JPS6150696A - Treatment of intermittently flowed-in waste water by activated sludge - Google Patents

Abstract

PURPOSE:To efficiently perform the treatment of waste water, by directly flowing waste water into an aeration tank to treat the same while continuously transferring a part of a liquid mixture of the waste water and activated sludge in the aeration tank to a sedimentation tank to remove activated sludge in the liquid mixture. CONSTITUTION:A liquid mixture after aeration treatment (activated sludge treatment) is stored in a sedimentation tank 15 and the sludge component therein is removed by sedimentation. Waste water of an aeration tank 1 is pumped up by a conduit 13 with a pump 13A for pumping up waste water to be sent to the sedimentation tank 15. The slow flowing tank 14 interposed to the conduit 13 with the pump 13A is alternately divided into horizontal flow passages by proper partition wall plates 14A-14A and waste water is slowly flowed in a meandering state. A discharge pipe 16 discharges the supernatant solution, that is, the treated water of the sedimentation tank 15. A sludge return pipe 18 allows a part of excessive sludge to return to the aeration tank 11.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention is directed to organic wastewater containing organic pollutants (hereinafter referred to as
Simply abbreviated as wastewater. ), and specifically relates to an activated sludge treatment method for intermittently flowing wastewater.

(Prior Art) Conventionally, in activated sludge treatment of wastewater from sewage or food factories, etc., as shown in FIG.
It is introduced into a cushion tank 27 via a bomb 26Δ and a gas tank 26, and guided through a conduit 28 with a pump 28A to a first settling tank 29 through a conduit 30, and then into an aeration tank 31 having an air pipe 32. Transferred to the second sedimentation tank 3 via the conduit 33
4, the sludge is removed, and the supernatant liquid is discharged as treated water through a conduit 35, and the wastewater is transferred to an aeration tank 32.
The sedimentation tank 22 and cushion tank 27
After passing through the first settling tank 29, it is introduced into the aeration tank 31 where it is aerated. The cushion tank 28 is made into a container that can sufficiently cope with fluctuations in the amount of inflow of wastewater so that predetermined skewers can be uniformly and continuously fed into the wastewater in subsequent processing steps. For this reason, a large cushion tank was required for wastewater with large inflow fluctuations. For example, in a factory that operates for 8 hours, a cushion tank (n) of about 273 volumes is required, which is the inflow amount for 8 hours, and the cushion tank occupies a large proportion of the activated sludge treatment equipment, causing the problem of increasing the size of the entire treatment equipment. there were.

Conventional cushion tanks are equipped with one or several pumps that operate constantly for stirring, and one or several pumps that operate when the inflow increases (peak operation). If there was an inflow that exceeded the inflow, all pumps were operated at full capacity to equalize the inflow wastewater and send it to the aeration tank in the subsequent process, which required a large number of pumps.

Also, if wastewater is left in the cushion tank for a long time,
Since the wastewater rots and floating substances are deposited, it is necessary to vent or diffuse air into the cushion tank and to stir the tank, which poses a problem that requires various equipment.

(Problems to be Solved by the Invention) However, this invention attempts to solve the above-mentioned problems. For example, there is wastewater that continuously flows in during daytime work hours, and wastewater flows in at night. The wastewater 1 flowing into the wastewater treatment facility is uneven and intermittent, such as when there is almost no wastewater, or when a large amount of wastewater is released only in the morning and evening, and only a small amount is released at other times. In this case, the treatment of the Kutsushikon tank is omitted.
Our objective is to provide a method for treating wastewater with activated sludge.

In addition, this invention not only allows the treatment of fixed sludge in wastewater to be carried out in just 11 minutes, but it also eliminates the treatment T-culm of the cushion tank, which was the essence of the conventional method, making it possible to reduce the size of the implementation equipment and making it easier to implement. This is what I did.

(Means for Solving the Problems) Therefore, as a result of research, this inventor achieved good results (q) and achieved the present invention. Looking at the wastewater flow in terms of time, in the morning in residential complexes, 3 of the hourly average inflow
There is ~5 times the inflow, and 1 to 4 times the inflow in the evening, and in a factory that works for 8 hours, wastewater flows in during the 8 hours of daytime work, and almost no inflow during the 16 hours after work. Therefore, the inventor of the present invention has made it possible to omit the cushion tank when waste water is intermittently fed like this. Therefore, the means of the present invention, when treating wastewater that flows intermittently with activated sludge, allows the wastewater to flow directly into the aeration tank for activated sludge treatment, and while being treated with activated sludge, the wastewater is treated with activated sludge. A part of the mixed solution of wastewater and activated sludge is continuously transferred to a settling tank, and the activated sludge in the mixed solution is sedimented and removed to obtain treated water.

In the present invention, when treating wastewater with activated sludge, the cushion tank is completely removed, and the aeration tank, which is the main body of activated sludge treatment, is given some cushioning properties, so that it can also function as a conventional cushion tank. This is what I did. Conventionally, in an aeration tank, the mixed liquid flows into a settling tank due to overflow, and it was common knowledge that the water level was constant. The feature is that it also allows water level fluctuations.

That is, the present invention is carried out according to the flow sheet shown in FIG. Even if the amount of water fluctuates over time, the inflowing wastewater is immediately introduced into the aeration tank either as is or, if necessary, after passing through a small-capacity pump tank. Activated sludge is supplied to the aeration tank in advance. In addition, a water supply means (pumping means) is installed in the aeration tank so that the mixed liquid of wastewater and activated sludge is continuously sent to the final settling tank. If there is a temporal flow rate fluctuation in the inflowing wastewater, the water level in the aeration tank will rise and fall.

In the case of residential housing complex wastewater treatment, the water level in the aeration tank is low in the early morning due to pumping of mixed liquid at night.
The activated sludge continues to be aerated with a low load, and the inside of the aeration tank is in a starvation state.

In this state, there is an influx of wastewater in the morning, which places a high load on the inflowing wastewater and causes the water level to rise above the ground.The water level drops slightly during the day, and then rises again due to the load in the evening.
It will rise. This effectively extends the aeration period of the wastewater, and a difference occurs in the supply of nutrients to the microorganisms in the activated sludge, resulting in conditions that are normal for living organisms, significantly increasing the ability to decompose organic matter. Very useful.

Various methods can be considered for water supply means for the mixed liquid in the aeration tank. Pumping with an air lift pump is simple, as all you need to do is branch the air piping if the aeration method is used, but the pumping water level may change depending on the water level in the aeration tank. Inevitable. Therefore, the sedimentation tank needs to be divided into stages commensurate with the maximum amount of water to be lifted. When pumping with a centrifugal pump, care must be taken not to trap air bubbles in the pump, and a submersible motor pump is preferable. If a pump with a pumping volume suitable for the average water volume of the aeration tank is provided, this can be carried out satisfactorily as long as there is no sudden change in water m.

In such cases, it is desirable to provide a bypass that allows direct flow into the settling tank at the level of the controlled high water level of the aeration tank. A method using two types of pumps, one for regular use and one for peak use, is also safe.

The aeration tank is designed with a BOD volume load, which is the BOD 5 which is loaded per 1 m3 of tank capacity per day, but the tank capacity of the aeration tank used in the present invention is not constant because the water level fluctuates. However, in practice, sufficient sea performance can be guaranteed even if the aeration tank volume is designed to be midway between the control high water level and the low water level. Furthermore, when aeration is performed in an aeration tank using a blower, the number of aerated corals increases as the water level decreases, and decreases as the water level increases. Although this does not greatly affect functionality, it may be possible to detect the water level or dissolved oxygen and control the blower using an inverter or the like. If the mechanical stirring method causes problems, it is desirable to install the device on a float so that it can respond to fluctuations in the liquid level. Aeration systems using epiphthalmos or submersible pumps can also be used.

If the mixed liquid in the aeration tank is pumped up, there is a risk that the sludge in the mixed liquid will be broken up into small pieces by mechanical elements. Therefore, it is preferable to provide a slow-flow tank in which the flocs can grow again while slowly flowing the mixed solution before sending it to the final settling tank. The slow flow tank is formed by disposing partition plates alternately in a slow flow path where the flow remains for 3 to 5 minutes or more so that the mixed liquid flows in a meandering manner. The slow flow tank may be provided with a slow stirrer or a gentle aeration device, and if the flocculation function is insufficient, a polymer flocculant may be added.

(Function) The present invention causes wastewater that has passed through a settling tank and a screen to flow directly into an aeration tank without passing through a cushion tank. The water level in the aeration tank rises when wastewater flows in, and falls when the inflow is small or stops flowing. The inflowing wastewater is treated with activated sludge in the aeration tank. The wastewater after activated sludge treatment is transferred together with the sludge to a settling tank, where the sludge is removed and used as treated water.

(Example) Next, a first embodiment of the present invention will be described.

First, the outline of the apparatus used in this example will be explained with reference to FIGS. 2 and 3.

1 is a wastewater inlet pipe, 2 is a settling tank, 3 is a screen, and 5 is a pump tank, and wastewater from the settling tank 2 is introduced into a conduit 4. Reference numeral 11 denotes an aeration tank, and an aeration pipe 12 from which foamy air is released is provided at the bottom of the tank, and a predetermined amount of activated sludge is placed in the tank in advance. Wastewater from the pump tank 5 is sent to the aeration tank 11 through a conduit 6 with a pump 6A. Reference numeral 15 denotes a settling tank, in which the mixed liquid after aeration treatment (activated sludge treatment) is stored, and the sludge content is sedimented and removed. The waste water in the aeration tank 11 is pumped up by a conduit 13 with a pump 13A for pumping up and sent to a settling tank 15. 14 is a conduit 13 with a pump 13A
A slow flow tank is installed in the tank, and the horizontal flow channel is appropriately divided into n sections by partition plates 14A to 14A, so that the wastewater flows slowly in a meandering manner. Reference numeral 16 denotes a discharge pipe for discharging the supernatant liquid of the settling tank 15, that is, treated water.

18 is 1 ton of excess sludge! A sludge return pipe returns the sludge to i12, and 17 is a sludge discharge pipe that removes excess sludge.

However, in a residential complex, approximately 24,007yL3 per day
The sewage (wastewater) is treated using the above equipment.

The hourly average skew of sewage flowing in from inflow pipe 1 is 100 mm, but the peak time in the morning is 500 m/hour, and the peak time in the evening is 300 m/hour, and the BOD of this sewage is approximately 200 m/hour.
It is 0ON. On the other hand, the average BOD load is 0.4 to 9
When an activated sludge aeration tank with aeration method of BOD/m” day was installed, the length of the aeration tank became 1200 m.Aeration tank 1
1 is 1600m at controlled high water level and 800m at controlled low water level.
3 pumping pump (average pumping volume 100m3)
7 o'clock), the mixed liquid was transferred to the settling tank 15. The aeration amount was 220 ONm3/hour. The capacity of the slow flow tank 14 is approximately 10 m3, and the capacity of the sedimentation tank 15 is approximately 300 TrL.
It is 3. With this equipment, sewage treatment was carried out without any problems, and the BOD of the effluent was constantly kept below 20 ppm. The treated water will be discharged through a disinfection tank or reused as appropriate.

If the treatment of Example 1 were to be carried out using a conventional activated sludge treatment equipment, approximately 1,000,7713 cushion tanks would be required, and assuming that the inflow was from 10 m underground, the volume would be approximately 20 m.
00m3 and the aeration volume is about 4000m3/R in total.
It takes. Therefore, according to the treatment method of this example, the tank capacity could be reduced by more than half, the required space could be reduced by about 30%, and the amount of aeration could be reduced by about 40%.

Next, a second embodiment will be explained. As the implementation device, the first
The same type of processing apparatus as in the example was used (see FIGS. 2 and 3).

At a food factory, approximately 800 m'' of r-field wastewater per day was treated using the VZ equipment used in this example.
Although it is a loss on 3, Haku's 16 hours is almost no V[. The BOD of this wastewater is approximately 500 ppm. This wastewater treatment reduces the average BOD load to approximately 0.8! 9BOD/
m3-F3T”, the aeration tank volume will be approximately 500m3
become. A pump at the end of the aeration tank pumps the mixed liquid to 250 ml.
Transfer to a m3 sedimentation tank. By controlling the high water level of the aeration tank to approximately 700 m and the low water level to approximately 300 TrL3, it was possible to transport it using only a commonly used pump.

(Pumping fi 40m3/hour). The amount of air is about 1
500m”/hour.The average BOD of treated water is about 30
ppm, and the maximum was only 401) Din. The treated water passes through a disinfection tank and is disinfected before being discharged or used as appropriate.

If this treatment is carried out using a conventional activated sludge treatment equipment, approximately 60
0m" cushion tank is required, and the aeration amount is 2500
It took m3/hour.

Therefore, according to the treatment method of Example 2, the tank capacity is approximately 40
% reduction, the amount of airflow was reduced by approximately 40%, and the space required was also reduced by 40%.

(Effects of the Invention) When the present invention treats intermittently flowing wastewater with activated sludge, the wastewater is directly flowed into the aeration tank and treated with activated sludge, so that the pretreatment of the aeration tank is As a result, the cushion tank provided as an additional step can be omitted, and the above-mentioned objective of the present invention is achieved.

That is, in the present invention, unadjusted wastewater is directly supplied to an aeration tank containing activated sludge, activated sludge treatment is continued while aeration is carried out, and then the mixed solution of activated sludge and wastewater is transferred to a settling tank. The activated sludge is removed to obtain treated water.
Wastewater purification treatment is sufficient. According to the present invention, since the water base in the aeration tank is varied and the cushion bamboo is filled in the aeration tank, wastewater can be treated efficiently and there is little variation in the quality of the treated water. Although the function of the sedimentation tank, which uses the mixed liquid as treated water, is physically likely to be affected by the water suspension, since the load on that part is uniform, it is possible to reliably perform sedimentation separation.

However, in the present invention, since the conventional cushion tank is not required, it is convenient because the number of processing steps can be omitted, and since the cushion tank can be omitted, the implementation equipment can be reduced in quantity. Pumps and various devices for aeration and watering are not required, and equipment costs can be economically reduced and it is easy to implement.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the culm treatment of the present invention. 2 and 3 show examples of devices used in embodiments of the present invention, in which FIG. 2 is a sectional view of the entire device, and FIG.
The figure is an enlarged plan view of the main parts of the slow flow tank. FIG. 4 is an explanatory diagram of a conventional apparatus used for activated sludge treatment. 11... Aeration tank 12... Aeration pipe 13.
... Conduit 13A ... Pump 15 ... Sedimentation tank

Claims (1)

[Claims] When organic wastewater that flows intermittently is treated with activated sludge, the wastewater is directly flowed into an aeration tank to be treated with activated sludge and treated with activated sludge, while a mixture of wastewater and activated sludge in the aeration tank is An activated sludge treatment method for intermittently flowing wastewater, characterized in that a part of the mixed liquid is continuously transferred to a sedimentation tank, and the activated sludge in the mixture is removed by sedimentation and used as treated water.