CN112010427A - Construction method and application of two-step decay model of nitrite oxidizing bacteria - Google Patents

Abstract

The invention relates to a construction method and application of a two-step decay model of nitrite oxidizing bacteria. The invention overcomes that the traditional bacterial decay model is only applicable to the primary stage of NOB decay stage (live cells→dead cells), and cannot be used for dead cells. Converted to soluble COD for evaluation. The invention scientifically simulates the decay process of NOB under high concentration of nitrite, establishes a two-step decay model (live cells→dead cells→soluble COD), and determines the model parameters of NOB decay under the inhibition of nitrite. The present invention establishes for the first time a two-step decay and death mathematical model of nitrite oxidizing bacteria, and by using the model, the effect of short-range nitrification, denitrification and denitrification can be ensured by controlling the concentration of nitrite. Improve sludge treatment effect. It also provides technical support for further understanding of microbial inhibition and activation recovery.

Description

Construction method and application of a two-step decay model of nitrite oxidizing bacteria

technical field

The invention belongs to the field of sewage treatment, and relates to a construction method and application of a two-step decay model of nitrite oxidizing bacteria, in particular to a two-step decay model of nitrite oxidizing bacteria under the inhibition of high nitrite concentration.

Background technique

The traditional biological denitrification process is that ammonia nitrogen generates nitrite under the action of ammonia oxidizing bacteria, and then nitrite is oxidized to nitrate by Nitrite-oxidizing Bacteria (NOB), and finally nitrate is oxidized by denitrifying bacteria. The process of generating nitrogen under the action. The short-range nitrification and denitrification process is to control the formation of nitrite, so that the denitrifying bacteria directly use nitrite as an electron acceptor to complete the denitrification process. Compared with the traditional biological denitrification process, it has the significant advantages of less oxygen demand in the nitrification stage and less carbon source in the denitrification stage. How to inhibit the formation of nitrate is the key factor to ensure the efficiency of short-range nitrification and denitrification. High concentrations of nitrite will inhibit nitrite oxidizing bacteria, which can be used as a control condition for our development of short-range nitrification and denitrification. Therefore, evaluating the activity of nitrite-oxidizing bacteria (NOB) at high concentrations of nitrite is helpful for short-range nitrification. Control of denitrification. However, the traditional bacterial decay model is only applicable to the primary stage (live cells→dead cells) of the decay stage of nitrite oxidizing bacteria, and cannot evaluate the transformation of dead cells into soluble COD.

Therefore, in order to evaluate the activity of NOB under high concentration of nitrite and improve the control effect of short-range nitrification and denitrification, a new model of nitrite oxidizing bacteria decay and death is urgently needed. The present invention is proposed on the premise that there is no such type of model in the current field.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to establish a two-step decay model (live cells→dead cells→soluble COD) in order to scientifically simulate the decay process of nitrite oxidizing bacteria (NOB) under high concentration of nitrite. The invention establishes a perfect two-step decay mathematical model by measuring the model parameters of NOB decay under the inhibition of nitrite, so that the short-range nitrification and denitrification denitrification effect can be ensured by controlling the concentration of nitrite.

In order to achieve the above object, the technical scheme adopted in the present invention is: a method for constructing a two-step decay model of nitrite oxidizing bacteria, comprising:

(1) Calculate the net specific growth rate of simulated nitrite oxidizing bacteria, and use Eq.1 to obtain:

r=ub _tot (Eq.1)

Among them, r: NOB net specific growth rate (d ^-1 ), u, NOB specific growth rate (d ^-1 ), b _tot : NOB total specific decay rate (d ^-1 ).

(2) Considering the inhibitory effect of high concentration of nitrite on NOB, use Eq.2 to obtain:

NOB的最大比增长速率(d^-1),

亚硝酸盐浓度(mg-N/L),

NOB生长的半饱和系数(mg-N/L)，

NOB生长抑制的半饱和系数(mg-N/L)。in,

The maximum specific growth rate of NOB (d ^-1 ),

Nitrite concentration (mg-N/L),

Half-saturation coefficient of NOB growth (mg-N/L),

Half-saturation coefficient (mg-N/L) of NOB growth inhibition.

(3) The simulation calculation of NOB total specific decay rate, introducing the toxic effect of nitrite, the toxicity of nitrite is expressed by the S-type formula with power n>1; use Eq.3 to obtain:

NOB亚硝酸盐毒性衰亡率(d^-1)，

NOB亚硝酸盐毒性衰亡的半饱和系数(mg-N/L)，n：亚硝酸盐浓度的幂数。Among them, b: NOB inherent specific decay rate (d ^-1 ),

NOB nitrite toxicity mortality (d ^-1 ),

The half-saturation coefficient of NOB nitrite toxicity decay (mg-N/L), n: the power of nitrite concentration.

(4) Simulate the process of converting dead NOB into soluble COD and introduce the total specific degradation rate of NOB, using Eq.4 to obtain:

NOB亚硝酸盐抑制降解率(d^-1)，

NOB亚硝酸盐抑制降解半饱和系数(mg-N/L)，m：亚硝酸盐浓度的幂数。Where: b _l,tot : NOB total specific degradation rate (d ^-1 ), b _l : NOB intrinsic specific degradation rate (d ^-1 ),

NOB nitrite inhibited degradation rate (d ^-1 ),

NOB nitrite inhibition degradation half-saturation coefficient (mg-N/L), m: the power of nitrite concentration.

(5) Modeling

Table 1 Two-step decay model of nitrite-oxidizing bacteria

The two-step decay model of the present invention can be used for sewage treatment to improve the effect of sewage treatment. Further, the GPS-X software is used to simulate the aerobic rate OUR and COD of the nitrifying bacteria of the activated sludge based on the two-step decay model of the present invention. sewage treatment effect.

Based on the IWA activated sludge model NO.1 (ASM1) commonly used in the field, the present invention proposes for the first time a NOB enhanced decay (X _{B, L} → X _{B, D} ) and enhanced degradation (X _{B, D} → S _B ) The two-step decay model. The invention scientifically simulates the decay process of NOB under high concentration of nitrite, establishes a two-step decay model (live cells→dead cells→soluble COD), and determines the model parameters of NOB decay under the inhibition of nitrite, The two-step decay mathematical model is perfected, so that the effect of short-range nitrification, denitrification and denitrification can be guaranteed by controlling the concentration of nitrite. While establishing and perfecting the two-step decay mathematical model, the present invention also provides important support for further understanding the phenomenon of microbial inhibition and activation recovery.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention uses the mathematical model method to determine the effect of nitrite on NOB, and establishes a two-step decay model (live cells→dead cells→soluble COD) for the first time. Compared with the mathematical model that cannot evaluate the conversion of dead cells into soluble COD by traditional methods, the model of the present invention is obviously more complete, rigorous and precise.

(2) The present invention determines the nitrite concentration factor parameter of NOB in the process of model establishment, and introduces the toxicity effect of nitrite in the simulation calculation of NOB total specific decay rate for the first time. And in the second stage, the present invention introduces the total specific degradation rate of NOB in order to simulate the process of converting dead NOB into soluble COD. The present invention coordinates the influencing factors of various aspects, and achieves the purpose of perfecting and enriching the NOB mathematical model in the field.

(3) The NOB two-step decay model established by the present invention solves the problem that the existing models in the field cannot evaluate the conversion of dead cells into soluble COD. By using the model of the present invention, an optimum environmental condition can be sought, so that the formation of short-range nitrification and denitrification can be promoted by controlling the activity of NOB, and finally the effect of sewage treatment can be improved.

(4) The measuring method of the present invention is simple and easy to operate, has high repeatability, is convenient for popularization and application, and can promote the development and innovation of mathematical model methods in the field of sewage treatment. It also provides important support for further understanding of the phenomenon of microbial inhibition and activation recovery.

Description of drawings

Fig. 1 is a schematic diagram of the OUR experimental device of the present invention; in Fig. 1: 1. Magnetic stirrer in water bath; 2. Magnetic rotor; 3. BOD bottle; 4. Dissolved oxygen (DO) measuring probe; 5. Dissolved oxygen (DO) measuring instrument .

Fig. 2 is a simulation diagram of OUR and COD of NOB of nitrite oxidizing bacteria under the condition that the concentration of nitrous acid is 50 mg-N/L using the two-step decay model of the present invention in Example 2.

FIG. 3 is a simulation diagram of OUR and COD of NOB of nitrite oxidizing bacteria under the condition of 2000 mg-N/L nitrous acid concentration using the two-step decay model of the present invention in Example 3. FIG.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments. In the present invention, unless otherwise specified, the reagents used are conventional reagents in the field, and the methods used are conventional methods in the field.

Example 1 Construction of the two-step decay model of nitrite-oxidizing bacteria of the present invention

1. Synthesis with NaNO ₂ (500mg-N/L), NH ₄ CI (1.0mg-N/L), KH ₂ PO4 (0.13mg-P/L) and Na ₂ PO4 (1.67-P/L) The wastewater was enriched with sludge in a 5-L sequencing batch reactor (SBR) (the purpose of NOB enrichment was to eliminate the interference of other bacterial species). The pH, temperature and DO of the reactor were controlled at 7.3, 35±0.5°C and above 5 mg/L, respectively. The SRT of the SBR reactor was maintained at 50 days, and after 240 days of culture, the experiments were carried out with concentrated NOB sludge.

2. The concentrated NOB sludge was centrifuged three times (5000rpm) with synthetic wastewater of NH4CI (1.0mg-N/L), _KH2PO4 ( _0.13mg -P/L) and _Na2PO4 (1.67-P/L). ), every three minutes. Before carrying out NOB sludge culture, sludge samples were centrifuged three times using nitrite-free inorganic synthetic wastewater to ensure that the samples were free of nitrites. Obtain NOB concentrated sludge without nitrite for use.

3. The NOB concentrated sludge without nitrite is used for the respiration test, and the nitrite concentration is kept at 0mg-N/L, 50mg-N/L, 500mg-N/L, 2000mg-N/L. The NOB culture was carried out under the condition of 35 ± 0.2 °C in a constant temperature incubator for 7 days, and the dissolved oxygen in the culture vessel was required to be kept above 6 mg-O ₂ /L.

4. Use bacterial staining to identify changes in the number of live/dead bacteria in the incubator with different nitrite concentrations, and obtain model parameters based on the measured data. See Table 2 below:

Table 2 Kinetic parameters and stoichiometric parameters of NOB

5. Establish a model equation for the two-step decay of nitrite-oxidizing bacteria NOB:

(1) Calculate the net specific growth rate of simulated nitrite oxidizing bacteria, and use Eq.1 to obtain:

r=ub _tot (Eq.1)

Among them, r: NOB net specific growth rate (d ^-1 ), u, NOB specific growth rate (d ^-1 ), b _tot : NOB total specific decay rate (d ^-1 );

(2) Considering the inhibitory effect of high concentration of nitrite on NOB, use Eq.2 to obtain:

NOB的最大比增长速率(d^-1),

亚硝酸盐浓度(mg-N/L),

NOB生长的半饱和系数(mg-N/L)，

NOB生长抑制的半饱和系数(mg-N/L)；in,

The maximum specific growth rate of NOB (d ^-1 ),

Nitrite concentration (mg-N/L),

Half-saturation coefficient of NOB growth (mg-N/L),

Half-saturation coefficient of NOB growth inhibition (mg-N/L);

(3) In the simulation calculation of NOB total specific decay rate, the toxicity of nitrite is introduced, and the toxicity of nitrite is expressed by the S-type formula with power n>1; use Eq.3 to obtain:

NOB亚硝酸盐毒性衰亡率(d^-1)，

NOB亚硝酸盐毒性衰亡的半饱和系数(mg-N/L)，n：亚硝酸盐浓度的幂数。Among them, b: NOB inherent specific decay rate (d ^-1 ),

NOB nitrite toxicity mortality (d ^-1 ),

The half-saturation coefficient of NOB nitrite toxicity decay (mg-N/L), n: the power of nitrite concentration.

(4) In order to simulate the process of converting dead NOB into soluble COD, the total specific degradation rate of NOB was introduced, using Eq.4 to obtain:

NOB亚硝酸盐抑制降解率(d^-1)，

NOB亚硝酸盐抑制降解半饱和系数(mg-N/L)，m：亚硝酸盐浓度的幂数。Where: b _l,tot : NOB total specific degradation rate (d ^-1 ), b _l : NOB intrinsic specific degradation rate (d ^-1 ),

NOB nitrite inhibited degradation rate (d ^-1 ),

NOB nitrite inhibition degradation half-saturation coefficient (mg-N/L), m: the power of nitrite concentration.

(5) Modeled in Table 1 below

Table 1 Two-step decay model of nitrite-oxidizing bacteria

Example 2 Under the condition that the nitrous acid concentration is 50 mg-N/L, the model equation established in Example 1 is used to detect and simulate the OUR and COD of NOB.

(1) with NaNO ₂ (500mg-N/L), NH ₄ CI (1.0mg-N/L), KH ₂ PO ₄ (0.13mg-P/L) and Na ₂ PO ₄ (1.67-P/L) ) synthetic wastewater was enriched in sludge in a 5-L sequencing batch reactor (SBR) (the purpose of NOB enrichment was to eliminate the interference of other bacteria). The pH, temperature and DO of the reactor were controlled at 7.3, 35±0.5°C and above 5 mg/L, respectively. The SRT of the SBR reactor was maintained at 50 days, and after 240 days of culture, the experiments were carried out with concentrated NOB sludge.

(2) The concentrated NOB sludge was centrifugally washed with synthetic wastewater of NH ₄ CI (1.0 mg-N/L), KH ₂ PO ₄ (0.13 mg-P/L) and Na ₂ PO ₄ (1.67-P/L) Three times (5000rpm) for three minutes each. Before carrying out NOB sludge culture, sludge samples were centrifuged three times using nitrite-free inorganic synthetic wastewater to ensure that the samples were free of nitrites.

(3) The NOB concentrated sludge without nitrite was used for the respiration test, and NOB culture was carried out under the experimental condition that the nitrite concentration was kept at 50 mg-N/L, and the NOB was cultured in a constant temperature incubator at a temperature of 35±0.2 °C. The temperature was cultured for 7 days, while the dissolved oxygen requirement in the culture vessel was kept above 6 mg-O ₂ /L.

(4) In order to maintain the concentration of nitrite during the test, a computer program syringe pump was installed to continuously send high-concentration sodium nitrite solution (20000mg-N/L) into the culture vessel to control the nitrite concentration. around ±5% of the target.

(5) The activated sludge in the culture tank is manually sampled at intervals of 6-8 hours, and the nitrite concentration is adjusted to be the same as the predetermined concentration in each culture tank and placed in a 100 mL BOD bottle. Use O gas to set the initial dissolved oxygen concentration of the sample to over ₁₀ mg _- O/L, and use a portable dissolved oxygen meter to record the dissolved oxygen consumption in the BOD bottle every 1 min. The OUR of each culture tank was obtained from the decrease in dissolved oxygen concentration with time. Taking the dissolved oxygen concentration as the vertical axis and the time as the horizontal axis, make sure that the coefficient of determination R ² ≥ 99 for the drawn straight line, and the slope of the straight line is the oxygen consumption rate of NOB.

(6) 5 ml of NOB sludge was taken out from the culture tank, and washed three times with 0.85% NaCl solution centrifugation (10000 rpm, washing for three minutes) to remove the interference of impurities.

(7) The COD of the washed NOB sludge in the culture tank was measured using a COD analysis kit (TNT Plus 821 (COD range 3–150 ppm, Hach, USA).

(8) Make a scatter plot of nitrite concentration and NOB oxygen consumption rate (OUR) and sludge COD, use GPS-X software to fit the scatter plot based on the two-step decay model equation of the present invention, measure the data and The simulated data are shown in Tables 3 and 4, respectively, and the experimental results and fitting effects are shown in Figure 2.

table 3

t 50mg-N/L t 50mg-N/L OUR COD d measured value d measured value 0.034722222 4.23 0.010416667 74.29447853 0.25 5.71956 0.96875 78.52760736 0.415277778 5.46 1.948611111 79.95008841 0.96875 5.54046 2.943055556 82.68033429 1.208333333 6.4506 3.932638889 85.27607362 1.44375 5.69322 4.929861111 92.02453988 1.975 5.6592 5.932638889 97.98347717 2.208333333 5.7528 6.936111111 104.2944785 2.460416667 5.811 7.93125 117.8064389 2.919444444 5.50668 3.20625 6.5637 3.413888889 6.1425 3.943055556 6.75 4.2125 6.87 4.414583333 7.68 4.934722222 8.9 5.202083333 8.52 5.427777778 7.25724 5.944444444 8.814 6.207638889 9.4776 6.413888889 9.3636 6.941666667 10.8739726 7.211805556 10.67664 7.475694444 12.08064 8.099305556 11.8734

Table 4

Example 3 Under the condition that the nitrous acid concentration is 2000 mg-N/L, the model equation established in Example 1 is used to detect and simulate the OUR and COD of NOB.

(1) with NaNO ₂ (500mg-N/L), NH ₄ CI (1.0mg-N/L), KH ₂ PO ₄ (0.13mg-P/L) and Na ₂ PO ₄ (1.67-P/L) ) was enriched with sludge in a 5-L sequencing batch reactor (SBR). The pH, temperature and DO of the reactor were controlled at 7.3, 35±0.5°C and above 5 mg/L, respectively. The SRT of the SBR reactor was maintained at 50 days, and after 240 days of culture, the experiments were carried out with concentrated NOB sludge.

(2) The concentrated NOB sludge was centrifugally washed with synthetic wastewater of NH ₄ CI (1.0 mg-N/L), KH ₂ PO ₄ (0.13 mg-P/L) and Na ₂ PO ₄ (1.67-P/L) Three times (5000rpm) for three minutes each.

(3) The NOB concentrated sludge without nitrite was used for the respiration test, and NOB culture was carried out under the experimental condition that the nitrite concentration was kept at 2000 mg-N/L, and the temperature was 35±0.2°C in a constant temperature incubator. The temperature was cultured for 7 days, while the dissolved oxygen requirement in the culture vessel was kept above 6 mg-O ₂ /L.

(4) In order to maintain the concentration of nitrite during the test, a computer program syringe pump was installed to continuously send high-concentration sodium nitrite solution (20000mg-N/L) into the culture vessel to control the nitrite concentration. around ±5% of the target.

(5) The activated sludge in the culture tank is manually sampled at intervals of 6-8 hours, and the nitrite concentration is adjusted to be the same as the predetermined concentration in each culture tank and placed in a 100 mL BOD bottle. Use O gas to set the initial dissolved oxygen concentration of the sample to over ₁₀ mg _- O/L, and use a portable dissolved oxygen meter to record the dissolved oxygen consumption in the BOD bottle every 1 min. The OUR of each culture tank was obtained from the decrease in dissolved oxygen concentration with time.

(6) Take out 5 ml of NOB sludge from the culture tank, and wash it three times with 0.85% NaCl solution centrifugation (10000 rpm, washing for three minutes) to remove the interference of impurities.

(7) The COD of the washed NOB sludge in the culture tank was measured using a COD analysis kit (TNT Plus 821 (COD range 3–150 ppm, Hach, USA).

(8) Make a scatter plot of nitrite concentration, NOB oxygen consumption rate (OUR) and NOB sludge COD, use GPS-X software to fit the scatter plot based on the two-step decay model equation of the present invention, and the experimental data See Tables 5 and 6, and the experimental results and fitting effects are shown in Figure 3.

table 5

Table 6

t 50mg-N/L 50mg-N/L OUR COD d simulation simulation 0 4.351442 74 0.25 5.455606 74.70636 0.5 5.604481 75.47575 0.750001 5.729357 76.29351 1.000001 5.848524 77.14692 1.250001 5.966282 78.02398 1.500001 6.084471 78.91807 1.750001 6.203997 79.82719 2.000002 6.3253 80.75166 2.250002 6.448603 81.69247 2.500002 6.574032 82.6506 2.750002 6.701681 83.62686 3.000002 6.831623 84.62195 3.250003 6.963927 85.63643 3.500003 7.098653 86.67084 3.750003 7.235861 87.72568 4.000003 7.375605 88.80142 4.250003 7.517942 89.89853 4.500004 7.662924 91.01748 4.750004 7.810604 92.15872 5.000004 7.961036 93.32271 5.250004 8.114273 94.50991 5.500004 8.270367 95.72079 5.750005 8.429372 96.95581 6.000005 8.591342 98.21544 6.250005 8.756331 99.50016 6.500005 8.924395 100.8104 6.750005 9.095589 102.1468 6.958339 9.240683 103.2807

The data and simulation diagrams obtained in the above examples 2 and 3 fully prove the correctness of the two-step decay model of the nitrite oxidizing bacteria of the present invention. Therefore, the two-step decay model can be used to calculate the nitrite concentration required to inhibit the activity of NOB, so as to realize the control of the short-range nitrification and denitrification process. That is, the present invention realizes that the effect of short-range nitrification, denitrification, and denitrification can be ensured by controlling the concentration of nitrite.

Claims (4)

1. A method for constructing a two-step decay model of nitrite oxidizing bacteria is characterized by comprising the following steps of:

(1) the net specific growth rate of the simulated nitrous acid oxidizing bacteria was calculated and obtained using eq.1:

r＝u-b_tot (Eq.1)

wherein, r: net specific rate of NOB increase (d)^-1) Specific growth rate of u, NOB (d)^-1)，b_tot: total NOB specific decay Rate (d)^-1)；

(2) Considering the inhibition of NOB by nitrite at high concentrations, the results were obtained using Eq.2:

wherein,

maximum specific growth rate (d) of NOB^-1)，

Nitrite concentration (mg-N/L),

the half saturation factor (mg-N/L) for NOB growth,

the half saturation factor (mg-N/L) for NOB growth inhibition;

(3) simulating and calculating the total ratio decay rate of NOB, introducing the toxicity influence of nitrite, wherein the toxicity of the nitrite is expressed by an S-type formula with power n being more than 1; obtained using eq.3:

wherein, b: NOB intrinsic specific decay Rate (d)^-1)，

NOB nitrite toxic decay Rate (d)^-1)，

Half-saturation factor (mg-N/L) for NOB nitrite toxicity decay, N: the power of nitrite concentration;

(4) simulating the conversion of dead NOB to soluble COD, the overall specific degradation rate of the introduced NOB was obtained using Eq.4:

wherein: b_l，tot: NOB Total specific degradation Rate (d)^-1)，b_l: NOB intrinsic specific degradation rate (d)^-1)，

NOB nitrite inhibited degradation rate (d)^-1)，

NOB nitrite inhibited degradation half saturation factor (mg-N/L), m: the power of nitrite concentration;

(5) modeling

2. A two-step decay model of nitrite-oxidizing bacteria constructed by the method of claim 1.

3. The two-step decay model of nitrite oxidizing bacteria of claim 2, wherein the model is a two-step decay model of nitrite oxidizing bacteria under high nitrite concentration inhibition.

4. Use of the two-step decay model of claim 2 in wastewater treatment, wherein: calculating the nitrite concentration required to inhibit the activity of NOB by the two-step decay model; namely, the short-cut nitrification and denitrification nitrogen removal effect is ensured by controlling the concentration of the nitrite, and the sewage treatment effect is improved.

Images