Impact of Polluted Water

Think about how you use water. The water you drink, the water you use to shower, and even the water you cook your pasta with! This water, that we use daily, needs to be healthy and free of contaminants so that we do not consume dangerous chemicals or catch contagious diseases. Water Pollution is probably not a threat where you live, but in less developed countries where sewage treatment and waste disposal infrastructure are lacking, water Pollution is responsible for widespread disease. After air Pollution, water Pollution is the second largest threat to global health.

What is Water Pollution?

Water pollution is the addition of foreign chemicals, particulates, or energy to a body of water. These substances could be:

• Toxic chemicals
• Metal compounds
• Metal particulates
• Litter
• Animal waste
• Agrochemicals
• Pathogens
• Radioactive material
• Heat energy

What Causes Water Pollution?

Let's have a look at some of the causes of pollution.

Agriculture

The overuse of fertilisers and other agrochemicals like Pesticides and herbicides can result in the pollution of nearby water sources. When plants do not use the nitrogen and phosphorus from fertilisers they will remain in the soil and will be leached into nearby rivers and cause eutrophication. Pesticides contain poisonous chemicals that aim to kill and deter weeds and invasive species, so when they leach into rivers and lakes they may poison the wildlife and pollute water downstream.

Urban and Industrial Change

In densely populated areas by bodies of water and oceans, civilians will produce huge amounts of waste in the form of plastics, food, electronics, and metals. These materials may be disposed of incorrectly or simply littered. Industrial discharge pipes often run into water sources and contain all kinds of dangerous chemicals like hydrocarbons, metal compounds, and radioactive substances. The release of 'cooling water' from power plants can pollute water sources by adding heat as well.

Global Warming and Acid Rain

Impact of Water Pollution on the Environment

Water pollution is not just a concern for human populations, but also threatens ecosystems and habitats all over the world. Let's have a look at some of the environmental implications of water pollution:

Acid Rain Positive Feedback

Acid rain is one of the causes of water pollution, but the addition of nitrogen and sulphur compounds from other sources can result in even more acid rain. Fertilisers, for example, contain huge amounts of nitrogen for plant growth. When this nitrogen is not used it will runoff into nearby waterways and pollute them. When the water evaporates, it will take nitrogen with it. This nitrogen can react to form nitrous oxides and nitric acid in clouds and fall as acid rain. Even when acid rain falls on Soils and grounds it will still runoff into water, and eventually, evaporate to form acid rain.

Figure 1: acid rain destroys habitats.

Algal Blooms

We covered these earlier, but algal blooms are a threat to ecosystems and the water cycle. When these huge green colonies form, they will block sunlight and impair the functioning of the ecosystem, and their breakdown suffocates the ecosystem of oxygen. These eutrophication events can sometimes be so drastic that they form 'dead zones', which are areas where there is such little oxygen that no aerobic life can survive.

Sedimentation Fluxes

Agricultural, industrial, and urban runoff can cause sedimentation fluxes that contain huge amounts of nutrients and dangerous chemicals. Coastal ecosystems like coral reefs and Mangroves are often adapted to low-nutrient environments, so the sudden influx of nutrients can give rise to alternative producer populations that may not sustain the ecosystem as successfully. Heavy sedimentation influxes can smother bottom-dwelling organisms as well, which will have ramifications for entire ecosystems as these organisms are a food source for higher trophic levels.

Ocean Acidification

Ocean acidification by acid rain can stress organisms, while ocean acidification by carbon dioxide can affect millions of marine species requiring carbonates to manufacture their shells and exoskeletons. Carbon dioxide dissociates in water to form carbonic acid, which then reacts with carbonates to from bicarbonates. These bicarbonates are nowhere near as useful as carbonates for calcifying marine organisms, so species such as clams, oysters, and coral lose their structural integrity in acidified conditions.

Harming Ecosystems

The introduction of toxic chemicals can poison species, while radioactive and carcinogenic substances can cause mutations that rise and dismantle populations. Certain species will struggle to adapt to changing conditions and die off. Reduction in populations of these species will have consequences for other species in the ecosystem that they interacted with. Decreasing prey populations will put dependent predators at risk, while symbionts will die off at the same rate, even if one species is better adapted to the changing conditions.

• Diarrhoea: many disease-spreading bacteria and viruses cause diarrhoea, it causes uncontrollable and painful bowel movements that can be very dangerous, especially to children.
• Cholera- infection by the bacterium Vibrio cholera causes cholera disease, which involves infection and breakdown of the intestinal tract. Cholera was prominent in Industrial times when sewage systems were inefficient.
• Typhoid- contraction of typhoid fever infects and damages the intestine and is caused by the bacteria Salmonella typhi.
• Hepatitis A - a very contagious disease, you are often required to get jabs for Hepatitis A when you visit underdeveloped countries.
• Cancer- waters near radioactive power plants can become contaminated with radioactive chemicals. When ingested, these chemicals can cause mutations and cancerous tumours to form.
• Skin irritation- the use of contaminated water for bathing and showering can result in irritation of the skin.
• Fluorosis - consumption of water polluted with fluoride causes yellowing of the teeth.

In 1848, there was a cholera epidemic in Britain, London especially, where more than 50,000 people died from the disease. This led to the London sewage system being completely revolutionised in the Great sewage act of 1858.

Impacts of Water Pollution on Agricultural Production

The increasing global need for agricultural products and decreasing availability of freshwater has led some agricultural workers, especially those in underdeveloped countries, to use water of limited quality. Farmers use water from polluted lakes and rivers for irrigation and drinking water for livestock. Contaminants can cause diseases in livestock similarly to those experienced by humans and can poison crops. In extremely poor areas, farmers may resort to using wastewater because of its high-nutrient content. Wastewater often contains many bacteria that are dangerous for plants and animals.

Prevention of water pollution

• Legislations: the most important way to prevent water pollution is for governments to implement laws and legislations that control the amount of waste that is released into waters, especially from industry and agriculture.
• Agrochemicals: chemicals from agriculture like Pesticides and fertilisers have devastating impacts on local aquatic ecosystems, so farmers must shift to more sustainable methods that require less agrochemicals.
• Sewage treatment: septic tanks and sewage treatment plants must be improved all over the world. Most focus on poisonous and carcinogenic chemicals, but nutrients and microorganisms are threatening aquatic communities too, and need to be treated.
• Industrial discharge: factories and power plants release massive amounts of chemical discharge containing poisonous compounds (hydrocarbons, metals, radioactive substances). These discharges must be managed more efficiently to limit release into water bodies.
• NO_x and SO₂ emissions: nitrous oxides and sulphur dioxides are released as by-products in many industrial processes and cause acid rain, which pollutes water ways. These emissions need to be limited.

Figure 2: gaseous emissions (left) and Solid Waste (right).