JP2008093602A - Waste water treatment method and waste water treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment method of suitably removing ammonia and a COD component in waste water, and waste water treatment equipment. <P>SOLUTION: The waste water treatment method of treating the waste water containing ammonia and the COD component comprises carrying out a sludge treatment process of removing ammonia in the waste water by a nitrification reaction and a denitrification reaction with activated sludge, an ion exchange treatment process of bringing the waste water after this sludge treatment process into contact with a weak basic or a medium basic anion exchange resin after pH is adjusted at not less than 5 and less than 8.3, wherein ammonia can be removed from the waste water in the sludge treatment process and wherein the COD component not removed in the sludge treatment process can excellently be adsorbed and removed by the anion exchange resin in the ion exchange treatment process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method for treating wastewater containing ammonia and a COD component, and a wastewater treatment apparatus.

  For example, in facilities that operate and operate by burning fossil fuels such as refineries and power plants, a large amount of combustion exhaust gas is generated, which causes environmental pollution such as sulfur oxides and nitrogen oxides. Since various substances are contained, the exhaust gas is subjected to desulfurization / denitration treatment. The wastewater generated by such desulfurization / denitration treatment contains a large amount of ammonia and various COD components. Therefore, the wastewater cannot be discharged to the public water surface without removing these substances. .

  Here, conventionally, there is a method using activated sludge as a waste water treatment method for removing ammonia in waste water. In such a wastewater treatment method, when the ammonia concentration in the wastewater is as low as 100 ppm or less, it can be treated with general activated sludge. However, when the ammonia concentration is 300 ppm or more as in the above desulfurization / denitration wastewater, the general activated sludge is used. It is difficult to process with. When treating wastewater containing such a high concentration of ammonia, ammonia is converted to nitrite by ammonia-oxidizing bacteria, which are nitrifying bacteria, and nitrite is converted to nitric acid by nitrifying bacteria, which are nitrifying bacteria. A wastewater treatment method using a nitrification reaction and a denitrification reaction in which nitric acid is reduced to molecular nitrogen by denitrifying bacteria is preferable.

However, in the nitrification / denitrification reaction described above, it is not possible to decompose and remove hardly decomposable COD components such as hydroxyamines and inorganic COD components, and the COD components remain in the treated water after wastewater treatment. Therefore, the COD concentration of treated water cannot be reduced sufficiently.
It is also conceivable to oxidize and remove such a hardly decomposable COD component with an oxidizing agent such as hypochlorous acid or ozone, or to adsorb and remove with an activated carbon. However, since such a hardly decomposable COD component is a chemically stable substance, it is difficult to oxidize even with an oxidizing agent, and there are some COD components that cannot be adsorbed and removed by activated carbon.

Here, conventionally, various COD components contained in the flue gas desulfurization denitration wastewater are adsorbed and removed using a strongly basic anion exchange resin (for example, see Patent Documents 1 and 2), weakly basic or A technique for adsorption removal using a medium basic anion exchange resin is known (for example, see Patent Documents 3 and 4).
According to such a wastewater treatment method using an anion exchange resin, it is conceivable that a hardly degradable COD component that could not be decomposed / removed by biological treatment can be adsorbed and removed, and the COD concentration in the treated water can be sufficiently reduced.

JP 59-49891 A JP 59-95987 JP 59-95988 JP-A-7-75778

However, in the configuration using the strongly basic anion exchange resin as in Patent Documents 1 and 2, when sulfate ions or chlorine ions coexist in the wastewater, the COD component is selectively affected by these ions. There is a possibility that it cannot be adsorbed.
On the other hand, in the configuration using a weakly basic or moderately strong anion exchange resin as in Patent Documents 3 and 4, wastewater to be introduced into the anion exchange resin is relatively hardly affected by the above ions. If the state is inappropriate, the COD concentration in the treated water after the wastewater treatment may not be sufficiently reduced.

  In view of the above problems, an object of the present invention is to provide a wastewater treatment method and a wastewater treatment apparatus that can suitably remove ammonia and COD components in wastewater.

  The wastewater treatment method of the present invention is a wastewater treatment method for treating wastewater containing ammonia and a COD component, and a sludge treatment step for removing ammonia in the wastewater by nitrification reaction and denitrification reaction using activated sludge, and the sludge An ion exchange treatment step is performed in which the waste water after the treatment step is adjusted to pH 5 or more and less than 8.3, preferably pH 5 or more and 8 or less, and then contacted with a weakly basic or medium basic anion exchange resin. It is characterized by that.

  Here, in the present invention, as a method for adjusting the pH of the waste water, for example, a pH adjusting agent such as hydrochloric acid or sodium hydroxide is added. Moreover, as a weakly basic or medium basic anion exchange resin, for example, a particulate form in which a basic exchange group such as a secondary to quaternary amine is added to a base which is a copolymer of styrene and divinylbenzene. A synthetic resin can be used, but is not limited thereto.

According to the present invention, ammonia is decomposed by using nitrifying bacteria and denitrifying bacteria in activated sludge in the sludge treatment step, so that even when the ammonia concentration in the wastewater is high, it can be removed satisfactorily. In the ion exchange treatment process, the waste water after the sludge treatment process is brought into contact with a weakly basic or medium basic anion exchange resin, so that the COD component that could not be removed through the sludge treatment process is converted into an anion exchange resin. Can be removed with good adsorption. Furthermore, by adjusting the pH of the wastewater before being brought into contact with the anion exchange resin to 5 or more and less than 8.3, COD components can be adsorbed and removed efficiently at low cost, and the COD in the treated water after the wastewater treatment can be obtained. The concentration can be sufficiently reduced.
In addition, when the pH of waste water is 8.3 or more, the COD concentration in the treated water cannot be sufficiently reduced. Further, when the pH of the waste water is less than 5, the waste water treatment cost becomes high and the treatment operation becomes complicated, which is not preferable. That is, the pH of wastewater after sludge treatment is usually 7.4 to 7.6. In order to lower the pH of wastewater before treatment with an anion exchange resin to less than 5, a large amount of acidic pH adjuster is used. Must be administered to drainage. Further, when the treated water after treatment with an anion exchange resin is discharged to the public water surface, the pH of the treated water needs to be returned to neutral, and a large amount of basic pH adjuster is administered to the waste water. Must. As described above, since it is necessary to use a large amount of a pH adjusting agent in the ion exchange treatment, the wastewater treatment cost becomes high and the treatment operation becomes complicated.

Moreover, in this invention, it is preferable to implement the activated carbon treatment process which makes the waste water after the said sludge treatment process contact the activated carbon before or after implementing the said ion exchange treatment process.
Thus, the COD concentration in the treated water can be further reduced by performing the activated carbon treatment step before or after the ion exchange treatment step.
In particular, when the activated carbon treatment step is performed after the ion exchange treatment step, higher COD removal efficiency can be obtained than when the activated carbon treatment step is carried out before the ion exchange treatment step.
Further, when the activated carbon treatment step is performed before the ion exchange treatment step, it is particularly effective when the waste water contains COD components such as peroxosulfuric acid and humic substances. That is, peroxosulfuric acid is an oxidizing substance that degrades the ion exchange resin. If this peroxosulfuric acid is previously removed in the activated carbon treatment step, the COD component can be efficiently removed by the ion exchange resin. In addition, once the COD component having a large molecular weight such as humic substance is adsorbed to the ion exchange resin, it is difficult to desorb during the regeneration treatment, and the adsorption capacity of the ion exchange resin is reduced. If it is removed in advance, such a problem can be prevented.

In the present invention, after the ion exchange treatment step, the introduction of the waste water into the anion exchange resin is stopped, and the regeneration treatment agent is directed in the same direction as the introduction direction of the waste water with respect to the anion exchange resin. It is preferable to carry out a regeneration treatment step in which COD components adsorbed on the anion exchange resin are desorbed.
Here, as the regeneration treatment agent, for example, sodium hydroxide, calcium hydroxide, ammonia, sodium chloride, or the like can be used. In addition, an acid such as sulfuric acid or hydrochloric acid is introduced into the anion exchange resin after desorption of the COD component to complete the regeneration.

According to such a configuration, the anion exchange resin can be regenerated and repeatedly used by desorbing the COD component adsorbed on the anion exchange resin with the regeneration treatment liquid. And since the so-called co-current type is adopted, in which the regeneration treatment liquid is introduced in substantially the same direction as the drainage introduction direction, the regeneration treatment liquid can be brought into uniform contact with the anion exchange resin. Can be suitably reproduced.
In addition, when the so-called counter-current type in which the regeneration treatment liquid is introduced in the direction opposite to the direction in which the wastewater is introduced, the regeneration treatment liquid is likely to be rolled up, and the regeneration treatment liquid is uniformly contacted with the anion exchange resin. In some cases, a part of the anion exchange resin cannot be regenerated. As described above, when the ion exchange treatment step is performed again with the COD component attached to a part of the anion exchange resin, a slight amount of COD component is mixed in the treatment solution after the ion exchange treatment. There is a possibility that the COD concentration of the material cannot be sufficiently reduced.

Moreover, in this invention, it is preferable that the said anion exchange resin has at least any 1 type of a secondary amine, a tertiary amine, and a quaternary amine as an exchange group.
When such an anion exchange resin is used, even when sulfate ions, chlorine ions, etc. coexist in the waste water, the COD component can be selectively adsorbed and removed without being affected by these ions.

In the present invention, the waste water preferably contains at least one of hydroxylamine (NH ₂ OH), hydroxylamine sulfonic acid, and inorganic COD component as the COD component.
Here, as the hydroxylamine sulfonic acid, for example, hydroxylamine monosulfonic acid (HONHSO ₃ ), hydroxylamine disulfonic acid (HON (SO ₃ ) ₂ ), hydroxylamine-O-disulfonic acid (SO ₃ ONHSO ₃ ), hydroxyl And amine trisulfonic acid (SO ₃ ON (SO ₃ ) ₂ ). Examples of the inorganic COD component include dithionic acid.
These COD components are substances that are harmful to the environment and are difficult to decompose and remove by activated sludge, but they can be adsorbed and removed well by weakly or moderately basic anion exchange resins. . For this reason, it is possible to prevent the COD component from remaining in the treated water after the ion exchange treatment, and the treated water can be safely discharged to the public water surface.
The COD component contained in the waste water is not limited to those described above, and may include, for example, humic substances such as fulvic acid and humic acid, sulfamic acids such as ammonium sulfamate, and peroxosulfuric acid.

In the present invention, the waste water is preferably waste water generated when at least one of desulfurization treatment and denitration treatment is performed on combustion exhaust gas of super heavy oil or heavy residual oil. .
In such desulfurization and denitration wastewater of combustion exhaust gas of super heavy oil or heavy residual oil, high-concentration ammonia and various COD components such as hydroxylamine, hydroxylamine sulfonic acid, and inorganic COD components are contained.
In this regard, according to the present invention, ammonia in the wastewater can be suitably removed by the sludge treatment process, and COD components can be suitably adsorbed and removed by the ion exchange treatment process. Can be applied.

Furthermore, in the present invention, the waste water is preferably waste water generated when at least one of desulfurization treatment and denitration treatment is performed on the combustion exhaust gas discharged from the power generation facility.
Here, since the power generation facility is always operating, a large amount of combustion exhaust gas is continuously generated from the power generation facility. A large amount of wastewater generated when desulfurization / denitration treatment is performed on the combustion exhaust gas contains high-concentration ammonia and various COD components.
In this regard, according to the present invention, high-concentration ammonia in the wastewater can be suitably removed by the sludge treatment process, and COD components can be suitably adsorbed and removed by the ion exchange treatment process. On the other hand, the optimal waste water treatment can be performed.

Moreover, in this invention, it is preferable that the ammonia concentration in the said waste_water | drain is 300 ppm or more, Preferably it is 500 ppm or more and 3000 ppm or less.
According to the present invention, ammonia in the waste water is removed by nitrification reaction and denitrification reaction with activated sludge in the sludge treatment step, so that it is optimal for waste water having an ammonia concentration of 300 ppm or more, such as waste water from power generation equipment. Wastewater treatment can be carried out.

The present invention as described above can be established not only as a method invention but also as a product invention. That is, the wastewater treatment apparatus of the present invention is a wastewater treatment apparatus for treating wastewater containing ammonia and a COD component, and is filled with activated sludge, and the nitrification reaction and denitrification reaction by the activated sludge A sludge treatment tank for removing ammonia in the waste water, a pH adjusting means for adjusting the waste water treated in the sludge treatment tank to a pH of 5 or more and less than 8.3, and a weakly or medium basic anion exchange inside And an ion exchange treatment tank in which the waste water whose pH is adjusted by the pH adjusting means is brought into contact with the anion exchange resin.
According to such a wastewater treatment apparatus of the present invention, the same effects as the above-described wastewater treatment method of the present invention can be achieved. That is, ammonia and COD components in the waste water can be suitably removed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a wastewater treatment apparatus for carrying out a wastewater treatment method according to an embodiment of the present invention.

[Configuration of wastewater treatment equipment]
In FIG. 1, 1 is a waste water treatment apparatus, and this waste water treatment apparatus 1 is an apparatus for treating waste water containing ammonia and a COD component. Such a waste water treatment apparatus 1 includes a waste water storage tank 2, four nitrification tanks 3A to 3D, four denitrification tanks 4A to 4D, an oxidation tank 5, a precipitation tank 6, an activated carbon treatment tank 7, an ion The exchange processing tank 8 is provided, and these are connected in series.
In addition, the sludge processing tank in this invention is comprised by nitrification tank 3A-3D and denitrification tank 4A-4D.

  The drainage storage tank 2 stores desulfurization denitration wastewater therein. This desulfurization denitration wastewater is wastewater generated when desulfurization treatment and denitration treatment are performed on combustion exhaust gas generated when a power plant is operated using super heavy oil or heavy residual oil as fuel. This desulfurization denitration wastewater contains ammonia at a high concentration of 300 ppm or more, preferably 500 ppm or more and 3000 ppm or less. The desulfurization denitration wastewater also contains various COD components such as hydroxylamine, hydroxylamine sulfonic acid, and inorganic COD components.

The nitrification tanks 3 </ b> A to 3 </ b> D are aerobic tanks that nitrify ammonia contained in the desulfurization / denitration drainage from the drainage storage tank 2.
The nitrification tanks 3A to 3D are provided in series on the downstream side of the drainage storage tank 2, so that the desulfurization denitration wastewater introduced from the drainage storage tank 2 to the nitrification tank 3A flows in order to the nitrification tanks 3B to 3D. It has become.
Piping of the nitrification blower 9 is connected to the bottom of each of the nitrification tanks 3A to 3D, and air is blown from the nitrification blower 9 at a flow rate of, for example, 100 to 2000 ml / l · min (aeration). Thereby, the inside of the nitrification tanks 3A to 3D is uniformly stirred and an aerobic atmosphere is formed.

And the reactor 31 for making activated sludge adhere is each provided in nitrification tank 3A-3D. In the activated sludge adhering to the reactor 31, ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, which are aerobic nitrifying bacteria, mainly function. The means for attaching the activated sludge is not limited to the one in which the reactor 31 is installed, but an immobilization carrier that accommodates the activated sludge inside may be introduced into the nitrification tanks 3A to 3D.
Examples of ammonia oxidizing bacteria include Nitrosomonas europaea, and such ammonia oxidizing bacteria produce nitrous acid as described below, using ammonia in the desulfurization denitration wastewater as an electron donor.

(Chemical formula)
NH ₄ + 1.5O ₂ → NO ₂ ⁻ + H ₂ O + 2H ⁺ (1)

  Examples of nitrite oxidizing bacteria include Nitrobacter winogradskyi, and such nitrite oxidizing bacteria generate nitric acid as follows using nitrite generated by ammonia oxidizing bacteria as an electron donor.

(Chemical formula)
NO ₂ ⁻ + 0.5O ₂ → NO ₃ ⁻ (2)

Furthermore, a pH sensor 32 for measuring the pH of the desulfurization denitration wastewater in the tank is connected to the nitrification tank 3A. The nitrification tank 3A is connected with pH adjusting means 33 for introducing a sodium hydroxide aqueous solution or the like into the tank liquid and adjusting the pH of the desulfurization denitration wastewater in the tank to a predetermined value. With such a pH sensor 32 and pH adjusting means 33, the pH in the nitrification tanks 3A to 3D is maintained at a predetermined value.
The nitrification tanks 3A to 3D are provided with temperature control means (not shown) for controlling the temperature of the nitrification tanks 3A to 3D to a predetermined value.
An injection means 34 is connected to the nitrification tank 3A, and a potassium phosphate (KH ₂ PO ₄ , K ₂ HPO ₄ , K ₃ PO ₄ ) aqueous solution is appropriately injected by the injection means 34. Thereby, it becomes possible to improve the activity of sludge and to improve the processing efficiency of ammonia more.

The denitrification tanks 4A to 4D are anaerobic tanks that denitrify nitric acid contained in the desulfurization denitration waste water from the nitrification tank 3D.
The denitrification tanks 4A to 4D are provided in series on the downstream side of the nitrification tank 3D, and the desulfurization denitration wastewater introduced from the nitrification tank 3D to the denitrification tank 4A flows in order to the denitrification tanks 4B to 4D. ing.
The inside of such denitrification tanks 4A to 4D is an anaerobic atmosphere, and a stirring device 41 is provided at the bottom, and the inside of each tank is uniformly mixed by the stirring of the stirring device 41. ing.

In the activated sludge which distribute | circulates inside such a denitrification tank 4A-4D, the denitrification bacteria which are anaerobic microbial cells mainly function. Examples of such denitrifying bacteria include Paracoccus denitrificans, which are nitrate reducing bacteria.
An injection means 44 is connected to the denitrification tank 4A, and an electron donor such as methanol is appropriately injected from the injection means 44. Thereby, the nitrate-reducing bacteria take in the electron donor from the injection means 44 and generate molecular nitrogen from nitric acid as shown below. Nitrogen gas generated by the action of the nitrate-reducing bacteria is released to the atmosphere from above the denitrification tanks 4A to 4D.

(Chemical formula)
2NO ₃ ⁻ + 10H ⁺ → N ₂ + 4H ₂ O + 2OH ⁻ (3)

  The pH sensor 42 for measuring the pH of the tank liquid is connected to the denitrification tank 4A. The denitrification tank 4A is connected to pH adjusting means 43 for introducing an aqueous hydrochloric acid solution or the like into the desulfurization denitration wastewater in the tank and adjusting the pH of the desulfurization denitration wastewater in the tank to a predetermined value. With such a pH sensor 42 and pH adjusting means 43, the pH in the denitrification tanks 4A to 4D is maintained at a predetermined value. Further, the denitrification tanks 4A to 4D are provided with temperature control means (not shown) for controlling the temperature of the denitrification tanks 4A to 4D to a predetermined value.

  The oxidation tank 5 is an aerobic tank provided in series on the downstream side of the denitrification tank 4D, and oxidatively decomposes the COD components remaining in the desulfurization denitration waste water after the denitrification process from the denitrification tank 4D. The piping of the nitrification blower 9 is connected to the bottom of the oxidation tank 5 like the nitrification tanks 3A to 3D, and air is blown from the nitrification blower 9 at a flow rate of, for example, 100 to 2000 ml / l · min (aeration ). Thereby, the oxidation tank 5 becomes an aerobic atmosphere, and a part of COD component is oxidized and removed from the desulfurization denitration wastewater by the action of nitrifying bacteria.

The sedimentation tank 6 is provided on the downstream side of the oxidation tank 5, and desulfurization denitration waste water from the oxidation tank 5 can be introduced into the inside. The sedimentation tank 6 is configured such that activated sludge in the desulfurization denitration wastewater is precipitated at the bottom, and the supernatant liquid of the desulfurization denitration wastewater is introduced into the activated carbon treatment tank 7.
Sludge return means 61 is provided at the bottom of the sedimentation tank 6, and the activated sludge precipitated on the bottom is returned to the nitrification tank 3A at a predetermined frequency by the sludge return means 61. Thereby, it becomes possible to maintain the concentration of activated sludge in each of the nitrification tanks 3A to 3D and the denitrification tanks 4A to 4D to a predetermined value, and the proliferation ability of nitrifying bacteria and denitrifying bacteria having a relatively low proliferation ability. Can be supplemented.

  The activated carbon treatment tank 7 is provided on the downstream side of the settling tank 6, and desulfurization denitration waste water from the settling tank 6 can be introduced. The activated carbon treatment tank 7 is filled with activated carbon. By passing the desulfurization denitration waste water from the precipitation tank 6 into the activated carbon treatment tank 7, the COD component remaining in the waste water is activated by the activated carbon. It is possible to remove by adsorption.

The ion exchange treatment tank 8 is provided on the downstream side of the activated carbon treatment tank 7 so that desulfurization denitration waste water from the outlet of the activated carbon treatment tank 7 can be introduced into the inside. The ion exchange treatment tank 8 is filled with a weakly basic or medium basic anion exchange resin. As the anion exchange resin, for example, a particulate synthetic resin obtained by adding at least one exchange group of 2 to quaternary amines to a base material that is a copolymer of styrene and divinylbenzene can be used. By passing the desulfurization denitration waste water from the activated carbon treatment tank 7 through the ion exchange treatment tank 8, COD components such as hydroxylamine remaining in the waste water can be adsorbed and removed by the anion exchange resin. It has become.
Further, a pH sensor 81 and a pH adjusting means 82 are connected to the inlet side of the ion exchange treatment tank 8. The pH sensor 81 measures the pH of the desulfurization / denitration wastewater introduced into the ion exchange treatment tank 8. The pH adjusting means 82 introduces a pH adjusting agent such as a sodium hydroxide aqueous solution into the waste water based on the measurement result of the pH sensor 81, and the waste water is adjusted to pH 5 or more and less than 8.3, preferably pH 5 or more and 8 or less. adjust.
Desulfurization denitration wastewater (hereinafter referred to as treated water) after passing through the activated carbon treatment tank 7 is discharged from the outlet of the activated carbon treatment tank 7 to the public water surface.

  Furthermore, a regeneration treatment liquid introducing means 83 is connected to the inlet side of the ion exchange treatment tank 8, and a receiving tank 84 is provided on the outlet side of the ion exchange treatment tank 8. When the introduction of the desulfurization denitration wastewater into the ion exchange treatment tank 8 is stopped, the regeneration treatment liquid introduction means 83 introduces the regeneration treatment agent from the entrance of the ion exchange treatment tank 8 into the inside. As this regeneration treatment agent, for example, an aqueous solution of sodium hydroxide, calcium hydroxide, ammonia, sodium chloride, or the like can be used. The introduced regenerative treatment agent circulates in the anion exchange resin in substantially the same direction as the flow direction of the desulfurization denitration waste water, so that the COD component adsorbed on the anion exchange resin is desorbed. It is like that. Further, the regeneration treatment liquid introduction means 83 introduces an acid such as sulfuric acid or hydrochloric acid into the ion exchange treatment tank 8 after the introduction of the regeneration treatment agent. The receiving tank 84 receives the regenerated processing agent and acid after the regeneration processing discharged from the outlet of the ion exchange processing tank 8.

[Wastewater treatment method]
Next, a wastewater treatment method using the wastewater treatment apparatus 1 will be described.
First, desulfurization denitration wastewater from the power generation facility is stored in the drainage storage tank 2, and then this desulfurization denitration wastewater is introduced into the nitrification tank 3A. The desulfurization denitration wastewater introduced into the nitrification tank 3A flows in order from the nitrification tank 3B to the nitrification tank 3D. At this time, the aerobic nitrifying bacteria in the nitrification tanks 3A to 3D convert the ammonia in the desulfurization denitration wastewater into nitric acid.・ Proceed with nitrification reaction to convert to nitrous acid. Next, the desulfurization denitration waste water from the nitrification tank 3D is introduced into the denitrification tank 4A and flows in order from the denitrification tank 4A to the denitrification tank 4D. At this time, the anaerobic denitrifying bacteria in the denitrification tanks 4 </ b> A to 4 </ b> D cause a denitrification reaction to convert nitric acid in the desulfurization denitration wastewater into molecular nitrogen. Thereby, high concentration ammonia is removed from the desulfurization denitration waste water (sludge treatment process). In addition, the pH of the desulfurization denitration waste water after this sludge treatment process is about 7.4-7.6.

Thereafter, the desulfurization denitration waste water from the denitrification tank 4D is introduced into the oxidation tank 5 and again exposed to an aerobic atmosphere. Thereby, a part of COD component which remained in the said waste_water | drain is removed. Then, the desulfurization denitration waste water from the oxidation tank 5 is introduced into the precipitation tank 6.
Next, the supernatant liquid separated in the precipitation tank 6 is introduced into the activated carbon treatment tank 7. By passing the desulfurization denitration wastewater through the activated carbon treatment tank 7, most of the COD components remaining in the desulfurization denitration wastewater are adsorbed and removed by activated carbon (activated carbon treatment step).
Further, the desulfurization denitration wastewater from the outlet of the activated carbon treatment tank 7 is adjusted to pH 5 or more and less than 8.3, preferably pH 5 or more and 8 or less by the pH sensor 81 and the pH adjusting means 82, and then into the ion exchange treatment tank 8. And introduced. The desulfurization denitration wastewater passes through the ion exchange treatment tank 8, so that COD components such as hydroxylamine remaining in the wastewater are adsorbed and removed by the anion exchange resin (ion exchange treatment step).
In addition, for the ion exchange treatment tank 8 that has performed the ion exchange treatment step for a predetermined period, the introduction of desulfurization denitration wastewater into the ion exchange treatment tank 8 is stopped, and the regeneration treatment liquid introduction means 83 enters the inside of the ion exchange treatment tank 8. Introduce a regenerative treatment agent. The introduced regeneration treatment agent circulates in the anion exchange resin in substantially the same direction as that of the desulfurization denitration wastewater, and thereby the COD component adsorbed on the anion exchange resin is desorbed. Furthermore, the regeneration treatment liquid introduction means 83 introduces an acid such as sulfuric acid or hydrochloric acid into the ion exchange treatment tank 8 to complete the regeneration. The regenerated processing agent and acid containing the desorbed COD component are discharged from the outlet of the ion exchange processing tank 8 and received in the receiving tank 84 (regeneration processing step). After the regeneration processing step is completed, the above ion exchange processing step is performed again.

The treated water after the above ion exchange treatment step is discharged to public water surfaces such as the sea and rivers. This completes a series of desulfurization and denitration wastewater treatment.
By performing the above waste water treatment, high concentration ammonia and various COD components can be reliably removed from the desulfurization denitration waste water, and the COD concentration in the final treated water can be sufficiently reduced. Moreover, since the pH of the desulfurization denitration waste water before the ion exchange treatment step is adjusted to 5 or more and less than 8.3, the pH of the treated water after the ion exchange treatment is also substantially neutral, and particularly the pH is adjusted. There is no need. Therefore, such treated water can be safely discharged to the public water surface. Further, since it is not necessary to administer a large amount of pH adjusting agent in carrying out the ion exchange treatment step, the treatment operation is simple and the treatment cost can be reduced.

[Modification of Embodiment]
In addition, this invention is not limited to the above-mentioned embodiment, The deformation | transformation in the range which can achieve the objective of this invention, improvement, etc. are included in this invention.
For example, in the said embodiment, although the structure which treats the desulfurization denitration waste water containing high concentration ammonia and various COD components from a power generation facility was illustrated, this invention is not limited to this. That is, the present invention can be applied not only to desulfurization and denitration wastewater containing low-concentration ammonia and the like, but also to any wastewater containing ammonia and various COD components such as food factory wastewater and chemical facility wastewater.

  In the said embodiment, although the structure which provides nitrification tank 3A-3D and denitrification tank 4A-4D was illustrated as a sludge processing tank in this invention, it is not limited to this. That is, for example, a configuration in which the number of installed nitrification tanks and denitrification tanks is different, a configuration in which the installation order of nitrification tanks and denitrification tanks is reversed, and both nitrification reaction and denitrification reaction in one sludge treatment tank It is good also as a structure which advances. In other words, any sludge treatment tank can be employed as long as it can remove ammonia in the wastewater by nitrification reaction and denitrification reaction using activated sludge.

  In the said embodiment, although the structure which installs the activated carbon treatment tank 7 and the ion exchange treatment tank 8 in order in the downstream of the sedimentation tank 6 was illustrated, not only this but installation of the activated carbon treatment tank 7 and the ion exchange treatment tank 8 is demonstrated. The order may be reversed. That is, like the waste water treatment apparatus 1A shown in FIG. 2, the ion exchange treatment tank 8 and the activated carbon treatment tank 7 are sequentially installed on the downstream side of the settling tank 6, and the ion exchange treatment process and the activated carbon treatment process are performed after the sludge treatment process. It is good also as a structure which implements these in order. With such a configuration, a COD component removal efficiency equal to or higher than that of the waste water treatment apparatus 1 in the above embodiment can be obtained.

  In the above-described embodiment, the configuration in which only one activated carbon treatment tank 7 is provided in FIG. 1 is not limited to this, and the configuration in which two or more activated carbon treatment tanks 7 are provided in parallel is also possible. Good. With this configuration, more desulfurization denitration wastewater can be treated at the same time, and the adsorption removal efficiency of COD components can be further improved.

  In the above-described embodiment, the configuration in which only one ion exchange treatment tank 8 is provided in FIG. 1 is not limited to this, and two or more ion exchange treatment tanks 8 are provided in parallel. It is good. In the case of such a configuration, while the desulfurization denitration wastewater is introduced into one ion exchange treatment tank 8 and the ion exchange treatment is performed, the regeneration treatment liquid is introduced into the other ion exchange treatment tank 8 to perform the regeneration treatment. Can be implemented. Thereby, waste water treatment can be carried out continuously without stopping the introduction of desulfurization and denitration waste water from the activated carbon treatment tank 7 to the ion exchange treatment tank 8.

  In the said embodiment, although the structure which implements both an activated carbon treatment process and an ion exchange treatment process was illustrated, it is good also as a process which does not implement an activated carbon treatment process. Even in such a case, by carrying out the sludge treatment step and the ion exchange treatment step, ammonia and COD components in the waste water can be suitably removed, and the waste water treatment device 1 is manufactured by the amount not provided with the activated carbon treatment tank 7. Costs and wastewater treatment costs can be reduced.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.

(1) Operation of wastewater treatment apparatus Desulfurization denitration wastewater is provided with nitrification tanks 3A to 3D having a capacity of 1071 tons per tank and denitrification tanks 4A to 4D having a capacity of 344 tons per tank. The wastewater treatment apparatus 1 (see FIG. 1) was passed through and continuously treated.
The above desulfurization denitration wastewater is wastewater generated when desulfurization treatment and denitration treatment are performed on combustion exhaust gas generated when a power plant is operated using super heavy oil or heavy residual oil as fuel. It is. This waste water contains 1230 ppm of ammonium ions, 3 ppm of hydroxylamine, 15 ppm of hydroxylamine sulfonic acid, and 3 ppm of inorganic COD components.
The amount of desulfurization denitration wastewater introduced into the nitrification tank 3A was 2000 tons per day. The temperature of the activated sludge was controlled at 34 to 36.5 ° C., and the pH was controlled at 7.5 to 7.7 with sodium hydroxide. The sludge MLSS (mixed liquor suspended solids) ranged from 4400 to 6800 mg / L.
At the exit of the nitrification tank 3D, ammonia and nitrous acid were almost zero by the action of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, and the entire amount of ammonia was converted to nitric acid.
The sludge discharged from the nitrification tank 3D is led to the denitrification tank 4A, and the nitric acid generated in the nitrification tanks 3A to 3D is converted into nitrogen by the action of the denitrification bacteria while supplying methanol under anaerobic conditions while stirring the tank. And discharged as a gas body. As a result, nitric acid completely disappeared at the outlet of the denitrification tank 4D and was converted to nitrogen gas.
In the actual apparatus operated under such conditions, treated water from the denitrification tank 4D outlet was passed through the sand filtration tank, and then advanced treatment was performed.

(2) Examples 1-1 to 1-12 and Comparative Examples 1-1 to 1-6
A pH adjuster is administered to the desulfurization and denitration wastewater discharged from the sand filtration tank outlet in the actual apparatus operated in (1) above to adjust to a predetermined pH, and then the following advanced treatment is performed on this treated water. gave.
As experimental instruments, a 6 cm diameter glass column packed with 100 ml of ion exchange resin and a 6 cm diameter glass column packed with 100 ml of activated carbon were used. For the ion exchange resin, Bayer MP64 is used as a weakly basic ion exchange resin, Mitsubishi Chemical Diaion PA308 is used as a medium basic ion exchange resin, and Mitsubishi Chemical Diaion is used as a cation exchange resin. WK20 was used.
Using such an experimental instrument, a glass column containing an ion exchange resin for the measurement water under various conditions shown in Table 1, imitating the one obtained by removing the activated carbon treatment tank 7 from the waste water treatment apparatus 1 shown in FIG. (Examples 1-1, 3, 5, 7, 9, 11, Comparative Examples 1-1, 3, 5). Moreover, the activated water treatment tank 7 and the ion exchange treatment tank 8 were sequentially provided to simulate the waste water treatment apparatus 1 (see FIG. 1), and the measurement water was mixed with the activated carbon-containing glass column and ions under various conditions shown in Table 1. Water was passed through the glass column containing the exchange resin in order (Examples 1-2, 4, 6, 8, 10, 12, Comparative Examples 1-2, 4, 6). Note that the measurement water was passed through a glass column containing activated carbon at a flow rate of 200 t / m ³ · day. Moreover, the adsorption process by ion exchange resin was performed at 24-26 degreeC.
And the COD density | concentration of the measurement water before flowing in into the glass column containing an ion exchange resin, and the COD density | concentration of the measurement water which flowed out from this glass column exit were each measured. The COD concentration was measured by quantification using potassium permanganate (KMnO ₄ ) based on the official method (JIS K 0102). The measurement results are shown in Table 1.

In Table 1, when Examples 1-1 to 1-12 and Comparative Examples 1-1 to 1-4 are compared, when a weakly basic or medium basic anion exchange resin is used, a cation exchange resin is used. It can be seen that the COD concentration in the treated water after the ion exchange treatment can be reduced as compared with the case where is used.
Moreover, by adjusting Example 1-1 to 1-8 and Comparative Examples 1-5 to 1-6, the pH of the wastewater introduced into the ion exchange treatment tank 8 is adjusted to less than 8.3, It can be seen that the COD concentration in the treated water after the ion exchange treatment can be sufficiently reduced.
And from Examples 1-2, 4, 6, 8, 10, and 12, by performing the activated carbon treatment before the ion exchange treatment, the COD concentration in the treated water after the ion exchange treatment can be reduced to about 6 ppm. It can be seen that the wastewater treatment was realized.

(3) Examples 2-1 to 2-4
Using the experimental instrument of (2) above, the measurement water was measured under various conditions shown in Table 2 by imitating a wastewater treatment apparatus 1 (see FIG. 2) equipped with an ion exchange treatment tank 8 and an activated carbon treatment tank 7 in this order. Were sequentially passed through a glass column containing an ion exchange resin and a glass column containing activated carbon (Examples 2-1 to 2-4). Note that the measurement water was passed through a glass column containing activated carbon at a flow rate of 200 t / m ³ · day. Moreover, the adsorption process by ion exchange resin was performed at 24-26 degreeC.
In the same manner as in (2) above, the COD concentration of measurement water before flowing into the glass column containing ion exchange resin and the COD concentration of measurement water flowing out from the outlet of the glass column containing activated carbon were measured. The measurement results are shown in Table 2.

  As can be seen from the results in Table 2, even when the activated carbon treatment was performed after the ion exchange treatment, the COD concentration in the treated water after the activated carbon treatment could be reduced to about 5 to 6 ppm, and advanced wastewater treatment could be realized. I understand.

It is the schematic diagram which showed the waste water treatment apparatus for enforcing the waste water treatment method which concerns on one Embodiment of this invention. It is the schematic diagram which showed the modification of the waste water treatment apparatus in the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A ... Waste water treatment apparatus 2 ... Waste water storage tank 3A-3D ... Nitrification tank 31 ... Reactor 32 ... pH sensor 33 ... pH adjustment means 34 ... Injection means 4A-4D ... Denitrification tank 41 ... Stirrer 42 ... pH sensor 43 ... pH adjustment means 44 ... injection means 5 ... oxidation tank 6 ... sedimentation tank 61 ... sludge return means 7 ... activated carbon treatment tank 8 ... ion exchange treatment tank 81 ... pH sensor 82 ... pH adjustment means 83 ... regeneration treatment liquid introduction means 84 ... receiving tank 9 ... Nitrification blower

Claims (9)

A wastewater treatment method for treating wastewater containing ammonia and COD components,
A sludge treatment step for removing ammonia in the wastewater by nitrification reaction and denitrification reaction with activated sludge;
The waste water after the sludge treatment step is adjusted to a pH of 5 or more and less than 8.3, and then an ion exchange treatment step of contacting with a weakly basic or medium basic anion exchange resin is performed. Wastewater treatment method. The waste water treatment method according to claim 1,
A wastewater treatment method, wherein an activated carbon treatment step is performed in which the wastewater after the sludge treatment step is brought into contact with activated carbon before or after the ion exchange treatment step is carried out. In the waste water treatment method according to claim 1 or 2,
After the ion exchange treatment step, the introduction of the waste water into the anion exchange resin is stopped, and a regeneration treatment agent is introduced into the anion exchange resin in substantially the same direction as the waste water introduction direction. A wastewater treatment method comprising carrying out a regeneration treatment step of desorbing a COD component adsorbed on an anion exchange resin. In the waste water treatment method in any one of Claims 1 thru | or 3,
The anion exchange resin has at least one of a secondary amine, a tertiary amine and a quaternary amine as an exchange group. In the waste water treatment method according to any one of claims 1 to 4,
The waste water contains at least one of hydroxylamine, hydroxylamine sulfonic acid, and inorganic COD component as the COD component. In the waste water treatment method according to any one of claims 1 to 5,
The waste water treatment method is characterized in that the waste water is waste water generated when at least one of desulfurization treatment and denitration treatment is performed on combustion exhaust gas of super heavy oil or heavy residual oil. In the waste water treatment method according to any one of claims 1 to 6,
The wastewater is a wastewater treatment method generated when at least one of a desulfurization treatment and a denitration treatment is performed on combustion exhaust gas discharged from a power generation facility. In the wastewater treatment method according to any one of claims 1 to 7,
The ammonia concentration in the waste water is 300 ppm or more. A wastewater treatment apparatus for treating wastewater containing ammonia and COD components,
Activated sludge is filled inside, a sludge treatment tank for removing ammonia in the waste water by nitrification reaction and denitrification reaction with the activated sludge,
PH adjusting means for adjusting the wastewater treated in the sludge treatment tank to pH 5 or more and less than 8.3,
An ion exchange treatment tank that is filled with a weakly basic or medium basic anion exchange resin, and that makes the pH adjusted by the pH adjusting means contact the anion exchange resin. Wastewater treatment equipment characterized by.

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