KR20110109914A - Material for decontaminating water containing nitrate nitrogen, and method for decontaminating water containing nitrate nitrogen - Google Patents

Abstract

Sulfur denitrification is carried out from the initial stage of purification to provide a purifying material and a method for purifying acetic acid-nitrogen-containing water, which are capable of sufficiently purifying acetic acid-containing water. The purifying material of nitric acid-containing water contains dolomite and sulfur, and the magnesium content of the total mass of the purifying material exceeds 6.6% by mass and is 8.8% by mass or less.

Description

Purification of acetic acid-containing nitrogen and purification method of nitric acid-containing water {MATERIAL FOR DECONTAMINATING WATER CONTAINING NITRATE NITROGEN, AND METHOD FOR DECONTAMINATING WATER CONTAINING NITRATE NITROGEN}

The present invention relates to a purifying material and a method for purifying acetic acid-nitrogen-containing water, which are used for purifying wastewater containing acetic acid-nitrogen by denitrifying bacteria and groundwater.

Acetic acid nitrogen and nitrous acid nitrogen (hereinafter referred to collectively as "acetic acid nitrogen") included in drainage such as domestic drainage, industrial drainage, and agricultural drainage are eutrophication of water bodies such as rivers and lakes. It is one of the causes of chemical degradation and groundwater pollution. In particular, groundwater contamination by nitric acid nitrogen has a wide range of sources of contamination such as fertilization and livestock excretion.

Therefore, as a countermeasure against groundwater pollution, measures to reduce nitrogen load from the source, countermeasures against pollution, and countermeasures against contaminated drainage and groundwater have been promoted.

Acetic acid nitrogen was added to the item of the environmental standard about the water pollution of groundwater in 1999 in Japan. Acetic acid nitrogen has a high excess rate with respect to an environmental standard especially compared with other items. For this reason, it is required to sufficiently remove acetic acid nitrogen from waste water and groundwater and purify the water.

Sulfur denitrification by sulfur oxidative denitrification bacteria (hereinafter referred to as "denitrification bacteria") is known as a method for removing acetic acid from water and groundwater and purifying water.

Sulfur denitrification is a process in which sulfur, an inorganic substance, is acted as an electron donor to reduce and denitrate acetic acid in water. Specifically, under anaerobic conditions, denitrified bacteria inhale nitrate ions (NO ₃ ⁻ ) in water and breathe with oxygen in the nitrate ions, thereby reducing nitric acid nitrogen (NO ₃ -N) to nitrogen gas (N ₂ ). And exhausted into the atmosphere.

Sulfur denitrification is usually performed by passing wastewater containing nitric acid, groundwater or the like into a purifying material that promotes the activity of denitrifying bacteria.

As such a purifying material, a substance containing mainly calcium carbonate of calcium and / or magnesium (for example, calcium carbonate, limestone, dolomite, etc.) and sulfuric acid nitrogen denitrification substrate is proposed (Patent Documents 1 to 3). Reference).

Japanese Patent No. 3430364 Japanese Patent No. 3475390 Japanese Patent No. 4092199

By the way, in order to perform sulfur denitrification by denitrification bacteria for a long time, it is essential to provide nutrients to the denitrification bacteria through a purifying material. The acetic acid nitrogen denitrification substrates described in Patent Literatures 1 to 3 provide nutrients to denitrifying bacteria mainly using calcium as a nutrient source.

However, in these nitric acid denitrification substrates, since denitrifying bacteria take time to activate, sulfur denitrification is difficult to progress in the initial stages of purification such as drainage and groundwater, and the removal of nitric acid is insufficient.

The activation of denitrifying bacteria herein means a state in which denitrifying bacteria are exposed to nitric acid-containing water under anaerobic conditions and actively desulfurize in response to environmental changes.

The present invention has been made in view of the above circumstances, and provides a purifying material of nitric acid-containing nitrogen water and a method for purifying nitric acid-containing nitrogen water which can proceed with sulfur denitrification from the initial stage of purification to sufficiently purify nitric acid-containing water. For the purpose of

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining, the present inventors discovered that denitrifying bacteria tend to be activated by providing nutrients containing magnesium as a nutrient source to denitrifying bacteria, and as a result, sulfur denitrification proceeds from the initial stage of purification, thereby completing the present invention. Reached the

That is, the purification | cleaning material of this invention is a purification | cleaning material of nitric acid-containing water, it contains a dolomite and sulfur, and also the purification | cleaning material which is more than 6.6 mass% and 8.8 mass% or less with respect to the total mass of the said purification material.

In addition, the method for purifying nitric acid-containing water of the present invention is a method for purifying nitric acid-nitrogen-containing water in which the acetic acid-nitrogen-containing water containing nitric acid nitrogen is brought into contact with the purifying material in which denitrifying bacteria are fixed. Acidic nitrogen is a method for purifying acetic acid-containing water denitrified by the denitrifying bacteria.

According to the present invention, it is possible to provide a purifying material and a method for purifying acetic acid-nitrogen-containing water, by which sulfur denitrification is advanced from the initial stage of purification to sufficiently purify the acetic-acid-nitrogen-containing water.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows the purification apparatus used for the purification test of an Example and a comparative example.
2 is a graph showing the results of Examples and Comparative Examples.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The purifying material of the present invention is used for purifying water (acetic acid-containing nitrogen-containing water) such as wastewater containing nitric acid and groundwater, and contains dolomite and sulfur.

Dolomite is a bicarbonate mineral of calcium and magnesium. The chemical formula is CaMg (CO ₃ ) ₂ , and the composition ratio of calcium and magnesium is 1: 1, but the composition ratio may be slightly different depending on the place of origin. In addition, the quantity of magnesium contained in 100 mass% of dolomite is about 11 mass%.

Dolomite is available as a commercial item.

Dolomite-derived carbonate ions are used for metabolism as the carbon source of sulfur denitrification. On the other hand, calcium and magnesium combine with sulfate ions generated by sulfur denitrification to form sulfate. When sulfate ions are generated, the treated water becomes acidic, but acidification of the treated water can be suppressed by forming a sulfate. As a result, the load on the environment can be made very small.

In addition, calcium and magnesium in dolomite become a nutrient source for denitrifying bacteria, and thus sulfur denitrification over a long period of time becomes possible. In particular, magnesium can more effectively activate denitrifying bacteria in a shorter time than calcium. For this reason, sulfur denitrification tends to proceed from the initial stage of purification of the nitric acid-containing water, and the nitric acid-containing nitrogen-containing water is sufficiently purified.

Content of dolomite is more than 6.6 mass% in 100 mass% of purification materials in conversion of magnesium amount, and is 8.8 mass% or less. When the amount of magnesium in 100 mass% of purifiers exceeds 6.6 mass%, the metabolism regarding sulfur denitrification of denitrifying bacteria can be activated in a short time. On the other hand, when magnesium amount is 8.8 mass% or less, the quantity of the sulfur used as the electric donor mentioned later can fully be ensured, and denitrifying bacteria can breathe acetate. Since the amount of magnesium in 100 mass% of purifiers can activate denitrification bacteria in a short time, 7.1 mass% or more is preferable, and 8.3 mass% or less is preferable.

However, when the purification material contains a compound (Mg-containing compound) containing magnesium such as magnesite (MgCO ₃ ) as another component described later, the total amount of magnesium derived from dolomite and magnesium derived from Mg-containing compound is in the above range. The content of dolomite can be adjusted suitably so that it may become inside.

Sulfur is used as an electron donor of sulfur denitrification.

Examples of the sulfur include sulfur recovered from petroleum desulfurization and coal desulfurization plants, natural sulfur and the like, and the form may be in a solid state (powder or granular form) or a molten state.

20 mass% or more and less than 40 mass% are preferable in 100 mass% of purifiers, and, as for content of sulfur, 24.5-35.5 mass% is more preferable.

The purifying material of the present invention may contain other components other than dolomite and sulfur.

As another component, the metal carbonate etc. which represent magnesite etc. are mentioned, for example. Magnesite is a magnesium carbonate that, like dolomite, can activate denitrifying bacteria in a short time.

It is preferable that an average particle diameter is 3-100 mm, and, as for a purification material, it is more preferable that it is 10-50 mm. If the average particle diameter of the purifying material is too small, the purifying materials tend to be clogged tightly, and the nitrogen gas generated by sulfur denitrification becomes difficult to be exhausted into the atmosphere. If the average particle diameter of a purification material is 3 mm or more, nitrogen gas will be easy to be discharged | released from the clearance gap between purification materials. On the other hand, if the average particle diameter of a purification | cleaning material is 100 mm or less, a purification | cleaning material can be easily passed through without a crust of nitric acid-containing water.

In addition, the average particle diameter of a purification | cleaning material is the average value of the longest diameter measured using the vernier caliper etc. with respect to 100 purification | cleaning materials arbitrarily selected.

The purification | cleaning material of this invention can be manufactured as follows, for example.

First, dolomite and sulfur are mixed with other components as needed. Subsequently, the mixture is heated to heat-melt sulfur, and then quenched with cooling water or the like if necessary. After dolomite, sulfur, etc. are solidified, the solids are pulverized or granulated to a desired average particle diameter to obtain a purifying material.

In addition, you may use the liquid liquefied sulfur instead of heat-melting sulfur.

Since the purification | cleaning material obtained in this way contains dolomite and sulfur, it is not necessary to supply the carbon source of sulfur denitrification separately, and the in-system balance before and behind sulfur denitrification can be kept favorable. In addition, calcium and magnesium in dolomite become nutrient sources for denitrifying bacteria, and thus sulfur denitrification over a long period of time becomes possible. Therefore, the purifying material of the present invention is suitable for purifying nitric acid-containing water and is excellent in removing nitric acid nitrogen.

In addition, magnesium in dolomite contained in the purification material can effectively activate denitrifying bacteria in a short time. Therefore, according to the purifying material of the present invention, sulfur denitrification can be advanced from the initial stage of purification, and the acetic acid-containing water can be sufficiently purified.

In addition, since the purification | cleaning material of this invention can be manufactured easily by the method mentioned above, it does not require special manufacturing technique. In addition, materials for purifying materials such as dolomite and sulfur are inexpensive and readily available and can be produced at low cost.

The method for purifying nitric acid-containing water using the purifying agent of the present invention is performed by passing the acetic acid-nitrogen-containing water into a purifying material in which denitrifying bacteria are fixed. When acetic acid-containing water is passed through the purifying material, sulfur of the purifying material acts as an electron donor, nitrate ions in the water are blown by the denitrifying bacteria, and the nitric acid nitrogen is reduced to nitrogen gas and exhausted into the atmosphere. As a result, the nitric acid nitrogen is removed from the nitric acid-containing water to purify the nitric acid-containing nitrogen water.

As superacidic nitrogen-containing water used as the purification object, various wastewater, such as domestic wastewater, industrial wastewater, agricultural wastewater, groundwater, etc. are mentioned, for example.

There is no particular limitation on the method of water passing through the nitric acid-containing nitrogen water, and for example, a place in which a purifying material is filled in a column and the like, through which the nitric acid-containing water is passed or a permeable wall filled with the purifying material flows in drainage or groundwater. And a method of passing the permeable wall using these water flows.

In addition, for purification of the acetic acid-containing nitrogen water, one in which denitrifying bacteria are fixed (acclimation) in advance to the purifying material of the present invention may be used. If denitrifying bacteria are settled in the purification material in advance, sulfur denitrification is started more quickly.

Example

Hereinafter, an Example is given and this invention is demonstrated concretely. However, this invention is not limited to these.

[First Embodiment]

30 parts by mass of powdered sulfur and 70 parts by mass of dolomite (manufactured by Shin Koo Kogyo Co., Ltd., "Dolomite", a composition ratio of calcium and magnesium (Ca: Mg) = 1: 1) were mixed by a mixer. . The mixture was heated to 120 ° C. to heat-melt sulfur, and then quenched and solidified with cooling water. Subsequently, the solid was pulverized so that the average particle diameter might be set to 35 mm by a pulverizer, thereby obtaining purification material A (Ca / Mg material) having a magnesium content of 7.7% by mass.

[First Comparative Example]

Purifying material B (Ca / Mg material) whose amount of magnesium was 5.5 mass% was obtained like Example 1 except having changed the compounding quantity of powder sulfur into 50 mass parts and the dolomite compounding quantity in 50 mass parts.

Second Comparative Example

Purifying material C (Ca / Mg material) whose 3.3 mass% of magnesium amounts was obtained like Example 1 except having changed the compounding quantity of powder sulfur into 70 mass parts and the dolomite compounding quantity to 30 mass parts.

Third Comparative Example

Purifying material D (Ca material) was produced in the same manner as in Example 1 except that 50 parts by mass of calcium carbonate was used instead of 50 parts by mass of dolomite.

<Purification test 1>

The purification apparatus shown in FIG. 1 was used for the purification test.

The purification device 1 shown in FIG. 1 includes a raw water tank 10 storing superacetic nitrogen-containing water, and four columns 20a, 20b, 20c, and 20d in which purification is performed by sulfur denitrification. And a treated water tank (30a, 30b, 30c, 30d) for recovering the treated water purified by each column, and a raw water pump (40) for supplying nitric acid-containing water to each column from the raw water tank (10). It is provided.

In the raw water tank 10, raw water in which potassium nitrate (KNO ₃ ) was dissolved in tap water was stored as acetic acid nitrogen-containing water so that the acetic acid concentration was 30 mg / L.

As the columns 20a, 20b, 20c, and 20d, glass columns having an inner diameter of 26 mm and a length of 600 mm were used to connect each column in parallel.

The column 20a was filled with gravel (average particle diameter 2 mm) to form a support layer 21a. Subsequently, the purification material A (Ca / Mg material) produced in the 1st Example was filled on the support layer 21a, and the purification layer 22a was formed. The height of the support layer 21a was 20 mm, the filling amount of the purification material was 290 mL, and the height of the purification layer 22a was 550 mm.

The column 20b was filled with gravel (average particle diameter 2 mm) to form a support layer 21b. Subsequently, the purification material B (Ca / Mg material) produced by the 1st comparative example was filled on the support layer 21b, and the purification layer 22b was formed. The height of the support layer 21b was 20 mm, the filling amount of the purification material was 290 mL, and the height of the purification layer 22b was 550 mm.

The column 20c was filled with gravel (average particle diameter 2 mm) to form a support layer 21c. Subsequently, the purification material C (Ca / Mg material) produced by the 2nd comparative example was filled on the support layer 21c, and the purification layer 22c was formed. The height of the support layer 21c was 20 mm, the filling amount of the purification material was 290 mL, and the height of the purification layer 22c was 550 mm.

The column 20d was filled with gravel (average particle diameter 2 mm) to form a support layer 21d. Subsequently, the purification material D (Ca material) produced by the 4th comparative example was filled on the support layer 21d, and the purification layer 22d was formed. The height of the support layer 21d was 20 mm, the filling amount of the purification material was 290 mL, and the height of the purification layer 22d was 550 mm.

Using the purification apparatus 1, the purification test was performed as follows.

From the raw water tank 10, acetic acid-containing water (raw water) was continuously supplied to each column under a supply condition of 1.0 mL / min of water flow rate and 4.8 hours of residence time in the column, and acetic acid-containing nitrogen water was supplied to the first embodiment. And water purifying materials produced in the first to third comparative examples, respectively, to carry out a purification test.

In addition, the purification test was performed at water temperature 15-20 degreeC. In addition, the treated water purified by the column 20a is treated in the treated water tank 30a, and the treated water purified by the column 20b is treated in the treated water tank 30b, and the treated water purified by the column 20c. Was recovered to the treated water tank 30c and the treated water purified by the column 20d to the treated water tank 30d.

During the purification test, each of the treated water immediately before passing through the acetic acid-containing water before purification and each column stored in the raw water tank and recovered to each treated water tank is appropriately collected, and subjected to ion chromatography, The acetic acid ion concentration and the acetic acid ion concentration in the containing water and the treated water were measured, and these were converted to the acetic acid nitrogen concentration (mg / L). The obtained result is shown in FIG.

In addition, in FIG. 2, the "first example" passes through the column 20a, and as a result of the treated water purified by the purification material A, the "first comparative example" passes through the column 20b and passes to the purification material B. As a result of the treated water purified by the "Comparative Example 2" passes through the column 20c, and as a result of the treated water purified by the Purifier C, "Comparative Example 3" passes through the column 20d, and the purified material As a result of the treated water purified by D, "raw water" is the result of the acetic acid-containing nitrogen water before purification.

As is apparent from Fig. 2, in the purifying material A obtained in the first embodiment, nitric acid nitrogen could be efficiently removed from the initial stage of purification compared with the result of the raw water.

That is, in the first embodiment, activation of denitrifying bacteria was promoted from the initial stage of purification to allow sulfur denitrification to proceed.

On the other hand, in the case of the purification material B obtained by the 1st comparative example whose magnesium amount is 5.5 mass%, and the purification material C obtained by the 2nd comparative example whose magnesium amount is 3.3 mass%, on the 3rd day of passing days, nitric acid nitrogen is the same as the result of raw water, It was hardly removed and remained in the treated water. In addition, after 11 days of elapsed time, nitric acid nitrogen could be removed slightly compared with the result of raw water, but it fell remarkably compared with Example 1, and removal of nitric acid nitrogen was insufficient.

Also in the third comparative example using the purifying material D composed of calcium carbonate and sulfur, similarly to the results of the first and second comparative examples, the removal of nitric acid nitrogen was insufficient.

That is, in the first to third comparative examples, since denitrifying bacteria take time to be activated, sulfur denitrification was difficult to proceed in the initial stage of purification.

[Experimental Example]

The following experiment (purification test 2) was performed for the purpose of confirming the superiority of dolomite.

As the purifying material, the purifying test 1 described above was continued for 9 months using the purifying materials B and D produced in the first and third comparative examples. Before and after the purification test, the mass of each purification material used in the test was measured. In addition, about the purification material after a purification test, after drying at 60 degreeC for 16 hours, the mass was measured.

In addition, the amount of acetic acid nitrogen (g) which flowed through each column was calculated | required from the total capacity of the superacidic nitrogen containing water which passed through each column in the purification test 2. These results are shown in Table 1.

As is apparent from Table 1, it was found that the purification material B obtained in the first comparative example has less consumption (loss) of the purification material by the purification test and has a longer life than the purification material D obtained in the third comparative example.

This can be interpreted as follows.

Dolomite is a complex carbon salt of calcium and magnesium, and is represented by CaMg (CO ₃ ) ₂ as a general chemical formula. On the other hand, the chemical formula of calcium carbonate is CaCO ₃ . As can be seen from the above, the chemical formula of dolomite consists of two metal elements and two CO ₃ groups, and the chemical formula of calcium carbonate consists of one metal element and one CO ₃ group. Therefore, when calcium carbonate is described in the same manner as dolomite, Ca ₂ (CO ₃ ) ₂ is obtained. The molecular weight of dolomite and calcium carbonate represented by the chemical formula of the same type is 184 and 200, respectively.

Therefore, assuming that the amount of elements consumed by the activity of denitrifying bacteria is about the same, the consumption of the purifying agent is less in the case of using dolomite having a smaller molecular weight.

Furthermore, when the consumption amount of the purification | cleaning material per unit of the amount of nitric acid nitrogen was calculated | required, the purification | cleaning material B was 9.4g, and purifying material D was 10.0g, and this result also showed that dolomite consumes less than calcium carbonate.

Therefore, when purifying nitric acid-containing water by denitrifying bacteria, dolomite is superior to calcium carbonate.

Sulfur denitrification can be performed from the initial stage of purification to provide a purifying material for nitric acid-containing water and a method for purifying nitric acid-containing nitrogen water capable of sufficiently purifying nitric acid-containing nitrogen water.

1: purification device
10: raw water tank
20a, 20b, 20c, 20d: column
21a, 21b, 21c, 21d: support layer
22a, 22b, 22c, 22d: purification layer
30a, 30b, 30c, 30d: treated water tank
40: raw water pump

Claims (2)

It is a purifier of nitric acid-containing water,
A purifying material of nitric acid-containing water, which contains dolomite and sulfur and whose amount of magnesium to the total mass of the purifying material exceeds 6.6 mass% and is 8.8 mass% or less. It is a purification method of the nitric acid-containing water which passes the nitric acid-containing water containing nitric acid nitrogen to the purifying material of Claim 1 which settled the denitrification bacteria,
The said acetic acid nitrogen is a denitrification method by the denitrification bacterium, The purification method of acetic acid nitrogen containing water.

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