Water Quality: Information, Importance and Testing

Water quality refers to the suitability of water for different uses according to its physical, chemical, biological, and organoleptic (taste-related) properties. It is especially important to understand and measure water quality as it directly impacts human consumption and health, industrial and domestic use, and the natural environment. Regulations such as the EU Drinking Water Directive and regulatory agencies such as the US Environmental Protection Agency (EPA) set standards for enforcement of water quality, with local governments around the world usually acting as the front-line enforcers.

Water quality is measured using laboratory techniques or home kits. Laboratory testing measures multiple parameters and provides the most accurate results but takes the longest time. Home test kits, including test strips, provide rapid results but are less accurate.

Water suppliers including municipalities and bottled water companies often make their water quality reports publicly available on their websites. The tested water quality parameters must meet standards set by their local governments which are often influenced by international standards set by industry or water quality organizations such as the World Health Organization (WHO).

What Is Water Quality?

Water quality is “a measure of the suitability of water for a particular use based on selected physical, chemical, and biological characteristics” according to the United States Geological Survey (USGS). Therefore, it is a measure of water conditions relative to the need or purpose of humans or even the requirements of various land or aquatic animal species.

Three types of parameters of water quality are measured. These include physical, chemical, and biological/microbiological parameters.

• Physical parameters of water quality are those that are determined by the senses of sight, smell, taste, and touch. These physical parameters include temperature, color, taste and odor, turbidity, and content of dissolved solids.
• Chemical parameters of water quality are measures of those characteristics which reflect the environment with which water has contact. These chemical parameters can measure pH, hardness, amount of dissolved oxygen, biochemical oxygen demand (BOD), chemical oxygen demand (COD), and levels of chloride, chlorine residual, sulfate, nitrogen, fluoride, iron and manganese, copper and zinc, toxic organic and inorganic substances, as well as radioactive substances.
• Biological parameters of water quality are those measurements that reflect the number of bacteria, algae, viruses, and protozoa that are present in water.

Water quality is influenced by anthropogenic activities and natural factors. These are some of the factors which affect water quality.

• Atmospheric pollution
• Runoff
• Erosion and Sedimentation

Water quality is tested in a laboratory or at home based on the local conditions and needs. Laboratory evaluation of water quality is based on instrumental and chemical analysis of collected field water samples. Laboratories are able to measure multiple physical, chemical, and biological parameters of these samples and provide highly accurate results. Unfortunately, laboratory tests for water quality are costly and require time.

At-home water quality testing methods, such as strips, color disks, and digital instruments, are used to rapidly check for the presence and/or concentration of common water contaminants. These at-home tests can be used as screening tools to determine whether further laboratory analysis of water quality is warranted. They are used in commercial or industrial settings for initial screening tools. This is a picture of typical water test strips, in this case, used for testing aquarium water quality.

What Are the Categories of Water Quality?

The categories of water quality based on its different uses are as follows.

1. Water Quality for Human Consumption
2. Water Quality for Industrial and Domestic Use
3. Environmental Water Quality

1. Water Quality for Human Consumption

Water quality for human consumption covers safe drinking and cooking water which are both vital for maintaining human health and form part of public health policy. Access to high-quality water fit for human consumption, known as “potable water”, is a fundamental human right and a necessity for healthy life and development for individuals and societies. This right was enshrined in international law by UN Resolution 64/292 in July of 2010.

Throughout the world, not all people have access to high-quality water. According to WHO statistics, approximately 785 million people lack basic drinking-water service and over 2 billion consume potable water that is contaminated with feces. This is often linked with the transmission of diseases such as cholera, diarrhea, dysentery, hepatitis A, typhoid, and polio. The WHO estimates that 829,000 people, out of which 297,000 are children under the age of 5 years, die annually due to diarrheal disease resulting from consumption of unsafe water.

This map of death rates from diarrhea-related illnesses by country comes from the public Our World in Data project.

2. Water Quality for Industrial and Domestic Use

In industrial settings, a specific type of water called “process water” is used. Process water refers to water that is used in industry, manufacturing processes, power generation, and similar applications. Water quality standards for process water are meant to prevent damage to industrial machinery and to prevent the contamination of industrially processed products.

Process water quality standards for different industries and plants vary enormously. In the United States some, but not all, process water parameters for industrial use can be found in the Report of the Committee on Water Quality Criteria, the "Green Book" (FWPCA, 1968) and Water Quality Criteria 1972, the "Blue Book" (NAS/NAE, 1973). Furthermore, according to the US Environmental Protection Agency (EPA) in the case of non-existent standards for a given industry, which is often the case, criteria developed for human consumption can be substituted to protect these uses.

To highlight the complexity of industrial use of water quality standards, WHO international parameters for water used in the pharmaceutical industry can be taken as an example. Process water for the pharmaceutical industry is subject to water quality regulations relating to its storage, distribution, sanitization, bioburden control, as well as its distribution system monitoring, maintenance, and inspection.

Water used for non-drinking domestic purposes covers uses like water for sanitation and hygiene which are critical aspects of public health. Although one would imagine that an organization such as the EPA would have separate standards for the quality of non-drinking domestic water, the regulation for domestic use water appears to be the same as those of potable water.

This is a diagram of various water treatment processes and related industrial uses according to the Water Quality Criteria 1972 report.

3. Environmental Water Quality

Environmental water quality is highly important for the well-being of flora and fauna in oceans, rivers, lakes, swamps, and wetlands. It impacts people and higher-order species which depend on these ecosystems for food and transfer of nutrients. As such, governmental organizations have regulated different subcategories of environmental water quality.

The US EPA regulates environmental water quality parameters for the protection and propagation of fish and shellfish populations, waterfowl, shorebirds, and other water-oriented wildlife. Environmental water quality parameters are regulated for the protection and preservation of coral reefs, marinas, groundwater, and aquifers.

Poor environmental water quality related to contamination by chemicals or microorganisms from farms, towns, and factories is an ever-growing issue. According to United Nation statistics, more than 80 percent of the world’s wastewater flows back into the environment without being treated. This degree of contamination poses risks to humans and aquatic wildlife alike.

Particularly notable examples of environmental water quality degradation as a result of chemical contamination have occurred in Japan during the 20th century. These include Itai-Itai and Minamata diseases, which were the result of industrial contamination by cadmium and methyl mercury of important water sources used for irrigation, drinking water, washing, and fishing by downstream populations. This video from Hank Green of SciShow tells the story of Minamata disease in the 1950s.

What Is the Importance of Water Quality?

Water quality’s importance is the manner in which it assures that end-users will remain healthy and well-functioning if proper standards are maintained. The end users may be people drinking healthily, industries operating without impediments caused by off-spec water, or natural environments thriving thanks to lack of pollution. Each user has a concentration threshold for the different contaminants, beyond which poorer quality water will have adverse effects.

Water Quality Effects on Human Health: Poor quality of potable, domestic use, or even recreational water due to contamination can lead to human illness. Drinking water contaminated with microbial organisms contributes heavily to the global burden of disease in the form of diarrhea, cholera, dysentery, hepatitis A, typhoid, and polio. According to the WHO, cholera affects 1.4 to 4 million people and accounts for 21,000 to 143,000 deaths globally every year. This map from the WHO shows countries where cholera was reported from 2010 to 2015.

Contamination of water sources by chemicals such as solvents, heavy metals, and pesticides poses human risk. Chronic exposure to heavy metals such as arsenic, chromium, lead, mercury, and cadmium can increase the risk of cancers of the blood, lung, liver, urinary bladder, and kidney.

Water Quality Effects on the Environment: Contamination of water has negative effects on the environment and on the flora and fauna that depend on it. Oil spills, radioactive leaks, garbage, chemical leaks, and many other forms of contamination can kill, injure, or disrupt the biological processes of plants and animals.

This video from the US National Oceanic and Atmospheric Administration (NOAA) reviews the impact of the infamous Deepwater Horizon oil spill in 2010 and the subsequent decade of efforts to clean it up.

One of the most significant problems is eutrophication. Eutrophication occurs when the environment becomes enriched with nutrients such as nitrates and phosphates.

A significant source of eutrophic nutrients is fertilizers from agricultural pollution. The excessive nutrients cause harmful algal blooms which consume massive amounts of oxygen and produce hypoxic dead zones and massive fish kills. The US National Oceanic and Atmospheric Administration (NOAA) reports that up to 65 percent of estuaries and coastal waters in the United States are affected by mild to moderate degrees of eutrophication, with prominent examples being the dead zones of the northern Gulf of Mexico and Laurentian Great Lakes.

Water Quality Effects on Industry: Almost all industrial manufacturing processes require significant amounts of water. Different industries require specific qualities of water in order to manufacture precise and sensitive products. As an example, the manufacturing of semiconductors and chips for use in computers and medical electronics requires deionized, ultrapure water that is devoid of minerals, dissolved gasses, and solid particles. As such, the use of possibly polluted water that contains heavy metals or other contaminants in this manufacturing process could lead to the production of imprecise and faulty end products.

Similarly, according to the SUEZ Water Technologies Handbook, water that is used for cooling of processes or equipment must be devoid of chemical, mineral, and microbiological contaminants as high temperatures can affect their behavior and result in the tendency of a system to corrode, scale, or support microbiological growth. Similar water quality requirements can be found in pharmaceutical, oil, gas, and other industries.

What Are the Factors and Indicators That Affect Water Quality?

These are factors that affect water quality.

• Atmospheric pollution: Environmental air pollution with gasses such as carbon dioxide, sulfur dioxide, and nitrogen oxides mix with water particles in the air to produce polluted rain, sometimes referred to as acid rain. Acid rain then pollutes water systems.
• Runoff: Runoff refers to the flow of excess water across the surface of the land and into waterways. As the water flows, it can pick up agricultural and industrial pollutants such as litter, petroleum, chemicals, fertilizers, and other toxic substances which then contaminate water.
• Erosion and Sedimentation: Soil erosion increases the amount of sediment which enters the water. This can contribute to the degradation of water quality because toxic chemicals or naturally occurring but unhealthy elements can become attached or adsorbed to sediment particles and then be transported to bodies of water.

This video from the University of Notre Dame’s Environmental Change Initiative describes how fertilizer runoff pollutes environmental and drinking water, and some possible solutions to the problem.

These are water quality indicators and parameters that reflect the impact of natural and artificial processes.

• Turbidity: Turbidity refers to the cloudiness of water and is a measure of the ability of light to pass through it. Turbidity is caused by different suspended materials in water such as organic material, clay, silt, and other particulate matter. High turbidity is aesthetically unappealing and increases the cost of water treatment. Particulate matter provides hiding places for harmful microorganisms, shields them from disinfection processes, and absorbs heavy metals and other harmful chemicals.
• Temperature: Temperature has indirect influences on water quality. It influences the palatability, viscosity, solubility, and odor of water. It affects the disinfection and chlorination processes, biological oxygen demand (BOD), and the way heavy metals behave in water.
• Color: Color reflects the concentration of vegetation and inorganic matter in water. Although it has no direct influence on the safety of water, it makes water aesthetically unappealing.
• Taste and Odor: Taste and odor affect the aesthetic qualities of water. They are determined by the presence of natural, domestic, or agricultural foreign matter in water.Total Solids (TS): In water two types of solids are present, Total Dissolved Solids (TDS) and Total Suspended Solids (TSS). Solids represent the amount of minerals (good or bad) and contamination present in water. When harmful solids are present, it affects the quality of water by affecting turbidity, temperature, color, taste, odor, electrical conductivity, and dissolved oxygen content.
• Electrical conductivity (EC): Electrical conductivity indirectly measures the ionic concentration of water by measuring its ability to carry or conduct an electrical current. Higher conductivity means more solids are present in the water.
• pH: pH measures how acidic or basic water is. Excessively high or low (<4 or >11) pH is detrimental for the use of water as it alters the taste, effectiveness of its chlorine disinfection process, and increases the solubility of heavy metals in water making them more toxic.
• Hardness: Hardness is a property of mineralized water, and it measures the concentrations of certain dissolved minerals, particularly calcium and magnesium. Hard water can cause mineral buildup in hot water pipes and cause difficulty in producing lather with soap. Very hard water (>500 mg/L of CaCO3) can even have laxative properties.
• Dissolved oxygen (DO): Dissolved oxygen is an indirect measure of water pollution in streams, rivers, and lakes. The lower the concentration of dissolved oxygen, the worse the water quality. Water with very little or no oxygen tastes bad to most users.
• Biochemical oxygen demand (BOD): Biochemical oxygen demand indirectly measures the degree of microbial contamination, and is primarily used as a measurement of the power of sewage water. As microorganisms metabolize organic substances for food, they consume dissolved oxygen (DO) in water. As such, BOD is an indirect indicator of organic material in water.
• Chemical oxygen demand (COD): Chemical oxygen demand measures the oxygen necessary to oxidize all biodegradable and non-biodegradable substances in the water.
• Toxic inorganic substances: Toxic inorganic substances measure the concentrations of metallic and nonmetallic compounds such as arsenic, silver, mercury, lead, cadmium, nitrates, and cyanide. The parameters regarding toxic inorganic substances are essential for assessing the quality of water, as their presence, sometimes even in trace amounts, poses a danger to public health.
• Toxic organic substances: Toxic organic substances refer to compounds such as insecticides, pesticides, solvents, detergents, and disinfectants that degrade water quality and pose a danger to human health.
• Radioactive substances: Radioactive substances decay to emit beta, alpha, and gamma radiation, which has numerous detrimental effects on human health. Radiation primarily affects hematopoietic, gastrointestinal, reproductive, and nervous systems; and is highly carcinogenic. Water quality parameters therefore commonly monitor the concentrations of alpha particles, beta particles, radium, and uranium.
• Bio-indicators: Biological parameters of water quality analyze the presence or absence of various bacteria, algae, viruses, and protozoa.

How to Test Water Quality

Water quality can be tested at a water quality laboratory or at home using prefabricated testing kits.

Laboratory water quality testing requires collecting samples in sterile bottles and sending them to an accredited laboratory for analysis. General chemistry samples are preserved and chilled before being transported, but microbiological samples need to be transported to laboratories within 24 hours of sampling. Laboratory testing results take days but are the most accurate testing method as well as the most expensive. Analysis is done for hundreds of physical, chemical, biological, and radiological parameters.

Home water quality testing is a simpler approach for checking for the presence and/or concentrations of some of the more common water constituents at home or other small sites. The results of home testing are rapid and come in seconds or minutes. According to World Bank water and sanitation specialists Jessica Anne Lawson and Pratibha Mistry, home water quality testing is done via the following 3 methods.

• Test strips are strips of paper with squares that change color when dipped in water depending on the presence and concentration of the parameter being tested. They are generally the cheapest form of water quality testing and exist for many parameters including TDS, pH, hardness, nitrates, chemical cleansers, and others. Some strips measure only a single parameter while others may have multiple measurements on one strip. To interpret the results, the user waits a specified amount of time after dipping the strip in the water, then compares the new color of the square with those on a color chart supplied with the kit.
• Color disk kits are a little more expensive than strips and only test for one parameter at a time. A water sample is added into a plastic container simultaneously with a liquid or powder reagent. The container is inserted into a small viewing box with a color disk for observation. The color disk is rotated until the color of the water sample matches that of the disk and the concentration is read off from the disk.
• Digital instruments are non-disposable, handheld, battery-powered electronic devices that are the most accurate and expensive home water quality testing tools. Inexpensive digital instruments can be found for US$15 or less that measure pH, temperature, Total Dissolved Solids (TDS), or Electrical Conductivity (EC). Handheld salinity meters may cost four times as much. Colorimeters can cost many hundreds to well over a thousand US dollars but can measure dozens of chemical and physical water properties by measuring which wavelengths of light are absorbed by the material in the water.

This video shows how a handheld electronic TDS meter works.

How Can You Learn about Water Quality in Your Area?

You can learn about water quality in your area from government services that provide links to their official water quality reports, and from non-government organizations that provide databases to access a wide variety of public and private reports, sometimes even carrying out their own tests and research.

Services: Most municipalities and utilities in the US and Europe provide regular water quality reports that are available on their websites. Similar transparency is found in much of the developed world such as municipal governments in Australia and New Zealand, though it is less consistent in the developing world. Larger government agencies provide links to local water quality information.

In the US, the EPA provides Consumer Confidence Reports (CCR), which are annual reports that inform consumers about the quality of their local drinking water, and many states have links for such information. In the European Union, such information is available on the website of the European Environment Agency. Some developing countries like South Africa and India have local water quality data published by their Departments of Water and Sanitation and the Department of Water Resources respectively.

This is an example of a typical public utility water report. In this case, the report is from the UK’s Thames Water Utilities in London showing the parameters being measured, regulatory limits, and sample numbers and results.

Organizations: Some international and non-governmental organizations (NGOs) such as the World Health Organization (WHO), United Nations Educational, Scientific and Cultural Organization (UNESCO), World Water Council, The World Bank, The Water Project as well as numerous others provide reports and guidelines on water quality.

For example, The World Water Development Report (WWDR) published by UNESCO provides information on challenges and opportunities for improved water management throughout the world. The United Nations Environment Program (UNEP) publishes the Global Drinking Water Quality Index Development and Sensitivity Analysis Report which analyzes and combines numerous international indices such as the Scatterscore index, Chemical Water Quality Index, and the Well-being of Nations Environmental Performance Index.

What Water Quality Organizations Exist?

The following water quality organizations exist to provide consumers, industry, and government with reports on water quality in order to ensure that proper standards for high quality, safe water are maintained. There are literally thousands of such organizations around the world, but these are some of the most important.

• The United States Environmental Protection Agency (EPA) publishes Annual Water Quality Reports from regional water suppliers. These reports, called Consumer Confidence Reports (CCR), offer Americans information on source water, the levels of detected contaminants, and compliance with drinking water rules for their respective regions.
• In Canada, all municipalities publish annual drinking water quality reports which are compliant with federal regulatory requirements such as Guidelines for Canadian Drinking Water Quality and often with respective regional health authority requirements. These reports provide information about monitoring and safety of source and transmission water systems, water conservation, as well as information on physical, chemical, and bacteriological parameters.
• The United Nations Environment Programme offers “A Snapshot of the World’s Water Quality” which was published in 2016. This document provides information on important water quality problems including pathogen pollution, organic pollution, salinity pollution, and eutrophication chiefly in the developing countries of Latin America, Africa, and Asia.
• Water Quality Association, an NGO which focuses on water safety for private consumers, publishes a Contaminant Occurrence Study and Map which compiles data for different drinking water parameters across the United States. The report contains data on contaminant levels that are above health-based goal levels as well as data on the aesthetic parameters of water.
• The World Water Council is an “organization of organizations” that upholds international water quality standards by regularly assessing water resources and monitoring their use. This raises awareness of water security and helps bring together different public policies to ensure access to water. The World Water Council holds frequent water forums which produce case studies and fact sheets regarding water quality and access.

In this video, members of the World Water Council discuss the mission of the organization and the key issues they focus on.

What Are the Responsibilities of Water Quality Associations?

The responsibilities of water quality associations are to ensure the safety of water for public and environmental health. They develop and write regulations in accordance with local governments and set standards for water quality. They assist with the enforcement of these regulations by helping individuals and other organizations to understand and adhere to them.

Local water quality associations publish water quality assessment reports which provide consumers with essential information on the safety parameters of the water they consume. Additionally, water quality associations are heavily involved in pursuing and funding research that focuses on identifying and solving problems that revolve around the safety and sustainability of water resources.

What Water Quality Standards Exist?

Water quality standards exist in every country in the world including the EU’s Drinking Water Directive and the US Clean Water Act. These standards set limits on the maximum or minimum levels of key physical, chemical, and biological components found in water. They are normally set by national or regional authorities for drinking water or treated wastewater. Their purpose is to ensure that safe drinking water is supplied to the public and wastewater is treated to an acceptable level that is safe for discharge into public streams, rivers, and waterways. These are some of the key water quality standards around the world.

• The US Clean Water Act for tap water and wastewater, which is enforced by the US Environmental Protection Agency (EPA).
• The unhelpfully cryptically named CFR 21 rules for US bottled water as enforced by the US Food and Drug Authority (FDA).
• The EU Drinking Water Directive as enforced by the European Environment Agency (EEA).
• The Australian National Water Quality Management Strategy of the Australian Government (NWQMS) offers guidance in the forms of Australian Drinking Water Guidelines (ADWG), Effluent Management in Australia, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Guidelines for Groundwater Quality Protection in Australia, Guidelines for Managing Risks in Recreational Water, and the Australian Guidelines for Water Recycling.
• The National Environmental Water Quality Standards formulated under the Environmental Protection Law and Law of Water Pollution Prevention and Control of the People’s Republic of China.
• The Department of Water and Sanitation of the Republic of South Africa offers guidelines and parameters for water quality in domestic, recreational, industrial, agricultural, and aquatic environments.
• The National Environmental Agency(NAE) of Singapore regulates water pollution and quality in Singapore's sewerage system, as well as inland bodies of water and coastal areas.
• The Central Water Commission (CWC) of the government of India is responsible for the control, assessment, conservation, and utilization of water resources throughout the country.

This video from the LawShelf project at the National Paralegal College explains the origins, requirements, and enforcement of the US Clean Water Act.

Many countries develop national water quality standards based on international guidelines like the World Health Organization’s Guidelines for Drinking Water Quality (GDWQ), and the joint WHO-FAO Codex Alimentarius for bottled water. The GDWQ and Codex Alimentarius guidelines act as a minimum guiding mechanism from which countries adapt, sometimes setting stricter standards. Currently, the Codex Alimentarius Commission has 189 codex members made up of 188 member countries which have used these standards as a baseline for developing their own regulations.

How to Treat Water and Improve Its Quality

Treatment of water to improve its quality such that it is suitable for subsequent use by humans can require physical, chemical, or biological processes. Some degree of “treatment” occurs even in nature, however higher water contamination levels require sophisticated engineering processes. The following are some of the major processes by which water can be treated and purified.

• Distillation involves evaporation and condensation of water to produce to leave behind only pure water. Though volatile organic substances that evaporate at or below the boiling point of water can remain and may require other treatment processes to remove. Distillation is used to produce desalinated water or when water with special qualities is needed.
• Gas Exchange and Aeration adds oxygen to water and removes dissolved gasses such as carbon dioxide and hydrogen sulfide. Gas exchange helps reduce unpleasant tastes and odors and helps the oxidation of iron and manganese, making the metals more easily removable.
• Coagulation and Flocculation can occur naturally or be aided by adding coagulants such as aluminum sulfate or other synthetic polymers. Coagulation causes colloidal and suspended particles that impart turbidity, odor, or taste to water to come together and form large “flocs” that settle easily during the purification process and can be physically removed by passing the water through sediment beds or filters.
• Sedimentation uses engineered water purification facilities in which water flow is minimized such that gravity allows water-borne particulates including bacteria to settle and be captured in a sediment layer. This process is aided by coagulation and flocculation, as larger particulate matter settles faster.
• Filtration can first occur naturally as water percolates through the soil. However, in engineered water purification facilities, water is passed through granular media or membranes which capture fine particulate matter. Filtration is important for removing very fine particles including any floc particles that escape the earlier sedimentation tank.
• Adsorption involves passing water through special media such as activated carbon, both in granular form as filters and in powdered form as an additive to water, which then adsorbs water contaminants. This process is used to remove unpleasant tastes and odors and a wide variety of organic chemical contaminants that may have made it through the previous phases of purification.
• Ion Exchange passes water through natural and synthetic resins that remove specific ion contaminants. The most common products are zeolites that remove calcium and magnesium (the main components which make water hard) and replace them with sodium.
• Disinfection processes destroy pathogenic microorganisms that may cause water-borne disease. The most widespread disinfection procedure for water purification is chlorination, with UV light treatment and ozonation (O₃) common.

This video gives detailed illustrations of typical municipal drinking water and wastewater treatment plants and the processes they use.

Other water treatment processes are available for specific applications, such as to help prevent corrosion, to manage the solids or sludge that accumulate during the water treatment process, or to remove substances such as ammonia, phosphorus, radioactivity, or other contaminants specific to the community’s geological location or industrial activities.

The selection of treatment processes is dependent on the quality of the water source and the end target for it. For potable water that is derived from protected groundwater sources, only aeration and disinfection may be needed. While for heavily polluted surface water sources, multiple treatment processes for physical, chemical, and biological contaminants may be appropriate.

What Are the Best Countries for Water Quality?

The best countries for water quality in the world are the following according to the Environmental Performance Index (EPI) from the Yale Center for Environmental Law & Policy. The EPI measures water quality based on data for years of life lost per 100,000 people due to unsafe water. The first six countries are tied for number 1 because they all scored a full 100 out of 100 on the EPI’s metrics.

• Finland: According to the Finnish Environment Institute, groundwater can be found in almost every part of Finland, with over 6000 aquifers throughout the country. The quality of these aquifers rank among the best reserves of groundwater in the world, is generally soft, has low concentrations of dissolved solids, and has a low pH of 6 to 7.
• Iceland: A study by the Faculty of Civil and Environmental Engineering at the University of Iceland evaluated the quality of drinking water in Iceland and found its compliance with the Icelandic Drinking Water Regulation (IDWR) was 99.97% for health-related chemicals and 99.44% in key indicator parameters.
• Netherlands: Drinking water in the Netherlands is of very high quality, with 60% sourced from groundwater and 40% from surface water. According to the National Institute for Public Health and the Environment of the Netherlands, drinking water quality meets EU requirements in over 99.9% of all measurements.
• Norway: The Norwegian Institute of Public Health (NIPH) reports that “Norway has access to good water sources that can be protected against pollution. The level of pollutants, pesticides, heavy metals, and other unwanted substances in water is low.” A 2017 research paper by Beka Abiyos of the Norwegian University of Life Sciences sampled 201 water systems covering 5% of Norway’s population and found none that exceeded national nitrate limits. In Norway’s isolated arctic islands of Svalbard, icebergs naturally calving off glaciers provide water preserved from snow that fell thousands of years before modern pollution. Lab tests for Svalbarði Polar Iceberg Water are often unable to detect any nitrates.
• Switzerland: According to the Association of Swiss Water Suppliers (SVGW), Swiss drinking water is of very high quality and meets stringent standards regarding hygiene and safety. Switzerland derives its water supply from both ground (40%) and spring (40%) water equally, with the pristine environment of the Alps playing a major role in their natural processing.
• United Kingdom: According to the annual reports of the UK Drinking Water Inspectorate, over 99% of samples in England, Wales, Scotland, and Northern Ireland are in compliance with UK and European drinking water standards.
• Malta: Malta’s presence on the top 10 best quality water list may come as a surprise given the negative discussion of its taste and claims of unhealthiness. However, testing confirms it meets EU, WHO, and Maltese standards at a high level of compliance. It is derived from both groundwater and desalinated seawater. It is hard and has a fair amount of chloride, so the taste may not always be to many people’s liking.
• Germany: According to the German Environment Agency’s (UBA) drinking water report, 99.9% of samples taken from the utilities which supply 88 percent of Germany's households were found to be in compliance with the EU Drinking Water Directive.
• Luxembourg: This small country utilizes a mix of surface and spring water. Despite being a traditionally mineral-water-focused country, an August 2020 study by the country’s Association of Water Services found that 80% of people drink tap water regularly with half saying they consider the taste as good or better than bottled water.
• Sweden: Sweden has one of the highest surveyed satisfaction rates when it comes to water quality, coming in at 95%. The Organization for Economic Co-operation and Development (OECD) and the European Commission in their environmental performance review on Sweden stated that Sweden rated very high (99-100%) for all microbiological, chemical, and indicator parameters set out in the European Drinking Water Directives.

This map shows the EPI sanitation and drinking water scores for all countries in the survey, with blue the highest quality and red the lowest.

A slightly different approach that covers only the OECD countries is the Better Life Index’s water quality series. It measures the percentage of people in the Gallup World Poll satisfied with their local water quality and comes up with a similar though not identical top 10 list of countries with the best water quality.

1. Iceland (98%)
2. Norway (94%)
3. Sweden (96%)
4. Denmark (95%)
5. Finland (95%)
6. Switzerland (95%)
7. Australia (93%)
8. Netherlands (93%)
9. Austria (92%)
10. Canada (91%)

What Is the Best Quality Water?

The best quality water in terms of meeting human, industrial, and environmental needs is Icelandic public water. Icelandic water, such as at the Hvítá river in this picture, is clean, abundant, lightly mineralized by volcanic rock, slightly alkaline, and subject to minimal human contamination.

The best quality water meets the needs of the user while requiring the least amount of treatment. Water that needs minimal processing before usage has fewer potential contamination fail points in the process of purification. On this basis, the best quality water meets the following criteria.

• For human drinking needs. Naturally free of pollutants at the source. Has a clean distribution system that does not require disinfectants. Has a healthy mineral composition. Has a taste users enjoy. Is regularly tested to ensure constant purity until it reaches the consumer.
• For industrial purposes. Soft with minimal minerals and contaminants so that it cannot foul machinery, end products, or water delivery or disposal systems. But it must have a light mineral content as near-zero would cause it to easily absorb materials it passes by and through, potentially causing damage. pH should be 7 or slightly higher as being acidic would cause it to be corrosive and too alkaline could be corrosive with certain specific metals such as zinc.
• For natural environments. This refers to used wastewater that will be returned to the environment after treatment. The source and usage locations have a minimal amount of industrial and agricultural runoff. It must be in a location with good post-usage water treatment systems. And it must have high natural purity and light mineral content before usage such that it will have the least possible reactions with the impurities it passes through before being treated.

On this basis and according to 2020 lab results reported by Veitur Utilities (as measured at Akranes), Icelandic tap water in the Reykjavik region fulfills the criteria best in the world.

• The Environmental Performance Index (EPI) ranks Icelandic tap water in the number 1 position for human safety.
• Veitur Utilities reports it requires no chemical, physical, or biological treatment because of its purity at its borehole source from whence it is immediately fed into the distribution system.
• Water quality is constantly monitored throughout the Reykjavik region’s water distribution system.
• TDS of 75 mg/l. Low enough to prevent most industrial fouling and have relatively few components to react with when used (i.e., before treatment and re-release into the environment). Yet high enough to prevent corrosion and provide at least a light mineral supplement to drinkers.
• Slightly alkaline pH of 7.3 for water, sufficient to be non-corrosive on either the acidic or alkaline sides of the spectrum.
• Low population country with minimal sources of industrial and agricultural runoff and high-quality water treatment facilities.
• Number 1 position on the OECD Better Life water quality index, with 98% of people surveyed satisfied with their water quality.

There are of course other countries with very high-quality water that could come in a close second, including many of the Scandinavian countries and Switzerland. But Iceland, at least in the Reykjavik region, has a unique combination of factors that make it the best quality water.

Svalbarði Polar Iceberg Water is unique from other high-quality Scandinavian waters because of its iceberg source making it a luxury water. Having been preserved inside a glacier for hundreds or even thousands of years before modern pollution, when it emerges as an iceberg it has extreme chemical and physical purity. The fact that it can be preserved in its solid ice state until right before bottling keeps it safe. It is not quite as ideal for industrial purposes since it has the slightly acidic pH of clean precipitation (caused by interacting with natural atmospheric gasses when it originally fell as snow), but it does have a light and airy taste that consumers regularly report is among their favorites.