JP2020104101A - Method for strengthning removal of diclofenac in sewage by means of enrichment of nitrifying bacteria - Google Patents

Abstract

To effectively remove diclofenac by a sewage treatment system.SOLUTION: A method for strengthening the removal of diclofenac in sewage by means of enrichment of nitrifying bacteria, which comprises: 1) a step in which sewage is allowed to flow by gravity into a secondary precipitation tank to carry out solid-liquid separation; 2) a step in which the sewage is treated at an initial concentration of nitrifying sludge of 1000 mg/L, at a pH of 7.5±0.5, at an ammonia oxidation rate (SAOR) of 0.05 to 0.4 mg NH4+-N/g MLSS min, at dissolved oxygen (DO) of 2 to 4 mg/L, and at a hydraulic holding time (HRT) of 0.5 to 10 hours; and 3) a step in which effluent is collected to analyze the results of the treatment.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention belongs to the technical field of sewage purification, and specifically relates to a method for enhancing the removal of diclofenac in sewage by concentrating nitrifying bacteria.

Diclofenac is a non-steroidal anti-inflammatory drug that is widely used in anti-inflammatory and analgesic drugs, and due to its widespread use and persistence, it is detected in large quantities in environmental waters, and sewage treatment plants are exposed to various types of water. It has been widely noticed as a gathering place. As a new type of pollutant, there are few studies on its eco-environmental risk, but existing studies indicate that diclofenac may cause a significant attenuation of Indian Bald Eagles. Therefore, how to effectively remove diclofenac in a sewage treatment system has attracted people's attention.

As an important part of ensuring the safe discharge of sewage, sewage treatment processes are of great importance for studying the impact of various cost-effective processes on the removal of diclofenac. Although these removal methods are better able to remove diclofenac precursors, advanced oxidation and disinfection can produce more toxic intermediates, while at the same time the economic cost of large scale application of these technologies. To limit. Biological treatment should be emphasized as a technology with low toxicity and low economic cost. Numerous studies have shown that ammonia-oxidizing bacteria can be co-metabolized by the produced ammonia monooxygenase to remove trace pollutants, and have a strong removal ability. However, there are no systematic studies on the use of nitrifying bacteria to enhance the removal of trace pollutants, namely diclofenac, in actual wastewater.

In order to solve the deficiencies of the prior art, the object of the present invention is to provide a method for enhancing the removal of diclofenac in sewage by concentrating nitrifying bacteria, which effectively removes diclofenac in sewage. , Can meet the requirements of sewage treatment.

The technical solution of the present invention is a method for enhancing the removal of diclofenac in sewage by concentrating nitrifying bacteria,
First, in the MBR, by gradually increasing the ammonia nitrogen load and gradually reducing the organic carbon load (until the inflowing organic carbon load is 0), the nitrifying bacteria are domesticated and concentrated, and generally, The period of domestication of concentrated nitrifying bacteria is 3 months or more, and the following diclofenac enhanced removal operation takes concentrated and domesticated nitrifying sludge.
1) a step of flowing sewage into a secondary precipitation tank for solid-liquid separation, and obtaining a supernatant and a precipitate by separation,
2) MBR of the nitrifying sludge that was concentrated and domesticated with the supernatant liquid separated in step 1)
Pump to control the initial concentration of nitrifying sludge to 1000 mg/L, and adjust the pH to 7.5 ±
It was adjusted to 0.5, the dissolved oxygen was controlled to 2 to 4 mg/L, the HRT was 0.5 to 10 hours, and the ammonia oxidation rate (high ammonia nitrogen wastewater pumped with the sludge nitrification solution) (
SAOR) at 0.05-0.4 mg NH4 ^<+> _- N/g MLSS min.
3) Collect the wastewater from step 2), analyze the results, and, if the content of diclofenac in the water meets the emission standard, send it to the UV disinfection tank for disinfection and then discharge the wastewater to the municipal sewer network. Steps to
4) if not, returning to step 2) for processing.

Naturally, as one aspect of the present invention, during the process of concentrating the nitrifying bacteria and the domestication process, it is possible to compensate for the influence of the hydraulic pressure holding time, the ammonia nitrogen load gradually increases, and the organic carbon load gradually decreases. The cooperation of the influence of the matrix concentration and the influence of the hydraulic pressure holding time makes it difficult for NOB to form a resistance mechanism in a short period of time, which is useful for suppressing and removing it.

As another aspect of the present invention, the enrichment and domestication of nitrifying bacteria may employ an excess aeration method to facilitate the removal of anaerobic bacteria in the sludge, thereby rapidly enriching the nitrifying bacteria. ..

As one aspect of the present invention, in step 2), the pH is adjusted using 500 mg/L of sodium bicarbonate, and the pH is adjusted in real time by a pH sensor so as to ensure a pH environment necessary for the growth of nitrifying bacteria. And add sodium bicarbonate stock solution if necessary to control the pH within the range of 7.5±0.5.

As one aspect of the present invention, the HRT in step 2) is set to 6 hours.

As one aspect of the present invention, in the step 2), the dissolved oxygen concentration is measured by a dissolved oxygen meter, and a valve of the aeration device is adjusted to prevent the anaerobic substance from settling down to 3.2 mg of DO. Control to /L.

In one aspect of the invention, step 2) uses pulsed aeration and the pulse frequency is 10
Process ~15 minutes for 4-6 hours.

One aspect of the present invention, in step 2), SAOR is 0.05 mg NH4 ⁺ _- N
/G MLSS min, which shortens aerobic time, improves short-range nitrification and saves more aeration energy consumption.
As one aspect of the present invention, step 2) adopts a pulse aeration method, and the pulse aeration process is performed for 4 to 6 hours at a speed of 700 to 900 r/min through a stirrer and a pulse frequency of 10.
~15 minutes.

In one aspect of the invention, the MBR membrane element is a hollow fiber membrane filled with a polyurethane foam material and a zeolite filler to promote the decomposition of organic matter and reduce fouling of the membrane assembly.

As one aspect of the present invention, the result analysis in step 3) includes a concentration detection of diclofenac and a removal rate analysis of diclofenac.

As one aspect of the present invention, the step of concentrating nitrifying bacteria in step 1) is as follows.
First, pulse aeration treatment is carried out for 2 to 3 hours under the condition that the mass ratio of nitrifying bacteria and influent water is maintained at 1:100 and dissolved oxygen is maintained at 6 mg/L, and the supernatant is obtained by standing and filtering. ..
The supernatant is pumped into the MBR reactor and at a temperature of 15 to 25°C and a pH of 7.2 to 7.
8, the dissolved oxygen was controlled to 1.2 to 1.5 mg/L, and the inoculated sludge concentration was adjusted to 15
-18g/L, then add concentrated medium, the addition amount is 0.2mg/L, the amount of inflow water is kept constant, the initial ammonia nitrogen concentration is 20-300mg/L. Yes, when the ammonia nitrogen concentration is less than 20 mg/L, the ammonia nitrogen concentration of the inflow water is 40 to 1
The nitrifying bacteria are concentrated and cultivated so that the amount is increased to 30 mg/L and the nitrifying bacteria become the dominant bacterial group.
The composition of the culture medium has a mass ratio of 1:1:5:2:2:3:1:2 MgCl ₂ .6H _{2
O, CaCl 2, NaHCO 3,} KH 2 PO 4, NH 4 Cl, FeSO 4 · 7H 2 O, sodium pyruvate, and trace elements.
During the concentration and culturing process, first, the inflow water was stirred, and the sewage was stopped by the MBR reactor according to the reflux ratio of 110-115%, and the stop time was 1:1.5. The sludge is continuously stirred by a rod, and then the sludge is separated. The separated sludge is first stirred at a stirring speed of 200 to 300 r/min, treated for 5 to 10 minutes, and has a concentration coefficient of 0.
． It is controlled to 85 to 0.95 and refluxed at a reflux ratio of 80 to 98%.
Finally, the treated sewage is allowed to settle, the sludge is still refluxed, and after the settling is complete, the sludge's reflux is stopped, drained and concentrated to improve impact load capacity, the MBR membrane is It promotes retention and reduces the processing load on the reactor.

The beneficial effects of the present invention as compared to the prior art are as follows.
1) The present invention has a simple device, easy to operate, low cost, no pollution, and high stability.
2) The method of the present invention can effectively remove diclofenac in the sewage, and the sewage meets the discharge criteria, thereby avoiding the toxic effects of the remaining diclofenac in the sewage on the downstream organisms.
3) It made up for the shortcomings of the current sewage purification process, improved the shortcomings of the prior art that the removal effect of diclofenac was low, and filled the black of domestic technology for the removal of diclofenac in sewage.
4) The present invention also provides a method for concentrating and domesticating nitrifying bacteria, by which the dominant strains are screened, concentrated and fixed, ensuring that the nitrifying bacteria have a strong adaptability and at the same time total nitrogen. And ammoniacal nitrogen can be removed.

FIG. 1 shows an MBR device for concentrating and domesticating the nitrifying sludge of the present invention. FIG. 2 shows an apparatus for removing diclofenac in sewage by the nitrifying bacteria of the present invention. FIG. 3 is a graph showing the effect of the HRT of the present invention on the diclofenac removal effect. FIG. 4 is a graph showing the effect of SAOR of the present invention on the effect of removing diclofenac.

By gradually increasing the ammonia nitrogen load of the MBR and gradually reducing the organic carbon load (until the inflowing organic carbon load becomes zero), the nitrifying bacteria are domesticated and concentrated, and generally concentrated. The period of domestication of the nitrifying bacteria thus prepared is 3 months or more, and the enriched and removed nitrifying sludge obtained in each of the following enhanced removal examples is taken.

Targeting the drainage from a sewage secondary sedimentation tank in a city in Nanjing, strengthen the removal of diclofenac nitrifying bacteria in the sewage as follows.

Example 1
1) Sewage is allowed to flow by gravity into a secondary precipitation tank, and solid-liquid separation is performed in the secondary precipitation tank, and a supernatant and a precipitate are obtained by separation.
2) The supernatant was concentrated and pumped into the MBR of domesticated nitrifying sludge, the initial concentration of nitrifying sludge was controlled to 1000 mg/L, the pH was adjusted to 7.5, and the dissolved oxygen was 3.2.
Controls in mg / L, HRT is 0.25 hours, the ammonia oxidation rate by a high ammonia nitrogen wastewater sludge digestion liquid is pumped (SAOR) 0.1mg NH4 ⁺ _- N
/G MLSS min.
3) Collect the wastewater from step 2) and analyze the results.
A 30 mL water sample was filtered through a 0.45 μm mixed fiber membrane and, after filtration, stored in a refrigerator at 4° C. for subsequent solid phase extraction and quantification of diclofenac, repeating each experiment three times,
Mean ± standard deviation is used for analysis.
(A) Determination of diclofenac concentration by liquid chromatography-mass spectrometry:
The Liquid Chromatography-Mass Spectrometer of choice is the API 4000 Selected Liquid Chromatography-Mass Spectrometer of the US AB company, Electrospray Ion Source (
ESI) and negative ionization multiple reaction monitoring mode (MRM). The parameters monitored by the multiple reaction are shown in Table 1.


Here, the column used for the liquid phase separation was Acquity UPL at a column temperature of 30°C.
C BEH C18 column (2.1 x 50 mm, 1.7 um). The mobile phases selected are water (A) and methanol (B) and 0.1% aqueous ammonia is added to both phases.
The mobile phase is degassed before use. The liquid phase flow rate is 0.1 mL/min, isocratic elution is used, and the isocratic elution procedure is 10% A: 90% B. The injection volume is 5 μL and injection is performed using an autosampler.
(B) Analysis of diclofenac removal rate:
Here, the concentration unit of diclofenac is μg/L.
Removal rate of diclofenac=(1-Ct/C0)×100%, C0 is the initial concentration, and Ct is the concentration of the diclofenac agent at the reaction time t.
In this example, when the HRT was 0.5 hour, the removal rate of diclofenac was 21.84.
% Was determined.

Example 2
HRT is 1 hour, the operating method and parameters are the same as in Example 1, the detection method of diclofenac is the same as in Example 1, and the removal rate of diclofenac in water is 27.49%.
Was measured.

Example 3
The HRT was 2 hours, the operation method and parameters were the same as in Example 1, the diclofenac detection method was the same as in Example 1, and the removal rate of diclofenac in water was 55.14%.
Was measured.

Example 4
HRT was 4 hours, the operating method and parameters were the same as in Example 1, the diclofenac detection method was also the same as in Example 1, and the removal rate of diclofenac in water was 67.25%.
Was measured.

Example 5
The HRT was 6 hours, the operating method and parameters were the same as in Example 1, the diclofenac detection method was the same as in Example 1, and the removal rate of diclofenac in water was 73.16%.
Was measured.

Example 6
The HRT was 10 hours, the operating method and parameters were the same as in Example 1, the diclofenac detection method was the same as in Example 1, and the removal rate of diclofenac in water was 76.79.
% Was determined.
The results of Examples 1 to 6 above were statistically and analyzed, and the influence results of different HRT values on the removal effect of diclofenac were obtained. Specifically, refer to FIG.
Conclusion 1: As can be seen from Fig. 3, when the remaining parameters are constant, the removal rate of diclofenac gradually increases with HRT from 0.5 hours to 10 hours. When the HRT was 0.5 hours, the removal rate of diclofenac was only 21.84%, the HRT was extended from 1 hour to 2 hours, and the removal rate of diclofenac was significantly increased from 27.49% to 55.14%. Increased.
HRT increased from 55.14% to 76.79% when HRT was extended from 2 hours to 10 hours
Slowly rose to. Considering the economic result of the sewage treatment plant and the increase of removal rate, it is more appropriate to select HRT for 6 hours.

Example 7
The initial SAOR is 0.05 mg NH4 _- N/g MLSS min, the operating method and parameters are the same as in Example 5, the diclofenac detection method is also the same as in Example 5,
The removal rate of diclofenac in water was determined to be 57.05%.

Example 8
The initial SAOR was 0.1 mg NH4 _- N/g MLSS min, the operation method and parameters were the same as in Example 5, the diclofenac detection method was the same as in Example 5, and the removal rate of diclofenac in water was 65. It was determined to be 0.22%.

Example 9
The initial SAOR was 0.2 mg NH4 _- N/g MLSS min, the operation method and parameters were the same as in Example 5, the diclofenac detection method was the same as in Example 5, and the removal rate of diclofenac in water was 75. It was determined to be .15%.

Example 10
The initial SAOR is 0.4 mg NH4 _- N/g MLSS min, the operating method and parameters are the same as in Example 5, the diclofenac detection method is the same as in Example 5, and the removal rate of diclofenac in water is 85. It was determined to be .66%.
Analysis of the effect of SAOR on the removal effect of diclofenac:
Conclusion 2: As can be seen from FIG. 4, when the remaining parameters are constant, the removal rate of diclofenac increases with SAOR. SAOR is 0.05 mg NH4 _- N/g MLSS
In the case of min, the removal rate is 57.05%. SAOR is 0.4 mg NH4 _-
In the case of N/g MLSS min, the removal rate is 85.66%. The increase of diclofenac removal rate with the increase of SAOR is small, and considering the problem that the concentration of exhausted ammoniacal nitrogen reaches the standard, 0.05 mg NH4 _- N/g MLSS min SAOR is optimal.

Example 11
The dissolved oxygen concentration was 1 mg/L, the operating method and parameters were the same as in Example 7, the diclofenac detection method was the same as in Example 7, and the diclofenac removal rate in water was 42.
It was determined to be 18%.

Example 12
The dissolved oxygen concentration was 2 mg/L, the operating method and parameters were the same as in Example 7, the diclofenac detection method was the same as in Example 7, and the diclofenac removal rate in water was 56.
It was determined to be 50%.

Example 13
The dissolved oxygen concentration was 4 mg/L, the operation method and parameters were the same as in Example 7, the diclofenac detection method was the same as in Example 7, and the diclofenac removal rate in water was 54.
It was determined to be 08%.

Example 14
The dissolved oxygen concentration was 5 mg/L, the operation method and parameters were the same as in Example 7, the diclofenac detection method was the same as in Example 7, and the diclofenac removal rate in water was 45.
It was determined to be 05%.
Analysis of the effect of dissolved oxygen concentration on the removal effect of diclofenac:
Conclusion 3: As can be seen from the results of Examples 11 to 14, when the remaining parameters were constant and when the dissolved oxygen concentration was in the range of 2 to 4 mg/L, the removal rate of diclofenac was almost changed by the dissolved oxygen concentration. If the dissolved oxygen concentration exceeds 2 mg/L or 4 mg/L,
The removal rate of diclofenac begins to decrease, and the removal rate of diclofenac becomes maximum when the dissolved oxygen concentration is 3.2 mg/L, which is the same as in Example 7, and the removal rate is 57.05%.
Is. Optimally, the dissolved oxygen concentration is 3.2 mg/L SAOR in combination with other considerations.

Example 15
The nitrifying bacteria are domesticated and concentrated by gradually increasing the ammonia nitrogen load of the MBR and gradually reducing the organic carbon load, and the specific steps are as follows.
First, pulse aeration treatment is performed for 3 hours under the condition that the mass ratio of nitrifying bacteria and inflow water is 1:10 and dissolved oxygen is 6 mg/L, and the mixture is left standing and filtered to obtain a supernatant.
The supernatant liquid was pumped into the MBR reactor, the pH was adjusted to 7.8, the dissolved oxygen was controlled to 1.5 mg/L, the inoculated sludge concentration was 18 g/L, and the inflow was carried out at a temperature of 25°C. Keeping the amount constant, the initial ammonia nitrogen concentration is 300 mg/L, and when the ammonia nitrogen concentration decreases to 20 mg/L, the inflow ammonia nitrogen concentration increases to 130 mg/L.
The sewage is shut down in the MBR reactor according to a reflux ratio of 115%, the shutdown time is 1:1.5, continuously stirred by the electromagnetic rod during the shut down, then the sludge is separated, and the separated sludge is separated. First, stir at a stirring rate of 300 r/min, then at 80 kHz
Treated with ultrasonic frequency of 10 minutes, control the concentration coefficient to 0.95, reflux at 98% reflux ratio, finally, treated sewage is allowed to settle, the sludge is still refluxed. , After the settling is complete, stop the sludge reflux, drain and concentrate, domesticate the concentrated nitrifying bacteria for a period of 3 months, then mix the activated sludge with the concentrated nitrifying bacteria, Obtain domesticated and concentrated nitrifying sludge.
By analysis, the dominant strains screened, enriched and fixed by this method can ensure strong adaptability of nitrifying bacteria and have a shorter domestication and enrichment period, only 7
It turned out to be day 0.

Example 16
On the basis of Example 15, when inoculating the sludge, 0.2 mg/L concentrated medium was added, the concentrated medium having a mass ratio of 1:1:5:2:2:3:1:2 MgCl 2. ₂ · _{6H 2} O, CaC
_{l 2, NaHCO 3, KH 2} PO 4, NH 4 Cl, FeSO 4 · 7H 2 O, sodium pyruvate, and trace elements.
Analysis showed that during the domestication and enrichment process of nitrifying bacteria, the nitrifying bacteria obtained after adding the enriched medium were more adaptable, with a domestication and enrichment period of 63 days.

Example 17
The domesticated and concentrated nitrifying bacteria of Example 16 were treated with diclofenac sewage, the treatment method and operating parameters were the same as in Example 10, and the removal rate of diclofenac in water was determined to be 88.25%. It can be seen that the method for domesticating and concentrating nitrifying bacteria provided by the present invention can improve the removal effect of diclofenac to some extent.

Claims (6)

A method for enhancing the removal of diclofenac in sewage by concentrating nitrifying bacteria, comprising:
1) a step of flowing sewage into a secondary precipitation tank for solid-liquid separation, and obtaining a supernatant and a precipitate by separation,
2) MBR of the nitrifying sludge that was concentrated and domesticated with the supernatant liquid separated in step 1)
Pump to control the initial concentration of nitrifying sludge to 1000 mg/L, and adjust the pH to 7.5 ±
It was adjusted to 0.5, the dissolved oxygen was controlled to 2 to 4 mg/L, the HRT was 0.5 to 10 hours, and the ammonia oxidation rate (high ammonia nitrogen wastewater pumped with the sludge nitrification solution) (
A step of maintaining the N / g MLSS min, _- a SAOR) 0.05~0.4mg NH4 ⁺
3) Collect the wastewater from step 2), analyze the results, and, if the content of diclofenac in the water meets the emission standard, send it to the UV disinfection tank for disinfection and then discharge the wastewater to the municipal sewer network. Steps to
1) if the content of diclofenac in the water does not meet the emission standards, return to step 2) and process;
A method for enhancing the removal of diclofenac in sewage by concentrating nitrifying bacteria, which comprises: In step 2), the pH was adjusted using 500 mg/L sodium bicarbonate, the pH was measured in real time by a pH sensor, and a sodium bicarbonate stock solution was added to adjust the pH to 7.5. It is characterized by controlling within a range of ±0.5,
A method for enhancing the removal of diclofenac in sewage by concentrating the nitrifying bacteria according to claim 1. In the step 2), the dissolved oxygen concentration is measured by a dissolved oxygen meter, and DO is controlled to 3.2 mg/L by adjusting the valve of the aeration device.
A method for enhancing the removal of diclofenac in sewage by concentrating the nitrifying bacteria according to claim 1. In the step 2), the HRT is set to 6 hours,
A method for enhancing the removal of diclofenac in sewage by concentrating nitrifying bacteria according to claim 3. In step 2), 0.05 mg of _{^{SAOR NH4 + - N / g MLSS}} min
To maintain,
A method for enhancing the removal of diclofenac in sewage by concentrating the nitrifying bacteria according to claim 1. Wherein the result analysis in step 3) includes diclofenac concentration detection and diclofenac removal rate analysis.
A method for enhancing the removal of diclofenac in sewage by concentrating the nitrifying bacteria according to claim 1.