Water Quality: Understanding Common Pollutant Categories And Their Impact

Water pollution is a pressing issue that poses a threat to human health and the environment. It refers to the contamination of water sources by various substances, including chemicals, waste, plastic, and other harmful pollutants. These pollutants can be categorised into three main groups: substances that cause disease or physical harm to humans and animals; substances that decrease oxygen levels in water, leading to anaerobic conditions and the death of aquatic life; and substances that are indirectly harmful, such as those that make water unpleasant for human use or damage the natural beauty of water bodies. Point source pollution arises from a single source, like a pipe or channel, while nonpoint source pollution comes from multiple sources and is more challenging to regulate.

Sewage and wastewater

Wastewater contains a wide range of contaminants, including complex organic materials, nitrogen and phosphorus compounds, and pathogenic organisms (bacteria, viruses, and protozoa). Synthetic organic chemicals, inorganic chemicals, microplastics, sediments, radioactive substances, oil, and heat may also be present in sewage.

Wastewater treatment facilities in the United States process approximately 34 billion gallons of wastewater every 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. However, aging and overwhelmed sewage treatment systems in the country also release more than 850 billion gallons of untreated wastewater each year.

According to the United Nations, more than 80% of the world's wastewater flows back into the environment without proper treatment or reuse; this figure exceeds 95% in some underdeveloped countries.

Septic systems, which locally treat wastewater for approximately 20% of homes in the United States, can become a source of nutrient pollution if not properly maintained. Common causes of septic system failure include aging infrastructure, inappropriate design, overloading, and poor maintenance.

To address sewage and wastewater pollution, it is crucial to understand the source of pollution (point source or nonpoint source) and the type of water body being impacted (groundwater, surface water, or ocean water). Point source pollution originates from a single source, such as a manufacturer, oil refinery, or wastewater treatment facility, while nonpoint source pollution comes from diffuse sources like agricultural or stormwater runoff.

Upgrading wastewater treatment systems to enhance nutrient removal can be expensive but may pay off in the long run. In some cases, optimization, which involves adjusting operations and repurposing existing equipment, offers a more cost-effective approach to reducing nutrient loads from wastewater treatment plants.

Industrial waste

The types of industrial waste generated include cafeteria garbage, dirt and gravel, masonry and concrete, scrap metals, trash, oil, solvents, chemicals, weed grass and trees, wood and scrap lumber, and similar wastes. Industrial waste is one of the most polluting sources of water contamination, along with city sewage. It can be toxic, ignitable, corrosive, or reactive, and has been found to contain high levels of toxic contaminants that are detrimental to both human and animal health.

The introduction of new products, such as computers, drugs, textiles, paints and dyes, and plastics, has also led to the generation of hazardous waste, including toxic chemicals. These chemicals are often unknown in terms of their health and environmental impacts. Industrial wastewater usually contains specific and readily identifiable chemical compounds, with water pollution concentrated within a few subsectors, mainly in the form of toxic wastes and organic pollutants.

The agricultural sector, with its use of fertilizers, pesticides, and animal waste, is the leading cause of water degradation in the United States. However, industrial waste is a major contributor to contamination in estuaries and groundwater. It is important to note that wastewater treatment facilities reduce the amount of pollutants in sewage and industrial waste before discharging treated waters back into waterways.

To address the issue of industrial waste and its impact on water quality, various treatment methods have been developed. These include biological, chemical, and physical processes to treat wastewater and remove contaminants before they are released into water bodies. The proper treatment of industrial wastewater is crucial to maximize the quality and quantity of potable water, as the escalating population increases the demand for water.

Oil pollution

Sources of Oil Pollution

• Spills from large tankers or pipelines: Accidental spills from tankers, drill platforms, barges, ships, or pipelines are often the most visible and devastating events, with the potential to release millions of litres of oil into the environment.
• Land-based sources: Nearly half of the estimated annual oil discharge into marine environments comes from land-based sources such as factories, farms, and cities. This includes runoff from roads, parking lots, and other impervious surfaces, as well as deliberate discharges and leaks from refineries, depots, and storage facilities.
• Natural seepage: Oil can also seep naturally from the ocean floor through fractures and eroding sedimentary rocks. While this contributes a smaller amount to overall oil pollution, it is still a notable source.

Effects of Oil Pollution

• Ecological damage: Oil spills can coat the feathers and fur of birds and marine animals, impairing their insulation and mobility. It also harms marine plants by blocking sunlight needed for photosynthesis. Oil pollution can lead to the closure of beaches and harm fishing and hunting activities, impacting communities that rely on these resources.
• Contamination of drinking water sources: Oil pollution can contaminate water intended for drinking and other purposes, posing risks to human health.
• Harm to sensitive ecosystems: Coral reefs, mangroves, and marshes are particularly vulnerable to oil pollution, and even small spills can have devastating effects on these ecosystems.

Mitigation and Clean-up Strategies

Addressing oil pollution requires a combination of preventive measures and effective clean-up techniques:

• Prevention: The United Nations treaty MARPOL, which came into effect in 1983, mandates the use of oil-pollution prevention equipment on tankers and ships, such as double hulls and reliable navigation systems. This has significantly reduced oil spills.
• Containment and clean-up: In the event of a spill, it is crucial to act quickly to contain the oil and prevent it from spreading. Booms, skimmers, and sorbents are commonly used to contain and absorb the oil. Other methods include burning, chemical dispersants, and bioremediation using natural microorganisms.
• Long-term monitoring: Some effects of oil pollution may not be immediately apparent, and long-term monitoring is necessary to assess the impact on ecosystems and human communities.

Radioactive substances

Radioactive contamination can be classified into two groups: natural and human-made. Natural radioactive contamination arises from the presence of radionuclides in the environment, such as uranium, thorium, and their decay products in rock and soil. These radionuclides can dissolve in water or release radioactive gases, leading to groundwater and surface water contamination.

Human-made radioactive contamination, on the other hand, is primarily associated with nuclear activities. This includes nuclear weapon testing, nuclear reactor breaches, nuclear power plants, and the improper disposal of radioactive waste. Accidents or breaches at nuclear facilities can result in the release of nuclear fuel and fission products, contaminating the surrounding air, soil, and water sources. Additionally, the use of radioactive elements in medical equipment, such as X-rays and MRI machines, can expose individuals to radiation.

The impact of radioactive substances on water quality is a growing concern. Radioactive contamination has been reported in many parts of the globe, affecting both groundwater and surface water. Radioactive elements, such as uranium and radium, can dissolve in water, leading to contamination. Radioactive waste disposal and nuclear accidents have resulted in the release of radioactive particles into water bodies, causing water pollution.

The consequences of radioactive water pollution on human health can be severe. Ingesting or inhaling contaminated water can result in internal irradiation, where radioactive substances emit radiation from inside the human body. This can lead to various health issues, including acute radiation syndrome, cutaneous radiation injury, cancer, leukaemia, genetic mutations, and chromosomal disruptions. The World Health Organization and the United States Environmental Protection Agency have set guidelines and standards for drinking water quality to protect public health.

To address radioactive water pollution, proper analysis, monitoring, and treatment methods are essential. Techniques such as aeration, reverse osmosis, ion exchange, and granule carbon adsorption can be used to remediate contaminated water. Additionally, prevention and precaution measures are crucial to control anthropogenic sources of radioactive contamination in water resources.

Agricultural pollution

Water pollution occurs when harmful substances contaminate a body of water, degrading water quality and making it toxic to humans and the environment. There are several categories of common pollutants that affect water quality, including agricultural pollution, sewage and wastewater, oil pollution, and radioactive substances.

Nutrient pollution, caused by excess nitrogen and phosphorus in water or air, is the leading threat to water quality worldwide. It can cause algal blooms, or toxic algae, which can be harmful to people and wildlife. Agricultural pollution is the top source of contamination in rivers and streams in the United States, the second-biggest source in wetlands, and the third main source in lakes. It also significantly contributes to contamination in estuaries and groundwater.

The use of pesticides and fertilizers in agriculture can increase the risk of cancer and reproductive problems and impair eye, liver, kidney, and other body functions in humans. These chemicals can also have detrimental effects on aquatic ecosystems, including fish and other aquatic organisms.

To address agricultural pollution, proper waste management practices, such as the treatment and safe disposal of wastewater, are essential. Additionally, reducing the use of pesticides and fertilizers, and implementing sustainable farming practices, such as organic farming or integrated pest management, can help mitigate the impact of agriculture on water quality.

Frequently asked questions