Sewage treatment device and sewage treatment method

Abstract

To provide a sewage treatment apparatus and a sewage treatment method capable of automatic settling of a scum in a sedimentation tank.SOLUTION: A sewage water is purified by using an active sludge in an aeration tank, a sludge is allowed to be sedimented in a sedimentation tank to separate a supernatant water. A treatment water which is the supernatant water prepared by sedimenting the sludge in the sedimentation tank and before a sterilization treatment is sprinkled intermittently by using sprinkling means from an upper part of the sedimentation tank. By this, a scum can be sedimented automatically, hence time and work needed by manual labor can be drastically reduced. Also, treatment water is reused, hence a concept of cascade utilization applied to water treatment technique has been followed, and effective use of water resource and reduction of water rate can be enabled.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a wastewater treatment device and a wastewater treatment method for microbially treating organic pollutants contained in wastewater. [Background technology]

[0002] Methods for treating wastewater such as domestic wastewater include, for example, those that utilize microorganisms. In this wastewater treatment method, for example, wastewater is temporarily stored in an adjustment tank, then sent to an aeration tank for aeration, and then activated sludge is separated by settling in a settling tank, and the supernatant water is discharged. At this time, some of the sludge may not accumulate at the bottom of the settling tank, but may rise to the water surface as scum. Scum is sludge that contains air and rises to the water surface due to the influence of aeration, and hardens and floats on the water surface. If this scum is generated in excess, there is a concern that it may have a negative effect on water quality, such as a decrease in transparency. For this reason, in large-scale wastewater treatment devices, for example, a scum recovery device that uses a scum scraping plate to scrape and collect scum is installed above the settling tank to remove the scum (see, for example, Patent Document 1).

[0003] On the other hand, in the case of small and medium-sized wastewater treatment plants that are not large enough to install a scum recovery device, the area of ​​the settling tank is small and the depth is deep, so sludge tends to sink, and operation is controlled to prevent scum from forming. However, it is difficult to control the plant to completely prevent scum from forming, so regular inspections are required, and when scum does form, tap water must be sprayed on the scum or a rod-shaped member must be used to stir it, crushing the lumps of scum and allowing them to settle. This work is performed by workers, which is time-consuming and labor-intensive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-101858 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above problems, and has an object to provide a sewage treatment apparatus and a sewage treatment method capable of automatically settling scum in a settling tank. [Means for solving the problem]

[0006] The sewage treatment device of the present invention purifies sewage by utilizing activated sludge, and is equipped with an aeration tank for storing and aerating sewage together with activated sludge, a sedimentation tank for storing the sewage that has been aerated in the aeration tank and for settling the sludge, a treated water tank for storing treated water which is the supernatant water obtained by settling the sludge in the sedimentation tank and which has not yet been sterilized, and a sprinkling means for intermittently spraying the treated water from the treated water tank over the top of the sedimentation tank.

[0007] The wastewater treatment method of the present invention involves purifying wastewater with activated sludge in an aeration tank, then settling the sludge in a settling tank and separating it from supernatant water. The supernatant water obtained by settling the sludge in the settling tank, which is treated water prior to sterilization, is intermittently sprayed from above the settling tank to break up and settle the scum. Effect of the Invention

[0008] According to the present invention, the treated water is intermittently sprayed from above the settling tank, so that the scum can be automatically settled, and the time and effort required for manual work can be significantly reduced. In addition, the treated water is reused, so that the concept of cascade utilization used in recent water treatment technology is followed, and it is possible to effectively utilize water resources and reduce water charges. Furthermore, since the treated water is used, clogging of the spraying means can be suppressed, and since it is treated water before sterilization, the occurrence of rust in the spraying means and the effect on microorganisms can be suppressed.

[0009] Furthermore, if the sprinkler pipe is provided with a first sprinkler hole that sprays the treated water downward, a second sprinkler hole that sprays the treated water diagonally downward to the right, and a third sprinkler hole that sprays the treated water diagonally downward to the left, water can be sprayed more effectively and the scum can be allowed to settle.

[0010] Furthermore, if the sprinkling of water by the sprinkling means and the transport of sludge by the sludge transporting means are each carried out intermittently, and a predetermined time is then passed between the sprinkling of water by the sprinkling means and the transport of sludge by the sludge transporting means, then the sludge can be transported efficiently and the wastewater can be treated efficiently. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a configuration of a wastewater treatment device according to an embodiment of the present invention. [Diagram 2] 2 shows the configuration of the water sprinkling means shown in FIG. 1. [Diagram 3] This shows the configuration of the sprinkler pipe shown in Figure 2. [Figure 4] 3 shows a cross-sectional configuration of the sprinkler pipe shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0013] 1 is a diagram showing a schematic configuration of a wastewater treatment device 10 according to an embodiment of the present invention. This wastewater treatment device 10 can be preferably used in small- to medium-sized facilities such as parking areas installed on expressways.

[0014] The sewage treatment device 10 includes, for example, a grit basin 11 for settling and removing sand and the like in the sewage M1, an adjustment tank 12 for temporarily storing the sewage M1 flowing in from the grit basin 11 and adjusting fluctuations in the flow rate and water quality of the sewage M1, an aeration tank 13 for storing the sewage M1 flowing in from the adjustment tank 12 together with activated sludge and aerating it, a settling tank 14 for storing the sewage M1 that has been aerated in the aeration tank 13 and settling the sludge M2 to separate it into the sludge M2 and the supernatant water, treated water M3, and a sludge transfer means 15 for intermittently returning a portion of the sludge M2 that has settled at the bottom of the settling tank 14 to the aeration tank 13.

[0015] The adjustment tank 12 is connected to, for example, the grit basin 11 and the aeration tank 13 by piping (not shown). For example, a water level sensor and an adjustment pump (not shown) are provided in the adjustment tank 12, and the sewage M1 is caused to flow into the aeration tank 13 by the adjustment pump in response to a signal from the water level sensor. The aeration tank 13 purifies the sewage M1 by using activated sludge, and sends air into the sewage M1 to decompose organic matter contained in the sewage M1 by microorganisms. The aeration tank 13 and the sedimentation tank 14 are connected to, for example, by piping (not shown). The lower part of the sedimentation tank 14 is preferably popper-shaped. The sludge transfer means 15 has, for example, a sludge transfer pipe 15A for transferring the sludge M2 from the bottom of the sedimentation tank 14 to the aeration tank 13, and is configured to transfer the sludge by a sludge transfer pump 15B. The drive of the sludge transfer pump 15B is controlled by a sludge transfer control means 15C such as a timer.

[0016] The sewage treatment apparatus 10 also includes, for example, a treated water tank 16 that contains treated water M3, which is the supernatant water obtained by settling sludge M2 in the sedimentation tank 14, a sterilization tank 17 that sterilizes the treated water M3 flowing in from the treated water tank 16, a discharge tank 18 that stores the treated water M3 sterilized in the sterilization tank 17, and a storage tank 19 that stores a portion of the excess sludge that has settled at the bottom of the sedimentation tank 14.

[0017] The settling tank 14 and the treated water tank 16 are connected, for example, by a pipe not shown. Note that between the settling tank 14 and the treated water tank 16, a second aeration tank, an attachment aeration tank not shown, and a second settling tank, a re-sedimentation tank not shown, may be provided. The treated water M3 in the treated water tank 16 is the supernatant water obtained by settling sludge in the settling tank 14, and is the water before sterilization. The treated water tank 16 and the sterilization tank 17 are connected, for example, by a pipe not shown. The sterilization tank 17 is disposed, for example, above the discharge tank 18, so that the treated water M3 after sterilization overflowing from the sterilization tank 17 falls into the discharge tank 18. Note that the sterilization tank 17 and the discharge tank 18 may be connected by a pipe. The storage tank 19 and the settling tank 14 are connected, for example, by a pipe not shown.

[0018] The wastewater treatment device 10 further includes, for example, a sprinkling means 20 that intermittently sprinkles treated water M3 from the treated water tank 16 from above the settling tank 14. Fig. 2 shows the configuration of the sprinkling means 20. The sprinkling means 20 is for intermittently sprinkling water from above the settling tank 14 to break up and settle scum floating on the water surface of the settling tank 14. The sprinkling means 20 includes, for example, a treated water pipe 21 that guides the treated water M3 from the treated water tank 16 to the settling tank 14, and a sprinkling pipe 22 that is connected to the treated water pipe 21, is disposed above the settling tank 14, and sprinkles the treated water M3 into the settling tank 14.

[0019] The treated water pipe 21 and the sprinkler pipe 22 are preferably made of polyvinyl chloride resin piping, for example. The sprinkler pipe 22 may be arranged in any shape, but is preferably arranged so that it has an H-shape when viewed from above, for example. This is because it allows water to be sprinkled over a wide area. The diameter of the sprinkler pipe 22 is preferably within a range of, for example, a nominal diameter of 20 mm to 25 mm.

[0020] FIG. 3 shows a configuration of a part of the sprinkler pipe 22 viewed from below (i.e., viewed from the side of the settling tank 14). The sprinkler pipe 22 is provided with a plurality of sprinkler holes 23 spaced apart. The sprinkler holes 23 preferably have a first sprinkler hole 23A provided so that the treated water M3 is sprayed downward, a second sprinkler hole 23B provided so that the treated water M3 is sprayed diagonally downward to the right in the direction in which the treated water M3 flows through the sprinkler pipe 22, and a third sprinkler hole 23C provided so that the treated water M3 is sprayed diagonally downward to the left in the direction in which the treated water M3 flows through the sprinkler pipe 22. This is because the area over which the treated water M3 is sprayed can be made larger. Note that in FIG. 3, an example of the flow direction of the treated water M3 is indicated by an arrow.

[0021] For example, the first sprinkler holes 23A are provided at intervals along the direction in which the treated water M3 flows, and the second sprinkler holes 23B and the third sprinkler holes 23C are preferably provided between two adjacent first sprinkler holes 23A in the direction in which the treated water M3 flows. The positions of the second sprinkler holes 23B and the third sprinkler holes 23C in the cross section of the sprinkler pipe 22 perpendicular to the direction in which the treated water M3 flows are preferably within a range of 30 degrees to 60 degrees, and more preferably within a range of 35 degrees to 55 degrees, from the lower vertical line L, based on the center O of the sprinkler pipe 22, as shown in FIG. 4. This is because water can be more effectively sprinkled with a wider spread.

[0022] The size of the water sprinkler holes 23 can be set arbitrarily, but for example, it is preferable that the diameter is within the range of 3 mm to 5 mm, and more preferably within the range of 3.5 mm to 4.5 mm. If the size is too small, the amount of water sprinkled is small and the effect of the water sprinkler is small, and if the size is too large, the water droplets become large and tend to fall straight down, reducing the effect of the water sprinkler.

[0023] The treated water pipe 21 is provided with, for example, a valve 24, so that the amount of water sprinkling can be adjusted. In addition, the treated water pipe 21 is connected with, for example, a sprinkling pump 25 for sending the treated water M3. The drive of the sprinkling pump 25 is controlled by a sprinkling control means 26 such as a timer, so that the treated water M3 can be intermittently sprinkled. The sprinkling time and the interval between sprinkling can be set arbitrarily depending on the amount of wastewater M1 to be treated and the size of the device. For example, the sprinkling time can be set to 10 to 20 minutes, and the sprinkling stop time can be set to 2 to 4 hours, so that the sprinkling and stop are repeated in sequence. This is because if the sprinkling time is short, the scum cannot be sufficiently settled, but the scum can be sufficiently settled with this amount of sprinkling time. In addition, if the sprinkling stop time is short, the treated water M3 may become turbid, and if it is long, the scum may rise to the surface and the treated water M3 may become turbid.

[0024] In addition, the sprinkling of the treated water M3 by the water sprinkling means 20 and the transfer of the sludge M2 by the sludge transfer means 15 are both performed intermittently, but it is preferable to control the transfer of the sludge M2 by the sludge transfer means 15 to be performed a predetermined time after the water sprinkling by the water sprinkling means 20. That is, it is preferable to perform water sprinkling by the water sprinkling means 20 for a predetermined time, and transfer the sludge M2 by the sludge transfer means 15 for a predetermined time after the water sprinkling is stopped. This is because scum settles and the sludge can be efficiently transferred. The time from the stop of the water sprinkling by the water sprinkling means 20 to the start of the transfer of the sludge M2 by the sludge transfer means 15 is preferably, for example, 10 to 40 minutes, and more preferably 15 to 30 minutes. These controls can be performed, for example, by adjusting the water sprinkling control means 26 and the sludge transfer control means 15C. An adjustment unit for adjusting the settings of the water sprinkling control means 26 and the sludge transfer control means 15C may be provided.

[0025] This sewage treatment device 1 treats sewage, for example, as follows: First, for example, sewage M1 is caused to flow into the aeration tank 13 through the grit basin 11 and the adjustment tank 12, where it is purified with activated sludge and then sent to the sedimentation tank 14. Next, for example, in the sedimentation tank 14, the sludge M2 is allowed to settle and separated from the supernatant water, and the supernatant water is sent as treated water M3 through the treated water tank 16 to the sterilization tank 17, where it is sterilized and sent to the discharge tank 18 for discharge.

[0026] At this time, the water sprinkling means 20 intermittently sprinkles the treated water M3 contained in the treated water tank 16, i.e., the supernatant water obtained by settling the sludge M2 in the settling tank 14 and the treated water M3 prior to sterilization, from above the settling tank 14. This causes the scum floating on the water surface of the settling tank 14 to be crushed and settled. In addition, a portion of the sludge M2 that has settled to the bottom of the settling tank 14 is intermittently returned to the aeration tank 13 by the sludge transfer means 15. It is preferable that the transfer of the sludge M2 by the sludge transfer means 15 be performed a predetermined time after the water sprinkling by the water sprinkling means 20.

[0027] The wastewater treatment device 10 of this embodiment was installed in a parking area on a highway, and the sprinkling means 20 was used to intermittently perform water sprinkling for one month. The sprinkling time was 10 to 20 minutes, and the sprinkling stop time was 2 to 4 hours. The sludge M2 was transferred intermittently by the sludge transfer means 15, and after the sprinkling by the sprinkling means 20 was performed, the transfer was performed 10 to 40 minutes after the sprinkling was stopped. As a result, it was confirmed that no scum was observed to float, and the quality of the treated water M3 was good.

[0028] As described above, according to this embodiment, the treated water is intermittently sprayed from above the settling tank 14, so that the scum can be automatically settled, and the time and effort required for manual work can be significantly reduced. In addition, the treated water M3 is reused, so that the concept of cascade utilization used in recent water treatment technology is followed, and it is possible to effectively utilize water resources and reduce water charges. Furthermore, since the treated water M3 is used, clogging of the water spraying means 20 can be suppressed, and since it is treated water M3 before sterilization, the occurrence of rust in the water spraying means 20 and the effect on microorganisms can be suppressed.

[0029] Furthermore, if the sprinkler pipe 22 is provided with a first sprinkler hole 23A from which the treated water sprays downward, a second sprinkler hole 23B from which the treated water sprays diagonally downward to the right, and a third sprinkler hole 23C from which the treated water sprays diagonally downward to the left, water can be sprayed more effectively and the scum can be allowed to settle.

[0030] Furthermore, by performing the sprinkling of water by the sprinkling means 20 and the transport of sludge M2 by the sludge transport means 15 intermittently, and then allowing a predetermined time after the sprinkling of water by the sprinkling means 20 to occur, the transport of sludge by the sludge transport means 15 can be performed efficiently, thereby enabling efficient wastewater treatment.

[0031] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment and can be modified in various ways. For example, in the above embodiment, each component is specifically described, but it is not necessary to include all the components, and other components may be included. [Explanation of symbols]

[0032] 10... sewage treatment device, 11... grit basin, 12... adjustment tank, 13... aeration tank, 14... sedimentation tank, 15... sludge transfer means, 15A... sludge transfer piping, 15B... sludge transfer pump, 15C... sludge transfer control means, 16... treated water tank, 17... sterilization tank, 18... discharge tank, 19... storage tank, 20... sprinkling means, 21... treated water piping, 22... sprinkling pipe, 23... sprinkling hole, 23A... first sprinkling hole, 23B... second sprinkling hole, 23C... third sprinkling hole, 24... valve, 25... sprinkling pump, 26... sprinkling control means

Claims

1. A wastewater treatment device that purifies wastewater using activated sludge, an aeration tank for storing and aerating wastewater together with activated sludge; a settling tank for storing the wastewater aerated in the aeration tank and for settling sludge; a treated water tank for containing treated water which is the supernatant water obtained by settling the sludge in the settling tank and which has not yet been sterilized; a sprinkling means for intermittently sprinkling the treated water from the treatment water tank from above the settling tank; a sludge transport means for intermittently returning the sludge settled at the bottom of the settling tank to the aeration tank, A wastewater treatment device according to claim 1, wherein the transfer of sludge by said sludge transfer means is controlled to be performed a predetermined time after the spraying of water by said water spraying means.

2. The wastewater treatment device described in claim 1, characterized in that the sprinkler means is arranged above the settling tank and has a sprinkler pipe with a plurality of sprinkler holes, the sprinkler holes including a first sprinkler hole arranged so that the treated water is sprayed downward, a second sprinkler hole arranged so that the treated water is sprayed diagonally downward to the right in the direction in which the treated water flows through the sprinkler pipe, and a third sprinkler hole arranged so that the treated water is sprayed diagonally downward to the left in the direction in which the treated water flows through the sprinkler pipe.

3. A wastewater treatment method comprising the steps of: purifying wastewater with activated sludge in an aeration tank; settling the sludge in a settling tank; and separating the sludge from supernatant water, The supernatant water obtained by settling the sludge in the settling tank and the treated water before the sterilization treatment is intermittently sprayed from above the settling tank to break up and settle the scum, and A wastewater treatment method comprising the steps of: spraying the treated water from above the settling tank; and then intermittently transferring, at predetermined intervals, the sludge that has settled to the bottom of the settling tank to the aeration tank.

Images