JPH01123696A - Aerobic biological treatment of organic waste water - Google Patents

Abstract

PURPOSE:To avert the destruction of microorganism mass and to effectively utilize the self-flocculating power of the microorganisms so that org. waste water is efficiently and aerobically cleaned by previously dissolving a required quantity of oxygen into the org. waste water, then passing the water upward through a mixed microorganism bed in which the microorganism are grained by the self-flocculating power. CONSTITUTION:The living waste water is admitted through a raw water supplying line 8 by a raw water pump 4 into an oxygen dissolution tank 1. Part of the treated water is admitted through a circulation line 10 by a circulation pump 6 into the tank 1. On the other hand, the oxygen produced in an oxygen generator 3 is supplied via an air diffuser 7 into the tank 1. The liquid mixture composed of the living waste water dissolved therein with the required quantity of the oxygen and the treated water is passed through a water feed line 9 in upward flow into a biological reaction vessel 2 from the lower part thereof. The granular mixed microorganisms 12 and the waste water flowing in this vessel 2 are brought into contact with each other aerobically clean the living waste water. The cleaned and treated water separated from the microorganisms 12 in the upper part of the vessel 2 is discharged through an outflow line 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for biologically treating organic wastewater such as sewage, industrial wastewater, human waste, etc. under aerobic conditions.

[Conventional technology and its problems]

In the activated sludge method, which is a typical aerobic biological treatment method, a mixed liquid consisting of wastewater and activated sludge is aerated in an aeration tank, and then solid-liquid is separated in a settling tank.The activated sludge is completely settled and separated, and the supernatant water is used as treated water. This is the way to obtain it. The microorganisms in the activated sludge method have an irregular shape and are floc-like with a sparse density, so their solid-liquid separation requires a settling tank with a large area. On the other hand, since the floc adsorbs and removes fine particles in the water during precipitation, the treated water has a high degree of clarity.

"New Sewage Treatment Technology - Upflow Oxygen Activated Sludge Method" edited by Yoshiaki Uehara (published by Industrial Water Research Association).

The upflow oxygen activated sludge method described in 1980) is a technology that aims to reduce the size of equipment by integrating a biological reaction tank and a settling tank and using oxygen gas as an oxygen source. Since the mixed liquid consisting of activated sludge and wastewater is directly aerated with oxygen gas, the form of the activated sludge is the same floc as in the above activated sludge method, and the area required for solid-liquid separation is the same as that of the conventional activated sludge method. Ruru〇On the other hand, in the biofilm method, since microorganisms exist as a biofilm on an attached carrier, a vast sedimentation tank is not required for solid-liquid separation, but (I) the presence of activated sludge in the form of flocs is Because the amount is small, the activated sludge method has problems such as the purity of the treated water is not high (the ID-attached carrier is expensive, leading to an increase in equipment costs).

[Purpose of the invention]

The purpose of the present invention is to form a granular mixed microbial bed with excellent sedimentation properties and clarification of treated water without using any adhesion carrier by effectively utilizing the self-cohesive power of microorganisms. The purpose of the present invention is to provide an aerobic biological treatment method that utilizes kW efficiency.

[Structure of the Invention] The outstanding feature of the present invention is that it excludes the direct aeration of wastewater containing microorganisms, which is the rRX supply method that was conventionally considered to be a common-sense means. The destruction of microbial clusters caused by frequent aeration, which is a major inhibiting factor for self-agglomeration, is eliminated, and as a result, microorganisms form round granules with excellent sedimentation properties, making solid-liquid separation much easier than conventional methods. And so.

In addition, by bringing the treated water in which oxygen has been dissolved into contact with the mixed microbial sludge bed that has been granulated by self-cohesive force in an upward flow, fine SS in the treated water can be removed compared to the normal activated sludge method. The present invention provides a method that is equally adsorbed and has a high clarification effect.

A granular mixed microbial bed can be produced by placing a required amount of activated sludge in a biological reaction tank and passing organic wastewater with dissolved oxygen upward through the activated sludge.

In addition, it is better to initially lower the flow rate above and below the liquid to prevent the sludge from flowing out, and increase the flow rate as the sludge becomes granular.

In addition, if the mixture is stirred gently at this time, granules are likely to be formed. Usually, complete granulation is achieved within two weeks, and 1
Granules of ~8 snow grain size are formed.

According to the present invention, after agitating organic wastewater and dissolving the necessary amount of oxygen, water is passed upward through a mixed microbial bed that has become granular due to self-cohesive force, and is treated without breaking the microbial mass. This is an aerobic biological treatment method for organic wastewater.

In the present invention, the formation of granules is promoted, the sludge becomes blocked by adhesion of the granules to each other, and a dead zone is formed due to this. To prevent this, it is preferable to gently agitate the granular mixed microbial bed.

In addition, in the present invention, when the above-liquid flow rate is less than 80 m7 days, the flow of the granular mixed microorganism bed becomes inactive and the contact efficiency with the wastewater decreases, so it is necessary to maintain the above-liquid flow rate at 80 m7 days or more. There is.

In addition, if the flow rate above and below the liquid is too high, the granular mixed microorganism bed will be 98%
Microbial bed sludge fjk to form a large fluidized bed in the military
This results in a decrease in processing speed.

The flow rate above and below the liquid is preferably 80 to 250 m/day, more preferably 100 to 210 m/day.

Further, in the present invention, dissolving oxygen under pressure can increase the dissolved oxygen concentration, which is advantageous for aerobic treatment. However, when pressurizing to more than 5 kg 7 cm, supersaturated gas becomes bubbles in a biological reaction tank at a practical depth, resulting in the same result as aerating a granular mixed microbial bed, and the formation of granular bodies is inhibited. Therefore, it is preferable to dissolve oxygen into the water to be treated under pressure of 3 to 7 or less than 2.

In addition, it is preferable to use oxygen-enriched gas or pure oxygen in order to maintain a high dissolved oxygen concentration. Also, depending on the concentration of organic wastewater, the treated water may be circulated to eliminate the lack of oxygen supply. After dissolving the oxygen, it is necessary to send the water to the biological reaction tank.

Further, when the amount of mixed granular microorganisms increases, it is sufficient to remove them from the biological reaction tank from time to time.

Example 1 The present invention was carried out on the domestic wastewater of an OE housing complex as explained based on FIG. 1. The equipment used was as follows.

Biological reaction tank Inner diameter 500m + Height 4200m Effective volume α25- 1 Stirring rod 0 rotation speed 1-5 rpm (variable type) with round II attached at 200- intervals in the height direction Oxygen dissolution tank Inner diameter 300- High 4000 m Effective volume 12- E with impurities removed in advance using a fine mesh screen
Raw water supply line 8 by housing complex domestic wastewater t-raw water Boise 4
After that, it flows into the oxygen dissolution tank 1. Further, a part of the treated water is caused to flow into the oxygen dissolving tank 1 via the circulation line 10 by the circulation pump 6. On the other hand, oxygen produced by the oxygen generator 3 (effective oxygen concentration 91% V/V) is supplied to the oxygen dissolving tank 1 via the aeration device 7.

The dissolved oxygen concentration obtained by this method is 20 to 40 da/l, and since it is insufficient to simply supply oxygen to the raw water, treated water is circulated to supply oxygen.

A mixed solution of raw water and treated water in which oxygen has been dissolved is passed through a water supply line 9 by a water supply pump 5 in an upward flow from the lower part of the biological reaction tank 2.

A stirring rod 13 is provided inside the biological reaction tank 2.
Due to the interaction between the upward flow caused by the inflow water and the gentle traveling flow caused by the stirring rod 13, the particulate mixed microorganisms 12 come into contact with the wastewater while flowing, and purify the wastewater aerobically.

The granular mixed microorganisms 12 are separated from the treated water in the upper part of the biological reaction tank 2, and the separated water flows out from the upper part of the biological reaction tank 2 as treated water through the treated water outflow line 11t, and a part of it is sent to the circulation line by the circulation pump 6. 10 to oxygen dissolution tank 1
The surplus particulate mixed microorganisms 12 are discharged from the particulate mixed microorganism discharge line 14 as a result of the zero-order operation. The returned sludge of the normal activated sludge method is charged into the so tw biological reaction tank, raw water flow t CL 5 m"/eL % Circulating water t 1.6 m"/d, flow rate above and below the liquid 50 m
When the acclimatization operation was started at /d, the sludge gradually became granular and the sedimentation rate increased.The raw water flow rate and circulating water amount were increased in response to the increase in the O sedimentation rate, which resulted in approximately 2°C.
After a week, the sludge became granular with a diameter of 1 to 5 wm, so steady operation was started.

Table 1 shows the results of steady-state operation.

Table 1 Operation Results Since microorganisms exist in granular form different from flocs in the normal activated sludge process, solid-liquid separation is possible even at high liquid flow rates as shown in Table 1, and the quality of the treated water is also good. I failed.

Although the granular mixed microorganisms discharged as surplus have already disintegrated due to the shearing force within the discharge pipe during discharge, their concentration is somewhat better than that of surplus sludge from the normal activated sludge method. The concentration after standing for an hour was 55-4%.

As described above, the present invention can provide a compact and high-performance biological treatment method by effectively utilizing the cohesive power of microorganisms. It is believed that the present invention will be effectively utilized in future wastewater treatment.

[Brief explanation of the drawing]

FIG. 1 is the ninth flow diagram illustrating the present invention in detail. 1...Oxygen dissolution tank, 2...Biological reaction tank, 3...#
1. Accumulator generator, 4... raw water pump, 7-- air diffuser,
10... Circulation line, 11... Treated water outflow line,
12... Particulate mixed microorganisms, 13... Stirring offering, 14-
・・Excess granular mixed microorganism discharge line

Claims (1)

[Claims] 1. After dissolving a required amount of oxygen in organic wastewater in advance, the water is passed upward through a mixed microbial bed that has become granular due to self-cohesive force, and is treated without breaking the microbial mass. An aerobic biological treatment method for organic wastewater characterized by 2. The method according to claim 1, wherein the mixed microorganism bed is stirred. 3. The method according to claim 1 or 2, wherein the rising flow rate of the liquid is 80 to 250 m/day. 4. The method according to claim 1, 2 or 3, wherein oxygen is dissolved in organic wastewater under pressure of 3 kg/cm^2 or less gauge pressure. 5. The method according to claim 1, 2, 3 or 4, which uses oxygen-enriched gas or pure oxygen.