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New Research

Fouls Bio-Foulingery recently, it was announced that Mr J Antony Prince, a Research & Development

scientist in Membrane Science and Engineering from Environmental and Water Technology Center of Innovation (EWTCOI) at Ngee Ann Polytechnic who is also doing PhD in Newcastle University, UK, led a team to develop a breakthrough in bio-fouling. As Mr Prince described, bio-fouling is the biggest drawback and the most difficult type of fouling to clean or regenerate the membrane when using membrane technology for water treatment. Water & Wastewater Asia was privileged to be able to speak to Mr Prince at Ngee Ann Polytechnic in Singapore to better understand this research breakthrough, as well as its future.

One of the most pervasive problems afflicting mankind throughout the world is poor access to clean freshwater and sanitation. United Nations’ FAO states that by 2025, around 1.8 billion people will be living in countries or regions with absolute water scarcity, and UNICEF has estimated that 2,000 children under the age of five die every day from diarrhoeal diseases. Of these, some 1,800 deaths are linked to water, sanitation and hygiene.

With the growing demand for high quality water, many new technologies of water purification are being developed to cater for potable and non-potable use. The reliability and ease of operation of membrane-based filtration systems have led to

their proliferation in wastewater treatment. Ultrafiltration (UF) is one such well-developed low pressure membrane separation process used in different applications, such as water & wastewater treatment, reverse osmosis pretreatment and separations in the food, dairy, paper, textile, pharmaceuticals, chemical and biochemical industr ies . However, membrane fouling remains an inevitable problem in all pressure-driven membrane processes causing deterioration of the membrane performance and membrane breakage, which lead to high operational costs and short replacement intervals and increase the chemical usage. In fact, while there are several cleaning methods – such as physical (backwash) and chemical (chemical cleaning) methods – available to regenerate the membrane, they require high energy consumption and more chemical usage.

This issue is what motivated Mr Prince to embark on his research journey for a solution to combat bio-fouling. He believes that while membrane technology has been well established in the last half century, present methods to combat bio-fouling not only require high energy consumption and chemical usage, t h e y a r e a l s o ineffective:

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“Current state of the art methods to overcome bio-fouling are to modify the membranes with either hydrophilic additives or with an antibacterial compound (most commonly silver). It has been proven that silver can kill the bacteria by rupturing the plasma membrane. However, once the plasma membrane ruptures, the negatively charged protoplasm compounds deposits onto the positive surface of the membrane by electrostatic attraction which will inactivate the silver ion/particle eventually.”

Mr Prince strongly believes that prevention is always better than cure, and with this in mind, he led his team to develop an ultrafiltration membrane with a self-cleaning surface which can prevent the fouling on the surface.

“If this is commercialised,” commented Mr Prince, “the novel concept can help to reduce chemical

usage and operating costs significantly.”

How It Came to BeEvery research comes with a form of support, and for Mr Prince, this was a collaboration between Ngee Ann Polytechnic, Environmental and Water Technology Centre of Innovation (EWTCOI)) and Newcastle University International Singapore (NUIS), and funded by the Singapore Ministry of Education (MOE) under the Translational & Innovation Fund in 2013. The research was the result of positive preliminary studies while Mr Prince received the NU-Poly-SIT scholarship from Newcastle University for his PhD in 2012, and this partnership allowed Mr Prince to access NUIS’ expertise on new material development, as well as a local water treatment company to apply this technology.

Figure 1: schematic representation of the self-cleaning property of the membrane.

source: prince, J.A. et al. self-cleaning Metal Organic Framework (MOF) based ultrafiltration membranes - A solution to bio-fouling in membrane separation processes. sci. Rep. 4, 6555; Doi:10.1038/srep06555 (2014)

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The StudyIn this study, Mr Prince and his team proposed and practised a novel concept to prevent bio-fouling by developing a killing and self-cleaning membrane surface having additional enhanced hydrophilicity with highly negatively charged – NH2, - C00H and – OH functional groups in addition to covalently attached silver nanoparticles on the membrane surface Mr Prince explained his thesis as follows:

“These functional groups have been shown to be effective in combating the deposition of the negatively charged colloidal particles, proteins, lipids, amino acids and et cetera via an electrostatic repulsion and hydrophobic-hydrophilic repulsion mechanisms.

“The anti-bio-fouling mechanism of the novel membrane is illustrated in Figure 1. From the figure, it can be easily understood that, when the bacteria approaches the membrane surface, the antimicrobial silver will kill them by rupturing their negatively charged plasma wall (which leads to the leakage of negatively charged protein molecules through the ruptured bacterial cell wall), whereas the highly hydrophilic, negatively charged acid, hydroxyl and amine functionalities will prevent the deposition of these protein molecules onto the membrane surface by electrostatic repulsion. Thereby, the membrane can exhibit the self-cleaning property. In addition to it, since the AgNPs are embedded (covalently attached) in PEI matrix, the leaching of AgNPs is completely prevented.”

The ProblemAccording to Mr Prince, the team has been working in the field of water treatment for the last five years, and encountered various types of fouling issues in low pressure (UF & MF) membranes. Thus, they wanted to focus on the development of a robust membrane material that could combat this fouling issue by increasing the membrane hydrophilicity. Mr Prince explained this further:

“The current state-of-art technology in membrane modifications blends silver nanoparticles and hydrophilic water soluble pore forming agents with polymeric dope solution. Elution of these additives is unavoidable due to the harsh operating condition. In this project, we have carefully chosen the functional groups and the silver nanoparticle which are chemically (covalently) attached to them in order to overcome the elution of hydrophilic additives and the leaching of nanoparticles.

“In the initial stages, we tried different methods of increasing the hydrophilicity by blending hydrophilic copolymers which eventually leached out during harsh operations, and blending of sparingly soluble hydrophilic

additives resulted in the swelling of membranes. When we tried to blend silver and other metal oxide nano particle as a way to alleviate this fouling, it resulted in leaching of these nano materials in the treated water. Hence, we designed this unique polymer with covalently attached hydrophilic functional groups and silver nano particles to overcome this swelling and leaching issues and to impart a permanent anti-fouling property.

“With this invention, we plan to develop unique membrane materials with highly hydrophilic functionality and antibacterial properties to reduce membrane fouling in future.”

Future DirectionsMr Prince told WWA that, in addition to developing a unique membrane material with Newscastle University, the team intends to work closely with a local industrial partner to test the technology in a realistic environment. The team will also co-develop a pilot plant with the company for further commercialisation purposes. When prompted further about their plans, he added that the technology is still in a premature stage for commercialisation, and that at this point in time, the company is not too much involved in the research.

Other Research AreasWhile this research comes in very handy for businesses that are demanding better water services, Mr Prince has identified material development in membrane technology where improvements could be made:

“Existing technologies have their own drawbacks, and there is always room for improvements.

“For instance, in our recent research called GLASSwater, we have developed a low cost ceramic membrane by using used glass, which can reduce costs by two to three times compared to commercial ceramic membranes [1]. This research was conducted in line with expectations that new generation membrane materials will improve the performance of the membranes due to the recent popularity of ceramic membrane applications. However, its high costs limit its usage in wastewater treatment and hence, our development of low-cost ceramic membranes could help water industry for specific application like industrial waste water pre-treatment.”

In addition to membrane technology, Mr Prince highlighted that desalination systems are a viable research area as well:

“Water is needed by every living object on the earth. Fresh water shortage around the world is increasing at a rapid rate due to the human population growth and the scarcity of fresh water resources. The earth is covered by

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Antony with his phD supervisor

almost 71% water by volume, 97% of which is seawater and is inconsumable. The remaining 3% of the earth water sources is considered fresh water. However, 98.8% of the 3% is found in polar caps and underground. Only about 0.03% of the world’s total water can be accessed by humans, making fresh water a scarce resource. Since such a high percentage of earth is filled with seawater, converting seawater into potable water will solve many of the water shortage problems. To be able to drink the seawater, desalination is required.

“The current popular method of desalination is reverse osmosis. Reverse osmosis is also based on membrane technology and works by pressure difference across the membrane. However, reverse osmosis involves high energy and operating pressures, causing it to have high operating costs. Other desalination processes include multi-stage flash (MSF), multiple effect evaporation (MEE), and thermal or mechanical vapour compression (VC). However, on a large scale

basis, those thermal processes are too costly and energy inefficient due to high energy consumption rates. Hence, despite all the available desalination processes, an alternative desalination offering lower energy consumption is desired. Forward osmosis (FO) and membrane distillation (MD) are two emerging low-cost desalination technologies. These technologies are in the developmental stage and many research groups are focusing on these technologies.

Recently, we have developed a low cost desalination system based on membrane distillation called Distil™. The Distil™ system can reduce the desalination energy by 40-50% compared to the conventional desalination technologies [2] [3].”

Mr Prince also believes that, in order to accelerate the uptake of new technologies in the municipal and industrial sectors, it is important to close the gap between fundamental research and commercialisation. WWA

About the study

the study was led by J Antony prince who received the NU-poly-sit scholarship from Newcastle University for his phD in 2012 under the guidance of Dr Kamelia Boodhoo (senior lecturer Newcastle University), Dr s Bhuvana (R&D scientist) and

Dr gurdev singh (Deputy Director) from eWtCoi with the support of two other researchers Ms V Anbharasi and Mr N Ayyanar from eWtCoi.

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Newcastle University international singapore (NUis) is an established provider of top quality research in singapore. Building on its excellent research reputation in the UK, we are engaging industry partners and high quality research degree candidates in singapore and south east Asia. NUis’ areas of expertise are broad and cover Food & human Nutrition, Chemical engineering and Advanced Materials, Marine engineering, Naval Architecture, offshore engineering, Mechanical and system Design, electrical and power engineering, Civil engineering and Computing.

As a research-intensive institution, fostering links with industry and local tertiary institutions are important to NUis. through research partnerships, we aim to develop long- and short-term research collaborations which are of mutual interest, establish strategic collaboration focus and submit joint research proposals for research funding. our industry partners include Danone, sembCorp, singapore technologies electronics ltd, large scale systems group (lsg), international paint limited, and soil Machine Dynamics (sMD).

NUis has a well-funded and growing research program

with over sgD7 million of projects currently being worked on. Research funding comes from a mix of local and international companies, government and independent agencies and through collaborations with local tertiary institutes.

NUis’ aim is to develop partnerships with international academic establishments to provide teaching and research opportunities. Newcastle University strives for world-class academic excellence. NUis’ business is to invest in people, build capacities, export knowledge, develop skills, unleash intellect, create future leaders and materialise dreams.

Newcastle University in the UK has been a destination of choice for singaporean students for decades. Newcastle’s close relationship with many singaporean industries together with the excellent performance of graduates has meant that our academic alliance with the singapore institute of technology is an outstanding success. Newcastle’s excellent reputation in many subject areas will equip singapore with cutting edge science and technology, pioneering knowledge and techniques to address global challenges for generations to come.

About Newcastle University international singapore

References1. http://www.eco-business.com/news/researchers-use-recycled-glass-to-filter-raw-water/2. http://www.dutchcham.sg/novel-membrane-distillation-technology-for-desalination-unveiled3. http://www.innovfest.sg/2013/pitch/Ntp-e04-Np.pdf

team photo