Bacterial TEP fouling on NF membranes and visualization of bacterial TEP on fouled membranes

In this study, TEP-like substances from marine bacteria (P.atlantica) was isolated for nanofiltration (NF) filtration experiments to investigate the fouling behavior of different fractions of bacterial TEP substances. First of all, the isolated TEP were fractionated into three groups by conducting dialysis and filtration: particulate TEP > 0.4 μm; colloidal TEP between 0.4 μm and 3500 Da; and non-colloidal TEP < 3500 Da. Different fraction was filtered with DOW NF90 membranes at a constant pressure (8 bars) for 3 days. The decrease in flux was recorded for each experiment, and the fouled membrane was stained with alcian blue dye and photographed. Results showed that all fractions of bacterial TEP caused organic fouling on NF membranes. That is probably because the sticky property of TEP, allowing them to adhere on NF membranes. This is an important finding, since the TEP/TEP precursors covers a wide range of size (from nm-scale to μm-scale), and when they pass through the pretreatment and enter NF/RO system, they can deposit on NF/RO membrane surface and thereby agglutinate bacteria present in the NF/RO feed, promoting biofouling on NF/RO membranes.