JP4013123B2 - Operating method of aerobic treatment tank, aerobic treatment tank and sewage septic tank - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating an aerobic treatment tank, an aerobic treatment tank, and sewage that are preferably used for biochemically purifying human waste, other domestic wastewater, and combined sewage (also simply referred to as sewage). It relates to septic tanks.
[0002]
[Prior art]
Various sewage septic tanks are conventionally known. One of them is, as disclosed in JP-A-9-248484, in order from the upstream side, the first anaerobic filter bed tank, the second anaerobic filter bed tank, the aerobic filter bed tank, the treated water tank, and It is a sewage purification tank provided with a disinfection tank. Here, the aerobic filter bed tank is divided into an upper compartment (biological reaction part) filled with a particulate carrier and a lower compartment (filtration part) also filled with a particulate carrier. Air is discharged from the member to form a fluidized bed in the upper section, and a fixed bed (filtering section) is formed in the lower section (filtering section).
[0003]
[Problems to be solved by the invention]
The present invention further improves the above-described aerobic treatment tank or sewage purification tank, and improves the SS (floating solid content; suspended solids) filtration performance in the filtration unit (fixed bed). ”, An object is to provide an aerobic treatment tank and a sewage purification tank using the same.
[0004]
[Means for Solving the Problems]
In general, the filtering performance is improved as the filter medium filling height (H) is higher, and as the linear velocity (LV) and superficial velocity (SV) are smaller. However, the higher the filter medium filling height is, and the smaller the linear velocity and superficial velocity are, the larger the filtration section of the filtration chamber becomes. As a result of various studies using a test filtration apparatus filled with a predetermined amount of filter medium, the present inventors have been able to clarify the optimum filtration flow rate (flow velocity), and have completed the present invention.
[0005]
That is, in the present invention, when operating the aerobic treatment tank 1 in which the biological reaction chamber 2 and the filtration chamber 3 are arranged in this order, the filtration flow rate (speed) in the filtration chamber 3 is set to the superficial velocity (SV). ) As an index, this is an operation method of the aerobic treatment tank 1 which is controlled to be 2.0 or more and 10 h ⁻¹ or less .
[0006]
Here, the filtration rate in the filtration chamber, further, the linear velocity (LV), that controls the following range 3.0 m / h.
[0007]
Further, the present invention is an aerobic treatment tank 1 in which a biological reaction chamber 2 and a filtration chamber 3 are arranged in this order, and the filtration flow rate in the filtration chamber 3 is at most 10 hours at the superficial velocity (SV). It is also an aerobic treatment tank 1 that is controlled to be ^-1 .
[0008]
The present invention also relates to a sewage purification tank provided with the aerobic treatment tank 1 (biological reaction chamber 2 + filtration chamber 3).
Here, an anaerobic treatment tank having a flow rate adjusting function is preferably provided upstream of the aerobic treatment tank 1.
[0009]
Note that the superficial velocity SV (h ⁻¹ ) in the filtration chamber 3 is obtained by dividing the filtration flow rate Q (m ³ / h) in the filtration chamber 3 by the volume V (m ³ ) of the filtration part (filtration layer) including the filter medium. Define the value with The linear velocity LV (m / h) is defined by the value of the filtration flow rate Q (m ³ / h) ÷ filtration section sectional area (m ² ).
[0010]
[Action]
In order to clear the BOD allowable concentration of 20 mg / L (or less) in the popular household septic tank from the separate data (FIG. 6) accumulated by the present inventors, the SS concentration must be approximately 8 mg / L or less. I know. And this invention is the experiment which used the test filtration apparatus so that it may mention later, and the limit filtration flow rate of the filtration part which achieves SS concentration 8mg / L or less of a processed liquid is 10h < ^-1 > as superficial velocity (SV). It is based on finding out that. That is, in the operation method, the aerobic treatment tank or the sewage purification tank according to the present invention, the superficial velocity (SV) in the filtration chamber is controlled to 10 h ^-1 at the highest, so the SS concentration of the treated liquid is 8 mg / L or less. Therefore, the BOD allowable concentration of 20 mg / L (below) can be cleared. However, if the superficial velocity (SV) is too small, the capacity of the filtration section in the filtration chamber becomes large and the entire apparatus does not become compact. Therefore, the superficial velocity (SV) is at least 2.0 h ⁻¹ or more, preferably 5 0.0h ^-1 or more, more preferably 7.0 h ^-1 or more. The linear velocity (LV) is at least 0.6 m / h or more, preferably 1.5 m / h or more, more preferably 2.0 m / h or more.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more specifically. First, test examples will be described.
(Test example)
The test filtration apparatus (schematic cross-sectional view) used is shown in FIG. The size of the apparatus is a cylindrical shape having an inner diameter of 100 mm and an effective capacity of 5 L. The filled filter medium is a porous hollow cylindrical filter medium (outer diameter: 10 mm, inner diameter: 7 mm, length: 10 mm, manufactured by Kansai Kako Co., Ltd.) having an open cell part and a closed cell part based on polypropylene. There are irregularities, and the specific gravity is 1.01.
The filter medium has a filling height H of 200, 350, and 500 mm, and LV is 0.5, 2.0, 3.0, and 5.0 m / h (SV is 0.8, 3. 2, 4.7 and 7.9 h ⁻¹ ) and tested. The influent (raw water) to the equipment is a diluted sludge of activated sludge from the sewage treatment plant (diluted with tap water so that the SS concentration becomes 50 mg / L), and is 3 times the capacity of the equipment (that is, in the equipment) The processed liquid was sampled after passing through (the amount of liquid in which the liquid was almost completely replaced with raw water).
[0012]
FIG. 2 (a) plots the filter medium filling height as the horizontal axis and the vertical axis as the SS concentration of the treated liquid, and FIG. 2 (b) shows SV as the horizontal axis and the vertical axis as the SS of the treated liquid. Re-plotted as concentration. From FIG. 2 (b), it can be seen that the SS concentration of the treated liquid is a curve depending on SV, and the SS concentration of the treated liquid is 8 mg / L or less (the BOD concentration of the popular household septic tank is 20 mg / L). It can be seen that the upper limit of SV is 10h ⁻¹ to clear (equivalent). Moreover, it turns out that the upper limit of LV at that time is about 3.0 m / h.
[0013]
Next, the aerobic treatment tank of the present invention will be described.
FIG. 3 shows an aerobic treatment tank according to an example of the present invention. The aerobic treatment tank 1 includes a biological reaction chamber 2 and a filtration chamber 3 juxtaposed. The biological reaction chamber 2 is provided with a sewage inlet 4 at the upper side wall (on the left side in FIG. 3), and an advection chamber 5 erected so as to surround the inlet 4 on the inner wall side of the tank. The sewage is transferred to the bottom of the tank. In addition, an outlet 6 is provided at the upper part of the side wall opposite to the inlet 4 (right side in FIG. 3). Further, the advection chamber 5 is provided with a water passage portion (made of a slit, a mesh or the like) 8 that allows the inflowing sewage to pass but does not allow the biological carrier 7 to pass, in the vicinity of the bottom of the tank.
[0014]
In order to flow and agitate the biological carrier 7 and the liquid in the tank, and to supply oxygen together, the air supplied from the blower 10 is a loop-like (biological reaction) powder having a square shape in plan view arranged at the bottom of the tank. The gas member 9 is discharged. Further, below the water level surface of the biological reaction chamber 2, a fluid passage member is formed by disposing a water passage member (including a slit, a mesh, etc.) 11 that allows liquid to pass but does not allow the biological carrier 7 to pass.
[0015]
The biological reaction chamber 2 can also be made circular in plan view. However, considering that it is incorporated into the sewage septic tank, it is preferably a substantially rectangular shape.
The advection chamber 5 can be semicircular or triangular in plan view.
The outlet 6 is preferably disposed on the opposite wall side far from the inlet 4 in order to prevent a short circuit of the sewage that has flowed in.
The air diffusing member 9 may be formed in a circular or triangular loop shape, an eye shape, a single character shape, or the like instead of the quadrangular loop shape in plan view (the same applies to the air diffusing member 16).
The water flow member 11 may be provided above the water level surface and may be removed depending on the case as long as the biological carrier 7 does not flow out from the outlet 6. The water passage member 11 may be provided with an inlet / outlet port or an inspection port for the biological carrier 7.
Moreover, the advection chamber 5 can also be arrange | positioned at the outflow port 6 side. In this case, a water passage is provided near the bottom.
[0016]
The biological carrier 7 has a bulk volume of 30 to 60%, preferably 35 to 55% with respect to the effective volume of the biological reaction chamber 2 (the volume obtained by subtracting the volume of the advection chamber 5 below the water level from the volume below the water level). % Is charged into the biological reaction chamber 2. This is because the liquid in the tank and the biological carrier 7 are brought into contact with each other by being aerated or agitated well by aeration from the air diffusing member 9, and further the organic matter is decomposed satisfactorily by the uniform diffusion of dissolved oxygen.
[0017]
Further, the biological carrier 7 is preferably one that floats and flows in the liquid with a little stirring force. The specific gravity is preferably 0.9 to 1.1, and can be flowed well. When the specific gravity is less than 0.9, the flow of the biological carrier 7 is difficult to spread over the entire area. When the specific gravity exceeds 1.1, a part of the biological carrier 7 tends to be collected at the bottom or bottom corner of the biological reaction chamber 2. In such a state, the ability of decomposing organic matter tends to decrease. The specific gravity is determined by measuring the weight of the filter medium in the air in advance (the weight is W ₁ ) and heating it in distilled water at 95 ° C. for 30 minutes so that the filler is sufficiently impregnated with water. ℃ after cooling, and the weight was measured under the influence of buoyancy (for the weight and W _2), a value calculated by _{W 1 / (W 1 -W 2} ).
[0018]
The base material of the biological carrier 7 is preferably polypropylene from the viewpoint of moldability, and more preferably a porous body having a large surface area. In addition, it can be molded from a synthetic resin such as polyethylene, polyvinyl chloride, polyvinyl alcohol, and polyvinyl formal. Further, an inorganic substance such as activated carbon, ceramics, anthracite (a kind of coal), calcium carbonate, talc, or silica sand may be added to the base material.
[0019]
The shape of the biological carrier 7 is preferably a hollow cylindrical shape, and the size is preferably about 5 to 20 mm in diameter and length when viewed as a lump. In addition, a spherical shape, a cylindrical shape, a cubic shape, a net-like cylindrical shape, a loofah shape, a skeleton sphere shape, and the like can be used. The biological carrier 7 has a larger specific surface area.
[0020]
Sewage flows into the filtration chamber 3 from the outlet 6 at the upper side wall on the biological reaction chamber 2 side. Further, an advection chamber 12 and an outlet 13 are provided on the side wall opposite to the outlet 6 or at a right angle. Moreover, in order to form the filtration part (filtration layer) which hold | maintains the filter medium 14 in the filtration chamber 3, the water-permeable member (slit, mesh, etc.) 15 (15a, 15b) which lets a liquid pass but does not let the filter medium 14 pass. Are provided above and below the filtration section.
[0021]
A diffuser member 16 is disposed below or below the filtration unit in order to bubble the filtration unit during cleaning. Further, a cleaning drainage pump 17 for extracting the cleaning drainage from the lower side of the filtering unit is also disposed when the filtering unit is cleaned. The flow direction of the liquid is a downward flow. Air is supplied from the blower 10 to the cleaning drainage pump 17.
[0022]
The water passage member 15a can be provided with an inlet / outlet or an inspection port for the filter medium 14.
[0023]
The filter medium 14 filled in the filtration chamber 3 will be described. The filter medium 14 is preferably set to have a specific gravity of 1.0 to 1.1 in order to settle during normal times and flow with a little stirring force during washing. If the specific gravity is less than 1.0, the filtration part will flow when sewage flows in, and the filtration performance will deteriorate. On the other hand, if the specific gravity exceeds 1.1, the filter medium is difficult to flow even when bubbling at the time of washing the filtration unit, the captured SS does not peel off, and the filtration unit is easily blocked.
[0024]
Further, the filling rate of the filter medium 14 is preferably 60 to 90% in terms of the bulk volume with respect to the effective volume of the filtration part. When the filling rate is 90% or more, the filter medium 14 hardly moves during the cleaning of the filtration part, and the captured SS is difficult to peel off. On the other hand, if it is 60% or less, the capacity of the filtration chamber is increased, and the time required for cleaning the filtration part is also increased.
[0025]
The base material of the filter medium 14 is preferably polypropylene from the viewpoint of moldability, and more preferably has irregularities on the surface. In addition, it can be molded from a synthetic resin such as polyethylene, polyvinyl chloride, polyvinyl alcohol, and polyvinyl formal. Further, an inorganic substance such as activated carbon, ceramics, anthracite (a kind of coal), calcium carbonate, talc, or silica sand may be added to the base material.
[0026]
The shape of the filter medium 14 is preferably a hollow cylindrical shape, and the size is preferably about 5 to 20 mm in diameter and length when viewed as a lump. In addition, a spherical shape, a cylindrical shape, a cubic shape, a net-like cylindrical shape, a loofah shape, a skeleton sphere shape, and the like can be used.
[0027]
In addition, the advection chamber 12 of the filtration chamber 3 can be provided on the outlet 6 side of the biological reaction chamber 2 so that the liquid flow in the filtration section is directed upward. In this case, the specific gravity of the filter medium is preferably 0.9 or more and less than 1.0.
[0028]
Next, an example of a sewage purification tank provided with a flow rate adjusting unit 27 on the upstream side of the aerobic treatment tank 1 will be described with reference to FIG. From the upstream side, the sewage purification tank 20 includes a first solid-liquid separation chamber 21 serving as a first anaerobic treatment tank, a second solid-liquid separation chamber 22 serving as a second anaerobic treatment tank, the aerobic treatment tank 1, and a disinfection tank 24. It consists of
[0029]
The first solid-liquid separation chamber 21 has a sewage inlet 25, and the first solid-liquid separation chamber 21 and the second solid-liquid separation chamber 22 are connected by an opening 26 at the bottom of the second solid-liquid separation chamber 22. . Further, in the first solid-liquid separation chamber 21 and the second solid-liquid separation chamber 22, a flow rate adjusting unit 27 (low water level L) for averaging the sewage inflow fluctuation and transferring it to the subsequent aerobic treatment tank 1 and later. .. between W.L and high water level H.W.L). The second solid-liquid separation chamber 22 is provided with a transfer pump 28 for quantitatively transferring the liquid in the tank to the aerobic treatment tank 1, and the suction port 29 has a low water level L.P. W. L is provided.
[0030]
The transfer pump 28 has a low water level L.P. W. L to high water level W. At any water level of L, the filtration flow rate in the filtration chamber is such that the pumping capacity is such that the SV is 10 h ⁻¹ or less and the LV is 3.0 m / h or less. FIG. 5 shows pump characteristics in the case of an air lift pump using a tube having an inner diameter of 13 mm. As shown in FIG. W. L to high water level W. At any water level of L, the filtration flow rate in the filtration chamber is 10 h ⁻¹ or less for SV and 3.0 m / h or less for LV. The transfer pump 28 may be an electric pump having the same pumping capacity.
The first solid-liquid separation chamber 21 and the second solid-liquid separation chamber 22 may be an anaerobic filter bed tank having a filter bed filled with a bioadhesive material (also referred to as a biological carrier, a filter material, or a contact material). There may be only one tank.
[0031]
The description of the aerobic treatment tank 1 in the sewage purification tank 20 is omitted because it overlaps with the description in FIG. However, in the advection chamber 18, a circulation air lift pump 30 that circulates a part of the advection liquid from the biological reaction chamber 2 to the first solid-liquid separation chamber 21 and the washing waste water from the filtration chamber 3 are drawn out to the first solid liquid. A cleaning drainage pump 17 that is transferred to the liquid separation chamber 21 is disposed. The circulation air lift pump 30 and the cleaning drainage pump 17 may be a transfer pump such as an electric pump. Further, the circulating air lift pump 30 can be removed.
[0032]
The sewage treatment in the sewage septic tank 20 (FIG. 4) will be described. The inflowing sewage enters the first solid-liquid separation chamber 21 from the sewage inlet 25 as indicated by solid arrows, and solid-liquid separation and anaerobic biological treatment are performed. The advection liquid that has passed through here enters the second solid-liquid separation chamber 22, and further undergoes solid-liquid separation and anaerobic biological treatment. The liquid is quantitatively transferred to the aerobic treatment tank 1 by the transfer air lift pump 28 while the flow rate fluctuation of the incoming sewage is reduced in the first solid-liquid separation chamber 21 and the second solid-liquid separation chamber 22.
[0033]
The liquid that has flowed into the aerobic treatment tank 1 is sufficiently brought into contact with the air discharged from the diffuser member 9 and the flowing biological carrier 7, and aerobic biodegradation proceeds. A part of the decomposed organic matter is converted into a microorganism, and a part of the microorganism adheres to the biological carrier 7 or floats (as SS) in the liquid. A part of the liquid flowing into the advection chamber 18 from the water flow section 8 is continuously or intermittently returned to the first solid-liquid separation chamber 21 by the circulation air lift pump 30, and SS is separated. The remaining liquid enters the filtration chamber 3 from the outlet 6. In the liquid that has entered, SS is captured and removed by the filter medium 14, and the biological treatment is subsequently performed. The liquid from which the organic matter and SS have been removed is discharged as a processed liquid from the discharge port 31 through the disinfection tank 24.
[0034]
Cleaning in the filtration chamber 3 is performed as follows. First, air is discharged from the air diffuser 16 (for cleaning), and the filtration part is bubbled to separate the SS. At this time, the cleaning drainage pump 17 is operated, and the cleaning drainage is extracted from the bottom of the filtration chamber 3 and returned to the first solid-liquid separation chamber 21. At this time, it is preferable to draw out the entire amount of washing waste water as much as possible. Washing is completed when the drainage of the washing drain is completed. This washing is preferably performed when the water level in the first solid-liquid separation chamber 21 is in the vicinity of a low water level (LWL) (that is, when there is no inflow of sewage).
[0035]
【The invention's effect】
According to the operation method of the present invention or the aerobic treatment tank or sewage septic tank of the present invention, the sewage septic tank as disclosed in JP-A-9-248484 is further improved, and the SS filtration performance in the filtration chamber is increased and stabilized. Can treat sewage.
In addition, according to the aerobic treatment tank or the sewage septic tank of the present invention, the filtration flow rate in the filtration chamber is optimized, so that a smaller amount of filter medium is required than in the prior art. Contributes to
In addition, the sewage septic tank with an anaerobic treatment tank with a flow adjustment function located upstream of the aerobic treatment tank makes it easy to filter the filtration flow rate (linear speed and flight speed) in the filtration chamber even when the flow rate of incoming sewage is large. Can be controlled.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a test filtration device used.
FIG. 2 is a graph of test results, where (a) shows the height of the filter medium packed on the horizontal axis, and (b) shows SV on the horizontal axis.
FIG. 3 is a schematic sectional view of an aerobic treatment tank according to an example of the present invention.
FIG. 4 is a schematic sectional view of an example of the sewage septic tank of the present invention.
FIG. 5 is a graph showing characteristics of an air lift pump according to an example of the present invention.
FIG. 6 is a graph showing the correlation between SS concentration and BOD concentration in a popular household septic tank.
[Explanation of symbols]
1: Aerobic treatment tank 2: Biological reaction chamber 3: Filtration chamber 4: Inlet 5: Advection chamber 6: Outlet 7: Biological carrier 8: Water passage 9: (For biological reaction) Aeration member 10: Blower 11 : Water flow member 12: Advection chamber 13: Outlet 14: Filter medium 15a, 15b: Water flow member 16: (For filtration chamber washing) Aeration member 17: Cleaning air lift pump 18: Advection chamber 20: Sewage septic tank 21: Anaerobic Processing chamber first chamber (first solid-liquid separation chamber)
22: Anaerobic treatment tank second chamber (second solid-liquid separation chamber) 24: Disinfection tank 25: Sewage inlet 26: Opening 27: Flow rate adjusting unit 28: Transfer air lift pump 29: Suction port 30: Circulation air lift pump 31: Outlet

Claims (1)

Filtration in which a biological reaction chamber filled with 30 to 60% of the biological carrier with a bulk volume with respect to the effective volume, and a filter medium with a bulk volume of 60 to 90% with respect to the effective volume is filled, and a washing drainage pump is disposed below. The chambers are arranged in this order, and the superficial velocity SV in the filtration chamber (the value obtained by dividing the filtration flow rate Q in the filtration chamber by the volume V of the filtration part including the filter medium) is 2.0 or more and 10 h ⁻¹ or less. The operating method of the aerobic treatment tank is controlled so that the linear velocity LV (value obtained by dividing the filtration flow rate Q by the sectional area of the filtration portion) is 3.0 m / h or less .

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