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Dr Graham Rideal, former Chairman and currently Science Correspondent for the Filtration Society, discusses our dependence on clean water, some of the steps we need to take to ensure its availability and the impact of new filtration techniques.
Since man first started exploring for other forms of life in our galaxy, our primary quest has been the search for water, the fundamental building block of life. More than 70% of the earth’s surface is covered by water, but although water is seemingly abundant, the real issue is the amount of fresh water available to sustain life.
97.5% of all water on Earth is salt water, leaving only 2.5% as fresh water. Nearly 70% of that fresh water is frozen in the icecaps of the Arctic, Antarctic and glaciers while most of the remainder is present as soil moisture, or lies deep underground, not readily available for human consumption.
Less than 1% of the world’s fresh water (approximately 0.007% of all water on Earth) is accessible for direct human uses. This is the water found in lakes, rivers, reservoirs and those underground sources that are shallow enough to be tapped at an affordable cost. Only this amount is regularly renewed by rain and snowfall, and is therefore available on a sustainable basis. And mankind has a sad history of abusing its most precious resource.
Settlement and sanitation
More than 12,000 years ago our predecessors, the hunter-gatherers, followed the seasons and continually returned to fertile river valleys. As man settled, agriculture became dependent on irrigation, first developed more than 7,000 years ago. In more recent times one of the most significant and disastrous consequences of water shortages was the drought 1,100 years ago that caused the collapse of the Mayan civilisation.
By the mid 1800s the industrial revolution and consequential population concentrations in large cities resulted in water contamination on a catastrophic scale. For example, in London 1858 was known as the ‘year of the great stink’ due to sewage and waste in the Thames, while in Chicago around the same time, faecal contamination of surface water caused an epidemic of waterborne diseases such as typhoid and cholera.
The impact of industrial activity on the availability of fresh drinking water became particularly significant as we entered the 20th century, when an exponential increase in production was required to service an expanding world population.
It is estimated that the world’s population is growing at roughly 80 million each year, with freshwater requirement having tripled in the last half century. This has resulted in demand for freshwater increasing by a staggering 64 billion cubic metres a year (1 cubic metre = 1,000 litres).
Water usage
Looking at the overall worldwide use of water, agriculture accounts for the most at 70%, followed by industry at 20%, and finally, human consumption at 10%. However, the international per capita consumption is far from even, with the developed countries taking the lion’s share of the world’s capacity.
Furthermore, in industrialised regions, industry consumes more than half of the water available for human use. Belgium industry, for example, uses 80% of the available water.
This partly explains why there is more than a 100-fold difference in the average human daily consumption between, for example, Mozambique, using 4 litres, compared with the 575 litres a day of the USA.
Paradoxically, Western Australia has one of the lowest rainfalls in the world yet has the highest daily use per person, so the statistics are not based solely on rainfall, but on water management.
Ever since records began, access to water has been one of the major sources of conflict in the world. For example, in biblical times, Abraham was continually at war with his neighbours over the water rights of his wells. And there is no doubt that future conflicts will also centre around water.
River resources
Rivers provide one of the biggest sources of fresh water, sometimes passing through many different countries; notable are the Nile, which passes through nine different countries and the Amazon and Yangtse, all about 4,000 miles long.
What happens upstream has a profound effect on those living downstream. For example, the Colorado River once had a thriving delta like that of the Nile, providing fertile growing conditions. It is now a salt basin desert because its entire flow has been syphoned off upstream for agriculture, industry and leisure activities such as hotels and golf courses. To put this water extraction in context, the Hoover dam has a capacity of 2.5 million cubic metres.
However, in the case of the Colorado, the more even redistribution of the water has prevented the neighbouring states of Arizona and Nevada from being overtaken by deserts through global warming.
A further advantage of dam construction is the ability to produce environmentally clean power (more later) at the rate of more than 4 billion kilowatt hours per year.
Contamination challenges
The excessive removal of water from a river is not the only potential source of problems downstream. With increasing industrialisation and population growth, water contamination has become the issue of the decade, if not the century. gThe Clean Water Act of 1972 was the first step in trying to protect water sources; all well and good in the UK, for example, where it can be reasonably well enforced, but on a 4,000 mile long river, policing becomes a serious issue.
The source of water contamination need not necessarily originate locally. Airborne contamination is also a significant threat. As the world pursues its quest for industrialisation, the driving force or fuel for the expansion is energy, without which the development would stall.
Traditionally, coal fired power stations have generated electricity with little regard to the impact on the environment. Initially, the principal contaminant was thought to be sulphur dioxide produced from high sulphur content coal, which, when entering the atmosphere and combining with water, produced an acid rain that devastated agriculture thousands of miles away.
Enormous strides have been made in recent years in the desulphurisation process and it is now possible to remove up to 98% of sulphur dioxide from the flue gases. Coal fired power stations are usually built near a source of fresh water, used both in the steam generators and the cooling towers. One of the positive consequences of the Clean Water Act is that water used for any industrial process must conform to a certain standard before being returned to the river. This means that if the water is contaminated upstream, then the power station can act as a giant purifier to clean up the river.
However, in terms of cleaning up the environment, the real challenge is the removal of carbon dioxide. Carbon dioxide, compared to sulphur dioxide is a silent killer in that it is colourless and odourless, yet could have an even greater impact on our eco structures.
While the world has been focussing on the hole in the ozone layer and the effect on global warming, carbon dioxide has been insidiously acidifying the oceans, the consequences of which could be devastating to many species of sea life.
It is a thought provoking statistic that a single power station in the UK can produce carbon dioxide at a rate of 750 kg per second! Multiply that by the number of coal fired power stations in existence, and the two per week currently being built in China, and we see the magnitude of the problem facing our environment in the future.
It is hardly surprising, therefore, that the world is searching for the ‘golden ticket’, which would both stabilise water redistribution for agriculture while providing the power for industrial expansion, at no cost to the environment. Hydroelectric power is perceived as a prime solution especially where the terrain permits the construction of dams. Northern Canada is a prime example.
However, how clean is hydroelectric power? When we look at so-called ‘green’ power generation, we think of tidal generators, wind farms and perhaps the oldest of them all, hydroelectric generators.
When we dig a little deeper, however, some of these systems are not as ‘green’ as we might think. I recently had the opportunity of spending some time with bushcraft and survival expert Ray Mears in northern Canada as he was filming for the BBC. Having had a very interesting visit with The Filtration Society to Ratcliffe-on-Soar (UK) coal fired power stations and seen the tremendous developments in cleaning up stack emissions over the last 20 years, I was particularly interested in investigating the impact, if any, of hydroelectric power generation.
I was introduced to Pinock, a native Canadian and asked him to comment on any impact that hydroelectric power has had on his way of life. I was very surprised at what I discovered.
The thousands of lakes and dams in Saskatchewan are the engine house which generates power, not only for itself but for the USA, from which it receives a very substantial income. Sadly, many of the lakes in this picturesque province are so contaminated that their waters are not fit to drink.
The contamination is both self-inflicted and a consequence of environmental pollution. Historic mining for copper, diamond and uranium have all had their devastating consequences on the water courses, but a sinister development in recent years has been the mercury contamination environmentally imported from the rest of the world.
It is a well known phenomenon that pollutants released into the atmosphere can travel thousands of miles before they are precipitated to earth. For thousands of years, Pinock’s tribe has lived on the fruits of the land, in particular, elk and fish. In recent years, however, mercury contamination of the lakes has meant that the water is undrinkable, the fish inedible and only certain parts of the elk can be eaten. Polar bears, too, are suffering increasing miscarriages and deformities also attributed to pollution.
So although hydroelectric power generation is perceived to be one of the cleanest forms of power generation, the formation of reservoirs themselves can result in water pollution.
The mechanism is as follows: trees in the northern part of the globe not only absorb carbon dioxide, which is a good thing, but other pollutants as well, in particular, mercury. When a dam is created and a forest is flooded, the trees, which are uneconomic to harvest, act like giant tea bags ultimately releasing the mercury into the water.
As a consequence Pinock and his tribe are advised to drink bottled water, only eat two fish a month and stay away from the liver of an elk.
It is therefore hardly surprising that there is a major international effort being placed in the way we handle our toxic wastes. Prior to 1990, the concentration of mercury in the feed stream to incinerators was regulated at 4mg/kg, so trees that are between 20 and 100 years old would have been exposed to a considerably higher level of mercury. This is the legacy we are reaping today.
The current mercury content of feed streams to incinerators has been reduced to less than 2mg/kg and the stack emissions from industrial processing restricted to less than 0.5 mg per cubic metre, so we are moving in the right direction.
The main reason for such clean incinerator stacks is the development of hot gas filtration. Here special catalytic ceramic filters have been developed not only to strip out the particulates, but to lock in the toxins by chemical reaction.
The heavy metals can then be released safely (and profitably) in the regeneration of the spent filter cartridges.
Although most western countries adhere to the latest environmental legislation, this cannot always be guaranteed elsewhere. Furthermore, mercury is such a chemically inert element that its build up in the food chain is cumulative and, once there, it is almost impossible to remove.
It was reported recently that Alzheimer’s disease is increasing at an exponential rate. As rational scientists, we would be foolish to exclude a link to heavy metal atmospheric pollution. But then the Curies saw no danger in radiation.
Developing or degenerating countries
The world’s population is expanding at the rate of more than 80 million a year, which puts an ever increasing pressure of being able to supply adequate fresh water. It is estimated that half of the world’s 500 major rivers are either seriously depleted or polluted, resulting in more than one billion people without access to safe drinking water. As a result, more than three million people in developing countries, mostly children, die every year from diseases associated with a lack of access to safe drinking water, inadequate sanitation and poor hygiene.
Paradoxically, therefore, development comes at a cost if there are insufficient water supplies. It is interesting to note that, of the predicted most populous countries in 2050, the African continent accounts for a significant proportion.
However, in terms of global pollution, the developing countries even when combined, are minor contributors when compared to the might of China and India. Viewed from outer space
When the first satellite photographs were taken over India, the terrain took on a brown tinge resulting predominantly from the domestic coal and peat fires used for cooking.
Similarly in China, some coastal cities totally disappeared under a blanket of smog from coal fires, both domestic and industrial – 80% of China’s power comes from high sulphur content coal fired power stations.
In order to prevent the export of toxic gases as acid rain, carbon dioxide as the arch global warmer, and carcinogenic particulates to the rest of the world via the jet streams, addressing the pollution issues in India and China must be the number one priority. To be fair, both India and China are now meeting the pollution problem head on with new legislation to ban the burning of coal in the major cities, and are reducing the dependency on coal fired power stations in favour of ‘green’ alternatives, but it could take another 20 years before the impact is felt.
In the meantime, the cumulative effect of water pollution, whether nationally or internationally derived, and the acceleration of desert areas through global warming, will continue to have a devastating effect on water supplies.
This is forcing countries, especially those having substantial desert areas, to re-examine the extraction of pure water from the biggest resource in the world – the oceans.
Tapping the ultimate resource
Desalination has seen an exponential growth in the last 30 years. The demand, particularly in predominantly desert countries, has never been in doubt.
Developing efficient filter media has been the rate determining step. According to the International Desalination Association, the newly installed capacity in 2009 represented a 6.6 million m³/d increase on the previous year and was the largest amount of desalination capacity brought online in a single year. The largest plant commissioned was the 880,000 m³/d Shoaiba 3 project in Saudi Arabia, which was one of 700 new plants worldwide.
There are now almost 15,000 desalination plants online, under contract or in construction – an additional capacity of 9.1 million m³/d. Since the IDA World Congress in Maspalomas in November 2007, the installed capacity of seawater desalination plants has expanded by a third to almost 40 million m³/d. Demand is predicted to grow rapidly and is taking place not only in the Middle East, led by the GCC countries (Gulf Cooperation Council), but also in other countries led by Algeria, Australia and Spain.
Interestingly, the biggest new markets correspond to the countries predicted to have the greatest population growth in the future, notably USA, China and India.
A question of filtration
The key to cleaning up our contaminated world is without question the development of new filtration systems, in particular, advances in filter media. We are now living in the nano-tech generation where science is moving to smaller and smaller sizes and filtration is no exception. There are already exciting new filters using nano fibres which, when used in syringe filters, can turn black Indian ink into pure water with a gentle press of the thumb.
Without the advances in membrane technology of the last 20 years, the installation of such large desalination plants would not have been commercially viable. But it’s not just about the filter media. Telemetric development, pioneered by Formula One racing cars, is now being applied to filtration processes so that desalination plants can be located anywhere in the world, and be remotely controlled so eliminating many of the errors associated with manual data collection.
New international standards regarding airborne contamination are also coming into force to reduce the intercontinental pollution of the world’s water reserves.
This has spurred industry to develop new and exciting technologies. For example, in waste disposal by incineration (hitherto one of the greatest sources of mercury release into the environment) new high temperature filter materials can now not only remove toxic products from flue gases but, by the use of sophisticated chemistry, convert the erstwhile problematic waste into commercially valuable by products.
Japan, in particular, deserves credit for developing one of the most sophisticated and efficient incineration systems in the world. Chemical scrubbing combined with enhanced electrostatic filtration is making great inroads into eliminating particulate and toxic flue gases in coal fired power stations, but the biggest challenge remaining is the carbon capture programme to remove carbon dioxide.
As the pore size engineered into filter media becomes smaller and smaller, filtration is heading below the nanometre range into the molecular as we are now able to selectively filter gases such as carbon dioxide.
These new molecular cages are of Angstrom proportions and act on the ‘lobster pot’ principle to selectively remove the desired molecules. The amazing surface areas equivalent to six football pitches per gram are hard to conceive.
However, the process is still on a laboratory scale, but commercialisation is not so far away. Industry in the western world and, increasingly in the fastest growing developing countries, is at last addressing the pollution of the water sources in the world, but one of the biggest issues remains on the domestic front.
The history of the London and Chicago epidemics in the nineteenth century, where thousands died as a result of water contamination, is still repeating itself in other countries today, but on a significantly larger scale. Waterborne disease caused by untreated sewerage is the biggest killer in the world by a considerable margin; more than 14,000 deaths per day, most of which could be prevented by sewerage treatment.
New Micro Bio Reactors offer an excellent solution in terms of efficacy, small foot print and economical use of water, but the uptake by municipalities is still slow. Ray Mears likens our planet to a bird cage, in that unless it is regularly cleaned out, it will eventually kill the occupants. Similarly, we only have one world and we must look after it for the sake of our survival.
Author
Dr Graham Rideal, CEO and Chief Scientist, Whitehouse Scientific Limited After gaining his PhD in chemistry from Lancaster University in the UK, Dr Graham Rideal joined ICI, where he was involved in conducting pioneering nanoparticle research. This successful 15 year period with ICI was followed by his appointment as the company’s consultant in particle size analysis.
In 1983 Dr Rideal founded Whitehouse Scientific Ltd to develop, manufacture and market a range of specialised particle size standards. The company thrived and has since attained a global reputation for its calibration standards, which are used in all types of particle sizing techniques, for its award-winning method of calibrating test sieves using glass microspheres, and for its filter cut-point testing techniques.
Dr Rideal spent a period with the British Standards Institution (BSI) advising on test sieve specifications and has also served as specialist adviser for sub-micron analysis on the Bureau of Certified Reference (BCR) panel in Brussels, to help develop a new international range of reference standards for particle size analysis.
He is the author of more than 60 academic papers on filtration and related topics, has lectured widely and owns several patents describing the construction of inorganic materials such as foams, films and coatings from nano-sized mineral particles.
Dr Rideal also served for two years as Chairman of the Filtration Society (2004-2006) and today takes an active role in the society as Science Correspondent, and additionally supports the organisation’s meetings and conferences.
E: [email protected] T: +44 (0) 1244 332626 www.whitehousescientific.com
Published: 01st Sep 2011 in AWE International
