JPH07144120A - Reverse osmosis membrane device, method for cleaning reverse osmosis membrane device, and method for operating reverse osmosis membrane device - Google Patents

Abstract

(57) [Summary] [Purpose] Membrane contaminants such as all scales can be efficiently removed regardless of the type of contaminants. Moreover, not only the desalination rate and the amount of permeated water can be recovered, but also the differential pressure The present invention provides a method for cleaning a reverse osmosis membrane device capable of effectively reducing the recovery rate, that is, the pressure loss in the reverse osmosis membrane, a reverse osmosis membrane device therefor, and a cleaning operation method for the reverse osmosis membrane device. [Structure] The hydrazine solution is circulated in the reverse osmosis membrane device 1 and then left in the container (vessel) on which the reverse osmosis membrane is mounted. After that, the hydrogen peroxide solution is circulated in the reverse osmosis membrane device, and the film accumulation is completely separated from the film surface by the stirring action and the dispersing force of the generated nitrogen gas as well as the separation action by the oxidation of the film surface accumulation. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to CaCO ₃ , Fe ₂ O ₃ , CaSO ₄ , and S attached to a reverse osmosis membrane of a reverse osmosis membrane device.
The present invention relates to a method for cleaning a reverse osmosis membrane device for cleaning and removing scales such as iO _{2 and the} like, microbial slime, a reverse osmosis membrane device therefor, and a cleaning operation method for the reverse osmosis membrane device.

[0002]

2. Description of the Related Art In general, a reverse osmosis membrane device is used for desalination of fresh water, brackish water, seawater, and TOC (Total Organic Carbon) fine particles in fresh water and pure water. It is widely used for removal, separation and purification of substances.

By the way, the reverse osmosis membrane incorporated in the reverse osmosis membrane device has CaCO ₃ , Fe ₂ O ₃ , CaSO ₄ , and S existing in the feed water as the operating time of the device elapses.
The membrane surface is contaminated by the accumulation and accumulation of impurities such as iO ₂ and scale, turbidity, and microbial slime on the reverse osmosis membrane. As a result, the water resistance of the reverse osmosis membrane device of the feed water, that is, the differential pressure is increased. Increased (pressure loss increased), produced water volume,
If the desalination rate declines and the operation is continued as it is, the reverse osmosis membrane module will eventually break down,
It may not be recoverable.

In order to remove the contamination of the reverse osmosis membrane surface due to such scales, conventionally, acid chemicals such as oxalic acid, citric acid and phosphoric acid, or alkaline chemicals such as caustic soda and sodium ethylenediaminetetraacetate. Medicine,
Alternatively, a surfactant such as sodium dodecyl sulfate is used. That is, the reverse osmosis membrane mounted on the reverse osmosis membrane device is contaminated, and a phenomenon such as an increase in the differential pressure between the inlet and the outlet of the reverse osmosis membrane mounted portion, a decrease in the desalination rate, a decrease in the amount of permeated water, etc. When such a phenomenon occurs, a reverse osmosis membrane washing step is carried out using such a chemical agent to recover the membrane performance.

However, in the case of such a conventional cleaning method, generally, depending on contaminants, acid-based chemicals or alkaline-based chemicals for scales, surfactants for organic oils, and microbial slime. Since chlorine (sodium hypochlorite) etc. is selectively used for the above, it is not suitable for removing the pollutant against complex pollution, and further, all pollutants are removed. In order to remove it, a plurality of washing steps must be carried out, and the steps become complicated, resulting in a decrease in operating rate.

Further, with the above-mentioned chemicals, a chemical solution may remain, which may not be preferable depending on the purpose of use of filtered water, for example, industrial water for manufacturing semiconductors.

Further, in the conventional cleaning method as described above, contaminants are removed by utilizing neutralization with an acid / alkali, dissolution action, chelating action of metal by chelating agent, or dispersing action of phosphate ion. However, since the cleaning action is not so strong, it is difficult to recover the differential pressure to the level at the beginning of using the device. Therefore, in particular, when the recovery rate of the differential pressure is low, the reverse osmosis membrane module is physically damaged, which makes continuous use impossible and lowers productivity.

In view of the above situation, the present invention can efficiently remove membrane contaminants such as all scales regardless of the type of contaminants, and only recover the desalination rate and the amount of permeated water. In particular, the recovery rate of the differential pressure, that is,
A method for cleaning a reverse osmosis membrane device capable of effectively reducing the pressure loss in the reverse osmosis membrane, and a reverse osmosis membrane device therefor,
Another object of the present invention is to provide a cleaning operation method for a reverse osmosis membrane device.

[0009]

The present invention has been made to achieve the above-mentioned objects and objects, and has the following structures (1) to (6). .

(1) Permeated water recovery in which a plurality of reverse osmosis membrane vessel groups in which a plurality of reverse osmosis membrane vessels are connected in parallel are connected in series and the permeated water is recovered for each of the osmosis membrane vessel groups. In a reverse osmosis membrane apparatus configured to collect permeated water by providing a path, from the final vessel group of the reverse osmosis membrane vessel group, raw water or pretreated water,
A reverse osmosis membrane device comprising: a cleaning liquid supply device that supplies a cleaning liquid to the cleaning path by providing a cleaning path that reaches a first group of vessels of the reverse osmosis membrane vessel group.

(2) In the method for operating the reverse osmosis membrane apparatus according to the above (1), the washing path is closed and raw water or pretreated water is supplied to the first group of the reverse osmosis membrane vessel group.
After performing filtration in each osmosis membrane vessel group by supplying to the vessel group of stages, and performing filtration collection operation for collecting permeated water from each osmosis membrane vessel group through the permeation water collection path for a certain period of time. Characterized in that the raw water or pretreatment water supply path is closed, the cleaning path is opened, and the cleaning solution is circulated and supplied from the cleaning solution supply device to remove scale and the like adhering to the reverse osmosis membrane. Cleaning operation method of reverse osmosis membrane device.

(3) The cleaning liquid is circulated and supplied after the hydrazine (N ₂ H ₄ ) solution is circulated and then the hydrogen peroxide (H ₂ O ₂ ) solution is supplied. The method for operating the reverse osmosis membrane device according to paragraph 3,

(4) A method for cleaning a reverse osmosis membrane device, comprising:
After circulating the hydrazine (N ₂ H ₄ ) solution in the reverse osmosis membrane device, the hydrazine solution is left in the vessel in which the reverse osmosis membrane of the reverse osmosis membrane device is mounted, and then hydrogen peroxide (H 2 ₂ O ₂ ) solution is circulated in the reverse osmosis membrane device to obtain the hydrazine (N ₂ H ₄ ) solution and hydrogen peroxide (H ₂ O ₂ )
A reverse osmosis membrane device characterized in that the scale and the like are removed by a redox reaction with a solution, and the efficiency of removal of the scale and the like is promoted by the stirring / dispersing force of nitrogen gas generated by the redox reaction. Cleaning method.

(5) Prior to the circulation of the hydrazine solution, the dilute acids are circulated in the reverse osmosis membrane device to dissolve the heavy metals attached to the reverse osmosis membrane. ) The method for cleaning a reverse osmosis membrane device according to [1].

(6) Before circulating the hydrazine solution, E
The reverse osmosis according to (4) above, wherein the catalytic action of heavy metals attached to the reverse osmosis membrane is suppressed by circulating DTA, oxalic acid, and citric acid in the reverse osmosis membrane device. Membrane device cleaning method.

More specifically, in the cleaning method of the present invention, a hydrazine (N ₂ H ₄ ) solution which is a reducing agent and a hydrogen peroxide solution which is an oxidizing agent are used. Differently, it utilizes the oxidation / reduction effect. First, the reducing action of hydrazine causes the film-adhering contaminants to be easily peeled off, and then the oxidizing action of hydrogen peroxide causes the film-adhering contaminants to be more easily separated. Therefore, CaCO ₃ , Fe ₂ O ₃ , CaS
Regardless of the scale of O ₄ , SiO _2, etc., turbidity, and the type of microbial slime, they have a strong action of removing them, and when the hydrazine (N ₂ H ₄ ) and hydrogen peroxide react, By utilizing the stirring / dispersing force of the nitrogen gas generated as shown in the formula, contaminants such as scale attached to the surface of the reverse osmosis membrane can be efficiently recovered at the time of use.

N ₂ H ₄ + 2H ₂ O ₂ → 4H ₂ O + N ₂ Specifically, the cleaning operation is performed as follows.

First, a hydrazine solution is circulated in a reverse osmosis membrane device, and then a container (vessel) on which a reverse osmosis membrane is mounted.
Remain inside. After that, the hydrogen peroxide solution is circulated in the reverse osmosis membrane device, and the membrane accumulation is formed by the above reaction, that is, the stirring / dispersing force of the generated nitrogen gas together with the peeling action by the oxidation of the membrane surface accumulation. It is to be completely peeled from the surface.

In this case, considering the safety of the membrane, the concentration of the hydrazine solution is preferably about 2%, and the temperature and the circulation time are around 60 minutes, although it depends on the ambient temperature. It is preferable from the viewpoint of the stability of the film. Further, the concentration of the hydrogen peroxide solution is preferably an aqueous solution of 1 wt / vol% or less in consideration of the oxidative deterioration of the film.

In consideration of the heat resistance of the membrane, the reaction time is within 30 minutes or the liquid temperature in the vessel is 35 ° C.
It is preferable that the time is up to.

Further, when there is a risk of accumulation of heavy metals such as iron, manganese and cobalt on the surface of the reverse osmosis membrane, the oxidizing action of the oxidizing agent is excessively promoted by the catalytic action of the heavy metals. Therefore, the performance of the reverse osmosis membrane is deteriorated, so it is preferable to perform the following pretreatment. That is, (1) dilute acids, for example, a 0.1% solution of dilute hydrochloric acid is circulated in the reverse osmosis membrane device to dissolve heavy metals attached to the reverse osmosis membrane.

(3) By circulating EDTA, oxalic acid and citric acid in the reverse osmosis membrane device, the heavy metals adhering to the reverse osmosis membrane are masked to suppress their catalytic action.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The cleaning method for a reverse osmosis membrane device, the reverse osmosis membrane device therefor, and the cleaning operation method for a reverse osmosis membrane device according to the present invention will be described in more detail with reference to the accompanying drawings.

First, FIG. 1 shows the reverse osmosis membrane device of the present invention.
For example, it is a flow chart when incorporated into a pure water production system for use as industrial pure water for semiconductors.
As shown in Fig. 1, first, the raw water taken in is subjected to coagulation sedimentation / filtration or coagulation filtration with a pretreatment device, then the temperature is raised with a heat exchanger through a pretreatment water tank, and microfiltration with a micron filter. After that, most of the dissolved salts in the pretreated water are removed by the reverse osmosis membrane device. Furthermore, about 5% of the remaining dissolved salts are removed by the ion exchange device and supplied to the secondary pure water device.

By the way, even if the pretreatment device is arranged in this way, the reverse osmosis module mounted on the reverse osmosis device is gradually contaminated, and the inlet of the FRP container (vessel) loaded with the reverse osmosis module. And the reading of the pressure gauge installed at the outlet rises, and the water flow resistance of the reverse osmosis membrane device of the feed water, that is, the differential pressure increases (pressure loss increases).

The reverse osmosis membrane device of the present invention has the structure shown in FIG. 2 in order to recover it.

That is, the pretreated water (feed water) that has been pretreated in the pretreatment process according to the quality of the raw water is fed through the feed line 10 into a plurality of first-stage reverse osmosis arranged in parallel. Supplied to the membrane vessel groups 20a, 20b ...
Desalination is performed in each of the reverse osmosis membrane vessel groups 20a, 20b .... The reverse osmosis membrane vessel groups 20a, 20b ... Are FRP vessels (containers) loaded with a reverse osmosis membrane module mounted with a reverse osmosis membrane (the same applies hereinafter).

Then, each vessel group 20a, 20b ...
Part of the supply water supplied to the
4, and then supplied to a plurality of second-stage reverse osmosis membrane vessel groups 30a, 30b, ... Arranged in parallel, and the reverse osmosis membrane vessel groups 30a, 30b. Salt is supposed to be done.

Further, similarly, each vessel group 30
Part of the supply water supplied to a, 30b ... Is collected in the supply line 18, and then a plurality of third-stage (final stage in this embodiment) reverse osmosis membranes arranged in parallel. It is supplied to the vessel groups 40a, 40b ... And desalted in each of the reverse osmosis membrane vessel groups 40a, 40b.

On the other hand, the permeated water filtered by the vessel group at each stage is collected in the water collecting path 50 through the water collecting paths 22, 32 and 42 and used as the permeated water. It has become.

By the way, in this apparatus, a recovery path 60 for recovering a part of the feed water supplied to each of the final-stage reverse osmosis membrane vessel groups 40a, 40b ... Is extended to provide the final-stage vessel group 40a. , 40b ... from the first stage Bessel group 2
A cleaning path 70 leading to 0a, 20b ... A cleaning tank 74 having a stirring device 72 and a supply pump 76 are provided in the path.

In the case of this embodiment, the number of reverse osmosis membrane vessel groups and the number of stages of the reverse osmosis membrane vessel groups can be appropriately changed, and two cleaning tanks 74 are collected in parallel. Of course, it is also possible to provide in the path 60 and prepare and supply the oxidizing agent and the reducing agent, respectively. Also,
In FIG. 2, P1 to P4 are pressure gauges.

In the reverse osmosis membrane device thus constructed, an operating method for carrying out the cleaning step will be described below.

First, in FIG. 2, a regulating valve A provided in a supply line 10 for supplying the supply water of the reverse osmosis membrane device 1,
And the regulating valve B provided in the recovery path 60 is closed to close the normal operation line. Next, the adjusting valves C and D provided in the cleaning path 70 are opened, and the hydrazine solution that is a reducing agent prepared in advance in the cleaning tank 74 is supplied with the supply pump 76.
Through the reverse osmosis membrane device 1 for a predetermined time. In this case, the water collection path 50 is closed.

After that, the adjusting valves C and D provided in the cleaning passage 70 are closed, and the drain valve E of the cleaning tank 74 and the
Circulated hydrazine is discharged as much as possible through the sample valves P, Q, and R arranged at the lower position of the cleaning path 70 in advance.

Next, a hydrogen peroxide solution, which is an oxidant, is prepared in the cleaning tank 74, and is circulated in the reverse osmosis membrane device 1 in the same manner as the above-mentioned hydrazine to oxidize and reduce, and generate nitrogen gas. The scale and the like attached to the reverse osmosis membrane are washed and removed by the stirring and dispersing force of.

Example 1 A reverse osmosis membrane device (120 inches of 8-inch reverse osmosis membrane module) as shown in FIG. 2 under the conditions shown in Table 1 below.
The operation experiment of was done.

In Table 1, the data in the column "at the beginning of operation" is the value obtained after several weeks from the continuous operation after the test operation of the apparatus. Further, in Table 1, the data in the column "before cleaning" is the operation data at the time when about one and a half years have passed thereafter.

From the results shown in the table, the total differential pressure of ¹ to 3 BANK is 2.6 kg / cm ² to 7.8 kg / cm at the beginning of the operation.
It has risen to cm ² . The “differential pressure” referred to here is the pressure difference between the pressure gauges P1 to P4 shown in FIG. Although the chemical cleaning with the 2% citric acid solution has been carried out several times since the start of operation, the cleaning effect was small and the differential pressure gradually increased.

Therefore, at the time of about one and a half years, acid cleaning (2%
After performing pH 2-3 with citric acid and circulating for 1 hour), alkali cleaning at pH 11-12 (predetermined pH concentration with caustic soda and circulating for 4 hours) was performed. The data is the data in the column “after alkaline cleaning” in Table 1.

According to this "after alkaline cleaning" data, the total 1 to 3 BANK differential pressure after "after alkaline cleaning" is about 50% lower than the total 1 to 3 BANK differential pressure before "before cleaning". In addition, the value was also considerably larger than the differential pressure decrease rate of 17% in the case of “acid solution cleaning” calculated in the same way, and the differential pressure has recovered, but it has reached the value at the “initial operation”. By comparison, it is 1.5 times, which is far from recovering to the differential pressure at the beginning of operation.

Therefore, according to the cleaning method of the present invention, 2 pieces are prepared for 120 pieces of 8-inch reverse osmosis membrane modules.
Prepare 3000 wt% / vol% hydrazine solution, circulate the solution in the reverse osmosis membrane device at 21 ° C. for 2 hours and discharge as much as possible, and then add 3000% of 1% hydrogen peroxide solution at 21 ° C. , Circulated for 30 minutes. After that, the so-called "flushing" is performed in which a high flow rate of supply water is poured to wash away dirt.
Then, the operation was performed under the specified conditions. The result is the data of “after oxidation / reduction cleaning” in Table 1.

As is clear from these results, when cleaning is performed by the method of the present invention, the total differential pressure is almost "at the beginning of operation".
Has recovered to the level of. Further, no decrease in the desalination rate was observed, and the amount of permeated water increased by 1 m ³ / h as compared with the case of “after alkaline cleaning”. Therefore, it can be seen that the cleaning method of the present invention is significantly superior to the conventional cleaning method in its cleaning effect.

[0044]

[Table 1]

[0045]

INDUSTRIAL APPLICABILITY The cleaning method, the reverse osmosis membrane apparatus therefor, and the cleaning operation method of the reverse osmosis membrane apparatus according to the present invention include a hydrazine (N ₂ H ₄ ) solution which is a reducing agent and a peroxide which is an oxidizing agent. Using hydrogen oxide solution, by utilizing the oxidation / reduction effect, the reducing action of hydrazine causes the film-adhering contaminants to be easily separated, and then the oxidizing action of hydrogen peroxide makes it easier to remove the film-adhering contaminants. It becomes a state.

Then, by utilizing the stirring / dispersing power of nitrogen gas generated when hydrazine (N ₂ H ₄ ) and hydrogen peroxide react, contaminants such as scale attached to the surface of the reverse osmosis membrane are removed. It is a thing.

Therefore, CaCO ₃ , Fe ₂ O ₃ , CaS
Regardless of the type of scale such as O ₄ and SiO ₂ , turbidity, and microbial slime, it has a strong effect of removing these, and efficiently removes contaminants such as scale attached to the reverse osmosis membrane surface,
Moreover, it can be recovered just as it was at the beginning.

That is, regardless of the type of pollutant,
Membrane contaminants such as all scales can be removed efficiently, and not only the desalination rate and the amount of permeated water are recovered, but also the recovery rate of the differential pressure, that is, the pressure loss in the reverse osmosis membrane, is effective. It is possible to provide a method for cleaning a reverse osmosis membrane device that can be reduced, a reverse osmosis membrane device therefor, and a cleaning operation method for a reverse osmosis membrane device.

[Brief description of drawings]

FIG. 1 is a flowchart when the reverse osmosis membrane device of the present invention is incorporated into a pure water production system.

FIG. 2 is a schematic view of a reverse osmosis membrane device of the present invention.

[Explanation of symbols]

1 ... Reverse osmosis membrane device 10 ... Supply line 14 ... Supply line 18 ... Supply line 20a, 20b ... The first stage reverse osmosis membrane vessel group 22, 32, 42 ... Water collection path 30a, 30b ... Reverse osmosis membrane vessel group 40a, 40b, ... Third stage (final stage) reverse osmosis membrane vessel group 50 ... Water collecting path 60 ... Recovery path 70 ... Washing path 72 ... Stirring device 74 ... Washing tank 76 ... Supply Pumps P1 to P4 ... Pressure gauge A, B, C, D ... Regulator valve E ... Drain valve P, Q, R ... Sample valve

Claims (6)

[Claims] 1. A permeated water recovery route for connecting a plurality of reverse osmosis membrane vessel groups in which a plurality of reverse osmosis membrane vessels are connected in parallel in series and collecting permeated water for each of the osmosis membrane vessel groups. In the reverse osmosis membrane apparatus configured to collect permeated water, raw water or pretreated water is supplied from the final stage vessel group of the reverse osmosis membrane vessel group to the first group of the reverse osmosis membrane vessel group.
A reverse osmosis membrane device, wherein a cleaning path is provided up to a path for supplying to a vessel group of stages, and a cleaning solution supply device for supplying a cleaning solution is arranged in the cleaning path. 2. The washing operation method for a reverse osmosis membrane device according to claim 1, wherein the washing passage is closed to supply raw water or pretreated water to the vessel of the first stage of the reverse osmosis membrane vessel group. By carrying out the filtration in each osmosis membrane vessel group by supplying to the group,
Through the permeated water recovery path, after carrying out a filtration recovery operation for recovering permeated water from each osmosis membrane vessel group for a certain period of time, while closing the raw water or pretreated water supply path, opening the cleaning path, A cleaning operation method for a reverse osmosis membrane device, characterized in that the cleaning liquid is circulated and supplied from the cleaning liquid supply device to remove scale and the like attached to the reverse osmosis membrane. 3. The cleaning solution is circulated and supplied after hydrogen hydrazine (N ₂ H ₄ ) solution is circulated and supplied.
The cleaning operation method for a reverse osmosis membrane device according to claim 2, wherein a ₂ O ₂ ) solution is supplied. 4. A method for cleaning a reverse osmosis membrane device, wherein a hydrazine (N ₂ H ₄ ) solution is circulated in the reverse osmosis membrane device and then the reverse osmosis membrane of the reverse osmosis membrane device is mounted. leaving a hydrazine solution into the vessel, then hydrogen peroxide (H ₂ O ₂₎ solution was circulated in the reverse osmosis membrane apparatus, the hydrazine (N ₂ H ₄₎ solution and hydrogen peroxide (H ₂ O ₂ ) A reverse osmosis membrane characterized by removing the scale and the like by a redox reaction with a solution and promoting the removal efficiency of the scale and the like by stirring and dispersing force of nitrogen gas generated by the redox reaction. How to clean the equipment. 5. The heavy metal adhering to the reverse osmosis membrane is dissolved by circulating a dilute acid in the reverse osmosis membrane device before circulating the hydrazine solution. Method for cleaning reverse osmosis membrane device. 6. EDT before circulation of the hydrazine solution
The reverse osmosis membrane device according to claim 4, wherein the catalytic action of heavy metals attached to the reverse osmosis membrane is suppressed by circulating A, oxalic acid, and citric acid in the reverse osmosis membrane device. Cleaning method.