Water Pollutants: Understanding The Main Contaminants

Water pollution is a pressing issue that affects one in three people on the planet, according to the United Nations. Our rivers, reservoirs, lakes, and seas are contaminated with chemicals, waste, plastic, and other pollutants, rendering the water unsafe for drinking, cooking, cleaning, and swimming. The main water pollutants include bacteria, viruses, parasites, fertilisers, pesticides, pharmaceutical products, nitrates, phosphates, plastics, faecal waste, and even radioactive substances. These contaminants enter water bodies through human activities such as industrial and agricultural processes, sewage treatment plants, and runoff from farming activities.

Agricultural chemicals and waste

Water pollution is a widespread issue that poses a significant threat to both the environment and human health. Agricultural activities, including the use of chemicals and the generation of waste, are major contributors to this problem.

Agricultural chemicals, such as fertilizers and pesticides, are designed to enhance crop growth and protect against pests. However, their excessive use can lead to water contamination. When it rains, these chemicals are washed away from fields and farms, seeping into nearby rivers, streams, and groundwater. This runoff contains high concentrations of nutrients like nitrogen and phosphorus, which can cause excessive algae growth, leading to the depletion of oxygen levels in the water and creating "dead zones" where aquatic life cannot survive.

Pesticides, designed to kill insects, weeds, and fungi, pose an even more direct threat to aquatic ecosystems. These chemicals are often toxic, and their presence in water bodies can lead to the death of non-target organisms, including fish and other aquatic life. Additionally, pesticides can contaminate drinking water sources, potentially harming human health.

Agricultural waste, arising from both plant and animal sources, is another significant contributor to water pollution. Animal waste from concentrated animal feeding operations (CAFOs), where animals are raised in confined spaces, can contain high levels of bacteria and viruses. When this waste enters water bodies, it can contaminate drinking water and spread diseases. Plant-based agricultural waste, such as crop residues and forestry debris, can also impact water quality. When left unmanaged, this waste can wash into water bodies, decomposing and depleting oxygen levels, or releasing harmful chemicals during natural processes.

The impact of agricultural chemicals and waste on water pollution is not limited to rural areas. Urban and industrial wastewater treatment plants often receive agricultural runoff, which contains a complex mixture of pollutants. These treatment plants may not effectively remove all contaminants, leading to the discharge of partially treated wastewater into natural water bodies. This can result in the spread of pollutants over a wider area, affecting both aquatic ecosystems and human populations that rely on these water sources.

Addressing the issue of agricultural water pollution requires a multi-faceted approach. Implementing best management practices in agriculture, such as precision farming and controlled irrigation techniques, can help reduce the amount of chemical runoff and improve waste management. Additionally, investing in advanced wastewater treatment technologies, such as membrane separation and advanced oxidation processes, can enhance the removal of pollutants before water is released back into the environment or supplied for human use.

Industrial chemicals and waste

Industrial waste is defined as waste generated by manufacturing or industrial processes. It is one of the most polluting sources of water contamination, along with city sewage. This waste is generated at every stage of the production, use, and disposal of manufactured products. The types of industrial waste 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.

The nature of the contaminants present in industrial wastewater depends on the type of factory and industry. For example, the mining industry, steel/iron production plants, industrial laundries, power plants, oil and gas fracking plants, metal finishers, and the food and beverage industry are all sources of industrial wastewater.

The contaminants commonly found in industrial water outlets are chemicals, heavy metals, oils, and pesticides. These materials, in the form of elements or in combination with other compounds, may be considered inorganic pollutants if their limit exceeds permissible values, which in turn harms the environment. Heavy metals and other inorganic pollutants such as trace elements, mineral acids, sulfates, inorganic salts, metals, complexes of metals with organic compounds, and cyanides of higher concentrations pollute water bodies. These inorganic impurities are non-biodegradable and pose threats to aquatic flora and fauna and public health.

The EPA regulates 94 chemicals in drinking water sources but doesn’t set standards for many others that could be potentially dangerous. A News21 analysis of EPA data shows that the drinking water of more than 244 million people contains contaminants that can be linked back to industrial practices and are not currently regulated.

Sewage and wastewater treatment

There are two main types of sewage treatment systems: decentralized systems and centralized systems. Decentralized systems, also known as on-site treatment systems, treat sewage close to where it is created and may include septic tanks and other on-site facilities. On the other hand, centralized systems involve a network of pipes and pump stations, known as sewerage, that convey sewage to a municipal treatment plant. This treatment plant can be further categorized as high-tech (high-cost) or low-tech (low-cost) options, with some plants employing a combination of both.

The sewage treatment process typically consists of primary and secondary treatment stages, with advanced treatment incorporating a tertiary treatment stage. Primary treatment includes aerating the wastewater to restore oxygen levels, which removes about 60% of suspended solids. Secondary treatment removes more than 90% of suspended solids, leaving an effluent that can be safely discharged. Advanced treatment includes additional polishing processes and nutrient removal.

Wastewater treatment plants aim to reduce pollutants in wastewater to levels that nature can handle. This is crucial because while nature can cope with small amounts of water waste and pollution, it would be overwhelmed by the billions of gallons of wastewater produced daily without treatment. Wastewater contains various substances, including human waste, food scraps, oils, soaps, and chemicals. These substances can pose threats to human health, aquatic life, and wildlife if not properly treated before release back into the environment.

It is important to note that even treated wastewater can still contain emerging organic wastewater pollutants (EOWPs) at concentrations that can disrupt aquatic ecosystems. These EOWPs are present in water used for irrigation and sludge used as fertilizer. Therefore, ongoing research and development are necessary to improve sewage and wastewater treatment technologies and ensure the protection of our water resources.

Radioactive materials

Radioactive contamination is the deposition of, or presence of, radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable. Radioactive contamination may also be ingested as the result of eating contaminated plants and animals or drinking contaminated water or milk from exposed animals. Radioactive iodine-131, for instance, is a common fission product that can impair or destroy the thyroid if inhaled or ingested in large quantities.

The degree of hazard posed by radioactive contamination depends on the concentration of the contaminants, the energy and type of radiation being emitted, and the proximity of the contamination to the body's organs. The sources of radioactive pollution can be classified as sealed or unsealed, direct or indirect, and point or non-point. The United States Nuclear Regulatory Commission defines the type and amount of radioactive or hazardous material released into the environment following an accident as the "source term".

Public drinking water systems test and filter out contaminants, including radionuclides, to ensure that the water they provide meets all federal, state, and local drinking water standards. The EPA sets limits, called Maximum Contaminant Levels (MCLs), for radionuclides in public drinking water under the Safe Drinking Water Act.

Plastic

The average consumer now comes into daily contact with all kinds of plastic materials, with lightweight, single-use plastic products and packaging materials accounting for approximately 50% of all plastics produced. These single-use plastics have a lifespan of minutes to hours but can persist in the environment for hundreds of years. The issue is further exacerbated by the low recovery rate of plastics, which are relatively inefficient to reuse in the manufacturing process due to processing difficulties.

The consequences of plastic pollution are dire for both wildlife and human populations. Plastic trash has been found in every corner of the globe, from Mount Everest to the Mariana Trench. It is estimated that between 4.8 and 12.7 million metric tons of plastic are discarded into the oceans annually, with rivers acting as conveyor belts, carrying trash downstream. Once in the oceans, plastic waste is broken down by sunlight, wind, and wave action into microplastics, which are spread throughout the water column. These microplastics have been found in municipal drinking water systems, the air, and even in people, with scientists now urgently trying to determine the impact on human health.

Millions of animals are killed by plastics every year, with nearly 2,100 species, including endangered ones, known to be affected. Most deaths are caused by entanglement or starvation, with seals, whales, turtles, and other animals strangled by abandoned fishing gear or discarded plastic items.

To combat this global issue, some governments have taken steps to limit or ban the use of plastic bags, with California recently passing legislation to ban all plastic bags by 2026. It is also recommended that individuals reduce their plastic consumption and reuse or recycle plastic when possible.

Frequently asked questions