Nirajan Dhakal1,2,3, Sergio G Salinas-Rodriguez1, Joshua Ampah1, Jan C Schippers1, Maria D Kennedy1,3. 1. Water Supply Sanitation and Environmental Engineering Department, IHE Delft Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands. 2. Wetsus European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, The Netherlands. 3. Faculty of Civil Engineering, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands.
Abstract
Measuring the bacterial growth potential of seawater reverse osmosis (SWRO) feed water is an issue that is receiving growing attention. This study developed and demonstrated the applicability of the flow-cytometry (FCM)-based bacterial growth potential (BGP) method to assess the biofouling potential in SWRO systems using natural microbial consortium. This method is relatively fast (2-3 days) compared to conventional bioassays. The effect of the potential introduction of nutrients during measurement has been studied thoroughly to achieve the lowest measure value of about 45,000 cells/mL, which is equivalent to about (10 µg-C glucose/L). The BGP method was applied in two full-scale SWRO plants that included (i) dissolved air flotation (DAF) and ultra-filtration (UF); (ii) dual-media filtration (DMF) and cartridge filter (CF), which were compared with the cleaning frequency of the plants. A significant reduction (54%) in BGP was observed through DAF-UF as pre-treatment (with 0.5 mg Fe3+/L), while there was a 40% reduction by DMF-CF (with 0.8 mg Fe3+/L). In terms of the absolute number, the SWRO feed water after DAF-UF supports 1.5 × 106 cells/mL, which is 1.25 times higher than after DMF-CF. This corresponds to the higher cleaning-in-place (CIP) frequency of SWRO with DAF-UF compared to DMF-CF as pre-treatment, indicating that the BGP method has an added value in monitoring the biofouling potential in SWRO systems.
Measuring the bacterial growth potential of seawater reverse osmosis (SWRO) feed pan> class="Chemical">water is an issue that is receiving growing attention. This study developed and demonstrated the applicability of the flow-cytometry (FCM)-based bacterial growth potential (BGP) method to assess the biofouling potential in SWRO systems using natural microbial consortium. This method is relatively fast (2-3 days) compared to conventional bioassays. The effect of the potential introduction of nutrients during measurement has been studied thoroughly to achieve the lowest measure value of about 45,000 cells/mL, which is equivalent to about (10 µg-C glucose/L). The BGP method was applied in two full-scale SWRO plants that included (i) dissolved air flotation (DAF) and ultra-filtration (UF); (ii) dual-media filtration (DMF) and cartridge filter (CF), which were compared with the cleaning frequency of the plants. A significant reduction (54%) in BGP was observed through DAF-UF as pre-treatment (with 0.5 mg Fe3+/L), while there was a 40% reduction by DMF-CF (with 0.8 mg Fe3+/L). In terms of the absolute number, the SWRO feed water after DAF-UF supports 1.5 × 106 cells/mL, which is 1.25 times higher than after DMF-CF. This corresponds to the higher cleaning-in-place (CIP) frequency of SWRO with DAF-UF compared to DMF-CF as pre-treatment, indicating that the BGP method has an added value in monitoring the biofouling potential in SWRO systems.