JPS5939391A - Treatment of organic waste water with activated sludge - Google Patents

Abstract

PURPOSE:To enable to inhibit bulking, by treating organic waste water in a plurality of aeration tanks including the first and second ones provided in series, providing a packed layer to the first aeration tank, and specifying a load on the first aeration tank. CONSTITUTION:Organic waste water is treated in a plurality of aeration tanks including the first and second ones provided in series, and a mixed liquid in the final one is separated into a liquid and solid matter. In this activated sludge process, a packed layer is provided to the first aeration tank, a load on the first aeration tank is held above 3kg-BOD/m<2>.day expressed in terms of load on the tank and above 30g-BOD/m<2>.day expressed in terms load to the surface of fillers, an outflow liquid from the first aeration tank is let flow into the second aeration tank without separating it into a liquid and solid matter, and a part of sludge formed by solid-liquid separation is returned to the second aeration tank without returning it to the first aeration tank. As a result, the minimum amount of microbes in the tanks necessary for the treatment can be held, and bulking caused by filiform bacteria such as sphaerocillus can be inhibited.

Description

[Detailed description of the invention] This invention relates to a method for treating organic wastewater with activated sludge.

In the activated sludge treatment method e, wastewater is mixed with return sludge and aerated, the aerated mixture is precipitated and separated into supernatant liquid and activated sludge, and the separated activated sludge is returned to the aeration process and treated as wastewater. This is a treatment method that removes BOD components in organic wastewater, and is widely used as a treatment method for organic wastewater. However, depending on the type of wastewater, such as food factory wastewater, the sludge may cause so-called bulking, making precipitation separation difficult and making it impossible to treat. This palkink phenomenon usually occurs when filamentous bacteria such as Sphaerochilus become a dominant species in activated sludge. Therefore, in order to suppress the rise of Sphaerochilus and make flocculent bacteria such as Zooglaia the dominant species, the load is increased in the first aeration tank to allow all the flocculent bacteria to proliferate, and in the second aeration tank, flocculent bacteria are grown. Residual BO along with coarse bacterial flocs
A method for removing D has been proposed. This method is an excellent method, but in order to control the load in the first aeration tank against fluctuations in the amount of wastewater inflow and fluctuations in the base a concentration,
Sludge must be returned to the first aeration tank in addition to the second aeration tank, and control of the amount of returned sludge is complicated and difficult. l
Another method is to use two different types of biochords by separating the effluent from the first aeration tank with one layer of packing and then spreading it into the second aeration tank. The disadvantage is that the installation costs are high.

The entire purpose of the present invention is to provide an activated sludge treatment method for organic wastewater that completely prevents bulking without performing complicated control of the amount of returned sludge. That is, the present invention provides an activated sludge treatment method in which organic wastewater is treated in a plurality of aeration tanks including first and second aeration tanks arranged in series, and the final mixed liquid is separated into solid and liquid. A packed layer is provided in the aeration tank, and the load of the first aeration tank is 3 ky-B OD with tank capacity load.
/ n (・30 fi' on daily basis and filler surface area load
-BOL) m' day and flows into the first aeration tank,
This activated sludge treatment method for organic wastewater is characterized in that the activated sludge separated into solid and liquid is returned to the second and subsequent aeration tanks without being returned to the first aeration tank.

In the present invention, a filler layer of gold film is formed in the first aeration tank. Commercially available fillers such as plastic corrugated plates and honeycomb tubes can be used. The load of the first aeration tank is 3 kg-BOD/n1'·day in terms of tank capacity load, preferably 5 to 1'Okg-BOD/m'·day, and 30 kg-BOD/n1'·day in terms of filler volume load. jil-BOD/
nl!・On the date, good” L L < r, E, so
〜5o9−BOD/ηL2・day, which requires 3 ky/,,,, respectively, for the minimum value of the inflow BOD amount.
J・day and 30 f-BOD/pi″・day. Tank capacity load k 3 ky-B OD/m
If the total surface load is less than 30 y--BOD/rIl-day, there is a risk that Sphaerochilus will occur in large numbers depending on the wastewater Ill. There is a risk that this will occur frequently.

When the wastewater is introduced into the first aeration tank and aerated, the solids are decomposed and sludge is generated. A part of the generated sludge adheres to the filler, and most of it becomes dispersed, but Sphaerochilus does not form a dominant glaze because of its high load. That is, the first
In the aeration tank, the soluble BOD component is 70-95
% removed, and instead, dispersible floc-like bacteria proliferate and become dispersed. In addition, the biofilm attached to the filler grows and thickens, and when it gets old, it naturally peels off, and new sludge comes in and forms a biofilm.

The effluent from the first aeration tank flows into the second aeration tank without being separated, resulting in sludge regulation. By aerating for 3 days or more, preferably for 5 days or more, most preferably for 10 days or more, the dispersed floc-like bacteria and exfoliated sludge are improved and become settled flocs with good habitability. . Rinde Reikin 3
If it is less than 2 days, the sedimentation property of sludge will not be improved, and the sludge will become a dense floc and the SS in the treated water separated in the settling tank will be reduced.
sVI'17 (100ml/
To achieve a level of 9- or so, it is necessary to set the sludge period to 10 days or more. The sludge command can be set by controlling the amount of excess sludge extracted.

The effluent from the second aeration tank is subjected to solid-liquid separation with or without further aeration, and a portion of the separated activated sludge is returned to the second aeration tank, and the remainder is discharged as surplus sludge. This extraction of excess sludge may be continuous or intermittent. As a solid-liquid separation means for the final mixed liquid c1. Generally, a sedimentation tank is employed, but a pressure flotation device or a centrifugal separator may also be used.

In the second invention, the effluent from the 8F41 aeration tank may be diluted with treated water or aqua regia before flowing into the second aeration tank. In addition, other wastewater or raw water, i.e., to the second aeration tank,
It is okay to sweat the water flowing into the first aeration tank. Alternatively, a one-time aeration tank that does not completely cool the returned sludge may be provided between the first aeration tank and the second aeration tank.

¥: According to the invention, a packed bed is provided in the first aeration tank, so even if the substrate concentration of the raw water changes, the minimum amount of microorganisms in the tank necessary for treatment can be secured. The load of the first aeration tank is 3 kg-J30 D/m' in tank capacity load and 3 o y--B OD/ in filler surface area load.
The high load of nt"・8 or more prevents bulking caused by filamentous #1 bacteria such as Sphaerochilus, and there is no need to return sludge to the @1 aeration tank, making it possible to control the amount of returned sludge, which is complicated. becomes a sachet.

The present invention will be explained below using examples.

Example 1 Washed rice (glutinous rice) with a BOD of 730 to 1200 da/no was introduced into the first aeration tank where wastewater gold sludge was not returned, and the effluent was
The returned sludge is aerated in a second aeration tank, and the Takigawa mixed liquid is separated into solid and liquid in a settling tank (capacity 3!) to obtain treated water and precipitated sludge. It was returned to the aeration tank.The operating conditions were as follows.

As a result of continuing this operation for 4 months, B OIJ 5m7/
-g or less, 5851nl//-e or less stable treated water was obtained, and the SVI of the mixed liquid collected from the second aeration tank was
was 100 to 140 me/f/, indicating that the sludge had good settling properties. In addition, as a result of the tax collection of the mixture, Sphaerotelus was not recognized at all. In addition, the p paper of the formed metal INL15A flowing out of the first aeration tank is 05
The BOD concentration of the cypress was calculated using an aeration tank with a volume (7, e) equal to the total volume of the cypress, and a residence time of 26.8 br.
Tank load 0.66-1.1kg-130D/nl/day, sludge amount <a 0.31-0.36ky-BUD/ky-V
When the operation was carried out under the conditions of SS day and sludge volume of 7 to 14 days, Sphaerochilus was detected in the mixed liquid on the 7th day after the start of operation, and the SVI was 300 to 450 ml/l/l.
57, and the sludge sedimentation and separation became problematic and the operation had to be completely halted.

Applicant Kurita Industries Co., Ltd.

Claims (1)

[Claims] l) An activated sludge treatment method in which organic wastewater is treated in a plurality of aeration tanks including first and second aeration tanks arranged in series, and a final mixing surface is separated into solid and liquid. A packed moon layer is provided in the first aeration tank, and the load of the first aeration tank (I-Hydrostatic load is 3).
ky-B OI)/n?・The daily intake and filler surface area load was 301-BOD/rti'・1] or more, and the effluent from the first aeration tank flowed into the second aeration tank without solid-liquid separation, resulting in solid-liquid separation. A method for treating organic wastewater with activated sludge, characterized in that a part of the activated sludge is returned to a second aeration tank without being returned to the first aeration tank. 2) The sludge table of active sludge inside the second IMA is 5 days'
The activated sludge treatment method for organic wastewater according to claim 1, as set forth above.