JPH04284894A - Controlling method of biological treatment of sewage and its apparatus - Google Patents

Abstract

PURPOSE:To control biological treatment of sewage to stably obtain treated water with good quality by grasping the living things adhering conditions in a filled bed and carry out backwash properly in the biological treatment of sewage when the sewage is led to pass the filled bed of the living things adhering medium. CONSTITUTION:In a biological treatment apparatus like an anaerobic filtration bed tank 2, turbidity of the treated water flowing out after being brought into contact with a filtration bed 9 is measured by a turbidity meter 14 and, according to the measaured value, the treatment is controlled to carry out sludge discharge from a sludge accumulating part 11 through a sludge drawing out pipe 2 and/or to carry out back wash by sending air to a backwash pipe 10.

Description

Description: [Industrial Application Field] The present invention relates to a method and apparatus for controlling biological treatment of sewage. It can be applied to biological treatment facilities using oxidation methods, anaerobic treatment facilities and aerobic treatment facilities for human waste, sewage, and industrial wastewater, and combinations thereof. [0002] Biological treatment of sewage is roughly divided into two types, the suspended organism method and the fixed biofilm method, depending on the form of microbial retention.The fixed biofilm method includes the trickling filter method and the rotating circle method. plate method,
There are contact methods, etc. Among these methods, the contact method is a method in which a tank is filled with a contact material (also called a "medium"), and microorganisms adhere to and proliferate on this contact material to decompose organic matter. be. There are two types of decomposition: aerobic and anaerobic, and the contact method can perform either of these depending on the conditions. [0003] As the contact material used in this case, granular materials made of other plastic materials such as bamboo shinobu or crushed stone, and materials with good biofilm adhesion properties such as plate-like materials, cylindrical materials, and net-like materials are used. . In addition, as the contact material, in addition to the above,
For example, a string-like body can also be used, and microorganisms can be attached to a number of string-like bodies that are stretched. Conventionally, in biological treatment using a contact method in which contact digestion and catalytic oxidation are performed sequentially, emphasis has been placed on improving the quality of treated water by improving the structure of the treatment tank and setting an appropriate residence time. Due to the complexity of biological treatment, it is not possible to proactively adjust the processing conditions of the treatment tank.
During biological treatment, the state of the treatment is determined by measuring the dissolved oxygen concentration (DO) and oxidation-reduction potential (ORP) in the liquid, and the amount of oxygen supplied is adjusted accordingly. there were. [Problems to be Solved by the Invention] However, in biological treatment using such a contact material (hereinafter referred to as "medium"), as mentioned above, it is accompanied by the growth of living organisms, so In addition to the clogging of the medium due to the resulting solid content, the amount of attached organisms on the medium increases, or the medium is clogged due to microbial clumps falling off from the medium, and the microbial clumps falling from the medium fall to the bottom of the tank. As a result, sludge accumulates at the bottom of the treatment tank. And with these,
For example, changes in treatment conditions due to changes in the amount of attached organisms, decreases in flow rate or changes in treatment conditions due to clogging of the media, or quality of treated water due to increases in the amount of sludge deposited or an increase in the amount of microbial clumps falling from the media. Problems such as destabilization without deterioration and difficulty in maintenance and management due to these factors were occurring. [0006] Conventionally, methods for solving this problem include visually observing the amount of sludge deposited at the bottom of the treatment tank and discharging the sludge when the amount is large, or observing the amount of attached organisms in the medium and performing backwashing if necessary. However, these methods only involve visual inspection of the outside of the media, and it is not possible to accurately determine the clogging condition inside the media. The quality of the treated water was also unstable. [0007] The present invention provides a control method and device for biological treatment of sewage that can accurately grasp the clogging state of the medium and perform sludge discharge and/or backwashing of the medium at an appropriate time. The purpose is to Another object of the present invention is to provide a biological treatment control method and device that can maintain the adhesion state of organisms in a medium appropriately and stably obtain treated water of good quality. [Means for Solving the Problems] The present inventor has studied various control conditions for biological treatment and has measured various factors that allow biological treatment to be carried out efficiently and treated water of good quality to be obtained. However, it was discovered that the measured turbidity of treated water from a treatment tank with a packed bed of biofouling media has a correlation with the clogging state of the media, and it became clear that this could be used as a control factor. Based on this, we have arrived at the present invention. That is, the present invention achieved the above object by the following means. 1. In a wastewater treatment method in which wastewater is brought into contact with a packed bed of biofouling media for biological treatment, the turbidity of the treated water after contact with the medium is measured, and when the measured value exceeds or exceeds a set value. A method for controlling biological treatment of sewage characterized by discharging sludge from a sludge reservoir below a packed bed and/or performing a backwashing operation at a predicted time. 2. A biological treatment device for sewage comprising a packed bed made of a biofouling medium in a tank provided with a sewage inflow pipe and a treated water outflow pipe, and a cleaning gas inflow part below the packed bed, the treated water outflow part A turbidity measuring device is installed in the tank, and the signal from the turbidity measuring device is sent to the control device, and when the measured value exceeds the set value or is expected to exceed the set value, the control device sends a signal from the sludge reservoir installed at the bottom of the tank. sludge discharge and/or
Alternatively, a control device for a biological treatment device for sewage, characterized in that a cleaning gas is caused to flow into a cleaning gas inflow section. [0011] In the present invention, when the clogging of the biofouling medium progresses in the biological treatment, the turbidity of the treated water flowing out from the treatment tank having the packed bed increases, or the increase is in a waveform, and then the turbidity decreases once. It discovers that the wave changes, such as the next increasing wave, and uses this to control. The biological treatment to which the present invention is applied may be either aerobic treatment or anaerobic treatment, or both may be performed in combination. Examples of the medium for attaching organisms used in the present invention include honeycomb tubes, string-like bodies,
Corrugated plates, ball-shaped bodies, etc. are preferred. These are included in those conventionally known as media in biological filter beds, but among these media, granular materials such as anthracite and sand are not suitable for the present invention. Generally, it is preferable to use a medium having a shape that has gaps such that microbial masses separated from the medium fall below the packed bed. In the following, the packed bed of the present invention may be referred to as a "biological filter bed". [0012] The turbidity measuring device used in the present invention includes a turbidity meter, an SS meter, a fluorometer, etc., and an SS meter is preferred. Although it is preferable to measure turbidity continuously in order to understand the state of increase in turbidity, it is also possible to measure it intermittently at short intervals, such as every minute. The control method and apparatus of the present invention will be specifically explained using the drawings. The sewage biological treatment equipment shown in Figure 1 is
An anaerobic filter bed tank and a contact aeration tank are combined to perform both anaerobic treatment and oxidative treatment. In this biological treatment device, wastewater 1 enters the first chamber 7 of the anaerobic filter bed tank 2,
The anaerobic bacteria retained in the filter bed 9 perform anaerobic treatment, and the liquid that has passed through the filter bed 9 and exits below it passes through the liquid pipe 15 and enters the second chamber 8, where it is similarly subjected to anaerobic treatment. Ru. During this treatment, in the anaerobic filter bed tank 2, microorganisms that have grown on the filter bed 9 are accumulated in the sludge reservoir 11 at the bottom of the chamber. This sludge is taken out from the sludge drawing pipe 12 by periodically driving the pump 13. The anaerobically treated wastewater then enters the first chamber 16 of the contact aeration tank 3, where a filter bed 9 is provided,
Aeration air 18 enters from the diffuser 19 and is aerated, subjected to biological oxidative treatment, and then to the second chamber 1.
Similar processing is performed in step 7. Note that a part of the liquid is taken out from the upper part of the second chamber 17 and sent to the first chamber 7 of the anaerobic filter bed tank 2 as return water 22. The liquid that has undergone the above treatment enters the sedimentation tank 4, where the sludge is separated by sedimentation, and the supernatant liquid enters the disinfection tank 5, where it is sterilized with a disinfectant supplied from the disinfector 24, and is discharged as treated water 6. Ru. In addition, sedimentation tank 4
Sludge 23 is discharged from the bottom. In the liquid pipe 15 of the first chamber 7 and the upper part of the second chamber 8 of the anaerobic filter bed tank 2 of this biological treatment apparatus, and the first chamber 16 and the second chamber 17 of the contact aeration tank 3. A turbidity recorder 14 is provided at each upper part of the tank, a flow rate indicator recorder 20 is provided at the air pipe of the aeration air 18, and an ORP recorder is provided at the upper part of the first chamber 16 and second chamber 17 of the contact aeration tank 3. A total of 21 will be provided. When the treatment is continued in this biological treatment apparatus, the measured value of the turbidity recorder 14 provided in the anaerobic filter bed tank 2 may become a curve as shown in FIG. It has been found that the reason why the pulse-like peak 1 like this curve appears is because the amount of sludge extracted by the pump 13 from the sludge reservoir 11 is small. Further, if the treatment is continued as it is, the turbidity value increases and peak 2 appears, but at this time, the amount of microorganisms attached to the filter bed 9 becomes too large, and the microorganisms from the filter bed 9 are removed. This is thought to be because the amount of water falling increases and the microorganisms in the liquid flow away. In addition, it is thought that the reason why peak 1 and peak 2 appear is that a large amount of sludge accumulates in the sludge reservoir 11, and as the sludge surface rises, the sludge is periodically entrained by the liquid flow sent to the next tank. but,
This is just an estimate, and the exact phenomenon is not known. [0015] As described above, when peak 1 or peak 2 appears on the curve of the measured values of the turbidity recorder 14, or when it is expected, clogging of the medium and accumulation of sludge occur, resulting in deterioration of the treatment. Therefore, either the pump 13 is driven to take out the sludge from the sludge reservoir 11 through the sludge withdrawal pipe 12, and/or the cleaning gas inflow section (hereinafter referred to as "backwash pipe") is ) 10 to backwash the filter bed 9 and remove excess microorganisms in the filter bed 9. Although this control may be performed by a human, it is preferable to use an electrical control device. In the apparatus shown in FIG. 1, a control circuit is configured to send a signal from the turbidity recorder 14 to a control device 26 via a discriminator 25, thereby opening a valve 27 and sending a cleaning gas 28. Although only the first chamber 7 is shown in FIG. 1, the other chambers are similarly provided. Note that the second chamber 8 is also provided with a sludge reservoir, a sludge extraction pipe, etc., but their illustration is omitted in FIG. In addition,
If the measured values do not form a curve as shown in FIG. 4, a curve based on the measured values is obtained in advance, and control values that match the curve are set. Further, the measured values of the turbidity recorder 14 in the first chamber 16 and second chamber 17 of the contact aeration tank 3 show a curve as shown in FIG. 5, for example. This is similar to an anaerobic filter bed tank,
This is because the turbidity (SS) in the tank begins to rise as organic matter is removed, and by measuring the SS in the tank,
Automatic backwashing is performed when a turbidity corresponding to filter bed clogging or sludge accumulation is reached or predicted. Figure 2 shows an example of the present invention applied to an anaerobic filter bed tank. In this case, the tank consists of only one chamber, and the structure of the tank is almost the same as that shown in Figure 1. And,
The symbols attached to each part are also the same as in FIG. However, in this tank, a baffle 29 is provided next to the filter bed 9 to form an ascending path for the treated water passing through the filter bed 9, and a turbidity recorder 14 and an ORP recorder are installed at the top of this ascending path. 21 is provided. In the case of this structure, since the sludge accumulated in the sludge reservoir 11 is likely to be accompanied by the water flow entering the ascending path, it is considered that the turbidity is likely to exhibit a pulse-like peak as shown in FIG. 4. Further, FIG. 3 shows an example in which the present invention is applied to a contact aeration tank, and the tank consists of only one chamber, and the structure of the tank is almost the same as that shown in FIG. The reference numerals given to each part are also the same as in FIG. In this tank, the sewage in the tank is fluidized by the air blown in from the air diffuser 19, so the sludge does not settle to the bottom of the tank much. The turbidity of the liquid in the tank is measured by a turbidity recorder 14 provided at the outlet of the treated water, and when it reaches a predetermined value, air is sent to the backwash pipe 10 to backwash the filter bed 9. Additionally, the oxidation-reduction potential of the liquid is measured by the ORP recorder 21, and the amount of aeration air sent to the aeration device 19 is controlled to ensure that sufficient oxidizing biological treatment is performed within the filter bed 9. . In any case, the setting value changes depending on the difference between anaerobic treatment and aerobic treatment, and the difference in the water to be treated, so it is best to set it each time.For example, in the case of anaerobic treatment, the SS 100 mg/liter or more, preferably 1
00-150mg/liter, S for aerobic treatment
S is 30 mg/liter or more, preferably 30 to 70 m
It is preferable to use g/liter as a guideline for the set value, and to perform control such that sludge is discharged and/or backwashed when the set value is exceeded or is expected to be exceeded. [Examples] The present invention will be specifically explained below with reference to Examples. However, the present invention is not limited to this example. Example 1 Actual wastewater was treated with a biological treatment device whose basic configuration is similar to the biological treatment device shown in FIG. However, both the anaerobic filter bed tank and the contact aeration tank consist of three chambers. The specific configuration of this biological treatment device is shown below. (1) Treatment facility Anaerobic filter bed tank 3.0m x 4.8m x 3
．． 6m (H) x 3 tanks Medium 1st
Chamber string-like pitch 100m
m
Volume 3
1m3 2nd and 3rd chambers ball shape diameter 150mm
Volume 39m3
Contact aeration tank 1st room 4.0m
x 3.0m x 3.5m (H) x 1 tank Rooms 2 and 3 4.0m x 1.35m x 3.5m
(H) x 2 tanks Media type
Corrugated sheet surface area 52m2/m3

Corrugated plate pitch 80mm Media filling amount 1st chamber
26.5m3
Rooms 2 and 3 11.
9m3 (2) Measuring instrument SS measuring instrument: Continuous turbidity meter (light scattering type) ORP
Measuring device: 2-wire insulated type (3) Operating conditions Average daily sewage supply amount 77.8 m
3/day (3.24m3/hour) Hourly maximum sewage supply amount 9.0m3/hour
Water quality of raw water and treated water
BOD
SS Raw water quality
12.4mg/l 140mg/l
Treated water quality 7.
0mg/l 3mg/l 0023
] Wastewater was treated with the above biological treatment equipment. The measurement results at that time are shown below. (4) Measurement Results The SS measurement results of the outflow water from the first chamber of the anaerobic filter bed tank and the first chamber of the contact aeration tank are shown in FIGS. 6 and 7. Since the SS of the effluent water from the anaerobic filter bed tank does not rise in a short period of time, data is shown only for the period before and after the rise. Further, although the outflow water in the contact aeration tank differs from room to room, in this case, the outflow water SS from the first room was used as a representative example. a. Changes in the SS value of the effluent from the first chamber of the anaerobic filter bed This treatment equipment has a high removal rate of SS in the first chamber of the anaerobic filter bed, and once every 2 to 3 months, a large amount of SS is removed from the treated water. S.S.
Contamination was observed. As shown in FIG. 6, the backwashing operation was started at point A, when the SS in the treated water was about 100 mg/liter. Backwash air volume: 2.0m3/
When this was carried out for about a minute, the SS of the water in the tank temporarily rose to about 4200 mg/liter due to backwashing. SS discharged from the filter bed during backwashing is removed to the outside of the tank as cleaning wastewater, and the treated water is allowed to flow out after the filter bed is stabilized. The next day after backwashing, SS decreased significantly, and after one day it was 30mg/
The value was around liters, and stable operation continued. b. Changes in the SS value of the outflow water from the first chamber of the contact aeration tank This first
In the chamber, the SS value of the treated water increased once every 2 to 3 weeks, and a backwash operation was performed at point A, where the SS became 70 mg/liter. Backwashing was carried out for 10 minutes at an air flow rate of 2.0 m3/min. The SS concentration in the tank after backwashing temporarily rose to about 1540 mg/liter as shown at point B in FIG. 7, but returned to the normal value two days later. As described above, by controlling the biological treatment apparatus, treated water with a low SS value could be continuously obtained without clogging the filter bed. Effects of the Invention The present invention enables biological treatment of sewage by bringing it into contact with a packed bed of biofouling media, and by measuring the turbidity of the treated water flowing out from the packed bed. By controlling the water quality and/or backwashing of the packed bed, it is possible to prevent clogging of the packed bed from occurring or worsening, which cannot be directly measured, and to improve the water quality. It is possible to stably obtain treated water with good quality over a long period of time. Furthermore, biological treatment can be easily controlled using a packed bed of biofouling media that cannot be measured directly.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of a biological treatment device that is an example of the present invention.

FIG. 2 shows a schematic diagram of an anaerobic filter bed tank that is an example of the present invention.

FIG. 3 shows a schematic diagram of a contact aeration tank which is an example of the present invention.

FIG. 4 shows an example of a graph showing changes in turbidity of treated water flowing out from the anaerobic filter bed tank in FIG. 2.

5 shows an example of a graph showing changes in turbidity of treated water flowing out from the contact aeration tank of FIG. 3. FIG.

FIG. 6 shows a graph showing changes in the turbidity of treated water flowing out from the anaerobic filter bed tank in the biological treatment apparatus of Example 1 of the present invention.

FIG. 7 shows a graph showing changes in the turbidity of treated water flowing out from the contact aeration tank in the biological treatment apparatus of Example 1 of the present invention.

[Explanation of symbols]

1. Sewage 2 Anaerobic filter bed tank 3 Contact aeration tank 4 Sedimentation tank 5 Disinfection tank 6. Treated water 7　Room 1 8 Second room 9 Filter bed 10 Backwash pipe 11 Sludge sump 12 Sludge extraction pipe 13 Pump 14 Turbidity recorder 15 Liquid pipe 16 1st room 17 Second room 18 Aeration air 19　Air diffuser 20 Flow rate indicator recorder 21 ORP recorder 22 Returned water 23 Sludge 24 Disinfector 25 Discriminator 26 Control device 27 Valve 28 Cleaning gas 29 Baffle

Claims (2)

[Claims] Claim 1: A method for treating wastewater in which wastewater is brought into contact with a packed bed of biofouling media for biological treatment, wherein the turbidity of the treated water after contact with the medium is measured, and the measured value exceeds a set value. A method for controlling biological treatment of sewage characterized by discharging sludge from a sludge reservoir below a packed bed and/or performing a backwashing operation when the level exceeds the level or is expected to exceed the level. 2. A biological treatment device for sewage comprising: a packed bed made of a biofouling medium in a tank provided with a sewage inflow pipe and a treated water outflow pipe; and a cleaning gas inflow section below the packed bed. A turbidity measuring device is installed at the outflow of the treated water, and a signal from the turbidity measuring device is sent to a control device, and when the measured value exceeds the set value or is expected to exceed the set value, the control device sends a signal to the bottom of the tank. Discharge of sludge from established sludge basin and/or
Alternatively, a control device for a biological treatment device for sewage, characterized in that a cleaning gas is caused to flow into a cleaning gas inflow section.