DefinitionA 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 human impact on the environment, 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.
AgricultureAgriculture 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 tanks and feedlots (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 wastewaterUsing 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).
SewageSewage typically consists of 99.9% water and 0.1% solids. Globally, about 4.5 billion people do not have Improved sanitation, safely managed sanitation as of 2017, according to an estimate by the Joint Monitoring Programme for Water Supply and Sanitation.WHO and UNICEF (2017
Pathogens from sewageThe source of high levels of pathogens in water bodies can be from human feces (due to open defecation), sewage, Blackwater (waste), 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 tanks, pit latrines), Sewage treatment, sewage treatment plants without disinfection steps, sanitary sewer overflows and Combined sewer overflow, combined sewer overflows (CSOs) during storm events and Intensive farming, 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, Helminths, parasitic worms including the ''Schistosoma'' type.' A study published in 2017 stated that "polluted water spread gastrointestinal diseases and Parasitic disease, parasitic infections and killed 1.8 million people" (these are also referred to as waterborne diseases).
Urban runoffUrban 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 pollutionThermal 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 pollutionThe introduction of aquatic Invasive species, invasive organisms is a form of water pollution as well. It causes biological pollution.
By type of sourceSources of surface water pollution can be grouped into two categories based on their origin: point sources and nonpoint sources.
Point sourcesPoint source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a water pipe, pipe or ditch. Examples of sources in this category include discharges from a Sewage treatment, sewage treatment plant, a factory, or a city storm drain. The U.S. Clean Water Act (CWA) defines point source for regulation, 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.
MeasurementWater 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), Hard water, total hardness, nutrients (nitrogen and phosphorus compounds, e.g. nitrate and orthophosphates), metals (including copper, zinc, cadmium, lead and mercury (element), mercury), oil and grease, total petroleum hydrocarbons (TPH), surfactants and pesticides.
Biological testingThe use of a biomonitor is described as Biomonitoring, 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 indicator species, 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.
PrevalenceWater pollution is a problem in developing country, developing countries as well as in developed countries.
By countryFor example, water pollution in India and Water resources of China, China is wide spread. About 90 percent of the Water resources of China, water in the cities of China is polluted.
Control and reduction
Pollution control philosophyOne 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, Best Available Technology (BAT) or Best practicable environmental option, 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 assessment, 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, sewage treatment plants and industrial wastewater treatment, 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 treatmentMunicipal wastewater (or sewage) can be treated by centralized sewage treatment plants, decentralized wastewater systems, nature-based solutionsUN-Water (2018
Industrial wastewater treatment
Agricultural wastewater treatment
Management of erosion and sediment controlSediment from construction sites can be managed by installation of erosion controls, such as mulching 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)
LegislationSome 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 United States Environmental Protection Agency, 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 resource management, Water resources management