JP2894894B2 - Water treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment method for biologically treating raw tap water whose source is relatively polluted river water, lake water or groundwater.

[0002]

2. Description of the Related Art In recent years, the effects of eutrophication and an increase in the concentration of dissolved organic substances have been observed in raw tap water, and in the conventional water purification treatment process mainly composed of coagulation sedimentation and rapid sand filtration, the problem of unpleasant taste of tap water has been raised. It was not possible to sufficiently cope with the increase in nitrogen compounds such as ammonia and nitrogen, trace organic substances including trihalomethane. Therefore, for the purpose of removing ammonia nitrogen, odorous substances, and the like of tap water having deteriorated water quality, water quality improvement has been put to practical use by biological treatment of a catalytic oxidation method using a honeycomb tube or a rotating disk. Furthermore, in order to increase the efficiency of biological treatment, a biological filtration method using a granular medium of various materials such as sand, gravel, anthracite, activated carbon, ceramics, and plastics has been studied (Japanese Patent Publication No. 1-54115). , 42nd National Water Research Conference 4-10).

[0003]

The biofiltration system forms a biofilm on a packed bed composed of a granular medium, so that the amount of retained organisms in the system is larger than that of a catalytic oxidation system using a honeycomb tube or a rotating disk. It is characterized by being resistant to load fluctuation of raw water and capable of removing suspended substances simultaneously with the removal of soluble substances. However, the suspended substances inhabit the surface of the granular medium when they are removed, and cover the surface of microorganisms useful for purification and form a new surface. Hinder. For this reason, when the concentration of the suspending substance in the liquid to be treated reaches a certain level or more,
There is a disadvantage that the biological treatment function of the biological filtration system is reduced. On the other hand, the packed bed formed by the granular medium has a drawback that the head loss increases as the suspended substance is trapped and accumulated, and the water level rises, so that the flow rate cannot be easily increased. In particular, a granular medium having a small particle size such as sand, activated carbon, and anthracite has a large tendency. further,
In the case of granular media such as sand, gravel, anthracite, activated carbon, ceramics, and plastics, microorganisms attached to the surface of the granular media contribute to purification of the liquid to be treated, but the liquid to be treated does not flow to the solid inside of the granular medium. However, there are various problems such that the inside of the granular medium is not effectively used, and as a result, most of the volume of the packed bed that occupies most of the processing apparatus is not effectively used.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides a water treatment method which can be effectively used for purifying a liquid to be treated even inside a solid granular medium, and which can shorten the treatment time and reduce the installation area of the apparatus. It is something to offer.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the suspension liquid in the water to be treated has been removed, so that the liquid to be treated has a high permeation flowability and can be internally circulated. It has been found that the liquid to be treated can be purified in a short time without any problem by passing water through the packed bed of the granular medium at high speed, and based on this finding, the present invention has been reached. That is, in the present invention, in FIGS. 2 and 3, the packed layer 3 of the granular medium 2 for supporting the microorganisms in the reaction tank 1 is formed below the liquid level, and the liquid 4 to be treated is placed below the reaction tank 1 from above. In the biological filtration method in which the liquid is passed in countercurrent and the removal of the suspending substance and the biological treatment are performed simultaneously, the suspension in the liquid to be treated 4 is preliminarily performed before flowing the liquid 4 to be treated into the reaction tank 1. Substances are removed by the solid-liquid separation device 5,
Next, the liquid to be treated 4 is placed in the upper part of the reaction vessel 1 in a reaction vessel 1 in which a packed layer 3 of a granular medium 2 having a high permeation flow rate for carrying microorganisms and capable of internally flowing the liquid to be treated is formed below the water surface. This is a water treatment method in which water is passed at a high speed of 600 m / day or more. As a method for removing the suspending substance, a solid-liquid separation step such as precipitation, sand filtration, biological filtration, or microfiltration membrane may be provided before the liquid to be treated flows into the reaction tank 1. The granular medium 2 can be produced according to the method described in JP-B-62-11637, and the resulting granular medium is shown in FIG. This granular medium 2 has a length of 20
It is composed of a lump aggregate of short fibers 6 of mm or less.

In FIG. 3, reference numeral 7 denotes a gas blowing pipe,
8 is treated water. By the way, when the water flow speed is 6
The reason for the high speed of not less than 00 m / day is that the granular medium 2 having a high permeation flow rate for carrying microorganisms and capable of internally flowing the liquid to be treated is provided in the packed bed 3. In some cases, the above effects cannot be obtained even if the water flow speed is 600 m / day or more.

[0007]

[Action] Decomposition and removal of soluble components by the biological filtration method is the action of microorganisms attached and inhabiting the granular medium. However, the conventional granular medium uses only the surface but does not effectively use the inside. Therefore, increase the concentration of microorganisms in the reaction tank,
As a method for increasing the treatment efficiency, the granular media used in the biological filtration method, those having fine irregularities on the surface, those having pores, or those having a fine particle size were considered, The granular medium uses only the surface, and in that respect, a large part of the volume in the reaction tank is not effectively used as in the related art. According to the present invention, the water treatment is carried out using a packed bed made of a granular medium having a high permeability and a high permeability after the removal of the suspending substances in the liquid to be treated, so that the volume of the reaction tank can be reduced. Can be used effectively, the volume load and the processing speed can be set higher than in the past, and the size of the processing apparatus can be reduced.

[0008]

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Example 1 In a column made of vinyl chloride and having an inner diameter of 30 cm and a height of about 2 m, 5
Granular media (average diameter 5.8mm, specific gravity 1.38) made of polyester fiber of about 20μm diameter cut into mm length, anthracite (average diameter 5.1mm, specific gravity 1.45), ceramic ball (average diameter 5.5mm, specific gravity 2.25, main component) SiO ₂ , Al ₂ O ₃ )
Is filled to a height of 1m (filled amount of about 70 liters)
The following experimental results were obtained by passing water in a downward flow mode. (1) raw water ... river water to remove suspended material and sand filtration, NH ₄ ⁺ and -N concentration NH ₄ Cl those that have been adjusted to 2.0 mg / l NH ₄ ⁺ -N: 2.0mg / l SS : 3.6 mg / l alkalinity: 34.0 mg / liter (2) passing water condition nitrogen ^{_{load: 0.4 ~4.0 kg-NH 4 +}} -N / m 3 / day water flow rate: 200 to 2000 m / day space velocity: 8.3 8383 1 / hour (3) Result Nitrification rate Nitrification rate (water flow rate (water flow rate 600 m / day) 2000 m / day) Granular medium made of polyester fiber 98 (%) 94 (%) Anthracite 83 (%) It believed 56 (%) ceramic balls 79 (%) 53 (%) example 1 in water flow rate increased from 600 to 2000 m / day, and nitrogen load even excessive and 4.0kg -N / m ³ / D 0.4 Despite the increase in size, the nitrification rate of the granular medium composed of polyester fibers is stable at 94% or more. On the other hand, as for the anthracite and the ceramic balls, the nitrification rate is greatly reduced as the water flow rate and the nitrogen load are increased, and the difference in the treatment results due to the difference in the structure of the granular medium is remarkably apparent.

Comparative Example 1 A column made of vinyl chloride and having an inner diameter of 30 cm and a height of about 2 m
Granular media (average diameter 5.8mm, specific gravity 1.38), anthracite (average diameter 5.1mm, specific gravity 1.45), ceramic balls (average diameter 5.5mm, specific gravity 2.25, main component Sio) made of polyester fibers of about 20μm in diameter cut into mm length ₂ , Al ₂ O ₃ ) were each filled to a height of 1 m (filling amount: about 70 liters), and water was passed in a downward flow system to obtain the following experimental results. (1) raw water ... suspended substances in river water NH ₄ ⁺ -N those adjusted to 2.0 mg / liter NH ₄ Cl and NH ₄ ⁺ -N concentration in the intact: 2.0 mg / l SS: 21.0 mg / Liters Alkalinity: 36.6 mg / L (2) Water flow conditions Nitrogen load: 0.4 to 1.6 kg-NH ₄ ⁺ -N / m ³ / day Water flow speed: 200 to 800 m / day Space velocity: 8.3 to 33.3 1 / Time (3) Result Nitrification rate Nitrification rate (water flow rate (water flow rate 200 m / day) 800 m / day) Granular medium made of polyester fiber 94 (%) 77 (%) Anthracite 94 (%) 71 (% ) Ceramic balls 93 (%) 72 (%) In Comparative Example 1, the nitrification rates of 200 m / day and 800 m / day were compared. When water is passed without removing the suspended solids (SS) in the raw water, the granular medium made of polyester fiber also increases the water flow speed from 200 m / day to 800 m / day,
As in the case of anthracite and ceramic balls, the nitrification rate was greatly reduced. Although there is a slight difference in the nitrification rate depending on the granular medium, the nitrification rate is remarkable due to the difference in the structure of the granular medium as compared with the case where the suspending substance is removed and the liquid to be treated is placed in the reaction tank as in Example 1. There is no significant difference. In other words, the filling tank made of a granular medium having a structure in which the liquid to be treated can flow through the inside of the tank only exhibits an effect by removing suspended substances and then passing water through the tank.

[0010]

As described above, according to the present invention, after a suspended substance in a liquid to be treated is removed in advance, a packed bed is formed in a reaction tank using a granular medium having an internal flow path. By using the biological filtration method, the inside of the granular medium can be utilized for the treatment, and the large space occupied by the internal volume of the granular medium in the reaction tank can be effectively utilized. As a result, a stable treated water quality can be obtained even when a considerably larger load is applied than in the conventional method. Further, since the processing apparatus can be considerably reduced in size, the installation area can be reduced. Further, since the height of the apparatus can be reduced, there is an advantage that the energy required for pumping can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a granular medium of the present invention.

FIG. 2 is an explanatory diagram showing a processing flow in the present invention.

FIG. 3 is a sectional view of a reaction tank in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Granular medium 3 Packing layer 4 Liquid to be treated 5 Solid-liquid separation step 6 Short fiber 7 Gas blowing pipe 8 Treated water

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C02F 3/06 C02F 3/10 C02F 3/34 101

Claims (2)

(57) [Claims] 1. A packed bed composed of a granular medium for supporting microorganisms is formed below the liquid surface, and the liquid to be treated is passed downward from the upper part of the reaction tank to remove suspended substances. In the biological filtration method in which the biodegradation of the soluble component and the biodegradation of the soluble component are simultaneously performed in the packed bed, the suspended substance in the liquid to be treated is removed before the liquid to be treated flows into the reaction tank, and the microorganisms are supported. The liquid to be treated is flowed from the upper part of the reaction tank at a high flow rate of 600 m / day or more into a reaction tank in which a packed layer composed of a granular medium having a structure through which the liquid to be treated can flow is formed below the liquid level. A water treatment method characterized by passing through. 2. The water treatment method according to claim 1, wherein the granular medium comprises a mass of short fibers.