Reverse Osmosis Chemicals
Unit B Badex Building
Westbrook Park
Old Trafford
Manchester M17 1AY
United Kingdom

t: +44 (0) 161 877 2334
f: +44 (0) 870 135 6389
e: info@rochemicals.com

Common Failures - Reverse Osmosis Systems Print E-mail

Common Failures - The following table identifies a number of the most common failures affecting reverse osmosis systems, thier effects and recommended monitoring practices.

Failure
Effect
Recommended Monitoring Practice
Antiscalant Scale formation on membranes, usually in the back-end stages – high salt passage, Pressure difference in final stage. Check dosing equipment and monitor changes in water quality.
Ineffective sanitization procedures Bio-fouled pipe-work, cartridge filters and membranes - high Pressure difference. Sanitize sand filters and GAC filters. Microbiological analysis, chlorine dosing, contamination in chemical dosing tanks.
High iron content Iron loading on cartridge filters. Iron fouling of membranes – high Pressure difference, low permeate flow. Pipe-work corrosion, ferric breakthrough from media beds, failure of media filters.
High organic content Humic substances and organic fouling on membrane – low permeate flow, high feed Pressure Feed water composition, review flocculation procedures, feed watercolor, TOC.
Colloidal breakthrough Colloidal particles foul micron filters and membranes – high Pressure difference, low permeate flow. Silt Density Index (SDI), condition of cartridge filters, eliminate media fines.
Granular activated carbon filters Carbon fines foul micro filters and membranes. Check washing procedure to remove fines from GAC filters.
Overdosing of coagulant Cationic coagulant fouls membrane – low permeate flow, high feed Pressure. Check dosing levels and detect excess traces.
Overdosing of chlorine Membrane damage – high salt passage and increased flux. Dosing equipment, Redox meters, bisulfite dosing levels and positioning of dosing point, chlorine test kit.
Permeate tube “O” ring failure High salt passage. Check individual pressure vessel conductivity, probe suspect PV’s to check individual membrane product conductivity.
Ineffective biocide High bacterial / fungal counts in water samples. Biofouling of membranes – high Pressure difference. Biocide adsorption on GAC, check contact times and dose rate, select broad-spectrum biocide, Select biocide for organic content.
Sand / Multi-media filter breakthrough Colloidal and bacterial fouling of micron filters and membranes. Check wash procedures to remove fines.
Acid dosing Scale formation – CaCO3 only. pH monitor / controller.
Seasonal algae blooms (sea water) High microbiological loading, biofilm, severe cartridge filter fouling. Microbiological counts in water samples, evidence of biofilms, check algae counts.
Poor performance on start up after shutdown Fouling / scaling of membranes. Check membrane flush procedures on shut down and preservation procedures on extended shutdown.

 

Technical support and advice

Please note that various RO membrane preservation procedures are available and you should follow the membrane manufacturers recommendations.

Reverse Osmosis Chemicals International work closely with a diverse range of global organisations, intelligently combining advanced treatment technologies with practical solutions to resolve complex issues. If you have a project you would like to discuss, or you require technical support and assistance; or if you simply have a question about our reverse osmosis technology solutions please contact one of our specialist advisors using our Technical Support page or call us on +44 (0) 161 877 2334.