Evaluation of potential particulate/colloidal TEP foulants on a pilot scale SWRO desalination study

• TEP fouling was investigated through a SWRO pilot study.
• Chlorination caused a higher TEP concentration in water.
• Cartridge filters served as an incubator for the regrowth of bacteria.
• Chemicals addition in pretreatment may have enhanced the biofouling potential.
• RO membrane fouling is proportionally related to TEP concentration in feed water.

This pilot study investigated the variation of potential foulants and different fractions of transparent exopolymer particles (TEP), along the treatment scheme under different conditions. The objectives are to provide a comprehensive understanding on which fraction of TEP is more problematic in seawater reverse osmosis (SWRO) fouling, and which pretreatment can better reduce the concentration of TEP. Results showed that TEP deposited on the RO membranes, and the extent of RO fouling increased with the increase of TEP concentration in RO feed water. More TEP was produced in water after chlorination, probably because of the breakdown of bacterial cells and thus the release of internal exopolymers. Moreover, the cartridge filters could behave as an incubator for the regrowth of bacteria deactivated by chlorination and a spot for potential foulant (bacterial TEP) production, and thus enhance the RO membranes fouling. The presence of residual iron and addition of phosphate based antiscalant may also contribute to the higher biofouling of RO membranes. This pilot study provided an opportunity to identify the TEP related issues under different operational conditions in RO desalination of Red Sea water.