JPH0576876A - Treatment of waste water containing fluorine and manganese - Google Patents

Abstract

PURPOSE:To reduce the concns. of fluorine and manganese dissolved in waste water to regulation standard values of waste water by subjecting acidic waste water having component ions such as a fluorine ion, a manganese ion or the like dissolved therein to neutralization treatment to obtain a precipitate and holding the pH of a mixed suspension to 8.5-10. CONSTITUTION:Acidic raw water to be treated, the emulsion of slaked lime prepared in a dissolving tank 2 and the high concn. suspension refluxed from a sedimentation tank 3 are mixed and stirred in a neutralization tank 1. The addition amount of the slaked lime emulsion is set to an amount neutralizing the raw water to be treated to adjust the pH thereof 8.5-10. Subsequently, the mixed suspension is introduced into a flocculation tank 5 and the backwashing liquid in a sand filter tank 6 is injected in the tank 5 and a polymeric flocculant is further added to the tank 5 to flocculate a precipitate. Thereafter, the suspension is introduced into the sedimentation tank 3 to settle and concentrate the flocculated precipitate and overflow water is discharged. Next, the overflow water of the sedimentation tank 3 is introduced into the sand filter tank 6 to be filtered. As a result, the concns. of fluorine and manganese in water to be treated respectively become waste water regulation standard values or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing fluorine and manganese by treating acidic wastewater (hereinafter referred to as treated raw water) in which fluorine, manganese and other metal ions are dissolved.

[0002]

2. Description of the Related Art There are cases where relatively high concentrations of ions such as fluorine and manganese are dissolved in wastewater discharged from mines. In this case, it is necessary to reduce the concentration of these ions by treating the wastewater. There is.

In such wastewater treatment, a method called neutralization treatment has been conventionally used. In this neutralization treatment, while adding slaked lime to the treated raw water to maintain the pH at 10 or more, aluminum sulfate is also used to produce a mixed precipitate of metal hydroxide and calcium fluoride, and a method such as filtration is used. By removing this mixed precipitate by using it, the concentration of fluorine and manganese dissolved in the discharged water is treated to be 8 mg / l and 1 mg / l or less, which are the drainage regulation standard values, respectively. A flow sheet diagram of the above conventional wastewater treatment method is shown in FIG.

Further, slaked lime is further added to a suspension containing a high-concentration precipitate obtained by adding slaked lime and aluminum sulphate to the treated raw water, and then mixed and stirred with the treated raw water to form a mixed suspension. A method called an HDS method for filtering this mixed suspension is also known. In the case of the HDS method, there is an advantage that fluorine is newly adsorbed on the surface of the precipitate particles by subjecting the precipitate to the alkali treatment again.

Further, as a method for treating manganese-containing wastewater by applying the neutralization treatment, there is a method disclosed in Japanese Patent Publication No. 61-156. This is a mixture of a neutralizing agent such as limestone and manganese to obtain a combined body of both, which is added to the treated raw water to form a mixed suspension of the combined body and manganese in the treated raw water, The mixed suspension is filtered.

[0006]

However, in the above-mentioned neutralization treatment method, since the mixed precipitate of metal hydroxide and calcium fluoride produced is extremely fine, it is difficult to concentrate by sedimentation consolidation, and However, there is a problem that the dehydration treatment is difficult because the viscosity of the precipitate is high.

On the other hand, in the HDS method, the suspension concentrated to a high concentration by sedimentation is refluxed to the treated raw water,
In the case where the neutralization treatment is further performed, the pH in the neutralization treatment step is set to 8 in order to keep both the concentrations of fluorine and manganese dissolved in the discharged water below the drainage regulation standard value without adding aluminum sulfate. It should be maintained in the range of 0.5 to 10.

[0008] However, in the neutralization treatment by the HDS method, since slaked lime is added to the suspension of high-concentration precipitate, the suspension becomes highly alkaline with a pH of about 10.5, and the high-concentration precipitate There is a problem that part of the calcium fluoride contained in the solution is redissolved and the concentration of fluorine ions in the suspension increases. As a result, even in the neutralization reaction of the mixed suspension, it is extremely difficult to fix these fluorine ions as calcium fluoride, and the addition of aluminum sulfate or the treatment with activated carbon is indispensable, which causes an increase in running cost. It was It was also difficult to concentrate the precipitate by settling consolidation.

Further, when the amount of slaked lime added to the treated raw water is reduced and the pH of the suspension is lowered, the precipitation of fluorine becomes relatively easy, but manganese forms a precipitate. There was a problem that it would stop.

In addition, in the method of adding the combination of manganese and the neutralizing agent to the raw water for treatment, it is necessary to add manganese to the neutralizing agent in advance. There was a problem that the processing efficiency was relatively low.

The present invention has been made in view of the above circumstances, and in the neutralization treatment of acidic wastewater in which component ions such as fluorine and manganese are dissolved, a precipitate having a high concentration and excellent in dehydration property is obtained, and the reaction is performed. An object of the present invention is to provide a wastewater treatment method in which fluorine and manganese under different treatment conditions are treated under the above-mentioned pH conditions so that the concentrations of fluorine and manganese dissolved in the discharged water are both below the regulation standard value on the wastewater. ..

[Means for Solving the Problems]

In order to solve the above problems, the method for treating wastewater containing fluorine and manganese according to the present invention comprises:

The waste water and the suspension produced in the following third step are mixed and stirred with slaked lime to form a mixed suspension, and a small amount of a coagulant is added to the mixed suspension produced in the first step. And a second step of condensing and concentrating the precipitate and discharging overflow water containing a small amount of the precipitate, and a third step of refluxing the precipitate concentrated in the second step to the wastewater, By introducing the overflow water discharged in the second step into a filter device to collect fine precipitates and discharging clear treated water, and by backwashing the filter device in the fourth step. In addition to the fifth step of refluxing the discharged fine precipitate to the wastewater,

The pH of the mixed suspension in the first step is maintained in the range of 8.5 to 10, and the mass of the precipitate refluxed in the third step and the fifth step is adjusted to the mass in the second step. It is characterized by being 50 times or more the mass of the generated precipitate.

[0015]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. Here, FIG. 1 is a flow sheet diagram of the waste water treatment method of the embodiment, and FIG. 2 is a system diagram of a waste water treatment apparatus corresponding to the flow sheet of FIG.

In the wastewater treatment method of this embodiment, first,
As the first step, in the neutralization tank 1, acidic treated raw water, an emulsion of slaked lime prepared in the dissolution tank 2, and a sedimentation tank 3
To the high-concentration suspension which is refluxed by the reflux pump 4 from above. The amount of the slaked lime emulsion added is an amount necessary for neutralizing the treated raw water to pH = 8.5 to 10.

Then, as a second step, the mixed suspension after the neutralization reaction treatment is introduced into the flocculation tank 5. And the following fourth
The suspension flowing out as a result of the backwashing of the sand filter tank 6 in the step is injected, and a small amount of the polymer coagulant is further added, and the mixture is slowly stirred to coagulate the precipitate in the suspension. After that, the suspension is introduced into the settling tank 3 to settle and concentrate the aggregated precipitate, and the overflow water containing a small amount of partially fined precipitate is discharged.

Further, as a third step, a high-concentration suspension of the precipitate concentrated in the settling tank 3 is continuously withdrawn from the bottom of the settling tank 3 and is recirculated to the neutralization tank 1 using a reflux pump 4. .. Since this high-concentration suspension has a concentration of 60 to 80 g / l even when the neutralization treatment step is in a steady state, it can be easily sent by an ordinary slurry pump.

Then, in the fourth step, the waste water overflowed from the settling tank 3 is introduced into the sand filter tank 6 and filtered, and if necessary, diluted sulfuric acid is added to adjust the pH range to 7-8. Perform neutralization treatment. As a result, the concentrations of fluorine and manganese in the treated water are 8 mg / l or less of fluorine and 1 mg / l or less of manganese, which are the wastewater regulation standard values, respectively.
The treated water is temporarily stored in the filtered water tank 7 and then discharged.

On the other hand, in the fifth step, the fine precipitate solid-liquid separated and washed in the sand filter tank 6 is backwashed with the treated water in the filtered water tank 7 at a fixed time, and the backwash water is pumped by the pump 8. It is introduced into the flocculation tank 5 and mixed with the suspension containing the precipitate flowing from the neutralization tank 1.

A part of the high-concentration suspension withdrawn from the bottom of the settling tank 3 is sequentially deposited in the deposition site 9 without being returned to the neutralization tank 1. Then, it is appropriately dried in that state, or dehydrated by a dehydrator (not shown) and then discarded.

In the wastewater treatment method of the above embodiment, the method shown in FIG.
In the conventional wastewater treatment equipment as shown in, a reflux pump for refluxing the high-concentration suspension from the sedimentation tank to the neutralization tank, and a sand filtration tank for filtering the overflow water of the sedimentation tank containing fine precipitates. The wastewater can be treated by simply installing a pump for injecting the backwashing water containing the precipitate after the backwashing into the flocculation reaction tank.

[Experimental Example] Next, an experimental example will be shown to describe the effect of the present invention. Under the condition that the treatment according to the present invention is constantly maintained, treated raw water of the same water quality was treated by the following two methods, and the results were compared.

(1) Treatment Method of Comparative Example A fixed amount of aluminum sulfate was added to the treated raw water, which was further mixed with a slaked lime solution and stirred in a neutralization tank for a certain period of time.
An aggregating agent was added to the suspension containing the precipitate to carry out an aggregating reaction. Further, after solid-liquid separation was performed in the settling tank, the residual precipitate precipitate was extracted from the bottom of the settling tank and sent to the sediment. On the other hand, the overflow water from the settling tank was added with diluted sulfuric acid as needed, neutralized until it was within a predetermined pH range, and then discharged.

As a result, the sediment produced in the treatment of these wastewaters had a low concentration and it was extremely difficult to increase the concentration by compression sedimentation in the sedimentation tank, and the maximum was about 10 g / l. In addition, it is quite difficult to reduce the dissolved components in the overflow water to fluorine 8 mg / l or less and Mn 1 mg / l or less in spite of adding a sulfuric acid band to the treated raw water and adjusting the set pH of the neutralization tank. It was a situation with. Therefore, in this method, it was necessary to perform further treatment in order to keep the concentrations of fluorine and manganese below the above-mentioned reference values. In the same method, when aluminum sulfate was not used together, the fluorine concentration in the overflow water tended to increase considerably.

(2) Treatment Method of Example A fixed amount of sedimentation tank concentrated sediment suspension is added to the treated raw water and mixed with the slaked lime solution and stirred in the neutralization tank for a certain period of time. The suspension containing the liquid was subjected to a flocculation reaction in a flocculation tank, solid-liquid separation was further performed in the sedimentation tank, and the residual precipitate was sent again to the neutralization tank.

On the other hand, the waste water overflowed from the settling tank was introduced into a sand filter tank, filtered, and if necessary, diluted sulfuric acid was added to neutralize the solution until the pH was within a predetermined range and then discharged.

As a result, the overflow water contained a suspension containing a small amount of fine precipitates, but as a result of filtration treatment with a sand filtration tank, the dissolved component of the filtration water was 8 mg of fluorine.
/ L and manganese 1 mg / l were below the standard values.
Further, the concentration of the residual precipitate obtained by solid-liquid separation in the settling tank increased to 70 g / l, and its dehydrating property was also very good.

The water quality of the treated raw water used in the experiments (1) and (2) is shown in Table 1, the experimental conditions and the measurement results of (1) are shown in Table 2, and the experimental conditions and the measurement results of (2). Are shown in Table 2, respectively.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

Here, the unit of the concentration of the concentrated precipitate added to the treated raw water is g / l, and the flow ratio of the added concentrated precipitate and the addition ratio of the concentrated precipitate to the treated raw water are based on the following formulas, respectively. Calculated.

[0034]

[0035]

As can be seen from the above experimental results, according to this example, both fluorine and manganese can be neutralized, and the dissolved components in the discharged water can be removed without using aluminum sulfate. It was possible to reduce the target values of fluorine to 8 mg / l or less and manganese to 1 mg / l or less. Furthermore, the concentration of the concentrated precipitate after the sedimentation treatment is 70-80 g /
l, which is significantly higher than the conventional processing method,
The dewatering property was also good, and it was confirmed that it was effective in reducing the volume of sludge due to the decrease in cake water content.

[0037]

As described above, according to the present invention, the concentration of fluorine and manganese dissolved in the discharged water are both the drainage regulation standard values in the neutralization treatment of the acidic wastewater in which the component ions such as fluorine and manganese are dissolved. It is possible to make the following, and further, the removed fluorine and manganese can be obtained as a precipitate having a high concentration and excellent dehydration property. Moreover, since it is not necessary to use aluminum sulfate in the treatment, the running cost is reduced, and since it is an invention that can be realized by simply modifying the conventional neutralization treatment facility, it is also effective in reducing the capital investment. is there.

[Brief description of drawings]

FIG. 1 is a flow sheet diagram of a first embodiment of a wastewater treatment method of the present invention.

FIG. 2 is a system diagram of a wastewater treatment device corresponding to the flow sheet of FIG.

FIG. 3 is a flow sheet diagram of a conventional wastewater treatment method.

[Explanation of symbols]

 1 Neutralization tank 2 Dissolution tank 3 Settling tank 4 Reflux pump 5 Coagulation tank 6 Sand filtration tank 7 Filtration water tank 8 Pump 9 Sedimentation site

Claims (3)

[Claims] 1. Emission by adding slaked lime to an alkaline wastewater containing fluorine, manganese, and other metal ions to make it alkaline and separating a mixed precipitate of metal hydroxide and calcium fluoride to be produced. A method for treating wastewater containing fluorine and manganese, which maintains fluorine and manganese in water at a predetermined concentration or less, wherein the wastewater and the suspension produced in the third step below are mixed and stirred with slaked lime to form a mixed suspension. A first step, and a second step of adding a small amount of a coagulant to the mixed suspension produced in the first step, concentrating the precipitate by sedimentation and discharging overflow water containing a small amount of the precipitate, A third step of refluxing the precipitate concentrated in the second step to the wastewater, and the overflow water discharged in the second step are introduced into a filtering device to collect fine precipitates and clarify Discharge treated water A method for treating wastewater containing fluorine and manganese, comprising: a fourth step, and a fifth step, in which the fine precipitate discharged by backwashing the filtration device in the fourth step is returned to the wastewater. .. 2. The pH of the mixed suspension in the first step
The method for treating wastewater containing fluorine and manganese according to claim 1, characterized in that the water content is maintained in the range of 8.5 to 10. 3. The mass of the precipitate refluxed in the third step and the fifth step is 50 times or more the mass of the precipitate generated in the second step. A method for treating wastewater containing fluorine and manganese described in the above.