JP2022023698A - Sewage sludge fermentation raw material - Google Patents

Abstract

To provide a sewage sludge fermentation raw material that can easily and stably promote fermentation without adjusting a composition according to a fermentation state each time.SOLUTION: A sewage sludge fermentation raw material of the present invention for aerobic fermentation treatment contains sewage sludge and hydrated lime, and contains 1.5 mass.pts or more and 2.5 mass.pts or less of the hydrated lime with respect to 100 mass.pts of the sewage sludge. It is also preferable that the sewage sludge fermentation raw material further contain a nutritional auxiliary material, and it is also preferable that the nutritional auxiliary material be contained in the amount of 5 mass.pts or more and 50 mass.pts or less with respect to 100 mass.pts of the sewage sludge. It is also preferable that the sewage sludge fermentation raw material further contain an aeration auxiliary material, and it is also preferable that the aeration auxiliary material be contained in the amount of 5 mass.pts or more and 50 mass.pts or less with respect to 100 mass.pts of the sewage sludge.SELECTED DRAWING: Figure 1

Description

The present invention relates to a raw material for aerobic fermentation of sewage sludge.

Sewage sludge is a muddy substance containing organic matter and water, and is inevitably discharged in the process of sewage treatment associated with daily activities. The amount of sewage sludge discharged increases with the increase in the amount of sewage treatment, and the treatment of sewage sludge has become a problem, as with urban waste. In order to treat sewage sludge, for example, an attempt has been made to incinerate the sludge and use the heat generated at that time as an energy source, but in order to carry out a more efficient incineration treatment, sewage It is desired to reduce the water content of sludge.

As a technique for inexpensively reducing the water content of sewage sludge, a technique for aerobically fermenting sewage sludge is known. For example, Patent Documents 1 to 3 disclose a method of mixing and fermenting organic sludge and fly ash in order to improve dehydration efficiency and prevent malodor.

Further, Patent Document 4 discloses a technique of adding a breathability improving material to sewage sludge and fermenting it aerobically to reduce the water content.

Japanese Unexamined Patent Publication No. 63-185881 Japanese Unexamined Patent Publication No. 09-074899 Japanese Unexamined Patent Publication No. 11-228257 Japanese Unexamined Patent Publication No. 2005-11374

In general, in order to stably perform aerobic fermentation, it is necessary to optimize various conditions such as the amount of nutrients and water that reduce the nutrition of microorganisms contained in the object to be treated, pH, etc., in addition to the aeration amount. Is. When aerobic fermentation is performed under closed conditions from the viewpoint of preventing environmental pollution such as foul odors, anaerobic fermentation progresses and the pH of the entire fermentation system becomes low due to the tendency for the aeration amount to be insufficient, resulting in organic matter. Decomposition speed slows down. As a result, the aerobic fermentation treatment of the object may not be sufficiently performed.

For the purpose of maintaining a good fermentation state by adjusting the pH of the entire fermentation system, which has become low pH due to the progress of fermentation, to the neutral or alkaline side, it is alkaline for raw materials such as stocks and organic waste. There is a method of adding alkaline substances such as fermented compost. However, when sewage sludge is used as an object of aerobic fermentation treatment, the pH of the entire fermentation system does not change much due to the buffering action of the sewage sludge, and it may be difficult to adjust the pH to a desired range. .. In particular, when treating sewage sludge with a large-scale continuous device such as a closed vertical fermenter, the fermentation state near the raw material input port differs from the fermentation state near the discharge port, so the fermentation conditions are adjusted. Was difficult.

As described above, in the aerobic fermentation of sewage sludge, when the fermentation is promoted by adjusting the pH, a formulation that can stably obtain the promoting effect of the aerobic fermentation has been required. In this regard, in the techniques described in Patent Documents 1 to 4, no studies have been made on appropriately adjusting the fermentation conditions in the aerobic fermentation process and optimizing the fermentation conditions at the time of sealing or compression. ..

Therefore, an object of the present invention is to provide a sewage sludge fermentation raw material that can easily and stably promote fermentation without adjusting the composition according to the fermentation state each time.

As a result of diligent studies to solve the above problems, the present inventors have found that the fermentation of sewage sludge, which is a fermentation target, is stably promoted by adding a specific amount of sewage sludge to sewage sludge. , The present invention has been achieved.

That is, the present invention contains sewage sludge and sewage sludge, and contains 1.5 parts by mass or more and 2.5 parts by mass or less of the sewage sludge with respect to 100 parts by mass of the sewage sludge. It provides a fermented raw material.

Further, as a preferred embodiment of the present invention, there is provided a sewage sludge fermentation raw material for aerobic fermentation treatment, which further contains a nutritional auxiliary material.

Further, as a preferred embodiment of the present invention, there is provided a sewage sludge fermentation raw material for aerobic fermentation treatment, which comprises the nutritional auxiliary material in an amount of 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the sewage sludge. ..

Further, as a preferred embodiment of the present invention, there is provided a sewage sludge fermentation raw material for aerobic fermentation treatment, which further comprises an aeration auxiliary material.

Further, as a preferred embodiment of the present invention, there is provided a sewage sludge fermentation raw material for aerobic fermentation treatment, which comprises 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the sewage sludge. ..

According to the present invention, aerobic fermentation can be rapidly promoted and sewage sludge can be stably fermented only by a simple operation of adding a specific material to sewage sludge. As a result, even in industrial areas such as cement factories and areas adjacent to houses, sewage sludge with different properties can be fermented in large quantities, leading to effective use of resources.

FIG. 1 is a cross-sectional view schematically showing an embodiment of a closed vertical fermenter. FIG. 2A is a perspective view showing the appearance and dimensions of the fermentation vessel used for the evaluation of aerobic fermentation in Examples and Comparative Examples, and FIG. 2B shows the arrangement position of each member at the time of temperature measurement. It is a cross-sectional view.

Suitable embodiments of the present invention will be described below. The present invention is not limited to the following embodiments.

The sewage sludge fermentation raw material of the present invention contains sewage sludge and slaked lime as the raw materials. This sewage sludge fermentation raw material is suitably used for aerobic fermentation treatment of sewage sludge.

The sewage sludge used in the present invention is waste generated in the process of wastewater treatment or sewage treatment, and is a muddy substance containing organic matter, inorganic matter and water. Examples of such sewage sludge include general sewage sludge, industrial sewage sludge, and the like, and these can be used alone or in combination. The sewage sludge may be used as it is as undigested sludge, or a self-fermented product of sewage sludge such as dehydrated sludge and digested sludge may be used.

The sewage sludge fermentation raw material of the present invention further contains slaked lime (Ca (OH) ₂ , calcium hydroxide). The slaked lime used in the present invention is a powder having a particle size of preferably 600 μm or less, more preferably 150 μm or less, from the viewpoint of appropriately adjusting the microscopic environmental conditions described later and further promoting aerobic fermentation. The shape can be used more preferably. The particle size of powdered slaked lime is realistically 1 μm or more, preferably 25 μm or more. As the slaked lime, for example, a powdery solid may be used, or a solution or a dispersion may be used. As long as the effect of the present invention is exhibited, commercially available products such as slaked lime for gardening and various industrial slaked lime can be used. When industrial slaked lime is used, for example, slaked lime conforming to JIS R9001 can be used. The particle size of slaked lime may be the smallest nominal opening of the sieves that 95% by mass or more of the slaked lime powder has passed through, for example, when the slaked lime powder is sieved using a sieve compliant with JIS Z8801-1: 2019. can.

The content of sewage lime in the sewage sludge fermentation raw material of the present invention is preferably 1 part by mass or more and 4 parts by mass or less, and more preferably 1.5 parts by mass or more and 2.5 parts by mass or less with respect to 100 parts by mass of sewage sludge. be. At this time, the mass of the reference sewage sludge is the mass in the water-containing state. Within such a range, aerobic fermentation of sewage sludge can be easily promoted, and the progress of fermentation can be stabilized at a high level. Since the content of this slaked lime is much lower than the typical content of slaked lime used in the present technology, the whole sewage sludge fermentation raw material resulting from the addition of slaked lime within the above-mentioned content range. No effect on pH is observed.

The slaked lime that can be used in the present art typically has a function as a pH adjuster for adjusting the pH of the fermentation object to the alkaline side. However, when slaked lime is contained for the purpose of adjusting the pH of sewage sludge or fermented raw materials containing sewage sludge, the sewage sludge has a pH buffering action, and therefore, in order to efficiently proceed with aerobic fermentation, the entire fermentation system is used. Attempts to uniformly adjust the pH require a large amount of slaked lime, resulting in increased processing costs.
As a result of diligent studies by the present inventor regarding the promotion of aerobic fermentation of sewage sludge, the content of slaked lime is not determined for the purpose of uniformly adjusting the pH (macro pH) of the entire fermentation system, but fermentation. Surprisingly, aerobic fermentation of sewage sludge is easy and stable by determining the content of slaked lime in consideration of the microscopic (micro) environmental conditions in the region where slaked lime is present in the system. It was found that it can be promoted and the processing cost can be significantly reduced. The ability to promote aerobic fermentation of sewage sludge even when the sewage content is much lower than the typical content used in the art has not been investigated in any prior art. It was first discovered by the inventor.

The present inventor speculates the reason why aerobic fermentation proceeds efficiently and progressively by containing sewage sludge fermentation raw material of the present invention in a specific addition amount as follows. When slaked lime is added to sewage sludge, a pH increase in the entire system (macro pH increase) is hardly observed due to the pH buffering action of the sewage sludge, but the region where slaked lime exists (for example, slaked lime particles), which is a microscopic environment, is observed. It is considered that the pH is adjusted to the alkaline side on the surface and in the vicinity of the microscopic region, and the pH rises to a value suitable for the decomposition of organic substances by microorganisms, and aerobic fermentation is proceeding efficiently.
When the amount of slaked lime added is less than the above range, the supply of alkali is insufficient, and it becomes difficult to raise the microscopic pH of sewage sludge. When the amount of slaked lime added is larger than the above range, the portion occupied by slaked lime becomes excessive as compared with sewage sludge and microorganisms, and a plurality of regions having an excessively high pH are locally formed. Aerobic fermentation is less likely to be promoted. Therefore, by controlling the content of slaked lime to the above range, the pH of the whole sewage sludge fermentation raw material does not change, but the microscopic region where the pH becomes a value suitable for the decomposition of organic substances is appropriate. Since it is uniformly distributed in the sewage sludge fermentation raw material, aerobic fermentation of sewage sludge can be easily and efficiently proceeded.

The raw material for fermenting sewage sludge of the present invention may be composed only of sewage sludge and sewage lime, and in addition to this, materials other than sewage sludge and sewage lime (hereinafter, this) as long as the effects of the present invention are not impaired. Is also simply referred to as “material”). Examples of the material include a material for promoting stable aerobic fermentation when the sewage sludge fermentation raw material is subjected to fermentation, and specifically, a material for reducing the water content of the sewage sludge or a sewage sludge fermentation raw material. Examples of the material are intended to improve the air permeability during fermentation of sewage, and to supply easily decomposable organic components that are nutrient sources for microorganisms that contribute to aerobic fermentation.

It is preferable to further include a nutritional auxiliary material as a material for supplying the nutrient source of microorganisms contributing to aerobic fermentation to the sewage sludge fermentation raw material. Specific examples of such nutritional aids include food sludge, waste white soil, meat-and-bone meal, paper sludge, waste cooking oil, swill, human waste, feces of poultry and livestock, compost and the like. These can be used alone or in combination. Further, as the compost, a commercially available product may be used, or a sludge fermented product (a fermented product produced by aerobic fermentation treatment of the sewage sludge fermentation raw material of the present invention) may be used.
Of these, using meat-and-bone meal as a nutritional aid is convenient so that the nutritional components (components such as fats and oils, proteins, nitrogen, etc.) when mixed with sewage sludge become the optimum conditions for the activity of aerobic microorganisms. It is preferable in that it can be easily adjusted and aerobic fermentation of sewage sludge can be further promoted. Further, it is preferable to use compost as a nutritional auxiliary material in that various aerobic microorganisms present in the compost can be sufficiently supplied into the sewage sludge fermentation raw material to further promote the aerobic fermentation of the sewage sludge. In particular, nutritional assistance is made from the viewpoint of facilitating the progress of aerobic fermentation to be easily adjusted to the optimum range from both the nutritional aspect and the diversity of aerobic microorganisms, and further promoting the aerobic fermentation of sewage sludge. It is more preferable to use meat-and-bone meal and compost in combination as the material.

When the sewage sludge fermentation raw material further contains a nutritional auxiliary material, the content of the nutritional auxiliary material in the sewage sludge fermentation raw material is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 10 parts by mass with respect to 100 parts by mass of sewage sludge. It is 5 parts by mass or more and 35 parts by mass or less, more preferably 15 parts by mass or more and 25 parts by mass or less. At this time, the mass of the reference sewage sludge and the nutrient aid material shall be the mass in the water-containing state. When multiple kinds of nutritional aids are included, the content of the nutritional aids is based on the total amount. By being in such a range, it is possible to easily adjust the balance of nutritional components necessary for the activity of aerobic microorganisms, which further promotes aerobic fermentation of sewage sludge and keeps the progress of fermentation at a high level. Can be stabilized.

When the nutrient aid is further contained in the sewage sludge fermentation raw material, it is preferable to use a nutrient auxiliary material having a solid content calorific value of 3000 kcal / kg or more, and further preferably to use one having a solid content calorific value of 3300 kcal / kg or more. It is more preferable to use one having a temperature of 3500 kcal / kg or more. This calorific value of solid content is the calorific value per type of nutritional aid. In general, a high solid content calorific value means that a large amount of organic content, which is one of the nutritional components useful for the progress of aerobic fermentation, is contained. By using the auxiliary material, aerobic fermentation can be further promoted, and the fermentation treatment of sewage sludge can be efficiently performed. Examples of the nutritional aid having such a calorific value include meat-and-bone meal, feces of poultry and livestock, compost and the like.

It is preferable to further include a ventilation auxiliary material as a material for improving the air permeability of the sewage sludge fermentation raw material and promoting the aerobic fermentation of the sewage sludge. The above-mentioned slaked lime is excluded from the ventilation aids in the present specification. By including the aeration auxiliary material, the air permeability of the sewage sludge fermentation raw material can be easily improved without depending on the compressed state of the sewage sludge fermentation raw material, and the aerobic fermentation of the sewage sludge can be stably performed. can. In particular, in the case of aerobic fermentation using, for example, a vertical fermenter, which will be described later, the sewage sludge in the fermenter is compressed due to the accumulation of the sewage sludge fermentation raw material, and the aerobic fermentation of the sewage sludge becomes difficult to proceed. By including the aeration auxiliary material, it is possible to further secure the aeration while further suppressing the excessive compression state, and it is possible to stably and effectively promote the aerobic fermentation of sewage sludge. Is advantageous.

Aeration aids include, for example, organic aeration aids such as rice straw, fir tree, vegetation or dried or crushed products thereof, and inorganic aeration such as pearlite, zeolite, diatomaceous earth, or coal ash such as fly ash. Auxiliary materials and the like can be mentioned, and these can be used alone or in combination. Of these, by using coal ash, it is relatively fine particles and contains oxide components such as CaO and MgO, so that it has high dispersibility in the sewage sludge fermentation raw material and forms flocs. Since it can be performed uniformly, it is preferable in that the air permeability during aerobic fermentation can be further enhanced.

When the sewage sludge fermentation raw material further contains a ventilation auxiliary material, the content of the ventilation auxiliary material 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 with respect to 100 parts by mass of sewage sludge. It is 5 parts by mass or more and 30 parts by mass or less, more preferably 5 parts by mass or more and 15 parts by mass or less. At this time, the mass of the reference sewage sludge and the ventilation auxiliary material shall be the mass in the water-containing state. 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 compression of the sewage sludge fermentation raw material for a long period from the start to the end of fermentation, which is favorable for sewage sludge. The air fermentation can proceed stably and effectively. In particular, coal ash is treated as waste in the same way as sewage sludge, and by reusing coal ash together with sewage sludge, there is an advantage that it contributes to effective use of resources and environmental protection.

When coal ash is used as a ventilation aid, the bulk density of the coal ash is preferably 0.2 g / cm ³ or more and 1.5 g / cm ³ or less, and the brain specific surface area is preferably 1000 cm ² / g or more and 20000 cm ² /. It is less than or equal to g. Bulk density can be measured, for example, according to JIS R1628. The specific surface area of the brain can be measured according to, for example, JIS R5201.

The shapes of various materials such as the above-mentioned nutritional aids and ventilation aids are not particularly limited, and may be, for example, solid, granular, powdery, paste, fluid, liquid or the like. The total total content of the material can be appropriately adjusted according to the physical properties and purpose of the material used, but the total mass part of the material with respect to 100 parts by mass of sewage sludge is preferably 1 part by mass or more and 180 parts by mass with respect to 100 parts by mass of sewage sludge. It can be less than or equal to 5 parts by mass, more preferably 5 parts by mass or more and 100 parts by mass or less. At this time, the mass of the reference sewage sludge is the mass in the water-containing state.

From the viewpoint of ensuring sufficient water content for stable progress of 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 70% by mass or less. It is more preferably 40% by mass or more and 60% by mass or less. The water content can be measured, for example, using a commercially available halogen moisture meter based on the difference in mass before and after drying when dried at a heating temperature of 120 ° C. Alternatively, the measurement can be performed according to JIS A 1203 “Soil water content ratio test method”. The water content of the sewage sludge fermentation raw material can be appropriately adjusted, for example, by selecting a raw material so as to have a desired water content, or by adding water to the raw material or the sewage sludge fermentation raw material.

The sewage sludge fermentation raw material containing such a material can be produced as a mixture or a deposit by mixing or depositing, for example, sewage sludge and sewage lime and various materials as needed. Specifically, a method of mixing sewage sludge and sewage lime with various materials as needed to obtain a sewage sludge fermentation raw material, or sewage as a deposit in which each material is deposited indoors or outdoors in any order. Examples thereof include a method of obtaining a sludge fermentation raw material. Alternatively, one of the materials is supplied to a container such as a fermenter, and then the other raw materials are supplied into the container in an arbitrary order, and the respective raw materials are alternately or randomly deposited in the container. Examples thereof include a method of obtaining a sewage sludge fermentation raw material as a product as it is, or as a mixture in which the deposit is mixed in a container such as a fermenter.

The above-mentioned sewage sludge fermentation raw material, in either form of sediment or mixture, is suitable for aerobic fermentation treatment of sewage sludge. The sewage sludge fermentation raw material can be arranged outdoors or indoors as it is, or it can be contained in a container as a deposit or a mixture to perform an aerobic fermentation treatment of sewage sludge.
Specifically, the sewage sludge fermentation raw material can be deposited in a compost house or housed in an open or closed fermenter to ferment the sewage sludge aerobically. When the raw material for sewage sludge fermentation is supplied to the fermenter and used for aerobic fermentation treatment, stable aerobic fermentation is performed for a long period of time from the initial stage of fermentation regardless of the presence or absence of a stirring facility in the fermenter or the stirring method. Sludge can be treated efficiently. From the viewpoint of reducing adverse effects on the surrounding environment such as foul odors, when the sewage sludge in the sewage sludge fermentation raw material is subjected to aerobic fermentation treatment, it is preferable to perform aerobic fermentation in a closed fermenter. The closed system refers to a reaction system in which the ingress of solids and liquids is prevented during aerobic fermentation and the ingress of gases such as air is not hindered, and the open system refers to solids, liquids and gases during aerobic fermentation. Refers to a reaction system in which the entry of the gas is not hindered.

In particular, the sewage sludge fermentation raw material of the present invention is aerobically fermented in a closed state using a hermetically sealed and vertical fermenter (hereinafter, also referred to as a "sealed vertical fermenter") to sewage sludge. In the case of fermenting the sewage sludge, it is preferable because the aerobic fermentation of sewage sludge can proceed stably for a long period of time without changing the environmental conditions such as the composition of the components and the pH each time according to the fermentation state. .. That is, as a method for fermenting sewage sludge, sewage sludge and slaked lime and, if necessary, materials are supplied into a closed vertical fermenter in an arbitrary order, or a mixture containing these raw materials is sealed. It is preferable to have a step of supplying into a vertical fermenter for aerobic fermentation, and it is more preferable that the step is performed in a closed system. The closed vertical fermenter may be provided with a stirring device for stirring the inside of the fermenter, and each raw material supplied into the fermenter may be continuously or intermittently stirred.

When aerobic fermentation is performed in a closed state using a closed vertical fermenter, the sewage sludge fermentation raw material in the fermenter is compressed due to the accumulation of the sewage sludge fermentation raw material, and it is difficult for the sewage sludge to proceed with aerobic fermentation. By the way, preferably, by including an aeration auxiliary material such as coal ash, it is possible to secure the air permeability while suppressing the sewage sludge fermentation raw material in the fermenter from becoming an excessively compressed state, and the uncompressed state. Regardless of the compressed state, it is advantageous in that aerobic fermentation of sewage sludge can proceed stably and effectively.

FIG. 1 shows an embodiment of a closed vertical fermenter in which the sewage sludge fermentation raw material of the present invention is suitably used for fermentation treatment. The closed vertical fermenter 10 extends vertically with respect to the installation surface and has a tubular tank portion 20 capable of accommodating sewage sludge and sewage lime and, if necessary, a mixture of materials, and an upper portion thereof. In addition, a charging port 30 capable of charging the mixture into the tank section 20 and a discharging port 40 capable of discharging the aerobic fermentation-treated sewage sludge fermentation raw material to the outside of the tank section 20 are provided at the lower portion of the tank section 20. ing. Both the charging port 30 and the discharging port 40 are provided with a lid-shaped member (not shown) that can be opened and closed or detached, and by attaching the lid-shaped member to the charging port 30 and the discharging port 40, the tank in the fermentation tank 10 The portion 20 is configured to be hermetically sealed. That is, the closed vertical fermenter 10 can perform aerobic fermentation of sewage sludge in a closed system to treat the sewage sludge.

From the viewpoint of further improving the aerobic fermentation efficiency, it is preferable that the closed vertical fermentation tank 10 has a heat insulating structure by, for example, arranging a heat insulating material on the outer peripheral surface of the tank portion 20. Further, it is also preferable that the closed vertical fermenter 10 is provided with a stirring device 50 for mixing the raw materials in the fermenter to make the presence state of the components and the air permeability uniform.
The stirring equipment 50 shown in FIG. 1 includes, for example, a stirring blade 51 provided inside the tank portion 20, a stirring shaft 52 connected to the stirring blade 51, and a motor provided outside the tank portion 20 (not shown). And have. The stirring blade 51 is connected to a motor provided outside the tank portion 20 via a stirring shaft 52, and rotates in a fixed direction using the motor as a drive source. By further providing the stirring equipment 50, the aerobic fermentation efficiency of the sewage sludge fermentation raw material can be further improved.

Further, the closed vertical fermenter 10 has an air flow facility 60 for supplying oxygen-containing gas such as air and oxygen into the fermenter, and an exhaust gas capable of exhausting the gas in the tank 20 to the outside of the tank 20. It is also preferable to have a mouth 70.
In the embodiment shown in FIG. 1, the oxygen-containing gas F is vertically connected to the stirring blade 51 from the air flow facility 60 provided outside the tank portion 20, preferably via the inside of the hollow stirring shaft 52 and the stirring blade 51. It can be supplied to the lower side in the direction. It is also preferable that the stirring blade 51 is provided with a plurality of gas flow holes (not shown) capable of flowing the oxygen-containing gas F on the lower side in the vertical direction. The oxygen-containing gas existing in the tank portion 20 and the gas generated by aerobic fermentation are exhausted from the upper part of the tank portion 20 as exhaust air through the exhaust port 70.

From the viewpoint of increasing the supply efficiency of the oxygen-containing gas and increasing the aerobic fermentation efficiency of the sewage sludge, the oxygen-containing gas F is supplied from the lower side in the vertical direction of the tank portion 20, and the oxygen-containing gas F and the gas are in the tank. It is preferable that the gas is exhausted from the upper side of the portion 20 in the vertical direction. The sewage sludge fermentation raw material is continuously or intermittently put into the tank section 20 in the fermenter from the inlet, and the sewage sludge fermentation raw material is aerobically fermented in the fermenter for about 2 weeks, and then fermented sewage sludge fermentation. The raw material is discharged from the discharge port as a fermented sludge.

The sludge fermented product produced by subjecting the sewage sludge fermentation raw material to aerobic fermentation can be used for, for example, fertilizer, soil conditioner, green farmland material such as horticultural soil, cement clinka raw material, solid fuel and the like. , Effective use of resources becomes possible. In particular, it is preferable to mix the fermented sludge with a raw material such as limestone and use it as a raw material for cement clinker because the amount of the fermented sludge produced can be increased and the effective use of resources can be further contributed. .. Further, this sludge fermented product can be reused as a nutritional auxiliary material of the present invention in the preparation of a sewage sludge fermentation raw material, which also contributes to the effective utilization of resources.

As is clear from the above description, the present specification discloses not only a sewage sludge fermentation raw material, but also a method for producing a sewage sludge fermentation raw material, and a method for treating sewage sludge using the sewage sludge fermentation raw material.

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

[Example 1 and Comparative Examples 1 to 3]
[Preparation of raw materials for sewage sludge fermentation]
The following sewage sludge and sewage lime, nutritional aids (meat-and-bone meal and compost) as materials, and aeration aids (coal ash) are mixed at the content ratios shown in Table 1 below, and the water content is 62. A raw material for fermenting sewage sludge of 0.8% by mass to 65.2% by mass was prepared.
(1) Sewage sludge: Undigested sludge obtained from a sewage treatment plant (moisture content 80.35% by mass)
(2) Smelting lime: Commercially available shaving lime for horticulture (3) Meat-and-bone meal: Meat-and-bone meal for fertilizer (moisture content 0.7% by mass, calorific value 3600 kcal / kg)
(4) Compost: Commercially available agricultural compost (moisture content 28% by mass)
(5) Coal ash: Coal ash collected from a coal-fired private power plant (manufactured by Ube Industries, Ltd., moisture content 16.18% by mass)

[Aerobic fermentation test]
The sewage sludge fermentation raw materials of Examples and Comparative Examples were subjected to aerobic fermentation treatment, and the progress of aerobic fermentation of sewage sludge was evaluated as a temperature change of a sample. As a fermentation container, a polybeaker having a capacity of 500 mL and a simple heat insulating container covering the sides and bottom of the beaker were used. These arrangement positions and dimensions are as shown in FIG. 2 (a). About 400 mL each of the sewage sludge fermentation raw materials of Example 1 and Comparative Examples 1 to 3 was placed in a polybeaker to prepare a sample.

Next, a polybeaker containing each sample was placed in a heat insulating container as shown in FIG. 2B, and a T-type thermocouple (manufactured by Chino Corporation) was inserted into the center of the sample in the polybeaker. A data logger was connected to the thermocouple and the sample was subjected to aerobic fermentation in a state where the temperature of the sample could be continuously measured. These experiments were performed in a room set at 20 ° C. The degree of progress of aerobic fermentation was evaluated by the peak temperature and the number of days required to reach the peak temperature, with the measured maximum temperature as the peak temperature. The higher the peak temperature and the shorter the number of days required to reach the peak temperature, the faster and more efficient the aerobic fermentation of sewage sludge is. The results are shown in Table 1.

As shown in Table 1, the sewage sludge fermentation raw material of Example 1 containing sewage sludge and slaked lime and having the slaked lime content within a predetermined range has a higher peak temperature and reaches the peak temperature as compared with the comparative example. It can be seen that the required number of days is short. Therefore, the sewage sludge fermentation raw material of the example can stably and efficiently proceed with aerobic fermentation of sewage sludge by a simple operation without adjusting the composition each time according to the fermentation state.

Claims (8)

A sewage sludge fermentation raw material for aerobic fermentation treatment, which comprises sewage sludge and sewage lime, and contains the sewage sludge by 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of sewage sludge. The sewage sludge fermentation raw material according to claim 1, further comprising a nutritional aid. The sewage sludge fermentation raw material according to claim 2, wherein the nutritional auxiliary material is contained in an amount of 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the sewage sludge. The sewage sludge fermentation raw material according to any one of claims 1 to 3, further comprising a ventilation auxiliary material. The sewage sludge fermentation raw material according to claim 4, wherein the aeration auxiliary material is contained in an amount of 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the sewage sludge. A step of aerobically fermenting a sewage sludge fermentation raw material containing sewage sludge and slaked lime to treat the sewage sludge is provided.
A method for treating sewage sludge, wherein the slaked lime contains 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the sewage sludge. Using the sewage sludge fermentation raw material further containing a nutritional aid and a ventilation aid,
The nutritional aid contains 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the sewage sludge.
The method for treating sewage sludge according to claim 6, wherein the ventilation auxiliary material contains 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the sewage sludge. The method for treating sewage sludge according to claim 6 or 7, wherein the sewage sludge fermentation raw material is aerobically fermented in a closed and vertical fermenter.

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