JPH1028979A - Posttreatment of drinking water and swimming water sterilized with chlorine dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely remove chlorine dioxide remaining in the water which is sterilized by chlorine dioxide, by using a column, filter or filter bed containing water-insoluble iron sulfide ore and/or natural magnesium hydroxide to reduce and remove the chlorine dioxide. SOLUTION: Granular iron sulfide ore such as pyrrhotite is used to pack a column or formed into a filter or added to a filtering bed. Alternatively, natural magnesium hydroxide as a water-insoluble magnesium hydroxide fiber is used to pack a column, formed into a filter or added to a filtering bed. Magnesium hydroxide has an effect to remove chlorine dioxide remaining in water, perchloric acid or oxidizing material by the reducing effect of bivalent iron in the magnesium hydroxide. The column diameter and the treating amt. can be determined according to the concentration of oxidizing material such as the remaining chlorine dioxide, treating time of water. By this method, water can be surely treated and continuous feeding of water is possible for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for sterilizing water. More particularly, the present invention relates to a method for removing residual chlorine dioxide and derived oxidizing substances such as chlorite and the like for drinking water and swimming pool water sterilized with chlorine dioxide.

[0002]

2. Description of the Related Art Conventionally, chlorine is almost always used for sterilizing drinking water and swimming pool water. For example, the tap water law requires that chlorine remain in tap water, and chlorine is generally used for sterilizing drinking water such as well water. However, the sterilization method using chlorine has a problem in terms of safety that harmful substances such as trihalomethane are generated.
In addition, swimming pool water has a large amount of accumulated organic matter in the water and consumes a lot of chlorine compared to drinking water,
A large amount of chlorine needs to be added. For this reason, they are often used excessively with an emphasis on safety, resulting in the production of more trihalomethane, haloacetonitrile, haloacetic acid, etc., as well as problems such as causing damage to eyes and throat and bleaching of hair. was there. In addition, because the water for swimming pools is continuously sterilized, when sterilized using chlorine, mutagenicity tends to increase, and trihalomethanes and haloacetonitriles, which are said to have carcinogenic properties Alternatively, the production ratio of haloacetic acids is high (Japanese Society for Environmental Mutagen Research), and improvement of the sterilization method has been desired.

As one method of avoiding such a problem, sterilization using chlorine dioxide which does not generate harmful substances such as trihalomethanes and decomposes a trihalomethane precursor such as humic substances has been considered. For example, JP-A-6-3
No. 9376, JP-A-60-61510,
A method of disinfecting swimming pool water with chlorine dioxide is shown. However, in the method described in Japanese Patent Application Laid-Open No. 6-39376, a method for circulating water for a swimming pool, which is a commonly used method, has not been clarified. JP-A-60-61510 and JP-A-6-233985 describe a method using stabilized chlorine dioxide, but do not consider removal of by-products and the like after sterilization. Moreover, since stabilized chlorine dioxide is obtained by adding inorganic salts to chlorite, the efficiency of chlorine dioxide generation is increased by treatment such as addition of an acid. Therefore, the mere addition to the water for swimming pools is inefficient in the generation of chlorine dioxide, which increases the cost and is not practical.

[0004] When sterilizing drinking water and swimming pool water using chlorine dioxide, it is necessary to remove or reduce the concentration of residual oxidizing substances such as chlorine dioxide and derived chlorine oxide ions. When the water for the swimming pool is sterilized by chlorine dioxide, the concentrations of the remaining chlorine dioxide and chlorite ions are each 0.1%.
It is determined by the Ministry of Health and Welfare to be 0.4 mg / l or less and 1.2 mg / l or less. It is also determined by the Ministry of Health and Welfare that potassium permanganate consumption is 12 mg / l or less. Standards for the concentration of chlorine dioxide and chlorite ions in tap water used as drinking water are not set, but in the United States, etc., when chlorine dioxide is used for primary sterilization, it is preferable to remove all chlorite ions It has been.

Conventionally, chlorine dioxide has been widely used for bleaching pulp and fiber in Japan, but has not been used for drinking water, swimming pool water and the like. One of the reasons is that there is a limited method to remove chlorous acid, acidic substances or residual chlorine dioxide after sterilization with chlorine dioxide, and it is hoped that a new removal method will be developed. Was rare.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to effectively or almost completely remove residual chlorine dioxide and derived oxidizing substances such as chlorous acid after sterilization of tap water or swimming pool water with chlorine dioxide. Is to provide a way.

[0007]

SUMMARY OF THE INVENTION The present inventors have developed a method for effectively removing chlorine dioxide and derived oxidizing substances such as chlorite remaining after sterilization of tap water or swimming pool water with chlorine dioxide. As a result of intensive studies, the present inventors have found that the above problem can be solved by using a water-insoluble iron sulfide mineral or a water-insoluble magnesium hydroxide fiber, and completed the present invention based on this finding.

That is, the present invention relates to (1) a method for removing residual chlorine dioxide, chlorite ions or oxidizing substances in drinking water or swimming water sterilized by chlorine dioxide by using water-insoluble iron sulfide ore and / or natural sulfide ore. A method of reducing and removing by a column, a filter or a filtration bed containing magnesium hydroxide fiber. (2) The method according to (1) above, wherein at least one ore of pyrrhotite, pyrite ore, ore is used as the iron sulfide ore. It is.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention is also called a pyrrhotite ore (pyrrhotite as sulfide ore, iron sulfide contained in the ore is Fe 1 _{over x} S. Where x is a 0 to 0.2 ), Pyrite ore (also called pyrite and the iron sulfide contained in the ore is FeS ₂ ) or marble ore (also called marker site and the iron sulfide contained in the ore is Fe
It is S _2. ) Can be suitably used. In addition, minerals containing FeS and / or S can also be used. The ore can be satisfactorily used by the following method after first forming the ore into a granular material. (A) Pack into a column. (B) To be included in a filter-like molded product. (C) Add to the filtration bed.

As the magnesium hydroxide fiber insoluble in water, a natural magnesium hydroxide fiber containing FeO can be suitably used. Magnesium hydroxide FeO approximately 5-7 wt% during, Fe ₂ O ₃ is small amount, SiO
₂ is contained in an amount of about 1 to 2% by weight, of which it is considered that the reducing action by divalent iron acts on the removal of residual chlorine dioxide, chlorite or oxidizing substances. The magnesium hydroxide fiber can be favorably used by the following method. (A) Pack into a column. (B) Assemble into cartridge filter.

In the methods (a) to (c) and the methods (a) and (b), the column diameter, the length, the amount of the treating agent and the like are determined based on the residual chlorine dioxide, the oxidizing ability of the derived chlorous acid and the like. It can be determined by the substance concentration, the contact time between water and the treatment agent, and the like. According to the methods (a) to (c) and the method (a) or (b), the treatment is reliable and long-term continuous water injection is possible. Therefore, if the equipment cost is kept low,
The economic effect is high because the maintenance is simple.

[0012]

Next, the present invention will be described more specifically with reference to examples.

Example 1 A test for removing chlorite ions with iron sulfide was performed as follows. Adjustment of column using iron sulfide: A lump of iron sulfide for hydrogen sulfide generation (Kanto Chemical's reagent) was crushed in an iron mortar,
The passing powder was removed by a 2-mesh sieve, and a particle size of 3 mm or less was collected. The granules were filled up to a diameter of 10 mm × a length of 300 mm, a G4 glass filter, and a glass column with a lower cock having a diameter of 200 mm. Preparation of aqueous solution containing chlorite ion: A 25% by weight aqueous solution of sodium chlorite was prepared as a standard solution of chlorite ion, which was evaluated with a standard solution of sodium thiosulfate, diluted with water, and then diluted with water. 5.0 mg / l (5 pp)
An aqueous solution containing chlorite ion of m) was prepared.

Test for removal of chlorite ion: A separating funnel containing 1,000 ml of the above aqueous solution having a chlorite ion concentration of 5 ppm was connected to the column head filled with the iron sulfide granules. 3 per minute from separation funnel to column
The solution was added dropwise at 0 milliliter. After 2 minutes, 5 minutes, 10 minutes, 20 minutes, and 30 minutes after the start of the dropping, the treatment liquid flowing out from the lower part of the column was collected. As a result of measuring the chlorite ion concentration in the collected processing solutions by DPD (diethyl-p-phenylenediamine) absorption spectrophotometry, the chlorite ion concentration was 0 ppm in all the processing solutions.
PH of treatment liquid collected before treatment and 30 minutes after the start of dropping
Was 5.8 and the pH did not change.

Example 2 A test for removing chlorite ions with iron sulfide was conducted as follows. The same test as in Example 1 was performed except that the chlorite ion concentration was set to 50 ppm. As a result, irrespective of the time after the start of dropping, the chlorite ion concentration of all the processing solutions was 0.8 ppm, and 98% of chlorite ion could be removed. As a result, it was found that chlorite ions could be sufficiently removed even when the concentration of chlorite ions was high. The pH of the aqueous solution before the treatment was 8.6, and the pH of the treatment liquid collected 30 minutes after the start of the dropping was 5.8.

Reference Example 1 A test for the ability of pyrite to remove chlorite ions was conducted as follows. Peru, Huanuco Huanzal
a) Pure pyrite ore from the mine (composition by chemical analysis is iron 4
6.5%, sulfur content 52.5%, copper 0.04%, acid-insoluble content 0.7% weight%) were ground in an iron mortar, and the passing powder was removed with a 12-mesh sieve to remove 3 mm. The following granules were collected: 2 g of this granulate is mixed with 5 g of NaClO ₂
The solution was added to the 00 ml solution, and the mixture was stirred with a magnetic stirrer for 180 minutes at normal temperature (19 ° C.) for 180 minutes. As a result, 99.4% of the chlorite ions were removed. 1 g of pyrite ore
It was found that approximately 5 g of chlorite ion could be removed by the reduction reaction.

Example 3 A test for removing chlorite ions by the pyrite ore according to the present invention was performed as follows. Adjustment of column using pyrite ore: 140 g of granular pyrite ore prepared in the same manner as in Example 1 was packed into a glass column having a diameter of 10 mm, a length of 300 mm, a cotton stopper and a lower cock up to 200 mm. Test for removal of chlorite ion and chlorine dioxide: 1500 ml of sodium chlorite solution having a water temperature of 16 ° C. and a concentration of 4.5 mg / l from the column head, and a linear velocity of 0.02 to 0.1 m / h.
r, and the mixture was allowed to flow down in a stepwise manner. The mixture was divided into eight fractions, and the residual chlorite ion of each fraction was measured by a DPD colorimetric method. The column is further filled with 1500 ml of chlorine dioxide water having a concentration of 20 mg / l.
Was allowed to flow down in the same manner as the sodium chlorite solution described above. Similarly, it was divided into 8 fractions, and chlorine dioxide was detected. As a result, chlorite ion and chlorine dioxide were not detected at all in the effluent, and it was found that chlorite ion and chlorine dioxide could be removed by the present invention.

[0018]

According to the present invention, residual chlorine dioxide after chlorine dioxide sterilization and oxidizing substances such as chlorite ions which are derivatives thereof can be completely reduced and removed. In addition, since the reduction and removal method according to the present invention can employ a column packing method, a filter-like molded product, a filtration bed method, or the like, it can be easily added to existing water treatment plants and pool water treatment facilities, and also has economical efficiency. ing. By the reduction removal method according to the present invention, harmless chlorine ions by reducing and removing residual oxidizing substances after decomposing and removing carcinogenic substances and their precursors contained in drinking water such as tap water source water by chlorine dioxide sterilization. It has become easy to establish a sterilization system for tap water using chlorine dioxide. This facilitated the provision of safe tap water without off-flavors under the current law. In addition, since it is easy to establish a chlorine dioxide disinfection-recycling system for swimming pool water, it has become easier to provide more comfortable physical education and leisure facilities with no chlorine odor and sufficient consideration for human health.

Claims (2)

[Claims] 1. A column containing water-insoluble iron sulfide and / or natural magnesium hydroxide fiber, which contains residual chlorine dioxide, chlorite ions and oxidizing substances in drinking water and swimming water sterilized by chlorine dioxide. , A filter or a filtration bed for reduction. 2. The method according to claim 1, wherein at least one ore selected from pyrrhotite ore, pyrite ore, and ore ore is used as the iron sulfide.