JPH10216698A - Deodorizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove hydrogen sulfide and mercaptans in a medium containing hydrogen sulfide and mercaptans and to prevent diffusion of malodor and corrosion in facilities by adding hydrogen peroxide, nitrate ion, and preferably a metal salt into the medium. SOLUTION: A medium such as raw sludge and excess sludge produced in the treating processes of sewage, night soil and industrial waste water is treated with a peroxide and nitrate ion. As for the peroxide used, peracetates, persulfates, percarbonates, perborates and other inorg. or org. oxides can be used, and preferably hydrogen peroxide is used. The amt. of the peroxide used is not specified, and preferably 2 to 2000mg/l, preferably 5 to 1000mg/l calculated as 100wt.% to the medium. When the peroxide and nitrate ion are added, a metal salt is preferably added. As for the metal salt, at least one salt of element selected from VIA, VIIA, VIII, IB, IIB, IVB groups is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for deodorizing. More specifically, raw sludge, excess sludge, digested sludge, coagulated sludge, etc. generated when treating wastewater or wastewater,
Alternatively, it is a method in which the odor generated from the cleaning water of the cleaning device or a mixture thereof can be quickly removed with a small amount of chemical injection.

[0002]

2. Description of the Related Art The amount of general wastewater from households has been increasing rapidly with the recent population increase in cities and suburbs. Therefore, the maintenance of sewerage is urgently required, and the amount of wastewater is increasing year by year. These wastewaters contain a large amount of organic and inorganic substances, and produce raw sludge, excess sludge, digested sludge, etc. while being treated at the sewage treatment plant.

[0003] In addition, in the case of factories and other business establishments, due to severe environmental pollution of rivers and oceans, wastewater regulations have been strengthened and it is obligatory to treat water to a predetermined quality. Activated sludge treatment produces a large amount of sludge.

As described above, general household wastewater, wastewater from business establishments, and sludge produced in the process of treating wastewater contain various organic and inorganic substances. Further, various organic and inorganic substances are also contained in the cleaning water of the cleaning device and the like.

[0005] Among these various organic and inorganic substances,
Contains sulfur compounds. Sulfate is generated in the process of these decay. Sulfate-reducing bacteria are usually present in sludge, and sulfate is reduced to hydrogen sulfide in sludge for production activities. By generating hydrogen sulfide, the sludge is further anaerobic, the sulfate-reducing bacteria proliferate, and the amount of generated hydrogen sulfide further increases. The generated hydrogen sulfide is released to the gas phase. Hydrogen sulfide is a toxic and unpleasant odor substance, which is not only dangerous for workers, but also causes odor problems to the local residents. In addition, hydrogen sulfide is oxidized by sulfur oxidizing bacteria and air adhering in concrete facilities, and dissolves in the mist to generate sulfuric acid. The sulfuric acid produced in this way corrodes concrete and metal, causing fatal defects in the structure of buildings.

As a means for preventing the generation of these odors and the corrosion of structures, there is an activated carbon treatment for adsorbing hydrogen sulfide on activated carbon. However, when the adsorption amount reaches saturation, it is necessary to replace the activated carbon with new activated carbon or regenerate it. However, there is also a problem in economics such as complicated replacement work and high regeneration cost.

[0007] As another method, there is a method of deodorizing by passing through a packed phase of organisms held on a carrier. However, this method has problems such as an increase in size of the apparatus and difficulty in maintaining and managing living things.

As a method using a chemical, there is a method of adding hydrogen peroxide, which can remove hydrogen sulfide and mercaptans. However, if the added amount is small, it is not possible to sufficiently sterilize sulfate-reducing bacteria. When the sludge is left for a long time, there is a problem that oxidized sulfur or sulfate ions generate hydrogen sulfide again by the sulfate-reducing bacteria.

As a method of immobilizing hydrogen sulfide as a metal salt, there is a method of adding a metal salt as shown in the following reaction formula. In this method, hydrogen sulfide reacts with metal ions,
There is a disadvantage that a large amount of sludge is generated as metal sulfide. Furthermore, there is a method of suppressing the generation of hydrogen sulfide by adding nitrate to wastewater, but nitrate itself cannot oxidize sulfide.

[0010]

In the prior art, the removal of hydrogen sulfide and mercaptans is inadequate, the maintenance is complicated, and there is a problem in terms of economy. The present invention
It is an object of the present invention to provide a method for efficiently decomposing and removing hydrogen sulfide and mercaptans in a medium under mild conditions to prevent the spread of offensive odors and the corrosion of facilities.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the method of removing odors from a medium. As a result, the medium containing hydrogen sulfide and mercaptans was added with peroxide and nitrate ions, more preferably The present inventors have found that hydrogen sulfide and mercaptans in a medium can be efficiently removed by adding a metal salt, and that the removal can be imparted with sustainability, thereby completing the present invention. That is, the present invention is a deodorizing method characterized in that in the odor treatment, treatment is performed with a peroxide and a nitrate ion, preferably a metal salt.

[0012]

Next, the method of the present invention will be described specifically. The medium of the present invention includes general wastewater from homes, wastewater from factories and the like, and washing water and the like contained in a washing device and the like. Further, the sludge includes raw sludge, excess sludge, digested sludge, coagulated sludge, and the like, and mixtures thereof generated when treating sewage, human waste, or industrial wastewater.

In the method according to the invention, the medium is a peroxide,
Treat with nitrate ions. As the peroxide used in the method according to the present invention, hydrogen peroxide, peracetic acid, persulfate, percarbonate, perborate, and other inorganic and organic peroxides can be used, but it is preferable. Hydrogen peroxide is used. The amount of peroxide used is 2 to 2000 mg / L, preferably 5 to 100 mg / L, based on 100% by weight of hydrogen peroxide and based on the medium.
Use 0 mg / L.

Although hydrogen peroxide having a concentration of 35% by weight or 60% by weight is commercially available, it may be used as it is, or may be used after being diluted so as to be easily mixed with a medium. .

The nitrate ions used in the process according to the invention are supplied as nitric acid and nitrates. Examples of the nitrate include, but are not particularly limited to, alkali and alkaline earth metal salts such as sodium salt, potassium salt and calcium salt. You may use this as it is,
It may be used after being diluted so as to be easily mixed with a medium.

The amount of nitrate ion used is 1 to the medium.
It is an amount that results in a concentration of １０００1000 mg / L, preferably 2-500 mg / L. The peroxide and the nitrate ion may be added at the same time, or a premixed one may be added.

When adding peroxide and nitrate ion, it is preferable to add a metal salt. The metal salts used in the process according to the invention include groups VIA, VIIA, VIII, IB
Group, group IIB, group IVB, at least one salt selected from the group consisting of chromium for group VIA, manganese for group VIIA, iron, cobalt, nickel for group VIII, copper, silver for group IB, Group IIB is exemplified by zinc, and group IVB is exemplified by lead and tin. Salts of these metals include sulfates, nitrates, halides, perchlorates, inorganic salts such as hydroxides, oxalates,
Examples thereof include organic salts such as formate, oxides and the like, and may be any of anhydrous salts and hydrated salts. Further, as the iron salt, ferric polysulfate can be used.

The amount of the metal salt used is from 0.01 mg / L to 2 mg relative to the wastewater and sludge flowing as the weight of metal atoms.
00 mg / L, preferably 0.05 mg / L to 100 m
g / L.

The peroxide, the nitrate ion and the metal salt may be added at the same time, or may be added in a premixed state. When mixing in advance, a chelating agent such as an organic aminophosphonic acid type or an organic carboxylic acid type can be added as a stabilizer. Further, the peroxide, the nitrate ion, and the metal salt may be added sequentially, and the order of addition is not particularly limited.

In order to carry out the method according to the invention efficiently,
When adding peroxides, nitrate ions, and metal salts, it is preferable to stir for mixing with a medium. Any method may be used as long as it can mix oxides, nitrate ions, and metal salts.

As a method of adding a chemical, any method such as a diaphragm type or a plunger type metering pump may be used as long as it can accurately supply the chemical.

[0022]

Next, the method of the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples. The percentages in the examples are% by weight unless otherwise specified.

Example 1 To 100 ml of building wastewater retained in a building pit having a pH of 6.8 containing 20 mg / L of hydrogen sulfide, a 7% by weight aqueous solution of hydrogen peroxide was converted to 30 mg / L of 100% hydrogen peroxide based on the wastewater. (42.9 mg: 1.
5 moles), and then nitrate ion was added at 20 mg / L.
Then, 2.74 mg of sodium nitrate was added and the change over time in the concentration of hydrogen sulfide in the liquid phase was measured by a colorimetric method using lead acetate test paper. Table 1 shows the results.

Example 2 The same treatment as in Example 1 was carried out except that 2.4 mg of ferric chloride hexahydrate was added as an amount of iron (III) ion to be 5 mg / L as a metal salt. Table 1 shows the results.

Example 3 As a metal salt, 2.6 mg of manganese nitrate hexahydrate was added in such an amount that manganese (II) ion became 5 mg / L.
Processing was performed in the same manner as in Example 1. Table 1 shows the results.

Example 4 A treatment was carried out in the same manner as in Example 1 except that 2.0 mg of copper sulfate pentahydrate was added as a metal salt so that copper ions became 5 mg / L. Table 1 shows the results.

Example 5 A treatment was carried out in the same manner as in Example 1 except that 1.0 mg of zinc chloride was added as a metal salt so that zinc ions became 5 mg / L. Table 1 shows the results.

Example 6 A treatment was carried out in the same manner as in Example 1 except that 0.8 mg of silver nitrate was added as a metal salt so that silver ions became 5 mg / L. Table 1 shows the results.

Example 7 A treatment was carried out in the same manner as in Example 1 except that 3.9 mg of chromium nitrate nonahydrate was added as a metal salt so that chromium ions became 5 mg / L. Table 1 shows the results.

Example 8 The same treatment as in Example 1 was performed except that 2.0 mg of cobalt chloride hexahydrate was added as an amount of a metal salt so that cobalt ions became 5 mg / L. Table 1 shows the results.

Example 9 The same treatment as in Example 1 was carried out except that 2.5 mg of nickel nitrate hexahydrate was added as a metal salt so that nickel ions became 5 mg / L. Table 1 shows the results.

Example 10 A treatment was carried out in the same manner as in Example 1, except that 1.5 mg of tin chloride pentahydrate was added as an amount of tin ions to be 5 mg / L as a metal salt. Table 1 shows the results.

Example 11 A treatment was carried out in the same manner as in Example 1 except that 0.9 mg of lead acetate trihydrate was added as a metal salt so that lead ion became 5 mg / L. Table 1 shows the results.

Example 12 Example 1 was repeated except that 1.8 mg of ferrous chloride tetrahydrate was added in an amount such that iron (II) ion was 5 mg / L as a metal salt.
The same processing was performed. Table 1 shows the results.

Comparative Example 1 Table 1 shows the results of standing without adding hydrogen peroxide and a metal salt.

Table 1 Changes over time in hydrogen sulfide (mg / L) in wastewater Elapsed time (minutes) 1 60 480 ──────────────────────── ──────── Example 1 4 1 0 0 Example 2 3 0 0 0 Example 3 3 0 0 0 Example 4 4 0 0 0 0 Example 5 3 0 0 0 Example 6 1 0 0 0 0 Example 7 300 0 0 Example 8 2 0 0 0 Example 9 3 0 0 0 Example 10 3 0 0 0 Example 11 3 0 0 0 Example 12 3 0 0 0 Comparative example 1 20 21 28 30 ───────────────────────────────

Example 13 10 ml of sewage sludge composed of raw sludge and excess sludge
After adding and mixing 16.3 mg of hydrogen peroxide in an amount of 100 mg / L as 0% hydrogen peroxide and potassium nitrate in an amount of 100 mg / L of nitrate ions, the mixture was left for 5 minutes and 4 hours after the treatment. Table 2 shows the results of measurement of hydrogen sulfide and methyl mercaptan by the headspace method.

Example 14 Potassium nitrate was reduced to 8.1 mg so that the nitrate ion became 50 mg / L, and zinc chloride was converted to zinc at 25 mg / L.
The same processing as in Example 13 was performed except that the amount of L was added. Table 2 shows the results.

Comparative Example 2 Potassium nitrate and zinc chloride were not added and only hydrogen peroxide was added.
The same processing as in Example 13 was performed except that 00 mg / L was added. Table 2 shows the results.

Table 2 Hydrogen sulfide and methyl mercaptan concentrations in sewage sludge deodorization treatment Hydrogen sulfide (ppm) Methyl mercaptan (ppm) 5 minutes after 4 hours 5 minutes after 4 hours {Example 13 0 1 1 2 Example 14 0 0 1 1 Comparative Example 2 0 100 4 7} ───────────────────────────

The removal of hydrogen sulfide using only hydrogen peroxide has a quick effect, but after standing for 4 hours, the hydrogen sulfide is restored. By adding potassium nitrate, sustainability of removing hydrogen sulfide and methyl mercaptan could be provided. The addition of zinc chloride was effective even when the amount of potassium nitrate was reduced.

Example 15 7% hydrogen peroxide was added to sludge produced by treating factory wastewater in an amount of 150 mg / L as 100% hydrogen peroxide, and after stirring for 1 minute, nitrate ions were reduced to 30 mg / L. Was added and the mixture was stirred for 1 minute, and a 20% zinc chloride solution was added in an amount of 15 mg / L as zinc to perform deodorization treatment. Table 5 shows the results of measuring hydrogen sulfide by the headspace method after 5 minutes of treatment and after standing for 4 hours.

Example 16 The same treatment as in Example 15 was performed except that the order of the chemical injection was 20% zinc chloride solution, 7% hydrogen peroxide and nitric acid. Table 3 shows the results.

Example 17 The same treatment as in Example 15 was carried out except that a 7% hydrogen peroxide, nitric acid and 20% zinc chloride solution were simultaneously added. Table 3 shows the results.

[0045]

As described above, it was found that there was no difference in the effect depending on the order of adding the peroxide, the nitrate ion, and the metal salt.

[0047]

According to the present invention, the odor of hydrogen sulfide and mercaptans in a medium can be instantaneously removed with a small amount of chemical injection,
The device is simple and compact. Further, the effect can be maintained. As a result, the emission of harmful and unpleasant odorous hydrogen sulfide and mercaptans can be greatly suppressed, and a practical method for preventing the corrosion of cement, metal, and the like can be provided.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Tadashi Shimomura 6-1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Tokyo Research Laboratory

Claims (8)

[Claims] 1. A deodorizing method comprising treating a medium containing at least one of hydrogen sulfide and mercaptans with a peroxide and nitrate ions. 2. A deodorizing method comprising treating a medium containing at least one of hydrogen sulfide and mercaptans with a peroxide, a nitrate ion and a metal salt. 3. The method according to claim 1, wherein the metal salt is selected from the group consisting of VIA, VIIA, VIII,
3. The deodorizing method according to claim 2, which is at least one salt selected from the group consisting of Group IB, Group IIB, and Group IVB. 4. The method according to claim 1, wherein the metal salt is iron, copper, manganese, zinc, silver,
The method according to claim 3, wherein the method is chromium, nickel, tin or lead. 5. The deodorizing method according to claim 1, wherein the peroxide is hydrogen peroxide. 6. The deodorizing method according to claim 1, wherein the medium to be treated is wastewater, sludge, or washing water of a washing device. 7. A deodorant containing peroxide and nitrate ions for deodorizing a medium containing at least one of hydrogen sulfide and mercaptans. 8. A deodorizing agent containing a peroxide, a nitrate ion and a metal salt for deodorizing a medium containing at least one of hydrogen sulfide and mercaptans.