JP6688705B2 - Wastewater recycling method and wastewater recycling unit - Google Patents

Description

  The present invention relates to a wastewater recycling method and a wastewater recycling unit.

The need for wastewater recycling is increasing in order to save water for the purpose of reducing the environmental load. In order to recycle wastewater, various water treatment technologies are used to treat water that can be recycled. In particular, RO membranes, ion exchange resins, and wastewater treated by electrodialysis can be used in a wide range of applications because recycled water of good quality can be obtained.
Patent Document 1 proposes a method of reusing the tertiary treated water obtained by treating wastewater with an RO membrane as boiler water.

JP, 2016-117017, A

However, although the method of Patent Document 1 describes that the treated water is reused (reused), it is not proposed to recycle (circulate), so the treated water after reuse is discharged as wastewater. Will be. Then, the amount of water equivalent to the amount of reuse will be supplemented in the system, and water cannot be saved sufficiently. Further, in the method of Patent Document 1, since the wastewater is entirely treated with the RO membrane, the concentrated water (discharged water) containing the components removed by the RO membrane increases. Since the discharged water is discharged to the outside of the system, a large amount of the discharged water will be filled into the system, and water cannot be saved sufficiently.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wastewater recycling method and a wastewater recycling unit that can save water highly.

The wastewater recycling method and wastewater recycling unit of the present invention have the following aspects.
[1] a step (1) of removing solids from the waste water to obtain treated water (A),
A step (2) of removing ions from a part of the treated water (A) to obtain treated water (B);
A step (3) of using the rest of the treated water (A) as an application (A) to collect wastewater (A),
A step (4) of collecting the wastewater (B) by using the treated water (B) as an application (B),
A method of recycling wastewater, comprising a step (5) of mixing the wastewater (A) and the wastewater (B) to produce the wastewater.
[2] The method further includes a step (6) of adjusting the amount of the treated water (A) supplied to the step (2) so that the ion concentration in the treated water (A) becomes equal to or lower than an arbitrary concentration. The wastewater recycling method described in [1].
[3] The use (A) is equipment cleaning water,
The wastewater recycling method according to [1] or [2], wherein the use (B) is water for a boiler or cooling water for a heat exchanger.
[4] Solid content removing means for removing the solid content from the waste water to obtain the treated water (A),
Ion removal means for removing ions from a part of the treated water (A) to obtain treated water (B),
A collecting means (A) for supplying the rest of the treated water (A) to the purpose (A) and collecting the wastewater (A) for the purpose (A);
A collection means (B) for supplying the treated water (B) to the purpose (B) and collecting the wastewater (B) for the purpose (B);
A wastewater recycling unit comprising: wastewater preparation means for mixing the wastewater (A) and the wastewater (B) to produce the wastewater.
[5] An adjusting unit is further provided for adjusting the amount of the treated water (A) supplied to the ion removing unit so that the ion concentration in the treated water (A) is equal to or lower than an arbitrary concentration. Wastewater recycling unit described in.
[6] The use (A) is water for cleaning equipment,
The wastewater recycling unit according to [4] or [5], wherein the application (B) is boiler water or heat exchanger cooling water.

  According to the present invention, it is possible to provide a wastewater recycling method and a wastewater recycling unit capable of highly saving water.

It is a flowchart which shows the drainage recycling method of this invention. It is a schematic block diagram which shows an example of the wastewater recycling unit of this invention. It is a schematic block diagram which shows the specific example of the wastewater recycling unit of this invention. It is a schematic block diagram which shows the example of the wastewater recycling unit of an Example. It is a graph which shows the sodium ion concentration of an Example.

≪Wastewater recycling method≫
FIG. 1 is a flow chart showing the recycling method of the present invention. The wastewater recycling method of the present invention comprises a step (1) S1 of removing solids from wastewater to obtain treated water (A) and a treated water (B) by removing ions from a part of the treated water (A). (2) S2 for obtaining water, and (3) S3 for collecting wastewater (A) by using the rest of the treated water (A) as the purpose (A), and the treated water (B) for the purpose (B) (4) S4 of recovering the wastewater (B) by using the same as above, and a step (5) S5 of mixing the wastewater (A) and the wastewater (B) to obtain the wastewater.

In the step (1), it is preferable to remove the solid content contained in the wastewater by using at least one selected from the group consisting of biological treatment, coagulation filtration treatment, and activated carbon treatment.
The solid content means a non-solubilized component contained in the waste water.
The biological treatment is a treatment for removing organic matter in wastewater by utilizing the decomposition action of organic matter by microorganisms.
The coagulation filtration treatment is a treatment in which particles are aggregated to form a larger agglomerate, which is then removed using a filter medium or a filter. Examples of the filter medium include sand, anthracite, and fibrous filter medium, and examples of the filter include a UF membrane (ultrafiltration membrane) and an MF membrane (microfiltration membrane).
The activated carbon treatment is a treatment for adsorbing particles to activated carbon to remove them.
The method for removing the solid content in the wastewater is determined in consideration of the water quality required for the treated water (A).

In the step (2), at least one kind selected from the group consisting of ion exchange resin treatment, RO membrane treatment, and electrodialysis treatment is used to remove ions in the treated water (A) to treat the treated water (B). Is preferably obtained.
Examples of the ions to be removed include sodium ion, chloride ion, calcium ion and the like.
For example, in the case of sodium ions, it is preferable that the ions are removed so that the ion concentration in the resulting treated water (B) is 200 mg / L or less.
The ion exchange resin treatment is a treatment for removing ions using a cation exchange resin and / or an anion exchange resin.
The RO film process is a process of removing ions using the RO film.
The electrodialysis treatment is a treatment for removing ions by electrodialysis.
The method of removing the ions in the wastewater is determined in consideration of the water quality required for the treated water (B).
The discharged water containing the removed components is discarded outside the system.

In the step (3), the rest of the treated water (A) is used as the purpose (A), and the waste water (A) is recovered after the use.
Examples of the application (A) include water for washing equipment, and examples of the water for washing equipment include water for washing filter media, activated carbon, ion exchange resins and the like.
In the step (4), the treated water (B) is used as the purpose (B), and the waste water (B) is recovered after the use.
Examples of the use (B) include water for boilers and cooling water for heat exchangers.
Ions have been removed from the treated water (B), so even if the use (B) is used as boiler water or heat exchanger cooling water, ion concentration will not occur even if the wastewater (B) after use is contaminated with ions. Therefore, the ion concentration in the wastewater (B) can be kept low. By mixing the wastewater (B) and the wastewater (A) thus obtained to obtain the wastewater, the ion concentration in the treated water (A) obtained by treating the wastewater can be reduced.

In the step (5), the wastewater (A) and the wastewater (B) are mixed to produce wastewater.
The mixing method is not particularly limited, and may be a method of mixing the wastewater (A) and the wastewater (B) before supplying to the step (1), or in the step (1) the wastewater (A) and the wastewater ( It may be a method of mixing with B).
The wastewater obtained in the step (5) is recycled as the wastewater in the step (1).

  The wastewater recycling method of the present invention comprises at least one selected from the group consisting of coagulation treatment, pressure floating treatment, and catalytic oxidation treatment before the step of removing solids from wastewater to obtain treated water (A). The preliminary step of may be included. By including this preliminary step, it becomes easy to remove the solid matter.

  The wastewater recycling method of the present invention may include a step of treating the treated water (A) with hypochlorite after the step of removing the solid content from the wastewater to obtain the treated water (A). By including this step, the treated water (A) can be sterilized.

  When the wastewater recycling method of the present invention includes a step of treating the treated water (A) with hypochlorite, the treated water (A) is reduced with a sulfite before the step (2). It may include a reduction treatment step. By including this step, it is possible to suppress deterioration of instruments such as the ion exchange resin and RO membrane used in step (2) due to hypochlorite.

In the wastewater recycling method of the present invention, the treated water supplied to the step (2) between the step (1) and the step (2) so that the ion concentration in the treated water (A) is not more than an arbitrary concentration. It may include a step (6) of adjusting the amount of (A). If the recycling is repeated only with the treated water (A), the concentration of ions contained in the treated water (A) increases and the water quality deteriorates. Therefore, for example, when the ion concentration of the treated water (A) is higher than an arbitrary value, the amount of the treated water (A) supplied to the step (2) is increased to be the treated water (B). It is possible to reduce the ion concentration of the treated water (A) obtained in the above cycle and maintain the water quality of the treated water (A). For example, when the ion concentration of the treated water (A) is lower than an arbitrary value, the amount of the treated water (A) supplied to the step (2) can be reduced to reduce the amount of discharged water. You can save more water.
In the step (6), for example, a part of the treated water (A) is sampled and analyzed by an ion chromatograph, and based on the result, the concentration of the treated water (A) is adjusted to be equal to or lower than an arbitrary concentration, The method of adjusting the quantity of the treated water (A) supplied to a process (2) is mentioned.

  The wastewater recycling method of the present invention may be a wastewater recycling unit utilizing an existing wastewater treatment facility. When using the existing wastewater treatment equipment, analyze the water quality in advance and repeat the calculation assuming circulation use, and supply it to the process (2) for maintaining the water quality of the treated water (A) at an arbitrary ion concentration. By calculating the amount of treated water (A) to be processed, it is possible to predict the downsizing of the step (2) in advance. In this calculation, even if the existing wastewater treatment facility is not used, it is possible to predict the downsizing by substituting the provisional numerical value.

≪Drainage recycling unit≫
FIG. 2 is a schematic configuration diagram showing an example of the wastewater recycling unit of the present invention. The waste water recycling unit 10 of the present invention includes a solid content removing means 1 for removing solids from waste water to obtain treated water (A), and a portion of the treated water (A) for removing ions from the treated water (B). ) Is obtained, the rest of the treated water (A) is supplied to the application (A), and the wastewater (A) of the application (A) is recovered, and the treated water. (B) is supplied as a use (B), and the collecting means (B) 4 for collecting the wastewater (B) for the use (B), the wastewater (A) and the wastewater (B) are mixed, and A drainage adjusting means 5 for drainage is provided.

The solid content removing means 1 for removing the solid content from the waste water to obtain the treated water (A) includes, for example, one selected from the group consisting of a biological treatment tank, a coagulation filtration treatment tank, and an activated carbon treatment tank. These are tanks for carrying out biological treatment, coagulation filtration treatment, and activated carbon treatment, respectively. This removes the solid content contained in the wastewater.
The solid content removing means 1 is determined in consideration of the water quality required for the treated water (A).

The ion removing means 2 for removing the ions from a part of the treated water (A) to obtain the treated water (B) is selected from the group consisting of, for example, an ion exchange resin treatment tank, an RO membrane treatment tank, and an electrodialysis treatment tank. At least one kind is included. These are tanks for performing ion exchange resin treatment, RO membrane treatment, and electrodialysis treatment, respectively. Thereby, the ions contained in the treated water (A) are removed.
The ion removing means 2 is determined in consideration of the water quality required for the treated water (B).
The discharged water 6 containing the removed components is discarded outside the system.

The recovery means (A) 3 that uses the rest of the treated water (A) as the purpose (A) and collects the wastewater (A) for the purpose (A) is a treatment that supplies the treated water (A) to the purpose (A). Water (A) supply pipe 3a, treated water (A) utilization device 3b for using treated water (A) as purpose (A), wastewater (A) recovery means for collecting wastewater (A) for purpose (A) It consists of a tube 3c. Examples of the treated water (A) utilization device 3b include a filter, an activated carbon tower, an ion exchanger, and the like.
Examples of the use (A) include the same as those mentioned above.

The recovery means (B) 4 that uses the treated water (B) as the purpose (B) and collects the wastewater (B) for the purpose (B) is a treated water (B) that supplies the treated water (B) to the purpose (B). B) Supply pipe 4a, treated water (B) utilization device 4b for using treated water (B) as purpose (B), drainage (B) recovery pipe 4c for collecting wastewater (B) of purpose (B) Become. Examples of the treated water (B) utilization device 4b include a boiler and a heat exchanger.
Examples of the use (B) include the same as those mentioned above.

  As the wastewater preparation means 5 for mixing the wastewater (A) and the wastewater (B) into the wastewater, a drainage tank for storing the wastewater (A) and the wastewater (B), the wastewater (A) and the wastewater ( A pipe or the like for supplying B) to the solid matter removing means 1 may be mentioned.

  The wastewater recycling unit of the present invention has at least one pretreatment means selected from the group consisting of a flocculation treatment tank, a pressure flotation treatment tank, and a catalytic oxidation treatment tank before the solid content removing means 1. May be. By including this means, it becomes easy to remove the solid matter.

  The wastewater recycling unit of the present invention may have a hypochlorite treatment means for treating with hypochlorite in the latter stage of the solid content removing means 1 and before the ion removing means 2. . Examples of the hypochlorite treatment means include a hypochlorite treatment tank. This is a tank for treating the treated water (A) with hypochlorite. By having the hypochlorite treatment means, the treated water (A) can be sterilized.

  When the waste water recycling unit of the present invention includes a step of treating the treated water (A) with hypochlorite, the sulphite is added after the solid content removing means 1 and before the ion removing means 2. It may have a sulfite reduction treatment means for reduction treatment. Examples of the sulfite reduction treatment means include a pump continuously added to the supply pipe, or a sulfite reduction treatment tank. This is a pump or tank for treating the treated water (A) with sulfite. By having the sulfite reduction treatment means, deterioration of the ion removal means due to hypochlorite can be suppressed.

In the wastewater recycling unit of the present invention, the treated water supplied between the solid matter removing means 1 and the ion removing means 2 is supplied to the ion removing means 2 so that the ion concentration in the treated water (A) becomes an arbitrary concentration. It is preferable to have an adjusting means for adjusting the amount of (A).
Examples of the adjusting means include a combination of an ion chromatograph for measuring the ion concentration and a valve for adjusting the amount of treated water (A).

  FIG. 3 is a schematic configuration diagram showing a specific example of the wastewater recycling unit of the present invention. In the waste water recycling unit 100, the supplied industrial water L24 is used as a filter, an activated carbon tower, water for cleaning the ion exchanger 31, a boiler, water for the heat exchanger 32, etc., and waste water (A) L25 after use. The wastewater (B) L26 is mixed in the wastewater tank 20 and becomes wastewater. The wastewater is purified in the order of the coagulation treatment tank 21, the pressure floating treatment tank 22, and the contact oxidation treatment tank 23. The flocculation treatment tank 21, the pressure floating treatment tank 22, and the contact oxidation treatment tank 23 correspond to the above-mentioned pretreatment means. Subsequently, the coagulation filtration treatment tank 24 and the activated carbon treatment tank 25 are purified in this order. The coagulation filtration treatment tank 24 and the activated carbon treatment tank 25 correspond to solid content removing means. Then, a purification treatment is carried out in the hypochlorite treatment tank 26. A part of the obtained treated water (A) L21 is purified in the order of the sulfite reduction treatment tank 27, the ion exchange resin treatment tank 28, and the RO membrane treatment tank 29 to obtain treated water (B) L22. The ion exchange resin processing tank 28 and the RO membrane processing tank 29 correspond to ion removing means. The discharged water L23 containing the components removed by the RO membrane is discharged outside the system. The rest of the treated water (A) is used as cleaning water for the filter, the activated carbon tower, and the ion exchanger 31. On the other hand, the treated water (B) is used as water for the boiler and the heat exchanger 32. At this time, the industrial water L24 corresponding to the discharged water L23 is added to the system. The drainage (A) L25 and the drainage (B) L26 after use are mixed in the drainage tank 20 to be drained again.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Method of measuring sodium ion concentration>
(1) Pretreatment The sample (wastewater) was filtered. When the electrical conductivity of the sample was 10 mS / m (100 μS / cm) (25 ° C.) or more, the sample was diluted with water to a certain ratio so that the electrical conductivity was 10 mS / m or less.
(2) Analysis 1) The ion chromatograph was made operable, and the eluent was passed through the separation column at a constant flow rate (for example, 1 to 2 mL / min). In a suppressor device that requires a regenerant, the regenerant was kept flowing at a constant flow rate.
2) Sodium ion mixed standard solution [Na 10 μg] (for example, a fixed amount of 20 to 200 μL) was injected into an ion chromatograph using a microsyringe and a chromatogram was recorded to obtain a peak corresponding to the retention time of sodium ion. I confirmed the position.
3) A fixed amount (for example, 20 to 200 μL of fixed amount) of the pretreated sample was injected into an ion chromatograph using a microsyringe, and a chromatogram was recorded.
4) The indicated value was read for the peak corresponding to sodium ion on the chromatogram.
5) When the sample was diluted, as a blank test, 1) to 4) were performed for the same amount of water as the sample, and the results obtained for the sample were corrected.
6) The sodium ion concentration was determined from the calibration curve, and the sodium ion concentration (mg / L) in the sample was calculated.
[Measurement condition]
Measuring device: ICS-90 (made by Thermo Fisher)
Separation column: IonPac CS12A
Guard column: IonPacCG12A
Eluent: 10 mmol / L methanesulfonic acid Eluent flow rate: 1.5 mL / min
Suppressor: Dionex ERS 500 Ionization regeneration suppressor 4mm
Loop volume: 200 μl

<Calculation method of sodium ion>
FIG. 4 is a schematic configuration diagram showing the wastewater recycling unit used in the examples. In the wastewater recycling unit 101, the wastewater L1 moves from the wastewater tank 11 to the pretreatment means 12, and the pretreatment raw water L2 purified by the pretreatment means 12 is purified by the solid matter removing means 13 to obtain the treated water ( A) It becomes LA. Further, a part of the treated water (A) LA is purified by the ion removing means 14 to be treated water (B) LB. The rest of the treated water (A) LA is used as washing water for the filter and the activated carbon tower 15, and then collected in the drain tank 11 as drainage (A) LE. The treated water (B) LB is used as the feed water for the boiler 16 and then collected in the drainage tank 11 as the drainage (B) LF. The collected wastewater L1 is purified again and is recycled. At this time, the discharged water LC containing the components removed by the RO membrane (ion removing means) is discharged to the outside of the system, and the industrial water LD corresponding to the discharged water LC is replenished. In the examples, as the pretreatment means 12, an aggregation treatment tank, a pressure floating treatment tank, and a contact oxidation treatment tank were used.
According to the above <Measurement method of sodium ion concentration>, a filter, drainage (A) LE after using as washing water for the activated carbon tower 15, drainage (B) LF after using as feed water for the boiler 16, pretreatment raw water L2 The sodium ion concentrations of the treated water (A) LA and the supplemental water LD were measured. Based on the water amount ratio X of some treated water (A) / total treated water (A) and the RO membrane recovery rate Y, the water quality Z1 of the treated water (A) once recycled is assumed, and circulation is assumed. After repeated calculation, the equilibrium concentration Zn (n: number of repeated calculations) was calculated by the following formula. The RO membrane recovery rate Y was calculated as 89% assuming that water satisfying the tap water quality standard was passed. The calculation results are shown in Table 1.

Zn = A1 (1- (1-X) * (1-Y))-A3 * X + A3-A2 + A4
× (1-X) × (1-Y) + A3
= (A4-A1) * (1-X) * (1-Y) + (2-X) * A3 + A1-A2
[In the formula, A1 is a filter, each sodium ion concentration of the wastewater (A) LE after being used as washing water for the activated carbon tower 15 and the wastewater (B) LF after being used as the feed water for the boiler 16 is weighted. A2 is the sodium ion concentration of the pretreated raw water L2, A3 is the sodium ion concentration of the treated water (A) LA, and A4 is the sodium ion concentration of the supplemented water LD. Yes, X is a water amount ratio represented by some treated water (A) / all treated water (A), and Y is RO membrane recovery rate. ]

<Calculation method of drainage rate>
The drainage rate (%) was calculated by the following formula based on the amount of discharged water containing the components removed by the RO membrane.
Drainage rate = some treated water (A) x (1-RO membrane recovery rate) / 100

  As shown in Table 1, the amount of sodium ions obtained from the water quality analysis varies in concentration depending on the ratio of the remaining treated water (A) / partial treated water (A). For example, when the ratio of the balance of treated water (A) / part of treated water (A) is in the range of 90/10 to 80/20, the concentration of sodium ion, which is the standard for tap water quality, satisfies 200 mg / L or less. The quality of the treated water (A) cannot be maintained because it is not available. On the other hand, when the calculation result of the sodium ion concentration is 0/100, which is low, the RO membrane treatment is performed on all the treated water (A), and thus the sodium ion concentration is naturally low. However, since the amount of discharged water containing the components removed by the RO membrane increases, the drainage rate increases and water cannot be saved sufficiently. Therefore, in order to achieve both water quality and water saving, it is understood that the ratio of the remaining treated water (A) / partial treated water (A) in this sample is preferably 70/30 to 30/70. .

In FIG. 5, the remaining treated water (A) is set to 60% and a part of the treated water (A) is set to 40%, and the recycled use of the treated water (A) and the treated water (B) is about 150. It shows the sodium ion concentration of the treated water (A) when it was carried out for a day. Here, the application (A) was used as a filter and water for washing the activated carbon tower, and the application (B) was used as boiler feed water. According to FIG. 5, after several days have passed from the start of recycling, the concentration of sodium ions by recycling occurs. However, the concentration of ions peaked at around 160 mg / L, which is almost the same as the calculation result in Table 1.
This result shows that it is possible to predict the degree of concentration of the ion content by the actual recycling by calculating the degree of concentration of the ion content from the analysis result of the ion concentration in the treated water (A) at the initial stage of recycling. means. Based on this prediction, the amount of the treated water (A) supplied to the step of obtaining the treated water (B) can be adjusted to achieve both water quality and water saving.

1 Solid content removing means 2 Ion removing means 3 Recovery means (A)
4 Collection means (B)
5 Wastewater preparation means

Claims (4)

A step (1) of removing solids from the waste water to obtain treated water (A),
A step (2) of removing ions from a part of the treated water (A) to obtain treated water (B);
A step (3) of using the rest of the treated water (A) as an application (A) to collect wastewater (A),
A step (4) of collecting the wastewater (B) by using the treated water (B) as an application (B),
A step (5) of mixing the wastewater (A) and the wastewater (B) to obtain the wastewater;
The amount of the treated water (A) supplied to the step (2) is adjusted so as to be increased when the ion concentration in the treated water (A) is higher than an arbitrary value, and the treated water (A) is adjusted. When the ion concentration in the treated water (A) is lower than an arbitrary value, the ion concentration in the treated water (A) is adjusted to be equal to or lower than an arbitrary concentration (6). , Wastewater recycling method. The use (A) is water for cleaning equipment,
The wastewater recycling method according to claim 1 , wherein the use (B) is boiler water or heat exchanger cooling water. Solid content removing means for removing the solid content from the waste water to obtain the treated water (A),
Ion removal means for removing ions from a part of the treated water (A) to obtain treated water (B),
A collecting means (A) for supplying the rest of the treated water (A) to the purpose (A) and collecting the wastewater (A) for the purpose (A);
A collection means (B) for supplying the treated water (B) to the purpose (B) and collecting the wastewater (B) for the purpose (B);
Wastewater preparation means for mixing the wastewater (A) and the wastewater (B) to produce the wastewater,
In the treated water (A), the amount of the treated water (A) supplied to the ion removing means is adjusted so as to increase when the ion concentration in the treated water (A) is higher than an arbitrary value. When the ion concentration in the treated water (A) is adjusted to be lower than an arbitrary value, the wastewater recycling unit is provided with an adjusting unit for adjusting the ion concentration in the treated water (A) to be an arbitrary concentration or less. . The use (A) is water for cleaning equipment,
The wastewater recycling unit according to claim 3 , wherein the application (B) is boiler water or heat exchanger cooling water.

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