JPS59166292A - Backwashing method of fixed bed type sewage cleaning up tank - Google Patents

Abstract

PURPOSE:To perform backwashing in an optimum timing by operating a biological membrane sensor consisting of a light emitting part, photodetecting part and biological film removing mechanism dipped in a tank and backwashing automatically a packing material when a preset number of operations are attained. CONSTITUTION:When a sewage treatment is continued, a biological film grows thickly on the surface of a packing material 3, and the degree thereof is detected with a biological film sensor 11. When the detected intensity of light attains a certain set value or below, a small sized motor 28 is rotated a washing brush 26 is rotated via a disc 29, a crank 30 and a washing brush supporting bar 27, on the inside of a sensor housing part 25 to that the brush 26 removes the biological film on the surface of the window 22 in the light emitting part and the window 24 in the photodetecting part. The biological film on the surface of the material 3 is stripped until an adequate thickness is attained and in succession, sludge is settled in the bottom of a cleaning up tank 2 and is discharged to the outside of the tank through a sludge discharging pipe 7 and a sludge discharging valve 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to backwashing of a filler in a fixed bed type sewage purification apparatus in which wastewater is purified by the action of microorganisms grown on the surface of the filler.

Activated sludge method, trickling filter method, and fixed bed method are well known as methods for purifying wastewater through the action of microorganisms. In the fixed bed method, a tank is filled with fillers such as plastic corrugated plates or nets, and the wastewater is stirred using a mechanical agitator or an air lift with aeration, and the microorganisms that have grown on the surface of the filler are circulated and brought into contact. 1. Generally, there are two types of methods: aerobic fixed bed method in which air is diffused into the tank, and anaerobic fixed bed method in which air is not diffused.In aerobic fixed bed method, microorganisms attached to the surface of the filler are In the anaerobic fixed powder method, microorganisms anaerobically digest the organic matter in wastewater, thereby purifying it by oxidizing and decomposing the organic matter.

However, if such treatment is continued for several months, the thickness of the biofilm on the surface of the filler increases due to microorganisms that proliferate as wastewater is purified, and eventually the biofilm itself becomes supported on the surface of the filler. It becomes difficult to clean, peels off, and mixes with treated water, causing deterioration of water quality. In addition, biofilm grows in the voids of the filler, which causes a phenomenon in which the volume of the voids gradually decreases, that is, clogging, which worsens the circulation of wastewater in the septic tank and impairs purification efficiency. For this reason, in normal treatment, when the thickness of the biofilm reaches a certain level and clogging progresses, backwashing is performed to forcibly peel off the biofilm, and the sludge and sludge are discharged to the outside of the septic tank. ing.

For backwashing methods, in the case of an aerobic fixed bed, the flow rate of air discharged from the aeration device is rapidly increased to increase the circulation flow rate of wastewater in the septic tank, or the backwashing method is to increase the flow rate of air discharged from the aeration device, or to increase the circulation flow rate of wastewater in the septic tank. A common method is to remove the thickened biofilm by blowing air bubbles through the gaps in the filler. The backwashing method for anaerobic fixed beds is almost the same, but a digestion gas containing methane gas as the main component may be used instead of air. In this way, in the fixed powder method, sewage is purified by repeating backwashing, but conventional methods for deciding when to backwash have been based on experience, such as manually carrying out the process after a certain period of time, or using a timer. Methods such as setting a time and performing it periodically have been used.

However, these methods do not necessarily accurately reflect the state of clogging of the filler material, and the backwashing period is too early, causing the biofilm to be peeled off more than necessary, reducing the treatment capacity, and reducing the quality of the treated water. There were many cases where the water quality deteriorated and was left unattended due to slow backwashing.

The present invention solves the problems of these conventional methods, and provides a method for backwashing a fixed-bed type sewage purification device that always accurately grasps the clogging situation of the filling material and performs backwashing at the optimal time. With the goal.

The present invention includes a light-emitting section having a light source, a light-receiving section that receives light from the light-emitting section and measures its intensity, and a biofilm removal mechanism that removes biofilm attached to the surfaces of the windows of the light-emitting section and the light-receiving section. A fixing method characterized by immersing a biofilm sensor equipped in a septic tank into a septic tank and accurately detecting the growth status of biofilm on the surface of the filler material, thereby determining the time for backwashing according to the growth status of the biofilm. This is a method for backwashing a floor-type sewage septic tank.

Examples will be described below based on the drawings. The embodiment shown in FIG. 1 includes an inlet pipe 1 through which sewage flows, a septic tank 2 for treating the sewage, a cover 12 for blocking air, a filler 3 in which biofilm is formed, and a diffuser for discharging digestion gas for stirring. Aeration device 4, backwashing aeration device 5, outflow pipe 6 through which treated water flows out, and sludge drainage pipe 7 for removing sludge made of biofilm peeled off during backwashing.
This is an anaerobic fixed-bed type sewage purification device consisting of a sludge valve 8, a first compressor 9 that sends digestion gas, and a second compressor 10 that supplies air for backwashing. A biofilm sensor 11 that detects the backwashing period is fixed to the wall of the septic tank 2.
Part of it is immersed in sewage inside the tank.

The sewage that has flowed in through the inflow pipe 1 is agitated in the septic tank 2 and is purified by coming into contact with microorganisms that have grown on the surface of the filler 30 and formed a biofilm. Septic tank 2 for stirring
An air lift using anaerobic digestion gas mainly composed of methane gas is used, and the purified treated water is discharged through an outflow pipe 6. Further, excess sickle gas digestion gas is similarly discharged through the outflow pipe 6.

If such processing continues, the biofilm will thicken on the surface of the filler 3, and the extent of this will be detected by the biofilm sensor 11. Here, the structure and function of the biofilm sensor 11 will be explained in detail with reference to the drawings.

FIG. 2 is an exploded perspective view showing the structure of the biofilm sensor 11. The biofilm sensor 11 includes a light emitting section 21 that emits light, a light emitting section window n through which the light passes, and a light receiving section n that detects the intensity of the light.
, a cleaning brush 26 for cleaning dirt from the light receiving window row through which the light to be detected passes, the senna storage section 1 for holding and storing them, the light emitting window n, and the light receiving window row. Furthermore, the cleaning brush support rod 27. 2 discs with 4 small motors to drive the cleaning brush section.

It consists of a crankshaft and a fixing pipe 31 for holding these together. A tungsten lamp or a light emitting diode is usually used as a light source for the light emitting section 21, and a silicon photodiode or a cadmium sulfide cell is used as a photoelectric conversion element for the light receiving section B.

The light emitting section window section and the light receiving section window row are made of glass or transparent plastic, and are attached in close contact with the sensor storage section B.

Next, the functions will be explained. When the sensor storage part 6 and the cleaning brush of the biofilm sensor 11 having the above-described structure are immersed in waste water in the tank, the sensor storage part 5 has a cylindrical shape, so the waste water can freely pass through the inside. can6
Therefore, like the filler 3, as time passes, biofilm grows on the surfaces of the light emitting window 22 and the light receiving window 240, blocking the passage of light and reducing the intensity of light detected at the light receiving part. lower. On the other hand, the cleaning brush section is driven when the detected intensity of light falls below a certain set value. In other words,
When the original strength falls below a certain predetermined value, a small motor rotates, disk 4, crank 30. The cleaning brush U moves up and down inside the sensor housing section via the cleaning brush support rod M, and removes biofilm on the surfaces of the light emitting section window 22 and the light receiving section window array.

Note that a mechanism such as a rack and pinion may be used as a method for driving the cleaning brush 26 up and down. It is sufficient to set the cleaning time to about 1 minute, and when the predetermined time elapses and a part of the small motor is turned off, the cleaning brush is lowered by its own weight and released from the sensor storage part 6.

Since the wastewater stops at a low position, it is possible for the dirty water to pass through the inside of the sensor housing section 5 again.

That is, the cleaning brush 26 is driven every time the biofilm on the surfaces of the light emitting window n and the light receiving window array reaches a certain thickness. By the way, the light emitting part window n of the biofilm sensor 11
Looking at the relationship between the biofilm on the surface of the light-receiving window row and the biofilm on the surface of the filler 3, since both are immersed in the same tank, the microorganisms forming each biofilm are It can be considered that there is no major difference between the types, and the growth rate of each biofilm can be considered to be almost the same. This is the number of times the cleaning brush of the biofilm sensor 11 is operated after that time (hereinafter referred to as the number of cleaning times), starting from a certain point in time, for example, immediately after backwashing the filling material 3.
indicates that there is a proportional relationship with the increase in biofilm thickness on the surface of the filler 3.

Therefore, if the d relationship is determined experimentally in advance, then the thickness of the biofilm on the surface of the filling material 3, that is, the degree of clogging of the filling material 3, can be estimated from the number of times the biofilm sensor 11 is washed. I can do it.

This is true regardless of the concentration of organic matter in the inflowing sewage or the amount of inflowing sewage. This is because if the amount of organic matter increases,
The growth rate of biofilm on the incandescent filler 3@ surface is fast (although
This is because the number of times the biofilm sensor 11 is washed also increases.

To further explain the backwashing timing detection method and backwashing method using the above-mentioned principle in this embodiment, the number of times the biofilm sensor 11 is washed in a state where the biofilm is about to thicken and begin to peel off is determined in advance during backwashing. If we find it as a starting point, we get
Thereafter, backwashing may be automatically performed when the number of washings reaches a predetermined number. In other words, the number of times of cleaning is automatically counted, and when the set value is reached, the waste water is inflowed into the first compressor 9.
The operation of the septic tank 2 is stopped, the second compressor 10 is started, and air is blown from the backwashing air diffuser 5 to peel off the biofilm on the surface of the filler 3 to an appropriate thickness, and then to the bottom of the septic tank 2. The sludge is allowed to settle and is taken out of the tank via the sludge pipe 7 and sludge valve 8. When the backwashing is completed, sewage is allowed to flow in again, the first compressor 9 is activated, the number of times the biofilm sensor is washed is reset to 0, and normal operation is resumed.

As described above, in the present invention, by immersing the biofilm sensor 11 in the septic tank and accurately detecting the growth status of biofilm on the surface of the filler material, the backwashing timing can be determined according to the clogging status. It is possible to prevent backwashing from occurring too early, resulting in excessive exfoliation of biofilms and reducing treatment capacity, resulting in deterioration of treated water quality, or conversely, from backwashing being delayed and leaving water with poor quality. Furthermore, even if the amount of organic matter flowing into the septic tank or the flow rate of inflowing sewage fluctuates, the appropriate backwashing timing can be automatically detected in accordance with the fluctuations. Furthermore, compared to the conventional method of determining the time for backwashing without looking at the water quality, it automatically determines the time for backwashing, so backwashing can be carried out unattended, making it easier for maintenance. You can save a lot of labor costs.

The present invention can be applied not only to the anaerobic fixed-bed type septic tank described above but also to an aerobic fixed-bed septic tank that performs air aeration.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a biofilm sensor used in the present invention. 2...Septic tank, 3...Filling material, 4...Diffuser,
5... Backwash diffuser, 9... First compressor,
10°゛・Second compressor, 11...biofilm sensor, 21...light emitting section, oh...light receiving section, ah...cleaning brush. te 20 of ya 1

Claims (1)

[Claims] 1) A method for backwashing a fixed bed type sewage septic tank in which sewage flows into a tank in which a filler is deposited and is circulated through microorganisms grown on the surface of the filler, comprising: a light-emitting part, a light-receiving part,
A biofilm sensor consisting of a biofilm removal mechanism is immersed in a tank,
A fixed device that operates a biofilm removal mechanism depending on the degree of dirt on the light emitting part and the light receiving part, and automatically backwashes the filling material when the number of activations reaches a preset number of times. How to backwash a floor-type sewage septic tank.