JP3668358B2 - Structure of bioreactor with carrier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improved apparatus for treating BOD-containing wastewater such as urban wastewater and factory wastewater by an activated sludge method (water treatment is performed using microorganisms). In particular, in order to increase the concentration of microorganisms, a carrier attached with microorganisms or a carrier containing microorganisms (in the present invention, these are collectively referred to as a microorganism-attached carrier) and oxygen or oxygen-enriched air is used to increase the concentration. The present invention relates to a bioreactor combined with a carrier having a structure that facilitates inspection and maintenance of a carrier separation device for preventing outflow of a microorganism-adhering carrier in a biological reaction vessel that efficiently performs water treatment at a microorganism concentration.
[0002]
[Prior art]
As a wastewater treatment method using living organisms, a method of increasing the concentration of microorganisms and a method of increasing the concentration of specific microorganisms using a carrier attached with microorganisms or a carrier containing organisms have been proposed.
In this method, as shown in FIG. 2, a biological reaction tank 1 and a sedimentation tank 2 are provided, and the waste water 7 supplied to the biological reaction tank 1 is consumed by microorganisms under the aerobic condition due to the action of activated sludge. Is done. The treated water having a reduced BOD is sent to the sedimentation tank 5 together with the activated sludge, where the activated sludge is separated, and the treated water with improved water quality is discharged into a river or the like. A part of the separated activated sludge is returned to the biological reaction tank 1 as the return sludge 8, but the remainder is treated as excess sludge 12.
[0003]
In this treatment, the biological reaction tank 1 is often performed in an open state, but is preferably sealed and performed under aerobic conditions in an oxygen or oxygen-enriched air atmosphere. In particular, since the speed of wastewater treatment is proportional to the concentration of microorganisms, recently, a microorganism-adhering carrier in which microorganisms are immobilized on a polymer-containing hydrogel (carrier) containing polyethylene glycol as a main component is introduced into the biological reaction tank 1. Methods for maintaining a high microorganism concentration and improving the reaction rate have been proposed and actively studied.
[0004]
In such a method, it is necessary to prevent the microorganism adhesion carrier from flowing out of the biological reaction tank 1, and a screen 4 for separating the microorganism adhesion carrier from the treatment liquid at the treatment liquid outlet inside the biological reaction tank 1. To prevent spillage and prevent a decrease in microbial concentration. The provision of the screen 4 at the outlet of the treatment liquid not only separates and deposits the microorganism-adhering carrier on the screen 4, but also various solid components floating in the waste water 7 that could not be settled and separated at the initial settling site. It deposits, causing the screen to become dirty and clogged, and hinders the outflow of the processing liquid from the biological reaction tank 1. If this is obstructed, the operation of the entire bioreaction apparatus combined with a carrier will be hindered, resulting in a decrease in the processing capacity of the entire apparatus, and in the worst case, even the operation stoppage.
For this reason, in order to prevent the screen 4 from becoming dirty and clogged, a backwashing device (not shown) provided in the biological reaction tank 1 is installed, and the screen 4 is regularly backwashed or screened. An air diffuser (not shown) for ejecting gas toward the screen is provided at the lower part of the screen, and bubbles are ejected to prevent clogging of the screen 4 by causing bubbles and carriers to collide with the screen 4 (Japanese Patent No. 2579122). ) Etc. have been made.
[0005]
In this way, in the biological reaction tank 1, when the microbial concentration for biological reaction becomes high, the consumption rate of oxygen per unit volume of the biological reaction tank increases in proportion to this concentration.
In the conventional biological treatment reaction using a carrier with a microorganism attached, most of them supply oxygen and agitate by aeration of air. Since a good dispersion is required, a relatively light floating polymer-containing gel carrier has been used as a microorganism-adhering carrier. These carriers are high-viscosity gels, and are easily broken by strong stirring such as a stirrer. As the oxygen consumption rate increases, the stirring power of the biological reaction tank is increased to improve the oxygen dissolution rate. This is a problem, and it is difficult to maintain a high dissolved oxygen concentration by air aeration.
[0006]
On the other hand, technological innovations in oxygen gas separation methods have made it possible to obtain high-concentration oxygen at a relatively low cost, so oxygen or oxygen-enriched air has come to be used in wastewater activated sludge treatment. . This method is extremely effective for maintaining a high dissolved oxygen concentration in the treatment zone, but a small amount of air diffused to dissolve the oxygen consumption is sufficient. For this reason, this amount is insufficient to effectively disperse the microorganism-adhering carrier with this amount of aeration, and when a high-concentration oxygen atmosphere is adopted, it is more efficient than gas agitation to disperse the microorganism-adhering carrier. Preferably by stirring.
However, mechanical agitation has the effect of breaking and crushing soft solids such as polymer-containing hydrogels, and this gel breakage further promotes clogging of the screen of the carrier separation device. In other words, the solid components, activated sludge, etc. that could not be settled in the first sedimentation basin were mixed, and the required frequency of cleaning the screen 4 was considerably high, resulting in a decrease in operation efficiency.
[0007]
In addition, this problem is in the case where the activated sludge treatment is performed using a carrier for increasing the microorganism concentration in each treatment tank, and using a microorganism-adhered carrier to which microorganisms acclimatized in each treatment tank are attached. Similar problems have arisen for the screens 4 provided for the respective treatment tanks, and a fundamental solution has been demanded as a major problem of the activated sludge method using a microorganism-adhering carrier.
[0008]
[Problems to be solved by the invention]
The present invention relates to an activated sludge treatment apparatus using oxygen or oxygen-enriched air and using a microorganism-adhering carrier in order to increase the microorganism concentration, and a carrier separation device provided for each treatment tank to prevent the microorganism-adhering carrier from flowing out. The purpose is to develop a structure of a bioreactor with a carrier that is easy to maintain and check.
[0009]
[Means for Solving the Problems]
The present invention
(1) An apparatus for performing water treatment in a sealed biological reaction tank while flowing a microorganism-adhering carrier, wherein a carrier separation apparatus having a screen open to the atmosphere in a state of being communicated at the bottom outside the biological reaction tank. (2) By developing the structure of the biological reaction tank with the carrier according to (1), wherein the sealed biological reaction tank is an aeration tank using oxygen or oxygen-enriched air. Solved the above problem.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described below with reference to the drawings.
As the bioreactor used in the present invention, an apparatus as shown in FIG. 1 can be used, and a bioreactor combined with a carrier used for activated sludge wastewater treatment using ordinary oxygen or oxygen-enriched air is preferable. .
This apparatus comprises a biological reaction tank 1 having a screen 4 and a sedimentation tank 5, and the biological reaction tank 1 may be open, but is preferably sealed and can be biologically treated in an oxygen or oxygen-enriched air atmosphere. A treatment tank is preferred.
[0011]
This biological reaction tank 1 is a sealed type biological reaction tank because it is necessary to perform a biological reaction in an atmosphere of oxygen or oxygen-enriched air, and oxygen or oxygen-enriched air is supplied to the upper part of the treatment liquid or in the liquid. As the upper part of the biological reaction tank is filled, a part of it is discarded as exhaust gas in order to maintain the oxygen concentration. In order to perform biological treatment, it is necessary to dissolve this high-concentration oxygen gas in the treated water. For this reason, a stirring device 2 for dissolving oxygen and dispersing the microorganism-adhering carrier is used. This type is a mechanical stirring using a surface aerator or a submersible pump, a gas using a diffuser tube or a diffuser plate. Either stirring or a combination of both may be used and the type is arbitrary. However, from the viewpoint of stirring energy efficiency, it is preferable to use a mechanical stirrer, particularly a stirrer capable of simultaneously stirring a surface aerator and a liquid phase.
[0012]
Here, the reaction solution that has undergone the biological reaction treatment is sent to the screen 4 where the microorganism-adhering carrier is separated, and this separated solution is sent to the next sedimentation tank 5. This carrier separation device communicates with the bottom of the biological reaction tank, and the top thereof is open to the atmosphere. In addition, a screen 4 is provided inside, so that the microorganism adhesion carrier in the treatment liquid can be separated from the treatment liquid.
In addition to the microorganism-adhering carrier, this treatment liquid contains solid components (SS) that could not be separated in the sedimentation basin at the beginning, and activated sludge produced as a by-product during the biological reaction. Will be.
[0013]
Unlike the conventional apparatus in the biological reaction tank, the carrier separation apparatus of the present invention is easily maintained and inspected because the screen 4 that is dirty or clogged is open to the atmosphere. In this case, cleaning can be easily performed, and it is possible to easily prevent the outflow of the processing solution. When the microorganism-adhering carrier used here is heavier than the specific gravity of the treated water, screen clogging can be greatly reduced. Furthermore, it is advantageous that the bottom communicating with the bioreactor is such that the microbial adhesion carrier can automatically settle and move in the direction of the bioreactor.
[0014]
The treatment liquid containing the activated sludge and the like that has passed through the carrier separation device is sent to the sedimentation tank 5 to separate the activated sludge and the like, and the supernatant is discharged as a treated water 11 to a river or the like. A part of the precipitated activated sludge is sent as a return sludge 8 to the biological reaction tank, mixed with the influent water 7 and used for a biological reaction, and the remaining activated sludge is treated as surplus sludge.
The microorganism-adhering carrier used in the present invention is not particularly limited, and may be a polymer hydrous gel. However, from the viewpoint of the mechanical strength of the microorganism-adhering carrier, the density is adjusted with an inorganic filler such as calcium carbonate. It is preferable to use a carrier made of a polyolefin foam such as polypropylene and polyethylene and having a density adjusted to about 0.95 to 1.10 g / cm ³ . If the density is 1.0 g / cm ³ or less, it should not settle in water, but after a while after being stirred in water, it settles unexpectedly. This is considered to be because the density exceeds 1.0 g / cm ³ as a result of water absorption of the filler or adhesion of microorganisms. The shape of the carrier is not particularly limited, such as a cylindrical body, cylindrical body, spherical body, cube, or indefinite shape. The smaller the carrier size, the larger the surface area, but it is limited because it is greatly affected by the flow rate of the treated water. However, if possible, a cylindrical body having an outer diameter of 5 to 30 mmφ, a thickness of 0.5 to 5 mm, and a length of about 0.8 to 1.2 times the outer diameter is preferable.
[0015]
Since such a carrier has a rough surface due to the filler and foaming material, it is suitable for the adhesion of microorganisms, and since it is cylindrical, the microorganisms adhering to the inside adhere to the carrier in a stable state unless the carrier is destroyed. It is effective for microbial treatment in the treatment section.
Even if the amount of the microorganism-adhering carrier in the biological reaction tank is varied over a wide range, the effect can be exerted. The larger the effect, the more effective, but usually 15 to 20% by volume of the treatment volume of the biological reaction tank is energy efficiency in stirring. From the viewpoint of the above, it is preferable.
Moreover, the ratio of surplus sludge and return sludge should just be operated in the same manner as in the general case, and it can be operated at about 50%.
[0016]
The biological reaction tank 1 using the microorganism adhesion carrier shows a strong dependence on the dissolved oxygen concentration in the treatment using the microorganism adhesion carrier, and the biological reaction rate is almost proportional to the concentration. In general, when a biological reaction is carried out at a high dissolved oxygen concentration, the settleability of the activated sludge contained in the treated water is improved. However, it is preferable to operate at a dissolved oxygen concentration of at least about 3 mg / liter, although not limited thereto.
[0017]
【The invention's effect】
In the treatment method using activated sludge of wastewater, it is attempted to improve the treatment speed by using a microorganism-adhering carrier. However, as the treatment speed improves, oxygen or oxygen can be used as a method for supplying oxygen corresponding to the oxygen consumption rate. The use of oxygen-enriched air is conceivable. In this case, a screen has been installed in each treatment tank so far to prevent the microorganism-adhering carrier from flowing out, but there is no appropriate means for preventing clogging of the screen.
In the present invention, by changing the installation location of the carrier separation device including the screen provided inside the biological reaction tank to the outside of the reaction tank, the carrier separation device is likely to cause clogging due to microbial adhesion carrier, activated sludge, SS, etc. The screen of this product can be cleaned, maintained, and inspected extremely easily, so even if a microbial adhesion carrier is used together to improve the processing capacity, it is possible to prevent a decrease in operational efficiency due to troubles caused by clogging of the screen. It was.
As a result, this bioreactor has a high oxygen supply rate and a high bioreaction rate, which can prevent clogging of the screen without opening the bioreaction tank. Even if it is deposited, it can be removed easily without opening the sealed biological reaction tank. For this reason, not only long-term continuous operation became possible, but also an extremely advantageous wastewater treatment method could be developed, such as the activated sludge produced as a by-product having a high density and easy separation.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an example of a bioreactor combined with a microorganism-adhering carrier of the present invention.
FIG. 2 is a conceptual diagram of a conventional bioreactor device combined with a microorganism adhesion carrier.
[Explanation of symbols]
1 Biological reaction tank 2 Stirrer 4 Screen 5 Sedimentation tank 6 Sludge scraping machine 7 Waste water (inflow water)
8 Return sludge 9 Oxygen (oxygen-enriched air)
10 Exhaust gas 11 Treated water (discharged water)
12 Surplus sludge

Claims (2)

In an apparatus for performing water treatment in a closed biological reaction tank while flowing a microorganism-adhering carrier, a carrier separation device having a screen open to the atmosphere in a state of being communicated at the bottom outside the biological reaction tank is provided. The structure of the bioreactor combined with the characteristic carrier. The structure of the biological reaction tank with a carrier according to claim 1, wherein the sealed biological reaction tank is an aeration tank using oxygen or oxygen-enriched air.

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