Understanding Freshwater Pollution: Major Causes And Impacts

Water is a vital resource, essential for all living beings and crucial for social and economic development. However, water pollution, particularly in freshwater sources, is a significant global issue, with nearly half of all rivers and over a third of lakes now polluted and unfit for swimming, fishing, or drinking. The main sources of this pollution include industrial waste, agricultural waste and run-off, municipal waste, power generation, and automobiles. These sources introduce toxic chemicals, bacteria, viruses, fertilisers, pesticides, pharmaceuticals, nitrates, plastics, and heavy metals into water systems, causing severe health issues and environmental damage.

Industrial waste

The production of industrial goods generates wastewater that can be contaminated with toxic substances. This wastewater can be discharged into nearby public waters, polluting rivers, lakes, and seas. In some parts of the world, such as emerging economies, environmental policies are not yet stringent enough, and the illegal discharge of wastewater from industry into freshwater sources is common.

The impurities in industrial wastewater can consist of lubricants, mainly mineral oils, which cause a high COD value. In electroplating, for example, heavy metals such as zinc, nickel, copper, or cadmium contaminate the water. Other types of industrial wastewater include petroleum products, hazardous wastes, and sediments. These wastes can be highly flammable, corrosive, or carcinogenic, and they can accumulate in water sediments for years, slowly entering the groundwater and affecting drinking water sources.

The release of pollutants from industrial sites has increased due to growing industrial setups and an increased demand for goods. This has resulted in more industrial waste, which pollutes not only water but also the air and soil. The quality and quantity of wastewater generated depend on the type of industry, with some industries producing non-biodegradable waste such as heavy metals, pesticides, and plastics. Without proper treatment and management strategies, the discharge of this waste into water bodies can have detrimental effects on the environment and human health.

To address the environmental and health issues created by industrial wastewater, it is crucial to treat and manage it adequately before discharging it into freshwater systems. This can be done through physical, chemical, and biological means, and new technologies, such as microbial fuel cells, are being developed to treat industrial wastewater more effectively and eco-friendly.

Agricultural waste

Agriculture is the largest user of freshwater resources, accounting for about 70% of water withdrawals worldwide. It is both a cause and victim of water pollution. Agricultural activities discharge pollutants and sediments into surface and groundwater, leading to eutrophication and ecosystem damage.

Farmers use pesticides, nitrogen fertilizers, and organic waste to protect their crops from bacteria and insects. These substances can seep into groundwater, harming animals, plants, and humans. Additionally, when it rains, these chemicals mix with rainwater, flowing into rivers and streams, eventually filtering into the ocean, causing further water pollution.

In recent years, a new class of agricultural pollutants has emerged: veterinary medicines (antibiotics, vaccines, and growth promoters). These substances move from farms through water to ecosystems and drinking water sources, potentially impacting human health.

To mitigate the impact of agricultural waste on water pollution, buffer strips and integrated farming systems can be implemented. Buffer strips are vegetated filter strips at the margins of farms and along rivers, helping to decrease pollutant concentrations entering waterways. Integrated farming optimizes resource use and reduces pollution by ensuring that waste from one enterprise becomes input for another.

Oil spills

The negative effects of oil spills are exacerbated the longer the oil remains in freshwater. Research by the American Chemical Society has shown that as spilled oil spends more time in the environment, it undergoes chemical changes, creating products that can persist in the environment and potentially increasing the impact on aquatic organisms. This emphasizes the importance of rapid responses to oil spills and the need for long-term remediation efforts.

Overall, oil spills are a significant contributor to water pollution, causing environmental, ecological, and economic damage that can persist for years.

Sewage and wastewater

Sewage contains high levels of nitrogen and phosphorus, which stimulate the growth of algae, leading to algal blooms. These blooms can block light necessary for photosynthesis, causing the death of plants and algae, which are then consumed by bacteria. This process reduces oxygen levels in the water, leading to the death of fish and other organisms. Additionally, sewage often contains toxic contaminants derived from cleaning and beauty products, pharmaceuticals, and other sources, posing risks to both the environment and human health.

Wastewater treatment facilities aim to mitigate the impact of sewage on freshwater sources. However, even treated sewage can have detrimental effects on freshwater ecosystems. Research has shown that treated wastewater released into an unpolluted stream in northern Spain caused subtle yet fundamental shifts in ecosystem function, indicating that advanced treatment may not be sufficient to protect freshwater ecosystems. The challenge of reducing sewage pollution is further compounded by ageing infrastructure and poorly planned development, which increase the amount of stormwater and pollution entering sewer systems.

The issue of sewage and wastewater pollution in freshwater sources has sparked public outcry and led to legislative changes. For example, the Clean Water Act in the United States and the European Water Framework Directive have driven investments in wastewater treatment infrastructure. While these efforts have improved water quality, the task of updating wastewater infrastructure to eliminate sewage overflows and leaks entirely remains a costly and time-consuming endeavour.

To address the issue of sewage and wastewater pollution in freshwater sources, a multi-faceted approach is necessary. This includes investing in wastewater treatment technologies, improving infrastructure, implementing notification programs to alert the public about sewage contamination, and promoting natural solutions such as planting trees, restoring wetlands, and creating green roofs to expand the capacity of sewer systems.

Radioactive waste

Radioactive pollution of freshwater sources can occur through several anthropogenic activities. Nuclear power plants and nuclear weapon testing contribute significantly to radioactive waste, which, if not properly disposed of, can contaminate water bodies. The Fukushima Daiichi nuclear disaster in 2011, caused by an earthquake and tsunami, released thousands of tons of radioactive water into the Pacific Ocean. This is an example of the devastating impact natural disasters can have on nuclear facilities and the consequent release of radioactive material into the environment.

Mining activities for radioactive elements like uranium and thorium also contribute to freshwater pollution. Uranium, a naturally occurring element in seawater, can be found in higher concentrations in areas of greater salinity. Coastal nuclear power plants release atomic waste, and the water used as a coolant in these facilities can also become contaminated, further polluting marine water.

Radioactive contamination can enter the food chain through plankton and kelp, eventually reaching and contaminating fish. This contamination has already been observed in seals and porpoises in the Irish Sea, where low levels of radioactive waste have been discharged since 1952. Radioactive caesium and plutonium have the potential to spread across countries, carried by invisible radiation in the form of clouds.

The health impacts of radioactive water pollution are severe. According to the United Nations, water pollution causes more deaths annually than all forms of violence, including war. Radioactive water pollution can lead to the spread of diseases and the disruption of entire ecosystems, posing significant risks to both human health and the environment.

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