RO Pre & Post Treatment

Where RO membranes are used it is advised to prefilter the feed water to remove particulate matter that could foul the membrane. RO membranes are constructed as a spiral wrap and so there is no easy method to remove particulates that may have entered the RO filter. Prefilters will reduce the particulate load entering the RO filter so that the RO membrane can perform at its optimum output.

If thin film composite (TFM or TFC) RO membranes are used, carbon prefiltration should be used to remove chlorine from the incoming water since chlorine attacks the TFM membrane material. However, if cellulose triacetate (CTA) RO membranes are used, carbon prefilters are not required since these are not at risk from chlorine.

Ion exchange products can enhance pre-treatment to the RO membranes. One of Graver’s Ecodex® powdered ion exchange resin products can be applied to RO prefilters to remove objectionable ionic and some organic species to help limit RO membrane fouling. Ecosorb products are also useful for reduction of organics.

While RO membranes can remove some heavy metal contaminants such as arsenic V, they are ineffective at removing arsenic III. Graver MetSorb® HMRG is a highly specialized adsorbent material that effectively removes arsenic III, as well as arsenic V, lead, and other heavy metals. Placed downstream of the RO membrane, MetSorb HMRG adsorbent can achieve the water purity required for your end use.

 

Graver Product Selection

Product Application
MBF™ or STC™ Melt blown depth filters for Pre RO filtration to prevent membrane fouling.  5 micron is most typically used.
CarbTEC™ COT+ Carbtec extruded carbon block filters effectively remove chlorine to protect TFC type RO membranes
Ecodex® P-202-H Apply Ecodex to the top of sand filters as a precoated layer up to several inches in depth to remove ionic contaminants and some organics
Ecosorb® W-701 Apply in the same manner as Ecodex to enhance organic removal.  Ecodex and Ecosorb may be used together
MetSorb® HMRG Highly specialized adsorbent material removes heavy metals, lead, and arsenic from water. MetSorb even removes the arsenic III, which is not readily removed by RO membranes (RO effective at arsenic V removal)

Application Case Study