Direct observation of macromolecular deposition on a nanofiltration membrane

The mechanistic aspects of membrane fouling have been studied extensively using direct observation, but limited to early stages of particulate deposition. Herein, we describe a versatile method extending direct observation to organic fouling, facilitating real-time monitoring of fouling formation and detachment. A transparent gel-like fouling layer is visualized using epi-fluorescent microscopy with the aid of labeled marker beads, trapped at various distances from the membrane, enabling monitoring of variations within the deposit. Fouling and cleaning experiments were conducted, examining alginate deposition and detachment, and illustrating the utility of the proposed method for studying the kinetics of fouling processes.