JPS5815035B2 - High concentration activated sludge treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly concentrated activated sludge treatment method using an aeration tank.

In the treatment of activated sludge such as human waste in an aeration tank, air or oxygen gas is blown into the sludge in the aeration tank to treat the activated sludge, and then the treated aeration tank mixture is separated into sludge and treated liquid in a settling tank by gravity. Separated.

By the way, if the sludge concentration in the aeration tank mixture is too high, sedimentation and separability will deteriorate, so conventionally, the mixed liquid is diluted in advance so that the MLSS concentration in the aeration tank is 3,000 to 5,000 ppm. The sludge concentration is lowered and the sludge is separated by sedimentation.

However, treating the inside of the aeration tank with high dilution results in poor aeration efficiency and requires a large aeration tank.Though treating with low dilution solves the above problems, there is the problem of worsening sedimentation separation. .

Furthermore, in order to maintain a high dilution inside the aeration tank, a large amount of dilution water is required, and securing a water source becomes a problem.

This invention provides a dilution adjustment tank at the next stage of the aeration tank to dilute the aeration tank mixed liquid with treated water, making it possible to perform activated sludge treatment at a high concentration. The present invention provides a highly concentrated activated sludge treatment method that solves the above-mentioned problems by feeding the activated sludge into a settling tank.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in Figure 1, highly concentrated wastewater such as human waste flows into the aeration tank 1, and dilution water flows into the aeration tank 1 as appropriate.
LSS concentration (sludge concentration) is 10,000 to 30,000
kept at ppm.

The treated liquid in the aeration tank 1 flows into the next stage dilution adjustment tank 2, where it is mixed and stirred with the circulating treated water from the treated water tank, which will be described later, and is adjusted to a degree of dilution that optimizes sludge sedimentation and separability. .

The residence time of the mixed liquid in the dilution adjustment tank 2 is approximately 2 hours.

This adjusted mixed liquid flows into the settling tank 3 and is separated into solid and liquid, and the supernatant liquid flows into the treated water tank 4.

The treated water in the treated water tank 4 is sent to higher-level treatment equipment such as a denitrification treatment device, and a portion is circulated as dilution water in the dilution adjustment tank 2 as described above.

The sludge drawn from the settling tank 3 is concentrated in the sludge thickener 5 and then returned to the aeration tank 1 to maintain the sludge concentration in the aeration tank 1 at the above-mentioned high value.The liquid separated by the thickener 5 is sent to the dilution adjustment tank 2.
is flowing into the country.

In addition, a part of the thickened sludge is disposed of as surplus sludge after treatment such as incineration.

Although various commercially available dehydrators can be used as the concentrator 5, a centrifugal dehydrator is preferable.

Note that if the aeration tank 1 contains highly concentrated sludge, it is not necessarily necessary to return the drawn sludge.

The high-concentration activated sludge treatment method of the present invention is as described above, and next, it will be explained that this method is excellent in the activation treatment of high-concentration sludge.

First, the flow rate V and the MLSS concentration S in each process shown in FIG. 1 are set as follows.

Vl, Sl: sewage flow rate and concentration to the aeration tank 1 v2: diluted liquid flow rate to the aeration tank 1 S2: sludge concentration in the aeration tank 1 S3: sludge concentration in the dilution adjustment tank 2 V4. S4: Flow rate of circulating water and sludge concentration of treated water V3. S, : Amount of drawn sludge and sludge concentration v6:
Separated liquid volume V7. S7: Amount of returned sludge and sludge concentration However, the sludge concentration of the dilution water and separated liquid is O.

Therefore, when calculating the sludge balance in the treatment method shown in FIG. 1, v xs + v xs S2 = □...■ v1+v2+V7 10000ppm<82<30000ppmS2. X
(Vt + V2 + V7) S, -□・・・・・・
■ V1+v2+v4+v6+V7 Here, the mixed liquid sludge concentration to obtain the optimum settling property is 5.0.
00 ppm<83 (8,000 ppm, and the sludge concentration of returned sludge that can be dispersed in aeration tank 1 is 87≦50.00
0 ppm.

i) Consider the relationship between each flow rate V of this invention in the case where the sewage is human waste and is not diluted (v2=0) c Human waste is usually 1
Since 5,000 ppm = 81.

52=20,000 ppm, 57=40,000
If it is ppm, then V7=0.25V1 from equation (2).

Also, S3 = 5000 ppm1S4kiOppm%
s.

= 10,000 ppm, ■7×57=v,
From ×S5, v5 = 4V7, Va = 3V7 ('-
'Vs=Vo + V7), 1V6=0.75 Vl(
", "V7=0.25 Vl).

Therefore, from equation (2), V4=2.25V1.

That is, based on the method of the present invention, when human waste is treated with activated sludge without dilution in the aeration tank MLSS concentration of 20,000 ppm, the sludge concentrated to 40,000 ppm is returned to the aeration tank 1 at a return rate of 25%. In the dilution adjustment tank 2, the treated water in the treated water tank 4 is circulated and returned 2.25 times the amount of sewage input.
After the sludge concentration in the dilution adjustment tank 2 is reduced to 5,000 ppm or less, solid-liquid separation is performed in the settling tank 3.

311) Consider the relationship between each flow rate V of this invention in the case where the wastewater is sewage and is not diluted.

Sewage usually has 300 ppm = 81, so 52
=20,000ppm, 57=40,000ppm
Then, from equation (2), V7=0.985V1.

Also, S3=5000ppm, 84 cows 0pprr+, 8
If 5 = 10,000 ppm, then V7 = 0.75V1 in the same way as above, and from formula (■) V4 = 6.2
05 Vl.

In other words, in the case of sewage, the return sludge rate is 9 g, 51%.
.

The treated water will be recycled and returned 6.205 times the amount of sewage input.

Here, when comparing the two, when operating the MLSS concentration in aeration tank 1 at 20,000 ppm and the MLSS concentration in dilution adjustment tank 2 at 5,000 ppm, approximately 4 times the amount of returned sludge is required compared to sewage human waste. Therefore, the amount of water circulated and returned to the dilution adjustment tank 2 is also about three times larger.

This is due to the extremely low 81 level of sewage.

In addition, the amount of sewage input V1 in sewage treatment is very large compared to human waste treatment (human waste treatment: 100,771"/8. Sewage treatment tens of thousands to 100,000, 11 days), so the dilution adjustment tank 2
If the amount of water to be circulated and returned is 6.205 times the input amount (1), the electricity bill for that pump will be enormous.

As is clear from the above, the treatment method of the present invention can be used to treat highly concentrated organic wastewater such as human waste, and the amount of sewage input is 1.
It can be seen that it is effective for a relatively small number of cases.

However, this does not mean that the present invention cannot be applied to low-concentration organic wastewater and wastewater such as sewage with a large amount of input water v1G).

Next, comparative clothing will be shown when human waste was treated using the treatment method of the present invention and when it was treated using the conventional highly diluted treatment method.

Therefore, there is no major difference in the properties of the treated water, and the present invention allows the capacity of the aeration tank to be reduced compared to the conventional method.

In addition, even in the conventional method of human waste treatment shown in Fig. 2, this aeration tank portion (Fig. a is the activated sludge treatment tank, Fig. B is the second aeration tank) is made of highly concentrated sludge, and this aeration tank is This invention can be applied by installing a dilution adjustment tank at the next stage of the tank and further installing a sludge thickener.

As described above, according to the high-concentration activated sludge treatment method of the present invention, since aeration is performed at a high concentration, the activation efficiency is high, and the aeration tank can be made smaller compared to conventional treatment methods. This is very advantageous in terms of area.

In particular, in recent years, human waste has been increasingly treated with low dilution, and the present invention follows this trend.

In addition, the amount of dilution water in the dilution adjustment tank is relatively small and can be supplied by circulating treated water, which has the effect of eliminating the problem of securing a water source.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the highly concentrated activated sludge treatment method of the present invention, and FIGS. 2A and 2B are schematic diagrams of each side of the conventional human waste treatment method 1, respectively. 1... Aeration tank, 2... Dilution adjustment tank, 3
... Sedimentation tank, 4 ... Treatment water tank, 5 ...
...Sludge thickener.

Claims (1)

[Claims] 1 After treating highly concentrated human waste with activated sludge, it is mixed and stirred with the treated liquid in a dilution adjustment tank to dilute it, and this diluted liquid is separated into solid and liquid in a sedimentation tank, and a portion of the supernatant liquid in the sedimentation tank is A highly concentrated activated sludge treatment method characterized in that the above-mentioned treatment liquid is circulated to a dilution adjustment tank.