Controlling Biofouling In Seawater Reverse Osmosis Membrane Systems

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.

The study of membrane biofouling has increased strongly in the past four years, compared to the previous twenty two years, indicated by the more than doubling of the number of scientific papers. However, no single source gives an updated overview of biofouling. Biofouling of Spiral Wound Membrane Systems gives a complete and comprehensive overview of all aspects of biofouling, bridging the gap between microbiology, hydraulics and membrane technology. High quality drinking water can be produced with membrane filtration processes like reverse osmosis (RO) and nanofiltration (NF). As the global demand for fresh clean water is increasing, these membrane technologies are increasingly important. One of the most serious problems in RO/NF applications is biofouling – excessive growth of biomass – affecting the performance of the RO/NF systems. This can be due to the increase in pressure drop across membrane elements (feed-concentrate channel), the decrease in membrane permeability or the increase in salt passage. These phenomena result in the need to increase the feed pressure to maintain constant production and to clean the membrane elements chemically. Biofouling of Spiral Wound Membrane Systems relates biomass accumulation in spiral wound RO and NF membrane elements with membrane performance and hydrodynamics and determines parameters influencing biofouling. It focuses on the development of biomass in the feed-concentrate (feed-spacer) channel and its effect on pressure drop and flow distribution. It can be used to develop an integral strategy to control biofouling in spiral wound membrane systems. Most past and present methods to control biofouling have not been very successful. An overview of several potential complementary approaches to solve biofouling is given and an integrated approach for biofouling control is proposed.

Because of the uneven distribution of fresh water in time and space and the increasing human population, a large number of regions are experiencing water scarcity and stress. Membrane-based desalination technologies like reverse osmosis have the potential to solve the fresh water crisis in coastal areas. However, in many cases membrane performance is restricted by biofouling. Biofouling of Membrane Systems gives a comprehensive overview on the state of the art strategies to control biofouling in spiral wound reverse osmosis membrane systems and point to possible future research directions. Despite the fact that much research and development has been done to overcome biofouling in spiral wound membrane systems used for water treatment, biofouling is still a major practical problem causing performance decline and increased energy demand. Biofouling of Membrane Systems is divided into three sections including modelling and numerical analysis, non-destructive characterization and feed spacer geometry optimization. It focuses on the development of biomass in the feed channel of the membrane module and its effect on pressure drop and hydrodynamics. This book can be used to develop an integral strategy to control biofouling in spiral wound membrane systems. An overview of several potential complementary approaches to solve biofouling is given and an integrated approach for biofouling control and feed spacer design is proposed.

Seawater desalination is increasingly being used as a means to augment freshwater supplies in regions with high water stress, and reverse osmosis is increasingly the technology of choice because of the low energy consumption. However, seawater reverse osmosis (SWRO) systems suffer from various types of fouling, which can increase energy consumption and the use of chemicals during SWRO operation. In practice, pre-treatment systems are put in place to reduce the particulate and biological fouling potential of SWRO feed water. However, simple, reliable and accurate methods to assess the extent to which biological fouling potential is reduced during pre-treatment are not available for seawater. This research developed a new method to measure bacterial growth potential (BGP) using the native bacterial consortium in seawater. New reagents to extract and detect ATP in microbial cells were specifically developed for seawater. The new lysis and detection reagents overcame the salt interference in seawater and allow low detection of total ATP, free ATP and microbial ATP in seawater. Incorporating a filtration step further increased the sensitivity of the method six fold, enabling ATP detection of ultra-low levels of microbial ATP in seawater. The newly developed ATP-based BGP method was applied to monitor and assess the pre-treatment of five full-scale seawater desalination plants around the world. A good correlation was observed between BGP measured in SWRO feed water and the pressure drop increase in the SWRO systems, suggesting the applicability of using the ATP-based BGP method as a biofouling indicator in SWRO. Furthermore, a safe level of BGP ( In the future, on-line monitoring of BGP in SWRO feed water may further reduce the consumption of chemicals and energy and improve the overall sustainability of seawater desalination by reverse osmosis.

Osmotically Driven Membrane Processes provides an overview of membrane systems and separation processes, recent trends in membranes and membrane processes, and advancements in osmotically driven membrane systems. It focuses on recent advances in monitoring and controlling wastewater using membrane technologies. It explains and clarifies important research studies as well as discusses advancements in the field of organic-inorganic pollution.

Removal of Pollutants from Saline Water: Treatment Technologies provides a comprehensive understanding of technologies that are currently adopted in the treatment of pollutants present in saline water systems. It provides information on the treatment technologies for saline water systems, including seawater, brackish water, oil-produced water, and other industrial saline wastewaters. FEATURES Presents information exclusively for saline water pollutant removal Introduces current treatment technologies and addresses why and how the techniques differ between fresh and salt water Offers an inclusive overview of physicochemical, biological, membrane, and advanced oxidation treatment technologies Features various perspectives and case studies from relevant global experts Provides a comprehensive one-stop source for the treatment of pollutants in all saline water systems Aimed at students, academicians, researchers, and practicing engineers in the fields of chemical, civil, marine, and environmental engineering who wish to be acquainted with the most recent developments in the treatment of pollutants present in saline water systems. Prof. Dr. Shaik Feroz works at Prince Mohammad Bin Fahd University, Kingdom of Saudi Arabia. He has 30 years of experience in teaching, research, and industry. He has more than 190 publications to his credit in journals and conferences of international repute. He was awarded "Best Researcher" by Caledonian College of Engineering for the year 2014. Prof. Dr. Detlef W. Bahnemann is Head of the Research Unit, Photocatalysis and Nanotechnology at Leibniz University Hannover (Germany), Director of the Research Institute "Nanocomposite Materials for Photonic Applications" at Saint Petersburg State University (Russian Federation), and Distinguished Professor at Shaanxi University of Science and Technology in Xi’an (People's Republic of China). His research topics include photocatalysis, photoelectrochemistry, solar chemistry, and photochemistry focused on synthesis and physical-chemical properties of semiconductor and metal nanoparticles. His 500-plus publications have been cited more than 65,000 times (h-index: 100).

Desalination as a method to provide clean drinking water has become vital – particularly in a context where drought, water scarcity and rapid quality decrease of water bodies have become an undeniable reality. After more than half a century of membrane-based desalination, fouling and scaling is still a dominant challenge. In membrane technologies, in particular, fouling and scaling are a major issue with respect to design, operation, reliability of the technologies and cost. This textbook covers theory and practice and is intended for designers, operators, consultants, suppliers and students. Principles of ultra- and nanofiltration and reverse osmosis (RO) are discussed, enabling the reader to understand the link between design, operation and fouling and scaling. Fouling (particulate, organic -including algal bloom events, inorganic, and biofouling) and scaling are treated in detail, including parameters to determine fouling and scaling potential of feed waters. Principles of conventional and advanced pre-treatment processes are highlighted and their effect on preventing fouling and scaling. In addition, the process design of RO systems and the recent advances in seawater RO and emerging membrane-based processes for seawater desalination are presented.

Reverse Osmosis Systems: Design, Optimization and Troubleshooting Guide describes in depth knowledge of designing and operating reverse osmosis (RO) systems for water desalination, and covers issues which will effect the probability for the long-standing success of the application. It also provides guidelines that will increase the performance of seawater RO desalination systems by avoiding errors in the design and operation and suggest corrective measures and troubleshooting of the problems encountered during RO operation. This book also provides guidelines for the best RO design and operational performance. In the introductory section, the book covers the history of RO along with the fundamentals, principles, transport models, and equations. Following sections cover the practical areas such as pretreatment processes, design parameters, design software programs (WAVE, IMSDesign, TORAYDS2, Lewaplus, ROAM Ver. 2.0, Winflows etc.), RO performance monitoring, normalization software programs (RODataXL and TorayTrak), troubleshooting as well as system engineering. Simplified methods to use the design software programs are also properly illustrated and the screenshots of the results, methods etc. are also given here along with a video tutorial.The final section of the book includes the frequently asked questions along with their answers. Moreover, various case studies carried out and recent developments related to RO system performance, membrane fouling, scaling, and degradation studies have been analyzed. The book also has several work out examples, which are detailed in a careful as well as simple manner that help the reader to understand and follow it properly. The information presented in some of the case studies are obtained from existing commercial RO desalination plants. These topics enable the book to become a perfect tool for engineers and plant operators/technicians, who are responsible for RO system design, operation, maintenance, and troubleshooting. With the right system design, proper operation, and maintenance program, the RO system can offer high purity water for several years. Provides guidelines for the optimum design and operational performance of reverse osmosis desalination plants Presents step-by-step procedure to design reverse osmosis system with the latest design software programs along with a video tutorial Analyzes some of the issues faced during the design and operation of the reverse osmosis desalination systems, suggest corrective measures and its troubleshooting Discusses reverse osmosis desalination pretreatment processes, design parameters, system performance monitoring, and normalization software programs Examines recent developments related to system performance, membrane fouling, and scaling studies Presents case studies related to commercial reverse osmosis desalination plants Perfect training guide for engineers and plant operators, who are responsible for reverse osmosis system design, operation and maintainance