III. What is water pollution?

Water pollution occurs when harmful substances, often chemicals or microorganisms, contaminate a stream, river, lake, ocean, aquifer or other body of water, degrading the quality of water. water and making it toxic to humans or the environment. This widespread problem of water pollution puts our health at risk. Unsafe water kills more people each year than war and all other forms of violence combined. At the same time, our sources of drinking water are limited: less than 1% of the planet's fresh water is actually accessible to us. Without action, the challenges will only increase by 2050, when global demand for fresh water is expected to be a third higher than it is now.

What Are the Causes of Water Pollution?

Water is particularly vulnerable to pollution. Known as a “universal solvent,” water is capable of dissolving more substances than any other liquid on earth.  This is why water is so easily polluted. Toxic substances from farms, cities and factories easily dissolve and mix, causing water pollution.

Here are some of the major sources of water pollution around the world:

1. Agricultural

The agricultural sector is not only the biggest consumer of the world's freshwater resources, since agriculture and livestock farming use around 70% of the planet's surface water reserves, it is also a serious water polluter. Around the world, agriculture is the main cause of water degradation. In the United States, agricultural pollution is the number one source of contamination in rivers, number two in wetlands and number three in lakes. It is also one of the main sources of contamination of estuaries and groundwater. Every time it rains, fertilizers, pesticides and animal waste from farms and livestock operations carry nutrients and pathogens, such as bacteria and viruses, into our waterways. Nutrient pollution, caused by excess nitrogen and phosphorus in the water or air, is the number one threat to water quality worldwide, and can lead to algal blooms, a toxic soup of blue-green algae that can be harmful to humans and wildlife.

Figure1: Toxic green algae in Copco Reservoir, northern California/Aurora

2. Sewage and wastewater

Used water is wastewater. It comes from our sinks, showers, and toilets (think sewage) and from commercial, industrial, and agricultural activities (think metals, solvents, and toxic sludge). The term also includes stormwater runoff, which occurs when rainfall carries road salts, oil, grease, chemicals, and debris from impermeable surfaces into our waterways.

According to the United Nations, over 80% of the world's wastewater is returned to the environment without being treated or reused; in some less-developed countries, this figure rises to 95%. In the United States, wastewater treatment facilities process around 34 billion gallons of wastewater per day. These facilities reduce the amount of pollutants such as pathogens, phosphorus, and nitrogen in sewage, as well as heavy metals and toxic chemicals in industrial waste, before discharging the treated waters back into waterways. That’s when all goes well.

3. Oil Spills

Large oil spills and oil leaks are among the most significant causes of water pollution. These are often caused by oil drilling operations in the ocean, but almost half of the estimated 1 tons of oil that ends up in marine environments each year does not come from oil tankers, but from land-based sources such as factories, farms and cities. Oil makes drinking water unsafe, and a significant amount of oil released into oceans or polluting river waters will destroy marine life and the ecosystems that support it. Additionally, oil reduces the supply of oxygen to the aquatic environment. Oil is also naturally released beneath the ocean floor through fractures called seeps.

4. Industrial Waste

Industrial waste is one of the main sources of water contamination. Many industrial sites produce waste in the form of toxic chemicals and pollutants, and some do not have proper waste management systems. Sometimes industrial waste is dumped into nearby freshwater systems. Toxic chemicals released from these wastes can make the water unfit for human consumption and can also cause the temperature of freshwater systems to change, making them dangerous for marine life. Finally, industrial waste can cause “dead zones,” which are areas of water with so little oxygen that marine life cannot survive.

Figure 2: The Deepwater Horizon oil spill in the Gulf of Mexico in 2010.

5. Radioactive substances

Radioactive waste is any pollution that emits radiation in excess of that naturally released by the environment. It is generated by uranium mines, nuclear power plants, military weapons production and testing, and by universities and hospitals that use radioactive materials for research and medicine. Radioactive waste can persist in the environment for thousands of years, making its disposal a major challenge. Consider the decommissioned Hanford nuclear weapons production site in Washington, where the cleanup of 56 million gallons of radioactive waste is expected to cost more than $100 billion and take until 2060. Contaminants released accidentally or improperly disposed of threaten groundwater, surface water and marine resources.

6. Marine Dumping and Plastic Pollution in the Sea

Most items collected and dumped into the oceans by many countries can take between two and 200 years to completely decompose! Other sources of waste at sea include plastic and other materials blown or washed from land. Currently, around 11 million tons of plastic end up in the oceans each year. Research has shown that if this rate of pollution continues; the amount of ocean plastics will reach 29 million tons per year by 2040. The damage to wildlife habitats and land life is incalculable.