JP4518893B2 - Wastewater treatment method and apparatus containing heavy metal - Google Patents

Description

  The present invention relates to a heavy metal-containing wastewater treatment method and apparatus for separating and recovering heavy metals from wastewater containing heavy metals containing at least ferrous iron.

Conventionally, heavy metals mainly composed of iron such as ferrous iron (Fe ²⁺ ) and containing many heavy metal components such as manganese (Mn), copper (Cu), zinc (Zn), aluminum (Al) and arsenic (As) There is known a method in which mine drainage as contained wastewater is neutralized using slaked lime (calcium hydroxide: Ca (OH) ₂ ) and agglomerates and precipitates hydroxides of these heavy metals (for example, Patent Documents 1 to 3). 3).

  In the method of coagulating and precipitating heavy metal hydroxide using these slaked lime, the heavy metal components in the mine drainage are neutralized and aerated in the neutralization tank using slaked lime, and the water of these heavy metals is removed. The oxide is settled and separated in a sedimentation tank to obtain clear treated water, and a part of the precipitate separated by precipitation in the sedimentation tank is returned to the neutralization tank to increase the concentration of the precipitate. Improving the dewaterability of sludge.

Furthermore, as a method for treating this type of mine drainage, magnesium hydroxide (Mg (OH) ₂ ) or magnesium oxide (MgO) is excessively added to the mine drain to neutralize it, and the magnesium hydroxide settles. A method of using it as an auxiliary agent is also known (for example, see Patent Document 4).
US Pat. No. 3,738,932 (page 1-3, FIG. 1) JP-A-3-137987 (page 3-5, Fig. 1-3) JP-A-4-176384 (page 3-5, Fig. 1) JP-A-60-22991 (page 2-3)

However, most of the mine drainage that exhibits acidity is sulfuric acid acidity. Therefore, when this mine drainage is neutralized with a calcium-based neutralizing agent such as slaked lime or calcium carbonate (CaCO ₃ ), ferric hydroxide (Fe (OH) ₃ ) or In addition to hydroxides of other heavy metals, gypsum (CaSO ₄ ) is generated by the reaction of sulfate ions (SO ₄ ²⁻ ) and calcium ions (Ca ²⁺ ). For this reason, a large amount of sludge generated in the mine drainage is discharged as waste. At this time, arsenic and silicon in the mine drain are also aggregated and precipitated.

  And as a method of solving this problem, when neutralizing mine drainage that exhibits acidity using a magnesium-based neutralizer such as magnesium hydroxide or magnesium oxide, heavy metals produced by this magnesium-based neutralizer Since most of the hydroxide is ferric hydroxide, the sedimentation and dehydration properties are poor. For this reason, it is necessary to add the magnesium hydroxide or calcium oxide excessively, or add a polymer flocculant or the like to improve the sedimentation property and dewaterability of the sludge. However, in this case, a large amount of sludge is generated, and maintenance costs related to chemicals such as magnesium hydroxide, calcium oxide, and polymer flocculant are increased. In particular, when the mine drainage contains arsenic, cadmium, lead, copper, or zinc which are harmful substances, it is necessary to bury sludge generated from the mine drainage in a management-type treatment plant or the like.

  Further, in the above-described solution, heavy metals such as iron, manganese, copper, zinc, and aluminum contained in the mine drainage are all precipitated and removed in the sludge without being separated. Therefore, in this case, there is no method other than discharging as a waste, and there is a problem that it is not easy to reuse as a metal resource.

  The present invention has been made in view of such points, and an object of the present invention is to provide a heavy metal-containing wastewater treatment method and apparatus capable of reducing the amount of sludge generated, separating and recovering heavy metals and reusing them as resources. To do.

請 Motomeko 1 heavy metal-containing wastewater treatment method according adjusts the pH of the heavy metal-containing wastewater containing heavy metals comprising at least a first iron 3 to 6, it causes insolubilize heavy metals in the heavy metal-containing waste water, Solid matter is solidified from the first pH adjustment step of oxidizing at least part of ferrous iron in the heavy metal-containing wastewater to ferric iron and the heavy metal-containing wastewater whose pH is adjusted in the first pH adjustment step. a first solid-liquid separation step of liquid separation, and the first solid-liquid aeration step of oxidizing by aerating the heavy metal-containing waste water the solid material is solid-liquid separated in the separation step, in this aeration step A second pH adjusting step for adjusting the pH of the aerated heavy metal-containing wastewater to 7 to 11 and generating sludge containing ferrite in the heavy metal-containing wastewater, and the second pH adjusting step PH is adjusted with A second solid-liquid separation step for solid-liquid separation of the sludge containing ferrite from the heavy metal-containing waste water, and at least a part of the sludge containing ferrite separated by solid-liquid separation in the second solid-liquid separation step A return step for returning to the heavy metal-containing wastewater in the second pH adjustment step, wherein the first pH adjustment step is performed by solid-liquid separation of the solid matter in the first solid-liquid separation step. The pH of the heavy metal-containing wastewater is adjusted so that the molar ratio of ferric iron and ferrous iron in the heavy metal-containing wastewater is 0.2 or more and 2.0 or less.

And so that the molar ratio of the ferric iron and the ferrous iron in the heavy metal containing waste water from which the solid matter was solid-liquid separated in the first solid-liquid separation step is 0.2 or more and 2.0 or less. When the pH of the heavy metal-containing wastewater containing heavy metal containing at least ferrous iron is adjusted to 3 or more and 6 or less and the heavy metal in the heavy metal-containing wastewater is insolubilized in the pH adjustment step of 1, the heavy metal in the heavy metal-containing wastewater Will not interfere with the formation of ferrite. At this time, at least a part of the ferrous iron in the heavy metal-containing wastewater is oxidized to ferric iron by adjusting the pH of the heavy metal-containing wastewater in the first pH adjusting step. In addition, solids are separated from the heavy metal-containing wastewater in the first solid-liquid separation step. Thereafter, the heavy metal-containing wastewater from which the solid is separated into solid and liquid is aerated in the aeration step and oxidized, and then the pH of the heavy metal-containing wastewater is adjusted to 7 to 11 in the second pH adjustment step. Thus, sludge containing ferrite is generated in the heavy metal-containing wastewater. Further, the sludge containing ferrite is solid-liquid separated from the heavy metal-containing wastewater as a second solid-liquid separation step, and at least a part of the sludge containing ferrite is returned to the heavy metal-containing wastewater of the second pH adjustment step. And return. As a result, by insolubilizing the heavy metal in the heavy metal-containing wastewater in the first pH adjustment step, it is possible to prevent the formation of ferrite by the heavy metal and to prevent the sludge containing the solid-liquid separated ferrite in the return step. By returning to the heavy metal-containing wastewater in the pH adjusting step 2, sludge containing ferrite is efficiently generated from the heavy metal-containing wastewater, and the amount of sludge containing ferrite from the heavy metal-containing wastewater can be reduced. Moreover, before producing | generating the sludge containing a ferrite in heavy metal containing waste_water | drain, the heavy metal in this heavy metal containing waste_water | drain can be removed as a solid-liquid substance. Therefore, the sludge generated in the second pH adjustment step can contain ferrite more efficiently, and the sludge does not contain heavy metals, so the ferrite in the sludge can be reused. .

Heavy metal-containing wastewater treatment method according to claim 2, wherein, in the heavy metal-containing wastewater treatment method of claim 1 Symbol placement, aging the ferrite heavy metal-containing waste water sludge was generated containing ferrite in the second pH adjustment step An aging step is provided, and the second solid-liquid separation step solid-liquid separates the sludge containing ferrite aged in the aging step from the heavy metal-containing wastewater.

And after aging the ferrite in the heavy metal containing wastewater in which the sludge was generated in the second pH adjusting step in the aging step, the sludge containing the ferrite in the heavy metal containing wastewater is used in the second solid-liquid separation step. To separate into solid and liquid. As a result, the concentration and dewaterability of the sludge containing ferrite in the heavy metal-containing wastewater can be improved, and the pH of the heavy metal-containing wastewater after solid-liquid separation of the sludge containing ferrite in the second solid-liquid separation step Stabilize.

Heavy metal-containing wastewater treatment method according to claim 3, in claim 1 or 2 containing heavy metals wastewater treatment method described before the first pH adjustment step, before adjusting the pH in the first pH adjustment step This comprises a sulfide separation step of precipitating heavy metals in the heavy metal-containing wastewater as sulfides.

  And since the heavy metal in the heavy metal containing waste water before adjusting pH in the 1st pH adjustment process is precipitated in the sulfide separation process as a sulfide, heavy metals that cannot be separated by simple neutralization can be removed in advance. For this reason, the heavy metal can be reused, and the sludge generated in the second pH adjustment step contains almost no heavy metal. Therefore, the ferrite in the sludge can be reused.

The heavy metal-containing wastewater treatment method according to claim 4 is the heavy metal-containing wastewater treatment method according to claim 3, wherein the sulfide separation step adjusts the pH of the heavy metal-containing wastewater to 2.0 or more and 3.5 or less. .

  Then, by adjusting the pH of the heavy metal-containing wastewater to 2.0 or more and 3.5 or less in the sulfide separation step, the heavy metal in the heavy metal-containing wastewater is more reliably precipitated as sulfide.

Heavy metal-containing wastewater treatment apparatus 請 Motomeko 5 described, by adjusting the pH of the heavy metal-containing wastewater containing heavy metals comprising at least a first iron 3 to 6, causes insolubilize heavy metals in the heavy metal-containing waste water, A first pH adjusting means for oxidizing at least a part of ferrous iron in the heavy metal-containing wastewater to ferric iron, and solid matter from the heavy metal-containing wastewater whose pH is adjusted by the first pH adjusting means are solidified. a first solid-liquid separation means for liquid separation, and the first solid-liquid aerating means for oxidized by aerating the heavy metal-containing waste water the solid material is a solid-liquid separation in the separation means, in said aeration means A second pH adjusting means for adjusting the pH of the aerated and oxidized heavy metal-containing waste water to 7 to 11 and generating sludge containing ferrite in the heavy metal-containing waste water; and the second pH adjusting means. PH is adjusted with And second solid-liquid separation means for solid-liquid separation of the sludge containing ferrite from the heavy metal-containing wastewater, and at least a part of the sludge containing ferrite separated by solid-liquid separation by the second solid-liquid separation means. Return means for returning to the heavy metal-containing wastewater whose pH is adjusted by the second pH adjusting means, wherein the first pH adjusting means is the solid matter by the first solid-liquid separation means. The pH of the heavy metal-containing wastewater is adjusted so that the molar ratio of ferric iron and ferrous iron in the heavy metal-containing wastewater separated by solid-liquid separation is 0.2 or more and 2.0 or less.

Then, the second ratio of ferric iron and ferrous iron in the heavy metal-containing wastewater from which the solid matter is solid-liquid separated by the first solid-liquid separation means is 0.2 to 2.0. When the pH of the heavy metal-containing wastewater containing heavy metal containing at least ferrous iron is adjusted to 3 or more and 6 or less by the pH adjusting means 1 and the heavy metal in the heavy metal-containing wastewater is insolubilized, the heavy metal in the heavy metal-containing wastewater Will not interfere with the formation of ferrite. At this time, at least part of the ferrous iron in the heavy metal-containing wastewater is oxidized to ferric iron by adjusting the pH of the heavy metal-containing wastewater by the first pH adjusting means. In addition, solids are separated from the heavy metal-containing wastewater by the first solid-liquid separation means. Thereafter, the heavy metal-containing wastewater from which the solid matter is separated into solid and liquid is oxidized by aeration means, and then the pH of the heavy metal-containing wastewater is adjusted to 7 to 11 by the second pH adjusting means. Then, sludge containing ferrite is generated in the heavy metal-containing wastewater. Further, the sludge containing ferrite is solid-liquid separated from the heavy metal-containing wastewater by the second solid-liquid separation means, and the pH of at least a part of the sludge containing ferrite is adjusted by the second pH adjusting means. Return to heavy metal containing wastewater by return means. As a result, by making the heavy metal in the heavy metal-containing wastewater insoluble by the first pH adjusting means, it is possible to prevent the formation of ferrite by the heavy metal and to prevent the sludge containing the solid-liquid separated ferrite from being returned by the return means. The sludge containing ferrite is efficiently generated from the heavy metal-containing wastewater by returning the wastewater to the heavy metal-containing wastewater whose pH is adjusted by the pH adjusting means of 2, and the amount of sludge containing ferrite from the heavy metal-containing wastewater is generated. Can be reduced. Moreover, before producing | generating the sludge containing a ferrite in heavy metal containing waste_water | drain, the heavy metal in this heavy metal containing waste_water | drain can be removed as a solid-liquid substance. Accordingly, ferrite can be more efficiently contained in the sludge generated by the second pH adjusting means, and heavy metals are not contained in the sludge, so that the ferrite in the sludge can be reused. .

The heavy metal-containing wastewater treatment apparatus according to claim 6 is the heavy metal-containing wastewater treatment apparatus according to claim 5, wherein the ferrite in the heavy metal-containing wastewater in which sludge containing ferrite is generated by the second pH adjusting means is aged. Means, and the second solid-liquid separation means separates the sludge containing the ferrite aged by the aging means from the heavy metal-containing wastewater.

  And after aging the ferrite in the heavy metal containing wastewater in which the sludge was generated by the second pH adjusting means by the aging means, the sludge containing the ferrite in the heavy metal containing wastewater is used as the second solid-liquid separation means. To separate into solid and liquid. As a result, the concentration and dewaterability of the sludge containing ferrite in the heavy metal-containing wastewater can be improved, and the pH of the heavy metal-containing wastewater after the sludge containing ferrite is solid-liquid separated by the second solid-liquid separation means. Stabilize.

Heavy metal-containing wastewater treatment apparatus according to claim 7, wherein, in the heavy metal-containing wastewater treatment apparatus according to claim 5 or 6, wherein, prior to the first pH-adjusting means, before adjusting the pH in the first pH-adjusting means This is equipped with a sulfide separation means for precipitating heavy metals in the wastewater containing heavy metals as sulfides.

  And since the heavy metal in the heavy metal containing waste water before adjusting pH by the 1st pH adjustment means is precipitated as a sulfide by a sulfide separation means, the heavy metal which cannot be fractionated by simple neutralization can be removed beforehand. For this reason, the heavy metal can be reused, and the sludge generated in the second pH adjustment step contains almost no heavy metal. Therefore, the ferrite in the sludge can be reused.

According to 請 Motomeko 1 heavy metal-containing wastewater treatment method described by insolubilizing the heavy metals in the heavy metal-containing waste water, from this to prevent interfere with the formation of ferrite by heavy metals, and solid-liquid separated from the heavy metal containing waste water sludge Is returned to the heavy metal-containing wastewater in the second pH adjustment step, so that sludge containing ferrite can be efficiently generated in the wastewater containing heavy metal, and the amount of sludge containing ferrite from the wastewater containing heavy metal is reduced. it can. Also , before generating sludge containing ferrite in wastewater containing heavy metal, it is possible to remove the heavy metal in wastewater containing heavy metal as a solid liquid, so that ferrite is more efficiently contained in the sludge produced in wastewater containing heavy metal. Since the sludge does not contain heavy metals, the ferrite in the sludge can be reused.

According to claim 2 containing heavy metals wastewater treatment method according, in addition to the effects of heavy metal-containing wastewater treatment method of claim 1, wherein, can improve concentrating property and dehydration property of sludge containing ferrite in heavy metal-containing waste water, the ferrite The pH of the heavy metal-containing wastewater after solid-liquid separation of the sludge containing slag in the second solid-liquid separation step is stabilized.

According to claim 3 heavy metal-containing wastewater treatment method according, in addition to the effects of heavy metal-containing wastewater treatment method according to claim 1 or 2 wherein the removal of heavy metals which can not be separated just neutralized in front of the first pH adjustment step Therefore, the heavy metal can be reused, and the sludge generated in the second pH adjustment step contains almost no heavy metal, so the ferrite in the sludge can be reused.

According to the heavy metal containing wastewater treatment method according to claim 4 , in addition to the effect of the heavy metal containing wastewater treatment method according to claim 3 , the pH of the heavy metal containing wastewater is set to 2.0 or more and 3.5 or less in the sulfide separation step. By adjusting, the heavy metal in heavy metal containing waste water can be more reliably precipitated as a sulfide.

According to the heavy metal-containing wastewater treatment apparatus of claim 5 , the heavy metal in the heavy metal-containing wastewater is insolubilized to prevent the formation of ferrite by the heavy metal, and then the sludge separated from the heavy metal-containing wastewater is solid-liquid separated. By returning to the heavy metal containing wastewater of the second pH adjusting means, sludge containing ferrite can be efficiently generated in the heavy metal containing wastewater, and the generation amount of sludge containing ferrite from the heavy metal containing wastewater can be reduced. . In addition, before generating ferrite in the heavy metal-containing wastewater, since the heavy metal in the heavy metal-containing wastewater can be removed as a solid matter, the sludge generated in the heavy metal-containing wastewater can contain ferrite more efficiently. Since this sludge does not contain heavy metals, the ferrite in this sludge can be reused.

According to the heavy metal-containing wastewater treatment device of claim 6, in addition to the effect of the heavy metal-containing wastewater treatment device of claim 5, the concentration and dewaterability of sludge containing ferrite in the heavy metal-containing wastewater can be improved. The pH of the heavy metal-containing wastewater after solid-liquid separation of the sludge containing slag in the second solid-liquid separation step is stabilized.

According to the heavy metal-containing wastewater treatment apparatus according to claim 7, in addition to the effects of heavy metal-containing wastewater treatment apparatus according to claim 5 or 6, wherein the removal of heavy metals which can not be separated just neutralized in front of the first pH-adjusting means Therefore, the heavy metal can be reused, and the sludge generated in the second pH adjustment step contains almost no heavy metal, so that the ferrite in the sludge can be reused.

  The configuration of the first embodiment of the heavy metal removing apparatus of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 1 denotes a heavy metal removing device as a heavy metal-containing wastewater treatment device, and this heavy metal removing device 1 is from treated raw water W that is heavy metal-containing wastewater as treated water such as mine wastewater, factory wastewater, anti-wastewater, etc. Remove heavy metal components. Here, this treated raw water W is a wastewater containing a heavy metal component mainly containing iron such as at least ferrous iron, that is, ferrous ions (Fe ²⁺ ), and exhibiting acidity. In addition to ferrous iron and ferric iron, that is, ferric ions (Fe ³⁺ ), this treated raw water W includes manganese (Mn), copper (Cu), zinc (Zn), aluminum (Al), silicon ( It is sulfuric acid (H ₂ SO ₄ ) acidic waste water in which heavy metal components such as Si), arsenic (As), and lead (Pb) are dissolved.

  And this heavy metal removal apparatus 1 is provided with the bottomed cylindrical raw | natural water storage tank 2 which is a raw | natural water tank as a raw | natural water tank in which predetermined amount of process raw | natural water W is stored. In this raw water storage tank 2, treated raw water W to be processed by the heavy metal removing device 1 is previously introduced and stored. Further, a raw water pump 3 as a pressure feeding means is attached to the downstream side of the raw water storage tank 2. The raw water pump 3 draws out the treated raw water W stored in the raw water storage tank 2 from the raw water storage tank 2 at a predetermined flow rate.

  Further, on the downstream side of the raw water storage tank 2, a bottomed cylindrical first aggregation tank 11 which is a magnesium oxide (MgO) aggregation tank is installed. Into the first flocculation tank 11, the treated raw water W drawn out from the raw water storage tank 2 by the raw water pump 3 flows, and a predetermined amount of the treated raw water W is stored. Specifically, the first flocculation tank 11 adjusts the pH of the treated raw water W stored in the first flocculated tank 11 and agglomerates heavy metals in the treated raw water W to insolubilize them. At the same time, at least a part of the ferrous iron in the treated raw water W is oxidized to ferric iron.

  The first flocculating tank 11 is supplied with an aqueous solution of magnesium oxide as an alkaline agent and added to the raw raw water W in the first flocculating tank 11 as a first pH adjusting means. An adjusting device 12 is attached. The first pH adjusting device 12 adjusts the pH of the treated raw water W in the first coagulation tank 11 to be acidic, that is, 3 or more and 6 or less, more preferably 3.5 or more and 6.0 or less. The first pH adjusting device 12 includes a bottomed cylindrical first storage tank 13 as a magnesium oxide storage tank in which a predetermined amount of magnesium oxide aqueous solution is filled and stored. The first storage tank 13 is provided with a first infusion pump 14 as pressure feeding means. The first injection pump 14 draws out the magnesium oxide aqueous solution in the first storage tank 13 and adds the magnesium oxide aqueous solution to the treated raw water W in the first coagulation tank 11.

  Further, the first injection pump 14 is provided with a first pH controller 15 that controls the driving of the first injection pump 14 to control the pH of the raw water W in the first coagulation tank 11. It has been. The first pH controller 15 includes a pH electrode (not shown), and an aqueous solution of magnesium oxide from the first storage tank 13 to the treated raw water W in the first coagulation tank 11 by the first injection pump 14. The amount of addition is adjusted.

  That is, the first pH control device 15 controls the driving of the first injection pump 14 based on the pH value of the raw water W in the first flocculation tank 11, and The amount of magnesium oxide aqueous solution added to the treated raw water W is adjusted. Specifically, the first pH control device 15 sets the pH of the treated raw water W to a predetermined value, that is, 3 to 6, preferably 3.5 to 6.0, more preferably 4.0 to 5.5. Adjust to:

  In other words, the first pH controller 15 is configured so that the molar ratio of ferrous iron to ferric iron in the treated raw water W in the first coagulation tank 11 is 0.1 or more and 2.0 or less. The pH of this treated raw water W is adjusted. Here, when the aluminum in the treated raw water W is 50 mg / l and the silicon is 35 mg / l, the first pH control device 15 has a molar ratio of ferrous and ferric iron (secondary (Iron ion / ferrous ion) is adjusted to 0.1 or more and 0.6 or less. Further, the first pH controller 15 adjusts the molar ratio of ferrous iron to ferric iron to 0.1 or more and 0.8 or less when the aluminum in the treated raw water W is 50 mg / l. To do.

  Furthermore, when the silicon in the treated raw water W is 35 mg / l, the first pH control device 15 sets the molar ratio of ferrous iron to ferric iron to 0.1 or more and 1.0 or less. . In addition, when the raw water W does not contain aluminum and silicon, the first pH control device 15 sets the molar ratio of ferrous iron to ferric iron to 0.2 or more and 2.0. Below.

That is, the first pH control device 15 corresponds to the amount of ions that hinder the generation of the sludge M containing ferrite in the treated raw water W, that is, aluminum ions (Al ³⁺ ) and silicon ions (Si ⁴⁺ ). And lowering the upper limit of the ratio of ferric ions. Therefore, the first pH control device 15 is configured so that the molar ratio of ferrous iron to ferric iron is 0.1 or more and 2.0 or less, depending on the concentrations of aluminum and silicon in the treated raw water W. Then, air or other oxidizing agent is added to oxidize some of the ferrous ions to ferric ions, thereby stabilizing the ferritization in the treated raw water W.

  Furthermore, a first air supply device 16 for supplying air to the raw raw water W in the first aggregation tank 11 is attached to the first aggregation tank 11. The first air supply device 16 is a stirring and aeration device that agitates the processing raw water W while aeration of the processing raw water W in the first coagulation tank 11. Further, the first air supply device 16 aspirates and oxidizes the treated raw water W by air in parallel with the pH adjustment of the treated raw water W in the first coagulation tank 11 by the first pH adjusting device 12. .

Next, on the downstream side of the first flocculation tank 11, a bottomed cylindrical second flocculation tank 21 that is a ferritization tank is disposed. The second raw coagulation tank 21 is supplied with treated raw water W, which is an outflow water flowing out from the first coagulating tank 11, and stores a predetermined amount of the treated raw water W. Specifically, the second flocculating tank 21 adjusts the pH of the treated raw water W in the second flocculating tank 21 to generate sludge M containing ferrite in the treated raw water W. Here, the ferrite is an unstable compound of a strong base such as sodium ferrite (NaFeO ₂ ) and iron oxide (Fe ₂ O ₃ ) present in an alkaline solution.

  The second flocculating tank 21 is supplied with an aqueous solution of sodium hydroxide (NaOH), which is a strong alkali agent, added to the treated raw water W in the second flocculating tank 21 as second pH adjusting means. The second pH adjusting device 22 is attached. The second pH adjusting device 22 adjusts the pH of the treated raw water W in the second flocculation tank 21 to be alkaline, that is, from 7 to 11.

  Further, the second pH adjusting device 22 includes a bottomed cylindrical second storage tank 23 as a sodium hydroxide storage tank in which a predetermined amount of an aqueous solution of sodium hydroxide is filled and stored. The second storage tank 23 is provided with a second infusion pump 24 as a pressure feeding means. The second injection pump 24 draws out the aqueous solution of sodium hydroxide in the second storage tank 23 and adds the aqueous solution of sodium hydroxide to the raw material water W in the second flocculation tank 21.

  Further, the second injection pump 24 is provided with a second pH controller 25 that controls the driving of the second injection pump 24 to control the pH of the raw water W in the second coagulation tank 21. It has been. The second pH control device 25 includes a pH electrode (not shown), and the sodium hydroxide is supplied from the second storage tank 23 to the treated raw water W in the second coagulation tank 21 by the second injection pump 24. Adjust the amount of aqueous solution added.

  That is, the second pH control device 25 controls the driving of the second injection pump 24 based on the pH value of the treated raw water W in the second flocculation tank 21, and The amount of sodium hydroxide aqueous solution added to the treated raw water W is adjusted. Specifically, the second pH control device 25 adjusts the pH of the treated raw water W to a predetermined value, that is, 7 or more and 11 or less, preferably 10.5.

  Further, a first agitation device 26 for agitating the raw water W in the second agglomeration tank 21 is attached to the second agglomeration tank 21. The first stirrer 26 includes a propeller 27 as a stirring blade immersed in the treated raw water W in the second flocculation tank 21. That is, the first stirring device 26 stirs the treated raw water W in the second flocculation tank 21 by immersing the propeller 27 in the treated raw water W and rotationally driving it.

Next, on the downstream side of the second aggregating tank 21, a bottomed cylindrical second sedimentation tank 31 which is a solid-liquid separation tank as a second solid-liquid separation means is installed. In this second settling tank 31, treated raw water W which is an outflow water flowing out from the second flocculating tank 21 is introduced, and a predetermined amount of this treated raw water W is stored. And the bottom part of this 2nd sedimentation tank 31 is provided with the funnel-shaped bottom face part 32 which is reverse cone shape. Here, the second sedimentation tank 31 separates the sludge M produced in the treated raw water W in the second flocculating tank 21 from the treated raw water W by solid-liquid separation.

Further, a sludge extraction port 33 for separating the sludge M containing ferrite precipitated in the second settling tank 31 from the raw water W into a solid and liquid is opened at the center portion of the bottom surface portion 32 projecting downward. Has been provided. The sludge extraction port 33 is a sludge that is a discharge means as a return means for returning at least a part of the sludge M extracted from the sludge extraction port 33 to the second flocculation tank 21 and discharging it out of the system. A return discharge device 34 is attached.

This sludge return discharge device 34 includes an elongated cylindrical sludge return pipe 35 whose upstream end is connected to a sludge extraction port 33. The downstream end of the sludge return pipe 35 is installed on the upstream side of the second flocculation tank 21. A return pump 36 is attached to the sludge return pipe 35 as pressure feeding means for pumping the sludge M drawn from the sludge withdrawal port 33 of the second sedimentation tank 31 through the sludge return pipe 35.

The return pump 36 is solid-liquid separated from the second sedimentation tank 31, and at least a portion of the sludge M is pulled out through the sludge return pipe 35 from the second sedimentation tank 31 of the sludge withdrawal port 33, the 2 is returned to the treated raw water W in the coagulation tank 21. Further, the upstream end of the slender cylindrical sludge discharge pipe 37 is connected to the upstream side of the sludge return pipe 35 with respect to the return pump 36. This sludge discharge pipe 37 is used to collect the remaining sludge M that has not been returned to the second flocculation tank 21 by the sludge return pipe 35 out of the sludge M drawn from the second sedimentation tank 31 through the sludge return pipe 35. Pull out and drain.

The sludge M discharged through the sludge discharge pipe 37 is sludge treated by a sludge treatment device (not shown), and the ferrite in the sludge M is reused. Further, the treated raw water W after the sludge M is solid-liquid separated in the second sedimentation tank 31 is treated water, and this treated water flows out from the second sedimentation tank 31 and is discharged to a river (not shown). To be released.

  Next, the waste water treatment method by the heavy metal removing apparatus of the first embodiment will be described.

  First, the treated raw water W stored in the raw water storage tank 2 is caused to flow out and stored in the first flocculation tank 11 by a raw water pump. In this state, as a first pH adjustment step, a predetermined amount of a magnesium oxide aqueous solution is added to the treated raw water W in the first flocculation tank 11 by the first pH adjusting device 12, and the treated raw water W is added. The pH is neutralized to 3 or more and 6 or less.

At this time, most of the aluminum in the treated raw water W in the first coagulation tank 11 aggregates and insolubilizes as sludge S, which is a solid substance of hydroxide, that is, aluminum hydroxide (Al (OH) ₃ ). In addition, about 50% of silicon in the treated raw water W is aggregated and insolubilized as sludge S which is a precipitate.

  At the same time, most of the iron content in the treated raw water W is present as ferrous ions. However, by adjusting the pH with the first pH adjusting device 12, the ferrous ions in the treated raw water W can be reduced. Oxidation to ferric ions proceeds, and some of the ferrous ions in the treated raw water W are present as ferric ions.

  Accordingly, in the first pH adjustment step, aluminum and silicon that prevent ferrite from being formed in the treated raw water W are insolubilized, and at the same time, oxidation of ferrous ions in the treated raw water W to ferric ions partially proceeds. To do.

  Subsequently, the processing raw water W that has flowed out from the first flocculation tank 11 is caused to flow into the second flocculation tank 21 to be stored. In this state, as a second pH adjustment step, a predetermined amount of an aqueous solution of sodium hydroxide is added to the treated raw water W in the second flocculating tank 21 by the second pH adjusting device 22, and the treated raw water W The pH is adjusted to 7 or more and 11 or less.

At this time, ferrite is generated by the reaction between ferrous ions and ferric ions in the raw water W in the second agglomeration tank 21. Specifically, in the presence of these ferrous ions and ferric ions, ferrite is generated by the reaction formula of Fe ²⁺ + 2Fe ³⁺ + 8OH ⁻ → Fe ₃ O ₄ + 4H ₂ O. Therefore, as shown in this reaction formula, the formation of ferrite proceeds at a ratio of 2 to 1 between ferric ions and ferrous ions.

  However, the raw material water W in the second flocculation tank 21 contains a substance that prevents ferritization such as aluminum and silicon. In this case, the ratio of ferric ions to ferrous ions changes, and as a condition for more efficiently generating ferrite, the amount of ferric ions in the treated raw water W may be reduced.

  Therefore, by adjusting the treatment raw water W in the first coagulation tank 11 to pH 3 or more and 6 or less in the first pH adjustment step, even if the amount of ferric ions present in the treatment raw water W is about The ferritization reaction in which ferrite is generated in the treated raw water W in the second agglomeration tank 21 is caused by the pH adjusting step 2.

Thereafter, the treated raw water W that has flowed out of the second flocculation tank 21 is caused to flow into the second settling tank 31. In this state, as the second solid-liquid separation step, the sludge M containing ferrite in the treated raw water W in the second sedimentation tank 31 is precipitated.

Then, as a return process, the return pump 36 is driven and the sludge M precipitated in the second settling tank 31 is separated from the sludge extraction port 33 by solid-liquid separation, and a part of the sludge M is returned to the sludge return pipe 35. To the treated raw water W in the second flocculation tank 21.

  As a result, ferrite crystals are present in the second agglomeration tank 21 from the beginning. For this reason, the ferrite crystal in the second agglomeration tank 21 serves as a nucleus, and the generation of ferrite in the second agglomeration tank 21 becomes more efficient.

  Further, the sludge M in the second flocculation tank 21 is aged by repeating the return of the sludge M in the return step, thereby allowing the settling and dehydrating properties of the sludge M generated in the second flocculation tank 21 to be improved. Each is improved.

  Thereafter, the sludge M discharged from the sludge discharge pipe 37 is sludge treated, and the ferrite in the sludge M is reused.

Further, the treated raw water W after the sludge M is solid-liquid separated in the second settling tank 31 is discharged from the second settling tank 31 as treated water and discharged to a river or the like.

  As described above, according to the first embodiment, the pH of the processing raw water W such as mine drainage is adjusted to 3 or more and 6 or less in the first coagulation tank 11 by the first pH adjusting device 12. . As a result, heavy metals such as aluminum and silicon that hinder the formation of ferrite in the treated raw water W are insolubilized as hydroxides and become sludge S. That is, by insolubilizing these heavy metals as hydroxides, the influence of ferrite formation interference by these heavy metals is reduced, so that the prevention of ferrite generation by these heavy metals can be prevented.

  At the same time, by adjusting the pH of the treated raw water W by the first pH adjusting device 12, some of the ferrous ions in the treated raw water W are oxidized to ferric ions. For this reason, the pH of this treated raw water W is adjusted to 7 or more and 11 or less in the second coagulation tank 21 by the second pH adjusting device 22. As a result, without generating heavy metal hydroxide in the treated raw water W as in the past, ferrous ions and ferric ions in the treated raw water W are used to generate ferrite in the treated raw water W. Can be generated.

Therefore, after insolubilizing the heavy metal that hinders the formation of ferrite in the treated raw water W, ferrite is produced in the treated raw water W. As a result, the generation of ferrite in the treated raw water W can be efficiently performed, and the amount of sludge M containing ferrite in the treated raw water W can be greatly reduced. At the same time, since the sedimentation and dewatering properties of the sludge M produced in the treated raw water W are improved, the solid-liquid separation of the sludge M containing ferrite from the treated raw water W in the second sedimentation tank 31 is performed. Can be more efficient.

Further, the sludge M containing ferrite in the treated raw water W is precipitated in the second settling tank 31, and the sludge M is drawn from the sludge drawing port 33 of the second settling tank 31 to be separated into solid and liquid. As a result, heavy metals mainly composed of iron and the like can be reliably removed from the treated raw water W with a simple configuration, and the ferrite contained in the sludge M can be recovered as a valuable material, so that the ferrite in the sludge M can be recovered. Industrial reuse becomes possible.

Further, the sludge M solid-liquid separated from the treated raw water W in the second sedimentation tank 31 is returned to the treated raw water W in the second flocculating tank 21 through the sludge return pipe 35. As a result, ferrite crystals can be present in the second agglomeration tank 21 from the beginning. For this reason, the ferrite crystals in the second agglomeration tank 21 generate ferrite more efficiently in the treated raw water W in the second agglomeration tank 21.

  Therefore, since the ferritization of the treated raw water W in the second flocculating tank 21 can be promoted, the generation of ferrite in the treated raw water W in the second flocculating tank 21 can be more efficiently performed with a simple configuration. . At the same time, ferrite crystals in the second agglomeration tank 21 can be aged, so that the sedimentation and dehydration properties of the ferrite can be improved.

  Further, the pH is adjusted by the first pH adjusting device 12, and the molar ratio of ferrous ions and ferric ions in the treated raw water W in the first coagulation tank 11 is 0.1 or more and 2.0. It was made to become the following. As a result, heavy metal components such as aluminum and silicon are insolubilized as hydroxides in the treated raw water W, and these heavy metal components efficiently become sludge S. Therefore, by generating sludge M containing ferrite in the treated raw water W from which these heavy metal components have been efficiently removed, it is possible to stabilize and promote the formation of ferrite by neutralization of iron ions in the treated raw water W. The amount of sludge M generated in the treated raw water W can be further reduced.

  As a result, the amount of sludge M generated can be reduced by 50% or more than the neutralization method using conventional slaked lime, and the amount of sludge M generated by 30% or more can be reduced compared with the neutralization method using magnesium oxide. . Furthermore, without adding a polymer flocculant or the like to the treated raw water W, it is possible to improve each of the sedimentation property and dewaterability of the sludge M generated in the treated raw water W.

  For this reason, the density | concentration of the amount of concentration sludge before dehydrating the sludge M solid-liquid-separated from this process raw | natural water W can be raised, and the generation amount of this sludge M can be reduced. Therefore, the number of dehydrators (not shown) for dewatering the sludge M and the power consumed by these dehydrators can be reduced. For this reason, the amount of work for dewatering the sludge M can be greatly reduced, and at the same time, the running cost of chemicals of the sludge M dewatering equipment can be greatly reduced.

Here, as an alkaline agent added to the raw water W in the first coagulation tank 11 by the first pH adjusting device 12, in addition to magnesium oxide, slaked lime (calcium hydroxide: Ca (OH) ₂ ), Calcium carbonate (CaCO ₃ ), sodium hydroxide (NaOH) and the like can also be used. However, when slaked lime or calcium carbonate is used as the alkaline agent, gypsum (CaSO ₄ ) is produced in the treated raw water W, and therefore the sludge M produced in the treated raw water W cannot be reduced. . On the other hand, when sodium hydroxide is used as the alkaline agent, the sodium hydroxide is relatively expensive, so that the chemical cost becomes high, and there is a problem in terms of cost when the raw water W is treated.

  On the other hand, when magnesium oxide is used as the alkaline agent, the magnesium oxide slowly dissolves in the treated raw water W, and the neutralization of the treated raw water W is allowed to proceed slowly. 80% or more and 90% or less of the required alkali is consumed by the first pH adjusting device 12. Therefore, magnesium oxide is preferable as the alkaline agent added to the raw water W by the first pH adjusting device 12.

The second pH adjusting device 22 can also use slaked lime, magnesium oxide or the like in addition to sodium hydroxide. However, when slaked lime is used in the second pH adjusting device 22, there is a problem that gypsum is generated in the treated raw water W as in the first pH adjusting device 12, and the amount of slaked lime added As a result, the generation of gypsum is delayed, and the possibility that a gypsum scale is generated in the second precipitation tank 31 in the subsequent stage increases. On the other hand, when magnesium oxide is used in the second pH adjuster 22, it is not easy to sufficiently raise the pH of the treated raw water W. Therefore, it is desirable to use sodium hydroxide as the second pH adjusting device 22.

  Next, a second embodiment of the present invention will be described with reference to FIG.

The heavy metal removing apparatus 1 shown in FIG. 2 is basically the same as the heavy metal removing apparatus 1 shown in FIG. 1, but the first solid tank 11 and the second coagulating tank 21 are connected to each other. A first sedimentation tank 41 is provided as a liquid separation means. The first settling tank 41 is configured in substantially the same manner as the second settling tank 31, and treated raw water W that is an outflow water flowing out from the first coagulation tank 11 flows in and is stored.

And this 1st sedimentation tank 41 precipitates the sludge S containing the solid substance which is the hydroxide of the heavy metal component insolubilized in the process raw water W in the 1st coagulation tank 11, and carries out solid-liquid separation. . In other words, the first settling tank 41, by pulling out the sludge S that precipitated the first settling tank 41, from sludge withdrawal port 43 provided on the bottom portion 42 of the first precipitation tank 41, The sludge S is solid-liquid separated from the treated raw water W in the first sedimentation tank 41.

The first pH adjustment device 12 is stored in the first settling tank 41, the second processing raw W after the sludge S is the solid-liquid separation in the first settling tank 41 The pH of the treated raw water W in the first flocculation tank 11 is adjusted so that the molar ratio of iron ions to ferrous ions is 0.2 or more and 2.0 or less, and the second in the treated raw water W is adjusted. At least a portion of the ferrous ion is oxidized. The first aggregating tank 11 is provided with a second stirring device 44 configured in the same manner as the first stirring device 26. The second agitator 44 agitates the treated raw water W stored in the first agglomeration tank 11 by rotationally driving the propeller 45 of the second agitator 44.

Next, the second pH adjuster 22 treats the treated raw water W in the second flocculating tank 21 into which the treated raw water W after the sludge S is solid-liquid separated in the first sedimentation tank 41 is stored. Adjust the pH. A second air supply device 46 configured in the same manner as the first air supply device 16 is attached to the second aggregation tank 21. The second air supply device 46 supplies air to the treated raw water W in the second flocculating tank 21, thereby aeration of the treated raw water W in the second flocculating tank 21 and the treated raw water W. This is a stirring aeration device that stirs the water.

Further, the downstream end of the sludge return pipe 35 of the sludge return discharge device 34 is arranged between the first sedimentation tank 41 and the second agglomeration tank 21. That is, the sludge return pipe 35 returns the sludge M extracted from the second sedimentation tank 31 to the upstream side of the second agglomeration tank 21, which is downstream of the first sedimentation tank 41. Into the second agglomeration tank 21.

  As a result, according to the second embodiment, when neutralizing the treated raw water W which is an acidic mine drainage containing various heavy metals in addition to iron, ferrite is stably added to the treated raw water W. By generating, the amount of sludge M containing ferrite can be reduced, the settling and dewatering properties of the sludge M can be improved, and the dewatering work of the sludge M can be reduced. The same effect as the form can be achieved.

  Here, when a harmful substance such as arsenic is contained in the treated raw water W, the sludge M generated in the treated raw water W may contain arsenic. For this reason, there is a possibility that a problem may occur in the disposal and disposal of the sludge M, and a problem may also occur in the effective use of ferrite in the sludge M.

Therefore, the first precipitation tank 41 is provided between the first flocculation tank 11 and the second flocculation tank 21, ferric ions and a first processing raw water W flowing out of the first precipitation tank 41 The pH of the treated raw water W in the first coagulation tank 11 is adjusted by the first pH adjuster 12 so that the molar ratio with iron ions is 0.2 or more and 2.0 or less, and the second air The supply device 46 is agitated while supplying air to the raw raw water W in the second flocculation tank 21.

As a result, by adjusting the pH of the treated raw water W in the first flocculating tank 11 to 3 or more and 6 or less with the first pH adjusting device 12, most of the aluminum in the treated raw water W is 50% of silicon. The degree and other harmful substances can be agglomerated and insolubilized in the first agglomeration tank 11. For this reason, the treated raw water W in which the sludge S is generated flows into the first sedimentation tank 41 and is stored, so that the sludge S in the treated raw water W is precipitated in the first sedimentation tank 41. Can do.

Thus, the sludge withdrawal port 43 of the first precipitation tank 41 by precipitated solid Pull the sludge S-liquid separation in the first settling tank 41, Ya substances prevent the ferrite of this process the raw water W In addition, harmful substances such as arsenic can be removed in advance. As a result, the treated raw water W after the sludge S is separated in the first settling tank 41 does not contain substances that interfere with ferritization and harmful substances. By making it flow into the second agglomeration tank 21, ferrite can be generated more efficiently.

Furthermore, ferric ions in the treated raw water W are precipitated as sludge S in the range of pH 3 to 6. Therefore, the raw water W after the sludge S is separated in the first sedimentation tank 41 after the pH is adjusted to 3 or more and 6 or less by the first pH adjusting device 12 flows into the second coagulation tank 21. Then, ferric ions are insufficient in the formation of ferrite in the second agglomeration tank 21.

  Therefore, as the oxidation step, the first pH is adjusted so that the molar ratio of ferric ions to ferrous ions in the treated raw water W in the second coagulation tank 21 is 0.2 or more and 2.0 or less. The adjusting device 12 adjusts the pH of the treated raw water W in the first flocculating tank 11, and the second air supply device 46 supplies air to the treated raw water W in the second flocculating tank 21. Here, a part of the ferrous ions in the treated raw water W in the second coagulation tank 21 is provided by this oxidation step independently or by the second air supply device 46 of the second coagulation tank 21. Can be oxidized to ferric ions.

As a result, the generation of ferrite from ferrous ions and ferric ions in the treated raw water W in the second coagulation tank 21 can be realized more efficiently and more easily. At the same time, the purity of the ferrite produced in the second agglomeration tank 21 can be increased, and the magnetic susceptibility of the ferrite can be increased. Therefore, by flowing the treated raw water W, in which ferrite is generated in the second agglomeration tank 21, into the second precipitation tank 31, the second precipitation tank 31 has a high purity that does not contain harmful substances. Ferrite can be recovered. Therefore, this ferrite can be reused for industrial use rather than being discharged as waste.

  Next, a third embodiment of the present invention will be described with reference to FIG.

The heavy metal removing apparatus 1 shown in FIG. 3 is basically the same as the heavy metal removing apparatus 1 shown in FIG. 2, but as an aeration means between the first sedimentation tank 41 and the second aggregating tank 21. An oxidation tank 51 which is an oxidation means is provided. In this oxidation tank 51, as the aeration process, which is an oxidation process, the treated raw water W after the sludge S is solid-liquid separated in the first sedimentation tank 41 is introduced and stored. Further, a third air supply device 52 configured in the same manner as the first air supply device 16 is attached to the oxidation tank 51. The third air supply device 52 is an oxidation aeration device that aerates and oxidizes the treated raw water W in the oxidation tank 51 by supplying air to the treated raw water W in the oxidation tank 51.

Furthermore, the raw raw water W oxidized in the oxidation tank 51 is introduced into the second aggregating tank 21 and stored therein. Further, the downstream end of the sludge return pipe 35 is connected between the oxidation tank 51 and the second flocculation tank 21, and the sludge M extracted from the second sedimentation tank 31 is downstream of the oxidation tank 51. The sludge M is returned to the upstream side of the second flocculation tank 21 and flows into the second flocculation tank 21.

  As a result, according to the third embodiment, when the treated raw water W is neutralized, ferrite can be stably generated in the treated raw water W. Therefore, the amount of sludge M containing ferrite is reduced. While being able to reduce, the sedimentation property and dewatering property of this sludge M can be improved, and the dehydration work of this sludge M can be reduced, Therefore The effect similar to the said 2nd Embodiment can be show | played.

Here, in the pH adjustment of the treated raw water W in the first coagulation tank 11 by the first pH adjusting device 12, most of the ferric iron in the treated raw water W is taken into the sludge M which is a solid matter. Exists as. Moreover, only the ferrous iron exists in the treated raw water W after the solid-liquid separation in the first sedimentation tank 41. Therefore, an oxidation tank 51 is provided on the upstream side of the first sedimentation tank 41, and the raw water W in the oxidation tank 51 is aerated and oxidized by the third air supply device 52, and the second agglomeration is performed. The molar ratio of ferrous iron and ferric iron in the treated raw water W flowing into the tank 21 is set to a ratio necessary for the formation of ferrite. As a result, the sludge M containing ferrite can be generated more efficiently in the second agglomeration tank 21.

  In the third embodiment, the oxidation tank 51 is provided on the upstream side of the second flocculation tank 21, and the treated raw water W flowing into the second flocculation tank 21 is supplied to the third flocculation tank 21. Although it was oxidized by aeration with air in the air supply device 52, even if this third air supply device 52 is provided in the second coagulation tank 21, it flows into the second coagulation tank 21 and is stored. Since the molar ratio of the ferrous iron and the ferric iron in the treated raw water W can be set to a ratio necessary for the generation of ferrite, the same effects as those of the third embodiment can be achieved.

  Next, a fourth embodiment of the present invention will be described with reference to FIGS.

  The heavy metal removing device 1 shown in FIGS. 4 and 5 includes a sulfide removing device 61 as sulfide separating means. This sulfide removing device 61 is a facility provided in front of the first coagulation tank 11 of the heavy metal removing device 1 shown in FIGS. 1 to 3. That is, the sulfide removing device 61 is installed between the raw water storage tank 2 and the first coagulation tank 11. In other words, the sulfide removing device 61 is installed on the downstream side of the raw water pump 3 and on the upstream side of the first coagulation tank 11. Therefore, in the sulfide removing device 61, the treated raw water W supplied from the raw water storage tank 2 by the raw water pump 3 is supplied to the first flocculation tank 11, and the pH is adjusted by the first pH adjusting device 12. Supplied before.

The sulfide removing device 61 includes a sulfide generation tank 62 into which the treated raw water W is introduced at a predetermined flow rate. In the sulfide generation tank 62, only certain heavy metals in the treated raw water W are added by adding a sulfurizing agent V such as sodium sulfide (Na ₂ SO ₃ ) or hydrogen sulfide (H ₂ S) to the treated raw water W. Is insolubilized as a sulfide.

  Specifically, the sulfide generating tank 62 is filled with a predetermined amount of a liquid sodium sulfide solution or the like, and a third cylindrical storage tank 63 with a bottom as a sulfidizing agent storage tank is stored. It has. The third storage tank 63 is provided with a third infusion pump 64 as a pressure feeding means. The third injection pump 64 pulls out the sulfiding agent V in the third storage tank 63 and adds the sulfiding agent V to the treated raw water W in the sulfide generating tank 62.

  Further, the third injection pump 64 controls the driving of the third injection pump 64 to measure an oxidation reduction potential (ORP) of the raw water W in the sulfide generation tank 62. A total of 65 is attached via a control line 66. This ORP meter 65 uses the sulfurizing agent V in the third storage tank 63 in the sulfide generation tank 62 so that the oxidation-reduction potential of the treated raw water W in the sulfide generation tank 62 is, for example, −100 mV. In the raw water W in the sulfide production tank 62, the neutralization treatment such as copper (Cu), cadmium (Cd), lead (Pb), or zinc (Zn) is simply neutralized from iron. Insolubilize heavy metals that cannot be separated. That is, the ORP meter 65 adjusts an appropriate addition amount of the sulfurizing agent V.

  Here, the treated raw water W in the sulfide generation tank 62 is a predetermined value by a third pH controller (not shown), that is, 2.0 or more and 3.5 or less, more preferably 2.0 or more and 3.0 or less. Has been adjusted. Here, if the pH of the treated raw water W in the sulfide generation tank 62 is 2.0 or more and 3.5 or less, all of copper, cadmium, lead and zinc are insolubilized as sulfides, and these copper and cadmium Lead and zinc can be almost removed from the treated raw water W, and can be separated and recovered as sludge T.

  Further, a third stirring device 67 for stirring the raw raw water W in the sulfide generating tank 62 is attached to the sulfide generating tank 62. The third stirring device 67 is provided with a propeller 68 as a stirring blade immersed in the treated raw water W in the sulfide generation tank 62. That is, the third stirring device 67 stirs the treated raw water W in the sulfide generation tank 62 by immersing the propeller 68 in the treated raw water W and rotationally driving it.

  Further, on the downstream side of the sulfide generation tank 62, a bottomed cylindrical third precipitation tank 71 which is a solid-liquid separation tank as a third solid-liquid separation means is installed. In the third settling tank 71, the treated raw water W that has flowed out of the sulfide generating tank 62 is introduced, and a predetermined amount of the treated raw water W is stored. Further, a funnel-shaped bottom surface portion 72 having an inverted conical surface is provided at the bottom of the third sedimentation tank 71.

  Here, the third sedimentation tank 71 collects the sulfide sludge T, which has been insolubilized from the treated raw water W in the sulfide production tank 62, from the treated raw water W by solid-liquid separation. Further, the sludge T precipitated in the third settling tank 71 is separated from the treated raw water W by solid-liquid separation at the central portion protruding toward the bottom of the bottom surface portion 72 of the third settling tank 71. In addition, a sludge extraction port 73 is provided to be discharged out of the system. The treated raw water W from which the sludge T has been collected in the third settling tank 71 flows into the first coagulating tank 11 of the heavy metal removing apparatus 1 as sulfide separation process treated water.

  As a result, according to the fourth embodiment, the raw raw water W is generated as a sulfide as a sulfide separation step before the first pH adjustment step by the first pH adjustment device 12 of the heavy metal removing device 1. Flow into tank 62. Then, a sulfiding agent V is added to the treated raw water W stored in the sulfide generating tank 62, and heavy metals such as copper, cadmium, lead and zinc in the treated raw water W are insolubilized as sulfides. Thereafter, the treated raw water W in which these heavy metals are insolubilized as sulfides is caused to flow into the third settling tank 71, and the insoluble sulfide is precipitated in the treated raw water W in the third settling tank 71. Solid-liquid separation.

As a result, heavy metals such as copper, cadmium, lead and zinc that cannot be separated from iron by simple neutralization can be removed in advance. Therefore, it is possible to recycle these heavy metals, and the sludge M generated by the second pH adjusting device 22 of the heavy metal removing device 1 contains almost no heavy metal, so that the ferrite in the sludge M can be reused. Is possible. Furthermore, since aluminum or arsenic can be removed in the first settling tank 41, the sludge M to be generated by the second pH adjustment device, together with the ferrite can be more efficiently contained more heavy metals in the sludge M It will not be included. For this reason, the ferrite in the sludge M can be reused more efficiently.

  Further, when the sulfiding agent V is added from the third storage tank 63 to the treated raw water W in the sulfide generating tank 62 by the third injection pump 64, the heavy metal in the treated raw water W is insolubilized as sulfide. The pH of the treated raw water W is set to 2.0 or more and 3.5 or less. That is, when the pH of the treated raw water W is 3.5 or more, ferrous iron in the treated raw water W is insolubilized as sulfides, and the recovered amount as ferrite decreases, which is not preferable. On the other hand, when the pH of this treated raw water W is 2.0 or less, insolubilization due to zinc sulfide formation becomes insufficient, such being undesirable.

  Therefore, by setting the pH of the treated raw water W to 2.0 or more and 3.5 or less, heavy metals such as copper, cadmium, lead and zinc that cannot be separated from iron by simple neutralization treatment in the treated raw water W. Can be insolubilized more reliably. Accordingly, these heavy metals can be reused more efficiently, and the sludge M containing ferrite contains less heavy metal, so that the ferrite in the sludge M can be reused more efficiently.

  In addition, by adjusting the treated raw water W in the sulfide generation tank 62 so that the oxidation-reduction potential becomes −100 mV as an instruction value of the ORP meter 65, the mere neutralization treatment in the treated raw water W separates from iron. Most heavy metals that can not be insolubilized.

  As a result, the heavy metals contained in the treated raw water W can be recovered as sludge T in the third sedimentation tank 71 after copper, cadmium, lead and zinc are insolubilized in the sulfide production tank 62. Aluminum, arsenic and the like are insolubilized in the first coagulation tank 11 and can be recovered as sludge S in the second sedimentation tank 41, and iron is solubilized as ferrite in the second coagulation tank 21 to be first. It can be recovered as sludge M in the settling tank 31.

  Therefore, by providing the sulfide removing device 61 in the preceding stage of the heavy metal removing device 1, other heavy metals contained as impurities in the ferrite that can be recovered in the first precipitation layer 31 can be removed, and the three types of sludge M, S , T can be recovered, so that each of these three types of sludge M, S, T can be easily reused as resources.

  In the fourth embodiment, when the raw metal W does not contain heavy metals that cannot be separated from iron by simple neutralization such as copper, cadmium, lead, or zinc, the heavy metal removing device 1 Instead of installing the sulfide removing device 61 in the previous stage, it is only necessary to treat the treated raw water W only with the heavy metal removing device 1 shown in FIGS. 1 to 3 described above.

Furthermore, in each said embodiment, since the pH of the process raw water W in the 2nd coagulation tank 21 was adjusted to 7 or more and 11 or less in the 2nd pH adjustment apparatus 22, this process raw water W flows in . It is also conceivable that the pH of the treated water after the sludge M is solid-liquid separated in the second sedimentation tank 31 becomes high. However, in actuality, since the pH of the treated raw water W is lowered in the second sedimentation tank 31, the pH of the treated water flowing out from the second sedimentation tank 31 is not so high. Here, the reason why the pH of the treated raw water W in the second sedimentation tank 31 is lowered is that the formation reaction of ferrite in the treated raw water W does not proceed suddenly and the hydroxyl groups are gradually consumed. It is believed that there is.

Therefore, a ferrite ripening tank (not shown) is provided between the second flocculating tank 21 and the second sedimentation tank 31, and is produced in the second flocculating tank 21 as a ripening step in this ferrite ripening tank. The sludge M is brought into contact with the treated water, and the ferrite in the sludge M is aged. As a result, since the pH of the treated water flowing out from the second sedimentation tank 31 is lowered, the pH of the treated water can be stabilized, and ferrite crystals precipitated in the second sedimentation tank 31 can be obtained. Can be further grown. Therefore, this ferrite crystal can be further ripened, and the concentration and dewaterability of the sludge M containing this ferrite can be further improved. At this time, a ferrite ripening tank in which the treated water and the sludge M are in contact with each other can be provided in the second settling tank 31.

Further, magnesium oxide was added to the treated raw water W in the first coagulation tank 11 by the first pH adjusting device 12, but air other than this magnesium oxide, sodium hypochlorite (NaOCl), chlorine An oxidizing agent such as gas (Cl ₂ ), chlorine dioxide (ClO ₂ ), ozone (O ₃ ), hydrogen peroxide (H ₂ O ₂ ) or the like is contained in the first coagulation tank 11 by the first pH adjuster 12. It may be added to the treated raw water W, and a part of the ferrous ions in the treated raw water W may be oxidized to ferric ions.

  Next, examples of the heavy metal removing apparatus according to the first embodiment will be described.

  First, treated raw water W having the composition shown in Table 1 was used.

  Then, after this treated raw water W flows into the raw water storage tank 2 to be stored, the treated raw water W in this raw water storage tank 2 is flowed into the first flocculation tank 11 having a volume of 1 l by the raw water pump 3 at a flow rate of 2 l / h. And let it flow in.

  Here, air is supplied to the treated raw water W in the first flocculation tank 11 by the first air supply device 16, and the treated raw water W is stirred.

  At this time, the amount of air supplied to the treated raw water W in the first flocculating tank 11 by the first air supply device 16 is adjusted, and the treated raw water W is supplied into the second flocculating tank 21. In this case, the molar ratio of ferrous ions and ferric ions in the treated raw water W is adjusted.

  At the same time, the pH of the treated raw water W in the first flocculating tank 11 is adjusted by the first pH controller 15 so that the pH of the treated raw water W in the first flocculating tank 11 becomes 5.

  At this time, the pH adjustment of the treated raw water W by the first pH controller 15 is performed by driving the first infusion pump 14 with the magnesium oxide aqueous solution dissolved in the first storage tank 13 in the first coagulation tank. 11 to supply.

  Next, the treated raw water W in the first flocculation tank 11 adjusted to pH 5 by the first pH controller 15 is discharged, and the treated raw water W is supplied to the second flocculating tank 21 having a volume of 2 l. And store.

  Here, the treated raw water W in the second flocculation tank 21 is stirred by the propeller 27 of the first stirring device 26, and the pH of the treated raw water W is set to 10.5 by the second pH control device 25. adjust.

  At this time, the pH adjustment of the treated raw water W by the second pH controller 25 is performed by the second agglomeration of the sodium hydroxide aqueous solution dissolved in the second storage tank 23 by driving the second injection pump 24. Supply into the tank 21.

Thereafter, the treated raw water W in the second flocculation tank 21 neutralized to 10.5 by the second pH controller 25 is flowed out, and the treated raw water W is supplied to the second volume having a volume of 10 l . Is supplied to the settling tank 31 and stored.

At this time, the sludge M containing ferrite is precipitated in the treated raw water W in the second settling tank 31. Then, the sludge M is solid-liquid separated from the treated raw water W, and a part of the sludge M is returned to the second flocculation tank 21 by the return pump 36 at a flow rate of 0.2 l / h. It is used as a seed crystal for the formation of ferrite in the coagulation tank 21. Further, the treated raw water W after the sludge M is solid-liquid separated in the second sedimentation tank 31 is discharged from the second sedimentation tank 31 to be treated water F.

  As a result, the molar ratio of ferric ions to ferrous ions in the treated raw water W in the second flocculation tank 21 (ferric / ferrous concentration ratio) is 0.1 or more and 0.6 or less. In this range, the sludge M was moved to the magnet in the second agglomeration tank 21, so that the formation of ferrite in the second agglomeration tank 21 could be confirmed.

  Furthermore, ferritization of this treated raw water W was experimented by changing the concentrations of aluminum and silicon in the treated raw water W having the composition shown in Table 1.

  As a result, as shown in Table 2, when the concentrations of aluminum and silicon in the treated raw water W are reduced, the molar ratio of ferric ions and ferrous ions for generating ferrite in the treated raw water W is increased. Approached 2.0. In this state, when the molar ratio of ferric ions to ferrous ions in the treated raw water W is 2.0 or more, ferrite is not generated in the treated raw water W.

  Further, the SVI (Sludge Volume Index) of the sludge M obtained from the treated raw water W showed a very good value of 49%, and the dewaterability of the sludge M was also very good.

That is, by returning the sludge M from the second sedimentation tank 31 to the second agglomeration tank 21, the ripening of ferrite crystals produced in the second agglomeration tank 21 proceeds, and the crystal grains of this ferrite This is probably because the diameter has increased and, in general, ferrite does not incorporate water molecules around crystals, unlike heavy metal hydroxides.

  Moreover, as shown in Table 3, the average water quality of the treated water F after treating the treated raw water W was almost free of heavy metals such as iron, aluminum, silicon and arsenic. Therefore, these heavy metals are contained as impurities in the ferrite in the sludge M separated from the treated raw water W.

  Next, an example of the heavy metal removing apparatus according to the second embodiment will be described.

  First, similarly to Example 1, treated raw water W having the composition shown in Table 1 was used.

  Then, after this treated raw water W flows into the raw water storage tank 2 to be stored, the treated raw water W in this raw water storage tank 2 is flowed into the first flocculation tank 11 having a volume of 1 l by the raw water pump 3 at a flow rate of 2 l / h. And let it flow in.

  Here, the treated raw water W in the first aggregating tank 11 is stirred by the propeller 45 of the second stirring device 44. At the same time, the pH of the treated raw water W in the first flocculating tank 11 is adjusted by the first pH controller 15 so that the pH of the treated raw water W in the first flocculating tank 11 becomes 5.

  At this time, the pH adjustment of the treated raw water W by the first pH controller 15 is performed by driving the first infusion pump 14 with the magnesium oxide aqueous solution dissolved in the first storage tank 13 in the first coagulation tank. 11 to supply.

Next, the treated raw water W in the first flocculation tank 11 adjusted to pH 5 by the first pH control device 15 is flowed out, and the treated raw water W is supplied to the first sedimentation tank 41 and stored. .

At this time, the sludge S generated in the first coagulation tank 11 is precipitated in the first settling tank 41. Therefore, to remove the sludge S to solid-liquid separation from the treated raw water W in the first settling tank 41. Thereafter, the treated raw water W from which the sludge S has been removed in the first sedimentation tank 41 is supplied to the second aggregating tank 21 having a volume of 2 l and stored.

  Here, air is supplied to the treated raw water W in the second flocculation tank 21 by the second air supply device 46, and the treated raw water W is stirred. At the same time, the pH of the treated raw water W in the second flocculating tank 21 is adjusted by the second pH controller 25 so that the pH of the treated raw water W in the second flocculating tank 21 becomes 10.5. To do.

  At this time, the pH adjustment of the treated raw water W by the second pH controller 25 is performed by the second agglomeration of the sodium hydroxide aqueous solution dissolved in the second storage tank 23 by driving the second injection pump 24. Supply into the tank 21.

Thereafter, the treated raw water W in the second flocculation tank 21 neutralized to 10.5 by the second pH controller 25 is flowed out, and the treated raw water W is supplied to the second volume having a volume of 10 l . Is supplied to the settling tank 31 and stored.

At this time, the sludge M to precipitate containing ferrite during processing raw water W in this second sedimentation tank 31. Then, the sludge M is solid-liquid separated from the treated raw water W, and a part of the sludge M is returned to the second flocculation tank 21 by the return pump 36 at a flow rate of 0.2 l / h. It is used as a seed crystal for the formation of ferrite in the coagulation tank 21. Further, the treated raw water W after the sludge M is solid-liquid separated in the second sedimentation tank 31 is discharged from the second sedimentation tank 31 to be treated water F.

As a result, in the second embodiment, the first flocculation tank 41 is provided between the first flocculation tank 11 and the second flocculation tank 21 of the heavy metal removing apparatus 1 of the first embodiment, and the first flocculation tank 41 is provided. The sludge S, which is a hydroxide of a heavy metal component generated in the tank 11, is separately separated and recovered in the first settling tank 41. Therefore, it is possible to remove aluminum, silicon, and the like that prevent ferritization in the treated raw water W in the second flocculation tank 21, and it is possible to remove heavy metals such as arsenic, which is a harmful substance, and improve the quality of the generated ferrite. . Therefore, since the sludge S containing this ferrite does not contain a harmful substance, the ferrite in this sludge S can be reused.

However, in Example 2, ferric ions in the treated raw water W are removed in the first sedimentation tank 41 by adjusting the pH of the treated raw water W in the first flocculating tank 11. For this reason, in order not to remove ferric ions as much as possible in the first coagulation tank 11, the supply and stirring of air by the first air supply device 16 in the first coagulation tank 11 is stopped, and the propeller 45 is stopped. The raw raw water W in the first flocculation tank 11 is stirred by the second agitator 44 using the same, and the raw raw water in the first flocculation tank 11 is made to have a sealed structure. A structure that prevents the dissolution of oxygen in W as much as possible was adopted.

As a result, as shown in Table 4, in the treated raw water W in the first sedimentation tank 41, most ferrous ions remain without being oxidized, and most of the ferrous ions remain in the second aggregating tank. I was able to drain to 21.

Moreover, since we are able to process raw water W removing aluminum and arsenic more than 90% in at the first settling tank 41, the sludge S that precipitated the first settling tank 41, migrate these aluminum and arsenic Although it was made, silicon in the treated raw water W remained at a removal rate of about 50%.

  However, the molar ratio of ferric ions and ferrous ions in the treated raw water W in the second flocculation tank 21 is wider than that in Example 1, that is, in the range of 0.2 to 1.5. Thus, since the ferritization in the treated raw water W in the second coagulation tank 21 was possible, the ferritization in the treated raw water W can proceed efficiently within this range.

  Next, an example of the sulfide removing device of the fourth embodiment will be described.

  In this Example 3, the treated raw water W shown in Table 5 containing copper, lead and zinc was used in addition to the heavy metals contained in the treated raw water W used in the above Examples 1 and 2. .

  Then, the treated raw water W having the composition shown in Table 5 is caused to flow into the raw water storage tank 2 to be stored, and then the treated raw water W in the raw water storage tank 2 is stored in the sulfide generation tank 62 having a volume of 1 l by the raw water pump 3. Is fed at a flow rate of 2 l / h.

  Here, the treated raw water W in the sulfide production tank 62 is stirred by the propeller 68 of the third stirring device 67. At the same time, the sodium sulfide solution stored as the sulfiding agent V in the third storage tank 63 is adjusted so that the oxidation-reduction potential of the treated raw water W in the sulfide generation tank 62 is -100 mV as indicated by the ORP meter 65. The third injection pump 64 supplies the sulfide generation tank 62 for injection control.

  Furthermore, the treated raw water W in the sulfide generation tank 62 is discharged and stored in a third sedimentation tank 71 having a volume of 3 l. At this time, the sludge T generated in the sulfide generation tank 62 is precipitated in the third precipitation tank 71.

  Then, the sludge T precipitated in the third settling tank 71 is separated from the treated raw water W in the third settling tank 71 by solid-liquid separation. To discharge. Thereafter, the treated raw water W after the sludge T is solid-liquid separated in the third sedimentation tank 71 is discharged from the third sedimentation tank 71 and used as the sulfide separation process treated water.

  Here, in Example 1 described above, iron in the treated raw water W could be ferritized, but other heavy metals contained in the treated raw water W are contained as impurities in the ferrite. In Example 2 described above, most of aluminum and arsenic and part of silicon in the treated raw water W can be extracted from the second sedimentation tank 41 and separated and collected as sludge S. Therefore, the aluminum and arsenic are contained in excess. Thus, the sludge M containing ferrite could be obtained.

  However, in the case where heavy metals that cannot be separated from iron by simple neutralization treatment such as copper, cadmium, lead, zinc, etc. are contained in the treated raw water W, from the relationship between the solubility of these heavy metals and pH, the above-mentioned examples In each of 1 and Example 2, heavy metal is contained in the sludge M extracted from the first sedimentation tank 31.

  Therefore, as described above, before the treated raw water W is treated in the first and second embodiments, the sulfide removing device 61 shown in the third embodiment is used to treat the sulfide removing device 61. The treated raw water, which is the sulfide separation process treated water treated in, has the composition shown in Table 6.

  As a result, as shown in Table 6, in the treated raw water W treated by the sulfide removing device 61, copper, lead, zinc and the like are removed as sulfides. The third precipitation tank of the sulfide removing device 61 In 71, it can be collected in sludge T and recovered.

It is explanatory drawing which shows the heavy metal removal apparatus of the 1st Embodiment of this invention. It is explanatory drawing which shows 2nd Embodiment of the heavy metal removal apparatus of this invention. It is explanatory drawing which shows 3rd Embodiment of the heavy metal removal apparatus of this invention. It is explanatory drawing which shows a part of 4th Embodiment of the heavy metal removal apparatus of this invention. It is explanatory drawing which shows a heavy metal removal apparatus same as the above.

1 Heavy metal removal equipment as wastewater treatment equipment containing heavy metals
12 First pH adjusting device as first pH adjusting means
22 Second pH adjusting device as second pH adjusting means
31 second sedimentation tank as a second solid-liquid separation means
34 Sludge return discharge device as return means
41 First settling tank as first solid-liquid separation means
51 Oxidation tank as aeration means
61 Sulfide removal equipment as sulfide separation means M Sludge S Sludge as solid W Raw water treated as wastewater containing heavy metals

Claims (7)

Adjusting the pH of the heavy metal-containing wastewater containing heavy metal containing at least ferrous iron to 3 or more and 6 or less to insolubilize the heavy metal in the heavy metal-containing wastewater, and at least a part of the ferrous iron in the heavy metal-containing wastewater A first pH adjusting step for oxidizing the iron to ferric iron,
A first solid-liquid separation step for solid-liquid separation of solid matter from the heavy metal-containing wastewater whose pH has been adjusted in the first pH adjustment step;
An aeration process in which the heavy metal-containing wastewater from which the solid matter has been solid-liquid separated in the first solid-liquid separation process is aerated and oxidized ;
Adjusting the pH of the heavy metal-containing wastewater aerated and oxidized in this aeration step to 7 to 11 and generating a sludge containing ferrite in the heavy metal-containing wastewater; and
A second solid-liquid separation step for solid-liquid separation of the sludge containing ferrite from the heavy metal-containing wastewater whose pH has been adjusted in the second pH adjustment step;
A return step of returning at least a part of the sludge containing the ferrite solid-liquid separated in the second solid-liquid separation step to the heavy metal-containing wastewater in the second pH adjustment step;
In the first pH adjustment step, the molar ratio of ferric iron to ferrous iron in the heavy metal-containing wastewater from which the solid matter is solid-liquid separated in the first solid-liquid separation step is 0.2 or more. 2.0 as follows becomes heavy metal-containing wastewater treatment method you and adjusting the pH of the heavy metal-containing waste water. Comprising an aging step of aging ferrite in heavy metal-containing wastewater in which sludge containing ferrite is generated in the second pH adjustment step;
Second solid-liquid separation step, the heavy metal-containing wastewater treatment method of claim 1 Symbol mounting, characterized in that to solid-liquid separation of sludge from the heavy metal-containing waste water containing the ferrite which has been aged in the aging step. Prior to the first pH adjustment step, a sulfide separation step of precipitating heavy metals in the heavy metal-containing wastewater before adjusting the pH in the first pH adjustment step as sulfides is provided. Item 3. A heavy metal-containing wastewater treatment method according to any one of Items 1 and 2 . The heavy metal-containing wastewater treatment method according to claim 3 , wherein the sulfide separation step adjusts the pH of the heavy metal-containing wastewater to 2.0 or more and 3.5 or less. Adjusting the pH of the heavy metal-containing wastewater containing heavy metal containing at least ferrous iron to 3 or more and 6 or less to insolubilize the heavy metal in the heavy metal-containing wastewater, and at least a part of the ferrous iron in the heavy metal-containing wastewater First pH adjusting means for oxidizing iron to ferric iron,
A first solid-liquid separation means for solid-liquid separation of solids from heavy metal-containing wastewater pH is adjusted by the first pH-adjusting means,
Aeration means for aeration and oxidation of the heavy metal-containing wastewater from which the solid matter has been solid-liquid separated by the first solid-liquid separation means ;
Adjusting the pH of the heavy metal-containing wastewater aerated and oxidized by the aeration means to 7 to 11 and generating second sludge containing ferrite in the heavy metal-containing wastewater;
Second solid-liquid separation means for solid-liquid separation of the sludge containing ferrite from the heavy metal-containing wastewater whose pH is adjusted by the second pH adjustment means;
Returning means for returning at least a part of the sludge containing ferrite solid-liquid separated by the second solid-liquid separating means to the heavy metal-containing wastewater whose pH is adjusted by the second pH adjusting means; Equipped,
In the first pH adjusting means, the molar ratio of ferric iron to ferrous iron in the heavy metal-containing wastewater from which the solid matter is solid-liquid separated by the first solid-liquid separating means is 0.2 or more. 2.0 as follows made, heavy metal-containing wastewater treatment apparatus and adjusting the pH of the heavy metal-containing waste water. Aging means for aging ferrite in heavy metal-containing wastewater in which sludge containing ferrite is generated by the second pH adjusting means;
The second solid-liquid separation means solid-liquid separates the sludge containing the ferrite aged by the aging means from the heavy metal-containing wastewater.
The heavy metal-containing drainage device according to claim 5, wherein the drainage device contains heavy metal. Prior to the first pH adjusting means, there is provided a sulfide separating means for precipitating heavy metals in the heavy metal-containing wastewater as sulfides before adjusting the pH by the first pH adjusting means. Item 7. A heavy metal-containing wastewater treatment apparatus according to Item 5 or 6 .

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