water, a substance composed of the chemical elements hydrogen and oxygen and existing in gaseous, liquid, and solid states. It is one of the most plentiful and essential of compounds. A tasteless and odourless liquid at room temperature, it has the important ability to dissolve many other substances.

1. 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).

2. 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.

3. 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
4. Water Quality for Human Consumption
5. 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.
6. 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.

4. 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.

5. 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.
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.

6. 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

7. 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

8. microbiological growth. Similar water quality requirements can be found in
pharmaceutical, oil, gas, and other industries.
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.

9. 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.
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.
n 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.

10. 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.
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.

11.  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.
 on 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.
 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

12. 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

13. 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.

14. 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

15. picture, is clean, abundant, lightly mineralized by volcanic rock, slightly alkaline,
and subject to minimal human contamination.

17. 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.

18.  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.