JP3348446B2 - Method and apparatus for removing nitrate ions and / or nitrite ions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for removing nitrate ions and / or nitrite ions, and more particularly to treating raw water containing nitrate ions with an anion exchange resin and adsorbing nitrate ions. The present invention relates to a method and an apparatus for removing nitrate ions and / or nitrite ions for efficiently regenerating a resin.

[0002]

2. Description of the Related Art If drinking water contains nitrate ions, infants may suffer from oxygen deficiency (methemoglobinemia).
It is regulated to g-N / l or less (10 mg or less in 1 liter in terms of nitrogen).

Conventionally, nitrate ion removal methods include:
A method using an ion-exchange resin (basic anion-exchange resin) is generally used as described in “Guidelines and explanations for water supply facility design”.

[0004] Nitrate ions are one of the causes of eutrophication of lakes and marshes, and in this case, are removed by biological treatment (biological denitrification treatment).

[0005]

The above-mentioned conventional method for removing nitrate ions has the following problems.

That is, in the method using an ion exchange resin, a high concentration of nitrate ions is contained in the regenerated waste liquid.
The recycled waste liquid cannot be discharged out of the system as it is, and waste liquid treatment is required. Since the regenerated waste liquid also contains a salt such as a high concentration of salt, there is also a problem of salt damage. The amount of salt used for regeneration is large, and the regeneration cost is high.

There is such a problem.

Further, in biological treatment, in the treatment of water containing low-concentration nitrate ions, it is necessary to excessively supply a BOD source. In order to treat a large amount of water, facilities such as a biological reaction tank and a sedimentation tank become very large. There is a problem.

In order to solve these problems, a method of combining ion exchange treatment and biological treatment, concentrating nitrate ions in the regenerated waste liquid by ion exchange treatment, and biologically treating the regenerated waste liquid has been studied. However, even in this case, since salt is used for regeneration, the regeneration cost is high. There is a problem of salt discharge into the environment. Under a high salt concentration condition such as a recycle waste liquid, the biological treatment efficiency is poor, and a sufficient treatment effect cannot be obtained. There is a problem.

The present invention relates to the above-mentioned conventional ion exchange treatment and / or
Or solve the problems in the method of removing nitrate ions by biological treatment, without discharging the wastewater containing a high concentration of nitrate ions and salts, without using an expensive regenerant, a large biological treatment tank and Removal of nitrate and / or nitrite ions from raw water containing nitrate and / or nitrite ions at low cost and efficiently without the need for a sedimentation basin It is an object to provide a method and a removal device.

[0011]

The method for removing nitrate ions and / or nitrite ions according to the present invention comprises contacting raw water containing nitrate ions and / or nitrite ions with an anion exchange resin to remove nitrate ions and / or nitrite ions. Removing nitrite ions from the raw water to obtain treated water;
Alternatively, a step of biologically regenerating an anion exchange resin adsorbing nitrite ions with denitrifying bacteria, and an anion exchange resin after the regeneration.
Washing the exchange resin with washing water and separating the washing waste water into solid and liquid
And the separated sludge obtained by solid-liquid separation
And a step used for reproduction .

The apparatus for removing nitrate ions and / or nitrite ions according to the present invention comprises an anion exchange resin column having an inlet and an outlet for liquid, and feeds raw water containing nitrate ions and / or nitrite ions to the column. A means for introducing, a means for introducing a denitrifying bacterium and a hydrogen donor into the tower to regenerate the anion exchange resin, a means for introducing washing water to the tower, and a washing from the tower.
Separation of sludge by solid-liquid separation of purified wastewater
And means for raw use .

That is, the present inventors have repeatedly studied a method of regenerating an anion exchange resin to which nitrate ions and nitrite ions are adsorbed. The inventors have found that processing can be performed, and completed the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In the following, the removal of nitrate ions will be described. According to the method and apparatus of the present invention,
Nitrite ions can be removed as well.

FIG. 1 is a system diagram showing one embodiment of the apparatus for removing nitrate ions and / or nitrite ions of the present invention.
(A) shows the time of the ion exchange treatment, (b) shows the time of the regeneration, and (c) shows the time of the backwash. In the figure, 1 is an ion exchange tower, 2 is an anion exchange resin, 3 is a sedimentation / separation tank, 11, 12, and 2.
1, 22, 31, 32, 33, and 34 are pipes, and P is a pump.

In the method of the present embodiment, first, the ion exchange tower 1 is filled with the anion exchange resin 2, and raw water containing nitrate ions is passed through a pipe 11 having a pump P. Thereby, the nitrate ions in the raw water are adsorbed by the anion exchange resin 2, and the treated water from which the nitrate ions have been removed is discharged out of the system through the pipe 12 (FIG. 1 (a)).

When the amount of adsorbed nitrate ions of the anion exchange resin 2 reaches saturation by such ion exchange treatment and the ion exchange capacity decreases, the flow of raw water is stopped and the denitrifying bacteria and hydrogen donor The anion exchange resin is regenerated by supplying ethanol in an upward flow and subjecting the nitrate ions adsorbed to the anion exchange resin 2 to a biological denitrification treatment (FIG. 1 (b)). The discharged liquid is discharged from the pipe 21.

After the regeneration, washing water for back washing is supplied from the pipe 32 in an upward flow, the back washing of the anion exchange resin 2 is performed, and denitrifying bacteria are separated from the anion exchange resin 2 and washed. The backwash wastewater is sent from the pipe 31 to the sedimentation separation tank 3 to be separated into solid and liquid. This supernatant water is discharged from the pipe 33, while
The separated sludge is extracted from the pipe 34 (FIG. 1 (c)). Separated sludge is recycled for biological regeneration of anion exchange resin
You. Also, the supernatant water can be reused for backwashing.

The backwashed anion exchange resin can be used repeatedly for the nitrate ion adsorption treatment.

The anion exchange resin used in the present invention may be any of a strongly basic anion exchange resin and a weakly basic anion exchange resin, and the types of the exchange groups may be trimethylamine, triethylamine, tributylamine, dimethylethanolamine. , And other various things can be adopted. Further, the form of such an anion exchange resin may be any of granular, fibrous, crushed, and powder.

The hydrogen donor supplied together with the denitrifying bacteria includes BOD sources such as methanol, ethanol, acetic acid, hydrogen and glucose.

In the present invention, the flow rate of raw water, the amounts of denitrifying bacteria and hydrogen donors to be added, and other treatment conditions are not particularly limited, and may be determined according to the quality of the raw water to be treated and the required quality of treated water. Is determined as appropriate.

In the method of the present invention, in addition to passing raw water through the anion exchange resin filled in the ion exchange tower, the raw water and the anion exchange resin are mixed and stirred, and then the anion exchange resin is taken out. It can also be carried out by batch processing such as mixing and stirring.

In the apparatus of the present invention, a plurality of ion exchange towers are arranged in parallel, and raw water, denitrifying bacteria and a hydrogen donor, or washing water are supplied to each ion exchange tower by sequentially switching valves and the like. Alternatively, the ion exchange treatment, the regeneration, and the backwashing can be repeatedly performed.

[0026]

[Function] The nitrate ion adsorbed on the anion exchange resin is
Biological treatment is carried out by denitrifying bacteria by the following reaction, and the anion exchange resin is efficiently regenerated. In the following, S
BR is a strong basic anion exchange resin, WBR is a weak basic anion exchange resin, and methanol (CH ₃ OH) as a hydrogen donor can be replaced with ethanol, acetic acid, H ₂ or the like.

[0027]

Embedded image

The adsorbed nitrate ions are removed.
The anion exchange resin thus regenerated can be used for the next adsorption treatment by separating and washing from the denitrifying bacteria by back washing or the like.

[0029]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 A sodium nitrate solution (50 g-NaNO ₃ / l) was mixed with a strongly basic anion exchange resin (“Lewatit M-50”).
0 "(manufactured by Bayer AG)) was passed through a column (inner diameter 25 mm x length 400 m) packed with 100 ml of SV at 3 hr ^-1 , and nitrate ions were passed through 10 g-N / l-resin (per liter of anion exchange resin). And 10 g of nitrogen equivalent). 100 ml of this anion exchange resin is placed in an Erlenmeyer flask, and 200 ml of activated sludge containing denitrifying bacteria (MLSS
4000 mg / l) and 2 g of ethanol
/ L and stirred gently under anaerobic conditions. The pH was 7.0 and the temperature was 25 ° C.

At this time, the decreasing rate of the added ethanol is 110 mg-ethanol / g-MLSS · hr (1 h
r, 110 mg of ethanol per 1 g of MLSS). In addition, nitrogen gas (analyzed by gas chromatography) was generated in the flask, and foaming occurred.

Twenty-four hours later, the anion exchange resin was taken out of the flask, washed with water, packed again in a column, and treated with 4% Na.
Table 1 shows the results of ion analysis of the effluent after passing 1 liter of the OH aqueous solution.

[0033]

[Table 1]

From Table 1, it is clear that the anion exchange resin after treatment with the denitrifying bacteria contains almost no nitrate ion and is regenerated to the bicarbonate form.

The raw water containing nitrate ions having the following water quality was added to the column filled with the regenerated anion exchange resin by SV = 1.
The results of measuring the nitrate ion concentration of the treated water obtained by passing water at ⁰ hr ^-1 are shown in Table 2.

As is clear from Table 2, the nitrate ion concentration of the treated water was 5 mg until breakthrough of the anion exchange resin was reached.
−N / l or less, and good results were obtained.

Raw water quality pH: 7.3 Conductivity: 310 (μS / cm) Total hardness: 40 (mg / l) M-Al: 50 (mg / l) Cl: 24 (mg / l) SO ₄ : 8 (Mg / l) NO ₃ : 60 (mg / l)

[0038]

[Table 2]

Comparative Example 1 In the same manner as in Example 1, 300 ml of a 10% saline solution was passed through an anion exchange resin through which a sodium nitrate solution was passed.
Subsequently, regeneration was performed by passing 500 ml of water.

Table 3 shows the water quality of the recycled waste liquid at this time.

[0041]

[Table 3]

Activated sludge containing denitrifying bacteria was added to the regenerated waste liquid to a concentration of 400 mg / l MLSS, and 2 g / l of ethanol was added, followed by gentle stirring under anaerobic conditions. The pH was 7.0 and the temperature was 25 ° C.

At this time, the decreasing rate of the added ethanol is 30 to 20 mg-ethanol / g-MLSS · hr, which is 30 to 20 mg / ml lower than the activity when the salt concentration is low (for example, 0.5% or less). Showed only% activity. Even when the sludge acclimated with the salt was used, only the same activity was obtained under the condition of the salt concentration of 3% or more. For this reason, the biological treatment tank volume needs to be 3 to 5 times as large as that in the case of low salt concentration, or it is necessary to dilute the liquid to be treated 5 times or more.

The regenerated anion exchange resin was packed in a column, and raw water having the same water quality as that treated in Example 1 was passed at SV = 10 hr ^-1. The nitrate ion concentration of the water was 5 mg-N / l or less.

From these results, it is possible to regenerate the anion exchange resin when the conventional ion exchange method and the biological treatment method are simply combined, but it is possible to regenerate the anion exchange resin. In addition to the necessity of a regenerating solution, a large amount of high-salt-concentration regenerating waste solution is discharged, and a large-capacity biological treatment tank is required for the treatment of this reclaimed waste solution, which is obviously industrially disadvantageous. is there.

[0046]

As described above in detail, according to the method and apparatus for removing nitrate ions and / or nitrite ions of the present invention, nitrate ions and / or nitrite ions are removed from raw water containing nitrate ions and / or nitrite ions. When removing nitrate ions, wastewater containing high concentrations of nitrate ions and / or nitrite ions is not discharged. Wastewater containing high concentration of salt is not discharged,
Therefore, there is no fear of salt damage. No regeneration agent for the ion exchange resin is required, and the regeneration cost is low. Even when treating a large amount of raw water containing low-concentration nitrate ions and / or nitrite ions, a large-capacity biological treatment tank and sedimentation pond are not required, and the apparatus can be downsized. Thus, raw water containing nitrate ions and / or nitrite ions can be easily and efficiently treated at low cost to obtain high-quality treated water.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a device for removing nitrate ions and / or nitrite ions of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion exchange tower 2 Anion exchange resin 3 Precipitation separation tank

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 1/42 B01J 41/04 B01J 49/00 C02F 3/34

Claims (2)

(57) [Claims] 1. A step of contacting raw water containing nitrate ions and / or nitrite ions with an anion exchange resin to remove nitrate ions and / or nitrite ions from the raw water to obtain treated water; Or a step of biologically regenerating the anion exchange resin adsorbing nitrite ions with denitrifying bacteria , and washing the regenerated anion exchange resin with washing water
And solid-liquid separation of the cleaning wastewater and the solid-liquid separation
Of using separated sludge for regeneration of anion exchange resin
A method for removing nitrate ions and / or nitrite ions comprising: 2. An anion having an inlet and an outlet for a liquid.
An exchange resin tower, and raw water containing nitrate ions and / or nitrite ions is supplied to the tower.
Means for introducing, introducing denitrifying bacteria and hydrogen donor into the towerAnion exchange
Regenerate resinMeans for introducing washing water into the tower, Separating sludge by solid-liquid separation of the washing wastewater from the tower
The means used to regenerate the exchange resin A nitric acid comprising
On and / or nitrite ion removal equipment.