Water pollution


Water covers well over two thirds of the Earth’s surface; only less than one third of the Earth’s surface is taken up by land. As global population increases, humans’ need for water increases also; and this tends to put pressure on the Earth’s water bodies, either by usage or taking up the resources in them. Due to this human activities, oceans, rivers, and inland waters shrink, which, not only reduce the size of the water bodies, but also reduce their quality. When water quality is impacted negativity, it simply means that the water has been polluted or contaminated.

Environmental pollution in general, is a problem caused by humans because it is relatively a recent development in the history of the planet earth. Before the industrial revolution in the 19th century, people lived more harmoniously with their immediate environment. The wastes produced prior to the industrial revolution were very little and more of organic substances which can easily decay and does not pose much threat to the environment. As industrialization spread around the world, so has the problems of environmental pollution spread with it (Woodford 2006,2022).

Water pollution can destroy important food sources and also contaminates drinking water with chemicals that can cause immediate and long-term harm to human health.

Water pollution also often damages aquatic ecosystems severely. This happens when rivers, lakes, and oceans are used as open sewers for industrial and residential waste. Pesticides, herbicides, oil products, heavy metals (such as mercury, lead, and zinc), detergents, and industrial wastes can kill aquatic organisms outright or make the environment so inhospitable that species can no longer thrive. For instance, water pollution is a threat to 90% of the endangered fishes and freshwater mussels in the US (Richard and Rachel, 2013).

What is water pollution?

Water pollution is simply the contamination of water bodies. This contamination usually happens as a result of human activities which negativity impact on the quality of water. When this happens, the water bodies will no longer be fit for its initial legitimate purpose.

Water pollution occurs when harmful substances, which are often chemicals or microorganisms contaminate a stream, river, lake, ocean, aquifer, or other body of water; thereby, degrading water quality and rendering it toxic to humans or the environment. Contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhoea, dysentery, hepatitis A, typhoid, and polio (W.H.O 2019).

Some of the facts noted by the World Health Organization in the 2019 fact sheets on drinking water include;

  • Globally, at least 2 billion people use a drinking water source contaminated with faeces.
  • Contaminated water can transmit diseases such diarrhoea, cholera, dysentery, typhoid, and polio. Contaminated drinking water is estimated to cause 485 000 diarrhoeal deaths each year.
  • By 2025, half of the world’s population will be living in water-stressed areas.
  • In least developed countries, 22% of health care facilities have no water service, 21% no sanitation service, and 22% no waste management service.

The statistics above simply points out that water pollution problem is not something to joke about because i) as the global population increases, water pollution problems follow suit and ii) globally, not less than 2 billion people are at risk of dying due to water pollution related diseases.

Types of water pollution:

Different types of water pollution include; point source and non-point source.

Point source water pollution

This image shows a point source of industrial pollution along the Calumet River. Photo: U.S. Environmental Protection Agency, Region V. Source: https://oceanservice.noaa.gov

Point source water pollution is defined as any single identifiable source of pollution from which pollutants or contaminants are discharged or released. When water body is polluted from a known single source or direct source such as, a pipe, ship or factory, it is referred to as point source water pollution.

Non-point source (NPS) water pollution

This is the opposite of point source water pollution. Unlike the point source, non-point source water pollution comes from many diffuse sources. NPS water pollution is caused by rainfalls, or snowmelt moving through the ground. As the runoff moves, it picks up and carries along with it, any natural or man-made pollutants in its route and dumps them into water bodies; such as, lakes, coastal waters, ground waters, rivers, and wetlands (EPA).

Source: Merrimack Valley Planning Commission

Some of the pollutants carried into the water bodies from non-point sources include; microorganisms and nutrients from livestock, pet wastes and faulty septic systems; atmospheric depositions; salt from irrigation practices and acid drainage from abandoned mines; excess fertilizers, herbicides and insecticides from agricultural lands and residential areas; oil, grease and toxic chemicals from urban runoff and energy production; and sediments from improperly managed construction sites, crop and forest lands etc.

Categories of water pollution:

Water pollution can be categorized into surface and groundwater pollution.

Surface water pollution

Surface water are natural water bodies found on the Earth’s crust. They include; the oceans, rivers, lakes, streams, wetlands and creeks. According to the Environmental Protection Agency (EPA), almost 68 percent of water provided to the communities come from surface water.

Surface water pollution mostly happens as a result of human activities. Agricultural activities, mining, factory effluent, landfills, human/animal waste and localized pollution are some of the most common sources of surface water pollutants.

Groundwater pollution

Groundwater referrers to the water collected under the Earth’s surface in cracks and spaces in the soil, sand and rocks.

Groundwater pollution occurs when man-made products such as chemicals, sediments and microorganisms get into the groundwater and cause it to become unsafe and unfit for human use. Materials from the land’s surface can move through the soil and end up in the groundwater. For example, pesticides and fertilizers can find their way into groundwater supplies over time.

Water pollutants/contaminants

Water pollutants can be classified as organic pollutants, inorganic pollutants, pathogens, suspended solids, nutrients and agriculture pollutants, thermal, radioactive, and other pollutants. Organic and inorganic pollutants are mainly discharged from industrial effluents and sewage into the water bodies (Kailas L et al; 2020). Water bodies can be polluted by a wide variety of substances, including pathogenic microorganisms, putrescible organic waste, plant nutrients, toxic chemicals, sediments, heat, petroleum (oil), and radioactive substances.

Sources of water pollutants

Sewage (Wastewater)

Sewage or wastewater is a mixture of water and other wastes generated from normal human living activities in their residences, commercial, institutional and public facilities. Some of these wastes include; human excreta, used water from the bathroom, food preparation wastes, laundry wastewater, etc.

Sewage contains, organic and inorganic matter which find their way into the surface and groundwater bodies and cause pollution. Excess plant nutrients such as nitrates and phosphatases enhance the growth of algae which causes algal bloom.

The death of the algae causes dissolved oxygen in the water to reduce. This is because, aerobic microorganisms use the dissolved oxygen to eat up algae in a process known as decomposition which increases the biochemical oxygen demand (BOD) in the water body.

Anaerobic organisms (organisms that do not need oxygen to live) on the other hand, metabolize the organic wastes. When they do that, they release gases such as methane and hydrogen sulphide, which are very harmful to the aerobic organisms in the water.

Gradually, as more wastes are introduced into the water body, such as the lake, it changes from a clean and clear water – with a relatively low amount of dissolved nutrients and a balanced aquatic community, to a water rich in nutrients, filled with algae and oxygen deficient, and dirty. This process is known as eutrophication; and it happens slowly and naturally. But human activities (constant waste introduction in the water) causes eutrophication to happen faster, and this leads to the premature aging and death of the water body.

Sewage, if not properly managed can leak into the ground and contaminate the groundwater body (aquifer).

Sewage also contains pathogens (disease causing organisms) which can cause serious health problems when ingested by living organisms and humans.


Agricultural water pollution is a problem globally and is anticipated to increase as the human population grows and demand for food increases and changes towards a diet consisting of higher levels of protein. The predicted outcomes will be more livestock, greater intensity of production and increased use of chemicals including pharmaceuticals (Alexandra et al; 2018). This global burden will definitely put pressure on local and commercial farmers to produce a huge sum of quality produce within a limited period of time. And to achieve this, the use of different chemicals to maximize output will be employed.

Many farming activities are responsible for water pollution due to excessive use of pesticides and chemical fertilizers, which ultimately leaches in groundwater and drains into surface water bodies—the change in Physico-chemical properties of water due to agricultural activities detriment the aquatic ecosystem (Naveen et al; 2021).

Livestock farming also contribute to water pollution. Bacteria, nutrients and other wastes generated in livestock farming also leach into underground water and other surface water bodies during rainfalls and runoffs. Pet wastes, salts from irrigation practices together also contribute to water pollution.

Oil exploration and exploitation activities

During crude oil and gas exploration and exploitation, the major environmental pollutants are i) effluent water contaminated with oily effluents such as oil & grease, chemicals and solids from drilling fluid, ii) formation water produced along with crude oil and iii) gaseous emissions having CO, S02, NOx, hydrocarbons, particulate from gasflare (Chand J).

During drilling operations, the seepage/leakage of effluent water to the surrounding areas is a major source of pollution

Mining activities

During mining, water is used for the extraction of minerals that may be in the form of solids, such as coal, iron, sand, and gravel; liquids, such as crude petroleum; and gases, such as natural gas

Mine drainage is metal-rich water formed from a chemical reaction between water and rocks containing sulfur-bearing minerals. The resulting chemicals in the water are sulfuric acid and dissolved iron. Some or all of this iron can come out as solids to form the red, orange, or yellow sediments in the bottom of streams containing mine drainage (Water Science School).

The Problems associated with mine drainage include contaminated drinking water, disrupted growth and reproduction of aquatic plants and animals, and the corroding effects of the acid on parts of infrastructures such as bridges.

Construction sites

Poorly managed construction sites also contribute to water pollution. Sediments, spilled fluids, loose soils, debris, and chemicals are some of the pollutants generated from a construction site.

During construction, some human activities such as demolition and grading creates these pollutants which can be transported directly into water bodies such as lakes, local creeks, or water reservoirs.

Atmospheric depositions

Atmospheric deposition is the contamination of water by air pollution. Atmospheric deposition is a very important transport process for gases and particles from the atmosphere to the water surfaces. The environmental consequences of this process can be harmful or beneficial. The beneficial aspect of atmospheric deposition is that it helps in the cleansing of air and also aid in the transportation of additional nutrients to plants. On the other hand, atmospheric deposition of sulphur and nutrients may contribute to acidification and eutrophication of various aquatic ecosystems.

Radioactive substances

Radioactive pollution of water is newly emerging but is of grave concern for water pollution and human health. Recently, radioactive contamination and associated health impacts have been reported in many parts of the globe. The application of radioactive elements in nuclear weapons, X-rays, Magnetic resonance imaging (MRI) and other medical equipment causes their exposure to human beings. Dumping of these radioactive wastes in surface waterbodies causes water pollution. Radioactive contamination is more prevalent in groundwater as compared to surface water since it is much exposed to radioactive elements found in the rocks (Sughosh and Ritu).

Marin dumping

Marine Dumping is the deliberate or intentional disposal of wastes at sea or disposal of other matter from vessels, aircraft, platforms or other man-made structures, as well as the deliberate disposal of these vessels or platforms themselves into the sea. Marine dumping can destroy or degrade important habitats for aquatic species and cause coastal erosion and salutation, which affect the health and productivity of the aquatic environment.

Health Problems associated with water pollution

Water pollution can affect us directly or indirectly. It affects us directly through consumption of polluted water or bathing in a polluted stream (for example; consumption of municipal water, as well as bathing in polluted lakes or beach water); and it affects us indirectly through the consumption of vegetables irrigated with contaminated water, as well as of fish or other animals that live in the polluted water or consume animals grown in the polluted water.

When we consume or use polluted water, we simply expose ourselves to pathogens that cause series of serious health issues which includes;

  • Cholera
  • Diarrhea
  • Typhoid
  • Amoebiasis
  • Dysentery
  • Schistosomiasis
  • Cancer
  • Hepatitis
  • Intestinal worms
  • Dracunculiasis
  • Lead poisoning
  • Fluorosis
  • Arsenicosis
  • Polio
  • Trachoma
  • Gastroenteritis, encephalitis, stomach cramps and ulcers
  • Respiratory infections
  • Neurological problems
  • Liver damage
  • Kidney damage

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