Role of dissolved air flotation (DAF) and liquid ferrate on mitigation of algal organic matter (AOM) during algal bloom events in RO desalination

Abstract
Harmful Algal Blooms (HABs) are considered a major contributor to membrane biofouling in Seawater Reverse Osmosis (SWRO) desalination plants. The presence of HABs in the raw feed water leads to an increase in membrane fouling rate, increase of chemical consumption, and can cause temporary shutdown of plants. Effective pretreatment can reduce the amount of organic foulants reaching the RO membrane and alleviate the problem of flux decline during RO operation and frequent membrane cleaning using chemicals. This study compared the effect of in-situ generated liquid ferrate and ferric chloride in combination with dissolved air flotation (DAF) as a pretreatment strategy to remove algal cells and algal organic matter (AOM) during algal bloom events. Experiments were performed using a bench-scale DAF unit. HABs conditions were simulated by harvesting AOM from cultivating Chaetoceros affinis (CA) in raw seawater to a concentration of around 10 mg C/L of dissolved organic carbon (DOC). The liquid ferrate was generated in-situ by wet oxidation of ferric chloride in analkaline media. The best performance was achieved with the combined use of liquid ferrate and DAF, removing up to 100% of algal cells, 99.99% of adenosine tri-phosphate (ATP), and up to 92% of AOM.

Citation
Alshahri, A. H., Fortunato, L., Zaouri, N., Ghaffour, N., & Leiknes, T. (2021). Role of dissolved air flotation (DAF) and liquid ferrate on mitigation of algal organic matter (AOM) during algal bloom events in RO desalination. Separation and Purification Technology, 256, 117795. doi:10.1016/j.seppur.2020.117795

Acknowledgements
The research reported in this paper was supported by funding from King Abdullah University of Science and Technology (KAUST). The authors acknowledge help, assistance and support from the Water Desalination and Reuse Center (WDRC) staff.

Publisher
Elsevier BV

Journal
Separation and Purification Technology

DOI
10.1016/j.seppur.2020.117795

Additional Links
https://linkinghub.elsevier.com/retrieve/pii/S1383586620322693

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