Role of NOM in the performance of adsorption-membrane hybrid systems applied for the removal of pharmaceuticals

Adsorption-membrane hybrid systems present an interesting alternative for the treatment of contaminated waters. This study aims to understand the role of NOM on membrane performance and on removal of pharmaceuticals during the combined application of powdered activated carbon and submerged membranes. A focus was on investigations of the interactions between particles, membrane surface and NOM constituents and how they affect membrane filtration. PAC-particles played a minor role in the flux decline during filtration of demineralised water and phosphate puffer (pH value = 7). Filtration experiments in the presence of NOM resulted in the formation of irreversible fouling, of a thick cake layer and thus a significant flux decline. The results suggest that NOM can bridge PAC particles together and to the membrane surface so that they become part of the foulants in the hybrid system. The pharmaceuticals were rejected in the hybrid system predominantly more than 99.8% and the removal of DOC was about 60%.

The results presented in this work showed that the presence of NOM slightly reduced the adsorption of PhACs on activated carbon. There is almost no influence of NOM on the removal of PhACs in the investigated concentration range. However, NOM played an important role in the deterioration of the membrane performance and in the formation of irreversible fouling. NOM can bind PAC particles to one another and to the membrane surface, so that the particles become part of the foulants in the hybrid system. The addition of PAC to the raw water led to a reduction of NOM concentration and thereby reducing the fouling potential of the water. However, this positive effect lost its importance due to the increase in fouling associated with the interactions between NOM and particles [5].