JPH01237000A - Apparatus for biologically treating waste water - Google Patents

Abstract

PURPOSE:To permit a stable biological treatment of waste water even under a large variation of fluid load, by making a circulating waterway horizontal and dividing the same into upper and lower passageways, i.e., aerobic and anaerobic zones. CONSTITUTION:An elliptic ditch constituting a circulating waterway is divided into an upper passageway 1A and a lower passageway 1B by a separating wall 2. The upper passageway 1A is made an aerobic zone and provided with an aerator 3 which supplies the oxygen required for aerobic microorganisms to maintain an aerobic environment and imparts a required running speed to waste water, while the lower passageway 1B is made an anaerobic zone and provided with an agitator 4 which imparts to the waste water a running speed not less than 10cm/sec to keep to from settling and multiplies denitrification bacteria by agitation to maintain an anaerobic environment. Also provided are a plurality of openings 21 in the separating wall 3 for providing communication passages between the aerobic and anaerobic zones for mixing the two.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to an apparatus for biologically treating wastewater more efficiently by circulating wastewater in a horizontal circulation waterway having two levels, upper and lower.

[Conventional technology]

Conventionally, the treatment tank was partitioned into upper and lower parts, with the upper layer being an aerobic treatment section and the lower layer being an anaerobic treatment section.
It is known from Publication No. 00. This system forms channels that penetrate the partition walls at both longitudinal ends of the tank, and circulates the wastewater that has entered the treatment tank from the anaerobic treatment section in the lower layer to the aerobic treatment section in the upper layer, and then guides it back to the lower layer for treatment. It is something to do.

[Problem to be solved by the invention]

In the above-mentioned equipment, if there are large fluctuations in the load of wastewater, for example if the load is too large, only a part of the upper layer of the "aerobic treatment section" will be in an aerobic state, and most of the entire ditch will be in an anaerobic state; If the load is too small, the lower part of the ``anaerobic treatment section'' may become aerobic. Therefore, it is difficult to perform stable denitrification.

[Means to solve the problem]

A circulation waterway is provided horizontally, and this waterway forms a circuit in two levels, above and below an aerobic zone and an anaerobic zone.

Furthermore, an lf1 air generator is provided in the upper part to supply oxygen necessary for aerobic microorganisms to maintain an aerobic state and provide the necessary flow rate to the wastewater.

Additionally, a stirrer is installed in the lower layer to prevent sludge from settling10.
While giving a flow rate of c11/sec or more, the denitrifying bacteria are grown by stirring and an anaerobic state is maintained.

Alternatively, if necessary, arrange one of the stirrers in the lower layer to generate an upward flow so that the substrates in the upper and lower layers are mixed with each other. , efficiently perform biological treatment while maintaining aerobic and anaerobic zones.

When a partition wall is provided to separate the upper and lower layers, openings are provided at multiple locations so that the aerobic zone and anaerobic zone mix at the openings.

If no partition wall is provided, wastewater will be mixed between the aerobic and anaerobic zones, but in order to achieve proper mixing, the location, angle and number of aerators and agitators should be selected.

[For production]

Since the flow path of sewage is divided into upper and lower layers in the horizontal direction and with two layers, upper and lower layers, the upper and lower layers are not completely replaced or mixed, and therefore the substrate in the wastewater is That is, nitrate nitrogen (NO3-N), ammonia nitrogen (NH4-N), BOD5, etc. can be mutually transferred by diffusion.

Therefore, the upper layer always maintains an aerobic state and mainly promotes the growth of nitrifying bacteria, while the lower layer always maintains an anaerobic state and promotes the growth of denitrifying bacteria, so even if there are load fluctuations, a stable aerobic zone and anaerobic zone are maintained. Can stay in the zone.

〔Example〕

The present invention will be explained below based on the illustrated embodiments.

In the figure, reference numeral 1 denotes an oval ditch, in which partition walls 11 and 12 are provided at the center of the ditch and in its longitudinal direction to form a circulation waterway. In addition, a partition wall 2 is provided in the middle part in the vertical direction to divide the upper layer IA and the lower layer IB, so that wastewater can be circulated independently in the upper layer IA and the lower layer IB.
The water depth of A and lower IIB should be 2 to 3 m, which is suitable for sufficient circulation of wastewater, and the total height of the ditch should be 4 to 6 m. Furthermore, the upper layer IA and the lower layer IB are not completely separated by the partition wall 2, but in order to allow the substrates in the wastewater of each layer to mix with each other, the partition wall 2 is provided with a wall along the flow of the wastewater. Frontage portions 21 are provided at one to several locations.

In this frontage aB21, sewage is above ditch lff1lA
A water flow guide 22 is provided to guide water from the water to the lower layer or vice versa. One or more mechanical aerators 3 are installed in the upper IA to supply air into the wastewater, and the activity of aerobic microorganisms (BOD decomposing bacteria, nitrifying bacteria, etc.) is stimulated in the wastewater in the upper IA. It supplies the necessary oxygen and creates a flow in the upper layer.

The most suitable rs% IN installed in the upper layer IA is the V4 air blower 3 that blows air into the water using a screw shadow as shown in FIG. 3, but other mechanical surface aerators may also be used.

One or more agitators 4 are provided in the lower layer IB to prevent sludge from settling. The stirrer 4 is preferably of a propeller or screw rotation type or an axial flow pump type, but is not particularly limited. The number of agitators installed varies depending on the tank capacity and agitation power in the lower layer of the ditch 1, but in order to prevent the sludge from settling, the flow rate at the bottom must be 10 (!1
It is necessary to select the installation location and number of units so that the ratio is 1/1 or more.

Furthermore, the mounting angle of the stirrer 4 is normally installed horizontally to the bottom surface as shown in Figure 3, but if the substrate does not move sufficiently between the upper and lower layers, the angle of installation is as shown in Figure 4. A part of the stirrer may be installed diagonally upward to provide a flow rate so that part of the wastewater in the lower layer IB flows into the upper NIA.

However, in order to obtain stable denitrification performance, it is necessary to maintain aerobic conditions for the growth of nitrifying bacteria in the upper layer and anaerobic conditions for the growth of denitrifying bacteria in the lower layer, so that the upper and lower layers are completely Set the number and angle of the stirrers to prevent mixing. Furthermore, the partition wall 2 does not necessarily need to be placed in the center, but may be shifted so that the water depth in the lower layer is slightly smaller than the water depth in the upper layer, as shown in FIG.

Further, it is desirable that the wastewater flows into the lower layer in order to cause denitrifying bacteria to proliferate in the anaerobic zone.

This is because denitrifying bacteria require organic matter when reducing nitrate or nitrite nitrogen and converting it into nitrogen gas. In this way, denitrification is promoted in the upper layer by causing wastewater containing organic matter to flow into the anaerobic zone.

In addition, it is preferable that the mixed solution of treated water and sludge be discharged at a position behind the aerator where the dissolved oxygen is sufficiently high, and that the flow be overflowed from the upper layer. This is because denitrification is likely to occur in the downstream sedimentation tank if the water is discharged from a location with low dissolved oxygen, and there is a risk that the nitrogen gas generated by denitrification will adhere to the sludge and cause it to float.

When operating the oxidation ditch of the present invention, the inflow, outflow, aeration machine, and agitator are basically operated continuously, but for the Di machine, depending on the amount and concentration fluctuations of inflow sewage, part of the aerator or All units may be operated intermittently. Since the agitator is often installed with the minimum capacity necessary to prevent sludge from settling, it is desirable that all the agitators be operated continuously, but this is not necessarily limited.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

In the biological treatment Ha of sewage according to claim 1, since the circulation channel is horizontal and has two layers, upper and lower, stable biological treatment of sewage can be performed even if the inflow load fluctuation is large, and the ditch can be made deep. Can be done.

In the biological treatment device for wastewater according to claim 2, an aerobic condition is maintained in the upper layer to mainly promote the growth of nitrifying bacteria,
By constantly maintaining an anaerobic state in the lower layer, the growth of denitrifying bacteria is promoted, so that stable aerobic and anaerobic zones can be maintained even with load fluctuations, allowing efficient biological treatment of wastewater.

In the sewage biological treatment apparatus according to claim 3, a necessary amount of sewage flows from the upper layer to the lower layer, or vice versa, from the lower layer to the upper layer, so that the substrate can be sufficiently transferred between the upper layer and the lower layer.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the upper layer of the biological treatment system for wastewater, Fig. 2 is a plan view of the lower layer, Fig. 3 is a cross-sectional view taken along line A-A in Fig. 1, and Fig. 4 is a cross-section of another embodiment. It is a diagram. l is the ditch, 11.12 is the bulkhead, IA is the upper layer,
IB is the lower layer, 2 is the partition wall, 3 is the aerator, and 4 is the stirrer. bell trowel

Claims (3)

[Claims] (1) In a biological treatment device that treats wastewater using activated sludge while circulating it through a circulation waterway, the circulation waterway is provided horizontally, and the waterway is arranged in two levels above and below an aerobic zone and an anaerobic zone. A biological treatment device for sewage characterized by forming. (2) A biological treatment system for sewage that divides a horizontal circulation waterway into two levels, upper and lower, and is equipped with an agitator on the lower floor and an aerator on the upper floor. (3) The sewage biological treatment apparatus according to claim 2, wherein one of the agitators on the lower floor is arranged to generate an upward flow.