Method for automatically controlling thickness of MABR biological membrane

Abstract

The invention discloses a method for automatically controlling the thickness of an MABR biological membrane. The theoretical tail gas oxygen content O2out is calculated according to the oxygen transfer efficiency OTE of an MABR membrane assembly and the intake oxygen content O2in, wherein the oxygen transfer efficiency OTE of the MABR membrane assembly is equal to (O2in-FvO2out) / O2in; the oxygen reduction coefficient Fv is equal to (1-O2in) / (1-O2out); the theoretical tail gas oxygen content O2out is equal to 1 / [(1-O2in) / (1-OTE) O2in + 1]; monitoring the ammonia nitrogen concentration in the effluent treated by the MABR membrane module and the oxygen content in the tail gas; and adaptively adjusting the process according to the monitored ammonia nitrogen concentration and the oxygen content in the tail gas. According to the method and the device for automatically controlling the thickness of the MABR biological membrane, the thickness of the biological membrane can be automatically controlled, the energy consumption is reduced, and the sewage treatment efficiency is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a method for automatically controlling the thickness of a MABR biofilm. Background Art

[0002] The Membrane Aerated Biofilm Reactor (MABR) uses organic material membrane as a carrier of microorganisms and provides bubble-free oxygen to the microorganisms with high oxygen transfer efficiency. At the same time, it has multiple denitrification functions and high denitrification efficiency due to the various denitrification microorganisms it carries, making it a highly promising innovative process for future sewage biological treatment.

[0003] The various microorganisms attached to the surface of MABR membranes have diverse functions and are the core of MABR's efficient pollution reduction and carbon reduction functions. The appropriate biofilm thickness is extremely critical to the performance of MABR functions.

[0004] If the biofilm on the surface of the MABR membrane is too thin, the microorganisms will not accumulate enough to provide enough biomass to degrade pollutants, resulting in low pollutant (substrate) removal efficiency. In addition, a too thin biofilm may allow dissolved oxygen to penetrate the entire biofilm, thereby inhibiting the denitrification process outside the biofilm and resulting in low denitrification efficiency. If the biomass on the surface of the MABR membrane accumulates excessively, the thickness of the biofilm (especially the thickness of the outer anoxic zone) will increase. A too thick biofilm will increase the resistance to the diffusion of oxygen from the aeration membrane to the biofilm, and also increase the resistance to the diffusion of ammonia nitrogen and organic matter from the mainstream liquid phase to the aerobic zone inside the biofilm, resulting in a decrease in the flux of pollutants (substrates) and oxygen, thereby greatly reducing the effectiveness of MABR in removing COD, ammonia nitrogen and total nitrogen.

[0005] Monitoring biofilm thickness is helpful for studying the best method of controlling biofilm thickness in MABR. At present, the biofilm control on the surface of MABR membrane is usually carried out by regular aeration, scrubbing and flushing, which is relatively blind and hysteresis, and the accuracy is not high, making it difficult to effectively and quickly exert the advantages of MABR; and regular scrubbing consumes high energy consumption of fan operation. Summary of the invention

[0006] The purpose of the present invention is to provide a method for automatically controlling the thickness of a MABR biofilm, which can control the thickness of the biofilm, reduce energy consumption, and ensure sewage treatment efficiency.

[0007] Based on the above problems, the technical solution provided by the present invention is: A method for automatically controlling the thickness of MABR biofilm, According to the oxygen transfer efficiency (OTE) of the MABR membrane module of the MABR membrane system and the oxygen content (O) of the inlet gas 2in Calculate the theoretical exhaust oxygen content O2out : The oxygen transfer efficiency of MABR membrane module is OTE = (O 2in -F v O 2out ) / O 2in ; Oxygen reduction factor F v = (1-O 2in ) / (1-O 2out ); The theoretical exhaust oxygen content O 2out =1 / [(1-O 2in ) / (1-OTE)O 2in +1]; Monitor the ammonia nitrogen concentration in the effluent treated by the MABR membrane module and the oxygen content in the tail gas: When the exhaust oxygen content is ≤O 2out Or it keeps decreasing for twice the HRT, and the effluent ammonia nitrogen concentration is less than 30% of the discharge standard value. At this time, the scrubbing fan is turned off; When the exhaust oxygen content is greater than O 2out Or it continues to increase for twice the HRT, and the effluent ammonia nitrogen concentration is less than 30% of the emission standard value. At this time, turn off the scrubbing fan and reduce the process gas flow until the tail gas oxygen content is ≤O 2out ; When the exhaust oxygen content is ≤O 2out Or it continues to decrease for twice the HRT, and the outlet ammonia nitrogen concentration is ≥30% of the emission standard value. At this time, the scrubbing fan is turned on until the outlet ammonia nitrogen concentration is <30% of the emission standard value; When the exhaust oxygen content is greater than O 2out Or it continues to increase for twice the HRT, and the outlet ammonia nitrogen concentration is ≥30% of the emission standard value. At this time, turn on the scrubbing fan until the outlet ammonia nitrogen concentration is <30% of the emission standard value. If the exhaust oxygen content is >O 2out Or continue to increase and reduce the process gas flow until the tail gas oxygen content is ≤O 2out .

[0008] In some of the embodiments, the inlet pressure and the tail gas pressure of the MABR membrane assembly are monitored, and when the difference between the inlet pressure and the tail gas pressure is greater than a set value, the condensate valve is opened to remove the condensate in the membrane cavity.

[0009] In some embodiments, the MABR membrane system comprises: A MABR membrane reactor, wherein the MABR membrane reactor is connected to an inlet pipe and an outlet pipe, and a plurality of MABR membrane modules are arranged inside the MABR membrane reactor; A process air intake assembly, used to provide oxygen to the plurality of MABR membrane assemblies, comprising an air intake pipeline connected to the plurality of MABR membrane assemblies, and an air intake fan, an air intake flow meter and an air intake electric regulating valve sequentially arranged on the air intake pipeline along the air intake direction; A tail gas assembly, used to discharge tail gas after the wastewater is treated by the MABR membrane assemblies, comprising a tail gas pipeline connected to the MABR membrane assemblies and an online oxygen content monitor arranged on the tail gas pipeline; A scrubbing assembly, used for scrubbing the plurality of MABR membrane assemblies, comprising a scrubbing aerator disposed below the plurality of MABR membrane assemblies, a scrubbing pipeline connected to the scrubbing aerator, and a scrubbing fan, a scrubbing flow meter and a scrubbing electric regulating valve sequentially disposed on the scrubbing pipeline along an air inlet direction; An ammonia nitrogen online monitor, which is arranged at the outlet side of the MABR reactor and is used to monitor the ammonia nitrogen concentration in the treated effluent; The control unit, the air intake fan, the air intake flow meter, the air intake electric regulating valve, the oxygen content online monitor, the scrubbing fan, the scrubbing flow meter, the scrubbing electric regulating valve, and the ammonia nitrogen online monitor are respectively connected to the control unit signal.

[0010] In some embodiments, the MABR membrane system further comprises: An intake pressure sensor, which is arranged on the intake pipe and located between the intake flow meter and the intake electric regulating valve, and is used to monitor the intake pressure; A tail gas pressure sensor is arranged on the tail gas pipeline and located between the oxygen content online monitor and the MABR membrane assembly, and is used to monitor the tail gas pressure; A condensate water pipeline connected to the membrane cavity of the MABR membrane module, wherein a condensate water valve is provided on the condensate water pipeline; The intake pressure sensor, the exhaust pressure sensor, and the condensate valve are respectively connected to the control unit by signals.

[0011] In some of the embodiments, a water inlet flow meter is provided on the water inlet pipe.

[0012] Compared with the prior art, the advantages of the present invention are: 1. By monitoring the ammonia nitrogen concentration in the treated water and the oxygen content in the tail gas, the change in the biofilm thickness can be indirectly reflected, so that the control unit can perform operations such as scrubbing and reducing the gas volume in time to keep the biofilm thickness at an appropriate thickness, effectively respond to fluctuations in the quality and volume of incoming water, improve the sewage treatment efficiency, reduce unnecessary regular scrubbing, reduce energy consumption, and reduce operating costs; 2. It is only necessary to add an online ammonia nitrogen monitor and an online oxygen content monitor to the original sewage treatment equipment, so as to indirectly reflect the changes in the biofilm through monitoring data, so as to make timely process adjustments. The monitoring equipment is mature and reliable, with low purchase and maintenance costs, which makes the cost of controlling the biofilm thickness low. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. The accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0014] Figure 1 A schematic structural diagram of an embodiment of a MABR membrane system according to a method for automatically controlling the thickness of a MABR biofilm of the present invention; in: 1. MABR reactor; 2. MABR membrane assembly; 3. Air intake pipe; 4. Air intake fan; 5. Air intake flow meter; 6. Air intake pressure sensor; 7. Air intake electric regulating valve; 8. Scrubbing aerator; 9. Scrubbing pipe; 10. Scrubbing fan; 11. Scrubbing flow meter; 12. Scrubbing electric regulating valve; 13. Exhaust gas pipe; 14. Online oxygen content monitor; 15. Exhaust gas pressure sensor; 16. Ammonia nitrogen online monitor; 17. Condensate pipe; 18. Water inlet pipe; 19. Water inlet flow meter; 20. Water outlet pipe. DETAILED DESCRIPTION

[0015] See also Figure 1 , which is a structural schematic diagram of an embodiment of the present invention, provides a MABR membrane system involving a method for automatically controlling the thickness of a MABR biofilm, including a MABR reactor 1, a process air intake component, a scrubbing component, an exhaust gas component, an ammonia nitrogen online monitor 16 and a control unit.

[0016] The MABR reactor 1 is connected to an inlet pipe 18 and an outlet pipe 20 on opposite sides. A plurality of MABR membrane modules 2 are arranged in the MABR reactor 1. An inlet flow meter 19 is arranged on the inlet pipe 18 to monitor the inlet flow rate. The MABR membrane module 2 adopts a commonly used membrane module in the prior art, which will not be described in detail in the present invention.

[0017] The process air intake assembly is used to provide oxygen to a plurality of MABR membrane assemblies 2, and includes an air intake pipe 3 connected to the plurality of MABR membrane assemblies 2, and an air intake fan 4, an air intake flow meter 5 and an air intake electric regulating valve 7 sequentially arranged on the air intake pipe 3 along the air intake direction.

[0018] The tail gas assembly is used to discharge the tail gas after the wastewater is treated by the MABR membrane assemblies 2, and includes a tail gas pipeline 13 connected to the MABR membrane assemblies 2 and an online oxygen content monitor 14 arranged on the tail gas pipeline 13.

[0019] The scrubbing assembly is used to scrub a plurality of MABR membrane assemblies 2, and includes a scrubbing aerator 8 arranged below the plurality of MABR membrane assemblies 2, a scrubbing pipe 9 connected to the scrubbing aerator 8, and a scrubbing fan 10, a scrubbing flow meter 11 and a scrubbing electric regulating valve 12 sequentially arranged on the scrubbing pipe 9 along the air inlet direction.

[0020] The ammonia nitrogen online monitor 16 is arranged on one side of the MABR reactor 1 close to the outlet pipe 20 and is used to monitor the ammonia nitrogen concentration in the treated outlet water.

[0021] The above-mentioned air intake fan 4, air intake flow meter 5, air intake electric regulating valve 7, oxygen content online monitor 14, scrubbing fan 10, scrubbing flow meter 11, scrubbing electric regulating valve 12, and ammonia nitrogen online monitor 16 are respectively connected to the control unit signal to realize automatic control of the process and automatic adjustment of the biofilm thickness.

[0022] In order to further optimize the implementation effect of the present invention, when the membrane cavity of the MABR membrane assembly 2 is blocked, it is convenient to clean the membrane cavity in time, and an intake pressure sensor 6, an exhaust gas pressure sensor 15 and a condensate pipe 17 are also provided. The intake pressure sensor 6 is arranged on the intake pipe 3 and is located between the intake flowmeter 5 and the intake electric regulating valve 7, and is used to monitor the intake pressure. The exhaust gas pressure sensor 15 is arranged on the exhaust pipe 13 and is located between the oxygen content online monitor 14 and the MABR membrane assembly 2, and is used to monitor the exhaust gas pressure. The condensate pipe 17 is connected to the membrane cavity of the MABR membrane assembly 2, and a condensate valve is provided on the condensate pipe 17. The above-mentioned intake pressure sensor 6, exhaust gas pressure sensor 15, and condensate valve are respectively connected to the control unit signal. When the difference between the intake pressure and the exhaust pressure is greater than the set value, it means that the membrane cavity is blocked, and the condensate valve is controlled to open to discharge the condensate in the membrane cavity.

[0023] The method for automatically controlling the thickness of the MABR biofilm in the above system is: According to the oxygen transfer efficiency OTE of the MABR membrane module and the oxygen content of the inlet gas O 2in Calculate the theoretical exhaust oxygen content O 2out : The oxygen transfer efficiency of MABR membrane module is OTE = (O 2in -F v O 2out ) / O 2in ; Oxygen reduction factor F v = (1-O2in ) / (1-O 2out ); The theoretical exhaust oxygen content O 2out =1 / [(1-O 2in ) / (1-OTE)O 2in +1]; Monitor the ammonia nitrogen concentration in the effluent treated by the MABR membrane module and the oxygen content in the tail gas: When the exhaust oxygen content is ≤O 2out Or it continues to decrease for a duration of two times the HRT, and the outlet ammonia nitrogen concentration is less than 30% of the discharge standard value, at which time, the scrubbing fan 10 is turned off; When the exhaust oxygen content is greater than O 2out Or it continues to increase for a duration of two times HRT, and the effluent ammonia nitrogen concentration is less than 30% of the emission standard value. At this time, turn off the scrubbing fan 10 and reduce the process gas flow until the tail gas oxygen content is ≤O 2out ; When the exhaust oxygen content is ≤O 2out Or it continues to decrease for a duration of two times the HRT, and the outlet ammonia nitrogen concentration is ≥30% of the emission standard value. At this time, the scrubbing fan 10 is turned on until the outlet ammonia nitrogen concentration is <30% of the emission standard value; When the exhaust oxygen content is greater than O 2out Or it continues to increase for a duration of two times HRT, and the outlet ammonia nitrogen concentration is ≥30% of the emission standard value. At this time, the scrubbing fan 10 is turned on until the outlet ammonia nitrogen concentration is <30% of the emission standard value. If the exhaust oxygen content is >O 2out Or continue to increase and reduce the process gas flow until the tail gas oxygen content is ≤O 2out .

[0024] Monitor the inlet pressure and tail gas pressure of the MABR membrane assembly. When the difference between the inlet pressure and the tail gas pressure is greater than the set value, open the condensate valve to remove the condensate in the membrane cavity.

[0025] The following are specific embodiments: The oxygen transfer efficiency (OTE) of MABR membrane modules is generally between 30% and 40%. Assuming that OTE is 30%, the oxygen content of the inlet air is O 2in Constant 20.9%, calculated theoretical exhaust oxygen content O 2out The emission standard requires that ammonia nitrogen is less than 3 (5) mg / L. In order to ensure the safe and stable operation of the treatment system, about 30% of the emission standard value is generally used as the warning value, that is, when the ammonia nitrogen in the MABR effluent is close to about 30% of the emission standard value, that is, C N =1(1.5)mg / L (the values ​​outside the brackets are the control indicators when the water temperature is >12℃, and the values ​​inside the brackets are the control indicators when the water temperature is ≤12℃), the system needs to make changes to the biofilm thickness control conditions.

[0026] HRT is the hydraulic retention time, and the hydraulic retention time of a general MABR reactor is 16~24h. When a parameter change lasts twice the hydraulic retention time, it means that a certain condition has changed, and the fluctuation of online monitoring instruments or manual detection can be ignored, indicating that the system needs to make corresponding operational adjustments to cope with parameter changes.

[0027] MABR operation includes biofilm formation period (generally 15 to 30 days, depending on water temperature, water quality, and influent load), load increase period (60 to 90 days) and stable operation period. The present invention is mainly aimed at the operation management of the load increase period and stable operation period after biofilm formation. There is no need to control the biofilm thickness during biofilm formation.

[0028] When the exhaust gas oxygen content is ≤15.6% or continues to decrease (duration T=2 times HRT), the effluent ammonia nitrogen is <1 (1.5) mg / L, indicating that the biofilm thickness on the surface of the MABR membrane is moderate, and the microbial oxygen consumption rate is greater than the membrane oxygen supply rate. At this stage, the timed aeration scrubbing program is turned off.

[0029] When the exhaust gas oxygen content is greater than 15.6% or continues to increase (duration T = 2 times HRT), and the effluent ammonia nitrogen concentration is less than 1 (1.5) mg / L, it indicates that the biofilm is too thin or the total amount of pollutants is too low. At this stage, the aeration scrubbing program is shut down and the process gas flow rate is appropriately reduced until the exhaust gas oxygen content is below 15.6%.

[0030] When the exhaust gas oxygen content is ≤15.6% or continues to decrease (duration T=2 times HRT), and the effluent ammonia nitrogen concentration is ≥1 (1.5) mg / L, it indicates that the biofilm is too thick, most of the oxygen is consumed in the inner layer of the biofilm, and the ammonia nitrogen cannot be transferred from the outer layer of the biofilm to the inner layer. The aeration scrubbing mode is turned on and the operation lasts for 7 times the HRT. If the ammonia nitrogen concentration is still ≥1 (1.5) mg / L, continue the operation until the ammonia nitrogen concentration is < (1.5) 1 mg / L, then stop the operation.

[0031] When the tail gas oxygen content is greater than 15.6% or continues to increase (duration T = 2 times HRT), and the effluent ammonia nitrogen concentration is greater than 1 (1.5) mg / L, it indicates that the biofilm is too thick and the oxygen supply resistance is large. Oxygen cannot be transferred to the outer layer of the biofilm, and ammonia nitrogen cannot be transferred from the outer layer of the biofilm to the inner layer. The aeration scrubbing mode is turned on and the operation lasts for 7 times the HRT. If the ammonia nitrogen concentration is still greater than 1 (1.5) mg / L, continue the operation. When the ammonia nitrogen concentration is less than 1 (1.5) mg / L, stop the operation. After the aeration scrubbing lasts for 7 times the HRT, if the tail gas oxygen content is greater than 15.6% or continues to increase, appropriately reduce the process gas flow rate to reduce the tail gas oxygen content to below 15.6%.

[0032] When the membrane cavity diameter is 300 microns, if the difference between the intake pressure sensor 6 and the exhaust pressure sensor 15 is greater than the set value (10~15kPa), it means that the membrane cavity is blocked and the condensate valve needs to be opened in time to remove the condensate inside the membrane cavity so that the pressure difference is less than 10kPa. When the membrane cavity diameter is other values, the timing of opening the condensate valve is adaptively adjusted according to the set value of the intake pressure and exhaust pressure difference.

[0033] In summary, the device and method can automatically control the biofilm thickness, reduce energy consumption, ensure sewage treatment efficiency, and have low cost.

[0034] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for automatically controlling the thickness of MABR biofilm, characterized in that : According to the oxygen transfer efficiency (OTE) of the MABR membrane module of the MABR membrane system and the oxygen content (O) of the inlet gas 2in Calculate the theoretical exhaust oxygen content O 2out : The oxygen transfer efficiency of MABR membrane module is OTE = (O 2in -F v O 2out ) / O 2in ; Oxygen reduction factor F v = (1-O 2in ) / (1-O 2out ); The theoretical exhaust oxygen content O 2out =1 / [(1-O 2in ) / (1-OTE)O 2in +1]; Monitor the ammonia nitrogen concentration in the effluent treated by the MABR membrane module and the oxygen content in the tail gas: When the exhaust oxygen content is ≤O 2out Or it keeps decreasing for twice the HRT, and the effluent ammonia nitrogen concentration is less than 30% of the discharge standard value. At this time, the scrubbing fan is turned off; When the exhaust oxygen content is greater than O 2out Or it continues to increase for twice the HRT, and the effluent ammonia nitrogen concentration is less than 30% of the emission standard value. At this time, turn off the scrubbing fan and reduce the process gas flow until the tail gas oxygen content is ≤O 2out ; When the exhaust oxygen content is ≤O 2out Or it continues to decrease for twice the HRT, and the outlet ammonia nitrogen concentration is ≥30% of the emission standard value. At this time, the scrubbing fan is turned on until the outlet ammonia nitrogen concentration is <30% of the emission standard value; When the exhaust oxygen content is greater than O 2out Or it continues to increase for twice the HRT, and the outlet ammonia nitrogen concentration is ≥30% of the emission standard value. At this time, turn on the scrubbing fan until the outlet ammonia nitrogen concentration is <30% of the emission standard value. If the exhaust oxygen content is >O 2out Or continue to increase and reduce the process gas flow until the tail gas oxygen content is ≤O 2out .

2. The method for automatically controlling the thickness of the MABR biofilm according to claim 1, characterized in that: Monitor the inlet pressure and tail gas pressure of the MABR membrane assembly. When the difference between the inlet pressure and the tail gas pressure is greater than the set value, open the condensate valve to remove the condensate in the membrane cavity.

3. The method for automatically controlling the thickness of the MABR biofilm according to claim 1, characterized in that: The MABR membrane system includes: A MABR membrane reactor, wherein the MABR membrane reactor is connected to an inlet pipe and an outlet pipe, and a plurality of MABR membrane modules are arranged in the MABR membrane reactor; A process air intake assembly, used to provide oxygen to the plurality of MABR membrane assemblies, comprising an air intake pipeline connected to the plurality of MABR membrane assemblies, and an air intake fan, an air intake flow meter and an air intake electric regulating valve sequentially arranged on the air intake pipeline along the air intake direction; A tail gas assembly, used to discharge tail gas after the wastewater is treated by the MABR membrane assemblies, comprising a tail gas pipeline connected to the MABR membrane assemblies and an online oxygen content monitor arranged on the tail gas pipeline; A scrubbing assembly, used for scrubbing the plurality of MABR membrane assemblies, comprising a scrubbing aerator disposed below the plurality of MABR membrane assemblies, a scrubbing pipeline connected to the scrubbing aerator, and a scrubbing fan, a scrubbing flow meter and a scrubbing electric regulating valve sequentially disposed on the scrubbing pipeline along an air inlet direction; An ammonia nitrogen online monitor, which is arranged at the outlet side of the MABR reactor and is used to monitor the ammonia nitrogen concentration in the treated effluent; The control unit, the air intake fan, the air intake flow meter, the air intake electric regulating valve, the oxygen content online monitor, the scrubbing fan, the scrubbing flow meter, the scrubbing electric regulating valve, and the ammonia nitrogen online monitor are respectively connected to the control unit signal.

4. The method for automatically controlling the thickness of the MABR biofilm according to claim 3, characterized in that: The MABR membrane system further comprises: An intake pressure sensor, which is arranged on the intake pipe and located between the intake flow meter and the intake electric regulating valve, and is used to monitor the intake pressure; A tail gas pressure sensor is arranged on the tail gas pipeline and located between the oxygen content online monitor and the MABR membrane assembly, and is used to monitor the tail gas pressure; A condensate water pipeline connected to the membrane cavity of the MABR membrane module, wherein a condensate water valve is provided on the condensate water pipeline; The intake pressure sensor, the exhaust pressure sensor, and the condensate valve are respectively connected to the control unit by signals.

5. The method for automatically controlling the thickness of the MABR biofilm according to claim 4, characterized in that: A water inlet flow meter is arranged on the water inlet pipeline.

Images