Why UF Systems as Pretreatment for RO?

One of the toughest problems of osmosis systems is the pretreatment. Years have been spent on deliberation and repeated tests, yet in most well-utilized osmosis systems, i.e., those operating many hours a day, it is still impossible to maintain a high recovery ratio in order to save water, and also avoid having to perform frequent CIP (Clean-in-Place) membrane cleaning.

The phenomenon of reduction in output as a result of penetration and development of organic residue and gradual clogging of membranes by scale deposits constitutes a major problem in operation of osmosis systems.

To avoid such phenomena as much as possible, it is common practice to install filtration systems with quartz media in order to maintain the required murkiness, a carbon media to prevent biological development and adsorb free chlorine and microfiltration to protect the membranes from suspended particles larger than 5 microns.

These systems perform flushing with large amounts of water and require replacement of media and filter elements at a high cost.

In recent years, Winter Engineering has manufactured and installed several reverse osmosis systems with UF (Ultra Filtration) pretreatment as a substitute for the standard treatment.

UF systems perform filtration to a size of 0.01 micron. At such a filtration size, there is no passage of any significant particles. At the biological level, hardly any germs can get through either.

In light of these data, it is clear that when manufacturing systems are equipped with UFRO, media filters and micronic filters are no longer necessary.

What this means is no more need to replace expensive sand and carbon filtration media and microfiltration elements. This creates a savings of tens of NIS per each m3 of water produced.

The feed water to the system is filtered to a very high degree; thus, the osmosis membranes need to handle only chlorides. The reduced load enables working with an improved recovery ratio without increasing the membranes’ surface area.

The recovery ratio of UF systems is in the range of 96% to 98% depending on the type of membrane.

Infiltration systems equipped with dosing systems, GRUNDFOS 4 dosing pumps are used to dispense various chemical preparations.

·        For dealing with hardness salts, anti-scalant is dosed to all reverse osmosis systems, regardless of the type of pretreatment used.

·        SMBS is a preparation used as a substitute for carbon in neutralizing the presence of free chlorine.

·        For cleaning UF membranes, hydrochloric acid and soda are used in minimal controlled doses.

All integrated systems manufactured and installed by Winter Engineering have been in operation for several years, without a reduction in output. This, without replacement of RO membranes or any other maintenance.

UFRO system 3×12.5 m3/h at Rambam Health Care Campus 

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