The causes of Water Pollution

Domestic households, industrial and agricultural practices produce wastewater that can cause pollution of many lakes and rivers.

Sewage is the term used for wastewater that often contains faeces, urine and laundry waste.
There are billions of people on Earth, so treating sewage is a big priority.
Sewage disposal is a major problem in developing countries as many people in these areas don’t have access to sanitary conditions and clean water.
Untreated sewage water in such areas can contaminate the environment and cause diseases such as diarrhoea.
Sewage in developed countries is carried away from the home quickly and hygienically through sewage pipes.
Sewage is treated in water treatment plants and the waste is often disposed into the sea.
Sewage is mainly biodegradable and most of it is broken down in the environment.
In developed countries, sewage often causes problems when people flush chemical and pharmaceutical substances down the toilet. When people are ill, sewage often carries harmful viruses and bacteria into the environment causing health problems

Dumping of litter in the sea can cause huge problems. Litter items such as 6-pack ring packaging can get caught in marine animals and may result in death. Different items take different lengths of time to degrade in water:

Cardboard – Takes 2 weeks to degrade.
Newspaper – Takes 6 weeks to degrade.
Photodegradable packaging – Takes 6 weeks to degrade.
Foam – Takes 50 years to degrade.
Styrofoam – Takes 80 years to degrade.
Aluminium – Takes 200 years to degrade.
Plastic packaging – Takes 400 years to degrade.
Glass – It takes so long to degrade that we don’t know the exact time.

Industry is a huge source of water pollution, it produces pollutants that are extremely harmful to people and the environment.
Many industrial facilities use freshwater to carry away waste from the plant and into rivers, lakes and oceans.
Pollutants from industrial sources include:
Asbestos – This pollutant is a serious health hazard and carcinogenic. Asbestos fibres can be inhaled and cause illnesses such as asbestosis, mesothelioma, lung cancer, intestinal cancer and liver cancer.
Lead – This is a metallic element and can cause health and environmental problems. It is a non-biodegradable substance so is hard to clean up once the environment is contaminated. Lead is harmful to the health of many animals, including humans, as it can inhibit the action of bodily enzymes.
Mercury - This is a metallic element and can cause health and environmental problems. It is a non-biodegradable substance so is hard to clean up once the environment is contaminated. Mercury is also harmful to animal health as it can cause illness through mercury poisoning.
Nitrates – The increased use of fertilisers means that nitrates are more often being washed from the soil and into rivers and lakes. This can cause eutrophication, which can be very problematic to marine environments.
Phosphates - The increased use of fertilisers means that phosphates are more often being washed from the soil and into rivers and lakes. This can cause eutrophication, which can be very problematic to marine environments.
Sulphur – This is a non-metallic substance that is harmful for marine life.
Oils – Oil does not dissolve in water, instead it forms a thick layer on the water surface. This can stop marine plants receiving enough light for photosynthesis. It is also harmful for fish and marine birds.
Petrochemicals – This is formed from gas or petrol and can be toxic to marine life.

Nuclear waste is produced from industrial, medical and scientific processes that use radioactive material. Nuclear waste can have detrimental effects on marine habitats. Nuclear waste comes from a number of sources:

Operations conducted by nuclear power stations produce radioactive waste. Nuclear-fuel reprocessing plants in northern Europe are the biggest sources of man-made nuclear waste in the surrounding ocean. Radioactive traces from these plants have been found as far away as Greenland.
Mining and refining of uranium and thorium are also causes of marine nuclear waste.
Waste is also produced in the nuclear fuel cycle which is used in many industrial, medical and scientific processes.

Oceans are polluted by oil on a daily basis from oil spills, routine shipping, run-offs and dumping.

Oil spills make up about 12% of the oil that enters the ocean. The rest come from shipping travel, drains and dumping.
An oil spill from a tanker is a severe problem because there is such a huge quantity of oil being spilt into one place.
Oil spills cause a very localised problem but can be catastrophic to local marine wildlife such as fish, birds and sea otters.
Oil cannot dissolve in water and forms a thick sludge in the water. This suffocates fish, gets caught in the feathers of marine birds stopping them from flying and blocks light from photosynthetic aquatic plants.

A tank or piping network that has at least 10 percent of its volume underground is known as an underground storage tank (UST). They often store substances such as petroleum, that are harmful to the surrounding environment should it become contaminated. Many UST’s constructed before 1980 are made from steel pipes that are directly exposed to the environment. Over time the steel corrodes and causes leakages, affecting surrounding soil and groundwater.

Atmospheric deposition is the pollution of water caused by air pollution.
In the atmosphere, water particles mix with carbon dioxide sulphur dioxide and nitrogen oxides, this forms a weak acid.
Air pollution means that water vapour absorbs more of these gases and becomes even more acidic.
When it rains the water is polluted with these gases, this is called acid rain.
When acid rain pollutes marine habitats such as rivers and lakes, aquatic life is harmed.

An increase in water temperature can result in the death of many aquatic organisms and disrupt many marine habitats. For example, a rise in water temperatures causes coral bleaching of reefs around the world. This is when the coral expels the microorganisms of which it is dependent on. This can result in great damage to coral reefs and subsequently, all the marine life that depends on it.

The rise in the Earth's water temperature is caused by global warming.

Global warming is a process where the average global temperature increases due to the greenhouse effect.
The burning of fossil fuel releases greenhouse gasses, such as carbon dioxide, into the atmosphere.
This causes heat from the sun to get ‘trapped’ in the Earths atmosphere and consequently the global temperature rises.

Eutrophication is when the environment becomes enriched with nutrients. This can be a problem in marine habitats such as lakes as it can cause algal blooms.

Fertilisers are often used in farming, sometimes these fertilisers run-off into nearby water causing an increase in nutrient levels.
This causes phytoplankton to grow and reproduce more rapidly, resulting in algal blooms.
This bloom of algae disrupts normal ecosystem functioning and causes many problems.
The algae may use up all the oxygen in the water, leaving none for other marine life. This results in the death of many aquatic organisms such as fish, which need the oxygen in the water to live.
The bloom of algae may also block sunlight from photosynthetic marine plants under the water surface.
Some algae even produce toxins that are harmful to higher forms of life. This can cause problems along the food chain and affect any animal that feeds on them.