JPS6320596B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is an aerobic biological treatment method in which aerobic microorganisms are generated to adsorb, oxidize, and decompose pollutants in wastewater in order to purify organic wastewater such as sewage, industrial wastewater, and other wastewater. It is about the method. [Prior Art] Various methods have recently been studied for purifying organic wastewater by attaching aerobic microorganisms to the surface of granular fillers such as sand, anthracite, activated carbon, and plastic filter media. Among these methods, methods in which sewage is brought into contact with air or oxygen in a granular packed bed in a fixed bed state, and the sludge is drained out of the system through intermittent cleaning, can be treated without circulating sludge or water and do not cause bulking. It is attracting attention because of its advantages, such as being able to prevent sludge clogging, having a filtration effect and not requiring a sedimentation separation section, and requiring only the amount of air that is needed to remove BOD since there is no expectation of stirring by air. . This biological treatment method is similar to clarifying filtration, which is often used in water treatment, by passing water through a bed of granular packing material in a fixed bed state. Therefore, the intermittent cleaning method was similar to clarifying filtration. In other words, water backwashing (water backwashing speed: harmonic mean diameter 3
~ ^1.3m3 / ^m2・min for 4mm anthracite)
This method expands the filler layer by about 30% and washes the filler by fluidizing the filler layer. In addition, in order to suppress the occurrence of matte balls, a method of performing air washing before surface washing or water backwashing is also used. [Problems to be Solved by the Invention] However, the principle of the biological treatment method is fundamentally different from that of clarification filtration, and it is highly unlikely that the cleaning method used in clarification filtration would be applicable.
In fact, when the cleaning method used in clarification filtration is used, a considerable amount of cleaning water is required, and in extreme cases, it often exceeds 50% of the amount of treated water, so it cannot be said to be a good cleaning method, and it is not efficient. There were problems, such as the fact that it could not be called a biological treatment method. The present invention takes these conventional problems into consideration and aims to provide an effective method that enables reliable, economical, and simple cleaning and efficient biological treatment. [Means for Solving the Problems] The present invention provides wastewater with one or more granular media selected from various granular media with a specific gravity of 2.2 or less and a particle size of 2 to 10.
When conducting aerobic biological treatment in a tank filled with granular media of 1.5 mm and intermittent cleaning of the granular media, air cleaning is performed in advance at a flow rate of 1.5 m ³ /m ² min or less, and after air cleaning is performed. Air of 1.5m ³ /m ²・min or less and water of 0.6m ³ /m ²・min or less are simultaneously injected from the bottom of the filling tank, and then backwashed with water of 0.6m ³ /m ²・min or less for cleaning. This method of purifying wastewater is characterized by performing the step of discharging wastewater at least twice. [Example] To explain the embodiment of the present invention, first, intermediate water is drained, and the water level in the packed tank filled with granular media with a specific gravity of 2.2 or less and a particle size of 2 to 10 mm is raised above the interface of the filler layer. Preferably, it is lowered to an intermediate drainage port located at 150 to 300 mm. Next, close the intermediate drainage valve,
Perform air cleaning. This air cleaning is performed at an air cleaning rate of 1.5 m ³ /m ² ·min or less, preferably 0.6 to 1.2
m ³ /m ² ·min, and the air cleaning time is preferably 1 to 5 minutes. This operation is mainly aimed at removing the biofilm from the surface layer of the filler layer. While continuing to clean the air, backwash with water at the same time. This water backwash rate is 0.6
m ³ /m ² · min or less, preferably 0.2 to 0.6 m ³ /m ² ·
It is min. The time required for simultaneous air and water cleaning is about 3 minutes. In this operation, the cleaning effects of air and water are used synergistically, and the purpose is to peel off the biofilm from the entire filling material layer and transfer the separated biofilm to the upper part of the filling tank. During this operation, cleaning waste water is not discharged to the outside of the filling tank. Next, air washing is stopped and only water backwashing is performed. The water backwashing speed may be the same as in the previous operation. A suitable time for water backwashing is 1 to 3 minutes. The purpose of this operation is to transfer the detached biofilm from the filler layer to the upper part of the fill tank. After water backwashing is completed, the intermediate drainage valve is opened and the cleaning wastewater is discharged out of the system.
All these processes are considered as one unit, and this is divided into at least 2
Although this process is repeated several times, the discharge of cleaning wastewater is not limited to the intermediate drainage port, and may be performed using other methods such as an overflow type. In addition, in the air or water cleaning step, generally speaking, the higher the cleaning speed of both air and water, the higher the cleaning effect. However, when cleaning at a high cleaning rate of 1.5 m ³ /m ² ·min or higher, mixing of the granular media with supporting members such as gravel occurs, which adversely affects the treatment situation. According to experimental results, the most effective combination of cleaning speeds when simultaneously cleaning air and water is: air: 0.6 to 1.5 m ³ /
m ² ·min, water: 0.2 to 0.6 m ³ /m ² ·min. In addition, the water cleaning speed should be adjusted to 0.2 to ^{0.6 m3} / ^m2 .
If it is set to min, there is no need to discharge cleaning water outside the filling tank during simultaneous air/water cleaning, and there is no need to install a specially shaped buttful plate at the discharge port. The negative effects of leaking the data will also be completely eliminated. Furthermore, the purpose of air cleaning alone can be sufficiently achieved at the same speed as the air cleaning speed when air and water are simultaneously cleaned, and the purpose can be achieved similarly when cleaning water alone. Therefore, in the method of the present invention, the air and water cleaning rates can always be kept at constant values, and no special consideration is required in each operation. In addition, the number of washings is 1 as shown in Figure 1.
Just doing it once will not have much effect. It is better to do this at least twice, preferably three or four times. The granular media used in the method of the present invention include anthracite, plastic filter media,
One or more types of sand selected from granular media such as artificial aggregate, artificial silica sand, and activated carbon are used, and the sand has a true specific gravity of 2.2 or less and a particle size of 2 to 10 mm. Next, when comparing the method of the present invention and the conventional method,
The washing conditions shown in Table 1 resulted in the results shown in Table 2. That is,

[Table] Note-1 The method of the present invention is repeated twice.
-2 Filler layer is 1.5m
-3 The granular medium uses anthracite (harmonic mean diameter 3 mm)

〔Effect of the invention〕

The present invention provides reliable and economical cleaning with a small amount of washing water in a method of adsorbing, oxidizing and decomposing pollutants in wastewater by passing wastewater under aerobic conditions through a filler layer made of a filler for contact with microorganisms. This method enables efficient biological treatment, does not cause bulking, and can be backwashed as appropriate, which prevents sludge clogging and solves the conventional problems, allowing the filler to be constantly submerged in water. If this treatment is carried out, deodorizing measures can be easily taken and operation management can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the cleaning rate and the number of cleaning steps, showing the cleaning effect.

Claims (1)

[Scope of Claims] 1. Sewage is subjected to aerobic biological treatment in a tank filled with one or more types of granular media selected from various granular media with a specific gravity of 2.2 or less and a particle size of 2 to 10 mm, and is treated intermittently. When cleaning granular media,
Perform air cleaning at a flow rate of 1.5m ³ /m ²・min or less,
At the same time with air below 1.5m ³ /m ²・min after air cleaning
Water of 0.6m ³ /m ²・min or less is injected from the bottom of the filling tank, and then backwashed with water of 0.6m ³ /m ²・min or less.
A method for purifying sewage characterized by performing the step of discharging washing wastewater at least twice. 2. The granular medium is selected from granular media such as anthracite, plastic filter media, sand, activated carbon, etc., and the gas is preferably introduced into the filler layer from an aeration device provided at the bottom of the filler layer. A method for purifying wastewater according to claim 1, wherein the wastewater is treated while maintaining an air condition. 3. The wastewater purification method according to claim 1 or 2, wherein the cleaning wastewater after the cleaning is completed is discharged from the upper part of the interface of the filler layer and treated. 4. Claim 2 or 3, wherein the cleaning step is performed in advance by performing intermediate water drainage to lower the water level in the filling tank to a position above and near the filling material layer interface to perform air cleaning. Method for purifying sewage as described in section.