JP2694982B2 - Recycled waste liquid recovery system for pure water production equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reclaimed waste liquid recovery system for a pure water producing device that treats a reclaimed waste liquid from a pure water producing device in various treatment plants using an electrodialysis device. is there.

[Conventional technology]

In various treatment plants such as semiconductor manufacturing and processing, a closed or semi-closed integrated water treatment facility is often used. In this case, how to recycle the waste liquid from the pure water production equipment by the ion exchange resin method is used. It is important to process at low initial cost and low running cost.

In the conventional method, the recycled waste liquid from the pure water producing device is used alone or mixed with the recycled waste liquid that has passed through the recovery device discharged from the treatment plant, concentrated to 10 to 20 times with an evaporator, and then with a drum dryer. After drying, it is processed as a cake (solid matter).

This evaporator system is very expensive both for initial and running, and at the same time, calcium, silica, hydrofluoric acid, etc. coming from the recycled waste liquid become sources of scale, which clogs the plate of the heat exchanger in the evaporator and the plate This requires frequent cleaning or replacement, which is extremely disadvantageous in terms of operation management and cost of the evaporator.

[Problems to be solved by the invention]

Therefore, the present inventors collect the dialysis-treated water (diluted water) into the raw water of the pure water production apparatus by treating the recycled waste liquid from the pure water production apparatus with an electrodialysis apparatus, or cool the factory building. , At the same time it was recovered as water for tap water, and at the same time, the concentrated water concentrated 10 to 30 times was treated as a solid matter with a drum dryer to reduce the initial waste treatment cost and the running cost.

However, in this case, the silica that is brought in from the raw water is mixed into the recycled waste liquid of the pure water production device, so when this is applied to the electrodialysis device, it is mixed with the above-mentioned silica and the recycled waste liquid at the cation membrane surface. Scales due to the binding of calcium and magnesium ions adhere, and the problem of clogging of the dialysis membrane frequently occurs.

The present invention has been made to address such a problem.

[Means for solving the problem]

The gist of the present invention is to adjust each cation exchange resin and anion exchange resin of a pure water production apparatus by an ion exchange resin method to a liquid having a pH of 10 or more by mixing with or without adding alkali. The solid waste produced in the mixed solution is solid-liquid separated, and the obtained liquid is treated with an electrodialysis device. It eliminates the points and contains the intended purpose.

The above-mentioned ion exchange resin method-based pure water production equipment collects waste water that is used in the factory and when producing pure water from raw water such as industrial water, city water, well water, and river water. For this reason, there are cases in which recovered water is produced from a recovery device using an ion-exchange resin.In the latter case, if hydrofluoric acid is mixed in the wastewater that comes out of the factory, this will result in a waste liquid recycled from the recovery device. As it comes in, if this is treated in the electrodialyzer together with the waste liquid recycled from the deionizer in the former case, calcium fluoride etc. will be generated which will cause clogging of the dialysis membrane. It is preferable to treat the regenerated waste liquid from the apparatus separately and separately in the electrodialysis apparatus.

[Action]

Next, a closed system or a semi-closed system to which the recycled waste liquid recovery system of the present invention is applied is shown as a first embodiment showing a preferred embodiment.
This will be described with reference to the flow sheet in the figure. The supplemental raw water (1) is treated by a pure water production system (A) using an ion exchange resin method, and the pure water obtained here is subjected to removal of fine particles, TOC (total organic carbon), etc. by a reverse osmosis membrane system (B). Then, it enters the ultrapure water production system (C) by the ion exchange resin method, and the ultrapure water obtained here is supplied to, for example, a factory building (D) for semiconductor production.

On the other hand, the cation exchange resin regeneration waste liquid (2) and the anion exchange resin regeneration waste liquid (3) discharged from the pure water producing apparatus (A) are mixed and then, for example, alkali is added with caustic soda of 5% concentration (4). In response to this, the pH of the liquid is adjusted to 10 or higher, preferably pH 11 to 12, but both regeneration waste liquids (2)
When pH of 10 or more is achieved by only mixing (3), addition of alkali (4) is unnecessary.

This mixed waste liquid adjusted to pH 10 or higher produces calcium silicate or magnesium silicate solids due to the reaction of silica, magnesium ions, calcium ions, etc. which are mixed in the mixed waste liquor. However, the solid matter can be removed by an appropriate solid-liquid separation method such as a sedimentation method and a centrifugal separation method in addition to filtration. Next, the cake is subjected to a known dehydration step such as a belt press and is discarded outside the system. .

The liquid obtained by solid-liquid separation in this manner is adjusted to pH 10 or lower by addition of an acid (6) such as aqueous hydrochloric acid, if necessary, and then passed through a 10 μm membrane filtration device (7), It is supplied to the electrodialyzer (E).

The above acid addition is for the purpose of avoiding damage to the dialysis membrane in the electrodialyzer due to alkali. This is necessary depending on the pH value after alkali addition (4) and the performance of the dialysis membrane. You can do it accordingly.

On the other hand, the waste liquid (8) from the factory building (D) is sent to a recovery device (same configuration as the pure water production device) (F) by the ion exchange resin method, and the recovered pure water (9) obtained here is pure water. It is used as raw water (1) of the manufacturing apparatus (A) or as water (10) for cooling or tap water.

Further, the non-permeate water (11) of the reverse osmosis membrane device (B) and the waste water (12) of the ultrapure water producing device (C) are also used as the above-mentioned water (10).

Approximately 90 VOl desalted by the above-mentioned electrodialysis device (E)
The dilute liquid (dialysis treated water) (13) in the amount of% is used as the water (10). Further, the concentrated liquid (14) having an amount of about 10 VOL% is dried by a drum dryer (dryer) (G) and is discarded as a cake (solid matter) (15). When the concentrated liquid is dried, it is not limited to the drum dryer (G) described above, and various other drying means can be used.

In addition, the regenerated waste liquid (16) from the recovery device (F) is treated with another electrodialysis device (E ') and desalted diluted water (1).
7) is also used as water (10) and concentrated water (18)
Is processed in a drum dryer (G).

〔Example〕

Next, examples and comparative examples carried out along the flow sheet of FIG. 1 will be shown.

Example 1 Using the replenishment raw water (1) having the above composition, the respective regenerated waste liquids (2) and (3) from the pure water production system (A) were mixed, and a 5% caustic soda aqueous solution was added (4) to adjust the pH to 11.5. However, formation of solid matter was observed. This was made into a liquid from which solids were removed through a sand filtration device (5), and the liquid was supplied to the electrodialysis device (E) through the membrane filtration device (7) without adding acid (6). The results of the electrodialysis device (E) at this time were as follows.

Table 1 Dilute liquid (13) flow rate 1 / min Constant at 3.4 to 4.0 Electric conductivity of dilute liquid (13) Initial 1300 to 1800μs / cm Steady period 2200 to 2500μs / cm End 1800 to 1600μs / cm Concentrated liquid ( 14) Electric conductivity 7000 to 8000 μs / cm Under the above conditions, steady operation was possible for 7 consecutive hours without the clogging phenomenon of the dialysis membrane.

Example 2 An aqueous solution of hydrochloric acid was added (6) to the liquid from which solids had been removed by the sand filter (5) of Example 1 to lower its pH to around 10.0, and then the membrane dialyzer (7) was used to electrodialyze. It was supplied to (E).

The results of the electrodialysis device (E) at this time were as follows.

Table 2 Dilute solution (13) flow rate 1 / min 4.0 is almost constant Electric conductivity of dilute solution (13) is almost constant at 2200 μs / cm Concentrate (14) conductivity 6400 to 6600 μs / cm Continuous under the above conditions Stable steady operation for 7 hours was possible.

Comparative Example 1 After mixing the regenerated waste liquids (2) and (3) in Example 1, the pH was adjusted to 4 to 7 by adding an acid (6), and the mixture was passed through a membrane filtration device (7) to an electrodialysis device ( E).

The results of the electrodialysis method at this time were as follows.

[Effects of the Invention] According to the system of the present invention, by treating the regeneration waste liquid from the pure water production apparatus or the recovery apparatus by the ion exchange resin method with the electrodialysis apparatus, there is no fear of the clogging phenomenon of the dialysis membrane, and the long-term It is possible to operate stably over a long period of time, and the diluted liquid is reused as water for cooling and tap water, and the concentrated liquid is discarded as a cake through a drum dryer, resulting in low initial cost and low running cost. It enables a closed or semi-closed wastewater treatment system and has great industrial value.

[Brief description of the drawings]

FIG. 1 shows a flow sheet of a recycled waste liquid system of a pure water production apparatus of a closed system or a semi-closed system according to the present invention. Drawing A …… Pure water production equipment B …… Reverse osmosis membrane equipment C …… Ultrapure water production equipment D …… Factory building E, E ′ …… Electrodialysis equipment F …… Recovery equipment G …… Drum dryer 1 …… Replenishment raw water 2 …… Cation exchange resin regeneration waste liquid 3 …… Anion exchange resin regeneration waste liquid 4 …… Alkali addition 5 …… Filtration device 6 …… Acid addition 13 …… Diluted liquid 14 …… Concentrated liquid 15 …… Cake

Claims (7)

(57) [Claims] 1. A cation exchange resin and anion exchange resin regeneration waste liquid in a pure water production apparatus using an ion exchange resin method are mixed with or without addition of an alkali to adjust to a liquid having a pH of 10 or more. A reclaimed waste liquid recovery system for a pure water production device, characterized in that a liquid obtained by solid-liquid separation of solid matter generated in a mixed liquid is treated with an electrodialysis device. 2. The system according to claim 1, wherein the liquid obtained by solid-liquid separation is treated with an electrodialyzer after adjusting its pH to a low level. 3. The system according to claim 1, wherein the concentrate obtained from the electrodialysis device is dried using a drum dryer to obtain a cake. 4. The system according to claim 1, wherein the dilute liquid obtained from the electrodialysis device is used as raw water for a pure water production device, cooling of a factory building, river water such as tap water. 5. The system according to claim 1, wherein the solid matter separated by solid-liquid separation is made into a cake through a dehydration step. 6. The system according to claim 1, wherein the recycled waste liquid of the pure water producing apparatus is treated as a closed system or a semi-closed system. 7. When treating each regenerated liquid of a cation exchange resin and an anion exchange resin of a pure water production apparatus by an ion exchange resin method with an electrodialysis device, an alkali is added to or added to each regenerated waste solution. Without mixing to adjust the liquid to a pH of 10 or more, and the liquid obtained by solid-liquid separation of the solid matter generated in the mixed liquid by this is passed through an electrodialysis device for dialysis. A method of preventing membrane scale blockage.