JPH05337492A - Biological treatment of sewage - Google Patents

Abstract

PURPOSE:To reduce the equipment cost and installation area and to biologically and efficiently treat sewage under high loading by nitrifying and denitrifying the sewage in a single tank. CONSTITUTION:When sewage is biologically treated, a self-granulating sludge bed 7 is formed at the lower part of the ascent passage of the biological reaction vessel 1 provided with a descent passage 4 and the ascent passage 5, an oxygen-enriched gas 8 is intermittently supplied to the descent passage 4 to alternately generate aerobic and anaerobic conditions, and the sewage is treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic wastewater such as sewage, which alternately produces aerobic and anaerobic states in a single biological reaction tank and forms a self-sludge bed for treatment. Biological treatment method of.

[0002]

2. Description of the Related Art As a conventional biological treatment method, a biofilm method such as a floating activated sludge method, a rotating disk method, or a catalytic oxidation method has been mainly used, but in recent years, self-granulation of microorganisms An upflow sludge blanket method has also been used in which sewage is supplied in an upward flow into a biological reaction tank in which a sludge bed has been formed, and the sludge bed is made to flow in the lower part of the reaction tank and treated in an anaerobic or aerobic state. In particular, anaerobic treatment is actively implemented.

In the above-mentioned upflow sludge blanket method, since the microorganisms that biologically decompose the components to be treated are made into particles and retained at a high density, it is possible to operate at a high volume load and efficiently. There is an advantage that sewage can be treated.

On the other hand, aeration in the reaction tank is performed intermittently,
A batch process, which is a modified version of the activated sludge process, in which aerobic and anaerobic conditions are alternately generated in the tank to promote nitrification and denitrification, and solid-liquid separation is also performed in the tank and treated in a single tank. Formula processing methods are also used. Since this method does not require a settling tank or the like, the installation area of the equipment is small, and the operation is easy, so it is particularly applied as a small-scale treatment method.

[0005]

In the above-mentioned conventional treatment method, the upward flow sludge blanket method is provided with nitrification or denitrification treatment as a separate step, and the sedimentation for separating sludge and treated water. Since a separate tank is required, there is a drawback that the equipment cost and the installation area are too large.

Further, in the batch treatment method, as in the case of the ordinary activated sludge method, the microbial concentration cannot be kept high, so that the wastewater cannot be treated with a high volume load,
There is a drawback that processing efficiency is low.

Therefore, the present invention makes use of the advantages of the above-mentioned upflow sludge blanket method, batch type treatment method, etc., can treat sewage with a high load, and can perform nitrification and denitrification treatment in a single tank to improve efficiency. The purpose of the present invention is to provide a biological treatment method for sewage that enables efficient treatment, inexpensive equipment cost, and reduction of installation area.

[0008]

The gist of the present invention is to provide a method for biologically treating sewage in a biological reaction tank having a descending channel and an ascending channel through which sewage flows, the lower part of the ascending channel. Biological treatment of sewage, characterized in that a self-granulating sludge bed is formed in and the oxygen-rich gas is intermittently supplied to the descending channel to alternately generate aerobic and anaerobic states. And adding a flocculant to the bioreactor,
This is a biological treatment method for wastewater, which is characterized by promoting the formation of a self-granulating sludge bed.

[0009]

In the initial stage of operation, light sludge is produced by filling the biological reaction tank with sewage and sewage sludge, supplying the sewage from the descending channel, and circulating the ascending channel at a predetermined rate for a certain period of time. Only the heavy microbial sludge is discharged and proliferates, and finally it is made into particles and a self-granulating sludge bed is formed in the lower part of the ascending channel.

In the above, by appropriately adding an aggregating agent into the biological reaction tank, the agglomeration of microorganisms is promoted and the particle formation period can be shortened. Further, in order to further shorten the period, it is also possible to appropriately fill the granulated sludge generated by another device from the beginning.

By supplying oxygen-rich gas intermittently to the sewage supplied from the descending flow path at regular time intervals, the aerobic and anaerobic states are alternately changed in the ascending flow path of the biological reaction tank. Give rise to.

[0012] During steady operation, the sewage is produced by the BOD in the sewage due to the biological action of the particulate microorganisms in the self-granulating sludge bed.
The components are digested and decomposed, nitrogen is decomposed by nitrification in aerobic conditions and denitrification in anaerobic conditions, and phosphorus is released in anaerobic conditions and excessive intake in aerobic conditions. Taken in and removed.

[0013]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a system diagram of an apparatus to which the method of one embodiment of the present invention is applied. 1
Is a bioreaction tank, which is composed of an inner cylinder 2 that forms a descending flow path 4 of the supplied wastewater and dissolves oxygen, and an outer cylinder 3 that forms an ascending flow path 5 and performs biological treatment in a self-granulating sludge bed 7. It has a double cylinder structure.

At the lower end of the inner cylinder 2, an air diffuser 6 connected to a supply pipe 15 for oxygen-rich gas supplied from an oxygen-rich gas supply device 8 is arranged. Further, at the upper part of the inner cylinder 2, a wastewater supply pipe 12 and a polyaluminum chloride (P
AC) and coagulant supply pipes 16 and 17 from coagulant tanks 9 and 10 for calcium hydroxide and the like are connected.

Although not shown, a control device for adjusting the addition amount of the coagulant depending on the property of the sewage and the supply amount is attached. Further, as the oxygen-rich gas supply device 8, an oxygen cylinder, a PSA device, a membrane separation device or the like can be used.

An overflow reservoir 11 of treated water is provided in an annular shape on the upper end of the outer cylinder 3, and a treated water discharge pipe 13 is connected to the outer cylinder 3, and an intermediate portion and a lower portion of the outer cylinder 3 are connected. Excess sludge discharge pipes 14a and 14b for discharging excess sludge are connected.

A microbial self-granulating sludge bed 7 is formed in the lower part of the ascending flow path 5 formed by the inner cylinder 2 and the outer cylinder 3, and this sludge bed 7 is It is kept balanced while flowing at a certain height.

Although not shown, if necessary, in order to improve the contact between the self-granulating sludge and the water to be treated, and to desorb carbon dioxide, nitrogen gas and the like generated in the biological treatment, It is preferable to provide a stirring device for performing gentle stirring.

An example in which the primary treated water of the sewage is treated as raw water by the apparatus of the above construction and treated by the method of the present invention will be described below. The biological reaction tank 1 was filled with sewage sludge, and raw water was supplied from the upper part of the descending flow path 4 so that the ascending speed in the ascending flow path 5 was 1 to 2 m / Hr.

At the same time, the oxygen-rich gas from the oxygen-rich gas supply device 8 is intermittently supplied at a supply time / stop time of 30 minutes / 30 minutes, and polyaluminum chloride (PAC) as a coagulant is 40 mg / 1 was added.

As a result, the self-granulating sludge was confirmed after about 4 weeks, and the self-granulating sludge bed 7 was formed after 1.5 months, and the steady operation became possible. Operating conditions during steady operation were liquid retention time: 6 hours, average sludge concentration in the granulated sludge bed: 58400 mg / l, and liquid temperature: 22 ° C.
Further, the intermittent supply of the oxygen-rich gas caused the dissolved oxygen concentration in the biological reaction tank 1 to alternate between an aerobic state of 0.5 to 1.5 ppm and an anaerobic state without dissolved oxygen.

As a result of treatment under the above conditions, the raw water had a pH of 7.8, a BOD of 140 ppm, and an SS of 16
2 ppm, TN: 36 ppm, TP: 4.5 ppm
After the treatment, the water quality was pH 6.6 ppm, BOD:
8.5 ppm, SS: 12 ppm, TN: 3.3 pp
m ,, and T-P: 0.3 ppm.

As shown in the above example, the formation of the self-granulating sludge bed, which takes about 3 months without the addition of the coagulant, was about 1.5 months, which was shortened in an extremely short period of time. It was also found that 90% or more of the denitrification and dephosphorization treatments were performed.

[0024]

According to the method of the present invention, the following effects can be obtained. B) By alternately repeating aerobic and anaerobic treatments, BOD components, nitrogen and phosphorus can be removed in a single tank, and a settling tank for separating treated water and sludge is not required. Can be reduced. B) By forming a self-granulating sludge bed, microorganisms can be retained at a high density and efficient treatment is possible. C) There is no need to return sludge, and the equipment is simplified and the operation is easy.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment to which the present invention is applied.

[Explanation of symbols]

1: biological reaction tank, 2: inner cylinder, 3: outer cylinder, 4: downflow passage,
5: Ascending channel, 6: Air diffuser, 7: Self-granulating sludge bed, 8:
Oxygen-rich gas supply device, 9, 10: Flocculant tank, 11: Overflow reservoir, 12: Waste water supply pipe, 13: Treated water discharge pipe, 14a, 14b: Excess sludge discharge pipe, 15: Oxygen rich Gas supply pipes 16, 17: Coagulant supply pipes.

Claims (2)

[Claims] 1. A method for biologically treating sewage in a biological reaction tank having a descending flow path through which sewage flows and an ascending flow path, wherein a self-granulating sludge bed is formed below the ascending flow path, A biological treatment method for sewage, characterized in that an oxygen-rich gas is intermittently supplied to the descending passage to alternately generate aerobic and anaerobic states for treatment. 2. The biological treatment method for sewage according to claim 1, wherein a coagulant is added to the biological reaction tank to promote formation of a self-granulating sludge bed.