Water Contaminants: Common Pollutants To Look Out For

Water pollution is a widespread issue that poses a significant threat to human health and the environment. It occurs when harmful substances contaminate bodies of water, degrading water quality and making it unsafe for human consumption and use. Common water pollutants include chemicals, waste, plastic, sediments, heavy metals, agrochemicals, and microbial contaminants. These pollutants can come from various sources, such as agricultural activities, industrial operations, landfills, and sewage treatment processes. Understanding and addressing these common water pollutants are crucial to ensure the availability and safety of our finite drinkable water sources.

Human activities and natural features

Water pollution is caused by a combination of human activities and natural features. While some pollution is derived from natural processes such as volcanic eruptions, evaporation, and the weathering of arsenic-rich minerals, most pollution is a result of human activity.

Human Activities

Human activities that contribute to water pollution include:

• Industrial operations: Industries such as distilleries, tanneries, pulp and paper, textiles, food, and steel often release toxic chemicals, organic and inorganic substances, toxic solvents, and volatile organic chemicals into aquatic ecosystems.
• Agricultural activities: Farms and livestock operations contribute to water pollution through the use of fertilizers, pesticides, and animal waste, which wash nutrients and pathogens (such as bacteria and viruses) into waterways when it rains.
• Sewage and wastewater treatment: Sewage is the primary source of pathogens (disease-causing microorganisms) and putrescible organic substances. Domestic sewage also often contains active pharmaceutical ingredients, which can harm aquatic organisms.
• Urbanization and population growth: These factors can lead to increased pollution through improper disposal of solid waste, sand, and gravel, as well as the release of untreated wastewater into aquatic ecosystems.
• Climate change: Rising global temperatures caused by CO2 emissions heat the water, reducing its oxygen content.
• Religious activities: Religious gatherings and practices can contribute to water pollution, particularly in sacred rivers such as the Ganges.

Natural Features

Natural features that can contribute to water pollution include:

• Mineral-rich geologic formations: Water can be contaminated by minerals such as arsenic, which enters the water supply naturally through the weathering of arsenic-rich minerals.
• Mercury: Mercury filters from the Earth's crust, polluting oceans, rivers, lakes, canals, and reservoirs.
• Algal blooms: While algal blooms can be caused by human activities, they can also occur naturally through a process called eutrophication. This is when a lake changes from a clean, clear condition to a nutrient-rich, algae-filled state, leading to an oxygen-deficient, waste-filled environment that can be harmful to people and wildlife.

Agricultural activities

Agriculture is a major cause of water pollution, and it is also affected by it. About 40% of the land in the United States is used for agriculture, and farms discharge large quantities of agrochemicals, organic matter, drug residues, sediments, and saline drainage into water bodies.

Excessive use and misuse of fertilizers and pesticides in agriculture can contaminate both groundwater and surface water. Increased levels of nitrogen and phosphorus from fertilizer and manure can stimulate algal blooms in lakes and rivers, leading to the development of hypoxic (low oxygen) conditions that are harmful to aquatic life. Algae can also affect the recreational use of local streams, downstream reservoirs, and estuaries.

Pesticide runoff to streams poses risks to aquatic life, fish-eating wildlife, and drinking water supplies. Older chlorinated agricultural pesticides have been implicated in a variety of human health issues and causing significant and widespread ecosystem dysfunction through their toxic effects on organisms. There is now an international effort to ban these pesticides worldwide as part of a protocol for Persistent Organic Pollutants (POPs).

A new class of agricultural pollutants has emerged in the form of veterinary medicines (antibiotics, vaccines, and growth promoters). These medicines move from farms through water to ecosystems and drinking water sources. The use of non-conventional water sources, such as domestic and municipal wastewater, can also lead to the accumulation of microbiological and chemical pollutants in crops, livestock products, and soil and water resources.

Industrial operations

Industries that use fossil fuels, such as coal-fired plants, are a significant source of industrial wastewater. These plants discharge wastewater with high levels of metals, including lead, mercury, cadmium, and chromium, as well as arsenic, selenium, and nitrogen compounds. The wastewater from these plants also often contains oil and grease, and industrial salts.

Chemical industries also contribute significantly to water pollution. Pollutants discharged from petroleum refineries and petrochemical plants include conventional pollutants like oil and grease, suspended solids, ammonia, chromium, phenols, and sulfides.

Mining operations generate mine tailings, a mixture of water and finely ground rock left over after the removal of the desired mineral concentrate. Mine tailings pose a significant environmental challenge, as they can contaminate water if not properly treated or disposed of.

Other sources of industrial water pollution include agricultural sites, manufacturing plants, and textile services. These industries produce waste that contains toxic chemicals, heavy metals, and organic compounds, which can pollute rivers, streams, and other bodies of water leading to the sea.

To address industrial water pollution, regulations and policies have been developed, such as the US Clean Water Act and the European Union's water policy and industrial emission policy. However, enforcement and compliance with these regulations vary, and some argue that the regulations are not stringent enough to effectively protect water sources from industrial pollution.

Microbial and organic contaminants

Water pollution occurs when harmful substances contaminate a body of water, degrading water quality and rendering it toxic to humans or the environment. Microbial and organic contaminants are a significant category of water pollutants, encompassing a range of substances that can have detrimental effects on aquatic ecosystems and human health.

Sources of Microbial and Organic Contaminants

Types of Microbial and Organic Contaminants

The types of microbial and organic contaminants found in water can vary widely. Some common examples include:

• Bacteria: Fecal streptococci and Clostridium perfringens, Escherichia coli, Salmonella, and Vibrio cholerae are examples of pathogenic bacteria that can contaminate water sources, particularly through sewage and animal waste.
• Viruses: Hepatitis A and E viruses, rotavirus, and other waterborne viruses can cause significant health risks if present in drinking water.
• Parasites: Contamination by parasites such as Giardia, Entamoeba, and parasitic worms can occur through sewage or animal waste, leading to waterborne diseases.
• Organic Matter: Decomposing plant and animal debris, as well as biodegradable organic carbon, can contribute to organic pollution in water.
• Nutrients: Phosphorus and nitrogen, commonly found in agricultural and residential runoff, can promote eutrophication, leading to the rapid biological aging of lakes and streams.
• Pesticides and Agrochemicals: The use of pesticides and other agrochemicals in agriculture can result in water contamination, posing risks to aquatic life and ecosystems.

Health and Environmental Risks

Sediments and solids

Sediments and suspended solids are inorganic materials washed into a stream as a result of land cultivation, construction, demolition, and mining operations. They are classified as water pollutants and can interfere with fish spawning by covering gravel beds and blocking light penetration, making it harder for fish to find food.

Sediments can also directly damage the gill structures of aquatic insects and fish, and organic sediments can deplete the water of oxygen, creating anaerobic conditions. This can cause unpleasant odors and unsightly conditions. Sediments can also promote the accelerated eutrophication, or rapid biological "aging" of lakes, streams, and estuaries.

Sediments are often contaminated with chemicals, including pesticides, heavy metals, and fertilizers. These contaminants can be transported and deposited in the bed sediment of a downstream lake or ocean, impacting the health of benthic organisms. Sediment-associated contaminants can include "legacy" chemicals, such as DDT, PCBs, and chlordane, which were banned decades ago but persist in the environment. Other contaminants, such as the pesticide bifenthrin, flame retardant chemicals, and polycyclic aromatic hydrocarbons (PAHs), are still being released into the environment.

Human activities, such as stirring up sediment in a watercourse, can increase TSS levels downstream, impacting water quality and the survival of aquatic organisms. Suspended solids in drinking water or wastewater can also have gastrointestinal and other negative health impacts on humans.

Frequently asked questions