Abstract: In the treatment, a reverse osmosis membrane element having a polyamide skin layer is loaded in a pressure vessel in a membrane separator and contacted with a bromide-containing aqueous solution of free chlorine. The thus treated reverse osmosis membrane element retains for a long time its effect of reducing solute concentration in a solution treated with the reverse osmosis membrane and rejects efficiently non-electrolytic organic materials or substances such as boron that will not be dissociated in a neutral region. A reverse osmosis membrane module having the thus treated reverse osmosis membrane element is provided as well.

Abstract: At the time of back washing of a treatment system, filtrate 2 is reverse-osmosis-filtrated by a reverse osmosis membrane separation device 51 so as to be separated into permeate 3 and concentrate 4. The concentrate 4 obtained from the reverse osmosis membrane separation device 51 is supplied as washing water into a spiral membrane element 10 through pipes 21 and 21a. On this occasion, the concentrate 4 is pressurized by a supply pump 104, so that a separation membrane is back-washed under a back pressure higher than 0.05 MPa but not higher than 0.3 MPa.

Abstract: In the treatment, a reverse osmosis membrane element having a polyamide skin layer is loaded in a pressure vessel in a membrane separator and contacted with a bromide-containing aqueous solution of free chlorine. The thus treated reverse osmosis membrane element retains for a long time its effect of reducing solute concentration in a solution treated with the reverse osmosis membrane and rejects efficiently non-electrolytic organic materials or substances such as boron that will not be dissociated in a neutral region. A reverse osmosis membrane module having the thus treated reverse osmosis membrane element is provided as well.

Abstract: A novel process for the production of fluorine-containing multi-component copolymers having functional groups is disclosed, which process is characterized in that tetrafluoroethylene having the formula: CF.sub.2 .dbd.CF.sub.2 ; one or two or more .alpha.,.beta.,.beta.-trifluoroacrylate having the generic formula: CF.sub.2 .dbd.CFCOOC.sub.n H.sub.2n+1 wherein n represents an integer of 1 or greater; and one or two or more .alpha.-olefin having the generic formula: ##STR1## wherein j and m each independently represents an integer of 0 to 11 inclusive; are copolymerized with one another in the presence of a radical initiator. The resultant interpolymer is hydrolyzed and cross-linked using ionizing radiation.

Abstract: A novel process for the production of fluorine-containing multi-component copolymers having functional groups is disclosed, which process is characterized in that tetrafluoroethylene having the formula: CF.sub.2 .dbd.CF.sub.2 ; one or two or more .alpha.,.beta.,.beta.-trifluoroacrylate having the generic formula: CF.sub.2 .dbd.CFCOOC.sub.n H.sub.2n+1 wherein n represents an integer of 1 or greater; and one or two or more .alpha.-olefin having the generic formula: ##STR1## wherein j and m each independently represents an integer of 0 to 11 inclusive; are copolymerized with one another in the presence of a radical initiator.