From Wikipedia, the free encyclopedia
Water quality refers to the chemical, physical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which compliance can be assessed. The most common standards used to assess water quality relate to health of ecosystems, safety of human contact and drinking water.
In the setting of standards, agencies make political and technical/scientific decisions about how the water will be used. In the case of natural water bodies, they also make some reasonable estimate of pristine conditions. Different uses raise different concerns and therefore different standards are considered. Natural water bodies will vary in response to environmental conditions.Environmental scientists work to understand how these systems function, which in turn helps to identify the sources and fates of contaminants. Environmental lawyers and policymakers work to define legislation with the intention that water is maintained at an appropriate quality for its identified use.
The vast majority of surface water on the planet is neither potable nor toxic. This remains true even if seawater in the oceans (which is too salty to drink) is not counted. Another general perception of water quality is that of a simple property that tells whether water is polluted or not. In fact, water quality is a complex subject, in part because water is a complex medium intrinsically tied to theecology of the Earth. Industrial and commercial activities (e.g. manufacturing, mining, construction, transport) are a major cause of water pollution as are runoff from agricultural areas, urban runoffand discharge of treated and untreated sewage.
The parameters for water quality are determined by the intended use. Work in the area of water quality tends to be focused on water that is treated for human consumption, industrial use, or in the environment.
Contaminants that may be in untreated water include microorganisms such as viruses and bacteria; inorganic contaminants such as salts and metals; organic chemical contaminants from industrial processes and petroleum use; pesticides and herbicides; and radioactive contaminants. Water quality depends on the local geology and ecosystem, as well as human uses such as sewage dispersion, industrial pollution, use of water bodies as a heat sink, and overuse (which may lower the level of the water).
The United States Environmental Protection Agency (EPA) limits the amounts of certain contaminants in tap water provided by US public water systems. The Safe Drinking Water Act authorizes EPA to issue two types of standards: primary standards regulate substances that potentially affect human health, and secondary standards prescribe aesthetic qualities, those that affect taste, odor, or appearance. The U.S. Food and Drug Administration (FDA) regulations establish limits for contaminants in bottled water that must provide the same protection for public health. Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of these contaminants does not necessarily indicate that the water poses a health risk.
In urbanized areas around the world, water purification technology is used in municipal water systems to remove contaminants from the source water (surface water or groundwater) before it is distributed to homes, businesses, schools and other users. Water drawn directly from a stream, lake, or aquifer and that has no treatment will be of uncertain quality.
Dissolved minerals may affect suitability of water for a range of industrial and domestic purposes. The most familiar of these is probably the presence of ions of calcium and magnesium which interfere with the cleaning action of soap, and can form hard sulfate and soft carbonate deposits in water heaters or boilers. Hard water may be softened to remove these ions. The softening process often substitutes sodium cations. Hard water may be preferable to soft water for human consumption, since health problems have been associated with excess sodium and with calcium and magnesium deficiencies. Softening decreases nutrition and may increase cleaning effectiveness.
Environmental water quality, also called ambient water quality, relates to water bodies such as lakes, rivers, and oceans. Water quality standards for surface waters vary significantly due to different environmental conditions, ecosystems, and intended human uses. Toxic substances and high populations of certain microorganisms can present a health hazard for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses. These conditions may also affect wildlife, which use the water for drinking or as a habitat. Modern water quality laws generally specify protection of fisheries and recreational use and require, as a minimum, retention of current quality standards.
There is some desire among the public to return water bodies to pristine, or pre-industrial conditions. Most current environmental laws focus on the designation of particular uses of a water body. In some countries these designations allow for some water contamination as long as the particular type of contamination is not harmful to the designated uses. Given the landscape changes (e.g., land development, urbanization, clearcutting in forested areas) in thewatersheds of many freshwater bodies, returning to pristine conditions would be a significant challenge. In these cases, environmental scientists focus on achieving goals for maintaining healthy ecosystems and may concentrate on the protection of populations of endangered species and protecting human health.
The complexity of water quality as a subject is reflected in the many types of measurements of water quality indicators. The most accurate measurements of water quality are made on-site, because water exists in equilibrium with its surroundings. Measurements commonly made on-site and in direct contact with the water source in question include temperature, pH, dissolved oxygen, conductivity, oxygen reduction potential (ORP), turbidity, and Secchi disk depth.
More complex measurements are often made in a laboratory requiring a water sample to be collected, preserved, transported, and analyzed at another location. The process of water sampling introduces two significant problems. The first problem is the extent to which the sample may be representative of the water source of interest. Many water sources vary with time and with location. The measurement of interest may vary seasonally or from day to night or in response to some activity of man or natural populations of aquatic plants and animals. The measurement of interest may vary with distances from the water boundary with overlying atmosphere and underlying or confining soil. The sampler must determine if a single time and location meets the needs of the investigation, or if the water use of interest can be satisfactorily assessed by averaged values with time and/or location, or if critical maxima and minima require individual measurements over a range of times, locations and/or events. The sample collection procedure must assure correct weighting of individual sampling times and locations where averaging is appropriate.:39-40 Where critical maximum or minimum values exist, statistical methods must be applied to observed variation to determine an adequate number of samples to assess probability of exceeding those critical values.
The second problem occurs as the sample is removed from the water source and begins to establish chemical equilibrium with its new surroundings - the sample container. Sample containers must be made of materials with minimal reactivity with substances to be measured; and pre-cleaning of sample containers is important. The water sample may dissolve part of the sample container and any residue on that container, or chemicals dissolved in the water sample may sorb onto the sample container and remain there when the water is poured out for analysis.:4 Similar physical and chemical interactions may take place with any pumps, piping, or intermediate devices used to transfer the water sample into the sample container. Water collected from depths below the surface will normally be held at the reduced pressure of the atmosphere; so gas dissolved in the water may escape into unfilled space at the top of the container. Atmospheric gas present in that air space may also dissolve into the water sample. Other chemical reaction equilibria may change if the water sample changes temperature. Finely divided solid particles formerly suspended by water turbulence may settle to the bottom of the sample container, or a solid phase may form from biological growth or chemical precipitation. Microorganisms within the water sample may biochemically alter concentrations of oxygen, carbon dioxide, and organic compounds. Changing carbon dioxide concentrations may alter pH and change solubility of chemicals of interest. These problems are of special concern during measurement of chemicals assumed to be significant at very low concentrations.
Sample preservation may partially resolve the second problem. A common procedure is keeping samples cold to slow the rate of chemical reactionsand phase change, and analyzing the sample as soon as possible; but this merely minimizes the changes rather than preventing them.:43-45 A useful procedure for determining influence of sample containers during delay between sample collection and analysis involves preparation for two artificial samples in advance of the sampling event. One sample container is filled with water known from previous analysis to contain no detectable amount of the chemical of interest. This blank sample is opened for exposure to the atmosphere when the sample of interest is collected, then resealed and transported to the laboratory with the sample for analysis to determine if sample holding procedures introduced any measurable amount of the chemical of interest. The second artificial sample is collected with the sample of interest, but then spiked with a measured additional amount of the chemical of interest at the time of collection. The blank and spiked samples are carried with the sample of interest and analyzed by the same methods at the same times to determine any changes indicating gains or losses during the elapsed time between collection and analysis.
Inevitably after events such as earthquakes and tsunamis, there is an immediate response by the aid agencies as relief operations get underway to try and restore basic infrastructure and provide the basic fundamental items that are necessary for survival and subsequent recovery. Access to clean drinking water and adequate sanitation is a priority at times like this. The threat of disease increases hugely due to the large numbers of people living close together, often in squalid conditions, and without proper sanitation.
After a natural disaster, as far as water quality testing is concerned there are widespread views on the best course of action to take and a variety of methods can be employed. The key basic water quality parameters that need to be addressed in an emergency are bacteriological indicators of fecal contamination, free chlorine residual, pH, turbidity and possibly conductivity/total dissolved solids. There are a number of portable water test kits on the market widely used by aid and relief agencies for carrying out such testing.
After major natural disasters, a considerable length of time might pass before water quality returns to pre-disaster levels. For example, following the 2004 Indian Ocean Tsunami the Colombo-based International Water Management Institute (IWMI) monitored the effects of saltwater and concluded that the wells recovered to pre-tsunami drinking water quality one and a half years after the event. IWMI developed protocols for cleaning wells contaminated by saltwater; these were subsequently officially endorsed by the World Health Organization as part of its series of Emergency Guidelines.
Disclamer : You use my name KEES, I use a name similar to your name.
The simplest methods of chemical analysis are those measuring chemical elements without respect to their form. Elemental analysis for dissolved oxygen, as an example, would indicate a concentration of 890,000 milligrams per litre (mg/L) of water sample because water is made of oxygen. The method selected to measure dissolved oxygen should differentiate between diatomic oxygen and oxygen combined with other elements. The comparative simplicity of elemental analysis has produced a large amount of sample data and water quality criteria for elements sometimes identified asheavy metals. Water analysis for heavy metals must consider soil particles suspended in the water sample. These suspended soil particles may contain measurable amounts of metal. Although the particles are not dissolved in the water, they may be consumed by people drinking the water. Adding acid to a water sample to prevent loss of dissolved metals onto the sample container may dissolve more metals from suspended soil particles.Filtration of soil particles from the water sample before acid addition, however, may cause loss of dissolved metals onto the filter. The complexities of differentiating similar organic molecules are even more challenging.
Making these complex measurements can be expensive. Because direct measurements of water quality can be expensive, ongoing monitoring programs are typically conducted by government agencies. However, there are local volunteer programs and resources available for some general assessment. Tools available to the general public include on-site test kits, commonly used for home fish tanks, and biological assessment procedures.
The following is a list of indicators often measured by situational category:
From Wikipedia, the free encyclopedia
Water chemistry analyses are carried out to identify and quantify the chemical components and properties of a certain water. This include pH, major cations and anions, trace elements andisotopes. Water chemistry analysis is used extensively to determine the possible uses a water may have or to study the interaction it has with its environment. Water chemistry analysis is often the groundwork of studies of water quality, pollution, hydrology and geothermal waters.
Components commonly analyzed are pH, the cations Na, K, Ca, Mg, Si, the anions Cl, F, SO4, the trace metals and metalloids Rb, Ti, Fe, Mn, etc., unstable volatiles such as CO2, H2S and O2, isotope ratios of 18O and 2H, organic material and nutrients.
Depending on the components, different methods are applied to determine the quantities or ratios of the components. While some methods can be performed with standard laboratory equipment, others require advanced devices, such as Inductively coupled plasma mass spectrometry (ICP-MS).
You might be interested in a recent journal paper of mine that focuses on the impact of politics on drinking water. The paper seeks to address a growing lack of historical knowledge in the water industry of how European Union (EU) water policy has developed and been responded to. It also aims to overcome the lack of comparative studies that explore the role politics has played in the development and application of EU water policy. As a result, the paper develops an historical comparative understanding of how England and Wales and the Republic of Ireland have responded to the Drinking Water Directive (80/778/EEC). It does so from the perspectives of political priority and ideology. Political ideology is shown as having had a greater impact on facilitating achievement of the Directives standards in England and Wales. However, it is established that the political priority national governments have accorded compliance has been central to ensuring the application and enforcement of the Directives standards. Despite the apparent success of political ideology in England and Wales, the paper sounds a note of caution with regard to judging privatisation as being uniformly successful, for it has not, particularly if issues of water charges, customer debt, and financial and reporting irregularities are considered.
The European Drinking Water Directive (DWD), Council Directive 98/83/EC concerns the quality of water intended for human consumption and forms part of the regulation of Water supply and sanitation in the European Union.
The Directive is intended to protect human health by laying down healthiness and purity requirements which must be met by drinking water within the Community (see water quality). It applies to all water intended for human consumption apart from natural mineral waters and waters which are medicinal products.
Member States shall ensure that such drinking water:
In setting contaminant levels the directive applies the precautionary principle. For example, the EU contaminant levels for pesticides are up to 20 times lower than those in the WHO drinking water guidelines, because the EU directive not only aims at protecting human health but also the environment. The WHO contaminant levels themselves are already set so that there would be no potential risk if the contaminant was absorbed continuously over a person's lifetime. EU drinking water standards and cases where these standards are temporarily exceeded by a small margin should be interpreted in this context.
With effect from Dec 2003, Directive 80/778/EC was repealed and replaced by 98/83/EC.  The new directive saw the number of parameters reduced whilst allowing member to add parameters such as magnesium, total hardness, phenols, zinc, phosphate, calcium and chlorite.
The directive requires member states to regularly monitor the quality of water intended for human consumption by using the methods of analysis specified in the directive, or equivalent methods. Member states also have to publish drinking water quality reports every three years, and the European Commission is to publish a summary report. Within five years Member States had to comply with the Directive. Exemptions can be granted on a temporary basis, provided that they do not affect human health. from wikipedia
Water Supply and Sanitation (WSS) in the European Union (EU) is still under the responsibility of each member state, but in the 21st century union-wide policies have come into effect. Water resources are limited and supply and sanitation systems are under pressure from urbanization and climate change. The water policy of the EU is primarily codified in three directives:
EU member states have enacted national legislation in accordance with these directives. The institutional organization of public water supply and sanitation does not fall under the purview of the EU, but remains a prerogative of each member state.
Water is a chemical compound with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atomsconnected by covalent bonds. Water is a liquid at temperatures above 0 °C (273.15 K, 32 °F) at sea level, but it often co-exists on Earthwith its solid state, ice, and gaseous state (water vapor or steam). Water also exists in a liquid crystal state near hydrophilicsurfaces.
Water covers 71% of the Earth's surface, and is vital for all known forms of life. On Earth, 96.5% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products.
Water on Earth moves continually through the hydrological cycle of evaporation and transpiration (evapotranspiration), condensation,precipitation, and runoff, usually reaching the sea. Evaporation and transpiration contribute to the precipitation over land.
Safe drinking water is essential to humans and other lifeforms. Access to safe drinking water has improved over the last decades in almost every part of the world, but approximately one billion people still lack access to safe water and over 2.5 billion lack access to adequate sanitation. There is a clear correlation between access to safe water and GDP per capita. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A recent report (November 2009) suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%. Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of the fresh water used by humans goes to agriculture. ( from Wikipedia )
Drinking water or potable water is water safe enough to be consumed by humans or used with low risk of immediate or long term harm. In mostdeveloped countries, the water supplied to households, commerce and industry meets drinking water standards, even though only a very small proportion is actually consumed or used in food preparation. Typical uses (for other than potable purposes) include toilet flushing, washing andlandscape irrigation.
Over large parts of the world, humans have inadequate access to potable water and use sources contaminated with disease vectors, pathogens or unacceptable levels of toxins or suspended solids. Drinking or using such water in food preparation leads to widespread acute and chronic illnesses and is a major cause of death and misery in many countries. Reduction of waterborne diseases is a major public health goal in developing countries.
Water has always been an important and life-sustaining drink to humans and is essential to the survival of all known organisms. Excluding fat, water composes approximately 70% of the human body by mass. It is a crucial component of metabolic processes and serves as a solvent for many bodilysolutes. The United States Environmental Protection Agency in risk assessment calculations previously assumed that the average American adult ingests 2.0 litres per day. However, the United States Environmental Protection Agency now suggests that either science-based age-specific ranges or an all ages level (based on National Health and Nutrition Examination Survey 2003-2006 data) be used. Drinking water of a variety of qualities is bottled. Bottled water is sold for public consumption throughout the world.
Some health authorities have suggested that people drink at least eight glasses, eight fl oz each (240 mL), of water per day (64 fl oz, or 1.89 litres),and the British Dietetic Association recommends 1.8 litres. This common misconception is not supported by scientific research. Various reviews of all the scientific literature on the topic performed in 2002 and 2008 could not find any solid scientific evidence that recommended drinking eight glasses of water per day. In the US, the reference daily intake (RDI) for water is 3.7 litres per day (L/day) for human males older than 18, and 2.7 L/day for human females older than 18 including water contained in food, beverages, and drinking water. The amount of water varies with the individual, as it depends on the condition of the subject, the amount of physical exercise, and on the environmental temperature and humidity. An individual's thirst provides a better guide for how much water they require rather than a specific, fixed quantity.
In terms of mineral nutrients intake, it is unclear what the drinking water contribution is. Inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust. Treatment processes also lead to the presence of some minerals. Examples include calcium,zinc, manganese, phosphate, fluoride and sodium compounds. Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. For example sodium, potassium andchloride are common chemicals found in small quantities in most waters, and these elements play a role in body metabolism. Other elements such asfluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels.
Profuse sweating can increase the need for electrolyte (salt) replacement. Water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal.
Although covering some 70% of the Earth's surface, most water is saline. Freshwater is available in almost all populated areas of the earth, although it may be expensive and the supply may not always be sustainable. Sources where water may be obtained include:
Spring water is groundwater that rises to the ground surface. Springs are often used as sources for bottled waters. Tap water, delivered by domestic water systems in developed nations, refers to water piped to homes and delivered to a tap or spigot. For these water sources to be consumed safely they must receive adequate treatment and meet drinking water regulations.
The most efficient way to transport and deliver potable water is through pipes. Plumbing can require significant capital investment. Some systems suffer high operating costs. The cost to replace the deteriorating water and sanitation infrastructure of industrialized countries may be as high as $200 billion a year. Leakage of untreated and treated water from pipes reduces access to water. Leakage rates of 50% are not uncommon in urban systems.
Because of the high initial investments, many less wealthy nations cannot afford to develop or sustain appropriate infrastructure, and as a consequence people in these areas may spend a correspondingly higher fraction of their income on water. 2003 statistics from El Salvador, for example, indicate that the poorest 20% of households spend more than 10% of their total income on water. In the United Kingdom authorities define spending of more than 3% of one's income on water as a hardship.
The World Health Organization/UNICEF Joint Monitoring Program (JMP) for Water Supply and Sanitation  is the official United Nations mechanism tasked with monitoring progress towards the Millennium Development Goal (MDG) relating to drinking-water and sanitation (MDG 7, Target 7c), which is to: "Halve, by 2015, the proportion of people without sustainable access to safe drinking-water and basic sanitation". The JMP is required to use the following MDG indicator for monitoring the water component of this: Proportion of population using an improved drinking-water source.
According to this indicator on improved water sources, the MDG was met in 2010, five years ahead of schedule. Over 2 billion more people used improved drinking water sources in 2010 than did in 1990. However, the job is far from finished. 780 million people are still without improved sources of drinking water, and many more still lack safe drinking water: complete information about drinking water safety is not yet available for global monitoring of safe drinking water. Continued efforts are needed to reduce urban-rural disparities and inequities associated with poverty; to dramatically increase coverage in countries in sub-Saharan Africa and Oceania; to promote global monitoring of drinking water quality; and to look beyond the MDG target towards universal coverage.
In the U.S, the typical single family home uses 69,3 gallons (262 litres) of water per day. This includes (in decreasing order) toilet use, washing machine use, showers, baths, faucet use, and leaks. In some parts of the country there are water supplies that are dangerously low due to drought, particularly in the West and the South East region of the U.S.[better source needed]
One of the Millennium Development Goals (MDGs) set by the UN includes environmental sustainability. In 2004, only 42% of people in rural areas had access to clean water.
Solar water disinfection is a low-cost method of purifying water that can often be implemented with locally available materials. Unlike methods that rely on firewood, it has low impact on the environment.
One organisation working to improve the availability of safe drinking water in some the world's poorest countries is WaterAid International. Operating in 26 countries, WaterAid is working to make lasting improvements to peoples' quality of life by providing long-term sustainable access to clean water in countries such as Nepal, Tanzania, Ghana and India. It also works to educate people about sanitation and hygiene.
The Global Framework for Action (GF4A) is an organization that brings together stakeholders, national governments, donors and NGOs (such as Water aid) to define manageable targets and deadlines. 23 Countries are off-track to meet the MDG goals for improved water availability.
Some efforts at increasing the availability of safe drinking water have been disastrous. When the 1980s were declared the "International Decade of Water" by the United Nations, the assumption was made that groundwater is inherently safer than water from rivers, ponds, and canals. While instances of cholera, typhoid and diarrhea were reduced, other problems emerged.
Sixty million people are estimated to have been poisoned by well water contaminated by excessive fluoride, which dissolved from granite rocks. The effects are particularly evident in the bone deformations of children. Similar or larger problems are anticipated in other countries including China, Uzbekistan, and Ethiopia. Although helpful for dental health in low dosage, fluoride in large amounts interferes with bone formation.
Half of the Bangladesh's 12 million tube wells contain unacceptable levels of arsenic due to the wells not being dug deep enough (past 100 metres). The Bangladeshi government had spent less than US$7 million of the 34 million allocated for solving the problem by the World Bank in 1998. Natural arsenic poisoning is a global threat, 140 million people affected in 70 countries on all continents. These examples illustrate the need to examine each location on a case by case basis and not assume what works in one area will work in another.
Over 90% of deaths from diarrheal diseases in the developing world today occur in children under 5 years old. Malnutrition, especially protein-energy malnutrition, can decrease the children's resistance to infections, including water-related diarrheal diseases. From 2000-2003, 769,000 children under five years old in sub-Saharan Africa died each year from diarrheal diseases. As a result of only thirty-six percent of the population in the sub-Saharan region having access to proper means of sanitation, more than 2000 children's lives are lost every day. In South Asia, 683,000 children under five years old died each year from diarrheal disease from 2000-2003. During the same time period, in developed countries, 700 children under five years old died from diarrheal disease. Improved water supply reduces diarrhea morbidity by twenty-five percent and improvements in drinking water through proper storage in the home and chlorination reduces diarrhea episodes by thirty-nine percent.
Parameters for drinking water quality typically fall under three categories:
Physical and chemical parameters include heavy metals, trace organic compounds, total suspended solids (TSS), and turbidity.
Microbiological parameters include Coliform bacteria, E. coli, and specific pathogenic species of bacteria (such as cholera-causing Vibrio cholerae),viruses, and protozoan parasites.
Chemical parameters tend to pose more of a chronic health risk through buildup of heavy metals although some components like nitrates/nitrites andarsenic can have a more immediate impact. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens.
Originally, fecal contamination was determined with the presence of coliform bacteria, a convenient marker for a class of harmful fecal pathogens. The presence of fecal coliforms (like E. Coli) serves as an indication of contamination by sewage. Additional contaminants include protozoan oocysts such as Cryptosporidium sp., Giardia lamblia, Legionella, and viruses (enteric). Microbial pathogenic parameters are typically of greatest concern because of their immediate health risk.
Throughout most of the world, the most common contamination of raw water sources is from human sewage and in particular human faecal pathogens and parasites. In 2006, waterborne diseases were estimated to cause 1.8 million deaths each year while about 1.1 billion people lacked proper drinking water. It is clear that people in the developing world need to have access to good quality water in sufficient quantity, water purification technology and availability and distribution systems for water. In many parts of the world the only sources of water are from small streams often directly contaminated by sewage.
There is increasing concern over the health effects of engineered nanoparticles (ENPs)released into the natural environment. One potential indirect exposure route is through the consumption of contaminated drinking waters. In order to address these concerns, the U.K. Drinking Water Inspectorate (DWI) has published a "Review of the risks posed to drinking water by man-made nanoparticles" (DWI 70/2/246). The study, which was funded by the Department for Food and Rural Affairs (Defra), was undertaken by the Food and Environment Research Agency (Fera) in collaboration with a multi-disciplinary team of experts including scientists from the Institute of Occupational Medicine/SAFENANO. The study explored the potential for ENPs to contaminate drinking water supplies and to establish the significance of the drinking water exposure route compared to other routes of exposure.
Access to safe drinking water is indicated by proper sanitary sources. These improved drinking water sources include household connection, public standpipe, borehole condition, protected dug well, protected spring, and rain water collection. Sources that don't encourage improved drinking water to the same extent as previously mentioned include: unprotected wells, unprotected springs, rivers or ponds, vender-provided water, bottled water (consequential of limitations in quantity, not quality of water), and tanker truck water. Access to sanitary water comes hand in hand with access to improved sanitation facilities for excreta. These facilities include connection to public sewer, connection to septic system, pour-flush latrine, and ventilated improved pit latrine. Unimproved sanitation facilities are: public or shared latrine, open pit latrine, or bucket latrine.
Most water requires some type of treatment before use, even water from deep wells or springs. The extent of treatment depends on the source of the water. Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) designs. A few large urban areas such as Christchurch, New Zealand have access to sufficiently pure water of sufficient volume that no treatment of the raw water is required.
Over the past decade, an increasing number of field-based studies have been undertaken to determine the success of POU measures in reducing waterborne disease. The ability of POU options to reduce disease is a function of both their ability to remove microbial pathogens if properly applied and such social factors as ease of use and cultural appropriateness. Technologies may generate more (or less) health benefit than their lab-based microbial removal performance would suggest.
The current priority of the proponents of POU treatment is to reach large numbers of low-income households on a sustainable basis. Few POU measures have reached significant scale thus far, but efforts to promote and commercially distribute these products to the world's poor have only been under way for a few years.
In emergency situations when conventional treatment systems have been compromised, water borne pathogens may be killed or inactivated by boiling but this requires abundant sources of fuel, and can be very onerous on consumers, especially where it is difficult to store boiled water in sterile conditions and is not a reliable way to kill some encysted parasites such asCryptosporidium or the bacterium Clostridium. Other techniques, such as filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of water-borne disease among users in low-income countries, but these suffer from the same problems as boiling methods.
Guidelines for the assessment and improvement of service activities relating to drinking water have been published in the form of International standards for drinking water such as ISO 24510.
The EU sets legislation on water quality. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy, known as the water framework directive, is the primary piece of legislation governing water. The Drinking water directive relates specifically to water intended for human consumption.
Each member state is responsible for establishing the required policing measures to ensure that the legislation is implemented. For example, in the UK the Water Quality Regulations prescribe maximum values for substances that affect wholesomeness and the Drinking Water Inspectorate polices the water companies.
In the United States, the Environmental Protection Agency (EPA) sets standards for tap and public water systems under the Safe Drinking Water Act (SDWA). The Food and Drug Administration (FDA) regulates bottled water as a food product under the Federal Food, Drug, and Cosmetic Act (FFDCA). Bottled water is not necessarily more pure, or more tested, than public tap water. There is evidence that the United States federal drinking water regulations do not ensure safe water, as some of the regulations have not been updated with more recent science. Dr. Peter W. Preuss, who became the head of the U.S. EPA's division analyzing environmental risks in 2004, has been "particularly concerned", and has faced controversy in studies which suggest that regulations against certain chemicals should be tightened.
In 2010 the EPA showed that 54 active pharmaceutical ingredients and 10 metabolites had been found in treated drinking water. An earlier study from 2005 by the EPA and the Geographical Survey states that 40% of water was contaminated with nonprescription pharmaceuticals, and it has been reported that of the 8 of the 12 most commonly occurring chemicals in drinking water are estrogenic hormones. Of the pharmaceutical components found in drinking water, the EPA only regulates lindane and perchlorate. In 2009, the EPA did announce another 13 chemicals, hormones, and antibiotics that could potentially be regulated. The decision on whether or not they are sufficiently harmful to be regulated may not be decided upon until 2012 as it takes time for testing.
The qualitative and quantitative aspects of drinking water requirements of domesticated animals are studied and described within the context of animal husbandry. However, relatively few studies have been focused on the drinking behavior of wild animals. A recent study has shown that feral pigeons do not discriminate drinking water according to its content of metabolic wastes, such asuric acid or urea (mimicking faeces-pollution by birds or urine-pollution by mammals respectively).
Like many substances, water can take numerous forms that are broadly categorized by phase of matter. The liquid phase is the most common among water's phases (within the Earth's atmosphere and surface) and is the form that is generally denoted by the word "water." The solid phase of water is known as ice and commonly takes the structure of hard, amalgamated crystals, such as ice cubes, or loosely accumulated granularcrystals, like snow. For a list of the many different crystalline and amorphous forms of solid H2O, see the article ice. The gaseous phase of water is known as water vapor (or steam), and is characterized by water assuming the configuration of a transparent cloud. (Note that the visible steam and clouds are, in fact, water in the liquid form as minute droplets suspended in the air.) The fourth state of water, that of a supercritical fluid, is much less common than the other three and only rarely occurs in nature, in extremely uninhabitable conditions. When water achieves a specific critical temperature and a specific critical pressure (647 K and 22.064 MPa), liquid and gas phase merge to one homogeneous fluid phase, with properties of both gas and liquid. One example of naturally occurring supercritical water is found in the hottest parts of deep water hydrothermal vents, in which water is heated to the critical temperature by scalding volcanic plumes and achieves the critical pressure because of the crushing weight of the ocean at the extreme depths at which the vents are located. Additionally, anywhere there is volcanic activity below a depth of 2.25 km (1.40 mi) can be expected to have water in the supercritical phase.
Vienna Standard Mean Ocean Water is the current international standard for water isotopes. Naturally occurring water is almost completely composed of the neutron-less hydrogen isotope protium. Only 155 ppm include deuterium (2H or D), a hydrogen isotope with one neutron, and fewer than 20 parts per quintillion include tritium (3H or T), which has two.
Heavy water is water with a higher-than-average deuterium content, up to 100%. Chemically, it is similar but not identical to normal water. This is because the nucleus of deuterium is twice as heavy as protium, and this causes noticeable differences in bonding energies. Because water molecules exchange hydrogen atoms with one another, hydrogen deuterium oxide (DOH) is much more common in low-purity heavy water than pure dideuterium monoxide (D2O). Humans are generally unaware of taste differences, but sometimes report a burning sensation or sweet flavor. Rats, however, are able to avoid heavy water by smell. Toxic to many animals, heavy water is used in the nuclear reactor industry to moderate (slow down) neutrons. Light water reactors are also common, where "light" simply designates normal water.
Light water more specifically refers to deuterium-depleted water (DDW), water in which the deuterium content has been reduced below the standard155 ppm level.
Water is the chemical substance with chemical formula H2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygenatom. Water is a tasteless, odorless liquid at ambient temperature and pressure, and appears colorless in small quantities, although it has its own intrinsic very light blue hue. Ice also appears colorless, and water vapor is essentially invisible as a gas.
Water is primarily a liquid under standard conditions, which is not predicted from its relationship to other analogous hydrides of the oxygen family in the periodic table, which are gases such as hydrogen sulfide. The elements surrounding oxygen in the periodic table, nitrogen, fluorine, phosphorus, sulfur and chlorine, all combine with hydrogen to produce gases under standard conditions. The reason that water forms a liquid is that oxygen is more electronegative than all of these elements with the exception of fluorine. Oxygen attracts electrons much more strongly than hydrogen, resulting in a net positive charge on the hydrogen atoms, and a net negative charge on the oxygen atom. The presence of a charge on each of these atoms gives each water molecule a net dipole moment. Electrical attraction between water molecules due to this dipole pulls individual molecules closer together, making it more difficult to separate the molecules and therefore raising the boiling point. This attraction is known as hydrogen bonding. The molecules of water are constantly moving in relation to each other, and the hydrogen bonds are continually breaking and reforming at timescales faster than 200 femtoseconds. However, this bond is sufficiently strong to create many of the peculiar properties of water, such as those that make it integral to life. Water can be described as a polar liquid that slightly dissociates disproportionately into the hydronium ion (H3O+(aq)) and an associated hydroxide ion (OH−(aq)).
The dissociation constant for this dissociation is commonly symbolized as Kw and has a value of about 10−14 at 25 °C; see "Water (data page)" and "Self-ionization of water" for more information.
Percentage of elements in water by mass: 11.1% hydrogen, 88.9% oxygen.
Product certification or product qualification is the process of certifying that a certain product has passed performance tests and quality assurance tests, and meets qualification criteria stipulated in contracts, regulations, or specifications (typically called "certification schemes" in the product certification industry).
Most product certification bodies (or product certifiers) are accredited to ISO/IEC Guide 65:1996, an international standard for ensuring competence in those organizations performing product certifications. The organizations which perform this accreditation are called Accreditation Bodies, and they themselves are assessed by international peers against the ISO 17011 standard.Accreditation bodies which participate in the International Accreditation Forum (IAF) Multilateral Agreement (MLA) also ensure that these accredited Product Certifiers meet additional requirements set forth in "IAF GD5:2006 - IAF Guidance on the Application of ISO/IEC Guide 65:1996".
Examples of some certification schemes include the Safety Equipment Institute for protective headgear, the U.S. Federal Communications Commission (FCC) Telecommunication Certification Body (TCB) program for radio communication devices, the U.S. Environmental Protection Agency Energy Star program, the International Commission on the Rules for the Approval of Electrical Equipment Product Safety Certification Body Scheme (IEECE CB Scheme), and the Greenguard Environmental Institute Indoor Air Quality program. Certification schemes are typically written to include both the performance test methods that the product must be tested to, as well as the criteria which the product must meet to become Certified.
Certifications (and the certificates that document their existence) are often called "certs" in the everyday jargon of various industries.
A product might be verified to comply with a specification or stamped with a specification number. This does not, by itself, indicate that the item is fit for any particular use. The person or group of persons who own the certification scheme (i.e., engineers, trade unions, building code writers, government, industry, etc.) have the responsibility to consider the choice of available specifications, choose the correct ones, set qualification limits, and enforce compliance with those limits. The end users of the product have the responsibility to use the item correctly. Products must be used in accordance with their listing for certification to be effective.
Product certification is often required in sensitive industry and marketplace areas where a failure could have serious consequences, such as negatively effecting the health and welfare of the people or person using that product. For example, certification is stringent in aerospace applications, since the demands for low weight tend to lead to high stress on components, requiring appropriate metallurgy and accuracy in manufacturing. Other sensitive product area examples include food, pharmaceuticals, healthcare products, dangerous goods, and products which have RF emissions such as computers and cellular telephones.
The process for certification of a product is generally summed up in four steps:
In many instances, prior to applying for certification, a product supplier will send a product to a testing laboratory (some certification schemes require the product to be sent out for testing by the product certifier instead). When the product to be certified is received at the testing laboratory, it is tested in accordance with the laboratory's internal procedures and with the methods listed in the test standards specified by the certification scheme. The resulting data collected by the testing laboratory, and is then forwarded either back to the manufacturer, or directly to the product certifier.
The product certifier then reviews the product supplier's application information, including the testing data. If the certifier's evaluation concludes that the test data shows that the product meets all required criteria as listed in the certification scheme, and the decision maker(s) of the product certifier concur with the evaluation, then the product is deemed "certified" and is listed in a directory which the Product certifier is required to keep. ISO Guide 65 requires that the final decision to grant or not grant certification be made only by a person or group of persons not involved in the evaluation of the product.
Products often need periodic recertification, also known as surveillance. This requirement is typically identified within the certification scheme that the product is certified to. Certification bodies may require product suppliers to perform some sort of surveillance activity, such as pulling sample products from the marketplace for testing, in order to maintain their "listed" or "certified" status. Other examples of Surveillance activities include surprise audits of the manufacturing plant, supervision of the manufacturing and/or testing process, or a simple paperwork submittal from the supplier to the product certifier to ensure that the certified product has not changed. Other causes for recertification may include complaints issued against the product's functionality which would require removal from the marketplace, and expiration of the original certification. These lists of examples are by no means all inclusive.
Some certification schemes, or the product certifiers which operate those Schemes, may require that the product supplier operate a Quality Management System registered to ISO 9000, or that the testing be performed by a laboratory accredited to ISO 17025. The decision to set these requirements is most often made by the person or group which owns the Certification Scheme.
Certified products are typically endorsed with a certification mark provided by the product certifier. Issuance of a certification mark is at the discretion of the individual product certifier. ISO Guide 65 does not require the product certifier to offer a certification mark in the event that a certificate is offered. When certification marks are issued and used on products, they are usually easy to see and enable users to track down the certification listings to determine the criteria that the product meets, and whether or not the listing is still active.
An active certification listing must minimally include indication of the following information:
Product certifiers may choose to include much more information than that listed above, but ISO Guide 65 specifies the bare minimum which must be made available regarding the certification status of a product.
These listings are typically used by an Authority Having Jurisdiction (AHJ), such as a municipal building inspector, fire prevention officer, or electrical inspector, to compare the product's use or installation with the intent of the rating by testing. In order to comply with the code, the product listing must be "active", as products and companies can become "de-listed" due to re-testing showing that a product no longer meets qualification criteria, or a business decision by the manufacturer.
The International Accreditation Forum (IAF) has a listing of all recognized Accreditation Bodies whose accreditations to the ISO Guide 65 standard are deemed equivalent. From the IAF MLA informational page:
Most countries only have a single Accreditation Body representing their economy in the IAF MLA. The two exceptions are the United States with American National Standards Institute (ANSI), American National Standards Institute - American Society for Quality National Accreditation Board (ANAB, a subdivision of ANSI), American Association for Laboratory Accreditation (A2LA), and International Accreditation Service (IAS) as signatory members, and Korea which is represented by Korea Accreditation Board (KAB) and Korean Accreditation System (KAS). These listings are current as of March 2012, but will likely change in the future as more Accreditation Bodies undergo the required peer evaluations in order to become signatory members of the MLA.
Each Accreditation Body is required to keep a listing of those organizations it accredits, as well as a Scope of Accreditation which details the activities that the organizations can perform, whether that be testing, inspection, or product certification.
Accreditation Bodies routinely audit the Product Certifiers whom they have accredited in order to determine if the performance or actions of the organization have changed and do not meet the requirements of the Accreditation Body and the International Standards they are to conform to.
North America's nuclear industry is exempt from mandatory certification. This has allowed situations leading to large amounts of remedial work, especially for fireproofing of electrical circuits (circuit integrity) between nuclear reactor and control rooms in the U.S. In this case, submitors were permitted to dictate not only their test procedures, but also to construct test specimens in their own facilities, prior to fire tests on the part of laboratories. The primary example of this situation is the Theromo-Lag Scandal, which came about as a result of disclosures bywhistleblower Gerald W. Brown to the Nuclear Regulatory Commission as well as watchdog groups, members of US Congress, and the press.
The United Kingdom is also unique among western industrialized nations, as product certification is entirely optional.
In Germany, the accredited testing organizations routinely audit manufacturing locations and submit quality control test results to DIBt. While the German laboratories do not possess process standards, their methodology can uncover changes in the nature and quality of ingredients, as DIBt establishes very clear tolerances for performance.
Where product certification is optional, one must rely on the ethics of the manufacturer that the item being sold is identical to the item that was tested, and that the item that was tested was in fact installed the way the test report reads. The test report by itself also does not afford its bona fide interpretation in terms of the tolerances that a certification listing would provide.