CN111847614A - Accurate dosing method and system - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 76
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 185
- 239000000701 coagulant Substances 0.000 claims abstract description 171
- 239000000126 substance Substances 0.000 claims abstract description 53
- 230000036284 oxygen consumption Effects 0.000 claims abstract description 24
- 230000008569 process Effects 0.000 claims abstract description 24
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 23
- 239000001301 oxygen Substances 0.000 claims abstract description 23
- 239000003814 drug Substances 0.000 claims abstract description 7
- 238000004364 calculation method Methods 0.000 claims description 13
- 230000007547 defect Effects 0.000 claims description 11
- 238000005189 flocculation Methods 0.000 claims description 7
- 230000016615 flocculation Effects 0.000 claims description 7
- 238000004062 sedimentation Methods 0.000 claims description 7
- 239000004576 sand Substances 0.000 claims description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 3
- 238000011156 evaluation Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 11
- 238000004519 manufacturing process Methods 0.000 abstract description 11
- 229940079593 drug Drugs 0.000 abstract 1
- 230000015271 coagulation Effects 0.000 description 12
- 238000005345 coagulation Methods 0.000 description 12
- 238000002474 experimental method Methods 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- 230000000875 corresponding effect Effects 0.000 description 5
- 239000003643 water by type Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
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- 238000012360 testing method Methods 0.000 description 3
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- 230000008859 change Effects 0.000 description 2
- 230000002596 correlated effect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 238000003556 assay Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000005352 clarification Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 239000012286 potassium permanganate Substances 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
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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
- G01N33/18—Water
- G01N33/1806—Biological oxygen demand [BOD] or chemical oxygen demand [COD]
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/08—Chemical Oxygen Demand [COD]; Biological Oxygen Demand [BOD]
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Abstract
The invention provides an accurate dosing method, which comprises the following steps: measuring the chemical oxygen demand of the water to be treated; determining the coagulant dosage based on the measured chemical oxygen consumption of the water to be treated; and adding a coagulant into the water to be treated according to the determined coagulant adding amount. The inventor finds that the chemical oxygen consumption of the water to be treated and the coagulant dosage have strong correlation, so that the coagulant dosage can be directly obtained based on the chemical oxygen consumption of the water to be treated, accurate, rapid and simple determination of the coagulant dosage is realized, the method gives the correlation between the water quality of the water to be treated and the treatment process, provides basis support for guiding production, reasonably applying medicines, ensuring the water quality and the treatment effect, and can improve the water treatment effect, reduce the water treatment cost and reduce the labor intensity of operators. In addition, the invention also provides an accurate dosing system capable of implementing the accurate dosing method.
Description
Technical Field
The invention relates to an accurate dosing method and an accurate dosing system.
Background
In water treatment, it is usually necessary to add an appropriate amount of coagulant to the water to be treated to cause coagulation reaction to remove impurities in the water to be treated. The dosage of the coagulant is crucial to the water treatment process, and if the dosage is too small, the water treatment effect is affected, so that impurities are not completely removed; the excessive dosage will cause unnecessary waste and increase the cost. Because the components of the water to be treated in different environments and different time periods are greatly changed, the required dosage is changed, and how to accurately control the dosage is an important problem in practice.
At present, most water plants adopt a beaker experiment mode to determine the coagulant dosage. The method comprises the steps of manually and regularly carrying out a dosing test on a water sample to be treated under laboratory conditions, observing the treatment effect of the water to be treated under different coagulant dosing amounts, observing and detecting the turbidity change of a supernatant liquid by naked eyes, or detecting the change of ultraviolet absorbance (the absorbance of ultraviolet rays with the wavelength of 254nm is called as a UV254 index) by an instrument, determining the optimal dosing amount, and then guiding the actual dosing amount produced by a water plant based on the dosing amount. Obviously, the beaker experiment mode is time-consuming and labor-consuming, has components judged by experience, is only suitable for regular work, and is difficult to timely and effectively give a coagulant dosage adjustment suggestion for the frequently-changed water quality to be treated.
A small number of water plants adopt a system for automatically determining and controlling the coagulant dosage. The system summarizes the beaker experiment results for a period of time, establishes a relational expression between the turbidity of the water to be treated (the UV254 index can be adopted in individual cases) and the coagulant dosage, and then determines the required coagulant dosage according to the turbidity/UV 254 of the water to be treated based on the relational expression. Although this method can improve the efficiency of determining the coagulant dosage to some extent, the method requires frequent beaker experiments to correct and update the relational expression to adapt to the changing water quality of the water to be treated due to poor regularity between the turbidity/UV 254 of the water to be treated and the coagulant dosage. Moreover, since the beaker experiment is difficult to completely simulate real water treatment conditions, the coagulant dosing amount is determined based on the turbidity/UV 254 of the water to be treated and highly depends on the experience of operators, so that the coagulant dosing amount is not very accurate. For safety reasons, coagulant dosage usually recommended in practice is large and conservative, so that the running cost of a water plant is increased.
Therefore, it is desirable to provide a precise dosing method and a corresponding precise dosing system to overcome the problems in the prior art.
Disclosure of Invention
In a first aspect of the present invention, there is provided a precise dosing method, comprising:
-measuring the chemical oxygen demand of the water to be treated;
-determining the coagulant dosage based on the measured chemical oxygen demand of the water to be treated; and
-adding coagulant to the water to be treated according to the determined coagulant dosing amount.
The inventor finds that the chemical oxygen consumption of the water to be treated and the coagulant dosage have strong correlation, so that the coagulant dosage can be directly controlled based on the chemical oxygen consumption of the water to be treated, the coagulant dosage can be accurately, quickly and simply determined, the water treatment effect can be improved, the water treatment cost can be reduced, and the labor intensity of operators can be reduced. The method gives the relevance between the water quality of the water to be treated and the treatment process, and provides a basis support for guiding production, reasonably using medicine, ensuring the water quality of the effluent and the treatment effect.
Alternatively, the method may comprise determining a relationship between the chemical oxygen demand of the water to be treated and the coagulant dosage, and determining the coagulant consumption per unit based on the relationship and the measured chemical oxygen demand of the water to be treated.
Optionally, the relationship is of the form: and Y is k.X + b, wherein Y is the coagulant dosage, X is the chemical oxygen consumption of the water to be treated, and k and b are constants determined by a fitting method.
Preferably, the value of k in the relation is in the range of 1.0 to 1.5, and the value of b is in the range of-1.5 to-0.5.
Further optionally, k has a value of 1.357 and b has a value of-0.926 in the relationship.
Optionally, plus and minus two times of standard deviation is superimposed on the basis of the relational expression to obtain a first reference line and a fifth reference line respectively, and plus and minus one times of standard deviation is superimposed on the basis of the relational expression to obtain a second reference line and a fourth reference line respectively.
Preferably, the adjusted unit consumption of the coagulant is between the curve of the relational expression and a fourth reference line on the basis of the relational expression, wherein the fourth reference line is superposed with one standard deviation minus. This region is the preferred coagulant specific consumption range recommended by the inventors.
Alternatively, the method may comprise measuring the flow rate of water to be treated and determining the coagulant dosing amount based on the coagulant consumption per unit and the flow rate of the water to be treated.
Alternatively, the method may comprise measuring the actual amount of coagulant added to the mixing tank and adjusting the coagulant dosing amount based on this actual amount.
Optionally, the method can comprise measuring any index of the water to be treated in the temperature, pH value, turbidity, UV254 and TOC of the water to be treated, and adjusting the unit consumption of the coagulant based on the index of the water to be treated.
Optionally, the method may include measuring any one of effluent indicators of chemical oxygen demand, temperature, PH, turbidity, UV254, TOC of the effluent, and adjusting the coagulant unit consumption based on the effluent indicator.
Optionally, the method may comprise assessing the flow load of the system or a process defect, adjusting the coagulant consumption per unit based on the flow load of the system or based on the process defect.
Optionally, the coagulant is polyaluminium chloride.
In a second aspect of the invention, there is provided an accurate dosing system comprising: a mixing tank that receives water to be treated; a coagulant adding pump which adds coagulant to the mixing tank; a chemical oxygen consumption meter for water to be treated, which measures the chemical oxygen consumption of the water to be treated; and the controller determines the coagulant adding amount based on the chemical oxygen consumption of the water to be treated and controls a coagulant adding pump to add the coagulant according to the coagulant adding amount. The accurate dosing system can improve the water treatment effect, reduce the water treatment cost and reduce the labor intensity of operators.
Optionally, the controller has a unit consumption calculation module which determines coagulant unit consumption based on the measured chemical oxygen demand of the water to be treated and a predetermined relational expression between the chemical oxygen demand of the water to be treated and the coagulant addition amount.
Optionally, the relationship is of the form: and Y is k.X + b, wherein Y is the coagulant dosage, X is the chemical oxygen consumption of the water to be treated, and k and b are constants determined by a fitting method.
Preferably, the value of k in the relation is in the range of 1.0 to 1.5, and the value of b is in the range of-1.5 to-0.5.
Further optionally, k has a value of 1.357 and b has a value of-0.926 in the relationship.
Optionally, plus and minus two-fold standard deviations are superimposed on the basis of the relational expression to obtain a first reference line and a fifth reference line respectively, plus and minus one-fold standard deviations are superimposed on the basis of the relational expression to obtain a second reference line and a fourth reference line respectively, and the unit consumption calculation module adjusts the unit consumption of the coagulant so that the adjusted unit consumption of the coagulant is between any adjacent two of the first reference line, the second reference line, the curve of the relational expression, the fourth reference line and the fifth reference line.
Preferably, the adjusted unit consumption of the coagulant is between the curve of the relational expression and a fourth reference line on the basis of the relational expression, wherein the fourth reference line is superposed with one standard deviation minus. This region is the preferred coagulant specific consumption range recommended by the inventors. Optionally, the system further comprises a water to be treated flow meter which measures the flow rate of water to be treated; the controller is also provided with a proportion control module which receives the unit consumption of the coagulant and the measured flow rate of the water to be treated and determines the adding amount of the coagulant according to the unit consumption of the coagulant and the measured flow rate of the water to be treated.
Optionally, the system further comprises a liquid medicine flow meter which measures the actual amount of coagulant dosed into the mixing tank from the coagulant dosing pump; the proportion control module receives the actual amount of the coagulant and adjusts the coagulant adding amount based on the actual amount.
Optionally, the system further comprises a water to be treated meter which measures any index of water to be treated in the temperature, the pH value, the turbidity, the UV254 and the TOC of the water to be treated; and the unit consumption calculation module receives the index of the water to be treated and adjusts the unit consumption of the coagulant based on the index of the water to be treated.
Optionally, the system further comprises a water outlet meter, which measures any one of the effluent indexes of chemical oxygen consumption, temperature, PH value, turbidity, UV254, and TOC of the effluent; and the unit consumption calculation module receives the effluent index and adjusts the unit consumption of the coagulant based on the effluent index.
Optionally, the system further comprises a measuring device that measures a flow load or a process defect of the system; and the unit consumption calculating module is used for adjusting the unit consumption of the coagulant based on the flow load of the system or process defects.
Optionally, the system may further include a flocculation basin that receives and processes the first intermediate water from the mixing basin and produces a second intermediate water. Additionally, the system may further include a sand filter that receives and processes the second intermediate water from the flocculation basin and produces an effluent.
Drawings
FIG. 1 shows the relationship between coagulant usage and chemical oxygen demand (CODmn) of water to be treated;
FIG. 2 shows a flow chart of a precision dosing method according to the present invention;
figure 3 shows a schematic of a precision dosing system according to the present invention.
Detailed Description
In order to make the objects, aspects and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. Unless otherwise indicated, terms used herein have the ordinary meaning in the art. Like reference symbols in the various drawings indicate like elements.
Before the invention, few people think that the coagulant dosage is directly related to the water quality analysis index, and even though the coagulant dosage is related to the water quality analysis index, the relationship between the coagulant dosage and the water quality analysis index is usually considered to be quite complicated. Through systematic research on the relevance between common water quality indexes and coagulant dosage, the invention finally discovers that: the Chemical Oxygen Demand (COD) and the coagulant dosage are related, and the method can be used for accurately determining the coagulant dosage.
Chemical oxygen demand COD refers to the oxygen equivalent of organic matter in the water to be treated that can be oxidized by strong oxidants. If potassium permanganate is used as a strong oxidant, the chemical oxygen demand (COD mn) can be expressed. For water to be treated, the COD value is a relatively stable index, the influence of the water to be treated on the hydraulics conditions (such as standing time and the like) is small, and the removal rate of the water to be treated is high by conventional water treatment. Moreover, the COD testing technology in the prior art is mature, and a COD measuring instrument can be used for determining the COD value of the water to be treated in real time, quickly and accurately.
After researching various water quality indexes (including turbidity, UV245, TOC and the like), the inventor finds that only COD has high correlation with the coagulant dosage and the linear fitting result is the best, mainly because the organic matter related to COD is mainly hydrophilic organic matter which is similar to the surface property of aluminum hydroxide and is easy to be correlated with the coagulation reaction process. In contrast, although the UV254 index also reflects organic substances, it reflects more hydrophobic organic substances, which cannot directly affect the coagulation process; the total organic carbon TOC reacts the sum of all forms of organic matters, including hydrophobic organic matters and hydrophilic organic matters, wherein the hydrophobic organic matters are not easily associated with the coagulation process. Therefore, the COD index is a better option for determining the content of coagulant than the UV254 index and the total organic carbon TOC index. In addition, the turbidity of the water to be treated mainly reflects the condition of mg/l inorganic insoluble substances, the detection value is unstable under the influence of sampling and detection conditions, and part of the insoluble substances are precipitated by gravity without considering the coagulation process.
The inventor also proves that the COD is highly correlated with the coagulant dosage through experiments, and the experimental process is as follows. The inventor collects the production and test data of 31 waterworks in the SUEZ NWS WO system in 2017 year all year, and based on the monthly mean value, 372 data points are counted. These water plants involve the treatment of 24 surface source waters (river and reservoir waters), the process being mainly conventional, all coagulants being polyaluminium chloride, the leaving water implementing the standards for Chinese drinking water and a more stringent internal control index of turbidity (0.2 NTU). The inventors collected corresponding production and assay data, including: coagulant unit consumption, water quality indexes of water to be treated (including turbidity, water temperature, CODmn, UV254, PH and TOC values of the water to be treated), water quality of factory water (including turbidity, water temperature, CODmn, UV254, PH and TOC values of the outlet water) and the like. The inventor researches the correlation between each water quality index and the unit consumption of the coagulant in turn, and finds that the unit consumption of the coagulant has higher correlation with the CODmn of the water to be treated and the linear fitting result is the best.
Fig. 1 shows the coagulant consumption per unit versus CODmn of water to be treated, where the scatter points represent data samples from different water plants. FIG. 1 shows five lines, the middle most curve being the best linear fit to the scatter points, with the equation:
Y＝1.357X-0.926
wherein X is the water to be treated CODmn (unit mg/l), Y is the unit consumption of coagulant (unit ppm, using Al)2O3Meter) of the fitting relation20.491, and 0.977 as the standard deviation STDEV.
On the basis of the discovery of the correlation, the inventor proposes that the coagulant dosage required per unit of water to be treated (i.e. the unit consumption of the coagulant) can be calculated by measuring the water CODmn of the water to be treated and combining the relational expression obtained above, and then the actual required coagulant dosage can be obtained by combining the water flow to be treated.
As can be seen from fig. 1, the data points of each water plant are spread above and below the fitting relation, and the deviation is related to the actual working condition of each water plant. Therefore, in practice, the above relation needs to be adjusted to some extent by comprehensively considering the field conditions. As shown in fig. 1, in addition to the fitting relation curve, fig. 1 further shows four reference lines, which are sequentially a first reference line, a second reference line, a fitting relation curve, a fourth reference line, and a fifth reference line from top to bottom, wherein the second reference line and the fourth reference line are generated by superimposing a standard deviation of plus and minus one times on the basis of the fitting linear fitting curve; the first reference line and the fifth reference line are generated by superimposing two times the standard deviation of plus and minus on the fitted linear fit curve. These four reference lines, along with the intervening linearly fitted curve, are referred to as a "pentagraph" and are used to guide the operator in adjusting the dosage. The operator can adjust the dosing amount according to the actual production situation on site, so that the adjusted dosing amount is positioned between any adjacent two of the first reference line, the second reference line, the fitting relational curve, the fourth reference line and the fifth reference line. The inventor has realized that the region between the linear fitting curve and the negative one-time standard deviation curve (fourth reference line) is the recommended region, and the dosing amount in the region is preferable, and the water treatment effect is good. Specifically, if the field condition is judged to be more favorable for the implementation of the coagulation reaction process, a negative adjustment item can be superimposed on the basis of the linear fitting curve to move the fitting curve downwards, and then a smaller amount of coagulant for actually guiding the operation can be obtained on the basis of the adjusted curve, which is favorable for saving the coagulant; on the contrary, if the field condition is judged to be unfavorable for the coagulation reaction process, a positive adjustment item can be superposed on the basis of the linear fitting curve to enable the fitting curve to move upwards, and then a larger coagulation amount for actually guiding operation can be obtained based on the adjusted curve, which is helpful for ensuring the effect of water treatment under complex working conditions. The determination of the field condition can be based on the water quality index (water temperature, pH value, turbidity, UV254, TOC, etc.) of the water to be treated, the water quality index (water temperature, pH value, turbidity, UV254, TOC, COD, etc.) of the outlet water, the specificity (flow load condition, process defect condition, etc.) of the field, and the like.
It should be noted that the above relational equation is only a specific example. The specific use may vary depending on many factors such as coagulant type, effluent standard, etc. The person skilled in the art can determine different forms of relations by himself or herself under the teaching of the present invention.
Accurate dosing method
In order to solve the problems that the method for determining the coagulant addition amount in the prior art is not accurate enough and is complex to operate, based on the conception, the invention provides the method for determining the coagulant addition amount directly based on the Chemical Oxygen Demand (COD) of the water to be treated.
Fig. 1 shows a precise dosing method based on chemical oxygen consumption COD according to the present invention. The method comprises steps 101-105.
Step 101 is an empirical formula between the determination of Chemical Oxygen Demand (COD) and the dosage of the coagulant. In the step of determining the empirical formula in step 101, the chemical oxygen demand COD of various different waters to be treated is first measured, then the coagulant addition amount required for treating the different waters to be treated to meet the standard is measured, and then a conversion relational formula (called empirical formula) between the COD index of the waters to be treated and the coagulant addition amount is established by a mathematical fitting method.
One general empirical form is:
Y＝k·X+b
wherein Y is the coagulant dosage, X is the Chemical Oxygen Demand (COD) of the water to be treated, and k and b are constants determined by a fitting method. k can be in the range of 1-1.5, b can be in the range of-1.5 to-0.5; preferably, k may be 1.357 and b may be-0.926. This determined empirical formula is stored in the memory of the controller, which may be subsequently invoked by the processor of the controller; or may be re-determined in a periodic corrective action.
Step 102 is to measure the chemical oxygen demand COD of the water to be treated by using a water quality meter. The water quality meter can be arranged in a water inlet channel or a pipeline of water to be treated so as to realize online measurement. Alternatively, a dedicated water conduit may be provided to direct the water to be treated to the water quality meter for measurement at a location remote from the channel or pipe of the water to be treated.
Step 103 is to calculate the actual coagulant dosage based on the empirical formula determined in step 101 and the chemical oxygen demand COD measured in step 102. Specifically, the chemical oxygen demand COD measured in step 102 is substituted as X into the empirical formula determined in step 101, and the corresponding coagulant dosing amount Y is obtained.
And 105, adding a coagulant into the water to be treated based on the coagulant adding amount.
Usually, the coagulant dosage Y obtained in step 103 is the unit consumption of coagulant required for a unit volume of water to be treated, and in this case, the actual coagulant dosage can be obtained by multiplying the unit consumption of coagulant obtained in step 103 by the water flow rate to be treated obtained by measurement. Then, in step 105, a coagulant addition pump is controlled based on the actual coagulant addition amount, and a required amount of coagulant is added to the water to be treated.
The steps shown as dashed box 104 in fig. 1 are optional. Step 104 is between step 103 and step 105, which is an adjustment step 104. In step 104, an adjustment term Δ is added on the basis of the coagulant dosing amount Y obtained in step 103, thereby obtaining an adjusted coagulant dosing amount Y', that is, according to the following equation:
Y’＝Y+Δ
the adjustment term delta can be a positive value or a negative value, and is a small-range adjustment value for the empirical formula based on other measured indicators of the quality of the water to be treated (such as water temperature, pH value, turbidity, total organic carbon TOC, UV254 and the like), indicators of the quality of the effluent (such as water temperature, pH value, turbidity, total organic carbon TOC, UV254 and the like) and conditions of special conditions of a production field (such as flow load conditions and process defects). In the case of optional step 104, the operation of the coagulant dosing pump is controlled with the adjusted coagulant dosing amount Y' obtained in this step as the coagulant consumption per unit.
On the spot, an operator can correct the empirical formula according to the actual production condition on the spot, obtain the adjustment term delta according to the actual condition on the production spot, and adjust the empirical formula according to the adjustment term delta to obtain the empirical formula for actual use. Specifically, as shown in fig. 1, in addition to the fitting relation curve, fig. 1 further shows four reference lines, which are sequentially a first reference line, a second reference line, a fitting relation curve, a fourth reference line, and a fifth reference line from top to bottom, where the second reference line and the fourth reference line are generated by superimposing a standard deviation of plus and minus one times on the basis of the fitting linear fitting curve; the first reference line and the fifth reference line are generated by superimposing two times the standard deviation of plus and minus on the fitted linear fit curve. These four reference lines, along with the intervening linearly fitted curve, are referred to as a "pentagraph" and are used to guide the operator in adjusting the dosage. The operator can adjust the dosing amount according to the actual production situation on site, so that the adjusted dosing amount is positioned between any adjacent two of the first reference line, the second reference line, the fitting relational curve, the fourth reference line and the fifth reference line. For example, the water temperature is low in winter, the production load is high, the coagulation reaction speed is low, the sedimentation time is required to be long, and in order to ensure the effluent quality, a plurality of coagulants are required to be added to promote the coagulation sedimentation. Therefore, it is necessary to add a positive adjustment term Δ to the original empirical formula to obtain the empirical formula for practical use. According to the method, the proper dosage of the coagulant is completely converted from the water quality data of the water to be treated and can be used for production control. Namely, the coagulant dosage is really determined from the water quality, and the accuracy of controlling the coagulant dosage is greatly improved. Moreover, the Chemical Oxygen Demand (COD) is a stable and easily-measured water quality index, so that the method has strong universality, namely, the method can be basically applied to almost all occasions only by simple adjustment based on one set of system. Moreover, the method greatly reduces the intervention of operators, only needs the operation of technicians in the empirical determination process, and automatically determines the dosage in the subsequent dosage link, thereby eliminating the condition that the beaker experiment operation is frequently carried out in the past. Compared with the traditional method, the coagulant dosing amount obtained by the method is more accurate, and the effects of better controlling water quality and saving medicament dosage can be achieved.
Accurate medicine system
Figure 3 shows a precision dosing system that can perform the precision dosing method described above in connection with figure 2.
The system may include a mixing tank 10, a flocculation sedimentation tank 20, a sand filter 30, a coagulant dosing pump 40, and a controller 50. The water to be treated enters the mixing tank 10, and is mixed with the coagulant from the coagulant adding pump 40 in the mixing tank 10 to generate coagulation reaction. The mixing tank 10 may also be a coagulation tank, a clarification tank, etc., which may take many different specific tank types. The flocculation sedimentation tank 20 and the sand filter 30 are positioned at the downstream of the mixing tank 10 and are used for performing further filtering treatment on the effluent of the mixing tank 10 to obtain clean effluent meeting effluent standards. It is noted that the flocculation and sedimentation tank 20 and the sand filter 30 shown here are merely examples, and a greater or lesser number of tank bodies and other functions may be practically employed downstream of the mixing tank 10. Also, while fig. 3 shows the mixing tank 10 directly receiving water to be treated, in practice, other suitable tank bodies or apparatus may be provided upstream of the mixing tank 10.
The controller 50 has corresponding components adapted to implement the above-described methods and may include, for example, a computing module, a memory module, an interface module, etc., which may be implemented in a combination of hardware, firmware and/or software in a manner known in the art. The computing module performs a data computing function; the storage module stores corresponding programs and calculation results, and particularly, the storage module can store empirical formulas of the chemical oxygen consumption of the water to be treated and the coagulant addition amount, which are obtained in advance. The interface module is used to interface with peripheral devices for transmission and reception of data, and may be implemented as a wired or wireless communication module.
In one embodiment of the present invention, the controller 50 may employ a supervisory control and data acquisition System (SCADA) that is commonly used in central offices of water plants, which may include a unit consumption calculation module 501 and a proportional control module 502. The unit consumption calculating module 501 is used for generating unit consumption of coagulant based on the COD of the water to be treated. As shown in fig. 3, the COD value (i) of the water to be treated measured by the COD meter of the water to be treated is used as an input and transmitted to the unit consumption calculation module 501, the unit consumption calculation module 501 calls an empirical formula, the coagulant input amount (ii) is obtained based on the COD value of the water to be treated, and the coagulant input amount (ii) is sent to the proportional control module 502 as an output.
Optionally (as shown by the dashed line in fig. 3), the unit consumption calculation module 501 may also receive a number of other metrics: for example, other parameters of water to be treated measured by various meters of water to be treated (for example, temperature, PH value, turbidity, UV245, TOC, etc.) and water outlet parameters measured by various meters of water outlet (for example, temperature, PH value, turbidity, UV245, TOC, CODmn, etc.) and/or parameters characterizing special factors on site (for example, whether overload is produced or not, whether process defects exist or not, etc.) are determined, and then coagulant dosing amount is adjusted based on the indexes as reference factors.
The proportion control module 502 receives coagulant dosage from the unit consumption calculation module 501, and receives water flow rate to be treated obtained by using a water flow meter to be treated, determines actual coagulant dosage according to the water flow rate to be treated, and sends the actual coagulant dosage to the coagulant dosing pump 40. The coagulant adding pump 40 adds coagulant into the mixing tank 10 based on this.
In addition, as shown in fig. 3, the proportional control module 502 may further receive the amount of coagulant actually fed by the coagulant feeding pump 40 obtained by the chemical flow meter, and apply proportional adjustment by using the amount of coagulant fed by the chemical flow meter as an adjustment factor to facilitate achieving the desired coagulant feeding amount. In other embodiments, other forms of control, such as proportional-integral control, proportional-integral-derivative control, etc., may also be performed on the coagulant dosing pump 40, so as to control the coagulant dosing pump 40 to quickly and accurately achieve the desired coagulant dosing amount (c).
According to the accurate dosing system, accurate coagulant dosing can be achieved, and therefore the effects of better controlling water quality and saving the dosage of the chemicals are achieved. Moreover, the system realizes automatic operation to a great extent, greatly reduces the labor intensity of operators, and provides the accuracy and stability of control.
Exemplary embodiments of the present invention have been described in detail herein with reference to the preferred embodiments, however, it will be understood by those skilled in the art that various changes and modifications may be made to the specific embodiments described above and various combinations of the various features and structures presented in the present invention without departing from the spirit of the invention, the scope of which is defined by the appended claims.
Claims (26)
1. An accurate dosing method is characterized by comprising the following steps:
measuring the chemical oxygen demand of the water to be treated;
determining the coagulant dosage based on the measured chemical oxygen consumption of the water to be treated; and
adding a coagulant into the water to be treated according to the determined coagulant adding amount.
2. The method of claim 1,
determining a relational expression between the chemical oxygen demand of the water to be treated and the dosage of the coagulant,
and determining the unit consumption of the coagulant based on the relational expression and the measured chemical oxygen consumption of the water to be treated.
3. The method of claim 2,
the form of the relation is: and Y is k.X + b, wherein Y is the coagulant dosage, X is the chemical oxygen consumption of the water to be treated, and k and b are constants determined by a fitting method.
4. The method of claim 3, wherein k has a value in the range of 1.0 to 1.5 and b has a value in the range of-1.5 to-0.5.
5. The method of claim 4, wherein k has a value of 1.357 and b has a value of-0.926.
6. The method of claim 2,
superposing plus and minus two times of standard deviation on the basis of the relational expression to respectively obtain a first reference line and a fifth reference line,
superposing plus and minus one-time standard deviation on the basis of the relational expression to respectively obtain a second reference line and a fourth reference line,
and adjusting the unit consumption of the coagulant to enable the adjusted unit consumption of the coagulant to be positioned between any adjacent two of the first reference line, the second reference line, the curve of the relational expression, the fourth reference line and the fifth reference line.
7. The method according to claim 6, characterized in that the adjusted coagulant specific consumption is between the curve of the relation and a fourth reference line on the basis of which minus one standard deviation is superimposed.
8. The method of claim 2, further comprising:
measuring the flow of water to be treated;
and determining the coagulant adding amount based on the unit consumption of the coagulant and the flow of the water to be treated.
9. The method of claim 8, further comprising:
measuring the actual amount of coagulant added to the mixing tank;
the coagulant addition amount is adjusted based on the actual amount.
10. The method of claim 2, further comprising:
measuring any index of the water to be treated in the temperature, the PH value, the turbidity, the UV254 and the TOC of the water to be treated;
and adjusting the unit consumption of the coagulant based on the index of the water to be treated.
11. The method of claim 2, further comprising:
measuring any effluent index of chemical oxygen consumption, temperature, PH value, turbidity, UV254 and TOC of the effluent;
and adjusting the unit consumption of the coagulant based on the effluent index.
12. The method of claim 2, further comprising:
evaluating the flow load or process defects of the system;
the coagulant specific consumption is adjusted based on the flow load of the system or based on process defects.
13. The method according to any one of claims 1 to 12,
the coagulant is polyaluminium chloride.
14. An accurate medicine feeding system, which is characterized by comprising:
a mixing tank that receives water to be treated;
a coagulant adding pump which adds coagulant to the mixing tank;
a chemical oxygen consumption meter for water to be treated, which measures the chemical oxygen consumption of the water to be treated;
and the controller determines the coagulant adding amount based on the chemical oxygen consumption of the water to be treated and controls a coagulant adding pump to add the coagulant according to the coagulant adding amount.
15. The system of claim 14,
the controller is provided with a unit consumption calculation module which determines the unit consumption of the coagulant based on the measured chemical oxygen consumption of the water to be treated and a predetermined relational expression between the chemical oxygen consumption of the water to be treated and the coagulant adding amount.
16. The system of claim 15,
the form of the relation is: and Y is k.X + b, wherein Y is the coagulant dosage, X is the chemical oxygen consumption of the water to be treated, and k and b are constants determined by a fitting method.
17. The system of claim 16, wherein k has a value in the range of 1.0 to 1.5 and b has a value in the range of-1.5 to-0.5.
18. The system of claim 17, wherein k has a value of 1.357 and b has a value of-0.926.
19. The system of claim 15,
superposing plus and minus two times of standard deviation on the basis of the relational expression to respectively obtain a first reference line and a fifth reference line,
superposing plus and minus one-time standard deviation on the basis of the relational expression to respectively obtain a second reference line and a fourth reference line,
and the unit consumption calculating module adjusts the unit consumption of the coagulant, so that the adjusted unit consumption of the coagulant is between any adjacent two of the first reference line, the second reference line, the curve of the relational expression, the fourth reference line and the fifth reference line.
20. The system according to claim 19, characterized in that the adjusted coagulant specific consumption is between the curve of the relation and a fourth reference line on the basis of the relation superimposed by minus one standard deviation.
21. The system of claim 15,
the system further comprises a water-to-be-treated flow meter which measures the flow rate of water to be treated;
the controller is also provided with a proportion control module which receives the unit consumption of the coagulant and the measured flow rate of the water to be treated and determines the adding amount of the coagulant according to the unit consumption of the coagulant and the measured flow rate of the water to be treated.
22. The system of claim 21,
the system further comprises a liquid medicine flow meter which measures the actual amount of coagulant added to the mixing tank from the coagulant adding pump;
the proportion control module receives the actual amount of the coagulant and adjusts the coagulant adding amount based on the actual amount.
23. The system of claim 15, further comprising:
the water to be treated instrument is used for measuring any index of the water to be treated in the temperature, the PH value, the turbidity, the UV254 and the TOC of the water to be treated;
and the unit consumption calculation module receives the index of the water to be treated and adjusts the unit consumption of the coagulant based on the index of the water to be treated.
24. The system of claim 15, further comprising:
the water outlet instrument is used for measuring any water outlet index of chemical oxygen consumption, temperature, PH value, turbidity, UV254 and TOC of the outlet water;
and the unit consumption calculation module receives the effluent index and adjusts the unit consumption of the coagulant based on the effluent index.
25. The system of claim 15, further comprising:
an evaluation device that evaluates a flow load or a process defect of the system;
and the unit consumption calculating module is used for adjusting the unit consumption of the coagulant based on the flow load of the system or process defects.
26. The system of any one of claims 14-25, further comprising:
a flocculation sedimentation tank that receives and processes the first intermediate water from the mixing tank and produces a second intermediate water;
and the sand filter receives and processes the second intermediate water from the flocculation sedimentation tank and generates outlet water.
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