JPH07136474A - Washing of filter membrane module - Google Patents

Abstract

PURPOSE:To simply wash a filter membrane module clogged by the adhesion of a non-transmitted substance by a specific chemical agent. CONSTITUTION:In the washing of a filter membrane module in a surface flow water purifying system, the filter membrane module is immersed in an NaClO soln. with concn. of 5-95mg/l and the product of the concn. and the immersion time is 1X10-7X10 (mg/ l).h. When the water purifying systgem consists of two or more filter membrane modules, while at least one filter membrane module is used, the other filter membrane module can be washed in the state fitted to the water treatment system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a filtration membrane module of a water purification system using the filtration membrane module, more specifically, by immersing the filtration membrane module in a specific drug. The present invention relates to a method for cleaning a filtration membrane module, which removes non-permeable substances attached to the filtration membrane module and restores the function of the filtration membrane module.

[0002]

2. Description of the Related Art Conventionally, as a water purification system for obtaining tap water from surface water such as river water or lake water, it is common to go through a coagulation-precipitation-sand filtration-chlorine sterilization process. In order to realize such a process, a flocculation basin, a sedimentation basin, a sand filtration basin, and chlorine sterilization equipment are required, and a vast installation space is required. In addition, it has been proposed in recent years to add an activated carbon treatment system or an ozone treatment system to cope with pollution of water sources such as rivers, but these have caused a further increase in installation space and have become a new problem. On the other hand, practical application of a water purification system using a filtration membrane module which does not require the above-mentioned vast facilities is being studied.

In a water purification system for surface water using a filtration membrane module, permeated water is generally produced by cross flow filtration. However, during the operation,
Non-permeate components in the feed water accumulate on the filtration membrane surface of the filtration membrane module and the permeate outlet of the filtration membrane, causing clogging of the filtration membrane module. Therefore, in order to remove such clogging and to remove the non-permeated substances that have adhered, backwashing is periodically performed in which part of the permeate is supplied to the filtration membrane module in the opposite direction to normal operation. ing. That is, the continuous operation of the water purification system is carried out while alternately carrying out cross-flow filtration and backwashing. However, in a long-term continuous operation, non-permeable components that are not peeled off only by backwashing are accumulated, resulting in a decrease in water treatment capacity. Therefore, once a few months, the filtration membrane module is treated with a chemical to remove the non-permeable components adhering to the surface of the filtration membrane module and recovering the water treatment ability of the filtration membrane module. Is being done.

[0004]

The chemicals used for cleaning the filtration membrane module with the above chemicals include surfactants, acids and alkalis. However, in the case of washing the filter membrane module used to purify surface water, for example, when using a surfactant, an enzyme-containing detergent, etc., it is necessary to completely rinse the filter membrane module after washing. If it is not used, the chemicals will remain, which will adversely affect the human body using the final product, clean water. In addition to the great difficulty in removing the used chemicals from the filtration membrane module, the amount of washing water is increased. Moreover, untreated wastewater containing surfactants also has a negative impact on the environment. On the other hand, when an acid or alkali is used, the filtration membrane module
In order to perform the cleaning of the module, it is required to use a high-concentration chemical cleaning agent, but this causes damage to the filtration membrane module itself, and it is difficult to set the cleaning conditions. Furthermore, post-treatment such as neutralization of used waste water is also required, which leads to water pollution of the water environment due to waste water as in the case of using a surfactant or the like. Therefore, in cleaning the filtration membrane module for purifying surface water, there is a strong demand for the development of a cleaning method that has little effect on the filtration membrane module itself, has a stable cleaning power, and can be treated at the site of the purification system. It is rare.

[0005]

[Means for Solving the Problems] In view of such a current situation,
The present inventors have used a specific concentration of Na to wash the filtration membrane module.
When a ClO solution was used, it was found that the material of the filtration membrane module was not impaired, the post-treatment of waste water was unnecessary, and the management was simple, and the present invention was completed.

[0006] That is, the present invention has a concentration of 5 to 5 in the washing of the filtration membrane module in the surface water purification system.
Filter membrane module in 95 mg / l NaClO solution
A method of immersing a filter membrane, wherein the product of the concentration of the NaClO solution and the immersing time is in the range of 1 × 10 ^{3 to} 7 × 10 ⁴ (mg / liter) · h.
The present invention provides a method of cleaning a package. Hereinafter, the present invention will be described in detail.

The filtration membrane module to which the cleaning method according to the present invention can be applied is preferably a filtration membrane module used in a water purification system for surface water, and the filtration membrane module is not particularly limited. The membrane form of the filtration membrane module includes a plate-and-frame type, a pleated type, a spiral type, a tubular (tubular) type, a hollow fiber type, and the like, all of which are applicable. Further, as the material of the film, it is possible to use polymers such as polyethylene sulfone, polyacrylonitrile copolymer and cellulose acetate. In particular, since cellulose acetate is easily decomposed by an alkaline chemical, the effect of the cleaning method according to the present invention is remarkable.

The drug used in the present invention is Na
Use a ClO solution. NaClO is a chemical that is originally used as a sterilizing agent for waterworks, and is particularly preferable as a cleaning agent for a filtration membrane module in the surface water purification system of the present invention. Its concentration is 5-95 mg
/ Liter is preferable, more preferably 10 to 50 mg
/ Liter. Further, in the present invention, the product of the concentration of the NaClO solution and the time during which the NaClO solution is in contact with the filter membrane for washing the filter membrane is 1 × 10 ^{3 to} 7 × 10 ⁴ (mg
/ Liter) · h.
That is, the value of this product is 1 × 10 ³ (mg / liter)
-If it is less than h, the filter membrane cannot be sufficiently washed with a detergent and the water treatment ability of the filter membrane module cannot be recovered. When the product value is larger than 7 × 10 ⁴ (mg / liter) · h, the filtration membrane module with NaClO solution is used.
Deterioration of the package will occur. Therefore, by washing in this range, a sufficient washing effect can be expected, and even if the washing is carried out for a long period of time, the deterioration of the filtration membrane module itself does not occur.

The cleaning method according to the present invention involves immersing the filtration membrane module in a NaClO solution,
In particular, it is not necessary to pressurize or constantly apply water flow or vibration to the NaClO solution. The time required for washing depends on the degree of adhesion of the non-permeable substance to the filtration membrane module and the NaCl used.
Depending on the O solution concentration, if it is usually 25 days or more,
The flux of the filtration membrane module is restored to at least 90% or more at the start of new use. If the washing time is too long, the strength of the filtration membrane will decrease, so the upper limit of the washing time is 6
It is preferably 0 days or less, but 40 days or less is suitable because the economy and the cleaning effect approach saturation with time.

In the cleaning method according to the present invention, it is possible to remove the filtration membrane module from the water purification system for washing, or to carry out the washing while the filtration membrane module is mounted in the water purification system. When the filtration membrane module is removed from the system, it is preferable to immerse the filtration membrane module in a previously prepared NaClO solution. On the other hand, when the water purification system is provided with a switching circuit for cleaning the filtration membrane module,
It is also possible to wash with the tool attached to the system. Note that the circuit for cleaning is a circuit different from the circuit for generating permeated water in normal use, which is supplied with a NaClO solution and rinsing water instead of the supply raw water, and is capable of discharging the treatment waste liquid by cleaning. is there. For example, in a water purification system for four filtration membrane modules, 5
If four filtration membrane modules are installed, the remaining one filtration membrane module can be washed while operating the four filtration membrane modules. If chemical cleaning of the filtration membrane module is required every 6 months, the filtration membrane module of the cleaning circuit is washed by immersing it in a NaClO solution for 36 days, and another filtration is performed every 36 days. It is only necessary to change to the membrane module in order, and it is not necessary to stop the operation of the water purification system for cleaning the filtration membrane module.

The NaClO in the present invention has a strong oxidizing action and a decomposing action and emits oxygen while releasing NaC.
It becomes l. Therefore, no special treatment facility is required as the wastewater treatment liquid for cleaning. Therefore, there is no need for a special treatment facility for cleaning, so that the operation can be performed easily at the site of the water purification system.

[0012]

The present invention will be described in more detail below with reference to Reference Examples and Examples, but the present invention is not limited thereto.

(Example) A filtration membrane module of cellulose acetate used under the same conditions in a water purification system,
Na at concentrations of 0, 10, 50 and 100 mg / liter
Immerse in ClO solution, and after immersion, 6, 15, 22, 29
And 43 days later, when the pure water was permeated through the filtration membrane module, and after the dipping process 22, 4
Tensile strength (break point) of filter membranes on days 3, 63 and 96
Was measured.

The flux of unused cellulose acetate is 5
It was 50 liter / m ² · hr. NaClO solution 0
When mg / liter was used, the recovery of the permeated water generation ability of the filtration membrane module was not obtained at all by the immersion for 45 days. With the NaClO solution of 10 to 50 mg / liter, a substantially stable recovery of permeated water production was observed from the 10th day of immersion. When the NaClO solution of 100 mg / liter was used, the permeated water-forming ability of the filtration membrane module was rapidly recovered in about 5 days of immersion. However, after the 7th day, the flux dropped with the lapse of time, and the permeated water-producing ability of the filtration membrane module was not recovered by long-term immersion (Fig. 1). Further, the strength of the filter membrane dipped in the NaClO solution 50 mg / l decreased from about 60 days after the immersion, and deterioration of the filter membrane occurred (Table-1).

[0015]

[Table 1]

[0016]

According to the cleaning method of the present invention, the treatment ability can be recovered without requiring special management of the filtration membrane module. Moreover, it is possible to perform the washing while continuously operating the water treatment system without stopping. Furthermore, unlike strong alkalis, strong acids, or surfactants, NaClO does not require neutralization or other post-treatments, and can be conveniently used in water purification plants.

[Brief description of drawings]

FIG. 1 Effect of NaClO concentration on flux recovery of filtration membrane module

Claims (3)

[Claims] 1. A method of immersing a filtration membrane module in a NaClO solution having a concentration of 5 to 95 mg / liter in the washing of the filtration membrane module in a surface water purification system, which comprises: A method for cleaning a filtration membrane module, wherein the product of the immersion time is in the range of 1 × 10 ^{3 to} 7 × 10 ⁴ (mg / liter) · h. 2. A method for cleaning a filtration membrane module according to claim 1, wherein the membrane material of the filtration membrane module is cellulose acetate. 3. A water treatment system comprising two or more filtration membrane modules, wherein at least one filtration membrane module is used while another filtration membrane module is mounted on the water treatment system for washing. Claim 1 characterized by the above.
A method for cleaning a filtration membrane module as described above.