JP2005185935A - Septic tank and sewage treating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a septic tank in which problems of an ozone-used sterilizing method are solved, the maintenance of which is facilitated and in which the production of sterilization by-products such as trihalomethane and aldehydes is restrained and to provide a sewage treating method. <P>SOLUTION: This septic tank is provided with an anaerobic treatment tank, an aerobic treatment tank, and a sterilization tank. The sterilization tank has a diffuser for discharging ozone-containing air and a transfer pipe for returning a part of the treated water sterilized in the sterilization tank to the anaerobic treatment tank. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a septic tank for purifying sewage and a sewage treatment method, which are intended to purify manure, other domestic wastewater, or combined sewage (hereinafter also referred to as sewage).

  Various methods for operating a sewage septic tank have been known. A typical method is a method of disinfecting solid substances contained in influent sewage and performing biological treatment of organic substances. And conventionally, the liquid after disinfection was discharged as it is.

As a disinfection method in the sewage septic tank, a disinfection tank is provided before the treated water is discharged, and a chlorine-based chemical is placed in this disinfection tank, so that the treated water that has undergone biological treatment and the chlorine-based chemical are brought into contact with each other. The method of doing is generally adopted. As another disinfecting method, as described in Patent Document 1, a method of disinfecting by supplying air containing ozone to a disinfecting tank and bringing the ozone into contact with water to be treated has been proposed. (See Utility Model Reference 1).
Utility model registration No. 2508406

  However, the method of deploying a chlorinated drug in a disinfecting tank and bringing it into contact with the sterilization tank usually requires replenishment of a new drug every 3 to 6 months, which requires time and effort for maintenance. In addition, when the amount of free chlorine eluted from the drug becomes excessive, there is a problem that organic substances contained in the water to be treated may react with free chlorine to produce disinfection by-products such as trihalomethane.

  In addition, although a disinfection method using ozone has been proposed to solve the problem of generating disinfection byproducts such as trihalomethane, the disinfection method using ozone is easy to maintain, but as a disinfection byproduct, trihalomethane is used. There is a problem that substances other than aldehydes, ketones, carboxylic acids and the like are produced.

  The present invention is intended to solve the above-mentioned problems of the disinfection method using ozone, and is a septic tank that is easy to maintain and suppresses the generation of disinfection byproducts such as trihalomethanes and aldehydes, and a sewage treatment method. The purpose is to provide.

  (1) The present invention includes an anaerobic treatment tank, an aerobic treatment tank, and a disinfection tank, and the disinfection tank discharges ozone-containing air, and the treated water disinfected in the disinfection tank. It is a septic tank which has a transfer pipe which returns a part to the anaerobic processing tank.

  (2) Moreover, this invention is a sewage treatment method which performs anaerobic treatment, aerobic treatment, and disinfection one by one, Comprising: The said disinfection is performed using ozone containing air, and treated water is said anaerobic after disinfection. This is a sewage treatment method that is returned to the tank that is performing the treatment.

  When the sewage purification tank and sewage treatment method of the present invention are used, ozone-containing air is injected into the liquid that has undergone biological treatment in the sterilization tank to sterilize, and a part of the sterilized liquid is circulated to the anaerobic treatment tank. Thus, production of substances such as trihalomethane and aldehydes can be suppressed. Furthermore, the amount of stored sludge can be reduced, and the deodorization effect by ozone released into the space in the tank can be obtained.

In the present invention, ozone-containing air is used for disinfection. However, when air containing ozone is aerated in the treated water, ozone is decomposed into oxygen (O ₂ ) and oxygen radicals (O) in the liquid. It is considered that some OH radicals are generated. These radicals have a very strong oxidizing action, and in particular, can effectively break the polymer chain and break the unsaturated bond of the hardly biodegradable organic substance. In addition, due to the oxidizing action of ozone, sterilization and disinfection of microorganisms contained in wastewater, and reduction in molecular weight of refractory biodegradable organic substances to easily biodegradable organic substances (for example, aldehydes, ketones, carboxylic acids, etc.) Is done.

  If a part of the liquid is circulated to the anaerobic treatment tank without discharging the treated liquid after ozone treatment (disinfection) in the disinfection tank, aldehydes, ketones, carboxylic acids, etc. contained in the treated liquid Biodegradable organic substances can be easily biodegraded in the biological treatment process of the septic tank. In addition, when the treated liquid containing dissolved ozone is circulated to the anaerobic treatment tank, the hardly biodegradable organic matter contained in the influent will react with the dissolved ozone and oxidize to easily biodegradable organic matter. The amount of incombustible biodegradable organic matter flowing in can be reduced. By these actions, the production of aldehydes, ketones, carboxylic acids and the like can be suppressed.

  FIG. 1 is one embodiment of a treatment flow showing the sewage treatment method of the present invention. The influent (sewage) first enters the anaerobic treatment tank, and solids are separated. In the anaerobic treatment tank, concentrated sludge (solid matter) that has settled is stored at the bottom of the tank, and scum generated by anaerobic storage is stored at the top of the tank. The advection liquid from the anaerobic treatment tank is transferred to the aerobic treatment tank. In the aerobic treatment tank, the organic matter in the advection liquid is aerobically biodegraded by sending air from the blower. The advection liquid from the aerobic treatment tank is transferred to the disinfection tank and is sterilized by the ozone-containing air supplied from the ozone generator. Thereafter, a part of the treated liquid (hereinafter referred to as “circulating liquid”) is circulated to the inflow portion of the anaerobic treatment tank, and the remaining treated liquid is discharged.

  Here, various types of anaerobic treatment tanks, aerobic treatment tanks, and disinfection tanks can be used, and are not particularly limited. Specifically, a treated water tank (precipitation tank) is provided after the aerobic treatment tank, a flow rate adjusting unit is provided in one part of the anaerobic treatment tank and / or the aerobic treatment tank, and two anaerobic treatment tanks are provided. You can also.

  The ozone concentration supplied from the ozone generator is usually 0.1 to 20 mg / L, preferably 0.5 to 5 mg / L, and the air supply amount is 1 to 30 L / min, preferably 5 to 10 L / min. It is. The operation of the ozone generator can also perform both ozone generation and air supply, or ozone generation intermittently, or change the ozone concentration, depending on the inflow pattern in the inflowing sewage, the organic matter concentration, and the like. In FIG. 1 described above, a common blower is used for both the aerobic treatment tank and the ozone generator, but a blower dedicated to the ozone generator may be provided.

  In FIG. 1, the circulating fluid is returned to the inflow portion of the anaerobic treatment tank, but when the anaerobic treatment tank is divided into two chambers, or between the first chamber and the second chamber of the anaerobic treatment tank, or It can also be returned to the outflow part of the second chamber of the anaerobic treatment tank. Preferably, it is an inflow part of an anaerobic processing tank. This is because returning the circulating fluid to the inflow portion of the anaerobic treatment tank 1 can reduce the influence of dissolved ozone on the aerobic microorganisms of the aerobic treatment tank 30. The circulating fluid does not necessarily have to be returned from the inflow portion, and may be directly introduced into a tank that performs anaerobic treatment.

  The ratio (circulation ratio) of the circulating fluid volume to the daily average flow rate of the influent is 1 to 6, preferably 2 to 4. If the circulation ratio is less than 1, the proportion of aldehydes, ketones, carboxylic acids, etc. contained in the effluent is biodegraded and the effluent is discharged without being removed so much. When the circulation ratio is larger than 6, it is necessary to increase the capacity of the sterilization tank or set the ozone concentration high in order to ensure the liquid residence time in the sterilization tank.

FIG. 2 shows one embodiment of the septic tank of the present invention.
The septic tank is an anaerobic treatment tank first chamber 11, an anaerobic treatment tank second chamber 12, an aerobic treatment tank 30 in which an aerobic treatment and a filtration chamber 32 are arranged vertically, a treatment water tank 54, and a disinfection tank. 33 is provided.

  The shape of the filter bed 20 provided in the anaerobic treatment tank 1 is not particularly limited, and plate-like members such as loofah-like, corrugated plate-like, and porous shapes, and honeycomb-like (honeycomb core) members are preferable. Used. Further, the filter bed 20 may be a skeletal spherical or mesh-like cylindrical member. The filter bed 20 may be provided only in the anaerobic filter bed tank second chamber 12, and can be removed from both the anaerobic filter bed tank first chamber 11 and the anaerobic filter bed tank second chamber 12.

  In the biological reaction chamber 31 constituting a part of the aerobic treatment tank 30, a reaction aeration member 34 is disposed as an aeration tube for aeration from the bottom, and air from the blower 35 is discharged. The biological reaction chamber 31 is formed with a biological reaction bed 31a filled with a carrier (a microbial carrier, a microorganism adhesion material, and a contact material), and sewage is aerobically treated in the biological reaction bed 31a. Here, the biological reaction bed 31a may be a fluidized bed or a fixed bed.

  The shape of the microbial carrier can be various shapes such as plate, net plate, loofah, porous, cylinder, rod, skeleton sphere, string, and granular, irregular lump, cube, and fiber lump. What was processed into can be used. Examples of the base material include synthetic resin processed products such as polyvinyl chloride, polyester, polyvinylidene chloride, polyvinyl formal, polyurethane, and melamine resin, inorganic processed products such as ceramics and silica sand, and fossils such as anthracite. A processed product, activated carbon or the like having a specific gravity of about 1 or 1 or more, a polyolefin resin such as polyethylene or polypropylene, or a specific gravity of about 1 or 1 or less such as polystyrene can be used.

  A filtration bed 32a filled with a filter medium is formed in the filtration chamber 32, and the SS in the flowing liquid is captured there. As the filter medium to be filled, those floating in the liquid can be used, but a sedimentation filter medium is preferable. Examples of sedimentary filter media include synthetic resin processed products such as polyvinyl chloride, polyester, polyvinylidene chloride, polyvinyl formal, polyurethane, and melamine resin, inorganic processed products such as ceramics and quartz sand, and fossil processing such as anthracite. Products, activated carbon, etc., with specific gravity of about 1 or more, or polyolefin resin such as polyethylene, polypropylene, etc., and those with a specific gravity of about 1 or more adjusted by adding fillers to polystyrene. It may be formed and processed into a lump shape, a cylindrical shape, a net shape, a rod shape, a fiber lump shape, or a porous shape.

  A cleaning air diffuser member 36 is disposed at the bottom of the filter chamber 32 as an air diffuser for backwashing the filter bed 32a, and is connected to a blower 35 for supplying air. In addition, although the said biological reaction chamber 31 and the filtration chamber 32 are piled up and installed in the perpendicular direction in FIG. 2, the structure juxtaposed in a horizontal direction may be sufficient.

  When the operation of the septic tank is continued, clogged with SS accumulated in the filter bed 32a, the SS is removed by washing the filter bed 32a regularly or appropriately. In this cleaning, air from the blower 35 is discharged from the cleaning diffuser member 36 to bubble the filter bed 32a, and a part of the air from the blower 35 is also supplied to an air lift type cleaning drainage pump 37.

  The peeled SS becomes cleaning wastewater together with the liquid in the tank, descends the filtration bed 32a, returns to the anaerobic treatment tank 1 through the cleaning drainage discharge pipe 37a by the cleaning drainage pump 37. Note that an electric pump or the like can be used as the cleaning drainage pump 37. Cleaning of the filter bed 32a is usually preferably performed at midnight when sewage is rarely discharged in a general household.

  The disinfection tank 33 performs disinfection or sterilization by bringing the ozone-containing air generated by the ozone generator 3 into contact with the advection liquid from the filtration chamber 32 based on the raw air of the blower 35. At the bottom of the disinfection tank 33, an air diffuser 15 is arranged as an air diffuser for supplying ozone-containing air, and this is connected to the ozone generator 3.

  The disinfection tank 33 is provided with an air lift type circulation device 41 that transfers the liquid in the disinfection tank 33 to the anaerobic treatment tank 1 through the transfer pipe 9. Moreover, it is preferable to send the ozone containing air from the ozone generator 3 to the air sent to the circulation device 41. This is because microorganisms can be prevented from adhering to the air lift pipe by utilizing the sterilizing action of ozone.

  The septic tank is provided with a manhole so that maintenance and management such as inspection and cleaning of each tank can be performed, and a manhole cover 39 is usually attached. In addition, an ozone treatment device that decomposes residual ozone discharged into the space inside the septic tank and exhausts it outside the manhole can be provided outside the septic tank or outside the septic tank. (Not shown)

It is a flowchart which shows the wastewater treatment method which is an Example of this invention. It is a longitudinal cross-sectional view of the sewage septic tank which is another Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Anaerobic treatment tank, 2 ... Inflow liquid, 3 ... Ozone generator, 7 ... Outflow liquid, 8 ... Circulating liquid, 9 ... Transfer pipe, 11 ... Anaerobic treatment tank 1st chamber, 12 ... Anaerobic treatment tank 2nd chamber, DESCRIPTION OF SYMBOLS 15 ... Aeration member, 20 ... Filter bed, 30 ... Aerobic treatment tank, 31 ... Biological reaction chamber, 31a ... Biological reaction bed, 32 ... Filtration chamber, 32a ... Filtration bed, 33 ... Disinfection tank, 34 ... Reaction diffuser 35: blower, 36: air diffuser for cleaning, 37: cleaning drain pump, 37a: cleaning drain pipe, 39: manhole cover, 41: circulation device, 54: treated water tank

Claims (2)

  An anaerobic treatment tank, an aerobic treatment tank, and a disinfection tank, wherein the disinfection tank discharges ozone-containing air and a part of the treated water disinfected in the disinfection tank A septic tank having a transfer pipe to be returned. A sewage treatment method that sequentially performs anaerobic treatment, aerobic treatment, and disinfection, wherein the disinfection is performed using ozone-containing air, and the treated water is returned to the tank that is performing the anaerobic treatment after disinfection. Wastewater treatment method.

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