KR20020002341A - method of cohesion reagent for water treatment - Google Patents

Abstract

PURPOSE: Provided is a method for injecting coagulant for wastewater treatment. According to the method, coagulants are injected with consideration of pH, alkalinity, and concentration of organics. Alkalinity, pH, and concentration of organics wastewater are analyzed automatically in real time for determining quantity of coagulants. CONSTITUTION: Quantity of coagulants is decided with consideration of relationship of pH and alkalinity. Continuously quantity of coagulants is decided with consideration of concentration of organics. And total quantity of coagulants is decided by summing of quantity of coagulants decided by consideration of relationship of pH and alkalinity and quantity of coagulants decided by consideration of concentration of organics. Coagulants used in the method are alum, PAC, PSOM, PASS, and PACS.

Description

Method of adding coagulant for water treatment

The present invention relates to a method of injecting a flocculant for water treatment, and more specifically, to a qualitative relationship between the various coagulation factors and the flocculant present in each water quality to enable proper aggregation of each water quality within a short time. It relates to a flocculant input method.

In general, tap water used in homes is purified and supplied to various households by various treatments. This water treatment process is carried out step by step, such as mixing, flocculation, precipitation, filtration. The coagulation step of the purified water treatment process is the most important process for determining the quality of the purified water. Only when the appropriate amount of flocculant is injected, it is possible to exert sufficient particulate pollutant removal effect in the continuous process of sedimentation and filter paper, and satisfactory water quality can be expected.

In this flocculation process, various kinds of flocculants are used, and the use of a suitable flocculant is essential. In other words, the use of less coagulant than the required amount of coagulant is not sufficient to cause the deterioration of the water quality, and when using a large amount of coagulant, even if coagulation is made, the remaining unreacted coagulant itself will be present as a new pollutant. In addition, excessive costs are incurred. Therefore, the use of the appropriate flocculant for each water quality is the most important factor.

In order to effectively inject coagulant in the water treatment process, it is important to calculate an appropriate coagulant injection rate according to various water qualities, and to accurately inject coagulant amount according to these coagulant injection rates. In general, the quality of the raw water flowing into the water purification plant is determined by the quality of the river, etc., which is the source of inflow, and varies depending on the season. Accurate water quality measurement and flocculant injection volume control are required to select and control the appropriate coagulant injection rate according to the change of raw water quality, which is greatly influenced by various factors that change depending on the season and the type of pollutant.

In the flocculation process, the flocculant injected according to the quality of raw water depends on various complex factors such as turbidity, pH, alkalinity, and COD of the raw water. Jar-tests have generally been widely used in order to determine the input rate of the flocculant, which is varied by such complex factors.

Jatest tests the raw water flowing into the water treatment plant by hand and tests it until the proper injection rate of coagulant is determined for each raw water. Such jatest has a disadvantage that the time required for selecting the flocculant injection rate is usually about 1-2 hours. In addition, the jatest has a problem in that it cannot be actively replaced according to the sensitively changing water quality because the experiment must be repeated every time according to the water quality of the raw water that changes every moment.

In order to solve this problem, many studies have been conducted to automatically determine the appropriate coagulant input rate according to each water quality by analyzing the water quality automatically, and this automatic coagulant input system has been previously filed by the Korea Water Resources Corporation. According to the Korean patent (Publication No. 97-26935), the water quality is automatically analyzed and the coagulant is added accordingly, so that the appropriate coagulant is added in a shorter time than could be realized in the jatest.

However, such a flocculant input system has the following problems.

Various data of the water quality are measured, and the result of the measurement is used to find the existing data stored in the DB so that the input rate of the flocculant used at that time is determined. Of course, various factors such as temperature, pH, alkalinity, etc. of the water quality can be automatically measured, and the resultant results can be determined in a shorter time than the J-test by using the same year (5 year data) data. However, there is a problem in that the flocculant input rate cannot be determined when the result of the measurement is not in the previous year's data. In other words, the number of factors represented by water quality is changing every year due to various factors. Therefore, there is a fatal problem that can not determine the flocculant input rate when a new measurement appears.

In addition, most of the year data stored in DB do not consider all factors of each water quality, but are mostly determined by jatest. Jatest can't represent accurate coagulant input rate simply by considering two variables, pH and turbidity, to determine coagulant input rate. Above all, this test depends on the five senses of humans, so even if the same water quality has different results depending on the measurer It is not accurate with me.

In addition, the coagulant input rate should be considered by various complex factors, but the existing methods measure various factors of the water quality itself, but do not consider the effect of these factors on the flocculation, but simply refer to the previous year data. There is a problem that the coagulant input rate cannot be determined. In other words, although various organic materials exist in the water quality recently, it is known that these organic materials have a great influence on the consumption of the flocculant, but in reality, the flocculant injection is not accurate because the organic matters are not considered at all. There is this.

Recently, various new flocculants have been developed. These coagulants are made to show higher efficiency in a smaller amount, and the coagulant is newly changed by being made harmless to the human body. However, since there is no input rate data for these new coagulants, the conventional coagulant dosing system is not applied at all. There is a problem that cannot be done.

Accordingly, an object of the present invention is to provide a coagulant injecting method in which an optimal coagulant is added regardless of the water quality in consideration of various factors represented by each water quality.

Another object is to provide a flocculant dosing method in which all kinds of water quality are analyzed in real time and an appropriate flocculant dosage rate can be determined regardless of the kind of flocculant.

1-Schematic diagram of a flocculant dosing method according to the present invention.

According to a first aspect of the present invention for achieving the above object, the amount of flocculant consumption according to the measured value of each water quality factor that consumes the flocculant is determined in advance to analyze the measured value related to the quality of the raw water, In the coagulation method of water treatment using the coagulant automatic injector which automatically adds the coagulant required to the original water, the coagulant consumption amount for each individual water quality factor is analyzed according to the amount of each water quality factor that consumes the coagulant. And measure the present value of each individual water quality factor of raw water, extract the coagulant consumption amount corresponding to each individual water quality factor measurement value from the built-in program, and determine the amount of coagulant consumption for each individual water quality factor. Aggregation for water treatment to add the coagulant automatically by adding up to determine the total coagulant input ratio There is the technological base to provide automatic input method.

And, preferably, the water quality factor is a pH-alkalinity correlation, the amount of organic matter, and the flocculant is liquid (ALUM), poly aluminum chloride (PAC), poly sulfate organic magnesium (PSOM), poly aluminum sulfate silicate (PASS) And polyaluminum chloride (PACS). Therefore, regardless of the type of flocculant, there is an advantage that the flocculant corresponding to the water quality factor that changes from time to time in real time can be added immediately.

Hereinafter, with reference to the drawings showing the present invention having the features as described above will be described in more detail. 1 is a view showing a flocculant input method according to the present invention. As shown, it is characterized in that the coagulant input ratio required by each factor in consideration of a variety of factors, and finally added to determine the coagulant input rate.

First, the factors to be considered for the addition of flocculant will be described. In the description of the present invention, the factors to be considered for the input of the flocculant are classified into three types: pH, alkalinity, and organic matter concentration. However, of course, other factors can be considered. The key point of the present invention is to determine the flocculant input rate by considering each of these factors individually. Conventionally, although several factors are simply measured, no qualitative analysis has been made on how these individual factors affect coagulant input, but the present invention considers these factors.

That is, as shown in FIG. 1, the coagulant input amount is determined according to the correlation between pH and alkalinity rather than simply distinguishing pH and alkalinity, and after that, the coagulant input amount is determined according to the amount of organic matter. The final coagulant dose is determined by summing up the coagulant dose. By considering each of the factors in the water quality as described above, it is possible to determine a more accurate amount of flocculant input, the value of each of these factors can be made in real time, so that the appropriate flocculant input of the water quality changes every time. In order to determine the amount of flocculant input according to the real-time measurement of each factor as described above, an accurate analysis of the amount of flocculant input consumed by each factor should be made. Hereinafter, a method for determining the amount of flocculant input of each factor will be described.

Determination of flocculant input amount by correlation between pH and alkalinity

First, the determination of coagulant dosage by the pH and alkalinity of water quality will be described as measurement factors. These are already widely known factors that should be considered first when adding flocculants. In the related art, the alkalinity and pH were simply measured separately, and each of them was added. However, in the present invention, the addition rate of the flocculant is determined according to the correlation between the alkalinity and the pH. That is, even if each individual pH of the measured water quality is the same, the input amount of the flocculant varies according to the difference in alkalinity. Therefore, it is adjusted to have several different alkalinity under each individual pH, and accordingly, a coagulant is added to determine the input amount of the coagulant according to the change in residual turbidity. Such flocculant dose is determined by field experiments.

Hereinafter, this experimental process will be described. In order to determine the coagulant consumption rate by pH and alkalinity, pH was 7.0, 8.0, 9.0, 10.0 using sodium bicarbonate (NaHCO3) and sodium carbonate (NaCO3) to prepare a sample water having any alkalinity according to each pH. Phosphorus alkalinity 8000 to 20000 mg / l stock solution was prepared. The pH of raw water was adjusted to 7.0, 8.0, 9.0 and 10.0 using sulfuric acid or caustic soda, and the alkalinity required for the experiment was prepared at the required concentration using alkaline stock solution.

When the jatest is performed while changing the alkalinity of sample water at each pH using five kinds of flocculants, the appropriate flocculant injection ratio can be determined according to pH and alkalinity. The appropriate flocculant injection ratio at and alkalinity can be determined.

Example 1

When using ALUM as a flocculant, the appropriate flocculant injection ratio is shown in Table 1 under different alkalinity according to each pH.

Table 1

By using the table to show the appropriate flocculant injection ratio according to each pH and alkalinity, and regression analysis, a graph as shown in Figure 1 is formed.

Figure 1

That is, at pH 7.0, the appropriate coagulant injection ratio according to alkalinity is 4.4693 × (alkali) ^0.4234 , 3.4875 × (alkali) ^0.5287 at pH 8.0, 2.369 × (alkali) ^{0.6776 at pH9.0} and ^pH10.0 4.9969x (alkali) ^0.6074 . In fact, their correlation coefficient is more than 0.96, indicating that the reliability is high. In the same manner as described above, the injection ratio of the coagulant according to the correlation between pH and alkalinity can be determined by experiments and regression analysis according to different alkalinities at each pH.

By processing the values and graphs by the regression analysis and programming them on a computer, it is possible to simply determine the coagulant injection ratio according to pH and alkalinity. This is to determine the coagulant injection ratio of the actual water simply by measuring the pH and alkalinity of the water quality is automatically determined according to the injection ratio of the coagulant. Therefore, simply measuring the pH and alkalinity of the water quality determines the coagulant injection ratio, so that it can be immediately applied to the water quality changes every moment.

Example 2

PAC was used as the flocculant, and the correlation between pH and alkalinity was shown in Table 2 and Figure 2) in the same manner as in Example 1.

Table 2

Figure 2)

Example 3

PACS was used as a flocculant, and the correlation between pH and alkalinity was shown in Table 3 and Figure 3) in the same manner as in Example 1.

Table 3

Figure 3)

Example 4

PASS was used as the flocculant, and the correlation between pH and alkalinity was shown in Table 4 and Figure 4 in the same manner as in Example 1.

Table 4

Figure 4

Example 5

PSOM was used as the flocculant, and the correlation between pH and alkalinity was shown in Table 5 and Figure 5 in the same manner as in Example 1.

Table 5

Figure 5

As shown in each of the above examples, although the amount of flocculant consumed according to the correlation between each flocculant and pH and alkalinity is different, it can be seen that the amount of flocculent consumption changes with a certain regularity as a whole. Therefore, by programming and embedding data on the amount of flocculant consumption, it is possible to easily and accurately determine the amount of flocculant consumption by simply measuring the pH and alkalinity of each raw water.

Determination method of flocculant input amount according to the amount of organic matter

Actually, the organic matter in the water has a very small particle size and a small amount in total, but the surface area of the organic particles is large, which increases the amount of flocculant required. Previously, the total organic compound (TOC) was not considered, but the present invention determines the amount of flocculant added according to the amount of the organic material. The organic material was used as humic acid, and the concentration of humic acid was prepared at 1200 mg / l, and then diluted in raw water as needed to obtain the required TOC concentration.

After injecting 3 mg / l of humic acid into the sample water, check the appropriate amount of flocculant according to pH and alkalinity. In this case, comparing the amount of coagulant input according to pH and alkalinity and the case of injecting humic acid, it can be seen that the amount of coagulant consumption consumed by the humic acid by the difference.

Example 6

Table 6 shows the results of investigating the total coagulant dosage according to the pH and alkalinity of the sample water containing 3 mg / l of humic acid using ALUM as the coagulant.

Table 6)

Table 6 shows the sum of the amount of flocculant consumed by pure pH and alkalinity and the amount of flocculant consumed by organic matter. Subtracting the value derived from Table 1 and Figure 1) from the value of Table 6 yields 3 mg / l of pure organic matter. The amount of flocculant consumed is determined by this. This is shown as the amount of flocculant consumed per 1mg / l of organic matter, as shown in Table 6-1.

Table 6-1

Figure 6)

Therefore, when the graph is regressed, the equation shown in Fig. 6 is established, and the amount of flocculant injection according to pH and alkalinity can be determined to remove organic matter.

Example 7

By using PAC as the flocculant, the correlation by the flocculant input amount by the amount of organic matter according to pH and alkalinity is shown in the same manner as in Example 6.

Figure 7

Example 8

By using PACs as the flocculant, the correlation by the flocculant input amount by the amount of organic matter according to pH and alkalinity is shown in the same manner as in Example 6.

Figure 8

Example 9

By using PAss as the flocculant, the correlation between the flocculant input amount and the amount of organic matter according to pH and alkalinity is shown in the same manner as in Example 6.

Figure 9

Example 10

By using Psom as the flocculant, the correlation by the flocculant input amount by the amount of organic matter according to pH and alkalinity is shown in the same manner as in Example 6.

Figure 10

As shown in Examples 6 to 10, the appropriate amount of coagulant input consumed to remove the same organic material is consumed as the pH and alkalinity increases, and thus it is useful because it has a certain regularity. have. Therefore, the amount of flocculant consumed according to the amount of these organics is also programmed to determine the amount of flocculant consumption by measuring the amount of organic matter in each raw water.

As described above, by substituting the above values by simply measuring the pH, alkalinity and the amount of organic matter in the raw water, the coagulant consumption according to the correlation of pH-alkalinity appears in the analyzed graph, and the organic matter at that time Since the amount of flocculant consumed is calculated according to the amount, simply add the two amounts and add it to the raw water. Therefore, the graph of the coagulant consumption amount and the formula according to each pH-alkaline and the graph of the coagulant consumption amount according to the amount of organic matter at that time can be programmed in advance by the formula can be easily adapted to the ever-changing water quality.

Next, the results of the comparative test to see if the amount of flocculant input of each factor obtained by the above method is practically appropriate.

First, in order to find out whether the amount of flocculant input according to the present invention is appropriate, samples were prepared under the same conditions based on data previously observed in water purification plants, and the results were compared as shown in the following table.

Table a)

B)

As shown in the table, Table a) is the actual data of the past year, Table b) shows the pH-alkaline degree correlation and the amount of flocculant input according to the measurement of organic matter concentration (TOC) according to the present year data. Filtrate is usually measured on the basis of turbidity, and if the turbidity is 0.5NTU or less, it is judged that it is sufficiently filtered.

As shown in the table, it can be seen that the amount of flocculant added according to the present invention is less than the amount introduced in the field. And it can be seen that filtration is sufficiently performed despite the addition of a small amount of flocculant. That is, the amount of coagulant added, which is, in other words, it was found that more than necessary coagulant was introduced and wasted in the field. According to the present invention, an appropriate coagulant can be added, so that not only the coagulant is reduced, but also the appropriate response and the manpower reduction of the water quality are constantly changed. It can be done.

As described above, according to the present invention, the addition of a coagulant suitable for the state of the water changes every time, as well as the effect of reducing the time and manpower due to the addition of the coagulant.

In addition, according to the present invention, there is another effect that it is possible to add a coagulant suitable for each water quality regardless of the type of coagulant.

Claims (3)

The amount of flocculant consumed according to the measured value of each water quality factor that consumes the flocculant is determined and analyzed the measurement value related to the quality of the raw water, and the coagulant automatic injector which automatically puts the required flocculant into the raw water according to the analyzed value. In the flocculating agent input method for water treatment, The amount of coagulant consumption for each individual water quality factor according to the quantity of each water quality factor that consumes the coagulant is pre-analyzed and built into the program to measure the current value of each individual water quality factor of the raw water, The amount of flocculant consumption is determined by extracting from a built-in program, and the amount of flocculant consumption is added to each individual water quality factor to determine the total flocculant input ratio, so that the flocculant is automatically added. The method of claim 1, wherein the water quality factor is pH-alkaliness correlation, and the amount of organic matter. 3. The coagulant according to claim 1 or 2, wherein the flocculant is any one of ALUM, polyaluminum chloride (PAC), polysulfate organic magnesium (PSOM), polyaluminum sulfate silicate (PASS) and polyaluminum chloride silicate (PACS). Automatic injection method of flocculant for water treatment, characterized in that one.