water pollution

Water pollution (or aquatic pollution) is the contamination of

water bodies

, usually as a result of human activities, in such a manner that negatively affects its legitimate uses. Water pollution reduces the ability of the body of water to provide the ecosystem services that it would otherwise provide. Water bodies include for example

lake

s,

river

s,

ocean

s,

aquifer

s,

reservoir

s and

groundwater

. Water pollution results when contaminants are introduced into these water bodies. In addition to damage to many

species

, water pollution can also lead to water-borne diseases for people. Water pollution traditionally is attributed to four sources, which provide the organization of this article:
*sewage
*industry
*agriculture
*urban runoff including stormwater.

Water pollution can also be classified as surface water pollution (for example lakes, streams, estuaries, and parts of the ocean in marine pollution) or

groundwater

pollution. Sources of water pollution are either point sources or non-point sources. Point sources have one identifiable cause, such as a

storm drain

or a wastewater treatment plant. Non-point sources are more diffuse, such as agricultural runoff. Pollution is the result of the cumulative effect over time. Supplying clean

drinking water

is an important ecosystem service provided by some freshwater systems, but approximately 785 million people in the world do not have access to clean drinking water because of pollution.

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

, or undergoes a marked shift in its ability to support its biotic communities, such as fish.

Agriculture

Agriculture is a major contributor to water pollution. The use of fertilizers leads to Nutrient pollution, in which excess nutrients, usually caused by

nitrogen

- or

phosphorus

-containing compounds that are the main components. Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from

septic tank

s and

feedlot

s (sewage - see below - is also high in nutrients). In addition to plant-focused agriculture, fish-farming is also a source of pollution.

Additionally, ag runoff often contains high levels of pesticides.

Industrial wastewater

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 such as nutrients. Certain industries (e.g. food processing) discharge high concentrations of biochemical oxygen demand (BOD) and oil and grease. Some industrial discharges include persistent organic pollutants such as per- and polyfluoroalkyl substances (PFAS).

Sewage

Sewage typically consists of 99.9% water and 0.1% solids.
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 often leads to water pollution, e.g. via the practice of open defecation. Simple pit latrines may also get flooded during rain events. When sewers overflow during storm events this can lead to water pollution from untreated sewage. Such events are called sanitary sewer overflows or combined sewer overflows.

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

, cosmetics, pharmaceutical drugs] (see also drug pollution), and their metabolites Even at very low concentrations,

hormones

(from animal husbandry and residue from human hormonal contraception methods) and synthetic materials such as

phthalates

that mimic hormones in their action, can have an adverse impacts. Water pollution due to environmental persistent pharmaceutical pollutants can have wide-ranging consequences:

Pathogens from sewage

The source of high levels of pathogens in water bodies can be from

human feces

(due to open defecation), sewage, blackwater,

manure

that has found its way into the water body. The cause for this can be lack of sanitation or poorly functioning on-site

sanitation

systems (

septic tank

s, pit latrines), sewage treatment plants without disinfection steps, sanitary sewer overflows and combined sewer overflows (CSOs) during storm events and intensive agriculture (poorly managed livestock operations). 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,'' ''

Cryptosporidium parvum

,'' ''

Giardia lamblia

,'' ''Salmonella,'' norovirus and other viruses, parasitic worms including the ''

Schistosoma

'' type.'

A study published in 2017 stated that "polluted water spread gastrointestinal diseases and parasitic infections and killed 1.8 million people" (these are also referred to as waterborne diseases).

Urban runoff

Urban runoff is stormwater discharged to surface waters from rooftops, roads and parking lots, and reservoirs. Often it is captured in large retaining ponds. It is subject to high suspended solids as well and elevated nitrogen and phosphorus concentrations.

Other forms of water pollution

Thermal pollution

Thermal pollution, sometimes called "thermal enrichment," is the degradation of water quality by any process that changes ambient water temperature. Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers.

Biological pollution

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

By type of source

Sources of surface water pollution can be grouped into two categories based on their origin: point sources and nonpoint sources.

Point sources

Point source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a

pipe

or

ditch

. 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). 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.

Nonpoint sources

Measurement

Water pollution may be analyzed through several broad categories of methods: physical, chemical and biological. Some methods may be conducted ''

in situ

'', 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 (TSS)) and

turbidity

. Water samples may be examined using analytical chemistry methods. Many published test methods are available for both organic and inorganic compounds. Frequently used parameters that are quantified are

pH

, biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), total hardness, nutrients (

nitrogen

and

phosphorus

compounds, e.g.

nitrate

and orthophosphates), metals (including copper,

zinc

,

cadmium

, lead and

mercury

), oil and grease, total

petroleum

hydrocarbons (TPH),

surfactant

s and pesticides.

Sampling

Biological testing

The use of a biomonitor 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

. 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

copepod

s 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.

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 (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 treatment plants. Agricultural wastewater treatment 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 (or sewage) can be treated by centralized sewage treatment plants, decentralized wastewater systems, nature-based solutionsUN-Water (2018
World Water Development Report 2018: Nature-based Solutions for Water
Geneva, Switzerland or in onsite sewage facilities and

septic tank

s. For example, waste stabilization ponds 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 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

ing and hydroseeding, and sediment controls, such as sediment basins and silt fences. 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

Some examples for legislation to control water pollution are listed below:

* 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.
* The Clean Water Act is the primary federal law in the United States governing water pollution in surface waters. It is implemented by the U.S. Environmental Protection Agency in collaboration with states, territories, and tribes.

Groundwater

protection provisions are included in the Safe Drinking Water Act, Resource Conservation and Recovery Act, and the Superfund act.

See also

* Aquatic toxicology
*
*

Pollution

* Trophic state index (water quality indicator for lakes)
*

Water treatment

*Water resources management

References

External links

UN Environment Program page on water pollution

{{DEFAULTSORT:Water Pollution

Aquatic ecology
Aquifers
Environmental science
Water and the environment
Water supply
Sanitation
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