Measuring Biofouling Potential in SWRO Plants with a Flow-Cytometry-Based Bacterial Growth Potential Method.

Nirajan Dhakal,Maria Kennedy,Sergio Salinas-Rodriguez,Jan Schippers,Joshua Ampah

doi:10.3390/membranes11020076

Nirajan Dhakal, Maria Kennedy + Show 3 more

Open Access

https://doi.org/10.3390/membranes11020076

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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.

Highlights

Biofouling in seawater reverse osmosis (SWRO) systems remains the major challenge for its cost-effective operation [1,2,3,4,5]
The rate of biofouling measured as development of head loss across the feed/brine channel in membrane fouling simulator (MFS) and biofilm formation rate (BFR) systems occurs at the same rate as in the full-scale SWRO plant
We investigated the possibility of using the flow-cytometry-based bacterial growth potential method to assess the biofouling potential in SWRO systems

Summary

Introduction

Biofouling in seawater reverse osmosis (SWRO) systems remains the major challenge for its cost-effective operation [1,2,3,4,5]. While membranes remain in operation, is of great importance to avoid costly sacrifice of SWRO elements for autopsy [7]. Kurihara et al [9] recently found a good correlation between the BFR and a chemical cleaning intervals in SWRO plants. The rate of biofouling measured as development of head loss across the feed/brine channel in MFS and BFR systems occurs at the same rate as in the full-scale SWRO plant. The application of bacterial growth potential (BGP) methods gained attention in the membrane-based desalination industry. Ross et al [15] showed that bacterial growth using an indigenous microbial consortium was 20% higher than when using pure culture strain

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