JP2020146667A - Sludge treatment method and sludge treatment facility - Google Patents

Abstract

To provide a sludge treatment method and a sludge treatment facility capable of suppressing generation of scum in a gravity concentration facility.SOLUTION: Provided are a method of sludge treatment and a sludge treatment facility in which sludge 38 sent from sewage treatment plant 70 is allowed to flow into a gravity concentration facility provided in a sludge treatment plant 88 and settled by gravity to obtain concentrated sludge, the improvement which comprises foreign substances contained in the sludge 38 are cut, in the flow of sludge 38, into a predetermined size to give cuttings, and the resulting sludge 39 that contains the cuttings is allowed to flow into a sewage distribution tank 89 and then a gravity concentration tank 90.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sludge treatment method and a sludge treatment facility.

Conventionally, sewage such as domestic effluent, business establishment effluent, and factory effluent is drained to a sewage pipe, and is collected and treated at a sewage treatment plant via a relay pumping station and a sewer trunk line. The treated water is discharged into rivers and the sea.

The drained sewage includes, for example, plastics, underwear, rags, fibers such as absorbent cotton, and various impurities such as waste cloth, toilet paper, and hair. These contaminants cannot be discharged into rivers or the sea together with the water treated at the sewage treatment plant, for example, they are collected by screens installed in the sand basins of relay pumping stations and sewage treatment plants and are industrial waste. Is processed as.

Many of the contaminants penetrate the screen, and the contaminants that penetrate the screen flow into the first sedimentation basin, which is provided downstream of the sand basin, while still contained in the sewage.

Of the contaminants that first flowed into the settling basin, those that settled are first extracted from the settling basin as raw sludge and sent to the sludge treatment plant. Of the impurities that flowed out (overflow) from the first settling basin without settling, those that flowed into the final settling basin settled with the settling of activated sludge, and these sediments were pulled out from the final settling basin and used as surplus sludge. Sent to a sludge treatment plant. The sludge (raw sludge and / or excess sludge) sent to the sludge treatment plant is concentrated by a gravity concentrating facility and volume-reduced by a dehydrator or an incinerator, which is a downstream facility.

By the way, there is a problem that scum is generated in various facilities of the sewage treatment plant and the sludge treatment plant. Scum is not a little generated in places where sludge and contaminants are present, but it is generated in large quantities especially in gravity concentrating facilities where sludge is temporarily stored. It is desirable to eliminate this scum as much as possible because it causes problems such as blockage of equipment piping, generation of hydrogen sulfide, deterioration of returned water, and reduction of equipment volume.

Examples of the scum elimination method include methods such as human power, recovery by a suction device, crushing by a crushing device, and suppression of scum destruction and growth by hydraulic cleaning, but the scum must be eliminated each time it occurs. It is not a fundamental countermeasure.

Patent Document 1 and Patent Document 2 are techniques related to a method for treating contaminants that cause scum. Patent Document 1 is a technique for making equipment compact by providing a crushing pump for crushing contaminants mixed in organic sludge, and Patent Document 2 crushes concentrated raw sludge with a raw sludge crusher and crushes it. This is a technique in which sludge flows into a denitrification tank and is used as a BOD source, but neither technique suppresses the generation of scum.

Japanese Patent No. 4235591 Japanese Unexamined Patent Publication No. 2001-205300 Special Table 2012-521285 Special Table 2013-537103

A main problem to be solved by the present invention is to provide a sludge treatment method and a sludge treatment facility for suppressing the generation of scum in a gravity concentration facility.

Typical aspects of the present invention that have solved the above problems are as follows.

<First aspect>
This is a sludge treatment method in which sludge sent from a sewage treatment plant is allowed to flow into a gravity concentration facility installed in a sludge treatment plant and settled by gravity to obtain concentrated sludge.
In the flow of the sludge, the contaminants contained in the sludge are cut to a predetermined size to obtain a cut product.
Sludge containing the cut material is allowed to flow into the gravity concentrating facility.
A sludge treatment method characterized by that.

The contaminants contained in the sludge are one of the factors that generate scum in the gravity concentrator. The contaminants adhere to each other and become entangled to form a bundle (contamination group). A large amount of sludge adheres to this group of impurities and forms a large mass.

In addition, the sludge that has flowed into the gravity concentration facility settles due to gravity over time and is concentrated to form a layer of concentrated sludge. Oxygen is dissolved in the layer of this concentrated sludge, and under an anaerobic state, this oxygen is consumed by the concentrated sludge, and gases (bubbles) such as nitrogen, carbon dioxide, and hydrogen sulfide are generated. Gas (bubble) has a lighter specific gravity than liquid and floats from the liquid to the liquid surface. When the gas (bubbles) floats, the above-mentioned large mass to which the gas (bubbles) adheres also floats and floats on the water surface. This large floating mass is a scum.

If the contaminants that cause scum are cut to a predetermined size in advance before becoming a contaminant group to make a cut, the cuts will adhere to each other and become less likely to be entangled, so that the contaminant group is less likely to occur. ..

<Second aspect>
In addition to the first aspect,
Sludge containing the cut material is intermittently flowed into the gravity concentrating facility.
Aspects can be mentioned.

Not a little oxygen molecules are dissolved in the sludge sent from the sewage treatment plant to the sludge treatment plant. That is, it contains dissolved oxygen. When sludge containing dissolved oxygen flows into the gravity concentrating facility, the anaerobic state is alleviated and gasification (bubbles) is suppressed. Further, when the sludge is allowed to flow intermittently, the raw sludge and excess sludge are settled to some extent and the concentration becomes appropriate, so that the concentration efficiency in the gravity concentrating facility is good.

<Third aspect>
In addition to the first aspect,
The sludge is raw sludge,
Aspects can be mentioned.

Contaminants are overwhelmingly contained in the raw sludge settled in the first settling basin than in the activated sludge settled in the final settling basin. By cutting the contaminants contained in the raw sludge, it has the effect of suppressing the contamination of the contaminants.

<Fourth aspect>
In addition to the first aspect,
The scum generated in the gravity concentration facility is mixed with the sludge sent from the sewage treatment plant.
Aspects can be mentioned.

For example, if the scum is destroyed by hydraulic cleaning, the destroyed scum will sink. In other words, when the scum is destroyed, the gas (bubbles) adhering to the scum is separated from the scum, so that the scum cannot keep floating on the liquid surface and sinks.

In the process of mixing the scum into the sludge and flowing it into the cutting device, the gas (bubbles) contained in the scum is separated from the scum. By letting the sludge discharged from the cutting device flow into the gravity concentrating facility, as a result, the amount of scum excluded from the system is reduced.

<Fifth aspect>
In addition to the first aspect,
The cut piece is cut by a cutting device and
The cutting device includes a cutting blade held by a holder that rotates around a rotation axis in the sludge flow direction, and a facing plate having a plurality of through holes provided intersecting with the sludge flow. The cutting blade rotates in a state of being close to or in contact with the facing plate.
Aspects can be mentioned.

Of the impurities contained in the sludge sent to the cutting device, the impurities having a size that cannot pass through the through holes of the facing plate stay (catch) on the facing plate. The contaminants that have stayed (caught) on the facing plate are cut by the rotation of the cutting blade. The contaminants remaining on the facing plate are cut and permeate through the through holes along the flow of sludge.

If the contaminants remain attached to the facing plate, the continuous or intermittent inflow of sludge may cause the contaminants to gradually accumulate on the facing plate, solidify or enlarge, resulting in blockage of the facing plate. is there. When the cutting blade is rotated in a state of facing or in contact with the facing plate, impurities adhering to the facing plate are scraped off by the cutting blade. As a result, it is possible to prevent impurities from accumulating on the facing plate.

<Sixth aspect>
The sludge sent from the sewage treatment plant is allowed to flow into a cutting device provided on the upstream side of the gravity concentrating facility.
The cutting device has an inflow portion into which the sludge flows in, a cutting portion in which contaminants contained in the sludge are cut, and an outflow portion in which the cut product obtained by cutting is discharged.
The inflow portion, the cut portion, and the outflow portion are sequentially arranged on the same straight line along the flow of the sludge.
Aspects can be mentioned.

Since the inflow part, the cutting part, and the outflow part are arranged in order on the same straight line along the sludge flow, the sludge flow direction does not change significantly from the inflow part to the outflow part, and the pressure due to the sludge flow does not change significantly. Has the effect of small loss. Further, since the sludge flows in a straight line direction, the pressure loss is small, and it is possible to prevent the sludge from staying at a specific place in the cutting device and corroding.

<7th aspect>
A cutting device in which impurities contained in sludge sent from a sewage treatment plant are cut in the sludge flow to obtain a cut piece.
It is provided with a gravity concentration facility in which sludge containing the cut pieces is settled by gravity to obtain concentrated sludge.
A sludge treatment facility characterized by this.

The same effect as in the first aspect can be obtained.

According to the present invention, the generation of scum is suppressed in the gravity concentrating facility.

It is a figure which shows the flow which treats sewage. It is a figure which shows the flow which treats sewage. It is explanatory drawing of the cutting device. It is explanatory drawing of the angle formed by the facing plate and the inflow direction of sludge in the inflow part. It is a figure which shows the main part of crushing of a cutting apparatus. It is a figure which shows an example of the facing plate. It is a figure which shows another form of the cutting apparatus. It is a figure which shows the gravity concentration tank. It is a figure which shows the flow which treats sewage. It is explanatory drawing of the cutting device.

A mode for carrying out the present invention will be described. The embodiment of the present invention is an example of the present invention.

(sewage)
Conventionally, sewage was mainly composed of domestic wastewater, industrial wastewater, and business site wastewater. In addition, sewage may be contaminated with plants such as branches and leaves, stems and grass, and soil. In recent years, taking advantage of the economies of scale of sewage treatment plants, there is a tendency to incinerate sludge generated by consolidating septic tank wastewater, agricultural wastewater, food waste, diapers, etc. into the sewerage system to convert it into energy. However, if these are allowed to flow into a sewage treatment plant together with sewage and are intensively treated, the amount of contaminants will also increase.

(Contaminants)
Contaminants contained in the sewage of sewage treatment facilities (for example, pump stations, storage pipes, sewage pipes, sewage pipes, sewer trunk lines, pumped sludge pipes, sewage treatment plants, etc.) include plastics and underwear. Examples thereof include fibers such as sewage and defatted cotton, waste cloth, toilet paper, hair, food waste, oil balls, oils and fats, diaper pieces, mud lumps, and sand lumps, but are not limited thereto.

(Sewage treatment facility)
The sewage treatment process is roughly as follows. Since sewage drained from homes and business establishments is sewage, it flows into sewer pipes and sewer trunk lines, and also flows into the sewage treatment plant 70 via a relay pumping station. The sewage 10 flowing into the sewage treatment plant 70 passes through a landing well, a sand basin, a first settling basin 71, a reaction tank 72, a final settling basin 73, an advanced treatment facility 74, a chlorine mixing basin 75, etc., in that order. , Released. The sand basin is provided with a screen having a plurality of slits as an example. Among the contaminants contained in the sewage 10, those that do not pass through the slit are collected and removed by this screen. However, the contaminants that have passed through this screen, while still contained in the sewage 10, flow into the first sedimentation basin 71 provided downstream thereof. In the first settling basin 71, heavy substances among the impurities contained in the inflowing sewage 10 are settled (sedimented) by gravity. Non-sedimentary contaminants are discharged (overflow) from the final settling basin 73. It should be noted that the substances that initially settle in the settling basin 71 include not only contaminants but also sand and mud deposited on the sewage pipe and the sewer trunk line, which have flowed in together with the sewage 10 (hereinafter, What is first settled in the settling basin 71 is also referred to as "raw sludge 62"). The water that first flowed out (overflowed) from the overflow weir of the settling basin 71, that is, the primary treated water 82, flowed into the reaction tank 72 together with the returned sludge 61a described later, and was aerated by air, high-concentration oxygen, or the like. After that, it is discharged from the reaction tank 72 as sludge mixed water 83. The sludge mixed water 83 flows into the final settling basin 73, and the sludge component of the sludge mixed water 83 is settled (sedimented). At this time, the contaminants contained in the sludge mixed water 83 are also settled (sedimented) together with the sludge content (the sediment settled in the final settling basin 73 is also referred to as "activated sludge 61"). The water flowing out (overflowing) from the overflow weir of the final settling basin 73, that is, the secondary treated water 84, flows into an ozone treatment facility or other advanced treatment facility 74, which may be provided, and is highly treated and highly treated. It is discharged as water 85. The highly treated water 85 is disinfected in the chlorine mixing pond 75 and discharged into the river as discharged water 86. On the other hand, a part of the activated sludge 61 is sent to the sludge treatment plant 88 as excess sludge 61b, and the rest is flowed into the reaction tank 72 as return sludge 61a.

(Sludge treatment plant)
The raw sludge 62 and the surplus sludge 61b are mixed or separately sent to the sludge treatment plant 88. The raw sludge 62 and / or the surplus sludge 61b (hereinafter, also simply referred to as “sludge 38”) flows into the cutting device 30 provided in the sludge treatment plant 88, and the contaminants contained in the sludge 38 are cut by the cutting device 30. Will be done. The sludge 39 containing the cut material, which has flowed out from the cutting device 30, is a gravity concentrating facility (sludge distribution tank 89 and a gravity concentrating tank 90. If the sludge distribution tank 89 is not provided, the gravity concentrating tank 90 is provided thereafter. Is sent to.). The sludge concentrated by the gravity concentrator is sequentially treated in the digestion tank 91, the dehydrator 92, and the incinerator 94. On the other hand, the digestion gas generated in the digestion tank 91 is sent to, for example, a boiler, an incinerator 94, a gas engine generator, etc. via the desulfurization apparatus 93. The digestion tank 91, the desulfurization device 93, and the incinerator 94 may not be provided.

In addition, although scum is generated in the gravity concentration facility, the generated scum may be mixed with the sludge sent from the sewage treatment plant. As a means for mixing the scum into the sludge sent from the sewage treatment plant, for example, a device such as a scum skimmer that collects the scum is attached at the height of the liquid level of the gravity concentrating facility. Then, the collected scum can be returned to the sludge sent from the sewage treatment plant by piping and mixed with the sludge.

In the case of the sludge treatment plant 88 in which the sludge distribution tank 89 is not provided, the sludge 39 containing the cut pieces flows into the gravity concentration tank 90. When the raw sludge 62 and the surplus sludge 61b are sent to the sludge treatment plant 88 by different routes (piping), only the raw sludge 62 flows into the cutting device 30 and the surplus sludge 61b is sent to the cutting device 30. It may flow directly into the gravity concentrator without flowing into the equipment.

It is assumed that the "sludge 38" contains impurities, and that the "sludge 39" contains impurities (cuts) cut by the cutting device 30.

Contaminants can be collected on a screen provided at a pumping station or sand basin, but they are generally not collected on the same screen due to the variety of contaminants (eg, size and length). There are also impurities that are transmitted through the screen. The contaminants that have passed through the screen are first extracted from the settling basin 71 as raw sludge 62, and then extracted from the final settling basin 73 as excess sludge 61b, and sent to the sludge treatment plant.

(Scum)
The sludge sent to the gravity concentrating facility is settled by gravity to facilitate subsequent dehydration, and solid-liquid separation is performed to concentrate the sludge. When this solid-liquid separation is performed, sludge containing impurities floats from the liquid to the liquid surface and becomes a scum. The scum refers to a sponge-like or lump-like foreign substance floating on the liquid surface of the sewage flowing through the sewage treatment plant 70 and the sludge flowing through the sludge treatment plant 88. In addition, some scums gradually harden while floating on the liquid surface. In particular, in the gravity concentration facility, the sludge containing impurities sent to the facility is the sludge that has surfaced on the liquid surface.

There are various causes of scum. The scum generated by the generation of gas in sludge is considered to be generated as follows, for example.

The sludge solid concentration of the sludge 38 to which the scum is sent to the gravity concentrating facility is about 10 to 40 kg / m ³ , and nitrate nitrogen, nitrite nitrogen and the like are dissolved in the liquid containing this sludge. When sludge is stored in the gravity concentrating facility, the liquid containing sludge becomes anaerobic (that is, a state where dissolved oxygen is low), and oxygen atoms and hydrogen atoms bonded to nitrate nitrogen, nitrite nitrogen, etc., that is, oxygen Minutes and hydrogen are consumed and the chemical reaction that produces innumerable nitrogen gases is promoted, that is, the denitrification reaction shown in the following formula (1) is promoted.
[Chemical 1]
aHNO _X → bH ₂ O + cN ₂ ↑ ・ ・ ・ Equation (1)
Here, _X = 2 or 3, and a, b, and c are coefficients.
Nitrogen gas has a lower specific gravity than the same liquid and rises from the liquid to the liquid surface. At this time, sludge containing impurities floats together with nitrogen and is scummed.

Further, in the gravity concentrating facility, oxygen is dissolved in a liquid containing sludge stored in the gravity concentrating facility. This oxygen is called dissolved oxygen, and when this dissolved oxygen decreases, the liquid containing sludge becomes anaerobic. Under this state, for example, sulfate is reduced by sulfate-reducing bacteria to generate hydrogen sulfide gas. Also, acidic fermentation can occur. Furthermore, the liquid containing sludge may become viscous due to fats and oils.

Among the impurities in the sludge, for example, hair, fibers, toilet paper, food waste, oils and fats, mud, sand, etc. may adhere to each other or via sludge and become enlarged. A large amount of sludge adheres to the bloated impurities and becomes a lump. When this mass floats on the liquid surface and becomes a scum, it easily gets caught in burrs, rakes, and overflows of various facilities. Further, when a plurality of scums float on the liquid surface, they gradually adhere to each other scums to form a large mass of scums and grow. If this large mass of scum is left unattended, the entire liquid level of the gravity concentrator will be covered with the mass of scum, and as a result, the operation of the gravity concentrator will be seriously hindered.

In addition, when the scum rots, it solidifies, and the solidified scum can cause blockage in the pipe. Hydrogen sulfide, which is a toxic gas, is generated from scum, which may corrode equipment and cause odor, resulting in deterioration of the working environment. Some of the impurities contained in the scum are 50 cm to 100 cm or more, and when the scum containing the contaminants is sent to the next process, it may get entangled in the digestion tank 91, the dehydrator 92, the equipment piping, the waterway, etc. , Stagnation and causes problems in proper operation.

In order to avoid such deterioration, at present, measures such as manually removing the scum manually, sucking it with a suction device, and hydraulically cleaning it are taken to suppress the growth of the scum. ing. However, these measures have not been the ultimate solution to the generation and growth of scum.

Therefore, taking measures to prevent the enlargement of contaminants can suppress the generation and growth of scum as a result. As a means for suppressing the enlargement of contaminants, known means can be adopted, but it is preferable to use the cutting device 30 shown below. The contaminants cut to an appropriate size by the cutting device 30 are less likely to be entangled with each other and to be bundled, and as a result, are less likely to be enlarged.

(Cutting device)
As the cutting device, the configuration of the cutting device is not particularly limited as long as it is crushed by a cutting blade, but the cutting device 30 shown in the present embodiment can be preferably used for cutting contaminants. .. Further, the cutting device disclosed in Patent Document 3 and Patent Document 4 and the product "Rotacut" sold by Tsukishima Technomente Service Co., Ltd. may be used. The cutting device 30 shown in the present embodiment intersects the cutting blade 35 held by the holder 32 that rotates around the rotation axis of the sludge 38 in the flow direction 38b and the sludge 38 in the flow direction 38b in the flow of the sludge 38. It is possible to provide a facing plate 34 having a plurality of through holes 34a. Further, the flow direction 38b and the rotation axis of the holder 32 may be parallel or may have an acute angle. The cutting blade 35 may have a cutting blade main body as a blade, or may have a rotary blade 35b provided with a cutting edge 35a. The contaminants are sandwiched between the cutting blade 35 and the facing plate 34, and are cut by receiving a shearing force. Explaining with reference to FIG. 3, the cutting device 30 is provided with a cutting blade 35 (rotary blade 35b and a cutting edge 35a provided on the rotary blade) facing the facing plate 34 surface. A plurality of transmission holes 34a penetrating the facing plate 34 are provided on the surface of the facing plate 34. The facing plate 34 may or may not include a blade. When the blade is provided, for example, the blade may be provided on the upstream side surface 34A of the sludge 38 in the facing plate 34, or the edge of the through hole may be formed in a blade shape. The form of the facing plate 34 may be a net-like one, or a so-called net blade in which the net itself is a cutting edge. Further, a perforated plate, a cribriform plate, or a lattice plate may be used, and a form in which the edge of the through hole in the perforated plate, the cribriform plate, or the lattice plate is formed by the cutting edge can be presented. Further, as shown in FIG. 6, it may be in the form of a facing plate in which transmission holes 34a having a substantially quadrangular shape or a substantially triangular shape are arranged while gradually expanding from the center to the outside in a spiral shape.

The cutting blade 35 may be installed so as to rotate in a state of facing or in contact with the facing plate 34. When arranged in this way, the contaminants staying (or being caught) on the facing plate 34 among the impurities contained in the first treatment liquid flowing through the cutting apparatus 30 are cut by the rotating cutting blade 35, which is preferable. The cutting blade 35 may be installed on the upstream side in the sludge flow direction with respect to the facing plate 34.

The cutting blade 35 is provided in a rotatable holder 32, and when the holder 32 rotates, the cutting blade 35 rotates along the upstream plane 34A. The cutting blade 35a and the upstream plane 34A of the facing plate 34 rotate in close or in contact with each other.

When the cutting blade 35 is in contact with the upstream flat surface 34A of the facing plate 34, the rotation of the cutting blade 35 causes the cutting blade 35 to scrape off the contaminants adhering to the upstream flat surface 34A, and the contaminants are surely removed. It is suitable for being cut into. As an example of a means for maintaining the state in which the cutting edge 35a of the cutting blade 35 is in contact with the upstream flat surface 34A, the holder 32 provided in the cutting blade 35 is moved from the cutting blade 35 toward the facing plate 34 (biasing direction) 42. The means 33a for urging the vehicle can be mentioned. As a result, the cutting blade 35 can rotate while being pulled (biased) in the urging direction 42 and in contact with the upstream plane 34A of the facing plate 34. As the urging means 33a, known means such as a spring and a hydraulic cylinder can be used. The holder 32 may be rotated by a gear motor or the like.

The cutting blade 35 can be formed in the shape of a rotary blade. In this case, the number of blades can be set as appropriate. For example, it may be one sheet, or it may be any number of 2 to 8 sheets such as 2, 3, 4, 5, 5, and 8.

The shape of the transmission hole 34a of the facing plate 34 is not particularly limited, and for example, a plurality of polygons having a substantially circular shape, a substantially triangular shape to a substantially hexagonal shape, a grid shape, a net shape, or the like can be provided. The width (or diameter) of the transmission hole 34a can be appropriately set, and is preferably 10 to 40 mm because impurities are appropriately cut and transmitted through the transmission hole 34a.

In the cutting device 30 of the present embodiment, the inflow portion 36 into which the sludge 38 sent from the sewage treatment plant flows in, and the outflow where the cut material obtained by cutting the contaminants contained in the sludge 38 flows out. The unit 37 can be provided. The facing plate 34 is provided on the downstream side of the inflow portion 36 and on the upstream side of the outflow portion 37. The facing plate 34 is provided so as to intersect the inflow direction 38a of the sludge 38 in the inflow portion 36. The sludge 38 can be made to flow into the inflow section 36 in the flow direction 38a, pass through the facing plate 34 without changing the flow direction 38a, and flow out from the outflow section 37. However, the sludge 38 that has flowed into the inflow section 36 in the flow direction 38a may change the flow direction 38b to pass through the facing plate 34 and flow out from the outflow section 37. The angle θ formed by the facing plate 34 (that is, the inclination 34r of the facing plate 34 surface) and the inflow direction 38a of the sludge 38 in the inflow portion 36 of the cutting device 30 may be a right angle, but as shown in FIG. Then it is preferable. In particular, it is preferable that the angle θ when the angle is acute is 15 ° or more. When the angle is sharp, the contaminants are easily caught by the facing plate 34 and stay there, so that the amount of contaminants to be cut increases, and as a result, the sludge 39 containing a large amount of the cut contaminants flows out from the cutting device 30. When the angle θ is smaller than 15 °, the inflow direction 38a of the sludge 38 and the plane of the facing plate 34 are close to parallel, and the speed at which the sludge 38 penetrates the facing plate 34 surface is hydraulically reduced. The flow rate of the sludge 38 that permeates the facing plate 34 is reduced, and as a result, the amount of sludge processed per unit time is reduced.

As shown in FIGS. 4 and 10, the facing plate 34 and the cutting blade 35 can be provided in the casing. The casing can be composed of two chambers, and a facing plate 34 may be provided so as to partition the first chamber 40 and the second chamber 41. The first chamber is provided with the above-mentioned cutting blade 35 and the inflow portion 36, and the second chamber is provided with the outflow portion 37. In this case, the holder 32 provided in the cutting blade 35 may be extended toward the second chamber and arranged so as to extend to the urging means 33a provided in the upper part of the second chamber. The sludge 38 that has flowed into the first chamber passes through the facing plate 34 and is guided to the second chamber, and is discharged from the outflow portion 37 as sludge 39 after passing through the cutting device 30. The flow direction of the sludge 38 in the first chamber 40 changes at any time depending on the inner wall 40a forming the first chamber 40. Sludge 38 flowing in the direction of passing through the facing plate 34 in the first chamber penetrates the facing plate 34. Further, as an example, when viewed in the inflow direction 38a of the sludge 38 in the inflow portion 36 (that is, when projected from the left to the right of the paper surface in FIG. 4), all or part of the position of the outflow portion 37 flows in. It may be provided so as to overlap the position of the portion 36. In other words, the inflow portion 36, the cut portion, and the outflow portion 37 may be provided in order on the same straight line along the flow of the sludge 38. Further, the position of the outflow portion 37 may be provided so that all or a part thereof does not overlap on the extension line in the inflow direction of the sludge 38 flowing through the inflow portion 36. As an example, on the paper of FIG. 10, the entire outflow portion 37 is located below the virtual line 36a extending from the lower end of the inflow portion 37 in the inflow direction. When the sludge 38 is provided in an overlapping manner, the resistance to the flow of the sludge 38 is small, and when the sludge 38 is provided so as not to overlap, the resistance to the flow of the sludge 38 is large. Specifically, if the outflow portion is not located on the inflow direction axis of the sludge in the inflow portion and is arranged so as to be offset from the inflow direction axis, the sludge flow direction from the inflow portion to the outflow portion is changed. It has changed, and the loss of water pressure is relatively large. On the other hand, since the outflow portion is located on the inflow direction axis of the sludge in the inflow portion, the sludge flow direction does not change significantly from the inflow portion to the outflow portion, and the water pressure loss is relatively small.

Further, a cutting device having a facing plate 34 and a cutting blade 35 may be provided in a water channel or a pipe through which sludge 38 flows without providing a casing. In this case, needless to say, the cutting blade 35 is arranged on the upstream side and the facing plate 34 is arranged on the downstream side of the sludge 38 in the flow direction.

All of the sludge 38 may be permeated through the facing plate 34, or a part of the sludge 38 may be permeated, but it is preferable that all of the sludge 38 is permeated.

The contaminants contained in the sludge 38, particularly thread-like objects and strip-like objects, are cut by receiving a cutting force (shearing force) by the rotatable cutting blade 35 and / or the facing plate 34. Therefore, most of the contaminants contained in the sludge 39 after passing through the cutting device 30 have a length of 50 mm or less, so that they may adhere to or get entangled with various facilities provided on the downstream side of the cutting device 30. Can be suppressed.

Explaining another embodiment of the cutting device with reference to FIG. 7, the cutting device 130 is provided with a cutting blade 135 (a blade 135a attached to the rotary blade 135b) on the side facing the facing plate 134. .. The facing plate 134 is provided with a plurality of through holes penetrating the facing plate 134. The cutting blade 135 is provided with a holder 132 that is rotated by a gear motor 152 or the like, and the cutting blade 135 is rotated along the surface of the facing plate 134 by the rotation of the holder 132. The cutting blade 135 and the upstream side surface of the sludge 38 in the facing plate 134 are in contact with each other. A means 133 is provided for urging the cutting blade 135 in the direction (biasing direction) from the cutting blade 135 toward the facing plate 134 in order to bring the cutting blade 135 into contact with the facing plate 134. Further, the contaminants that cannot be completely cut and cannot pass through the facing plate 134 can be taken out from the take-out unit 151 provided in the lower part of the cutting device 130. Further, when the operation of the main body is stopped, the upper portion of the cutting device 130 (above the facing plate 134) can be moved counterclockwise with respect to the paper surface of FIG. 7 to open the cutting device 130 around the fulcrum shaft 100 provided in the main body 130. .. Then, the inside of the casing 136 can be visually recognized from above, and the maintenance inside the main body can be easily performed. When the cutting device 130 is operated with the upper portion of the cutting device 130 closed, the sludge 38 sent to the cutting device 130 permeates the facing plate 134, and as a result, the sludge 39 after passing through the cutting device 30 is released. can get.

Cutting device 30, the flow rate of the sludge 38 to be flowed into the cutting device 130 may When 15~300m ³ / h, in particular, preferably set to 20~180m ³ / h. If it is less than 15 m ³ / h, the total amount of sludge treated in the sludge treatment plant is small and the treatment process is hindered. If it is more than 300 m ³ / h, the shear length of the contaminants becomes long because the cutting device 30 and the cutting device 130 and the equipment piping block the contaminants and the speed of the sludge passing through the cutting portion increases. It may be difficult to obtain the desired shear length (size).

(Gravity concentration tank)
The sludge 39 that has passed through the cutting device 30 is sent to the gravity concentrating facility. The gravity concentration facility is composed of a sludge distribution tank 89 and a gravity concentration tank 90 installed downstream thereof. The gravity concentration facility may be composed of only the gravity concentration tank 90 without providing the sludge distribution tank 89.

The sludge 39 containing the cut material, which has flowed out from the cutting device 30, may be continuously flowed into the gravity concentrating facility or may be flowed intermittently. In the case of continuous inflow, it is advisable to prevent the concentration of sludge 38 sent from the sewage treatment plant from becoming too low. For example, when the raw sludge accumulated in the sludge extraction hopper of the first settling basin 71 is continuously extracted, the concentration of the extracted sludge gradually decreases with the passage of time. Even if low-concentration sludge is introduced into the gravity concentration facility, it takes a long time to be concentrated, which is not preferable. Considering this point, the sludge solid concentration of the sludge 38 is preferably 5 kg / m ³ or more. On the other hand, when flowing into the sludge intermittently, for example, the sludge 38 may flow into the gravity concentration facility so that the sludge solid concentration of the sludge 38 does not fall below 5 kg / m ³ . As for the intermittent interval, for example, it is preferable to stop the inflow of sludge 38 into the gravity concentrating facility, allow 6 hours (preferably 4 hours) to elapse, and then restart the inflow of sludge 38.

The sludge distribution tank 89 is a tank for temporarily storing sludge 39 containing cut contaminants. It has a function as a flow buffer for adjusting the flow rate of sludge flowing into the gravity concentration tank 90 according to the processing flow rate of the gravity concentration tank 90.

The gravity concentration tank 90 is a tank in which the inflowing sludge 39 is settled by gravity to form concentrated sludge, which is separated from the supernatant liquid 103. In addition, it is a tank that is responsible for scraping concentrated sludge. The scraper 96 provided in the gravity concentrating facility guides the concentrated sludge settled at the bottom of the gravity concentrating facility to the sludge extraction portion provided at the bottom of the gravity concentrating facility. The sludge extraction portion and the digestion tank 91 are connected by a sludge pipe or the like. The sludge extraction pump 97 provided in the sludge pipe or the like sends the concentrated sludge accumulated in the sludge extraction portion to the digestion tank 91. As the scraper 96, a known scraper 96 can be appropriately used, and the scraper 96 of the present embodiment is an example. The scraper 96 includes a scraping blade 96r that rotates in close proximity to or in contact with the bottom of the gravity concentrating equipment, a rotating shaft 96s that rotates the scraping blade 96r, and a motor 96m that rotates the rotating shaft 96s. The scraping blade 96r scrapes the concentrated sludge that has settled at the bottom of the gravity concentration facility to the sludge extraction section, and the concentrated sludge extracted from the sludge extraction section by the sludge extraction pump 97 is sent to the digestion tank 91, which is the next step. The supernatant 103 flows out (overflows) from the overflow weir provided in the upper part of the peripheral wall of the gravity concentration tank 90.

The peripheral speed of the scraping blade 96r is preferably 1 to 5 m / min, more preferably 2 to 4 m / min. If the peripheral speed exceeds 5 m / min, the concentrated sludge will be diluted and the sludge will be insufficiently concentrated. If it is less than 1 m / min, the resistance of the excessively concentrated sludge becomes strong, and excessive torque is applied to the scraping blade 96r, which causes premature wear.

Contaminations of relatively large size adhere to each other and become bloated, become viscous, and solidify, which causes damage to the scraper 96. For this reason as well, it is preferable that the sludge 38 containing the contaminants is cut into an appropriate size by the cutting device 30 prior to flowing into the gravity concentrating facility. Since the cut contaminants have a relatively small size, they are less likely to adhere to each other, and the enlargement of the contaminants is suppressed.

The sludge 39 that has flowed into the gravity concentration facility settles and is concentrated over time to form a layer of concentrated sludge. The lower layer 101 of the concentrated sludge layer receives the consolidation from the upper layer 102 and becomes an over-concentrated and densified layer of concentrated sludge. The densified layer of concentrated sludge is highly viscous and may cause clogging (clogging) of sludge piping and the like. In such a case, even if the sludge extraction pump 97 is operated, the sludge of a desired flow rate cannot be sent to the digestion tank 91, which hinders the continuous operation of the sludge treatment plant 88. Further, if the sludge is allowed to stay in the gravity concentrating facility for a long time, the inside of the tank becomes anaerobic, the denitrification reaction is promoted, and hydrogen sulfide and carbon dioxide are generated. Then, sludge containing impurities floats along with the floating of these gas gases in the liquid, and as a result, scum is generated, proliferated, and causes enlargement.

Known means can be used as a means for preventing the density of concentrated sludge, and one example is a method for controlling the residence time of sludge in a gravity concentrating facility. The residence time (h) of the gravity concentrating facility is defined by the following equation. When the gravity concentration facility is composed of the sludge distribution tank 89 and the gravity concentration tank 90, the residence time (h) of the gravity concentration facility is the sum of the residence time of the sludge distribution tank 89 and the residence time of the gravity concentration tank 90. Say time. When the gravity concentrating equipment consists of only the gravity concentrating tank 90, the residence time (h) of the gravity concentrating equipment means the residence time of the gravity concentrating tank 90.
[Number 1]
(Dwelling time of gravity concentrating equipment) = (Volume of gravity concentrating equipment (m ³ )) / (Flow rate of sludge flowing into gravity concentrating equipment (m ³ / h))
Similarly, the residence time (h) of the sludge distribution tank 89 is defined by the following equation.
[Number 2]
(Stay time of sludge distribution tank 89) = (Volume of sludge distribution tank 89 (m ³ )) / (Flow rate of sludge flowing into sludge distribution tank 89 (m ³ / h))
Similarly, the residence time (h) of the gravity concentration tank 90 is defined by the following equation.
[Number 3]
(Dwelling time of gravity concentration tank 90) = (Volume of gravity concentration tank 90 (m ³ )) / (Flow rate of sludge flowing into gravity concentration tank 90 (m ³ / h))

The residence time of sludge in the gravity concentrating facility is preferably 12 hours or less, preferably 10 hours or less, and more preferably 8 hours or less. If it exceeds 12 hours, the sludge will rot and the scum will become bloated. Further, although it depends on the concentration of the dry solid matter of the sludge 39 flowing into the gravity concentration facility, it is preferable to allow the sludge to stay for 30 minutes or more. If it is less than 30 minutes, the sludge will not settle sufficiently and the desired concentration will not be achieved, which will hinder the sludge incineration in the subsequent steps.

Further, a known means can be used as a means for preventing the density of concentrated sludge, and another example is a method for controlling a solid matter load (kg / (m ² · day)) in a gravity concentration facility. Can be done. The solid matter load is defined by the following equation.
[Number 4]
(Sludge load) = (Amount of input sludge ((m ³ / day)) x (Concentration of input sludge solid (kg / m ³ )) x (Gravity concentration facility water area (m ² ))
Here, the input sludge solid matter concentration means the concentration of sludge 39 flowing into the gravity concentrating facility.

The solid load should be 100 kg · DS / (m ² · day) or less. Further, 30 to 90 kg / DS / (m ² / day) is better, and 50 to 60 kg / DS / (m ² / day) is preferable. In the present embodiment, the contaminants are sheared by the cutting device to a predetermined size, so that the generation of scum in the gravity concentrator is suppressed. However, if the generation of scum exceeds 100 kg / DS / (m ² / day), it causes sludge putrefaction, a large amount of scum, and enlargement.

If sludge flows into the gravity concentrating facility in excess of a predetermined solid matter load, the sludge concentration in the gravity concentrating facility becomes too high, and the generation of gas (bubbles) is accelerated. As a result, the ascent of large lumps in the liquid is accelerated, resulting in a large amount of scum.

By setting the load to a predetermined solid matter or less, the generation of gas (bubbles) can be suppressed, and as a result, the generation of scum is suppressed.

The concentrated sludge may be withdrawn from the sludge extraction portion continuously or intermittently.

The effective water depth of the gravity concentrator is preferably 4 m or more, and controlling the sludge interface to be lower than 2 m from the liquid level is preferable because the risk of sludge overflow can be prevented.

As described above, large-sized impurities adhere to or become entangled in the sludge treatment plant's equipment, but it is desirable to cut the hair appropriately because the hair becomes coarse. When the hair is present in the sludge 38, organic substances, oils and fats, and other hair adhere to the cuticle portion on the surface of the hair. In addition, when these adhere, bacteria propagate. Since the hair is made of enamel-like tissue, it is hard and is not easily biodegraded and remains in the sewage treatment facility. If there are a plurality of hairs, they may be entangled with each other to form a bundle or connected in the length direction, and may exceed 50 cm. Furthermore, fibers, sludge and other contaminants adhere to the bundled hair groups and become enlarged and become large lumps. This large mass adheres to the piping and various equipment, blocking the flow of sludge and hindering the stable operation of the equipment.

One or more sludge distribution tanks 89 and one or more gravity concentration tanks 90 may be provided. For example, when two sludge distribution tanks 89 and two gravity concentration tanks 90 are provided as shown in FIG. 9, an upstream pipe (that is, a pipe through which sludge 39a1 flows) connected to an inflow portion of the first sludge distribution tank). The first cutting device 301 may be installed in the above, and the second cutting device 302 may be installed in the upstream pipe (that is, the pipe through which the sludge 39a2 flows) connected to the inflow portion of the second sludge distribution tank. In this case, piping is provided so that the sludge 38 flows into each of the first cutting device 301 and the second cutting device 302. Further, it is also possible to provide a bypass pipe in which the sludge flowing out from the first cutting device 301 and the second cutting device 302 are mixed. The first downstream pipe (that is, the pipe through which sludge 39b1 flows) connected to the outflow portion of the first sludge distribution tank 891 and the second downstream pipe (that is, the sludge 39b2) connected to the outflow portion of the second sludge distribution tank 892 The flowing pipe) may be separately connected to the first gravity concentration tank 901 and the second gravity concentration tank 902, respectively. Further, a confluence pipe (bypass pipe) at which the first downstream pipe and the second downstream pipe are once merged is provided, and the sludge 39b1 discharged from the first sludge distribution tank 891 and the sludge 39b1 discharged from the second sludge distribution tank 892 are discharged. The sludge 39b2 may be mixed with the sludge 39b2. It is preferable that sludge flows into the first gravity concentrating tank 901 from the downstream of the first downstream pipe and sludge flows into the second gravity concentrating tank 902 from the downstream of the second downstream pipe. When the piping is provided in this way, for example, when the first gravity concentrating tank 901 breaks down, the inflow of sludge into the first gravity concentrating tank 901 is stopped and the sludge 39b1 is passed through the confluence pipe to the first. 2 It is possible to flow into the gravity concentration tank 902. Then, the first cutting device 301, the second cutting device 302, the first sludge distribution tank 891, the second sludge distribution tank 892, and the second gravity concentration tank 902 are used without urgently stopping the operation of the sludge treatment plant 88. It will be possible to continue operation.

It is also preferable that the cutting device 30 is provided in the upstream pipe connected to the sludge distribution tank 89 and the downstream pipe (for example, a piping portion connecting the sludge distribution tank 89 and the gravity concentration tank 90). The sludge 38 is cut by the cutting device 30 provided on the upstream side, and the generation of scum in the sludge distribution tank 89 is suppressed. Further, the sludge flowing out from the sludge distribution tank 89 is further cut by the cutting device 30 provided in the downstream pipe, and the generation of scum in the gravity concentration tank 90 is further suppressed.

In the present specification, the sludge treatment facility including the cutting device 30 and the gravity concentration tank 90 (including the sludge distribution tank 89 when the sludge distribution tank 89 is provided) in the sludge treatment plant 88 is referred to as a sludge treatment facility.

The sewage of the present embodiment is not particularly limited, but for example, septic tank drainage, agricultural / fishery village drainage, rainwater, factory drainage, workplace drainage, unknown water, underflow water, spring water, groundwater, industrial water, sewage pipe water. , Sewerage trunk water, raw sludge, active sludge, sewage treatment plant and / or process water flowing through each treatment process of the sludge treatment plant.

The terms described in this specification are based on the terms described in "Japan Sewerage Association: Sewerage Facility Planning / Design Guidelines and Explanation 2001 Edition".

The sludge treatment method and sludge treatment equipment disclosed in the present invention are not particularly limited, and can be used in, for example, public sewerage, basin sewerage, and urban sewerage sewage treatment facility.

10 Sewage 30 Cutting device 32 Holder 34 Facing plate 34A Upstream plane 34a Permeation hole 35 Cutting blade 38 Sludge 39 Sludge 89 Sludge distribution tank 90 Gravity concentration tank of the first treatment liquid in the facing plate

The present invention relates to a sludge treatment method and a sludge treatment facility.

Conventionally, sewage such as domestic effluent, business establishment effluent, and factory effluent is drained to a sewage pipe, and is collected and treated at a sewage treatment plant via a relay pumping station and a sewer trunk line. The treated water is discharged into rivers and the sea.

The drained sewage includes, for example, plastics, underwear, rags, fibers such as absorbent cotton, and various impurities such as waste cloth, toilet paper, and hair. These contaminants cannot be discharged into rivers or the sea together with the water treated at the sewage treatment plant, for example, they are collected by screens installed in the sand basins of relay pumping stations and sewage treatment plants and are industrial waste. Is processed as.

Many of the contaminants penetrate the screen, and the contaminants that penetrate the screen flow into the first sedimentation basin, which is provided downstream of the sand basin, while still contained in the sewage.

Of the contaminants that first flowed into the settling basin, those that settled are first extracted from the settling basin as raw sludge and sent to the sludge treatment plant. Of the impurities that flowed out (overflow) from the first settling basin without settling, those that flowed into the final settling basin settled with the settling of activated sludge, and these sediments were pulled out from the final settling basin and used as surplus sludge. Sent to a sludge treatment plant. The sludge (raw sludge and / or excess sludge) sent to the sludge treatment plant is concentrated by a gravity concentrating facility and volume-reduced by a dehydrator or an incinerator, which is a downstream facility.

By the way, there is a problem that scum is generated in various facilities of the sewage treatment plant and the sludge treatment plant. Scum is not a little generated in places where sludge and contaminants are present, but it is generated in large quantities especially in gravity concentrating facilities where sludge is temporarily stored. It is desirable to eliminate this scum as much as possible because it causes problems such as blockage of equipment piping, generation of hydrogen sulfide, deterioration of returned water, and reduction of equipment volume.

Examples of the scum elimination method include methods such as human power, recovery by a suction device, crushing by a crushing device, and suppression of scum destruction and growth by hydraulic cleaning, but the scum must be eliminated each time it occurs. It is not a fundamental countermeasure.

Patent Document 1 and Patent Document 2 are techniques related to a method for treating contaminants that cause scum. Patent Document 1 is a technique for making equipment compact by providing a crushing pump for crushing contaminants mixed in organic sludge, and Patent Document 2 crushes concentrated raw sludge with a raw sludge crusher and crushes it. This is a technique in which sludge flows into a denitrification tank and is used as a BOD source, but neither technique suppresses the generation of scum.

Japanese Patent No. 4235591 Japanese Unexamined Patent Publication No. 2001-205300 Special Table 2012-521285 Special Table 2013-537103

A main problem to be solved by the present invention is to provide a sludge treatment method and a sludge treatment facility for suppressing the generation of scum in a gravity concentration facility.

Typical aspects of the present invention that have solved the above problems are as follows.

<First aspect>
This is a sludge treatment method in which sludge sent from a sewage treatment plant is allowed to flow into a gravity concentration facility installed in a sludge treatment plant and settled by gravity to obtain concentrated sludge.
In the flow of the sludge, the contaminants contained in the sludge are cut to a predetermined size to obtain a cut product.
Sludge containing the cut material is allowed to flow into the gravity concentrating facility.
A sludge treatment method characterized by that.

The contaminants contained in the sludge are one of the factors that generate scum in the gravity concentrator. The contaminants adhere to each other and become entangled to form a bundle (contamination group). A large amount of sludge adheres to this group of impurities and forms a large mass.

In addition, the sludge that has flowed into the gravity concentration facility settles due to gravity over time and is concentrated to form a layer of concentrated sludge. Oxygen is dissolved in the layer of this concentrated sludge, and under an anaerobic state, this oxygen is consumed by the concentrated sludge, and gases (bubbles) such as nitrogen, carbon dioxide, and hydrogen sulfide are generated. Gas (bubble) has a lighter specific gravity than liquid and floats from the liquid to the liquid surface. When the gas (bubbles) floats, the above-mentioned large mass to which the gas (bubbles) adheres also floats and floats on the water surface. This large floating mass is a scum.

If the contaminants that cause scum are cut to a predetermined size in advance before becoming a contaminant group to make a cut, the cuts will adhere to each other and become less likely to be entangled, so that the contaminant group is less likely to occur. ..

<Second aspect>
In addition to the first aspect,
Sludge containing the cut material is intermittently flowed into the gravity concentrating facility.
Aspects can be mentioned.

Not a little oxygen molecules are dissolved in the sludge sent from the sewage treatment plant to the sludge treatment plant. That is, it contains dissolved oxygen. When sludge containing dissolved oxygen flows into the gravity concentrating facility, the anaerobic state is alleviated and gasification (bubbles) is suppressed. Further, when the sludge is allowed to flow intermittently, the raw sludge and excess sludge are settled to some extent and the concentration becomes appropriate, so that the concentration efficiency in the gravity concentrating facility is good.

<Third aspect>
In addition to the first aspect,
The sludge is raw sludge,
Aspects can be mentioned.

Contaminants are overwhelmingly contained in the raw sludge settled in the first settling basin than in the activated sludge settled in the final settling basin. By cutting the contaminants contained in the raw sludge, it has the effect of suppressing the contamination of the contaminants.

<Fourth aspect>
In addition to the first aspect,
The scum generated in the gravity concentration facility is mixed with the sludge sent from the sewage treatment plant.
Aspects can be mentioned.

For example, if the scum is destroyed by hydraulic cleaning, the destroyed scum will sink. In other words, when the scum is destroyed, the gas (bubbles) adhering to the scum is separated from the scum, so that the scum cannot keep floating on the liquid surface and sinks.

In the process of mixing the scum into the sludge and flowing it into the cutting device, the gas (bubbles) contained in the scum is separated from the scum. By letting the sludge discharged from the cutting device flow into the gravity concentrating facility, as a result, the amount of scum excluded from the system is reduced.

<Fifth aspect>
In addition to the first aspect,
The cut piece is cut by a cutting device and
The cutting device includes a cutting blade held by a holder that rotates around a rotation axis in the sludge flow direction, and a facing plate having a plurality of through holes provided intersecting with the sludge flow. The cutting blade rotates in a state of being close to or in contact with the facing plate.
Aspects can be mentioned.

Of the impurities contained in the sludge sent to the cutting device, the impurities having a size that cannot pass through the through holes of the facing plate stay (catch) on the facing plate. The contaminants that have stayed (caught) on the facing plate are cut by the rotation of the cutting blade. The contaminants remaining on the facing plate are cut and permeate through the through holes along the flow of sludge.

If the contaminants remain attached to the facing plate, the continuous or intermittent inflow of sludge may cause the contaminants to gradually accumulate on the facing plate, solidify or enlarge, resulting in blockage of the facing plate. is there. When the cutting blade is rotated in a state of facing or in contact with the facing plate, impurities adhering to the facing plate are scraped off by the cutting blade. As a result, it is possible to prevent impurities from accumulating on the facing plate.

<Sixth aspect>
The sludge sent from the sewage treatment plant is allowed to flow into a cutting device provided on the upstream side of the gravity concentrating facility.
The cutting device has an inflow portion into which the sludge flows in, a cutting portion in which contaminants contained in the sludge are cut, and an outflow portion in which the cut product obtained by cutting is discharged.
The inflow portion, the cut portion, and the outflow portion are sequentially arranged on the same straight line along the flow of the sludge.
Aspects can be mentioned.

Since the inflow part, the cutting part, and the outflow part are arranged in order on the same straight line along the sludge flow, the sludge flow direction does not change significantly from the inflow part to the outflow part, and the pressure due to the sludge flow does not change significantly. Has the effect of small loss. Further, since the sludge flows in a straight line direction, the pressure loss is small, and it is possible to prevent the sludge from staying at a specific place in the cutting device and corroding.

<7th aspect>
A cutting device in which impurities contained in sludge sent from a sewage treatment plant are cut in the sludge flow to obtain a cut piece.
It is provided with a gravity concentration facility in which sludge containing the cut pieces is settled by gravity to obtain concentrated sludge.
A sludge treatment facility characterized by this.

The same effect as in the first aspect can be obtained.

According to the present invention, the generation of scum is suppressed in the gravity concentrating facility.

It is a figure which shows the flow which treats sewage. It is a figure which shows the flow which treats sewage. It is explanatory drawing of the cutting device. It is explanatory drawing of the angle formed by the facing plate and the inflow direction of sludge in the inflow part. It is a figure which shows the main part of crushing of a cutting apparatus. It is a figure which shows an example of the facing plate. It is a figure which shows another form of the cutting apparatus. It is a figure which shows the gravity concentration tank. It is a figure which shows the flow which treats sewage. It is explanatory drawing of the cutting device.

A mode for carrying out the present invention will be described. The embodiment of the present invention is an example of the present invention.

(sewage)
Conventionally, sewage was mainly composed of domestic wastewater, industrial wastewater, and business site wastewater. In addition, sewage may be contaminated with plants such as branches and leaves, stems and grass, and soil. In recent years, taking advantage of the economies of scale of sewage treatment plants, there is a tendency to incinerate sludge generated by consolidating septic tank wastewater, agricultural wastewater, food waste, diapers, etc. into the sewerage system to convert it into energy. However, if these are allowed to flow into a sewage treatment plant together with sewage and are intensively treated, the amount of contaminants will also increase.

(Contaminants)
Contaminants contained in the sewage of sewage treatment facilities (for example, pump stations, storage pipes, sewage pipes, sewage pipes, sewer trunk lines, pumped sludge pipes, sewage treatment plants, etc.) include plastics and underwear. Examples thereof include fibers such as sewage and defatted cotton, waste cloth, toilet paper, hair, food waste, oil balls, oils and fats, diaper pieces, mud lumps, and sand lumps, but are not limited thereto.

(Sewage treatment facility)
The sewage treatment process is roughly as follows. Since sewage drained from homes and business establishments is sewage, it flows into sewer pipes and sewer trunk lines, and also flows into the sewage treatment plant 70 via a relay pumping station. The sewage 10 flowing into the sewage treatment plant 70 passes through a landing well, a sand basin, a first settling basin 71, a reaction tank 72, a final settling basin 73, an advanced treatment facility 74, a chlorine mixing basin 75, etc., in that order. , Released. The sand basin is provided with a screen having a plurality of slits as an example. Among the contaminants contained in the sewage 10, those that do not pass through the slit are collected and removed by this screen. However, the contaminants that have passed through this screen, while still contained in the sewage 10, flow into the first sedimentation basin 71 provided downstream thereof. In the first settling basin 71, heavy substances among the impurities contained in the inflowing sewage 10 are settled (sedimented) by gravity. Non-sedimentary contaminants are discharged (overflow) from the final settling basin 73. It should be noted that the substances that initially settle in the settling basin 71 include not only contaminants but also sand and mud deposited on the sewage pipe and the sewer trunk line, which have flowed in together with the sewage 10 (hereinafter, What is first settled in the settling basin 71 is also referred to as "raw sludge 62"). The water that first flowed out (overflowed) from the overflow weir of the settling basin 71, that is, the primary treated water 82, flowed into the reaction tank 72 together with the returned sludge 61a described later, and was aerated by air, high-concentration oxygen, or the like. After that, it is discharged from the reaction tank 72 as sludge mixed water 83. The sludge mixed water 83 flows into the final settling basin 73, and the sludge component of the sludge mixed water 83 is settled (sedimented). At this time, the contaminants contained in the sludge mixed water 83 are also settled (sedimented) together with the sludge content (the sediment settled in the final settling basin 73 is also referred to as "activated sludge 61"). The water flowing out (overflowing) from the overflow weir of the final settling basin 73, that is, the secondary treated water 84, flows into an ozone treatment facility or other advanced treatment facility 74, which may be provided, and is highly treated and highly treated. It is discharged as water 85. The highly treated water 85 is disinfected in the chlorine mixing pond 75 and discharged into the river as discharged water 86. On the other hand, a part of the activated sludge 61 is sent to the sludge treatment plant 88 as excess sludge 61b, and the rest is flowed into the reaction tank 72 as return sludge 61a.

(Sludge treatment plant)
The raw sludge 62 and the surplus sludge 61b are mixed or separately sent to the sludge treatment plant 88. The raw sludge 62 and / or the surplus sludge 61b (hereinafter, also simply referred to as “sludge 38”) flows into the cutting device 30 provided in the sludge treatment plant 88, and the contaminants contained in the sludge 38 are cut by the cutting device 30. Will be done. The sludge 39 containing the cut material, which has flowed out from the cutting device 30, is a gravity concentrating facility (sludge distribution tank 89 and a gravity concentrating tank 90. If the sludge distribution tank 89 is not provided, the gravity concentrating tank 90 is provided thereafter. Is sent to.). The sludge concentrated by the gravity concentrator is sequentially treated in the digestion tank 91, the dehydrator 92, and the incinerator 94. On the other hand, the digestion gas generated in the digestion tank 91 is sent to, for example, a boiler, an incinerator 94, a gas engine generator, etc. via the desulfurization apparatus 93. The digestion tank 91, the desulfurization device 93, and the incinerator 94 may not be provided.

In addition, although scum is generated in the gravity concentrating facility, the generated scum may be mixed with the sludge sent from the sewage treatment plant. As a means for mixing the scum into the sludge sent from the sewage treatment plant, for example, a device such as a scum skimmer that collects the scum is attached at the height of the liquid level of the gravity concentrating facility. Then, the collected scum can be returned to the sludge sent from the sewage treatment plant by piping and mixed with the sludge.

In the case of the sludge treatment plant 88 in which the sludge distribution tank 89 is not provided, the sludge 39 containing the cut pieces flows into the gravity concentration tank 90. When the raw sludge 62 and the surplus sludge 61b are sent to the sludge treatment plant 88 by different routes (piping), only the raw sludge 62 flows into the cutting device 30 and the surplus sludge 61b is sent to the cutting device 30. It may flow directly into the gravity concentrator without flowing into the equipment.

It is assumed that the "sludge 38" contains impurities, and that the "sludge 39" contains impurities (cuts) cut by the cutting device 30.

Contaminants can be collected on a screen provided at a pumping station or sand basin, but they are generally not collected on the same screen due to the variety of contaminants (eg, size and length). There are also impurities that are transmitted through the screen. The contaminants that have passed through the screen are first extracted from the settling basin 71 as raw sludge 62, and then extracted from the final settling basin 73 as excess sludge 61b, and sent to the sludge treatment plant.

(Scum)
The sludge sent to the gravity concentrating facility is settled by gravity to facilitate subsequent dehydration, and solid-liquid separation is performed to concentrate the sludge. When this solid-liquid separation is performed, sludge containing impurities floats from the liquid to the liquid surface and becomes a scum. The scum refers to a sponge-like or lump-like foreign substance floating on the liquid surface of the sewage flowing through the sewage treatment plant 70 and the sludge flowing through the sludge treatment plant 88. In addition, some scums gradually harden while floating on the liquid surface. In particular, in the gravity concentration facility, the sludge containing impurities sent to the facility is the sludge that has surfaced on the liquid surface.

There are various causes of scum. The scum generated by the generation of gas in sludge is considered to be generated as follows, for example.

The sludge solid concentration of the sludge 38 to which the scum is sent to the gravity concentrating facility is about 10 to 4 kg / m ³ , and nitrate nitrogen, nitrite nitrogen and the like are dissolved in the liquid containing this sludge. When sludge is stored in the gravity concentrating facility, the liquid containing sludge becomes anaerobic (that is, a state where dissolved oxygen is low), and oxygen atoms and hydrogen atoms bonded to nitrate nitrogen, nitrite nitrogen, etc., that is, oxygen Minutes and hydrogen are consumed and the chemical reaction that produces innumerable nitrogen gases is promoted, that is, the denitrification reaction shown in the following formula (1) is promoted.
[Chemical 1]
aHNO _X → bH ₂ O + cN ₂ ↑ ・ ・ ・ Equation (1)
Here, _X = 2 or 3, and a, b, and c are coefficients.
Nitrogen gas has a lower specific gravity than the same liquid and rises from the liquid to the liquid surface. At this time, sludge containing impurities floats together with nitrogen and is scummed.

Further, in the gravity concentrating facility, oxygen is dissolved in a liquid containing sludge stored in the gravity concentrating facility. This oxygen is called dissolved oxygen, and when this dissolved oxygen decreases, the liquid containing sludge becomes anaerobic. Under this state, for example, sulfate is reduced by sulfate-reducing bacteria to generate hydrogen sulfide gas. Also, acidic fermentation can occur. Furthermore, the liquid containing sludge may become viscous due to fats and oils.

Among the impurities in the sludge, for example, hair, fibers, toilet paper, food waste, oils and fats, mud, sand, etc. may adhere to each other or via sludge and become enlarged. A large amount of sludge adheres to the bloated impurities and becomes a lump. When this mass floats on the liquid surface and becomes a scum, it easily gets caught in burrs, rakes, and overflows of various facilities. Further, when a plurality of scums float on the liquid surface, they gradually adhere to each other scums to form a large mass of scums and grow. If this large mass of scum is left unattended, the entire liquid level of the gravity concentrator will be covered with the mass of scum, and as a result, the operation of the gravity concentrator will be seriously hindered.

In addition, when the scum rots, it solidifies, and the solidified scum can cause blockage in the pipe. Hydrogen sulfide, which is a toxic gas, is generated from scum, which may corrode equipment and cause odor, resulting in deterioration of the working environment. Some of the impurities contained in the scum are 50 cm to 100 cm or more, and when the scum containing the impurities is sent to the next process, it may get entangled in the digestion tank 91, the dehydrator 92, the equipment piping, the waterway, etc. , Stagnation and causes problems in proper operation.

In order to avoid such deterioration, at present, measures such as manually removing the scum manually, sucking it with a suction device, and hydraulically cleaning it are taken to suppress the growth of the scum. ing. However, these measures have not been the ultimate solution to the generation and growth of scum.

Therefore, taking measures to prevent the enlargement of contaminants can suppress the generation and growth of scum as a result. As a means for suppressing the enlargement of contaminants, known means can be adopted, but it is preferable to use the cutting device 30 shown below. The contaminants cut to an appropriate size by the cutting device 30 are less likely to be entangled with each other and to be bundled, and as a result, are less likely to be enlarged.

(Cutting device)
As the cutting device, the configuration of the cutting device is not particularly limited as long as it is crushed by a cutting blade, but the cutting device 30 shown in the present embodiment can be preferably used for cutting contaminants. .. Further, the cutting device disclosed in Patent Document 3 and Patent Document 4 and the product "Rotacut" sold by Tsukishima Technomente Service Co., Ltd. may be used. The cutting device 30 shown in the present embodiment intersects the cutting blade 35 held by the holder 32 that rotates around the rotation axis of the sludge 38 in the flow direction 38b and the sludge 38 in the flow direction 38b in the flow of the sludge 38. It is possible to provide a facing plate 34 having a plurality of through holes 34a. Further, the flow direction 38b and the rotation axis of the holder 32 may be parallel or may have an acute angle. The cutting blade 35 may have a cutting blade main body as a blade, or may have a rotary blade 35b provided with a cutting edge 35a. The contaminants are sandwiched between the cutting blade 35 and the facing plate 34, and are cut by receiving a shearing force. Explaining with reference to FIG. 3, the cutting device 30 is provided with a cutting blade 35 (rotary blade 35b and a cutting edge 35a provided on the rotary blade) facing the facing plate 34 surface. A plurality of transmission holes 34a penetrating the facing plate 34 are provided on the surface of the facing plate 34. The facing plate 34 may or may not include a blade. When the blade is provided, for example, the blade may be provided on the upstream side surface 34A of the sludge 38 in the facing plate 34, or the edge of the through hole may be formed in a blade shape. The form of the facing plate 34 may be a net-like one, or a so-called net blade in which the net itself is a cutting edge. Further, a perforated plate, a cribriform plate, or a lattice plate may be used, and a form in which the edge of the through hole in the perforated plate, the cribriform plate, or the lattice plate is formed by the cutting edge can be presented. Further, as shown in FIG. 6, it may be in the form of a facing plate in which transmission holes 34a having a substantially quadrangular shape or a substantially triangular shape are arranged while gradually expanding from the center to the outside in a spiral shape.

The cutting blade 35 may be installed so as to rotate in a state of facing or in contact with the facing plate 34. When arranged in this way, the contaminants staying (or being caught) on the facing plate 34 among the impurities contained in the first treatment liquid flowing through the cutting apparatus 30 are cut by the rotating cutting blade 35, which is preferable. The cutting blade 35 may be installed on the upstream side in the sludge flow direction with respect to the facing plate 34.

The cutting blade 35 is provided in a rotatable holder 32, and when the holder 32 rotates, the cutting blade 35 rotates along the upstream plane 34A. The cutting blade 35a and the upstream plane 34A of the facing plate 34 rotate in close or in contact with each other.

When the cutting blade 35 is in contact with the upstream flat surface 34A of the facing plate 34, the rotation of the cutting blade 35 causes the cutting blade 35 to scrape off the contaminants adhering to the upstream flat surface 34A, and the contaminants are surely removed. It is suitable for being cut into. As an example of a means for maintaining the state in which the cutting edge 35a of the cutting blade 35 is in contact with the upstream flat surface 34A, the holder 32 provided in the cutting blade 35 is moved from the cutting blade 35 toward the facing plate 34 (biasing direction) 42. The means 33a for urging the vehicle can be mentioned. As a result, the cutting blade 35 can rotate while being pulled (biased) in the urging direction 42 and in contact with the upstream plane 34A of the facing plate 34. As the urging means 33a, known means such as a spring and a hydraulic cylinder can be used. The holder 32 may be rotated by a gear motor or the like.

The cutting blade 35 can be formed in the shape of a rotary blade. In this case, the number of blades can be set as appropriate. For example, it may be one sheet, or it may be any number of 2 to 8 sheets such as 2, 3, 4, 5, 5, and 8.

The shape of the transmission hole 34a of the facing plate 34 is not particularly limited, and for example, a plurality of polygons having a substantially circular shape, a substantially triangular shape to a substantially hexagonal shape, a grid shape, a net shape, or the like can be provided. The width (or diameter) of the transmission hole 34a can be appropriately set, and is preferably 10 to 40 mm because impurities are appropriately cut and transmitted through the transmission hole 34a.

In the cutting device 30 of the present embodiment, the inflow portion 36 into which the sludge 38 sent from the sewage treatment plant flows in, and the outflow where the cut material obtained by cutting the contaminants contained in the sludge 38 flows out. The unit 37 can be provided. The facing plate 34 is provided on the downstream side of the inflow portion 36 and on the upstream side of the outflow portion 37. The facing plate 34 is provided so as to intersect the inflow direction 38a of the sludge 38 in the inflow portion 36. The sludge 38 can be made to flow into the inflow section 36 in the flow direction 38a, pass through the facing plate 34 without changing the flow direction 38a, and flow out from the outflow section 37. However, the sludge 38 that has flowed into the inflow section 36 in the flow direction 38a may change the flow direction 38b to pass through the facing plate 34 and flow out from the outflow section 37. The angle θ formed by the facing plate 34 (that is, the inclination 34r of the facing plate 34 surface) and the inflow direction 38a of the sludge 38 in the inflow portion 36 of the cutting device 30 may be a right angle, but as shown in FIG. Then it is preferable. In particular, it is preferable that the angle θ when the angle is acute is 15. or more. When the angle is sharp, the contaminants are easily caught by the facing plate 34 and stay there, so that the amount of contaminants to be cut increases, and as a result, the sludge 39 containing a large amount of the cut contaminants flows out from the cutting device 30. When the angle θ is smaller than 15, the inflow direction 38a of the sludge 38 and the plane of the facing plate 34 become close to parallel, and the speed at which the sludge 38 penetrates the facing plate 34 surface is hydraulically reduced. The flow rate of the sludge 38 that permeates the facing plate 34 is reduced, and as a result, the amount of sludge processed per unit time is reduced.

As shown in FIGS. 4 and 10, the facing plate 34 and the cutting blade 35 can be provided in the casing. The casing can be composed of two chambers, and a facing plate 34 may be provided so as to partition the first chamber 40 and the second chamber 41. The first chamber is provided with the above-mentioned cutting blade 35 and the inflow portion 36, and the second chamber is provided with the outflow portion 37. In this case, the holder 32 provided in the cutting blade 35 may be extended toward the second chamber and arranged so as to extend to the urging means 33a provided in the upper part of the second chamber. The sludge 38 that has flowed into the first chamber passes through the facing plate 34 and is guided to the second chamber, and is discharged from the outflow portion 37 as sludge 39 after passing through the cutting device 30. The flow direction of the sludge 38 in the first chamber 40 changes at any time depending on the inner wall 40a forming the first chamber 40. Sludge 38 flowing in the direction of passing through the facing plate 34 in the first chamber penetrates the facing plate 34. Further, as an example, when viewed in the inflow direction 38a of the sludge 38 in the inflow portion 36 (that is, when projected from the left to the right of the paper surface in FIG. 4), all or part of the position of the outflow portion 37 flows in. It may be provided so as to overlap the position of the portion 36. In other words, the inflow portion 36, the cut portion, and the outflow portion 37 may be provided in order on the same straight line along the flow of the sludge 38. Further, the position of the outflow portion 37 may be provided so that all or a part thereof does not overlap on the extension line in the inflow direction of the sludge 38 flowing through the inflow portion 36. As an example, on the paper of FIG. 10, the entire outflow portion 37 is located below the virtual line 36a extending from the lower end of the inflow portion 37 in the inflow direction. When the sludge 38 is provided in an overlapping manner, the resistance to the flow of the sludge 38 is small, and when the sludge 38 is provided so as not to overlap, the resistance to the flow of the sludge 38 is large. Specifically, if the outflow portion is not located on the inflow direction axis of the sludge in the inflow portion and is arranged so as to be offset from the inflow direction axis, the sludge flow direction from the inflow portion to the outflow portion is changed. It has changed, and the loss of water pressure is relatively large. On the other hand, since the outflow portion is located on the inflow direction axis of the sludge in the inflow portion, the sludge flow direction does not change significantly from the inflow portion to the outflow portion, and the water pressure loss is relatively small.

Further, a cutting device having a facing plate 34 and a cutting blade 35 may be provided in a water channel or a pipe through which sludge 38 flows without providing a casing. In this case, needless to say, the cutting blade 35 is arranged on the upstream side and the facing plate 34 is arranged on the downstream side of the sludge 38 in the flow direction.

All of the sludge 38 may be permeated through the facing plate 34, or a part of the sludge 38 may be permeated, but it is preferable that all of the sludge 38 is permeated.

The contaminants contained in the sludge 38, particularly thread-like objects and strip-like objects, are cut by receiving a cutting force (shearing force) by the rotatable cutting blade 35 and / or the facing plate 34. Therefore, most of the contaminants contained in the sludge 39 after passing through the cutting device 30 have a length of 50 mm or less, so that they may adhere to or get entangled with various facilities provided on the downstream side of the cutting device 30. Can be suppressed.

Explaining another embodiment of the cutting device with reference to FIG. 7, the cutting device 130 is provided with a cutting blade 135 (a blade 135a attached to the rotary blade 135b) on the side facing the facing plate 134. .. The facing plate 134 is provided with a plurality of through holes penetrating the facing plate 134. The cutting blade 135 is provided with a holder 132 that is rotated by a gear motor 152 or the like, and the cutting blade 135 is rotated along the surface of the facing plate 134 by the rotation of the holder 132. The cutting blade 135 and the upstream side surface of the sludge 38 in the facing plate 134 are in contact with each other. A means 133 is provided for urging the cutting blade 135 in the direction (biasing direction) from the cutting blade 135 toward the facing plate 134 in order to bring the cutting blade 135 into contact with the facing plate 134. Further, the contaminants that cannot be completely cut and cannot pass through the facing plate 134 can be taken out from the take-out unit 151 provided in the lower part of the cutting device 130. Further, when the operation of the main body is stopped, the upper portion of the cutting device 130 (above the facing plate 134) can be moved counterclockwise with respect to the paper surface of FIG. 7 to open the cutting device 130 around the fulcrum shaft 100 provided in the main body 130. .. Then, the inside of the casing 136 can be visually recognized from above, and the maintenance inside the main body can be easily performed. When the cutting device 130 is operated with the upper portion of the cutting device 130 closed, the sludge 38 sent to the cutting device 130 permeates the facing plate 134, and as a result, the sludge 39 after passing through the cutting device 30 is released. can get.

Cutting device 30, the flow rate of the sludge 38 to be flowed into the cutting device 130 may When 15~300m ³ / h, in particular, preferably set to 20~180m ³ / h. If it is less than 15 m ³ / h, the total amount of sludge treated in the sludge treatment plant is small and the treatment process is hindered. If it is more than 300 m ³ / h, the shear length of the contaminants becomes long because the cutting device 30 and the cutting device 130 and the equipment piping block the contaminants and the speed of the sludge passing through the cutting portion increases. It may be difficult to obtain the desired shear length (size).

(Gravity concentration tank)
The sludge 39 that has passed through the cutting device 30 is sent to the gravity concentrating facility. The gravity concentration facility is composed of a sludge distribution tank 89 and a gravity concentration tank 90 installed downstream thereof. The gravity concentration facility may be composed of only the gravity concentration tank 90 without providing the sludge distribution tank 89.

The sludge 39 containing the cut material, which has flowed out from the cutting device 30, may be continuously flowed into the gravity concentrating facility or may be flowed intermittently. In the case of continuous inflow, it is advisable to prevent the concentration of sludge 38 sent from the sewage treatment plant from becoming too low. For example, when the raw sludge accumulated in the sludge extraction hopper of the first settling basin 71 is continuously extracted, the concentration of the extracted sludge gradually decreases with the passage of time. Even if low-concentration sludge is introduced into the gravity concentration facility, it takes a long time to be concentrated, which is not preferable. Considering this point, the sludge solid concentration of the sludge 38 is preferably 5 kg / m ³ or more. On the other hand, when flowing into the sludge intermittently, for example, the sludge 38 may flow into the gravity concentration facility so that the sludge solid concentration of the sludge 38 does not fall below 5 kg / m ³ . As for the intermittent interval, for example, it is preferable to stop the inflow of sludge 38 into the gravity concentrating facility, allow 6 hours (preferably 4 hours) to elapse, and then restart the inflow of sludge 38.

The sludge distribution tank 89 is a tank for temporarily storing sludge 39 containing cut contaminants. It has a function as a flow buffer for adjusting the flow rate of sludge flowing into the gravity concentration tank 90 according to the processing flow rate of the gravity concentration tank 90.

The gravity concentration tank 90 is a tank in which the inflowing sludge 39 is settled by gravity to form concentrated sludge, which is separated from the supernatant liquid 103. In addition, it is a tank that is responsible for scraping concentrated sludge. The scraper 96 provided in the gravity concentrating facility guides the concentrated sludge settled at the bottom of the gravity concentrating facility to the sludge extraction portion provided at the bottom of the gravity concentrating facility. The sludge extraction portion and the digestion tank 91 are connected by a sludge pipe or the like. The sludge extraction pump 97 provided in the sludge pipe or the like sends the concentrated sludge accumulated in the sludge extraction portion to the digestion tank 91. As the scraper 96, a known scraper 96 can be appropriately used, and the scraper 96 of the present embodiment is an example. The scraper 96 includes a scraping blade 96r that rotates in close proximity to or in contact with the bottom of the gravity concentrating equipment, a rotating shaft 96s that rotates the scraping blade 96r, and a motor 96m that rotates the rotating shaft 96s. The scraping blade 96r scrapes the concentrated sludge that has settled at the bottom of the gravity concentration facility to the sludge extraction section, and the concentrated sludge extracted from the sludge extraction section by the sludge extraction pump 97 is sent to the digestion tank 91, which is the next step. The supernatant 103 flows out (overflows) from the overflow weir provided in the upper part of the peripheral wall of the gravity concentration tank 90.

The peripheral speed of the scraping blade 96r is preferably 1 to 5 m / min, more preferably 2 to 4 m / min. If the peripheral speed exceeds 5 m / min, the concentrated sludge will be diluted and the sludge will be insufficiently concentrated. If it is less than 1 m / min, the resistance of the excessively concentrated sludge becomes strong, and excessive torque is applied to the scraping blade 96r, which causes premature wear.

Contaminations of relatively large size adhere to each other and become bloated, become viscous, and solidify, which causes damage to the scraper 96. For this reason as well, it is preferable that the sludge 38 containing the contaminants is cut into an appropriate size by the cutting device 30 prior to flowing into the gravity concentrating facility. Since the cut contaminants have a relatively small size, they are less likely to adhere to each other, and the enlargement of the contaminants is suppressed.

The sludge 39 that has flowed into the gravity concentration facility settles and is concentrated over time to form a layer of concentrated sludge. The lower layer 101 of the concentrated sludge layer receives the consolidation from the upper layer 102 and becomes an over-concentrated and densified layer of concentrated sludge. The densified layer of concentrated sludge is highly viscous and may cause clogging (clogging) of sludge piping and the like. In such a case, even if the sludge extraction pump 97 is operated, the sludge of a desired flow rate cannot be sent to the digestion tank 91, which hinders the continuous operation of the sludge treatment plant 88. Further, if the sludge is allowed to stay in the gravity concentrating facility for a long time, the inside of the tank becomes anaerobic, the denitrification reaction is promoted, and hydrogen sulfide and carbon dioxide are generated. Then, sludge containing impurities floats along with the floating of these gas gases in the liquid, and as a result, scum is generated, proliferated, and causes enlargement.

Known means can be used as a means for preventing the density of concentrated sludge, and one example is a method for controlling the residence time of sludge in a gravity concentrating facility. The residence time (h) of the gravity concentrating facility is defined by the following equation. When the gravity concentration facility is composed of the sludge distribution tank 89 and the gravity concentration tank 90, the residence time (h) of the gravity concentration facility is the sum of the residence time of the sludge distribution tank 89 and the residence time of the gravity concentration tank 90. Say time. When the gravity concentrating equipment consists of only the gravity concentrating tank 90, the residence time (h) of the gravity concentrating equipment means the residence time of the gravity concentrating tank 90.
[Number 1]
(Dwelling time of gravity concentrating equipment) = (Volume of gravity concentrating equipment (m ³ )) / (Flow rate of sludge flowing into gravity concentrating equipment (m ³ / h))
Similarly, the residence time (h) of the sludge distribution tank 89 is defined by the following equation.
[Number 2]
(Stay time of sludge distribution tank 89) = (Volume of sludge distribution tank 89 (m ³ )) / (Flow rate of sludge flowing into sludge distribution tank 89 (m ³ / h))
Similarly, the residence time (h) of the gravity concentration tank 90 is defined by the following equation.
[Number 3]
(Dwelling time of gravity concentration tank 90) = (Volume of gravity concentration tank 90 (m ³ )) / (Flow rate of sludge flowing into gravity concentration tank 90 (m ³ / h))

The residence time of sludge in the gravity concentrating facility is preferably 12 hours or less, preferably 10 hours or less, and more preferably 8 hours or less. If it exceeds 12 hours, the sludge will rot and the scum will become bloated. Further, although it depends on the concentration of the dry solid matter of the sludge 39 flowing into the gravity concentration facility, it is preferable to allow the sludge to stay for 30 minutes or more. If it is less than 30 minutes, the sludge will not settle sufficiently and the desired concentration will not be achieved, which will hinder the sludge incineration in the subsequent steps.

Further, a known means can be used as a means for preventing the density of concentrated sludge, and another example is a method for controlling a solid matter load (kg / (m ² · day)) in a gravity concentration facility. Can be done. The solid matter load is defined by the following equation.
[Number 4]
(Solids loading) = (input amount of sludge ((m3 / day)) (input sludge solids concentration (kg / m ³⁾⁾ - (gravity concentration equipment water area (m ²⁾⁾
Here, the input sludge solid matter concentration means the concentration of sludge 39 flowing into the gravity concentrating facility.

The solid load should be 100 kg · DS / (m ² · day) or less. Further, 30 to 90 kg / DS / (m ² / day) is better, and 50 to 60 kg / DS / (m ² / day) is preferable. In the present embodiment, the contaminants are sheared by the cutting device to a predetermined size, so that the generation of scum in the gravity concentrator is suppressed. However, if the generation of scum exceeds 100 kg / DS / (m ² / day), it causes sludge putrefaction, a large amount of scum, and enlargement.

If sludge flows into the gravity concentrating facility in excess of a predetermined solid matter load, the sludge concentration in the gravity concentrating facility becomes too high, and the generation of gas (bubbles) is accelerated. As a result, the ascent of large lumps in the liquid is accelerated, resulting in a large amount of scum.

By setting the load to a predetermined solid matter or less, the generation of gas (bubbles) can be suppressed, and as a result, the generation of scum is suppressed.

The concentrated sludge may be withdrawn from the sludge extraction portion continuously or intermittently.

The effective water depth of the gravity concentrator is preferably 4 m or more, and controlling the sludge interface to be lower than 2 m from the liquid level is preferable because the risk of sludge overflow can be prevented.

As described above, large-sized impurities adhere to or become entangled in the sludge treatment plant's equipment, but it is desirable to cut the hair appropriately because the hair becomes coarse. When the hair is present in the sludge 38, organic substances, oils and fats, and other hair adhere to the cuticle portion on the surface of the hair. In addition, when these adhere, bacteria propagate. Since the hair is made of enamel-like tissue, it is hard and is not easily biodegraded and remains in the sewage treatment facility. If there are a plurality of hairs, they may be entangled with each other to form a bundle or connected in the length direction, and may exceed 50 cm. Furthermore, fibers, sludge and other contaminants adhere to the bundled hair groups and become enlarged and become large lumps. This large mass adheres to the piping and various equipment, blocking the flow of sludge and hindering the stable operation of the equipment.

One or more sludge distribution tanks 89 and one or more gravity concentration tanks 90 may be provided. For example, when two sludge distribution tanks 89 and two gravity concentration tanks 90 are provided as shown in FIG. 9, an upstream pipe (that is, a pipe through which sludge 39a1 flows) connected to an inflow portion of the first sludge distribution tank). The first cutting device 301 may be installed in the above, and the second cutting device 302 may be installed in the upstream pipe (that is, the pipe through which the sludge 39a2 flows) connected to the inflow portion of the second sludge distribution tank. In this case, piping is provided so that the sludge 38 flows into each of the first cutting device 301 and the second cutting device 302. Further, it is also possible to provide a bypass pipe in which the sludge flowing out from the first cutting device 301 and the second cutting device 302 are mixed. The first downstream pipe (that is, the pipe through which sludge 39b1 flows) connected to the outflow portion of the first sludge distribution tank 891 and the second downstream pipe (that is, the sludge 39b2) connected to the outflow portion of the second sludge distribution tank 892 The flowing pipe) may be separately connected to the first gravity concentration tank 901 and the second gravity concentration tank 902, respectively. Further, a confluence pipe (bypass pipe) at which the first downstream pipe and the second downstream pipe are once merged is provided, and the sludge 39b1 discharged from the first sludge distribution tank 891 and the sludge 39b1 discharged from the second sludge distribution tank 892 are discharged. The sludge 39b2 may be mixed with the sludge 39b2. It is preferable that sludge flows into the first gravity concentrating tank 901 from the downstream of the first downstream pipe and sludge flows into the second gravity concentrating tank 902 from the downstream of the second downstream pipe. When the piping is provided in this way, for example, when the first gravity concentrating tank 901 breaks down, the inflow of sludge into the first gravity concentrating tank 901 is stopped and the sludge 39b1 is passed through the confluence pipe to the first. 2 It is possible to flow into the gravity concentration tank 902. Then, the first cutting device 301, the second cutting device 302, the first sludge distribution tank 891, the second sludge distribution tank 892, and the second gravity concentration tank 902 are used without urgently stopping the operation of the sludge treatment plant 88. It will be possible to continue operation.

It is also preferable that the cutting device 30 is provided in the upstream pipe connected to the sludge distribution tank 89 and the downstream pipe (for example, a piping portion connecting the sludge distribution tank 89 and the gravity concentration tank 90). The sludge 38 is cut by the cutting device 30 provided on the upstream side, and the generation of scum in the sludge distribution tank 89 is suppressed. Further, the sludge flowing out from the sludge distribution tank 89 is further cut by the cutting device 30 provided in the downstream pipe, and the generation of scum in the gravity concentration tank 90 is further suppressed.

In the present specification, the sludge treatment facility including the cutting device 30 and the gravity concentration tank 90 (including the sludge distribution tank 89 when the sludge distribution tank 89 is provided) in the sludge treatment plant 88 is referred to as a sludge treatment facility.

The sewage of the present embodiment is not particularly limited, but for example, septic tank drainage, agricultural / fishery village drainage, rainwater, factory drainage, workplace drainage, unknown water, underflow water, spring water, groundwater, industrial water, sewage pipe water. , Sewerage trunk water, raw sludge, active sludge, sewage treatment plant and / or process water flowing through each treatment process of the sludge treatment plant.

The terms described in this specification are based on the terms described in "Japan Sewerage Association: Sewerage Facility Planning / Design Guidelines and Explanation 2001 Edition".

The sludge treatment method and sludge treatment equipment disclosed in the present invention are not particularly limited, and can be used in, for example, public sewerage, basin sewerage, and urban sewerage sewage treatment facility.

10 Sewage 30 Cutting device 32 Holder 34 Facing plate 34A Upstream plane 34a Permeation hole 35 Cutting blade 38 Sludge 39 Sludge 89 Sludge distribution tank 90 Gravity concentration tank of the first treatment liquid in the facing plate

Claims (7)

This is a sludge treatment method in which sludge sent from a sewage treatment plant is allowed to flow into a gravity concentration facility installed in a sludge treatment plant and settled by gravity to obtain concentrated sludge.
In the flow of the sludge, the contaminants contained in the sludge are cut to a predetermined size to obtain a cut product.
Sludge containing the cut material is allowed to flow into the gravity concentrating facility.
A sludge treatment method characterized by that. Sludge containing the cut material is intermittently flowed into the gravity concentrating facility.
The sludge treatment method according to claim 1. The sludge is raw sludge,
The sludge treatment method according to claim 1. The scum generated in the gravity concentration facility is mixed with the sludge sent from the sewage treatment plant.
The sludge treatment method according to claim 1. The cut piece is cut by a cutting device and
The cutting device includes a cutting blade held by a holder that rotates around a rotation axis in the sludge flow direction, and a facing plate having a plurality of through holes provided intersecting with the sludge flow. The cutting blade rotates in a state of being close to or in contact with the facing plate.
The sludge treatment method according to claim 1. The sludge sent from the sewage treatment plant is allowed to flow into a cutting device provided on the upstream side of the gravity concentrating facility.
The cutting device has an inflow portion into which the sludge flows in, a cutting portion in which contaminants contained in the sludge are cut, and an outflow portion in which the cut product obtained by cutting is discharged.
The inflow portion, the cut portion, and the outflow portion are sequentially arranged on the same straight line along the flow of the sludge.
The sludge treatment method according to claim 1. A cutting device in which impurities contained in sludge sent from a sewage treatment plant are cut in the sludge flow to obtain a cut piece.
It is provided with a gravity concentration facility in which sludge containing the cut pieces is settled by gravity to obtain concentrated sludge.
A sludge treatment facility characterized by this.

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