JPH09290261A - Purified water manufacturing equipment - Google Patents

Abstract

(57) [Abstract] [Problem] Simplification of the overall structure of an apparatus when raw turbid water such as river water is pretreated with a microfiltration membrane or an ultrafiltration membrane and purified by a reverse osmosis membrane module. Provided is an apparatus for producing purified water which can guarantee the simplification of operation and the reliable elimination of deterioration of a reverse osmosis membrane module due to chlorine and bacteria. SOLUTION: A full-volume filtration type microfiltration or ultrafiltration membrane element 2 is immersed in a raw water tank 1 and a filtrate outlet 810 of the filtration membrane element 2 is passed through a pump 4 to a cross flow type reverse osmosis membrane. Undiluted solution supply port 31 of module 3
And a concentrated stock solution outlet 32 of the reverse osmosis membrane module 3.
Was communicated with the inlet side of the pump 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purified water producing apparatus used when producing purified water using river water or the like as raw water.

[0002]

2. Description of the Related Art When obtaining purified water from river water, lake water, groundwater, etc. as raw water, the coagulation sedimentation sand filtration method has been traditionally used, but recently, maintenance and management is simplified, running cost is reduced, and installation space is reduced. -The membrane separation method is emphasized in order to reduce the amount of waste. Membranes used in the membrane separation method include microfiltration membranes, ultrafiltration membranes and reverse osmosis membranes, but they also contain harmful substances such as trihalomethane that are difficult to remove with microfiltration membranes or ultrafiltration membranes. The use of reverse osmosis membrane modules is required for complete removal.

The mainstream of this reverse osmosis membrane module is a spiral wound type membrane module. In this spiral type membrane module, a membrane envelope containing a permeated liquid flow path holding material (for example, non-woven fabric, plastic net) inside is provided with a raw liquid flow path holding material (for example, plastic net) around a liquid collection tube.
A spiral wound with the membrane element, the membrane element having the opening of the membrane envelope communicated with the liquid collection tube is housed in the tubular case,
A stock solution supply port is provided at one end of the cylindrical case, and a concentrated stock solution outlet is provided at the other end of the barrel case. The raw water is circulated between the spirally wound layers, and the permeate is taken out from the liquid collection tube.
In this spiral type membrane module, in order to suppress the outer diameter and widen the membrane area, the gap of the raw solution flow path between the spiral winding layers is considerably narrowed, and when the raw water of turbidity is directly flowed, Since clogging of the raw water passage is unavoidable, it is necessary to pretreat the raw water to a sewage index of 4 or less. For the pretreatment, a microfiltration membrane module or an ultrafiltration membrane module is required.
It is known to use

FIG. 5 shows a reverse osmosis membrane module after pretreatment with a microfiltration membrane module or an ultrafiltration membrane module.
A well-known water purification line for main treatment is shown in FIG. 1 in which raw water is stored in a raw water tank 1 ′ through a raw water supply pipe 11 ′, and the raw water is pumped into a pretreatment membrane module 2 ′ by a pump 41 ′ to cross flow. The concentrated solution is filtered by the method and returned to the raw water tank 1 ', the filtrate is once stored in the primary treated water tank 10', and this primary treated water is pumped into the reverse osmosis membrane module 3'by the pump 42 '. Then, the concentrated liquid is returned to the primary treated water tank 10 'by permeation treatment by a cross flow method and the filtrate is stored in the purified water tank 7'and used as purified water.

[0005]

However, in the above-mentioned purified water production equipment, although the bacterial cells are removed by the microfiltration membrane module or the ultrafiltration membrane module 2'in the pretreatment step, Bacteria easily proliferate during water storage in the primary treated water tank 10 ', which is unsanitary, and depending on the type of membrane of the reverse osmosis membrane module 3', there is a fear that the membrane will be decomposed by variteria, and sterilization is also possible. If chlorine for injection is injected, there is a risk of film oxidation and deterioration. Furthermore, three tanks are required, and the expansion of the installation space is inevitable,
It requires two pumps, which increases running costs and complicates the control device for interlocking the entire system.

The object of the present invention is to simplify the overall structure of the apparatus when raw turbid water such as river water is pretreated with a microfiltration membrane or an ultrafiltration membrane and then purified with a reverse osmosis membrane module. Another object of the present invention is to provide an apparatus for producing purified water which can guarantee the simplification of operation and the reliable elimination of deterioration of the reverse osmosis membrane module due to chlorine and bacteria.

[0007]

One of the apparatus for producing purified water according to the present invention is a raw water tank in which a total filtration type microfiltration or ultrafiltration membrane element is immersed and installed, and a filtrate outlet of the filtration membrane element. Is connected to a stock solution supply port of a cross flow type reverse osmosis membrane module via a pump, and a concentrated stock solution outlet of the reverse osmosis membrane module is connected to an inlet side of the pump. is there. Another apparatus for producing purified water according to the present invention is a total water filtration type microfiltration or ultrafiltration membrane element immersed in a raw water tank, and a pump is installed at the concentrated stock solution outlet of a reverse osmosis membrane module. The ejector is communicated with the outlet, and the filtrate outlet of the filtration membrane element is communicated with the intake of the ejector.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing an embodiment of an apparatus for producing purified water according to the present invention. In FIG. 1, 1 is a raw water tank, and 11 is a raw water supply pipe. Two
Is a microfiltration or ultrafiltration membrane element immersed in the raw water tank 1 and operated by a total volume filtration method by the transmembrane pressure difference generated by suction / decompression on the filtrate side. A flat membrane or a hollow fiber membrane can be used as the membrane of the microfiltration or ultrafiltration membrane element. For example, as shown in (a) of FIG. 2 and (b) of FIG. 2 [a cross sectional view taken along line (a) of FIG. 2], a flat film 82 is fused to a frame edge 81 having ducts 811 at both ends. Alternatively, the filtered liquid flow path holding material 83 (nonwoven fabric,
As shown in FIG. 3, a membrane element member a having a filtered liquid take-out pipe 812 attached to a duct 811 via a plastic net or the like may be attached to a rack 84 as shown in FIG.

In FIG. 1, reference numeral 3 denotes a reverse osmosis membrane module used in a cross flow system, and a filtrate outlet 810 of a filtration membrane element 2 is pumped to a stock solution supply port 31 of the reverse osmosis membrane module 3. It communicates via 4. Reference numeral 5 is a return pipe that connects the concentrated liquid outlet 32 of the reverse osmosis membrane module 3 to the inlet side of the pump 4, and 6 is a pressure regulating valve provided in the return pipe 5. Reference numeral 7 is a water purification tank communicating with the permeate outlet 33 of the reverse osmosis membrane module 3.

The purified water producing apparatus according to the present invention is used for obtaining purified water by using river water, lake water, groundwater, etc. as raw water.
In FIG. 1, raw water is stored in a raw water tank 1. To produce purified water, the pump 4 is driven to increase the stock solution chamber pressure of the reverse osmosis membrane module 3 while adjusting the degree of restriction of the pressure regulating valve 6. This pressure increase causes reverse osmosis membrane module 3
And the filtrate side of the filtration membrane element 2 is decompressed and filtration is performed by the filtration membrane element 2.
When the steady state is reached, the filtration flux of the filtration membrane element 2 and the permeation flux of the reverse osmosis membrane module 3 are balanced, and the permeate outlet 33 of the reverse osmosis membrane module 3 is almost constant in the purified water tank 7. Purified water flows in at a flow rate. The steady-state filtration flux or permeation flux is determined by the rotation speed of the pump 4 and the throttling degree of the pressure regulating valve 6, and unlike the conventional example shown in FIG. 5, interlocking between pumps and troublesome operation are unnecessary. .

FIG. 4 is an explanatory view showing an embodiment of another apparatus for producing purified water according to the present invention. In FIG. 4, reference numeral 9 denotes an ejector, which communicates the filtrate outlet 810 of the microfiltration or ultrafiltration membrane element 2 with the inlet 91, and the concentrated stock solution outlet 32 of the reverse osmosis membrane module 3 to the inlet of the pump 40. The outlet of the pump 40 communicates with the inlet 92 of the ejector 9, and the outlet 93 of the ejector 9 communicates with the stock solution supply port 31 of the reverse osmosis membrane module 3. 4, the configuration other than the above is substantially the same as that of the embodiment shown in FIG.
Is a raw water tank, 11 is a raw water supply pipe, and 7 is a water purification tank.

In the purified water producing apparatus shown in FIG. 4, the suction force of the ejector 9 filters the membrane element 2, and the outlet pressure of the ejector 9 causes the reverse osmosis membrane module 3 to permeate. In this case, the suction force of the ejector 9 is given by the flow velocity in the ejector 9, and this flow velocity is determined by the output of the pump 40 and the resistance of the ejector 9, and the pressure at the ejector outlet 93 is also the output of the pump 40 and the ejector 9. Therefore, the filtration flux of the filtration membrane element 2 and the permeation flux of the reverse osmosis membrane module 3 reach a steady value determined by the output of the pump 40 and the characteristics of the ejector 9, and the reverse osmosis membrane module -The purified water flows into the purified water tank 7 from the permeated liquid outlet 33 of the valve 3 at a substantially constant flow rate.

[0013]

Since the purified water producing apparatus according to the present invention is operated by a single pump, there is no need to interlock the pumps when using a plurality of pumps, and the operation is simple. Since there are few tanks, the installation space can be reduced. Furthermore, a closed pipe is provided between the filtrate side of the microfiltration or ultrafiltration membrane element and the reverse osmosis membrane module until the reverse osmosis membrane module is sterilized by the filtration membrane element. It is hygienic because it can eliminate the growth of bacteria between them and there is no fear of bacterial degradation of the membrane of the reverse osmosis membrane module.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an apparatus for producing purified water according to the present invention.

FIG. 2 is an explanatory view showing an example of a filtration membrane element member used in the present invention.

FIG. 3 is an explanatory diagram showing an example of a filtration membrane element used in the present invention.

FIG. 4 is an explanatory view showing an example of an apparatus for producing purified water according to the present invention.

FIG. 5 is an explanatory view showing a conventional purified water manufacturing apparatus.

[Explanation of symbols]

1 Raw water tank 2 Total filtration type microfiltration or ultrafiltration membrane element 3 Reverse osmosis membrane module 4 Pump 40 Pump 7 Water purification tank 9 Ejector

Claims (2)

[Claims] 1. A full-filtration type microfiltration or ultrafiltration membrane element is immersed in a raw water tank, and a filtrate outlet of the filtration membrane element is connected to a crossflow type reverse osmosis membrane module via a pump. An apparatus for producing purified water, characterized in that the concentrated stock solution outlet of the reverse osmosis membrane module communicates with the stock solution supply port and communicates with the inlet side of the pump. 2. A total filtration type microfiltration or ultrafiltration membrane element is immersed in a raw water tank, and a pump is connected to the concentrated stock solution outlet of the reverse osmosis membrane module and an ejector is connected to the outlet of the pump. An apparatus for producing purified water, wherein the filtered liquid outlet of the filtration membrane element is communicated with the suction port of the ejector.