RO, RO Membranes, Membranes Filtration


The benefits of pre treating feedwater are Increased life of RO membrane filtration elements Better quality of water Decrease in maintenance time Materials from the feed stream collect near the surface of the RO membrane filtration and adversely affects water permeation. Fouling can be of several kinds. Cake fouling occurs when there are layers of deposition on the surface. Scale fouling is when there is a hardened layer on the membrane surface. Pore blockage may occur due to a particle insertion or adsorption which is the chemical attachment of particles to the RO membrane filtration, may affect performance. The table below depicts the various membrane foulants.


Foulant
Effects
Action
Inorganic Salts Reduced permeate flow Remove hardness via pretreatment and softening
Scale formation on membrane surface Add antiscalant or dispersant
Increased salt passage Decrease feed pH
Increased differential pressure Clean with an acid cleaner

Organics
(oils, grease)

Decreased permeate flow Optimize pretreatment
Increased salt passage Install an activated carbon filter
Clean with suitable detergent

Iron

Stains membrane surface Remove iron with pretreatment
Rapid reduction in permeate flow Clean with chelating agent

Silica

Decreased permeate flow Evaluate recovery and pH
Slight increase in salt passage Optimize pretreatment for colloidal removal

Biological

Foul odor or taste Perform routine sanitizing

Slime

Reduced permeate flow Employ continuous operation
Slime formation
Increased differential pressure