JPH0118239Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is a method for treating organic wastewater such as sewage and domestic sewage.
This relates to a processing device that has BOD decomposition and nitrification and denitrification functions.

The activated sludge in the aeration tank in the activated sludge treatment method is a mixed system of microorganisms that have the function of decomposing organic matter, and BOD decomposition and nitrogen nitrification proceed simultaneously, but the nitrification rate is usually slower than the organic matter decomposition.
After BOD decomposition, nitrification is generally carried out in a separate tank. Also, while nitrification is an aerobic reaction, denitrification is an anaerobic reaction, so for reasons such as operational management, a nitrification tank and a denitrification tank are installed separately to separate nitrification and denitrification. It is common to do so.

However, using multiple treatment tanks requires a long residence time in each tank.
The disadvantage is that the total tank volume becomes larger, which requires more site area and higher construction costs.

In addition, in order to improve the oxygen absorption efficiency in the treatment tank, it is necessary to increase the amount of ventilation into the treatment tank or deepen the effective water depth of the nitrification tank, but if the water depth becomes deeper, However, there is a drawback that the power consumption of the blower of the air diffuser increases.

Therefore, this invention attempts to eliminate the above-mentioned drawbacks of the above-mentioned activated sludge treatment method,
The purpose of the present invention is to provide a treatment device that can efficiently perform BOD decomposition and nitrification/denitrification treatment of organic wastewater.

This invention will be described below based on embodiments shown in the accompanying drawings.

As shown in the figure, an air diffuser 2 is provided above a deep treated water tank 1. In this treated water tank 1, sewage,
Organic wastewater 3 such as domestic sewage is allowed to flow in.

The mixed liquid 4 in the treated water tank 1 is drawn out from the bottom of the treated water tank 1 by the pump 5, and the drawn out mixed liquid 4 is introduced into the air pipe 7 of the aeration device 2 as a circulating liquid 6. Send it back. The return port 8 for the circulating fluid 6 provided in the air pipe 7 is formed in the shape of a slit, and the circulating fluid 6 is circulated from the aeration device 2 into the treated water tank 1 in a sprayed state. 9 in the figure indicates a blower.

Next, the depth from the aeration device 2 of the treated water tank 1 to the bottom of the treated water tank 1 is determined by the dissolved oxygen concentration (DO) while the mixed liquid 4 at the top of the treated water tank 1 flows to the bottom of the treated water tank 1. The depth is sufficient for oxygen in the mixed liquid 4 at the top of the treated water tank 1 to be digested by nitrifying bacteria, and the dissolved oxygen concentration in the mixed liquid 4 at the bottom of the treated water tank 1 to be reduced to a value suitable for the denitrification reaction. Satoru.
In addition, in order to facilitate the nitrification and denitrification reaction, the dissolved oxygen concentration in the treated water tank 1 must be set to 0.5 ppm or higher during the nitrification process, and 1 ppm or higher during the denitrification process.
Since it is necessary to do the following, measure the dissolved oxygen concentration in the upper and lower parts of the treated water tank 1, and make sure that the dissolved oxygen concentration in the upper part of the treated water tank 1 is 0.5 ppm or more.
The amount of air in the diffuser 2 and the amount of circulating fluid 6 are controlled so that the dissolved oxygen concentration in the lower part of the treated water tank 1 is 1 ppm or less. In addition, along with the dissolved oxygen concentration,
It is desirable to control the amount of air in the diffuser 2 and the amount of circulating fluid 6 by also measuring the oxidation-reduction potential (ORP). Note that 10 in the figure indicates a dissolved oxygen meter.

The treatment liquid 11 treated as described above is discharged from the upper part of the treatment water tank 1.

Next, the operation of the processing device of this invention will be explained. That is, above the aeration device 2 in the treated water tank 1, a large amount of air is sent from the aeration device 2, so the mixed liquid becomes an aerobic state and a nitrification zone is formed in the upper part of the treatment water tank 1. , BOD decomposition and nitrification occur simultaneously. Further, the mixed liquid 4 is circulated from the bottom to the upper part of the treated water tank 1, and dissolved oxygen in the mixed liquid 4 is digested by nitrifying bacteria. becomes anaerobic, a denitrification zone is formed in the lower part of the treated water tank 1, and denitrification is performed.

As described above, the organic wastewater treatment device of this invention has an aeration device installed in the upper part of the treated water tank, and the mixed water in the treated water tank is returned from the lower part of the treated water tank into the air pipe of the aeration device. However, a nitrification zone is formed in the upper part of the treated water tank, and a denitrification zone is formed in the lower part, and the following effects are obtained.

(1) Since BOD decomposition and nitrification and denitrification are performed in a single treatment water tank, the installation area of the treatment equipment can be reduced.

(2) The mixed liquid in the treated water tank is circulated from the nitrification zone to the denitrification zone and back to the nitrification zone, so treatment efficiency is high and nitrification and denitrification treatment can be completed.

(3) Since the circulating fluid is returned to the air pipe of the air diffuser, the contact efficiency between the circulating fluid and air is extremely high, and BOD decomposition and nitrification are performed extremely smoothly. Furthermore, when the circulating fluid return port of the air pipe is formed in the shape of a slit, the circulating fluid is in a spray state, so that the efficiency of contact between the circulating fluid and air is further improved.

(4) As mentioned in (2) and (3) above, because the treatment efficiency is extremely high, it is possible to install the diffuser at a shallower depth compared to the water depth of conventional nitrification tanks, which reduces power costs. This can be reduced. Further, in the conventional denitrification tank, a stirring device was required, but in the treated water tank of this invention, since the mixed liquid is flowing, a special stirring device is not required in the denitrification zone.

[Brief explanation of the drawing]

The drawing is a schematic diagram of the nitrification and denitrification treatment apparatus of this invention. 1... Treated water tank, 2... Air diffuser, 4... Mixed water, 7... Air pipe.

Claims (1)

[Scope of utility model registration request] An air diffuser is installed in the upper part of the treated water tank, and the mixed water in the treated water tank is returned from the lower part of the treated water tank into the air pipe of the above-mentioned air diffuser.The upper part of the treated water tank is a nitrification zone, and the lower part is a denitrification zone. An organic wastewater treatment device characterized by forming zones.