JP2006015310A - Nitrate nitrogen treatment material and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pretreatment method for culturing and carrying denitrifying bacteria including autotrophic sulfur oxidizing denitrifying bacteria stably in a short time, to obtain a treatment agent which exhibits a denitrification performance in an early stage. <P>SOLUTION: A nitrate nitrogen treatment material mainly is used for denitrifying nitrate nitrogen in water by biological treatment using the denitrifying bacteria, and comprises a carbonate and sulfur. The nitrate nitrogen treatment material is treated with a solution of an inorganic acid or of an organic acid to make its surface rough, which facilitates the carrying of the denitrifying bacteria on the nitrate nitrogen treatment material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sulfur-alkali (earth) metal carbonate-based nitrate nitrogen treatment material used for denitrification of nitrate nitrogen in water.

  Autotrophic sulfur oxidation is a technology that removes nitrate nitrogen in domestic wastewater, industrial wastewater, livestock wastewater, agricultural wastewater, aquaculture wastewater that causes eutrophication in rivers, lakes, closed water areas, closed sea areas, etc. Unlike the system using heterotrophic denitrifying bacteria, the nitrate nitrogen removal system using denitrifying bacteria (hereinafter referred to as sulfur-oxidizing bacteria) does not require high maintenance costs such as the addition of methanol. Attention has been paid.

Regarding nitrate nitrogen removal system using sulfur-oxidizing bacteria (hereinafter referred to as denitrification system), for example, Japanese Patent Publication No. 62-56798, Japanese Patent Publication No. 63-45274, Japanese Patent Publication No. 60-3876, Japanese Patent Publication No. 1 -31958, JP 4-9199, JP 4-74598, JP 4-151000, JP 4-197498, JP 6-182393, etc. .
Patent Documents 1 and 2 propose a denitrification system in which a sulfur-oxidizing bacterium is cultured and supported on a molten mixture of sulfur and limestone, and are excellent in terms of ease of maintenance and cost for denitrification treatment. Is shown. Patent Document 3 shows that the sulfur powder and carbonate powder can be integrated with an organic binder to realize a significantly superior denitrification treatment efficiency and a simple method for producing a denitrification treatment material. Yes.

  However, in Patent Documents 1 and 2, etc., since sulfur and limestone are heated and melted at about 150 ° C. or higher, the surface of the treated material is covered with molten sulfur and becomes quite smooth, and sufficient denitrification is achieved. The problem was that a period of several months was required before performance was achieved. Further, in Reference 3, by solidifying sulfur powder and carbonate powder with a binder, the surface state is considerably uneven, and thus denitrifying bacteria are easily carried, but depending on the granulation method of the treatment material However, since the surface is considerably smoothed, the period may be several weeks. Thus, it is thought that the reason for requiring a long time is related to the breeding period on the surface and inside of the treatment material of denitrifying bacteria.

Japanese Patent Laid-Open No. 2001-47086 Japanese Patent Laid-Open No. 2001-104993 JP 2004-167471 A

  Therefore, the objective of this invention is providing the processing agent which exhibits denitrification performance at an early stage. Another object is to provide a pretreatment method for stably culturing and supporting denitrifying bacteria such as autotrophic sulfur oxidizing denitrifying bacteria in a short period of time.

  As a result of intensive studies in order to solve such problems, the inventors of the present invention mainly cultivated denitrifying bacteria before using the treatment material in the nitrate nitrogen denitrification treatment material mainly composed of carbonate and sulfur. It was found that the above object can be achieved by roughening the surface of the nitrate nitrogen denitrification material with an acid before the supporting step, and the present invention has been completed.

  The present invention relates to a nitrate nitrogen treatment material mainly composed of carbonate and sulfur, which is used for denitrification of nitrate nitrogen in water by biological treatment with denitrifying bacteria, and is a solution of an inorganic acid or an organic acid. The nitrate nitrogen treatment material is characterized by roughening the surface of the nitrate nitrogen treatment material. Moreover, this invention is a manufacturing method of the nitrate nitrogen processing material which carry | supported the denitrification bacteria characterized by attaching and culture | cultivating a denitrification bacterium on the nitrate nitrogen treatment material which roughened the surface. Furthermore, the present invention is a nitrate nitrogen treatment method characterized by bringing the nitrate nitrogen treatment material having a roughened surface into contact with water containing denitrifying bacteria and nitrate nitrogen.

  The nitrate nitrogen treatment material mainly composed of alkali (earth) metal carbonate and sulfur used in the present invention is known in Patent Documents 1 to 3 and the like, and these can be used. For example, as an alkaline (earth) metal carbonate, an alkaline earth metal carbonate powder such as calcium carbonate (limestone) or magnesium carbonate (dolomite) is suitable. It is obtained by heating such a mixture of carbonate and sulfur to melt and solidify and solidify the sulfur, or by integrating carbonate powder and sulfur powder with an organic or inorganic binder. There are things. However, it is not limited by the manufacturing method. The composition of the nitrate nitrogen treatment material is preferably a ratio of 30 to 70 parts by weight of sulfur with respect to 30 to 70 parts by weight of carbonate. When a binder is used, 0. A proportion of 1 to 30 parts by weight is preferred. In addition, inorganic fibers, porous materials, and the like can be blended as necessary. The nitrate nitrogen treatment material is usually used after being molded or crushed into a granular shape, a block shape, or an indefinite shape.

  It is considered that the nitrate nitrogen treatment material exhibits its denitrification ability by supporting denitrifying bacteria on the surface or inside thereof. For this reason, it is first necessary to carry out a supporting treatment that attaches and cultures denitrifying bacteria to a nitrate nitrogen treatment material in a solution containing denitrifying bacteria and nitrate nitrogen, or attaches and cultures denitrifying bacteria while performing denitrification treatment. Will be done. In any case, there is no difference in denitrification when cultivating denitrifying bacteria, so the initial stage of using this nitrate nitrogen treatment material is a loading process mainly intended to support denitrifying bacteria. Even if it exists, the denitrification process which makes a denitrification process the main objective and carries out carrying | supporting by carrying out attachment culture | cultivation of denitrifying bacteria may be sufficient. Hereinafter, the process at the initial stage of using the nitrate nitrogen treatment material and at the stage where the adherent culture of denitrifying bacteria is insufficient is also referred to as a supporting process. In any case, it is desirable that the adherent culture of denitrifying bacteria is completed early and the denitrifying ability is exhibited early. In the denitrification treatment method of the present invention, the denitrification bacteria are not necessarily present in the water to be denitrified after the denitrification bacteria have been supported or after the denitrification treatment for a certain period of time. Does not interfere with the presence of denitrifying bacteria.

  It is important that the nitrate nitrogen-treated material is roughened before the supporting step so that microorganisms can easily adhere to the surface. As a method of roughening the surface, for example, there is a method of physically giving unevenness such as a blasting method such as sand or iron powder. In that case, not only a large amount of sulfur or carbonate powder is generated, but also the treatment material itself Will wear out. Moreover, separation becomes very difficult, and they remain as contamination.

  Therefore, by treating with inorganic acid or organic acid (hereinafter sometimes referred to as acid treatment) and decomposing or dissolving a part of the carbonate existing on the surface of the nitrate nitrogen treatment material, a large number of irregularities are formed. This is used as an anchor to enhance the adhesion effect. In this acid treatment, carbon dioxide in the carbonate is generated as a gas, and metals such as Ca and Mg in the carbonate are dissolved in water, and the carbonate is removed, so that the portion forms a recess. However, surface irregularities develop as a whole.

  The inorganic acid and organic acid to be used are not limited as long as the carbonate in the nitrate nitrogen denitrification material can be decomposed and removed. For example, hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, chromic acid and the like can be raised as inorganic acids, but hydrochloric acid is easy to use because of safety and environmental problems. Examples of the organic acid include water-soluble carboxylic acids such as formic acid, acetic acid, citric acid, and lactic acid. Citric acid is easy to use because of odor problems.

  As an acid treatment method, a method of immersing a nitrate nitrogen treatment material in an appropriately diluted acid is simple. The concentration of the acid is not limited, but if it is too thin, it takes a long time and the effect of roughening is lost, so that an acid diluted to 0.5 to 5 wt% is easy to use. Carbon dioxide gas is generated during the acid treatment, but in order to effectively roughen the surface in a short time, stirring and water circulation may be performed as appropriate in order to remove the gas and make the acid concentration uniform. .

  The acid treatment time is not specified because it varies depending on the type and concentration of the acid used, the shape of the nitrate nitrogen treatment material and the manufacturing method, but it is not specified in the surface layer from the surface of the nitrate nitrogen treatment material to 0.1 mm. It is desirable that 10% or more of the carbonate present in the be removed.

  After the acid treatment, it is preferable to perform sufficient water washing. Washing with water removes the acid adhering to the surface. In order to facilitate adherence culture of microorganisms, it is preferable to wash with water until the water-washed solution has a pH of 5 or more. In order to shorten the cleaning time, if necessary, it may be washed with weak alkaline water such as sodium hydroxide and then washed with water.

  Nitrate-nitrogen-treated materials whose surface has been sufficiently roughened after acid treatment are usually immersed in nitrate, and then added to the culture solution, sludge, soil, etc. where denitrifying bacteria are present, Incubate to carry denitrifying bacteria. Alternatively, the denitrification treatment is performed by contact with these by immersing in denitrifying bacteria and nitrate nitrogen. In the latter case, denitrifying bacteria are attached and cultured as a secondary, and are supported. After the loading is completed, it is possible to treat nitrate nitrogen-containing wastewater containing no denitrifying bacteria, but it does not interfere with the presence of denitrifying bacteria present in nature. Here, nitrate nitrogen refers to nitrate ion or nitrite ion or a compound that generates these. Without acid treatment, attachment is difficult, and it is difficult to carry denitrifying bacteria and to demonstrate early denitrification performance. It becomes possible to promote, and it is possible to demonstrate the denitrification performance early. Furthermore, the time can be shortened by adjusting the culture temperature, pH, nitrate, nutrient source, and the like. The nitrate nitrogen treatment material of the present invention is useful for treatment of various wastewaters and lake water containing nitrate nitrogen (nitrate ions, nitrite ions, etc.).

  A material obtained by acid-treating a nitrate nitrogen treatment material can exhibit a high nitrate nitrogen treatment rate at an early stage. This is considered to be due to the fact that the surface of the nitrate nitrogen treatment material is roughened by acid treatment, so that the irregularities become severe, the microorganisms easily propagate, and the adhesion culture period is greatly shortened.

  For the preparation of the nitrate nitrogen treatment material, a powder of 200 mesh (manufactured by Karuizawa Seisen) was used for sulfur, and a powder of T-200 (manufactured by Nichetsu) was used for calcium carbonate. Sulfur was heated and melted at 180 ° C. with the composition shown in Table 1, calcium carbonate was added and mixed well, then quenched with water and pulverized to 5 to 20 mm with a pulverizer. 200 g of this was immersed in 200 ml of a 1% hydrochloric acid aqueous solution for 2 hours. Carbon dioxide gas is generated by soaking, but the carbon dioxide gas adhering to the treatment material was removed by stirring every 30 minutes. Thereafter, hydrochloric acid adhering to the surface was sufficiently removed with tap water.

  Table 1 shows an organic binder (acrylic resin: Chuo Rika Co., Ltd. acrylic emulsion, solid content 45%, product name: ES-45) and tap water using sulfur and calcium carbonate used in Example 1. After mixing by a kneader, 6 mmΦ × 3 mm cylindrical pellets were granulated with a disk pelletizer and dried at 80 ° C. for 10 hours to prepare a nitrate nitrogen treatment material. The composition percentage of the organic binder indicates the solid content. 200 g of this was immersed in 200 ml of a 3% lactic acid aqueous solution for 2 hours. Carbon dioxide gas is generated by soaking, but the carbon dioxide gas adhering to the treatment material was removed by stirring every 30 minutes. Thereafter, hydrochloric acid adhering to the surface was sufficiently removed with tap water.

Comparative Examples 1-2
The treatment material used in Example 1 or 2 was used as it was without acid treatment.

Using the nitrate nitrogen-treated materials of Examples 1 and 2 and Comparative Examples 1 and 2, the carrying treatment or denitrification treatment with sulfur-oxidizing bacteria attached and cultured was performed under the following conditions.
For the loading treatment, 200 g of each nitrate nitrogen treatment material and 100 ml of potassium nitrate aqueous solution having a nitrate nitrogen concentration of 200 mg / l are put into 250 ml of polybin, and further dried sludge containing sulfur-oxidizing bacteria (soil is collected from the leek field in Saitama Prefecture). Then, after culturing with the sulfur-calcium carbonate denitrification treatment material prepared in Example 2 for 1 year, 0.5 g of sludge generated was naturally dried) and stirred well, and the temperature was kept at 25 ° C. Left in the tank. After 3 and 7 days, the concentration of nitrate ion was measured by ion chromatography to confirm the culture condition.

  Table 1 shows the mixing ratio and denitrification treatment results. In Table 1, the numbers indicating the blending amounts are parts by weight.

Claims (3)

  Nitrate nitrogen treatment material mainly composed of carbonate and sulfur used to denitrify nitrate nitrogen in water by biological treatment with denitrifying bacteria, treated with a solution of inorganic acid or organic acid A nitrate nitrogen treatment material characterized by roughening the surface of the nitrate nitrogen treatment material.   In supporting denitrifying bacteria on nitrate nitrogen treatment materials mainly composed of carbonate and sulfur, which are used to denitrify nitrate nitrogen in water by biological treatment with denitrifying bacteria, inorganic acids or organic acids Production of nitrate-treated nitrogenous material carrying denitrifying bacteria, characterized in that the surface of nitrate-treated nitrogenous material is roughened by treatment with a solution, and then denitrifying bacteria are attached to and cultured on nitrated nitrogen-treated material. Method.   A denitrification treatment method using a nitrate nitrogen treatment material mainly composed of carbonate and sulfur, which is used for denitrification of nitrate nitrogen in water by biological treatment with denitrification bacteria, which is an inorganic acid or organic A method for denitrification of nitrate nitrogen, comprising treating with a solution of an acid to roughen the surface of the nitrate nitrogen treatment material and then bringing it into contact with water containing denitrification bacteria and nitrate nitrogen.