JP2022159814A - Method and apparatus for treating manganese-containing water - Google Patents

Abstract

To provide a method and an apparatus for treating manganese-containing water capable of efficiently removing manganese ions from water to be treated.SOLUTION: A method for treating manganese-containing water that includes a step in which manganese-containing water to be treated is introduced into a reaction tank in which sludge that contains active manganese oxide is present, and reacted with manganese ions to obtain inactive manganese oxide; a step in which the inactive manganese oxide-containing sludge is subjected to flocculation treatment by introducing the sludge into a flocculation tank to which a flocculant is added; a step in which the flocculated sludge is subjected to sedimentation and separation by introducing it into a sedimentation tank to obtain treated water; a step in which a part of the separated sludge is introduced into a manganese regeneration tank to oxidize the inactive manganese oxide in the sludge; and a step in which the oxidized sludge is returned to the reaction tank, wherein the oxidation of the inactive manganese oxide is performed by aeration in the manganese regeneration tank.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for treating manganese-containing water, and more particularly to a method and apparatus for treating manganese-containing water capable of efficiently removing manganese ions.

Manganese is abundantly present on the earth, and representative water sources containing manganese are surface water, groundwater, and pit drainage. A water source containing manganese ions in the water to be treated causes various problems. When manganese ions are contained in the surface water, the manganese ions are oxidized to manganese dioxide in the process of transporting the water to be treated through piping. Once converted to manganese dioxide, manganese dioxide serves as an oxidation catalyst for manganese ions, which promotes the oxidation of manganese ions, deposits as scale in the piping, and clogs the piping. Manganese ions are oxidized to manganese dioxide by oxygen in the air or microorganisms when manganese ions are present in surface water or when manganese-containing water to be treated is discharged into the environment. Since manganese dioxide is black, the riverbed becomes black.

As a method for removing manganese ions from water to be treated, a contact filtration method, a coagulation sedimentation method, and the like are performed.

In the contact filtration method, water to be treated containing manganese ions is passed through a contact filtration tower filled with manganese sand, and an oxidizing agent (hypochlorous acid, etc.) is added to cause a catalytic reaction on the surface of the manganese sand. Manganese ions are continuously oxidized, and solid-liquid separation is performed in the filtration tower.

In the coagulation-sedimentation method, by setting the pH at the time of treatment to a high alkaline range, manganese ions are insolubilized as manganese hydroxide, or an inorganic coagulant such as ferric chloride is added to produce iron hydroxide. Manganese ions are adsorbed on it to make it insoluble, and the insolubilized matter is removed by solid-liquid separation in a sedimentation tank.

Patent Document 1 describes a method of adding manganese dioxide powder to waste water containing heavy metals such as manganese, stirring in a neutral region, adsorbing heavy metal ions such as manganese ions to manganese dioxide, and then sedimentation and separation. there is In this patent document 1, after sedimentation and separation, the sludge containing manganese dioxide adsorbed with bivalent manganese ions is adjusted to about pH 7.0 with an alkaline agent such as slaked lime, and then strongly stirred and oxidized with air to obtain the sludge containing manganese dioxide. and to reuse it as the manganese dioxide powder.

JP-A-62-53789

In the above contact filtration method, chlorine-based oxidizing agents such as hypochlorous acid and bleaching powder are generally used to treat manganese. It is not easy from the aspect of operation management. In addition, since manganese ions in the water to be treated are oxidized and deposited on the surface of the manganese sand, the gaps between the filter media in the contact filtration tower become smaller and clogged, making water flow impossible. Therefore, it is necessary to periodically replace the manganese sand in the contact filtration tower, which becomes a burden of maintenance. In addition, if the water to be treated contains high concentrations of turbidity and iron, a coagulating sedimentation treatment or pressure flotation treatment to remove the turbidity components is required in the previous stage, making the treatment system large and complicated. .

In order to treat manganese ions by the coagulation sedimentation method, the pH of the treated water is adjusted to 10 or higher with an alkaline agent. Slaked lime, which is generally inexpensive, is used as this alkaline agent. Therefore, when the water to be treated contains carbonate ions or sulfate ions, calcium carbonate or calcium sulfate precipitates, increasing the amount of sludge generated. As a result, the cost of disposing of the sludge as industrial waste increases, resulting in a significant increase in running costs. In addition, in the coagulation sedimentation method, after solid-liquid separation in the sedimentation tank, it is necessary to lower the pH of the wastewater to a neutral range, and it is necessary to permanently install an acid addition facility such as sulfuric acid or hydrochloric acid and a neutralization tank.

In the method of Patent Document 1, the precipitated manganese dioxide-containing sludge is recovered, neutralized with slaked lime at around pH 7, and then vigorously stirred to oxidize the divalent manganese ions. Strong stirring in a neutral region) does not sufficiently oxidize divalent manganese ions, resulting in inferior manganese ion removal efficiency in waste water.

An object of the present invention is to provide a method and apparatus for treating manganese-containing water that can efficiently remove manganese ions in the water to be treated.

In the present invention, MnO ₂ .H ₂ O is called active manganese oxide, and MnO ₂ .MnO.H ₂ O is called inactive manganese oxide.

In the method for treating manganese-containing water of the present invention, manganese ion-containing water to be treated is introduced into a reaction tank in which active manganese oxide-containing sludge is present, reacted with manganese ions to obtain inert manganese oxide, and then The sludge containing the inert manganese oxide is introduced into a flocculation tank in which a flocculant is added to flocculate, and then the flocculated sludge is introduced into a sedimentation tank and sedimentation is separated to obtain treated water, and the sludge is separated. In a water treatment method in which part of sludge is introduced into a manganese regeneration tank to oxidize inert manganese oxides in the sludge and the oxidized sludge is returned to the reaction tank, aeration is performed in the manganese regeneration tank. characterized by oxidizing inert manganese oxide by

The manganese-containing water treatment apparatus of the present invention is a reaction tank in which active manganese oxide-containing sludge is present. A reaction tank for generating active manganese oxide and a means for adding a flocculating agent. A part of the sludge is introduced, the sedimentation tank for sedimentation and separation of the flocculated sludge to separate the treated water and sludge, and an aeration means for oxidizing the inert manganese oxide in the sludge are provided. It has a manganese regeneration tank into which part of the sludge separated in the sedimentation tank is introduced, and return means for returning the sludge oxidized in the manganese regeneration tank to the reaction tank.

In one aspect of the present invention, the pH of the manganese regeneration tank is 9 or higher.

In one aspect of the present invention, the manganese regeneration tank has a hydraulic retention time of 30 minutes or longer.

In one aspect of the present invention, the manganese regeneration tank has a DO concentration of 1 mg/L or more.

In one aspect of the present invention, the return sludge flow rate and/or the treated water flow rate are such that the ratio of the treated water flow rate to the returned sludge flow rate in the reaction tank (treated water flow rate/returned sludge flow rate) is 2 to 50 to adjust.

In one aspect of the present invention, an inorganic flocculant is added to the reaction vessel.

In one aspect of the present invention, the ratio R of the manganese oxide load in the sludge to the manganese load in the water to be treated in the reaction tank is 10 (g-Mn/g-Mn) or more.

In the present invention, divalent manganese ions in the water to be treated react with active manganese oxides according to the following formula (1) to form inactive manganese oxides.
_Mn2 ^{++ MnO2.H2O→MnO2.MnO.H2O+2H+} _{( 1 )}

In the present invention, water to be treated containing manganese ions and sludge containing active manganese oxides are brought into contact with each other in a reaction tank to cause the active manganese oxides to adsorb divalent manganese ions. After that, flocs are coarsened by adding a polymer flocculant in a flocculation tank, and sludge containing manganese oxide is sedimented, separated and recovered in a sedimentation tank. The recovered manganese oxide is oxidized by aeration with an oxygen-containing gas in a manganese regeneration tank without using chemicals such as oxidizing agents.

The present invention oxidizes MnO in inert manganese oxide by aeration in the manganese regeneration tank in this way, and does not require oxidizing agents such as chlorine. There is no need to do so, and operation management is easier than with conventional processing.

In addition, the reaction tank and the coagulation tank can be treated in a neutral region, and there is no need for acid and alkali addition equipment and pH adjustment tanks in the latter stage, so space can be saved and economically. Operation cost and equipment cost of water treatment equipment can be reduced. INDUSTRIAL APPLICABILITY The present invention can stably remove manganese ions in water to be treated while having the above effects.

1 is a flow showing a method for treating manganese-containing water according to an embodiment.

An embodiment of the present invention will be described based on the drawings. In addition, these embodiments show an example, and do not limit the present invention.

FIG. 1 is a flow showing a method for treating manganese-containing water according to an embodiment, in which a reaction tank 1, a coagulation tank 2, a sedimentation tank 3, and a manganese regeneration tank 4 are installed. The reaction tank 1 is provided with an inorganic flocculant adding means 6, an alkali adding means 8b and an acid agent adding means 9 as means for adding a pH adjuster. The flocculation tank 2 is provided with means 7 for adding a polymer flocculant.

The manganese regeneration tank 4 is provided with an air diffuser 5 and an alkali agent addition means 8a. A transfer pipe for the alkaline agent is branched into 8a and 8b.

The water to be treated contains manganese ions Mn ²⁺ and is exemplified by, but not limited to, surface water, groundwater, and mine drainage.

To the reaction tank 1, water to be treated containing manganese ions is introduced, and sludge containing solid active manganese oxide regenerated in the manganese regeneration tank 4 is introduced through the pipe 11, and the pH is 6 or more. are contact-mixed in a neutral to low alkaline range, and manganese ions are adsorbed on the active manganese oxide. The pH of the reaction tank is preferably about pH 7 to 10 (particularly pH 8 to 9), since a higher pH is better from the viewpoint of removing manganese ions. The chemical reaction formula for this reaction is as shown in formula (1) above. The inert manganese oxide produced by the reaction does not adsorb manganese ions.

For adjusting the pH in the reaction tank 1, sodium hydroxide or slaked lime can be used as an alkaline agent, and hydrochloric acid or sulfuric acid can be used as an acid agent. These are supplied as aqueous solutions or slurries.

By adding inorganic flocculants such as iron salts such as ferric chloride and ferric sulfate polysulfate, and aluminum salts such as polyaluminum chloride and aluminum sulfate to the reaction tank 1, fine manganese oxides are charged. Summation is performed, and recovery of manganese oxides in the sedimentation tank 3 is facilitated. When the water to be treated contains heavy metal ions other than manganese, it is preferable to use an iron-based inorganic coagulant such as ferric chloride or ferric polysulfate as the inorganic coagulant.

It is preferable to adjust the return sludge flow rate and/or the treated water flow rate so that the ratio of the treated water flow rate to the returned sludge flow rate to the reaction tank 1 (treated water flow rate/returned sludge flow rate) is 2 to 50. .

The manganese oxide concentration in the reaction tank 1 is preferably 20-4,000 mg-Mg/L, particularly 50-300 mg-Mg/L. When the ratio of the manganese load derived from the return sludge to the manganese load of the water to be treated is R, R is 10 g-Mn/g-Mn or more, particularly 20 g-Mn/g-Mn or more, for example 20 to 100 g-Mn/g-Mn. is preferred.

A reaction treatment liquid containing inert manganese oxides adsorbed with manganese ions flows from a reaction tank 1 into a flocculation tank 2 and is added with a polymer flocculating agent to coarsen flocs of the inert manganese oxides. become The amount of polymer flocculant added is preferably 1 mg/L to 10 mg/L. The type of polymer flocculant is preferably an anionic polymer flocculant, but is not limited to this, and a cationic or nonionic polymer flocculant may be used.

The coagulation treatment liquid containing coarsened inert manganese oxides is introduced to the sedimentation tank 3, where it is sedimented and separated into sludge containing the inert manganese oxides and treated water. The separated treated water is discharged outside the tank, and is discharged outside the system as the final treated water after being subjected to subsequent filtration and the like. It is preferable that the manganese concentration of the treated water is 0.2 mg/L or less.

Part of the sludge containing inert manganese oxide deposited and concentrated in the sedimentation tank 3 is withdrawn from the lower part of the sedimentation tank 3, and part of it is discharged outside the system through the withdrawal pipe 10a as a surplus, and the remainder is sludge. It is transported to the manganese regeneration tank 4 through the return pipe 10b.

The manganese regeneration tank 4 has a tank volume that can ensure aeration by the air diffuser 5 for a long time (30 minutes or more in terms of hydraulic retention time).

In the manganese regeneration tank 4, the pH is preferably adjusted to 9 or more using an alkaline agent. The pH in the manganese regeneration tank 4 is preferably about 9-12, more preferably about 10-12. Alkali agents include sodium hydroxide and slaked lime, but if the water to be treated contains other heavy metal ions, it should be relatively soluble compared to sodium hydroxide in order to avoid dissolution of sludge due to a local pH rise. From the viewpoint of pH control, it is preferable to use slaked lime which is difficult to dissolve.

In the manganese regeneration tank 4, aeration is performed for a long time using an air diffuser 5 (air is supplied from a blower through an air diffuser pipe) as an oxygen dissolving means. Air aeration oxidizes the inactive manganese oxide that has adsorbed manganese ions to regenerate active manganese oxide. The DO concentration in the manganese regeneration tank 4 is preferably 1 mg/L or more, particularly 2 mg/L or more, for example 2 to 7.0 mg/L, and the hydraulic mean retention time (HRT) is 30 minutes or more, for example 30 to 60 minutes. is preferred.

The manganese oxide concentration in the manganese regeneration tank 4 is preferably 1,000 to 20,000 mg-Mn/L, particularly 1,000 to 4,000 mg-Mn/L.

The regenerated active manganese oxide is again introduced into the reaction tank 1 and adsorbs and removes manganese ions in the water to be treated. In this manner, manganese ions in the water to be treated can be stably removed at low cost.

In the present invention, since the manganese oxide-containing sludge is circulated, when the water to be treated contains other heavy metal ions or an inorganic flocculant such as ferric chloride is added, water excluding manganese oxides It is expected that the concentration of other precipitated sludge such as iron oxide will be improved, the water content of the sludge that is discharged outside the system will be reduced, and the sludge disposal cost will be reduced.

Manganese oxide is stored in the reaction tank 1 when the apparatus of the present invention is started up (started to operate). As the manganese oxide, naturally occurring manganese mud or commercially available manganese dioxide (first grade) can be used.

As the water to be treated, manganese sulfate was dissolved in pure water to prepare simulated waste water having a water temperature of 25° C., a pH of 7.0 to 7.5, and a manganese ion concentration of 2.5 mg/L. Manganese ions were continuously removed according to the processing flow shown in FIG.

The pH of the reaction tank 1 was set to 8.0, and the ratio of the manganese load in the returned sludge to the manganese load in the water to be treated was set to 40 (g-Mn/g-Mn). Iron (III) chloride was added to reaction tank 1 so as to be 50 mg/L. In the flocculation tank 2, an anionic polymer flocculant (“Cliff Rock” manufactured by Kurita Water Industries Ltd.) was added as a polymer flocculant so as to be 1 mg/L.Sulfuric acid and slaked lime were used as pH adjusters. The manganese concentration of the supernatant water was measured and taken as the treated water Mn concentration.

[Examples 1-1 to 1-5 (comparison of manganese regeneration tank pH)]
<Experimental conditions>
The pH of the manganese regeneration tank 4 was set to pH 9.0, 9.5, 10.0, 10.5, or 11.0, and the conditions other than pH were substantially the same as shown in Table 1, and experiments were conducted. rice field. Table 1 shows the measurement results of the treated water Mn concentration.

<Discussion>
As shown in Table 1, if the pH of the manganese regeneration tank is 9 or higher, the treated water Mn concentration is sufficiently reduced, and as the pH increases, the treated water Mn concentration decreases further. It was recognized that the values of the water Mn concentration became almost the same and leveled off a little.

[Examples 2-1 to 2-3 (comparison of average residence time in tank)]
<Experimental conditions>
In Examples 1-4, experiments were conducted under the same conditions other than the HRT, with the tank mean residence time (HRT) in the manganese regeneration tank 4 set at 40 minutes, 30 minutes, or 20 minutes. Table 2 shows the measurement results of the treated water Mn concentration.

<Discussion>
As the HRT of the manganese regeneration tank became shorter, the treated water tended to have a higher Mn concentration. There was no significant difference between 40 minutes and 30 minutes of HRT, but the Mn concentration in the treated water clearly deteriorated between 30 minutes and 20 minutes. From this, it was confirmed that the HRT of the manganese regeneration tank is preferably 30 minutes or more.

However, when comparing the quality of the treated water with that of Example 1, it was found that the pH of the treated water had a greater effect on manganese treatment than the HRT in the manganese regeneration tank.

[Examples 3-1 to 3-5 (comparison of manganese regeneration tank DO concentration)]
<Experimental conditions>
In Example 1-4, the DO concentration in the manganese regeneration tank was changed to 0.52, 1.05, 2.10, 3.90, or 7.20 mg/ The experiment was carried out under the same conditions except for the DO concentration. Nitrogen gas was sealed in the manganese regeneration tank 4 in order to suppress the dissolution of oxygen in the air from the liquid surface. Table 3 shows the measurement results of the treated water Mn concentration.

<Discussion>
As shown in Table 3, the Mn concentration in the treated water was higher under the DO concentration of 0.52 mg/L than under the DO concentration of 1.05 mg/L or higher. From this, it was confirmed that the operation with a DO concentration of 1 mg/L or more in the manganese regeneration tank is preferable.

[Examples 4-1 to 4-4 (comparison of 1 manganese load in reaction tank with respect to manganese load in treated water)]
<Experimental conditions>
In Example 1-4, the concentration of sludge in the sludge returned from the sedimentation tank to the manganese regeneration tank was changed, and the manganese concentration in the sludge introduced into the reaction tank 1 was changed to change the manganese concentration in the reaction tank 1. was changed in the range of 10 to 120 mg-Mg/L, the ratio R of the manganese load derived from the return sludge to the manganese load of the water to be treated was varied between 5, 10, 20 and 41. Conditions other than R were the same. Table 4 shows the measurement results of the Mn concentration in the treated water.

<Discussion>
As shown in Table 4, when R was 10 or more, the Mn concentration in the treated water was 0.2 mg/L or less, but when R was 5, the Mn concentration in the treated water did not become 0.2 mg/L or less. From this, it was found that it was necessary to feed manganese oxides into the reaction tank 1 more than necessary with respect to the raw water. It was found that R of 10 (g-Mn/g-Mn) or more is preferable for manganese removal.

REFERENCE SIGNS LIST 1 reaction tank 2 coagulation tank 3 sedimentation tank 4 regeneration tank 5 air diffuser

Claims (14)

Manganese ion-containing water to be treated is introduced into a reaction tank in which activated manganese oxide-containing sludge is present, reacted with manganese ions to obtain inert manganese oxides, and then introduced into a coagulation tank where a coagulant is added. Sludge containing inert manganese oxide is introduced and coagulated, then the coagulated sludge is introduced into a sedimentation tank and sedimentation is separated to obtain treated water, and part of the separated sludge is introduced into a manganese regeneration tank. and oxidizing the inert manganese oxide in the sludge, and returning the oxidized sludge to the reaction tank,
A method for treating manganese-containing water, comprising oxidizing inactive manganese oxides by aeration in the manganese regeneration tank. 2. The method for treating manganese-containing water according to claim 1, wherein the manganese regeneration tank has a pH of 9 or higher. 3. The method for treating manganese-containing water according to claim 1, wherein the manganese regeneration tank has a hydraulic retention time of 30 minutes or longer. The method for treating manganese-containing water according to any one of claims 1 to 3, wherein the manganese regeneration tank has a DO concentration of 1 mg/L or more. The return sludge flow rate and/or the treated water flow rate are adjusted so that the ratio of the treated water flow rate to the returned sludge flow rate in the reaction tank (treated water flow rate/returned sludge flow rate) is 2 to 50. 5. The method for treating manganese-containing water according to any one of 4. The method for treating manganese-containing water according to any one of claims 1 to 5, wherein an inorganic flocculant is added to the reaction tank. Manganese-containing water according to any one of claims 1 to 6, wherein the ratio R of the manganese oxide load in the sludge to the manganese load in the water to be treated in the reaction tank is 10 (g-Mn/g-Mn) or more. How to handle. a reaction tank containing sludge containing active manganese oxide, into which water to be treated containing manganese ions is introduced and in which active manganese oxides and manganese ions are reacted to form inactive manganese oxides;
A flocculation tank having a flocculant addition means, in which sludge containing inert manganese oxide is introduced from the reaction tank and flocculation treatment is performed;
A sedimentation tank for introducing a part of the flocculated sludge from the flocculation tank and sedimenting and separating the flocculated sludge into treated water and sludge;
a manganese regeneration tank equipped with aeration means for oxidizing inert manganese oxides in the sludge, into which part of the sludge separated in the sedimentation tank is introduced;
and a means for returning sludge oxidized in the manganese regeneration tank to the reaction tank. 9. The apparatus for treating manganese-containing water according to claim 8, wherein said manganese regeneration tank has pH adjusting means for adjusting the pH in said manganese regeneration tank to 9 or higher. 10. The apparatus for treating manganese-containing water according to claim 8 or 9, wherein said manganese regeneration tank has a hydraulic retention time of 30 minutes or more. 11. The apparatus for treating manganese-containing water according to any one of claims 8 to 10, wherein the manganese regeneration tank has a DO concentration of 1 mg/L or more. Flow rate adjusting means for adjusting the flow rate of the returned sludge and/or the flow rate of the water to be treated so that the ratio of the flow rate of the water to be treated to the flow rate of the returned sludge in the reaction tank (flow rate of treated water/flow rate of returned sludge) is 2 to 50. Manganese-containing water treatment equipment according to any one of claims 8 to 11. 13. The apparatus for treating manganese-containing water according to any one of claims 8 to 12, wherein said reaction tank has means for adding an inorganic coagulant. Manganese-containing water according to any one of claims 8 to 13, wherein the ratio R of the manganese oxide load in the sludge to the manganese load in the water to be treated in the reaction tank is 10 (g-Mn/g-Mn) or more. processing equipment.

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