JPH0724499A - Treatment of sludge - Google Patents

Abstract

PURPOSE:To efficiently reduce the volume of the org. sludge, such as excess sludge or anaerobically digested sludge, etc., generated by an activated sludge method by subjecting the org. sludge to oxidation decomposition by an oxidizing agent with metal ions as a catalyst in a narrow space and at a short period of time. CONSTITUTION:The excess sludge is introduced into an oxidizing vessel where the excess sludge is subjected to the oxidation decomposition by adjusting the sludge to required pH (about 2 to 8) and adding the oxidizing agent and catalyst thereto at the time of subjecting the excess sludge or anaerobically digested sludge, etc. (hereafter, excess sludge) generated by an activated sludge treatment to a volume reduction treatment. More preferably, the sludge prior to the oxidation treatment is sufficiently previously deflocculated by an ultrasonic treatment so that the oxidation decomposition reaction of the sludge is sufficiently executed. The sludge after the oxidation decomposition is introduced through a neutralizing vessel into a settling basin where the liquid component is desorbed from the sludge component. This liquid is discharged. The metal ions which are preferably iron ions are used as the catalyst and hydrogen peroxide is used as the oxidizing agent, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating organic sludge, and more specifically, an excess portion of sludge generated by treating wastewater with an activated sludge system or anaerobic nitrification caused by anaerobic nitrification of excess sludge. The present invention relates to a method for treating organic sludge such as sludge to reduce the amount of the sludge.

[0002]

2. Description of the Related Art Conventionally, in the removal of organic pollutants in wastewater indicated by BOD, a biological treatment method such as an activated sludge system which has been put into practical use has been satisfactory at a relatively low cost. Has been obtained. In the activated sludge system, as shown in FIG. 1, the wastewater to be treated is first introduced into a settling tank to precipitate the one having a large specific gravity, and then the organic matter in the wastewater is decomposed by the activated sludge in the aeration tank. In this activated sludge treatment, 50 to 7 out of the decomposed BOD
Since 0% by weight is consumed for living energy of microorganisms and the remaining 30 to 70% by weight is used for the growth of bacterial cells, excess sludge is generated.

Excess sludge generated by the activated sludge treatment is biodegradable and has a high viscosity, so that the treatment of the excess sludge generated in the activated sludge treatment system is a serious problem. At present, as shown in FIG. 2, the method for treating excess sludge is to remove excess sludge from methane gas, carbon dioxide, hydrogen, by anaerobic nitrification.
Excess sludge and other solids that are not decomposed after being decomposed into hydrogen sulfide and the like to reduce the amount are separated by a dehydrator or the like and incinerated or disposed as industrial waste.
In some cases, excess sludge is directly separated by a dehydrator or the like without performing anaerobic treatment, and similarly incinerated or disposed of as industrial waste.

[0004]

[Problems to be Solved by the Invention] The conventional reduction of excess sludge by anaerobic nitrification has the advantage that energy is recovered as methane gas, but the number of days required for nitrification is as long as 20 to 40 days. In addition, the decomposition rate of excess sludge is as low as about 60%, so a large site area is required, and undecomposed excess sludge and other solid matter are separated by a dehydrator, etc. and incinerated or disposed of as industrial waste. However, there is a problem that it is inefficient and the processing cost is high. Further, when the excess sludge is directly concentrated by a dehydrator or the like without performing anaerobic nitrification and incinerated or disposed of as industrial waste, the excess sludge is not reduced,
Further, there is a problem that the processing cost becomes high. The current sludge disposal cost is as high as 20,000 yen / m ^3, and this disposal cost tends to rise further in the future. Therefore, an object of the present invention is to provide a method capable of efficiently reducing the amount of excess sludge generated by an activated sludge system or organic sludge such as anaerobic nitrifying sludge.

[0005]

The above object can be achieved by the present invention described below. That is, the present invention is a treatment of an organic sludge characterized by oxidatively decomposing an excess sludge generated in an activated sludge system or an organic sludge such as an anaerobic nitrifying sludge with an oxidizing agent using a metal ion as a catalyst. Is the way.

[0006]

[Function] The excess amount of sludge generated by treating wastewater by the activated sludge system or anaerobic nitrifying sludge is efficiently decomposed in a narrow space in a short time by oxidizing and decomposing it with an oxidizing agent using metal ions as a catalyst. You can do it.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. One preferred embodiment of the present invention is to transfer excess sludge or anaerobic nitrification sludge generated by a conventionally known wastewater treatment system as shown in FIG. 1 or FIG. 2 to an oxidation tank as shown in FIG. The required pH is adjusted and an oxidizing agent and a catalyst are added to oxidize and decompose excess sludge or anaerobic nitrifying sludge. In the method of the present invention, the oxidative decomposition reaction of sludge can be remarkably made efficient by subjecting the sludge before oxidization treatment to ultrasonic treatment to sufficiently deflocculate it.

The oxidant used in the present invention is an oxidant used in a conventionally known chemical oxidation method, for example, hydrogen peroxide, calcium peroxide, ammonium persulfate, alkyl hydroperoxide, perester, dialkyl peroxide. Alternatively, diacyl or the like is used, but hydrogen peroxide is most preferable in terms of cost and by-products. Hereinafter, hydrogen peroxide will be described as a typical example. The amount of hydrogen peroxide used is not particularly limited and varies depending on the content of the excess sludge or the anaerobic nitrifying sludge, but the preferred amount is about 10 parts by weight per 100 parts by weight (solid content) of the excess sludge or the anaerobic nitrifying sludge. ˜500 parts by weight (as oxygen).

The metal ions used in the present invention include iron, titanium, cerium, copper, manganese, cobalt,
Ions of vanadium, chromium, lead, and the like are used, and any of these metals, metal oxides, metal salts, complexes, and the like may be used. Since iron ions are particularly preferable in the present invention, iron ions will be described below as a representative example. As the iron ion to be used, ferrous iron was used in the prior art, but ferrous ion as well as ferric ion is effective in the present invention, and further, metallic iron such as iron scrap or iron It is also possible to use fixed iron ions in which ions are fixed with an ion exchange resin or the like. The amount of iron ion used as the catalyst is about 10 ^{−3 to} 0.1 mol per mol of hydrogen peroxide, and sufficient treatment effect can be obtained.

In the method of the present invention, it is preferable to oxidize excess sludge or anaerobic nitrifying sludge by adjusting the pH of the reaction solution to about 2-8. The oxidation reaction may be carried out at room temperature, but the preferred range is 40 ° C to 100 ° C, more preferably 50 ° C to 8 ° C.
It is in the range of 0 ° C. The excess sludge or the anaerobic nitrifying sludge can be heated by using any heating means such as blowing in steam or heat exchange with other hot water in the factory, and the heating method is not particularly limited.

When the treatment temperature is lower than 40 ° C., it takes time to oxidize, the oxidation efficiency is insufficient, and the utilization efficiency of hydrogen peroxide is insufficient. Further, if the temperature exceeds 100 ° C., no further treatment effect can be expected, and the self-decomposition of hydrogen peroxide is large, so that the utilization efficiency is lowered and the consumption of heating energy is large. There is no advantage. The oxidation reaction time varies depending on the size of the oxidation tank, the performance of the stirrer, the temperature, etc. For example, the amount of excess sludge or anaerobic nitrification sludge (solid content: about 1% by weight) is 10 m ³ , and the oxidation temperature is 50 ° C. Approximately 1 if sufficient agitation is provided
Reaction temperatures of up to 3 hours are sufficient and can decompose about 70-80% by weight of excess sludge or anaerobic nitrifying sludge.

[0012]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. Example 1 300 ml of activated sludge (sludge concentration: 11,000 mg / liter) in a wastewater treatment facility that treats the wastewater of a food factory
Take 100 ml in a beaker and adjust to pH 3, ferrous ion 250 mg / liter and hydrogen peroxide 10,000
Iron content and hydrogen peroxide solution were added so that the amount became 0 mg / liter. After that, the mixture was reacted with shaking at 70 ° C for 1 hour, and the soluble TOC (Total organic carbon) and the residue (insoluble TOC) after the reaction were measured. The soluble TOC before the treatment was about 200 mg / liter, and the insoluble TOC
Was about 6,000 mg / liter, the soluble TOC after treatment was about 4000 mg / liter, and the amount of insoluble TOC was about 1,800 mg / liter.

From the above results, it is clear that 70% of the total TOC in the activated sludge is mineralized or solubilized by oxidation. Since this solubilized TOC can be returned to the aeration tank and easily biodegraded by the activated sludge, the desorbed liquid (supernatant liquid) from the oxidation tank and the filtered water from the dehydrator etc. are returned to the aeration tank. Therefore, biodegradation can be easily performed. The insoluble TOC is about 30% of the TOC before the treatment, and it is dehydrated by a dehydrator or the like and discarded. The BOD and TOC of the activated sludge before treatment and the activated sludge after treatment obtained in the above experiment were measured, and the results are shown in Table 1 below.
It was the street.

[0014]

[Table 1] From Table 1 above, BOD / TOC before treatment is 0.3.
The BOD / TOC after treatment is 1.3, and the BOD generated by the method of the present invention can be returned to the aeration tank and biodegraded, so that the amount of activated sludge finally disposed is significantly reduced. Has been done.

Example 2 The same activated sludge as used in Example 1 was subjected to high temperature nitrification for 30 days in STR, and anaerobic nitrification sludge (sludge concentration: 18,0).
00mg / l) 100m in a 300ml beaker
After adjusting the pH to 3, the iron content and hydrogen peroxide solution were added so that the ferrous ion was 250 mg / liter and the hydrogen peroxide was 20,000 mg / liter. afterwards,
After reacting at 50 ° C for 1 hour with shaking, the soluble TOC and insoluble TOC after the reaction were measured. The soluble TOC before the treatment was about 2,000 mg / liter, and the amount of insoluble TOC was about 8 It was 1,000 mg / liter,
The soluble TOC after the treatment was about 3,000 mg / liter, and the amount of insoluble TOC was about 4,000 mg / liter.

Example 3 The same activated sludge used in Example 1 was subjected to high temperature nitrification at STR 30 days for anaerobic nitrification sludge (sludge concentration 18,0).
00mg / l) 100m in a 300ml beaker
l, deflocculate with an ultrasonic generator (output 200W) for 10 minutes, adjust to pH 3, ferrous ion 250 mg /
Iron and hydrogen peroxide solution were added so that liter and hydrogen peroxide were 20,000 mg / liter, respectively. After that, the mixture was reacted with shaking at 50 ° C. for 1 hour, and the soluble TOC and insoluble TOC after the reaction were measured. The soluble TOC before the treatment was about 2,000 mg / liter, and the amount of insoluble TOC was Although it was about 8,000 mg / liter, the soluble TOC after the treatment was about 3,000 mg / liter, and the amount of insoluble TOC was about 2,000 mg / liter. From the above results, it was revealed that in the anaerobic nitrifying sludge, 50% by weight of insoluble TOC is mineralized or solubilized by oxidation. Further, it was revealed that 75% by weight of insoluble TOC was mineralized or solubilized by oxidation by ultrasonic treatment of anaerobic nitrification sludge as a pretreatment.

[0017]

[Effects] According to the present invention as described above, it is possible to highly efficiently reduce the amount of organic sludge such as excess sludge or anaerobic nitrification sludge by a reaction of several hours, and to perform nitrification for a long time in the conventional technique. In addition, the problems of requiring a large space and having a low weight reduction efficiency have been sufficiently solved.

[0018]

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a standard treatment process of the activated sludge method.

FIG. 2 is a diagram schematically illustrating an anaerobic nitrification treatment process.

FIG. 3 is a diagram schematically illustrating the method of the present invention.

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[Procedure amendment]

[Submission date] December 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

[Title of Invention] Method for treating organic sludge

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to method of treating organic sludge, more particularly anaerobic occurs in anaerobic digestion of the excess portion or excess sludge sludge produced by treating the waste water with activated sludge method digestion The present invention relates to a method for treating organic sludge such as sludge to reduce the amount of the sludge.

[0002]

2. Description of the Related Art Conventionally, in the removal of organic pollutants in wastewater indicated by BOD, a biological treatment method such as an activated sludge system which has been put into practical use has been satisfactory at a relatively low cost. Has been obtained. In the activated sludge system, as shown in FIG. 1, the wastewater to be treated is first introduced into a settling tank to precipitate the one having a large specific gravity, and then the organic matter in the wastewater is decomposed by the activated sludge in the aeration tank. In this activated sludge treatment, 50 to 7 out of the decomposed BOD
Since 0% by weight is consumed for living energy of microorganisms and the remaining 30 to 70% by weight is used for the growth of bacterial cells, excess sludge is generated.

Excess sludge generated by the activated sludge treatment is biodegradable and has a high viscosity, so that the treatment of the excess sludge generated in the activated sludge treatment system is a serious problem. Currently, the treatment methods of the excess sludge is, as shown in FIG. 2, anaerobic consumption
By the excess sludge methane gas, carbon dioxide, hydrogen,
Excess sludge and other solids that are not decomposed after being decomposed into hydrogen sulfide and the like to reduce the amount are separated by a dehydrator or the like and incinerated or disposed as industrial waste.
In some cases, excess sludge is directly separated by a dehydrator or the like without performing anaerobic treatment, and similarly incinerated or disposed of as industrial waste.

[0004]

Problems to be Solved by the Invention In the conventional reduction of excess sludge by anaerobic digestion, there is an advantage that energy is recovered as methane gas, but it is required for digestion. The number of days is as long as 20 to 40 days, and the decomposition rate of excess sludge is as low as about 60%, so a large site area is required, and undecomposed excess sludge and other solid matter are separated by a dehydrator and incinerated. Alternatively, it must be disposed of as industrial waste, which is inefficient and requires a large treatment cost. Also, when the excess sludge is directly concentrated by a dehydrator or the like without performing anaerobic digestion and incinerated or disposed of as industrial waste, the excess sludge is not reduced,
Further, there is a problem that the processing cost becomes high. The current sludge disposal cost is as high as 20,000 yen / m ^3, and this disposal cost tends to rise further in the future. Therefore, an object of the present invention is to provide a method capable of efficiently reducing the amount of organic sludge such as surplus sludge or anaerobic digestion sludge generated by an activated sludge system.

[0005]

The above object can be achieved by the present invention described below. That is, the present invention is a treatment of an organic sludge characterized by oxidatively decomposing an excess sludge generated in an activated sludge system or an organic sludge such as an anaerobic digestion sludge with an oxidizing agent using a metal ion as a catalyst. Is the way.

[0006]

[Function] Efficient reduction in a narrow space in a short time by oxidizing and decomposing excess part of sludge or anaerobic digestion sludge generated by treating wastewater by activated sludge system with an oxidizing agent using a metal ion as a catalyst. You can do it.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. In a preferred embodiment of the present invention, excess sludge or anaerobic digested sludge generated by a conventionally known wastewater treatment system as shown in FIG. 1 or 2 is transferred to an oxidation tank as shown in FIG. The required pH is adjusted and an oxidizing agent and a catalyst are added to oxidize and decompose excess sludge or anaerobic digestion sludge. In the method of the present invention, the oxidative decomposition reaction of sludge can be remarkably made efficient by subjecting the sludge before oxidization treatment to ultrasonic treatment to sufficiently deflocculate it.

The oxidant used in the present invention is an oxidant used in a conventionally known chemical oxidation method, for example, hydrogen peroxide, calcium peroxide, ammonium persulfate, alkyl hydroperoxide, perester, dialkyl peroxide. Alternatively, diacyl or the like is used, but hydrogen peroxide is most preferable in terms of cost and by-products. Hereinafter, hydrogen peroxide will be described as a typical example. The amount of hydrogen peroxide used is not particularly limited and varies depending on the content of the excess sludge or the anaerobic digested sludge, but the preferred amount of hydrogen peroxide is about 10 parts by weight per 100 parts by weight (solid content) of the excess sludge or the anaerobic digested sludge. ˜500 parts by weight (as oxygen).

The metal ions used in the present invention include iron, titanium, cerium, copper, manganese, cobalt,
Ions of vanadium, chromium, lead, and the like are used, and any of these metals, metal oxides, metal salts, complexes, and the like may be used. Since iron ions are particularly preferable in the present invention, iron ions will be described below as a representative example. As the iron ion to be used, ferrous iron was used in the prior art, but ferrous ion as well as ferric ion is effective in the present invention, and further, metallic iron such as iron scrap or iron It is also possible to use fixed iron ions in which ions are fixed with an ion exchange resin or the like. The amount of iron ion used as the catalyst is about 10 ^{−3 to} 0.1 mol per mol of hydrogen peroxide, and sufficient treatment effect can be obtained.

In the method of the present invention, it is preferable to oxidize excess sludge or anaerobic digestion sludge by adjusting the pH of the reaction solution to about 2-8. The oxidation reaction may be carried out at room temperature, but the preferred range is 40 ° C to 100 ° C, more preferably 50 ° C to 8 ° C.
It is in the range of 0 ° C. For heating the excess sludge or the anaerobic digested sludge, any heating means such as blowing of steam or heat exchange with other hot water in the factory can be used, and the heating method is not particularly limited.

When the treatment temperature is lower than 40 ° C., it takes time to oxidize, the oxidation efficiency is insufficient, and the utilization efficiency of hydrogen peroxide is insufficient. Further, if the temperature exceeds 100 ° C., no further treatment effect can be expected, and the self-decomposition of hydrogen peroxide is large, so that the utilization efficiency is lowered and the consumption of heating energy is large. There is no advantage. Although the oxidation reaction time varies depending on the size of the oxidation tank, the performance of the stirrer, the temperature, etc., for example, the amount of excess sludge or anaerobic digestion sludge (solid content: about 1% by weight) is 10 m ³ , and the oxidation temperature is 50 ° C. Approximately 1 if sufficient agitation is provided
~ 3 hours reaction temperature is sufficient, excess sludge or anaerobic
About 70 to 80% by weight of digested sludge can be decomposed.

[0012]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. Example 1 300 ml of activated sludge (sludge concentration: 11,000 mg / liter) in a wastewater treatment facility that treats the wastewater of a food factory
Take 100 ml in a beaker and adjust to pH 3, ferrous ion 250 mg / liter and hydrogen peroxide 10,000
Iron content and hydrogen peroxide solution were added so that the amount became 0 mg / liter. After that, the mixture was reacted with shaking at 70 ° C. for 1 hour, and the soluble TOC (Total organo
ic carbon) and the residue (insoluble TOC) were measured, the soluble TOC before treatment was about 200 mg / liter and the amount of insoluble TOC was about 6,000 mg / liter, but the solubility after treatment was TOC is about 4000m
The amount of insoluble TOC is about 1,800 m in g / liter
It was g / liter.

From the above results, it is clear that 70% of the total TOC in the activated sludge is mineralized or solubilized by oxidation. Since this solubilized TOC can be returned to the aeration tank and easily biodegraded by the activated sludge, the desorbed liquid (supernatant liquid) from the oxidation tank and the filtered water from the dehydrator etc. are returned to the aeration tank. Therefore, biodegradation can be easily performed. The insoluble TOC is about 30% of the TOC before the treatment, and it is dehydrated by a dehydrator or the like and discarded. The BOD and TOC of the activated sludge before treatment and the activated sludge after treatment obtained in the above experiment were measured, and the results are shown in Table 1 below.
It was the street.

[0014]

[Table 1] From Table 1 above, BOD / TOC before treatment is 0.3.
The BOD / TOC after treatment is 1.3, and the BOD generated by the method of the present invention can be returned to the aeration tank and biodegraded, so that the amount of activated sludge finally disposed is significantly reduced. Has been done.

[0015] Example 2 The same activated sludge as used in Example 1 is carried out STR30_nichidekoon digestion anaerobic digestion sludge (sludge concentration 18,0
00mg / l) 100 in a 300ml beaker
After taking up ml and adjusting to pH 3, ferrous ion 250 mg /
Iron and hydrogen peroxide solution were added so that liter and hydrogen peroxide were 20,000 mg / liter, respectively. After that, the mixture was reacted with shaking at 50 ° C. for 1 hour, and the soluble TOC and insoluble TOC after the reaction were measured. The soluble TOC before the treatment was about 2,000 mg / liter, and the amount of insoluble TOC was Although it was about 8,000 mg / liter, the soluble TOC after the treatment was about 3,000 mg / liter and the amount of insoluble TOC was about 4,000 mg / liter.

[0016] Example 3 The same activated sludge as used in Example 1 is carried out STR30_nichidekoon digestion anaerobic digestion sludge (sludge concentration 18,0
00mg / l) 100 in a 300ml beaker
Take ml and deflocculate for 10 minutes with an ultrasonic generator (output 200W), adjust to pH 3 and ferrous ion 250mg
/ Liter and hydrogen peroxide of 20,000 mg / liter were added with iron and hydrogen peroxide water, respectively. After that, the mixture was reacted with shaking at 50 ° C. for 1 hour, and the soluble TOC and insoluble TOC after the reaction were measured. The soluble TOC before the treatment was about 2,000 mg / liter, and the amount of insoluble TOC was Although it was about 8,000 mg / liter, the soluble TOC after the treatment was about 3,000 mg / liter, and the amount of insoluble TOC was about 2,000 mg / liter. From the above results, it was revealed that in the anaerobic digested sludge, 50% by weight of insoluble TOC is mineralized or solubilized by oxidation. Also, as pretreatment, anaerobic elimination
It was clarified that 75% by weight of insoluble TOC was mineralized or solubilized by oxidation by subjecting the activated sludge to ultrasonic treatment.

[0017]

[Effect] According to the present invention as described above, it is possible to reduce the amount of organic sludge such as excess sludge or anaerobic digestion sludge with a high efficiency in a reaction of several hours, and to digest for a long time in the conventional technique. In addition, the problems of requiring a large space and having a low weight reduction efficiency have been sufficiently solved.

[0018]

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a standard treatment process of the activated sludge method.

FIG. 2 is a diagram schematically illustrating an anaerobic digestion treatment process.

FIG. 3 is a diagram schematically illustrating the method of the present invention.

[Procedure 3]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiro Yamamoto 1-5-7 Kajimachi, Chiyoda-ku, Tokyo Inside Environmental Engineering Co., Ltd.

Claims (4)

[Claims] 1. A method for treating organic sludge, which comprises oxidatively decomposing an excess portion of sludge generated by an activated sludge system or an organic sludge such as anaerobic nitrifying sludge with an oxidizing agent using a metal ion as a catalyst. . 2. The method for treating organic sludge according to claim 1, wherein the metal ions are iron ions and the oxidizing agent is hydrogen peroxide. 3. The method for treating organic sludge according to claim 1 or 2, wherein the oxidation treatment is carried out under heating by adjusting the pH of the reaction solution within a range of 2 to 8. 4. The method for treating organic sludge according to claim 1, wherein the organic sludge is subjected to ultrasonic treatment before the oxidation treatment.