JPS5838233B2 - Sewage treatment method and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to sewage treatment methods and apparatus, particularly to improvements in batch activated sludge treatment.

In conventional batch-type wastewater activated sludge treatment equipment, wastewater generally flows in only during the aeration process, and a large-capacity storage tank is essential when dealing with wastewater whose inflow time is not limited. It was a requirement.

: For this reason, batch processing was not used to treat such wastewater, and was only used when the sewage flow met certain conditions, such as factory wastewater where sewage was generated only during the day.

However, if the inflow of sewage is continuous without being restricted in the sedimentation and discharge processes, and the cycle of aeration, sedimentation, and discharge is repeated in the tank, the effect of batch treatment is that there is no need for a sedimentation chamber or return of settled sludge. can efficiently treat general wastewater that continuously flows in as it is.

However, there were doubts as to whether this continuous inflow process, which repeats the cycle of aeration, sedimentation, and discharge, would be able to adequately treat the wastewater that flows in during the sedimentation and discharge processes.

Therefore, by installing a partition wall near the inlet end of the tank to define the inflow zone and communicating with the aeration chamber at the lower end, the sewage flowing in during the sedimentation and discharge processes can be treated in contact with the sludge without being short-circuited. It has become possible to do so.

When we tried it in an actual treatment facility, we found that equipment equipped with this inflow zone had good settling properties, with no sludge bulking occurring under conditions where a moderate amount of sludge accumulated in the inflow zone. .

This is thought to be because the organic matter load on the sludge is extremely high in this inflow zone, creating conditions that make it difficult for microorganisms that cause bulking to grow.

It was also found that due to the high loading conditions in the inlet zone, the sludge is widely dispersed in the wastewater, so that organic matter is adsorbed into the sludge very efficiently.

However, since the inflow zone receives inflow water and communicates with the aeration chamber, it is difficult to maintain a suitable amount of sludge in the inflow zone.

In other words, if the opening area of the communicating portion is increased, the mixing between the inflow zone and the aeration chamber becomes too intense, making it impossible to achieve a high load in the inflow zone, resulting in sludge bulking and insufficient adsorption of organic matter.

Furthermore, if the area of the opening is made small, the inflow zone becomes a mere storage chamber in which only inflow water exists.

This invention eliminates the above problems and returns the liquid in the main aeration chamber to the inlet zone, thereby maintaining the sludge concentration in the inlet zone at an appropriate level, allowing efficient treatment of wastewater without causing bulking. The purpose of the present invention is to provide a processing method and apparatus for this.

Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS.

A generally rectangular tank 1 made of reinforced concrete or other suitable material is provided.

One end 3 of this tank 1 is provided with an inlet 2 and adjacent to this inlet 2 a partition wall 4 is provided, for example in the form of a concrete block wall, which forms an inlet zone 5 at one end 3.
It is composed of

Further, an opening 4a is provided at the lower edge of the partition wall 4, so that the dirty water flowing into the tank 1 from the inlet 2 flows into the main air chamber 6 of the tank 1 through the opening 4a.

A gas-liquid mixing diffusion nozzle 7, which is a double-H jet aeration nozzle, is provided in this kunk 1, and these nozzles 7 are arranged adjacent to the side wall near the bottom of the tank so that they are immersed in the tank 1 during use. It is connected to a liquid pipe 8 and an air pipe 9 communicating with a pump in the main air chamber 6.

Air forced through the air pipe 9 by the blower 9a and liquid supplied through the liquid pipe 8 are mixed in the nozzle 7 and injected to aerate the inside of the tank.

Further, since the nozzle 7 is also provided in the inflow zone 5, the liquid supply to this nozzle serves as a means for returning the liquid in the main air vent 6.

On the other hand, at the other end of the main air chamber 6 in the tank 1, a supernatant discharge device, for example, a decanter 10, which is held so as to discharge the supernatant liquid from the surface of the sewage contained in the tank 1 after precipitation treatment, is disposed. ing.

This decanter 10 has a discharge pipe 10 with a wear cutout.
A float }10d for adjusting the wear position during descent is installed on both sides of a, and a descending pipe 10b that communicates the discharge pipe 10a and the shaft pipe 10c (this float also serves as a scum baffle) is installed on both sides of the It is shaped from.

Fine adjustment of the position of the garment during the ejection process is accomplished by filling the float with water to hold it in place.

In order to discharge the liquid, the shaft pipe 10c is rotated by hydraulic drive and lowered below the water surface, and the supernatant liquid overflowing from the wear is discharged through the descending pipe 10b. .

Although the descending pipe 10a is a straight pipe, if it is made into a curved pipe, the flow will be maintained even if the width of the upper limit water level and the lower limit water level is made larger.
10a etc. do not get in the way.

Inflow zone 5 and main aeration area 6 during the treatment of the sewage
The liquid is sequentially subjected to aeration treatment, precipitation treatment, and supernatant discharge treatment.

That is, the inside of the tank 1 is controlled to repeat a cycle of, for example, an aeration process of 4.5 hours, a precipitation process of 1 hour, and a supernatant discharge process of 0.5 hours.

A control panel is provided as this device.

It is desirable to be able to change the time of one cycle of each of these steps.

This is because when the amount of water flowing in is very large, by shortening the time of one cycle, the amount of water flowing in during one cycle can be reduced.

Furthermore, the sewage that flows in during the discharge step of the sedimentation step flows into the main aeration chamber 7 from the bottom of the inflow zone 5, so that it comes into contact with the sludge zone at the bottom of both zones, and the inflow water is not discharged as it is.

Furthermore, since the jet aeration nozzle 7 atomizes the gas by shearing force caused by the flow velocity of the fluid, unlike an aeration pipe or the like which makes air bubbles smaller by passing through a narrow gap, it is not noticeable even when performing intermittent aeration treatment. There is no fear of clogging.

Also, with this device, the inflowing sewage is transferred to the inflow zone 5.
The organic matter is adsorbed by the sludge, and then the adsorbed organic matter is metabolized in the main aeration chamber to activate the sludge (increase its adsorption capacity).

Since this activated sludge is returned to the inflow zone 5, the sludge adsorption capacity is sufficient.In addition, the organic matter load in the inflow zone 5 is very high, and the sludge concentration is lower than that in the main aeration chamber. Therefore, the adsorption effect is very good.

In this manner, the sludge is sufficiently adsorbed in the inlet zone, and the adsorbed sludge is advected to the main air chamber, where the adsorbed organic matter is oxidized and decomposed, resulting in good treatment efficiency.

Figures 2A, 2C and 2C show other embodiments of the apparatus of the present invention, in which the inflowing sewage has a high concentration, for example, BOD 500 /
This structure is suitable for cases where the flow rate is 1 or more, particularly 200 .mu./l or more.

Figures 2A and 2B show a plan view and a perspective view of this embodiment, and the tank 1 has an inflow zone 5 at one end thereof, into which wastewater continuously flows.

Since the inflow wastewater is highly concentrated, it requires a considerable amount of time and volume for adsorption, and the inflow zone 5 is divided into the first inflow zone 5A and the second inflow zone 5A.
The inlet zone 5B is separated from the inflow zone 5B by a partition wall 11 having an opening 11a at the lower edge.

The inflow zone 5 and the main air chamber 6 are separated by a partition wall 12.

The upper part of the partition wall 12 on the side of the second inflow zone 5B is cut out, and the second inflow zone 5B and the air chamber 6 communicate with each other here.

A diffusion nozzle 17 consisting of a plurality of jet aeration nozzles is arranged at the bottom of each tank, and the liquid in the tank 1 is supplied to the diffusion nozzle 17 via a liquid pipe 8 by a pump P.

An air pipe 9 is also connected to the diffusion nozzle 17, where gas-liquid mixing is performed and the gas-liquid mixture is sprayed radially.

Further, each diffusion nozzle 17 arranged in the first inflow zone 5A
Since the liquid in the main aeration chamber is fed under pressure, this serves as an aeration device and a liquid return means.

A decanter 10 is provided at one end of the main air chamber 6 in the tank 1 to discharge supernatant liquid from the surface of the liquid.

The inside of the tank 1 is controlled so that the steps of aeration treatment, precipitation treatment, and supernatant discharge treatment are repeated in sequence.

C is a control spring C that controls these.

FIG. 3 shows a diagram of an example of this control.

Aeration step 4.5 hours, precipitation step 1 hour, supernatant discharge step Q. 1.5 6 hour cycles of 5 hours and only the aeration step
It has two 3-hour cycles, which can be switched as needed.

Then, when the inflow amount is large, the cycle is switched to a 3-hour cycle.

By dividing the inflow zone 5 into two in this way, the sludge and sewage come into contact with each other sufficiently to complete the adsorption of organic matter in the sewage, and then flow into the main aeration chamber 6. is sufficiently activated, and wastewater treatment efficiency is high.

Furthermore, when the inflow zone is divided into a plurality of sections in this way, the amount of microorganisms in the inflow zone cannot be maintained unless the liquid from the main vent is directly sent to the inflow zone, so a return means is essential.

FIG. 4 is a graph showing time changes in the oxygen utilization rate (0.U.R) of activated sludge in the inflow zone and main aeration chamber.

In the inflow zone of the sewage treatment method and apparatus of this invention, 0. U. R is initially very high and then decreases rapidly.

O. U. A high R value indicates that a large amount of organic matter is adsorbed, whereas a low R value indicates that the organic matter is oxidized and decomposed and the sludge is activated.

Therefore, 0. U. It is necessary that R be as high as this, and it is desirable that R be 20 or less in the main air chamber.

On the other hand, the main air chamber's 0. U. When R is high, CO2 and N2 are generated during the sedimentation treatment and discharge treatment steps, and sludge floats to the surface.

Ascent time and 0. U. According to actual measurements, the relationship between H is as shown in the table below.

(MLS8 3000 ~ 4000m9
/lj conditions) Therefore, 90% of the precipitation and discharge steps
In order for sludge not to surface in 1 minute, 0. U. R20■
Therefore, it is desirable to make it less than /l.

Furthermore, FIG. 5 shows another example, in particular raw human urine,
It is suitable for treating highly concentrated organic wastewater containing a large amount of nitrogen, such as digestive desorption fluid.

In this example, the inlet zone 5 is divided into a continuous aeration chamber 5C, a denitrification chamber 5, and a conventional inlet zone 5E.

The liquid in the main air chamber 6 is then returned to the continuous air chamber 5C by the pump P.

Here, the liquid returned from the main ventilation chamber is further vented,
Oxidation of nitrogen content, that is, nitrification, progresses.

Then, the liquid nitrified in the continuous aeration chamber 5C is transferred to the denitrification chamber 5D.
is flowing into the country.

Dirty water also flows into the denitrification chamber 5D and is mixed and contacted by a stirrer.

The denitrification chamber is in an anaerobic state because only stirring is performed, and nitrate reduction and denitrification occur because of the presence of organic matter and nitrification liquid in the inflowing wastewater.

As a result of this denitrification treatment, wastewater with reduced organic matter and nitrogen content flows into the main air chamber 6 through the inflow zone 5E.

The inflow zone 5E, main air chamber 6, etc. are the same as those described above, so their description will be omitted.

According to this device, highly concentrated organic waste liquid containing a large amount of nitrogen can be effectively treated, including the removal of nitrogen.

According to the above sewage treatment method and equipment? The inlet zone is a mixture of inflow water and liquid returned from the main aeration chamber, and contains an appropriate amount of sludge, so the organic matter load on the sludge is much higher than in the main aeration chamber, but is still appropriate, and bulking of the sludge can be prevented.

Furthermore, since the treatment can be carried out in a single tank, there is no need for a sedimentation tank, and there is no need for a storage tank for sewage as in general batch processing.

In the inlet zone, the sludge has a low concentration and a high organic matter load, so adsorption is very good, and after the adsorption is finished, it is oxidized and decomposed in the main aeration chamber, so the treatment effect is good.

Furthermore, since there is an inflow zone, short circuits can be prevented even with continuous inflow.

In addition to the above-mentioned embodiments, the wastewater treatment method and apparatus of the present invention may be configured such that the inflow zone and the main air chamber are separate tanks and communicated with each other through a pipe, or the partition wall may be inclined, or the It is also possible to open in multiple places and extend the other parts to the bottom.

This will also make it easier to fix the partition wall. In addition, depending on the nature of the wastewater to be treated, the inflow zone may be constantly aerated or treated.
There is no need to repeat aeration treatment, precipitation treatment, and discharge treatment in the same cycle as in the main aeration chamber, such as constant stirring treatment.

In the above example, the cycle control device for aeration, sedimentation, and discharge is also controlled by a timer, but the liquid level in the tank may be set as WL1, WL2, and WL3 from below and controlled as follows. good.

At WL1, the decanter is driven from the bottom to the top to stop the discharge and the blower is turned on for the aeration process.

At WL2, turn off the blower and start the precipitation step.

Use W and Ls to drive the decanter from above to below for the discharge process.

The setting of this water level can be optimally determined based on the inflow pattern.

Next, regarding the shape of the tank, although a substantially rectangular shape was used in each embodiment, it may also be circular, and in this case, it is preferable to provide the inflow zone in the center for better volumetric efficiency.

In addition to the liquid supply pump to the jet aeration nozzle, the return means includes simple pump transport, and the aeration nozzle of the main air chamber is placed facing the inflow zone to generate a liquid flow toward the inflow zone by air treatment. It is also possible to return the liquid in the air chamber.

In addition, regarding the opening position of the decanter and the main air chamber, for relatively small equipment, such as equipment with a tank width to length ratio of 1:4 or less, it is recommended to move the decanter closer to the center than the end to reduce the flow from the opening. It is preferable to allow the liquid to pass through the back side of the decanter.

A flocculant may be added to the wastewater flowing into the tank to strengthen the flocculating property. Adding an inorganic flocculant such as AA salt or Ca salt has the effect of removing phosphates.

Further, oxygen gas or the like may be sent instead of air, and in this case, the same processing can be performed with a small amount of gas supply.

[Brief explanation of the drawing]

Figure 1A is a sectional view of a sewage treatment equipment showing an embodiment of the present invention, Figure 1A is a plan view of Figure 1A, Figure 1C is a sectional view taken along line AA of Figure 1A, Figure A is a plan view showing another embodiment of the present invention, the opening of Figure 2 is an enlarged sectional view of the main part of the jet aeration shown in Figure 2 A, Figure 2 C is a perspective view of Figure 2 A, and Figure 3 4 is a cycle diagram of the sewage treatment of this invention, FIG. 4 is a diagram of the oxygen utilization rate and time characteristics of the inflow zone and main air chamber of the sewage treatment apparatus of this invention, and FIG. 5 is a sectional view showing another embodiment. be. 1...tank, 2...inlet, 3...
···one end,. 4...Batsuful, 4a...
··Aperture. , 5...Inflow zone, 5A...
...First inflow zone, 5B...Second inflow zone, 6...Main air chamber, 8...Liquid pipe, 9...・Air pipe, 10...
・Decanter, P... Ponfu, C... Control device ffi (control panel).

Claims (1)

[Claims] 1. A step in which wastewater flows into an inlet zone provided at one end of the tank without being controlled during the settling step and the discharge step;
a step of flowing the liquid in the inflow zone into the main aeration chamber; a step of returning the liquid that has flowed into the main aeration chamber to the inflow zone; and aeration treatment of at least the liquid in the main aeration chamber;
A method for treating wastewater comprising a control step of operating in a cycle of precipitation treatment and supernatant discharge treatment, and a step of discharging the supernatant liquid subjected to the precipitation treatment at one end of the main aeration chamber of the tank. 2. An inflow zone provided at one end of the tank interior through which the water flows without restriction during the sedimentation process and discharge process, a main air chamber provided in communication with this inflow zone, and an aeration device placed within this main air chamber. a return means for returning the liquid in the main aeration chamber to the inflow zone; and a control device for controlling the operation of at least the liquid in the main aeration chamber in a cycle of aeration treatment, precipitation treatment, and supernatant discharge treatment; and a supernatant discharge device held in a main aeration chamber in the tank and arranged to discharge supernatant liquid after precipitation according to instructions from the control device. 3. The sewage treatment device according to claim 2, wherein the inflow zone comprises a plurality of divided tanks. 4. The means for returning the liquid to the inflow zone is the method described in claim 2 or 3 by forcefully feeding the liquid in the main air vent to a jet nozzle for jet aeration installed in the inflow zone. Sewage treatment equipment.