JP5990706B2 - Method for suppressing hydrogen sulfide generation in sludge treatment process - Google Patents

Description

  The present invention relates to a method for suppressing the generation of hydrogen sulfide in a sludge treatment process. More specifically, the present invention relates to a method capable of effectively suppressing hydrogen sulfide generated from factory sludge or sewage derived from protein.

  Organic matter such as food factories, pulp and paper factories, sewage treatment plants, and human waste treatment plants, especially sludge and sewage containing high concentrations of protein, will become anaerobic due to the activity of microorganisms such as sulfate-reducing bacteria when the forced supply of oxygen is lost. And sulfur-containing compounds such as hydrogen sulfide and methyl mercaptan are generated. In the vicinity of these anaerobic sludge and sewage treatment processes, the working environment is deteriorated by the generated hydrogen sulfide, etc., which may lead to poisoning or death. In addition, when transporting sludge and its dehydrated cake, there is a problem that odor on ordinary roads becomes a problem, which causes trouble for ordinary citizens.

As these countermeasures, (1) a method of suppressing the generation of hydrogen sulfide by antibacterial or sterilizing bacteria in sludge or sewage by adding a bactericidal agent, and (2) oxidizing the generated hydrogen sulfide with an oxidizing agent There are a method of removing, (3) a method of removing generated hydrogen sulfide by adsorbing it to a metal salt or the like, and a method of combining them.
In the method (1), as the bactericidal agent, for example, 2-bromo-2-nitropropane-1,3-diol, 2-bromo-2-nitropropane-1,3-diacetoxypropane, 2,2-dibromo- 2-nitroethanol, 1,2-benzisothiazolone, 5-chloro-2-methylisothiazolone, bisbromoacetoxy-2-butene, bisbromoacetoxyethane, α-chlorobenzaldoxime, 3-iodo-2-propargylbutyl Carbamate, 2,2-dibromo-2-cyanopropionamide and 1-bromo-3-chloro-5,5-dimethylhydantoin are used.

In the method (2), as an oxidizing agent, for example, hydrogen peroxide, benzoyl peroxide, sodium hypochlorite, sodium chlorite, sodium chlorate, sodium perchlorate, sodium hypobromite, sodium bromite And chlorinated cyanurates are used.
In the method (3), examples of the metal salt include ferrous chloride, ferric chloride, zinc chloride, zinc nitrate, copper chloride, copper sulfate, copper carbonate, silver salt, cobalt salt, nickel salt, titanium salt and tin. Salts are used.

For example, in Japanese Patent Application Laid-Open No. 63-209798 (Patent Document 1), an isothiazolone compound is effective as a sludge deodorant for preventing bad odor such as hydrogen sulfide and methyl mercaptan, and the effect is 2-bromo-2- It is disclosed that it is superior to nitropropane-1,3-diol (see the comparative example in Table 3 which is the test result of the claims and Example 2).
Japanese Patent Laid-Open No. 4-126597 (Patent Document 2) discloses a method for suppressing the generation of malodor such as hydrogen sulfide and methyl mercaptan from a dehydrated sludge cake by using an oxidizing agent and a bacteriostatic agent in combination. (See claims).
Furthermore, Japanese Patent Application Laid-Open No. 2004-275541 (Patent Document 3) discloses a method for suppressing sludge odor by adding 2-bromo-2-nitropropane-1,3-diol and zinc chloride to sludge slurry or sludge dewatered cake. Is disclosed (see claim 8).

JP-A-9-24396 (Patent Document 4) discloses that if ozone treatment is performed until the ORP (oxidation-reduction potential) of the sludge becomes -100 mV or more, the growth of sulfate-reducing bacteria can be suppressed and the ORP is monitored. Thus, it is disclosed that the effect of preventing sludge decay can be monitored (see the specification, paragraph 0034).
Japanese Patent Application Laid-Open No. 7-128322 (Patent Document 5) discloses a method for measuring the amount of dissolved oxygen in an aqueous liquid material stored in an open system container over time, and based on the measured value, decay of the aqueous liquid material. A method of predicting the degree of progress and adding a preservative such as management treatment means, for example, 2-bromo-2-nitropropane-1,3-diol is disclosed (claims 1, 5 and 6 and specification). Book, paragraph 0014). The ORP states that even if an attempt is made to predict the degree of corruption, the change cannot be confirmed and cannot be predicted (see the specification, paragraph 0027).

JP-A 63-209798 Japanese Patent Laid-Open No. 4-126597 JP 2004-275541 A Japanese Patent Laid-Open No. 9-24396 Japanese Patent Laid-Open No. 7-128322

Including the above-mentioned prior art, the properties of the target sludge, particularly sulfate-reducing bacteria and facultative anaerobic bacteria, have been added to the target systems such as sludge and sewage. The relationship between the activity state of the microorganisms, the place of addition of the drug, and the effective addition concentration has not been particularly studied, and it should have been possible to perform stirring and mixing in a place where addition is easy.
For example, Patent Document 1 describes that a chemical is added to sludge, and the amount of the chemical added may be about 10 to 2000 mg / L (for example, see the specification, page 2, lower right column). .
Patent Document 2 discloses that if it is before dewatering sludge, it is added to a desired place from the front of the sludge storage tank to the dehydrator and the conveyor. Is 100 to 5000 ppm and the bacteriostatic deodorant is 1 to 2000 ppm (for example, see the specification, page 3 and FIG. 1).
Furthermore, Patent Document 3 discloses that a drug is added between a first sedimentation basin and a gravity concentrated layer, a mixed sludge reservoir, a cake hopper, and 2-bromo-2-nitropropane-1,3-diol as a drug. It is described that the preferable addition amount is 10 to 1500 mg / L (see the specification, paragraphs 0009 and 0012 and FIG. 1).

  This invention makes it a subject to reduce the addition amount of a chemical | medical agent in the method which suppresses generation | occurrence | production of the hydrogen sulfide in a sludge process process by adding the chemical | medical agent which has a disinfection and / or oxidation action to sludge or sewage.

  As a result of investigation aimed at reducing the running cost of the drug, the inventors of the present invention have found that the effective addition amount differs depending on the place where the drug is added, and that the reason is the active state of microorganisms such as sludge of the target system. As a result of further research, the inventor of the present invention added the drug at a stage before the target sludge becomes anaerobic, compared with the case of adding the drug after becoming anaerobic. The present inventors have found that the same effect of suppressing the generation of hydrogen sulfide can be achieved even if the amount of added chemical is reduced to about 1/4.

Specifically, properties such as oxidation-reduction potential, presence or absence of hydrogen sulfide or dissolved sulfide (S ²⁻ ) in the sludge and sewage of the target system are measured, and sterilization and / or oxidation action is based on the measurement result. The inventors have found the fact that the same effect of suppressing the generation of hydrogen sulfide can be achieved even if the amount of the drug added is reduced by determining the addition location of the drug and completed the present invention.

  In addition, although it is disclosed by said patent document 4 that the sterilization effect of ozone can be monitored using ORP, it is disclosed that ORP is used as an index for confirming whether or not the target sludge is anaerobic. Not. Further, as described above, Patent Document 5 describes that in ORP, even if an attempt is made to predict the degree of progress of corruption, the change cannot be confirmed and prediction is impossible.

Thus, according to the present invention, by adding a chemical having a sterilizing and / or oxidizing action to sludge or sewage in a sludge treatment process comprising a plurality of treatment stages and paths connecting them, sulfidization from the sludge or sewage A method for suppressing the generation of hydrogen,
In order to confirm whether the sludge or sewage is in an anaerobic state or a non-anaerobic state, the concentration of hydrogen sulfide or dissolved sulfide (S ²⁻ ) in the treatment stage and route or the treatment step and route Measure the redox potential of sludge or sewage,
Determine the treatment stage or pathway in which the measured hydrogen sulfide or dissolved sulfide (S ²⁻ ) concentration exceeds 0 ppm or the redox potential is less than −100 mV and changes from non-anaerobic to anaerobic,
Comprising adding the agent to a treatment step or route prior to the determined treatment step or route to inhibit the generation of hydrogen sulfide from the sludge or sewage ,
Provided is a method for suppressing the generation of hydrogen sulfide in a sludge treatment process , wherein the chemical is 2-bromo-2-nitropropane-1,3-diol or sodium chlorite .

ADVANTAGE OF THE INVENTION According to this invention, the addition amount of a chemical | medical agent can be reduced in the method which suppresses generation | occurrence | production of the hydrogen sulfide in a sludge process process by adding the chemical | medical agent which has a disinfection and / or oxidation action to sludge and sewage.
That is, according to the present invention, since the generation of hydrogen sulfide in the sludge treatment process can be suppressed by adding a minimum amount of chemicals such as bactericides and oxidizing agents, food factories, paper pulp factories, sewage treatment plants, human waste It can be applied to a sludge or sewage treatment process containing a high concentration of organic matter such as a treatment plant, particularly protein, and cost reduction can be achieved.

  In the method for suppressing the generation of hydrogen sulfide according to the present invention, when the drug is 2-bromo-2-nitropropane-1,3-diol or sodium chlorite, the drug is added as a water-soluble liquid composition. In this case, the above-described effect is particularly exerted when the chemical is added as an active ingredient to the sludge and / or sewage at a concentration of 1 to 300 ppm.

It is the schematic which shows an example of the sludge process process which can apply the generation | occurrence | production suppression method of the hydrogen sulfide of this invention.

The method for suppressing the generation of hydrogen sulfide in the sludge treatment process of the present invention adds a chemical agent having a sterilizing and / or oxidizing action to sludge or sludge in a sludge treatment process comprising a plurality of treatment stages and a path connecting them. It is a method of suppressing the generation of hydrogen sulfide from the sludge or sewage,
(1) As anaerobic properties of the sludge or sewage, measure the concentration of hydrogen sulfide or dissolved sulfide (S ²⁻ ) in the treatment stage and route or the redox potential of sludge or sewage in the treatment step and route. ,
(2) Determine the treatment stage or route in which the measured hydrogen sulfide or dissolved sulfide (S ²⁻ ) concentration exceeds 0 ppm or the redox potential is less than −100 mV and changes from non-anaerobic to anaerobic. ,
(3) It is characterized in that generation of hydrogen sulfide from the sludge or sewage is suppressed by adding the chemical to a processing stage or path before the determined processing stage or path.
That is, the present invention is characterized in that a sterilizing and / or oxidizing agent is added at a stage before sludge or sewage becomes anaerobic.

Hereinafter, the present invention will be specifically described with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a schematic view showing an example of a sludge treatment process to which the method for suppressing generation of hydrogen sulfide of the present invention can be applied.
In this sludge treatment process, wastewater containing organic substances generated in factories and the like, particularly protein, at a high concentration passes through the inflow tank 1, the oil separation tank 2 and the adjustment tank 3, and the drainage pressure floating tank 4 or sedimentation tank. Solid-liquid separation is carried out (not shown). The solid content separated here is once stored in the storage tank 5 as a slurry of about 50 g / L. Subsequently, a coagulation treatment using the polymer coagulant is performed in the polymer coagulation tank (coagulant mixing tank) 10 and dehydrated by a dehydrator 6 such as a press to form a sludge cake. Subsequently, the obtained sludge cake is transported and stored in the dewatered sludge hopper (container) 8 by the conveyor 7 and then subjected to any one of composting treatment, landfill disposal, and incineration disposal. In the figure, reference numeral 9 indicates a measuring rod.

Usually, oxygen supply shortage occurs between the storage tank after the solid-liquid separation and the sludge cake, the sludge cake becomes anaerobic, and hydrogen sulfide and methyl mercaptan are generated. Sludge cakes are usually kept for 1 to 3 days or 7 days if they are long, depending on the factory, and prevention of the generation of hydrogen sulfide and methyl mercaptan during that period is required.
Even when wastewater is treated in an activated sludge tank, solid-liquid separation is performed after aeration, and the solid part is subjected to a storage tank, polymer aggregation treatment, dehydration treatment, and hopper storage in the same manner as described above. Therefore, in the same manner as described above, oxygen supply is insufficient between the storage tank after the solid-liquid separation and the sludge cake, and the gas becomes anaerobic and hydrogen sulfide and methyl mercaptan are generated.

In the method for suppressing generation of hydrogen sulfide of the present invention, first, (1) the concentration of hydrogen sulfide or dissolved sulfide (S ²⁻ ) in the treatment stage and route or the treatment step and route as the anaerobic properties of sludge or sewage. Measure the redox potential of sludge or sewage.
The hydrogen sulfide concentration and the oxidation-reduction potential can be measured using a commercially available hydrogen sulfide detector tube and oxidation-reduction potentiometer as used in the examples. If the pH of sludge or sewage is neutral to alkaline, measure the concentration of dissolved sulfide (S ²⁻ ) using a liquid detector tube (Gastec's liquid detector tube No. 211LL, etc.). Can do.

In the present invention, “anaerobic” means a state in which hydrogen sulfide is generated in sludge and sewage with almost no bound oxygen such as dissolved oxygen and nitrate nitrogen. Conversely, “non-anaerobic” means a state in which sludge and sewage have bound oxygen such as dissolved oxygen and nitrate nitrogen and no hydrogen sulfide is generated.
Such a state of “anaerobic” or “non-anaerobic” is referred to as “anaerobic property”.
These states can be confirmed using the presence or absence of hydrogen sulfide or a specific oxidation-reduction potential as an index, and these are measured in the present invention.

  In the present invention, “a plurality of treatment stages” means a coarse solid separation process, an oil separation process, a solid-liquid separation process, an agglomeration process such as a fine solid, a dehydration process, and the like. The term “distribution pipe”, “distribution pipe”, “water channel”, etc. connecting these processing stages.

Next, (2) a treatment stage or route in which the measured hydrogen sulfide concentration exceeds 0 ppm or the oxidation-reduction potential becomes less than −100 mV and changes from non-anaerobic to anaerobic is determined.
The presence or absence of hydrogen sulfide or a dissolved sulfide (S ^2-) is judged by whether hydrogen sulfide or dissolved sulfide (S ^2-) concentration or a 0 ppm (lower than the detection limit), or more than 0 ppm.
In addition, in the measurement of the oxidation-reduction potential, the state of sludge and sewage may be slightly different, but the former is judged to be non-anaerobic and the latter to be anaerobic depending on whether it is -100 mV or more or less than -100 mV. .
Based on the above determination, a processing stage or route that changes from non-anaerobic to anaerobic is determined.

Next, (3) a chemical is added to the treatment stage or route immediately before the decided treatment stage or route to suppress generation of hydrogen sulfide from the sludge or waste water.
The agent having a sterilizing and / or oxidizing action that can be used in the method for suppressing the generation of hydrogen sulfide of the present invention can sterilize or oxidize the sludge to be added and the microorganisms therein and exhibit the effects of the present invention. If it is, it will not specifically limit, For example, a disinfectant and oxidizing agent well-known in the said technical field are mentioned, What is necessary is just to select suitably by the kind and quantity, etc. of the sludge of addition object, and the microorganisms in it.

In the present invention, the “processing stage or path before the determined processing stage or path” means, for example, a non-anaerobic condition in the C processing stage in a sludge processing process in which the A processing stage, the B path, and the C processing stage are sequentially provided. When the hydrogen sulfide or dissolved sulfide (S ²⁻ ) concentration, which was 0 ppm in the B path, exceeded 0 ppm in the C treatment stage, or when the oxidation was more than −100 mV in the B path When the reduction potential is less than −100 mV in the C treatment stage, it means the B path or the A treatment stage.
Here, it is most preferable that the place where the drug is added is the B path immediately before, but it may be the A process stage immediately before depending on the apparatus configuration, the stirring conditions of the added drug, and the like.

  Specific examples of such bactericides and oxidizing agents include 2-bromo-2-nitropropane-1,3-diol, 2-bromo-2-nitropropane-1,3-diacetoxypropane, 2, 2-dibromo-2-nitroethanol, 1,2-benzisothiazolone, 5-chloro-2-methylisothiazolone, bisbromoacetoxy-2-butene, bisbromoacetoxyethane, α-chlorobenzaldoxime, 3-iodo-2 -Propargyl butyl carbamate, 2,2-dibromo-2-cyanopropionamide, 1-bromo-3-chloro-5,5-dimethylhydantoin, hydrogen peroxide, benzoyl peroxide, sodium hypochlorite, chlorous acid Sodium, sodium chlorate, sodium perchlorate, sodium hypobromite, sodium bromite, chlorinated cyanide Such as Le acid salts.

  In the present invention, a drug having a sterilizing and / or oxidizing action is added to sludge or sewage as a water-soluble liquid composition dissolved in water or a water-soluble solvent such as diethylene glycol, so that the sludge or sewage can be brought into contact quickly. It is preferable in that it can be performed.

  Among the above-mentioned chemicals having sterilization and / or oxidation action, 2-bromo-2-nitropropane is effective in suppressing the generation of hydrogen sulfide, handleability, economy, and can be easily made into a water-soluble liquid composition. Particularly preferred are -1,3-diol and sodium chlorite.

  In addition, the method for adding the water-soluble liquid composition to sludge or sewage is not particularly limited, and a method capable of accurately supplying a drug is preferable, for example, a method using a diaphragm type or plunger type metering pump or the like. It is done. In these methods, the drug concentration can be managed by continuous or intermittent addition of the drug.

  The amount of the agent having a sterilizing and / or oxidizing action in the present invention varies depending on the storage period of the sludge cake, etc., but is usually 1 to 300 ppm as an active ingredient with respect to sludge and / or sewage. Is preferred. A particularly preferred concentration is 1-210 ppm.

  The present invention will be described more specifically with formulation examples and test examples, but the present invention is not limited to these formulation examples and test examples.

(Formulation example 1)
68.75 g of ion-exchanged water was added to and mixed with 31.25 g of 80% sodium chlorite (white powder) as a reagent to obtain a colorless transparent liquid (water-soluble liquid composition, referred to as “Formulation 1”).
(Formulation example 2)
2-Bromo-2-nitropropane-1,3-diol (white crystals) 35.0 g, diethylene glycol 55.0 g and ion-exchanged water 10.0 g were mixed and stirred for 1 hour to obtain a colorless transparent liquid (water-soluble liquid composition). Product, “formulation 2”).

(Test Example 1)
In this test, slurry sludge (SS content: 54 g / L, pH: 5.4, soluble BOD: 600 mg) immediately after being separated and collected from a wastewater pressure floatation tank of a salmon food processing plant using eggs and milk as raw materials. / L) was used to measure the concentration of hydrogen sulfide and methyl mercaptan when the time of addition of the drug was changed.

Specifically, 200 mL of sludge was put in a 1 L capacity plastic bottle and sealed, and this was left in a constant temperature bath at a set temperature of 30 ° C. Within 10 minutes from the separation and collection of sludge, 1 hour, 2 hours and 6 hours later, as shown in Table 1, each of the preparations 1 and 2 was added to the slurry sludge at a concentration of 300 mg / L or 600 mg / L. Add to the bottle and shake and mix each plastic bottle 10 times after 1.1 hours, 2.1 hours, 6.1 hours, 24 hours, 72 hours and 168 hours. Immediately thereafter, the hydrogen sulfide (H ₂ S) concentration in the head space of each poly bottle was measured using a gas detector tube (manufactured by Gastec Co., Ltd., detector tubes 4LK, 4LL, 4HM). Further, after 168 hours, methyl mercaptan (MM) concentration was measured using a gas detector tube (manufactured by Gastec Co., Ltd., detector tubes 70 and 70L).

The obtained results are shown in Table 1.
Test No. 2, 3, 6, 7, 10, 11, 14 and 15 are examples. 1, 4, 5, 8, 9, 12, 13, 16 and 17 are comparative examples.
In the table, “ND” means less than the detection limit.

From the results in Table 1, it can be seen that the sludge without any chemical added (test No. 1) first becomes anaerobic within a short time and hydrogen sulfide is generated after 2 hours.
Preparation 1 (sodium chlorite aqueous solution) or preparation 2 (2-bromo-2-nitropropane-1,3-diol solution) must be prepared 1 hour before sludge becomes anaerobic (1 hour after separation and collection). There is a clear difference in the suppression effect of hydrogen sulfide and methyl mercaptan between the case where it is added and the case where Formulation 1 or 2 is added after 2 hours after the sludge becomes anaerobic (2 hours after separation and collection) It is done.
Therefore, the effectiveness of adding a drug before becoming anaerobic can be seen.

(Test Example 2)
It was tested using equipment from a coffee processing factory using soy milk as a raw material.
As shown in FIG. 1, this equipment consists of (A) Flotation sludge of drainage pressurization floating tank (Figure 4) → (B) Storage tank (Figure 5) → (C) Polymer coagulation tank (Figure 10) → (D) A dehydrator (Fig. 6) → (E) A device comprising a dewatered sludge hopper (Fig. 8) is provided. In this factory, the devices from (C) to (E) are operated at a rate of 7 hours per 48 hours due to the amount of drainage. (A) to (D) are installed in the same building, and the hydrogen sulfide concentration in the vicinity of (D) in the building is less than the regulation value (allowable concentration) of the Industrial Safety and Health Act, but the building has an average of 2 ppm. It showed the highest value indoors.

Formulation 2 (2-bromo-2-nitropropane-1,3-diol) was directly added to (B) storage tank inlet pipe (drug addition point A) (ORP: -100 mV, hydrogen sulfide concentration: 0 ppm). Intermittent injection was performed every 15 minutes at a rate of 0.6 kg per hour (addition concentration: 500 mg / L). When this operation was continued for 2 weeks (added amount: 8.4 kg / 14 days), (D) the hydrogen sulfide concentration in the vicinity of the dehydrator was below the detection limit (Example).
The ORP was measured using a portable ORP meter (manufactured by Toa DKK Co., Ltd., model: RM-20P).

  Formulation 2 (2-bromo-2-nitropropane-1,3-diol) was agglomerated and dehydrated into (B) storage tank outlet piping (drug addition point B) (ORP: -248 mV, hydrogen sulfide concentration: 50 ppm). Continuous uniform injection (addition concentration: 1000 mg / L) was carried out at a rate of 2.4 kg in 7 hours when the machine was operating. When this operation was continued for 2 weeks (added amount: 16.8 kg / 14 days), the hydrogen sulfide concentration in the vicinity of the dehydrator decreased to an average of 1 ppm, but did not reach the detection limit (Comparative Example). In the comparative example, it can be seen that the hydrogen sulfide concentration did not fall below the detection limit even when twice the amount of the drug was used.

  From these results, the effectiveness of adding the drug to the point A before becoming anaerobic and the effectiveness of adding the drug using the ORP value as an index can be understood.

DESCRIPTION OF SYMBOLS 1 Inflow tank 2 Oil separation tank 3 Adjustment tank 4 Drain pressure pressurization levitation tank 5 Storage tank 6 Dehydrator 7 Conveyor 8 Dehydrated sludge hopper (container)
9 Weighing bowl 10 Polymer coagulation tank A, B Drug addition point

Claims (3)

A method for suppressing the generation of hydrogen sulfide from the sludge or sewage by adding a sterilizing and / or oxidizing agent to the sludge or sewage in the sludge treatment process comprising a plurality of treatment stages and paths connecting them. Yes,
In order to confirm whether the sludge or sewage is in an anaerobic state or a non-anaerobic state, the concentration of hydrogen sulfide or dissolved sulfide (S ²⁻ ) in the treatment stage and route or the treatment step and route Measure the redox potential of sludge or sewage,
Determine the treatment stage or pathway in which the measured hydrogen sulfide or dissolved sulfide (S ²⁻ ) concentration exceeds 0 ppm or the redox potential is less than −100 mV and changes from non-anaerobic to anaerobic,
Comprising adding the agent to a treatment step or route prior to the determined treatment step or route to inhibit the generation of hydrogen sulfide from the sludge or sewage ,
The method for suppressing generation of hydrogen sulfide in a sludge treatment step , wherein the chemical is 2-bromo-2-nitropropane-1,3-diol or sodium chlorite . The method for suppressing hydrogen sulfide generation according to claim 1, wherein the drug is added as a water-soluble liquid composition. The method for suppressing the generation of hydrogen sulfide according to claim 1 or 2 , wherein the chemical is added to the sludge and / or sewage as an active ingredient at a concentration of 1 to 300 ppm.