JP2011078901A - Water treatment apparatus, and water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To treat organic wastewater at a lower cost than before. <P>SOLUTION: The water treatment apparatus includes a sulfate ion adding device for adding sulfate ions to organic wastewater being raw water in an amount equivalent to BOD (Biochemical Oxygen Demand) of the organic wastewater, an anaerobic reaction tank for anaerobically treating the organic wastewater to which the sulfate ions are added and an oxidative reaction tank for applying oxidative treatment to the treated water of the anaerobic reaction tank. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water treatment apparatus and method.

  Patent Document 1 below discloses an anaerobic treatment method for organic wastewater containing sulfate ions. In this wastewater treatment method, when organic wastewater containing sulfate ions is subjected to methane fermentation treatment (anaerobic treatment), the generated gas in the treatment tank (fermenter) is desulfurized in the desulfurization tank and then returned to the treatment tank. It reduces the hydrogen sulfide concentration inside. According to such a waste water treatment method, a decrease in the activity of methane bacteria in the treatment tank can be suppressed.

JP 05-007894 A

  By the way, the desulfurization tank has a dry type and a wet type (including biological treatment), both of which have high operating costs, and the wet type generates a lot of excess sludge. There is a problem that processing is also expensive.

  This invention is made | formed in view of the situation mentioned above, and aims at processing organic waste_water | drain at lower cost than before.

  In order to achieve the above-mentioned object, in the present invention, as a first solution for the water treatment apparatus, sulfate ion equivalent to BOD (Biochemical Oxygen Demand) of the organic waste water is added to the organic waste water as raw water. Means comprising: a sulfate ion addition device; an anaerobic reaction tank for anaerobically treating the organic wastewater to which the sulfate ion is added; and an oxidation reaction tank for oxidizing the treated water of the anaerobic treatment tank. adopt.

  As a second solving means relating to the water treatment apparatus, in the first solving means, the oxidation reaction tank includes an air layer portion in which aerobic microorganisms are disposed, and a liquid layer portion disposed under the air layer portion. This is an aerobic reaction tank comprising: an anaerobic reaction tank treated water from above, and air supplied from below to the liquid layer part.

  As the third solving means relating to the water treatment apparatus, a means is adopted in which part of the treated water in the oxidation reaction tank is returned to the anaerobic reaction tank as circulating water in the first or second solving means.

As a fourth solving means related to the water treatment apparatus, in any of the first to third solving means, the sulfate ion adding device adds sodium sulfate (Na ₂ SO ₄ ) for generating sulfate ions to the organic waste water. Adopt the means to do.

  As a fifth solving means related to the water treatment apparatus, in any one of the first to fourth solving means, the organic waste water as the raw water is less than the sulfate ion equivalent to the BOD of the organic waste water. In the case where it contains, the sulfate ion addition device adopts a means of adding sulfate ions, which are deficient in sulfate ions equivalent to the BOD of the organic waste water, to the organic waste water.

  Further, in the present invention, as a first solution for the water treatment method, a sulfate ion addition step of adding sulfate ions equivalent to BOD (Biochemical Oxygen Demand) of the organic wastewater to the organic wastewater as raw water, A means is adopted that includes an anaerobic treatment step for anaerobically treating the organic waste water that has undergone the sulfate ion addition step and an oxidation treatment step for oxidizing the treated water of the anaerobic treatment step.

  As a second solving means related to the water treatment method, in the first solving means, the oxidation treatment step is performed in an aerobic reaction tank in which an air layer part and a liquid layer part in which aerobic microorganisms are arranged are arranged vertically. In addition, a method is adopted in which the treated water in the anaerobic reaction tank is supplied to the gas layer portion from above and air is supplied to the liquid layer portion from below.

  As a third solving means relating to the water treatment method, a means is adopted in which part of the treated water in the oxidation treatment step is returned to the anaerobic treatment step as circulating water in the first or second solving means.

As a fourth solving means relating to the water treatment method, a means is adopted in which sulfate ions are added to the organic waste water with sodium sulfate (Na ₂ SO ₄ ) in any of the first to third solving means.

  As a fifth solving means related to the water treatment method, in any of the first to fourth solving means, the organic waste water as the raw water has a smaller amount of sulfate ion than the sulfate ion equivalent to the BOD of the organic waste water. In the case where the organic wastewater is contained, a method is adopted in which sulfate ions that are deficient in sulfate ions equivalent to the BOD of the organic wastewater are added to the organic wastewater.

According to the present invention, hydrogen sulfide (H ₂ S) can be generated with good yield by anaerobic treatment, and valuable sulfur (S) is collected by oxidizing the hydrogen sulfide (H ₂ S). Since it can be obtained efficiently, it is possible to treat organic wastewater at a lower cost than in the prior art in which hydrogen sulfide (H ₂ S) is desulfurized in a desulfurization tank.

It is a block diagram which shows the system configuration | structure of the water treatment apparatus A which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the water treatment apparatus A according to the present embodiment includes an adjustment tank 1, an anaerobic reaction tank 2, an aerobic reaction tank 3 (oxidation reaction tank), a BOD measuring device 4, a sodium sulfate addition device 5, and An air supply device 6 is used. In such a water treatment apparatus A, the BOD (Biochemical Oxygen Demand) of raw water X1 (organic wastewater containing sulfate ions) supplied from the outside is below the wastewater standard or environmental standard of the establishment. It is processed as follows.

The raw water X1, which is an organic wastewater containing sulfate ions, is, for example, food production wastewater, pulp production wastewater, or sewage. Such raw water X1 is a wastewater containing 50 to 2000 mg-BOD / L of organic matter (≈BOD) and 50 to 3000 mg-SO ₄ / L of sulfate ions (SO ₄ ²⁻ ). The content of sulfate ion (SO ₄ ²⁻ ) in such raw water X1 is the sulfuric acid reduction reaction in the anaerobic reaction tank 2 described later, that is, the organic component and sulfate ion (SO ₄ ²⁻ ) contained in the raw water X1. The amount is insufficient with respect to the amount necessary for the reaction to form hydrogen sulfide (H ₂ S) without excess or deficiency.

  The adjustment tank 1 is a container having a predetermined capacity for mixing and stirring the raw water X1 supplied from the outside and the sodium sulfate aqueous solution X2 supplied from the sodium sulfate addition device 5, and the mixed water X3 after mixing and stirring is anaerobic. Discharge into reaction vessel 2.

  The anaerobic reaction tank 2 is a reaction tank in which methane bacteria, which are anaerobic microorganisms, are provided as a sludge bed 2a. The mixed water X3 injected from the lower part and the circulating water X7, which will be described later, act on the action of the methane producing bacteria. Methane fermentation (anaerobic treatment).

In the anaerobic reaction tank 2, the organic components contained in the raw water X1 are decomposed by the action of the methanogen, and methane gas (CH ₄ ) and carbon dioxide (CO ₄ ) are mainly generated. The sulfate ions (SO ₄ ²⁻ ) contained in the mixed water X 3 are subjected to a sulfuric acid reduction treatment to generate hydrogen sulfide (H ₂ S). In such an anaerobic reaction tank 2, the supernatant liquid in which such hydrogen sulfide (H ₂ S) is dissolved is taken out from the upper portion as intermediate treated water X 4 and drained into the aerobic reaction tank 3.

  The treatment conditions in the anaerobic reaction tank 2 are pH 5-8 (optimum value: pH 6), temperature 15-40 ° C. (optimum value: 30 ° C.), and pressure is equivalent to the retentate depth in the reaction tank (optimum value: 0.05 MPa).

  The aerobic reaction tank 3 includes an air layer part 3b (upper part) in which aerobic microorganisms are arranged as a sludge bed 3a and a liquid layer part 3c (lower part) arranged under the gas layer part 3b. The intermediate treated water X4 is supplied to the part 3b from above, and the air X5 of the air supply device 6 is supplied to the liquid layer part 3c accumulated in the lower part by the intermediate treated water X4 from below. In such an aerobic reaction tank 3, the intermediate treated water X4 falls like a shower from above and passes through the sludge bed 3a, while the air X5 aerated (absorbed) from the liquid layer portion 3c is sludge bed 3a from below. Pass through.

In the sludge bed 3a, hydrogen sulfide (H ₂ S) contained in the intermediate treated water X4 and oxygen (O ₂ ) contained in the air X5 cause a sulfide oxidation reaction to cause sulfur (S) and water (H ₂ ). O). In such an aerobic reaction tank 3, while the supernatant of the liquid layer part 3c containing sulfur (S) and water (H ₂ O) is discharged to the outside as treated water X6, the lower part of the liquid layer part 3c The treated water taken out from the water is supplied to the lower part of the anaerobic reaction tank 2 as the circulating water X7.

  The treatment conditions in the aerobic reaction tank 3 are pH 4-8 (optimum value: pH 6), temperature 15-40 ° C. (optimum value: 30 ° C.), and pressure is equivalent to the retentate depth in the reaction tank (optimum value: 0. 05 MPa).

  The BOD measuring device 4 is a measuring device that measures the BOD of the raw water X1 in the adjustment tank 1 regularly or irregularly, and outputs the measured value to the sodium sulfate addition device 5. The BOD measuring instrument 4 measures the BOD based on, for example, a comparatively high measuring method for evaluating the amount of dissolved oxygen specified in JIS or a simple measuring method using a biosensor. The measurement timing may be either a regular timing every predetermined number of days or an irregular timing at which the type of raw water X1 such as food production wastewater, pulp production wastewater, or sewage is changed. Set to

The sodium sulfate addition device 5 supplies an aqueous solution (sodium sulfate aqueous solution) of sodium sulfate (Na ₂ SO ₄ ), which is a kind of sulfate, to the adjustment tank 1 as sulfate ions (SO ₄ ²⁻ ). This sodium sulfate addition device 5 stores in advance a raw water table in which the amount of sodium sulfate aqueous solution added to the adjustment tank 1, the BOD and the amount of sulfate ions are registered for each type of raw water X1 such as food production wastewater, pulp production wastewater or sewage. The amount of sodium sulfate aqueous solution corresponding to the type of raw water X1 that is actually processed based on the addition amount table is supplied to the adjustment tank 1.

That is, the amount of sulfate ion M0 required for the organic component and sulfate ion (SO ₄ ²⁻ ) contained in the raw water X 1 to react with each other without excess or deficiency in the anaerobic reaction tank 2 to form hydrogen sulfide (H ₂ S), If the amount of sulfate ion M1 originally contained in the raw water X1 is M1, the sodium sulfate addition device 5 is an amount M2 (= M0−M1) obtained by subtracting the amount of sulfate ion M1 from the amount of sulfate ion M, that is, sulfate ion relative to the amount of sulfate ion M0. A sodium sulfate aqueous solution corresponding to a shortage of sulfate ions (SO ₄ ²⁻ ) of an amount M 1 is supplied to the adjustment tank 1.

  Since the BOD can be estimated in advance for each type of raw water X1 (food manufacturing wastewater, pulp manufacturing and distribution wastewater, general sewage, etc.), the fixed amount is stored in advance in the sodium sulfate addition device 5 for each type of raw water X1. ing. The air supply device 6 is a blower that sends air to the lower portion of the liquid layer portion 3c at a predetermined pressure.

Next, operation | movement of the water treatment apparatus A comprised in this way is demonstrated in detail.
When the water treatment apparatus A is in operation, the BOD measuring instrument 4 measures the BOD of the raw water X1 stored in the adjustment tank 1 at a preset timing, and outputs the measured value to the sodium sulfate addition apparatus 5. As a result, the sodium sulfate addition device 5 is configured so that sodium sulfate (Na ₂ SO ₄ ) corresponding to the BOD of the raw water X1, that is, chemically equivalent to the BOD is added to the raw water X1. The aqueous solution X2 is supplied to the adjustment tank 1.

  The sodium sulfate addition device 5 generates an alarm when the BOD of the raw water X1 registered in the raw water table is significantly different from the measurement result of the BOD measuring device 4, and this situation is indicated by the administrator of the water treatment device A. To inform.

The adjustment tank 1 mixes and stirs the sodium sulfate aqueous solution X2 thus supplied from the sodium sulfate addition device 5 with the raw water X1, and outputs the resulting mixed water X3 to the anaerobic reaction tank 2.
As is well known, sodium sulfate (Na ₂ SO ₄ ), which is a kind of sulfate, is water-soluble and dissolves in water to form sodium ions (Na ⁺ ) and sulfate ions (SO ₄ ²⁻ ). Decompose.

In the anaerobic reaction tank 2 into which the mixed water X3 flows, the organic components are subjected to methane fermentation (anaerobic treatment) by the action of the methane-producing bacteria in the sludge bed 2a, and methane gas (CH ₄ ) and carbon dioxide (CO ₄ ), and the sulfate ions (SO ₄ ²⁻ ) are sulfate-reduced by the action of sulfate-reducing bacteria coexisting with the methanogenic bacteria on the sludge bed 2a to produce hydrogen sulfide (H ₂ S). Is done. That is, in the anaerobic reaction tank 2, carbohydrates that are organic components react with sulfate ions (SO ₄ ²⁻ ) by the action of sulfate reducing bacteria to react with carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ S), and water. Change to (H ₂ O).

Here, the mixed water X3 to be treated in the anaerobic reaction tank 2 is chemically added to the BOD of the raw water X1 by adding a predetermined amount of aqueous sodium sulfate solution from the sodium sulfate addition device 5 to the adjustment tank 1. It contains sulfate ions (SO ₄ ²⁻ ) which are equivalent. Therefore, the organic component contained in the raw water X1 and sulfate ions (SO ₄ ²⁻ ) react without excess or deficiency to generate hydrogen sulfide (H ₂ S). That is, most of the sulfur (S) component contained in the sulfate ion (SO ₄ ²⁻ ) of the raw water X1 is reduced to hydrogen sulfide (H ₂ S).

The anaerobic reaction tank 2 drains the intermediate treated water X4 (supernatant liquid) in which such hydrogen sulfide (H ₂ S) is dissolved into the aerobic reaction tank 3. In the aerobic reaction tank 3, the intermediate treated water X4 passes through the sludge bed 3a downward from above, and the air X5 similarly passes through the sludge bed 3a upward from below. When the intermediate treated water X4 and air X5 pass through the sludge bed 3a as such counterflows, hydrogen sulfide (H ₂ S) is oxidized with oxygen (O ₂ ) and sulfide by the action of aerobic microorganisms in the sludge bed 3a. Reaction occurs to produce sulfur (S) and water (H ₂ O).

That is, in the anaerobic reaction tank 2, an oxidation reaction along the following reaction formula (1) occurs.
H ₂ S + O ₂ → SO ₄ ²⁻ + H ₂ O
→ S + H ₂ O (1)

Here, in order for the sulfate ion (SO ₄ ²⁻ ) converted from hydrogen sulfide (H ₂ S) to further participate and be oxidized to sulfur (S), which is a single element, oxygen relative to the amount of hydrogen sulfide. It is necessary to optimally set the amount, but in this embodiment, sulfate ions that are chemically equivalent to the BOD of the raw water X1 by adding a predetermined amount of aqueous sodium sulfate solution from the sodium sulfate addition device 5 to the adjustment tank 1. Since (SO ₄ ²⁻ ) is contained, the amount of hydrogen sulfide (H ₂ S) generated in the anaerobic reaction tank 2 can be estimated. Therefore, in this embodiment, it is easy to supply oxygen (O ₂ ) in an amount optimally set with respect to the generation amount of hydrogen sulfide (H ₂ S) from the air supply device 6 to the anaerobic reaction tank 2. .

According to this embodiment, by adding a predetermined amount of an aqueous sodium sulfate solution from the sodium sulfate addition device 5 to the adjustment tank 1, the mixed water X3, which is the treatment target of the anaerobic reaction tank 2, is converted into the BOD of the raw water X1. On the other hand, since it contains sulfate ions (SO ₄ ²⁻ ) that are chemically equivalent, hydrogen sulfide (H ₂ S) can be generated with good yield. Then, the hydrogen sulfide (H ₂ S) thus obtained is subjected to aerobic treatment (oxidation treatment) in the aerobic reaction tank 3 to obtain valuable sulfur (S) in a high yield. Organic wastewater can be treated at a lower cost than in the prior art in which (H ₂ S) is desulfurized in a desulfurization tank.

Moreover, according to this embodiment, since the circulating water X7 discharged | emitted from the aerobic reaction tank 3 is returned to the anaerobic reaction tank 2, the hydrogen sulfide (H) which could not be converted into sulfur (S) in the aerobic reaction tank 3 ₂ S) can be treated again in the aerobic reactor 3, so that the yield of sulfur (S) can be improved.
In the aerobic reaction tank 3, since the intermediate treated water X4 and air X5 pass through the sludge bed 3a as counterflows, sulfur (S) is efficiently converted from hydrogen sulfide (H ₂ S). Even with such a configuration of the aerobic reaction tank 3, the yield of sulfur (S) can be improved.

Furthermore, since relatively inexpensive sodium sulfate (Na ₂ SO ₄ ) is used as a source of sulfate ions (SO ₄ ²⁻ ), the cost of adding and consuming an aqueous sodium sulfate solution to the raw water X1 can be reduced. it can.

In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the organic waste water containing sulfate ions (SO ₄ ²⁻ ) is treated water (raw water X 1), but the present invention is not limited to this. The present invention may be applied to water to be treated that hardly contains sulfate ions (SO ₄ ²⁻ ).
(2) Although the aerobic reaction tank 3 is employed as the oxidation reaction tank in the above embodiment, the present invention is not limited to this. An oxidation reaction tank based on a principle other than the aerobic reaction may be used.

(3) In the above embodiment, the BOD measuring device 4 is used to detect an abnormality in the BOD of the raw water X1, but the present invention is not limited to this. For example, when applying the present invention to water to be treated containing little sulfate ion _(SO ^{4 2-),} sulfate ion equivalent to BOD of the detection result is shown in accordance with the detection result of the BOD meter ⁴ _(SO 4 ^2- ) May be calculated and added to the raw water X1. According to such raw X1 to addition control of sulfate ions _(SO ^{4 2-),} since the addition amount of sulfate ions in accordance with the BOD of the raw water X1 _(SO ^{4 2-)} is feedback controlled, BOD of raw water X1 Even when fluctuates over time, sulfate ions (SO ₄ ²⁻ ) equivalent to the BOD of the raw water X 1 can be added accurately. Therefore, the yield of sulfur (S) can be improved.

(4) Further, in addition to the BOD measuring device 4, an ion concentration meter for measuring the sulfate ion concentration of the raw water X1 is provided. Based on the measured value of the BOD measuring device 4 and the measured value of the ion concentration meter, sulfate ions (SO _You may make it adjust the addition amount of ₄ ^2- ).

  DESCRIPTION OF SYMBOLS 1 ... Adjustment tank, 2 ... Anaerobic reaction tank, 3 ... Aerobic reaction tank (oxidation reaction tank), 4 ... BOD measuring device, 5 ... Sodium sulfate addition apparatus, 6 ... Air supply apparatus

Claims (10)

A sulfate ion addition device for adding sulfate ions equivalent to BOD (Biochemical Oxygen Demand) of the organic wastewater to the organic wastewater as raw water;
An anaerobic reaction tank for anaerobically treating the organic wastewater to which the sulfate ion is added;
An oxidation reaction tank that oxidizes the treated water of the anaerobic treatment tank.   The oxidation reaction tank is an aerobic reaction tank composed of an air layer part in which aerobic microorganisms are arranged and a liquid layer part arranged under the air layer part. The water treatment apparatus according to claim 1, wherein treated water is supplied and air is supplied to the liquid layer portion from below.   The water treatment apparatus according to claim 1 or 2, wherein a part of the treated water in the oxidation reaction tank is returned to the anaerobic reaction tank as circulating water. The water treatment device according to any one of claims 1 to 3, wherein the sulfate ion addition device adds sodium sulfate (Na ₂ SO ₄ ) that generates sulfate ions to the organic waste water.   When the organic waste water as raw water contains a smaller amount of sulfate ions than the sulfate ion equivalent to the BOD of the organic waste water, the sulfate ion addition device is a sulfuric acid deficient in the sulfate ion equivalent to the BOD of the organic waste water. Ion is added to organic waste water, The water treatment apparatus as described in any one of Claims 1-4 characterized by the above-mentioned. A sulfate ion addition step of adding sulfate ions equivalent to BOD (Biochemical Oxygen Demand) of the organic wastewater to the organic wastewater as raw water;
An anaerobic treatment step for anaerobically treating the organic wastewater that has undergone the sulfate ion addition step;
An oxidation treatment step of oxidizing the treated water in the anaerobic treatment step.   In the aerobic reaction tank in which the aerobic microorganisms are disposed in the aerobic reaction tank in which the aerobic microorganisms are arranged up and down, the treatment process of the anaerobic reaction tank is supplied to the air layer part from above. The water treatment method according to claim 6, wherein air is supplied to the part from below.   The water treatment method according to claim 6 or 7, wherein a part of the treated water in the oxidation treatment step is returned to the anaerobic treatment step as circulating water. The water treatment method according to any one of claims 6 to 8, wherein sulfate ions are added to the organic waste water with sodium sulfate (Na ₂ SO ₄ ).   When organic wastewater as raw water contains a lower amount of sulfate ions than sulfate ions equivalent to the BOD of the organic wastewater, sulfate ions that are deficient in sulfate ions equivalent to the BOD of the organic wastewater are converted into organic wastewater. It adds, The water treatment method as described in any one of Claims 6-9 characterized by the above-mentioned.

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