JPS63242394A - Treatment of drainage and equipment therefor - Google Patents

Abstract

PURPOSE:To prevent clogging by lowering drainage while solubilizing oxygen in drainage and furthermore bringing it into contact with aerobic microorganisms in an up flow type reaction part. CONSTITUTION:Both downflow type reaction parts 1a-1e and up flow type reaction parts 2a-2e are communicated in the reverse parts 3 of the lower parts thereof and alternately joined in many steps. Drainage is introduced into the lower part of the up flow type reaction part 2' with a pump 5, raised and thereafter overflowed and introduced into the downflow type reaction part 1a and lowered therethrough. Then it is reversed in the reverse part 3 and introduced into the up flow type reaction part 2a and raised therethrough, overflowed and introduced into the downflow type reaction part 1b in a second step. It is discharged from the up flow type reaction part 2e in the final step by repeating this raising and lowering. Thereby treated water having good quality is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a wastewater treatment method for removing solid matter, organic pollutants, nutrient salts, etc. from wastewater such as urban sewage, industrial wastewater, and domestic wastewater. Regarding equipment.

(Prior technology) Wastewater treatment facilities such as urban sewage often use biological treatment methods, which basically use microorganisms that ingest and grow various pollutants to perform treatment. It is something to do. This biological treatment method is classified into an aerobic biological treatment method in which the microorganisms used require oxygen, and an anaerobic biological treatment method in which the microorganisms used do not like oxygen. Furthermore, both aerobic and anaerobic biological treatment methods are significantly different from the suspended biological treatment method, which uses microorganisms suspended in water, and the sessile biological method, which uses microorganisms attached to the surfaces of crushed stones, plastic, etc. Separated.

(Problems to be solved by the invention) Aerobic suspended organism methods such as activated sludge methods generally require supply of oxygen, etc. in the air in order to grow microorganisms that require oxygen. A considerable amount of power is required to operate the blower, etc. Furthermore, floating microorganisms must be separated from treated water in a settling tank or the like, but various conditions often deteriorate the sedimentation properties of floating microorganisms, making separation difficult. Furthermore, even if we attempt to grow microorganisms at high density and reduce facility capacity, there is a certain limit because there is a limit to the concentration of oxygen dissolved in water. The aerobic sessile organism method requires oxygen and, like the floating organism method, requires a considerable amount of power, and also has the disadvantage that the sessile organisms gradually increase and cause clogging.

Next, anaerobic biological treatment methods generally have the disadvantage of requiring a reaction tank several times larger than that of aerobic biological treatment methods. Among them, anaerobic planktonic treatment method mainly deals with chemical oxygen demand (Chemical Oxygen Demand,
C0D) It is used for wastewater with a relatively high concentration of 5000 mg #1 or more, and for wastewater with a lower concentration than this, anaerobic microorganisms have a tendency to disperse in the water, so these should not be used within the facility. It is difficult to detain them. In addition, the quality of treated water is determined by biological oxygen demand (Biological Oxygen Demand).
ygenDemand, BOD) of 50 mg/Q or more, which is inferior to aerobic treatment. The treated water quality of the anaerobic sessile organism method is similar to that of the planktonic organism treatment method, and clogging occurs due to solid matter in the inflowing water.

Compared to the above four methods of microbial growth conditions, this invention
The purpose is to grow a new group of microorganisms by providing completely different growth conditions and to solve the above-mentioned drawbacks.

(Means for Solving the Problems) The first aspect of the present invention to achieve the above object is a wastewater treatment method, in which the wastewater is lowered while dissolving oxygen in the wastewater in a downward flow reaction section, and then The wastewater is slowly raised in the upflow reaction section, and the self-granulated sludge containing aerobic microorganisms, anaerobic microorganisms, and solids formed in the upflow reaction section is retained in the reaction section. It is characterized by:

The second aspect of this invention is an apparatus for carrying out the above method, in which a downward flow reaction section provided with an aeration device and an upward flow reaction section connected to the lower part of this reaction section are alternately arranged in multiple stages. It is characterized by being connected to.

(Example) This invention will be described below based on an example shown in the drawings.

The drawing shows an example of the device, with downward flow reaction sections la and lb.
,...1e and upflow reaction sections 2a, 2b,...2
e are communicated with each other at the inverted part 3 at the bottom thereof, and these two reaction parts 1a, lb, ... 1e and 2
A, 2b, . . . 2e are alternately connected in multiple stages. The waste water from the inflow pump tank 4 flows into the lower part of the pre-treatment upflow type reaction section 2' by the pump 5 and gradually rises.
It overflows and flows into the first stage downward flow type reaction section 1a, descends through this reaction section 1a, is reversed at the reversing section 3, flows into the first stage upward flow type reaction section 2a, and this reaction It gradually rises through the section 2a, overflows, and flows into the second stage downward flow reaction section 1b, and thereafter repeats such rising and falling and is discharged from the final stage upward flow reaction section 2e.

The cross-sectional area of each of the upflow reaction sections 2a, 2b, . Among the solid substances contained in the inflow water in the countercurrent reaction section 2', those having a settling velocity faster than the rising velocity of the water are retained in the reaction section 2'. However, if there are no solids in the inflow water, or if there is only a small amount of solid matter, the upstream reaction section 2' for pretreatment may be omitted, and the upper part of the first stage downward flow reaction section 1a may be used. It is also possible to allow wastewater to flow directly into the tank.

An aeration device 6 is installed at the bottom of each stage of the downward flow type reaction sections 1a, lb, . . . 1e, and aeration with air or oxygen is performed to dissolve oxygen in the water. The solid material that has flowed into the first-stage downward flow type reaction section 1a is not retained in the same reaction section, but directly flows into the first-stage upward flow type reaction section 2a. Since the water flowing into the reaction section 2a contains oxygen, it is possible for aerobic microorganisms to proliferate here. However, the oxygen concentration supplied in the downward flow reaction section 1a of the same stage has a limit of 1 degree of saturated dissolution of oxygen in water (approximately 8 to 1.0 mg#l when aerated with air); Since the biological oxygen demand of normal wastewater is between 100 and several thousand mgIQ (100-200mgIQ in urban sewage),
Oxygen supply is clearly insufficient. Therefore, in the first stage upflow reaction section 2a, an aerobic microorganism group and an anaerobic microorganism group coexist. In addition, in the reaction section, gentle agitation is constantly occurring due to the downward flow, and the solid matter in the wastewater and the microorganisms mentioned above are constantly in repeated gentle contact with each other.

It was confirmed that under such an environment, solid matter and microorganisms self-granulate. In other words, the solid matter and microorganisms form an agglomerate, forming a spherical shape with a diameter of about 2 to 20 mm. This spherical material is hereinafter referred to as self-granulating sludge. The inside of self-granulated sludge is pitch black anaerobic sludge, and a large number of anaerobic microorganisms grow in this part. The surface of self-granulating sludge is covered with a thin white film, which can be seen under a microscope 1i1'! By inspection,
This coating was confirmed to be aerobic filamentous bacteria containing sulfur particles within the cells.

Self-granulated sludge has such strength that it can be pinched with fingertips, and its sedimentation speed is extremely fast.
It does not flow out and accumulates in a suspended state in the reaction area. In the reaction section, these aerobic and anaerobic microorganisms ingest some of the organic pollutants and nutrient salts in the wastewater. Some solid substances and microorganisms flow into the first stage downward flow type reaction part 1a without becoming self-granulated sludge in the pretreatment reaction part 2', but in the second stage and subsequent stages the upward flow Self-granulating sludge also grows in the reaction sections 2b...2e by the same mechanism as described above. Through the process described above, organic pollutants in the wastewater continue to decrease, and the desired quality of treated water can be obtained in the final stage.

Self-granulating sludge has the characteristics of combining the advantages of aerobic microorganisms and anaerobic microorganisms and complementing each other's problems. In other words, anaerobic microorganisms make up a large portion of self-granulating sludge and coexist with aerobic microorganisms to remove organic pollutants, so the amount of oxygen consumed is lower than when only aerobic microorganisms are used. It is possible to reduce power costs.

Since it is mainly composed of anaerobic microorganisms, it is possible to grow microorganisms at high density without being limited by dissolved oxygen concentration, and the capacity of the facility can be reduced. The problem when using anaerobic microorganisms for low-concentration wastewater, which is the tendency for microorganisms to disperse into water, can be resolved by using self-granulating sludge through the action of aerobic filamentous bacteria. In addition, using only anaerobic microorganisms had problems with the water quality after treatment, but with this invention, a sufficiently aerobic condition can be maintained at the final stage of the facility, and the water quality after treatment can be improved by using aerobic microorganisms. The process will be equivalent to the one previously used. Furthermore, in general suspended organism methods, it sometimes becomes difficult to separate suspended microorganisms from treated water, but self-granulating sludge does not cause any problems due to its fast settling speed. In addition, clogging, which is a problem with the general sessile method, is not usually a problem because self-granulated sludge is fluidized in the middle of the reaction section by upward flow in the upflow reaction section. .

In addition, in the reversing section 3 that connects the downward flow reaction sections 1a, lb, . . . 1e to the upflow reaction sections 2a, 2b, . This is unavoidable, and some of the self-granulating sludge tends to accumulate in this area. If this is left unattended, it will eventually cause clogging, so when the inflow pump 5 is stopped, aeration holes 7 are installed from the bottoms of the upward flow reaction sections 2a, 2b, ... 2e for stirring. are doing. Therefore, by slightly increasing the capacity of the inflow pump tank 4, the inflow pump can be operated intermittently.

By aerating and stirring the upflow reaction section when the inflow pump is stopped, the accumulated self-granulating sludge can be fluidized again and clogging can be prevented. At this time, since the inflow pump is stopped, the fluidized self-granulated sludge does not flow out from the reaction section.

(Experimental Example) An example in which urban sewage (after sedimentation treatment) was treated by the method of this invention is shown below.

(1) Equipment Specifications Acrylic experimental equipment with a total capacity of 213Q, including a five-stage downward flow reaction section and an upflow reaction section.

Total hydraulic residence time 4.5 hours.

(2) Operating conditions Processed water amount: 1,136 fl/day. The average suspended solids concentration in the upflow reaction section is 7,000 μ/Q.

(3) Treatment performance (unit ■/Q) (Effect of the invention) As described above, according to the present invention, self-granulating sludge containing both anaerobic and aerobic microorganisms is generated by taking advantage of the advantages of anaerobic and aerobic microorganisms. As a result, the amount of power and facility capacity required for treatment is reduced, the separation of microorganisms and treated water is simple and reliable, good quality of treated water can be obtained, and problems such as clogging do not occur. In addition, the device does not require a special solid-liquid separation device such as a settling tank or a device for returning separated microorganisms, and has a very simple structure, so the number of personnel required for maintenance and management can be reduced.

[Brief explanation of drawings]

The drawing is a schematic diagram showing an embodiment of the present invention. la, lb,...1e: Downward flow reaction section 2a,
2b,...2e: Upflow reaction section 3: Inversion section 4: Inflow pump tank 5: Inflow pump 6: Aeration device 7: Aeration device

Claims (1)

[Claims] 1. In a downward flow type reaction section, the waste water is lowered while dissolving oxygen in the waste water, and then in an upward flow type reaction section, the waste water is slowly raised, and this up flow type reaction is performed. A wastewater treatment method characterized by retaining self-granulated sludge containing aerobic microorganisms, anaerobic microorganisms, and solid matter formed in the reaction section. 2. A wastewater treatment device characterized in that a downward flow reaction section provided with an aeration device and an upward flow reaction section connected to the lower part of this reaction section are alternately connected in multiple stages. .