Nitto-denko Corporation

Masaaki Ando

Katsumi Ishii

Satoru Ishihara

Masahiko Hirose

Tomomi Ohara

Takuji Shintani

Hiroki Ito

A spiral wound membrane element allowing back wash reverse filtration at 0.05 MPa to 0.3 MPa is employed for a spiral wound membrane module. Air injection of injecting air of not more than 0.3 MPa into a permeate outlet of the spiral wound membrane module from a pressurized air feeder through a pipe, back wash reverse filtration with permeate and flushing with raw water are performed as recovery of a filtration velocity. Another spiral wound membrane module comprises a spiral wound membrane element including a separation membrane having high back pressure strength. Raw water into which bubbles are diffused by an air diffuser is fed to the spiral wound membrane element stored in a pressure vessel. Part of the raw water is axially fed through the spiral wound membrane element, discharged from a raw water outlet of the pressure vessel and thereafter returned to a raw water tank through a pipe.

Running method and treatment system for spiral wound membrane element and spiral wound membrane module

A spiral wound membrane module comprises a spiral wound membrane element including a separation membrane having high back pressure strength. The flow rate of permeate in filtration of the spiral wound membrane element is preferably set to 0.5 to 2.0 m/m/day, and the filtration time is preferably set to 10 to 300 minutes. The flow rate of wash water in washing is preferably set to 1.0 to 4.0 m/m/day, and the washing time is preferably set to 10 to 300 seconds. In such ranges, the ratio of the permeate volume in filtration to the permeate volume in back wash reverse filtration is set to be not more than 600.

Running method and washing method for spiral wound membrane element and spiral wound membrane module

A spiral wound membrane module comprises a spiral wound membrane element including a separation membrane having high back pressure strength. In filtration running, raw water introduced from a raw water inlet of a pressure vessel is subjected to dead end filtration, and permeate is taken out from a permeate outlet. In washing, wash water containing a chemical having a contaminant separating function is introduced from an end of a water collection pipe through the permeate outlet for performing back wash reverse filtration with a back pressure of 0.05 to 0.3 MPa. The filtration running is temporarily stopped for maintaining the pressure vessel in a state sealed with the raw water and the permeate for a prescribed time. Thus, contaminants adhering to the membrane surface of the spiral wound membrane element are separated. A treatment system is formed by connecting units comprising spiral wound membrane modules in parallel with each other. In the treatment system, one of the units is subjected to filtration running when another one of the units is washed. In washing, back wash reverse filtration and chemical soaking are performed.

Spiral wound membrane element, spiral wound membrane module and treatment system employing the same as well as running method and washing method therefor

A liquid separation membrane module includes a semipermeable membrane receiving a pressure of a feed liquid, and a channel material arranged so as to support the back side of the semipermeable membrane. The channel material is a tricot knitted fabric knitted by a tricot knitting machine with two reeds and has a ground stitch portion and a convex portion. The tricot knitted fabric includes a thermoplastic synthetic filament yarn with a core/sheath type conjugated fiber having a high melting point polymer as a core component and a low melting point polymer as a sheath component. Thermoplastic synthetic filament yarns for forming the ground stitch portion and the convex portion have a substantially same fineness, and the yarns in the tricot knitted fabric are bonded with one another by melt adhesion of the low melting point component to rigidity the entire knitted fabric.

Liquid separation membrane module

A module that can be practically used at a pressure of about 3 kgf/cm,is obtained by treating a polyamide based reverse osmosis membrane with an oxidizing agent. A composite reverse osmosis membrane comprises a thin film which is a polyamide based skin layer obtained by polycondensation of a compound having two or more reactive amino groups and a polyfunctional acid halide compound having two or more reactive acid halide groups, and a microporous support for supporting the thin film. The polyamide based skin layer formed on the surface of the membrane has a mean roughness of 50 nm or more. The composite reverse osmosis membrane is treated with an oxidizing agent. A salt rejection of 99% or more and a flux of 1.5 m,/m,&middot;day or more are obtained when evaluated by using a solution having pH 6.5 containing 500 ppm of sodium chloride at an operating pressure of 7.5 kgf/cm,and a temperature of 25&deg; C.

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Ibaraki, Japan

Masaaki Ando