Unsafe water executes more people every year than all other forms of violence combined. Meanwhile, our potable water sources are limited: We have access to less than 1% of the world’s freshwater supply. 

If nothing is done, the problems will only worsen in the future, when global freshwater demand rises by a considerable margin. 

The peaceful lives of marine animals are in danger due to the rigorous sources of water pollution and the wastes produced by human beings distributed in the water sources. 

Table of Contents

What is water pollution? 

When harmful substances—often chemicals or microorganisms—contaminate a stream, river, lake, ocean, aquifer, or other body of water, the water quality is degraded, and the water becomes toxic to humans or the environment.

Let’s take a closer look at the diverse sorts of water contamination.

Pollution type by Water source

1. Groundwater Contamination

ground water - water contamination
Diagram from groundwater quality (source)

Groundwater is formed when rain falls and seeps deep into the earth, filling the aquifer’s fractures, crevices, and porous areas (essentially underground water storage). 

Nearly 40% of Americans get their drinking water from groundwater pumped to the earth’s surface. It is their only clean water supply for some individuals in rural areas. 

When contaminants such as pesticides, fertilizers, and trash leached from landfills and septic systems find their way into an aquifer, they make it unsuitable for human consumption. 

An aquifer that has been poisoned may be unusable for decades, if not thousands, of years. As it seeps into streams, lakes, and oceans, groundwater can spread contaminants far from the initial contaminating source.

Some potential sources of groundwater pollution are storage tanks, as they can be above or below ground and contain gasoline, oil, chemicals, or other forms of liquids. 

Over 10 million water storage tanks are projected to be buried in the United States, and these tanks can corrode, crack, and leak over time. There is a risk of severe pollution if the toxins break out and enter the groundwater.

There are about 20,000 known abandoned and uncontrolled hazardous waste sites in the United States today; every year, the number increases. 

If barrels or other containers are hanging about full of dangerous materials, hazardous waste sites can lead to groundwater contamination. The leak causes toxins that gradually go down through the soil and into the groundwater.

Landfills are the locations where our waste is taken to be buried. The landfills are meant to have a protective bottom layer to prevent toxins from entering the water. 

Contaminants from the landfill (vehicle battery acid, paint, home cleaners, etc.) can make their way down into the groundwater if there is no layer or fractured.

2. Surface Water Contamination

Surface water - water contamination
Plastic waste floating on the sea surface (source)

Surface water, which makes up around 70% of the earth’s surface, fills our oceans, lakes, rivers, and other blue spots on the globe map. 

According to the Environmental Protection Agency, more than a third of lakes and nearly half of rivers and streams are filthy and unsafe for swimming, fishing, or drinking in the US. 

Nutrient pollution is the most common type of contamination in these freshwater sources., including nitrates and phosphates. 

While plants and animals require these minerals to develop, agriculture waste and fertilizer runoff have become a serious contaminant. 

Municipal and industrial waste discharges also contribute a significant amount of pollutants. There’s also all the trash that businesses and individuals dump into waterways.

Nutrients, bacteria, plastics, and chemicals such as antibiotics, heavy metals, and pesticides are all known to pollute surface water. 

The contaminants have a variety of environmental consequences as excess nutrients, for example, in rivers and coastal seas, can cause harmful algal blooms and hypoxia. 

Human health is at risk from pathogens in waterways. Toxic consequences can be caused by chemical contamination. Multiple pollutants often have a combined influence on surface waterways.

3. Ocean water Contamination

Ocean Pollution - water contamination
Plastic waste and juvenile fish together in the ocean (source)

Eighty percent of ocean pollution (also known as marine pollution) comes from land, whether along the coast or far inland. 

Chemicals, nutrients, and heavy metals are conveyed into our bays and estuaries from farms, industries, and towns and then out to sea. Meanwhile, wind-blown sea trash, notably plastic, gets swept into storm drains and sewers. 

Oil spills and leaks, both large and tiny, pollute our waters, which are constantly soaking up carbon pollution from the atmosphere. The ocean can absorb up to a quarter of all carbon emissions produced by humans.

Many ocean pollutants are released far upstream from coastlines into the environment. Fertilizers with high nutrient content used on farmland, for example, frequently wind up in local streams and are eventually deposited in estuaries and bays.

Excess nutrients cause large algae blooms that deplete oxygen in the sea, resulting in dead zones where few marine species can survive.

Some chemical pollutants, such as DDT, the insecticide that put the bald eagle on the endangered species list of the United States Fish and Wildlife Service, penetrate deep into food webs.

Pollution type by Contamination Source

1. Point source

Point source pollution occurs when contamination comes from a single source. Contamination from leaking septic systems, chemical and oil spills, and illegal dumping are examples of wastewater (also known as effluent) released lawfully or illegally by manufacturing, oil refinery, or wastewater treatment plant.

The Environmental Protection Agency (EPA) coordinates point source pollution by defining restrictions on what can be released directly into a body of water by a facility. While point source pollution originates in a single location, it can pollute miles of streams and the ocean.

Factories and power plants can cause point-source pollution, affecting the air and the water. Effluent—wastewater carrying dangerous chemical pollutants—can be discharged into rivers, lakes, or the ocean by oil refineries, paper mills, and auto factories that employ water in their industrial processes.

Another prominent source of point-source pollution is municipal wastewater treatment plants. Effluent from a treatment facility can contaminate waterways with fertilizers and hazardous bacteria. Algae can grow out of control in water as a result of nutrients.

2. Non- point source

Pollution from dispersed sources is referred to as nonpoint source pollution. Agricultural or stormwater runoff, as well as debris blown into streams from land, are examples.

Nonpoint source pollution is the most common cause of water contamination in US waters, yet it’s challenging to control because there’s no single identifiable source.

Consider a city street in the middle of a thunderstorm. Rainwater takes away drips of oil from car engines, tire rubber particles, dog excrement, and debris as it rushes over asphalt. 

The discharge enters a storm drain and eventually flows into a nearby river. Nonpoint-source pollution is primarily caused by runoff. It is a significant issue because of all the hard surfaces in cities, such as streets and roofs. 

Although the number of pollutants washed away from a single city block is small, you have a significant problem when adding up the miles and miles of pavement in a large city.

Runoff from a logged-over forest tract can wash dirt from the roads in rural regions. It can also flush chemicals and fertilizer from agriculture fields and carry acid from abandoned mines. This pollution will most likely end up in rivers, lakes, and streams.

Pollution type by Factor

1. Microbiological pollution

Polluted water - water contamination
Impure, polluted water (source)

Unlike the majority of the others on this list, Microbiological pollution is a naturally occurring form of water contamination. 

Bacteria, protozoa, and viruses can contaminate water supplies, resulting in diseases like bilharzia and cholera. 

Humans are particularly vulnerable to this type of contamination in areas where proper water treatment facilities are lacking. 

People in poorer countries are more likely to get these diseases because they lack the resources to remediate dirty water. 

Contamination happens when any portion of a system, product, or medicine comes into contact with microbiological pathogens in an area where it should be sterile. 

A surgical wound infection, for example, could occur if a surgical instrument is infected with bacteria. When diseases are transferred into the infusion system, contamination can occur in infusion settings; it usually happens during manipulation. 

2. Oxygen depletion pollution 

oxygen depletion - water contamination
Washed up dead fish on the beach (source)

Another impact of algal blooms is that they deplete oxygen supplies. It means that species that rely on oxygen to survive will perish, while anaerobic species thrive. 

Some anaerobic microorganisms can produce harmful toxins such as ammonia, sulfides, and other toxins, Increasing the risk to animals in the sea (and humans, too).

3. Nutrient Pollution

While nutrients are necessary for underwater plants and animals to thrive, too much of them can disrupt the delicate balance of water-based ecosystems. 

Fertilizers have a high concentration of nutrients, which can generate algae blooms in rivers, lakes, and coastal areas, blocking out sunlight and inhibiting the growth of other creatures.

4. Chemical Pollution

Chemical pollution is the most frequent sort of water contamination, and it can permeate both subsurface and surface water sources. 

It’s expected that pesticides and fungicides used in farming are a significant source of chemical contamination; metals and solvents from industrial sites, on the other hand, are substantial contributors.

5. Petroleum (Oil) Pollution

fuel leak - water contamination
A massive oil spill from a bulk carrier in Mauritius (source)

When oil from highways and parking lots is transferred into aquatic bodies by surface runoff, it is known as petroleum (oil) contamination. 

Accidental oil spills, such as those caused by the vessel Exxon Valdez (which spewed more than 260,000 barrels in Alaska’s Prince William Sound in 1989) and the Deepwater Horizon oil rig, are also a source of pollution (which released more than 4 million barrels of oil into the Gulf of Mexico in 2010). 

Oil slicks eventually make their way to the coast, endangering marine life and causing damage to recreational areas.


Consequently, numerous sorts of water contamination are evident globally. It is critical to understand and serve as a wake-up call to be more aware of and responsible for our environment.

(Last Updated on October 24, 2021 by Sadrish Dabadi)

Thinley Doma Ghale holds a Bachelor’s degree in Social Work from Kathmandu University. She enjoys writing articles on climate change animals and loves to travel and experience new ideas, places, meeting people, and learning from them. As a social science student, research has always been her area of interest.