JP2000185290A - Deodorizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the diffusion of a malodor and the corrosion of facilities by efficiently decomposing and removing hydrogen sulfide and mercaptans in a medium containing a sulfureous offensive smell substances under a mild condition by treating the medium with a peroxide and nitrite ions. SOLUTION: A medium such as waste water or sludge is treated with a peroxide and nitrite ions. As the peroxide, hydrogen peroxide, peracetic acid, a percarbonate, a perborate, calcium peroxide and other inorg. and org. peroxides can be used and hydrogen peroxide or a percarbonate is pref. Nitrite ions are supplied by nitrous acid and nitrite. As nitrite, alkali and alkaline earth metal salts such as a sodium salt, a potassium salt or a calcium salt and an ammonium salt are designated. When peroxide and nitrite ions are premixed, the pH of a mixture is pref. set to 6-12. When peroxide and nitrite ions are added, it is pref. to add a metal salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to raw sludge, surplus sludge, digested sludge, coagulated sludge, etc. generated when treating wastewater or wastewater, or odor generated from washing water of a washing apparatus or a mixture thereof. The present invention relates to a method or a deodorant which can be quickly removed with a small dose.

[0002]

2. Description of the Related Art In recent years, population density in cities and suburbs has been increasing.
It leads to the consumption of large amounts of water resources, and the water resources used are
Wastewater containing various organic and inorganic substances is discharged to public sewers and residence tanks in buildings. In addition, they produce large amounts of raw sludge, excess sludge, and digested sludge in the process of being treated in a sewage treatment plant. In addition, large-scale factories and other business establishments are required to treat wastewater to a specified water quality due to severe drainage regulations due to severe environmental pollution of rivers and oceans. Activated sludge treatment produces a large amount of sludge. Among these wastewater and sludge,
Contains sulfates and large amounts of BOD components. Sulfate-reducing bacteria are usually present in wastewater and sludge, and sulfates in sludge are reduced to hydrogen sulfide for production activities.

[0003] The produced hydrogen sulfide is a gas at normal temperature and is released to the gas phase. This hydrogen sulfide is a toxic substance with an unpleasant odor, so it leaks from manholes and underground buildings in sewerage facilities, causing odor problems to nearby residents and hazards to workers when treating sludge. Is worried. In addition, hydrogen sulfide is oxidized by sulfur oxidizing bacteria and air adhering in the concrete facility, and dissolves in the mist to generate sulfuric acid. The sulfuric acid thus produced corrodes alkaline concrete and metal, causing fatal defects in the structure of the building. Furthermore, as in the case of hydrogen sulfide, mercaptans are produced in the process of spoilage of wastewater and sludge, which causes odor problems.

As a means for preventing the generation of these odors and the corrosion of structures, there is a method in which the pH is made alkaline by using caustic soda or the like to suppress the emission of hydrogen sulfide. However, this method decomposes or removes hydrogen sulfide itself. This is not a sufficient treatment, for example, when neutralized, hydrogen sulfide is regenerated and alkali scale is generated. As a method of oxidizing the offensive odor component, there is a method of adding hydrogen peroxide, which can remove hydrogen sulfide and mercaptans.However, if the added amount is small, the sludge is left for a long time. However, there is a problem that oxidized sulfur or sulfate ions produce hydrogen sulfide again by bacteria. As a method of fixing hydrogen sulfide as a metal salt, there is a method of adding a metal salt.In this method, hydrogen sulfide reacts with metal ions to fix metal sulfide and hydrogen sulfide. There was a disadvantage that it was produced in large quantities.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to efficiently decompose and remove hydrogen sulfide and mercaptans in a medium under mild conditions, to diffuse odors and It provides a method of preventing the corrosion of facilities.

[0006]

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, and as a result, have found that a medium containing a sulfur-based odorant such as hydrogen sulfide, mercaptans, dimethyl sulfide, etc. The inventors have found that hydrogen sulfide and mercaptans in a medium can be efficiently removed by adding an oxide and a nitrite ion, preferably a metal salt, and that the removal can be sustained, thereby completing the present invention. That is, the present invention relates to a deodorizing method characterized by treating a medium containing a sulfur-based odorant with peroxide and nitrite ions.

[0007]

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 present invention, the medium is treated with peroxide and nitrite ions. As the peroxide, hydrogen peroxide, peracetic acid, persulfate, percarbonate, perborate, calcium peroxide and other inorganic and organic peroxides can be used, but preferably hydrogen peroxide or peroxide is used. It is a carbonate. The amount of peroxide used is 1 to 100% by weight of hydrogen peroxide relative to the medium.
Use 2000 mg / L, preferably 2-1000 mg / L. Hydrogen peroxide is commercially available at 35% by weight or 60% by weight, but it may be used as it is or may be used after being diluted so as to be easily mixed with a medium.

The nitrite ions of the present invention are supplied as nitrite and nitrite. Examples of the nitrite include, but are not particularly limited to, alkali and alkaline earth metal salts such as sodium salt, potassium salt and calcium salt, and ammonium salt. The nitrite may be an anhydrous salt or a hydrated salt. You may use this as it is,
It may be used by diluting with water so as to be easily mixed with the medium. The amount of nitrite ion used is 1 to 10
It is an amount that gives a concentration of 00 mg / L, preferably 2-1000 mg / L. The peroxide and the nitrite ion may be added at the same time, or a premixed one may be added.

When the peroxide and the nitrite ion are mixed in advance, the pH of the mixture is preferably in the range of 6 to 12, more preferably 7 to 10. The pH adjuster is not particularly limited, but inorganic alkalis such as caustic soda and caustic potash, organic alkalis and the like are preferably used.

In the case of mixing in advance, a chelating agent such as an organic phosphonic acid type, an organic aminophosphonic acid type, or an organic carboxylic acid type can be added as a stabilizer. The chelating agent is not particularly limited, but ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, polyhydroxycarboxylic acid,
-Hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), 1,2-propylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), hexamethylenediamine Tetra (methylenephosphonic acid), triethylenetetraminehexa (methylenephosphonic acid), triaminotriethylaminehexa (methylenephosphonic acid), trans-1,2-cyclohexanediaminetetra (methylenephosphonic acid), glycol etherdiaminetetra (methylene Phosphonic acid), tetraethylene hepta (methylene phosphonic acid), polyhydroxycarboxylic acid, phenylurea and the like, and at least one of them is used. Also,
These may be free acids or in the form of salts. When used in the form of a salt, alkali metal salts, alkaline earth metal salts,
Ammonium salts and organic amine salts can be used,
Sodium salts and ammonium salts are preferably used. The amount of the chelating agent used depends on the content of nitrite ions, but is 1 to 5 with respect to the total amount of peroxide and nitrite ions.
0.000 ppm by weight is preferred. If necessary, another stabilizer such as phosphoric acid may be used in combination. The amount of nitrite ion with respect to the peroxide is not particularly limited, but is usually 1 to 1 as nitrite ion with respect to 100% conversion of hydrogen peroxide.
About 300% by weight is used.

When adding peroxide and nitrite ions, it is preferable to add a metal salt. Examples of the metal salt used in the present invention include Group 5, Group 7, Group 8, Group 9, Group 10, and Group 11.
At least one metal salt selected from the group consisting of Group 12, Group 14 and Group 14; for example, chromium for Group 6, manganese for Group 7, iron for Group 8, cobalt for Group 9, nickel for Group 10, nickel, Group 11 Is copper, silver, group 12 is zinc, group 14 is lead and tin. Salts of these metals include inorganic salts such as sulfates, nitrates, halides, perchlorates, and hydroxides,
Oxalates, organic salts such as formate, oxides and the like are exemplified,
Either an anhydrous salt or a hydrated salt may be used. The metal salt may have any oxidation number. Further, as the iron salt, ferric polysulfate can be used. The metal salts may be used alone or in combination of two or more. The amount of the metal salt used is such that the concentration becomes 0.01 mg / L to 500 mg / L, preferably 0.05 mg / L to 300 mg / L, with respect to the wastewater and sludge flowing in as the weight of metal atoms.

The peroxide, nitrite ion and metal salt are
The mixture may be added at the same time, a premixed mixture may be added, or a part of the components may be mixed in advance, and the mixture and the remaining components may be added. Further, peroxide, nitrite ion, and metal salt may be added sequentially, and there is no particular limitation on the order of addition. As described above, a chelating agent or an alkali can be added as a stabilizer.

When adding peroxide and nitrite ion, nitrate ion may be allowed to coexist. When peroxide and nitrite ions are mixed in advance and used, nitrate ions may be mixed in advance and used at the same time. Further, treatment with a solution in which peroxide and nitrite ions are preliminarily mixed and nitrate ions may be performed, or treatment with a solution in which peroxide and nitrite ions are preliminarily mixed and nitrite ions may be performed. Further, when adding a metal salt, nitrate ions may be added. The nitrate ion used at this time is not particularly limited, but is supplied as nitric acid and nitrate. Examples of the nitrate include an alkali metal such as a sodium salt, a potassium salt, and a calcium salt, an alkaline earth metal, an ammonium salt, and the like. The nitrate may be an anhydrous salt or a hydrated salt, and may be used as an aqueous solution.

In order to carry out the method according to the invention efficiently,
It is preferred to stir to mix the peroxide, nitrite ion, or a mixture or peroxide, nitrite ion, metal salt or mixture thereof with the medium. As a stirring method, any method such as a stirring and mixing tank, a stirring blade, and an in-line mixer may be used.

As a method of adding the chemical, any method can be used as long as it can accurately supply the chemical, such as a diaphragm type or plunger type metering pump. As a place to add the drug,
Any place that can be mixed with sewage, wastewater and sludge may be used, such as wastewater pits of buildings, pits and sewage removal tanks of sewage pump stations, sludge concentration tanks of sewage treatment plants, sludge mixing tanks, sludge storage tanks and the like. The coagulant may be directly charged into a mixing tank or a transfer pipe for sewage, wastewater or sludge. Further, it is preferable that the transfer of the medium is detected, and the pump for adding the deodorant is started and stopped in conjunction therewith. The detection of the transfer of the medium is based on a start signal of a transfer pump for the medium, a signal indicating the open / closed state of a valve of the transfer pipe, a flow rate instruction of the medium, or the like.

[0017]

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. In addition,% is weight%.

Example 1 100 ml of sewage sludge collected from a sludge storage tank
% Hydrogen peroxide in an amount of 100 mg / L and 15 mg of sodium nitrite (an amount of 50 mg / L in nitrite ion) were added and mixed.
After standing for 4 hours, the results of measuring hydrogen sulfide and all mercaptans by the headspace method are shown in Table 1.

Comparative Example 1 The same treatment as in Example 1 was performed, except that 15 mg of sodium nitrate (an amount of 55 mg / L as nitrate ions) was added instead of nitrite ions. Table 1 shows the results.

Comparative Example 2 Nitrite ion was 100 mg / L without adding hydrogen peroxide
The same treatment as in Example 1 was carried out except that 30 mg of sodium nitrite was added to the amount of と. Table 1 shows the results.

Comparative Example 3 Hydrogen peroxide was added in an amount of 200 mg / without adding sodium nitrite.
The same processing as in Example 1 was performed except that L was added. Table 1 shows the results.

Comparative Example 4 The same treatment as in Example 1 was performed except that no drug was added. The results are shown in Table 1.

[0023]

Table 1 Table 1 Hydrogen sulfide concentration (unit: ppm) in sewage sludge deodorization treatment

The treatment with hydrogen peroxide alone has a quick effect, but after standing for 24 hours, hydrogen sulfide and all mercaptans have been restored. By adding sodium nitrite, it was possible to provide sustained removal of hydrogen sulfide and all mercaptans. Further, nitrite was more effective than nitrate in controlling hydrogen sulfide and all mercaptans.

Example 2 To 100 ml of sewage containing 10 mg / L of hydrogen sulfide, 2.4 mg of ferric chloride hexahydrate was added in such an amount that iron (III) ion was 5 mg / L as a metal salt. 7% by weight
Of hydrogen peroxide aqueous solution of 100% hydrogen peroxide to wastewater in an amount of 15 mg / L (21.4 mg: 1.5 times mol of hydrogen sulfide) and 10% of an amount of nitrite ion in an amount of 10 mg / L. After adding and mixing 18.7 mg of an aqueous solution of sodium nitrate, the change over time in the concentration of hydrogen sulfide in the liquid phase was measured.
Table 2 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.
The processing was performed in the same manner as in Example 2. Table 2 shows the results.

Example 4 A treatment was carried out in the same manner as in Example 2 except that 2.0 mg of copper sulfate pentahydrate was added as a metal salt so that copper ions became 5 mg / L. Table 2 shows the results.

Example 5 A treatment was carried out in the same manner as in Example 2, except that 1.0 mg of zinc chloride was added as a metal salt so that zinc ions became 5 mg / L. Table 2 shows the results.

Example 6 A process was performed in the same manner as in Example 2 except that 0.8 mg of silver nitrate was added as a metal salt so that silver ions became 5 mg / L. Table 2 shows the results.

Example 7 The same treatment as in Example 2 was carried out, except that 3.9 mg of chromium nitrate nonahydrate was added as a metal salt so that chromium ions became 5 mg / L. Table 2 shows the results.

Example 8 A treatment was carried out in the same manner as in Example 2 except that 2.0 mg of cobalt chloride hexahydrate was added as a metal salt so that cobalt ions became 5 mg / L. Table 2 shows the results.

Example 9 The same treatment as in Example 2 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 2 shows the results.

Example 10 A treatment was carried out in the same manner as in Example 2, 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 2 shows the results.

Example 11 A treatment was carried out in the same manner as in Example 2 except that 0.9 mg of lead acetate trihydrate was added as a metal salt so that lead ion became 5 mg / L. Table 2 shows the results.

Example 12 Example 2 was repeated except that 1.8 mg of ferrous chloride tetrahydrate was added as a metal salt in such an amount that iron (II) ion was 5 mg / L.
The same processing was performed. Table 2 shows the results.

Example 13 An amount of 2 mg / L as 100% hydrogen peroxide (2
8.6 mg) and 24.9 mg of a 10% aqueous solution of potassium nitrite in which the amount of nitrite ion became 15 mg / L was used. Table 2 shows the results.

COMPARATIVE EXAMPLE 5 Table 2 shows the results of standing without adding hydrogen peroxide, potassium nitrite and metal salts.

[0038]

[Table 2] Table 2 Time course of hydrogen sulfide (mg / L) in sewage

Embodiment 14 FIG. 1 is a diagram showing the configuration of an apparatus in which the present invention is applied to a dehydrator of a sludge treatment facility and a deodorizer of a hopper. The sludge stored in the sludge storage tank (101) is transferred to the flocculant mixing tank (104) by the sludge pump (102). Here, the sludge is mixed with a coagulant and a dehydrator (10
It is dehydrated in 5). The dewatered sludge cake is stored in a sludge cake hopper (106) by a belt conveyor and stored until sludge is carried out. During this process, sulfur-based odors of hydrogen sulfide and mercaptans are generated in the dehydrator. In addition, sulfur-based odors such as hydrogen sulfide and mercaptans are generated even when the dewatered sludge cake is stored.

Hydrogen peroxide is supplied to a sludge pipe (103) through a chemical pipe (108) using a chemical injection pump (107).
100 mg / 100% hydrogen peroxide conversion to sludge
L was added. Also, sodium nitrite
Using the chemical injection pump (109), the solution was dropped into the coagulant mixing tank via the chemical pipe (110). Sodium nitrite is 4
A 0% aqueous solution was used and added dropwise to the sludge so as to have a nitrite ion concentration of 100 mg / L. Mud pump (10
2) is started every day from 9:00 to 15:00, but the activation of the chemical pumps (107, 109) is performed by the mud pump (102).
Linked to the startup. FIGS. 2 and 3 show the results of continuous measurement of hydrogen sulfide in the dehydrator and the dehydrated cake hopper.

Comparative Example 6 The results of measuring the concentration of hydrogen sulfide when no chemical injection was performed are shown in FIGS. By treating with hydrogen peroxide and nitrite, the odor in the dehydrator and the dehydrated cake hopper could be greatly reduced. In addition, the chemical injection pump was started in conjunction with the sludge pump, so that it could be efficiently mixed with the sludge in the pipe and the medicine was accurately injected.

Example 15 A mixture of 100 g of 35% hydrogen peroxide adjusted to pH 8.5 and 52.5 g of sodium nitrite was mixed with 3 parts of diethylenetriaminepenta (methylenephosphonic acid) as a chelating agent.
000 ppm was added. Table 3 shows the stability of hydrogen peroxide and nitrite ions after 24 hours of this mixed solution. Stability = (concentration (%) 24 hours after mixing / concentration (%) immediately after mixing) × 100

Comparative Example 7 Table 3 shows a case where the procedure was the same as that of Example 15 except that the pH was not adjusted.

Comparative Example 8 Table 3 shows a case where the procedure was the same as that of Example 15 except that no chelating agent was used.

[0045]

Table 3 Stability of the mixture

[0046]

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 the corrosion of cement, metal and the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram in which the present invention is applied to sewage sludge treatment.

FIG. 2 shows the concentration of hydrogen sulfide in the dehydrator of Example 14 and Comparative Example 6.

FIG. 3 shows the concentration of hydrogen sulfide in the dehydrated cake hoppers of Example 14 and Comparative Example 6.

[Explanation of symbols]

 101: Sludge storage tank 102: Sludge pump 104: Coagulant mixing tank 105: Dehydrator 106: Sludge cake hopper 107: Chemical injection pump 109: Chemical injection pump

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Tadashi Okazaki 6-1-1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Company, Ltd. Tokyo Research Laboratory (72) Inventor Tomonori Kato 6-1-1 Shinjuku, Katsushika-ku, Tokyo No. 1 Mitsubishi Gas Chemical Co., Ltd. Tokyo Plant

Claims (9)

[Claims] 1. A deodorizing method comprising treating a medium containing a sulfur-based odorant with peroxide and nitrite ions. 2. The deodorizing method according to claim 1, further comprising treating with a metal salt. 3. The deodorizing method according to claim 1, wherein peroxide and nitrite ions are added in conjunction with the transfer of the medium. 4. The deodorizing method according to claim 1, wherein a peroxide and a nitrite ion are added to a pipe for transferring the medium. 5. The method according to claim 1, further comprising adding peroxide and nitrite ions to a pipe for transferring the medium in conjunction with the transfer of the medium.
Or the deodorizing method according to 2. 6. The pH of a mixture of peroxide and nitrite ions.
The deodorizing method according to claim 1 or 2, wherein the treatment is performed at 6 to 12. 7. The method according to claim 1, wherein a chelating agent is added. 8. A deodorant for a medium containing a sulfur-based odorant comprising a peroxide and a nitrite ion. 9. The deodorant according to claim 8, further comprising a combination of a metal salt.