JP7354744B2 - Wastewater utilization system - Google Patents

Description

The present invention relates to a system for treating and utilizing wastewater.

Wastewater collection technology to alleviate severe water shortages is a technology that is attracting attention around the world. As a system for recovering and reusing wastewater, Patent Document 1 describes that after primary to tertiary treatment of organic wastewater is performed, the system is switched to a boiler or cooling tower, etc., and an ion exchange resin regenerating device for supply. Are listed.

Japanese Patent Application Publication No. 2016-123906

An object of the present invention is to provide a wastewater utilization system that improves the reuse rate of wastewater.

The wastewater utilization system of the present invention includes a wastewater pretreatment device, a desalination device that desalinates pretreated water treated by the pretreatment device, and water usage equipment to which desalination water from the desalination device is supplied. A wastewater utilization system comprising: a return means for sending the wastewater to the upstream side of the pretreatment device when the wastewater discharged from the water-using equipment is of better quality than a predetermined water quality. shall be.

In one aspect of the present invention, the water-using equipment includes a low concentration device in which the water quality of the discharged water is better than the predetermined water quality, and a high concentration device in which the water quality of the discharged water is poorer than the predetermined water quality. The return means is for conveying the discharged water of the low concentration device.

In one aspect of the present invention, the low concentration device is at least one of an outside air processing air conditioner and a scrubber, and the high concentration device is at least one of a cooling tower, a boiler, and a retort sterilized water production device.

In the wastewater utilization system of the present invention, desalinated water produced by pre-treating and desalinating raw water (wastewater) is supplied to water-using equipment for use.

If the water quality of the waste water from the water-using equipment is good, the waste water from the water-using equipment is returned to the upstream side of the pre-treatment device and used again. This improves the utilization rate of wastewater.

It is a flow diagram of a drainage utilization system concerning an embodiment.

An embodiment will be described with reference to FIG.

Waste water such as waste water from a dicer in a semiconductor manufacturing process and RO brine water from a pure water production device is introduced into a raw water tank 1. The raw water in the raw water tank 1 is sent to a pre-treatment device 2, where it is made into pre-treated water from which fine particles are removed through treatments such as coagulation and filtration, and then sent to a desalination device 4 via a pre-treatment tank 3. Ru.

As the desalination device 4, an RO device (reverse osmosis membrane device) is used, and the concentrated water is discharged into sewage, a river, etc. via a pipe 4a.

The desalinated water from the desalination device 4 is sent to one or both of the high concentration devices 11, 12, 13 and the low concentration devices 21, 22, 23 via the desalination treated water tank 5. In this embodiment, industrial water, city water, well water, membrane-filtered water, etc. are supplied to the desalinated water tank 5 via a backup pipe 5a as necessary.

In the high concentration devices 11 to 13, highly concentrated wastewater is produced. This highly concentrated wastewater is discharged into sewers, rivers, etc.

In the low concentration devices 21 to 23, waste water that is not very concentrated (for example, drain water from an external conditioning machine) is produced. This low concentration wastewater is returned to the raw water tank 1 via piping 30 and reused.

In this way, the low-concentration wastewater generated in the low-concentration devices 21 to 23 is returned to the raw water tank 1 and used again, so the reuse rate of the wastewater is higher than when the low-concentration wastewater is also discharged. .

In FIG. 1, three high concentration devices and three low concentration devices are shown, but the number is not particularly limited as long as it is one or more.

In one aspect of the present invention, the high concentration device is one that produces concentrated wastewater that is five times or more concentrated, and includes cooling towers, boilers, retort sterilized water production devices, and the like. Further, the low concentration device is one that generates low concentration wastewater with a concentration ratio of less than 5 times, and includes an outside air conditioner (outside air processing air conditioner), a scrubber, and the like.

Note that in the pretreatment device 2, an oxidizing agent may be added. When an oxidizing agent is added in the pretreatment device 2, it is preferable to add a reducing agent such as sodium bisulfite to the RO feed water.

As the oxidizing agent, a chlorine-based oxidizing agent or the like is used, but there are no particular restrictions, and various types such as sodium hypochlorite and chlorine dioxide can be used, and one type may be added alone or two or more types may be added in combination. . The amount of the chlorine-based oxidizing agent added is usually 0.3 to 1.0 mg/LasCl ₂ , and it is preferable that it is constantly added.

There are no particular restrictions on the type of flocculant used in the pretreatment device 2 or the type of flocculation aid added as needed.

The filter may be a general gravity filter, a pressure filter, or a turbidity membrane, but a turbidity membrane is preferred. When a turbidity removing membrane is employed, it may be of a cross-flow type or a total filtration type.

The turbidity removal process using a turbidity membrane consists of water passage, air bubbling, backwashing, and water filling. It is preferable that the filtration water passage time is 20 to 40 minutes (usually 30 minutes) and the operation is performed at a differential pressure (inlet pressure - outlet pressure) of about 0.02 to 0.04 MPa. When the differential pressure reaches 0.07 to 0.10 MPa, it is preferable to perform cleaning in place. The material for the turbidity membrane is preferably polyvinylidene fluoride, which has good chemical resistance, and the pore diameter is preferably 0.02 μm or more, for example, about 0.02 to 0.1 μm, but is not limited thereto.

As the desalting device 4, an RO device is preferable, and it is preferable to ensure a line flow rate of 3.6 m ³ /h or more. Note that equipment other than the RO device may be further provided.

There are no particular restrictions on reverse osmosis membranes. An ultra-low pressure membrane with a standard pressure of 0.735 MPa may be employed. The membrane area is preferably about 35 to 41 ^m2 . The initial pure water flux is preferably 1.0 m/d (25° C., 0.735 MPa) or more, and the initial desalination rate is preferably 98% or more. It is preferable to set the recovery rate so that the Langelier index is 0 or less and the silica concentration in the brine water is within the solubility. The recovery rate is usually 50-80%.

Preferably, a slime control agent is added to the RO feed water. Slime control agents include free chlorine agents such as sodium hypochlorite (NaClO), combined chlorine agents such as chloramine and monochlorosulfamic acid, which are reacted with chlorine and amidosulfuric acid, and compounds having an amidosulfate group, and bromine agents such as dibromohydantoin. One or more organic agents such as DBNPA (dibromonitrilopropionic acid) and MIT (methylisothiazolone) can be used.

In the case of a combined chlorine-based oxidizing agent, it is preferable to add it in an amount of 0.3 to 1.0 mg/LasCl ₂ .

The sodium chlorosulfamate oxidizing agent is, for example, a chlorine-based oxidizing agent with an available chlorine concentration of 1 to 8% by weight, preferably 3 to 6% by weight, and 1.5 to 9% by weight, preferably 4.5 to 8% by weight. It is preferable to use it as an aqueous solution containing a sulfamic acid compound and having a pH≧12.

Other additives may be added to the RO feedwater, such as scale dispersants.

Note that an electrodeionization device, an ion exchange tower, or the like may be installed downstream of the RO device.

In the present invention, it is preferable to decide whether or not to return the water used in the high concentration devices 11 to 13 and the low concentration devices 21 to 23, etc., based on the required water quality of the raw water. In other words, if the water quality is better than the water quality, it is possible to reduce the load on the wastewater recovery device (pretreatment device 2 and desalination device 4), so it is used as raw water for the wastewater recovery device, and if it is bad, it is discharged outside the system. .

The quality of water used as raw water for wastewater recovery equipment is determined by the specifications of the recovery equipment.

In one aspect of the present invention, the conductivity of discharged water from water-using equipment such as high concentration devices 11 to 13 and low concentration devices 21 to 23 is measured, and if the conductivity is higher than a predetermined value, the water-using equipment is The water-using equipment may be set as a high concentration device, and when the water consumption is lower than a predetermined value, the water-using device may be set as a low concentration device.

The predetermined value of the conductivity may be, for example, a value selected from 0.1 to 500 mS/m, specifically 10 mS/m, but is not limited thereto. When the desalting device 4 includes an RO device, the SS concentration in the desalted water is extremely low, so the SS concentration does not affect the determination of whether it is a high concentration device or a low concentration device.

2 Pretreatment device 4 Desalination device 11-13 High concentration device 21-23 Low concentration device

Claims (3)

A wastewater utilization system comprising a wastewater pretreatment device, a desalination device that desalinates pretreated water treated by the pretreatment device, and water usage equipment to which desalinated water from the desalination device is supplied,
A wastewater utilization system comprising a return means for sending the wastewater to the upstream side of the pre-treatment device when the wastewater discharged from the water-using equipment is of better quality than a predetermined water quality,
The water-using equipment includes a low concentration device in which the water quality of the discharged water is better than the predetermined water quality, and a high concentration device in which the water quality of the discharged water is poorer than the predetermined water quality,
The return means is for sending the discharged water of the low concentration device to the upstream side of the pretreatment device,
A wastewater utilization system characterized in that the discharged water of the high concentration device is discharged . The wastewater utilization system according to claim 1 , wherein the low concentration device is at least one of an outside air processing air conditioner and a scrubber. The wastewater utilization system according to claim 1 or 2, wherein the high concentration device is at least one of a cooling tower, a boiler, and a retort sterilized water production device.

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