JPH08182999A - Treatment of sewerage sludge and sewerage sludge-treated material - Google Patents

Abstract

PURPOSE: To stably and effectively utilize a sewerage sludge by adding a specific quantity of a specific powder into a mixture of sludge and lime, obtained by mixing quick lime with the sewerage sludge followed by dehydrating, to remove malodor generated from the sewerage sludge in a large quantity. CONSTITUTION: After the sewerage sludge is mixed with quick lime and dehydrated, 0.5-15wt.% powder having >=50wt.% SiO2 content and showing acidity of <=5.0 hydrogen ion concentration in the case of its 3%aq. suspension is added into the mixture of the sludge and lime to remove malodor. As the acidic powder, diatomaceous earth of gapanese acid clay is exemplified. By this way, the sewerage sludge is substantially deodorized, and then, is easily used in wide fields. Since the treated produet consists essentially of calcium and silica, the product is effectively used in a large quantity as a raw material for cement or iron and steel, further exhibits remarkable effect on denitrification, improvement of acidic soil and fatting of plants, and is useful as a soil conditioner, a fertilizer or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of organic sewage sludge produced by treating industrial wastewater and general domestic wastewater.

[0002]

2. Description of the Related Art In recent years, the amount of sewage sludge generated has been increasing along with the expansion of the sewer network. Conventionally, as a method of treating sewage sludge, it was general to incinerate by adding an auxiliary fuel such as heavy oil and to dispose of the incinerated ash in landfill, but it becomes difficult to secure the landfill site of the final disposal destination. Going on,
There is an urgent need to reduce the volume of sewage treatment products or develop effective utilization methods. As a method for reducing the volume of incinerated ash, a method of melting and vitrifying has been attempted at some treatment plants, but the energy cost is high and the problem of treating ash discharged remains and the fundamental solution is is not. In addition, as an effective use of incineration ash, such as manufacturing brick products and use for organic fertilizer,
Many methods have been tried, but it is necessary to open new markets, and to compete with existing competitors, quality and
However, there are some problems such as cost problems, and it does not lead to large-scale and stable use of sludge.

A technique in which sludge is mixed and dehydrated with quick lime and the like and used as a raw material for cement or a sintering raw material for iron making (Japanese Patent Laid-Open Nos. 3-98700 and 3-207497).
No.) is drawing attention. 1 for cement production or steelmaking
The raw materials are sintered using a furnace of 000 ° C or higher, and when sludge is put into these furnaces, the organic matter in the sludge burns without adding the fuel for supporting combustion, so that the conventional fuel that requires supporting fuel is burned. It is energetically advantageous compared to the treatment method. Moreover, inorganic substances are effectively used as siliceous raw materials and calcareous raw materials,
In addition, there is an advantage that existing cement manufacturing facilities and steelmaking facilities can be used as they are, and waste gas measures can be achieved by waste gas treatment of existing facilities. In addition, these methods enable large-scale treatment of sludge to be used as industrial raw materials for continuous operation such as cement or steel, and can treat sewage sludge stably without the market development effort accompanying new product development. It can be said that this is an epoch-making solution, and it is hoped that the usage in this direction will spread in the future.

[0004]

On the other hand, these methods still have the following problems. That is, in the activated sludge method, which is the mainstream of the present sewage treatment method, the nitrogen content is concentrated and adsorbed in the sludge, so the sewage sludge discharged from the treatment plant contains a large amount of nitrogen content. In the above treatment method in which quicklime is added to sewage sludge, the nitrogen content in the sludge is decomposed by the heat generated when the quicklime is mixed with the sludge, and a large amount of ammonia gas is generated and volatilized, so that a foul odor diffuses around. Most of the generated ammonia gas can be collected when mixed with quick lime, but part of it is adsorbed on a mixture of slaked lime and dry sludge with a high specific surface area after quick lime hydration (hereinafter referred to as "dry powder"). Is left behind. This residual ammonia content is volatilized as the temperature rises, and when the temperature rises above 30 ° C. in the dry powder storage silo, ammonia gas having a concentration of several percent or more is filled, and the working environment becomes poor. Even if this dry powder is stored in a closed manner, leakage of ammonia gas is unavoidable and a foul odor drifts when it is taken in and out, transferred, or put into a furnace as a cement raw material. By the way, the human sense of odor can be detected even at an ammonia concentration of about 1 ppm, so a deodorizing treatment method for removing the ammonia concentration is required below this.

As a measure against ammonia odor, a method of adsorbing it on an organic high specific surface area substance such as activated carbon is known, as is often done with pet sand. But,
This method is not suitable for the odor control of dry powder. That is, activated carbon and the like adsorb water, dust, and the like in addition to ammonia and saturate the surface in a short period of time, resulting in a drastic decrease in adsorption force. Also, if used in large amounts, it will increase the processing cost,
If it is pulverized in order to obtain an effect even if it is used in a small amount, it easily binds to oxygen in the air during storage or transportation, which causes a risk of so-called dust explosion. It is possible to neutralize ammonia by dropping gas phase or liquid phase acid instead of using activated carbon, but the acid storage itself is a hazardous material storage, which is troublesome to manage. There is a problem that the treatment cost is considerably increased due to the need for corrosion resistance measures such as.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the problems in the conventional treatment methods as described above, and provides a method capable of removing the bad odor of a large amount of sewage sludge and stably and effectively utilizing the sewage sludge. The purpose is to provide. According to the present invention, the malodor of a mixture of sewage sludge and quick lime is removed at low cost, which facilitates the use of the mixture as a raw material for cement or a raw material for iron making, and further has a new application in a field that has not been conventionally used. Will also be possible.

[0007]

According to the present invention, there is provided a sewage sludge treatment method and a sewage sludge treated product having the following constitution. (1) After mixing quicklime with sewage sludge for dehydration,
To deodorize the sludge / lime mixture by adding 0.5 to 15% by weight of powder having an SiO ₂ content of 50% by weight or more and having a hydrogen ion concentration of 5.0 or less when suspended in 3% water. A method for treating sewage sludge, which is characterized by: (2) The above wherein the acidic powder is diatomaceous earth or acidic clay
The method described in (1). (3) A sludge-lime mixture obtained by mixing quicklime with sewage sludge and dehydrated to obtain a powder exhibiting an acidity of 50% by weight or more of SiO _{2 and} a hydrogen ion concentration of 5.0 or less when suspended in 3% water. A deodorized sewage sludge composition, which is mixed in an amount of 0.5 to 15% by weight. (4) The above, wherein the acidic powder is diatomaceous earth or acidic clay
The composition according to (3).

[0008]

[Detailed Description] (I) Dehydration Step Using Quick Lime The sewage sludge treated in the present invention is mainly sludge generated at a sewage treatment plant. In addition to this, human waste, domestic wastewater, industrial wastewater Includes sludge generated by treatment. These sludges are dehydrated by a filter press or the like at a sewage treatment plant to a water content of about 60 to 100%, and the present invention uses this sewage sludge. The quicklimes mixed with sewage sludge are those that contain CaO as a main component and take in the water of the sewage sludge to form slaked limes. Be done. The particle size of quicklime is 70 mm or less, preferably 30 mm or less. The mixing amount of quicklime depends on the water content of the sewage sludge, but is generally 80 to 1 with respect to 100 parts by weight of the sewage sludge.
About 30 parts by weight is preferable. If the amount of quicklime added is less than this range, the sludge will not be dried and is not suitable as a raw material for cement or iron making. If the amount of quicklime added is too large, the cost will be high, which is not preferable. When sewage sludge having a water content of 80% is mixed with the same amount of quicklime, a dry powder having a water content of almost zero is obtained.

(II) Deodorizing step with acidic siliceous powder To the mixture of sludge and lime dehydrated as described above, S
The hydrogen ion concentration when the iO ₂ content is 50% or more and is suspended in water 3% (in the present specification, "3%
Suspension pH in water ". ) Is less than 5.0 and deodorized by adding siliceous powder. If the SiO ₂ content of the above powder is less than 50%, it is difficult to generate a protic acid, and 3%
When the pH of the suspension in water exceeds 5.0, the effect of neutralizing ammonia is not sufficiently exerted.

As the siliceous powder satisfying the above conditions, diatomaceous earth, acid clay and activated clay which is a processed product thereof are suitable. First, they are widely distributed in the volcanic region from Hokkaido to Kyushu, are easily available, are cheaper than activated carbon of the same weight, and are economical. Moreover, because it is easy to mine,
Since it is already in the form of powder, there is no need to crush it. Secondly, in addition to being low in water absorption, they may have acid groups required to continue neutralization for about 2 hours to 7 days with respect to a dry powder containing a few% of ammonia gas. Third, the chemical composition is SiO ₂
-The fact that it is an Al ₂ O ₃ system means that the cement
Another advantage is that there is no particular problem in terms of steel and soil improvement.

Diatomaceous earth is a soil whose main component is hydrous silicon dioxide composed of diatom shells. The acid clay is a white clay containing montmorillonite as a main component, has a strong adsorption capacity, and the pH of the suspension shows weak acidity. Clay mineral montmorillonite is rich in silicic acid (SiO ₂ ), some of Si atoms are replaced by Al, Fe and Mg atoms, and this negative charge is neutralized by cations such as K ⁺ and Na ⁺ between layers. It has a structure. When this is exposed to wind and rain and the cations are replaced by protons, protonic acids (Bronsted acids) are generated and become acidic, and become acid clay. A in the crystal structure with sulfuric acid, etc.
When l and Mg atoms are eluted, the activated clay has high porosity and extremely high activity. PH of 3% activated clay suspension in water
Is approximately 3.0 or less, and the ammonia deodorizing effect is greater. If the composition of diatomaceous earth, acid clay, and activated clay is not particularly high in phosphorus and alkali metals, which are unsuitable for cement / steel applications, the amount of Al or Fe is not a problem, and petroleum It may be a low-grade one that cannot be used for refining or papermaking.

In the above-mentioned diatomaceous earth, acid clay and activated clay, the protons and ammonia molecules existing in the metal cation elution part on the particle surface or in the particles of these powders are bound and captured as ammonium ions on the particle surface or in the particles. It On the other hand, silica gel, zeolite, activated carbon, etc. are also known to have an ammonia adsorption effect, but their adsorption ability depends on their porosity, and not only the ammonia component but also other components, especially water vapor. Adsorb a particularly large amount. As a result, the porous surface is saturated immediately and the essential ammonia cannot be adsorbed sufficiently. Saturation by water vapor can be avoided by reducing the water content of sludge, but a large amount of heat is required for drying, which is inferior in economic efficiency. However, the above-mentioned diatomaceous earth, acid clay and activated clay used in the present invention are not merely adsorption ability due to porosity, and as described above, ammonia is effective because it adsorbs ammonia molecules by its acidity together with porosity. The deodorant effect is great because it is captured by.

Incidentally, silica gel, zeolite, cristobalite, talc, sepiolite, etc., which have silicic acid as a main component and have an ammonia adsorbing ability, have a low adsorbing effect because the particle surface cannot hold an acid group, so that the deodorization of ammonia is complete. Not. Further, bentonite is composed of montmorillonite like acid clay, but bentonite is different from acid clay in that its suspension is neutral to weakly alkaline. Bentonite is neutral or weakly alkaline because its SiO ₂ / Al ₂ O ₃ ratio is 6 or less and has more aluminum content than acid clay, so it is easy to adsorb Na ⁺ , Ca ^2+, etc. This is because the acid group cannot be retained. The SiO ₂ / Al ₂ O ₃ ratio of the acid clay is 6 to 10, which is significantly different from bentonite.

The amount of acid clay or the like added is 0.5 to 15 parts by weight per 100 parts by weight of dry powder. Addition amount is 0.5
If it is less than 1 part by weight, the deodorizing effect is not sufficient, and the addition amount is 1
Even if the amount exceeds 5 parts by weight, the deodorizing effect does not change, but rather the weight increases and the cost increases, which is not preferable. The particle size of the above-mentioned acid clay used as a deodorant is not limited, and is appropriately 3 mm or less, preferably 1 mm or less.

(III) Example of Process Steps of this Method FIG. 1 shows an example of process steps of this method. The illustrated treatment process is composed of a sewage sludge supply unit 1, a quick lime supply unit 2, a dry powder production unit 3, an exhaust gas wastewater treatment unit 4, and a transfer system connecting them. In the sewage sludge supply unit 1, the sludge cake that has been dehydrated to a water content of 70 to 80% by a filter press or the like in a sewage treatment plant is sent to the dry powder production unit 3 by a predetermined amount through the supply device 11. On the other hand, the quick lime supply unit 2 is provided with a quick lime measuring unit 14, and a fixed amount of quick lime is sent to the dry powder production unit 3.

The dry powder production section 3 comprises a raw material mixer 12 and an aging mixer 13. The raw material mixer 12 mixes the sludge cake with a certain amount of quick lime sent from the quick lime supply unit 2. After adding 50 to 150 parts by weight of quicklime to 100 parts by weight of solid content of sludge and uniformly mixing, the mixture is transferred to an aging mixer 13 and mixed until the water content is sufficiently reduced. To do. An exhaust gas wastewater treatment unit 4 including a bag filter 15, an exhaust gas cooling device 16, a scrubber 17, a neutralization tank 18, a mist separator 19 and an activated carbon adsorber 20 is attached to the exhaust system of these mixers 12 and 13.

When the ripening proceeds, a deodorant such as acid clay is added to the aging mixture. The amount of acid clay or the like added is 0.5 to 15 parts by weight per 100 parts by weight of dry powder. By adding acidic soil and the like, the residual ammonia amount of the mixture is reduced to 1 ppm or less, which is the threshold value at which a person feels an odor, and the ammonia odor is removed.

The dry powder (treated product) deodorized by the treatment method of the present invention is stored in a storage tank or the like and used as a raw material for cement or steel, or a soil conditioner or fertilizer. Specifically, in the cement manufacturing process, the treated product can be used by being put into a raw material system together with other cement raw materials. The slaked lime and the sludge solid matter inorganic matter of the above-mentioned treated matter serve as cement components, and the organic matter of sludge serves as fuel at the time of firing. Further, the treated product can be used as a part of the sintering raw material in the iron making process.

The soil conditioner may be used alone or in combination with known soil conditioner components such as silica, lime powder and fly ash. As a fertilizer, it is used alone or together with other nutrients. In the sludge treatment product of the present invention deodorized using acid clay or the like, ammonium ions are not completely neutralized and are weakly bound to the anion group constituting the silicic acid unit in the mineral. The effect of denitration by ammonia is different from the case of completely neutralizing the soil, and the fact that it has a large amount of carbon source and that it has a neutralizing effect on acidic soil because it contains lime, It has a significant effect on fertility.

[0020]

EXAMPLES Examples and comparative examples of the present invention will be shown below.
It should be noted that the present embodiment is merely an example and does not limit the scope of the present invention.

Example 1 and Comparative Example (1) Materials Used The materials used in Examples and Comparative Examples are as follows. (A) Sewage sludge: Sewage sludge treated with activated sludge having a water content of 80%. Organic matter content of dried product is 94%. (B) Quick lime: C
Calcined limestone product with aO content of 94% or more. (C) Deodorizing powder: diatomaceous earth, acid clay, activated clay, zeolite, silica powder, sepiolite, bentonite, Kanuma soil, activated carbon. Diatomaceous earth to acid clay are examples, and others are comparative examples. The physical properties of each powder are shown in Table 1.

[0021]

[Table 1]

(2) Dehydration step 1 kg of sludge and 1 kg of quick lime were put into a Hobart mixer, and
Mix at low speed for minutes. With the hydration of quicklime, the temperature inside the machine reached a maximum of 170 ° C, and the water vaporized to vaporize.
1 mixture containing 15% water (slaked lime and dehydrated sludge)
The mixture was aged for 2 hours, and then mixed so that the water and ammonia contents were uniform. As a result, a dry mixture (dry powder) having a water content of 3% to 8% was obtained.

(3) Measurement of Ammonmonia Concentration As a preliminary test, the dry powder having a water content of 8% was used at a flow rate of 20 cm / sec.
Then, the ammonia gas generated was introduced into water to collect it, and its concentration was measured using a gas chromatograph. The ammonia concentration of the dry powder not subjected to the deodorizing treatment of the present invention was 6000 ppm. By the way,
According to the standard of odor intensity according to the Offensive Odor Control Law, it is said that at a concentration of 1 ppm, everyone feels an odor of ammonia.
The concentration of is an extremely intense ammonia odor. Similarly, when other malodorous components were analyzed, hydrogen sulfide was 1 ppm or less,
Trimethylamine was 0.04 ppm or less and normal valeric acid was 0.001 ppm or less. Examples and comparative examples are
The ammonia concentration was measured using a suction type detection tube in accordance with the actual usage. That is, 20 g of dry powder was placed in a 100-ml capacity collection bottle, and the temperature was kept at 40 ° C. for 16 hours, after which the concentration of ammonia vapor retained in the upper space was measured with a detector tube. The results are shown in Tables 2 and 3.

(4) Deodorizing Step Each soil powder was put into the above collection bottle together with 20 g of dry powder, and the concentration of the generated ammonia gas was measured. The measurement results of each sample are shown in Tables 2 and 3 for each powder addition amount (0.5 to 7%). In addition, Table 2 uses dry powder having a water content of 3%, and Table 3 uses dry powder having a water content of 8%.

[0025]

[Table 2]

[0026]

[Table 3]

As shown in these results, in the treatment method of the present invention, the ammonia concentration is 1 ppm or less even if the amount of the acid clay added is 0.5%. On the other hand, in the case where zeolite or activated carbon is mixed instead of acid clay, even if the activated carbon with the highest deodorizing effect is used, in order to reduce the ammonia concentration to 1 ppm or less, the activated carbon is used against dry powder with a water content of 3%. Is required to be 3% or more, and a good deodorizing effect cannot be obtained even if the amount of activated carbon is increased with respect to dry powder having a water content of 8%. Moreover, those using activated carbon or the like have a great influence on the mixing state, and those not mixing well have a high ammonia concentration and a low deodorizing effect.

[0028]

[Example 2] The above dry powder having a water content of 3% with 3% each of diatomaceous earth, acid clay and activated clay was used as a cement raw material, and this was used as another cement raw material (limestone, clay, copper kalami). Addition of a fixed amount to a pulverized raw material) to make a 10% internal ratio and pelletization
It was baked at 50 ° C. The cement clinker obtained was ground to a Blaine value of 3500 m ² / g. This Portland cement was evaluated according to JIS R5201. As shown in the results of Table 4, it was confirmed that the product to which the treated product of the present invention was added can be used as a cement raw material without much difference in setting time and mortar strength as compared with the cement to which the treated product is not added. Was done.

[0029]

[Table 4]

[0030]

[Example 3] 15 to the volcanic ash acidic soil in the central area of Hokkaido
The above dry powder with a moisture content of 3% at a rate of 0 g / m ² (5% of acid clay)
Was sprayed before planting, and the pH of the soil when suspended in 3% water was adjusted to 6.9 even when the pH was 5.2. When strawberries (damage variety) were cultivated in a greenhouse using this soil, it was 20 compared with those cultivated in dry powder non-dispersed soil.
Increased sales were seen around%. Also, the color tone of strawberries was improved. When the same experiment was conducted using melon (Arsfeborg variety), there was an increase of around 15% in comparison with the one cultivated on dry powder unsprayed soil, and the net pattern on the melon surface became clear. It was seen.

[0031]

According to the sewage sludge treatment method of the present invention, dry powder, which is a sludge treatment product, is substantially deodorized at a low cost, and its handleability is remarkably improved. Therefore, this dry powder is easy to use for a wide range of purposes. In addition, since the treated product obtained by the treating method of the present invention mainly contains calcium and silica, it can be treated effectively as a raw material for cement and steel and can be treated in large quantities. Further, this treated product has a remarkable denitrification effect, an acidic soil improving effect, a plant fattening effect, and the like due to the contained organic components, calcium and other inorganic nutrients, and ammonium ions. It is also useful as fertilizer.

[Brief description of drawings]

FIG. 1 is a process diagram of the present invention.

[Explanation of symbols]

 1 ... sewage sludge supply unit 2 ... quick lime supply unit 3 ... dry powder production unit 4 ... exhaust gas wastewater treatment unit

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[Procedure amendment]

[Submission date] February 8, 1995

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021]

[Table 1]

Front Page Continuation (72) Inventor Keiichi Usura 2-14-1, Nishishimbashi, Minato-ku, Tokyo Chichibu Onoda Co., Ltd. Resource Business Division

Claims (4)

[Claims] 1. An acid having a hydrogen ion concentration of 5.0 or less when suspended in 3% water with a SiO ₂ content of 50% by weight or more is added to the sludge / lime mixture after dehydration by mixing quicklime with the sewage sludge. A method for treating sewage sludge, which comprises adding 0.5 to 15% by weight of the present powder to deodorize. 2. The method according to claim 1, wherein the acidic powder is diatomaceous earth or acidic clay. 3. A sludge-lime mixture obtained by mixing quick lime with sewage sludge and dehydrating the sewage sludge with a SiO ₂ content of 50% by weight or more.
% 0.5 to 15% by weight of powdered powder having a hydrogen ion concentration of 5.0 or less when suspended in water is mixed, and the deodorized sewage sludge composition is characterized. 4. The composition according to claim 3, wherein the acidic powder is diatomaceous earth or acidic clay.