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RO Pretreatment

RO has been utilized widely in recent years because costs have fallen during the past two decades. However, an RO system is only as good as the effectiveness of its pretreatment. Colloidal particles, bacteria, and other contaminants must be removed from the influent to protect the RO membranes from fouling and eventual failure. The cleaner the feed stream entering the RO process, the longer the membranes will last. Because of the required high effluent quality, MF/UF is more effective than conventional cartridge filters or multi-media filters for RO pretreatment. However, there are two issues that continue to limit the wider adoption of MF/UF membrane pre-treatment, (1) hollow-fiber/spiral-wound membrane filters often require additional processes to produce a feed suitable for RO, and (2) inefficient operating periods at reduced flux due to caking require higher maintenance with additional operational steps to control physical fouling like a chemical enhanced backwash or clean-in-place on a regular basis.


With its open tubular channels/large diameter lumens, the coiled membrane filters (CMF) developed by FSI have excelled for applications with high solids concentration as well as large particle sizes. In addition, the unique Dean Flow technology of the CMF creates a self-cleaning mechanism resulting in an enhanced flux rate, longer membrane service life, and reduced energy footprint. These characteristics make the CMF an ideal pretreatment choice for many industrial applications that require pH adjustment, water softening, or the addition of flocculent/coagulant/polymers. For applications with no chemical additives, the CMF is still capable of removing submicron solids in many water and wastewater treatment processes to provide a sustainable high-quality feed to improve RO system Reliability, Availability and Maintainability (RAM). The CMF was originally developed for an Army field application. It is also used by other support organizations for military, humanitarian assistance, and disaster relief operations when integrated with an RO system.


With the improved feed water quality provided by the CMF, the following highest cost components of membrane desalination and wastewater treatment are addressed:


  • Higher flux and reduced fouling of primary RO membrane downstream

  • Increased production and lower OEM budgets due to less required maintenance

  • Less CIP and downtime than conventional pretreatments including multi-media and MF/UF filters


The CMF provided by FSI is an ideal system for RO Pretreatment.

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