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).
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.
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.
Water Quality for Human Consumption
Water Quality for Industrial and Domestic Use
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.
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.