Aquatech’s Concentrate Recycle Reverse Osmosis (CRRO™) is a process that operates on the concept of osmotically assisted reverse osmosis. Unlike conventional RO, where the permeate concentration approaches zero, CRRO, to start with, has a permeate-side equal to or slightly lower salinity solution to reduce the osmotic pressure gradient across the membrane. This enables water transport evenly and facilitates permeate flow even when the osmotic pressure is higher.
The process produces a permeate product with 40-50% salt rejection in a single stage. When multiple CRRO units are linked in series, this process progressively enables the recovery of lower concentrations than feed from high salinity brines and has been successfully used to further concentrate RO brines to more than 20% salt concentration.
The concept also allows reduction of osmotic pressure by generating higher permeate concentration like sea water RO feed utilizing Seawater Reverse Osmosis (SWRO) reject as the feed water. The permeate water generated in this water can be mixed with an upstream SWRO feed or treated in a separate downstream seawater desalination plant. The CRRO process may use a hollow fiber or spiral flat sheet membrane. Though each membrane uses a slightly different approach in the flow scheme, both approaches involve the progressive concentration of brine while diluting the permeate to allow for treatment through an SWRO system.