Print Email Facebook Twitter Controlling Biofouling in Seawater Reverse Osmosis Membrane Systems Title Controlling Biofouling in Seawater Reverse Osmosis Membrane Systems Author Dhakal, N. (TU Delft Sanitary Engineering) Contributor Kennedy, M.D. (promotor) Salinas Rodriguez, S.G. (copromotor) Degree granting institution Delft University of Technology Date 2017-12-30 Abstract Seawater desalination is a rapidly growing coastal industry that is increasingly threatened by algal blooms. Depending on the severity of algal blooms, desalination systems may be forced to shut down because of clogging and/or poor feed water quality. To maintain stable operation and provide good feed water quality to seawater reverse osmosis (SWRO) systems, ultrafiltration (UF) pre-treatment is proposed. This research focused on assessing the ability of UF and other pre-treatment technologies to reduce biofouling in SWRO systems. An improved method to measure bacterial regrowth potential (BRP) was developed and applied at laboratory, pilot and full scale to assess the ability of conventional UF (150 kDa) and tight UF (10 kDa) alone and in combination with a phosphate adsorbent to reduce regrowth potential and delay the onset of biofouling in SWRO. The improved bacterial regrowth potential method employs a natural consortium ofmarine bacteria as inoculum and flow cytometry. The limit of detection of the BRP method was lowered to 43,000 ± 12,000 cells/mL,which is equivalent to 9.3 ± 2.6 μg-Cglucose/L. The reduction in bacterial regrowth potential after tight UF (10 kDa) was 3 to 4 times higher than with conventional UF (150 kDa). It was further reduced after the application of a phosphate adsorbent, independent of pore size of the UF membrane. Pilot studies demonstrated that the application of tight UF (10 kDa) coupled with a phosphate adsorbent consistently lowered the bacterial regrowth potential and no feed channel pressure drop increase was observed in membrane fouling simulators (MFS) over a period of 21 days. The study also showed that nonbackwashable fouling of UF membranes varied strongly with the type of algal species and the algal organic matter (AOM) they release. The presence of polysaccharide (stretching - OH) and sugar ester groups (stretching S=O) was the main cause of nonbackwashable fouling. In conclusion, this study showed that an improved BRP method is suitable for the assessment of SWRO pre-treatment systems and it can be a useful tool to develop potential strategies to mitigate biofouling and improve the sustainability of SWRO systems. Subject BiofoulingReverse Osmosis To reference this document use: http://resolver.tudelft.nl/uuid:2ca51c8c-bd91-47a2-adc4-52ee59d3add5 Publisher CRC Press / Balkema - Taylor & Francis Group ISBN 978‐0‐8153‐5718‐6 Bibliographical note Dissertation submitted in fulfillment of the requirements of the Board for Doctorates of Delft University of Technology and of the Academic Board of the UNESCO-IHE Institute for Water Education. Part of collection Institutional Repository Document type doctoral thesis Rights © 2017 N. Dhakal Files PDF 2017_unesco_ihe_phd_thesi ... akal_i.pdf 15.38 MB Close viewer /islandora/object/uuid:2ca51c8c-bd91-47a2-adc4-52ee59d3add5/datastream/OBJ/view