JPS6111108A - Process for washing membrane module - Google Patents

Abstract

PURPOSE:To improve washing efficiency of a membrane module by equalizing the pressure of a permeated liquid chamber to the pressure of a feed liquid chamber and thus circulating the washing liquid. CONSTITUTION:The washing liquid is circulated by closing a valve 2 and through a passage from a washing liquid tank 3 toward a pump 4, feed liquid chamber 11 of the membrane module and the washing liquid chamber 3 in order. The solvent for the washing liquid permeates from the feed liquid chamber 11 to the permeated liquid chamber 13 of the membrane module. Thus, the permeated liquid chamber 13 is filled gradually with the permeated liquid, and the pressure in the feed liquid chamber is equalized to the pressure of the permeated liquid chamber 13. Under this condition of the pressure, pressing effect of suspended matters accumulated on the membrane surface is avoided, and the accumulated matters are smoothly flowed off by the stream of the washing liquid. The washing is performed effectively by the succeeding circulation of washing liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in a method for cleaning membrane modules.

Prior Art and Problems A solution (undiluted solution) containing suspended solids is made to flow under pressure in contact with the membrane of a membrane module, and the liquid that permeates through the membrane (permeated liquid) is taken out and the stock solution chamber of the membrane module is taken out. When purification, separation, or concentration is performed by removing the permeate (concentrate), suspended substances in the stock solution gradually adhere to and accumulate on the membrane surface, resulting in poor membrane performance, especially the permeate volume, due to membrane contamination. A decline is inevitable.

Therefore, it is necessary to incorporate a cleaning agent liquid circulation system into the liquid separation system and to periodically clean the membrane module. However, conventionally, during cleaning, a cleaning agent liquid circulation circuit as shown in FIG.
The liquid is circulated through the stock solution chamber 11'(ill' is the stock solution inlet and 112' is the stock solution outlet), and the liquid that has permeated into the permeated liquid chamber 13' is collected in the cleaning agent liquid tank 3'. However, in this conventional method, the cleaning efficiency is low; for example, even after cleaning for 1 hour at a pump flow rate of 30115+, the cleaning efficiency is 50%.
Even the recovery rate is difficult.

Therefore, the inventors of the present invention conducted various studies to improve the cleaning efficiency, and found that it is most effective to make the pressure in the permeate chamber equal to the pressure in the stock solution chamber during circulation of the cleaning solution. Ta. There are many reasons for this improvement in cleaning efficiency, but the main reason is that under the above pressure conditions, the cleaning liquid can be brought into contact with the membrane surface with zero differential force, and the suspended solids accumulated on the membrane surface can be removed from the membrane. This is thought to be due to the fact that it is possible to avoid being pushed onto the membrane surface, and as a result, the accumulation that has been released from the restraint by the cleaning liquid can be smoothly washed away by the flow of the cleaning liquid.

OBJECTS OF THE INVENTION The object of the present invention is to provide a membrane module cleaning method with excellent cleaning efficiency based on the above knowledge.

In other words, the method for cleaning a membrane module according to the present invention involves supplying a cleaning agent liquid to a membrane module equipped with a concentrate chamber having a concentrate inlet and an outlet, and a permeate chamber adjacent to the concentrate chamber via a permeable membrane. This method of cleaning a permeable membrane by circulating the cleaning agent is characterized in that the cleaning agent is circulated while the pressure in the permeate chamber is made equal to the pressure in the stock solution chamber.

It may be any module and is not particularly limited. There are no particular restrictions on the selectively permeable membrane, and cellulose-based, polyolefin-based, polysulfone-based, ethylene-vinyl alcohol copolymer-based, polyvinyl alcohol-based, polyacrylonitrile-based, polyamide-based, polyimide-based membranes or composites of these materials can be used. The present invention can be applied to any case where a membrane or the like is used.

Furthermore, there is no particular restriction on the type of module, and the present invention can be applied to any of the flat membrane type, front type, spiral type, hollow fiber type, and pleated type.

For the cleaning solution, use a cleaning agent that is dispersible and/or soluble for suspended substances, and commercially available synthetic detergents, acidic solutions, alkaline solutions, enzyme agents, etc. can be used, and the concentration is usually 0.2.
~5.0%. The washing temperature is usually 20-40°C. The cleaning time depends on the nature of the adhered substances, the amount of adhered substances, the type of cleaning agent,
It usually takes from 10 minutes to 5 hours, although it varies depending on the concentration etc. To carry out the present invention, a cleaning agent liquid tank is built into the liquid separation system, and a valve is operated during membrane cleaning as shown in Figure 1. A cleaning agent liquid circulation circuit is constructed, and the cleaning agent liquid is circulated through the membrane module through the circuit. The valve operation in this case may be performed either manually or automatically.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an example of a cleaning liquid circulation circuit used in the present invention.

In FIG. 1, 1 is a membrane module, 11 is a stock solution chamber, 12 is a selective permeation membrane, and 13 is a permeate chamber. Ill is a stock solution inlet, and 112 is a stock solution outlet.・2 is the pulp installed in the permeate extraction pipe. 3 is a cleaning agent liquid tank. 4 is a pump. 5 and 6 are piping.

The cleaning agent liquid tank 3 described above is installed in a liquid separation system to which the present invention is applied, and the pump 4 is usually used in common with the stock solution feed pump of the same system.

In order to clean the membrane module according to the present invention, the cleaning circuit shown in FIG. 1 is configured by operating the valves in the above system,
After closing the valve 2, the pump 4 is driven to transfer the cleaning liquid from the cleaning liquid tank 3 to the pump 4 to the raw solution chamber 1 of the membrane module.
1 → Circulate through the cleaning liquid tank 3 path. When the cleaning liquid passes through the stock solution chamber 11 of the membrane module, the solvent of the cleaning solution permeates into the permeate chamber 13 of the membrane module, and the permeate chamber 13 is gradually filled with the permeate, and the solution chamber 11 and the permeate chamber are gradually filled with the permeate. 13 are at the same pressure, and the subsequent circulation of the cleaning fluid allows cleaning to proceed effectively. This cleaning is performed by continuous circulation of the cleaning solution, or by repeatedly circulating and leaving the cleaning solution to fill.

Examples of the present invention will be described below.

Example 1 The amount of permeated water of the ultrafiltration membrane module (NT'tJ-3150-54 manufactured by Nitto Electric Industry Co., Ltd.) used for the concentration separation treatment of polishing wastewater is such that suspended solids (Mgt A11, inorganic substances such as Sn and resins Due to the adhesion of organic substances such as
minutes to 3 lV minutes, the cleaning circuit shown in Fig. 1 above was constructed, and the cleaning solution (composition: PH2, citric acid aqueous solution 0.5%) was supplied at a flow rate of 301y% (C flow rate at the stock solution outlet), temperature = Pressurized circulation at 25-30℃ for 30 minutes, then 2
When the water was left to be filled for 0 minutes and then pressurized and circulated again for 30 minutes at the above-mentioned flow rate of 301/min, the amount of permeated water recovered to 171/min. This recovery rate is 85%.

In contrast to Example 1 above, as shown in Figure 2, the permeate that permeated into the permeate chamber of the membrane module was returned to the cleaning liquid tank, and the other conditions were the same as in Example 1. The recovery rate was approximately 50%.

Example 2 The amount of permeated water of the same upper limit filtration membrane module being used for the concentration separation treatment of textile factory wastewater decreased from the initial 221/min to 41/min, so a cleaning circuit similar to that of Example 1 was configured,
Cleaning liquid (composition: PH1l anionic surfactant 0.5%
) was circulated under pressure at a flow rate of 351/min and a temperature of 30 to 35°C for 1 hour, and the water permeation rate recovered to 211/lA-.

This recovery rate is 95%.

In Example 2, the permeated liquid that permeated into the permeated liquid chamber of the membrane module was returned to the cleaning liquid tank, and the other conditions were the same as in Example 2, and the water permeation rate recovery rate was 65%. .

Effects of the Invention As described above, according to the membrane module cleaning method according to the present invention, the water permeation amount can be recovered more effectively than the conventional method, and the operation is also performed by closing the permeate extraction pulp of the membrane module. Since it is only necessary to wash the container with water, the effects of the present invention can be achieved very easily.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a membrane module cleaning method according to the present invention, and FIG. 2 is an explanatory diagram showing a conventional membrane module cleaning method.

Claims (1)

[Claims] In a method of cleaning a permeate membrane by circulating a cleaning agent liquid through a membrane module comprising a concentrate chamber having a concentrate inlet and an outlet, and a permeate chamber adjacent to the concentrate chamber via a permeable membrane, the pressure in the permeate chamber is A method for cleaning a membrane module, characterized in that the cleaning solution is circulated in a state where the pressure is equal to the pressure in the stock solution chamber.