Waste water treatment method

Abstract

To provide a waste water treatment method more excellent in treatability.SOLUTION: This apparatus has a waste water supply tank 2 for impregnating the absorbent medium 1 with water in the waste water W, and a heat treatment mechanism 3 for raising the temperature of the absorbent medium 1, and the absorbent medium 1 impregnated with water is transferred to the heat treatment mechanism 3 to raise the temperature and evaporate the water and thermally decompose the organic components in the waste water W, and the raised absorbent medium 1 is sent to the waste water supply tank 2. The temperature (amount of heat) of the absorbent medium after raising the temperature can be transferred to the newly supplied waste water for heat treatment. Combustible gas generated from the waste water W may be used as fuel. The waste water supply tank 2 may have an inert gas atmosphere.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wastewater treatment method (waste treatment method) with improved treatability. [Background technology]

[0002] Conventionally, there have been proposals relating to methods and treatment devices for organic wastewater (Patent Document 1). That is, this proposal aims to provide a method for treating organic wastewater that can easily control the amount of powdered activated carbon used in treating organic wastewater containing persistent organic matter, thereby reducing operating costs. Therefore, it was discovered that there is a correlation between the electrical conductivity or chloride ion concentration in the biologically treated water and the soluble COD concentration, and the soluble COD concentration is estimated from the measured electrical conductivity or chloride ion concentration in the biologically treated water, and the required amount of powdered activated carbon is determined based on the COD equilibrium adsorption amount of powdered activated carbon corresponding to that COD concentration. In response to this, there was a demand for a wastewater treatment method with better treatability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2015-221424 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, the present invention aims to provide a wastewater treatment method with superior treatability. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention takes the following technical measures. (1) The wastewater treatment method of this invention is characterized by comprising a wastewater supply tank for impregnating an absorbent medium with the moisture in the wastewater, and a heat treatment mechanism for heating the absorbent medium, in which the moisture-impregnated absorbent medium is transported to the heat treatment mechanism and heated to evaporate the moisture and thermally decompose (e.g., carbonize) the organic components in the wastewater, and the heated absorbent medium is sent to the wastewater supply tank. The inner wall surface of the heat treatment mechanism may be made of Si-C, for example.

[0006] This wastewater treatment method includes a wastewater supply tank that impregnates an absorbent medium with the moisture in the wastewater, and a heat treatment mechanism that heats the absorbent medium. The moisture-impregnated absorbent medium is transferred to the heat treatment mechanism and heated to evaporate the moisture and thermally decompose the organic components in the wastewater. Therefore, the moisture in the wastewater supplied to the wastewater supply tank is impregnated into the absorbent medium and heated in the heat treatment mechanism, and the moisture in the wastewater can be evaporated and the organic components can be thermally decomposed in the heat treatment mechanism.

[0007] In addition, the water evaporated from the wastewater and the organic components that have been thermally decomposed are sent to an (electrolytic) scrubber mechanism where they undergo a purification process (using electrolytic water, activated carbon, etc.). Furthermore, since the heated absorbent medium is sent to the wastewater supply tank, the temperature (calorific value) of the heated absorbent medium can be transferred to the newly supplied wastewater for heat treatment.

[0008] Furthermore, since the heat treatment mechanism is supplied with an absorbent medium that has been impregnated and dispersed with water, rather than water itself, damage caused by direct contact of the liquid with the heat treatment mechanism (kettle) itself can be reduced. The absorbent medium also functions as a medium, allowing the evaporation of water in the wastewater and the thermal decomposition of organic components to be carried out efficiently.

[0009] Examples of the wastewater (unwanted materials) include industrial wastewater, photoresist wastewater, high-concentration hydrocarbon wastewater, alcohol (methanol, ethanol, etc.), thinner components, and leftover paint. The temperature inside the heat treatment mechanism can be raised to, for example, 900 to 1100°C, and then rapidly cooled from this point to take measures against dioxins. By supplying an appropriate amount of oxygen gas to the heat treatment mechanism, the carbon in the organic wastewater can be converted to CO2, thereby preventing the accumulation of carbonized solids within the mechanism.

[0010] Examples of the water-absorbing medium include granular activated carbon (e.g., φ0.6-1.0 mm), chamotte (e.g., φ1.5 mm), heat-resistant granular Si-C (e.g., φ1.2-2.0 mm), diatomaceous earth, volcanic ash, silica gel, porous alumina (e.g., φ1-2 mm), fibrous materials (e.g., cloth), and porous materials such as spongy or sponge-like materials. This water-absorbing medium functions as a dispersion carrier (carrier material) and swelling material for the wastewater to be treated. Furthermore, moisture is dispersed in the porous pores in the form of a thin film, facilitating evaporation.

[0011] When powdered activated carbon (powder form) is used as the water-absorbing medium, its large specific surface area allows it to impregnate and retain a larger amount of wastewater and moisture in the wastewater supply tank, and then efficiently transport it to the heat treatment mechanism for thermal decomposition treatment (e.g., carbonization of organic components).

[0012] Powdered activated carbon tends to be fragile due to its powdery form, and is subject to wear and tear due to CO2 generation during heat treatment and carryover during water treatment. Therefore, during the activation process, powdered activated carbon can be coated with an aqueous solution of silica or alumina. For example, adding a diluted solution of water glass (a silica source) to powdered activated carbon before and after use reactivates it at around 900-1100°C, strengthening its skeletal strength and significantly reducing the wear and tear of powdered activated carbon over time.

[0013] Examples of the water-absorbing medium include swellable medium, porous medium, hydrophilic medium, medium that has been subjected to hydrophilic treatment, medium that is compatible with water, medium that allows water to easily penetrate, medium that allows water to easily evaporate, medium that is thermally decomposable, medium that has a small specific heat, and the like. An example of the temperature increase is to use a rotary kiln to heat the container while rotating it (for example, at 1 to 5 rpm). When the container is rotated, the water-absorbing medium moves upward and falls down, striking the bottom surface, which facilitates evaporation of the water and promotes evaporation.

[0014] Examples of heating media for the heat treatment mechanism include LNG gas and electricity. If the unit price of LNG gas is around 40-50 yen / m³ and the unit price of electricity is 3-5 yen / kWh, the estimated unit cost of wastewater treatment will be less than 5,000 yen / m³, making it economically and practically viable. In other words, if wastewater is treated as industrial waste, it would cost 20,000-30,000 yen per cubic meter of wastewater (depending on the company), but this cost can be significantly reduced. Furthermore, when treating wastewater with an adsorbent (such as activated carbon) (our conventional technology), a considerable amount of adsorbent is required depending on the COD concentration of the wastewater, which results in considerable initial costs for the adsorbent, activation and regeneration costs, and running costs for replenishing consumed amounts. However, this invention can significantly reduce these costs (estimated to be about half the cost of the adsorbent).

[0015] (2) The combustible gas generated from the wastewater may be used as fuel. In this case, the combustible gas (e.g., methane) generated by thermal decomposition of the organic components of the wastewater can be used as a combustion aid for the LNG burner of the heat treatment mechanism. The combustible gas can also be temporarily stored in a chamber or the like.

[0016] (3) The wastewater supply tank may be filled with an inert gas atmosphere. This reduces the flammability of organic components volatilized from the wastewater, ensuring safety. Examples of inert gases include nitrogen gas, argon gas, and CO2 gas. Nitrogen gas can be produced using a PSA device.

[0017] (4) In the wastewater supply tank, solid components in the wastewater may be adsorbed onto an absorbent medium to prevent the solid components from adhering to the wall surface of the heat treatment mechanism. Examples of the solid component include inorganic substances such as silica components and salts (table salt, etc.) An example of the solid component that adheres to the wall surface of the heat treatment mechanism is clinker.

[0018] In this way, the solid components in the wastewater are adsorbed by the absorbent medium in the wastewater supply tank and removed, and the solid components become stuck to the wall surfaces of the heat treatment mechanism and cannot be removed, functioning as an insulating material, thereby avoiding a situation in which the inherent thermal conductivity of the heat treatment mechanism is reduced.

[0019] (5) As shown in Figure 2, a method (not publicly known) is also conceivable in which high-concentration raw waste liquid (on the left side of the figure) is supplied to a heat treatment mechanism EO CD1 (where activated carbon is stored and heated to approximately 900 to 1100°C), the thermally decomposed and evaporated waste liquid is injected into a scrubber degassing and aeration tank (upper part of the figure), and the thermally decomposed organic components are adsorbed and purified in an activated carbon filtration device (lower layer). In contrast, with the present invention, the high-temperature activated carbon (absorbent medium) discharged from the heat treatment mechanism is used as a carrier (transport medium) for the wastewater in the wastewater supply tank, thereby making effective use of the waste heat (high heat of the absorbent medium) (the pyrolysis vapor is purified by the scrubber mechanism). [Effects of the Invention]

[0020] The present invention has the above-described configuration and has the following effects. The temperature (calorific value) of the absorbent medium after the temperature increase can be transferred to newly supplied wastewater for heat treatment, so that a wastewater treatment method with superior treatability can be provided. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a conceptual diagram of a system flow illustrating an embodiment of a wastewater treatment method of the present invention. [Figure 2]FIG. 1 is a block flow diagram illustrating another processing method proposed by the present inventors. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in Figure 1, the wastewater treatment method of this embodiment includes a wastewater supply tank 2 for impregnating an absorbent medium 1 with moisture contained in wastewater W (factory wastewater), and a heat treatment mechanism 3 (a rotary kiln) for heating the absorbent medium 1. The moisture-impregnated absorbent medium 1 is transferred to the heat treatment mechanism 3 and heated to evaporate the moisture and thermally decompose the organic components in the wastewater W, and the heated absorbent medium 1 is then sent to the wastewater supply tank 2.

[0023] Activated carbon (shown larger in the figure for ease of explanation) was used as the water-absorbing medium. This water-absorbing medium functioned as a dispersion carrier (carrier material) for the industrial wastewater to be treated (wastewater W). The absorbent medium 1 was heated by rotating the housing (1 to 5 rpm) using a heat treatment mechanism 3 (heated by an LNG burner). Then, in the wastewater supply tank 2, the absorbent medium 1 was impregnated with the moisture in the wastewater W (factory wastewater) and transported to the entrance of the heat treatment mechanism 3 by the ascending conveyor C and the inclined conveyor C. Next, the absorbent medium 1 was heated to about 900°C (for dioxin countermeasures) in the heat treatment mechanism 3 to evaporate the moisture and thermally decompose the organic components in the wastewater W, and the heated absorbent medium 1 was sent back to the wastewater supply tank 2.

[0024] The wastewater supply tank 2 was filled with an inert gas atmosphere, which reduced the flammability of organic components volatilized from the wastewater and ensured safety. Nitrogen gas was used as the inert gas, and this nitrogen gas was produced by a PSA device. The water evaporated from the wastewater W and the exhaust gas G containing the thermally decomposed organic components were sent to the electrolytic scrubber mechanism 4, where they were purified by the purifying action of electrolytic water, activated carbon, etc.

[0025] Next, the use of the wastewater treatment method of this embodiment will be described. This wastewater treatment method includes a wastewater supply tank 2 for impregnating an absorbent medium 1 with the moisture contained in the wastewater W, and a heat treatment mechanism 3 for heating the absorbent medium 1. The moisture-impregnated absorbent medium 1 is transferred to the heat treatment mechanism 3 and heated to evaporate the moisture and thermally decompose the organic components in the wastewater W. Therefore, the moisture contained in the wastewater W supplied to the wastewater supply tank 2 is impregnated into the absorbent medium 1, and the heat treatment mechanism 3 heats it up, allowing the moisture in the wastewater W to evaporate and the organic components to thermally decompose.

[0026] Furthermore, the heated absorbent medium 1 is sent to the wastewater supply tank 2, so that the temperature (calorific value) of the heated absorbent medium 1 can be transferred to the newly supplied wastewater W for heat treatment, thereby making more effective use of the heat. Furthermore, since the heat treatment mechanism 3 is supplied with absorbent medium 1 that has been impregnated with and dispersed with moisture, rather than with moisture itself, damage caused by direct contact of the liquid with the heat treatment mechanism 3 (kettle) itself can be reduced. [Industrial Applicability]

[0027] The superior treatability makes it possible to apply it to various wastewater treatment methods. [Explanation of symbols]

[0028] 1. Absorbent Media 2 Wastewater supply tank 3 Heat treatment mechanism W Wastewater

Claims

1. A wastewater treatment method comprising: a wastewater supply tank (2) for impregnating an absorbent medium (1) with the moisture contained in wastewater (W); and a heat treatment mechanism (3) for heating the absorbent medium (1), wherein the water-impregnated absorbent medium (1) is transferred to the heat treatment mechanism (3) and heated to evaporate the moisture and thermally decompose the organic components in the wastewater (W), and the heated absorbent medium (1) is sent to the wastewater supply tank (2).

2. 2. A method for treating wastewater according to claim 1, wherein the combustible gas produced from the wastewater (W) is used as fuel.

3. 3. A method for treating wastewater according to claim 1, wherein the wastewater supply tank (2) is filled with an inert gas atmosphere.

4. 4. A wastewater treatment method according to claim 1, wherein solid components in the wastewater (W) are adsorbed onto an absorbent medium (1) in the wastewater supply tank (2) so that the solid components do not adhere to the wall surfaces of the heat treatment mechanism (3).

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