JP2008023417A - Water purifying apparatus and water purifying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water purifying apparatus capable of sufficiently efficiently reducing a manganese and nickel content derived from raw water and a flocculant, and to provide a water purifying method. <P>SOLUTION: This water purifying apparatus 10 is used for purifying water to be treated containing raw water taken in from a water source selected from surface water and ground water, and at least one of manganese and nickel comprises an alkali agent mixing tank (pH adjustment means) 5 so as to increase the pH of the water to be treated by loading the water to be treated with an alkali agent, and a dewaterer (solid-liquid separation means) 6 for carrying out solid-liquid separation of the water to be treated loaded with the alkali agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water purification apparatus and a water purification method for surface water and groundwater.

  The raw water used for tap water is taken from surface water and groundwater. In the water purification facility, treatment such as removal of chemical substances and disinfection is performed on the water to be treated. Through these treatments, clean water that satisfies various standards is supplied to demand areas. Surface water means land water on the ground surface, such as river and lake water.

Surface water and groundwater often contain manganese, and it can be said that efficient removal of manganese is one of the important treatment techniques. If water in which manganese is not sufficiently removed and manganese is dissolved in the form of ions (Mn ²⁺ ) is transferred through a water pipe, Mn ²⁺ is oxidized by residual chlorine, and MnO ₂ adheres to the inner wall of the water pipe. Since MnO ₂ adhering to the inner wall acts as a catalyst for oxidizing Mn ²⁺ , the adhesion of MnO ₂ is accelerated. The adhesion of MnO ₂ may cause problems such as scale contamination in tap water and blockage of water pipes. Manganese contained in tap water causes odor and coloring (black water).

  Moreover, in the water purification treatment facility, a flocculant is generally used in order to promote aggregation of floating substances contained in the raw water. One typical flocculant is an iron-based flocculant. Iron-based flocculants contain manganese and nickel as impurities.

  Depending on the water source, the manganese concentration of surface water may be about 0.1 mg / L, and the manganese concentration of groundwater may reach several mg / L. As reference values, the WHO drinking water quality guideline stipulates that the manganese concentration is 0.1 mg / L or less, and the ministerial ordinance related to the water quality standard in Japan sets the manganese concentration to 0.05 mg / L or less.

As a method for removing manganese in water purification equipment, a method is known in which manganese is oxidized with sodium hypochlorite or the like, insolubilized in the form of MnO ₂ , and then separated and removed. In addition, a method of passing water through a filter medium called manganese sand is also known (see Non-Patent Document 1).
"Water Purification Technology Guidelines (2000 version)", Water Technology Research Center, December 2000, p. 33-36

  By the way, in the water purification treatment facility, not all of the raw water taken is available as clean water. Part of the raw water is discharged from the purification treatment facility as waste water. For wastewater from the purification treatment facility, a reference value with a higher upper limit is set in comparison with the above water quality standard for clean water. For example, in the drainage regulations based on the Water Pollution Control Law, the manganese concentration is set to 10 mg / L or less as the drainage standard.

  The method described in Non-Patent Document 1 is currently widely used as a method for removing manganese contained in clean water. However, this method has a high removal rate of manganese and can reliably perform water purification that satisfies water quality standards. However, this method requires an oxidizing agent such as sodium hypochlorite and is discharged from the water purification facility. It can be said that the method for removing manganese contained in the wastewater is inefficient in terms of workability and economy.

  This invention is made | formed in view of such a situation, and it aims at providing the water purification apparatus and the water purification method which can perform the process which satisfy | fills a waste_water | drain standard efficiently.

  The water purification apparatus of the present invention is for purifying water to be treated containing raw water taken from a water source selected from surface water and groundwater, and containing at least one of manganese and nickel. PH adjusting means for adjusting the treated water to have a higher pH by adding an alkaline agent to the treated water, first solid-liquid separating means for solid-liquid separating the treated water to which the alkaline agent has been added, It is characterized by providing.

  According to the present invention, an alkali agent is added to the water to be treated, and the pH is raised, and then the water to be treated is subjected to solid-liquid separation treatment, thereby separating the manganese and nickel contents sufficiently reduced. A liquid can be obtained. That is, manganese and nickel can be sufficiently separated and removed together with the separated solid matter.

  The mechanism by which manganese and nickel are removed together with solids by increasing the pH of the water to be treated has not been completely elucidated. However, by increasing the pH of the water to be treated, the present inventors promote the adsorption of ionic manganese and nickel on suspended substances (hereinafter referred to as “SS”) contained in the water to be treated. I think because. Specific examples of SS include granular substances made of inorganic or organic substances, and algae. In addition, although the to-be-processed water contains the oxidation type manganese and nickel which generate | occur | produced in the purification process, these can also be removed like an ionic thing.

  The water purification apparatus of the present invention preferably further comprises a flocculant mixing means for adding a flocculant to the water to be treated upstream of the pH adjusting means and mixing them. When a flocculant is added to the water to be treated, the recovery rate of SS in the solid-liquid separation process can be sufficiently increased. Since much SS is recovered as a solid, manganese and nickel can be separated and removed together with the solid more efficiently. In addition, the upstream side said by this invention represents the relative position of each means or to-be-processed water in a water purification apparatus, Comprising: The side nearer the part to which raw | natural water is supplied is meant.

  Moreover, the water purification apparatus of the present invention further includes a second solid-liquid separation means for solid-liquid separation of the water to be treated to which the flocculant is added, and the separated sludge separated by the second solid-liquid separation means has a pH. The configuration is preferably supplied to the adjusting means.

  Separation and removal of manganese and nickel can be performed more efficiently by supplying separated sludge having an increased SS concentration to the pH adjusting means as treated water, and performing pH adjustment and solid-liquid separation treatment on this. . This is because SS is concentrated in the second solid-liquid separation means, and the amount of water to be processed in the subsequent pH adjusting means and the first solid-liquid separation means is reduced. In addition, a high removal rate of manganese and nickel is achieved. In the separated sludge in which SS is present at a high concentration, it is considered that the contact efficiency between SS, manganese and nickel is high, and these metals are easily adsorbed by SS.

  Moreover, it is preferable that the water purification apparatus of this invention is further equipped with the return path which returns at least one part of the separated liquid from a 1st solid-liquid separation means to the upstream of the said water purification apparatus. If the water purification apparatus has such a return path, the amount of waste water discharged from the apparatus to the outside of the system can be reduced. Moreover, since the return water in which the contents of manganese and nickel are sufficiently reduced is returned, the concentration of manganese and nickel in the water in the apparatus system can be maintained at a sufficiently low value.

  The water purification method of the present invention is for purifying water to be treated containing raw water taken from a water source selected from surface water and groundwater, and containing at least one of manganese and nickel. A pH adjustment step of increasing the pH of the water to be treated by adding an alkaline agent to the water to be treated, and a solid-liquid separation step of subjecting the water to be treated after the pH adjustment to a solid-liquid separation treatment are provided.

  According to the present invention, the separation liquid in which the contents of manganese and nickel are sufficiently reduced by solid-liquid separation of the water to be treated after adding an alkali agent to the water to be treated and raising the pH. Can be obtained. That is, manganese and nickel can be sufficiently separated and removed together with the separated solid matter.

  According to the present invention, it is possible to provide a water purification apparatus and a water purification method capable of sufficiently efficiently reducing the contents of manganese and nickel derived from raw water and a flocculant.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a first embodiment of a water purification apparatus according to the present invention. A water purification treatment apparatus 10 shown in FIG. 1 includes a landing well 1, a coagulant admixing tank (coagulant admixing means) 2, a sedimentation tank (second solid-liquid separation means) 3, a filtering device 4, an alkaline agent admixing tank (pH adjustment). Means) 5 and a dehydrator (first solid-liquid separation means) 6.

  The landing well 1 is a tank for stabilizing the fluctuation of the water level of raw water supplied directly from a water source such as a river or groundwater or via a water intake.

  The flocculant mixing tank 2 is a tank for mixing the water to be treated and the flocculant.

  The sedimentation tank 3 is a tank for separating the water to be treated from the flocculant mixing tank 2 into separated sludge and a separated liquid. A line L1 for discharging separated sludge having an increased SS concentration is connected to the bottom of the sedimentation tank 3. On the other hand, the separation liquid is a so-called supernatant liquid, and the SS content is sufficiently reduced. The sedimentation tank 3 includes a line L2 for supplying the separated liquid to the filtration device 4. In the present specification, “line” means a pipeline.

  The filtration device 4 is a device for removing SS that has not precipitated in the settling tank 3. A sand layer (not shown) for attaching fine SS is provided inside the filtration device 4. The filtration device 4 includes a line L3 for discharging filtered water. The filtration device 4 is not limited to the one provided with a sand layer. For example, a filtration device using a carbide or fiber filter material such as anthracite or activated carbon, an organic polymer membrane such as cellulose acetate, or an inorganic membrane such as ceramic. You may employ | adopt the membrane filtration apparatus etc. which become.

  The filtration device 4 of the water purification apparatus 10 includes a sand layer therein. The SS contained in the separation liquid from the settling tank 3 is adsorbed and removed by the sand layer. In order to maintain this adsorption capacity, the sand layer is generally backwashed regularly.

  The filtration device 4 includes a water supply pump (not shown) that supplies water from the line L3 so that the flow of water is opposite to that during normal operation. The filtration device 4 is connected to a line L15 for discharging the backwash waste water containing the removed SS.

  The backwash drainage is supplied to the drainage tank 15 through the line L15. The drainage tank 15 is a tank for separating the backwash drainage from the filtration device 4 into drainage tank sludge and drainage tank treatment liquid. The drain tank sludge is supplied to a later-described drain tank 11 through a line L16. On the other hand, the drainage tank treatment liquid can be added to the return water through a line L17 connected to the return line (return path) L6.

  The backwashing treatment means is constituted by a water pump, a drainage tank 15, and a line connecting them.

  The sludge tank 11 is a tank for separating the separated sludge from the sedimentation tank 3 and the drain tank sludge from the drain tank 15 into the drain mud tank sludge and the waste mud tank treatment liquid. The sludge tank sludge is supplied to a sludge concentration tank 12 described later through a line L11. On the other hand, the sludge tank treatment liquid can be added to the return water through a line L12 connected to the return line L6.

  The sludge concentration tank 12 is a tank for separating the sludge tank sludge from the sludge tank 11 into concentrated sludge and sludge concentration tank treatment liquid. The concentrated sludge is supplied to the alkaline agent mixing tank 5 through the line L13. On the other hand, the sludge concentration tank treatment liquid can be added to the return water through the line L14 connected to the return line L6. The concentration means is constituted by a sludge tank 11, a sludge concentration tank 12, and a line connecting them. In addition, the sludge concentration tank 12 can also be abbreviate | omitted by fully concentrating sludge in the sludge tank 11. FIG.

  In addition, the chlorine addition apparatus which inject | pours chlorine into the filtered water from the filtration apparatus 4 and disinfects can be installed in the back | latter stage of the filtration apparatus 4. FIG.

  The alkaline agent mixing tank 5 is a tank for adjusting the pH of the separated sludge supplied through the line L1. Although not shown, the alkaline agent mixing tank 5 is preferably provided with an alkaline agent supply device and a pH measuring device. The alkaline agent mixing tank 5 is preferably provided with a stirrer (not shown) in order to sufficiently mix the added alkaline agent and the separated sludge. If the supply amount of the alkaline agent is controlled so that the pH of the separated sludge becomes a predetermined value based on the measurement result of the pH measuring device, the pH can be adjusted more accurately. In addition, by adding an inorganic flocculant or a polymer flocculant to the alkali agent mixing tank 5, dehydration can be performed at a low moisture content more quickly.

  The dehydrator 6 is for performing solid-liquid separation processing of the separated sludge from the alkaline agent mixing tank 5. From the dehydrator 6, the dehydrated separation liquid from which the solids (dehydrated sludge) contained in the separated sludge has been removed is discharged. The dehydrator 6 is connected to a line L4 and a line L5. These lines are for discharging dewatered sludge and dewatered separation liquid, respectively.

  Any dehydrator can be used as the dehydrator 6, and examples thereof include a filter press dehydrator and a vacuum dehydrator. These dehydrators may be used alone or in combination of two or more.

  The line L5 is connected to a return line (return path) L6 for returning at least a part of the dehydrated separation liquid to the landing well 1. The water returned on the return line L6 is referred to as return water. The return water is mixed with the raw water in the landing well 1 and supplied again to the flocculant mixing tank 2 as part of the water to be treated.

  Next, a method for purifying water to be treated using the water purification apparatus 10 will be described.

  Raw water and return water are mixed in the landing well 1, and this mixed water (treated water) is introduced into the flocculant mixing tank 2. In the flocculant mixing tank 2, a predetermined amount of flocculant is added to the water to be treated. It is preferable to add the flocculant while stirring the water to be treated in the flocculant mixing tank 2 (flocculating agent mixing step).

  What is necessary is just to set the addition amount of a flocculant according to the turbidity or SS density | concentration of to-be-processed water.

  Examples of the flocculant include iron-based flocculants such as ferric chloride, ferric sulfate, and polysilica iron flocculant (PSI), and aluminum-based flocculants such as polyaluminum chloride (PAC) flocculant. These flocculants may be used individually by 1 type, and may be used in combination of 2 or more type.

  The iron-based flocculant contains manganese and nickel as impurities. For this reason, depending on the kind of inorganic flocculant to be added, the concentration of manganese and nickel in the water to be treated may increase with the addition of the inorganic flocculant.

  In addition to manganese and nickel, the concentration of other metals may increase due to the addition of an inorganic flocculant. For example, when an aluminum-based flocculant is added, the aluminum concentration of water to be treated may increase. Since there is concern about the causal relationship with neurological diseases, the ministerial ordinance on water quality standards in Japan stipulates that the aluminum concentration is 0.2 mg / L or less.

  The water to be treated to which the flocculant is added in the flocculant mixing tank 2 is introduced into the precipitation tank 3. In the sedimentation tank 3, SS contained in the water to be treated is settled, and sludge is precipitated at the bottom of the sedimentation tank 3. Thereby, the separation sludge with which SS density | concentration was raised is obtained (sludge concentration process). The sludge precipitated from the line L1 connected to the bottom of the settling tank 3 is discharged as separated sludge.

  The separated sludge is introduced into the alkaline agent mixing tank 5 through the line L1. In the alkaline agent mixing tank 5, an alkaline agent is added to the separated sludge. While stirring the separated sludge in the alkaline agent mixing tank 5, the pH of the separated sludge is adjusted to a predetermined value (pH adjusting step). The pH can be adjusted automatically by the pH meter of the alkali agent mixing tank 5 and the alkali agent supply device. In addition, you may add an alkali agent manually, confirming the measured value of a pH measuring device.

  The pH of the separated sludge in the alkaline agent mixing tank 5 is preferably adjusted to 7.0 or higher, and more preferably adjusted to 8.0 or higher. If this pH is less than 7.0, the removal of manganese and nickel tends to be insufficient. When aluminum is contained in the separated sludge, the pH of the separated sludge is preferably adjusted to 7.0 to 9.0, and more preferably adjusted to 7.5 to 8.5. This is because the pH region where the solubility of aluminum is low is limited to a range of about 4.0 to 9.0. When the pH of the separated sludge is adjusted to a value higher than 9.0, aluminum in an insoluble state is eluted and it is difficult to efficiently remove the aluminum.

  When the pH is raised to 7 or more, there may be a problem that the dehydrating property is lowered. In this case, this problem can be improved by using a calcium hydroxide suspension as an alkaline agent. In addition, in the alkaline agent mixing tank 5, an inorganic flocculant or a polymer flocculant may be added in order to enhance dehydrating properties.

  The separated sludge whose pH is adjusted in the alkaline agent mixing tank 5 is introduced into the dehydrator 6. By the dehydration process in the dehydrator 6, the separated sludge is separated into the dehydrated sludge and the dehydrated separation liquid (solid-liquid separation step). The dewatered sludge is discharged from the line L4 connected to the dehydrator 6. Manganese and the like can be discharged together with the dewatered sludge discharged here.

  At this time, it is considered that manganese and the like are adsorbed on the dewatered sludge. Thereby, a dehydration separation liquid in which the content of manganese or the like is sufficiently reduced can be obtained. When the dehydrated separation liquid is discharged into the public water area, it is necessary to reduce the manganese concentration to 10 mg / L or less and the iron concentration to 10 mg / L or less, which are the drainage standard values. On the other hand, when returning the dehydrated separation liquid to the landing well 1, it is preferable to perform an operation to increase the removal rate of manganese and nickel in order to reduce the load of the water purification process as much as possible. The removal rate of these substances depends on the pH and SS concentration of the liquid to be treated, and high manganese and nickel removal can be achieved by adjusting the pH and SS concentration.

  The dewatered sludge from the dehydrator 6 can be used for agricultural land reduction or as a cement material by performing industrial waste disposal or drying treatment outside the field.

  The separated liquid separated in the settling tank 3 is introduced into the filtration device 4 through the line L2. The separated liquid is passed through the sand layer inside the filtration device 4 to obtain filtered water having a further reduced SS concentration. In addition, you may disinfect by adding chlorine with respect to the filtered water from a filtration apparatus.

  According to the water purification apparatus according to the present embodiment, it is possible to sufficiently efficiently remove manganese and the like contained in the separated sludge. That is, manganese and the like can be removed by an extremely simple process such as pH adjustment in the alkaline agent mixing tank 5 and solid-liquid separation process in the dehydrator 6.

  This embodiment has an advantage that the amount of the oxidizing agent used can be sufficiently reduced as compared with the conventional method. Compared with the case where the treated water mixed with the return water that has not undergone the removal treatment of manganese and the like is purified, according to the present embodiment, filtered water having a sufficiently reduced concentration of manganese and the like is obtained. It is because it can do.

  According to the water purification apparatus 10, the backwash waste water which arises by a backwash process can be reused, and the quantity of the waste_water | drain discharged | emitted out of the system from the said apparatus can be reduced.

  Moreover, since the wastewater tank 11 and the sludge concentration tank 12 which can raise SS density | concentration are provided, it is easy to adjust SS density | concentration of concentrated sludge to the value suitable for removal processes, such as manganese.

  Furthermore, the water purification apparatus 10 can mix the concentrated sludge and the dehydrating aid in the alkaline agent mixing tank 5. This makes it possible to achieve excellent dewaterability (high dewatering speed, high SS removal rate, low water content of dewatered sludge) in the dehydrator 6.

  As mentioned above, although embodiment of the water purification apparatus and method which concerns on this invention was described, it is not limited to the said embodiment, The following forms may be sufficient. For example, the flocculant mixing tank may be configured such that other chemicals can be added to the water to be treated together with the flocculant. Examples of other drugs include an antifoaming agent and a deodorizing agent. These drugs may be used alone or in combination of two or more. In the above embodiment, a mixing tank is adopted as a means for mixing the flocculant and the alkaline agent. However, the mixing tank is not limited as long as these drugs and liquid can be mixed. Absent.

  EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

<Purified water sludge treatment test>
(Example 1)
On January 24, 2006, sludge (hereinafter referred to as “purified water sludge”) was collected from a concentration tank of a water purification treatment facility (Rokuyo WTP). To this purified water sludge, MnSO ₄ · 5H ₂ O and NiSO ₄ · 6H ₂ O are added so that the Mn ²⁺ content per 1 kg of purified water sludge is 1000 mg and the Ni ²⁺ content is 100 mg. did. By containing a predetermined amount of these metal salts, water to be treated was prepared that simulates the contents of manganese and nickel when ferric chloride is used. In addition, to-be-processed water is the sludge in the reducing atmosphere which left still for 3 days or more. Table 1 shows the results of various measurements performed on purified water sludge and treated water. The DS concentration and VTS concentration in Table 1 indicate the soluble substance concentration and the volatile evaporation residue, respectively.

  200 ml of the water to be treated was transferred to another container, sodium hydroxide was added as an alkali agent to the container, and the mixture was stirred for 10 minutes, and the pH was adjusted so that the pH was 7.

  After the pH adjustment, the water to be treated was filtered to perform solid-liquid separation. A filter paper for fine precipitation (No. 5C) was used. The Mn, Ni, Al and Fe concentrations of the filtrate were measured using an ICP mass spectrometer. The measurement results are shown in Table 2.

(Example 2)
Except that the sodium hydroxide aqueous solution was added to 200 ml of water to be treated prepared in the same manner as the water to be treated used in Example 1 and stirred to adjust the pH so that the pH was 8. The treated water was treated in the same manner as in Example 1. The measurement results are shown in Table 2.

(Example 3)
Except that the sodium hydroxide aqueous solution was added to 200 ml of the water to be treated prepared in the same manner as the water to be treated used in Example 1 and stirred to adjust the pH so that the pH became 9. The treated water was treated in the same manner as in Example 1. The measurement results are shown in Table 2.

Example 4
Except that the sodium hydroxide aqueous solution was added to 200 ml of water to be treated prepared in the same manner as the water to be treated used in Example 1 and stirred to adjust the pH so that the pH became 10. The treated water was treated in the same manner as in Example 1. The measurement results are shown in Table 2.

(Example 5)
Except that the aqueous solution of sodium hydroxide was added to 200 ml of water to be treated prepared in the same manner as the water to be treated used in Example 1 and stirred to adjust the pH so that the pH was 11. The treated water was treated in the same manner as in Example 1. The measurement results are shown in Table 2.

(Comparative Example 1)
The treated water was treated in the same manner as in Example 1 except that 200 ml of treated water prepared in the same manner as the treated water used in Example 1 was filtered without adjusting the pH. Table 3 shows the measurement results.

(Comparative Example 2)
Example 1 except that sulfuric acid was added to 200 ml of water to be treated prepared in the same manner as the water to be treated used in Example 1 and the mixture was stirred to adjust the pH to 6. The treated water was treated in the same manner. Table 3 shows the measurement results.

(Comparative Example 3)
Example 1 except that sulfuric acid was added to 200 ml of water to be treated prepared in the same manner as the water to be treated used in Example 1, and the pH was adjusted so that the pH became 5. The treated water was treated in the same manner. Table 3 shows the measurement results. The measurement results are shown in Table 2.

(Comparative Example 4)
Except that sulfuric acid was added to 200 ml of water to be treated prepared in the same manner as the water to be treated used in Example 1, and the pH was adjusted so that the pH became 4, Example 1 The treated water was treated in the same manner. Table 3 shows the measurement results. The measurement results are shown in Table 2.

<Purified water sludge treatment test (with aeration treatment)>
(Examples 6 to 10 and Comparative Examples 5 to 8)
In order to investigate the influence of the difference in the oxidation state of the substances contained in the water to be treated, the water to be treated was subjected to aeration treatment for 12 hours before adjusting the pH of the water to be treated with sodium hydroxide or sulfuric acid. The treated water was treated in the same manner as in Examples 1 to 5 and Comparative Examples 1 to 4 except that the aeration treatment was performed. Water to be treated before the aeration treatment was prepared by the same method as in Example 1 above. In addition, the example which added the aeration process to the process in Examples 1-5 and Comparative Examples 1-4 corresponds to Examples 6-10 and Comparative Examples 5-8, respectively.

<Dehydration aid addition test>
Removal treatment of manganese and the like contained in water to be treated to which polyaluminum chloride (PAC) and ferric chloride (FeCl ₃ ), which are representative dehydration aids, were added. The purpose of this test is to confirm the influence of the dehydration auxiliary component for improving the dehydration property.

Specifically, the dewatering aid was added as described below, and the purified water sludge treatment test was performed. That is, each treatment was performed in the same manner as in the above-described purified water sludge treatment test (without aeration treatment) except that PAC or FeCl ₃ was used as a dehydration aid and a predetermined amount thereof was added to the water to be treated. Incidentally, the addition of PAC, or FeCl ₃ so that the TS material 1kg per 10g of the water to be treated before dewatering aid added.

  The results of the water purification sludge treatment test (without aeration treatment) and the dehydration aid addition test are shown in graphs in FIGS. 2 to 5 are graphs in which the pH of the water to be treated is plotted on the horizontal axis and the Mn, Ni, Al, and Fe concentrations of the filtrate are plotted on the vertical axis.

It is a schematic block diagram which shows suitable embodiment of the water purification apparatus which concerns on this invention. It is a graph which shows the relationship between the manganese concentration of a filtrate, and pH of to-be-processed water. It is a graph which shows the relationship between the nickel concentration of a filtrate, and pH of to-be-processed water. It is a graph which shows the relationship between the aluminum concentration of a filtrate, and pH of to-be-processed water. It is a graph which shows the relationship between the iron concentration of a filtrate, and the pH of to-be-processed water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Water well, 2 ... Coagulant mixing tank (coagulant mixing means), 3 ... Precipitation tank (2nd solid-liquid separation means), 4 ... Filtration apparatus, 5 ... Alkaline agent mixing tank (pH adjustment means), 6 ... dehydrator (first solid-liquid separation means), L6 ... return line (return path), 10 ... water purification apparatus.

Claims (5)

A water purification apparatus that purifies treated water containing raw water taken from a water source selected from surface water and groundwater and containing at least one of manganese and nickel,
PH adjusting means for adjusting the pH of the water to be treated to be high by adding an alkali agent to the water to be treated;
First solid-liquid separation means for solid-liquid separation of the water to be treated to which the alkaline agent has been added;
The water purification apparatus characterized by comprising.   The water purification apparatus according to claim 1, further comprising a flocculant admixing means for adding a flocculant to the water to be treated upstream of the pH adjusting means and mixing them.   A configuration further comprising second solid-liquid separation means for solid-liquid separation of the water to be treated with the flocculant added thereto, wherein the separated sludge separated by the second solid-liquid separation means is supplied to the pH adjustment means. The water purification apparatus according to claim 2, wherein   The water purification apparatus according to claim 3, further comprising a return path for returning at least a part of the separated liquid from the first solid-liquid separation means to the upstream side of the water purification apparatus. A method for purifying treated water containing raw water taken from a water source selected from surface water and groundwater and containing at least one of manganese and nickel,
A pH adjusting step for increasing the pH of the water to be treated by adding an alkali agent to the water to be treated;
a solid-liquid separation step of subjecting the water to be treated after pH adjustment to a solid-liquid separation treatment;
A water purification method comprising:

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