The longest day at work is the one before you go on vacation. I'm now at my mother-in-laws in Potter Bar Hertfordshire and soup of the day is my last job of the day. I had have quite some time to reflect on water since we last met. The thing that has stayed with me most since Belfast is "water work is womens work" and we have just talked about her water supply as a child. Christine Conry (my mother-in-law) grew up on a farm in rural Ireland before WW2. The source of potable water a well in the town and it was more than a kilometre from the house. Before school, she and here sibling would pump and carry water, in enamalled buckets. Another source of water for the house was rain-butts - used for bathing and washing clothes. Tomorrow I'll regale you with all her tales of water sources as we'll be flying to Florida together. I didn't realise quite how close I was to the WHO definition of patable water supply.
Last night I introduced the 6th Annual Roberts Lecture at the University of Sheffield. The guest speaker, Maureen McTeer, is both a graduate and an honorary graduate of The University of Sheffield. She is an academic lawyer, author and speaker who has made a important contributions to the public understanding of complex legal and ethical questions about science and technology in the 21st century. Her work in this field, and her advocacy for the legal and health rights of women, has been a source of inspiration to countless people throughout the world. She was born in Ottawa and attended its university, graduating with a bachelor’s degree in History and Communications, and later in Common Law. In 1993 she received a Master of Laws degree in Health Law from Dalhousie University, Halifax. She has been a member of the Ontario Bar since 1980. Having searched world-wide for a top-ranking Law School that would offer her advanced studies about relationships between law, health, science and ethics, she identified Sheffield as a leading centre and graduated here in 2004 with a Master’s degree in Biotechnology, Law and Ethics. The title of her Sheffield degree describes aptly the subjects for which Maureen McTeer has an international reputation and in July this year our University honoured her with the degree of Doctor of Laws honoris causa. In great demand as a speaker on aspects of law, science and technology, she is known for her ability to convey, in a clear and concise way, how these phenomena affect our everyday lives. She is a world-renowned expert on intellectual property in relation to biotechnology and health and holds robust views on the ethical implications of ownership. In May of this year Maureen McTeer received the DIVA award for her long-standing commitment to women’s health in Canada. This, and the many other awards she has gained, bring to the fore her work as a social activist for women’s rights, particularly their rights to health care and to full participation in democratic politics, not least in the developing world. Her autobiography, In My Own Name, was a bestseller, inspiring and encouraging thousands of Canada’s women to seek equality and to pursue their personal goals. Even her private life is distinguished – her husband, Joe Clark who was there with us last night, is a former Prime Minister of Canada. In all her public speaking, in her writing and research, in her advocacy, personal issues become public problems. The personal and the political spheres are linked, just as a public academic should link them. And she gave a great lecture on the topic ‘Designs on Life: Being Human in the 21st Century’.
We had a fascinating and wide ranging conversation over dinner and it struck me that she would be a great addition to our Universities United team,. We did discuss the feminist issues surrounding water and the education of girls in the 3rd world, perhaps I should have asked her to join us? But given the need for me to concentrate on implementing some of our UK focussed projects I decided not to ask!
Thursday, 23 October 2008
Monday, 6 October 2008
Solving water problems through nanotechnology
Since we're talking about water on Wednesday, here's a summary (recycled from my own blog Soft Machines) of a recent review article in Nature about potential technological solutions to world water problems. The big question for me is to what extent the lack of access to clean water is a political problem rather than a technological problem. We'll be hearing from David Grimshaw, from the charity Practical Action, which has been looking into nanotechnology's potential for water; this recent entry on Practical Action's own blog seems to show some guarded optimism - Some nano progress towards targets on clean water.
The lack of availability of clean water to many of the world's population currently leads to suffering and premature death for millions of people, and as population pressures increase, climate change starts to bite, and food supplies become tighter (perhaps exacerbated by an ill-considered move to biofuels) these problems will only intensify. It's possible that nanotechnology may be able to contribute to solving these problems (see this earlier post, for example). A couple of weeks ago, Nature magazine ran a special issue on water, which included a very helpful review article: Science and technology for water purification in the coming decades. This article (which seems to be available without subscription) is all the more helpful for not focusing specifically on nanotechnology, instead making it clear where nanotechnology could fit into other existing technologies to create affordable and workable solutions.
One sometimes hears the criticism that there's no point worrying about the promise of new nanotechnological solutions, when workable solutions are already known but aren't being implemented, for political or economic reasons. That's an argument that's not without force, but the authors do begin to address it, by outlining what's wrong with existing technical solutions. "These treatment methods are often chemically, energetically and operationally intensive, focused on large systems, and thus require considerable infusion of capital, engineering expertise and infrastructure" Thus we should be looking for decentralised solutions, that can be easily, reliably and cheaply installed using local expertise and preferably without the need for large scale industrial infrastructure.
To start with the problem of the sterilisation of water to kill pathogens, traditional methods start with chlorine. This isn't ideal, as some pathogens are remarkably tolerant of it, and it can lead to toxic by-products. Ultra-violet sterilisation, on the other hand, offers a lot of promise - it's good for bacteria, though less effective for viruses. But in combination with photocatalytic surfaces of titanium dioxide nanoparticles it could be very effective. Here what is required is either much cheaper sources of ultraviolet light, (which could come from new nanostructured semiconductor light emitting diodes) or new types of nanoparticles with surfaces excited by lower wavelength light, including sunlight.
Another problem is the removal of contamination by toxic chemicals, which can arise either naturally or through pollution. Problem contaminants include heavy metals, arsenic, pesticide residues, and endocrine disrupters; the difficulty is that these can have dangerous effects even at rather low concentrations, which can't be detected without expensive laboratory-based analysis equipment. Here methods for robust, low cost chemical sensing would be very useful - perhaps a combination of molecular recognition elements integrated in nanofluidic devices could do the job.
The reuse of waste water offers hard problems because of the high content organic matter that needs to be removed, in addition to the removal of other contaminants. Membrane bioreactors combine the use of the sorts of microbes that are exploited in activated sludge processes of conventional sewage treatment with ultrafiltration through a membrane to get faster throughputs of waste water. The tighter the pores in this sort of membrane, the more effective it is at removing suspended material, but the problem is that this sort of membrane quickly gets blocked up. One solution is to line the micro- and nano- pores of the membranes with a single layer of hairy molecules - one of the paper's co-authors, MIT's Anne Mayes, developed a particularly elegant scheme for doing this exploiting self-assembly of comb-shaped copolymers.
Of course, most of the water in the world is salty (97.5%, to be precise), so the ultimate solution to water shortages is desalination. Desalination costs energy - necessarily so, as the second law of thermodynamics puts a lower limit on the cost of separating pure water from the higher entropy solution state. This theoretical limit is 0.7 kWh per cubic meter, and to date the most efficient practical process uses a not at all unreasonable 4 kWh per cubic meter. Achieving these figures, and pushing them down further, is a matter of membrane engineering, achieving precisely nanostructured pores that resist fouling and yet are mechanically and chemically robust.
The lack of availability of clean water to many of the world's population currently leads to suffering and premature death for millions of people, and as population pressures increase, climate change starts to bite, and food supplies become tighter (perhaps exacerbated by an ill-considered move to biofuels) these problems will only intensify. It's possible that nanotechnology may be able to contribute to solving these problems (see this earlier post, for example). A couple of weeks ago, Nature magazine ran a special issue on water, which included a very helpful review article: Science and technology for water purification in the coming decades. This article (which seems to be available without subscription) is all the more helpful for not focusing specifically on nanotechnology, instead making it clear where nanotechnology could fit into other existing technologies to create affordable and workable solutions.
One sometimes hears the criticism that there's no point worrying about the promise of new nanotechnological solutions, when workable solutions are already known but aren't being implemented, for political or economic reasons. That's an argument that's not without force, but the authors do begin to address it, by outlining what's wrong with existing technical solutions. "These treatment methods are often chemically, energetically and operationally intensive, focused on large systems, and thus require considerable infusion of capital, engineering expertise and infrastructure" Thus we should be looking for decentralised solutions, that can be easily, reliably and cheaply installed using local expertise and preferably without the need for large scale industrial infrastructure.
To start with the problem of the sterilisation of water to kill pathogens, traditional methods start with chlorine. This isn't ideal, as some pathogens are remarkably tolerant of it, and it can lead to toxic by-products. Ultra-violet sterilisation, on the other hand, offers a lot of promise - it's good for bacteria, though less effective for viruses. But in combination with photocatalytic surfaces of titanium dioxide nanoparticles it could be very effective. Here what is required is either much cheaper sources of ultraviolet light, (which could come from new nanostructured semiconductor light emitting diodes) or new types of nanoparticles with surfaces excited by lower wavelength light, including sunlight.
Another problem is the removal of contamination by toxic chemicals, which can arise either naturally or through pollution. Problem contaminants include heavy metals, arsenic, pesticide residues, and endocrine disrupters; the difficulty is that these can have dangerous effects even at rather low concentrations, which can't be detected without expensive laboratory-based analysis equipment. Here methods for robust, low cost chemical sensing would be very useful - perhaps a combination of molecular recognition elements integrated in nanofluidic devices could do the job.
The reuse of waste water offers hard problems because of the high content organic matter that needs to be removed, in addition to the removal of other contaminants. Membrane bioreactors combine the use of the sorts of microbes that are exploited in activated sludge processes of conventional sewage treatment with ultrafiltration through a membrane to get faster throughputs of waste water. The tighter the pores in this sort of membrane, the more effective it is at removing suspended material, but the problem is that this sort of membrane quickly gets blocked up. One solution is to line the micro- and nano- pores of the membranes with a single layer of hairy molecules - one of the paper's co-authors, MIT's Anne Mayes, developed a particularly elegant scheme for doing this exploiting self-assembly of comb-shaped copolymers.
Of course, most of the water in the world is salty (97.5%, to be precise), so the ultimate solution to water shortages is desalination. Desalination costs energy - necessarily so, as the second law of thermodynamics puts a lower limit on the cost of separating pure water from the higher entropy solution state. This theoretical limit is 0.7 kWh per cubic meter, and to date the most efficient practical process uses a not at all unreasonable 4 kWh per cubic meter. Achieving these figures, and pushing them down further, is a matter of membrane engineering, achieving precisely nanostructured pores that resist fouling and yet are mechanically and chemically robust.
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