Controlling Biofouling in Seawater Reverse Osmosis Membrane Systems: 1st Edition (Paperback) book cover

Controlling Biofouling in Seawater Reverse Osmosis Membrane Systems

1st Edition

By Nirajan Dhakal

CRC Press

208 pages

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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 of marine 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 non-backwashable 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 non-backwashable 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.

Table of Contents

1 General introduction

2 Perspectives and challenges for desalination

3 Measuring bacterial regrowth potential (BRP) in seawater reverses osmosis using a natural bacterial consortium and flow cytometry

4 Fouling of ultrafiltration membranes by organic matter generated by four marine algal species

5 The role of tight UF on reducing fouling potential of SWRO feed water during algal blooms

6 Phosphate removal in seawater reverse osmosis feed water: An option to control biofouling during algal blooms

7 Conclusions and outlook

About the Author

Nirajan Dhakal is a Lecturer in Water Supply Engineering at IHE-Delft Institute for Water Education in the Netherlands. He completed his MSc degree in Water Supply Engineering at UNESCO-IHE in 2011 and he will be awarded with a PhD degree at the Technical University of Delft on November 2017. He has a second MSc degree in Regional Development Planning and Management from the University of Dortmund, Germany, and University of the Philippines in 2009. He has more than 6 years of consultancy and research experience in water supply engineering. For the last 5 years, Nirajan has been involved in various research projects related to algal blooms and membrane based seawater desalination in collaboration with the Wetsus European Centre of Excellence for Sustainable Water Technology. He is broadly interested in desalination with particular emphasis on algal blooms and membrane fouling and scaling mechanisms, mitigation, and control, pre-treatment technologies and modelling.

About the Series

IHE Delft PhD Thesis Series

IHE Delft PhD programme leads to a deepening of a field of specialisation. PhD fellows do scientific research, often with conclusions that directly influence their region. At IHE Delft, PhD researchers from around the world participate in problem-focused and solution-oriented research on development issues, resulting in an inspiring research environment. PhD fellows work together with other researchers from many countries dealing with topics related to water and the environment.

PhD research is often carried out in the ‘sandwich’ model. Preparation and final reporting – the first and last portion of the programme – are carried out in Delft, while actual research is done in the fellow’s home country, under co-supervision of a local institute. Regular contacts with the promotor are maintained through visits and long-distance communication. This enables researchers to employ solutions directly to problems in their geographical region.

IHE Delft PhD degrees are awarded jointly with a university. The degrees are highly valued and fully recognised in all parts of the world.

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Subject Categories

BISAC Subject Codes/Headings:
SCIENCE / Environmental Science
TECHNOLOGY & ENGINEERING / Environmental / Water Supply