CN115266835A - Wastewater salinity measurement method based on multiple compensations of conductivity measurement - Google Patents
Wastewater salinity measurement method based on multiple compensations of conductivity measurement Download PDFInfo
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Abstract
The invention provides a wastewater salinity measuring method based on multiple compensations of conductivity measurement, belonging to the technical field of wastewater treatment. The method comprises the following steps: selecting waste water to be measured, eliminating organic matter interference, and performing salt content test; measuring the pH value of the treated wastewater, and performing volatile substance compensation; collecting test data, carrying out assay data analysis, carrying out outlier screening on each pair of conductivity and salt content analysis data, and determining a relation formula of the conductivity and the salt content by using a data analysis method; and calculating the salt content of the wastewater according to a relation formula of the conductivity and the salt content. The high-salinity wastewater can be accurately measured by various compensation calculation methods such as laboratory water quality analysis, analysis data calculation and management, wastewater temperature and the like.
Description
Technical Field
The invention relates to a wastewater salinity measuring method based on multiple compensations of conductivity measurement, belonging to the technical field of wastewater treatment.
Background
The salt content is an index for monitoring wastewater, and the existing method for measuring the salt content of the wastewater is mainly used for measuring and analyzing according to 'gravimetric method for measuring total salt content of water' (HJ/T51-1999). In "inspection method for water quality standard of town sewage" (CJ/T51-2018) and "method for monitoring water and wastewater" (fourth edition), there is proposed a method for analyzing soluble solids and filterable residues, and in actual measurement, there is also measurement of dissolved solids or filterable residues of wastewater to express a value of salt content. The above methods have the same measurement procedures, all require the steps of filtration, evaporation to dryness, constant weight and weighing, and only have slight differences in the operating conditions such as sampling volume, evaporation to dryness temperature and the like. The method has the disadvantages of complicated measurement operation, large workload, long operation time (generally about 4 hours), and incapability of realizing online measurement in actual production or wastewater discharge.
Along with the continuous deepening of the implementation of water pollution treatment, the pollution treatment of general high-salinity wastewater (wastewater without dangerous wastes such as heavy metals) finally achieves the fixation of the salt content by two methods, namely a thermal method and a membrane method, thereby realizing the recycling and zero discharge of the wastewater. Due to the influence of environmental regulations, construction cost, operation cost and the like, more and more wastewater treatment adopts a flue method to concentrate desulfurized wastewater (a device is generally called as a low-temperature concentration tower), and then drying is carried out, so that zero discharge of wastewater is realized.
In actual operation, the concentration ratio of the low-temperature concentration tower is actually used for controlling the salt content in the wastewater, and the salt content measurement operation is complicated, the required time is long, and the operation control cannot be guided, so that the concentration ratio of the low-temperature concentration tower cannot be controlled in actual operation, and the salt content of concentrated brine is large in fluctuation. The concentration rate is low, the amount of treated high-salinity wastewater is small, and the energy consumption is high; the concentration multiple rate is high, and the problems of pipeline crystallization blockage after pump disturbance and the like occur. The real-time measurement of the salt content is urgently needed, and the stable and reliable operation of the low-temperature concentration tower is realized.
Disclosure of Invention
The invention aims to provide a wastewater salinity measuring method based on multiple compensations of conductivity measurement, which is simple and convenient to operate and high in measuring accuracy.
In order to achieve the purpose, the invention is realized by the following technical scheme:
step 1: selecting waste water to be measured, eliminating organic matter interference, and carrying out salt content test; evaporating the selected wastewater to dryness in a water bath, and slowly adding a small amount of H2O2 solution before the water bath and before the wastewater is evaporated to dryness in the water bath process until the wastewater or the residue becomes white or the color is stable and does not change;
carrying out parallel sample test on the wastewater, keeping a test result that the absolute value of the relative standard deviation of the parallel samples is less than 0.5%, and taking the arithmetic mean value of the parallel samples according to the salt content;
step 2: measuring the pH value of the treated wastewater, and performing volatile substance compensation;
pH is less than or equal to 2, and CL in the wastewater is measured-Content [ CL-]If [ CL)-]More than or equal to 400mg/L, and the hydrogen chloride compensation is carried out on the salt contentThe calculation formula is as follows: pH is not less than-lg ([ CL)-]/35500), salt content 10-pHHydrogen chloride compensation of x 36500 mg/L; if the pH is less than-lg [ CL-]The salt content is added with [ CL-]X 1.028mg/L hydrogen chloride;
pH is more than or equal to 12, and the content of ammonia ions (NH) in water is measured4 +]If [ NH ]4 +]More than or equal to 180mg/L, NH is carried out on the salt content3Compensation, the calculation formula is: [ NH ]4 +]≤18×10(pH-11)The salt content is increased by [ NH ]4 +]X1.89 mg/L NH3Compensating; if [ NH ]4 +]≥18 ×10(pH-11)Salt content is increased by 10(pH-14)X44000 mg/L of NH3Compensation;
and step 3: collecting test data, carrying out assay data analysis, carrying out outlier screening on each pair of conductivity and salt content analysis data, and determining a relation formula of the conductivity and the salt content by using a data analysis method;
and 4, step 4: and calculating the salt content of the wastewater according to a relation formula of the conductivity and the salt content.
Preferably, the conductivity and salt content analysis data is used for carrying out outlier screening, and a data analysis method is used for determining a relation formula of conductivity and salt content, and the specific steps are as follows:
step 1: carrying out outlier detection on the data by using a salt conductivity ratio parameter, wherein the salt conductivity ratio is equal to the ratio of the salt content to the conductivity, screening the data outliers, and screening out analysis data participating in data measurement and calculation;
step 2: taking 20% of the analysis data as test data, and 80% of the analysis data is used for sample training, and establishing a relational formula of high salt conductivity to salt content:
Y＝(axb+Obj)/2
in the formula: a is a power function coefficient, b is a power exponent, x is conductivity, Y is salinity, n is the number of training function samples, and l is for a single sampleLoss of (y)i、y′iRespectively the true value and the predicted value f of the salt content of the ith sample of the modeltFor the base model, t is an accumulation variable representing the number of trees, i.e., the complexity of each tree.
Preferably, the value of a is 465.6852, and the value of b is 1.3051.
Preferably, the outlier screening is performed by comparing standard deviations in normal distribution with conductivity per value interval 1 as a dividing unit, and when the standard deviations exceed 1.5, the outlier is filtered and removed.
The invention has the advantages that: the invention can utilize the conductivity generated by ionization of dissolved salt in water, quickly measure the salt content in the wastewater by using the conductivity, and has the advantages of high sensitivity, simple operation, high accuracy of measurement result in measurement range, economy and convenience.
Drawings
FIG. 1 is a diagram of a conductivity-salinity power function fit according to the present invention. Correlation R2=0.91, sample mean absolute deviation mae =9201.41.
FIG. 2 is a schematic diagram of XGboost fitting regression according to the present invention. Correlation R2=0.89, sample mean absolute deviation mae =11946.34.
FIG. 3 is a diagram illustrating integration of the power function and the XGboost model according to the present invention. Correlation R2=0.94, sample mean absolute deviation mae =8932.94.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
A method for measuring the salinity of wastewater based on multiple compensations of electrical conductivity can utilize the conductive capability brought by the ionization of salt in the wastewater to accurately measure the salinity, and comprises the following steps;
1. the high-salinity wastewater with the salt content of 20g/L-400g/L is selected, and for the wastewater generated by the same water source and the same production process, various components in the wastewater are relatively stable, so that the method is more suitable for carrying out full-salinity measurement.
2. The conductivity is accurately measured, a proper measuring range and the conductivity with sensitive and accurate temperature compensation are selected, corrosion, pollution and polarization effects can be resisted, and the accurate and reliable measurement of the conductivity is met.
3. The water source was tested for salinity according to HJ/T51.
(1) Eliminating organic matter interference, evaporating in water bath, removing evaporating dish, cooling, and adding 30% H slowly and uniformly in water bath according to water quality2O2And (3) slowly rotating the evaporating dish until bubbles disappear, evaporating to dryness, and repeatedly treating for several times until evaporation residues do not generate steam pockets and become white or have stable color and do not change.
In the step, the organic matter treatment process is optimized, and H is added in advance2O2Preventing the solution from evaporating to dryness, and adding H2O2The solution causes the splashing of the residue after evaporation, or when the salt content is high, the organic matter in the residue is not completely removed, which causes measurement error. The limestone-gypsum wet desulphurization system adopts forced oxidation, reducing salts in the desulphurization waste water almost do not exist, and H2O2The solution may foam during the removal of the organic material and even cause the sample to boil. In the step, part of H is added before the water bath is evaporated to dryness2O2Solution, low temperature solution state, H2O2The reaction is mild, most organic matters are removed, and then H is added in advance before the water bath is evaporated to dryness2O2Dissolving to ensure thorough removal of oxides and preventing addition of H after evaporation to dryness2O2The solution causes splashing of the residue after evaporation, causing measurement errors.
(2) Testing each water sample with a relative standard deviation absolute value of less than 0.5%, retaining the test result, and measuring the arithmetic mean value x of the parallel samples with salt contentp。
In the formula: cv is the relative deviation of the parallel samples; s is the absolute deviation of the parallel sample; x is the number ofpIs the average value of the parallel samples,
4. volatile matter compensation is carried out, and accurate measurement of the salt content of the high-salt water is realized.
(1) Measuring pH to less than or equal to 2, and determining CL in the wastewater-Content (by [ CL)-]Expressed in mg/L), [ CL-]More than or equal to 400mg/L, and performing hydrogen chloride compensation on the salt content, wherein the calculation formula is as follows: pH is not less than-lg ([ CL)-]/35500), salt content plus 10-pHHydrogen chloride compensation of x 36500 mg/L; if the pH is less than-lg [ CL-]Salt content plus [ CL-]×1.028mg/L。
(2) pH is more than or equal to 12, and the content of ammonia ions (by using [ NH ]) in water is measured4 +]Expressed in mg/L), [ NH ]4 +]More than or equal to 180mg/L, NH is carried out on the salt content3Compensation, the calculation formula is: [ NH ]4 +]≤18×10(pH-11)Salt content plus [ NH ]4 +]X 1.89mg/L NH3Compensation; [ NH ]4 +]≥18×10(pH-11)Salt content plus 10(pH-14)X44000 mg/L NH3And (6) compensation.
5. Collecting test data, carrying out analysis of assay data, carrying out outlier screening on each pair of conductivity and salt content analysis data, and determining a relation formula of conductivity and salt content by using a data analysis method.
(1) Introducing salt conductivity parameters to carry out outlier detection on the data, collecting test data which is more than or equal to 50 groups, introducing salt conductivity d parameters to each pair of conductivity and salt content, wherein the salt conductivity d is equal to the ratio of the salt content to the conductivity, carrying out r value outlier data screening on d, and determining that the analysis data which finally participates in data measurement and calculation is more than or equal to 45 groups.
And (4) outlier screening, wherein the interval of each numerical value of the conductivity is 1 as a division unit, deviation analysis is carried out by comparing standard deviations in normal distribution, and when the standard deviations exceed 1.5, outliers are filtered and removed.
Taking 20% of the analysis data as test data, using 80% of the analysis data for sample training, and establishing a measuring and calculating model of high salt conductivity to salt content:
Y＝(465.6852x1.3051+Obj)/2
in the formula: a is the coefficient of the power function, b is the power exponent, x is the conductivity, Y is the salinity, n is the number of samples of the training function, l is the loss to a single sample, Y is the loss to a single samplei、y′iRespectively the true value and the predicted value f of the salt content of the ith sample of the modeltΩ is a regular term for the base model.
The calculation process of the model for measuring and calculating the salt content by fitting regression high salt conductivity is as follows:
fitting regression:
after the outlier is removed, the conductivity-salinity sampling data still conform to the characteristics of the increasing function and are matched with the power function image. Exponentiation function y = axb(ii) a When performing power function fitting regression, firstly, linearly converting the regression into ln y = ln a + b ln x; substituting the filtered data into a formula, establishing a power function fitting regression equation, and solving the values of a and b, wherein a =465.6852 and b =1.3051, and the power function fitting regression equation is y =465.6852x1.3051。
As shown in fig. 3, the real data may fluctuate, which may cause a large error in the value directly predicted by the power function, so that the XGBoost model needs to be combined to adjust the smoothness of the power function.
XGboost data modeling:
and performing second-order Taylor expansion when solving the extreme value of the loss function by utilizing the XGboost to approximate the minimum value of the loss function. When the model is trained using data, its objective function Obj is as follows:
as shown in fig. 2, the predicted value and the actual value may have a certain error in some cases.
Algorithm optimization and integration:
integrating the average of the predicted values of the power function formula and the XGboost formula to obtain a new prediction model, as shown below:
Y＝(465.6852x1.3051+Obj)/2
the correlation R2=0.94, and the mean absolute deviation mae =8932.94 of the samples, which are significantly improved compared with the individual power function and XGboost.
6. And carrying out wastewater conductivity analysis, and rapidly obtaining the salt content of the wastewater according to a relation formula of the conductivity and the salt content.
Claims (4)
1. A method for measuring the salinity of wastewater based on multiple compensations of conductivity measurement is characterized by comprising the following steps:
step 1: selecting waste water to be measured, eliminating organic matter interference, and performing salt content test; evaporating the selected waste water in water bath, and slowly adding small amount of H before and during evaporation in water bath2O2Solution until the waste water or residue becomes white or the color is stable and does not change any more;
carrying out a parallel sample test on the wastewater, keeping a test result that the absolute value of the relative standard deviation of the parallel sample is less than 0.5%, and measuring the arithmetic mean value of the parallel sample by using salt;
and 2, step: measuring the pH value of the treated wastewater, and performing volatile substance compensation;
pH is less than or equal to 2, and CL in the wastewater is measured-Content [ CL-]If [ CL)-]The content of the salt is compensated by hydrogen chloride, and the calculation formula is as follows: pH is not less than-lg ([ CL)-]/35500), salt content 10-pHHydrogen chloride compensation of x 36500 mg/L; if the pH is less than-lg [ CL-]The salt content is added with [ CL-]1.028mg/L hydrogen chloride compensation;
pH is more than or equal to 12, and the content of ammonia ions (NH) in water is measured4 +]If [ NH ]4 +]More than or equal to 180mg/L, NH is carried out on the salt content3Compensation, the calculation formula is: [ NH ]4 +]≤18×10(pH-11)The salt content is added [ NH ]4 +]X 1.89mg/L NH3Compensation; if [ NH ]4 +]≥18×10(pH-11)Salt content is increased by 10(pH-14)X44000 mg/L NH3Compensation;
and step 3: collecting test data, carrying out assay data analysis, carrying out outlier screening on each pair of conductivity and salt content analysis data, and determining a relation formula of the conductivity and the salt content by using a data analysis method;
and 4, step 4: and calculating the salt content of the wastewater according to a relation formula of the conductivity and the salt content.
2. The method for measuring salinity content in wastewater based on multiple compensations in electrical conductivity measurement as claimed in claim 1, wherein said analytical data of electrical conductivity and salinity is used to perform outlier screening, and the relational formula between electrical conductivity and salinity is determined by using the analytical data method, and the concrete steps are as follows:
step 1: carrying out outlier detection on the data by using a salt conductivity ratio parameter, wherein the salt conductivity ratio is equal to the ratio of the salt content to the conductivity, screening the data outliers, and screening out analysis data participating in data measurement and calculation;
and 2, step: taking 20% of the analysis data as test data, and 80% of the analysis data is used for sample training, and establishing a relation formula of high salt conductivity to salt content:
Y＝(axb+Obj)/2
in the formula: a is the coefficient of the power function, b is the power exponent, x is the conductivity, Y is the salinity, n is the number of samples of the training function, l is the loss to a single sample, Y is the loss to a single samplei、y′iAre respectively a modelTrue and predicted values of salt content of i samples, ftFor the basis model, the number of k is the number of predicted values minus 1, i.e., k = n-1.
3. The method for measuring the salinity of wastewater based on various compensations of conductivity measurement as claimed in claim 2, wherein the value of a is 465.6852 and the value of b is 1.3051.
4. The method for measuring salinity of wastewater based on various compensations of conductivity as claimed in claim 2, wherein the outlier screening is performed by comparing the standard deviation in the normal distribution according to the division unit of conductivity per value interval of 1, and when it exceeds 1.5 standard deviations, it is filtered out as an outlier.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117147974A (en) * | 2023-10-19 | 2023-12-01 | 北京江云智能科技有限公司 | Underground water collecting and quality analyzing device with integrated temperature, water level and conductivity |
| CN117147974B (en) * | 2023-10-19 | 2024-05-10 | 北京江云智能科技有限公司 | Underground water collecting and quality analyzing device with integrated temperature, water level and conductivity |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117147974A (en) * | 2023-10-19 | 2023-12-01 | 北京江云智能科技有限公司 | Underground water collecting and quality analyzing device with integrated temperature, water level and conductivity |
| CN117147974B (en) * | 2023-10-19 | 2024-05-10 | 北京江云智能科技有限公司 | Underground water collecting and quality analyzing device with integrated temperature, water level and conductivity |
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