Removal of different fractions of NOM foulants during demineralized water backwashing

The effectiveness of demineralized water backwashing on fouling by different fractions of NOM was investigated in this study. Two types of natural surface water (Schie canal and Biesbosch reservoir) were tested to confirm the improvement of demineralized water backwashing on fouling control, and LC-OCD analysis was conducted on Schie canal water to find out which fraction of NOM was removed with those backwashes. Results derived from natural waters showed that demineralized water backwashing substantially improved UF fouling control. LC-OCD analyses showed both UF permeate and demineralized water backwashes were effective on removing part of biopolymers, but demineralized water is also effective for humic substances and a limited amount of low molecular weight substances. However, based on the LC-OCD results, even demineralized water backwashing is not effective to remove all humic substances and biopolymers rejected on the UF membranes.

► Demineralized water backwashing remove more foulants than UF permeate.
► Some biopolymers can be flushed by both demineralized water and UF permeate Backwash.
► Demineralized water backwashing was able to remove a substantial amount of Humics.
► Demineralized water backwashing also cannot remove all foulants.