JPS6325839B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for further processing organic sludge that has been subjected to wet oxidation treatment or heat treatment, and specifically relates to a method for further treating organic sludge such as sewage sludge, digested sludge, human waste, etc., which is discharged after wet oxidation treatment or heat treatment. The present invention relates to a method for treating an organic treated material, which is a treated product discharged by wet oxidation treatment of a high concentration waste liquid such as effluent sludge or effluent, or industrial wastewater. Currently, wet oxidation treatment methods and heat treatment methods are employed as methods for treating organic sludge and the like. The wet oxidation method is a liquid phase oxidation method called the Zimmerman method, in which organic matter in water is oxidized and decomposed using oxygen from an oxygen-containing gas such as air under a pressure that maintains water in a liquid phase at a specific temperature. It is. On the other hand, heat treatment methods are typified by the Portias process, which thermally denatures organic matter such as sludge by heating it at a specific temperature, changing the colloidal components in the sludge into a complete solid form. This method improves concentration and dehydration properties by destroying cells and separating bound water. However, in this wet oxidation method, the degree of wet oxidation is usually less than about 70%, and the chromaticity components are not destroyed and an unpleasant color remains in the treated effluent. Since substances elute and migrate into the liquid, treatment of these liquids has been a problem. In the currently operating wet oxidation treatment equipment and heat treatment equipment, the discharged liquid is treated with biological treatment facilities such as activated sludge method, but the oxidation liquid and heat treatment liquid are highly
It contained BOD and COD, resulting in a considerable overload, and it was impossible to remove the pigment components. By the way, conventional treatment methods that solve some of the above problems and effectively utilize the thermal energy of the processing liquid subjected to wet oxidation treatment or heat treatment are disclosed in Japanese Patent Publication Nos. 1511-1982, 123246-1980, and 1989-123246. This was proposed in Japanese Patent Application No. 124555/1982, and the present applicant had previously filed a patent application in Japanese Patent Application No. 98824/1983. FIG. 1 shows the outline steps of these treatment methods. In these treatment methods, organic sludge discharged from the sewage treatment process 1 is first concentrated in a thickening tank 2, and then introduced into an anaerobic digestion tank 3 for digestion treatment. Next, the digested sludge is introduced into a concentration step 4 such as a settling tank and separated, the separated liquid is returned to the sewage treatment step 1, and the settled sludge is sent to a wet oxidation treatment device or a heat treatment device 5. The treated material treated in the wet oxidation treatment device or the heat treatment device 5 is separated into solid and liquid into a desorbed liquid L and a solid content S, and a part or the entire amount of the desorbed liquid L is returned to the anaerobic digestion tank 3. It is something that will be done. However, due to the wet oxidation treatment or heat treatment, substances undesirable to the anaerobic digester organisms are generated in the treated product, that is, the desorbed liquid L, and the anaerobic digester 3
There was a problem that the operating conditions of the vehicle were restricted. In the treatment method of Japanese Patent Publication No. 46-1511, increasing the treatment temperature in the wet oxidation treatment increases ammonia nitrogen, but on the other hand, the ammonia nitrogen content in the contents of the anaerobic digestion tank 3 is reduced to 1.0. If the CODcr consumption rate (degree of oxidation) in the wet oxidation treatment is further increased, the oxidized desorbed liquid L will be poor in nutrients for the digester organisms; If L is returned to the anaerobic digestion tank 3, undesirable dilution will occur in the tank 3. Therefore, in the above treatment method, the wet oxidation treatment temperature is set at 150 to 175°C to keep the degree of oxidation to 55% or less, thereby producing L. A part of the oxidized desorption liquid L is returned to the anaerobic digestion tank 3 to solve the above problem. On the other hand, in Japanese Patent Application No. 1988-98824, which solves the above problems, increases the degree of oxidation in wet oxidation treatment, and allows the entire amount of oxidized desorbed liquid to be returned to the anaerobic digestion tank, the oxidized desorbed liquid Adjust the production amount by adjusting the digested sludge concentration in the concentration step 4,
The volume mixing ratio of the oxidized desorbed liquid and organic sludge introduced into the anaerobic digestion tank 3 is set to 0.4:1 to 0.8:1, and at the same time, the
It was necessary to adjust the CODcr load to 2 to 5.7 Kg/m ³ ·day, and there were complaints that the desorbed liquid from other wet oxidation treatment equipment produced in processes other than the above treatment process could not be treated. Furthermore, in the heat treatment method, there is a similar problem that when heat-treated sewage is added to digested sludge, the amount of gas generated initially increases, but as the number of days of digestion increases, the amount of gas generated decreases.
Also introduced in Poll.Contr.Fed., 50 , 73 (1978). The present invention has been made in view of the above circumstances, and is an efficient wet oxidation treatment that solves the above-mentioned problems and at the same time further increases the amount of digestion gas generated from the anaerobic digestion process. Another object of the present invention is to provide a method for treating a heat-treated organic material. In order to achieve the above objective, as a result of intensive research, we found that the substance that is produced in the wet oxidation method and is unfavorable to the anaerobic digester organisms is not ammonia nitrogen;
Up to about 3.2 g/kg is tolerable, and the details of this harmful substance to organisms in the anaerobic digester are unknown, but the treated material discharged from the wet oxidation process is coagulated with ferric salt. Furthermore, even in heat treatment that causes thermal denaturation of organic matter, which has a different reaction form from wet oxidation reactions, the treated materials discharged from the heat treatment process can be removed by a second process.
It was discovered that the above-mentioned harmful substances could be similarly removed by coagulation treatment with iron salts, leading to the present invention. Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 is a process diagram showing one embodiment of the present invention,
This is an example in which the treatment method of the present invention is applied to a treatment liquid discharged from a wet oxidation treatment step. Furthermore, this treatment process consists of a wet oxidation treatment system A and an anaerobic digestion treatment system B, and is convenient for expanding existing treatment equipment in which either system is already installed. Reference numeral 10 in the figure indicates a sludge concentration step. This sludge concentration step 10 consists of concentration means such as pressurized flotation, centrifugation, gravity separation, and belt filters in some cases, and the introduced organic sludge such as sewage sludge and digested sludge is adjusted to an appropriate concentration. This adjustment is made so that this organic sludge can self-combust in the next wet oxidation treatment step 11. Usually, organic sludge is separated into sludge with a suspended solids concentration of about 3 to 4% and a separated liquid, although this varies depending on the type of organic sludge. This decomposed liquid has a lower concentration of organic substances than the wet oxidized product, and can be treated by ordinary activated sludge treatment or the like. In addition, for highly concentrated organic wastewater such as pulp cooking waste liquid (black liquor) or highly concentrated organic sludge such as human waste, this sludge concentration step 10 can be omitted and direct wet oxidation treatment can be performed. The feed such as organic sludge thus concentrated is
It is sent to a wet oxidation treatment step 11 and subjected to oxidation treatment. In this wet oxidation treatment step 11, a feed material such as organic sludge to be treated is increased in pressure by a high-pressure pump 101, and further heated through a heat exchanger 102 to a temperature at which reaction can be started, and then introduced into a reactor 103. On the other hand, air, which is the oxygen source necessary for oxidation, is compressed by the compressor 104 to the same pressure as the pressure at the outlet of the high-pressure pump 101 and added to the feed at the inlet of the heat exchanger 102 or the inlet of the reactor 103. In the reactor 103, oxygen-requiring substances in the feed are oxidized with oxygen, and heat of oxidation is generated accordingly. The oxidized feed liquid is sent from the reactor 103 to the heat exchanger 102, where it is cooled by exchanging heat with the raw material feed, and sent to the gas-liquid separator 105, where the exhaust gas is 0.
and the oxidized product _L1 . This gas-liquid separator 105 may be provided between the reactor 103 and the heat exchanger 102 in some cases to exchange heat with the feed using only the oxidized product _L1 . In this wet oxidation treatment step 11, the feed such as organic sludge is supplied with 1.1 to 1.5 times the required amount of oxygen, and the oxidation degree is 60 to 60 under the conditions of 200 to 280°C and 55 to 100 Kg/cm ² G. A high oxidation treatment of 85% is applied, and the solid content in the resulting treated material _L1 , that is, the weight loss due to heating, is reduced to 15% or less, which is the acceptable standard for waste dumping in Japan. Next, the treated material _L1 discharged from the wet oxidation treatment step 11 is introduced into the aggregation treatment step 12, and the second
Coagulation treatment with iron salts is applied to remove substances undesirable to anaerobic digester organisms. This flocculation treatment step 12 consists of a coagulation-sedimentation tank 106, accompanying flocculant addition and mixing means 107, PH adjustment means 108, and a filter 109 such as a filter press, vacuum dehydrator, centrifugal dehydrator, belt filter, etc. . First, in the flocculating sedimentation tank 106 into which the treated material L ₁ is introduced, ferric salt, especially ferric chloride and ferric sulfate, is added as a flocculant to the flocculant addition mixing means 1.
From 07, iron content is 100 mg per L ₁ of processed material.
or more, preferably 500 to 2000 mg/added, and PH
PH2.5-7.0 by adjusting means 108, preferably
The pH is adjusted to 3 to 5, flocculation treatment is performed, and the flocculation separation liquid _L2 and flocculated solids are separated by gravity. This aggregated solid content is dehydrated by a filter 109 and examined for ash.
The separated liquid is discharged as S ₁ and added to the flocculated separated liquid L ₂ . The pH of this coagulated and separated liquid _L2 is adjusted to around neutrality for the next anaerobic digestion treatment step 14, if necessary. In addition, the coagulation sedimentation tank 106
may be a single flocculating sedimentation tank, a flocculating mixed tank and a settling tank may be provided, and other flocculants such as polymer flocculants may be used in combination with or mixed with ferric salt. , in short, adding a flocculant containing ferric salt,
This means that the treatment can be carried out in the presence of a ferric salt.
Further, the pH adjustment in the aggregation step may be performed before or after adding the ferric salt, and it is sufficient that the pH of the treated material L ₁ reaches a predetermined value. In addition, this agglomeration treatment step 1
Since the dehydration properties of the treated material L ₁ flowing into 2 are greatly improved by wet oxidation, if necessary, the filter 109 separates it into ash test S and a separated liquid, and this separated liquid is subjected to a coagulation process. You can also do that. Agglomerated separation liquid separated in the above aggregation treatment step 12
L ₂ is introduced into the anaerobic digestion treatment step 14 . In this anaerobic digestion treatment step 14, the flocculated separation liquid is
Besides L ₂ , other organic wastes are being processed.
This organic waste is not particularly limited as long as it can be treated by anaerobic digestion, but examples include organic sludge such as sewage sludge, human waste, municipal waste mainly consisting of kitchen waste, and highly concentrated industrial wastewater such as pulp cooking waste. can be harvested. These organic wastes are appropriately adjusted in a pretreatment step 13 and introduced into an anaerobic digestion treatment step 14. In this pre-treatment step 13, in order to increase the sludge concentration and reduce the absolute amount of sludge, sludge with an SS concentration of less than 2% is collected by concentration means such as pressure flotation or centrifugation. Concentrate to about 6%, preferably about 2 to 4%. Note that sludge concentration is not performed for materials such as human waste whose SS concentration is approximately 2 to 6% from the beginning. In addition, garbage, which is mainly kitchen waste, is subject to adjustments such as addition of water such as sewage sludge and human waste, and addition of nutrient salts. The organic sludge pretreated in this manner is introduced into the anaerobic digestion treatment step 14 together with the flocculation separation liquid L ₂ as described above. In the anaerobic digestion treatment step 14, the treatment conditions are determined according to the type of organic waste without considering the flocculated separation liquid _L2 . For example, in the case of sewage sludge, the digestion temperature is 30 to 37°C, and the number of days for digestion is 15.
Digested under conditions of ~30 days, organic matter is 40~60
%Decrease. The flocculation separation liquid L ₂ has been subjected to flocculation treatment to remove substances undesirable to the anaerobic digestion tank organisms generated in the wet oxidation treatment step 11, and in the operation of the anaerobic digestion treatment step 14, the above-mentioned organic waste is removed. The anaerobic digestion process 14 can be performed without reducing the amount of gas generated without any restrictions on the volumetric mixing ratio. Further, the generated gas is stored in the gas holder 15,
Used as a heat source within the system. The digested sludge is then separated into a dehydrated cake and a digested liquid in a dehydration treatment step 16 using a conventional method.
The dewatered cake is incinerated in a sludge incineration step 17, and the digested and separated liquid is treated in an activated sludge treatment step 18. In the above example, since substances undesirable for anaerobic digestion tank organisms are removed in the flocculation treatment step 12, even if system B of the anaerobic digestion treatment method for sewage sludge treatment is already installed, There is no need to add the anaerobic digestion process 14, and the same volume of flocculation and separation liquid _L2 as the sewage sludge can be treated. That is,
Even if the actual residence time in the digestion tank in the anaerobic digestion treatment step 14 is halved, the amount of digestion gas generated does not decrease, and the digested separated liquid treated in the digestion tank is not subjected to the flocculation treatment of the present invention. Compared to this, BOD and chromaticity are reduced to 1/5 to 1/4, and there is no need to place a large burden on subsequent processing steps. The embodiment of the process diagram shown in FIG. 3 is an example in which the present invention is applied to organic treated materials discharged from a heat treatment process, and the same components as those shown in FIG. 2 are given the same reference numerals. Therefore, the explanation will be omitted. Organic sludge such as sewage sludge is first concentrated in a sludge concentration step 10 and then sent to a heat treatment step 19. In the heat treatment step 19, the concentrated sludge is pressurized by a high-pressure pump 101 and then transferred to a heat exchanger 10.
2 to the reactor 103. Reactor 10
3 is supplied with high-temperature, high-pressure steam from a steam boiler (not shown), with a temperature of 170 to 210°C and a pressure of 10 to 16 kg/kg.
Heat treatment is performed at cm ² G to thermally denature the organic sludge. This treated product is transferred from the reactor 103 to the heat exchanger 10
2, and the next agglomeration treatment step 1 as treated material L ₃
2. Note that instead of such heat treatment step 19, a wet oxidation treatment using a partial oxidation method may be performed. Wet oxidation using the partial oxidation method reduces the amount of oxygen supplied to an oxidation degree of 5 to 15.
%, and the temperature is 170-210℃.
Wet oxidation is carried out under mild conditions at a pressure of 10 to 15 kg/cm ² G, and as with heat treatment, flocculation and sedimentation of sludge are promoted and partial oxidation is carried out, so bad odors are removed. The treated material L ₃ from the heat treatment step 19 is then subjected to a flocculation treatment in the flocculation treatment step 12, but since the raw material organic sludge contains a large amount of organic matter that can be digested anaerobically, as much as possible Since the sedimentation property has been significantly improved by heat treatment, a solid-liquid separation tank 110 is installed in front of the coagulation-sedimentation tank 106, and the treated material L ₃ is first transferred to the solid-liquid separation tank 110. Introduce. The settled sludge separated in the solid-liquid separation tank 110 is directly sent to the anaerobic digestion process 14, and the desorbed liquid _L4 is sent to the coagulation sedimentation tank 10.
Sent to 6. Further, the gas generated by the heat treatment may be separated here. Then, the desorbed liquid L ₄ is sent to the coagulation sedimentation tank 106 in the second embodiment of the present invention.
It is coagulated and precipitated at pH 2.5 to 7 in the presence of iron salts.
This flocculated separation liquid _L5 is used in the next anaerobic digestion process 1.
4, the flocculated solid content is dehydrated in a filter 109, the residue of the flocculated precipitate is discharged, and the desorbed liquid is added to the flocculated separation liquid _L5 . Next, the settled sludge and flocculated separation liquid L ₅ from the solid-liquid separation tank 110 are passed through the anaerobic digestion treatment step 14.
However, as in the example shown in Figure 2, substances unfavorable to the anaerobic digester organisms are removed in the flocculation treatment step 12, so that the digested sludge is Adding heat-treated material to the water will solve the problem that the amount of gas generated increases at first, but then decreases as the number of days of digestion increases, and the amount of gas generated becomes stable and the amount of gas generated increases. will also increase. The process shown in FIG. 4 is an application of the treatment method of the present invention to sewage sludge treatment, and is a process in which the sludge is completely treated and the solids do not need to be incinerated, only by ash inspection, and can be disposed of immediately. In this example as well, the same components as those shown in FIG. 2 are designated by the same reference numerals, and their explanation will be omitted. The raw sewage introduced into the sewage treatment process 20 is sequentially treated by ordinary treatment means including an initial settling tank, an aeration tank, a final settling tank, etc., and is separated into sludge and treated water. The treated water is then discharged, while the sludge is sent to the sludge concentration step 10. In this sludge concentration step 10, in order to increase the sludge concentration and reduce the absolute amount of sludge, concentration means such as pressure flotation method and centrifugation method are used to increase the SS concentration to 1.5% or more, and furthermore, as water-containing organic matter, CODcr20 to 80g. Concentrate to / degree. This CODcr concentration is selected from the viewpoint of increasing the treatment efficiency and the energy efficiency of the entire treatment system of this process when anaerobically digesting water-containing organic matter. In addition, like raw human urine, etc.
If the CODcr concentration is 20g/or more from the beginning,
Sludge thickening will not be performed. In addition, if the CODcr concentration exceeds 80g/, such as initial sedimentation tank sludge, the sludge is not concentrated and is directly passed through the next anaerobic digestion process 14.
Although it is possible to introduce it into
It is preferable that the CODcr concentration is 20-80 g/. The organic sludge thus prepared is then introduced into the anaerobic digestion process 14. In the anaerobic digestion treatment step 14, the digestion temperature is 30 to 37°C, and the number of days for digestion is 15 to 30.
Digested under day conditions, organic matter is reduced by 40-60%. Digestion gas generated in this anaerobic digestion process 14 is captured in a gas holder 15 to be described later.
The digested sludge is sent to the digested sludge concentration step 2.
1. The digested sludge concentration step 21 consists of concentration means such as a centrifuge, pressurized flotation, and weight separation in some cases, and the introduced digested sludge is adjusted to an appropriate concentration to have a suspended solids concentration of 3 to 4. % of digested sludge and separated liquid. This separated liquid has a lower concentration of organic substances than the separated liquid discharged when organic sludge is subjected to direct wet oxidation treatment, and is either returned to the sewage treatment process 20 and treated, or treated separately. I do. On the other hand, the concentrated digested sludge is sent to wet oxidation treatment step 11, where it is subjected to high oxidation treatment with an oxidation degree of 60 to 85% under the conditions of 180 to 280°C and 55 to 100 Kg/cm ² G, The resulting weight loss due to heat during the ash inspection is considered to be 15% or less. Next, the wet-oxidized product is supplied to a flocculation treatment step 12, where a flocculation treatment is performed in the presence of the ferric salt of the present invention. The concentration of the ferric salt is 100 mg/or more, preferably 500 to 2000 mg/in terms of iron content, and the pH is adjusted to 2.5 to 7, preferably 3 to 5. This flocculation process separates the flocculated liquid and flocculated sludge, and this flocculated liquid is returned to the anaerobic digestion process 14. This is because this flocculated separation liquid still contains easily digestible substances. Note that a part of this flocculated and separated liquid may be returned to the sewage treatment process 20, or may be treated separately. On the other hand, the flocculated sludge is dehydrated together with the ash produced by the wet oxidation treatment, the dehydrated solids are discharged, and the filtrate is returned to the anaerobic digestion process 14 together with the flocculated separation liquid. The above flocculation treatment can remove substances that are unfavorable to anaerobic digester organisms in the wet oxidation product produced by wet oxidation treatment, and can separate organic sludge and oxidized separation liquid during operation of the anaerobic digestion tank. The volume of the oxidized separation liquid can be treated without being limited by the volume mixing ratio of the anaerobic digestion treatment 14, and the amount of gas generated from the anaerobic digestion treatment 14 can be treated without decreasing even at a high CODcr load. In addition, in this case, the digested sludge introduced into the wet oxidation treatment step 11 is subjected to anaerobic digestion treatment in the previous stage, and the amount of solid matter is reduced to about 2/3, and the organic matter content is also 40 to 60%. %. Further, the wet oxide generated in the wet oxidation treatment step 11 is separated into an ash sample and an oxidized separation liquid, the ash residue is discharged, and the entire amount of the oxidation separation liquid is returned to the anaerobic digestion treatment step 14. Since the oxidized separated liquid is mixed with the organic sludge and treated here, the amount of the oxidized separated liquid is smaller than that of the sewage sludge. Therefore, in this process, the mixing ratio of organic sludge and oxidized separation liquid can be kept at around 1:1, so that it is possible to maintain the mixing ratio of organic sludge and oxidized separation liquid up to about 1:1, so that the wet type treatment system of other treatment systems can be used as shown by the dotted line in Figure 4. The oxidized separated liquid from the oxidation treatment process is passed through the coagulation treatment process 12 to the anaerobic digestion treatment process 1
4 can also be introduced. Furthermore, since the temperature of the oxidized separation liquid mentioned above is 65 to 70°C, by simply returning the entire amount to the anaerobic digestion treatment process 14, the treatment temperature of the above-mentioned process 14 can be lowered to the normal 30-day digestion process. can be maintained at 30°C or higher all year round without any other heat source. Next, one method of recovering energy from the digestion gas generated in the anaerobic digestion process 14 will be described. For digestion gas, first use gas holder 1.
5 is temporarily stored. A part of the digestion gas stored in the gas holder 15 is used for the exhaust gas deodorization combustion process in the wet oxidation process 11 and as fuel for the starting boiler, and the rest is all sent to the gas engine 22 and used as the power fuel. used.
The gas engine 22 includes a generator, which recovers electric power from the digestion gas.
High-temperature exhaust gas discharged from the gas engine 22 is introduced into the exhaust gas boiler 23, and heats the water by exchanging heat with the water introduced at the same time. The heated hot water is sent to the anaerobic digestion treatment step 14, and even if the oxidizing liquid is returned to the anaerobic digestion tank in this step 14, it remains at a predetermined temperature (generally about 37°C).
It is used as a heating source when the temperature is not high. In this way, by effectively utilizing digestive gas,
This treatment method does not require any auxiliary fuel such as heavy oil, and can significantly reduce the energy consumption required for sludge treatment. The process shown in Fig. 5 employs a heat treatment process in place of the wet oxidation process in the process shown in Fig. 4, and the same components as those shown in Fig. 4 are given the same reference numerals. The explanation will be omitted. The organic sludge discharged from the sewage treatment process 20 is concentrated in the sludge concentration process 10, introduced into the anaerobic digestion process 14, and subjected to anaerobic digestion. The generated digested gas is sent to the gas holder 15, and the digested sludge is passed through the digested sludge concentration step 21 and then into the heat treatment step 19.
sent to. Here temperature 170~210℃, pressure 10~16
The processed material heat-treated at Kg/cm ² G is subjected to agglomeration treatment step 1.
2, and is first subjected to solid-liquid separation as shown in FIG. The separated desorbed liquid is treated in the presence of ferric salt,
It is coagulated at pH 2.5 to 7 and separated into coagulated separation liquid and coagulated sludge. On the other hand, the solid-liquid separated heat-treated sludge is returned to the anaerobic digestion treatment step 14.
In addition, the above-mentioned flocculated separated liquid is also used in the anaerobic digestion treatment step 14.
However, a portion may be returned to the sewage treatment process 20 or may be treated separately. The above flocculated sludge is dehydrated, and the dehydrated solid content is removed from the sludge incineration process 1.
The filtrate is incinerated in step 7, and the filtrate is similarly sent to anaerobic digestion step 14. In this process as well, the treated material from the heat treatment step 19 is flocculated in the presence of ferric salt in the flocculation treatment step 12, so even if this desorbed liquid is introduced into the anaerobic digestion treatment step, no Digestion gas is stably generated without decreasing the amount of digestion gas generated. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 Anaerobically digested sludge was subjected to wet oxidation treatment using a shaking batch type autoclave at a treatment temperature of 210°C, a treatment pressure of 70 Kg/cm ² , a treatment time of 1 hour, and an oxidation degree of 60%, and the wet oxides discharged were Before returning the material to the anaerobic digestion process after flocculation treatment, we investigated (1) selection of flocculant, (2) appropriate pH range, and (3) appropriate amount of addition in the flocculation treatment process. Here, as a simple method, a Warburg pressure measuring device was used, the digestion temperature was 37℃, and the CODcr (oxygen consumption by potassium dichromate) load was 3Kg.
Anaerobic digestion treatment under CODcr/m ³・day conditions,
The amount of digestive gas generated after 24 hours was defined as the flocculation treatment effect. In addition, when only sewage sludge is subjected to anaerobic digestion, which is a common treatment method, and when anaerobic digested sludge is subjected to wet oxidation treatment, the oxidized separated liquid separated from the processed material discharged is mixed with sewage sludge without coagulation treatment. Anaerobic digestion was also performed at the same time, and the results will be compared with the amount of digestive gas generated.
The method is to add 3 ml of digested sludge as seed sludge to the reaction vessel (content capacity: approximately 18 ml) of a Warburg pressure measuring device.
Then, 0.18 ml of sewage sludge and 0.36 ml of flocculation liquid were added, and after replacing the inside of the container with nitrogen gas, the container was placed in a constant temperature bath, and the amount of digestion gas generated was measured from the difference in liquid level using a manometer connected to the container. (1) Selection of flocculant Ferrous chloride, ferric chloride, aluminum sulfate, and polyaluminum chloride were used as flocculants, and iron salts were added as Fe and aluminum salts as Al in an amount of 1000 mg/ to the wet oxide. After flocculation treatment, the pH was adjusted to 7, and the above-mentioned anaerobic digestion treatment was performed. Table 1 shows the relationship between the amount of digestive gas generated and the type of flocculant.

[Table] In this table, (a) shows the case where only sewage sludge was subjected to anaerobic digestion, and (b) shows the case where wet oxidation separated liquid was mixed with sewage sludge without flocculation treatment and anaerobically digested. From this table, the amount of digestion gas generated increases only when flocculating with ferric chloride than when the wet oxidation separated liquid in (b) is mixed with sewage sludge without flocculating treatment and treated with anaerobic digestion, and furthermore, ( b) The amount of digestion gas generated increases compared to when only sewage sludge is subjected to anaerobic digestion. This result shows that the flocculation treatment with ferric chloride can remove substances unfavorable to anaerobic digester organisms in the wet oxide. (2) Appropriate PH range Wet oxide with ferric chloride as Fe 1000
After adjusting the pH to 2.9 to 8.6 and performing a flocculation treatment, the pH was adjusted to 7 and the above-mentioned anaerobic digestion process was performed. Table 2 shows the relationship between the amount of digestive gas generated and the flocculation pH.

[Table] From this table, the pH of flocculation treatment with ferric chloride is
If the pH is 2.5 to 7.0, preferably 3 to 5, the amount of digestive gas generated will increase. From this result, the appropriate pH range for wet oxide coagulation treatment with ferric chloride is PH2.5.
It can be seen that the pH is ~7.0, preferably PH3-5. Ferrous chloride, aluminum sulfate, and polyaluminum chloride were also subjected to the anaerobic digestion treatment by changing their pH and coagulating, but it was not possible to increase the amount of digestive gas generated. (3) Appropriate amount of addition: 0 to 0 to 100% Fe of ferric chloride to the wet oxide.
2000mg/was added, adjusted to pH 3 and subjected to aggregation treatment, then adjusted to pH 7 and subjected to the above-mentioned anaerobic digestion treatment. Table 3 shows the relationship between the amount of digestion gas generated and the amount of ferric chloride added.

[Table] From this table, the amount of ferric chloride added is calculated as iron content.
The amount of digestive gas generated increases at 100mg/ or more, and
The increase stops at ~2000mg/. This result shows that the amount of digestion gas generated can be efficiently increased by adding ferric chloride as iron content of 100 mg/or more, and 500 to 2000 mg/in consideration of treatment effect and economic efficiency. According to the above, the wet oxide contains ferric chloride as an iron content of 100 mg/or more, preferably 500 to 2000 mg/
It can be seen that substances undesirable to anaerobic digester organisms can be removed by adding and coagulating at a pH of 2.5 to 7.0, preferably 3 to 5. In addition, the anaerobically digested sludge was treated in a nitrogen atmosphere using a shaking batch type autoclave at a temperature of 200℃.
The heat-treated liquid discharged from the heat treatment at a treatment pressure of 15 kg/cm ² was also subjected to aggregation treatment in the same manner, and then subjected to anaerobic digestion treatment. As a result, 100mg/Fe of ferric chloride was obtained, similar to the wet oxide agglomeration treatment.
Preferably 500 to 2000 mg/addition, PH
The amount of digestive gas generated increased by flocculation treatment at 2.5 to 7.0. Example 2 Concentrated organic sludge from sewage treatment equipment was subjected to anaerobic digestion using 30 anaerobic digestion tanks according to the treatment process shown in Figure 4, and concentrated using a centrifuge.
Next, this was subjected to wet oxidation treatment using a shaking batch type autoclave, and the wet oxide was flocculated with ferric chloride, and the flocculated separated liquid was returned to the anaerobic digestion tank for treatment without adjusting the pH. At this time, the anaerobic digestion treatment is a continuous test, but the wet oxidation treatment is a batch test. In addition, the pH after agglomeration treatment
As a result of returning the flocculated separation liquid, which had a pH of 5 without adjustment, to the anaerobic digestion tank for treatment, it was possible to treat it. Regarding the digestion efficiency and the amount of digestive gas generated, the oxidized separated liquid after wet oxidation treatment was returned to the anaerobic digestion tank without flocculation treatment, and when only organic sludge was used, which is a general treatment method. This will be compared with the case of anaerobic digestion. The treatment conditions and properties of the organic sludge and the obtained oxidized separated liquid and coagulated separated liquid in Example 2 are as shown below. ●Treatment conditions Anaerobic digestion temperature 37℃ Concentrated digested sludge concentration Approximately 3.5% Wet oxidation treatment temperature 210℃ Wet oxidation treatment pressure 70Kg/ ^cm2Wet oxidation treatment oxidation degree 60% Wet oxidation treatment time 1 hour Coagulation treatment Ferric chloride addition Amount (as Fe) 1000
mg/ coagulation treatment PH range 5.0 ●Properties of organic sludge, oxidized separated liquid, and coagulated separated liquid

[Table] (1) Regarding the volumetric mixing ratio of the oxidized separated liquid (or coagulated separated liquid) and organic sludge that flow into the anaerobic digestion tank, organic sludge treatment was performed according to the method of the present invention described above, and this was Digestion efficiency when anaerobic digestion reaches a steady state after continuing for more than a month,
Table 4 shows the relationship between the amount of digestive gas generated and the volumetric mixing ratio of the oxidized separated liquid (or coagulated separated liquid) and organic sludge (separated liquid mixed ratio).

[Table] In this table, (a) is when only organic sludge is subjected to anaerobic digestion (b) is when the oxidized separated liquid after wet oxidation treatment is returned to the anaerobic digestion tank without flocculation treatment. C) is a case where the wet oxide after wet oxidation treatment is flocculated and the flocculated separated liquid is returned to the anaerobic digestion tank for treatment. In addition, the number of days for digestion is defined as the capacity of the digester/the amount of organic sludge input, and when the oxidized separated liquid or flocculated separated liquid is returned to the anaerobic digester for treatment, the actual number of days of retention in the digester is as shown in the table. Thus, at a separation liquid mixing ratio of 1:1, the amount is 1/2 of that when only organic sludge is subjected to anaerobic digestion. As can be seen from this table, when the wet oxide in (c) is coagulated and returned to the anaerobic digestion tank, the wet oxidation separated liquid in (b) is sent to the anaerobic digestion tank without being coagulated. Compared to the case where the separated liquid is returned for treatment, the digestion efficiency is almost the same as when organic sludge with a separated liquid mixing ratio of 1:1 is anaerobically digested (a), and furthermore, the separated liquid mixed ratio is 0.8: In the case of 1, the amount of digestive gas generated is increasing. Also, digested sludge
We also analyzed the BOD ₅ and chromaticity of the filtrate filtered with No. 5C filter paper, but when the wet oxides in (c) were flocculated and returned to the anaerobic digestion tank, the wet The concentration can be reduced to 1/4 to 1/5 of that when the oxidized separated liquid is returned to the anaerobic digestion tank without flocculation treatment. The chromaticity analysis method at this time is the clean water test method.
A perspective colorimetric method was followed. These results show that when anaerobic digestion is carried out using the method of the present invention, the organic matter load (VSS load) of 1.7Kg-VS, which is the general operating condition of (a), is not limited to the separation liquid mixing ratio. It is possible to obtain almost the same CODcr removal rate under the conditions of /m ³ days and increase the amount of digested gas generated by approximately 15%, and when the digested sludge removed liquid is returned to the sewage treatment facility or treated separately. can reduce pollutant load. (2) Regarding the CODcr load in the anaerobic digestion tank Digestion efficiency when changing the CODcr load by changing the number of days of digestion under the conditions of the separated liquid mixing ratio of 0.8:1 and 1:1 in the anaerobic digestion tank, Table 5 shows the amount of digestive gas generated.

[Table] In this table, (a), (b), and (c) are for the case of anaerobic digestion treatment as described above. Moreover, indigestibility is a state in which there is almost no amount of digestive gas generated. From this table, when anaerobic digestion is performed using the method of the present invention in (c), under the condition of a separation liquid mixing ratio of 1:1
If the operating conditions are CODcr load 8.0Kg-CODcr/m ³ days or less, the actual retention period will be longer than the conventional method (a) where only organic sludge with separated liquid mixing ratio of 0:1 is subjected to anaerobic digestion treatment. It can be seen that almost the same CODcr removal rate can be obtained even if the amount is reduced to 1/2, and the amount of digestion gas generated can also be increased. These results show that when anaerobic digestion is performed using the present invention, organic matter load (VSS load) of 1.5 to 3.0 Kg-VSS/m ³ days, which is the general operating condition, can be used without any restrictions. Almost the same CODcr as when only sludge is treated with anaerobic digestion
It is possible to obtain a high removal rate and increase the amount of digestive gas generated by approximately 15%. As explained above, the processing method of this invention is
An organic treated product subjected to wet oxidation treatment or heat treatment, or a desorbed liquid obtained by solid-liquid separation of this organic treated product, is coagulated at pH 2.5 to 7.0 in the presence of a ferric salt. Since at least a part of the separated liquid is subjected to anaerobic digestion treatment, the flocculation treatment under the above conditions eliminates undesirable effects on the anaerobic digester organisms contained in the wet oxidation treated or heat treated organic matter. The substances are removed, and even if the flocculated separation liquid is supplied to the anaerobic digestion tank, it will not have any adverse effect on the digestion process. Therefore, the volumetric mixing ratio of the organic sludge supplied to the anaerobic digestion process and the flocculated separation liquid can be adjusted to about 1:1,
This means that the desorbed liquid from the wet oxidation treatment equipment in other treatment steps can also be treated. Furthermore, the drawback that the amount of generated gas fluctuates and gradually decreases when a heat-treated organic product is added to the digested sludge is solved, and the digested gas can be stably recovered. Furthermore, the amount of digestion gas in the anaerobic digester increases, and there are advantages such as more efficient energy recovery.

[Brief explanation of the drawing]

Figure 1 is a process diagram showing an example of a conventional sewage sludge treatment method, and Figures 2 to 5 are process diagrams each showing a process in which the treatment method of the present invention is applied to an organic sludge treatment method. be. 11... Wet oxidation treatment step, 12... Coagulation treatment step, 106... Coagulation sedimentation tank, 107... Coagulant addition and mixing means, 108... PH adjustment means, 109...
...filter, L ₂ ... flocculated separation liquid, 14 ... anaerobic digestion treatment step, 19 ... heat treatment step, 110 ...
Solid-liquid separation tank.

Claims (1)

[Claims] 1. An organic treated product subjected to wet oxidation treatment or heat treatment, or a separated liquid obtained by solid-liquid separation of this organic treated product, to a pH of 2.5 to 7.0 in the presence of a ferric salt. 1. A method for treating an organic material that has been subjected to a wet oxidation treatment or a heat treatment, the method comprising performing a flocculation treatment with a wet oxidation treatment or a heat treatment, and subjecting at least a portion of the separated liquid obtained by the flocculation treatment to an anaerobic digestion treatment. 2 For the above organic treated product or desorbed liquid,
2. The treatment method according to claim 1, characterized in that the ferric salt is added as an iron content of 100 mg or more, preferably 500 to 2000 mg. 3. Claim 1, characterized in that the ferric salt is ferric chloride and/or ferric sulfate.
The treatment method described in Section 2 or Section 2. 4. The treatment method according to any one of claims 1 to 3, wherein the aggregation treatment is performed at a pH of 3 to 5.