JPH0767558B2 - Sewage 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 sewage treatment method using a sewage treatment device filled with an iron filter medium as a contact filter medium ,
In particular, the present invention relates to a sewage treatment method that enables elution of iron ions from an iron filter medium during treatment for a long period of time and simultaneously removes phosphorus as well as organic components in sewage.

[0002]

It has been known for a long time that iron ions will be eluted when iron material is immersed in waste water. Products formed by binding iron ions to the surface of the iron material, biofilms, dust, etc. It is also known that the elution of iron ions from the surface of the iron material naturally decreases with the lapse of time due to the adhesion of iron.

In the treatment of wastewater such as industrial wastewater and household wastewater, a sewage treatment apparatus using an iron material as a contact filter medium is used to elute iron ions from the surface of the iron filter medium to remove the iron ions and the organic phosphorus in the wastewater. There has been proposed a method for removing the phosphorus content in wastewater by binding phosphate ions by decomposition to produce an insoluble iron phosphate salt (Japanese Patent Laid-Open No. 61-90792, Japanese Patent Laid-Open No. 61-90792). 178092).

[0004]

However, according to the sewage treatment by the contact aeration method using the iron filter medium carried out by the present inventors, as the treatment is continued, the surface of the iron filter medium in the treatment tank is treated with iron phosphate or the like. It was found that a film was formed and the phosphorus removal rate was reduced. Further, even in the sewage treatment by the intermittent aeration method, the phosphorus removal rate tends to decrease and become irregular with the passage of time after the iron filter medium is immersed in the treatment tank. Further, even in the iron rotating disk method, if the treatment is continued for a long time, a film of iron phosphate is formed on the surface of the iron disk, and the phosphorus removal rate is reduced.

Further, in the case of the anaerobic sewage treatment method using an iron filter medium, iron sulfides produced by the presence of sulfate-reducing bacteria as the treatment time elapses, and iron phosphate as an iron anticorrosion coating on the iron filter medium surface. It adheres along with dust.
However, this iron sulfide coating is a dense and strong iron sulfide elution-preventing product that reduces the elution amount of iron ions. This iron ion elution-prevented product was tested by using the hollow sewage treatment filter made of cast iron (Jukei hei 2-2476) proposed by the present applicant and having a very large contact surface area with sewage. In the above, the filter medium was immersed in an anaerobic tank for sewage treatment, and the deposits on the surface of the filter medium were analyzed 5 months and 11 months after the filter medium had been dipped. Sulfide was 4.61% on the surface after 5 months. It was 13.4 after 11 months.
It showed a very high value of 7%, and it was recognized that it had a great influence on the elution of iron ions from the surface of the filter medium.

As described above, in the treatment of sewage using an iron filter medium, iron phosphates and the like are formed on the surface of the iron filter medium as the treatment time elapses under either aerobic or anaerobic conditions. Iron ion elution is reduced because the amount of iron ion elution disturbing products such as iron sulfide film related to the presence of biofilms, dust, or sulfate-reducing bacteria decreases. A reduction in the dephosphorization effect of removing the phosphorus content by binding with the phosphate ion in the inside is recognized, and this is a major problem of the wastewater treatment method using the iron filter medium. However, a method for effectively and economically sustaining the elution of iron ions for a long time has not yet been clarified.

The present inventors have solved the above-mentioned problems in the treatment of sewage using an iron filter medium as a contact filter medium, and made it possible to stably elute iron ions over a long period of time.
As a result, phosphorus is simultaneously added to the organic components in the wastewater,
Moreover, they have come to find a sewage treatment method that can be continuously removed.

[0008]

That is, according to the first aspect of the present invention, when performing sewage treatment in a sewage treatment apparatus using an iron filter medium as a contact filter medium, the iron filter medium is treated during the treatment.
Iron picked up from the device and exposed to the atmosphere
The iron elution from the iron filter material is decomposed by oxidative decomposition of the ion elution disturbing product
Wastewater treatment method characterized by sustaining the elution of ON
According to the second invention, the iron filter medium is vibrated during the treatment.
Iron phosphates and biofilms attached to the surface of the filter media
Remove the dust and remove the iron filter material from the processor.
It was pulled up and exposed to the atmosphere at the same time, and it adhered to the iron filter medium surface.
From the iron filter media by oxidative decomposition of
Sewage treatment characterized by continuous elution of iron ions
Is the way.

[0009]

As described above, the present invention makes contact with the sewage treatment apparatus.
The iron filter medium used as a filter medium is iron sulfide during the treatment of sewage.
Products that interfere with the elution of iron ions, such as
Since the elution amount of ON is reduced, this iron filter medium is
By exposing it to the atmosphere for a suitable time.
A large number of cracks in the iron sulfide film due to oxidative decomposition in an oxidizing atmosphere.
Can be generated to recover the elution amount of iron ions
In addition, iron ions adhering to the surface of the iron filter medium and wastewater
The iron phosphate formed by the binding of phosphate ion
In order to make the iron sulfide film and its detachment,
For better contact and efficient oxidation
, It is decreasing by applying vibration to the iron filter media.
It is possible to increase the elution amount of iron ions from the iron filter media.
Wear.

The formation of this iron sulfide can be judged by the fact that the surface exhibits a blackish brown color, but it can also be judged by the fact that hydrogen sulfide odor is produced by the addition of a few drops of hydrochloric acid. This iron sulfide film is so strong that it cannot be removed by washing with water or brushing after three months have passed since its formation. Therefore, the oxidative decomposition in such a case is not only exposed to the atmosphere but also forced blast. It is preferable to carry out. The air is blown by blowing normal temperature air onto the iron filter medium to which the iron sulfide film or the like pulled up from the processing device is attached. Since it is possible to shorten the spraying time to 1/10 or less by this, it is possible to select it according to the situation.

An example of the structure of the iron filter medium unit used in the present invention will be described. As shown in FIG.
The iron filter medium unit A includes, for example, a steel plate (SS41) 1 of 10
Fasten with the upper and lower vinyl chloride pipes 2 and 2 at the required space,
A mounting plate 4 having a vibrator 3 installed thereon is attached to the upper vinyl chloride pipe 2 so as to be in contact with the upper end of the steel plate 1, and this is set in an anaerobic tank for use. In addition, 5 is a vibration transmission part using SUS304 etc., 6 is a leg part of this iron filter medium unit.

[0012]

The present invention will be described in detail below with reference to examples and examples . Reference example Using a certified 5 person type small combined tank, domestic wastewater (raw water) is supplied to this at 1.0 m ³ / day, and an iron filter medium unit equipped with a vibrator is immersed in the separation chamber used as an anaerobic chamber. The treatment was performed by setting a target so that the phosphorus content in the treated water was 1.0 mg / l or less. The results are shown in Table 1. The test date in Table 1 is the number of months from the process start date.

[0013]

[Table 1]

In the above reference example , two months after the start of sewage treatment,
After 3 months, the iron content in the anaerobic chamber where the iron filter medium unit was installed was high, so the phosphorus content in the treated water was low and the dephosphorization rate was over 80%, which was good. Processing proceeded. And, in the measurement after 13 months, the iron content in the anaerobic chamber was 1.40 mg / l.
And the phosphorus content in the treated water increased to 0.81 mg / l, the dephosphorization rate decreased to 76%. This decrease indicates that the amount of iron phosphate and dust adhering to the surface of the iron filter medium is increasing and the amount of iron ions eluted from the iron filter medium is decreasing. Then, the vibrating machine installed on the iron filter medium was operated and the iron filter medium was vibrated with an amplitude of 10 microns or more for 1 hour to remove the deposits on the surface of the iron filter medium. The iron content in the anaerobic chamber increased to 3.68 mg / l in the measurement half a month after the vibration was given (13 and a half months after the treatment was started), and the phosphorus content in the treated water was 0.61 mg / l and the dephosphorization was performed. The rate was improved to 82.1 %, and the treatment was successfully performed for four months thereafter, but the dephosphorization rate was decreased to 72.4% as shown in Table 1 after 18 months. For this reason, when the adhered matter was removed again by applying vibration for 2 hours in the same manner as above, the iron content in the anaerobic chamber was 3.26 mg / even after the treatment in the second half of the removal (18 months and a half from the start of treatment). 1, the dephosphorization rate was 80%, which was normal.

As described above, when the amount of iron ions eluted from the iron filter medium is reduced and the dephosphorization rate is reduced, the iron filter medium is vibrated by a vibrator to elute the iron ions. It was found that the amount recovered and the sewage treatment proceeded smoothly. In addition, the vibration application time by the vibrator is at least 1
Although it takes time, it may be appropriately determined depending on the elution amount of iron ions and the dephosphorization rate measured immediately before.

Example : An anaerobic tank is used for two chambers, a contact aeration tank is for three chambers, and a settling tank is used for treating 1.5 m ³ / day of treated water. Different from Example 1, both were filled with an iron filter medium without a vibrator and treated for sewage. The results are shown in Table 2. The test date in Table 2 indicates the total number of days from the day when the iron filter medium was filled in the anaerobic tank and the sewage treatment was started.

[0017]

[Table 2]

In the above-mentioned examples , the treatment was carried out satisfactorily with the phosphorus content in the treated water being 1.0 mg / l or less and the dephosphorization rate being 80% or more from the beginning of the treatment.
However, the phosphorus content was 1.62 m when measured after 16 months.
It increased to g / l and the dephosphorization rate decreased to 65.2%. When the elution amount of iron ions from the iron filter medium at this time was measured, it decreased to 1.54 mg / l in the first chamber of the anaerobic tank and 2.04 mg / l in the second chamber.

Therefore, the wastewater treatment is interrupted, and the iron filter media in the first and second chambers are pulled out of the treatment tank. The iron filter media in the first chamber is exposed to the atmosphere for 12 hours and the iron filter media in the second chamber is exposed to the atmosphere for 48 hours. I went. After that, the iron filter media were returned to the respective anaerobic tanks, and the sewage treatment was continued. Then, the dephosphorization rate was good in the measurement after one month and four months (17 months and 20 months in total).
However, after 21 months, the decrease in the dephosphorization rate was measured again, so the iron filter medium was pulled up, the iron filter medium in the first chamber was for 12 hours, the iron filter medium in the second chamber was for 24 hours, and the ambient air was blown. Exposed. Then, the iron filter media were returned to the respective anaerobic tanks, the sewage treatment was continued, and the measurements were made one month later (22 months after the total). As a result, the iron ion elution amount in the anaerobic tank was 4.91 mg / in the first chamber. 1, the second chamber had 7.68 mg / l, the phosphorus content in the treated water was 0.60 mg / l, and the dephosphorization rate was 83.4%, which was good.

By thus exposing to the atmosphere,
The iron sulfide film adhering to the surface of the iron filter media that interferes with the elution of iron ions from the iron filter media is crystallized by an oxidation reaction, destroying the denseness of the film and causing cracks, and the iron ions on the iron filter media surface. The elution area can be restored. This atmospheric exposure should be performed following the removal of iron phosphates, etc., biofilms and dust on the surface of the iron filter medium by applying vibration, using the iron filter medium with the vibrator set above as in the reference example. By operating the vibrator either during exposure to the atmosphere or after returning to the anaerobic tank after exposure to the atmosphere, iron sulfide can be treated along with iron phosphate and dust on the surface of the iron filter medium, and sewage treatment can be continued. Can be done more effectively.

[0021]

As described in the foregoing, the present invention is in a sewage treatment with iron filter medium as a contact medium in the anaerobic tank, punished
As the process progresses, iron phosphate, dust, and
Iron-ion elution-preventing products such as iron oxide adhere to
If the iron filter media with reduced dephosphorization rate was
Or by exposing it to the atmosphere
Before and after or at the same time as exposure to the atmosphere
Vibration is applied to the iron filter media with the vibrator installed in contact with it.
As a result, it was possible to recover the elution amount of iron ions and improve the dephosphorization rate, and it was confirmed that the practical effect is great.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a configuration of an iron filter medium unit used in the present invention.

[Explanation of symbols]

 A Iron filter medium unit 1 Steel plate 2 Vinyl chloride pipe 3 Vibrator 4 Mounting plate 5 Vibration transmission part 6 Legs

Claims (3)

[Claims] 1. A sewage treatment using an iron filter medium as a contact filter medium.
During the treatment of sewage with the equipment, the iron filter
The material is pulled up from the processing equipment, exposed to the atmosphere, and attached to the surface of the filter media.
The iron ion elution-deteriorated product that has adhered is oxidatively decomposed to obtain an iron filter medium.
Wastewater characterized by sustaining the elution of iron ions
Processing method. 2. Sewage treatment using an iron filter medium as a contact filter medium.
During the treatment of sewage with the equipment, the iron filter
By vibrating the material, iron phosphates, etc. adhering to the filter surface and
And desorption of biofilm and dust, and pulling iron filter media from the treatment equipment.
Raise the iron ion elution disturbing products adhering to the surface of the filter media.
From iron filter media that is oxidatively decomposed by exposure to the air
Sewage treatment characterized by maintaining the elution of iron ions in water
Reasoning method. 3. The surface of a filter medium in an oxidizing atmosphere exposed to the atmosphere
Oxidative decomposition of deposits is performed by blowing air at room temperature or warm air
The sewage treatment method according to claim 1 or 2, characterized in that
Law.