JP4137591B2 - Sewage treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sewage treatment apparatus that can replace the conventional sewage treatment by the activated sludge method .
[0002]
[Prior art]
In the national or local public organizations, the purification of sewage from the sewerage is currently based on the activated sludge method. In the activated sludge method, sewage from the settling basin is first led to the aeration tank, and the organic components in the sewage are precipitated and aggregated by aerobic microorganisms under aeration in the aeration tank. The separated sludge is separated in the final sedimentation basin , a part of the separated sludge is returned to the aeration tank as a microorganism source, and the excess sludge is dried and incinerated.
[0003]
In the activated sludge method, the organic component in the sewage was agglomerated and recovered by solid-liquid separation, and the solidified organic component was separated and incinerated. Therefore, it is necessary to consume a large amount of energy for incineration. According to one theory, about half of the energy for incineration of sludge in public disposal including garbage by the national or local government. It is said that it is costing (fuel cost).
[0004]
A so-called supercritical water oxidation method has been proposed as a treatment that does not depend on the activated sludge method (a treatment that does not involve solid-liquid separation for removing organic components in the sludge) (see Patent Document 1). In this supercritical water oxidation method, sewage is introduced into a high-temperature and high-pressure reaction tank having a temperature of 660 to 700 ° C. and a pressure of about 25 MPa, and organic components in the sewage are directly treated by oxidation. That is, in such a high temperature and high pressure state, a supercritical water liquid state that is neither a liquid nor a gas is obtained. In this state, water molecules are repeatedly violently moved. It is said that organic matter can be oxidized and decomposed instantly.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-90494 [Problems to be Solved by the Invention]
In the supercritical water oxidation method, activated sludge conversion, that is, a solid-liquid separation step in the current mainstream sewage treatment method can be omitted by direct oxidation of organic components in sewage. However, a high-temperature and high-pressure reaction tank with a temperature of 660 to 700 ° C and a pressure of about 25 MPa is required for direct oxidation, and not only the equipment cost but also the running cost is high for the treatment of a large amount of sewage. There is a problem that the processing cost is extremely high.
[0006]
The present invention has been made in view of the above problems, and an object thereof is to enable purification of wastewater by direct oxidation with low-cost equipment.
[0007]
According to invention of Claim 1, it is a sewage treatment apparatus, Comprising: The sewage flow path which connects the inflow port of the sewage which should be processed in a sewer, the discharge port of the treated sewage, and the said inflow port and an discharge port A septic tank on the sewage flow path on the inlet side, and a solid-liquid separation tank on the sewage flow path on the outlet side, the septic tank having a take-out passage for branching the sewage from the septic tank, and the branched sewage being an oxidizing agent A pressurized sewage flow forming means that pressurizes under the presence of water, a cavitation generator that directly oxidizes organic components in the sewage by generating cavitation in the flow of pressurized sewage mixed with an oxidizer, and a cavitation generator It is equipped with a reflux passage for returning the sewage after passing to the septic tank, and a means for stirring the sewage in the septic tank. From the solids removal, such as residual inorganic matter, said agitating means, the agitator to agitate the liquid in the septic tank by the rotation of the vane installed in the septic tank, a rotary drive motor for rotating the the stirring拌器 in The sewage from the septic tank to the take-out passage is branched on the side away from the stirrer, and the sewage is returned from the reflux path to the septic tank on the side closer to the stirrer. A sewage treatment apparatus is provided.
[0008]
The action and effect of the invention of claim 1 will be explained. Cavitation is generated in the sewage water mixed with a gaseous oxidant such as air, oxygen or ozone, and a large amount of bubbles containing the oxidant is formed in the sewage. Is done. These bubbles instantly collapse, but at that time, high-temperature and high-pressure conditions such as 5,000 to tens of thousands of degrees and pressures of 1,000 to tens of thousands of atmospheres are generated, and the bubbles contain an oxidizing agent. The organic matter can be instantly decomposed by direct oxidation . Also, the ultrasonic wave reaching 40 KHz generated by cavitation can act on the cell membrane in the organic matter and directly destroy it. Oxidation under cavitation enables decomposition of organic matter without the sludge solid-liquid separation process in the conventional activated sludge process, and high-temperature and high-pressure reaction tanks such as supercritical water oxidation Therefore, the equipment can be made relatively small and construction costs can be saved. Further, since no sludge is generated, the incineration process is unnecessary or the burden on the incineration process is reduced, and the energy cost can be reduced also in this respect.
[0010]
Together but areas may perform direct oxidation of sewage by key Yabiteshon is immediate very limited area of the bubbles due to cavitation (are said to several microns in diameter) allowed to undergo the action of cavitation while sewage is circulated from septic tank By stirring the sewage in the septic tank, the oxidization effect due to cavitation can be finally applied to the entire sewage in the septic tank, so that substantially the entire sewage in the septic tank can be purified.
[0014]
Sewage from the flow inlet sand is removed by being introduced into the settling basin through the sewage channel, the sewage after settling removal is introduced into the septic tank, it was caused to contain an oxidizing agent by applying圧汚water flow forming means The sewage from the septic tank is caused to cause cavitation by a cavitation generator and is returned to the septic tank again, while in the septic tank, the sewage is continuously stirred by the stirring means. Through a series of treatments such as agitation of sewage in the septic tank, the sewage in the septic tank is thoroughly oxidized by cavitation, and then inorganic substances are removed in the solid-liquid separation tank. Therefore, according to the present invention, it becomes possible to constitute a self-contained sewage purification system capable of purifying organic matter substantially completely by direct oxidation after eliminating the solid-liquid separation step of organic components in sewage, and activated sludge. Compared with the conventional method, it is possible to reduce the size, save energy required for conventional incineration of sludge, and reduce the equipment cost and energy cost compared with the supercritical water oxidation system. .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an outline of the overall configuration of a sewage purification system according to an embodiment of the present invention. This sewage purification system is a system that directly oxidizes organic matter without relying on activated sludge adopted in a normal sewage purification treatment system. In the purification system using activated sludge, the organic components in the sewage are agglomerated by aerobic microorganisms in the aeration tank, and then agglomerated by the aerobic microorganisms. The activated sludge is precipitated, and the activated sludge as the precipitate is separated. Is used as a microbial source for new wastewater, but the remaining part is precipitated and concentrated and incinerated. However, the energy (fuel consumption) required for this incineration is great, and a great deal of electrical energy is required for the rotational drive of the aeration electric fan, resulting in a problem of energy cost. The present invention does not rely on the activated sludge method. In other words, the present invention aims to purify sewage by direct oxidation of organic matter without performing solid-liquid separation of the organic matter by activated sludge formation. That is, as shown in FIG. 1, the sewage purification system of the present invention includes a sand basin 10, a septic tank 12, and a solid-liquid separation tank 14 in a sewage flow path 6 connecting the inlet 2 and the outlet 4 as constituent elements. However, it does not have an aeration tank for activated sludge or a route for returning sludge to the aeration tank. The direct oxidation of the organic matter in the septic tank 12 is carried out by cavitation, and a cavitation generator 16 described later is provided as means for that purpose. There is also installed a pump 20 (pressure sewage flow forming means of the present invention) that takes out sewage from the septic tank 12 to the cavitation generator 16 and guides it under pressure while mixing a gaseous oxidant such as air, oxygen or ozone. The
[0016]
In FIG. 1, a sand basin 10 having a structure similar to that used in an activated sludge type normal sewage treatment system can be employed. That is, this type of sand basin is equipped with a sand scouring machine for scraping the sand deposited on the bottom surface of the sand basin and a screen residue removing machine for removing the screen residue.
[0017]
2 shows the configuration of the septic tank 12 in more detail, and includes a sewage inlet 12-1 from the sand basin 10 of FIG. 1 and a sewage outlet 12-2 to the solid-liquid separation tank 14. A stirrer 22 (stirring means of the present invention) is disposed in the septic tank 12, and a rotating shaft 22-1 of the stirrer 22 is connected to a rotation driving motor 24, and the agitator 22 is driven by the rotation driving motor 24. Thus, the liquid in the septic tank 12 can be stirred. The sewage in the septic tank 12 is taken out from the take-out passage 19 by a pump 20 in a suction manner, and at the time of the suction, gaseous oxidizers such as air, oxygen and ozone are mixed at the same time. That is, it is possible to mix gaseous oxidizers such as air and ozone into the suction sewage by configuring the pump 20 to leak some air and ozone on the suction side. The sewage mixed with a gaseous oxidant such as air or ozone passes through the cavitation generator 16 to generate cavitation and is returned to the septic tank 12 through the reflux passage 25.
[0018]
3 to 5 show an example of the configuration of the cavitation generator 16. Although any cavitation generator can be used, this example employs a structure based on the principle of cavitation generation by swirling flow. The cavitation generator 16 includes a rotating tube body 26, an inlet tube 28, and an outlet tube 30. The rotary tube 26 is connected to the inlet and outlet tubes 28 and 30 by rotary joints 32 and 34, respectively. The inlet pipe 28 is connected to the outlet of the pump 20 in FIG. 2, and the outlet pipe 30 is connected to the reflux passage 25. The rotary tube body 26 is connected to a rotation drive motor 42 (not shown) by a pulley 36, a belt 38, and a pulley 40, and is rotated at a high speed at a rotational speed of several hundred min- ¹ or more. The rotary joint 32 rotatably connects a joint pipe 44 extending from the inlet end of the rotary tube body 26 to the inlet pipe 28, and the rotary joint 34 connects a joint pipe 46 extending from the outlet end of the rotary pipe body 26. Rotatingly coupled to the outlet tube 30, thereby allowing rotation of the rotating tube 26 relative to the inlet and outlet tubes 28, 30. Further, a central shaft body 48 made of a pipe closed at both ends is disposed concentrically on the inner periphery of the rotary tube body 26, and an annular passage 50 is formed between the rotary tube body 26 and the central shaft body 48. The upstream side of the annular passage 50 communicates with the inlet pipe 28, and the downstream side communicates with the outlet pipe 30. The central shaft body 48 is provided with feed blades 52 and 54 at the inlet and outlet ends, respectively, and each of the feed blades 52 and 54 is provided with two symmetric diameters as shown in FIG. The outer end of the central shaft body 48 is fixed to the inner periphery of the rotary tube 26. A gap S is formed between the feed blades 52 and 54 in the circumferential direction, and a liquid can flow through the gap S. Further, a large number of protrusions 56 are formed on the outer peripheral surface of the central shaft body 48.
[0019]
The sewage from the septic tank 12 pressurized to a predetermined pressure by the pump 20 is introduced into the rotary tube body 26 through the inlet pipe 28 and the joining pipe 44 as indicated by an arrow f, and is connected to the annular passage through the rotating feed blade 52. 50, the liquid is discharged from the feed blade 54 on the outlet side through the joint pipe 46 to the outlet pipe 30 as indicated by the arrow g and is returned to the septic tank 12. In the annular passage 50, a powerful swirling flow (arrow h in FIG. 5) is obtained by the high-speed rotation of the feed blade 52. Since the flow path diameter is reduced when flowing into the annular passage 50, the flow velocity increases, and a large number of protrusions 56 are provided on the surface of the central shaft body 48 on the downstream side of the feed blade 52. The high-speed swirling flow in the passage 50 violently collides with the protrusion 56, and countless turbulent vortices are generated under severe disturbance in the flow of liquid (sewage). In the vicinity of the turbulent vortex, bubbles (vapor bubbles) are caused by a negative pressure lower than the saturated vapor pressure at the liquid temperature. Innumerable bubbles generated by such turbulent vortices collapse immediately upon pressure recovery. Such bubble generation-disintegration process, that is, cavitation, can help decompose organic matter in wastewater. That is, the collapse of bubbles in cavitation is a very localized region, but generates super high temperature and high pressure states of 5,000 to tens of thousands of degrees and 1,000 to tens of thousands of atmospheres. The collapsing bubbles contain an oxidant such as oxygen or ozone, and the organic matter in the sewage can be efficiently oxidized directly by ultra high temperature and high pressure by cavitation. In addition, ultrasonic waves generated due to cavitation can also contribute to the decomposition of organic matter in the sewage (destruction of the cell membrane). Further, direct oxidation of organic components in wastewater including such cavitation is limited to a local region close to the bubble generation site in the cavitation generator 16, but it is continuously with the high-speed swirling flow protrusion 56. An infinite number of turbulent vortices are generated in the entire region of the annular passage 50 due to the intense disturbance action caused by no collision, and the sewage in the septic tank 12 is repeatedly introduced into the cavitation generator 16 through the take-out passage 19, and the cavitation generator 16 is returned to the septic tank 12 via the reflux passage 25, and the sewage in the septic tank 12 is constantly stirred by the stirrer 22 installed in the septic tank 12, so that the sewage stays in the septic tank 12 appropriately. By setting, the direct oxidation action by the cavitation generator 16 is uniformly applied to the entire sewage in the septic tank 12. It is possible.
[0020]
In FIG. 2, the solid-liquid separation tank 14 has a structure similar to that of the final sedimentation basin in the purification system using the activated sludge method, and includes a treated water introduction passage 14-1 from which organic substances from the purification tank 12 have been removed. The treated water from the septic tank 12 does not contain organic substances, but some inorganic substances are precipitated. The bottom surface of the solid-liquid separation tank 12 is provided with a reciprocating scraping device 58 (for example, having the same configuration as the sludge scraping device described in Japanese Patent Laid-Open No. 5-245308). The precipitate is collected in the pit 60 by a) and sucked and discharged by a jet pump (not shown). A scum recovery device 62 such as a known rotary trough type is provided on the liquid surface of the solid-liquid separation tank 14, and the scum that has floated on the liquid surface of the solid-liquid separation tank 14 has the slit 62-1 of the scum recovery device 62 facing sideways. Is collected by the scum collecting device 62. The treated water is discharged from the outlet 14-2.
[0021]
In the embodiment described above, cavitation is generated by hydrodynamic means such as the cavitation generator 16 by swirling flow, but it is generated by directly generating ultrasonic waves by mechanical means and propagating the ultrasonic waves to sewage. Direct oxidation may be performed by cavitation. As for the phosphorus in the sewage, appropriate known recovery means such as a coagulation sedimentation method and a crystal stone method can be separately installed as a countermeasure.
[Brief description of the drawings]
FIG. 1 is an overall schematic view of a sewage purification system of the present invention.
FIG. 2 is a detailed cross-sectional view of the septic tank and the solid-liquid separation tank in FIG.
FIG. 3 is a schematic longitudinal sectional view of a cavitation generator.
FIG. 4 is a schematic cross-sectional view of the cavitation generator represented along line IV-IV in FIG.
FIG. 5 is a schematic cross-sectional view of the cavitation generator represented along line VV in FIG. 3;
[Explanation of symbols]
2 ... Inlet 4 ... Discharge 6 ... Sewage channel 10 ... Sand basin 12 ... Septic tank
12-1 ... Inlet
12-2 ... Discharge port 14 ... Solid-liquid separation tank 16 ... Cavitation generator
DESCRIPTION OF SYMBOLS 19 ... Extraction passage 20 ... Pump 22 ... Stirrer 24 ... Rotation drive motor 25 ... Reflux passage 26 ... Rotating pipe body 28 ... Inlet pipe 30 ... Outlet pipe
32, 34… Rotary joint

Claims (1)

A sewage treatment apparatus, an sewage inlet to be treated in a sewage system, an outlet for treated sewage, a sewage channel connecting the inlet and the outlet, and a septic tank on the sewage channel on the inlet side And a solid-liquid separation tank on the sewage flow path on the discharge port side, the septic tank has a take-out passage for branching sewage from the septic tank, and a pressurized sewage flow formation that pressurizes the branched sewage in the presence of an oxidizing agent Means, a cavitation generator that generates cavitation in the flow of pressurized sewage mixed with an oxidizer, and directly oxidizes organic components in the sewage, and a reflux passage that returns the sewage after passing through the cavitation generator to the septic tank And an agitation means for sewage in the septic tank, the organic content in the sewage is removed by the septic tank, and the sewage after the organic content is removed is solid solids such as residual inorganic content in the solid-liquid separation tank. There is removed, the stirring means is constituted by a stirrer to agitate the liquid in the septic tank by the rotation of the vane installed in the septic tank, a rotary drive motor for rotating the the stirring拌器, to the extraction passage The sewage treatment apparatus is characterized in that the sewage from the septic tank is branched on the side away from the stirrer, and the sewage is returned from the reflux passage to the septic tank on the near side .

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