JP2585187B2 - Organic wastewater biological treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for biologically and physicochemically treating organic wastewater containing SS, BOD, etc., such as sewage, human wastewater, and various kinds of organic industrial wastewater.

[0002]

2. Description of the Related Art The most typical method of treating organic sewage, for example, sewage treatment, is an activated sludge method, which has an important advantage of wide applicability and is most often employed. On the other hand, in recent years, an aerobic biofilm filter method has been developed. In this method, sewage is passed downflow through a filter bed made of particulate solids such as sand, anthracite, and activated carbon, and air bubbles are raised upflow from a diffuser tube or the like and brought into contact with countercurrent to treat the air bubbles. Is what you do. In this case, an aerobic biofilm such as BOD-utilizing bacteria and nitrifying bacteria is attached to the filter medium surface of the filter bed, and the greatest feature is that biological treatment and filtration and removal of SS are performed simultaneously in this filter bed. It has become.

[0003]

However, this conventional activated sludge treatment method has the following major drawbacks. Since it requires three separate tanks: the first settling tank → the aeration tank → the last settling tank, the installation area is large and the construction cost is high. Since aeration power efficiency is not good, aeration cost becomes large. The carryover of SS in the final sedimentation basin is unavoidable, and the SS removal effect of the first sedimentation basin is only about 70%. In order to reduce the SS of the treated water discharged to 20 mg / l or less, a sand filter is required after the final sedimentation tank. The settling of activated sludge often deteriorates. Further, the aerobic biofilm filter method also has the following disadvantages. If the raw water SS is large, a sedimentation tank must be provided in the preceding stage. Otherwise, the filter bed clogs quickly and is not practical. Even when the raw water BOD is high, the growth amount of the biofilm increases, and the clogging of the filter bed progresses quickly,
Not applicable. The clarified filtered water from the aerobic biofilm filter device must be consumed as washing water at the time of filter bed clogging, so that the efficiency of treated water production is poor. Separate sedimentation tanks are required for treatment of washing wastewater. Since the filter bed support structure below the filter bed and the aeration system are complicated, construction costs are high and scale-up is not always easy. An object of the present invention is to solve all the drawbacks of the above-mentioned prior art and to provide a biological treatment method for organic wastewater capable of obtaining extremely high treated water with high production efficiency.

[0004]

According to the present invention, in order to achieve the above object, a filter medium layer is provided in an upper part of a tank, and a raw water inflow part and a diffuser part are provided in a lower part of the tank, respectively. A first tank provided with a primary treated water outflow portion, a floating filter medium layer provided in an upper portion of the tank, and an air diffuser provided in a lower portion or inside the floating filter layer, and a lower portion of the air diffuser is provided. A second set-up with a settling section and a secondary treated water outflow section at the top of the tank
When the aerobic biological treatment is performed at the time of filtration of the filter medium layer of the first tank, the tank is used in communication with the primary treated water outflow part of the first tank and the lower settling part in the second tank. Was discharged from the diffuser to develop an aerobic biofilm on the surface of the filter medium, and during washing of the filter medium layer, the air was discharged from the diffuser to disturb the filter medium layer and was trapped in the filter medium layer. The SS is driven out and the washing wastewater is precipitated in the sedimentation section of the second tank. The washing wastewater in the second filter medium layer is introduced into the sedimentation section of the first tank or the second tank, and the SS is transferred to the sedimentation section. It is allowed to settle.

[0005]

The raw water containing the SS substance such as sewage and the soluble BOD flows into the lower part of the first tank from the raw water inflow portion to settle and separate the settling SS in the raw water. S at the bottom of the first tank
The raw water from which most of the S has settled and separated is turned upside down and enters the filter medium layer from below, and fine SS that has not settled is removed by filtration, and is developed on the filter medium surface in the filter medium layer. Soluble B by anaerobic or aerobic biofilm
OD components are decomposed and removed. In order to develop an aerobic biofilm on the surface of the filter medium in the filter medium layer, it is sufficient to diffuse oxygen-containing gas from the filter medium layer or from the air diffuser below the filter medium layer. The biofilm can be developed without bleeding. Thus, the primary treated water flowing out from the upper part of the filter medium layer flows from the primary treated water outflow part into the lower settling part in the second tank, and thereafter enters the filter medium layer from below, and is preferably It reaches an aerobic biofilm such as BOD-utilizing bacteria or nitrifying bacteria on the surface of the filter medium of the filter medium layer maintained in the aerobic state. Therefore, the residual BOD and ammonia remaining in the primary treatment water flowing out of the first tank are extremely effectively removed by the aerobic biofilm developed in the filter medium layer, and at the same time, the remaining fine SS is also highly filtered and removed. ,
In both SS and BOD, several mg / l of clear second treated water flows up like a spring from the upper part of the filter medium layer and flows out of the second treated water outlet. As the treatment is continued, the amount of SS trapped in the filter medium layer of the first tank and the filter medium layer of the second tank increases, and the filter resistance increases, so that a predetermined filter resistance (for example, 500 mmH
_When it reaches about ₂ O), each filter medium layer is washed. As an example, the washing of the filter medium layer in the first tank is performed without stopping the inflow of the raw water, together with the inflow of the raw water. The amount of air diffused from the air diffuser at the lower portion of the filter medium layer is rapidly increased, causing a violent gas-liquid multiphase flow in the filter medium layer, and pushing out the SS that has been captured and accumulated in the filter medium layer. The washing wastewater containing the SS washed out from the filter medium layer of the first tank flows into the lower settling portion in the second tank, and the SS in the washing wastewater is settled and separated. If a polymer flocculant can be added to the washing wastewater flowing into the washing wastewater, sedimentation and separation of SS in the washing wastewater can be remarkably promoted. Next, in the filter medium layer of the second tank, since most of the SS and BOD in the raw water have been removed by the sedimentation separation and the filter medium layer in the first tank in the former stage, the increase rate of the filter resistance is Although it is slow, as the operation continues for a long time, the filter reaches a predetermined value, so it is necessary to perform cleaning.This cleaning increases the amount of air discharged from the air diffuser significantly more than during normal operation. , S in the filter media layer
S is washed out, and the washing wastewater is flowed into the lower part of the first tank through the raw water tank together with the raw water to separate SS, or the washing wastewater of the filter medium layer is recycled to the lower settling part in the second tank. Then, the SS is settled and separated, and the clarified washing wastewater can be reused as washing water for the filter medium layer. If a polymer flocculant is added during the recycling, the SS in the recycled washing wastewater can be reused. Sedimentation separation can be promoted. By the above-described washing operation, the filter medium layer and the SS in the filter medium layer are washed out, and when the filter resistance returns to the initial value, the amount of air diffused from the air diffuser is returned to the normal processing, and the processing is restarted. further,
Other preferred processing operations of the present invention are listed below. When the solubility BOD concentration of raw water is high (for example, BOD1
2,000 mg / l), a part of the secondary treatment water flowing out of the aerobic filter medium layer of the second tank is guided to the lower part in the first tank to dilute the raw water, and the filter medium layer in the tank is reduced. Anaerobic inside can be prevented. Of course, when performing anaerobic biofilm treatment in the filter medium layer, it is not necessary to perform such an operation. When simultaneously removing the biodegradable COD, powdered activated carbon is added to the primary treated water flowing out of the first tank,
When the powdered activated carbon particles are captured by the filter medium layer of the second tank and COD is removed by the same mechanism as that of the granular activated carbon adsorption tower, the COD adsorption capacity of the powdered activated carbon can be maximized, and Bioregeneration of activated carbon by aerobic organisms in the filter medium layer can also be expected. When the filter medium particle size of the filter medium layer of the first tank is made larger than the filter medium of the filter medium layer of the second tank and the porosity is increased, the amount of SS trapped in the filter medium layer of the first tank is improved. When the raw water BOD is at a high concentration, it is preferable to maintain the filter medium layer of the first tank in an anaerobic state, develop a methane fermentation bacterium biofilm, and collect the generated methane gas. When removing phosphate ions, an inorganic coagulant such as aluminum sulfate, polyaluminum chloride, or ferric chloride is injected into water, and a floc containing insolubilized phosphorus is added to the first tank or the second tank. Settle and separate. When performing the nitrification denitrification treatment, the filter medium layer in the first tank is maintained in an anaerobic state, and a part of the second treated water in the second tank is removed from the first tank.
Circulate under the filter media layer of the tank.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the example of FIG. 1. A sedimentation / concentration section 2 'is formed at the bottom of a first tank 1, and a filter medium layer 3 filled with a filter medium is provided at an upper part in the tank. Is immersed and held. As the filter medium of the filter medium layer 3, a known granular filter medium can be used, but it is preferable to use a foamed plastic or other floating filter medium floating in water.
In the case of using a filter material having a size of less than 0, the upper portion of the filter medium layer 3 is covered with a water-permeable supporting member 4 such as a wire mesh to prevent the filter medium layer 3 from flowing out. When the specific gravity of the filter medium is about 0.5 to 0.9, the rate at which the filter medium is exposed on the water surface is small, and the support member 4 is not necessarily required.

[0007] A diffuser, for example, a diffuser tube 5 is provided inside or below the filter medium layer 3 to guide air from the blower 6, in order to develop an aerobic biofilm on the filter medium surface of the filter medium layer 3. Perform air diffusion, but do not perform air diffusion to develop an anaerobic biofilm on the surface of the filter medium. However, filter medium layer 3
At the time of cleaning, air is diffused in any case. A raw water inflow pipe 9 through which the raw water in the raw water tank 7 flows in by the pump 8 is opened in a lower part in the first tank 1, and a coagulant injection pipe 10 may be connected in the middle of the raw water inflow pipe 9. It is preferable that the lower part in the first tank 1 is the sedimentation part 2. In the upper part of the first tank 1, there is opened a primary treatment water outlet 11 for letting out the primary treatment water rising from below and flowing through the filter medium layer 3, and a liquid phase portion above the filter medium layer 3 Pump 1 connecting lower part of filter medium layer 3
It is also preferable to provide a circulation pipe 13 having 2. In addition,
In the figure, reference numeral 14 denotes a drainage pipe connected to the bottom of the first tank 1.

Reference numeral 21 denotes a second tank provided in parallel with the first tank 1. The lower part of the second tank 21 is a sedimentation part 22, and a sedimentation concentration part 22 'is formed at the bottom. The part is provided with a filter medium layer 23 filled with a granular filter medium having a specific gravity of less than 1.0 such as foamed plastic and floating in water, and an upper part of the filter medium layer 23 is covered with a water-permeable supporting member 24 such as a wire mesh, The outflow of the filter medium layer 23 is prevented. A diffuser 25 for diffusing oxygen-containing gas, for example, air from a blower 26 is provided below or inside the filter medium layer 23.
The upper filter medium layer portion is kept in the aerobic state. Also,
An overflow launder 27 is provided above the second tank 21, and a secondary treated water outflow pipe 28 is connected to the overflow launder 27. Reference numeral 29 denotes a drainage pipe connected to the bottom of the sedimentation / concentration unit 22 '. Furthermore, the primary treatment water outlet 1 of the first tank 1
1 and the lower settling part 22 in the second tank 21 are communicated by a flow path 30, and the coagulant injection pipe 1 is
It is also preferable to open 0 '. In addition, 2 of the second tank 21
A cleaning drainage pipe 31 is branched to the next treated water outflow pipe 28, and this cleaning drainage pipe 31 is opened and connected to the raw water tank 7 via an on-off valve 32. In addition, the cleaning drainage tank 33 is opened to the cleaning drainage tank 33, and the cleaning drainage in the cleaning drainage tank 33 is returned from the return pipe 35 to the lower settling part 22 in the second tank 21 by the pump 34. Furthermore, if the liquid phase portion above the filter medium layer 23 of the second tank 21 and the lower part of the filter medium layer 3 of the first tank 1 are connected by a circulation pipe 37 having a pump 36, nitrification and denitrification can be performed very suitably. .

[0009]

As described above, according to the present invention, an oxygen-containing gas such as air is injected from the air diffuser below the filter medium layer to disturb the filter medium layer, to remove the trapped SS and to wash it. Since the SS in the wastewater is precipitated in the sedimentation section of the second tank, and the washing wastewater in the filter medium layer of the second tank is supplied to the sedimentation section of the first tank or the second tank, the prior art is used. The following effects that cannot be obtained can be expected. 1. It is an extremely compact device that sedimentation and separation of organic wastewater, removal of SS by filtration, and two-stage treatment of anaerobic biofilm treatment and aerobic biofilm treatment, or two steps of aerobic biofilm treatment
Step processing can be performed. As a result, the first settling basin, the aeration tank, the final settling basin, and the sand filtration basin in the activated sludge method are not required, so that the space can be saved and the construction cost can be significantly reduced. 2. In the conventional biofilm filter method, a separate precipitating tank which is indispensable in the case where the amount of raw water SS is large can be omitted. 3. It is not necessary to consume clear treated water at the time of washing the filter medium layer, it is not necessary to stop the inflow of raw water, and the raw water itself and the washing wastewater itself can be effectively used as washing water for the filter medium layer. It is reasonable. 4. The washing wastewater in the filter medium layer of the first tank is introduced into the sedimentation section of the second tank, and the washing wastewater in the filter medium layer of the second tank is introduced into the sedimentation section of the first or second tank. SS contained in the washing wastewater can be separated and settled in the sedimentation section of the first or second tank. There is no need to install a separate sedimentation tank, and space and construction costs can be significantly reduced. Becomes 5. Even when the solubility BOD of the raw water is high, satisfactory treatment can be achieved without any problem. 6. The separation efficiency of SS is very excellent,
10 mg / l or less of clarified water is obtained. Further, the processing effect can be stabilized even when the flow rate of the raw water changes. 7. The application of powdered activated carbon can also effectively remove hard biodegradable COD. In addition, the COD adsorption capacity of the powdered activated carbon can be used to the maximum. 8. If the later aerobic biofilm filter bed is used as a filter medium layer, at least a troublesome support structure at the lower part of the filter medium layer becomes unnecessary,
Through this, construction can be expected to be easier. 9. Since the progress of clogging of the filter bed of the subsequent aerobic biofilm is extremely slow, the frequency of washing can be reduced. As a result, the biofilm that has developed on the surface of the filter medium layer does not need to be washed out of the system more than necessary, and the treatment effect of the aerobic biofilm can be improved. 10. The amount of excess sludge generated is small.

[Brief description of the drawings]

FIG. 1 is a system explanatory diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st tank 2,22 Sedimentation part 2 ', 22' Sedimentation concentration part 3 Filter medium layer 4,24 Support member, 5,25 Aeration tube 6,26 Blower 7 Raw water tank 8,12,34,36 Pump 9 Raw water inflow pipe 10, 10 ', 10 "flocculant injection pipe 11 Primary treatment water outlet 13, 37 Circulation pipe, 14, 29 Mud drain pipe 21 Second tank 23 Floating filter layer 27 Overflow launder 28 Secondary treatment water outlet pipe 30 Flow Road 31 Cleaning drainage pipe 32 On-off valve 33 Cleaning drainage tank 35 Return pipe

Claims (1)

(57) [Claims] The method according to claim 1] tank upper portion filter material layer, water inlet and diffusing the gas section with setting Keru respectively the lower portion in the tank, the first tank having a primary treatment water outlet unit to the tank top, the floating filter media layer in the upper part the tank, a spraying component lower or inside of the floating filter media layer
Respectively deployment, when precipitated portion below the diverging air portion Tomo
A second tank provided with a secondary treated water outflow part at the top of the tank, and a primary treated water outflow part of the first tank and a lower sedimentation part in the second tank used in communication with each other; When aerobic biological treatment is performed during filtration of the filter medium layer of the first tank, air is discharged from the air diffuser to develop an aerobic biofilm on the surface of the filter medium , and when the filter medium layer is washed, air is diffused from the air diffuser. Discharge and disturb the filter media layer
Then, the SS trapped in the filter medium layer is expelled, and the washing wastewater is settled in the sedimentation section of the second tank .
Washing wastewater introduced into the settling section of the first tank or the second tank
A biological treatment method for organic wastewater, wherein the SS is precipitated in a precipitation section .