Selection of the most problematic biofoulant in fouled RO membrane and the seawater intake to develop biosensors for membrane biofouling

Biofoulants by autopsy of RO membrane and microbiological quality of the intake water were investigated with the samples obtained from existing RO desalination plant. The analysis of organic matters of the biofilm on the membrane surface showed that macromolecular substances such as proteins and carbohydrates were the major composites and contributed to the biofilm formation. Comparison of microbial communities between the RO membrane and seawater intake samples revealed that α-proteobacteria was the most abundant bacterial group both in the membrane surface and the intake water, and the phylum Firmicute and Planctomycetes, which were proposed not to be originated from the seawater intake, appeared as the potential biofoulants target. The final goal of this research project is to develop a rapid and sensitive biosensor system to detect the problematic biofoulants on RO system in seawater desalination process, with the tool of fluorescence nanoparticles. Preliminary result of this study showed that RO biofouling was contributed both by microbial cells and the extra organic substances and these identification and sensing of specific biofoulant targets will be beneficial to process efficiency.

In this study, fouled and less fouled membranes from the real desalination plant were investigated to characterize the biofoulants of the membrane surface. In addition, the microbial diversities were compared to that of seawater intake. Autopsy suggested that foulants on the RO membrane were unevenly distributed and deposited in parallel with the direction of water flow. Electron microscopy observation showed microorganism-like forms and bulky layers were placed on the surface of the RO membrane and total bacteria were calculated as approximately 107 cells/cm2. Organic matters were composed of 90% dry weight of foulants. Comparison of microbial community between the RO membrane and seawater intake samples was summarized that α-Proteobacteria were composed of the largest fraction of total sequences and the phylum Firmicute and Plactomycetes, which were proposed not to be originated from the seawater intake, need more investigation to sort a potential microorganism target in order to develop biofilm sensor system.