A Journey Through Water: A Scientific Exploration of the Most Anomalous Liquid on Earth E-Book
Jestin Baby Mandumpal
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- Herausgeber: Bentham Science Publishers
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
A Journey Through Water: A Scientific Exploration of The Most Anomalous Liquid on Earth, is a monograph about water at molecular level. The monograph explores how its peculiar properties are related to its molecular structure. Readers are introduced to water through information about water in a wider perspective, properties of its liquid state, experimental techniques for molecular level investigations of liquid water, and computer simulation techniques. This is followed by chapters explaining the structural properties and principal applications of various phases of water (water as a normal liquid, supercooled water, ice and supercritical water). Key features of this reference include:
- easy to understand, sequential and structured text making this reference ideal for readers with limited scientific knowledge of water physics
- a list of institutions where water research is promoted in larger scales
- 130 figures which supplement the text
- an explanation of ten principal anomalies of water and associated theories
The book is an excellent resource for novice researchers (physicists, chemists and chemical engineers) working on water and laymen who are interested in furthering their understanding of this precious liquid.
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Veröffentlichungsjahr: 2017
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A Journey Through Water:
A Scientific Exploration of The
Most Anomalous Liquid on Earth
Jestin Baby Mandumpal
BENTHAM SCIENCE PUBLISHERS LTD.
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FOREWORD
On the surface of the Earth planet, water is everywhere: very visible in oceans, rivers, rain or clouds, less visible in rocks or even in the body of living organisms. Being almost the only easily accessible natural liquid, many processes depend on its properties. No life would be possible without the presence of water in its three states. Moreover, its properties play a major role in seasonal cycles and in weather stability. From the largest scales of ocean currents till the molecular scale of biological reactions the singularity of water is evident. As a consequence, water is at the core of research in a large variety of scientific disciplines, as it is nicely presented in the first chapter of this book.
One may ask why, more than any other substance, is water so important and subject of a huge literature, given the apparent simplicity of both the chemical composition and shape of the molecules. The answer cannot be simple because, indeed, complexity comes from different origins, such as the local tetrahedral arrangement or the intermolecular hydrogen bonds and their fast dynamics.
The great merit of the presentation of J. B. Mandumpal is the gradual introduction of the main concepts of the physics of water, with a pedagogical approach based on experimental results and on computer simulations. The text encompasses essentially all the properties of water from the better known till the still controversial models of supercooled water and glass transition.
Given the amount of data available and the enormous number of research papers (more than 400 publication every day!), the content of the book constitutes a remarkable review of the state-of-the-art in water physics, which will be source of information and inspiration for graduate students, scientists and engineers.
PREFACE
Water is one of the most puzzling substances on earth despite its relatively small size and simple molecular formula. Importance of water in our life need not mention to the scientific community any further as numerous theoretical and experimental investigations have already been performed on water, and staggering volume of research work has been appeared for last several decades in hundreds of scientific journals and books. The second half of twentieth century witnessed a sudden expansion of scientific repertoire due to the refinement of the existing experimental equipment with better resolution and the introduction of computer simulations into basic and applied sciences. It has been widely accepted by now that both experiments and simulations are not independent subjects; rather they are mutually complimentary disciplines; this warrants much more concerted effort in future for better understanding of complex systems like water. The proposed book, titled, “A JOURNEY THROUGH WATER: A scientific exploration of the most anomalous liquid on earth”, is an attempt to provide the reader an account of computational and experimental investigations on water.
This work is expected to serve the reader as a useful secondary source of information, with appropriate references to the primary sources, research articles and reviews by pioneers in the field. In addition to the anticipated readers of the book (physicists and chemists), scientists and engineers who indulge in water−based investigations, for example cryobiologists and chemical engineers, can also make use of this work for sharpening their understanding on water. The contents of this book are presented in such a manner that a person with minimal understanding of physics and chemistry can comprehend most of them without much laborious effort. An important feature of this book is the way by which the introductory chapter has been presented, contrary to the traditional approaches: I venture into providing a wider outlook to water from a socio−economic, political and technological perspectives. This, I hope, will make the scientific community much more aware of the importance of their research, and prompt to design their aim according to social needs as well. The first four chapters serve as a platform for the subsequent five core chapters (5-9). Chapters from 2 to 4 are devoted to cater the needs of people who do not have fundamental understanding of various simulation and experimental methods as well as theories that have been developed over the years for explaining the properties of water and liquids in general.
Conceived in the beautiful city of the South African coast, Capetown, I proceeded to write this book part by part in several countries including the Republic of Maldives where I was later appointed as a Teaching Service Officer (TSO) under the Ministry of Education of the Republic, and Baku, where I am living now. Completion of this book was a long haul, and took more than three years to the present form after several reorganisations of the chapters. Even the title of the book has been revised several times: initially I thought of focussing mainly on computational investigations of water, but had to change my mind since such a move would become futile attempt given the fact that neither experiments nor computer simulations are standalone as I mentioned before, at least in the case of water. I thought to include clathrates suggested by one of the reviewers, but had to abandon this idea due to the never ending task of completion and also non−familiarity of the topic, but it will definitely be included in my future assignments!
This book is dedicated to my departed father Baby Mandumpal, who has been very inspirational in my life, and other family members including my mother Filomina, wife Priyanka and our little daughter Joann. I would like to thank Professor Ricardo L. Mancera at Curtin University for introducing me to this marvellous topic and for the stimulating discussions during my PhD research. I owe much to him for the training I obtained during my stay in Perth in the art of scientific presentations and more importantly structured academic writing. I would like to mention my gratitude to Professor Hamlet Izaxanli, the president of Khazar University, and Professor Hassan Niknafs, rector of Khazar University for inviting me to the wonderful city, Baku. I confer gratitude to my friends Rev. Dr. Paul Kattookaran (Co-ordinator, Art-i (Indian Christian Artists’ Forum)) for motivating me towards fulfilling this task, Dr. Rajesh Komban (Research Scientist at Center for Applied Nanotechnology (CAN) Hamburg, Germany) and Dr. Thiruvancheril Gopakumar (Assistant Professor at Indian Institute of Technology, Kanpur) for providing numerous manuscripts for the completion of this book. Without these vital supports, this book could not have been materialised. I thank Professor José Teixeira (Laboratoire Léon Brillouin, France) for his willingness for writing an appropriate “Foreword” to this treatise. Finally I thank Bentham Science publishers for inviting me to write this book and in particular their acquisition editors Ms. Dur−e−Shahnaz Shafi and Ms. Humaira Hashmi for reminding me the deadline constantly. In fact, there are more people that I could mention here, I tender my apology for not including all of them here.
As one of the prominent theoretical physicists of our era Stephen Hawking in the preface of his seminal book “A brief history of time − from big bang to black holes” mentioned, the more one includes complex mathematical equations in a book, the more readers can be deterred from it. I support for the notion of books written in plain language, especially when they are aimed at general audience, for quick understanding of the subject. As a result, I tried to minimize the number of mathematical equations as far as I can, without losing the rigour of the subject. I have tried my level best to provide the already available research work (most of which are written in academic language with complex physics and mathematics) that has been carried out hitherto on water as much as I can. Nevertheless, the expanding volume of research on water year by year makes this work an endless task. I would therefore encourage readers for making constructive criticisms on the content of this work. This book’s shortcomings, in terms of its contents and style, weigh heavily upon me. I can only say that this book does not serve to account of everything we know about water. Nevertheless, I venture to hope that the readers will enjoy a short journey through this book!
Water, The Centre of Life
Jestin Baby Mandumpal*Abstract
The ever increasing demand for clean water has prompted the world to consider water scarcity in a serious way. Some regions in the world are already at the brink of war over the ownership of major water resources, and it is feared that the situations may become worse. The marginalised people living in the impoverished regions of the world are struggling to obtain clean water, non−availability of which puts their life in utmost misery. Despite the fact that technological innovation provides some solution to this matter, water’s growing demand surpasses what technology can offer. A joint approach unifying various facets of human life is necessary to overcome the issue, and hence they are discussed in detail. It must be appreciated that several organisations including the U. N., representing all nations around the globe, is taking proactive steps to curb this problem by setting up various committees to study the matter in depth and taking appropriate measures to decentralise the resources to all. With the development of robust computer simulation methods, and water models, it is now possible to study water at microscopic level. Together with state−of−the−art experimental techniques the properties of water can be unravelled further. This is expected to have tremendous impact upon improving the quality of water refinement process since most of them are fundamentally of a chemical nature.
INTRODUCTION
Our earth, a blue water planet when observed from space, contains approximately 75% of water, but the vast majority of it (a whopping 97%) is salty and too concentrated to be useful for most of the habitats. This means that the sustainability of life heavily depends on the remaining 3% of water on earth (fresh water). The need for pure water, in particular, creeps through all spheres of life has become foci of our attention: from political summits to economic and scienti-
fic conferences, as evident from the emergence of specialist academic journals, particularly aimed at discussing different perspectives of water and life [1]. Ever increasing demand for this substance in quality (in its pure state) and in quantity is a challenge for the world in the coming years. Since the global human population is skyrocketing and proportional increase in natural water resources does not seem to be realistic, finding an overarching solution for this problem is a daunting task. The explosion in population also means proportional rise in water−consuming industries, both leading to a reduction in per capita water availability [2]. Other detrimental effects such as climate change, over−exploitation of natural resources and environmental degradation are also associated with them. It has been pointed out by the experts that the demographic explosion generates much more water scarcity than the environmental hazards such as climate change [3]. The studies conducted by Lazarova et al. underline this observation: with the environment forecast for the coming 80 years, they demonstrate that the effect of Climate Change does not necessarily have negative influence around the world at the same level [4]. This can be explained by the fact that Climate Change does not reduce amount of rain received on earth, but it only alters volume and timings of river flow, causing damages only at some places. Hence it is very evident that only with proper water management involving the following core principles, namely development of new water technologies, inter basin water transfer, efficient irrigation systems and incurring appropriate charges for water, these issues can be resolved [4]. Before going to a deep analysis of various aspects of water, we need to define “water crisis”.
Water Crisis
Water crisis is the shortage of water for internal and external consumption, which occurs due to growing imbalance between supply restricted by stagnated natural resources and demand increased by growing number of consumers. This is a much oversimplified statement because under this definition only human being’s needs (internal consumption (for e.g. clean drinking water) and external consumption (for e.g. irrigation, industry operations and power generation)) are included at the expense of the basic rights of other organisms, inclusion of which magnifies the issue than it is appeared now.
The following facts describe in a nutshell the gravity of water crisis. There are 345 million people living in Africa without proper water access. 3.4 million people (equal to the population of Los Angeles city in the United States) die every year due to water related diseases such as diarrhoea, a potential threat that killed a child in the continent in every 6 seconds between 1980−1990. Every year almost 60 million people migrate to the major cities in the world, overwhelming majority of which live in slums and do not have proper water access [5]. Another issue is the gender discrimination (against women) existing in many parts of the world related to transporting water: to collect water from long distance (usually miles away from their living places) falls upon women’s shoulders. One of the World Health Organisation (WHO) reports indicates that women and young girls work approximately over 150 million hours a year for just bringing drinking water for their household activities. These distressing facts have been summed up by a report by the International Water Management Institute (IWMI), set up for overcoming water crisis in the developing world, according to which approximately 40% percent of people are living in the developing world affected by water shortage [6]. In Fig. (1.1), some representative pictures of water crisis have been shown.
Fig. (1.1)) Snapshots of the water crisis. (a) Shrinking volume of primary water sources due to human encroachment and climate change. (b) A sample of impure, undrinkable water containing pathogens spreading diseases. (c) A large chunk of population has only got access to dirty water.Having rummaged through the introduction section, an intelligent reader may come forward with an immediate solution to the water crisis by stressing upon strong birth control policy. There may have some truth in it, but we must also consider the fact that the population growth is also contributed by better life care in many parts of the world. Average life expectancies all over the world, with exception to war−torn regions, have risen due to the appropriate intervention of the local governments and non−governmental organisations. This evidently rules out birth control as one and only viable option in order to overcome issues like water shortage. Since the crisis curbs the living population, a concerted effort is required to find overarching solution to this cataclysmic issue within the coherent framework of political, economic, scientific and technological aspects. In the following sections, I would like to investigate various grass root issues that are associated with the problem of water scarcity.
POLITICS OF WATER
Countless problems do exist between and within countries in sharing world’s fresh water resources [7]. Several countries are already in political turmoil in various parts of the world in particular the Middle East and North Africa [6] and claims over water is one of the principal reasons for this situation. This region (also known as MENA), accommodating 5% of the world population but has only 0.9% of the world water resources, can be very vulnerable to conflicts, if the rate of population grows at the current alarming rate. It is predicted that within next fifteen years the population in the zone would reach twice as that was in 2000, indicating that the non−availability of clean water will aggravate accordingly [3, 8].
In countries including Saudi Arabia, United Arab Emirates (UAE), Oman, Qatar, Kuwait, Jordan, Israel, Bahrain & Palestinian territories in the Middle East, all conventional water resources have been completely utilised [4]. Tensions of similar nature are growing at the confluence of Turkey, Syria and Iraq over water in Tigris River. Several academicians also point out to the role of water in another notorious conflict that is boiling the Middle East for over more than sixty years: tensions between Israel and Palestine over the ownership of mountain aquifers between these two countries [9]. Gaza is the most vulnerable place to the scarcity of water in this region or even in the whole world due to several reasons: it does not have independent natural water resources that cater the need of its citizens which forces them to rely on Israel for highly expensive water transportation [10]. The bitter irony is that these two countries spend billions of dollars for buying or developing defence equipment that always had lethargic impact upon the ordinary citizens of both countries. In North Africa, where most of the people are under the poverty line, countries such as Egypt, Sudan, Somalia and Ethiopia are already at loggerheads over building up of new dams in the river Nile. Without any doubt, MENA can be considered as an extreme stress region as per Water Resource Index (WRI): a region is water−stressed if region has water availability of less than 17,000 m3/person/year (water threshold) [4, 11]. In addition to MENA countries, countries surrounding Mediterranean, Eastern and Southern Africa, South West Asia are either under high stress or extreme stress with water threshold 1000 and 500 m3 per person per year respectively [4, 11].
It must also be noted that akin to economic disparity, there emerges another disquieting difference in the form of water availability in the region. Iraq, Sudan and Mauritania are well ahead in terms of per capita of water availability; whereas countries like Kuwait, Djibouti and Palestine read the lowest [3]. It is feared that the gap could widen in the coming years. Situation is not so promising in other parts of the world either: in the European Union (EU), several countries including Germany, Belgium and The Netherlands have utilised more than 50% of their natural water resources, strongly suggesting that relying on alternative methods for safe and clean water is becoming mandatory.
Not all is that bleak as per the latest global developments as several local and international agencies are actively engaged in several target setting initiatives. Some of such notable endeavours is Clean Water Act (CWA) introduced in the United States in 1972 [12], UNESCO’s (United Nations Educational Scientific and Cultural Organisations) Dublin principles [13] and more recent Europe’s Water Framework Directive (WFD) [14].
One of the aims of CWA was to put a strong restriction on waste disposal into the natural water resources in the United States, which have polluted ever since the industrialisation and urbanisation started in 19th century. This target was primarily met by constructing numerous wastewater treatments plants across the United States [15].
The Dublin Accord was of broader perspective, and made four key resolutions, as summarised below, to meet water quality at acceptable standards:
Clean water is very fundamental for sustaining life on earth but is a depleting resource.A concerted effort is required for better water management incorporating users and policy makers at all levels.The role of women is so crucial in water management.Since water is a public property, its social and economic value cannot be undermined.An expansive version of Dublin principles (Dublin Accord) with more pragmatic approaches can be found in [2]. The principal objective of Water Framework Directive (WFD) was to centralise the initiatives taken by the member states of European Union (EU), ensuring the water quality equal across the continent [16]. As a result, the map of Europe was redrawn by hydrological parameters instead of political or administrative considerations in order to meet the water requirement.
Responding positively to the UNESCO’s propositions, several countries have reached in mutually acceptable settlements. One of such initiatives is known as Inter Basin Transfer, transfer of water from one geographically distinct river catchment to other locations [17]. The Senqu−Vaal transfer, between South Africa and Lesotho, and South−North water project in China are some of the glittering examples for solving water crisis by water management. The estimates show that around 43% water withdrawal in North America was Inter Basin Transfer, suggesting that many water−related conflicts can be alleviated by properly executed plans [17]. Senegal’s recent progress in resolving water issues demonstrates that empowerment of women can tackle water issues to a great extent [18]. In Asia Pacific, “The Living Murray”, the famous river restoration project is Australia’s initiative to bring back river Murray to its former glory. The project encompasses various disciplines such as ecological modelling and empirical research for ensuring high rate of success in the endeavour [19]. Australia has also reached two bilateral agreements with Japan and China to ensure the preservation of natural habitat: JAMBA (Japan Australia Migratory Bird Agreement) and China-Australia Migratory Bird Agreement (CAMBA) [19].
SOCIAL AND ECONOMIC IMPACTS OF WATER
The economic disparities among various classes of society and nations also play a key role in the water crisis. The statistics below sums up the precarious economic situation of unprivileged people: people living in slums (informal settlements) often have to pay five or ten times higher than the privileged living in wealthier regions of the same city. Since the urban water is more affected than water in rural areas due to the discharge of municipal and industrial waste, this situation is likely to worsen. Most of the people who can’t have access to clean drinking water live on very paltry amount of money (1−2 dollars per day). It is important to note that nearly 95% of the problems related to the scarcity of clean water are reported from the developing world [20].
The developed world too is not spared from this growing menace albeit the reasons are different. Increasing demand for agriculture, and various thermal and hydroelectric projects has eroded natural water resources beyond recovery in the Western World. Researchers have found that over 65% of ground water is consumed for agriculture, which is non−recoverable, followed by industries and hydroelectric projects [21]. The required volume of water has been skyrocketed in many cities after Second World War due to the huge influx of people from urban areas, which led to the emergence of private companies commercialising water. Often tinted with corruption this move resulted in violent protests in many countries, including Argentina and Philippines [1].
An important economic pact has been signed to placate growing tensions between various countries under the auspice of academicians from the Middle East and North America [10]. The pact, The Harvard Middle East Water Project (HMEWP) aims to promote peace and harmony among the warring countries in the Middle East by implementing a protocol that is based on effective distribution of water among the countries and setting up infrastructure for posterity [10]. The major finding of the project was that the monetary value of water claimed by Israel, Palestine and Jordan is “surprisingly low” such that an amicable settlement can be achieved to ease the strained relationship between these countries [10]. The current water deals between countries, for instance between Israel and Jordan, were monitored in the project. It found that the current water transaction between these two countries is very negligible compared to actual need, and suggested increasing the transaction fivefold to meet the requirement by 2020 [10]. The report recommends for constructing better water conveyance facilities across the region, facilitating an increase in transporting of water 10−15 times higher than that of the current capacity. The project, in addition, proposes the development of various national water pipeline systems, for example connecting Jordanian water transporting facility to Nablus region of Palestine, and water pipelines in Gaza to Israeli National Water Carrier [10]. Nevertheless, the success of this proposal heavily depends upon the political climate of this region: as Israel and Palestine fight over their sovereignty on yearly basis, the economic viability of such plans cannot be guaranteed.
External consumption of water (not necessarily in its pure form) also serves as basis for our existence: for example the water we use for generating electricity or agricultural purposes, shortage of which clearly push us into two more perilous crises pertaining to energy and food. Though alternative modes of generation of electricity replaced the traditional hydro power electricity in many parts of the world, 20% of the global electricity is still obtained from this way, notably in China and India where 50% of the electricity is produced from hydro electrical projects [22]. In some countries, hydropower is the principal source accounting for more 90% of electricity generated underpinning the importance of water among the essential commodities that sustain human life. Statistics predicts that the amount of water required for agricultural purposes will see a dramatic leap from merely 1021 million tons in 1993 to 1634 million tons by 2020 [22a].
Is there an effective economic model for water management? Hydro−economic modelling, a post war discipline initiated in the United States and Israel is a powerful mathematical model in which hydrologic engineering is integrated with economic nature of demands and costs of water [23]. Unlike most of the management models proposed over the years, it amalgamates various perspectives of water management: geographical, economic, environmental and technological, and offers an optimum solution to the water related issues. Compared to the traditional approaches which relied either on economic aspects or technological aspects, hydro−economic modelling is demand related in nature considering the dynamic nature of demographic landscape, agricultural and industrial water requirements which can cope with any surge in demands [23]. Hydro−dynamic modelling has been employed for various purposes such as water supply, engineering infrastructure, capacity expansion, ground and surface water management, water monetizing, trans−boundary management, managing weather fluctuations, floods and improving water quality. Countries in the developed world including the United States, Australia, France, Germany and Spain and in the developing world such as India, Iran and Palestine are greatly benefitted by this state−of−the−art tool [23].
WATER AND ENVIRONMENT
Natural resources of water depend first and foremost upon hydrological cycle, but activities and priorities of the world reshape this natural landscape of water in a negative way. Hydrological cycle (precipitation−absorption−evaporation) is nature’s delicate way for providing clean water to its inhabitants. Solar energy distils approximately 40% of water in earth’s atmosphere, and out of these 14% is from land and the rest from oceans. But a higher proportion, 24% of the water, returns onto earth as precipitation falls on land which is stored in lakes, streams, ice caps, glaciers, soil moisture and ground water [7]. Around one fourth of the total fresh water on earth is store as ground water than any other forms, making it the most important source of fresh water across our globe. A huge volume of water, approximately 7 x 1015 m3, in aquifers underneath the earth’s surface has been stored from annual hydrological cycles occurring for millions of years [7].
Increasing demand for water has led to over exploitation of the ground water mostly by ground water mining, for example in countries like the United States, which results in two environmental problems in several parts of the world: increasing salinity of water and water logging [7, 24]. Other anthropogenic activities such as building dams over rivers, creation of artificial lakes, altering the natural course of water ways and discharging treated water to water bodies too have adverse effect on quality of water. Industrialisation has made very serious fingerprints on the purity of water such as change in temperature (thermal pollution); turbidity; presence of organic or inorganic chemicals such as heavy metals, oxygen depleting substances, nutrients; and alteration of pH [15, 25].
Thermal pollution is primarily caused by nuclear and thermal power generating industries. The chemical waste ejected by these industries reduce the capacity of water to absorb oxygen, and hence diminishes the purity of natural clean water reserves as well as systematically terminate the existence of aquatic species such as fish [15]. Growing concerns over the pollution (including water impairment) caused by these energy sources, accounting for over 20% of greenhouse gas emission in the world, prompted technologists to search for other sustainable means for power generation, for example Ocean Thermal Energy Conversion (OTEC), economically viable for smaller and poor developing nations like Ghana, Somalia, Cuba, Bahamas, Fiji and Maldives crippled by water scarcity [26].
Aquatic life is also severely perturbed by the presence of materials such as metals (arsenic, lead, mercury), halogenated aromatics such as DDT, solvents like benzene and toluene, nitrosoamines, nitrates and phosphates (the list is endless). These materials often cause cancerous tumours on the skins of fish and birth defects on aquatic birds [15]. Traces of toxic materials like poly chlorinated biphenyls and mercury have been found in several species such as Weddell seals in Rose sea in Antarctica and Cree Indians of Canadian High Arctic respectively, putting them at the brink of extinction [27]. Dissolved oxygen in water is very fundamental for the survival of many aquatic species. Lack of sufficient oxygen dissolved in water (minimum 4 milli grams per litre) puts their existence into perilous situation. Industrialisation has played a non−negligible role in the discharge of various oxygen depleting substances including food processing waste, pulp from news paper industries and animal waste into fresh water sources [15].
The non−expansion of natural resources upon the rising demands can be clearly noticeable in shrinking capability of water aquifers [2]. There exists a huge imbalance between average annual recharge and average annual use in several aquifers across the globe: Saharan basin, Saq, Tenerife and Ogallala are some among them [2]. In most of these aquifers, the amount of water withdrawal is three or four times higher than annual water recharge, suggesting that these aquifers are on the brink of extinction. The major environmental threat to safe, clean and fresh water is the presence of pathogens such as a variety of helminthes, protozoa, fungi, bacteria, rickettsiae, viruses and prions in water which can cause disease in humans, animals or plants, threatening the very existence of human beings in many parts of the world, in particular Asia and Africa [20]. Contaminated water is responsible for many contagious diseases such as hepatitis gastroenteritis, meningitis, fever, rash, conjunctivitis which can be spread at amazing pace due to the presence of human enteric viruses in water [28]. The following Fig. (1.2) outlines outbreak of waterborne diseases by direct and indirect ways. In addition, behavioural abnormalities, cancer, genetic mutations, physiological malfunctions are also common in communities devoid of access to clean water [15].
Fig. (1.2)) Different routes of enteric virus transmission. (a) Direct virus transmission to human body occurs from ground water through water supply. (b) Virus enters into human body indirectly from oceans, rivers and lakes polluted by sewage water.One of the classical examples of deteriorating quality of water upon the natural habitat is Georgia’s (in the United States) decreasing availability of natural edible species such as oysters [29]. Oyster reef, built by accretion of oysters over the years, is central to the preservation of the land against shore line erosion, to maintenance of water quality by filtering pollutants and excessive nutrients, and to provide breeding environment for other species such as shrimps and blue crabs [29]. Impaired water does not stifle the growth of all species on earth but promotes pervasive growth of certain species called Invasive species which endanger the very existence of natural habitat like oyster reef in Georgia as studies indicate [29]. An invasive species is a plant or animal that foreign to a specific location, has a tendency to spread to become the dominant species in the location, suppressing the growth of native species. They are characterised by high breeding rate, broad diets, wide environmental tolerance, longevity, and being gregarious [29]. Notable invasive species include Australian tube worm, Island Apple Snail, Charrua Mussel, Green Mussel, Green Porcelain Crab, Alligator weed, Water Hyacinth, Hydrilla, Marsh Dewflower, Giant Salvinia, Red Lionfish, and Titan Acorn Barnacle. Some of these are found universally, whereas others grow at specific geographical areas. Some invasive species in particular those grow in water known as Aquatic Invasive Species pose threat to its purity since they impair water quality by altering pH and lowering oxygen levels.
None can deny the benefits of modernisation achieved through industrialisation, but a key question remains is “how to reap the benefits of industrialisation without costing the sanctity of nature”. One may argue that industrialisation cannot be unavoidable, but there must be proper regulations and their implementations must be put in place strictly. Even CWA was only a partial success due to lack of propositions to cut the several other water contaminating activities that are more individualistic in nature such as farming and timber harvesting [15].
WATER FROM BIOLOGICAL PERSPECTIVE
The role of water in biological activities of human beings and other living creatures is not by any means negligible. Water is the most abundant chemical in our body, and its presence is pivotal in many functions in animals and plants including nutrient transportation, biochemical reactions, reproduction and fertilisation. Transportation of fluids is very fundamental for the survival of organisms with which essential nutrients are carried through. In plants, vital molecules such as sugars, amino acids and hormones are transported in the water medium. A huge proportion of water is contained in blood and cytoplasm, major transporting fluids in animals. Complete solubility of molecules such as glucose, amino acids and certain minerals in water is essential for metabolism, by which new cells are generated, and energy is produced. High stability of water in the normal temperature domain and excellent solvation properties make water indispensable reaction medium for various enzymatic reactions in our body, for example photosynthesis. Our reproduction system is primarily based on water, without which male and female gametes cannot move freely rendering the fertilisation process impossible. Water also acts as a comfortable cushion for the development of embryo for the whole gestational period.
Water is absorbed into human body from the food intake; it is then consumed for the biological functions inside organs such as lungs and kidneys and goes out via perspiration and urination. Smooth repetition of this cycle (physiological water cycle) warrants the quality of water very high in order to safeguard one’s body from serious pathological conditions. The water circulating inside participates in variety of reactions including redox, condensation and hydrolysis [6]. Water’s role in photosynthesis is critical and well known: in one of the steps of ATP synthesis, water releases oxygen that combines with glucose and Adinosine Di Phosphate (ADP) to form Adinosine Tri Phosphate (ATP), the store house of chemical energy, with water being one of the by−products of this reaction itself.
Water’s role is much more versatile, inside the cell, in interacting delicately with wide range of biomolecules. Numerous volume of research work is published every year on these interactions in relevance to various cellular activities, yet researchers have not been successful in developing a coherent understanding of structural, dynamic and morphological properties of water in this biochemical context. The activity of biological macromolecules such as proteins and nucleic acids (DNA and RNA) is negligible without water. One of the notable properties water is that the macromolecular interactions in cells are mediated by water through hydrogen bonding (an electrostatic attraction when a hydrogen atom bonded to highly electronegative atoms such as nitrogen, oxygen and fluorine in a molecule experiences attraction towards highly electronegative atom of a neighbouring molecule), hydrophobic association (tendency of nonpolar substances to aggregate themselves in the presence of water) and hydrophobic hydration (the orientation of water molecules around macromolecules resulting in a formation of microscopic cage of water molecules around them) [30].
Water indulges in its characteristic hydrogen bonding network composed of vast number of water molecules especially in low temperature and normal temperature domains. Albeit reduced in terms of coordination number, water retains the network with large proteins, crucial in mitigating protein−water dynamics [31]. Consequence of hydrogen bonding is extended to another peculiar phenomenon that occurs in confined water trapped between large macromolecules, proton hopping, by which proton is passed through water via rearrangement of hydrogen bond network [32]. Fig. (1.3) demonstrates water in the cellular environment.
Fig. (1.3)) Schematic diagram of water in cellular environment. Water (shown in blue) sequestered between large macromolecules participates in numerous activities in cell, the smallest part of an animal or plant that is able to function independently. The water molecules trapped between the macromolecules behave differently with respect to the bulk water.Hydrophobic association is so critical in protein folding, a process by which proteins fold into a more compact form (three dimensional structure) by reconfiguring its nonpolar residues to the core and polar residues to the surface to carry out vital functions in every cells. It also plays a central role in aggregation of lipid bilayers. Lipids contain two different molecular segments that are different in their solvation characteristics: polar units and non−polar units. Hydrophobic interactions keep the non−polar segment away from water, whereas interactions between water and polar units are strengthened by hydrogen bonding. These two concomitant interactions result in layering of non−polar (hydrophobic) segments in lipids. Hydrophobic hydration on the other hand has been found to enhance the catalytic activity of proteins, known as functional tuning [33].
Other amazing properties of water have also been found out from experimental and computer simulations. Water facilitates protein dynamics, the motion of peptide bonds (the chemical bond that connect various amino acids in a macromolecule) by maintaining the optimum balance between rigidity and mobility of protein structure [30]. Water has an exceptional ability to speed up biochemical reactions (its catalytic activity), making use of which it can act as both proton acceptor and proton donor fulfilling several roles including splitting ring closures, hydrolysis of peptide bonds, eliminating chemical groups from substrates and proton transfer between adjacent protein surfaces [34, 35]. Recent theoretical and experimental investigations indicate water’s amazing morphological transitions within the close proximity of large macromolecules, which are otherwise observed only at very low temperatures [36]. These morphological transitions in the presence of large macromolecules enable water to suppress its crystallisation temperature further below. This clearly explains the natural ability of several species living in extreme conditions such as polar bear to overcome very extreme cold weather [30]. The binding of smaller molecules (ligands) from adjacent protein surface to protein receptors either by hydrophobic association or hydrogen bonding is known as ligand binding.
Water’s role in ligand binding is also a subject of immense debates [30]. One school argues that during ligand binding water molecules are completely replaced by other molecules, while the other advocates that the water molecules confined between the protein surface and the approaching ligand act as flexible adhesive facilitating ligand−protein interactions. Both arguments can be plausible, as accounted for the natural cryopreservation conferred by sugars [37]. Disaccharides, a class of sugars, interact with the biological membranes in two ways: sugars replace water molecules, and offer protective shells around the membranes by indulging in hydrogen bonds. This stabilisation mechanism is known as Water Replacement Hypothesis; whilst the presence of sugars increases the degree of hydration known as Water Entrapment Hypothesis [37]. Water present between two adjacent proteins is reported to have a role in generating different protein conformations, observed in cytochrome c2 redox protein and haemoglobin (the oxygen carrier in blood), which facilitates improved functionalities of protein substrates [38].
The properties of water are so unique in organising biological functions in our body. Contamination of water due to the presence of salts and other organic compounds limits the multi−functional role of water. Every person living on earth has right to have access to clean drinking water, non−availability of which can lead to perennial diseases that continue to pose a constant threat to our health, which in some cases may even lead to loss of life.
WATER FROM TECHNOLOGICAL PERSPECTIVE
Development of robust technologies for producing clean water can mitigate the impact of water scarcity to a greater extent. These techniques are based on two concepts: water reuse and water retrieval from an impure water source. Affluent countries such as Belgium, England and Germany have implemented successful water reuse technology to face growing demand for water in their cities [4]. I venture into explain various classes of these techniques in this section, some of which have been in use for over centuries and others are in developmental phase. The most applicability of these methods critically depends upon three factors: the geographical peculiarity, the size of targeted communities and economic viability. For example, implementing a method suitable for a large city in a small town can be considered as economic mismanagement. Similarly, techniques suitable for cold conditions of Finland might be inappropriate for hot and humid Indian conditions.
Water purifying techniques can fundamentally be divided into two: treatments in which chemicals are used for (e.g. osmosis), and treatments that are based on physical methods (for e.g. treatments driven by solar energy). The fundamental protocols for water cleaning techniques by traditional chemical methods are based on disinfection, decontamination and re−use and reclamation [20
