Understanding Water Pollutants: Definition And Impact

Water pollution is the release of substances into bodies of water that make it unsafe for human use and disrupt aquatic ecosystems. Water pollution can be caused by a wide variety of contaminants, including toxic waste, petroleum, and disease-causing microorganisms. Human activities such as industrialisation and urbanisation are major sources of water pollution. Water pollutants can be categorised as either point sources or non-point sources. Point sources are specific and identifiable, such as a factory or sewage treatment plant, while non-point sources are diffuse, like agricultural runoff or atmospheric deposition. The main water pollutants include bacteria, viruses, fertilisers, pesticides, pharmaceuticals, plastics, faecal waste, and even radioactive substances.

Characteristics and Values of Water Pollutants

Point-source and non-point-source pollution

Water pollution is the release of substances into bodies of water, making it unsafe for human use and disrupting aquatic ecosystems. Water pollution can be caused by a wide variety of contaminants, including toxic waste, petroleum, disease-causing microorganisms, chemicals, trash, and radioactive substances.

Point-source pollution

Point-source pollution is defined by the EPA as any pollutant that comes from a discernible, confined, and discrete conveyance. This includes pipes, ditches, channels, tunnels, conduits, wells, and containers, among others. Municipal wastewater treatment plants are another common source of point-source pollution, where effluent can introduce nutrients and harmful microbes into waterways, leading to rampant algae growth.

Non-point-source pollution

Non-point-source pollution, or dispersed source pollution, is the opposite of point-source pollution, with pollutants released across a wide area. An example is rainwater flowing over asphalt during a storm, washing away leaked car oil, tire particles, waste, and trash. This runoff goes into storm sewers and ends up in nearby water bodies, contributing to water pollution. Non-point-source pollution is challenging to control and address due to its dispersed nature.

Examples of Point-source and non-point-source pollution

• Point-source: Industrial wastewater discharged from a pipe into a wetland.
• Non-point-source: Agricultural runoff carrying fertilizers, pesticides, and animal waste into nearby waterways.
• Point-source: Sewage spills from a city sewerage system into a river.
• Non-point-source: Stormwater runoff carrying oil, trash, and pollutants from a city street into a storm sewer.

Oil pollution

Water pollution is the release of substances into bodies of water, making it unsafe for human use and disrupting aquatic ecosystems. Oil pollution is a significant aspect of water pollution, with a range of detrimental effects on the environment, human health, and the economy.

The impact of oil spills on the environment and wildlife can be devastating. Oil spreads over the water surface, creating a thin layer that blocks oxygen from reaching plants and animals. This leads to a process called eutrophication, where the lake or water body transitions to a nutrient-rich, algae-filled state, eventually becoming oxygen-deficient and waste-filled. Anaerobic organisms then metabolize the organic wastes, releasing harmful gases like methane and hydrogen sulfide. Oil pollution also directly harms wildlife, such as wildfowl, by damaging their waterproofing and affecting their health when ingested.

To summarize, oil pollution is a critical component of water pollution, with far-reaching consequences. It affects both the natural environment and human communities, underscoring the importance of safe disposal practices and effective measures to reduce oil pollution.

Agricultural pollution

Water pollution is the release of substances into bodies of water, including subsurface groundwater, lakes, streams, rivers, estuaries, and oceans, which make the water unsafe for human use and disrupt aquatic ecosystems. Water pollution can be caused by a variety of contaminants, including toxic waste, petroleum, and disease-causing microorganisms.

Agricultural activities such as the use of pesticides, fertilizers, and manure can contaminate water sources. These substances can be washed into waterways by rain or transported through runoff, infiltration, and irrigation return flows. Increased levels of nitrogen and phosphorus from these sources can stimulate algal blooms, leading to hypoxic (low oxygen) conditions that are harmful to aquatic life. This process, known as eutrophication, can also impact biodiversity and fisheries.

Additionally, agricultural pollution can include the release of agrochemicals, organic matter, drug residues, sediments, and saline drainage. The expansion of irrigation and the increase in livestock production have also contributed to the transfer of agricultural pollution to water bodies.

The effects of agricultural pollution on water quality can vary depending on factors such as the type of operation, landscape conditions, soils, climate, and farm management practices. However, it is clear that agricultural activities have a significant impact on water quality and the health of aquatic ecosystems.

Chemical contaminants

Water pollution is the release of substances into bodies of water that makes water unsafe and disrupts aquatic ecosystems. Chemical contaminants are a type of water pollutant that can be defined as elements or compounds. These contaminants may be naturally occurring, such as mercury filtering from the Earth's crust, or man-made.

Some examples of chemical contaminants include nitrogen, bleach, salts, pesticides, metals, and toxins produced by bacteria. Pesticides and fertilizers are also chemical contaminants that can enter water sources through agricultural activities. These contaminants can increase the risk of cancer and cause reproductive problems, as well as impair eye, liver, and kidney functions.

Another example of chemical contamination is disinfection byproducts, solvents, and pesticides, which can have chronic effects on human health. Emerging contaminants, such as pharmaceuticals, personal care products, and endocrine-disrupting compounds, are also of concern as their risks to human health and the environment are not yet fully understood. Up to 90% of oral drugs pass through the human body and end up in the water supply.

Oil pollution is another significant form of chemical contamination in water bodies, with land-based sources such as factories, farms, and cities contributing to the majority of oil pollution in the seas. Radioactive waste, generated by uranium mining, nuclear power plants, and military weapons production, is also a severe form of chemical contamination that poses risks to human health and the environment.

Physical and biological contaminants

Water pollution is a serious global problem, with around 2 billion people forced to drink water contaminated by excrement, exposing them to diseases such as cholera, hepatitis A, and dysentery. The World Health Organization (WHO) estimates that approximately 1.7 million people die each year from diarrhoeal diseases associated with unsafe drinking water.

Water pollution can be caused by a variety of physical, chemical, and biological contaminants. Physical properties of water include electrical conductivity, total dissolved solids, and suspended solids. Physical pollutants like temperature change might produce visible water pollution.

Biological contaminants refer to the presence of various types of microbes and pathogens, especially viruses, bacteria, algae, protozoan, nematodes, insects, and their propagules. Waterborne diseases are any sickness caused by drinking water polluted with pathogenic microorganisms such as Salmonella, Shigella, Vibrio cholerae, viruses, parasites, etc. Sewage can promote algae growth, which can eventually result in eutrophic "dead zones" where aquatic life cannot survive due to a lack of oxygen.

The agricultural sector is the biggest consumer of global freshwater resources, and it is also a serious water polluter. Every time it rains, fertilizers, pesticides, and animal waste from farms and livestock operations wash nutrients and pathogens—such as bacteria and viruses—into our waterways.

Frequently asked questions