JPS59115794A - Treatment of organic sewage - Google Patents

Abstract

PURPOSE:To remove efficiently BOD and nitrogen in org. sewage by subjecting successively and repeatedly the org. sewage to a stage for decreased aeration or stopping of aeration and a stage for repeating aeration and stopping of aeration or decreased aeration. CONSTITUTION:Org. sewage 1 is subjected to decreased aeration or stopping of aeration and is put in an anaerobic state to accelerate the denitrification reaction of the residual NO3-N in the previous treatment by the BOD of a high concn. in the sewage 1 in a batch type activated sludge treatment method which introduces the org. sewage 1 into an aeration tank 2, aerates the same by an aerator 3 and discharges the treated water 4 cleaned up by a biological reaction. The aerobic treatment by aeration and the anaerobic treatment by stopping of aeration or decreased aeration are then repeated by a desired number to remove BOD and to nitrate and denitrify the nitrogen component, whereafter the aeration is stopped and activated sludge is settled; at the same time, the supernatant liquid is discharged as treated water 4. The sewage 1 is thereafter put into the tank 2 and the above-mentioned process is successively repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a batch activated sludge treatment method, which is one of the biological treatment methods for organic wastewater.

FIG. 1 is a flow sheet diagram showing a conventional batch activated sludge method. In this batch activated sludge method, organic sewage 1 is first introduced into an aeration tank 2.
Oxygen-containing gas (generally air) is sent in from the pump to stir the activated sludge and organic sewage 1 in @Keika 2.
Mix and contact to perform sewage treatment using activated sludge.

After performing the aeration treatment for a certain period of time, the aeration is stopped and the activated sludge mixture is allowed to stand to settle the activated sludge. Thereafter, the reduced water due to precipitation is discharged to the outside of the system as treated water 4, and organic sewage approximately equal in volume to the discharged treated water is introduced into the warming tank 2 to start the aeration process again. This is shown in an operation time chart as shown in FIG. 2 (1).

In this way, in the batch activated sludge method, the aeration tank 2 is also used as a sedimentation tank, and the two functions of aeration and sedimentation are performed by the heating device 3.
This is one of the biological treatment methods in which organic wastewater 1 is introduced intermittently and treated water 4 is discharged intermittently, depending on whether the system is in operation or not. In this biological treatment 1A, BOD, nitrogen, etc. can be mentioned as pollutants that can be treated. The reaction formula in these biological treatments is as follows.

[BOD removal reaction] 1 →x CO2 + doctor y■■20 ・・・・・・・・・・・・
...(1) [Nitrogen removal reaction] NH4+202 →No +HO+2H+ ......(2)2 2NO3+1011 →N2↑+4 H2O+ 20H......'(
3) The mold nests in wastewater are not only in the form of NH4, but also organic nitrogen.
As a typical example of nitrogen in wastewater, N
H4 is listed and shown in the reaction formula above.

BOD removal is an aerobic reaction as shown in equation (1). Therefore, the reaction proceeds by providing sufficient aeration reaction conditions. On the other hand, nitrogen removal consists of an aerobic reaction shown in equation (2) and an anaerobic reaction shown in equation (3). Therefore, nitrogen is not removed only by providing aeration reaction conditions, and even if a sufficient aeration reaction is carried out, nitrogen remains in the treated water in the form of nitrate nitrogen (No3-N).

In the conventional batch activated sludge method, in order to effectively use the entire aeration tank for the oxidation reaction, an aeration method was used in which the entire aeration tank became aerobic. Therefore, in the conventional batch activated sludge method, BOD removal is pJ-capable, but nitrogen removal is almost impossible.

In recent years, efforts have been made to add and strengthen denitrification capabilities to the batch activated sludge process by improving the air flow process. An example of this is shown in Figure 2 (■).

It is shown in the operation time chart of ω0. (II), (I
[L is to operate the aeration tank under aerobic conditions (with the two aerators in motion) and under aerobic conditions (with the aeration device stopped) for the desired number of times from 1 to Equation (1) in , (
2> reaction and the reaction of formula (3) under anaerobic conditions are caused.

However, these recent improved methods also have some problems.

One of them is that since BOD removal proceeds first, BOD is insufficient for the rattan reaction. That is, equation (1)
This is a harmonious and harmonious balance among the three reactions: the BOD removal reaction shown in equation (2), the nitrification reaction shown in equation (2), and the dehydration reaction shown in equation (3).

Both the BOD removal reaction and the nitrification reaction are aerobic reactions, but their reaction rates are different, and the former reaction is faster. For this reason, wastewater containing BOD and NH4+-N is
:・;The BOD removal reaction progresses faster when air treated. However, in the recently improved method shown in (1) and (flD in Figure 2), aspiration starts immediately after 772 people of raw sewage, so BOD removal takes 711 lines without sloughing, and the nitrification reaction is delayed. Therefore, because the nitrification reaction is insufficient, the removal treatment is also insufficient.Furthermore, in the denitrification reaction shown in equation (3), an organic carbon source (equation (3) A water atmosphere donor (indicated by H) is required, but when organic substances such as methanol are added from the outside, denitrification reactions occur immediately, so 11. It is necessary to effectively utilize the organic matter component, that is, BOD.However, Ql) and Q in Figure 2
In the recent improved method shown in ID, aeration is started immediately after raw sewage (F;/person), and BOD is preceded by aerobic removal treatment. Therefore, when the nitrification reaction is completed and the denitrification process begins, the OD required for the denitrification reaction is insufficient.

Another problem is that the single BOD needle becomes a rate-limiting factor. In other words, the No.
5-N is treated by the desugarization reaction of formula (3),
In order to prevent the presence of BOD as a carbon source from becoming a rate-determining factor, it is necessary to have a large amount of BOD.1. In that case, Fi anaerobic conditions must be applied. However, Figure 2
(1), (Even in the recent improved method shown in IID, since step 1 is carried out immediately after introducing the raw wastewater, BOD is removed during this time, and in the next step it is made anaerobic and de-removed. , even if it does not occur, the BOD is less harmful and becomes the rate-limiting factor.

The present invention has been made in view of the above circumstances, and its purpose is to provide a method for efficiently removing BOD and nitrogen in a batch activated sludge method. I am trying to find a method.

In other words, the present invention (1) reduces the amount of sewage put into the air tank [1-Kimata rl Elm-[-Ki・ξ゛1''
process, aeration and 1'/1 air 44 reduction, n
The process of threading, processing, and returning i% qi, and exhalation (ri'; , +l
:, L, sink the live V4 sludge! ! As well as above? (
] Process of discharging water and 1mm 1q 4Hl after discharging supernatant water
! Condition/fil: Process of putting sewage into i! and li'
The property (characteristic) is to perform the primary or i4 return.

The method of the present invention will be explained below based on the example of the 31J rotation time chart shown in Part 3 (1).

First of all...Sewage (raw water for 1° i person @ ape reduction: l
! ) 4 Qi state change +, +:,, l, Qi stop j:, as a state, put it in a disgusting state. As a result, in the post-process, by returning -low V gas (or Okibe 1 stop city) at each exposure, the generated and residual No3-N is brought into contact with the BOD of the ν + YBN island, resulting in an anaerobic state. Under the eaves, we aim to promote the despondency reaction of formula (3).

In addition, BOD is used in the demolding reaction under anaerobic conditions immediately after the raw wastewater is introduced, and is reduced. For this reason, in the next step (((:, %
% of BOI), the removal efficiency is high. The processing time for the kernels is, for example, about 30 to 240 minutes.

Next, 1) repeat the aeration operation and reduced aeration or aeration stop +, I- for the wastewater in the air tank as many times as desired,
Forming aerobic conditions and expiratory conditions. When repeating the aerobic state and the lying state, it is effective to divide the II time into *ii<< for parental processing.

This means that as the aeration time becomes longer, the BOD will increase during the aeration process.
This is because the carbon is processed and is not used as a source of carbon for denitrification. Normally, the w1g time in one cycle is, for example, 3~
It will take about 22 hours. According to recent research, the operation of repeating aerobic and anaerobic conditions is said to be effective in removing phosphorus, and is also effective from this point of view. This repetition is
For example, do this about 3 to 10 times. In order to form an aerobic state and an anaerobic state in the same aeration tank, it is most convenient to operate the aeration tank + (ill, stop the operation). In order to achieve this, it is not necessarily necessary to completely stop the aeration equipment1, but to use a low N, n5r゛9 (,
It may also be a state. Rather, from the point of view of increasing the catalytic efficiency between the sludge, which is the main body of the room removal reaction, and No3-N on the water side, it is preferable to reduce β1 (stirring the inside of the air tank) by reducing Yes. Here, reduce 41il!, in case of Ki,
It is necessary to keep the cumulative amount of dissolved P in the tank as low as 0.5 m9/or less. On the other hand, in the case of aerobic force 1, it is f(smart) to divide 1'\4 so that (dissolved 1'1 in V'1; elementary 4÷ or 1. Om(?/) becomes more than 1'\4.

As in aeration - low offshore air (11."I"tee',
+l-,) and the desired number of lies I4 □'/-υ after puhi 11
．． ) The air was stopped and the activated sludge was allowed to settle for 11'c.
1') Treat the drained supernatant water and discharge it out of the system as water. This ll? The stopping time for the culm is 60 to 120 minutes.

Then, after this aeration treatment, ; (@-1 sewage (1 mol 1 water) is flowed in to make it into a reduced 1jA air condition or aeration stop condition, and leave it in an egg molten state.

In this process, the BOD load for the total aeration time is 0.3 kg・BOD/l for the entire one hour period.・Δ4
L, SS /day or less, total nitrogen load or 0.1kg・
Setting it to be less than T-N/kg・MLS S/day-1) IP is preferable.

In addition, for 1 hour of total reduced exposure (or total exhalation cessation time), the total nitrogen load for the total time is 0.4 kli'・T
-N It is possible to set it so that it is less than 7kg・MLSS/day! Delicious. Furthermore, the main settling time is determined in relation to the settling rate of the sludge, the shape of the aeration hole ψ11, and the amount of water to be treated. Allow enough outside time to obtain 7 fr water above +TL precipitation. Also, raw water inflow time, treated water discharge 41
iljll←I, raw water generation status, storage + 8 tank capacity E゛,
Inflow/discharge pump capacity h: Determine comprehensively from other circumstances.

Next, an actual MO example in which sewage treatment was performed using the method of the present invention will be explained based on the time chart shown in the third article.

In this example, school lunch center wastewater was used as raw wastewater. Its composition is as shown in Table 1. As a conventional method for comparison, batch-type activated sludge treatment based on the time chart shown in (Ir) in FIG. 2 was also carried out. The aeration tank capacity is 100 tons, and the amount of treated water is 20 tons/day. When the treatment was stable, the MLSS in the four tanks was about 2600 I++/l.

Table 1 shows the quality of the treated water obtained by the method of the present invention and the conventional method.

? i'! : From the results shown in Table 1, it was found that the method of the present invention yields treated water with a lower content of both BOD 11' element and phosphorus than the conventional method.

Phosphorus removal row in the method of the present invention +C°, ), <7. As for H, it is currently unknown, but as has been observed in recent years, it is possible for sludge to be absorbed into the sludge by being exposed to both ll' and aerobic conditions. It is thought that the

More than n? As explained above, according to the present invention, the nitrogen content of the water can be effectively reduced by effectively forming the anaerobic state and the anaerobic state. In addition to being able to reduce the content of BOD and phosphorus, the three factors of reducing the content of BOD and phosphorus are significantly impaired.

4. Cylindrical part in drawing C11. Figure 71 (dl) is a flow sheet diagram showing batch type activated sludge, equipment blue, Figure 2 is an operation time chart diagram for conventional batch type activated sludge, and No. 3.1 ¥1 is the present invention. It is an operation time chart figure of the batch type activated sludge method in a method.

1... Treatment sewage, 2... Aeration 1.3 - Aeration! -1, 2 false, 4... place 1゛ water.

Claims (1)

[Claims] A step of reducing aeration or stopping aeration for organic wastewater placed in an aeration tank, a step of repeating aeration and stopping or reducing aeration, and a step of stopping aeration to precipitate activated sludge and discharge supernatant water, 1. A method for treating organic sewage characterized by sequentially repeating the step of pouring organic sewage into an aerated tank after discharging supernatant water, 1