Fouling investigation of cartridge filter (CF) used as "firewall" in a nanofiltration drinking water plant.

The cartridge filter (CF) as a "firewall" is crucial between pretreatment and nanofiltration (NF) units, but CF fouling with risk has received limited attention. The systematic autopsy for CFs (CF1 and CF2) applied in a NF drinking water plant was conducted to reveal CF fouling profile. Herein, scale blocks, irregular-shaped particles, and stacked-floc clusters were observed as the main morphologies of foulants. The major elements from foulants included Fe, Ca, Al, Mg, Na, P, and Si. The dissolved matters especially bioproducts resulted in the secondary pollution of permeated water. Biofouling was mainly caused by Proteobacteria phyla, and consisted of a large proportion of polysaccharides (11% and 25.1%), proteins (10.3% and 22.7%), lipids (21.7% and 22.4%), respectively. In addition, an obvious contrast was observed regarding the antifouling performance of CFs. The surface scaling degree of CF1 with horizontal irregular loose-pleats was more serious than CF2 with vertical regular compact-pleats, while the latter with high-density pleats appeared the higher fouling potential due to a greater capacity for organic foulants in the inner layers of "firewall" and better bio-diversity and bio-evenness of microbial communities. This study provides a deeper insight into CF fouling and contributes to the application of CFs.