JP2011115708A - Method for denitrification of sewage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cleaning sewage containing nitrate nitrogen, which can improve the removal rate of the nitrate nitrogen by activating Thiobacillus denitrificans. <P>SOLUTION: In the method for denitrification of sewage, a cleaning material containing sulfur and calcium carbonate as main components and having Thiobacillus denitrificans adhered thereto is allowed to coexist, in the sewage, with a bacteria activator including one or a mixture of two or more of yeast extract, peptone, malt extract and meat extract. Preferably, the sewage contains fluorine, and contains the bacteria activator in an amount of at least 40 mg per liter of the sewage. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for denitrifying wastewater in which nitrogen contained in water contaminated with nitrate nitrogen is discharged as harmless nitrogen gas (N ₂ ) by sulfur oxidizing denitrifying bacteria. Specifically, it promotes denitrification treatment of sulfur-oxidizing denitrifying bacteria that remove nitrate nitrogen and / or nitrite nitrogen contained in water such as groundwater, factory wastewater, sewage, domestic wastewater, and livestock wastewater, and purifies them. The present invention relates to a method for denitrifying sewage.

Nitrate nitrogen and nitrite nitrogen were added to the environmental standards for groundwater water pollution in 1999, but the excess rate is higher than other items. Groundwater contamination by nitrate nitrogen is often caused by fertilization, livestock excretion, etc., and the contamination is widespread in many cases. Therefore, as countermeasures against groundwater contamination, it is necessary to promote measures for reducing nitrogen load, which is a source countermeasure, as well as measures for preventing pollution and purifying contaminated groundwater.
As a method of removing nitrate nitrogen and / or nitrite nitrogen, a purification material mainly composed of sulfur and calcium carbonate is immersed in sewage containing nitrate nitrogen and / or nitrite nitrogen, and the purification material. There is a method of denitrification by inhabiting sulfur oxidation denitrification bacteria.

  Various proposals have been made regarding methods for purifying sewage. For example, in Japanese Patent No. 3430364 (Patent Document 1 below), it is used as a substrate for water purification or microbial culture solution related to removal of nitrate nitrogen. A composition for imparting microbial activity, and a method for producing the same, comprising a granular or massive purification material in which calcium carbonate and sulfur coexist in a single body are described. ing.

  JP 2002-159993 A (Patent Document 2 below) applies a denitrification method using an autotrophic sulfur oxidative denitrification bacterium, and includes a purifier bed with a sulfur-containing purifier in the tank. The water supply piping system that feeds the sewage into the tank is disposed in the lower part of the tank below the purification material floor, and the drainage piping system that delivers the treated water to the outside of the tank is disposed in the upper part of the tank above the purification material floor. Constructed as an up-flow type water treatment tank that flows from the bottom to the top of the purification material floor, and is used for distributed water supply. By providing the water supply piping system provided as, the influence of external factors such as the amount of inflow of sewage, flow state, flow rate, water temperature, viscosity, suspended suspension amount or coexisting ions is suppressed. Efficient denitrification function by preventing sulfur from being oxidized Nitrate ion removal processing device constituting the ability of nitrate ion removal apparatus is described.

  However, in the above prior art, nitrite nitrogen accumulates in the denitrification process, and if the concentration of nitrite nitrogen increases, denitrification treatment cannot be performed, and the removal rate of nitrate nitrogen may decrease. However, when fluorine is contained in the sewage, there is a problem that the above phenomenon easily occurs.

Japanese Patent No. 3430364 JP 2002-159993 A

The present invention solves the problems of the prior art as described above, activates sulfur oxidative denitrifying bacteria, and improves the removal rate of nitrate nitrogen in wastewater even when the concentration of nitrite nitrogen is high. It is an object of the present invention to provide a method for denitrifying sewage.

The present invention has been made as a result of intensive studies in order to solve the above-mentioned problems, and the gist of the present invention is the following contents as described in the claims.
(1) A purifying material mainly composed of sulfur and calcium carbonate, to which sulfur oxidative denitrifying bacteria are attached, and a bacterial active material comprising one or a mixture of two or more of yeast extract, peptone, malt extract, meat extract, A denitrification method for sewage characterized by coexisting in sewage.
(2) The sewage denitrification method according to (1), wherein the sewage contains fluorine.
(3) The method for denitrifying sewage according to (1) or (2), wherein the bacterial active material is contained in an amount of 40 mg or more per liter of the sewage.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for denitrifying sewage containing nitrate nitrogen that can activate a sulfur-oxidizing denitrifying bacterium to improve the removal rate of nitrate nitrogen, and is industrially useful. There is a remarkable effect.

It is a figure explaining the principle of denitrification used for this invention. It is a figure which illustrates the sulfur oxidation denitrification bacteria used for this invention.

Embodiments of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram for explaining the principle of denitrification used in the present invention.

  The principle of denitrification used in the present invention is nitrate nitrogen treatment by sulfur oxidizing denitrification bacteria, and biological treatment using so-called general soil fungi. In the present invention, nitrate nitrogen is treated by using this sulfur oxidative denitrifying bacterium and a purification material comprising, for example, sulfur and calcium carbonate.

As shown in FIG. 1, water nitrate ion (NO ₃ ^-) is incorporated taken by sulfur oxidation denitrifying bacteria (Thiobacillus denitrificans), sulfur oxide denitrifying bacteria takes the nitrate ion, the nitrogen content of the harmless nitrogen gas It can be exhausted as (N ₂ ). At that time, sulfur oxidative denitrifying bacteria take in sulfur and discharge sulfate ions (SO ₄ ^2- ). At this time, calcium (Ca) mixed with sulfur is combined with the sulfate ions to form calcium sulfate. (So-called gypsum (CaSO ₄ ) can be formed and acidification of the sewage being treated can be prevented.

Note that the sulfur oxidative denitrification reaction in the purification material of the present application is confirmed to be in good agreement with the KOENIG & LIU equation based on the data collected at the field demonstration site and its reaction analysis.
^{_{1.06NO 3 - + 1.11S + 0.3CO 2}} + 0.785H 2 O → 0.5N 2 + 1.11SO 4 2- + 1.16H + + 0.06C 5 H 7 O 2 N

FIG. 2 is a diagram illustrating sulfur oxidizing denitrifying bacteria used in the present invention.
As shown in FIG. 2, when the surface of the purification material actually treated with nitrate nitrogen is observed with an electron microscope, sulfur oxidizing / denitrifying bacteria having a length of about 2 to 3 μm can be confirmed. Nitrogen bacteria convert NO ₃ ^- to harmless N ₂ while oxidizing sulfur in the purification material.

  The present inventors have found that nitrite nitrogen accumulates in the denitrification process by sulfur oxidizing denitrification bacteria, and if the nitrite nitrogen concentration becomes high, denitrification treatment cannot be performed and the nitrate nitrogen removal rate decreases. In particular, paying attention to the problem that the above phenomenon is likely to occur when fluorine is contained in the sewage, in the sewage in which the purifying material mainly composed of sulfur and calcium carbonate is immersed, Removal of nitrate nitrogen by desulfurization treatment by activating sulfur oxidation denitrification bacteria adhering to the purification material in the presence of one or more of yeast extract, peptone, malt extract, meat extract It has been found that the rate can be improved.

That is, the method for purifying sewage according to the present invention comprises a purifying material mainly composed of sulfur and calcium carbonate and having sulfur oxidative denitrifying bacteria attached thereto, and one or a mixture of two or more of yeast extract, peptone, malt extract and meat extract. It is characterized by coexisting with the bacteria active material which consists of in waste water. For example, a method for denitrifying sewage by exhausting and purifying nitrogen contained in water contaminated with nitrate nitrogen as harmless nitrogen gas (N ₂ ) by sulfur oxidative denitrifying bacteria, comprising sulfur and calcium carbonate 1 or 2 or more types of yeast extract, peptone, malt extract, meat extract are coexisted in the sewage in which the purification material mainly composed of and is soaked to activate the sulfur-oxidizing denitrifying bacteria adhering to the purification material. To denitrify.

  Here, the yeast extract, peptone, malt extract, and meat extract act as nutrient salts of sulfur oxidative denitrifying bacteria, so that the sulfur oxidative denitrifying bacteria adhering to the purification material are activated for denitrification treatment. The sulfur oxidizing denitrifying bacteria adhering to the purification material can be activated by allowing one or more of them to coexist in the sewage.

  Yeast extract is a water-soluble component obtained by self-melting baker's yeast or beer yeast, and contains amino acids and abundant vitamins (particularly B-complex).

Peptone digests protein material enzymatically, decomposes it into polypeptides, oligopeptides and amino acids, making it easier to use as a nitrogen source for bacteria.
The malt extract is a water-soluble component of malt, and is preferably used in a yeast or filamentous fungus medium.
The meat extract is a mud that is obtained by concentrating meat juice obtained by adding a normal solution to animal meat such as cattle or fish, heating and extracting the solution, and filtering it.

  In addition, meat extract, etc. not only acts as a nutrient, but also does not reduce the removal rate of nitrate nitrogen and nitrite nitrogen contained in sewage (treated water) even in the presence of nitrite nitrogen It is thought that the component which plays is included.

  In addition, as a result of investigating the amount of the bacterial active material coexisting in the sewage, the present inventor has found that the bacterial active material is added to 1 liter of the waste water in order to activate the sulfur oxidative denitrifying bacteria attached to the purification material. It has been found that it is desirable to contain 40 mg or more.

Moreover, it is preferable that the particle diameter of the purification material which has the said sulfur and calcium carbonate as a main component is 1-50 mm. The reason why the particle size is 1 to 50 mm is that the material constituting the purification material is an indeterminate particle size, and gas can easily escape from the gap. If the thickness exceeds 50 mm, the surface area decreases, and the purification efficiency decreases.
Further, according to the present invention, even if the sewage contains 1 to 20 mg / l of fluorine, the sewage is denitrified and purified by using nitrate nitrogen or nitrite nitrogen as harmless nitrogen gas. can do.

Using groundwater mixed with fluorine 15 mg / l and nitrate nitrogen 50 mg / l as sewage, purifying material with a particle size of 20 to 50 mm mainly composed of sulfur and calcium carbonate (trade name; Denical made by Nichetsu Co., Ltd.) Fill a water tank of 80 x 80 x 85 mm (effective capacity 544 ml) and let it flow in an upward flow with a residence time of 1 day. Denitrification treatment with sulfur-oxidizing denitrifying bacteria adhering to the purification material was performed.
When the nitrite nitrogen increased to 3 mg / l or more during the treatment process, the removal rate of both nitrite nitrogen and nitrate nitrogen decreased, so water flow was stopped and 0.1 g of the bacterial active material of the present application was added (added) The concentration of nitrate nitrogen and nitrite nitrogen after standing for 1 day was measured. The test results are shown in Table 1. A simple water quality test paper (trade name; Aqua Check N) was used for the measurement of nitrate nitrogen and nitrite nitrogen.

As a result, as shown in Table 1, yeast extract, polypeptone, the invention examples 1 to 3 were added to malt extract, added after day _{^{NO 2 - N, NO 3 -}} N is denitrification be 0 mg / l good (○) in which the other hand, in Comparative examples 1-3, the addition of one day after NO ₂ ^- N is 3 mg / l or more, NO ₃ ^- N is denitrification be 20 mg / l is a bad (×) Thus, the effect of the present invention was confirmed.

  Using groundwater mixed with fluorine 15mg / l and nitrate nitrogen 50mg / l as sewage, purifying material (product name: Nichetsu Co., Ltd. Denical) with a particle size of 20-50mm, which is mainly composed of sulfur and calcium carbonate Fill a water tank of 80 x 80 x 85 mm (effective capacity 544 ml) and let it flow in an upward flow with a residence time of 1 day. Denitrification treatment by sulfur oxidation denitrification bacteria adhering to the purification material.

  When the nitrite nitrogen is increased to 3 mg / l or more during the treatment process, the removal rate of both nitrite nitrogen and nitrate nitrogen decreases, so the water flow is stopped and the yeast extract is 0.01 g (37 mg / l). , 0.02 g (74 mg / l), 0.03 g (110 mg / l), 0.06 g (220 mg / l), 0.1 g (330 mg / l) were added (additional concentration in parentheses) and left for 1 day. The concentrations of nitrite nitrogen and nitrate nitrogen were measured. The test results are shown in Table 2. Nitrite nitrogen and nitrate nitrogen were measured using a simple water quality test paper (trade name: Aqua Check N).

As a result, as shown in Table 2, Inventive Example 4 the yeast extract was added 0.01g (37mg / l) are added after day NO ₂ ^- N is 3 mg / l or more, NO ₃ ^- N is 10 mg / l by and whereas denitrification is applicability (△), invention examples 5-8 where the yeast extract was added 0.02~0.1g (74~330mg / l), the following day the addition NO ₂ ^- N is 1 mg / l or less, NO ₃ ^- N is denitrification be below 5 mg / l the effect of the present invention was confirmed by the fact that a good (○).

Claims (3)

  A purification material mainly composed of sulfur and calcium carbonate, with sulfur-oxidizing denitrifying bacteria attached, and a bacterial active material consisting of one or a mixture of two or more of yeast extract, peptone, malt extract, and meat extract, in sewage A denitrification method for wastewater characterized by coexistence.   The sewage denitrification method according to claim 1, wherein the sewage contains fluorine. The method for denitrifying sewage according to claim 1 or 2, wherein the bacterium active material is contained in an amount of 40 mg or more per liter of the sewage.

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