritation tank at 1.5 mg / L-2.0 mg / L, and control the DO of the second stage nitritation tank at 1.0 mg / L-2.0 mg / L; control the pH of the first stage nitritation tank at 6.5-7.5, and control the water temperature in the first stage nitritation tank at 35℃-40℃.

[0033] Step S34, maintain the system MLSS at 10 g / L-15 g / L through sludge discharge, increase the original sludge discharge amount by 20%-50% to shorten the SRT, eliminate the NOB bacteria, and maintain the AOB bacteria.

[0034] As a further improvement of the application, in step S12, the influent is gradually increased by 10%-20% according to the design influent nitrogen load of 0.3 kg N / (m 3 ·d), and each time the increasing period is 3 d-5 d, until the design nitrogen load is reached.

[0035] As a further improvement of the present application, in the step S13, the water temperature in the first nitritation tank is controlled to be 35-40 DEG C, the pH in the first nitritation tank is kept at 6.0-7.0, if the pH is lower than 6.0, the alkalinity is added; the ratio of the sludge internal return flow from the first nitritation tank to the first denitrification tank to the water inflow of the first nitritation tank is 200%-400%, and the ratio of the sludge external return flow of the UF unit to the water inflow of the first nitritation tank is 200%-400%.

[0036] As a further improvement of the present application, in the step S21, the C / N ratio parameter is gradually increased by 10%-20% based on the C / N ratio of 3.0, and each increasing period is 1-3 days.

[0037] As a further improvement of the present application, in the step S32, the water inflow load is controlled to be increased by 5%-10% with an interval period of 3-5 days, and the maximum load is set to be 0.5 kgN / (m 3 ·d).

[0038] Compared with the prior art, the present application has the following advantages:

[0039] 1. The short-cut nitrification and denitrification system of the present application utilizes the conventional MBR biochemical tank body, including a first denitrification tank, a first nitritation tank, a second denitrification tank, a second nitritation tank, a gas supplier, a UF unit and the like, and by adding specific automatic modules and local facilities, a short-cut nitrification and denitrification system with starting conditions is formed, and the present application can fully utilize the existing tank body in the process technology upgrading of the wastewater plant without changing the existing tank structure, thereby greatly reducing the infrastructure cost and having good engineering applicability; the pH detector of the first nitritation tank and the alkalinity tank are interlocked to automatically add alkali to keep the pH in the tank within a specific process range, the DO detector and the gas supplier are interlocked to automatically adjust the frequency of the gas supplier to reach the set DO parameter range, the NO 2- X detector, a wastewater pipe flow meter and a carbon source tank adding flow meter are interlocked to automatically add carbon source in a certain amount, the present application has high automation degree and accurate control, can save labor intensity and auxiliary material consumption, avoids many problems caused by the long-distance transportation and storage of the short-cut nitrification sludge, realizes the utilization of the existing tank body and the in-situ starting, cultivation and engineering operation, and realizes the continuous and stable operation of the system.

[0040] 2、The short-cut nitrification and denitrification process method of the application uses the residual sludge of conventional nitrification and denitrification as seed sludge, under the condition of not changing the existing pool structure and function, through the combination of phased start-up and operation mode and specific control conditions, the short-cut nitrification and denitrification system mainly with ammonia oxidizing bacteria (AOB) and dynamically eliminating nitrite oxidizing bacteria (NOB) is gradually domesticated, a set of short-cut nitrification and denitrification start-up, culture and operation system and process flow is established, and the effects of fast sludge start-up and culture speed, good effect, low energy consumption and low cost are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is the structure principle schematic diagram of the short-cut nitrification and denitrification system in the specific embodiment of the application.

[0042] Figure 2 It is the automatic control logic schematic diagram in the specific embodiment of the application.

[0043] Figure 3 It is the process flow schematic diagram of the short-cut nitrification and denitrification in the specific embodiment of the application.

[0044] Legend: 1, primary denitrification tank; 2, primary nitritation tank; 3, secondary denitrification tank; 4, secondary nitritation tank; 5, UF unit; 6, air supply machine; 7, aeration head; 8, agitator; 9, alkalinity tank; 10, carbon source tank; 11, switch valve; L1, wastewater pipe; L2, drain pipe; L3, sludge internal reflux pipe; L4, sludge external reflux pipe; L5, sludge discharge pipe. DETAILED DESCRIPTION

[0045] The application is further described below in combination with the drawings of the specification and specific preferred embodiments, but the protection scope of the application is not limited therefore.

[0046] Example 1

[0047] As Figure 1As shown, the short-cut nitrification-denitrification system of the present invention includes a primary denitrification tank 1, a primary nitrification tank 2, a secondary denitrification tank 3, a secondary nitrification tank 4, and a UF unit 5 connected in sequence. The primary denitrification tank 1 and the primary nitrification tank 2 are connected at the bottom, the primary nitrification tank 2 and the secondary denitrification tank 3 are connected at the top, the secondary denitrification tank 3 and the secondary nitrification tank 4 are connected at the bottom, the bottom of the secondary nitrification tank 4 is connected to the UF unit 5, and the UF unit 5 is connected to a drain pipe L2, a sludge external return pipe L4, and a sludge discharge pipe L5. Sludge from the primary nitrification tank 2 enters the primary denitrification tank 1 through the sludge internal return pipe L3, and sludge generated by the UF unit 5 enters the primary denitrification tank 1 through the sludge external return pipe L4. The aeration unit 6 provides dissolved oxygen to the primary nitrification tank 2 and the secondary nitrification tank 4 through the aeration head 7. Both the primary denitrification tank 1 and the secondary denitrification tank 3 are equipped with a mixer 8.

[0048] In this embodiment, without adding packing material for biofilm formation, biofilm, or artificially adding inhibitors, the existing tanks can be fully utilized for upgrading the wastewater treatment process technology. There is no need to change the existing tank structure, which greatly reduces infrastructure costs and has good engineering applicability. Moreover, it avoids many problems caused by off-site transportation and storage of short-cut nitrification sludge, realizes the use of existing tanks for on-site start-up, cultivation, and engineering operation, and achieves continuous and stable operation of the system.

[0049] like Figure 1 As shown, in this embodiment, alkalinity tank 9 and carbon source tank 10 are also included. Alkalinity tank 9 is connected to primary nitrification tank 2, and carbon source tank 10 is connected to primary denitrification tank 1. Both primary denitrification tank 1 and primary nitrification tank 2 are connected to wastewater pipe L1, and the inlet point is switched by switching valve 11.

[0050] In this embodiment, the air supply unit 6 uses a Roots blower, a magnetic levitation blower, or jet aeration. The mixer 8 uses a hyperboloid mixer, a stirring paddle, or a submersible agitator.

[0051] In this embodiment, a cooling device (not shown in the figure) is installed on the sludge external return pipe L4 to achieve overall temperature control of the system. The cooling device adopts a closed cooling tower or a plate heat exchanger.

[0052] In this embodiment, the short-cut nitrification-denitrification system is automatically controlled and operated using a PLC control system to achieve precise control of various parameters and improve the degree of automation. The automatic control logic diagram is as follows: Figure 2The first stage nitrosation tank 2 and the second stage nitrosation tank 4 are both installed with an on-line pH detector and an on-line DO detector, wherein the pH detector is interlocked with the alkalinity tank 9 to realize automatic addition of alkali liquor into the first stage nitrosation tank 2, so as to reach the pH parameter range set in the PLC control system; the DO detector is interlocked with the air supply machine 6 to realize automatic adjustment of the frequency of the air supply machine 6, so as to reach the DO parameter range set in the PLC control system.

[0053] The first stage denitrification tank 1 is installed with an on-line NO 2- detector, the water inlet end of the wastewater pipe L1 and the outlet end of the carbon source tank 10 are both installed with on-line flow meters, and the on-line NO 2- detector and the on-line flow meter are interlocked in the PLC control system. 废水 The running logic is as follows: input the cod 废水 value, the ammonia nitrogen 碳源 value and the cod 碳源 value, and the carbon source addition flow is Q 废水 =Q 废水 ×(3.0×ammonia nitrogen 废水 -cod 碳源 ) / cod - When the NO2 - detection value is greater than 10 mg / L, the carbon source addition amount is automatically increased by 5% each time according to the preset value 3.0 until it is lower than 10 mg / L; when the NO2 - detection value is 0, the carbon source addition amount is automatically decreased by 5% each time according to the preset value 3.0 until it is within the range of 0-10 mg / L. Through accurate control of the carbon source addition amount, the total nitrogen removal rate is ensured, meanwhile, the cost waste caused by excessive carbon source addition is avoided, and the dominant effect of the short-cut denitrification bacteria is maintained.

[0054] Example 2

[0055] As shown in FIG. 2, the short-cut nitrification-denitrification process method of the present application is implemented based on the short-cut nitrification-denitrification system in Example 1, and comprises the following steps:

[0056] Step S1, start the short-cut nitrification.

[0057] Step S11, inoculate the first stage nitrosation tank 2 and the second stage nitrosation tank 4 with nitrification active sludge, and control the MLSS of the system at 5 g / L-10 g / L and the MLVSS / MLSS to be greater than 60% after inoculation.

[0058] Step S12, the switching valve 11 on the wastewater pipe L1 feeds water into the first stage nitrosation tank 2 to perform the aeration nitrification reaction.

[0059] Step S13, adjust the air supply machine 6 so that the DO of the first nitrosation tank 2 is controlled at 2.0 mg / L-2.5 mg / L, and the DO of the second nitrosation tank 4 is controlled at 1.5 mg / L-2.0 mg / L; at this time, the first denitrification tank 1 does not add carbon source.

[0060] Step S14, keep the MLSS at 5 g / L-10 g / L by sludge discharge, and inhibit the NOB bacterial population by the multiple effects of higher nitrous acid (FNA) concentration, shorter sludge age and higher load, until the short-cut nitrification feature is obvious, in this embodiment, the determination mark for reaching the short-cut nitrification phenomenon in the system is set as: c (NO2 - ) / c (NH4 + ) > 1.0, and c (NO2 - ) / c (NO3 - ) > 5.

[0061] Step S2, after the start of step S1, start the short-cut denitrification stage.

[0062] Step S21, keep the influent of the first nitrosation tank 2, set the C / N ratio parameter in the control system to realize the automatic addition of carbon source in the first denitrification tank 1, and do not add alkalinity in the first nitrosation tank 2; the ratio of the sludge internal return flow of the first nitrosation tank 2 to the influent of the first nitrosation tank 2 is 200%-400%, and the ratio of the sludge external return flow of the UF unit 5 to the influent of the first nitrosation tank 2 is 200%-400%; in this embodiment, the carbon source addition adopts one or more of acetic acid, sodium acetate, methanol, flour, glucose or high-concentration organic wastewater (such as fresh landfill leachate, kitchen wastewater, etc.).

[0063] Step S22, adjust the air supply machine 6 so that the DO of the first nitrosation tank 2 is controlled at 2.0 mg / L-2.5 mg / L, and the DO of the second nitrosation tank 4 is controlled at 1.5 mg / L-2.0 mg / L.

[0064] Step S23, when the NO2 - concentration of the first denitrification tank 1 drops below 10 mg / L, it indicates that the short-cut denitrification domestication is successful.

[0065] Step S3, after the start of step S2, enter the cultivation running stage.

[0066] Step S31, the wastewater pipe L1 cuts the wastewater into the influent of the first denitrification tank 1, in the first denitrification tank 1, the ratio of the sludge internal return flow to the influent is 100%-200%, and the ratio of the sludge external return flow to the influent is 200%-400%.

[0067] Step S32, according to the concentration variation of ammonia nitrogen and nitrite nitrogen in the first-stage denitrification tank 1, the influent load is gradually increased on the basis of step S2, and the C / N ratio is set to 3.0 in the control system, so as to keep the NO2 - concentration in the first-stage denitrification tank 1 below 10 mg / L.

[0068] Step S33, the air supply machine 6 is adjusted so that the DO in the first-stage nitritation tank 2 is controlled to be 1.5 mg / L-2.0 mg / L, and the DO in the second-stage nitritation tank 4 is controlled to be 1.0 mg / L-2.0 mg / L; the pH in the first-stage nitritation tank 2 is controlled to be 6.5-7.5, and the water temperature in the first-stage nitritation tank 2 is controlled to be 35℃-40℃.

[0069] Step S34, the MLSS is controlled to be 10 g / L-15 g / L by sludge discharge, if the nitrite nitrogen concentration shows a rising trend, the sludge discharge amount is increased by 20%-50% on the basis of the original sludge discharge amount to shorten the SRT, and the AOB bacteria are dynamically kept dominant and the NOB bacteria are dynamically eliminated by using the characteristic that the generation period of the AOB bacteria is smaller than that of the NOB bacteria.

[0070] In the embodiment, the short-cut nitrification process is started and applied in engineering without changing the existing tank structure and function, and has the effects of fast starting and culturing speed, good effect, low energy consumption and low cost.

[0071] In step S12 of the embodiment, the influent amount is gradually increased by 10%-20% of the design influent nitrogen load 0.3 kg N / (m 3 ·d) every time, and the increasing period is 3 d-5 d until the design nitrogen load is reached.

[0072] In step S13 of the embodiment, the water temperature in the first-stage nitritation tank 2 is controlled to be 35℃-40℃, the pH in the first-stage nitritation tank 2 is kept at 6.0-7.0, if the pH is lower than 6.0, the alkalinity is added, the ratio of the sludge internal return flow of the first-stage nitritation tank 2 to the influent amount of the first-stage nitritation tank 2 is 200%-400%, and the ratio of the sludge external return flow of the UF unit 5 to the influent amount of the first-stage nitritation tank 2 is 200%-400%.

[0073] In the embodiment, the alkalinity addition adopts one or more of liquid alkali, tablet alkali, sodium carbonate and sodium bicarbonate.

[0074] In step S21 of the embodiment, the C / N ratio parameter is gradually increased by 10%-20% on the basis of the C / N ratio of 3.0 every time, and the increasing period is 1 d-3 d.

[0075] In step S32 of the embodiment, the water inflow load is controlled to increase by 5% to 10%, the interval period is 3d to 5d, the maximum load is set to 0.5kgN / (m 3 ·d.

[0076] In the embodiment, the conventional nitrification-denitrification residual sludge is used as the seed sludge, the start-up and operation modes are combined with specific control conditions, the differences in the suitable metabolic and proliferation conditions of the two bacterial populations are used for screening and control, and the residual sludge is gradually domesticated into a short-cut nitrification-denitrification system mainly composed of ammonia oxidizing bacteria (AOB) and dynamically eliminating nitrite oxidizing bacteria (NOB), so as to establish a system and process flow for starting, cultivating and operating the short-cut nitrification-denitrification.

[0077] Embodiment 3

[0078] The indexes of the digested liquid wastewater generated by a municipal sludge project are as follows: the pH is 7.9, the ammonia nitrogen concentration is about 1900mg / L, the total nitrogen concentration is about 2000mg / L, the COD concentration is about 2200mg / L, the total alkalinity is about 3000mg / L, the water temperature is 45℃, and the wastewater is a typical high-ammonia-nitrogen, low-C / N-ratio and low-alkalinity wastewater. The layout of the wastewater treatment tank is two-stage nitrification-denitrification, and the short-cut nitrification-denitrification system and process method in the embodiments 1 and 2 are used for starting and operating the short-cut nitrification-denitrification:

[0079] Step S1, starting the short-cut nitrification.

[0080] The residual sludge generated by the sludge digestion liquid treatment of the project or the landfill leachate treatment in the park is used as the seed sludge to be connected to the tank. After inoculation, the system MLSS concentration is 5g / L, the wastewater is fed from the first-stage nitritation tank 2, the DO of the first-stage nitritation tank 2 is controlled to be 2.0mg / L to 2.5mg / L, the DO of the second-stage nitritation tank 4 is controlled to be 1.5mg / L to 2.0mg / L, and no carbon source is added to the first-stage denitrification tank 1. The water temperature of the first-stage nitritation tank 2 and the second-stage nitritation tank 4 is maintained at 35℃ to 40℃, the pH of the first-stage nitritation tank 2 is maintained at 6.0 to 7.0, and the pH is controlled by adding liquid alkali. The influent nitrogen load is gradually increased by 20% of the design nitrogen load of 0.3kg N / (m 3 ·d every time, the increasing period is 3d, and the process lasts for 15 days until the design nitrogen load is reached. The ratio of the sludge internal return flow of the first-stage nitritation tank 2 to the influent of the first-stage nitritation tank 2 is 300%, and the ratio of the sludge external return flow of the UF unit 5 to the influent of the first-stage nitritation tank 2 is 300%. During the period, the residual sludge is discharged to maintain the sludge concentration in the process range of 5g / L to 10g / L. On the 20th day, the NH4 + concentration in the second-stage nitritation tank 4 gradually decreases to 550mg / L, the NO2 -concentration gradually increased to 670 mg / L, NO3 - concentration gradually decreased to 110 mg / L, indicating that the start-up of short-cut nitrification was successful. Among them, due to the presence of part of COD in the influent, the total nitrogen removal rate of the system was 33%.

[0081] Step S2, after the successful start-up of step S1, the short-cut denitrification stage is started.

[0082] On the basis of step S1 operation, carbon source is added to the first denitrification tank 1, and the carbon source is industrial acetic acid (mass fraction 70%). The set value is gradually increased by 15% according to the C / N ratio of 3.0, and each increase period is 1d. The first nitritation tank 2 does not add alkalinity. The gradual reduction of nitrite nitrogen is realized through the sludge internal reflux from the first nitritation tank 2 to the first denitrification tank 1 and the sludge external reflux from the UF unit 5 to the first denitrification tank 1, and the alkalinity produced by the first denitrification tank 1 is supplemented to the first nitritation tank 2. With the supplement of denitrification alkalinity to the first nitritation tank 2, the DO content of the first nitritation tank 2 will gradually decrease. At this time, the air blower 6 increases the frequency to control the DO in the first nitritation tank 2 to remain in the range of 2.0 mg / L-2.5 mg / L. After 7d, the NO2 - concentration gradually decreased to 8 mg / L, NH4 + concentration decreased to 290 mg / L, NO3 - concentration decreased to 50 mg / L, and alkalinity was 120 mg / L. Due to the insufficient alkalinity of the system, the ammonia oxidation rate was limited, and it was comprehensively indicated that the short-cut denitrification domestication was successful.

[0083] Step S3, after the successful start-up of step S2, the cultivation operation stage is entered.

[0084] The influent point is the first denitrification tank 1 by switching the influent valve, and the pre-denitrification operation mode is adopted. The influent load is gradually increased, and the load lifting amplitude is controlled at 10% with an interval period of 3d. The first denitrification tank 1 adds acetic acid as carbon source, and the C / N ratio is set to 3.0 in the program. When the NO2 - When the detection value is greater than 10 mg / L, the carbon source dosage is automatically increased by 5% each time according to the preset value of 3.0, until it is lower than 10 mg / L; NO2 -When the detection value is 0, the carbon source dosage is automatically reduced by 5% each time according to the preset value of 3.0, until 0 mg / L-10 mg / L. The DO of the first nitritation tank 2 is controlled at 1.5 mg / L-2.0 mg / L, the DO of the second nitritation tank 4 is controlled at 1.0 mg / L-2.0 mg / L, the liquid alkali is added to control the pH of the first nitritation tank 2 at 6.5-7.5, the water temperature in the tank is controlled at 35-40 DEG C, the internal return flow / influent ratio is 150%, the external return flow / influent ratio is 300%, and the MLSS in the system is maintained at 10-15 g / L by sludge discharge. After 15 days, the nitrogen load of the influent in the tank reaches 0.45 kg N / (m 3 ·d), the NH4 + - concentration of the second nitritation tank 4 gradually decreases to 20 mg / L, the NO2 - - concentration is 25 mg / L, the NO3 - - concentration is 10 mg / L, and after UF membrane treatment, the water reaches the reuse water standard or RO membrane deep treatment, and reaches the nanometer pipe standard.

[0085] According to the energy consumption calculation, the C / N ratio of the original full nitrification and denitrification process is about 4.5, and at present, it is about 3.0, and the reduction is 33%, which is close to the 40% carbon source saving of the shortcut denitrification theory. At the same time, the energy consumption of the fan is reduced by about 20%, which is close to the 25% oxygen saving of the shortcut nitrification theory, and the tank capacity load is higher.

[0086] Although the present application is disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any skilled person in the art can make many possible changes and modifications to the technical solutions of the present application, or modify equivalent embodiments with equivalent changes, without departing from the spirit and technical solutions of the present application, by using the disclosed methods and technical contents. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the technical solutions of the present application, still belongs to the protection scope of the technical solutions of the present application.

Claims

1. A process based on a short-cut nitrification-denitrification system, characterized in that, The short-range nitrification denitrification system comprises a first-stage denitrification tank (1), a first-stage nitration tank (2), a second-stage denitrification tank (3), a second-stage nitration tank (4) and a UF unit (5) connected in sequence, and an alkalinity tank (9) and a carbon source tank (10), the first-stage denitrification tank (1) and the first-stage nitration tank (2) are connected through the bottom, the first-stage nitration tank (2) and the second-stage denitrification tank (3) are connected through the upper part, the second-stage denitrification tank (3) and the second-stage nitration tank (4) are connected through the bottom, the bottom of the second-stage nitration tank (4) is connected with the UF unit (5), and the UF unit (5) is connected with a drainage pipe (L2), a sludge external return pipe (L4) and a sludge discharge pipe (L5); the sludge in the first-stage nitration tank (2) enters the first-stage denitrification tank (1) through a sludge internal return pipe (L3), and the sludge generated by the UF unit (5) enters the first-stage denitrification tank (1) through the sludge external return pipe (L4); a gas supply machine (6) provides dissolved oxygen for the first-stage nitration tank (2) and the second-stage nitration tank (4) through an aeration head (7), and the first-stage denitrification tank (1) and the second-stage denitrification tank (3) are each provided with a stirrer (8); the alkalinity tank (9) is connected with the first-stage nitration tank (2), the carbon source tank (10) is connected with the first-stage denitrification tank (1), and the first-stage denitrification tank (1) and the first-stage nitration tank (2) are both connected with a wastewater pipe (L1) and switch the water inlet point through a switching valve (11); The process method comprises the following steps: Step S1, starting short-range nitrification: Step S11, inoculating the residual activated sludge generated in the treatment of high-ammonia-nitrogen municipal wastewater in the first-stage nitration tank (2) and the second-stage nitration tank (4), and controlling the MLSS of the system at 5 g / L-10 g / L and the MLVSS / MLSS at greater than 60% after inoculation; Step S12, switching the switching valve (11) on the wastewater pipe (L1) to feed water into the first-stage nitration tank (2) to perform aeration nitrification reaction; Step S13, adjusting the gas supply machine (6) to control the DO of the first-stage nitration tank (2) at 2.0 mg / L-2.5 mg / L, the DO of the second-stage nitration tank (4) at 1.5 mg / L-2.0 mg / L, and not adding a carbon source to the first-stage denitrification tank (1); Step S14, the MLSS is controlled at 5-10 g / L by the sludge discharge system, which inhibits the formation of NOB bacterial population until the c(NO2 - ) / c(NH4 + )>1.0 and c(NO2 - ) / c(NO3 - )>5 in the pool. Step S2, starting short-range denitrification: Step S21, keeping the first-stage nitration tank (2) fed with water, setting the C / N ratio parameter in the control system to realize automatic addition of a carbon source to the first-stage denitrification tank (1) and not adding alkalinity to the first-stage nitration tank (2); Step S22, adjusting the gas supply machine (6) to control the DO of the first-stage nitration tank (2) at 2.0 mg / L-2.5 mg / L and the DO of the second-stage nitration tank (4) at 1.5 mg / L-2.0 mg / L; Step S23, when the NO2 - concentration of the primary denitrification tank (1) drops below 10 mg / L, indicating that the short-cut denitrification domestication is successful; Step S3, cultivating operation: Step S31, feeding wastewater into the first-stage denitrification tank (1) through the wastewater pipe (L1), and controlling the ratio of the sludge internal return amount to the water inlet amount in the first-stage denitrification tank (1) at 100%-200% and the ratio of the sludge external return amount to the water inlet amount at 200%-400%; Step S32, according to the concentration change of ammonia nitrogen and nitrite nitrogen in the first-stage denitrification tank (1), the influent load is gradually increased on the basis of step S2, and the C / N ratio is set to 3.0 in the control system, so as to keep the NO2 - concentration in the first-stage denitrification tank (1) below 10 mg / L; Step S33, adjust the air supply machine (6) so that the DO of the first nitrosation tank (2) is controlled at 1.5 mg / L-2.0 mg / L, and the DO of the second nitrosation tank (4) is controlled at 1.0 mg / L-2.0 mg / L; the pH of the first nitrosation tank (2) is controlled at 6.5-7.5, and the water temperature in the first nitrosation tank (2) is controlled at 35℃-40℃; Step S34, maintain the system MLSS at 10 g / L-15 g / L by sludge discharge, increase the sludge discharge amount by 20%-50% on the basis of the original sludge discharge amount to shorten the SRT, eliminate NOB bacteria, and maintain AOB bacteria.

2. The process of claim 1, wherein, The air supply machine (6) adopts a Roots blower, a magnetic suspension blower or a jet aeration; the agitator (8) adopts a double-curved-surface agitator, an agitator paddle or a submersible plug flow agitator.

3. The process of claim 1, wherein, The cooling device is used to realize the overall temperature control of the system, and the cooling device adopts a closed cooling tower or a plate heat exchanger.

4. The process according to any one of claims 1 to 3, characterized in that, The short-range nitrification denitrification system adopts a PLC control system for automatic control and operation; the first-stage nitrosation tank (2) and the second-stage nitrosation tank (4) are both provided with online pH detectors and DO detectors, wherein the pH detector is interlocked with the alkalinity tank (9) to automatically add alkali, so as to reach the pH parameter range set in the PLC control system; the DO detector is interlocked with the air supply machine (6) to automatically adjust the frequency of the air supply machine (6), so as to reach the DO parameter range set in the PLC control system; the first-stage denitrification tank (1) is provided with an online NO 2- detector, the water inlet end of the wastewater pipe (L1) and the outlet end of the carbon source tank (10) are both provided with online flow meters, and the online NO 2- detector and the online flow meter are interlocked in the PLC control system.

5. The process according to any one of claims 1 to 3, characterized in that, In the step S12, the influent nitrogen load is gradually increased by 10% to 20% of d) per 3 to 5 days until the design nitrogen load is reached. 3 d) 10% to 20% of the influent is gradually increased per 3 to 5 days until the design nitrogen load is reached.

6. The process according to any one of claims 1 to 3, characterized in that, In step S13, the water temperature in the first nitrosation tank (2) is controlled at 35℃-40℃, the pH of the first nitrosation tank (2) is maintained at 6.0-7.0, if the pH is lower than 6.0, the alkalinity is added, the internal sludge return amount of the first nitrosation tank (2) to the first denitrification tank (1) is 200%-400% of the water inflow amount of the first nitrosation tank (2), and the external sludge return amount of the UF unit (5) is 200%-400% of the water inflow amount of the first nitrosation tank (2).

7. The process according to any one of claims 1 to 3, characterized in that, In step S21, the C / N ratio parameter is gradually increased by 10%-20% on the basis of the C / N ratio of 3.0, and each increase period is 1d-3d.

8. The process according to any one of claims 1 to 3, characterized in that, The step S32, the water load is raised to the extent of 5% to 10%, the interval period is 3d to 5d, and the maximum load is set to 0.5kgN / (m 3 ·d).

Images