JP2003305343A - Dechlorination treatment method and dechlorination treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently carry out dechlorination even when salt concentrations in raw water are varied. <P>SOLUTION: Flow rates of a reverse osmosis pump 114 and an electrodialyzer pump 118 are controlled by the measurement of salt concentrations in raw water by using an electro-conductivity meter 112. The ratio of the treatment capacity of a reverse osmosis device 116 to that of an electro-osmosis device 120 is controlled in a way that the treatment capacity of the reverse osmosis device 116 is increased when the salt concentrations are high and that the treatment capacity of the electro-osmosis device 120 is increased when the salt concentrations are low. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reverse osmosis device for performing desalting treatment by applying pressure through a reverse osmosis membrane, and an electrodialysis device for performing desalting treatment by applying an electric field through an ion exchange membrane. Are provided in parallel, and both devices are operated in parallel to perform a desalination process.

[0002]

2. Description of the Related Art Conventionally, brine (groundwater having a lower salinity concentration than seawater, for example, a salinity concentration of 1,700 mg
-Cl / L or more solution) or brackish water (surface water having a lower salt concentration than seawater) may be used as raw water to generate tap water. If raw water with the best possible water quality is obtained, it will be easier to treat, but in some cases it may be necessary to use raw water with a considerably high salinity due to regional restrictions.

Reverse osmosis membrane method (RO) and electrodialysis method (ED (El
ectroDialysis) or EDR (ElectroDialysis Revers
al: polarity conversion type electrodialysis method)) and the like are known.

RO has an advantage that it can surely perform desalting even when the salt concentration is high. However, RO has a problem that it is vulnerable to an oxidizing agent such as residual chlorine in water, and is easily clogged with fine particles and organic substances. further,
RO has a drawback that power consumption is large and high-pressure operation is performed, so attention must be paid to blowing out high-pressure water.

On the other hand, EDs or EDRs (hereinafter, collectively referred to as EDs) have advantages that clogging is less likely to occur and power consumption is not so large. But E
D is poor in maintainability and has a high salt concentration,
There is a drawback that the salt concentration of the treated water cannot be lowered sufficiently.

[0006] Therefore, generally, the water quality of raw water, especially the salt concentration is investigated in advance and the one with higher efficiency is selected.

[0007]

However, when the water quality of raw water changes drastically throughout the year, it becomes difficult to select it. That is, if raw water with high salt concentration needs to be treated even for a short period, RO should be selected. However, the salt concentration is low for many periods, and since the reverse osmosis device is used also during this period, there is a problem that power consumption becomes large, and in particular, it is inefficient in terms of cost.

[0008]

The present invention is directed to a reverse osmosis device for performing desalting treatment by applying pressure through a reverse osmosis membrane and an electrodialysis for performing desalting treatment by applying an electric field through an ion exchange membrane. In a desalination treatment method in which devices are provided in parallel and both devices are operated in parallel to perform desalination treatment, depending on the salt concentration of the raw water, the throughput ratio of the reverse osmosis device is high when the raw water salt concentration is high, It is characterized in that when the raw water salt concentration is low, the throughput ratio of the reverse osmosis device is lowered and the throughput ratio of the reverse osmosis device and the electrodialysis device is changed.

Further, the present invention comprises a reverse osmosis device for performing desalting treatment by applying pressure through a reverse osmosis membrane and an electrodialysis device for performing desalting treatment by applying an electric field through an ion exchange membrane in parallel. In preparation for this, in a desalination treatment system in which both devices are operated in parallel to perform desalination treatment, salt concentration measuring means for measuring the salt concentration of the raw water is provided, and the salt concentration of the raw water measured by this salt concentration measuring means is adjusted. , When the raw water salt concentration is high, the throughput ratio of the reverse osmosis device is high, when the raw water salt concentration is low, the throughput ratio of the reverse osmosis device is low, and the throughput ratio of the reverse osmosis device and the electrodialysis device is changed. Is characterized by.

As described above, according to the present invention, the treatment ratio of the reverse osmosis device and the electrodialysis device is changed according to the raw water salt concentration. As a result, the installation area of the entire desalination facility can be reduced as compared with the installation area of the electrodialysis device alone, and the salt concentration of the treated water can be maintained at a low concentration even when the salt concentration of the raw water becomes high. Moreover, when the raw water salt concentration is low, power consumption can be saved. As described above, the system of the present embodiment enables efficient operation while suppressing the power consumption while maintaining the quality of the treated water to be good.

In addition, even if either the reverse osmosis device or the electrodialysis device fails, a certain amount of treated water can be secured by using the device that has not failed.

Further, each of the reverse osmosis device and the electrodialysis device is characterized by having a processing capacity of 60% or less of a planned maximum throughput.

As a result, even if either the reverse osmosis device or the electrodialysis device fails, it is possible to secure about half the planned amount of treated water by using the device that has not failed. Even if only one of the devices is installed, a margin of about 20% is normally secured for the planned maximum throughput for maintenance. Therefore, the treatment of the reverse osmosis device and the electrodialysis device is performed. 120% of planned maximum throughput
Even if it is set to a level (each device has a processing capacity of about 60% of the maximum planned throughput), it does not become an excess facility.

Further, it is preferable that the reverse osmosis device and the electrodialysis device change the treatment amount within a range of 40 to 60% of the planned maximum treatment amount. By making such a change, efficient operation can be performed using both devices.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a desalination treatment system according to an embodiment. A conductivity meter 112 is provided in the raw water pipe 110 through which the water to be treated for desalination flows, and the conductivity of the raw water is measured. Since the conductivity has a nearly one-to-one relationship with the salt concentration, the conductivity meter 112 measures the salt concentration.

In this raw water pipe 110, the reverse osmosis pump 1
The reverse osmosis pump 114 supplies raw water to the reverse osmosis device 116. Reverse osmosis device 116
Has a reverse osmosis membrane inside and is supplied with raw water.
It is divided into a permeated water chamber 116b in which permeated water that has passed through 16a and the reverse osmosis membrane is obtained. And the permeate chamber 116b
The permeated water obtained in step 1 is discharged as treated water. Further, concentrated wastewater in which salt is concentrated is obtained in the raw water chamber 116a and is discharged to the outside of the system. In this example, part of the concentrated waste water discharged from the raw water chamber 116a is circulated to the suction side of the reverse osmosis pump 114. The reverse osmosis membrane used in the reverse osmosis device 116 includes various types such as a hollow fiber type and a flat membrane type, and is not particularly limited.

An electrodialysis pump 118 is also connected to the raw water pipe 110, by which raw water is supplied to the electrodialysis device 120. This electrodialysis device 120
Is basically a desalination chamber 1 which is partitioned on both sides by ion exchange membranes (one side is a cation exchange membrane and the other side is an anion exchange membrane).
20a and concentration chambers 120b on both sides thereof are provided, and a pair of electrodes 120c is provided outside these. And
By applying a DC electric field to the whole by the pair of electrodes 120c, the ions in the raw water escape to the concentrating chamber 120b through the ion exchange membrane. Therefore, the desalted treated water is obtained in the desalination chamber 120a, and the concentrated waste water in which the salt content is concentrated is obtained in the concentration chamber 120b.

In the usual case, a plurality of cation exchange membranes and a plurality of anion exchange membranes are alternately arranged to alternately partition the desalting chamber and the concentrating chamber, and the plurality of desalting chambers 120a and 120b are separated. The electrodes 120c are disposed on both sides of the.

In addition, the electrodialysis device has an ED as described above.
In EDR, a direct current of the same polarity is always applied to the pair of electrodes 120c, but in EDR, the pair of electrodes 12c is used.
The polarity of direct current with respect to 0c is reversed at a predetermined frequency. ED
Although R has an advantage that scale can be prevented from being generated on the electrode (cathode), any form can be used in the present embodiment.

The treated water from the reverse osmosis device 116 and the electrodialysis device 120 is combined, and then the disinfectant (for example, sodium hypochlorite) from the disinfectant storage tank 122 is added by the disinfectant pump 124, and the disinfected process is performed. Water is distributed as clean water.

In the present embodiment, the output of the conductivity meter 112 is supplied to the control unit 126, which controls the reverse osmosis pump 114 and the electrodialysis pump 11.
8 to control the ratio of the throughputs of the reverse osmosis device 116 and the electrodialysis device 120. That is, when the raw water salt concentration measured by the conductivity meter 112 is high, the flow rate of the reverse osmosis pump 114 is increased and the flow rate of the electrodialysis pump 118 is decreased to increase the throughput of the reverse osmosis apparatus 116 and the electrodialysis apparatus. The processing amount of 120 is reduced. On the other hand, when the raw water salt concentration is low, the flow rate of the reverse osmosis pump 114 is decreased and the flow rate of the electrodialysis pump 118 is increased to decrease the throughput of the reverse osmosis device 116 and increase the throughput of the electrodialysis device 120. This means that the reverse osmosis device 116 can maintain good treated water quality even if the raw water salt concentration is high, but the operating cost is high. On the other hand, the electrodialysis device 12
When the raw water salt concentration is 0, the treated water quality cannot be maintained well, but the operating cost is low.

For example, the maximum treatment capacities of the reverse osmosis device 116 and the electrodialysis device 120 are set to about 60% of the planned maximum treated water amount of raw water flowing into this system, respectively. Then, it is advisable to change the treatment amount in the range of 40% to 60% of the planned maximum treated water amount according to the salt concentration. Even when only one of the devices is installed, a margin of about 20% is secured for normal maintenance. Therefore, the total processing capacity of the reverse osmosis device 116 and the electrodialysis device 120 is the maximum planned. 12 of treated water
Even if it is set to about 0% (60% for each device), it does not become an excess facility.

The conductivity of the raw water is 600 to 8,000.
Conductivity 2 when changing in the range of 0 μS / cm
Reverse osmosis device 40%, electrodialysis device 60%, conductivity 2000 to 2500 μS / cm when 000 μS / cm or less
Reverse osmosis device 50%, electrodialysis device 50%, conductivity 2,500 μS / cm or more reverse osmosis device 60%,
The treatment rate is changed in three steps like the electrodialyzer 40%.

In this way, 40% to 6% of the planned maximum throughput
0% (66.7% to 1 for each device)
(00%) has no particular effect on the operation of each device, and can be dealt with only by controlling the water amount of the pump.

That is, the salt concentration is 700 mg-Cl / L
When it exceeds the level (electrical conductivity 2500 μS / cm), the salt concentration of the treated water by the electrodialyzer 120 is stabilized to 200.
It becomes difficult to maintain the concentration below mg-Cl / L (electrical conductivity 600 μS / cm). Therefore, in the case of such a raw water salt concentration, the processing amount of the reverse osmosis device 116 is increased.

On the other hand, if the salt concentration is about 600 mg-Cl / L (electrical conductivity 2000 μS / cm) or less, the salt concentration of the treated water by the electrodialyzer 120 is stable at 200 m.
It can be maintained below g-Cl / L (electrical conductivity 600 μS / cm). Therefore, in such a case, the throughput of the electrodialysis device 120 is increased.

As described above, according to the system of this embodiment, the treatment ratios of the reverse osmosis device 116 and the electrodialysis device 120 are changed according to the raw water salt concentration. As a result, even if the salt concentration of the raw water changes, the desalination treatment can be efficiently performed especially in terms of power consumption. Further, the installation area of the entire desalination facility can be reduced as compared with the installation area of the ED alone, and the salt concentration of the treated water can be kept low even when the salt concentration of the raw water becomes high. Moreover, when the raw water salt concentration is low, power consumption can be saved. As described above, the system of the present embodiment enables efficient operation while suppressing the power consumption while maintaining the quality of the treated water to be good. Further, there is a possibility that the reverse osmosis device 116 will break down when the oxidizer remains in the raw water before desalting, but even in this case, the electrodialysis device 120 can secure about half the amount of treated water.

Next, the overall construction of a water purification facility for obtaining tap water using the desalination system of this embodiment as raw water having a high salt concentration will be described with reference to FIG. Intake well 1 for obtaining raw water (eg groundwater) to be treated
At 0, a raw water pump 12 is provided, from which raw water is taken. The raw water from the raw water pump 12 is supplied to the mixing tank 14, and a raw water turbidity meter 16 is provided in the raw water pipe. The raw water turbidity meter 16 allows the raw water as the treated water to be turbid. The degree is detected.

The coagulant from the coagulant storage tank 18 is supplied to the mixing tank 14 by the coagulant pump 20, and the oxidant from the oxidant storage tank 22 is supplied by the oxidant pump 24. Here, polyaluminum chloride (PAC) is preferable as the aggregating agent, but other aluminum-based or iron-based aggregating agents can be used, and a pH adjusting agent may be added if necessary. Further, a polymer flocculant may be added as a flocculation aid. Although sodium hypochlorite is generally used as the oxidizing agent, chlorine gas may be used.
Thereby, the pre-chlorination process is performed. The chlorine-based oxidizing agent may be replaced by another oxidizing agent such as ozone, and the injection of the oxidizing agent may be omitted.

The mixing tank 14 is provided with a stirrer, in which the raw water and the aggregating agent are agitated and mixed, and the solid matter in the raw water is agglomerated.

The coagulated water from the mixing tank 14 is supplied to the long fiber filtration device 26. This long fiber filtration device 26 is
It has a long fiber filtering device body 26a, a long fiber filtering material 26b, a floating filler 26c and the like. This floating filler 26
c is a specific gravity that floats during normal filtration, so that the floating filler 26c is suppressed by the floating filler 2
Only above 6. Further, by providing such a floating filler 26c, the filtration capacity can be improved and sufficient treatment can be performed even when the quality of raw water is poor, as compared with the case where only the long fiber filter 26b is provided. The backwashing device and the like are not shown.

The treated water of the long fiber filter 26 is supplied to the activated carbon adsorption tower 28. This activated carbon adsorption tower 28 is
The inside thereof is filled with activated carbon, and the activated carbon adsorbs and removes organic matter in water that could not be removed by coagulation filtration. The activated carbon-treated water is the activated carbon-treated water tank 3
It is saved to 0. An activated carbon treated water pump 32 is connected to the activated carbon treated water tank 30, whereby the activated carbon treated water is supplied to the two-layer filter 34. The two-layer filter 34 is, for example, a filter having two layers of anthracite and sand, and performs a precise filtration process by the long fiber filtration device 26 described above. In particular, in the case of the present embodiment, the solid load on the two-layer filter 34 is very small, because a considerable amount of solid matter has been removed by the long fiber filtration device 26.
Therefore, the filtration duration can be extended to perform a very efficient filtration process. Then, as the treated water of the two-layer filter 34, the two-layer filtered treated water having sufficiently low turbidity is obtained.

The filtered water from the two-layer filter 34 is introduced into the filtered water storage tank 42.

The filtered and treated water from the filtered and treated water storage tank 42 is supplied to the reverse osmosis device 11 by the reverse osmosis pump 114.
6 and also to the electrodialysis device 120 by the electrodialysis pump 118. Also, the two-layer filter 3
The electrical conductivity of the treated water of No. 4 is measured by the conductivity meter 112, and the measurement result is supplied to the control unit 126. The control unit 126 controls the flow rates of the reverse osmosis pump 114 and the electrodialysis pump 118 according to the supplied measurement result,
The ratio of the throughput of the reverse osmosis device 116 and the electrodialysis device 120 is controlled. In addition, the reverse osmosis device 116 and the electrodialysis device 1
A disinfectant (for example, sodium hypochlorite) from the disinfectant storage tank 122 is added to the treated water of 20 (post-chlorination). In this way, the post-chlorination treatment is performed, and the treated water containing an appropriate amount of residual chlorine is distributed as clean water through a water distribution tank or the like.

[0036]

EXAMPLE An example of processing using the reverse osmosis device 116 and the electrodialysis device 120 will be described below.

<Condition> (I) Raw water; brine Salt concentration 350-2,200 mg-Cl / L (electrical conductivity
1,300-6,600 μS / cm) (Ii) Maximum planned treated water amount: 360 m^Three/ D (Iii) Processing flow; system of FIG. Mixing tank (coagulation
Agent and pre-chlorine addition) 14 → long fiber filter 26 (water flow
Speed 480 m / d) → Activated carbon adsorption tower 28 (SV10h
^-1) → two-layer filter 34 (filtration speed 150 m / d) → reverse
Penetration device 116 and electrodialysis device 120 (EDR device)
→ (Post-chlorine) → Distribution of treated water (Iv) Specifications of reverse osmosis device 116 Element: diameter 8 inches x length 1m, cross-linked polyamide
System spiral membrane, System: 1st stage 4 elements x 2 series, 2nd stage 4
Element x 1 series, total 12 elements, Performance: Maximum amount of treated water 216m^Three/ Day, water recovery rate 80%,
Desalination rate 98%. (V) Specifications of electrodialysis device (EDR) 120 Membrane size: 80 cm x 70 cm (membrane area 0.56
m^Two), Number of membranes: 100 cell pairs / tank (membrane area 56m
^Two/ Tank), number of tanks: 6 tanks, performance: maximum treated water amount of 216 m ^Three
/ Day, water recovery rate 85%, desalination rate 95% (Vi) Target water quality; salt concentration 200 mg-Cl / L (electricity
Conductivity 600 μS / cm) or less

The coagulant was added to the mixing tank 14 in proportion to the raw water turbidity measured by the raw water turbidimeter 16.

The pre-chlorination (chlorine injection amount) in the mixing tank 14 was a constant injection of 1.0 mg / L.

Then, the conductivity of the two-layer filtered treated water was measured by the conductivity meter 112, and (i) the electric conductivity was 2,500 μm.
In the case of S / cm or more, the amount of treated water of the reverse osmosis device (RO) is 216 m ³ / d, and the amount of treated water of EDR is 144 m ³ / d.
(Water ratio RO: EDR = 6: 4), and (ii) electric conductivity of 2,000 μS / cm or more, 2,500 μS / c
If less than m, the amount of RO treated water is 180 m ³ / d, ED
The treated water amount of R is 180 m ³ / d (water amount ratio RO: EDR =
5: 5), and (iii) electric conductivity is 2,000 μS.
If less than / cm, the treated water amount of RO is 144 m ³ / d,
The treated water volume of EDR is 216 m ³ / d (water volume ratio RO: ED
R = 4: 6).

As a result, the reverse osmosis device (RO) 116
And, water having a salt concentration of 180 mg-Cl / L or less was obtained as the water obtained by combining the treated water of the electrodialyzer (EDR) 120, and chlorine was added to this to obtain purified water.

Here, the power consumption in the desalination system of this embodiment will be described. Salt concentration is 700 mg-
Consider the case of around Cl / L (electrical conductivity of 2,500 μS / cm).

The power consumption per unit amount of treated water of RO is
The power consumption per unit treated water amount of 9 kWh / m ³ and EDR is about 5 kWh / m ³ .

Therefore, when the processing is performed with RO: EDR = 6: 4, the power consumption becomes 7.4 kWh / m ³ . Also,
When RO: EDR = 5: 5, the power consumption is 7 kWh / m
It becomes ³ . Power consumption 9kWh when processing all in RO
/ ^M compared to ^3, power consumption per day is 1.6
2.0 kWh / m ³ × 360 m ³ = 576 to 720 kW
It is possible to save h. Therefore, if 1 kW = 17 yen, the savings will be 9,792 to 14,620 yen / day.

[0045]

As described above, according to the present invention,
The treatment ratio of the reverse osmosis device and the electrodialysis device is changed according to the raw water salt concentration. As a result, compared with the installation area of the electrodialysis machine alone, the installation area of the entire desalination equipment can be reduced,
Even if the salt concentration of the raw water becomes high, the salt concentration of the treated water can be kept low. Moreover, when the raw water salt concentration is low, power consumption can be saved. As described above, the system of the present embodiment enables efficient operation while suppressing the power consumption while maintaining the quality of the treated water to be good.

In addition, even if either the reverse osmosis device or the electrodialysis device fails, a certain amount of treated water can be secured by using the device that has not failed.

Further, since the reverse osmosis device and the electrodialysis device have a processing capacity of 60% or less of the planned maximum throughput, even if either the reverse osmosis device or the electrodialysis device fails, it does not fail. About half of the treated water can be secured using the equipment. Even if only one of the devices is installed, a margin of about 20% is usually secured for maintenance. Therefore, the sum of the processing capacities of the reverse osmosis device and the electrodialysis device should be the maximum water amount. Even if it is set to about 120%, it will not cause excess equipment.

By changing the treatment amount of the reverse osmosis filtration device and the electrodialysis device within the range of 40 to 60% of the planned maximum treatment amount, both devices can be used for efficient operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a desalination treatment system according to an embodiment.

FIG. 2 is a block diagram showing a configuration of a processing system including a desalination processing system according to an embodiment.

[Explanation of symbols]

112 conductivity meter, 114 reverse osmosis pump, 116 reverse osmosis device, 118 electrodialysis pump, 120 electrodialysis device, 126 control unit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toyoaki Ohta             Olga 1-2-8 Shinsuna, Koto-ku, Tokyo             Within the corporation F-term (reference) 4D006 GA03 GA17 KA01 KA67 KB12                       KB13 KB14 KD08 KD09 KD24                       KE02Q KE12P MA01 MA03                       MA13 MA14 PA01 PB04 PB05                 4D061 DA02 DB13 EA09 EB13 EB17                       EB19 EB37 EB39 FA06 FA10                       FA11 FA13 FA14 GA06 GC02

Claims (4)

[Claims] 1. A reverse osmosis device for performing desalting treatment by applying pressure through a reverse osmosis membrane and an electrodialysis device for performing desalting treatment by applying an electric field through an ion exchange membrane, both of which are provided in parallel. In the desalination treatment method, in which the devices are operated in parallel to perform desalination treatment, the reverse osmosis unit treats a high treatment amount ratio when the raw water salt concentration is high and reverses it when the raw water salt concentration is low. A desalination treatment method characterized in that the throughput ratio of an osmosis device is low and the throughput ratio of a reverse osmosis device and an electrodialysis device is changed. 2. A reverse osmosis device for performing desalting treatment by applying pressure through a reverse osmosis membrane and an electrodialysis device for performing desalting treatment by applying an electric field through an ion exchange membrane, both of which are provided in parallel. In the desalination system that operates the above equipment in parallel to perform desalination treatment, a salt concentration measuring means for measuring the salt concentration of the raw water is provided, and the salt concentration of the raw water is measured according to the salt concentration of the raw water. When the water content is high, the reverse osmosis device has a high throughput ratio, when the raw water salt concentration is low, the reverse osmosis device has a low throughput ratio, and the throughput ratio of the reverse osmosis device and the electrodialysis device is changed. Desalination treatment system. 3. The desalination treatment method or desalination treatment system according to claim 1, wherein the reverse osmosis device and the electrodialysis device each have a treatment capacity of 60% or less of a planned maximum treatment amount. The desalination treatment method or the desalination treatment system, wherein 4. The desalination treatment method or system according to any one of claims 1 to 3, wherein the reverse osmosis device and the electrodialysis device are in a range of 40 to 60% of a planned maximum treatment amount. A desalination treatment method or a desalination treatment system, characterized in that the treatment amount is changed within.