KR100736513B1 - A suction pressure/time detector by batch type for water supply and a treating method of water using the same - Google Patents

Abstract

A water purification method of calculating an optimum coagulant injection quantity using a suction pressure and a suction time indexed by measuring suction pressure, filtering time and temperature in a membrane filtration process, a batch type suction pressure/time measuring system used in the water purification method, and a water purification apparatus comprising the batch type suction pressure/time measuring system are provided. A batch type suction pressure measuring system for an apparatus of purifying raw water by membrane filtration comprises: a sample injection part into which the coagulated sample is injected after extracting a predetermined amount of coagulated sample; a suction pump for applying a suction pressure to the sample; a filtering part for filtering the sample through a membrane filter in a state that the suction pressure is applied to the sample by the suction pump; a filtrate storage part for storing a filtrate of the sample passing through the membrane filter; and a pressure/time measuring part for measuring a suction pressure generated when the sample is sucked, and a time that is taken until filtration of the sample is finished. An apparatus of purifying raw water by membrane filtration comprises: a mixer for forming floc by injecting a coagulant into raw water flown in; and a coagulant injection control device for controlling an injection quantity of the coagulant, and the batch type suction pressure measuring system installed between the mixer and a membrane filtering unit to measure suction pressure/time by extracting a portion of mixed water in which floc is formed by the mixer.

Description

A Suction Pressure / Time Detector by batch type for water supply and a treating method of water using the same}

1 is a unit process diagram showing a general water treatment process,

2 is a unit process of the water treatment process using membrane filtration,

Figure 3 is a batch suction pressure / time measuring device (STD, Suction Pressure / Time Detector) according to the present invention,

Figure 4 is a schematic diagram showing a coagulant input amount control method using a batch suction pressure / time measuring device (STD, Suction Pressure / Time Detector) according to the present invention,

5 is a graph showing a change in the difference between the final pressure and the initial pressure (ΔP) after filtration according to the flocculant concentration,

Figure 6 is a graph showing the concentration change of the indexed temperature (TI) and UV254 value according to the flocculant concentration.

Description of the main parts of the drawings

1 Sample input part 2 Filtration part 3 Filtrate storage part

4 pressure / time measuring unit 5 suction pump

The present invention relates to a batch suction pressure / time detector (STD, Suction Pressure / Time Detector) for the purification of raw water and a water treatment method using the same, more specifically, the suction pressure, filtration time and temperature in the membrane filtration process The present invention relates to a purified water treatment method and a purified water treatment device for calculating an optimal amount of flocculant input using a suction pressure and a suction time (Suction Time / Pressure) measured by indexing.

In parallel with the increase in population, industrialization, and urbanization, water supplies are becoming increasingly polluted. On the other hand, consumer demand for water is increasing due to the improvement of living standards. Therefore, in order to supply raw water to consumers and use it as drinking water, a process for purifying raw water must be accompanied, and water purification technology is also being developed according to increasing demands. In general, the water treatment process generally goes through a process as shown in FIG. 1. In general, the water purification process passes raw water, passes through a screen for removing suspended solids, and then passes through a settling basin where the sand is submerged. Raw water, which has been screened and settled, is collected in the pit and then moved to the mixing tank, where coagulant is introduced to agglomerate the raw water. The raw water mixed with the flocculant reacts with the flocculant in the mixing tank and is then transferred to the floc forming tank. In floc forming tanks, flocculant and raw water reacted with each other form a floc of a suitable size so that precipitation is easy, and the floc formed raw water is precipitated in a sedimentation tank, which is the next step. After precipitation, the supernatant is passed through rapid filter paper to remove residual suspended solids, color, and turbidity, and is then transferred to purified water after injecting chlorine for disinfection. And it goes through the process from the water purification basin to supply to the general household. In this series of water purification processes, the process from injecting flocculant to precipitation greatly improves turbidity by precipitating fine particles, and is a particularly important process for stable treatment in various subsequent processes. Various kinds of flocculants are used to precipitate the fine particles in the flocculation and precipitation process, and the injection amount of the flocculants has been generally evaluated by Jar-test.

Jar-test is a method of adding flocculant to a certain concentration to form floc, and then depositing the floc, and then analyzing the water quality of the supernatant to determine the optimum amount of flocculant. Analyze TOC, UV254, etc., and calculate the initial flocculant dose.

However, the Jar-test has a problem in that it is difficult to cope quickly when the water quality of the influent changes rapidly due to a long analysis time, and a coagulant injection by experience is performed. In particular, in the water treatment process using membrane filtration as shown in Figure 2, since the amount of flocculant to minimize the fouling phenomenon of the membrane cannot be determined, the Jar-test result is not reliable.

In order to overcome the Jar-test, which has such drawbacks, methods for estimating flocculant input by measuring the streaming potential or particle size have been developed. Streaming Potential Detector (SPD) is a method based on the theoretical approach to the phenomenon of flocculation and the nature of the charged interface. It is a device that measures the flow potential that occurs when a fluid flows. The closer the streaming potential (SP) to zero is, the lower the filtration resistance ratio of the membrane is. The closer the SP (Streaming Potential) is to 0, the closer the electrical charge of the floc made of flocculant and organic matter in the raw water is to 0, and the stability is unstable, making it easy to cause entanglement. The fouling of the membrane can be minimized because more smaller colloidal components can be aggregated.

However, in the case of the Streaming Potential Detector (SPD), the point of time when the flow potential (SP, Streaming Potential) becomes zero can be determined by comparing with the Zeta Potential, so if the inflow water quality changes significantly, a reliable result is obtained. In order to do this, periodic corrections are necessary. In addition, the membrane filtration process in which the differential pressure and filtration time of the membrane acts as the biggest variables because the flow potential (SP, Streaming Potential) and the fouling of the membrane are not identified in the membrane filtration water purification process. Is somewhat unsuitable. In addition, in the case of particle size measurement method, it is difficult to select an accurate flocculant input amount only by particle analysis, and thus, it is necessary to determine the particle size in connection with other items such as turbidity. In addition, since these methods analyze the properties of the mixed solution after aggregation, it is difficult to determine the influence of pressure and filtration time applied directly to the membrane when the mixed solution is filtered.

The present invention is to overcome the problems of the prior art described above, one object of the present invention is to optimize the flocculant using the suction pressure and the suction time indexed by measuring the suction pressure, filtration time and temperature in the membrane filtration process It is to provide a water treatment method for calculating the input amount.

Another object of the present invention relates to a water treatment apparatus including the batch suction pressure / time measuring apparatus.

One aspect of the present invention for achieving the above object is

A mixing step (a) of adding flocculant to the introduced raw water to form a floc; And a membrane filtration step (b) for filtering the mixed water passed through the mixing step (a), wherein the mixing step (a) is performed between the mixing step (a) and the membrane filtration step (b). Membrane filtration of raw water, comprising the step (c) of measuring a suction pressure / time (STP) by extracting a portion of the mixed water having a floc formed thereon and adjusting the amount of the flocculant input (d) It is about how.

Another aspect of the invention

Sample input unit for storing and injecting a certain amount of aggregated sample before filtering;

A filtration section configured to support a membrane filter and a support for filtering the sample subjected to a suction pressure through the membrane filter;

A filtrate storage unit for storing a filtrate of a sample having passed through the membrane filter;

A pressure / time measuring unit for measuring the suction pressure generated when the sample is sucked and the time taken until the filtration of the sample is finished; And

A batch suction pressure measuring device including a suction pump for supplying suction pressure to a sample.

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

Figure 3 is a schematic diagram showing a coagulant input amount adjusting step using a batch suction pressure / time detector (STD, Suction Pressure / Time Detector) according to the present invention, Figure 4 is the difference between the final pressure and the initial pressure after filtration according to the flocculant concentration (ΔP) is a graph showing the change, Figure 5 is a graph showing the concentration change of the TI and UV254 value according to the flocculant concentration, Figure 6 is a batch suction pressure / time measuring device (STD, Suction Pressure / Time Detector).

3 shows a step (b) of measuring a suction pressure / time (STP) by extracting a portion of the mixed water in which a floc is formed through a mixing step between the mixing step (a) and the membrane filtration step (b) and a flocculant The overall process of the purified water treatment method using the membrane filtration including the step (c) of adjusting the dosage of the is shown.

Table 1 shows the names and functions of each unit process (part) of the overall process.

In the case of water treatment using a general membrane filtration process as shown in Table 1, since the solid-liquid separation is performed using a membrane immediately after aggregation and blending, a sedimentation tank is not required as compared to the existing water treatment process, and the processing efficiency is a stable process. However, due to the characteristics of the membrane, as the time passes, the membrane's fouling phenomenon occurs such that the differential pressure of the membrane increases and the flux decreases, thereby decreasing efficiency. In particular, no direct evaluation of the effect of flocculant amount on the membrane filtration process has been made. Therefore, in the present invention, the pressure and filtration time applied to the membrane, which is one of the most influential factors in the membrane filtration process, are measured, and the difference between the final pressure and the initial pressure (ΔP) or the indexed suction time (TI) (Time Index) ) Provides a method for estimating the optimal flocculant dosage. The method according to the present invention measures suction pressure by measuring the pressure applied to the membrane and the time the sample is filtered by filtering a predetermined amount of agglomerated samples using a membrane filter under conditions similar to the membrane filtration process. And minimizing fouling of the membrane by adjusting the flocculant input amount by calculating the suction time and pressure, and determining the adequacy of the flocculant input amount using the measured suction pressure and suction time / pressure value. Optimum coagulation efficiency can be expected.

The membrane used in the membrane filtration process in the present invention can be variously applied depending on the pore size of the membrane, such as ultrafiltration or microfiltration, or the form of the membrane such as hollow fiber, flat plate, monolithic.

As the flocculant used in the present invention, all kinds of flocculants such as poly aluminum chloride (PAC), aluminum sulfate (Alum), lime (Lime) or ferric chloride (Ferric Chloride) can be used.

Since the mixing step and the membrane filtration step in the process of the present invention may use a known method, the following steps (c) and the flocculant are measured for the suction pressure / time (STP) added between the mixing step and the membrane filtration step. Only the step (d) of adjusting the dosage of the will be described in detail.

Suction pressure / hour ( STP Measuring (c)

First, when raw water flows in, a certain amount of flocculant (the amount of flocculant set to the initial value) and the raw water are mixed in the flocculation / mixing tank. Then, the mixed raw water is moved to membrane filtration. In this process, a part of the mixed liquid is taken and the suction pressure and time are measured by the suction pressure measuring device (STD).

The suction time and pressure (STP) is influenced by pressure and temperature by measuring the time taken for a certain amount of sample to filter the membrane filter.

The method of measuring the suction pressure / time (STP) may be a batch (batch) or continuous (continuous). Batch type is a method of measuring the suction pressure / time (STP) by taking a certain amount of raw water aggregated through the flocculation mixing tank and measuring the suction pressure / time (STP) once. In the continuous type membrane filtration water treatment process, the flocculated raw water is continuously supplied to the continuous suction pressure measuring device to calculate a change in the filtration pressure / time according to the characteristics of the raw water and the degree of flocculation of the mixed water to determine the appropriate amount of flocculant. If the change of raw water occurs frequently by crystallization and injection method, it is necessary to control the flocculant injection amount by including it in the water treatment device.

Step (c) of measuring the suction pressure / time (STP) is a sample input step of storing a predetermined amount of aggregated sample before filtering; Filtering a sample subjected to suction pressure through a membrane filter and a support supporting the membrane filter; Storing the filtrate of the sample passing through the membrane filter; And a pressure / time measurement step of measuring a suction pressure generated when the sample is sucked and a time taken until the filtration of the sample is finished.

The sample input step is a step of introducing a predetermined amount of raw water into the sample injection unit to measure the suction pressure / time (STP) of the flocculated / mixed raw water. When raw water is introduced into the sample injection section, foreign substances such as sand should not be introduced. The level control step is a step of automatically controlling the start of the sample feed pump so that a constant amount of raw water can be stored at all times so that the aggregated / mixed raw water stored in the sample injection unit does not overflow or run short. The filtration step is a step of filtering the sample by applying a suction pressure to the membrane filter at room temperature using a suction pump. Storing the filtrate of the sample is storing the sample filtered through the membrane filter. The pressure / time measurement step is a step of measuring the pressure while the sample is filtered using a digital manometer at a predetermined time unit, storing this value as data, and measuring the time when all of a certain amount of the sample is filtered.

Adjusting the coagulant input amount (d)

In step (d) of adjusting the coagulant input amount, the coagulant input amount may be calculated so that the slope of the graph showing the suction index (TI) value indexed with respect to the coagulant input amount becomes zero.

TI may be calculated using the following equations 1 and 2 for the suction pressure and time measured by the suction pressure measuring device STD. Equation 1 is a formula for obtaining the temperature correction of the filtration time.

   -T: Water temperature (℃), t: Filtration time before temperature compensation (sec)

   a: -1.64779

   -b: 262.37

   c: 273.15

   -d: -133.98

Equation 2 is a value obtained by dividing the filtration time (sec) of the sample after temperature correction (20 ° C.) by the filtration time (sec) × 5 of ultrapure water after temperature correction (20 ° C.). Value. The smaller the value is, the shorter the filtration time is, which is very useful because the value can be compared even if the temperature is different by TI.

-t _s : Filtration time (sec) of sample after temperature correction (20 ℃)

-t ₀ : Filtration time of ultrapure water after temperature correction (20 ℃) (sec)

In the present invention, the amount of flocculant added may be calculated so that the difference between the final pressure and the initial pressure (ΔP) applied to the membrane filter with respect to the flocculant injection concentration is minimized.

Based on the calculated amount, it is determined whether the amount of flocculant added is appropriate. If the amount of flocculant is appropriate, the water purification process is performed without any action. However, if the coagulant dose is not adequate (the amount of coagulant injected exceeds or falls short of the appropriate coagulant amount), the coagulant injection control unit calculates the appropriate coagulant amount and sends the result to the coagulant reservoir. In the coagulant storage tank, the appropriate coagulant input amount determined by the coagulant injection control device is injected again into the coagulant mixing tank so that coagulation proceeds.

The present invention includes a batch suction pressure / time measuring device (STD, Suction Time / Pressure Detector). The measuring device is shown in FIG. 6. The measuring device includes a sample input unit for storing and inputting a predetermined amount of aggregated sample before being filtered; A filtration section configured to support a membrane filter and a support for filtering the sample subjected to a suction pressure through the membrane filter; A filtrate storage unit for storing a filtrate of a sample having passed through the membrane filter; A pressure / time measuring unit for measuring the suction pressure generated when the sample is sucked and the time taken until the filtration of the sample is finished; And a suction pump for supplying suction pressure to the sample. Table 2 shows the components and functions of the measuring device.

The present invention is mixed with the flocculant to the introduced raw water to form a floc (floc); And a membrane filtration device for filtering the mixed water having passed through the admixture, wherein the portion of the mixed water in which a floc is formed is passed between the admixture device and the membrane filtration device through the admixture. Batch suction pressure measuring device for measuring the suction pressure / time (STP) and flocculant injection control device for adjusting the input amount of the flocculant.

The coagulant injection control device calculates the coagulant input amount so that the slope of the graph showing the TI value indexed with respect to the coagulant input amount becomes zero.

In the coagulant input amount control device, the suction pressure and the time (Suction Time / Pressure) are calculated based on the measured pressure and time, and at this time, the coagulant input amount is adjusted by determining whether the amount of the injected coagulant is appropriate. For example, when the difference between the final pressure and the initial pressure (ΔP) or time is exponentially high, an additional amount of flocculant may be added when additional flocculant is required.

The coagulant is actually added in the coagulant reservoir in which excess coagulant is always stored in response to the signal of the coagulant input amount adjusting device.

4 and 5 are experimental results of the suction pressure and time (Suction Time / Pressure) measured by the batch carried out in order to calculate the optimum flocculant input amount using the OO water inlet water as a sample. Figure 5 shows the change in the final pressure and the initial pressure difference (ΔP) applied to the membrane filter (membrane filter) at the end of the filtration when the flocculant concentration is different. The lowest pressure difference was observed when coagulant was injected at a concentration of 35-40 mg / L.

Figure 5 shows the concentration change of the TI and UV254 value according to the flocculant concentration using the equation 1 and 2 after the suction pressure measurement experiment using the OO water inlet water as a sample. In the case of UV254, the value decreased significantly at the time of injecting 5 mg / L of flocculant, but there was no significant change in the UV254 value even after increasing the flocculant concentration. However, the suction pressure and time were the lowest at 25 ~ 30mg / L flocculant concentration. This value is similar to 35mg / L of coagulant input, which had the lowest final pressure, and when the 25 ~ 30mg / L coagulant is injected, the clogging of the membrane may be reduced.

The experimental procedure for measuring suction pressure and time is as follows. 1) Clean the test container with ultrapure water before measurement, and 2) measure the water temperature of the ultrapure water. Next, set the filter and the triangular frasco in the filtration device. 4) Prepare 100 ml of ultrapure water. 5) Wet the filter with a small amount of ultrapure water. 6) Switch on the suction pump and wait for 1 minute. 7) Filter 100 ml of ultrapure water with a filter and record the filtered time. ） Turn off the suction pump, depressurize and discard the ultra pure water of the triangular fraco. 10) Measure the water temperature of the agglomerated sample and 11) prepare 500 ml of the agglomerated sample. 12) Set the triangular fraco again on the suction filter. At this time, the filter is left as it is. 13. Switch on the suction pump, wait 1 minute, and then filter the 500 ml of the flocculating sample with a filter and record the time when the filtration is finished. 15) Measure the suction pressure after filtration. １６) Switch off the suction pump, depressurize and analyze the filtered water of the triangular fraco.

The experimental equipment necessary to conduct the experiment is a filtration device, a suction pump, a 0.1 μm membrane filter, a stopwatch, a thermometer, a 100 ml Mess frasco, a 500 ml Mess cylinder, a 500 ml Erlenmeyer flask, a certain amount of ultrapure water, 0 It is a pressure gauge of ~ 100 kPa.

According to the present invention, it is possible to determine the optimal flocculant input amount in a short time according to the inflow water quality of raw water to improve the stability of water purification treatment, and to calculate the appropriate flocculant input amount for the membrane filtration process to minimize the fouling phenomenon of the membrane. In addition, since the system is configured to inject the optimal amount of flocculant, it is possible to minimize the damage of the membrane during the membrane filtration process, to minimize the cost loss due to the excessive flocculant input, and to measure the pressure change according to the filtration time. Depending on the time of the filtration process can be set.

Claims (8)

A mixing step (a) of adding flocculant to the introduced raw water to form a floc; And In the water treatment method comprising the membrane filtration step (b) of filtering the mixed water passed through the mixing step (a), the mixing step (a) between the mixing step (a) and the membrane filtration step (b) Extracting a portion of the mixed water formed floc through the step (c) to measure the suction pressure / time (STP) and the step of controlling the input amount of the flocculant (d) . The method of claim 1, wherein the step (c) of measuring the suction pressure / time (STP) Extracting a predetermined amount of aggregated sample and inserting the sample into the sample injection unit; Filtering the sample subjected to a suction pressure by a suction pump through a membrane filter; Storing the filtrate of the sample passed through the membrane filter; And And a pressure / time measurement step of measuring a suction pressure generated when sucking the sample and a time taken until the filtration of the sample is completed. The method of claim 1, wherein the step (d) of adjusting the amount of flocculant A method for treating membrane filtration of raw water, characterized in that the amount of flocculant added is calculated so that the slope of a graph showing a time index (TI) value indexed to the amount of flocculant is zero. The method of claim 1, wherein the step (d) of adjusting the amount of flocculant A method for treating membrane filtration of raw water, characterized in that the amount of flocculant added is calculated so that the difference between the final pressure and the initial pressure (ΔP) applied to the membrane filter with respect to the amount of flocculant is minimized. A sample input unit which extracts a certain amount of aggregated sample and inputs the sample to the sample injection unit; A suction pump for supplying suction pressure to the sample; A filtration unit for filtering the sample subjected to the suction pressure by the suction pump through a membrane filter; A filtrate storage unit for storing the filtrate of the sample passing through the membrane filter; And Pressure / time measuring unit for measuring the suction pressure generated when the sample is sucked and the time taken until the filtration of the sample is finished Batch suction pressure measuring device for membrane filtration purified water treatment device comprising raw water. Admixture to inject flocculant into the introduced raw water to form a floc (floc); And A water purification apparatus including a membrane filtration device for filtering mixed water having passed through the mixing device, wherein a portion of the mixed water in which a floc is formed is sucked through the mixing device between the mixing device and the membrane filtration device and suctioned. Membrane suction pressure measuring device according to claim 5 for measuring the pressure / time (STP) and flocculant injection control device for adjusting the input amount of the flocculant, characterized in that it comprises a membrane filtration purified water treatment device. 7. The membrane of raw water according to claim 6, wherein the flocculant injection control device calculates the flocculant input amount so that the slope of the graph showing the time index (TI) value indexed with respect to the flocculant input amount becomes zero. Filtration water treatment device. 7. The membrane filtration constant of raw water according to claim 6, wherein the flocculant injection control device calculates a flocculant input amount such that a difference (ΔP) between the final pressure and the initial pressure applied to the membrane filter is minimized with respect to the flocculant input amount. Treatment method.

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