Archive for September, 2012

RO system trouble shooting —– membrane elements fouling and solution

September 5, 2012 Leave a comment

RO system trouble shooting —– membrane elements fouling and solution

Symptoms of trouble:

PP cartridges of security filter seriously blocked after 7 working days by yellow colloidal fouling, and this colloidal substance also follow through the security filter and effect the RO membrane elements, especially the first stage.

Cause: By analyzing the process, we conclude the sulfur bacteria increasing due to the Sodium Bisulfite (SBS) overdosing. At the pretreatment process, the Chloride Dioxide is dosed as bactericide in the depositing reservoir, and before the water go to the RO unit, the Sodium Bisulfite (SBS) is dosed to protect RO membranes. The overdosed SBS reduce not only residual chlorine, but also free oxygen, this will create an anaerobic environment, and the remnant sulfur compounds provide energy source for sulfur bacteria metabolism, which are anaerobic.


To cut off the energy source of sulfur bacteria and inhibit its growth. There are two ways to avoid SBS overdoing: to get accurate value of residual chlorine, then recalculate SBS dosing; or to get ORP value of feed water (without any chemical dosing) as reference value, to decide SBS dosing