JP6474301B2 - Dehydration method, wastewater treatment method, and wastewater treatment device - Google Patents

Description

  The present invention relates to a technique for a dehydration method, a wastewater treatment method, and a wastewater treatment apparatus.

As a method for biologically treating wastewater containing organic matter or the like, an activated sludge method using an aggregate of microorganisms called floc (floating sludge) has been used. However, in the activated sludge method, when separating floc and treated water in the sedimentation basin, flocs that are floating sludge have a problem that the sedimentation basin surface area must be very large because the sedimentation rate is slow. There is. The treatment rate of the activated sludge method depends on the sludge concentration in the tank, and the treatment rate can be increased by increasing the sludge concentration. The sludge concentration is from 1500 mg / L to 5000 mg / L at the highest. If it is about L and increases further, solid-liquid separation in the sedimentation basin becomes difficult, and the treatment may not be maintained. Therefore, the BOD processing rate per tank volume of the conventional activated sludge method is about 0.2 to 0.8 kg / m ³ / day.

  In anaerobic biological treatment, it is common to use aggregates (granular biological sludge) in which microorganisms called granules are densely aggregated and granulated. Granules have a very fast sedimentation rate, and microorganisms gather densely, so that the sludge concentration in the treatment tank can be increased and high-speed wastewater treatment can be realized. However, the anaerobic biological treatment has problems such as the fact that the wastewater species to be treated is limited compared to the aerobic treatment (activated sludge method) and that the treated water temperature needs to be maintained at 30 to 35 ° C. May have. In addition, when the anaerobic biological treatment alone is poor in the quality of the treated water, it may be necessary to separately perform an aerobic treatment such as an activated sludge method when discharged into a river or the like.

  In recent years, treatment has been carried out using a semi-batch treatment device that allows wastewater to flow into the reaction tank intermittently, and the sedimentation time of biological sludge is shortened, so that it is not limited to anaerobic biological sludge. It has become clear that it is possible to form a biological sludge (hereinafter sometimes referred to as granular sludge) (see, for example, Patent Documents 1 to 4). In a semi-batch treatment device, generally, (1) inflow of wastewater, (2) biological treatment of wastewater, (3) sedimentation of biological sludge, (4) discharge of treated water in one reaction tank. The process is performed through three steps.

  As described above, high-speed treatment can be achieved by granulating biological sludge, but when using a semi-batch treatment device for large-scale wastewater treatment facilities such as sewage treatment, a huge wastewater storage tank May have to be installed.

Therefore, it is equipped with a continuous biological treatment device that continuously treats wastewater by flowing in and a semi-batch biological treatment tank that generates aerobic granular sludge. A treatment apparatus that granulates biological sludge in a continuous biological treatment apparatus by supplying it to the continuous biological treatment apparatus has been proposed (for example, see Patent Documents 5 and 6). According to the devices of Patent Documents 5 and 6, the sedimentation basin and the reaction tank can be miniaturized, and the BOD treatment speed per tank volume is 0.4 to 1.6 kg / m ³ / day depending on the concentration of raw water. Is possible.

International Publication No. 2004/024638 JP 2008-212878 A JP 2009-18263 A JP 2009-18264 A JP 2007-136367 A JP 2008-284427 A

  By the way, the dewatered sludge obtained by dehydrating flocs (floating sludge) used in the conventional activated sludge method has a problem that the moisture content is high and the amount of dewatered sludge is increased. In the past, studies have been made to reduce the moisture content of sludge after dehydration, but it requires energy such as electricity, pressure, heat, etc., and there is a problem that the cost for dehydration increases. In addition, in the treatment apparatus for granulating biological sludge in the continuous biological treatment apparatus of Patent Documents 5 and 6, the water content of the dewatered sludge after dehydration has not been sufficiently studied and needs to be improved. There is.

  Therefore, an object of the present invention is to provide a dehydration method, a wastewater treatment method, and a wastewater treatment apparatus that can reduce the water content of dehydrated sludge after dehydration.

  The dehydration method of the present invention is a dehydration method in which biological sludge containing suspended sludge is dehydrated to obtain dehydrated sludge. In the dehydration process, the biological sludge has a particle size of 200 μm or more. The sludge is added so that the proportion of the granular sludge in the biological sludge is 15% or more.

In the wastewater treatment method of the present invention, the wastewater is biologically treated with biological sludge while continuously flowing the wastewater into a continuous biological treatment tank, and then biological sludge is separated from the biological treatment liquid by solid-liquid separation means. a continuous biological treatment process, the continuous and dehydrated solid-liquid separated biological sludge in the biological treatment step, pre-Symbol dehydration and dehydration to obtain dehydrated sludge, the granular sludge with a particle size of more than 200μm and a sludge supplying step of supplying the organism sludge in processing, among the biological sludge being dehydrated by the dehydration treatment step, granular sludge with a particle size of more than 200μm is present more than 15% Yes.

  In addition, in the wastewater treatment method, a semi-batch type biological process includes an inflow process for inflowing wastewater, a biological treatment process for biologically treating the wastewater with biological sludge, a sedimentation process for sedimenting the biological sludge, and a discharge process for discharging treated water. A semi-batch biological treatment process is performed repeatedly in a treatment tank to form granular sludge, and the granule sludge in the sludge supply process is a granule sludge formed in the semi-batch biological treatment process. It is preferable.

Further, the wastewater treatment apparatus of the present invention comprises a continuous biological treatment tank for biologically treating the wastewater with biological sludge while continuously flowing the wastewater, and solid-liquid separation means for solid-liquid separation of biological sludge from the biological treatment liquid. A dehydration treatment means for dehydrating the biological sludge solid-liquid separated by the continuous biotreatment device, and a granular sludge having a particle size of 200 μm or more. and a sludge supply means for supplying to the organism sludge when pre Symbol dewatering processes, among the biological sludge being dehydrated by the dehydration means, granular sludge with a particle size of more than 200μm 15% There are more.

  According to the present invention, it is possible to reduce the water content of dehydrated sludge after dehydration.

It is a schematic diagram which shows an example of a structure of the waste water treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows an example of a structure of the semibatch type biological treatment tank used with the waste water treatment apparatus of FIG. It is a schematic diagram which shows another example of a structure of the waste water treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows another example of a structure of the waste water treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows another example of a structure of the waste water treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows an example of a structure of the semibatch type biological treatment tank used for the waste water treatment apparatus shown in FIG.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a wastewater treatment apparatus according to the present embodiment. The wastewater treatment apparatus 1 shown in FIG. 1 includes a continuous biological treatment apparatus including a continuous biological treatment tank 10 and a solid-liquid separation tank 14, a semi-batch biological treatment tank 12, a wastewater storage tank 16, and a dehydration apparatus 18. . In this specification, the “continuous type” is a method for a batch type, and, like a semi-batch type, the inflow of wastewater, biological treatment, sludge settling, and discharge of treated water are repeated in one reaction tank. It is distinguished from semi-batch processing. Further, in the present embodiment, the continuous type is not limited to a method in which drainage is continuously poured into the reaction tank and is operated, but the reaction is performed by a pump using a principle such as a reciprocating motion such as a diaphragm pump. The system may be operated by supplying wastewater to the tank, or a raw water tank is installed in front of the reaction tank, and the pump operation is controlled according to the water level of the raw water tank (when the water level is high). May be a simulated continuous water supply system that operates the pump and stops the pump when the water level is low) to supply waste water to the reaction tank.

  The wastewater treatment apparatus 1 shown in FIG. 1 includes drainage inflow lines 20a, 20b, and 20c, treated water discharge lines 22a and 22b, a sludge return line 24, a sludge discharge line 26, and a biological sludge supply line 28. 1 includes a first drainage inflow pump 30, a second drainage inflow pump 32, a treated water discharge pump 34, a sludge supply pump 36, and a sludge return pump 38. The first drainage inflow pump 30 is installed in the drainage inflow line 20a, the second drainage inflow pump 32 is installed in the drainage inflow line 20b, the treated water discharge pump 34 is installed in the treated water discharge line 22b, and the sludge supply pump 36 is The sludge return line 38 is installed in the biological sludge supply line 28, and the sludge return pump 38 is installed in the sludge return line 24. The sludge discharge line 26 is provided with a valve 40.

  One end of the drainage inflow line 20 a is connected to the drainage outlet of the drainage storage tank 16, and the other end is connected to the drainage inlet of the continuous biological treatment tank 10. One end of the drainage inflow line 20 b is connected to the drainage outlet of the drainage storage tank 16, and the other end is connected to the drainage inlet of the semi-batch biological treatment tank 12. One end of the drainage inflow line 20 c is connected to the drainage outlet of the continuous biological treatment tank 10, and the other end is connected to the drainage inlet of the solid-liquid separation tank 14. The treated water discharge line 22 a is connected to the treated water outlet of the solid-liquid separation tank 14. One end of the sludge return line 24 is connected to the sludge outlet of the solid-liquid separation tank 14, and the other end is connected to the sludge inlet of the continuous biological treatment tank 10. One end of the sludge discharge line 26 is connected to the sludge return line 24, and the other end is connected to the dehydrator 18. One end of the biological sludge supply line 28 is connected to the sludge outlet of the semi-batch biological treatment tank 12, and the other end is connected to the sludge supply port of the continuous biological treatment tank 10. One end of the treated water discharge line 22b is connected to the treated water outlet of the semi-batch biological treatment tank 12, and the other end is connected to the treated water inlet of the continuous biological treatment tank 10.

  FIG. 2 is a schematic diagram showing an example of the configuration of a semi-batch biological treatment tank used in the wastewater treatment apparatus of FIG. In the semi-batch biological treatment tank 12 shown in FIG. 2, there are four steps: (1) inflow of wastewater, (2) biological treatment of wastewater with biological sludge, (3) sedimentation of biological sludge, and (4) discharge of treated water. The granule sludge is formed by repeating the above. The semi-batch biological treatment tank 12 shown in FIG. 2 includes a stirring device 48, an air pump 50, and an aeration device 52. The air diffuser 52 is connected to the air pump 50, and the air supplied from the air pump 50 is supplied into the tank through the air diffuser 52. In addition, the stirring device 48 has a structure in which a shaft attached to the motor rotates by driving the motor, and a stirring blade attached to the tip of the shaft rotates with the rotation of the shaft. The stirring device 48 is not limited to the above configuration. The semi-batch biological treatment tank 12 is provided with a drainage inlet 12a and a treated water outlet 12b, a drainage inflow line 20b is connected to the drainage inlet 12a, and a treated water discharge line 22b is connected to the treated water outlet 12b. Yes. The semi-batch biological treatment tank 12 is provided with a sludge outlet 12c, and a biological sludge supply line 28 is connected thereto.

  The drainage inflow line 20b and the second drainage inflow pump 32 shown in FIG. 2 function as a semi-batch type drainage supply device that intermittently supplies wastewater to the semi-batch type biological treatment tank 12. In the present embodiment, intermittent supply of drainage is performed by operating / stopping the second drainage inflow pump 32. For example, a valve or the like is installed in the drainage inflow line 20b, and intermittent supply of drainage is performed by opening and closing the valve. May be.

  The treated water discharge line 22 b and the treated water discharge pump 34 shown in FIG. 2 function as a treated water supply device that supplies treated water to the continuous biological treatment tank 10. In addition, you may install a valve | bulb etc. in the treated water discharge line 22b suitably. In the present embodiment, the treated water discharge line 22b is connected to the continuous biological treatment tank 10, but is not limited thereto, and is connected to the solid-liquid separation tank 14 and the treated water discharge line 22a. It is good also as a structure.

  The biological sludge supply line 28 and the sludge supply pump 36 shown in FIG. 2 function as a sludge supply device that supplies granular sludge to the continuous biological treatment tank 10. In addition, you may install a valve | bulb etc. in the biological sludge supply line 28 suitably.

  The drainage inflow line 20 a and the first drainage inflow pump 30 shown in FIG. 1 function as a continuous-side drainage supply device that supplies drainage to the continuous biological treatment tank 10.

  The continuous biological treatment tank 10 shown in FIG. 1 is, for example, the presence of biological sludge such as granule sludge supplied from the semi-batch biological treatment tank 12 under aerobic conditions in which wastewater is aerated by an air diffuser or the like. Below, the wastewater which flows in continuously is biologically treated (for example, the organic matter in the wastewater is oxidized to carbon dioxide).

  The solid-liquid separation tank 14 shown in FIG. 1 is a separation device for separating biological sludge-containing water (biologically treated water) into biological sludge and treated water. For example, sedimentation separation, pressurized flotation, filtration, membrane Separation devices such as separation may be mentioned.

  The dehydrating device 18 shown in FIG. 1 functions as a device that dehydrates the biological sludge separated in the solid-liquid separation tank 14 to obtain dehydrated sludge (cake). A desorbed water discharge line 19 is connected to the discharge port of the dehydrator 18. Examples of the dehydrating apparatus 18 include a filter press type dehydrating apparatus, a screw press type dehydrating apparatus, a belt press type dehydrating apparatus, a centrifugal dehydrating apparatus, and a multiple disk type dehydrating apparatus.

  In the present embodiment, for example, the above-described pumps are not necessarily installed as long as the apparatus configuration and the piping configuration are capable of feeding wastewater, sludge, and the like passing through the line by gravity or extrusion flow.

  An example of operation | movement of the waste water treatment equipment 1 of this embodiment is demonstrated.

  In the waste water storage tank 16 shown in FIG. 1, waste water to be treated is stored. Examples of the wastewater to be treated include wastewater such as food processing factory wastewater, chemical factory wastewater, semiconductor factory wastewater, machine factory wastewater, sewage, human waste, and river water. Further, the wastewater generally contains biodegradable organic substances. In addition, when the biologically indegradable organic substance is contained in the waste water, it is desirable to remove by performing physicochemical treatment such as flotation separation, agglomeration pressure flotation device, and an adsorption device in advance.

  First, the first drainage inflow pump 30 is operated, and the wastewater to be treated in the drainage storage tank 16 is supplied to the continuous biological treatment tank 10 from the drainage inflow line 20a. In the continuous biological treatment tank 10, biological treatment of wastewater with biological sludge is performed under aerobic conditions.

  The biological treatment liquid treated in the continuous biological treatment tank 10 is supplied to the solid-liquid separation tank 14 from the wastewater inflow line 20c to separate biological sludge from the biological treatment liquid. The sludge return pump 38 is operated, and the solid-liquid separated sludge is returned from the sludge return line 24 to the continuous biological treatment tank 10. Further, the valve 40 is opened, and the biological sludge separated from the sludge discharge line 26 is supplied to the dehydrator 18. In addition, the biological sludge separated into solid and liquid may be supplied to the dehydrator 18 by installing a pump in the sludge discharge line 26 and operating the pump.

  Further, the treated water in the solid-liquid separation tank 14 is also discharged out of the system from the treated water discharge line 22a. The biological sludge is dehydrated by the dehydrator 18 to obtain dehydrated sludge. During the dehydration treatment, water desorbed from the biological sludge (desorbed water) is discharged from the desorbed water discharge line 19.

  When the semi-batch biological treatment tank 12 is operated, the second drainage inflow pump 32 is operated, and the wastewater in the drainage storage tank 16 is supplied from the drainage inflow line 20b to the semi-batch biological treatment tank 12 ((1 ) Inflow of wastewater). Waste water is introduced into the semi-batch biological treatment tank 12 until a predetermined amount is reached, and the second waste water inflow pump 32 is stopped. Next, the air pump 50 is operated to introduce air into the semi-batch biological treatment tank 12 from the air diffuser 52, and the agitator 48 is operated to stir the wastewater in the semi-batch biological treatment tank 12. Then, biological treatment of wastewater is performed ((2) biological treatment of wastewater).

  After performing the biological treatment process of wastewater for a predetermined time, the air pump 50 and the stirring device 48 are stopped, and the biological treatment process is ended. After completion of the biological treatment, the biological sludge in the semi-batch biological treatment tank 12 is allowed to settle for a predetermined time, and is separated into biological sludge and treated water in the semi-batch biological treatment tank 12 ((3) sedimentation of biological sludge). . Next, the treated water discharge pump 34 is operated, the treated water in the semi-batch biological treatment tank 12 is discharged from the treated water discharge line 22b ((4) discharged treated water), and the continuous biological water is discharged from the treated water discharge line 22b. Supply to the treatment tank 10. And the biological sludge in the semi-batch type biological treatment tank 12 is granulated by repeating the steps (1) to (4), and granulated sludge is formed.

  Further, the sludge supply pump 36 is operated to supply the granular sludge formed in the semi-batch type biological treatment tank 12 to the continuous biological treatment tank 10 from the biological sludge supply line 28. The supply of granule sludge from the semi-batch biological treatment tank 12 may be performed in the (3) biological sludge sedimentation process, (2) the biological treatment process of wastewater, or (4 ) You may carry out at the process water discharge process. The granular sludge formed in the semi-batch biological treatment tank 12 is a sludge that has been self-granulated, for example, a biological sludge having an average particle diameter of 200 μm or more. In the present embodiment, whether or not granulated sludge has been formed is determined by measuring the particle size distribution of the sludge in the semi-batch biological treatment tank 12, and when the average particle size reaches 200 μm or more. It can be judged that le sludge has been formed. Alternatively, the SVI value is periodically measured by a sedimentation test of sludge in the semi-batch biological treatment tank 12, and the value of SVI5 calculated from the volume ratio after settling for 5 minutes is equal to or less than a predetermined value (for example, 80 mL / g or less). ), It may be determined that granule sludge has been formed (the lower the SVI value, the larger the average particle size, the better the granular sludge can be determined).

  In the present embodiment, the granular sludge generated in the semi-batch biological treatment tank 12 is supplied from the biological sludge supply line 28 to the continuous biological treatment tank 10, and 200 μm among the biological sludge in the continuous biological treatment tank 10. By increasing the proportion of granule sludge having the above particle size, the proportion of granule sludge in the biological sludge supplied to the dehydrator 18 via the continuous biological treatment tank 10 and the solid-liquid separation tank 14 is increased. doing. Specifically, the granular sludge generated in the semi-batch biological treatment tank 12 is supplied to the continuous biological treatment tank 10 from the biological sludge supply line 28 and is 200 μm or more among the biological sludge to be dehydrated by the dehydrator 18. The ratio of granular sludge having a particle size of 15% or more, preferably 25% or more. And it is possible to reduce the moisture content of the dewatered sludge dehydrated by the dewatering device 18 by making the ratio of the granular sludge having a particle size of 200 μm or more out of the biological sludge to be dehydrated to 15% or more. Become. As a result, among biological sludge to be dehydrated, the proportion of granular sludge having a particle size of 200 μm or more is 15% or more, compared with the case where the proportion is less than 15%. Can be reduced.

  An example of a method for adjusting the proportion of granular sludge in the biological sludge supplied to the dehydrator 18 will be described below. When the granule sludge formed in the semi-batch biological treatment tank 12 is added to the continuous biological treatment tank 10, the amount of granule sludge depends on the amount of granule sludge formed in the semi-batch biological treatment tank 12. . That is, when the same waste water is branched in the semi-batch biological treatment tank 12 and the continuous biological treatment tank 10, for example, the waste water treatment in the semi-batch biological treatment tank 12 and the continuous biological treatment tank 10 is performed. In the solid-liquid separation tank 14 by adjusting the ratio and introducing the granular sludge formed in the continuous biological treatment tank 10 with the treatment ratio in the semi-batch biological treatment tank 12 in the waste water to be treated being 15% or more. Of the biological sludge, the ratio of granular sludge having a particle size of 200 μm or more can be made 15% or more.

  In the present embodiment, the granular sludge generated in the semi-batch biological treatment tank 12 is supplied from the biological sludge supply line 28 to the continuous biological treatment tank 10, so that the granules in the biological sludge supplied to the dehydrator 18 can be obtained. Although the ratio of sludge is adjusted, it is not limited to this. Other embodiments will be described below.

  3 and 4 are schematic views showing another example of the configuration of the waste water treatment apparatus according to the present embodiment. In the waste water treatment apparatuses 2 and 3 shown in FIGS. 3 and 4, the same components as those in the waste water treatment apparatus 1 shown in FIG.

  In the wastewater treatment apparatus 2 shown in FIG. 3, one end of the biological sludge supply line 28 is connected to the semi-batch type biological treatment tank 12 and the other end is connected to the solid-liquid separation tank 14. In the wastewater treatment apparatus 2 shown in FIG. 3, a biological treatment liquid containing biological sludge in the continuous biological treatment tank 10 is supplied from the wastewater inflow line 20 c to the solid-liquid separation tank 14 and in the semi-batch biological treatment tank 12. The granular sludge is supplied to the solid-liquid separation tank 14 through the biological sludge supply line 28. By opening the valve 40, the biological sludge separated from the sludge discharge line 26 is supplied to the dehydrator 18. In addition, the biological sludge separated into solid and liquid may be supplied to the dehydrator 18 by installing a pump in the sludge discharge line 26 and operating the pump.

  In the wastewater treatment apparatus 3 shown in FIG. 4, one end of the biological sludge supply line 28 is connected to the semi-batch biological treatment tank 12 and the other end is connected to the dehydration apparatus 18. In the waste water treatment apparatus 3 shown in FIG. 4, the biological sludge in the continuous biological treatment tank 10 is supplied from the sludge discharge line 26 to the dehydrator 18 via the solid-liquid separation tank 14 and is also semi-batch biological treatment tank 12. The inner granular sludge is supplied from the biological sludge supply line 28 to the dehydrator 18. In the wastewater treatment apparatus 3 shown in FIG. 4, the granular sludge formed in the semi-batch biological treatment tank 12 is not supplied to the continuous biological treatment tank 10 or the solid-liquid separation tank 14. Sludge is mainly floating sludge (floc). The suspended sludge is biological sludge having an average particle size of less than 200 μm. Therefore, the amount of biological sludge supplied from the sludge discharge line 26 and the biological sludge supply so that the granular sludge having a particle diameter of 200 μm or more among the biological sludge supplied to the dehydrator 18 becomes 15% or more. It is necessary to adjust the supply amount of the granular sludge supplied from the line 28. In FIG. 4, the biological sludge separated from the sludge discharge line 26 is supplied to the dewatering device 18 by opening the valve 40, but a pump is installed in the sludge discharge line 26 to operate the pump. By doing so, the biological sludge separated into solid and liquid may be supplied to the dehydrator 18.

  In any of the above wastewater treatment apparatuses, the proportion of granular sludge having a particle size of 200 μm or more is 15% or more with respect to the biological sludge to be dehydrated by the dehydration apparatus 18. It becomes possible to reduce the moisture content.

  In the wastewater treatment apparatus of FIGS. 1, 3 and 4, the semi-batch biological treatment tank 12 is used from the viewpoint of reducing the moisture content of the dewatered sludge and improving the wastewater treatment speed by the continuous biological treatment tank 10. It is preferable to use the wastewater treatment apparatus 1 shown in FIG. 1 that supplies the generated granular sludge from the biological sludge supply line 28 to the continuous biological treatment tank 10. Moreover, the granular sludge produced in the semi-batch biological treatment tank 12 is biologically reduced because the moisture content of the dehydrated sludge is reduced and the ratio of the granular sludge during the dehydration process can be easily adjusted. It is preferable to use the waste water treatment equipment (2, 3) shown in FIG. 3 and FIG.

  The MLSS concentration of the semi-batch biological treatment tank 12 is preferably operated in the range of 2000 to 20000 mg / L. In order to maintain the soundness (sedimentation, activity, etc.) of biological sludge, it is desirable to maintain an appropriate sludge load, preferably in the range of 0.05 to 0.60 kg BOD / MLSS / day, more preferably It is desirable to pull out the granular sludge from the tank so that it is kept in the range of 0.1 to 0.5 kg BOD / MLSS / day.

  In the formation of granular sludge in the semi-batch biological treatment tank 12, it is desirable to properly control the settling time and the wastewater inflow rate per batch. The settling time for stopping the agitation (including agitation by aeration) and settling the sludge is calculated from the distance from the water surface to the target sludge interface position and the sludge settling speed, for example, 4 min / m to 15 min / It is preferably set between m and more preferably set between 5 minutes / m and 10 minutes / m. Moreover, the wastewater inflow rate (ratio of inflow water to the effective volume during reaction) is preferably in the range of 20% to 120%, for example, and more preferably in the range of 40% to 120%. As sludge repeatedly experiences a state in which the concentration of organic matter, which is the treatment target substance, is very high (immediately after the inflow process, a satiety state) and a state in which the organic matter concentration is very low (the end of the biological treatment process, starvation state), Since granulation is considered to progress, the drainage inflow rate should be as high as possible from the viewpoint of forming granular sludge. On the other hand, the higher the drainage inflow rate, the more the inflow pump This increases the capacity and the cost. Therefore, the drainage inflow rate is preferably in the range of 40% or more and 120% or less in terms of formation of granule sludge and cost reduction.

  The pH in the semi-batch biological treatment tank 12 is preferably adjusted to a range of 6 to 9 suitable for general biological treatment, and more preferably adjusted to a range of 6.5 to 7.5. When the pH value is out of the above range, it is preferable to adjust the pH using an acid or an alkali. When pH adjustment is performed in the semi-batch biological treatment tank 12, the pH adjustment is performed in a state where the semi-batch biological treatment tank 12 is stirred rather than in a state where the pH value is appropriately measured. It is desirable to do. The dissolved oxygen (DO) in the semi-batch biological treatment tank 12 is preferably 0.5 mg / L or more, more preferably 1 mg / L or more, which is suitable for general biological treatment.

  In this embodiment, (1) inflow of wastewater, (2) biological treatment of wastewater, (3) sedimentation of biological sludge, and (4) discharge of treated water are repeatedly performed, so that granular sludge having a particle size of 200 μm or more is obtained. However, the semi-batch biological treatment tank 12 is not necessarily used. In addition to the semi-batch biological treatment tank 12, any apparatus (granule sludge forming apparatus) capable of forming granule sludge may be used, and examples thereof include anaerobic UASB and EGEB.

  Moreover, in the waste water treatment apparatus of this embodiment, for example, a granule sludge forming apparatus such as the semi-batch type biological treatment tank 12 is provided, but it is not always necessary to have a granule sludge forming apparatus. For example, when a granular sludge having a particle diameter of 200 μm or more is formed in a separate wastewater treatment system, the granular sludge is converted into a continuous biological treatment tank 10, a solid-liquid separation tank 14, and a dehydrator 18. A biological sludge supply device (biological sludge supply line 28) may be installed so as to be supplied to at least one of the above.

  In the continuous biological treatment tank 10, an example in which biological treatment is performed by a standard activated sludge method for treating organic substances or the like has been described as an example. However, the present invention is not limited to this. For example, A2O (Anaerobic-Anoxic-Oxic) Biological treatment by systems such as nutrient removal systems (systems equipped with anaerobic treatment tanks and anaerobic treatment tanks) such as Process and AO (Anaerobic-Oxic Process), oxidation ditch method, step inflow type multi-stage activated sludge method, etc. It may be a device that performs the above. Moreover, the apparatus which performs biological treatment in presence of carriers, such as a polyurethane, a plastics, resin, may be sufficient.

  It is desirable that the continuous biological treatment tank 10 is operated, for example, in a range where the sludge concentration in the tank is 1500 to 20000 mg / L. In order to maintain the soundness (sedimentation, activity, etc.) of biological sludge, the sludge load is preferably in the range of 0.05 to 0.6 kg BOD / MLSS / day, and 0.1 to 0.5 kg BOD. More preferably, the range is / MLSS / day.

  The pH in the continuous biological treatment tank 10 is preferably adjusted to a range of 6 to 9 suitable for general biological treatment, and more preferably adjusted to a range of 6.5 to 7.5. In addition, the dissolved oxygen (DO) in the continuous biological treatment tank 10 is preferably 0.5 mg / L or more, more preferably 1 mg / L or more, which is suitable for general biological treatment.

  The continuous biological treatment apparatus of this embodiment is a form in which biological treatment and solid-liquid separation are performed in separate tanks, but is not limited to this. For example, biological treatment and solid-liquid separation are performed in one tank. It may be a submerged membrane separator. The submerged membrane separation apparatus includes, for example, a continuous biological treatment tank and a submerged membrane module as solid-liquid separation means installed in the continuous biological treatment tank.

  In the wastewater treatment apparatus of the present embodiment, the biological sludge (including granule sludge) discharged from the solid-liquid separation tank 14 is continuous from the viewpoint of improving the treatment efficiency of wastewater by circulating the granule sludge. It is preferable to provide a sludge return line 24 for returning to the biological treatment tank 10.

  FIG. 5 is a schematic diagram illustrating another example of the configuration of the waste water treatment apparatus according to the present embodiment. In the waste water treatment apparatus 4 of FIG. 5, the same components as those of the waste water treatment apparatus 1 shown in FIG. In the waste water treatment apparatus 4 shown in FIG. 5, the waste water inflow pump 31 and the valve 44 are provided in the waste water inflow line 20a, and the valve 46 is provided in the waste water inflow line 20b. One end of the drainage inflow line 20 b is connected to the drainage inflow line 20 a between the drainage inflow pump 31 and the valve 44, and the other end is connected to the drainage inlet of the semi-batch biological treatment tank 15. 5 includes a sludge treated water supply line 58 that supplies treated water and granulated sludge discharged from the semi-batch biological treatment tank 15 to the continuous biological treatment tank 10. A valve 60 is provided in the sludge treated water supply line 58. The sludge treated water supply line 58 functions as a treated water supply device for supplying treated water discharged from the semi-batch biological treatment tank 15 to the continuous biological treatment tank 10 and granulated sludge to the continuous biological treatment tank 10. It functions as a sludge supply device.

  FIG. 6 is a schematic diagram showing an example of the configuration of a semi-batch biological treatment tank used in the wastewater treatment apparatus shown in FIG. In the semi-batch biological treatment tank 15 shown in FIG. 6, the same components as those in the semi-batch biological treatment tank 12 shown in FIG. In the semi-batch biological treatment tank 15 shown in FIG. 6, a sludge treated water outlet 12d for discharging treated water and granular sludge is provided, and one end of a sludge treated water supply line 58 is connected to the sludge treated water outlet 12d. Yes. The other end of the sludge treated water supply line 58 is connected to the continuous biological treatment tank 10. In the semi-batch biological treatment tank 15 shown in FIG. 6, the drainage inlet 12a into which drainage flows is provided at a position lower than the sludge treated water outlet 12d.

  In the semi-batch biological treatment tank 15 shown in FIG. 6, the inflow of waste water and the discharge of treated water are performed simultaneously. That is, steps such as inflow of wastewater and discharge of treated water, biological treatment of a treatment target substance, and sedimentation of biological sludge are repeatedly performed. An example of the operation of the semi-batch biological treatment tank 15 shown in FIG. 6 will be described below together with the operation of the waste water treatment apparatus 4 shown in FIG.

  First, the drainage inflow pump 31 is operated, the valve 44 is opened, and the wastewater to be treated in the drainage storage tank 16 is continuously supplied from the drainage inflow line 20a to the continuous biological treatment tank 10. After the biological treatment of the wastewater is performed in the continuous biological treatment tank 10, the treated water is supplied to the solid-liquid separation tank 14 from the drainage inflow line 20c. When the semi-batch biological treatment tank 15 is operated, the valve 46 and the valve 60 are opened, and the waste water is supplied from the drainage inflow line 20b to the semi-batch biological treatment tank 15, and the semi-batch biological treatment tank 15 is provided. 15 is supplied from the sludge treated water supply line 58 to the continuous biological treatment tank 10 (inflow of wastewater / discharge of treated water). At this time, by operating the stirring device 48, the granular sludge in the semi-batch biological treatment tank 15 can be efficiently supplied from the sludge treated water supply line 58 to the continuous biological treatment tank 10. Then, the valve 46 and the valve 60 are closed, the air pump 50 is operated while the stirring device 48 is operated, the supply of air into the semi-batch biological treatment tank 15 is started, and the wastewater is biologically treated (biological treatment). Process).

  After a predetermined time has elapsed, the supply of air is stopped by stopping the operation of the air pump 50, and the biological treatment is ended by stopping the stirring device 48. After completion of the biological treatment, the biological sludge in the semi-batch biological treatment tank 15 is allowed to settle for a predetermined time, and is separated into biological sludge and treated water in the semi-batch biological treatment tank 15 (sedimentation of biological sludge). Then, the process proceeds again to the inflow of wastewater / discharge process water.

  Further, as described above, the granular sludge from the semi-batch biological treatment tank 15 is increased until the granular sludge having a particle size of 200 μm or more among the biological sludge in the solid-liquid separation tank 14 becomes 15% or more. Repeat the supply. Then, when the granular sludge having a particle size of 200 μm or more among the biological sludge in the solid-liquid separation tank 14 becomes 15% or more, the valve 40 is opened and the biological sludge is removed from the sludge discharge line 26 to the dehydrator 18. Supply sludge. In addition, the biological sludge separated into solid and liquid may be supplied to the dehydrator 18 by installing a pump in the sludge discharge line 26 and operating the pump. In the waste water treatment apparatus 4 shown in FIG. 5, the granular sludge formed in the semi-batch biological treatment tank 15 is supplied to the continuous biological treatment tank 10, but as described above, the solid-liquid separation tank 14 and the dehydrator 18 may be supplied.

  In this embodiment, since the waste water inlet 12a provided in the semi-batch biological treatment tank 15 is disposed at a position lower than the sludge treated water outlet 12d, the waste water flowing into the semi-batch biological treatment tank 15 is biologically treated. Without being discharged from the semi-batch biological treatment tank 15 (short-cut of drainage) is suppressed. As a result, it is possible to efficiently form granular sludge in the semi-batch biological treatment tank 15. In addition, the treated water in the semi-batch biological treatment tank 15 is discharged in a form that is pushed up by the inflowing waste water, so that biological sludge with low sedimentation (such as sludge that is not granulated) is actively treated. It becomes possible to discharge outside. As a result, biological sludge having a high sedimentation property remains in the semi-batch biological treatment tank 15, so that the granular sludge can be formed more efficiently.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail more concretely, this invention is not limited to a following example.

  In the examples, using the semi-batch biological treatment tank shown in FIG. 2, the inflow of wastewater, biological treatment of wastewater, sedimentation of biological sludge, and discharge of treated water were repeated to form granules. The drainage used was simulated drainage mainly composed of fish extract and peptone.

  Using a continuous biological treatment tank, biological treatment by the activated sludge method was performed on the simulated waste water. The biological sludge in the continuous biological treatment tank was taken out, and the granular sludge formed in the semi-batch biological treatment tank was mixed. The particle size distribution of the mixed sludge was measured with a laser diffraction particle size distribution meter. By dividing the peak area with a particle size of 200 μm or more in the obtained particle size distribution by the total peak area, the ratio of the granular sludge to the mixed sludge was determined. As a result, granule sludge having a particle size of 200 μm or more with respect to the mixed sludge was 15.1%.

  In the comparative example, the biological treatment by the activated sludge method was performed on the simulated waste water using a continuous biological treatment tank. The biological sludge in the continuous biological treatment tank was taken out, and the particle size distribution of the biological sludge was measured with a laser diffraction particle size distribution meter. From the obtained particle size distribution, the ratio of granular sludge having a particle size of 200 μm or more to the biological sludge was obtained as in the example, and the result was 4.5%.

  The mixed sludge of the example and the biological sludge of the comparative example were respectively put into a pressure dehydration leaf tester, and a dehydration test was performed under the following test conditions.

<Test conditions>
Press-in pressure: 0.7 MPa
Press-in time: 60 minutes Pressing pressure: 0.7 MPa
Squeeze time: 60 minutes (or end when the filtrate flow rate reaches 1 mL / 5 minutes)
<Pressure dehydration leaf tester>
Model: Single-side filtration side feed type Dimensions: 144mm x 144mm
Filter cloth: N856
Filtration area: 0.0209 m ²
Filter chamber thickness: 15mm
Filter chamber volume: 0.314 L / room

  The moisture content of the dewatered sludge after the dehydration test of the examples and comparative examples was measured according to a sewage test method (issued by the Japan Sewerage Association). The moisture content of the dewatered sludge of the example was 72.5%, whereas the moisture content of the dehydrated sludge of the comparative example was 85.2%. As a result of this reduction in water content, the amount of sludge discarded is 53.8, with sludge with a water content of 85.2% being 100, and a sludge reduction of about 46% is possible with 72.5%. . From this result, it can be said that the moisture content of the dewatered sludge could be reduced by dehydrating the biological sludge having a granular sludge having a particle size of 200 μm or more in an amount of 15% or more.

  1-4 Wastewater treatment device, 10 continuous biological treatment tank, 12, 15 semi-batch biological treatment tank, 12a wastewater inlet, 12b treated water outlet, 12c sludge outlet, 12d sludge treated water outlet, 14 solid-liquid separation tank, 16 Wastewater storage tank, 18 Dewatering device, 19 Desorption water discharge line, 20a, 20b, 20c Drainage inflow line, 22a, 22b Treated water discharge line, 24 Sludge return line, 26 Sludge discharge line, 28 Biological sludge supply line, 30 Wastewater inflow pump, 31 Wastewater inflow pump, 32 Second wastewater inflow pump, 34 Treated water discharge pump, 36 Sludge supply pump, 38 Sludge return pump, 40, 44, 46, 60 Valve, 48 Stirrer, 50 Air pump, 52 Scatter Gas equipment, 58 sludge treated water supply line.

Claims (4)

A dehydration method for obtaining dehydrated sludge by dehydrating biological sludge containing floating sludge,
In the dehydration treatment, a granular sludge having a particle size of 200 μm or more is added to the biological sludge so that the proportion of the granular sludge in the biological sludge is 15% or more. Processing method. A continuous biological treatment step of separating biological sludge from biological treatment liquid by solid-liquid separation means after biological treatment of the wastewater with biological sludge while continuously flowing wastewater into a continuous biological treatment tank;
Dehydrating the biological sludge solid-liquid separated in the continuous biological treatment step to obtain a dehydrated sludge; and
And a sludge supplying step of supplying the organism sludge when pretreated Symbol dehydrated granular sludge having a particle size of more than 200 [mu] m,
Of the biological sludge to be dehydrated in the dehydration treatment step, 15% or more of the granular sludge having a particle size of 200 μm or more is present. An inflow process for introducing wastewater, a biological treatment process for biologically treating the wastewater with biological sludge, a sedimentation process for sedimenting the biological sludge, and a discharge process for discharging treated water are repeated in a semi-batch biological treatment tank, It has a semi-batch biological treatment process that forms granular sludge,
The wastewater treatment method according to claim 2, wherein the granule sludge in the sludge supply step is granule sludge formed in the semi-batch biological treatment step. A continuous biological treatment apparatus comprising: a continuous biological treatment tank that biologically treats the wastewater with biological sludge while continuously flowing wastewater; and a solid-liquid separation means that separates biological sludge from the biological treatment liquid. ,
Dehydration treatment means for dehydrating biological sludge separated into solid and liquid by the continuous biological treatment apparatus to obtain dehydrated sludge;
And a sludge supply means for supplying to the organism sludge when pretreated Symbol dehydrated granular sludge having a particle size of more than 200 [mu] m,
Of the biological sludge to be dewatered by the dewatering means, 15% or more of the granular sludge having a particle size of 200 μm or more is present.

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