JP7496786B2 - Water purification method and water purification device - Google Patents

Description

The present invention relates to a water purification method and a water purification device for removing picoplankton contained in raw water such as river water and groundwater.

In the treatment of raw water such as river water or groundwater, insoluble components such as turbidity components and algae are removed using solid-liquid separation techniques such as coagulation and sedimentation and sand filtration. In the process of coagulating and filtering raw water, coagulation inhibition can occur due to various factors, and one cause of this is the presence of picoplankton, which has become a problem in recent years. Picoplankton are plankton with sizes of 0.2 to 2 μm, and it has been reported that they increase the turbidity of filtered water (Non-Patent Document 1).

Picoplankton are classified into two groups based on the mechanism of nutrient uptake. One is heterotrophic picoplankton, which are mainly composed of bacteria that break down organic matter and use it as a source of nutrition, and the other is plant picoplankton, which perform photosynthesis. Picoplankton contain pigments such as chlorophyll and can be observed under a fluorescent microscope. It has been confirmed that they are present in raw water or treated water in water purification treatment processes.

In recent years, the Ministry of Health, Labor and Welfare has been instructing that filtered water turbidity be maintained at 0.1 degrees or less in response to infections caused by Cryptosporidium transmitted through tap water (see Non-Patent Document 2). For this reason, water suppliers in each region have positioned constant management of filtered water turbidity at 0.1 degrees or less as one of the most important water quality management items.

However, in recent years, there have been frequent outbreaks of picoplankton caused by eutrophication in tap water sources all over the country. Picoplankton are tiny, measuring just 0.2 to 2 μm in size, and leak out of filtration ponds, causing the turbidity of the filtered water to rise to 0.1 degrees or higher. Water utilities are currently struggling to come up with treatment measures.

As picoplankton is a suspended solid of biological origin, chlorine injection has been considered an effective means of treatment. However, trihalomethanes, which are generated as a by-product of chlorine injection, are carcinogenic and pose a health problem, so a safer removal method that can replace chlorine injection is needed.

For example, JP 2014-240760 A (Patent Document 1) describes a biological particle counting method and a biological particle counter that calculate the number of different types of algae contained in water. However, Patent Document 1 only describes a general method for removing turbidity, and does not mention picoplankton or its removal.

JP 2011-110504 A (Patent Document 2) discloses a continuous control system for the water purification process that determines whether or not the cause of poor water purification is a filtration disorder caused by microplankton based on information on the turbidity of the precipitated water and the turbidity of the filtered water obtained from an automatic continuous water purification process monitoring device, and automatically injects a flocculant in the coagulation treatment process when it is determined that the filtration disorder is caused by microplankton. However, Patent Document 2 only discloses the technology of automatically injecting a flocculant as a means of dealing with filtration disorders caused by microplankton.

JP 2004-195304 A (Patent Document 3) discloses a flocculant injection control device that measures the turbidity of the water to be treated (filtrate) at the outlet of the filter basin and adds a flocculant to the inlet of the filter basin according to the detected turbidity. However, this is a technology for injecting a flocculant into the filter basin based on the results of turbidity detection, and does not disclose picoplankton or the means for removing them.

JP 2016-059867 A (Patent Document 4) discloses a treatment method and equipment technology for use in water purification plants that uses ultraviolet light irradiation to prevent picoplankton proliferation. However, this invention has the problem of increasing labor hours and costs because it requires a process and equipment for ultraviolet light irradiation.

JP 2006-007086 A (Patent Document 5) is an invention related to a method and device for treating water by coagulation and sedimentation, and describes the characteristics of a coagulation improver (coagulation aid) and the treatment method. However, Patent Document 5 does not mention picoplankton or the means for removing it.

JP 2012-228673 A (Patent Document 6) describes the formation of good microflocs using a flocculation improver (flocculation aid). However, it does not describe picoplankton or the means for removing them.

Patent Publication No. 3225266 (Patent Document 7) describes a method for obtaining clear water for industrial use from algae-containing lakes and rivers, and describes how a mixture of polyaluminum chloride and polydimethyldiallylammonium chloride is highly effective in removing algae as well as general turbidity components. However, Patent Document 7 does not mention picoplankton, which leaks from the filtration pond and causes an increase in the turbidity of the filtered water, and the method of Patent Document 7 cannot be expected to be effective in removing algae with fine particle sizes such as picoplankton.

JP 2014-240760 A JP 2011-110504 A JP 2004-195304 A JP 2016-059867 A JP 2006-007086 A JP 2012-228673 A Japanese Patent No. 3225266

Japan Water Works Association, Water Purification Treatment Guide to Prevent Biological Hazards, March 2006, p. 57 Ministry of Health, Labor and Welfare Notification, Yakuseisuihatsu 0529 No. 1, "Guidelines for Countermeasures against Cryptosporidium, etc. in Water Supply", Appendix 2, page 3, May 29, 2019

As mentioned above, none of the conventional treatment technologies have been adequately studied to address the increase in turbidity caused by the occurrence of picoplankton in the raw water.

In view of the above problems, the present invention provides a water purification method and water purification device that can safely and efficiently remove picoplankton, which is one of the factors that increases the turbidity of filtered water, and can stably obtain filtered water with low turbidity.

As a result of intensive research conducted by the present inventors to solve the above problems, it was discovered that it is effective to add a specific flocculant to reduce the number of picoplankton in the raw water or filtered water according to the number of picoplankton.

One embodiment of the present invention, which has been completed based on the above findings, is a water purification method that includes, in one aspect, adding a coagulant to raw water containing picoplankton, filtering the treated water to obtain filtered water from the treated water after the addition of the coagulant, measuring the number of picoplankton in the raw water, treated water, or filtered water, and controlling the amount of coagulant added depending on the results of the picoplankton number measurement, and adding polyaluminum chloride with a basicity of 60% or more as a coagulant to reduce the number of picoplankton.

In one embodiment, the water purification method according to the present invention includes adding two or more types of flocculants, at least one of which includes polyaluminum chloride, and further includes controlling the type and supply of the flocculants to be added depending on the picoplankton count.

In another embodiment of the water purification method according to the present invention, a flocculant for reducing the number of picoplankton is added to the treated water flowing into the filtration process.

In yet another embodiment of the water purification method according to the present invention, the method further includes predicting future measurement results of the picoplankton count based on analysis information obtained by analyzing the relationship between the operating conditions of the filtration process, the water quality information of the filtered water, and the measurement results of the picoplankton count based on past performance, and determining the amount of flocculant to be added based on the prediction result so as to maintain the turbidity of the filtered water at or below the standard value.

In another aspect, an embodiment of the present invention is a water purification treatment device that includes a flocculant adding means for adding a flocculant to raw water containing picoplankton, a flocculation means for forming flocs in the raw water and performing a flocculation treatment, a filtration means for filtering the treated water after the flocculation treatment to obtain filtered water, a measurement means for measuring the number of picoplankton in the raw water, the treated water, or the filtered water, and a control means for adding polyaluminum chloride having a basicity of 60% or more as a flocculant to reduce the number of picoplankton according to the measurement results of the number of picoplankton, and controlling the amount of polyaluminum chloride added.

In one embodiment of the water purification treatment device according to the present invention, the flocculant addition means includes a plurality of supply paths for adding two or more types of flocculant, one of which is a path for supplying polyaluminum chloride, and the control means controls switching of the supply of flocculant through the plurality of supply paths in accordance with the results of the measurement of the picoplankton count.

In another embodiment of the water purification treatment device according to the present invention, the path for supplying polyaluminum chloride is connected to at least one of a filtration means, an inlet pipe for inflowing treated water after solid-liquid separation into the filtration means, or a settling tank for settling and separating flocs formed in the raw water.

In yet another embodiment, the water purification treatment device according to the present invention further includes a flocculant addition support means for predicting the future picoplankton count by performing machine learning using the operating conditions of the filtration means, water quality information of the filtered water, and the measurement results of the picoplankton count of the filtered water by the measurement means, and for determining the amount of flocculant to be added based on the prediction results so as to maintain the turbidity of the filtered water at or below a reference value.

The present invention provides a water purification method and water purification device that can safely and efficiently remove picoplankton, which is one of the factors that increases the turbidity of filtered water, and can stably produce filtered water with low turbidity.

1 is a schematic diagram illustrating an example of a water purification method according to an embodiment of the present invention. 1 is a schematic diagram illustrating an example of a water purification treatment device according to an embodiment of the present invention. FIG. 11 is a schematic diagram illustrating a water purification treatment device according to a modified example of an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration example of a flocculant addition support means using machine learning according to an embodiment of the present invention. 11 is an explanatory diagram showing an example of data acquired by an acquisition unit of the flocculant addition support means. FIG. FIG. 2 is a schematic diagram showing a processing flow of the first embodiment. FIG. 11 is a schematic diagram showing a process flow of a second embodiment.

The following describes the embodiments of the present invention with reference to the drawings. In the following description of the drawings, identical or similar parts are given the same or similar reference numerals. Note that the embodiments shown below are examples of devices and methods for embodying the technical idea of this invention, and the technical idea of this invention does not specify the structure, arrangement, etc. of the components as described below.

(Aggregation Treatment Method)
As shown in FIG. 1, a water purification method according to a first embodiment of the present invention includes adding a coagulant to raw water containing picoplankton, filtering the treated water to obtain filtered water from the treated water after the addition of the coagulant, measuring the number of picoplankton in the raw water, treated water or filtered water, and controlling the amount of coagulant to be added depending on the results of the measurement of the picoplankton number.

[Flocculant addition step]
In the flocculant addition step, a flocculant is added to the raw water. The raw water is not particularly limited as long as it is usable for water purification treatment. For example, river water, lake water, reservoir water, rainwater, subsurface water, groundwater, wells, etc., which are used as raw water for water supply, can be suitably used as the raw water according to this embodiment. For example, raw water with a turbidity of 100 degrees or less, more typically 20 degrees or less, and even more typically about 2 to 10 degrees is used. The raw water is typically subjected to coagulation and sedimentation treatment through a grit chamber or a water receiving well.

In this embodiment, a flocculant for reducing the number of picoplankton in the raw water is used as the flocculant added to the raw water. A polyaluminum chloride (PAC) solution with a basicity of 60% or more is used as the flocculant for reducing the number of picoplankton.

The higher the basicity of the PAC solution used to remove picoplankton, the higher the charge neutralization ability in the raw water and the more effective it is at capturing fine particles. In addition, when maintaining the same processing ability, the higher the basicity of the PAC solution, the lower the addition rate can be, which improves processing efficiency and is economically advantageous. In this embodiment, it is preferable to use a PAC solution with a basicity of 65% or more, more preferably 70% or more, and even more preferably 75% or more, as a flocculant to be added to the raw water. If the basicity of the PAC solution is too high, the flocculation properties and stability of the flocculant may be impaired. There is no upper limit to the basicity, but in order to perform more stable processing, it is preferable that the basicity of the PAC solution be 90% or less, and even more preferably 85% or less.

Such a highly basic PAC solution (hereinafter also referred to as "high basicity PAC") can be produced, for example, by preparing a basic aluminum chloride solution having an Al ₂ O ₃ concentration of 5-17%, Cl/Al ₂ O ₃ (molar ratio) = 1.80-3.60, SO ₄ /Al ₂ O ₃ (molar ratio) = 0-0.35, and a basicity of 40-63%, and then adding an alkali metal and/or alkaline earth metal compound such as sodium carbonate or potassium carbonate to this basic aluminum chloride solution at a temperature of 85°C or less so that M/Al ₂ O ₃ (molar ratio) = 0.08-1.40 (wherein M represents twice the number of moles of the alkali metal and/or the number of moles of the alkaline earth metal), further adding an aluminum raw material as necessary, and aging the solution at 65-85°C for 0.5-2 hours.

According to this embodiment, by using a PAC solution with a basicity of 60% or more as a flocculant, fine picoplankton of about 0.2 to 2 μm in size can be more effectively flocculated and removed from the raw water compared to using a general PAC solution with a basicity of about 50%.

It is preferable to add two or more types of flocculants to the raw water. In addition to the high basicity PAC solution (hereinafter also referred to as "high basicity PAC") described above, other flocculants that can be used include, for example, general PAC with a basicity of about 50 to 55%, aluminum sulfate (aluminum sulfate), polyferrous sulfate, etc., either alone or in combination of two or more types. These flocculants are agents that have the ability to neutralize the charge of suspended particles and colloidal substances in the water, agglomerate them, and form flocs.

A chemical called a flocculation aid can be added as the flocculant according to this embodiment to improve the sedimentation and capture of flocs in the flocculation treatment and in the rapid filtration basin, and to form large-diameter, dense, and strong flocs. Examples of such flocculation aids that can be used include floc formation aids, alkaline agents, activated silicic acid, alginic acid, organic flocculation aids, polymer flocculants, and flocculation improvers. As the polymer flocculant, it is preferable to appropriately select one or more of cationic polymer flocculants, anionic polymer flocculants, and nonionic polymer flocculants, taking into consideration the surface charge of the particles in the heavy liquid.

The amount of flocculant added is selected appropriately depending on the basicity of the selected flocculant. Typically, the amount of flocculant added is 1 to 50 mg/L. In the control process described below, the amount and type of flocculant added can be controlled within this range.

[Aggregation treatment step]
The raw water to which the coagulant has been added is subjected to coagulation treatment. For example, the coagulant is added to the raw water, and the raw water is stirred and mixed in a mixing tank to form flocs, and then the flocs formed in the raw water are coarsened in a flocculation tank. The treated water obtained by the coagulation treatment is sent to a filtration process after solid-liquid separation of the flocs in a settling tank as necessary.

[Filtration process]
In the filtration step, the treated water to which the coagulant has been added is filtered. The filtration method may be a conventional method, and generally, sand filtration is used.

[Particle measurement process]
In the particulate measurement process, the number of particulates contained in the raw water and the filtrate is measured, thereby measuring the number of picoplankton contained in the particulates. In this embodiment, particulates refer to particles with a particle size of 0.1 μm to several hundred μm. In the particulate measurement process, the number of picoplankton with a particle size of 0.2 μm to 2.0 μm among the particulates is measured. Picoplankton is a general term that refers to microplankton, phytoplankton, small plankton, small algae, and biological particles of algae.

In this embodiment, the particle size of picoplankton refers to the minimum length of the picoplankton. In addition, a method for extracting only picoplankton with a size between 0.2 μm and 2.0 μm from among fine particles of all sizes can be performed by passing raw water or filtered water through a filter with an opening size of 0.2 μm and a filter with an opening size of 2.0 μm.

The method used to measure the number of picoplankton in the fine particle measurement process can be, for example, fluorescence measurement using a fluorescence microscope. In fluorescence measurement, the presence of picoplankton is confirmed by measuring the fluorescence emitted by the chlorophyll contained in the picoplankton, and the number of picoplankton present is counted using a counter. In the fine particle measurement process, it is more preferable to measure the turbidity of the raw water and the filtered water at the same time as measuring the number of picoplankton. Turbidity can be measured using a conventional turbidity meter.

[Control process]
In the control step, the amount of flocculant added is adjusted based on the picoplankton count measured in the fine particle measurement step. For example, when the picoplankton count in the raw water, treated water, or filtered water is equal to or greater than a predetermined value within the range of 10 ⁷ to 10 ³ cells/mL, it is preferable to control the amount of flocculant added so as to increase it. If the measurement result of the picoplankton count decreases as a result of increasing the amount of flocculant added, it is also preferable to control the amount of flocculant added so as to decrease it. In this embodiment, the unit "cells/mL" refers to the number of picoplankton per 1 mL of raw water or filtered water.

More specifically, it is preferable to set a threshold value for the picoplankton count in the raw water, treated water, or filtered water within the range of ¹⁰ to 2 x ¹⁰ cells/mL and for obtaining filtered water with a turbidity of 0.1 degrees or less, and to control the addition of an increased amount of flocculant to reduce the picoplankton count when the measured picoplankton count is equal to or greater than the threshold value.

The threshold value of the picoplankton count can be set according to its relationship with the turbidity of the filtered water obtained at a water purification plant. For example, it is known that in a certain water purification plant, when the picoplankton count of the filtered water is 2×10 ⁵ cells/mL, the turbidity is 0.1 degrees or less. In such a case, the threshold value of the picoplankton for adding a flocculant is set to 2×10 ⁵ cells/mL, and when the measured picoplankton count is equal to or greater than the threshold value, the amount of flocculant added is increased, thereby making it easy to manage the turbidity of the filtered water to 0.1 degrees or less.

The picoplankton count can be measured in one or more of the raw water, treated water, or filtered water, but it is particularly preferable to measure the number of particles in the filtered water. By directly measuring the picoplankton count in the filtered water, which can directly affect changes in the turbidity of the filtered water, the goal of maintaining the turbidity of the filtered water at a stable low value can be reliably achieved.

In the control process, in addition to controlling the amount of flocculant added, it is more preferable to control the type and supply of the flocculant according to the results of the picoplankton count measurement. For example, in combination with the high basicity PAC described above, normal basicity PAC, flocculation aids, alkaline agents, active silicic acid, alginic acid, organic flocculation aids, polymer flocculants, flocculation improvers, etc. can be added, and these types of flocculants can be used in appropriate combinations depending on the properties of the raw water, treated water, or filtered water.

For example, during normal operation, 1 to 50 mg/L of PAC with normal basicity is used, and a larger amount is added when the filtrate water is highly turbid. If it is found during the fine particle measurement process that the concentration of non-flocculating picoplankton is tending to increase, then high basicity PAC with a basicity of 60% or more is further added to reach the specified amount. Alternatively, the supply of flocculant is switched, and a similar amount of high basicity PAC is added in place of the PAC with normal basicity.

In the control process, the location of addition of the flocculant can also be controlled. For example, depending on the increase or decrease in the number of picoplankton, the flocculant can be controlled to be added to any location, such as the inlet pipe of the filtration basin or the top of the filtration basin, or to the settling tank, not only before the flocculation treatment but also after the flocculation treatment. This makes it possible to reduce picoplankton more effectively.

According to the water purification method of the embodiment of the present invention, polyaluminum chloride with a basicity of 60% or more is added as a flocculant to reduce the picoplankton count according to the results of the picoplankton count measurement. Therefore, even if a sudden change in the properties of the raw water causes a large outbreak of picoplankton due to eutrophication, the picoplankton can be safely and efficiently removed, making it possible to obtain stably low-turbidity filtered water.

(Water purification treatment equipment)
As shown in FIG. 2, the water purification treatment device according to an embodiment of the present invention comprises a flocculant addition means 1 that adds a flocculant to raw water containing picoplankton, a flocculation means 2 that performs a flocculation treatment by forming flocs in the raw water, a filtration means 3 that filters the treated water after the flocculation treatment to obtain filtered water, a measurement means 4 that can measure the number of picoplankton in the raw water, the treated water, or the filtered water, and a control means 5.

The flocculant adding means 1 is a device capable of adding a flocculant to raw water, treated water after flocculation treatment, or filtered water. The flocculant adding means 1 preferably includes a plurality of supply paths 11, 12 for adding two or more types of flocculants to the raw water. The number of supply paths 11, 12 can be changed as appropriate depending on the type of flocculant. However, it is preferable that one of the supply paths 11, 12 is a path for supplying high basicity PAC.

The supply path 12 for supplying the high basicity PAC is preferably connected to the filtration means 3 or to an inlet pipe 31 for inflowing the treated water from the flocculation means 2 into the filtration means 3. By connecting the supply path 12 to the filtration means 3 or the inlet pipe 31, treatment for effectively reducing picoplankton can be focused on the treated water, which has a lower turbidity than the raw water after flocculation, so that the turbidity of the filtered water can be more effectively reduced. The supply path 12 may be connected to a settling tank 22.

The flocculation means 2 can typically include a flocculation tank 21 composed of a mixing tank and a floc formation tank, etc., and a sedimentation tank 22 composed of a settling tank, etc., for settling and separating flocs formed in the raw water, but is not limited to the above configuration. For example, the flocculation treatment may be performed in a single flocculation tank rather than divided into multiple tanks. If solid-liquid separation is not required, the sedimentation tank 22 can be omitted. As the filtration means 3, a sand filter can typically be used, but other known filtration devices such as a membrane filter can also be used.

The measuring means 4 is not particularly limited as long as it is an instrument capable of measuring the number of picoplankton with particle sizes between 0.2 μm and 2.0 μm. For example, the number of picoplankton can be measured more easily and accurately by using a fluorescence microscope or the like that utilizes fluorescence measurement. For example, a counter capable of measuring biological particles including phytopicoplankton can be used for the raw water, treated water, or filtered water to be measured. Although not shown, the measuring means 4 is preferably further equipped with a measuring device for measuring the water quality such as turbidity, water temperature, and pH of the raw water, treated water, and filtered water, and is configured so that the measurement results of the raw water, treated water, and filtered water are output to the control means 5.

The control means 5 is connected to the measurement means 4 and the flocculant addition means 1, and is configured to output a control signal for controlling the measurement means 4 and the flocculant addition means 1. The control means 5 controls the amount of high basicity PAC and other flocculants added as flocculants to reduce the picoplankton count, controls the addition position, and controls the switching of the flocculants to be added, depending on the measurement results of the picoplankton count.

The water purification treatment device according to the embodiment of the present invention is equipped with a measuring means 4 capable of measuring the number of picoplankton in raw water, treated water, or filtered water, and a control means 5 for controlling the amount of flocculant added depending on the results of the picoplankton number measurement, so that picoplankton, which is one of the factors that increases the turbidity of the filtered water, can be more appropriately detected, and appropriate treatment can be performed when an increase in picoplankton may cause an increase in turbidity. As a result, filtered water with a stable low turbidity can be obtained.

(Modification)
As shown in Figure 3, the water purification treatment device of a modified embodiment of the present invention differs from the water purification treatment device shown in Figure 2 in that it further includes a flocculant addition support means 6 that predicts the future picoplankton count in the raw water, treated water, or filtered water, and determines the amount of flocculant to be added based on the prediction results.

The flocculant addition support means 6 is connected to the measurement means 4 and the control means 5. The flocculant addition support means 6 does not necessarily need to be located adjacent to the control means 5, and may be installed in a location different from the water purification treatment device in FIG. 3 via a network or the like, or may be stored in a general-purpose computer in the form of a program or the like.

The flocculant addition support means 6 determines the amount of flocculant to be added so that the turbidity of the filtered water is maintained below the standard value, based on analysis information obtained by analyzing the relationship between the operating conditions of the filtration process, the water quality information of the filtered water, and the measurement results of the picoplankton count, based on past performance.

The operation information for the filtration process includes water quality information (temperature, conductivity, pH, organic matter concentration, turbidity, etc.) of the raw water or influent water (flocculated water), and the operating conditions of the filtration device (material of the filter media, particle size, height of the filter layer, pressure, flow rate, filtration time, filtration resistance, etc.). It is even better if the operation information for the filtration process includes maintenance information such as the timing of cleaning the filtration device.

The water quality information of the filtered water includes the water temperature, pH, concentration of metals such as aluminum, information on organic matter such as COD and BOD, conductivity of the permeate, picoplankton count, etc. In addition to the operating status of the filtration process and the water quality conditions of the filtered water, it is preferable that the operating information of the filtration process includes coagulant injection control data.

The average removal rate of picoplankton in a settling tank is said to be about 70%, and depending on the number of picoplankton generated, it may not be possible to remove it completely by filtration. For example, when the water temperature exceeds 20°C, the turbidity is less than 10°C, and the raw water pH exceeds 7.5, the picoplankton concentration in the raw water may be high. Therefore, in general water purification treatment, the picoplankton in the filtered water may not be completely removed, and the turbidity of the filtered water may increase due to an increase in picoplankton. The operator uses, for example, past data on the turbidity, water temperature, organic matter concentration, and picoplankton count of the raw water and the turbidity, water temperature, and picoplankton count of the filtered water to create analytical information for predicting the number of picoplankton in the filtered water based on the relationship between the type and injection rate of the coagulant, and prepares in advance a relational equation for determining the addition rate of the coagulant according to the measurement results of the number of picoplankton in the filtered water. For example, a relational equation is created that gradually increases the flocculant addition rate when conditions that predict a future increase in picoplankton, such as at least one of the above-mentioned temperature, turbidity, and raw water pH, continue for a certain period of time or more.The flocculant addition support means 6 then uses the relational equation and the measurement results of the number of picoplankton in the filtered water, and can determine the amount of flocculant to be added so that the turbidity of the filtered water is stably maintained below the reference value.

The prediction of the picoplankton count can be made more accurate by utilizing a machine learning function using artificial intelligence (AI). For example, the flocculant addition support means 6 is composed of a computer system equipped with a storage device capable of storing information necessary for operation control of the water purification treatment device, an input device, an output device, and a communication means, and may be connected to another water purification treatment device or a server via a network so as to be able to communicate with each other. The learned model created by the flocculant addition support means 6, or various information recorded in the server or another water purification treatment device, may be configured to be able to be shared with each other.

For example, as shown in FIG. 4, the flocculant addition support means 6 can include an acquisition unit 61, a learning unit 62, a model storage unit 63, a prediction unit 64, a determination unit 65, and an output unit 66. As shown in FIG. 5, for example, the acquisition unit 61 acquires raw water quality data indicating past raw water quality information, flocculant injection data indicating the type of flocculant and its injection rate, operation data including filtration time, filtration resistance, flow rate, conductivity, temperature, etc., and filtered water data including filtered water quality information such as pH, turbidity, COD, and picoplankton count. The acquisition unit 61 further acquires operation information of the water purification treatment device by acquiring measurement results of each measuring device (time, thermometer, pH meter, filtration resistance pressure meter, flow meter, conductivity meter, etc.) obtained during operation of the water treatment device.

The learning unit 62 creates a trained model of the water purification treatment device by machine learning using a predetermined machine learning algorithm based on the information acquired by the acquisition unit 61. As the machine learning algorithm, for example, an analysis tool using the PCR method (principal component regression method), the PLS method (partial least squares method), the SVR method (support vector regression method), the ARIMA, the LSTM, the neural network (ANN or RNN) method, the random forest method, or the decision tree method can be appropriately selected and used.

The parameters of the machine learning model, for example the number of layers in the neural network method and the number of neurons in each layer, are not particularly limited, but for example the number of neurons in each layer can be 1 to 50, or even 1 to 30, and the number of layers can be 1 or more, or even 1 to 4. The trained model created in this way is configured to receive a specified explanatory variable and output a specified objective variable.

For example, when using the neural network method, raw water quality data indicating past water quality information of raw water, flocculant injection data indicating the type of flocculant and its injection rate, operation data including filtration time, filtration resistance, flow rate, conductivity, temperature, etc., filtered water data including filtered water quality information such as pH, turbidity, COD, picoplankton count, weather condition data including past air temperature, and past picoplankton count measurement results are input to the input layer, and the number of particles including the picoplankton count of future filtered water after a predetermined time (for example, several minutes to several hours) is output from the output layer. The weighting coefficients between the neurons of the neural network are optimized by supervised learning using data linked to the data input to the input layer and the data output from the output layer. The learned model is stored in the model storage unit 63.

The prediction unit 64 uses the trained model created by the learning unit 62 to at least predict the future picoplankton count of the raw water, treated water, or filtered water of the water purification system. For example, the prediction unit 64 inputs the measurement results of each measuring device obtained during operation of the water treatment device acquired by the acquisition unit 61 into the input layer of the learning model, and outputs the picoplankton count of the filtered water after a predetermined time from the output layer.

The determination unit 65 determines the optimal amount of flocculant to be added based on past data so as to maintain the turbidity of the filtered water below the reference value according to the prediction result of the prediction unit 64. The output unit 66 outputs control information on the optimal combination of flocculants and the amounts to be added determined by the determination unit 65 to the control means 5.

According to the water purification method according to the modified embodiment of the present invention, the number of picoplankton in the raw water, treated water, or filtered water is measured, and the number of picoplankton after a predetermined time has elapsed is predicted. Based on the prediction result, if the number of picoplankton increases, an appropriate flocculant can be added to reduce the number of picoplankton. This makes it possible to safely and efficiently remove picoplankton, which is one of the factors that increases the turbidity of the filtered water, and to obtain stably low-turbidity filtered water.

The present invention has been described using the above embodiments, but the descriptions and drawings that form part of this disclosure should not be understood as limiting this invention. In other words, this disclosure is not limited to the above-mentioned embodiments, and it goes without saying that the components can be combined and modified to be embodied within the scope of the gist of the disclosure.

The following examples of the present invention are presented together with comparative examples, but these examples are provided to provide a better understanding of the present invention and its advantages, and are not intended to limit the invention.

Example 1
Water purification was carried out according to the treatment flow shown in Figure 6. PAC of normal basicity was added to the coagulation tank, and the treated water obtained by solid-liquid separation in the settling tank was subjected to sand filtration to obtain filtrate. When the amount of PAC of normal basicity added to the coagulation tank was 30 mg/L, the turbidity of the filter tank rose to 0.08 degrees and the picoplankton concentration rose to 10 ⁶ cells/mL. Therefore, a polyaluminum chloride (PAC) solution with a basicity of 65% to 85% was added at 5 mg/L in the upstream of the filter tank, and the turbidity of the filtered water after 24 hours was reduced to 0.02 degrees and the picoplankton concentration to 10 ⁴ cells/mL.

(Reference Example 1)
Treatment was carried out under the same conditions as in Example 1, except that no control was performed to add a polyaluminum chloride (PAC) solution with a basicity of 65% to 85% in the upstream stage of the filtration basin. When the amount of PAC with normal basicity added to the coagulation tank was 30 mg/L, the turbidity of the filtration basin increased to 0.08 degrees and the picoplankton concentration to ¹⁰⁶ cells/mL. When this condition was continued for 24 hours, the turbidity increased to 0.20 degrees and the picoplankton concentration increased to ¹⁰⁷ cells/mL.

Example 2
Water purification was performed according to the process flow shown in Figure 7. Trends in measurement data of the number of particulates and picoplankton in the filtered water for the past two years, trends in turbidity data of the filtered water, pH, water volume data, and operating data including filtration time, filtration resistance, flow rate, conductivity, temperature, etc. as operating conditions of the filtration device are learned as explanatory variables. The prediction unit is configured to incorporate a model for predicting the number of picoplankton in the filtered water created from the learning data, and to predict the turbidity in the filtered water one hour later by sensing the learning data and inputting the data.

When the amount of PAC added to the coagulation tank with normal basicity was 30 mg/L, the turbidity of the filter basin rose to 0.08 degrees and the picoplankton concentration rose to 10 ⁶ cells/mL. The AI prediction predicted that the turbidity of the filtered water after one hour would be 0.12 degrees. Therefore, when a control was implemented by adding 5 mg/L of polyaluminum chloride (PAC) solution with a basicity of 65% to 85% in the upstream of the filter basin, the turbidity after one hour fell to 0.06 degrees, and operation was possible without exceeding a turbidity of 0.1 degrees.

In this way, according to the present disclosure, picoplankton, which is one of the factors that increase the turbidity of filtered water, can be safely and efficiently removed, and filtered water with a stable low turbidity can be obtained.

1... flocculant addition means 2... flocculation means 3... filtration means 4... measurement means 5... control means 6... flocculant addition support means 11, 12... supply path 21... flocculation tank 22... sedimentation tank 31... inlet pipe 61... acquisition unit 62... learning unit 63... model storage unit 64... prediction unit 65... determination unit 66... output unit

Claims (8)

A flocculant adding means for adding a flocculant to raw water containing picoplankton;
a flocculation means for forming flocs in the raw water to perform flocculation treatment;
A filtering means for filtering the treated water after the coagulation treatment to obtain filtrate;
A measuring means capable of measuring the picoplankton count of the raw water, the treated water, or the filtered water;
A control means for controlling the amount of polyaluminum chloride added so that polyaluminum chloride having a basicity of 60% or more is added as a flocculant for reducing the picoplankton count according to the measurement result of the picoplankton count;
Equipped with
the flocculant adding means includes a plurality of supply paths for adding the flocculant, one of the supply paths being a path for supplying the polyaluminum chloride having a basicity of 60% or more;
a path for supplying the polyaluminum chloride having a basicity of 60% or more is connected to at least one of the filtration means, an inlet pipe for inflowing the treated water after the coagulation treatment into the filtration means, or a settling tank for settling and separating flocs formed in the raw water,
a control means for controlling the supply of the coagulant through the multiple supply paths so as to supply the polyaluminum chloride having a basicity of 60% or more to at least one of the filtration means, an inlet piping for allowing the treated water after the coagulation treatment to flow into the filtration means, or a settling tank for settling and separating flocs formed in the raw water, when the measurement result of the picoplankton count is equal to or greater than a predetermined value . the plurality of feed lines include a line for adding polyaluminum chloride having a normal basicity of less than 60% to the flocculation means;
The water purification treatment device according to claim 1, wherein the control means controls switching between adding the coagulant via the path for adding polyaluminum chloride having a normal basicity and adding the coagulant via the path for adding polyaluminum chloride having a basicity of 60% or more, depending on the measurement results of the picoplankton count. The water purification treatment device according to claim 1 or 2, further comprising a flocculant addition support means for determining the amount of flocculant to be added so as to maintain the turbidity of the filtered water at or below a standard value based on analysis information obtained by analyzing the operating conditions of the filtration means, water quality information of the filtered water, and the relationship with the measurement results of the picoplankton count by the measurement means based on past performance. The water purification treatment device according to claim 1 or 2, further comprising a flocculant addition support means for predicting the future picoplankton count by performing machine learning using the operating conditions of the filtration means, water quality information of the filtered water, and the measurement results of the picoplankton count of the filtered water by the measurement means, and determining the amount of flocculant to be added based on the prediction result so as to maintain the turbidity of the filtered water below a standard value. A flocculant is added to raw water containing picoplankton through a flocculant adding means having a plurality of supply paths ;
Filtration of the treated water to obtain filtrate from the treated water after the addition of the coagulant;
Measure the picoplankton count of the raw water, the treated water, or the filtered water;
and controlling the amount of the flocculant added according to the measurement result of the picoplankton count;
one of the plurality of supply paths is a path for supplying polyaluminum chloride having a basicity of 60% or more, and the path for supplying polyaluminum chloride having a basicity of 60% or more is connected to at least one of a filtration means for performing the filtration treatment, an inflow pipe for flowing the treated water after the addition of the coagulant into the filtration means, or a settling tank for settling and separating flocs formed in the raw water,
A water purification method comprising the steps of: adding polyaluminum chloride having a basicity of 60% or more as a flocculant for reducing the picoplankton count when the measurement result of the picoplankton count is equal to or greater than a predetermined value to at least one of a filtration means for performing the filtration treatment of the treated water, an inlet piping for flowing the treated water after the addition of the flocculant into the filtration means, or a settling tank for settling and separating flocs formed in the raw water . The plurality of supply paths include a path for adding polyaluminum chloride having a normal basicity of less than 60% to the raw water to a flocculation means,
The water purification method according to claim 5, further comprising switching between adding a flocculant via a path for adding polyaluminum chloride having a basicity of 60% or more and adding a flocculant via a path for adding polyaluminum chloride having a basicity of 60% or more depending on the results of the measurement of the picoplankton count. The water purification method according to claim 5 or 6, further comprising: predicting future measurement results of the picoplankton count based on analytical information obtained by analyzing the relationship between the operating conditions of the filtration process, the water quality information of the filtered water, and the measurement results of the picoplankton count based on past performance; and determining the amount of the coagulant to be added based on the prediction result so as to maintain the turbidity of the filtered water at or below a standard value. The water purification method according to any one of claims 5 to 7, further comprising: predicting the future picoplankton count by performing machine learning using the operating conditions of the filtration process, water quality information of the filtered water, and the measurement results of the picoplankton count of the filtered water; and determining the amount of the coagulant to be added based on the prediction result so as to maintain the turbidity of the filtered water at or below a reference value.