Water Pollutants: Understanding The Contaminants In Our Waterways

Water is often referred to as a 'universal solvent, as it is able to dissolve more substances than any other liquid on Earth. This makes water highly susceptible to pollution. Water pollution is the contamination of water bodies, which can negatively impact their use. Water pollution is usually a result of human activities, with agricultural, industrial, and urban sources being the most common. These activities introduce a range of pollutants into water bodies, including toxic substances such as oil, metals, plastics, pesticides, organic compounds, and industrial waste products. Water pollution can lead to the degradation of aquatic ecosystems, the spread of water-borne diseases, and a reduction in ecosystem services such as drinking water provision.

Characteristics and Values of Water Pollutants

Industrial and municipal waste

Industries such as petrochemical, pharmaceutical, food and beverage, and manufacturing, release a variety of pollutants into water sources. These include dissolved solids (salts), naturally occurring radionuclides, metals, and other drilling-related contaminants. Additionally, industrial solvents, personal care products, and disinfection by-products can also find their way into water bodies.

Municipal wastewater, on the other hand, can contain various contaminants, including human feces, sewage, blackwater, and manure. Inadequate sanitation procedures or poorly functioning sanitation systems can lead to high levels of pathogens in water bodies. Municipal waste can also introduce organic substances, such as petroleum hydrocarbons (fuels and lubricants) and their combustion by-products, into water sources.

The treatment of industrial and municipal wastewater is crucial to mitigate the impact on water pollution. Off-site treatment facilities collect wastewater from municipal and industrial drainage systems, employing various methods to separate and treat different types of waste. Technologies such as reverse osmosis are used to remove pollutants before releasing the treated water into natural water bodies. However, there is no one-size-fits-all solution to wastewater management, and treatment methods must be tailored to the specific context, including water source, pollutant types, and geographical location.

Furthermore, programs such as the Total Maximum Daily Load (TMDL) in the US, Integrated Pollution Prevention and Control (IPPC) in Europe, and the Central Pollution Control Board (CPCB) in India, have been established to set standards and regulate the release of municipal and industrial wastes into water bodies. These programs aim to ensure that wastewater is treated effectively to maximize the quality and quantity of potable water available.

Agricultural activities

Excessive fertiliser use is another concern. Fertilisers contain nutrients like nitrogen and phosphorus, which can act as pollutants when they enter water bodies in large quantities. These nutrients cause excessive growth of algae and other aquatic plants, leading to a phenomenon known as eutrophication. Eutrophication can result in the depletion of oxygen levels in the water as the excess plant matter decomposes, leading to the death of fish and other aquatic organisms. Eutrophication can also cause the production of toxins, further endangering aquatic life and making the water unsafe for human use.

Soil erosion from agricultural lands is another source of water pollution. When soil is eroded by wind or water, it can end up in nearby rivers, lakes, or other water sources. This sediment can cloud the water, reducing light penetration and hindering the growth of aquatic plants. The sediment can also smother aquatic habitats, damaging the complex ecosystems that depend on them. Additionally, eroded soil can carry pesticides, fertilisers, and other contaminants, introducing these pollutants into the water.

Agricultural runoff is a major contributor to water pollution. When rainwater or irrigation water flows over fields, it can pick up sediment, nutrients, pesticides, and other contaminants, carrying them into nearby streams, rivers, or groundwater. This runoff can have detrimental effects on water quality and the health of aquatic ecosystems. To mitigate these issues, farmers can adopt sustainable practices, such as precision agriculture, conservation tillage, and integrated pest management, which can help reduce the amount of pollutants entering water bodies.

Sewage and sanitation

Sewage discharge leads to a significant decline in water quality. The pathogens in the waste not only harm aquatic ecosystems but also make the water unsafe for human and animal use. These pathogens include bacteria, viruses, protozoans, and parasitic worms, which can cause various diseases. In addition, nutrient-rich sewage can lead to eutrophication, resulting in excessive algae growth that depletes oxygen in water bodies, causing a decline in aquatic life and often fish die-offs. Sewage pollutants are particularly damaging to coral reefs, which are essential for maintaining marine biodiversity and spawning.

The infiltration of sewage into groundwater and other water sources can also lead to contamination. Groundwater, which accounts for nearly 40% of drinking water in the United States, is highly susceptible to pollution from contaminants such as pesticides, fertilizers, and waste from landfills and septic systems. Once polluted, an aquifer may be unusable for decades or even thousands of years.

To address sewage pollution, proper sanitation and wastewater control are crucial. This includes the regular maintenance of septic systems, the proper disposal of hazardous materials and non-biodegradable items, and the reduction of water usage to lessen the load on sewage treatment facilities. Innovative solutions, such as waste-free toilets and resource recovery to generate fuel and drinking water, are also being explored.

The impact of sewage pollution is not limited to environmental and health concerns but also extends to economic and social realms. For example, in Barbados, coral reefs have been impacted by eutrophication, altering the species composition of the corals. Similarly, poorly designed and failing sewage systems have repeatedly led to fish kills and beach closures. Additionally, the tourism industry in Costa Rica and Chetumal Bay has suffered losses due to pollution from untreated sewage.

Chemical compounds

Organic Chemicals

Organic chemicals are human-made compounds used in a variety of products, such as pesticides, gasoline, dry-cleaning solvents, and degreasing agents. Volatile organic compounds (VOCs) and synthetic organic compounds (SOCs) are two types of organic chemicals that can contaminate groundwater and drinking water supplies. VOCs are substances that contain carbon and evaporate at room temperature, while SOCs are synthetic variants that do not occur naturally in water. Improper storage, disposal, or spills of products containing VOCs and SOCs can lead to water contamination. Pesticides, for instance, when sprayed too close to a well or water source, can contaminate groundwater. Additionally, the treatment of drinking water with chlorine can also lead to the formation of certain organic chemicals.

Industrial Chemicals

Industrial activities contribute significantly to water pollution by releasing toxic chemicals into rivers, lakes, and drinking water sources. Per- and polyfluoroalkyl substances (PFAS) are a class of manufactured chemicals used in various products and manufacturing processes since the 1940s. PFAS are now prevalent in water, soil, air, and food. They have been linked to health issues, and exposure to multiple toxic pollutants simultaneously poses an even greater threat to communities. Other industrial chemicals, such as bromides, 1,4-dioxane, and GenX, have also been detected in water sources and are known to cause health problems.

Agricultural Chemicals

Agricultural practices contribute to water pollution through the use of fertilizers, pesticides, and animal waste. Every time it rains, these chemicals and waste are washed into waterways, leading to nutrient pollution. Excess nitrogen and phosphorus in water can cause algal blooms, which are harmful to both people and wildlife. Additionally, agricultural crops can absorb cadmium compounds from the soil, leading to cadmium contamination in water sources. Cadmium exposure can occur through drinking water and has been linked to health issues, including a signature painful bone disease.

Petroleum-Related Compounds

Motor oil drips and vehicle leaks contribute to water pollution through the release of petroleum-related compounds. These compounds account for a significant portion of the total estimated initial release of such contaminants. While not all hazard thresholds for these compounds are known, studies have shown that some, such as PBDEs, are present at concerning levels.

Heavy Metals

Heavy metals, such as copper and zinc, are also considered chemical compounds that can pollute water. They can be released into water bodies through various sources, including urban runoff from building materials, fencing, streetlights, and roof gutters. Heavy metals can have detrimental effects on the environment and human health, and their presence in water can pose significant risks.

Oil and plastics

Oil and plastic pollution are major contributors to the degradation of water bodies. Oil pollution is primarily caused by oil spills, which can have disastrous consequences for aquatic ecosystems. Oil spills can result from accidents involving oil tankers, pipelines, or offshore drilling operations. The toxic hydrocarbons in oil are extremely harmful to marine life, affecting a wide range of organisms, from plankton to marine mammals. Oil slicks on the water surface block sunlight, hindering the ability of aquatic plants to photosynthesize, and the oil can smother animals, impairing their ability to move and reproduce. Oil can also contaminate drinking water sources, rendering them unsafe for human consumption.

In addition to acute incidents, there is also a more gradual form of oil pollution that comes from stormwater runoff. This type of pollution is often associated with urban areas, where oil and grease from roads, parking lots, and industrial sites can accumulate and eventually find their way into nearby water bodies.

Plastic pollution, similarly, has insidious and far-reaching effects on aquatic ecosystems. Plastics are derived from oil, and the production and refining of plastics contribute to environmental degradation and climate change. When plastics are discarded improperly, they can find their way into oceans, rivers, and lakes, polluting these water bodies and threatening the health of both wildlife and humans.

Plastic waste can be ingested by marine animals, leading to starvation as their stomachs become filled with indigestible material. It is estimated that plastic waste is responsible for the deaths of over a million seabirds and 100,000 marine mammals annually. Moreover, plastics can break down into microplastics, which are then consumed by smaller organisms, leading to the bioaccumulation of toxic chemicals in the food chain. These chemicals, such as carcinogenic substances and heavy metals, can eventually reach humans through the consumption of contaminated seafood.

The impact of plastic pollution extends beyond the ecological realm and has significant economic implications. Plastic debris can negatively affect sectors such as tourism, fisheries, and agriculture. The build-up of plastic waste can also hinder social well-being and food production capabilities, underscoring the urgency of addressing this global crisis.

Frequently asked questions