CN110108848B - Method for preventing sludge bulking by applying safety boundary value of process index of sewage plant - Google Patents
Method for preventing sludge bulking by applying safety boundary value of process index of sewage plant Download PDFInfo
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- CN110108848B CN110108848B CN201910389822.6A CN201910389822A CN110108848B CN 110108848 B CN110108848 B CN 110108848B CN 201910389822 A CN201910389822 A CN 201910389822A CN 110108848 B CN110108848 B CN 110108848B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
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- G01N33/1806—Water biological or chemical oxygen demand (BOD or COD)
Abstract
The invention discloses a method for preventing sludge bulking by applying a safety boundary value of a process index of a sewage plant, and relates to a method for preventing system risks of a sewage treatment process by applying an early warning effect of the process index of the sewage plant on sludge bulking in the process of treating urban sewage. The invention provides a method for preventing sludge bulking by applying the safety boundary value of the process index of the sewage plant, has higher accuracy of an evaluation result, and solves the limitation of preventing the sludge bulking of a sewage treatment process system at the present stage to a certain extent.
Description
Technical Field
The invention relates to a method for preventing the system risk of a sewage treatment process by applying the early warning effect of the process indexes of a sewage plant on the sludge bulking in the urban sewage treatment process.
Background
At present, basically, various types of activated sludge processes generate sludge bulking, and the sludge bulking has the characteristics of high occurrence rate, common occurrence, difficult control once generation, long recovery time consumption and the like. The process index of the sewage plant is an important index for judging the performance of the sludge. Where Chemical Oxygen Demand (COD) and Dissolved Oxygen (DO) are important control parameters in the operation of the activated sludge process, low dissolved oxygen concentrations have been recognized as one of the major factors causing filamentous sludge bulking, with corresponding DO concentrations being low when the COD concentration is high.
The safety Margin (MOS) is estimated by analyzing the uncertainty of the relationship between the pollutant and the water quality index of the sewage treatment system, or may be set by analysis to maintain a suitable ratio from the load capacity. The total amount of pollutants can be calculated by utilizing the daily maximum load according to MOS (metal oxide semiconductor), and the method is used for monitoring the water quality in rivers and lakes and controlling and managing point source and non-point source pollution. But the research and the application of the correlation between MOS and the process index of the sewage plant in the sewage treatment process do not exist at present. The introduction of MOS has important significance and practical requirements for reducing and preventing the occurrence of uncertain events in the sewage treatment process, and the invention carries out correlation analysis between MOS and sewage plant process indexes and provides a method for preventing the occurrence of sludge bulking by applying the safety boundary value of the sewage plant process indexes.
Disclosure of Invention
In order to make up the defects of the prior art, the invention realizes the risk prevention and control effect on the sewage treatment system by finding out the safety boundary value of the process index of the sewage plant.
The safety margin MOS may be defined as a maximum limit LN designed for a process index of a sewage plantmaxAnd a threshold value LNcriticalThe difference between them. Defining a fault event as a sewage plant process indicator exceeding a system design Limit (LN)max) The event of (2). The process indexes herein DO not include all biochemical indexes of the sludge, mainly including BOD, COD, DO, TOC, etc., because there is a clear linear correlation therebetween.
MOS＝LNmax-LNcritical (1)
If the variable W is defined as the ratio of the wastewater plant process index N to the determined limit standard S (S being the maximum concentration of the index N emissions set by the wastewater plant according to national or regional standards), the success event (system compliance) and the failure event (system non-compliance) can be represented as W < 1 and W > 1, respectively.
The sludge bulking risk is a failure event W > 1, defined as
Where p (W) is the probability density function of W, which can be assumed to be a normal distribution. Critical value LNcriticalCan be regarded as a maximum limit value LNmaxThe difference from the safety margin value MOS, therefore, when the sewage plant process index is normally distributed, the calculation can be performed by the equation (4):
MOS＝LNmax-(LNmax-ZriskS*)＝ZriskS* (4)
in the formula: s*: the standard deviation of the process indexes of the sewage plant,
wherein xiTo determine the value of the ith process indicator,
the average value of i times of measurement is shown, i is the measurement times, and n is the maximum value of the measurement times;
Zrisk: the standard normal quantile for any given acceptable risk level can be looked up.
The invention provides a method for preventing sludge bulking by applying the safety boundary value of the process index of the sewage plant, has higher accuracy of an evaluation result, and prevents the limitation caused by the sludge bulking of a sewage treatment process system to a certain extent.
Drawings
FIG. 1 is a normal distribution curve of COD in water obtained by 10 sampling in example 1 of the present invention.
Detailed Description
The invention is described in more detail below with reference to specific examples, without limiting the scope of the invention. Unless otherwise specified, the experimental methods and reagents involved in the present invention are commercially available.
The standard normal quantile table related by the invention can inquire the website by the following steps: https:// wenku. baidu.com/view/6a05ffeef61fb7360b4c65db.
According to various aspects of the study, the critical value of DO effect on sludge bulking is not determined. COD is basically all organic matters in water, and the trends of COD and DO are synchronous and have certain representativeness, so the COD is taken as an example in the invention.
S1, determining a maximum limit value LN of process indexes according to the design of a sewage plant systemmaxAnd the limit standard S
The activated sludge of this example was obtained from A2In the aeration tank of a certain sewage treatment system under the O process, the COD of the effluent of the system is designed to be 50mg/L, namely 50mg/L is considered to be the maximum LN of the COD of the normal effluent of the plantmax. For the whole urban sewage treatment process, according to the better COD removal condition given in most documents, the removal rate is at least over 60 percent, so when the COD removal rate is lower than 60 percent, the sewage treatment system has no obvious effect on removing organic matters. The COD removal rate of the plant is 62.3-97.0%, and the sewage treatment effect is relatively stable. The COD mean value of the effluent measured by 10 times of sampling is 33.6mg/L, and the standard deviation:
TABLE 1 COD and corresponding W values measured from 10 samplings of a certain sewage treatment plant
| CODInto/mg/L | 336 | 168 | 208 | 172 | 106 | 568 | 432 | 200 | 260 | 808 |
| COD*/mg/L | 201.6 | 100.8 | 124.8 | 103.2 | 63.6 | 340.8 | 259.2 | 120 | 156 | 484.8 |
| W* | 4.032 | 2.016 | 2.496 | 2.064 | 1.272 | 6.816 | 5.184 | 2.4 | 3.12 | 9.696 |
| CODGo out/mg/L | 48 | 48 | 32 | 8 | 40 | 48 | 32 | 24 | 32 | 24 |
| W | 0.96 | 0.96 | 0.64 | 0.16 | 0.80 | 0.96 | 0.64 | 0.48 | 0.64 | 0.48 |
| Removal rate/%) | 85.7 | 71.4 | 84.6 | 95.4 | 62.3 | 91.6 | 92.6 | 88.0 | 87.7 | 97.0 |
As can be seen from the formula (2), in Table 1
Wherein COD is a chemical oxygen demand value with a removal rate of 60%;
w is the W value corresponding to a COD removal rate of 60%;
s-50 mg/L in the formula is the COD maximum emission concentration set in the plant as described above.
S2, calculating the probability density function of W
Since W > 1 is a failure event and the maximum W value of more than 60% of the removal rate in 10 samplings is set as the upper limit, the interval of W is (1, 10).
S3, according to MOS ═ ZriskS*Calculating MOS value
From this standard normal fractional order table (shown as bold frame numbers in the table below) Z is obtainedrisk＝1.82501，
......
So that MOS is equal to ZriskS*＝1.82501×12.955＝23.64。
S4, obtaining a process index safety boundary range
The COD critical value LN can be obtained according to the formula (1)critical＝LNmax-MOS 50-23.64-26.36 mg/L. Therefore, the COD safe boundary range is 26.36-50 mg/L, namely the area between two dotted lines in figure 1; the area enclosed by the dotted line, the abscissa axis and the normal distribution curve and pointed by the arrow is a risk area.
According to the calculation of the sewage treatment process index of the sewage treatment plant, if the COD value is lower than 26.36mg/L, the stability of the sewage treatment system is prompted, and the treatment effect meets the requirement; if the COD value is distributed in the MOS region by 26.36-50 mg/L, prompting that close attention is needed, analyzing the process condition and strictly preventing the occurrence of uncertain risks; if the COD value is higher than 50mg/L, the existence of the risk is prompted, and the sludge is expanded immediately.
In order to verify the feasibility of the method of the present invention, the process indexes of different treatment processes from different sewage treatment plants were further measured, and the results are shown in table 2, which shows that the measured COD values in the non-swelling period are all smaller than the safety boundary value, while the measured COD values in the swelling period are within the range of the safety boundary value, and the results are consistent with the calculation results of the method described in the present invention. Therefore, the method has feasibility and accurate predictability for preventing sludge bulking by applying the safety boundary value of the process index of the sewage plant.
TABLE 2 COD in expansion and non-expansion phases of different treatment processes
The above description is only for the purpose of creating a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.
Claims (3)
1. A method for preventing sludge bulking by applying a safety boundary value of a process index of a sewage plant is characterized in that,
s1, determining a maximum limit value LN of process indexes according to the design of a sewage plant systemmaxAnd the limit standard S
The variable W is defined as the ratio of the sewage plant process index N to the determined limit criterion S, then success events and failure events can be represented as W < 1 and W > 1, respectively;
s2, as the sludge bulking risk is a fault event W > 1, defining as:
where p (W) is the probability density function of W,
s3, the safety boundary value of the sewage plant process index is the maximum limit value LN of the sewage plant process indexmaxAnd a threshold value LNcriticalDifference therebetween
MOS＝LNmax-LNcritical (3)
When W is normally distributed, the following formula is obtained:
MOS＝LNmax-(LNmax-ZriskS*)＝ZriskS* (4)
in the formula: s*: standard deviation of sewage plant process index;
Zrisk: any given standard normal quantile of acceptable risk level can be looked up;
s4, obtaining a critical value LN of the process index according to the formula (1) and the MOS value obtained in the step S3criticalObtaining a process index safety margin range of LNcritical～LNmax
LNcritical＝LNmax-MOS。
2. The method of claim 1,
wherein xiTo determine the value of the ith process indicator,
the average value of i measurements, i the number of measurements and n the maximum value of the number of measurements.
3. Method according to claim 1, characterized in that the value of the limit standard S is equal to the maximum concentration value of the index N emissions set by the sewage plant according to national or regional standards.
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Citations (4)
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| KR20030026175A (en) * | 2001-09-25 | 2003-03-31 | 박종순 | Waste water treatment system by micro-filter & bio-filter. |
| CN104914213A (en) * | 2015-05-13 | 2015-09-16 | 西安建筑科技大学 | Method for early warning of activated sludge filamentous bacterium expansion |
| CN107540099A (en) * | 2017-10-18 | 2018-01-05 | 河海大学 | A kind of sewage plant activated sludge bulking early warning analysis device and its application method |
| CN108516653A (en) * | 2018-05-25 | 2018-09-11 | 哈尔滨工程大学 | A kind of MBBR couples boat domestic sewage treatment device and method with electric flocculation |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20030026175A (en) * | 2001-09-25 | 2003-03-31 | 박종순 | Waste water treatment system by micro-filter & bio-filter. |
| CN104914213A (en) * | 2015-05-13 | 2015-09-16 | 西安建筑科技大学 | Method for early warning of activated sludge filamentous bacterium expansion |
| CN104914213B (en) * | 2015-05-13 | 2016-10-19 | 西安建筑科技大学 | A kind of method of early warning activated sludge filamentary discharges |
| CN107540099A (en) * | 2017-10-18 | 2018-01-05 | 河海大学 | A kind of sewage plant activated sludge bulking early warning analysis device and its application method |
| CN108516653A (en) * | 2018-05-25 | 2018-09-11 | 哈尔滨工程大学 | A kind of MBBR couples boat domestic sewage treatment device and method with electric flocculation |
Non-Patent Citations (3)
| Title |
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| Research on online trend omen extraction algorithm of sludge bulking;Yu Guang-ping等;《 2015 IEEE International Conference on Cyber Technology in Automation, Control, and Intelligent Systems (CYBER)》;20151005;第1617-1621页 * |
| 城市污水处理厂污泥膨胀控制;王申;《市政技术》;20151231;第145-147页 * |
| 软/硬质悬浮填料对MBR中EPS的影响;仉春华等;《安全与环境学报》;20151231;第15卷(第6期);第255-259页 * |
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