JP3685552B2 - Solid-liquid separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid-liquid separation HanareSo location, details, a solid-liquid separation in water treatment facilities of wastewater treatment plants, etc., relating to solid-liquid separation HanareSo location performed by a combination of the on gravity sedimentation and floatation.
[0002]
[Prior art]
Conventionally, for solid-liquid separation for obtaining secondary treated water in sewage treatment or the like, gravity sedimentation separation in which particles in a suspension are settled by gravity has been widely adopted. At this time, the sedimentation speed of flocs in the activated sludge to be subjected to solid-liquid separation varies greatly depending on its density, shape and size, and is in a wide range. Therefore, the final sedimentation basin has a sufficient water area so that the sludge having a relatively slow sedimentation speed can be sufficiently settled and separated in order to achieve the SS 20 mg / l which is the reference value of the discharged water. Designed to have For example, in the case of sewage treatment by the high-load activated sludge method, the water area load of the final sedimentation basin is 20 to 30 m ³ / m ² · day.
[0003]
[Problems to be solved by the invention]
However, in small-scale treatment plants that are easily affected by fluctuations in the amount of inflow water, SS components sometimes flowed out from the final sedimentation basin during the time when the sewage pump is operating. Moreover, the sedimentation property and compaction property of activated sludge are extremely lowered, and a phenomenon (bulking) in which activated sludge and treated water cannot be sufficiently separated may occur. Furthermore, the activated sludge may be dismantled due to abrupt changes in the composition of the inflowing sewage, inflow of harmful substances, excessive aeration and low pH due to nitrification, and some fine flocs may flow out. In particular, in gravity sedimentation separation, floating solids that are difficult to settle may flow out together with the treated water, which causes the quality of the treated water to deteriorate.
[0004]
The present invention provides water quality of the inflow water, regardless of the variation of the amount of water or the like, always together with treated water satisfying the reference value is obtained, to provide a solid-liquid separation HanareSo location which can be suppressed increase in operating costs It is an object.
[0007]
[Means for Solving the Problems]
Solid-liquid separator of the present invention, an injection section for injecting pressurized air dissolved water in gravity sedimentation pond, a discharge means for discharging the floating levitation sludge, detecting the turbidity of the treated water flowing out from the gravity settling tank And a control means for controlling the injection amount of the pressurized air-dissolved water from the injection portion in accordance with the measured value of the turbidimeter.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings. First, as a reference example of the present invention, a sewage treatment facility adopting an activated sludge method as a secondary treatment method shown in FIG. 1 will be described. This sewage treatment facility includes a sand basin 1 similar to a conventional sewage treatment facility, A sedimentation basin 2, an aeration tank 3, a final sedimentation basin 4, and a chlorine mixing basin 5, and between the final sedimentation basin 4, which is a gravity sedimentation basin, and the chlorine mixing basin 5, A bypass flow path 7 that passes through the pressure levitation separation device 6 is provided.
[0009]
Further, a turbidity meter 8 for detecting the turbidity of the treated water (gravity precipitation separation treated water) is provided at the treated water outflow portion of the final sedimentation basin 4, and the inflow portion of the pressurized flotation separation device 6 is bypassed. The flow path 7 is automatically opened and closed by a signal from the turbidimeter 8, and the gravity precipitation separation treated water flow path from the final sedimentation basin 4 is connected to the pressurized flotation separation device 6 and the bypass flow path 7. Automatic valves 9 and 10 are provided as means for switching to the above.
[0010]
The pressurized levitation separator 6 injects pressurized air-dissolved water into the inflow water to the apparatus, and reduces the pressure to atmospheric pressure to generate fine bubbles from the pressurized air-dissolved water. Is attached to the suspended components in the inflowing water and the apparent specific gravity of the suspended components is reduced, so that the suspended components are floated and separated. Compared with normal precipitation treatment by gravity, suspended components It is possible to reliably remove fine activated sludge flocs with a high removal rate and a slow sedimentation rate, and to completely remove easily floating components such as hair, oil and scum that are difficult to separate by gravity precipitation. Can do.
[0011]
In addition, the turbidimeter 8 is set so that the correlation between the SS and the turbidity of the gravity sediment separation treated water is measured in advance, and the SS of the gravity sediment separation treated water can be calculated from the measured value of the turbidimeter 8. It is.
[0012]
In such a sewage treatment facility, the inflow sewage is treated in the sand basin 1 and the first sedimentation basin 2 in the same manner as before, and then mixed with the return sludge from the return sludge flow path 11 in the aeration tank 3 to activate the activated sludge method. Water treatment is performed. The activated sludge flocs produced in this aeration tank 3 have various sedimentation speeds depending on their density, shape and size, but these sludges are usually produced by gravity sedimentation in the next final sedimentation basin 4. Solid-liquid separation. In other words, the final sedimentation basin 4 is set to have a capability of performing sufficient solid-liquid separation when the amount of normal inflow sewage and the average water quality, for example, the water area load is 20 to 30 m ³ / m ^2.・ The date is set.
[0013]
Therefore, when the load is small, such as when the amount of inflow water is small or when the sewage pump is not operating, the SS of the gravity sediment separation treated water flowing out from the final sedimentation basin 4 becomes a value that satisfies the treated water reference value. Therefore, it can be discharged into a river or the like by adding chlorine in the chlorine-mixing basin 5 and performing sterilization with chlorine.
[0014]
The measured value of the turbidimeter 8 at this time is below a preset reference value, and the automatic valves 9 and 10 that are opened and closed by the signal of the turbidimeter 8 are The automatic valve 9 in the inflow portion is closed, and the automatic valve 10 in the bypass flow path 7 is open.
[0015]
On the other hand, if the amount of inflow water increases or the sewage pump is operated and solid-liquid separation by gravity sedimentation in the final sedimentation basin 4 cannot be performed sufficiently, sludge having a slow sedimentation rate is separated from the final sedimentation basin 4 by gravity sedimentation. May flow into treated water. In this way, when sludge or the like flows into the gravity precipitation separation treated water and the SS of the gravity precipitation separation treated water increases, the turbidity of the gravity precipitation separated treatment water detected by the turbidimeter 8 increases, and the detected turbidity. When the reference value exceeds or is predicted to exceed the reference value, an open / close signal is output from the turbidimeter 8 to the automatic valves 9 and 10, the automatic valve 9 is opened and the automatic valve 10 is closed. . Thereby, the gravity precipitation separation treated water having increased turbidity is supplied to the pressurized flotation separation device 6 via the automatic valve 9 and is sent to the chlorine mixing basin 5 after the pressurized flotation separation process is performed.
[0016]
Note that the control circuit is set so that the pressurized levitation separator 6 starts operation when the automatic valve 9 is opened and stops when the automatic valve 9 is closed. In addition, some of the sludge generated during the operation of the pressurized flotation separation device 6 is sent to the sludge treatment facility, and is also returned to the aeration tank 3 as return sludge from the return sludge channel 11 together with sludge from the final sedimentation basin 4. Sent.
[0017]
That is, when it is judged that the SS of the gravity precipitation separated water calculated by the turbidity measured by the turbidimeter 8 exceeds or exceeds the effluent water reference value, the gravity precipitation separated water is pressurized. It is introduced into the levitation separator 6 so as to perform a pressure levitation separation process.
[0018]
Furthermore, by changing the amount of pressurized air-dissolved water added (pressurized water ratio) according to the turbidity of gravity precipitation separation treated water, for example, by reducing the pressurized water ratio when the turbidity is low, The power cost of a pump or a compressor for generating compressed air dissolved water can be reduced.
[0019]
Further, when the turbidity of the gravity precipitation separation treated water becomes lower than the reference value, the automatic valve 9 is closed by the signal from the turbidimeter 8 and the automatic valve 10 is closed. 7 flows into the chlorine-mixing basin 5 and the pressurized flotation separator 6 stops its operation.
[0020]
Thus, by performing the pressurized flotation separation process according to the turbidity of the gravity precipitation separation treated water, SS20 mg / l which is the discharge water reference value can be reliably achieved, and the pressurized flotation separation apparatus 6 The power cost can be reduced, and the size of the gravity sedimentation basin such as the final sedimentation basin can be reduced, so that the equipment ratio and running cost can be reduced while maintaining the water quality standard. Furthermore, even when the gravity sedimentation process cannot be sufficiently performed due to scum, bulking, or the like, the necessary levitation separation process can be performed by the pressurized levitation separation device 6 to perform a necessary and sufficient solid-liquid separation process.
[0021]
Next, an embodiment of the present invention will be described based on the sewage treatment facility shown in FIG . In this sewage treatment facility, injecting pressurized air-dissolved water into a final sedimentation basin 4 of a facility having a sedimentation basin, a first sedimentation basin, an aeration tank 3, a final sedimentation basin 4 and a chlorine mixing basin, as in the above-described reference example. Unit 21, discharge means 22 for discharging the levitated sludge, turbidity meter 23 for detecting the turbidity of the treated water flowing out from the gravity sedimentation basin, and the injection unit according to the measured value of the turbidity meter 23 The control means 24 which controls the injection amount of the pressurized air dissolution water from 21 is provided.
[0022]
The injection part 21 is provided at an appropriate depth position in the intermediate part of the final sedimentation basin 4 and is used to supply pressurized air dissolved water supplied from a pressurized air dissolved water production apparatus 25 equipped with a pump, a compressor and the like. It is ejected into water, and suspended components in water are levitated on the same principle as the pressurized flotation separator.
[0023]
The discharge means 22 utilizes a sludge scraper 26 that is usually provided in the final sedimentation basin 4. The return portion of the sludge scraper 26 is disposed on the water surface, and the sludge scraper 26 The flying sludge is scraped by the flight 26a and discharged out of the pond through a pipe skimmer 27 provided on the downstream side.
[0024]
The turbidity meter 23 detects the turbidity of the treated water that has flowed over the overflow weir 28 of the final sedimentation basin 4 into the treated water tank 29, and the detected turbidity is the same as the reference example. When the reference value is exceeded or when it is predicted that the reference value will be exceeded, an operation signal is output to the pressurized air dissolved water production apparatus 25 via the control unit 24. This operation signal may be a signal that simply controls ON / OFF, or a signal that changes the production amount of the pressurized air-dissolved water according to turbidity. Further, the floating sludge discharging means 22 may be provided with a dedicated scraper or the like.
[0025]
In this way, by injecting the pressurized air-dissolved water into an appropriate position in the final sedimentation basin 4, the floating solids can be reliably separated and removed, and the quality of the treated water can be improved. At this time, the pressurized air-dissolved water may be continuously injected without providing the turbidimeter 23, and the pressurized air-dissolved water production apparatus 25 is operated in accordance with the change in the inflow water amount. Even if the operation is performed according to the set time schedule, sufficient solid-liquid separation can be performed. However, as described above, the pressurized air is used depending on the turbidity of the treated water detected by the turbidimeter 23, that is, the degree of SS. By controlling the operation of injecting dissolved water, the operating cost can be minimized.
[0026]
In the above-described embodiment, the activated sludge method is adopted as the secondary treatment method, but the present invention is not limited to this, but also in sewage treatment facilities employing other treatment methods such as the oxidation ditch method. The present invention can be applied to various other solid-liquid separation processes.
[0027]
【The invention's effect】
As described above, according to the present invention, it is possible to always obtain a predetermined treated water quality regardless of fluctuations in the quality of the influent water, the amount of water, etc. It is possible to reduce equipment costs such as sewage treatment equipment and running costs. Moreover, automatic operation is also possible, and it is possible to cope with solid-liquid separation failures due to causes such as scum and bulking.
[Brief description of the drawings]
FIG. 1 is a system diagram of a sewage treatment facility showing a reference example of the present invention.
FIG. 2 is a schematic view of a sewage treatment facility showing one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sand basin, 2 ... First sedimentation basin, 3 ... Aeration tank, 4 ... Final sedimentation basin, 5 ... Chlorine mixing basin, 6 ... Pressurization floating separator, 7 ... Bypass flow path, 8 ... Turbidimeter, 9, DESCRIPTION OF SYMBOLS 10 ... Automatic valve, 11 ... Return sludge flow path, 21 ... Injection | pouring part, 22 ... Discharge means, 23 ... Turbidimeter, 24 ... Control means, 25 ... Pressurized-air dissolved-water production apparatus, 26 ... Sludge scraper, 26a ... Flight, 27 ... Pipe skimmer, 28 ... Overflow weir, 29 ... Treated water tank

Claims (1)

An injection unit for injecting a pressurized air dissolved water in the gravity settling tank, a discharge means for discharging the floating levitation sludge, a turbidity meter for detecting turbidity of treatment water flowing out from the gravity settling tank,該濁degree A solid-liquid separation device comprising: a control means for controlling an injection amount of the pressurized air-dissolved water from the injection portion in accordance with a measured value of the meter .

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