JPH10314778A - Tertiary treatment device for waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tertiary treatment device for waste water which captures and removes suspended solids(SS) and sufficiently enables the decomposition of organic matters using bacteria. SOLUTION: In the treatment device in which an oxygen feed tank 1 having an air diffusing member 3 at its bottom, a carrier attachment filter tank 2, and a washing water discharge pump tank 7 with a washing water discharge pump 8 are disposed in this order, in the tank 2, a diffuser member 6 is provided on the bottom of the tank 2 and a carrier bed 4 filled with granular carriers between upper and lower perforated plates 5, 5 is provided above the diffuser member 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tertiary treatment apparatus used for inflowing sewage that has undergone secondary treatment and for performing more advanced sewage treatment.

[0002]

2. Description of the Related Art Sewage treatment includes primary treatment,
It is classified into secondary processing and tertiary processing. To describe each treatment step in detail, the primary treatment is a precipitation separation, and indicates a pretreatment for separating a solid component and a liquid component of wastewater. The secondary treatment is a treatment of activated sludge (biological treatment) of the wastewater after the primary treatment.
This secondary treatment is completed, and is discharged outside the system after chlorine disinfection. However, in consideration of environmental problems, there is a case where the treated water at the stage of performing the secondary treatment is not satisfactory, and a more advanced sewage treatment may be performed. Such a treatment process is called a tertiary treatment.

A conventional tertiary treatment apparatus will be described with reference to FIG. 2. The tertiary treatment apparatus is composed of a carrier adhesion filtration tank 9 and a washing water discharge pump tank 10. Is a carrier bed 11 packed with granular carriers.
Are provided above and below the carrier bed 11, and perforated plates 12, 12 which allow the water to be treated and the treated water to pass therethrough but do not allow the granular carrier to pass through. Further, a diffusing member 13 for washing the carrier bed 11 is provided at the bottom of the carrier-attached filtration tank 9. On the other hand, the washing water discharge pump tank 10 is provided with a washing water discharge pump 14 for discharging washing water to be described later out of the system.

[0004] The processing method of the conventional tertiary treatment apparatus will be described. The water to be treated (water that has already undergone the secondary treatment) 15 that has flowed into the tertiary treatment apparatus is caused to flow into the carrier-attached filtration tank 9 and is subjected to downward flow. Pass through the carrier bed 11. At this time, the water to be treated 15
The organic matter is decomposed by microorganisms inhabiting the carrier bed 11, and at the same time, suspended matter (hereinafter referred to as SS) is captured and removed. Thereafter, the water to be treated 15 is transferred to the cleaning water discharge pump tank 10 and discharged out of the system as treated water 16.

[0005] As described above, the carrier bed 11 is clogged by SS if it is continuously processed to capture and remove SS in addition to decomposing organic substances. For this reason,
As an operation for removing SS from the carrier bed 11, the washing water containing SS is discharged out of the system by periodically operating the air diffusing member 13 and simultaneously operating the washing water discharge pump 14.

[0006]

However, in the conventional tertiary treatment apparatus described above, the SS
Although the treated water 16 having a sense of transparency can be obtained by trapping and removing, there is a problem that organic matter decomposition by microorganisms becomes insufficient because there is almost no dissolved oxygen in the carrier-attached filtration tank 9.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a tertiary treatment apparatus capable of not only capturing and removing SS but also sufficiently decomposing organic substances by microorganisms.

[0008]

According to the present invention, as shown in FIG. 1 (a), an oxygen supply tank 1 provided with a diffusing member 3 at the bottom is provided.
And a washing water discharge pump tank 7 provided with a washing water discharge pump 8 in this order. The carrier adhesion filtration tank 2 has a bottom The air diffusion member 6 is provided, and a carrier bed 4 filled with granular carriers is provided between the upper and lower two perforated plates 5, 5 above the air diffusion member 6.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The tertiary treatment apparatus of the present invention is for treating water that has already undergone secondary treatment, and may be used adjacent to a septic tank that performs activated sludge treatment.
It is also possible to use it by directly incorporating it into a septic tank that performs secondary treatment.

The diffuser member 3 installed in the oxygen supply tank 1 is used to increase the concentration of dissolved oxygen in the water to be treated flowing into the tertiary treatment apparatus. In order to increase the oxygen concentration uniformly, it is desirable that the oxygen supply tank 1 be located at the bottom. It is preferable that the amount of air discharged from the air diffusion member 3 is such that the oxygen concentration of the water to be treated is 7 mg / l or more, and if it is less than 7 mg / l, the decomposition of the organic matter is not sufficiently performed. There are cases.

The carrier to be filled into the carrier-attached filtration tank 2 has a large amount of microorganisms attached and can be easily washed in consideration of its processing function in addition to its physical and chemical durability. Required. That is, from the viewpoint of the amount of microorganisms adhering, it is preferable that the carrier has a large number of pores inside and the pores communicate with each other. It is preferable that the specific gravity is about 0.9 to 1.1 which can be easily moved by the water flow generated by the above. Specifically, communicating cells such as polyethylene, polypropylene, and polyurethane can be used as appropriate.

In the present invention, by disposing the oxygen supply tank 1 upstream of the carrier-attached filtration tank 2, it becomes possible to supply dissolved oxygen to the water to be washed, and it is possible to sufficiently decompose organic substances. became.

FIG. 1B is a cross-sectional view illustrating a normal processing step, and FIG. 1C is a cross-sectional view illustrating a cleaning step of the carrier-attached filtration tank 2. First, the ordinary treatment process will be described with reference to FIG. 1B. The water 17 to be treated flows into the oxygen supply tank 1 and is dissolved by the air discharge from the air diffusing member 3 installed at the bottom of the oxygen supply tank 1. Oxygen concentration can be increased. The water to be treated 18 having an increased dissolved oxygen concentration is transferred to the upper portion of the carrier-attached filtration tank 2 and passes through the carrier-attached filtration tank 2 in a downward flow. At this time, the carrier bed 4 performs SS capture removal of the water to be treated 18 and decomposition removal of organic substances. The water to be treated 18 that has passed through the carrier-attached filtration tank 2 is discharged out of the system as treated water 19 via the washing water discharge pump tank 7.

When the normal processing steps described above are continued,
Since the SS trapped in the carrier bed 4 is accumulated, the carrier bed 4 gradually closes. Therefore, in the tertiary processing apparatus of the present invention, a cleaning step as shown in FIG. In the washing step, air is diffused from the air diffusing member 6 provided at the bottom of the carrier-attached filtration tank 2 to generate a water flow so that the carriers collide with each other and the trapped SS is separated from the carrier. Simultaneously with the start of the air diffusion from the air diffusion member 6, the washing water discharge pump 8 is also operated, and the separated sludge is drawn out in a downward flow. The extracted SS may be processed separately or returned to the primary processing. The washing step ends when the entire amount of water in the tank 2 of the carrier-attached filtration tank 2 is discharged out of the system, and shifts to a normal treatment step.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a sectional view showing an embodiment of the present invention, in which a 10 mm square polyethylene communicating foam is used as a carrier in a carrier bed 4. The effective volume of the carrier-attached filtration tank 2 is:
0.420 m ³ (Dimensions: 680 mm (L), 530 mm
(W), 1170 mm (H)), and the height of the carrier bed 4 was 700 mm. The inflow of the water to be treated 20 is
8. Adjust the degree of filtration in the carrier bed 4 to 1.5 m / h.
And 2m ³ / day, the dissolved oxygen concentration of water in the oxygen supply tank 1 was adjusted air discharge amount from the air diffuser member 3 so as to 7~8mg / l. Washing of the carrier bed 4 was performed once / day, and the washing water discharge pump 8 at the time of washing was designed to draw out washing water at a rate of 13 l / min.

The biochemical oxygen demand (hereinafter referred to as BO) when the tertiary treatment apparatus is operated under the above conditions (A) and when the air diffuser 3 for adjusting the dissolved oxygen concentration is not operated (B).
FIG. 4 is a graph showing the D amount) and the SS amount. From FIG. 4, the amount of SS and the BOD derived from SS
(Hereinafter referred to as S-BOD) is removed at substantially the same ratio in both (A) and (B), but soluble BOD (hereinafter referred to as D-BOD) is hardly decomposed in (B),
Only in the case of (A), it was found that about 70% of the removal could be performed.

[0017]

According to the present invention, the SS in the secondary treated water is used.
It is possible to provide a tertiary processing apparatus capable of removing not only components but also S-BOD and D-BOD, and capable of performing highly transparent processing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a tertiary processing apparatus according to the present invention;
(A) is a drawing that does not show the flow of water, (b) is a drawing in a normal processing state, and (c) is a drawing that shows a cleaning state.

FIG. 2 is a cross-sectional view illustrating a conventional tertiary processing apparatus.

FIG. 3 is a cross-sectional view of a tertiary processing apparatus showing an embodiment of the present invention.

FIG. 4 is a graph showing changes in water quality depending on whether dissolved oxygen is adjusted or not.

[Explanation of symbols]

1. Oxygen supply tank 2. 2. Carrier-attached filtration tank Aeration member
4. 4. carrier bed Perforated plate 6. Air diffuser 7. 7. Cleaning water discharge pump tank Wash water discharge pump 9. Carrier-attached filtration tank 10. Wash water discharge pump tank 11. Carrier bed 12. Perforated plate 13. Aeration member
14． Wash water discharge pump 15. Treated water 16. Treated water 17. Treated water 18. Water to be treated 19. Treated water
20. Water to be treated 21. Treated water with adjusted dissolved oxygen concentration

Claims (1)

[Claims] An oxygen supply tank provided with an air diffusion member at a bottom portion;
A carrier-attached filtration tank and a washing water discharge pump tank equipped with a washing-water discharge pump, and a treatment apparatus in which the carrier-attached filtration tank is provided with an air diffusing member at the bottom, A tertiary sewage treatment apparatus characterized by providing a carrier bed filled with granular carriers between upper and lower two perforated plates above the air diffusing member.