JP2008133150A - Method of manufacturing sludge compost - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing compost in which hairs or the like contained in a sewage are not remained in a compost obtained from a sludge discharged after treating the sewage with an active sludge, and particles constituting the compost are not mutually combined by fibrous inclusions and independently treatable. <P>SOLUTION: The method is for manufacturing the sludge compost from a sludge generated accompanying an active sludge treatment of an organic drainage; the sludge contains fibrous inclusions; and the method is implemented through a process for concentrating the sludge, a process for removing the fibrous inclusions from the concentrated sludge by using a removing apparatus formed by combining a filter through which the fibrous inclusions are difficult to permeate and an impeller rotating at just before the filter, and a process for composting the sludge from which the fibrous inclusions are removed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a method for efficiently removing fibrous impurities such as hair contained in organic wastewater such as sewage discharged from households from sewage sludge with low energy consumption and producing improved quality compost. About.

  Organic wastewater (hereinafter simply referred to as sewage) such as sewage, rural village drainage, and livestock manure is often purified through biological treatment with activated sludge. Although 80% of the excess sludge generated by this activated sludge treatment is disposed of in landfills, suitable landfill sites are decreasing year by year. Although excess sludge is incinerated, it is not a preferable measure because it consumes a large amount of heavy oil and discharges carbon dioxide.

  Accordingly, various technological developments have been made to produce compost that can be used as fertilizer by separating water from sludge. However, sewage contains a large number of fibrous impurities such as hair, and many of these fibrous impurities are not decomposed by biological treatment using activated sludge. Therefore, it settles and separates from the sewage together with the activated sludge suspended solids (MLSS) in the settling tank in the activated sludge treatment, and remains in the sludge. When particulate compost is produced from such sludge, fibrous impurities are entangled and a large lump of compost is easily formed, and each process such as switching between steps, crushing, aeration, etc. is liable to cause trouble. In addition, such a large lump becomes incomplete compost that emits an odor because the inside is kept in an anaerobic state.

  In addition, it is also a big problem that fibrous impurities are mixed into the obtained compost and a plurality of compost particles are connected to each other like a rosary. Compost particles in such a state must be dispersed while peeling the particles from each other when fertilizer is spread, making the work considerably cumbersome and difficult to use, causing discomfort to hair mixing, It has been a big problem because the particles formed during the peeling are broken and the chemical components of the hair dye attached to the hair are scattered on the farmland.

  In conventional compost manufacturing, slit-type drum filters and scoop bar screens are often used to remove fibrous contaminants from sludge, and slit-type drum filters are often used especially when there is a lot of hair. Has been. Many slit-type drum filters have a slit width of 1 mm, but this causes a lot of hair to pass through. For this reason, devices with a slit width of 0.7 mm have recently been used, but the fact is that many hairs still pass through the slit and are present in the compost. In addition, a mesh drum filter may be used instead of the slit type, but there is a problem that this is easily clogged.

  Thus, there is no suitable method for removing effective fibrous contaminants, so there are sludges in the actual sewage basin, similar to Kenzan used in tea ceremony, with a number of nails protruding from the board. Some have adopted a method that pours and catches fibrous impurities. However, this requires considerable labor for the maintenance of the instrument, and the capture rate of fibrous impurities is not high at all.

  By the way, from an aqueous dispersion in which waste paper fibers and other foreign matters are dispersed, using a screen filter and an impeller that rotates at a high speed immediately before that, while the impeller causes cavitation by rotation, the filter is prevented from being clogged, A waste paper processing method for separating waste paper fibers and other foreign matters is disclosed (see, for example, Patent Document 1). However, in the technique disclosed in Patent Document 1, since the waste paper fibers easily pass through the filter, even if this is applied to sludge, fibrous impurities represented by hair easily pass through the filter. It is clear.

Although not related to the production of sludge compost, long-fiber contaminants such as hair and sludge were immersed in the activated sludge tank when the organic waste liquid was treated using the membrane separation activated sludge method. In order to prevent clogging of the filtration membrane module, a long-fiber-like material removing device that combines a long-fiber-like contaminant in raw water with a screen-like filter and a rotary blade that rotates along the screen surface of the screen-like filter. Is disclosed (for example, see Patent Document 2). However, since the operation of removing the long fibrous impurities is performed on the total amount of sewage, there is a problem that a considerable electricity cost is required for the operation of the removing device.
JP-A-57-56593 JP 2004-261663 A

  In the present invention, fibrous contaminants such as hair contained in sewage do not remain in compost obtained from sludge discharged when sewage is treated with activated sludge, and particles constituting compost are bound by fibrous contaminants. An object is to provide a method for producing sludge compost that can be handled independently of each other.

  The present invention is a method for producing sludge compost from sludge generated with activated sludge treatment of organic wastewater, wherein the sludge contains fibrous impurities, the step of concentrating the sludge, and the concentration Removing the fibrous contaminants from the sludge using a removing device that combines a filter that hardly allows the fibrous contaminants to permeate and an impeller that rotates immediately before the filter; and It is a manufacturing method of the sludge compost characterized by passing through the process of composting the removed sludge.

  Here, the sludge is located in the previous stage of the activated sludge treatment, the first settling sludge discharged from the first settling step for settling and removing relatively small water insoluble matter contained in the organic waste water, and the activated sludge treatment It is preferable to include excess sludge discharged from the activated sludge tank. Moreover, it is preferable that each particle | grain of the obtained sludge compost can be sprayed independently mutually. Moreover, it is preferable that the organic wastewater is sewage, rural village wastewater or livestock manure. Further, the filter has a screen shape having a large number of cylindrical apertures, and the impeller rotates along the screen-like surface of the filter, and is close to the surface of the filter in the removing step. It is preferable that the fibrous impurities are separated from the surface by the rotation of the impeller. In the filter, it is preferable that the diameter of the cylindrical aperture is 0.5 mm or more and 1.6 mm or less, and the aperture ratio is 15% or more and 30% or less.

  Since the fibrous contaminants can be almost removed from the sludge settled and separated from the sewage, the fibrous contaminants do not remain in the finally obtained compost, and the compost particles are not connected by the fibrous contaminants. Therefore, it does not take the trouble of peeling off the particles when handling the compost, and the required number of compost particles as a fertilizer can be easily sprayed to the required place. Further, when compost is manufactured, incomplete compost with an anaerobic inside is not generated with a large lump that becomes an obstacle during the manufacture. In addition, since the sludge separated from the sewage can be further concentrated and almost all of the fibrous contaminants can be removed, the volume of the liquid to be treated is greatly reduced compared to the case of removing the entire sewage. ing. Therefore, the operation energy (electricity cost) necessary for removing fibrous impurities is also greatly reduced, and low cost suitable for application to sewage treatment can be realized.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an outline of the processing steps of the production method of the present invention, and uses a current general sewage treatment plant sewage treatment flow. First, the sewage 1 flows into the sand basin 2 of the sewage treatment plant and stays in the sand basin 2 for a certain period of time. During this time, large dust or sand contained in the sewage 1 is settled and removed. The sewage from which sand and the like have been removed moves from the settling basin 2 to the initial settling tank 3. In the initial settling tank 3, the sewage is allowed to flow more slowly to settle and remove microorganisms, mud, some fibrous impurities, etc. that could not be removed in the settling basin 2. The sludge composed of relatively small water insoluble matter settled and removed here is referred to as primary sedimentation sludge.

  The sewage from which the first settling sludge has been removed in the first settling tank 3 moves to the aeration tank 4. In the aeration tank 4, in an aerobic atmosphere, the activated sludge dissolves the soil dissolved in the sewage as nutrients and changes the mud to easily settle. However, fibrous impurities are hardly decomposed and remain in the sludge. The biologically treated sewage moves to the final settling tank 5, and the activated sludge and other insoluble components typified by fibrous impurities contained in the sewage are settled and removed. The supernatant liquid from which activated sludge and the like are settled and removed is sterilized with chlorine, and then discharged as discharged water 6 into public water areas such as rivers and lakes. The discharged water 6 does not include fibrous impurities. On the other hand, part of the activated sludge 22 and the fibrous contaminants settled and removed in the final settling tank 5 are returned to the aeration tank 4 as return sludge 23, and the rest are sent to the concentration tank 24.

  Initial concentration sludge 24 settled and removed in the initial sedimentation tank 3 is also sent to the concentration tank 25, and both the sludge from the final sedimentation tank 5 and the initial sedimentation sludge 24 are used as the sludge 7 as a compost raw material. The process of concentrating with the concentration tank 25 is performed. As described above, not only the sludge from the final sedimentation tank 5 but also the primary sedimentation sludge 24 including some fibrous contaminants may be used as the raw material sludge 7, but the fibrous contamination included in any of the subsequent steps. Since almost all the substances can be removed, almost the entire amount of sludge generated by the sewage treatment can be composted satisfactorily.

  In the concentration tank 25, the sludge 7 is stored in a state in which the valve 30 is closed, and the sludge components are further precipitated and concentrated. Further, if necessary, it may be mechanically concentrated using centrifugal force. Concentration is preferably carried out so that the volume ratio is about 1/100 to 1/50 of sewage. The concentration of the concentrated sludge is preferably high, but if the concentration is high, the viscosity becomes high and the treatment becomes difficult, so about 5% is the upper limit for normal sludge. In addition, in digested sludge once concentrated sludge is heated to about 40 ° C. in an anaerobic atmosphere and reacted for about one month, the upper limit is about 7% because the pulp quality is degraded and the viscosity is lowered.

  The electric power consumed by the fibrous contaminant removal apparatus described later is in a proportional relationship with the volume of sludge to be processed. Therefore, by concentrating in this way, it becomes possible to remove fibrous impurities from sludge with low energy consumption. At that time, fibrous contaminants are also concentrated by concentrating the sludge, so there was concern that the removal performance of the filter would be adversely affected. It was found that impurities can be removed.

  The sludge concentrated in the concentration tank 25 is sent to the waiting tank 8. The remaining waste water from which the sludge has been removed in the concentration tank 25 is returned to the settling basin 2. The sludge stored in the waiting tank 8 is sent to the primary side chamber 13 of the fibrous contaminant removal apparatus 10 by the pressure pump 9 through the valve 8. The removal device 10 is a device that combines a filter 12 that hardly allows fibrous impurities to pass therethrough and an impeller 11 that is rotated by a motor 19 immediately before the filter 12, and the fibrous impurities 26 are less likely to pass through the filter 12. However, other soluble components can easily pass through the filter 12 due to the pressure applied by the pressure pump 9 and be transferred to the secondary side chamber 14.

  Specifically, the filter is preferably a flat screen, and specifically, a filter in which a large number of cylindrical holes are formed in a metal plate is preferable. The diameter of the cylindrical aperture is preferably 0.5 mm or greater and 1.7 mm or less. If it is 0.5 mm or more, the pulp contained in the sludge permeates the filter and the pulp is not concentrated in the primary side chamber 13. Moreover, if it is 1.7 mm or less, fibrous impurities, such as hair, will not pass through a filter easily. A more preferable diameter is 1.0 mm or more and 1.4 mm or less.

  In addition, the aperture ratio of the screen filter is preferably high in terms of securing the amount of filtered water, but is preferably low from the viewpoint of ensuring the mechanical strength of the screen filter under pressure. The hole area ratio is preferably 15% or more and 30% or less, and more preferably 20% or more and 25% or less.

  An impeller 11 that rotates along the screen surface of the filter 12 is provided immediately before the screen-like filter 12. Here, “immediately before the filter” means that the filter is close to the upstream side of the screen surface with respect to the filtration direction from the pressurizing pump 9 toward the screen surface. The impeller 11 has a function of rotating by a motor 19 to generate a flow in a direction opposite to the filtration direction. A pressure reducing part (cavitation) is generated between the impeller 11 and the screen filter 12, and the filtration is performed. As a result, the fibrous contaminants 26 that are likely to accumulate on the screen filter 12 are pulled away from the filter 12. Thus, the filter 12 is prevented from being clogged and the fibrous impurities 26 are retained in the primary side chamber 13. Therefore, the impeller 11 is not limited as long as it can cause cavitation. Further, the number of revolutions of the impeller 11 may be appropriately set depending on the degree of pressurization by the pressurization pump 9.

  In the operation of the removing device 10, it is important to manage the differential pressure across the screen filter 12. It is preferable to adjust the differential pressure to about 10 kPa to 30 kPa from the viewpoint of the balance between the removal performance of fibrous impurities and the filtration performance. More preferably, it is 15 kPa to 25 kPa.

  It is preferable that the fibrous contaminants 26 accumulated in the primary side chamber 13 by the removal operation for a certain period of time are discharged from the valve 33 at regular intervals, and the inside of the removal apparatus is further washed. The time for performing one removal operation is within a range that does not reach the upper limit of the differential pressure allowed before and after the screen filter, for example, 30 kPa, while taking into account the change state of the SS concentration of concentrated sludge and the amount of hair included. You can decide in advance. The operation of the removing device is preferably performed by automatic operation using a timer set according to the time determined in this way. The fibrous contaminants 26 discharged from the removing device are finally disposed after dehydration.

  Further, when cleaning the inside of the removing device 10, while the impeller 11 is rotated, the cleaning water 15 is introduced into the removing device 10 from the valve 32, passes through the filter 12, and moves to the secondary side chamber 14. May be returned from the valve 34 to the initial settling tank 3. The cleaning start differential pressure of the screen filter may be set to the upper limit value of the differential pressure, for example, 30 kPa. By carrying out the cleaning operation regularly, it becomes possible to remove the fibrous impurities stably.

  The filtrate that has passed through the filter 12 contains almost no fibrous impurities, and the filtrate is sent from the secondary side chamber 14 to the dehydrator 21 via the valve 35. In the dehydrator 21, organic substances in the filtrate are separated from moisture by centrifugation, and the obtained organic substances are used as a part of the composting raw material, and are combined with other composting raw materials as sub-materials. 27 is put into composting.

  As other composting raw materials that can be used for composting, conventionally known materials can be used without particular limitation. For example, garbage such as waste wood, sawdust, moss, rice husk, bark, vegetable waste, and the like can be mentioned.

  The composting method in the composting device 27 is not particularly limited, and a known composting method can be used. In the composting process, it becomes a situation similar to heat sterilization at a high temperature of 70 ° C. or more during aerobic fermentation. Pest eggs and weed seeds are killed. At that time, since there is no fibrous contaminant such as hair in the composting raw material, there is no effect of forming a large sludge mass due to the fibrous contaminant during aerobic fermentation. Therefore, a large lump that tends to become an obstacle is not generated in various operations such as switching between various processes, crushing, and aeration. Therefore, the obtained compost particles are kept aerobic to the inside and no odor remains, and a good compost that matches the purpose of use as a fertilizer can be obtained.

  As a specific composting method, for example, a composting raw material is put into a processing drum such as a rotary kiln, and these are fed, crushed, scraped, etc., and subjected to fermentation and moisture adjustment according to the processing stage. Method, method of manufacturing by adjusting the processing atmosphere of compost raw material charged in the processing drum, temperature, and air amount, the processing drum is devised, the supply system from the input pipe of the rotating shaft, and rotation A method of composting using an apparatus provided with an exhaust system on the other side of the shaft, storing the composting raw material in a heating container, performing heat drying and heat treatment at 100 to 200 ° C. without aeration, Various methods such as a method for obtaining compost particles can be used.

  The compost obtained by the above process is not in a state where the particles composing the compost are independent of each other and connected in a rosary shape by fibrous impurities such as hair. There is no need to peel it off with one hand. For this reason, the necessary number of particles can be easily applied to the required place, and it is not time-consuming, and there is no discomfort due to the inclusion of hair.

  Further, the obtained compost contains nitrogen and phosphorus necessary for plants, does not contain heavy metals in accordance with the fertilizer control method, and chemical components such as hair dye attached to the hair are also removed at the same time. Therefore, it is useful as an organic fertilizer or soil conditioner for agricultural land and green space. EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to the following specific aspects.

A treatment process similar to that shown in FIG. 1 was installed in the A sewage treatment plant using the existing treatment facilities of the A sewage treatment plant except that the initial sludge was not composted. The amount of excess sludge withdrawn from the final settling tank of the A sewage treatment plant is 100 m ³ / day, and the SS concentration of the solid matter of excess sludge is 1.5%. In accordance with the flow of FIG. 1, surplus sludge from the final settling basin is introduced into the concentration tank in the apparatus for removing fibrous impurities. In the concentration tank, the sludge is concentrated to about 98% at room temperature by gravity concentration (capacity ratio with respect to the original sewage is 1/100 to 1/300) and transferred to a waiting tank.

Subsequently, the concentrated sludge was sent from the waiting tank to the fibrous contaminant removal device (trade name Fib Filter FF-250-LS, manufactured by Asahi Kasei Clean Chemical Co., Ltd.) with a pressure pump to remove the fibrous contaminants. . The screen-like filter of the removing device was provided with a large number of cylindrical apertures having a diameter of 1.5 mm, a filter aperture ratio of 22%, and a filter diameter of 150 mm. The operating conditions of the removal device are as follows.
(1) Motor output: 2.2Kw (400V)
(2) Surplus sludge supply amount: 4.3 m ³ / Hr
(3) Supply pressure: 200 kPa
(4) Filtrate pressure ... 180kPa
(5) Differential pressure across the screen filter: 20 kPa
(6) Filtration time ····················· 2 hours

  Since hair, long fibers, and paper are concentrated in the primary side chamber during the filtration operation, washing water is introduced after the filtration time has passed to wash the primary side chamber. Next, the valve at the outlet of the primary side chamber is opened, and accumulated hair, long fibers and paper are discharged. The discharge and washing time was set to 120 seconds as described above. The washing wastewater discharged from the secondary side chamber was returned to the initial settling tank.

  This filtration and discharge cycle was automatically repeated using a timer and an automatic valve. During that time, the differential pressure of the screen filter gradually increased, and the operation was stopped when it reached 30 kPa. The primary side chamber was opened and the screen filter was cleaned. The operation period from the start of operation to the first cleaning was 2 months.

  FIG. 2 shows a photograph of the dried fibrous impurities such as concentrated hair and solids discharged from the primary side chamber during the filtration operation. In FIG. 2, many hairs are observed, and it can be confirmed that many hairs in the concentrated sludge have been removed. A small amount of paper that was not decomposed by activated sludge is also observed. In addition, the spherical object in FIG. 2 is a plant seed.

  On the other hand, the hair in the filtrate that has passed through the filter is opaque because the sludge concentration is 1.5% and cannot be visually observed as it is. Therefore, the filtrate was diluted 100 times and observed on a glass plate, but no hair or other contaminants were observed. Despite the use of concentrated sludge, the ability to remove fibrous impurities was high, and a good filtrate was obtained. To this filtrate, slaked lime and ferric chloride were added according to a conventional method, applied to a dehydrator, and concentrated by centrifugation to obtain a dehydrated sludge having a water content of 70%.

  Subsequently, composting was performed using this dewatered sludge. Initially, the dewatered sludge was mixed with compost produced at another compost production facility using a mixing granulator and charged into the fermenter. The fermenter was a horizontal fermenter with four tanks that could be turned over. Hereafter, according to the usual compost manufacturing method, the sludge temperature was controlled, the fermentation aeration amount was adjusted, and switching was performed as appropriate. Commenced continuous production with a compost return rate of 60%. The water content of the obtained compost was 30 to 35%. The compost after 2 months of continuous production, which was considered to have no effect from the use of compost from other production facilities, was visually observed, but no compost particles involving hair were found.

Using the B sewage treatment plant that digests the first settling sludge and surplus sludge, the same treatment process as shown in Fig. 1 is installed in the B sewage treatment plant using the existing treatment facilities of the B sewage treatment plant. did. The amount of digested sludge in the B sewage treatment plant was 120 m ³ / day, the SS concentration of the solid material of the digested sludge was 6.0% after concentration, and the volume ratio before concentration was 1/600. Digested sludge was guided from the compression tank and stored in the waiting tank, and then the sludge was supplied from the pressurization pump to the fibrous contaminant removal device. The specification of the removal device was the same as that of Example 1 except that the motor was changed to a drive voltage of 200V. The operating conditions are as follows.
(1) Electric motor: 2.2Kw (200V)
(2) Digested sludge supply amount: 4.9m ³ / Hr
(3) Supply pressure: 250 kPa
(4) Filtrate pressure ... 225kPa
(5) Differential pressure across the screen filter: 25 kPa
(6) Filtration time ················· 25 minutes (7) Washing and hair discharge time ·············· 5 minutes

  The cycle consisting of the filtration time and the washing and discharging time is repeated, and the differential pressure before and after the screen filter gradually increases accordingly, so the filtration operation is stopped when the differential pressure reaches 30 kPa, and the removal device is Opened and cleaned screen filter. The operation period from the start of operation to the first cleaning was one month.

  FIG. 3 shows a photograph of the dried fibrous contaminants such as hair and solids discharged from the primary room during the filtration operation. In FIG. 3, many hairs can be observed with a dark brown color overall. Also included are plastic products made from first settling sludge and their fragments. Note that the paper is not disassembled. On the other hand, when the filtrate which permeate | transmitted the filter was diluted 500 times, and it developed and observed on the glass plate, it turned out that fibrous impurities, such as hair, are not contained.

  In the same manner as in Example 1, slaked lime and ferric chloride were added to this filtrate, and the mixture was applied to a dehydrator and centrifuged to obtain dehydrated sludge having a water content of 60%. Using this dewatered sludge, composting was carried out in the same manner as in Example 1. The obtained compost had a moisture content of 30 to 60%, and a good compost free from fibrous impurities such as hair was obtained.

It is the flowchart which showed the whole process process outline of the manufacturing method of sludge compost. It is the figure which photographed what dried the solid substance in concentrated sludge. It is the figure which photographed what dried the solid substance in digested sludge.

Claims (6)

  A method for producing sludge compost from sludge generated by the activated sludge treatment of organic wastewater, wherein the sludge contains fibrous impurities, the step of concentrating the sludge, and the concentrated sludge A step of removing the fibrous contaminants using a removal device that combines a filter through which the fibrous contaminants are difficult to permeate and an impeller rotating immediately before the filter; and sludge from which the fibrous contaminants have been removed. A process for producing sludge compost, characterized by undergoing a composting process.   The sludge is located in the previous stage of the activated sludge treatment, and the first settling sludge discharged from the first settling step for settling and removing relatively small water insoluble matter contained in the organic waste water, and the activity for performing the activated sludge treatment. The method for producing sludge compost according to claim 1, further comprising excess sludge discharged from the sludge tank.   The method for producing sludge compost according to claim 1 or 2, wherein each particle of the obtained sludge compost can be sprayed independently of each other.   The method for producing sludge compost according to any one of claims 1 to 3, wherein the organic wastewater is sewage, rural settlement or livestock manure.   The filter is in the form of a screen having a large number of cylindrical apertures, and the impeller rotates along the screen-like surface of the filter, and in the removing step, the fibers close to the surface of the filter The method for producing a sludge compost according to any one of claims 1 to 4, wherein the impurities are separated from the surface by rotation of the impeller.   The sludge compost according to claim 5, wherein the filter has a diameter of the cylindrical opening of 0.5 mm or more and 1.6 mm or less and an opening ratio of 15% or more and 30% or less. Production method.