Water quality prediction method nad water quality controlling method

Abstract

To provide a water quality prediction method of analyzing values of a few water quality items to predict other water quality items.SOLUTION: There is provided a water quality prediction method comprising a step of obtaining a correlation between values of water quality items (A) and values of water quality items (B) of a water system, to subsequently obtain measured values of the water quality items (A) and to obtain prediction values of the water quality items (B) based on the measured values of the water quality items (A) and the correlation. The water quality item (A) is electrical conductivity for example, and the water quality items (B) are one or two or more of the chloride ion concentration, the calcium hardness, and the Fe ion concentration.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for predicting the quality of water such as wastewater and water for use, and a method for controlling the water quality of a water system using this method. [Background technology]

[0002] When treating wastewater or using water for industrial purposes, the quality of the water is measured and, based on the results, chemicals are added, the water is blown, or other treatments are carried out.

[0003] For example, in boiler water systems and cooling water systems, the injection amounts of various chemicals and the blowdown amounts are controlled by measuring electrical conductivity, pH, oxidation-reduction potential, chloride ion concentration, sulfate ion concentration, magnesium hardness, calcium hardness, silica concentration, metal (iron, copper, zinc, etc.) ion concentration, ammonium ion concentration, TOC (total organic carbon), COD (chemical oxygen demand), turbidity, etc. In this case, control based on only a few items such as electrical conductivity, pH, and oxidation-reduction potential may not be able to manage water quality appropriately.

[0004] Therefore, after collecting water on-site and bringing it back, the water is analyzed for multiple water quality parameters, and the injection amount of various chemicals and the blowdown amount are adjusted based on the obtained measured values ​​(Patent Document 1). However, in this case, the time from water collection to analysis is long, which is likely to cause control delays. In addition, the cost of analysis is high. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-58857 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a water quality prediction method for predicting the values ​​of other water quality items by analyzing the values ​​of a small number of water quality items, and a water quality control method for a water system using this method. [Means for solving the problem]

[0007] The gist of the present invention is as follows.

[0008] [1] A water quality prediction method in which the correlation between the value of water quality item (A) and the value of water quality item (B) in a water system is determined in advance, the actual value of water quality item (A) is obtained, and the predicted value of water quality item (B) is obtained based on the actual measured value of water quality item (A) and the correlation.

[0009] [2] The water quality prediction method according to [1], wherein the water quality item (A) is electrical conductivity, and the water quality item (B) is one or more of chloride ion concentration, calcium hardness, and Fe ion concentration.

[0010] [3] A water quality control method for a water system that performs chemical injection control, blow control, or RO operation control, blower control, and pH control based on water quality values ​​of multiple water quality items of the water in the water system, consisting of the actual measured value of water quality item (A) of the water system and the predicted value of water quality item (B) obtained by the water quality prediction method of [1] or [2]. [Effects of the Invention]

[0011] According to the water quality prediction method of the present invention, some water quality items (A) are measured to obtain measured values, and the values ​​of other water quality items (B) are predicted from these measured values. Therefore, by actually measuring water quality items that are easy to analyze and predicting the water quality of items that require time or effort to analyze based on these measured values, values ​​for many water quality items can be easily obtained. Furthermore, by actually measuring water quality items that require low analysis costs and predicting water quality items that require high analysis costs from these measured values, values ​​for many water quality items can be obtained inexpensively.

[0012] According to the water quality control method of the present invention, chemical injection control, blower control, RO operation control, blower control, and pH control are performed based on water quality values ​​of multiple water quality items of the water in the water system, which are composed of the actual measured value of water quality item (A) of the water system and the predicted value of water quality item (B) obtained by this water quality prediction method. Therefore, control costs can be reduced while appropriate control is performed based on the water quality values ​​of multiple water quality items. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a graph showing the relationship between electrical conductivity and chloride ion concentration. [Figure 2] 1 is a graph showing the relationship between electrical conductivity and calcium hardness. [Figure 3] 1 is a graph showing the relationship between electrical conductivity and iron ion concentration. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in further detail below.

[0015] In the present invention, the quality of water such as wastewater and service water is predicted. Examples of wastewater include, but are not limited to, industrial wastewater, mine wastewater, building wastewater, and household wastewater, as well as wastewater from wastewater treatment facilities.

[0016] Examples of water include industrial water, tap water, groundwater, and river water, but are not limited to these.

[0017] Examples of water quality parameters include electrical conductivity, pH, oxidation-reduction potential, chloride ion concentration, sulfate ion concentration, acid consumption (pH 4.8), acid consumption (pH 8.3), magnesium hardness, calcium hardness, silica concentration, iron concentration, copper concentration, zinc concentration, other metal ion concentration, ammonium ion concentration, total phosphate concentration, residual chlorine concentration, TOC (total organic carbon), COD (chemical oxygen demand), and turbidity.

[0018] In the present invention, among these water quality items, those that satisfy requirements such as being able to be measured in a short time, requiring simple measuring equipment, and being inexpensive to measure, and that are correlated with other water quality items, are selected as water quality items (A), i.e., actually measured water quality items. Furthermore, water quality items (B) that are correlated with the actually measured water quality items are selected as non-measured water quality items. Then, the correlations (e.g., calibration curves) between these actually measured water quality items (A) and non-measured water quality items (B) are determined in advance from past measurement data for the water system.

[0019] An example of a suitable measured water quality parameter (A) is electrical conductivity. Examples of non-measured water quality parameters (B) that are correlated with electrical conductivity include chloride ion concentration, calcium hardness, and iron ion concentration.

[0020] The number of measured water quality items (A) may be two or more.

[0021] Suitable examples of actually measured water quality items (A) other than electrical conductivity include a: chloride ions, b: silica, c: iron, etc. Of these, examples of non-measured water quality items (B) that are correlated with a: chloride ions include sodium and sulfate ions, examples of non-measured water quality items (B) that are correlated with b: silica include total hardness and calcium hardness, and examples of non-measured water quality items (B) that are correlated with c: iron include trace aluminum and nitrate ions.

[0022] It is desirable to store the above correlation in the computer's memory and configure the computer so that predicted water quality values ​​are output when actual measured values ​​are input.

[0023] The past data for obtaining the correlation is not limited to data on the water system in question, but may be data on water systems of the same water source, region, industry, etc. Furthermore, analytical data on a wide area within Japan or various regions and industries other than these may also be used.

[0024] In the water quality prediction method of the present invention, the correlation between the values ​​of the measured water quality item (A) and the values ​​of the unmeasured water quality item (B) of a water system is determined in advance. Then, the measured water quality item (A) is measured for the water system to obtain the measured value, and the water quality value of the unmeasured water quality item (B) is predicted based on the measured value and the correlation.

[0025] In the water quality control method for an aqueous system of the present invention, chemical injection control, blow control, RO operation control, blower control, pH control, etc. are performed based on water quality values ​​of multiple water quality items of the water in the aqueous system, which are made up of the actual measured values ​​of these actually measured water quality items (A) and the predicted values ​​of the non-actually measured water quality items (B). [Example]

[0026] [Example 1] In industrial water systems across Japan, where chemical injection is controlled to maintain water quality below the required standards for products manufactured at each factory based on measured values ​​of electrical conductivity, chloride ion concentration, calcium hardness, and Fe ion concentration, the electrical conductivity, chloride ion concentration, calcium hardness, and Fe ion concentration of the water in the systems were measured over a period of 60 months, and the correlations between electrical conductivity and chloride ion concentration, calcium hardness, and Fe ion concentration were determined. The results are shown in Figures 1, 2, and 3.

[0027] As shown in Figures 1 to 3, a strong correlation was observed between electrical conductivity and chloride ion concentration, calcium hardness, and Fe ion concentration. Therefore, we decided to measure only the electrical conductivity of this water system and calculate predicted values ​​for chloride ion concentration, calcium hardness, and Fe ion concentration based on the correlation from the measured electrical conductivity value.

[0028] Chemicals were added to the water system based on these measured and predicted values, and the same results were obtained as before.

Claims

1. A water quality prediction method that determines the correlation between the value of a water quality item (A) and the value of a water quality item (B) in a water system, obtains an actual measured value of the water quality item (A), and obtains a predicted value of the water quality item (B) based on the actual measured value of the water quality item (A) and the correlation.

2. 2. The water quality prediction method according to claim 1, wherein the water quality item (A) is electrical conductivity, and the water quality item (B) is one or more of chloride ion concentration, calcium hardness, and Fe ion concentration.

3. A water quality control method for a water system, which performs chemical injection control, blow control, or RO operation control, blower control, and pH control based on water quality values ​​of multiple water quality items of the water in the water system, which include an actual measurement value of water quality item (A) of the water system and a predicted value of water quality item (B) obtained by the water quality prediction method of claim 1 or 2.

Images