JPH06182340A - Treatment method for water supply - Google Patents

Abstract

PURPOSE:To control the decrease of permeated water amount generated by membrane fouling, reduce the frequency of chemical cleanings for a membrane in a large extent and operate a membrane device stably by heating the water supply at the specified temperature, cooling and then supplying the water to a filter with a separating membrane, and filtering. CONSTITUTION:Raw water is supplied to a heat exchanger 2 for recovering heat after removing solides such as sand and others by a strainer 1, and heat exchange is performed between raw temperature raw water and heat treated raw water of a high temperature. Raw water heated in a heat exchanger 2 is supplied to a heat exchanger 3 heated with steam by a boiler 4 and heated up to 100-200 deg.C and supplied to a reaction column 5. Raw water of a high temperature coming out of the reaction column 5 is supplied to the heat exchanger 2, and cooled down to 40 deg.C usually by the heat exchange with the low temperature raw water before heat tread, and then supplied to a filter 6 using a separating membrane and filtered therein. The lowering of permeated water amount to be generated by membrane fouling can be controlled by high temperature treatment of raw water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for treating feed water. More specifically, the present invention is capable of suppressing a decrease in the amount of permeated water due to membrane contamination by heating the feed water at a high temperature and then cooling it, and then passing it through a separation membrane, and significantly reducing the number of times of chemical cleaning of the membrane. The present invention relates to a method for treating water supply that enables stable operation of the membrane device.

[0002]

2. Description of the Related Art The use of water has become more important as industrial water, domestic water, and agricultural water have been used. The demand for water is also emerging. On the other hand, due to the conservation of water resources, the use of miscellaneous water such as reclaimed water from sewage and industrial wastewater, rainwater, and other low-quality water is also popular, and for example, for flush toilets, cooling / cooling water, and sprinkling water. As a miscellaneous use, it is used in buildings such as buildings. Various methods have been developed as technologies for treating industrial water, sewage, industrial wastewater, etc. to obtain higher quality water, from a simple coagulation-sedimentation method to advanced technology using a membrane or the like. As the separation membrane used for water treatment,
For example, microfiltration membrane (MF membrane), ultrafiltration membrane (UF membrane),
Reverse osmosis membranes (RO membranes), dialysis membranes, electrodialysis membranes, etc. are known and are appropriately selected and used according to the quality of the water to be treated and the intended use of the treated water. By the way, the tertiary treated water of middle water and sewage contains a relatively large amount of organic matter,
Usually, it is treated by the following method and is supplied to a filtration device equipped with a separation membrane. That is, first, sodium hypochlorite, polyaluminum chloride, etc. are added to raw water, and the mixture is supplied to a flocculation pressure flotation device or a flocculation sedimentation device to separate flocculates, and then passed through a two-layer filter, and then a separation membrane. A method of supplying water to a filtration device equipped with is adopted. In such water treatment, the separation membrane is contaminated with organic substances in raw water, and the amount of water permeated through the membrane decreases in a relatively short time. When the amount of water permeated through the membrane decreases, chemical cleaning is usually carried out, but in this case, a great deal of labor is required and a large amount of drainage is unavoidable.

[0003]

Under these circumstances, the present invention reduces the amount of permeated water due to contamination of the membrane when a separation membrane is used in the treatment of tertiary treated water such as intermediate water and sewage. The present invention has been made for the purpose of providing a method of treating water supply which can suppress the number of times of chemical cleaning of the membrane and can stably operate the membrane device.

[0004]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have conducted a high-temperature heat treatment of feed water, cooled it to room temperature, and installed it in a filtration device equipped with a separation membrane. It was found that the object can be achieved by providing the information, and the present invention has been completed based on this finding. That is, the present invention provides a method for treating feed water, which comprises heating the feed water at a temperature of 100 to 200 ° C., cooling it, and then supplying it to a filtration device equipped with a separation membrane for filtration. is there. Hereinafter, the present invention will be described in detail.
Raw water (water to be treated) to which the method of the present invention is applied is not particularly limited as long as it contains a membrane-contaminating organic substance. Such raw water includes industrial water, rainwater,
Examples thereof include tertiary treated water of medium / sewage, and tertiary treated water of medium / sewage containing a relatively large amount of organic substances is preferable. In the present invention, the raw water may be directly supplied to the heat treatment step, but depending on the water quality of the raw water, sodium hypochlorite and polyaluminum chloride are added to the raw water, and the flocculation pressurization flotation device or the flocculation device is used. After separating the agglomerates in the settling device, the one that has passed through the two-layer filter may be supplied to the heat treatment step. The heat treatment in the present invention is
It is carried out at a temperature in the range 100 to 200 ° C, preferably 130 to 180 ° C. If the temperature is lower than 100 ° C., the effect of the present invention is not sufficiently exerted, and if the temperature exceeds 200 ° C., the effect is not improved despite the high temperature. It will be a disadvantage. Further, the treatment time depends on the treatment temperature, that is, if the treatment temperature is high, the treatment time is short, and if the treatment temperature is low, the treatment time is long, which cannot be determined unconditionally, but usually about 5 to 60 minutes. is there. In the present invention, the raw water heat-treated as described above is usually added to 40
After cooling to room temperature below ℃, it is supplied to a filtration device equipped with a separation membrane for filtration treatment. At this time, in order to recover heat, it is advantageous to perform heat exchange between the high temperature raw water after the heat treatment and the low temperature raw water before the heat treatment. The separation membrane is not particularly limited, and those conventionally used for water treatment, such as microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, dialysis membranes, electrodialysis membranes, etc., can be used. Microfiltration membranes, ultrafiltration membranes and reverse osmosis membranes are preferred.

FIG. 1 shows a schematic diagram of an example of steps for carrying out the method of the present invention. The raw water is supplied to the heat exchanger 2 for heat recovery after the solid content such as sand is removed by the strainer 1. In this heat exchanger, heat exchange is performed between the low temperature raw water and the heat-treated high temperature raw water. The raw water heated by the heat exchanger 2 is supplied to the heat exchanger 3 that is steam-heated by the boiler 4, heated to a temperature of 100 to 200 ° C., and then supplied to the reaction tower 5. This reaction tower 5 is for taking residence time, and in this reaction tower,
The heat treatment of the raw water is completed. The high temperature raw water leaving the reaction tower 5 is supplied to the heat exchanger 2 and is usually cooled to 40 ° C. or lower by heat exchange with the low temperature raw water before the heat treatment, and then the filtration device 6 equipped with the separation membrane. And is filtered.
As described above, by subjecting the raw water to the high-temperature heat treatment, it is possible to suppress a decrease in the amount of permeated water due to membrane contamination. The reason for this is not clear, but it is considered that microorganisms in raw water, mucilage of bacteria, diatoms, etc. are modified by heat treatment into substances that are easily filtered by, for example, reverse osmosis membranes. .

[0006]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. In addition, raw water having the following properties was used for the test. Characteristics of raw water for test Kind: Central Research Laboratory, Kurita Water Industries Ltd. Conductivity: about 200 μs / cm, pH: about 6.5 Turbidity: 10 degrees or less TOC: about 4 ppm, COD (Mn): about 1 ppm Fe : 0.2 ppm M-alkalinity: Approximately 20 ppm (CaCO ₃ conversion) Calcium hardness: Approximately 50 ppm (CaCO ₃ conversion) Silica: Approximately 25 ppm (SiO ₂ conversion) MF filtration time: 15 minutes 2 seconds / liter Example 1 For test Heat treatment device for raw water (treatment amount: 5 liters / hr)
And heated at 170 ° C. Residence time is about 1
0 minutes. Then, it cooled to normal temperature in the heat processing apparatus. A glass filter with a diameter of 47 mm made of cellulose microfiltration membrane (manufactured by Japan Millipore, Type: HA, 0.45).
The thick tube Erlenmeyer flask equipped with a branch pipe is attached to the thick-tube Erlenmeyer flask, the branch pipe is connected to a vacuum pump, the treated water is supplied to a glass filter, and the vacuum pump is operated to 500 mm.
The pressure was reduced to about Hg, and the time for filtering 1 liter of treated water was measured. The filtration time was 1 minute and 30 seconds (90 seconds).
The longer this time is, the worse the filterability of the water supply is. In addition, in the case of this water, TOC was hardly reduced even if it heat-processed at 170 degreeC. Comparative Example 1 A filtration test was performed in the same manner as in Example 1 except that untreated raw water for test was used instead of the heat-treated water. As a result, filtration time 15 minutes 2 seconds (902 seconds)
Met. Comparative Example 2 In Example 1, instead of the heat-treated water, polyaluminum chloride (30 ppm) was added to the test raw water (pH 6.5), and sodium hypochlorite (20 ppm) was further added to perform coagulation pressure floating filtration treatment. A filtration test was conducted in the same manner as in Example 1 except that was used. As a result, the filtration time is 4 minutes 25
Seconds (265 seconds). Reference Example 1 A filtration test was performed in the same manner as in Example 1 except that ultrapure water was used instead of the heat-treated water.
As a result, the filtration time was 1 minute 25 seconds (85 seconds). The above results are shown together in FIG. As is apparent from FIG. 2, the heat treatment according to the method of the present invention has a filtration time as short as that of ultrapure water, and the heat treatment exhibits a very remarkable effect.

[0007]

According to the present invention, it is possible to suppress the decrease in the amount of permeated water due to the contamination of the membrane, and it is possible to greatly reduce the number of times the membrane is chemically cleaned. The conventional method requires chemical cleaning of the membrane at least 6 times a year, but the method of the present invention requires no more than 2 times a year, which enables stable operation of the membrane device.

[Brief description of drawings]

FIG. 1 is a process schematic view of an example for carrying out the method of the present invention.

FIG. 2 is a diagram showing the results of Examples of the present invention, Comparative Examples and Reference Examples.

[Explanation of symbols]

 1 Strainer 2 Heat Exchanger (for heat recovery) 3 Heat Exchanger (for temperature rise) 4 Boiler 5 Reaction tower 6 Membrane device

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Naoki Matsukei 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. (72) Inventor Hiroshi Kurobe 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. After heating the feed water at a temperature of 100 to 200 ° C.,
After the cooling treatment, the treatment method of water supply is characterized in that the water is supplied to a filtration device equipped with a separation membrane for filtration.