KR20010045035A - Water corrosivity control method to reduce corrosion in water distribution system and the method of the same - Google Patents

Abstract

PURPOSE: A step type system for controlling corrosive water is provided, which semi-automatically infuses calcium hydroxide and carbon dioxide. Also provided are a standard and a method for controlling water, which are flexible and easily operated according to the standard for controlling corrosive water by using the system for controlling corrosive water. CONSTITUTION: The system for controlling corrosive water during purification of water for corrosion reduction of a water supply conduit comprises a calcium hydroxide infusion means (11) infusing calcium hydroxide in the water purification process for reducing corrosion of the water supply conduit; a carbon dioxide infusion means (12) infusing carbon dioxide so that calcium carbonate is produced by reacting carbon dioxide with calcium hydroxide supplied from the calcium hydroxide infusion means; a chemical manufacturing means forming a chemical by dissolving after receiving calcium hydroxide and carbon dioxide from the calcium hydroxide infusion means and the carbon dioxide infusion means respectively; a chemical control means (14) controlling a supply amount of calcium carbonate produced from the chemical manufacturing means depending on the water quality of the water supply raw water; and chemical injection means (17,18) injecting chemicals produced from the chemical manufacturing means as much as the amount by controlled value of the chemical control means into a clean water reservoir (16).

Description

WATER CORROSIVITY CONTROL METHOD TO REDUCE CORROSION IN WATER DISTRIBUTION SYSTEM AND THE METHOD OF THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment technology, and more particularly, to a stepwise corrosive water quality control method and a system for controlling the corrosiveness of tap water during periods of treatment, in particular, due to the water quality characteristics of highly corrosive purified water. It is possible to reduce the phenomena of corrosion and the water quality change of the purified water, and to control the pH and alkalinity at the same time to introduce the purified water with proper corrosion index into the water supply pipe. The present invention relates to a corrosive water quality control system and a method for significantly improving water quality safety by minimizing water quality change.

In general, most of Korea's water supplies are dam water or river water, which has low hardness, so the CCPP (Calcium Carbonate Precipitation Potential), which shows the precipitation ability of calcium carbonate, is less than 0, and the Langellier Index, which is a representative corrosion index, is also less than 0. It shows corrosion resistance and promotes corrosion of pipelines. Corrosion of the pipelines leads to a reduction in the service life of the pipeline and a decrease in water supply capacity, resulting in economic losses by increasing the load of the pump, and also causing consumer complaints and complaints due to deterioration of water quality due to corrosion. to be.

Therefore, there is an urgent need for water quality control during water treatment that can reduce corrosion and deterioration of water quality pipelines.

Corrosion of water supply pipes varies according to the characteristics of hydraulic and water quality factors. The water quality of water is the most basic factor. In particular, pH is the most important factor to determine the solubility of the material in water, and the pH behavior in water is well known, so the pH control method of purified water is the most common and widely used method of corrosion protection of water supply pipe. If sufficient carbonate and calcium are not present in the water, the protective film of calcium carbonate will not be formed. By supplementing this, carbonate ions, alkalinity, carbon dioxide, and ionic strength, which are factors influencing the formation of the protective film together with pH, are considered. As a result, simultaneous control of pH and alkalinity has been reported, and systems for controlling the corrosiveness of purified water have been studied in advanced foreign countries, and some have been put into practical use.

However, despite the flexibility of the water quality control in the operation and maintenance of the corrosive water quality control system, the water quality is basically controlled. Therefore, if the water quality control is not suitable according to the characteristics of the purified water quality, which changes frequently, Accordingly, there is a disadvantage that the corrosion rate may be increased. In addition, various aspects should be considered when applying the site because it depends on the general conditions of the site such as location conditions, water quality conditions, and environmental conditions. In particular, the establishment of water quality control standards for the operation of control systems, the determination of the amount of drug injection, and the establishment of appropriate injection facilities vary from site to site, and these conditions are likely to be the biggest obstacles to practical use. Therefore, there is an urgent need for a method of automating the control system in the most effective way to supplement the conditions of different sites.

Such an automated system can detect quantitative and qualitative change information such as raw water quality, flow rate, chemical injection rate, and water quality status of each process in real time and continuously deliver the information to the manager in real time. Therefore, the automated system will be able to fully complement the conditions of different sites to achieve the efficiency of operation. However, the basic water quality factors such as alkalinity and calcium in operating the corrosive water quality control system have a problem that automatic water quality measurement is impossible.

Accordingly, the present invention has been made to solve the above problems, semi-automatic slaked lime and carbon dioxide injection is possible as part of the safety of the treatment efficiency in the corrosive water quality control system, ease of operation and maintenance and economical water treatment system development Its purpose is to provide a staged corrosive water quality control system.

It is another object of the present invention to provide a water quality control standard and a method which enables flexible and easy operation of corrosive water quality according to a control standard using the above control system.

1 is a schematic process diagram showing an embodiment configuration of a corrosive water quality control system according to the present invention.

Figure 2 is a corrosive water quality control of the present invention and the corrosion reduction of each type of conventional water treatment tap water

(Metal elution) Efficiency comparison chart.

Figure 3 is a comparison of the corrosive index of water control and corrosive water treatment of the present invention.

Figure 4 is a diagram reference diagram for determining the dosage amount of the drug of the present invention.

* Brief description of the main parts of the drawing

11: slaked lime injection device 12: carbon dioxide injection device

13: dissolution tank 14: chemical control panel

15: metering pump 16: purified water

17: front end chemical injection part of water purifier 18: end chemical injection part of water purifier

19: flow meter 20: water meter / alarm

21: screen 22: filter paper

23: pH automatic measuring device

In order to achieve the above object, the present invention, calcined lime injection means for injecting slaked lime in the water treatment process for reducing corrosion of the water supply pipe; Carbon dioxide injecting means for injecting carbon dioxide so as to react with the slaked lime supplied from the slaked lime injecting means to produce a carbonate chemical; Chemical manufacturing means for supplying and dissolving lime and carbon dioxide from the limestone injection means and the carbon dioxide injection means to form a medicine; Chemical control means for controlling the supply amount of carbonic acid ions produced by the chemical manufacturing means according to the water quality of the tap water; And it provides a corrosive water quality control system for water purification treatment for reducing the corrosion of the water supply pipe including a chemical input means for injecting the chemicals produced by the chemical manufacturing means to the purified water by the amount by the control value of the chemical control means.

In addition, the present invention provides a corrosive water quality control method for water purification treatment for reducing corrosion of the water supply pipe, the first step of identifying the water quality characteristics of the source water; A second step of determining a range of water quality standards to control corrosiveness according to water quality characteristics of the constant raw water; A third step of determining the amount of the injected alkali agent and the medicine according to the water quality reference range; And it provides a corrosive water quality control method for water purification treatment to reduce the corrosion of the water supply pipe comprising a fourth step of determining the amount of chemicals based on the amount of the alkali agent and the drug.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Corrosive water quality control system and method for water purification treatment for corrosion reduction of water supply pipe according to the present invention is a stepped corrosive water quality control method and control system using simultaneous control of pH and alkalinity of purified water quality for corrosion reduction of water supply pipe In order to reduce the water quality change and corrosion generated in the water supply pipeline system to prevent aging and deterioration of the pipeline, in the present invention, as shown in FIG. Sintered lime injector 11 for supplying Ca (OH) ₂ ), a carbon dioxide injector 12 for supplying carbon dioxide dissolved and dissolved with the hydrated lime supplied from the calcined lime injector 11, and the calcined lime injector ( And a dissolution tank 13 for dissolving the slaked lime supplied from 11 and carbon dioxide supplied from the carbon dioxide injection device 12 and the dissolution tank 13. In the control panel 14 to determine the injection amount of the drug dissolved in the water quality control criteria, the metering pump 15 for appropriately injecting the drug according to the amount of the drug determined by the control panel 14, and the quantitative A water purifier front end injection unit 17 and a water purifier back end injection unit 18 for injecting a chemical flowing out of the pump 15 into the front and rear pipe passages of the water purification unit 16 are configured.

Here, the slaked lime injector 11 is a slaked lime injector for the present control system, which is composed of a slaked lime storage tank 11a, an infusion amount adjusting tank 11b, and a meter 11c, and the infusion amount adjusting tank 11b. Serves to discharge a certain amount while keeping the residence time of the slaked lime flowing out of the slaked lime storage tank 11a as short as possible. The meter (11c) checks the overall quantitative flow of the slaked lime injection device (11) to check and adjust the remaining amount of slaked lime in the injection amount adjusting tank (11b) and the slaked lime injection amount into the dissolution tank (13).

The carbon dioxide injector 12 is a carbon dioxide injector for the control system, the carbon dioxide storage tank 12a, a control valve 12b for adjusting the injection amount of carbon dioxide stored in the carbon dioxide storage tank 12a, and the The meter 12c which measures the residual amount and injection amount in the carbon dioxide storage tank 12a is provided.

The dissolution tank 13 dissolves the slaked lime and carbon dioxide, and is provided at the rear ends of the respective meters 11c and 12c of the slaked lime injection device 11 and the carbon dioxide injection device 12, and the dissolution tank 13. One side of the water supply pond 23 for storing the water for dissolving the slaked lime and carbon dioxide is provided. In order to keep the level of the dissolution tank 13 constant, a flow meter 19 is provided on the dissolution tank 13 line connected to the water supply pond 23, and in particular, the level of the dissolution tank 13 is varied on the dissolution tank 13 line. In contrast, a water gauge and an alarm 20 are provided, and an outlet to the dissolution tank 13 is provided with a screen 21 for removing foreign matters in preparation for the possibility of leakage of turbidity-induced substances.

The control panel 14 has a water level control criteria (pH, LI) suitable for the water quality characteristics of the constant water source is input to be suitable for the seasonal and monthly water quality characteristics in a step-type type, so that the amount of chemicals is automatically controlled in accordance with the input value normally. do.

The water purification front end chemical injection unit 17 and the water purification end chemical injection unit 18 may be applied to the front end and the rear end of the water purification unit 16 according to the facility characteristics of the water purification plant, and the injection method is injected into the pipeline. This is the inlet method. In addition, at the rear end of the water purification sheet front chemical injection unit 17 and the water purification rear end chemical injection unit 18 is always equipped with a pH automatic measuring device 23 to check the water quality change according to the chemical injection to adjust the amount of chemical injection according to the water quality change do.

When the minimum limit of the pH input to the pH automatic measuring unit 23 as the water quality control criterion is reached, an emergency alarm is triggered, thereby increasing the chemical injection amount in the control panel 14 by one step.

Reference numeral 22 is a filter paper is introduced to the purified water paper 16 after filtering the raw water inflow.

Referring to the working state of the present invention configured as described above are as follows.

First, the slaked lime and carbon dioxide introduced from the slaked lime injector 11 and the carbon dioxide injector 12 flow into the dissolution tank 13 provided at the lower ends of the slaked lime infused device 11 and the carbon dioxide injector 12. do. At this time, the slaked lime and carbon dioxide introduced into the dissolution tank 13 is dissolved in an appropriate concentration in the dissolution tank 13, the chemical dissolved in the appropriate concentration is the water quality control standards (pH) inherent in the control panel 14 , LI) flows into the metering pump 15. The chemicals introduced into the metering pump 15 are introduced into the rear end line of the purified water paper 16 and the raw water from the filter paper 22 to the purified water paper 16 in an inlet manner.

When explaining the effects of the action state of the present invention as described above with reference to the following scheme.

^{_{Ca (OH) 2 ↔ Ca 2+}} + 2OH - ( only the case of injecting slaked lime)

_{Ca (OH) 2 + 2CO 2} ↔ Ca 2+ + 2HCO 3 - ( in consideration of carbon dioxide in water)

In order to control the pH and alkalinity of purified water, a method of injecting CaO and CO ₂ gas together is common. However, when the calcined lime alone is used, the pH is adjusted to compensate for the disadvantage that the pH is increased beyond a desired range. Use this easy carbon dioxide together. Accordingly, pH is easier to control than when calcined alone, and carbon dioxide can be properly generated to form a film on the tube surface. That is, the carbonate produced in the above reaction formula forms an appropriate calcium carbonate film on the surface of the pipeline.

FIG. 2 compares the tap water used in the corrosive water quality control system of the present invention with respect to corrosion reduction (metal dissolution) efficiency according to the type of pipe compared to conventional tap water treatment. Based on the amount eluted from the water, the elution reduction rate of iron (Fe) in the cement mortar ductile cast iron pipe, copper (Cu) in the copper pipe, and zinc (Zn) in the galvanized steel pipe was shown. The pH condition was carried out in three stages to derive the water quality control criteria according to each water quality characteristic. The optimum water quality control criteria for corrosion reduction in this water quality characteristic was pH 7.7 ~ 7.8. At this time, the dissolution rate of each tube was reduced to 71%, 92%, and 48% in iron, copper, and zinc, respectively, compared to the existing purified water. In particular, the corrosive water quality control system of the present invention has a very high corrosion reduction effect of the Doctile cast iron pipe, which is a dominant type among the drain pipes, and thus has a very high practicality and economic efficiency.

3 is a comparison chart of the corrosive water quality control system according to the present invention and the existing corrosive water treatment. The change in the corrosive index LI value derived from the experiment applying the purified water quality of a water purification plant using the Han River water system as a constant source water is shown in FIG. Is a comparison. On the average, the Corrosion Index LI value of the existing water purification was adjusted from -2.4 to -0.5, which is very weak due to water quality control, and the variation according to the water quality is almost disappeared, thereby stabilizing the overall water quality. Therefore, according to the water quality control system of the present invention, other secondary water quality deterioration problems such as disinfection by-products and microbial reproduction in the water supply pipeline can be reduced.

4 is a diagram illustrating a diagram for determining a drug injection amount of the present invention. Referring to FIG. 4, a method of determining an optimal drug dosage amount of the water quality control system of the present invention is as follows.

The first step to determine the optimum chemical dosage is to determine the water quality characteristics of the purified water, if the total alkalinity is 0.5 meq / L, pH is 6.6 and calcium is 5 mg / L, the second step is to determine the range of water quality standards for corrosion control do. The third step shows the water quality of the influent and the treated water in the Deffeyes diagram of FIG. 4 (the influent water quality is A ¹ , and the treated water quality is B ¹ ). In the step of determining, if hydrated lime and carbon dioxide are injected, hydrated lime injection (0.5meq / L × 37mg / meq = 18.5mgCa (OH) ₂ / L) and carbon dioxide injection (0.3mM / L × 44 = 13.2mg CO ₂ / L) is determined, and the calcium in the treated water becomes ((5 + 10) mg / L = 15 mg / L). The last five steps, because in determining a medicine usage, if the amount of water used 100,000m ³ / day if the amount of calcium hydroxide is drug injection amount × Water Usage ^{(18.5g / m 3 × 100,000m 3} / day) 1,850 kgCa (OH) _{It is 2} / day, and the amount of carbon dioxide is 1,320 kgCO ₂ / day since the amount of chemical injection × water use (13.2 g / m ³ × 100,000 m ³ / day).

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention. It will be apparent to those who have knowledge.

As described above, according to the present invention, by controlling the pH and alkalinity at the same time by injecting the alkaline agent and carbon dioxide in the existing water treatment process to reduce the corrosiveness of the water quality to suppress the metal leaching generated in the water supply pipe and at the same time microorganisms due to stable water quality By suppressing the regrowth and disinfection by-products, supplying safe water and reducing the deterioration of the water pipe due to corrosion, it has the advantages of reducing the leakage and extending the life of the pipe, thereby maintaining an economic and stable water pipe system. .

Claims (11)

Slaked lime injection means for injecting slaked lime in a water treatment process for reducing corrosion of a water supply pipe; Carbon dioxide injecting means for injecting carbon dioxide to react with the slaked lime supplied from the calcined lime injecting means to produce carbonic acid ions; Chemical manufacturing means for supplying and dissolving lime and carbon dioxide from the limestone injection means and the carbon dioxide injection means to form a medicine; Chemical control means for controlling the supply amount of carbonic acid ions produced by the chemical manufacturing means according to the water quality of the tap water; And Chemical input means for injecting the chemical produced by the chemical manufacturing means into the purified water by the amount by the control value of the chemical control means Corrosion water quality control system for water treatment to reduce corrosion of water pipes, including. The method of claim 1, The slaked lime injection means is a storage tank for storing the slaked lime therein; An injection amount adjusting tank for discharging a predetermined amount while maintaining the residence time of the slaked lime flowing out of the storage tank by a predetermined time; Corrosion water quality control system for water treatment to reduce the corrosion of the water supply pipe including a meter for checking the quantitative flow of slaked lime discharged from the injection amount control tank. The method of claim 1, The carbon dioxide injection means and the carbon dioxide storage tank for storing carbon dioxide therein; Corrosion water quality control system during water treatment to reduce the corrosion of the water supply pipe including a control valve for opening and closing to discharge a certain amount of carbon dioxide flowing out of the carbon dioxide storage tank and a meter for checking the amount of carbon dioxide discharged through the control valve . The method according to any one of claims 1 to 3, The drug manufacturing means, A dissolution tank for receiving carbon dioxide from the slaked lime and carbon dioxide injection means of the slaked lime injection means, Corrosion water quality control system for water treatment for reducing corrosion of water supply pipe including means for supplying water to react the slaked lime and carbon dioxide introduced into the dissolution tank. The method of claim 4, wherein A flow meter which is mounted at a predetermined position on a line connecting the dissolution tank and the water supply means to maintain the level of the dissolution tank; An alarm means located at one side of the flow meter to notify the outside of the water level change; Corrosion water quality control system for water purification treatment to reduce the corrosion of the water supply pipe including a screen for removing the turbidity-induced material is provided at the water inlet of the dissolution tank. The method of claim 1, The chemical control means is a water quality control criteria (pH, LI) suitable for the water quality characteristics of running water is set at seasonal and monthly stages, so that the constant for reducing corrosion of the water supply pipe that automatically controls the chemical input amount according to the water quality characteristics of the raw water. Corrosive water quality control system. The method of claim 1, The chemical injection means is installed at the front and rear ends of the purified water, respectively, the corrosive water quality control system during water treatment to reduce the corrosion of the water supply pipe that is introduced in the inlet (inlet) method. The method according to claim 1 or 7, Corrosion water quality control system for water purification treatment to reduce the corrosion of the water supply pipe further comprises a pH measuring instrument which is installed at the rear end of the input unit of the chemical input means for measuring the water quality change according to the chemical injection. In the corrosive water quality control method for water purification treatment to reduce corrosion of water supply pipe, A first step of grasping the water quality characteristics of the source water; A second step of determining a range of water quality standards to control corrosiveness according to water quality characteristics of the constant raw water; A third step of determining the amount of the injected alkali agent and the medicine according to the water quality reference range; And A fourth step of determining a drug usage amount based on the alkali agent and the drug amount; Corrosion water quality control method for water treatment to reduce corrosion of water supply pipe including. The method of claim 9, The first step, A method for controlling corrosive water quality during water treatment to reduce corrosion of water supply pipes by measuring total alkalinity, pH and calcium concentration. The range of the water quality standard of the second stage, Corrosion water quality control method for water purification treatment to reduce corrosion of water supply pipe that sets pH considering alkalinity, pH, hardness and corrosion index.