Aerobic MBBR biological membrane thickness control method

Abstract

The invention discloses a method for controlling the thickness of an aerobic MBBR (Moving Bed Biofilm Reactor) biological membrane, and belongs to the technical field of sewage treatment. The technical problems that in the prior art, the MBBR process is poor in process operation effect and poor in impact resistance due to the fact that the thickness of a biological membrane is unreasonably controlled are solved. The method comprises the following steps: firstly, establishing a positive correlation relation between the thickness of a biological membrane and the ammonia nitrogen concentration of inlet water; then calculating the annual standard deviation sigma NH3N of the influent ammonia nitrogen concentration, and adjusting the thickness target value Ttarget of the biological membrane according to the fluctuation intensity of the annual standard deviation of the influent ammonia nitrogen concentration; periodically acquiring a filler sample, and measuring the thickness T of the biological membrane with water by adopting an industrial microscope; and finally, comparing the T with the Ttarget, and adjusting aeration to ensure that the biological membrane is at a proper thickness. According to the invention, the dilemma that no standard can be depended on and no method can be used in the prior art is solved, and an innovative scheme is provided for efficient and stable operation of the MBBR process.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for controlling the thickness of an aerobic MBBR biofilm. Background Technology

[0002] The MBBR (Moving Bed Biofilm Reactor) process achieves efficient degradation of pollutants through a biofilm attached to the surface of suspended packing material. Its operational performance is highly dependent on the stability of the biofilm thickness. Biofilm thickness not only determines the microbial density per unit surface area of ​​the packing material (directly affecting biomass and treatment efficiency), but is also a core indicator of the shock resistance of the pure membrane MBBR process. For example, when the influent load suddenly increases (such as a sharp rise in ammonia nitrogen concentration), a thicker biofilm can buffer the shock through the stratified metabolism of its internal microorganisms, maintaining system stability; while a biofilm that is too thin, due to insufficient surface area for microbial activity, is prone to fluctuations in effluent quality or even treatment failure. However, existing technologies have significant shortcomings in biofilm thickness control, making precise dynamic management difficult.

[0003] In current MBBR projects, biofilm thickness settings largely rely on experience or local experimental data, lacking quantitative standards based on water quality parameters (such as ammonia nitrogen concentration and fluctuation intensity). Operators typically judge biofilm status by visual observation or simple tools (such as transparent tube observation windows), which is highly subjective and difficult to quantify (e.g., the definition of "thick" and "thin" is ambiguous). While some studies have proposed fixed biofilm thickness ranges (e.g., 100-500 μm), they fail to consider the varying impact of influent fluctuations on the system's shock resistance, making it difficult to balance treatment efficiency and stability in practical applications. Furthermore, existing technologies lack scientific dynamic control methods, relying heavily on fixed aeration strategies or dissolved oxygen (DO) feedback control. For example, fixed aeration rates are difficult to adapt to changes in biofilm thickness, while DO feedback control is easily affected by water quality fluctuations, leading to delayed or incorrect aeration adjustments. Passive sludge removal methods only intervene when biofilm thickens abnormally (e.g., clogging of packing materials), lacking proactive prevention mechanisms and further exacerbating system operational risks.

[0004] Existing methods for measuring biofilm thickness also have significant limitations. Traditional sampling often involves randomly selecting a small amount of packing material, failing to consider the impact of packing material structural differences (such as hexagonal pore distribution) on biofilm distribution, which can easily lead to data deviation. During measurement, biofilm thickness measurements under dry conditions are prone to data distortion due to dehydration and shrinkage, while measurement techniques with water are not yet widely adopted and cannot accurately reflect actual operating conditions.

[0005] The aforementioned problems collectively result in insufficient shock resistance of MBBR systems when dealing with influent fluctuations, large fluctuations in treatment efficiency, and difficulties in energy consumption control. Therefore, the existing technology needs further improvement. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the thickness of an aerobic MBBR biofilm. By establishing a dynamic control formula based on ammonia nitrogen concentration and fluctuations, and combining scientific measurement methods with aeration adjustment strategies, this invention solves the dilemma of "no standards to follow and no methods to use" in the prior art, and provides an innovative solution for the efficient and stable operation of the MBBR process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for controlling the thickness of an aerobic MBBR biofilm includes the following steps:

[0009] a. Establish the positive correlation between biofilm thickness and influent ammonia nitrogen concentration, as shown in equation (1):

[0010] T base =aC NH3-N +b (1);

[0011] In equation (1): T base As the baseline biofilm thickness, C NH3−N The influent ammonia nitrogen is the annual average value, a = 5 μm / mg / L, b = 50 μm;

[0012] b. Calculate the annual standard deviation σ of the influent ammonia nitrogen concentration. NH3−N The target value T for biofilm thickness is adjusted based on the fluctuation intensity of the annual standard deviation of the influent ammonia nitrogen concentration. target :

[0013] When σ NH3−N / C NH3−N When <20%: T target =T base ;

[0014] When 20%≤σ NH3−N / C NH3−N When <30%: T target =T base +50μm;

[0015] When σ NH3−N / C NH3−N When ≥30%: T target =T base +100μm;

[0016] c. Periodically obtain packing material samples and use an industrial microscope to measure the biofilm thickness T with water.

[0017] d. Compare T with T target :

[0018] When T < 0.85T targetAt that time, increase the aeration rate to 110% of the current value, and remeasure after 20 days of operation;

[0019] When T>1.15T target At that time, reduce the aeration rate to 90% of the current value, and remeasure after 20 days of operation;

[0020] When 0.85T target ≤T≤1.15T target At that time, the current aeration rate is kept unchanged, and the measurement is repeated after 20 days of operation.

[0021] In the above-mentioned method for controlling the thickness of an aerobic MBBR biofilm, step c, the procedure for determining the biofilm thickness T is as follows:

[0022] Immerse the packing sample in pure water to keep the biofilm naturally moist.

[0023] The thickness of each filler sample was recorded by scanning each side of the polygonal hole with an industrial microscope in both the transverse and longitudinal directions.

[0024] Image processing software was used to summarize the thickness of each filler sample and automatically calculate the average thickness.

[0025] In the above-mentioned method for controlling the thickness of an aerobic MBBR biofilm, in step c, if the packing sample has a honeycomb columnar structure with a cross-section divided into three rings from the inside out, and each layer contains hexagonal pores, then one pore in each ring is selected for measurement; a point is selected on each of the six sides of the hexagonal pore to measure the biofilm thickness; the number of packing samples is ≥3.

[0026] The above-mentioned method for controlling the thickness of an aerobic MBBR biofilm involves selecting three packing samples.

[0027] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0028] (1) This invention proposes a method for controlling the biofilm thickness of aerobic MBBR, which first establishes a positive correlation between biofilm thickness and influent ammonia nitrogen concentration; and calculates the annual standard deviation σ of influent ammonia nitrogen concentration. NH3−N And set the target value T for biofilm thickness. target Then, packing material samples were periodically obtained to measure the biofilm thickness T; finally, the biofilm thickness T was compared with the target value of biofilm thickness, and the biofilm thickness was controlled at an appropriate level by adjusting the aeration rate.

[0029] (2) It can significantly improve the system's resistance to shocks. Under the condition that the influent ammonia nitrogen fluctuation intensity (standard deviation / mean) is ≥30%, the system's ability to buffer against sudden load changes is enhanced by actively thickening the biofilm.

[0030] (3) The efficiency of pollutant removal is greatly improved. After precise control of biofilm thickness, the activity of denitrifying bacteria is stable, and the effluent quality can achieve ammonia nitrogen below 0.5 mg / L and TN below 2 mg / L.

[0031] (4) Reduce operating energy consumption and maintenance costs. By using a fine aeration adjustment strategy of ±10%, over-aeration or insufficient oxygen supply can be avoided, and the overall aeration energy consumption can be reduced by 20%-25%. Detailed Implementation

[0032] This invention proposes a method for controlling the thickness of an aerobic MBBR biofilm. To make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.

[0033] The packing sample used in this invention is a commonly used packing sample for water treatment. If the packing sample has a honeycomb columnar structure and the cross-section is divided into three rings from the inside out, and each layer contains hexagonal pores, then one pore in each ring is taken for measurement; a point is taken on each of the six sides of the hexagonal pore to measure the biofilm thickness.

[0034] The industrial microscopes described in this invention have a magnification of ≥200x and a numerical aperture (NA) value of ≥0.4, with stereomicroscopes being the preferred choice.

[0035] This invention proposes a method for controlling the thickness of aerobic MBBR biofilm, the specific steps of which are as follows:

[0036] Step 1: Establish the positive correlation between biofilm thickness and influent ammonia nitrogen concentration, as shown in equation (1):

[0037] T base =aC NH3-N +b (1);

[0038] In equation (1): T base As the baseline biofilm thickness, C NH3−N The influent ammonia nitrogen is the annual average value, a = 5 μm / mg / L, b = 50 μm;

[0039] In step (1), formula T base =5C NH3−N +50 applies to values ​​20 ≤ C NH3−N ≤80mg / L, corresponding to T base The range is 150μm-450μm.

[0040] Step 2: Calculate the annual standard deviation σ of the influent ammonia nitrogen concentration. NH3−N The target value T for biofilm thickness is adjusted based on the fluctuation intensity of the annual standard deviation of the influent ammonia nitrogen concentration. target :

[0041] When σNH3−N / C NH3−N When <20%: T target =T base ;

[0042] When 20%≤σ NH3−N / C NH3−N When <30%: T target =T base +50μm;

[0043] When σ NH3−N / C NH3−N When ≥30%: T target =T base +100μm;

[0044] Step 3: Periodically obtain packing material samples and determine the biofilm thickness T with water using an industrial microscope; the specific steps for periodically obtaining packing material samples are as follows:

[0045] Packing structure layering: If there are 3 layers from the inner ring to the outer ring of the packing, and each layer contains hexagonal holes, then one hole from each layer is taken for measurement;

[0046] Single-well measurement: The biofilm thickness was measured on each of the six sides of the hexagonal well, for a total of six measurements.

[0047] Total sample size: Three filler samples were randomly selected, and the thickness of each sample was measured at 18 points (3 layers × 6 sides), for a total of 54 data points. The mean value was taken as the final biofilm thickness T.

[0048] The specific steps for determining the biofilm thickness T using an industrial microscope with water are as follows: immerse the packing sample in sterile water to keep the biofilm naturally moist; use an industrial microscope to perform a transverse cross-sectional scan of each side of the hexagonal pores and record the biofilm thickness; and automatically calculate the average thickness using the image processing software ImageJ.

[0049] Step 4: Compare T with T target :

[0050] When T < 0.85T target At that time, increase the aeration rate to 110% of the current value, and remeasure after 20 days of operation;

[0051] When T>1.15T target At that time, reduce the aeration rate to 90% of the current value, and remeasure after 20 days of operation;

[0052] When 0.85T target ≤T≤1.15T target At that time, the current aeration rate is kept unchanged, and the measurement is repeated after 20 days of operation.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] Example 1:

[0055] An aerobic MBBR system (treatment capacity 10,000 m³) at a municipal wastewater treatment plant in northern my country 3 / d), the effluent ammonia nitrogen must be consistently below 3.0 mg / L. Verification of the implementation process of this invention: the influent water quality and fluctuations are as follows:

[0056] Annual average ammonia nitrogen in influent C NH3−N =50.32mg / L, annual standard deviation σ NH3−N =14.86 mg / L;

[0057] Wave intensity R=σ NH3−N / C NH3−N ×100%=29.53%;

[0058] Step (1) Establish the baseline biofilm thickness formula:

[0059] Formula: T base =aC NH3−N +b, where a=5 and b=50;

[0060] Calculate: T base =5×50.32+50=301.6μm.

[0061] Step (2) Calculate the fluctuation intensity and adjust the target thickness:

[0062] Fluctuation intensity: R = 29.53% (meets the requirement of 20% ≤ R < 30%);

[0063] Adjustment rules:

[0064] When 20%≤R<30%: T target =T base +50μm;

[0065] Target thickness: T target =301.6 + 50 = 351.6 μm

[0066] Step (3) Periodically measure the thickness of the biofilm.

[0067] Measurement frequency: Once every 20 days;

[0068] Measurement method:

[0069] The packing structure consists of three layers, from the inner ring to the outer ring, with one hole taken from each layer for measurement (a total of three holes).

[0070] Single-hole measurement: All 6 sides of each hexagonal hole were measured, totaling 54 data points for 3 packing materials;

[0071] Measurement tool: Industrial microscope for water content measurement;

[0072] The measured thickness records are shown in Table 1 (100 consecutive days, once every 20 days):

[0073] Table 1

[0074]

[0075] Step (4) Compare the measured thickness with the target value and adjust the aeration rate.

[0076] Adjustment rules:

[0077] When T < 0.85T target Increase aeration intensity to 110%;

[0078] When T>1.15T target Reduce aeration intensity to 90%;

[0079] When 0.85T target ≤T≤1.15T target Maintain the current aeration intensity;

[0080] Calculate the threshold:

[0081] 0.85T target =0.85×351.6=298.86μm, 1.15T target =1.15×351.6=404.34μm

[0082] Adjustment records are shown in Table 2 (all measured values ​​are within the threshold):

[0083] Table 2

[0084]

[0085] Step (5) System operation monitoring:

[0086] Results (for 100 consecutive days):

[0087] Ammonia nitrogen in effluent: stable at 0.42±0.11 mg / L, with no exceedance events (exceedance rate 0%).

[0088] Aeration energy consumption: average 0.24 kWh / m³ 3 This reduces the rate by 22.3% compared to traditional methods.

[0089] Comparative Example 1: A pilot-scale system was used for verification, and the influent water quality was consistent with that of Example 1 (verification using values ​​a and b).

[0090] Comparative Example 1-1:

[0091] The formula takes the following values: a=3, b=30.

[0092] Reference thickness: T base =3×50.32+30=180.96μm.

[0093] Target thickness: T target =180.96+50=230.96μm (wave intensity 29.53%, add 50μm according to the rule).

[0094] Adjustment strategy: Measure every 20 days and adjust aeration according to the threshold;

[0095] Results (100-day average):

[0096] The biofilm thickness T = 195.3 μm;

[0097] Ammonia nitrogen in effluent: 1.85±0.75 mg / L, with a maximum value reaching 3.09 mg / L. Both the effluent and fluctuation levels are significantly higher than normal, and there are instances of exceeding standards. Aeration energy consumption: 0.28 kWh / m³. 3 .

[0098] Comparative Examples 1-2:

[0099] The formula takes the following values: a=7, b=70.

[0100] Reference thickness: T base =7×50.32+70=422.24μm.

[0101] Target thickness: T target =422.24+50=472.24μm.

[0102] Adjustment strategy: Same as above.

[0103] Results (100-day average):

[0104] The biofilm thickness T = 458.7 μm;

[0105] Ammonia nitrogen in effluent: 1.65±0.85 mg / L, with a maximum value reaching 3.47 mg / L. The effluent fluctuated significantly and exceeded the standard. Aeration energy consumption: 0.30 kWh / m³ 3 ;

[0106] Comparative Examples 1-3:

[0107] The formula takes the following values: a=5, b=30.

[0108] Reference thickness: T base =5×50.32+30=281.6μm.

[0109] Target thickness: T target =281.6+50=331.6μm.

[0110] Adjustment strategy: Same as above;

[0111] Results (100-day average):

[0112] The biofilm thickness T = 315.4 μm;

[0113] Ammonia nitrogen in effluent: 1.91±0.92 mg / L, with a maximum value of 3.92 mg / L. Both the effluent and fluctuation levels were significantly higher than normal, and there were instances of exceeding the standard. Aeration energy consumption: 0.27 kWh / m³. 3 .

[0114] Comparative Example 2: The necessity of graded adjustment of volatility intensity.

[0115] Comparative Example 2-1:

[0116] Adjustments are not made according to fluctuation intensity levels;

[0117] Target thickness: T target =T base =301.6μm (fixed value);

[0118] Adjustment strategy: Same as above;

[0119] Results (100-day average):

[0120] The biofilm thickness T = 320.26 μm;

[0121] Ammonia nitrogen in effluent: 1.22±0.85mg / L, with a maximum value of 3.55mg / L. The overall effluent concentration fluctuated significantly, indicating that the concentration exceeded the standard.

[0122] Aeration energy consumption: 0.31 kWh / m³ 3 ;

[0123] Comparative Example 2-2:

[0124] Only high volatility adjustment.

[0125] Target thickness: T target =T base +100=401.6μm (regardless of wave intensity);

[0126] Adjustment strategy: Same as above;

[0127] Results (100-day average):

[0128] Biofilm thickness T = 420.3 μm (long-term thicker);

[0129] Ammonia nitrogen in effluent: 0.62±0.35 mg / L;

[0130] Aeration energy consumption: 0.35 kWh / m³ 3 The operating energy consumption is significantly high;

[0131] Comparative Example 3: The necessity of a method for measuring biofilm thickness.

[0132] Comparative Example 3-1:

[0133] Drying determination method.

[0134] Measurement method: The thickness of the filler sample was measured after it was removed from the water;

[0135] Adjustment strategy: Same as above;

[0136] Results (100-day average):

[0137] The measured thickness T = 140.8 μm (351.6 μm with water); the drying method caused the thickness measurement to be lower, and the actual biofilm was thicker.

[0138] Ammonia nitrogen in effluent: 0.95±0.62 mg / L;

[0139] Aeration energy consumption: 0.39 kWh / m³ 3 The operating energy consumption is significantly high.

[0140] Comparative Example 3-2:

[0141] Single-well random determination method.

[0142] Measurement method: Randomly select one well for measurement;

[0143] Adjustment strategy: Same as above;

[0144] Results (100-day average):

[0145] The measured thickness T = 345.6 μm;

[0146] Ammonia nitrogen in effluent: 1.83±0.51 mg / L. The ammonia nitrogen level in the effluent is too high, with the highest value reaching 2.98 mg / L, indicating that it may exceed the standard.

[0147] Aeration energy consumption: 0.28 kWh / m³ 3 ;

[0148] Comparative Example 3-3:

[0149] Only the outer layer pores were measured.

[0150] Measurement method: Only the thickness of the outer layer pores is measured;

[0151] Adjustment strategy: Same as above;

[0152] Results (100-day average):

[0153] The measured thickness T = 265.1 μm (the outer layer is generally lower, the actual thickness is 351.6 μm).

[0154] Ammonia nitrogen in effluent: 0.75±0.48 mg / L;

[0155] Aeration energy consumption: 0.37 kWh / m³ 3 The operating energy consumption has been significantly increased.

[0156] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0157] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A method for controlling the thickness of an aerobic MBBR biofilm, characterized in that, The steps are as follows: a. Establish the positive correlation between biofilm thickness and influent ammonia nitrogen concentration, as shown in equation (1): T base = aC NH3-N +b (1); In equation (1): T base As the baseline biofilm thickness, C NH3−N The influent ammonia nitrogen is the annual average value, a = 5 μm / mg / L, b = 50 μm; b. Calculate the annual standard deviation σ of the influent ammonia nitrogen concentration. NH3−N The target value T for biofilm thickness is adjusted based on the fluctuation intensity of the annual standard deviation of the influent ammonia nitrogen concentration. target : When σ NH3−N / C NH3−N When <20%: T target =T base ; When 20%≤σ NH3−N / C NH3−N When <30%: T target =T base +50μm; When σ NH3−N / C NH3−N When ≥30%: T target =T base +100μm; c. Periodically obtain packing material samples and use an industrial microscope to measure the biofilm thickness T with water. d. Compare T with T target : When T < 0.85T target At that time, increase the aeration rate to 110% of the current value, and remeasure after 20 days of operation; When T>1.15T target At that time, reduce the aeration rate to 90% of the current value, and remeasure after 20 days of operation; When 0.85T target ≤T≤1.15T target At that time, the current aeration rate is kept unchanged, and the measurement is repeated after 20 days of operation.

2. The method for controlling the thickness of an aerobic MBBR biofilm according to claim 1, characterized in that: In step c, the procedure for determining the biofilm thickness T is as follows: Immerse the packing sample in pure water to keep the biofilm naturally moist. The thickness of each filler sample was recorded by scanning each side of the polygonal hole with an industrial microscope in both the transverse and longitudinal directions. Image processing software was used to summarize the thickness of each filler sample and automatically calculate the average thickness.

3. The method for controlling the thickness of an aerobic MBBR biofilm according to claim 1, characterized in that: In step c, if the packing sample has a honeycomb columnar structure with a cross-section divided into three rings from the inside out, and each layer contains hexagonal pores, then one pore in each ring is taken for measurement; a point is taken on each of the six sides of the hexagonal pore to measure the biofilm thickness; the number of packing samples is ≥3.

4. The method for controlling the thickness of an aerobic MBBR biofilm according to claim 3, characterized in that: Three packing samples were selected.

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