JPH08197095A - Treatment of sewage sludge and treated sewage sludge - Google Patents

Abstract

PURPOSE: To remove the malodor of sewage sludge and to stably and effectively utilize the sewage sludge by mixing quick lime with sewage sludge to dehydrate the mixture and adding a powder contg. aluminum sulfate to deodorize the sludge. CONSTITUTION: In the sewage sludge supply part 1, a sludge cake dehydrated to 70-80% water content by a filter press, etc., in a sewage disposal plant is supplied to a raw material mixer 12 by a feeder 11. Meanwhile, in a quick lime supply part 2, quick lime is weighed by a weighing means 14 and supplied to the mixer 12 in a fixed amt. The sludge cake and quick lime are uniformly mixed in the mixer 12, and the mixture is transferred to an ageing mixer 13, aged and mixed until the water content is sufficiently decreased. The waste gas and waste water are treated in the waste gas treating part 4 connected to the exhaust line of the mixers 12 and 13. A deodorizing powder contg. about 5wt.% aluminum sulfate is added when the ageing proceeds sufficiently. The amt. to be added is controlled to 0.1-15wt.% of the sludge-lime mixture. The obtained deodorized material contg. calcium and sulfate is utilized as the raw material for cement and steel.

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 silicate 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 because they are used as industrial raw materials for continuous operation such as cement or steel, and they can stably treat sewage sludge without the efforts to develop the market accompanying new product development. Therefore, it can be said that this is a revolutionary 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) A method of treating sewage sludge, which comprises mixing quicklime with sewage sludge for dehydration, and then adding powder containing aluminum sulfate to the sludge / lime mixture to deodorize. (2) The treatment method according to (1) above, wherein the powder is a powder containing 5% by weight or more of aluminum sulfate, and 0.1 to 15% by weight is added to the sludge / lime mixture. (3) The treatment method according to (1) or (2) above, wherein the powder containing aluminum sulfate is bansulfuric acid soil, alum, or a mixture of two or more thereof. (4) A deodorized sewage sludge treated product obtained by mixing powder containing aluminum sulfate with a sludge-lime mixture obtained by mixing quicklime with sewage sludge. (5) The deodorized sewage sludge treated product according to (4) above, which is used as a cement raw material, an iron making raw material, a soil improving material, a fertilizer or a water treatment material.

[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 generally dehydrated 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 50 to 150 parts by weight, preferably 80 to 13 parts by weight with respect to 100 parts by weight of the sewage sludge.
About 0 parts by weight is used. 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) Desorption with powder containing aluminum sulfate
Odor process A powder containing aluminum sulfate is added to the mixture of sludge and lime dehydrated as described above to deodorize. As the aluminum sulfate, a single salt represented by Al ₂ (SO ₄ ) ₃ , a double salt of aluminum sulfate and another salt, and a hydrate (hydrated salt) thereof can be used. Examples of the double salt include potassium aluminum sulfate [KAl (SO ₄ ) ₂ and potassium alum] and sodium aluminum sulfate [NaAl (SO ₄ ) ₂ ,
Sodium alum] and so-called alum are included. Alum has the general formula: XAl ₃ (SO ₄ ) ₂ (OH) ₆
Although X is K, Na, NH ₄ , (1/2) Pb or the like is effectively used. Furthermore, the Al portion partially substituted with Fe, Cu, Zn may also be used.

When aluminum sulfate is added to and mixed with the dry powder, it reacts with water in the dry powder to hydrolyze. Since the hydrolyzate contains sulfuric acid, it exhibits strong acidity. It is speculated that the deodorizing action of the present invention is basically based on the synergistic action of the adsorption action of aluminum sulfate powder and the neutralization reaction of sulfuric acid and ammonia generated by the hydrolysis of aluminum sulfate. That is, the deodorizing effect of silica gel, zeolite and activated carbon, which have been conventionally used as deodorants, is based solely on their surface adsorption action and adsorbs a large amount of water vapor in addition to the ammonia component of dry powder. Therefore, the adsorption effect is saturated, and the important ammonia gas cannot be adsorbed sufficiently,
Deodorizing effect is reduced. On the other hand, the aluminum sulfate powder of the present invention produces sulfuric acid with an appropriate amount of moisture, so that even when water vapor is adsorbed, this sulfuric acid neutralizes ammonia.
Therefore, unlike silica gel or the like, a high deodorizing effect can be exhibited without lowering the deodorizing effect due to saturation of the adsorption action due to the adsorption of water vapor.

The finer the particle size of aluminum sulfate powder, the greater the deodorizing effect, but excessive pulverization is not preferable because it leads to an increase in cost and tends to cause moisture absorption. Specifically, 3 mm or less is suitable, and 0.05 to 1 mm or less is more preferable. By the way, even conventional deodorants such as silica gel are used in the form of fine powder so that the specific surface area is increased in order to enhance the adsorption effect. Since it is saturated, even if it is pulverized, the deodorizing effect is not so improved. On the other hand, the aluminum sulphate powder of the present invention deodorizes due to the synergistic action of the adsorption action and the neutralization action with sulfuric acid, so the finer the particle size, the greater the deodorizing effect due to the adsorption ability, but as shown in Examples and Comparative Examples described later. In addition, it does not need to be pulverized more than necessary.

Aluminum sulphate is usually obtained as a hydrate having water of crystallization, and since this water of crystallization is bound in the crystals, there is no particular adverse effect, but excessive adhesion of the surface of the particles (crystals). Moisture causes acid before contacting with dry powder, invades containers and pipelines, causes aggregation of aluminum sulfate powder and causes clogging of pipelines and feeders, etc., causing fluidity deterioration. When it is saturated with, the adsorption effect decreases. Therefore, it is preferable to use the aluminum sulfate powder in a dry state. Specifically, the water content is preferably 50% or less.

Aluminum sulphate may be used alone or in combination with other powder having an odor eliminating effect. As the powder used in combination, for example, silica gel, cristobalite, siliceous powder such as diatomaceous earth,
Examples thereof include various clays, activated clay, acid clay, zeolite, talc, silicate mineral powder such as sepiolite, calcium carbonate and the like. Among these, diatomaceous earth, acid clay and activated clay which is a processed product thereof are preferable. Since they retain an acid group on the particle surface, ammonia molecules can be effectively captured, and an excellent deodorizing effect can be obtained in combination with the deodorizing effect of the aluminum sulfate powder. Further, since the chemical component is the SiO ₂ —Al ₂ O ₃ system, it is convenient when the deodorized sewage treatment product is used as a raw material for cement, a raw material for iron making, or a soil conditioner.

The content of aluminum sulfate in the above-mentioned mixed powder is preferably 10% by weight or more, and the amount of the mixed powder used is 0.1 to 100 parts by weight of dry powder.
70 parts by weight, preferably 1 to 10 parts by weight are suitable.
When the content of aluminum sulfate is less than 10% by weight, the amount of the mixed powder used for obtaining a sufficient deodorizing effect increases, and the treatment cost increases. Further, when the amount of the mixed powder used is less than 0.1% by weight, the deodorizing effect is poor and the mixing is difficult,
Even if the amount used exceeds 70% by weight, the deodorizing effect does not change, but rather the weight increases and the cost increases, which is not preferable.

(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, sludge cake 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 a 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 aging has proceeded, the deodorizing powder containing aluminum sulfate is added to the aging mixture. The amount of deodorant powder added is 0.1 to 70 per 100 parts by weight of dry powder.
Parts by weight. By adding deodorant powder, the residual ammonia content of the mixture is 1ppm, which is the threshold value for people to feel odor.
It is reduced to below 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 as a soil conditioner or fertilizer and a water treatment material. 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. In addition, the treated product can be used as a part of the sintering raw material in the iron making process. The soil improving agent may be used alone or in combination with known soil improving components such as silica, lime powder and fly ash. As a fertilizer, it is used alone or together with other nutrients. As the water treatment material, it is used as it is or after adjusting the components.

[0019]

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: In the examples, commercially available van sulphate, sodium alum, potassium alum and iron sulfate were used, and diatomaceous earth, activated clay and calcium carbonate were used as the combined components. In the comparative example, zeolite, silica powder, sepiolite,
A powder consisting only of bentonite, Kanuma soil and activated carbon was used. The physical properties of each powder are as shown in Table 1 (Examples) and Table 2 (Comparative Examples).

[0020]

[Table 1]

[0021]

[Table 2]

(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 3 and 4.

(4) Deodorizing Step Each sample powder listed in Tables 1 and 2 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 result of each sample is the addition amount of powder (0.1-5%)
The results are shown in Table 3 and Table 4. In addition, Table 3 shows water content 3
% Dry powder was used, and Table 4 shows a dry powder having a water content of 8%.

[0025]

[Table 3]

[0026]

[Table 4]

As shown in these results, according to the treatment method of the present invention, the ammonia concentration can be reduced to about 1 to several ppm or less even if the addition amount of the deodorizing powder is 0.1%. On the other hand, a mixture of zeolite, activated carbon, etc. in place of the deodorizing powder of the present invention is a dry powder having a water content of 3% in order to reduce the ammonia concentration to 1 ppm or less even when the activated carbon having the highest deodorizing effect is used. On the other hand, 3% or more of activated carbon is required, and a good deodorizing effect cannot be obtained for dry powder having a water content of 8% even if the amount of activated carbon is increased. 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] A cement raw material was prepared by adding 3% of each of the above-mentioned dry powder having a water content of 3% with bansulfuric acid soil, potassium alum, bansulphate soil + activated clay mixture (1: 1).
This was added to another cement raw material (prepared raw material obtained by adding a predetermined amount of limestone, clay, and copper kalami) so as to be 10% internally divided, and pelletized and fired at 1450 ° C. The cement clinker obtained had a Blaine value of 3500.
Crushed to m ² / g. This Portland cement was evaluated according to JIS R 5201. As shown in the results of Table 5, it was confirmed that the one to which the treated product of the present invention was added had no significant difference in the setting time and the mortar strength as compared with the cement to which the treated product was not added, and that the above treated product could be used as a cement raw material. It was

[0029]

[Table 5]

[0030]

Example 3 Similar to Example 2, van sulphate soil and potassium alum were added to and mixed with dry powder having a water content of 3%, and blast furnace raw materials (iron ore, limestone and coke were added in predetermined amounts and pulverized to a predetermined particle size). Stuff) to add 5% to the inner part,
The pelletized product was sintered in a rotary kiln at 1380 ° C. The compressive strengths of the sintered bodies of both the sulphate containing sulphate and the alum were within ± 5% as compared with those without the addition. In addition, no significant difference was observed in specific gravity, fluidity and other characteristics with and without the addition of dry powder.

[0031]

[Embodiment 4] As in the case of Embodiment 2, van sulphate soil and potassium alum are added to and mixed with a dry powder having a water content of 3% to adjust the pH.
It was added to a sulfuric acid waste solution of 1.5 and neutralized to have a pH of 6.9 to 7.4. The resulting precipitate was recovered and found to have a purity of 9
2% gypsum was obtained. As a result of examining calcination characteristics and the like, it was a level that could be effectively used.

[0032]

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. Further, since the treated product obtained by the treating method of the present invention mainly contains calcium and sulfate, it can be treated effectively and in large quantities as a raw material for cement and steel. Furthermore, this treated product has a remarkable denitrification effect, soil improvement effect and plant fattening effect due to the organic components, calcium and other inorganic nutrients and ammonium sulfate contained, and since it is odorless, it is a ground improvement material / fertilizer / It is also useful as a water treatment material.

[Brief description of drawings]

FIG. 1 is a process chart 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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Usura 2-14-1, Nishishimbashi, Minato-ku, Tokyo Chichibu Onoda Co., Ltd. Resource Business Division

Claims (5)

[Claims] 1. A method for treating sewage sludge, which comprises mixing quicklime with sewage sludge for dehydration, and then adding powder containing aluminum sulfate to the sludge / lime mixture to deodorize. 2. The powder is a powder containing 5% by weight or more of aluminum sulfate, and is 0.1 to 1 with respect to the sludge / lime mixture.
The processing method according to claim 1, wherein 5% by weight is added. 3. The treatment method according to claim 1, wherein the powder containing aluminum sulfate is bansulfuric acid soil, alum, or a mixture of two or more thereof. 4. A deodorized sewage sludge treatment product obtained by mixing a sludge / lime mixture obtained by mixing sewage sludge with quicklime and dehydrating it, and mixing a powder containing aluminum sulfate. 5. The deodorized sewage sludge treated product according to claim 4, which is used as a cement raw material, an iron making raw material, a soil improving material, a fertilizer or a water treatment material.