JP2023090456A - Sewage sludge fermentation raw material and sewage sludge treatment method - Google Patents

Abstract

To provide a fermentation raw material that can stably progress aerobic fermentation and stably ferment sewage sludge without depending on the type of sewage sludge or the type of nutrient source material.SOLUTION: A sewage sludge fermentation raw material for aerobic fermentation includes sewage sludge and a nutrient source. The raw material contains 3.5 or more and 130 or less mass parts of crude fat and crude protein derived from the nutrient source per 100 mass parts of sewage sludge based on the total of the crude oil and the crude protein. It is preferable that the raw material contains 0.07 or more and 104 or less mass parts of the crude oil derived from the nutrient source per 100 mass parts of the sewage sludge. It is also preferable that the raw material contains 0.7 or more and 127 or less mass parts of the crude protein derived from the nutrient source per 100 mass parts of the sewage sludge.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a raw material for aerobic fermentation of sewage sludge and a method for treating sewage sludge.

Sewage sludge is a muddy substance containing organic matter and water, and is inevitably discharged during the process of sewage treatment associated with living activities. The discharge amount of sewage sludge is increasing along with the increase in the amount of sewage treatment, and its disposal has become a problem like urban garbage. In order to treat sewage sludge, for example, attempts have been made to incinerate the sludge and use the heat generated at that time as an energy source. It is desired to lower the moisture content of sludge.

As a technique for inexpensively lowering the water content of sewage sludge, a technique for aerobic fermentation of sewage sludge is known. For example, Patent Literatures 1 to 3 disclose a method of mixing and fermenting organic sludge and organic materials in order to improve dehydration efficiency and reduce volume.

JP-A-11-079873 JP 2005-111374 A JP 2009-274908 A

In general, in order to stably carry out aerobic fermentation, it is necessary to optimize various conditions such as nutrients that serve as nutrients for microorganisms contained in the object to be treated, moisture content, pH, and aeration rate. When aerobic fermentation treatment is performed on sewage sludge with low nutrient content, such as digested sludge that has undergone methane fermentation in the process of sewage treatment, microbial activity is inhibited due to lack of nutrients. It becomes sluggish and the aerobic fermentation treatment of the object may not be performed sufficiently.

As a method for improving the aerobic fermentation state of a fermentation system in which the activity of such microorganisms has become sluggish, Patent Documents 1 to 3 disclose materials rich in nutrients (hereinafter also referred to as "nutrient sources" or "nutrient source materials"). ) is added. However, when sewage sludge is used as the object of aerobic fermentation treatment, nutrients suitable for microorganisms contained in sewage sludge may be insufficient depending on the type of sewage sludge and the type and amount of nutrient material added. Therefore, it may be difficult to maintain good conditions for aerobic fermentation. Therefore, in order to promote good aerobic fermentation, it is important to design appropriate materials for each sewage sludge and material used.

In the material design of raw materials for fermentation of sewage sludge, conventionally, tests have been conducted using test equipment consisting of actual facilities or large-capacity fermenters, and there has been the problem that a large amount of samples are required and time is required. Furthermore, in recent years, the fermentation process of sewage sludge has begun to be deployed all over the country, and it is recommended that the sewage sludge and materials to be used be those that are easily available in neighboring areas. There are many types of materials. Therefore, even when the types of nutrient source materials are different, there has been a demand for a material blend of sewage sludge fermentation raw materials that allows aerobic fermentation to proceed satisfactorily.

Accordingly, an object of the present invention is to provide a raw material for fermentation of sewage sludge that can stably promote fermentation regardless of the type of nutrient material added to sewage sludge.

As a result of intensive studies to solve the above problems, the present inventors found that among the components contained in the nutrients added to the sewage sludge, the total amount of crude fat and crude protein greatly changes the fermentability of the sewage sludge. I found out. Based on these findings, the present inventors added a nutrient source to sewage sludge so that the total amount of crude fat and crude protein derived from the nutrient source is within a predetermined range. The inventors have found that the fermentation of sewage sludge, which is a fermentation target, is stably promoted regardless of the type of nutrient source, and have completed the present invention.

That is, the present invention is a sewage sludge fermentation raw material for aerobic fermentation treatment containing sewage sludge and a nutrient source,
Sewage sludge fermentation raw material for aerobic fermentation treatment, containing 3.5 parts by mass or more and 130 parts by mass or less of crude fat and crude protein derived from the nutrient source with respect to 100 parts by mass of the sewage sludge It provides

In addition, the present invention comprises a step of aerobic fermentation of a sewage sludge fermentation raw material containing sewage sludge and a nutrient source to treat the sewage sludge,
Using the sewage sludge fermentation raw material containing 3.5 parts by mass or more and 130 parts by mass or less of crude fat and crude protein derived from the nutrient source with respect to 100 parts by mass of the sewage sludge. A processing method is provided.

According to the present invention, aerobic fermentation can be stably progressed only by a simple operation of adding a specific amount of nutrient material to sewage sludge, regardless of the type of sewage sludge or the type of nutrient material. , can stably ferment sewage sludge. Furthermore, in industrial areas such as cement factories and sources of sewage sludge such as sewage treatment plants, a plurality of sewage sludges with different properties and nutrient source materials can be used to easily and stably ferment. , can lead to effective use of resources.

FIG. 1 is a cross-sectional view schematically showing one embodiment of a closed vertical fermenter. FIG. 2(a) is a schematic perspective view showing the appearance and dimensions of a fermentation vessel used for aerobic fermentation evaluation in Examples and Comparative Examples, and FIG. 2(b) is an arrangement of each member during temperature measurement. It is a sectional view showing a position typically.

Preferred embodiments of the invention are described below. In addition, this invention is not limited to the following embodiment.

The sewage sludge fermentation raw material of the present invention contains sewage sludge and a nutrient source as its materials. This sewage sludge fermentation raw material is suitably used for the aerobic fermentation treatment of sewage sludge.

The sewage sludge used in the present invention is waste generated in the course of sewage treatment, and is a muddy substance containing organic matter, inorganic matter and water. Sewage sludge is typically obtained by dewatering surplus sludge discharged from an activated sludge process wastewater treatment facility. Examples of such sewage sludge include general sewage sludge generated at sewage treatment plants, night soil sludge generated at night soil treatment facilities, and septic tank sludge, and these can be used alone or in combination. Sewage sludge may be used as it is as undigested sludge, or self-fermented sewage sludge such as digested sludge may be used. According to the present invention, there is an advantage that aerobic fermentation can be sufficiently performed even with digested sludge that is low in nutrients that serve as a nutrient source for microorganisms.
Although the water content of the sewage sludge is not particularly limited, it is, for example, approximately 50% by mass or more and 90% by mass or less, preferably 50% by mass or more and 85% by mass or less. The type of sewage sludge can be selected based on at least one of its moisture content, whether it has been digested, and how it has been dewatered.

Nutrient sources used in the present invention include crude fat and crude protein. Generally, nutrient sources for aerobic microorganisms include raw sugar, crude protein, crude fat, crude fiber, etc. from those having a high decomposition rate. is that aerobic fermentation proceeds stably by adding nutrient source material to sewage sludge so that the total amount of crude fat and crude protein, which are decomposed at a moderate rate by aerobic microorganisms, reaches a predetermined amount. Found it. In addition, many of the materials used as a nutrient source for aerobic microorganisms contain relatively large amounts of crude fat and crude protein, and therefore have the advantage of being readily available.

Crude fat is a fat-soluble substance contained in foods, feeds, and the like. Crude fat includes not only pure fat but also vitamins and other ingredients dissolved in fat. The content of crude fat contained in the nutrient source can be determined by the Soxhlet extraction method. The Soxhlet extraction method takes advantage of the fact that lipids are insoluble in water but soluble in organic solvents. It is a method of weighing the remaining fat content by evaporation.

On the other hand, crude protein is protein contained in foods, feeds, and the like. Crude protein contains amino acids and amines. The content of crude protein is determined by oxidatively decomposing the sample with hot concentrated sulfuric acid, converting all ammonia and amino groups into ammonium ions, and quantifying the amount of nitrogen. Multiply by the reciprocal of .

The sewage sludge fermentation raw material of the present invention preferably contains 3.5 parts by mass or more and 130 parts by mass or less of the total amount of crude fat and crude protein derived from the nutrient source with respect to 100 parts by mass of sewage sludge. , 4.0 to 80 parts by mass, more preferably 4.5 to 50 parts by mass.

The present inventors speculate as follows why the aerobic fermentation is stably progressed by allowing the sewage sludge fermentation raw material of the present invention to contain a specific amount of crude fat and crude protein derived from a nutrient source. .
Crude fat and crude protein contained in the nutrient source are suitable nutrients for microorganisms present in sewage sludge. In this case, the total amount of crude fat and crude protein is added to the sewage sludge in a specific range, that is, as described above, preferably 3.5 parts by mass or more and 130 parts by mass or less with respect to 100 parts by mass of sewage sludge It is considered that the necessary and sufficient supply of nutrients to the microorganisms is obtained when the aerobic fermentation proceeds stably. If the blending amount of crude fat and crude protein is too small relative to the amount of sewage sludge, the amount of nutrients supplied to microorganisms is insufficient, and poor mixing of sewage sludge and nutrients tends to occur. If the blending amount of crude fat and crude protein is excessively large relative to the amount of sewage sludge, the amount of sewage sludge treated will decrease, and the amount of microorganisms in the fermentation raw material will be insufficient, making it impossible to stably carry out aerobic fermentation. there is a possibility.

The preferred ranges for the total amount of crude fat and crude protein relative to sewage sludge are as described above, while the respective preferred ranges for the amounts of crude fat and crude protein relative to sewage sludge are as follows.
Regarding crude fat, the sewage sludge fermentation raw material of the present invention preferably contains 0.07 parts by mass or more and 104 parts by mass or less of crude fat derived from a nutrient source with respect to 100 parts by mass of sewage sludge, and 0.28 mass parts. Part or more and 50 mass parts or less is more preferable, and 0.56 mass part or more and 25 mass parts or less is even more preferable. By setting the amount of crude fat within this range, the amount of nutrients supplied to microorganisms becomes necessary and sufficient, which is preferable.
On the other hand, with respect to crude protein, the sewage sludge fermentation raw material of the present invention preferably contains 0.7 parts by mass or more and 127 parts by mass or less of crude protein derived from a nutrient source with respect to 100 parts by mass of sewage sludge. More preferably 4 parts by mass or more and 74 parts by mass or less, and even more preferably 2.2 parts by mass or more and 44 parts by mass or less. By setting the amount of crude protein within this range, the amount of nutrients supplied to microorganisms becomes necessary and sufficient, which is preferable.

Nutrient sources containing crude fat and crude protein include, for example, food, feed, food sludge, waste white clay, meat and bone meal, waste cooking oil, garbage, night soil, feces of poultry and livestock, and seed sludge. These nutrient sources can be used singly or in combination of two or more. Among these, one or more selected from the group consisting of rice bran, bean curd refuse and oil cake as a nutrient source because it has particularly high nutritional value and the total amount of crude fat and crude protein can be easily set within the above range. is preferably used. As oil cake, it is preferable to use residue obtained by squeezing oil from, for example, rapeseed, sesame, cottonseed, soybean and corn.

The nutrient source used in the present invention contains 1 part by mass or more and 20 parts by mass or less of crude fat with respect to 100 parts by mass of the nutrient source so that the decomposition rate by aerobic microorganisms in sewage sludge is optimal. It is preferable from the viewpoint of supplying a sufficient amount of crude fat for aerobic fermentation. From the viewpoint of making this advantage more remarkable, the nutrient source further preferably contains 3 parts by mass or more and 17.5 parts by mass or less of crude fat with respect to 100 parts by mass of the nutrient source, and 5 parts by mass or more and 15 parts by mass. It is more preferable to include less than or equal to

On the other hand, the nutrient source used in the present invention contains 5 parts by mass or more and 45 parts by mass or less of crude protein with respect to 100 parts by mass of the nutrient source. It is preferable from the viewpoint of being able to supply a sufficient amount of crude protein for aerobic fermentation. From the viewpoint of making this advantage more remarkable, the nutrient source further preferably contains 10 parts by mass or more and 40 parts by mass or less of crude protein relative to 100 parts by mass of the nutrient source, and more preferably 15 parts by mass or more and 35 parts by mass or less. It is more preferable to include

The ratio of crude fat and crude protein contained in the nutrient source used in the present invention is expressed as a mass ratio, and the value of crude fat/crude protein is 0.02 or more and 4 or less. It is preferable from the viewpoint of balance as a source. From the viewpoint of making this advantage more remarkable, the mass ratio of crude fat/crude protein in the nutrient source is more preferably 0.075 or more and 1.75 or less, and more preferably 0.14 or more and 1 or less. More preferred.

The nutrient source used in the present invention is not particularly limited as long as the amounts of crude fat and crude protein are the values described above, but the nutrient loss on ignition is preferably 90% by mass or more, It is more preferably 95% by mass or more. The ignition loss of a nutrient source reflects the amount of organic components contained in the nutrient source, and by using a nutrient source having such an ignition loss, aerobic fermentation can be further promoted, Fermentation treatment of sewage sludge can be efficiently performed. The ignition loss of the nutrient source is measured according to JIS R 5202:2015 "Method for chemical analysis of cement".

The nutrient source used in the present invention preferably has a solid content calorific value of 4000 kcal/kg or more, more preferably 4300 kcal/kg or more, and more preferably 4500 kcal/kg or more. is more preferably used. This solid content calorific value is the calorific value per nutrient source. In general, a high solid content calorific value means that it contains a large amount of organic matter, which is one of the nutrient components useful for the progress of aerobic fermentation. By using the source, aerobic fermentation can be further promoted, and sewage sludge can be efficiently fermented. Nutrient sources having such a calorific value include, for example, rice bran, bean curd refuse, and oil cake.

Furthermore, the nutrient source used in the present invention preferably has a moisture content of 10% by mass or less, more preferably 7.5% by mass or less, and even more preferably 5% by mass or less. By using a nutrient source having such a water content, when the nutrient source is mixed with sewage sludge, an increase in viscosity and adhesiveness of the mixture can be suppressed, and good air permeability can be maintained. As a result, aerobic fermentation can be stably performed.
The lower limit of the water content of the nutrient source is determined from the viewpoint of viscosity and adhesion when mixed with sewage sludge. From this point of view, the lower limit of the moisture content of the nutrient source is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more.
The moisture content of a nutrient source is measured by weight loss after drying at 135°C for 2 hours in accordance with the Feed Analysis Method.

The nutrient source used in the present invention can be used as it is in a water-containing state immediately after collection, or can be used after being dried. The hydrated nutrient source can be dried by a common method, for example, forced drying using a hot air convection dryer or natural drying in the sun. The water content mentioned above is the value when the nutrient source is mixed with the sewage sludge.

The sewage sludge fermentation raw material of the present invention may be composed only of sewage sludge and nutrients. Alternatively, in addition to these, it is also preferable to further contain materials other than sewage sludge and nutrients (hereinafter also simply referred to as "materials").

Materials include, for example, materials for promoting stable aerobic fermentation when the sewage sludge fermentation raw material is subjected to fermentation. Specifically, the purpose is to reduce the water content of sewage sludge, improve the aeration of sewage sludge fermentation raw materials during fermentation, and supply a wide variety of microorganisms that contribute to aerobic fermentation. materials

In particular, the sewage sludge fermentation raw material preferably further contains an aeration aid as a material for improving the air permeability of the sewage sludge fermentation raw material and promoting aerobic fermentation of the sewage sludge. By including the aeration aid, the aeration of the sewage sludge fermentation raw material can be easily improved without depending on the consolidation state of the sewage sludge fermentation raw material, and the aerobic fermentation of the sewage sludge can be stably performed. can. In particular, for example, when aerobic fermentation is performed using a vertical fermentation tank described later, the sewage sludge in the fermentation tank is compacted due to the accumulation of sewage sludge fermentation raw materials, making it difficult for the aerobic fermentation of the sewage sludge to proceed. , By including the aeration aid, it is possible to further ensure aeration while further suppressing excessive compaction, and to allow the aerobic fermentation of sewage sludge to proceed stably and effectively. is advantageous.

Examples of ventilation aids include organic ventilation aids such as rice straw, rice husks, plants, or their dried or crushed materials, and inorganic ventilation aids such as perlite, zeolite, diatomaceous earth, or coal ash such as fly ash. Auxiliary materials, etc. are mentioned. These materials can be used alone or in combination.

When the sewage sludge fermentation raw material further contains an aeration aid, the content of the aeration aid in the sewage sludge fermentation raw material is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or less per 100 parts by mass of sewage sludge. It is more than 30 parts by mass and more preferably more than 5 parts by mass and less than 15 parts by mass. At this time, the reference masses of the sewage sludge and the ventilation aid are both in the state of containing water. When multiple types of ventilation aids are included, the content of the ventilation aids is based on the total amount. By being in such a range, it is possible to ensure uniform air permeability while suppressing excessive consolidation of the sewage sludge fermentation raw material over a long period from the start to the end of fermentation, which is favorable for sewage sludge. Air fermentation can be progressed stably and effectively.

From the viewpoint of ensuring a sufficient amount of water to stably progress aerobic fermentation from the initial stage of fermentation, the water content of the entire sewage sludge fermentation raw material is preferably 30% by mass or more and 90% by mass or less. It is more preferably 40% by mass or more and 85% by mass or less. The moisture content can be measured, for example, using a commercially available halogen moisture meter based on the difference in mass before and after drying at a heating temperature of 120°C. Alternatively, it can be measured in accordance with JIS A 1203 "Testing Method for Moisture Content of Soil". The water content of the raw material for sewage sludge fermentation is selected so that the raw material has a desired water content, for example, by using sewage sludge with a high water content and a nutrient source in a dry state. It can be appropriately adjusted by adding water to the raw material.

A sewage sludge fermentation raw material containing such materials can be produced as a mixture or sediment by, for example, mixing or sedimenting sewage sludge and a nutrient source and, if necessary, various materials. Specifically, sewage sludge and nutrient sources are mixed with various materials as necessary to obtain sewage sludge fermentation raw materials, or indoors or outdoors as a sediment in which each material is deposited in any order A method of obtaining a raw material for fermentation of sewage sludge, and the like. Alternatively, one of the materials is supplied to a container such as a fermenter, and then the other materials are supplied into the container in any order, and each raw material is deposited alternately or randomly within the container. A method of obtaining a raw material for fermentation of sewage sludge as a substance, as it is, or as a mixture in which the sediment is mixed in a container such as a fermenter.

The sewage sludge fermentation feedstock described above is suitable for use in the aerobic fermentation treatment of sewage sludge, whether in sediment or mixture form. The sewage sludge fermentation raw material can be placed outdoors or indoors as it is, or it can be stored in a container as a sediment or mixture to perform an aerobic fermentation treatment of sewage sludge.

Specifically, the raw material for sewage sludge fermentation can be deposited in a compost house or placed in an open or closed fermentation tank for aerobic fermentation of sewage sludge. When sewage sludge fermentation raw materials are supplied to a fermenter and subjected to aerobic fermentation treatment, aerobic fermentation is stably performed from the beginning of fermentation for a long period of time regardless of the presence or absence of agitation equipment in the fermenter or the agitation method. Sludge can be treated efficiently. From the viewpoint of reducing adverse effects on the surrounding environment such as offensive odors, when the sewage sludge in the sewage sludge fermentation raw material is subjected to the aerobic fermentation treatment, it is preferable to carry out the aerobic fermentation in a closed fermentation tank. A closed system refers to a reaction system in which the intrusion of air from the external environment and the outflow of fermentation gas generated from the fermentation tank to the outside are controlled during aerobic fermentation. Refers to a reaction system in which gas ingress and egress are not controlled in any way.

In particular, the sewage sludge fermentation raw material of the present invention is aerobicly fermented in a sealed vertical fermentation tank (hereinafter also referred to as a "closed vertical fermentation tank") to produce sewage sludge. When fermenting, the aerobic fermentation of sewage sludge can be stably progressed over a long period of time without changing the environmental conditions such as the composition of ingredients and the amount of aeration according to the fermentation state. be. That is, as a method of fermenting sewage sludge, sewage sludge, nutrients, and materials as necessary are supplied in an arbitrary order into a closed vertical fermenter, or a mixture containing these raw materials is closed. It is preferable to have a step of supplying into a type vertical fermenter and subjecting it to aerobic fermentation, and more preferably, the step is performed in a closed system. The closed vertical fermenter may be equipped with stirring equipment for stirring the inside of the fermenter, and may continuously or intermittently stir the raw materials supplied into the fermenter.

FIG. 1 shows one embodiment of a closed vertical fermenter in which the sewage sludge fermentation raw material of the present invention is suitably used for fermentation. The closed vertical fermentation tank 10 extends in the vertical direction with respect to the installation surface, and has a cylindrical tank part 20 that can accommodate a mixture of sewage sludge and nutrients and, if necessary, materials. An input port 30 capable of inputting the mixture into the tank portion 20 is provided at the upper portion, and an outlet port 40 capable of discharging the aerobic fermentation-treated sewage sludge fermentation raw material to the outside of the tank portion 20 is provided at the lower portion of the tank portion 20. I have. Both the input port 30 and the discharge port 40 are provided with openable and detachable lid-like members (not shown). It is configured such that the portion 20 can be sealed. In other words, the closed vertical fermentation tank 10 is a closed system capable of performing aerobic fermentation of sewage sludge to treat the sewage sludge.

From the viewpoint of further improving aerobic fermentation efficiency, the closed vertical fermentation tank 10 preferably has a heat insulating structure, for example, by placing a heat insulating material on the outer peripheral surface of the tank portion 20 . In addition, the closed vertical fermenter 10 is preferably equipped with a stirring facility 50 for mixing the raw materials in the fermenter to uniformize the state of existence of the ingredients and the air permeability.
The stirring equipment 50 shown in FIG. 1 includes, for example, a stirring blade 51 provided in the tank portion 20, a stirring shaft 52 connected to the stirring blade 51, and a motor (not shown) provided outside the tank portion 20. and The stirring blade 51 is connected to a motor provided outside the tank section 20 via a stirring shaft 52, and rotates in a certain direction using the motor as a drive source. By further providing the agitating equipment 50, the air permeability in the reaction system can be increased, and the aerobic fermentation efficiency of the sewage sludge fermentation raw material can be further improved.

In addition, the closed vertical fermentation tank 10 includes an air circulation device 60 for supplying oxygen-containing gas such as air and oxygen into the fermentation tank, and an exhaust that can exhaust the gas in the tank part 20 to the outside of the tank part 20. A mouth 70 is also preferably provided. As a result, the circulation of air and gas inside and outside the reaction system can be appropriately controlled, and aerobic fermentation can be promoted more efficiently, especially in a closed system.

In the form shown in FIG. 1, the oxygen-containing gas F is supplied from the air circulation equipment 60 provided outside the tank section 20, preferably through the hollow stirring shaft 52 and the stirring blades 51, in the vertical direction of the stirring blades 51. It is designed so that it can be supplied downward in the direction. It is also preferable that a plurality of gas flow holes (not shown) through which the oxygen-containing gas F can flow are provided below the stirring blade 51 in the vertical direction. Oxygen-containing gas present in the tank section 20 and gas generated by aerobic fermentation are discharged from the upper portion of the tank section 20 as exhaust air through the exhaust port 70 .

From the viewpoint of making it easier to supply the oxygen-containing gas to the entire fermentation tank and increasing the efficiency of aerobic fermentation of sewage sludge, the oxygen-containing gas F is supplied from the bottom side in the vertical direction of the tank part 20, and the oxygen-containing gas The F and gas are preferably exhausted from the vertically upper side of the tank section 20 . The sewage sludge fermentation raw material is continuously or intermittently fed into the tank part 20 of the fermentation tank from the inlet 30, and the sewage sludge fermentation raw material is aerobicly fermented in the fermentation tank for about two weeks, and then the fermented sewage sludge. The raw material for fermentation is discharged from the outlet as fermented sludge.

Fermented sludge produced by subjecting sewage sludge fermented raw materials to aerobic fermentation can be used for applications such as fertilizers, soil conditioners, green agricultural land materials such as horticultural soil, cement clinker raw materials, and solid fuels. , the effective use of resources becomes possible. In particular, the fermented sludge can be mixed with a raw material such as limestone and used as a raw material for cement clinker. preferable. In addition, this fermented sludge can be reused as a nutritional supplement of the present invention in the preparation of sewage sludge fermented raw materials, which also contributes to effective utilization of resources.

As evident from the above description, the present specification discloses not only the sewage sludge fermentable material, but also the method of producing the sewage sludge fermentative material and the method of treating the sewage sludge using the sewage sludge fermentative material.
A method for treating sewage sludge comprises a step of aerobic fermentation of sewage sludge and sewage sludge fermentation raw materials containing nutrients to treat the sewage sludge. Regarding the sewage sludge and the nutrient source contained in the sewage sludge fermentation raw material used in the present treatment method, and the types and contents of various materials contained as necessary, the above explanations are appropriately applied.

EXAMPLES The present invention will be described in more detail below with reference to examples. The scope of the invention is not limited to such examples. The moisture content of the raw materials shown below was calculated from the difference in mass when dried at a heating temperature of 120° C. using a halogen moisture meter (HM1105 manufactured by AS ONE Corporation). Further, the calorific value shown below indicates the solid content calorific value.

[Examples 1 to 6 and Comparative Examples 1 to 2]
[Preparation of sewage sludge fermentation raw material]
A case of using rice bran as a nutrient source will be described. The sewage sludge and rice bran shown in the following (1) and (2) are mixed at the content ratios shown in Table 1 below to obtain a sewage sludge fermentation raw material with a water content of 45.9% by mass to 80.7% by mass. prepared.

(1) Sewage sludge: Digested sludge obtained from a sewage treatment plant (water content 84.4% by mass)
(2) Rice bran: crude fat 14.2% by mass, crude protein 11.9% by mass, water content 7.4% by mass, ignition loss 92.2% by mass, calorific value 4669 kcal/kg

[Aerobic fermentation test]
The sewage sludge fermentation raw materials of Examples and Comparative Examples were subjected to an aerobic fermentation treatment, and the degree of progress of the aerobic fermentation of the sewage sludge was evaluated as the temperature change of the sample. A poly beaker with a volume of 500 mL and a simple heat-insulating container covering the sides and bottom of the beaker were used as the fermentation vessel. These arrangement positions and dimensions were as shown in FIG. 2(a). About 400 mL of the sewage sludge fermentation raw material of each example and comparative example was placed in a poly beaker to prepare a sample.

Next, the poly beaker containing each sample was placed in a heat-insulating container as shown in FIG. A data logger was connected to the thermocouple and subjected to aerobic fermentation in a state in which the temperature of the sample could be continuously measured. These experiments were performed in a room set at 20°C for 8 days.
The degree of progress of aerobic fermentation was evaluated by the maximum temperature measured. A higher maximum temperature means that aerobic fermentation of sewage sludge is progressing stably. From the viewpoint of stable aerobic fermentation treatment of sewage sludge, samples with a peak temperature of 38°C or higher were accepted. The results are shown in Table 1 below.

As shown in Table 1, the sewage sludge fermentation raw materials of Examples 1 to 6 to which rice bran was added so that the total amount of crude fat and crude protein derived from nutrients was within a predetermined range with respect to sewage sludge, each The peak temperature was higher than that of the comparative example. The reason for this is considered to be that the nutrients necessary for fermentation were sufficiently supplied by mixing predetermined amounts of crude fat and crude protein derived from nutrients into the sewage sludge. As described above, the raw material for fermentation of sewage sludge in the example can stably progress aerobic fermentation of sewage sludge by a simple operation of adding a specific amount of a specific material to sewage sludge.

[Examples 7 to 11 and Comparative Examples 3 to 5]
[Preparation of sewage sludge fermentation raw material]
A case of using bean curd refuse as a nutrient source will be described. The above-mentioned sewage sludge (1) is mixed with the okara shown in the following (3) at the content ratio shown in Table 2 below, and sewage with a water content of 42.6% by mass to 84.0% by mass. A sludge fermentation raw material was prepared.

(3) Okara: crude fat 10.5% by mass, crude protein 31.6% by mass, moisture content 0.8% by mass, ignition loss 95.8% by mass, calorific value 4623 kcal/kg

[Aerobic fermentation test]
The progress of aerobic fermentation of each sewage sludge fermentation raw material was evaluated in the same manner as in Example 1 above. From the viewpoint of stable aerobic fermentation treatment of sewage sludge, samples with a peak temperature of 38°C or higher were accepted. The results are shown in Table 2 below.

As shown in Table 2, even when bean curd refuse was added as a nutrient source, the sewage sludge fermented raw materials of Examples 7 to 11 in which the total amount of crude fat and crude protein derived from the nutrient source relative to the sewage sludge was within a predetermined range , the peak temperature was higher than that of each comparative example. The reason for this is considered to be that the nutrients necessary for fermentation were sufficiently supplied by mixing predetermined amounts of crude fat and crude protein derived from nutrients into the sewage sludge. As described above, the raw material for fermentation of sewage sludge in the example can stably progress aerobic fermentation of sewage sludge by a simple operation of adding a specific amount of a specific material to sewage sludge.

[Examples 12 to 17 and Comparative Examples 6 to 7]
[Preparation of sewage sludge fermentation raw material]
A case where oil cake is used as a nutrient source will be described. The above-mentioned sewage sludge (1) is mixed with the oil cake shown in the following (4) at the content ratio shown in Table 3 below, and the water content is 46.2% by mass to 83.3% by mass. Sewage sludge. A fermentation raw material was prepared.

(4) Oil cake: rapeseed oil extraction residue (crude fat 3.2% by mass, crude protein 36.8% by mass, water content 8.0% by mass, ignition loss 93.6% by mass, calorific value 4821 kcal/kg)

[Aerobic fermentation test]
The progress of aerobic fermentation of each sewage sludge fermentation raw material was evaluated in the same manner as in Example 1 above. From the viewpoint of stable aerobic fermentation treatment of sewage sludge, samples with a peak temperature of 38°C or higher were accepted. The results are shown in Table 3 below.

As shown in Table 3, even when oil cake was added as a nutrient source, the sewage sludge fermentation raw materials of Examples 12 to 17 in which the total amount of crude fat and crude protein derived from the nutrient source with respect to the sewage sludge was within a predetermined range, The peak temperature was higher than that of each comparative example. The reason for this is considered to be that the nutrients necessary for fermentation were sufficiently supplied by mixing predetermined amounts of crude fat and crude protein derived from nutrients into the sewage sludge. As described above, the raw material for fermentation of sewage sludge in the example can stably progress aerobic fermentation of sewage sludge by a simple operation of adding a specific amount of a specific material to sewage sludge.

10 closed vertical fermentation tank 20 tank part 30 inlet 40 outlet 51 stirring blade 52 stirring shaft 60 air distribution equipment 70 exhaust port

Claims (9)

A sewage sludge fermentation raw material for aerobic fermentation treatment comprising sewage sludge and a nutrient source,
Sewage sludge fermentation raw material for aerobic fermentation treatment, containing 3.5 parts by mass or more and 130 parts by mass or less of crude fat and crude protein derived from the nutrient source with respect to 100 parts by mass of the sewage sludge . The raw material for fermentation of sewage sludge according to claim 1, comprising 0.07 parts by mass or more and 104 parts by mass or less of crude fat derived from the nutrient source with respect to 100 parts by mass of the sewage sludge. The raw material for fermentation of sewage sludge according to claim 1 or 2, comprising 0.7 parts by mass or more and 127 parts by mass or less of crude protein derived from the nutrient source with respect to 100 parts by mass of the sewage sludge. The raw material for fermentation of sewage sludge according to any one of claims 1 to 3, wherein the nutrient source contains 1 part by mass or more and 20 parts by mass or less of crude fat with respect to 100 parts by mass of the nutrient source. The raw material for fermentation of sewage sludge according to any one of claims 1 to 4, wherein the nutrient source contains 5 parts by mass or more and 45 parts by mass or less of crude protein with respect to 100 parts by mass of the nutrient source. The raw material for fermentation of sewage sludge according to any one of claims 1 to 5, wherein said nutrient source is one or more selected from the group consisting of rice bran, bean curd refuse and oil cake. 7. The raw material for fermentation of sewage sludge according to any one of claims 1 to 6, further comprising an aeration aid. A step of aerobic fermentation of sewage sludge fermentation raw materials containing sewage sludge and nutrients to treat the sewage sludge,
Using the sewage sludge fermentation raw material containing 3.5 parts by mass or more and 130 parts by mass or less of crude fat and crude protein derived from the nutrient source with respect to 100 parts by mass of the sewage sludge. Processing method. 9. The method for treating sewage sludge according to claim 8, wherein the sewage sludge fermentation raw material is aerobicly fermented in a closed vertical fermentation tank.

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