JP2795490B2 - Osmotic backwashing device for semipermeable membrane - Google Patents

Description

The present invention relates to a semi-permeable membrane osmosis type backwashing device, and more particularly, to reverse a dirt on a semi-permeable membrane such as a reverse osmosis membrane to a desired amount of permeated water. The present invention relates to a semi-permeable membrane osmosis-type backwashing device that can be discharged by being discharged.

(B) Conventional technology When obtaining purified water using a reverse osmosis membrane, if the salt concentration of the raw water is high (for example, 50 ppm or more), the salt of the raw water precipitates and deposits on the reverse osmosis membrane surface of the module, and the permeation capacity is increased. In addition, the purified water capacity is reduced, and the life of the module is shortened.

Conventionally, when the permeation capacity of the reverse osmosis membrane is reduced due to such precipitation and deposition of salts, the performance of the module is restored by an acidic or alkaline detergent.
Sufficient recovery is difficult, and repeated washing with detergents deteriorates the reverse osmosis membrane and shortens the life of the module.

(C) Means and Action for Solving the Problems The present invention provides a semipermeable membrane module, a permeated water tank,
A read pipe connected to the permeate tank from the permeate outlet of the semipermeable membrane module so that the permeate can be transported to the permeate tank, and the connection pipe permeates due to the head difference when the raw water side of the semipermeable membrane module is released. In order to allow the desired amount of water to permeate backward through the membrane of the semipermeable membrane module, the open end of the pipe on the side of the permeated water tank is
This is a semi-permeable membrane osmosis type backwashing device arranged below the set water level of the permeated water tank.

That is, according to the present invention, by connecting a specific connection pipe between the semipermeable membrane module and the permeated water tank, when the pressure on the raw water side of the semipermeable membrane module is reduced, the desired amount of permeated water is reduced by half due to the head difference. Backflow osmosis into the membrane of a permeable membrane module, thereby allowing backwashing of dirt such as salts deposited and deposited on the membrane surface of the semipermeable membrane with a simple structure, thereby extending the life of the module. It is.

In the present invention, the connection pipe has its permeated water tank-side opening end disposed below the set water level of the permeated water tank so that a desired amount of permeated water can flow backward. Here, the desired amount of permeated water is preferably 60 to 500% of the volume of the semipermeable membrane module.
, Or 3-15% of its module capacity (the amount of treated water per unit time).

In the present invention, the permeated water tank includes a main permeated water tank and an intermediate tank to which the connection pipe is connected and which can supply overflowed permeated water to the main permeated water tank.

(D) Example (including Reference Example) Reference Example First, referring to FIG. 1 showing a reference example, a reverse osmosis membrane osmosis type backwashing device 1 includes a reverse osmosis membrane module 2, a permeated water tank 3, And a connection pipe 4 for connecting the tank and the module 2.

The osmosis membrane module 2 includes a pressurizing pump 5 on the raw water supply side and a drain pipe 6 on the raw water discharge (circulation) side.

The permeated water tank 3 is made of a pressure-resistant closed container, and the set liquid level L ₀ is controlled by the liquid level controller 7.

The connection pipe 4 extends from the permeated water side of the reverse osmosis membrane module 2 to the permeated water tank 3 in an inverted U-shape, and connects the permeated water tank side opening end 8 to a water level lower than the set liquid level L ₀ of the permeated water. Placed at ₁ . About 300 here water occupying the set liquid level L ₀ to the height of the water level L ₁ is a reverse osmosis membrane module 2 volumes
%.

Thus, raw water (eg, seawater) is supplied to the raw water side of the reverse osmosis membrane module 2 at 35 kg / cm ² by the operation of the pressurizing pump 5, and the permeated water (pure water) is supplied through the connection pipe 4 to the permeated water tank 3. Transferred to On the other hand, the raw water that has not passed through the reverse osmosis membrane is discharged (circulated) through the drain pipe 6.

When the salts are deposited and deposited on the raw water side membrane surface of the reverse osmosis membrane module 2 by continuing the operation as described above, the operation of the pressurizing pump 5 is stopped or the raw water side valve (not shown) is closed (may be periodic). Then, the raw water side of the reverse osmosis membrane module 2 is released (approximately 0 kg / cm ² ), whereby the desired amount of permeated water (about 300% of the module volume) from the permeated water tank 3 is brought to a higher pressure state than the raw water side. Is permeated backward through the reverse osmosis membrane module 2, whereby the salts deposited and deposited on the raw water side of the module 2 are backwashed and discharged from the water discharge pipe 6.

In addition, the reading pipe is not inverted U-shaped as shown in FIG.
It is configured in a substantially L-shape, and it is possible to prevent air from being generated in the pipe.

In addition, reverse osmosis membrane modules are usually designed with some margin for nominal capacity, in anticipation of deterioration of membrane performance. If the apparatus 1 is automatically operated at the time of temporary suspension or load reduction for control of a margin of the module, it is convenient because the equipment capacity does not decrease.

When the reverse osmosis membrane module is restarted after backwashing,
If the operation is performed such that the internal raw water side is replaced (leaving for a certain period of time) without abrupt pressurization, contamination of the peeled film can be prevented from reattaching. It is also effective to open and blow the drain valve on the raw water side for a short time.

Embodiment Unlike the reference example described above, as in the embodiment shown in FIG. 3, the permeated water tank is divided into a main permeated water tank and an intermediate tank so that the permeated water for backwash can be supplied from the intermediate tank. You can also. That is, in FIG.
Is a main permeate tank, 11 is an intermediate tank, and this intermediate tank is connected to the connection pipe 4b, and overflows permeate through the overflow pipe 13 into the main permeate tank 10.
Can be supplied. Incidentally, the effective amount of water of the intermediate tank 11 is 60 to 500% of the module volume, only the fixed amount of water (height alpha _b equivalent) is, the backwashing without being influenced by the water level in the main permeate tank 10 used.

In addition, as in the case of seawater treatment equipment for seawater washing, in the case of large-scale equipment, the semipermeable membrane module is divided into a plurality,
A connection pipe can be provided from each of the divided modules to the permeated water tank. Of course, the connection pipe is submerged at one end in a permeated water tank (or an intermediate tank), and the pressurizing pump provided in each divided module is stopped or the valve on the pressurizing pump side is closed or operated as desired or periodically. ,
The pressure inside each module is released, thereby backwashing the module as described above. In this case, a flow meter or a timer control of a valve can be used together to set the amount of backwash water. In this case, a low-pressure backwash pump can also be used.

(E) Effects of the Invention According to the present invention, when the semi-permeable membrane module is depressurized on the raw water side, the desired amount of permeated water is not affected by the head difference, that is, the fixed level in the intermediate tank is not affected by the water level of the main permeated water tank. A small amount of permeated water is allowed to permeate back into the membrane of the semipermeable membrane module, so that with a simple structure, dirt such as salts deposited and deposited on the membrane surface of the semipermeable membrane can be reliably backwashed. , The life of the module can be extended.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view showing a reference example, FIG. 2 is a schematic structural explanatory view of a main part showing another reference example, and FIG.
FIG. 2 is a diagram corresponding to FIG. 2 showing one embodiment. DESCRIPTION OF SYMBOLS 1 ... Reverse osmosis type | system | group backwashing device of a reverse osmosis membrane, 2 ... Reverse osmosis membrane module, 3 ... Permeate tank, 4 ... Connection piping, 8 ... Open end part, 10 ... Main permeate tank, 11 …… Intermediate tank.

Claims (1)

(57) [Claims] 1. A semi-permeable membrane module, a permeated water tank, and a connection pipe connected to a permeate outlet from a permeate outlet of the semi-permeable membrane module to a permeate tank, and further comprising a connection pipe, At the time of pressure release on the raw water side of the semipermeable membrane module, in order to allow the desired amount of permeated water to flow back into the membrane of the semipermeable membrane module due to the head difference, the open end of the permeated water tank side of the pipe should be Osmotic reverse of a semi-permeable membrane, which is disposed at the lower level and has a permeated water tank, a main permeated water tank, and an intermediate tank to which a connection pipe is connected and which can supply permeated water overflowing to the main permeated water tank. Washing equipment.