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Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers,
ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
s, aquifers, reservoirs and groundwater. Water pollution results when
contaminant Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc. Types of contamination Wi ...
s are introduced into these water bodies. Water pollution can be attributed to one of four sources: sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. It can be grouped into surface water pollution (either fresh water pollution or marine pollution) or
groundwater pollution Groundwater pollution (also called groundwater contamination) occurs when pollutants are released to the ground and make their way into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwante ...
. For example, releasing inadequately treated
wastewater Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...
into natural waters can lead to
degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradatio ...
of these aquatic ecosystems. Water pollution can also lead to
water-borne diseases Waterborne diseases are conditions (meaning adverse effects on human health, such as death, disability, illness or disorders) caused by pathogenic micro-organisms that are transmitted in water. These diseases can be spread while bathing, washing ...
for people using polluted water for drinking, bathing, washing or
irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...
. Water pollution reduces the ability of the body of water to provide the ecosystem services (such as
drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
) that it would otherwise provide. Sources of water pollution are either point sources or non-point sources. Point sources have one identifiable cause, such as a storm drain, a
wastewater treatment plant Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environmen ...
or an oil spill. Non-point sources are more diffuse, such as agricultural runoff. Pollution is the result of the cumulative effect over time. Pollution may take the form of toxic substances (e.g., oil, metals, plastics, pesticides,
persistent organic pollutant Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
s, industrial waste products), stressful conditions (e.g., changes of pH, hypoxia or anoxia, increased temperatures, excessive turbidity, unpleasant taste or odor, and changes of salinity), or pathogenic organisms. Contaminants may include organic and
inorganic In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...
substances. Heat can also be a pollutant, and this is called thermal pollution. A common cause of thermal pollution is the use of water as a
coolant A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosi ...
by
power plants A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many pow ...
and industrial manufacturers. Control of water pollution requires appropriate infrastructure and management plans as well as legislation. Technology solutions can include improving sanitation, sewage treatment, industrial wastewater treatment, agricultural wastewater treatment, erosion control, sediment control and control of
urban runoff Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain , storms and other precip ...
(including stormwater management). Effective control of
urban Urban means "related to a city". In that sense, the term may refer to: * Urban area, geographical area distinct from rural areas * Urban culture, the culture of towns and cities Urban may also refer to: General * Urban (name), a list of people ...
runoff includes reducing speed and quantity of flow.


Definition

A practical definition of water pollution is: "Water pollution is the addition of substances or energy forms that directly or indirectly alter the nature of the water body in such a manner that negatively affects its legitimate uses". Therefore, pollution is associated with concepts attributed to humans, namely the negative alterations and the uses of the water body. Water is typically referred to as polluted when it is impaired by anthropogenic contaminants. Due to these contaminants it either does not support a human use, such as
drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
, or undergoes a marked shift in its ability to support its biotic communities, such as fish.


Contaminants


Contaminants with an origin in sewage

The following compounds can all reach water bodies via raw sewage or even treated sewage discharges: * Various chemical compounds found in personal
hygiene Hygiene is a series of practices performed to preserve health. According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...
and cosmetic products. * Disinfection by-products found in chemically disinfected
drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
(whilst these chemicals can be a pollutant in the water distribution network, they are fairly volatile and therefore not usually found in environmental waters). * Hormones (from animal husbandry and residue from human hormonal contraception methods) and synthetic materials such as
phthalate Phthalates (, ), or phthalate esters, are esters of phthalic acid. They are mainly used as plasticizers, i.e., substances added to plastics to increase their flexibility, transparency, durability, and longevity. They are used primarily to soften ...
s that mimic hormones in their action. These can have adverse impacts even at very low concentrations on the natural biota and potentially on humans if the water is treated and utilized for drinking water. * insecticides and herbicides, often from agricultural runoff. If the water pollution stems from sewage (municipal wastewater), the main pollutants are: suspended solids, biodegradable organic matter, nutrients and pathogenic (disease-causing) organisms.


Pathogens

The major groups of pathogenic organisms are: (a) bacteria, (b) viruses, (c) protozoans and (d) helminths. In practice,
indicator organism Indicator organisms are used as a proxy to monitor conditions in a particular environment, ecosystem, area, habitat, or consumer product. Certain bacteria, fungi and helminth eggs are being used for various purposes. Types Indicator bacteria ...
s are used to investigate pathogenic pollution of water because the detection of pathogenic organisms in water sample is difficult and costly, because of their low concentrations. The indicators ( bacterial indicator) of fecal contamination of water samples most commonly used are: total coliforms (TC), fecal coliforms (FC) or thermotolerant coliforms, E. coli. Pathogens can produce waterborne diseases in either human or animal hosts. Some microorganisms sometimes found in contaminated surface waters that have caused human health problems include: ''
Burkholderia pseudomallei ''Burkholderia pseudomallei'' (also known as ''Pseudomonas pseudomallei'') is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium. It is a soil-dwelling bacterium endemic in tropical and subtropical regions worldwide, particularly in T ...
,'' '' Cryptosporidium parvum,'' ''
Giardia lamblia ''Giardia duodenalis'', also known as ''Giardia intestinalis'' and ''Giardia lamblia'', is a flagellated parasitic microorganism of the genus '' Giardia'' that colonizes the small intestine, causing a diarrheal condition known as giardiasis. ...
,'' '' Salmonella,''
norovirus Norovirus, sometimes referred to as the winter vomiting disease, is the most common cause of gastroenteritis. Infection is characterized by non-bloody diarrhea, vomiting, and stomach pain. Fever or headaches may also occur. Symptoms usually devel ...
and other viruses,
parasitic worms Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as sc ...
including the '' Schistosoma'' type.' The source of high levels of pathogens in water bodies can be from human feces (due to
open defecation Open defecation is the human practice of defecating outdoors ("in the open") rather than into a toilet. People may choose fields, bushes, forests, ditches, streets, canals, or other open spaces for defecation. They do so either because they d ...
), sewage, blackwater, or
manure Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the Soil fertility, fertility of soil by adding organic ma ...
that has found its way into the water body. The cause for this can be lack of sanitation procedures or poorly functioning on-site sanitation systems ( septic tanks,
pit latrine A pit latrine, also known as pit toilet, is a type of toilet that collects human feces in a hole in the ground. Urine and feces enter the pit through a drop hole in the floor, which might be connected to a toilet seat or squatting pan for use ...
s), sewage treatment plants without disinfection steps,
sanitary sewer overflow Sanitary sewer overflow (SSO) is a condition in which untreated sewage is discharged from a sanitary sewer into the environment prior to reaching sewage treatment facilities. When caused by rainfall it is also known as wet weather overflow. Cause ...
s and combined sewer overflows (CSOs) during storm events and intensive agriculture (poorly managed livestock operations).


Organic compounds

Organic substances that enter water bodies are often toxic. * Petroleum hydrocarbons, including fuels (
gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organi ...
, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion byproducts, from oil spills or
storm water Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed land ...
runoff *
Volatile organic compounds Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a t ...
, such as improperly stored industrial solvents. Problematic species are
organochloride An organochloride, organochlorine compound, chlorocarbon, or chlorinated hydrocarbon is an organic compound containing at least one covalently bonded atom of chlorine. The chloroalkane class (alkanes with one or more hydrogens substituted by chlo ...
s such as polychlorinated biphenyl (PCBs) and
trichloroethylene The chemical compound trichloroethylene is a halocarbon commonly used as an industrial solvent. It is a clear, colourless non-flammable liquid with a chloroform-like sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, w ...
, a common solvent. Per- and polyfluoroalkyl substances (PFAS) are
persistent organic pollutant Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
s.


Inorganic contaminants

Inorganic water pollutants include for example: * Ammonia from food processing waste * Heavy metals from motor vehicles (via urban storm water runoff) and
acid mine drainage Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines. Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
* Nitrates and phosphates, from sewage and agriculture (''see''
nutrient pollution Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or ...
) * Silt (
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...
) in runoff from construction sites or sewage, logging, slash and burn practices or land clearing sites. * Salt:
Freshwater salinization Freshwater salinization is the process of salty runoff contaminating freshwater ecosystems, which can harm aquatic species in certain quantities and Drinking water, contaminate drinking water. It is often measured by the increased amount of dissolv ...
is the process of salty runoff contaminating freshwater ecosystems. Human-induced salinization is termed as secondary salinization, with the use of
de-icing Deicing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only deice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or prev ...
road salts as the most common form of runoff.


Pharmaceutical pollutants

*
Environmental persistent pharmaceutical pollutant The term environmental persistent pharmaceutical pollutants (EPPP) was first suggested in the nomination in 2010 of pharmaceuticals and environment as an emerging issue in a Strategic Approach to International Chemicals Management ( SAICM) by t ...
s, which can include various pharmaceutical drugs and their metabolites (''see also'' drug pollution), such as antidepressant drugs, antibiotics or the
contraceptive pill Oral contraceptives, abbreviated OCPs, also known as birth control pills, are medications taken by mouth for the purpose of birth control. Female Two types of female oral contraceptive pill, taken once per day, are widely available: * The combin ...
. *Metabolites of
illicit drugs The prohibition of drugs through sumptuary legislation or religious law is a common means of attempting to prevent the recreational use of certain intoxicating substances. While some drugs are illegal to possess, many governments regulate t ...
(see also wastewater epidemiology), for example methamphetamine and ecstasy.


Solid waste and plastics

Solid waste can enter water bodies through untreated sewage, combined sewer overflows, urban runoff, people discarding garbage into the environment, wind carrying municipal solid waste from landfills and so forth. This results in
macroscopic The macroscopic scale is the length scale on which objects or phenomena are large enough to be visible with the naked eye, without magnifying optical instruments. It is the opposite of microscopic. Overview When applied to physical phenomena a ...
pollution– large visible items polluting the water– but also
microplastics Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a v ...
pollution that is not directly visible. The terms marine debris and
marine plastic pollution Marine plastic pollution (or plastic pollution in the ocean) is a type of marine pollution by plastics, ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material ...
are used in the context of pollution of oceans. Microplastics persist in the environment at high levels, particularly in aquatic and
marine ecosystem Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the sur ...
s, where they cause water pollution. 35% of all ocean microplastics come from textiles/clothing, primarily due to the erosion of polyester, acrylic, or nylon-based clothing, often during the washing process.


Types of surface water pollution

Surface water pollution includes pollution of rivers, lakes and oceans. A subset of surface water pollution is marine pollution which affects the oceans.
Nutrient pollution Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or ...
refers to contamination by excessive inputs of nutrients. Globally, about 4.5 billion people do not have safely managed sanitation as of 2017, according to an estimate by the Joint Monitoring Programme for Water Supply and Sanitation.WHO and UNICEF (2017
Progress on Drinking Water, Sanitation and Hygiene: 2017 Update and SDG Baselines
Geneva: World Health Organization (WHO) and the United Nations Children's Fund (UNICEF), 2017
Lack of access to sanitation is concerning and often leads to water pollution, e.g. via the practice of
open defecation Open defecation is the human practice of defecating outdoors ("in the open") rather than into a toilet. People may choose fields, bushes, forests, ditches, streets, canals, or other open spaces for defecation. They do so either because they d ...
: during rain events or floods, the human feces are moved from the ground where they were deposited into surface waters. Simple pit latrines may also get flooded during rain events.


Marine pollution


Nutrient pollution


Thermal pollution

Elevated water temperatures decrease
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
levels (due to lower levels of
dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...
, as gases are less soluble in warmer liquids), which can kill fish (which may then rot) and alter
food chain A food chain is a linear network of links in a food web starting from producer organisms (such as grass or algae which produce their own food via photosynthesis) and ending at an apex predator species (like grizzly bears or killer whales), de ...
composition, reduce species
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
, and foster invasion by new
thermophilic A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...
species.


Biological pollution

The introduction of aquatic invasive organisms is a form of water pollution as well. It causes biological pollution.


Groundwater pollution

In many areas of the world, groundwater pollution poses a hazard to the wellbeing of people and ecosystems. One-quarter of the world's population depends on groundwater for drinking, yet concentrated recharging is known to carry short-lived contaminants into carbonate aquifers and jeopardize the purity of those waters.


Pollution from point sources

Point source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a
pipe Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circular ...
or
ditch A ditch is a small to moderate divot created to channel water. A ditch can be used for drainage, to drain water from low-lying areas, alongside roadways or fields, or to channel water from a more distant source for plant irrigation. Ditches ar ...
. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain. The U.S. Clean Water Act (CWA) defines point source for regulatory enforcement purposes (''see''
United States regulation of point source water pollution Point source water pollution comes from discrete conveyances and alters the chemical, biological, and physical characteristics of water. In the United States, it is largely regulated by the Clean Water Act (CWA). Among other things, the Act req ...
). The CWA definition of point source was amended in 1987 to include municipal storm sewer systems, as well as industrial storm water, such as from construction sites.


Sewage

Sewage typically consists of 99.9% water and 0.1% solids. Sewage contributes many classes of nutrients that lead to eutrophication. It is a major source of phosphate for example. Sewage is often contaminated with diverse compounds found in personal
hygiene Hygiene is a series of practices performed to preserve health. According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...
, cosmetics, pharmaceutical drugs (see also drug pollution), and their metabolites Water pollution due to environmental persistent pharmaceutical pollutants can have wide-ranging consequences. When sewers overflow during storm events this can lead to water pollution from untreated sewage. Such events are called
sanitary sewer overflow Sanitary sewer overflow (SSO) is a condition in which untreated sewage is discharged from a sanitary sewer into the environment prior to reaching sewage treatment facilities. When caused by rainfall it is also known as wet weather overflow. Cause ...
s or combined sewer overflows.


Industrial wastewater

Industrial processes that use water also produce wastewater. This is called
industrial wastewater Industrial wastewater treatment describes the processes used for Wastewater treatment, treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reuse ...
. Using the US as an example, the main industrial consumers of water (using over 60% of the total consumption) are power plants, petroleum refineries, iron and steel mills, pulp and paper mills, and food processing industries. Some industries discharge chemical wastes, including solvents and heavy metals (which are toxic) and other harmful pollutants.
Industrial wastewater could add the following pollutants to receiving water bodies if the wastewater is not treated and managed properly: * Heavy metals, including mercury,
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, and chromium * Organic matter and nutrients such as
food waste Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...
: Certain industries (e.g. food processing, slaughterhouse waste, paper fibers, plant material, etc.) discharge high concentrations of BOD, ammonia nitrogen and oil and grease. *
Inorganic In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...
particles such as sand, grit, metal particles, rubber residues from tires, ceramics, etc.; * Toxins such as pesticides, poisons, herbicides, etc. * Pharmaceuticals, endocrine disrupting compounds, hormones, perfluorinated compounds, siloxanes, drugs of abuse and other hazardous substances *
Microplastics Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a v ...
such as polyethylene and polypropylene beads, polyester and polyamide * Thermal pollution from
power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many ...
s and industrial manufacturers * Radionuclides from uranium mining, processing nuclear fuel, operating nuclear reactors, or disposal of radioactive waste. * Some industrial discharges include
persistent organic pollutant Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
s such as per- and polyfluoroalkyl substances (PFAS).


Oil spills


Pollution from nonpoint sources


Agriculture

Agriculture is a major contributor to water pollution from nonpoint sources. The use of fertilizers as well as surface runoff from farm fields, pastures and feedlots leads to nutrient pollution. In addition to plant-focused agriculture, fish-farming is also a source of pollution. Additionally, agricultural runoff often contains high levels of pesticides.


Atmospheric contributions (air pollution)

Air deposition is a process whereby air pollutants from industrial or natural sources settle into water bodies. The deposition may lead to polluted water near the source, or at distances up to a few thousand miles away. The most frequently observed water pollutants resulting from industrial air deposition are sulfur compounds, nitrogen compounds, mercury compounds, other heavy metals, and some pesticides and industrial by-products. Natural sources of air deposition include forest fires and microbial activity. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. Some governments have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the atmosphere. The main source of sulfur and nitrogen compounds that result in acid rain are anthropogenic, but nitrogen oxides can also be produced naturally by lightning strikes and sulphur dioxide is produced by
volcanic eruptions Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...
. Acid rain can have harmful effects on plants, aquatic ecosystems and infrastructure. Carbon dioxide concentrations in the atmosphere have increased since the 1850s due anthropogenic influences ( emissions of greenhouse gases). This leads to
ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...
and is another form of water pollution from atmospheric contributions.


Sampling, measurements, analysis

Water pollution may be analyzed through several broad categories of methods: physical, chemical and biological. Some methods may be conducted ''
in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
'', without sampling, such as temperature. Others involve collection of samples, followed by specialized analytical tests in the laboratory. Standardized, validated analytical test methods, for water and wastewater samples have been published. Common physical tests of water include temperature, Specific conductance or electrical conductance (EC) or conductivity, solids concentrations (e.g.,
total suspended solids Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus known as sintered glass crucible. TSS is a water qu ...
(TSS)) and turbidity. Water samples may be examined using
analytical chemistry Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separati ...
methods. Many published test methods are available for both organic and inorganic compounds. Frequently used parameters that are quantified are pH, BOD,
chemical oxygen demand In environmental chemistry, the chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution whic ...
(COD),
dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...
(DO), total hardness, nutrients (
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and phosphorus compounds, e.g. nitrate and
orthophosphate A phosphoric acid, in the general sense, is a phosphorus oxoacid in which each phosphorus (P) atom is in the oxidation state +5, and is bonded to four oxygen (O) atoms, one of them through a double bond, arranged as the corners of a tetrahedron. ...
s), metals (including copper,
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
, cadmium, lead and mercury), oil and grease, total petroleum hydrocarbons (TPH), surfactants and pesticides. The use of a biomonitor or
bioindicator A bioindicator is any species (an indicator species) or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. For example, copepods and other sma ...
is described as biological monitoring. This refers to the measurement of specific properties of an organism to obtain information on the surrounding physical and chemical environment. Biological testing involves the use of plant, animal or microbial indicators to monitor the health of an
aquatic ecosystem An aquatic ecosystem is an ecosystem formed by surrounding a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms that are dependent on each other and on their environment. The t ...
. They are any biological species or group of species whose function, population, or status can reveal what degree of ecosystem or environmental integrity is present. One example of a group of bio-indicators are the copepods and other small water crustaceans that are present in many water bodies. Such organisms can be monitored for changes (biochemical, physiological, or behavioral) that may indicate a problem within their ecosystem.


Impacts


Ecosystems

Water pollution is a major global environmental problem because it can result in the degradation of all
aquatic ecosystem An aquatic ecosystem is an ecosystem formed by surrounding a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms that are dependent on each other and on their environment. The t ...
s – fresh, coastal, and ocean waters. The specific contaminants leading to pollution in water include a wide spectrum of
chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...
s, pathogens, and physical changes such as elevated temperature. While many of the chemicals and substances that are regulated may be naturally occurring ( calcium, sodium, iron, manganese, etc.) the concentration usually determines what is a natural component of water and what is a contaminant. High concentrations of naturally occurring substances can have negative impacts on aquatic flora and fauna. Oxygen-depleting substances may be natural materials such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.


Public health and waterborne diseases

A study published in 2017 stated that "polluted water spread
gastrointestinal disease Gastrointestinal diseases (abbrev. GI diseases or GI illnesses) refer to diseases involving the gastrointestinal tract, namely the oesophagus, stomach, small intestine, large intestine and rectum, and the accessory organs of digestion, the liver, ...
s and parasitic infections and killed 1.8 million people" (these are also referred to as waterborne diseases).


Eutrophication from nitrogen pollution

Nitrogen pollution can cause eutrophication, especially in lakes. Eutrophication is an increase in the concentration of chemical nutrients in an
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
to an extent that increases the
primary productivity In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...
of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur, affecting fish and other animal populations.


Ocean acidification

Ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...
is another impact of water pollution. Ocean acidification is the ongoing decrease in the pH value of the Earth's oceans, caused by the uptake of carbon dioxide () from the atmosphere.


Prevalence

Water pollution is a problem in developing countries as well as in developed countries.


By country

For example, water pollution in India and China is wide spread. About 90 percent of the water in the cities of China is polluted.


Control and reduction


Pollution control philosophy

One aspect of environmental protection are mandatory regulations but they are only part of the solution. Other important tools in pollution control include environmental education, economic instruments, market forces and stricter enforcements. Standards can be "precise" (for a defined quantifiable minimum or maximum value for a pollutant), or "imprecise" which would require the use of
Best available technology The best available technology or best available techniques (BAT) is the technology approved by legislators or regulators for meeting output standards for a particular process, such as pollution abatement. Similar terms are ''best practicable means ...
(BAT) or Best practicable environmental option (BPEO). Market-based economic instruments for pollution control can include: charges, subsidies, deposit or refund schemes, the creation of a market in pollution credits, and enforcement incentives. Moving towards a holistic approach in chemical pollution control combines the following approaches: Integrated control measures, trans-boundary considerations, complementary and supplementary control measures, life-cycle considerations, the impacts of chemical mixtures. Control of water pollution requires appropriate infrastructure and management plans. The infrastructure may include wastewater treatment plants, for example sewage treatment plants and
industrial wastewater Industrial wastewater treatment describes the processes used for Wastewater treatment, treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reuse ...
treatment plants.
Agricultural wastewater treatment Agricultural wastewater treatment is a farm management agenda for controlling pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer, pesticides, animal slurry, crop residues or i ...
for farms, and erosion control at construction sites can also help prevent water pollution. Effective control of urban runoff includes reducing speed and quantity of flow. Water pollution requires ongoing evaluation and revision of water resource policy at all levels (international down to individual aquifers and wells).


Sanitation and sewage treatment

Municipal wastewater can be treated by centralized sewage treatment plants,
decentralized wastewater system Decentralized wastewater systems (also referred to as decentralized wastewater treatment systems) convey, treat and dispose or reuse wastewater from small and low-density communities, buildings and dwellings in remote areas, individual public or ...
s,
nature-based solutions The term Nature-based solutions (NBS) refers to the sustainable management and use of natural features and processes to tackle socio-environmental challenges. These challenges include issues such as climate change ( mitigation and adaptation), ...
UN-Water (2018
World Water Development Report 2018: Nature-based Solutions for Water
Geneva, Switzerland
or in onsite sewage facilities and septic tanks. For example,
waste stabilization pond Waste stabilization ponds (WSPs or stabilization ponds or waste stabilization lagoons) are ponds designed and built for wastewater treatment to reduce the organic content and remove pathogens from wastewater. They are man-made depressions confine ...
s are a low cost treatment option for sewage, particularly for regions with warm climates. UV light (sunlight) can be used to degrade some pollutants in waste stabilization ponds (sewage lagoons). The use of safely managed sanitation services would prevent water pollution caused by lack of access to sanitation. Well-designed and operated systems (i.e., with secondary treatment stages or more advanced tertiary treatment) can remove 90 percent or more of the pollutant load in sewage. Some plants have additional systems to remove nutrients and pathogens. While such advanced treatment techniques will undoubtedly reduce the discharges of micropollutants, they can also result in large financial costs, as well as environmentally undesirable increases in energy consumption and greenhouse gas emissions. Sewer overflows during storm events can be addressed by timely maintenance and upgrades of the sewerage system. In the US, cities with large combined systems have not pursued system-wide separation projects due to the high cost, but have implemented partial separation projects and
green infrastructure Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature.Hiltrud Pötz & Pierre Bleuze (2011). Urban green-blue grids for sustainab ...
approaches. In some cases municipalities have installed additional CSO storage facilities or expanded sewage treatment capacity.


Industrial wastewater treatment


Agricultural wastewater treatment


Management of erosion and sediment control

Sediment from construction sites can be managed by installation of erosion controls, such as
mulch A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area. A mu ...
ing and hydroseeding, and sediment controls, such as
sediment basin A sediment basin is a temporary pond built on a construction site to capture eroded or disturbed soil that is washed off during rain storms, and protect the water quality of a nearby stream, river, lake, or bay. The sediment-laden soil settl ...
s and
silt fence A silt fence, sometimes (misleadingly) called a "filter fence," is a temporary sediment control device used on construction sites to protect water quality in nearby streams, rivers, lakes and seas from sediment (loose soil) in stormwater runof ...
s. Discharge of toxic chemicals such as motor fuels and concrete washout can be prevented by use of spill prevention and control plans, and specially designed containers (e.g. for concrete washout) and structures such as overflow controls and diversion berms. Erosion caused by deforestation and changes in hydrology (soil loss due to water runoff) also results in loss of sediment and, potentially, water pollution.


Control of urban runoff (storm water)


Legislation


Philippines

In the Philippines, Republic Act 9275, otherwise known as the Philippine Clean Water Act of 2004, is the governing law on wastewater management. It states that it is the country's policy to protect, preserve and revive the quality of its fresh, brackish and marine waters, for which wastewater management plays a particular role.


United States


See also

*
Aquatic toxicology Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communit ...
* * Human impacts on the environment * Pollution *
Trophic state index The Trophic State Index (TSI) is a classification system designed to rate water bodies based on the amount of biological productivity they sustain. Although the term "trophic index" is commonly applied to lakes, any surface water body may be inde ...
(water quality indicator for lakes) * Water resources management *
Water security Water security is the focused goal of water policy and water management. A society with a high level of water security makes the most of water's benefits for humans and ecosystems and limits the risk of destructive impacts associated with water. T ...


References


External links


Tackling global water pollution
- UN Environment Programme {{DEFAULTSORT:Water Pollution Aquatic ecology Aquifers Environmental science Water and the environment Water supply Sanitation Articles containing video clips