ABSTRACT
42 43The study assessed bacterial regrowth potential (BRP) and flow cytometry (FCM) as a method for measuring the biofouling potential of seawater reverse osmosis (SWRO) feed water. The method involves the removal of bacteria from the water sample, followed by reinoculation with a natural consortium of marine bacteria (104 cells/mL), with incubation (30 °C), and bacterial enumeration using FCM. Result illustrated that the BRP method is a potential tool to evaluate the biofouling potential of SWRO feed water. The method was relatively fast (2-3 days) compared to the conventional bioassays. The BRP method has the limit of detection of43,000±12,000 cells/mL (9.3±2.6 pg-Cglucose/L), which was improved by introducing the heating of chemical (NaCl) and bottle at 550 °C for 6 hours during blank preparation. The method was calibrated with glucose as a standard substrate and showed a good linearity (R2=0.88 to 0.95) between a range of0-2,000 pg-Cglucose/L. The method was applied to monitor the reduction of bacterial regrowth potential by pre-treatment schemes of full-scale SWRO plants. Results showed that the DAF-UF as pre-treatment reduced the bacterial regrowth potential of SWRO feed water by 54%, while it was 40% with DMF-CF. Furthermore, the measured bacterial regrowth potential of SWRO feed water especially in the DAF-UF-RO scheme was found consistent with the frequency of chemical cleaning in SWRO systems. However, more investigation is still needed to demonstrate the link between the measured bacterial regrowth potential of SWRO feed water and the rate of biofouling development in SWRO systems.
