JPH0373358B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Application of the Invention) The present invention mainly applies to household gray water, industrial wastewater,
A wastewater treatment method in which wastewater such as food processing wastewater is biologically treated in a treatment medium containing wood chips as a main component, and more specifically, notes on the wastewater treatment medium preferably used in such a treatment method. This relates to the addition method. (Background of the Invention) In recent years, methods that utilize the activities of various microorganisms for fermentation, decomposition, digestion, overtreatment, deodorization, etc. of wastewater have been put into practical use in various fields. However, on the other hand, a large amount of sludge is generated, and appropriate treatment and disposal of this is required. The main chemical compositions, contents, and physicochemical properties of various sludges are shown in Tables 1 to 3 below.

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[Table] In general, there are many difficulties in properly disposing of these various sludges, including the applicability of thickening and dewatering, various operational problems, and the cost of final disposal. Based on biological knowledge, the present inventors have conducted various studies on such wastewater, and have found that wood chips are extremely excellent as a culture substrate for microorganisms, and no sludge is observed. It has been discovered that this processing device using wood chips has an extremely simple structure and can function stably over a long period of time with almost no need for maintenance or renewal (replacement). In the microbial treatment of sludge wastewater, the treatment mechanism is that the wood chips create optimal environmental conditions as a treatment medium layer and treat wastewater extremely efficiently without generating sludge in the layer. This is presumed to be due to the coexistence of microorganisms and their mutual interaction to carry out biochemical processes such as decomposition, digestion, and fermentation. Must be avoided. The following factors are presumed to create such optimal environmental conditions for the wood chips having a diameter of 0.2 to 5 mm. (a) It has a large specific surface area of about ^200m2 , so it has appropriate water retention and breathability. (b) The pores and surface structure grown in a natural environment are optimal for the coexistence of microorganisms. (c) Uniform water permeation and dispersion throughout the treatment medium layer prevents uneven flow within the layer (commonly known as water path). (d) During the process of adding wastewater to the treatment medium layer, the wastewater that permeates through the layer introduces an appropriate amount of air from the surface of the layer, allowing aerobic microorganisms to survive and operate in an anaerobic atmosphere within the layer. We are creating an enabling environment. Therefore, if the anaerobic atmosphere in the layer is thought to be too strong, it is also a good idea to forcibly ventilate from the lower layer direction. Based on this knowledge, the present inventors have filed patent applications for various proposals regarding wastewater (sludge) treatment methods that use wood chips as the main component of the treatment medium to allow microorganisms to propagate and become active. It has been provided. This wastewater treatment method basically involves pouring 1 volume part of the wastewater to be treated into 1 to 10 volume parts of a treatment medium layer whose main component is wood chips with a constant particle size, and treating it at ambient temperature. The apparatus for the treatment is typically constructed in such a way that a treatment medium is filled in a tank and waste water is poured into the tank. Note that the treatment effect can be improved by aerating the treatment medium. The wood chips used in such microbial engineering treatments are used with their particle size, particle size distribution, and wood component composition falling within desired ranges. 0.5~3
Should be in the mm range. If the particle diameter is less than 0.2 mm, it will easily become clogged when used as a material, etc.
Moreover, if it is more than 5 mm, the surface area per unit area as microbial culture material becomes small and sufficient processing capacity cannot be obtained. Also, particle size distribution: 0.2-1mm: 30%, 1-2mm: 30%
%, 2-3mm: 40%, and the component composition is cellulose 60-65%, lignin 15-25%, pentozan.
Those containing 15 to 25% and moisture content of 11 to 16% are preferably used. In addition, the treatment medium mainly composed of wood chips may be the wood chips alone, or may be partially replaced with a porous inorganic material such as zeolite. percentage of 40
% or less, preferably 25% or less. By the way, when performing the above-mentioned treatment, if water is sprinkled or normally poured from the upper part of the treatment tank according to the general method of filling the treatment medium with water to be treated, the treatment medium, which is wood, There was a problem in that clogging occurred near the upper surface of the layer of fine particles (hereinafter referred to as wood particles, including the case where some of them were made of inorganic material), which significantly reduced the permeation rate of wastewater. The cause of such surface clogging is presumed to be the generation of suspended matter in the wastewater and aerobic activated sludge that is generated due to the quality of the wastewater. In addition, when the free surface is submerged in water, anaerobic sludge is generated, and it is assumed that this sludge adheres and accumulates on the free surface, resulting in clogging. Therefore, when using the above-mentioned general pouring method, operations such as clearing the surface or stirring the layer are also required in order to eliminate clogging of the surface of the processing medium layer. (Objective of the Invention) The present invention was made in view of the current situation, and an object of the present invention is to provide a method for injecting wastewater into a packed bed of wood chips extremely efficiently and while maintaining conditions suitable for the breeding environment of microorganisms. With the goal. (Summary of the Invention) The gist of the present invention to achieve the above object is to pour wastewater to be treated into a treatment medium layer made of wood chips or inorganic porous particles mixed therein. A method for treating wastewater in which a biological treatment is carried out using a method for treating wastewater, characterized in that the addition of the wastewater is carried out by discharging the added wastewater into a treatment medium without directly contacting the atmosphere. It is in. In this way, if we use a method in which the wastewater is not brought into direct contact with the atmosphere, but is instead brought into contact with the air by suctioning the air indirectly, sludge will not be generated, and the sludge added as suspended matter will be digested. , clogging does not occur near the injection area. This means that clogging is likely to occur if wastewater is simply poured onto the upper free surface of the treatment medium layer, but it is necessary to prevent the poured wastewater from coming into direct contact with the atmosphere. It is also supported by experimental results that clogging becomes less likely to occur if a cover is placed over the surface of the area with a diameter equivalent to twice that, and if air is sucked into the layer from the outside around the cover. However, in practice, the above conditions are usually satisfied by inserting the wastewater injection pipe into the inside of the treatment medium layer. It is preferable to use a water pipe at a depth of 10 to 50 cm or more from the upper surface of the layer, and preferably at a height of about 80 cm or more from the bottom of the layer. This is because it is necessary to effectively create anaerobic conditions and aerobic conditions by taking into consideration the entrainment of air when adding wastewater. The shape of the water injection pipe used in the method is, for example, such that the lower end inserted into the processing medium is open, and
In addition, it is possible to use a round cylindrical tube or the like in which a radial through hole is formed in the peripheral wall inside the processing medium, and the size of the through hole is 10 to 16 mm, and the hole interval is 40 to 40 mm.
It is preferably about 60 mm. The water injection pipe in the method of the present invention is typically inserted vertically downward from the center of the upper surface of the treatment medium layer, but depending on the capacity and spread of the treatment medium layer, multiple The water injection pipes may be inserted and arranged at appropriate intervals, and the point is that the wastewater discharged from the through holes of the water pipes into the surrounding area spreads out in a parachute-like manner and permeates downward. do it. The wastewater to be treated by the method of the present invention mainly refers to household gray water, industrial wastewater, food processing wastewater, etc., but if it contains a large amount of insoluble inorganic substances, especially sand, it may be treated by the precipitation method. It is preferable that the sludge be removed by pre-treatment such as the like, and as a preferred practical example, it is desirable that the sludge concentration in the wastewater is diluted as necessary to be about 1000 ppm or less. (Embodiment of the invention and its effects) The present invention will be described below based on an embodiment carried out using the illustrated apparatus. FIG. 1 shows an example of the wastewater injection method according to the present invention. In the figure, 1 is a water injection pipe for introducing wastewater;
2 indicates wood chips, and 3 indicates a treatment tank filled with the wood chips. In such an apparatus, when wastewater to be treated is introduced into the treatment tank through the water injection pipe 1, the wastewater comes into contact with the wood chips 2, and either adheres to the surface of the chips or permeates into the porous parts. Furthermore, when the treated water moves to the lower part of the filling tank, air is introduced through the wooden strips in contact with the atmosphere at the upper part of the treatment tank 3, making the treatment tank 3 appear as if it were breathing. Therefore, an air replenishment action suitable for a microbial breeding environment is performed. In addition, by making the buried part of the water injection pipe porous, it has the advantage of being able to cope with sudden changes in the flow rate of wastewater injection by expanding the contact area between the wood chips 3 and the water, which can sufficiently cope with excessive water flow. be. Note that 4 is a wastewater inlet, and 5 is a drain pipe provided at the bottom of the tank 3. Furthermore, FIG. 2 is for showing the shape of a part of the water injection pipe 1, particularly the porous part. The slightly larger diameter is connected to the 7th part of the porous pipe,
From the viewpoint of durability, it is desirable to use synthetic resin tubes for these tubes. Note that the water injection pipe may be of other types, and FIG. 3 shows another example of this type in which the periphery of the pipe on the surface of the processing medium is covered with a cover 8. The present inventors conducted experiments under the following conditions using the apparatus shown in FIG. 1. (Experiment) Apparatus used In the apparatus with the structure shown in Fig. 1, processing medium Wood particle size range 0.2 to 5 mm Horizontal cross-sectional area 1.0 m ² layers Height 3.0 m Water injection pipe Diameter 10 cm Insertion depth 150 cm Top position of porous hole 30 cm Experimental method: Standard domestic gray water with a BOD of 150 and a pH of 7 was poured from the top of the tank through a cylinder pipe at a flow rate of 20/min for 1 minute, followed by intermittent pouring with 10-minute pauses, and treated at room temperature. . Through the above operations, all of the wastewater was digested extremely quickly, and after 24 hours, almost no treatment residue was observed in the wood debris layer in the treatment tank. The pH of the effluent from the treatment tank was 6.0, and the BOD value was 8, and the BOD value was significantly reduced compared to the wastewater before treatment. Further, Table 4 below shows the results of test examples conducted with different target sludges and treatment conditions, and in all cases, a sufficient reduction in BOD was achieved.

[Table] In addition to the above examples, household gray water, industrial wastewater,
Even when food processing wastewater and the like were treated in the same manner as in these Examples, all of the treated wastewater satisfied the standards for wastewater treatment. BOD300, PH7.5 food processing wastewater ^10m2 particle size 0.2
~5 mm of wood chips were filled into the treatment tank 3 and poured into the tank from the top at a flow rate of 300/hour for 12 hours. Thereafter, the injection was stopped, and the operation of blowing air from the bottom of the treatment tank at a flow rate of 60/hour for 12 hours was repeated to perform microbial treatment at room temperature. All of the wastewater was digested extremely quickly, and almost no treatment residue was observed in the curtain layer in the treatment tank after 24 hours. PH of the liquid discharged from the treatment layer
was 6.3, and the BOD value was 10. (Effects of the Invention) According to the method of the present invention, it is possible to suitably inject wastewater into a treatment medium containing wood chips as a main component, thereby providing a favorable microbial breeding environment within the treatment medium. The advantages of this type of wastewater treatment in practical use are extremely large, especially since no other operations are required other than the addition of wastewater and appropriate aeration. There is.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a processing medium filling tank used in the method of the present invention, FIG. 2 is a view showing a water injection pipe for introducing waste water, and FIG. 3 is a view showing an example of the type of the injection pipe.

Claims (1)

[Scope of Claims] 1. A wastewater treatment method in which biological treatment is performed by pouring wastewater to be treated into a treatment medium layer in which wood chips or inorganic porous particles are mixed therein. A wastewater treatment method characterized in that the added wastewater is discharged into a treatment medium without coming into direct contact with the atmosphere. 2. The method for treating wastewater according to claim 1, characterized in that the wastewater is injected at a depth of 10 to 50 cm or more from the upper surface through a water injection pipe inserted into the treatment medium.