Drink­ing wa­ter fil­tra­tion with mem­branes widely adopted

DEMM Engineering & Manufacturing - - PRODUCT WATCH -

With mem­brane fil­tra­tion pro­cesses be­com­ing more popular across a range of in­dus­tries, pre-treat­ing raw wa­ter has be­come in­creas­ingly im­por­tant to ex­tend the life of down­stream fil­ters, re­duce main­te­nance costs and en­ergy con­sump­tion and en­sure re­li­a­bil­ity.

All waste­water and wa­ter treat­ment pro­cesses where mem­branes are used are fun­da­men­tally multi-stage pro­cesses.

Mi­cro­fil­tra­tion and ul­tra-fil­tra­tion re­quire only pre-fil­tra­tion of coarse con­tam­i­nants (>50 μm), whereas with nano-fil­tra­tion and re­verse os­mo­sis there is a fur­ther re­quire­ment that the raw so­lu­tion should be free of par­ti­cle and col­loidal con­tam­i­na­tion. This ex­plains why good pre-treat­ment of the raw wa­ter is so im­por­tant, to be able to en­sure re­li­able and above all eco­nom­i­cal mem­brane fil­tra­tion.

In ad­di­tion to me­chan­i­cal pre-clean­ing us­ing con­ven­tional fil­ters, chem­i­cal and physic­o­chem­i­cal pro­cesses are also of­ten used in the pre-treat­ment for mem­brane pro­cesses.

The first step in pre­treat­ment gen­er­ally con­sists of coarse fil­tra­tion. This re­moves the coarse-grained solid ma­te­rial that can pen­e­trate the sys­tem from the raw wa­ter. Screens or coarse fil­ters in sizes 1 to 5 mm are used.

In the next stage, the raw wa­ter is fur­ther treated to ob­tain the re­quired raw wa­ter qual­ity for the mem­brane fil­tra­tion that fol­lows. This can be done both by us­ing me­chan­i­cal fine fil­tra­tion and also in com­bi­na­tion us­ing physic­o­chem­i­cal pro­cesses such as co­ag­u­la­tion, floc­cu­la­tion and pre­cip­i­ta­tion.

Mem­brane fil­tra­tion is usu­ally fol­lowed by an af­tertreat­ment, e.g. dis­in­fec­tion.

De­pend­ing on the qual­ity of the raw wa­ter and the wa­ter qual­ity re­quired after treat­ment, the en­gi­neer­ing pro­cesses are adapted to the spe­cial re­quire­ments.

For HYDAC Process Tech­nol­ogy di­vi­sion, pre-fil­tra­tion up­stream of mem­branes is an im­por­tant mar­ket sec­tor. HYDAC prod­ucts such as the au­to­matic back-f lush fil­ters Au­toFilt RF3 / RF4 / RF5 / RF7, the Au­toFilt TwistFlow Strainer ATF and an ar­ray of strainer fil­ters and in­line fil­ters are avail­able for th­ese ap­pli­ca­tions.

With its new depth fil­ter PLF1, HYDAC has the per­fect high-f low fine fil­ter which will pro­tect the mem­branes ef­fec­tively.

www.demm.co.nz/reader-en­quiry#140910

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