JPH0367756B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a wastewater treatment method and apparatus for removing solid matter, organic pollutants, nutrient salts, etc. from wastewater such as urban sewage, industrial wastewater, and domestic wastewater. (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 an aerobic biological treatment method in which the microorganisms used require oxygen,
Oxygen is classified as anaerobic biological treatment method. 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, plastics, 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. In addition, floating microorganisms must be separated from treated water in a settling pond 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 that can be dissolved in water. The aerobic sessile method requires oxygen;
Like the planktonic method, it requires a considerable amount of power,
Another disadvantage is that the attached 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. Of these, anaerobic planktonic treatment methods mainly deal with chemical oxygen demand (Chemical oxygen demand).
Oxygen Demand (COD) is used for wastewater with a relatively high concentration of 5000mg/ or more, and for wastewater with a lower concentration than this, anaerobic microorganisms have a tendency to disperse in the water, so they are used. It is difficult to detain them within the facility. In addition, the quality of treated water is determined by biological oxygen demand (Biological Oxygen Demand).
BOD) is 50mg/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 the same type of substances in the inflow water. The purpose of this invention is to grow a new group of microorganisms by providing completely different growth conditions to those of the four methods described above, and to solve the above-mentioned runner-up problem. (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 organisms, and solids formed in the upflow reaction section is retained in the same 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 a downward flow reaction section 1
a, 1b, ... 1e and upflow reaction sections 2a, 2
b, .
b, . . . 1e and 2a, 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 reaction section 2' by the pump 5 and rises gently, then overflows and flows into the first stage downward flow reaction section 1a. It descends through this reaction section 1a, is reversed at the reversing section 3, flows into the first stage upward flow type reaction section 2a, slowly rises through this reaction section 2a, overflows, and enters the second stage downward flow type reaction section 2a. It flows into the reaction section 1b, repeats such rise and fall, and is discharged from the final stage, the upward flow type reaction section 2e. The cross-sectional area of each of the upflow reaction sections 2a, 2b, . Among the solids contained in the inflow water in the upflow type reaction section 2', solids that have a settling speed faster than the rising speed of water are
be detained within. 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, 1b, . . . 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, aerobic microorganisms can grow here. However, the concentration of oxygen supplied in the downward flow reaction section 1a of the same stage is limited to the saturated dissolved concentration of oxygen in water (approximately 8 to 10 mg/when aerated with air); Biological oxygen demand is 100~
Since the amount is between several thousand mg/(100-200 mg/in urban sewage), the amount of oxygen supplied is clearly insufficient. Therefore, aerobic microorganisms and anaerobic microorganisms coexist in the first stage upflow reaction section 2a. In addition, in the reaction section, gentle agitation is constantly occurring due to the upward 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, solid matter and microorganisms form agglomerates, 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 the self-granulating sludge was covered with a thin white film, and microscopic observation confirmed that this film was aerobic filamentous bacteria containing sulfur particles within its cells. Self-granulated sludge is strong enough to be pinched with your fingertips, and its sedimentation speed is extremely fast.
They do not flow out from a, 2b, . . . 2e, and accumulate in the reaction area in a floating state. In the reaction section, these aerobic and anaerobic microorganisms
Some of the organic pollutants and nutrient salts in the wastewater are ingested. 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 characteristics that combine the advantages of aerobic microorganisms and anaerobic microorganisms, and complement 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 solved by self-granulating sludge through the action of aerobic filamentous bacteria. In addition, with only anaerobic microorganisms, there was a problem with the water quality after treatment, but with this invention, it is possible to maintain a sufficiently aerobic condition at the final stage of the facility.
The water quality after treatment shall be equivalent to treatment using aerobic microorganisms. Furthermore, with the floating organism method in general, it has sometimes been difficult to separate suspended microorganisms from treated water, but self-granulating sludge does not cause any problems due to its high settling speed. In addition, clogging, which is a common problem with the sessile method, is usually not a problem because self-granulated sludge is fluidized in the middle of the reaction section by the upward flow in the upflow reaction section. Things that must not happen. Note that in the reversing section 3 that connects the downward flow reaction sections 1a, 1b, . . . 1e to the upward flow 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,
Operation of the inflow pump can be performed 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: An acrylic experimental equipment with a total capacity of 213 cm, including a 5-stage downward flow reaction section and an upflow reaction section. Total hydraulic residence time 4.5 hours. (2) Operating conditions: Processed water volume: 1136/day. Average suspended solids concentration in the upflow reaction section is 7000mg/. (3) Processing performance (unit: mg/)

[Table] (Effects 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 both anaerobic and aerobic microorganisms, so the amount of power required for treatment is , the capacity of the facility is reduced, the separation of microorganisms and treated water becomes simple and reliable, good quality of treated water can be obtained, and problems such as clogging do not occur. Furthermore, the device does not require a special solid-liquid separation device such as a sedimentation 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. 1a, 1b,...1e: Downward flow reaction section, 2
a, 2b,...2e: Upflow reaction section, 3: Inversion section, 4: Inflow pump tank, 5: Inflow pump, 6: Aeration device, 7: Aeration device.

Claims (1)

[Scope of 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 gently raised, and this up flow type reaction section is performed. A wastewater treatment method characterized by retaining self-granulated sludge containing an aerobic microorganism group, an anaerobic microorganism group, and solid matter formed in the same reaction section. 2. A wastewater treatment device characterized in that a downward flow type reaction section provided with an air diffuser and an upward flow type reaction section connected to the lower part of the reaction section are alternately connected in multiple stages.